Effects of oxidative stress, PSMB5, TFEB, and lysosomes on sodium arsenite-induced liver injury in rats

Background Liver damage presented in endemic arsenic poisoning is usually serious. Studies have shown that oxidative stress, proteasome beta 5 subunit (PSMB5), regulatory transcription factor EB (TFEB), and lysosomes are associated with liver injury, but their specific links to arsenic-induced liver injury remain unclear.

Objective Using a sodium arsenite (NaAsO₂)-induced rat liver injury model established earlier by the research group, the expressions of PSMB5, TFEB, and lysosomal associated membrane protein 1 (LAMP1) in liver tissues were detected.

Methods Twenty-four SPF Wistar rats were randomly divided into control group, and low, medium, and high dose groups, with 6 rats in each group, half male and half female. The exposure concentrations were 0, 25, 50, and 100 mg·L⁻¹ NaAsO₂ solutions for 24 weeks. At the end of the experiment, liver was dissected after rats were anesthetized. The levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), total bile acid (TBA), and catalase (CAT) in liver tissues were detected by chemical colorimetry, and the levels of lipid peroxide (LPO), 4-hydroxynonenal (4-HNE), LAMP1, and cathepsin D (CTSD) in liver tissues were detected by enzyme-linked immunosorbent assay (ELISA); the transcriptional expression levels of PSMB5 and TFEB in liver tissues were detected by real-time fluorescence quantitative PCR (RT-qPCR), and the protein expressions of PSMB5, TFEB, and phosphorylated TFEB (p-TFEB) in liver tissues were detected by immunohistochemistry.

Results The results of chemical colorimetry and ELISA showed that compared with the control group, the liver homogenate levels of ALP, TBA, and LAMP1 of each arsenic-exposed group, the ALT and LPO in the medium and high concentration groups, the 4-HNE and CTSD in the high concentration group were increased, while the CAT activity of each arsenic-exposed group was decreased (P<0.05). The results of real-time fluorescence quantitative PCR showed that the transcription levels of PSMB5 and TFEB in the liver tissues of each arsenic-exposed group were decreased compared with those of the control group (P<0.05). The results of immunohistochemistry showed that compared with the control group, the expression of PSMB5 of each arsenic-exposed group were decreased, the expression of TFEB in the medium and high concentration groups was decreased, while the expression of p-TFEB of each arsenic-exposed group was increased (P<0.05). The expression of TFEB protein gradually decreased in the nucleus, while the expression of p-TFEB protein gradually increased in the cytoplasm, but no expression of p-TFEB was found in the nucleus. The results of Pearson correlation analysis showed that PSMB5 in liver tissues was positively correlated with CAT (r=0.818, P＜0.05), and negatively correlated with 4-HNE and p-TFEB (r=−0.582, r=−0.899; P＜0.05); TFEB was negatively correlated with CTSD and LAMP1 (r=−0.457, r=−0.564; P＜0.05); CTSD was positively correlated with ALT and ALP (r=0.529, r=0.485; P＜0.05).

Conclusion Long-term exposure to NaAsO₂ can induce oxidative stress, inhibit the expression of PSMB5 and TFEB, promote the accumulation of p-TFEB in the cytoplasm, decrease the nuclear entry of active TFEB, damage the lysosome, and cause liver damage.