Polymyxin B exerts nephrotoxicity effects via inhibition of the Nrf2/NQO1 pathway-mediated antioxidant response.

Polymyxin B (PMB) is a polypeptide antibiotic widely used in treating multidrug-resistant Gram-negative bacteria. However, nephrotoxicity is a serious adverse effect that limits its clinical use. Therefore, clarification of the molecular mechanism of PMB-induced renal injury is essential. Our study aimed to explore possible mechanisms of PMB-induced nephrotoxicity in vivo and in vitro. Mice were treated with PMB to construct the kidney injury model. The antioxidant capacity was assessed by measuring the superoxide dismutase (SOD) and catalase (CAT) activities and the glutathione (GSH) and malondialdehyde (MDA) contents. The pathway of the nuclear factor erythroid 2-related factor 2/NADH quinone oxidoreductase 1 (Nrf2/NQO1) was examined after PMB treatment in NRK-52E cells and mice. Finally, the expressions of genes and proteins (Bax, Bcl-2, Caspase-3, Caspase-9) related to apoptosis were evaluated through quantitative polymerase chain reaction and western blot assay. The study verified PMB-induced nephrotoxicity in mice and NRK-52E cells in a dose- and time-dependent manner. PMB treatment significantly decreased the expression of Nrf2 and its downstream target gene NQO1 and increased the apoptosis-related proteins expression. In summary, our results suggested that PMB-induced oxidative stress damage by inhibiting the Nrf2/NQO1 pathway and promoting apoptosis in kidney tissues.

DNMT3A R882H mutation promotes acute leukemic cell survival by regulating glycolysis through the NRF2/NQO1 axis.

BACKGROUND: Studies have confirmed that acute myeloid leukemia (AML) cells with DNA methyltransferase 3A Arg882His (DNMT3A R882H) mutation show an increased proliferation capability. However, the associated mechanism is still unclear. Glycolysis is involved in regulating malignant proliferation of cancer cell. Hence, we analyzed whether the DNMT3A R882H mutation interferes with glycolysis and thereby influences AML cell proliferation. METHODS: We generated AML cell line carrying a DNMT3A-R882H mutation and compared it with the wild type (DNMT3A-WT) with regard to glycolysis regulation. Moreover, we analyzed the cell line's proliferation and apoptosis by a CCK-8 assay, western blotting, and flow cytometry. The role of NRF2/NQO1 signaling in regulating glycolysis was investigated by NRF2-knockdown and Brusatol (specific inhibitor of NRF2) treatment. RESULTS: DNMT3A R882H cells had a higher glucose transport capacity compared to WT cells and their viability could be reduced by glucose deprivation. Moreover, daunorubicin had a slight inhibitory effect on glycolysis while glycolysis inhibition re-sensitized mutant cells to daunorubicin. Obviously, DNMT3A R882H mutation activated the NRF2/NQO1 pathway and enhanced the glycolytic activity in mutant cells. CONCLUSION: Taken together, these results suggest a novel mechanism by which a DNMT3A R882H mutation promotes glycolysis via activation of NRF2/NQO1 pathway. A parallel glycolysis inhibition adds to the anticancer effects of daunorubicin which might lead to a novel therapeutic approach for the treatment of AML patients carrying a DNMT3A R882H mutation.

The Potential Key Role of the NRF2/NQO1 Pathway in the Health Effects of Arsenic Pollution on SCC.

Arsenic is widely present in nature and is a common environmental poison that seriously damages human health. Chronic exposure to arsenic is a major environmental poisoning factor that promotes cell proliferation and leads to malignant transformation. However, its molecular mechanism remains unclear. In this study, we found that arsenite can promote the transformation of immortalized human keratinocyte cells (HaCaT) from the G0/G1 phase to S phase and demonstrated malignant phenotypes. This phenomenon is accompanied by obviously elevated levels of NRF2, NQO1, Cyclin E, and Cyclin-dependent kinase 2 (CDK2). Silencing the NRF2 expression with small interfering RNA (siRNA) in arsenite-transformed (T-HaCaT) cells was shown to reverse the malignant phenotype. Furthermore, the siRNA silencing of NQO1 significantly decreased the levels of the cyclin E-CDK2 complex, inhibiting the G0/G1 to S phase cell cycle progression and transformation to the T-HaCaT phenotypes. Thus, we hypothesized that the NRF2/NQO1 pathway played a key role in the arsenite-induced malignancy of HaCaT cells. By increasing the expression of Cyclin E-CDK2, the NRF2/NQO1 pathway can affect cell cycle progression and cell proliferation. A new common health effect mechanism of arsenic carcinogenesis has been identified; thus, it would contribute to the development of novel treatments to prevent and treat skin cancer caused by arsenic.