Drp1-mediated mitochondrial fission induced autophagy attenuates cell apoptosis caused by 3-chlorpropane-1,2-diol in HEK293 cells

Mitochondrial Damage-Associated Molecular Patterns and Metabolism in the Regulation of Innate Immunity

The innate immune system, as the host's first line of defense against intruders, plays a critical role in recognizing, identifying, and reacting to a wide range of microbial intruders. There is increasing evidence that mitochondrial stress is a major initiator of innate immune responses. When mitochondria's integrity is disrupted or dysfunction occurs, the mitochondria's contents are released into the cytosol. These contents, like reactive oxygen species, mitochondrial DNA, and double-stranded RNA, among others, act as damage-related molecular patterns (DAMPs) that can bind to multiple innate immune sensors, particularly pattern recognition receptors, thereby leading to inflammation. To avoid the production of DAMPs, in addition to safeguarding organelles integrity and functionality, mitochondria may activate mitophagy or apoptosis. Moreover, mitochondrial components and specific metabolic regulations modify properties of innate immune cells. These include macrophages, dendritic cells, innate lymphoid cells, and so on, in steady state or in stimulation that are involved in processes ranging from the tricarboxylic acid cycle to oxidative phosphorylation and fatty acid metabolism. Here we provide a brief summary of mitochondrial DAMPs' initiated and potentiated inflammatory response in the innate immune system. We also provide insights into how the state of activation, differentiation, and functional polarization of innate immune cells can be influenced by alteration to the metabolic pathways in mitochondria.

Rapamycin ameliorates brain damage and maintains mitochondrial dynamic balance in diabetic rats subjected to middle cerebral artery occlusion

To investigate the effect of rapamycin on mitochondrial dynamic balance in diabetic rats subjected to cerebral ischemia-reperfusion injury. Male Sprague Dawley (SD) rats (n = 78) were treated with high fat diet combined with streptozotocin injection to construct diabetic model in rats. Transient middle cerebral artery occlusion (MCAO) of 2 hours was induced and the brains were harvested after 1 and 3 days of reperfusion. Rapamycin was injected intraperitoneally for 3 days prior to and immediately after operation, once a day. The neurological function was assessed, infarct volumes were measured and HE staining as well as immunohistochemistry were performed. The protein of hippocampus was extracted and Western blotting were performed to detect the levels of mTOR, mitochondrial dynamin related proteins (DRP1, p-DRP1, OPA1), SIRT3, and Nix/BNIP3L. Diabetic hyperglycemia worsened the neurological function performance (p < 0.01), enlarged infarct size (p < 0.01) and increased ischemic neuronal cell death (p < 0.01). The increased damage was associated with elevations of p-mTOR, p-S6, and p-DRP1; and suppressions of SIRT3 and Nix/BNIP3L. Rapamycin ameliorated diabetes-enhanced ischemic brain damage and reversed the biomarker alterations caused by diabetes. High glucose activated mTOR pathway and caused mitochondrial dynamics toward fission. The protective effect of rapamycin against diabetes-enhanced ischemic brain damage was associated with inhibiting mTOR pathway, redressing mitochondrial dynamic imbalance, and elevating SIRT3 and Nix/BNIP3L expression.

The inhibitory effect of Yam polysaccharides on acrylamide-induced programmed cell death in RAW 264.7 cells

Acrylamide has been well known for its neurotoxicity, genotoxicity, carcinogenicity, etc. Recently, the immunotoxicity of acrylamide has been reported by different research groups, although the underlying mechanisms of acrylamide endangering immune systems have not been fully elucidated. In this study, mouse monocyte-macrophage cells model was used to clarify the toxic mechanism of acrylamide and the inhibitory effect of Yam polysaccharides (YPS) on acrylamide-induced damage. We found that acrylamide induced RAW 264.7 cell death in a time- and concentration-dependent manner. After acrylamide (2.0, 3.0, 4.0 mmol/L) treatment for 24 h, cell apoptosis, autophagy, and pyroptosis were observed. However, the levels of autophagy and pyroptosis decreased at a high concentration of acrylamide (4.0 mmol/L). Acrylamide upregulated P2X7 expression, but the P2X7 level was not showing a monotone increasing trend. When the P2X7 antagonist was applied, the effect of acrylamide on autophagy and pyroptosis was weakened. Additionally, acrylamide triggered the occurrence of oxidative stress and a decreased nitric oxide (NO) level. However, reactive oxygen species (ROS) generation, the decrease of heme oxygenase-1 (HO-1) expression, and the increase of inducible nitric oxide synthase (iNOS) expression were reversed by the inhibition of P2X7. Yam polysaccharides (50.0 μg/ml) significantly inhibited acrylamide-induced oxidative stress and cell death (including apoptosis, autophagy, and pyroptosis). Yam polysaccharides also effectively reversed the increase of iNOS expression induced by acrylamide. However, Yam polysaccharides promoted the expression of P2X7 rather than prohibit it. These results indicated that acrylamide caused RAW 264.7 cell death due to pro-apoptosis as well as excessive autophagy and pyroptosis. Apoptosis might be more predominant than autophagy and pyroptosis under a higher concentration of acrylamide (4.0 mmol/L). P2X7-stimulated oxidative stress was responsible for acrylamide-induced programmed cell death (PCD), but P2X7 showed limited regulatory effect on apoptosis. Yam polysaccharides with antioxidant activity inhibited acrylamide-induced cell death (apoptosis, autophagy, and pyroptosis), but exerted limited effect on the acrylamide-induced P2X7 expression. These findings would offer an insight into elucidating the immunotoxic mechanism of acrylamide and the potential approaches to control its toxicity.

Two-in-One Nanoparticle Formulation to Deliver a Tyrosine Kinase Inhibitor and microRNA for Targeting Metabolic Reprogramming and Mitochondrial Dysfunction in Gastric Cancer

Dysregulational EGFR, KRAS, and mTOR pathways cause metabolic reprogramming, leading to progression of gastric cancer. Afatinib (Afa) is a broad-spectrum tyrosine kinase inhibitor that reduces cancer growth by blocking the EGFR family. MicroRNA 125 (miR-125) reportedly diminishes EGFRs, glycolysis, and anti-apoptosis. Here, a one-shot formulation of miR-125 and Afa was presented for the first time. The formulation comprised solid lipid nanoparticles modified with mitochondrial targeting peptide and EGFR-directed ligand to suppress pan-ErbB-facilitated epithelial–mesenchymal transition and mTOR-mediated metabolism discoordination of glycolysis–glutaminolysis–lipids. Results showed that this cotreatment modulated numerous critical proteins, such as EGFR/HER2/HER3, Kras/ERK/Vimentin, and mTOR/HIF1-α/HK2/LDHA pathways of gastric adenocarcinoma AGS cells. The combinatorial therapy suppressed glutaminolysis, glycolysis, mitochondrial oxidative phosphorylation, and fatty acid synthesis. The cotreatment also notably decreased the levels of lactate, acetyl-CoA, and ATP. The active involvement of mitophagy supported the direction of promoting the apoptosis of AGS cells, which subsequently caused the breakdown of tumor-cell homeostasis and death. In vivo findings in AGS-bearing mice confirmed the superiority of the anti-tumor efficacy and safety of this combination nanomedicine over other formulations. This one-shot formulation disturbed the metabolic reprogramming; alleviated the “Warburg effect” of tumors; interrupted the supply of fatty acid, cholesterol, and triglyceride; and exacerbated the energy depletion in the tumor microenvironment, thereby inhibiting tumor proliferation and aggressiveness. Collectively, the results showed that the two-in-one nanoparticle formulation of miR-125 and Afa was a breakthrough in simplifying drug preparation and administration, as well as effectively inhibiting tumor progression through the versatile targeting of pan-ErbB- and mTOR-mediated mitochondrial dysfunction and dysregulated metabolism.

Autophagy and mitochondrial dynamics contribute to the protective effect of diosgenin against 3-MCPD induced kidney injury

3-Chloro-1, 2-propanediol (3-MCPD) is a widespread food contaminant with kidney as the main target organ. The exploration of ingredients as intervention strategy towards 3-MCPD induced nephrotoxicity is needed. Diosgenin (DIO) is a steroidal saponin presented in several plants and foods. Here we assessed whether DIO attenuates nephrotoxicity induced by 3-MCPD using Human embryonic kidney 293 (HEK293) cells and Sprague-Dawley (SD) rats. The results showed that DIO (2, 6, 8 μM) increased cell viability and exerted inhibitory effect on caspase 3 and caspase 9 activities. Histological examination of rats showed that 15 mg/kg bw DIO ameliorated renal pathological changes caused by 3-MCPD (30 mg/kg bw). DIO also induced autophagy and the blockade of autophagy with 3-Methyladenine (3-MA) aggravated mitochondrial apoptosis induced by 3-MCPD in HEK293 cells. Moreover, treatment with DIO caused an increase in p-LKB1/LKB1 and p-AMPK/AMPK expressions and a decrease in p-mTOR/mTOR, p-ULK1(Ser⁷⁵⁷), p-P70S6K and p-4EBP1 expressions. Additionally, DIO improved mitochondrial dynamics mainly through inhibiting the relocation of DRP1 on mitochondria and enhancing MFN1 and MFN2 expressions. In conclusion, our study demonstrated for the first time that DIO protected against kidney injury induced by 3-MCPD through the induction of autophagy via LKB1-AMPK-mTOR pathway and the improvement of mitochondrial fission and fusion.

BDE-47 induces nephrotoxicity through ROS-dependent pathways of mitochondrial dynamics in PK15 cells

2,2',4,4'-tetrabromodiphenyl ether (BDE-47)-induced nephrotoxicity is closely associated with oxidative stresses and mitochondrial abnormalities. Mitochondrial fusion and fission dynamics are crucial for maintaining mitochondrial and cellular physiological homeostasis. However, the detailed mechanisms through which BDE-47 disrupts this dynamic and contributes to renal injuries are still not fully understood. The porcine kidney-15 (PK15) cell line, a well-defined in vitro animal renal toxicological model, was exposed to BDE-47 with concentrations of 12.5, 25, 50, and 100 μM, respectively. Cell viability, the levels of reactive oxygen species (ROS) and adenosine triphosphate (ATP), the mitochondrial membrane potential (MMP), and the expression levels of key mitochondrial fusion and fission proteins were assessed. BDE-47 reduced cell viability and disrupted mitochondrial dynamics by inhibiting mitochondrial fusion and fission simultaneously, leading to MMP decreases, ROS overgeneration, ATP depletion, and cellular disintegration in a dose-dependent manner. Additionally, the mitochondrial division inhibitor (Mdivi-1) with the concentration of 20 μM observed to restore the downregulation of mitochondrial fusion and fission proteins, alleviate damages in mitochondrial morphology and functionality, correct ROS overproduction, and enable cell survival. The antioxidant N-acety-L-cysteine (NAC) with the concentration of 1 mM also simultaneously reversed the imbalance of mitochondrial dynamics, decreased ROS production, and restored mitochondrial morphology in PK15 cells exposed to BDE-47. Our data provide new insights indicating that BDE-47 disrupts mitochondrial fusion/fission dynamics to induce mitochondrial abnormalities, triggering oxidative stresses and thus contributing to PK15 cell dysfunction. ROS-dependent pathways in mitochondrial dynamics may provide a new avenue for developing effective strategies to protect cells against BDE-47-induced nephrotoxicity.

LKB1/AMPKα signaling pathway and mitochondrial fission/fusion dynamics regulate apoptosis induced by 3-chlorpropane-1,2-diol in HEK293 cells

Mitochondrial dynamics and bioenergetics are considered play pivotal roles in the maintenance of mitochondrial function and cell viability. During the widely distributed food contaminant 3-chlorpropane-1,2-diol (3-MCPD) induced nephrotoxicity, mitochondrial morphology and function were impaired, but the specific mechanism responsible for the process has not been fully elucidated. In the present study, using an in vitro human embryonic kidney 293 (HEK293) cell culture model, the role of LKB1/AMPK pathway and mitochondrial fission and fusion dynamics in 3-MCPD-induced cell apoptosis was investigated by using the AMPK inhibitor dorsomorphin and mitochondrial division inhibitor 1 (Mdivi-1), respectively. The results revealed that 3-MCPD significantly decreased the ATP levels, activated the energy-sensing regulator AMPKα and its upstream protein kinase LKB1, disrupted mitochondrial dynamics equilibrium characterized by promoting division and inhibiting fusion, thus inducing cell apoptosis. Notably, suppression of AMPK by dorsomorphin mitigated 3-MCPD-induced cytotoxicity through improvement of the function and dynamics of mitochondria and alleviated apoptosis via the mitochondria-dependent pathway. Moreover, inhibition of mitochondrial fission by Mdivi-1 protected against apoptosis induced by 3-MCPD. Taken together, these results suggest that 3-MCPD triggers apoptosis through activation of LKB1/AMPKα signaling pathway and regulation of mitochondrial fission and fusion dynamics in HEK293 cells.

Mitochondria at Work: New Insights into Regulation and Dysregulation of Cellular Energy Supply and Metabolism

Mitochondria are of great relevance to health, and their dysregulation is associated with major chronic diseases. Research on mitochondria-156 brand new publications from 2019 and 2020-have contributed to this review. Mitochondria have been fundamental for the evolution of complex organisms. As important and semi-autonomous organelles in cells, they can adapt their function to the needs of the respective organ. They can program their function to energy supply (e.g., to keep heart muscle cells going, life-long) or to metabolism (e.g., to support hepatocytes and liver function). The capacity of mitochondria to re-program between different options is important for all cell types that are capable of changing between a resting state and cell proliferation, such as stem cells and immune cells. Major chronic diseases are characterized by mitochondrial dysregulation. This will be exemplified by cardiovascular diseases, metabolic syndrome, neurodegenerative diseases, immune system disorders, and cancer. New strategies for intervention in chronic diseases will be presented. The tumor microenvironment can be considered a battlefield between cancer and immune defense, competing for energy supply and metabolism. Cancer cachexia is considered as a final stage of cancer progression. Nevertheless, the review will present an example of complete remission of cachexia via immune cell transfer. These findings should encourage studies along the lines of mitochondria, energy supply, and metabolism.