NADPH oxidase-dependent H2O2 production mediates salicylic acid-induced salt tolerance in mangrove plant Kandelia obovata by regulating Na+/K+ and redox homeostasis.

Salicylic acid (SA) is known to enhance salt tolerance in plants. However, the mechanism of SA-mediated response to high salinity in halophyte remains unclear. Using electrophysiological and molecular biological methods, we investigated the role of SA in response to high salinity in mangrove species, Kandelia obovata, a typical halophyte. Exposure of K. obovata roots to high salinity resulted in a rapid increase in endogenous SA produced by phenylalanine ammonia lyase pathway. The application of exogenous SA improved the salt tolerance of K. obovata, which depended on the NADPH oxidase-mediated H2O2. Exogenous SA and H2O2 increased Na+ efflux and reduced K+ loss by regulating the transcription levels of Na+ and K+ transport-related genes, thus reducing the Na+/K+ ratio in the salt-treated K. obovata roots. In addition, exogenous SA-enhanced antioxidant enzyme activity and its transcripts, and the expressions of four genes related to AsA-GSH cycle as well, then alleviated oxidative damages in the salt-treated K. obovata roots. However, the above effects of SA could be reversed by diphenyleneiodonium chloride (the NADPH oxidase inhibitor) and paclobutrazol (a SA biosynthesis inhibitor). Collectively, our results demonstrated that SA-induced salt tolerance of K. obovata depends on NADPH oxidase-generated H2O2 that affects Na+/K+ and redox homeostasis in response to high salinity.

Brassinosteroid enhances salt tolerance via S-nitrosoglutathione reductase and nitric oxide signaling pathway in mangrove Kandelia obovata.

Brassinosteroid (BR) has been shown to modulate plant tolerance to various stresses. S-nitrosoglutathione reductase (GSNOR) is involved in the plant response to environment stress by fine-turning the level of nitric oxide (NO). However, whether GSNOR is involved in BR-regulated Na+ /K+ homeostasis to improve the salt tolerance in halophyte is unknown. Here, we firstly reported that high salinity increases the expression of BR-biosynthesis genes and the endogenous levels of BR in mangrove Kandelia obovata. Then, salt-induced BR triggers the activities and gene expressions of GSNOR and antioxidant enzymes, thereafter decrease the levels of malondialdehyde, hydrogen peroxide. Subsequently, BR-mediated GSNOR negatively regulates NO contributions to the reduction of reactive oxygen species generation and induction of the gene expression related to Na+ and K+ transport, leading to the decrease of Na+ /K+ ratio in the roots of K. obovata. Finally, the applications of exogenous BR, NO scavenger, BR biosynthetic inhibitor and GSNOR inhibitor further confirm the function of BR. Taken together, our result provides insight into the mechanism of BR in the response of mangrove K. obovata to high salinity via GSNOR and NO signaling pathway by reducing oxidative damage and modulating Na+ /K+ homeostasis.

[Effect of Electroacupuncture Stimulation of "Guanyuan" (CV 4) and "Zusanli" (ST 36) on Spleen Lymphocytes Treg/Th 17 Immune Balance in Ulcerative Colitis Mice].

OBJECTIVE: To observe the effect of electroacupuncture (EA) intervention on spleen T-helper 17 (Th 17) and regulatory T (Treg) cell levels in mice with ulcerative colitis (UC), so as to reveal its mechanisms underlying improvement of UC. METHODS Kunming mice were randomized into control, UC model and EA groups, with 8 mice in each group. The UC model was established by giving the mice with 3% Dextran Sulfate Sodium (DSS) for 5 days. EA (15 Hz/25 Hz, 0.1-0.2 mA) was applied at "Guanyuan" (CV 4) and bilateral "Zusanli" (ST 36, used alternatively) for 10 min, once a day for 5 days. The animals' disease activity index [DAl, = (body weight index score + stool score + bleeding score)/3; 0-4 points] were calculated. The pathological changes of colon tissues were observed by light microscopy after H. E. stain, and spleen Treg (CD4⁺ CD²5⁺ Foxp³âº Treg) and Th 17 (CD³âº CD8⁺ IL-17⁺ Th 17) lymphocyte levels were determined by flow cytometry. RESULTS: Compared to the control group, the DAl score and the ratio of Th 17/CD8⁺ T cells were significantly increased, while the ratio of Treg/CD4⁺ T cells obviously decreased in the model group (P < 0.05). After EA intervention, the increased DAI score and the ratio of Th 17/CD8⁺ T cells and the decreased Treg/CD4⁺ T cells were reversed (P < 0.05), and the inflammatory cell infiltration degree of the colon tissue was attenuated. CONCLUSION: EA intervention can improve the, UC rats' symptoms of activity state, bloody or viscidity stool and colonic inflammation, probably by regulating the balance between the spleenic Treg and Th 17 lymphocytes.

[Effect of pentoxifylline on the expression of hepatic TGF-beta 1, type I and type III collagen in mice with liver fibrosis due to Schistosoma japonicum infection].

OBJECTIVE: To study the effect of pentoxifylline (PTX) on the content of hepatic TGF-beta 1, type I and type III collagen in schistosome-infected mice with liver fibrosis. METHODS: Forty mice with schistosomiasis were divided into four groups: one group as control without any treatment, other three were treated with praziquantel 500 mg/(kg.d) for 2 d, high dose PTX 360 mg/(kg.d) for 8 wk, and low dose PTX 180 mg/(kg.d) for 8 wk respectively. Immunohistochemical technique and multimedia color pathographic analysis system were applied to observe the content of hepatic TGF-beta 1, type I and type III collagen in mice infected with S. japonicum before and after treatment. RESULTS: The effect of PTX on the content of hepatic TGF-beta 1, type I and type III collagen in mice was related to the dosage of PTX. High dose PTX treatment significantly reduced the content of TGF-beta 1, type I and type III collagen compared to the control (P < 0.01), whereas no difference was found between the group of low dose PTX treatment and control (P > 0.05). CONCLUSION: High dose PTX treatment could reduce the content of hepatic TGF-beta 1, type I and type III collagen significantly in schistosome-infected mice with liver fibrosis.