Semino-Mora M C, Leon-Monzon M E, Dalakas M C
Neuromuscular Diseases Section, National Institutes of Neurological Diseases and Stroke, National Institutes of Health, Bethesda, Maryland.
Lab Invest. 1994 Jul;71(1):102-12.
Zidovudine (AZT) as used in the treatment of AIDS, causes a mitochondrial myopathy characterized by depletion of mitochondrial DNA, enzymatic defects in the respiratory chain system, and accumulation of lipid droplets. Most of these changes are also seen in normal human myotubes treated with AZT. Because L-carnitine plays a major role in the transport of long chain fatty acids across the inner mitochondrial membrane and facilitates the beta-oxidation of fatty acids, we examined the effect of L-carnitine in preventing the destructive effect of AZT on the mitochondria and the myotubes of human muscle in tissue culture.
Myotubes, prepared from human muscle biopsies, were exposed to various concentrations of AZT for up to 3 weeks. One-third of the flasks were treated with AZT alone, another third with AZT plus L-carnitine and another third were untreated. The cultures were evaluated with: (a) immunocytochemistry counting the number of myotubes stained with antibodies to Leu-19; (b) enzyme histochemistry for NADH reaction and oil-red-O stain to assess mitochondrial enzymatic activity and lipid droplet accumulation; and (c) electron microscopy counting all the organelles within representative sections of the myotubes, at x24,000, and calculating the volumetric density of each organelle/unit volume of tissue.
AZT, at concentrations 250 microM and above, caused depopulation of the Leu-19-positive myotubes, destructive changes in the mitochondria consisting of swelling, lamellar inclusions and multiple concentric cristae, accumulation of lipid droplets, and increase lysosomes. L-Carnitine increased the number of Leu-19-positive myotubes from 3.4 +/- 0.6 to 9.4 +/- 1.2, preserved the morphology of the mitochondria, increased their volumetric density from 2.5 +/- 0.4 to 6.0 +/- 0.7, and reduced the volumetric density of the lipid droplets from 12.2 +/- 4.9 to 1.4 +/- 0.7 and of the lysosomes from 15.6 +/- 3.6 to 3.9 +/- 1.4 (p < 0.001).
L-Carnitine, used concurrently with AZT, prevents the human myotubes from the AZT-associated destruction, preserves the structure and volume of mitochondria and prevents the accumulation of lipids. The findings may have potential clinical implications in preventing the myotoxicity of AZT in patients with AIDS.
齐多夫定（AZT）用于治疗艾滋病时，会引发一种线粒体肌病，其特征为线粒体DNA耗竭、呼吸链系统酶缺陷以及脂滴积聚。在用AZT处理的正常人类肌管中也可见到这些变化中的大多数。由于左旋肉碱在长链脂肪酸跨线粒体内膜的转运中起主要作用，并促进脂肪酸的β氧化，我们研究了左旋肉碱在组织培养中预防AZT对人肌肉线粒体和肌管的破坏作用的效果。
从人肌肉活检标本制备的肌管暴露于不同浓度的AZT中长达3周。三分之一的培养瓶仅用AZT处理，另外三分之一用AZT加左旋肉碱处理，还有三分之一不做处理。通过以下方法对培养物进行评估：（a）免疫细胞化学，计数用抗Leu - 19抗体染色的肌管数量；（b）酶组织化学检测NADH反应以及油红O染色，以评估线粒体酶活性和脂滴积聚情况；（c）电子显微镜检查，在放大24,000倍下对肌管代表性切片内的所有细胞器进行计数，并计算每个细胞器在单位组织体积中的体积密度。
浓度在250 microM及以上的AZT导致Leu - 19阳性肌管数量减少，线粒体出现破坏性变化，包括肿胀、板层状内含物和多个同心嵴，脂滴积聚以及溶酶体增多。左旋肉碱使Leu - 19阳性肌管数量从3.4±0.6增加到9.4±1.2，保持了线粒体的形态，使其体积密度从2.5±0.4增加到6.0±0.7，并使脂滴的体积密度从12.2±4.9降低到1.4±0.7，溶酶体的体积密度从15.6±3.6降低到3.9±1.4（p<0.001）。
与AZT同时使用时，左旋肉碱可防止人肌管受到AZT相关的破坏，保持线粒体的结构和体积，并防止脂质积聚。这些发现可能对预防艾滋病患者中AZT的肌毒性具有潜在的临床意义。
