Vitamin D, immune function, and atherosclerosis. Where are we now?

The role of vitamin D in regulating calcium metabolism and skeletal growth and disease is widely recognized. Indeed, current recommendations for serum vitamin D concentrations are based on these parameters. A serum vitamin D <20 ng/mL is considered deficient, concentrations between 20 and 30 ng/mL are insufficient, and >30 ng/mL is adequate.

Cardioprotective antihyperglycemic drugs ameliorate endoplasmic reticulum stress.

Cellular stress, notably oxidative, inflammatory, and endoplasmic reticulum (ER) stress, is implicated in the pathogenesis of cardiovascular disease. Modifiable risk factors for cardiovascular disease such as diabetes, hypercholesterolemia, saturated fat consumption, hypertension, and cigarette smoking cause ER stress whereas currently known cardioprotective drugs with diverse pharmacodynamics share a common pleiotropic effect of reducing ER stress. Selective targeting of oxidative stress with known antioxidative vitamins has been ineffective in reducing cardiovascular risk.

Transcription factor EB protects against endoplasmic reticulum stress in human coronary artery endothelial cells.

Oxidative stress and endoplasmic reticulum (ER) stress promote atherogenesis while transcription factor EB (TFEB) inhibits atherosclerosis. Since reducing oxidative stress with antioxidants have failed to reduce atherosclerosis possibly because of aggravation of ER stress, we studied the effect of TFEB on ER stress in human coronary artery endothelial cells. ER stress was measured using the secreted alkaline phosphatase assay.

Endoplasmic reticulum stress: A common pharmacologic target of cardioprotective drugs.

Despite the advances made in cardiovascular disease prevention, there is still substantial residual risk of adverse cardiovascular events. Contemporary evidence suggests that additional reduction in cardiovascular disease risk can be achieved through amelioration of cellular stresses, notably inflammatory stress and endoplasmic reticulum (ER) stress. Only two clinical trials with anti-inflammatory agents have supported the role of inflammatory stress in cardiovascular risk.

Potential Therapeutic Agents That Target ATP Binding Cassette A1 (ABCA1) Gene Expression.

The cholesterol efflux protein ATP binding cassette protein A1 (ABCA) and apolipoprotein A1 (apo A1) are key constituents in the process of reverse-cholesterol transport (RCT), whereby excess cholesterol in the periphery is transported to the liver where it can be converted primarily to bile acids for either use in digestion or excreted. Due to their essential roles in RCT, numerous studies have been conducted in cells, mice, and humans to more thoroughly understand the pathways that regulate their expression and activity with the goal of developing therapeutics that enhance RCT to reduce the risk of cardiovascular disease. Many of the drugs and natural compounds examined target several transcription factors critical for ABCA1 expression in both macrophages and the liver.

The effect of black seed (Nigella sativa) extract on lipid metabolism in HepG2 cells.

Black seed extract stimulates apolipoprotein A-I (apo A-I) gene expression in hepatocytes and intestinal cells in part by elevating peroxisome proliferator-activated receptor α (PPARα) and retinoid X receptor α (RXRα) levels. To explore potential ramifications of these observations, we examined the effects of black seed extract on hepatocyte lipid content and expression of key transcriptional regulators of fatty acid β-oxidation and lipogenesis in HepG2 cells. PPARα, peroxisome proliferator-activated receptor γ (PPARγ), RXRα, thyroid hormone receptor β (TRβ), sterol-responsive element binding protein 1 (SREBP1), and sterol-responsive element binding protein 2 (SREBP2) levels were measured in black seed extract treated liver-derived HepG2 cells.

Insulin mimetic effect of D-allulose on apolipoprotein A-I gene.

Several nutrients modulate the transcriptional activity of the apolipoprotein A-I (apo A-I) gene. To determine the influence of rare sugars on apo A-I expression in hepatic (HepG2) and intestinal derived (Caco-2) cell lines, apo A-I, albumin, and SP1 were quantified with enzyme immunoassay and Western blots while mRNA levels were quantified with real-time polymerase chain reaction. The promoter activity was measured using transient transfection assays with plasmids containing various segments and mutations in the promoter.

Differential effects of cyclooxygenase-2 (COX-2) inhibitors on endoplasmic reticulum (ER) stress in human coronary artery endothelial cells.

Selective cyclooxygenase-2 (COX-2) inhibitor rofecoxib was pulled off the market because of its association with increased risk of adverse cardiovascular effects. The precise underlying mechanism for the differential effects of COX-2 inhibitors on cardiovascular risk is not known. Since endoplasmic reticulum (ER) stress is implicated in atherogenesis, we examined the effects of COX-2 inhibitors on ER stress in primary human coronary artery endothelial cells (HCAEC), human umbilical vein endothelial cells (HUVEC), and human pulmonary artery endothelial cells (HPAEC).

Effect of anti-hyperglycemic drugs on endoplasmic reticulum (ER) stress in human coronary artery endothelial cells.

Endoplasmic reticulum (ER) stress plays a critical role in progression of diabetes and development of complications, notably cardiovascular disease. Some of the contemporary anti-hyperglycemic drugs have been shown to inhibit ER stress. To extend these observations, the effects of various anti-hyperglycemic agents were screened for their effects on ER stress.

The effect of nicotine and dextrose on endoplasmic reticulum stress in human coronary artery endothelial cells.

Cigarette smoking is one of the major causes of coronary artery disease (CAD) as is diabetes. However, nicotine has been generally regarded as safe and is used in smoking cessation programs. This presumption of nicotine safety was examined in human coronary artery endothelial cells (HCAEC).

Reduced cellular glucose transport confers natural protection against dextrose-induced superoxide generation and endoplasmic reticulum stress in domestic hen.

Normal blood glucose levels in avian species are two to fourfold higher than that in humans and the higher blood glucose levels in birds do not cause adverse effects. Endothelial cells isolated from the aorta of the domestic hen (Gallus gallus domesticus) and chicken aortic smooth muscle cells (CAOSMC) were compared to human coronary artery endothelial cells (HCAEC) and human primary aortic smooth muscle cells (HASMC). Superoxide (SO) generation was measured using a superoxide-reactive probe.

High-throughput analysis identifying drugs that reduce oxidative and ER stress in human coronary artery endothelial cells.

Endoplasmic reticulum (ER) stress as well as oxidative stress have been shown to play important roles in metabolic and cardiovascular disease, and drugs that counteract the effects of ER and oxidative stresses may be clinically useful. To identify novel compounds that ameliorate ER and oxidative stresses, we screened two drug libraries purchased from Evotec, San Francisco, CA; the NIH clinical collection 1 (446 compounds) and the NIH clinical collection 2 (281 compounds). Human coronary artery endothelial cells (HCAEC) were tested for ER and oxidative stress.

Inhibition of Pro-Inflammatory Cytokine Secretion by Select Antioxidants in Human Coronary Artery Endothelial Cells.

Inflammatory and oxidative stress in endothelial cells are implicated in the pathogenesis of premature atherosclerosis in diabetes. To determine whether high-dextrose concentrations induce the expression of pro-inflammatory cytokines, human coronary artery endothelial cells (HCAEC) were exposed to either 5.5 or 27.

Naturally occurring rare sugars are free radical scavengers and can ameliorate endoplasmic reticulum stress.

Because of potential use of naturally occurring rare sugars as sweeteners, their effect on superoxide (SO), hydroxyl and peroxyl radicals and endoplasmic reticulum (ER) stress was examined in human coronary artery endothelial cells. SO generation was measured using the superoxide-reactive probe 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-A]pyrazin-3-one hydrochloride chemiluminescence. Phycoerythrin fluorescence based assay was used to monitor scavenging activity of sugars in the presence of hydroxyl or peroxyl radical generators [CuSO and azobis (2 amidinopropane) hydrochloride respectively].

Regulation of apolipoprotein A-I gene expression by the histamine H1 receptor: Requirement for NF-κB.

Aims: Earlier it had been found by us that apolipoprotein A-I (apo A-I) is suppressed by histamine in HepG2 cells. Histamine has been shown to regulate NF-κB activity, though not in hepatocytes. Therefore we examined the role of the histamine receptors and NF-κB in histamine-mediated apo A-I gene expression in HepG2 liver cells.

Inhibition of hepatic apolipoprotein A-I gene expression by histamine.

In a recent high throughput analysis to identify drugs that alter hepatic apolipoprotein A-I (apo A-I) expression, histamine receptor one (H) antagonists emerged as potential apo A-1 inducing drugs. Thus the present study was undertaken to identify some of the underlying molecular mechanisms of the effect of antihistaminic drugs on apo AI production. Apo A-I levels were measured by enzyme immunoassay and Western blots.

The Effects of Known Cardioprotective Drugs on Proinflammatory Cytokine Secretion From Human Coronary Artery Endothelial Cells.

Background: Endothelial cell dysfunction in diabetes is involved in the pathogenesis and progression of premature atherosclerosis. High-dextrose has been shown to induce both oxidative stress and endoplasmic reticulum stress in cultured human coronary artery endothelial cells (HCAEC).

Study Question: To determine whether or not several classes of cardioprotective drugs inhibit proinflammatory cytokine expression by HCAEC.

High-Throughput Analysis Identifying Drugs That Regulate Apolipoprotein A-I Synthesis.

Apolipoprotein A-I (apo A-I) is the primary antiatherogenic protein in high-density lipoprotein (HDL). Despite the controversy as to the clinical effectiveness of raising HDL, the search is ongoing for safe and effective drugs that increase HDL and apo A-I levels. To identify novel compounds that can increase hepatic apo A-I production, two drug libraries were screened.

Inhibition of endoplasmic reticulum stress and oxidative stress by vitamin D in endothelial cells.

Endoplasmic reticulum (ER) stress and oxidative stress promote endothelial dysfunction and atherosclerosis. Since vitamin D has been shown in several studies to lower the risk of cardiovascular disease, we examined the effects of vitamin D on ER stress and oxidative stress in endothelial cells. ER stress was measured using the placental secreted alkaline phosphatase assay and oxidative stress was measured by hydroethidine fluorescence.

Angiotensin II receptor one (AT1) mediates dextrose induced endoplasmic reticulum stress and superoxide production in human coronary artery endothelial cells.

Background: Renin-angiotensin-aldosterone system (RAAS) has been implicated in diabetes-related vascular complications partly through oxidative stress.

Objective: To determine the role of angiotensin II receptor subtype one (AT1) in dextrose induced endoplasmic reticulum (ER) stress, another cellular stress implicated in vascular disease.

Methods: Human coronary artery endothelial cells with or without AT1 receptor knock down were treated with 27.

Pro-inflammatory signaling by 24,25-dihydroxyvitamin D3 in HepG2 cells.

The vitamin D metabolite 24,25-dihydroxyvitamin D3 (24, 25[OH]2D3) was shown to induce nongenomic signaling pathways in resting zone chondrocytes and other cells involved in bone remodeling. Recently, our laboratory demonstrated that 24,25-[OH]2D3 but not 25-hydroxyvitamin D3, suppresses apolipoprotein A-I (apo A-I) gene expression and high-density lipoprotein (HDL) secretion in hepatocytes. Since 24,25-[OH]2D3 has low affinity for the vitamin D receptor (VDR) and little is known with regard to how 24,25-[OH]2D3 modulates nongenomic signaling in hepatocytes, we investigated the capacity of 24,25-[OH]2D3 to activate various signaling pathways relevant to apo A-I synthesis in HepG2 cells.

Inhibition of ABCA1 Protein Expression and Cholesterol Efflux by TNF α in MLO-Y4 Osteocytes.

Hip fracture and myocardial infarction cause significant morbidity and mortality. In vivo studies raising serum cholesterol levels as well as pro-inflammatory cytokines such as TNF α manifest bone loss and atherosclerotic vascular disease, suggesting that abnormalities of cholesterol transport may contribute to osteoporosis. We used the mouse osteocyte cell line (MLO-Y4) to investigate the effects of TNF α on the expression of cholesterol acceptor proteins such as apolipoprotein A-I (apo A-I) and apolipoprotein E (apo E), as well as on the cholesterol transporters ATP-binding cassette-1 (ABCA1), scavenger receptor class B type 1 (SRB1), and cluster of differentiation 36 (CD36).

Asymmetrical cross-talk between the endoplasmic reticulum stress and oxidative stress caused by dextrose.

Aims: Oxidative and endoplasmic reticulum (ER) stresses are implicated in premature cardiovascular disease in people with diabetes. The aim of the present study was to characterize the nature of the interplay between the oxidative and ER stresses to facilitate the development of therapeutic agents that can ameliorate these stresses.

Main Methods: Human coronary artery endothelial cells were treated with varying concentrations of dextrose in the presence or absence of three antioxidants (alpha tocopherol, ascorbate and ebselen) and two ER stress modifiers (ERSMs) (4-phenylbutyrate and taurodeoxycholic acid).

T2D and Depression Risk Gene Proteasome Modulator 9 is Linked to Insomnia.

Insomnia increases type-2 diabetes (T2D) risk. The 12q24 locus is linked to T2D, depression, bipolar disorder and anxiety. At the 12q24 locus, the Proteasome-Modulator 9 (PSMD9) single nucleotide polymorphisms (SNPs) rs74421874 [intervening sequence (IVS) 3+nt460-G>A], rs3825172 (IVS3+nt437-C>T) and rs14259 (E197G-A>G) are linked to: T2D, depression, anxiety, maturity-onset-diabetes-of the young 3/MODY3, obesity, waist circumference, hypertension, hypercholesterolemia, T2D-macrovascular disease, T2D-microvascular disease, T2D-neuropathy, T2D-carpal-tunnel syndrome, T2D-nephropathy, T2D-retinopathy and non-diabetic retinopathy.

The glutathione mimic ebselen inhibits oxidative stress but not endoplasmic reticulum stress in endothelial cells.

Aims: Reactive oxygen species are associated with cardiovascular disease, diabetes, and atherosclerosis, yet the use of antioxidants in clinical trials has been ineffective at improving outcomes. In endothelial cells, high-dextrose-induced oxidative stress and endoplasmic reticulum stress promote endothelial dysfunction leading to the recruitment and activation of peripheral blood lymphocytes and the breakdown of barrier function. Ebselen, a glutathione peroxidase 1 (GPX1) mimic, has been shown to improve β-cell function in diabetes and prevent atherosclerosis.