Potential protective effect of quercetin on the male reproductive system against exposure of Wistar rats to crude oil vapor: Genetic, biochemical, and histopathological evidence

Toxic compounds in crude oil vapor (COV), including polycyclic aromatic hydrocarbons (PAHs), are associated with adverse effects on reproduction in living organisms. Quercetin (QT) is the most plentiful flavonoid in vegetables and fruits, with antioxidant activities. This study aimed to evaluate the protective role of QT on testicular toxicity induced by COV. Twenty-four adult male Wistar rats were randomly divided into four groups (n = 6) including control, quercetin (QT) (50 mg/kg), crude oil vapors (COV), and COV + QT. The inhalation method was used to expose the rats to crude oil vapors for 5 h daily, and QT was administered orally. After 30 days, the rats were euthanized, then, the testes were removed for gonadosomatic index (GSI), sperm parameters, H & E staining, the activity of the antioxidant enzymes, and apoptotic gene expression assessments. The COV statistically significantly (P < 0.05) reduced GSI, sperm count, motility, viability, and sperm normal morphology, histological indexes, and antioxidant enzyme activities than control. Also, COV statistically significantly (P < 0.05) increased the expression of caspase-3, p-53, and Bax genes and decreased Bcl-2 gene expression. Co-administration of QT + COV caused a statistically significant (P < 0.05) decrease in Bax gene expression and increased antioxidant enzyme activities, Bcl-2 gene expression, and reproductive parameters than the COV group. Based on the results of this study, it appears that crude oil vapor causes side effects on male reproduction. Yet, quercetin has the potential to reduce the side effects of crude oil vapor on the male reproductive system.