刚地弓形虫感染对大鼠细胞因子和生精细胞的影响

Effect of Toxoplasma gondii Infection on Cytokines and Spermatogenic Cells in Rats

目的研究弓形虫感染对雄性大鼠血清1型T辅助细胞（Th1）和2型T辅助细胞（Th2）细胞因子水平，以及睾丸的病理损伤和各级生精细胞凋亡的影响。方法将9～10周龄雄性SD大鼠88只随机分为感染组和健康对照组（每组44只）。感染组腹腔注射弓形虫速殖子1×10^4个／只，健康对照组注射等量PBS，于感染前和感染后第3、6、9、12、……和30天取两组大鼠各4只，分离血清及取睾丸，EUSA检测血清1干扰素（IFN-γ）和白细胞介素-4（IL-4）水平变化．对睾丸进行病理学检查和免疫组化检测生精小管凋亡蛋白Bel-2和Bax的表达改变。结果感染组大鼠感染速殖子后血清IFN-γ迅速升高，在感染后第6天出现峰值[（518．3±83．6）pg/ml]后迅速降低；血清114升高缓慢，于第12天达到峰值[（325．0±38．6）pg/ml]后逐渐降低。两者在感染后30d内均显著高于健康对照组（P〈0．01）。病理学检查发现，感染组大鼠感染后第6天睾丸生精小管细胞层次紊乱，初级精母细胞和次级精母细胞明显减少，管腔内精子稀少甚至管腔闭合，感染后30d内未见明显改善。感染组大鼠于感染后第3天睾丸细胞的Bax表达即显著增加（P〈0．01），第6天达到峰值（0．547±0．037）后逐渐减少，15d后恢复至正常水平。感染组大鼠睾丸细胞Bel-2表达无明显变化。结论弓形虫可导致生精细胞严重的病理损伤，在急性期出现Th1细胞因子极化，伴有精母细胞凋亡蛋白Bax的高表达；Th1／Th2重新平衡后，Bax蛋白表达减少。但生精过程无明显恢复。

Objeetlve To study on the fluctuation of cytokines of T helper type 1 （Thl） and T helper type 2 （Th2） after Toxoplasma gondii infection, as well as pathological damage of testis and apoptosis of spermatogenic ceils in male rats. Methods Eighty-eight SD male rats （9-10 week old） were randomly and equally divided into normal control group and infection group. Rats in infection group were infected with 1×10^4 tachyzoites by intraperitoneal injection, while those in normal control group received same volume of PBS. On the day before infection and at the 3rd, 6th, 9th, 12th, , and 30th day post infection, four rats from each group were sacrificed for sera and testes, v-interferon （IFN-γ） and interleukin-4 （IL-4） levels in sera were measured by ELISA. The testes were sliced and observed by microscope. The levels of apoptosis relative proteins Bcl-2 and Bax in seminiferous tubules were detected by immunohistochemistry. Results IFN-γ in sera of infected rats increased rapidly with the peak [（518.3±83.6） pg/ml] at the 6th day post infection, and then decreased rapidly. IL-4 increased slowly with the peak [（325.0±38.6）pg/ml] at the 12th day, and then decreased. Both cytokines were significantly higher than the control （P〈0.01） in the 30-day period. Pathological examination at the 6th day post infection showed that the cell levels of testicular seminiferous tubule disturbed. The number of primary and secondary spermatoeytes decreased significantly. There were few sperms within the lumen or cavity which even closed. All the changes did not recover during 30 days. Bax expression in infected rats significantly increased in spermatogenic cells especially in spermatocytes at the 3rd day （P〈0.05）, reached a peak （0.547±0.037） at the 6th day, and then gradually decreased to normal after 15 days. The expression of Bel-2 in infected rats did not change significantly （P〉0.05）. Conclusion T. gondii causes severe pathological damage in spermatogenic cells of the host. During the acute phase there appears Thl eytokine polarization accompanied by high expression of apoptosis protein Bax, which is mainly expressed in spermatocytes. After re-balance of Th1/Th2, Bax protein expression decreases without noticeable recovery of spermatogenesis.