New evidence for nicotinic acid treatment to reduce atherosclerosis

Hydroxycarboxylic Acid Receptor 2 Is a Zika Virus Restriction Factor That Can Be Induced by Zika Virus Infection Through the IRE1-XBP1 Pathway

Zika virus (ZIKV) is an emerging arthropod-borne virus and belongs to the Flaviviridae family. The infection of ZIKV has become the global health crisis because of its rapid spread and association with severe neurological disorders, including congenital microcephaly and Guillain-Barre Syndrome. To identify host factors contributing to ZIKV pathogenesis, transcriptomic landscape in ZIKV-infected cells was examined with mRNA microarray analysis and we observed that the expression of hydroxycarboxylic acid receptor 2 (HCAR2) could be significantly induced by ZIKV infection. By utilizing two IRE1 inhibitors and XBP1-specific shRNAs, we revealed that the up-regulation of HCAR2 expression induced by ZIKV was dependent on the IRE1-XBP1 pathway. Through the CRISPR/Cas9 system, we generated HCAR2-deficient cell clones in two cell types (human lung carcinoma epithelial A549 cell and human hepatoma Huh7.5 cell). We found that the depletion of HCAR2 significantly increased the replication level of ZIKV, including RNA levels, protein expression levels, and viral titers. In addition, our data demonstrated that the antiviral effect of HCAR2 was not involved in viral entry process and was not dependent on its antilipolytic effect on nicotinic acid/HCAR2-mediated signaling pathway. Taken together, our results indicated that HCAR2 could function as a restriction factor in control of ZIKV replication, potentially providing a novel molecular target for anti-ZIKV therapeutics.

Lead Structures for Applications in Photodynamic Therapy. 6. Temoporfin Anti-Inflammatory Conjugates to Target the Tumor Microenvironment for In Vitro PDT

Due to the ongoing development of clinical photodynamic therapy (PDT), the search continues for optimized photosensitizers that can overcome some of the side effects associated with this type of treatment modality. The main protagonists being: post-treatment photosensitivity, due to only limited cellular selectivity and post-treatment tumor regrowth, due to the up-regulation of pro-inflammatory agents within the tumor microenvironment. A photosensitizer that could overcome one or both of these drawbacks would be highly attractive to those engaged in clinical PDT. Certain non-steroidal anti-inflammatory drugs (NSAIDs) when used in combination with PDT have shown to increase the cytotoxicity of the treatment modality by targeting the tumor microenvironment. Temoporfin (m-THPC), the gold standard chlorin-based photosensitizer (PS) since its discovery in the 1980's, has successfully been conjugated to non-steroidal anti-inflammatory compounds, in an attempt to address the issue of post-treatment tumor regrowth. Using a modified Steglich esterification reaction, a library of "iPorphyrins" was successfully synthesized and evaluated for their PDT efficacy.

Stress triggers coronary mast cells leading to cardiac events

OBJECTIVE

Stress precipitates and worsens not only asthma and atopic dermatitis but also acute coronary syndromes (ACSs), which are associated with coronary inflammation. Evidence linking stress to ACS was reviewed and indicated that activation of coronary mast cells (MCs) by stress, through corticotropin-releasing hormone (CRH) and other neuropeptides, contributes to coronary inflammation and coronary artery disease.

DATA SOURCES

PubMed was searched (2005-2013) for articles using the following keywords: allergies, anaphylaxis, anxiety, coronary arteries, coronary artery disease, C-reactive protein, cytokines, chymase, histamine, hypersensitivity, interleukin-6 (IL-6), inflammation, mast cells, myocardial ischemia, niacin, platelet-activating factor, rupture, spasm, statins, stress, treatment, tryptase, and uroctortin.

STUDY SELECTIONS

Articles were selected based on their relevance to how stress affects ACS and how it activates coronary MCs, leading to coronary hypersensitivity, inflammation, and coronary artery disease.

RESULTS

Stress can precipitate allergies and ACS. Stress stimulates MCs through the activation of high-affinity surface receptors for CRH, leading to a CRH-dependent increase in serum IL-6. Moreover, neurotensin secreted with CRH from peripheral nerves augments the effect of CRH and stimulates cardiac MCs to release IL-6, which is elevated in ACS and is an independent risk factor for myocardial ischemia. MCs also secrete CRH and uroctortin, which induces IL-6 release from cardiomyocytes. The presence of atherosclerosis increases the risk of cardiac MC activation owing to the stimulatory effect of lipoproteins and adipocytokines. Conditions such as Kounis syndrome, mastocytosis, and myalgic encephalopathy/chronic fatigue syndrome are particularly prone to coronary hypersensitivity reactions.

CONCLUSION

Inhibition of cardiac MCs may be a novel treatment approach.

The high-fat high-fructose hamster as an animal model for niacin's biological activities in humans

OBJECTIVE

Niacin has been used for more than 50 years to treat dyslipidemia, yet the mechanisms underlying its lipid-modifying effects remain unknown, a situation stemming at least in part from a lack of validated animal models. The objective of this study was to determine if the dyslipidemic hamster could serve as such a model.

MATERIALS/METHODS

Dyslipidemia was induced in Golden Syrian hamsters by feeding them a high-fat, high-cholesterol, and high-fructose (HF/HF) diet. The effect of high-dose niacin treatment for 18 days and 28 days on plasma lipid levels and gene expression was measured.

RESULTS

Niacin treatment produced significant decreases in plasma total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and free fatty acids (FFA), but had no measureable effect on high-density lipoprotein cholesterol (HDL-C) in the dyslipidemic hamster. Niacin treatment also produced significant increases in hepatic adenosine ATP-Binding Cassette A1 (ABCA1) mRNA, ABCA1 protein, apolipoprotein A-I (Apo A-I) mRNA, and adipose adiponectin mRNA in these animals.

CONCLUSIONS

With the exception of HDL-C, the lipid effects of niacin treatment in the dyslipidemic hamster closely parallel those observed in humans. Moreover, the effects of niacin treatment on gene expression of hepatic proteins related to HDL metabolism are similar to those observed in human cells in culture. The HF/HF-fed hamster could therefore serve as an animal model for niacin's lowering of proatherogenic lipids and mechanisms of action relative to lipid metabolism.

Niaspan attenuates the adverse effects of bone marrow stromal cell treatment of stroke in type one diabetic rats

AIMS

Our previous studies have found that bone-marrow-stromal cells (BMSC) therapy improves functional recovery after stroke in non-diabetic rats while increases brain hemorrhage and induces arteriosclerosis-like changes in type-one-diabetic (T1DM) rats. Niaspan treatment of stroke increases vascular stabilization, decreases brain hemorrhage and blood-brain-barrier (BBB) leakage in T1DM rats. We therefore tested the hypothesis that combination therapy of BMSC with Niaspan attenuates the side effects of BMSC monotherapy in T1DM rats.

METHODS

T1DM-rats induced by streptozotocin were subjected to 2 hours of middle-cerebral-artery occlusion (MCAo) and treated with: 1) PBS; 2) BMSC (5×10(6)); 3) Niaspan (40 mg/kg) daily for 14 days; 4) BMSC (5×10(6)) +Niaspan (40 mg/kg, daily for 14 days) combination starting at 24 hours after MCAo. All rats were monitored for 14 days.

RESULTS

Combination BMSC+Niaspan treatment of T1DM-MCAo rats did not increase brain hemorrhage, and significantly decreased BBB leakage and vascular arteriosclerosis-like changes as well as decreased Angiogenin, matrix metalloproteinase 9 (MMP9) and ED1 expression in ischemic brain and internal-carotid-artery compared to non-treatment control and BMSC monotherapy animals.

CONCLUSIONS

Combination therapy using BMSC with Niaspan decreases BBB leakage and cerebral arteriosclerosis-like changes. These beneficial effects may be attributed to the decreased expression of Angiogenin, MMP9 and ED1.

GPR109A as an anti-inflammatory receptor in retinal pigment epithelial cells and its relevance to diabetic retinopathy

PURPOSE

Retinal pigment epithelium (RPE) expresses GPR109A, a receptor for the vitamin niacin and the ketone body β-hydroxybutyrate (β-HB). Because diabetes results in elevated levels of β-HB, here we studied expression of the receptor in diabetic retina. We also investigated its functional relevance in RPE.

METHODS

Retinal expression of GPR109A in diabetic mice and postmortem human eyes was evaluated by quantitative PCR (qPCR). ARPE-19 cells and primary wild-type and Gpr109a(-/-) mouse RPE cells were exposed to TNF-α in the presence or absence of niacin or β-HB, followed by analysis of IL-6 and Ccl2 expression via real-time qPCR and ELISA.

RESULTS

GPR109A expression was increased in diabetic mouse and human retina. TNF-α increased the expression and secretion of IL-6 and Ccl2 in ARPE-19 cells. Niacin and β-HB suppressed these effects, implicating GPR109A as the target responsible for mediation of the observed effects. Primary RPE cells from wild-type mice behaved similarly. In contrast, GPR109A ligands failed to suppress TNF-α-induced expression and secretion of IL-6 and Ccl2 in primary RPE cells from Gpr109a(-/-) mice, confirming that the observed anti-inflammatory effects were mediated specifically by Gpr109a.

CONCLUSIONS

GPR109A plays an anti-inflammatory role in RPE and its expression is upregulated in diabetes. Inflammation is a key causative factor in the pathogenesis of diabetic retinopathy. We speculate that the increased expression of GPR109A and elevation of its ligand β-HB in diabetes are mechanisms by which the tissue attempts to fight inflammation in this disease. Pharmacological activation of GPR109A may therefore have therapeutic potential in clinical management of diabetic retinopathy.

Treatment of nonalcoholic fatty liver disease in adults and children: a closer look at the arsenal

Nonalcoholic fatty liver disease encompasses a spectrum of disease from asymptomatic steatosis, with or without elevated aminotransferases, to cirrhosis with relative complications and hepatocellular carcinoma. Owing to the increasing prevalence of nonalcoholic fatty liver disease and the potential for nonalcoholic steatohepatitis to progress to cirrhosis and liver-related mortality, more research has been focused on therapy of this important liver disease over the last two decades. To date, weight loss and physical activity represent the cornerstone of treatment, with interventions being limited to subjects at risk of disease progression, but the type of treatment remains a matter of debate. A few medications have shown promising results in preliminary pilot studies, but few agents have been tested rigorously. Today, multiple therapeutic approaches are considered the way to go in treating nonalcoholic steatohepatitis patients. In this paper we review the status of current and emerging therapeutic strategies for children and adult patients with nonalcoholic steatohepatitis.

Inflammation in the pathogenesis of microvascular complications in diabetes

Diabetes and hyperglycemia create a proinflammatory microenvironment that progresses to microvascular complications such as nephropathy, retinopathy, and neuropathy. Diet-induced insulin resistance is a potential initiator of this change in type 2 diabetes which can increase adipokines and generate a chronic low-grade inflammatory state. Advanced glycation end-products and its receptor, glycation end-products AGE receptor axis, reactive oxygen species, and hypoxia can also interact to worsen complications. Numerous efforts have gained way to understanding the mechanisms of these modulators and attenuation of the inflammatory response, however, effective treatments have still not emerged. The complexity of inflammatory signaling may suggest a need for multi-targeted therapy. This review presents recent findings aimed at new treatment strategies.

Mast cells squeeze the heart and stretch the gird: their role in atherosclerosis and obesity

Mast cells are crucial for the development of allergic and anaphylactic reactions, but they are also involved in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases through activation by non-allergic triggers such as neuropeptides and cytokines. This review discusses how mast cells contribute to the inflammatory processes associated with coronary artery disease and obesity. Animal models indicate that mast cells, through the secretion of various vasoactive mediators, cytokines and proteinases, contribute to coronary plaque progression and destabilization, as well as to diet-induced obesity and diabetes. Understanding how mast cells participate in these inflammatory processes could help in the development of unique inhibitors with novel therapeutic applications for these diseases, which constitute the greatest current threat to global human health and welfare.

Niacin inhibits skin dendritic cell mobilization in a GPR109A independent manner but has no impact on monocyte trafficking in atherosclerosis

High-dose niacin therapy in humans reduces mortality from cardiovascular disease and may also protect against death from other causes, with benefits apparent more than a decade beyond the therapeutic period. Niacin therapy modulates circulating lipids, raising HDL and lowering LDL, but has the unwanted side effect of inducing skin flushing in response to treatment. Skin flushing results from niacin-induced activation of GPR109A and subsequent release of prostaglandins that promote vasodilation. GPR109A may also mediate HDL elevation. Recent data suggest that high-dose niacin may have benefits beyond improved lipid profiles, such as quelling inflammation, suggesting a potential role in immune cell trafficking. To explore effects of niacin on immune cell trafficking independently of its effects on lipid profiles, we took advantage of the fact that niacin therapy does not raise HDL in wild-type or apoE⁻/⁻ mouse strains. Wild-type and apoE⁻/⁻ C57BL/6 mice were fed standard chow or high-fat diets supplemented or not with 1% niacin. Against our predictions, this treatment did not modulate monocyte recruitment to or retention within atherosclerotic plaques. By contrast, stimulating the skin of niacin-treated mice with a contact sensitizer revealed impaired dendritic cell accumulation in draining lymph nodes and associated impaired adaptive immunity. Surprisingly, niacin-mediated impaired dendritic cell mobilization could not be reversed by cyclooxygenase inhibitor treatment nor deletion of the niacin receptor GPR109A, suggesting that the effects of niacin on modulating the migration of dendritic cells are not directly linked to skin flushing. Overall, these data suggest the existence of novel pathways triggered by niacin that, through suppression of dendritic cell migration, might impact adaptive immune responses that participate in sustained therapeutic benefits independent of niacin's cardioprotective capabilities.