Abstract
Glycyrrhiza glabra
root (licorice) is a widely used herb for its beneficial effects on health. This study explored the protective effects of licorice extract against oxidative stress and testicular dysfunction caused by methotrexate (MTX). Mice were allocated into (i) negative control group that received saline; (ii) licorice extract group, orally administered with 200 mg/kg body weight (bw) licorice extract for 12 days; (iii) positive MTX-intoxicated group, injected with a single intraperitoneal dose of MTX (20 mg/kg bw) on day 7; and (iv) a protective group that received licorice extract for 12 days and then MTX on day 7 as in groups 2 and 3. Total proteins, albumin, globulins, malondialdehyde, glutathione peroxidase, reduced glutathione, IL-1, and IL-6 were measured in blood and testis samples collected from all groups. Testicular oxidative stress, serum reproductive hormones, and spermogram were examined. The expression of steroidogenesis-associated genes (translocator protein; and P450scc) was examined by quantitative real-time PCR. Bcl-2-associated X protein and cyclogenase-2 genes were examined by immunohistochemical analysis. The bioactive contents of licorice extract were confirmed by gas chromatography–mass spectrometry analysis. Pretreatment with licorice extract ameliorated the toxic effects of MTX on total proteins, albumin, and globulins and oxidative stress biomarkers and reversed the effect of MTX on examined serum and tissue antioxidants. Besides, MTX down-regulated mRNA expression of translocator protein and P450scc genes. Licorice extract averted the decrease in serum testosterone and the increase in IL-1β and IL-6 levels induced by MTX. Moreover, MTX increased sperm abnormalities and percentage of dead sperms and reduced sperm motility. These changes were absent in the licorice preadministered group. Licorice prevented the increase in immunoreactivity of testis for Bcl-2-associated X protein and cyclogenase-2 that were overexpressed in MTX-injected mice. Licorice extracts positively regulated the expression of steroidogenesis genes suppressed by MTX, increased antioxidant enzymes (glutathione peroxidase, reduced glutathione, and catalase) and reduced biomarker of oxidative stress (testicular malondialdehyde) and inflammatory cytokines (IL-1 and -6). Moreover, reduction in testicular tissue immunoreactivity to Bcl-2-associated X protein and cyclogenase-2. In conclusion, licorice extract mitigated the toxic effects of MTX-induced testicular dysfunction at biochemical, molecular, and cellular levels.