Table of Contents Author Guidelines Submit a Manuscript
Mediators of Inflammation
Volume 2015, Article ID 835910, 12 pages
http://dx.doi.org/10.1155/2015/835910
Review Article

Natural Products: Insights into Leishmaniasis Inflammatory Response

1Departamento de Produtos Naturais e Alimentos, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, 21941-902 Rio de Janeiro, RJ, Brazil
2Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902 Rio de Janeiro, RJ, Brazil
3Programa de Pos-Graduação em Imunologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902 Rio de Janeiro, RJ, Brazil
4Departamento de Produtos Naturais, Farmanguinhos, FIOCRUZ, 21041-250 Rio de Janeiro, RJ, Brazil
5Departamento de Química, Universidade Federal do Amazonas, Japiim, 69077-000 Manaus, AM, Brazil
6Departamento de Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro, 21941-909 Rio de Janeiro, RJ, Brazil

Received 5 June 2015; Accepted 22 July 2015

Academic Editor: Barbara Romano

Copyright © 2015 Igor A. Rodrigues et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Leishmaniasis is a vector-borne disease that affects several populations worldwide, against which there are no vaccines available and the chemotherapy is highly toxic. Depending on the species causing the infection, the disease is characterized by commitment of tissues, including the skin, mucous membranes, and internal organs. Despite the relevance of host inflammatory mediators on parasite burden control, Leishmania and host immune cells interaction may generate an exacerbated proinflammatory response that plays an important role in the development of leishmaniasis clinical manifestations. Plant-derived natural products have been recognized as bioactive agents with several properties, including anti-protozoal and anti-inflammatory activities. The present review focuses on the antileishmanial activity of plant-derived natural products that are able to modulate the inflammatory response in vitro and in vivo. The capability of crude extracts and some isolated substances in promoting an anti-inflammatory response during Leishmania infection may be used as part of an effective strategy to fight the disease.

1. Introduction

Human leishmaniasis is an infectious disease caused by 20 different Leishmania species reported in 98 countries and territories spread across four continents (Africa, Americas, Asia, and Europe). Leishmaniasis is considered a major public health issue as it currently affects 12 million people [1]. The anthroponotic and zoonotic forms of transmission may occur. In the last case, the primary reservoirs of Leishmania are sylvatic mammals such as forest rodents, hyraxes, and wild canids. However, urban or domestic dogs are the most relevant species in the epidemiology of this disease [2].

Leishmania infection occurs during the hematophagy of female sand flies belonging to Phlebotomus (Old World) and Lutzomyia (New World) genus. The metacyclic promastigote forms present in the foregut of the sand flies are inoculated in the dermis-epidermis junction of the vertebrate host, infecting cells of the mononuclear phagocyte system [3]. The interaction between parasites and host immune cells leads to an inflammatory response essential for parasite control. However, an exacerbated proinflammatory response may cause tissue damage, such as those easily observed in cutaneous leishmaniasis cases [4, 5]. On the other hand, the lack of an effective inflammatory response may promote increased parasite burden. In this scenario, a moderate inflammatory response would be ideal for an effective control of the disease.

Plants have been long recognized as a rich source of biologically active extracts, essential oils, and isolated substances. In fact, research laboratories around the world search in plants for active substances against diverse illnesses such as microbial and protozoal infections, cancer, diabetes, and inflammatory processes [6]. Indeed, plant-derived natural products such as phenolic compounds, steroids, quinones, coumarins, terpenoids, and alkaloids have been widely investigated for their antileishmanial potential [7, 8].

In the present review, we start with an introduction about the current scenario of leishmaniasis epidemiology and treatment, followed by some highlights on the inflammatory response generated by Leishmania infection. The last part of this work focuses on the modulatory effects of plant-derived natural products over inflammatory mediators and their impact on parasite burden in vivo and in vitro.

2. Leishmaniasis: A Global Threat

It is estimated that leishmaniasis has about 1.6 million new cases per year. However, only 600,000 cases are reported annually. Socioeconomic conditions such as poverty and malnutrition, environmental changes such as atmospheric temperature and humidity, ecological conditions affecting the vector, parasite, and its reservoir, and population movements caused by migration and tourism are all risk factors that directly interfere with the world’s distribution of leishmaniasis [911]. In addition, the ecology of sand fly species also plays a significant role in the spread of the disease [12].

According to geographical criteria, leishmaniasis can be divided into two main syndromes: (1) Old World Leishmaniasis, which includes two clinical manifestations: cutaneous leishmaniasis (CL), a disease confined to the skin, and visceral leishmaniasis (VL), involving the bloodstream and inner organs; (2) New World Leishmaniasis, which includes CL and mucocutaneous leishmaniasis (MCL). The latter involves mucous membranes in addition to the skin. Currently, new terminology regarding leishmaniasis forms was introduced such as mucosal leishmaniasis (ML). ML involves mucosal tissues, particularly those of the upper respiratory tract and oral cavity. It is typically a consequence of infection by New World Leishmania species, such as L. braziliensis, L. panamensis, L. amazonensis, and L. guyanensis [10].

Cutaneous leishmaniasis is found in South America, Asia, Europe, and Africa. Latin America is the most important endemic area, particularly the Amazon. Different Leishmania species cause Old World (Eastern hemisphere) versus New World (America) CL: in the Old World, the etiologic agents include L. tropica, L. major, L. aethiopica, L. infantum, and L. donovani; the main species in the New World are either those of the L. mexicana complex (L. mexicana, L. amazonensis, and L. venezuelensis) or the ones of the subgenus Viannia (L. (V.) braziliensis, L. (V.) guyanensis, L. (V.) panamensis, and L. (V.) peruviana).

The general term visceral leishmaniasis can refer to different degrees of disease severity, including chronic, subacute, or acute, affecting internal organs, particularly spleen, liver, and bone marrow. The two most important causative agents of VL are L. donovani, which shows anthroponotic transmission (human to human), and L. infantum, with zoonotic transmission (canine to human). Together, they cause 40,000 deaths per year [13]. L. donovani is only found in the Old World, being responsible for VL cases in East Africa and the northeast of India. On the other hand, L. infantum is found in the Mediterranean and in Latin American regions [14]. Over 90% of VL cases occur in Bangladesh, Brazil, Ethiopia, India, South Sudan, and Sudan [11].

3. Available Chemotherapy for Leishmaniasis

Chemotherapy is the current method for human leishmaniasis treatment since there are no vaccines available. Usually, the therapeutic approach starts with the use of pentavalent antimonials such as sodium stibogluconate and meglumine antimoniate. However, when these drugs exhibit low efficacy or simply cannot be prescribed for leishmaniasis treatment, second-line drugs are indicated [12, 15, 16].

Several Leishmania-killing mechanisms have been attributed to pentavalent antimonials including apoptosis, disturbance of fatty acids β-oxidation, adenosine diphosphate phosphorylation, and redox balance. In addition, antimonials inhibit the glycolysis pathway and are able to directly act on infected macrophages eliciting an oxidative/nitrosative stress against internalized parasites [17, 18]. Despite the variety of antileishmanial targets, the use of pentavalent antimonials has been extensively discussed due to their toxic effects to liver and heart tissues. Regarding the use of amphotericin B, this drug targets ergosterol, an essential plasma membrane sterol found in Leishmania spp. Also, amphotericin B recognizes cholesterol in mammalian cells, which leads to high toxicity and severe side effects, including kidney failure, anemia, fever, and hypokalemia [19].

Miltefosine and paromomycin are two other drugs that have been introduced for the treatment of leishmaniasis. Miltefosine was the first orally administered drug effective against VL. The mechanism of antileishmanial action of miltefosine remains unclear but apoptosis preceded by drug intracellular accumulation has been described. Other possible mechanisms include cytochrome c oxidase inhibition, which leads to mitochondrial dysfunction and immunomodulation [20]. The recommended dose of miltefosine for VL treatment is approximately 2.5 mg/kg/day for 4 weeks. The long term therapy in conjunction with miltefosine long half-life (about 150 h) can accelerate the onset of drug resistance. Moreover, recent studies have pointed out that miltefosine has a potential teratogenic and abortifacient effect, preventing its prescription during pregnancy [18, 21]. Paromomycin is an aminoglycoside antibiotic that has shown important results in leishmaniasis treatment, mainly for the cutaneous form of the disease [22]. However, in vitro studies have already reported the emergence of paromomycin-resistant parasites, compromising its use as a wide antileishmanial agent in the future [23]. In addition, the toxicity of miltefosine and paromomycin has also been described [12].

In summary, the current chemotherapy scenario urges for more efficient and secure antileishmanial treatments, encouraging the search for new bioactive compounds such as those from natural origin. In fact, plant-derived natural products represent a promising class of drug candidates against leishmaniasis.

4. Inflammatory Response to Leishmania Infection

Parasite-host interaction is a complex process that modulates Leishmania infection and the immunological response to it, including inflammation. Several molecules are involved in inflammation during leishmaniasis, such as cytokines and the lipid mediator leukotriene B4 (LTB4). Many of the molecules that promote inflammation also activate phagocytes leading to the production of nitric oxide (NO), the main effector molecule in parasite killing. However, an exacerbated production of these molecules may also lead to tissue damage.

Tumor necrosis factor (TNF) and interleukin-1 (IL-1) are cytokines produced by macrophages after the recognition of pathogens, including Leishmania. They promote inflammation by inducing the expression of adhesion molecules (selectin and integrin ligands) on the endothelial surface. TNF- or TNF-receptor 1- (TNFR1-) deficient mice are able to control L. major replication but develop larger lesions [24, 25]. The role of IL-1 in leishmaniasis is controversial, as IL-1 contributes to Th1 priming at early infection but worsens the disease outcome in established infection [26].

IL-10 is an important anti-inflammatory cytokine responsible for peripheral tolerance to self-antigens and preventing exacerbated immune responses to foreign antigens. However, when expressed in large quantities, IL-10 may have deleterious effects during leishmaniasis, leading to an early suppression of innate and acquired immune responses, pathogen proliferation, and aggravation of the disease [27]. In leishmaniasis, phagocytes are stimulated to produce IL-10, which leads to a reduced production of cytokines related to the Th1 profile, such as IL-12 and interferon gamma (IFN-γ) [28]. This causes a reduction in NO production that consequently reduces the microbicidal capacity of macrophages. IL-10 may be secreted by numerous cells, including macrophages, T cells, and B cells.

The cytokines IL-12 and IL-4 also play an important role during Leishmania infection. They define the cell profile through the polarization of CD4+ T cells and modulate the response from other cells [29, 30]. IL-12 activates NK cells and CD8+ T cells, leading to IFN-γ production [31]. In addition, IL-12 induces the differentiation of CD4+ T cells to the Th1 profile, which also produces IFN-γ, a potent inducer of NO production in macrophages. Thus, IL-12 possesses an indirect microbicidal action. In contrast, IL-4 induces the differentiation of CD4+ T cells to a Th2 profile, which produces IL-4, IL-5, and IL-13. This profile suppresses NO production and leads to an increase in eosinophils [32].

LTB4 is an eicosanoid with chemotactic function synthesized from leukotriene A4 by leukotriene-A4 hydrolase. In vitro, LTB4 contributes to the microbicidal action of macrophages through the production of NO and reactive oxygen species while, in vivo, LTB4 reduces the parasite load and the footpad swelling [33, 34].

The importance of the type of immune response, if Th1 or Th2, lies in the fact that Th1 immune response characterizes the resistance mechanism to Leishmania infection, while Th2 response has been associated with susceptibility to parasite infection. The Th1 immune response is associated with production of proinflammatory cytokines such as IFN-γ, TNF-α, and IL-12, while the susceptibility profile of Th2 response is characterized by anti-inflammatory cytokines expression such as IL-10 and IL-4 (Figure 1) [35].

Figure 1: Cytokine profile regulates the type of immune response to Leishmania infection. The balance between IL-10 and IL-12 produced by macrophages regulates the parasitic load by controlling NO production, CD4 + T lymphocytes profile, and IFN-y production by NK and CD8 + cells.

In humans, protection against VL is mediated by Th1 immune response whereas pathogenesis is associated with Th2 response. Most studies suggest that poor Th1-type responses are associated with severe clinical forms of leishmaniasis [36]. Some studies have demonstrated the importance of proinflammatory cytokines IFN-γ, TNF-α, and IL-12 in L. donovani infection. Depletion of these cytokines aggravated the disease progression or made hosts susceptible to infection by L. donovani [37].

However, studies about CL showed that higher frequency of proinflammatory cytokine production leads to larger lesions. Some studies pointed that high production of IFN-γ, TNF, and NO is not always beneficial [38]. Thus, inadequately controlled immune responses could potentially lead to pathological manifestations and tissue damage. This is contradictory since many studies pointed out that the Th1-mediated response is important for disease control. The activation of type effector cells that produce the macrophage-activating cytokines (i.e., IFN-γ) is necessary for host control over parasite replication [39]. Increasing evidence suggests that the paradigm established about the necessity of a Th1 response for a better prognosis of leishmaniasis is not a rigid concept and the balance between proinflammatory and anti-inflammatory cytokines determines the outcome of the infection [4042].

5. Natural Products Effects on Host Immunological Response

As mentioned earlier, leishmaniasis treatment is primarily based on antimonial compounds followed by amphotericin B as a second choice drug. However, high toxicity, severe side effects, and elevated costs hinder the use of these drugs in countries where leishmaniasis is endemic. In many instances, traditional medicines are the alternative for accessible treatments against parasitic diseases [41]. Unfortunately, most of them are hardly explored and their mechanisms of action are mainly unknown. Plants possess a large repertoire of secondary metabolites that display a wide variety of pharmacological activities. Indeed, numerous plant-derived bioactive compounds have been described, such as terpenoids, flavonoids, alkynes, alkaloids, saponins, sterols, phenylpropanoyl esters, lactones, tannins, and coumarins [4345].

Traditional herbal medicines are gaining increased attention as they can reduce the risk of chronic diseases and act as antibiotics, antioxidants, and/or immunomodulators. Several studies have described the effects of plant extracts or isolated compounds in immune cells and cytokine production [43]. Thus, the study of active compounds obtained from plants used in traditional medicine plays a pivotal role in the search for new antileishmanial molecules [39, 41].

Several raw extracts from different plants have been shown to exhibit antileishmanial activity, which may not only be due to their direct action on the parasite, but also due to a concomitant effect on the host immune response [41]. Therefore, the search for plant extracts with a wide spectrum of antileishmanial and immunomodulatory activities may enable the discovery of substances suitable for the disease control. Some studies have focused on the effects of leishmanicidal essential oils and plant extracts in the production of pro- and anti-inflammatory soluble mediators. Altogether, these studies suggest that the induction or inhibition of cytokine production is a critical factor for effective parasite destruction without producing excessive tissue damage. Table 1 summarizes the currently known plant extracts and their effects on inflammatory mediators.

Table 1: Plant extracts and isolated compounds with antileishmanial and immunomodulatory activities.

The plant popularly known as Evanta (Angostura longiflora (Krause) Kallunki) is used for the treatment of leishmaniasis and other parasitic diseases in Bolivia [41]. In addition to having direct activity against L. braziliensis, Evanta extracts also interfere with the activation of both mouse and human T cells. Calla-Magarinos et al. (2009) [41] showed that the alkaloid-rich extract from Evanta barks (AEE) reduced INF-γ expression in J774 and spleen cells, despite its lack of effect on TNF-α and NO production. Similar effects were observed in human peripheral blood mononuclear cells (PBMCs). The major compound in the alkaloid-rich extract from Evanta barks is 2-phenylquinoline. Interestingly, the isolated substance (Figure 2) showed a similar effect to that observed for AEE. Moreover, 2-phenylquinoline reduced INF-γ production and cell proliferation in vitro, suggesting that it may contribute to the control of the chronic inflammatory reaction that characterizes Leishmania infection.

Figure 2: Structures of the compounds assayed in vitro and in vivo against Leishmania species and cytokines activity.

Recently, Calla-Magariños et al. (2013) demonstrated that the alkaloid-rich Evanta extract interferes with in vitro antigen-specific lymphocyte activation [40]. When spleen cells from L. braziliensis-immunized mice were pretreated with AEE and stimulated with Leishmania lysate or Leishmania-infected bone marrow macrophages (L-BMM), the levels of IFN-γ decreased. In addition, in vivo treatment with the Evanta extract affected reactivation of primed lymphocytes, reducing the production of IFN-γ, IL-12, and TNF-α by spleen cells induced with L-BMM. AEE treatment also affected the kinetics of infection. Mice infected with L. braziliensis promastigotes in the left hind footpad showed a more effective decrease in the footpad thickness when treated with AEE than those treated with meglumine antimoniate. These results suggest that AEE can control both Leishmania infection and the inflammatory reaction against it.

The leaf methanol extract and the essential oil from Xylopia discreta display antileishmanial activity and immune stimulatory effects over infected murine macrophages [42]. To evaluate the effects of the methanol extract and the essential oil from X. discreta, López et al. (2009) infected J774 cells with L. panamensis and measured the levels of proinflammatory mediators. IL-12, IL-10, IL-6, MCP-1, and TNF-α were quantified after treatment with different concentrations of X. discreta extract or essential oil. No statistical differences in the production of interleukins and TNF-α were observed between treated and untreated cells. However, a significant increase in MCP-1 production was observed after cell treatment. Surprisingly, no differences in cytokine production were detected when pentamidine was used as antileishmanial drug [42].

The extract produced from the leaf of Neem (Azadirachta indica) presents antileishmanial and immunomodulatory activities [46]. The leaf and seed extracts of A. indica were shown to possess immunomodulatory, insecticidal, antiseptic, anticancer, antiviral, antifungal, and antiprotozoal properties. Its oil, bark, and leaf extracts have therapeutic efficacy against leprosy, intestinal helminthiasis, and respiratory disorders in children [47]. Similar to the X. discreta extract [42], the ethyl acetate extract fraction of Neem also induces a Th1 response. Cytokine production was evaluated by real time quantitative PCR (RT-qPCR) on THP-1 and PBMCs infected with L. donovani strain Dd8. Cells treated with Neem extract showed a significant increase in TNF-α, IL-8, and IL-1β production, while IL-10 expression was unaltered, indicating a strong Th1 response. However, the expression of TNF-α and IFN-γ was unaltered in spleen tissue (in vivo analysis), whereas the expression of Th2 cytokines (IL-10, IL-4, and TGF-β) was significantly reduced [46]. These results suggest that the leaf extract of Neem induces a protective immune polarization during leishmaniasis.

Chouhan et al. (2015) evaluated the antileishmanial and immunomodulatory activities of the ethanol extract of leaves (ALE), seeds (ASE), and bark (ABH) from A. indica. In contrast to Dayakar et al. (2015) [46], they used other parts of the plant and different extraction methods. ABH is not effective against L. donovani promastigotes, while ALE and ASE exhibited leishmanicidal activity in both promastigote and amastigote cells. Sera of treated mice infected with L. donovani were analyzed for IgG2a (induced by INF-γ) and IgG1 (induced by IL-4) levels. Highest levels of IgG2a are indicative of Th1 response, while IgG1 indicate Th2 activation. ALE and ASE stimulated the production of high levels of IgG2a and low levels of IgG1. As expected, ALE and ASE treatment induced NO generation by macrophages primed with SLA. Confirming these results, Th1/Th2 cytokine levels were quantified in culture supernatants of spleen cells from animals treated with ALE and ASE. The extracts significantly increased the levels of Th1 cytokines, such as INF-γ, TNF-α, and IL-2, and decreased the IL-10 and IL-4 levels [47]. Although Chouhan et al. (2015) and Dayakar et al. (2015) have used different parts of A. indica, both of them showed the proinflammatory effects of bioactive molecules derived from this plant.

The genus Laennecia and the correlated genus Conyza are known to produce bioactive substances displaying antimicrobial, antiparasitic, antidiarrhoeal, antinociceptive, antioxidant, and anti-inflammatory activities. Aiming to evaluate the potential of L. confusa, Ruiz et al. (2012) investigated the inhibitory effect of different extracts from its stems against several pathogenic microorganisms. In addition, the anti-inflammatory activity of these extracts was evaluated. The aqueous and chloroform extracts, as well as a chloroform fraction, named, CE2, presented antiparasitic activity against L. donovani. However, these extracts and fractions did not affect the production of proinflammatory cytokines (IL-6) in THP-1 cells [48].

A similar approach was conducted by Bolivar et al. (2011) with Galium mexicanum and by Paredes et al. (2013) with Lopezia racemosa, with both of them being traditional medicinal plants used in Mexico [49, 50]. Flavonoids, iridoid glycosides, iridoid acids, triterpene saponins, and anthraquinones have been isolated from the Galium genus. Among the G. mexicanum extracts and fractions analyzed, the hexane fractions HE 5 and HE 14b presented anti-L. donovani promastigotes activity, while the hexane fraction HE 5 and methanol fractions ME 13–15 reduced the LPS-induced macrophage production of IL-6, suggesting an anti-inflammatory character of these samples [49].

The aerial parts of L. racemosa were submitted to extraction with various solvents and the extracts were fractionated. The hexane fractions HF 11–14b, methanol fractions MF 28–36, and the chloroform extract were able to inhibit L. donovani growth. In relation to the reduction of IL-6 production by macrophages exposed to LPS, the fractions HF 11–14b showed significant anti-inflammatory activity by reducing the secretion of the aforementioned cytokine [50].

Croton caudatus leaves extract is a promising extract against visceral leishmaniasis. Stems and leaves of C. caudatus have been used for the treatment of rheumatic arthritis, malaria, convulsions, ardent fever, numbness, worm-infested animals, vomiting, and dysentery in India [39]. Terpenes as crotocaudin, isocrotocaudin, crotoncaudatin, and crocaudatol have been isolated from this extract. Dey et al. (2015) demonstrated that the semipurified hexane extract of C. caudatus leaves (JDHex) inhibited the proliferation of L. donovani promastigotes (IC50 = 10 μg/mL) and intracellular amastigotes (IC50 = 2.5 μg/mL). To evaluate the immunomodulatory activity of JDHex, the production of proinflammatory cytokines, such as IL-12 and TNF-α, as well as anti-inflammatory cytokines, IL-10 and TGF-β, was investigated in vitro and in vivo. L. donovani-infected murine peritoneal macrophages treated with JDHex showed an increase in intracellular IL-12 (p70 fraction) and a reduction in TGF-β and IL-10 production. In addition, JDHex induced an increase in NO that could be directly correlated with the induction of TNF-α expression in infected macrophages. These results suggest that the immunomodulatory activity of JDHex occurs via a Th1 response. In vivo experiments performed with mice infected with L. donovani and treated orally with different concentrations of JDHex for 5 days after 1 month of infection showed that treated mice had an induction in IFN-γ production. In addition, the parasite load in spleen was reduced dose-dependently. As JDHex was efficient against L. donovani intracellular amastigotes, the authors suggested that the proinflammatory activity of JDHex may be useful for antileishmanial therapy [39]. Using a similar in vivo model, Bhattacharjee et al. (2012) and Chouhan et al. (2015) found comparable results for treatment of L. donovani with glycyrrhizic acid (Figure 1) extract from liquorice (Glycyrrhiza glabra) and ethanol extract of A. indica, respectively [37, 47].

In accordance with Dey et al. (2015) [39], Yamamoto et al. (2014) also described an antileishmanial compound that induces Th1 response. L. amazonensis-infected mice were treated with a triterpene-rich fraction of Bacchari suncinella during five days. The analysis of immune response revealed that treated mice presented higher levels of IL-12 and IFN-γ than the control group. Treatment with the triterpenic fraction reduced the size of lesions, as well as the parasitism and the parasite load [51]. It is worth noting that the triterpenic fraction of B. suncinella stimulated the inflammatory process while reducing the size of mice lesions.

The flavonoid-rich Artemisia annua L. extract has been shown to possess antioxidant, antimicrobial, and anti-inflammatory activities [52]. Studies carried out with the leaves and seeds of A. annua against L. donovani-infected mice caused increased production of Th1 cytokines (IFN-γ) and a simultaneous decrease in Th2 cytokines (IL-4 and IL-10). Moreover, A. annua extracts resulted in higher CD4+ and CD8+ T cell numbers, lymphoproliferation, upregulation of costimulatory molecules (CD80 and CD86) on APCs, and generation of NO [53].

The nor-triterpene 6α,7α,15β,16β,24-pentacetoxy-22α-carbometoxy-21β,22β-epoxy-18β-hydroxy-27,30-bisnor-3,4-secofriedela-1,20(29)-dien-3,4 R-olide (LLD-3), extracted from Lophanthera lactescens Ducke, showed a remarkable antileishmanial activity against intracellular amastigotes (IC50 = 0.41 μg/mL) but no cytotoxicity to mouse peritoneal macrophages or B cells, which makes it a promising drug candidate for leishmaniasis treatment [54]. In addition, piperine (Figure 1), the main alkaloid of Piper nigrum, and its analogue phenylamide are active against L. amazonensis promastigotes and amastigotes. They act synergistically to boost the leishmanicidal effect and reduce the NO production in infected macrophages [55]. The hexane extract of the twigs of Nectandra leucantha Nees and Mart displayed activity against the promastigote forms of L. donovani. Isolated phenylpropanoid dimers suppressed the production of disease exacerbatory cytokines IL-6 and IL-10 but had minimal effect on NO production in L. donovani-infected macrophages. Thus, the antileishmanial activities appear to be mediated by molecular mechanisms that are independent of NO production [56].

6. Conclusion

Promising drug candidates for leishmaniasis treatment should be able to eliminate the parasite but also elicit an appropriate immune response. Plant-derived natural products such as crude extracts, purified fractions, or isolated substances have demonstrated their effectiveness as immunomodulatory agents. The anti-inflammatory activity of the natural products pointed here could be useful for the control of an exacerbated proinflammatory response, ameliorating leishmaniasis clinical symptoms, such as tissue damage.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgments

The authors thank the Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento Pessoal de Nível Superior (CAPES), and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) for the financial support.

References

  1. WHO, Leishmaniasis: Situation and Trends, World Health Organization, 2015, http://www.who.int/gho/neglected_diseases/leishmaniasis/en/.
  2. B. S. Mcgwire and A. R. Satoskar, “Leishmaniasis: clinical syndromes and treatment,” QJM, vol. 107, no. 1, Article ID hct116, pp. 7–14, 2014. View at Publisher · View at Google Scholar · View at Scopus
  3. J. C. F. Rodrigues, J. L. P. Godinho, and W. de Souza, “Biology of human pathogenic trypanosomatids: epidemiology, lifecycle and ultrastructure,” Sub-Cellular Biochemistry, vol. 74, pp. 1–42, 2014. View at Google Scholar · View at Scopus
  4. C. da Silva Santos, S. Attarha, R. K. Saini et al., “Proteome profiling of human cutaneous leishmaniasis lesion,” The Journal of Investigative Dermatology, vol. 135, no. 2, pp. 400–410, 2014. View at Publisher · View at Google Scholar
  5. C. D. S. Santos, V. Boaventura, C. R. Cardoso et al., “CD8+ granzyme B+-mediated tissue injury vs. CD4+IFNγ+-mediated parasite killing in human cutaneous leishmaniasis,” The Journal of Investigative Dermatology, vol. 133, no. 6, pp. 1533–1540, 2013. View at Publisher · View at Google Scholar · View at Scopus
  6. A. L. Harvey, “Natural products in drug discovery,” Drug Discovery Today, vol. 13, no. 19-20, pp. 894–901, 2008. View at Publisher · View at Google Scholar · View at Scopus
  7. I. de Almeida Rodrigues, A. C. F. Amaral, and M. do Socorro dos Santos Rosa, “Trypanosomatid enzymes as targets for plant-derived compounds: new perspectives for phytotherapeutic approaches,” Current Enzyme Inhibition, vol. 7, no. 1, pp. 32–41, 2011. View at Publisher · View at Google Scholar · View at Scopus
  8. A. B. Vermelho, C. T. Supuran, V. Cardoso et al., “Leishmaniasis: possible new strategies for treatment,” in Leishmaniasis—Trends in Epidemiology, Diagnosis and Treatment, D. Claborn, Ed., chapter 15, InTech, Rijeka, Croatia, 2014. View at Publisher · View at Google Scholar
  9. G. Dawit, Z. Girma, and K. Simenew, “A review on biology, epidemiology and public health significance of leishmaniasis,” Journal of Bacteriology & Parasitology, vol. 4, article 166, 2013. View at Publisher · View at Google Scholar
  10. A. Strazzulla, S. Cocuzza, M. R. Pinzone et al., “Mucosal leishmaniasis: an underestimated presentation of a neglected disease,” BioMed Research International, vol. 2013, Article ID 805108, 7 pages, 2013. View at Publisher · View at Google Scholar · View at Scopus
  11. J. Alvar, I. D. Vélez, C. Bern et al., “Leishmaniasis worldwide and global estimates of its incidence,” PLoS ONE, vol. 7, no. 5, Article ID e35671, 2012. View at Publisher · View at Google Scholar · View at Scopus
  12. S. Sundar and J. Chakravarty, “An update on pharmacotherapy for leishmaniasis,” Expert Opinion on Pharmacotherapy, vol. 16, no. 2, pp. 237–252, 2015. View at Publisher · View at Google Scholar · View at Scopus
  13. T. Yangzom, I. Cruz, C. Bern et al., “Endemic transmission of visceral leishmaniasis in Bhutan,” American Journal of Tropical Medicine and Hygiene, vol. 87, no. 6, pp. 1028–1037, 2012. View at Publisher · View at Google Scholar · View at Scopus
  14. P. D. Ready, “Epidemiology of visceral leishmaniasis,” Clinical Epidemiology, vol. 6, no. 1, pp. 147–154, 2014. View at Publisher · View at Google Scholar · View at Scopus
  15. D. S. Alviano, A. L. S. Barreto, F. D. A. Dias et al., “Conventional therapy and promising plant-derived compounds against trypanosomatid parasites,” Frontiers in Microbiology, vol. 3, article 283, 2012. View at Publisher · View at Google Scholar · View at Scopus
  16. S. L. Croft, K. Seifert, and V. Yardley, “Current scenario of drug development for leishmaniasis,” The Indian Journal of Medical Research, vol. 123, no. 3, pp. 399–410, 2006. View at Google Scholar · View at Scopus
  17. S. Decuypere, M. Vanaerschot, K. Brunker et al., “Molecular mechanisms of drug resistance in natural Leishmania populations vary with genetic background,” PLoS Neglected Tropical Diseases, vol. 6, no. 2, Article ID e1514, 2012. View at Publisher · View at Google Scholar · View at Scopus
  18. N. Singh, M. Kumar, and R. K. Singh, “Leishmaniasis: current status of available drugs and new potential drug targets,” Asian Pacific Journal of Tropical Medicine, vol. 5, no. 6, pp. 485–497, 2012. View at Publisher · View at Google Scholar · View at Scopus
  19. L. Lachaud, N. Bourgeois, M. Plourde, P. Leprohon, P. Bastien, and M. Ouellette, “Parasite susceptibility to amphotericin B in failures of treatment for visceral leishmaniasis in patients coinfected with HIV type 1 and Leishmania infantum,” Clinical Infectious Diseases, vol. 48, no. 2, pp. e16–e22, 2009. View at Publisher · View at Google Scholar · View at Scopus
  20. T. P. C. Dorlo, M. Balasegaram, J. H. Beijnen, and P. J. de vries, “Miltefosine: a review of its pharmacology and therapeutic efficacy in the treatment of leishmaniasis,” Journal of Antimicrobial Chemotherapy, vol. 67, no. 11, Article ID dks275, pp. 2576–2597, 2012. View at Publisher · View at Google Scholar · View at Scopus
  21. H. C. Maltezou, “Drug resistance in visceral leishmaniasis,” Journal of Biomedicine & Biotechnology, vol. 2010, Article ID 617521, 8 pages, 2010. View at Publisher · View at Google Scholar · View at Scopus
  22. M. den Boer and R. N. Davidson, “Treatment options for visceral leishmaniasis,” Expert Review of Anti-Infective Therapy, vol. 4, no. 2, pp. 187–197, 2006. View at Publisher · View at Google Scholar · View at Scopus
  23. A. Jhingran, B. Chawla, S. Saxena, M. P. Barrett, and R. Madhubala, “Paromomycin: uptake and resistance in Leishmania donovani,” Molecular and Biochemical Parasitology, vol. 164, no. 2, pp. 111–117, 2009. View at Publisher · View at Google Scholar · View at Scopus
  24. R. Chakour, R. Guler, M. Bugnon et al., “Both the Fas ligand and inducible nitric oxide synthase are needed for control of parasite replication within lesions in mice infected with Leishmania major whereas the contribution of tumor necrosis factor is minimal,” Infection and Immunity, vol. 71, no. 9, pp. 5287–5295, 2003. View at Publisher · View at Google Scholar · View at Scopus
  25. C. F. Oliveira, D. Manzoni-De-Almeida, P. S. Mello et al., “Characterization of chronic cutaneous lesions from TNF-receptor-1-deficient mice infected by Leishmania major,” Clinical & Developmental Immunology, vol. 2012, Article ID 865708, 12 pages, 2012. View at Publisher · View at Google Scholar · View at Scopus
  26. S. L. Kostka, J. Knop, A. Konur, M. C. Udey, and E. von Stebut, “Distinct roles for IL-1 receptor type I signaling in early versus established Leishmania major infections,” The Journal of Investigative Dermatology, vol. 126, no. 7, pp. 1582–1589, 2006. View at Publisher · View at Google Scholar · View at Scopus
  27. M. Saraiva and A. O'Garra, “The regulation of IL-10 production by immune cells,” Nature Reviews Immunology, vol. 10, no. 3, pp. 170–181, 2010. View at Publisher · View at Google Scholar · View at Scopus
  28. D. Nandan, C. C. De Oliveira, A. Moeenrezakhanlou et al., “Myeloid cell IL-10 production in response to Leishmania involves inactivation of glycogen synthase kinase-3β downstream of phosphatidylinositol-3 kinase,” Journal of Immunology, vol. 188, no. 1, pp. 367–378, 2012. View at Publisher · View at Google Scholar · View at Scopus
  29. A. K. Abbas, K. M. Murphy, and A. Sher, “Functional diversity of helper T lymphocytes,” Nature, vol. 383, no. 6603, pp. 787–793, 1996. View at Publisher · View at Google Scholar · View at Scopus
  30. F. Y. Liew, “TH1 and TH2 cells: a historical perspective,” Nature Reviews: Immunology, vol. 2, no. 1, pp. 55–60, 2002. View at Publisher · View at Google Scholar · View at Scopus
  31. J. C. Sun and L. L. Lanier, “NK cell development, homeostasis and function: parallels with CD8+ T cells,” Nature Reviews Immunology, vol. 11, no. 10, pp. 645–657, 2011. View at Publisher · View at Google Scholar · View at Scopus
  32. N. E. Rodríguez and M. E. Wilson, “Eosinophils and mast cells in leishmaniasis,” Immunologic Research, vol. 59, no. 1–3, pp. 129–141, 2014. View at Publisher · View at Google Scholar · View at Scopus
  33. C. I. Morato, I. A. da Silva, A. F. Borges et al., “Essential role of leukotriene B4 on Leishmania (Viannia) braziliensis killing by human macrophages,” Microbes and Infection, vol. 16, no. 11, pp. 945–953, 2014. View at Publisher · View at Google Scholar · View at Scopus
  34. C. H. Serezani, J. H. Perrela, M. Russo, M. Peters-Golden, and S. Jancar, “Leukotrienes are essential for the control of Leishmania amazonensis infection and contribute to strain variation in susceptibility,” Journal of Immunology, vol. 177, no. 5, pp. 3201–3208, 2006. View at Publisher · View at Google Scholar · View at Scopus
  35. R. Kumar and S. Nylén, “Immunobiology of visceral leishmaniasis,” Frontiers in Immunology, vol. 3, article 251, 2012. View at Publisher · View at Google Scholar · View at Scopus
  36. A. Kharazmi, K. Kemp, A. Ismail et al., “T cell response in human leishmaniasis,” Immunology Letters, vol. 65, no. 1-2, pp. 105–108, 1999. View at Publisher · View at Google Scholar · View at Scopus
  37. S. Bhattacharjee, A. Bhattacharjee, S. Majumder, S. B. Majumdar, and S. Majumdar, “Glycyrrhizic acid suppresses cox-2-mediated anti-inflammatory responses during Leishmania donovani infection,” Journal of Antimicrobial Chemotherapy, vol. 67, no. 8, Article ID dks159, pp. 1905–1914, 2012. View at Publisher · View at Google Scholar · View at Scopus
  38. M. T. M. Roberts, “Current understandings on the immunology of leishmaniasis and recent developments in prevention and treatment,” British Medical Bulletin, vol. 75-76, no. 1, pp. 115–130, 2005. View at Publisher · View at Google Scholar · View at Scopus
  39. S. Dey, D. Mukherjee, S. Chakraborty et al., “Protective effect of Croton caudatus Geisel leaf extract against experimental visceral leishmaniasis induces proinflammatory cytokines in vitro and in vivo,” Experimental Parasitology, vol. 151-152, pp. 84–95, 2015. View at Publisher · View at Google Scholar
  40. J. Calla-Magariños, T. Quispe, A. Giménez, J. Freysdottir, M. Troye-Blomberg, and C. Fernández, “Quinolinic alkaloids from Galipealongi flora krause suppress production of proinflammatory cytokines in vitro and control inflammation in vivo upon Leishmania infection in mice,” Scandinavian Journal of Immunology, vol. 77, no. 1, pp. 30–38, 2013. View at Publisher · View at Google Scholar · View at Scopus
  41. J. Calla-Magarinos, A. Giménez, M. Troye-Blomberg, and C. Fernández, “An alkaloid extract of evanta, traditionally used as anti-leishmania agent in bolivia, inhibits cellular proliferation and interferon-gamma production in polyclonally activated cells,” Scandinavian Journal of Immunology, vol. 69, no. 3, pp. 251–258, 2009. View at Publisher · View at Google Scholar · View at Scopus
  42. R. López, L. E. Cuca, and G. Delgado, “Antileishmanial and immunomodulatory activity of Xylopia discreta,” Parasite Immunology, vol. 31, no. 10, pp. 623–630, 2009. View at Publisher · View at Google Scholar · View at Scopus
  43. G. M. Cragg and D. J. Newman, “Natural products: a continuing source of novel drug leads,” Biochimica et Biophysica Acta, vol. 1830, no. 6, pp. 3670–3695, 2013. View at Publisher · View at Google Scholar · View at Scopus
  44. J. Ma, L. Zheng, T. Deng et al., “Stilbene glucoside inhibits the glucuronidation of emodin in rats through the down-regulation of UDP-glucuronosyltransferases 1A8: application to a drug–drug interaction study in Radix Polygoni Multiflori,” Journal of Ethnopharmacology, vol. 147, no. 2, pp. 335–340, 2013. View at Publisher · View at Google Scholar · View at Scopus
  45. M. Mazid, T. A. Khan, and F. Mohammad, “Role of secondary metabolites in defense mechanisms of plants,” Biology and Medicine, vol. 3, no. 2, pp. 232–249, 2011. View at Google Scholar · View at Scopus
  46. A. Dayakar, S. Chandrasekaran, J. Veronica, S. Sundar, and R. Maurya, “In vitro and in vivo evaluation of anti-leishmanial and immunomodulatory activity of Neem leaf extract in Leishmania donovani infection,” Experimental Parasitology, vol. 53, pp. 45–54, 2015. View at Publisher · View at Google Scholar
  47. G. Chouhan, M. Islamuddin, M. Y. Want et al., “Apoptosis mediated leishmanicidal activity of Azadirachta indica bioactive fractions is accompanied by Th1 immunostimulatory potential and therapeutic cure in vivo,” Parasites & Vectors, vol. 8, article 183, 2015. View at Publisher · View at Google Scholar
  48. M. G. M. Ruiz, M. Richard-Greenblatt, Z. N. Juárez, Y. Av-Gay, H. Bach, and L. R. Hernández, “Antimicrobial, anti-inflammatory, antiparasitic, and cytotoxic activities of Laennecia confusa,” TheScientificWorldJournal, vol. 2012, Article ID 263572, 8 pages, 2012. View at Publisher · View at Google Scholar · View at Scopus
  49. P. Bolivar, C. Cruz-Paredes, L. R. Hernández et al., “Antimicrobial, anti-inflammatory, antiparasitic, and cytotoxic activities of Galium mexicanum,” Journal of Ethnopharmacology, vol. 137, no. 1, pp. 141–147, 2011. View at Publisher · View at Google Scholar · View at Scopus
  50. C. C. Paredes, P. B. Balbás, A. Gómez-Velasco et al., “Antimicrobial, antiparasitic, anti-inflammatory, and cytotoxic activities of Lopezia racemosa,” The Scientific World Journal, vol. 2013, Article ID 237438, 6 pages, 2013. View at Publisher · View at Google Scholar · View at Scopus
  51. E. S. Yamamoto, B. L. S. Campos, M. D. Laurenti et al., “Treatment with triterpenic fraction purified from Baccharis uncinella leaves inhibits Leishmania (Leishmania) amazonensis spreading and improves Th1 immune response in infected mice,” Parasitology Research, vol. 113, no. 1, pp. 333–339, 2014. View at Publisher · View at Google Scholar · View at Scopus
  52. J. F. S. Ferreira, D. L. Luthria, T. Sasaki, and A. Heyerick, “Flavonoids from Artemisia annua L. As antioxidants and their potential synergism with artemisinin against malaria and cancer,” Molecules, vol. 15, no. 5, pp. 3135–3170, 2010. View at Publisher · View at Google Scholar · View at Scopus
  53. M. Islamuddin, G. Chouhan, A. Farooque, B. S. Dwarakanath, D. Sahal, and F. Afrin, “Th1-Based immunomodulation and therapeutic potential of Artemisia annua in murine visceral leishmaniasis,” PLoS Neglected Tropical Diseases, vol. 9, no. 1, 2015. View at Publisher · View at Google Scholar · View at Scopus
  54. M. G. M. Danelli, D. C. Soares, H. S. Abreu, L. M. T. Peçanha, and E. M. Saraiva, “Leishmanicidal effect of LLD-3 (1), a nor-triterpene isolated from Lophanthera lactescens,” Phytochemistry, vol. 70, no. 5, pp. 608–614, 2009. View at Publisher · View at Google Scholar · View at Scopus
  55. C. Ferreira, D. C. Soares, C. B. Barreto-Junior et al., “Leishmanicidal effects of piperine, its derivatives, and analogues on Leishmania amazonensis,” Phytochemistry, vol. 72, no. 17, pp. 2155–2164, 2011. View at Publisher · View at Google Scholar · View at Scopus
  56. T. A. D. Costa-Silva, S. S. Grecco, F. S. de Sousa et al., “Immunomodulatory and antileishmanial activity of phenylpropanoid dimers isolated from Nectandra leucantha,” Journal of Natural Products, vol. 78, no. 4, pp. 653–657, 2015. View at Publisher · View at Google Scholar
  57. A. Ukil, A. Biswas, T. Das, and P. K. Das, “18β-glycyrrhetinic acid triggers curative Th1 response and nitric oxide up-regulation in experimental visceral leishmaniasis associated with the activation of NF-κB,” The Journal of Immunology, vol. 175, no. 2, pp. 1161–1169, 2005. View at Publisher · View at Google Scholar · View at Scopus
  58. T. S. Tiuman, T. Ueda-Nakamura, D. A. G. Cortez et al., “Antileishmanial activity of parthenolide, a sesquiterpene lactone isolated from Tanacetum parthenium,” Antimicrobial Agents and Chemotherapy, vol. 49, no. 1, pp. 176–182, 2005. View at Publisher · View at Google Scholar · View at Scopus
  59. J. A. Jesus, J. H. Lago, M. D. Laurenti, E. S. Yamamoto, and L. F. Passero, “Antimicrobial activity of oleanolic and ursolic acids: an update,” Evidence-Based Complementary and Alternative Medicine, vol. 2015, Article ID 620472, 14 pages, 2015. View at Publisher · View at Google Scholar
  60. D. C. Soares, T. C. Calegari-Silva, U. G. Lopes et al., “Dolabelladienetriol, a compound from Dictyota pfaffii algae, inhibits the infection by Leishmania amazonensis,” PLoS Neglected Tropical Diseases, vol. 6, no. 9, Article ID e1787, 2012. View at Publisher · View at Google Scholar · View at Scopus
  61. R. Sen, S. Ganguly, P. Saha, and M. Chatterjee, “Efficacy of artemisinin in experimental visceral leishmaniasis,” International Journal of Antimicrobial Agents, vol. 36, no. 1, pp. 43–49, 2010. View at Publisher · View at Google Scholar · View at Scopus
  62. S. Bhattacharjee, G. Gupta, P. Bhattacharya et al., “Quassin alters the immunological patterns of murine macrophages through generation of nitric oxide to exert antileishmanial activity,” Journal of Antimicrobial Chemotherapy, vol. 63, no. 2, pp. 317–324, 2009. View at Publisher · View at Google Scholar · View at Scopus
  63. C. Ferreira, D. C. Soares, M. T. C. Do Nascimento et al., “Resveratrol is active against Leishmania amazonensis: in vitro effect of its association with amphotericin B,” Antimicrobial Agents and Chemotherapy, vol. 58, no. 10, pp. 6197–6208, 2014. View at Publisher · View at Google Scholar · View at Scopus
  64. D. Granados-Falla, C. Coy-Barrera, L. Cuca, and G. Delgado, “Seco-limonoid 11α,19β-dihydroxy-7-acetoxy-7- deoxoichangin promotes the resolution of Leishmania panamensis infection,” Advances in Bioscience and Biotechnology, vol. 4, pp. 304–315, 2013. View at Publisher · View at Google Scholar
  65. J. H. Waknine-Grinberg, J. El-On, V. Barak, Y. Barenholz, and J. Golenser, “The immunomodulatory effect of Sambucol on Leishmanial and malarial infections,” Planta Medica, vol. 75, no. 6, pp. 581–586, 2009. View at Publisher · View at Google Scholar · View at Scopus
  66. K. A. D. F. Rodrigues, L. V. Amorim, C. N. Dias, D. F. C. Moraes, S. M. P. Carneiro, and F. A. D. A. Carvalho, “Syzygium cumini (L.) Skeels essential oil and its major constituent α-pinene exhibit anti-Leishmania activity through immunomodulation in vitro,” Journal of Ethnopharmacology, vol. 160, pp. 32–40, 2015. View at Publisher · View at Google Scholar · View at Scopus
  67. S. Kumar, V. Singhal, R. Roshan, A. Sharma, G. W. Rembhotkar, and B. Ghosh, “Piperine inhibits TNF-α induced adhesion of neutrophils to endothelial monolayer through suppression of NF-κB and IκB kinase activation,” European Journal of Pharmacology, vol. 575, no. 1–3, pp. 177–186, 2007. View at Publisher · View at Google Scholar · View at Scopus
  68. H. Sachdeva, R. Sehgal, and S. Kaur, “Tinospora cordifolia as a protective and immunomodulatory agent in combination with cisplatin against murine visceral leishmaniasis,” Experimental Parasitology, vol. 137, no. 1, pp. 53–65, 2014. View at Publisher · View at Google Scholar · View at Scopus
  69. H. Sachdeva, R. Sehgal, and S. Kaur, “Studies on the protective and immunomodulatory efficacy of Withania somnifera along with cisplatin against experimental visceral leishmaniasis,” Parasitology Research, vol. 112, no. 6, pp. 2269–2280, 2013. View at Publisher · View at Google Scholar · View at Scopus