| Objective To observe whether chronically exposed systemic inflammatory cytokines of PM2.5 in female SD rats affect postmenopausal bone metabolism.Methods Three-week-old female SD rats(SPF grade)were randomly divided into castration group and sham operation group after 1 week of adaptation,and the two groups were further divided into control group(PBS 20μl)and low(PM2.5 7.8μg(3.9μl)+PBS 16.1μl),medium(PM2.5 16.5μg(8.25μl)+PBS 11.75μl),high(PM2.533.3μg(16.65μl)+PBS 3.35μl)PM2.5 exposure group,Each group had N=24 animals,and they were exposed to continuous tracheal instillation(3 doses were given at a time,once every 3 days),for a total of 8 months of exposure.Femur,tibia and lumbar spine bone mineral density were measured at the end of February,April,June and August at the exposure of PM2.5 airway in rats,and the peripheral venous blood of rats was collected for ELISA to determine inflammatory cytokines IL-6,TNF α)expression level.At the end of the fifth month of PM2.5 airway exposure in rats,surgery was performed.Both ovaries were removed in the ovariectomized group and adipose tissue the size of the ovary was removed in the sham-operated group.Results(1)Exposure to different concentrations of PM2.5:①.The density of tibia and femur in the castration group did not show significant(F=1.882,P=0.1320;Z=5.881,P=0.118),while the lumbar spine bone density showed Significance(Z=28.890,P=0.000);sham operation group did not show significant tibial density(F=1.888,P=0.132),while femoral density and lumbar spine bone density showed significant(Z=15.671,P=0.001;Z=9.757,P=0.021)(see Table 3,Table 4).②.It is known from Tables 6 and 7 that lumbar spine bone density,femoral bone density and tibial bone density showed a significant level of 0.05 in the castration group and the sham operation group(Z=-3.101,P=0.002;Z=-3.310,P=0.001;t=8.567,P=0.000),and the tibial density,femoral density,and lumbar spine density in the ovariectomized group were significantly lost compared with the sham-operated group.(2)Under chronic(time)PM2.5 exposure:①.The castration group had significant differences in tibia density,femur density,and lumbar spine density(F=47.463,P=0.000;Z=82.193,P=0.000;Z=118.775,P=0.000);sham-operation group showed tibia density of 0.05 level(F=3.683,P=0.013),while femur density and lumbar spine density did not show 0.05 level significance(Z=4.406,P=0.221;Z=5.941,P=0.115)(see Table 8 and Table 10).That is,the bone density of the femur and lumbar spine in the castration group showed significant bone loss under chronic(time)PM2.5 exposure(Table 10).②.Bone mineral density of tibia,femur and lumbar spine showed a significant level of 0.05 in castration group and sham operation group(t=3.254,P=0.001;Z=-4.797,P=0.000;Z=-6.782,P=0.000),and the mean tibial density(0.2452± 0.0153),the median femoral density(0.3345)and the median lumbar vertebral bone density(0.3442)in the ovariectomized group were higher than the average tibial density in the sham group(0.2511±0.0170),the median of femoral bone density(0.3448)and the median of lumbar bone density(0.3638)were significantly lost(see Table 12 and Table 13),(3)Exposure at different concentrations of PM2.5:①.TNF a in the ovariectomized group showed a significant level of 0.01(Z=30.783,P=0.000),while IL-6 and IL-1α did not have a significant level at 0.05 Sex difference(Z=6.733,P=0.081;Z=5.792,P=0.122);the sham operation group IL-1α,IL-6 and TNF a showed a significant level of 0.01(Z=15.816,P=0.001;Z=20.747,P=0.000;Z=27.694,P=0.000)(see Table 14).②.Inflammatory cytokines(IL-1α,IL-6,TNF α)in the ovariectomized group and the sham-operated group showed 0.05 levels of significance(Z=-2.243,P=0.025;Z=-2.342,P=0.019;Z=-3.546,P=0.000).The inflammatory cytokines(IL-1α,IL-6,TNF α)in the ovariectomized group were significantly higher than those in the sham-operated group(IL-1α,IL-6,TNF α)(see Table 16).(4)Under chronic(time)PM2.5 exposure:①.The inflammatory cytokines(IL-1α,IL-6,TNF α)in the ovariectomized group showed a significant level of 0.05(Z=18.39,P=0.000;Z=46.995,P=0.000;Z=113.023,P=0.000);the inflammatory cytokines(IL-1α,IL-6,TNF α)in the sham operation group also showed a significant level of 0.05(Z=14.436,P=0.002;Z=31.473,P=0.000;Z=85.033,P=0.000)(see Table 17).②.The levels of serum inflammatory cytokines(IL-1α,IL-6,TNF α)in the two groups(between)showed a significant level of 0.05(Z=-2.243,P=0.025;Z=-2.342,P=0,019;Z=-3.546,P=0.000),the differences were statistically significant.Moreover,the levels of inflammatory cytokines(IL-1α,IL-6,TNF α)in the ovariectomized group were significantly higher than those in the sham operation group(IL-1α,IL-6,TNF α)(see Table 19).(5)Comparison between the two groups before and after the operation:①.Compare the pre-operation(ie the end of February and the end of April)and the post-operation(ie the end of June and the end of August)exposed to PM2.5,we can see that the castration group Femoral density,lumbar vertebral bone density and tibial bone density showed a significant level of 0.01 before and after surgery(Z=9.050,P=0.000;Z=11.079,P=0.000;t=18.618,P=0.000),and The postoperative femoral,lumbar,and tibial densities of the potential group were significantly higher than those of the preoperative femoral,lumbar,and tibia.Sham operation group:The lumbar spine BMD showed 0.01 level significance before and after the operation(t=3.246,P=0.001),and the lumbar spine BMD was significantly lost after the operation compared with the preoperative lumbar spine BMD.It was not significant before and after surgery(Z=-0.895,P=0.371;t=0.690,P=0.491)(see Table 20 and Table 21).Comparing the bone mineral density of the two groups after operation(at the end of June and the end of August):the tibia density,femur density and lumbar spine bone density in the two groups showed a significant level of 0.01(Z=-9.710,P=0.000;Z=-6.500,P=0.000;Z=-6.782,P=0.000).The bone density of the tibia,femur and lumbar vertebrae in the ovariectomized group was significantly lower than that in the sham-operated group(see Table 22).②.The difference in inflammatory cytokine levels between castration group and sham operation group before and after operation was statistically significant(P<0.05),and the level of inflammatory cytokine in castration group was significantly higher than that in sham operation group Level(see Table 23).At the same time,the comparison of postoperative inflammatory cytokine levels between the two groups(between groups)showed a significant level of 0.05(Z=2.701,P=0.007;Z=-2.344,P=0.019;Z=-3.981,P=0.000),And the level of inflammatory factors in the castration group was significantly higher than the sham operation group(see Table 24).(6)Bone density at different sites was negatively correlated with the levels of inflammatory cytokines(IL-1α,IL-6,TNF α),the difference was statistically significant(P<0.05).It is known by multiple linear regression(Table 26):Increased levels of inflammatory cytokines(TNF α)can promote bone destruction in different parts,the difference is statistically significant P<0.05;The increase is not linearly related to the destruction of bone.The significantly increased inflammatory cytokines at the end of June had no correlation with bone destruction.Conclusion Chronic PM2.5 airway exposure can cause bone loss in female rats and significantly increase the levels of peripheral blood inflammatory cytokines(IL-1α,IL-6,TNF α),both of which show a significant time dependence and certain The degree of dose dependence.At the same time,after castration(that is,low estrogen levels)can significantly accelerate the bone damage caused by PM2.5 exposure(the lumbar spine bone loss is the most significant)and the level of inflammatory cytokines is significantly increased.From the multivariate linear analysis,it can be seen that bone density in different parts is negatively correlated with the levels of inflammatory cytokines(IL-1α,IL-6,TNF α).Increased levels of TNF a can promote bone destruction in different parts.Elevated IL-6 levels contribute to the small contribution of bone destruction,suggesting that long-term chronic exposure of PM2.5 promotes bone loss and there may be multiple effect molecules involved in bone metabolism.Inflammatory cytokines(IL-1α,IL-6,TNF α)produced during acute conditions are not involved in bone destruction. |
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