Arsenic induced autophagy-dependent apoptosis in hippocampal neurons via AMPK/mTOR signaling pathway

Down-regulation of O-GlcNAcylation alleviates insulin signaling pathway impairment following arsenic exposure via suppressing the AMPK/mTOR-autophagy pathway

Impairment of the insulin signaling pathway is a key contributor to insulin resistance under arsenic exposure. Specifically, O-GlcNAcylation, an important post-translational modification, plays a crucial role in insulin resistance. Nevertheless, the concrete effect and mechanism of O-GlcNAcylation in arsenic-induced impairment of the insulin signaling pathway remain elusive. Herein, C57BL/6 mice were continuously fed arsenic-containing food, with a total arsenic concentration of 30 mg/kg. We observed that the IRS/Akt/GSK-3β insulin signaling pathway was impaired, and autophagy was activated in mouse livers and HepG2 cells exposed to arsenic. Additionally, O-GlcNAcylation expression in mouse livers and HepG2 cells was elevated, and the key O-GlcNAcylation homeostasis enzyme, O-GlcNAc transferase (OGT), was upregulated. In vitro, non-targeted metabolomic analysis showed that metabolic disorder was induced, and inhibition of O-GlcNAcylation restored the metabolic profile of HepG2 cells exposed to arsenic. In addition, we found that the compromised insulin signaling pathway was dependent on AMPK activation. Inhibition of AMPK mitigated autophagy activation and impairment of insulin signaling pathway under arsenic exposure. Furthermore, down-regulation of O-GlcNAcylation inhibited AMPK activation, thereby suppressing autophagy activation, and improving the impaired insulin signaling pathway. Collectively, our findings indicate that arsenic can impair the insulin signaling pathway by regulating O-GlcNAcylation homeostasis. Importantly, O-GlcNAcylation inhibition alleviated the impaired insulin signaling pathway by suppressing the AMPK/mTOR-autophagy pathway. This indicates that regulating O-GlcNAcylation may be a potential intervention for the impaired insulin signaling pathway induced by arsenic.

Ginsenoside Rk1 induces autophagy-dependent apoptosis in hepatocellular carcinoma by AMPK/mTOR signaling pathway

Hepatocellular carcinoma (HCC) is the third most lethal cancer in the world. Recent studies have shown that suppression of autophagy plays an important role in the development of HCC. Ginsenoside Rk1 is a protopanaxadiol saponin isolated from ginseng and has a significant anti-tumor effect, but its role and mechanism in HCC are still unclear. In this study, a mouse liver cancer model induced by diethylnitrosamine and carbon tetrachloride (DEN + CCl4) was employed to investigate the inhibitory effect of Rk1 on HCC. The results demonstrate that ginsenoside Rk1 effectively inhibits liver injury, liver fibrosis, and cirrhosis during HCC progression. Transcriptome data analysis of mouse liver tissue reveals that ginsenoside Rk1 significantly regulates the AMPK/mTOR signaling pathway, autophagy pathway, and apoptosis pathway. Subsequent studies show that ginsenoside Rk1 induces AMPK protein activation, upregulates the expression of autophagy marker LC3-II protein to promote autophagy, and then downregulates the expression of Bcl2 protein to trigger a caspase cascade reaction, activating AMPK/mTOR-induced toxic autophagy to promote cells death. Importantly, co-treatment of ginsenoside Rk1 with autophagy inhibitors can inhibit apoptosis of HCC cells, once again demonstrating the ability of ginsenoside Rk1 to promote autophagy-dependent apoptosis. In conclusion, our study demonstrates that ginsenoside Rk1 inhibits the development of primary HCC by activating toxic autophagy to promote apoptosis through the AMPK/mTOR pathway. These findings confirm that ginsenoside Rk1 is a promising new strategy for the treatment of HCC.

Proteomic-miRNA Biomics Profile Reveals 2D Cultures of Human iPSC-Derived Neural Progenitor Cells More Sensitive than 3D Spheroid System Against the Experimental Exposure to Arsenic

The iPSC-derived 3D models are considered to be a connective link between 2D culture and in vivo studies. However, the sensitivity of such 3D models is yet to be established. We assessed the sensitivity of the hiPSC-derived 3D spheroids against 2D cultures of neural progenitor cells. The sub-toxic dose of Sodium Arsenite (SA) was used to investigate the alterations in miRNA-proteins in both systems. Though SA exposure induced significant alterations in the proteins in both 2D and 3D systems, these proteins were uncommon except for 20 proteins. The number and magnitude of altered proteins were higher in the 2D system compared to 3D. The association of dysregulated miRNAs with the target proteins showed their involvement primarily in mitochondrial bioenergetics, oxidative and ER stress, transcription and translation mechanism, cytostructure, etc., in both culture systems. Further, the impact of dysregulated miRNAs and associated proteins on these functions and ultrastructural changes was compared in both culture systems. The ultrastructural studies revealed a similar pattern of mitochondrial damage, while the cellular bioenergetics studies confirm a significantly higher energy failure in the 2D system than to 3D. Such a higher magnitude of changes could be correlated with a higher amount of internalization of SA in 2D cultures than in 3D spheroids. Our findings demonstrate that a 2D culture system seems better responsive than a 3D spheroid system against SA exposure.

Salvianolic acid A attenuates arsenic-induced ferroptosis and kidney injury via HIF-2α/DUOX1/GPX4 and iron homeostasis

Arsenic (As) is a prevalent pollutant in the environment and causes a high frequency of kidney disease in areas of high arsenic contamination, but its pathogenic mechanisms have yet to be completely clarified. Ferroptosis is a new form of cell death mainly dependent on lipid peroxidation and iron accumulation. Several reports have suggested that ferroptosis is operative in a spectrum of diseases caused by arsenic exposure, including in the lungs, pancreas, and testis. However, the mechanism and exact role of ferroptosis in arsenic-induced kidney injury is not known. Firstly, by constructing in vivo and in vitro arsenic exposure models, we confirmed the occurrence of ferroptosis based on the identification of the ability of NaASO2 to cause kidney injury. In addition, we found that arsenic exposure could upregulate DUOX1 expression in kidney and HK-2 cells, and after knocking down DUOX1 using siRNA was able to significantly upregulate GPX4 expression and attenuate ferroptosis. Subsequently using bioinformatics, we identified and proved the involvement of HIF-2α in the course of ferroptosis, and further confirmed by dual luciferase assay that HIF-2α promotes DUOX1 transcription to increase its expression. Finally, intervention with the natural ingredient SAA significantly attenuated arsenic-induced ferroptosis and kidney injury. These results showed that arsenic could cause ferroptosis and kidney injury by affecting HIF-2α/DUOX1/GPX4 and iron homeostasis and that SAA was an effective intervention component. This study not only discovered the molecular mechanism of sodium arsenite-induced kidney injury but also explored an active ingredient with intervention potential, providing a scientific basis for the prevention and treatment of sodium arsenite-induced kidney injury.

Insights into Autophagic Machinery and Lysosomal Function in Cells Involved in the Psoriatic Immune-Mediated Inflammatory Cascade

Impaired autophagy, due to the dysfunction of lysosomal organelles, contributes to maladaptive responses by pathways central to the immune system. Deciphering the immune-inflammatory ecosystem is essential, but remains a major challenge in terms of understanding the mechanisms responsible for autoimmune diseases. Accumulating evidence implicates a role that is played by a dysfunctional autophagy-lysosomal pathway (ALP) and an immune niche in psoriasis (Ps), one of the most common chronic skin diseases, characterized by the co-existence of autoimmune and autoinflammatory responses. The dysregulated autophagy associated with the defective lysosomal system is only one aspect of Ps pathogenesis. It probably cannot fully explain the pathomechanism involved in Ps, but it is likely important and should be seriously considered in Ps research. This review provides a recent update on discoveries in the field. Also, it sheds light on how the dysregulation of intracellular pathways, coming from modulated autophagy and endolysosomal trafficking, characteristic of key players of the disease, i.e., skin-resident cells, as well as circulating immune cells, may be responsible for immune impairment and the development of Ps.