A107-15 Loxl2 Drives Fibrotic Remodeling and Right Ventricular Failure in Pulmonary Arterial Hypertension

Background

Right ventricular (RV) function is a significant prognostic determinant of morbidity and mortality in patients with pulmonary arterial hypertension (PAH). The adaptation of the RV to PAH can lead to maladaptive RV remodeling. However, the underlying molecular mechanisms of adverse RV remodeling are poorly understood. Here, we dissect the RV transcriptome of PAH patients and animal models to identify dysregulated biological pathways involved in PAH-induced RV failure. Further bioinformatic approaches allowed us to identify lysyl oxidase-like 2 (LOXL2), a key extracellular matrix (ECM) protein contributing to RV failure. We hypothesize that upregulation of LOXL2 leads to RV fibrosis and dysfunction in PAH, and specific inhibition of LOXL2 can rescue PAH-induced RV failure.

Methods

Adults male Sprague Dawley rats received either a single subcutaneous injection of pulmonary endothelial toxin Monocrotaline (MCT), VEGF-receptor antagonist SU5416 with 3-weeks of hypoxia (10% oxygen) followed by 2-weeks of normoxia (SuHx). PAH and RV failure were confirmed by echocardiography and RV-catheterization. LOXL2 RNA and protein expression validated by qPCR, immunofluorescence, and western blot. PAT-1251, a selective inhibitor of LOXL2 administered via oral gavage to rescue RV failure from PAH rats. Trichrome staining was used to assess for fibrosis. Immunohistochemistry staining was performed to assess for LOXL2 localization and myofibroblast formation. Bulk RNA-sequencing performed on treated rats. Human cardiac fibroblast grown in TGF-β with or without LOXL2 inhibitors were used for in vitro cell culture studies.

Results

Transcriptomic analysis of differentially expressed genes (DEG) in the RV of PAH patient patients with decompensated RV (HdRV) showed comparable signature to PAH rats. Further analysis of DEGs involved in ECM remodeling revealed significant upregulation of LOXL2 in HdRV and PAH rats. We find a significant upregulation of LOXL2 in the RV that appears to localize in cardiac fibroblasts and endothelial cells. Administration of PAT-1251 in PAH rats with RV failure led to improved RV hemodynamics and reversed fibrosis. The RV transcriptome showed significant reversal in DEGs involved in myofibroblast formation and ECM remodeling. We found LOXL2 to be localized in fibroblasts and endothelial cells involved in mesenchymal transition, which was dose-dependently inhibited with PAT-1251. We showed that LOXL2 activates TGF-β signaling via PI3K/AKT pathway to promote myofibroblast formation.

Conclusions

Our RV transcriptomic analysis of PAH patients and animal models revealed a novel mechanism involving LOXL2 in PAH-induced RV failure. We propose a potential therapeutic strategy where blockade of LOXL2 can rescue RV failure by attenuation of fibrosis.

This abstract is funded by: FAER, ATS