Oxidative Stress Contributes to Status Epilepticus Associated Mortality

Status epilepticus is a common manifestation of nerve agent toxicity and represents a serious medical emergency with high rates of mortality and neurologic injury in those that survive. The aim of the current study was to determine if targeting oxidative stress with the catalytic antioxidant, AEOL10150, would reduce pilocarpine-induced mortality and attenuate neuronal death and neuroinflammation. We found that treatment with AEOL10150 in conjunction with scopolamine and diazepam following pilocarpine-induced SE was able to significantly reduce mortality compared to treatment with just scopolamine and diazepam. Mortality was further reduced when AEOL10150 was used in conjunction with atropine and diazepam which is considered the standard of care for nerve agent exposures. Both treatment paradigms offered significant protection against SE-induced oxidative stress. Additionally, treatment with scopolamine, AEOL10150 and diazepam attenuated SE-induced neuronal loss and neuroinflammation. Taken together, the data suggest that pharmacological targeting of oxidative stress can improve survival and attenuate secondary neurological damage following SE induced by the nerve agent surrogate pilocarpine.     

The Cch1-Mid1 High-Affinity Calcium Channel Contributes to the Virulence of Cryptococcus neoformans by Mitigating Oxidative Stress

Pathogenic fungi have developed mechanisms to cope with stresses imposed by hosts. For Cryptococcus spp., this implies active defense mechanisms that attenuate and ultimately overcome the onslaught of oxidative stresses in macrophages. Among cellular pathways within Cryptococcus neoformans'' arsenal is the plasma membrane high-affinity Cch1-Mid1 calcium (Ca²⁺) channel (CMC). Here we show that CMC has an unexpectedly complex and disparate role in mitigating oxidative stress. Upon inhibiting the Ccp1-mediated oxidative response pathway with antimycin, strains of C. neoformans expressing only Mid1 displayed enhanced growth, but this was significantly attenuated upon H₂O₂ exposure in the absence of Mid1, suggesting a regulatory role for Mid1 acting through the Ccp1-mediated oxidative stress response. This notion is further supported by the interaction detected between Mid1 and Ccp1 (cytochrome c peroxidase). In contrast, Cch1 appears to have a more general role in promoting cryptococci survival during oxidative stress. A strain lacking Cch1 displayed a growth defect in the presence of H₂O₂ without BAPTA [(1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid, cesium salt] or additional stressors such as antimycin. Consistent with a greater contribution of Cch1 to oxidative stress tolerance, an intracellular growth defect was observed for the cch1Δ strain in the macrophage cell line J774A.1. Interestingly, while the absence of either Mid1 or Cch1 significantly compromises the ability of C. neoformans to tolerate oxidative stress, the absence of both Mid1 and Cch1 has a negligible effect on C. neoformans growth during H₂O₂ stress, suggesting the existence of a compensatory mechanism that becomes active in the absence of CMC.     

PerR-Regulated Manganese Ion Uptake Contributes to Oxidative Stress Defense in an Oral Streptococcus

Metal homeostasis plays a critical role in antioxidative stress. Streptococcus oligofermentans, an oral commensal facultative anaerobe lacking catalase activity, produces and tolerates abundant H₂O₂, whereas Dpr (an Fe²⁺-chelating protein)-dependent H₂O₂ protection does not confer such high tolerance. Here, we report that inactivation of perR, a peroxide-responsive repressor that regulates zinc and iron homeostasis in Gram-positive bacteria, increased the survival of H₂O₂-pulsed S. oligofermentans 32-fold and elevated cellular manganese 4.5-fold. perR complementation recovered the wild-type phenotype. When grown in 0.1 to 0.25 mM MnCl₂, S. oligofermentans increased survival after H₂O₂ stress 2.5- to 23-fold, and even greater survival was found for the perR mutant, indicating that PerR is involved in Mn²⁺-mediated H₂O₂ resistance in S. oligofermentans. Mutation of mntA could not be obtained in brain heart infusion (BHI) broth (containing ∼0.4 μM Mn²⁺) unless it was supplemented with ≥2.5 μM MnCl₂ and caused 82 to 95% reduction of the cellular Mn²⁺ level, while mntABC overexpression increased cellular Mn²⁺ 2.1- to 4.5-fold. Thus, MntABC was identified as a high-affinity Mn²⁺ transporter in S. oligofermentans. mntA mutation reduced the survival of H₂O₂-pulsed S. oligofermentans 5.7-fold, while mntABC overexpression enhanced H₂O₂-challenged survival 12-fold, indicating that MntABC-mediated Mn²⁺ uptake is pivotal to antioxidative stress in S. oligofermentans. perR mutation or H₂O₂ pulsing upregulated mntABC, while H₂O₂-induced upregulation diminished in the perR mutant. This suggests that perR represses mntABC expression but H₂O₂ can release the suppression. In conclusion, this work demonstrates that PerR regulates manganese homeostasis in S. oligofermentans, which is critical to H₂O₂ stress defenses and may be distributed across all oral streptococci lacking catalase.     

Interaction of TNF with Angiotensin II Contributes to Mitochondrial Oxidative Stress and Cardiac Damage in Rats

Recent evidence suggests that tumor necrosis factor alpha (TNF) and angiotensin II (ANGII) induce oxidative stress contribute to cardiovascular disease progression. Here, we examined whether an interaction between TNF and ANGII contributes to altered cardiac mitochondrial biogenesis and ATP production to cause cardiac damage in rats. Rats received intraperitoneal injections of TNF (30 µg/kg), TNF + losartan (LOS, 1 mg/kg), or vehicle for 5 days. Left ventricular (LV) function was measured using echocardiography. Rats were sacrificed and LV tissues removed for gene expression, electron paramagnetic resonance and mitochondrial assays. TNF administration significantly increased expression of the NADPH oxidase subunit, gp91phox, and the angiotensin type 1 receptor (AT-1R) and decreased eNOS in the LV of rats. Rats that received TNF only had increased production rates of superoxide, peroxynitrite and total reactive oxygen species (ROS) in the cytosol and increased production rates of superoxide and hydrogen peroxide in mitochondria. Decreased activities of mitochondrial complexes I, II, and III and mitochondrial genes were observed in rats given TNF. In addition, TNF administration also resulted in a decrease in fractional shortening and an increase in Tei index, suggesting diastolic dysfunction. TNF administration with concomitant LOS treatment attenuated mitochondrial damage, restored cardiac function, and decreased expression of AT1-R and NADPH oxidase subunits. Mitochondrial biogenesis and function is severely impaired by TNF as evidenced by downregulation of mitochondrial genes and increased free radical production, and may contribute to cardiac damage. These defects are independent of the downregulation of mitochondrial gene expression, suggesting novel mechanisms for mitochondrial dysfunction in rats given TNF.     

新型光敏剂分子二乙醇胺基竹红菌乙素光诱导HeLa细胞死亡中的氧化应激研究

二乙醇胺基竹红菌乙素(2-ethanolamino-2-demethoxy-17-ethanolimino-hypocrellin B,EAHB)是一种新型的可吸收600 nm以上红光的竹红菌乙素衍生物。本文研究了二乙醇胺基竹红菌乙素-光动力诱导HeLa细胞死亡的效果及其氧化应激机制。结果发现,红光诱导后,MTT法检测到二乙醇胺基竹红菌乙素-光动力作用使HeLa细胞的存活率显著降低,且存活率与光敏剂浓度和光照剂量成反比;二乙醇胺基竹红菌乙素-光动力诱导HeLa细胞内产生活性氧自由基;同时,胞内超氧化物歧化酶和还原型谷胱甘肽水平显著降低,细胞脂质过氧化标志分子丙二醛显著升高,并检测到细胞质膜损伤标志分子乳酸脱氢酶的渗出显著增加。研究结果说明新型光敏剂二乙醇胺基竹红菌乙素可有效光诱导肿瘤细胞死亡,而细胞内氧化应激反应可能是二乙醇胺基竹红菌乙素光诱导肿瘤细胞死亡的重要作用机制。     

Ralstonia solanacearum Dps Contributes to Oxidative Stress Tolerance and to Colonization of and Virulence on Tomato Plants

Ralstonia solanacearum, an economically important soilborne plant pathogen, infects host roots to cause bacterial wilt disease. However, little is known about this pathogen''s behavior in the rhizosphere and early in pathogenesis. In response to root exudates from tomato, R. solanacearum strain UW551 upregulated a gene resembling Dps, a nonspecific DNA binding protein from starved cells that is critical for stress survival in other bacteria. An R. solanacearum dps mutant had increased hydrogen peroxide sensitivity and mutation rate under starvation. Furthermore, dps expression was positively regulated by the oxidative stress response regulator OxyR. These functional results are consistent with a Dps annotation. The dps mutant caused slightly delayed bacterial wilt disease in tomato after a naturalistic soil soak inoculation. However, the dps mutant had a more pronounced reduction in virulence when bacteria were inoculated directly into host stems, suggesting that Dps helps R. solanacearum adapt to conditions inside plants. Passage through a tomato plant conferred transient increased hydrogen peroxide tolerance on both wild-type and dps mutant strains, demonstrating that R. solanacearum acquires Dps-independent oxidative stress tolerance during adaptation to the host environment. The dps mutant strain was also reduced in adhesion to tomato roots and tomato stem colonization. These results indicate that Dps is important when cells are starved or in stationary phase and that Dps contributes quantitatively to host plant colonization and bacterial wilt virulence. They further suggest that R. solanacearum must overcome oxidative stress during the bacterial wilt disease cycle.Bacterial wilt caused by Ralstonia solanacearum is a lethal disease affecting diverse economically important crops worldwide (20). The pathogen attacks over 200 species in more than 50 plant families (21). Although known primarily as a soilborne plant pathogen, R. solanacearum also survives in soil, water, and latently infected plants (20). The bacterium typically invades its host through natural or mechanical root wounds, multiplies in the root cortex, and then rapidly colonizes the xylem, where it reaches high cell densities. Once wilt symptoms develop, plants usually die, releasing the pathogen back into the soil (42).R. solanacearum is a tropical bacterium adapted to warmer climates, with the exception of a clonal group belonging to phylotype II, sequevar 1, of the R. solanacearum species complex (13). This group, historically and for regulatory purposes known as race 3 biovar 2 (R3bv2), causes brown rot of potato and bacterial wilt of tomato in tropical highlands and some temperate zones (11, 41, 45, 46). Because of its virulence at relatively cool temperatures, R3bv2 is a quarantine pest in Europe and Canada and a select agent pathogen in the United States (27).R. solanacearum virulence is quantitative and complex, with many contributing factors such as type II-secreted proteins, type III-secreted effectors, extracellular polysaccharide, and several plant cell wall-degrading enzymes (16, 17, 36, 38). Much of what is known about R. solanacearum comes from studies focusing on mid- or end-stage disease caused by tropical or warm-temperate strains (8, 30). A few virulence factors are known to function early in disease development: motility, energy taxis, and type IV pili, which collectively direct the bacterium toward and facilitate attachment to the host root (26, 44, 49, 50). However, R. solanacearum traits that contribute to fitness and virulence in the rhizosphere are not well understood for either tropical or R3bv2 strains.In soil, bacteria experience environmental stressors, such as pH and temperature extremes and water and oxygen limitation, as well as competition for nutrients (47). Plant roots release exudates and sloughed-off cells, supplying sufficient energy to sustain large microbial communities, provided other nutrients such as N, P, and Fe are present (19, 47). While rhizosphere bacteria can enjoy rapid growth in this relatively rich environment, fluctuating nutrient availability means that soil-dwelling microbes must survive periods of starvation (47).R. solanacearum also encounters oxidative stress in the rhizosphere. Plant roots produce reactive oxygen species (ROS) in response to many stimuli (25, 32). Several studies implicate ROS in root development and in interactions between roots and microbes (5, 24). We previously found that during plant colonization R. solanacearum is exposed to host-derived ROS, which triggers a bacterial oxidative stress response that adapts the pathogen to the xylem environment and is necessary for full virulence (8, 14).We previously described an in vivo expression technology (IVET)-like screen that identified R. solanacearum genes upregulated in the tomato rhizosphere (12). These genes encoded several known bacterial wilt virulence factors, such as the type 3 secretion regulator HrpG, the type IV pilus assembly protein PilP, global virulence regulator VsrA, and early virulence regulator PehR. The screen further identified a high-affinity cytochrome c oxidase necessary for R. solanacearum growth in microaerobic conditions (12). This paper presents our analysis of another rhizosphere-induced gene that encodes Dps, a DNA binding protein from starved cells originally described in Escherichia coli (2). Dps belongs to a family of ferritin-like stress-induced proteins that bind nonspecifically to DNA in stationary-phase bacteria (2, 29, 40). In E. coli, Dps helps maintain DNA integrity under environmentally challenging conditions, including starvation, oxidative damage, pH shock, and thermal stress (2, 10, 18, 29, 33). Dps also protects the soilborne plant-associated bacteria Agrobacterium tumefaciens and Pseudomonas putida from oxidative stress (9, 37).Traits that adapt R. solanacearum to detrimental conditions in the rhizosphere are likely to be important for pathogenic success. We hypothesized that Dps is required for adaptation to nutrient and oxidative stress and, thus, for bacterial wilt disease development. We found that Dps was highly expressed after starvation and contributed to oxidative stress tolerance in starved R. solanacearum cells. Furthermore, this protein was necessary for wild-type bacterial wilt disease development and for colonization of tomato xylem, suggesting that the bacterium must overcome a nutrient-poor and/or oxidative environment in the rhizosphere and xylem of host plants.     

长穗颈水稻的内源GA1、IAA和ABA含量变化

分别以携有长穗颈基因eui1、eui2和野生型基因Eui的协青早不育系和保持系6个水稻品种为材料,测定它们在抽穗始期植株中内源GA1、IAA和ABA含量的变化。结果表明,携有eui1和eui2基因的水稻可以在植株体内产生大量内源GA1,携有eui1基因的GA1含量比携有eui2基因的高。携有eui1基因的ABA含量最高,携有eui2基因的其次,而携有Eui基因的最低。IAA含量也表现出同样的趋势。表明长穗颈基因主要是通过调节内源GA1含量促进水稻最上节间的剧烈伸长。     

OsGSTU6 Contributes to Cadmium Stress Tolerance in Rice by Involving in Intracellular ROS Homeostasis

Journal of Plant Growth Regulation - Glutathione S-transferases (GSTs) are multifunctional proteins that play important roles in cellular detoxification as well as in plant growth and development....     

ABA Inducible Rice Protein Phosphatase 2C Confers ABA Insensitivity and Abiotic Stress Tolerance in Arabidopsis

Arabidopsis PP2C belonging to group A have been extensively worked out and known to negatively regulate ABA signaling. However, rice (Oryza sativa) orthologs of Arabidopsis group A PP2C are scarcely characterized functionally. We have identified a group A PP2C from rice (OsPP108), which is highly inducible under ABA, salt and drought stresses and localized predominantly in the nucleus. Genetic analysis revealed that Arabidopsis plants overexpressing OsPP108 are highly insensitive to ABA and tolerant to high salt and mannitol stresses during seed germination, root growth and overall seedling growth. At adult stage, OsPP108 overexpression leads to high tolerance to salt, mannitol and drought stresses with far better physiological parameters such as water loss, fresh weight, chlorophyll content and photosynthetic potential (Fv/Fm) in transgenic Arabidopsis plants. Expression profile of various stress marker genes in OsPP108 overexpressing plants revealed interplay of ABA dependent and independent pathway for abiotic stress tolerance. Overall, this study has identified a potential rice group A PP2C, which regulates ABA signaling negatively and abiotic stress signaling positively. Transgenic rice plants overexpressing this gene might provide an answer to the problem of low crop yield and productivity during adverse environmental conditions.     

Downregulation of PHLPP Expression Contributes to Hypoxia-Induced Resistance to Chemotherapy in Colon Cancer Cells

Hypoxia is a feature of solid tumors. Most tumors are at least partially hypoxic. This hypoxic environment plays a critical role in promoting resistance to anticancer drugs. PHLPP, a novel family of Ser/Thr protein phosphatases, functions as a tumor suppressor in colon cancers. Here, we show that the expression of both PHLPP isoforms is negatively regulated by hypoxia/anoxia in colon cancer cells. Interestingly, a hypoxia-induced decrease of PHLPP expression is attenuated by knocking down HIF1α but not HIF2α. Whereas the mRNA levels of PHLPP are not significantly altered by oxygen deprivation, the reduction of PHLPP expression is caused by decreased protein translation downstream of mTOR and increased degradation. Specifically, hypoxia-induced downregulation of PHLPP is partially rescued in TSC2 or 4E-BP1 knockdown cells as the result of elevated mTOR activity and protein synthesis. Moreover, oxygen deprivation destabilizes PHLPP protein by decreasing the expression of USP46, a deubiquitinase of PHLPP. Functionally, downregulation of PHLPP contributes to hypoxia-induced chemoresistance in colon cancer cells. Taken together, we have identified hypoxia as a novel mechanism by which PHLPP is downregulated in colon cancer, and the expression of PHLPP may serve as a biomarker for better understanding of chemoresistance in cancer treatment.     

GA3、ABA对未成熟‘博Ⅱ优15’水稻种子萌发的影响

以未成熟水稻'博II优15'种子为材料,用不同浓度GA3、ABA浸种24 h,研究其对水稻种子萌发的影响.结果表明,GA3 0.10～2.00 g/L处理能极显著促进种子萌发,其中0.50 g/L效果最好,第4天发芽率高于对照(CK)56%;浓度大于0.50 g/L ABA处理显著抑制种子萌发;GA3与ABA协同处理时, GA3/ABA = 1:1(浓度0.05 g/L)和 GA3/ABA = 1:2(浓度0.01 g/L)均能极显著促进种子萌发,第7天种子发芽率分别比CK高30%和20%.进一步研究表明,GA3和ABA对未成熟水稻种子萌发的影响与α-淀粉酶活性相关.     

氧化胁迫下稻苗体内积累的脯氨酸的抗氧化作用

水稻幼苗在外源·OH和1O2氧化胁迫下,体内脯氨酸明显积累,而和H2O2处理对稻苗体内脯氨酸含量无影响。强光亦能诱导稻苗体内脯氨酸积累。脯氨酸预处理则显著抑制·OH、1O2及强光所诱导的稻苗膜脂过氧化作用。在活性氧的产生／检测系统中,脯氨酸对·OH和1O2所引发反应有明显的竞争效应,但对和H2O2的作用没有形响。这些都表明,氧化胁迫下稻苗体内积累的脯氨酸具有抗氧化作用;脯氨酸对活性氧的清除有一定的专一性,即只对·OH和1O2有明显的清除活性。     

Seasonal Changes of GA1, GA19 and Abscisic Acid in Three Rice Cultivars

The levels of endogenous gibberellin A₁ and A₁₉ (GA₁ and GA₁₉)and abscisic acid (ABA) in three rice (Oryza sativa L.) cultivars,Nihonbare (normal), Tan-ginbozu (semid-warf) and Tong-il (semi-dwarf),were measured at various stages of internode elongation andear development. GA₁₉ was the main GA in Nihonbare and Tong-ilthroughout the life cycle but was not detected in Tan-ginbozu.The levels of GA₁ in the ears of all three cultivars were lowand reached their maxima after anthesis. Similarly, the earsof all three cultivars contained high ABA levels which peakedafter anthesis. Shoots contained low quantities of ABA throughoutthe life cycle. The roles of GAs and ABA are discussed withrespect to physiological phenomena, such as internode elongation,ear development and dwarfism. (Received May 9, 1981; Accepted July 18, 1981)     

水稻叶片中过氧化氢与核酮糖-1，5-二磷酸羧化酶/加氧酶降解的关系

甲基紫精(MV)处理水稻植株能快速诱导核酮糖-1,5-二磷酸羧化酶／加氧酶(Rubisco,EC4．1．1．39)及其它可溶性蛋白的降解。MV浓度越高,降解速率越高。MV能诱发叶片内源H     

OsJAR1 Contributes Mainly to Biosynthesis of the Stress-Induced Jasmonoyl-Isoleucine Involved in Defense Responses in Rice

Jasmonate plays key roles in plant growth and stress responses, as in defense against pathogen attack. Jasmonoyl-isoleucine (JA-Ile), a major active form of jasmonates, is thought to play a pivotal role in plant defense responses, but the involvement of JA-Ile in rice defense responses, including phytoalexin production, remains largely unknown. Here we found that OsJAR1 contributes mainly to stress-induced JA-Ile production by the use of an osjar1 Tos17 mutant. The osjar1 mutant was impaired in JA-induced expression of JA-responsive genes and phytoalexin production, and these defects were restored genetically. Endogenous JA-Ile was indispensable to the production of a flavonoid phytoalexin, sakuranetin, but not to that of diterpenoid phytoalexins in response to heavy metal stress and the rice blast fungus. The osjar1 mutant was also found to be more susceptible to the blast fungus than the parental wild type. These results suggest that JA-Ile production makes a contribution to rice defense responses with a great impact on stress-induced sakuranetin production.