SERTOLI CELL TOXICANT INJURY AND MECHANISMS OF TESTICULAR GERM CELL APOPTOSIS

项目总结/摘要 该项目的目标是破译睾丸巨噬细胞和其他白细胞在睾丸发育中的功能作用。 暴露于支持细胞毒物邻苯二甲酸单（2-乙基己基）酯（MEHP）后的青春期睾丸。虽然这些 细胞传统上以其吞噬和抗原呈递功能而闻名， 大量证据表明，这些细胞对正常发育，稳态和修复/再生至关重要。 中毒性损伤后的组织。我们之前已经描述了CD 11b+免疫反应细胞的强烈浸润， 代表巨噬细胞，中性粒细胞，单核细胞，自然杀伤细胞和树突细胞，进入睾丸间质 青春期老年大鼠（PND 28）在MEHP（700 mg/kg，p.o.）治疗最明显的渗透 这些细胞的数量在青春期大鼠中出现，在成年大鼠中较少。此外，两个年龄段的C57 BL/6 J小鼠都 没有由于MEHP暴露而导致的显著浸润。MEHP的物种和年龄依赖性敏感性- 虽然导致这些差异的机制仍然存在， 悬而未决对位于生精细胞基底膜附近的细胞的详细评估 肾小管显示了一个特定的睾丸巨噬细胞亚群，即肾小管周围巨噬细胞（ptMφs），即 在数量和特定区域定位增加沿着曲细精管的外围， MEHP暴露后的持续时间（>2周）。ptMφ亚型在睾丸领域已引起关注 生物学，因为它们被预测在维持微环境方面发挥关键作用， 精原细胞龛这些发现导致了一种假设，即MEHP诱导的支持细胞损伤 刺激不同睾丸巨噬细胞亚型的数量和定位增加， 机制，以促进精子发生的有效修复和恢复。为了验证这一假设， 第一个具体的目标是表征和确定青春期睾丸中巨噬细胞亚型的定位 在对一系列MEHP剂量（从10 mg/kg的下限开始，给药间隔增加至100、250、500 或700 mg/kg）。在第二个目标中，诱导白细胞浸润到睾丸中的细胞机制 将被定义。在最终的目标，睾丸巨噬细胞亚型参与介导的程度， 亚慢性低剂量MEHP治疗方案后精子发生的恢复将被确定为 该战略旨在更准确地将该研究项目的结果转化为与人类相关的暴露。见解 从这项工作中获得的将是有价值的预测个人对有毒物质引起的不孕症和 预防与这种无处不在的环境毒物有关的生殖健康风险。评估 个体对环境毒物与免疫系统相互作用的敏感性与目标一致 NIEHS 2018-2023战略计划

PROJECT SUMMARY/ABSTRACT The goal of this project is to decipher the functional role of testicular macrophages and other leukocytes in the pubertal testis after exposure to the Sertoli cell toxicant mono-(2-ethylhexyl) phthalate (MEHP). Although these cells have traditionally been known for their phagocytic and antigen presentation functions, there is a growing body of evidence that these cells are critical for normal development, homeostasis and repair/regeneration of tissues after toxicant injury. We have previously described a robust infiltration of CD11b+ immunoreactive cells, representing macrophages, neutrophils, monocytes, natural killer and dendritic cells, into the testicular interstitial space in pubertal aged rats (PND 28) after MEHP (700 mg/kg, p.o.) treatment. The most pronounced infiltration of these cells occurs in pubertal rats, with lesser amounts in adult rats. Further, C57BL/6J mice at both ages do not have a significant infiltration due to MEHP exposure. The species and age-dependent sensitivity of MEHP- induced testicular injury is well recognized, although the mechanisms that account for these differences remain unresolved. A detailed evaluation of the cells that lie adjacent to the basement membrane of the seminiferous tubules revealed a specific testicular macrophage sub-population, the peritubular macrophages (ptMφs), that is increased in number and in specific regional localization along the periphery of the seminiferous tubules for a sustained period (>2 weeks) after MEHP exposure. The ptMφ subtype has gained attention in the field of testis biology because they are predicted to play a critical role in the maintenance of the microenvironment supporting the spermatogonial niche. These findings have led to the hypothesis that MEHP-induced Sertoli cell injury incites an increase in the number and localization of distinct testicular macrophage subtypes as a mechanism to facilitate the efficient repair and recovery of spermatogenesis. To test this hypothesis, the first specific aim will characterize and determine the localization of macrophages subtypes in the pubertal testis in response to a range of MEHP doses (from a low of 10 mg/kg with increased dose intervals of 100, 250, 500 or 700 mg/kg). In the second aim, the cellular mechanisms that induce an infiltration of leukocytes into the testis will be defined. In the final aim, the extent that testicular macrophage subtypes are involved in mediating the recovery of spermatogenesis after a sub-chronic low dose MEHP treatment regimen will be determined as a strategy to more accurately translate the findings of this research project to human relevant exposures. Insights gained from this work will be valuable for predicting individuals susceptible to toxicant-induced infertility and the prevention of reproductive health risks associated with this ubiquitous environmental toxicant. Assessing the individual susceptibility to interactions of environmental toxicants with the immune system is consistent with goals of the NIEHS 2018-2023 strategic plan.