Puerarin Restores Autophagosome-Lysosome Fusion to Alleviate Cadmium-Induced Autophagy Blockade via Restoring the Expression of Rab7 in Hepatocytes

Preserving mitochondrial homeostasis protects against drug-induced liver injury via inducing OPTN (optineurin)-dependent Mitophagy

Disruption of mitochondrial function is observed in multiple drug-induced liver injuries (DILIs), a significant global health threat. However, how the mitochondrial dysfunction occurs and whether maintain mitochondrial homeostasis is beneficial for DILIs remains unclear. Here, we show that defective mitophagy by OPTN (optineurin) ablation causes disrupted mitochondrial homeostasis and aggravates hepatocytes necrosis in DILIs, while OPTN overexpression protects against DILI depending on its mitophagic function. Notably, mass spectrometry analysis identifies a new mitochondrial substrate, GCDH (glutaryl-CoA dehydrogenase), which can be selectively recruited by OPTN for mitophagic degradation, and a new cofactor, VCP (valosin containing protein) that interacts with OPTN to stabilize BECN1 during phagophore assembly, thus boosting OPTN-mediated mitophagy initiation to clear damaged mitochondria and preserve mitochondrial homeostasis in DILIs. Then, the accumulation of OPTN in different DILIs is further validated with a protective effect, and pyridoxine is screened and established to alleviate DILIs by inducing OPTN-mediated mitophagy. Collectively, our findings uncover a dual role of OPTN in mitophagy initiation and implicate the preservation of mitochondrial homeostasis via inducing OPTN-mediated mitophagy as a potential therapeutic approach for DILIs.Abbreviation: AILI: acetaminophen-induced liver injury; ALS: amyotrophic lateral sclerosis; APAP: acetaminophen; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CHX: cycloheximide; Co-IP: co-immunoprecipitation; DILI: drug-induced liver injury; FL: full length; GCDH: glutaryl-CoA dehydrogenase; GOT1/AST: glutamic-oxaloacetic transaminase 1; GO: gene ontology; GSEA: gene set enrichment analysis; GPT/ALT: glutamic - pyruvic transaminase; INH: isoniazid; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MMP: mitochondrial membrane potential; MST: microscale thermophoresis; MT-CO2/COX-II: mitochondrially encoded cytochrome c oxidase II; OPTN: optineurin; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; TIMM23: translocase of inner mitochondrial membrane 23; TOMM20: translocase of outer mitochondrial membrane 20; TSN: toosendanin; VCP: valosin containing protein, WIPI2: WD repeat domain, phosphoinositide interacting 2.

B-cell lymphoma-2 phosphorylation at Ser70 site-related autophagy mediates puerarin-inhibited the apoptosis of MC3T3-E1 cells during osteoblastogenesis

OBJECTIVE

To explore the relationship between autophagy and apoptosis regulated by puerarin during osteoblastogenesis.

METHODS

In this study, the effects of puerarin on the autophagic activity and apoptosis level of osteoblast precursors (MC3T3-E1 cells) was observed. Subsequently, the roles of puerarin on B-cell lymphoma-2 (Bcl-2) phosphorylation at different sites in osteoblast precursors were observed. The effect of puerarin on the interaction between Bcl-2 and autophagy regulatory molecule or pro-apoptotic molecule was also investigated using Co-immunoprecipitation assays. In addition, the effect of puerarin on mitochondrial membrane potential of osteoblast precursors was also identified by mitochondrial membrane potential fluorescence probe assays.

RESULTS

Our results showed that puerarin can promote the autophagic activity and apoptosis level of MC3T3-E1 cells. In addition, puerarin promoted Bcl-2 phosphorylation at Ser70 site, and the dissociation of Bcl-2-Beclin1 complex. Moreover, puerarin could enhance the binding of Bcl-2-Bcl-2-Associated X (Bax) complex in MC3T3-E1 cells. Furthermore, puerarin increased the mitochondrial membrane potential of MC3T3-E1 cells.

CONCLUSIONS

Therefore, puerarin promotes Beclin1 into autophagy flux through Bcl-2 phosphorylation at Ser70, thereby enhancing autophagy of osteoblast precursors, which mediates its anti-apoptotic role during osteoblastogenesis. Furthermore, the dissociation of Bcl-2-Beclin1 complex is conducive to the binding of Bcl-2-Bax complex, which resists the apoptosis of osteoblast precursors viathe increased mitochondrial membrane potential.

Puerarin Prevents Cadmium-Induced Neuronal Injury by Alleviating Autophagic Dysfunction in Rat Cerebral Cortical Neurons

Autophagic dysfunction is one of the main mechanisms of cadmium (Cd)-induced neurotoxicity. Puerarin (Pue) is a natural antioxidant extracted from the medicinal and edible homologous plant Pueraria lobata. Studies have shown that Pue has neuroprotective effects in a variety of brain injuries, including Cd-induced neuronal injury. However, the role of Pue in the regulation of autophagy to alleviate Cd-induced injury in rat cerebral cortical neurons remains unclear. This study aimed to elucidate the protective mechanism of Pue in alleviating Cd-induced injury in rat cerebral cortical neurons by targeting autophagy. Our results showed that Pue alleviated Cd-induced injury in rat cerebral cortical neurons in vitro and in vivo. Pue activates autophagy and alleviates Cd-induced autophagic blockade in rat cerebral cortical neurons. Further studies have shown that Pue alleviates the Cd-induced inhibition of autophagosome-lysosome fusion, as well as the inhibition of lysosomal degradation. The specific mechanism is related to Pue alleviating the inhibition of Cd on the expression levels of the key proteins Rab7, VPS41, and SNAP29, which regulate autophagosome-lysosome fusion, as well as the lysosome-related proteins LAMP2, CTSB, and CTSD. In summary, these results indicate that Pue alleviates Cd-induced autophagic dysfunction in rat cerebral cortical neurons by alleviating autophagosome-lysosome fusion dysfunction and lysosomal degradation dysfunction, thereby alleviating Cd-induced neuronal injury.

Taurine Alleviates Cadmium-Induced Hepatotoxicity by Regulating Autophagy Flux

Our previous studies have confirmed that cadmium (Cd) exposure causes hepatotoxicity; it also induces autophagy and blocks the autophagy flux. Therefore, we hypothesized that Cd hepatotoxicity could be alleviated through nutritional intervention. Taurine (Tau) has various biological functions such as acting as an antioxidant, acting as an anti-inflammatory, and stabilizing cell membranes. In order to explore the protective effect and internal mechanism of Tau on Cd-induced hepatotoxicity, normal rat liver cell line BRL3A cells were treated with Cd alone or in combination with Tau to detect cell injury and autophagy-related indexes in this study. We found that Tau can alleviate Cd-induced cell-proliferation decline and morphological changes in the cell. In addition, Tau activates autophagy and alleviates the blockage of Cd-induced autophagy flux. In this process, lysosome acidification and degradation were enhanced, and autophagosomes were further fused with lysosomes. Then, we found that Tau alleviated autophagic flux block by promoting the transfer of membrane fusion proteins STX17 and SNAP29 to autophagosomes and the translocation of VAMP8 to lysosomes, which in turn attenuated the hepatocyte injury induced by Cd exposure. This will further reveal the hepatotoxicity mechanism of Cd and provide the theoretical basis for the prevention and treatment of Cd poisoning.

Gap junction intercellular communication mediates cadmium-induced apoptosis in hepatocytes via the Fas/FasL pathway

As a common environmental pollutant, cadmium (Cd) causes damage to many organs of the body. Gap junction intercellular communication (GJIC) represents one of the most important routes of rapid signaling between cells. However, the mechanisms underlying GJIC's role in hepatotoxicity induced by Cd remain unknown. We established a Cd poisoning model in vitro by co-culturing Cd-exposed and unexposed hepatocytes and found that 18β-glycyrrhetinic acid (GA), a GJIC inhibitor, can effectively reduce the apoptosis rate of healthy cells co-cultured with apoptotic cells treated with Cd. We also found that anti-FasL antibody had the same effect. However, in mono-cultured cells, GA treatment in combination with Cd was found to aggravate the damage induced by Cd exposure, increase the level of oxidative stress and protein expression of HO-1, decrease the mitochondrial membrane potential, incur more serious morphological damage to mitochondria than Cd treatment alone. Moreover, compared with Cd-only exposure, GA and Cd co-treatment further increased the expression levels of the apoptosis-related proteins Fas, FasL, FADD and the ratio of Bax/Bcl-2, inhibited the protein expression of ASK1 and Daxx. We also found that the protein expression of Daxx in siFADD + Cd hepatocytes was significantly higher than in Cd-treated cells. Thus, our study suggests that gap junction inhibition may play a dual role in Cd-induced cell damage by inhibiting the transmission of death signals from damaged cells to healthy cells but also aggravating the transmission of death signals between damaged cells, and that the Fas/FasL-mediated death receptor pathway may play an important role in this process.

Pharmacological Activity, Pharmacokinetics, and Clinical Research Progress of Puerarin

As a kind of medicine and food homologous plant, kudzu root (Pueraria lobata (Willd.) Ohwi) is called an "official medicine" in Chinese folk medicine. Puerarin is the main active component extracted from kudzu root, and its structural formula is 8-β-D-grapes pyranose-4, 7-dihydroxy isoflavone, with a white needle crystal; it is slightly soluble in water, and its aqueous solution is colorless or light yellow. Puerarin is a natural antioxidant with high health value and has a series of biological activities such as antioxidation, anti-inflammation, anti-tumor effects, immunity improvement, and cardio-cerebrovascular and nerve cell protection. In particular, for the past few years, it has also been extensively used in clinical study. This review focuses on the antioxidant activity of puerarin, the therapy of diverse types of inflammatory diseases, various new drug delivery systems of puerarin, the "structure-activity relationship" of puerarin and its derivatives, and pharmacokinetic and clinical studies, which can provide a new perspective for the puerarin-related drug research and development, clinical application, and further development and utilization.

Radix Actinidia chinensis Suppresses Renal Cell Carcinoma Progression: Network Pharmacology Prediction and In Vivo Experimental Validation

Background

Renal cell carcinoma (RCC) is a frequent disease with limited curative methods. This study is aimed at investigating the role and mechanism of Radix Actinidia chinensis (RAC) on RCC.

Methods

The ingredients, target, and crucial pathways of RAC in RCC therapy were analyzed by network pharmacology. Then, an RCC animal model was established by subcutaneously injecting A498 cell suspension to BALB/c nude mice. After 1 week, the mice in the RAC-L/M/H groups were administered with RAC at 5, 10, and 20 mg/kg/d, respectively. The histopathology of the tumor was evaluated. The contents of tumor inflammatory cytokines and serum oxidative stress factors were detected by ELISA. The apoptosis of tumor tissues was assessed by TUNEL staining. The expressions of apoptosis-, proliferate-, autophagy-, and MAPK-related proteins were measured.

Results

There were 13 active ingredients, and 20 RCC-relevant targets were selected from RAC; KEGG pathway indicated that these targets were enriched in the PI3K/AKT/mTOR and MAPK pathway. In in vivo experiments, RAC not only obviously damaged tumor cells and decreased the release of inflammatory cytokines and oxidative stress factors but also enhanced the apoptosis of the tumor cell in RCC mice. Besides, the expressions of apoptosis-, proliferate-, autophagy-, PI3K/AKT/mTOR path-, and MAPK path-related proteins were all affected by RAC.

Conclusion

RAC attenuated RCC by regulating inflammation response, oxidative stress, apoptosis, proliferation, and autophagy, and its effects were partly linked to the PI3K/AKT/mTOR and MAPK pathway, which indicated that RAC may be a candidate drug for RCC.

Puerarin alleviates cadmium-induced oxidative damage to bone by reducing autophagy in rats

Autophagy is a regulatory mechanism involved in cadmium (Cd)-induced bone toxicity and is suppressed by various stimuli, including oxidative stress. Puerarin is an isoflavonoid compound isolated from Pueraria, a plant used in traditional Chinese medicine. The underlying mechanisms of action of puerarin remain unclear. The objective of this study was to explore the mitigating effects of puerarin on cadmium-induced oxidative damage in the bones of rats. Cadmium exposure increased oxidative damage in rat bones; this was markedly decreased by puerarin treatment, as demonstrated by changes in the activity of antioxidative enzymes. Cadmium-induced blockage of the expression of key bone regulatory proteins, autophagy-related markers, and signaling molecules was also alleviated by puerarin treatment. Additionally, cadmium reduced expression of the autophagic protein Rab7 and of late endosomal/lysosomal adaptor and MAPK and mTOR activator 1 (LAMTOR1); the decrease in these proteins was not restored by puerarin treatment. We speculate that puerarin relieves the inhibition of fusion of autophagosomes with lysosomes that is induced by cadmium; however, this specific effect of puerarin and downstream effects on bone regulatory mechanisms require further investigation. In conclusion, puerarin alleviates cadmium-induced oxidative damage in the bones of rats by attenuating autophagy, which is likely associated with the antioxidant activity of puerarin.