Effects of BKCa and Kir2.1 Channels on Cell Cycling Progression and Migration in Human Cardiac c-kit+ Progenitor Cells

Concanavalin A promotes angiogenesis and proliferation in endothelial cells through the Akt/ERK/Cyclin D1 axis

CONTEXT

Concanavalin A (Con A) exhibited multiple roles in cancer cells. However, the role of Con A in endothelial cells was not reported.

OBJECTIVE

Our present study investigated the potential angiogenic role of Con A in endothelial cells and ischaemic hind-limb mice.

MATERIALS AND METHODS

Human umbilical vein endothelial cells and Ea.hy926 cells were employed to determine the effect of Con A (0.3, 1, and 3 μg/mL) or vehicle on angiogenesis and cell proliferation with tube formation, ELISA, flow cytometry, EdU, and western blot. Hind-limb ischaemic mice were conducted to determine the pro-angiogenic effect of Con A (10 mg/kg) for 7 days.

RESULTS

Con A promoted tube formation to about three-fold higher than the control group and increased the secretion of VEGFa, PDGFaa, and bFGF in the medium. The cell viability was promoted to 1.3-fold by Con A 3 μg/mL, and cell cycle progression of G0G1 phase was decreased from 77% in the vehicle group to 70% in Con A 3 μg/mL, G2M was promoted from 15 to 19%, and S-phase was from 7 to 10%. Con A significantly stimulated phosphorylation of Akt and ERK1/2 and expression of cyclin D1 and decreased the expression of p27. These effects of Con A were antagonised by the PI3K inhibitor LY294002 (10 μM) and MEK pathway antagonist PD98059 (10 μM). Moreover, Con A (10 mg/kg) exhibited a repair effect in ischaemic hind-limb mice.

DISCUSSION AND CONCLUSIONS

This study will provide a new option for treating ischaemic disease by local injection with Con A.

Inhibition of KIR2.1 decreases pulmonary artery smooth muscle cell proliferation and migration

The investigation of effective therapeutic drugs for pulmonary hypertension (PH) is critical. KIR2.1 plays crucial roles in regulating cell proliferation and migration, and vascular remodeling. However, researchers have not yet clearly determined whether KIR2.1 participates in the proliferation and migration of pulmonary artery smooth muscle cells (PASMCs) and its role in pulmonary vascular remodeling (PVR) also remains elusive. The present study aimed to examine whether KIR2.1 alters PASMC proliferation and migration, and participates in PVR, as well as to explore its mechanisms of action. For the in vivo experiment, a PH model was established by intraperitoneally injecting Sprague-Dawley rats monocrotaline (MCT). Hematoxylin and eosin staining revealed evidence of PVR in the rats with PH. Immunofluorescence staining and western blot analysis revealed increased levels of the KIR2.1, osteopontin (OPN) and proliferating cell nuclear antigen (PCNA) proteins in pulmonary blood vessels and lung tissues following exposure to MCT, and the TGF-β1/SMAD2/3 signaling pathway was activated. For the in vitro experiments, the KIR2.1 inhibitor, ML133, or the TGF-β1/SMAD2/3 signaling pathway blocker, SB431542, were used to pre-treat human PASMCs (HPASMCs) for 24 h, and the cells were then treated with platelet-derived growth factor (PDGF)-BB for 24 h. Scratch and Transwell assays revealed that PDGF-BB promoted cell proliferation and migration. Immunofluorescence staining and western blot analysis demonstrated that PDGF-BB upregulated OPN and PCNA expression, and activated the TGF-β1/SMAD2/3 signaling pathway. ML133 reversed the proliferation and migration induced by PDGF-BB, inhibited the expression of OPN and PCNA, inhibited the TGF-β1/SMAD2/3 signaling pathway, and reduced the proliferation and migration of HPASMCs. SB431542 pre-treatment also reduced cell proliferation and migration; however, it did not affect KIR2.1 expression. On the whole, the results of the present study demonstrate that KIR2.1 regulates the TGF-β1/SMAD2/3 signaling pathway and the expression of OPN and PCNA proteins, thereby regulating the proliferation and migration of PASMCs and participating in PVR.

Elevated Kir2.1/nuclear N2ICD defines a highly malignant subtype of non-WNT/SHH medulloblastomas

Medulloblastoma (MB) is one of the most common childhood malignant brain tumors (WHO grade IV), traditionally divided into WNT, SHH, Group 3, and Group 4 subgroups based on the transcription profiles, somatic DNA alterations, and clinical outcomes. Unlike WNT and SHH subgroup MBs, Group 3 and Group 4 MBs have similar transcriptomes and lack clearly specific drivers and targeted therapeutic options. The recently revised WHO Classification of CNS Tumors has assigned Group 3 and 4 to a provisional non-WNT/SHH entity. In the present study, we demonstrate that Kir2.1, an inwardly-rectifying potassium channel, is highly expressed in non-WNT/SHH MBs, which promotes tumor cell invasion and metastasis by recruiting Adam10 to enhance S2 cleavage of Notch2 thereby activating the Notch2 signaling pathway. Disruption of the Notch2 pathway markedly inhibited the growth and metastasis of Kir2.1-overexpressing MB cell-derived xenograft tumors in mice. Moreover, Kir2.1^high/nuclear N2ICD^high MBs are associated with the significantly shorter lifespan of the patients. Thus, Kir2.1^high/nuclear N2ICD^high can be used as a biomarker to define a novel subtype of non-WNT/SHH MBs. Our findings are important for the modification of treatment regimens and the development of novel-targeted therapies for non-WNT/SHH MBs.

Pretreatment of cardiac progenitor cells with bradykinin attenuates H2O2-induced cell apoptosis and improves cardiac function in rats by regulating autophagy

Background

Previous studies have demonstrated that human cardiac c-Kit⁺ progenitor cells (hCPCs) can effectively improve ischemic heart disease. However, the major challenge in applying hCPCs to clinical therapy is the low survival rate of graft hCPCs in the host heart, which limited the benefit of transplanted hCPCs. Bradykinin (BK) is a principal active agent of the tissue kinin-kallikrein system. Our previous studies have highlighted that BK mediated the growth and migration of CPCs by regulating Ca²⁺ influx. However, the protective effect of BK on CPCs, improvement in the survival rate of BK-pretreated hCPCs in the infarcted heart, and the related mechanism remain elusive.

Methods

HCPCs were treated with H₂O₂ to induce cell apoptosis and autophagy, and different concentration of BK was applied to rescue the H₂O₂-induced injury detected by MTT assay, TUNEL staining, flow cytometry, western blotting, and mitoSOX assays. The role of autophagy in the anti-apoptotic effect of BK was chemically activated or inhibited using the autophagy inducer, rapamycin, or the inhibitor, 3-methyladenine (3-MA). To explore the protective effect of BK on hCPCs, 3-MA or BK-pretreated hCPCs were transplanted into the myocardial infarcted rats. An echocardiogram was used to determine cardiac function, H&E and Masson staining were employed to assess pathological characteristics, HLA gene expression was quantified by qRT-PCR, and immunostaining was applied to examine neovascularization using confocal microscopy.

Results

The in vitro results showed that BK suppressed H₂O₂-induced hCPCs apoptosis and ROS production in a concentration-dependent manner by promoting pAkt and Bcl-2 expression and reducing cleaved caspase 3 and Bax expression. Moreover, BK restrained the H₂O₂-induced cell autophagy by decreasing LC3II/I, Beclin1, and ATG5 expression and increasing P62 expression. In the in vivo experiment, the transplanted BK- or 3-MA-treated hCPCs were found to be more effectively improved cardiac function by decreasing cardiomyocyte apoptosis, inflammatory infiltration, and myocardial fibrosis, and promoting neovascularization in the infarcted heart, compared to untreated-hCPCs or c-kit^- cardiomyocytes (CPC^- cells).

Conclusions

Our present study established a new method to rescue transplanted hCPCs in the infarcted cardiac area via regulating cell apoptosis and autophagy of hCPCs by pretreatment with BK, providing a new therapeutic option for heart failure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02503-6.

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.

The effects of membrane potential and extracellular matrix composition on vascular differentiation of cardiac progenitor cells

Historically, the field of tissue engineering has been adept at modulating the chemical and physical microenvironment. This approach has yielded significant progress, but it is imperative to further integrate our understanding of other fundamental cell signaling paradigms into tissue engineering methods. Bioelectric signaling has been demonstrated to be a vital part of tissue development, regeneration, and function across organ systems and the extracellular matrix is known to alter the bioelectric properties of cells. Thus, there is a need to bolster our understanding of how matrix and bioelectric signals interact to drive cell phenotype. We examine how cardiac progenitor cell differentiation is altered by simultaneous changes in both resting membrane potential and extracellular matrix composition. Pediatric c-kit⁺ cardiac progenitor cells were differentiated on fetal or adult cardiac extracellular matrix while being treated with drugs that alter resting membrane potential. Smooth muscle gene expression was increased with depolarization and decreased with hyperpolarization while endothelial and cardiac expression were unchanged. Early smooth muscle protein expression is modified by matrix developmental age, with fetal ECM appearing to amplify the effects of resting membrane potential. Thus, combining matrix composition and bioelectric signaling represents a potential alternative for guiding cell behavior in tissue engineering and regenerative medicine.

Functional Roles of the Ca2+-activated K+ Channel, KCa3.1, in Brain Tumors

BACKGROUND

Glioblastoma is the most aggressive and deadly brain tumor, with low disease-free period even after surgery and combined radio and chemotherapies. Among the factors contributing to the devastating effect of this tumor in the brain are the elevated proliferation and invasion rate, and the ability to induce a local immunosuppressive environment. The intermediateconductance Ca2+-activated K+ channel KCa3.1 is expressed in glioblastoma cells and in tumorinfiltrating cells.

METHODS

We first describe the researches related to the role of KCa3.1 channels in the invasion of brain tumor cells and the regulation of cell cycle. In the second part we review the involvement of KCa3.1 channel in tumor-associated microglia cell behaviour.

RESULTS

In tumor cells, the functional expression of KCa3.1 channels is important to substain cell invasion and proliferation. In tumor infiltrating cells, KCa3.1 channel activity is required to regulate their activation state. Interfering with KCa3.1 activity can be an adjuvant therapeutic approach in addition to classic chemotherapy and radiotherapy, to counteract tumor growth and prolong patient's survival.

CONCLUSION

In this mini-review we discuss the evidence of the functional roles of KCa3.1 channels in glioblastoma biology.

Cell Cycle Regulation by Ca2+-Activated K⁺ (BK) Channels Modulators in SH-SY5Y Neuroblastoma Cells

The effects of Ca²⁺-activated K⁺ (BK) channel modulation by Paxilline (PAX) (10⁻⁷–10⁻⁴ M), Iberiotoxin (IbTX) (0.1–1 × 10⁻⁶ M) and Resveratrol (RESV) (1–2 × 10⁻⁴ M) on cell cycle and proliferation, AKT1p^Ser473 phosphorylation, cell diameter, and BK currents were investigated in SH-SY5Y cells using Operetta-high-content-Imaging-System, ELISA-assay, impedentiometric counting method and patch-clamp technique, respectively. IbTX (4 × 10⁻⁷ M), PAX (5 × 10⁻⁵ M) and RESV (10⁻⁴ M) caused a maximal decrease of the outward K⁺ current at +30 mV (Vm) of −38.3 ± 10%, −31.9 ± 9% and −43 ± 8%, respectively, which was not reversible following washout and cell depolarization. After 6h of incubation, the drugs concentration dependently reduced proliferation. A maximal reduction of cell proliferation, respectively of −60 ± 8% for RESV (2 × 10⁻⁴ M) (IC50 = 1.50 × 10⁻⁴ M), −65 ± 6% for IbTX (10⁻⁶ M) (IC50 = 5 × 10⁻⁷ M), −97 ± 6% for PAX (1 × 10⁻⁴ M) (IC50 = 1.06 × 10⁻⁵ M) and AKT1p^ser473 dephosphorylation was observed. PAX induced a G1/G2 accumulation and contraction of the S-phase, reducing the nuclear area and cell diameter. IbTX induced G1 contraction and G2 accumulation reducing diameter. RESV induced G2 accumulation and S contraction reducing diameter. These drugs share common actions leading to a block of the surface membrane BK channels with cell depolarization and calcium influx, AKT1p^ser473 dephosphorylation by calcium-dependent phosphatase, accumulation in the G2 phase, and a reduction of diameter and proliferation. In addition, the PAX action against nuclear membrane BK channels potentiates its antiproliferative effects with early apoptosis.

Bradykinin-mediated Ca2+ signalling regulates cell growth and mobility in human cardiac c-Kit+ progenitor cells

Our recent study showed that bradykinin increases cell cycling progression and migration of human cardiac c‐Kit⁺ progenitor cells by activating pAkt and pERK1/2 signals. This study investigated whether bradykinin‐mediated Ca²⁺ signalling participates in regulating cellular functions in cultured human cardiac c‐Kit⁺ progenitor cells using laser scanning confocal microscopy and biochemical approaches. It was found that bradykinin increased cytosolic free Ca²⁺ (Cai2+) by triggering a transient Ca²⁺ release from ER IP3Rs followed by sustained Ca²⁺ influx through store‐operated Ca²⁺ entry (SOCE) channel. Blockade of B2 receptor with HOE140 or IP3Rs with araguspongin B or silencing IP3R3 with siRNA abolished both Ca²⁺ release and Ca²⁺ influx. It is interesting to note that the bradykinin‐induced cell cycle progression and migration were not observed in cells with siRNA‐silenced IP3R3 or the SOCE component TRPC1, Orai1 or STIM1. Also the bradykinin‐induced increase in pAkt and pERK1/2 as well as cyclin D1 was reduced in these cells. These results demonstrate for the first time that bradykinin‐mediated increase in free Cai2+ via ER‐IP3R3 Ca²⁺ release followed by Ca²⁺ influx through SOCE channel plays a crucial role in regulating cell growth and migration via activating pAkt, pERK1/2 and cyclin D1 in human cardiac c‐Kit⁺ progenitor cells.

Kir2.1 Interaction with Stk38 Promotes Invasion and Metastasis of Human Gastric Cancer by Enhancing MEKK2-MEK1/2-ERK1/2 Signaling

Potassium ion channels are emerging as promalignant factors involved in cancer progression. In this study, we found that invading human gastric cancer cells express high levels of inwardly rectifying potassium channel 2.1 (Kir2.1). Silencing Kir2.1 markedly reduced the invasive and metastatic capabilities as well as the epithelial-mesenchymal transition (EMT) of gastric cancer cells. The promalignant nature of Kir2.1 in gastric cancer cells was independent of potassium permeation but relied on its interaction with serine/threonine-protein kinase 38 (Stk38) to inhibit ubiquitination and degradation of mitogen-activated protein kinase kinase kinase 2 (MEKK2). Degradation of MEKK2 was mediated by small mothers against decapentaplegic-specific E3 ubiquitin protein ligase 1 (Smurf1), which resulted in activation of the MEK1/2-ERK1/2-Snail pathway in gastric cancer cells. In human gastric cancer tissues, expression was high and positively correlated with invasion depth and metastatic status of the tumors as well as poor overall patient survival. Cox regression analysis identified Kir2.1 as an independent prognostic indicator for patients with gastric cancer. Our results suggest that Kir2.1 is an important regulator of gastric cancer malignancy and acts as a novel prognostic marker and a therapeutic target for gastric cancer.Significance: Kir2.1 contributes to invasion and metastasis by a noncanonical ion permeation-independent signaling pathway and may act as a novel prognostic marker and therapeutic target for gastric cancer. Cancer Res; 78(11); 3041-53. ©2018 AACR.

Functional BKCa channel in human resident cardiac stem cells expressing W8B2

Recently, a new population of resident cardiac stem cells (CSCs) positive for the W8B2 marker has been identified. These CSCs are considered to be an ideal cellular source to repair myocardial damage after infarction. However, the electrophysiological profile of these cells has not been characterized yet. We first establish the conditions of isolation and expansion of W8B2⁺ CSCs from human heart biopsies using a magnetic sorting system followed by flow cytometry cell sorting. These cells display a spindle-shaped morphology, are highly proliferative, and possess self-renewal capacity demonstrated by their ability to form colonies. Besides, W8B2⁺ CSCs are positive for mesenchymal markers but negative for hematopoietic and endothelial ones. RT-qPCR and immunostaining experiments show that W8B2⁺ CSCs express some early cardiac-specific transcription factors but lack the expression of cardiac-specific structural genes. Using patch clamp in the whole-cell configuration, we show for the first time the electrophysiological signature of BKCa current in these cells. Accordingly, RT-PCR and western blotting analysis confirmed the presence of BKCa at both mRNA and protein levels in W8B2⁺ CSCs. Interestingly, BKCa channel inhibition by paxilline decreased cell proliferation in a concentration-dependent manner and halted cell cycle progression at the G0/G1 phase. The inhibition of BKCa also decreased the self-renewal capacity but did not affect migration of W8B2⁺ CSCs. Taken together, our results are consistent with an important role of BKCa channels in cell cycle progression and self-renewal in human cardiac stem cells.

Mesenchymal stem cell differentiation: Control by calcium-activated potassium channels

Mesenchymal stem cells (MSCs) are widely used in modern medicine for which understanding the mechanisms controlling their differentiation is fundamental. Ion channels offer novel insights to this process because of their role in modulating membrane potential and intracellular milieu. Here, we evaluate the contribution of calcium-activated potassium (K_Ca ) channels to the three main components of MSC differentiation: initiation, proliferation, and migration. First, we demonstrate the importance of the membrane potential (V_m ) and the apparent association of hyperpolarization with differentiation. Of K_Ca subtypes, most evidence points to activity of big-conductance channels in inducing initiation. On the other hand, intermediate-conductance currents have been shown to promote progression through the cell cycle. While there is no information on the role of K_Ca channels in migration of MSCs, work from other stem cells and cancer cells suggest that intermediate-conductance and to a lesser extent big-conductance channels drive migration. In all cases, these effects depend on species, tissue origin and lineage. Finally, we present a conceptual model that demonstrates how K_Ca activity could influence differentiation by regulating V_m and intracellular Ca²⁺ oscillations. We conclude that K_Ca channels have significant involvement in MSC differentiation and could potentially enable novel tissue engineering approaches and therapies.

Bradykinin regulates cell growth and migration in cultured human cardiac c-Kit+ progenitor cells

Bradykinin is a well-known endogenous vasoactive peptide. The present study investigated the bradykinin receptor expression in human cardiac c-Kit⁺ progenitor cells and the potential role of bradykinin in regulating cell cycling progression and mobility. It was found that mRNA and protein of bradykinin type 2 receptors, but not bradykinin type 1 receptors, were abundant in cultured human cardiac c-Kit⁺ progenitor cells. Bradykinin (1-10 nM) stimulated cell growth and migration in a concentration-dependent manner. The increase of cell proliferation was related to promoting G0/G1 transition into G2/M and S phase. Western blots revealed that bradykinin significantly increased pAkt and pERK1/2 as well as cyclin D1, which were countered by HOE140 (an antagonist of bradykinin type 2 receptors) or by silencing bradykinin type 2 receptors. The increase of pAkt, pERK1/2 and cyclin D1 by bradykinin was prevented by the PI3K inhibitor Ly294002, the PLC inhibitors U73122 and neomycin, and/or the PKC inhibitor chelerythrine and the MAPK inhibitor PD98059. Our results demonstrate the novel information that bradykinin promotes cell cycling progression and migration in human cardiac c-Kit⁺ progenitor cells via activating PI3K, PLC, PKC, cyclin D1, pERK1/2, and pAkt.

Functional TRPV2 and TRPV4 channels in human cardiac c-kit(+) progenitor cells

The cellular physiology and biology of human cardiac c-kit(+) progenitor cells has not been extensively characterized and remains an area of active research. This study investigates the functional expression of transient receptor potential vanilloid (TRPV) and possible roles for this ion channel in regulating proliferation and migration of human cardiac c-kit(+) progenitor cells. We found that genes coding for TRPV2 and TRPV4 channels and their proteins are significantly expressed in human c-kit(+) cardiac stem cells. Probenecid, an activator of TRPV2, induced an increase in intracellular Ca(2+) (Ca(2+) i ), an effect that may be attenuated or abolished by the TRPV2 blocker ruthenium red. The TRPV4 channel activator 4α-phorbol 12-13-dicaprinate induced Ca(2+) i oscillations, which can be inhibited by the TRPV4 blocker RN-1734. The alteration of Ca(2+) i by probenecid or 4α-phorbol 12-13-dicprinate was dramatically inhibited in cells infected with TRPV2 short hairpin RNA (shRNA) or TRPV4 shRNA. Silencing TRPV2, but not TRPV4, significantly reduced cell proliferation by arresting cells at the G0/G1 boundary of the cell cycle. Cell migration was reduced by silencing TRPV2 or TRPV4. Western blot revealed that silencing TRPV2 decreased expression of cyclin D1, cyclin E, pERK1/2 and pAkt, whereas silencing TRPV4 only reduced pAkt expression. Our results demonstrate for the first time that functional TRPV2 and TRPV4 channels are abundantly expressed in human cardiac c-kit(+) progenitor cells. TRPV2 channels, but not TRPV4 channels, participate in regulating cell cycle progression; moreover, both TRPV2 and TRPV4 are involved in migration of human cardiac c-kit(+) progenitor cells.