04 February 2019 by Dr. Olivier Boucherat

Inhibition of CHK1 Elicits Therapeutic Effects in Pulmonary Arterial Hypertension

Background:

Pulmonary arterial hypertension (PAH) is a vascular remodeling disease characterized by persistent elevation of pulmonary arterial (PA) pressure and premature death. PA smooth muscle cells (PASMCs) from PAH patients present a cancer-like hyperproliferative and apoptosis-resistant phenotype contributing to obliteration of the vascular lumen. Although prevention of DNA damage-induced cell death appears to be an adaptive mechanism used by PAH-PASMCs to growth, the molecular players engaged to orchestrate the repair of DNA lesion remain largely unknown. Cancer cells presenting elevated levels of DNA damage/replication stress (RS) rely on activation of the CHK1 pathway to restrain the accumulation of deleterious levels of DNA damage.

Objective:

We hypothesize that PAH-PASMCs have developed an orchestrated response mediated by CHK1 to overcome RS/DNA damage, allowing their survival and proliferation.

Methods and Results:

Using Western blot (WB), we showed that, compared to control cells, isolated PAH-PASMCs display elevated levels of DNA damage/RS (pRPA32 and γH2AX, p<0.05) and exhibit constitutive activation of the ATR/CHK1 pathway. Consistently, CHK1 was overexpressed (Immunofluorescence) in distal PAs from PAH patients as well as in three animal models of PAH; the monocrotaline (MCT) rat, the Fawn-Hooded rat (FHR) and the simian immunodeficiency virus (SIV)-infected macaque models. In vitro, we demonstrated that reduced miR-424 expression (qPCR, p<0.05) accounts for CHK1 up-regulation in PAH-PASMCs. Pharmacological (MK-8776) and molecular (siCHK1) inhibition of CHK1 exacerbates the levels of RS and DNA damage. These effects were associated with diminished PAH-PASMCs proliferation (Ki67 labeling, p<0,01) and resistance to apoptosis (TUNEL labeling, p<0.5). In vivo, we provide evidence that MK-8776 significantly improves established PAH by decreasing the mean PA pressure (right heart catheterization) and PA medial wall thickness (EVG staining) in the MCT and FHR models.

Conclusion:

CHK1 promotes vascular remodeling in PAH by mitigating DNA damage and represents a new promising therapeutic target.

 

Key Contributors

Olivier BOUCHERAT, Alice BOURGEOIS, Sandra BREUILS-BONNET, Steeve PROVENCHER and Sébastien BONNET. Pulmonary Hypertension Research Group, Centre de Recherche de l’Institut Universitaire de Cardiologie et de Pneumologie de Québec, Québec, QC, Canada.


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