Walnut Leaf Extract: A Natural Antioxidant to Improve Sperm Parameters and Testicular Dysfunction in Rats Under In Vitro Heat Stress

Heat stress causes damage to testicular tissue and spermatogenesis in males. Walnut leaf extract (WLE) has antioxidant properties. This study aimed to investigate the effect of WLE on testicular tissue and sperm quality in rats under in vitro heat stress. For this purpose, 60 male albino rats were divided into five groups: healthy control group (T1), heated‐control group (T2), and treatments with 40, 60, and 150 mg/kg of the extract (T3, T4, and T5, respectively). The WLE was administered orally for 55 days after inducing heat stress for 45 days. The rats were then dissected and their testis tissues were evaluated for pathological changes, sperm parameters, antioxidant status, and gene expression of heat shock protein‐70 ( HSP70 ), heat shock factor‐1 ( HSF1 ), nuclear factor erythroid 2–related factor 2 ( NRF2 ), and silent information regulator 1 ( SITR1 ) by real‐time PCR (RT‐PCR). Complete tissue destruction and the lowest sperm motility and antioxidant activity were observed in T2. Rats in the group T3 exhibited slightly improved motility, malondialdehyde (MDA), and superoxide dismutase (SOD) levels. The T4 and T5 groups showed notable improvements in sperm quality and antioxidant status ( p < 0.05). In the T4 and T5 groups, the expression levels of HSP70, HSF1, STR1, and NRF2 were significantly higher than those in the T2 group ( p < 0.05). In conclusion, WLE has antioxidant activity that controls testis dysfunction and sperm quality under heat stress conditions.