Inhibition of the Expression of Inducible NO Synthase by Neuroactive Amino Acid Derivatives Phenibut and Glufimet In Vitro and Ex Vivo

The role of iNOS inhibition in the mechanism of the cardioprotective effect of new GABA and glutamic acid derivatives in the model of acute alcoholic myocardial injury in rats

The cardioprotective effects of new derivatives of glutamic acid (glufimet) and GABA (mefargin) were studied in rats exposed to acute alcohol intoxication (AAI) under conditions of selective blockade of inducible NO-synthase (iNOS). AAI induced a pronounced decrease in the contractile function of the myocardium during exercise tests (load by volume, test for adrenoreactivity, isometric exercise), caused mitochondrial dysfunction and increased processes of lipid peroxidation (LPO) in heart cells. A decrease in NO production during iNOS inhibition and AAI improved the respiratory function of mitochondria, a decreased the level of LPO products, and increased mitochondrial superoxide dismutase activity of heart cells. This led to an increase in myocardial contractility. The studied compounds, glufimet and mefargin, caused a statistically significant increase in the rates of myocardial contraction and relaxation, left ventricular pressure, and also reduced NO production. This was accompanied by a decrease in the intensity of LPO processes and an increase in the respiratory control ratio (RCR), reflecting the coupling between respiration and phosphorylation processes during activation of the respiratory chain complexes I and II. The decrease in NO concentration during selective blockade of iNOS and administration of the studied substances was less pronounced than without blockade of the enzyme. This suggests the putative effect of new derivatives of neuroactive amino acids on the NO system.

Pharmacological correction of the sequelae of acute alcohol-induced myocardial damage with new derivatives of neuroactive amino acids coupled with the blockade of the neuronal NO synthase isoform

Introduction: Acute alcohol intoxication (AAI) induces a number of myocardial disorders, which result in mitochondrial dysfunction in cardiomyocytes, oxidative stress, and decreased cardiac contractility. Nitric oxide produced by the nNOS is one of the major modulators of cardiac activity. New derivatives of GABA (RSPU-260 compound) and glutamate (glufimet) can be potentially regarded as such agents as the interaction between the NO system and the GABA and glutamatergic systems has been proved.

Materials and methods: All the studies were performed on female white Wistar rats, aged 10 months, whose weight was 280–320g AAI intoxication was modeled of 32% ethanol (gavage, 4g/kg).

Results and discussion: Glufimet and the RSPU-260 compound caused a significant improvement in myocardial contractility, increased oxygen consumption in the V3 state according to Chance, raised the respiratory control ratio and decreased the intensity of LPO intensity. Their effectiveness exceeded that of mildronate, their comparator. nNOS inhibition resulted in a pronounced aggravation of oxidative stress implicated in MDA accumulation in cardiac mitochondria and decreased activity of SOD; myocardial contractility and mitochondrial function indicators did not show a significant difference from the control group. The compounds under study coupled with nNOS inhibition had a cardioprotective effect.

Conclusion: Glufimet and the RSPU-260 compound, derivatives of neuroactive amino acids, have a pronounced cardioprotective effect, restrict LPO processes, enhance SOD activity, improve the mitochondrial respiratory function after acute alcohol intoxication when coupled with neuronal NO-synthase inhibition, the expression of which persists after AAI.

Graphical abstract:

Cardioprotective effects of a new glutamic acid derivative in chronic alcohol intoxication

Alcohol abuse is a risk factor for heart damage and deterioration of its inotropic function. Currently, there is no pathogenetic pharmacological treatment for alcohol-induced myocardial injury. Therefore, the study of drugs with cardioprotective action is of current interest. Our earlier studies of stress-induced heart damage showed that a new derivative of glutamic acid - glufimet - protects the myocardium's inotropic function and limits lipid peroxidation. Additionally, we found that it increases the activity of antioxidant enzymes and improves mitochondrial respiration. The purpose of our study was to assess the effect of glufimet on the heart after chronic alcohol intoxication (CAI). The comparison drug was mildronate, which possesses cardioprotective properties and is used to treat alcohol withdrawal. We conducted our study using female Wistar rats (10 months old, 280-320 g). CAI was simulated by replacing drinking water with a 10% ethanol solution sweetened with sucrose (50 g/L) over a period of 24 weeks. The day after the animals stopped ethanol solution drinking, the control group was injected intraperitoneally (i.p.) with a saline solution once a day for 14 days, while the experimental groups received glufimet (28.7 mg/kg) and the drug of comparison mildronate (50 mg/kg), respectively. After that, we studied the heart contractility by measuring volume load, adrenergic reactivity, and maximum isometric load. Under CAI, the control group showed significantly lower growth in left ventricular pressure (LVP), myocardium contraction rate, and relaxation rate during functional tests. Higher concentrations of LPO products (malondialdehyde) and low activity of antioxidant enzymes (superoxide dismutase, glutathione peroxidase), indicating a disturbance in mitochondrial respiration compared to the control group, were registered. While being treated with glufimet and mildronate, the animals demonstrated higher growth rates of myocardial contraction, myocardial relaxation, and LVP, compared to the control group. Mitochondrial functioning and activity of the antioxidant enzymes increased in the same group as well.