Nephrotoxic effects of combined exposure to 85 dB(a) noise and 300 ppm toluene in <i>Wistar</i> rats: biochemical and histopathological analysis

Abstract

Abstract Toluene, a widely used industrial solvent, and environmental noise, a pervasive physical stressor, are both recognized for their harmful effects on health. This study examined the individual and combined effects of toluene and noise exposure on oxidative stress, renal function, pro-inflammatory response, and kidney histopathology. Twenty-four adult male Wistar rats were randomly divided into four groups: control (C), noise exposure (N; 85 dB SPL white noise, 8–16 kHz), toluene exposure (T; 300 ppm), and combined Noise + Toluene exposure (NT; 85 dB + 300 ppm). Oxidative stress was assessed by measuring malondialdehyde (MDA) levels and the activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). Renal function was evaluated using serum urea and creatinine levels, along with serum concentrations of the pro-inflammatory cytokines TNF-α and IL-1β. Histopathological analyses were performed to identify structural alterations in the kidneys. All exposed groups exhibited significant renal impairment, as indicated by elevated urea and creatinine levels. MDA levels were markedly increased, confirming oxidative stress. Noise exposure induced elevated SOD and CAT activities, whereas toluene exposure led to a reduction in these activities. Combined exposure exacerbated biochemical imbalances, elevated pro-inflammatory cytokine levels, and intensified renal tissue damage, including glomerular atrophy, tubular degeneration, vascular congestion, and leukocyte infiltration in the renal tissue. These findings demonstrate that toluene and noise are potent nephrotoxic agents whose co-exposure amplifies oxidative and inflammatory injuries. This highlights the critical need to consider combined environmental exposure in toxicological risk assessments.