Effects of the expressionof matrix metalloproteinase 9 on chronic alcoholic muscle injury

：Objective To investigatethe effects of matrix metslloproteinase 9(MMP-9)on chronic alcohol muscleinjury(CAMI).Methods Sixty male Sprague-Dawley(SD)rats were randomly divided into controlgroup(A group,15 rats)and experimental group(B group,45 rats).All rats were administeredintragagtfically by gavage.Group A was treated with physiological saline.Group B wastreated with alcohoL Initial dose was 4 g·kg~(-1)·d~(-1).Then dose wagincreased by 2 g·kg~(-1)·d~(-1)weekly until 10 g·kg~(-1)·d~(-1).GroupA were randomly divided into 3 subset groups(A1-3),which would be sacrificed at 2,6 and 12weeks after feeding physiological saline.Each group had 5 rats.Group B were randomlydivided into 3 subset groups(B1-3),which would be sacrificed at 2,6 and 12 weeks afterfeeding alcohol.Each group had 15 rats.Then the histopathological changes in rat skeletalmuscles were observed by HE and NADH-TR staining.The expression of MMP-9 mRNA was detectedby RT-PCR MMP-9 protein was detected by Western blot The enzymatic activity of MMP-9 weagdetected by gelatin zymography.Results The observation of histechemistry showed that therewere obviously atrophic type-Ⅱmuscle fibers of plantaris in the B grouprats,infiltration of inflammatory cells and accrementition of connective tissue betweenmuscles.in which type-I collagen was obviously proliferative.The expression of MMP-9 mRNAin group A1 and group B1 was much lower.The precursor of MMP-9 in group AI and group B1wag detected by Western blot and gelatin zymography.The mRNA expression of MMP-9 ofplantaris in the group B2(0.0579±0.0046)was significantly elevated than that in the groupA2(0.0198±0.0023,t=-9.151,P<0.01).The mRNA expression of MMP-9 of plantaris andgastrocnemius in the group B3(0.1417±0.0116,0.0599±0.0057)was significantly higher thanthat in the group A3(0.0249±0.0049,t=-18.095,P<0.01;0.0237±0.0021,t=-5.933,P<0.05).Meanwhile,theexpression and enzymatic activity of MMP-9 of nJantaris and gastroenemius in the group B2Were detected by Western blot and gelatin zymography.The expression and enzymatic activityof M MP-9 of plantaris and gastrocnemius in the group B3 were significantly inereasedcompared with the group B2.Conclusions The inereased expression and the increasedenzymatic activity of MMP-9 may be involved in interstitial fibrosis of CAMI and aggravatethe development of CAMI. Key words: Alcoholism; Muscular diseases; Matrix metalloproteinase 9