VPS41-mediated incomplete autophagy aggravates cadmium-induced apoptosis in mouse hepatocytes

Selenium restored mitophagic flux to alleviate cadmium-induced hepatotoxicity by inhibiting excessive GPER1-mediated mitophagy activation

Cadmium (Cd) is a common environmental pollutant, while selenium (Se) can ameliorate heavy metal toxicity. Consequently, this study aimed to investigate the protective effects of Se against Cd-induced hepatocyte injury and its underlying mechanisms. To achieve this, we utilized the Dongdagou-Xinglong cohort, BRL3A cell models, and a rat model exposed to Cd and/or Se. The results showed that Se counteracted liver function injury and the decrease in GPER1 levels caused by environmental Cd exposure, and various methods confirmed that Se could protect against Cd-induced hepatotoxicity both in vivo and in vitro. Mechanistically, Cd caused excessive mitophagy activation, evidenced by the colocalization of LC3B, PINK1, Parkin, P62, and TOMM20. Transfection of BRL3A cells with mt-keima adenovirus indicated that Cd inhibited autophagosome-lysosome fusion, thereby impeding mitophagic flux. Importantly, G1, a specific agonist of GPER1, mitigated Cd-induced mitophagy overactivation and hepatocyte toxicity, whereas G15 exacerbates these effects. Notably, Se supplementation attenuated Cd-induced GPER1 protein reduction and excessive mitophagy activation while facilitating autophagosome-lysosome fusion, thereby restoring mitophagic flux. In conclusion, this study proposed a novel mechanism whereby Se alleviated GPER1-mediated mitophagy and promoted autophagosome-lysosome fusion, thus restoring Cd-induced mitophagic flux damage, and preventing hepatocyte injury.

Selenium nanoparticles alleviates cadmium induced hepatotoxicity by inhibiting ferroptosis and oxidative stress in vivo and in vitro

Cadmium (Cd) is an important environmental toxicant that could cause serious damage to various organs including severe hepatotoxicity in intoxicated animals. Selenium has been reported to possess the protective effects against Cd toxicity, but the specific mechanism is still unclear. The purpose of this study was to explore the effects and mechanism of chitosan coated selenium nanoparticles (CS-SeNPs) against Cd-induced hepatotoxicity in animal and cellular models. ICR mice and rat hepatocyte BRL-3A cells were exposed to cadmium chloride (CdCl2) to evaluate the therapeutic efficiency of CS-SeNPs. Analysis of histopathological images, mitochondrial membrane potential (MMP) and ultramicrostructure, serum liver enzyme activities, ferroptosis-related indicators contents, and further molecular biology experiments were performed to investigate the underlying mechanisms. In vivo experiment results showed that CdCl2 caused significant pathological damage involving significant increase of liver index, contents of tissue MDA and serum ALT and AST, and significant decrease of serum GSH-Px activity. Moreover, CdCl2 exposure upregulated ACSL4 and HO-1 protein levels, downregulated GPX4, TfR1, ferritin protein levels in the liver. Notably, CS-SeNPs increased the expression level of GPX4 and ameliorated CdCl2-induced changes in above-mentioned indicators. In vitro experimental results showed that treatment with CS-SeNPs significantly elevated GSH-Px activity and GPX4 protein level, reversed CdCl2-induced expression of several ferroptosis-related proteins TfR1, FTH1 and HO-1, and repressed ROS production and increased MMP of the cells exposed to CdCl2. Our research indicated that CdCl2 induced hepatocyte injury by inducing ferroptosis, while CS-SeNPs can inhibit ferroptosis and reduce the degree of hepatocyte injury. This study is of great significance for further revealing the mechanism of Cd hepatotoxicity and expanding the clinical application of SeNPs.

SIRT5-Mediated Desuccinylation of RAB7A Protects Against Cadmium-Induced Alzheimer's Disease-Like Pathology by Restoring Autophagic Flux

Cadmium (Cd) is a neurotoxic contaminant that induces cognitive decline similar to that observed in Alzheimer's disease (AD). Autophagic flux dysfunction is attributed to the pathogenesis of AD, and this study aimed to investigate the effect of autophagy on environmental Cd-induced AD progression and the underlying mechanism. Here, Cd exposure inhibited autophagosome-lysosome fusion and impaired lysosomal function, leading to defects in autophagic clearance and then to APP accumulation and nerve cell death. Proteomic analysis coupled with Ingenuity Pathway Analysis (IPA) identified SIRT5 as an essential molecular target in Cd-impaired autophagic flux. Mechanistically, Cd exposure hampered the expression of SIRT5, thus increasing the succinylation of RAB7A at lysine 31 and inhibiting RAB7A activity, which contributed to autophagic flux blockade. Importantly, SIRT5 overexpression led to the restoration of autophagic flux blockade, the alleviation of Aβ deposition and memory deficits, and the desuccinylation of RAB7A in Cd-exposed FAD4T mice. Additionally, SIRT5 levels decrease mainly in neurons but not in other cell clusters in the brains of AD patients according to single-nucleus RNA sequencing data from the public dataset GSE188545. This study reveals that SIRT5-catalysed RAB7A desuccinylation is an essential adaptive mechanism for the amelioration of Cd-induced autophagic flux blockade and AD-like pathogenesis.

Cadmium promoted LPS-induced inflammation through TLR4/IκBα/NFκ-B signaling by increasing ROS-mediated incomplete autophagy

Cadmium (Cd) exposure is considered as non-infectious stressor to human and animal health. Recent studies suggest that the immunotoxicity of low dose Cd is not directly apparent, but disrupts the immune responses when infected with some bacteria or virus. But how Cd alters the adaptive immunity organ and cells remains unclear. In this study, we applied lipopolysaccharide (LPS, infectious stressor) to induced inflammation in spleen tissues and T cells, and investigated the effects after Cd exposure and the underlying mechanism. Cd exposure promoted LPS-induced the expressions of the inflammatory factors, induced abnormal initiation of autophagy, but blocked autophagic flux. The effects Cd exposure under LPS activation were reversed by the autophagy promoter Rapamycin. Under LPS activation conditions, Cd also induced oxidative stress by increasing the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and reducing total antioxidant capacity (T-AOC) activity. The increased superoxide dismutase (SOD) activity after Cd exposure might be a negative feedback or passive adaptive regulation of oxidative stress. Cd-increased autophagic flux inhibition and TNF-α expression were reversed by ROS scavenger α-tocopherol (TCP). Furthermore, under LPS activation condition, Cd promoted activation of toll-like receptor 4 (TLR4)/IκBα/NFκ-B signaling pathway and increased TLR4 protein stability, which were abolished by the pretreatment of Rapamycin. The present study confirmed that, by increasing ROS-mediated inhibiting autophagic degradation of TLR4, Cd promoted LPS-induced inflammation in spleen T cells. This study identified the mechanism of autophagy in Cd-aggravated immunotoxicity under infectious stress, which could arouse public attention to synergistic toxicity of Cd and bacterial or virus infection.

Structure-Guided Discovery and Preclinical Assessment of Novel (Thiophen-3-yl)aminopyrimidine Derivatives as Potent ERK1/2 Inhibitors

The RAS-RAF-MEK-ERK signaling cascade is abnormally activated in various tumors, playing a crucial role in mediating tumor progression. As the key component at the terminal stage of this cascade, ERK1/2 emerges as a potential antitumor target and offers a promising therapeutic strategy for tumors harboring BRAF or RAS mutations. Here, we identified 36c with a (thiophen-3-yl)aminopyrimidine scaffold as a potent ERK1/2 inhibitor through structure-guided optimization for hit 18. In preclinical studies, 36c showed powerful ERK1/2 inhibitory activities (ERK1/2 IC50 = 0.11/0.08 nM) and potent antitumor efficacy both in vitro and in vivo against triple-negative breast cancer and colorectal cancer models harboring BRAF and RAS mutations. 36c could directly inhibit ERK1/2, significantly block the phosphorylation expression of their downstream substrates p90RSK and c-Myc, and induce cell apoptosis and incomplete autophagy-related cell death. Taken together, this work provides a promising ERK1/2 lead compound for multiple tumor-treatment drug discovery.

Loss of the HOPS complex disrupts early-to-late endosome transition, impairs endosomal recycling and induces accumulation of amphisomes

The multisubunit HOPS tethering complex is a well-established regulator of lysosome fusion with late endosomes and autophagosomes. However, the role of the HOPS complex in other stages of endo-lysosomal trafficking is not well understood. To address this, we made HeLa cells knocked out for the HOPS-specific subunits Vps39 or Vps41, or the HOPS-CORVET-core subunits Vps18 or Vps11. In all four knockout cells, we found that endocytosed cargos were trapped in enlarged endosomes that clustered in the perinuclear area. By correlative light-electron microscopy, these endosomes showed a complex ultrastructure and hybrid molecular composition, displaying markers for early (Rab5, PtdIns3P, EEA1) as well as late (Rab7, CD63, LAMP1) endosomes. These "HOPS bodies" were not acidified, contained enzymatically inactive cathepsins and accumulated endocytosed cargo and cation-independent mannose-6-phosphate receptor (CI-MPR). Consequently, CI-MPR was depleted from the TGN, and secretion of lysosomal enzymes to the extracellular space was enhanced. Strikingly, HOPS bodies also contained the autophagy proteins p62 and LC3, defining them as amphisomes. Together, these findings show that depletion of the lysosomal HOPS complex has a profound impact on the functional organization of the entire endosomal system and suggest the existence of a HOPS-independent mechanism for amphisome formation.