Linking Endotoxins, African Dust PM₁₀ and Asthma in an Urban and Rural Environment of Puerto Rico

Figure 9

Proposed schematic model of the in vitro toxic and inflammatory responses stimulated in the bronchial epithelium. Once African dust (ADE) reaches the urban environment it adds to local particle pollution (increasing PM₁₀) augmenting endotoxins and other biological (glucans, peptidoglycans/PGN, and lipopeptides) and chemical constituents (metals and other organics). Biological molecules are recognized by TLRs (TLR4 and TLR2 heterodimerized with TLR1 or TLR6) at the cell surface leading to the activation of signaling pathways and transcription factor, NF-κB which enter the nucleus and induce the expression of proinflammatory genes: IL-6 and IL-8. This effect will aid the bronchial epithelial cells to mediate the microbial respiratory insults. Red arrows and path represent the respective increases found in the present study with ADE at the urban site; and the white arrows and path refer to ADE at the rural site.