ClC-3 deficiency prevents apoptosis induced by angiotensin II in endothelial progenitor cells via inhibition of NADPH oxidase

Marine Compound Exerts Antiaging Effect in Human Endothelial Progenitor Cells via Increasing Sirtuin1 Expression

Aging is associated with an increased risk of cardiovascular disease. Previous studies have demonstrated that compound 3 (C3), a derivative of marine compound xyloallenoide A isolated from the mangrove fungus Xylaria sp. (no. 2508), exhibited strong angiogenic activities in zebrafish. In this study, we examined the effects of C3 on the senescence of endothelial progenitor cells isolated from human peripheral blood (hEPCs). The results showed that treatment with angiotensin II (AngII) for 24 h induced hEPC senescence, as demonstrated by increased SA-β-galactosidase staining. Moreover, there is a significant decrease in telomerase activity and cellular viability in AngII-treated hEPCs. These changes in aging hEPCs were greatly recovered by C3 in a dose-dependent manner. Furthermore, C3 significantly restored the AngII-induced decrease of sirtuin type 1 (SIRT1) expression, a well-known antiaging protein. In addition, AngII increased AMP-activated protein kinase (AMPK) phosphorylation and reduced Akt phosphorylation in aging hEPCs, which were also reversed by C3. Importantly, the inhibition of C3 on hEPC senescence and AMPK/Akt dysregulation was significantly attenuated by the SIRT1-specific inhibitor nicotinoyl. These results indicated that C3 protects hEPC against AngII-induced senescence by increasing SIRT1 expression levels and balancing the AMPK/Akt signaling pathway. The inhibition of hEPCs senescence by C3 might protect EPCs against dysfunction induced by pathological factors in the elderly population. C3 may provide a novel drug candidate for the treatment of aging-related disorders.

Angiotensin-(1-7) ameliorates high glucose-induced vascular endothelial injury through suppressing chloride channel 3

Diabetes Mellitus (DM) is a significant risk factor for cardiovascular disease (CVD), which is leading cause of deaths in DM patients. However, there are limited effective medical therapies for diabetic CVD. Vascular endothelial injury caused by DM is a critical risk factor for diabetic CVD. Previous study has indicated that Angiotensin-(1-7) (Ang-(1-7)) may prevent diabetic CVD, whereas it is not clear that Ang-(1-7) whether attenuates diabetic CVD through suppressing vascular endothelial injury. In this study, we found that Ang-(1-7) alleviated high glucose (HG)-induced endothelial injury in bEnd3 cells. Moreover, Ang-(1-7) ameliorated HG-induced endothelial injury through downregulating chloride channel 3 (CIC-3) via Mas receptor. Furthermore, HG-induced CIC-3 enhanced reactive oxygen species (ROS) and cytokine production and reduced the level of nitric oxide (NO), while Ang-(1-7) preserved the impact of HG-induced CIC-3 on productions of ROS, cytokine and NO through inhibiting CIC-3 via Mas receptor. Summarily, the present study revealed that Ang-(1-7) alleviated HG-induced vascular endothelial injury through the inhibition of CIC-3, suggested that Ang-(1-7) may preserve diabetic CVD through suppressing HG-induced vascular endothelial injury.

Acute exposure to gold nanoparticles aggravates lipopolysaccharide-induced liver injury by amplifying apoptosis via ROS-mediated macrophage-hepatocyte crosstalk

Background

Gold nanoparticles (AuNPs) are increasingly utilized in industrial and biomedical fields, thereby demanding a more comprehensive knowledge about their safety. Current toxicological studies mainly focus on the unfavorable biological impact governed by the physicochemical properties of AuNPs, yet the consequences of their interplay with other bioactive compounds in biological systems are poorly understood.

Results

In this study, AuNPs with a size of 10 nm, the most favorable size for interaction with host cells, were given alone or in combination with bacterial lipopolysaccharide (LPS) in mice or cultured hepatic cells. The results demonstrated that co exposure to AuNPs and LPS exacerbated fatal acute liver injury (ALI) in mice, although AuNPs are apparently non-toxic when administered alone. AuNPs do not enhance systemic or hepatic inflammation but synergize with LPS to upregulate hepatic apoptosis by augmenting macrophage-hepatocyte crosstalk. Mechanistically, AuNPs and LPS coordinate to upregulate NADPH oxidase 2 (NOX2)-dependent reactive oxygen species (ROS) generation and activate the intrinsic apoptotic pathway in hepatic macrophages. Extracellular ROS generation from macrophages is then augmented, thereby inducing calcium-dependent ROS generation and promoting apoptosis in hepatocytes. Furthermore, AuNPs and LPS upregulate scavenger receptor A expression in macrophages and thus increase AuNP uptake to mediate further apoptosis induction.

Conclusions

This study reveals a profound impact of AuNPs in aggravating the hepatotoxic effect of LPS by amplifying ROS-dependent crosstalk in hepatic macrophages and hepatocytes.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01203-w.

ClC-3: A Novel Promising Therapeutic Target for Atherosclerosis

Chloride channel 3 (ClC-3), a Cl^-/H⁺ antiporter, has been well established as a member of volume-regulated chloride channels (VRCCs). ClC-3 may be a crucial mediator for activating inflammation-associated signaling pathways by regulating protein phosphorylation. A growing number of studies have indicated that ClC-3 overexpression plays a crucial role in mediating increased plasma low-density lipoprotein levels, vascular endothelium dysfunction, pro-inflammatory activation of macrophages, hyper-proliferation and hyper-migration of vascular smooth muscle cells (VSMCs), as well as oxidative stress and foam cell formation, which are the main factors responsible for atherosclerotic plaque formation in the arterial wall. In the present review, we summarize the molecular structures and classical functions of ClC-3. We further discuss its emerging role in the atherosclerotic process. In conclusion, we explore the potential role of ClC-3 as a therapeutic target for atherosclerosis.

Protective effect of recombinant Lactobacillus plantarum against H2O2-induced oxidative stress in HUVEC cells

This study probed the protective effect of recombinant Lactobacillus plantarum against hydrogen peroxide (H₂O₂)-induced oxidative stress in human umbilical vein endothelial cells (HUVECs). We constructed a new functional L. plantarum (NC8-pSIP409-alr-angiotensin-converting enzyme inhibitory peptide (ACEIP)) with a double-gene-labeled non-resistant screen as an expression vector. A 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) colorimetric assay was carried out to determine the cell viability of HUVEC cells following pretreatment with NC8-pSIP409-alr-ACEIP. Flow cytometry (FCM) was used to determine the apoptosis rate of HUVEC cells. Cysteinyl aspartate specific proteinase (caspase)-3/8/9 activity was also assayed and western blotting was used to determine protein expression of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), inducible nitric oxide synthase (iNOS), nicotinamide adenine dinucleotide phosphate oxidase 2 (gp91phox), angiotensin II (AngII), and angiotensin-converting enzyme 2 (ACE2), as well as corresponding indicators of oxidative stress, such as reactive oxygen species (ROS), mitochondrial membrane potential (MMP), malondialdehyde (MDA), and superoxide dismutase (SOD). NC8-pSIP409-alr-ACEIP attenuated H₂O₂-induced cell death, as determined by the MTT assay. NC8-pSIP409-alr-ACEIP reduced apoptosis of HUVEC cells by FCM. In addition, compared to the positive control, the oxidative stress index of the H₂O₂-induced HUVEC (Hy-HUVEC), which was pretreated by NC8-pSIP409-alr-ACEIP, iNOS, gp91phox, MDA, and ROS, was decreased obviously; SOD expression level was increased; caspase-3 or -9 was decreased, but caspase-8 did not change; Bcl-2/Bax ratio was increased; permeability changes of mitochondria were inhibited; and loss of transmembrane potential was prevented. Expression of the hypertension-related protein (AngII protein) in HUVEC cells protected by NC8-pSIP409-alr-ACEIP decreased and expression of ACE2 protein increased. These plantarum results suggested that NC8-pSIP409-alr-ACEIP protects against H₂O₂-induced injury in HUVEC cells. The mechanism for this effect is related to enhancement of antioxidant capacity and apoptosis.

Soluble (pro)renin receptor induces endothelial dysfunction and hypertension in mice with diet-induced obesity via activation of angiotensin II type 1 receptor

Until now, renin-angiotensin system (RAS) hyperactivity was largely thought to result from angiotensin II (Ang II)-dependent stimulation of the Ang II type 1 receptor (AT1R). Here we assessed the role of soluble (pro)renin receptor (sPRR), a product of site-1 protease-mediated cleavage of (pro)renin receptor (PRR), as a possible ligand of the AT1R in mediating: (i) endothelial cell dysfunction in vitro and (ii) arterial dysfunction in mice with diet-induced obesity. Primary human umbilical vein endothelial cells (HUVECs) treated with a recombinant histidine-tagged sPRR (sPRR-His) exhibited IκBα degradation concurrent with NF-κB p65 activation. These responses were secondary to sPRR-His evoked elevations in Nox4-derived H2O2 production that resulted in inflammation, apoptosis and reduced NO production. Each of these sPRR-His-evoked responses was attenuated by AT1R inhibition using Losartan (Los) but not ACE inhibition using captopril (Cap). Further mechanistic exploration revealed that sPRR-His activated AT1R downstream Gq signaling pathway. Immunoprecipitation coupled with autoradiography experiments and radioactive ligand competitive binding assays indicate sPRR directly interacts with AT1R via Lysine199 and Asparagine295. Important translational relevance was provided by findings from obese C57/BL6 mice that sPRR-His evoked endothelial dysfunction was sensitive to Los. Besides, sPRR-His elevated blood pressure in obese C57/BL6 mice, an effect that was reversed by concurrent treatment with Los but not Cap. Collectively, we provide solid evidence that the AT1R mediates the functions of sPRR during obesity-related hypertension. Inhibiting sPRR signaling should be considered further as a potential therapeutic intervention in the treatment and prevention of cardiovascular disorders involving elevated blood pressure.

Sesn2 attenuates the damage of endothelial progenitor cells induced by angiotensin II through regulating the Keap1/Nrf2 signal pathway

Endothelial progenitor cell (EPC) dysfunction is an important physiopathological mechanism in the dynamics of the formation of atherosclerosis. It has been reported that angiotensin II (Ang-II) damages the function of EPCs in atherosclerotic plaque through induction of oxidative stress. Sestrin 2 (Sesn2) serves as an antioxidant role in oxidative stress, however, the exact mechanisms underlying the dynamics of how Sesn2 may factor into EPCs after Ang-II treatments needs to be illustrated. We isolated EPCs from human umbilical cord blood samples and treated with Ang-II. Western blotting, qRT-PCR, transwell assays, immunofluorescence and so on were used to investigate the mechanisms underlying the roles of Sesn2 in EPCs treated with Ang-II. Ang-II was found to promote the apoptosis of EPCs as well as inhibited the mRNA and protein expression of Sesn2. Upregulation of Sesn2 attenuated the negative effect of Ang-II. Sesn2 increased the protein expression of Nrf2 by enhancing P62-dependent autophagy. Silencing of Nrf2 enhanced the degree of apoptosis of EPCs as well as resulted in the impairment of EPC functions through inducing the promotion of (reactive oxygen species) ROS production. Our study results indicated that Sesn2 facilitated the viability of EPCs After treatment with Ang-II, as well as provided a potential therapeutic target to alleviate the progression of atherosclerosis.

Long Non-coding RNA MEG3 Attenuates the Angiotensin II-Induced Injury of Human Umbilical Vein Endothelial Cells by Interacting With p53

Angiotensin II (Ang II)-induced damage to endothelial cells (ECs) plays a crucial role in the pathogenesis of cardiovascular disease. This study aimed to investigate the role of maternally expressed gene 3 (Meg3) in endothelial cell injury. A lncRNA human gene expression microarray analysis was used to identify differentially expressed lncRNAs in human umbilical vein endothelial cell (HUVECs). Cell viability, apoptosis, and migration were then assessed Ang II-treated HUVECs. qRT-PCR and western blotting were performed to detect the expression level of p53 after Meg3 knockdown and overexpression. We observed that Ang II treatment decreased the Meg3 level in HUVECs. Next, both knockdown of Meg3 and Ang II decreased cell viability, increased apoptotic cell rate and impair migration function in HUVECs. Furthermore, overexpression of Meg3 inhibited cell apoptosis, and increased cell migration by enhancing p53 transcription on its target genes, including CRP, ICAM-1, VEGF, and HIF-1α. Our findings indicate that Meg3 might be associated with cardiovascular disease development.

LRRC8A potentiates temozolomide sensitivity in glioma cells via activating mitochondria-dependent apoptotic pathway

Chloride (Cl^-), a primary anion in the extracellular fluid, plays an important role in a variety of physiological and pathological processes, such as cell apoptosis and proliferation. However, the information about Cl^- in cancer cell apoptosis and chemoresistance is poorly understood. In the present study, we found that temozolomide (TMZ) treatment led to a decrease in intracellular concentration of Cl^- ([Cl^-]_i) in both U87 and TMZ-resistant U87/R glioma cells. The decrease in [Cl^-]_i was more noticeable in U87 cells than in U87/R cells. Moreover, the expression of LRRC8A was reduced in U87/R cells compared with U87 cells. LRRC8A downregulation inhibited TMZ, induced the decrease in [Cl^-]_i and abolished the difference of [Cl^-]_i between U87 cells and U87/R cells. Knockdown of LRRC8A using small interfering RNA attenuated TMZ-induced U87 cell growth inhibition and apoptosis, while overexpression of LRRC8A by adenoviral infection enhanced the effect of TMZ on U87 and U87/R cell viability and apoptosis. Furthermore, LRRC8A downregulation inhibited TMZ-induced mitochondria-dependent apoptosis, including elevated Bcl-2 expression, reduced Bax expression, cytochrome c release, and caspase nine and caspase three activation. On the contrary, upregulation of LRRC8A augmented the activation of mitochondria-dependent apoptotic pathway in U87 and U87/R cells. In conclusion, this study demonstrates that LRRC8A potentiates TMZ-induced glioma cell apoptosis via promoting mitochondria-dependent apoptosis, suggesting that LRRC8A can be represented as a novel target for drug resistance treatment in glioma cells.

ClC-3 promotes angiotensin II-induced reactive oxygen species production in endothelial cells by facilitating Nox2 NADPH oxidase complex formation

Recent evidence suggests that ClC-3, a member of the ClC family of Cl^- channels or Cl^-/H⁺ antiporters, plays a critical role in NADPH oxidase-derived reactive oxygen species (ROS) generation. However, the underling mechanisms remain unclear. In this study we investigated the effects and mechanisms of ClC-3 on NADPH oxidase activation and ROS generation in endothelial cells. Treatment with angiotensin II (Ang II, 1 μmol/L) significantly elevated ClC-3 expression in cultured human umbilical vein endothelial cells (HUVECs). Furthermore, Ang II treatment increased ROS production and NADPH oxidase activity, an effect that could be significantly inhibited by knockdown of ClC-3, and further enhanced by overexpression of ClC-3. SA-β-galactosidase staining showed that ClC-3 silencing abolished Ang II-induced HUVEC senescence, whereas ClC-3 overexpression caused the opposite effects. We further showed that Ang II treatment increased the translocation of p47phox and p67phox from the cytosol to membrane, accompanied by elevated Nox2 and p22phox expression, which was significantly attenuated by knockdown of ClC-3 and potentiated by overexpression of ClC-3. Moreover, overexpression of ClC-3 increased Ang II-induced phosphorylation of p47phox and p38 MAPK in HUVECs. Pretreatment with a p38 inhibitor SB203580 abolished ClC-3 overexpression-induced increase in p47phox phosphorylation, as well as NADPH oxidase activity and ROS generation. Our results demonstrate that ClC-3 acts as a positive regulator of Ang II-induced NADPH oxidase activation and ROS production in endothelial cells, possibly via promoting both Nox2/p22phox expression and p38 MAPK-dependent p47phox/p67phox membrane translocation, then increasing Nox2 NADPH oxidase complex formation.

Opening of the CLC-3 chloride channel induced by dihydroartemisinin contributed to early apoptotic events in human poorly differentiated nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is a specific type of head and neck cancer that is prevalent in Southeast Asia. Dihydroartemisinin (DHA), a semisynthetic derivative of artemisinin, has specific anticancer activity. Here, we aimed to investigate the role of the CLC-3 chloride channel in the anticancer effect of DHA in poorly differentiated NPC CNE-2Z cells. First, we observed that DHA could specifically inhibit the proliferation, induce apoptosis, and increase cleaved caspase-3 expression in the CNE-2Z cells. Then, we found that DHA could activate chloride channels, which led to Cl^- efflux and apoptotic volume decrease (AVD) in the early stage in the CNE-2Z cells. DHA also specifically increased CLC-3 chloride channel protein expression in the CNE-2Z cells. Silencing of the CLC-3 protein expression depleted the Cl^- currents, and decreased the AVD capacity and cell apoptosis induced by DHA. Finally, we revealed that the [Ca²⁺ ]_i increased after around 6 hours of treatment with DHA, which was also inhibited by silencing of the CLC-3 protein expression. Our data demonstrated that the selective antitumor activities of DHA in NPC may occur through the specific activation of the CLC-3 Cl^- channel, leading to Cl^- efflux, and induced AVD, then led to [Ca²⁺ ]_i accumulation and caspase-3 activation, and finally induced apoptosis. The activation of the CLC-3 chloride channel played an essential and proximal upstream role in the antitumor activities of DHA.

Molecular Identities and ATP Release Activities of Two Types of Volume-Regulatory Anion Channels, VSOR and Maxi-Cl

An elaborate volume regulation system based on interplay of ion channels and transporters was evolved to cope with constant osmotic challenges caused by intensive metabolism, transport and other physiological/pathophysiological events. In animal cells, two types of anion channels are directly activated by cell swelling and involved in the regulatory volume decrease (RVD): volume-sensitive outwardly rectifying anion channel (VSOR), also called volume-regulated anion channel (VRAC), and Maxi-Cl which is the most major type of maxi-anion channel (MAC). These two channels have very different biophysical profiles and exhibit opposite dependence on intracellular ATP. After several decades of verifying many false-positive candidates for VSOR and Maxi-Cl, LRRC8 family proteins emerged as major VSOR components, and SLCO2A1 protein as a core of Maxi-Cl. Still, neither of these proteins alone can fully reproduce the native channel phenotypes suggesting existence of missing components. Although both VSOR and Maxi-Cl have pores wide enough to accommodate bulky ATP^4- and MgATP^2- anions, evidence accumulated hitherto, based on pharmacological and gene silencing experiments, suggests that Maxi-Cl, but not VSOR, serves as one of the major pathways for the release of ATP from swollen and ischemic/hypoxic cells. Relations of VSOR and Maxi-Cl with diseases and their selective pharmacology are the topics promoted by recent advance in molecular identification of the two volume-activated, volume-regulatory anion channels.

ClC-2 knockdown prevents cerebrovascular remodeling via inhibition of the Wnt/β-catenin signaling pathway

BACKGROUND

Mishandling of intracellular chloride (Cl-) concentration ([Cl-]i) in cerebrovascular smooth muscle cells is implicated in several pathological processes, including hyperplasia and remodeling. We investigated the effects of ClC-2-mediated Cl- efflux on the proliferation of human brain vascular smooth muscle cells (HBVSMCs) induced by angiotensin II (AngII).

METHODS

Cell proliferation and motility were determined using the CCK-8, bromodeoxyuridine staining, wound healing and invasion assays. ClC-2, PCNA, Ki67, survivin and cyclin D1 expression, and β-catenin and GSK-3β phosphorylation were examined using western blotting. Histological analyses were performed using hematoxylin and eosin staining and α-SMA staining.

RESULTS

Our results showed that AngII-induced HBVSMC proliferation was accompanied by a decrease in [Cl-]i and an increase in ClC-2 expression. Inhibition of ClC-2 by siRNA prevented AngII from inducing the efflux of Cl-. AngII-induced HBVSMC proliferation, migration and invasion were significantly attenuated by ClC-2 downregulation. The inhibitory effects of ClC-2 knockout on HBVSMC proliferation and motility were associated with inactivation of the Wnt/β-catenin signaling pathway, as evidenced by inhibition of β-catenin phosphorylation and nuclear translocation, and decrease of GSK-3β phosphorylation and survivin and cyclin D1 expression. Recombinant Wnt3a treatment markedly reversed the effect of ClC-2 knockdown on HBVSMC viability. An in vivo study revealed that knockdown of ClC-2 with shRNA adenovirus ameliorated basilar artery remodeling by inhibiting Wnt/β-catenin signaling in AngII-treated mice.

CONCLUSION

This study demonstrates that blocking ClC-2-mediated Cl- efflux inhibits AngII-induced cerebrovascular smooth muscle cell proliferation and migration by inhibiting the Wnt/β-catenin pathway. Our data indicate that downregulation of ClC-2 may be a viable strategy in the prevention of hyperplasia and remodeling of cerebrovascular smooth muscle cells.

Epigallocatechin-3-Gallate Ameliorates Angiotensin II-Induced Oxidative Stress and Apoptosis in Human Umbilical Vein Endothelial Cells through the Activation of Nrf2/Caspase-3 Signaling

INTRODUCTION

This study aimed to investigate whether epigallocatechin-3-gallate (EGCG) shows antioxidant activity against angiotensin II (Ang II)-induced human umbilical vein endothelial cell (HUVEC) apoptosis.

MATERIALS AND METHODS

The viability of HUVECs was revealed by MTT and LDH assay. The cell apoptosis was detected by FITC-PI assay. A fluorescent probe assay was used to measure the reactive oxygen species (ROS) generation in HUVECs. Mitochondrial permeability transition pore (MPTP) opening, mitochondrial membrane potential, and caspase-3, -4, -8, -9 activities were also measured.

RESULTS

We found that Ang II treatment increased the generation of ROS, enhanced MPTP opening and cytochrome c release, activated caspase-3/9, and consequently induced HUVEC apoptosis. EGCG treatment-suppressed Ang II induces the oxidative stress of HUVECs and mitochondria-related cell apoptosis. We also showed that the antioxidant activity pathway, including cytochrome c release, MPTP opening, and caspase-3/9 activation, is a key endogenous defensive system in HUVECs, provoking Ang II exposure. Our study revealed that increased expression of Nrf2 by EGCG could partially repress Ang II-induced injury effects.

CONCLUSIONS

All of our findings indicated that EGCG treatment provides a protective effect for Ang II-induced HUVEC apoptosis by decreasing oxidative stress and ameliorating mitochondrial injury.

ClC Channels and Transporters: Structure, Physiological Functions, and Implications in Human Chloride Channelopathies

The discovery of ClC proteins at the beginning of the 1990s was important for the development of the Cl^- transport research field. ClCs form a large family of proteins that mediate voltage-dependent transport of Cl^- ions across cell membranes. They are expressed in both plasma and intracellular membranes of cells from almost all living organisms. ClC proteins form transmembrane dimers, in which each monomer displays independent ion conductance. Eukaryotic members also possess a large cytoplasmic domain containing two CBS domains, which are involved in transport modulation. ClC proteins function as either Cl^- channels or Cl^-/H⁺ exchangers, although all ClC proteins share the same basic architecture. ClC channels have two gating mechanisms: a relatively well-studied fast gating mechanism, and a slow gating mechanism, which is poorly defined. ClCs are involved in a wide range of physiological processes, including regulation of resting membrane potential in skeletal muscle, facilitation of transepithelial Cl^- reabsorption in kidneys, and control of pH and Cl^- concentration in intracellular compartments through coupled Cl^-/H⁺ exchange mechanisms. Several inherited diseases result from C1C gene mutations, including myotonia congenita, Bartter's syndrome (types 3 and 4), Dent's disease, osteopetrosis, retinal degeneration, and lysosomal storage diseases. This review summarizes general features, known or suspected, of ClC structure, gating and physiological functions. We also discuss biophysical properties of mammalian ClCs that are directly involved in the pathophysiology of several human inherited disorders, or that induce interesting phenotypes in animal models.

Angiotensin II degrades myeloid cell leukemia 1 in human umbilical vein endothelial cells

Angiotensin II (Ang II) plays a central role in cardiovascular diseases by causing endothelial apoptosis and dysfunction. Myeloid cell leukemia 1 (Mcl-1) is an antiapoptotic member of the Bcl-2 family of apoptosis-regulating proteins. It has been reported that Mcl-1 plays a pivotal role in protecting cells against apoptosis. Presently, the effects of Ang II on the expression of Mcl-1 remain unknown. In this study, we report, for the first time, that the antiapoptotic protein Mcl-1 is degraded by the proteasome during Ang II-induced apoptosis in HUVECs. Notably, our results demonstrate that prior phosphorylation by GSK-3β is required for proteasomal degradation of Mcl-1. Notably, the reduced level of Mcl-1 was abolished by a specific GSK-3β inhibitor, suggesting that the phosphorylation of Mcl-1 by GSK-3β is required for proteasomal degradation of Mcl-1. Overexpression of Mcl-1 rescued apoptosis induced by Ang II, however, knockdown of Mcl-1 exacerbated Ang II-induced apoptosis, thereby indicating that the protein level of Mcl-1 determines the response of endothelial cells to this drug. © 2017 IUBMB Life, 69(5):321-327, 2017.

SodC modulates ras and PKB signaling in Dictyostelium

We have previously reported that the basal RasG activity is aberrantly high in cells lacking Superoxide dismutase C (SodC). Here we report that other Ras proteins such as RasC and RasD activities are not affected in sodC^- cells and mutagenesis studies showed that the presence of the Cys¹¹⁸ in the Ras proteins is essential for the superoxide-mediated activation of Ras proteins in Dictyostelium. In addition to the loss of SodC, lack of extracellular magnesium ions increased the level of intracellular superoxide and active RasG proteins. Aberrantly active Ras proteins in sodC^- cells persistently localized at the plasma membrane, but those in wild type cells under magnesium deficient medium exhibited intracellular vesicular localization. Interestingly, the aberrantly activated Ras proteins in wild type cells were largely insulated from their normal downstream events such as Phosphatidylinositol-3,4,5-P₃ (PIP3) accumulation, Protein Kinase B (PKB) activation, and PKBs substrates phosphorylation. Intriguingly, however, aberrantly activated Ras proteins in sodC^- cells were still engaged in signaling to their downstream targets, and thus excessive PKBs substrates phosphorylation persisted. In summary, we suggest that SodC and RasG proteins are essential part of a novel inhibitory mechanism that discourages oxidatively stressed cells from chemotaxis and thus inhibits the delivery of potentially damaged genome to the next generation.

Ion channels in regulated cell death

Activation of ion channels and pores are essential steps during regulated cell death. Channels and pores participate in execution of apoptosis, necroptosis and other forms of caspase-independent cell death. Within the program of regulated cell death, these channels are strategically located. Ion channels can shrink cells and drive them towards apoptosis, resulting in silent, i.e. immunologically unrecognized cell death. Alternatively, activation of channels can induce cell swelling, disintegration of the cell membrane, and highly immunogenic necrotic cell death. The underlying cell death pathways are not strictly separated as identical stimuli may induce cell shrinkage and apoptosis when applied at low strength, but may also cause cell swelling at pronounced stimulation, resulting in regulated necrosis. Nevertheless, the precise role of ion channels during regulated cell death is far from being understood, as identical channels may support regulated death in some cell types, but may cause cell proliferation, cancer development, and metastasis in others. Along this line, the phospholipid scramblase and Cl(-)/nonselective channel anoctamin 6 (ANO6) shows interesting features, as it participates in apoptotic cell death during lower levels of activation, thereby inducing cell shrinkage. At strong activation, e.g. by stimulation of purinergic P2Y7 receptors, it participates in pore formation, causes massive membrane blebbing, cell swelling, and membrane disintegration. The LRRC8 proteins deserve much attention as they were found to have a major role in volume regulation, apoptotic cell shrinkage and resistance towards anticancer drugs.

ROS and intracellular ion channels

Oxidative stress is a well-known driver of numerous pathological processes involving protein and lipid peroxidation and DNA damage. The resulting increase of pro-apoptotic pressure drives tissue damage in a host of conditions, including ischemic stroke and reperfusion injury, diabetes, death in acute pancreatitis and neurodegenerative diseases. Somewhat less frequently discussed, but arguably as important, is the signaling function of oxidative stress stemming from the ability of oxidative stress to modulate ion channel activity. The evidence for the modulation of the intracellular ion channels and transporters by oxidative stress is constantly emerging and such evidence suggests new regulatory and pathological circuits that can be explored towards new treatments for diseases in which oxidative stress is an issue. In this review we summarize the current knowledge on the effects of oxidative stress on the intracellular ion channels and transporters and their role in cell function.

P120 catenin attenuates the angiotensin II-induced apoptosis of human umbilical vein endothelial cells by suppressing the mitochondrial pathway

Hypertension Hypertension impairs the morphological and functional integrity of circulation. Previous research has shown that the loss of endothelial cells (ECs) is a common event in many cardiovascular diseases. p120 catenin (p120ctn) plays an important role in the regulation of inflammatory responses in ECs. However, the functional significance of p120ctn in angiotensin II (AngII)-induced apoptosis of human umbilical vein endothelial cells (HUVECs) had not previously received much scholarly attention. In the present study, using western blot analysis and RT-PCR, we found that AngII-induced cell apoptosis was correlated with a significant decrease in p120ctn expression. The effect of AngII on cell viability was measured by CCK-8 assay. Knockdown of p120ctn with small hairpin RNA (shRNA) increased AngII-induced apoptosis of HUVECs, as demonstrated by Annexin V/PI staining and flow cytometric analysis. Knockdown of p120ctn with shRNA also increased cytochrome c release into the cytoplasm, and cleaved caspase-3 and -9 protein expression. These were accompanied by a decrease in the Bcl-2/Bax ratio (Bcl-2 and Bax protein expression were measured by western blot analysis), and in mitochondrial membrane potential, as measured using JC-1. Overexpression of p120ctn with adenovirus produced opposite effects. In the present study, we demonstrated that p120ctn attenuated AngII-induced apoptosis of HUVECs through the mitochondria-dependent pathway, suggesting that p120ctn plays a critical role in protecting ECs against apoptosis during hypertension.

Angiotensin II triggers apoptosis via enhancement of NADPH oxidase-dependent oxidative stress in a dopaminergic neuronal cell line

Numerous studies reveal that Angiotensin II (Ang II), the main effector of renin-angiotensin system, contributes to the pathogenesis of Parkinson's disease (PD) via triggering dopaminergic cell loss. However, the underlying mechanisms remain largely unclear. In the current study, by using CATH.a cell, a dopaminergic neuronal cell line stably expressing Angiotensin II type 1 receptor (AT1R) and Angiotensin II type 2 receptor (AT2R), we showed that Ang II treatment triggered cell apoptosis in a dose-dependent manner, providing the first evidence that apoptotic cell death contributed to the dopaminergic cell loss induced by Ang II. Ang II treatment also led to a significant increment in intracellular reactive oxygen species generation, which could be fully abolished by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors apocynin or diphenylene iodonium, indicating that Ang II enhanced oxidative stress via a NADPH oxidase-dependent manner. More importantly, inhibition of oxidative stress by NADPH oxidase inhibitors partially attenuated cell apoptosis caused by Ang II, implying that the enhancement of NADPH oxidase-dependent oxidative stress contributed to the cell apoptosis triggered by Ang II. Furthermore, the Ang II-induced oxidative stress and subsequent apoptosis could be completely abolished by AT1R blocker losartan rather than AT2R blocker PD1223319, suggesting that the aforementioned detrimental effects of Ang II are mediated by AT1R. In summary, these findings have deepened our understanding on the role of Ang II in PD pathogenesis, and support the use of AT1R blockers in the treatment of this devastating disease.