Cell disruption of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> using active extracellular substances from <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> ITRI-G1 is a programmed cell death event

Microalgae are rich resources for high-value nutrients and biodiesel production. However, extraction of these valuable compounds from them requires costly energy-consuming procedures due to their rigid cell walls. Application of cell-disruptive agents, the AES-Bt agents, extracted from an algicidal bacterium, Bacillus thuringiensis ITRI-G1, are a promising way to reduce the cost of cell disruption. Treatment with AES-Bt agents resulted in a rapid decline of photosynthesis ability and caused cell death in Chlorella vulgaris. Hallmarks of programmed cell death (PCD), including chromatin condensation, DNA fragmentation, and phosphatidylserine externalization, were detected in C. vulgaris cells treated with the AES-Bt agents. Therefore, the cell disruption effect caused by application of the AES-Bt agents can be due to the occurrence of PCD. Similar to other PCDs, the PCD caused by AES-Bt agents was also associated with increased reactive oxygen species (ROS). However, co-treatments with diphenyleneiodonium chloride (DPI), an NAD(P)H oxidase inhibitor, or N,N′-dimethylthiourea (DMTU), a hydrogen peroxide (H₂O₂) trap, with the AES-Bt agents successfully reduced ROS production, and more cells displayed a feature of PCD detected after the co-treatments. In conclusion, the AES-Bt agents can promote PCD of microalgae; however, the mechanism may not be through induction of ROS.     

Multiple mediators of plant programmed cell death: interplay of conserved cell death mechanisms and plant-specific regulators

Programmed cell death (PCD) is a process aimed at the removal of redundant, misplaced, or damaged cells and it is essential to the development and maintenance of multicellular organisms. In contrast to the relatively well-described cell death pathway in animals, often referred to as apoptosis, mechanisms and regulation of plant PCD are still ill-defined. Several morphological and biochemical similarities between apoptosis and plant PCD have been described, including DNA laddering, caspase-like proteolytic activity, and cytochrome c release from mitochondria. Reactive oxygen species (ROS) have emerged as important signals in the activation of plant PCD. In addition, several plant hormones may exert their respective effects on plant PCD through the regulation of ROS accumulation. The possible plant PCD regulators discussed in this review are integrated in a model that combines plant-specific regulators with mechanisms functionally conserved between animals and plants.     

水稻细胞质雄性不育系幼穗发育过程中多胺与乙烯的关系初探(英文 )

利用ＨＰＬＣ和ＧＣ分别测定了水稻细胞质雄性不育系及其保持系幼穗多胺（ 腐胺,亚精胺和精胺） 含量和乙烯释放速率,并研究了外施多胺合成抑制剂ＭＧＢＧ 和乙烯前体ＡＣＣ生成抑制剂ＡＶＧ 对两系幼穗多胺含量和乙烯释放速率以及花粉育性的影响。结果表明, 不育系幼穗乙烯释放速率显著高于其保持系幼穗, 外施ＡＶＧ 引起两系幼穗乙烯释放速率下降,并使不育系花粉育性得以部分恢复; 不育系幼穗多胺含量显著低于保持系幼穗, 外施ＭＧＢＧ 使两系幼穗Ｓｐｄ 和Ｓｐｍ 含量下降, 并使保持系花粉育性降低。外施ＡＶＧ 抑制乙烯释放,促进多胺合成;而外施ＭＧＢＧ 抑制Ｓｐｄ和Ｓｐｍ 合成, 却促进乙烯的释放; 而且,乙烯释放速率与多胺（精胺和亚精胺） 含量呈显著负相关。提示在水稻ＣＭＳ 系及其保持系幼穗发育过程中乙烯与多胺（ 精胺和亚精胺） 的生物合成竞争ＳＡＭ。     

Glucocorticoids induce apoptosis in human monocytes: potential role of IL-1 beta.

Glucocorticoids (GC) are potent anti-inflammatory and immunosuppressive agents that act on a variety of immune cells, including monocytes and macrophages. However, the exact cellular mechanisms underlying this anti-inflammatory capacity are still unknown. In our study, we determined the induction of apoptosis by GC in human monocytes. Peripheral blood monocytes were isolated by density centrifugation methods with a purity of >90% and were cultured in RPMI 1640 medium. Monocyte apoptosis was determined by four independent methods, including annexin-V staining, TUNEL, DNA-laddering, and typical morphology by means of transmission electron microscopy. TNF-alpha and IL-1beta were measured by ELISA. GC receptor was blocked with mifepristone. Caspase 3 was inhibited with caspase-3 inhibitor (DEVD-CHO). Stimulation with different GC at therapeutic concentrations resulted in monocyte apoptosis in a time- and dose-dependent manner. Necrosis was excluded by propidium iodide staining. Proinflammatory cytokines such as IL-1beta and TNF-alpha were down-regulated by GC treatment. Continuous treatment of monocytes with IL-1beta, but not with TNF-alpha, could almost completely prevent GC-induced cell death. The addition of mifepristone or caspase-3 inhibitor could partially abrogate GC-induced apoptosis as well as GC-induced inhibition of IL-1beta. This is the first study to demonstrate induction of apoptosis by GC in human monocytes. GC-induced monocyte apoptosis may be partially mediated through effects on IL-1beta production. It is conceivable that GC exert their anti-inflammatory capacity in various diseases, at least in part, by the induction of apoptosis in monocytes.     

A critical role for ethylene in hydrogen peroxide release during programmed cell death in tomato suspension cells

Camptothecin, a topo isomerase-I inhibitor used in cancer therapy, induces apoptosis in animal cells. In tomato (Lycopersicon esculentum Mill.) suspension cells, camptothecin induces cell death that is accompanied by the characteristic nuclear morphological changes such as chromatin condensation and nuclear and DNA fragmentation that are commonly associated with apoptosis in animal systems. These effects of camptothecin can effectively be blocked by inhibitors of animal caspases, indicating that, in tomato suspension cells, camptothecin induces a form of programmed cell death (PCD) with similarities to animal apoptosis (A.J. De Jong et al. (2000) Planta 211:656-662). Camptothecin induced cell death was employed to study processes involved in plant PCD. Camptothecin induced a transient increase in H2O2 production starting within 2 h of application. Both camptothecin-induced cell death and the release of H2O2 were effectively blocked by application of the calcium-channel blocker lanthanum chloride, the caspase-specific inhibitor Z-Asp-CH2-DCB, or the NADPH oxidase inhibitor diphenyl iodonium, indicating that camptothecin exerts its effect on cell death through a calcium- and caspase-dependent stimulation of NADPH oxidase activity. In addition, we show that ethylene is an essential factor in camptothecin-induced PCD. Inhibition of either ethylene synthesis or ethylene perception by L-alpha-(2-aminoethoxyvinyl)glycine or silver thiosulphate, respectively, blocked camptothecin-induced H2O2 production and PCD. Although, in itself, insufficient to trigger H2O2 production and cell death, exogenous ethylene greatly stimulated camptothecin-induced H2O2 production and cell death. These results show that ethylene is a potentiator of the camptothecin-induced oxidative burst and subsequent PCD in tomato cells. The possible mechanisms by which ethylene stimulates cell death are discussed.     

Molecular ordering of ROS production,mitochondrial changes,and caspase activation during sodium salicylate-induced apoptosis

Salicylates and nonsteroidal anti-inflammatory drugs (NSAIDs) induce apoptosis in a variety of cancer cells, including those of colon, prostate, breast, and leukemia. We examined the effects of sodium salicylate (NaSal) on reactive oxygen species (ROS) production and the association of these effects with apoptotic tumor cell death. We demonstrate that NaSal mediates ROS production followed by a decrease in mitochondrial membrane potential (deltapsi(m)), release of cytochrome c, and activation of caspase-9 and caspase-3. However, expression of Bcl-2 or Bcl-x(L) prevents ROS production and subsequent loss of deltapsi(m), thereby inhibiting apoptotic cell death. The presence of ROS scavengers and an inhibitor of NADPH oxidase or expression of a dominant negative form of Rac1 blocks ROS production, deltapsi(m) collapse, and the subsequent activation of caspases. These observations indicate that NaSal mediates ROS production critical in the triggering of apoptotic tumor cell death through a Rac1-NADPH oxidase-dependent pathway. Our data collectively imply that NaSal-induced ROS are key mediators of deltapsi(m) collapse, which leads to the release of cytochrome c followed by caspase activation, culminating in tumor apoptosis.     

Proteasome function is required for activation of programmed cell death in heat shocked tobacco Bright-Yellow 2 cells

To find out whether and how proteasome is involved in plant programmed cell death (PCD) we measured proteasome function in tobacco cells undergoing PCD as a result of heat shock (HS-PCD). Reactive oxygen species (ROS) production, cytochrome c levels and caspase-3-like protease activation were also measured in the absence or presence of MG132, a proteasome inhibitor. We show that proteasome activation occurs in early phase of HS-PCD upstream of the caspase-like proteases activation; moreover inhibition of proteasome function by MG132 results in prevention of PCD perhaps due to the prevention of ROS production, cytochrome c release and caspase-3-like protease activation.     

Reactive oxygen species contribute to the release of volatile organic compounds from Chlamydomonas reinhardtii during programmed cell death

Acetic acid at pH 5.0 can induce programmed cell death (PCD) in Chlamydomonas reinhardtii cells, and abundant volatile organic compounds (VOCs) were released during the process. In this study, the caspase‐3‐like activity was determined during the PCD, and it was increased significantly after 1 h. During the PCD, the dynamic release of VOCs from the cells was analyzed, and the emissions of total VOCs were raised markedly and reached the highest level at 2 h. Among the seven types of VOCs, such as alkanes, alkenes, terpenoids, alcohols, aldehydes, ketones and esters, three oxygenated compounds (aldehydes, ketones and esters) showed the most significant increase. O₂^‐· and H₂O₂ were rapidly accumulated to high levels in the cells at the beginning of the PCD, but their content was reduced during the process. The activities of antioxidant enzymes were reduced gradually and even disappeared completely, demonstrating that the reduction of reactive oxygen species (ROS) may not be scavenged by the antioxidant enzyme system. ROS have an intense oxidation and scavenging ability to volatile compounds, and the oxidation results in the production of oxygenated compounds. Therefore, the abundant production of oxygenated compounds indicated that ROS may play an important role in the dynamic release of VOCs from C. reinhardtii cells during PCD.     

Pimaradienoic Acid Inhibits Carrageenan-Induced Inflammatory Leukocyte Recruitment and Edema in Mice: Inhibition of Oxidative Stress,Nitric Oxide and Cytokine Production

Pimaradienoic acid (PA; ent-pimara-8(14),15-dien-19-oic acid) is a pimarane diterpene found in plants such as Vigueira arenaria Baker (Asteraceae) in the Brazilian savannas. Although there is evidence on the analgesic and in vitro inhibition of inflammatory signaling pathways, and paw edema by PA, its anti-inflammatory effect deserves further investigation. Thus, the objective of present study was to investigate the anti-inflammatory effect of PA in carrageenan-induced peritoneal and paw inflammation in mice. Firstly, we assessed the effect of PA in carrageenan-induced leukocyte recruitment in the peritoneal cavity and paw edema and myeloperoxidase activity. Next, we investigated the mechanisms involved in the anti-inflammatory effect of PA. The effect of PA on carrageenan-induced oxidative stress in the paw skin and peritoneal cavity was assessed. We also tested the effect of PA on nitric oxide, superoxide anion, and inflammatory cytokine production in the peritoneal cavity. PA inhibited carrageenan-induced recruitment of total leukocytes and neutrophils to the peritoneal cavity in a dose-dependent manner. PA also inhibited carrageenan-induced paw edema and myeloperoxidase activity in the paw skin. The anti-inflammatory mechanism of PA depended on maintaining paw skin antioxidant activity as observed by the levels of reduced glutathione, ability to scavenge the ABTS cation and reduce iron as well as by the inhibition of superoxide anion and nitric oxide production in the peritoneal cavity. Furthermore, PA inhibited carrageenan-induced peritoneal production of inflammatory cytokines TNF-α and IL-1β. PA presents prominent anti-inflammatory effect in carrageenan-induced inflammation by reducing oxidative stress, nitric oxide, and cytokine production. Therefore, it seems to be a promising anti-inflammatory molecule that merits further investigation.     

Sulindac-derived reactive oxygen species induce apoptosis of human multiple myeloma cells via p38 mitogen activated protein kinase-induced mitochondrial dysfunction

Non-steroidal anti-inflammatory drugs are well known to induce apoptosis of cancer cells independent of their ability to inhibit cyclooxygenase-2, but the molecular mechanism for this effect has not yet been fully elucidated. The purpose of this study was to elucidate the potential signaling components underlying sulindac-induced apoptosis in human multiple myeloma (MM) cells. We found that sulindac induces apoptosis by promoting ROS generation, accompanied by opening of mitochondrial permeability transition pores, release of cytochrome c and apoptosis inducing factor from mitochondria, followed by caspase activation. Bcl-2 cleavage and down-regulation of the inhibitor of apoptosis proteins (IAPs) family including cIAP-1/2, XIAP, and survivin, occurred downstream of ROS production during sulindac-induced apoptosis. Forced expression of survivin and Bcl-2 blocked sulindac-induced apoptosis. Most importantly, sulindac-derived ROS activated p38 mitogen-activated protein kinase and p53. SB203580, a p38 mitogen-activated protein kinase inhibitor, and RNA inhibition of p53 inhibited the sulindac-induced apoptosis. Furthermore, p53, Bax, and Bak accumulated in mitochondria during sulindac-induced apoptosis. All of these events were significantly suppressed by SB203580. Our results demonstrate a novel mechanism of sulindac-induced apoptosis in human MM cells, namely, accumulation of p53, Bax, and Bak in mitochondria mediated by p38 MAPK activation downstream of ROS production.     

Oxalic acid is an elicitor of plant programmed cell death during Sclerotinia sclerotiorum disease development

Accumulating evidence supports the idea that necrotrophic plant pathogens interact with their hosts by controlling cell death. Sclerotinia sclerotiorum is a necrotrophic ascomycete fungus with a broad host range (>400 species). Previously, we established that oxalic acid (OA) is an important pathogenicity determinant of this fungus. In this report, we describe a mechanism by which oxalate contributes to the pathogenic success of this fungus; namely, that OA induces a programmed cell death (PCD) response in plant tissue that is required for disease development. This response exhibits features associated with mammalian apoptosis, including DNA laddering and TUNEL reactive cells. Fungal mutants deficient in OA production are nonpathogenic, and apoptotic-like characteristics are not observed following plant inoculation. The induction of PCD by OA is independent of the pH-reducing abilities of this organic acid, which is required for sclerotial development. Moreover, oxalate also induces increased reactive oxygen species (ROS) levels in the plant, which correlate to PCD. When ROS induction is inhibited, apoptotic-like cell death induced by OA does not occur. Taken together, we show that Sclerotinia spp.-secreted OA is an elicitor of PCD in plants and is responsible for induction of apoptotic-like features in the plant during disease development. This PCD is essential for fungal pathogenicity and involves ROS. Thus, OA appears to function by triggering in the plant pathways responsible for PCD. Further, OA secretion by Sclerotinia spp. is not directly toxic but, more subtly, may function as a signaling molecule.     

In vitro evaluation of antioxidant and anti-inflammatory properties of genistein-modified hemodialysis membranes

Genistein-modified poly(amide):poly(vinyl pyrrolidone) (PA:PVP/G) hemodialysis membranes have been fabricated by coagulation via solvent (dimethyl sulfoxide, DMSO)/nonsolvent (water) exchange. The antioxidant and anti-inflammatory properties of the unmodified PA:PVP membranes were evaluated in vitro using human blood. It was found that these unmodified PA:PVP membranes were noncytotoxic to peripheral blood mononuclear cells (PBMC) but raised intracellular reactive oxygen species (ROS) levels. Pure genistein (in DMSO solution) was not only nontoxic to PBMC, but also suppressed the ROS levels in a manner dependent on genistein dosage. A similar dose-dependent suppression of ROS was found in genistein-modified PA (i.e., PA/G) membranes. However, the PVP addition had little or no effect in the suppression of ROS levels for the ternary PA:PVP/G system; the membrane ROS suppression was largely controlled by the genistein dosage. The levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin (IL-6) in whole blood were measured by ex vivo stimulation with lipopolysaccharide (LPS). The unmodified PA:PVP membranes drastically increased the level of TNF-α; however, the concentration of IL-1β and IL-6 remained almost the same. The PA/G membranes reduced the concentration of IL-1β and TNF-α even at very low genistein loadings, but it required a higher genistein loading to realize a similar effect in the case of IL-6. Of particular importance is that the genistein-modified blend membranes (PA:PVP/G) showed greater suppression of the concentrations of all three cytokines (TNF-α, IL-1β, and IL-6) in comparison with those of the PA/G membranes, signifying the role of PVP in the enhanced anti-inflammatory properties of these genistein-modified membranes. Ultraviolet-visible (UV-vis) spectroscopy was employed to quantify any genistein leaching during the in vitro testing.     

Effect of common sage plant treatment with polyamines on the contents of proline and free and conjugated polyamines under oxidative stress

Common sage (Salvia officinalis L.) plants grown in water culture to the stage of 4–5 true leaves were treated with paraquat (PQ) ( 1 ml of the solution containing 0.1 μM PQ in 0.05% Tween 80), putrescine (Put), spermidine (Spd), or Spermine (Spm) (all polyamines (PA) at the concentration of 0.5 mM in 0.05% Tween 80) or PA plus PQ for 6, 12, 24, 36, or 48 h. Under normal conditions, treatment with individual PA did not induce any changes in the content of free proline. Under oxidative stress induced by PQ, oxidation of proline and free PA by ROS resulted in their spending and demanded restoration of free PA due to hydrolysis of their insoluble conjugates. As distinct from treatment with PQ only, its combination with PA in the light was accompanied by proline accumulation. Treatment with Put plus PQ induced accumulation of intracellular Put and its soluble and insoluble conjugates. Treatments with Spd and Spm in combination with PQ resulted similarly in the increase in the levels of their intracellular soluble and insoluble conjugates. In treatments with these high-molecular PA, polyamine oxidase was activated and diaminopropan formation was observed. It seems likely that, for restoration of high-molecular PA homeostasis, their degradation by polyamine oxidase or production of insoluble conjugates is induced. Thus, the amount of free and conjugated particular PA is under strict control and is maintained at a definite level. A decrease in the content of a particular free PA induces primarily a decrease in the content of its soluble and then insoluble conjugates. The data obtained demonstrate the effects of exogenous PA on the content of intracellular proline under oxidative stress but do not allow a conclusion about direct regulation of its content by PA.     

Apoptosis in Wheat Seedlings Grown under Normal Daylight

Apoptosis was observed in the coleoptile and initial leaf in 5-8-day-old wheat seedlings grown under normal daylight. Apoptosis is an obligatory event in early wheat plant ontogenesis, and it is characterized by cytoplasmic structural reorganization and fragmentation, in particular, with the appearance in vacuoles of specific vesicles containing intact organelles, chromatin condensation and margination in the nucleus, and internucleosomal fragmentation of nuclear DNA. The earliest signs of programmed cell death (PCD) were observed in the cytoplasm, but the elements of apoptotic degradation in the nucleus appeared later. Nuclear DNA fragmentation was detected after chromatin condensation and the appearance in vacuoles of specific vesicles containing mitochondria. Two PCD varieties were observed in the initial leaf of 5-day-old seedlings grown under normal daylight: a proper apoptosis and vacuolar collapse. On the contrary, PCD in coleoptiles under various growing (light) conditions and in the initial leaf of etiolated seedlings is only a classical plant apoptosis. Therefore, various tissue-specific and light-dependent PCD forms do exist in plants. Amounts of O2*- and H2O2 evolved by seedlings grown under normal daylight are less than that evolved by etiolated seedlings. The amount of H2O2 formed in the presence of sodium salicylate or azide by seedlings grown under normal daylight was increased. Contrary to etiolated seedlings, the antioxidant BHT (ionol) did not inhibit O2*- formation and apoptosis and it had no influence on ontogenesis in the seedlings grown under normal daylight. Thus, in plants grown under the normal light regime the powerful system controlling the balance between formation and inactivation of reactive oxygen species (ROS) does exist and it effectively functions. This system is responsible for maintenance of cell homeostasis, and it regulates the crucial ROS level controlling plant growth and development. In etiolated plants, this system seems to be absent, or it is much less effective.     

Regulation of mitochondrial NAD pool via NAD+ transporter 2 is essential for matrix NADH homeostasis and ROS production in Arabidopsis

Reactive oxygen species(ROS) play a crucial role in numerous biological processes in plants, including development, responses to environmental stimuli, and programmed cell death(PCD). Deficiency in MOSAIC DEATH 1(MOD1), a plastid-localized enoyl-ACP reductase essential for de novo fatty acid biosynthesis in Arabidopsis thaliana, leads to the increased malate export from chloroplasts to mitochondria, and the subsequent accumulation of mitochondria-generated ROS and PCD. In this study, we report the identification and characterization of a mod1 suppressor, som592. SOM592 encodes mitochondrion-localized NAD~+ transporter 2(NDT2). We show that the mitochondrial NAD pool is elevated in the mod1 mutant. The som592 mutation fully suppressed mitochondrial NADH hyper-accumulation, ROS production, and PCD in the mod1 mutant, indicating a causal relationship between mitochondrial NAD accumulation and ROS/PCD phenotypes. We also show that in wild-type plants, the mitochondrial NAD+uptake is involved in the regulation of ROS production in response to continuous photoperiod. Elevation of the alternative respiration pathway can suppress ROS accumulation and PCD in mod1, but leads to growth restriction. These findings uncover a regulatory mechanism for mitochondrial ROS production via NADH homeostasis in Arabidopsis thaliana that is likely important for growth regulation in response to altered photoperiod.     

家榆种子老化过程中ROS-类caspse-3途径的初步研究

以家榆种子为试材,在37℃、100%相对湿度下进行老化处理后,结合DAPI染色和细胞原位末端脱氧核苷酸转移酶标记法(TUNEL)、激光共聚焦技术以及生化分析,检测家榆种子人工诱导老化过程中细胞核、活性氧(ROS)和类半胱氨酸天冬氨酸蛋白酶3(caspase-3)活性的变化.结果显示:随着老化程度加深,种子细胞染色质皱缩、凝聚,继而解体并被排出体外;表皮中最先发现TUNEL凋亡核,而后逐渐延伸到子叶和胚轴;老化处理5d时种子活性氧信号最强,且其与程序性死亡相关事件的发生具有时空一致性,同时在胞浆中检测到较强的caspase-3活性.研究表明,家榆种子人工老化可导致细胞程序性死亡,且存在与ROS迸发及类caspase-3相关联的信号通路.     

Programmed cell death induced by cadmium stress and/or boron deprivation in tobacco (Nicotiana tabacum L.) cultivar Bright Yellow 2 cells

Cadmium (Cd) is one of the most toxic and widespread heavy metal pollutants in soil. As an essential mineral nutrient, boron (B) plays critical roles in physiological processes of plants. In the present study, programmed cell death (PCD) induced by Cd stress and/or B deprivation was assessed and the underlying mechanisms were clarified in suspension-cultured Nicotiana tabacum L. cultivar Bright Yellow 2 (TBY-2) cells. The PCD in TBY-2 cells was analyzed by Hoechst 33258 staining and the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, and then, expression analysis of PCD-related genes was performed using quantitative real-time polymerase chain reaction (qPCR) assays. The production of reactive oxygen species (ROS) was determined using fluorescence microscopy of 2′,7′-dichlorofluorescein diacetate–labeled cells. The levels of lipid peroxides were quantified by the thiobarbituric acid–reactive substances (TBARS) method. Cadmium stress and/or B deprivation treatments induced PCD that was characterized by a significant increase in the percentage of cells stained with Hoechst 33258 or TUNEL-positive cells, and upregulation or downregulation of the expression of PCD-related genes. Treatments with Cd stress and/or B deprivation increased ROS production and the level of lipid peroxides compared to those of the control group. These data showed that in TBY-2 cells Cd stress and/or B deprivation activated ROS signaling pathways, leading to gene expression that was connected with the PCD process.

     

Interactions between reactive oxygen species, ethylene and polyamines in leaves of Glycyrrhiza inflata seedlings under root osmotic stress

The interactions between reactive oxygen species (ROS), ethylene (ETH) and polyamines (PAs) in leaves of Glycyrrhiza inflata seedlings under root osmotic stress are reported. The results showed that the interactions between ROS, ETH and PAs were quite diverse at different degrees of damage. In slightly damaged leaves, the inhibition of ETH synthesis had no significant influence on ROS production and the content of putrescine (Put), spermidine (Spd) and spermine (Spm); the inhibition of Put synthesis had no significant influence on the production of ROS and ETH. However, in seriously damaged leaves, the inhibition of ETH production alleviated the increase in ROS production and the decrease in the content of Put, Spd and Spm; the reduction in polyamine content promoted the increase in the production of ROS and ETH; furthermore, exogenous H₂O₂ accelerated the increase in ETH production and the decrease in the content of these amines. Thus, it can be concluded that there is a close relationship between ROS content and the levels of ETH and PAs in the seriously damaged leaves. ROS production was modulated by the inhibition in ETH production and the reduction in polyamine content. Conversely, ROS promoted ETH production and reduced the polyamine content.     

Differential regulation of human monocyte programmed cell death (apoptosis) by chemotactic factors and pro-inflammatory cytokines

In the absence of appropriate stimuli, monocytes undergo programmed cell death (PCD) or apoptosis. IL-1 beta and TNF-alpha prevent monocyte PCD, which suggests that viability may be regulated by biologically active peptides released during inflammation. To explore this possibility, we evaluated several chemotactic factors and pro-inflammatory cytokines for their ability to regulate PCD. The recruitment factors, FMLP, C fragment C5a, monocyte chemotactic protein-1, or transforming growth factor-beta 1, were incapable of rescuing monocytes from PCD nor did they enhance PCD, whereas several inflammatory cytokines in addition to IL-1 beta and TNF-alpha, including granulocyte-monocyte-CSF and IFN-gamma, prevented monocyte PCD provided that sufficient levels of these cytokines were continuously maintained in the cultures. Cytokine-mediated inhibition of PCD could be blocked by specific antisera, ruling out potential effects caused by LPS contamination. When tested at equivalent concentrations, IL-2, IL-4, and IL-6 had no effect on PCD indicating selectivity in cytokine modulation of monocyte PCD. Because monocytes produce IL-1 beta, TNF-alpha, and granulocyte-monocyte CSF when activated, the data suggest autocrine as well as paracrine control of cell survival and accumulation. The results also suggest that monocytes recruited to a site of inflammation will undergo PCD in the absence of specific cytokines and/or other stimuli that block this process.