Dynamin-related protein 1 deficiency accelerates lipopolysaccharide-induced acute liver injury and inflammation in mice

Independent and interactive roles of hirudin and HMGB1 interference in protecting renal function by regulating autophagy, apoptosis, and kidney injury in chronic kidney disease

Chronic kidney disease (CKD) is a progressive disorder characterized by renal fibrosis, inflammation, and dysregulated autophagy and apoptosis. High-mobility group box 1 (HMGB1) plays a crucial role in regulating autophagy in CKD. Hirudin, a potent thrombin inhibitor, has demonstrated antifibrotic and anti-inflammatory properties, but its effects on autophagy and apoptosis in CKD remain unclear. In this study, a rat model of renal interstitial fibrosis (RIF) and an HK-2 cell culture model were established to assess the effects of varying doses of hirudin and HMGB1 interference. Molecular and histological analyses, including RTqPCR, Western blot, TUNEL staining, hematoxylin-eosin (H&E) staining, immunofluorescence, and immunohistochemistry (IHC), were performed to assess renal injury, fibrosis, apoptosis, and autophagy-related markers. Hirudin treatment significantly reduced the expression of LC3, ATG12, ATG5, α-SMA, COL1A1, caspase-3, and caspase-9 while increasing P62 levels (p<0.05). It also lowered the renal coefficient (p<0.001) and apoptosis levels. The optimal effective concentration of hirudin in vitro was determined to be 4.8 ATU/mL (p<0.001). HMGB1 interference suppressed autophagy and apoptosis, as indicated by decreased LC3-II/LC3-I, ATG12, ATG5, caspase-3, and caspase-9 levels, increased P62 expression (p<0.001), and reduced apoptosis. However, simultaneous HMGB1 interference in hirudin-treated cells weakened the therapeutic effects of hirudin, leading to increased autophagy and apoptosis markers, decreased P62 levels, and a higher renal coefficient. These findings indicate that hirudin exerts protective effects in CKD by modulating autophagy and apoptosis, potentially through HMGB1 regulation. These findings highlight the therapeutic potential of targeting these mechanisms in renal dysfunction and underscore the necessity for further research to support clinical applications.

The Role of Mdivi-1 in Reducing Mitochondrial Fission via the NF-kappaB/JNK/SIRT3 Signaling Pathway in Acute Kidney Injury

To explore the effects and underlying mechanisms of Mdivi-1 on three common clinical models of acute kidney injury (AKI). Three common AKI cell models were constructed, classified into the control group (human renal tubular epithelial cells [HK-2] cells), the Iohexol group (HK-2 cells treated with Iohexol), the Genta group (HK-2 cells treated with Gentamicin), and the Cis group (HK-2 cells treated with Cisplatin). To explore the optimal protective concentration of Mdivi-1 for each AKI cell model, the experimental design consisted of the following seven groups: the control group (HK-2 cells cultured in medium), three injury groups (HK-2 cells subjected to Iohexol, Gentamicin, or Cisplatin), and the corresponding protection groups (with a certain concentration of Mdivi-1 added to each injury group). Cellular survival and apoptosis, reactive oxygen species (ROS) levels, and the expression of recombinant Sirtuin 3 (SIRT3) in each group were measured. Mitochondrial fission and fusion dynamics in cells were observed under an electron microscope. To explore relevant pathways, the changes in relevant pathway proteins were analyzed through Western blotting. The half maximal inhibitory concentration (IC50) values were 150.06 mgI/ml at 6 h in the Iohexol group, 37.88 mg/ml at 24 h in the Gentamicin group, and 13.48 microM at 24 h in the Cisplatin group. Compared with the control group, the three injury groups showed increased cell apoptosis rates and higher expressions of apoptotic proteins in HK-2 cells, with an accompanying decrease in cell migration. After the addition of corresponding concentrations of Mdivi-1, the optimal concentrations were 3 µM in the Iohexo-3 group, 1 microM in the Genta-1 group, and 5 µM in the Cis-5 group, HK-2 cells showed the highest survival rate, reduced apoptosis, decreased mitochondrial ROS and SIRT3 expression, and reduced mitochondrial fission and autophagy when compared with each injury group. Further verification with Western blot analysis after the addition of Mdivi-1 revealed a reduction in the expressions of mitochondrial fission proteins DRP1, Nrf2, SIRT3, Caspase-3, Jun N-terminal Kinase (JNK)/P-JNK, NF-kappaB, Bcl2, and autophagic protein P62, as well as reduced ROS levels. Mdivi-1 had protective effects on the three common AKI cell models by potentially reducing mitochondrial fission in cells and inhibiting the production of ROS through the mediation of the NF- B/JNK/SIRT3 signaling pathway, thereby exerting protective effects. Key words AKI, Cisplatin, Gentamicin, Iohexol, Mdivi-1.

Maternal MitoQ Treatment Is Protective Against Programmed Alterations in CYP Activity Due to Antenatal Dexamethasone

Background/Objectives: In pregnancy threatened by preterm birth, antenatal corticosteroids (ACS) are administered to accelerate fetal lung maturation. However, they have side effects, including the production of reactive oxygen species that can impact cytochrome P450 (CYP) activity. We hypothesised that antioxidants could protect a fetus treated with ACS during gestation and prevent the programming of altered hepatic CYP activity in the offspring. The primary outcome of our study was the impact of different maternal treatments on the activity of hepatic drug-metabolising enzymes in offspring. Methods: At 100 ± 1 days gestational age (dGA, term = 147 dGA), 73 ewes were randomly allocated to the following: saline (5 mL IV daily 105-137 ± 2 dGA, n = 17), ACS (Dexamethasone (Dex); 12 mg IM at 115 and 116 dGA; n = 25), MitoQ (6 mg/kg MS010 IV, daily bolus 105-137 ± 2 dGA; n = 17) or Dex and MitoQ (Dex+MitoQ; n = 14). CYP activity and protein abundance were assessed using functional assays and Western blot. Results: Dex decreased the hepatic activity of fetal CYP3A (-56%, PDex = 0.0322), and 9 mo lamb CYP1A2 (-22%, PDex = 0.0003), CYP2B6 (-36%, PDex = 0.0234), CYP2C8 (-34%, PDex = 0.0493) and CYP2E1 (-57%, PDex = 0.0009). For all, except CYP1A2, activity returned to control levels with Dex+MitoQ in 9 mo lambs. In 9 mo lambs, MitoQ alone increased activity of CYP2B6 (+16%, PMitoQ = 0.0011) and CYP3A (midazolam, +25%, PMitoQ = 0.0162) and increased CAT expression (PMitoQ = 0.0171). Dex+MitoQ increased CYP3A4/5 activity (testosterone, +65%, PIntx < 0.0003), decreased CYP1A2 activity (-14%, PIntx = 0.0036) and decreased mitochondrial abundance (PIntx = 0.0051). All treatments decreased fetal hepatic DRP1, a regulator of mitochondrial fission (PDex = 0.0055, PMitoQ = 0.0006 and PIntx = 0.0034). Conclusions: Antenatal Dex reduced activity of only one CYP in the fetus but programmed the reduced activity of several hepatic CYPs in young adult offspring, and this effect was ameliorated by combination with MitoQ.

Myeloid DRP1 deficiency limits revascularization in ischemic muscles via inflammatory macrophage polarization and metabolic reprogramming

Macrophages play a crucial role in promoting perfusion recovery and revascularization after ischemia through antiinflammatory polarization, a process essential for the treatment of peripheral artery disease (PAD). Mitochondrial dynamics, particularly regulated by the fission protein DRP1, are closely linked to macrophage metabolism and inflammation. However, the role of DRP1 in reparative neovascularization remains unexplored. Here, we show that DRP1 expression was increased in F4/80+ macrophages within ischemic muscle on day 3 after hind limb ischemia (HLI), an animal model of PAD. Mice lacking Drp1 in myeloid cells exhibited impaired limb perfusion recovery, angiogenesis, and muscle regeneration after HLI. These effects were associated with increased proinflammatory M1-like macrophages, p-NF-κB, and TNF-α, and reduced antiinflammatory M2-like macrophages and p-AMPK in ischemic muscle of myeloid Drp1-/- mice. In vitro, Drp1-deficient macrophages under hypoxia serum starvation (HSS), an in vitro PAD model, demonstrated enhanced glycolysis via reducing p-AMPK as well as mitochondrial dysfunction, and excessive mitochondrial ROS production, resulting in increased proinflammatory M1-gene and reduced antiinflammatory M2-gene expression. Conditioned media from HSS-treated Drp1-/- macrophages exhibited increased proinflammatory cytokine secretion, leading to suppressed angiogenesis in endothelial cells. Thus, macrophage DRP1 deficiency under ischemia drives proinflammatory metabolic reprogramming and macrophage polarization, limiting revascularization in experimental PAD.

Mechanistic insights into metabolic function of dynamin-related protein 1

Dynamin-related protein 1 (DRP1) plays crucial roles in mitochondrial and peroxisome fission. However, the mechanisms underlying the functional regulation of DRP1 in adipose tissue during obesity remain unclear. To elucidate the metabolic and pathological significance of diminished DRP1 in obese adipose tissue, we utilized adipose tissue-specific DRP1 KO mice challenged with a high-fat diet. We observed significant metabolic dysregulations in the KO mice. Mechanistically, DRP1 exerts multifaceted functions in mitochondrial dynamics and endoplasmic reticulum (ER)-lipid droplet crosstalk in normal mice. Loss of function of DRP1 resulted in abnormally giant mitochondrial shapes, distorted mitochondrial membrane structure, and disrupted cristae architecture. Meanwhile, DRP1 deficiency induced the retention of nascent lipid droplets in ER, leading to perturbed overall lipid dynamics in the KO mice. Collectively, dysregulation of the dynamics of mitochondria, ER, and lipid droplets contributes to whole-body metabolic disorders, as evidenced by perturbations in energy metabolites. Our findings demonstrate that DRP1 plays diverse and critical roles in regulating energy metabolism within adipose tissue during the progression of obesity.

Drp1 depletion protects against ferroptotic cell death by preserving mitochondrial integrity and redox homeostasis

Mitochondria are highly dynamic organelles which undergo constant fusion and fission as part of the mitochondrial quality control. In genetic diseases and age-related neurodegenerative disorders, altered mitochondrial fission-fusion dynamics have been linked to impaired mitochondrial quality control, disrupted organelle integrity and function, thereby promoting neural dysfunction and death. The key enzyme regulating mitochondrial fission is the GTPase Dynamin-related Protein 1 (Drp1), which is also considered as a key player in mitochondrial pathways of regulated cell death. In particular, increasing evidence suggests a role for impaired mitochondrial dynamics and integrity in ferroptosis, which is an iron-dependent oxidative cell death pathway with relevance in neurodegeneration. In this study, we demonstrate that CRISPR/Cas9-mediated genetic depletion of Drp1 exerted protective effects against oxidative cell death by ferroptosis through preserved mitochondrial integrity and maintained redox homeostasis. Knockout of Drp1 resulted in mitochondrial elongation, attenuated ferroptosis-mediated impairment of mitochondrial membrane potential, and stabilized iron trafficking and intracellular iron storage. In addition, Drp1 deficiency exerted metabolic effects, with reduced basal and maximal mitochondrial respiration and a metabolic shift towards glycolysis. These metabolic effects further alleviated the mitochondrial contribution to detrimental ROS production thereby significantly enhancing neural cell resilience against ferroptosis. Taken together, this study highlights the key role of Drp1 in mitochondrial pathways of ferroptosis and expose the regulator of mitochondrial dynamics as a potential therapeutic target in neurological diseases involving oxidative dysregulation.

Eriocitrin prevents Sepsis-induced acute kidney injury through anti-inflammation and anti-oxidation via modulating Nrf2/DRP1/OPA1 signaling pathway

BACKGROUND

Severe inflammation and oxidative stress are characteristics of sepsis-associated kidney injury with high morbidity and mortality. Eriocitrin (ERI) has shown promise in suppressing sepsis-associated kidney injury and LPS-induced periodontal disease, however, its efficacy in alleviating SAKI remains unexplored. This study aimed to investigate the therapeutic potential of ERI on SAKI through in vivo and in vitro experiments, elucidating its underlying mechanism.

METHODS

The therapeutic effects of ERI against SAKI were evaluated by survival rate, changes of serum creatinine (Scr) and blood urea nitrogen (BUN) and statistic of renal histological score in a Cecal ligation and puncture (CLP)-induced septic mice. Impactions about anti-coagulation, anti-inflammation, anti-oxidative stress and improvement of mitochondrial damage and mitochondrial morphology were further assayed. In vitro, HUVECs upon stimulation of LPS with or without different dosage of ERI, followed by evaluating changes in inflammation, mitochondrial dynamic equilibrium and signaling pathways.

RESULTS

ERI demonstrated ameliorative effects on SAKI by attenuating inflammation, oxidative stress and coagulation evidenced by the improved survival rate, alleviated kidney histological injury, declined BUN and Scr in serum and diminished levels of inflammation cytokines, and coagulation factors. Mechanistically, ERI suppressed DRP1-regulated mitochondrial fission and promoted OPA1-modulated mitochondrial fusion by activating Nrf2 in septic mice and LPS-stimulated HUVECs, which maintained mitochondrial dynamic equilibrium, improved mitochondrial morphology, assured integrity of mitochondrial function, decreased oxidative stress, impeded overwhelming inflammation, and thus, played a pivotal role in ERI's protection against SAKI.

CONCLUSION

Our data confirmed the therapeutic potential of ERI in mitigating SAKI，suggesting its viability as a pharmacological agent in clinic settings.

The inhibition of inner mitochondrial fusion in hepatocytes reduces non-alcoholic fatty liver and improves metabolic profile during obesity by modulating bile acid conjugation

AIMS

Mitochondria are plastic organelles that continuously undergo biogenesis, fusion, fission, and mitophagy to control cellular energy metabolism, calcium homeostasis, hormones, sterols, and bile acids (BAs) synthesis. Here, we evaluated how the impairment of mitochondrial fusion in hepatocytes affects diet-induced liver steatosis and obesity.

METHODS AND RESULTS

Male mice selectively lacking the key protein involved in inner mitochondrial fusion, optic atrophy 1 (OPA1) (OPA1ΔHep) were fed a high fat diet (HFD) for 20 weeks. OPA1ΔHep mice were protected from the development of hepatic steatosis and obesity because of reduced lipid absorption; a profile which was accompanied by increased respiratory exchange ratio in vivo, suggesting a preference for carbohydrates in OPA1ΔHep compared to controls. At the molecular level, this phenotype emerged as a consequence of poor mitochondria-peroxisome- endoplasmic reticulum (ER) tethering in OPA1 deficient hepatocytes, which impaired BAs conjugation and release in the bile, thus impacting lipid absorption from the diet. Concordantly, the liver of subjects with non-alcoholic fatty liver disease (NAFLD) presented an increased expression of OPA1 and of the network of proteins involved in mitochondrial function when compared with controls.

CONCLUSION

Patients with NAFLD present increased expression of proteins involved in mitochondrial fusion in the liver. The selective deficency of OPA1 in hepatocytes protects mice from HFD-induced metabolic dysfunction by reducing BAs secretion and dietary lipids absorption as a consequence of reduced liver mitochondria-peroxisome-ER tethering.

Myeloid Drp1 Deficiency Limits Revascularization in Ischemic Muscles via Inflammatory Macrophage Polarization and Metabolic Reprograming

In the preclinical model of peripheral arterial disease (PAD), M2-like anti-inflammatory macrophage polarization and angiogenesis are required for revascularization. The regulation of cell metabolism and inflammation in macrophages is tightly linked to mitochondrial dynamics. Drp1, a mitochondrial fission protein, has shown context-dependent macrophage phenotypes with both pro- and anti-inflammatory characteristics. However, the role of macrophage Drp1 in reparative neovascularization remains unexplored. Here we show that Drp1 expression was significantly increased in F4/80+ macrophages within ischemic muscle at day 3 following hindlimb ischemia (HLI), an animal model of PAD. Myeloid-specific Drp1 -/- mice exhibited reduced limb perfusion recovery, angiogenesis and muscle regeneration after HLI. These effects were concomitant with enhancement of pro-inflammatory M1-like macrophages, p-NFkB, and TNFα levels, while showing reduction in anti-inflammatory M2-like macrophages and p-AMPK in ischemic muscle of myeloid Drp1 -/- mice. In vitro, Drp1 -/- macrophages under hypoxia serum starvation (HSS), an in vitro PAD model, demonstrated enhanced glycolysis via reducing p-AMPK as well as mitochondrial dysfunction and excessive mitochondrial ROS, resulting in increased M1-gene and reduced M2-gene expression. Conditioned media from HSS-treated Drp1 -/- macrophages exhibited increased secretion of pro-inflammatory cytokines and suppressed angiogenic responses in cultured endothelial cells. Thus, Drp1 deficiency in macrophages under ischemia drives inflammatory metabolic reprogramming and macrophage polarization, thereby limiting revascularization in experimental PAD.

Coagulation Dysfunctions in Non-Alcoholic Fatty Liver Disease-Oxidative Stress and Inflammation Relevance

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases. Its incidence is progressively rising and it is possibly becoming a worldwide epidemic. NAFLD encompasses a spectrum of diseases accounting for the chronic accumulation of fat within the hepatocytes due to various causes, excluding excessive alcohol consumption. In this study, we aimed to focus on finding evidence regarding the implications of oxidative stress and inflammatory processes that form the multifaceted pathophysiological tableau in relation to thrombotic events that co-occur in NAFLD and associated chronic liver diseases. Recent evidence on the pathophysiology of NAFLD suggests that a complex pattern of multidirectional components, such as prooxidative, proinflammatory, and prothrombotic components, better explains the multiple factors that promote the mechanisms underlying the fatty acid excess and subsequent processes. As there is extensive evidence on the multi-component nature of NAFLD pathophysiology, further studies could address the complex interactions that underlie the development and progression of the disease. Therefore, this study aimed to describe possible pathophysiological mechanisms connecting the molecular impairments with the various clinical manifestations, focusing especially on the interactions among oxidative stress, inflammation, and coagulation dysfunctions. Thus, we described the possible bidirectional modulation among coagulation homeostasis, oxidative stress, and inflammation that occurs in the various stages of NAFLD.

Systematic Transmission Electron Microscopy-Based Identification and 3D Reconstruction of Cellular Degradation Machinery

Various intracellular degradation organelles, including autophagosomes, lysosomes, and endosomes, work in tandem to perform autophagy, which is crucial for cellular homeostasis. Altered autophagy contributes to the pathophysiology of various diseases, including cancers and metabolic diseases. This paper aims to describe an approach to reproducibly identify and distinguish subcellular structures involved in macroautophagy. Methods are provided that help avoid common pitfalls. How to distinguish between lysosomes, lipid droplets, autolysosomes, autophagosomes, and inclusion bodies are also discussed. These methods use transmission electron microscopy (TEM), which is able to generate nanometer-scale micrographs of cellular degradation components in a fixed sample. Serial block face-scanning electron microscopy is also used to visualize the 3D morphology of degradation machinery using the Amira software. In addition to TEM and 3D reconstruction, other imaging techniques are discussed, such as immunofluorescence and immunogold labeling, which can be used to classify cellular organelles, reliably and accurately. Results show how these methods may be used to accurately quantify cellular degradation machinery under various conditions, such as treatment with the endoplasmic reticulum stressor thapsigargin or ablation of the dynamin-related protein 1.

Research progress on the mitochondrial mechanism of age-related non-alcoholic fatty liver

Non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease worldwide. Reduced activity and slower metabolism in the elderly affect the balance of lipid metabolism in the liver leading to the accumulation of lipids. This affects the mitochondrial respiratory chain and the efficiency of β-oxidation and induces the overproduction of reactive oxygen species. In addition, the dynamic balance of the mitochondria is disrupted during the ageing process, which inhibits its phagocytic function and further aggravates liver injury, leading to a higher incidence of NAFLD in the elderly population. The present study reviewed the manifestations, role and mechanism of mitochondrial dysfunction in the progression of NAFLD in the elderly. Based on the understanding of mitochondrial dysfunction and abnormal lipid metabolism, this study discusses the treatment strategies and the potential therapeutic targets for NAFLD, including lipid accumulation, antioxidation, mitophagy and liver-protecting drugs. The purpose is to provide new ideas for the development of innovative drugs for the prevention and treatment of NAFLD.

Mitoregulin controls mitochondrial function and stress-adaptation response during early phase of endoplasmic reticulum stress in breast cancer cells

The proper regulation of mitochondrial function is important for cellular homeostasis. Especially, in cancer cells, dysregulation of mitochondria is associated with diverse cellular events such as metabolism, redox status, and stress responses. Mitoregulin (MTLN), a micro protein encoded by LINC00116, recently has been reported to control mitochondrial functions in skeletal muscle cells and adipocytes. However, the role of MTLN in cancer cells remains unclear. In the present study, we found that MTLN regulates membrane potential and reactive oxygen species (ROS) generation of mitochondria in breast cancer cells. Moreover, MTLN deficiency resulted in abnormal mitochondria-associated ER membranes (MAMs) formation, which is crucial for stress adaptation. Indeed, the MTLN-deficient breast cancer cells failed to successfully resolve ER (endoplasmic reticulum) stress, and cell vulnerability to ER-stress inducers was significantly enhanced by the downregulation of MTLN. In conclusion, MTLN controls stress-adaptation responses in breast cancer cells as a key regulator of mitochondria-ER harmonization, and thereby its expression level may serve as an indicator of the responsiveness of cancer cells to proteasome inhibitors.