Perrella M A, Yoshizumi M, Fen Z, Tsai J C, Hsieh C M, Kourembanas S, Lee M E
Cardiovascular Biology Laboratory, Harvard School of Public Health, Boston, Massachusetts 02115.
J Biol Chem. 1994 May 20;269(20):14595-600.
Nitric oxide (NO), which accounts for the biologic properties of endothelium-derived relaxing factor, is synthesized from L-arginine by nitric-oxide synthase (NOS). Two classes of NOS have been identified: a constitutive, calcium-dependent isozyme (cNOS) and an inducible, calcium-independent isozyme (iNOS). NO is generated after the induction of iNOS by cytokines such as interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha. As a potent vasodilator, NO may have an important role in the severe hypotension of septic shock. We investigated whether dexamethasone and transforming growth factor-beta 1 (TGF-beta 1) suppress iNOS mRNA after its induction by IL-1 beta. We found that IL-1 beta induced iNOS mRNA in rat aortic smooth muscle cells (RASMC) in a dose- and time-dependent fashion. IL-1 beta promoted a dramatic and prolonged induction of RASMC iNOS mRNA that peaked at 48 h. Dexamethasone prevented this induction of iNOS mRNA only when given before the addition of IL-1 beta. In contrast, TGF-beta 1 inhibited the induction of iNOS mRNA and NO production in RASMC both before and after the addition of IL-1 beta. After 24 h of IL-1 beta stimulation, TGF-beta 1 down-regulated the iNOS mRNA that had been induced during this initial time period. In nuclear run-on experiments, we found that the down-regulation of iNOS mRNA by TGF-beta 1 in RASMC occurred at the transcriptional level. Our observation that TGF-beta 1 mediates inhibition of RASMC iNOS mRNA after its induction by cytokines may be an important insight into the treatment of septic shock.
一氧化氮（NO）具有内皮源性舒张因子的生物学特性，它由一氧化氮合酶（NOS）催化L-精氨酸合成。已鉴定出两类NOS：一种是组成型、钙依赖性同工酶（cNOS），另一种是诱导型、钙非依赖性同工酶（iNOS）。在白细胞介素-1β（IL-1β）和肿瘤坏死因子-α等细胞因子诱导iNOS后会产生NO。作为一种强效血管舒张剂，NO可能在脓毒性休克的严重低血压中起重要作用。我们研究了地塞米松和转化生长因子-β1（TGF-β1）在IL-1β诱导iNOS mRNA后是否能抑制它。我们发现IL-1β以剂量和时间依赖性方式诱导大鼠主动脉平滑肌细胞（RASMC）中的iNOS mRNA。IL-1β促进了RASMC中iNOS mRNA的显著且持久的诱导，在48小时达到峰值。地塞米松仅在添加IL-1β之前给予时才能阻止这种iNOS mRNA诱导。相比之下，TGF-β1在添加IL-1β之前和之后均抑制RASMC中iNOS mRNA的诱导和NO的产生。在IL-1β刺激24小时后，TGF-β1下调了在此初始时间段内诱导产生的iNOS mRNA。在核转录实验中，我们发现TGF-β1在RASMC中对iNOS mRNA的下调发生在转录水平。我们观察到TGF-β1在细胞因子诱导后介导对RASMC中iNOS mRNA的抑制，这可能是对脓毒性休克治疗的重要见解。
