Seldon P M, Barnes P J, Meja K, Giembycz M A
Department of Thoracic Medicine, Royal Brompton National Heart and Lung Institute, London, UK.
Mol Pharmacol. 1995 Oct;48(4):747-57.
We assessed the role of cyclic nucleotides in modulating lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF-alpha) generation in human peripheral blood monocytes. Exposure of monocytes to LPS (3 ng/ml) evoked a delayed, time-dependent generation of TNF-alpha that reached a maximum level 5-6 hr after LPS challenge and remained constant for up to 24 hr. This effect was concentration dependent and resulted in a 20-40-fold increase in the release of TNF-alpha that was sensitive to actinomycin D and cycloheximide. Treatment of monocytes with agents reputed to activate the cAMP/cAMP-dependent protein kinase (PKA) cascade in general inhibited LPS-induced TNF-alpha generation. Thus, the beta 2-adrenoceptor agonists albuterol and procaterol partially (approximately 40%) suppressed TNF-alpha generation in a propranolol-sensitive manner. Furthermore, 8-bromo-cAMP, cholera toxin, prostaglandin E2, and a number of drugs (i.e., rolipram (ZK 62711), denbufylline (BRL 30892), Ro 20-1724, benafentrine (AH 21-132), that inhibit the phosphodiesterase (PDE) 4 isoenzyme family abolished cytokine generation. In contrast, forskolin, inhibitors of PDE3 and PDE5, and activators of soluble and particulate guanylyl cyclase were essentially inactive. Interestingly, rolipram failed to potentiate the inhibitory effect of albuterol on LPS-induced TNF-alpha biosynthesis but, paradoxically, synergized with albuterol in the generation of cAMP and in the activation of PKA. When PGE2 was used to activate adenylyl cyclase, however, rolipram potentiated cAMP accumulation, PKA activation, and inhibition of TNF-alpha generation. In contrast, forskolin did not increase the cAMP content of monocytes in the absence or presence of rolipram. Collectively, these data suggest that LPS-induced TNF-alpha generation by human peripheral blood monocytes is due to increased transcription and subsequent translation of the TNF-alpha gene and that these effects are suppressed by a range of agents that activate the cAMP/PKA cascade. However, the failure of rolipram to potentiate the inhibitory effect of albuterol and procaterol on TNF-alpha generation suggests that beta 2-adrenoceptor agonists may affect gene expression and/or post-transcriptional regulatory processes by, at least in part, a cAMP-independent mechanism(s).
我们评估了环核苷酸在调节人外周血单核细胞中脂多糖（LPS）诱导的肿瘤坏死因子-α（TNF-α）生成中的作用。将单核细胞暴露于LPS（3 ng/ml）会引发TNF-α的延迟、时间依赖性生成，在LPS刺激后5 - 6小时达到最高水平，并在长达24小时内保持恒定。这种效应具有浓度依赖性，导致TNF-α释放增加20 - 40倍，且对放线菌素D和环己酰亚胺敏感。用一般认为可激活cAMP/依赖cAMP的蛋白激酶（PKA）级联反应的试剂处理单核细胞，通常会抑制LPS诱导的TNF-α生成。因此，β2肾上腺素能受体激动剂沙丁胺醇和丙卡特罗以普萘洛尔敏感的方式部分（约40%）抑制TNF-α生成。此外，8-溴-cAMP、霍乱毒素、前列腺素E2以及一些抑制磷酸二酯酶（PDE）4同工酶家族的药物（如咯利普兰（ZK 62711）、登布茶碱（BRL 30892）、Ro 20-1724、贝那非林（AH 21-132））可消除细胞因子生成。相比之下，福斯可林、PDE3和PDE5抑制剂以及可溶性和颗粒性鸟苷酸环化酶激活剂基本无活性。有趣的是，咯利普兰未能增强沙丁胺醇对LPS诱导的TNF-α生物合成的抑制作用，但矛盾的是，它在cAMP生成和PKA激活方面与沙丁胺醇协同作用。然而，当用PGE2激活腺苷酸环化酶时，咯利普兰增强了cAMP积累、PKA激活以及对TNF-α生成的抑制作用。相比之下，无论有无咯利普兰，福斯可林都不会增加单核细胞中的cAMP含量。总体而言，这些数据表明，人外周血单核细胞中LPS诱导的TNF-α生成是由于TNF-α基因转录增加及随后的翻译，并且这些效应被一系列激活cAMP/PKA级联反应的试剂所抑制。然而，咯利普兰未能增强沙丁胺醇和丙卡特罗对TNF-α生成的抑制作用，这表明β2肾上腺素能受体激动剂可能至少部分通过一种不依赖cAMP的机制影响基因表达和/或转录后调控过程。
