The impact of long-term dexamethasone administration on diaphragmatic atrophy in rats with acute respiratory distress syndrome
Objective To investigate the impact of dexamethasone(DEX)on diaphragmatic atrophy caused by acute respiratory distress syndrome(ARDS)and its correlation with diaphragmatic protein metabolism.Methods Twenty healthy male Sprague-Dawley(SD)rats were randomly assigned to control,ARDS model,low-dose DEX,and high-dose DEX group,with each group consisting of five rats.ARDS was induced in the rats by intratracheal administration of lipopolysaccharide(LPS)at 4 mg/kg.Conversely,intratracheal saline was administered to the control group at 2 mL/kg.Following the induction of the model,an intraperitoneal injection of DEX at 1 mg·kg-1·d-1 was administered to the low-dose DEX group.Conversely,DEX at 5 mg·kg-1·d-1 was administered to the high-dose group for 7 consecutive days.Subsequently,on the eighth day of the experiment,the diaphragmatic weight of all rats was measured.Real-time quantitative polymerase chain reaction(PCR)was utilized to assess the mRNA expression of interleukins(IL-1β,IL-18)in each group.Western blotting was employed to determine the protein expression levels of nuclear factor-κB(NF-κB)p65,NOD-like receptor protein 3(NLRP3),caspase-1,Gasdermin D(GSDMD),myosin heavy chain 2(Myh2),and F-box protein 32(Fbxo32).Additionally,immunohistochemistry was utilized to evaluate the ratio of fast to slow muscle fibers in the diaphragm.Results The ARDS model group showed significant reductions in body weight,diaphragm weight,fast muscle fibers,and Myh2 protein expression compared to the control group[body weight(g):266±17 vs.292±15,diaphragm weight(g):0.77±0.02 vs.0.92±0.08,fast muscle fibers:(74±1)%vs.(78±3)%,Myh2 protein expression(Avalue):0.75±0.07 vs.0.95±0.05,all P<0.05].Conversely,significant increases were observed in the expressions of IL-1β and IL-18 mRNA,slow muscle fibers,and the proteins NF-κB p65,NLRP3,caspase-1,GSDMD,Fbxo32[IL-1β mRNA(IL-1β/GAPDH):2.2±0.3 vs.1.0±0.2,IL-18 mRNA(IL-18/GAPDH):2.3±0.3 vs.1.0±0.3,slow muscle fibers:(26±1)%vs.(22±3)%,NF-κB p65 protein expression(A value):0.40±0.15 vs.0.17±0.05,NLRP3 protein expression(A value):0.51±0.05 vs.0.27±0.08,caspase-1 protein expression(A value):0.54±0.12 vs.0.30±0.19,GSDMD protein expression(A value):0.40±0.12 vs.0.20±0.05,Fbxo32 protein expression(A value):0.51±0.15 vs.0.33±0.08,all P<0.05].Compared with the ARDS group,both low and high doses of DEX were found to further reduce body weight,diaphragm weight,fast muscle fibers,and Myh2 protein expression,and further increase the expressions of IL-1β and IL-18 mRNA,slow muscle fibers,and the proteins NF-κB p65,NLRP3,caspase-1,GSDMD,Fbxo32,with the changes in the high dose DEX group being more significant than those in the low dose group[body weight(g):198±14 vs.222±16,diaphragm weight(g):0.57±0.04 vs.0.68±0.04,fast muscle fibers:(56±5)%vs.(69±2)%,Myh2 protein expression(A value):0.29±0.16 vs.0.57±0.15,IL-1βmRNA expression:5.6±1.4 vs.3.3±0.6,IL-18 mRNA expression(IL-18/GAPDH):5.8±1.2 vs.3.9±0.6,slow muscle fibers:(44±5)%vs.(31±2)%,NF-κB p65 protein expression(A value):0.87±0.04 vs.0.70±0.07,NLRP3 protein expression(A value):0.75±0.08 vs.0.63±0.04,caspase-1 protein expression(A value):0.99±0.06 vs.0.82±0.08,GSDMD protein expression(Avalue):0.85±0.11 vs.0.61±0.10,Fbxo32 protein expression(Avalue):1.00±0.10 vs.0.78±0.12,all P<0.05].Normal muscle fiber structure was revealed by microscopic observation in the control group,clear fiber separation in the ARDS model group,and disordered muscle fiber arrangement with structural distortion was noted in both low and high-dose DEX groups.Conclusion Prolonged administration of DEX may worsen diaphragmatic atrophy induced by ARDS,possibly by promoting the activation of the NLRP3 inflammasome and cell pyroptosis.
Acute respiratory distress syndromeDiaphragmAtrophyNOD-like receptor protein 3 inflammasomePyroptosis
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