NF-κB and innate immunity in ischemic stroke

Systems approach to the study of brain damage in the very preterm newborn

Background: A systems approach to the study of brain damage in very preterm newborns has been lacking.

Methods: In this perspective piece, we offer encephalopathy of prematurity as an example of the complexity and interrelatedness of brain-damaging molecular processes that can be initiated inflammatory phenomena.

Results: Using three transcription factors, nuclear factor-kappa B (NF-κB), Notch-1, and nuclear factor erythroid 2 related factor 2 (NRF2), we show the inter-connectedness of signaling pathways activated by some antecedents of encephalopathy of prematurity.

Conclusions: We hope that as biomarkers of exposures and processes leading to brain damage in the most immature newborns become more readily available, those who apply a systems approach to the study of neuroscience can be persuaded to study the pathogenesis of brain disorders in the very preterm newborn.

Time-dependent variation of pathways and networks in a 24-hour window after cerebral ischemia-reperfusion injury

Background

Cerebral ischemia-reperfusion injury may simultaneously result in functional variation of multiple genes/pathways. However, most prior time-sequence studies on its pathomechanism only focused on a single gene or pathway. Our study aimed to systematically analyze the time-dependent variation in the expression of multiple pathways and networks within 24 h after cerebral ischemia-reperfusion injury.

Results

By uploading 374 ischemia-related genes into the MetaCore software, the variation in the expression of multiple pathways and networks in 3 h, 12 h, and 24 h after cerebral ischemia-reperfusion injury had been analyzed. The conserved TNFR1-signaling pathway, among the top 10 pathways, was consistently enriched in 3 h, 12 h, and 24 h groups. Three overlapping pathways were found between 3 h and 12 h groups; 2 between 12 h and 24 h groups; and 1 between 3 h and 24 h groups. Five, 4, and 6 non-overlapping pathways were observed in 3 h, 12 h, and 24 h groups, respectively. Apart from pathways reported by earlier studies, we identified a novel pathway related to the time-dependent development of cerebral ischemia pathogenesis. The process of apoptosis stimulation by external signals, among the top 10 processes, was consistently enriched in 3 h, 12 h, and 24 h groups; 2, 1, and 2 processes overlapped between 3 h and 12 h groups, 12 h and 24 h groups, and 3 h and 24 h groups, respectively. Four, 5, and 5 non-overlapping processes were found in 3 h, 12 h and 24 h groups, respectively. The presence of apoptotic processes was observed in all the 3 groups; while anti-apoptotic processes only existed in 3 h and 12 h groups. Additionally, according to node degree, network comparison identified 1, 8,and 5 important genes or proteins (e.g. Pyk2, PKC, E2F1, and VEGF-A) in 3 h, 12 h, and 24 h groups, respectively. The Jaccard similarity index revealed a higher level of similarity between 12 h and 24 h groups than that between 3 h and 12 h groups.

Conclusion

Time-dependent treatment can be utilized to reduce apoptosis, which may activate anti-apoptotic pathways within 12 h after cerebral ischemia-reperfusion injury. Pathway and network analyses may help identify novel pathways and genes implicated in disease pathogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0152-4) contains supplementary material, which is available to authorized users.

The use of microRNAs to modulate redox and immune response to stroke

SIGNIFICANCE

Cerebral ischemia is a major cause of death and disability throughout the world, yet therapeutic options remain limited. The interplay between the cellular redox state and the immune response plays a critical role in determining the extent of neural cell injury after ischemia and reperfusion. Excessive amounts of reactive oxygen species (ROS) generated by mitochondria and other sources act both as triggers and effectors of inflammation. This review will focus on the interplay between these two mechanisms.

RECENT ADVANCES

MicroRNAs (miRNAs) are important post-transcriptional regulators that interact with multiple target messenger RNAs coordinately regulating target genes, including those involved in controlling mitochondrial function, redox state, and inflammatory pathways. This review will focus on the regulation of mitochondria, ROS, and inflammation by miRNAs in the chain of deleterious intra- and intercellular events that lead to brain cell death after cerebral ischemia.

CRITICAL ISSUES

Although pretreatment using miRNAs was effective in cerebral ischemia in rodents, testing treatment after the onset of ischemia is an essential next step in the development of acute stroke treatment. In addition, miRNA formulation and delivery into the CNS remain a challenge in the clinical translation of miRNA therapy.

FUTURE DIRECTIONS

Future research should focus on post-treatment and potential clinical use of miRNAs.

Piperlonguminine is neuroprotective in experimental rat stroke

Inflammatory damage plays an important role in cerebral ischemic pathogenesis and may represent a target for treatment. Piperlonguminine (PE) has been proved to have anti-inflammatory actions. In this study, we investigated the effects of PE on cultured neuronal cell line, SH-SY5Y in vitro and experimental rat ischemic stroke in vivo. For oxygen-glucose deprivation (OGD) and tumor necrosis factor-α (TNF-α) stimulated SH-SY5Y cell line in vitro, SH-SY5Y cells were incubated with PE. In vivo, rats were subjected to middle cerebral artery occlusion (MACO) for 1h, followed by reperfusion for 23 h. The results of this study showed that treatment of SH-SY5Y cells with PE reduced the OGD-induced cytotoxicity and apoptosis and blocked TNF-α-induced activation of NF-κB and MAPK. Intraperitoneal injection of PE (2.4 mg/kg) produced a significant neuroprotective potential in rats with cerebral ischemia. PE attenuated neurological deficit scores, brain infarct volume and brain water content in rats, and inhibited activation of NF-κB and MAPK. These data show that PE protects the brain against ischemic cerebral injury via alleviating blood-brain barrier (BBB) breakdown, which may be mediated via inhibiting NF-κB and MAPK signaling pathways.

Post-stroke treatment with miR-181 antagomir reduces injury and improves long-term behavioral recovery in mice after focal cerebral ischemia

miR-181 has deleterious effects on stroke outcome, and reducing miR-181a levels prior to middle cerebral artery occlusion (MCAO) was shown previously to be protective. Here we tested the effect of post-ischemic treatment with miR-181a antagomir by intracerebroventricular and intravenous routes of administration on infarct size, neurological outcome, inflammatory response and long term behavioral outcome. Post-treatment with miR-181a antagomir significantly reduced infarction size, improved neurological deficits and reduced NF-κB activation, numbers of infiltrating leukocytes and levels of Iba1. Targets affected by miR-181a antagomir administered after stroke onset include BCL2 and X-linked inhibitor of apoptosis protein (XIAP). Post-treatment with miR-181a antagomir significantly improved behavioral outcome assessed by rotarod at one month. These findings indicate that post-treatment with miR-181a antagomir has neuroprotective effects against ischemic neuronal damage and neurological impairment in mice, and the protection is long lasting including recovery of motor function and coordination over one month. The ability to protect the brain with post-treatment with miR-181a antagomir with long lasting effect makes this a promising therapeutic target and may be an innovative and effective new approach for stroke therapy.

Gene polymorphism of rs556621 but Not rs11984041 is associated with the risk of large artery atherosclerotic stroke in a Xinjiang Uyghur population

BACKGROUND

Stroke is one of the main causes of death and adult chronic disability. Recently, 2 independent genome-wide association studies reported that the genetic variants (rs556621 and rs11984041) are significantly associated with large artery atherosclerosis (LAA).

METHODS

To determine whether these 2 variants are associated with the pathogenesis of LAA in stroke patients from the Xinjiang Uyghur autonomous region of China, both variants were evaluated in a series of 733 LAA stroke patients (434 Han and 299 Uyghur) and 725 age-, gender-, smoking-, alcohol habits- and ethnicity-matched controls (401 Han and 324 Uyghur).

RESULTS

For rs556621, significant differences in genotypic and allelic distributions were observed between Uyghur patients and controls (P = .045 for genotypic distribution, P = .042 for allelic distribution) but not in the Chinese Han cohort (P > .05). No significant differences were found in genotypic and allele distributions between patients and controls for rs11984041 in either the Chinese Han or Uyghur cohort (P > .05).

CONCLUSIONS

The variant rs556621 but not rs11984041 may increase susceptibility of LAA stroke in the Xinjiang Uyghur population.

Perillyl alcohol improves functional and histological outcomes against ischemia-reperfusion injury by attenuation of oxidative stress and repression of COX-2, NOS-2 and NF-κB in middle cerebral artery occlusion rats

Perillyl alcohol (PA) is a monoterpene found in essential oils of mints, cherries, citreous fruits and lemon grass, reported to have antioxidant and anti-inflammatory properties. However, the role of PA in stroke is still illusive. Since oxidative stress and inflammation play a pivotal role in ischemia-reperfusion (I-R) injury, this study was designed to elucidate the potential effects of PA against I-R induced pathology in rat׳s brain. Middle cerebral artery occlusion (MCAO) for 2h followed by 22h reperfusion in Wistar male rats (250-280g, 14-16 weeks old) induced the behavioral and histological alterations along with exhausted antioxidant status and enhanced inflammatory mediators. However, PA administration (25, 50 and 100mg/kg b.wt orally once daily for 7 days) prior to MCAO significantly attenuated neurological deficits related to flexion test and spontaneous motor activity, improved grip strength and motor coordination in a dose dependent manner. PA treatment also inhibited oxidative stress in MCAO rats as evident from decreased lipid peroxidation and augmented level of reduced glutathione and restored activities of catalase, glutathione peroxidase, and glutathione reductase and thus, reduced infarct volume and protected the brain histology after I-R injury. Furthermore, PA markedly suppressed the level of proinflammatory cytokines (IL-1β, TNF α and IL-6) and down regulated expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (NOS-2) and nuclear factor κB (NF-κB) in MCAO group. In conclusion, PA mediates neuroprotection against I-R injury via mitigation of oxidative stress and inflammation and thus, may be a good therapeutic approach in stroke prone patient.

Astrocytic Toll-like receptor 3 is associated with ischemic preconditioning-induced protection against brain ischemia in rodents

Background

Cerebral ischemic preconditioning (IPC) protects brain against ischemic injury. Activation of Toll-like receptor 3 (TLR3) signaling can induce neuroprotective mediators, but whether astrocytic TLR3 signaling is involved in IPC-induced ischemic tolerance is not known.

Methods

IPC was modeled in mice with three brief episodes of bilateral carotid occlusion. In vitro, IPC was modeled in astrocytes by 1-h oxygen-glucose deprivation (OGD). Injury and components of the TLR3 signaling pathway were measured after a subsequent protracted ischemic event. A neutralizing antibody against TLR3 was used to evaluate the role of TLR3 signaling in ischemic tolerance.

Results

IPC in vivo reduced brain damage from permanent middle cerebral artery occlusion in mice and increased expression of TLR3 in cortical astrocytes. IPC also reduced damage in isolated astrocytes after 12-h OGD. In astrocytes, IPC or 12-h OGD alone increased TLR3 expression, and 12-h OGD alone increased expression of phosphorylated NFκB (pNFκB). However, IPC or 12-h OGD alone did not alter the expression of Toll/interleukin receptor domain-containing adaptor-inducing IFNβ (TRIF) or phosphorylated interferon regulatory factor 3 (pIRF3). Exposure to IPC before OGD increased TRIF and pIRF3 expression but decreased pNFκB expression. Analysis of cytokines showed that 12-h OGD alone increased IFNβ and IL-6 secretion; 12-h OGD preceded by IPC further increased IFNβ secretion but decreased IL-6 secretion. Preconditioning with TLR3 ligand Poly I:C increased pIRF3 expression and protected astrocytes against ischemic injury; however, cells treated with a neutralizing antibody against TLR3 lacked the IPC- and Poly I:C-induced ischemic protection and augmentation of IFNβ.

Conclusions

The results suggest that IPC-induced ischemic tolerance is mediated by astrocytic TLR3 signaling. This reprogramming of TLR3 signaling by IPC in astrocytes may play an important role in suppression of the post-ischemic inflammatory response and thereby protect against ischemic damage. The mechanism may be via activation of the TLR3/TRIF/IRF3 signaling pathway.

Poly(ADP-ribose) polymerase-1 and its cleavage products differentially modulate cellular protection through NF-kappaB-dependent signaling

Poly(ADP-ribose) polymerase-1 (PARP-1) and its cleavage products regulate cell viability and NF-kappaB activity when expressed in neurons. PARP-1 cleavage generates a 24 kDa (PARP-1(24)) and an 89 kDa fragment (PARP-1(89)). Compared to WT (PARP-1WT), the expression of an uncleavable PARP-1 (PARP-1(UNCL)) or of PARP-1(24) conferred protection from oxygen/glucose deprivation (OGD) or OGD/restoration of oxygen and glucose (ROG) damage in vitro, whereas expression of PARP-1(89) was cytotoxic. Viability experiments were performed in SH-SY5Y, a human neuroblastoma cell line, as well as in rat primary cortical neurons. Following OGD, the higher viability in the presence of PARP-1UNCL or PARP-1(24) was not accompanied with decreased formation of poly(ADP-riboses) or higher NAD levels. PARP-1 is a known cofactor for NF-kappaB, hence we investigated whether PARP-1 cleavage influences the inflammatory response. All PARP-1 constructs mimicked PARP-1WT in regard to induction of NF-kappaB translocation into the nucleus and its increased activation during ischemic challenge. However, expression of PARP-1(89) construct induced significantly higher NF-kB activity than PARP-1WT; and the same was true for NF-kappaB-dependent iNOS promoter binding activity. At a protein level, PARP-1UNCL and PARP-1(24) decreased iNOS (and lower levels of iNOS transcript) and COX-2, and increased Bcl-xL The increased levels of NF-kB and iNOS transcriptional activities, seen with cytotoxic PARP-189, were accompanied by higher protein expression of COX-2 and iNOS (and higher levels of INOS transcript) and lower protein expression of Bcl-xL Taken together, these findings suggest that PARP-1 cleavage products may regulate cellular viability and inflammatory responses in opposing ways during in vitro models of "ischemia".

Polyinosinic-polycytidylic acid has therapeutic effects against cerebral ischemia/reperfusion injury through the downregulation of TLR4 signaling via TLR3

Recent reports have shown that preconditioning with the TLR3 ligand polyinosinic-polycytidylic acid (poly(I:C)) protects against cerebral ischemia/reperfusion (I/R) injury. However, it is unclear whether poly(I:C) treatment after cerebral I/R injury is also effective. We used mouse/rat middle cerebral artery occlusion and cell oxygen-glucose deprivation models to evaluate the therapeutic effects and mechanisms of poly(I:C) treatment. Poly(I:C) was i.p. injected 3 h after ischemia (treatment group). Cerebral infarct volumes and brain edemas were significantly reduced, and neurologic scores were significantly increased. TNF-α and IL-1β levels were markedly decreased, whereas IFN-β levels were greatly increased, in the ischemic brain tissues, cerebral spinal fluid, and serum. Injuries to hippocampal neurons and mitochondria were greatly reduced. The numbers of TUNEL-positive and Fluoro-Jade B(+) cells also decreased significantly in the ischemic brain tissues. Poly(I:C) treatment increased the levels of Hsp27, Hsp70, and Bcl2 and decreased the level of Bax in the ischemic brain tissues. Moreover, poly(I:C) treatment attenuated the levels of TNF-α and IL-1β in serum and cerebral spinal fluid of mice stimulated by LPS. However, the protective effects of poly(I:C) against cerebral ischemia were abolished in TLR3(-/-) and TLR4(-/-)mice. Poly(I:C) downregulated TLR4 signaling via TLR3. Poly(I:C) treatment exhibited obvious protective effects 14 d after ischemia and was also effective in the rat permanent middle cerebral artery occlusion model. The results suggest that poly(I:C) exerts therapeutic effects against cerebral I/R injury through the downregulation of TLR4 signaling via TLR3. Poly(I:C) is a promising new drug candidate for the treatment of cerebral infarcts.

Neuroprotective effects of erythropoietin pretreatment in a rodent model of transient middle cerebral artery occlusion

OBJECT.: There is an unmet clinical need to develop neuroprotective agents for neurosurgical and endovascular procedures that require transient cerebral artery occlusion. The aim in this study was to explore the effects of a single dose of recombinant human erythropoietin (rhEPO) before middle cerebral artery (MCA) occlusion in a focal cerebral ischemia/reperfusion model.

METHODS

Twenty-eight adult male Wistar rats were subjected to right MCA occlusion via the intraluminal thread technique for 60 minutes under continuous cortical perfusion monitoring by laser Doppler flowmetry. Rats were divided into 2 groups: control and treatment. In the treated group, rhEPO (1000 IU/kg intravenously) was administered 10 minutes before the onset of the MCA ischemia. At 24-hour reperfusion, animals were examined for neurological deficits, blood samples were collected, and animals were killed. The following parameters were evaluated: brain infarct volume, ipsilateral hemispheric edema, neuron-specific enolase plasma levels, parenchyma histological features (H & E staining), Fluoro-Jade-positive neurons, p-Akt and total Akt expression by Western blot analysis, and p-Akt-positive nuclei by immunohistochemical investigation.

RESULTS

Infarct volume and Fluoro-Jade staining of degenerating neurons in the infarct area did not vary between groups. The severity of neurological deficit (p < 0.001), amount of brain edema (78% reduction in treatment group, p < 0.001), and neuron-specific enolase plasma levels (p < 0.001) were reduced in the treatment group. Perivascular edema was histologically less marked in the treatment group. No variations in the expression or localization of p-Akt were seen.

CONCLUSIONS

Administration of rhEPO before the onset of 60-minute transient MCA ischemia protected the brain from this insult. It is unlikely that rhEPO pretreatment leads to direct neuronal antiapoptotic effects, as supported by the lack of Akt activation, and its benefits are most probably related to an indirect effect on brain edema as a consequence of blood-brain barrier preservation. Although research on EPO derivatives is increasing, rhEPO acts through distinct neuroprotective pathways and its clinical safety profile is well known. Clinically available rhEPO is a potential therapy for prevention of neuronal injury induced by transitory artery occlusion during neurovascular procedures.

NLRP3 deficiency ameliorates neurovascular damage in experimental ischemic stroke

Although the innate immune response to induce postischemic inflammation is considered as an essential step in the progression of cerebral ischemia injury, the role of innate immunity mediator NLRP3 in the pathogenesis of ischemic stroke is unknown. In this study, focal ischemia was induced by middle cerebral artery occlusion in NLRP3(-/-), NOX2(-/-), or wild-type (WT) mice. By magnetic resonance imaging (MRI), Evans blue permeability, and electron microscopic analyses, we found that NLRP3 deficiency ameliorated cerebral injury in mice after ischemic stroke by reducing infarcts and blood-brain barrier (BBB) damage. We further showed that the contribution of NLRP3 to neurovascular damage was associated with an autocrine/paracrine pattern of NLRP3-mediated interleukin-1β (IL-1β) release as evidenced by increased brain microvessel endothelial cell permeability and microglia-mediated neurotoxicity. Finally, we found that NOX2 deficiency improved outcomes after ischemic stroke by mediating NLRP3 signaling. This study for the first time shows the contribution of NLRP3 to neurovascular damage and provides direct evidence that NLRP3 as an important target molecule links NOX2-mediated oxidative stress to neurovascular damage in ischemic stroke. Pharmacological targeting of NLRP3-mediated inflammatory response at multiple levels may help design a new approach to develop therapeutic strategies for prevention of deterioration of cerebral function and for the treatment of stroke.

Immune mechanisms in cerebral ischemic tolerance

Stressor-induced tolerance is a central mechanism in the response of bacteria, plants, and animals to potentially harmful environmental challenges. This response is characterized by immediate changes in cellular metabolism and by the delayed transcriptional activation or inhibition of genetic programs that are not generally stressor specific (cross-tolerance). These programs are aimed at countering the deleterious effects of the stressor. While induction of this response (preconditioning) can be established at the cellular level, activation of systemic networks is essential for the protection to occur throughout the organs of the body. This is best signified by the phenomenon of remote ischemic preconditioning, whereby application of ischemic stress to one tissue or organ induces ischemic tolerance (IT) in remote organs through humoral, cellular and neural signaling. The immune system is an essential component in cerebral IT acting simultaneously both as mediator and target. This dichotomy is based on the fact that activation of inflammatory pathways is necessary to establish IT and that IT can be, in part, attributed to a subdued immune activation after index ischemia. Here we describe the components of the immune system required for induction of IT and review the mechanisms by which a reprogrammed immune response contributes to the neuroprotection observed after preconditioning. Learning how local and systemic immune factors participate in endogenous neuroprotection could lead to the development of new stroke therapies.

Combination treatment with N-acetyl-seryl-aspartyl-lysyl-proline and tissue plasminogen activator provides potent neuroprotection in rats after stroke

BACKGROUND AND PURPOSE

N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), an endogenously produced circulating peptide in humans and rodents, exerts anti-inflammatory and cardioprotective activities in various cardiovascular diseases.

METHODS

The present study evaluated the neuroprotective effect of AcSDKP alone and in combination with thrombolytic therapy in a rat model of embolic focal cerebral ischemia.

RESULTS

We found that treatment with AcSDKP alone at 1 hour or the combination treatment with AcSDKP and tissue plasminogen activator (tPA) at 4 hours after stroke onset substantially increased AcSDKP levels in plasma and cerebrospinal fluid and robustly reduced infarct volume and neurological deficits, without increasing the incidence of brain hemorrhage compared with ischemic rats treated with saline, AcSDKP alone at 4 hours, and tPA alone at 4 hours. Moreover, the combination treatment considerably reduced the density of nuclear transcription factor-κB (NF-κB), transforming growth factor β (TGF-β), and plasminogen activator inhibitor-1 (PAI-1) positive cerebral blood vessels in the ischemic brain, all of which were associated with reduced microvascular fibrin extravasation and platelet accumulation compared with tPA monotherapy. In vitro, AcSDKP blocked fibrin-elevated TGF-β1, PAI-1, and NF-κB proteins in primary human brain microvascular endothelial cells.

CONCLUSIONS

Our data indicate that AcSDKP passes the blood-brain barrier, and that treatment of acute stroke with AcSDKP either alone at 1 hour or in combination with tPA at 4 hours of the onset of stroke is effective to reduce ischemic cell damage in a rat model of embolic stroke. Inactivation of TGF-β and NF-κB signaling by AcSDKP in the neurovascular unit may underlie the neuroprotective effect of AcSDKP.

ROS and brain diseases: the good, the bad, and the ugly

The brain is a major metabolizer of oxygen and yet has relatively feeble protective antioxidant mechanisms. This paper reviews the Janus-faced properties of reactive oxygen species. It will describe the positive aspects of moderately induced ROS but it will also outline recent research findings concerning the impact of oxidative and nitrooxidative stress on neuronal structure and function in neuropsychiatric diseases, including major depression. A common denominator of all neuropsychiatric diseases including schizophrenia and ADHD is an increased inflammatory response of the brain caused either by an exposure to proinflammatory agents during development or an accumulation of degenerated neurons, oxidized proteins, glycated products, or lipid peroxidation in the adult brain. Therefore, modulation of the prooxidant-antioxidant balance provides a therapeutic option which can be used to improve neuroprotection in response to oxidative stress. We also discuss the neuroprotective role of the nuclear factor erythroid 2-related factor (Nrf2) in the aged brain in response to oxidative stressors and nanoparticle-mediated delivery of ROS-scavenging drugs. The antioxidant therapy is a novel therapeutic strategy. However, the available drugs have pleiotropic actions and are not fully characterized in the clinic. Additional clinical trials are needed to assess the risks and benefits of antioxidant therapies for neuropsychiatric disorders.

MicroRNAs regulate the chaperone network in cerebral ischemia

The highly evolutionarily conserved 70 kDa heat shock protein (HSP70) family was first understood for its role in protein folding and response to stress. Subsequently, additional functions have been identified for it in regulation of organelle interaction, of the inflammatory response, and of cell death and survival. Overexpression of HSP70 family members is associated with increased resistance to and improved recovery from cerebral ischemia. MicroRNAs (miRNAs) are important posttranscriptional regulators that interact with multiple target messenger RNAs (mRNA) coordinately regulating target genes, including chaperones. The members of the HSP70 family are now appreciated to work together as networks to facilitate organelle communication and regulate inflammatory signaling and cell survival after cerebral ischemia. This review will focus on the new concept of the role of the chaperone network in the organelle network and its novel regulation by miRNA.

Systemic revealing pharmacological signalling pathway networks in the hippocampus of ischaemia-reperfusion mice treated with baicalin

Background. Baicalin (BA) exhibits ill understood neuroprotective, anti-inflammatory, and antioxidative effects in brain injury. Objective. To identify the differential network pathways associated with BA-related biological effects. Methods. MCAO-induced mice received BA 5 mg/Kg (BA group). Controls received vehicle only. Following ischaemia-reperfusion, ArrayTrack analysed the whole genome microarray of hippocampal genes, and MetaCore analysed differentially expressed genes. Results. Four reversing pathways were common to BA and controls, but only 6 were in the top 10 for BA. Three of the top 5 signalling pathways in controls were not observed in BA. BA treatment made absent 3 pathways of the top 5 signalling pathways from the top 5 in controls. There were 2 reversing pathways between controls and BA that showed altered gene expression. Controls had 6 networks associated with cerebral ischaemia. After BA treatment, 9 networks were associated with cerebral ischaemia. Enrichment analysis identified 10 significant biological processes in BA and controls. Of the 10 most significant molecular functions, 7 were common to BA and controls, and only 3 occurred in BA. BA and controls had 7 significant cellular components. Conclusions. This study showed that the clinical effectiveness of BA was based on the complementary effects of multiple pathways and networks.

Effects of Tetramethylpyrazine on Microglia Activation in Spinal Cord Compression Injury of Mice

Secondary mechanisms, including inflammation and microglia activation, serve as targets for the development and application of pharmacological strategies in the management of spinal cord injury (SCI). Tetramethylpyrazine (TMP), an active ingredient of Ligusticum wallichii (chuanxiong), has shown anti-inflammatory and neuroprotective effects against SCI. However, it remains uncertain whether the inflammation-suppressive effects of TMP play a modulatory role over microglia activation in SCI. The present study investigated the effects of TMP on microglia activation and pro-inflammatory cytokines in spinal cord compression injury in mice. For a real-time PCR measurement of pro-inflammatory cytokines, SCI was induced in mice by the clip compression method (30 g force, 1 min) and TMP (15 or 30 mg/kg, i.p.) was administered once, 30 minutes before the SCI induction. For immunohistochemistry, TMP (30 mg/kg, i.p.) treatment was given three times during the first 48 hours after the SCI. 30 mg/kg of TMP treatment reduced the up-regulation of TNF-α, IL-1β and COX-2 mRNA in the spinal tissue at four hours after the SCI induction. TMP also significantly attenuated microglia activation and neutrophil infiltration at 48 hours after the SCI induction. In addition, iNOS expression in the spinal tissue was attenuated with TMP treatment. These results suggest that TMP plays a modulatory role in microglia activation and may protect the spinal cord from or potentially delay secondary spinal cord injury.

From mechanosensitivity to inflammatory responses: new players in the pathology of glaucoma

PURPOSE OF THE STUDY

Many blinding diseases of the inner retina are associated with degeneration and loss of retinal ganglion cells (RGCs). Recent evidence implicates several new signaling mechanisms as causal agents associated with RGC injury and remodeling of the optic nerve head. Ion channels such as Transient receptor potential vanilloid isoform 4 (TRPV4), pannexin-1 (Panx1) and P2X7 receptor are localized to RGCs and act as potential sensors and effectors of mechanical strain, ischemia and inflammatory responses. Under normal conditions, TRPV4 may function as an osmosensor and a polymodal molecular integrator of diverse mechanical and chemical stimuli, whereas P2X7R and Panx1 respond to stretch- and/or swelling-induced adenosine triphosphate release from neurons and glia. Ca(2+) influx, induced by stimulation of mechanosensitive ion channels in glaucoma, is proposed to influence dendritic and axonal remodeling that may lead to RGC death while (at least initially) sparing other classes of retinal neuron. The secondary phase of the retinal glaucoma response is associated with microglial activation and an inflammatory response involving Toll-like receptors (TLRs), cluster of differentiation 3 (CD3) immune recognition molecules associated with the T-cell antigen receptor, complement molecules and cell type-specific release of neuroactive cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). The retinal response to mechanical stress thus involves a diversity of signaling pathways that sense and transduce mechanical strain and orchestrate both protective and destructive secondary responses.

CONCLUSIONS

Mechanistic understanding of the interaction between pressure-dependent and independent pathways is only beginning to emerge. This review focuses on the molecular basis of mechanical strain transduction as a primary mechanism that can damage RGCs. The damage occurs through Ca(2+)-dependent cellular remodeling and is associated with parallel activation of secondary ischemic and inflammatory signaling pathways. Molecules that mediate these mechanosensory and immune responses represent plausible targets for protecting ganglion cells in glaucoma, optic neuritis and retinal ischemia.

Sustained, neuron-specific IKK/NF-κB activation generates a selective neuroinflammatory response promoting local neurodegeneration with aging

Background

Increasing evidence indicates that neuroinflammation is a critical factor contributing to the progression of various neurodegenerative diseases. The IKK/NF-κB signalling system is a central regulator of inflammation, but it also affects neuronal survival and differentiation. A complex interplay between different CNS resident cells and infiltrating immune cells, which produce and respond to various inflammatory mediators, determines whether neuroinflammation is beneficial or detrimental. The IKK/NF-κB system is involved in both production of and responses to these mediators, although the precise contribution depends on the cell type as well as the cellular context, and is only partially understood. Here we investigated the specific contribution of neuronal IKK/NF-κB signalling on the regulation of neuroinflammatory processes and its consequences. To address this issue, we established and analysed a conditional gain-of-function mouse model that expresses a constitutively active allele of IKK2 in principal forebrain neurons (IKK2^nCA). Proinflammatory gene and growth factor expression, histopathology, microgliosis, astrogliosis, immune cell infiltration and spatial learning were assessed at different timepoints after persistent canonical IKK2/NF-κB activation.

Results

In contrast to other cell types and organ systems, chronic IKK2/NF-κB signalling in forebrain neurons of adult IKK2^nCA animals did not cause a full-blown inflammatory response including infiltration of immune cells. Instead, we found a selective inflammatory response in the dentate gyrus characterized by astrogliosis, microgliosis and Tnf-α upregulation. Furthermore, downregulation of the neurotrophic factor Bdnf correlated with a selective and progressive atrophy of the dentate gyrus and a decline in hippocampus-dependent spatial learning. Neuronal degeneration was associated with increased Fluoro-jade staining, but lacked activation of apoptosis. Remarkably, neuronal loss could be partially reversed when chronic IKK2/NF-κB signalling was turned off and Bdnf expression was restored.

Conclusion

Our results demonstrate that persistent IKK2/NF-κB signalling in forebrain neurons does not induce overall neuroinflammation, but elicits a selective inflammatory response in the dentate gyrus accompanied by decreased neuronal survival and impaired learning and memory. Our findings further suggest that chronic activation of neuronal IKK2/NF-κB signalling, possibly as a consequence of neuroinflammatory conditions, is able to induce apoptosis-independent neurodegeneration via paracrine suppression of Bdnf synthesis.

Immediate splenectomy down-regulates the MAPK-NF-κB signaling pathway in rat brain after severe traumatic brain injury

BACKGROUND

The treatment of severe traumatic brain injury (TBI) remains a difficult process. One key to improving treatment efficacy is to reduce secondary brain injury. Local and systemic inflammatory responses play an important role in secondary injury after TBI, which if unchecked can lead to fatal cerebral edema. Previous studies focused mainly on local brain tissue, whereas little is known about the contribution of peripheral organs in the pathogenesis of TBI. We previously showed that immediate splenectomy decreases mortality and improves cognitive function in rats after severe TBI by inhibiting the release of proinflammatory cytokines both systematically and locally in the injured brain. In this study, we further investigated the molecular mechanisms responsible for the effect of the spleen on local brain inflammation after TBI.

METHODS

We established a severe TBI model with rats and performed splenectomy to study the effect of the spleen on mitogen-activated protein kinase (MAPK)-NF-κB activation in the brain tissue. The expression of p38 MAPK, extracellular regulated protein kinases (ERK), and NF-κB protein in the trauma region was examined by Western blotting. The neuron-like PC-12 cell line and microglia-like BV-2 cell line were used for in vitro experiments to test the effects of spleen supernatant after TBI. Cell apoptosis (annexin V/propidium iodide staining), NF-κB nuclear translocation (immunofluorescence microscopy), and MAPK signaling (phosphorylation of p-p38 and p-ERK) were examined.

RESULTS

We found that TBI significantly up-regulated MAPK signaling in the injured brain region, whereas immediate splenectomy suppressed MAPK activation. In vitro, the spleen supernatant from rats after TBI also resulted in increased MAPK activation and NF-κB nuclear translocation in microglia-like BV-2 cells, whereas the application of interleukin (IL)-1R antagonist (IL-1Ra) significantly reduced the expression of p-p38 and p-ERK as well as NF-κB nuclear translocation. In addition, spleen supernatant after TBI induced apoptosis in neuron-like PC-12 cells, and IL-1Ra could effectively reduce apoptosis.

CONCLUSION

Our study demonstrates that immediate splenectomy down-regulates the MAPK-NF-κB signaling pathway in rat brain after severe TBI. We also provide experimental evidence for the potential use of IL-1Ra to alleviate brain inflammation after TBI.

The regulatory role of NF-κB in autophagy-like cell death after focal cerebral ischemia in mice

Autophagy may contribute to ischemia-induced cell death in the brain, but the regulation of autophagic cell death is largely unknown. Nuclear factor kappa B (NF-κB) is a regulator of apoptosis in cerebral ischemia. We examined the hypothesis that autophagy-like cell death could contribute to ischemia-induced brain damage and the process was regulated by NF-κB. In adult wild-type (WT) and NF-κB p50 knockout (p50(-/-)) mice, focal ischemia in the barrel cortex was induced by ligation of distal branches of the middle cerebral artery. Twelve to 24h later, autophagic activity increased as indicated by enhanced expression of Beclin-1 and LC3 in the ischemic core and/or penumbra regions. This increased autophagy contributed to cell injury, evidenced by terminal deoxynucleotidyltransferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) co-staining and a protective effect achieved by the autophagy inhibitor 3-methyladenine. The number of Beclin-1/TUNEL-positive cells was significantly more in p50(-/-) mice than in WT mice. Neuronal and vascular cell death, as determined by TUNEL-positive cells co-staining with NeuN or Collagen IV, was more abundant in p50(-/-) mice. Immunostaining of the endothelial cell tight junction marker occludin revealed more damage to the blood-brain barrier in p50(-/-) mice. Western blotting of the peri-infarct tissue showed a reduction of Akt-the mammalian target of rapamycin (mTOR) signaling in p50(-/-) mice after ischemia. These findings provide the first evidence that cerebral ischemia induced autophagy-like injury is regulated by the NF-κB pathway, which may suggest potential treatments for ischemic stroke.

Compromised regulation of tissue perfusion and arteriogenesis limit, in an AT1R-independent fashion, recovery of ischemic tissue in Cx40(-/-) mice

Recently, we reported that recovery of tissue perfusion in the ischemic hindlimb was reduced, inflammatory response increased, and survival of distal limb tissue compromised in connexin 40 (Cx40)-deficient (Cx40(-/-)) mice. Here we evaluate whether genotype-specific differences in tissue perfusion, native vascular density, arteriogenesis, blood pressure, and chronic ANG II type 1 receptor (AT1R) activation contribute to poor recovery of ischemic hindlimb tissue in Cx40(-/-) mice. Hindlimb ischemia was induced in wild-type (WT), Cx40(-/-), and losartan-treated Cx40(-/-) mice by using surgical procedures that either maintained (mild surgery) or compromised (severe surgery) perfusion of major collateral vessels supplying the distal limb. Pre- and postsurgical hindlimb perfusion was evaluated, and tissue survival, microvascular density, and macrophage infiltration were documented during recovery. Hindlimb perfusion was compromised in presurgical Cx40(-/-) versus WT mice despite comparable native microvascular density. Hindlimb perfusion 24 h postsurgery in Cx40(-/-) and WT mice was comparable after mild surgery (collateral vessels maintained), but compromised arteriogenesis in Cx40(-/-) animals nevertheless limited subsequent recovery of tissue perfusion and compromised tissue survival. Prolonged pre- and postsurgical treatment of Cx40(-/-) mice with losartan (an AT1R antagonist) normalized blood pressure but did not improve tissue perfusion or survival, despite reduced macrophage infiltration. Thus it appears Cx40 is necessary for normal tissue perfusion and for recovery of perfusion, arteriogenesis, and tissue survival in the ischemic hindlimb. Our data suggest that Cx40(-/-) mice are at significantly greater risk for poor recovery from ischemic insult due to compromised regulation of tissue perfusion, vascular remodeling, and prolonged inflammatory response.

Interleukin-1β accelerates the onset of stroke in stroke-prone spontaneously hypertensive rats

High blood levels of inflammatory biomarkers and immune cells in stroke lesions have been recognized as results of stroke. However, recent studies have suggested that inflammation occurs prior to stroke onset. In this study, we aimed to clarify the role of inflammation in stroke onset among stroke-prone spontaneously hypertensive rats (SHRSP). At 4 weeks of age (before stroke onset), the plasma level of IL-1β was significantly higher in SHRSP (153.0 ± 49.7 pg/ml) than in Wistar Kyoto rats (WKY) (7.7 ± 3.4 pg/ml, P < 0.001 versus SHRSP) or spontaneously hypertensive rats (SHR) (28.0 ± 9.1 pg/ml, P < 0.001 versus SHRSP) (n = 6 per strain). Stimulated IL-1β signal was also observed in cerebrovascular endothelial cells of SHRSP. Gene expressions of IL-1β, IL-1 receptors, caspase-1, and downstream genes (MCP-1 and ICAM-1), which associated with immune cell recruitment, were significantly greater in SHRSP than in WKY or SHR, coincident with greater NFκB protein levels in SHRSP compared to WKY or SHR. In addition, continuous administration of IL-1β (2 μg/day) using an osmotic pump slightly increased the incidence of stroke in SHR (P = 0.046) and significantly accelerated the onset of stroke in SHRSP (P = 0.006) compared to each control (n = 10 per group). These results suggest that a stimulated IL-1β signal might be a cause of stroke onset when concomitant with severe hypertension.

NF-κB-regulated, proinflammatory miRNAs in Alzheimer's disease

Abundant neurochemical, neuropathological, and genetic evidence suggests that a critical number of proinflammatory and innate immune system-associated factors are involved in the underlying pathological pathways that drive the sporadic Alzheimer's disease (AD) process. Most recently, a series of epigenetic factors - including a select family of inducible, proinflammatory, NF-κB-regulated small noncoding RNAs called miRNAs - have been shown to be significantly elevated in abundance in AD brain. These upregulated miRNAs appear to be instrumental in reshaping the human brain transcriptome. This reorganization of mRNA speciation and complexity in turn drives proinflammatory and pathogenic gene expression programs. The ensuing, progressively altered immune and inflammatory signaling patterns in AD brain support immunopathogenetic events and proinflammatory features of the AD phenotype. This report will briefly review what is known concerning NF-κB-inducible miRNAs that are significantly upregulated in AD-targeted anatomical regions of degenerating human brain cells and tissues. Quenching of NF-κB-sensitive inflammatory miRNA signaling using NF-κB-inhibitors such as the polyphenolic resveratrol analog trans-3,5,4'-trihydroxystilbene (CAY10512) may have some therapeutic value in reducing inflammatory neurodegeneration. Antagonism of NF-κB-inducing, and hence proinflammatory, epigenetic and environmental factors, such as the neurotrophic herpes simplex virus-1 and exposure to the potent neurotoxin aluminum, are briefly discussed. Early reports further indicate that miRNA neutralization employing anti-miRNA (antagomir) strategies may hold future promise in the clinical management of this insidious neurological disorder and expanding healthcare concern.

Immune regulation toward immunomodulation for neuroprotection in glaucoma

Although the immune system functions to preserve and restore tissue homeostasis, accumulating risk factors, prolonged glial activation, and sustained release of pro-inflammatory mediators in glaucoma may lead to a failure in the regulation of stress-induced immune response, and innate immune cells, autoreactive T cells, autoantibodies, and excess complement attack may exhibit potent stimuli that harm retinal ganglion cell somas, axons, and synapses. Identification of the cellular and molecular components of immune response pathways can provide immunomodulatory treatment strategies to attenuate neuroinflammation, protect neural tissue from collateral injury, and enhance endogenous recovery processes. This review highlights the current knowledge of molecular mechanisms regulating neuroinflammation in glaucoma.

Association of plasma osteoprotegerin levels with stroke severity and functional outcome in acute ischaemic stroke patients

Osteoprotegerin (OPG) is known to regulate processes involved in vascular injury and inflammation. We investigated the relationship between plasma OPG levels and stroke subtype, stroke severity at admission and functional outcome at 3 months in 172 patients with acute ischaemic stroke. Patients with large artery atherosclerosis and those with multiple causes had higher plasma OPG levels than patients with lacune. Increased plasma OPG levels were independently associated with more severe stroke and poor functional outcome. These results suggest pleiotropic roles of OPG in mediating atherosclerosis and ischaemic brain injury. OPG is a potential biomarker for predicting neurologic outcome in stroke.

Toll-like receptor 3 agonist Poly I:C protects against simulated cerebral ischemia in vitro and in vivo

AIM

To examine the neuroprotective effects of the Toll-like receptor 3 (TLR3) agonist Poly I:C in acute ischemic models in vitro and in vivo.

METHODS

Primary astrocyte cultures subjected to oxygen-glucose deprivation (OGD) were used as an in vitro simulated ischemic model. Poly I:C was administrated 2 h before OGD. Cell toxicity was measured using MTT assay and LDH leakage assay. The levels of TNFα, IL-6 and interferon-β (IFNβ) in the media were measured using ELISA. Toll/interleukin receptor domain-containing adaptor-inducing IFNβ (TRIF) protein levels were detected using Western blot analysis. A mouse middle cerebral artery occlusion (MCAO) model was u sed for in vivo study. The animals were administered Poly I:C (0.3 mg/kg, im) 2 h before MCAO, and examined with neurological deficit scoring and TTC staining. The levels of TNFα and IL-6 in ischemic brain were measured using ELISA.

RESULTS

Pretreatment with Poly I:C (10 and 20 μg/mL) markedly attenuated OGD-induced astrocyte injury, and significantly raised the cell viability and reduced the LDH leakage. Poly I:C significantly upregulated TRIF expression accompanied by increased downstream IFNβ production. Moreover, Poly I:C significantly suppressed the pro-inflammatory cytokines TNFα and IL-6 production. In mice subjected to MCAO, administration of Poly I:C significantly attenuated the neurological deficits, reduced infarction volume, and suppressed the increased levels of TNFα and IL-6 in the ischemic striatum and cortex.

CONCLUSION

Poly I:C pretreatment exerts neuroprotective and anti-inflammatory effects in the simulated cerebral ischemia models, and the neuroprotection is at least in part due to the activation of the TLR3-TRIF pathway.

Walnut diet reduces accumulation of polyubiquitinated proteins and inflammation in the brain of aged rats

An increase in the aggregation of misfolded/damaged polyubiquitinated proteins has been the hallmark of many age-related neurodegenerative diseases. The accumulation of these potentially toxic proteins in brain increases with age, in part due to increased oxidative and inflammatory stresses. Walnuts, rich in omega fatty acids, have been shown to improve memory, cognition and neuronal effects related to oxidative stress (OS) and inflammation (INF) in animals and human trials. The current study found that feeding 19-month-old rats with a 6% or 9% walnut diet significantly reduced the aggregation of polyubiquitinated proteins and activated autophagy, a neuronal housekeeping function, in the striatum and hippocampus. Walnut-fed animals exhibited up-regulation of autophagy through inhibiting phosphorylation of mTOR, up-regulating ATG7 and Beclin 1, and turnover of MAP1BLC3 proteins. The clearance of polyubiquitinated protein aggregates such as p62/SQSTM1 was more profound in hippocampus, a critical region in the brain involved in memory and cognitive performance, than striatum. The clearance of ubiquitinated aggregates was in tandem with significant reductions in OS/INF, as indicated by the levels of P38-MAP kinase and phosphorylations of nuclear factor kappa B and cyclic AMP response element binding protein. The results demonstrate the effectiveness of a walnut-supplemented diet in activating the autophagy function in brain beyond its traditionally known antioxidant and anti-inflammatory benefits.

Astrocyte-specific IKK2 activation in mice is sufficient to induce neuroinflammation but does not increase susceptibility to MPTP

A key regulator of inflammatory gene expression is the transcription factor NF-κB that is controlled by the IκB proteins. We used a transgenic mouse model expressing a constitutively active IκB-kinase-2 (IKK2-CA) in astrocytes under control of the human glial fibrillary acidic protein promotor (IKK2-mice) to investigate neuroinflammation, proinflammatory cytokine expression, microglial activation and a potential enhanced susceptibility to the neurotoxin MPTP (4×10 mg/kg). Readouts included the determination of cytokines, striatal dopamine (DA), nigral tyrosine hydroxylase (TH) positive neurons, microglial activation and motor activity. IKK2-CA expression in astrocytes conditionally induced by the tet-off system resulted in a widespread neuroinflammation indicated by the increased expression of inflammatory cytokines and the presence of activated microglia and astrogliosis. Additionally, striatal DA concentrations but not nigral TH-positive neurons were reduced in IKK2-mice by 20%. Motor activity of IKK2-mice was not affected. Surprisingly, there was a similar reduction in striatal DA concentrations and the number of nigral TH-positive neurons in IKK2 and control mice after MPTP treatment. In conclusion, although naïve IKK2-mice showed reduced striatal DA concentrations and an increase in inflammatory markers in the brain, a higher susceptibility to MPTP was not observed. This finding argues against a prominent role of astrocyte specific, IKK2-mediated neuroinflammation in MPTP-induced neurodegeneration.

An astrocyte-specific proteomic approach to inflammatory responses in experimental rat glaucoma

PURPOSE

To delineate astrocyte-mediated inflammatory processes in glaucoma, we analyzed proteomic responses of retinal astrocytes in an experimental rat model using a cell-specific approach.

METHODS

IOP elevation was induced in rats by hypertonic saline injections into episcleral veins. Enriched samples of astrocytes were isolated through the immunomagnetic cell selection process established originally for retinal ganglion cell (RGC) sampling. Ocular hypertensive and control samples were collected by pooling from rat eyes matched for the cumulative IOP exposure. Protein expression was analyzed complementarily by quantitative two-dimensional capillary liquid chromatography and linear ion trap mass spectrometry (LC-MS/MS) followed by quantitative Western blot analysis and retinal tissue immunolabeling using specific antibodies to selected proteins.

RESULTS

Following validation of enriched astrocyte samples, LC-MS/MS analysis resulted in the identification of over 2000 proteins with high confidence. Bioinformatic comparison analysis of the high-throughput MS/MS data along with the findings of immunoblotting and immunohistochemistry supported distinct responses of ocular hypertensive astrocytes during the experimental paradigm, which exhibited predominantly cellular activation and immune/inflammatory responses as opposed to activation of cell death signaling in ocular hypertensive RGCs. Inflammatory responses of astrocytes in experimental glaucoma included up-regulation of a number of immune mediators/regulators linked to TNF-α/TNFR signaling, nuclear factor kappa-B (NF-κB) activation, autophagy regulation, and inflammasome assembly.

CONCLUSIONS

These findings validate an astrocyte-specific approach to quantitatively identify proteomic alterations in experimental glaucoma, and highlight many immune mediators/regulators characteristic of the inflammatory responses of ocular hypertensive astrocytes. By dissecting the complexity of prior data obtained from whole tissue, this pioneering approach should enable astrocyte responses to be defined and new treatments targeting astrocytes to be developed.

Variations in target gene expression and pathway profiles in the mouse hippocampus following treatment with different effective compounds for ischemia-reperfusion injury

In order to elucidate the overlapping and diverse pharmacological protective mechanisms of different Chinese medicinal compounds, we investigated the alteration of gene expression and activation of signaling pathways in the mouse hippocampus after treatment of cerebral ischemia-reperfusion injury with various compounds. A microarray including 16,463 genes was used to identify differentially expressed genes among six treatment groups: baicalin (BA), jasminoidin (JA), cholic acid (CA), concha margaritiferausta (CM), sham, and vehicle. The US Food and Drug Administration (FDA) ArrayTrack system and Kyoto Encyclopedia of Genes and Genomes (KEGG) database were used to screen significantly altered genes and pathways (P < 0.05, fold change >1.5). Vehicle treatment alone resulted in alteration of 726 genes (283 upregulated, 443 downregulated) compared to the sham treatment group. BA, JA, and CA treatments, but not CM treatment, were effective in reducing infarct volume compared with vehicle treatment (P < 0.05). Compared with the CM group, a total of 167 (73 upregulated, 94 downregulated), 379 (211 upregulated, 168 downregulated), and 181 (76 upregulated, 105 downregulated) altered genes were found in the BA, JA, and CA groups, respectively. The numbers of overlapping genes between the BA and JA, BA and CA, and JA and CA groups were 28 (16 upregulated, 12 downregulated), 14 (4 upregulated, 10 downregulated), and 31 (8 upregulated, 23 downregulated), respectively. Three overlapping genes were identified among the BA, JA, and CA treatment groups: Il1rap, Gnb5, and Wdr38. Based on KEGG pathway analysis, two, seven, and four pathways were significantly activated in the BA, JA, and CA groups, respectively, when compared to the CM group. The ATP-binding cassette (ABC) transporters general pathway was activated by BA and JA treatment, and the mitogen-activated protein kinase (MAPK) signaling pathway was activated by JA and CA treatment. Alteration of IL-1 and Hspa1a expression was found by real time reverse transcription polymerase chain reaction, confirming the results of the microarray analysis. Our data demonstrated that polytypic profiles of 167-379 altered genes exist in the mouse hippocampus treated with different compounds known to be therapeutically effective in cerebral ischemia-reperfusion injury, and we were able to identify overlapping genes and pathways among these groups. Therefore, these different compounds may function through both overlapping and distinct pharmacological mechanisms to exert their therapeutic action.

Effects of chronic and acute oestrogen replacement therapy in aged animals after experimental stroke

The effect of oestrogen replacement therapy (ERT) on stroke incidence and severity has been extensively debated. Clinical trials of ERT have demonstrated an increased risk of stroke in treated women, although the study participants were well past menopause when therapy was initiated. It has been suggested that detrimental effects of ERT may be unmasked after prolonged periods of hypoestrogenicity. To date, very few studies have examined the effect of ERT in aged animals, although the timing of replacement may be critical to the neuroprotective effects of ERT. We hypothesised that chronic ERT initiated in late middle age would decrease infarct size in the brain after an induced stroke, whereas acute ERT would have no beneficial effects in aged females. To test this hypothesis, two paradigms of ERT were administered to aged mice of both sexes aiming to determine the effects on stroke outcome and to explore the possible mechanisms by which ERT interacts with age. Female mice that received chronic ERT from 17-20 months of age showed improved stroke outcomes after experimental stroke, whereas females that had acute ERT initiated at 20 months of age did not. Chronic ERT females exhibited diminished levels of nuclear factor kappa B (NF-κB) translocation compared to acute ERT females after stroke. Acute ERT females demonstrated both an increase in nuclear NF-κB and enhanced expression of pro-inflammatory cytokines. In addition, a sexual dimorphic effect of ERT was seen because males benefited from ERT, regardless of the timing of initiation. Aged males had significantly reduced expression of pro-inflammatory markers after stroke compared to age-matched females, suggesting a pro-inflammatory milieu emerges with age in females. These results are consistent with the emerging clinical literature suggesting that ERT should be initiated at the time of menopause to achieve beneficial effects. The present study demonstrates the importance of using appropriate animal models in preclinical studies.

Neurodegenerative and inflammatory pathway components linked to TNF-α/TNFR1 signaling in the glaucomatous human retina

PURPOSE

This study aimed to determine retinal proteomic alterations in human glaucoma, with particular focus on links to TNF-α/TNFR1 signaling.

METHODS

Human retinal protein samples were obtained from 20 donors with (n = 10) or without (n = 10) glaucoma. Alterations in protein expression were individually analyzed by quantitative LC-MS/MS. Quantitative Western blot analysis with cleavage or phosphorylation site-specific antibodies was used for data validation, and cellular localization of selected proteins was determined by immunohistochemical analysis of the retina in an additional group of glaucomatous human donor eyes (n = 38) and nonglaucomatous controls (n = 30).

RESULTS

Upregulated retinal proteins in human glaucoma included a number of downstream adaptor/interacting proteins and protein kinases involved in TNF-α/TNFR1 signaling. Bioinformatic analysis of the high-throughput data established extended networks of diverse functional interactions with death-promoting and survival-promoting pathways and mediation of immune response. Upregulated pathways included death receptor-mediated caspase cascade, mitochondrial dysfunction, endoplasmic reticulum stress, calpains leading to apoptotic cell death, NF-κB and JAK/STAT pathways, and inflammasome-assembly mediating inflammation. Interestingly, retinal expression pattern of a regulator molecule, TNFAIP3, exhibited prominent variability between individual samples, and methylation of cytosine nucleotides in the TNFAIP3 promoter was found to be correlated with this variability among glaucomatous donors.

CONCLUSIONS

Findings of this study reveal a number of proteins upregulated in the glaucomatous human retina that exhibit many links to TNF-α/TNFR1 signaling. By highlighting various signaling molecules and regulators involved in cell death and immune response pathways and by correlating proteomic findings with epigenetic alterations, these findings provide a framework motivating further research.

Unraveling the ischemic brain transcriptome in a permanent middle cerebral artery occlusion mouse model by DNA microarray analysis

Brain ischemia, also termed cerebral ischemia, is a condition in which there is insufficient blood flow to the brain to meet metabolic demand, leading to tissue death (cerebral infarction) due to poor oxygen supply (cerebral hypoxia). Our group is interested in the protective effects of neuropeptides for alleviating brain ischemia, as well as the underlying mechanisms of their action. The present study was initiated to investigate molecular responses at the level of gene expression in ischemic brain tissue. To achieve this, we used a mouse permanent middle cerebral artery occlusion (PMCAO) model in combination with high-throughput DNA microarray analysis on an Agilent microarray platform. Briefly, the right (ipsilateral) and left (contralateral) hemispheres of PMCAO model mice were dissected at two time points, 6 and 24 hours post-ischemia. Total RNA from the ischemic (ipsilateral) hemisphere was subjected to DNA microarray analysis on a mouse whole genome 4x44K DNA chip using a dye-swap approach. Functional categorization using the gene ontology (GO, MGD/AMIGO) of numerous changed genes revealed expression pattern changes in the major categories of cellular process, biological regulation, regulation of biological process, metabolic process and response to stimulus. Reverse-transcriptase PCR (RT-PCR) analysis on randomly selected highly up- or downregulated genes validated, in general, the microarray data. Using two time points for this analysis, major and minor trends in gene expression and/or functions were observed in relation to early- and late-response genes and differentially regulated genes that were further classified into specific pathways or disease states. We also examined the expression of these genes in the contralateral hemisphere, which suggested the presence of bilateral effects and/or differential regulation. This study provides the first ischemia-related transcriptome analysis of the mouse brain, laying a strong foundation for studies designed to elucidate the mechanisms regulating ischemia and to explore the neuroprotective effects of agents such as target neuropeptides.

LPS preconditioning redirects TLR signaling following stroke: TRIF-IRF3 plays a seminal role in mediating tolerance to ischemic injury

Background

Toll-like receptor 4 (TLR4) is activated in response to cerebral ischemia leading to substantial brain damage. In contrast, mild activation of TLR4 by preconditioning with low dose exposure to lipopolysaccharide (LPS) prior to cerebral ischemia dramatically improves outcome by reprogramming the signaling response to injury. This suggests that TLR4 signaling can be altered to induce an endogenously neuroprotective phenotype. However, the TLR4 signaling events involved in this neuroprotective response are poorly understood. Here we define several molecular mediators of the primary signaling cascades induced by LPS preconditioning that give rise to the reprogrammed response to cerebral ischemia and confer the neuroprotective phenotype.

Methods

C57BL6 mice were preconditioned with low dose LPS prior to transient middle cerebral artery occlusion (MCAO). Cortical tissue and blood were collected following MCAO. Microarray and qtPCR were performed to analyze gene expression associated with TLR4 signaling. EMSA and DNA binding ELISA were used to evaluate NFκB and IRF3 activity. Protein expression was determined using Western blot or ELISA. MyD88-/- and TRIF-/- mice were utilized to evaluate signaling in LPS preconditioning-induced neuroprotection.

Results

Gene expression analyses revealed that LPS preconditioning resulted in a marked upregulation of anti-inflammatory/type I IFN-associated genes following ischemia while pro-inflammatory genes induced following ischemia were present but not differentially modulated by LPS. Interestingly, although expression of pro-inflammatory genes was observed, there was decreased activity of NFκB p65 and increased presence of NFκB inhibitors, including Ship1, Tollip, and p105, in LPS-preconditioned mice following stroke. In contrast, IRF3 activity was enhanced in LPS-preconditioned mice following stroke. TRIF and MyD88 deficient mice revealed that neuroprotection induced by LPS depends on TLR4 signaling via TRIF, which activates IRF3, but does not depend on MyD88 signaling.

Conclusion

Our results characterize several critical mediators of the TLR4 signaling events associated with neuroprotection. LPS preconditioning redirects TLR4 signaling in response to stroke through suppression of NFκB activity, enhanced IRF3 activity, and increased anti-inflammatory/type I IFN gene expression. Interestingly, this protective phenotype does not require the suppression of pro-inflammatory mediators. Furthermore, our results highlight a critical role for TRIF-IRF3 signaling as the governing mechanism in the neuroprotective response to stroke.

Prodigiosin inhibits gp91(phox) and iNOS expression to protect mice against the oxidative/nitrosative brain injury induced by hypoxia-ischemia

This study aimed to explore the mechanisms by which prodigiosin protects against hypoxia-induced oxidative/nitrosative brain injury induced by middle cerebral artery occlusion/reperfusion (MCAo/r) injury in mice. Hypoxia in vitro was modeled using oxygen-glucose deprivation (OGD) followed by reoxygenation of BV-2 microglial cells. Our results showed that treatment of mice that have undergone MCAo/r injury with prodigiosin (10 and 100μg/kg, i.v.) at 1h after hypoxia ameliorated MCAo/r-induced oxidative/nitrosative stress, brain infarction, and neurological deficits in the mice, and enhanced their survival rate. MCAo/r induced a remarkable production in the mouse brains of reactive oxygen species (ROS) and a significant increase in protein nitrosylation; this primarily resulted from enhanced expression of NADPH oxidase 2 (gp91(phox)), inducible nitric oxide synthase (iNOS), and the infiltration of CD11b leukocytes due to breakdown of blood-brain barrier (BBB) by activation of nuclear factor-kappa B (NF-κB). All these changes were significantly diminished by prodigiosin. In BV-2 cells, OGD induced ROS and nitric oxide production by up-regulating gp91(phox) and iNOS via activation of the NF-κB pathway, and these changes were suppressed by prodigiosin. In conclusion, our results indicate that prodigiosin reduces gp91(phox) and iNOS expression possibly by impairing NF-κB activation. This compromises the activation of microglial and/or inflammatory cells, which then, in turn, mediates prodigiosin's protective effect in the MCAo/r mice.

Notch Activation Enhances the Microglia-Mediated Inflammatory Response Associated With Focal Cerebral Ischemia

Background and Purpose—

Activation of Notch worsens ischemic brain damage as antisense knockdown or pharmacological inhibition of the Notch pathway reduces the infarct size and improves the functional outcome in a mouse model of stroke. We sought to determine whether Notch activation contributes to postischemic inflammation by directly modulating the microglial innate response.

Methods—

The microglial response and the attendant inflammatory reaction were evaluated in Notch1 antisense transgenic (Tg) and in nontransgenic (non-Tg) mice subjected to middle cerebral artery occlusion with or without treatment with a γ-secretase inhibitor (GSI). To investigate the impact of Notch on microglial effector functions, primary mouse microglia and murine BV-2 microglial cell line were exposed to oxygen glucose deprivation or lipopolysaccharide in the presence or absence of GSI. Immunofluorescence labeling, Western blotting, and reverse-transcription polymerase chain reaction were performed to measure microglial activation and production of inflammatory cytokines. The nuclear translocation of nuclear factor-κB in microglia was assessed by immunohistochemistry. The neurotoxic potential of microglia was determined in cocultures.

Results—

Notch1 antisense mice exhibit significantly lower numbers of activated microglia and reduced proinflammatory cytokine expression in the ipsilateral ischemic cortices compared to non-Tg mice. Microglial activation also was attenuated in Notch1 antisense cultures and in non-Tg cultures treated with GSI. GSI significantly reduced nuclear factor-κB activation and expression of proinflammatory mediators and markedly attenuated the neurotoxic activity of microglia in cocultures.

Conclusions—

These findings establish a role for Notch signaling in modulating the microglia innate response and suggest that inhibition of Notch might represent a complementary therapeutic approach to prevent reactive gliosis in stroke and neuroinflammation-related degenerative disorders.

Photochemical control of DNA decoy function enables precise regulation of nuclear factor κB activity

DNA decoys have been developed for the inhibition of transcriptional regulation of gene expression. However, the present methodology lacks the spatial and temporal control of gene expression that is commonly found in nature. Here, we report the application of photoremovable protecting groups on nucleobases of nuclear factor κB (NF-κB) DNA decoys to regulate NF-κB-driven transcription of secreted alkaline phosphatase using light as an external control element. The NF-κB family of proteins is comprised of important eukaryotic transcription factors that regulate a wide range of cellular processes and are involved in immune response, development, cellular growth, and cell death. Several diseases, including cancer, arthritis, chronic inflammation, asthma, neurodegenerative diseases, and heart disease, have been linked to constitutively active NF-κB. Through the direct incorporation of caging groups into an NF-κB decoy, we were able to disrupt DNA:DNA hybridization and inhibit the binding of the transcription factor to the DNA decoy until UV irradiation removed the caging groups and restored the activity of the oligonucleotide. Excellent light-switching behavior of transcriptional regulation was observed. This is the first example of a caged DNA decoy for the photochemical regulation of gene expression in mammalian cells and represents an important addition to the toolbox of light-controlled gene regulatory agents.