Effect Of Erythromycin On Skeletal Muscle Inflammation And Relative Mechnisms In A Mouse Modle Of Tobacco Smoke-induced Emphysema

Objective To observe changes of inflammatory cytokine,histone deacetylase 2(HDAC2)and nuclear factor-?B(NF-?B)in skeletal muscle from emphysematous mice.Furthermore,observing effect of erythromycin on skeletal muscle inflammation.Methods In current study,murine modles of emphysema were established with tobacco smoke exposure.Based on the models,BALB/c mice were randomly divided into TS group and EM group,with 6 mice in each group.Control group(C group)was also allocated.Mice in EM group would receive erythromycin while those in TS group received saline orally,at a dose of 80 mg/kg,1 h before exposure to tobacco smoke everyday.All of the mice were sacrificed after 4 weeks.Hematoxylin and eosin(H&E)staining was performed in order to observed pathomorphological changes in lung tissue and skeletal muscle of quadriceps femoris muscle.Pulmonary mean linear intercept(MLI)and the mean cross-sectional area(CSA)of myofibers in the quadriceps femoris muscle were measured.The levels of interleukin-8(IL-8)and tumor necrosis factor-?(TNF-a)in the homogenates of skeletal muscle were measured by enzyme linked immunosorbent assay(ELISA).The protein level of HDAC2,NF-?B p65 and myosin heavy chain(MyHC)in skeletal muscle were detected by Western blotting(WB).The mRNA level of HDAC2 and NF-?B in skeletal muscle were determined by real-time quantitative PCR(qRT-PCR).Results 1.Assessment of emphysematous models:The mice in TS group showed destructive alveolar wall and enlargement of alveolar space,along with infiltration of inflammatory cells in airway and pulmonary parenchyma,which mainly dominated by lymphocytes.The MLI of TS group was grater than that of C group(P<0.05).When compared with C group,lung function of specific airway resistance(sRaw)was higher(P<0.001),while tidal volume(TV),peak expiratory flow(PEF)and EF50 were lower in TS group(all of P<0.05).2.The changes in body weight:During the exposure period,body weights of mice in TS group remained unchanged(P>0.05).Body weights of mice in EM group were increased,though slowly(till the end of week 28 the mean weight was greater than that of week 0,P<0.05).Both weights of tihese two groups were lower than C group(both P<0.05).3.Histopathologi-cal findings of skeletal muscle:Myofibers of quadriceps femoris muscle from TS group and EM group were disorganized,some of which were lysed,ruptured or necrotic.The mean myofiber CS A of TS group and EM group showed no signficant difference,but both were smaller than that of C group(both P<0.001).4.Levels of inflammatory cytocine IL-8 and TNF-? in homogenates of skeletal muscle:The levels of IL-8 and TNF-? in TS group were significantly higher than C group(all of P<0.001).VWhen compared with TS group,the levels of IL-8 and TNF-? in EM group were dramatically reduced(P<0.01,P<0.001).5.The expression of MyHC protein in murine skeletal muscle:The level of MyHC protein dramatically decreased in TS group compared with C group(P<0.001).After treatment with erythromycin,the level of MyHC protein increased compared with TS group(P<0.05)while still lower than that of C group(P<0.001).6.The expression level of NF-?B in murine skeletal muscle:The expression levels of NF-K?B mRNA and p65 protein significantly increased in TS group compared with C group(P<0.001,P<0.01),while decreased dramatically in EM group compared with TS group(P<0.01,P<0.01).7.The expression level of HDAC2 in murine skeletal muscle:The relative expression levels of HDAC2 mRNA and protein in TS group were significantly lower than those of C group(P<0.001,P<0.01).The levels of HDAC2 mRNA and protein in EM group were significantly higher than TS group(P<0.001,P<0.001)while still lower than those of C group(P<0.001,P<0.05).Conclusion 1.Structural changes and inflammatory response occur in skeletal muscle of emphysematous mice exposed to tobacco smoke.The level of HDAC2,which regulates inflammatory process,is reduced while transcription factor NF-?B increases its expression.2.Erythromycin can alleviate inflammatory response in skeletal muscle of emphysematous mice,possibly by improving the expression of HDAC2 and inhibiting the expression of NF-kB.