Linli Huang

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.

Arabidopsis ein2-1 and npr1-1 Response to Al Stress

An enhanced Al3+ tolerance has been observed in ethylene insensitive mutant ein2-1 and salicylic acid insensitive mutant npr1-1 of Arabidopsis. However, we found that the tolerant phenotype of ein2-1 and npr1-1 under Al stress was dependent on NPR and EIN function, respectively, because the double mutant ein2-1/npr1-1 displayed more sensitive to Al stress than wild-type plants. We analysed the differential performance between ein2-1/npr1-1 and their respective single mutant in response to Al stress, and found that antioxidant defence rather than malate exudation was the determinant factor.

Aluminum tolerance in Arabidopsis thaliana as affected by endogenous salicylic acid

Endogenous salicylic acid (SA) functions in plant response to an aluminum stress were assessed. We used different Arabidopsis thaliana genotypes including snc1 with a constitutively high content of SA, sid2 and nahG (transgenic lines) both with a low content of SA, SA insensitive mutant npr1-1, and snc1/nahG (i.e., the nahG expression in the snc1 background) with a similar SA content as in wild type (WT) plants. Results show that the snc1 plants displayed obvious growth retardation of roots and shoots under the Al3+ stress, whereas the sid2, nahG, and npr1-1 plants exhibited alleviated symptoms in comparison with the WT plants. The Al3+ content increased in all the tested genotypes with the increasing AlCl3 concentration applied, but no significant variations were detected among the tested genotypes. The snc1 had much higher superoxide dismutase and peroxidase activities, and a lower catalase activity and the ratio of reduced to oxidized glutathione accompanied by higher accumulations of H2O2 and malondialdehyde compared with the WT plants. These changes were largely reversed by the introduction of nahG; the sid2, nahG, and npr1-1 plants were less affected than WT plants in all the above-mentioned parameters. The Al3+ stress significantly enhanced malate exudation in all the tested genotypes, but no significant correlation was observed between the SA-involved response to the Al3+ stress and the malate exudation. Based on these data, it was concluded that the SA-related functions in Arabidopsis response to the Al3+ stress were associated with the control of oxidative stress, but not of malate exudation.

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.

Exogenous salicylic acid prevents nitrogen dioxide-induced oxidative injury and nitrate accumulation in Brassica campestris L. ssp. chinensis seedlings.

Summary An earlier study had shown that exposure to nitrogen dioxide (NO2) at 1.0 µl l–1 caused a decrease in plant biomass and an accumulation of nitrate in Brassica campestris seedlings. The present study was aimed at evaluating whether pre-treatment with salicylic acid (SA) could promote tolerance to NO2 and prevent NO2-induced nitrate accumulation in leaves, thus improving the quality of pak choi (B. campestris L. spp. chinensis). Thirty-day-old B. campestris plants grown in a 3:1 (v/v) soil:sand mix were sprayed with SA solutions at 0, 0.5, 1.0, or 1.5 mM and, after 24 h, fumigated with 1.0 µl l–1 NO2 for 6 h d–1 for 10 d in a growth chamber. The results showed that SA applied at 1.0 mM was most effective at reducing the NO2-induced decrease in biomass and accumulation of nitrate. The photosynthetic rate, chlorophyll content, maximum quantum efficiency, and nitrate reductase activity also achieved their highest values at this dose of SA compared to all other concentrations. Furthermore, the application of SA protected the activities of superoxide dismutase, peroxidase, and catalase in leaves, and maintained a high level of reduced glutathione and a high ratio of reduced:oxidised glutathione compared to non-SA-treated samples. This may be responsible for the decreased levels of H2O2, low malondialdehyde contents, and electrolyte leakage observed in SA-treated plant leaves. Our results suggest that exogenous SA may play an important role in plant responses to reduce NO2-induced stress and to reduce in vivo nitrate levels.