Thymoquinone Attenuates Aluminum Chloride-Induced Testicular Injury by Inhibiting NLRP3/Caspase 1/IL-1β Inflammasome Signaling and Polarizing the Macrophages Toward Anti-Inflammatory M2 Phenotype

In recent decades, the quantity of sperm and the quality of semen have decreased, causing an increased incidence of male infertility. The increased exposure to environmental pollutants and metals, including aluminum, is one of the causes. Aluminum is reported to activate the proinflammatory macrophages and the NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome pathway in many organs. Thymoquinone (TQ), the bioactive component of Nigella sativa, possesses immunomodulatory, anti-inflammatory, anti-apoptotic, and antioxidant properties. The purpose of this work is to investigate how thymoquinone affects aluminum chloride (AlCl3)-induced testicular damage and to study, for the first time, its role in modifying the inflammasome pathway, specifically NLRP3/caspase-1/IL-1β, and in targeting macrophage polarization. Negative control, TQ control (10 mg/kg/d), AlCl3 group (100 mg/kg/d), and AlCl3 + TQ group were the rat groups. Serum testosterone, FSH, and LH were measured, along with a seminal analysis, evaluation of testicular oxidative stress markers, and assessment of testicular enzymes LDH, SDH, and ACP. NLRP3, caspase-1, IL-1β, CD68, and CD163 immunohistochemical staining, as well as histological alterations, were evaluated. TQ could lower oxidative stress markers, limit the AlCl3-induced activation of the NLRP3/caspase-1/IL-1β inflammasome pathway, and induce macrophage polarization toward an M2 anti-inflammatory phenotype, thereby restoring testicular enzymes, histological structure, semen quality, and hormone levels. Thymoquinone attenuates aluminum chloride-induced testicular injury by inhibiting NLRP3/caspase-1/IL-1β inflammasome signaling and polarizing the macrophages toward an anti-inflammatory M2 phenotype.