| 摘要: | 研究期間：10108~10207;Both asthma and rheumatoid arthritis (RA) are chronic inflammatory diseases, each affecting at least 0.5% population worldwide. Allergic asthma is considered a Th2 cytokine-driven disease, characterized by chronic airway inflammation, airway hyperresponsiveness (AHR), mucosal edema, and airway obstruction. RA is an autoimmune disorder, characterized by synovial inflammation and destruction of joint cartilage and bone, and is thought to be mediated by persistent synthesis of proinflammatory cytokines and matrix metalloproteinases (MMP) in macrophages, Th1 and/or Th17 cells, and synovial tissue cells. Although the modulatory effects of cAMP signaling in inflammatory cells have been widely explored, the exact physiological functions of this regulatory pathway in these two diseases remain to be defined. Here we will test the hypothesis that a gene (PDE4B) coding for the family cAMP-specific phosphodiesterases (PDE4s), enzymes that degrade and inactivate the second messenger cAMP, plays a critical role in modulating inflammatory responses, and hence the clinical symptoms in these two diseases. Of the four PDE4 genes present in mammals (PDE4A, 4B, 4C, and 4D), three (4A, 4B, and 4D) are expressed in inflammatory cells. Although ablation of each of these genes protects against AHR, only ablation of PDE4B causes marked disruption in airway inflammation and Th2 cytokine production. The expression of PDE4B in macrophages is up-regulated by activation of Toll-like receptor signaling, and TNF- production to LPS is greatly reduced in PDE4B-null mice but not in PDE4A- or PDE4D-null mice. Preliminary results also showed that PDE4B null mice are more resistant to collagen-induced arthritis (CIA) compared with the wild-type mice. On the basis of these preliminary findings, we propose to use these knockout models to further understand how ablation of PDE4B, and thereby disruption of cAMP signaling impacts inflammatory responses and AHR in a model of allergic asthma as well as joint destruction in a CIA model. Experiments are organized along four main specific aims carried out in three years. With the first Specific Aim, we propose to further determine the cellular basis of the reduced airway responses in PDE4B null mice using the adoptive transfer strategy. Experiments described in the second Specific Aim will define the molecular mechanisms that underlie the effects of PDE4B on Th2 cell functions by determining PDE4 expression pattern during Th2 cell differentiation as well as assessing the effects of TNF- and IL-10 in PDE4 null mice. The third Specific Aim is to test the newly developed PDE4B-selective inhibitor Compound 33 in vitro and in vivo to determine whether the acute pharmacological effects resemble the findings observed in PDE4B null mice. The fourth Specific Aim will be devoted to defining the role of individual PDE4 subtypes in the pathogenesis of RA using a CIA model. The effect of PDE4s on Th1/Th17 differentiation and their cytokine production will be assessed. These studies will provide new insights into the role of PDE4B in the Th cell functions associated with the pathogenesis of allergic asthma and RA. Given the established potential of nonselective PDE4 inhibitors as non steroidal anti-inflammatory drugs, a better understanding of the function of PDE4s, in particular of PDE4B, in these inflammatory diseases will open new opportunities for PDE4 drug design. |
