Abstract P2024: Novel Inhibitor Of P38 Mitogen-activated Protein Kinase Reverses Hypoxia-induced Pulmonary Hypertension In Rats

Abstract

Pulmonary arterial hypertension (PAH) is a disease characterized by pulmonary vascular changes with subsequent right ventricular (RV) failure. This work investigated the hypothesis that a new p38-alpha mitogen-activated protein kinase (p38-alpha MAPK) inhibitor, named LASSBio-1824, could interfere on PH model in rats. Methods: HP was induced in male Wistar rats through the exposure to hypoxia (10% O2) during 3 weeks, in combination to i.p. injection of an antagonist of vascular endothelial growth factor receptor (SU5416; 20 mg/kg/weekly). Control rats were kept in normoxia. After 3 weeks, echocardiography images confirmed PH using the pulmonary artery (PA) outflow waveform. After disease onset, animals were randomly divided into three groups: control + vehicle (DMSO), PH + vehicle and PH + LASSBio-1824 (50 mg/kg/day), in which vehicle and LASSBio-1824 were orally administered (gavage) during two weeks. All experiments were in accordance with the Animal Care and Use Committee at Federal University of Rio de Janeiro (039/19). Results: Pulmonary acceleration time (PAT; ms) was reduced from 40.0 ± 2.1 (control) to 24.2 ± 1.8 in PH + vehicle group (p < 0.05) and restored to 36.8 ± 2.9 after treatment with LASSBio-1824 (p < 0.05). RV afterload was detected in PH group because of the increase of systolic pressure (mmHg) from 23.2 ± 1.5 (control) to 46.7 ± 2.8 (p < 0.05) which was reduced to 19.4 ± 2.7 with LASSBio1824 treatment. Medial wall thickness (%) of distal pulmonary arteries (PA, < 50 μm) was evaluated by using immunohistochemistry for alpha smooth muscle actin (alpha-SMA) which was increased from 64.0 ± 4.9 (control) to 80.8 ± 2.7 in PH group (p < 0.05), but it was significantly reduced to 55.0 ± 1.3 after treatment with the inhibitor (p < 0.05). Acetylcholine (ACh)-induced maximal relaxation (%) of PA from normal and PH rats, was reduced from 67.5 ± 1.6 to 51.9 ± 4.9 (p < 0.05). Therefore, the treatment with the p38 inhibitor normalized vascular reactivity to 73.0 ± 3.3 %. The immunohistochemistry for c-fos protein, a product of the p38 pathway related to cell proliferation, showed an increase of stained myocyte nuclei (%) in PH animals of 36.5 ± 1.5 when compared to normal group of 20.2 ± 4.2. The inhibitor significantly reduced ratio to 24.0 ± 2.3% (p < 0.05). PH increased the inflammatory condition because the expression of inducible nitric oxide synthase altered from 10.4 ± 1.9% (control) to 31.9 ± 2.2% and it was recovered by the inhibitor to 15.5 ± 2.2% (p < 0.05). In conclusion, the new p38-alpha MAPK inhibitor represents an important approach for the future treatment of PH, since it improves the underlying remodeling and inflammation processes.