Ochratoxin A treated rat derived urinary exosomes enhanced cell growth and extracellular matrix production in normal kidney cells through modulation of TGF-β 1 /smad2/3 signaling pathway

Kidney is the main target organ for ochratoxin A (OTA) toxicity; however, the mechanism(s) involved in OTA-induced nephrotoxicity is not fully understood. Recently, exosomes, nano-sized vesicles have been found to play an important role in promotion and progression of disease as well as environmental toxicant-induced patho-physiology of toxicity. Hence, we aimed to investigate the role of exosomes in OTA-mediated nephrotoxicity. Male Wistar rats were divided in to two groups. Rats of one group were treated with OTA (210 μg/kg b. wt) and another with vehicle control through oral gavage (5 days/week) for 270 days. At the end of experiment, exosomes concentrations from rat's urine were measured. To examine the OTA-induced nephrotoxicity, histopathology was performed using H & E, Masson's trichome and PAS staining. For mechanistic study, normal rat kidney (NRK52E) cells were exposed with either vehicles treated rat's urinary exosomes (NEx) or OTA treated rat's urinary exosomes (OEx) and effects on cell proliferation, cell growth, extracellular matrix production and TGF-β /smad2/3 pathway was analyzed. OTA treatment to Wistar rats caused histopathological changes such as tubular degeneration, glomeruli shrinkage and hypercellularity in kidney tissue. Interestingly, OTA treated rat's urine has more exosomes secretion. Moreover, treatment of NRK52E cells with OEx caused increased cell proliferation, cell growth, enhanced the expression of extracellular matrix proteins and activation of TGF-β /smad2/3 pathway. Our investigations exogenous exposure of OTA derived urinary exosomes caused TGF-β /smad2/3 pathway-mediated activation of pro-fibrotic changes in kidney will helpful for deeper understanding the OTA-induced nephrotoxicity.