Alox15/15-HpETE Aggravates Myocardial Ischemia-Reperfusion Injury by Promoting Cardiomyocyte Ferroptosis

by Selleckchem | Nov 01 2023

Background: Myocardial ischemia-reperfusion (I/R) injury causes cardiac dysfunction to myocardial cell loss and fibrosis. Prevention of cell death is important to protect cardiac function after I/R injury. The process of reperfusion can lead to multiple types of cardiomyocyte death, including necrosis, apoptosis, autophagy, and ferroptosis. However, the time point at which the various modes of cell death occur after reperfusion injury and the mechanisms underlying ferroptosis regulation in cardiomyocytes are still unclear.

Methods: Using a left anterior descending coronary artery ligation mouse model, we sought to investigate the time point at which the various modes of cell death occur after reperfusion injury. To discover the key molecules involved in cardiomyocyte ferroptosis, we performed a metabolomics study. Loss/gain-of-function approaches were used to understand the role of 15-lipoxygenase (Alox15) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc1α) in myocardial I/R injury.

Results: We found that apoptosis and necrosis occurred in the early phase of I/R injury, and that ferroptosis was the predominant form of cell death during the prolonged reperfusion. Metabolomic profiling of eicosanoids revealed that Alox15 metabolites accumulated in ferroptotic cardiomyocytes. We demonstrated that Alox15 expression was specifically increased in the injured area of the left ventricle below the suture and colocalized with cardiomyocytes. Furthermore, myocardial-specific knockout of Alox15 in mice alleviated I/R injury and restored cardiac function. 15-Hydroperoxyeicosatetraenoic acid (15-HpETE), an intermediate metabolite derived from arachidonic acid by Alox15, was identified as a trigger for cardiomyocyte ferroptosis. We explored the mechanism underlying its effects and found that 15-HpETE promoted the binding of Pgc1α to the ubiquitin ligase ring finger protein 34, leading to its ubiquitin-dependent degradation. Consequently, attenuated mitochondrial biogenesis and abnormal mitochondrial morphology were observed. ML351, a specific inhibitor of Alox15, increased the protein level of Pgc1α, inhibited cardiomyocyte ferroptosis, protected the injured myocardium, and caused cardiac function recovery.

Conclusions: Together, our results established that Alox15/15-HpETE-mediated cardiomyocyte ferroptosis plays an important role in prolonged I/R injury.

Comments:

The study described above investigated the different modes of cell death occurring at various time points after myocardial ischemia-reperfusion (I/R) injury and explored the mechanisms involved in cardiomyocyte ferroptosis regulation. Here are the key findings and conclusions of the study:

1. Cell Death Modes: The study found that apoptosis and necrosis occur in the early phase of I/R injury, while ferroptosis is the predominant form of cell death during prolonged reperfusion. Ferroptosis is a specific type of cell death characterized by iron-dependent lipid peroxidation.

2. Metabolomic Profiling: Metabolomic profiling of eicosanoids, which are lipid mediators derived from arachidonic acid metabolism, revealed that metabolites of 15-lipoxygenase (Alox15) accumulated in ferroptotic cardiomyocytes. Alox15 is an enzyme involved in the synthesis of specific eicosanoids.

3. Alox15 Expression: The study demonstrated that Alox15 expression specifically increased in the injured area of the left ventricle following I/R injury and colocalized with cardiomyocytes. This suggests that Alox15 may play a role in regulating cardiomyocyte ferroptosis.

4. Role of Alox15: Myocardial-specific knockout of Alox15 in mice alleviated I/R injury and restored cardiac function. This indicates that Alox15 is involved in the pathogenesis of I/R injury and its inhibition can protect the myocardium.

5. Identification of Trigger: The intermediate metabolite 15-hydroperoxyeicosatetraenoic acid (15-HpETE), derived from arachidonic acid by Alox15, was identified as a trigger for cardiomyocyte ferroptosis. This suggests that the accumulation of 15-HpETE in cardiomyocytes contributes to the initiation of ferroptosis.

6. Mechanism: The study explored the mechanism underlying the effects of 15-HpETE and found that it promotes the binding of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc1α) to the ubiquitin ligase ring finger protein 34 (RNF34), leading to its ubiquitin-dependent degradation. This, in turn, results in attenuated mitochondrial biogenesis and abnormal mitochondrial morphology.

7. Inhibition of Alox15: Treatment with ML351, a specific inhibitor of Alox15, increased the protein level of Pgc1α, inhibited cardiomyocyte ferroptosis, protected the injured myocardium, and led to the recovery of cardiac function.

8. Overall Conclusions: The study establishes that Alox15-mediated cardiomyocyte ferroptosis plays a significant role in prolonged I/R injury. Inhibition of Alox15 or its downstream metabolite 15-HpETE can protect against myocardial damage and improve cardiac function.

These findings provide insights into the molecular mechanisms underlying cell death processes in myocardial I/R injury and suggest Alox15 and its downstream signaling as potential therapeutic targets for preventing myocardial damage and improving cardiac function after reperfusion injury.