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Of the various transcription factors that play a role in controlling oxidative stress, the role of FoxO proteins in skin aging has recently become of interest. Unlike other FoxOs, FoxO6 remains in the nucleus due to the lack of nuclear export signal, so that it may respond sensitively to intracellular stimuli for the induction of target genes. However, the role of FoxO6 in melanogenesis and its related signaling pathways are unclear. We used UV exposed and intrinsically aged mice that exhibited skin aging. Our data showed that FoxO6 activation was markedly decreased in the skin of aging mice and UVB-exposed hairless mice that exhibited an increase in melanogenesis. The reduced FoxO6 activity was closely associated with the elevation of oxidative stress in the skin of these animal models. To our interest, siRNA-mediated FoxO6 knockdown markedly increased melanin content and related signaling pathways in B16F10 cells even without any stimulation. On the contrary, adenovirus-mediated FoxO6 activation significantly reduced melanin content in UVB-exposed B16F10 cells, which is closely associated with the induction of antioxidant genes including MnSOD and catalase, leading to a decrease in oxidative stress. Furthermore, vitamin C treatment reversed the elevated melanogenesis by the FoxO6 knockdown, indicating that the decreased antioxidant capacity greatly contributes to increased melanogenesis in the FoxO6 knockdown condition. For the upstream of a FoxO6 signaling pathway in melanocytes, FoxO6 phosphorylation by Akt appears to be essential evidenced by the reduction of FoxO6 activity and the increase in melanogenesis by PI3K/AKT inhibitor treatment. Our study suggests that FoxO6 is an antioxidant gene that prevents oxidative stress-induced melanogenesis.
Klotho is an aging-suppressor gene which leads to accelerated aging when disrupted. This study was designed to investigate whether glutathione reductase (GR), a critical intracellular antioxidant enzyme, is involved in the pathogenesis of kidney damages associated with accelerated aging in Klotho-haplodeficient (KL
) mice.
Klotho-haplodeficient (KL
) mice and WT mice were used. We found that Klotho haplodeficiency impaired kidney function as evidenced by significant increases in plasma urea and creatinine and a decrease in urinary creatinine in KL
mice. The expression and activity of GR was decreased significantly in renal tubular epithelial cells of KL
mice, suggesting that Klotho deficiency downregulated GR. We constructed adeno-associated virus 2 (AAV2) carrying GR full-length cDNA (AAV-GR). Interestingly, in vivo AAV-GR delivery significantly improved Klotho deficiency-induced renal functional impairment and structural remodeling. Furthermore, in vivo expression of GR rescued the downregulation of the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio, which subsequently diminished oxidative damages in kidneys, as evidenced by significant decreases in renal 4-HNE expression and urinary 8-isoprostane levels in KL mice.
This study provides the first evidence that Klotho deficiency-induced kidney damage may be partly attributed to downregulation of GR expression. In vivo delivery of AAV-GR may be a promising therapeutic approach for aging-related kidney damage.
This study provides the first evidence that Klotho deficiency-induced kidney damage may be partly attributed to downregulation of GR expression. In vivo delivery of AAV-GR may be a promising therapeutic approach for aging-related kidney damage.Cofilins are small protein of the actin depolymerizing family. Actin polymerization/depolymerization is central to a number of critical cellular physiological tasks making cofilin a key protein for several physiological functions of the cell. Cofilin activity is mainly regulated by phosphorylation on serine residue 3 making this post-translational modification key to the regulation of myofilament integrity. In fact, in this form, the protein segregates in myocardial aggregates in human idiopathic dilated cardiomyopathy. Since myofilament network is an early target of oxidative stress we investigated the molecular changes induced by oxidation on cofilin isoforms and their interplay with the protein phosphorylation state to get insight on whether/how those changes may predispose to early protein aggregation. Using different and complementary approaches we characterized the aggregation properties of cofilin-2 and its phosphomimetic variant (S3D) in response to oxidative stress in silico, in vitro and on isolated cardiomyocytes. selleck products We found that the phosphorylated (inactive) form of cofilin-2 is mechanistically linked to the formation of an extended network of fibrillar structures induced by oxidative stress via the formation of a disulfide bond between Cys39 and Cys80. Such phosphorylation-dependent effect is likely controlled by changes in the hydrogen bonding network involving Cys39. We found that the sulfide ion inhibits the formation of such structures. This might represent the mechanism for the protective effect of the therapeutic agent Na2S on ischemic injury.Epithelial cells require attachment to a support, such as the extracellular matrix, for survival. During cancer progression and metastasis, cancerous epithelial cells must overcome their dependence on adhesion signals. Dependence on glucose metabolism is a hallmark of cancer cells, but the nutrient requirements of cancer cells under anchorage-deficient conditions remain uncharacterized. Here, we report that cancer cells prioritize glutamine-derived tricarboxylic acid cycle energy metabolism over glycolysis to sustain anchorage-independent survival. Moreover, glutamine-dependent metabolic reprogramming is required not only to maintain ATP levels but also to suppress excessive oxidative stress through interaction with cystine. Mechanistically, AMPK, a central regulator of cellular responses to metabolic stress, participates in the induction of the expression of ASCT2, a glutamine transporter, and enhances glutamine consumption. Most interestingly, AMPK activation induces Nrf2 and its target proteins, allowing cancer cells to maintain energy homeostasis and redox status through glutaminolysis. Treatment with an integrin inhibitor was used to mimic the alterations in cell morphology and metabolic reprogramming caused by detachment. Under these conditions, cells were vulnerable to glutamine starvation or glutamine metabolism inhibitors. The observed preference for glutamine over glucose was more pronounced in aggressive cancer cell lines, and treatment with the glutaminase inhibitor, CB839, and cystine transporter inhibitor, sulfasalazine, caused strong cytotoxicity. Our data clearly show that anchorage-independent survival of cancer cells is supported mainly by glutaminolysis via the AMPK-Nrf2 signal axis. The discovery of new vulnerabilities along this route could help slow or prevent cancer progression.
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