Search Results (119)

Nitrite pollution in aquatic environments, often driven by human activity, can disrupt fish physiology. Nitrite is absorbed by freshwater fish through their gills, leading to internal accumulation and interference with nitric oxide (NO) signaling, redox state, and the oxygen-carrying capacity of blood. The effects of nitrite are concentration-dependent. Although moderate environmental nitrite levels have little impact on oxygen transport, they may still interfere with NO homeostasis and cellular metabolism. We report the effects of 72 h of exposure to 10 μM nitrite on adult zebrafish blood’s O₂-carrying capacity and on muscle mitochondrial activity, metabolism, and redox state. The results show that this environmentally relevant but moderate concentration of nitrite leads to decreases in fish routine oxygen consumption (rMO₂) and spontaneous activity, an increase in blood nitrosyl hemoglobin (HbNO), indicating increased NO production in the blood, accumulation of nitrite in muscle tissue, oxidative stress, and changes in muscle aerobic capacity linked to a rise in mitochondrial efficiency. Parallel to these effects, increases in antioxidant capacity, arginase activity, and urea and lactate levels were observed. Globally, these results are consistent with altered NO homeostasis in the fish body induced by nitrite stress. Full article

Carbon dioxide capture and storage (CCS) is a technology that can be used to reduce carbon dioxide (CO₂) emissions generated by both natural and anthropogenic industrial processes, particularly petroleum production. To mimic and investigate the effects of CO₂ leakage that may result from CCS, the acute toxicity of seawater acidification induced by continuous CO₂ injection was studied in Asian seabass (Lates calcarifer) fry under static bioassay conditions. Fry (0.828 ± 0.22 g) were exposed to seawater with different pH levels (5.5, 6.0, 6.5, 7.5, and 8.3). Rapid and 100% mortality within 15 min was observed in the pH 5.5 exposure group, while mortality rates ranging from 10.00–41.67% were recorded at 6–96 h in the pH 6.0 exposure group; no mortality was noted in the other pH exposure groups. According to these mortality data, the median lethal concentration at 96 h (96 h LC₅₀) was determined to be a pH of 5.884. Interestingly, after exposure to seawater with pH levels of 5.5 and 6.0, histopathological alterations in the skin, gills, trunk kidney and liver were evident. Additionally, some water quality parameters, especially dissolved oxygen (DO) levels, alkalinity, ammonia levels, and nitrite levels, vary depending on the pH. To further investigate the effects of seawater with pH levels of 8.3 and 5.884 (96 h LC₅₀) and 6.5 (10% safety level) on health status, immune responses and disease susceptibility, fingerling fish (21.25 ± 3.89 g) were studied. Unexpectedly, fish exposed to seawater with a pH of 5.884 rapidly lost muscle control and gradually died, reaching 100% mortality within 24 h, and all response analyses were aborted. Interestingly, with the exception of hematocrit and some immune parameters, various serum innate immune indices, blood biochemistry parameters and immune-related gene expression patterns were similar in fish exposed to seawater with pH levels of 8.3 and 6.5. Additionally, fish were challenged with 0 (control), 1 × 10⁷ and 1 × 10⁹ CFU/mL Vibrio vulnificus, and fish in seawater with a pH level of 6.5 showed a higher sensitivity to 1 × 10⁹ CFU/mL Vibrio vulnificus than fish in seawater with a pH level of 8.3, with mortality rates of 71.24% and 25.44%, respectively (p < 0.05). These findings enhance the understanding of the toxicity effects of seawater acidification caused by CO₂, which will be useful for further assessing the site-specific effects of CCS projects. Full article

Copper (Cu) pollution poses environmental and health risks. Owing to its adaptability and potential for water purification, Nymphoides peltata (N. peltata) is being considered for use in the remediation of Cu pollution. However, the feasibility of using N. peltata for the remediation of Cu-polluted water bodies has not yet been assessed. Here, the physiological response of N. peltata to Cu stress was determined. N. peltata samples were exposed to varying Cu concentrations (0.2, 0.4, 0.6 and 0.8 mg∙L⁻¹), and the activities of glutamine synthetase (GS), nitrate reductase (NR), nitrite reductase (NiR), ribulose-1,5-diphosphate carboxylase (Rubisco), and glycolate oxidase (GO) were measured together with the concentrations of photosynthetic pigments. The results revealed that under Cu stress, NR and GS activities significantly decreased, while NiR activity significantly increased. Exposure to 0.2 mg∙L⁻¹ Cu promoted chlorophyll synthesis and enhanced Rubisco and GO activities; in contrast, exposure to Cu concentrations above 0.4 mg∙L⁻¹ significantly inhibited the aforementioned parameters. These findings indicate that Cu stress, regardless of concentration, significantly affects nitrogen metabolism in N. peltata by decelerating nitrate reduction and impairing the ammonification process. Meanwhile, only high Cu concentrations significantly affected photosynthesis. N. peltata can survive low Cu stress by regulating its photosynthetic enzymes. Therefore, N. peltata has potential for the ecological restoration of water bodies polluted with low Cu concentrations. Full article

It has been demonstrated that prolonged exposure to stress engenders a plethora of neuropsychiatric, immune and metabolic disorders. However, its pathophysiology transcends the conventional hypothalamic–pituitary–adrenal (HPA) axis. This review addresses the central question of how integrated neural and microbial pathways regulate stress responses and resilience. We present a model in which the parasympathetic nervous system (particularly the vagus nerve) and the gut microbiota interact to form a bidirectional neuroimmune network that modulates the HPA axis, immune function, neurotransmitter balance, and metabolic adaptation. Key molecular pathways include nitric oxide synthesis via the classical nitric oxide synthase (NOS)-dependent and microbiota-mediated nitrate–nitrite routes, inducible nitric oxide synthase (iNOS) regulation, nuclear factor erythroid 2-related factor 2 (Nrf2) signalling, lysosomal function, autophagy and the cholinergic anti-inflammatory reflex. Other pathways include the gamma-aminobutyric acid (GABA) and serotonin (5-HT) systems, NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signalling, polyamine metabolism and peroxisome proliferator-activated receptor gamma (PPARγ). Intermittent hypoxia training (IHT) enhances mitochondrial function, oxidative stress responses, autonomic balance and gut microbiota composition. This promotes parasympathetic activity and stress resilience that is tailored to the individual. These adaptations support the concept of personalised stress response profiles based on hypoxic adaptability. Clinical implications include combining IHT with vagus nerve stimulation, probiotics, dietary strategies, and stress reduction techniques. Monitoring vagal tone and microbiota composition could also serve as predictive biomarkers for personalised interventions in stress-related disorders. This integrative framework highlights the therapeutic potential of targeting the parasympathetic system and the gut microbiota to modulate stress. Full article

Dengue and COVID-19 are viral diseases characterized by coagulopathies, with Dengue associated with fibrinolysis and COVID-19 with prothrombotic events. Furthermore, cross-reactivity between anti-SARS-CoV-2 and anti-DENV antibodies may confer protective immunity or exacerbate disease severity. Our investigation explored the impact of prior COVID-19 exposure on the immunopathogenesis of Dengue, focusing on hemostatic parameters. We quantified nitrites, procoagulant, anticoagulant, and fibrinolytic mediators in the plasma of Dengue patients before and after the COVID-19 pandemic. We also evaluated the influence of plasma from dengue patients on platelet activation in vitro using platelets from healthy donors exposed to DENV-2. Hemorrhagic manifestations were more frequent in pre-COVID-19 Dengue, while nitrite levels were elevated in post-COVID-19 Dengue patients, particularly among those without hemorrhagic signs. Among procoagulant factors, tissue factor (TF) levels were increased in post-COVID-19 Dengue, whereas Factor XIII was higher in pre-COVID-19 Dengue. In contrast, antithrombin (an anticoagulant) and plasminogen (a profibrinolytic factor) were more elevated in pre-COVID-19 Dengue than in post-COVID-19 cases. In vitro, DENV-2-infected platelets exposed to plasma of Dengue patients before and after COVID-19 showed decreased nitrite production in relation to DENV-2 alone. These findings suggest that prior COVID-19 exposure may influence hemostatic responses in Dengue, potentially modulating disease pathophysiology and opening new avenues for research and therapeutic strategies. Full article

Nitrosamines (NAs) pose a risk due to their carcinogenic properties, especially in processed and cured meats where nitrites and nitrates are widely used. The objective of this study was to develop an integrated Ultra-High-Performance Liquid Chromatography–High-Resolution Mass Spectrometry (UHPLC–HRMS) workflow for detecting both volatile (VNAs) and non-volatile (NVNAs) nitrosamines in meat matrices. Comparison of two ionization techniques showed that heated electrospray ionization (HESI) and atmospheric pressure chemical ionization (APCI) provided complementary coverage and sensitivity. Extraction and cleanup were optimized for meat, although recovery rates remained variable, underscoring the analytical complexity. The method was applied to raw, cooked, cured, and grilled meats, as well as to in vitro gastric digestion and co-digestion with spinach. Results revealed that some NAs were present even in untreated raw meat (≈3.0 µg/kg, N-nitrosodi-n-butylamine), while the addition of nitrites and nitrates significantly increased their levels (more than 10 µg/kg, N-nitrosodiethylamine, N-nitrosodimethylamine, N-nitrosodi-n-butylamine). Gastric digestion was the most critical condition, further promoting nitrosamine formation, particularly for N-nitrosodiethylamine, N-nitrosodi-n-butylamine, and N-nitrosopiperidine. Ascorbate exhibited a dual role, acting as an inhibitor at low nitrite concentrations but becoming pro-oxidant at high levels (300 mg/kg). Cooking alone had limited impact, whereas cooking combined with digestion yielded the highest and most consistent nitrosamine concentrations. The inclusion of spinach during digestion modestly altered nitrosamine levels, reflecting both its nitrate content and polyphenolic profile. Nonparametric ANOVA (aligned rank transform) confirmed that preservative treatment, rather than processing or interaction effects, was the main driver of variability (total nitrosamines: H = 24.15, p = 2.33 × 10⁻⁵), with the combination of preservative ascorbate plus nitrite producing significantly higher levels than other treatments (q = 0.000656). N-nitrosodimethylamine consistently emerged as the most relevant marker for dietary exposure, in agreement with EFSA guidance. Overall, this study underscores both the analytical and biochemical complexity of nitrosamine detection and formation in meat products, while highlighting the importance of preservative formulation and the potential role of dietary antioxidants in mitigating exposure. Full article

We adapted two photochemical methods to generate radicals and assess their impact on anion exchange membrane stability, independent of base-induced degradation. Through the exposure of aqueous solutions of potassium nitrite or suspensions of TiO₂ to UV light at 365 nm, we generated hydroxyl radicals or a combination of hydroxyl and superoxide radicals. The methods’ applicability to anion exchange membranes (AEMs) is demonstrated on three commercial AEMs: PiperION-40, FM-FAA-3-PK-75, and PNB-R45. Changes in ion-exchange capacity, along with FT-IR and NMR analyses, revealed significant degradation in thinner, non-reinforced membranes, while thicker and reinforced membranes showed greater resistance. We attribute this to the limited penetration depth of highly reactive radicals into the membrane. Both methods are practical and inexpensive tools for benchmarking AEM stability against radical attack. Full article

Nitrite is a common environmental pollutant in aquaculture systems, where high levels can severely impair fish physiology and survival. This study aimed to evaluate the acute toxicity of waterborne nitrite in starry flounder (Platichthys stellatus). Fish (mean weight 145.69 ± 16.06 g, mean total length 22.78 ± 0.70 cm) were exposed to nitrite concentrations of 0, 25, 50, 100, 200, 400, and 800 mg NO₂⁻/L for 96 h. The lethal concentration 50 (LC₅₀) of nitrite for P. stellatus was determined to be 574.47 mg NO₂⁻/L. Hematological parameters such as red blood cell counts (RBCs), hemoglobin (Hb), and hematocrit (Hct) were significantly decreased by nitrite exposure. Plasma components including calcium (Ca²⁺), glucose, cholesterol, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were significantly changed by nitrite exposure. The results of this study suggest that acute exposure to waterborne nitrite (>200 mg NO₂⁻/L) adversely affects survival rates, hematological parameters, and plasma components in P. stellatus. These findings provide important baseline data for nitrite toxicity assessment in P. stellatus. Full article

The search for natural alternatives to sodium nitrite in meat products is driven by concerns about consumer health and the need to maintain product quality and safety. In this study, the effect of sodium nitrite reduction on the quality parameters of canned pork meat with 1% lyophilized cell-free supernatant (CFS) from L. paracasei B1, during 30 days of storage, was assessed. Reduction of sodium nitrite content led to measurable changes in the color, texture, and oxidative stability of canned pork; however, the presence of 1% CFS helped preserve color, alleviated the negative impact on textural parameters, and limited lipid oxidation, thereby counteracting the typical consequences of nitrite reduction. Among the tested variants, S_75, containing 75% of the standard nitrite dose, showed the best overall balance between color retention, textural integrity, and oxidative stability. Samples without nitrite (S_0) exhibited a noticeable increase in lightness (L*) and decrease in redness (a*) over time, accompanied by a shift towards yellow-brown hues (b*, C*, H°). Importantly, the total color difference (ΔE) was least pronounced in the S_75 variant, with values of approximately 2.5 after 1 day and 2.7 after 30 days, which was markedly lower than in S_50 (ΔE ≈ 6.0 and 3.9) and S_0 (ΔE ≈ 7.9 and 8.5), thereby confirming superior color retention and overall stability during storage. Texture analysis showed that initial hardness and chewiness were higher in nitrite-free samples (S_0), suggesting that the complete omission of nitrite may negatively affect product structure. Nevertheless, all variants softened during storage, and samples with higher nitrite content, particularly S_75, retained better elasticity and cohesiveness. Lipid oxidation, expressed as TBARS values, progressed fastest in samples completely depleted of nitrite (S_0), increasing from 0.31 mg MDA/kg (day 1) to 1.35 mg MDA/kg (day 30), which confirms the antioxidant role of sodium nitrite. Interestingly, the presence of 1% CFS in the variants with reduced nitrite content partially mitigated this effect, as TBARS values in S_75 increased only from 0.29 to 0.46 mg MDA/kg, and, in S_50, from 0.45 to 0.66 mg MDA/kg, compared to the nitrite-free variant. This suggests that CFS may also have contributed to antioxidant protection. Fatty acid profiles remained relatively consistent across methods. Microbiological analysis revealed no significant differences between groups. These results demonstrate that partial nitrite reduction combined with CFS is effective, highlighting the potential of CFS as a promising functional additive in clean label meat preservation. Furthermore, reducing the sodium nitrite content in canned pork products may contribute to improved consumer health by reducing exposure to potentially harmful nitrosamine precursors. Full article

The research investigates nitrate and nitrite concentrations in vegetables sold at agri-food markets in Craiova, Dolj County. Vegetable samples were purchased from markets and sourced from the primary agricultural regions of Dolj County, ensuring a representative selection. A total of 300 samples were collected, with 20 samples taken from each of 15 vegetable species at commercial maturity. This research also aimed to estimate the contribution of each type of vegetable to the intake of nitrates/nitrites ingested through consumption, as well as to carry out an assessment of the risk to human health associated with the consumption of these vegetables. Our analysis showed that only three vegetables (tomatoes, eggplants, and bell peppers) exceeded the maximum permissible nitrate levels (MPL). The MPL for nitrite content was exceeded in several vegetables, including eggplant, green bean, lettuce, cabbage, dill, spinach, and lovage. For nitrates, the Hazard Risk Index (HRI) was consistently below 1 across all samples, with the sole exception of children’s consumption scenario. The HRI for nitrite was also below 1 for all samples, suggesting an absence of exposure risk. The findings from this study suggest that the consumption of vegetable products poses an insignificant risk in terms of nitrate and nitrite intake. Full article

Background: Pre-season training is critical for developing tolerance to high physical demands in professional soccer, and nitric oxide (NO) precursors such as dietary nitrate (NO₃⁻) and citrulline malate (CM) can support performance and recovery during this demanding phase. This study aimed to examine the effects of a four-week supplementation protocol combining 500 mg of NO₃⁻ from amaranth extract and 8 g of CM (NIT + CM) on external training load and post-match recovery in professional female soccer players during pre-season. Methods: A randomized, double-blind, placebo-controlled trial was conducted with 34 female soccer players who received either the NIT + CM product or a placebo for four weeks during pre-season. Global positioning system (GPS)-derived external load was recorded throughout the intervention. Performance tests—a countermovement jump (CMJ) test and the Wingate anaerobic test (WAnT)—and blood sampling for plasma NO₃⁻ and nitrite (NO₂⁻) concentrations were conducted at baseline and the day after a competitive match. Results: The supplementation with NIT + CM increased maximal speed (Vmax) throughout training and match play. During post-match testing, the NIT + CM group exhibited a significantly smaller decline in mean (P_mean) and minimum (P_min) power during the WAnT, along with reduced power loss in both the first (0–15 s) and second (15–30 s) intervals. Plasma NO₃⁻ concentrations significantly increased from baseline in the NIT + CM group and remained elevated 24 h after the final dose, confirming sustained systemic exposure. Conclusions: Chronic NIT + CM supplementation may enhance Vmax and help preserve anaerobic performance the day after a match. These effects could reflect improved tolerance to high training loads and sustained NO₃⁻ availability during recovery. Full article

Nitrite is a common pollutant in aquaculture systems and can pose serious threats to fish health, especially under high-temperature conditions. This study aimed to investigate the impact of nitrite stress on the growth, glycolipid metabolism, and hepatic metabolomic profiles in the spotted seabass fry (Lateolabrax maculatus) under elevated temperature conditions at 33 °C. A total of 450 fish (28.52 ± 0.84 g) were randomly distributed into nine tanks and exposed to three nitrite concentrations (0, 8, and 16 mg/L), with samples collected on days 1, 3, 7, 14, 21, and 28. Results showed that higher nitrite levels significantly reduced final body weight, weight gain, survival rate, hepatosomatic index, and viscerosomatic index. Blood glucose and triglyceride levels, whole-body crude lipid, liver total cholesterol, and hepatic glycogen content also declined significantly under higher nitrite stress. In contrast, hepatic lactate and lactate dehydrogenase increased in the high-nitrite group. Gene expression analysis revealed suppressed lipid synthesis and enhanced lipolysis under nitrite exposure. Metabolomic analysis further demonstrated disruptions in key energy-related pathways, including the TCA cycle, pentose phosphate pathway, and insulin signaling. These findings indicate that nitrite stress impairs growth and energy metabolism in spotted seabass, which respond by mobilizing energy reserves to cope with combined stress of high temperature and nitrite. Full article

Nitrosamines (NAs) are a class of chemical compounds predominantly formed during the processing, curing, and storage of meat products through the reaction of nitrites with amines. Decades of toxicological and epidemiological evidence have unequivocally established several NAs as potent human carcinogens, with strong associations with gastrointestinal, pancreatic, and liver cancers. This review critically examines the pathways of NA formation in meat, the influence of processing conditions, and the factors contributing to their variability in food products. It also outlines state-of-the-art analytical techniques for their detection and summarizes recent scientific efforts to reduce their formation. Despite scientific consensus on the health hazards posed by dietary exposure to NAs, regulatory control remains fragmented and insufficient. Therefore, this review highlights the pressing need for coordinated international action and the development of a harmonized regulatory framework to mitigate public health risks. Full article

Nitrite and carbon dioxide (CO₂) are common environmental substances in intensive aquaculture ponds. However, the effects and mechanisms of their combined exposure on aquatic animals remain unclear. In this study, we investigated the toxic effects of 2.5, 5, and 10 mg/L CO₂ in the presence of 2 mg/L nitrite on hematological, blood gas parameters, and liver physiological and pathological changes in zebrafish (Danio rerio) over 14 days and 28 days. Our results demonstrated a reduced nitrite uptake and accumulation in the gills and liver of zebrafish exposed to nitrite and varying levels of CO₂. Increased CO₂ levels also led to a decrease in the expression of gill ae1, whereas the transcriptional levels of nhe1 and nhe3b, nkcc and nbc1 were notably upregulated. Moreover, there was a decrease in Cl⁻ and Na⁺ concentrations, along with an increase in K⁺ concentrations. These changes suggested that zebrafish responded to increased CO₂ stress by reducing their absorption of chloride-dependent nitrite, excreting H⁺ and maintaining their internal pH. Exposure to higher CO₂ levels in the presence of nitrite resulted in lower blood MetHb levels and liver oxidative stress compared to the nitrite single-exposure treatment. Furthermore, co-treatment with CO₂ and nitrite attenuated the nitrite-induced damage to genes related to mitochondrial respiratory chain function (ndufs1, mtnd5, mtycb, atp5f1b, mtatp8), leading to elevated ATP levels. Exposure to nitrite alone increased the expression of lipolytic genes (hsla, cpt1aa, atgl) and decreased the expression of lipid synthesis genes (fasn, acaca), resulting in a decrease in TG and TC content in zebrafish liver. However, co-treatment with CO₂ and nitrite prevented the nitrite-induced disruption of lipid metabolism, as evidenced by the improvement in TG and TC levels, as well as transcriptional levels of lipid metabolism-related genes. In conclusion, our study suggests that in the presence of 2 mg/L nitrite, increased CO₂ (2.5–10 mg/L) may modulate ion transporter genes to reduce the chloride-dependent nitrite uptake and maintain pH homeostasis, concurrently alleviating oxidative stress, restoring mitochondrial respiratory function, and improving lipid metabolism in a dose-dependent manner. These changes may be related to the increase in the concentration of bicarbonate ions in the water as the CO₂ level rises. These findings shed light on the potential protective effects of CO₂ in mitigating the harmful effects of nitrite exposure in aquatic animals. Full article

Hyperthermia and nitrogenous pollutants like ammonia and nitrite are common risk factors that adversely affect fish health and pose significant threats to the aquaculture industry. However, the impacts of high temperatures on the accumulation of nitrogenous pollutants in the water of the aquaculture systems and their toxicity to farmed fish are not well understood. In this study, juvenile largemouth bass (Micropterus salmoides, LMB) were kept at 28 °C and 34 °C in a closed aquatic system to investigate the effects of higher temperatures on ammonia and nitrite accumulation. The fish were fed 2% of their body weight daily for a 14-day experiment. Ammonia levels gradually increased, peaking on day 7 at 34 °C and on day 9 at 28 °C, then decreased to near zero. Nitrite levels remained low initially and increased rapidly along with the reduction in ammonia levels at both temperatures. The 34 °C high temperature accelerated the accumulation of ammonia and its transformation into nitrite compared to 28 °C. Fish were sampled on day 1 (low ammonia and low nitrite, LALN), day 8 (high ammonia and low nitrite, HALN), and day 14 (low ammonia and high nitrite, LAHN) to explore toxic effects. Successive exposure to high levels of ammonia and nitrite caused oxidative stress in the liver and significant pathogenic changes in the liver and spleen, with more pronounced impacts observed at 34 °C. Significant changes in gene expression were detected in the liver and spleen of fish sampled at HALN and LAHN, compared to those at LALN, with upregulated genes primarily associated with extracellular matrix (ECM) and cytoskeleton organization. A second experiment was conducted at the same temperatures but without ammonia/nitrite accumulation. The results of this experiment confirmed the combined effects of hyperthermia and ammonia/nitrite toxicity on the expression of genes involved in ECM–receptor interaction and TGF-beta signaling. These findings are valuable for optimizing cultivation environments and promoting the health of farmed LMB. Full article