S-nitrosoglutathione诱导胸腺细胞凋亡的机制

目的 研究NO供体亚硝酰谷胱甘肽(GSNO)诱导胸腺细胞凋亡与p53表达的相互关系。方法 体外培养：BALB／C小鼠胸腺细胞，用地塞米松(DXM)作为阳性对照，再分别加不同剂量GSNO及NO抑制剂，孵育3h。用透射电镜观察胸腺细胞形态；用琼脂糖凝胶电泳检测DNA梯型带纹；采用末端脱氧核酸转移酶(TdT)介导的末端标记在流式细胞仪上检测胸腺细胞凋亡；用RT-PCR的方法分析抑癌基因p53的表达在此过程中的变化及作用。结果胸腺细胞在无巯基S-77培养液中孵育可产生自然凋亡，用不同处理后在透射电镜下可见各组早、中、晚期不同阶段的凋亡细胞的形态，琼脂糖电泳显示DXM组出现较多中、晚期凋亡的胸腺细胞，有明显的DNA梯形条纹，加不同剂量的NO和NO抑制剂组则较弱，NO浓度愈高则梯形条纹愈不明显，0．3mmol／L和0．6mmol／L GSNO呈早中期凋亡形态学变化，1．2mmol／LGSNO主要呈早期改变；PCR结果同DNA电泳结果基本一致；流式细胞仪检测各组的凋亡率也有相同的趋势，各组之间差异有显著性。结论 胸腺细胞在无巯基培养液内孵育3h会产生自然凋亡，GSNO诱导胸腺细胞凋亡随浓度增加反而抑制胸腺细胞凋亡，NOS抑制剂可抑制凋亡，NO供体GSNO通过p53的表达来诱导细胞凋亡是NO引起细胞凋亡的可能机制之一。

S-Nitrosoglutathion Reductase Activity Modulates the Thermotolerance of Seeds Germination by Controlling ABI5 Stability under High Temperature

Seed germination or dormancy status is strictly controlled by endogenous phytohormone and exogenous environment signals.Abscisic acid(ABA)is the important phytohormone to suppress seed germination.Ambient high temperature(HT)also suppressed seed germination,or called as secondary seed dormancy,through upregulating ABI5,the essential component of ABA signal pathway.Previous result shows that appropriate nitric oxide(NO)breaks seed dormancy through triggering S-nitrosoglutathion reductase(GSNOR1)-dependent S-nitrosylation modification of ABI5 protein,subsequently inducing the degradation of ABI5.Here we found that HT induced the degradation of GSNOR1 protein and reduced its activity,thus accumulated more reactive nitrogen species(RNS)to damage seeds viability.Furthermore,HT increased the S-nitrosylation modification of GSNOR1 protein,and triggered the degradation of GSNOR1,therefore stabilizing ABI5 to suppress seed germination.Consistently,the ABI5 protein abundance was lower in the transgenic line overexpressing GSNOR1,but higher in the gsnor mutant after HT stress.Genetic analysis showed that GSNOR1 affected seeds germination through ABI5 under HT.Taken together,our data reveals a new mechanism by which HT triggers the degradation of GSNOR1,and thus stabilizing ABI5 to suppress seed germination,such mechanism provides the possibility to enhance seed germination tolerance to HT through genetic modification of GNSOR1.

Hypoxia inducible factor-1 alpha stabilization for regenerative therapy in traumatic brain injury

Mild traumatic brain injury（TBI）, also called concussion, initiates sequelae leading to motor deficits, cognitive impairments and subtly compromised neurobehaviors. While the acute phase of TBI is associated with neuroinflammation and nitroxidative burst, the chronic phase shows a lack of stimulation of the neurorepair process and regeneration. The deficiency of nitric oxide（NO）, the consequent disturbed NO metabolome, and imbalanced mechanisms of S-nitrosylation are implicated in blocking the mechanisms of neurorepair processes and functional recovery in the both phases. Hypoxia inducible factor-1 alpha（HIF-1α）, a master regulator of hypoxia/ischemia, stimulates the process of neurorepair and thus aids in functional recovery after brain trauma. The activity of HIF-1α is regulated by NO via the mechanism of S-nitrosylation of HIF-1α. S-nitrosylation is dynamically regulated by NO metabolites such as S-nitrosoglutathione（GSNO） and peroxynitrite. GSNO stabilizes, and peroxynitrite destabilizes HIF-1α. Exogenously administered GSNO was found not only to stabilize HIF-1α and to induce HIF-1α-dependent genes but also to stimulate the regeneration process and to aid in functional recovery in TBI animals.

Superoxide and hydrogen peroxide productions by NO-inhibited complex Ⅲ

Complex Ⅲ plays a central role in the mitochondrial respiratory chain transferring electrons from ubiquinol to cytochrome c and pumping protons to the intermembrane space,contributing to the protonmotive force.Furthermore,complex Ⅲ can act as a source of O_(2^(·-))in the presence of ubiquinol and antimycin,an expermiental condition in which the oxidation of the cytochrome b hemes is blocked.The O_(2^(·-))dismutation catalyzed by superoxide dismutase produces H2O2,a known second messenger in redox signalling.Results from our laboratory have shown that NO,released from GSNO or from SPER-NO or generated by mtNOS,inhibits electron transfer at ubiquinone-cytochrome b area producing antimycin-like effects.Thus,both antimycin-and NO-inhibited complex Ⅲ showed a high content of cytochromes b in the reduced state(79 and 71%,respectively)and an enhancement in the ubisemiquinone EPR signal at g=1.99(42 and 35%,respectively).As consequence,O_(2^(·-))and H2O2 productions were increased,being the O_(2^(·-))/H_(2)O_(2) ratio equal to 1.98 in accordance with the stoichiometry of the O_(2^(·-))disproportionation.The interruption of the oxidation of cytochromes b by NO leads to an enhancement of the steady-state concentration of UQH·,allowing cytochrome bc1 complex to act as a source of reactive oxygen species in physiological conditions.

Loss of GSNOR1 Function Leads to Compromised Auxin Signaling and Polar Auxin Transport

Cross talk between phytohormones, nitric oxide （NO）, and auxin has been implicated in the control of plant growth and development. Two recent reports indicate that NO promoted auxin signaling but inhibited auxin transport probably through S-nitrosylation. However, genetic evidence for the effect of S-nitrosylation on auxin physiology has been lacking. In this study, we used a genetic approach to understand the broader role of S-nitrosylation in auxin physiology in Arabidopsis. We compared auxin signaling and transport in Col-0 and gsnorl-3, a loss-of-function GSNOR1 mutant defective in protein de-nitrosylation. Our results showed that auxin signaling was impaired in the gsnorl-3 mutant as revealed by significantly reduced DR5-GUS/ DR5-GFP accumulation and compromised degradation of AXR3NT-GUS, a useful reporter in interrogating auxin-mediated degradation of Aux/IAA by auxin receptors. In addition, polar auxin transport was compro- mised in gsnorl-3, which was correlated with universally reduced levels of PIN or GFP-PIN proteins in the roots of the mutant in a manner independent of transcription and 26S proteasome degradation. Our results suggest that S-nitrosylation and GSNORl-mediated de-nitrosylation contribute to auxin physiology, and impaired auxin signaling and compromised auxin transport are responsible for the auxin-related morpho- logical phenotypes displayed by the gsnorl-3 mutant.