Neuronal expression of inducible nitric oxide synthase after oxygen and glucose deprivation in rat forebrain slices

Effects of Acute Hypobaric Hypoxia Exposure on Cardiovascular Function in Unacclimatized Healthy Subjects: A "Rapid Ascent" Hypobaric Chamber Study

Background: This study aimed to observe the effects of a fast acute ascent to simulated high altitudes on cardiovascular function both in the main arteries and in peripheral circulation. Methods: We examined 17 healthy volunteers, between 18 and 50 years old, at sea level, at 3842 m of hypobaric hypoxia and after return to sea level. Cardiac output (CO) was measured with Doppler transthoracic echocardiography. Oxygen delivery was estimated as the product of CO and peripheral oxygen saturation (SpO2). The brachial artery’s flow-mediated dilation (FMD) was measured with the ultrasound method. Post-occlusion reactive hyperemia (PORH) was assessed by digital plethysmography. Results: During altitude stay, peripheral oxygen saturation decreased (84.9 ± 4.2% of pre-ascent values; p < 0.001). None of the volunteers presented any hypoxia-related symptoms. Nevertheless, an increase in cardiac output (143.2 ± 36.2% of pre-ascent values, p < 0.001) and oxygen delivery index (120.6 ± 28.4% of pre-ascent values; p > 0.05) was observed. FMD decreased (97.3 ± 4.5% of pre-ascent values; p < 0.05) and PORH did not change throughout the whole experiment. Τhe observed changes disappeared after return to sea level, and normoxia re-ensued. Conclusions: Acute exposure to hypobaric hypoxia resulted in decreased oxygen saturation and increased compensatory heart rate, cardiac output and oxygen delivery. Pre-occlusion vascular diameters increase probably due to the reduction in systemic vascular resistance preventing flow-mediated dilation from increasing. Mean Arterial Pressure possibly decrease for the same reason without altering post-occlusive reactive hyperemia throughout the whole experiment, which shows that compensation mechanisms that increase oxygen delivery are effective.

Full-Face Mask Use during SCUBA Diving Counters Related Oxidative Stress and Endothelial Dysfunction

Impaired flow mediated dilation (FMD), an index of vascular stress, is known after SCUBA diving. This is related to a dysfunction of nitric oxide (NO) availability and a disturbance of the redox status, possibly induced by hyperoxic/hyperbaric gas breathing. SCUBA diving is usually performed with a mask only covering “half face” (HF) and therefore forcing oral breathing. Nasal NO production is involved in vascular homeostasis and, as consequence, can significantly reduce NO possibly promoting vascular dysfunction. More recently, the utilization of “full-face” (FF) mask, allowing nasal breathing, became more frequent, but no reports are available describing their effects on vascular functions in comparison with HF masks. In this study we assessed and compared the effects of a standard shallow dive (20 min at 10 m) wearing either FF or a HF mask on different markers of vascular function (FMD), oxidative stress (ROS, 8-iso-PGF2α) and NO availability and metabolism (NO₂, NOx and 3-NT and iNOS expression). Data from a dive breathing a hypoxic (16% O₂ at depth) gas mixture with HF mask are shown allowing hyperoxic/hypoxic exposure. Our data suggest that nasal breathing might significantly reduce the occurrence of vascular dysfunction possibly due to better maintenance of NO production and bioavailability, resulting in a better ability to counter reactive oxygen and nitrogen species. Besides the obvious outcomes in terms of SCUBA diving safety, our data permit a better understanding of the effects of oxygen concentrations, either in normal conditions or as a strategy to induce selected responses in health and disease.

Nitric Oxide-Dependent Pathways as Critical Factors in the Consequences and Recovery after Brain Ischemic Hypoxia

Brain ischemia is one of the leading causes of disability and mortality worldwide. Nitric oxide (NO^•), a molecule that is involved in the regulation of proper blood flow, vasodilation, neuronal and glial activity constitutes the crucial factor that contributes to the development of pathological changes after stroke. One of the early consequences of a sudden interruption in the cerebral blood flow is the massive production of reactive oxygen and nitrogen species (ROS/RNS) in neurons due to NO^• synthase uncoupling, which leads to neurotoxicity. Progression of apoptotic or necrotic neuronal damage activates reactive astrocytes and attracts microglia or lymphocytes to migrate to place of inflammation. Those inflammatory cells start to produce large amounts of inflammatory proteins, including pathological, inducible form of NOS (iNOS), which generates nitrosative stress that further contributes to brain tissue damage, forming vicious circle of detrimental processes in the late stage of ischemia. S-nitrosylation, hypoxia-inducible factor 1α (HIF-1α) and HIF-1α-dependent genes activated in reactive astrocytes play essential roles in this process. The review summarizes the roles of NO^•-dependent pathways in the early and late aftermath of stroke and treatments based on the stimulation or inhibition of particular NO^• synthases and the stabilization of HIF-1α activity.

Effect of atherosclerosis and the protective effect of the antioxidant vitamin E on the rabbit cerebellum

BACKGROUND

Atherosclerosis is a major cardiovascular disease and one of the commonest causes of mortality in the world. Speech, balance, fine motor control and cognition are affected by atherosclerosis of cerebellar arteries. This study investigated the protective role of vitamin E against induced atherosclerosis in the rabbit cerebellum.

MATERIALS AND METHODS

Forty Rex New Zealand adult male rabbits were randomly divided into four groups (10 rabbits each). Group I was designated as the control and received an ordinary diet. Group II received an ordinary diet, but with vitamin E (12 mg/kg/day) added. Group III were given an ordinary diet along with 1% cholesterol powder for 6 weeks. Finally, group IV received an ordinary diet with both 1% cholesterol powder and vitamin E (12 mg/kg/day). Cerebellum samples were stained with haematoxylin and eosin and examined using light microscopy, along with quantitative immunohistochemical assessments of the expression of caspase-3, glial fibrillary acidic protein (GFAP) and inducible nitric oxide synthase (iNOS).

RESULTS

Cerebellum sections from cholesterol-treated rabbits showed ischaemic changes as fibre density decreased, with vacuolation of the molecular layer, and deformed and shrunken Purkinje cells. A significant increase in caspase-3, GFAP and iNOS immunoreactivity was found. However, vitamin E administration reduced these ischaemic manifestations.

CONCLUSIONS

The results demonstrate the neurological protective role of vitamin E therapy in atherosclerosis.

Nitric oxide regulates homeoprotein OTX1 and OTX2 expression in the rat myenteric plexus after intestinal ischemia-reperfusion injury

Neuronal and inducible nitric oxide synthase (nNOS and iNOS) play a protective and damaging role, respectively, on the intestinal neuromuscular function after ischemia-reperfusion (I/R) injury. To uncover the molecular pathways underlying this dichotomy we investigated their possible correlation with the orthodenticle homeobox proteins OTX1 and OTX2 in the rat small intestine myenteric plexus after in vivo I/R. Homeobox genes are fundamental for the regulation of the gut wall homeostasis both during development and in pathological conditions (inflammation, cancer). I/R injury was induced by temporary clamping the superior mesenteric artery under anesthesia, followed by 24 and 48 h of reperfusion. At 48 h after I/R intestinal transit decreased and was further reduced by N^ω-propyl-l-arginine hydrochloride (NPLA), a nNOS-selective inhibitor. By contrast this parameter was restored to control values by 1400W, an iNOS-selective inhibitor. In longitudinal muscle myenteric plexus (LMMP) preparations, iNOS, OTX1, and OTX2 mRNA and protein levels increased at 24 and 48 h after I/R. At both time periods, the number of iNOS- and OTX-immunopositive myenteric neurons increased. nNOS mRNA, protein levels, and neurons were unchanged. In LMMPs, OTX1 and OTX2 mRNA and protein upregulation was reduced by 1400W and NPLA, respectively. In myenteric ganglia, OTX1 and OTX2 staining was superimposed with that of iNOS and nNOS, respectively. Thus in myenteric ganglia iNOS- and nNOS-derived NO may promote OTX1 and OTX2 upregulation, respectively. We hypothesize that the neurodamaging and neuroprotective roles of iNOS and nNOS during I/R injury in the gut may involve corresponding activation of molecular pathways downstream of OTX1 and OTX2.NEW & NOTEWORTHY Intestinal ischemia-reperfusion (I/R) injury induces relevant alterations in myenteric neurons leading to dismotility. Nitrergic neurons seem to be selectively involved. In the present study the inference that both neuronal and inducible nitric oxide synthase (nNOS and iNOS) expressing myenteric neurons may undergo important changes sustaining derangements of motor function is reinforced. In addition, we provide data to suggest that NO produced by iNOS and nNOS regulates the expression of the vital transcription factors orthodenticle homeobox protein 1 and 2 during an I/R damage.

Hippocampus and cerebral cortex present a different autophagic response after oxygen and glucose deprivation in an ex vivo rat brain slice model

AIMS

To evaluate the neuroprotective role of autophagy in the cerebral cortex and hippocampus using an ex vivo animal model of stroke in brain slices.

METHODS

Brain slices were maintained for 30 min in oxygen and glucose deprivation (OGD) followed by 3 h in normoxic conditions to simulate the reperfusion that follows ischaemia in vivo (RL, reperfusion-like). Phagophore formation (Beclin 1 and LC3B) as well as autophagy flux (p62/SQSTM1, Atg5, Atg7 and polyubiquitin) markers were quantified by Western blot and/or qPCR. The release of lactate dehydrogenase (LDH) and glutamate in the medium was used as a measure of the mortality in the absence and in the presence of the autophagy inhibitor 3-methyladenine.

RESULTS

Striking differences in the autophagy markers were observed between the hippocampus and cerebral cortex in normoxic conditions. OGD/RL induced increases both in the phagophore formation and in the autophagy flux in the first three hours in the cerebral cortex that were not observed in the hippocampus. The blocking of autophagy increased the OGD/RL-induced mortality, increased the glutamate release in both the cerebral cortex and hippocampus and abolished the OGD-induced decrease in the polyubiquitinated proteins in the cerebral cortex.

CONCLUSIONS

We conclude that OGD induces a rapid autophagic response in the cerebral cortex that plays a neuroprotective role. Polyubiquitination levels and control of the glutamate release appear to be involved in the neuroprotective role of autophagy.

Potential advantages of Chinese medicine Taohong Siwu Decoction () combined with tissue-plasminogen activator for alleviating middle cerebral artery occlusion-induced embolic stroke in rats

OBJECTIVE

To investigate whether combination treatment with Taohong Siwu Decoction (, TSD) and recombinant tissue-type plasminogen activator (rt-PA) potentiate in reducing infarct volume and alleviate thromboembolic stroke in an in vivo rat model.

METHOD

Adult male Wistar rats were subjected to embolic middle cerebral artery occlusion (MCAO) and treated with rt-PA (4 and 8 mg/kg) alone (n=5), TSD [0.7 g/(kg·day)] alone (n=5), combination of rt-PA and TSD, 24 h after stroke. Rats were sacrificed at 14 days after treatment and lesion volumes were measured. To investigate the underlying mechanism of neuroprotective effect of the combination treatment, cleaved caspase-3, tumor necrosis factor alpha (TNF-α), hypoxia-inducible factor (HIF)-1α, and inducible nitric oxide synthase (iNOS) immunostaining were performed.

RESULTS

Combination treatment significantly reduced infarct volume of cerebral ischemic regions compared with treatment of rt-PA and TSD alone and that of the saline control group (P<0.01). A combined treatment of rt-PA (4 mg/kg) with TSD [0.7 g/(kg·day)] significantly increased cerebral blood flow in a time (100 and 120 min) dependent manner (P<0.05). Interestingly, despite treatment of rt-PA (4 mg/kg) alone significantly reduced the expressions of HIF-1α, TNF-α, and iNOS in ischemic regions, reduction of these expressions were more potentiated when combined with TSD (P<0.05). Combination treatment also reduced apoptosis as measured by a significant reduction in active caspase-3 expression in the ischemic brain compared with the MCAO group (P<0.01).

CONCLUSIONS

A combination of low-dose rt-PA and TSD after embolic stroke reduced infarct volume, improved cerebral blood flow and provided neuroprotection and these effects were associated with reduction of apoptosis and attenuation of HIF-1α, TNF-α and iNOS expression. These results provide a positive contribution to better understand the therapeutic value of the combination of TSD with rt-PA in ischemic stroke and may support further clinical evaluation.

Maslinic acid, a natural phytoalexin-type triterpene from olives--a promising nutraceutical?

Maslinic acid is a pentacyclic triterpene found in a variety of natural sources, ranging from herbal remedies used in traditional Asian medicine to edible vegetables and fruits present in the Mediterranean diet. In recent years, several studies have proved that maslinic acid exerts a wide range of biological activities, i.e. antitumor, antidiabetic, antioxidant, cardioprotective, neuroprotective, antiparasitic and growth-stimulating. Experimental models used for the assessment of maslinic acid effects include established cell lines, which have been often used to elucidate the underlying mechanisms of action, and also animal models of different disorders, which have confirmed the effects of the triterpene in vivo. Overall, and supported by the lack of adverse effects in mice, the results provide evidence of the potential of maslinic acid as a nutraceutical, not only for health promotion, but also as a therapeutic adjuvant in the treatment of several disorders.

Neuroprotective effect of exercise in rat hippocampal slices submitted to in vitro ischemia is promoted by decrease of glutamate release and pro-apoptotic markers

The role of physical exercise as a neuroprotective agent against ischemic injury has been extensively discussed. Nevertheless, the mechanisms underlying the effects of physical exercise on cerebral ischemia remain poorly understood. Here, we investigate the hypothesis that physical exercise increases ischemic tolerance by decreasing the induction of cellular apoptosis and glutamate release. Rats (n = 50) were submitted to a swimming exercise protocol for 8 weeks. Hippocampal slices were then submitted to oxygen and glucose deprivation. Cellular viability, pro-apoptotic markers (Caspase 8, Caspase 9, Caspase 3, and apoptosis-inducing factor), and glutamate release were analyzed. The percentage of cell death, the amount of glutamate release, and the expression of the apoptotic markers were all decreased in the exercise group when compared to the sedentary group after oxygen and glucose deprivation. Our results suggest that physical exercise protects hippocampal slices from the effects of oxygen and glucose deprivation, probably by a mechanism involving both the decrease of glutamatergic excitotoxicity and apoptosis induction.

Hinokitiol, a natural tropolone derivative, offers neuroprotection from thromboembolic stroke in vivo

Hinokitiol (β-thujaplicin), a tropolone-related compound found in the heartwood cupressaceous plants, is widely used in hair tonics, tooth pastes, cosmetics, and food as an antimicrobial agent. Increasing evidence has confirmed that hinokitiol exhibits anticancer activity in a variety of cancers through inhibition of cell proliferation. In the present study, we have investigated the neuroprotective effect and mechanisms of hinokitiol in rats against middle cerebral artery occlusion (MCAO)-induced thromboembolic stroke. Treatment with hinokitiol (0.2 and 0.5 mg/kg; intraperitoneally) 30 min before MCAO dose dependently attenuated cerebral ischemia and improved neurobehavioral deficits in cerebral ischemic rats. Intraperitoneal administration of hinokitiol significantly reduced infarct size compared to that in control rats. MCAO-induced focal cerebral ischemia was associated with increased expressions of hypoxia-inducible factor (HIF)-1α, inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF)-α, and active caspase-3 in ischemic regions. However, these expressions were obviously inhibited by hinokitiol (0.2 and 0.5 mg/kg) treatment. This study demonstrates for the first time that in addition to being originally considered as an agent against microbes and variety of cancers, hinokitiol possesses potent neuroprotective activity. This activity is mediated, at least in part, by inhibition of inflammatory responses (i.e., HIF-1α, iNOS expression) and apoptosis (i.e., TNF-α, active caspase-3), resulting in a reduction of infarct volume and improvement in neurobehavior in rats with cerebral ischemia. Therefore, the therapeutic potential of hinokitiol may lead to novel role for treatment or prevention of ischemia/reperfusion injury-related disorders.

Sleep, its regulation and possible mechanisms of sleep disturbances

The state of sleep consists of different phases that proceed in successive, tightly regulated order through the night forming a physiological program, which for each individual is different but stabile from one night to another. Failure to accomplish this program results in feeling of unrefreshing sleep and tiredness in the morning. The program core is constructed by genetic factors but regulated by circadian rhythm and duration and intensity of day time brain activity. Many environmental factors modulate sleep, including stress, health status and ingestion of vigilance-affecting nutrients or medicines (e.g. caffeine). Acute sleep loss results in compromised cognitive performance, memory deficits, depressive mood and involuntary sleep episodes during the day. Moreover, prolonged sleep curtailment has many adverse health effects, as evidenced by both epidemiological and experimental studies. These effects include increased risk for depression, type II diabetes, obesity and cardiovascular diseases. In addition to voluntary restriction of sleep, shift work, irregular working hours, jet lag and stress are important factors that induce curtailed or bad quality sleep and/or insomnia. This review covers the current theories on the function of normal sleep and describes current knowledge on the physiologic effects of sleep loss. It provides insights into the basic mechanisms of the regulation of wakefulness and sleep creating a theoretical background for understanding different disturbances of sleep.

Role of neuronal and inducible nitric oxide synthases in the guinea pig ileum myenteric plexus during in vitro ischemia and reperfusion

BACKGROUND

Intestinal ischemia and reperfusion (I/R) injury leads to abnormalities in motility, namely delay of transit, caused by damage to myenteric neurons. Alterations of the nitrergic transmission may occur in these conditions. This study investigated whether an in vitro I/R injury may affect nitric oxide (NO) production from the myenteric plexus of the guinea pig ileum and which NO synthase (NOS) isoform is involved.

METHODS

The distribution of the neuronal (n) and inducible (i) NOS was determined by immunohistochemistry during 60 min of glucose/oxygen deprivation (in vitro ischemia) followed by 60 min of reperfusion. The protein and mRNA levels of nNOS and iNOS were investigated by Western-immunoblotting and real time RT-PCR, respectively. NO levels were quantified as nitrite/nitrate.

KEY RESULTS

After in vitro I/R the proportion of nNOS-expressing neurons and protein levels remained unchanged. nNOS mRNA levels increased 60 min after inducing ischemia and in the following 5 min of reperfusion. iNOS-immunoreactive neurons, protein and mRNA levels were up-regulated during the whole I/R period. A significant increase of nitrite/nitrate levels was observed in the first 5 min after inducing I/R and was significantly reduced by N(ω) -propyl-l-arginine and 1400 W, selective inhibitors of nNOS and iNOS, respectively.

CONCLUSIONS & INFERENCES

Our data demonstrate that both iNOS and nNOS represent sources for NO overproduction in ileal myenteric plexus during I/R, although iNOS undergoes more consistent changes suggesting a more relevant role for this isoform in the alterations occurring in myenteric neurons following I/R.

Neuroprotective effects of xanthohumol, a prenylated flavonoid from hops (Humulus lupulus), in ischemic stroke of rats

Xanthohumol is the principal prenylated flavonoid in hops (Humulus lupulus L.), an ingredient of beer. Xanthohumol was found to be a potent chemopreventive agent; however, no data are available concerning its neuroprotective effects. In the present study, the neuroprotective activity and mechanisms of xanthohumol in rats with middle cerebral artery occlusion (MCAO)-induced cerebral ischemia were examined. Treatment with xanthohumol (0.2 and 0.4 mg/kg; intraperitoneally) 10 min before MCAO dose-dependently attenuated focal cerebral ischemia and improved neurobehavioral deficits in cerebral ischemic rats. Xanthohumol treatment produced a marked reduction in infarct size compared to that in control rats. MCAO-induced focal cerebral ischemia was associated with increases in hypoxia-inducible factor (HIF)-1α, tumor necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS), and active caspase-3 protein expressions in ischemic regions. These expressions were obviously inhibited by treatment with xanthohumol. In addition, xanthohumol (3-70 μM) concentration-dependently inhibited platelet aggregation stimulated by collagen (1 μg/mL) in human platelet-rich plasma. An electron spin resonance (ESR) method was used to examine the scavenging activity of xanthohumol on free radicals which had formed. Xanthohumol (1.5 and 3 μM) markedly reduced the ESR signal intensity of hydroxyl radical (OH•) formation in the H₂O₂/NaOH/DMSO system. In conclusion, this study demonstrates for the first time that in addition to its originally being considered an agent preventing tumor growth, xanthohumol possesses potent neuroprotective activity. This activity is mediated, at least in part, by inhibition of inflammatory responses (i.e., HIF-1α, iNOS expression, and free radical formation), apoptosis (i.e., TNF-α, active caspase-3), and platelet activation, resulting in a reduction of infarct volume and improvement in neurobehavior in rats with cerebral ischemia. Therefore, this novel role of xanthohumol may represent high therapeutic potential for treatment or prevention of ischemia-reperfusion injury-related disorders.

RNA interference-produced autoregulation of inducible nitric oxide synthase expression

Vector-mediated delivery of short-hairpin RNA (shRNA) to regulate gene expression holds a great therapeutic promise. We hypothesize that gene expression can be autoregulated with RNA interference. We used inducible nitric oxide synthase (iNOS) as a gene model to test this hypothesis. Lipopolysaccharide dose-dependently increased iNOS in rat aortic smooth muscle cells and the nitrite production from these cells. These increases were attenuated in cells transfected with plasmids containing code for iNOS shRNA whose expression was controlled by an iNOS promoter. The production of shRNA was lipopolysaccharide dose-dependent. The lipopolysaccharide-induced iNOS expression in rat C6 glioma cells also was attenuated by transfection with plasmids containing the iNOS shRNA code. These results provide proof-of-concept evidence for using RNA interference technique to achieve autoregulation of gene expression.

Traditional Chinese medicine, Xue-Fu-Zhu-Yu decoction, potentiates tissue plasminogen activator against thromboembolic stroke in rats

AIM OF THIS STUDY

The Xue-Fu-Zhu-Yu decoction (XFZYD) is a well-known traditional Chinese medicine for treating cardiovascular diseases. The therapeutic effects of this XFZYD have been well documented especially in treating of atherosclerosis and hyperlipidemia. Since this decoction can induce endothelial progenitor cell angiogenesis, it can provide experimental evidence for the treatment of ischemic diseases. Patients who are admitted to the hospital with acute ischemic stroke are initially considered candidates for the recombinant tissue plasminogen activator (rt-PA). However, rt-PA therapy is still lesser than ideal due to its major side effect of hemorrhaging. Therefore, medical research has been devoted to finding an alternative and/or complementary therapy for ischemic stroke. In the present study, we evaluated the protective effect of the combination of XFZYD with or without rt-PA in a rat model of thromboembolic stroke.

MATERIALS AND METHODS

A cerebral thromboembolic stroke animal model and immunoblotting analysis were used to assess the effects of XFZYD and rt-PA.

RESULTS

Treatment with rt-PA (8 mg/kg) or XFZYD (1.5 and 3.0 g/kg/day) alone showed slight reductions in the infarct volume compared to solvent-treated rats. However, XFZYD (1.5 and 3.0 g/kg/day) obviously potentiated rt-PA-mediated reduction in the infarct volume in cerebral ischemic regions. In addition, treatment with rt-PA significantly reduced both tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) but not hypoxia-inducible factor (HIF)-1 α or active caspase-3 expressions in ischemic regions, whereas treatment with XFZYD (3.0 g/kg/day) significantly reduced all of these protein expressions in ischemic regions. Moreover, treatment with XFZYD (1.5 and 3.0 g/kg/day) obviously potentiated rt-PA-mediated reductions in TNF-α, iNOS, HIF-1 α, and active caspase-3 expressions.

CONCLUSIONS

Results of this study suggest that XFZYD potentiated rt-PA-mediated neuroprotection against thromboembolic stroke in rats. This neuroprotection is probably mediated by the inhibition of HIF-1 α and TNF-α, followed by the inhibition of inflammatory responses (i.e., iNOS) and apoptosis (active caspase-3). These results provide a better understanding of the scientific validation of the therapeutic value of the combination of XFZYD with rt-PA in ischemic stroke.

Neuroprotection by the Traditional Chinese Medicine, Tao-Hong-Si-Wu-Tang, against Middle Cerebral Artery Occlusion-Induced Cerebral Ischemia in Rats

Tao-Hong-Si-Wu-Tang (THSWT) is a famous traditional Chinese medicine (TMC). In the present study, oral administration of THSWT (0.7 and 1.4 g kg⁻¹day⁻¹) for 14 days before MCAO dose-dependently attenuated focal cerebral ischemia in rats. MCAO-induced focal cerebral ischemia was associated with increases in hypoxia-inducible factor (HIF)-1α, inducible nitric oxide synthase (iNOS), tumor necrosis factor (TNF)-α, and active caspase-3 expressions in ischemic regions. These expressions were obviously inhibited by 0.7 g kg⁻¹day⁻¹ THSWT treatment. In addition, THSWT inhibited platelet aggregation stimulated by collagen in washed platelets. In an in vivo study, THSWT (16 g kg⁻¹) significantly prolonged platelet plug formation in mice. However, THSWT (20 and 40 μg mL⁻¹) did not significantly reduce the electron spin resonance (ESR) signal intensity of hydroxyl radical (OH^•) formation. In conclusion, the most important findings of this study demonstrate for the first time that THSWT possesses potent neuroprotective activity against MCAO-induced focal cerebral ischemia in vivo. This effect may be mediated, at least in part, by the inhibition of both HIF-1α and TNF-α activation, followed by the inhibition of inflammatory responses (i.e., iNOS expression), apoptosis formation (active caspase-3), and platelet activation, resulting in a reduction in the infarct volume in ischemia-reperfusion brain injury.

Sleep deprivation triggers inducible nitric oxide-dependent nitric oxide production in wake-active basal forebrain neurons

Sleep loss negatively impacts performance, mood, memory, and immune function, but the homeostatic factors that impel sleep after sleep loss are imperfectly understood. Pharmacological studies had implicated the basal forebrain (BF) inducible nitric oxide (NO) synthase (iNOS)-dependent NO as a key homeostatic factor, but its cellular source was obscure. To obtain direct evidence about the cellular source of iNOS-generated NO during sleep deprivation (SD), we used intracerebroventricular perfusion in rats of the cell membrane-permeable dye diaminofluorescein-2/diacetate (DAF-2/DA) that, once intracellular, bound NO and fluoresced. To circumvent the effects of neuronal NOS (nNOS), DAF-2/DA was perfused in the presence of an nNOS inhibitor. SD led to DAF-positive fluorescence only in the BF neurons, not glia. SD increased expression of iNOS, which colocalized with NO in neurons and, more specifically, in prolonged wakefulness-active neurons labeled by Fos. SD-induced iNOS expression in wakefulness-active neurons positively correlated with sleep pressure, as measured by the number of attempts to enter sleep. Importantly, SD did not induce Fos or iNOS in stress-responsive central amygdala and paraventricular hypothalamic neurons, nor did SD elevate corticosterone, suggesting that the SD protocol did not provoke iNOS expression through stress. We conclude that iNOS-produced neuronal NO is an important homeostatic factor promoting recovery sleep after SD.

Asymmetric dimethylarginine potentiates lung inflammation in a mouse model of allergic asthma

Nitric oxide (NO), formed by nitric oxide synthase (NOS), is an important mediator of lung inflammation in allergic asthma. Asymmetric dimethylarginine (ADMA), a competitive endogenous inhibitor of NOS, is metabolized by the enzyme dimethylarginine dimethylaminohydrolase (DDAH). Elevated ADMA has been shown to affect lung function in mice, and by inhibiting NOS it alters NO and reactive oxygen species production in mouse lung epithelial cells. However, the effects of altered ADMA levels during lung inflammation have not been explored. A model of allergen-induced airway inflammation was utilized in combination with the modulation of endogenous circulating ADMA levels in mice. Airway inflammation was assessed by quantifying inflammatory cell infiltrates in lung lavage and by histology. Lung DDAH expression was assessed by quantitative PCR and immunohistochemistry. Nitrite levels were determined in lung lavage fluid as a measure of NO production. iNOS expression was determined by immunohistochemistry, immunofluorescence, Western blot, and quantitative PCR. NF-κB binding activity was assessed by a transcription factor binding assay. Allergen-induced lung inflammation was potentiated in mice with elevated circulating ADMA and was reduced in mice overexpressing DDAH. Elevated ADMA reduced nitrite levels in lung lavage fluid in both allergen-challenged and control animals. ADMA increased iNOS expression in airway epithelial cells in vivo following allergen challenge and in vitro in stimulated mouse lung epithelial cells. ADMA also increased NF-κB binding activity in airway epithelial cells in vitro. These data support that ADMA may play a role in inflammatory airway diseases such as asthma through modulation of iNOS expression in lung epithelial cells.

Nitric oxide plays a key role in myelination in the developing brain

Inhaled nitric oxide (iNO) is one of the most promising therapies used in neonates, but there is little information available about its effect on the developing brain. We explored the effects of both iNO and endogenous NO on developing white matter in rodents. Rat or mouse pups and their mothers were placed in a chamber containing 5 to 20 ppm of NO for 7 days after birth. Neonatal exposure to iNO was associated with a transient increase in central nervous system myelination in rats and C57BL/6 mice without any deleterious effects at low doses (5 ppm) or behavioral consequences in adulthood. Exposure to iNO was associated with a proliferative effect on immature oligodendrocytes and a subsequent promaturational effect. The role of endogenous NO in myelination was investigated in animals treated with the nitric oxides synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) in the neonatal period; this led to protracted myelination defects and subsequent behavioral deficits in adulthood. These effects were reversed by rescuing L-NAME-treated animals with iNO. Thus, we demonstrate considerable effect of both exogenous and endogenous NO on myelination in rodents. These data point to potential new avenues for neuroprotection in human perinatal brain damage.

Bovine herpesvirus 5 induces an overproduction of nitric oxide in the brain of rabbits that correlates with virus dissemination and precedes the development of neurological signs

We herein report an investigation of nitric oxide (NO) levels, a candidate molecule for neuronal toxicity and dysfunction, in the brain of rabbits during experimental neurological infection by bovine herpesvirus 5 (BoHV-5). Spectrophotometry for NO products (NO(2) and NO(3)) revealed that NO levels were significantly increased (F(4, 40) = 3.33; P <.02) in several regions of the brain of rabbits with neurological disease, correlating with moderate to high BoHV-5 titers. Immunohistochemistry of brain regions revealed a group of cells with neuronal and astrocyte morphology expressing the enzyme inducible NO synthase (iNOS) close to virus antigen-positive neurons. In addition, the investigation of nitric oxide levels between 2 and 6 days post infection (d.p.i.) revealed an initial increase in NO levels in the olfactory bulb and cortex (OB/OC) and anterior cortex (AC) at day 3 p.i., correlating with the initial detection of virus. As the infection proceeded, increased NO levels-and infectivity-were progressively being detected in the OB/CO and AC at day 4 p.i. (F(12, 128) = 2.82; P <.003); at day 5 p.i. in several brain regions (P <.003 in the OB/OC); and at day 6 p.i. in all regions (P <.003) but the thalamus. These results show that BoHV-5 replication in the brain of rabbits induces an overproduction of NO. The increase in NO levels in early infection correlated spatially and temporally with virus dissemination within the brain and preceded the development of neurological signs. Thus, the overproduction of NO in the brain of BoHV-5-infected rabbits may be a component of the pathogenesis of BoHV-5-induced neurological disease.

Nitric oxide system alteration at spinal cord as a result of perinatal asphyxia is involved in behavioral disabilities: hypothermia as preventive treatment

Perinatal asphyxia (PA) is able to induce sequelae such as spinal spasticity. Previously, we demonstrated hypothermia as a neuroprotective treatment against cell degeneration triggered by increased nitric oxide (NO) release. Because spinal motoneurons are implicated in spasticity, our aim was to analyze the involvement of NO system at cervical and lumbar motoneurons after PA as well as the application of hypothermia as treatment. PA was performed by immersion of both uterine horns containing full-term fetuses in a water bath at 37 degrees C for 19 or 20 min (PA19 or PA20) or at 15 degrees C for 20 min (hypothermia during PA-HYP). Some randomly chosen PA20 rats were immediately exposed for 5 min over grain ice (hypothermia after PA-HPA). Full-term vaginally delivered rats were used as control (CTL). We analyzed NO synthase (NOS) activity, expression and localization by nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) reactivity, inducible and neuronal NOS (iNOS and nNOS) by immunohistochemistry, and protein nitrotyrosilation state. We observed an increased NOS activity at cervical spinal cord of 60-day-old PA20 rats, with increased NADPH-d, iNOS, and nitrotyrosine expression in cervical motoneurons and increased NADPH-d in neurons of layer X. Lumbar neurons were not altered. Hypothermia was able to maintain CTL values. Also, we observed decreased forelimb motor potency in the PA20 group, which could be attributed to changes at cervical motoneurons. This study shows that PA can induce spasticity produced by alterations in the NO system of the cervical spinal cord. Moreover, this situation can be prevented by perinatal hypothermia.

Inhaled nitric oxide to prevent bronchopulmonary dysplasia in preterm neonates

Bronchopulmonary dysplasia is a chronic lung disease that affects premature infants and contributes to their morbidity and mortality. With the advent of prenatal steroids and postnatal exogenous surfactant and less aggressive respiratory support, premature infants can develop chronic oxygen dependency without even acute respiratory distress. This 'new bronchopulmonary dysplasia' could be the result of impaired postnatal growth. Several experimental studies have suggested a possible role of the vascular endothelial growth factor/nitric oxide (VEGF/NO) pathway in restoring pulmonary angiogenesis and enhancing distal lung growth. The results of the clinical studies are, however, inconclusive, and it is currently unclear which subsets of premature infants might benefit from inhaled nitric oxide. Besides, severe intracranial haemorrhage and/or cystic periventricular leucomalacia may affect the most immature babies, many of whom are spared from severe initial respiratory disease. Recently, inhaled nitric oxide was shown to significantly decrease the incidence of these neurological events, and to improve the long-term outcome in a few clinical trials. At times neuroprotective, at times neurotoxic, nitric oxide is capable of divergent effects depending upon the extent of cerebral damage, the redox state of the cell, and the experimental model used. Recently, our group found that inhaled nitric oxide had remote effects including angiogenesis and maturation on the developing brain in rodent pups. Thus, we await the results of the recently completed randomised clinical trial of inhaled nitric oxide to prevent bronchopulmonary dysplasia (the European Nitric Oxide or 'EUNO' trial) where, besides the primary endpoint of chronic oxygen dependency reduction at 36 weeks' postconceptional age, long-term lung and brain will be followed-up until 7 years of age.

Neuroprotective mechanisms of puerarin in middle cerebral artery occlusion-induced brain infarction in rats

Puerarin, a major isoflavonoid derived from the Chinese medical herb Radix puerariae (kudzu root), has been reported to be useful in the treatment of various cardiovascular diseases. In the present study, we examined the detailed mechanisms underlying the inhibitory effects of puerarin on inflammatory and apoptotic responses induced by middle cerebral artery occlusion (MCAO) in rats. Treatment of puerarin (25 and 50 mg/kg; intraperitoneally) 10 min before MCAO dose-dependently attenuated focal cerebral ischemia in rats. Administration of puerarin at 50 mg/kg, showed marked reduction in infarct size compared with that of control rats. MCAO-induced focal cerebral ischemia was associated with increases in hypoxia-inducible factor-1α (HIF-1α), inducible nitric oxide synthase (iNOS), and active caspase-3 protein expressions as well as the mRNA expression of tumor necrosis factor-α (TNF-α) in ischemic regions. These expressions were markedly inhibited by the treatment of puerarin (50 mg/kg). In addition, puerarin (10~50 μM) concentration-dependently inhibited respiratory bursts in human neutrophils stimulated by formyl-Met-Leu-Phe. On the other hand, puerarin (20~500 μM) did not significantly inhibit the thiobarbituric acid-reactive substance reaction in rat brain homogenates. An electron spin resonance (ESR) method was conducted on the scavenging activity of puerarin on the free radicals formed. Puerarin (200 and 500 μM) did not reduce the ESR signal intensity of hydroxyl radical formation. In conclusion, we demonstrate that puerarin is a potent neuroprotective agent on MCAO-induced focal cerebral ischemia in vivo. This effect may be mediated, at least in part, by the inhibition of both HIF-1α and TNF-α activation, followed by the inhibition of inflammatory responses (i.e., iNOS expression), apoptosis formation (active caspase-3), and neutrophil activation, resulting in a reduction in the infarct volume in ischemia-reperfusion brain injury. Thus, puerarin treatment may represent a novel approach to lowering the risk of or improving function in ischemia-reperfusion brain injury-related disorders.

Hypoxia regulates iNOS expression in human normal peritoneal and adhesion fibroblasts through nuclear factor kappa B activation mechanism

OBJECTIVE

To determine the mechanism by which hypoxia increases expression of iNOS in human normal peritoneal and adhesion fibroblasts.

DESIGN

Prospective experimental study.

SETTING

University medical center.

PATIENT(S)

Primary cultures of fibroblasts from normal peritoneum and adhesion tissues.

INTERVENTION(S)

Hypoxia-treated cells.

MAIN OUTCOME MEASURE(S)

We used real-time reverse transcription-polymerase chain reaction to quantify mRNA levels of iNOS and nuclear factor kappa B (NF-kappaB). Western blots were used to determine iNOS, NF-kappaB, IkappaB-alpha, and phospho-IkappaB expression levels in normal peritoneal and adhesion fibroblasts in response to hypoxia.

RESULT(S)

Hypoxia resulted in a significant increase in iNOS and NF-kappaB expression in normal and adhesion fibroblasts. Furthermore, both cell types manifested lower levels of NF-kappaB, cytoplasmic phospho-IkappaB-alpha, and iNOS proteins. In contrast, they manifested higher levels of cytoplasmic IkappaB-alpha and IkappaB-alpha/NF-kappaB ratios as well as a phosphorylated-IkappaB-alpha/NF-kappaB ratio. Under hypoxic conditions, both cell types exhibited significantly decreased cytoplasmic NF-kappaB, IkappaB-alpha levels, and significantly increased cytoplasmic phospho-IkappaB-alpha, iNOS, and NF-kappaB protein levels.

CONCLUSION(S)

Hypoxia increases iNOS expression by a mechanism involving activation of NF-kappaB. The ratio of IkappaB-alpha/NF-kappaB or IkappaB-alpha/p-IkappaB-alpha can be used to monitor activation.

Profile of glutamate uptake and cellular viability in hippocampal slices exposed to oxygen and glucose deprivation: developmental aspects and protection by guanosine

Stroke syndromes are a major cause of disability in middle and later life resulting in severe neuronal degeneration and loss of brain functions. In situations with energy failure, glutamate transport is impaired and high levels of this amino acid accumulate on the synaptic cleft. Our group has showed that guanosine exerts neuroprotection against neurotoxicity situations. The aim of this work is draw a post-ischemic profile of glutamate uptake and cell damage using an oxygen and glucose deprivation model (OGD) in hippocampal slices from young (P10) and adult (P60) rats, analyzing guanosine effect. OGD decreases glutamate uptake in both ages and recovery times, although decrease in cell viability was only observed 1 and 3 h after OGD in young and adult animals, respectively. Guanosine partially protected cell damage from 1 h in P10 and at 3 h in P60 rats and avoided glutamate uptake decrease from P10 rats at 3 h. The impairment of glutamate transporters since immediately after the insult observed here is probably due to an energetic failure; loss of cell viability was only observed from 1 h after OGD. The mechanism by which guanosine acts in the 'ischemic' model used here is still unknown, but evidence leads to its antiapoptotic effect.

Neuroprotective effects of cactus polysaccharide on oxygen and glucose deprivation induced damage in rat brain slices

1. The neuroprotective effect of cactus polysaccharide (CP) on oxygen and glucose deprivation (OGD) and reoxygenation (REO)-induced damage in the cortical and hippocampal slices of rat brain was investigated. 2. Cell viability was evaluated by using the 2, 3, 5-triphenyl tetrazolium chloride (TTC) method. The fluorescence of propidium iodide (PI) staining was used for quantification of cellular survival, and lactate dehydrogenase (LDH) activity in incubation medium was assessed by LDH assay to evaluate the degree of injury. 3. The OGD ischemic condition significantly decreased cellular viability and increased LDH release in the incubation medium. CP (0.2 mg/l approximately 2 mg/l) protected brain slices from OGD injury in a dosage dependent manner as demonstrated by increased A 490 value of TTC, decreased PI intensity and LDH release. At the above concentration, CP also prevented the increase of nitric oxide (NO) content and inducible nitric oxide synthase (iNOS) activity induced by OGD. 4. CP can protect the brain slices (cortical and hippocampus) against injury induced by OGD. Its neuroprotective effect may be partly mediated by the NO/iNOS system induced by OGD insult.

Effect of treadmill exercise on cell damage in rat hippocampal slices submitted to oxygen and glucose deprivation

We have recently demonstrated that high intensity training exercise exacerbates brain damage, while a moderate intensity (2 weeks of 20 min/day of treadmill training) reduces the injury caused by in vitro ischemia, oxygen and glucose deprivation (OGD), to hippocampal slices from Wistar rats. In the present paper, the effect of different running programs on severity of ischemic OGD lesion was examined, by the evaluation of three protocols designed to simulate exercise conditions common to humans: one or three 20-min sessions per week, during 12 weeks (moderate intensity), and two 20-min daily sessions for 3 weeks. OGD caused an increase of lactate dehydrogenase (LDH) release into the incubation media, a marker of tissue necrosis, and a decline of cell viability, as assessed by the decrease of mitochondrial dehydrogenase activity (MTT method). Moderate exercise, three times a week during 12-week treadmill training, decreased LDH release after OGD, while one weekly session and 3 weeks of two daily sessions did not affect OGD-induced LDH released. No exercise protocol evaluated altered MTT reduction. Our data support the hypothesis that moderate intensity exercise reduces hippocampal susceptibility to in vitro ischemia.

Neuroprotective effects of PMC, a potent α-tocopherol derivative, in brain ischemia-reperfusion: Reduced neutrophil activation and anti-oxidant actions

2,2,5,7,8-Pentamethyl-6-hydroxychromane (PMC) is the most potent analogue of alpha-tocopherol for anti-oxidation. It is more hydrophilic than other alpha-tocopherol derivatives and has potent free radical-scavenging activity. In the present study, PMC significantly attenuated middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia in rats. Administration of PMC at 20mg/kg, showed marked reductions in infarct size compared with that of control rats. MCAO-induced focal cerebral ischemia was associated with increases in HIF-1alpha, active caspase-3, iNOS, and nitrotyrosine expressions in ischemic regions. These expressions were markedly inhibited by treatment with PMC (20mg/kg). In addition, PMC (4-12 microM) inhibited respiratory bursts in human neutrophils stimulated by fMLP (800 nM) and PMA (320 nM). Furthermore, PMC (6, 12, and 60 microM) also significantly inhibited neutrophil migration stimulated by leukotriene B(4) (160 nM). An electron spin resonance (ESR) method was conducted on the scavenging activity of PMC on the free radicals formed. PMC (12 microM) greatly reduced the ESR signal intensities of superoxide anion, hydroxyl radical, and methyl radical formation. In conclusion, we demonstrate a potent neuroprotective effect of PMC on MCAO-induced focal cerebral ischemia in vivo. This effect may be mediated, at least in part, by inhibition of free radical formation, followed by inhibition of HIF-1alpha activation, apoptosis formation (active caspase-3), neutrophil activation, and inflammatory responses (i.e., iNOS and nitrotyrosine expressions), resulting in a reduction in the infarct volume in ischemia-reperfusion brain injury. Thus, PMC treatment may represent a novel approach to lowering the risk or improving function in ischemia-reperfusion brain injury-related disorders.

The expression of nNOS, iNOS and nitrotyrosine is increased in the rat cerebral cortex in experimental hepatic encephalopathy

The changes in the distribution and amount of nitric oxide (NO) synthases (nNOS and iNOS) and the appearance of nitrotyrosine (NT) in the rat cerebral cortex were investigated following portacaval anastomosis (PCA), an experimental hepatic encephalopathy (HE) model. One month after PCA, rats showed more neurones immunoreactive to nNOS than did control animals. At 6 months post PCA, the number of neurones expressing nNOS had again increased and the intensity of the immunoreactions was stronger. Immunohistochemical analysis also showed that iNOS was increasingly expressed in pyramidal-like cortical neurones and in perivascular astrocytes from 1 to 6 months post PCA. In addition, a significant increase in cerebral iNOS concentration, at both post-PCA periods, was determined by Western blotting. The iNOS induction appears to be correlated with the length of the post-PCA period. PCA also induced the expression of NT, a nitration product of peroxynitrite. NT immunoreactivity was found in pyramidal-like cortical neurones. At 6 months, NT immunoreactivity was also evident in perivascular astrocytes, which was concomitant with a significant increase in NT protein level. PCA therefore not only increases the expression of nNOS but also induces the expression of iNOS and NT in both neurones and astrocytes. Taken together, these findings indicate that the induction of iNOS in pyramidal neurones and cortical astrocytes 6 months after PCA contributes to the generation of NT, and demonstrate the clear participation of NO in the pathogenic process of HE in this model.

Inducible and neuronal nitric oxide synthases (NOS) have complementary roles in recovery sleep induction

Sleep homeostasis is the process by which recovery sleep is generated by prolonged wakefulness. The molecular mechanisms underlying this important phenomenon are poorly understood. We have previously shown that nitric oxide (NO) generation increases in the basal forebrain (BF) during sleep deprivation (SD). Moreover, both NO synthase (NOS) inhibition and a NO scavenger prevented recovery sleep induction, while administration of a NO donor during the spontaneous sleep-wake cycle increased sleep, indicating that NO is necessary and sufficient for the induction of recovery sleep. Next we wanted to know which NOS isoform is involved in the production of recovery sleep. Using in vivo microdialysis we infused specific inhibitors of NOS into the BF of rats during SD, and found that an inhibitor of inducible NOS (iNOS), 1400W, prevented non-rapid eye movement (NREM) recovery, while an inhibitor of neuronal NOS (nNOS), L-N-propyl-arginine, decreased REM recovery but did not affect NREM recovery. Using immunoblot analysis we found that iNOS was not expressed during the spontaneous sleep-wake cycle, but was induced by prolonged wakefulness (increased by 278%). A known iNOS inducer, lipopolysaccharide, evoked an increase in sleep that closely resembled recovery sleep, and its effects were abolished by 1400W. These results suggest that the elevation of NO produced by induction of iNOS in the BF during prolonged wakefulness is a specific mechanism for producing NREM recovery sleep and that the two NOS isoforms have a complementary role in NREM and REM recovery induction.

Hypothermic preconditioning reduces Purkinje cell death possibly by preventing the over-expression of inducible nitric oxide synthase in rat cerebellar slices after an in vitro simulated ischemia

We showed that hypothermic preconditioning (HPC) increased survival of Purkinje neurons in rat cerebellar slices after oxygen-glucose deprivation (OGD). HPC also reduced the OGD-increased expression of high mobility group I (Y) proteins, a transcription factor that can enhance inducible nitric oxide synthase (iNOS) expression. iNOS is a putatively damaging protein that contributes to ischemic brain injury. Heat shock proteins (HSPs) can be induced by various stimuli to protect cells. We hypothesize that HPC induces neuroprotection by reducing the expression of putatively damaging proteins such as iNOS and/or by increasing the expression of putatively protective proteins such as HSPs. Cerebellar slices were prepared from adult male Sprague-Dawley rats and incubated in circulating artificial cerebrospinal fluid. OGD was for 20 min at 37 degrees C and was followed by a 5-h recovery at 37 degrees C before slices were used for morphological, immunohistochemical and Western analyses. HPC was performed by incubating slices at 33 degrees C for 20 min at 1 h before the OGD. HPC and aminoguanidine, an iNOS inhibitor, prevented OGD-induced Purkinje cell death/injury. OGD increased the expression of iNOS and nitrosylated proteins. These increases were abolished by aminoguanidine and HPC. Interestingly, the expression of HSP70 was increased by OGD but not by HPC. Our results suggest that an increased iNOS expression contributes to the pathophysiology of OGD-induced Purkinje neuronal death in our model. Our results also suggest the involvement of inhibiting the expression of the putatively damaging iNOS proteins in the HPC-induced neuroprotection. HSP70 may not contribute to the HPC-induced neuroprotection.

Distribution of inducible nitric oxide synthase and cell proliferation in rat brain after transient middle cerebral artery occlusion

Nitric oxide (NO) can be neuroprotective or neurotoxic during cerebral ischemia, depending on the NO synthase (NOS) isoform involved. In addition to neurotoxic effect in ischemic brain, inducible NOS (iNOS) also adversely affect ischemic outcome by blocking neurogenesis. In the present study, therefore, we studied the chronological and spatial change of the distribution of iNOS and cell proliferation in subventricular zone (SVZ) after transient focal cerebral ischemia. After 90 min of transient middle cerebral artery occlusion (tMCAO), iNOS-positive cells decreased in the ischemic core at 1 to 21 days, and increased in the ipsilateral periischemic area at 1 and 3 days. 5-Bromodeoxyuridine (BrdU)-positive cells appeared in the ischemic core at 3 to 21 days, appeared in the periischemic area at 3 and 7 days, and increased in the ipsilateral SVZ at 7 days. ED-1-positive cells appeared in the ischemic core at 3 to 21 days, and some of them were double positive with BrdU or iNOS, but the majority were BrdU-negative. The present study suggests that astrocytes are born within the periischemic area at early stage after tMCAO and migrate from SVZ into periischemic area at later stage, and that time-dependent and spatial changes of iNOS expression may be involved in the proliferation and differentiation of adult neurogenesis after focal cerebral ischemia.

Preoperative plasma vascular endothelial growth factor but not nitrite is a useful complementary tumor marker in patients with colorectal cancer

PURPOSE

Vascular endothelial growth factor and nitric oxide are both related to tumor progression. This study was designed to measure preoperative plasma vascular endothelial growth factor and nitrite levels in patients with colorectal cancer to evaluate their clinical applications as tumor markers.

METHODS

In total, 279 patients with primary colorectal cancer and 20 patients with hemorrhoids (as a control) were included in this study. Plasma vascular endothelial growth factor was measured by quantitative, solid-phase, enzyme-linked immunosorbent assay (R&D Systems), whereas nitrite was measured by a high-performance liquid chromatographic method.

RESULTS

The vascular endothelial growth factor (mean, 220.6 pg/ml, P < 0.005) and nitrite (mean, 29.4 microM, P = 0.043) levels of patients with cancer were significantly higher than those of controls (mean vascular endothelial growth factor, 67 pg/ml; mean nitrite, 23 microM). Preoperative plasma vascular endothelial growth factor levels were positively correlated with tumor stage, T class, M class, and tumor size (Spearman correlation, P < 0.01), but were not associated with gender, N class, tumor location, histology type, or grade. There were no statistical differences in nitrite levels among different groups of patients with cancer. Higher vascular endothelial growth factor levels also were correlated with leukocytosis, elevated carcinoembryonic antigen, and a higher platelet count. The positive rates of vascular endothelial growth factor elevation (>148.6 pg/ml) compared with carcinoembryonic antigen elevation were 36.9 to 14.6 percent in Stage I, 60.9 to 33 percent in Stage II, 62.9 to 48.7 percent in Stage III, and 86 to 70.2 percent in Stage IV, respectively. The overall positive rate of vascular endothelial growth factor elevation also was higher than that of carcinoembryonic antigen elevation (63 percent for vascular endothelial growth factor vs. 42.5 percent for carcinoembryonic antigen, P = 0.016). More than one-half of the patients without carcinoembryonic antigen elevation still had elevated vascular endothelial growth factor levels. The combined assessment using vascular endothelial growth factor and carcinoembryonic antigen was superior to individual assessment using vascular endothelial growth factor or carcinoembryonic antigen. In node-negative tumor, the patients with vascular endothelial growth factor elevation had worse disease-free survival than those without vascular endothelial growth factor elevation (P = 0.0367). There was no association of vascular endothelial growth factor elevation with survival in patients with node-positive tumor.

CONCLUSIONS

Plasma vascular endothelial growth factor is a useful complementary tumor marker; however, synchronous measurement of white blood cells, platelets, and carcinoembryonic antigen is suggested in the clinical application of vascular endothelial growth factor to colorectal cancer.

Effect of ischemia in vivo and oxygen-glucose deprivation in vitro on NOS pools in the spinal cord: comparative study

1. This study was performed to compare both the Ca(2+)-dependent nitric oxide synthase (NOS) activity and the neuronal nitric oxide synthase immunoreactivity (nNOS-IR) in the rabbit lumbosacral spinal cord after 15 min abdominal aorta occlusion (ischemia in vivo) and oxygen-glucose deprivation of the spinal cord slices for 45 and 60 min (ischemia in vitro). All ischemic periods were followed by 15, 30 and 60 min reoxygenation in vitro. 2. Catalytic nitric oxide synthase activity was determined by the conversion of (L)-[(14)C]arginine to (L)-[(14)C]citrulline. Neuronal nitric oxide synthase immunoreactivity in the spinal cord was detected by incubation of sections with polyclonal sheep-nNOS-primary antibody and biotinylated anti-sheep secondary antibody. 3. Our results show that ischemia in vivo and the oxygen-glucose deprivation of spinal cord slices in vitro result in a time-dependent loss of constitutive NOS activity with a partial restoration of enzyme activity during 15 and 45 min ischemia followed by 30 min of reoxygenation. A significant decrease of enzyme activity was found during 60 min ischemia alone, which persisted up to 1 h of oxygen-glucose restoration. The upregulation of neuronal nitric oxide synthase was observed in the ventral horn motoneurons after all ischemic periods. The remarkable changes in optical density of neuronal nitric oxide synthase immunoreactive motoneurons were observed after 45 and 60 min ischemia in vitro followed by 30 and 60 min reoxygenation. 4. Our results suggest that the oxygen-glucose deprivation followed by reoxygenation in the spinal cord is adequately sensitive to monitor ischemia/reperfusion changes. It seems that 15 min ischemia in vivo and 45 min ischemia in vitro cause reversible changes, while the decline of Ca(2+)-dependent nitric oxide synthase activity after 60 min ischemic insult suggests irreversible alterations.

Cross-talk between constitutive and inducible NO synthase: an update

Inducible nitric oxide synthase (iNOS) is expressed upon exposure of some cell types to bacterial lipopolysaccharides (LPS) and/or a variety of proinflammatory cytokines. The authors present an overview of some of the recent findings further supporting the notion that this response takes place after an early decline in constitutive nitric oxide (NO) levels (i.e., NO released by constitutive NOS, cNOS). This response is indeed critical for allowing activation of the transcription factor NF-kappaB. Thus, generation of NO by cNOS represents a limiting factor for iNOS expression. Some of the physiological and pathological implications of the cross-talk between these two NOS isoforms are discussed. In addition, the results of recent studies are summarized, suggesting possible mechanisms whereby LPS and/or proinflammatory cytokines may cause inhibition of cNOS.

Neuroprotection and protein damage prevention by estradiol replacement in rat hippocampal slices exposed to oxygen-glucose deprivation

Here we investigated the effects of estradiol replacement in ovariectomized female rats using hippocampal slices exposed to oxygen-glucose deprivation (OGD). OGD induced lactate dehydrogenase (LDH) release to the incubation medium, what was assumed as a parameter of cellular death. In the estradiol-treated group the LDH release was markedly decreased by 23% as compared to the vehicle-treated group. In attempt to study a possible mechanism by which estradiol acts, we investigated some parameters of oxidative stress. In both vehicle-treated and estradiol-treated groups, OGD significantly increased the free radical production by 34% and 16%, respectively, although no significant differences on total antioxidant capacity were observed. Interestingly, estradiol replacement prevented the significant reduction in tryptophan and tyrosine contents caused by OGD observed in vehicle-treated animals. Our results show that estradiol replacement in ovariectomized female rats decreases cellular susceptibility to an ischemic-like injury and suggest a role for the hormone on protein damage prevention.

Immature rat brain slices exposed to oxygen-glucose deprivation as an in vitro model of neonatal hypoxic-ischemic encephalopathy

To analyze whether exposure to oxygen-glucose deprivation (OGD) of immature rat brain slices might reproduce the main pathophysiologic events leading to neuronal death in neonatal hypoxic-ischemic encephalopathy (NHIE), 500 microm-thick brain slices were obtained from 7-day-old Wistar rats, and incubated in oxygenated physiological solution. In OGD group, oxygen and glucose were removed from the medium for 10-30 min (n = 25); then, slices were re-incubated in normal medium. In control group the medium composition remained unchanged (CG, n = 30). Medium samples were obtained every 30 min for 3 h. To analyze neuronal damage, slices were stained with Nissl and CA1 area of hippocampus and cortex were observed under microscopy. In addition, neuronal death was quantified as LDH released to the medium determined by spectrophotometry. Additionally, medium glutamate (Glu) levels were determined by HPLC and those of TNFalpha by ELISA, whereas inducible nitric oxide synthase expression was determined by Western blot performed on slices homogenate. Optimal OGD time was established in 20 min. After OGD, a significant decrease in the number of neurones in hippocampus and cortex was observed. LDH release was maximal at 30 min, when it was five-fold greater than in CG. Furthermore, medium Glu concentrations were 200 times greater than CG levels at the end of OGD period. A linear relationship between Glu and LDH release was demonstrated. Finally, 3 h after OGD a significant induction of iNOS as well as an increase in TNFalpha release were observed. In conclusion, OGD appears as a feasible and reproducible in vitro model, leading to a neuronal damage, which is physiopathologically similar to that found in NHIE.

Norepinephrine protects cortical neurons against microglial-induced cell death

Interleukin-1 beta (IL-1beta) is one of the main cytokines involved in the inflammatory response; it has multiple effects that can contribute to cell damage, one of which is the upregulation of the inducible form of nitric oxide (NO) synthase (NOS2) in certain cell types. We demonstrated previously that in vivo, cortical microglial inflammatory responses were increased when noradrenaline (NE) levels were depleted, suggesting that NE can reduce microglial activation. In the present report, we examined the role of IL-1beta in neurotoxicity induced by microglial-conditioned media, and possible neuroprotective effects of NE. Incubation of cortical neurons with conditioned media (CM) obtained from lipopolysaccharide (LPS)-treated microglia induced neuronal NOS2 expression and increased neuronal cell death, and these responses were reduced if the neurons were coincubated with interleukin-1 receptor antagonist. Cotreatment of microglial cells with LPS plus NE potently blocked IL-1beta production and reduced the ability of the CM to induce neuronal NOS2 and cell death. These results suggest that microglial release of IL-1beta is an important activator of neuronal inflammatory responses, and that protective effects of NE upon neurons involve a reduction of microglial-derived IL-1beta.

Intrinsic optical signal of retinal spreading depression: Second phase depends on energy metabolism and nitric oxide

Spreading depression (SD) is a wave-like phenomenon that spreads through the gray matter of central nervous tissue. The aim of this work is to investigate how cellular energy supply and nitric oxide (NO) influence the recovery period after SD wave propagation. We have examined the SD wave in chicken retina by registration of the intrinsic optical signal (IOS). The changes of the IOS were observed via a microscope, transferred to a photomultiplier and amplified. The IOS of the SD wave consists of two phases. The first phase of IOS coexists with cellular swelling induced by ion distribution; the second phase is thought to reflect metabolic changes and reflects the refractory (recovery) period. To analyze the IOS, the amplitude, the duration and the front and the back maximal slopes of the both phases were analyzed. To reduce the cellular level of ATP the blocker of glucose transport-dexamethasone (glucocorticoid hormone) and the blocker of the respiratory chain-potassium cyanide were used. Sodium nitroprusside and trinitroglycerine were chosen as NO-donors. Our results show that during and after SD wave propagation (i) increased NO concentration changes the first and the second phases of IOS (duration of both phases is NO independent), (ii) reduced glucose uptake leads to an increased second phase duration and (iii) block of the respiratory chain prolongs the first phase. According to the results here presented, we propose that glycogen synthesis is one of the mechanisms reflected by the second phase of the IOS.

Acute and repeated restraint stress influences cellular damage in rat hippocampal slices exposed to oxygen and glucose deprivation

Several studies have shown that high corticosteroid hormone levels increase neuronal vulnerability. Here we evaluate the consequences of in vivo acute or repeated restraint stress on cellular viability in rat hippocampal slices suffering an in vitro model of ischemia. Cellular injury was quantified by measuring lactate dehydrogenase (LDH) and neuron-specific enolase released into the medium. Acute stress did not affect cellular death when oxygen and glucose deprivation (OGD) was applied both immediately or 24h after restraint. The exposure to OGD, followed by reoxygenation, resulted in increased LDH in the medium. Repeated stress potentiated the effect of OGD both, on LDH and neuron-specific enolase released to the medium. There was no effect of repeated stress on the release of S100B, an astrocytic protein. Additionally, no effect of repeated stress was observed on glutamate uptake by the tissue. These results suggest that repeated stress increases the vulnerability of hippocampal cells to an in vitro model of ischemia, potentiating cellular damage, and that the cells damaged by the exposure to repeated stress+OGD are mostly neurons. The uptake of glutamate was not observed to participate in the mechanisms responsible for rendering the neurons more susceptible to ischemic damage after repeated stress.

Neuronal and inducible nitric oxide synthase expression in the rat cerebellum following portacaval anastomosis

In order to determine the role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in the pathogenesis of experimental hepatic encephalopathy (HE), the expression of both was analyzed in the cerebellum of rats 1 month and 6 months after performing portacaval anastomosis (PCA). In control cerebella, nNOS immunoreactivity was mainly observed in the molecular layer (ML), whereas the Purkinje cells did not express nNOS. However, nNOS expression was detected in the Purkinje cells at 1 month after PCA, correlating with a decrease in nNOS expression in the ML--part of an overall reduction in cerebellar nNOS concentrations (as determined by Western blotting). At 6 months post-PCA, a significant increase in nNOS expression was observed in the ML, as well as increased nNOS immunoreactivity in the Purkinje cells. nNOS immunoreactivity was also observed in the Bergmann glial cells of PCA-treated rats. While no immunoreactivity for iNOS was seen in the cerebella of control rats, iNOS immunoreactivity was significantly induced in the cerebellum 1 month after PCA. In addition, the expression of iNOS was greater at 6 months than at 1 month post-PCA. Immunohistochemical analysis revealed this iNOS to be localized in the Purkinje cells and Bergmann glial cells. The induction of iNOS in astroglial cells has been associated with pathological conditions. Therefore, the iNOS expression observed in the Bergmann glial cells might play a role in the pathogenesis of HE, the harmful effects of PCA being caused by them via the production of excess nitric oxide. These results show that nNOS and iNOS are produced in the Purkinje cells and Bergmann glial cells following PCA, implicating nitric oxide in the pathology of HE.

Inhibition of iNOS activity by 1400W decreases glutamate release and ameliorates stroke outcome after experimental ischemia

BACKGROUND AND PURPOSE

It has been shown that the reversed operation of glutamate transporters when ATP levels fall accounts for most glutamate release induced by severe cerebral ischemia. Nitric oxide (NO) is formed after ischemia and causes ATP depletion. Our purpose is to test if NO release from inducible NO synthase (iNOS) after stroke may cause a delayed glutamate release due to ATP depletion that might underlie progression of the ischemic infarct. We have studied the effect of the highly selective inhibitor of iNOS activity 1400W on brain ATP levels, extracellular glutamate, and stroke outcome after transient focal cerebral ischemia in rats.

METHODS

To induce focal ischemia, the middle cerebral artery (MCA) was occluded by using the intraluminal thread technique (tMCAO). 1400W was administered, after tMCAO, by using an Alzet osmotic pump to yield a drug delivery rate of 2.5 mg/kg/h. Results. Postischemic treatment with 1400W induced a reduction in the neurofunctional impairment and in the total volume of brain infarct. Western blot analysis showed ischemia-induced expression of iNOS. Treatment with 1400W partially prevented delayed ATP reduction and produced inhibition of the subsequent delayed increase in glutamate levels caused by the ischemic insult.

CONCLUSIONS

Our data indicate that 1400W improves stroke outcome, an effect concomitant to the inhibition of both ischemia-induced decrease in brain ATP levels and increase in glutamate release. These results provide evidence indicating that the expression of iNOS induced by ischemia may contribute to the progression of the ischemic infarct and have important therapeutic implications for the management of stroke.

Inhibition of mitochondrial respiration by nitric oxide rapidly stimulates cytoprotective GLUT3-mediated glucose uptake through 5'-AMP-activated protein kinase

Recently, we have reported that the inhibition of mitochondrial respiration by nitric oxide (NO) leads to an up-regulation of glycolysis and affords cytoprotection against energy failure through the stimulation of AMPK (5'-AMP-activated protein kinase) [Almeida, Moncada and Bolanos (2004) Nat. Cell Biol. 6, 45-51]. To determine whether glucose transport contributes specifically to this effect, we have now investigated the possible role of NO in modulating glucose uptake through GLUT3, a facilitative high-affinity glucose carrier that has been suggested to afford cytoprotection against hypoglycaemic episodes. To do so, GLUT3-lacking HEK-293T cells (human embryonic kidney 293T cells) were transformed to express a plasmid construction encoding green fluorescent protein-tagged GLUT3 cDNA. This carrier was preferentially localized to the plasma membrane, was seen to be functionally active and afforded cytoprotection against low glucose-induced apoptotic death. Inhibition of mitochondrial respiration by NO triggered a rapid, cGMP-independent enhancement of GLUT3-mediated glucose uptake through a mechanism that did not involve transporter translocation. Furthermore, the functional disruption of AMPK by the RNA interference strategy rendered cells unable to respond to NO by activating GLUT3-mediated glucose uptake. These results suggest that the inhibition of mitochondrial respiration by NO activates AMPK to stimulate glucose uptake, thereby representing a novel survival pathway during pathophysiological conditions involving transient reductions in the supply of cellular glucose.

Response of Purkinje neurons to hypobaric hypoxic exposure as shown by alteration in expression of glutamate receptors, nitric oxide synthases and calcium binding proteins

Hypobaric hypoxia is known to impair muscular coordination. It is not known whether hypobaric hypoxia causes any damage to the Purkinje neurons which may be responsible for impairment of muscular coordination. Expression of ionotropic glutamate receptors N-methyl-d-aspartate receptor subunit 1, amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid GluR2/3, calcium binding proteins and nitric oxide synthases in the Purkinje neurons was examined in rats exposed to hypobaric hypoxia. The mRNA expression of N-methyl-d-aspartate receptor subunit 1, GluR2, GluR3 and nitric oxide synthases [neuronal, endothelial and inducible] was upregulated at 3 h peaking at 24 h after the exposure. This was sustained up to 3 days; thereafter, it was comparable to the controls. Immunohistochemical analysis confirmed a marked expression of N-methyl-d-aspartate receptor subunit 1 and GluR2/3 at the above time intervals. Immunoexpression of calbindin-D28k (calbindin) and parvalbumin was intense in the soma of Purkinje neurons in the control rats. It was, however, drastically downregulated up to 3 days after exposure. At 3 days the neuronal dendrites showed intense expression of calbindin which returned to control levels at 7 days. Expression of neuronal nitric oxide synthase and inducible nitric oxide synthase was markedly upregulated from 3 h to 3 days whereas endothelial nitric oxide synthase expression, localized in the blood vessels and Purkinje neurons, remained elevated up to 24 h after the exposure. A progressive darkening of the Purkinje neuron cell bodies was observed at ultrastructural level up to 3 days but degenerating cells were not observed. A salient alteration was the dilation and stacking of smooth endoplasmic reticulum in the dendrites up to 14 days after the exposure. The present results suggest that hypobaric hypoxia leads to overexpression of N-methyl-d-aspartate receptor subunit 1 and GluR2/3 in Purkinje neurons that may be responsive to altered calcium levels as manifested by decreased expression of calcium binding proteins. This together with excess nitric oxide production may have led to transient ultrastructural changes. We propose that the functions of the Purkinje neurons may be altered in response to an acute exposure to hypobaric hypoxia resulting in impairment of motor coordination.