Scrotal heat stress causes a transient alteration in tight junctions and induction of TGF-β expression

Specialized junctions, which occur at sites of Sertoli-Sertoli and Sertoli-germ cell contact of seminiferous epithelium, play pivotal roles in spermatogenesis. Slight increase in scrotal temperature can induce oligospermia or azoospermia via increasing germ cell apoptosis. In this study, we demonstrated that the expression of tight junction (TJ) components, such as occludin, claudin-3 and zonula occludens-1 (ZO-1), was reduced 24-48 h after a single mild scrotal heat exposure (43 degrees C for 30 min), whereas mRNA levels of claudin-11 were increased. Moreover, the protein localization of occludin and ZO-1 was lost from the blood-testis barrier (BTB) site, whereas claudin-11 immunostaining became diffuse and cytoplasmic 2 days following heat exposure. Electron microscopic analysis showed that 2 days after the heat treatment, the intercellular space between the two adjacent Sertoli cells was expanded, coupled with defragmentation of actin bundles and the endoplasmic reticulum. In addition, the TJ permeability increased significantly 2 days after the heat exposure and recovered approximately 10 days later. Heat-induced reversible BTB disruption was associated with a transient induction of transforming growth factor (TGF)-beta 2, -3 and p38 mitogen-activated protein kinase activation. However, the TGF-beta antagonist only partially prevented the heat-induced BTB disruption. In conclusion, the expression of TJ-associated molecules and BTB were reversibly perturbed after mild testicular hyperthermia, and the induction of TGF-beta expression may be partially involved in heat-induced BTB damage.