The effect of NF-κB pathway on proliferation and apoptosis of human umbilical vein endothelial cells induced by intermittent high glucose

Glucose Variability: How Does It Work?

A growing body of evidence points to the role of glucose variability (GV) in the development of the microvascular and macrovascular complications of diabetes. In this review, we summarize data on GV-induced biochemical, cellular and molecular events involved in the pathogenesis of diabetic complications. Current data indicate that the deteriorating effect of GV on target organs can be realized through oxidative stress, glycation, chronic low-grade inflammation, endothelial dysfunction, platelet activation, impaired angiogenesis and renal fibrosis. The effects of GV on oxidative stress, inflammation, endothelial dysfunction and hypercoagulability could be aggravated by hypoglycemia, associated with high GV. Oscillating hyperglycemia contributes to beta cell dysfunction, which leads to a further increase in GV and completes the vicious circle. In cells, the GV-induced cytotoxic effect includes mitochondrial dysfunction, endoplasmic reticulum stress and disturbances in autophagic flux, which are accompanied by reduced viability, activation of apoptosis and abnormalities in cell proliferation. These effects are realized through the up- and down-regulation of a large number of genes and the activity of signaling pathways such as PI3K/Akt, NF-κB, MAPK (ERK), JNK and TGF-β/Smad. Epigenetic modifications mediate the postponed effects of glucose fluctuations. The multiple deteriorative effects of GV provide further support for considering it as a therapeutic target in diabetes.

Astragaloside IV prevents high glucose‑induced cell apoptosis and inflammatory reactions through inhibition of the JNK pathway in human umbilical vein endothelial cells

Endothelial dysfunction is a key pathophysiological step in early stage diabetes mellitus (DM) macrovascular complications and is also crucial in the inflammatory mechanisms of macrovascular complications. However, there is currently no effective intervention to improve endothelial dysfunction associated with DM macrovascular complications. Astragaloside IV (AS-IV), which can be extracted from the traditional Chinese medicine Astragalus membranaceus, has potential therapeutic effects on DM and its complications. The present study evaluated the effect of AS-IV on high glucose-induced human umbilical vein endothelial cell (HUVEC) injury and its possible mechanism. The result indicated that AS-IV has a significant protective effect on high glucose-induced HUVEC injury. AS-IV could significantly promote cell proliferation, reduce apoptosis and decrease the protein and mRNA expression levels of tumor necrosis factor-α and interleukin-1β in HUVECs. Furthermore, AS-IV could decrease the expression of phosphorylated c-Jun NH₂-terminal kinase (JNK) phosphorylated apoptosis signal-regulating kinase 1, cytochrome c, cleaved-caspase-9, cleaved-caspase-3 and the relative ratio of B-cell lymphoma-2 associated X protein/B-cell lymphoma-2 in HUVECs. In conclusion, the present study demonstrated that AS-IV could suppress apoptosis and inflammatory reactions promoted by high glucose conditions in HUVECs by inhibiting the JNK signaling pathway. These findings suggest that AS-IV could inhibit the process of endothelial dysfunction in diabetic macrovascular complications.

Ethyl Rosmarinate Protects High Glucose-Induced Injury in Human Endothelial Cells

Ethyl rosmarinate (RAE) is one of the active constituents from Clinopodium chinense (Benth.) O. Kuntze, which is used for diabetic treatment in Chinese folk medicine. In this study, we investigated the protective effect of RAE on high glucose-induced injury in endothelial cells and explored its underlying mechanisms. Our results showed that both RAE and rosmarinic acid (RA) increased cell viability, decreased the production of reactive oxygen species (ROS), and attenuated high glucose-induced endothelial cells apoptosis in a dose-dependent manner, as evidenced by Hochest staining, Annexin V⁻FITC/PI double staining, and caspase-3 activity. RAE and RA both elevated Bcl-2 expression and reduced Bax expression, according to Western blot. We also found that LY294002 (phosphatidylinositol 3-kinase, or PI3K inhibitor) weakened the protective effect of RAE. In addition, PDTC (nuclear factor-κB, or NF-κB inhibitor) and SP600125 (c-Jun N-terminal kinase, or JNK inhibitor) could inhibit the apoptosis in endothelial cells caused by high glucose. Further, we demonstrated that RAE activated Akt, and the molecular docking analysis predicted that RAE showed more affinity with Akt than RA. Moreover, we found that RAE inhibited the activation of NF-κB and JNK. These results suggested that RAE protected endothelial cells from high glucose-induced apoptosis by alleviating reactive oxygen species (ROS) generation, and regulating the PI3K/Akt/Bcl-2 pathway, the NF-κB pathway, and the JNK pathway. In general, RAE showed greater potency than RA equivalent.

CRISPR/Cas9-mediated gene knockout reveals a guardian role of NF-κB/RelA in maintaining the homeostasis of human vascular cells

Vascular cell functionality is critical to blood vessel homeostasis. Constitutive NF-κB activation in vascular cells results in chronic vascular inflammation, leading to various cardiovascular diseases. However, how NF-κB regulates human blood vessel homeostasis remains largely elusive. Here, using CRISPR/Cas9-mediated gene editing, we generated RelA knockout human embryonic stem cells (hESCs) and differentiated them into various vascular cell derivatives to study how NF-κB modulates human vascular cells under basal and inflammatory conditions. Multi-dimensional phenotypic assessments and transcriptomic analyses revealed that RelA deficiency affected vascular cells via modulating inflammation, survival, vasculogenesis, cell differentiation and extracellular matrix organization in a cell type-specific manner under basal condition, and that RelA protected vascular cells against apoptosis and modulated vascular inflammatory response upon tumor necrosis factor α (TNFα) stimulation. Lastly, further evaluation of gene expression patterns in IκBα knockout vascular cells demonstrated that IκBα acted largely independent of RelA signaling. Taken together, our data reveal a protective role of NF-κB/RelA in modulating human blood vessel homeostasis and map the human vascular transcriptomic landscapes for the discovery of novel therapeutic targets.

Effects of Glucose Variability on Short-Term Outcomes in Non-Diabetic Patients After Coronary Artery Bypass Grafting: A Retrospective Observational Study

BACKGROUND

Postoperative hyperglycaemia has been shown to have adverse effects on patients after coronary artery bypass grafting surgery (CABG). However, whether glucose variability has an effect on patients' outcomes is still uncertain. The aim of this study is to explore the effects of glucose variability on short-term outcomes in non-diabetic patients undergoing coronary artery bypass grafting.

METHODS

This is a retrospective observational study utilising data collected after patients had left the hospital. This study was performed on 137 non-diabetic patients undergoing coronary artery bypass grafting from January 2011 to June 2013. Blood glucose at 72hours post operation was obtained and glucose variability was measured by mean postoperative blood glucose and mean of daily difference (MODD). Short-term outcomes included duration of intensive care unit (ICU) stay, mechanical ventilation time, length of hospital stay, and occurrence of arrhythmia. Patients with mean postoperative blood glucose ≥7.00mmol/L were defined as hyperglycaemic, and patients with MODD ≥1.40mmol/L were considered to be abnormal. Outcome variables were compared between patients in euglycaemic and hyperglycaemic groups, and between patients in normal and abnormal groups.

RESULTS

In our study, patients with hyperglycaemia spent more time staying in ICU (p<0.01), and patients with large glucose variability (abnormal MODD) had higher incidences of arrhythmia (23% vs 4.2%, p<0.05). Regression analysis showed that MODD can affect occurrence of arrhythmia (p=0.004) and that mean postoperative blood glucose levels can affect duration of ICU stay (p<0.001).

CONCLUSIONS

Patients' postoperative glucose variability after CABG is an important predictor of the negative outcomes regarding duration of ICU stay and occurrence of arrhythmia. Large glucose variability can have negative effects on short-term outcomes in patients.

Endothelial cell oxidative stress in diabetes: a key driver of cardiovascular complications?

Atherothrombotic disease is a well-recognized complication of diabetes and is a major contributor to the high morbidity and mortality associated with diabetes. Although there is substantial evidence linking diabetes with cardiovascular disease, the specific effect of hyper- (or hypo-) glycaemia is less well understood. The present review focuses on the impact that glycaemic dysregulation has on respiratory function and ROS (reactive oxygen species) generation in the endothelial cells that are critical in preventing several key steps in the atherothrombotic process. Endothelial cells are particularly susceptible to ROS-mediated dysfunction not only because of reduced cell viability and increased senescence, but also because one of the major endothelium-derived factors that help to protect against atherosclerosis, nitric oxide, is rapidly deactivated by superoxide radicals.

Heat shock protein 27 phosphorylation in the proliferation and apoptosis of human umbilical vein endothelial cells induced by high glucose through the phosphoinositide 3‑kinase/Akt and extracellular signal‑regulated kinase 1/2 pathways

In the present study, the effect of the heat shock protein 27 (HSP27) signaling pathway on the proliferation and apoptosis of human umbilical vein endothelial cells (HUVECs) induced by high glucose (HG) was investigated. HUVEC proliferation in the indicated conditions was measured by the alamarBlue® assay. Apoptosis in HUVECs cultured with HG was analyzed by an Annexin V‑fluorescein isothiocyanate/propidium iodide apoptosis detection kit. HSP27 activity was evaluated by western blotting with specific phospho‑HSP27 antibody. HUVEC proliferation induced by HG was observed to be reduced by the HSP27 inhibitor quercetin in a concentration‑dependent manner, with a concomitant increase in apoptosis. The phosphorylation of HSP27 induced by HG was blocked by the specific phosphoinositide 3‑kinase (PI3K) inhibitor LY294002 and the specific extracellular signal‑regulated kinase (ERK) 1/2 inhibitor U0126 in a concentration‑dependent manner, with peak inhibition rates of 62.6 and 56.1%, respectively. LY294002 and U0126 also reduced HUVEC proliferation with a concomitant increase in apoptotic rate. In conclusion, HSP27 phosphorylation is important in mediating the proliferation and apoptosis of HUVECs induced by high glucose, and PI3K/Akt and ERK1/2 are important signaling pathways that contribute to HSP27 phosphorylation.

The cytotoxic role of intermittent high glucose on apoptosis and cell viability in pancreatic beta cells

OBJECTIVES

Glucose fluctuations are both strong predictor of diabetic complications and crucial factor for beta cell damages. Here we investigated the effect of intermittent high glucose (IHG) on both cell apoptosis and proliferation activity in INS-1 cells and the potential mechanisms.

METHODS

Cells were treated with normal glucose (5.5 mmol/L), constant high glucose (CHG) (25 mmol/L), and IHG (rotation per 24 h in 11.1 or 25 mmol/L) for 7 days. Reactive oxygen species (ROS), xanthine oxidase (XOD) level, apoptosis, cell viability, cell cycle, and expression of cyclinD1, p21, p27, and Skp2 were determined.

RESULTS

We found that IHG induced more significant apoptosis than CHG and normal glucose; intracellular ROS and XOD levels were more markedly increased in cells exposed to IHG. Cells treated with IHG showed significant decreased cell viability and increased cell proportion in G0/G1 phase. Cell cycle related proteins such as cyclinD1 and Skp2 were decreased significantly, but expressions of p27 and p21 were increased markedly.

CONCLUSIONS

This study suggested that IHG plays a more toxic effect including both apoptosis-inducing and antiproliferative effects on INS-1 cells. Excessive activation of cellular stress and regulation of cyclins might be potential mechanism of impairment in INS-1 cells induced by IHG.

Nicorandil inhibits hypoxia-induced apoptosis in human pulmonary artery endothelial cells through activation of mitoKATP and regulation of eNOS and the NF-κB pathway

Apoptosis of human pulmonary artery endothelial cells (HPAECs) is the initial step and triggering event for pulmonary hypertension (PH). However, little is known about the actions of nicorandil on HPAECs in vitro. In the present study, we investigated the anti-apoptotic effect of nicorandil on HPAECs exposed to hypoxia, and explored the underlying mechanism(s) of action. Cell viability was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). Annexin V and propidium iodide staining, and Hoechst 33342 staining assay were employed to detect apoptosis. In addition, the protein expression of Bax, Bcl-2, caspase-9 and -3, endothelial nitric oxide synthase (eNOS), nuclear factor-κB (NF-κB) and IκBα were determined by western blotting to investigate the possible mechanisms. We found that exposure to hypoxia for 24 h significantly decreased cell viability and increased cell apoptosis. Pretreatment with nicorandil (100 µM) effectively abolished the influence of hypoxia on HPAECs. However, these protective effects of nicorandil were significantly inhibited by an antagonist of mitochondrial adenosine triphosphate-sensitive potassium (mitoKATP) channels, 5-hydroxydecanoate (5-HD, 500 µM), and by an eNOS inhibitor, NG-nitro-L-arginine methyl ester (L-NAME, 300 µM). We further observed that nicorandil could upregulate the decreased protein expression of eNOS and IκBα, and downregulate the increased protein expression of NF-κB, induced by hypoxia. In addition, nicorandil inhibited the enhancement of caspase-3 and -9 expression, and the increase in the Bax/Bcl-2 expression ratio, induced by hypoxia. However, these effects were also abolished by 5-HD and L-NAME. Collectively, these findings suggest that nicorandil inhibits hypoxia-induced apoptosis of HPAECs through activation of mitoKATP channels and increased eNOS expression, which in turn inhibits the NF-κB pathway and the mitochondrial apoptotic pathway.

Effect of RNAi-induced down regulation of nuclear factor kappa-B p65 on acute monocytic leukemia THP-1 cells in vitro and vivo

NF-κB p65 is found constitutively active in acute monocytic leukemia, and has been considered an important factor for poor prognosis. Therefore, develop specifically target p65 inhibitors will be substantial interest. Until now, although several p65 inhibitors are currently in preclinical and clinical development, none of them are targeting. In this study, siRNA targeting p65 was introduced into the acute monocytic leukemia cell line THP-1 and THP-1 xenograft tumors in nude mice, and then, we measured p65 mRNA and protein levels by real-time RT-PCR and Western blotting, and levels of related protein cyclin D1, Bc1-2, and SMRT by Western blotting. We also investigated the cell cycle and apoptosis via FCM, and cell proliferation by Cell Counting Kit-8 assay. We found that p65 siRNA could effectively reduce the p65 mRNA and protein expression, arrest cells in G0/G1 phase, inhibit the proliferation and increase the apoptosis of THP-1 cells, and intratumoral injection of p65 siRNA could suppress tumor growth in nude mice. We also found that when down regulation of p65, the expression of cyclin D1 and Bc1-2 decreased, and the expression of SMRT increased in vitro and vivo. All these findings suggest that NF-κB p65 maybe an attractive candidate for the therapeutic targeting of acute monocytic leukemia.