Nicotinamide pretreatment alleviates mitochondrial stress and protects hypoxic myocardial cells via AMPK pathway

The aim of this study was to explore the protective effect of nicotinamide on hypoxic cardiomyocytes and to investigate its possible mechanism.

Primary cardiomyocytes were used as study subjects. They were divided into three groups, including the blank group, control group and nicotinamide pretreatment group. Cell counting kit-8 (CCK-8) was used to detect cell viability. Lactate dehydrogenase (LDH) was used to detect cytotoxicity and flow cytometry was used to detect cell apoptosis. Polymerase Chain Reaction (PCR) and Western blot were used to measure the expressions of genes in adenosine monophosphate-activated protein kinase (AMPK) pathway. JC-1 detected the levels of mitochondrial membrane potential and reactive oxygen species (ROS). NAD was used for nicotinamide adenine dinucleotide (NAD)+, and NAD phosphate (NADP)+ levels. Adenosine triphosphate (ATP) assay was performed for the detection of intracellular energy metabolism.

In the absence of oxygen, nicotinamide had a protective effect on primary cardiomyocytes. Meanwhile, nicotinamide could markedly inhibit the increase of caspase3 mRNA in cardiomyocyte apoptosis pathway, and suppress the expression of apoptotic proteins. Furthermore, it could significantly induce the increase of intracellular ATP and activate the AMPK pathway. The detection of mitochondria indicated that nicotinamide alleviated hypoxic cardiomyocytes. In addition, the mitochondrial membrane potential disrupted and inhibited mitochondrial oxidative stress levels.

Nicotinamide pretreatment protects hypoxic cardiomyocytes and reduces intracellular mitochondrial stress. This protection may be related to the induction of the AMPK pathway and the increase of intracellular energy production.