Transcription Factor VlbZIP14 Inhibits Postharvest Grape Berry Abscission by Directly Activating VlCOMT and Promoting Lignin Biosynthesis.

Sulfur dioxide (SO2) is the most effective preservative for table grapes as it reduces the respiratory intensity of berries and inhibits mold growth. However, excessive SO2 causes berry abscission during storage, resulting in an economic loss postharvest. In this study, grapes were exogenously treated with SO2, SO2 + 1.5% chitosan, SO2 + 1.5% eugenol, and SO2 + eugenol-loaded chitosan nanoparticles (SN). In comparison to SO2 treatment, SN treatment reduced the berries' abscission rate by 74% while maintaining the quality of the berries. Among the treatments, SN treatment most effectively inhibited berry abscission and maintained berry quality. RNA-sequencing (RNA-seq) revealed that SN treatment promoted the expression of genes related to cell wall metabolism. Among these genes, VlCOMT was detected as the central gene, playing a key role in mediating the effects of SN. Dual luciferase and yeast one-hybrid (Y1H) assays demonstrated that VlbZIP14 directly activated VlCOMT by binding to the G-box motif in the latter's promoter, which then participated in lignin synthesis. Our results provide key insights into the molecular mechanisms underlying the SN-mediated inhibition of berry abscission and could be used to improve the commercial value of SO2-treated postharvest table grapes.

A biodegradable calcium sulfite nanoreactor for pH triggered gas therapy in combination with chemotherapy.

As a gasotransmitter, endogenous sulfur dioxide (SO2) plays an important role in cardiovascular regulation. In addition, excessive SO2 can react with overexpressed hydrogen peroxide (H2O2) in tumor cells to generate toxic radicals, which can induce severe oxidative damage to tumor cells and result in cell apoptosis. This highlights the potential of SO2 in oncotherapy. However, the limited availability of endogenous H2O2 and uncontrolled release of SO2 gas significantly impede the effectiveness of SO2 gas therapy. To address this challenge, a biodegradable calcium sulfite (CS) nanocarrier loaded with 10-hydroxycamptothecin (HCPT) was developed for tumor pH-triggered SO2 gas therapy in combination with chemotherapy. This nanoreactor could be degraded in an acidic tumor microenvironment to release SO2 gas and the HCPT drug. The released SO2 gas induced serious oxidative damage to tumor cells by depleting glutathione (GSH) and generating toxic radicals through a reaction with intracellular H2O2. Simultaneously, the HCPT drug promoted tumor cell apoptosis through chemotherapy and boosted SO2 gas therapy by elevating the H2O2 level within the tumor cells. Consequently, the combination of SO2 gas therapy and chemotherapy provided a promising approach for effective tumor treatment.

A novel theranostic strategy for myocardial infarction through neutralization of endogenous SO2 using an endoplasmic reticulum-targeted fluorescent probe.

Myocardial infarction (MI), one of the leading causes of death worldwide, urgently needs further understanding of the pathological process and effective therapies. SO2 in endoplasmic reticulum in several cardiovascular diseases has been reported to be particularly important. However, the role of endogenous SO2 in endoplasmic reticulum in treating myocardial infarction is still ambiguous and needs to be elucidated. Herein, we developed TPA-HI-SO2 as the first endoplasmic reticulum-targeting fluorescent agent for specific imaging and detection of sulfur dioxide derivatives both in vitro and in vivo. TPA-HI-SO2 shows a highly sensitive and selective response to SO2 derivatives over other anions in aqueous solution with a satisfactory response time and detection limit. Furthermore, TPA-HI-SO2 decreased the SO2 concentration in H9C2 cells treated with H2O2 and in an MI mouse model. Most importantly, TPA-HI-SO2 protects H9C2 cells from H2O2-induced apoptosis and obviously protects against myocardial infarction in vivo through neutralization of endogenous SO2. Taken together, we developed the first ER-targeting ratiometric fluorescent probe for endogenous SO2 with excellent biocompatibility, high selectivity and sensitivity in this paper. More importantly, we demonstrated an obvious increase of the endogenous SO2 concentration in a myocardial infarction mouse model for the first time, which suggests that neutralization of endogenous SO2 in endoplasmic reticulum could be a promising therapeutic strategy for myocardial infarction.

A chemically engineered water-soluble block copolymer for redox responsive SO2 release in antibacterial therapy.

Sulfur dioxide (SO2) has emerged as a promising gasotransmitter for various therapeutic applications, including antibacterial activities. However, the potential of polymeric SO2 donors for antimicrobial activities remains largely unexplored. Herein, we report a water-soluble, redox-responsive, SO2-releasing amphiphilic block copolymer poly(polyethylene glycol methyl ether methacrylate) (PPEGMA)-b-poly(2-((2,4-dinitrophenyl)sulfonamido)ethyl methacrylate (PM)) (BCPx) to investigate their antibacterial properties. BCPx contains hydrophilic polyethylene glycol (PEG) pendants and a hydrophobic SO2-releasing PM block, facilitating the formation of self-assembled nanoparticles (BCPxNp) in an aqueous medium, studied by critical aggregation concentration (CAC) measurements, dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). BCPxNp exhibits sustained SO2 release up to 12 h in the presence of glutathione (GSH), with a yield of 30-80% of theoretical SO2 release. In vitro antibacterial studies unveil the outstanding antibacterial activity of BCP3Np against Gram-positive bacteria Bacillus subtilis, as evidenced by FESEM and live/dead cell fluorescence assay. We further elucidate the antibacterial mechanism through reactive oxygen species (ROS) generation studies. Overall, the polymer exhibits excellent biocompatibility at effective antimicrobial concentrations and provides insights into the design of a new class of SO2-releasing polymeric antibacterial agents.

Influence of different stress factors during the elaboration of grape must's pieddecuve on the dynamics of yeast populations during alcoholic fermentation.

The pieddecuve (PdC) technique involves using a portion of grape must to undergo spontaneous fermentation, which is then used to inoculate a larger volume of must. This allows for promoting autochthonous yeasts present in the must, which can respect the typicality of the resulting wine. However, the real impact of this practice on the yeast population has not been properly evaluated. In this study, we examined the effects of sulphur dioxide (SO2), temperature, ethanol supplementation, and time on the dynamics and selection of yeasts during spontaneous fermentation to be used as PdC. The experimentation was conducted in a synthetic medium and sterile must using a multi-species yeast consortium and in un-inoculated natural grape must. Saccharomyces cerevisiae dominated both the PdC and fermentations inoculated with commercial wine yeast, displaying similar population growth regardless of the tested conditions. However, using 40 mg/L of SO2 and 1% (v/v) ethanol during spontaneous fermentation of Muscat of Alexandria must allowed the non-Saccharomyces to be dominant during the first stages, regardless of the temperature tested. These findings suggest that it is possible to apply the studied parameters to modulate the yeast population during spontaneous fermentation while confirming the effectiveness of the PdC methodology in controlling alcoholic fermentation.

Sulfur dioxide inhibits mast cell degranulation by sulphenylation of galectin-9 at cysteine 74.

Objectives: Mast cell (MC) degranulation is a key process in allergic reactions and inflammatory responses. Aspartate aminotransferase 1 (AAT1)-derived endogenous sulfur dioxide (SO2) is an important regulator of MC function. However, the mechanism underlying its role in MC degranulation remains unclear. This study aimed to investigate the mechanism by which endogenous SO2 controlled MC degranulation. Methods: HMC-1 and Rat basophilic leukemia cell MC line (RBL-2H3) were used in the cell experiments. SO2 content was detected by in situ fluorescent probe. MC degranulation represented by the release rate of MC ß-hexosaminidase was determined using a colorimetric assay. Sulfenylation of galectin-9 (Gal-9) in MCs and purified protein was detected using a biotin switch assay. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine the exact sulfenylation sites of Gal-9 by SO2. Animal models of passive cutaneous anaphylaxis (PCA) and hypoxia-driven pulmonary vascular remodeling were used to investigate the effect of SO2 on mast cell activation in vivo. Site-directed mutation of Gal-9 was conducted to confirm the exact site of SO2 and support the significance of SO2/Gal-9 signal axis in the regulation of MC degranulation. Results: Degranulation was increased in AAT1-knockdowned MCs, and SO2 supplementation reversed the increase in MC degranulation. Furthermore, deficiency of endogenous SO2 contributed to IgE-mediated degranulation in vitro. Besides, SO2 inhibited IgE-mediated and hypoxia-driven MC degranulation in vivo. Mechanistically, LC-MS/MS analysis and site-directed mutation results showed that SO2 sulfenylated Gal-9 at cysteine 74. Sulfenylation of the 74th cysteine of Gal-9 protein was required in the SO2-inhibited MC degranulation under both physiological and pathophysiological conditions. Conclusion: These findings elucidated that SO2 inhibited MC degranulation via sulfenylating Gal-9 under both physiological and pathophysiological conditions, which might provide a novel treatment approach for MC activation-related diseases.

Release of ATP in the lung evoked by inhalation of irritant gases in rats.

Adenosine triphosphate (ATP) can be released into the extracellular milieu from various types of cells in response to a wide range of physical or chemical stresses. In the respiratory tract, extracellular ATP is recognized as an important signal molecule and trigger of airway inflammation. Chlorine (Cl2), sulfur dioxide (SO2), and ammonia (NH3) are potent irritant gases and common industrial air pollutants due to their widespread uses as chemical agents. This study was carried out to determine if acute inhalation challenges of these irritant gases, at the concentration and duration simulating the accidental exposures to these chemical gases in industrial operations, triggered the release of ATP in the rat respiratory tract; and if so, whether the level of ATP in bronchoalveolar lavage fluid (BALF) evoked by inhalation challenge of a given irritant gas was elevated by chronic allergic airway inflammation. Our results showed: 1) inhalation of these irritant gases caused significant increases in the ATP level in BALF, and the magnitude of evoked ATP release was in the order of Cl2 > SO2 > NH3. 2) Chronic airway inflammation induced by ovalbumin-sensitization markedly elevated the ATP level in BALF during baseline (breathing room air) but did not potentiate the release of ATP in the lung triggered by inhalation challenges of these irritant gases. These findings suggested a possible involvement of the ATP release in the lung in the regulation of overall airway responses to acute inhalation of irritant gases and the pathogenesis of chronic allergic airway inflammation.NEW & NOTEWORTHY Extracellular adenosine triphosphate (ATP) is a contributing factor and signaling molecule of airway inflammation. This study demonstrated for the first time that the ATP release in the lung was markedly elevated after acute inhalation challenges of three common industrial air pollutants; the order of the response magnitude was chlorine > sulfur dioxide > ammonia. These findings provided new information and improved our understanding of the adverse pulmonary effects caused by accidental inhalation exposures to these irritant gases.

Endogenous sulfur dioxide deficiency as a driver of cardiomyocyte senescence through abolishing sulphenylation of STAT3 at cysteine 259.

OBJECTIVE: Cardiomyocyte senescence is an important contributor to cardiovascular diseases and can be induced by stressors including DNA damage, oxidative stress, mitochondrial dysfunction, epigenetic regulation, etc. However, the underlying mechanisms for the development of cardiomyocyte senescence remain largely unknown. Sulfur dioxide (SO2) is produced endogenously by aspartate aminotransferase 2 (AAT2) catalysis and plays an important regulatory role in the development of cardiovascular diseases. The present study aimed to explore the effect of endogenous SO2 on cardiomyocyte senescence and the underlying molecular mechanisms. APPROACH AND RESULTS: We interestingly found a substantial reduction in the expression of AAT2 in the heart of aged mice in comparison to young mice. AAT2-knockdowned cardiomyocytes exhibited reduced SO2 content, elevated expression levels of Tp53, p21Cip/Waf, and p16INk4a, enhanced SA-ß-Gal activity, and elevated level of γ-H2AX foci. Notably, supplementation with a SO2 donor ameliorated the spontaneous senescence phenotype and DNA damage caused by AAT2 deficiency in cardiomyocytes. Mechanistically, AAT2 deficiency suppressed the sulphenylation of signal transducer and activator of transcription 3 (STAT3) facilitated its nuclear translocation and DNA-binding capacity. Conversely, a mutation in the cysteine (Cys) 259 residue of STAT3 blocked SO2-induced STAT3 sulphenylation and subsequently prevented the inhibitory effect of SO2 on STAT3-DNA-binding capacity, DNA damage, and cardiomyocyte senescence. Additionally, cardiomyocyte (cm)-specific AAT2 knockout (AAT2cmKO) mice exhibited a deterioration in cardiac function, cardiomegaly, and cardiac aging, whereas supplementation with SO2 donors mitigated the cardiac aging and remodeling phenotypes in AAT2cmKO mice. CONCLUSION: Downregulation of the endogenous SO2/AAT2 pathway is a crucial pathogenic mechanism underlying cardiomyocyte senescence. Endogenous SO2 modifies STAT3 by sulphenylating Cys259, leading to the inhibition of DNA damage and the protection against cardiomyocyte senescence.

Glutathione-triggered release of SO2 gas to augment oxidative stress for enhanced chemodynamic and sonodynamic therapy.

Recently, gas therapy has emerged as a promising alternative treatment for deep-seated tumors. However, some challenges regarding insufficient or uncontrolled gas generation as well as unclear therapeutic mechanisms restrict its further clinical application. Herein, a well-designed nanoreactor based on intracellular glutathione (GSH)-triggered generation of sulfur dioxide (SO2) gas to augment oxidative stress has been developed for synergistic chemodynamic therapy (CDT)/sonodynamic therapy (SDT)/SO2 gas therapy. The nanoreactor (designed as CCM@FH-DNs) is constructed by employing iron-doped hollow mesoporous silica nanoparticles as carriers, the surface of which was modified with the SO2 prodrug 2,4-dinitrobenzenesulfonyl (DNs) and further coated with cancer cell membranes for homologous targeting. The CCM@FH-DNs can not only serve as a Fenton-like agent for CDT, but also as a sonosensitizer for SDT. Importantly, CCM@FH-DNs can release SO2 for SO2-mediated gas therapy. Both in vitro and in vivo evaluations demonstrate that the CCM@FH-DNs nanoreactor performs well in augmenting oxidative stress for SO2 gas therapy-enhanced CDT/SDT via GSH depletion and glutathione peroxidase-4 enzyme deactivation as well as superoxide dismutase inhibition. Moreover, the doped iron ions ensure that the CCM@FH-DNs nanoreactors enable magnetic resonance imaging-guided therapy. Such a GSH-triggered SO2 gas therapy-enhanced CDT/SDT strategy provides an intelligent paradigm for developing efficient tumor microenvironment-responsive treatments.

Recent advances in sulfur dioxide releasing nanoplatforms for cancer therapy.

Sulfur dioxide (SO2), long considered to be a harmful atmospheric pollutant, has recently been posited as the fourth gasotransmitter, as it is produced endogenously in mammals and has important pathophysiological effects. The field of tumor therapy has witnessed a paradigm shift with the emergence of SO2-based gas therapy. This has been possible because SO2 is a potent glutathione consumer that can promote the production of reactive oxygen species, eventually leading to oxidative-stress-induced cancer cell death. Nevertheless, this therapeutic gas cannot be directly administrated in gaseous form. Thus, various nano formulations incorporating SO2 donors or prodrugs capable of storing and releasing SO2 have been developed in an attempt to achieve active/passive intratumoral accumulation and SO2 release in the tumor microenvironment. In this review article, the advances over the past decade in nanoplatforms incorporating sulfur SO2 prodrugs to provide controlled release of SO2 for cancer therapy are summarized. We first describe the synthesis of polypeptide SO2 prodrugs to overcome multiple drug resistance that was pioneered by our group, followed by other macromolecular SO2 prodrug structures that self-assemble into nanoparticles for tumor therapy. Second, we describe nanoplatforms composed of various small-molecule SO2 donors with endogenous or exogenous stimuli responsiveness, including thiol activated, acid-sensitive, and ultraviolet or near-infrared light-responsive SO2 donors, which have been used for tumor inhibition. Combinations of SO2 gas therapy with photodynamic therapy, chemotherapy, photothermal therapy, sonodynamic therapy, and nanocatalytic tumor therapy are also presented. Finally, we discuss the current limitations and challenges and the future outlook for SO2-based gas therapy. STATEMENT OF SIGNIFICANCE: Gas therapy is attracting increasing attention in the scientific community because it is a highly promising strategy against cancer owing to its inherent biosafety and avoidance of drug resistance. Sulfur dioxide (SO2) is recently found to be produced endogenously in mammals with important pathophysiological effects. This review summarizes recent advances in SO2 releasing nanosystems for cancer therapy, including polymeric prodrugs, endogenous or exogenous stimulus-activated SO2 donors delivered by nanoplatform and combination therapy strategies.

[Regulative effects of endogenous sulfur dioxide on oxidant stress in myocardium of rat with sepsis].

OBJECTIVE: To explore the modulating effect of endogenous sulfur dioxide (SO2) on the ba-lance of oxidation/reduction in the cecal-ligation-and-puncture-induced septic rat myocardium. METHODS: Forty male Sprague Dawley rats were randomized into control group, SO2group, sepsis group and sepsis + SO2group. The levels of procalcitonin (PCT), creatine kinase isoenzyme (CK-MB), cardiac troponin Ⅰ (cTn Ⅰ) and fatty acid binding protein (FABP) in plasma in each group of the rats were measured; The level of hydrogen peroxide (H2O2), level of nitric oxide (NO), activity of myeloperoxidase (MPO), activity of hydroxyl free radical (·OH) and level of malondialdehyde (MDA) in myocardial tissue were measured; Total antioxidant capacity (T-AOC), activity of catalase (CAT), level of cytochrome oxidase (CO), level of glutathione (GSH), level of glutathione oxidase (GSH-px) and activity of superoxide dismutase (SOD) in myocardial tissue were measured. RESULTS: The level of PCT in plasma in the rats with sepsis increased from (0.93±0.26) µg/L to (2.45±0.52) µg/L (P < 0.01), and decreased to (1.58±0.36) µg/L after the intervention of sulfur dioxide donor (P < 0.01). In sepsis, the plasma CK-MB, cTn Ⅰ and FABP levels in the rats increased respectively from (14.46±6.48) µg/L, (151.25±30.14) ng/L and (2.72±0.65) µg/L to (23.72±7.72) µg/L, (272.78±52.70) ng/L and (5.22±1.01) µg/L (P all < 0.01), and decreased to (16.74±3.63) µg/L, (184.86±37.72) µg/L and (3.31±0.84) µg/L (all P < 0.05) after the intervention of sulfur dioxide donor. The level of H2O2, level of NO, activity of MPO, activity of ·OH and level of MDA in myocardial tissue in the rats with sepsis increased respectively from (67.26±8.77) mmol/g, (38.39±6.93) µmol/g, (358.25±68.12) U/g, (648.42±93.69) U/ mg and (4.55±0.96) µmol/g to (111.45±17.35) mmol/g, (51.04±5.91) µmol/g, (465.88±76.76) U/g, (873.75±123.47) U/mg and (7.25±0.86) µmol/g (all P < 0.01), and decreased respectively to (75.99±10.52) mmol/g, (39.39±7.80) µmol/g, (393.17±51.5) U/g, (710.54±106.33) U/mg and (5.16±0.65) µmol/g after the intervention of the sulfur dioxide donor (all P < 0.05). The activity of T-AOC, activity of CAT, level of CO, level of GSH, level of GSH-px and activity of SOD in myocardial tissue in the rats with sepsis increased respectively from (2.07±0.37) U/mg, (169.25±36.86) U/g, (1.35±0.32) µmol/g, (103.51±16.62) µmol/g, (38.40±7.97) µmol/g and (38.50±8.30) U/mg to (1.42±0.39) U/mg, (98.44±26.56) U/g, (0.96±0.21) µmol/g, (68.05±7.35) µmol/ g, (23.83±5.04) µmol/g and (23.11±4.63) U/mg (P all < 0.01), and increased respectively to (1.83±0.37) U/mg, (146.14±31.63) U/g, (1.28±0.20) µmol/g, (92.10±11.84) µmol/g, (37.16±3.01) µmol/g and (37.29±2.62) U/mg (P all < 0.05) after the intervention of the sulfur dioxide donor. CONCLUSION: Endogenous SO2 can protect rat myocardium in sepsis by modulating the ba-lance of oxidation and reduction.

Bioprotection by non-Saccharomyces yeasts in oenology: Evaluation of O2 consumption and impact on acetic acid bacteria.

Bioprotection by yeast addition is increasingly used in oenology as an alternative to sulfur dioxide (SO2). Recent studies have also shown that it is likely to consume dissolved O2. This ability could limit O2 for other microorganisms and the early oxidation of the grape must. However, the ability of yeasts to consume O2 in a context of bioprotection was poorly studied so far considering the high genetic diversity of non-Saccharomyces. The first aim of the present study was to perform an O2 consumption rate (OCR) screening of strains from a large multi species collection found in oenology. The results demonstrate significant inter and intra species diversity with regard to O2 consumption. In the must M. pulcherrima consumes O2 faster than Saccharomyces cerevisiae and then other studied non-Saccharomyces species. The O2 consumption was also evaluate in the context of a yeast mix used as industrial bioprotection (Metschnikowia pulcherrima and Torulaspora delbrueckii) in red must. These non-Saccharomyces yeasts were then showed to limit the growth of acetic acid bacteria, with a bioprotective effect comparable to that of the addition of sulfur dioxide. Laboratory experiment confirmed the negative impact of the non-Saccharomyces yeasts on Gluconobacter oxydans that may be related to O2 consumption. This study sheds new lights on the use of bioprotection as an alternative to SO2 and suggest the possibility to use O2 consumption measurements as a new criteria for non-Saccharomyces strain selection in a context of bioprotection application for the wine industry.

The role of FGF9-mediated TGF-ß1/Smad signaling in enamel hypoplasia induced by exposure to fluoride and SO2 in rats.

Many geographical areas of the world are polluted by both fluoride and sulfur dioxide (SO2). However, the effects of simultaneous exposure to fluoride and SO2 on teeth are unknown. Fibroblast growth factor-9 (FGF9) and transforming growth factor-ß1 (TGF-ß1) are key signaling molecules in enamel development. The purpose of the study was to explore the effects of co-exposure to fluoride and sulfur dioxide on enamel and to investigate the role and mechanism of FGF9 and TGF-ß1. First, sodium fluoride (NaF) and SO2 derivatives were used to construct rat models and evaluate the enamel development of rats. Then, TGF-ß1 (cytokine) treatment, SIS3 (inhibitor) treatment and FGF9 gene knockdown were used to explore the mechanism of enamel damage in vitro. The results showed that enamel column crystals in the exposed group were characterized by enamel hypoplasia, as indicated by alterations such as disarrangement of enamel column crystals, space widening and breakage. Ameloblasts also showed pathological changes such as ribosome loss, mitochondrial swelling, nuclear fragmentation and chromatin aggregation. The protein expression of FGF9 was higher and the protein expression of AMBN, TGF-ß1 and p-Smad2/3 protein was lower in the groups treated with fluoride and SO2 individually or in combination compared with the control group. Further studies showed that TGF-ß1 significantly upregulated p-Smad2/3 and AMBN protein expression and reduced the inhibitory effects of fluoride and SO2; furthermore, SISI blocked the effect of TGF-ß1. In addition, knockdown of FGF9 upregulated TGF-ß1 protein expression, further activated Smad2/3 phosphorylation, eliminated the inhibitory effects of fluoride and SO2, and increased the protein expression of AMBN. In brief, the study confirms that co-exposure to fluoride and SO2 can result in enamel hypoplasia in rats and indicates that the underlying mechanism may be closely related to the effect of FGF9 on enamel matrix protein secretion through inhibition of the TGF-ß1/Smad signaling pathway.

Sulfur dioxide improves the thermotolerance of maize seedlings by regulating salicylic acid biosynthesis.

Heat stress (HS) has become a serious threat to crop growth and yield. Sulfur dioxide (SO2) is being verified as a signal molecule in regulating the plant stress response. However, it is unknown whether SO2 plays a significant role in the plant heat stress response (HSR). Herein, maize seedlings were pretreated with various concentrations of SO2 and then kept at 45 °C for heat stress treatment, aiming to study the effect of SO2 pretreatment on HSR in maize by phenotypic, physiological, and biochemical analyses. It was found that SO2 pretreatment greatly improved the thermotolerance of maize seedlings. The SO2-pretreated seedlings showed 30-40% lower ROS accumulation and membrane peroxidation, but 55-110% higher activities of antioxidant enzymes than the distilled water-pretreated seedlings under heat stress. Interestingly, endogenous salicylic acid (SA) levels were increased by ∼85% in SO2-pretreated seedlings, as revealed by phytohormone analyses. Furthermore, the SA biosynthesis inhibitor paclobutrazol markedly reduced SA levels and attenuated SO2-triggered thermotolerance of maize seedlings. Meanwhile, transcripts of several SA biosynthesis and signaling, and heat stress-responsive genes in SO2-pretreated seedlings were significantly elevated under HS. These data have demonstrated that SO2 pretreatment increased endogenous SA levels, which activated the antioxidant machinery and strengthened the stress defense system, thereby improving the thermotolerance of maize seedlings under HS. Our current study provides a new strategy for mitigating heat stress damage for safe crop production.

Inhibitory effect of sulfur dioxide inhalation on Hering-Breuer inflation reflex in mice: role of voltage-gated potassium channels.

Slowly adapting receptors (SARs), vagal mechanosensitive receptors located in the lung, play an important role in regulating the breathing pattern and Hering-Breuer inflation reflex (HBIR). Inhalation of high concentration of sulfur dioxide (SO2), a common environmental and occupational air pollutant, has been shown to selectively block the SAR activity in rabbits, but the mechanism underlying this inhibitory effect remained a mystery. We carried out this study to determine if inhalation of SO2 can inhibit the HBIR and change the eupneic breathing pattern, and to investigate further a possible involvement of voltage-gated K+ channels in the inhibitory effect of SO2 on these vagal reflex-mediated responses. Our results showed 1) inhalation of SO2 (600 ppm; 8 min) consistently abolished both the phasic activity of SARs and their response to lung inflation in anesthetized, artificially ventilated mice, 2) inhalation of SO2 generated a distinct inhibitory effect on the HBIR and induced slow deep breathing in anesthetized, spontaneously breathing mice, and these effects were reversible and reproducible in the same animals, 3) This inhibitory effect of SO2 was blocked by pretreatment with 4-aminopyridine (4-AP), a nonselective blocker of voltage-gated K+ channel, and unaffected by pretreatment with its vehicle. In conclusion, this study suggests that this inhibitory effect on the baseline breathing pattern and the HBIR response was primarily mediated through the SO2-induced activation of voltage-gated K+ channels located in the vagal bronchopulmonary SAR neurons.NEW & NOTEWORTHY This study demonstrated that inhaled sulfur dioxide completely and reversibly abolished the activity of vagal bronchopulmonary slowly adapting receptors, significantly inhibited the apneic response to lung inflation, and induced slow deep breathing in anesthetized mice. More importantly, our results further suggested that this inhibitory effect was mediated through an action of sulfur dioxide and its derivatives on the voltage-gated potassium channels expressed in the slowly adapting receptor sensory neurons innervating the lung.

Sodium Fluoride and Sulfur Dioxide Derivatives Induce TGF-ß1-Mediated NBCe1 Downregulation Causing Acid-Base Disorder of LS8 Cells.

The aim of the present work was to assess whether the combination of sodium fluoride (NaF) and sulfur dioxide derivatives (SO2 derivatives) affects the expression of the electrogenic sodium bicarbonate cotransporter NBCe1 (SLC4A4), triggering an acid-base imbalance during enamel development, leading to enamel damage. LS8 cells was taken as the research objects and fluorescent probes, quantitative real-time polymerase chain reaction (qRT-PCR), western blot, and factorial analysis were used to clarify the nature of the fluoro-sulfur interaction and the potential signaling pathway involved in the regulation of NBCe1. The results showed that exposure to fluoride or SO2 derivatives resulted in an acid-base imbalance, and these changes were accompanied by inhibited expression of NBCe1 and TGF-ß1; these effects were more significant after fluoride exposure as compared to exposure to SO2 derivatives. Interestingly, in most cases, the toxic effects during combined exposure were significantly reduced compared to the effects observed with fluoride or sulfur dioxide derivatives alone. The results also indicated that activation of TGF-ß1 signaling significantly upregulated the expression of NBCe1, and this effect was suppressed after the Smad, ERK, and JNK signals were blocked. Furthermore, fluoride and SO2 derivative-dependent NBCe1 regulation was found to require TGF-ß1. In conclusion, this study indicates that the combined effect of fluorine and sulfur on LS8 cells is mainly antagonistic. TGF-ß1 may regulate NBCe1 and may participate in the occurrence of dental fluorosis through the classic TGF-ß1/Smad pathway and the unconventional ERK and JNK pathways.

Elucidating the role of circNFIB in myocardial fibrosis alleviation by endogenous sulfur dioxide.

BACKGROUND: To investigate the role of circNFIB in the alleviation of myocardial fibrosis by endogenous sulfur dioxide (SO2). METHODS: We stimulated cultured neonatal rat cardiac fibroblasts with transforming growth factor-ß1 (TGF-ß1) and developed an in vitro myocardial fibrosis model. Lentivirus vectors containing aspartate aminotransferase 1 (AAT1) cDNA were used to overexpress AAT1, and siRNA was used to silence circNFIB. The SO2, collagen, circNFIB, Wnt/ß-catenin, and p38 MAPK pathways were examined in each group. RESULTS: In the in vitro TGF-ß1-induced myocardial fibrosis model, endogenous SO2/AAT1 expression was significantly decreased, and collagen levels in the cell supernatant and type I and III collagen expression, as well as α-SMA expression, were all significantly increased. TGF-ß1 also significantly reduced circNFIB expression. AAT1 overexpression significantly reduced myocardial fibrosis while significantly increasing circNFIB expression. Endogenous SO2 alleviated myocardial fibrosis after circNFIB expression was blocked. We discovered that circNFIB plays an important role in the alleviation of myocardial fibrosis by endogenous SO2 by inhibiting the Wnt/ß-catenin and p38 MAPK pathways. CONCLUSION: Endogenous SO2 promotes circNFIB expression, which inhibits the Wnt/ß-catenin and p38 MAPK signaling pathways, consequently alleviating myocardial fibrosis.

Effects of exercise on the cardiovascular function of rats in a sulfur dioxide polluted environment.

The purpose of the study is to further explore the combined effects of exercise and sulfur dioxide (SO2) exposure on the cardiovascular function as well as the underlying mechanisms. Rats were randomly divided into 4 groups: rest group (RG), exercise group (EG), SO2 pollution group (SG) and SO2 pollution + exercise group (SEG). Changes of aortic pressure and left ventricular pressure, Ang II concentration, ACE concentration and ACE activity in rats' myocardial tissue were observed. Compared with RG, the systolic blood pressure, pulse pressure, LVSP, +dp/dtmax and -dp/dtmax of EG increased significantly, diastolic blood pressure, resting heart rate and ACE activity decreased significantly; For rats of SG, 4 weeks SO2 exposure increased LVEDP, Ang II concentration, ACE concentration and ACE activity, decreased the +dp/dtmax and -dp/dtmax; For rats of SEG, the systolic blood pressure, pulse pressure, LVSP, +dp/dtmax and -dp/dtmax decreased significantly, HR, LVEDP, Ang II concentration, ACE concentration and ACE activity increased significantly. Results indicate that, the combination of aerobic exercise and SO2 exposure can aggravate the negative effects of SO2 inhalation on cardiovascular function. Renin-angiotensin system plays an important role in mediating the negative effect of SO2 inhalation.

Role of hydrogen sulfide in sulfur dioxide production and vascular regulation.

Both hydrogen sulfide (H2S) and sulfur dioxide (SO2) are produced endogenously from the mammalian metabolic pathway of sulfur-containing amino acids and play important roles in several vascular diseases. However, their interaction during the control of vascular function has not been fully clear. Here, we investigated the potential role of H2S in SO2 production and vascular regulation in vivo and in vitro. Wistar rats were divided into the vehicle, SO2, DL-propargylglycine (PPG) + SO2, ß-cyano-L-alanine (BCA) + SO2 and sodium hydrosulfide (NaHS) + SO2 groups. SO2 donor was administered with or without pre-administration of PPG, BCA or NaHS for 30 min after blood pressure was stabilized for 1 h, and then, the change in blood pressure was detected by catheterization via the common carotid artery. Rat plasma SO2 and H2S concentrations were measured by high performance liquid chromatography and sensitive sulfur electrode, respectively. The isolated aortic rings were prepared for the measurement of changes in vasorelaxation stimulated by SO2 after PPG, BCA or NaHS pre-incubation. Results showed that the intravenous injection of SO2 donors caused transient hypotension in rats compared with vehicle group. After PPG or BCA pretreatment, the plasma H2S content decreased but the SO2 content increased markedly, and the hypotensive effect of SO2 was significantly enhanced. Conversely, NaHS pretreatment upregulated the plasma H2S content but reduced SO2 content, and attenuated the hypotensive effect of SO2. After PPG or BCA pre-incubation, the vasorelaxation response to SO2 was enhanced significantly. While NaHS pre-administration weakened the SO2-induced relaxation in aortic rings. In conclusion, our in vivo and in vitro data indicate that H2S negatively controls the plasma content of SO2 and the vasorelaxant effect under physiological conditions.

Endogenous Sulfur Dioxide Improves the Survival Rate of Sepsis by Improving the Oxidative Stress Response during Lung Injury.

Objective: To explore the regulation of endogenous sulfur dioxide on oxidative stress in lung injury induced by sepsis. Method: Forty male Sprague Dawley rats were divided into control, sepsis, sepsis + SO2, and SO2 group randomly used to observe survival rate. The other group of twenty-eight rats were randomly divided as the same manner for mechanism research. The number of WBCS and the percentage of PMN cells were calculated. The microphotographs of morphological changes and the index of quantitative assessment (IQA) of lung tissues were calculated. The ratio of wet/dry (W/D) of lung tissues was calculated. Levels of H2O2, MDA, NO, MPO, SOD, GSH-px, and TNF-α in plasma and lung tissues were measured. Result: The number of WBCS and the percentage of PMN cells decreased in sepsis (p all < 0.05), and rebound in sepsis+SO2 (p all < 0.05). The IQA and W/D of lung tissues increased in sepsis (p for W/D < 0.05), and decreased in sepsis+SO2 (p all < 0.05). H2O2 and MDA of plasma and lung tissues increased in sepsis (p all < 0.05) and rebound in sepsis+SO2 (p for H2O2 of plasma and lung tissues <0.05). NO and MPO of plasma and lung tissues increased in sepsis (p for NO and MPO of lung tissues <0.05) and rebound in sepsis+SO2 (p all < 0.05). SOD of plasma and lung tissues in sepsis group decreased (p all <0.05) and increased in sepsis+SO2 (p all < 0.05). GSH-px of plasma and lung tissues decreased in sepsis (p for plasma <0.05) and increased in sepsis+SO2 (p for GSH-px of lung tissues <0.05). TNF-α of plasma and lung tissues increased in sepsis (p all<0.05) and decreased in sepsis+SO2 (p for lung tissue <0.05). Conclusion: Endogenous sulfur dioxide improves the survival rate of sepsis by improving the oxidative stress response during lung injury.