Arsenic exposure induces small intestinal toxicity in mice by barrier damage and inflammation response via activating RhoA/ROCK and TLR4/Myd88/NF-κB signaling pathways.

Numerous studies have shown that arsenic (As) is an important hazardous metalloid that is commonly considered to have systemic toxicity. The main pathway of arsenic exposure is oral; however, many of the events that occur during its passage through the gastrointestinal tract are unclear, and there are few reports on the effect of arsenic on small intestinal mucosal barrier. This study aimed to investigate arsenic-induced mucosal barrier damage in the small intestine of mice induced by oral exposure and its potential mechanisms. In the present study, histomorphometric and immunohistochemical analyses showed that arsenic-treated mice exhibited signs of irregularly arranged and atrophied small intestinal villi, reduced villus lengths, inflammatory cells infiltration, along with up-regulated expression of inflammatory factors TNF-α, IL-6 and IL-1ß in the small intestine of mice. The myeloperoxidase (MPO) activity was also increased in As-exposed mice. Transmission electron microscopy (TEM) analysis demonstrated that intestinal epithelial tight junctions (TJs) were impaired in the small intestines of mice in As group. In addition, arsenic down-regulated mRNA levels of TJ-related genes (ZO-1, ZO-2, occludin, claudin-1, and claudin-7) and protein levels of ZO-1, occludin and claudin-1 were significantly reduced in arsenic-treated groups, while arsenic also increased levels of TLR4, Myd88, NF-κB, RhoA, and ROCK mRNA and protein expression. In summary, these results indicate that the small intestine toxicity in mice evoked by arsenic was correlated with the activation of TLR4/Myd88/NF-κB and RhoA/ROCK pathways.

Arsenic interferes with spermatogenesis involving Rictor/mTORC2-mediated blood-testis barrier disruption in mice.

Ingestion of arsenic interferes with spermatogenesis and increases the risk of male infertility, but the underlying mechanism remines unclear. In this study, we investigated spermatogenic injury with a focus on blood-testis barrier (BTB) disruption by administrating 5 mg/L and 15 mg/L arsenic orally to adult male mice for 60 d. Our results showed that arsenic exposure reduced sperm quality, altered testicular architecture, and impaired Sertoli cell junctions at the BTB. Analysis of BTB junctional proteins revealed that arsenic intake downregulated Claudin-11 expression and increased protein levels of ß-catenin, N-cadherin, and Connexin-43. Aberrant localization of these membrane proteins was also observed in arsenic-treated mice. Meanwhile, arsenic exposure altered the components of Rictor/mTORC2 pathway in mouse testis, including inhibition of Rictor expression, reduced phosphorylation of protein kinase Cα (PKCα) and protein kinase B (PKB), and elevated matrix metalloproteinase-9 (MMP-9) levels. Furthermore, arsenic also induced testicular lipid peroxidative damage, inhibited antioxidant enzyme (T-SOD) activity, and caused glutathione (GSH) depletion. Our findings suggest that disruption of BTB integrity is one of the main factors responsible for the decline in sperm quality caused by arsenic. PKCα-mediated rearrangement of actin filaments and PKB/MMP-9-increased barrier permeability jointly contribute to arsenic-induced BTB disruption.

Sulfur dioxide-enhanced asthma susceptibility is involved with inhibition of bitter taste transduction in mouse lung.

Sulfur dioxide (SO2) may induce asthma-like symptoms or worsen existing asthma, but the underlying mechanism is still unclear. In this study, the relationship between SO2 exposure, asthma development, and bitter taste transduction was analyzed using ovalbumin (OVA)-induced and SO2-aggravated asthma models. The results showed that twenty-seven and twelve bitter taste receptors (Tas2rs) were detectable in mouse trachea and lung, respectively, and that all of them were nearly down-regulated in OVA-induced BALB/c and C57BL/6 asthmatic mice. SO2 exposure alone did not trigger a distinct asthma-like phenotype, but the combination of SO2 and OVA allergen caused more severe asthma symptoms in mice including enhanced inflammatory cells infiltration, thickened airway walls, increased mucus secretion, and elevated expression of proinflammatory and Th2 cytokines (TNF-α, IL-4, IL-5, IL-13). Furthermore, SO2 enhanced the transcriptional repression of Tas2rs in OVA-induced asthmatic mice. These results indicated that the occurrence of mice asthma was correlated with the inhibition of bitter taste transduction, and more severe airway inflammation and injury were accompanied with an enhanced inhibition of bitter taste transduction. Our findings suggest that SO2 inhalation may amplify Th2 inflammatory responses in the lung of asthmatic mice by inhibiting bitter taste transduction, and thereby exacerbate asthma symptoms.

Enhancement of drought tolerance in Arabidopsis plants induced by sulfur dioxide.

Sulfur dioxide (SO2) is a common air pollutant that has multiple effects on plants. In the present study, the improvement of drought tolerance in Arabidopsis plants by SO2 fumigation was investigated. The results showed that pre-exposure to 30 mg/m3 SO2 for 72 h could reduce water loss, stomatal conductance (Gs) and the transpiration rate (Tr) but increased the net photosynthetic rate (Pn), water use efficiency (iWUE) and photosynthetic pigment contents under drought conditions. The activities of superoxide dismutase (SOD) and peroxidase (POD) were significantly increased, while the contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were decreased in SO2-pretreated Arabidopsis plants under drought stress. Additionally, the activity of o-acetylserine(thio)lyase (OASTL) and the content of cysteine (Cys), the rate-limiting enzyme and the first organic product of sulfur assimilation, were significantly increased in drought-stressed plants after SO2 pretreatment, along with increases in other thiol-containing compounds, such as glutathione (GSH) and nonprotein thiol (NPT). Meanwhile, SO2 pre-exposure induced a higher level of proline accumulation, with increased activity of proline synthase P5CS and decreased activity of proline dehydrogenase ProDH. Consistent with the changes in enzyme activity, their corresponding gene expression patterns were different after SO2 treatment. Overall, the enhanced drought tolerance afforded by SO2 might be related to the improvement of plant photosynthesis, antioxidant defense, sulfur assimilation and osmotic adjustment. These findings provide new insights into the role of SO2 in plant adaptation to environmental stress.

Arsenic intake-induced gastric toxicity is blocked by grape skin extract by modulating inflammation and oxidative stress in a mouse model.

Arsenic (As) is known to induce toxic responses in many organs of human beings and animals. However, research concerning toxicity in the stomach is limited. In this study, arsenic-induced gastric toxicity was investigated in a mouse model, and grape skin extract (GSE) was confirmed to have protective effects against arsenic toxicity. Our experimental results showed that exposure to 10 mg/l arsenic via drinking water for 56 days caused oxidative damage and inflammatory responses. The H2O2 and malondialdehyde (MDA) contents were significantly increased, accompanied by significant decreases in total superoxide dismutase (T-SOD) activity and glutathione (GSH) content in the gastric tissue of arsenic-treated mice. Two inflammatory signalling pathways, i.e., TLR2/MyD88/NF-κB and IL-6/STAT-3, were activated, along with inflammatory cell infiltration and the elevated mRNA expression of pro-inflammatory cytokines (TNF-α, IL-1ß and IFN-γ) and myeloperoxidase (MPO) in the gastric tissue of mice exposed to arsenic. Meanwhile, the mRNA levels of the ZO-1, ZO-2 and occludin genes, which encode the key components of tight junction (TJ) complexes, were downregulated. However, the application of GSE (300 mg/kg bw) significantly inhibited the arsenic-induced increases in H2O2 and MDA contents and the decreases in T-SOD activity and GSH content. The arsenic-mediated gene expression of pro-inflammatory cytokines (TNF-α, IL-1ß and IFN-γ), MPO and IL-6/STAT3 and TLR2/MyD88/NF-κB pathways was found down-regulated. Moreover, the arsenic-induced inflammatory cell infiltration and inhibition of TJ genes transcription were markedly attenuated in the As+GSE (300 mg/kg bw) group. Based on the present findings, arsenic intake appears to cause gastric toxicity via oxidative stress and inflammation, and the application of GSE offers significant protection against arsenic toxicity in a mouse model by attenuating the oxidative stress and inflammatory response. Our results suggest that GSE by oral administration might function as a candidate therapeutic supplement to antagonize arsenic toxicity.

Potential antitumor and anti-inflammatory activities of an extracellular polymeric substance (EPS) from Bacillus subtilis isolated from a housefly.

Bacillus subtilis, a probiotic, has been applied in the medical, food, and feed industries among others. However, the mechanisms of its benefits to hosts are not yet fully understood. Here the characterization and bioactivities of an extracellular polymeric substance (EPS) from Bacillus subtilis were investigated to reveal its partial mechanisms and provide the theoretical basics for further development and utilization of Bacillus subtilis. In this study, the novel strain Bacillus subtilis xztubd1 (GenBank: MG458322.1) was isolated from a housefly's body, identified according to phenotypical and genotypical analyses, and found to produce large amounts of an EPS. Through ultraviolet spectroscopy and Fourier transform infrared spectroscopy (FTIR spectroscopy), the EPS was found to contain a variety of chemical functional groups, such as O-H groups, C=C, C=O, CH3, C-O-H and C-O-C bonds, and alpha-type pyranose. Furthermore, the in vitro antioxidant activity of the EPS on DPPH radicals at a concentration of 90 µg/ml was 62%; on the superoxide radical at a concentration of 90 µg/ml, this value was 75%; and on hydroxyl radicals at a concentration of 90 µg/ml, the activity was 54%. EPS also enhanced significantly phagocytosis, lysozyme activity in macrophages, IL-2 content in mice and inhibited dramatically the growth of HeLa cells. These results showed that the EPS with reductive groups have the strong capacity to scavenge reactive oxygen species (ROS), reinforce the immune system and inhibit the growth of cancer cell, which helps theirs hosts defence against many diseases, including inflammation and cancer. The EPS from Bacillus subtilis has the potential to be an anticancer and anti-inflammatory drug candidate in the pharmaceutical industries, which provide scientific evidence for the development and utilization of probiotic-derived medicines.

An exopolysaccharide from Bacillus subtilis alleviates airway inflammatory responses via the NF-κB and STAT6 pathways in asthmatic mice.

Bacillus subtilis is an intestinal probiotic for immune homeostasis and its exopolysaccharide (EPS) is known to possess anti-inflammatory and antioxidant properties. The underlying mechanisms are not yet fully understood. In the present study, we investigated the effects of the EPS (50, 100, 200 mg/kg) on airway inflammation in asthmatic mice. Our results showed that EPS treatment of asthmatic mice significantly alleviated pathological damage in the lungs, remarkably decreased the counts of total inflammatory cells including lymphocytes, and eosinophils in the bronchoalveolar lavage fluid (BALF) and reduced indexes of oxidative damage. Moreover, the expression of type II T-helper cell (Th2) cytokines (interleukin- (IL)4 and -5) subsequent to EPS treatment was found to be dramatically down-regulated in a concentration-dependent manner. Additionally, the EPS treatment reduced JAK1, STAT6 and nuclear factor-κB (NF-κB) expression in the lungs of asthmatic mice. Taken together, these results suggest that the EPS from B. subtilis alleviates asthmatic airway inflammation, which involves the reduction in reactive oxygen species (ROS) and the down-regulation of the STAT6 and NF-κB inflammatory pathways, which can further reduce Th2 cytokine expression and eosinophilic inflammation. Thus, our findings provide a potential mechanism through which the EPS mitigates asthma, suggesting that the EPS could be a potential source of an anti-asthmatic drug.

Sulfur dioxide-induced exacerbation of airway inflammation via reactive oxygen species production and the toll-like receptor 4/nuclear factor-κB pathway in asthmatic mice.

Sulfur dioxide (SO2) is a common air pollutant that can exacerbate asthmatic airway inflammation. The mechanisms underlying these effects are not yet fully understood. In this study, we investigated the effects of SO2 exposure (10 mg/m3) on asthmatic airway inflammation in ovalbumin-induced asthmatic mice. Our results showed that SO2 exposure alone induced slight airway injury, decreased superoxide dismutase activity, and increased nuclear factor-κB (NF-κB) expression in the lungs of mice. Moreover, SO2 exposure in asthmatic mice induced marked pathological damage, significantly increased the counts of inflammatory cells (e.g., macrophages, lymphocytes, and eosinophils) in bronchoalveolar lavage fluid, and significantly enhanced malondialdehyde and glutathione levels in the lungs. Moreover, the expression of toll-like receptor 4 (TLR4), NF-κB, pro-inflammatory cytokines (e.g., tumor necrosis factor α and interleukin-6), and type II T-helper cell (Th2) cytokines was found to be elevated in the mice exposed to SO2 and ovalbumin compared to those exposed to ovalbumin alone. These results suggest that SO2 amplifies Th2-mediated inflammatory responses, which involve reactive oxygen species and TLR4/NF-κB pathway activation; these can further enhance Th2 cytokine expression and eosinophilic inflammation. Thus, our findings provide important evidence to understand a potential mechanism through which SO2 may exacerbate airway asthmatic inflammation.

Sulfur dioxide enhance drought tolerance of wheat seedlings through H2S signaling.

Drought is one of the most common factors that limit plant growth and productivity. Sulfur dioxide (SO2) has recently been found to play a benefical role in protection of plants against environmental stress. In this study, we investigated the effect of SO2 on the physiological and molecular response of wheat seedlings to drought stress. Pretreatment with 10 mg/m3 SO2 significantly increased the survival rate and relative water content (RWC) of wheat seedlings under drought stress, indicating that pre-exposure to appropriate level of SO2 could enhance drought tolerance of plants. These responses were related to the enhanced proline accumulation in the drought-treated wheat seedlings that induced by SO2 pretreatment. Meanwhile, SO2 pretreatment increased the activities of superoxide dismutase (SOD) and peroxidase (POD), and effectively reduced the content of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in drought-treated wheat seedlings, suggesting SO2 could alleviate drought-induced oxidative damage by enhancing antioxidant defense system in plants. Expression analysis of transcription factor genes also showed that SO2 pretreatment decreased the expression of TaNAC69, but the expression of TaERF1 and TaMYB30 changed slightly and maintained at higher levels in wheat seedlings in response to drought stress. Furthermore, SO2 pretreatment triggered marked accumulation of hydrogen sulfide (H2S) in wheat seedlings under drought stress. When scavenged H2S by spraying Hypotaurine (HT), the activities of antioxidant enzymes and the expression of transcription factor genes were decreased, and the content of H2O2 and MDA increased to the level of drought treatment alone, suggesting a regulatory role of SO2-induced H2S in plant adaptation to drought stress. Together, this study indicated that SO2 enhanced drought tolerance of wheat seedlings through H2S signaling, and provided new strategy for enhancing plant tolerance to drought stress.

Photosynthetic responses of Arabidopsis to SO2 were related to photosynthetic pigments, photosynthesis gene expression and redox regulation.

Sulfur dioxide (SO2) is one of the most common and harmful air pollutants. High concentrations of SO2 can induce a series of defensive responses in Arabidopsis plants. However, the role of photosynthesis in the plant response to SO2 stress is not clear. Here, we report the photosynthetic responses of Arabidopsis plants to SO2 stress. Exposure to 30 mg/m3 SO2 decreased stomatal conductance (Gs) and transpiration rate (Tr) but increased photosynthetic pigments and net photosynthetic rate (Pn). The contents of carbohydrates and sucrose were not altered. The transcript levels of most genes related to photosystem II (PSII), cytochrome b6/f (Cytb6f), photosystem I (PSI) and carbon fixation were upregulated, revealing one important regulatory circuit for the maintenance of chloroplast homeostasis under SO2 stress. Exposure to SO2 triggered reactive oxygen species (ROS) generation, accompanied by increases in superoxide dismutase (SOD) activity and the contents of cysteine (Cys), glutathione (GSH) and non-protein thiol (NPT), which maintained cellular redox homeostasis. Together, our results indicated that chloroplast photosynthesis was involved in the plant response to SO2 stress. The photosynthetic responses were related to photosynthetic pigments, photosynthesis gene expression and redox regulation.

SO2 derivatives and As co-exposure promote liver cancer metastasis through integrin αvß3 activation.

Arsenic (As) and sulfur dioxide (SO2) are two environmental pollutants that have been shown to promote the development of human cancer. In recent years, due to increased pollution, humans are often exposed to SO2, in addition to As. Despite the development and implementation of standards for environment and air quality, cases of disease caused by As or SO2 continue to rise alarmingly. It is currently unknown whether simultaneous exposure to As and SO2 results in increased cancer promoting activity. In this study, concentrations of As and SO2 below the limits established by the world health organization (WHO) in force environmental standards (concentrations of As should be lower than 1×10-2 mg/L and SO2 should be lower than 50 µg/m3), were employed to investigate possible, long-term, synergistic effects of As and SO2, by using cell-based assays. We found that co-exposure to these pollutants significantly promotes HepG2 cancer cell migration, while As or SO2 alone have no remarkable effects. Integrins αvß3 play a key role in this process, as cilengitide, an integrin αvß3 inhibitor, substantially prevented As and SO2-induced cell migration. MMPs, IL-8, and TGF-ß were also involved in the induced cell migration. In summary, combined exposure to As and SO2 promotes integrin-dependent cell migration and may be of relevance for the activation of mechanisms underlying liver cancer progression.

Enhanced drought tolerance of foxtail millet seedlings by sulfur dioxide fumigation.

Recently, sulfur dioxide (SO2) has been considered to be a beneficial bio-regulator in animals. However, the positive roles of SO2 in plant adaptation to drought stress are still unclear. In this study, we investigated the physiological and molecular changes that are induced by SO2 fumigation to improve the drought tolerance of foxtail millet seedlings. The relative water content in the leaves of drought-stressed seedlings was significantly improved by pre-exposure to 30 mg/m3 SO2. These responses might be related to decreased stomatal apertures and a reduced leaf transpiration rate, which were induced by SO2 under drought conditions. In addition, the SO2 pretreatment markedly enhanced proline accumulation in the leaves of drought-stressed seedlings, which was supported by increased Δ1-pyrroline-5-carboxylate synthetase (P5CS) activity, decreased proline dehydrogenase (ProDH) activity, and the corresponding transcripts. Moreover, the SO2 application upregulated the enzyme activity of catalase (CAT) and peroxidase (POD) in the leaves of drought-stressed plants, as well as their transcripts, which contributed to the scavenging of hydrogen peroxide (H2O2) and alleviated drought-induced oxidative damage, as indicated by the decreased malondialdehyde (MDA) level in SO2-pretreated plants. Together, these results indicate that the application of SO2 might enhance drought tolerance by reducing stomatal apertures, increasing proline accumulation, and promoting antioxidant defence in foxtail millet seedlings. This study presents new insight into the beneficial roles of SO2 in plant responses to drought stress.

Arsenic and sulfur dioxide co-exposure induce renal injury via activation of the NF-κB and caspase signaling pathway.

Although emerging evidence suggests positive association of arsenic (As) or sulfur dioxide (SO2) exposure with human diseases, reports concerning the effects of co-exposure of As and SO2 are lacking. Moreover, there is insufficient information in the literature about As and SO2 co-exposure to renal injury. In this study, we focus on the environmental problems of excessive As and SO2 that co-exist in many coal consumption areas. We used both C57BL/6 mice and 293T cells to detect toxicities of As and SO2 exposure alone or in combination. Our results showed that co-exposure significantly increased the hazard compared with exposure to As or SO2 alone. Mouse kidney tissue slices showed that co-exposure caused more severe diffuse sclerosing glomerulonephritis than As and SO2 exposure alone. Meanwhile experiments showed that apoptosis was aggravated by co-exposure of As and SO2 in 293T cells. Because As and SO2 cause cell toxicity through increasing oxidative stress, next we detected ROS and other oxidative stress parameters, and the results showed oxidative stress was increased by co-exposure compared with the other three groups. The expression levels of downstream genes in the NF-κB and caspase pathways were higher in the co-exposure group than in the groups of As or SO2 exposure alone in mice and 293T cells. Based on the above results, co-exposure could induce higher toxicity in vitro and in vivo compared with single exposure to As or SO2, indicating that people living in places that contaminated by As and SO2 may have higher chance to get renal injury.

Long-term arsenite exposure induces testicular toxicity by redox imbalance, G2/M cell arrest and apoptosis in mice.

Inorganic arsenic (iAs), a ubiquitous element and a natural drinking water contaminant, has been found to impair male reproductive function. However, the effect of long-term exposure to arsenic on testis damage and its underlying mechanisms still require further evaluation. In the study, male C57BL/6 mice (4 weeks) were treated with sodium arsenite at the doses of 5 or 50 ppm arsenic via drinking water for 180 days. Sperm count, histology in testes, oxidative stress biomarkers, cell cycle progress and apoptosis were assessed. Our results showed that arsenite seriously destroyed the structure of the testes and reduced the sperm count. Arsenite significantly decreased the activity of total superoxide dismutase (T-SOD) and glutathione (GSH) content but increased the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) in testes. Furthermore, arsenite could induce G2/M phase arrest in testes, concurrent with a significant decrease in mRNA and protein levels of cdc2 and cyclin B1, the upregulation of p-cdc2, and an increase in mRNA levels of p53 and p21. Arsenite induced testicular apoptosis with a significant increase in Bax mRNA and protein levels, especially the caspase-3 activation. Testicular toxicity of the high dose group was stronger than that of the low dose group. In conclusion, testicular toxicity due to long-term exposure to arsenite may relate to oxidative damage, G2/M arrest and promoted apoptosis in the testes of mice, which contributed to the increased risk of spermatogenesis disorders and male infertility.

Reduced testosterone and Ddx3y expression caused by long-term exposure to arsenic and its effect on spermatogenesis in mice.

Arsenic (As) has been recognized as a cause of male reproductive toxicity. However, effects of long-term arsenic exposure (puberty-adult) on spermatogenesis, testosterone synthesis, and the expression of androgen binding protein (ABP) and Ddx3y remain unclear. The objective of this investigation was to explore these effects and the underlying mechanisms. Male mice were treated with 5 and 50 ppm arsenic for 6 months via drinking water. The results showed that arsenic reduced sperm count and sperm motility and enhanced the abnormal sperm percentage. The decrease in the number of spermatogenic cells and sperm in seminiferous tubules and the decline in the Johnsen score were observed in both arsenic-treated groups, suggesting spermatogenesis disorders. Moreover, arsenic diminished serum testosterone, along with the reduced expression of luteinizing hormone receptor (LHR), steroidogenic acute regulatory protein (StAR) and 17-ß-hydroxysteroid dehydrogenase (17ß-HSD) genes. Arsenic also down-regulated mRNA levels of ABP and Ddx3y in a dose-dependent manner. Meanwhile, the protein levels of StAR, 17ß-HSD and Ddx3y were significantly reduced in arsenic-treated groups. Taken together, these results suggest that the reduced testosterone through inhibition of the expression of multiple genes responsible for the biosynthesis, the damaged androgen homeostasis partially via lessening the expression levels of the ABP gene and the down-regulated expression of Ddx3y, may contribute to spermatogenesis disorders in mice exposed to arsenic.

Sulphur dioxide and arsenic affect male reproduction via interfering with spermatogenesis in mice.

As two potential environmental hazards, sulphur dioxide (SO2) and arsenic have adverse effects on male reproduction, but the mechanism of which and their combined toxicity are not clear. In this study, we investigate male reproductive toxicity with a focus on spermatogenesis by treating mice with 5 mg/m3 SO2 and/or 5 mg/L arsenic. Our results showed that arsenic exposure caused significant decreases in water and food consumption and body weight in mice, whereas these changes were not observed in the SO2-only group. Both SO2 and arsenic reduced sperm counts, increased the percentage of sperm malformation, and induced abnormal testicular pathological changes. Elevated H2O2 and MDA contents, declined T-SOD activity, decreased spermatogenic cell counts, enhanced caspase-3 activity, and increased TUNEL-positive cells were also observed in mice exposed to SO2 and/or arsenic. Moreover, SO2 and arsenic co-exposure changed the mRNA levels of Bax and Bcl-2, decreased serum testosterone levels, and downregulated the expression of steroidogenic-related genes (LHR, StAR, and ABP) in mice. These findings provide a new theoretical basis for understanding how SO2 and arsenic interfere with spermatogenesis leading to infertility. These results also suggest that SO2 and arsenic co-exposure likely result in an additive effect on male reproductive toxicity in mice.

Sulfur dioxide derivatives alleviate cadmium toxicity by enhancing antioxidant defence and reducing Cd2+ uptake and translocation in foxtail millet seedlings.

Sulfur dioxide (SO2) was recently proposed as a novel bio-regulator in mammals. However, the possible advantageous effects of SO2 in plant adaptation to heavy metal-contaminated environments are largely unknown. In the present study, using Na2SO3/NaHSO3 derivatives as SO2 donors, we investigated the possible roles and regulation mechanisms of SO2 in alleviating Cd2+ toxicity in foxtail millet seedlings. Exogenous SO2 derivatives (0.5 mM) application significantly reduced the seedling growth inhibition caused by Cd2+ stress. Cd2+-induced oxidative damage was also alleviated by SO2 derivatives, which was supported by the decreased malondialdehyde (MDA) level in the leaves of seedlings pretreated with SO2 derivatives. These responses were related to the enhanced activities of representative antioxidant enzymes, including catalase and superoxide dismutase, as well as the up-regulation of ascorbate-glutathione cycle, which contributed to the scavenging of Cd2+-elicited O2•－ and H2O2 within the leaves of foxtail millet seedlings. Also, SO2 derivative application promoted sulfur assimilation and increased the content of glutathione and phytochelatins, which may help to enhance Cd2+ detoxification capacity in foxtail millet seedlings. Moreover, application of SO2 derivatives caused down-regulation of the transcript expression levels of several genes involved in Cd2+ uptake and translocation, such as NRAMP1, NRAMP6, IRT1, IRT2, HMA2, and HMA4, thus resulting in reduced Cd2+ accumulation in the shoots and roots of Cd2+-stressed seedlings. Collectively, these results suggest that exogenous SO2 derivative application can alleviate oxidative damage and restrict Cd2+ buildup, thereby reducing Cd2+-induced growth inhibition in foxtail millet seedlings upon Cd2+ exposure. This novel finding indicates that the usage of SO2 derivatives may be an effective approach for enhancing Cd2+ tolerance in foxtail millet and other crops.

Aggravated gut inflammation in mice lacking the taste signaling protein α-gustducin.

Inflammatory bowel disease (IBD) is a debilitating immune-related condition that affects over 1.4 million Americans. Recent studies indicate that taste receptor signaling is involved in much more than sensing food flavor, and taste receptors have been localized in a variety of extra-oral tissues. One of the newly revealed functions of taste receptors and downstream signaling proteins is modulation of immune responses to microbes and parasites. We previously found that components of the taste receptor signaling pathway are expressed in subsets of the intestinal epithelial cells. α-Gustducin, a key G-protein α subunit involved in sweet, umami, and bitter taste receptor signaling, is expressed in the intestinal mucosa. In this study, we investigated the role of α-gustducin in regulation of gut mucosal immunity and inflammation using α-gustducin knockout mice in the dextran sulfate sodium (DSS)-induced IBD model. DSS is a chemical colitogen that can cause intestinal epithelial damage and inflammation. We analyzed DSS-induced colitis in α-gustducin knockout versus wild-type control mice after administration of DSS in drinking water. Our results show that the knockout mice had aggravated weight loss, diarrhea, intestinal bleeding, and inflammation over the experimental period compared to wild-type mice, concurrent with augmented immune cell infiltration and increased expression of TNF and IFN-γ but decreased expression of IL-13 and IL-5 in the colon. These results suggest that the taste receptor signaling pathway may play critical roles in regulating gut immune balance and inflammation.

Sulfur dioxide exposure enhances Th2 inflammatory responses via activating STAT6 pathway in asthmatic mice.

Sulfur dioxide (SO2) is one of potential risk factors for induction and/or exacerbation of asthma, but the underlying mechanisms are not well understood. In this study, we investigate the role of SO2 in asthma using a classical asthmatic model with allergic airway inflammation by treating C57BL/6 mice with ovalbumin (OVA) and/or 10 mg/m3 SO2. Our results showed that SO2 exposure alone induced slight pathological changes but did not significantly increase inflammatory cell counts, pro-inflammatory cytokine expression, and mucus production in the airway of mice, whereas SO2 exposure in OVA-induced asthmatic mice caused marked pulmonary pathological changes and significantly increased the counts of eosinophil-rich leukocytes compared with OVA alone asthmatic mice. The expression of MUC5AC, TNF-α, Th2 cytokines (IL-4, IL-5, and IL-13) and STAT6 was further up-regulated in OVA plus SO2 treated mice compared with OVA alone treated mice. In addition, exposure to SO2 alone markedly elevated STAT6 mRNA levels and hydrogen peroxide (H2O2) content in the lung. These findings suggest that SO2 amplifies Th2 inflammatory responses in OVA-induced asthmatic mice by activating STAT6, which can further induce Th2 cytokine expression. Induction of STAT6 expression might be an important mechanism underlying the increased risk for asthma after environmental exposure.

Enhanced Arabidopsis disease resistance against Botrytis cinerea induced by sulfur dioxide.

Sulfur dioxide (SO2) is a common air pollutant that has complex impacts on plants. The effect of prior exposure to 30mgm-3 SO2 on defence against Botrytis cinerea (B. cinerea) in Arabidopsis thaliana and the possible mechanisms of action were investigated. The results indicated that pre-exposure to 30mgm-3 SO2 resulted in significantly enhanced resistance to B. cinerea infection. SO2 pre-treatment significantly enhanced the activities of defence-related enzymes including phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), ß-1,3-glucanase (BGL) and chitinase (CHI). Transcripts of the defence-related genes PAL, PPO, PR2, and PR3, encoding PAL, PPO, BGL and CHI, respectively, were markedly elevated in Arabidopsis plants pre-exposed to SO2 and subsequently inoculated with B. cinerea (SO2+ treatment group) compared with those that were only treated with SO2 (SO2) or inoculated with B. cinerea (CK+). Moreover, SO2 pre-exposure also led to significant increases in the expression levels of MIR393, MIR160 and MIR167 in Arabidopsis. Meanwhile, the expression of known targets involved in the auxin signalling pathway, was negatively correlated with their corresponding miRNAs. Additionally, the transcript levels of the primary auxin-response genes GH3-like, BDL/IAA12, and AXR3/IAA17 were markedly repressed. Our findings indicate that 30mgm-3 SO2 pre-exposure enhances disease resistance against B. cinerea in Arabidopsis by priming defence responses through enhancement of defence-related gene expression and enzyme activity, and miRNA-mediated suppression of the auxin signalling pathway.