Use of Kv11.1 channel inhibitors for treatment of pulmonary hypertension

#Kv11.1 potassium-selective channels, also known as EAG-related gene (ERG) channels, or hERG1 channels, are best known for their function in the heart where they are responsible for the repolarization of the cardiac action potential1-4. Inhibition of Kv11.1 currents due to genetically occurring mutations or as a side effect of a prescription medication lengthens the QT interval in electrocardiogram, causing long-QT syndrome (LQTS), a potentially lethal cardiac arrhythmia5-8. Kv11.1 channels also play a role in cancer, where inhibition of Kv11.1 channel expression and/or Kv11.1 currents decreases proliferation of cancer cells9, 10. In addition to cardiac tissue, Kv11.1 channels are also expressed in the brain11, 12, retina13, gallbladder14, stomach15 and intestines16-18. However, surprisingly little is known about the Kv11.1 channel expression and function in normal lung tissue.

#Potassium channels are essential for proper lung function, and defects in ion channels are linked to various respiratory diseases19. Potassium channels are especially intimately involved in vascular remodeling in pulmonary hypertension, and associated respiratory diseases such as pulmonary arterial hypertension (PAH) and chronic obstructive pulmonary disease (COPD)20-22.

#PAH is a lethal disease associated with narrowing arteries in the lung23, 24. The constriction of the arteries decreases blood flow through the lungs and leads to decreased oxygen levels in the blood. Although with current treatments the symptoms of PAH can be relieved, there is no known cure23, 24. Similar to PAH, COPD-associated pulmonary hypertension also results in the constriction of arteries in the lung.

#FIGS. 1A-1F: Histological examinations of lung structure of healthy humans of different age. Normal human lung hematoxylin and eosin (H&E) staining for a 41-year-old (FIG. 1A) and 65-year-old (FIG. 1B) individuals. Shown are sections of lung composed of terminal bronchioles (b) and thin-walled alveoli (a). Also shown is a thin layer of alveoli connective tissue and a multitude of pulmonary vessels (pv, arrows). Images display Kv11.1-positive cells in bronchial smooth muscle layer (asterisk) and in the media of pulmonary arteries >100 μm in diameter (asterisk) in the 41-year-old (FIG. 1C) and 65-year-old (FIG. 1D) individuals. FIGS. 1E and 1F show Kv11.1-negative cells in small pulmonary arterioles (<100 μm diameter) (arrows). FIGS. 1A and 1B, bar=1 mm. FIGS. 1C-1F, bar=200 μm.

#FIGS. 2A-2B: Histological examinations of lung structure of a 65-year-old human individual with COPD. FIG. 2A shows H&E staining of lung tissue; bar=1 mm. FIG. 2B shows positive Kv11.1 antibody staining of media of large pulmonary arteries (>100 μm diameter, asterisk), and of small pulmonary arteries (<100 μm diameter, arrows); bar=200 μm.

#FIGS. 3A-3C: Histological examinations of lung structure of control Fischer rats. Normal lung parenchyma with a bronchiole (b), alveoli (a), alveolar walls and different diameter pulmonary vessels (pv). FIG. 3A shows H&E staining of lung tissue showing a normal structure of a bronchiole (b), thin interstitial alveolar wall (magnification ×200), and normal arterial wall thickness (arrow, magnification ×400) in control rats. FIG. 3B shows anti-smooth muscle actin (anti-SMA) antibody staining in the smooth muscle cell (SMC) layer of a bronchiole (asterisk) and in the media of pulmonary arteries (asterisk, >100 μm in diameter). Image in ×400 magnification shows no expression of anti-SMA in small pulmonary arteries (<100 μm in diameter). FIG. 3C shows Kv11.1 antibody staining in bronchial SMC layer (asterisk) and in the media of pulmonary arteries (asterisk, >100 μm in diameter). Image in ×400 magnification illustrates Kv11.1-negative cells of small pulmonary arterioles (arrows). FIGS. 3A-3C, left-hand images, bar=200 μm; right-hand images, bar=100 μm.

#Kv11.1 potassium selective channels are essential for the heart repolarization. Prescription medication that blocks Kv11.1 channels lengthens the ventricular action potential and causes cardiac arrhythmias. Surprisingly, little is known about the Kv11.1 channel expression and function in the lung tissue. As disclosed herein, Kv11.1 channel expression in healthy and pulmonary hypertension-affected human and rat lungs was investigated, and the effect of Kv11.1 channel-specific blocker dofetilide, also known as antiarrhythmic drug TIKOSYN®, on vascular remodeling in pulmonary arterial hypertension (PAH) was tested.

#Kv11.1 channel expression in human postmortem tissue from healthy individuals and patients with chronic obstructive pulmonary disease (COPD)—associated pulmonary hypertension, and in rat smooth muscle cells (SMCs) from healthy and PAH-induced animals was detected with Kv11.1-specific antibody. While in healthy human and rat lung tissues Kv11.1 channels were expressed in the SMCs of large pulmonary arteries, in humans with COPD-associated pulmonary hypertension and rats with PAH, Kv11.1 channels were expressed not only in the large pulmonary arteries but also in small pulmonary arteries. The increase in the expression of Kv11.1 channels closely followed the time course of the development of pulmonary vascular remodeling in PAH-induced rats. Treatment of PAH-induced rats with Kv11.1 channel blocker dofetilide inhibited PAH-associated pulmonary vascular remodeling while having no effect on the pulmonary vasculature of control rats.

#The present inventors believe they are the first to report abundant expression of Kv11.1 channels in the large pulmonary arteries of healthy human and rat lung tissues. Kv11.1 channel expression increased in human lungs affected by COPD and in lungs of PAH-induced rats, indicating the importance of Kv11.1 channels for lung function and their potential as new drug targets in the treatment of pulmonary hypertension. Kv11.1 channel blocker dofetilide reversed the vascular remodeling in PAH-induced rats. The protective effect of dofetilide in PAH-induced rats raises the possibility of repurposing this antiarrhythmic drug for the treatment of patients with pulmonary hypertension.