Sodium/calcium overload and Sirt1/Nrf2/OH-1 pathway are critical events in mercuric chloride-induced nephrotoxicity

Mercury (Hg), a significant toxic metal for nephrotoxicity, can be found in food (vegetable and seafood) and drinking water by contamination. Oxidative stress is involved in inorganic Hg-induced nephrotoxicity, but the Sirtuin1 (Sirt1)/Nrf2/OH-1 pathway and sodium (Na)/calcium (Ca) ions actions in mercuric chloride (HgCl₂)-induced nephrotoxicity remains unclear to date. In this study, Kunming mice were treated HgCl₂ (5 mg/kg) for 24 h to evaluate potential mechanism. Here, along with Sirt1 activation, pale kidney, hisologic conditions, typical apoptotic changes and TUNEL positive nuclei were observed under acute HgCl₂ exposure. Specifically, although HgCl₂ increased the expression of Nrf2, Keap1, OH-1 and NQO1, the mRNA levels of GSS, GCLC and GCLM showed no significant alterations in mice kidney. Moreover, mice exposed to HgCl₂ decreased the concentrations of Mg, K, P, Mn, Fe, Zn, and elevated Na, Ca, Cu and Se in kidney. It was also observed that HgCl₂ suppressed the ATPases (Na⁺-K⁺-ATPase, Ca²⁺-ATPase, Mg²⁺-ATPase and Ca²⁺-Mg²⁺-ATPase) activities and decreased the mRNA levels of Atp1a1, Atp1a2 in the kidney. Further study showed that HgCl₂ elevated Na⁺ concentrations by markedly increased the mRNA levels of Na⁺ transporter. The present study revealed that HgCl₂ induced Sirt1/Nrf2/OH-1 pathway activation while did not inhibit apoptosis in kidney of mice. Additionally, HgCl₂ regulates Na⁺ concentrations, which might create secondary disorders in absorption and excretion of other ions. Altogether we assume that Sirt1/Nrf2/Na⁺/Ca²⁺ pathway might be a potential therapeutic target for treating acute HgCl₂ induced nephrotoxicity.

Pxr- and Nrf2- mediated induction of ABC transporters by heavy metal ions in zebrafish embryos

Transcription factors including pregnane X receptor (Pxr) and nuclear factor-erythroid 2-related factor-2 (Nrf2) are important modulators of Adenosine triphosphate-binding cassette (ABC) transporters in mammalian cells. However, whether such modulation is conserved in zebrafish embryos remains largely unknown. In this manuscript, pxr- and nrf2-deficient models were constructed with CRISPR/Cas9 system, to evaluate the individual function of Pxr and Nrf2 in the regulation of ABC transporters and detoxification of heavy metal ions like Cd²⁺ and Ag⁺. As a result, both Cd²⁺ and Ag⁺ conferred extensive interactions with ABC transporters in wild type (WT) embryos: their accumulation and toxicity were affected by the activity of ABC transporters, and they significantly induced the mRNA expressions of ABC transporters. These induction effects were reduced by the mutation of pxr and nrf2, but elevations in the basal expression of ABC transporters compensated for the loss of their inducibility. This could be an explanation for remaining transporter function in both mutant models as well as the unaltered toxicity of metal ions in pxr-deficient embryos. However, mutation of nrf2 disrupted the production of glutathione (GSH), resulting in the enhanced toxicity of Cd²⁺/Ag⁺ in zebrafish embryos. In addition, elevated expressions of other transcription factors like aryl hydrocarbon receptor (ahr) 1b, peroxisome proliferator-activated receptor (ppar)-β, and nrf2 were found in pxr-deficient models without any treatment, while enhanced induction of ahr1b, ppar-β and pxr could only be seen in nrf2-deficient embryos after the treatment of metal ions, indicating different compensation phenomena for the absence of transcription factors. After all, pxr-deficient and nrf2-deficient zebrafish embryos are useful tools in the functional investigation of Pxr and Nrf2 in the early life stages of aquatic organisms. However, the compensatory mechanisms should be taken into consideration when interpreting the results and need in-depth investigations.

Denervation aggravates renal ischemia reperfusion injury via BMAL1-mediated Nrf2/ARE pathway

AIM

To explore the change of clock gene rhythm under renal denervation (RDN) and its effect on renal function and oxidative stress during renal ischemia-reperfusion (IR) injury.

METHOD

C57/BL6 mice were randomly divided into 4 groups at daytime 7 A M (zeitgeber time [ZT] 0) or at nighttime 7 P M (ZT12) in respectively: Sham (S) group, RDN group, IR group and RDN + IR (DIR) group. Renal pathological and functional changes were assessed by H&E staining, and serum creatinine, urea nitrogen and neutrophil gelatinase-associated lipocalin levels. Renal oxidative stress was detected by SOD and MDA levels, and renal inflammation was measured by IL-6, IL-17 A F and TNF-ɑ levels. BMAL1, CLOCK, Nrf2 and HO-1 mRNA and protein expressions were tested by qPCR and Western Blot.

RESULT

Compared with S groups, the rhythm of BMAL1, CLOCK and Nrf2 genes in the kidney were disordered in RDN groups, while renal pathological and functional indexes did not change significantly. Compared with IR groups, renal pathological and functional indexes were significantly higher in the DIR groups, as well as oxidative stress and inflammation in renal tissues. The nocturnal IR injury in the RDN kidney was the worst while the BMAL1, Nrf2 and HO-1 expressions were the highest. In DIR groups, renal injury was aggravated after the Brusatol treatment, but there was no significant improvement after the t-BHQ treatment at night, which might be consistent with the changes of Nrf2 and HO-1 protein expressions.

CONCLUSION

RDN lead to the disruption of BMAL1-mediated Nrf2 rhythm accumulation in the kidney, which reduced the renal ability to resist oxidative stress and inflammation, due to the impaired effect of activating Nrf2/ARE pathway in renal IR injury at nighttime.

[Effect of benazepril on nuclear factor E2 related factor 2, nicotinamide adenine dinucleotide phosphate oxidase and reactive oxygen species in rats with hepatic fibrosis]

Objective: To study the effect of benazepril on the expression of nuclear factor E2 related factor 2 (Nrf2), nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) and reactive oxygen species (ROS) concentration in rats with hepatic fibrosis and to explore the possible antifibrotic mechanism of benazepril. Methods: Twenty-two healthy male Sprague-Dawley rats were randomly divided into 3 groups: control group (6 rats), model group (8 rats) and benazepril treatment group (8 rats). Two rats died during modeling and treatment in the model group and the benazepril treatment group, and a model of hepatic fibrosis induced by carbon tetrachloride (CCL(4)) was established. The rats in benazepril group were given benazepril for 8 weeks by gastric gavage. The assessment of liver tissue damage in each group was measured using conventional hematoxylin-eosin and Masson staining. The mRNA level of Nrf2, NOX4 in liver tissue was detected by RT-PCR, and serum ROS concentration was determined by colorimetry. All data were expressed in mean ± standard deviations, and were analyzed using SPSS21.0 statistical software. The data were compared using one-way analysis of variance, and the LSD-t method was used for pairwise comparison between the two groups. The correlation analysis was performed by Spearman's correlation analysis. Results: In the liver of the model group, with the aggravation of liver fibrosis the expression of Nrf2mRNA, NOX4 mRNA and ROS concentration were higher than control group [(4.01 ± 3.40), (31.78 ± 3.96), (1.82 ± 0.46) μg/ ml vs. (0.12 ± 0.11), (2.03 ± 0.31), (1.56±0.84) μg/ml, P < 0.05]. After benazepril treatment, NOX4 mRNA expression and ROS concentration were decreased than the model group [(15.93 ± 5.01), (0.78 ± 0.44) μg/ml vs. (31.78 ± 3.96), (1.82 ± 0.46) μg /ml, P < 0.05], while Nrf2 mRNA expression was higher than the model group [(6.69 ± 4.86) vs. (4.01 ± 3.40), P < 0.05]. There was a positive correlation between Nrf2 and NOX4, Nrf2 and ROS, and NOX4 and ROS (r = 0.616, 0.411, 0.802, P < 0.05). Conclusion: Benazepril may exert an anti-hepatic fibrosis effect by activating Nrf2 expression, or may inhibit the ROS-mediated oxidative stress in response to NOX4.