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Activation of DP1 by PGD2 in macrophages induces the binding of PRKAR2A to the IFN-γR2 transmembrane region, inhibits JAK2/STAT1 signaling, and triggers the expression of antiinflammatory and reparative genes in myocardial infarction and sepsis.

Pulmonary arterial hypertension (PAH) is a life-threatening disease characterized by progressive pulmonary artery (PA) remodeling. T helper 2 cell (Th2) immune response is involved in PA remodeling during PAH progression. Here, we found that CRTH2 (chemoattractant receptor homologous molecule expressed on Th2 cell) expression was up-regulated in circulating CD3CD4 T cells in patients with idiopathic PAH and in rodent PAH models. CRTH2 disruption dramatically ameliorated PA remodeling and pulmonary hypertension in different PAH mouse models. CRTH2 deficiency suppressed Th2 activation, including IL-4 and IL-13 secretion. Both CRTH2 bone marrow reconstitution and CRTH2 CD4 T cell adoptive transfer deteriorated hypoxia + ovalbumininduced PAH in CRTH2 mice, which was reversed by dual neutralization of IL-4 and IL-13. CRTH2 inhibition alleviated established PAH in mice by repressing Th2 activity. In culture, CRTH2 activation in Th2 cells promoted pulmonary arterial smooth muscle cell proliferation through activation of STAT6. These results demonstrate the critical role of CRTH2-mediated Th2 response in PAH pathogenesis and highlight the CRTH2 receptor as a potential therapeutic target for PAH.

Activation of RAGE facilitates the development of hypoxia-induced pulmonary hypertension by increase of ECM deposition in pulmonary arteries. Our results indicate that sRAGE may be a potential biomarker for PAH diagnosis and disease severity, and that RAGE may be a promising target for PAH treatment.

Background-Pulmonary arterial remodeling characterized by increased vascular smooth muscle proliferation is commonly seen in life-threatening disease, pulmonary arterial hypertension (PAH). Clinical studies have suggested a correlation between osteoprotegerin serum levels and PAH severity. Here, we aimed to invhestigate vascular osteoprotegerin expression and its effects on pulmonary arterial smooth muscle cell proliferation in vitro and in vivo, as well as examine the signal transduction pathways mediating its activity. Methods and Results-Serum osteoprotegerin levels were significantly elevated in patients with PAH and correlated with disease severity as determined by the World Health Organization (WHO) functional classifications and 6-minute walking distance tests. Similarly, increased osteoprotegerin expression was observed in the pulmonary arteries of hypoxia plus SU5416-and monocrotaline-induced PAH animal models. Moreover, osteoprotegerin disruption attenuated hypoxia plus SU5416-induced PAH progression by reducing pulmonary vascular remodeling, whereas lentiviral osteoprotegerin reconstitution exacerbated PAH by increasing pulmonary arterial smooth muscle cell proliferation. Furthermore, pathway analysis revealed that osteoprotegerin induced pulmonary arterial smooth muscle cell proliferation by interacting with integrin α v β 3 to elicit downstream focal adhesion kinase and AKT pathway activation. Conclusions-Osteoprotegerin facilitates PAH pathogenesis by regulating pulmonary arterial smooth muscle cell proliferation, suggesting that it may be a potential biomarker and therapeutic target in this disease. Jia et al Osteoprotegerin in Pulmonary HypertensionIn addition, experimental results indicated that osteoprotegerin promotes the proliferation of various cancer cells and endothelial cells in a TRAIL-independent manner. 14,15 These data expand the functional significance of osteoprotegerin beyond its presumed role as a receptor activator of nuclear factor-κB ligand and TRAIL decoy receptor, and suggest that it may interact with integrins or fatty acid synthase. 8,14,15 This is greatly relevant because pulmonary arterial smooth muscle cells (PASMCs) express several integrin molecules that regulate pulmonary vascular remodeling and contribute to PAH progression. 16,17 Integrins are a large family of structurally related heterodimeric transmembrane receptors that regulate cell-cell and cell-matrix contacts. 18 Of the 18α and 8β subtypes identified, pulmonary vascular smooth muscles express α 1-5 , α 7 , α 8 , α v , β 1 , β 3 , and β 4 .17 On the basis of these observations, we hypothesize that osteoprotegerin may contribute to pulmonary vascular remodeling in an integrindependent manner.In this study, we demonstrated that osteoprotegerin expression was increased in both murine and human pulmonary arterial SMCs (mPASMCs and hPASMCs) in response to hypoxia and in the lung tissue and pulmonary arteries of hypoxia plus SU5416 (HySu)-induced PAH model mice. Moreover, integrin α 1 , α 8 , α v , and β 3 express...

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Niacin is a well established drug used to lower cholesterol and prevent cardiovascular disease events. However, niacin also causes cutaneous flushing side effects due to release of the proresolution mediator prostaglandin D 2 (PGD 2 ). Recent randomized clinical trials have demonstrated that addition of niacin with laropiprant [a PGD 2 receptor subtype 1 (DP1) blocker] to statin-based therapies does not significantly decrease the risk of cardiovascular disease events, but increases the risk of serious adverse events. Here, we tested whether, and how, niacin beneficial effects on myocardial ischemia require the activation of the PGD 2 /DP1 axis. Myocardial infarction (MI) was reproduced by ligation of the left anterior descending branch of the coronary artery in mice. We found that niacin increased PGD 2 release in macrophages and shifted macrophages to M2 polarization both in vitro and in vivo by activation of DP1 and accelerated inflammation resolution in zymosan-induced peritonitis in mice. Moreover, niacin treatment facilitated wound healing and improved cardiac function after MI through DP1-mediated M2 bias and timely resolution of inflammation in infarcted hearts. In addition, we found that niacin intake also stimulated M2 polarization of peripheral monocytes in humans. Collectively, niacin promoted cardiac functional recovery after ischemic myocardial infarction through DP1-mediated M2 polarization and timely resolution of inflammation in hearts. These results indicated that DP1 inhibition may attenuate the cardiovascular benefits of niacin.