Impact of metal accumulation pattern on the annual rhythmicity of antioxidants and their interrelationship to maintain the oxidative balance in mollusc

Crosstalk between heat shock proteins, NRF2, NF-κB and different endogenous antioxidants during lead-induced hepatotoxicity in Puntius ticto

Present study aims to investigate interaction of molecular chaperons (heat shock protein 70, heat shock protein 90) with transcriptional factors (nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1) to evaluate their role during metal induced stress in fish hepatocytes. Adult Puntius ticto were exposed to lead nitrate at 0 mg/l (control), 1/50th (0.04 mg/l) and 1/20th (0.12 mg/l) of LC₅₀ for 30 days and sacrificed to collect liver tissues. Activity of selected liver enzymes, antioxidants and metallothionein were analyzed. Levels of heat shock protein 70, heat shock protein 90, nuclear factor kappa B, nuclear factor E2-related factor 2 and Kelch-like ECH-associated protein 1 were also measured. Liver enzymes showed a significant increase (p < 0.05) in both Pb exposed groups indicating that the liver might be at risk of damage. Increased level of lipid peroxidation due to metal stress was marked by significant increase (p < 0.05) in malondialdehyde level in fish exposed to the higher Pb concentration compared to control (+ 13.7 %). Significant increase (p < 0.05) in gluthathione reductase (+ 35 %, + 39.2 %), glutathione s-transferase (+ 22.4 %, + 50.4 %) activities and decrease in reduced glutathione level (- 6.75 %, - 12.25 %) in fish exposed to both lower and higher Pb concentration compared to control also indicated metal induced oxidative damage in fish liver. Super oxide dismutase and catalase activities increased significantly (p < 0.05) during exposure to lower Pb concentration, while decreased significantly (p < 0.05) during exposure to higher Pb concentration compared to those in control. Significant (P < 0.05) increase (+ 52.63 %, + 89.47 %) in metallothionein in Pb exposed groups confirmed its role in detoxification process of the metal. Heat shock protein 70 and heat shock protein 90 expression levels increased significantly (p < 0.05) during metal exposure indicating their role as modulator of stress-induced antioxidant protein remodelling. A positive correlation between nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1 with gluthathione regulatory enzymes (gluthathione reductase and glutathione s-transferase) was noted. Current study effectively illuminates the critical role of different factors (heat shock proteins/nuclear factor kappa B/nuclear factor E2-related factor 2/Kelch-like ECH-associated protein 1) to influence the expression and synthesis of antioxidants and other functional enzymes in lead-exposed fish liver.