Sertoli cell toxicant injury and mechanisms of testicular germ cell apoptosis

支持细胞毒性损伤及睾丸生殖细胞凋亡机制

• 批准号: 8817927
• 负责人: JOHN H RICHBURG
• 金额: $ 32.21万
• 依托单位: UNIVERSITY OF TEXAS AT AUSTIN
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2019-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8817927
• 关键词: Accounting; Acute; Age; Antibodies; Antigens; Apoptosis; Blood-Testis Barrier; CCL2 gene; Cells; Chemicals; Data; Dendritic Cells; Development; Endotoxins; Environment; Exposure to; Foundations; Funding; Gelatinase A; Germ Cells; Goals; Health; Human; ITGAM gene; Immune; Immune Tolerance; Immune system; Inbred F344 Rats; Individual; Infiltration; Inflammation; Inflammatory; Injury; Interferons; Interleukin-1; Leukocytes; Lipopolysaccharides; Monocyte Chemoattractant Protein-1; Monocyte Chemoattractant Proteins; Mus; Natural Killer Cells; Organ; Pathogenesis; Pathway interactions; Predisposition; Production; Proteins; Rattus; Recruitment Activity; Reproductive Health; Research; Research Proposals; Risk; Role; Signal Pathway; Signal Transduction; Source; Testing; Testis; Time; Tissue Inhibitor of Metalloproteinases; Tissues; Toxic effect; Tumor Necrosis Factor-alpha; Work; age related; aged; cell injury; chemokine; consumer product; cytokine; in vivo; inhibitor/antagonist; insight; interstitial; macrophage; male; mono-(2-ethylhexyl)phthalate; monocyte; neutrophil; novel; paracrine; phthalates; postnatal; prevent; public health relevance; research study; response; sertoli cell; toxicant

DESCRIPTION (provided by applicant): The goal of this project is to decipher the cellular signals that instigate leukocyte infiltration into the testis after exposure to mono-(2-ethylhexyl) phthalate (MEHP) and to determine the functional significance of these cells in the pathogenesis of MEHP-induced germ cell apoptosis. We have previously revealed a paracrine interaction between Sertoli cells (SCs) and germ cells (GCs) that initiates GCs to undergo apoptosis via FasL- Fas signaling. Central to this pathway is the inhibition of TIMP2 (tissue inhibitor of metalloproteinase 2) production by SCs after MEHP exposure. This allows for the consequent activation of matrix metalloproteinase 2 (MMP2) in the adluminal space that both generates a soluble form of tumor necrosis factor-? (sTNF?) as well as cause a disorganization of proteins that compose the blood-testis barrier (BTB) between adjacent SCs. A preliminary characterization of Fischer rat testis after MEHP (1 g/kg, p.o.) treatment at two peripubertal ages (PND 28 and 35) showed a robust infiltration of CD11b+ immunoreactive cells in the interstitial space prior to the peak induction of GC apoptosis. The CD11b antibody recognizes an antigen expressed on macrophages, neutrophils, monocytes, natural killer and dendritic cells. Intriguingly, we observed that the most pronounced infiltration of these cells occurs in peripubertal aged rats versus mature rats; and that C57BL/6J mice at both ages do not have a significant infiltration in response to MEHP exposure. The differential species and age- dependent sensitivity to MEHP-induced testicular injury is well recognized, although the mechanisms that account for these differences remain unresolved. Further, preliminary studies also show a dramatic increase in the expression of monocyte chemoattractant protein-1 (MCP-1) in peritubular myoid cells (PTMCs) in testis from PND 28 rats, but not in mature rats. MCP-1 is a prototypical chemokine for signaling the influx of leukocytes into tissues and is itself secreted in response to cytokines such as sTNF?, IL-1?, Il-1? and/or interferon-?. Taken together, our previous work and preliminary data, have led to the development of the hypothesis that MEHP-induced SC injury incites the production of cytokines, such as sTNF?, that trigger PTMCs to release chemokines that initiate the infiltration of leukocytes into the testis and act to enhance the extent of GC apoptosis. Moreover, a provocative underlying hypothesis of this proposal is that leukocytes account, in part, for the mechanism of the observed age- and species-dependent sensitivity to MEHP. To test these hypotheses, the first specific aim will use both acute and repeated MEHP treatments to characterize the leukocyte subtypes and timing of their influx into the testis following exposure. In the second aim, the chemokines and cytokines elicited, as well as their specific cellular source in the testis, will be examined. In the last ai, the functional significance of testis leukocyte infiltration in the pathogenesis of MEHP-induced injury will be directly tested. It is predicted that insights gained from this work will be useful or predicting susceptible individuals and preventing human reproductive health risks this class of chemicals.

描述（由申请人提供）：本项目的目标是破译暴露于单（2-乙基己基）后引起白细胞浸润到睾丸中的细胞信号。 邻苯二甲酸酯（MEHP），并确定这些细胞在MEHP诱导的生殖细胞凋亡的发病机制的功能意义。我们先前已经揭示了支持细胞（SC）和生殖细胞（GC）之间的旁分泌相互作用，通过FasL- Fas信号传导启动GC进行凋亡。该途径的核心是在MEHP暴露后抑制SC产生TIMP 2（金属蛋白酶组织抑制剂2）。这使得随后的激活基质金属蛋白酶2（MMP 2）的近腔空间，既产生了可溶性形式的肿瘤坏死因子-？(sTNF?)以及引起构成相邻SC之间的血睾屏障（BTB）的蛋白质的解体。在MEHP（1 g/kg，p.o.）在两个青春期前后年龄（PND 28和35）的处理显示在GC凋亡的诱导峰值之前，CD 11b+免疫反应性细胞在间质空间中的强烈浸润。CD 11b抗体识别在巨噬细胞、中性粒细胞、单核细胞、自然杀伤细胞和树突细胞上表达的抗原。有趣的是，我们观察到，这些细胞的最明显的浸润发生在青春期前后的老年大鼠与成熟大鼠;和C57 BL/6 J小鼠在这两个年龄没有显着的浸润在MEHP暴露的反应。MEHP诱导的睾丸损伤的不同物种和年龄依赖性敏感性是公认的，尽管解释这些差异的机制尚未解决。此外，初步研究还表明，单核细胞趋化蛋白-1（MCP-1）在PND 28大鼠睾丸管周肌样细胞（PTMCs）中的表达显著增加，但在成熟大鼠中没有。MCP-1是一种典型的趋化因子，用于发出白细胞流入组织的信号，其本身在响应细胞因子（如sTNF？）时分泌，IL-1？，IL-1？和/或干扰素-β。综上所述，我们之前的工作和初步数据导致了MEHP诱导的SC损伤刺激细胞因子（如sTNF？）产生的假设，触发PTMCs释放趋化因子，启动白细胞向睾丸的浸润， 增强胃癌细胞凋亡的程度。此外，这一提议的一个挑衅性的潜在假设是，白细胞部分解释了所观察到的对MEHP的年龄和物种依赖性敏感性的机制。为了检验这些假设，第一个特定目标将使用急性和重复MEHP治疗来表征暴露后白细胞亚型及其流入睾丸的时间。在第二个目标中，将检查引起的趋化因子和细胞因子，以及它们在睾丸中的特异性细胞来源。在最后的ai中，将直接测试睾丸白细胞浸润在MEHP诱导的损伤的发病机制中的功能意义。据预测，从这项工作中获得的见解将是有用的或预测易感个体和预防人类生殖健康风险这类化学品。