Salivary nitrate (NO3[-]) and nitrite (NO2[-]) are key components of the entero-salivary nitrate-nitrite-nitric oxide pathway and have been associated with cardiovascular, metabolic, and oral health. A reliable method that is reproducible in clinical environments (and potentially suitable for self-use) would democratize monitoring of nitric oxide-related pathways. However, despite advances in this field, commercially available test strips are not widely accessible. This study aimed to evaluate the feasibility of adapting colorimetric reagent strips originally developed for water analysis to assess NO3[-] and NO2[-] concentrations in human saliva. Artificial saliva containing sodium nitrate and sodium nitrite was used for standardization. Measurements obtained with the adapted strips were compared with a spectrophotometric reference method and with nitric oxide-specific salivary test strips in samples from systemically healthy donors. Agreement and reproducibility were assessed using intraclass correlation coefficients (ICC) and Bland-Altman analysis, while associations were evaluated using Spearman's correlation. The adapted strips demonstrated high agreement and strong correlation with the reference method for nitrate (ICC = 0.926; rho = 0.868; p = 0.001) and good performance for nitrite (ICC = 0.886; rho = 0.814; p = 0.004), with minimal mean bias in Bland-Altman analysis. Inter-rater reliability was moderate. Positive correlations were observed between salivary NO3[-] and blood pressure, with weaker associations for NO2[-]. Overall, the findings support the initial feasibility of adapting commercially available reagent strips for salivary NO3[-] and NO2[-] assessment, particularly for nitrate, offering a practical and low-cost alternative for clinical and research applications.

This study aimed to characterize the temporal responses of plasma and urinary nitrate (NO3[-]) and nitrite (NO2[-]) during acute ingestion and 14 days of beetroot powder supplementation, and to compare exercise performance and physiological responses under normoxia and normobaric hypoxia before and after supplementation. Twenty-four healthy male university students consumed 40 g of beetroot powder (approximately 11.2 mmol NO3[-]) once daily for 14 doses. Plasma and urine were sampled at multiple time points over 24 h after the first dose and in the fasting state on the mornings after the 7th and 14th doses (Days 8 and 15). NO3[-] and NO2[-] were quantified by UPLC-MS/MS, and urinary measures were normalized to urinary creatinine. Participants completed incremental cycling tests under normoxia and normobaric hypoxia (FiO2= 13.5%) before and after supplementation; countermovement jump performance was assessed only under normoxia. Plasma NO3[-] and urinary NO3[-]/Cr showed significant time effects (both P < 0.001), reaching their highest observed levels at 1 and 2 h, respectively, and remaining above baseline at 24 h and on the mornings after the 7th and 14th doses. Plasma NO2[-] did not change significantly over time (P = 0.444). Urinary NO2[-] was summarized as the proportion of quantifiable samples because some results were below the lower limit of quantification. After 14 days of supplementation, time to exhaustion increased under both normoxic and normobaric hypoxic conditions (P = 0.018 and P = 0.014, respectively), with moderate effect sizes; countermovement jump performance, maximal heart rate, and most cardiovascular measures did not change significantly. Beetroot powder elicited clear temporal responses in plasma and urinary NO3[-], whereas NO2[-] responses were inconsistent. After 14 days of supplementation, incremental exercise tolerance improved under both normoxic and normobaric hypoxic conditions, whereas countermovement jump performance and most cardiovascular measures did not change significantly. Given the single-group pre-post design, these findings require confirmation in randomized, placebo-controlled studies.

The global spread of antimicrobial-resistant bacteria has emerged as one of the most pressing public health challenges worldwide. Because the development of novel antibiotics remains slow and increasingly difficult, innovative therapeutic strategies are urgently needed. Supersulfides, including persulfides and polysulfides, are ubiquitous sulfur species found in both prokaryotes and eukaryotes. Owing to their exceptional nucleophilicity and antioxidant capacity, they play central roles in cellular redox signaling and stress adaptation. Recent studies have further revealed that bacterial supersulfides contribute to antibiotic resistance through multiple mechanisms, including the direct chemical inactivation of β-lactam antibiotics, activation of multidrug efflux pumps, and detoxification of reactive oxygen species generated during antibiotic treatment. These findings identify bacterial supersulfide biosynthetic pathways as promising targets for the development of next-generation antimicrobial therapies. In this Review, we summarize current knowledge of supersulfide biosynthesis, with particular emphasis on recently identified pathways unique to bacteria. We also discuss the diverse mechanisms by which bacterial supersulfides promote antibiotic resistance and highlight recent advances in pharmacological strategies targeting supersulfide biosynthesis. Finally, we discuss the translational potential of targeting bacterial supersulfide metabolism and the key challenges that must be overcome for clinical application.

Hydrogen sulfide (H2S) is a signaling molecule that affects multiple (patho)physiological pathways. Deficiency of H2S due to cystathionine γ-lyase (CSE) deletion has been proven to accelerate atherosclerotic plaque formation. However, the role of 3-mercaptopyruvate sulfurtransferase (MPST), a related H2S-producing enzyme that impacts metabolism, has not been studied in atherogenic dyslipidemia. We generated a double Apoe/Mpst knockout mouse (Apoe[-/-]Mpst[-/-]) in the C57BL/6 background. C57Bl/6, Mpst[-/-], Apoe[-/-] and Apoe[-/-]Mpst[-/-]mice were fed a western diet for 14 weeks, after which blood and tissues (aorta and liver) were collected; the circulating lipid profile, atherosclerotic plaque formation and expression of enzymes involved in lipid biosynthetic pathways in the liver were evaluated in the four mouse lines. H2S production was reduced in the liver of double knockout mice, while the expression of CBS and CSE was not altered. In the serum of Apoe[-/-]Mpst[-/-], we observed decreased levels of total cholesterol, low-density lipoproteins (LDL) and triglycerides (TGs) compared to Apoe[-/-]; hepatic apolipoprotein B (ApoB) levels were also downregulated. However, the expression of other key enzymes that participate in cholesterol and fatty acid synthesis remained unchanged. In addition, hepatic lipid deposition was not significantly altered among genotypes. In line with the reduced circulating LDL and TGs levels, atherosclerotic lesions were found to be reduced in the aorta of Apoe[-/-]Mpst[-/-]. Our results indicate that MPST deletion in the Apoe[-/-] dyslipidemia model leads to decreased circulating lipid levels and atherosclerosis, that correlate with a downregulation of hepatic ApoB expression.

Although nitric oxide synthase (NOS) proteins homologous to mammalian NOS are absent in terrestrial plants (embryophytes), they are present in various algal groups. Of the 367 algal species for which genome data is available on the NCBI database, 40 proteins belonging to 36 species in various algal classes have been identified. The sporadic distribution of NOS orthologues across the algae phylogenetic tree raises the question of why this enzyme is absent in most species. Genome and recent transcriptome sequencing in Klebsormidiophyceae provided an opportunity to study the evolution of NOS sequences in closely related organisms. Based on a dataset comprising 18 species, including 13 Klebsormidium species, we showed that only eight species possess complete or partial NOS sequences. Both in silico and experimental approaches suggest that the divergence observed in Klebsormidiophyceae NOS genes, compared to their human homologs, reflect specific modifications, including putative pseudogenization. Indeed, although copies of genes encoding NOS are expressed in certain species of algae, some are evolving into non-functional copies through the accumulation of mutations, which could affect the synthesis of a functional protein. This process may be considered relatively recent in Charophytes history since the presence or absence of a gene can be observed in very closely related species.

Nitric oxide (NO) gas continues to be a widely studied and versatile treatment given its broad spectrum of physiological effects such as pulmonary vasodilation, improvement of oxygenation, anti-inflammatory, and antimicrobial effects. The idea of administering a pulsed dose of inhaled NO (PiNO) at the beginning of inhalation was developed in the last 20 years as an alternative to continuous inhalation of NO (CiNO) through the respiratory cycle. Across multiple studies, PiNO has repeatedly demonstrated similarly efficacious pulmonary vasodilation and oxygenation improvement as CiNO administration while consistently reducing total NO exposure and nitrogen dioxide (NO2) formation. PiNO has proven to be an effective adjunctive treatment for patients with primary pulmonary hypertension among spontaneously breathing patients. In patients with chronic obstructive pulmonary disease (COPD), PiNO reduced pulmonary vascular resistance (PVR) in the short term, though further research remains necessary to demonstrate long-term benefits. Similarly, PiNO use in patients with interstitial lung disease has been associated with subjective improvements in exercise tolerance and quality of life. The effect of PiNO on PVR was also confirmed in mechanically ventilated subjects. In this setting, PiNO reduced anesthesia-associated hypoxemia and improved shunt fraction and oxygenation. Overall, the scientific body of evidence surrounding PiNO supports it as a safe, effective, and efficient alternative to CiNO delivery that can be utilized in a wide range of clinical settings. Future research may continue to expand the application of PiNO to different clinical settings.

Nitric oxide (•NO) is a central regulator of plant development and stress responses, but recent evidence shows that reactive nitrogen signaling involves more than •NO alone. Nitroxyl (HNO), the one-electron-reduced and protonated form of •NO, has emerged as a distinct signaling molecule in plants with unique chemical and functional properties. Unlike •NO, HNO is a non-radical, thiophilic species that acts as a selective redox modulator rather than a freely diffusible messenger. Improved detection methods have confirmed endogenous HNO formation in plant cells, with basal nanomolar concentrations under optimal conditions and reversible changes during key developmental stages and stress responses, such as senescence and hypoxia. HNO production and stability are closely regulated by intracellular redox status and interconvert dynamically with •NO through non-enzymatic reactions involving cellular reductants such as ascorbate, hydrogen sulfide, and low-molecular-weight thiols. This interplay establishes the •NO/HNO balance as a redox-sensitive signaling switch, increasing the informational capacity of reactive nitrogen networks. Functional and transcriptomic studies indicate that HNO participates in hormone signaling, especially in ethylene-mediated pathways, and supports plant adaptation to redox-related stresses. This review summarizes current knowledge of HNO chemistry, regulation, detection, and function in plants, and identifies key open questions. Including HNO in plant signaling frameworks provides a more nuanced and comprehensive view of redox-regulated plant physiology.

Reactive nitrogen species (RNS) are signalling molecules triggering several defence responses during plant stress. The highest importance has nitric oxide (NO), involved in the post-translational modifications, including protein S-nitrosation of target cysteine residues. Aminoaldehyde dehydrogenases (AMADHs) catalyze the NAD(P)[+]-dependent oxidation of various ω-amino aldehydes to the corresponding amino acids. Here, we focused on the dynamic redox regulation of AMADH activity in pea (Pisum sativum). We used the reversible S-nitrosation approach and studied the effect of NO donors on the activity of two AMADHs. LC-MS/MS analysis combined with structural mapping revealed selective modification of spatially accessible cysteine residues, whereas the catalytic Cys294 was detected predominantly in the methylthionylated form, consistent with its largely reduced state under the applied experimental conditions. These findings suggest that S-nitrosation modulates PsAMADH activity in a structurally constrained manner without directly disrupting the catalytic core. Inhibition of AMADH activity in roots of different pea genotypes was accompanied by increased RNS/NO accumulation, suggesting that nitrosative modulation of PsAMADH activity represents an important component of redox regulation in vivo.

Pulmonary function tests are performed throughout the day, yet time-of-day effects on spirometry and pulmonary diffusing capacities for nitric oxide (DLNO) and carbon monoxide (DLCO) are poorly characterized, and DLNO's diurnal behavior is unknown. We examined whether these measurements vary in healthy men and derived within-day limits of change. Thirty-eight men (median age, 29.8 years) underwent up to six testing sessions during one waking day. Each session included spirometry (FVC, FEV1, SVC, and FEV1/FVC), followed by single-breath DLNO/DLCO testing to obtain DLCO, DLNO, alveolar volume (VA), transfer coefficients KCO and KNO, and the DLNO/DLCO ratio. Time-of-day effects were assessed using linear mixed-effects models with subject-specific random intercepts; within-subject variability was quantified using the within-subject standard deviation. After quality filtering and multiplicity adjustment, FVC, FEV1, SVC, DLNO, DLCO, and VA decreased across the day (q ≤ 0.014). KCO declined before but not after false-discovery-rate adjustment (p = 0.041, q = 0.058); FEV1/FVC, KNO, and DLNO/DLCO did not change significantly. Within-day variability ranged from 1.5% for SVC to 3.5% for DLCO. One-sided 95% within-day change limits were approximately 11 mL/min/mmHg for DLNO (z-score, 0.59), 2.8 mL/min/mmHg for DLCO (z-score, 0.59), 0.28 L for VA (z-score, 0.35), and 0.27 for DLNO/DLCO. Spirometric volumes and absolute diffusing capacities declined from morning to evening, consistent with decreasing VA, whereas ratio and transfer-coefficient indices were largely stable. Serial measurements should be performed at consistent times. These limits reflect measurement error plus short-term physiological or procedural variation and are specific to this device, protocol, and population.

The activity of S-nitrosoglutathione reductase (ADH5/GSNOR) has been proposed being essential to limit oxidative stress and preserve mitochondrial quality control. Here we identify a redox-dependent ATM-CHK2-SOD1 signaling axis that drives ADH5/GSNOR transcription in SH-SY5Y cells expressing the ALS-associated SOD1[G93A] mutant. ATM-CHK2 activation promotes the interaction of SOD1 with CHK2, leading to SOD1 nuclear translocation and binding to the ADH5 promoter. Pharmacological inhibition of ATM or CHK2 abolishes these effects. ADH5/GSNOR overexpression protects cells from SOD1[G93A]-induced toxicity suggesting that the modulation of GSNOR activity may represent a potential strategy to restore redox homeostasis in ALS.