Colchicine Depolymerizes Microtubules, Increases Junctophilin‐2, and Improves Right Ventricular Function in Experimental Pulmonary Arterial Hypertension

Abstract

BackgroundPulmonary arterial hypertension (PAH) is a lethal disease characterized by obstructive pulmonary vascular remodeling and right ventricular (RV) dysfunction. Although RV function predicts outcomes in PAH, mechanisms of RV dysfunction are poorly understood, and RV‐targeted therapies are lacking. We hypothesized that in PAH, abnormal microtubular structure in RV cardiomyocytes impairs RV function by reducing junctophilin‐2 (JPH2) expression, resulting in t‐tubule derangements. Conversely, we assessed whether colchicine, a microtubule‐depolymerizing agent, could increase JPH2 expression and enhance RV function in monocrotaline‐induced PAH.Methods and ResultsImmunoblots, confocal microscopy, echocardiography, cardiac catheterization, and treadmill testing were used to examine colchicine's (0.5 mg/kg 3 times/week) effects on pulmonary hemodynamics, RV function, and functional capacity. Rats were treated with saline (n=28) or colchicine (n=24) for 3 weeks, beginning 1 week after monocrotaline (60 mg/kg, subcutaneous). In the monocrotaline RV, but not the left ventricle, microtubule density is increased, and JPH2 expression is reduced, with loss of t‐tubule localization and t‐tubule disarray. Colchicine reduces microtubule density, increases JPH2 expression, and improves t‐tubule morphology in RV cardiomyocytes. Colchicine therapy diminishes RV hypertrophy, improves RV function, and enhances RV–pulmonary artery coupling. Colchicine reduces small pulmonary arteriolar thickness and improves pulmonary hemodynamics. Finally, colchicine increases exercise capacity.ConclusionsMonocrotaline‐induced PAH causes RV‐specific derangement of microtubules marked by reduction in JPH2 and t‐tubule disarray. Colchicine reduces microtubule density, increases JPH2 expression, and improves both t‐tubule architecture and RV function. Colchicine also reduces adverse pulmonary vascular remodeling. These results provide biological plausibility for a clinical trial to repurpose colchicine as a RV‐directed therapy for PAH.

Excess Protein O-GlcNAcylation Links Metabolic Derangements to Right Ventricular Dysfunction in Pulmonary Arterial Hypertension

“…While we previously documented colchicine combats pathological microtubule remodeling and augments right ventricular function in MCT rats [ 31 ], we did not see significant improvements in right ventricular function in PAB rats treated with colchicine ( Figure 2 ). There are potential explanations for this finding.…”

“…There are potential explanations for this finding. First, the relative increase in tubulin, the individual subunits of microtubules, in PAB ( Supplemental Figure S6 ) are less than what we observed in MCT rats [ 31 ], and there may be a threshold of microtubule remodeling needed for a pathological response. Second, it is possible that chronic colchicine treatment and microtubule depolymerization could have adverse effects on cardiac function as a previous manuscript showed high dose colchicine causes cardiac conduction abnormalities, however at much higher doses than we used [ 32 ].…”

“…Immunoblots were performed on RV and LV specimens as described [ 31 ] using the Odyssey Infrared Imaging system (Li-Cor, Lincoln, NE, USA). Post transfer SDS-PAGE gels were stained with Coomassie brilliant blue and imaged at the 700-nm wavelength on the Odyssey Imaging system as the loading control, with the band corresponding to the myosin heavy chain used as the reference [ 31 , 38 ].…”

Microtubules Provide a Viscoelastic Resistance to Myocyte Motion

“…In contrast, measurements of steady-state elasticity by myocyte stretch have shown a small (10) or insignificant (7) role of the MT network in axial stiffness. Multiple groups have observed increased contractility with MT destabilization (11)(12)(13), which is most often attributed to decreased mechanical resistance, but this finding has not been supported by all (14).…”

Nicotinic ACh receptor α7 inhibits PDGF‐induced migration of vascular smooth muscle cells by activating mitochondrial deacetylase sirtuin 3

“…The cells were scraped using sterilized 10 μL pipette tips and washed with 0.1% serum media and stimulated with PDGF‐BB (20 ng·mL −1 ) (Du et al, ). For the signalling pathway study, the following chemical inhibitors were used: S3I‐201 (100 μM) (Li et al, ), U0126 (1 μM) (Pathria et al, ), LY294002 (30 μM) (Liao et al, ), staurosporine (50 nM) (Prins et al, ) and 3‐TYP (20 nM) (Shumin et al, ). All these inhibitors were purchased from Selleck Chemicals (Houston, TX, USA).…”