Fcγ and Complement Receptors and Complement Proteins in Neutrophil Activation in Rheumatoid Arthritis: Contribution to Pathogenesis and Progression and Modulation by Natural Products

Table 3

In vitro effect of plant extracts, isolated compounds, and dietary antioxidants on the effector functions of neutrophils specifically stimulated via Fcγ and complement receptors.

Therapy	Source	Effect	Reference
Areca catechu; (aqueous extract of dried ripe nuts)		↓ expression of FcγRs and CRs in human neutrophils.; ↓ neutrophil phagocytic ability towards complement- and IgG-opsonized microspheres.	[148]
Chrysoeriol^a; Eriodictyol^b; Isorhamnetin^c; 4′-Methoxyeriodictyol^d	Lychnophora granmongolense	↓ production of ROS in rabbit neutrophils stimulated via FcγRs and/or CRs.	[149]
Quercetin; (3,5,7,3′,4′-pentahydroxyflavone)	Lychnophora ericoides	↓ oxidative metabolism in rabbit and human neutrophils specifically stimulated via FcγRs and CRs, either alone or in combination, without affecting the phagocytic and microbial killing capacity.	[149–151]
	Commercial	↓ human neutrophil degranulation, ↓ the activity of elastase, myeloperoxidase, and NADPH oxidase.	[151–153]
		Scavenges , H2O2, HOCl, and chloramines.	[151, 154]
		↓ FcγR-stimulated ROS generation in neutrophils from RA patients with active disease who do not respond to anti-TNF-α drug therapy.	[151]
Galangin; (3,5,7-trihydroxyflavone)	Commercial	Strongly inhibits oxidative metabolism in rabbit and human neutrophils specifically stimulated via FcγRs and CRs, either alone or in combination.	[150, 151]
		↓ myeloperoxidase and horseradish peroxidase activity.	[150, 151]
		↓ activity of NADPH oxidase in FcγR- and/or CR-stimulated human and rabbit neutrophils.	[153]
		Scavenges H2O2, HOCl, and chloramines.	[151]
		↓ FcγR-stimulated ROS generation in neutrophils from RA patients with active disease who are refractory to anti-TNF-α drug therapy.	[151]
Kaempferol; (3,5,7,4′-tetrahydroxyflavone)	Commercial	↓ oxidative metabolism in rabbit and human neutrophils specifically stimulated via FcγRs and/or CRs.	[150, 151]
		↓ NADPH oxidase activity in human and rabbit neutrophils stimulated via FcγRs and/or CRs.	[153]
		↓ myeloperoxidase and horseradish peroxidase activity.	[150, 151]
		Scavenges H2O2, HOCl, and chloramines.	[151]
Myricetin; (3,5,7,3′,4′,5′-hexahydroxyflavone)	Commercial	Slightly ↓ oxidative metabolism in rabbit and human neutrophils specifically stimulated via FcγRs and/or CRs.	[150, 151]
		↓ human neutrophil degranulation.	[152]
		↓ activity of elastase, myeloperoxidase, NADPH oxidase, and horseradish peroxidase.	[150–153]
		Scavenges , H2O2, HOCl, and chloramines.	[151, 154]
Hydroxylated phenylcoumarins; Acetoxylated phenylcoumarins	Laboratory synthesis	↓ oxidative metabolism in rabbit and human neutrophils specifically stimulated via FcγRs.	[155, 156]
		Scavenges HOCl.	[156]
		↓ activity of myeloperoxidase, NADPH oxidase, and horseradish peroxidase.	[156, 157]
Vitamin C plus vitamin E	Commercial	↓ ROS generation by human neutrophils stimulated via FcγRs.	[158]

CR: complement receptor; FcγR: Fcγ receptor; IgG: immunoglobulin G; RA: rheumatoid arthritis; ROS: reactive oxygen species; TNF-α: tumor necrosis factor-α.
^a5, 7, 4′-trihydroxy-3′-methoxyflavone.
^b5, 7, 3′, 4′-tetrahydroxyflavanone.
^c3, 5, 7, 3′-tetrahydroxy-4′-methoxyflavone.
^d5, 7, 3′-trihydroxy-4′-methoxyflavanone.