Free Radical Biology and Medicine最新文献

Introduction: Epidemiological studies have demonstrated higher incidence and mortality rate of nonalcoholic steatohepatitis (NASH) in the elderly population than in younger groups. However, the mechanisms underlying this age-related exacerbation remain poorly understood.

Objective: This study aimed to elucidate the specific pathways through which aging exacerbates NASH progression, using an integrated in vivo and in vitro model.

Methods: Aged (18-month-old) and young (6-week-old) mice were fed a high-fat diet (HFD) for 16 weeks to induce NASH. A senescence-associated cellular model of NASH was established by co-treating murine hepatocyte AML-12 with H₂O₂ and free fatty acid (FFA). Gene expression profiling of liver tissue was performed using RNA sequencing to identify molecular signatures. Interventions were as follows: (1) In vitro, BMAL1 overexpression plasmids were transfected into AML-12 cells, followed by treatment with 2-deoxy-D-glucose (2-DG, a glycolysis inhibitor) and 2-methoxyestradiol (2-ME2, a HIF-1α inhibitor); (2) in vivo, hepatocyte-specific BMAL1 overexpression was achieved in aged HFD-fed mice through adeno-associated virus serotype 8 (AAV8) delivery. Mechanism validation was performed using biochemical assays, Western blot, cell staining, molecular docking, and Co-IP.

Results: Aged HFD-fed mice exhibited more severe NASH phenotypes than young mice. Transcriptomic analysis identified NLRP3-related signaling and circadian rhythm pathways as central contributors to age-specific NASH pathogenesis. These mice also exhibited elevated NLRP3 inflammasome activity, enhanced glycolysis, and reduced BMAL1 expression. In senescent NASH cells, BMAL1 overexpression along with 2-DG or 2-ME2 treatment significantly downregulated NLRP3 expression and attenuated lipid accumulation, inflammation, oxidative stress, and fibrosis. Mechanistically, BMAL1 directly bound to HIF-1α, thereby suppressing glycolysis. Hepatocyte-specific BMAL1 overexpression in aged HFD-fed mice markedly inhibited glycolysis and NLRP3 activation, resulting in an improvement in NASH-related pathologies.

Conclusion: This study revealed a novel mechanism in which BMAL1 downregulation under aging and HFD conditions promotes NASH progression by binding to HIF-1α and modulating the glycolysis-NLRP3 inflammasome axis.

Extrusion of damaged mitochondria is emerging as a trigger of innate immune activation. Parkinson's disease (PD), characterized by profound mitochondrial dysfunction, may involve similar mechanisms. Here, we report that dopaminergic neurons release damaged mitochondria into the extracellular space in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. These neuron-derived mitochondria were subsequently engulfed by glial cells, eliciting robust inflammatory responses. Autophagy inhibition did not affect mitochondrial release, indicating a non-canonical extrusion pathway. Upon mitochondrial damage, Rab27a and Rab27b translocated to the outer mitochondrial membrane, mediating mitochondrial export from dopaminergic neurons. Conditional Rab27 knockdown in dopaminergic neurons reduced extracellular mitochondrial accumulation, microglial activation, antiviral signaling, and dopaminergic neurodegeneration. Together, these findings identify Rab27-dependent mitochondrial extrusion as a critical mechanism coupling dopaminergic neuronal injury to neuroinflammation and neurodegeneration in PD.

Myocardial infarction (MI) stands as a leading contributor to global cardiovascular morbidity and mortality, defined by ischemic myocardial cell death and subsequent impairment of cardiac function. The tripartite motif (TRIM) protein family has been shown to regulate myocardial ischemia-reperfusion injury. As a key member of the TRIM protein family, tripartite motif-containing protein 28 (TRIM28) exhibits dysregulated expression in the heart during MI yet its pathophysiological role remains to be fully elucidated. This study aimed to investigate the functional roles and underlying mechanisms of TRIM28 in MI. We observed a significant upregulation of TRIM28 in ischemic myocardium and hypoxic cardiomyocytes. Genetic knockout of TRIM28 ameliorated cardiac function and attenuated apoptosis in MI mice, whereas its overexpression exacerbated contractile dysfunction, and promoted cardiomyocyte apoptosis and mitochondrial injury. Mechanistically, TRIM28 directly interacts with activating transcription factor 5 (ATF5) and suppresses its SUMOylation, thereby enhancing the ubiquitin-mediated degradation of ATF5, inhibiting the mitochondrial unfolded protein response (UPRmt), and ultimately culminating in increased apoptosis. Via molecular docking, we identified a TRIM28-targeting compound, Oolonghomobisflavan B (OFB), which attenuated post-MI apoptosis and facilitated cardiac function recovery. Collectively, these findings demonstrate that TRIM28 acts as a critical regulator of MI progression, and OFB holds therapeutic potential as a candidate drug.

Metformin (Met), a first-line therapeutic agent for type 2 diabetes, has been widely recognized for its antifibrotic properties in various pathological conditions. However, its effects on hypertrophic scars (HS) and the underlying mechanisms remain insufficiently explored. The present study aimed to elucidate the role of metformin in HS and to investigate its associated molecular mechanisms. Both in vitro and in vivo experiments demonstrated that metformin markedly inhibited the proliferation, migration, and collagen deposition of hypertrophic scar fibroblasts (HSFs), and alleviated HS formation in a rabbit ear model. Mechanistic investigations further revealed that these effects were closely associated with the downregulation of ribonucleotide reductase regulatory subunit M2 (RRM2). Notably, reduced RRM2 expression suppressed the production of glutathione synthetase (GSS), thereby impairing glutathione (GSH) synthesis. This, in turn, indirectly downregulated glutathione peroxidase 4 (GPX4), leading to the intracellular accumulation of peroxides and triggering ferroptosis in vivo and in vitro. Collectively, these findings suggest that metformin may attenuate HS fibrosis by inducing HSFs ferroptosis through the RRM2/GSS/GPX4 signaling axis. This study not only expands the potential clinical application of metformin in the treatment of skin fibrosis but also provides a theoretical foundation for the development of novel anti-scar therapeutics.

The cutaneous tissue is persistently exposed to environmental stressors, including a wide range of airborne pollutants. This chronic exposure often leads to a condition of oxidative stress, with the outermost layer of epidermis, the stratum corneum (SC), being especially vulnerable due to its high lipid content. Notably, approximately 40 % of SC lipids consist of cholesterol, present in both esterified and unesterified forms. The oxidative imbalance induced by environmental stressors and constantly associated with inflammatory skin diseases promotes the formation and accumulation of cholesterol oxidation products, belonging to the oxysterols' family, which are known for their potent pro-oxidant and pro-inflammatory properties. In addition, harmful oxysterols of dietary origin could reach the epidermis via the vascularized dermis, thus adding another route of exposure. 7β-Hydroxycholesterol (7βOHC) and 7-ketocholesterol (7 KC), two highly toxic oxysterols of non-enzymatic origin, have been shown to significantly downregulate proteins involved in adherens and tight junctions in the intestinal epithelium. Given the structural similarity of extracellular junction proteins across tissues, it is reasonable to expect that oxysterols may similarly disrupt the integrity of the epidermal barrier. To investigate this, supraphysiologic concentrations of 7 KC and 7βOHC were added to the medium of human keratinocytes. Immunofluorescence analysis revealed a consistent and significant reduction in the levels of Claudin-1, Zonulin-1 (ZO1), and E-cadherin, key proteins of tight and adherens junctions, respectively, in oxysterol-treated cells compared to controls. Notably, oxysterol exposure also led to a reduction of mitochondrial membrane potential and an increased mitochondrial reactive oxygen species (ROS) production. Both mitochondrial damage and the disruption of skin junctions were efficiently prevented by mitoTEMPO, a selective mitochondrial superoxide scavenger, suggesting the pro-oxidant activity of oxysterols mediates these effects in keratinocytes. Finally, experiments conducted using a 3D skin model corroborated findings observed in keratinocyte cultures, reinforcing the role of oxysterols in compromising the skin barrier integrity.