The BET Bromodomain Inhibitor I-BET-151 Induces Structural and Functional Alterations of the Heart Mitochondria in Healthy Male Mice and Rats.

The bromodomain and extra-terminal domain family inhibitors (BETi) are a promising new class of anticancer agents. Since numerous anticancer drugs have been correlated to cardiomyopathy, and since BETi can affect non-cancerous tissues, we aimed to investigate in healthy animals any ultrastructural BETi-induced alterations of the heart as compared to skeletal muscle. Male Wistar rats were either treated during 3 weeks with I-BET-151 (2 or 10 mg/kg/day) (W3) or treated for 3 weeks then allowed to recover for another 3 weeks (W6) (3-weeks drug washout). Male C57Bl/6J mice were only treated during 5 days (50 mg/kg/day). We demonstrated the occurrence of ultrastructural alterations and progressive destruction of cardiomyocyte mitochondria after I-BET-151 exposure. Those mitochondrial alterations were cardiac muscle-specific, since the skeletal muscles of exposed animals were similar in ultrastructure presentation to the non-exposed animals. I-BET-151 decreased the respiration rate of heart mitochondria in a dose-dependent manner. At the higher dose, it also decreased mitochondrial mass, as evidenced by reduced right ventricular citrate synthase content. I-BET-151 reduced the right and left ventricular fractional shortening. The concomitant decrease in the velocity-time-integral in both the aorta and the pulmonary artery is also suggestive of an impaired heart function. The possible context-dependent cardiac side effects of these drugs have to be appreciated. Future studies should focus on the basic mechanisms of potential cardiovascular toxicities induced by BETi and strategies to minimize these unexpected complications.

Bromodomain and extra-terminal protein mimic JQ1 decreases inflammation in human vascular endothelial cells: Implications for pulmonary arterial hypertension.

BACKGROUND AND OBJECTIVE: Nuclear factor kappa B (NF-kB)-mediated inflammatory gene expression and vascular endothelial cell proliferation/remodelling are implicated in the pathophysiology of the fatal disease, pulmonary arterial hypertension (PAH). Bromodomain and extra-terminal (BET) proteins are essential for the expression of a subset of NF-kB-induced inflammatory genes. BET mimics including JQ1+ prevent binding of BETs to acetylated histones and down-regulate the expression of selected genes. METHODS: The effects of JQ1+ on the proliferation of primary human pulmonary microvascular endothelial cells (HPMECs) from healthy subjects were measured by bromodeoxyuridine (BrdU) incorporation. Cell cycle progression was assessed by flow cytometry; mRNA and protein levels of cyclin-dependent kinases (CDKs), inhibitors and cytokines were determined by reverse transcription-quantitative PCR (RT-qPCR), Western blotting or ELISA. Histone acetyltransferase (HAT) and deacetylase (HDAC) activities were determined in nuclear extracts from whole lung of PAH and control patients. RESULTS: JQ1+ significantly inhibited IL6 and IL8 (IL6 and CXCL8) mRNA and protein in HPMECs compared with its inactive enantiomer JQ1-. JQ1+ decreased NF-kB p65 recruitment to native IL6 and IL8 promoters. JQ1+ showed a concentration-dependent decrease in HPMEC proliferation compared with JQ1--treated cells. JQ1+ induced G1 cell cycle arrest by increasing the expression of the CDK inhibitors (CDKN) 1A (p21cip ) and CDKN2D (p19INK4D ) and decreasing that of CDK2, CDK4 and CDK6. JQ1+ also inhibited serum-stimulated migration of HPMECs. Finally, HAT activity was significantly increased in the lung of PAH patients. CONCLUSION: Inhibition of BETs in primary HPMECs decreases inflammation and remodelling. BET proteins could be a target for future therapies for PAH.

Nuclear factor κ-B is activated in the pulmonary vessels of patients with end-stage idiopathic pulmonary arterial hypertension.

OBJECTIVES: To assess activation of the inflammatory transcription factor NF-kappa B (NF-κB) in human idiopathic pulmonary arterial hypertension (PAH). BACKGROUND: Idiopathic PAH is a severe progressive disease characterized by pulmonary vascular remodeling and excessive proliferation of vascular cells. Increasing evidence indicates that inflammation is important in disease pathophysiology. METHODS: NF-κB-p65 and CD68, CD20 and CD45 were measured by immunohistochemistry and confocal microscopy on lung specimens from patients with idiopathic PAH (n = 12) and controls undergoing lung surgery (n = 14). Clinical data were recorded for all patients including invasive pulmonary hemodynamics for the PAH patients. Immunohistochemical images were analyzed by blinded observers to include standard pulmonary vascular morphometry; absolute macrophage counts/mm(2) and p65-positivity (p65+) using composite images and image-analysis software; and cytoplasmic:nuclear p65+ of individual pulmonary arterial endothelial and smooth muscle cells (PASMC) in 10-20 pulmonary arteries or arterioles per subject. The expression of ET-1 and CCL5 (RANTES) in whole lung was determined by RT-qPCR. RESULTS: Macrophage numbers were increased in idiopathic PAH versus controls (49.0±4.5 vs. 7.95±1.9 macrophages/100 mm(2), p<0.0001): these macrophages demonstrated more nuclear p65+ than in macrophages from controls (16.9±2.49 vs. 3.5±1.25%, p<0.001). An increase in p65+ was also seen in perivascular lymphocytes in patients with PAH. Furthermore, NF-κB activation was increased in pulmonary arterial endothelial cells (62.3±2.9 vs. 14.4±3.8, p<0.0001) and PASMC (22.6±2.3 vs. 11.2±2.0, p<0.001) in patients with PAH versus controls, with similar findings in arterioles. Gene expression of both ET-1 mRNA ((0.213±0.069 vs. 1.06±0.23, p<0.01) and CCL5 (RANTES) (0.16±0.045 vs. 0.26±0.039, p<0.05) was increased in whole lung homogenates from patients with PAH. CONCLUSIONS: NF-κB is activated in pulmonary macrophages, lymphocytes, endothelial and PASMC in patients with end-stage idiopathic PAH. Future research should determine whether NF-κB activation is a driver or bystander of pulmonary vascular inflammation and if the former, its potential role as a therapeutic target.

Bone morphogenetic proteins protect pulmonary microvascular endothelial cells from apoptosis by upregulating α-B-crystallin.

OBJECTIVE: To investigate the role of bone morphogenetic proteins (BMPs) on α-B-crystallin (CRYAB) expression and its physiological consequences on endothelial cells (ECs). APPROACH AND RESULTS: We report that the gene encoding for the small heat shock protein, CRYAB, is a transcriptional target of the BMP signaling pathway. We demonstrate that CRYAB expression is upregulated strongly by BMPs in an EC line and in human lung microvascular ECs and human umbilical vein ECs. We show that BMP signals through the BMPR2-ALK1 pathway to upregulate CRYAB expression through a transcriptional indirect mechanism involving Id1. We observed that the known antiapoptotic effect of the BMPs is, in part, because of the upregulation of CRYAB expression in EC. We also show that cryab is downregulated in vivo, in a mouse model of pulmonary arterial hypertension induced by chronic hypoxia where the BMP pathway is downregulated. CONCLUSIONS: We demonstrate a cross-talk between BMPs and CRYAB and a major effect of this regulatory interaction on resistance to apoptosis.

Cytotoxic cells and granulysin in pulmonary arterial hypertension and pulmonary veno-occlusive disease.

RATIONALE: Pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease (PVOD) both display occlusive remodeling of the pulmonary vasculature responsible for increased pulmonary vascular resistances. Cytotoxic T (CTL), natural killer (NK), and natural killer T (NKT) cells play a critical role in vascular remodeling in different physiological and pathological conditions. Granulysin (GNLY) represents a powerful effector protein for all these subpopulations. OBJECTIVES: To analyze the cytolytic compartment of inflammatory cells in patients with PAH and PVOD. METHODS: The overall functional status of the cytolytic compartment was studied through epigenetic analysis of the GNLY gene in explanted lungs and in peripheral blood mononuclear cells. Flow cytometry technology allowed analysis of specific circulating cytolytic cells and GNLY contents. A GNLY-specific ELISA allowed measurement of GNLY serum concentrations. MEASUREMENTS AND MAIN RESULTS: A decrease in GNLY demethylation in the gDNA extracted from peripheral blood mononuclear cells and explanted lungs was found specifically in PVOD but not in PAH. This was associated with a decrease in populations and subpopulations of CTL and NKT and an increase of NK populations. Despite the reduced granulysin-containing cells in patients with PVOD, GNLY serum levels were higher, suggesting these cells were wasting their content. Furthermore, the increase of GNLY concentration in the serum of PVOD was significantly higher than in patients with PAH. CONCLUSIONS: PVOD is characterized by alterations of circulating cytotoxic cell subpopulations and by epigenetic dysregulation within the GNLY gene. Our findings may be helpful in the quest to develop needed diagnostic tools, including flow cytometry analyses, to screen for suspected PVOD in patients with pulmonary hypertension.

Leptin and regulatory T-lymphocytes in idiopathic pulmonary arterial hypertension.

Immune mechanisms and autoimmunity seem to play a significant role in idiopathic pulmonary arterial hypertension (IPAH) pathogenesis and/or progression, but the pathophysiology is still unclear. Recent evidence has demonstrated a detrimental involvement of leptin in promoting various autoimmune diseases by controlling regulatory T-lymphocytes. Despite this knowledge, the role of leptin in IPAH is currently unknown. We hypothesised that leptin, synthesised by dysfunctional pulmonary endothelium, might play a role in the immunopathogenesis of IPAH by regulating circulating regulatory T-lymphocytes function. First, we collected serum and regulatory T-lymphocytes from controls, and IPAH and scleroderma-associated pulmonary arterial hypertension (SSc-PAH) patients; secondly, we recovered tissue samples and cultured endothelial cells after either surgery or transplantation in controls and IPAH patients, respectively. Our findings indicate that serum leptin was higher in IPAH and SSc-PAH patients than controls. Circulating regulatory T-lymphocyte numbers were comparable in all groups, and the percentage of those expressing leptin receptor was higher in IPAH and SSc-PAH compared with controls, whereas their function was reduced in IPAH and SSc-PAH patients compared with controls, in a leptin-dependent manner. Furthermore, endothelial cells from IPAH patients synthesised more leptin than controls. Our data suggest that endothelial-derived leptin may play a role in the immunopathogenesis of IPAH.

C-kit-positive cells accumulate in remodeled vessels of idiopathic pulmonary arterial hypertension.

RATIONALE: C-kit(+) cells, including bone marrow (BM)-derived progenitors and mast cells, may participate in vascular remodelling. Because recent studies suggest that c-kit may be a target for innovative therapies in experimental pulmonary hypertension, we investigated the contribution of c-kit(+) cells in human idiopathic pulmonary arterial hypertension (IPAH). OBJECTIVES: To investigate the contribution of c-kit(+) cells in human IPAH. METHODS: Single c-kit, CXCL12/SDF-1α, CXCR4, CD34, and multiple c-kit, α-smooth muscle actin (α-SMA) and tryptase immunostainings were performed in IPAH lungs. C-kit mRNA expression was quantified by real-time polymerase chain reaction in microdissected pulmonary arteries from patients with IPAH and control subjects. Phenotype and function of circulating progenitors were analyzed by flow cytometry. Plasma levels of soluble c-kit and CXCL12/SDF-1α were measured by ELISA. MEASUREMENTS AND MAIN RESULTS: Infiltration of c-kit(+) cells in pulmonary arterial lesions was associated with an increase in c-kit mRNA expression (P < 0.01 compared with control subjects). Both c-kit(+)/tryptase(+) mast cells and c-kit(+)/tryptase(-) BM-derived cells were increased in pulmonary arteries of patients with IPAH compared with control subjects (106.6 ± 54.5 vs. 28 ± 16.8/mm(2) and 143.8 ± 101.1 vs. 23.3 ± 11.9/mm(2); all P<0.01). Plasma-soluble c-kit was increased in IPAH compared with control subjects (27.4 ± 12.4 vs. 19.5 ± 5.8 ng/ml; P<0.05). Two populations of circulating BM-derived cells (lin-CD34(high)CD133(high) [c-kit(high)CXCR4(low)] and lin-CD34(low)CD133(-) [c-kit(low)CXCR4(high)]) were increased in IPAH compared with control subjects (P=0.01). Pulmonary arterial lesions were associated with vasa vasorum expansion expressing CXL12/SDF-1α that may recruit c-kit(+) cells. CONCLUSIONS: In IPAH, c-kit(+) cells infiltrate pulmonary arterial lesions and may participate to vascular remodeling. Therefore, c-kit may represent a potential target for innovative PAH therapy.