Inhibition of the INa/K and the activation of peak INa contribute to the arrhythmogenic effects of aconitine and mesaconitine in guinea pigs.

Aconitine (ACO), a main active ingredient of Aconitum, is well-known for its cardiotoxicity. However, the mechanisms of toxic action of ACO remain unclear. In the current study, we investigated the cardiac effects of ACO and mesaconitine (MACO), a structurally related analog of ACO identified in Aconitum with undocumented cardiotoxicity in guinea pigs. We showed that intravenous administration of ACO or MACO (25 µg/kg) to guinea pigs caused various types of arrhythmias in electrocardiogram (ECG) recording, including ventricular premature beats (VPB), atrioventricular blockade (AVB), ventricular tachycardia (VT), and ventricular fibrillation (VF). MACO displayed more potent arrhythmogenic effect than ACO. We conducted whole-cell patch-clamp recording in isolated guinea pig ventricular myocytes, and observed that treatment with ACO (0.3, 3 µM) or MACO (0.1, 0.3 µM) depolarized the resting membrane potential (RMP) and reduced the action potential amplitude (APA) and durations (APDs) in a concentration-dependent manner. The ACO- and MACO-induced AP remodeling was largely abolished by an INa blocker tetrodotoxin (2 µM) and partly abolished by a specific Na+/K+ pump (NKP) blocker ouabain (0.1 µM). Furthermore, we observed that treatment with ACO or MACO attenuated NKP current (INa/K) and increased peak INa by accelerating the sodium channel activation with the EC50 of 8.36 ± 1.89 and 1.33 ± 0.16 µM, respectively. Incubation of ventricular myocytes with ACO or MACO concentration-dependently increased intracellular Na+ and Ca2+ concentrations. In conclusion, the current study demonstrates strong arrhythmogenic effects of ACO and MACO resulted from increasing the peak INa via accelerating sodium channel activation and inhibiting the INa/K. These results may help to improve our understanding of cardiotoxic mechanisms of ACO and MACO, and identify potential novel therapeutic targets for Aconitum poisoning.

Genome-wide association study of growth and reproductive traits based on low-coverage whole-genome sequencing in a Chubao black-head goat population.

The Chubao black-head goat is a novel hybrid breed that combines the advantages of Macheng black goats, such as good reproductive performance, strong adaptability, and resistance to rough feeding, with the superior growth and meat characteristics of Boer goats. Given the substantial economic importance of growth (such as birth weight, body height, body length, and chest circumference across different growth stages) and reproductive traits (particularly average litter size after first parity), the aim of this study was to identify significant SNPs and candidate genes associated with these traits in Chubao black-head goats. Through whole-genome sequencing (with 34 goats at approximately 15× coverage and 466 goats at approximately 1× coverage), genotype imputation, and quality control, 22,665,331 SNPs were identified and subsequently used for genetic analyses. Heritability estimates indicated that growth traits exhibit moderate to high heritability (ranging from 0.297 ± 0.071 to 0.535 ± 0.118), while reproductive traits demonstrated low to moderate heritability (with a value of 0.220 ± 0.108). By performing FarmCPU-based genome-wide association studies, we identified 48 potentially significant SNPs associated with growth traits and 7 with reproductive traits. Additionally, 85 candidate genes (such as COL14A1, ZNF148, and TTC39C) linked to growth traits were identified and enriched in pathways associated with fundamental molecular biological activities such as protein deubiquitination, regulation of mRNA stability, and the MAPK signaling pathway. Furthermore, 10 candidate genes (such as SOHLH2, CCNA2, and SOX7) associated with reproductive traits were identified and enriched in pathways related to specific reproductive processes such as oocyte differentiation, endoderm formation, and progesterone-mediated oocyte maturation. Overall, these findings provide valuable preliminary insights into the molecular mechanisms underlying growth and reproductive traits in Chubao black-head goats. However, further functional validation is needed to effectively use these potential SNPs and candidate genes in improving the breeding of these traits in this breed.

WTAP affects intracranial aneurysm progression by regulating m6A methylation modification.

Intracranial aneurysm (IA) is a type of cerebrovascular disease that mainly occurs in the circle of Willis. Abnormalities in RNA methylation at the N6-methyladenosine (m6A) site have been associated with numerous types of human diseases. WTAP recruits the m6A methyltransferase complexes to the mRNA targets, and its expression is positively correlated with m6A methylation levels. This research aimed to explore the potential mechanisms of m6A methylation in IA. A selective arterial ligation method was used to establish an IA rat model; thereafter, the m6A methylation level and m6A methylation-related genes were determined in blood and circle of Willis samples using a commercial kit and real-time quantitative PCR, respectively. Subsequently, rat brain microvascular endothelial cells (rBMVECs) were treated with TNF-α, and the expression of m6A methylation-related genes within the cells were assessed. Lastly, the effects of WTAP on TNF-α-induced rBMVECs were further investigated through in vitro experiments. In result, the m6A RNA methylation level evidently declined in the blood and circle of Willis' samples of the IA rats, as compared to the corresponding samples from the control rats (P < 0.05). Compared to the results in the control rats/cells, WTAP expression was significantly downregulated, whereas ALKBH1 expression was evidently upregulated in the blood and circle of Willis samples of the TNF-α-induced rBMVECs of IA rats. Consequently, TNF-α-induced rBMVECs and rBMVECs with WTAP overexpression were successfully established. TNF-α inhibited the viability of the rBMVECs, promoted apoptosis, and significantly upregulated cleaved-caspase3 and downregulated WTAP expression. In contrast, WTAP overexpression significantly reversed these changes caused by TNF-α (P < 0.05). In conclusion, WTAP overexpression may modulate the growth of TNF-α-induced rBMVECs by enhancing WTAP expression and its m6A methylation.

The role and mechanisms of mesenchymal stem cells regulating macrophage plasticity in spinal cord injury.

Spinal Cord Injury (SCI) is a devastating neurological disorder comprising primary mechanical injury and secondary inflammatory response-mediated injury for which an effective treatment is still unavailable. It is well known that secondary inflammatory responses are a significant cause of difficulties in neurological recovery. An immune imbalance between M1/M2 macrophages at the sites of injury is involved in developing and progressing the secondary inflammatory response. Recently, Mesenchymal Stem Cells (MSCs) have shown significant therapeutic potential in tissue engineering and regenerative medicine due to their potential multidirectional differentiation and immunomodulatory properties. Accumulating evidence shows that MSCs can regulate the balance of M1/M2 macrophage polarization, suppress downstream inflammatory responses, facilitate tissue repair and regeneration, and improve the prognosis of SCI. This article briefly overviews the impact of macrophages and MSCs on SCI and repair. It discusses the mechanisms by which MSCs regulate macrophage plasticity, including paracrine action, release of exosomes and apoptotic bodies, and metabolic reprogramming. Additionally, the article summarizes the relevant signaling pathways of MSCs that regulate macrophage polarization.

Soluble epoxide hydrolase and TRPC3 channels jointly contribute to homocysteine-induced cardiac hypertrophy: Interrelation and regulation by C/EBPß.

OBJECTIVES: Studies in certain cardiac hypertrophy models suggested the individual role of soluble epoxide hydrolase (sEH) and canonical transient receptor potential 3 (TRPC3) channels, however, whether they jointly mediate hypertrophic process remains unexplored. Hyperhomocysteinemia promotes cardiac hypertrophy while the involvement of sEH and TRPC3 channels remains unknown. This study aimed to explore the role of, and interrelation between sEH and TRPC3 channels in homocysteine-induced cardiac hypertrophy. METHODS: Rats were fed methionine-enriched diet to induce hyperhomocysteinemia. H9c2 cells and neonatal rat cardiomyocytes were incubated with homocysteine. Cardiac hypertrophy was evaluated by echocardiography, histological examination, immunofluorescence imaging, and expressions of hypertrophic markers. Epoxyeicosatrienoic acids (EETs) were determined by ELISA. TRPC3 current was recorded by patch-clamp. Gene promotor activity was measured using dual-luciferase reporter assay. RESULTS: Inhibition of sEH by 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) reduced ventricular mass, lowered the expression of hypertrophic markers, decreased interstitial collagen deposition, and improved cardiac function in hyperhomocysteinemic rats, associated with restoration of EETs levels in myocardium. TPPU or knockdown of sEH suppressed TRPC3 transcription and translation as well as TRPC3 current that were enhanced by homocysteine. Exogenous 11,12-EET inhibited homocysteine-induced TRPC3 expression and cellular hypertrophy. Silencing C/EBPß attenuated, while overexpressing C/EBPß promoted homocysteine-induced hypertrophy and expressions of sEH and TRPC3, resulting respectively from inhibition or activation of sEH and TRPC3 gene promoters. CONCLUSIONS: sEH and TRPC3 channels jointly contribute to homocysteine-induced cardiac hypertrophy. Homocysteine transcriptionally activates sEH and TRPC3 genes through a common regulatory element C/EBPß. sEH activation leads to an upregulation of TRPC3 channels via a 11,12-EET-dependent manner.

Lysine crotonylation of SERCA2a correlates to cardiac dysfunction and arrhythmia in Sirt1 cardiac-specific knockout mice.

Protein post-translational modifications (PTMs) are important regulators of protein functions and produce proteome complexity. SIRT1 has NAD+-dependent deacylation of acyl-lysine residues. The present study aimed to explore the correlation between lysine crotonylation (Kcr) on cardiac function and rhythm in Sirt1 cardiac-specific knockout (ScKO) mice and related mechanism. Quantitative proteomics and bioinformatics analysis of Kcr were performed in the heart tissue of ScKO mice established with a tamoxifen-inducible Cre-loxP system. The expression and enzyme activity of crotonylated protein were assessed by western blot, co-immunoprecipitation, and cell biology experiment. Echocardiography and electrophysiology were performed to investigate the influence of decrotonylation on cardiac function and rhythm in ScKO mice. The Kcr of SERCA2a was significantly increased on Lys120 (1.973 folds). The activity of SERCA2a decreased due to lower binding energy of crotonylated SERCA2a and ATP. Changes in expression of PPAR-related proteins suggest abnormal energy metabolism in the heart. ScKO mice had cardiac hypertrophy, impaired cardiac function, and abnormal ultrastructure and electrophysiological activities. We conclude that knockout of SIRT1 alters the ultrastructure of cardiac myocytes, induces cardiac hypertrophy and dysfunction, causes arrhythmia, and changes energy metabolism by regulating Kcr of SERCA2a. These findings provide new insight into the role of PTMs in heart diseases.

Mesenchymal Stem Cell Transplantation: Neuroprotection and Nerve Regeneration After Spinal Cord Injury.

Spinal Cord Injury (SCI), with its morbidity characteristics of high disability rate and high mortality rate, is a disease that is highly destructive to both the physiology and psychology of the patient, and for which there is still a lack of effective treatment. Following spinal cord injury, a cascade of secondary injury reactions known as ischemia, peripheral inflammatory cell infiltration, oxidative stress, etc. create a microenvironment that is unfavorable to neural recovery and ultimately results in apoptosis and necrosis of neurons and glial cells. Mesenchymal stem cell (MSC) transplantation has emerged as a more promising therapeutic options in recent years. MSC can promote spinal cord injury repair through a variety of mechanisms, including immunomodulation, neuroprotection, and nerve regeneration, giving patients with spinal cord injury hope. In this paper, it is discussed the neuroprotection and nerve regeneration components of MSCs' therapeutic method for treating spinal cord injuries.

Multiple strategies enhance the efficacy of MSCs transplantation for spinal cord injury.

Spinal cord injury (SCI) is a serious complication of the central nervous system (CNS) after spine injury, often resulting in severe sensory, motor, and autonomic dysfunction below the level of injury. To date, there is no effective treatment strategy for SCI. Recently, stem cell therapy has brought hope to patients with neurological diseases. Mesenchymal stem cells (MSCs) are considered to be the most promising source of cellular therapy after SCI due to their immunomodulatory, neuroprotective and angiogenic potential. Considering the limited therapeutic effect of MSCs due to the complex pathophysiological environment following SCI, this paper not only reviews the specific mechanism of MSCs to facilitate SCI repair, but also further discusses the research status of these pluripotent stem cells combined with other therapeutic approaches to promote anatomical and functional recovery post-SCI.

Mechanism of M2 macrophages modulating astrocyte polarization through the TGF-ß/PI3K/Akt pathway.

Recent studies have revealed that activated astrocytes (AS) are divided into two distinct types, termed A1 and A2. A2 astrocytes are neuroprotective and promote tissue repair and regeneration following spinal cord injury. Whereas, the specific mechanism for the formation of the A2 phenotype remains unclear. This study focused on the PI3K/Akt pathway and examined whether TGF-ß secreted by M2 macrophages could mediate A2 polarization by activating this pathway. In this study, we revealed that both M2 macrophages and their conditioned medium (M2-CM) could facilitate the secretion of IL-10, IL-13 and TGF-ß from AS, and this effect was significantly reversed after the administration of SB431542 (a TGF-ß receptor inhibitor) or LY294002 (a PI3K inhibitor). Moreover, immunofluorescence results demonstrated that TGF-ß secreted by M2 macrophages could facilitate the expression of A2 biomarker S100A10 in AS; combined with the results of western blot, it was found that this effect was closely related to the activation of PI3K/Akt pathway in AS. In conclusion, TGF-ß secreted by M2 macrophages may induce the conversion of AS to the A2 phenotype through the activation of the PI3K/Akt pathway.

A novel defined risk signature of interferon response genes predicts the prognosis and correlates with immune infiltration in glioblastoma.

BACKGROUND: Interferons (IFNs) have been implemented as anti-tumor immunity agents in clinical trials of glioma, but only a subset of glioblastoma (GBM) patients profits from it. The predictive role of IFNs stimulated genes in GBM needs further exploration to investigate the clinical role of IFNs. METHODS: This study screened 526 GBM patients from three independent cohorts. The transcriptome data with matching clinical information were analyzed using R. Immunohistochemical staining data from the Human Protein Atlas and DNA methylation data from MethSurv were used for validation in protein and methylation level respectively. RESULTS: We checked the survival effect of all 491 IFNs response genes, and found 54 genes characterized with significant hazard ratio in overall survival (OS). By protein-protein interaction analysis, 10 hub genes were selected out for subsequent study. And based on the expression of these 10 genes, GBM patients could be divided into two subgroups with significant difference in OS. Furthermore, the least absolute shrinkage and selection operator cox regression model was utilized to construct a multigene risk signature, including STAT3, STAT2 and SOCS3, which could serve as an independent prognostic predictor for GBM. The risk model was validated in two independent GBM cohorts. The GBM patients with high risk scores mainly concentrated in the GBM Mesenchymal subtype. The higher risk group was enriched in hypoxia, angiogenesis, EMT, glycolysis and immune pathways, and had increased Macrophage M2 infiltration and high expression of immune checkpoint CD274 (namely PD-L1). CONCLUSIONS: Our findings revealed the three-gene risk model could be an independent prognostic predictor for GBM, and they were crucial participants in immunosuppressive microenvironment of GBM.

Advances in the research of the role of macrophage/microglia polarization-mediated inflammatory response in spinal cord injury.

It is often difficult to regain neurological function following spinal cord injury (SCI). Neuroinflammation is thought to be responsible for this failure. Regulating the inflammatory response post-SCI may contribute to the recovery of neurological function. Over the past few decades, studies have found that macrophages/microglia are one of the primary effector cells in the inflammatory response following SCI. Growing evidence has documented that macrophages/microglia are plastic cells that can polarize in response to microenvironmental signals into M1 and M2 macrophages/microglia. M1 produces pro-inflammatory cytokines to induce inflammation and worsen tissue damage, while M2 has anti-inflammatory activities in wound healing and tissue regeneration. Recent studies have indicated that the transition from the M1 to the M2 phenotype of macrophage/microglia supports the regression of inflammation and tissue repair. Here, we will review the role of the inflammatory response and macrophages/microglia in SCI and repair. In addition, we will discuss potential molecular mechanisms that induce macrophage/microglia polarization, with emphasis on neuroprotective therapies that modulate macrophage/microglia polarization, which will provide new insights into therapeutic strategies for SCI.

Radical-Assisted Formation of Pd Single Atoms or Nanoclusters on Biochar.

Supported single atom or nanocluster catalysts have been widely studied due to their excellent catalytic properties. Many methods to prepare such catalysts start with constructing defects on supports, and the main focus is to improve dispersion and stability of the active sites. This paper for the first time reports a radical-assisted method to prepare single atom or nanocluster Pd on a biochar. The char was prepared by pyrolyzing walnut shell at 600°C under N2, and Pd was loaded on the char by impregnating with palladium acetate in toluene under an oxygen-free atmosphere. It is found that there are three types of radicals in the fresh char (F-Char-600), two of them may adsorb/bond with O2 or Pd2+ resulting in decreases in the char's radical concentration. The Pd on F-Char-600 for 24 h impregnation are single atoms (0.1-0.3 nm, 2%) and nanoclusters (0.3-1.2 nm, 98%), which grow larger (0.3-4 nm, 100%) for 84 h impregnation. The Pd on N2 purged O2-adsorbed-char (N-O-Char-600) is much larger in size. The bond between Pd and char is probably C-Pd in F-Char-600 or C-O-Pd in N-O-Char-600.

Protection of dilator function of coronary arteries from homocysteine by tetramethylpyrazine: Role of ER stress in modulation of BKCa channels.

OBJECTIVES: We recently reported the involvement of ER stress-mediated BKCa channel inhibition in homocysteine-induced coronary dilator dysfunction. In another study, we demonstrated that tetramethylpyrazine (TMP), an active ingredient of the Chinese herb Chuanxiong, possesses potent anti-ER stress capacity. The present study investigated whether TMP protects BKCa channels from homocysteine-induced inhibition and whether suppression of ER stress is a mechanism contributing to the protection. Furthermore, we explored the signaling transduction involved in TMP-conferred protection on BKCa channels. METHODS: BKCa channel-mediated relaxation was studied in porcine small coronary arteries. Expressions of BKCa channel subunits, ER stress molecules, and E3 ubiquitin ligases, as well as BKCa ubiquitination were determined in porcine coronary arterial smooth muscle cells (PCASMCs). Whole-cell BKCa currents were recorded. RESULTS: Exposure of PCASMCs to homocysteine or the chemical ER stressor tunicamycin increased the expression of ER stress molecules, which was significantly inhibited by TMP. Suppression of ER stress by TMP preserved the BKCa ß1 protein level and restored the BKCa current in PCASMCs, concomitant with an improved BKCa-mediated dilatation in coronary arteries. TMP attenuated homocysteine-induced BKCa ß1 protein ubiquitination, in which inhibition of ER stress-mediated FoxO3a activation and FoxO3a-dependent atrogin-1 and Murf-1 was involved. CONCLUSIONS: Reversal of BKCa channel inhibition via suppressing ER stress-mediated loss of ß1 subunits contributes to the protective effect of TMP against homocysteine on coronary dilator function. Inhibition of FoxO3a-dependent ubiquitin ligases is involved in TMP-conferred normalization of BKCa ß1 protein level. These results provide new mechanistic insights into the cardiovascular benefits of TMP.

Impairment of Coronary Endothelial Function by Hypoxia-Reoxygenation Involves TRPC3 Inhibition-mediated KCa Channel Dysfunction: Implication in Ischemia-Reperfusion Injury.

Despite increasing knowledge of the significance of calcium-activated potassium (KCa) and canonical transient receptor potential (TRPC) channels in endothelial physiology, no studies so far have investigated the link between these two distinct types of channels in the control of vascular tone in pathological conditions. We previously demonstrated that hypoxia-reoxygenation (H-R) inhibits endothelial KCa and TRPC3 channels in porcine coronary arteries (PCAs). The present study further investigated whether modulation of TRPC3 is involved in H-R-induced KCa channel inhibition and associated vasodilatory dysfunction using approaches of wire myography, whole-cell voltage-clamp, and coimmunoprecipitation. Pharmacological inhibition or siRNA silencing of TRPC3 significantly suppressed bradykinin-induced intermediate- and small-conductance KCa (IKCa and SKCa) currents in endothelial cells of PCAs (PCAECs). TRPC3 protein exists in physical association with neither IKCa nor SKCa. In H-R-exposed PCAECs, the response of IKCa and SKCa to bradykinin-stimulation and to TRPC3-inhibition was markedly weakened. Activation of TRPC3 channels restored H-R-suppressed KCa currents in association with an improved endothelium-derived hyperpolarizing factor (EDHF)-type vasorelaxation. We conclude that inhibition of TRPC3 channels contributes to H-R-induced suppression of KCa channel activity, which serves as a mechanism underlying coronary endothelial dysfunction in ischemia-reperfusion (I-R) injury and renders TRPC3 a potential target for endothelial protection in I-R conditions.

Activation of PERK branch of ER stress mediates homocysteine-induced BKCa channel dysfunction in coronary artery via FoxO3a-dependent regulation of atrogin-1.

The molecular mechanism of endoplasmic reticulum (ER) stress in vascular pathophysiology remains inadequately understood. We studied the role of ER stress in homocysteine-induced impairment of coronary dilator function, with uncovering the molecular basis of the effect of ER stress on smooth muscle large-conductance Ca2+-activated K+ (BKCa) channels. The vasodilatory function of BKCa channels was studied in a myograph using endothelium-denuded porcine small coronary arteries. Primary cultured porcine coronary artery smooth muscle cells were used for mRNA and protein measurements and current recording of BKCa channels. Homocysteine inhibited vasorelaxant response to the BKCachannel opener NS1619, lowered BKCa ß1 subunit protein level and suppressed BKCa current. Inhibition of ER stress restored BKCa ß1 protein level and NS1619-evoked vasorelaxation. Selective blockade of the PKR-like ER kinase (PERK) yielded similarly efficient restoration of BKCa ß1, preserving BKCa current and BKCa-mediated vasorelaxation. The restoration of BKCa ß1 by PERK inhibition was associated with reduced atrogin-1 expression and decreased nuclear localization of forkhead box O transcription factor 3a (FoxO3a). Silencing of atrogin-1 prevented homocysteine-induced BKCa ß1 loss and silencing of FoxO3a prevented atrogin-1 upregulation induced by homocysteine, accompanied by preservation of BKCa ß1 protein level and BKCa current. ER stress mediates homocysteine-induced BKCa channel inhibition in coronary arteries. Activation of FoxO3a by PERK branch underlies the ER stress-mediated BKCa inhibition through a mechanism involving ubiquitin ligase-enhanced degradation of the channel ß1 subunit.

Application of PD-1 inhibitor Camrelizumab in advanced malignancies / 解放军医学杂志

With the remarkable achievements made in the treatment targeted at tumor immune checkpoints, more and more new immunotherapy drugs have been applied to the malignancies treatment. Camrelizumab (AiRuiKa) is a novel human immunoglobulin G4 (IgG4) monoclonal antibody (mAb), which can target the programmed death 1 (PD-1) and block its binding to the programmed death ligand 1 (PD-L1), so as to restore the body's immune function and achieve anti-tumor effect. The drug was officially approved by National Medical Products Administration (NMPA) on May 29, 2019 for use in patients with recurrent or refractory classical Hodgkin's lymphoma (cHL) who are treated with at least second-line systemic therapy. In addition, the drug showed good anti-tumor activity in esophageal squamous cell carcinoma (ESCC), hepatocellular carcinoma (HCC), nasopharyngeal carcinoma (NPC), non-small cell lung cancer (NSCLC), and gastric cancer (GC) and gastroesophageal junction cancer (EGJC). The research progress of camrelizumab on mechanism of action, pharmacodynamics and pharmacokinetics, clinical studies, adverse reactions etc. were reviewed in present paper.

ER stress mediates homocysteine-induced endothelial dysfunction: Modulation of IKCa and SKCa channels.

OBJECTIVE: It remains incompletely understood how homocysteine impairs endothelial function. Whether mechanisms such as calcium-activated potassium (KCa) channels are involved is uncertain and the significance of endoplasmic reticulum (ER) stress in KCa channel-dependent endothelial function in hyperhomocysteinemia remains unexplored. We investigated the effect of homocysteine on endothelial KCa channels in coronary vasculature with further exploration of the role of ER stress. METHODS: Vasorelaxation mediated by intermediate- and small-conductance KCa (IKCa and SKCa) channels was studied in porcine coronary arteries in a myograph. IKCa and SKCa channel currents were recorded by whole-cell patch-clamp in coronary endothelial cells. Protein levels of endothelial IKCa and SKCa channels were determined for both whole-cell and surface expressions. RESULTS: Homocysteine impaired bradykinin-induced IKCa and SKCa-dependent EDHF-type relaxation and attenuated the vasorelaxant response to the channel activator. IKCa and SKCa currents were suppressed by homocysteine. Inhibition of ER stress during homocysteine exposure enhanced IKCa and SKCa currents, associated with improved EDHF-type response and channel activator-induced relaxation. Homocysteine did not alter whole-cell protein levels of IKCa and SKCa whereas lowered surface expressions of these channels, which were restored by ER stress inhibition. CONCLUSIONS: Homocysteine induces endothelial dysfunction through a mechanism involving ER stress-mediated suppression of IKCa and SKCa channels. Inhibition of cell surface expression of these channels by ER stress is, at least partially, responsible for the suppressive effect of homocysteine on the channel function. This study provides new mechanistic insights into homocysteine-induced endothelial dysfunction and advances our knowledge of the significance of ER stress in vascular disorders.