摘要目的 研究慢性氟中毒神经损伤大鼠过氧化物酶体增殖物激活受体γ(PPARγ)的表达改变,探讨其与氧化应激水平的关系.方法 健康纯系SD大鼠60只,体质量为100～ 120 g,按体质量采用随机数字表法分为对照组(饮水氟含量＜ 0.5 mg/L)、低氟组(饮水氟含量为5.0 mg/L)、高氟组(饮水氟含量为50.0 mg/L),每组20只,雌雄各半,染氟时间分别为3和6个月.染氟结束后,收集各组大鼠24h尿液;处死大鼠,取脑组织,采用氟离子选择电极法测定大鼠尿氟及脑氟含量;蛋白质免疫印迹法(Western blot)和实时荧光定量PCR(Real-time PCR)法分别检测大鼠脑组织中PPARγ蛋白和mRNA表达水平;黄嘌呤氧化酶法和硫代巴比妥酸法测定大鼠血清超氧化物歧化酶(SOD)活性及丙二醛(MDA)含量,并分析PPARγ蛋白表达与SOD及MDA的相关关系.结果 染氟3和6个月,低氟组大鼠尿氟及脑氟含量[(1.57±0.18)mg/L、(3.43±0.70)μg/g,(1.79±0.17)mg/L、(7.40±1.21) μg/g]高于对照组[(1.11±0.17)mg/L、(2.39±0.50)μg/g,(1.02±0.15)mg/L、(2.87±0.82)μg/g,P均＜0.05],且高氟组[(1.91±0.23)mg/L、(6.70±0.87) μg/g,(2.44±0.51)mg/L、(12.10±1.30)μg/g]明显高于低氟组(P均＜0.05).染氟3个月,高氟组大鼠脑组织海马及皮质的PPARγ蛋白[(79.00±3.46)％、(80.35±2.50)％]及mRNA[(79.11±11.18)％、(82.10±9.94)％]表达均低于低氟组[(104.01±5.77)％、(101.17±635)％,(112.88±22.15)％、(101.14±8.60)％,P均＜0.05];染氟6个月,高氟组大鼠脑组织海马及皮质的PPARγ蛋白[(6432±10.43)％、(60.20±10.92)％]及mRNA[(41.03±9.93)％、(52.25±11.48)％]表达低于对照组[(99.99±11.19)％、(100.00±11.30)％,(100.00±10.00)％、(100.00±9.00)％]和低氟组[(73.88±3.36)％、(81.50±14.90)％,(76.02±8.65)％、(73.36±7.43)％,P均＜0.05].染氟6个月,低、高氟组大鼠血清SOD活性[(37.94±1.92)、(35.54±2.53)U/ml]低于对照组[(41.24±0.66)U/ml,P均＜0.05],且高氟组低于低氟组(P＜0.05);染氟3和6个月,高氟组大鼠血清MDA含量[(8.29±1.49)、(11.63±1.04)nmol/mg pr]高于低氟组[(6.39±0.69)、(7.50±1.64)nmol/mg pr]和对照组[(5.02±0.71)、(5.87±1.03)nmol/mg pr,P均＜0.05].相关分析结果显示,大鼠脑组织海马及皮质PPARγ蛋白表达与脑氟含量呈负相关(3个月:r=-0.769、-0.793,6个月:r=-0.832、-0.870,P均＜0.05),与大鼠血清SOD活性呈正相关(3个月:r=0.550、0.826,6个月:r=0.822、0.896,P均＜0.05),与MDA含量呈负相关(3个月:r=-0.703、-0.609,6个月:r=-0.792、-0.657,P均＜0.05).结论 慢性氟中毒大鼠脑组织PPARγ蛋白及mRNA表达水平降低,与氧化应激水平升高有关,PPARγ参与了慢性氟中毒的发生.

abstractsObjective To detect the expression of peroxisome proliferator-activated receptor γ (PPARγ) in the brains of rats with chronic fluorosis and elucidate the relationship between PPARγand oxidative stress in chronic fluorosis.Methods According to body weight (100-120 g),sixty healthy SD rats were divided into control group (less than 0.5 mg/L fluoride in drinking water),low fluoride group (5.0 mg/L fluoride in drinking water,prepared by NaF),and high fluoride group (50.0 mg/L fluoride in drinking water) via the random number table method,20 rats in each group (half male and half female).The experiment periods were 3 and 6 months,respectively.Then 24-hour urine samples of rats were collected from each group,all rats were put to death and brain tissues were taken.The fluoride contents in urine and brain tissue were measured with fluoride-ion selective electrode;the levels of PPARγ protein and mRNA in the cortex and hippocampus were determined by Western blotting and Real-time fluorescence quantitative PCR,respectively;and the activities of superoxide dismutase (SOD) and level of malondialdehyde (MDA) in serum were detected by xanthine oxidase method and thiobarbituric acid method;the correlation between PPARγ protein expression and oxidative stress was analyzed.Results After 3 and 6 months of treatment,the contents of fluoride in urine and brain in low fluoride group [(1.57 ± 0.18) mg/L,(3.43 ± 0.70) μg/g;(1.79 ± 0.17) mg/L,(7.40 ± 1.21) μg/g] were higher than those of control group [(1.11 ± 0.17) mg/L,(2.39 ± 0.50) μg/g;(1.02 ± 0.15) mg/L,(2.87 ± 0.82) μg/g,P ＜ 0.05],and the values in high fluoride group [(1.91 ± 0.23) mg/L,(6.70 ± 0.87) μg/g;(2.44 ± 0.51) mg/L,(12.10 ± 1.30) μg/g] were significantly higher than those in low fluoride group (P ＜ 0.05).In high fluoride group after 3 months of treatment,the expression of PPARγprotein [(79.00 ± 3.46)％,(80.35 ± 2.50)％] and mRNA [(79.11 ± 11.18)％,(82.10 ± 9.94)％] in hippocampus and cortex of rat brains were significantly lower than those of low fluoride group [(104.01 ± 5.77)％,(101.17 ± 6.35)％;(112.88 ± 22.15)％,(101.14 ± 8.60)％,P＜ 0.05];the expression of PPARγprotein [(64.32 ± 10.43)％,(60.20 ± 10.92)％] and mRNA [(41.03 ± 9.93)％,(52.25 ± 11.48)％] in the same brain regions of the rats after 6 months of treatment in high fluoride group were significantly lower than those of control group [(99.99 ± 11.19)％,(100.00 ± 11.30)％;(100.00 ± 10.00)％,(100.00 ± 9.00)％] and low fluoride group [(73.88 ± 3.36)％,(81.50 ± 14.90)％;(76.02 ± 8.65)％,(73.36 ± 7.43)％,P ＜ 0.05].The activities of SOD in serum in low and high fluoride groups after 6 month treatment [(37.94 ± 1.92),(35.54 ± 2.53) U/ml] were significantly lower than that of control group [(41.24 ± 0.66) U/ml,P ＜ 0.05],and the value in high fluoride group was lower than that in low fluoride group (P ＜ 0.05);serum MDA contents in high fluoride group after 3 and 6 month treatment [(8.29 ± 1.49),(11.63 ± 1.04) nmol/mg pr] were higher than those in low fluoride group [(6.39 ± 0.69),(7.50 ± 1.64) nmol/mg pr] and control group [(5.02 ± 0.71),(5.87 ± 1.03) nmol/mg pr,P ＜ 0.05].The correlation analysis results showed the levels of PPARγprotein in hippocampus and cortex of rats were negatively correlated with fluoride contents in brain tissues (3 month:r=-0.769,-0.793;6 month:r =-0.832,-0.870;P ＜ 0.05),positively correlated with SOD activities (3 month:r =0.550,0.826;6 month:r =0.822,0.896;P ＜ 0.05) and negatively correlated with MDA contents (3 month:r =-0.703,-0.609,6 month:r =-0.792,-0.657;P ＜ 0.05) in serum.Conclusions Declined expression of PPARγat protein and mRNA levels has been detected in brains of rats with chronic fluorosis,which might be related to the increase of oxidative stress.PPARγ may be involved in the occurrence of chronic fluorosis.