The dynamic detection of NO during the ischemic postconditioning against global cerebral ischemia/reperfusion injury

Neuroprotective effect of ischemic postconditioning against hyperperfusion and its mechanisms of neuroprotection

Background

In recent years, stroke and ischemia-reperfusion injury has motivated researchers to find new ways to reduce the complications. Although reperfusion is essential for brain survival, it is like a double-edged sword that may cause further damage to the brain. Ischemic postconditioning (IPostC) refers to the control of blood flow in postischemia-reperfusion that can reduce ischemia-reperfusion injuries.

Materials and Methods

Articles were collected by searching for the terms: Ischemic postconditioning and neuroprotective and ischemic postconditioning and hyperperfusion. Suitable articles were collected from electronic databases, including ISI Web of Knowledge, Medline/PubMed, ScienceDirect, Embase, Scopus, Biological Abstract, Chemical Abstract, and Google Scholar.

Results

New investigations show that IPostC has protection against hyperperfusion by reducing the amount of blood flow during reperfusion and thus reducing infarction volume, preventing the blood-brain barrier damage, and reducing the rate of apoptosis through the activation of innate protective systems. Numerous mechanisms have been suggested for IPostC, which include reduction of free radical production, apoptosis, inflammatory factors, and activation of endogenous protective pathways.

Conclusion

It seems that postconditioning can prevent damage to the brain by reducing the flow and blood pressure caused by hyperperfusion. It can protect the brain against damages such as stroke and hyperperfusion by activating various endogenous protection systems. In the present review article, we tried to evaluate both useful aspects of IPostC, neuroprotective effects, and fight against hyperperfusion.

Roles of Nitric Oxide in Brain Ischemia and Reperfusion

Brain ischemia and reperfusion (I/R) is one of the most severe clinical manifestations of ischemic stroke, placing a significant burden on both individuals and society. The only FDA-approved clinical treatment for ischemic stroke is tissue plasminogen activator (t-PA), which rapidly restores cerebral blood flow but can have severe side effects. The complex pathological process of brain I/R has been well-established in the past few years, including energy metabolism disorders, cellular acidosis, doubling of the synthesis or release of excitotoxic amino acids, intracellular calcium homeostasis, free radical production, and activation of apoptotic genes. Recently, accumulating evidence has shown that NO may be strongly related to brain I/R and involved in complex pathological processes. This review focuses on the role of endogenous NO in pathological processes in brain I/R, including neuronal cell death and blood brain barrier disruption, to explore how NO impacts specific signaling cascades and contributes to brain I/R injury. Moreover, NO can rapidly react with superoxide to produce peroxynitrite, which may also mediate brain I/R injury, which is discussed here. Finally, we reveal several therapeutic approaches strongly associated with NO and discuss their potential as a clinical treatment for ischemic stroke.

Overexpression of inducible nitric oxide synthase in the diabetic heart compromises ischemic postconditioning

Ischemia postconditioning (PTC) can reduce myocardial ischemia/reperfusion injury. However, the effectiveness of PTC cardioprotection is reduced or lost in diabetes and the mechanisms are largely unclear. Hyperglycemia can induce overexpression of inducible nitric oxide synthesis (iNOS) in the myocardium of diabetic subjects. However, it is unknown whether or not iNOS especially its overexpression plays an important role in the loss of cardioprotection of PTC in diabetes. C57BL6 and iNOS^-/- mice were treated with streptozotocin to induce diabetes. Part of diabetic C57BL6 mice were also treated with an iNOS specific inhibitor, 1400 W. Mice were subjected to myocardial ischemia/ reperfusion with/without PTC. The hemodynamic parameters, plasma levels of cardiac troponin T (cTnT), TNF-α, IL-6 and nitric oxide (NO) were monitored. The myocardial infarct size, superoxide anion (O₂^-) generation, nitrotyrosine production and apoptosis were measured. The expression of phosphorylated Akt, endothelial NOS (eNOS), iNOS and Erk1/2 in ischemic heart were detected by immunoblot analysis. In diabetic C57BL6 and iNOS^-/- mice, the post-ischemic hemodynamics were impaired, the cTnT, TNF-α, IL-6 level, myocardial infarct size, apoptotic index, O₂^- and nitrotyrosine generation were increased and the Akt/eNOS signal pathways were inhibited. PTC improved hemodynamic parameters, reduced cTnT level, myocardial infarct size, apoptotic index, O₂^- and nitrotyrosine generation and activated Akt/eNOS and Erk1/2 signal pathways in both non-diabetic C57BL6 and iNOS^-/- mice as well as diabetic iNOS^-/- mice, but not in diabetic C57BL6 mice. PTC also increased NO production in both non-diabetic and diabetic C57BL6 and iNOS^-/- mice, and enhanced iNOS expression in non-diabetic C57BL6 mice. 1400 W restored the cardioprotection of PTC in diabetic C57BL6 mice. Our data demonstrated that PTC reduced myocardial ischemia/reperfusion injury in non-diabetic mice but not C57BL6 diabetic mice. Deletion of iNOS restored the cardioprotection of PTC in diabetic mice. Our findings suggest that iNOS plays a key role in the reduction of cardioprotection of PTC in diabetes and may provide a therapeutic target for diabetic patients.

The effect of iloprost and sildenafil, alone and in combination, on myocardial ischaemia and nitric oxide and irisin levels

Aim

Insufficient oxygen supply to organs and tissues due to reduced arterial or venous blood flow results in ischaemia, during which, although ATP production stops, AMP and adenosine continue to be produced from ATP. The fate of irisin, which causes the production of heat instead of ATP during ischaemia, is unknown. Iloprost and sildenafil are two pharmaceutical agents that mediate the resumption of reperfusion (blood supply) via vasodilatation during ischaemic conditions. Our study aimed to explore the effects of iloprost and sildenafil on irisin levels in the heart, liver and kidney tissues and whether these pharmaceutical agents had any impact on serum irisin and nitric oxide levels in rats with induced experimental myocardial ischaemia.

Methods

The study included adult male Sprague-Dawley rats aged 10 months and weighing between 250 and 280 g. The animals were randomly allocated to eight groups, with five rats in each group. The groups were: sham (control), iloprost (ILO), sildenafil (SIL), ILO + SIL, myocardial ischaemia (MI), MI + ILO, MI + SIL and MI + ILO + SIL. The treatment protocols were implemented before inducing ischaemia, which was done by occluding the left coronary artery with a plastic ligature for 30 minutes. Following the reperfusion procedure, all rats were sacrificed after 24 hours, and their heart, liver and kidney tissues and blood samples were collected for analyses. An immunohistochemical method was used to measure the change in irisin levels, the ELISA method to quantify blood irisin levels, and Griess’ assay to determine nitric oxide (NO) levels in the serum and tissue. Myocardial ischaemia was confirmed based on the results of Masson’s trichrome staining, as well as levels of troponin and creatine kinase MB.

Results

Irisin levels in biological tissue and serum dropped statistically significantly in the ischaemic group (MI), but were restored with ILO and SIL administration. Individual SIL administration was more potently restorative than individual ILO administration or the combined administration of the two agents. NO level, on the other hand, showed the opposite tendency, reaching the highest level in the MI group, and falling with the use of pharmaceutical agents.

Conclusions

Individual or combined administration of ILO and SIL reduced myocardial ischaemia and NO levels, and increased irisin levels. Elevated levels of irisin obtained by drug administration could possibly contribute to accelerated wound recovery by local heat production. Sildenafil was more effective than iloprost in eliminating ischaemia and may be the first choice in offsetting the effects of ischaemia in the future.

Exercise training with concomitant nitric oxide synthase inhibition improved anxiogenic behavior, spatial cognition, and BDNF/P70S6 kinase activation in 20-month-old rats

This study aimed to investigate the effect of exercise and nitric oxide synthase (NOS) inhibition on memory, anxiety, and protein levels of brain-derived neurotrophic factor (BDNF) and P70S6 kinase (P70S6K). Twenty-month-old rats were divided into 6 groups: a control group, 2 groups treated with l-nitro-arginine methyl ester (L-NAME) (25 or 100 mg/kg) for 63 days, 2 groups treated with L-NAME (25 or 100 mg/kg) for 63 days plus 2 months of exercise, and 1 group treated with exercise. Behavioral tests were conducted to determine the anxiolytic and memory-improving role of exercise and NOS inhibition. BDNF, P70S6K, and cleaved caspase-3 protein levels in the hippocampus and prefrontal cortex were evaluated by Western blotting. Exercise and L-NAME (25 mg/kg) or their combination had an anxiolytic effect and improved spatial memory in old rats compared with the control or exercised group, respectively. Exercise and treatment with a low dose of L-NAME (25 mg/kg) each increased BDNF and P70S6K in the hippocampus and prefrontal cortex compared with levels in control rats. In comparison with exercise alone, co-treatment with exercise and a low dose of L-NAME (25 mg/kg) also increased BDNF and P70S6K in the hippocampus. The neuronal level of cleaved caspase-3 was reduced in the L-NAME (25 mg/kg) + exercise group compared with the exercised group. The L-NAME (100 mg/kg) + exercise treatment had no positive behavioral or molecular effects compared with exercise alone. The protective role of NOS inhibition and aerobic exercise against aging is probably modulated via BDNF and P70S6K in the brain.

The effects of 7-nitroindazole on serum neuron-specific enolase and astroglia-derived protein (S100β) levels after traumatic brain injury

We investigated the possible role of 7-nitroindazole (7-NI) in regulating serum neuron-specific enolase (NSE) and S100β levels in a rat model of traumatic brain injury (TBI). We also explored the possible mechanism by which 7-NI may affect the level of NSE and S100β. A total of 160 healthy adult male Sprague-Dawley rats were randomly divided into 2 groups: i) The saline-treated group and ii) the 7-NI-treated group. Using the random number table, the groups were further divided into four subgroups: i) The sham-injured group; ii) the TBI 6 h group; iii) the TBI 12 h group; and iv) the TBI 24 h group (n=20). Controlled cortical impact in rats was established. Serum NSE and S100β levels, nitric oxide (NO) level, water content, Evans blue (EB) content, malondialdehyde (MDA) level and total superoxide dismutase (T-SOD) level in the brain tissue were measured. NO synthase (NOS) activity was measured at 6, 12 and 24 h after TBI. Pathological changes in brain tissue were studied by hematoxylin and eosin (H&E) staining at each time-point. NSE and S100β levels, NO content, water content, EB content and MDA level in the brain tissue increased significantly after TBI. NOS activity was also increased significantly after TBI while T-SOD content in brain tissue was significantly reduced after TBI. H&E staining showed that brain damage was aggravated gradually after TBI. We concluded that the early application of 7-NI significantly reduced serum NSE and S100β levels after TBI. The neuroprotective effects of 7-NI may be associated with reduced NOS activity, reduced NO content, alleviated brain edema, lower blood-brain barrier permeability and oxidative stress. Serum NSE and S100β levels can reflect the therapeutic effect of 7-NI, which suggest a good diagnostic value.

Overview of Experimental and Clinical Findings regarding the Neuroprotective Effects of Cerebral Ischemic Postconditioning

Research on attenuating the structural and functional deficits observed following ischemia-reperfusion has become increasingly focused on the therapeutic potential of ischemic postconditioning. In recent years, various methods and animal models of ischemic postconditioning have been utilized. The results of these numerous studies have indicated that the mechanisms underlying the neuroprotective effects of ischemic postconditioning may involve reductions in the generation of free radicals and inhibition of calcium overload, as well as the release of endogenous active substances, alterations in membrane channel function, and activation of protein kinases. Here we review the novel discovery, mechanism, key factors, and clinical application of ischemic postconditioning and discuss its implications for future research and problem of clinical practice.

Effect of the PGD2-DP signaling pathway on primary cultured rat hippocampal neuron injury caused by aluminum overload

In the present study, the agonists and antagonists of DP receptor were used to examine whether the PGD₂-DP signaling pathway affects neuronal function. Primary cultured hippocampal neuron was prepared and treated with aluminum maltolate (100 μM) to establish the neuronal damage model. PGD₂ and cAMP content was detected by ELISA. L-PGDS and DPs mRNA and protein expression were measured by RT-PCR and Western blotting, respectively. The aluminium-load neuron was treated with the DP₁ agonist BW245C, the DP₁ antagonist BWA868C, the DP₂ agonist DK-PGD_2, and the DP₂ antagonist CAY10471, respectively. Neuronal pathomorphology was observed using H-E staining. The cell viability and the lactate dehydrogenase leakage rates of neurons were measured with MTT and LDH kit, respectively. Ca²⁺ level was detected by Fluo-3/AM. In the model group, the MTT values obviously decreased; LDH leakage rates and PGD₂ content increased significantly; L-PGDS, DP₁ mRNA and protein expressions increased, and DP₂ level decreased. BW245C reduced the Ca²⁺ fluorescence intensity and protected the neurons. DK-PGD₂ increased the intensity of Ca²⁺ fluorescence, while CAY10471 had the opposite effect. In conclusion, contrary to the effect of DP₂, the PGD₂-DP₁ signaling pathway protects against the primary cultured rat hippocampal neuronal injury caused by aluminum overload.

Neuroprotective effects of bilobalide on cerebral ischemia and reperfusion injury are associated with inhibition of pro-inflammatory mediator production and down-regulation of JNK1/2 and p38 MAPK activation

BACKGROUND

Mitogen-activated protein kinase (MAPK) signaling pathways are implicated in inflammatory and apoptotic processes of cerebral ischemia and reperfusion (I/R) injury. Hence, MAPK pathways represent a promising therapeutic target. Exploring the full potential of inhibitors of MAPK pathways is a useful therapeutic strategy for ischemic stroke. Bilobalide, a predominant sesquiterpene trilactone constituent of Ginkgo biloba leaves, has been shown to exert powerful neuroprotective properties, which are closely related to both anti-inflammatory and anti-apoptotic pathways. We investigated the neuroprotective roles of bilobalide in the models of middle cerebral artery occlusion and reperfusion (MCAO/R) and oxygen-glucose deprivation and reoxygenation (OGD/R) of cerebral I/R injury. Moreover, we attempted to confirm the hypothesis that its protection effect is via modulation of pro-inflammatory mediators and MAPK pathways.

METHODS

Male Sprague-Dawley rats were subjected to MCAO for 2 h followed by reperfusion for 24 h. Bilobalide was administered intraperitoneally 60 min before induction of middle cerebral artery occlusion (MCAO). After reperfusion, neurological deficit scores, infarct volume, infarct weight, and brain edema were assessed. Ischemic penumbrae of the cerebral cortex were harvested to determine superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide, TNF-α, interleukin 1β (IL-1β), p-ERK1/2, p-JNK1/2, and p-p38 MAPK concentration. Similarly, the influence of bilobalide on the expression of nitric oxide, TNF-α, IL-1β, p-ERK1/2, p-JNK1/2, and p-p38 MAPK was also observed in an OGD/R in vitro model of I/R injury.

RESULTS

Pretreatment with bilobalide (5, 10 mg/kg) significantly decreased neurological deficit scores, infarct volume, infarct weight, brain edema, and concentrations of MDA, nitric oxide, TNF-α, IL-1β, and increased SOD activity. Furthermore, bilobalide (5, 10 mg/kg) pretreatment significantly down-regulated both p-JNK1/2 and p-p38 MAPK expression, whereas they had no effect on p-ERK1/2 expression in the ischemic penumbra. Supporting these observations in vivo, pretreatment with bilobalide (50, 100 μM) significantly down-regulated nitric oxide, TNF-α, IL-1β, p-JNK1/2, and p-p38 MAPK expression, but did not change p-ERK1/2 expression in rat cortical neurons after OGD/R injury.

CONCLUSIONS

These data indicate that the neuroprotective effects of bilobalide on cerebral I/R injury are associated with its inhibition of pro-inflammatory mediator production and down-regulation of JNK1/2 and p38 MAPK activation.