Role of KCa3.1 Channels in Macrophage Polarization and Its Relevance in Atherosclerotic Plaque Instability

Intermediate conductance calcium-activated potassium channel (KCa3.1) in cancer: Emerging roles and therapeutic potentials

The KCa3.1 channel (also known as the KCNN4, IK1, or SK4 channel) is an intermediate-conductance calcium-activated potassium channel that regulates the membrane potential and maintains calcium homeostasis. Recently, KCa3.1 channels have attracted increasing attention because of their diverse roles in various types of cancers. In cancer cells, KCa3.1 channels regulate key processes, including cell proliferation, cell cycle, migration, invasion, tumor microenvironments, and therapy resistance. In addition, abnormal KCa3.1 expression in cancers is utilized to distinguish between tumor and normal tissues, classify cancer stages, and predict patient survival outcomes. This review comprehensively examines the current understanding of the contribution of KCa3.1 channels to tumor formation, metastasis, and its mechanisms. We evaluated the potential of KCa3.1 as a biomarker for cancer diagnosis and prognosis. Finally, we discuss the advances and challenges of applying KCa3.1 modulators in cancer treatment and propose approaches to overcome these obstacles. In summary, this review highlights the importance of this ion channel as a potent therapeutic target and prognostic biomarker of cancer.

Cardiac macrophages in maintaining heart homeostasis and regulating ventricular remodeling of heart diseases

Macrophages are most important immune cell population in the heart. Cardiac macrophages have broad-spectrum and heterogeneity, with two extreme polarization phenotypes: M1 pro-inflammatory macrophages (CCR2-ly6Chi) and M2 anti-inflammatory macrophages (CCR2-ly6Clo). Cardiac macrophages can reshape their polarization states or phenotypes to adapt to their surrounding microenvironment by altering metabolic reprogramming. The phenotypes and polarization states of cardiac macrophages can be defined by specific signature markers on the cell surface, including tumor necrosis factor α, interleukin (IL)-1β, inducible nitric oxide synthase (iNOS), C-C chemokine receptor type (CCR)2, IL-4 and arginase (Arg)1, among them, CCR2+/- is one of most important markers which is used to distinguish between resident and non-resident cardiac macrophage as well as macrophage polarization states. Dedicated balance between M1 and M2 cardiac macrophages are crucial for maintaining heart development and cardiac functional and electric homeostasis, and imbalance between macrophage phenotypes may result in heart ventricular remodeling and various heart diseases. The therapy aiming at specific target on macrophage phenotype is a promising strategy for treatment of heart diseases. In this article, we comprehensively review cardiac macrophage phenotype, metabolic reprogramming, and their role in maintaining heart health and mediating ventricular remodeling and potential therapeutic strategy in heart diseases.

Deciphering the emerging landscape of HOX genes in cardiovascular biology, atherosclerosis and beyond (Review)

Atherosclerosis, a dominant driving force underlying multiple cardiovascular events, is an intertwined and chronic inflammatory disease characterized by lipid deposition in the arterial wall, which leads to diverse cardiovascular problems. Despite unprecedented advances in understanding the pathogenesis of atherosclerosis and the substantial decline in cardiovascular mortality, atherosclerotic cardiovascular disease remains a global public health issue. Understanding the molecular landscape of atherosclerosis is imperative in the field of molecular cardiology. Recently, compelling evidence has shown that an important family of homeobox (HOX) genes endows causality in orchestrating the interplay between various cardiovascular biological processes and atherosclerosis. Despite seemingly scratching the surface, such insight into the realization of biology promises to yield extraordinary breakthroughs in ameliorating atherosclerosis. Primarily recapitulated herein are the contributions of HOX in atherosclerosis, including diverse cardiovascular biology, knowledge gaps, remaining challenges and future directions. A snapshot of other cardiovascular biological processes was also provided, including cardiac/vascular development, cardiomyocyte pyroptosis/apoptosis, cardiac fibroblast proliferation and cardiac hypertrophy, which are responsible for cardiovascular disorders. Further in‑depth investigation of HOX promises to provide a potential yet challenging landscape, albeit largely undetermined to date, for partially pinpointing the molecular mechanisms of atherosclerosis. A plethora of new targeted therapies may ultimately emerge against atherosclerosis, which is rapidly underway. However, translational undertakings are crucially important but increasingly challenging and remain an ongoing and monumental conundrum in the field.

The role of macrophage ion channels in the progression of atherosclerosis

Atherosclerosis is a complex inflammatory disease that affects the arteries and can lead to severe complications such as heart attack and stroke. Macrophages, a type of immune cell, play a crucial role in atherosclerosis initiation and progression. Emerging studies revealed that ion channels regulate macrophage activation, polarization, phagocytosis, and cytokine secretion. Moreover, macrophage ion channel dysfunction is implicated in macrophage-derived foam cell formation and atherogenesis. In this context, exploring the regulatory role of ion channels in macrophage function and their impacts on the progression of atherosclerosis emerges as a promising avenue for research. Studies in the field will provide insights into novel therapeutic targets for the treatment of atherosclerosis.

Endothelial KCa channels: Novel targets to reduce atherosclerosis-driven vascular dysfunction

Elevated levels of cholesterol in the blood can induce endothelial dysfunction, a condition characterized by impaired nitric oxide production and decreased vasodilatory capacity. Endothelial dysfunction can promote vascular disease, such as atherosclerosis, where macrophages accumulate in the vascular intima and fatty plaques form that impair normal blood flow in conduit arteries. Current pharmacological strategies to treat atherosclerosis mostly focus on lipid lowering to prevent high levels of plasma cholesterol that induce endothelial dysfunction and atherosclerosis. While this approach is effective for most patients with atherosclerosis, for some, lipid lowering is not enough to reduce their cardiovascular risk factors associated with atherosclerosis (e.g., hypertension, cardiac dysfunction, stroke, etc.). For such patients, additional strategies targeted at reducing endothelial dysfunction may be beneficial. One novel strategy to restore endothelial function and mitigate atherosclerosis risk is to enhance the activity of Ca2+-activated K+ (KCa) channels in the endothelium with positive gating modulator drugs. Here, we review the mechanism of action of these small molecules and discuss their ability to improve endothelial function. We then explore how this strategy could mitigate endothelial dysfunction in the context of atherosclerosis by examining how KCa modulators can improve cardiovascular function in other settings, such as aging and type 2 diabetes. Finally, we consider questions that will need to be addressed to determine whether KCa channel activation could be used as a long-term add-on to lipid lowering to augment atherosclerosis treatment, particularly in patients where lipid-lowering is not adequate to improve their cardiovascular health.

Pancreatic KCa3.1 channels in health and disease

Ion channels play an important role for regulation of the exocrine and the endocrine pancreas. This review focuses on the Ca²⁺-regulated K⁺ channel K_Ca3.1, encoded by the KCNN4 gene, which is present in both parts of the pancreas. In the islets of Langerhans, K_Ca3.1 channels are involved in the regulation of membrane potential oscillations characterizing nutrient-stimulated islet activity. Channel upregulation is induced by gluco- or lipotoxic conditions and might contribute to micro-inflammation and impaired insulin release in type 2 diabetes mellitus as well as to diabetes-associated renal and vascular complications. In the exocrine pancreas K_Ca3.1 channels are expressed in acinar and ductal cells. They are thought to play a role for anion secretion during digestion but their physiological role has not been fully elucidated yet. Pancreatic carcinoma, especially pancreatic ductal adenocarcinoma (PDAC), is associated with drastic overexpression of K_Ca3.1. For pharmacological targeting of K_Ca3.1 channels, we are discussing the possible benefits K_Ca3.1 channel inhibitors might provide in the context of diabetes mellitus and pancreatic cancer, respectively. We are also giving a perspective for the use of a fluorescently labeled derivative of the K_Ca3.1 blocker senicapoc as a tool to monitor channel distribution in pancreatic tissue. In summary, modulating K_Ca3.1 channel activity is a useful strategy for exo-and endocrine pancreatic disease but further studies are needed to evaluate its clinical suitability.

Imaging of KCa 3.1 Channels in Tumor Cells with PET and Small-Molecule Fluorescent Probes

The Ca²⁺ activated K⁺ channel K_Ca 3.1 is overexpressed in several human tumor cell lines, e. g. clear cell renal carcinoma, prostate cancer, non-small cell lung cancer. Highly aggressive cancer cells use this ion channel for key processes of the metastatic cascade such as migration, extravasation and invasion. Therefore, small molecules, which are able to image this K_Ca 3.1 channel in vitro and in vivo represent valuable diagnostic and prognostic tool compounds. The [¹⁸ F]fluoroethyltriazolyl substituted senicapoc was used as positron emission tomography (PET) tracer and showed promising properties for imaging of K_Ca 3.1 channels in lung adenocarcinoma cells in mice. The novel senicapoc BODIPY conjugates with two F-atoms (9 a) and with a F-atom and a methoxy moiety (9 b) at the B-atom led to the characteristic punctate staining pattern resulting from labeling of single K_Ca 3.1 channels in A549-3R cells. This punctate pattern was completely removed by preincubation with an excess of senicapoc confirming the high specificity of K_Ca 3.1 labeling. Due to the methoxy moiety at the B-atom and the additional oxyethylene unit in the spacer, 9 b exhibits higher polarity, which improves solubility and handling without reduction of fluorescence quantum yield. Docking studies using a cryo-electron microscopy (EM) structure of the K_Ca 3.1 channel confirmed the interaction of 9 a and 9 b with a binding pocket in the channel pore.

Functional Potassium Channels in Macrophages

Macrophages are the predominant component of innate immunity, which is an important protective barrier of our body. Macrophages are present in all organs and tissues of the body, their main functions include immune surveillance, bacterial killing, tissue remodeling and repair, and clearance of cell debris. In addition, macrophages can present antigens to T cells and facilitate inflammatory response by releasing cytokines. Macrophages are of high concern due to their crucial roles in multiple physiological processes. In recent years, new advances are emerging after great efforts have been made to explore the mechanisms of macrophage activation. Ion channel is a class of multimeric transmembrane protein that allows specific ions to go through cell membrane. The flow of ions through ion channel between inside and outside of cell membrane is required for maintaining cell morphology and intracellular signal transduction. Expressions of various ion channels in macrophages have been detected. The roles of ion channels in macrophage activation are gradually caught attention. K⁺ channels are the most studied channels in immune system. However, very few of published papers reviewed the studies of K⁺ channels on macrophages. Here, we will review the four types of K⁺ channels that are expressed in macrophages: voltage-gated K⁺ channel, calcium-activated K⁺ channel, inwardly rectifying K⁺ channel and two-pore domain K⁺ channel.

Endothelium-Derived Relaxing Factors and Endothelial Function: A Systematic Review

BACKGROUND

The endothelium plays a pivotal role in homeostatic mechanisms. It specifically modulates vascular tone by releasing vasodilatory mediators, which act on the vascular smooth muscle. Large amounts of work have been dedicated towards identifying mediators of vasodilation and vasoconstriction alongside the deleterious effects of reactive oxygen species on the endothelium. We conducted a systematic review to study the role of the factors released by the endothelium and the effects on the vessels alongside its role in atherosclerosis.

METHODS

A search was conducted with appropriate search terms. Specific attention was offered to the effects of emerging modulators of endothelial functions focusing the analysis on studies that investigated the role of reactive oxygen species (ROS), perivascular adipose tissue, shear stress, AMP-activated protein kinase, potassium channels, bone morphogenic protein 4, and P2Y2 receptor.

RESULTS

530 citations were reviewed, with 35 studies included in the final systematic review. The endpoints were evaluated in these studies which offered an extensive discussion on emerging modulators of endothelial functions. Specific factors such as reactive oxygen species had deleterious effects, especially in the obese and elderly. Another important finding included the shear stress-induced endothelial nitric oxide (NO), which may delay development of atherosclerosis. Perivascular Adipose Tissue (PVAT) also contributes to reparative measures against atherosclerosis, although this may turn pathological in obese subjects. Some of these factors may be targets for pharmaceutical agents in the near future.

CONCLUSION

The complex role and function of the endothelium is vital for regular homeostasis. Dysregulation may drive atherogenesis; thus, efforts should be placed at considering therapeutic options by targeting some of the factors noted.

Regulatory role of KCa3.1 in immune cell function and its emerging association with rheumatoid arthritis

Rheumatoid arthritis (RA) is a common autoimmune disease characterized by chronic inflammation. Immune dysfunction is an essential mechanism in the pathogenesis of RA and directly linked to synovial inflammation and cartilage/bone destruction. Intermediate conductance Ca²⁺-activated K⁺ channel (KCa3.1) is considered a significant regulator of proliferation, differentiation, and migration of immune cells by mediating Ca²⁺ signal transduction. Earlier studies have demonstrated abnormal activation of KCa3.1 in the peripheral blood and articular synovium of RA patients. Moreover, knockout of KCa3.1 reduced the severity of synovial inflammation and cartilage damage to a significant extent in a mouse collagen antibody-induced arthritis (CAIA) model. Accumulating evidence implicates KCa3.1 as a potential therapeutic target for RA. Here, we provide an overview of the KCa3.1 channel and its pharmacological properties, discuss the significance of KCa3.1 in immune cells and feasibility as a drug target for modulating the immune balance, and highlight its emerging role in pathological progression of RA.

Imaging of the calcium activated potassium channel 3.1 (KCa 3.1) in vivo using a senicapoc-derived positron emission tomography tracer

The calcium-activated potassium channel 3.1 (K_Ca 3.1) is overexpressed in many tumor entities and has predictive power concerning disease progression and outcome. Imaging of the K_Ca 3.1 channel in vivo using a radiotracer for positron emission tomography (PET) could therefore establish a potentially powerful diagnostic tool. Senicapoc shows high affinity and excellent selectivity toward the K_Ca 3.1 channel. We have successfully pursued the synthesis of the ¹⁸ F-labeled derivative [¹⁸ F]3 of senicapoc using the prosthetic group approach with 1-azido-2-[¹⁸ F]fluoroethane ([¹⁸ F]6) in a "click" reaction. The biological activity of the new PET tracer was evaluated in vitro and in vivo. Inhibition of the K_Ca 3.1 channel by 3 was demonstrated by patch clamp experiments and the binding pose was analyzed by docking studies. In mouse and human serum, [¹⁸ F]3 was stable for at least one half-life of [¹⁸ F]fluorine. Biodistribution experiments in wild-type mice were promising, showing rapid and predominantly renal excretion. An in vivo study using A549-based tumor-bearing mice was performed. The tumor signal could be delineated and image analysis showed a tumor-to-muscle ratio of 1.47 ± 0.24. The approach using 1-azido-2-[¹⁸ F]fluoroethane seems to be a good general strategy to achieve triarylacetamide-based fluorinated PET tracers for imaging of the K_Ca 3.1 channel in vivo.

The contribution of ion channels to shaping macrophage behaviour

The expanding roles of macrophages in physiological and pathophysiological mechanisms now include normal tissue homeostasis, tissue repair and regeneration, including neuronal tissue; initiation, progression, and resolution of the inflammatory response and a diverse array of anti-microbial activities. Two hallmarks of macrophage activity which appear to be fundamental to their diverse cellular functionalities are cellular plasticity and phenotypic heterogeneity. Macrophage plasticity allows these cells to take on a broad spectrum of differing cellular phenotypes in response to local and possibly previous encountered environmental signals. Cellular plasticity also contributes to tissue- and stimulus-dependent macrophage heterogeneity, which manifests itself as different macrophage phenotypes being found at different tissue locations and/or after different cell stimuli. Together, plasticity and heterogeneity align macrophage phenotypes to their required local cellular functions and prevent inappropriate activation of the cell, which could lead to pathology. To execute the appropriate function, which must be regulated at the qualitative, quantitative, spatial and temporal levels, macrophages constantly monitor intracellular and extracellular parameters to initiate and control the appropriate cell signaling cascades. The sensors and signaling mechanisms which control macrophages are the focus of a considerable amount of research. Ion channels regulate the flow of ions between cellular membranes and are critical to cell signaling mechanisms in a variety of cellular functions. It is therefore surprising that the role of ion channels in the macrophage biology has been relatively overlooked. In this review we provide a summary of ion channel research in macrophages. We begin by giving a narrative-based explanation of the membrane potential and its importance in cell biology. We then report on research implicating different ion channel families in macrophage functions. Finally, we highlight some areas of ion channel research in macrophages which need to be addressed, future possible developments in this field and therapeutic potential.

Salvianolic acid B inhibits RAW264.7 cell polarization towards the M1 phenotype by inhibiting NF-κB and Akt/mTOR pathway activation

M1 macrophages secrete a large number of proinflammatory factors and promote the expansion of atherosclerotic plaques and processes. Salvianolic acid B (Sal B) exerts anti-inflammatory, antitumor and other effects, but no study has addressed whether Sal B can regulate the polarization of macrophages to exert these anti-atherosclerotic effects. Therefore, we investigated the inhibition of Sal B in M1 macrophage polarization and the underlying mechanism. The effects of different treatments on cell viability, gene expression and secretion of related proteins, phenotypic markers and cytokines were detected by MTT and western blot assays, RT‒qPCR and ELISAs. Cell viability was not significantly changed when the concentration of Sal B was less than 200 μM, and Lipopolysaccharide (LPS) (100 ng/mL) + interferon-γ (IFN-γ) (2.5 ng/mL) successfully induced M1 polarization. RT‒qPCR and ELISAs indicated that Sal B can downregulate M1 marker (Inducible Nitric Oxide Synthase (iNOS), Tumor Necrosis Factor-α (TNF-α), and Interleukin-6 (IL-6)) and upregulate M2 marker (Arginase-1 (Arg-1) and Interleukin-10 (IL-10)) expression. Western blotting was performed to measure the expression of Nuclear Factor-κB (NF-κB), p-Akt, p-mTOR, LC3-II, Beclin-1, and p62, and the results suggested that Sal B inhibits the M1 polarization of RAW264.7 macrophages by promoting autophagy via the NF-κB signalling pathway. The study indicated that Sal B inhibits M1 macrophage polarization by inhibiting NF-κB signalling pathway activation and downregulating Akt/mTOR activation to promote autophagy.

Downregulation of IL-8 and IL-10 by the Activation of Ca2+-Activated K+ Channel KCa3.1 in THP-1-Derived M2 Macrophages

THP-1-differentiated macrophages are useful for investigating the physiological significance of tumor-associated macrophages (TAMs). In the tumor microenvironment (TME), TAMs with the M₂-like phenotype play a critical role in promoting cancer progression and metastasis by inhibiting the immune surveillance system. We examined the involvement of Ca²⁺-activated K⁺ channel K_Ca3.1 in TAMs in expressing pro-tumorigenic cytokines and angiogenic growth factors. In THP-1-derived M₂ macrophages, the expression levels of IL-8 and IL-10 were significantly decreased by treatment with the selective K_Ca3.1 activator, SKA-121, without changes in those of VEGF and TGF-β1. Furthermore, under in vitro experimental conditions that mimic extracellular K⁺ levels in the TME, IL-8 and IL-10 levels were both significantly elevated, and these increases were reversed by combined treatment with SKA-121. Among several signaling pathways potentially involved in the transcriptional regulation of IL-8 and IL-10, respective treatments with ERK and JNK inhibitors significantly repressed their transcriptions, and treatment with SKA-121 significantly reduced the phosphorylated ERK, JNK, c-Jun, and CREB levels. These results strongly suggest that the K_Ca3.1 activator may suppress IL-10-induced tumor immune surveillance escape and IL-8-induced tumorigenicity and metastasis by inhibiting their production from TAMs through ERK-CREB and JNK-c-Jun cascades.

Cardiac Macrophages and Their Effects on Arrhythmogenesis

Cardiac electrophysiology is a complex system established by a plethora of inward and outward ion currents in cardiomyocytes generating and conducting electrical signals in the heart. However, not only cardiomyocytes but also other cell types can modulate the heart rhythm. Recently, cardiac macrophages were demonstrated as important players in both electrophysiology and arrhythmogenesis. Cardiac macrophages are a heterogeneous group of immune cells including resident macrophages derived from embryonic and fetal precursors and recruited macrophages derived from circulating monocytes from the bone marrow. Recent studies suggest antiarrhythmic as well as proarrhythmic effects of cardiac macrophages. The proposed mechanisms of how cardiac macrophages affect electrophysiology vary and include both direct and indirect interactions with other cardiac cells. In this review, we provide an overview of the different subsets of macrophages in the heart and their possible interactions with cardiomyocytes under both physiologic conditions and heart disease. Furthermore, we elucidate similarities and differences between human, murine and porcine cardiac macrophages, thus providing detailed information for researchers investigating cardiac macrophages in important animal species for electrophysiologic research. Finally, we discuss the pros and cons of mice and pigs to investigate the role of cardiac macrophages in arrhythmogenesis from a translational perspective.

KCa3.1 differentially regulates trachea and bronchi epithelial gene expression in a chronic-asthma mouse model

Ion channels are potentially exploitable as pharmacological targets to treat asthma. This study evaluated the role of KCa3.1 channels, encoded by Kcnn4, in regulating the gene expression of mouse airway epithelium and the development of asthma traits. We used the ovalbumin (OVA) challenge as an asthma model in wild type and Kcnn4^-/- mice, performed histological analysis, and measured serum IgE to evaluate asthma traits. We analyzed gene expression of isolated epithelial cells of trachea or bronchi using mRNA sequencing and gene ontology and performed Ussing chamber experiments in mouse trachea to evaluate anion secretion. Gene expression of epithelial cells from mouse airways differed between trachea and bronchi, indicating regional differences in the inflammatory and transepithelial transport properties of proximal and distal airways. We found that Kcnn4 silencing reduced mast cell numbers, mucus, and collagen in the airways, and reduced the amount of epithelial anion secretion in the OVA-challenged animals. Additionally, gene expression was differentially modified in the trachea and bronchi, with Kcnn4 genetic silencing significantly altering the expression of genes involved in the TNF pathway, supporting the potential of KCa3.1 as a therapeutic target for asthma.

Dysregulation of Immune Response Mediators and Pain-Related Ion Channels Is Associated with Pain-like Behavior in the GLA KO Mouse Model of Fabry Disease

Fabry disease (FD) is a rare life-threatening disorder caused by deficiency of the alpha-galactosidase A (GLA) enzyme with a characteristic pain phenotype. Impaired GLA production or function leads to the accumulation of the cell membrane compound globotriaosylceramide (Gb3) in the neurons of the dorsal root ganglia (DRG) of FD patients. Applying immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT PCR) analysis on DRG tissue of the GLA knockout (KO) mouse model of FD, we address the question of how Gb3 accumulation may contribute to FD pain and focus on the immune system and pain-associated ion channel gene expression. We show a higher Gb3 load in the DRG of young (<6 months) (p < 0.01) and old (≥12 months) (p < 0.001) GLA KO mice compared to old wildtype (WT) littermates, and an overall suppressed immune response in the DRG of old GLA KO mice, represented by a reduced number of CD206+ macrophages (p < 0.01) and lower gene expression levels of the inflammation-associated targets interleukin(IL)1b (p < 0.05), IL10 (p < 0.001), glial fibrillary acidic protein (GFAP) (p < 0.05), and leucine rich alpha-2-glycoprotein 1 (LRG1) (p < 0.01) in the DRG of old GLA KO mice compared to old WT. Dysregulation of immune-related genes may be linked to lower gene expression levels of the pain-associated ion channels calcium-activated potassium channel 3.1 (KCa3.1) and transient receptor potential ankyrin 1 channel (TRPA1). Ion channel expression might further be disturbed by impaired sphingolipid recruitment mediated via the lipid raft marker flotillin-1 (FLOT1). This impairment is represented by an increased number of FLOT1+ DRG neurons with a membranous expression pattern in old GLA KO mice compared to young GLA KO, young WT, and old WT mice (p < 0.001 each). Further, we provide evidence for aberrant behavior of GLA KO mice, which might be linked to dysregulated ion channel gene expression levels and disturbed FLOT1 distribution patterns. Behavioral testing revealed mechanical hypersensitivity in young (p < 0.01) and old (p < 0.001) GLA KO mice compared to WT, heat hypersensitivity in young GLA KO mice (p < 0.001) compared to WT, age-dependent heat hyposensitivity in old GLA KO mice (p < 0.001) compared to young GLA KO mice, and cold hyposensitivity in young (p < 0.001) and old (p < 0.001) GLA KO mice compared to WT, which well reflects the clinical phenotype observed in FD patients.

Harnessing the Membrane Potential to Combat Cancer Progression

Rapid fluctuations in the plasma membrane potential (Vm) provide the basis underlying the action potential waveform in electrically excitable cells; however, a growing body of literature shows that the Vm is also functionally instructive in nonexcitable cells, including cancer cells. Various ion channels play a key role in setting and fine tuning the Vm in cancer and stromal cells within the tumor microenvironment (TME), raising the possibility that the Vm could be targeted therapeutically using ion channel-modulating compounds. Emerging evidence points to the Vm as a viable therapeutic target, given its functional significance in regulating cell cycle progression, migration, invasion, immune infiltration, and pH regulation. Several compounds are now undergoing clinical trials and there is increasing interest in therapeutic manipulation of the Vm via application of pulsed electric fields. The purpose of this article is to update the reader on the significant recent and ongoing progress to elucidate the functional significance of Vm regulation in tumors, to highlight key remaining questions and the prospect of future therapeutic targeting. In particular, we focus on key developments in understanding the functional consequences of Vm alteration on tumor development via the activation of small GTPase (K-Ras and Rac1) signaling, as well as the impact of Vm changes within the heterogeneous TME on immune cell function and cancer progression.

Muscle Damage in Dystrophic mdx Mice Is Influenced by the Activity of Ca2+-Activated KCa3.1 Channels

Duchenne muscular dystrophy (DMD) is an X-linked disease, caused by a mutant dystrophin gene, leading to muscle membrane instability, followed by muscle inflammation, infiltration of pro-inflammatory macrophages and fibrosis. The calcium-activated potassium channel type 3.1 (K_Ca3.1) plays key roles in controlling both macrophage phenotype and fibroblast proliferation, two critical contributors to muscle damage. In this work, we demonstrate that pharmacological blockade of the channel in the mdx mouse model during the early degenerative phase favors the acquisition of an anti-inflammatory phenotype by tissue macrophages and reduces collagen deposition in muscles, with a concomitant reduction of muscle damage. As already observed with other treatments, no improvement in muscle performance was observed in vivo. In conclusion, this work supports the idea that K_Ca3.1 channels play a contributing role in controlling damage-causing cells in DMD. A more complete understanding of their function could lead to the identification of novel therapeutic approaches.

Blocking Intermediate-Conductance Calcium-Activated Potassium Channels in the Macrophages Around Ganglionated Plexi Suppresses Atrial Fibrillation Vulnerability in Canines With Rapid Atrial Pacing

Previous studies have indicated that ganglionated plexi (GP) function influences atrial fibrillation (AF) vulnerability, and intermediate-conductance calcium-activated potassium channels (SK4) have a close relationship with cardiomyocyte automaticity and the induction of AF. However, the effects of the SK4 inhibitor on GP function and AF vulnerability are unknown. Eighteen beagles were randomly divided into a control group (n = 6), rapid atrial pacing (RAP) group (n = 6), and triarylmethane-34 (TRAM-34, an SK4 inhibitor) group (n = 6). TRAM-34 (0.3 ml, 15 mmol/L) and saline were locally injected into GPs in the TRAM-34 group dogs and dogs from the other groups, respectively. After that, dogs in the RAP and TRAM-34 groups were subjected to RAP, and the neural activity of anterior right GP (ARGP) and atrial electrophysiology were measured. The levels of inflammatory cytokines and function of macrophages in the ARGP were measured in the three groups. At 10 min after TRAM-34 injection, ARGP activity and atrial electrophysiology did not significantly change. The atrial pacing shortened effective refractory period (ERP) values at all sites and increased the AF vulnerability and ARGP neural activity, while TRAM-34 reversed these changes. The levels of CD68 + cells, induced nitric oxide synthase (iNOS), interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in the ARGP tissues were higher in the RAP group and TRAM-34 group than they were in the control group. Furthermore, the levels of the CD68 + cells, iNOS, and inflammatory cytokines in the ARGP tissues were higher in the pacing group than those in the TRAM-34 group. Based on these results, administration of TRAM-34 into the atrial GP can suppress GP activity and AF vulnerability during atrial pacing. The effects of TRAM-34 might be related to macrophage polarization and the inflammatory response of GP.

Targeting the KCa3.1 channel suppresses diabetes-associated atherosclerosis via the STAT3/CD36 axis

BACKGROUND

In diet-induced arterial atherosclerosis, increased KCa3.1 channel was associated with atherosclerotic plaque progression and instability. Macrophages are involved in the formation of atherosclerotic plaques, and the release of inflammatory cytokines and oxygen free radicals promotes plaque progression. However, whether the macrophage KCa3.1 channel facilitates diabetes-accelerated atherosclerosis is still unclear. This study investigated atherosclerotic plaque in ApoE^-/- mice regulated by the KCa3.1 channel.

METHODS AND RESULTS

In vivo, blocking KCa3.1channel inhibit the development of the atherosclerotic lesion in diabetic ApoE^-/- mice fed with a high-fat diet. In vitro, upregulation of KCa3.1 channel level occurred in RAW264.7 cells treated with HG plus ox-LDL in a time-dependent manner. Blocking KCa3.1 significantly reduced the uptake of ox-LDL in mice peritoneal macrophages. Further studies indicated the KCa3.1 siRNA and TRAM-34 (KCa3.1 inhibitor) attenuated the scavenger receptor CD36 expression via inhibiting STAT3 phosphorylation.

CONCLUSION

Blockade of macrophage KCa3.1 channel inhibit cellular oxidized low-density lipoprotein accumulation and decrease proinflammation factors expression via STAT3/CD36 axis. This study provided a novel therapeutic target to reduce the risk of atherosclerosis development in diabetic patients.

Pharmacological inhibition of Kv1.3 channel impairs TLR3/4 activation and type I IFN response and confers protection against Listeria monocytogenes infection

Emerging data have demonstrated the critical roles of potassium efflux in the innate immune system. However, the role of potassium efflux in TLR3/4 activation and type I interferon (IFN) responses are not well elucidated. In the present study, we found potassium efflux is essential for TLR3/4 signaling, which mediates the expression of IFN and its inducible gene Cxcl10 and proinflammatory cytokine gene TNF-α. Furthermore, pharmacological inhibition of Kv1.3 channel (PAP-1), but not Kir2.1, KCa3.1 or TWIK2, attenuated TLR3/4 receptor activation in macrophages. Mechanistically, PAP-1 suppressed LPS-induced inflammatory function through marked suppressing the activation of JNK mitogen-activated protein kinase (MAPK) and p65 subunit of nuclear factor-kB (NF-kB). Notably, PAP-1 effectively protected mice against Listeria monocytogenes induced infection. Our findings reveal that potassium efflux mediated by the Kv1.3 channel is essential for TLR3/4 activation and suggest that pharmacological inhibition of Kv1.3 may help to treat type I IFN related autoimmune diseases and bacterial infections.

Synthesis and biological evaluation of PET tracers designed for imaging of calcium activated potassium channel 3.1 (KCa3.1) channels in vivo

Expression of the Ca²⁺ activated potassium channel 3.1 (K_Ca3.1) channel (also known as the Gàrdos channel) is dysregulated in many tumor entities and has predictive power with respect to patient survival. Therefore, a positron emission tomography (PET) tracer targeting this ion channel could serve as a potential diagnostic tool by imaging the K_Ca3.1 channel in vivo. It was envisaged to synthesize [¹⁸F]senicapoc ([¹⁸F]1) since senicapoc (1) shows high affinity and excellent selectivity towards the K_Ca3.1 channels. Because problems occurred during ¹⁸F-fluorination, the [¹⁸F]fluoroethoxy senicapoc derivative [¹⁸F]28 was synthesized to generate an alternative PET tracer targeting the K_Ca3.1 channel. Inhibition of the K_Ca3.1 channel by 28 was confirmed by patch clamp experiments. In vitro stability in mouse and human serum was shown for 28. Furthermore, biodistribution experiments in wild type mice were performed. Since [¹⁸F]fluoride was detected in vivo after application of [¹⁸F]28, an in vitro metabolism study was conducted. A potential degradation route of fluoroethoxy derivatives in vivo was found which in general should be taken into account when designing new PET tracers for different targets with a [¹⁸F]fluoroethoxy moiety as well as when using the popular prosthetic group [¹⁸F]fluoroethyl tosylate for the alkylation of phenols.

Expression of the Ca²⁺ activated potassium channel 3.1 (K_Ca3.1) channel (also known as the Gàrdos channel) is dysregulated in many tumor entities and has predictive power with respect to patient survival.

KCa3.1 Inhibition Decreases Size and Alters Composition of Atherosclerotic Lesions Induced by Low, Oscillatory Flow

Low, oscillatory flow/shear patterns are associated with atherosclerotic lesion development. Increased expression of K_Ca3.1 has been found in Vascular Smooth Muscle (VSM), macrophages and T-cells in lesions from humans and mice. Increased expression of K_Ca3.1, is also required for VSM cell proliferation and migration. Previously, we showed that the specific K_Ca3.1 inhibitor, TRAM-34, could inhibit coronary neointimal development following balloon injury in swine. Atherosclerosis develops in regions with a low, oscillatory (i.e. atheroprone) flow pattern. Therefore, we used the Partial Carotid Ligation (PCL) model in high-fat fed, Apoe^−/− mice to determine the role of K_Ca3.1 in atherosclerotic lesion composition and development. PCL was performed on 8–10 week old male Apoe^−/− mice and subsequently placed on a Western diet (TD.88137, Teklad) for 4 weeks. Mice received daily s.c. injections of TRAM-34 (120 mg/kg) or equal volumes of vehicle (peanut oil, PO). 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) treatment reduced lesion size ~50% (p < 0.05). In addition, lesions from TRAM-34 treated mice contained less collagen (6% ± 1% vs. 15% ± 2%; p < 0.05), fibronectin (14% ± 3% vs. 32% ± 3%; p < 0.05) and smooth muscle content (19% ± 2% vs. 29% ± 3%; p < 0.05). Conversely, TRAM-34 had no effect on total cholesterol (1455 vs. 1334 mg/dl, PO and TRAM, resp.) or body weight (29.1 vs. 28.8 g, PO and TRAM, resp.). Medial smooth muscle of atherosclerotic carotids showed diminished RE1-Silencing Transcription Factor (REST)/Neural Restrictive Silencing Factor (NRSF) expression, while REST overexpression in vitro inhibited smooth muscle migration. Together, these data support a downregulation of REST/NRSF and upregulation of K_Ca3.1 in determining smooth muscle and matrix content of atherosclerotic lesions.

HOXA5 induces M2 macrophage polarization to attenuate carotid atherosclerosis by activating MED1

Macrophage polarization is of great importance in the formation of atherosclerotic plaque. Homeobox A5 (HOXA5), one of the homeobox transcription factors, has been revealed to be closely associated with macrophage phenotype switching. This study aims to investigate the role of HOXA5 in carotid atherosclerosis (CAS). Herein, the role of HOXA5 was explored in polarized RAW264.7 macrophages in vitro and ApoE^-/- mice in vivo. Interestingly, compared with that in M0 macrophages, both the mRNA and protein expression levels of HOXA5 were decreased in lipopolysaccharide (LPS)/interferon (IFN)-γ-induced M1 macrophages, while increased in IL-4-induced M2 macrophages. In addition, in the presence of IL-4, HOXA5-overexpressing RAW264.7 cells preferred to polarizing toward M2 phenotypes. Furthermore, we found that HOXA5 bound to the promoter region and activated the expression of mediator subunit 1 (MED1), a gene known to regulate macrophage differentiation. Knocking MED1 down inhibited HOXA5-enhanced M2 macrophage polarization. In vivo, the CAS model was induced in ApoE^-/- mouse fed with a Western-type diet and placed a perivascular carotid collar. Decreased mRNA and protein expressions of HOXA5 were observed in carotid arteries of CAS mice. Forced overexpression of HOXA5 reduced intimal hyperplasia and lipid accumulation in carotid vessels, and it also promoted the polarization of macrophages to M2 subtypes. The expression of MED1 was decreased in atherosclerotic carotid vessels, while HOXA5 overexpression restored its change. Collectively, HOXA5 in carotid arteries is involved in the macrophage M1/M2 switching in atherosclerotic plaque, which may be associated with its transcriptional regulation of MED1.

Combined NOX/ROS/PKC Signaling Pathway and Metabolomic Analysis Reveals the Mechanism of TRAM34-Induced Endothelial Progenitor Cell Senescence

It has been shown that the KCa3.1 channel-specific blocker, TRAM34, is a promising antiatherosclerosis (AS) agent, but its side effects restrict its clinical application. Notably, its effect on endothelial progenitor cells (EPCs) is unclear. We aim to unravel the effect of TRAM34 on EPCs and identify the underlying mechanism. Rats were injected intraperitoneally with TRAM34, and EPCs were isolated from bone marrow. The gene and protein levels of corresponding factors were detected by real-time PCR, enzyme-linked immunosorbent assay, western blotting, and fluorescence-activated cell sorting. Liquid chromatography-tandem mass spectrometry (LC-MS) was applied to detect metabolite differences. We showed that when rats were treated with TRAM34 in vivo, colony formation and proliferation of early EPCs were reduced, but their senescence and apoptosis were enhanced. Moreover, TRAM34 enhanced NOX activity, promoted an increase in intracellular ROS levels, increased PKC expression, and subsequently promoted EPC senescence, which is unfavorable for EPC angiogenesis in vivo and in vitro. Combining these results with LC-MS data, we found that TRAM34 significantly promoted pyrimidine and purine metabolism, leading to cellular senescence. Furthermore, the NOX inhibitor, Setanaxib, enhanced antioxidant metabolic pathways, especially S-adenosylmethioninamine (SAM) metabolism, to exert an antisenescence effect. Finally, we confirmed that SAM alleviates TRAM34-induced cellular senescence, suggesting an efficient approach to improve the quality of endogenous EPCs. This study reveals the mechanism of TRAM34-induced EPC senescence, providing a solution for the extended application of KCa3.1 inhibitor in AS.

Inhibition of KCa3.1 Channels Suppresses Atrial Fibrillation via the Attenuation of Macrophage Pro-inflammatory Polarization in a Canine Model With Prolonged Rapid Atrial Pacing

Aims: To investigate the role of KCa3. 1 inhibition in macrophage pro-inflammatory polarization and vulnerability to atrial fibrillation (AF) in a canine model with prolonged rapid atrial pacing.

Materials and Methods: Twenty beagle dogs (weighing 8–10 kg) were randomly assigned to a sham group (n = 6), pacing group (n = 7) and pacing+TRAM-34 group (n = 7). An experimental model of AF was established by rapid pacing. TRAM-34 was administered to the Pacing+TRAM-34 group by slow intravenous injection (10 mg/kg), 3 times each day. After 7 days of pacing, the electrophysiology was measured in vivo. The levels of interleukin-1β (IL-1β), monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), CD68, c-Fos, p38, and NF-κB p65 in both atriums were measured by Western blotting, and the levels of inducible nitric oxide synthase (iNOS) and arginase1 (Arg-1) were measured by real-time PCR. Macrophage and KCa3.1 in macrophage in the atrium were quantized following double labeled immunofluorescent.

Results: Greater inducibility of AF, an extended duration of AF and lower atrial effective refractory period (AERP) were observed in the pacing group compared with those in the sham group. Both CD68-labeled macrophage and the expression of KCa3.1 in macrophage were elevated in the pacing group and inhibited by TRAM-34, led to higher iNOS expression, lower Arg-1 expression, elevated levels of IL-1β, MCP-1, and TNF-α in the atria, which could be reversed by TRAM-34 treatment (all P < 0.01). KCa3.1 channels were possibly activated via the p38/AP-1/NF-κB signaling pathway.

Conclusions: Inhibition of KCa3.1 suppresses vulnerability to AF by attenuating macrophage pro-inflammatory polarization and inflammatory cytokine secretion in a canine model with prolonged rapid atrial pacing.

Macrophage Plasticity and Atherosclerosis Therapy

Atherosclerosis is a chronic disease starting with the entry of monocytes into the subendothelium and the subsequent differentiation into macrophages. Macrophages are the major immune cells in atherosclerotic plaques and are involved in the dynamic progression of atherosclerotic plaques. The biological properties of atherosclerotic plaque macrophages determine lesion size, composition, and stability. The heterogenicity and plasticity of atherosclerotic macrophages have been a hotspot in recent years. Studies demonstrated that lipids, cytokines, chemokines, and other molecules in the atherosclerotic plaque microenvironment regulate macrophage phenotype, contributing to the switch of macrophages toward a pro- or anti-atherosclerosis state. Of note, M1/M2 classification is oversimplified and only represent two extreme states of macrophages. Moreover, M2 macrophages in atherosclerosis are not always protective. Understanding the phenotypic diversity and functions of macrophages can disclose their roles in atherosclerotic plaques. Given that lipid-lowering therapy cannot completely retard the progression of atherosclerosis, macrophages with high heterogeneity and plasticity raise the hope for atherosclerosis regression. This review will focus on the macrophage phenotypic diversity, its role in the progression of the dynamic atherosclerotic plaque, and finally discuss the possibility of treating atherosclerosis by targeting macrophage microenvironment.

Monitoring Lactate Dynamics in Individual Macrophages with a Genetically Encoded Probe

Lactate, the product of aerobic glycolysis, plays a dual role as fuel and intercellular signal in inflammation, immune evasion, and tumor progression. The production of lactate by macrophages has been associated with their polarization and function. Here we describe imaging protocols to characterize the metabolism of cultured human macrophages using a genetically encoded fluorescent sensor-specific for lactate. By superfusing cultures with increasing lactate concentrations and pharmacological inhibitors, it is possible to estimate the kinetic parameters of monocarboxylate transporter 4 (MCT4) and lactate production. Practical advice is given regarding sensor expression, imaging, and data analysis. The spatiotemporal resolution of this technique is amenable to the study of fast events at the single-cell level in different immune and other cell types.

KCa3.1 Inhibition of Macrophages Suppresses Inflammatory Response Leading to Endothelial Damage in a Cell Model of Kawasaki Disease

Purpose

Macrophages-mediated inflammation is linked with endothelial damage of Kawasaki disease (KD). KCa3.1, a calcium-activated potassium channel, modulates inflammation of macrophages. However, little is known about the role of KCa3.1 in inflammation by macrophages involved in KD. Hence, this study is aimed to explore the potential role of KCa3.1 in regulating inflammatory response by macrophages and subsequent vascular injury in an in vitro model of KD.

Methods

RAW264.7 cells were stimulated with Lactobacillus casei cell wall extract (LCWE) with or without TRAM-34 or PDTC or AG490. Subsequently, mouse coronary artery endothelial cells (MCAECs) were incubated with RAW264.7 cells-conditioned medium to mimic local inflammatory lesions in KD. CCKi8 assay was used to evaluate cell viability. The mRNA levels of inflammatory mediators were detected by qRT-PCR. Expressions of KCa3.1, MCAECs injury-associated molecules, proteins involved in signal pathways of nuclear factor-κB (NF-κB), signal transducers and activators of transcription (STAT) 3 and p38 were evaluated by Western blot.

Results

Our study showed that LCWE increased KCa3.1 protein level in RAW264.7 macrophages and KCa3.1 inhibition by TRAM-34 notably suppressed the expression of pro-inflammatory molecules in LCWE-treated macrophages via blocking the activation of NF-κB and STAT3 pathways. Besides, the inflammation and damage of MCAECs were attenuated in the TRAM-34-treated group compared with the KD model group. This vascular protective role was dependent on the down-regulation of NF-κB and STAT3 signal pathways, which was confirmed by using inhibitors of NF-κB and STAT3.

Conclusion

This study demonstrates that KCa3.1 blockade of macrophages suppresses inflammatory reaction leading to mouse coronary artery endothelial cell injury in a cell model of KD by hampering the activation of NF-κB and STAT3 signaling pathway. These findings imply that KCa3.1 may be a potential therapeutic target for KD.

The role of potassium in atherosclerosis

BACKGROUND

Atherosclerosis (AS) is a chronic progressive inflammatory condition with a leading prevalence worldwide. Endothelial dysfunction leads to low-density lipoprotein trafficking into subendothelial space and the subsequent form of oxidized LDL (ox-LDL) within intimal layer, perpetuating the vicious cycle of endothelial dysfunction. K+ exerts beneficial effects in vascular wall by reducing LDL oxidization, vascular smooth muscle cells (VSMCs) proliferation, and free radical generation. K+ also modulates vascular tone through a regulatory effect on cell membrane potential.

MATERIALS AND METHODS

The most relevant papers on the association between 'potassium channels' and 'atherosclerosis' were selected among those deposited on PubMed from 1990 to 2020.

RESULTS

Here, we provide a short narrative review that elaborates on the role of K+ in atherosclerosis. This review also update the current knowledge about potential pharmacological agents targeting K+ channels with a special focus on pleiotropic activities of agents such as statins, sulfonylureas and dihydropyridines.

CONCLUSION

In this review, the mechanism of different K+ channels on vascular endothelium will be summarized, mainly focusing on their pathophysiological role in atherosclerosis and potential therapeutic application.

Ion Channels Orchestrate Pancreatic Ductal Adenocarcinoma Progression and Therapy

Pancreatic ductal adenocarcinoma is a devastating disease with a dismal prognosis. Therapeutic interventions are largely ineffective. A better understanding of the pathophysiology is required. Ion channels contribute substantially to the "hallmarks of cancer." Their expression is dysregulated in cancer, and they are "misused" to drive cancer progression, but the underlying mechanisms are unclear. Ion channels are located in the cell membrane at the interface between the intracellular and extracellular space. They sense and modify the tumor microenvironment which in itself is a driver of PDAC aggressiveness. Ion channels detect, for example, locally altered proton and electrolyte concentrations or mechanical stimuli and transduce signals triggered by these microenvironmental cues through association with intracellular signaling cascades. While these concepts have been firmly established for other cancers, evidence has emerged only recently that ion channels are drivers of PDAC aggressiveness. Particularly, they appear to contribute to two of the characteristic PDAC features: the massive fibrosis of the tumor stroma (desmoplasia) and the efficient immune evasion. Our critical review of the literature clearly shows that there is still a remarkable lack of knowledge with respect to the contribution of ion channels to these two typical PDAC properties. Yet, we can draw parallels from ion channel research in other fibrotic and inflammatory diseases. Evidence is accumulating that pancreatic stellate cells express the same "profibrotic" ion channels. Similarly, it is at least in part known which major ion channels are expressed in those innate and adaptive immune cells that populate the PDAC microenvironment. We explore potential therapeutic avenues derived thereof. Since drugs targeting PDAC-relevant ion channels are already in clinical use, we propose to repurpose those in PDAC. The quest for ion channel targets is both motivated and complicated by the fact that some of the relevant channels, for example, KCa3.1, are functionally expressed in the cancer, stroma, and immune cells. Only in vivo studies will reveal which arm of the balance we should put our weights on when developing channel-targeting PDAC therapies. The time is up to explore the efficacy of ion channel targeting in (transgenic) murine PDAC models before launching clinical trials with repurposed drugs.

Inhibition of inflammatory cytokine production and proliferation in macrophages by Kunitz-type inhibitors from Echinococcus granulosus

The genus Echinococcus of cestode parasites includes important pathogens of humans and livestock animals. Transcriptomic and genomic studies on E. granulosus and E. multilocularis uncovered striking expansion of monodomain Kunitz proteins. This expansion is accompanied by the specialization of some family members away from the ancestral protease inhibition function to fulfill cation channel blockade functions. Since cation channels are involved in immune processes, we tested the effects on macrophage physiology of two E. granulosus Kunitz-type inhibitors of voltage-activated cation channels (K_v) that are close paralogs. Both inhibitors, EgKU-1 and EgKU-4, inhibited production of the Th1/Th17 cytokine subunit IL-12/23p40 by macrophages stimulated with the TLR4 agonist LPS. In addition, EgKU-4 but not EgKU-1 inhibited production of the inflammatory cytokine IL-6. These activities were not displayed by EgKU-3, a family member that is a protease inhibitor without known activity on cation channels. EgKU-4 potently inhibited macrophage proliferation in response to M-CSF, whereas EgKU-1 displayed similar activity but with much lower potency, similar to EgKU-3. We discuss structural differences, including a heavily cationic C-terminal extension present in EgKU-4 but not in EgKU-1, that may explain the differential activities of the two close paralogs.

The Role of Exosomal Non-Coding RNAs in Coronary Artery Disease

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality worldwide. Atherosclerosis (AS) is a major cause of CVD. Oxidative stress, endothelial dysfunction, and inflammation are key factors involved in the development and progression of AS. Exosomes are nano-sized vesicles secreted into the extracellular space by most types of cells, and are ideal substances for the transmission and integration of signals between cells. Cells can selectively encapsulate biologically active substances, such as lipids, proteins and RNA in exosomes and act through paracrine mechanisms. Non-coding RNAs (ncRNAs) are important for communication between cells. They can reach the recipient cells through exosomes, causing phenotypic changes and playing a molecular regulatory role in cell function. Elucidating their molecular mechanisms can help identify therapeutic targets or strategies for CVD. Coronary artery disease (CAD) is the most important disease in CVD. Here, we review the role and the regulatory mechanism of exosomal ncRNAs in the pathophysiology of CAD, as well as the potential contribution of exosomal ncRNA to diagnosis and treatment of CAD.

Dysregulated signalling pathways in innate immune cells with cystic fibrosis mutations

Cystic fibrosis (CF) is one of the most common life-limiting recessive genetic disorders in Caucasians, caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). CF is a multi-organ disease that involves the lungs, pancreas, sweat glands, digestive and reproductive systems and several other tissues. This debilitating condition is associated with recurrent lower respiratory tract bacterial and viral infections, as well as inflammatory complications that may eventually lead to pulmonary failure. Immune cells play a crucial role in protecting the organs against opportunistic infections and also in the regulation of tissue homeostasis. Innate immune cells are generally affected by CFTR mutations in patients with CF, leading to dysregulation of several cellular signalling pathways that are in continuous use by these cells to elicit a proper immune response. There is substantial evidence to show that airway epithelial cells, neutrophils, monocytes and macrophages all contribute to the pathogenesis of CF, underlying the importance of the CFTR in innate immune responses. The goal of this review is to put into context the important role of the CFTR in different innate immune cells and how CFTR dysfunction contributes to the pathogenesis of CF, highlighting several signalling pathways that may be dysregulated in cells with CFTR mutations.

Inhibition of notch enhances the anti-atherosclerotic effects of LXR agonists while reducing fatty liver development in ApoE-deficient mice

Liver X receptor (LXR) activation can achieve satisfactory anti-atherosclerotic activity, but can also lead to the development of fatty liver and hypertriglyceridemia. In contrast, Notch inhibition can suppress both atherosclerosis and the hepatic accumulation of lipids. In the present study, we sought to assess whether combining LXR ligand agonists (T317) with Notch receptor inhibitors (DAPT) would lead to enhanced anti-atherosclerotic activity while overcoming the adverse events associated with LXR ligand agonist therapy. The impact of the combined T317 + DAPT therapeutic regimen on atherosclerosis, fatty liver development, and hypertriglyceridemia was assessed using ApoE deficient (ApoE^-/-) mice. The results of this analysis suggested that DAPT was able to improve the anti-atherosclerotic activity of T317 without reducing the stability of lesion plaques while simultaneously reducing blood lipids in treated ApoE^-/- mice. This combination T317 + DAPT treatment was also linked with a significant upregulation of ABCA1 and the stimulation of reverse cholesterol transport (RCT), as well as with decreases in the levels of intercellular cell adhesion molecule-1 (ICAM-1) and p-p65, and with altered M1/M2 macrophage proportions within atherosclerotic plaques. Importantly, DAPT was also able to reduce T317-mediated lipid accumulation within the liver owing to its ability to reduce SREBP-1 expression while simultaneously increasing that of Pi-AMPKα and PPARα. Together, our results suggest that administering Notch receptor inhibitors to ApoE^-/- mice may be an effective means of enhancing the anti-atherosclerotic activity of LXR ligand agonists while simultaneously limiting associated fatty liver and hypertriglyceridemia development in these animals.

Role of Infiltrating Microglia/Macrophages in Glioma

In this chapter we describe the state of the art knowledge of the role played by myeloid cells in promoting and supporting the growth and the invasive properties of a deadly brain tumor, glioblastoma. We provide a review of the works describing the intercellular communication among glioma and associated microglia/macrophage cells (GAMs) using in vitro cellular models derived from mice, rats and human patients and in vivo animal models using syngeneic or xenogeneic experimental systems. Special emphasis will be given to 1) the timing alteration of brain microenvironment under the influence of glioma, 2) the bidirectional communication among tumor and GAMs, 3) possible approaches to interfere with or to guide these interactions, with the aim to identify molecular and cellular targets which could revert or delay the vicious cycle that favors tumor biology.

Macrophage polarization in atherosclerosis

Atherosclerosis is a chronic inflammatory response that increases the risk of cardiovascular diseases. An in-depth study of the pathogenesis of atherosclerosis is critical for the treatment of atherosclerotic cardiovascular disease. The development of atherosclerosis involves many cells, such as endothelial cells, vascular smooth muscle cells, macrophages, and others. The considerable effects of macrophages in atherosclerosis are inextricably linked to macrophage polarization and the resulting phenotype. Moreover, the significant impact of macrophages on atherosclerosis depend not only on the function of the different macrophage phenotypes but also on the relative ratio of different phenotypes in the plaque. Research on atherosclerosis therapy indicates that the reduced plaque size and enhanced stability are partly due to modulating macrophage polarization. Therefore, regulating macrophage polarization and changing the proportion of macrophage phenotypes in plaques is a new therapeutic approach for atherosclerosis. This review provides a new perspective for atherosclerosis therapy by summarizing the relationship between macrophage polarization and atherosclerosis, as well as treatment targeting macrophage polarization.

Macrophages facilitate post myocardial infarction arrhythmias: roles of gap junction and KCa3.1

Effective therapeutic targets against post-myocardial infarction (MI) arrhythmias remain to be discovered. We aimed to investigate the role of macrophages in post-MI arrhythmias.

Methods: Mononuclear cell accumulation, macrophage polarization from M0 to M1 subset, and gap junction formation were analyzed in MI patients and MI mice by flow cytometry, immunofluorescence and patch clamping. Differentially expressed genes were identified by RNA sequencing. Macrophages and cardiomyocytes were cocultured in vitro, and the effects of gap junction and KCa3.1 on electrophysiological properties were assessed by patch clamping. The effects of KCa3.1 inhibition on post-MI arrhythmias were assessed by intracardiac stimulation and ambulatory electrocardiograms in vivo.

Results: Percentage of pro-inflammatory mononuclear cells were significantly elevated in patients with post-MI arrhythmias compared with MI patients without arrhythmias and healthy controls (p<0.001). Macrophages formed gap junction with cardiomyocytes in MI border zones of MI patient and mice, and pro-inflammatory macrophages were significantly increased 3 days post-MI (p<0.001). RNA sequencing identified Kcnn4 as the most differentially expressed gene encoding ion channel, and the upregulation is mainly attributed to macrophage accumulation and polarization into pro-inflammatory subset. In vitro coculture experiments demonstrated that connection with M0 macrophages via gap junction slightly shortened the action potential durations (APDs) of cardiomyocytes. However, the APD90 of cardiomyocytes connected with M1 macrophages were significantly prolonged (p<0.001), which were effectively attenuated by gap junction inhibition (p=0.002), KCa3.1 inhibition (p=0.008), KCa3.1 silencing (p<0.001) and store-operated Ca²⁺ channel inhibition (p=0.005). In vivo results demonstrated that KCa3.1 inhibition significantly decreased the QTc durations (p=0.031), intracardiac stimulation-induced ventricular arrhythmia durations (p=0.050) and incidence of premature ventricular contractions (p=0.030) in MI mice.

Conclusion: Macrophage polarization leads to APD heterogeneity and post-MI arrhythmias via gap junction and KCa3.1 activation. The results provide evidences of a novel mechanism of post-MI heterogeneous repolarization and arrhythmias, rendering macrophages and KCa3.1 to be potential therapeutic targets.

M2 Macrophages as a Potential Target for Antiatherosclerosis Treatment

Atherosclerosis is a chronic progressive inflammation course, which could induce life-threatening diseases such as stroke and myocardial infarction. Optimal medical treatments for atherosclerotic risk factors with current antihypertensive and lipid-lowering drugs (for example, statins) are widely used in clinical practice. However, many patients with established disease still continue to have recurrent cardiovascular events in spite of treatment with a state-of-the-art therapy. Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of mortality worldwide. Hence, current treatment of atherosclerosis is still far from being satisfactory. Recently, M2 macrophages have been found associated with atherosclerosis regression. The M2 phenotype can secrete anti-inflammatory factors such as IL-10 and TGF-β, promote tissue remodeling and repairing through collagen formation, and clear dying cells and debris by efferocytosis. Therefore, modulators targeting macrophages' polarization to the M2 phenotype could be another promising treatment strategy for atherosclerosis. Two main signaling pathways, the Akt/mTORC/LXR pathway and the JAK/STAT6 pathway, are found playing important roles in M2 polarization. In addition, researchers have reported several potential approaches to modulate M2 polarization. Inhibiting or activating some kinds of enzymes, affecting transcription factors, or acting on several membrane receptors could regulate the polarization of the M2 phenotype. Besides, biomolecules, for example vitamin D, were found to affect the process of M2 polarization. Pomegranate juice could promote M2 polarization via unclear mechanism. In this review, we will discuss how M2 macrophages affect atherosclerosis regression, signal transduction in M2 polarization, and outline potential targets and compounds that affect M2 polarization, thus controlling the progress of atherosclerosis.

Ca2+-Activated K+ Channel KCa3.1 as a Therapeutic Target for Immune Disorders

In lymphoid and myeloid cells, membrane hyperpolarization by the opening of K⁺ channels increases the activity of Ca²⁺ release-activated Ca²⁺ (CRAC) channels and transient receptor potential (TRP) Ca²⁺ channels. The intermediate-conductance Ca²⁺-activated K⁺ channel K_Ca3.1 plays an important role in cell proliferation, differentiation, migration, and cytokine production in innate and adaptive immune systems. K_Ca3.1 is therefore an attractive therapeutic target for allergic, inflammatory, and autoimmune disorders. In the past several years, studies have provided new insights into 1) K_Ca3.1 pharmacology and its auxiliary regulators; 2) post-transcriptional and proteasomal regulation of K_Ca3.1; 3) K_Ca3.1 as a regulator of immune cell migration, cytokine production, and phenotypic polarization; 4) the role of K_Ca3.1 in the phosphorylation and nuclear translocation of Smad2/3; and 5) K_Ca3.1 as a therapeutic target for cancer immunotherapy. In this review, we have assembled a comprehensive overview of current research on the physiological and pathophysiological significance of K_Ca3.1 in the immune system.

Kcnn4 is a modifier gene of intestinal cystic fibrosis preventing lethality in the Cftr-F508del mouse

Nearly 70% of cystic fibrosis (CF) patients bear the phenylalanine-508 deletion but disease severity differs greatly, and is not explained by the existence of different mutations in compound heterozygous. Studies demonstrated that genes other than CFTR relate to intestinal disease in humans and CF-mouse. Kcnn4, the gene encoding the calcium-activated potassium channel KCa3.1, important for intestinal secretion, is present in a locus linked with occurrence of intestinal CF-disease in mice and humans. We reasoned that it might be a CF-modifier gene and bred a CF-mouse with Kcnn4 silencing, finding that lethality was almost abolished. Silencing of Kcnn4 did not improve intestinal secretory functions, but rather corrected increased circulating TNF-α level and reduced intestinal mast cell increase. Given the importance of mast cells in intestinal disease additional double mutant CF-animals were tested, one lacking mast cells (C-kitW-sh/W-sh) and Stat6-/- to block IgE production. While mast cell depletion had no effect, silencing Stat6 significantly reduced lethality. Our results show that Kcnn4 is an intestinal CF modifier gene partially acting through a STAT6-dependent mechanism.

Exosomal MALAT1 derived from oxidized low-density lipoprotein-treated endothelial cells promotes M2 macrophage polarization

Oxidized low-density lipoprotein (oxLDL)-induced injury and apoptosis of endothelial cells are important initial events in numerous cardiovascular diseases. Following activation by oxLDL, monocytes adhere to endothelial cells, migrate into the subendothelial spaces and then undergo differentiation into macrophages, which subsequently induces the formation of atherosclerotic lesions. However, the mechanisms underlying the activation of macrophage differentiation by oxLDL-treated endothelial cells remain unclear. In the present study, it was demonstrated that exosomal metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) was increased in oxLDL-treated human umbilical vein endothelial cells. When co-cultured with monocytes, exosomes extracted from oxLDL-treated HUVECs were endocytosed. Furthermore, exosomes derived from oxLDL-treated endothelial cells were revealed to promote M2 macrophage polarization, as reverse transcription-quantitative polymerase chain reaction, western blotting and ELISA analyses demonstrated increases in the expression of M2 macrophage markers, including macrophage mannose receptor 1 (also termed CD206), arginase-1 and interleukin (IL)-10, and decreases in the expression of the M1 macrophage marker, IL-12. Furthermore, the suppression of MALAT1 expression in monocytes was demonstrated to reverse exosome-mediated M2 macrophage polarization. In conclusion, the results of the present study revealed a novel mechanism underlying the onset of atherogenesis associated with endothelial cells and macrophages: Exosomal MALAT1 derived from oxLDL-treated endothelial cells promoted M2 macrophage polarization. This result may provide a novel scientific basis for the understanding of atherosclerosis progression.