Zinc stabilized Nrf2 by inhibition of HDAC3 in human peripheral blood mononuclear cells.

BACKGROUND: The transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2) induces several detoxifying proteins, which also include NAD(P)H quinone dehydrogenase 1 (NQO1) and heme oxygenase 1 (HO-1). The expression of these Nrf2-regulated proteins is important for the maintenance of the redox homeostasis in cells. The aim of this study was to investigate the effect of tert-butyl-hydrochinone (tBHQ) stimulation on human PBMC under normal condition and zinc depletion, respectively. METHOD: Human peripheral blood mononuclear cells (PBMC) were treated with the Nrf2 activator tBHQ in combination with zinc to examine a possible correlation between zinc and redox homeostasis. Therefore, mRNA expression of Nrf2 and its downstream molecules NQO1 and HO-1 were investigated, as well as the protein synthesis of these. In addition, the effect of zinc on histone deacetylase 3 (HDAC3), which is a negative regulator for Nrf2 activity, was analyzed. RESULTS: Either mRNA, protein expression or both of Nrf2, NQO1 and HO-1 are influenced by zinc. The analysis of HDAC3 shows a negative correlation between its activity and increasing zinc concentrations. By inhibiting HDAC3 zinc stabilizes Nrf2. CONCLUSION: The results indicate that zinc emphasizes the induction of Nrf2 by its activator tBHQ through increasing gene and protein expression. Additionally, zinc supplementation inhibits HDAC3 activity resulting in reduced Keap1 mRNA expression and thereby stabilizing cytoplasmatic Nrf2. These findings suggests that zinc supplementation has beneficial effects on the redox balance in human cells.

Zinc Status Impacts the Epidermal Growth Factor Receptor and Downstream Protein Expression in A549 Cells.

Zinc has been suggested to play a role in carcinogenesis and tumor progression. Serum zinc levels of lung cancer patients are for example lower than in healthy individuals. The activation and expression of the epidermal growth factor receptor (EGFR), which plays a role in tumor biology, are presumably influenced by zinc. EGFR activation influences cell adhesion and immune escape. This study provides insights into the impacts of zinc on the EGFR activation and expression of downstream proteins such as E-cadherin and PD-L1 in the alveolar carcinoma cell line A549. To model chronic changes in zinc homeostasis, A549 cells were cultured in media with different zinc contents. EGFR surface expression of unstimulated and stimulated A549 cells was determined by flow cytometry. EGFR phosphorylation as well as the protein expression of E-cadherin and PD-L1 were analyzed by Western blot. In our hands, chronic zinc deficiency led to increased EGFR surface expression, decreased E-cadherin protein expression and increased PD-L1 protein expression. Zinc supplementation decreased EGFR surface expression and PD-L1 protein expression. In summary, zinc-deficient A549 cells may display a more malignant phenotype. Thus, future clinical research should further focus on the possible benefits of restoring disturbed zinc homeostasis, especially in lung cancer patients.