KCNK3 channel A new therapeutic target in Pulmonary Arterial Hypertension – KAPAH

Pulmonary arterial hypertension (PAH) is a devastating disease, consequence of a progressive narrowing of the distal pulmonary arteries, resulting in high pulmonary vascular resistance, right ventricular hypertrophy (RVH) and ultimately right heart failure. The pathobiology of PAH is multifactorial and involves pulmonary arterial (PA) smooth muscle (PASMC), endothelial cells (PAEC) and RV cardiomyocytes dysfunctions, characterized by abnormal proliferation, inflammation, vasoconstriction and alteration of RV contractility. Despite current available treatments which target the nitric oxide, endothelin and prostacyclin pathways, mortality after 3 years remains as high as 30-40% and lung transplantation remains the destination therapy for eligible patients.
8 mutations in KCNK3 gene have been identified in PAH patients. KCNK3 encode for an outward rectifier K+ channel (or called TASK1). Each identified mutation leads to a loss of function and I recently showed that KCNK3 loss of function/expression are hallmarks of human and experimental PAH, at pulmonary vascular and cardiac levels. These recent findings highlighted that KCNK3 could be an attractive therapeutic target for all form of PAH and not only KCNK3 mutation carriers.
However, the pathophysiological role of KCNK3 dysfunctions in PAH and the molecular mechanisms responsible for KCNK3 dysfunction in PAH remains to be elucidated. Moreover additional experiments are needed to assess the efficiency of KCNK3 gene therapy or pharmacological targeting of KCNK3 signaling pathway in PAH.
It is important to emphasize that Kcnk3 deficient rats are crucial to decipher the cardio-pulmonary consequences of genetic Kcnk3 inactivation since mouse is not a suitable model to study the role played by KCNK3 in PH. Indeed, KCNK3 is not functional in mouse PASMC. That is why we generated Kcnk3 deficient rats using CRISPR-Cas9 technology inducing small deletion in Kcnk3 gene which led to a loss of initiation codon and a loss of KCNK3 protein.
This project has four main objectives, which address fundamental, experimental and preclinical questions related to KCNK3 in the pathobiology of PAH:
1: Deciphering the role of KCNK3 channel in the regulation of proliferation/apoptosis in PAH
2: Deciphering the mechanisms modulating pulmonary KCNK3 expression/function in PAH
3: Confirming the key role of KCNK3 in PAH using unique Kcnk3 deficient rats
4: Identifying an Ion Channel Therapy for PAH
Using relevant technical approaches (molecular biology, organ bath studies, and electrophysiology) and PASMC and PAEC isolated from control and PAH patients, we will understand the role of KCNK3 in PAH pathogenesis. Kcnk3-deficient rats allow us to decipher the consequence of KCNK3 dysfunction at the cardio-pulmonary level. Finally we expect that applied genetic and/or pharmacological strategies targeting KCNK3 function/expression will alleviate PAH.
Preliminary results obtained by patch–clamp technique, confirm that KCNK3 function is abolished in freshly isolated PASMC from Kcnk3 deficient rats and that consequently PASMC are significantly depolarized. At 3 month old, we show that Kcnk3 mutation induced distal neomuscularization, elevation of right ventricular systolic pressures, upregulation of MAP kinase pathways. These preliminary results validate a new in vivo tool to identify KCNK3 downstream signaling molecules involved in pulmonary vascular and RV remodeling occurring in PAH.
Because the proposal is supported by a strong rationale and a large amount of preliminary data, and performed in the Pulmonary Hypertension National Referal Center of PAH to which our INSERM unit belongs there is no doubt about its feasibility.
The groundbreaking nature of the project relies on the possibility to develop an Ion Channel Therapy for a devastating cardiopulmonary disorders thanks to the unique opportunity to study Kcnk3 deficient rats and pulmonary vascular cells from patients with severe PAH.