The nuclear orphan receptor peroxisome proliferator-activated receptor-gamma (PPAR-γ) is expressed in multiple cell types in addition to adipocytes. Upon its activation by natural ligands such as fatty acids and eicosanoids, or by synthetic agonists such as rosiglitazone, PPAR-γ regulates adipogenesis, glucose uptake and inflammatory responses. Recent studies establish a novel role for PPAR-γ signaling as an endogenous mechanism for regulating transforming growth factor-ß (TGF-ß)-dependent fibrogenesis. Here, we sought to characterize PPAR-γ function in the prototypic fibrosing disorder systemic sclerosis (SSc), and delineate the factors governing PPAR-γ expression. We report that PPAR-γ levels were markedly diminished in skin and lung biopsies from patients with SSc, and in fibroblasts explanted from the lesional skin. In normal fibroblasts, treatment with TGF-ß resulted in a time- and dose-dependent down-regulation of PPAR-γ expression. Inhibition occurred at the transcriptional level and was mediated via canonical Smad signal transduction. Genome-wide expression profiling of SSc skin biopsies revealed a marked attenuation of PPAR-γ levels and transcriptional activity in a subset of patients with diffuse cutaneous SSc, which was correlated with the presence of a “TGF-ß responsive gene signature” in these biopsies. Together, these results demonstrate that the expression and function of PPAR-γ are impaired in SSc, and reveal the existence of a reciprocal inhibitory cross-talk between TGF-ß activation and PPAR-γ signaling in the context of fibrogenesis. In light of the potent anti-fibrotic effects attributed to PPAR-γ, these observations lead us to propose that excessive TGF-ß activity in SSc accounts for impaired PPAR-γ function, which in turn contributes to unchecked fibroblast activation and progressive fibrosis.

No abstract

Analysis of deduced protein sequence and structural motifs of approximately 5500 residues of human fetal skeletal muscle nebulin reveals the design principles of this giant multifunctional protein in the sarcomere. The bulk of the sequence is constructed of approximately 150 tandem copies of approximately 35-residue modules that can be classified into seven types. The majority of these modules form 20 super-repeats, with each super-repeat containing a 7-module set (one of each type in the same order). These super-repeats are further divided into eight segments: with six segments containing adjacent, highly homologous super-repeats, one single repeat segment consisting of 8 nebulin modules of the same type, and a non-repeat segment terminating with a SH3 domain at the C terminus. The interactions of actin, tropomyosin, troponin, and calmodulin with nebulin fragments consisting of either repeating modules or the SH3 domain support its role as a giant actin-binding cofilament of the composite thin filament. Such affinity profiles also suggest that nebulin may bind to tropomyosin and troponin to form a composite calcium-linked regulatory complex on the thin filament. The modular construction, super-repeat structure, and segmental organization of nebulin sequence appear to encode thin filament length, periodicity, insertion, and sarcomere proportion in the resting muscle.

Glutamic acid decarboxylase (GAD) is a pancreatic beta cell autoantigen in humans and nonobese diabetic (NOD) mice. beta Cell-specific suppression of GAD expression in two lines of antisense GAD transgenic NOD mice prevented autoimmune diabetes, whereas persistent GAD expression in the beta cells in the other four lines of antisense GAD transgenic NOD mice resulted in diabetes, similar to that seen in transgene-negative NOD mice. Complete suppression of beta cell GAD expression blocked the generation of diabetogenic T cells and protected islet grafts from autoimmune injury. Thus, beta cell-specific GAD expression is required for the development of autoimmune diabetes in NOD mice, and modulation of GAD might, therefore, have therapeutic value in type 1 diabetes.

Macrophages are important mediators of chronic inflammation and are prominent in the synovial lining and sublining of patients with rheumatoid arthritis (RA). Recently, we demonstrated increased TLR2 and TLR4 expression and increased response to microbial TLR2 and TLR4 ligands in macrophages from the joints of RA. The current study characterized the expression of the 96-kDa heat shock glycoprotein (gp96) in the joints of RA and its role as an endogenous TLR ligand to promote innate immunity in RA. gp96 was increased in RA compared with osteoarthritis and arthritis-free control synovial tissues. The expression of gp96 strongly correlated with inflammation and synovial lining thickness. gp96 was increased in synovial fluid from the joints of RA compared with disease controls. Recombinant gp96 was a potent activator of macrophages and the activation was mediated primarily through TLR2 signaling. The cellular response to gp96 was significantly stronger with RA synovial macrophages compared with peripheral blood monocytes from RA or healthy controls. The transcription of TLR2, TNF-α, and IL-8, but not TLR4, was significantly induced by gp96, and the induction was significantly greater in purified RA synovial macrophages. The expression of TLR2, but not TLR4, on synovial fluid macrophages strongly correlated with the level of gp96 in the synovial fluid. The present study documents the potential role of gp96 as an endogenous TLR2 ligand in RA and provides insight into the mechanism by which gp96 promotes the chronic inflammation of RA, identifying gp96 as a potential new therapeutic target.

Introduction The aim of this study was to quantify the number of T-helper (TH)-17 cells present in rheumatoid arthritis (RA) synovial fluid (SF) and to determine the level of interleukin (IL)-17 cytokine in RA, osteoarthritis (OA) and normal synovial tissue, as well as to examine SF macrophages for the presence of IL-23, IL-27 and interferon (IFN)-γ.

In the present study, we developed transgenic mice overexpressing the N-terminal truncated cTnI (cTnI-ND) in the heart to examine its biochemical and physiological significance. Ca 2؉ -activated actomyosin ATPase activity showed that cTnI-ND myofibrils had lower affinity for Ca 2؉ than controls, similar to the effect of isoproterenol treatment. In vivo and isolated working heart experiments revealed that cTnI-ND hearts had a significantly faster rate of relaxation and lower left ventricular end diastolic pressure compared with controls. The higher baseline relaxation rate of cTnI-ND hearts was at a level similar to that of wild type mouse hearts under ␤-adrenergic stimulation. The decrease in cardiac output due to lowered preload was significantly smaller for cTnI-ND hearts compared with controls. These findings indicate that removal of the N-terminal extension of cTnI via restricted proteolysis enhances cardiac function by increasing the rate of myocardial relaxation and lowering left ventricular end diastolic pressure to facilitate ventricular filling, thus resulting in better utilization of the Frank-Starling mechanism.

No abstract