硝酸镧对成年雌性小鼠免疫功能及细胞病理学的影响

Effects of lanthanum nitrate on immune function and cell pathology in adult female mice

[背景]镧是一种重要的稀土元素,能引起多种器官和系统损伤,然而其对免疫系统影响的研究尚不全面,且目前我国尚未提出公认的镧的安全阈值。[目的]探讨硝酸镧对成年雌性小鼠免疫功能和细胞病理学的影响。[方法]将50只6^8周龄雌性BALB/c小鼠随机分为5组,每组10只,灌胃给予硝酸镧溶液,剂量分别为0(超纯水)、0.2、2.0、20.0、200.0 mg·kg^-1,每日灌胃1次,连续灌胃30 d。染毒结束后,颈椎脱臼法处死小鼠,分离胸腺、脾脏和肠系膜淋巴结称重并计算脏器系数,用刀豆蛋白A(ConA)和细菌脂多糖(LPS)诱导的淋巴细胞转化实验测定脾脏T、B细胞增殖能力,用乳酸脱氢酶法(LDH)测定脾脏NK细胞活性,用流式细胞术测定胸腺、脾脏和肠系膜淋巴结主要免疫细胞分型。[结果]与对照组相比,2.0、20.0、200.0 mg·kg^-1组小鼠脾T细胞增殖能力降低(分别是0.65±0.13、0.67±0.13、0.64±0.14 vs 0.85±0.20,P <0.05);20.0、200.0 mg·kg^-1组小鼠脾B细胞增殖能力降低(分别是0.34±0.10、0.29±0.05 vs 0.52±0.07,P <0.01),且存在剂量-效应关系(r=-0.96,P <0.01)。仅在2.0 mg·kg^-1组观察到小鼠脾脏NK细胞活性降低(0.28±0.06 vs0.45±0.04,P <0.01)。与对照组相比,2.0 mg·kg^-1组小鼠脾脏CD4^+/CD8^+值升高(2.27±0.29 vs1.81±0.33,P <0.01),200.0 mg·kg^-1组小鼠脾脏CD4^+CD8^-和CD4^-CD8^+型T细胞比例升高(分别是30.26±3.96 vs 24.19±2.70和21.01±5.11 vs 13.59±2.77,P <0.05)、脾脏B细胞比例下降(38.07±6.71 vs 50.63±6.71,P <0.01)、肠系膜淋巴结CD4^+CD8^-型T细胞比例下降(28.21±7.38vs 40.78±10.19,P <0.01);0.2、2.0 mg·kg^-1组小鼠肠系膜淋巴结CD4^+/CD8^+值升高(分别是3.64±0.24和4.55±1.01 vs 2.84±0.62,P <0.05和P <0.01);2.0 mg·kg^-1组肠系膜淋巴结CD4^+CD8^-型T细胞比例升高(55.55±4.03 vs 40.78±10.19,P <0.05),而CD4^-CD8^+型T细胞比例下降(0.43±0.30 vs 1.57±0.52,P <0.05)。[结论]经口摄入2.0、20.0、200.0 mg·kg^-1硝酸镧后能引起成年雌性小鼠机体免疫系统和肠系膜淋巴结局部免疫功能紊乱,产生免疫毒性作用。30 d硝酸镧灌胃染毒引起成年雌性小鼠免疫系统功能紊乱的最小毒性反应剂量为2.0 mg·kg^-1。

[Background]As an important rare earth element,lanthanum can cause damage to multiple organs and systems.However,the impacts of lanthanum on the immune system are not comprehensively studied and no recognized safety threshold of lanthanum has been established in China.[Objective]The present study is designed to explore the effects of lanthanum nitrate on the immune function and cell pathology in adult female mice.[Methods]Fifty female BALB/c mice(6-8 weeks old)were randomly divided into five groups of ten each.Lanthanum nitrate was administered once daily by gavage at concentrations of 0(ultrapure water),0.2,2.0,20.0,and 200.0mg·kg-1,respectively,per day for 30 d.After designed treatment,the mice were sacrificed by cervical dislocation and then the thymus,spleen,and mesenteric lymph nodes were isolated and weighed to calculate organ coefficients.Concanavalin A(ConA)and lipopolysaccharide(LPS)-induced lymphocyte proliferation test was conducted to evaluate the proliferation capacity of T and B cells from the spleen.Lactate dehydrogenase(LDH)release of target cells was measured to express the viability of NK cells.Flow cytometry was used to detect types of major immune cells in the thymus,spleen,and mesenteric lymph nodes.[Results]Compared with the control group,there was a decrease in T lymphocyte proliferation in the 2.0,20.0,and 200.0 mg·kg-1 lanthanum nitrate groups(0.65±0.13,0.67±0.13,and 0.64±0.14 vs 0.85±0.20,respectively,P<0.05);there was also a decrease in B lymphocyte proliferation in the 20.0 and 200.0 mg·kg-1 lanthanum nitrate groups(0.34±0.10 and 0.29±0.05 vs 0.52±0.07,respectively,P<0.01)in a dose-effect relationship(r=-0.96,P<0.01).The spleen NK cell viability was only reduced in the 2.0mg·kg-1 lanthanum nitrate group(0.28±0.06 vs 0.45±0.04,P<0.01).Compared with the control group,in the 2.0mg·kg-1 lanthanum nitrate group,the CD4+/CD8+ratio in spleen increased(2.27±0.29 vs 1.81±0.33,P<0.01);in the 200.0mg·kg-1 lanthanum nitrate group,the CD4+CD8-and CD4-CD8+T cell ratios increased(30.26±3.96 vs 24.19±2.70,21.01±5.11 vs 13.59±2.77,P<0.05),the spleen B cell percentage decreased(38.07±6.71 vs 50.63±6.71,P<0.01),and the CD4+CD8-T cell ratio in mesenteric lymph nodes decreased(28.21±7.38 vs 40.78±10.19,P<0.01);in the 0.2 and 2.0mg·kg-1 lanthanum nitrate groups,the CD4+/CD8+T cell ratio in mesenteric lymph nodes increased(3.64±0.24 and 4.55±1.01 vs 2.84±0.62,respectively,P<0.05 and P<0.01);in the 2.0mg·kg-1 lanthanum nitrate group,the CD4+CD8-T cell ratio in mesenteric lymph nodes increased(55.55±4.03 vs 40.78±10.19,P<0.05),and the CD4-CD8+T cell ratio decreased(0.43±0.30 vs 1.57±0.52,P<0.05).[Conclusion]Oral intake of lanthanum nitrate at the doses of 2.0,20.0,and 200.0mg·kg-1 could exert a toxic effect on the immune system of adult female mice,disrupting the function of immune system and local mesenteric lymph nodes.The lowest observed adverse effect level of lanthanum nitrate exposure by gavage for 30d inducing immune function disorder in adult female mice is 2.0mg·kg-1.