Unraveling the cytoprotective mechanism of polysaccharides in heat-stressed rabbits: antioxidant, anti-inflammatory, physiological status, and molecular docking assessment.

Heat stress (HS) is a critical environmental challenge that compromises immune function and triggers systemic inflammation in livestock. This study evaluates the efficacy of Ganoderma lucidum polysaccharides (GAP) in mitigating HS-induced damage in growing rabbits. Using a dual in vivo and in silico approaches, this work investigated the regulatory protective role of GAP on physio-metabolic markers, antioxidant capacity, and the modulation of immune and inflammatory pathways. A total of 120 healthy New Zealand White weaned rabbits were randomly assigned to four experimental groups. Over a 56-day period under natural HS conditions, the rabbits were fed a basal diet supplemented with GAP at concentrations of 0 (control, GAP0), 100 (GAP100), 250 (GAP250), or 500 (GAP500) mg/kg. Dietary supplementation with GAP (250 and 500 mg/kg) significantly enhanced final body weight and dressing percentage relative to the other groups (P < 0.01). Furthermore, GAP inclusion exerted a quadratic reduction in serum creatinine and GGT levels (P < 0.01). Conversely, triglyceride and LDH concentrations exhibited a significant linear decline (P < 0.01) in response to increasing GAP dosages. Under HS conditions, dietary fortification with GAP significantly strengthened antioxidant status, with SOD, and TAC levels increasing in a linear manner (P < 0.01). Conversely, GAP supplementation quadratically attenuated markers of oxidative damage (protein carbonyl, nitric oxide and malondialdehyde) and adipokines (visfatin and irisin) (P < 0.01). Dietary GAP inclusion produced a quadratic response in heat-stressed rabbits, evidenced by a significant levels of pro-inflammatory mediators, including IFN-γ, IL-6, and NF-κB (P < 0.05). This was accompanied by a concomitant reduction in the pro-apoptotic markers cytochrome c and caspase-3 (P < 0.05). GAP supplementation linearly augmented anti-inflammatory status (IL-10) and systemic immunity, as indicated by enhanced lysozyme activity and elevated immunoglobulin levels (IgG and IgM; P < 0.01). In silico molecular docking revealed high-affinity interactions between GAP and key apoptotic/antioxidant regulatory proteins. Specifically, GAP exhibited robust binding affinities against COX-2, SOD, BAX, and Caspase-3, yielding binding free energies of -12.29, -11.88, -11.87, and - 11.53 kcal/mol, respectively. By integrating advanced computational insights with concrete in vivo data, these findings demonstrate that dietary GAP supplementation (at 250 or 500 mg/kg) effectively rescues rabbits from the deleterious effects of heat stress. This protective mechanism is mediated by the potent antioxidant, anti-inflammatory, and cytoprotective properties of GAP, which synergistically fortify cellular resilience and optimize overall physiological health.