Preclinical Investigation of Mitochondrial Fission Inhibitors in Pulmonary Arterial Hypertension and Non-Small Cell Lung Cancer

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Breault, Nolan
Mitotic fission , DRP1 , Warburg effect , Cell proliferation , Drpitor1a
Background: Dynamin-related protein 1 (DRP1)-mediated mitochondrial fission is coordinated with nuclear division. This phenomenon, known as mitotic fission, is increased in hyperproliferative diseases, such as non-small cell lung cancer (NSCLC) and pulmonary arterial hypertension (PAH), due to increased DRP1 expression and activity. PAH is a progressive pulmonary vasculopathy that culminates in right ventricular failure (RVF). We identified two putative DRP1 inhibitors via in silico screening predicted to bind DRP1's guanosine triphosphatase (GTPase) domain. We hypothesize that inhibition of DRP1's GTPase activity by the novel DRP1 inhibitor, 2-(2-Phenyl-2-propanyl)-1,2-benzothiazol-3(2H)-one 1,1-dioxide (Compound 6) can suppress NSCLC and PAH phenotypes in vitro, and Drpitor1a, previously shown to reduce NSCLC hyperproliferation in vitro and ex vivo, can prevent PAH progression in vivo. Methods & Results: Only Drpitor1a was found to inhibit DRP1's GTPase activity in inorganic phosphate assays. While Compound 6 did not inhibit GTPase activity under the conditions tested, 4-hour treatment of PAH pulmonary artery smooth muscle cells (PASMC) and A549 adenocarcinoma cells with either Compound 6 or Drpitor1a inhibited mitochondrial fission as determined using an imaging-based machine learning algorithm. xCELLigence and EdU assays showed inhibition of cell proliferation in both PAH PASMC and A549 by Drpitor1a, though Compound 6 only reduced proliferation in A549. Drpitor1a also induced apoptosis in A549 as observed via annexin V assays, though Compound 6 did not. The monocrotaline (MCT) model of PAH (MCT-PAH) was created in female Sprague-Dawley rats by a single subcutaneous injection of MCT (60 mg/kg). 1 mg/kg Drpitor1a treatment in MCT-PAH over 12 days regressed vascular remodeling, improved hemodynamics, and reduced RV hypertrophy as shown by quantitative staining of lung tissue and RVs, echocardiography, and right heart catheterization. Conclusion: Drpitor1a is an efficacious treatment for PAH in female rodents. Drpitor1a prevents disease progression at the level of vascular remodeling, providing hemodynamic relief that benefits the structural and functional characteristics of the RV. Compound 6, though with an undetermined mechanism of action, inhibits mitochondrial fission in both cancer and PAH and additionally prevents cell proliferation in A549. Drpitor1a has promise for human study, while Compound 6 may have merit in NSCLC animal studies.
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