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Transforming growth factor-ß (TGF-ß) becomes rapidly activated in the infarcted heart. Hence, TGF-ß-mediated persistent activation of cardiac fibroblasts (CFs) and exaggerated fibrotic responses may result in adverse cardiac remodelling and heart failure. Additionally, peptidylarginine deiminase 4 (PAD4) was described to be implicated in organ fibrosis. Here, we investigated the impact of PAD4 on CF function and myofibroblast transdifferentiation in vitro. The expression of fibrosis-related genes was largely similar in cultured WT and PAD4-/- CFs of passage 3, although collagen III was reduced in PAD4-/- CFs. Exposure to TGF-ß inhibited proliferation and increased contractile activity and migration of WT CFs, but not of PAD4-/- CFs. However, under baseline conditions, PAD4-/- CFs showed comparable functional characteristics as TGF-ß- stimulated WT CFs. Although the SMAD-dependent TGF-ß pathway was not disturbed in PAD4-/- CFs, TGF-ß failed to activate protein kinase B (Akt) and signal transducer and activator of transcription 3 (STAT3) in these cells. Similar results were obtained in WT CFs treated with the PAD4 inhibitor Cl-amidine. Abrogated Akt activation was associated with diminished levels of phosphorylated, inactive glycogen synthase kinase-3ß (GSK-3ß). Consequently, PAD4-/- CFs did not upregulate collagen I and a-smooth muscle actin (a-SMA) expression after TGF-ß treatment. Thus, PAD4 is substantially involved in the regulation of non-canonical TGF-ß signalling and may represent a therapeutic target for the treatment of adverse cardiac remodelling. [ABSTRACT FROM AUTHOR]

Kynurenine, the major degradation product of tryptophan has been shown to directly damage various tissues. Its potential contribution to septic arthritis is unknown. In this study, we analyzed the putative diagnostic value of kynurenine for bacterial joint infection and its potential harmful effects on cartilage. In a prospective study 41 patients with a joint effusion who had undergone arthrocentesis were included. Tryptophan and kynurenine levels from synovial fluid were quantified by HPLC. Diagnostic value of kynurenine was evaluated and its effects on the proliferation of the chondrocyte cell line ATDC5 were determined. Synovial fluid kynurenine values from patients with septic arthritis (4.1 ± 0.8 µmol/L, n = 9) were significantly increased compared to patients with non-infectious inflammatory arthropathy (1.8 ± 0.2 µmol/L, n = 17) or osteoarthritis (1.2 ± 0.1 µmol/L, n = 15, p < 0.01). At a cut-off value of 2.28 µmol/L kynurenine had a sensitivity of 0.89 and a specificity of 0.87. Further, kynurenine inhibited chondrocyte (ATDC5) cell proliferation in a dose-dependent manner. Septic arthritis is associated with significantly increased values of synovial kynurenine. Furthermore kynurenine inhibits proliferation of chondrocytes, which strongly suggests a pathophysiological effect of kynurenine on cartilage in inflammatory arthropathies. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1490-1496, 2010 [ABSTRACT FROM AUTHOR]

The release of 'neutrophil extracellular traps' (NETs) has been identified as a novel immune response in innate immunity. NETs are composed of neutrophil-derived circulating free DNA (cf-DNA) and neutrophil cytoplasm-derived proteins such as proteases. In this study, we analyzed the putative diagnostic value of synovial cf-DNA/NETs for identification of septic arthritis. Forty-two patients with a joint effusion who had undergone arthrocentesis were included. From synovial fluid, cf-DNA/NETs (j-cf-DNA) levels were directly quantified. Diagnostic value of j-cf-DNA was compared with white blood cells (WBC), synovial white blood cells (j-WBC), C-reactive protein (CRP), j-IL-6, j-TNF alpha, j-IL-1 beta, and myeloperoxidase (j-MPO). Sensitivity, specificity, positive and negative predictive value, as well as ROC-curves for each parameter were calculated. Synovial fluid cf-DNA/NETs values from patients with septic arthritis (3,286 ± 386 ng/ml, n = 9) were significantly increased compared to patients with noninfectious joint inflammation (1,040 ± 208 ng/ml, n = 17) or osteoarthritis (278 ± 34 ng/ml, n = 16, p < 0.01). In conjunction with j-cf-DNA, j-IL-6 and j-IL-1 beta were significantly elevated ( p < 0.01), but WBC, CRP, and j-WBC were not. At a cut-off of 300 ng/ml, j-cf-DNA had a sensitivity of 0.89, a specificity of 1.0, a positive predictive value of 1.0, and a negative predictive value of 0.97. Receiver operation curves revealed largest areas under the curve for cf-DNA/NETs (0.933) and j-IL-6 (0.951). cf-DNA/NETs seem to be a valuable additional marker for the diagnosis of septic arthritis or periprosthetic infections. However, this result should be confirmed in a large clinical trial. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1401-1407, 2009 [ABSTRACT FROM AUTHOR]