Nicotinamide exerts antioxidative effects on senescent cells

Cellular senescence in Alzheimer's disease: from physiology to pathology

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders, characterized by the accumulation of Aβ and abnormal tau hyperphosphorylation. Despite substantial efforts in development of drugs targeting Aβ and tau pathologies, effective therapeutic strategies for AD remain elusive. Recent attention has been paid to the significant role of cellular senescence in AD progression. Mounting evidence suggests that interventions targeting cellular senescence hold promise in improving cognitive function and ameliorating hallmark pathologies in AD. This narrative review provides a comprehensive summary and discussion of the physiological roles, characteristics, biomarkers, and commonly employed in vivo and in vitro models of cellular senescence, with a particular focus on various cell types in the brain, including astrocytes, microglia, oligodendrocyte precursor cells, neurons, and endothelial cells. The review further delves into factors influencing cellular senescence in AD and emphasizes the significance of targeting cellular senescence as a promising approach for AD treatment, which includes the utilization of senolytics and senomorphics.

ASK-1 activation exacerbates kidney dysfunction via increment of glomerular permeability and accelerates cellular aging in diabetic kidney disease model mice

Diabetic kidney disease (DKD) is a major disease characterized by early albuminuria and heightened risk of renal deterioration. Increased reactive oxygen species (ROS) production, especially in glomeruli, plays an important role in the progression of DKD. ROS also cause activation of Apoptosis signal-regulating kinase 1 (ASK-1), which is implicated in various organ injuries. However, the detailed mechanisms remain unclear. This study investigates ASK-1 activation in advanced DKD and its underlying mechanisms using GS442172, an ASK-1 inhibitor. In the DKD mouse model, activation of ASK-1 was observed. Although inhibition of ASK-1 activation improved hyperpermeability in glomerular endothelial cells. ASK-1 inhibition significantly reduced glomerular injury and albuminuria, while also attenuating tubular damage and interstitial fibrosis. RNA-seq analysis revealed an aging phenotype associated with ASK-1 activation in DKD. In vitro experiments demonstrated ASK-1 activation-induced cellular senescence in tubular cells via redox signaling. These results suggested that the critical role of ASK-1 activation in DKD pathogenesis, implicating glomerular injury, tubular damage, and cellular senescence. ASK-1 inhibitors are promising therapeutic strategies to mitigate the progression of DKD.

Investigation of preconditioning and the protective effects of nicotinamide against cerebral ischemia-reperfusion injury in rats

This study investigated the antioxidant and neuroprotective effects of nicotinamide combined with ischemic preconditioning against cerebral ischemia reperfusion (CIR) injury. Thirty-five Wistar albino male rats were randomly divided into five groups: sham, preconditioned ischemia/reperfusion (IP+IR), ischemia/reperfusion (IR), preconditioned ischemia/reperfusion + nicotinamide (IP+IR+N), and ischemia/reperfusion + nicotinamide (IR+N). CIR was achieved with bilateral common carotid artery occlusion. IP+IR and IP+IR+N groups 30 min before ischemia; Three cycles of 10 sec ischemia/30 sec reperfusion followed by 20 min IR were applied. The IP+IR+N and IR+N groups received 500 mg/kg nicotinamide intraperitoneally. After 24 h of reperfusion, a neurological evaluation was performed and vertıcal pole test. Biochemically, malondialdehyde (MDA), glutathione (GSH) levels and catalase (CAT) activity were measured in blood and brain tissue samples. Rates of red neurons, sateliosis and spongiosis were determined histopathologically in the prefrontal cortex areas. After CIR, MDA levels increased significantly in serum and brain tissue in the IR group compared to the sham group, while GSH and CAT activity decreased in the brain tissue (p < 0.05). MDA levels in the tissues were found significantly decreased in the IR+N group compared to the IR group (p < 0.05). Administration of nicotinamide together with IP significantly decreased MDA levels in brain tissue and increased GSH and CAT activity (p < 0.05). Compared to the IR group, the morphological and neurological damage in the prefrontal cortex areas decreased in the IP+IR, IP+IR+N, and IR+N groups (p < 0.05). In addition, red neuron, sateliosis and spongiosis rates increased significantly in the IR group compared to the Sham, IP+IR+N, IR+N groups (p < 0.001 for all). In neurological evaluation, while the neurological score increased and the time on the vertical pole decreased significantly in the IR group, preconditioning, and nicotinamide groups reversed (p < 0.05). The study's results show that nicotinamide administration with ischemic preconditioning alleviates cerebral ischemia/reperfusion injury.

Effect of Selected Antioxidants on the In Vitro Aging of Human Fibroblasts

The modification of the replicative lifespan (RLS) of fibroblasts is of interest both from a knowledge point of view and for the attenuation of skin aging. The effect of six antioxidants at a concentration of 1 μM on the replicative lifespan of human dermal fibroblasts was studied. The nitroxide 4-hydroxy-TEMPO (TEMPOL), ergothioneine, and Trolox extended the replicative lifespan (RLS) (40 ± 1 population doublings (PD)) by 7 ± 2, 4 ± 1, and 3 ± 1 PD and lowered the expression of p21 at late passages. Coumaric acid, curcumin and resveratrol did not affect the RLS . The level of reactive oxygen species (ROS) was decreased or not affected by the antioxidants although TEMPOL and coumaric acid decreased the level of glutathione. Only ergothioneine and resveratrol decreased the level of protein carbonylation. The antioxidants that could prolong the RLS elevated the mitochondrial membrane potential. Protecting the activity of mitochondria seems to be important for maintaining the replicative capacity of fibroblasts.

The Role of Nicotinamide as Chemo-Preventive Agent in NMSCs: A Systematic Review and Meta-Analysis

BACKGROUND

Nicotinamide is the active form of vitamin B3 (niacin) obtained through endogenous synthesis, mainly through tryptophan metabolism and dietary supplements, fish, meats, grains, and dairy products. It participates in cellular energy metabolism and modulates multiple cellular survival and death pathways. Nicotinamide has been widely studied as a safe chemopreventive agent that reduces actinic keratosis (AKs) and non-melanoma skin cancers (NMSC).

METHODS

We used the Medline, EMBASE, PubMed, and Cochrane databases to search the concepts "nicotinamide", "chemoprevention", and "skin cancer" up to August 2023. Three independent authors screened titles and abstracts for intervention and study design before searching full texts for eligibility criteria. The primary outcome was the impact of oral nicotinamide on the incidence of NMSC in high-risk patients. We also conducted a systematic search to identify relevant epidemiological studies published evaluating dietary niacin intake and the risk of NMSC.

RESULTS

Two hundred and twenty-five studies were reviewed, and four met the inclusion criteria. There was no association between NAM consumption and risk for squamous cell carcinoma (SCC) (rate ratio (RR) 0.81, 95% CI 0.48-1.37; I2 = 0%), basal cell carcinoma (BCC) (RR 0.88, 95% CI 0.50-1.55; I2 = 63%), and NMSC (RR 0.82, 95% CI 0.61-1.12; I2 = 63%). Adverse events were rare and acceptable, allowing optimal compliance of patients to the treatment. We found only one article evaluating the association between niacin dietary intake and NMSC risk, supporting a potential beneficial role of niacin intake concerning SCC but not BCC or melanoma.

CONCLUSIONS

The present meta-analysis shows, by pooling immunocompetent and immunosuppressed patients, that there is insufficient evidence that oral nicotinamide therapy significantly reduces the number of keratinocyte cancers.

Integrated Analysis of Transcriptome and Metabolome Profiles in the Longissimus Dorsi Muscle of Buffalo and Cattle

Buffalo meat is gaining popularity for its nutritional properties, such as its low fat and cholesterol content. However, it is often unsatisfactory to consumers due to its dark color and low tenderness. There is currently limited research on the regulatory mechanisms of buffalo meat quality. Xinglong buffalo are raised in the tropical Hainan region and are undergoing genetic improvement from draught to meat production. For the first time, we evaluated the meat quality traits of Xinglong buffalo using the longissimus dorsi muscle and compared them to Hainan cattle. Furthermore, we utilized a multi-omics approach combining transcriptomics and metabolomics to explore the underlying molecular mechanism regulating meat quality traits. We found that the Xinglong buffalo had significantly higher meat color redness but lower amino acid content and higher shear force compared to Hainan cattle. Differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) were identified, with them being significantly enriched in nicotinic acid and nicotinamide metabolic and glycine, serine, and threonine metabolic pathways. The correlation analysis revealed that those genes and metabolites (such as: GAMT, GCSH, PNP, L-aspartic acid, NADP+, and glutathione) are significantly associated with meat color, tenderness, and amino acid content, indicating their potential as candidate genes and biological indicators associated with meat quality. This study contributes to the breed genetic improvement and enhancement of buffalo meat quality.

Impaired Autophagic Flux in Glucose-Deprived Cells: An Outcome of Lysosomal Acidification Failure Exacerbated by Mitophagy Dysfunction

Autophagy dysfunction is associated with human diseases and conditions including neurodegenerative diseases, metabolic issues, and chronic infections. Additionally, the decline in autophagic activity contributes to tissue and organ dysfunction and aging-related diseases. Several factors, such as down-regulation of autophagy components and activators, oxidative damage, microinflammation, and impaired autophagy flux, are linked to autophagy decline. An autophagy flux impairment (AFI) has been implicated in neurological disorders and in certain other pathological conditions. Here, to enhance our understanding of AFI, we conducted a comprehensive literature review of findings derived from two well-studied cellular stress models: glucose deprivation and replicative senescence. Glucose deprivation is a condition in which cells heavily rely on oxidative phosphorylation for ATP generation. Autophagy is activated, but its flux is hindered at the autolysis step, primarily due to an impairment of lysosomal acidity. Cells undergoing replicative senescence also experience AFI, which is also known to be caused by lysosomal acidity failure. Both glucose deprivation and replicative senescence elevate levels of reactive oxygen species (ROS), affecting lysosomal acidification. Mitochondrial alterations play a crucial role in elevating ROS generation and reducing lysosomal acidity, highlighting their association with autophagy dysfunction and disease conditions. This paper delves into the underlying molecular and cellular pathways of AFI in glucose-deprived cells, providing insights into potential strategies for managing AFI that is driven by lysosomal acidity failure. Furthermore, the investigation on the roles of mitochondrial dysfunction sheds light on the potential effectiveness of modulating mitochondrial function to overcome AFI, offering new possibilities for therapeutic interventions.

Lipofuscin Granule Accumulation Requires Autophagy Activation

Lipofuscins are oxidized lipid and protein complexes that accumulate during cellular senescence and tissue aging, regarded as markers for cellular oxidative damage, tissue aging, and certain aging-associated diseases. Therefore, understanding their cellular biological properties is crucial for effective treatment development. Through traditional microscopy, lipofuscins are readily observed as fluorescent granules thought to accumulate in lysosomes. However, lipofuscin granule formation and accumulation in senescent cells are poorly understood. Thus, this study examined lipofuscin accumulation in human fibroblasts exposed to various stressors. Our results substantiate that in glucose-starved or replicative senescence cells, where elevated oxidative stress levels activate autophagy, lipofuscins predominately appear as granules that co-localize with autolysosomes due to lysosomal acidity or impairment. Meanwhile, autophagosome formation is attenuated in cells experiencing oxidative stress induced by a doxorubicin pulse and chase, and lipofuscin fluorescence granules seldom manifest in the cytoplasm. As Torin-1 treatment activates autophagy, granular lipofuscins intensify and dominate, indicating that autophagy activation triggers their accumulation. Our results suggest that high oxidative stress activates autophagy but fails in lipofuscin removal, leaving an abundance of lipofuscin-filled impaired autolysosomes, referred to as residual bodies. Therefore, future endeavors in treating lipofuscin pathology-associated diseases and dysfunctions through autophagy activation demand meticulous consideration.

1-Methylnicotinamide (1-MNA) inhibits the activation of the NLRP3 inflammasome in human macrophages

The NLRP3 inflammasome is among the most potent intracellular sensors of danger and disturbances of cellular homeostasis that can lead to the release of IL-1β and cell death, or pyroptosis. Despite its protective role, this mechanism is involved in the pathogenesis of numerous inflammatory diseases; therefore, it is seen as a potential therapeutic target. 1-methylnicotinamide (1-MNA) is a direct metabolite of nicotinamide and was previously shown to display several immunomodulatory properties, including a reduction in the reactive oxygen species (ROS). Here, we investigated whether 1-MNA could influence the activation of the NLRP3 inflammasome in human macrophages. In differentiated human macrophages we observed that 1-MNA specifically reduced the activation of the NLRP3 inflammasome. This effect was related to the scavenging of ROS, as exogenous H₂O₂ was able to restore NLRP3 activation. Additionally, 1-MNA increased the mitochondrial membrane potential, indicating that it did not inhibit oxidative phosphorylation. Moreover, at high but not low concentrations, 1-MNA decreased NF-κB activation and the level of pro-IL-1β. Interestingly, 1-MNA did not reduce the secretion of IL-6 upon endotoxin stimulation, confirming that its primary immunomodulatory effect on human macrophages is dependent on the NLRP3 inflammasome. Taken together, we have shown for the first time that 1-MNA reduced the activation of the NLRP3 inflammasome in human macrophages via an ROS-dependent pathway. Our results indicate a novel potential use of 1-MNA in NLRP3-related disorders.

First cocrystal of esculetin: simultaneously optimized in vitro/vivo properties and antioxidant effect

Esculetin (ELT) is one of the best-known and simplest coumarins with powerful natural antioxidant effects but insoluble and difficult to absorb. In order to overcome the problems, cocrystal engineering was first applied to ELT in this paper. Nicotinamide (NAM) was selected as the coformer for its excellent water solubility and potential synergistic antioxidant effect with ELT. The structure of the ELT-NAM cocrystal was successfully prepared and characterized by IR, SCXRD, PXRD, and DSC-TG. Furthermore, the in vitro/vivo properties and antioxidant effects of the cocrystal were adequately studied. The results highlight that the ELT obtained tremendous improvements in water solubility and bioavailability after cocrystal formation. Meanwhile, the synergistic enhancement of ELT with NAM in antioxidant effect was demonstrated by the DPPH assay. Ultimately, the simultaneously optimized in vitro/vivo properties and antioxidant activity of the cocrystal created an improved practical effect of hepatoprotective in rat experiments. The investigation is significant for developing coumarin drugs represented by ELT.

Palladium‐Catalysed C−C Bond Forming 4‐Cyanophenyl‐nicotinamide Conjugates; Anti‐Pancreatic Cancer Screening on Capan‐1 Cell Line

Pancreatic cancer is the most severe, as a consequence of asymptomatic nature and ineffective therapies among all malignancies. Nicotinamides are effective ring systems in the treatment of pancreatic cancer with their wide range of applications. In the present investigation, nicotinamide and 4‐cyanophenyl ring systems are brought together to obtain greater potency. For the process of investigation, PARP1 protein is targeted and evaluated by docking at the active site to determine the protein‐ligand interaction, revealed the potential with the binding affinity of −9.0 to −11.0 Kcal/mol to inhibit the poly ADP‐ribose polymerase 1 (PARP1) pathway. The MTT‐assay assessment of a synthesized series has been performed against Capan‐1 pancreatic cancer cell line. The nicotinamide compounds demonstrated a significant inhibitory effect over Capan‐1 cell line, and 6‐(4‐cyanophenyl)‐N‐(3‐phenylpropyl)nicotinamide exhibited as a potential lead for the development of novel chemotherapeutics against pancreatic cancer.

Effects of nicotinamide on follicular development and the quality of oocytes

BACKGROUND

Nicotinamide (NAM) is an important antioxidant, which is closely related to female fertility, but its role has not been clearly elucidated. The purpose of the present study was to investigate the effects of NAM on follicular development at different stages and the quality of oocytes.

METHODS

The concentration of NAM in follicular fluid (FF) of 236 women undergoing in vitro fertilization (IVF) was ascertained by enzyme-linked immunosorbent assay (ELISA), and the correlation between NAM and clinical indexes was analyzed. During the in vitro maturation (IVM) of mice cumulus-oocyte complexes (COCs), different concentrations of NAM were added to check the maturation rate and fertilization rate. The reactive oxygen species (ROS) levels in the oocytes treated with different hydrogen peroxide (H₂O₂) and NAM were assessed. Immunofluorescence staining was performed to measure the proportion of abnormal spindles.

RESULTS

The level of NAM in large follicles was significantly higher than that in small follicles. In mature FF, the NAM concentration was positively correlated with the rates of oocyte maturation and fertilization. Five mM NAM treatment during IVM increased maturation rate and fertilization rate in the oxidative stress model, and significantly reduced the increase of ROS levels induced by H₂O₂ in mice oocytes.

CONCLUSIONS

Higher levels of NAM in FF are associated with larger follicle development. The supplement of 5 mM NAM during IVM may improve mice oocyte quality, reducing damage caused by oxidative stress.

Creatine and Nicotinamide Prevent Oxidant-Induced Senescence in Human Fibroblasts

Dermal fibroblasts provide structural support by producing collagen and other structural/support proteins beneath the epidermis. Fibroblasts also produce insulin-like growth factor-1 (IGF-1), which binds to the IGF-1 receptors (IGF-1Rs) on keratinocytes to activate signaling pathways that regulate cell proliferation and cellular responses to genotoxic stressors like ultraviolet B radiation. Our group has determined that the lack of IGF-1 expression due to fibroblast senescence in the dermis of geriatric individuals is correlated with an increased incidence of skin cancer. The present studies tested the hypothesis that pro-energetics creatine monohydrate (Cr) and nicotinamide (NAM) can protect normal dermal human fibroblasts (DHF) against experimentally induced senescence. To that end, we used an experimental model of senescence in which primary DHF are treated with hydrogen peroxide (H2O2) in vitro, with senescence measured by staining for beta-galactosidase activity, p21 protein expression, and senescence associated secretory phenotype cytokine mRNA levels. We also determined the effect of H2O2 on IGF-1 mRNA and protein expression. Our studies indicate that pretreatment with Cr or NAM protects DHF from the H2O2-induced cell senescence. Treatment with pro-energetics post-H2O2 had no effect. Moreover, these agents also inhibited reactive oxygen species generation from H2O2 treatment. These studies suggest a potential strategy for protecting fibroblasts in geriatric skin from undergoing stress-induced senescence, which may maintain IGF-1 levels and therefore limit carcinogenesis in epidermal keratinocytes.

Inhibition effect of nicotinamide (vitamin B3) and reduced glutathione (GSH) peptide on angiotensin-converting enzyme activity purified from sheep kidney

Angiotensin-converting enzyme (ACE, EC 3.4.15.1) plays a significant role in blood pressure regulation and inhibition of this enzyme is one of the significant drug targets for the treatment of hypertension. In this work, ACE was purified from sheep kidneys with the affinity chromatography method in one step. The purity and molecular weight of ACE were designated using the SDS-PAGE method and observed two bands at around 60 kDa and 70 kDa on the gel. The effects of nicotinamide (vitamin B₃) and reduced glutathione (GSH) peptide on purified ACE were researched. Nicotinamide and GSH peptide on purified ACE showed an inhibition effect. IC₅₀ values for nicotinamide and GSH were calculated as 14.3 μM and 7.3 μM, respectively. Type of inhibition and K_i values for nicotinamide and GSH from the Lineweaver-Burk graph were determined. The type of inhibition for nicotinamide and GSH was determined as non-competitive inhibition. K_i value was calculated as 15.4 μM for nicotinamide and 6.7 μM for GSH. Also, GSH peptide showed higher inhibitory activity on ACE activity than nicotinamide. In this study, it was concluded that nicotinamide and GSH peptide compounds, which show an inhibition effect on ACE activity, may have both protective and therapeutic effects against hypertension.

Effect of Dry-Aging on Quality and Palatability Attributes and Flavor-Related Metabolites of Pork Loins

This study evaluated the effect of dry-aging on quality, palatability, and flavor-related compounds of pork loins. Ten pork loins were obtained at 7 days postmortem, divided into three equal portions, randomly assigned into three different aging methods (wet-aging (W), conventional dry-aging (DA), and UV-light dry-aging (UDA)), and aged for 21 days at 2 °C, 70% RH, and 0.8 m/s airflow. The results showed similar instrumental tenderness values across all treatments (p > 0.05), while DA and UDA had a greater water-holding capacity than WA (p < 0.05). Both DA and UDA were observed to have comparable color stability to WA up to 5 days of retail display (p > 0.05). Greater lipid oxidation was measured in both DA and UDA at the end of display compared to WA (p < 0.05). The UV light minimized microorganisms concentration on both surface and lean portions of UDA compared to other treatments (p < 0.05). The consumer panel was not able to differentiate any sensory traits and overall likeness between the treatments (p > 0.05). Metabolomics analysis, however, identified more flavor-related compounds in dry-aged meat. These findings suggested that dry-aging can be used for pork loins for value-seeking consumers, as it has a potential to generate unique dry-aged flavor in meat with no adverse impacts on meat quality and microbiological attributes.

Mechanistic Basis and Clinical Evidence for the Applications of Nicotinamide (Niacinamide) to Control Skin Aging and Pigmentation

Vitamin B3 (nicotinic acid, niacin) deficiency causes the systemic disease pellagra, which leads to dermatitis, diarrhea, dementia, and possibly death depending on its severity and duration. Vitamin B3 is used in the synthesis of the NAD+ family of coenzymes, contributing to cellular energy metabolism and defense systems. Although nicotinamide (niacinamide) is primarily used as a nutritional supplement for vitamin B3, its pharmaceutical and cosmeceutical uses have been extensively explored. In this review, we discuss the biological activities and cosmeceutical properties of nicotinamide in consideration of its metabolic pathways. Supplementation of nicotinamide restores cellular NAD+ pool and mitochondrial energetics, attenuates oxidative stress and inflammatory response, enhances extracellular matrix and skin barrier, and inhibits the pigmentation process in the skin. Topical treatment of nicotinamide, alone or in combination with other active ingredients, reduces the progression of skin aging and hyperpigmentation in clinical trials. Topically applied nicotinamide is well tolerated by the skin. Currently, there is no convincing evidence that nicotinamide has specific molecular targets for controlling skin aging and pigmentation. This substance is presumed to contribute to maintaining skin homeostasis by regulating the redox status of cells along with various metabolites produced from it. Thus, it is suggested that nicotinamide will be useful as a cosmeceutical ingredient to attenuate skin aging and hyperpigmentation, especially in the elderly or patients with reduced NAD+ pool in the skin due to internal or external stressors.

New benzamide derivatives and their nicotinamide/cinnamamide analogs as cholinesterase inhibitors

In this study, a total of 18 new benzamide/ nicotinamide/ cinnamamide derivative compounds were designed and synthesized for the first time (except B1 and B5) by conventional and microwave irradiation methods. The chemical structures of the synthesized compounds were characterized by ¹H NMR, ¹³C NMR, and HRMS spectra. In vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibition effects of the compounds were evaluated to find out new possible drug candidate molecule/s. According to the inhibition results, the IC50 values of the compounds synthesized were in the range of 10.66-83.03 nM towards AChE, while they were in the range of 32.74-66.68 nM towards BuChE. Tacrine was used as the reference drug and its IC50 values were 20.85 nM and 15.66 nM towards AChE and BuChE, respectively. The most active compounds B4 (IC50: 15.42 nM), N4 (IC50: 12.14 nM), and C4 (IC50: 10.67 nM) in each series towards AChE were docked at the binding site of AChE enzyme to explain the inhibitory activities of each series. On the other hand, the compounds B4, N4, and C4 showed satisfactory pharmacokinetic properties via the prediction of ADME profiles.

Senescence in Bacteria and Its Underlying Mechanisms

Bacteria have been thought to flee senescence by dividing into two identical daughter cells, but this notion of immortality has changed over the last two decades. Asymmetry between the resulting daughter cells after binary fission is revealed in physiological function, cell growth, and survival probabilities and is expected from theoretical understanding. Since the discovery of senescence in morphologically identical but physiologically asymmetric dividing bacteria, the mechanisms of bacteria aging have been explored across levels of biological organization. Quantitative investigations are heavily biased toward Escherichia coli and on the role of inclusion bodies—clusters of misfolded proteins. Despite intensive efforts to date, it is not evident if and how inclusion bodies, a phenotype linked to the loss of proteostasis and one of the consequences of a chain of reactions triggered by reactive oxygen species, contribute to senescence in bacteria. Recent findings in bacteria question that inclusion bodies are only deleterious, illustrated by fitness advantages of cells holding inclusion bodies under varying environmental conditions. The contributions of other hallmarks of aging, identified for metazoans, remain elusive. For instance, genomic instability appears to be age independent, epigenetic alterations might be little age specific, and other hallmarks do not play a major role in bacteria systems. What is surprising is that, on the one hand, classical senescence patterns, such as an early exponential increase in mortality followed by late age mortality plateaus, are found, but, on the other hand, identifying mechanisms that link to these patterns is challenging. Senescence patterns are sensitive to environmental conditions and to genetic background, even within species, which suggests diverse evolutionary selective forces on senescence that go beyond generalized expectations of classical evolutionary theories of aging. Given the molecular tool kits available in bacteria, the high control of experimental conditions, the high-throughput data collection using microfluidic systems, and the ease of life cell imaging of fluorescently marked transcription, translation, and proteomic dynamics, in combination with the simple demographics of growth, division, and mortality of bacteria, make the challenges surprising. The diversity of mechanisms and patterns revealed and their environmental dependencies not only present challenges but also open exciting opportunities for the discovery and deeper understanding of aging and its mechanisms, maybe beyond bacteria and aging.

The redox-senescence axis and its therapeutic targeting

Significance

Cellular growth arrest, associated with ‘senescence’, helps to safeguard against the accumulation of DNA damage which is often recognized as the underlying mechanism of a wide variety of age-related pathologies including cancer. Cellular senescence has also been described as a ‘double-edged sword’. In cancer, for example, the creation of an immune-suppressive milieu by senescent tumor cells through the senescence-associated secretory phenotype contributes toward carcinogenesis and cancer progression.

Recent advances

The potential for cellular senescence to confer multi-faceted effects on tissue fate has led to a rejuvenated interest in its landscape and targeting. Interestingly, redox pathways have been described as both triggers and propagators of cellular senescence, leading to intricate cross-links between both pathways.

Critical issues

In this review, we describe the mechanisms driving cellular senescence, the interface with cellular redox metabolism as well as the role that chemotherapy-induced senescence plays in secondary carcinogenesis. Notably, the role that anti-apoptotic proteins of the Bcl-2 family play in inducing drug resistance via mechanisms that involve senescence induction.

Future directions

Though the therapeutic targeting of senescent cells as cancer therapy remains in its infancy, we summarize the current development of senotherapeutics, including recognized senotherapies, as well as the repurposing of drugs as senomorphic/senolytic candidates.

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.

Effect of Antioxidants on the Fibroblast Replicative Lifespan In Vitro

Replicative senescence is an unalterable growth arrest of primary cells in the culture system. It has been reported that aging in vivo is related to the limited replicative capacity that normal somatic cells show in vitro. If oxidative damage contributes to the lifespan limitation, antioxidants are expected to extend the replicative lifespan of fibroblasts. This article critically reviews the results of experiments devoted to this problem performed within the last decades under conditions of in vitro culture. The results of studied are heterogeneous, some papers showing no effects of antioxidants; most finding limited enhancement of reproductive capacity of fibroblasts, some reporting a significant extension of replicative lifespan (RLS). Both natural and synthetic antioxidants were found to extend the RLS of fibroblasts, either by a direct antioxidant effect or, indirectly, by activation of signaling pathways and activation of proteasomes or hormetic effects. Most significant prolongation of RLS was reported so far for nicotinamide, N-hydroxylamines, carnosine and Methylene Blue. These results may be of importance for the design of skin-protecting cosmetics.

Identification of a novel senomorphic agent, avenanthramide C, via the suppression of the senescence-associated secretory phenotype

Senescent cells are deeply involved in the induction of tissue damage and aging-related diseases. The identification of factors that eliminate senescent cells or inhibit the senescence-associated secretory phenotype (SASP) in these cells is necessary. Here, we report an avenanthramice C (Avn C) extracted from oat as a new SASP modulator. Treatment with Avn C led to a significant reduction in the levels of markers of senescent cells, with no toxicity observed. The SASP was also inhibited by Avn C treatment, similar to non-senescent cells, and the suppression of cell division by autocrine signals associated with SASP was restored. To investigate the mechanism underlying SASP inhibition by Avn C, we analyzed the effect of Avn C in lipopolysaccharide (LPS)-induced inflammation in non-senescent cells. Avn C inhibited nuclear factor κB (NF-κB) activity and the secretion of inflammatory cytokines before or after LPS treatment. Although the activity of MAP kinases, which are NF-κB upstream signals, was inhibited by Avn C in LPS-induced inflammation, only p38 activity was specifically inhibited in senescent cells. Interestingly, the inhibition of p38 in senescent cells was observed through Avn C-induced 5'-adenosine monophosphate-activated protein kinase (AMPK) activity. Avn C-induced inhibition of the SASP is triggered by senescence-related stress.

Effect of nicotinamide supplementation in in vitro fertilization medium on bovine embryo development

Increased oxidative stress is one of the main causes of poorly developed embryos in assisted reproductive technologies. Nicotinamide (NAM) has been shown to suppress reactive oxygen species (ROS) production through its potent antioxidative and anti-senescent effects. In the present study, we explored the effects of short-term NAM-treatment (3 and 5 h) during in vitro fertilization (IVF) on the development of bovine embryos. Treatment with 10 mM NAM for 3 h significantly increased the blastocyst formation but extending the treatment to 5 h did not enhance the benefits any further. Immunofluorescence analysis demonstrated that treatment with 10 mM NAM for 3 h decreased the expression of intracellular ROS, 8-oxo-7,8-dihydroguanine, caspase-3, and increased the expression of Sirt1, and incorporation of bromodeoxyuridine in one-cell stage embryos. Similarly, the level of H3K56ac significantly increased in the NAM-treated (3 and 5 h) one-cell stage embryos. Contrastingly, the treatment with 10 mM NAM for 5 h increased the caspase-9 level in blastocysts. Collectively, these findings suggest that NAM possesses antioxidant activity and supplementation of IVF medium with 10 mM NAM for 3 h improves the in vitro developmental competence of bovine embryos.

Treatment of melasma: a review of less commonly used antioxidants

Melasma, a common cause for seeking dermatologic care, is a chronic condition of skin hyperpigmentation. With a poorly understood pathogenesis, and no universal cure, melasma is a challenge for many dermatologists. For decades, there has been investigation into the role of oxidative stress in melasma. In this literature review, we introduce the role of oxidative stress in melasma and discuss the function of various topical and oral antioxidant therapies for patients suffering from melasma. Numerous studies have shown efficacy of various antioxidant therapies for treatment of hyperpigmentation, and in this review, we focus primarily on those with less widespread use. Vitamin E, niacinamide, polypodium leucotomos, pycnogenol, grape seed extract, amino fruit acids, phytic acid, zinc, silymarin, Korean red ginseng powder, plant extracts, and parsley all have well-demonstrated evidence of antioxidant properties, and these substances have been studied in the context of skin hyperpigmentation. Although there is conflicting evidence of their therapeutic efficacy, the use of these naturally occurring substances is promising for patients and medical providers seeking alternative therapeutic options.

Loss of Tdp-43 disrupts the axonal transcriptome of motoneurons accompanied by impaired axonal translation and mitochondria function

Protein inclusions containing the RNA-binding protein TDP-43 are a pathological hallmark of amyotrophic lateral sclerosis and other neurodegenerative disorders. The loss of TDP-43 function that is associated with these inclusions affects post-transcriptional processing of RNAs in multiple ways including pre-mRNA splicing, nucleocytoplasmic transport, modulation of mRNA stability and translation. In contrast, less is known about the role of TDP-43 in axonal RNA metabolism in motoneurons. Here we show that depletion of Tdp-43 in primary motoneurons affects axon growth. This defect is accompanied by subcellular transcriptome alterations in the axonal and somatodendritic compartment. The axonal localization of transcripts encoding components of the cytoskeleton, the translational machinery and transcripts involved in mitochondrial energy metabolism were particularly affected by loss of Tdp-43. Accordingly, we observed reduced protein synthesis and disturbed mitochondrial functions in axons of Tdp-43-depleted motoneurons. Treatment with nicotinamide rescued the axon growth defect associated with loss of Tdp-43. These results show that Tdp-43 depletion in motoneurons affects several pathways integral to axon health indicating that loss of TDP-43 function could thus make a major contribution to axonal pathomechanisms in ALS.

Transcriptome analysis reveals a molecular understanding of nicotinamide and butyrate sodium on meat quality of broilers under high stocking density

Background

In recent years, increased attention has been focused on breast muscle yield and meat quality in poultry production. Supplementation with nicotinamide and butyrate sodium can improve the meat quality of broilers. However, the potential molecular mechanism is not clear yet. This study was designed to investigate the effects of supplementation with a combination of nicotinamide and butyrate sodium on breast muscle transcriptome of broilers under high stocking density. A total of 300 21-d-old Cobb broilers were randomly allocated into 3 groups based on stocking density: low stocking density control group (L; 14 birds/m²), high stocking density control group (H; 18 birds/m²), and high stocking density group provided with a combination of 50 mg/kg nicotinamide and 500 mg/kg butyrate sodium (COMB; 18 birds/m²), raised to 42 days of age.

Results

The H group significantly increased cooking losses, pH decline and activity of lactate dehydrogenase in breast muscle when compared with the L group. COMB showed a significant decrease in these indices by comparison with the H group (P < 0.05). The transcriptome results showed that key genes involved in glycolysis, proteolysis and immune stress were up-regulated whereas those relating to muscle development, cell adhesion, cell matrix and collagen were down-regulated in the H group as compared to the L group. In contrast, genes related to muscle development, hyaluronic acid, mitochondrial function, and redox pathways were up-regulated while those associated with inflammatory response, acid metabolism, lipid metabolism, and glycolysis pathway were down-regulated in the COMB group when compared with the H group.

Conclusions

The combination of nicotinamide and butyrate sodium may improve muscle quality by enhancing mitochondrial function and antioxidant capacity, inhibiting inflammatory response and glycolysis, and promoting muscle development and hyaluronic acid synthesis.

The Role of Nicotinamide in Cancer Chemoprevention and Therapy

Nicotinamide (NAM) is a water-soluble form of Vitamin B3 (niacin) and a precursor of nicotinamide-adenine dinucleotide (NAD⁺) which regulates cellular energy metabolism. Except for its role in the production of adenosine triphosphate (ATP), NAD⁺ acts as a substrate for several enzymes including sirtuin 1 (SIRT1) and poly ADP-ribose polymerase 1 (PARP1). Notably, NAM is an inhibitor of both SIRT1 and PARP1. Accumulating evidence suggests that NAM plays a role in cancer prevention and therapy. Phase III clinical trials have confirmed its clinical efficacy for non-melanoma skin cancer chemoprevention or as an adjunct to radiotherapy against head and neck, laryngeal, and urinary bladder cancers. Evidence for other cancers has mostly been collected through preclinical research and, in its majority, is not yet evidence-based. NAM has potential as a safe, well-tolerated, and cost-effective agent to be used in cancer chemoprevention and therapy. However, more preclinical studies and clinical trials are needed to fully unravel its value.

Evolution of the use of antioxidants in anti-ageing cosmetics

OBJECTIVE

Skin health and beauty are a cornerstone of general well-being in humans. Anti-ageing cosmetics are used to provide a healthy and youthful appearance. Among the different cosmetic actives, antioxidants are incorporated in anti-ageing products due to their beneficial effects in preventing and minimizing the signs of skin ageing. This work aims to understand how anti-ageing formulations changed in the past 7 years regarding pure antioxidants composition.

METHODS

Data were collected from anti-ageing formulations commercialized in main stores and pharmacies in the Portuguese market. The study started on 2011 and was updated with products launched or whose composition has been renewed on 2013, 2015 or 2018.

RESULTS

Ascorbic acid and tocopherol and their derivatives were consistently the most used antioxidants in anti-ageing formulations; followed by niacinamide and retinyl palmitate. Seven ascorbic acid derivatives are currently used in anti-ageing formulations while only three tocopherol derivatives were identified in this study. Several combinations of antioxidants were routinely found, mainly tocopherol (or tocopherol derivatives) with other antioxidants and tocopherol with tocopherol derivatives. We have not identified emerging antioxidants with great impact in anti-ageing formulations even though niacinamide and retinyl palmitate exhibited over 10% more usage in 2018.

CONCLUSION

This insight is relevant to the cosmetic industry providing a better understanding of the scientific-based formulation of modern cosmetics and supports the need for innovative antioxidants in anti-ageing cosmetics.

Effect of supplementation of nicotinamide and sodium butyrate on the growth performance, liver mitochondrial function and gut microbiota of broilers at high stocking density

This study was conducted to investigate the effects of stocking density and dietary nicotinamide (NAM) and butyrate sodium (BA) supplementation on the growth performance, liver mitochondrial function and gut microbiota of broilers at high stocking density. A total of 342, 26-d-old Cobb500 broilers were divided into 5 groups with 6 replicates. Treatments were as follows: (a) Low stocking density (L, 9 birds per cage); (b) High stocking density (H, 12 birds per cage); (c) H + 50 ppm NAM; (d) H + 500 ppm BA; (e) H + 50 ppm NAM + 500 ppm BA (COMB). The results showed that high stocking density significantly reduced the feed intake and body weight gain of broilers, while COMB improved the growth performance at high stocking density. High stocking density significantly reduced the liver metallothionein content, liver mitochondrial membrane potential and the activities of Na⁺K⁺-ATPase and Ca²⁺Mg²⁺-ATPase. In contrast, the liver metallothionein contents in the NAM, BA and COMB fed group were higher than those in the H group. COMB increased the activity of ATPase as well, but it failed to enhance the mitochondrial membrane potential. Stocking density also affected gut microbiota of broilers. The high-density group increased the relative abundance of Blautia. Supplementation of BA and NAM increased the abundance of Lactobacillus and Bifidobacteria, respectively. In conclusion, a combination of NAM and BA can improve the performance, antioxidant capacity, mitochondrial function and intestinal microbiota of broilers at high stocking density.

Cellular senescence: Molecular mechanisms and pathogenicity

Cellular senescence is the arrest of normal cell division. Oncogenic genes and oxidative stress, which cause genomic DNA damage and generation of reactive oxygen species, lead to cellular senescence. The senescence-associated secretory phenotype is a distinct feature of senescence. Senescence is normally involved in the embryonic development. Senescent cells can communicate with immune cells to invoke an immune response. Senescence emerges during the aging process in several tissues and organs. In fact, increasing evidence shows that cellular senescence is implicated in aging-related diseases, such as nonalcoholic fatty liver disease, obesity and diabetes, pulmonary hypertension, and tumorigenesis. Cellular senescence can also be induced by microbial infection. During cellular senescence, several signaling pathways, including those of p53, nuclear factor-κB (NF-κB), mammalian target of rapamycin, and transforming growth factor-beta, play important roles. Accumulation of senescent cells can trigger chronic inflammation, which may contribute to the pathological changes in the elderly. Given the variety of deleterious effects caused by cellular senescence in humans, strategies have been proposed to control senescence. In this review, we will focus on recent studies to provide a brief introduction to cellular senescence, including associated signaling pathways and pathology.

The Good, the Bad, and the Ugly of ROS: New Insights on Aging and Aging-Related Diseases from Eukaryotic and Prokaryotic Model Organisms

Aging is associated with the accumulation of cellular damage over the course of a lifetime. This process is promoted in large part by reactive oxygen species (ROS) generated via cellular metabolic and respiratory pathways. Pharmacological, nonpharmacological, and genetic interventions have been used to target cellular and mitochondrial networks in an effort to decipher aging and age-related disorders. While ROS historically have been viewed as a detrimental byproduct of normal metabolism and associated with several pathologies, recent research has revealed a more complex and beneficial role of ROS in regulating metabolism, development, and lifespan. In this review, we summarize the recent advances in ROS research, focusing on both the beneficial and harmful roles of ROS, many of which are conserved across species from bacteria to humans, in various aspects of cellular physiology. These studies provide a new context for our understanding of the parts ROS play in health and disease. Moreover, we highlight the utility of bacterial models to elucidate the molecular pathways by which ROS mediate aging and aging-related diseases.

The bright side of reactive oxygen species: lifespan extension without cellular demise

Oxidative stress and the generation of reactive oxygen species (ROS) can lead to mitochondrial dysfunction, DNA damage, protein misfolding, programmed cell death with apoptosis and autophagy, and the promotion of aging –dependent processes. Mitochondria control the processing of redox energy that yields adenosine triphosphate (ATP) through the oxidation of glucose, pyruvate, and nicotinamide adenine dinucleotide. Ultimately, the generation of ROS occurs with the aerobic production of ATP. Although reduced levels of ROS may lead to tolerance against metabolic, mechanical, and oxidative stressors and the generation of brief periods of ROS during ischemia-reperfusion models may limit cellular injury, under most circumstances ROS and mitochondrial dysfunction can lead to apoptotic caspase activation and autophagy induction that can result in cellular demise. Yet, new work suggests that ROS generation may have a positive impact through respiratory complex I reverse electron transport that can extend lifespan. Such mechanisms may bring new insight into clinically relevant disorders that are linked to cellular senescence and aging of the body’s system. Further investigation of the potential “bright side” of ROS and mitochondrial respiration is necessary to target specific pathways, such as the mechanistic target of rapamycin, nicotinamidases, sirtuins, mRNA decoupling and protein expression, and Wnt signaling, that can impact oxidative stress-ROS mechanisms to extend lifespan and eliminate disease onset.

High-Dose Nicotinamide Suppresses ROS Generation and Augments Population Expansion during CD8(+) T Cell Activation

During T cell activation, mitochondrial content increases to meet the high energy demand of rapid cell proliferation. With this increase, the level of reactive oxygen species (ROS) also increases and causes the rapid apoptotic death of activated cells, thereby facilitating T cell homeostasis. Nicotinamide (NAM) has previously been shown to enhance mitochondria quality and extend the replicative life span of human fibroblasts. In this study, we examined the effect of NAM on CD8(+) T cell activation. NAM treatment attenuated the increase of mitochondrial content and ROS in T cells activated by CD3/CD28 antibodies. This was accompanied by an accelerated and higher-level clonal expansion resulting from attenuated apoptotic death but not increased division of the activated cells. Attenuation of ROS-triggered pro-apoptotic events and upregulation of Bcl-2 expression appeared to be involved. Although cells activated in the presence of NAM exhibited compromised cytokine gene expression, our results suggest a means to augment the size of T cell expansion during activation without consuming their limited replicative potential.

FoxO Transcription Factors and Regenerative Pathways in Diabetes Mellitus

Mammalian forkhead transcription factors of the O class (FoxO) are exciting targets under consideration for the development of new clinical entities to treat metabolic disorders and diabetes mellitus (DM). DM, a disorder that currently affects greater than 350 million individuals globally, can become a devastating disease that leads to cellular injury through oxidative stress pathways and affects multiple systems of the body. FoxO proteins can regulate insulin signaling, gluconeogenesis, insulin resistance, immune cell migration, and cell senescence. FoxO proteins also control cell fate through oxidative stress and pathways of autophagy and apoptosis that either lead to tissue regeneration or cell demise. Furthermore, FoxO signaling can be dependent upon signal transduction pathways that include silent mating type information regulation 2 homolog 1 (S. cerevisiae) (SIRT1), Wnt, and Wnt1 inducible signaling pathway protein 1 (WISP1). Cellular metabolic pathways driven by FoxO proteins are complex, can lead to variable clinical outcomes, and require in-depth analysis of the epigenetic and post-translation protein modifications that drive FoxO protein activation and degradation.