Parkin regulates neuronal lipid homeostasis through SREBP2-lipoprotein lipase pathway-implications for Parkinson's disease.

Abnormal lipid homeostasis has been observed in the brain of Parkinson's disease (PD) patients and experimental models, although the mechanism underlying this phenomenon is unclear. Notably, previous studies have reported that the PD-linked protein Parkin functionally interacts with important lipid regulators, including Sterol Regulatory Element-Binding Proteins (SREBPs) and cluster of differentiation 36 (CD36). Here, we demonstrate a functional relationship between Parkin and lipoprotein lipase (LPL), a triglyceride lipase that is widely expressed in the brain. Using a human neuroblastoma cell line and a Parkin knockout mouse model, we demonstrate that Parkin expression level positively correlates with neuronal LPL protein level and activity. Importantly, our study identified SREBP2, a major regulator of sterol and fatty acid synthesis, as a potential mediator between Parkin and LPL. Supporting this, SREBP2 genetic ablation abolished Parkin effect on LPL expression. We further demonstrate that Parkin-LPL pathway regulates the formation of intracellular lipid droplets, and that this pathway is upregulated upon exposure to PD-linked oxidative stress induced by rotenone. Finally, we show that inhibition of either LPL or SREBP2 exacerbates rotenone-induced cell death. Taken together, our findings reveal a novel pathway linking Parkin, SREBP2 and LPL in neuronal lipid homeostasis that may be relevant to the pathogenesis of PD.

Conditional disruption of AMP kinase in dopaminergic neurons promotes Parkinson's disease-associated phenotypes in vivo.

Emerging studies implicate energy dysregulation as an underlying trigger for Parkinson's disease (PD), suggesting that a better understanding of the molecular pathways governing energy homeostasis could help elucidate therapeutic targets for the disease. A critical cellular energy regulator is AMP kinase (AMPK), which we have previously shown to be protective in PD models. However, precisely how AMPK function impacts on dopaminergic neuronal survival and disease pathogenesis remains elusive. Here, we showed that Drosophila deficient in AMPK function exhibits PD-like features, including dopaminergic neuronal loss and climbing impairment that progress with age. We also created a tissue-specific AMPK-knockout mouse model where the catalytic subunits of AMPK are ablated in nigral dopaminergic neurons. Using this model, we demonstrated that loss of AMPK function promotes dopaminergic neurodegeneration and associated locomotor aberrations. Accompanying this is an apparent reduction in the number of mitochondria in the surviving AMPK-deficient nigral dopaminergic neurons, suggesting that an impairment in mitochondrial biogenesis may underlie the observed PD-associated phenotypes. Importantly, the loss of AMPK function enhances the susceptibility of nigral dopaminergic neurons in these mice to 6-hydroxydopamine-induced toxicity. Notably, we also found that AMPK activation is reduced in post-mortem PD brain samples. Taken together, these findings highlight the importance of neuronal energy homeostasis by AMPK in PD and position AMPK pathway as an attractive target for future therapeutic exploitation.

Generation of complement component C5a by ischemic neurons promotes neuronal apoptosis.

C5a receptors are found in the central nervous system (CNS), on both neurons and glia. However, the origin of the C5a, which activates these receptors, is unclear. In the present study, we show that primary cultured mouse cortical neurons constitutively express C5, the precursor of C5a, and express the classical receptor for C5a, CD88. With cell ischemia caused by 12 h glucose deprivation, or oxygen-glucose deprivation (OGD), neurons demonstrated increased apoptosis, up-regulation of CD88, and increased levels of C5a in the media. Exogenous murine C5a (100 nM) added to the neuronal cultures resulted in apoptosis, without affecting cell necrosis. Pretreatment of the cells with the specific CD88 receptor antagonist PMX53 (100 nM) significantly blocked ischemia-induced apoptosis (∼50%), and neurons from CD88(-/-) mice were similarly protected. In a murine model of stroke, using middle cerebral artery occlusion (MCAO), we found that C5a levels in the brain increased; this also occurred in cerebral slice cultures exposed to OGD. CD88(-/-) mice subjected to MCAO had significantly reduced infarct volumes and improved neurological scores. Taken together, our results demonstrate that neurons in the CNS have the capability to generate C5a following ischemic stress, and this has the potential to activate their C5a receptors, with deleterious consequences.

Intravenous immunoglobulin protects neurons against amyloid beta-peptide toxicity and ischemic stroke by attenuating multiple cell death pathways.

Intravenous immunoglobulin (IVIg) preparations obtained by fractionating blood plasma, are increasingly being used increasingly as an effective therapeutic agent in treatment of several inflammatory diseases. Its use as a potential therapeutic agent for treatment of stroke and Alzheimer's disease has been proposed, but little is known about the neuroprotective mechanisms of IVIg. In this study, we investigated the effect of IVIg on downstream signaling pathways that are involved in neuronal cell death in experimental models of stroke and Alzheimer's disease. Treatment of cultured neurons with IVIg reduced simulated ischemia- and amyloid ßpeptide (Aß)-induced caspase 3 cleavage, and phosphorylation of the cell death-associated kinases p38MAPK, c-Jun NH2 -terminal kinase and p65, in vitro. Additionally, Aß-induced accumulation of the lipid peroxidation product 4-hydroxynonenal was attenuated in neurons treated with IVIg. IVIg treatment also up-regulated the anti-apoptotic protein, Bcl2 in cortical neurons under ischemia-like conditions and exposure to Aß. Treatment of mice with IVIg reduced neuronal cell loss, apoptosis and infarct size, and improved functional outcome in a model of focal ischemic stroke. Together, these results indicate that IVIg acts directly on neurons to protect them against ischemic stroke and Aß-induced neuronal apoptosis by inhibiting cell death pathways and by elevating levels of the anti-apoptotic protein Bcl2.

Neutralizing and Total/IgG Spike Antibody Responses Following Homologous CoronaVac vs. BNT162b2 Vaccination Up to 90 Days Post-Booster.

INTRODUCTION: We documented the total spike antibody (S-Ab), IgG S-Ab and neutralizing antibody (N-Ab) responses of BNT162b2/CoronaVac vaccinees up to 90 days post-booster dose. METHODS: We included 32 homologous regimen CoronaVac vaccinees and 136 BNT162b2 mRNA vaccinees. We tested their total S-Ab (Roche), IgG (Abbott) and N-Ab (Snibe) levels at set time points from January 2021 to April 2022. All subjects were deemed to be COVID-19-naïve either via clinical history (CoronaVac vaccinees) or nucleocapsid antibody testing (BNT162b2 vaccinees). RESULTS: All antibodies peaked 20-30 days post-inoculation. In BNT162b2 vaccinees, all post-booster antibodies were significantly higher than second-dose peaks. In CoronaVac vaccinees, IgG showed no significant differences between peak third-/second-dose titers (difference of 56.0 BAU/mL, 95% CI of -17.1 to 129, p = 0.0894). The post-vaccination titers of all antibodies in BNT162b2 vaccinees were significantly higher than those in CoronaVac vaccinees at all time points. Post-booster, all antibodies declined in 90 days; the final total/IgG/N-Ab titers were 7536 BAU/mL, 1276 BAU/mL and 12.5 µg/mL in BNT162b2 vaccinees and 646 BAU/mL, 62.4 BAU/mL and 0.44 µg/mL in CoronaVac vaccinees. CONCLUSION: The mRNA vaccine generated more robust total S-Ab, IgG and N-Ab responses after the second and third vaccinations.

Evidence that gamma-secretase-mediated Notch signaling induces neuronal cell death via the nuclear factor-kappaB-Bcl-2-interacting mediator of cell death pathway in ischemic stroke.

Notch-1 (Notch) is a cell surface receptor that regulates cell-fate decisions in the developing nervous system, and it may also have roles in synaptic plasticity in the adult brain. Binding of its ligands results in the proteolytic cleavage of Notch by the γ-secretase enzyme complex, thereby causing the release of a Notch intracellular domain (NICD) that translocates to the nucleus, in which it regulates transcription. Here we show that activation of Notch modulates ischemic neuronal cell death in vitro and in vivo. Specifically, our findings from the use of Notch-1 siRNA or the overexpression of NICD indicate that Notch activation contributes to cell death. Using modified NICD, we demonstrate an apoptosis-inducing function of NICD in both the nucleus and the cytosol. NICD transfection-induced cell death was reduced by blockade of calcium signaling, caspase activation, and Janus kinase signaling. Inhibition of the Notch-activating enzyme, γ-secretase, protected against ischemic neuronal cell death by targeting an apoptotic protease, cleaved caspase-3, nuclear factor-κB (NF-κB), and the pro-death BH3-only protein, Bcl-2-interacting mediator of cell death (Bim). Treatment of mice with a γ-secretase inhibitor, compound E, reduced infarct size and improved functional outcome in a model of focal ischemic stroke. Furthermore, γ-secretase inhibition reduced NICD, p-p65, and Bim levels in vivo. These findings suggest that Notch signaling endangers neurons after ischemic stroke by modulating the NF-κB, pro-death protein Bim, and caspase pathways.

AMP Kinase Activation is Selectively Disrupted in the Ventral Midbrain of Mice Deficient in Parkin or PINK1 Expression.

Parkinson's disease (PD) is a prevalent neurodegenerative movement disorder that is characterized pathologically by the progressive loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc) of the midbrain. Despite intensive research, the etiology of PD remains poorly understood. Interestingly, recent studies have implicated neuronal energy dysregulation as one of the key perpetrators of the disease. Supporting this, we have recently demonstrated that pharmacological or genetic activation of AMP kinase (AMPK), a master regulator of cellular energy homeostasis, rescues the pathological phenotypes of Drosophila models of PD. However, little is known about the role of AMPK in the mammalian brain. As an initial attempt to clarify this, we examined the expression of AMPK in rodent brains and found that phospho-AMPK (pAMPK) is disproportionately distributed in the adult mouse brain, being high in the ventral midbrain where the SN resides and relatively lower in regions such as the cortex-reflecting perhaps the unique energy demands of midbrain DA neurons. Importantly, the physiologically higher level of midbrain pAMPK is significantly reduced in aged mice and also in Parkin-deficient mice; the loss of function of which in humans causes recessive Parkinsonism. Not surprisingly, the expression of PGC-1α, a downstream target of AMPK activity, and a key regulator of mitochondrial biogenesis, mirrors the expression pattern of pAMPK. Similar observations were made with PINK1-deficient mice. Finally, we showed that metformin administration restores the level of midbrain pAMPK and PGC-1α expression in Parkin-deficient mice. Taken together, our results suggest that the disruption of AMPK-PGC-1α axis in the brains of individuals with Parkin or PINK1 mutations may be a precipitating factor of PD, and that pharmacological AMPK activation may represent a neuroprotective strategy for the disease.

DAMPs and neurodegeneration.

The concept of neuroinflammation has come a full circle; from being initially regarded as a controversial viewpoint to its present day acceptance as an integral component of neurodegenerative processes. A closer look at the etiopathogenesis of many neurodegenerative conditions will reveal a patho-symbiotic relationship between neuroinflammation and neurodegeneration, where the two liaise with each other to form a self-sustaining vicious cycle that facilitates neuronal demise. Here, we focus on damage associated molecular patterns or DAMPs as a potentially important nexus in the context of this lethal neuroinflammation-neurodegeneration alliance. Since their nomenclature as "DAMPs" about a decade ago, these endogenous moieties have consistently been reported as novel players in sterile (non-infective) inflammation. However, their roles in inflammatory responses in the central nervous system (CNS), especially during chronic neurodegenerative disorders are still being actively researched. The aim of this review is to first provide a general overview of the neuroimmune response in the CNS within the purview of DAMPs, its receptors and downstream signaling. This is then followed by discussions on some of the DAMP-mediated neuroinflammatory responses involved in chronic neurodegenerative diseases. Along the way, we also highlighted some important gaps in our existing knowledge regarding the role of DAMPs in neurodegeneration, the clarification of which we believe would aid in the prospects of developing treatment or screening strategies directed at these molecules.

Mitochondrial dysfunction and Parkinson disease: a Parkin-AMPK alliance in neuroprotection.

Although a subject of intense research, the etiology of Parkinson disease (PD) remains poorly understood. However, a wide range of studies conducted over the past few decades have collectively implicated aberrant mitochondrial homeostasis as a key contributor to the development of PD. Particularly strong support for this came from the recent demonstration that parkin, a familial PD-linked gene, is a critical regulator of mitochondrial quality control. Indeed, Parkin appears to be involved in all stages of the mitochondrial life cycle (i.e., from biogenesis to its exit from the cell (via mitophagy). Interestingly, the role of Parkin in the biogenesis and clearance of mitochondria is akin to that performed by the energy sensor AMP-activated protein kinase (AMPK), suggesting that the two proteins might act in a functionally converging manner to maintain the quality of cellular mitochondria. In this review, we discuss the contribution of mitochondrial dysfunction to PD pathogenesis and the role of Parkin and AMPK in preserving neuronal mitochondrial homeostasis. Alongside this, we will also articulate our thoughts on the potential alliance between Parkin and AMPK in offering neuroprotection through their ability to maintain energy balance in the brain.

Evidence that the EphA2 receptor exacerbates ischemic brain injury.

Ephrin (Eph) signaling within the central nervous system is known to modulate axon guidance, synaptic plasticity, and to promote long-term potentiation. We investigated the potential involvement of EphA2 receptors in ischemic stroke-induced brain inflammation in a mouse model of focal stroke. Cerebral ischemia was induced in male C57Bl6/J wild-type (WT) and EphA2-deficient (EphA2(-/-)) mice by middle cerebral artery occlusion (MCAO; 60 min), followed by reperfusion (24 or 72 h). Brain infarction was measured using triphenyltetrazolium chloride staining. Neurological deficit scores and brain infarct volumes were significantly less in EphA2(-/-) mice compared with WT controls. This protection by EphA2 deletion was associated with a comparative decrease in brain edema, blood-brain barrier damage, MMP-9 expression and leukocyte infiltration, and higher expression levels of the tight junction protein, zona occludens-1. Moreover, EphA2(-/-) brains had significantly lower levels of the pro-apoptotic proteins, cleaved caspase-3 and BAX, and higher levels of the anti-apoptotic protein, Bcl-2 as compared to WT group. We confirmed that isolated WT cortical neurons express the EphA2 receptor and its ligands (ephrin-A1-A3). Furthermore, expression of all four proteins was increased in WT primary cortical neurons following 24 h of glucose deprivation, and in the brains of WT mice following stroke. Glucose deprivation induced less cell death in primary neurons from EphA2(-/-) compared with WT mice. In conclusion, our data provide the first evidence that the EphA2 receptor directly contributes to blood-brain barrier damage and neuronal death following ischemic stroke.

Adiponectin receptor signalling in the brain.

Adiponectin is an important adipocyte-derived hormone that regulates metabolism of lipids and glucose, and its receptors (AdipoR1, AdipoR2, T-cadherin) appear to exert actions in peripheral tissues by activating the AMP-activated protein kinase, p38-MAPK, PPARα and NF-kappa B. Adiponectin has been shown to exert a wide range of biological functions that could elicit different effects, depending on the target organ and the biological milieu. There is substantial evidence to suggest that adiponectin receptors are expressed widely in the brain. Their expression has been detected in regions of the mouse hypothalamus, brainstem, cortical neurons and endothelial cells, as well as in whole brain and pituitary extracts. While there is now considerable evidence for the presence of adiponectin and its receptors in the brain, their precise roles in brain diseases still remain unclear. Only a few research studies have looked at this facet of adiponectins in brain disorders. This brief review will describe the evidence for important functions by adiponectin, its structure and known actions, evidence for expression of AdipoRs in the brain, their involvement in brain disorders and the therapeutic potential of agents that could modify AdipoR signalling.

C5a receptor (CD88) inhibition improves hypothermia-induced neuroprotection in an in vitro ischemic model.

The concept of 'salvageble penumbra' has prompted both scientists and physicians to explore various neuroprotective approaches that could be beneficial during stroke therapy. Unfortunately, most of them have proved ineffective in targeting multiple cellular death cascades incited within the ischemic penumbra. Hypothermia has been shown to be capable of addressing this problem to some extent. Although many studies have shown that hypothermia targets several cellular processes, its effects on innate immune receptor-mediated apoptotic death still remain unclear. Moreover, whether inhibiting the signaling of innate immune receptors like complement anaphylatoxin C5a receptor (CD88) plays a role in this hypothermic neuroprotection still need to be deciphered. Using various types of ischemic insults in different neuronal cells, we confirm that hypothermia does indeed attenuate apoptotic neuronal cell death in vitro and this effect can be further enhanced by pharmacologically blocking or knocking out CD88. Thus, our study raises a promising therapeutic possibility of adding CD88 antagonists along with hypothermia to improve stroke outcomes.

Over-expression of DSCR1 protects against post-ischemic neuronal injury.

BACKGROUND AND PURPOSE: The Down syndrome candidate region 1 (DSCR1) gene is located on human chromosome 21 and its protein is over-expressed in brains of Down syndrome individuals. DSCR1 can modulate the activity of calcineurin, a phosphatase abundant in the brain, but its influence on stroke outcome is not clear. We compared stroke outcome in wildtype (WT) and transgenic (DSCR1-TG) mice which over-express isoform 1 of human DSCR1. METHODS: Transient cerebral ischemia was produced by occlusion of the middle cerebral artery for 0.5 h. After 23.5 h reperfusion, we assessed neurological impairment, brain infarct and edema volume, leukocyte infiltration and markers of inflammation. Intrinsic resistance to apoptosis following glucose deprivation was also assessed in primary cultures of WT and DSCR1-TG neurons. RESULTS: In contrast to WT, DSCR1-TG mice had an improved neurological deficit score, greater grip strength, attenuated infarct volume and brain swelling, and lacked hippocampal lesions after stroke. Expression of mouse DSCR1-1, but not DSCR1-4, mRNA and protein was increased by ischemia in both WT and DSCR1-TG. Brain calcineurin activity was increased to a similar degree after ischemia in each genotype. DSCR1-TG mice had fewer infiltrating neutrophils and activated microglia compared with WT, in association with an attenuated upregulation of several pro-inflammatory genes. Neurons from DSCR1-TG mice were more resistant than WT neurons to apoptotic cell death following 24 h of glucose deprivation. CONCLUSIONS: Over-expression of DSCR1 in mice improves outcome following stroke. Mechanisms underlying this protection may involve calcineurin-independent, anti-inflammatory and anti-apoptotic effects mediated by DSCR1 in neurons.

The flavonoid fisetin attenuates postischemic immune cell infiltration, activation and infarct size after transient cerebral middle artery occlusion in mice.

The development of the brain tissue damage in ischemic stroke is composed of an immediate component followed by an inflammatory response with secondary tissue damage after reperfusion. Fisetin, a flavonoid, has multiple biological effects, including neuroprotective and antiinflammatory properties. We analyzed the effects of fisetin on infarct size and the inflammatory response in a mouse model of stroke, temporary middle cerebral artery occlusion, and on the activation of immune cells, murine primary and N9 microglial and Raw264.7 macrophage cells and human macrophages, in an in vitro model of inflammatory immune cell activation by lipopolysaccharide (LPS). Fisetin not only protected brain tissue against ischemic reperfusion injury when given before ischemia but also when applied 3 hours after ischemia. Fisetin also prominently inhibited the infiltration of macrophages and dendritic cells into the ischemic hemisphere and suppressed the intracerebral immune cell activation as measured by intracellular tumor necrosis factor α (TNFα) production. Fisetin also inhibited LPS-induced TNFα production and neurotoxicity of macrophages and microglia in vitro by suppressing nuclear factor κB activation and JNK/Jun phosphorylation. Our findings strongly suggest that the fisetin-mediated inhibition of the inflammatory response after stroke is part of the mechanism through which fisetin is neuroprotective in cerebral ischemia.

Pathophysiology, treatment, and animal and cellular models of human ischemic stroke.

Stroke is the world's second leading cause of mortality, with a high incidence of severe morbidity in surviving victims. There are currently relatively few treatment options available to minimize tissue death following a stroke. As such, there is a pressing need to explore, at a molecular, cellular, tissue, and whole body level, the mechanisms leading to damage and death of CNS tissue following an ischemic brain event. This review explores the etiology and pathogenesis of ischemic stroke, and provides a general model of such. The pathophysiology of cerebral ischemic injury is explained, and experimental animal models of global and focal ischemic stroke, and in vitro cellular stroke models, are described in detail along with experimental strategies to analyze the injuries. In particular, the technical aspects of these stroke models are assessed and critically evaluated, along with detailed descriptions of the current best-practice murine models of ischemic stroke. Finally, we review preclinical studies using different strategies in experimental models, followed by an evaluation of results of recent, and failed attempts of neuroprotection in human clinical trials. We also explore new and emerging approaches for the prevention and treatment of stroke. In this regard, we note that single-target drug therapies for stroke therapy, have thus far universally failed in clinical trials. The need to investigate new targets for stroke treatments, which have pleiotropic therapeutic effects in the brain, is explored as an alternate strategy, and some such possible targets are elaborated. Developing therapeutic treatments for ischemic stroke is an intrinsically difficult endeavour. The heterogeneity of the causes, the anatomical complexity of the brain, and the practicalities of the victim receiving both timely and effective treatment, conspire against developing effective drug therapies. This should in no way be a disincentive to research, but instead, a clarion call to intensify efforts to ameliorate suffering and death from this common health catastrophe. This review aims to summarize both the present experimental and clinical state-of-the art, and to guide future research directions.

Intestinal ischemia-reperfusion injury leads to inflammatory changes in the brain.

Intestinal ischemia-reperfusion (I/R) injury is a well-established animal model of systemic inflammation and can lead to multiple organ failure as well as severe and lasting morbidity and even death. It can occur in humans as a result of vascular surgery or as secondary sequelae to many common conditions including low blood pressure, myocardial infarction, and necrotizing enterocolitis. Systemic inflammation induced through kidney I/R injury has been shown previously to lead to encephalopathic adverse effects, and it was theorized that intestinal injury would also cause secondary central nervous system effects. This study presents evidence that over a 6-h time frame, mouse intestinal I/R injury does not cause neuronal cell death in the brain in vivo. However, at the genetic level, certain inflammatory mediators such as endothelial nitric oxide synthase, intercellular adhesion molecule 1, P selectin, TNF-α, and IL-6 are significantly upregulated. There was a significant increase in brain edema observed in sham-operated animals as well as in fasted and nonfasted I/R groups, but neurons were not apoptotic, in the 6-h time period. Conversely, Iba1-expressing activated microglia cells and glial fibrillary acidic protein-expressing astrocytes were found to be markedly increased in fasted and nonfasted I/R mice compared with controls and sham-operated animals. These data demonstrate that intestinal I/R injury induces inflammatory changes in the brain.

Evidence that adiponectin receptor 1 activation exacerbates ischemic neuronal death.

BACKGROUND: Adiponectin is a hormone produced in and released from adipose cells, which has been shown to have anti-diabetic and anti-inflammatory actions in peripheral cells. Two cell surface adiponectin receptors (ADRs) mediate the majority of the known biological actions of adiponectin. Thus far, ADR expression in the brain has been demonstrated in the arcuate and the paraventricular nucleus of hypothalamus, where its activation affects food intake. Recent findings suggest that levels of circulating adiponectin increase after an ischemic stroke, but the role of adiponectin receptor activation in stroke pathogenesis and its functional outcome is unclear. METHODS: Ischemic stroke was induced in C57BL/6 mice by middle cerebral artery occlusion (MCAO) for 1 h, followed by reperfusion. Primary cortical neuronal cultures were established from individual embryonic neocortex. For glucose deprivation (GD), cultured neurons were incubated in glucose-free Locke's medium for 6, 12 or 24 h. For combined oxygen and glucose deprivation (OGD), neurons were incubated in glucose-free Locke's medium in an oxygen-free chamber with 95% N2/5% CO2 atmosphere for either 3, 6, 9, 12 or 24 h. Primary neurons and brain tissues were analysed for Adiponectin and ADRs using reverse transcriptase polymerase chain reaction (RT-PCR), immunoblot and immunochemistry methods. RESULTS: Cortical neurons express ADR1 and ADR2, and that the levels of ADR1 are increased in neurons in response to in vitro or in vivo ischemic conditions. Neurons treated with either globular or trimeric adiponectin exhibited increased vulnerability to oxygen and glucose deprivation which was associated with increased activation of a pro-apoptotic signaling cascade involving p38 mitogen-activated protein kinase (p38MAPK) and AMP-activated protein kinase (AMPK). CONCLUSIONS: This study reveals a novel pathogenic role for adiponectin and adiponectin receptor activation in ischemic stroke. We show that cortical neurons express ADRs and reveal a pro-apoptotic role for ADR1 activation in neurons, which may render them vulnerable to ischemic death.

Pivotal role for beta-1 integrin in neurovascular remodelling after ischemic stroke.

beta1 integrin is a cell surface molecule that is critical for endothelial cell adhesion, migration and survival during angiogenesis. In the present study we employed in vivo and in vitro models to elucidate the role of beta1 integrin in vascular remodelling and stroke outcomes. At 24 h after cerebral ischemia and reperfusion (I/R), the ischemic cortex (ipsilateral area) exhibited modest beta1 integrin immunoreactivity and a robust increase was observed at 72 h. Double-label immunohistochemical analysis for beta1 integrin with neuronal (NeuN), microglial (Iba-1), astrocyte (GFAP), progenitor cell (Ng2) and blood vessel (collagen 4) markers showed that beta1 integrin expression only localized to blood vessels. In vitro studies using cultured endothelial cells and a beta1 integrin blocking antibody confirmed that beta1 integrin is required for endothelial cell migration, proliferation and blood vessel formation. In vivo studies in the cerebral I/R model using the beta1 integrin blocking antibody further confirmed that beta1 integrin signaling is involved in vascular formation and recovery following ischemic stroke. Finally, we found that beta1 integrin is critically involved in functional deficits and survival after a stroke. These results suggest that beta1 integrin plays important roles in neurovascular remodelling and functional outcomes following stroke, and that targeting the beta1 integrin signalling may provide a novel strategy for modulating angiogenesis in ischemic stroke and other pathological conditions.

Toll-like receptors in ischemia-reperfusion injury.

Ischemia-reperfusion (I/R) injuries are implicated in a large array of pathological conditions such as myocardial infarction, cerebral stroke, and hepatic, renal, and intestinal ischemia, as well as following cardiovascular and transplant surgeries. The hallmark of these pathologies is excessive inflammation. Toll-like receptors (TLRs) are recognized as one of the main contributors to pathogen-induced inflammation and, more recently, injury-induced inflammation. Endogenous ligands such as low-molecular hyaluronic acid, fibronectin, heat shock protein 70, and heparin sulfate were all found to be cleaved in the inflamed tissue and to activate TLR2 and TLR4, initiating an inflammatory response even in the absence of pathogens and infiltrating immune cells. In this review, we discuss the contribution of TLR activation in hepatic, renal, cerebral, intestinal, and myocardial I/R injuries. A greater understanding of the role of TLRs in I/R injuries may aid in the development of specific TLR-targeted therapeutics to treat these conditions.