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

描述(由申请人提供)： 特应性和呼吸道暴露于空气变应原和微生物病原体是哮喘发生的主要危险因素。有证据表明，气道平滑肌(ASM)在调节气道哮喘表型中起关键作用，包括ASM表达代表上述危险因素的特应性和非特应性刺激的受体，并通过释放细胞因子(尤其是包括Th2型细胞因子)对这些致敏刺激做出反应，从而在ASM收缩和松弛反应中引起哮喘前期的变化。最近的研究表明，超抗原(SAG)呈递的ASM细胞激活CD4T细胞还会引起Th2细胞因子的释放，并伴随ASM反应性的变化。对比这些促哮喘作用，我们的新发现表明，ASM还表现出Th2细胞因子诱导的机制，使其能够激活内源性糖皮质激素(GC)，从而动态平衡地对抗Th2细胞因子信号对ASM功能的不利影响。这一新的证据，以及细胞因子在致敏ASM中诱导的致敏哮喘和稳态GC信号均归因于MAPK信号的激活，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致喘性改变，是由MAPK依赖的细胞因子表达和作用调节所介导的；II：GC介导的保护ASM免受细胞因子的致敏作用是由于MAPK依赖的GC信号在致敏状态上调所致；从哮喘患者分离的ASM表现出MAPK调节的促哮喘信号增强和MAPK调节的CG信号减弱。这些假说将在从非哮喘和哮喘呼吸道分离的ASM细胞的研究中得到解决。因此，I：为了研究MAPK依赖于诱导致敏ASM中促哮喘反应的改变，我们将检测：1)MAPK依赖于特应性(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中细胞因子的释放和作用；2)Gi蛋白介导的MAPK激活，导致PDE4表达的改变及其对ASM收缩和松弛的调节；3)MAPK依赖于SAG提呈的ASM细胞对CD4T细胞激活的调节。为了研究MAPK对GC信号的依赖调节，我们将研究MAPK对致敏ASM中GC激活酶、11ss-羟基类固醇脱氢酶-1(11ss-HSD1)和糖皮质激素受体(GR)信号的依赖调节；iii.为了确定哮喘ASM是否表现出MAPK依赖的促哮喘和GC信号调节的扰动，我们将比较哮喘和非哮喘致敏ASM细胞在PDE4表达和作用、GC激活和信号以及SAG呈递质ASM细胞激活T细胞方面的差异。这些研究的结果有望确定ASM信号机制中的关键内在扰动，这些信号机制是呼吸道哮喘表型表达的基础。(摘要结束)

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)