The Noncanonical Pathway for In Vivo Nitric Oxide Generation: The Nitrate-Nitrite-Nitric Oxide Pathway

Inhibition of hepatic gluconeogenesis in type 2 diabetes by metformin: complementary role of nitric oxide

Metformin is the first-line treatment for type 2 diabetes mellitus. Type 2 diabetes mellitus is associated with decreased nitric oxide bioavailability, which has significant metabolic implications, including enhanced insulin secretion and peripheral glucose utilization. Similar to metformin, nitric oxide also inhibits hepatic glucose production, mainly by suppressing gluconeogenesis. This review explores the combined effects of metformin and nitric oxide on hepatic gluconeogenesis and proposes the potential of a hybrid metformin-nitric oxide drug for managing type 2 diabetes mellitus. Both metformin and nitric oxide inhibit gluconeogenesis through overlapping and distinct mechanisms. In hepatic gluconeogenesis, mitochondrial oxaloacetate is exported to the cytoplasm via various pathways, including the malate, direct, aspartate, and fumarate pathways. The effects of nitric oxide and metformin on the exportation of oxaloacetate are complementary; nitric oxide primarily inhibits the malate pathway, while metformin strongly inhibits the fumarate and aspartate pathways. Furthermore, metformin effectively blocks gluconeogenesis from lactate, glycerol, and glutamine, whereas nitric oxide mainly inhibits alanine-induced gluconeogenesis. Additionally, nitric oxide contributes to the adenosine monophosphate-activated protein kinase-dependent inhibition of gluconeogenesis induced by metformin. The combined use of metformin and nitric oxide offers the potential to mitigate common side effects. For example, lactic acidosis, a known side effect of metformin, is linked to nitric oxide deficiency, while the oxidative and nitrosative stress caused by nitric oxide could be counterbalanced by metformin's enhancement of glutathione. Metformin also amplifies nitric oxide -induced activation of adenosine monophosphate-activated protein kinase. In conclusion, a metformin-nitric oxide hybrid drug can benefit patients with type 2 diabetes mellitus by enhancing the inhibition of hepatic gluconeogenesis, decreasing the required dose of metformin for maintaining optimal glycemia, and lowering the incidence of metformin-associated lactic acidosis.

Colorimetric nanozyme sensor based on chain-like PtNi nanoparticles for nitrite ion detection in food samples

Here, we combine the peroxidase-like activity of chain-like PtNi nanoparticles (PtNi CNPs) and diazotization reaction to construct a dual-signal ratiometric colorimetric platform for nitrite ion detection. Compared to Pt NPs, PtNi CNPs exhibit better peroxidase-like activities with Michaelis constant (Km) of 0.15 mM and maximum reaction rate (Vmax) of 8.09 × 10-8 Ms.-1 towards 3, 3', 5, 5'-tetramethylbenzidine (TMB) and Km of 5.08 mM and Vmax of 16.07 × 10-8 Ms.-1 towards H2O2. After adding nitrite ion, diazotization reaction between oxidized TMB and nitrite ion occurs, resulting in an attenuated absorption peak signal at 652 nm and an enhanced absorption peak signal at 450 nm, accompanied by a color change (blue-yellow green). This dual-signal ratiometric (A652 nm/A450 nm) method shows a good linear relationship ranging from 20 to 350 μM and 0.3237 μM of detection limit. Importantly, the method shows great potential in detecting nitrite ion in real food samples.

Reactive oxygen and nitrogen species: multifaceted regulators of ovarian activity†

Reactive oxygen and nitrogen species are essential components of diverse intracellular signaling pathways. In addition to their involvement in apoptosis, reactive oxygen and nitrogen species are crucial in the regulation of multiple developmental and physiological processes. This review aims to summarize their role in the regulation of key ovarian stages: ovulation, maturation and postovulatory ageing of the oocyte, and the formation and regression of the corpus luteum. At the cellular level, a mild increase in reactive oxygen and nitrogen species is associated with the initiation of a number of regulatory mechanisms, which might be suppressed by increased activity of the antioxidant system. Moreover, a mild increase in reactive oxygen and nitrogen species has been linked to the control of mitochondrial biogenesis and abundance in response to increased cellular energy demands. Thus, reactive oxygen and nitrogen species should also be perceived in terms of their positive role in cellular signaling. On the other hand, an uncontrolled increase in reactive oxygen species production or strong down-regulation of the antioxidant system results in oxidative stress and damage of cellular components associated with ovarian pathologies and ageing. Similarly, the disturbance of signaling functions of reactive nitrogen species caused by dysregulation of nitric oxide production by nitric oxide synthases in ovarian tissues interferes with the proper regulation of physiological processes in the ovary.

Oxidative stress products and managements in atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that affects a significant portion of the global population, severely impacting the quality of life and causing physical and psychological distress of patients. Oxidative stress, resulting from an imbalance between oxidation and antioxidation activities, plays a pivotal role in the pathogenesis of AD. Monitoring oxidative stress products can offer valuable insights into the development of AD and highlight essential clinical and therapeutic effects. Additionally, evidence suggests that antioxidant strategies can alleviate or avert oxidative damage induced by free radicals and offer significant promise in the treatment of AD. In addition to directly utilizing natural products and nanomaterials for antioxidant interventions, these can also be incorporated into hydrogels, which help repair the skin barrier and support the sustained release of therapeutic agents. Furthermore, microneedles provide a minimally invasive method for delivering antioxidants to the deeper layers of the skin, enhancing treatment efficacy. This review aims to summarize the role of the oxidative stress in the pathogenesis of AD, focusing in the main oxidative products (DNA, protein, and lipid oxidation products), as well as antioxidant therapeutic approaches involving natural products, nanomaterials, hydrogels, and microneedles. Understanding these biomarkers and antioxidant therapy approaches provides important insights into the management of AD.

Nitrate supplementation affects taste by changing the oral metabolome and microbiome

Nitrate, an inorganic anion found in various foods is also present in saliva and has emerged as a potential prebiotic for the oral microbiome. Salivary glands concentrate nitrate from the bloodstream and release it into the oral cavity via the anion transporter sialin SLC17A5. In previous studies dietary nitrate supplementation altered oral bacteria composition, favouring genera like Rothia and Neisseria while reducing Streptococcus, Veillonella, Prevotella, and Actinomyces. The present study hypothesized that taste intensity might adapt to changes in the oral microbiome caused by nitrate supplementation. Participants underwent taste tests before, during, and after supplementation. All subjects showed greater levels of salivary nitrate during supplementation and had higher levels of Neisseria compared to before. Subjects were then grouped according to taste tests (before vs. during) as responders (ANOVA p < 0.05, n = 7), and non-responders (ANOVA p > 0.05, n = 6) and their salivary metabolome and oral microbiome further analysed. Responders had significantly less 5-amino pentanoate, formate, propionate and butyrate in saliva while non-responders showed no metabolite changes between before and during supplementation. In contrast, non-responders had increased Capnocytophaga gingivalis and altered lysosomal degradation pathways. Overall, nitrate supplementation shifted the oral microbiome composition in all subjects and when taste intensity was altered this correlated to bacteria-derived short-chain fatty acid production. This suggests taste perception is affected by the oral microbiome.

Accelerating inflammatory resolution in humans to improve endothelial function and vascular health: Targeting the non-canonical pathway for NO

BACKGROUND

Chronic cardiovascular diseases (CVD) are characterised by low-grade systemic inflammation in part due to reduced nitric oxide (NO) bioavailability associated with endothelial dysfunction. Bioavailability of NO can be enhanced by activation of the non-canonical pathway, through increased dietary inorganic nitrate consumption with the potential to attenuate inflammation.

METHODS

We sought to determine whether dietary inorganic nitrate influences the inflammatory response in models of localised (cantharidin-induced blisters) and systemic inflammation (typhoid vaccine), in healthy male volunteers and conducted two clinical trials; Blister-NITRATE and Typhoid-NITRATE respectively.

RESULTS

We show that dietary nitrate attenuates endothelial dysfunction following typhoid vaccine administration and accelerates resolution of cantharidin-induced blisters. Both phenomena were associated with an increased level of pro-resolving mediators consequent to a reduction in the expression and activity of pro-inflammatory monocytes. Moreover, we show that leukocytes of the monocyte lineage express the nitrite reductase XOR, that may drive localised nitrite reduction to elevate NO (and cGMP) to drive the protective phenotype.

CONCLUSIONS

Inorganic nitrate improves endothelial function in the setting of systemic inflammation. Whilst the immediate inflammatory response appeared unaffected by inorganic nitrate treatment, during the resolution phase of the acute inflammatory response lower levels of pro-inflammatory classical inflammatory and intermediate monocytes and attenuated levels of inflammatory cytokines and chemokines were evident. We propose that this reflects a pro-resolution phenotype that may be of potential therapeutic benefit in patients with established CVD.

CLINICAL TRIAL REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; unique identifiers NCT02715635, NCT03183830.

S-nitrosylation of EZH2 alters PRC2 assembly, methyltransferase activity, and EZH2 stability to maintain endothelial homeostasis

Nitric oxide (NO), a versatile bio-active molecule modulates cellular functions through diverse mechanisms including S-nitrosylation of proteins. Herein, we report S-nitrosylation of selected cysteine residues of EZH2 in endothelial cells, which interplays with its stability and functions. We detect a significant reduction in H3K27me3 upon S-nitrosylation of EZH2 as contributed by the early dissociation of SUZ12 from the PRC2. Moreover, S-nitrosylation of EZH2 causes its cytosolic translocation, ubiquitination, and degradation. Further analysis reveal S-nitrosylation of cysteine 329 induces EZH2 instability, whereas S-nitrosylation of cysteine 700 abrogates its catalytic activity. We further show that S-nitrosylation-dependent regulation of EZH2 maintains endothelial homeostasis in both physiological and pathological settings. Molecular dynamics simulation reveals the inability of SUZ12 to efficiently bind to the SAL domain of EZH2 upon S-nitrosylation. Taken together, our study reports S-nitrosylation-dependent regulation of EZH2 and its associated PRC2 complex, thereby influencing the epigenetics of endothelial homeostasis.

Impact of chronic exposure to ternary metal mixtures on behavioral and cellular responses in Nauphoeta cinerea nymphs

There is a  growing concern about the impact of environmental contamination by metals on insects owing to their biodiversity and important ecological roles. We investigated the neurobehavioral traits, cellular responses, and levels of metals in tissues of Nauphoeta cinerea nymphs exposed, separately and in ternary mixtures, to arsenic (15 and 7.5 mg/L), copper (15 and 7.5 mg/L), and zinc (100 and 50 µg/L), in drinking water for 35 consecutive days. Results showed that the diminutions in locomotor parameters (maximum speed, motility time, and distance traveled), motor and turning capabilities (path efficiency, turn angle, and body rotation) and the increase in anxiety-like behavior (total time freezing and freezing episodes) were more pronounced in individual metal exposure than triple metal mixtures groups. Barring zinc alone group, acetylcholinesterase activity decreased significantly in all the treatment groups compared to the control. The diminutions in glutathione level and antioxidant enzyme activities were partially attenuated in the fat body, midgut, and head of insects in the triple metal mixtures groups. Further, the levels of nitric oxide, hydrogen peroxide, lipid peroxidation, and reactive oxygen and nitrogen species were higher in individual metal exposed insects than the ternary mixture groups. The concentrations of arsenic, copper, and zinc in the fat body, midgut, and head of insects were significantly higher in individual metal exposure groups than the ternary metal mixtures groups. Collectively, the detrimental effects of elevated ecological concentrations of arsenic, copper, and zinc were more pronounced in insects exposed to individual metal than those in ternary mixtures groups.

Nitrate ameliorates alcohol-induced cognitive impairment via oral microbiota

Alcohol use is associated with cognitive impairment and dysregulated inflammation. Oral nitrate may benefit cognitive impairment in aging through altering the oral microbiota. Similarly, the beneficial effects of nitrate on alcohol-induced cognitive decline and the roles of the oral microbiota merit investigation. Here we found that nitrate supplementation effectively mitigated cognitive impairment induced by chronic alcohol exposure in mice, reducing both systemic and neuroinflammation. Furthermore, nitrate restored the dysbiosis of the oral microbiota caused by alcohol consumption. Notably, removing the oral microbiota led to a subsequent loss of the beneficial effects of nitrate. Oral microbiota from donor alcohol use disordered humans who had been taking the nitrate intervention were transplanted into germ-free mice which then showed increased cognitive function and reduced neuroinflammation. Finally, we examined 63 alcohol drinkers with varying levels of cognitive impairment and found that lower concentrations of nitrate metabolism-related bacteria were associated with higher cognitive impairment and lower nitrate levels in plasma. These findings highlight the protective role of nitrate against alcohol-induced cognition impairment and neuroinflammation and suggest that the oral microbiota associated with nitrate metabolism and brain function may form part of a "microbiota-mouth-brain axis".

Nitrate reduction by salivary bacteria, glucose metabolism, and lifestyle

Background

Nitrate reductases (NR) expressed in oral bacteria reduce nitrate to nitrite. Depending on the environmental conditions and types of bacteria present nitrite can be further reduced to ammonium via Dissimilatory Nitrate Reduction to Ammonium (DNRA), or alternatively to nitric oxide (NO), which impacts cardiometabolic health.

Objective

To evaluate the associations between nitrate reduction by salivary bacteria, clinical markers of glucose metabolism, and lifestyle factors that can modulate the oral environment, potentially impacting DNRA and NR expression.

Methods

A cross-sectional study was conducted using a convenience sample of 144 participants from the San Juan Overweight Adult Longitudinal Study (SOALS), which includes data on glucose metabolism and lifestyle. DNRA and NR activities were measured in saliva under aerobic or CO2-enriched conditions.

Results

DNRA activity was inversely associated with insulin resistance (HOMA-IR) [aerobic3rd vs.1st tertile: β=-0.48 (-0.81, -0.15); CO2-enriched3rd vs.1st tertile β=-0.42 (-0.68, -0.17)], fasting blood glucose [aerobic3rd vs.1st tertile β=-0.144 (-0.268, -0.019); CO2-enriched3rd vs.1st tertile: β=-0.070 (-0.130, -0.011)], and 2-h glucose [CO2-enriched3rd vs.1st tertileβ=-0.21 (-0.37, -0.04)]. Current smokers had lower DNRA activity than non-smokers under aerobic conditions [β=-1.55 (-2.96, -0.14)], but higher under CO2-enriched conditions [β = 0.93 (0.15, 1.71)]. Toothbrushing frequency (twice/day vs. once/day) was positively associated with DNRA activity under CO2-enriched conditions [β = 4.11 (1.90, 6.32)] and with aerobic NR activity [β = 1.20, (0.14, 2.27)]. Physical activity was inversely associated with aerobic NR [β=-0.01, (-0.022, -0.003)]. Under CO2-enriched conditions NR was inversely associated with the BMI (β=-0.11, p = 0.007). Aerobic NR was higher when sucrose was added to the assays (NADP vs. sucrose β=-0.74, p = 0.02) and positively associated with salivary nitrate levels (β = 0.002, p = 0.002).

Conclusions

Nitrate reduction by salivary bacteria is inversely associated with insulin resistance and can be modulated by lifestyle factors. This knowledge could lead to the development of novel, non-invasive approaches for monitoring and preventing diabetes progression.

Do Nitrosative Stress Molecules Hold Promise as Biomarkers for Multiple Sclerosis?

Multiple sclerosis (MS), an auto-immune disease of the central nervous system (CNS) with inflammatory and neurodegenerative properties, remains an insufficiently understood disease despite more than 150 years of research. In contrast to diseases from other medical fields such as, for instance, oncology, a description of its clinical and non-clinical features based on readouts such as biomarkers is still in its infancy. While, in this regard, neurofilament light chain (NfL) seems to be a promising new tool, the significant intra- and interindividual variation of this serological marker somewhat limits its widespread applicability in everyday clinical reality. This has sparked novel studies in which glial fibrillary acidic protein (GFAP) was proposed as an on-top marker serving to improve overall specificity. In this context, it was found that MS disease progression was significantly more often associated with increased levels of both NfL and GFAP compared to increased NfL levels alone. This highlights the complexity of the disease while also emphasizing the potential benefits of introducing additional markers to enhance current options. We propose that nitrosative stress markers, such as nitrate, nitrite, and nitrotyrosine (3NT), could serve this purpose effectively.

Eight weeks of high-intensity interval training alters the tongue microbiome and impacts nitrate and nitrite levels in previously sedentary men

Nitric oxide (∗NO) is a key signalling molecule, produced enzymatically via ∗NO synthases (NOS) or following the stepwise reduction of nitrate to nitrite via oral bacteria. Exercise training upregulates NOS expression and improves systemic health, but its effect on oral health, and more particularly the oral microbiome, has not been investigated. We used an exercise training study design to investigate changes in the tongue dorsum microbiome, and in nitrate and nitrite levels in the saliva, plasma and muscle, before, during and after an exercise training period. Eleven untrained males (age 25 ± 5 years, mass 64.0 ± 11.2 kg, stature 171 ± 6 cm, V˙ O2peak 2.25 ± 0.42 l min-1) underwent 8-weeks of high-intensity interval training (HIIT), followed by 12-weeks of detraining. The tongue dorsum microbiome was examined using Pac-Bio long-read 16S rRNA sequencing. Nitrate and nitrite levels were quantified with high-performance liquid chromatography. Grouped nitrite-producing species did not change between any timepoints. However, HIIT led to changes in the microbiome composition, increasing the relative abundance of some, but not all, nitrite-producing species. These changes included a decrease in the relative abundance of nitrite-producing Rothia and a decrease in Neisseria, alongside changes in 6 other bacteria at the genus level (all p ≤ 0.05). At the species level, the abundance of 9 bacteria increased post-training (all p ≤ 0.05), 5 of which have nitrite-producing capacity, including Rothia mucilaginosa and Streptococcus salivarius. Post-detraining, 6 nitrite-producing species remained elevated relative to baseline. Nitrate increased in plasma (p = 0.03) following training. Nitrite increased in the saliva after training (p = 0.02) but decreased in plasma (p = 0.03) and muscle (p = 0.002). High-intensity exercise training increased the abundance of several nitrite-producing bacteria and altered nitrate and nitrite levels in saliva, plasma, and muscle. Post-detraining, several nitrite-producing bacteria remained elevated relative to baseline, but no significant differences were detected in nitrate or nitrite levels. Switching from a sedentary to an active lifestyle alters both the microbiome of the tongue and the bioavailability of nitrate and nitrite, with potential implications for oral and systemic health.

Salivary-Gland-Mediated Nitrate Recirculation as a Modulator for Cardiovascular Diseases

Cardiovascular diseases (CVDs), which include multiple disorders of the heart and blood vessels, are the leading causes of death. Nitric oxide (NO) is a vasodilator that regulates vascular tension. Endogenous NO is produced via the L-arginine-nitric oxide synthase (NOS) pathway. In conditions of cardiovascular dysfunction, NOS activity is impaired, leading to NO deficiency. In turn, the reduction in NO bioactivity exacerbates the pathogenesis of CVDs. Exogenous intake of inorganic nitrate supplements endogenous production via the nitrate-nitrite-NO pathway to maintain the NO supply. Salivary glands play an essential role in the conversion of nitrate to NO, with approximately 25% of circulating nitrate being absorbed and secreted into saliva. As a result, salivary nitrate concentrations can exceed that in the blood by more than tenfold. This recycled nitrate in saliva serves as a reservoir for NO and performs NO-like functions when endogenous NO production is insufficient. In this review, we summarize the emerging benefits of dietary nitrate in CVDs, with a particular focus on salivary-gland-mediated nitrate recirculation in maintaining NO bioavailability and cardiovascular homeostasis. Salivary-gland-mediated nitrate recirculation provides a novel perspective for potential intervention of CVDs.

Physical Exercise Alleviates Oxidative Stress and Autonomic Dysregulation in a Rat Model of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) induces immunological and autonomic imbalances. Exercise is a beneficial strategy for controlling IBD symptoms. We investigated the role of exercise on gastrointestinal (GI) motility changes and autonomic parameters in rats with ileitis. Rats were divided into control, ileitis, and exercise+ileitis groups. Ileitis was induced by TNBS (40 mM, intraileally). The exercise was swimming (1 h/day/4 weeks, 5%/bw). We assessed eating behaviour and oxidative stress. Body composition was assessed by bioimpedance. Autonomic balance and ECG parameters were measured by an electrocardiogram (ECG). Gastrointestinal motility was evaluated using the phenol red technique. In terms of body composition, total body water (TBW), body mass index (BMI), and fat-free mass (FFM) were higher in the ileitis group (216.80 ± 11.44 mL; 24.09 ± 2.15 g/cm2; 287.1 ± 14.66 g) (p < 0.05) vs. control rats (130.06 ± 28.23 mL; 16.38 ± 2.50 g/cm2; 193 ± 42.21 g) and exercise prevented (91.33 ± 12.33 mL; 11.73 ± 0.47 g/cm2; 133.8 ± 16.82 g) (p < 0.05) these changes. The exercise+ileitis group induces a reduction (p < 0.05) in gastric retention vs. ileitis and control (11.22 ± 1.91% vs. 35.17 ± 1.01% and 33.96 ± 1.77%). Ileitis increased intestinal retention in the duodenum (46.3 ± 2.56% vs. 24.98 ± 1.78%) and jejunum (34.22 ± 2.33% and 34.72 ± 2.83% vs. 47.32 ± 1.48%) (p < 0.05) and decreased intestinal retention in the ileum (p < 0.05) vs. the control group. Exercise+ileitis prevented (p < 0.05) changes in the duodenum (24.96 ± 1.66% vs. 46.3 ± 2.56%) and ileum (40.32 ± 3.75% vs. 14.08 ± 0.88%). Ileitis induces high MDA levels (p < 0.05) vs. control rats (4.43 ± 0.69 vs. 2.15 ± 0.12 nmol/mg of the tissue). This effect was prevented (p < 0.05) in the exercise+ileitis group (2.75 ± 0.21 vs. 4.43 ± 0.69 nmol/mg of the tissue). We observed a reduction in the LF component (p < 0.05) in the ileitis group vs. control group (31.32 ± 3.99 vs. 43.43 ± 3.86). The correlation indicated a stronger interrelationship between the autonomic parameter and intestinal retention in the ileum (r: 0.68; p: 0.04). The current study suggests intestinal ileitis alters GI motility and autonomic balance, and physical exercise can represent an essential non-pharmacological approach to IBD treatment.

Oxidative stress and obesity are associated with endothelial dysfunction and subclinical atherosclerosis in adolescents

OBJECTIVES

This study explores the relationship between obesity, endothelial dysfunction, and the critical role of oxidative stress biomarkers in subclinical atherosclerosis.

DESIGN & METHODS

The study included 114 adolescents aged 12-17 years from Juiz de Fora, Brazil, divided into 40 individuals with obesity and 74 controls. Physical and biochemical assessments were conducted, including measurements of Brachial Flow-Mediated Dilation (BFMD), Carotid Intima-Media Thickness (IMT), and oxidative biomarkers such as nitrite, nitrate, and 8-isoprostane. Multiple regression analyses were used to evaluate associations between obesity, oxidative biomarkers, and endothelial function.

RESULTS

Adolescents with obesity exhibited significantly reduced BFMD at 60 s (5.44 ± 2.31 % vs. 7.82 ± 2.07 % in controls; p < 0.05) and 90 s (5.27 ± 2.64 % vs. 7.93 ± 2.12 % in controls; p < 0.05). IMT was significantly higher in the group with obesity for both the right carotid artery (0.054 ± 0.005 cm vs. 0.047 ± 0.004 cm in controls; p < 0.05) and the left carotid artery (0.053 ± 0.005 cm vs. 0.047 ± 0.004 cm in controls; p < 0.05). Additionally, 8-isoprostane levels were higher in adolescents with obesity (49.75 ± 22.62 pg/mL vs. 42.36 ± 17.35 pg/mL in controls; p < 0.05), indicating increased oxidative stress. Nitrite levels were significantly lower in adolescents with obesity (42.98 ± 10.62 nM vs. 49.94 ± 17.71 nM in controls; p < 0.05). Additionally, nitrate levels were inversely associated with IMT in both the right (p = 0.01) carotid arteries in the multiple linear regression analyses.

CONCLUSIONS

The study highlights the association between obesity and early vascular changes in adolescents, evidenced by reduced BFMD, increased IMT, and altered oxidative stress biomarkers.

Mitochondria-Derived Vesicles and Inflammatory Profiles of Adults with Long COVID Supplemented with Red Beetroot Juice: Secondary Analysis of a Randomized Controlled Trial

In a recent clinical trial, beetroot juice supplementation for 14 days yielded positive effects on systemic inflammation in adults with long COVID. Here, we explored the relationship between circulating markers of mitochondrial quality and inflammation in adults with long COVID as well as the impact of beetroot administration on those markers. We conducted secondary analyses of a placebo-controlled randomized clinical trial testing beetroot juice supplementation as a remedy against long COVID. Analyses were conducted in 25 participants, 10 assigned to placebo (mean age: 40.2 ± 11.5 years, 60% women) and 15 allocated to beetroot juice (mean age: 38.3 ± 7.7 years, 53.3% women). Extracellular vesicles were purified from serum by ultracentrifugation and assayed for components of the electron transport chain and mitochondrial DNA (mtDNA) by Western blot and droplet digital polymerase chain reaction (ddPCR), respectively. Inflammatory markers and circulating cell-free mtDNA were quantified in serum through a multiplex immunoassay and ddPCR, respectively. Beetroot juice administration for 14 days decreased serum levels of interleukin (IL)-1β, IL-8, and tumor necrosis factor alpha, with no effects on circulating markers of mitochondrial quality control. Significant negative associations were observed between vesicular markers of mitochondrial quality control and the performance on the 6 min walk test and flow-mediated dilation irrespective of group allocation. These findings suggest that an amelioration of mitochondrial quality, possibly mediated by mitochondria-derived vesicle recycling, may be among the mechanisms supporting improvements in physical performance and endothelial function during the resolution of long COVID.

Emerging strategies for nitric oxide production and their topical application as nanodressings to promote diabetic wound healing

The challenges associated with prolonged healing or non-healing of chronic diabetic wounds contribute significantly to the increased incidence of lower limb amputation. A pivotal factor in the impediment of healing is the reduced production of endogenous nitric oxide (NO) due to the hyperglycemic microenvironment typical of chronic diabetes. While both endogenous and exogenous NO have been shown to promote the healing process of diabetic wounds, the direct application of NO in wound management is limited due to its gaseous nature and the risk of explosive release. This review summarizes recent advances of nanodressings incorporating NO donors in the treatment of diabetic wounds, detailing the specific conditions under which these nanodressings facilitate NO release, with a focus on the beneficial effects of NO, strategies for its supplementation, and the challenges encountered in the clinical translation of NO donors as a clinically viable nanomedicine in the context of improving diabetic wound healing.

Combination of inorganic nitrate and vitamin C prevents collagen-induced arthritis in rats by inhibiting pyroptosis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease characterized by synovial inflammation, cartilage damage, and bone loss. Although effective treatments are currently lacking, early interventions hold promise for alleviating RA symptoms. Inorganic nitrates and vitamin C (VC) are essential bioactive substances abundant in fruits and vegetables. Notably, nitrates and VC exhibit synergistic effects in a series of physiological and pathological conditions. In this study, we aim to examine the combination of nitrate and VC for preventing RA in a collagen-induced arthritis (CIA) rat model. Nitrate partly reduced foot swelling and arthritis scores and was more effective when combined with VC. Histopathological and radiological analyses revealed that nitrate + VC treatment alleviated synovial hyperplasia and bone loss. Additionally, nitrate + VC lowered the levels of TNF-α and IL-1β in serum as well as synovial tissue, decreased the expression of NF-κB and reduced the number of macrophages in synovial tissue. Compared to the CIA group, nitrate + VC decreased the levels of NLRP3 and GSDMD in macrophages, thus inhibiting pyroptosis. According to in vitro experiments, nitrate inhibited the activation of the NLRP3/caspase-1/GSDMD pathway in macrophages by conversion into nitrite. VC reduced the expression and phosphorylation of NF-κB in macrophages and thus reduced the expression levels of TNF-α and IL-1β. Therefore, nitrate/nitrite and VC may exert synergistic effects by blocking the interaction between NF-κB and NLRP3, further alleviating the inflammation and pyroptosis of macrophages, which provides a new strategy for RA prevention.

Chronic carbendazim exposure disrupts behavioral responses and redox-regulatory mechanisms in non-target detritivore Nauphoeta cinerea nymphs

Carbendazim is widely applied in agriculture to control various fungal diseases during pre-harvest and post-harvest processes owing to its efficacy and cost-effectiveness. However, environmental and food contamination by carbendazim has become a global health issue. Indeed, the declining biodiversity of beneficial insects owing to agricultural intensification is currently of keen concern to the scientific community. The toxicological responses of Nauphoeta cinerea nymphs, a non-target insect, to ecologically realistic concentrations of carbendazim at 0, 0.25, 2.5, 5.0 and 25 μg/L for 50 uninterrupted days were assessed. Neurobehavioral data generated by video-tracking software revealed that chronic nymphal exposure to carbendazim significantly diminished the path efficiency, body rotation, maximum speed, turn angle and distance traveled but increased the immobility time, total time of freezing and episodes of freezing in insects. The deterioration in the locomotor and exploratory abilities of carbendazim-exposed insects was substantiated by high heat map intensity and reduced track plots. Further, chronic carbendazim exposure diminished acetylcholinesterase activity in head of the insects. Chronic carbendazim exposure significantly decreased antioxidant defense mechanisms but increased nitric oxide, hydrogen peroxide and lipid peroxidation levels in fat body, midgut and head of exposed insects. Activities of acid and alkaline phosphatases which play important roles in detoxification and metabolic processes were also markedly decreased in carbendazim-exposed insects when compared with control. Altogether, carbendazim represents an ecological threat to non-target insects through induction of oxido-inflammatory injury, providing valuable insights into the behavioral dysfunction and toxicological mechanisms of carbendazim in beneficial insects.

Beetroot juice intake positively influenced gut microbiota and inflammation but failed to improve functional outcomes in adults with long COVID: A pilot randomized controlled trial

BACKGROUND & AIMS

Long-term effects of coronavirus disease 2019 (long COVID) develop in a substantial number of people following an acute COVID-19 episode. Red beetroot juice may have positive effects on multiple pathways involved in long COVID. The aim of this pilot study was to explore the impact of beetroot juice supplementation on physical function, gut microbiota, and systemic inflammation in adults with long COVID.

METHODS

A single-center, double-blind, placebo-controlled randomized trial was conducted to test the effects of 14 days of beetroot juice supplementation, rich in nitrates and betalains, on functional and biological outcomes in adults aged between 20 and 60 years with long COVID. Participants were randomized 1:1 to receive either daily oral supplementation with 200 mL beetroot juice (∼600 mg nitrate) or placebo (∼60 mg nitrate) for 14 days. The primary endpoint was the change from baseline to day 14 in a fatigue resistance test. Secondary outcomes included the distance walked on the 6-min walk test, handgrip strength, and flow-mediated dilation. Secondary endpoints also included changes from baseline in circulating inflammatory mediators and metagenomic and fecal water metabolomic profiles. Partial least squares discriminant analysis (PLS-DA) models were built to evaluate the differences in biological variables associated with the interventions.

RESULTS

Thirty-one participants were randomized in the study. Twenty-five of them (median (interquartile range) age 40 (10), 14 [56 %] women), received either beetroot juice (15) or placebo (10) and completed the study. At 14 days, fatigue resistance significantly improved from baseline (mean difference [standard error]: +21.8 [3.7] s; p < 0.001) with no significant differences between intervention groups. A significant increase from baseline in the distance walked on the 6-min walk test was observed (mean difference [standard error]: +30.0 [9.4] m; p = 0.03), which was not different between groups. Flow-mediated dilation did not differ between participants who received beetroot juice and those on placebo. PLS-DA models allowed correct classification of participants with 92.2 ± 4.4 % accuracy. Those who ingested red beetroot juice had a greater abundance of bacteria with well-known beneficial effects, including Akkermansia, Oscillospira, Prevotella, Roseburia, Ruminococcaceae, and Turicibacter, compared with placebo. Participants allocated to beetroot juice supplementation were also characterized by significantly higher levels of fecal nicotinate, trimethylamine, and markers of beetroot juice intake (e.g., 5,6-dihydroxyindole). Finally, higher levels of interferon gamma and macrophage inflammatory protein-1β were found in participants who consumed beetroot juice.

CONCLUSION

Beetroot juice supplementation for two weeks did not to induce significant improvements in functional outcomes in adults with long COVID compared with placebo. Beneficial effects were observed in both gut microbiota composition (i.e., increase in probiotic species) and inflammatory mediators.

TRIAL REGISTRATION

Trial was registered under ClinicalTrials.gov. Identifier no. NCT06535165.

Periodontal treatment causes a longitudinal increase in nitrite-producing bacteria

BACKGROUND

The oral microbiome-dependent nitrate (NO3 -)-nitrite (NO2 -)-nitric oxide (NO) pathway may help regulate blood pressure. NO2 --producing bacteria in subgingival plaque are reduced in relative abundance in patients with untreated periodontitis compared with periodontally healthy patients. In periodontitis patients, the NO2 --producing bacteria increase several months after periodontal treatment. The early effects of periodontal treatment on NO2 --producing bacteria and the NO3 --NO2 --NO pathway remain unknown. The aim of this study was to determine how periodontal treatment affects the oral NO2 --producing microbiome and salivary NO3 - and NO2 - levels over time.

METHODS

The subgingival microbiota of 38 periodontitis patients was analysed before (baseline [BL]) and 1, 7 and 90 days after periodontal treatment. Changes in NO2 --producing bacteria and periodontitis-associated bacteria were determined by 16s rRNA Illumina sequencing. Saliva samples were collected at all-time points to determine NO3 - and NO2 - levels using gas-phase chemiluminescence.

RESULTS

A significant increase was observed in the relative abundance of NO2 --producing species between BL and all subsequent timepoints (all p < 0.001). Periodontitis-associated species decreased at all timepoints, relative to BL (all p < 0.02). NO2 --producing species negatively correlated with periodontitis-associated species at all timepoints, with this relationship strongest 90 days post-treatment (ρ = -0.792, p < 0.001). Despite these findings, no significant changes were found in salivary NO3 - and NO2 - over time (all p > 0.05).

CONCLUSIONS

Periodontal treatment induced an immediate increase in the relative abundance of health-associated NO2 --producing bacteria. This increase persisted throughout periodontal healing. Future studies should test the effect of periodontal treatment combined with NO3 - intake on periodontal and cardiovascular health.

Potential Opportunities for Pharmacogenetic-Based Therapeutic Exploitation of Xanthine Dehydrogenase in Cardiovascular Disease

The majority of naturally occurring mutations of the human gene XDH, are associated with reduced or completely absent xanthine oxidoreductase (XOR) activity, leading to a disease known as classical xanthinuria, which is due to the accumulation and excretion of xanthine in urine. Three types of classical xanthinuria have been identified: type I, characterised by XOR deficiency, type II, caused by XOR and aldehyde oxidase (AO) deficiency, and type III due to XOR, AO, and sulphite oxidase (SO) deficiency. Type I and II are considered rare autosomal recessive disorders, a condition where two copies of the mutated gene must be present to develop the disease or trait. In most cases, xanthinuria type I and II result to be asymptomatic, and only occasionally lead to renal failure due to urolithiasis caused by xanthine deposition. However, in the last 10-15 years, new observations have been made about the link between naturally occurring mutations and pathological phenotypes particularly pertinent to cardiovascular diseases (CVD). These links have been attributed to a genetically driven increase of XOR expression and activity that is responsible for what is thought to be damaging uric acid (UA) and reactive oxygen species (ROS) accumulation, nitric oxide (·NO) depletion and endothelial dysfunction. In this review, we discuss the importance of genetics for interindividual variability of XOR expression and activity while focusing mainly on those variants thought to be relevant for CVD. In addition, we discuss the potential exploitation of the genetically driven increase of XOR activity to deliver more beneficial bioavailable ·NO. Finally, we examine the effect that non-synonymous mutations have on the tertiary structure of the protein and consequently on its capacity to interact with glycosaminoglycans (GAGs) localised on the outer surface of endothelial cells.

Cardiovascular effects of Roflumilast during sepsis: Risks or benefits?

BACKGROUND

Phosphodiesterase-4 (PDE4) is responsible for terminating cyclic adenosine monophosphate (cAMP) signalling. PDE4 inhibitors, such as roflumilast (RFM), have anti-inflammatory activity and have been studied in inflammation-induced tissue damage in sepsis. However, the role of RFM on cardiovascular derangements induced by sepsis is still unknown. Thus, we aimed to evaluate the potential effects of RFM on cardiovascular collapse and multiorgan damage caused by sepsis.

METHODS

Sepsis was induced by cecal ligation and puncture (CLP) in male rats. Six hours after the CLP or sham procedure, animals were randomly assigned to receive either RFM (0.3 mg/kg) or vehicle subcutaneously, and cardiovascular parameters were assessed 24 h after the surgery and organ/plasma samples were collected for further analyses.

RESULTS

Sepsis induced hypotension, tachycardia, reduced renal blood flow (RBF) and hyporeactivity to vasoconstrictors both in vivo and ex vivo. RFM treatment increased systemic cAMP levels and RBF. RFM also attenuated hypoperfusion and liver damage induced by CLP. Furthermore, RFM reduced systemic nitric oxide (NO) levels in septic rats, while there were no changes in hepatic NOS-2 expression. Nevertheless, RFM exacerbated sepsis-induced hypotension and tachycardia without ameliorating vascular hyporeactivity.

CONCLUSION

Our data show that PDE-4 inhibition protects septic rats from hepatic injury and improves renal perfusion. However, RFM worsened hemodynamic parameters and showed no protection against sepsis-induced cardiovascular dysfunction and mortality. Thus, despite the anti-inflammatory benefits of RFM, its application in sepsis should be approached cautiously.

Evidence-based sports supplements: A redox analysis

Despite the overwhelming number of sports supplements on the market, only seven are currently recognized as effective. Biological functions are largely regulated through redox reactions, yet no comprehensive analysis of the redox properties of these supplements has been compiled. Here, we analyze the redox characteristics of these seven supplements: bicarbonates, beta-alanine, caffeine, creatine, nitrates, carbohydrates, and proteins. Our findings suggest that all sports supplements exhibit some degree of redox activity. However, the precise physiological implications of these redox properties remain unclear. Future research, employing unconventional perspectives and methodologies, will reveal new redox pixels of the exercise physiology and sports nutrition picture.

The acute effects of dietary nitrate supplementation on postmenopausal endothelial resistance to ischemia reperfusion injury: a randomized, placebo-controlled, double blind, crossover clinical trial

Postmenopausal cardiovascular health is a critical determinant of longevity. Consumption of beetroot juice (BR) and other nitrate-rich foods is a safe, effective non-pharmaceutical intervention to increase systemic bioavailability of the vasoprotective molecule, nitric oxide, through the exogenous nitrate (NO3 -)-nitrite (NO2 -)-nitric oxide (NO) pathway. We hypothesized that a single dose of nitrate-rich beetroot juice (BRnitrate 600 mg NO3 -/140 mL, BRplacebo ∼ 0 mg/140 mL) would improve resting endothelial function and resistance to ischemia-reperfusion (IR) injury to a greater extent in early-postmenopausal (1-6 years following their final menstrual period (FMP), n = 12) compared to late-postmenopausal (6+ years after FMP, n = 12) women. Analyses with general linear models revealed a significant (p < 0.05) time*treatment interaction effect for brachial artery adjusted flow-mediated dilation (FMD). Pairwise comparisons revealed that adjusted FMD was significantly lower following IR-injury in comparison to all other time points with BRplacebo (early FMD 2.51 ± 1.18%, late FMD 1.30 ± 1.10, p < 0.001) and was lower than post-IR with BRnitrate (early FMD 3.84 ± 1.21%, late FMD 3.21 ± 1.13%, p = 0.014). A single dose of BRnitrate significantly increased resting macrovascular function in the late postmenopausal group only (p = 0.005). Considering the postmenopausal stage-dependent variations in endothelial responsiveness to dietary nitrate, we predict differing mechanisms underpin macrovascular protection against IR injury.

The NITRATE-OCT study-inorganic nitrate reduces in-stent restenosis in patients with stable coronary artery disease: a double-blind, randomised controlled trial

Background

Coronary angioplasty and stent insertion is a first line treatment for patients with coronary artery disease, however it is complicated in the long-term by in-stent restenosis (ISR) in a proportion of patients with an associated morbidity. Despite this, currently there are no effective treatments available for the prevention of ISR. Repeat percutaneous revascularisation carries increased risks of major adverse cardiovascular events and a higher incidence of stent failure. In this study we report the efficacy of dietary inorganic nitrate in the prevention of ISR in a prospective, double-blind, randomised controlled trial.

Methods

NITRATE-OCT is a double-blind, randomised, single-centre, placebo-controlled phase II trial. 300 patients who were planned to undergo percutaneous coronary intervention (PCI) and drug eluting stent (DES) implantation for stable angina were randomised on a 1:1 basis to receive a daily dose of either dietary inorganic nitrate or placebo for 6 months. Block randomisation was used and patients stratified according to diabetes status. The patients then underwent quantitative coronary angiography (QCA) at baseline and at 6 months and optical coherence tomography at 6 months to quantify ISR. The primary endpoint was the QCA quantified decrease of in-stent/in-segment diameter from the baseline measure at 6 months i.e., in-stent and in-segment late-lumen loss (LLL). The study is registered with ClinicalTrials.gov, number NCT02529189.

Findings

From November 1st 2015 and March 31st 2020, NITRATE-OCT enrolled 300 patients with angina, with 150 each randomised to receive 70 mL of nitrate-containing beetroot juice or placebo (nitrate-deplete) juice for 6 months. Procedural characteristics were similar between the groups. The primary endpoint was available in 208 patients: 107 and 101 in the nitrate and placebo groups, respectively. There was a statistically significant effect of inorganic nitrate on both primary endpoints: in-stent LLL decreased by 0.16 mm (95% CI:0.06-0.25; P = 0.001) with mean = 0.09 ± 0.38 mm in the inorganic nitrate group versus 0.24 ± 0.33 mm in the placebo group; (P = 0.0052); and in-segment LLL decreased by 0.24 mm (95% CI:0.12-0.36; P < 0.001) with mean = 0.02 ± 0.52 mm in the inorganic nitrate group and 0.26 ± 0.37 mm in the placebo group (P = 0.0002). Inorganic nitrate treatment was associated with a rise in the plasma nitrate concentration of ∼6.1-fold and plasma nitrite (NO2 -) of ∼2.0-fold at 6 months. These rises were associated with sustained decreases in systolic blood pressure (SBP) at 6 months compared to baseline with a change SBP of -12.06 ± 15.88 mmHg compared to the placebo group of 2.52 ± 14.60 mmHg (P < 0.0001).

Interpretation

In patients who underwent PCI for stable coronary artery disease, a once-a-day oral inorganic nitrate treatment was associated with a significant decrease in both in-stent and in-segment LLL.

Funding

This trial and KSR was funded by the National Institute for Health and Care Research (NIHR) (DRF-2014-07-008) and NIHR ACL, HW and this study were supported by The NIHR Barts Biomedical Research Centre, IC was funded by The North and East London Clinical Research Network, CL, GM were funded by The Barts Charity Cardiovascular Programme MRG00913 and MO was funded by The British Heart Foundation Project Grant PG/19/4/33995.

Potential Nephroprotective Effect of uPA against Ischemia/Reperfusion-Induced Acute Kidney Injury in αMUPA Mice and HEK-293 Cells

Background/Objectives: The incidence of acute kidney injury (AKI) has been steadily increasing. Despite its high prevalence, there is no pathogenetically rational therapy for AKI. This deficiency stems from the poor understanding of the pathogenesis of AKI. Renal ischemia/hypoxia is one of the leading causes of clinical AKI. This study investigates whether αMUPA mice, overexpressing the urokinase plasminogen activator (uPA) gene are protected against ischemic AKI, thus unraveling a potential renal damage treatment target. Methods: We utilized an in vivo model of I/R-induced AKI in αMUPA mice and in vitro experiments of uPA-treated HEK-293 cells. We evaluated renal injury markers, histological changes, mRNA expression of inflammatory, apoptotic, and autophagy markers, as compared with wild-type animals. Results: the αMUPA mice exhibited less renal injury post-AKI, as was evident by lower SCr, BUN, and renal NGAL and KIM-1 along attenuated adverse histological alterations. Notably, the αMUPA mice exhibited decreased levels pro-inflammatory, fibrotic, apoptotic, and autophagy markers like TGF-β, IL-6, STAT3, IKB, MAPK, Caspase-3, and LC3. By contrast, ACE-2, p-eNOS, and PGC1α were higher in the kidneys of the αMUPA mice. In vitro results of the uPA-treated HEK-293 cells mirrored the in vivo findings. Conclusions: These results indicate that uPA modulates key pathways involved in AKI, offering potential therapeutic targets for mitigating renal damage.

Emerging Targets and Treatments for Sarcopenia: A Narrative Review

BACKGROUND

Sarcopenia is characterized by the progressive loss of skeletal muscle mass, strength, and function, significantly impacting overall health and quality of life in older adults. This narrative review explores emerging targets and potential treatments for sarcopenia, aiming to provide a comprehensive overview of current and prospective interventions.

METHODS

The review synthesizes current literature on sarcopenia treatment, focusing on recent advancements in muscle regeneration, mitochondrial function, nutritional strategies, and the muscle-microbiome axis. Additionally, pharmacological and lifestyle interventions targeting anabolic resistance and neuromuscular junction integrity are discussed.

RESULTS

Resistance training and adequate protein intake remain the cornerstone of sarcopenia management. Emerging strategies include targeting muscle regeneration through myosatellite cell activation, signaling pathways, and chronic inflammation control. Gene editing, stem cell therapy, and microRNA modulation show promise in enhancing muscle repair. Addressing mitochondrial dysfunction through interventions aimed at improving biogenesis, ATP production, and reducing oxidative stress is also highlighted. Nutritional strategies such as leucine supplementation and anti-inflammatory nutrients, along with dietary modifications and probiotics targeting the muscle-microbiome interplay, are discussed as potential treatment options. Hydration and muscle-water balance are emphasized as critical in maintaining muscle health in older adults.

CONCLUSIONS

A combination of resistance training, nutrition, and emerging therapeutic interventions holds potential to significantly improve muscle function and overall health in the aging population. This review provides a detailed exploration of both established and novel approaches for the prevention and management of sarcopenia, highlighting the need for further research to optimize these strategies.

A systematic framework for understanding the microbiome in human health and disease: from basic principles to clinical translation

The human microbiome is a complex and dynamic system that plays important roles in human health and disease. However, there remain limitations and theoretical gaps in our current understanding of the intricate relationship between microbes and humans. In this narrative review, we integrate the knowledge and insights from various fields, including anatomy, physiology, immunology, histology, genetics, and evolution, to propose a systematic framework. It introduces key concepts such as the 'innate and adaptive genomes', which enhance genetic and evolutionary comprehension of the human genome. The 'germ-free syndrome' challenges the traditional 'microbes as pathogens' view, advocating for the necessity of microbes for health. The 'slave tissue' concept underscores the symbiotic intricacies between human tissues and their microbial counterparts, highlighting the dynamic health implications of microbial interactions. 'Acquired microbial immunity' positions the microbiome as an adjunct to human immune systems, providing a rationale for probiotic therapies and prudent antibiotic use. The 'homeostatic reprogramming hypothesis' integrates the microbiome into the internal environment theory, potentially explaining the change in homeostatic indicators post-industrialization. The 'cell-microbe co-ecology model' elucidates the symbiotic regulation affecting cellular balance, while the 'meta-host model' broadens the host definition to include symbiotic microbes. The 'health-illness conversion model' encapsulates the innate and adaptive genomes' interplay and dysbiosis patterns. The aim here is to provide a more focused and coherent understanding of microbiome and highlight future research avenues that could lead to a more effective and efficient healthcare system.

The role of nitric oxide synthase/ nitric oxide in infection-related cancers: Beyond antimicrobial activity

As a free radical and endogenous effector molecule, mammalian endogenous nitric oxide (NO) is mainly derived from nitric oxide synthase (NOS) via L-arginine. NO participates in normal physiological reactions and provides immune responses to prevent the invasion of foreign bacteria. However, NO also has complex and contradictory biological effects. Abnormal NO signaling is involved in the progression of many diseases, such as cancer. In the past decades, cancer research has been closely linked with NOS/ NO, and many tumors with poor prognosis are associated with high expression of NOS. In this review, we give a overview of the biological effects of NOS/ NO. Then we focus on the oncogenic role of iNOS/ NO in HPV, HBV, EBV and H. pylori related tumors. In fact, there is growing evidence that iNOS could be used as a potential therapeutic target in cancer therapy. We emphasize that the pro-tumor effect of NOS/ NO is greater than the anti-tumor effect.

Co-administration of thymol and sulfoxaflor impedes the expression of reproductive toxicity in male rats

This study investigated the capability of a co-delivery system of thymol (THY) and sulfoxaflor that can serve to minimize the development of epididymal and testicular injury arise from SFX exposures alone. Forty-eight adult male rats were orally treated by gavage for 28 consecutive days. The rats were divided into six groups comprising control, THY alone (30 mg/kg), low SFX alone (79.4 mg/kg), high SFX alone (205 mg/kg) and co-exposure groups. After euthanasia, the rats epididymal and testicular damage and antioxidant status markers, myeloperoxidase (MPO) activity, levels of nitric oxide, total antioxidant capacity (TAC), total oxidative stress (TOS) and lipid peroxidation (LPO) were analyzed. Levels of tumor necrosis factor alpha (TNF-α), interleukin-1 b (IL-1β) and caspase-3 activity were assessed using ELISA kits. The results revealed that SFX exposure caused a significant (p < 0.05) decrease in the body weight, sperm functional parameters, serum testosterone level with widespread histological abnormalities in a dose-dependent manner. Increased relative organ weights, serum levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were observed in low SFX-treated rats. Similarly, the epididymal and testicular myeloperoxidase activity, malondialdehyde (MDA), reactive oxygen species (RONS), tumor necrosis-α, interleukin-1β levels and caspase-3 activity were significant (p < 0.05) increased and a significant (p < 0.05) reduction in antioxidant enzyme activities and reduced glutathione (GSH) were revealed in SFX-treated rats. However, co-treatment of THY with SFX prevented SFX-induced epididymal and testicular toxicities. Thus, thymol protected against potential epididymis and testes alterations elicited by oxido-inflammatory mediators and up regulated antioxidant status.

Role of Nitric Oxide Synthases in Respiratory Health and Disease: Insights from Triple Nitric Oxide Synthases Knockout Mice

The system of nitric oxide synthases (NOSs) is comprised of three isoforms: nNOS, iNOS, and eNOS. The roles of NOSs in respiratory diseases in vivo have been studied by using inhibitors of NOSs and NOS-knockout mice. Their exact roles remain uncertain, however, because of the non-specificity of inhibitors of NOSs and compensatory up-regulation of other NOSs in NOS-KO mice. We addressed this point in our triple-n/i/eNOSs-KO mice. Triple-n/i/eNOSs-KO mice spontaneously developed pulmonary emphysema and displayed exacerbation of bleomycin-induced pulmonary fibrosis as compared with wild-type (WT) mice. Triple-n/i/eNOSs-KO mice exhibited worsening of hypoxic pulmonary hypertension (PH), which was reversed by treatment with sodium nitrate, and WT mice that underwent triple-n/i/eNOSs-KO bone marrow transplantation (BMT) also showed aggravation of hypoxic PH compared with those that underwent WT BMT. Conversely, ovalbumin-evoked asthma was milder in triple-n/i/eNOSs-KO than WT mice. These results suggest that the roles of NOSs are different in different pathologic states, even in the same respiratory diseases, indicating the diversity of the roles of NOSs. In this review, we describe these previous studies and discuss the roles of NOSs in respiratory health and disease. We also explain the current state of development of inorganic nitrate as a new drug for respiratory diseases.

Nitrate ingestion blunts the increase in blood pressure during cool air exposure: a double-blind, placebo-controlled, randomized, crossover trial

Cold exposure increases blood pressure (BP) and salivary flow rate (SFR). Increased cold-induced SFR would be hypothesized to enhance oral nitrate delivery for reduction to nitrite by oral anaerobes and to subsequently elevate plasma [nitrite] and nitric oxide bioavailability. We tested the hypothesis that dietary nitrate supplementation would increase plasma [nitrite] and lower BP to a greater extent in cool compared with normothermic conditions. Twelve males attended the laboratory on four occasions. Baseline measurements were completed at 28°C. Subsequently, participants ingested 140 mL of concentrated nitrate-rich (BR; ∼13 mmol nitrate) or nitrate-depleted (PL) beetroot juice. Measurements were repeated over 3 h at either 28°C (Norm) or 20°C (Cool). Mean skin temperature was lowered compared with baseline in PL-Cool and BR-Cool. SFR was greater in BR-Norm, PL-Cool, and BR-Cool than PL-Norm. Plasma [nitrite] at 3 h was higher in BR-Cool (592 ± 239 nM) versus BR-Norm (410 ± 195 nM). Systolic BP (SBP) at 3 h was not different between PL-Norm (117 ± 6 mmHg) and BR-Norm (113 ± 9 mmHg). SBP increased above baseline at 1, 2, and 3 h in PL-Cool but not BR-Cool. These results suggest that BR consumption is more effective at increasing plasma [nitrite] in cool compared with normothermic conditions and blunts the rise in BP following acute cool air exposure, which might have implications for attenuating the increased cardiovascular strain in the cold.NEW & NOTEWORTHY Compared with normothermic conditions, acute nitrate ingestion increased plasma [nitrite], a substrate for oxygen-independent nitric oxide generation, to a greater extent during cool air exposure. Systolic blood pressure was increased during cool air exposure in the placebo condition with this cool-induced blood pressure increase attenuated after acute nitrate ingestion. These findings improve our understanding of environmental factors that influence nitrate metabolism and the efficacy of nitrate supplementation to lower blood pressure.

Network analysis of S-nitrosylated synaptic proteins demonstrates unique roles in health and disease

Nitric oxide can covalently modify cysteine thiols on target proteins to alter that protein's function in a process called S-nitrosylation (SNO). S-nitrosylation of synaptic proteins plays an integral part in neurotransmission. Here we review the function of the SNO-proteome at the synapse and whether clusters of SNO-modification may predict synaptic dysfunction associated with disease. We used a systematic search strategy to concatenate SNO-proteomic datasets from normal human or murine brain samples. Identified SNO-modified proteins were then filtered against proteins reported in the Synaptome Database, which provides a detailed and experimentally verified annotation of all known synaptic proteins. Subsequently, we performed an unbiased network analysis of all known SNO-synaptic proteins to identify clusters of SNO proteins commonly involved in biological processes or with known disease associations. The resulting SNO networks were significantly enriched in biological processes related to metabolism, whereas significant gene-disease associations were related to Schizophrenia, Alzheimer's, Parkinson's and Huntington's disease. Guided by an unbiased network analysis, the current review presents a thorough discussion of how clustered changes to the SNO-proteome influence health and disease.

Beet supplementation mitigates post-exercise inflammation

Objectives

This study investigated the efficacy of a mixed beet-based supplement (BEET) versus placebo (PL) in countering inflammation during recovery from 2.25 h of intensive cycling in 20 male and female cyclists. A multi-omics approach was used that included untargeted proteomics and a targeted oxylipin panel.

Methods

A randomized, placebo-controlled, double-blind, crossover design was used with two 2-week supplementation periods and a 2-week washout period. Supplementation periods were followed by a 2.25 h cycling bout at close to 70%VO2max. The BEET supplement provided 212 mg of nitrates per day, 200 mg caffeine from green tea extract, 44 mg vitamin C from Camu Camu berry, B-vitamins from quinoa sprouts (40% Daily Value for thiamin, riboflavin, niacin, and vitamin B6), and 2.5 g of a mushroom blend containing Cordyceps sinensis and Inonotus obliquus. Six blood samples were collected before and after supplementation (overnight fasted state), immediately post-exercise, and at 1.5 h-, 3 h-, and 24 h-post-exercise.

Results

The 2.25 h cycling bout increased plasma levels of 41 of 67 oxylipins detected. BEET supplementation significantly increased plasma nitrate (NO3 -) and nitrite (NO2 -) (sum, NO3 - + NO2 -) concentrations (interaction effect, p < 0.001) and two anti-inflammatory oxylipins [18-hydroxyeicosapentaenoic acid (18-HEPE) and 4-hydroxy-docosahexanoic acid (4-HDoHE)]. The untargeted proteomics analysis identified 616 proteins (458 across all times points), and 2-way ANOVA revealed a cluster of 45 proteins that were decreased and a cluster of 21 that were increased in the BEET versus PL trials. Functional enrichment supported significant BEET-related reductions in inflammation-related proteins including several proteins related to complement activation, the acute phase response, and immune cell adhesion, migration, and differentiation.

Discussion

Intake of a BEET-based supplement during a 2-week period was linked to higher plasma levels of NO3 - + NO2 -, elevated post-exercise levels of two anti-inflammatory oxylipins, and a significant decrease in a cluster of proteins involved in complement activation and inflammation. These data support that 2-weeks intake of nitrate from a mixed beet-based supplement moderated protein biomarkers of exercise-induced inflammation in athletes.

Inorganic nitrate benefits contrast-induced nephropathy after coronary angiography for acute coronary syndromes: the NITRATE-CIN trial

BACKGROUND AND AIMS

Contrast-induced nephropathy (CIN), also known as contrast-associated acute kidney injury (CA-AKI) underlies a significant proportion of the morbidity and mortality following coronary angiographic procedures in high-risk patients and remains a significant unmet need. In pre-clinical studies inorganic nitrate, which is chemically reduced in vivo to nitric oxide, is renoprotective but this observation is yet to be translated clinically. In this study, the efficacy of inorganic nitrate in the prevention of CIN in high-risk patients presenting with acute coronary syndromes (ACS) is reported.

METHODS

NITRATE-CIN is a double-blind, randomized, single-centre, placebo-controlled trial assessing efficacy of inorganic nitrate in CIN prevention in at-risk patients presenting with ACS. Patients were randomized 1:1 to once daily potassium nitrate (12 mmol) or placebo (potassium chloride) capsules for 5 days. The primary endpoint was CIN (KDIGO criteria). Secondary outcomes included kidney function [estimated glomerular filtration rate (eGFR)] at 3 months, rates of procedural myocardial infarction, and major adverse cardiac events (MACE) at 12 months. This study is registered with ClinicalTrials.gov: NCT03627130.

RESULTS

Over 3 years, 640 patients were randomized with a median follow-up of 1.0 years, 319 received inorganic nitrate with 321 received placebo. The mean age of trial participants was 71.0 years, with 73.3% male and 75.2% Caucasian; 45.9% had diabetes, 56.0% had chronic kidney disease (eGFR <60 mL/min) and the mean Mehran score of the population was 10. Inorganic nitrate treatment significantly reduced CIN rates (9.1%) vs. placebo (30.5%, P < .001). This difference persisted after adjustment for baseline creatinine and diabetes status (odds ratio 0.21, 95% confidence interval 0.13-0.34). Secondary outcomes were improved with inorganic nitrate, with lower rates of procedural myocardial infarction (2.7% vs. 12.5%, P = .003), improved 3-month renal function (between-group change in eGFR 5.17, 95% CI 2.94-7.39) and reduced 1-year MACE (9.1% vs. 18.1%, P = .001) vs. placebo.

CONCLUSIONS

In patients at risk of renal injury undergoing coronary angiography for ACS, a short (5 day) course of once-daily inorganic nitrate reduced CIN, improved kidney outcomes at 3 months, and MACE events at 1 year compared to placebo.

Influence of acute dietary nitrate supplementation timing on nitrate metabolism, central and peripheral blood pressure and exercise tolerance in young men

PURPOSE

Dietary nitrate (NO3-) supplementation can lower systolic blood pressure (SBP) and improve exercise performance. Salivary flow rate (SFR) and pH are key determinants of oral NO3- reduction and purported to peak in the afternoon. We tested the hypotheses that NO3--rich beetroot juice (BR) would increase plasma [nitrite] ([NO2-]), lower SBP and improve exercise performance to a greater extent in the afternoon (AFT) compared to the morning (MORN) and evening (EVE).

METHOD

Twelve males completed six experimental visits in a repeated-measures, crossover design. NO3--depleted beetroot juice (PL) or BR (~ 13 mmol NO3-) were ingested in the MORN, AFT and EVE. SFR and pH, salivary and plasma [NO3-] and [NO2-], brachial SBP and central SBP were measured pre and post supplementation. A severe-intensity exercise tolerance test was completed to determine cycling time to exhaustion (TTE).

RESULTS

There were no between-condition differences in mean SFR or salivary pH. The elevation in plasma [NO2-] after BR ingestion was not different between BR-MORN, BR-AFT and BR-EVE. Brachial SBP was unchanged following BR supplementation in all conditions. Central SBP was reduced in BR-MORN (- 3 ± 4 mmHg), BR-AFT (- 4 ± 3 mmHg), and BR-EVE (- 2 ± 3 mmHg), with no differences between timepoints. TTE was not different between BR and PL at any timepoint.

CONCLUSION

Acute BR supplementation was ineffective at improving TTE and brachial SBP and similarly effective at increasing plasma [NO2-] and lowering central SBP across the day, which may have implications for informing NO3- supplementation strategies.

Integrated molybdenum single atom array sensors with multichannels for nitrite detection in foods

Nitrite (NO2-) is present in a variety of foods, but the excessive intake of NO2- can indirectly lead to carcinogenic, teratogenic, mutagenicity and other risks to the human body. Therefore, the detection of NO2- is crucial for maintaining human health. In this study, an integrated array sensor for NO2- detection is developed based on molybdenum single atom material (IMSMo-SAC) using high-resolution electrohydrodynamic (EHD) printing technology. The sensor comprises three components: a printed electrode array, multichannels designed on polydimethylsiloxane (PDMS) and an electronic signal process device with bluetooth. By utilizing Mo-SAC to facilitate electron transfer during the redox reaction, rapid and efficient detection of NO2- can be achieved. The sensor has a wide linear range of 0.1 μM-107.8 mM, a low detection limit of 33 nM and a high sensitivity of 0.637 mA-1mM-1 cm-2. Furthermore, employing this portable array sensor allows simultaneously measurements of NO2- concentrations in six different foods samples with acceptable recovery rates. This array sensor holds great potential for detecting of small molecules in various fields.

Dietary nitrate intake and net nitrite-generating capacity of the oral microbiome interact to enhance cardiometabolic health: Results from the Oral Infections Glucose Intolerance and Insulin Resistance Study (ORIGINS)

Background

We investigated the association between dietary nitrate intake and early clinical cardiometabolic risk biomarkers, and explored whether the oral microbiome modifies the association between dietary nitrate intake and cardiometabolic biomarkers.

Methods

Cross-sectional data from 668 (mean [SD] age 31 [9] years, 73% women) participants was analyzed. Dietary nitrate intakes and alternative healthy eating index (AHEI) scores were calculated from food frequency questionnaire responses and a validated US food database. Subgingival 16S rRNA microbial genes (Illumina, MiSeq) were sequenced, and PICRUSt2 estimated metagenomic content. The Microbiome Induced Nitric oxide Enrichment Score (MINES) was calculated as a microbial gene abundance ratio representing enhanced net capacity for NO generation. Cardiometabolic risk biomarkers included systolic and diastolic blood pressure, HbA1c, glucose, insulin, and insulin resistance (HOMA-IR), and were regressed on nitrate intake tertiles in adjusted multivariable linear models.

Results

Mean nitrate intake was 190[171] mg/day. Higher nitrate intake was associated with lower insulin, and HOMA-IR but particularly among participants with low abundance of oral nitrite enriching bacteria. For example, among participants with a low MINES, mean insulin[95%CI] levels in high vs. low dietary nitrate consumers were 5.8[5.3,6.5] vs. 6.8[6.2,7.5] (p=0.004) while respective insulin levels were 6.0[5.4,6.6] vs. 5.9[5.3,6.5] (p=0.76) among partcipants with high MINES (interaction p=0.02).

Conclusion

Higher dietary nitrate intake was only associated with lower insulin and insulin resistance among individuals with reduced capacity for oral microbe-induced nitrite enrichment. These findings have implications for future precision medicine-oriented approaches that might consider assessing the oral microbiome prior to enrollment into dietary interventions or making dietary recommendations.

Oral nitrate-reducing bacteria as potential probiotics for blood pressure homeostasis

Hypertension is a leading cause of morbidity and mortality worldwide and poses a major risk factor for cardiovascular diseases and chronic kidney disease. Research has shown that nitric oxide (NO) is a vasodilator that regulates vascular tension and the decrease of NO bioactivity is considered one of the potential pathogenesis of essential hypertension. The L-arginine-nitric oxide synthase (NOS) pathway is the main source of endogenous NO production. However, with aging or the onset of diseases, the function of the NOS system becomes impaired, leading to insufficient NO production. The nitrate-nitrite-NO pathway allows for the generation of biologically active NO independent of the NOS system, by utilizing endogenous or dietary inorganic nitrate and nitrite through a series of reduction cycles. The oral cavity serves as an important interface between the body and the environment, and dysbiosis or disruption of the oral microbiota has negative effects on blood pressure regulation. In this review, we explore the role of oral microbiota in maintaining blood pressure homeostasis, particularly the connection between nitrate-reducing bacteria and the bioavailability of NO in the bloodstream and blood pressure changes. This review aims to elucidate the potential mechanisms by which oral nitrate-reducing bacteria contribute to blood pressure homeostasis and to highlight the use of oral nitrate-reducing bacteria as probiotics for oral microbiota intervention to prevent hypertension.

Use of Genomics to Develop Novel Therapeutics and Personalize Hypertension Therapy

Hypertension is a prevalent public health problem, contributing to >10 million deaths annually. Though multiple therapeutics exist, many patients suffer from treatment-resistant hypertension or try several medications before achieving blood pressure control. Genomic advances offer mechanistic understanding of blood pressure variability, therapeutic targets, therapeutic response, and promise a stratified approach to treatment of primary hypertension. Cyclic guanosine monophosphate augmentation, aldosterone synthase inhibitors, and angiotensinogen blockade with silencing RNA and antisense therapies are among the promising novel approaches. Pharmacogenomic studies have also been done to explore the genetic bases underpinning interindividual variability in response to existing therapeutics. A polygenic approach using risk scores is likely to be the next frontier in stratifying responses to existing therapeutics.

Diphenyl Diselenide Through Reduction of Inflammation, Oxidative Injury and Caspase-3 Activation Abates Doxorubicin-Induced Neurotoxicity in Rats

Neurotoxicity associated with chemotherapy is a debilitating side effect of cancer management in humans which reportedly involves inflammatory and oxidative stress responses. Diphenyl diselenide (DPDS) is an organoselenium compound which exhibits its anti-tumoral, anti-oxidant, anti-inflammatory and anti-mutagenic effects. Nevertheless, its possible effect on chemotherapy-induced neurotoxicity is not known. Using rat model, we probed the behavioral and biochemical effects accompanying administration of antineoplastic agent doxorubicin (7.5 mg/kg) and DPDS (5 and 10 mg/kg). Anxiogenic-like behavior, motor and locomotor insufficiencies associated with doxorubicin were considerably abated by both DPDS doses with concomitant enhancement in exploratory behavior as demonstrated by reduced heat maps intensity and enhanced track plot densities. Moreover, with exception of cerebral glutathione (GSH) level, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, biochemical data demonstrated reversal of doxorubicin-mediated decline in cerebral and cerebellar antioxidant status indices and the increase in acetylcholinesterase (AChE) activity by both doses of DPDS. Also, cerebellar and cerebral lipid peroxidation, hydrogen peroxide as well as reactive oxygen and nitrogen species levels were considerably diminished in rats administered doxorubicin and DPDS. In addition, DPDS administration abated myeloperoxidase activity, tumour necrosis factor alpha and nitric oxide levels along with caspase-3 activity in doxorubicin-administered rats. Chemoprotection of doxorubicin-associated neurotoxicity by DPDS was further validated by histomorphometry and histochemical staining. Taken together, DPDS through offsetting of oxido-inflammatory stress and caspase-3 activation elicited neuroprotection in doxorubicin-treated rats.

Effect of long-term inorganic nitrate administration on myocardial ischemia-reperfusion injury in ovariectomized rats

Introduction: Menopause is associated with reduced nitric oxide (NO) bioavailability and lower tolerance against myocardial ischemia-reperfusion (IR) injury. This study investigated whether long-term nitrate administration provides resistance against myocardial IR injury in ovariectomized (OVX) rats. Method: After ovariectomy, female rats were assigned to the OVX and the OVX + nitrate groups (n = 14/group); the latter group consumed nitrate (100 mg/L) for 9 months. At month 9, each group was divided into two subgroups (n = 7/subgroup), of which one subgroup was exposed to myocardial IR (IR+ hearts) and the other was not exposed (IR- hearts). The hearts of rats were isolated, and NO metabolite (NOx), oxidative stress indices, and mRNA expressions of endothelial (eNOS), inducible (iNOS), and neuronal (nNOS) NO synthases, as well as markers of apoptosis, were measured in the IR- and IR+ hearts. In the IR+ hearts, cardiac function indices (CFI) and the infarct size were also measured. Results: Nitrate increased catalase activity (97%) and eNOS expression (2.94-fold) in the IR- hearts. In the IR+ hearts, nitrate reduced left ventricular (LV) end-diastolic pressure (11.6%) and infarct size (26.2%) and increased recovery of LV developed pressure (44.0%) and peak rate of positive (28.9%) and negative (15.4%) changes in LV pressure. In addition, in the IR+ hearts, nitrate increased eNOS and B-cell lymphoma-2 (Bcl-2) as well as decreased iNOS, Bcl-2 associated X protein (Bax), caspase-3, caspase-8, caspase-9, and tumor necrosis factor-α (TNF-α) expression. Nitrate increased total antioxidant capacity (TAC) and catalase (CAT) activity and decreased malondialdehyde (MDA) levels at month nine in serum and IR+ hearts. Conclusion: The favorable effects of nitrate against IR injury were associated with higher eNOS and Bcl-2 expression, CAT activity, TAC, and lower iNOS, Bax, caspase-3, caspase-8, caspase-9 and TNF-α expression, and MDA in the heart tissue. Nitrate preconditioning alleviated IR-induced myocardial injury in OVX rats; this effect was associated with eNOS upregulation before IR and the blunting of OVX-induced eNOS downregulation, iNOS upregulation, apoptosis, and oxidative stress in heart tissue after IR.

Nitrite Attenuates the In Vitro Inflammatory Response of Immune Cells to the SARS-CoV-2 S Protein without Interfering in the Antioxidant Enzyme Activation

SARS-CoV-2 induces a hyperinflammatory reaction due to the excessive release of cytokines during the immune response. The bacterial endotoxin lipopolysaccharide (LPS) contributes to the low-grade inflammation associated with the metabolic syndrome, enhancing the hyperinflammatory reaction induced by the SARS-CoV-2 infection. The intake of sodium nitrate, a precursor of nitrite and nitric oxide, influences the antioxidant and pro-inflammatory gene expression profile after immune stimulation with LPS in peripheral blood mononuclear cells from metabolic syndrome patients. We aimed to assess the inflammatory and antioxidant responses of immune cells from metabolic syndrome patients to exposure to the SARS-CoV-2 spike protein (S protein) together with LPS and the effect of nitrite in these responses. Whole blood samples obtained from six metabolic syndrome patients were cultured for 16 h at 37 °C with four different media: control medium, control medium plus LPS (100 ng/mL), control medium plus LPS (100 ng/mL) plus S protein (10 ng/mL), and control medium plus LPS (100 ng/mL) plus S protein (10 ng/mL) plus nitrite (5 µM). Immune stimulation with the LPS/S protein enhanced nitrate biosynthesis from nitrite oxidation and probably from additional organic precursors. In vitro incubations with the LPS/S protein enhanced the expression and/or release of pro-inflammatory TNFα, IL-6, IL-1β, and TLR4, as well as the expression of the anti-inflammatory IL-1ra and IL-10 and antioxidant enzymes. Nitrite attenuated the pro- and anti-inflammatory response induced by the S protein without interfering with the activation of TLR4 and antioxidant enzyme expression, raising the possibility that nitrite could have potential as a coadjutant in the treatment of COVID-19.

Mechanisms of Nitrosamine Mutagenicity and Their Relationship to Rodent Carcinogenic Potency

A thorough literature review was undertaken to understand how the pathways of N-nitrosamine transformation relate to mutagenic potential and carcinogenic potency in rodents. Empirical and computational evidence indicates that a common radical intermediate is created by CYP-mediated hydrogen abstraction at the α-carbon; it is responsible for both activation, leading to the formation of DNA-reactive diazonium species, and deactivation by denitrosation. There are competing sites of CYP metabolism (e.g., β-carbon), and other reactive species can form following initial bioactivation, although these alternative pathways tend to decrease rather than enhance carcinogenic potency. The activation pathway, oxidative dealkylation, is a common reaction in drug metabolism and evidence indicates that the carbonyl byproduct, e.g., formaldehyde, does not contribute to the toxic properties of N-nitrosamines. Nitric oxide (NO), a side product of denitrosation, can similarly be discounted as an enhancer of N-nitrosamine toxicity based on carcinogenicity data for substances that act as NO-donors. However, not all N-nitrosamines are potent rodent carcinogens. In a significant number of cases, there is a potency overlap with non-N-nitrosamine carcinogens that are not in the Cohort of Concern (CoC; high-potency rodent carcinogens comprising aflatoxin-like-, N-nitroso-, and alkyl-azoxy compounds), while other N-nitrosamines are devoid of carcinogenic potential. In this context, mutagenicity is a useful surrogate for carcinogenicity, as proposed in the ICH M7 (R2) (2023) guidance. Thus, in the safety assessment and control of N-nitrosamines in medicines, it is important to understand those complementary attributes of mechanisms of mutagenicity and structure-activity relationships that translate to elevated potency versus those which are associated with a reduction in, or absence of, carcinogenic potency.

The role of gut microbiota in intestinal disease: from an oxidative stress perspective

Recent studies have indicated that gut microbiota-mediated oxidative stress is significantly associated with intestinal diseases such as colorectal cancer, ulcerative colitis, and Crohn's disease. The level of reactive oxygen species (ROS) has been reported to increase when the gut microbiota is dysregulated, especially when several gut bacterial metabolites are present. Although healthy gut microbiota plays a vital role in defending against excessive oxidative stress, intestinal disease is significantly influenced by excessive ROS, and this process is controlled by gut microbiota-mediated immunological responses, DNA damage, and intestinal inflammation. In this review, we discuss the relationship between gut microbiota and intestinal disease from an oxidative stress perspective. In addition, we also provide a summary of the most recent therapeutic approaches for preventing or treating intestinal diseases by modifying gut microbiota.

A metabolic perspective on nitric oxide function in melanoma

Nitric oxide (NO) generated from nitric oxide synthase (NOS) exerts a dichotomous effect in melanoma, suppressing or promoting tumor progression. This dichotomy is thought to depend on the intracellular NO concentration and the cell type in which it is generated. Due to its central role in the metabolism of multiple critical constituents involved in signaling and stress, it is crucial to explore NO's contribution to the metabolic dysfunction of melanoma. This review will discuss many known metabolites linked to NO production in melanoma. We discuss the synthesis of these metabolites, their role in biochemical pathways, and how they alter the biological processes observed in the melanoma tumor microenvironment. The metabolic pathways altered by NO and the corresponding metabolites reinforce its dual role in melanoma and support investigating this effect for potential avenues of therapeutic intervention.

Dietary Nitrate from Plant Foods: A Conditionally Essential Nutrient for Cardiovascular Health

Under specific conditions, such as catabolic stress or systemic inflammation, endogenous nutrient production becomes insufficient and exogenous supplementation (for example, through dietary intake) is required. Herein, we propose consideration of a dietary nitrate from plant foods as a conditionally essential nutrient for cardiovascular health based on its role in nitric oxide homeostasis. Nitrate derived from plant foods may function as a conditionally essential nutrient, whereas nitrate obtained from other dietary sources, such as drinking water and cured/processed meats, warrants separate consideration because of the associated health risks. We have surveyed the literature and summarized epidemiological evidence regarding the effect of dietary nitrate on cardiovascular disease and risk factors. Meta-analyses and population-based observational studies have consistently demonstrated an inverse association of dietary nitrate with blood pressure and cardiovascular disease outcomes. Considering the available evidence, we suggest 2 different approaches to providing dietary guidance on nitrate from plant-based dietary sources as a nutrient: the Dietary Reference Intakes developed by the National Academies of Sciences, Engineering, and Medicine, and the dietary guidelines evaluated by the Academy of Nutrition and Dietetics. Ultimately, this proposal underscores the need for food-based dietary guidelines to capture the complex and context-dependent relationships between nutrients, particularly dietary nitrate, and health.

Astrocytes produce nitric oxide via nitrite reduction in mitochondria to regulate cerebral blood flow during brain hypoxia

During hypoxia, increases in cerebral blood flow maintain brain oxygen delivery. Here, we describe a mechanism of brain oxygen sensing that mediates the dilation of intraparenchymal cerebral blood vessels in response to reductions in oxygen supply. In vitro and in vivo experiments conducted in rodent models show that during hypoxia, cortical astrocytes produce the potent vasodilator nitric oxide (NO) via nitrite reduction in mitochondria. Inhibition of mitochondrial respiration mimics, but also occludes, the effect of hypoxia on NO production in astrocytes. Astrocytes display high expression of the molybdenum-cofactor-containing mitochondrial enzyme sulfite oxidase, which can catalyze nitrite reduction in hypoxia. Replacement of molybdenum with tungsten or knockdown of sulfite oxidase expression in astrocytes blocks hypoxia-induced NO production by these glial cells and reduces the cerebrovascular response to hypoxia. These data identify astrocyte mitochondria as brain oxygen sensors that regulate cerebral blood flow during hypoxia via release of nitric oxide.

"NO" Time in Fear Response: Possible Implication of Nitric-Oxide-Related Mechanisms in PTSD

Post-traumatic stress disorder (PTSD) is a psychiatric condition characterized by persistent fear responses and altered neurotransmitter functioning due to traumatic experiences. Stress predominantly affects glutamate, a neurotransmitter crucial for synaptic plasticity and memory formation. Activation of the N-Methyl-D-Aspartate glutamate receptors (NMDAR) can trigger the formation of a complex comprising postsynaptic density protein-95 (PSD95), the neuronal nitric oxide synthase (nNOS), and its adaptor protein (NOS1AP). This complex is pivotal in activating nNOS and nitric oxide (NO) production, which, in turn, activates downstream pathways that modulate neuronal signaling, including synaptic plasticity/transmission, inflammation, and cell death. The involvement of nNOS and NOS1AP in the susceptibility of PTSD and its comorbidities has been widely shown. Therefore, understanding the interplay between stress, fear, and NO is essential for comprehending the maintenance and progression of PTSD, since NO is involved in fear acquisition and extinction processes. Moreover, NO induces post-translational modifications (PTMs), including S-nitrosylation and nitration, which alter protein function and structure for intracellular signaling. Although evidence suggests that NO influences synaptic plasticity and memory processing, the specific role of PTMs in the pathophysiology of PTSD remains unclear. This review highlights pathways modulated by NO that could be relevant to stress and PTSD.