Inhibition of boldenone-induced aggression in rats by curcumin: Targeting TLR4/MyD88/TRAF-6/NF-κB pathway

The illicit abuse of anabolic steroids is associated with brutal aggression, which represents a serious health hazard and social threat. Boldenone is commonly used for doping by athletes and adolescents for esthetic purposes and to enhance performance and endurance during competitions. However, the mechanistic pathways underlying boldenone-induced behavioral deviations and neuronal toxicity have not yet been elucidated. On the other hand, the natural polyphenol curcumin is appreciated for its relative safety, potent antioxidant activity, and anti-inflammatory properties. Therefore, the present study was initiated to explore the signaling pathways underlying boldenone-induced anxiety and aggression in rats, and the protective effects of curcumin. To achieve this aim, male Wistar albino rats were randomly distributed into control, curcumin (100 mg/kg in sesame oil, p.o., once daily), boldenone (5 mg/kg, intramuscular, once weekly), and combination groups. Rats were challenged across the open field, irritability, defensive aggression, and resident-intruder tests. The prefrontal cortex was used to assess serotonin level, oxidative stress markers, and mRNA expression of myeloid differentiation primary response gene (MyD88), TNFR-associated factor 6 (TRAF-6), tumor necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), protein expression of toll-like receptor 4 (TLR4), and phosphorylated nuclear factor-kappa B transcription factor (NF-kappa B p65). Unprecedented, the current results showed that boldenone elicited aggression in rats accompanied by depleted serotonin, enhanced oxidative stress, and exaggerated inflammatory response via upregulation of TLR4/MyD88/TRAF-6/NF-kappa B pathway. Interestingly, curcumin mitigated boldenone-induced neurobehavioral disturbances in rats, normalized the oxidant/antioxidant balance, and suppressed TLR4/MyD88/TRAF-6/NF-kappa B pathway and its downstream proinflammatory signaling molecules TNF-alpha and IL-1 beta.