Dormancy of<Emphasis Type="Italic"> Arabidopsis</Emphasis> seeds and barley grains can be broken by nitric oxide

Seeds of Arabidopsis thaliana (L.) Heynh. and grains of barley (Hordeum vulgare L.) were used to characterize the affects of nitric oxide (NO) on seed dormancy. Seeds of the C24 and Col-1 ecotypes of Arabidopsis are almost completely dormant when freshly harvested, but dormancy was broken by stratification for 3 days at 4°C or by imbibition of seeds with the NO donor sodium nitroprusside (SNP). This effect of SNP on dormancy of Arabidopsis seeds was concentration dependent. SNP concentrations as low as 25 M reduced dormancy and stimulated germination, but SNP at 250 M or more impaired seedling development, including root growth, and inhibited germination. Dormancy was also reduced when Arabidopsis seeds were exposed to gasses that are generated by solutions of SNP. Nitrate and nitrite, two other oxides of nitrogen, reduced the dormancy of Arabidopsis seeds, but much higher concentrations of these were required compared to SNP. Furthermore, the kinetics of germination were slower for seeds imbibed with either nitrate or nitrite than for seeds imbibed with SNP. Although seeds imbibed with SNP had reduced dormancy, seeds imbibed with SNP and abscisic acid (ABA) remained strongly dormant. This may indicate that the effects of ABA action on germination are downstream of NO action. The NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3 oxide (cPTIO) strengthened dormancy of unstratified and briefly stratified Arabidopsis seeds. Dormancy of three cultivars of barley was also reduced by SNP. Furthermore, dormancy in barley grain was strengthened by imbibition of grain with cPTIO. The data presented here support the conclusion that NO is a potent dormancy breaking agent for seeds and grains. Experiments with the NO scavenger suggest that NO is an endogenous regulator of seed dormancy.Abbreviations ABA Abscisic acid - cPTIO 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3 oxide - GA Gibberellin - SNP Sodium nitroprusside - NO_x Gaseous oxides of nitrogen     

N-Acetylcysteine ameliorates lipopolysaccharide-induced organ damage in conscious rats

Lipopolysaccharide is strongly associated with septic shock, leading to multiple organ failure. It can activate monocytes and macrophages to release proinflammatory mediators such as tumor necrosis factor- (TNF-), interleukin-1 (IL-1), and nitric oxide (NO). The present experiments were designed to induce endotoxin shock by an intravenous injection ofKlebsiella pneumoniae lipopolysaccharide (LPS, 10 mg/kg) in conscious rats. Arterial pressure and heart rate (HR) were continuously monitored for 48 h after LPS administration. N-Acetyl-cysteine was used to study its effects on organ damage. Biochemical substances were measured to reflect organ functions. Biochemical factors included blood urea nitrogen (BUN), creatinine (Cre), lactic dehydrogenase (LDH), creatine phosphokinase (CPK), aspartate transferase (GOT), alanine transferase (GPT), TNF-, IL-1, methyl guanidine (MG), and nitrites/nitrates. LPS caused significant increases in blood BUN, Cre, LDH, CPK, GOT, GPT, TNF-, IL-1, MG levels, and HR, as well as a decrease in mean arterial pressure and an elevation of nitrites/nitrates. N-Acetylcysteine suppressed the release of TNF-, IL-1, and MG, but enhanced NO production. These actions ameliorate LPS-induced organ damage in conscious rats. The beneficial effects may suggest a potential chemopreventive effect of this compound in sepsis prevention and treatment.     

β-Arrestin-1 protects against endoplasmic reticulum stress/p53-upregulated modulator of apoptosis-mediated apoptosis via repressing p-p65/inducible nitric oxide synthase in portal hypertensive gastropathy

Portal hypertensive gastropathy (PHG) is a serious cause of bleeding in patients, and is associated with portal hypertension. β-Arrestins (β-arrestin-1 and β-arrestin-2) are well-established mediators of endocytosis of G-protein-coupled receptors (GPCRs), ubiquitination, and G-protein-independent signaling. The role of β-arrestin-1 (β-arr1) in mucosal apoptosis in PHG remains unclear. The aim of this study was to investigate the involvement of β-arr1 in PHG via its regulation of endoplasmic reticulum (ER) stress/p53-upregulated modulator of apoptosis (PUMA) apoptotic signaling. Gastric mucosal injury and apoptosis were studied in PHG patients and in PHG mouse models. The induction of β-arr1 and the ER stress/PUMA signaling pathway were investigated, and the mechanisms of β-arr1-regulated gastric mucosal apoptosis were analyzed in vivo and in vitro experiments. β-arr1 and ER stress/PUMA signaling elements were markedly induced in the gastric mucosa of PHG patients and mouse models. Blockage of ER stress demonstrably attenuated the mucosal apoptosis of PHG, while targeted deletion of β-arr1 significantly aggravated the injury and ER stress/PUMA-mediated apoptosis. β-arr1 limited the activation of p65 to repress TNF-α-induced inducible nitric oxide synthase (iNOS) expression and NO release, which could regulate ER stress/PUMA-mediated mucosal apoptosis in PHG. In vivo and in vitro experiments further demonstrated that β-arr1 protected against mucosal apoptosis by repressing TNF-α-induced iNOS expression via inhibiting the activation of p65. These results indicated that β-arr1 regulated ER stress/PUMA-induced mucosal epithelial apoptosis through suppression of the TNF-α/p65/iNOS signaling pathway activation and that β-arr1 is a potential therapeutic target for PHG.     

Nitric Oxide Participates in the Induction of Brain Ischemic Tolerance via Activating ERK1/2 Signaling Pathways

The present study was undertaken to observe in vivo changes of expression and phosphorylation of ERK1/2 proteins during brain ischemic preconditioning and effects of inhibiting generation of nitric oxide (NO) on the changes to determine the role of ERKs in the involvement of NO participating in the acquired tolerance. Fifty-five Wistar rats were used. Brain ischemic preconditioning was performed with four-vessel occlusion for 3 min. Total ERK1/2 proteins and phospho-ERK1/2 in the CA1 hippocampus were assayed with Western immunoblot. Total ERK1/2 proteins did not change in period from 5 min to 5 days of reperfusion after preconditioning stimulus. While the level of phospho-ERK1/2 increased obviously to 223, 237, 300, 385 and 254% of sham level at times of 5 min, 2 h, 1, 3 and 5 days after preconditioning stimulus, respectively (P < 0.01). Administration of L-NAME, an inhibitor of NO synthase, 30 min prior to preconditioning stimulus failed to induce change in total ERK1/2 proteins (P > 0.05). However, phospho-ERK1/2 increased only to 138 and 176% of sham level at 2 h and 3 days after preconditioning stimulus, respectively, when animals were pretreated with L-NAME. The magnitudes of the increase were obviously low compared with those (237 and 385%) in animals untreated with L-NAME at corresponding time points (P < 0.01), which indicated that phosphorylation of ERK1/2 normally induced by preconditioning stimulus was blocked apparently by administration of L-NAME. The results suggested that phosphorylation of ERK1/2, rather than synthesis of ERK1/2 proteins, was promoted in brain ischemic preconditioning, and that the promotion was partly mediated by NO signal pathway.     

Nitric oxide synthase inhibitors influence dynorphin A (1-17) immunoreactivity in the rat brain following hyperthermia

Summary.  The possibility that nitric oxide synthase (NOS) inhibitors influence dynorphin immunoreactivity following hyperthermia was examined in a rat model using a pharmacological approach. Previous reports from our laboratory show that hyperthermia induces an upregulation of NOS in several brain regions that seems to be instrumental in causing cell injury. Recent reports suggest that nitric oxide (NO) can influence dynorphin neurotransmission in the normal brain as well as in several pathological states. Since dynorphin is neurotoxic in different animal models of brain or spinal cord injury, it may be that the peptide will contribute to the cell injury in hyperthermia. The present investigation was carried out to determine whether hyperthermia can influence dynorphin immunoreactivity in the brain, and if so, whether inhibition of NOS will influence the peptide distribution in the brain following heat stress. Rats subjected to hyperthermia at 38°C for 4 h in a biological oxygen demand incubator (BOD) resulted in a marked upregulation of dynorphin immunoreactivity in several brain regions e.g., cerebral cortex, hippocampus, cerebellum and brain stem. Pretreatment of rats with two potent NOS inhibitors, L-NAME (30 mg/kg/day, i.p. for 7 days) or L-NMMA (35 mg/kg/day, i.p. for 7 days) significantly attenuated the dynorphin immunoreactivity in the brain. These drugs were also able to reduce hyperthermia induced blood-brain barrier (BBB) permeability, brain edema formation and cell injury. Taken together, our results suggest that (i) hyperthermia has the capacity to upregulate dynorphin immunoreactivity in the brain, (ii) inhibition of NOS considerably attenuates the dynorphin immunoreaction following heat stress and (iii) upregulation of dynorphin is somehow contributing to hyperthermia induced brain damage, not reported earlier. Received July 3, 2001 Accepted August 6, 2001 Published online July 31, 2002     

Forskolin and 3-Isobutyl-l-Methylxanthine Increase Basal and Sodium Nitroprusside-Elevated Cyclic GMP Levels in Adult Guinea-Pig Cerebellar Slices

Abstract: In this study, the interaction between 3′,5′-cyclic adenosine monophosphate (cAMP) and 3′,5′-cyclic guanosine monophosphate (cGMP) in [³H]adenine-or [³H]-guanine-prelabelled adult guinea-pig cerebellar slices was investigated. Basal levels of [³H]cGMP were enhanced by forskolin, although no plateau was reached over the concentration range tested (0.1-100 μM). However, forskolin elicited a concentration-dependent, saturable potentiation of sodium nitroprusside (SNP)-stimulated [³H]cGMP accumulation (forskolin EC₅₀ value of 0.98 β 0.23 μM; 10 μM forskolin produced a 1.8 β 0.3-fold potentiation of the SNP response at 2.5 min). The forskolin potentiation was observed at all concentrations of SNP tested (0.001-10 mM). forskolin also elicited a large stimulation of [³H]-cAMP in [³H]adenine-prelabelled guinea-pig cerebellar slices; however, 1,9-dideoxyforskolin failed to elicit either a [³H]cAMP response or a potentiation of the SNP-induced [³H]cGMP response at concentrations up to 100 μM. Pretreatment with oxyhaemoglobin (50 μM) inhibited the response to SNP (1 mM) and forskolin (10 μM), as well as the response evoked by the combination of SNP and forskolih. A^G-Nitro-l -arginine (100 μM) inhibited the response to forskolin alone, but did not change the response to SNP or the potentiation induced by forskolin on SNP-induced [³H]cGMP levels. The protein kinase inhibitors 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7; 100 μM), staurosporine (10 μM), polymyxin B (100 μM), and Ro 31-8220 (10 μM) had no effect on the [³H]cGMP response to either SNP or the combination of SNP plus forskolin. N⁶,2′-Dibutyryl cAMP, at concentrations up to 10 mM, was also without effect on [³H]cGMP levels induced by SNP. 3-lso-butyl-1-methylxanthine reproduced the effect of forskolin on SNP-induced [³H]cGMP levels, but a less-than-additive effect was observed when the response to SNP was studied in the presence of forskolin and 3-isobutyl-1-methylxanthine. Taken together, these results infer that crosstalk between cyclic nucleotides takes place in guinea-pig cerebellar slices, and that cAMP may regulate cGMP-mediated responses in this tissue.     

两种软体动物神经系统一氧化氮合酶的组织化学定位

运用一氧化氮合酶(NOS)组织化学方法研究了软体动物门双壳纲种类中国蛤蜊和腹足纲种类嫁Qi神经系统中NOS阳性细胞以及阳性纤维的分布。结果表明：在蛤蜊脑神经节腹内侧,每侧约有10-15个细胞呈强NOS阳性反应,其突起也呈强阳性反应,并经脑足神经节进入足神经节的中央纤维网中;足神经节内只有2个细胞呈弱阳性反应,其突起较短,进入足神经节中央纤维网中,但足神经节中,来自脑神经节阳性细胞和外周神经系统的纤维大多呈NOS阳性反应;脏神经节的前内侧部和后外侧部各有一个阳性细胞团,其突起分别进入后闭壳肌水管后外套膜神经和脑脏神经索。脏神经节背侧小细胞层以及联系两侧小细胞层的纤维也呈NOS阳性反应。嫁Qi中枢神经系统各神经节中没有发现NOS阳性胞体存在;脑神经节、足神经节、侧神经节以及脑—侧、脑—足、侧—脏连索中均有反应程度不同的NOS阳性纤维,这些纤维均源于外周神经。与已研究的软体动物比较,嫁Qi和前鳃亚纲其它种类一样,神经系统中NO作为信息分子可能主要存在于感觉神经。而中国蛤蜊的神经系统中一氧化氮作为信息分子则可能参与更广泛的神经调节过程。