Background-Inflammation is a feature of pulmonary arterial hypertension (PAH), and increased circulating levels of cytokines are reported in patients with PAH. However, to date, no information exists on the significance of elevated cytokines or their potential as biomarkers. We sought to determine the levels of a range of cytokines in PAH and to examine their impact on survival and relationship to hemodynamic indexes. Methods and Results-We measured levels of serum cytokines (tumor necrosis factor-␣, interferon-␥ and interleukin-1␤, -2, -4, -5, -6, -8, -10, -12p70, and -13) using ELISAs in idiopathic and heritable PAH patients (nϭ60). Concurrent clinical data included hemodynamics, 6-minute walk distance, and survival time from sampling to death or transplantation. Healthy volunteers served as control subjects (nϭ21). PAH patients had significantly higher levels of interleukin-1␤, -2, -4, -6, -8, -10, and -12p70 and tumor necrosis factor-␣ compared with healthy control subjects. Kaplan-Meier analysis showed that levels of interleukin-6, 8, 10, and 12p70 predicted survival in patients. For example, 5-year survival with interleukin-6 levels of Ͼ9 pg/mL was 30% compared with 63% for patients with levels Յ9 pg/mL (Pϭ0.008). In this PAH cohort, cytokine levels were superior to traditional markers of prognosis such as 6-minute walk distance and hemodynamics. Conclusions-This study illustrates dysregulation of a broad range of inflammatory mediators in idiopathic and familial PAH and demonstrates that cytokine levels have a previously unrecognized impact on patient survival. They may prove to be useful biomarkers and provide insight into the contribution of inflammation in PAH. (Circulation. 2010;122:920-927.)

The preclinical model of bleomycin-induced lung fibrosis, used to investigate mechanisms related to idiopathic pulmonary fibrosis (IPF), has incorrectly predicted efficacy for several candidate compounds suggesting that it may be of limited value. As an attempt to improve the predictive nature of this model, integrative bioinformatic approaches were used to compare molecular alterations in the lungs of bleomycin-treated mice and patients with IPF. Using gene set enrichment analysis we show for the first time that genes differentially expressed during the fibrotic phase of the single challenge bleomycin model were significantly enriched in the expression profiles of IPF patients. The genes that contributed most to the enrichment were largely involved in mitosis, growth factor, and matrix signaling. Interestingly, these same mitotic processes were increased in the expression profiles of fibroblasts isolated from rapidly progressing, but not slowly progressing, IPF patients relative to control subjects. The data also indicated that TGFβ was not the sole mediator responsible for the changes observed in this model since the ALK-5 inhibitor SB525334 effectively attenuated some but not all of the fibrosis associated with this model. Although some would suggest that repetitive bleomycin injuries may more effectively model IPF-like changes, our data do not support this conclusion. Together, these data highlight that a single bleomycin instillation effectively replicates several of the specific pathogenic molecular changes associated with IPF, and may be best used as a model for patients with active disease.

Mutations in bone morphogenetic protein receptor II (BMPR-II) underlie most heritable cases of pulmonary arterial hypertension (PAH). However, less than half the individuals who harbor mutations develop the disease. Interestingly, heterozygous null BMPR-II mice fail to develop PAH unless an additional inflammatory insult is applied, suggesting that BMPR-II plays a fundamental role in dampening inflammatory signals in the pulmonary vasculature. Using static-and flow-based in vitro systems, we demonstrate that BMPR-II maintains the barrier function of the pulmonary artery endothelial monolayer suppressing leukocyte transmigration. Similar findings were also observed in vivo using a murine model with loss of endothelial BMPR-II expression. In vitro, the enhanced transmigration of leukocytes after tumor necrosis factor ␣ or transforming growth factor ␤1 stimulation was CXCR2 dependent. Our data define how loss of BMPR-II in the endothelial layer of the pulmonary vasculature could lead to a heightened susceptibility to inflammation by promoting the extravasation of leukocytes into the pulmonary artery wall. We speculate that this may be a key mechanism involved in the initiation of the disease in heritable PAH that results from defects in BMPR-II expression. (Blood. 2011;117(1):333-341)

Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease of high unmet medical need. Although bromodomain (Brd) and extra terminal domain isoforms have recently been implicated in mediating inflammatory and oncologic indications, their roles in lung fibrosis have not been comprehensively assessed. We investigated the role of Brd on the profibrotic responses of lung fibroblasts (LFs) in patients with rapidly progressing IPF and a mouse bleomycin model of lung fibrosis. The enhanced migration, proliferation, and IL-6 release observed in LFs from patients with rapidly progressing IPF are attenuated by pharmacologic inhibition of Brd4. These changes are accompanied by enhanced histone H4 lysine5 acetylation and association of Brd4 with genes involved in the profibrotic responses in IPF LFs as demonstrated using chromatin immunoprecipitation and quantitative PCR. Oral administration of 200 mg/kg per day Brd4 inhibitor JQ1 in a therapeutic dosing regimen substantially attenuated lung fibrosis induced by bleomycin in C57BL/6 mice. In conclusion, this study shows that the Brd4 inhibitor JQ1, administered in a therapeutic dosage, is capable of inhibiting the profibrotic effects of IPF LFs and attenuates bleomycin-induced lung fibrosis in mice. These results suggest that Brd4 inhibitors may represent a novel therapy for the treatment of rapidly progressing IPF.

Agonist-mediated receptor phosphorylation by one or more of the members of the G-protein receptor kinase (GRK) family is an established model for G-protein-coupled receptor (GPCR) phosphorylation resulting in receptor desensitization. Our recent studies have, however, suggested that an alternative route to GPCR phosphorylation may be an operation involving casein kinase 1␣ (CK1␣). In the current study we investigate the involvement of CK1␣ in the phosphorylation of the human m3-muscarinic receptor in intact cells. We show that expression of a catalytically inactive mutant of CK1␣, designed to act in a dominant negative manner, inhibits agonist-mediated receptor phosphorylation by ϳ40% in COS-7 and HEK-293 cells. Furthermore, we present evidence that a peptide corresponding to the third intracellular loop of the m3-muscarinic receptor (Ser 345 -Leu 463 ) is an inhibitor of CK1␣ due to its ability to both act as a pseudo-substrate for CK1␣ and form a high affinity complex with CK1␣. Expression of this peptide was able to reduce both basal and agonist-mediated m3-muscarinic receptor phosphorylation in intact cells. These results support the notion that CK1␣ is able to mediate GPCR phosphorylation in an agonist-dependent manner and that this may provide a novel mechanism for GPCR phosphorylation. The functional role of phosphorylation was investigated using a mutant of the m3-muscarinic receptor that showed an ϳ80% reduction in agonist-mediated phosphorylation. Surprisingly, this mutant underwent agonist-mediated desensitization suggesting that, unlike many GPCRs, desensitization of the m3-muscarinic receptor is not mediated by receptor phosphorylation. The inositol (1,4,5)-trisphosphate response did, however, appear to be dramatically potentiated in the phosphorylation-deficient mutant indicating that phosphorylation may instead control the magnitude of the initial inositol phosphate response. It is now well established that G-protein-coupled receptor (GPCR)1 phosphorylation is a general phenomenon that controls specific key signaling properties of receptors. Originally associated with receptor desensitization (1, 2), GPCR phosphorylation has now been implicated in a number of processes including receptor internalization (3-6) and as a molecular switch that determines coupling to specific signaling pathways (7,8). The receptor-specific kinases involved are generally considered to belong to the G-protein-coupled receptor kinase (GRK) family which are characterized by their sequence homology to rhodopsin kinase (GRK-1) and that include the extensively studied ␤-adrenergic receptor kinases 1 and 2 (GRK-2 and -3, respectively) (2, 9). Reconstitution experiments using purified, or partially purified, receptors have demonstrated that in addition to the ␤ 2 -adrenergic receptor a number of GPCRs including muscarinic ((10 -12), substance P (13), bradykinin B 2 (14), and adenosine A 3 receptors (15) can act as GRK substrates. Furthermore, a GRK-2 dominant negative mutant (16) has been widely employed to probe the role of en...

Mutations in the bone morphogenetic protein (BMP) type II receptor (BMPR-II) underlie most cases of heritable pulmonary arterial hypertension (HPAH) and a significant proportion of sporadic cases. Pulmonary artery smooth muscle cells (PASMCs) from patients with pulmonary arterial hypertension (PAH) not only exhibit attenuated growth suppression by BMPs, but an abnormal mitogenic response to transforming growth factor (TGF)-β1. We sought to define the mechanism underlying this loss of the antiproliferative effects of TGF-β1 in BMPR-II-deficient PASMCs. The effect of TGF-β1 on PASMC proliferation was characterized in three different models of BMPR-II dysfunction: 1) HPAH PASMCs, 2) Bmpr2(+/-) mouse PASMCs, and 3) control human PASMCs transfected with BMPR-II small interfering RNA. BMPR-II reduction consistently conferred insensitivity to growth inhibition by TGF-β1. This was not associated with altered canonical TGF-β1/Smad signaling but was associated with a secreted factor. Microarray analysis revealed that the transcriptional responses to TGF-β1 differed between control and HPAH PASMCs, particularly regarding genes associated with interleukins and inflammation. HPAH PASMCs exhibited enhanced IL-6 and IL-8 induction by TGF-β1, an effect reversed by NF-κB inhibition. Moreover, neutralizing antibodies to IL-6 or IL-8 restored the antiproliferative effect of TGF-β1 in HPAH PASMCs. This study establishes that BMPR-II deficiency leads to failed growth suppression by TGF-β1 in PASMCs. This effect is Smad-independent but is associated with inappropriately altered NF-κB signaling and enhanced induction of IL-6 and IL-8 expression. Our study provides a rationale to test anti-interleukin therapies as an intervention to neutralize this inappropriate response and restore the antiproliferative response to TGF-β1.

The autotaxin-lysophophatidic acid (ATX-LPA) signaling pathway is implicated in a variety of human disease states including angiogenesis, autoimmune diseases, cancer, fibrotic diseases, inflammation, neurodegeneration, and neuropathic pain, among others. As a result, ATX-LPA has become of significant interest within both the industrial and the academic communities. This review aims to provide a concise overview of the development of novel ATX inhibitors, including the disclosure of the first ATX clinical trial data.

Epigenetic alterations, such as histone acetylation, regulate the signaling outcomes and phenotypic responses of fibroblasts after growth factor stimulation. The bromodomain and extraterminal domain-containing proteins (Brd) bind to acetylated histone residues, resulting in recruitment of components of the transcriptional machinery and subsequent gene transcription. Given the central importance of fibroblasts in tissue fibrosis, this study sought to determine the role of Brd proteins in human lung fibroblasts (LFs) after growth factor stimulation and in the murine bleomycin model of lung fibrosis. Using small interfering RNA against human Brd2 and Brd4 and pharmacologic Brd inhibitors, this study found that Brd2 and Brd4 are essential in mediating the phenotypic responses of LFs downstream of multiple growth factor pathways. Growth factor stimulation of LFs causes increased histone acetylation, association of Brd4 with growth factor-responsive genes, and enhanced transcription of these genes that could be attenuated with pharmacologic Brd inhibitors. Of note, lung fibrosis induced after intratracheal bleomycin challenge in mice could be prevented by pretreatment of animals with pharmacologic inhibitors of Brd proteins. This study is the first demonstration of a role for Brd2 and Brd4 proteins in mediating the responses of LFs after growth factor stimulation and in driving the induction of lung fibrosis in mice in response to bleomycin challenge.