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.

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.

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.