Neuroprotective effects of acetylsalicylic acid in an animal model of focal brain ischemia

Linalyl acetate prevents hypertension-related ischemic injury

Ischemic stroke remains an important cause of disability and mortality. Hypertension is a critical risk factor for the development of ischemic stroke. Control of risk factors, including hypertension, is therefore important for the prevention of ischemic stroke. Linalyl acetate (LA) has been reported to have therapeutic effects in ischemic stroke by modulating intracellular Ca2+ concentration and having anti-oxidative properties. The preventive efficacy of LA has not yet been determined. This study therefore investigated the preventive efficacy of LA in rat aortas exposed to hypertension related-ischemic injury, and the mechanism of action of LA.Hypertension was induced in vivo following ischemic injury to the aorta induced by oxygen-glucose deprivation and reoxygenation in vitro. Effects of LA were assayed by western blotting, by determining concentrations of lactate dehydrogenase (LDH) and reactive oxygen species (ROS) and by vascular contractility assays. LA significantly reduced systolic blood pressure in vivo. In vitro, LA suppressed ischemic injury-induced expression of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47phox, as well as ROS production, LDH release, and ROS-induced endothelial nitric oxide synthase suppression. These findings indicate that LA has anti-hypertensive properties that can prevent hypertension-related ischemic injury and can prevent NADPH oxidase-induced production of ROS.

Shengmai injection attenuates the cerebral ischemia/reperfusion induced autophagy via modulation of the AMPK, mTOR and JNK pathways

Context Shengmai injection (SMI) is a patented Chinese medicine originated from the ancient Chinese herbal compound Shengmai san, which is used extensively for the treatment of cardiovascular and cerebrovascular disease in the clinic. Objective To determine the neuroprotective effect of SMI, we investigated the effect of SMI on cerebral ischemia/reperfusion (I/R) injury in mice as well as the mechanisms underlying this effect. Materials and methods Right middle cerebral artery was occluded by inserting a thread through internal carotid artery for 1 h, and then reperfused for 24 h in mice. The neuroprotective effects were determined using transmission electron microscopic examination, the evaluation of infarct volume, neurological deficits and water brain content. Related mechanisms were evaluated by immunofluorescence staining and western blotting. SMI was injected intraperitoneally after 1 h of ischemia at doses of 1.42, 2.84 and 5.68 g/kg. The control group received saline as the SMI vehicle. Results Results showed that SMI (1.42, 2.84 and 5.68 g/kg) could significantly reduce the infarct volume, SMI (5.68 g/kg) could also significantly improve the neurological deficits, decreased brain water content, as well as the neuronal morphological changes. SMI (5.68g/kg) could significantly inhibit the expression of autophagy-related proteins: Beclin1 and LC3. It also reduced the increase in LC3-positive cells. SMI (5.68 g/kg) remarkably inhibited the phosphorylation of adenosine monophosphate activated protein kinase (AMPK), and down-regulated the phosphorylation of mammalian target of rapamycin (mTOR) and Jun N-terminal kinase (JNK) after 24 h of reperfusion. Discussion and conclusion The results indicate that SMI provides remarkable protection against cerebral ischemia/reperfusion injury, which may be partly due to the inhibition of autophagy and related signalling pathways.

Deciphering glycomics and neuroproteomic alterations in experimental traumatic brain injury: Comparative analysis of aspirin and clopidogrel treatment

As populations age, the number of patients sustaining traumatic brain injury (TBI) and concomitantly receiving preinjury antiplatelet therapy such as aspirin (ASA) and clopidogrel (CLOP) is rising. These drugs have been linked with unfavorable clinical outcomes following TBI, where the exact mechanism(s) involved are still unknown. In this novel work, we aimed to identify and compare the altered proteome profile imposed by ASA and CLOP when administered alone or in combination, prior to experimental TBI. Furthermore, we assessed differential glycosylation PTM patterns following experimental controlled cortical impact model of TBI, ASA, CLOP, and ASA + CLOP. Ipsilateral cortical brain tissues were harvested 48 h postinjury and were analyzed using an advanced neuroproteomics LC-MS/MS platform to assess proteomic and glycoproteins alterations. Of interest, differential proteins pertaining to each group (22 in TBI, 41 in TBI + ASA, 44 in TBI + CLOP, and 34 in TBI + ASA + CLOP) were revealed. Advanced bioinformatics/systems biology and clustering analyses were performed to evaluate biological networks and protein interaction maps illustrating molecular pathways involved in the experimental conditions. Results have indicated that proteins involved in neuroprotective cellular pathways were upregulated in the ASA and CLOP groups when given separately. However, ASA + CLOP administration revealed enrichment in biological pathways relevant to inflammation and proinjury mechanisms. Moreover, results showed differential upregulation of glycoproteins levels in the sialylated N-glycans PTMs that can be implicated in pathological changes. Omics data obtained have provided molecular insights of the underlying mechanisms that can be translated into clinical bedside settings.

Lack of antiapoptotic effects of antiplatelet drug, aspirin and clopidogrel, and antioxidant, MCI-186, against focal ischemic brain damage in rats

OBJECTIVES

This study evaluated the antiapoptotic effect of antiplatelet drugs, aspirin and clopidogrel, and the antioxidant drug, MCI-186, against focal cerebral ischemic rat brain damage.

METHODS

Cerebral ischemia was mechanically induced by 2-hour occlusion of the left middle cerebral artery (MCA) using an intraluminal filament followed by 24-hour reperfusion.

RESULTS

The cerebral infarct size was little affected by oral administration of 300 mg/kg aspirin, 30 mg/kg clopidogrel or 100 mg/kg MCI-186, but was significantly reduced by 30 mg/kg cilostazol. However, intravenous administration of 10 mg/kg MCI-186 suppressed the infarct size. DNA fragmentation observed in the cortical tissues corresponding to the penumbral zone was not suppressed by aspirin, clopidogrel or MCI-186, but was significantly suppressed by cilostazol. Increased phosphorylation of phosphatase and tensin homolog deleted from chromosome 10 (PTEN) and Bax protein, and decreased Akt/cyclic AMP response element binding protein (CREB) phosphorylation, including Bcl-2 protein in the vehicle-treated group were not affected by treatment with aspirin, clopidogrel and MCI-186, whereas those effects were reversed by cilostazol.

CONCLUSION

Thus, it is suggested that antiplatelet drugs, aspirin and clopidogrel, and antioxidant drug, MCI-186, showed little antiapoptotic effect in contrast to cilostazol.

Glutamate oxidative injury to RGC-5 cells in culture is necrostatin sensitive and blunted by a hydrogen sulfide (H2S)-releasing derivative of aspirin (ACS14)

Oxidative stress to RGC-5 cells in culture was delivered by exposure to a combination of glutamate (Glu) and buthionine-S,R-sulfoximine (BSO). The effect of the insult on cell survival was quantified by the resazurin-reduction and a dead/live assays. Moreover, breakdown of DNA, the localisation of phosphatidylserine and reactive radical species (ROS) and its quantification were determined. In addition, various proteins and mRNAs were studied using Western blot, real time PCR and immunocytochemistry. ACS14, its sulfurated moiety ACS1 and aspirin were tested for their ability to blunt the negative effects of Glu/BSO on RGC-5 cells. In addition assays were carried out to see whether any of these substances influenced glutathione (GSH). Glu/BSO dose-dependently kills RGC-5 cells by a mechanism that involves an elevation of ROS accompanied by a breakdown of DNA, expression of phosphatidylserine and the activation of p38 MAPK. The process is unaffected by the pan caspase inhibitor z-VAD-fmk, does not involve the activation of apoptosis inducing factor (AIF) but is sensitive to active necrostatin-1. In cell viability studies (resazurin-reduction assay), ACS1 and ACS14 equally counteracted the negative effects of 5mM Glu/BSO to RGC-5 cells but aspirin was only effective with a milder oxidative stress (1 mM Glu/BSO). In all other assays ACS14 was very much more effective than aspirin at counteracting the influence of 5mM Glu/BSO. Moreover, ACS14 and ACS1 directly stimulated GSH while aspirin was ineffective. In addition the neuroprotecive effect of ACS14 was specifically blunted by the non-specific potassium channel blocker glibenclamide. Also the up-regulation of Bcl-2, HO-1 and XIAP induced by 5mM Glu/BSO were all attenuated to a greater extent by ACS14 (20 μM) than aspirin (20 μM). These data show that ACS14 is a very effective neuroprotectant when compared with aspirin. ACS14 maintains its aspirin characteristics and has the ability to release H(2)S. The combined multiple actions of aspirin and H(2)S in the form of ACS14 is worthy to consider for possible use in the treatment of glaucoma.

Multifunctional actions of approved and candidate stroke drugs

Ischemic stroke causes brain damage by multiple pathways. Previous stroke trials have demonstrated that drugs targeting one or only a few of these pathways fail to improve clinical outcome after stroke. Drugs with multimodal actions have been suggested to overcome this challenge. In this review, we describe the mechanisms of action of agents approved for secondary prevention of ischemic stroke, such as antiplatelet, antihypertensive, and lipid-lowering drugs. These drugs exhibit considerable properties beyond their classical mechanisms, including neuroprotective and neuroregenerative properties. In addition, candidate stroke drugs currently studied in clinical phase III trials are described. Among these, albumin, hematopoietic growth factors, and citicoline have been identified as promising agents with multiple mechanisms. These drugs offer hope that additional treatment options for the acute phase after a stroke will become available in the near future.

Secondary stroke prevention: inside the vessels and beyond

Cerebral ischaemic stroke is frequently a relapsing, if not chronic, disease. Its incidence is age-dependent, and with the ageing of society the need for effective therapies increases. This review considers current and alternative hypotheses underlying secondary prevention of stroke. Currently, secondary stroke prevention is widely practiced with aspirin (acetylsalicylic acid), a drug that has been in use for more than 100 years. Newer drugs such as ticlopidine and clopidogrel have subsequently been developed, but their efficacy barely surpasses that of aspirin. Other drugs used in secondary stroke prevention include HMG-CoA reductase inhibitors and antihypertensive agents. The endovascular paradigm has shaped the thinking of secondary stroke prevention, and aspirin, ticlopidine and clopidogrel are known as 'platelet inhibitors'; however, their pharmacological and clinical effects are not fully explained within the platelet paradigm. Moreover, in recent years, reduction of stroke incidence has also been observed with HMG-CoA reductase inhibitors, regardless of their lipid-lowering effects. Hence, current understanding needs to be supplemented by considering mechanisms beyond platelet inhibition. Evidence has shown that aspirin, ticlopidine and clopidogrel share neuroprotective properties not explained by the platelet paradigm and that are reminiscent of a preconditioning effect. This neuroprotective mechanism is also shared with HMG-CoA reductase inhibitors.

Neuroprotection by early and delayed treatment of acute stroke with high dose aspirin

Acetylsalicylic acid (ASA; Aspirin) has a neuroprotective potential by its anti-excitotoxic and anti-inflammatory effects. A temporary middle cerebral artery occlusion (tMCAO) model was used in 80 Wistar rats to evaluate whether a high dose of Aspirin (40 mg/kg) applied with different initiation time points after stroke onset (30 min, 3 h, 6 h, 12 h, 20 rats for each time group) and followed by repeated administration (1, 2 and 3 days) is neuroprotective. Neurological score and brain infarct volume were analyzed and indicated that postischemic therapy initiation at 30 min and as late as 6 h led to better neurological recovery (6 h, p=0.0046) and significant smaller infarct size (6 h, 57+/-9 mm(3), n=10, p=0.0043) compared to the saline control group (110+/-13 mm(3), n=10). Thus, there may be a relatively wide time window for acute stroke therapy with high dose Aspirin.

Effects of Triflusal and Aspirin in a Rat Model of Cerebral Ischemia

Background and Purpose— Neuroinflammation plays a critical role in the pathogenesis of cerebral ischemia. Triflusal, a selective cyclooxygenase-2, and its active metabolite 3-hydroxy-4-trifluoromethylbenzoic acid may inhibit apoptosis and inflammation after cerebral ischemia. An in vivo model of cerebral ischemia was used to investigate the effects of triflusal and aspirin treatment on infarct volume, and inflammation after cerebral ischemia in the rat.

Methods— Male Wistar rats were subjected to a permanent right-sided middle cerebral artery occlusion. Rats received oral administration of either triflusal or aspirin. After 3 days after surgery, immunostaining was used to detect neuroinflammatory cells and molecules, and infarct volumes were measured.

Results— Both triflusal and aspirin at a dose of 30 mg/kg but not 10 mg/kg significantly reduced infarct volume compared with vehicle treatment. Middle cerebral artery occlusion resulted in increased astrocyte and heat shock protein-27 (Hsp27) immunostaining in the ipsilateral cortex. Triflusal (30 mg/kg) or aspirin treatment (30 mg/kg) did not reduce the levels of GFAP or Hsp27 immunostaining. Triflusal (30 mg/kg) also significantly decreased the protein levels of IL-Iβ but not nuclear factor kappa B or tumor necrosis factor-α in the cortex ipsilateral to the middle cerebral artery occlusion.

Conclusions— The results suggest that triflusal and aspirin appear to be equally neuroprotective against middle cerebral artery occlusion-induced cerebral ischemia. Therefore, strong rationale exists to continue the neuroprotective examination of triflusal in brain injury.

Melatonin reduces infarction volume in a photothrombotic stroke model in the wild-type but not cyclooxygenase-1-gene knockout mice

Cyclooxygenase (COX)-2 plays a harmful role in cerebral ischemic/reperfusion injury, but the role of COX-1 is uncertain. In the present study, cerebral infarct was induced by photothrombosis. Intraperitoneal injections of melatonin at 15 g/kg or its vehicle were made at 0.5 hr before stroke and 24 and 48 hr after stroke. Cerebral blood flow (CBF) in the penumbra was monitored during stroke using a laser Doppler flowmeter. Sensorimotor behavior was evaluated using the turning in an alley and falling from a pole tests at 1 hr before stroke and 24 and 48 hr after stroke. Infarct volume was determined from the T2-weighted magnetic resonance images at 72 hr after stroke. During the first 15 min of stroke, CBF decreased in the penumbra in both homozygous COX-1-gene knockout and wild-type mice. Melatonin treatment improved the penumbral CBF in the wild-type mice. Mild poststroke impairment in sensorimotor behavior was detected by the turning in an alley test in which the COX-1-gene knockout mice performed better. Melatonin treatment did not affect the poststroke sensorimotor behavior. The relative infarct volume at 72 hr after stroke was 8.1% and 8.4% in the COX-1-gene knockout and wild-type mice, respectively. Melatonin treatment reduced the relative infarct volume to 6.3% in the latter but not in the former (8.2%). Thus, COX-1-gene knockout does not affect the brain's susceptibility to photothrombotic stroke. Melatonin treatment reduces infarct size in the wild-type mice following photothrombotic stroke partly via maintenance of penumbral CBF in which the COX-1-gene may play a role.

Acetylsalicylic acid accelerates the antidepressant effect of fluoxetine in the chronic escape deficit model of depression

Evidence has accumulated suggesting that major depression is associated with dysfunction of inflammatory mediators. Moreover, antidepressants show an anti-inflammatory action possibly related to their clinical efficacy. An improvement in psychiatric symptoms has been recently reported in patients treated with anti-inflammatory drugs for other indications. These data imply that inflammation may be involved in the pathogenesis of depression and that anti-inflammatory drugs may be used as an adjunctive therapy. The aim of the present study was to evaluate the behavioural effect of the co-administration of acetylsalicylic acid (ASA, 45 mg/kg or 22.5 mg/kg) and fluoxetine (FLX, 5 mg/kg) in the chronic escape deficit model of depression. The chronic escape deficit model is based on the modified reactivity of rats to external stimuli induced by exposure to unavoidable stress and allows evaluation of the capacity of a treatment to revert the condition of escape deficit. In this model, FLX alone needs to be administered for at least 3 weeks to revert this condition. Our results show that combined treatment of fluoxetine and ASA completely reverted the condition of escape deficit by as early as 7 days, the effect being already partially present after 4 days. The effect was maintained after 14 and 21 days of treatment. ASA alone was ineffective at any time tested and the effect of fluoxetine was significant only at 21 days. These results, together with clinical data from preliminary results, suggest that ASA might accelerate the onset of action of selective serotonin reuptake inhibitor antidepressants.

Effects of aspirin and mefenamic acid on soman poisoning-induced neuropathology in mice

The efficacy of aspirin and mefenamic acid to counteract soman-induced brain damage was investigated in mice. Neuronal damage was evaluated in the hippocampus and amygdala by performing omega3 receptor density measurements and hemalun-phloxin staining. The effect of both drugs on the proliferation of neural progenitors after soman exposure was also assessed. Mefenamic acid aggravated the soman-induced hippocampal neuropathology. On the other hand, aspirin recorded a weak neuroprotective effect in the amygdala. However, this drug also diminished the proliferation of neural precursor cells. The possible neurochemical mechanisms underlying such differences in the efficacy of the two drugs are also reviewed.

Inflammation and stroke: putative role for cytokines, adhesion molecules and iNOS in brain response to ischemia

Ischemic stroke is a leading cause of death and disability in developed countries. Yet, in spite of substantial research and development efforts, no specific therapy for stroke is available. Several mechanism for neuroprotection have been explored including ion channels, excitatory amino acids and oxygen radicals yet none has culminated in an effective therapeutic effect. The review article on "inflammation and stroke" summarizes key data in support for the possibility that inflammatory cells and mediators are important contributing and confounding factors in ischemic brain injury. In particular, the role of cytokines, endothelial cells and leukocyte adhesion molecules, nitric oxide and cyclooxygenase (COX-2) products are discussed. Furthermore, the potential role for certain cytokines in modulation of brain vulnerability to ischemia is also reviewed. The data suggest that novel therapeutic strategies may evolve from detailed research on some specific inflammatory factors that act in spatial and temporal relationships with traditionally recognized neurotoxic factors. The dual nature of some mediators in reformatting of brain cells for resistance or sensitivity to injury demonstrate the delicate balance needed in interventions based on anti-inflammatory strategies.

Facilitatory effect of aspirin on glutamate release from rat hippocampal nerve terminals: involvement of protein kinase C pathway

The effect of aspirin on glutamate release from isolated nerve terminals (synaptosomes) from rat hippocampus was examined. The Ca(2+)-dependent release of glutamate evoked by 4-aminopyridine (4AP) was facilitated by aspirin in a concentration-dependent manner, but the 4AP-evoked Ca(2+)-independent release was not modified. Also, aspirin-mediated facilitation of glutamate release was completely inhibited by bafilomycin A1, which depletes vesicle content by inhibiting the synaptic vesicle H(+)-ATPase that drives glutamate uptake, not by l-trans-pyrrolidine-2,4-dicarboxylic acid (l-trans-PDC), a excitatory amino acid (EAA) transporter inhibitor, suggesting that the facilitation of glutamate release produced by aspirin originates from synaptic vesicle exocytosis rather than reversal of the plasma membrane glutamate transporter. In addition, aspirin did not alter either 4AP-evoked depolarization of the synaptosomal plasma membrane potential or Ca(2+) ionophore ionomycin-induced glutamate release, but significantly increased in 4AP-evoked Ca(2+) influx. A possible effect of aspirin on synaptosomal Ca(2+) channels was confirmed in experiments where synaptosomes pretreated with a combination of the N- and P/Q-type Ca(2+) channel blockers, which abolished the aspirin-mediated facilitation of glutamate release. The facilitatory action by aspirin observed in glutamate release was mimicked and occluded by arachidonic acid (AA) and eicosatetraynoic acid (ETYA), an analogue of AA that mimics the effect of AA but cannot be metabolized. Furthermore, this aspirin-mediated facilitation of glutamate release may depend on activation of protein kinase C (PKC), because PKC activator and PKC inhibitor, respectively, superseding or suppressing the facilitatory effect of aspirin. Together, these results suggest that aspirin exerts their presynaptic facilitatory effect, likely through AA directly to induce the activation of PKC, which subsequently enhances the Ca(2+) influx through voltage-dependent N- and P/Q-type Ca(2+) channels to cause an increase in evoked glutamate release from rat hippocampal nerve terminals.

5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) attenuates the expression of LPS- and Abeta peptide-induced inflammatory mediators in astroglia

BACKGROUND

Alzheimer's disease (AD) pathology shows characteristic 'plaques' rich in amyloid beta (Abeta) peptide deposits. Inflammatory process-related proteins such as pro-inflammatory cytokines have been detected in AD brain suggesting that an inflammatory immune reaction also plays a role in the pathogenesis of AD. Glial cells in culture respond to LPS and Abeta stimuli by upregulating the expression of cytokines TNF-alpha, IL-1beta, and IL-6, and also the expression of proinflammatory genes iNOS and COX-2. We have earlier reported that LPS/Abeta stimulation-induced ceramide and ROS generation leads to iNOS expression and nitric oxide production in glial cells. The present study was undertaken to investigate the neuroprotective function of AICAR (a potent activator of AMP-activated protein kinase) in blocking the pro-oxidant/proinflammatory responses induced in primary glial cultures treated with LPS and Abeta peptide.

METHODS

To test the anti-inflammatory/anti-oxidant functions of AICAR, we tested its inhibitory potential in blocking the expression of pro-inflammatory cytokines and iNOS, expression of COX-2, generation of ROS, and associated signaling following treatment of glial cells with LPS and Abeta peptide. We also investigated the neuroprotective effects of AICAR against the effects of cytokines and inflammatory mediators (released by the glia), in blocking neurite outgrowth inhibition, and in nerve growth factor-(NGF) induced neurite extension by PC-12 cells.

RESULTS

AICAR blocked LPS/Abeta-induced inflammatory processes by blocking the expression of proinflammatory cytokine, iNOS, COX-2 and MnSOD genes, and by inhibition of ROS generation and depletion of glutathione in astroglial cells. AICAR also inhibited down-stream signaling leading to the regulation of transcriptional factors such as NFkappaB and C/EBP which are critical for the expression of iNOS, COX-2, MnSOD and cytokines (TNF-alpha/IL-1beta and IL-6). AICAR promoted NGF-induced neurite growth and reduced neurite outgrowth inhibition in PC-12 cells treated with astroglial conditioned medium.

CONCLUSION

The observed anti-inflammatory/anti-oxidant and neuroprotective functions of AICAR suggest it as a viable candidate for use in treatment of Alzheimer's disease.

Underlying mechanism for NMDA receptor antagonism by the anti-inflammatory drug, sulfasalazine, in mouse cortical neurons

Sulfasalazine (SULFA), of anti-inflammatory drugs, shows a protective action against NMDA-induced neuronal toxicity. Here, we used an electrophysiological study of the pharmacological effects of SULFA on NMDA receptors to examine the molecular mechanisms underlying the neuroprotective role of SULFA. The drug acted as a typical noncompetitive inhibitor with neither agonist- nor use-dependency, and antagonized NMDA-evoked responses in a voltage-independent manner, suggesting that SULFA is not an open channel blocker. Noise and single channel analyses showed that SULFA-blocked NMDA responses by reducing the number of NMDA channels available for activation, and also reduced the channel open probability without changing single channel conductance. Moreover, SULFA accelerated NMDA desensitization without affecting the affinity of the receptor for NMDA or glutamate. Taken together, these data indicate that SULFA blocks the NMDA response by reducing the number of NMDA channels available for activation. This appears to occur via a SULFA-induced decrease in the channel open probability, and a concomitant acceleration of the desensitization response, which is likely associated with a reduced affinity for glycine. SULFA indeed decreased the glycine-potentiated NMDA response without binding directly to the glycine site. Our results suggest that SULFA acts as a noncompetitive NMDA receptor antagonist with an allosteric glycine modulation.

Interaction Between a Rat Model of Cerebral Ischemia and β-Amyloid Toxicity

Background and Purpose— Clinical data suggest that Alzheimer disease (AD) and stroke together potentiate cognitive impairment. Our rat model demonstrates that this interaction may be mediated through inflammatory cells and pathways. Thus, anti-inflammatory agents such as Triflusal, a nonsteroidal anti-inflammatory agent (NSAID), may provide neuroprotection for susceptible neurons in AD and cerebral ischemia.

Methods— AD was modeled by cerebroventricular injections of β-amyloid (Aβ25–35) and subcortical lacunar infarcts by striatal endothelin injections. Inflammatory mechanisms were examined by immunohistochemical analysis. Behavioral tasks were assessed with the Montoya staircase test.

Results— Triflusal reduced pathologic and inflammatory markers and functional deficits in rats receiving Aβ or endothelin alone but was less effective in the more severe pathology of the combined Aβ/endothelin model.

Conclusions— Higher doses or more prolonged treatment with NSAIDs may be required for more effective neuroprotection in combined AD and stroke conditions.

Effect of steroidal and non-steroidal drugs on the microglia activation pattern and the course of degeneration in the retinal degeneration slow mouse

BACKGROUND

In hereditary retinal degeneration, microglia cells become activated, migrate through the outer nuclear layer (ONL) and accumulate in the subretinal space. Although this inflammatory process is not likely to be responsible for the onset of photoreceptor apoptosis, cytotoxic substances secreted by activated microglia could potentially accelerate and perpetuate the degenerative process. Anti-inflammatory drugs have been shown to modulate the microglia response in neurodegenerative disorders and potentially ameliorate the disease progression in various animal model systems. In this study we wanted to test the impact of the most commonly used anti-inflammatory drugs (acetylsalicylate and prednisolone) on the microglia activation pattern, the rate of caspase-3-dependent photoreceptor apoptosis and the course of the degeneration in the retinal degeneration slow (rds) mouse retina.

METHODS

169 pigmented rds mice and 30 CBA wild-type mice were used for this study. The treatment groups were injected daily with either acetylsalicylate (200 mg/kg) or prednisolone (2 mg/kg) i.p. from day 0 up to 3 months. Animals were sacrificed at days 10, 14, 16, 18, 20, 30, 40, 60 and 90. Cryoprotected frozen sections were immunostained with F4/80 and cleaved caspase-3 antibodies. The main outcome measures were the total microglia count in the subretinal space, the total cleaved caspase-3-positive cells in the ONL and the averaged number of photoreceptor rows in the midperipheral retina.

RESULTS

Neither acetylsalicylate nor prednisolone reduced subretinal microglia accumulation in the rds mouse degeneration model. Moreover, they aggravated migration and accumulation in the early time course. The apoptotic cascade started earlier and was more pronounced in both treatment groups compared to the control group. The pace of retinal degeneration was not reduced in the treatment groups compared to the untreated control. In contrast, acetylsalicylate did significantly accelerate the photoreceptor cell degeneration in comparison to the prednisolone (p < 0.001) and to the control group (p < 0.001).

CONCLUSIONS

Acetylsalicylate and prednisolone do not decrease the microglia response in the rds mouse and are not neuroprotective. More research is needed to clarify the molecular mechanisms which lead to photoreceptor cell death and to elucidate the complex role of microglia in inherited retinal degeneration.

Effects of triflusal on oxidative stress, prostaglandin production and nitric oxide pathway in a model of anoxia-reoxygenation in rat brain slices

Acetylsalicylic acid (ASA) is the most widely used drug in the prevention of ischemic vascular accidents, mainly because of its antithrombotic effect. Recently, evidence of a neuroprotective effect has appeared. The aim of this study was to evaluate the neuroprotective effect of triflusal, a fluorinated derivative of ASA, in a model of anoxia-reoxygenation in rat brain slices. Rats (n=10 per group) were treated for 7 days with 1, 10 or 50 mg/kg/day p.o. of triflusal or ASA or solvent (control group), then brain slices were obtained and subjected to a period of anoxia followed by 180 min of reoxygenation. We measured oxidative stress parameters (lipid peroxidation, glutathione system), prostaglandins (PGE(2)), nitric oxide pathway activity (NO) (nitrites+nitrates, constitutive and inducible NO synthase activity) and cell death (lactate dehydrogenase (LDH) efflux). Triflusal decreased cell death in rat brain slices subjected to reoxygenation after anoxia by 21%, 42% and 47% with 1, 10 and 50 mg/kg/day, respectively. This effect was proportionately greater than the effect of ASA (0%, 25% and 24%). The antioxidant effects of triflusal on the biochemical mechanisms of cell damage studied here were also greater than the effects of ASA: lipid peroxidation was reduced by 29%, 35% and 36% with triflusal, and 0%, 19% and 29% with ASA. Inducible NO synthase activity was reduced by 25%, 27% and 30% with triflusal, and 0%, 25% and 24% with ASA. Triflusal can be considered an alternative to ASA as a neuroprotective agent, at least in the experimental model of anoxia-reoxygenation used in the present study.

High-dose aspirin is neuroprotective in a rat focal ischemia model

Acetylsalicylic acid (ASA) is neuroprotective through various pharmacological action sites. We used a temporary middle cerebral artery occlusion (tMCAO) model in 56 Wistar rats to assess whether repeated ASA injections at 30 min, 6 h, 1, 2, 3, and 4 days after stroke onset are neuroprotective. Animals were sacrificed 5 days after MCAO; infarct size was analyzed with 2,3,5-triphenyltetrazolium chloride staining. As compared to saline (164+/-13 mm(3), n=14), only repeated injections of 40 mg/kg ASA (79+/-18 mm(3), n=14, P=0.0029), but not of 20 mg/kg ASA (129+/-19 mm(3), n=15), reduced infarct volume significantly. No significant change was noted with 40 mg/kg ASA injected only once at 30 min after MCAO (117+/-16 mm(3), n=13).

Antioxidant effects of a single dose of acetylsalicylic acid and salicylic acid in rat brain slices subjected to oxygen-glucose deprivation in relation with its antiplatelet effect

The aim of the present study was to analyze the relative participation of the antiplatelet and the antioxidant effects of acetylsalicylic acid (ASA) and salicylic acid (SA) after a single dose (1 or 10 mg/kg i.p.) in an in vitro model of anoxia in slices of rat brain. After 20 min of drug administration, blood and brain were obtained (n=6 rats per group). We measured: lipid peroxidation, glutathione levels and lactate dehydrogenase efflux (LDH), ASA and SA concentrations and platelet aggregation in whole blood. An increase in lipid peroxidation (80%) and in LDH efflux (520%) and a decrease in glutathione levels (35%) were observed after 120 min anoxia in saline-treated rats. SA reduced this oxidative stress and LDH efflux, but it did not modify platelet aggregation. ASA strongly inhibited platelet aggregation but exerted a poor antioxidant effect. ASA was not detectable in brain tissue. We conclude that repeated doses of ASA are necessary to obtain a tissular antioxidant effect, probably when liver generates enough SA.

Antioxidant effect of acetylsalicylic and salicylic acid in rat brain slices subjected to hypoxia

Acetylsalicylic acid (ASA) reduces the incidence of ischemic stroke mainly through its antithrombotic action; however, it also has a direct neuroprotective effect. The present study was designed to evaluate the effect of ASA on oxidative stress and the activity of nitric oxide synthase (NOS) in an in vitro model of hypoxia in rat brain slices. Rat brain slices were perfused with nitrogen (hypoxia) for a maximum of 120 min, after which we measured lipid peroxidation, glutathione levels, glutathione-related enzyme activities, and constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) activities. In brain tissue subjected to hypoxia, ASA reduced oxidative stress and iNOS activity (all increased by hypoxia), but only when used at higher concentrations. The effects of salicylic acid (SA) were similar but more intense than were those of ASA. After oral administration, the effect of SA was much greater than that of ASA, and the decrease in cell death with SA was seen much more clearly. In view of the greater effect of SA compared to ASA on changes in oxidative stress parameters in a model of hypoxia, and higher brain concentrations of SA when it is administered alone than when ASA is given (undetectable levels), we conclude that SA plays an important role in the cytoprotective effect in brain tissue after ASA administration.

Synergistic inhibitory effect of ascorbic acid and acetylsalicylic acid on prostaglandin E2 release in primary rat microglia

Ascorbic acid (vitamin C) has been suggested to protect cerebral tissue in a variety of pathophysiological situations such as head trauma, ischemia or Alzheimer's disease. Most of these protective actions have been attributed to the antioxidative capacity of ascorbic acid. Besides the presence of elevated levels of oxygen radicals, prostaglandins produced by neurones and microglial cells seem to play an important role in prolonged tissue damage. We investigated whether ascorbic acid alone inhibits prostaglandin E2 (PGE2) synthesis and may augment the inhibitory effect of acetylsalicylic acid on prostaglandin synthesis. Ascorbic acid dose-dependently inhibited PGE2 synthesis in lipopolysaccharide-treated primary rat microglial cells (IC50 = 3.70 micro m). In combination with acetylsalicylic acid (IC50 = 1.85 micro m), ascorbic acid augmented the inhibitory effect of acetylsalicylic acid on PGE2 synthesis (IC50 = 0.25 micro m in combination with 100 micro m ascorbic acid). Ascorbic acid alone or in combination with acetylsalicylic acid did not inhibit cyclooxygenase-2 (COX-2) protein synthesis but inhibited COX-2 enzyme activity. Our results show that ascorbic acid and acetylsalicylic acid act synergistically in inhibiting PGE2 synthesis, which may help to explain a possible protective effect of ascorbic acid in various brain diseases.

The novel neuroprotective action of sulfasalazine through blockade of NMDA receptors

Sulfasalazine is widely used to treat inflammatory diseases. Besides anti-inflammatory actions such as blockade of nuclear factor-kappaB and cyclooxygenases, we found that 30 to 1000 micro M sulfasalazine dose dependently blocked N-methyl-D-aspartate receptor-mediated excitotoxicity without intervening kainate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid neurotoxicity. The neuroprotective effects of sulfasalazine were attributable to prevention of Ca(2+) influx and accumulation through N-methyl-D-aspartate receptors as a low-affinity antagonist. The systemic administration of sulfasalazine reduced neuronal death following transient cerebral and retinal ischemia in adult rat. The present findings suggest that the neuroprotective action of sulfasalazine can be therapeutically applied to halt devastating neuronal death following hypoxic ischemia, trauma, and neurodegenerative diseases.

Cyclooxygenase-1 gene knockout does not alter middle cerebral artery occlusion in a mouse stroke model

Cyclooxygenase (COX) is crucial in inflammation; COX-1 is constitutional, and COX-2 is inducible. In this study, neurological function and infarct volume were evaluated at 24 h after permanent endovascular middle cerebral artery occlusion (MCAO) in both COX-1-gene knockout (homozygous or heterozygous) and wide-type mice. Similar infarct volumes and neurological deficits were seen among mice of different genotypes. There was no difference among the groups in arterial blood pressure and regional cerebral blood flow during the first 30 min of ischemia. Our results failed to confirm the harmful effect of losing COX-1 activity due to gene knockout in a permanent endovascular MCAO mouse stroke model.

Aspirin provides cyclin-dependent kinase 5-dependent protection against subsequent hypoxia/reoxygenation damage in culture

Aspirin [acetylsalicylic acid (ASA)] is an anti-inflammatory drug that protects against cellular injury by inhibiting cyclooxygenases (COX), inducible nitric oxide synthase (iNOS) and p44/42 mitogen-activated protein kinase (p44/42 MAPK), or by preventing translocation of nuclear factor kappaB (NF-kappaB). We studied the effect of ASA pre-treatment on neuronal survival after hypoxia/reoxygenation damage in rat spinal cord (SC) cultures. In this injury model, COX, iNOS and NF-kappaB played no role in the early neuronal death. A 20-h treatment with 3 mm ASA prior to hypoxia/reoxygenation blocked the hypoxia/reoxygenation-induced lactate dehydrogenase (LDH) release from neurons. This neuroprotection was associated with increased phosphorylation of neurofilaments, which are substrates of p44/42 MAPK and cyclin-dependent kinase 5 (Cdk5). PD90859, a p44/42 MAPK inhibitor, had no effect on ASA-induced tolerance, but olomoucine and roscovitine, Cdk5 inhibitors, reduced ASA neuroprotection. Hypoxia/reoxygenation alone reduced both the protein amount and activity of Cdk5, and this reduction was inhibited by pre-treatment with ASA. Moreover, the protein amount of a neuronal Cdk5 activator, p35, recovered after reoxygenation only in ASA-treated samples. The prevention of the loss in Cdk5 activity during reoxygenation was crucial for ASA-induced protection, because co-administration of Cdk5 inhibitors at the onset ofreoxygenation abolished the protection. In conclusion, pre-treatment with ASA induces tolerance against hypoxia/reoxygenation damage in spinal cord cultures by restoring Cdk5 and p35 protein expression.

Combining antiplatelet and thrombolytic therapies for stroke

Pharmacological therapy for acute nonhaemorrhagic stroke has become a reality over the last 5 years. Mechanistically, both thrombolytic (tissue plasminogen activator and urokinase) and antiplatelet (aspirin) monotherapy have demonstrated efficacy. However, unintended actions limit the extent of clinical improvement in each circumstance. For example, in addition to excess bleeding, tissue plasminogen activator therapy has been associated with complement activation, neuronal toxicity and laminin degradation, while aspirin may reduce nitric oxide synthase activity and cerebral blood flow. Attention is now directed toward improving the therapeutic index for each class of agents. Generally, while thrombolytic therapy is focused on developing agents with greater fibrin specificity and safety (that is, a reduction in intracranial haemorrhage rate), the development of antiplatelet agents is primarily focused on achieving greater potency. The latter is being investigated by combining agents with different mechanisms (aspirin and dipyridamole, aspirin and clopidogrel) as well as agents designed to block the glycoprotein IIb/IIIa receptor, the final common pathway for platelet aggregation. Thus, combination therapy using both thrombolytic and antiplatelet agents will further attempt to improve the therapeutic index by increasing potency and improving the safety profile. Anecdotal case studies support the merits of this approach and are consistent with the data reported for myocardial ischaemia and interventional strategies. It is anticipated that drug therapy directed at both thrombolytic and antiplatelet targets will ultimately result in a widened therapeutic window that will allow acute stroke therapy to be administrated to a much greater number of patients than is currently possible.

Increased susceptibility to ischemic brain injury in cyclooxygenase-1-deficient mice

Cyclooxygenase-1 (COX-1), a rate-limiting enzyme in the synthesis of prostanoids, is involved in selected vasodilatatory responses of the cerebral circulation. Cyclooxygenase-1-null mice were used to determine whether COX-1 influences cerebral ischemic damage. The middle cerebral artery was occluded in COX-1 -/- and +/+ mice (n = 9/group), and lesion volume was determined in thionin-stained sections 24 or 96 hours later. Middle cerebral artery occlusion produced larger infarcts in COX-1 -/- mice, both at 24 (35 +/- 17%; P < 0.05) and 96 hours (41 +/- 16%; P < 0.05) after ischemia. The enlargement was not due to increased susceptibility to glutamate excitotoxicity, because microinjection of N-methyl-D-aspartate or kainate in the parietal cortex produced comparable lesions in COX-1 +/+ and -/- mice ( P > 0.05; n = 8/group). To examine the contribution of hemodynamic factors to the enlargement of the infarct, cerebral blood flow was monitored by laser-Doppler flowmetry in the ischemic territory (n = 6/group). Although the reduction in cerebral blood flow was comparable in the ischemic core ( P > 0.05), at the periphery of the ischemic territory the reduction was greater in COX-1 -/- mice (-58 +/- 4%) than in COX-1 +/+ mice (-34 +/- 5%; P < 0.05). It is concluded that mice lacking COX-1 are more susceptible to focal cerebral ischemia, an effect that can be attributed to a more severe cerebral blood flow reduction in vulnerable regions at the periphery of the ischemic territory. Thus, the vascular effects of COX-1 may contribute to maintain cerebral blood flow in the postischemic brain and, as such, play a protective role in ischemic brain injury.

Triflusal posttreatment inhibits glial nuclear factor-kappaB, downregulates the glial response, and is neuroprotective in an excitotoxic injury model in postnatal brain

BACKGROUND AND PURPOSE

Nuclear factor-kappaB (NF-kappaB) and the signal transducer and activator of transcription 3 (STAT3) are important transcription factors regulating inflammatory mechanisms and the glial response to neural injury, determining lesion outcome. In this study we evaluate the ability of triflusal (2-acetoxy-4-trifluoromethylbenzoic acid), an antiplatelet agent inhibitor of NF-kappaB activation, to improve lesion outcome after excitotoxic damage to the immature brain.

METHODS

Postnatal day 9 rats received an intracortical injection of the excitotoxin N-methyl-D-aspartate (NMDA) and oral administration of triflusal (30 mg/kg) either as 3 doses before NMDA injection (pretreatment) or as a single dose 8 hours after NMDA injection (posttreatment). After survival times of 10 and 24 hours, brains were processed for toluidine blue staining, tomato lectin histochemistry, and glial fibrillary acidic protein, NF-kappaB, and STAT3 immunocytochemistry.

RESULTS

NMDA-lesioned animals that were not treated with triflusal showed activation of NF-kappaB in neuronal cells at first and in glial cells subsequently. Animals that received pretreatment with triflusal showed a strong downregulation of neuronal and glial NF-kappaB but a similar development of the glial response and an equivalent lesion volume compared with nontreated animals. In contrast, animals receiving triflusal posttreatment showed increased early neuronal NF-kappaB but a reduction in the subsequent glial NF-kappaB, accompanied by important downregulation of the microglial and astroglial response and a drastic reduction in the lesion size. STAT3 activation was not affected by triflusal treatment.

CONCLUSIONS

Triflusal posttreatment diminishes glial NF-kappaB, downregulates the glial response, and improves the lesion outcome, suggesting a neuroprotective role of this compound against excitotoxic injury in the immature brain.

Neuroprotective effect of aspirin by inhibition of glutamate release after permanent focal cerebral ischaemia in rats

Aspirin reduces the size of infarcts after ischaemic stroke. Although this fact has been attributed to its anti-platelet actions, direct neuroprotective effects have also been reported. We have recently demonstrated that aspirin is neuroprotective by inhibiting glutamate release in 'in vitro' models of brain ischaemia, via an increase in ATP production. The present study was designed to determine whether the inhibition of glutamate release induced by aspirin might be protective in a whole-animal model of permanent focal brain ischaemia. Focal brain ischaemia was produced in male adult Fischer rats by occluding both the common carotid and middle cerebral arteries. Central and serum glutamate levels were determined at fixed intervals after occlusion. The animals were then killed and infarct volume was measured. Aspirin (30 mg/kg i.p. administered 2 h before the occlusion) produced a significant reduction in infarct volume, an effect that correlated with the inhibition caused by aspirin on ischaemia-induced increase in brain and serum glutamate concentrations after the onset of the ischaemia. Aspirin also inhibited ischaemia-induced decrease in brain ATP levels. Our present findings show a novel mechanism for the neuroprotective effects of aspirin, which takes place at concentrations in the anti-aggregant-analgesic range, useful in the management of patients with risk of ischaemic events.

Nitro-aspirin (NCX4016) reduces brain damage induced by focal cerebral ischemia in the rat

The potential neuroprotective effects of the novel nitro-derivate of aspirin (NCX4016) on permanent focal cerebral ischemia in spontaneously hypertensive rats (SHRs) was investigated. Reference compounds were acetylsalicilic acid (ASA) and FK506 (tacrolimus). Ten minutes after surgery, SHRs were randomly divided into four groups of ten, pharmacologically treated and sacrificed 24 h after treatment. Brains were removed and processed to measure infarct volume, 70 kDa heat shock protein (hsp70), glial fibrillary acidic protein (GFAP) and vimentin (Vim) immunoreactivity (IR), and apoptosis using terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end-labeling (TUNEL) assay. NCX-4016 significantly reduced total infarct volume compared to ASA (-20%, P < 0.05), FK506 (-18%, P < 0.05) and vehicle treatment (-20%, P < 0.05). Experimental groups did not differ in hsp70-IR and GFAP-IR. Conversely, hyperplastic astrocytes, measured by Vim-IR, were significantly lower in NCX-4016 than in the vehicle group (-36%, P<0.01). TUNEL assay indicated a significantly lower degree of apoptosis in NCX-4016 group than vehicle in both the homolateral (-27%, P < 0.01) and contralateral hemisphere (-29%, P < 0.05). These findings indicate that NO release associated with aspirin confers neuroprotective effects against ischemic injury.

Acetylsalicylic acid reduces ischemia-induced proliferation of dentate cells in gerbils

Transient global ischemia causes neurogenesis in the dentate gyrus of adult rodents. Ischemic insults to rodents also induce cyclooxygenase-2 (COX-2), an isoform of cyclooxygenases (COXs) and a rate-limiting enzyme for prostanoid synthesis. In the present experiments, adult Mongolian gerbils were chronically treated with acetylsalicylic acid (ASA), a non-selective COX inhibitor, and the proliferation of cells in the dentate gyrus was examined under ischemia. It was proved that BrdU-labeled cells in the dentate gyrus were significantly reduced in number following ASA treatment after 10 min global ischemia. The result strongly suggests that COX, probably COX-2, and prostanoids play an important role in the proliferation of neural cells after ischemia in gerbils.