Guangzhe Li

Protective Effects of Salicylic Acid and Vitamin C on Sulfur Dioxide-Induced Lipid Peroxidation in Mice

The antioxidant effects of exogenous salicylic acid (SA) and vitamin C (Vit C) on the oxidative stress induced by 56 mg/m3 of sulfur dioxide (SO2) in mouse livers and brains were investigated. The exposure of SO2 caused significant elevation of thiobarbituric acid-reactive substance (TBARS) levels and reduction of enzyme activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in brain and liver, accompanied by a decrease in relative growth rate, when compared with controls. Application of moderate concentrations of SA and Vit C markedly reduced the SO2-induced elevation of TBARS levels, with 5.5 mg/kg SA or 200 mg/kg Vit C being most effective. In contrast to the decrease of TBARS levels, the levels of SOD, POD, and CAT in liver and brain were significantly increased in comparison with controls. The polyacrylamide gel electrophoresis (PAGE) of total liver proteins showed that the SO2 inhalation caused a 30-kD protein band disappearance compared with the control. However, the band remained unchanged in the samples treated with 5.5 and 8.25 mg/kg SA or 100, 200, and 400 mg/kg Vit C. Therefore, this protein band may serve as a marker for the damage induced by SO2 and an additional basis for drug screening and selection.

Role of endogenous salicylic acid in Arabidopsis response to elevated sulfur dioxide concentration

The response of Arabidopsis thaliana plants to elevated sulfur dioxide could be related to their endogenous salicylic acid (SA) content and signaling. The wild type (WT, ecotype Columbia) and its mutant snc1 with high SA content, npr1-1 with a blockage in SA signaling, transgenic line nahG with low SA content and double mutant snc1nahG plants were exposed to 0.5 mm3 dm−3 SO2 for 3 h d−1 for 14 d in a growth chamber. Under unstressed conditions, total SA contents in snc1 and npr1-1 were 7- and 2-fold higher than those in WT, respectively, but in nahG SA content was only 28 % of that in WT. The expression of nahG in snc1 plants decreased SA content to the WT level. Increased SA contents were observed in snc1, npr1-1 and WT after 12-h SO2 exposure, whereas no major changes were detected in nahG and snc1nahG plants. The snc1 plants exhibited higher tolerance to SO2 exposure than snc1nahG plants and especially nahG and npr1-1 plants according to plant biomass, total chlorophyll content and photosynthetic rate. The SO2 exposure decreased net photosynthetic rate, maximum photochemical efficiency (Fv/Fm) and actual quantum efficiency of photosystem 2 (ΦPS2). SO2-induced oxidative damage in the tested plants was confirmed by increased malondialdehyde (MDA) content and electrolyte leakage. Increases in superoxide dismutase (SOD) and peroxidase (POD) activity, reduced glutathione (GSH) content and a ratio of reduced/oxidized glutathione (GSSG) might be responsible for the decreased contents of H2O2 and alleviation of oxidative injury in snc1 plants compared with other lines exposed to SO2. These observations implied that endogenous SA content and signaling may play an essential role in plant responses to SO2 stress.

Combined effect of ethylene- and salicylic acid-signaling insensitive mutation on Arabidopsis response to low temperature

The roles of ethylene (ET) or salicylic acid (SA) in plant response to low temperature (LT, 5 °C) have been implicated. However, the combined effect of ET- and SA-signaling on plant growth and metabolism under LT remains to be evaluated. In this study, we comparatively analyzed the response of Arabidopsis ethylene insensitive (ein) 2-1 (an ET insensitive mutant), nonexprressor of pathogenesis relative (npr)1-1 (an SA insensitive mutant) and double mutant ein2-1/npr1-1 plants to LT. The results show that a LT of 5 °C induced plant growth retardation to a less degree in ein2-1, an intermediate degree in npr1-1, but a much larger in ein2-1/npr1-1 compared to the wild-type (WT) plants. The LT susceptibility of the ein2-1/npr1-1 plants was correlated to a lower net photosynthetic rate and proline content, and a higher content of H2O2 and malondialdehyde and electrolyte leakage relative to the WT plants. Lower activities of superoxide dismutase, peroxidase, and catalase, as well as a lower glutathione content and a ratio of its reduced form to its oxidized form were also observed in the double mutant plants as compared with the WT plants. However, at normal conditions (23 °C), all the tested physiological and biochemical parameters were comparable between the ein2-1/npr1-1 and WT plants, and plant growth was even better in the double mutant than in the WT plants. On the contrary, most of the above-mentioned parameters were advantageous in the ein2-1 and npr1-1 plants over the WT plants under the LT conditions. These data suggest that a parallel function or physiological redundancy of nonexpressor of pathogenesis relative 1 and ethylene insensitive 2 existed in the Arabidopsis plant response to the LT. On the other hand, an interaction between ET- and SA-signaling occurred during this process.

Protective effect of salicylic acid on Hg0intoxication in mice

Abstract Elemental mercury (Hg0) is a hazardous metal with significant human exposure through diverse sources. In this study, the role of salicylic acid (SA) was assessed against Hg0-induced injury in mice, with the aim of screening alternative clinical drugs to prevent or treat Hg0 poisoning. An exposure to Hg0 (1.0 mg/m3 in a glass box) for 2 h per day for successive 15 d significantly increased Hg accumulation in mouse brain and lung, inhibited the animal growth and altered the neurobehavior such as impairing the spatial learning and memory in the Barnes maze test. However, although oral SA (5.5 mg/kg body weight) during the Hg0 exposure did not reduce the Hg levels in these organs, it effectively counteracted the Hg0-induced growth inhibition, and improved the behavioral performance, accompanied by a series of ameliorations in the antioxidative defense and anti-inflammatory response. For instance, when compared with control, Hg0-inhaled animals had significant decreases in the activities of superoxide dismutase and peroxidase, and in the levels of reduced form of glutathione and the ratio to its oxidized form, concomitantly with a high accumulation of hydrogen peroxide and malondialdehyde in the brain and lung. However, these values in Hg0 + SA-exposed animals were comparable with the basal levels in control. Likewise, interleukin-6 in the brain and lung of Hg0-exposed animals were dramatically elevated, whereas it was maintained to the basal level in Hg0 + SA-exposed animals. These data suggested that application of SA could protect mice against Hg0-induced injury.

Attenuation of Sulfur Dioxide Damage to Wheat Seedlings by Co-exposure to Nitric Oxide.

The protective function of nitric oxide (NO) has been extensively clarified in plant responses to abiotic stresses. However, little is known about the regulation of NO in plants exposed to sulfur dioxide (SO2). In the present study, we found that co-exposure to NO significantly attenuated SO2-induced wheat seedling growth inhibition. Data showed that NO efficiently prevented SO2-triggered oxidative stress, as indicated by decreasing reactive oxygen species production, lipid peroxidation, and electrolyte leakage. This might be attributed to the regulatory role of NO in antioxidative defense, such as increasing the activities of antioxidative enzymes and the contents of non-enzymatic antioxidants. The SO2-caused declines in soluble protein and chlorophyll content were efficiently recovered by NO application. Photosynthetic parameters, such as net photosynthetic rate, maximum photochemical efficiency, and actual photochemical efficiency, were protected by NO. In conclusion, this study demonstrated that during SO2 exposure, co-application of NO can efficiently alleviate plant damage probably by regulating the antioxidative defense, and protecting plant photosynthesis-related process.