Craig R G, Yu Z, Xu L, Barr R, Ramamurthy N, Boland J, Schneir M, Golub L M
Division of Basic Sciences, New York University College of Dentistry, NY 10010, USA.
Biochim Biophys Acta. 1998 Apr 24;1402(3):250-60. doi: 10.1016/s0167-4889(98)00008-1.
Wasting of connective tissues including skin, bone, and cartilage have been closely associated with elevated matrix metalloproteinase (MMP) activity and depressed collagen content in the streptozotocin (STZ)-induced diabetic rat, while tetracyclines have been reported to normalize total body weight, skin hydroxyproline and collagen content in this model, in part through inhibition of MMPs. In the present study, we report the effect of CMT-1, a chemically modified tetracycline that lacks antimicrobial properties but retains divalent cation binding and MMP inhibitory activity, on diabetic skin collagen synthesis and steady-state levels of procollagen alpha 1(I) mRNA. Male, 4-month old Sprague-Dawley rats received a single injection of 75 mg/kg STZ or citrate vehicle alone and diabetic status was confirmed by positive glucosuria. Some diabetic animals received 10 mg/day of CMT-1 by oral gavage and, 28 days after STZ treatment, body weight, blood glucose values and the in vivo rates of skin collagen production were measured using the pool-expansion technique. Steady-state levels of procollagen alpha 1(I) mRNA were analyzed 21 days after STZ treatment by hybridization of total RNA with a 32P labelled cDNA to rat type I procollagen alpha 1(I) mRNA in a dot-blot assay. STZ treatment was found to significantly depress body weight, skin collagen hydroxyproline content, the in vivo rate of collagen production, and hybridizable levels of type I procollagen alpha 1(I) mRNA. CMT-1 administered daily to STZ-treated rats inhibited the diabetic depression of these parameters but had little or no effect on non-diabetic controls or on STZ-induced hyperglycemia. Thus, in addition to the inhibition of MMP mediated extracellular collagen degradation, these results suggest CMT-1 also acts to inhibit diabetic connective tissue breakdown in STZ-induced diabetes by increasing both steady-state levels of type I procollagen mRNA and collagen synthesis through mechanism(s) that are independent of the antibacterial properties of tetracyclines.
在链脲佐菌素（STZ）诱导的糖尿病大鼠中，包括皮肤、骨骼和软骨在内的结缔组织消瘦与基质金属蛋白酶（MMP）活性升高和胶原蛋白含量降低密切相关，而据报道四环素可使该模型中的总体重、皮肤羟脯氨酸和胶原蛋白含量恢复正常，部分原因是通过抑制MMP。在本研究中，我们报告了CMT - 1（一种化学修饰的四环素，缺乏抗菌特性但保留二价阳离子结合和MMP抑制活性）对糖尿病皮肤胶原蛋白合成和前胶原α1（I）mRNA稳态水平的影响。4个月大的雄性Sprague - Dawley大鼠单次注射75 mg/kg STZ或单独注射柠檬酸盐载体，通过尿糖阳性确认糖尿病状态。一些糖尿病动物通过口服灌胃给予10 mg/天的CMT - 1，在STZ治疗28天后，使用池扩张技术测量体重、血糖值和皮肤胶原蛋白生成的体内速率。在STZ治疗21天后，通过斑点印迹法将总RNA与32P标记的大鼠I型前胶原α1（I）mRNA的cDNA杂交，分析前胶原α1（I）mRNA的稳态水平。发现STZ治疗显著降低体重、皮肤胶原蛋白羟脯氨酸含量、胶原蛋白生成的体内速率以及I型前胶原α1（I）mRNA的可杂交水平。每天给STZ处理的大鼠施用CMT - 1可抑制这些参数的糖尿病性降低，但对非糖尿病对照或STZ诱导的高血糖几乎没有影响。因此，除了抑制MMP介导的细胞外胶原蛋白降解外，这些结果表明CMT - 1还通过增加I型前胶原mRNA的稳态水平和胶原蛋白合成，以独立于四环素抗菌特性的机制来抑制STZ诱导的糖尿病中糖尿病性结缔组织分解。
