Effect of thymoquinone on Nrf2 expression in testicular torsion

Testicular torsion is a urological emergency that causes severe disruption of the spermatic cord and its surrounding blood supply or complete amputation. Ischemia and reperfusion (I/R) resulting from testicular torsion-detorsion causes testicular damage. Ischemic/reperfusion (I/R) injury is a pathological event that occurs as a result of decreased blood flow to the organ and subsequent reperfusion. Testicular tissue has certain defense mechanisms against oxidants to maintain the spermatogenesis process in a healthy way. However, it is known that some internal (endogenous) and external (exogenous) factors disrupt this balance and cause oxidative stress. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of redox balance and responds to various cellular stresses, of which oxidative stress is the best known. Nrf2 must undergo nuclear translocation to exert its protective effects and reduce ROS production. Thymoquinone (TQ) is the main active ingredient of the essential oil of black cumin (Nigella sativada L.). Thymoquinone is a natural compound with versatile pharmacological properties, including anti-inflammatory, antidiabetic and analgesic properties. However, it has also been reported to play a potential role in suppressing oxidative stress. In this study, we aimed to demonstrate whether thymoquinone, which has antioxidative properties, has a protective effect against testicular ischemia-reperfusion injury in rats by inducing Nrf2, mTOR, and PTEN expression. Adult Wistar male rats were divided into 5 groups: Control (n=6), Sham (n=6), Thymoquinone (n=6), Torsion/Detorsion (n=6), Thymoquinone + Torsion/Detorsion (n=6). In this study, thymoquinone was administered intraperitoneally to rats that would undergo torsion/detorsion model for 7 days. At the end of the 7th day, the left testes of the rats were rotated 720° and placed in an ischemic state for 2 hours; then the testes were rotated 720° again and reperfusion was achieved for 3 hours. At the end of reperfusion, the right and left testes of all rats were removed and evaluated for histological examination. In the examinations, spermatogenic activity of seminiferous tubules and Nrf2, mTOR expression levels were quantitatively evaluated using the Johnsen scoring system and immunohistochemical H-score method. According to histological analysis results, the Johnsen score decreased significantly in the torsion/detorsion group, while this score increased significantly in the treatment group. Likewise, Nrf2 and mTOR staining intensity increased in the torsion group, and the expression level in the treated group decreased significantly compared to the torsion group. In line with these results, thymoquinone can be considered as a potential therapeutic agent for preserving fertility thanks to its regulatory role on antioxidative mechanisms. Keywords: Rat, Testis, Torsion/Detorsion, Thymoquinone, Nrf2