Platelet-activating factor antagonist (ABT-491) decreases neuronal apoptosis in neonatal rat model of hypoxic ischemic brain injury

Ginsenoside Re mitigates memory impairments in aged GPx-1 KO mice by inhibiting the interplay between PAFR, NFκB, and microgliosis in the hippocampus

Ginsenoside Re (GRe) upregulates anti-aging klotho by mainly upregulating glutathione peroxidase-1 (GPx-1). However, the anti-aging mechanism of GPx-1 remains elusive. Here we investigated whether the GRe-mediated upregulation of GPx-1 modulates oxidative and proinflammatory insults. GPx-1 gene depletion altered redox homeostasis and platelet-activating factor receptor (PAFR) and nuclear factor kappa B (NFκB) expression, whereas the genetic overexpression of GPx-1 or GRe mitigated this phenomenon in aged mice. Importantly, the NFκB inhibitor pyrrolidine dithiocarbamate (PDTC) did not affect PAFR expression, while PAFR inhibition (i.e., PAFR knockout or ginkgolide B) significantly attenuated NFκB nuclear translocation, suggesting that PAFR could be an upstream molecule for NFκB activation. Iba-1-labeled microgliosis was more underlined in aged GPx-1 KO than in aged WT mice. Triple-labeling immunocytochemistry showed that PAFR and NFκB immunoreactivities were co-localized in Iba-1-positive populations in aged mice, indicating that microglia released these proteins. GRe inhibited triple-labeled immunoreactivity. The microglial inhibitor minocycline attenuated aging-related reduction in phospho-ERK. The effect of minocycline was comparable with that of GRe. GRe, ginkgolide B, PDTC, or minocycline also attenuated aging-evoked memory impairments. Therefore, GRe ameliorated aging-associated memory impairments in the absence of GPx-1 by inactivating oxidative insult, PAFR, NFkB, and microgliosis.

Neuro-protective role of nanocapsulated curcumin against cerebral ischemia-reperfusion induced oxidative injury

Cerebral ischemia-reperfusion (CIR) accelerates the progression of neurodegeneration by causing mitochondrial dysfunction to overproduce reactive oxygen species (ROS). Curcumin shows protective effects against CIR-induced oxidative damage. Free curcumin (FC) is effective at high doses due to its poor bioavailability. Also the blood-brain barrier (BBB) limits the passage of substances from circulation into the cerebral region. Thus, formulation of curcumin within polyethylene glycol (PEG)-ylated polylactide-co-glycolide (PLGA) nanoparticles (NC) was applied orally to aged rats to explore its role against CIR injury. Mitochondrial damage was evaluated. The levels of pro-inflammatory cytokines and components of apoptotic pathway were studied. Unlike FC, NC pre-treatment exerted better neuro-protection by ameliorating ROS-mediated oxidative damage and prevented CIR-induced neuronal apoptosis. Therefore, curcumin incorporated PEGylated PLGA nanoparticles may be used as a suitable delivery vehicle to the brain as they can increase curcumin bioavalability and the released curcumin may confer protection to the neurons against CIR-induced oxidative damage.

Immune responses in perinatal brain injury

The perinatal period has often been described as immune deficient. However, it has become clear that immune responses in the neonate following exposure to microbes or as a result of tissue injury may be substantial and play a role in perinatal brain injury. In this article we will review the immune cell composition under normal physiological conditions in the perinatal period, both in the human and rodent. We will summarize evidence of the inflammatory responses to stimuli and discuss how neonatal immune activation, both in the central nervous system and in the periphery, may contribute to perinatal hypoxic-ischemic brain injury.

Current Understanding of Platelet-Activating Factor Signaling in Central Nervous System Diseases

Platelet-activating factor (PAF) is a bioactive lipid mediator which serves as a reciprocal messenger between the immune and nervous systems. PAF, a pluripotent inflammatory mediator, is extensively expressed in many cells and tissues and has either beneficial or detrimental effects on the progress of inflammation-related neuropathology. Its wide distribution and various biological functions initiate a cascade of physiological or pathophysiological responses during development or diseases. Current evidence indicates that excess PAF accumulation in CNS diseases exacerbates the inflammatory response and pathological consequences, while application of PAF inhibitors or PAFR antagonists by blocking this signaling pathway significantly reduces inflammation, protects cells, and improves the recovery of neural functions. In this review, we integrate the current findings of PAF signaling in CNS diseases and elucidate topics less appreciated but important on the role of PAF signaling in neurological diseases. We propose that the precise use of PAF inhibitors or PAFR antagonists that target the specific neural cells during the appropriate temporal window may constitute a potential therapy for CNS diseases.

Platelet-activating factor receptor (PAFR) plays a crucial role in experimental global cerebral ischemia and reperfusion

Stroke is one of the most frequent causes of death and disability worldwide leading to a significant clinical and socioeconomic burden. Although different mechanisms are involved in the pathogenesis of stroke, inflammatory response occurs after ischemia and contributes to the expansion of brain injury. Platelet-activating factor receptor (PAF) plays crucial roles in both physiological and pathological conditions in the brain. PAF receptor (PAFR) may be expressed on cellular and nuclear membranes of various cell types, especially leukocytes, platelets, endothelial cells, neuronal cells and microglia. Herein, using mice lacking the PAFR receptor (PAFR(-/-)), we investigate a potential role for this receptor during experimental transient global cerebral ischemia and reperfusion (BCCAo). In PAFR deficiency, we observed a significant improvement in the neurological deficits, which were associated with a reduction of brain infarcted area as evaluated by triphenyltetrazolium chloride (TTC). Moreover, a decrease in the percentage of necrotic cavities areas and in the frequency of ischemic neurons was also found by employing histometric analysis. In addition, in PAFR(-/-) mice there was prevention of caspase-3 activation and decreased vascular permeability and brain edema. Decreased brain levels of the cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and the chemokine (C-X-C motif) ligand 1 (CXCL1) by ELISA were also detected in PAFR(-/-) BCCAo animals. Taken together, our results suggest that PAFR activation might be crucial for the global brain ischemia and reperfusion injury.

Attenuated Reactive Gliosis and Enhanced Functional Recovery Following Spinal Cord Injury in Null Mutant Mice of Platelet-Activating Factor Receptor

Platelet-activating factor (PAF) is a unique phosphoglycerine that mediates the biological functions of both immune and nervous systems. Excessive PAF plays an important role in neural injury via its specific receptor (PAFR). In this study, we hypothesized that PAF signaling activates reactive gliosis after spinal cord injury (SCI), and blocking the PAF pathway would modify the glia scar formation and promote functional recovery. PAF microinjected into the normal wild-type spinal cord induced a dose-dependent activation of microglia and astrocytes. In the SCI mice, PAFR null mutant mice showed a better functional recovery in grip and rotarod performances than wild-type mice. Although both microglia and astrocytes were activated after SCI in wild-type and PAFR null mutant mice, expressions of IL-6, vimentin, nestin, and GFAP were not significantly elevated in PAFR null mutants. Disruption of PAF signaling inhibited the expressions of proteoglycan CS56 and neurocan (CSPG3). Intriguingly, compared to the wild-type SCI mice, less axonal retraction/dieback at 7 dpi but more NFH-labeled axons at 28 dpi was found in the area adjacent to the epicenter in PAFR null mutant SCI mice. Moreover, treatment with PAFR antagonist Ginkgolide B (GB) at the chronic phase rather than acute phase enhanced the functional recovery in the wild-type SCI mice. These findings suggest that PAF signaling participates in reactive gliosis after SCI, and blocking of this signaling enhances functional recovery and to some extent may promote axon regrowth.

Neuroprotective Effect of Sodium Butyrate against Cerebral Ischemia/Reperfusion Injury in Mice

Sodium butyrate (NaB) is a dietary microbial fermentation product of fiber and serves as an important neuromodulator in the central nervous system. In this study, we further investigated that NaB attenuated cerebral ischemia/reperfusion (I/R) injury in vivo and its possible mechanisms. NaB (5, 10 mg/kg) was administered intragastrically 3 h after the onset of reperfusion in bilateral common carotid artery occlusion (BCCAO) mice. After 24 h of reperfusion, neurological deficits scores were estimated. Morphological examination was performed by electron microscopy and hematoxylin-eosin (H&E) staining. The levels of oxidative stress and inflammatory cytokines were assessed. Apoptotic neurons were measured by TUNEL; apoptosis-related protein caspase-3, Bcl-2, Bax, the phosphorylation Akt (p-Akt), and BDNF were assayed by western blot and immunohistochemistry. The results showed that 10 mg/kg NaB treatment significantly ameliorated neurological deficit and histopathology changes in cerebral I/R injury. Moreover, 10 mg/kg NaB treatment markedly restored the levels of MDA, SOD, IL-1β, TNF-α, and IL-8. 10 mg/kg NaB treatment also remarkably inhibited the apoptosis, decreasing the levels of caspase-3 and Bax and increasing the levels of Bcl-2, p-Akt, and BDNF. This study suggested that NaB exerts neuroprotective effects on cerebral I/R injury by antioxidant, anti-inflammatory, and antiapoptotic properties and BDNF-PI3K/Akt pathway is involved in antiapoptotic effect.

Role of immunoglobulin in neuronal apoptosis in a neonatal rat model of hypoxic ischemic brain injury

The objective of the present study was to evaluate the neuroprotective effects of immunoglobulin (Ig) in a neonatal hypoxic ischemic (HI) rat model. Seven-day-old rat pups were randomly assigned to control, hypoxia and hypoxia + Ig groups. The rats in the hypoxia +Ig group were intraperitoneally administered 1 g/kg Ig once, immediately after hypoxia. Saline was administered to the rats in the hypoxia group at the same time point. Eight rats from each of the Ig + hypoxia and hypoxia groups were sacrificed by decapitation 4 and 24 h following the administration of Ig or saline. The rats of the control group were sacrificed at the 4 h time-point. Caspase-3 activity, as well as IL-1β, IL-6 and TNF-α mRNA expression levels, were studied in the left ischemic hemispheres. Induction of cerebral ischemia increased the TNF-α, IL-6 and IL-1β mRNA expression levels significantly at 4 and 24 h in the left ischemic hemispheres in the hypoxia group compared with those in the control group. The systemic administration of Ig following HI encephalopathy significantly reduced the TNF-α, IL-6 and IL-1β mRNA expression levels in the ischemic tissue in the Ig + hypoxia group compared with those in the hypoxia group. In the hypoxia group, caspase-3 activity in the left half of the brain was found to be significantly increased compared with that in the control group. Caspase-3 activity in the Ig + hypoxia group was significantly lower than that in the hypoxia group. The observations of the present study indicate that Ig administration may be an efficient treatment approach for reducing cerebral apoptosis associated with hypoxic ischemia.

The effects of intraperitoneal pentoxifylline treatment in rat pups with hypoxic-ischemic encephalopathy

BACKGROUND

The aim of this study was to evaluate the effects of postischemic treatment with pentoxifylline on the cytokine gene expressions and neuronal apoptosis in neonatal rat model of hypoxic-ischemic encephalopathy.

METHODS

Seven-day-old Wistar rat pups (n = 40) of either sex, delivered spontaneously, were used in this experimental study. Control group (n = 8): after median neck incision was made, neither ligation nor hypoxia was performed, ischemia group (n = 16): 0.5 mL of saline was injected intraperitoneally immediately after hypoxia. Pentoxifylline and ischemia groups (n = 16): the rat pups were administered intraperitoneally 60 mg/kg of pentoxifylline immediately after hypoxia. Eight rats from ischemia and pentoxifylline + ischemia groups were sacrificed 4 and 24 hours after drug administration. Control group mice were decapitated 4 hours after hypoxia. Caspase-3 activity, interleukin-1β, and tumor necrosis factor-α messenger RNA expression levels were studied in the left half of the brain.

RESULTS

Induction of cerebral ischemia increased tumor necrosis factor-α and interleukin-1β messenger RNA expression levels significantly at 4 hours and 24 hours following ischemia in the left ischemic hemispheres in the ischemia group as compared with the control group. Systemic administration of pentoxifylline immediately after hypoxic-ischemic encephalopathy significantly reduced the tumor necrosis factor-α and interleukin-1β messenger RNA expression levels in ischemic tissue as compared with the ischemia group. Caspase-3 activities in the left half of the brains of ischemia group were found to be increased significantly as compared with control group. Caspase-3 activities in the brains of pentoxifylline + ischemia groups were significantly lower than in that of ischemia group.

CONCLUSIONS

Based on the significantly lower interleukin-1β and tumor necrosis factor-α gene expression measured after 4 and 24 hours and significantly reduced caspase-3 activity measured colorimetrically in the animals treated with pentoxifylline, our findings suggest that pentoxifylline may reduce brain damage due to hypoxic-ischemic injury.

Up-regulation of platelet-activating factor synthases and its receptor in spinal cord contribute to development of neuropathic pain following peripheral nerve injury

Background

Platelet-activating factor (PAF; 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a lipid mediator derived from cell membrane. It has been reported that PAF is involved in various pathological conditions, such as spinal cord injury, multiple sclerosis, neuropathic pain and intrathecal administration of PAF leads to tactile allodynia. However, the expression of PAF synthases and its receptor in the spinal cord following peripheral nerve injury is unknown.

Methods

Using the rat spared nerve injury (SNI) model, we investigated the expression of PAF synthases (LPCAT1 and 2) and PAF receptor (PAFr) mRNAs in the spinal cord. Reverse transcription polymerase chain reaction (RT-PCR) and double-labeling analysis of in situ hybridization histochemistry (ISHH) with immunohistochemistry (IHC) were employed for the analyses. Pain behaviors were also examined with PAFr antagonist (WEB2086).

Results

RT-PCR showed that LPCAT2 mRNA was increased in the ipsilateral spinal cord after injury, but not LPCAT1 mRNA. Double-labeling of ISHH with IHC revealed that LPCAT1 and 2 mRNAs were constitutively expressed by a subset of neurons, and LPCAT2 mRNA was increased in spinal microglia after nerve injury. RT-PCR showed that PAFr mRNA was dramatically increased in the ipsilateral spinal cord after nerve injury. Double-labeling analysis of ISHH with IHC revealed that after injury PAFr mRNA was predominantly colocalized with microglia in the spinal cord. Continuous intrathecal administration of the PAFr antagonist suppressed mechanical allodynia following peripheral nerve injury. Delayed administration of a PAFr antagonist did not reverse the mechanical allodynia.

Conclusions

Our data show the histological localization of PAF synthases and its receptor in the spinal cord following peripheral nerve injury, and suggest that PAF/PAFr signaling in the spinal cord acts in an autocrine or paracrine manner among the activated microglia and neurons, thus contributing to development of neuropathic pain.

Superior Neuroprotective Efficacy of LAU-0901, a Novel Platelet-Activating Factor Antagonist, in Experimental Stroke

Platelet-activating factor (PAF) accumulates during cerebral ischemia, and inhibition of this process plays a critical role in neuronal survival. Recently, we demonstrated that LAU-0901, a novel PAF receptor antagonist, is neuroprotective in experimental stroke. We used magnetic resonance imaging in conjunction with behavior and immunohistopathology to expand our understanding of this novel therapeutic approach. Sprague–Dawley rats received 2 h middle cerebral artery occlusion (MCAo) and were treated with LAU-0901 (60 mg/kg) or vehicle 2 h from MCAo onset. Behavioral function, T2-weighted imaging (T2WI), and apparent diffusion coefficients were performed on days 1, 3, and 7 after MCAo. Infarct volume and number of GFAP, ED-1, and NeuN-positive cells were conducted on day 7. Behavioral deficit was significantly improved by LAU-0901 treatment compared to vehicle on days 1, 3, and 7. Total lesion volumes computed from T2WI were significantly reduced by LAU-0901 on days 1, 3, and 7 (by 83%, 90%, and 96%, respectively), which was consistent with decreased edema formation. Histopathology revealed that LAU-0901 treatment resulted in significant reduction of cortical and subcortical infarct volumes, attenuated microglial infiltration, and promoted astrocytic and neuronal survival. These findings suggest LAU-0901 is a promising neuroprotectant and provide the basis for future therapeutics in patients suffering ischemic stroke.

Platelet activating factor: the good and the bad in the ischemic/reperfused heart

The present review is focused on the dual role played by platelet-activating factor (PAF) in ischemia and reperfusion (I/R) injury of the heart. Although the involvement of PAF in the pathogenesis of myocardial reperfusion injury is well established, in the last few years it has emerged that very low concentrations of PAF exert cardioprotective effects, comparable to that afforded by ischemic preconditioning (IP). PAF is a potent phosphoglyceride involved in different pathophysiological conditions affecting the cardiovascular system, including the development of myocardial I/R injury. PAF is released from the I/R myocardium in concentrations (1-10 nmol/L) high enough to negatively modulate coronary circulation as well as electrical and contractile activities. PAF may act either directly, via generation of secondary mediators, or through the activation of inflammatory cells like platelets and polymorphonuclear neutrophils, which exacerbate postischemic myocardial injury. The effects of PAF are mediated through specific receptors (PAFRs) that belong to the superfamily of G protein-coupled receptors. Since cardiomyocytes not only produce PAF but also possess PAFRs, it is likely that PAF acts as an autocrine/paracrine mediator. Although the negative effects exerted by high concentrations of PAF are well established, several recent findings from our and other laboratories have demonstrated that very low concentrations (pmol/L) of PAF infused before ischemia induce cardioprotective effects similar to those afforded by IP, and that endogenous PAF production participates in the induction of IP itself. The IP-like action exerted by low concentrations of PAF is due to the activation/phosphorylation of kinases included in the reperfusion injury salvage kinase (RISK) pathway, such as protein kinase C, Akt/PkB and nitric oxide synthase. Together with the activation of mitochondrial K(ATP) channels, these events may allow prevention of mitochondrial permeability transition pores opening at reperfusion. Moreover, the nitric oxide-dependent S-nitrosylation of L-type Ca(2+) channels induced by PAF reduces intracellular Ca(2+) overload.

LAU-0901, a novel platelet-activating factor receptor antagonist, confers enduring neuroprotection in experimental focal cerebral ischemia in the rat

LAU-0901, a novel platelet-activating factor (PAF) receptor antagonist, is highly neuroprotective in a rodent model of cerebral ischemia. This study was conducted to establish whether the neuroprotection induced by LAU-0901 persists with chronic survival. Male Sprague-Dawley rats were anesthetized with isoflurane and subjected to 2 h of temporary middle cerebral artery occlusion (MCAo) induced by means of a poly-L-lisine-coated intraluminal nylon suture. Animals were treated with either LAU-0901 (60 mg/kg) or vehicle (45% cyclodextran) administered i.p. at 2 h from onset of MCAo. They received neurobehavioral examinations during MCAo (60 min) and then at 1, 2, 3, 7, 14, 21 and 28 days followed by histopathology at 30 days. LAU-0901 significantly improved the behavior compared to the vehicle group, beginning on day 1 (by 29%, p=0.00007) and persisting throughout a 30-day survival period (42%, p=0.0001). Compared with vehicle treatment, LAU-0901 treatment significantly increased volume of non-infarcted brain tissue loss relative to the unlesioned hemisphere (16.3 +/- 4.6% vs. 46.0 +/- 10.3%, respectively). These results establish that LAU-0901 confers enduring ischemic neuroprotection.

LAU-0901, a novel platelet-activating factor antagonist, is highly neuroprotective in cerebral ischemia

Platelet-activating factor (PAF) is a bioactive phospholipid that accumulates during ischemia-reperfusion and is involved in the activation of platelets, neutrophils, and pro-inflammatory signaling. PAF has been suggested to enhance brain ischemia-reperfusion damage. LAU-0901, a novel PAF receptor antagonist, was examined in models of focal cerebral ischemia in rats and mice. Sprague-Dawley rats were anesthetized and received 2-hour middle cerebral artery occlusion (MCAo) by intraluminal suture. LAU-0901 (30, 60, 90 mg/kg; n=9-11) or vehicle (n=11) was administered i.p. at 2 h after onset of MCAo. The neurological status was evaluated at 60 min, and on days 1, 2, 3 and 7 after MCAo. In the dose-response study in mice, C57BL/6 mice were anesthetized and received 1 h MCAo by intraluminal suture. LAU-0901 (15, 30, 60 mg/kg; n=7-9) or vehicle (n=8) was given i.p. at 1 h after onset of MCAo. Local cerebral blood flow (LCBF) was measured at 1, 2, 4, and 6 h after MCAo in mice. LAU-0901 treated rats showed improved neurological score throughout the 7-day survival period. LAU-0901 treatment (30, 60 and 90 mg/kg) reduced total corrected infarct volume compared to vehicle rats by 76, 88 and 90%, respectively. Mice treated with LAU-0901 (30 and 60 mg/kg) reduced total infarction by 29% and 66%, respectively. LCBF was improved by treatment with LAU-0901 (30 mg/kg) by 77% of baseline at 6 h. In conclusion, we demonstrate for the first time that LAU-0901 improves behavioral scores, LCBF and reduces infarct volume after focal cerebral ischemia in rats and mice. Thus, this PAF receptor antagonist exhibits potent and sustained neuroprotection that may be of value for the design of stroke therapies.

Neuroprotective effect of curcumin on transient focal cerebral ischemia in rats

Curcumin, a member of the curcuminoid family of compounds, is a yellow colored phenolic pigment obtained from the powdered rhizome of C. longa Linn. Recent studies have demonstrated that curcumin has protective effects against cerebral ischemia/reperfusion injury. However, little is known about its mechanism. Hence, in the present study the neuroprotective potential of curcumin was investigated in middle cerebral artery occlusion (MCAO) induced focal cerebral IR injury. Administration of curcumin 100 and 300 mg/kg i.p. 60 min after MCAO significantly diminished infarct volume, and improved neurological deficit in a dose-dependent manner. Nissl staining showed that the neuronal injury was significantly improved after being treated with curcumin. Curcumin significantly decreased the expression of caspase-3 protein. A higher number of TUNEL-positive cells were found in the vehicle group, but they were significantly decreased in the treated group. Taken together, these results suggest that the neuroprotective potentials of curcumin against focal cerebral ischemic injury are, at least in part, ascribed to its anti-apoptotic effects.

The role of trapidil on neuronal apoptosis in neonatal rat model of hypoxic ischemic brain injury

BACKGROUND

Hypoxic ischemic brain injury (HIBI) is a common cause of neonatal mortality and morbidity. Trapidil is an antiplatelet agent and several studies demonstrate the beneficial effect of trapidil in various forms of tissue injury. The effects of trapidil on neuronal apoptosis in HIBI have not been reported previously.

AIMS

The aim of this study is to evaluate the effect of trapidil on neuronal apoptosis in neonatal rat model of HIBI.

STUDY DESIGN

Seven-day-old Wistar rat pups were subjected to right common carotid artery ligation and hypoxia (92% nitrogen and 8% oxygen) for 2h. They were treated with trapidil or saline either immediately before or after hypoxia. In sham group animals, neither ligation, nor hypoxia were performed. Neuronal apoptosis was evaluated by the terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) and caspase-3 staining methods.

RESULTS

Trapidil treatment either before or after hypoxia results in significant reduction of the numbers of apoptotic cells in both hemispheres, when it is compared with saline treatment group. The numbers of apoptotic cells in right hemispheres in all groups are significantly higher than that in the left hemispheres.

CONCLUSIONS

These results show that trapidil administration either before or after hypoxia reduces neuronal apoptosis and we propose that trapidil may be a novel approach for the therapy of HIBI.