Selective inhibition of p38 mitogen activated protein kinase with the pyridinyl

宿主炎症介质的过度释放直接导致败血症和感染性休克的发生。丝裂原活化蛋白激酶（MAPKs）是丝氨酸/苏氨酸细胞内信号蛋白，在这种炎症反应中起核心作用。这些mapk被磷酸化激活，并介导基因表达和其他细胞功能，以响应细胞外信号。哺乳动物细胞中的三种主要MAPKs是p38、细胞外信号调节激酶（ERK）和c-jun n -末端激酶（JNK）。这些MAPKs中的每一个都在脂多糖（LPS）的反应中调节炎症介质的产生，脂多糖是一种细菌毒素，与革兰氏阴性细菌性肺炎和败血症的发病机制密切相关。这些介质包括细胞因子、趋化因子、一氧化氮、活性氧和前列腺素代谢物。基于大量数据支持mapk在炎症中的关键作用，人们对这些蛋白的选择性抑制剂的治疗应用越来越感兴趣。然而，这些药物在脓毒症中的应用主要是在体内模型中进行的，仅采用LPS刺激。由于MAPKs调节的许多介质参与保护性先天免疫或宿主防御反应以及炎症损伤，因此在细菌感染期间抑制它们可能是有害的。我们对炭疽芽孢杆菌致死毒素（LeTx）进行的一项研究数据支持抑制MAPK可能存在风险和益处的可能性。LeTx的致死因子（LF）成分是一种锌蛋白酶，可切割和失活丝裂原活化蛋白激酶（MAPKKs）家族的几种不同成员及其下游靶点，包括p38。我们发现，当LeTx以亚致死剂量给予致死性LPS攻击的动物时，炎症细胞因子和一氧化氮的释放减少，血流动力学功能和生存得到改善。然而，在气管内大肠杆菌攻击的动物中，类似的预处理在减少细胞因子和一氧化氮释放的同时，也降低了存活率。这些发现表明，非选择性抑制这些MAPKs可能对活菌有害。然而，选择性抑制这些mapk可能仍然是有益的。

Excessive release of host inflammatory mediators contributes directly to the pathogenesis of sepsis and septic shock. Mitogen-activated protein kinases (MAPKs) are serine/threonine intracellular signaling proteins that have a central role in this inflammatory response. These MAPKs are activated by phosphorylation and mediate gene expression and other cellular functions in response to extracellular signals. Three major MAPKs in mammalian cells are p38, extracellular signal-regulated kinase (ERK), and c-jun N-terminal kinase (JNK). Each of these MAPKs regulates inflammatory mediator production in response to lipopolysaccharide (LPS), a bacterial toxin closely associated with the pathogenesis of gram-negative bacterial pneumonia and sepsis. These mediators include cytokines, chemokines, nitric oxide, reactive oxygen species, and prostaglandin metabolites. Based on substantial data supporting a pivotal role for MAPKs in inflammation, there is growing interest in the therapeutic application of selective inhibitors of these proteins. However, the application of such agents in sepsis has been primarily tested in in vivo models employing LPS challenge only. Since many of the mediators MAPKs regulate participate in protective innate immune or host defense responses as well as inflammatory injury, their inhibition could be harmful during bacterial infection. Data from a study we conducted with Bacillus anthracis lethal toxin (LeTx) supports the possibility that there may be risks as well as benefits with MAPK inhibition. The lethal factor (LF) component of LeTx is a zinc protease that cleaves and inactivates several different members of the mitogen-activated protein kinase (MAPKKs) family and their downstream targets including p38. We showed that when LeTx was administered in sublethal doses to animals challenged with lethal LPS, inflammatory cytokine and nitric oxide release were reduced and hemodynamic function and survival improved. However, similar pretreatment in animals challenged with intratracheal E. coli, while also reducing cytokine and nitric oxide release, decreased survival. These findings suggested that nonselective inhibition of these MAPKs may be harmful with live bacteria. Selective inhibition of these MAPKs may still be beneficial however. SB203580 4-(4-flurophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)imidazole is a pyridinyl imidazole that has been employed extensively as a selective inhibitor of p38, in both in vitro and in vivo models of inflammation. This agent competes for the ATP binding site on p38 and inhibits its phosphorylation and activation. In in vivo models, administration of this agent via several different routes, as well as both before and after inflammatory stimulus, has been shown to inhibit cytokine and nitric oxide release, leukocyte trafficking, and organ injury. This agent and a related one have also been shown to improve survival in LPS challenged models. Although the results of such studies have provided a major rational for the use of p38 inhibitors during states of inflammation such as sepsis, an extensive literature search has revealed only one published report (12) assessing the effects of this or related agents in an animal model of sepsis employing live bacterial challenge. This was a very limited study in mice undergoing cecal ligation and puncture (CLP) and did not incorporate antibiotic support or microbiological assessment. The results of this study did suggest however that the effectiveness of SB203580 was increased when its administration was delayed for 12 h after the onset of sepsis. We previously developed a mouse model of E. coli pneumonia in which antibiotics and fluids were shown to synergistically improve survival as they are believed to do clinically. This model is now being used to test the effects of SB203580. In initial experiments we have found that doses of this agent previously reported to be beneficial in very limited studies, actually appeard harmful when administered either 1 h before or 1 h after bacterial challenge in the mouse model. Delaying treatment for 12 h is did not result in harmful effects but was also not beneficial. Reducing the dose of SB203580 3 logs doses resulted in beneficial effects with the agent, but only if it is given prophylactically. Later treatment had no benefit. In subsequent studies we have now found that while high and low prophylactic doses of SB203580 have similar effects on myocardial function as assessed by echocardiography, their effects on inflammatory cytokine release differed. Importantly, while low doses were associated with increased cytokine release early and decreases later, high doses produce uniform reductions. Thus, the harmful effects of high but not low doses of SB203580 may relate to differential expression of host mediators that are important not only for inflammatory tissue injury but also for host defense as well. Additional studies are ongoing investigating the effects of SB203580 on P38 levels.