Nicotinamide: a vitamin able to shift macrophage differentiation toward macrophages with restricted inflammatory features

NAD+ metabolism and therapeutic strategies in cardiovascular diseases

Nicotinamide adenine dinucleotide (NAD+) is a central and pleiotropic metabolite involved in cellular energy metabolism, cell signaling, DNA repair, and protein modifications. Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Metabolic stress and aging directly affect the cardiovascular system. Compelling data suggest that NAD + levels decrease with age, obesity, and hypertension, which are all notable risk factors for CVD. In addition, the therapeutic elevation of NAD + levels reduces chronic low-grade inflammation, reactivates autophagy and mitochondrial biogenesis, and enhances oxidative metabolism in vascular cells of humans and rodents with vascular disorders. In preclinical models, NAD + boosting can also expand the health span, prevent metabolic syndrome, and decrease blood pressure. Moreover, NAD + storage by genetic, pharmacological, or natural dietary NAD + -increasing strategies has recently been shown to be effective in improving the pathophysiology of cardiac and vascular health in different animal models, and human health. Here, we review and discuss NAD + -related mechanisms pivotal for vascular health and summarize recent experimental evidence in NAD + research directly related to vascular disease, including atherosclerosis, and coronary artery disease. Finally, we comparatively assess distinct NAD + precursors for their clinical efficacy and the efficiency of NAD + elevation in the treatment of major CVD. These findings may provide ideas for new therapeutic strategies to prevent and treat CVD in the clinic.

Nicotinamide Riboside Augments Human Macrophage Migration via SIRT3-Mediated Prostaglandin E2 Signaling

NAD+ boosting via nicotinamide riboside (NR) confers anti-inflammatory effects. However, its underlying mechanisms and therapeutic potential remain incompletely defined. Here, we showed that NR increased the expression of CC-chemokine receptor 7 (CCR7) in human M1 macrophages by flow cytometric analysis of cell surface receptors. Consequently, chemokine ligand 19 (CCL19, ligand for CCR7)-induced macrophage migration was enhanced following NR administration. Metabolomics analysis revealed that prostaglandin E2 (PGE2) was increased by NR in human monocytes and in human serum following in vivo NR supplementation. Furthermore, NR-mediated upregulation of macrophage migration through CCL19/CCR7 was dependent on PGE2 synthesis. We also demonstrated that NR upregulated PGE2 synthesis through SIRT3-dependent post-transcriptional regulation of cyclooxygenase 2 (COX-2). The NR/SIRT3/migration axis was further validated using the scratch-test model where NR and SIRT3 promoted more robust migration across a uniformly disrupted macrophage monolayer. Thus, NR-mediated metabolic regulation of macrophage migration and wound healing may have therapeutic potential for the topical management of chronic wound healing.

Enterohemorrhagic Escherichia coli senses microbiota-derived nicotinamide to increase its virulence and colonization in the large intestine

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a foodborne pathogen that specifically colonizes and infects the human large intestine. EHEC O157:H7 engages intricate regulatory pathways to detect host intestinal signals and regulate virulence-related gene expression during colonization and infection. However, the overall EHEC O157:H7 virulence regulatory network in the human large intestine remains incompletely understood. Here, we report a complete signal regulatory pathway where the EvgSA two-component system responds to high-nicotinamide levels produced by microbiota in the large intestine and directly activates loci of enterocyte effacement genes to promote EHEC O157:H7 adherence and colonization. This EvgSA-mediated nicotinamide signaling regulatory pathway is conserved and widespread among several other EHEC serotypes. Moreover, disruption of this virulence-regulating pathway by the deletion of evgS or evgA significantly decreased EHEC O157:H7 adherence and colonization in the mouse intestinal tract, indicating that these genes could be potential targets for the development of new therapeutics for EHEC O157:H7 infection.

Biomarker identification and pathway analysis of Astragalus membranaceus and Curcuma zedoaria couplet medicines on adenine-induced chronic kidney disease in rats based on metabolomics

Background: Chronic kidney disease (CKD) is usually insidious, and most affected individuals are asymptomatic until the disease becomes advanced. The effective treatment of CKD would rely on the incorporation of multidisciplinary approaches. Astragalus membranaceus (AM) and Curcuma zedoaria (CZ) have been widely used in the treatment of CKD. However, the mechanism of AM and CZ in the treatment of CKD is still unclear.

Methods: This study was designed to evaluate the effects of AM and CZ on adenine-induced rats and to investigate the underlying mechanism by using metabolomic analysis. Addition of 0.75% adenine to the diet of rats for 3 weeks induced the animal model of CKD. The rats in the treatment group were treated with AM and CZ (2.1 g/kg/day) for 4 weeks. Blood and kidney samples were collected for biochemical and histological examination. Ultra-high-performance liquid chromatography/Q Exactive HFX mass spectrometer (UHPLC-QE-MS) was applied to analyze metabolic profiling variations in the kidney.

Results: The results showed that AM and CZ could significantly reduce serum creatinine (Scr) and blood urea nitrogen (BUN) levels in CKD rats and alleviate renal pathological injury. By comparing the endogenous components of the normal group and the model group in positive ion mode and negative ion mode, a total of 365 and 155 different metabolites were screened, respectively. A total of 117 and 73 metabolites with significantly different expressions were identified between model group and AM and CZ group in positive ion mode and negative ion mode, respectively. The pivotal pathways affected by AM and CZ included nicotinate and nicotinamide metabolism, and glycine, serine and threonine metabolism. Furthermore, significant changes in metabolites in CKD rats after AM and CZ therapies were observed, including L-Threonine, D-pantothenic acid, and nicotinamide. Moreover, we found that AM and CZ significantly reduced renal fibrosis and inflammation in CKD rats, which may be related to the regulation of SIRT1/JNK signaling pathway.

Conclusion: In conclusion, AM and CZ significantly reduced renal fibrosis and inflammation in CKD rats, which may be related to the regulation of SIRT1/JNK signaling pathway. Furthermore, L-Threonine, D-pantothenic acid, and nicotinamide may be potential biomarkers for the progression and treatment of CKD.

NAD+ Homeostasis and NAD+-Consuming Enzymes: Implications for Vascular Health

Nicotinamide adenine dinucleotide (NAD+) is a ubiquitous metabolite that takes part in many key redox reactions. NAD+ biosynthesis and NAD+-consuming enzymes have been attracting markedly increasing interest since they have been demonstrated to be involved in several crucial biological pathways, impacting genes transcription, cellular signaling, and cell cycle regulation. As a consequence, many pathological conditions are associated with an impairment of intracellular NAD+ levels, directly or indirectly, which include cardiovascular diseases, obesity, neurodegenerative diseases, cancer, and aging. In this review, we describe the general pathways involved in the NAD+ biosynthesis starting from the different precursors, analyzing the actual state-of-art of the administration of NAD+ precursors or blocking NAD+-dependent enzymes as strategies to increase the intracellular NAD+ levels or to counteract the decline in NAD+ levels associated with ageing. Subsequently, we focus on the disease-related and age-related alterations of NAD+ homeostasis and NAD+-dependent enzymes in endothelium and the consequent vascular dysfunction, which significantly contributes to a wide group of pathological disorders.

Schistosoma mansoni and the purinergic halo

Intravascular schistosomes may control immune and hemostatic responses by regulating the nature and amount of selected host purinergic signaling molecules - such as adenosine triphosphate (ATP), adenosine diphosphate (ADP), and nicotinamide adenine dinucleotide (NAD) - surrounding them. Such metabolites are collectively known as the worm's 'purinergic halo'. Host-interactive, membrane-bound, tegumental ectonucleotidases, notably SmATPDase1, SmNPP5, SmAP and SmNACE, can degrade proinflammatory, prothrombotic and immunomodulatory purinergic metabolites like those listed. A common catabolic product is the anti-inflammatory metabolite adenosine that can additionally be taken in by the worms as food. We envision the tegumental ectonucleotidases as having a twofold role at the worm surface: first, they degrade potentially harmful host signaling molecules, and second, they generate vital nutrients around the worms from where these can be conveniently imported.

NAD(H)-loaded nanoparticles for efficient sepsis therapy via modulating immune and vascular homeostasis

Sepsis is a life-threatening organ dysfunction responsible for nearly 270,000 deaths annually in the United States alone. Nicotinamide adenine dinucleotide (NAD+), an immunomodulator, can potentially treat sepsis; however, clinical application of NAD+ is hindered by its inability to be directly taken up by cells. To address this challenge, a family of nanoparticles (NPs) loaded with either NAD+ or the reduced form of NAD+ (NADH), hereafter NAD(H)-loaded NPs, were engineered to enable direct cellular transport and replenishment of NAD(H). The NAD(H)-loaded NPs improved cellular energy supply, suppressed inflammation and prevented inflammation-induced cell pyroptosis and apoptosis. Therefore, the NPs can help maintain immune homoeostasis and vascular function, two key factors in the pathogenesis of sepsis. The NAD(H)-loaded NPs demonstrated excellent therapeutic efficacies in treating endotoxemia and multidrug-resistant pathogen-induced bacteremia. In addition, the NAD(H)-loaded NPs prevented caecal ligation and puncture-induced multiorgan injury and improved outcomes of secondary Pseudomonas aeruginosa infections following caecal ligation and puncture, thus potentially leading to a highly innovative and translational approach to treat sepsis efficiently and safely.

Neuroinflammation in Parkinson's Disease - Putative Pathomechanisms and Targets for Disease-Modification

Parkinson’s disease (PD) is a progressive and debilitating chronic disease that affects more than six million people worldwide, with rising prevalence. The hallmarks of PD are motor deficits, the spreading of pathological α-synuclein clusters in the central nervous system, and neuroinflammatory processes. PD is treated symptomatically, as no causally-acting drug or procedure has been successfully established for clinical use. Various pathways contributing to dopaminergic neuron loss in PD have been investigated and described to interact with the innate and adaptive immune system. We discuss the possible contribution of interconnected pathways related to the immune response, focusing on the pathophysiology and neurodegeneration of PD. In addition, we provide an overview of clinical trials targeting neuroinflammation in PD.

NAD+ and Vascular Dysfunction: From Mechanisms to Therapeutic Opportunities

Nicotinamide adenine dinucleotide (NAD+) is an essential and pleiotropic coenzyme involved not only in cellular energy metabolism, but also in cell signaling, epigenetic regulation, and post-translational protein modifications. Vascular disease risk factors are associated with aberrant NAD+ metabolism. Conversely, the therapeutic increase of NAD+ levels through the administration of NAD+ precursors or inhibitors of NAD+-consuming enzymes reduces chronic low-grade inflammation, reactivates autophagy and mitochondrial biogenesis, and enhances oxidative metabolism in vascular cells of humans and rodents with vascular pathologies. As such, NAD+ has emerged as a potential target for combatting age-related cardiovascular and cerebrovascular disorders. This review discusses NAD+-regulated mechanisms critical for vascular health and summarizes new advances in NAD+ research directly related to vascular aging and disease, including hypertension, atherosclerosis, coronary artery disease, and aortic aneurysms. Finally, we enumerate challenges and opportunities for NAD+ repletion therapy while anticipating the future of this exciting research field, which will have a major impact on vascular medicine.

COVID-19: Are We Facing Secondary Pellagra Which Cannot Simply Be Cured by Vitamin B3?

Immune response to SARS-CoV-2 and ensuing inflammation pose a huge challenge to the host’s nicotinamide adenine dinucleotide (NAD⁺) metabolism. Humans depend on vitamin B3 for biosynthesis of NAD⁺, indispensable for many metabolic and NAD⁺-consuming signaling reactions. The balance between its utilization and resynthesis is vitally important. Many extra-pulmonary symptoms of COVID-19 strikingly resemble those of pellagra, vitamin B3 deficiency (e.g., diarrhoea, dermatitis, oral cavity and tongue manifestations, loss of smell and taste, mental confusion). In most developed countries, pellagra is successfully eradicated by vitamin B3 fortification programs. Thus, conceivably, it has not been suspected as a cause of COVID-19 symptoms. Here, the deregulation of the NAD⁺ metabolism in response to the SARS-CoV-2 infection is reviewed, with special emphasis on the differences in the NAD⁺ biosynthetic pathway’s efficiency in conditions predisposing for the development of serious COVID-19. SARS-CoV-2 infection-induced NAD⁺ depletion and the elevated levels of its metabolites contribute to the development of a systemic disease. Acute liberation of nicotinamide (NAM) in antiviral NAD⁺-consuming reactions potentiates “NAM drain”, cooperatively mediated by nicotinamide N-methyltransferase and aldehyde oxidase. “NAM drain” compromises the NAD⁺ salvage pathway’s fail-safe function. The robustness of the host’s NAD⁺ salvage pathway, prior to the SARS-CoV-2 infection, is an important determinant of COVID-19 severity and persistence of certain symptoms upon resolution of infection.

Boosting NAD+ blunts toll-like receptor-4 induced type-I interferon in control and systemic lupus erythematosus monocytes

BACKGROUND

Fasting and NAD+-boosting compounds including NAD+ precursor nicotinamide riboside (NR) confer anti-inflammatory effects. However, the underlying mechanisms and therapeutic potential are incompletely defined.

METHODS

We explored the underlying biology in myeloid cells from healthy volunteers following in-vivo placebo or NR administration and subsequently tested the findings in-vitro in monocytes extracted from subjects with systemic lupus erythematosus (SLE).

RESULTS

RNA sequencing of unstimulated and lipopolysaccharide (LPS)-activated monocytes implicate NR in the regulation of autophagy and type I interferon signaling. In primary monocytes NR blunts LPS-induced IFNβ production and genetic or pharmacologic disruption of autophagy phenocopies this effect. Given NAD+ is a co-enzyme in oxidoreductive reactions, metabolomics was performed and identified that NR increased inosine level. Inosine supplementation similarly blunts autophagy and IFNβrelease. Finally, as SLE exhibits type I interferon dysregulation, we assessed the NR effect on SLE patient monocytes and found that NR reduces autophagy and interferon-β release.

CONCLUSION

We conclude that NR, in an NAD+-dependent manner and in part via inosine-signaling, mediates suppression of autophagy and attenuates type I interferon in myeloid cells and identifies NR as a potential adjunct for SLE management.

TRIAL REGISTRATION

ClinicalTrails.gov registration numbers: NCT02812238, NCT00001846 and NCT00001372.

FUNDING

This work was supported by the NHLBI and NIAMS Divisions of Intramural Research.

Therapeutic Potential of Emerging NAD+-Increasing Strategies for Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death worldwide. Aging and/or metabolic stress directly impact the cardiovascular system. Over the last few years, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism to aging and other pathological conditions closely related to cardiovascular diseases have been intensively investigated. NAD+ bioavailability decreases with age and cardiometabolic conditions in several mammalian tissues. Compelling data suggest that declining tissue NAD+ is commonly related to mitochondrial dysfunction and might be considered as a therapeutic target. Thus, NAD+ replenishment by either genetic or natural dietary NAD+-increasing strategies has been recently demonstrated to be effective for improving the pathophysiology of cardiac and vascular health in different experimental models, as well as human health, to a lesser extent. Here, we review and discuss recent experimental evidence illustrating that increasing NAD+ bioavailability, particularly by the use of natural NAD+ precursors, may offer hope for new therapeutic strategies to prevent and treat cardiovascular diseases.

The probiotic L. casei Zhang slows the progression of acute and chronic kidney disease

The relationship between gut microbial dysbiosis and acute or chronic kidney disease (CKD) is still unclear. Here, we show that oral administration of the probiotic Lactobacillus casei Zhang (L. casei Zhang) corrected bilateral renal ischemia-reperfusion (I/R)-induced gut microbial dysbiosis, alleviated kidney injury, and delayed its progression to CKD in mice. L. casei Zhang elevated the levels of short-chain fatty acids (SCFAs) and nicotinamide in the serum and kidney, resulting in reduced renal inflammation and damage to renal tubular epithelial cells. We also performed a 1-year phase 1 placebo-controlled study of oral L. casei Zhang use (Chinese clinical trial registry, ChiCTR-INR-17013952), which was well tolerated and slowed the decline of kidney function in individuals with stage 3-5 CKD. These results show that oral administration of L. casei Zhang, by altering SCFAs and nicotinamide metabolism, is a potential therapy to mitigate kidney injury and slow the progression of renal decline.

NAicotinamide retains Klotho expression and ameliorates rhabdomyolysis-induced acute kidney injury

OBJECTIVES

Acute kidney injury (AKI) is a severe complication of rhabdomyolysis that significantly increases mortality. Unfortunately, the therapeutic approach is limited. Inflammation plays a critical role in the pathogenesis of rhabdomyolysis-induced AKI, which is a potential therapeutic target. Nicotinamide, a form of vitamin B3 and a precursor of nicotinamide adenine dinucleotide, has been shown to have potent antiinflammation effects. Klotho is a tubular highly expressed renoprotective protein. Therefore, we explored the effect of nicotinamide on rhabdomyolysis-induced AKI and the underlying mechanisms.

METHODS

We intramuscularly injected glycerol to induce rhabdomyolysis, and intraperitoneally administrated nicotinamide to observe the effect on kidney injury. Interleukin-1 beta, tumor necrosis factor alpha, nuclear factor kappa B (NF-κB), and Klotho were determined by Western blot. Chromatin immunoprecipitation was used to assess the interaction of NF-κB, nuclear receptor corepressor, and histone deacetylase 1 with Klotho promoters. Small interfering RNA was used to evaluate the role of Klotho in nicotinamide-related renoprotection.

RESULTS

The results showed that nicotinamide attenuated renal pathologic morphology, kidney functional abnormalities, and kidney inflammatory response in rhabdomyolysis. Moreover, nicotinamide effectively blocked the recruitment of NF-κB, nuclear receptor corepressor, and histone deacetylase 1 to the promoter of Klotho, and preserved Klotho expression. More importantly, the renoprotection effect of nicotinamide was abrogated when Klotho was knocked down by small interfering RNA in rhabdomyolysis mice.

CONCLUSIONS

Our study demonstrated that Klotho preservation is essential for the renoprotection effect of nicotinamide, and provides a new preventive strategy for rhabdomyolysis-induced AKI.

Nicotinamide Protects Against Diet-Induced Body Weight Gain, Increases Energy Expenditure, and Induces White Adipose Tissue Beiging

SCOPE

Interventions that boost NAD+ availability are of potential therapeutic interest for obesity treatment. The potential of nicotinamide (NAM), the amide form of vitamin B3 and a physiological precursor of nicotinamide adenine dinucleotide (NAD)+ , in preventing weight gain has not previously been studied in vivo. Other NAD+ precursors have been shown to decrease weight gain; however, their impact on adipose tissue is not addressed.

METHODS AND RESULTS

Two doses of NAM (high dose: 1% and low dose: 0.25%) are given by drinking water to C57BL/6J male mice, starting at the same time as the high-fat diet feeding. NAM supplementation protects against diet-induced obesity by augmenting global body energy expenditure in C57BL/6J male mice. The manipulation markedly alters adipose morphology and metabolism, particularly in inguinal (i) white adipose tissue (iWAT). An increased number of brown and beige adipocyte clusters, protein abundance of uncoupling protein 1 (UCP1), mitochondrial activity, adipose NAD+ , and phosphorylated AMP-activated protein kinase (P-AMPK) levels are observed in the iWAT of treated mice. Notably, a significant improvement in hepatic steatosis, inflammation, and glucose tolerance is also observed in NAM high-dose treated mice.

CONCLUSION

NAM influences whole-body energy expenditure by driving changes in the adipose phenotype. Thus, NAM is an attractive potential treatment for preventing obesity and associated complications.

Nicotinamide Prevents Apolipoprotein B-Containing Lipoprotein Oxidation, Inflammation and Atherosclerosis in Apolipoprotein E-Deficient Mice

The potential of nicotinamide (NAM) to prevent atherosclerosis has not yet been examined. This study investigated the effect of NAM supplementation on the development of atherosclerosis in a mouse model of the disease. The development of aortic atherosclerosis was significantly reduced (NAM low dose: 45%; NAM high dose: 55%) in NAM-treated, apolipoprotein (Apo)E-deficient mice challenged with a Western diet for 4 weeks. NAM administration significantly increased (1.8-fold) the plasma concentration of proatherogenic ApoB-containing lipoproteins in NAM high-dose (HD)-treated mice compared with untreated mice. However, isolated ApoB-containing lipoproteins from NAM HD mice were less prone to oxidation than those of untreated mice. This result was consistent with the decreased (1.5-fold) concentration of oxidized low-density lipoproteins in this group. Immunohistochemical staining of aortas from NAM-treated mice showed significantly increased levels of IL-10 (NAM low-dose (LD): 1.3-fold; NAM HD: 1.2-fold), concomitant with a significant decrease in the relative expression of TNFα (NAM LD: −44%; NAM HD: −57%). An improved anti-inflammatory pattern was reproduced in macrophages cultured in the presence of NAM. Thus, dietary NAM supplementation in ApoE-deficient mice prevented the development of atherosclerosis and improved protection against ApoB-containing lipoprotein oxidation and aortic inflammation.

Senescent cells promote tissue NAD+ decline during ageing via the activation of CD38+ macrophages

Declining tissue nicotinamide adenine dinucleotide (NAD) levels are linked to ageing and its associated diseases. However, the mechanism for this decline is unclear. Here, we show that pro-inflammatory M1-like macrophages, but not naive or M2 macrophages, accumulate in metabolic tissues, including visceral white adipose tissue and liver, during ageing and acute responses to inflammation. These M1-like macrophages express high levels of the NAD-consuming enzyme CD38 and have enhanced CD38-dependent NADase activity, thereby reducing tissue NAD levels. We also find that senescent cells progressively accumulate in visceral white adipose tissue and liver during ageing and that inflammatory cytokines secreted by senescent cells (the senescence-associated secretory phenotype, SASP) induce macrophages to proliferate and express CD38. These results uncover a new causal link among resident tissue macrophages, cellular senescence and tissue NAD decline during ageing and offer novel therapeutic opportunities to maintain NAD levels during ageing.

Randomized controlled study for the anti-aging effect of human adipocyte-derived mesenchymal stem cell media combined with niacinamide after laser therapy

BACKGROUND

Recent advancements in laser-assisted drug delivery have emphasized the importance of post-laser use of active ingredients.

AIMS

We evaluated the effect of topical post-laser treatment with adipocyte-derived stem cell-containing medium (ADSC-CM) in combination with niacinamide through a double-blind, randomized, vehicle-controlled study.

PATIENTS/METHODS

Twenty-five patients with aging skin underwent ablative fractional laser (AFL) treatment on both sides of the face for skin rejuvenation. Moisturizers with or without ADSC-CM plus 2% niacinamide was applied to the designated sides of faces for 3 weeks. The wrinkle and the melanin indices were assessed using a specialized digital photography analyzer. Additional in vitro assays were performed.

RESULTS

The wrinkle index, melanin index, patient satisfaction score, and the investigator's global esthetic improvement scale (GAIS) after use of ADSC-CM plus niacinamide were significantly higher than after use of the vehicle cream. The in vitro UVB irradiation assays with human keratinocytes showed decreased levels of pro-inflammatory cytokines upon incubation with ADSC-CM plus niacinamide, and the cell scratch assay displayed decreased MMP-1 and MMP-2 expression as well as increased Type 1 collagen expression.

CONCLUSIONS

We demonstrated that post-laser topical application of ADSC-CM in combination with niacinamide has anti-aging effect on skin.

Nicotinamide inhibits melanoma in vitro and in vivo

Background

Even though new therapies are available against melanoma, novel approaches are needed to overcome resistance and high-toxicity issues. In the present study the anti-melanoma activity of Nicotinamide (NAM), the amide form of Niacin, was assessed in vitro and in vivo.

Methods

Human (A375, SK-MEL-28) and mouse (B16-F10) melanoma cell lines were used for in vitro investigations. Viability, cell-death, cell-cycle distribution, apoptosis, Nicotinamide Adenine Dinucleotide⁺ (NAD⁺), Adenosine Triphosphate (ATP), and Reactive Oxygen Species (ROS) levels were measured after NAM treatment. NAM anti-SIRT2 activity was tested in vitro; SIRT2 expression level was investigated by in silico transcriptomic analyses. Melanoma growth in vivo was measured in thirty-five C57BL/6 mice injected subcutaneously with B16-F10 melanoma cells and treated intraperitoneally with NAM. Interferon (IFN)-γ-secreting murine cells were counted with ELISPOT assay. Cytokine/chemokine plasmatic levels were measured by xMAP technology. Niacin receptors expression in human melanoma samples was also investigated by in silico transcriptomic analyses.

Results

NAM reduced up to 90% melanoma cell number and induced: i) accumulation in G1-phase (40% increase), ii) reduction in S- and G2-phase (about 50% decrease), iii) a 10-fold increase of cell-death and 2.5-fold increase of apoptosis in sub-G1 phase, iv) a significant increase of NAD⁺, ATP, and ROS levels, v) a strong inhibition of SIRT2 activity in vitro. NAM significantly delayed tumor growth in vivo (p ≤ 0.0005) and improved survival of melanoma-bearing mice (p ≤ 0.0001). About 3-fold increase (p ≤ 0.05) of Interferon-gamma (IFN-γ) producing cells was observed in NAM treated mice. The plasmatic expression levels of 6 cytokines (namely: Interleukin 5 (IL-5), Eotaxin, Interleukin 12 (p40) (IL12(p40)), Interleukin 3 (IL-3), Interleukin 10 (IL-10) and Regulated on Activation Normal T Expressed and Secreted (RANTES) were significantly changed in the blood of NAM treated mice, suggesting a key role of the immune response. The observed inhibitory effect of NAM on SIRT2 enzymatic activity confirmed previous evidence; we show here that SIRT2 expression is significantly increased in melanoma and inversely related to melanoma-patients survival. Finally, we show for the first time that the expression levels of Niacin receptors HCAR2 and HCAR3 is almost abolished in human melanoma samples.

Conclusion

NAM shows a relevant anti-melanoma activity in vitro and in vivo and is a suitable candidate for further clinical investigations.

Nicotinamide restricts neural precursor proliferation to enhance catecholaminergic neuronal subtype differentiation from mouse embryonic stem cells

Emerging evidence indicates that a strong relationship exists between brain regenerative therapies and nutrition. Early life nutrition plays an important role during embryonic brain development, and there are clear consequences to an imbalance in nutritional factors on both the production and survival of mature neuronal populations and the infant’s risk of diseases in later life. Our research and that of others suggest that vitamins play a fundamental role in the formation of neurons and their survival. There is a growing body of evidence that nicotinamide, the water-soluble amide form of vitamin B₃, is implicated in the conversion of pluripotent stem cells to clinically relevant cells for regenerative therapies. This study investigated the ability of nicotinamide to promote the development of mature catecholaminergic neuronal populations (associated with Parkinson’s disease) from mouse embryonic stem cells, as well as investigating the underlying mechanisms of nicotinamide’s action. Nicotinamide selectively enhanced the production of tyrosine hydroxylase-expressing neurons and serotonergic neurons from mouse embryonic stem cell cultures (Sox1GFP knock-in 46C cell line). A 5-Ethynyl-2´-deoxyuridine (EdU) assay ascertained that nicotinamide, when added in the initial phase, reduced cell proliferation. Nicotinamide drove tyrosine hydroxylase-expressing neuron differentiation as effectively as an established cocktail of signalling factors, reducing the proliferation of neural progenitors and accelerating neuronal maturation, neurite outgrowth and neurotransmitter expression. These novel findings show that nicotinamide enhanced and enriched catecholaminergic differentiation and inhibited cell proliferation by directing cell cycle arrest in mouse embryonic stem cell cultures, thus driving a critical neural proliferation-to-differentiation switch from neural progenitors to neurons. Further research into the role of vitamin metabolites in embryogenesis will significantly advance cell-based regenerative medicine, and help realize their role as crucial developmental signalling molecules in brain development.

Metabolomic Profiles of Bovine Mammary Epithelial Cells Stimulated by Lipopolysaccharide

Bovine mammary epithelial cells (bMECs) are the main cells of the dairy cow mammary gland. In addition to their role in milk production, they are effector cells of mammary immunity. However, there is little information about changes in metabolites of bMECs when stimulated by lipopolysaccharide (LPS). This study describes a metabolomics analysis of the LPS-stimulated bMECs to provide a basis for the identification of potential diagnostic screening biomarkers and possible treatments for bovine mammary gland inflammation. In the present study, bMECs were challenged with 500 ng/mL LPS and samples were taken at 0 h, 12 h and 24 h post stimulation. Metabolic changes were investigated using high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF MS) with univariate and multivariate statistical analyses. Clustering and metabolic pathway changes were established by MetaboAnalyst. Sixty-three differential metabolites were identified, including glycerophosphocholine, glycerol-3-phosphate, L-carnitine, L-aspartate, glutathione, prostaglandin G2, α-linolenic acid and linoleic acid. They were mainly involved in eight pathways, including D-glutamine and D-glutamic acid metabolism; linoleic acid metabolism; α-linolenic metabolism; and phospholipid metabolism. The results suggest that bMECs are able to regulate pro-inflammatory, anti-inflammatory, antioxidation and energy-producing related metabolites through lipid, antioxidation and energy metabolism in response to inflammatory stimuli.

Diverse therapeutic efficacies and more diverse mechanisms of nicotinamide

BACKGROUND

Nicotinamide (NAM) is a form of vitamin B3 that, when administered at near-gram doses, has been shown or suggested to be therapeutically effective against many diseases and conditions. The target conditions are incredibly diverse ranging from skin disorders such as bullous pemphigoid to schizophrenia and depression and even AIDS. Similar diversity is expected for the underlying mechanisms. In a large portion of the conditions, NAM conversion to nicotinamide adenine dinucleotide (NAD⁺) may be a major factor in its efficacy. The augmentation of cellular NAD⁺ level not only modulates mitochondrial production of ATP and superoxide, but also activates many enzymes. Activated sirtuin proteins, a family of NAD⁺-dependent deacetylases, play important roles in many of NAM's effects such as an increase in mitochondrial quality and cell viability countering neuronal damages and metabolic diseases. Meanwhile, certain observed effects are mediated by NAM itself. However, our understanding on the mechanisms of NAM's effects is limited to those involving certain key proteins and may even be inaccurate in some proposed cases.

AIM OF REVIEW

This review details the conditions that NAM has been shown to or is expected to effectively treat in humans and animals and evaluates the proposed underlying molecular mechanisms, with the intention of promoting wider, safe therapeutic application of NAM.

KEY SCIENTIFIC CONCEPTS OF REVIEW

NAM, by itself or through altering metabolic balance of NAD⁺ and tryptophan, modulates mitochondrial function and activities of many molecules and thereby positively affects cell viability and metabolic functions. And, NAM administration appears to be quite safe with limited possibility of side effects which are related to NAM's metabolites.

Nicotinamide Augments the Anti-Inflammatory Properties of Resveratrol through PARP1 Activation

Resveratrol (RSV) and nicotinamide (NAM) have garnered considerable attention due to their anti-inflammatory and anti-aging properties. NAM is a transient inhibitor of class III histone deacetylase SIRTs (silent mating type information regulation 2 homologs) and SIRT1 is an inhibitor of poly-ADP-ribose polymerase-1 (PARP1). The debate on the relationship between RSV and SIRT1 has precluded the use of RSV as a therapeutic drug. Recent work demonstrated that RSV facilitates tyrosyl-tRNA synthetase (TyrRS)-dependent activation of PARP1. Moreover, treatment with NAM is sufficient to facilitate the nuclear localization of TyrRS that activates PARP1. RSV and NAM have emerged as potent agonists of PARP1 through inhibition of SIRT1. In this study, we evaluated the effects of RSV and NAM on pro-inflammatory macrophages. Our results demonstrate that treatment with either RSV or NAM attenuates the expression of pro-inflammatory markers. Strikingly, the combination of RSV with NAM, exerts additive effects on PARP1 activation. Consistently, treatment with PARP1 inhibitor antagonized the anti-inflammatory effect of both RSV and NAM. For the first time, we report the ability of NAM to augment PARP1 activation, induced by RSV, and its associated anti-inflammatory effects mediated through the induction of BCL6 with the concomitant down regulation of COX-2.

NAD metabolites interfere with proliferation and functional properties of THP-1 cells

Over the past few years the NAD-related compounds nicotinamide (NAM), nicotinamide riboside (NR) and 1-methylnicotinamide (MNA) have been established as important molecules in signalling pathways that contribute to metabolic functions of many cells, including those of the immune system. Among immune cells, monocytes/macrophages, which are the major players of inflammatory processes, are especially susceptible to the anti-inflammatory action of NAM. Here we asked whether NAM and the two other compounds have the potential to regulate differentiation and LPS-induced biological answers of the monocytic cell line THP-1. We show that treatment of THP-1 cells with NAM, NR and MNA resulted in growth retardation accompanied by enrichment of cells in the G0/G1-phase independent of p21 and p53. NAM and NR caused an increase in intracellular NAD concentrations and SIRT1 and PARP1 mRNA expression was found to be enhanced. The compounds failed to up-regulate the expression of the cell surface differentiation markers CD38, CD11b and CD14. They modulated the reactive oxygen species production and primed the cells to respond less effectively to the LPS induced TNF-α production. Our data show that the NAD metabolites interfere with early events associated with differentiation of THP-1 cells along the monocytic path and that they affect LPS-induced biological responses of the cell line.

Nicotinamide alleviates kidney injury and pregnancy outcomes in lupus-prone MRL/lpr mice treated with lipopolysaccharide

Systemic lupus erythematosus (SLE) increases the risk of preterm birth and preeclampsia (PE). The flares of SLE during pregnancy or after delivery are also problematic. We have previously demonstrated that nicotinamide (NAM), a non-teratogenic amide of vitamin B3, reduces inflammation and oxidative stress and improves PE-like phenotype and pregnancy outcomes in the mouse models of PE. The present study aimed to establish a model to investigate the pregnancy outcomes and flares of SLE in pregnant mice with SLE and to examine whether NAM is beneficial to pregnant mice with SLE. We used pregnant and non-pregnant lupus-prone MRL/lpr mice treated with or without a Toll-like receptor (TLR) ligand lipopolysaccharide (LPS) because TLR4 signaling reportedly exacerbates SLE and pregnancy; MRL/+ mice were used as controls. Blood pressure (BP) and urinary albumin excretion were increased only in the pregnant MRL/lpr-LPS mice. LPS together with pregnancy exacerbated glomerulonephritis, and the most severe inflammation was observed in the kidneys of the pregnant MRL/lpr-LPS mice. The shortening of pregnancy periods, increase in fetal demise percentage, and reduction in fetal weight were observed only in the pregnant MRL/lpr-LPS mice. NAM improved BP and kidney injury, prolonged pregnancy periods, and improved fetal growth in the pregnant MRL/lpr-LPS mice. The results suggest that SLE patients are prone to develop poor pregnancy outcome, and likely develop severe nephropathy and kidney inflammation. NAM may be a novel therapeutic option that improves kidney injury and pregnancy outcomes, thereby benefiting pregnant patients with SLE.

CD14 Counterregulates Lipopolysacharide-Induced Tumor Necrosis Factor-α Production in a Macrophage Subset

In response to GM-CSF or M-CSF, macrophages (MΦ) can acquire pro- or anti-inflammatory properties, respectively. Given the importance of CD14 and Toll-like receptor (TLR) 4 in lipopolysaccharide (LPS)-induced signaling, we studied the effect of anti-CD14 antibody mediated CD14 blockade on LPS-induced cytokine production, signal transduction and on the expression levels of CD14 and TLR4 in GM-MΦ and M-MΦ. We found M-MΦ to express higher levels of both surface antigens and to produce more interferon (IFN)-β and interleukin-10, but less tumor necrosis factor (TNF)-α than GM-MΦ. Blockage of CD14 at high LPS concentrations increased the production of proinflammatory cytokines and decreased that of IFN-β in M-MΦ but not in GM-MΦ. We show that phosphorylation states of signaling molecules of the MyD88 (myeloid differentiation primary response 88), TRIF (TIR-domain-containing adapter-inducing IFN-β) and MAPK (mitogen-activated protein kinase) pathways are not altered in any way that would account for the cytokine overshoot reaction. However, CD14 blockage in M-MΦ decreased TLR4 and CD14 expression levels, regardless of the presence of LPS, indicating that the loss of the surface molecules prevented LPS from initiating TRIF signaling. As TNF-α synthesis was even upregulated under these experimental conditions, we suggest that TRIF is normally involved in restricting LPS-induced TNF-α overproduction. Thus, surface CD14 plays a decisive role in the biological response by determining LPS-induced signaling.

Tissue Engineering Therapies Based on Folic Acid and Other Vitamin B Derivatives. Functional Mechanisms and Current Applications in Regenerative Medicine

B-vitamins are a group of soluble vitamins which are cofactors of some of the enzymes involved in the metabolic pathways of carbohydrates, fats and proteins. These compounds participate in a number of functions as cardiovascular, brain or nervous systems. Folic acid is described as an accessible and multifunctional niche component that can be used safely, even combined with other compounds, which gives it high versatility. Also, due to its non-toxicity and great stability, folic acid has attracted much attention from researchers in the biomedical and bioengineering area, with an increasing number of works directed at using folic acid and its derivatives in tissue engineering therapies as well as regenerative medicine. Thus, this review provides an updated discussion about the most relevant advances achieved during the last five years, where folic acid and other vitamins B have been used as key bioactive compounds for enhancing the effectiveness of biomaterials' performance and biological functions for the regeneration of tissues and organs.

The effects of monocytes on tumor cell extravasation in a 3D vascularized microfluidic model

Metastasis is the leading cause of cancer-related deaths. Recent developments in cancer immunotherapy have shown exciting therapeutic promise for metastatic patients. While most therapies target T cells, other immune cells, such as monocytes, hold great promise for therapeutic intervention. In our study, we provide primary evidence of direct engagement between human monocytes and tumor cells in a 3D vascularized microfluidic model. We first characterize the novel application of our model to investigate and visualize at high resolution the evolution of monocytes as they migrate from the intravascular to the extravascular micro-environment. We also demonstrate their differentiation into macrophages in our all-human model. Our model replicates physiological differences between different monocyte subsets. In particular, we report that inflammatory, but not patrolling, monocytes rely on actomyosin based motility. Finally, we exploit this platform to study the effect of monocytes, at different stages of their life cycle, on cancer cell extravasation. Our data demonstrates that monocytes can directly reduce cancer cell extravasation in a non-contact dependent manner. In contrast, we see little effect of monocytes on cancer cell extravasation once monocytes transmigrate through the vasculature and are macrophage-like. Taken together, our study brings novel insight into the role of monocytes in cancer cell extravasation, which is an important step in the metastatic cascade. These findings establish our microfluidic platform as a powerful tool to investigate the characteristics and function of monocytes and monocyte-derived macrophages in normal and diseased states. We propose that monocyte-cancer cell interactions could be targeted to potentiate the anti-metastatic effect we observe in vitro, possibly expanding the milieu of immunotherapies available to tame metastasis.

Molecular mechanism of LPS-induced TNF-α biosynthesis in polarized human macrophages

In response to environmental stimuli such as granulocyte-macrophage or macrophage colony stimulating factor (GM-CSF/M-CSF), macrophages (MΦ) can acquire distinct functional phenotypes that control inflammatory processes on the one hand and contribute to a broad spectrum of pathologies on the other. Potential intervention strategies will require an understanding of the signalling processes that are associated with macrophage polarization. In the present study, we show that M-MΦ produce more IFN-β and IL-10 and a lot less TNF-α than do GM-MΦ in response to LPS. To define the molecular mechanisms that underlie the biosynthesis of TNF-α we carried out a detailed investigation of the LPS-induced activation of the canonical and non-canonical myeloid differentiation primary response 88 (MyD88)-dependent signal transduction pathways as well as the TIR-domain-containing adapter-inducing interferon-β (TRIF)-dependent pathway. Our results show that all three pathways are activated in both cell types and that the activation is more pronounced in M-MΦ. While IL-10 was found to interfere with TNF-α production in M-MΦ, we exclude a decisive role for IFN-β in this respect. Furthermore, we demonstrate that TNF-α mRNA is markedly destabilized in M-MΦ and that expression of the mRNA destabilizing protein tristetraprolin is greatly enhanced in these cells. Collectively, our study suggests that differential effects of LPS on TNF-α mRNA turnover and on signal transduction pathways influence the amount of TNF-α finally produced by GM-MΦ and M-MΦ.

Niacin and its metabolites as master regulators of macrophage activation

Niacin is a broad-spectrum lipid-regulating drug used for clinical therapy of chronic high-grade inflammatory diseases. However, the mechanisms by which either niacin or the byproducts of its catabolism ameliorate these inflammatory diseases are not clear yet. Human circulating monocytes and mature macrophages were used to analyze the effects of niacin and its metabolites (NAM, NUA and 2-Pyr) on oxidative stress, plasticity and inflammatory response by using biochemical, flow cytometry, quantitative real-time PCR and Western blot technologies. Niacin, NAM and 2-Pyr significantly decreased ROS, NO and NOS2 expression in LPS-treated human mature macrophages. Niacin and NAM skewed macrophage polarization toward antiinflammatory M2 macrophage whereas a trend toward proinflammatory M1 macrophage was noted following treatment with NUA. Niacin and NAM also reduced the inflammatory competence of LPS-treated human mature macrophages and promoted bias toward antiinflammatory CD14⁺CD16⁺⁺ nonclassical human primary monocytes. This study reveals for the first time that niacin and its metabolites possess antioxidant, reprogramming and antiinflammatory properties on human primary monocytes and monocyte-derived macrophages. Our findings imply a new understanding of the mechanisms by which niacin and its metabolites favor a continuous and gradual plasticity process in the human monocyte/macrophage system.

Long-term treatment with nicotinamide induces glucose intolerance and skeletal muscle lipotoxicity in normal chow-fed mice: compared to diet-induced obesity

Nicotinamide (NAM), or vitamin B3, is an essential coenzyme for ATP synthesis and an inhibitor of sirtuin 1. Recently, conflicting results were reported regarding the treatment of NAM in type 2 diabetes and obesity. The aim of this study was to determine whether and how long-term treatment with NAM at lower dose would affect insulin sensitivity in mice fed chow diet. We treated mice with NAM (100 mg/kg/day) and normal chow for 8 weeks. Strikingly, NAM induced glucose intolerance and skeletal muscle lipid accumulation in nonobese mice. NAM impaired mitochondrial respiration capacity and energy production in skeletal muscle, in combination with increased expression of the mediators for mitophagy (p62, PINK1, PARK2 and NIX) and autophagy (FOXO3, Bnip3, CTSL, Beclin1 and LC-3b). Next, we treated mice with high-fat diet (HFD) and resveratrol (RSV; 100 mg/kg/day) for 8 weeks. RSV protected against HFD-induced insulin resistance and obesity. HFD increased skeletal muscle lipid content as well as NAM, but this increase was attenuated by RSV. In contrast to NAM, HFD enhanced fatty acid oxidative capacity. Muscle transcript levels of genes for mitophagy and autophagy were largely suppressed by HFD, whereas RSV did not rescue these effects. These differences suggest that skeletal muscle autophagy may represent adaptive response to NAM-induced lipotoxicity, whereas reduced autophagy in skeletal muscle may promote HFD-induced lipotoxicity. Our results demonstrate that chronic NAM supplementation in healthy individuals, although at lower dose than previously reported, is still detrimental to glucose homeostasis and skeletal muscle lipid metabolism.