Influence of hypothyroidism on testicular mitochondrial oxidative stress by activating the p38 mitogen-activated protein kinase and c-Jun NH2-terminal kinase signaling pathways in rats

Abstract

Thyroid hormone deficiency can impair testicular function. However, knowledge of the effects of mitogen-activated protein kinase (MAPK) pathways on testicular mitochondrial oxidative damage induced by hypothyroidism is still rudimentary. This study aims to explore the possible mechanisms of testicular mitochondrial oxidative damage in hypothyroidism rats. Wistar male rats were randomly divided into control (C), low- (L), and high-hypothyroidism (H) groups (1 ml/100 g body weights (BWs)/day 0, 0.001% and 0.1% propylthiouracil, respectively) by intragastric gavage for 60 days. Blood samples were collected to measure the levels of serum triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH). Testicular mitochondrial homogenates were used to measure the activities of superoxide dismutase (SOD), catalase (CAT), and Ca2+-ATPase as well as protein and mRNA expression of androgen receptor (AR), p38 MAPK, and c-Jun NH2-terminal kinase (JNK). Results showed that the BWs, testes weights, and levels of T3 and T4 were all significantly decreased and the testes coefficient and level of TSH were significantly increased in the H group. There were significant decreases in SOD activity in the H group as well as decreases in CAT and Ca2+-ATPase activities in the L and H groups. Additionally, protein expression of AR decreased significantly and protein expression of phosphorylated p38MAPK and JNK increased significantly in the H group. Therefore, the study suggests that hypothyroidism could affect male reproductive function by disturbing expression of AR, changing the activity of Ca2+-ATPase, inducing oxidative stress and then leading to activation of p38MAPK and JNK signaling in the testicular mitochondria.