吡啶甲酸镁联合地塞米松对急性呼吸窘迫综合征大鼠的治疗作用研究

Therapeutic effect of magnesium picolinate and dexamethasone on acute respiratory distress syndrome rats

目的探讨吡啶甲酸镁(MgPic)对接受地塞米松(Dex)治疗的急性呼吸窘迫综合征(ARDS)大鼠肺脏和膈肌的影响。方法将20只健康成年雄性Sprague-Dawley大鼠按照随机数字表法分为对照组、ARDS组、Dex组及MgPic组,每组各5只。对照组大鼠给予气管内雾化等渗NaCl溶液2 mL/kg,其他三组大鼠给予气管内雾化脂多糖4 mg/kg诱发ARDS。建模成功后,Dex组和MgPic组大鼠连续7 d腹腔注射Dex(1 mg·kg^(-1)·d^(-1))。对照组、ARDS组和Dex组饲喂标准饮食,而MgPic组则饲喂添加了MgPic(500 mg/kg)的标准饮食。连续饲养7 d并禁食12 h后,测量大鼠体质量及测定血清镁离子(Mg^(2+))浓度,并进行肺功能评估,包括吸气峰流速(PIF)、呼气峰流速(PEF)、潮气量(Vt)、分钟通气量(Mv)以及呼气中期流速(EF50)。计算肺组织湿干重(W/D)比值及测量膈肌重量。检测支气管肺泡灌洗液(BALF)中肿瘤坏死因子α(TNF-α)及Ⅲ型前胶原蛋白(PCⅢ)的浓度。采用western-blotting检测肺组织转化生长因子β1(TGF-β1)、膈肌组织抗肌球蛋白重链2(MYH2)蛋白表达水平。采用实时定量PCR(qRT-PCR)检测肺组织TGF-β1信使RNA(mRNA)的表达以及膈肌组织中肌肉环指蛋白1(MURF-1)和叉头转录因子O1(FoxO1)mRNA的表达水平。结果各组大鼠的体质量、PIF、PEF、Vt、Mv、EF50、血清Mg^(2+)浓度,肺组织W/D比值、TGF-β1 mRNA、TGF-β1蛋白水平,BALF中TNF-α、PCⅢ含量,膈肌重量、MURF-1 mRNA、FoxO1 mRNA和MYH2蛋白表达水平比较,差异均有统计学意义(F=21.248、57.536、34.547、26.022、32.458、90.029、79.975、20.767、37.857、99.653、64.862、46.587、19.187、32.653、41.110、71.535,P均<0.001)。进一步两两比较发现,与MgPic组比较,ARDS组大鼠体质量、膈肌重量及MYH2蛋白表达水平均显著升高,MURF-1 mRNA和FoxO1 mRNA表达水平均显著下降(P均<0.05);Dex组大鼠体质量、膈肌重量及MYH2蛋白表达水平均显著降低,MURF-1 mRNA和FoxO1 mRNA表达水平均显著升高(P均<0.05);ARDS组和Dex组大鼠PIF、PEF、Vt、Mv和EF50水平及Mg^(2+)浓度均显著降低,且ARDS组PIF、PEF、Vt、Mv和EF50水平更低,而Mg^(2+)浓度在Dex组更低(P均<0.05);ARDS组和Dex组肺组织的W/D比值、TGF-β1 mRNA、TGF-β1蛋白水平,BALF中TNF-α和PCⅢ水平均显著升高,且ARDS组更高(P均<0.05)。结论MgPic能够增强Dex对ARDS大鼠肺组织纤维化的抑制作用,改善Dex引起的膈肌萎缩,有助于改善肺功能。

Objective To investigate the effect of magnesium picolinate(MgPic)on lung and diaphragm of rats with acute respiratory distress syndrome(ARDS)treated with dexamethasone(Dex).Methods Twenty healthy adult male Sprague-Dawley rats were randomly assigned to a control group,an ARDS group,a Dex group,and a MgPic group,with five rats in each group.Rats in the control group were given 2 mL/kg isotonic NaCl solution with endotracheal atomization,and rats in the other three groups received endotracheally atomized lipopolysaccharide(4 mg/kg)to induce ARDS.After successful modeling,rats in the Dex and MgPic groups were intraperitoneally injected with Dex(1 mg·kg^(-1)·d^(-1))for seven consecutive days.Rats in the control,ARDS,and Dex groups were fed a standard diet,while rats in the MgPic group were fed a standard diet supplemented with 500 mg/kg MgPic.After continuous feeding for seven days and fasting for 12 h,the body mass and serum Mg^(2+)concentration of rats were measured,and the lung function was evaluated,including peak inspiratory flow rate(PIF),peak expiratory flow rate(PEF),tidal volume(Vt),minute ventilation(Mv),and mid-expiratory flow rate(EF50).The wet/dry weight(W/D)ratio of lung tissue was calculated and the diaphragmatic weight was measured.The concentrations of tumor necrosis factor-alpha(TNF-α)and typeⅢprocollagen(PCⅢ)in bronchoalveolar lavage fluid(BALF)were detected.The expression levels of transforming growth factor-beta1(TGF-β1)in lung tissue and myosin heavy chain 2(MYH2)in diaphragm tissue were detected by western-blotting.Quantitative real-time PCR(qRT-PCR)was used to detect the expression of TGF-β1 messenger RNA(mRNA)in lung tissue,and muscle ring finger 1(MURF-1)and forkhead box class O1(FoxO1)mRNA in diaphragm tissue.Results The body mass,PIF,PEF,Vt,Mv,EF50,serum Mg^(2+)concentration,W/D ratio,TGF-β1 mRNA and TGF-β1 protein in lung tissue,TNF-αand PCⅢcontent in BALF,diaphragmatic weight,MURF-1 mRNA,FoxO1 mRNA,and MYH2 protein in each group all showed significant differences(F=21.248,57.536,34.547,26.022,32.458,90.029,79.975,20.767,37.857,99.653,64.862,46.587,19.187,32.653,41.110,71.535;all P<0.001).Further pairwise comparison found that compared with the MgPic group,the body mass,diaphragmatic weight,and MYH2 protein expression were significantly increased,while MURF-1 and FoxO1 mRNA expression levels were significantly decreased in the ARDS group(all P<0.05).The body mass,diaphragmatic weight,and MYH2 protein expression were significantly decreased,while MURF-1 and FoxO1 mRNA expression levels were significantly increased in the Dex group compared with the MgPic group(all P<0.05).The PIF,PEF,Vt,Mv,EF50,and Mg^(2+)concentration were decreased in the ARDS and Dex groups,and the levels of PIF,PEF,Vt,Mv,and EF50 were lowest in the ARDS group,while the concentration of Mg^(2+)was lowest in the Dex group compared with the MgPic group(all P<0.05).The W/D ratio,TGF-β1 mRNA and TGF-β1 protein levels in lung tissue,and TNF-αand PCⅢlevels in BALF were obviously increased in the ARDS and Dex groups compared with the MgPic group,and the above indicators were highest in the ARDS group(all P<0.05).Conclusion MgPic can enhance the inhibitory effect of Dex on lung tissue fibrosis,improve diaphragm atrophy caused by Dex,and help to improve lung function in rats with ARDS.