Zinc deficiency causes oxidative stress, endoplasmic reticulum stress, apoptosis and inflammation in hepatocytes in grass carp.

A lack of the trace element zinc (Zn) in freshwater environments causes slow growth and malnutrition and affects the normal biological functions of organisms. In this study, a Zn deficiency model of grass carp hepatocytes was established with TPEN. Acetylcysteine (NAC) was used as an inhibitor. TPEN was added to L8824 cell culture medium, and LDH, AST, ALT, and AKP activities were enhanced in a Zn-deficient environment, leading to abnormal hepatopancreas function. Fluorescence microscopy showed an increase in ROS levels, and antioxidant enzyme activity assays revealed that SOD, CAT, GSH-PX, and T-AOC activities were decreased, indicating oxidative stress caused by Zn deficiency. The RT‒PCR results showed that the mRNA expression of GRP78, PERK, EIF2α, ATF4, and Chop was increased due to the addition of TPEN. Calcium kits showed increased Ca ²⁺ levels. The RT‒PCR results showed that the mRNA expression levels of Caspase-12, Caspase-9, Caspase-3, and PARP apoptotic were increased due to the addition of TPEN. RT‒PCR and ELISA showed that the expression levels of interleukin-1β (IL-1β), interleukin-8 (IL-8), tumour necrosis factor (TNF-α), and inducible nitric oxide synthase (iNOS) were increased. This led to the conclusion that Zn deficiency in the freshwater environment caused inflammation and apoptosis in hepatocytes in grass carp. For the first time, apoptosis caused by endoplasmic reticulum stress in grass carp hepatocytes due to Zn deficiency was studied in the context of Ca ²⁺ . The present study provided some insight into the adverse effects of Zn deficiency in freshwater environments on fish.
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