TNFα induces endothelial dysfunction in rheumatoid arthritis via LOX-1 and arginase 2: reversal by monoclonal TNFα antibodies.

AIMS: Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting joints and blood vessels. Despite low levels of low-density lipoprotein cholesterol (LDL-C), RA patients exhibit endothelial dysfunction and are at increased risk of death from cardiovascular complications, but the molecular mechanism of action is unknown. We aimed in the present study to identify the molecular mechanism of endothelial dysfunction in a mouse model of RA and in patients with RA. METHODS AND RESULTS: Endothelium-dependent relaxations to acetylcholine were reduced in aortae of two tumour necrosis factor alpha (TNFα) transgenic mouse lines with either mild (Tg3647) or severe (Tg197) forms of RA in a time- and severity-dependent fashion as assessed by organ chamber myograph. In Tg197, TNFα plasma levels were associated with severe endothelial dysfunction. LOX-1 receptor was markedly up-regulated leading to increased vascular oxLDL uptake and NFκB-mediated enhanced Arg2 expression via direct binding to its promoter resulting in reduced NO bioavailability and vascular cGMP levels as shown by ELISA and chromatin immunoprecipitation. Anti-TNFα treatment with infliximab normalized endothelial function together with LOX-1 and Arg2 serum levels in mice. In RA patients, soluble LOX-1 serum levels were also markedly increased and closely related to serum levels of C-reactive protein. Similarly, ARG2 serum levels were increased. Similarly, anti-TNFα treatment restored LOX-1 and ARG2 serum levels in RA patients. CONCLUSIONS: Increased TNFα levels not only contribute to RA, but also to endothelial dysfunction by increasing vascular oxLDL content and activation of the LOX-1/NFκB/Arg2 pathway leading to reduced NO bioavailability and decreased cGMP levels. Anti-TNFα treatment improved both articular symptoms and endothelial function by reducing LOX-1, vascular oxLDL, and Arg2 levels.

TGF-beta1 and TGF-beta2 strongly enhance the secretion of plasminogen activator inhibitor-1 and matrix metalloproteinase-9 of the human prostate cancer cell line PC-3.

BACKGROUND: Recently it was demonstrated that transforming growth factor beta 2 (TGF-beta 2) is the predominant TGF-beta isoform in the human prostate. However, with the human prostatic cancer cells PC-3 mostly effects of TGF-beta 1 were investigated. This study aimed to analyze the effects of TGF-beta 2 on its own secretion, on the secretion of plasminogen activator inhibitor-1 (PAI-1), and the matrix metalloproteinases (MMP)-2 and MMP-9 in comparison to stimulations with TGF-beta 1. MATERIALS AND METHODS: PC-3 cells were cultured with and without TGF-beta 1 and TGF-beta 2 to analyze autostimulation and their effects on protein secretion. ELISAs for TGF-beta 1, TGF-beta 2, TGF-beta 3, PAI-1, MMP-2 and MMP-9 were used to analyze protein levels in the supernatant. Cell proliferation was determined with a proliferation assay. RESULTS: A dose-dependent and significant suppression of cell proliferation with TGF-beta 1 (p < 0.05) and TGF-beta 2 (p < 0.05) was observed. PC-3 cells secrete higher amounts of total TGF-beta 2 compared to total TGF-beta 1. Only for TGF-beta 2, we found the active isoform. In contrast, the secretion of TGF-beta 3 was not detectable. Additionally, we observed a strong and significant increase in the secretion of MMP-9 and PAI-1 after stimulations with TGF-beta 1 and TGF-beta 2, respectively. However, no protein levels of MMP-2 were detectable. CONCLUSION: Our experiments revealed that TGF-beta 2 is the predominant TGF-beta isoform in PC-3 cells. Furthermore, a strong effect of TGF-beta 1 and TGF-beta 2 on the secretion of MMP-9 and PAI-1 was found. Thus, PC-3 cells not only secrete TGF-beta 1 and TGF-beta 2 but also respond to stimulations with the TGF-beta isoforms. The interesting observation that only TGF-beta 2 is activated points to different mechanisms of proteolytic activation of the diverse TGF-beta isoforms.