Diastolic dysfunction in the aging heart is a grave condition that challenges the life and lifestyle of a growing segment of our population. This report seeks to examine the role and interrelationship of inflammatory dysregulation in interstitial myocardial fibrosis and progressive diastolic dysfunction in aging mice. We studied a population of C57BL/6 mice that developed progressive diastolic dysfunction over 30 months of life. This progressive dysfunction was associated with increasing infiltration of CD45 + fibroblasts of myeloid origin. In addition, increased rates of collagen expression as measured by cellular procollagen were apparent in the heart as a function of age. These cellular and functional changes were associated with progressive increases in mRNA for MCP-1 and IL-13 which correlated both temporally and quantitatively with changes in fibrosis and cellular procollagen levels. MCP-1 protein was also increased and found to be primarily in the venular endothelium. Protein assays also demonstrated elevation of IL-4 and IL-13 suggesting a shift to a Th2 phenotype in the aging heart. In vitro studies demonstrated that IL-13 markedly enhanced monocyte fibroblast transformation.Our results indicate that immunoinflammatory dysregulation in the aging heart induces progressive MCP-1 production and an increased shift to a Th2 phenotype paralleled by an associated increase in myocardial interstitial fibrosis, cellular collagen synthesis, and increased numbers of CD45 + myeloid-derived fibroblasts that contain procollagen. The temporal association and functional correlations suggests a causative relationship between age-dependent immunoinflammatory dysfunction, fibrosis and diastolic dysfunction.

Cardiac fibroblasts are the most prevalent cell type in the heart. These cells exert a critical role in regulating normal myocardial function and in the adverse myocardial remodeling that occurs after myocardial infarction (MI). 1 Irreversible cardiomyocyte damage owing to cessation of oxygen supply during MI leads to necrosis, which stimulates inflammatory reactions that trigger reparative pathways and activate cells to form a scar. Cytokines released by inflammatory infiltrating leukocytes promote endogenous mesenchymal stem cell (MSC) proliferation and migration toward the infarct site, followed by differentiation into fibroblasts that deposit scar-forming collagen. The fibroblasts mature into myofibroblasts, expressing scar-contracting ␣-smooth muscle actin (␣-SMA). 2 Resident fibroblasts also become activated and participate in this process. After several weeks, a mature scar is formed, and most of the myofibroblasts undergo apoptosis. [3][4][5] We have previously established in a model of mouse MI that, compared with young animals, aged mice demonstrate greater infarct expansion and less effective myocardial repair. 6 Defective scar formation arises from a decreased number of myofibroblasts and diminished collagen deposition in the infarct, which results in a structurally unstable scar formed by loose connective tissue. 7 Evidence indicates that multipotent cells can be generated in vitro from several adult organs including the heart. 8 Tissue-resident progenitor cells of mesenchymal origin can differentiate into myogenic, adipocytic, chondrocytic, osteoblastic, and fibroblastic lineages. 9 -11 The potential of those stem cells to differentiate decreases

We determined whether salicylate at pharmacological concentrations inhibits nitric-oxide synthase-2 (NOS-2) and cyclo-oxygenase-2 (COX-2) expressions in RAW 264.7 stimulated with lipopolysaccharide (LPS) and interferon-γ (IFN-γ). Cells were treated with sodium salicylate (10−7-10−4m) or vehicle for 30 min followed by LPS+IFN-γ for up to 24 h. Salicylate suppressed NOS-2 and COX-2 protein levels and promoter activities stimulated by LPS+IFN-γ for 4 h in a concentration-dependent manner but had no effect on NOS-2 expression stimulated by the combined agonists for 24 h. Results from promoter analysis indicate that the binding of CCAAT/enhancer-binding protein β (C/EBPβ) to its cognate site at −150/−142 on the NOS-2 promoter region was essential for NOS-2 expression at 4 h but not at 24 h. Salicylate reduced C/EBPβ binding at 4 h and did not alter its binding at 24 h. NOS-2 and COX-2 protein levels and C/EBPβ binding stimulated by LPS+IFN-γ for 4 h were inhibited by a similar battery of signaling inhibitors, suggesting a common pathway for NOS-2 and COX-2 expression. Kinetic analysis indicates that NOS-2, similar to COX-2 expression, at 4 h was largely due to the action of LPS, which induced C/EBPβ binding, whereas its expression at a longer time point was contributed by IFN-γ. Our findings implicate two distinct pathways for NOS-2 expression induced by LPS+IFN-γ. Salicylate at pharmacological concentrations is capable of suppressing the early phase of NOS-2 and COX-2 expression by blocking C/EBPβ binding.