Mdivi-1 suppresses Drp1 mitochondrial fission to protect diabetic myocardium from ischemia-reperfusion injury
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Myocardial ischemia-reperfusion (MI/R) injury represents a severe clinical complication in ischemic heart disease, particularly within diabetic populations. Diabetic hearts exhibit heightened vulnerability to reperfusion-induced cellular death due to pre-existing metabolic perturbations and altered mitochondrial homeostasis. Dynamin-related protein 1 (Drp1), a cytosolic GTPase, serves as a central orchestrator of mitochondrial division. Under baseline physiological conditions, a dynamic equilibrium between fusion and fission processes maintains organelle network integrity and energetic efficiency. However, under diabetic ischemic stress, hyperactivation of Drp1 disrupts this balance, driving aberrant mitochondrial fragmentation. Cytosolic Drp1 undergoes post-translational modification and translocates to the outer mitochondrial membrane (OMM). At the OMM, Drp1 docks onto receptor complexes including mitochondrial fission factor (Mff) and mitochondrial dynamics proteins of 49 and 51 kDa (MiD49 and MiD51). Upon target engagement, Drp1 oligomerizes into spiraling rings that constrict both outer and inner mitochondrial membranes through GTP hydrolysis.
In a diabetic murine model subjected to transient coronary artery occlusion followed by reperfusion, Drp1 translocation to the mitochondrial fraction increased substantially within early reperfusion phases. This pathological recruitment induced severe mitochondrial network fragmentation, characterized by disrupted cristae architecture, loss of inner membrane potential, and organelle swelling. Pharmacological intervention using Mdivi-1 (1.2 mg/kg), administered 15 minutes prior to reperfusion, effectively blocked Drp1 migration to the mitochondrial outer membrane. By preventing Drp1 recruitment and oligomerization at the OMM, Mdivi-1 attenuated excessive fission, maintaining tubular mitochondrial morphology across diabetic ventricular cardiomyocytes.
The mitigation of aberrant fission by Mdivi-1 directly preserved mitochondrial bioenergetics. Uncontrolled mitochondrial division leads to physical disorganization of respiratory supercomplexes within the inner membrane. In vehicle-treated diabetic hearts, ischemia-reperfusion severely impaired electron transport chain (ETC) function, particularly complex I and complex III enzymatic throughput. Intervention with Mdivi-1 preserved complex I and complex III activities, which in turn maintained cellular adenosine triphosphate (ATP) content during early reperfusion. Preserving respiratory chain efficiency reduced electron leakage, limiting the generation of damaging superoxide radicals.
Targeting Drp1 also suppressed systemic oxidative stress and lipid damage within the reperfused diabetic tissue. Empirical assays revealed that Mdivi-1 treatment elevated the activity of manganese superoxide dismutase (MnSOD), a vital primary antioxidant enzyme localized within the mitochondrial matrix. Concurrently, levels of malondialdehyde (MDA), a quantitative product of lipid peroxidation, decreased significantly in Mdivi-1-treated myocardium compared to untreated diabetic controls. This dual reduction in ROS accumulation and lipid peroxidation protected cellular membrane structures from oxidative degradation.
This attenuation of mitochondrial dysregulation halted apoptotic cell death cascades in diabetic cardiomyocytes. Pathological fission and elevated ROS promote mitochondrial permeability transition pore (mPTP) opening, triggering cytochrome c release into the cytosol and activating caspase-3. Pre-reperfusion treatment with Mdivi-1 markedly suppressed cardiomyocyte apoptosis, as shown by reduced terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positivity within the peri-infarct border zone. Consequently, Mdivi-1 treatment produced a significant reduction in total myocardial infarct size relative to area at risk.
Cardioprotection at the cellular level translated directly into enhanced cardiac physiological recovery. Hemodynamic assessments demonstrated that Mdivi-1 improved left ventricular developed pressure (LVDP) and maximized rates of pressure development (+dP/dt max), while dampening left ventricular end-diastolic pressure (LVEDP) during post-ischemic reperfusion. These empirical findings demonstrate that pharmacological inhibition of Drp1 by Mdivi-1 exerts profound cardioprotective effects in diabetic hearts subjected to ischemia-reperfusion injury.
Pharmacological Evaluation and Cardiac Functional Preservation
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Mdivi-1 selectively inhibits Dynamin-related protein 1 (Drp1), blocking its translocation to the outer mitochondrial membrane during myocardial ischemia-reperfusion injury in diabetic hearts. Inhibiting Drp1 prevents excessive mitochondrial fission, preserving reticular architecture and electron transport chain complex activity. This bioenergetic stabilization decreases reactive oxygen species generation, enhances manganese superoxide dismutase activity, and limits lipid peroxidation. Consequently, Mdivi-1 suppresses mitochondrial apoptotic pathways, reduces cardiomyocyte death, decreases myocardial infarct size, and enhances functional cardiac recovery following ischemic insult.
Attenuation of Drp1 Translocation Restores Mitochondrial Bioenergetics
In diabetic murine models, reperfusion insult triggers cytosolic Drp1 phosphorylation and translocation to the outer mitochondrial membrane. Mdivi-1 blocks this spatial redistribution effectively. Mitochondrial reticular networks remained intact under treated conditions. Electron transport chain activities were preserved. Specifically, complex I and complex III activities remained higher in Mdivi-1 treated cohorts than in untreated diabetic controls. Adenosine triphosphate levels increased concurrently. Reduced mitochondrial fragmentation prevented the collapse of the mitochondrial membrane potential. Consequently, ROS production declined. Enzymatic assays revealed increased manganese superoxide dismutase activity alongside suppressed malondialdehyde production. These findings confirm that targeting Drp1 limits metabolic collapse during early reperfusion.
Inhibition of Fission Suppresses Apoptosis and Reduces Infarct Area
Excessive mitochondrial division precedes outer membrane permeabilization and pro-apoptotic factor release. In this diabetic ischemia-reperfusion setting, Drp1 inhibition limited apoptotic signal propagation. Cardiomyocyte death was quantified via TUNEL staining. Apoptotic indices dropped sharply in treated myocardium; nuclear fragmentation was reduced across peri-infarct zones. Myocardial infarct size decreased following pre-reperfusion administration of Mdivi-1 (1.2 mg/kg). Hemodynamic measurements reflected these structural benefits. Left ventricular end-diastolic pressure normalized, while peak rate of pressure rise improved significantly. However, these cardioprotective outcomes remain restricted to preclinical rodent models; translational efficacy in human diabetic populations requires further clinical evaluation.