Regulation of Pro-Asthmatic and Glucocorticoid Signaling by Airway Smooth Muscle

描述（由申请人提供）： 特应性和气道暴露于空气过敏原和微生物病原体是发生哮喘的主要危险因素。令人信服的证据表明，气道平滑肌（ASM）在调节气道哮喘表型中起着至关重要的作用，包括表明，ASM表达特应性和非特应性刺激，代表上述危险因素的受体，并响应于这些敏化刺激释放细胞因子，特别是包括Th 2型细胞因子，引起促哮喘的变化，在ASM收缩和舒张反应。最近的研究表明，CD 4 + T细胞的超抗原（SAg）呈递ASM细胞的激活也eliminate Th 2细胞因子的释放耦合ASM的反应性的变化。与这些促哮喘作用相反，我们的新发现表明，ASM还表现出Th 2细胞因子诱导的机制，使其能够激活内源性糖皮质激素（GC），从而稳态对抗Th 2细胞因子信号传导对ASM功能的不利影响。这一新的证据，连同证明在致敏的ASM中马槟榔碱诱导的促哮喘和稳态GC信号传导都归因于MAPK信号传导的活化的证据，提出了以下假设：I：由特应性和非特应性致敏刺激以及ASM/T细胞相互作用引起的ASM功能中的促哮喘变化是由细胞因子表达和作用的MAPK依赖性调节介导的; II：GC介导的保护ASM免受促哮喘细胞因子的影响是由于在致敏状态下GC信号传导的MAPK依赖性上调; III：从哮喘患者分离的ASM表现出增强的MAPK调节的促哮喘信号传导和受损的MAPK调节的CG信号传导。这些假设将在对从非哮喘和哮喘气道分离的ASM细胞的研究中得到解决。因此，我：为了研究MAPK依赖性诱导致敏ASM中促哮喘反应性变化，我们将研究：1）MAPK依赖性调节由特应性（IgE）和非特应性刺激（包括鼻病毒、尘螨变应原或脂多糖）致敏的ASM中细胞因子释放和作用; 2）Gi蛋白介导的MAPK活化，导致PDE 4表达改变及其对ASM收缩和舒张的调节; 3）MAPK依赖性调节SAg呈递的ASM细胞对CD 4 + T细胞的活化。二.为了研究MAPK依赖性调节GC信号传导，我们将研究MAPK依赖性调节GC活化酶，11 β-羟基类固醇脱氢酶-1（11 β-HSD 1）和糖皮质激素受体（GR）信号传导在致敏ASM中; III.为了确定哮喘ASM是否表现出促哮喘和GC信号转导的MAPK依赖性调节的扰动，我们将比较哮喘与非哮喘致敏的ASM细胞在调节PDE 4表达和作用、GC活化和信号转导以及由SAg呈递ASM细胞活化T细胞方面的差异。这些研究的结果有望确定ASM中信号传导机制的关键内在扰动，这些机制是气道哮喘表型表达的基础。(End摘要）

DESCRIPTION (provided by applicant): Atopy and airway exposure to aeroallergens and microbial pathogens are primary risk factors for development of asthma. Compelling evidence that airway smooth muscle (ASM) plays a critical role in regulating the airway asthmatic phenotype includes that demonstrating that ASM expresses receptors for atopic and non-atopic stimuli that represent the above risk factors, and responds to these sensitizing stimuli by releasing cytokines, notably including Th2-type cytokines, that evoke pro-asthmatic changes in ASM constrictor and relaxation responsiveness. Recent studies demonstrate that activation of CD4+ T cells by superantigen (SAg)-presenting ASM cells also elicits Th2 cytokine release coupled to changes in ASM responsiveness. Contrasting these pro- asthmatic actions, our new findings demonstrate that ASM also exhibits a Th2 cytokine-induced mechanism that enables it to activate endogenous glucocorticoids (GCs) and, thereby, homeostatically oppose the adverse effects of Th2 cytokine signaling on ASM function. This new evidence, together with that demonstrating that both the cytokine-induced pro-asthmatic and homeostatic GC signaling in sensitized ASM are attributed to activation of MAPK signaling, raise the hypotheses that: I: The pro-asthmatic changes in ASM function elicited by atopic and non-atopic sensitizing stimuli, and by ASM/T cell interaction, are mediated by MAPK-dependent regulation of both cytokine expression and action; II: GC-mediated protection of ASM from the pro-asthmatic effects of cytokines is due to MAPK-dependent upregulation of GC signaling in the sensitized state; and III: ASM isolated from asthmatic patients exhibits enhanced MAPK-regulated pro-asthmatic signaling and impaired MAPK-regulated CG signaling. These hypotheses will be addressed in studies on ASM cells isolated from non- asthmatic and asthmatic airways. Accordingly, I: To investigate MAPK-dependent induction of pro-asthmatic changes in responsiveness in sensitized ASM, we will examine: 1) MAPK-dependent regulation of cytokine release and action in ASM sensitized by atopic (IgE) and by non-atopic stimuli including rhinovirus, dust mite allergen, or lipopolysaccharide; 2) Gi protein-mediated MAPK activation, resulting in altered PDE4 expression and its regulation of ASM contraction and relaxation; 3) MAPK-dependent regulation of CD4+ T cell activation by SAg-presenting ASM cells. II. To investigate MAPK-dependent regulation of GC signaling, we will examine MAPK-dependent regulation of the GC-activating enzyme, 11ss-hydroxysteroid dehydrogenase-1 (11ss-HSD1), and glucocorticoid receptor (GR) signaling in sensitized ASM; III. To determine whether asthmatic ASM exhibits perturbations in MAPK-dependent regulation of pro-asthmatic and GC signaling, we will compare asthmatic vs. non-asthmatic sensitized ASM cells with respect to differences in regulation of PDE4 expression and action, GC activation and signaling, and T cell activation by SAg-presenting ASM cells. The results from these studies are anticipated to identify key intrinsic perturbations in the signaling mechanisms in ASM that underlie expression of the airway asthmatic phenotype. (End of Abstract)