Makita Y, Ishidoh K, Kominami E, Funabiki K, Koide H, Tomino Y
Department of Medicine, Juntendo University School of Medicine, Tokyo, Japan.
J Diabetes Complications. 1998 Nov-Dec;12(6):328-36. doi: 10.1016/s1056-8727(98)00008-7.
Matrix expansion in the glomerular mesangial area is observed in diabetic nephropathy. Intracellular breakdown of long-lived proteins was lower in mesangial cells in the high glucose medium than that in the control medium. Enzymatic activity of cathepsin L increased 1.4-fold after 6 h of treatment with the high glucose, and then declined gradually to 72% of control cells after treatment for 36 h. Change in the enzyme activity of cathepsin B showed a similar time course but less magnitude than that of cathepsin L. Immunoblot analysis with anti-cathepsin L antibody showed that change in the enzyme activity of cathepsin L was due to the change in the amount of cathepsin L, and that with anti-cathepsin B antibody showed no change in the amount of cathepsin B in the mesangial cells treated with high glucose. Intracellular cathepsin activities were controlled not only by the amounts but also by the inhibitor cystatin beta. Immunoblot analysis with anti-cystatin beta antibody showed that intracellular levels of cystatin beta increased slightly after 24 h of treatment with high glucose. These changes were derived from changes in mRNA level. These results, therefore, demonstrated that the decrease of intracellular protein breakdown in mesangial cells treated with high glucose medium was due to both suppression of cathepsins and increase of cystatin beta.
在糖尿病肾病中可观察到肾小球系膜区的基质扩张。高糖培养基中系膜细胞内长寿蛋白的分解低于对照培养基中的系膜细胞。用高糖处理6小时后，组织蛋白酶L的酶活性增加了1.4倍，然后在处理36小时后逐渐下降至对照细胞的72%。组织蛋白酶B的酶活性变化呈现相似的时间进程，但幅度小于组织蛋白酶L。用抗组织蛋白酶L抗体进行免疫印迹分析表明，组织蛋白酶L的酶活性变化是由于组织蛋白酶L量的变化，而用抗组织蛋白酶B抗体进行免疫印迹分析表明，高糖处理的系膜细胞中组织蛋白酶B的量没有变化。细胞内组织蛋白酶活性不仅受其数量控制，还受抑制剂胱抑素β的控制。用抗胱抑素β抗体进行免疫印迹分析表明，高糖处理24小时后，细胞内胱抑素β水平略有升高。这些变化源于mRNA水平的变化。因此，这些结果表明，高糖培养基处理的系膜细胞内蛋白质分解减少是由于组织蛋白酶的抑制和胱抑素β的增加。
