Urban fine particulate matter (PM2.5) exposure destroys blood-testis barrier (BTB) integrity through excessive ROS-mediated autophagy.

CONTEXT: Blood-testis barrier (BTB), constituted by tight junctions (TJs), adherens junctions and gap junctions, is important for spermatogenesis. PM2.5 is known to impair testicular functions and reproduction. However, its effects on BTB and the underlying mechanisms remain obscure. OBJECTIVE: To investigate the roles of autophagy in BTB toxicity induced by PM2.5. MATERIALS AND METHODS: Sprague-Dawley rats were developmentally exposed to normal saline (NS) or PM2.5 with the doses of 9 mg/kg b.w. and 24 mg/kg b.w. via intratracheal instillation for seven weeks. Success rate of mating, sperm quality, testicular morphology, expressions of BTB junction proteins and autophagy-related proteins were detected. In addition, expressions of oxidative stress markers were also analyzed. RESULTS: Our results demonstrated that developmental PM2.5 exposure induced noticeable decreased fertility, significantly reduced sperm count, increased sperm abnormality rate and severe testicular damage in histomorphology. The expressions of TJ (such as ZO-1 and occludin), gap junction (such as connexin43) were down-regulated significantly after PM2.5 treatment. Intriguingly, PM2.5 simultaneously increased the number of autophagosomes and the levels of autophagy marker LC3-II and p62, suggesting that the accumulated autophagosomes resulted from impaired autophagy degradation. Moreover, the expressions of HO-1 levels remarkably increased and expression levels of Gpx and SOD were significantly decreased after PM2.5 exposure. Vitamins E and C could alleviate the PM2.5-induced oxidative stress, reverse the autophagy defect and restore the BTB impairment. CONCLUSIONS: Taken together, the results suggest that PM2.5 exposure destroys BTB integrity through excessive ROS-mediated autophagy. Our finding could contribute to a better understanding of PM2.5-induced male reproductive toxicity.

[Long-term exposure to PM2.5 from automobile exhaust results in reproductive dysfunction in male rats].

OBJECTIVE: To explore the effects of long-term exposure to particulate matter 2.5 (PM2.5) from automobile exhaust on the reproductive function of Sprague Dawley (SD) rats. METHODS: Forty-five male SD rats, weighing 80 - 94 g and aged 28 days, were randomly assigned to receive intra-tracheal administration of 0.9% normal saline (control group, n = 15), PM2. 5 at 2 µg per 100 g body weight per day (low-dose PM2.5 group, n = 15), and PM2.5 at 16 µg per 100 g body weight per day (high-dose PM2.5 group, n = 15), qd, for 60 successive days. After the last 24-hour exposure, 10 rats were taken from each group for copulation with normal female ones, while the others were sacrificed, their testes removed for sperm count and deformity, pathological examination, and determination of the Connexin43 expression. RESULTS: The conception rate was significantly decreased in the low- and high-dose PM2.5 groups as compared with that of the control (70% and 50% vs 100%), and so were the sperm count and quality. The rats in the PM2.5-exposed groups showed significantly disordered histological structure of the seminiferous tubules, reduced sperm count in the testicular lumen, some exfoliated secondary spermatocytes, downregulated Connexin43 expression in the testis, and damaged blood-testis barrier. CONCLUSION: Long-term exposure to PM2.5 from automobile exhaust damages the reproductive function of male SD rats.

[Effect of Di-(2-ethylhcxyl) phthalate exposure on blood-testis barrier integrity in rats].

OBJECTIVE: To investigate mechanism of di-(2-ethylhcxyl)phthalate (DEHP) exposure in causing blood-testis barrier (BTB) impairment in rats. METHODS: Two-months-old male SD rats were randomly divided into corn oil control group and DEHP (750 mg/kg) exposure group for daily intragastic treatment for 30 consecutive days. After the treatments the rats were examined for histomorphological changes of the testicle using HE staining and the expressions of the junction proteins N-cadherin ß-catenin, occludin and connexin43 of the BTB using Western blot. In the in vitro study, the vitality and ROS generation level in Sertoli cells exposed to different concentrations of DEHP were examined with MTT and ROS assay kits, respectively, and Nrf2 and p-p38 expressions were detected with Western blot. RESULTS: Compared with the control group, the rats with DEHP exposure showed structural damage of the seminiferous tubule and polarity loss of the spermatids. DEHP exposure caused significantly decreased expressions of occludin and connexin43 but increased expressions of N-cadherin and ß-catenin in the testicle tissues of the rats (P<0.05). The vitality of Sertoli cells was obviously decreased and ROS level increased significantly after exposure of the cells to increasing concentrations of DEHP, which also resulted in significantly up-regulated Nrf2 and p-p38 expressions (P<0.05). CONCLUSIONS: DEHP exposure causes increased oxidative stress in the Sertoli cells of the testis, activates p38 MAPK signaling pathway, and results eventually in impaired spermatogenesis in rats.

Urban fine particulate matter exposure causes male reproductive injury through destroying blood-testis barrier (BTB) integrity.

Blood-testis barrier (BTB) provides a suitable microenvironment for germ cells that is required for spermatogenesis. Exposure to particulate matter (PM) is recognized to occasion male reproductive impairment, but the mechanism of which remains unclear. Male Sprague-Dawley (SD) rats were used to establish animal models with PM2.5 exposure concentration of 0, 10, and 20mg/kg.b.w. once a day for four weeks. Success rate of mating, sperm quality, epididymal morphology, expressions of spermatogenesis markers, superoxide dismutases (SOD) activity and expression in testicular tissues, and expressions of BTB junction proteins were detected. In addition, in vitro experiments were also performed. After PM2.5 treatment, reactive oxygen species (ROS) production and apoptosis of Sertoli cells were analyzed. Our results indicated that after PM2.5 exposure male rats presented inferior uberty and sperm quality, with decreased expressions of spermatogenesis markers, escalated SOD activity and expression levels, and reduced expressions of tight junction, adherens junction, and gap junction proteins in testicular tissues. Meantime, PM2.5-treated Sertoli cells displayed increased SOD production and apoptosis. PM2.5 exposure engenders male reproductive function injury through breaking BTB integrity.

Fine particulate matter leads to reproductive impairment in male rats by overexpressing phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway.

Maintenance of male reproductive function depends on normal sperm generation during which process Sertoli cells play a vital role. Studies found that fine particulate matter (PM) causes decreased male sperm quality, mechanism of which unestablished. We aim to investigate the definite mechanism of PM impairment on male reproduction. Male Sprague-Dawley rats were daily exposed to normal saline (NS) or PM2.5 with the doses of 9 mg/kg.b.w and 24 mg/kg.b.w. via intratracheal instillation for seven weeks. Reproductive function was tested by mating test and semen analysis after last exposure. Testes were collected to assess changes in histomorphology, and biomarkers including connexin 43 (Cx43), superoxide dismutase (SOD), phosphatidylinositol 3-kinase (PI3K) and phosphorylated protein kinase B (p-Akt). Male rats exposed to PM2.5 showed noticeable decreased fertility, significantly reduced sperm count, increased sperm abnormality rate and severe testicular damage in histomorphology. After PM2.5 exposure, the levels of Cx43 was significantly downregulated, and SOD was upregulated and downregulated significantly with different dose, respectively. Protein expression of PI3K and p-Akt dramatically enhanced, and the later one being located in Sertoli cells, the upward or declining trend was in dose dependent. PM2.5 exposure leads to oxidative stress impairment via PI3K/Akt signaling pathway on male reproduction in rats.