Effect of Metformin on Myocardial Injury Induced by Hepatic Ischemia-Reperfusion in Rats

Metformin attenuates myocardial ischemia/reperfusion-induced ferroptosis through the upregulation of Nur77-mediated IDH1

Current interventions for myocardial ischemia/reperfusion (I/R) injury focus on revascularization and the control of oxidative stress. Metformin can reduce I/R injury, with its protective effects extending beyond metabolic regulation. In this study, we investigated the cardioprotective mechanisms of metformin beyond AMPK activation, focusing on its effects on the Nur77-IDH1 axis. We employed myocardial I/R rat models and oxygen-glucose deprivation/reoxygenation in H9C2 cells, utilizing staining techniques, echocardiography, and molecular/cell-based assays. Metformin significantly mitigated myocardial I/R injury in rats, reducing PTGS2 expression, lowering iron content, decreased ROS accumulation, and increased mitochondrial function. Metformin also alleviated myocardial tissue damage and fibrosis and increased survival rates. In OGD/R-induced H9C2 cells, metformin suppressed ferroptosis, which could be reversed by Nur77 silencing. Metformin increased Nur77 and IDH1 expression by enhancing Nur77 translocation to the IDH1 promoter, inhibiting stress-related JNK/P38MAPK signaling. Catalytic site inhibitor IDH1 Inhibitor 5 (compound 2 AGI-5198) negated the protective effects of metformin. Collectively, these data reveal that metformin prevents myocardial I/R injury and ferroptosis through its effects on Nur77, IDH1 expression and inhibition of the JNK/P38 pathway. This highlights the novel therapeutic value of targeting ferroptosis with metformin to improve cardiac protection.

Vagus nerve stimulation alleviates myocardial injury following hepatic ischemia-reperfusion in rats by inhibiting ferroptosis via the activation of the SLC7A11/GPX4 axis

BACKGROUND

Vagus nerve stimulation (VNS) exhibits protective effects against remote organ injury following ischemia-reperfusion (I/R). However, its effects on acute myocardial injury induced by hepatic I/R in rats, and the underlying mechanisms, remain unclear.

METHODS

Thirty male rats were randomly assigned to five groups: Sham, I/R, VNS, VNS + Erastin, and VNS + DMSO. A hepatic I/R injury model was established by occluding the arterial and portal veins of the left and middle lobes of the liver for 1 h followed by 6 h of reperfusion. VNS was performed throughout the hepatic I/R process. Erastin was administered intraperitoneally 60 min before hepatic ischemia. Blood samples were collected from the left common carotid artery post-reperfusion to measure liver injury markers (alanine aminotransferase [ALT] and aspartate aminotransferase [AST]) and the myocardial injury marker (cardiac troponin I [cTnI]). Left ventricular myocardial tissue was also collected for ultrastructural analysis via transmission electron microscopy, reactive oxygen species (ROS) detection using dihydroethidium staining, and measurements of Fe2⁺ levels, malondialdehyde (MDA) concentration, glutathione (GSH) levels, and superoxide dismutase (SOD) activity. Western blotting assessed the expression of ferroptosis-related proteins SLC7A11 and GPX4 in the myocardial tissue.

RESULTS

VNS significantly reduced serum levels of ALT, AST, and cTnI, while also mitigating mitochondrial damage in cardiomyocytes. Additionally, VNS decreased ROS levels, alleviated iron overload, and reduced lipid peroxidation in myocardial tissue. These protective effects were associated with the activation of the SLC7A11/GPX4 axis, as evidenced by increased expression of these proteins in the VNS group. However, the cardioprotective effects of VNS were negated by the ferroptosis activator erastin, indicating that ferroptosis is involved in VNS-mediated cardioprotection.

CONCLUSION

VNS protects against myocardial injury from hepatic ischemia-reperfusion, likely by inhibiting oxidative stress and ferroptosis through activation of the SLC7A11/GPX4 axis.

Current status and perspective on molecular targets and therapeutic intervention strategy in hepatic ischemia-reperfusion injury

Hepatic ischemia‒reperfusion injury (HIRI) is a common and inevitable complication of hepatic trauma, liver resection, or liver transplantation. It contributes to postoperative organ failure or tissue rejection, eventually affecting patient prognosis and overall survival. The pathological mechanism of HIRI is highly complex and has not yet been fully elucidated. The proposed underlying mechanisms include mitochondrial damage, oxidative stress imbalance, abnormal cell death, immune cell hyperactivation, intracellular inflammatory disorders and other complex events. In addition to serious clinical limitations, available antagonistic drugs and specific treatment regimens are still lacking. Therefore, there is an urgent need to not only clarify the exact etiology of HIRI but also reveal the possible reactions and bottlenecks of existing drugs, helping to reduce morbidity and shorten hospitalizations. We analyzed the possible underlying mechanism of HIRI, discussed various outcomes among different animal models and explored neglected potential therapeutic strategies for HIRI treatment. By thoroughly reviewing and analyzing the literature on HIRI, we gained a comprehensive understanding of the current research status in related fields and identified valuable references for future clinical and scientific investigations.

Lipid droplets, autophagy, and ER stress as key (survival) pathways during ischemia-reperfusion of transplanted grafts

Ischemia-reperfusion injury is an event concerning any organ under a procedure of transplantation. The early result of ischemia is hypoxia, which causes malfunction of mitochondria and decrease in cellular ATP. This leads to disruption of cellular metabolism. Reperfusion also results in cell damage due to reoxygenation and increased production of reactive oxygen species, and later by induced inflammation. In damaged and hypoxic cells, the endoplasmic reticulum (ER) stress pathway is activated by increased amount of damaged or misfolded proteins, accumulation of free fatty acids and other lipids due to inability of their oxidation (lipotoxicity). ER stress is an adaptive response and a survival pathway, however, its prolonged activity eventually lead to induction of apoptosis. Sustaining cell functionality in stress conditions is a great challenge for transplant surgeons as it is crucial for maintaining a desired level of graft vitality. Pathways counteracting negative consequences of ischemia-reperfusion are autophagy and lipid droplets (LD) metabolism. Autophagy remove damaged organelles and molecules driving them to lysosomes, digested simpler compounds are energy source for the cell. Mitophagy and ER-phagy results in improvement of cell energetic balance and alleviation of ER stress. This is important in sustaining metabolic homeostasis and thus cell survival. LD metabolism is connected with autophagy as LD are degraded by lipophagy, a source of free fatty acids and glycerol-thus autophagy and LD can readily remove lipotoxic compounds in the cell. In conclusion, monitoring and pharmaceutic regulation of those pathways during transplantation procedure might result in increased/improved vitality of transplanted organ.

Hepatic ischemia-reperfusion syndrome and its effect on the cardiovascular system: The role of treprostinil, a synthetic prostacyclin analog

Hepatic ischemia-reperfusion syndrome has been the subject of intensive study and experimentation in recent decades since it is responsible for the outcome of several clinical entities, such as major hepatic resections and liver transplantation. In addition to the organ's post reperfusion injury, this syndrome appears to play a central role in the dysfunction of distant tissues and systems. Thus, continuous research should be directed toward finding effective therapeutic options to improve the outcome and reduce the postoperative morbidity and mortality rates. Treprostinil is a synthetic analog of prostaglandin I2, and its experimental administration has shown encouraging results. It has already been approved by the Food and Drug Administration in the United States for pulmonary arterial hypertension and has been used in liver transplantation, where preliminary encouraging results showed its safety and feasibility by using continuous intravenous administration at a dose of 5 ng/kg/min. Treprostinil improves renal and hepatic function, diminishes hepatic oxidative stress and lipid peroxidation, reduces hepatictoll-like receptor 9 and inflammation, inhibits hepatic apoptosis and restores hepatic adenosine triphosphate (ATP) levels and ATP synthases, which is necessary for functional maintenance of mitochondria. Treprostinil exhibits vasodilatory properties and antiplatelet activity and regulates proinflammatory cytokines; therefore, it can potentially minimize ischemia-reperfusion injury. Additionally, it may have beneficial effects on cardiovascular parameters, and much current research interest is concentrated on this compound.