Immunomodulatory effect of arsenic on cytokine and HSP gene expression in Labeo rohita fingerlings.

Immune system is fundamental for survival of an organism against invading pathogens and other harmful agents. Cytokines, the signaling proteins that are produced transiently after cell activation and exert pleiotropic effects on cells of the immune system, are important mediators of cell mediated immune response. When expressed in a dysregulated fashion cytokines can underlie either immunodeficient or immunopathologic states. Heat shock proteins (stress proteins, HSPs) are also key proteins, which play important role in immunomodulation, apoptosis and influence the immune responses. Arsenic is a major toxic environmental contaminant and a human carcinogen. Prolonged drinking of arsenic-contaminated water leads to chronic arsenic toxicity (arsenicosis). Arsenic is also immunotoxic and renders the host immunocompromised. Arsenic exposure has been reported to result in growth retardation, gross pathology including skin and eye lesions, ulcerations, cataract development etc. in different fish species. The present study was undertaken to investigate the effect of arsenic exposure on the expression of immune genes IFN-γ, IL-4, IL-10, IL-12, complement C3a and HSP genes HSP47, HSP60, HSP70, HSC71, HSP78, and HSP90 in Labeo rohita, an important aquacultured species, as such information is not available on this major carp. Cytokine and HSP gene expression analyses were carried out in kidney and liver tissues, respectively, in arsenic-exposed fishes by RT-PCR and HSPs were analyzed by immunoblotting. It was observed that arsenic has a generalized immune-suppressive effect leading to down regulation of both Th1 and Th2 cytokines; besides, it led to up regulation of the HSP genes indicating arsenic-induced cellular stress. Thus arsenic exposure makes L. rohita immunocompromised and could increase its susceptibility to pathogen attacks.