Corosolic acid ameliorates vascular remodeling in pulmonary arterial hypertension via the downregulation of STAT3 signaling

Pulmonary arterial hypertension (PAH) is a progressive and fatal disease that is characterized by vascular remodeling of the pulmonary artery. PAH remodeling is primarily caused by the excessive proliferation of pulmonary arterial smooth muscle cells (PASMCs). Therefore, an inhibitory mechanism is expected as a target for the treatment of PAH. Corosolic acid (CRA) is a pentacyclic triterpenoid extracted from the leaves of Banaba (Lagerstroemia speciosa) that exerts anti-diabetic, anti-inflammatory, and anti-tumor effects. In the present study, the effects of CRA on PAH remodeling were examined using PASMCs from idiopathic pulmonary arterial hypertension (IPAH) patients and monocrotaline (MCT)-induced pulmonary hypertensive (PH) rats. CRA inhibited the excessive proliferation of IPAH-PASMCs in a concentration-dependent manner (IC50 = 14.1 μM). It also reduced the migration of IPAH-PASMCs. The CRA treatment downregulated the expression of signal transducer and activator of transcription 3 (STAT3) in IPAH-PASMCs. In MCT-PH rats, the administration of CRA (1 mg/kg/day) attenuated increases in right ventricular systolic pressure, pulmonary vascular remodeling, and right ventricular hypertrophy. CRA also decreased the expression of STAT3 in pulmonary arterial smooth muscles from MCT-PH rats. In conclusion, the anti-proliferative and anti-migratory effects of CRA in PASMCs ameliorated PAH remodeling by downregulating STAT3 signaling pathways

Activity of Ca -activated Cl channels contributes to regulating receptor- and store-operated Ca entry in human pulmonary artery smooth muscle cells

Intracellular Ca(2+) plays a fundamental role in regulating cell functions in pulmonary arterial smooth muscle cells (PASMCs). A rise in cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) triggers pulmonary vasoconstriction and stimulates PASMC proliferation. [Ca(2+)](cyt) is increased mainly by Ca(2+) release from intracellular stores and Ca(2+) influx through plasmalemmal Ca(2+)-permeable channels. Given the high concentration of intracellular Cl(-) in PASMCs, Ca(2+)-activated Cl(-)(Cl(Ca)) channels play an important role in regulating membrane potential and cell excitability of PASMCs. In this study, we examined whether activity of Cl(Ca) channels was involved in regulating [Ca(2+)](cyt) in human PASMCs via regulating receptor- (ROCE) and store- (SOCE) operated Ca(2+) entry. The data demonstrated that an angiotensin II (100 nM)-mediated increase in [Ca(2+)](cyt) via ROCE was markedly attenuated by the Cl(Ca) channel inhibitors, niflumic acid (100 muM), flufenamic acid (100 muM), and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (100 muM). The inhibition of Cl(Ca) channels by niflumic acid and flufenamic acid significantly reduced both transient and plateau phases of SOCE that was induced by passive depletion of Ca(2+) from the sarcoplasmic reticulum by 10 muM cyclopiazonic acid. In addition, ROCE and SOCE were abolished by SKF-96365 (50 muM) and 2-aminoethyl diphenylborinate (100 muM), and were slightly decreased in the presence of diltiazem (10 muM). The electrophysiological and immunocytochemical data indicate that Cl(Ca) currents were present and TMEM16A was functionally expressed in human PASMCs. The results from this study suggest that the function of Cl(Ca) channels, potentially formed by TMEM16A proteins, contributes to regulating [Ca(2+)](cyt) by affecting ROCE and SOCE in human PASMCs

Heterodimerization of two pore domain K+ channel TASK1 and TALK2 in living heterologous expression systems.

Two-pore-domain K+ (K2P) channels sense a wide variety of stimuli such as mechanical stress, inhalational anesthetics, and changes in extracellular pH or temperature. The K2P channel activity forms a background K+ current and, thereby, contributes to resting membrane potentials. Six subfamilies including fifteen subtypes of K2P channels have been identified. Each K2P channel molecule with two pores consists of a homodimer of each subtype. In addition, a few heterodimers mainly within the same subfamilies have been found recently. In the present study, the possibility of heterodimerization between TASK1 (TWIK-Related Acid-Sensitive K+ channel) and TALK2 (TWIK-Related Alkaline pH-Activated K+ channel) was examined. These channels belong to separate subfamilies and show extremely different channel properties. Surprisingly, single molecular imaging analyses in this study using a total internal reflection microscope suggested the heterodimerization of TASK1 and TALK2 in a pancreatic cell line, QGP-1. This heterodimer was also detected using a bimolecular fluorescence complementation assay in a HEK293 heterologous expression system. Fluorescence resonance energy transfer analyses showed that the affinity between TASK1 and TALK2 appeared to be close to those of homodimers. Whole-cell patch-clamp recordings revealed that TASK1 currents in HEK293 cells were significantly attenuated by co-expression of a dominant-negative form of TALK2 in comparison with that of wild-type TALK2. The sensitivities of TASK1-TALK2 tandem constructs to extracellular pH and halothane were characterized as a unique hybrid of TASK1 and TALK2. These results suggested that heterodimerization of TASK1 and TALK2 provides cells with the ability to make multiple responses to a variety of physiological and pharmacological stimuli