Thioredoxin and HSP90α modulate ASK1–JNK1/2 signaling in stressed hepatocytes of Mugil cephalus

Induction of antioxidant proteins like thioredoxin (Trx) and heat shock protein 90α (HSP90α) is a crucial step in the cellular response to oxidative stress. Here, we report the impact of environmental stress on Trx and HSP90α expressions in freshly isolated hepatocytes of Mugil cephalus living in either a contaminated (Test; Ennore) or uncontaminated (Control; Kovalam) estuary. Modulation in the activities of signal transduction molecules like apoptosis signal-regulating kinase 1 (ASK1) and c-Jun NH₂-terminal kinase 1/2 (JNK1/2) were also investigated to understand their functional role under natural stressed condition. The expression pattern of the proteins was determined by immunoblotting and the relationship between the proteins was identified by regression analysis. Test fish hepatocytes demonstrated significant upregulation (P < 0.05) in the levels of Trx and HSP90α and insignificant inductions in the expression pattern of ASK1 and JNK1/2 than control fish hepatocytes. These findings provide direct evidence that Trx and HSP90α induction in fish hepatocytes under stress may aid cell survival by negatively regulating ASK1 expression and thereby functionally antagonizing the apoptotic role of JNK1/2 in natural aquatic systems.