NOS3 (rs61722009) gene variants testing in prediction of COVID-19 pneumonia severity

Background: There is a hypothesis that a sufficient level of endothelial nitric oxide synthase is important for reliable protection against COVID-19. Theoretical ideas about the NOS3 gene demonstrated that it can have an effect on links of the complications pathogenesis in COVID-associated pneumonia. We determined the goal - to investigate the association of the NOS3 gene variants with the occurrence of the disease and its clinical course in patients of the intensive care unit. Methods: The study group included 117 patients with a diagnosis of severe "viral COVID-19 pneumonia". Determination of NOS3 gene variants was performed using the PCR method. The probability of differences in the quantitative results were determined using ANOVA or Kruskal-Wallis test (depend of normality of studied parameters). Results: Our results indicate that the presence of the NOS3 gene 4a allele increase the risk of complicated COVID-19-associated pneumonia (chi 2 = 18.84, p = 0.00001, OR = 3.53 (1.95-6.39)). It was showed, that carriers of the 4aa genotype had a significantly higher ratio of SpO2/FiO2 on the first and second days after hospitalization (p = 0.017 and p = 0.03, respectively). Patients with the 4aa genotype also had the acid-base imbalances, as showed by indicators of base deficiency and standard bicarbonate, which were beyond the reference values. Potassium and sodium concentrations on the first and second day after hospitalization were also significantly lower in patients with 4aa genotype (p = 0.009 and p = 0.048, respectively), for whom, in the same time, the concen-trations of C-reactive protein and total bilirubin were significantly higher (p = 0.002 and p = 0.033, respectively). Conclusions: Our results confirmed that the rs61722009 variant of the NOS3 gene is associated with an increased risk of severe COVID-19-associated pneumonia and its adverse clinical course with potential progression of kidney and liver damage, and occurrence risk of systemic inflammatory response syndrome. These results require further research for the new metabolic strategy formation, in order to prevent the severe COVID-19 associated pneumonia and its complications.