Revisiting the Large-Conductance Calcium-Activated Potassium (BKCa) Channels in the Pulmonary Circulation

Tailored CD4+ lymphocytes expressing human CHAT protein as a novel vasodilator in attenuating RV pressure in PAH animal model

ChAT-expressing T cells represent ∼0.01 % of total circulating T lymphocytes in adult wild-type mice. However, we previously reported that systemic infusion of ChAT+ve Jurkat T cells into adult mice elicits vasodilation and instantaneous decline in the mean systolic blood pressure, suggesting potential as a biologic therapeutic to attenuate pathologic increases in pulmonary arterial pressures. We now report that ChAT gene-expressing Jurkat cells dose-dependently decrease right ventricular systolic pressures (RVSP) in hypoxic mice and that transgenic mice with ChAT KO restricted to endothelial cells (KO END/ChAT-/-) exhibit significantly elevated pulmonary arterial pressure and peripheral systemic resistance (compared to WT mice). To rigorously characterize the role of CD4 ChAT+ T cells in regulating pulmonary arterial hypertension (PAH) hemodynamics and molecular signatures, we infused CD4+ ChAT+ve cells (0.5 to 2.0 million cells/animal) into adult PAH mice and noted significant reductions in RVSP within 2-3 min post injection (∼ 50 % reduction). The tailored tail vein injection effect was sustained until the animal was euthanized (30-40 min). Mice KO END/ChAT-/-showed a significant and severe hypoxia-induced PAH phenotype compared to WT adult mice. Tail vein injection of biologically active CD4 ChAT+ve cells into either KO END/ChAT-/-mice with hypoxia-induced PAH or into adult rats with hypoxia/Sugen-induced PAH resulted in significant attenuation of RVP elevations. RNA seq data analysis of human pulmonary endothelial cells (HPAECs) incubated with CD4 ChAT+ve T cells showed significant differential regulation of pathways involved in systemic and pulmonary pressure regulation, NO synthesis/regulation, antioxidant expression, and vasodilation. In conclusion, CD4 ChAT+ve T cells have a unique, vasodilating innate immunity mechanism to augment nitric oxide release and potentially mitigate molecular and genetic pathways involved in PAH pathogenesis.

Salidroside ameliorates hypoxic pulmonary hypertension by regulating the two-pore domain potassium TASK-1 channel

BACKGROUND

Hypoxic pulmonary vasoconstriction (HPV) is a reflex constriction of vascular smooth muscle. This study aims to investigate the role of Salidroside (Sal) in pulmonary arterial dilatation and the potential mechanism of Sal regulating hypoxic pulmonary hypertension in vitro and in vivo.

METHODS

A rat model of hypoxic pulmonary hypertension (HPH) was constructed using hypoxic chamber. The effect of Sal on HPH were evaluated using vascular ring, whole cell patch-clamp, WGA staining, HE staining, and Sirius Scarlet staining assays.

RESULTS

Sal treatment alleviated the injury of acute hypoxia on pulmonary circulation in SD rats. Meanwhile, Sal treatment reduced the pulmonary vascular tone of acute hypoxia in a concentration-dependent manner, which was involved in the TWIK-related acid-sensitive potassium channel 1 (TASK-1) mediating diastolic effect. We found that Sal treatment significantly increased the TASK-1 current of pulmonary artery smooth muscle cells (PASMCs) in a concentration-dependent manner, as well as reversed the inhibitory effect of acute hypoxia on the TASK-1 current. Moreover, Sal treatment improved the TASK-1 current density, suppressed the proliferation, and enhanced the apoptosis of PASMCs in SD rats under continuous hypoxic condition. In addition, we found that the electrophysiological remodeling and pulmonary vascular remodeling of PASMCs were improved by the treatment of Sal through the regulation of TASK-1 channel.

CONCLUSIONS

Sal could alleviate HPH by restoring the function of TASK-1 channel, which may provide a novel method for the treatment of HPH.

Luteolin ameliorates hypoxic pulmonary vascular remodeling in rat via upregulating KV1.5 of pulmonary artery smooth muscle cells

BACKGROUND

Hypoxic pulmonary vascular remodeling (HPVR) is a key pathological feature of hypoxic pulmonary hypertension (HPH). Oxygen-sensitive potassium (K+) channels in pulmonary artery smooth muscle cells (PASMCs) play a crucial role in HPVR. Luteolin (Lut) is a plant-derived flavonoid compound with variety of pharmacological actions. Our previous study found Lut alleviated HPVR in HPH rat.

PURPOSE

To elucidate the mechanism by which Lut mitigated HPVR, focusing on oxygen-sensitive voltage-dependent potassium channel 1.5 (Kv1.5).

METHODS

HPH rat model was established using hypobaric chamber to simulate 5000 m altitude. Isolated perfused/ventilated rat lung, isolated pulmonary arteriole ring was utilized to investigate the impact of Lut on K+ channels activity. Kv1.5 level in lung tissue and pulmonary arteriole of HPH rat was assessed. CyclinD1, CDK4, PCNA, Bax, Bcl-2, cleaved caspase-3 levels in lung tissue of HPH rat were tested. The effect of Lut on Kv1.5, cytoplasmic free calcium concentration ([Ca2+]cyt), CyclinD1, CDK4, PCNA, Bax/Bcl-2 was examined in PASMCs under hypoxia, with DPO-1 as a Kv1.5 specific inhibitor. The binding affinity between Lut and Kv1.5 in PASMCs was detected by drug affinity responsive target stability (DARTS). The overexpression of KCNA5 gene (encoding Kv1.5) in HEK293T cells was utilized to confirm the interaction between Lut and Kv1.5. Furthermore, the impact of Lut on mitochondrial structure, SOD, GSH, GSH-Px, MDA and HIF-1α levels were evaluated in lung tissue of HPH rat and PASMCs under hypoxia.

RESULTS

Lut dilated pulmonary artery by directly activating Kv and Ca2+-activated K+ channels (KCa) in smooth muscle. Kv1.5 level in lung tissue and pulmonary arteriole of HPH rat was upregulated by Lut. Lut downregulated CyclinD1, CDK4, PCNA while upregulating Bax/Bcl-2/caspase-3 axis in lung tissue of HPH rat. Lut decreased [Ca2+]cyt, reduced CDK4, CyclinD1, PCNA, increased Bax/Bcl-2 ratio, in PASMCs under hypoxia, by upregulating Kv1.5. The binding affinity and the interaction between Lut and Kv1.5 was verified in PASMCs and in HEK293T cells. Lut also decreased [Ca2+]cyt and inhibited proliferation via targeting Kv1.5 of HEK293T cells under hypoxia. Furthermore, Lut protected mitochondrial structure, increased SOD, GSH, GSH-Px, decreased MDA, in lung tissue of HPH rat. Lut downregulated HIF-1α level in both lung tissue of HPH rat and PASMCs under hypoxia.

CONCLUSION

Lut alleviated HPVR by promoting vasodilation of pulmonary artery, reducing cellular proliferation, and inducing apoptosis through upregulating of Kv1.5 in PASMCs.

Exploring the Impact of BKCa Channel Function in Cellular Membranes on Cardiac Electrical Activity

This review paper delves into the current body of evidence, offering a thorough analysis of the impact of large-conductance Ca2+-activated K+ (BKCa or BK) channels on the electrical dynamics of the heart. Alterations in the activity of BKCa channels, responsible for the generation of the overall magnitude of Ca2+-activated K+ current at the whole-cell level, occur through allosteric mechanisms. The collaborative interplay between membrane depolarization and heightened intracellular Ca2+ ion concentrations collectively contribute to the activation of BKCa channels. Although fully developed mammalian cardiac cells do not exhibit functional expression of these ion channels, evidence suggests their presence in cardiac fibroblasts that surround and potentially establish close connections with neighboring cardiac cells. When cardiac cells form close associations with fibroblasts, the high single-ion conductance of these channels, approximately ranging from 150 to 250 pS, can result in the random depolarization of the adjacent cardiac cell membranes. While cardiac fibroblasts are typically electrically non-excitable, their prevalence within heart tissue increases, particularly in the context of aging myocardial infarction or atrial fibrillation. This augmented presence of BKCa channels' conductance holds the potential to amplify the excitability of cardiac cell membranes through effective electrical coupling between fibroblasts and cardiomyocytes. In this scenario, this heightened excitability may contribute to the onset of cardiac arrhythmias. Moreover, it is worth noting that the substances influencing the activity of these BKCa channels might influence cardiac electrical activity as well. Taken together, the BKCa channel activity residing in cardiac fibroblasts may contribute to cardiac electrical function occurring in vivo.

Potassium channels, tumorigenesis and targeted drugs

Potassium channels play an important role in human physiological function. Recently, various molecular mechanisms have implicated abnormal functioning of potassium channels in the proliferation, migration, invasion, apoptosis, and cancer stem cell phenotype formation. Potassium channels also mediate the association of tumor cells with the tumor microenvironment. Meanwhile, potassium channels are important targets for cancer chemotherapy. A variety of drugs exert anti-cancer effects by modulating potassium channels in tumor cells. Therefore, there is a need to understand how potassium channels participate in tumor development and progression, which could reveal new, novel targets for cancer diagnosis and treatment. This review summarizes the roles of voltage-gated potassium channels, calcium-activated potassium channels, inwardly rectifying potassium channels, and two-pore domain potassium channels in tumorigenesis and the underlying mechanism of potassium channel-targeted drugs. Therefore, the study lays the foundation for rational and effective drug design and individualized clinical therapeutics.

Effects of bisphenol A on human umbilical arteries

Bisphenol A (BPA) is an endocrine-disrupting chemical widely used in the plastics industry, including food container, toys, and medical equipment. We analyzed the effect of BPA in human umbilical artery contractility and expression of some proteins modulating this function, such as ionic channels and proteins involved in the cGMP pathway. Using standard organ bath technique, rings of human umbilical arteries without endothelium were contracted by 5-HT (1 μM) and histamine (10 μM) and the effect of different concentrations of BPA (1 nM-100 μM) was analyzed. The results showed that BPA is a vasodilator of these arteries in a concentration-dependent way. Besides, qPCR studies on human umbilical smooth muscle cells (HUSMC) allowed to analyze the effects of BPA on gene expression. Thus, 12-h exposition to BPA induced reduction of expression of L-type calcium channels (LTCC), alpha subunit of BK_Ca channels, and Kvβ1 and Kvβ3 from Kv channels. BPA also decreased the expression of soluble guanylate cyclase (sGC) and natriuretic peptide receptor type A (NPRA), meanwhile increasing that of PKG, proteins involved in vasodilation of human umbilical arteries (HUA) by cGMP. Further studies will be necessary to increase knowledge about the implications of these changes induced by BPA exposure.

Role of Ion Channels in the Development of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is an uncommon, progressive, and fatal disease [...].

Effects of Ion-Transporting Proteins on the Digestive System Under Hypoxia

Hypoxia refers to a state of oxygen limitation, which mainly mediates pathological processes in the human body and participates in the regulation of normal physiological processes. In the hypoxic environment, the main regulator of human body homeostasis is the hypoxia-inducible factor family (HIF). HIF can regulate the expression of many hypoxia-induced genes and then participate in various physiological and pathological processes of the human body. Ion-transporting proteins are extremely important types of proteins. Ion-transporting proteins are distributed on cell membranes or organelles and strictly control the inflow or outflow of ions in cells or organelles. Changes in ions in cells are often closely related to extensive physiological and pathological processes in the human body. Numerous studies have confirmed that hypoxia and its regulatory factors can regulate the transcription and expression of ion-transporting protein-related genes. Under hypoxic stress, the regulation and interaction of ion-transporting proteins by hypoxia often leads to diseases of various human systems and even tumors. Using ion-transporting proteins and hypoxia as targets to explore the mechanism of digestive system diseases and targeted therapy is expected to become a new breakthrough point.

Role of Ion Channel Remodeling in Endothelial Dysfunction Induced by Pulmonary Arterial Hypertension

Endothelial dysfunction is a key player in advancing vascular pathology in pulmonary arterial hypertension (PAH), a disease essentially characterized by intense remodeling of the pulmonary vasculature, vasoconstriction, endothelial dysfunction, inflammation, oxidative stress, and thrombosis in situ. These vascular features culminate in an increase in pulmonary vascular resistance, subsequent right heart failure, and premature death. Over the past years, there has been a great development in our understanding of pulmonary endothelial biology related to the genetic and molecular mechanisms that modulate the endothelial response to direct or indirect injury and how their dysregulation can promote PAH pathogenesis. Ion channels are key regulators of vasoconstriction and proliferative/apoptotic phenotypes; however, they are poorly studied at the endothelial level. The current review will describe and categorize different expression, functions, regulation, and remodeling of endothelial ion channels (K+, Ca2+, Na+, and Cl− channels) in PAH. We will focus on the potential pathogenic role of ion channel deregulation in the onset and progression of endothelial dysfunction during the development of PAH and its potential therapeutic role.