Plumbagin induces testicular damage via mitochondrial-dependent cell death

Different aspects of reproductive functions are regulated by mitochondrial-controlled events. This study investigated the effect of plumbagin (PL) on testicular mitochondria with a view to unravelling the mechanism of the antifertility potential of plumbagin in testis of healthy rats. Thirty-two male Wistar strain albino rats were randomly allocated into four groups of eight animals each. The control or healthy group received orally 0.1 % DMSO while animals in the remaining three groups received 2.5 mg PL/kg bdwt, 5.0 mg PL/kg bdwt and 10 mg PL/kg bdwt, respectively, for 14 days. In study two, twenty-four male Wistar rats were randomly divided into three (3) groups and were orally administered 0.1% DMSO (control), 30 and 100 mg/kg PL, respectively once daily for 72 h. Rat testis mitochondria were isolated using differential centrifugation. The mitochondrial Permeability Transition (mPT) pore, mitochondrial ATPase (mATPase) activity and mitochondrial lipid peroxidation were assessed spectrophotometrically. Expression of apoptotic proteins (p53, Bax, Bcl-2) and the release of cytochrome c were determined by immunochemical technique. Reproductive receptors (FSH, PR), the expression of aromatase, Testis Specific Kinase-1 {TESK-1} were quantified by RT-PCR. The various doses of plumbagin (2.5, 5.0 and 10 mg/kg bdwt) induced opening of the testicular mPT pore by 2, 5 and 8 folds, respectively, after 14 days of oral administration. These doses of plumbagin also caused enhancement of mATPase activity, elevated generation of mLPO as well as increases in the concentrations of caspases 9 and 3. Sperm analysis revealed that these doses of PL also caused significant decreases in sperm count and motility and increased sperm abnormalities compared to control. Interestingly, these effects were accompanied by dose-dependent expressions of the Bak, p53 and cytochrome c release. Conversely, the abundance of anti-apoptotic Bcl-2 protein decreased relative to control. The levels of transcripts of FSH and progesterone receptors as well as TESK-1 and aromatase decreased significantly relative to control. Furthermore, PL strongly inhibited p53-MDM2 compared to control. Altogether, these findings show that plumbagin damages testicular cells through the activation of mitochondrial pathway involving the p53 protein network.