Vol. 7, Issue 1, Part A (2025)

Micro fine crystalline silica particles constitute significant component of air borne particulate matters. Alveolar macrophage (AM), a phagocytic cell considered as first line of defense against infection. Macrophage comes in contact with various kinds of pathogen and particulate matters as silica particles. We hypothesized that silica could partially exert its effect on disease susceptibility by interfering with toll like receptors required for the generation of protective innate immune responses. Toll like receptors play an important role in development of innate immunity and are present on the macrophages which recognizes PAMP (pathogen associated molecular pattern) molecules. In the present study we examine the effect of silica on basal and PAMP induced TLRs expression on macrophages. BCG and LPS were used as PAMP and micro-crystalline silica particles were used as prototypes of pollutants. MHS, alveolar macrophage cell line and Broncho alveolar lavage (BAL) were used to execute the experiments. Our in vivo and in vitro experiment results show that silica significantly suppress basal TLR2 and TLR4 expression on MHS and BAL cells. TLR2 &TLR4 expression was increased in BCG and LPS treated cells. The increased expression in treated MHS cells was subsequently decreased upon addition of silica. Interactions of ligands to TLRs leads to activation of intracellular signaling pathway and secretion of proinflammatory cytokine like TNF α. Therefore, TNF alpha secretion by AM was examined in presence of silica. Combined results suggest that TLRs and TNF alpha both expressions are modulated in macrophages by silica particles.