Electron transfer flavoprotein subunit beta suppresses hypoxia/reoxygenation-induced mitochondrial dysfunction and apoptosis in cardiomyocytes

Megalin contributes to the early injury of proximal tubule cells during nonselective proteinuria

Reactive oxygen species (ROS) are hypothesized to play a key role in myocardial ischemia-reperfusion (IR) injury after cardiopulmonary bypass in children. Clinical studies in adults and several animal models suggest that myocardial IR injury involves cardiomyocyte apoptosis and necrosis. This study investigated a potential relationship between IR-induced ROS production and neonatal cardiomyocyte apoptosis using both in vitro and ex vivo techniques. For in vitro experiments, embryonic rat cardiomyocytes (H9c2 cells) exposed to hypoxia-reoxygenation (HR) showed a time-dependent increase in gp91 phox (a marker for ROS production by NADPH oxidases), caspase-3 (a key mediator of apoptosis) expression, and a decrease in the glutathione redox ratio. N-acetylcysteine (NAC; 0.25-2 mM), a potent antioxidant, decreased gp91 phox and caspase-3 expression, inhibited apoptosis and restored the glutathione redox ratio. For ex vivo study, IR injury significantly reduced left ventricular (LV) function and increased the expression of gp91 phox and caspase-3 in Langendorff-perfused neonatal (7-14 d) rabbit hearts. NAC (0.4 mM) treatment completely attenuated LV dysfunction after IR. In summary, neonatal myocardial IR injury is associated with an increase in cardiomyocyte oxidative stress and apoptosis. NAC attenuates apoptosis in an in vitro embryonic rat cardiomyocyte model of HR, and myocardial dysfunction in an ex vivo neonatal rabbit model of myocardial IR injury.

Genetic Podocyte Lineage Reveals Progressive Podocytopenia with Parietal Cell Hyperplasia in a Murine Model of Cellular/Collapsing Focal Segmental Glomerulosclerosis

Hederagenin (HDG), a medical herb, is known for its beneficial activities against diverse diseases. The cardioprotective effect of HDG has been preliminarily disclosed, but the efficacy and underlying mechanism by which HDG protects against myocardial ischemia-reperfusion (MI/R) injury have not been elucidated yet. To simulate MI/R injury, the left anterior descending artery was occluded for 30min and then reperfusion for 120min in a rat model, and the cellular model of hypoxia-reoxygenation (H/R) injury was constructed in H9c2 cardiomyocytes. Hematoxylin-eosin, Prussian blue, and 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) staining were conducted to assess the histological injury, iron deposition, and myocardial infarction. Myocardial enzymes and oxidative stress-related factors were detected using their commercial kits. Lipid peroxidation was measured using BODIPY581/591 probe, and iron content was detected. Cell counting kit (CCK)-8, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), and flow cytometry assays were performed to assess cell viability and apoptosis. Protein levels were investigated by western blot. The interaction between HDG and 5-lipoxygenase (ALOX5) was verified using molecular docking. Our findings indicated that HDG significantly attenuated myocardial dysfunction by reducing infarction and myocardial injury. HDG significantly attenuated myocardial apoptosis in vitro and in vivo, as well as alleviating oxidative stress via reducing reactive oxygen species (ROS) and maintaining the balance between antioxidant and oxidant enzymes. Meanwhile, HDG inhibited I/R-induced ferroptosis in myocardium and cardiomyocytes, including reducing lipid peroxidation and iron level. Moreover, the binding relationship between HDG and ALOX5 was verified, and HDG could concentration dependently downregulate ALOX5. Furthermore, ALOX5 overexpression eliminated the inhibition of HDG on H/R-induced apoptosis, oxidative stress, and ferroptosis in H9c2 cardiomyocytes. HDG ameliorated myocardial dysfunction and cardiomyocyte injury by reducing apoptosis, oxidative stress, and ferroptosis through inhibiting ALOX5, providing a new perspective on the prevention and treatment of MI/R injury.

Background Myocardial injury refers to a major complication that occurs in myocardial ischemia/reperfusion injury (MI/RI). Honokiol is a well-recognized active compound extracted from the traditional Chinese herb known as Magnolia officinalis and is utilized in treating different vascular diseases. This research is aimed at examining whether Honokiol might alleviate myocardial injury in an MI/RI model. Methods Seventy-eight male C57BL/6 mice were categorized randomly into three cohorts including the Sham operation (Sham) cohort, the MI/RI cohort (Con), and the Honokiol cohort (n = 26 for each cohort). The mice in the Honokiol cohort were treated with Honokiol before MI/RI surgery (0.2 mg/kg/day for 14 days, intraperitoneal), while the mice in the Con cohort were given an intraperitoneal injection with an equivalent volume of vehicle (DMSO) daily in 14 days prior to exposure to MI/RI. After the surgery, creatine kinase- (CK-) MB and cardiac troponin T (cTnT) levels, as well as the infarct area, were measured to assess the degree of myocardial damage. Apoptotic levels were detected using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. Electron microscopy was utilized to identify mitochondrial damage. Lastly, the expression levels of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), cleaved caspase-9, cytochrome C (Cyt-C), B cell lymphoma/leukemia-2 (Bcl-2), B cell lymphoma/leukemia-2 associated X (Bax), AKT, p-AKT, PI3K, and p-PI3K were analyzed utilizing western blotting. Results Honokiol can reduce the MI/RI-induced cTnT and CK-MB levels, apoptosis index, and mitochondrial swelling in cardiomyocytes via activating the PI3K/AKT signaling pathway. Conclusion Honokiol provides cardiac protection from MI/RI by suppressing mitochondrial apoptosis through the PI3K/AKT signaling pathway.

Background: Myocardial ischemia-reperfusion (IR) injury limits the beneficial effects of early reperfusion therapy for acute myocardial infarction. Emerging evidence suggests that 7-ketocholesterol (7-KC), one of the most common dietary oxysterols, has pro-inflammatory properties and correlates with cardiovascular diseases. However, the underlying mechanisms remain scant. Here we investigated the effects of 7-KC on myocardial IR injury in mice. Methods and Results: Wild type mice were fed either a control high-fat high-cholesterol diet (HFHCD) or HFHCD containing 7-KC (7KC-HFHCD) for three weeks. In a murine model of 30-min myocardial ischemia and subsequent reperfusion, dietary 7KC-HFHCD increased plasma 7-KC level (145 ± 89.7 ng/mL vs 399 ± 175 ng/mL, P<0.0005, N=8) and infarct size after myocardial IR (52 ± 7.3% vs 64 ± 6.9%, P<0.05, N=8-10) without affecting blood pressure and heart rate. The ratio of Ly-6C high inflammatory monocytes to total monocytes increased in 7KC-HFHCD group as assessed by flow cytometric analysis (49 ± 15% vs 61 ± 9.3%, P<0.05, N=6). We then took a systems approach to explore the pro-inflammatory effects of 7-KC on macrophages and performed unbiased RNA-sequencing using murine peritoneal macrophages stimulated with 7-KC. Pathway analysis of differentially expressed transcripts revealed that 7-KC regulated the expression of transcripts related to inflammation, cholesterol biosynthesis and endoplasmic reticulum (ER) stress. We further validated in vitro that 7-KC induced ER stress, mitochondrial reactive oxygen species, and nuclear factor-kappa B activation associated with increased mRNA levels of pro-inflammatory cytokines such as MCP-1 and TNF-α in murine peritoneal macrophages. Administration of N-acetyl-L-cysteine (5mM), an antioxidant, decreased 7-KC-induced pro-inflammatory cytokines, and this decrease was not observed in Tlr4 -/- murine macrophages, or in macrophages transfected with liver X receptor siRNA. Conclusions: Dietary 7-KC exacerbated myocardial IR injury through macrophage-mediated inflammation in mice. Oxidative stress is involved in the 7-KC-induced pro-inflammatory response in macrophages. Dietary oxysterols are a promising therapeutic target for IR injury.

Myocardial ischemia-reperfusion injury (MIRI) significantly compromises the clinical benefits of revascularization and constitutes a central pathological mechanism worsening prognosis in myocardial infarction patients. Accordingly, dissecting the molecular mechanisms underlying MIRI and formulating effective therapeutic interventions are of great clinical significance. Lycium barbarum polysaccharide (LBP), the primary active constituent of Lycium barbarum, has garnered considerable attention in the prevention and treatment of cardiovascular diseases due to its anti-inflammatory, antioxidant, vasomotor function-improving, and antithrombotic properties. This study aims to investigate the ability of LBP to alleviate MIRI, with a specific focus on its role in modulating the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome. Myocardial ischemia/reperfusion (I/R) models in rats and hypoxia/reoxygenation (H/R) models in H9c2 cells were established. Myocardial injury and the therapeutic effect of LBP were evaluated by 2,3,5-Triphenyl tetrazolium chloride (TTC) staining, Hematoxylin-eosin (H&E) staining, Terminal deoxynucleotidyl transferase dUTP Nick-End Labeling (TUNEL) staining, and Enzyme-linked immunosorbent assay (ELISA). To elucidate the specific mechanism underlying LBP against MIRI, an Nrf2-overexpressing cell line was generated in H9c2 cells, and pharmacological inhibition of Nrf2 with ML385 was applied for complementary validation. The effects of LBP on H/R-induced oxidative stress, inflammatory response (IL-18, IL-1β), and pyroptosis-related protein expression (NLRP3, apoptosis associated speck-like protein containing a CARD (ASC), cysteine-dependent aspartate-specific proteases (caspase)-1, Gasdermin D (GSDMD)) were systematically evaluated. LBP administration conferred robust cardioprotection in I/R rats, as evidenced by a significant reduction in myocardial infarct size, improved preservation of myocardial fiber architecture, and attenuated leakage of cardiac injury biomarkers (lactate dehydrogenase (LDH) and creatine kinase-MB (CK-MB)). Mirroring these in vivo findings, LBP pretreatment effectively shielded H9c2 cardiomyocytes from H/R insult, markedly enhancing cell viability while curtailing reactive oxygen species (ROS) accumulation and apoptotic activation. A pivotal finding was the pronounced downregulation of Nrf2 in the H/R group, a deficit that was conclusively reversed by LBP treatment. To decisively establish a causal role for Nrf2, we employed a loss-of-function approach; Nrf2 inhibition completely abrogated the protective benefits of LBP, culminating in exacerbated tissue damage, a surge in ROS, and the upregulation of key pyroptosis effectors (NLRP3, ASC, caspase-1, GSDMD). Conversely, a complementary gain-of-function experiment demonstrated that Nrf2 overexpression alone was sufficient to mimic LBP's effects, significantly blunting H/R-induced ROS production and pyroptosis. LBP alleviates MIRI by inhibiting pyroptosis through activating the Nrf2/NLRP3 axis, thus representing a promising therapeutic candidate for ischemic heart disease with the potential to improve patient outcomes.

Objective: To investigate the effect of the L-arginine (L-Arg) on function of the myocardial mitochondrial during myocardial ischemia - reperfusion (MIR). Methods: Thirty rabbits were randomly divided into three groups (n =10 per group), namely control group, myocardial ischemia-reperfusion group (MIR) and L-Arginine pre-treated group (L-Arg +MIR). The relevant parameters, including myocardial mitochondrial respiratory function, Ca 2 + concentration ((Ca 2 + ) m ), malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, myocardial adenosine triphosphate (ATP), Adenosine diphosphate (ADP), adenosine monophosphate (AMP) content, the total amount of AMP (TAN), and energy charge (EC), were respectively determined. Results: The mitochondrial respiratory control rate (RCR), Ⅲ state respiration rate (V3), and SOD in L-Arg +MIR group were significantly higher than those of MIR group, while Ⅳ state respiration rate (V4), ((Ca 2+ )m, and MDA were significantly lower than those of MIR group, myocardial ATP, ADP, TNA and the EC were significantly higher than those of group MIR; when compared with the group C, there was no significant difference in terms of V3, V4, SOD, MDA, and AMP, TAN between the L-Arg +MIR group and control group (group C). Conclusion: It is indicated that L-arginine can reduce the level of the oxygen free radicals and attenuate calcium overload to improve the function of myocardial mitochondria during myocardial ischemia reperfusion injury.

Hyperbaric oxygen preconditioning inhibits skin flap apoptosis in a rat ischemia–reperfusion model

Myocardial ischemia-reperfusion (IR) injury contributes to adverse cardiac outcomes after myocardial ischemia, cardiac surgery, or circulatory arrest. In this study, we evaluated the ability of combined SS31-mitochondria (Mito) therapy to protect heart cells from myocardial IR injury. Adult male SD rats (n = 8/each group) were randomized: group 1 (sham-operated control), group 2 (IR, 30-min ischemia/72 h reperfusion), group 3 (IR-SS31 (2 mg intra-peritoneal injection at 30 min/24 h/48 h after IR)), group 4 (IR-mitochondria (2 mg/derived from donor liver/intra-venous administration/30 min after IR procedure)), and group 5 (IR-SS31-mitochondria). In H9C2 cells, SS31 suppressed menadione-induced oxidative-stress markers (NOX-1, NOX-2, oxidized protein) while it increased SIRT1/SIRT3 expression and ATP levels. In adult male rats 72 h after IR, left ventricular ejection fraction (LVEF) was highest in sham-operated control animals and lowest in the IR group. LVEF was also higher in IR rats treated with SS31-Mito than untreated IR rats or those treated with Mito or SS31 alone. Areas of fibrosis/collagen-deposition showed the opposite pattern. Likewise, levels of oxidative-stress markers (NOX-1, NOX-2, oxidized protein), inflammatory markers (MMP-9, CD11, IL-1β, TNF-α), apoptotic markers (mitochondrial-Bax, cleaved-caspase-3, PARP), fibrosis markers (p-Smad3, TGF-β), DNA-damage (γ-H2AX), sarcomere-length, and pressure/volume overload markers (BNP, β-MHC) all showed a pattern opposite that of LVEF. Conversely, anti-apoptotic (BMP-2, Smad1/5) and energy integrity (PGC-1α/mitochondrial cytochrome-C) markers exhibited a pattern identical to that of LVEF. This study demonstrates that the combined SS31-Mito therapy is superior to either therapy alone for protecting myocardium from IR injury and indicates that the responsible mechanisms involved increased SIRT1/SIRT3 expression, which suppresses inflammation and oxidative stress and protects mitochondrial integrity.

Myocardial ischemia-reperfusion (IR) injury is a key pathological process that causes adverse outcomes following revascularization in acute myocardial infarction. This process is mainly driven by mitochondrial dysfunction, oxidative stress, and inflammatory cascades. Although procyanidin B2 (PCB2), a natural polyphenol, exhibits strong antioxidant and anti-inflammatory properties, its clinical use remains limited due to poor targeting, unfavorable pharmacokinetics, and oxidative instability. Herein, we developed a dual pH- and reactive oxygen species-responsive hydrogel (poly(vinyl alcohol)-TSPBA [N1-(4-boronobenzyl)-N3-(4-boronophenyl)-N1,N1,N3,N3-teramethylpropane-1,3-diaminium]) using phenylboronic acid ester cross-linking to enable the microenvironment-responsive, on-demand release of PCB2. Dynamic rheology, scanning electron microscopy, and degradation assays confirmed the hydrogel's excellent mechanical properties and responsiveness to microenvironmental changes. In vitro experiments demonstrated that the PCB2-loaded hydrogel effectively scavenged DPPH radicals and H2O2 while substantially reducing oxidative damage in H9C2 cardiomyocytes. Mechanistically, PCB2 may reduce NRF2 ubiquitination-mediated degradation, thereby modulating the KEAP1-NRF2 pathway to activate downstream antioxidant response elements and restore mitochondrial membrane potential. Additionally, PCB2 reversed lipopolysaccharide- and interferon-γ-induced M1 macrophage polarization, inhibited nuclear factor κB phosphorylation, and reduced the secretion of pro-inflammatory cytokines. Following intramyocardial injection of the PCB2-loaded hydrogel in a rat IR model, oxidative stress was significantly reduced, cardiac function was improved, infarct size was diminished, and fibrotic remodeling was inhibited. Transmission electron microscopy confirmed the restoration of mitochondrial cristae integrity. This study provides evidence for a synergistic multimodal approach that combines mitochondrial protection, antioxidant defense, and anti-inflammatory modulation, supported by comprehensive validation across material design, molecular mechanisms, and therapeutic efficacy. Our findings contribute to the advancement of a microenvironment-adaptive nanotherapeutic paradigm for precision intervention in myocardial IR injury.

Diabetes and myocardial ischemia reperfusion (MIR) injury are characterized by oxidative stress, inflammation, autophagy disorders, and cardiac contractile dysfunction. Klotho and SIRT1 regulate the level of oxidative stress to participate in the regulation of many physiological functions such as cell survival, aging, apoptosis, autophagy, mitochondrial biogenesis, and inflammation. We hypothesized that the activation of Klotho/SIRT1 signaling pathway could attenuate MIR in diabetic rats. Type 1 diabetes and MIR injury model were established to examine this hypothesis in vivo . Primary rat cardiomyocytes and H9c2 cells were exposed to high glucose conditions and hypoxia/reoxygenation (H/R) insult in vitro . Hemodynamic parameters of heart function, myocardial infarct size, oxidative stress, markers of MIR injury or cell viability, and the mRNA and protein expression of Klotho and SIRT1 were measured. There was lower expression of Klotho and SIRT1 in diabetic MIR hearts than in nondiabetic rats, as well as significantly increased oxidative stress levels and decreased autophagy levels. Recombinant Klotho (rKlotho) protein and the SIRT1 agonist SRT1720 could significantly attenuate MIR injury in diabetes by activating Klotho/SIRT1 signaling pathway to reduce oxidative stress and restore autophagy levels. These findings suggest that the Klotho/SIRT1 pathway plays an important role in MIR injury in diabetic rats, and rKlotho protein and agonist SRT1720 have therapeutic potential for alleviating diabetic myocardial IR injury by activating Klotho/SIRT1 to reduce oxidative stress and restore autophagy levels.

Nrf2 participates in the protective effect of exogenous mitochondria against mitochondrial dysfunction in myocardial ischaemic and hypoxic injury

This study aimed to evaluate the protective effects of total flavonoid extract from Coreopsis tinctoria Nutt. (CTF) against myocardial ischemia/reperfusion injury (MIRI) using an isolated Langendorff rat heart model. Left ventricular developed pressure (LVDP) and the maximum rate of rise and fall of LV pressure (±dp/dtmax) were recorded. Cardiac injury was assessed by analyzing lactate dehydrogenase (LDH) and creatine kinase (CK) released in the coronary effluent. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) levels were determined. Myocardial inflammation was assessed by monitoring tumor necrosis factor-alpha (TNF-α), C-reactive protein (CRP), interleukin-8 (IL-8), and interleukin-6 (IL-6) levels. Myocardial infarct size was estimated. Cell morphology was assessed by 2,3,5-triphenyltetrazolium chloride and hematoxylin and eosin (HE) staining. Cardiomyocyte apoptosis was determined by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining. Pretreatment with CTF significantly increased the heart rate and increased LVDP, as well as SOD and GSH-Px levels. In addition, CTF pretreatment decreased the TUNEL-positive cell ratio, infarct size, and levels of CK, LDH, MDA, TNF-α, CRP, IL-6, and IL-8. These results suggest that CTF exerts cardio-protective effects against MIRI via anti-oxidant, anti-inflammatory, and anti-apoptotic activities.

Objective: To investigate the effect of L-arginine (L-Arg) on the function of myocardial mitochondria during myocardia ischemia - reperfusion (IR). Methods: Dividing randomly the 30 rabbits into three groups (n=10): control group (C), myocardia ischemiareperfusion group (IR) and L-Arginine pretreatment group (L-Arg+IR). The relevant parameters, including myocardial mitochondria respiratory function, Ca2+ concentration ([Ca2+]), malondialdehyde (MDA) concentration, superoxide dismutase (SOD) activity, myocardial adenosine triphosphate (ATP), Adenosine diphosphate (ADP), adenosine monophosphate (AMP) content, the total amount of AMP (TAN, TAN=ATP+ADP+AMP) and energy charge (EC, EC=1/2ADP+ATP/TAN) were determined, respectively. Results: The mitochondria respiratory control rate (RCR), III state respiration rate (V3), and SOD in group L-Arg +IR were significantly higher than those in group IR, while IV state respiration rate (V4) , [Ca2+] m, and MDA were obviously lower than those of group IR, the levels of ATP, ADP, TNA and the EC of myocardium showed significantly higher than those in group IR. There were no significant differences in terms of V3, V4, SOD, MDA, AMP and TAN between group L-Arg+IR and group C. Conclusion: It indicated that L-arginine can reduce the level of the oxygen free radicals and partly attenuatecalcium overload to improve the function of myocardial mitochondria during myocardium ischemia reperfusion injury.