Riociguat normalizes altered lung expression of serotonin-related genes and renal damage markers in experimental pulmonary hypertension
Authors: Velasova E , Lelkova K , Veteskova J , Kmecova Z , Marusakova M , Doka G , Bies Pivackova L , Klimas J , Krenek P 
Published: October 2022

Abstract

Introduction
Pulmonary arterial hypertension (PAH) leads to a progressive increase in pulmonary vascular resistance, right heart failure, adverse cardiorenal interactions and mortality. Preclinical studies have shown an association between elevated serotonin (5-HT) levels and disease progression, however, the local pathogenic roles of individual components of serotoninergic system in the lung in PAH remain less well defined.

Purpose
To test the hypothesis that experimental PAH is associated with alterations in the expression of serotoninergic genes in the lung and right ventricle and that short treatment of experimental PAH with riociguat could have an impact on the serotoninergic system. In addition, we examined whether riociguat could alleviate renal damage associated with cardiorenal interactions in PAH.

Methods
We used rat monocrotaline model of PAH (60 mg/kg, s.c.). 2 weeks after MCT, we treated two groups with riociguat (10 mg/kg/d, p.o.) until week 4 when rats were sacrificed. We divided rats into 4 groups. CON-control group, MCT-rats with established PAH, RIO-healthy rats with administered riociguat, and MCT+RIO-rats with established PAH treated with riociguat. We used RT-qPCR to monitor mRNA changes of brain natriuretic peptide (Nppb), components of serotoninergic system in the lungs and right ventricle, biomarkers of renal tubular damage Kim1 and podocyte damage Nphs1, an indicator of neurohumoral activation renin (Ren) and marker of renal hypoxia erythropoietin (Epo). In addition, we measured plasma NT-proBNP, serotonin, cGMP and a heart failure marker sST2 using ELISA.

Results
As expected, MCT caused RV hypertrophy and increased lung weight (p&lt;0.05 vs CON). We observed a 10-fold increase of Nppb in the RV (p&lt;0.05 vs CON), however, plasma levels of NT-proBNP and sST2 did not change. Short-term RIO did not revert these changes. MCT increased cGMP plasma concentration by more than 80% (p&lt;0.05 vs CON), RIO did not influence plasma cGMP levels. However, in the lungs, MCT increased the expression Tph1, Htr1b and Htr2b genes and decreased that of Sert. Riociguat treatment in MCT+RIO normalized these changes (p&lt;0.05 vs MCT) with the exception of decreased Sert expression. In the kidney, we observed a 5-fold increase in expression of Kim1 and a 50% increase in Nphs1 mRNA by MCT (p&lt;0.05 vs CON), expression of both genes were normalized in MCT+RIO (p&lt;0.05 vs MCT). MCT-related increases in Ren and Epo expressions were unaffected by RIO.

Conclusion
Serotonin-related genes alterations in the lungs of rats with experimental PAH are indicative of increased serotonin signalling and they are partly normalized after of short-term treatment with riociguat. At the same time, riociguat had beneficial effects on renal damage markers in PAH without affecting neurohumoral activation associated with PAH.

Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): Research and Development Support AgencyScientific Grant Agency of the Ministry of Education, Science, Research and Sports of the Slovak Republic