Nicotinic acid induces antinociceptive and anti-inflammatory effects in different experimental models

Nicorandil antiallodynic activity in a model of neuropathic pain is associated with the activation of ATP-dependent potassium channels and opioidergic pathways, and reduced production of cytokines and neutrophils recruitment in paw, sciatic nerve, and dorsal root ganglia

BACKGROUND

Recently, we demonstrated that nicorandil inhibits mechanical allodynia induced by paclitaxel. In the present study, we evaluated the effect induced by nicorandil in a model of neuropathic pain induced by chronic constriction injury (CCI) in mice. We also investigated putative mechanisms underlying such an effect.

METHODS

CCI was induced by three ligatures of the left sciatic nerve. Mechanical allodynia was evaluated by measuring the paw withdrawal threshold with an electronic von Frey apparatus. Concentrations of cytokines and myeloperoxidase activity were determined in the paw tissue, sciatic nerve, and dorsal root ganglia (DRG).

RESULTS

Oral administration of two doses of nicorandil (150 mg/kg po), but not equimolar doses of nicotinamide or nicotinic acid, attenuated mechanical allodynia induced by CCI. Nicorandil activity was reduced by previous administration of glibenclamide (40 mg/kg) or naltrexone (5 mg/kg or 10 mg/kg). Two doses of nicorandil (150 mg/kg, po) reduced tumor necrosis factor-α, interleukin-1β and interleukin-6, but not CXCL-1, concentrations in the paw tissue of CCI mice. Two doses of nicorandil (150 mg/kg, po) reduced concentrations of all these mediators in the sciatic nerve and DRG. Two doses of nicorandil (150 mg/kg, po) also reduced the myeloperoxidase activity in the paw tissue, sciatic nerve, and DRG.

CONCLUSIONS

Nicorandil exhibits antiallodynic activity in a model of neuropathic pain induced by CCI. Inhibition of cytokines production and reduction of neutrophils recruitment in paw tissue, sciatic nerve, and DRG as well as activation of ATP-dependent potassium channels and opioidergic pathways, underlie nicorandil antiallodynic activity.

Association between niacin intake and knee osteoarthritis pain and function: a longitudinal cohort study

BACKGROUND

This research investigates the relationship between niacin intake and knee osteoarthritis (OA) severity, focusing on pain and functional ability due to niacin's role as a NAD(P)+ precursor, promoting cellular energy, and offering anti-inflammatory, analgesic, and antioxidant effects.

METHODS

The population-based Osteoarthritis Initiative (OAI) cohort with radiographically confirmed knee OA was analyzed through a Food Frequency Questionnaire determining niacin intake and scores from the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), using generalized additive mixed models.

RESULTS

A significant correlation was pinpointed in 2375 OA patients (1001 men and 1374 women; 55.96% aged between 45 and 65 and 44.04% aged ≥65) between niacin intake and reduced knee pain and functional degrees after a 48-month follow-up, evident in improved KOOS and WOMAC scores (P < 0.05). The fully adjusted models estimated a decrease of 0.26 points for every additional 1 unit of Ln-niacin intake of daily niacin intake on the WOMAC pain subscale, 0.83 points on the WOMAC function subscale, and an increase of 1.71 and 1.58 on the KOOS pain and quality of life score. Strikingly, subgroups including middle-aged individuals, women, white race, obese individuals, and those with specific dietary habits showed a more substantial improvement with increased niacin.

CONCLUSION

The association between increased niacin intake and reduced pain and function scores, as well improved quality of life in knee OA patients, is significant. Certain cohorts, according to a stratified analysis, could see more considerable benefits with increased niacin consumption.

HIGHLIGHTS

• Increased niacin intake is linked to reduced knee pain and better function in OA patients. • Specific subgroups, such as middle-aged individuals, women, and those with certain dietary habits, benefit more from increased niacin consumption. • Niacin shows promise for enhancing the quality of life in knee OA patients by reducing pain and improving function.

Alterations in Faecal and Serum Metabolic Profiles in Patients with Neovascular Age-Related Macular Degeneration

Neovascular age-related macular degeneration (nAMD) is a common and multifactorial disease in the elderly that may lead to irreversible vision loss; yet the pathogenesis of AMD remains unclear. In this study, nontargeted metabolomics profiling using ultra-performance liquid chromatography coupled with Q-Exactive Orbitrap mass spectrometry was applied to discover the metabolic feature differences in both faeces and serum samples between Chinese nonobese subjects with and without nAMD. In faecal samples, a total of 18 metabolites were significantly altered in nAMD patients, and metabolic dysregulations were prominently involved in glycerolipid metabolism and nicotinate and nicotinamide metabolism. In serum samples, a total of 29 differential metabolites were founded, involved in caffeine metabolism, biosynthesis of unsaturated fatty acids, and purine metabolism. Two faecal metabolites (palmitoyl ethanolamide and uridine) and three serum metabolites (4-hydroxybenzoic acid, adrenic acid, and palmitic acid) were selected as potential biomarkers for nAMD. Additionally, the significant correlations among dysregulated neuroprotective, antineuroinflammatory, or fatty acid metabolites in faecal and serum and IM dysbiosis were found. This comprehensive metabolomics study of faeces and serum samples showed that alterations in IM-mediated neuroprotective metabolites may be involved in the pathophysiology of AMD, offering IM-based nutritional therapeutic targets for nAMD.

Long-term exposure to environmental diclofenac concentrations impairs growth and induces molecular changes in Lymnaea stagnalis freshwater snails

As pharmaceutical substances are highly used in human and veterinary medicine and subsequently released in the environment, they represent emerging contaminants in the aquatic compartment. Diclofenac (DCF) is one of the most commonly detected pharmaceuticals in water and little research has been focused on its long-term effects on freshwater invertebrates. In this study, we assessed the chronic impacts of DCF on the freshwater gastropod Lymnaea stagnalis using life history, behavioral and molecular approaches. These organisms were exposed from the embryo to the adult stage to three environmentally relevant DCF concentrations (0.1, 2 and 10 μg/L). The results indicated that DCF impaired shell growth and feeding behavior at the juvenile stage, yet no impacts on hatching, locomotion and response to light stress were noted. The molecular findings (metabolomics and transcriptomic) suggested that DCF may disturb the immune system, energy metabolism, osmoregulation and redox balance. In addition, prostaglandin synthesis could potentially be inhibited by DCF exposure. The molecular findings revealed signs of reproduction impairment but this trend was not confirmed by the physiological tests. Combined omics tools provided complementary information and enabled us to gain further insight into DCF effects in freshwater organisms.

Niacin Attenuates Pulmonary Hypertension Through H-PGDS in Macrophages

RATIONALE

Pulmonary arterial hypertension (PAH) is characterized by progressive pulmonary vascular remodeling, accompanied by varying degrees of perivascular inflammation. Niacin, a commonly used lipid-lowering drug, possesses vasodilating and proresolution effects by promoting the release of prostaglandin D₂ (PGD₂). However, whether or not niacin confers protection against PAH pathogenesis is still unknown.

OBJECTIVE

This study aimed to determine whether or not niacin attenuates the development of PAH and, if so, to elucidate the molecular mechanisms underlying its effects.

METHODS AND RESULTS

Vascular endothelial growth factor receptor inhibitor SU5416 and hypoxic exposure were used to induce pulmonary hypertension (PH) in rodents. We found that niacin attenuated the development of this hypoxia/SU5416-induced PH in mice and suppressed progression of monocrotaline-induced and hypoxia/SU5416-induced PH in rats through the reduction of pulmonary artery remodeling. Niacin boosted PGD₂ generation in lung tissue, mainly through H-PGDS (hematopoietic PGD₂ synthases). Deletion of H-PGDS, but not lipocalin-type PGDS, exacerbated the hypoxia/SU5416-induced PH in mice and abolished the protective effects of niacin against PAH. Moreover, H-PGDS was expressed dominantly in infiltrated macrophages in lungs of PH mice and patients with idiopathic PAH. Macrophage-specific deletion of H-PGDS markedly decreased PGD₂ generation in lungs, aggravated hypoxia/SU5416-induced PH in mice, and attenuated the therapeutic effect of niacin on PAH.

CONCLUSIONS

Niacin treatment ameliorates the progression of PAH through the suppression of vascular remodeling by stimulating H-PGDS-derived PGD₂ release from macrophages.

Non-targeted metabolomics reveals diagnostic biomarker in the tongue coating of patients with chronic gastritis

Analysis of the properties of the tongue has been used in traditional Chinese medicine for disease diagnosis. Notably, tongue analysis, which is non-invasive and convenient compared with gastroscopy and pathological examination, can be used to assess chronic gastritis (CG). In order to find potential diagnostic biomarkers and study the metabolic mechanisms of the endogenous small molecules in the tongue coating related to CG, a non-targeted metabolomic analysis method was developed using ultra high performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UHPLC-Q/TOF-MS). It was performed using two different columns in positive and negative ion scanning modes separately. The stability of the samples was evaluated and the age and gender factors of the subjects were excluded to ensure the reliability of the data in this study. Finally, under the four analysis models, 130, 229, 113 and 92 differential compounds were found using multivariate statistical methods respectively. 37 potential biomarkers were putatively identified after removing the duplicate compounds and five potential diagnostic biomarkers were putatively identified by receiver operating characteristic (ROC) curve analysis, including inosine, oleamide, adenosine, N-acetylglucosamine (GlcNAc) and xanthine. The main metabolic pathways associated with CG were purine metabolism, amino acid metabolism, sphingolipid metabolism and energy metabolism, which suggested that oxygen free radicals and energy metabolism were altered in patients with CG. These results provided a potential new basis for the quantitative diagnosis and pathogenesis of CG.

Niacin in the Central Nervous System: An Update of Biological Aspects and Clinical Applications

Niacin (also known as "vitamin B₃" or "vitamin PP") includes two vitamers (nicotinic acid and nicotinamide) giving rise to the coenzymatic forms nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). The two coenzymes are required for oxidative reactions crucial for energy production, but they are also substrates for enzymes involved in non-redox signaling pathways, thus regulating biological functions, including gene expression, cell cycle progression, DNA repair and cell death. In the central nervous system, vitamin B₃ has long been recognized as a key mediator of neuronal development and survival. Here, we will overview available literature data on the neuroprotective role of niacin and its derivatives, especially focusing especially on its involvement in neurodegenerative diseases (Alzheimer's, Parkinson's, and Huntington's diseases), as well as in other neuropathological conditions (ischemic and traumatic injuries, headache and psychiatric disorders).

Sub-acute administration of lower doses of nicotine caused sex-dependent improvement of renal function in Wistar rats

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Exposure to nicotine is associated with sex-dependent variation in electrolyte disturbances.

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Lower doses of sub-acute nicotine administration enhanced renal function.

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Nicotine-enhanced renal function is more pronounced in female than in male Wistar rats.

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Nicotine-enhanced renal function may be mediated through α7-nAchR.

The adverse and beneficial health effects of nicotine (NIC), the major alkaloid found in cigarettes and tobacco, are controversial. Most studies on NIC have focused on its effects on cardiovascular and nervous functions. This study aimed at determining dose- and sex-specific effects of sub-acute (28 days) NIC administration on some indices of kidney function in Wistar rats. Forty rats (20 males and 20 females), 8–9 weeks old (each housed in separate metabolic cage), were used for this study such that graded doses of NIC (1, 2 and 4 mg/kg i.p. for 28 days) were administered to both sexes while each control received distilled water at 0.2 mL/100 g i.p. Blood was collected under ketamine anesthesia (10 mg/kg i.m) for analyses and results obtained were compared at p < 0.05. The result showed beneficial alterations in plasma and urine level of creatinine, urea and uric acid (p < 0.05) as well as plasma and urine electrolyte level (Na⁺ and K⁺) in both sexes (p < 0.05). Also, there was significant improvement in creatinine clearance (p < 0.05) with no appreciable difference in their histological examination. Although these beneficial effects were more pronounced in the female than in the male (p < 0.05), administration at the highest dose showed potentially deleterious alterations from normal beneficial trend (p < 0.05) in both sexes. It was concluded that sub-acute administration of lower doses of NIC improves kidney function of Wistar rats; an effect that was more pronounced in the females than their male counterparts.

Niacin ameliorates ulcerative colitis via prostaglandin D2-mediated D prostanoid receptor 1 activation

Niacin, as an antidyslipidemic drug, elicits a strong flushing response by release of prostaglandin (PG) D₂. However, whether niacin is beneficial for inflammatory bowel disease (IBD) remains unclear. Here, we observed niacin administration‐enhanced PGD₂ production in colon tissues in dextran sulfate sodium (DSS)‐challenged mice, and protected mice against DSS or 2,4,6‐trinitrobenzene sulfonic acid (TNBS)‐induced colitis in D prostanoid receptor 1 (DP1)‐dependent manner. Specific ablation of DP1 receptor in vascular endothelial cells, colonic epithelium, and myeloid cells augmented DSS/TNBS‐induced colitis in mice through increasing vascular permeability, promoting apoptosis of epithelial cells, and stimulating pro‐inflammatory cytokine secretion of macrophages, respectively. Niacin treatment improved vascular permeability, reduced apoptotic epithelial cells, promoted epithelial cell update, and suppressed pro‐inflammatory gene expression of macrophages. Moreover, treatment with niacin‐containing retention enema effectively promoted UC clinical remission and mucosal healing in patients with moderately active disease. Therefore, niacin displayed multiple beneficial effects on DSS/TNBS‐induced colitis in mice by activation of PGD₂/DP1 axis. The potential efficacy of niacin in management of IBD warrants further investigation.

Targeting the gut barrier for the treatment of alcoholic liver disease

Alcohol consumption remains one of the predominant causes of liver disease and liver-related death worldwide. Intriguingly, dysregulation of the gut barrier is a key factor promoting the pathogenesis of alcoholic liver disease (ALD). A functional gut barrier, which consists of a mucus layer, an intact epithelial monolayer and mucosal immune cells, supports nutrient absorption and prevents bacterial penetration. Compromised gut barrier function is associated with the progression of ALD. Indeed, alcohol consumption disrupts the gut barrier, increases gut permeability, and induces bacterial translocation both in ALD patients and in experimental models with ALD. Moreover, alcohol consumption also causes enteric dysbiosis with both numerical and proportional perturbations. Here, we review and discuss mechanisms of alcohol-induced gut barrier dysfunction to better understand the contribution of the gut-liver axis to the pathogenesis of ALD. Unfortunately, there is no effectual Food and Drug Administration-approved treatment for any stage of ALD. Therefore, we conclude with a discussion of potential strategies aimed at restoring the gut barrier in ALD. The principle behind antibiotics, prebiotics, probiotics and fecal microbiota transplants is to restore microbial symbiosis and subsequently gut barrier function. Nutrient-based treatments, such as dietary supplementation with zinc, niacin or fatty acids, have been shown to regulate tight junction expression, reduce intestinal inflammation, and prevent endotoxemia as well as liver injury caused by alcohol in experimental settings. Interestingly, saturated fatty acids may also directly control the gut microbiome. In summary, clinical and experimental studies highlight the significance and efficacy of the gut barrier in treating ALD.

Niacin Promotes Cardiac Healing after Myocardial Infarction through Activation of the Myeloid Prostaglandin D2 Receptor Subtype 1

Niacin is a well established drug used to lower cholesterol and prevent cardiovascular disease events. However, niacin also causes cutaneous flushing side effects due to release of the proresolution mediator prostaglandin D₂ (PGD₂). Recent randomized clinical trials have demonstrated that addition of niacin with laropiprant [a PGD₂ receptor subtype 1 (DP1) blocker] to statin-based therapies does not significantly decrease the risk of cardiovascular disease events, but increases the risk of serious adverse events. Here, we tested whether, and how, niacin beneficial effects on myocardial ischemia require the activation of the PGD₂/DP1 axis. Myocardial infarction (MI) was reproduced by ligation of the left anterior descending branch of the coronary artery in mice. We found that niacin increased PGD₂ release in macrophages and shifted macrophages to M2 polarization both in vitro and in vivo by activation of DP1 and accelerated inflammation resolution in zymosan-induced peritonitis in mice. Moreover, niacin treatment facilitated wound healing and improved cardiac function after MI through DP1-mediated M2 bias and timely resolution of inflammation in infarcted hearts. In addition, we found that niacin intake also stimulated M2 polarization of peripheral monocytes in humans. Collectively, niacin promoted cardiac functional recovery after ischemic myocardial infarction through DP1-mediated M2 polarization and timely resolution of inflammation in hearts. These results indicated that DP1 inhibition may attenuate the cardiovascular benefits of niacin.

Dietary nicotinic acid supplementation ameliorates chronic alcohol-induced fatty liver in rats

BACKGROUND

Alcohol abuse frequently causes niacin deficiency in association with the development of alcoholic liver disease. The objective of the present study was to determine whether dietary nicotinic acid (NA) deficiency exaggerates and whether dietary NA supplementation alleviates alcohol-induced fatty liver.

METHODS

Male Sprague-Dawley rats were pair-fed with 4 isocaloric liquid diets: control, ethanol (EtOH), EtOH with dietary NA deficiency, and EtOH with dietary NA supplementation, respectively, for 8 weeks. The control and EtOH diets contained normal levels of NA (7.5 mg/l). Dietary NA deficiency (0 mg NA/l) was achieved by removing NA from the vitamin mix, while NA was added to the liquid diet at 750 mg/l for dietary NA supplementation.

RESULTS

Chronic EtOH feeding induced significant lipid accumulation in the liver, which was not worsened by dietary NA deficiency, but was ameliorated by dietary NA supplementation. Liver total NAD, NAD(+) , and NADH levels were remarkably higher in the NA supplemented group than the NA deficient or EtOH alone groups. Dietary NA supplementation to EtOH-fed rats increased the protein levels of hepatic cytochrome P450 4A1 (CYP4A1) and acyl-coenzyme A oxidase 1 without affecting their mRNA levels. Interestingly, we found dietary NA supplementation reduced the ubiquitination level of CYP4A1. In addition, hepatic fatty acid synthase expression was reduced, while the serum β-hydroxybutyrate and adiponectin concentrations were significantly elevated by dietary NA supplementation. Moreover, dietary NA supplementation modulated EtOH-perturbed liver and serum metabolite profiles.

CONCLUSIONS

These results demonstrate that alcoholic fatty liver was not exaggerated by dietary NA deficiency, but was ameliorated by dietary NA supplementation. Increased hepatic fatty acid oxidation and decreased hepatic de novo lipogenesis contribute to the effects of dietary NA supplementation.

Drug repositioning: playing dirty to kill pain

The number of approved new molecular entity drugs has been decreasing as the pharmaceutical company investment in research and development is increasing. As we face this painful crisis, called an innovation gap, there is increasing awareness that development of new uses of existing drugs may be a powerful tool to help overcome this obstacle because it takes too long, costs too much and can be risky to release drugs developed de novo. Consequently, drug repositioning is emerging in different therapeutic areas, including the pain research area. Worldwide, pain is the main reason for seeking healthcare, and pain relief represents an unmet global clinical need. Therefore, development of analgesics with better efficacy, safety and cost effectiveness is of paramount importance. Despite the remarkable advancement in research on cellular and molecular mechanisms underlying pain pathophysiology over the past three decades, target-based therapeutic opportunities have not been pursued to the same extent. Phenotypic screening remains a more powerful tool for drug development than target-based screening so far. It sounds somewhat heretical, but some multi-action drugs, rather than very selective ones, have been developed intentionally. In the present review, we first critically discuss the utility of drug repositioning for analgesic drug development and then show examples of 'old' drugs that have been successfully repositioned or that are under investigation for their analgesic actions. We conclude that drug repositioning should be more strongly encouraged to help build a bridge between basic research and pain relief worldwide.

The anti-inflammatory action of Bothrops jararaca snake antithrombin on acute inflammation induced by carrageenan in mice

OBJECTIVE AND DESIGN

Antithrombin is known as the most important natural coagulation inhibitor and has been shown to have anti-inflammatory properties. The present study aimed to investigate the effects of Bothrops jararaca antithrombin on acute inflammation induced by carrageenan in mice.

METHODS

We evaluated the anti-inflammatory activity of antithrombin on models of paw edema formation, cell migration and leukocyte-endothelium interaction in mice (Swiss; n = 5). Acute inflammation was induced by the administration of carrageenan (15 mg kg⁻¹).

RESULTS

Treatment with B. jararaca antithrombin (1 mg kg⁻¹) 1 h before or after carrageenan administration significantly inhibited paw edema formation, reduced cell influx to the peritoneal cavity due to reduction in the migration of polymorphonuclear cells, and attenuated leukocyte rolling in the microcirculation of the cremaster muscle.The effects of antithrombin on vascular and cellular events of inflammation were completely abolished by treatment with the cyclo-oxygenase inhibitor indomethacin (4 mg kg⁻¹), suggesting the involvement of prostacyclin in the mechanism of inflammation inhibition by B. jararaca antithrombin.

CONCLUSION

This work showed for the first time the anti-inflammatory properties of B. jararaca antithrombin on vascular and cellular events of inflammation. These findings suggest that antithrombin is effective in preventing paw edema formation, cell migration and leukocyte rolling induced by carrageenan in mice.

Niacin inhibits carrageenan-induced neutrophil migration in mice

Several emerging lines of evidence support an anti-inflammatory role for nicotinic acid (niacin); however, its role in the regulation of leukocyte migration in response to inflammatory stimuli has not been elucidated until now. Herein, we have examined the effect of nicotinic acid on neutrophil recruitment in experimentally induced inflammation. We demonstrated that nicotinic acid treatment inhibited interleukin (IL)-8-induced, leukotriene (LT)B4-induced, and carrageenan-induced neutrophil migration into the pleural cavity of BALB/c mice and reduced neutrophil rolling and adherence in a mouse cremaster muscle preparation. Surprisingly, nicotinic acid treatment increased the level of the neutrophil chemoattractant KC in response to carrageenan. These results suggest that nicotinic acid plays an important role in the regulation of inflammation due to its ability to inhibit the actions of the neutrophil chemoattractants IL-8 and LTB4. Further inhibition of chemoattractants leads to impairment of leukocyte rolling and adherence to the vascular endothelium in the microcirculation of inflamed tissues.