Pulmonary hypertension: reduction of vascular and cardiac remodeling by a new inhibitor of p38-alpha MAPK
Authors: Silva G.R.A , Beltrame F , Alencar A.K.N , Silva M.M , Rocha B , Da Silva J.S , Montagnoli T.L , Freitas R.C , Fraga C.A.M , Sudo R.T , Zapata-Sudo G 
Published: November 2020

Abstract

Background
Pulmonary arterial hypertension (PAH) is a disease characterized by pulmonary vascular remodeling with subsequent right ventricular (RV) failure. This work investigated the effects of a new p38-alpha mitogen-activated protein kinase (p38-α MAPK) inhibitor, named LASSBio-1824, on PAH model in rats.

Methods
All experiments were in accordance with the Animal Care and Use Committee at our university (039/19). Male Wistar rats was exposed to hypoxia (10% O2) during 3 weeks plus i.p. injection of an antagonist of vascular endothelial growth factor receptor (SU5416; 20 mg/kg/week) to induce PAH. Control rats were kept in normoxia (21% O2). After 21 days of protocol, echocardiography images confirmed PAH using the pulmonary artery (PA) outflow waveform. After disease onset, animals were randomly divided into three groups: control + vehicle (DMSO), HAP + vehicle and HAP + LASSBio-1824 (50 mg/kg/day). Vehicle and LASSBio-1824 were administered by oral gavage during two weeks.

Results
Pulmonary acceleration time (PAT; ms) was reduced from 33.2±2.7 (control) to 22.7±1.1 in PAH + vehicle group (p&lt;0.05) and restored to 29.6±1.9 after treatment with LASSBio-1824 (p&lt;0.05). RV afterload was detected in HAP group because of the increase of systolic pressure (mmHg) from 22.2±1.5 (control) to 47.2±3.6 (p&lt;0.05) and reduced to 18.0±2.9 with LASSBio-1824. Medial wall thickness (%) of distal PA (&lt;50 μm) was measured by using immunohistochemistry for alpha smooth muscle actin (α-SMA) which was increased from 62.5±5.6 (control) to 78.0±7.9 in PAH group (p&lt;0.05), but it was significantly reduced to 54.4±2.3 in PAH + LASSBio-1824 group (p&lt;0.05). Vascular reactivity was evaluated comparing the acetylcholine (ACh)-induced maximal relaxation (%) in PA from normal and PAH rats, which was reduced from 67.5±2.1 to 49.63±5.6 (PAH group; p&lt;0.05). Therefore, the treatment with the p38 inhibitor normalized the ACh-induced response to 73.7±4.1%. The immunohistochemistry for c-fos protein, a product of the p38 pathway related to cell proliferation, showed an increased ratio of stained and total myocyte nuclei (%) in PAH animals of 38.0±0.5 compared to normal group of 20.2±4.2. LASSBio-1824 significantly reduced ratio to 24.0±2.3% (p&lt;0.05). PAH increased inflammatory condition because the expression of inducible nitric oxide synthase increased from 0.31±0.01 (control) to 0.57±0.02 and it was recovered by the treatment with LASSBio-1824 to 0.31±0.10 (p&lt;0.05).

Conclusion
LASSBio-1824, an inhibitor of p38-alpha MAPK represents an important approach for the future treatment of PAH which improves the underlying remodeling and inflammation processes in the cardiopulmonary system.

Funding Acknowledgement
Type of funding source: Foundation. Main funding source(s): Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES; Conselho Nacional de Desenvolvimento Científico e Tecnolόgico - CNPq