坐骨神经夹伤与心脏毒素注射导致腓肠肌功能损伤中Calpains和FoxOs的差异表达及相关性分析***◆

背景：钙蛋白酶家族和FoxO转录因子在肌萎缩过程中发挥着重要的作用。 目的：观察钙蛋白酶家族成员及FoxO转录因子(FoxO1和FoxO3a)在心脏毒素注射与坐骨神经夹伤致腓肠肌失功能损伤中表达的变化。 方法：分别采用坐骨神经夹伤和心脏毒素注射建立大鼠腓肠肌功能损伤模型,于造模后的第3,7,14,21天取大鼠腓肠肌进行实时荧光定量PCR检测,并采用线性回归法进行相关性分析。 结果与结论：结果显示,腓肠肌组织中的钙蛋白酶Ⅰ、钙蛋白酶Ⅱ和FoxO3a mRNA在坐骨神经夹伤7 d达到高峰,随后下降;钙蛋白酶Ⅲ和FoxO1 mRNA在坐骨神经夹伤后14 d达到高峰,随后下降。钙蛋白酶Ⅰ、钙蛋白酶Ⅱ、FoxO3a mRNA在心脏毒素注射后第3天达高峰,随后逐渐下降;FoxO1 mRNA在心脏毒素注射后7 d时达最高;而钙蛋白酶Ⅲ mRNA在心脏毒素注射后3 d时表达显著下降,随后逐渐恢复至正常水平。线性回归分析结果显示,在失神经肌损伤过程中钙蛋白酶Ⅲ的表达与FoxO1呈正相关(r=0.901 5);在心脏毒素注射肌损伤过程中钙蛋白酶Ⅰ(r=0.898 7)和钙蛋白酶Ⅱ(r=0.937 4)表达趋势与FoxO3a呈正相关。可见,在不同的肌损伤模型中,钙蛋白酶Ⅰ和钙蛋白酶Ⅱ的表达趋势相似,而钙蛋白酶Ⅲ的表达不同。     

肿瘤坏死因子受体相关因子6在大鼠失神经支配后胫前肌与比目鱼肌中的表达变化

目的 通过蛋白质组学方法分析失神经支配后胫前肌与比目鱼肌的蛋白表达变化,探讨肿瘤坏死因子受体相关因子6（TRAF6）在失神经支配后胫前肌与比目鱼肌中的表达变化及其意义。 方法 制备大鼠坐骨神经离断模型,通过同位素相对标记与绝对定量 (iTRAQ)技术方法分析胫前肌与比目鱼肌在失神经支配后的蛋白表达变化,比较差异表达的蛋白在胫前肌与比目鱼肌中的差异,筛选出在胫前肌与比目鱼肌中的表达变化差异显著的关键蛋白,并通过免疫印迹法验证其表达,进一步通过体外方法验证关键蛋白的生物学作用。 结果 失神经支配后比目鱼肌萎缩速度和程度明显大于胫前肌（P<0.05,n=20）,蛋白质组学研究发现有30个蛋白在胫前肌与比目鱼肌中表达变化差异较为明显,这些蛋白主要包括代谢相关蛋白、伴侣蛋白、收缩蛋白以及信号分子等,其中TRAF6在失神经支配后比目鱼肌中表达显著上升,蛋白免疫印迹法检测结果也证实了蛋白质组学的结果,TRAF6的靶基因肌肉环状指蛋白1（MuRF1）和肌肉萎缩盒F基因（MAFbx)在失神经支配后比目鱼肌中的表达也高于其在胫前肌中的表达（P<0.05,n=6）;为了进一步探讨TRAF6对肌萎缩的影响,在肌管中转染TRAF6 siRNA和对照siRNA,然后用地塞米松诱导C2C12肌管萎缩,发现TRAF6 siRNA转染组肌管的直径明显大于转染对照siRNA组（P<0.05,n=6）;TRAF6、MuRF1和MAFBx在TRAF6 siRNA转染组肌管中的表达显著低于转染对照siRNA组（P<0.05,n=6）,结果提示TRAF6 siRNA有效抑制了靶基因TRAF6的表达,也同时抑制了其下游靶基因MuRF1和MAFBx的表达。 结论 TRAF6在失神经支配后比目鱼肌中的表达量显著高于其在胫前肌中的表达,抑制TRAF6的表达可以减轻地塞米松引起的肌管萎缩,由此推测失神经支配后比目鱼肌萎缩较胫前肌严重可能与失神经支配后比目鱼肌中TRAF6的升高更显著有关。     

低频电刺激对坐骨神经损伤大鼠不同类型骨骼肌萎缩及内源性胰岛素样生长因子1表达的影响

背景：低频电刺激可以缓解骨骼肌的萎缩,但对肌纤维类型的影响尚不清楚,同时内源性胰岛素样生长因子1在萎缩后的肌纤维中的表达与电刺激的关系尚无公识。 目的：观察低频电刺激对坐骨神经损伤大鼠不同类型骨骼肌纤维萎缩情况及内源性胰岛素样生长因子1表达的影响。 方法：将健康雄性SD大鼠随机分为3组,切断模型组和电刺激组大鼠左侧坐骨神经制备失神经支配模型,适应5 d后,对电刺激组大鼠损伤侧腓肠肌施以2 Hz的电刺激,2次/d,每次持续20 min,正常组和模型组常规饲养。30 d后,取大鼠腓肠肌腹部,检测其肌纤维直径和数量;免疫组织化学法检测肌组织中胰岛素样生长因子1的水平。 结果与结论：失神经支配后,大鼠腓肠肌Ⅰ、Ⅱ型肌纤维直径减小,Ⅰ型肌纤维数比例增大。与模型组比较,电刺激组大鼠腓肠肌Ⅰ、Ⅱ型肌纤维直径有所增大,尤以Ⅰ型肌纤维直径增大更明显(P < 0.05)。同时,电刺激组大鼠腓肠肌中胰岛素样生长因子1的表达也明显高于模型组(P < 0.05)。提示,2 Hz的电刺激可促进胰岛素样生长因子1的表达,减轻Ⅰ型肌纤维的萎缩。     

高选择性神经损伤模型骨骼肌MyoD和myogenin mRNA的表达

为观察成肌调节因子MyoD和myogenin mRNA在单纯运动神经或/和单纯感觉神经损伤后萎缩骨骼肌中的表达,探讨其在失神经骨骼肌萎缩发生发展中的可能作用,我们分别切断大鼠左侧L4～L6脊神经腹根、背根或坐骨神经制备选择性神经损伤模型,并将动物分成腹根切断组(VRT),背根切断组(DRT)和坐骨神经切断组(SNT)。于术后2、4周应用逆转录-聚合酶链式反应(RT-PCR),分别检测和观察腹根、背根及坐骨神经切断组大鼠腓肠肌中MyoD和myogenin mRNA表达的变化。结果显示:与相同时间点正常对照侧相比较,各组大鼠腓肠肌MyoD和myogenin mRNA的表达均增加。4周时不同损伤类型间比较,myogenin mRNA表达差异具有显著性(P<0.05)。以上结果提示,MyoD和myogenin可能参与了神经损伤后骨骼肌的再生修复过程,但两者作用于成肌分化的不同阶段,且作用不同。     

去神经支配大鼠海马内MTSS1的表达变化

目的:探讨切割穹窿海马伞去神经支配大鼠海马内转移抑制蛋白1(metastasis suppressor 1,MTSS1)的表达变化。方法:SD大鼠随机分成正常组和切割穹窿海马伞后1、3、5、7、14 d组,采用Real-time PCR和免疫荧光组织化学技术观察穹窿海马伞切割后海马内MTSS1 mRNA的表达变化和MTSS1阳性细胞的分布情况。结果:(1)Real-time PCR结果显示:海马内MTSS1 mRNA的相对表达量在切割后3 d开始升高(P<0.05),5 d达到最高水平(P<0.01),7 d恢复至正常水平;(2)免疫荧光组织化学染色结果显示:MTSS1阳性细胞主要表达于海马齿状回门区及颗粒下层中,切割后5 d MTSS1阳性细胞数开始增多(P<0.01),7 d继续增多并达到高峰(P<0.01),14 d时开始下降至正常水平。结论:结合本课题组以往的工作,上述结果提示切割穹窿海马伞后MTSS1的高表达可能与海马神经再生过程中神经干细胞向神经元的分化有关。     

失神经骨骼肌萎缩中泛素蛋白连接酶Murf1和核转录因子NF-κB表达与被动运动干预

背景:蛋白质分解是延缓肌萎缩发生的关键环节,在慢性病性、制动性肌萎缩中泛素蛋白连接酶Murf1和核转录因子NF-κB的表达增加,被动运动已被证实可以有效抑制肌萎缩的发生。目的:探讨泛素蛋白连接酶Murf1和核转录因子NF-κB在大鼠失神经肌萎缩中不同时段的表达,以及被动运动对失神经骨骼肌Murf1和NF-κB表达的影响。方法:假手术组大鼠不切断右下肢坐骨神经,失神经组、失神经被动运动组大鼠切断右下肢坐骨神经。术后1d起,将失神经被动运动组大鼠置于自制的网夹内,拉出右后肢,抓住趾部,与脊柱呈45°向后外方牵拉,至右后肢完全伸直,再将右后肢推向身体,使之完全屈曲紧贴身体,每天训练2次,每次屈伸运动300下,3min/次,直至切取标本之日。干预2,14,28d后,采用RT-PCR与WesternBlot技术分别检测Murf1,NF-κBmRNA和蛋白质的表达。结果与结论:与假手术组比较,各时间点失神经组Murf1,NF-κBmRNA及蛋白的表达均明显增加(P0.05);与失神经组比较,各时间点失神经被动运动组Murf1及NF-κBmRNA的表达均显著降低(P0.01)。失神经支配后肌湿质量比明显下降,被动运动14d时肌湿质量比明显高于失神经组(P0.05)。失神经腓肠肌中Murf1,NF-κBmRNA和蛋白的表达与肌湿质量呈负相关(r=-0.795,P0.01;r=-0.834,P0.01),提示被动运动可能通过降低Murf1和NF-κB的表达发挥肌萎缩防治作用。     

Nnat基因在大鼠脑发育过程中表达的初步研究

目的:观察Nnat基因在大鼠脑发育过程中基因表达的变化规律,藉以探讨Nnat在神经系统发育过程中的作用。方法:采用半定量RT-PCR法分析出生前后大鼠脑内Nnat表达水平的变化,Western blot检测Nnat蛋白的表达。结果:在大鼠胚胎第9 d(E9)脑内Nnat mRNA开始表达,但表达量较低,以后其表达量逐渐升高,出生前有轻微下调。出生后大鼠的不同脑区Nnat mRNA的表达量都呈现下降趋势,60 d时达到较低的水平。Nnat蛋白在不同脑区都具有表达,但不同亚型蛋白量的相对比例不同。结论:Nnat基因在胚胎期及出生后大鼠脑内的表达量与中枢神经系统发育及分化过程的时间上有一定的同步性,提示Nnat的作用可能与神经元分化的调节有关。     

快肌与慢肌失神经支配后的形态学变化

目的:探讨快肌(胫前肌)与慢肌(比目鱼肌)在失神经支配过程中的形态学差异。方法:本研究拟采用大鼠坐骨神经离断模型,通过组织病理学系统分析失神经支配过程中胫前肌与比目鱼肌在形态学方面的变化。结果:在坐骨神经损伤后不同时间点,将比目鱼肌的萎缩程度与胫前肌相比,显示比目鱼肌的萎缩程度较胫前肌严重,主要表现在比目鱼肌的肌肉湿重比较小、肌纤维截面积比率较低、超微结构较不完整、运动终板破损较严重。结论:失神经支配后慢肌萎缩程度较快肌严重。     

小鼠前脑线粒体蛋白的增龄性变化

目的　探讨小鼠前脑不同发育阶段线粒体蛋白的表达变化。 方法　分别取妊娠12.5 d（E12.5）及17.5 d（E17.5）的胎鼠、出生2 d的新生鼠、出生3周的幼鼠和2月龄成年鼠的前脑组织,利用QRT-PCR和Western blotting检测小鼠前脑发育不同阶段中COX IV、HSP60、OGDH、PDHE1α的mRNA和蛋白表达水平。 结果　在E12.5 ~2 d的前脑组织中COX IV mRNA呈低水平表达,3周时表达量明显升高并达到顶峰;HSP60和PDHE1α mRNA在E17.5表达明显增高,OGDH mRNA则在2 d显著上升,三者表达水平均于2月达到顶峰。COX IV、HSP60、OGDH的蛋白水平从E12.5 ~3周无明显差异,但在2月时表达显著上升;PDHE1α蛋白随前脑发育其表达水平不断提高,并于2月达到高峰。此外,COX IV、HSP60、OGDH、PDHE1α mRNA与蛋白表达水平呈正相关。 结论　COX IV、HSP60、OGDH和PDHE1α可能参与了小鼠前脑发育过程且与年龄密切相关。     

失神经支配的骨骼肌萎缩与防治

背景:随着当今医学的发展,失神经支配骨骼肌萎缩的防治已取得了显著的进步,但临床疗效仍不十分满意。目的:对失神经支配骨骼肌萎缩防治方法的研究现状作一总结,试图寻找更为有效的失神经支配骨骼肌萎缩防治方法。方法:以denervation,muscle atrophy,treatment为检索词,检索Medline数据库(1998-01/2008-01)。以失神经,肌萎缩,治疗为检索词,检索中国期刊全文数据库(1998-01/2008-01)、万方数据库(1998-01/2008-01)和《中国临床康复》杂志(1998-01/2008-01)。文献检索语种限制为英文和中文。以肌肉的耐力及收缩力、失神经的肌湿重和骨骼肌的修复情况为评价指标。纳入研究失神经支配骨骼肌萎缩的显微外科手术方法、物理疗法、生物和化学疗法、基因疗法。排除上述方法之外失神经支配骨骼肌萎缩的其他疗法。结果与结论:周围神经损伤后,骨骼肌失神经支配将不可避免的发生萎缩。因此,探索失神经支配骨骼肌萎缩的防治方法,吸引了国内外许多学者的兴趣,必将成为21世纪周围神经领域内的重要任务和研究热点。显微外科手术、物理疗法、生物和化学疗法、基因疗法等都是失神经支配骨骼肌萎缩有效的防治手段。目前,该领域的研究已经呈现多角度、多方面的趋势。失神经肌萎缩的防治方面已经有了针对性的措施,但在改善微循环、防止细胞凋亡、抑制胶原过度生长以及如何应用基因治疗的方法在基因水平改变生肌调节因子的表达等方面,还有大量工作需要进行。随着组织工程学、细胞培养学、分子生物学、基因工程等方面的不断发展,防治失神经肌萎缩必定会有新的突破。     

Expression of myostatin RNA transcript and protein in gastrocnemius muscle of rats after sciatic nerve resection

Myostatin, a member of the transforming growth factor-beta (TGF-beta) superfamily, has been identified as an inhibitor of skeletal muscle mass. To have an insight into the expression pattern of myostatin and its potential role in skeletal muscle atrophy induced by denervation, we used an animal model of peripheral nerve resection to examine the time-dependent changes in myostatin mRNA and protein levels in the denervated gastrocnemius muscle of rats after sciatic neurectomy by the aid of quantitative real-time RT-PCR and Western blotting, respectively. We also conducted morphometric analyses to measure the wet weight ratio of the denervated muscle (the operated side/contralateral non-operated side) and the cross sectional area of muscle fibers and to observe muscle morphology. The experimental results showed that myostatin mRNA and protein levels in rat gastrocnemius muscle persistently elevated after denervation, despite a fluctuation of myostatin mRNA level at day 3 after denervation, reached their respective peaks at day 28 after denervation, and then depressed slightly until day 56 after denervation. Furthermore, a significant negative linear correlation was found between myostatin abundance and muscle atrophy degree, suggesting that myostatin might probably play an important role in denervation-induced muscle atrophy. Our present study perhaps provides a new window into myostatin regulation in association with a specific type of muscle atrophy.     

Content and localization of myostatin in mouse skeletal muscles during aging,mechanical unloading and reloading

Changes in myostatin content and localization in mouse skeletal muscles were investigated during aging, hindlimb suspension (HS) and reloading after HS. During aging, the content of myostatin among solubilized proteins in gastrocnemius and plantaris muscles (Gast/Plant) was initially low and increased until their wet weight/body weight ratio reached a peak. It remained unchanged with further aging, although gradual atrophy of the muscles was seen to occur. Also, the myostatin content did not change significantly during HS (up to 14 days) in both Gast/Plant and soleus muscles, though the muscles showed morphological signs of atrophy. However, reloading for 2 days after a 14-day HS caused significant decreases in the myostatin content in both of these muscles. Immunohistochemical observations showed the sarcoplasmic existence of myostatin, the amount of which appeared to decrease after reloading. The results suggest that myostatin plays a part in the processes of muscular growth and loading-induced hypertrophy, but is not involved in either aging-related or unloading-induced muscular atrophy. This revised version was published online in July 2006 with corrections to the Cover Date.     

氯化胆碱与制动性骨骼肌萎缩肌肉生成抑制素mRNA的表达

背景：研究发现类胆碱物质可增加乙酰胆碱的弥散及终板电流的幅度,对神经肌肉接点功能退化有一定的对抗作用。 目的：观察氯化胆碱对制动性骨骼肌萎缩的防治作用及对骨骼肌萎缩大鼠肌肉生成抑制素mRNA表达的影响。 方法：将30只雄性SD大鼠随机分为对照组、模型组和治疗组,每组10只。采用可塑性石膏固定模型组和治疗组大鼠右后肢制备肌萎缩模型。治疗组每日灌胃氯化胆碱(150 mg/kg),对照组和模型组灌胃等体积蒸馏水。4周后解剖右后肢腓肠肌,检测腓肠肌收缩张力、肌湿质量、蛋白质水平及肌肉生成抑制素mRNA的表达。 结果与结论：与对照组比较,模型组大鼠腓肠肌的收缩张力、肌湿质量、蛋白质水平均显著降低(P < 0.05或P < 0.01),肌肉生成抑制素mRNA表达显著增高(P < 0.01)。与模型组比较,治疗组大鼠腓肠肌的收缩张力、肌湿质量、蛋白质水平均显著升高(P < 0.05),肌肉生成抑制素mRNA表达显著降低(P < 0.05)。说明氯化胆碱能够显著提高制动性萎缩骨骼肌的收缩张力、肌湿质量、蛋白质水平,减少肌肉生成抑制素mRNA的表达,从而有效抑制骨骼肌制动性萎缩的发生。     

PPM1B and P-IKKβ expression levels correlated inversely with rat gastrocnemius atrophy after denervation

Activated inhibitor of nuclear factor-κB kinase β (IKKβ) is necessary and sufficient for denervated skeletal muscle atrophy. Although several studies have shown that Mg²⁺/Mn²⁺-dependent protein phosphatase 1B (PPM1B) inactivated IKKβ, few studies have investigated the role of PPM1B in denervated skeletal muscle. In this study, we aim to explore the expression and significance of PPM1B and phosphorylated IKKβ (P-IKKβ) during atrophy of the denervated gastrocnemius. Thirty young adult female Wistar rats were subjected to right sciatic nerve transection and were sacrificed at 0 (control), 2, 7, 14, and 28 days after denervation surgery. The gastrocnemius was removed from both the denervated and the contralateral limb. The muscle wet weight ratio was calculated as the ratio of the wet weight of the denervated gastrocnemius to that of the contralateral gastrocnemius. RT-PCR and Western blot analysis showed that mRNA and protein levels of PPM1B were significantly lower than those of the control group at different times after the initiation of denervation, while P-IKKβ showed the opposite trends. PPM1B protein expression persistently decreased while P-IKKβ expression persistently increased for 28 days after denervation. PPM1B expression correlated negatively with P-IKKβ expression by the Spearman test, whereas decreasing PPM1B expression correlated positively with the muscle wet weight ratio. The expression levels of PPM1B and P-IKKβ were closely associated with atrophy in skeletal denervated muscle. These results suggest that PPM1B and P-IKKβ could be markers in skeletal muscle atrophy.     

The decrease in mature myostatin protein in male skeletal muscle is developmentally regulated by growth hormone

Myostatin inhibits myogenesis and there is reduced abundance of the mature protein in skeletal muscles of adult male compared with female mice. This reduction probably occurs after translation, which suggests that it is a regulated mechanism to reduce the availability of myostatin in males. Reduced myostatin may, thereby, contribute to the development of sexually dimorphic growth of skeletal muscle. Our first objective was to determine if the decrease in mature myostatin protein occurs before the linear growth phase to aid growth, or afterwards to maintain the mass of adult muscle. Mice were killed from 2 to 32 weeks and the gastrocnemius muscle was excised. Myostatin mRNA increased from 2 to 32 weeks and was higher in males than females ( P < 0.001). In contrast, mature protein decreased in males after 6 weeks ( P < 0.001). Our second objective was to determine if growth hormone (GH) induces the decrease in mature myostatin protein. GH increased myostatin mRNA and decreased the abundance of mature protein in hypophysectomised mice ( P < 0.05). Our final objective was to determine if the decrease in mature protein occurs in skeletal muscles of male Stat5b ^−/− mice (Stat5b mediates the actions of GH). As expected, mature myostatin protein was not reduced in Stat5b ^−/− males compared with females. However, myostatin mRNA remained higher in males than females irrespective of genotype. These data suggest that: (1) the decrease in mature myostatin protein is developmentally regulated, (2) GH acting via Stat5b regulates the abundance of mature myostatin and (3) GH acts via a non-Stat5b pathway to regulate myostatin mRNA.     

陈旧性坐骨神经缺损对大鼠腓肠肌组织蛋白含量及泛素表达的影响

目的：了解陈旧性坐骨神经缺损后肌肉萎缩过程中蛋白质降解的机制。方法：用SD大鼠建立坐骨神经缺损模型,切断大鼠右侧坐骨神经,形成10 mm缺损。测定术后1、2、3、4、6、9及12个月腓肠肌肌总蛋白的含量;免疫组化法观察组织中泛素的表达变化;Western印迹法测定组织中泛素蛋白的表达水平。结果：坐骨神经缺损后腓肠肌肌总蛋白含量随缺损时间延长呈进行性下降;正常腓肠肌组织中泛素呈低表达,随缺损时间延长泛素表达水平增强,持续到9个月,随后呈下调趋势。结论：陈旧性坐骨神经缺损后腓肠肌蛋白的降解、肌总蛋白量下降及肌萎缩可能和泛素-蛋白酶体途径有关。