Amin A R, Attur M G, Thakker G D, Patel P D, Vyas P R, Patel R N, Patel I R, Abramson S B
Department of Rheumatology, Hospital for Joint Diseases, New York, NY 10003, USA.
Proc Natl Acad Sci U S A. 1996 Nov 26;93(24):14014-9. doi: 10.1073/pnas.93.24.14014.
Tetracyclines have recently been shown to have "chondroprotective" effects in inflammatory arthritides in animal models. Since nitric oxide (NO) is spontaneously released from human cartilage affected by osteoarthritis (OA) or rheumatoid arthritis in quantities sufficient to cause cartilage damage, we evaluated the effect of tetracyclines on the expression and function of human OA-affected nitric oxide synthase (OA-NOS) and rodent inducible NOS (iNOS). Among the tetracycline group of compounds, doxycycline > minocycline blocked and reversed both spontaneous and interleukin 1 beta-induced OA-NOS activity in ex vivo conditions. Similarly, minocycline > or = doxycycline inhibited both lipopolysaccharide- and interferon-gamma-stimulated iNOS in RAW 264.7 cells in vitro, as assessed by nitrite accumulation. Although both these enzyme isoforms could be inhibited by doxycycline and minocycline, their susceptibility to each of these drugs was distinct. Unlike acetylating agents or competitive inhibitors of L-arginine that directly inhibit the specific activity of NOS, doxycycline or minocycline has no significant effect on the specific activity of iNOS in cell-free extracts. The mechanism of action of these drugs on murine iNOS expression was found to be, at least in part, at the level of RNA expression and translation of the enzyme, which would account for the decreased iNOS protein and activity of the enzyme. Tetracyclines had no significant effect on the levels of mRNA for beta-actin and glyceraldehyde-3-phosphate dehydrogenase nor on levels of protein of beta-actin and cyclooxygenase 2 expression. These studies indicate that a novel mechanism of action of tetracyclines is to inhibit the expression of NOS. Since the overproduction of NO has been implicated in the pathogenesis of arthritis, as well as other inflammatory diseases, these observations suggest that tetracyclines should be evaluated as potential therapeutic modulators of NO for various pathological conditions.
最近研究表明，四环素在动物模型的炎性关节炎中具有“软骨保护”作用。由于一氧化氮（NO）会从受骨关节炎（OA）或类风湿性关节炎影响的人体软骨中自发释放，其释放量足以导致软骨损伤，因此我们评估了四环素对人OA相关一氧化氮合酶（OA-NOS）和啮齿动物诱导型一氧化氮合酶（iNOS）表达及功能的影响。在四环素类化合物中，强力霉素>米诺环素可在体外条件下阻断并逆转自发的以及白细胞介素1β诱导的OA-NOS活性。同样，米诺环素>或 = 强力霉素在体外可抑制RAW 264.7细胞中脂多糖和干扰素-γ刺激的iNOS，这通过亚硝酸盐积累来评估。尽管强力霉素和米诺环素均可抑制这两种酶同工型，但它们对每种药物的敏感性不同。与直接抑制NOS比活性的乙酰化剂或L-精氨酸竞争性抑制剂不同，强力霉素或米诺环素对无细胞提取物中iNOS的比活性无显著影响。发现这些药物对小鼠iNOS表达的作用机制至少部分是在该酶的RNA表达和翻译水平，这可以解释iNOS蛋白和酶活性的降低。四环素对β-肌动蛋白和甘油醛-3-磷酸脱氢酶的mRNA水平以及β-肌动蛋白和环氧合酶2表达的蛋白水平均无显著影响。这些研究表明，四环素的一种新作用机制是抑制NOS的表达。由于NO的过量产生与关节炎以及其他炎症性疾病的发病机制有关，这些观察结果表明，四环素应作为各种病理状况下NO的潜在治疗调节剂进行评估。
