Aims: The histone deacetylase 6 (HDAC6) inhibitor, tubastatin A (TubA), reduces myocardial ischaemia/reperfusion injury (MIRI) in type 1 diabetic rats. It remains unclear whether HDAC6 regulates MIRI in type 2 diabetic animals. Diabetes augments the activity of HDAC6 and the generation of tumour necrosis factor alpha (TNF-α) and impairs mitochondrial complex I (mCI). Here, we examined how HDAC6 regulates TNF-α production, mCI activity, mitochondria, and cardiac function in type 1 and type 2 diabetic mice undergoing MIRI.
Methods and results: HDAC6 knockout, streptozotocin-induced type 1 diabetic, and obese type 2 diabetic db/db mice underwent MIRI in vivo or ex vivo in a Langendorff-perfused system. We found that MIRI and diabetes additively augmented myocardial HDAC6 activity and generation of TNF-α, along with cardiac mitochondrial fission, low bioactivity of mCI, and low production of adenosine triphosphate. Importantly, genetic disruption of HDAC6 or TubA decreased TNF-α levels, mitochondrial fission, and myocardial mitochondrial nicotinamide adenine dinucleotide levels in ischaemic/reperfused diabetic mice, concomitant with augmented mCI activity, decreased infarct size, and improved cardiac function. Moreover, HDAC6 knockout or TubA treatment decreased left ventricular dilation and improved cardiac systolic function 28 days after MIRI. H9c2 cardiomyocytes with and without HDAC6 knockdown were subjected to hypoxia/reoxygenation injury in the presence of high glucose. Hypoxia/reoxygenation augmented HDAC6 activity and TNF-α levels and decreased mCI activity. These negative effects were blocked by HDAC6 knockdown.
Conclusion: HDAC6 is an essential negative regulator of MIRI in diabetes. Genetic deletion or pharmacologic inhibition of HDAC6 protects the heart from MIRI by limiting TNF-α-induced mitochondrial injury in experimental diabetes.
Keywords: Histone deacetylase 6; Ischaemia/reperfusion; Mitochondria; Tumour necrosis factor alpha; Type 1 diabetes; Type 2 diabetes.
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