Thyme (Thymus vulgaris) is an herbal plant with pleiotropic medicinal properties. In this study, we examined the possible protective effect of an ethanolic extract of thyme leaves against the renal oxidative stress induced by sodium nitrite (NaNO₂). Male Swiss mice received either saline or thyme extract for 15 days (0.5 g/kg body weight, orally). NaNO₂ (60 mg/kg) was injected intraperitoneally at Day 14. The protective group received the thyme extract for 15 days and NaNO₂ on Day 14. Blood and kidney samples were taken from all groups to measure serum urea, blood urea nitrogen (BUN), creatinine, serum, tissue antioxidant activity, and the inflammatory cytokines IL-1β and IL-6. Quantitative real-time PCR (qRT-PCR) was used to examine the expression of kidney injury marker-1 (Kim-1), TNF-α, nuclear factor erythroid-2 related factor 2 (Nrf2), and hemoxygenase-1 (HO-1), all of which are associated with kidney redox and oxidative stress. Pretreatment with thyme extract reduced the effects of NaNO₂ on urea, BUN, and creatinine, and reversed its effect on tissue and serum antioxidants. NaNO₂-induced nephritis as demonstrated by the upregulation in mRNA expression of Kim-1 and TNF-α, which was, however, recovered and protected by pretreatment with thyme extract. Expression of Nrf2 and HO-1 was upregulated by treatment with thyme extract and downregulated by NaNO₂ intoxication. NaNO₂-induced congestion in glomeruli and dilatation of the renal tubules, conditions that were restored in the group pretreated with thyme extract. NaNO₂ upregulated Bax immunoreactivity and caused apoptosis in renal structures. Thus, thyme extract is effective in managing the renal toxicity associated with oxidative stress and renal redox.

Practical applications

The results from this study have shown that use of thyme extract may promote better health due to its high antioxidant activity. For instance, it could be ingested to alleviate the symptoms of renal inflammation and oxidative stress associated with nitrite toxicity. Thyme extract regulated renal redox, oxidative stress, antioxidant levels, and inflammation-associated genes at the molecular, biochemical, and cellular immunohistochemical levels.