Melittin Attenuates Against Circadian Rhythm Disruption-Induced Hepatic Injury Through Antioxidant and Anti-Inflammatory Effects

Abstract

Background Circadian rhythm disruption (CRD) is a risk factor for metabolic and hepatic disorders. This study aimed to investigate the potential hepatoprotective effects of melittin against liver injury induced by constant light exposure in a rat model. Materials and methods Twenty-two female Wistar rats were divided into four groups: Group 1 (Control), Group 2 (Melittin), Group 3 (Circadian Rhythm Disruption-CRD), and Group 4 (CRD + Melittin). Melittin was administered at a dose of 0.1 µg/g/day. Following the experimental period, liver injury was evaluated using histopathological scoring, serum biochemical analysis, hepatic oxidative stress markers, and immunohistochemical evaluation of Cluster of Differentiation 68 (CD68) and Circadian Locomotor Output Cycles Kaput (CLOCK) proteins. Results CRD-induced marked hepatic injury, characterized by increased hemorrhage, inflammatory infiltration, sinusoidal dilatation, vascular congestion, and disruption of hepatic architecture. It also impaired metabolic and liver function parameters, as demonstrated by increased serum glucose, total cholesterol, triglyceride, bilirubin, and Aspartate Aminotransferase (AST) levels, together with decreased High-Density Lipoprotein (HDL), albumin, and total protein levels. In addition, circadian rhythm disruption increased hepatic Malondialdehyde (MDA) levels and reduced antioxidant defense markers, including Superoxide Dismutase (SOD), Reduced Glutathione (GSH), and Catalase (CAT). Immunohistochemical analysis showed that CLOCK H-score values were significantly increased in the group 3 compared with the group 1 and were significantly decreased in the group 4 compared with the group 3. CD68 immunoreactivity was also significantly increased in the group 3 compared with the group 1 and group 2, indicating enhanced macrophage-related inflammatory cell accumulation. Melittin treatment attenuated several of these alterations by preserving hepatic architecture, reducing sinusoidal dilatation, improving biochemical and oxidative stress parameters, decreasing CLOCK immunoreactivity toward control levels, and showing a tendency to reduce CD68-associated inflammatory cell accumulation. Conclusion CRD-induced hepatic injury through structural damage, metabolic imbalance, oxidative stress, altered CLOCK immunoreactivity, and increased CD68-positive inflammatory cell accumulation. Melittin exerted partial hepatoprotective effects against CRD-induced hepatic injury, possibly through improvement of hepatic architecture, oxidant/antioxidant balance, metabolic parameters, and circadian clock-related alterations. Graphical Abstract