The initial acute phase response predicts long-term stroke recovery

Corneal nerve loss in patients with TIA and acute ischemic stroke in relation to circulating markers of inflammation and vascular integrity

Vascular and inflammatory mechanisms are implicated in the development of cerebrovascular disease and corneal nerve loss occurs in patients with transient ischemic attack (TIA) and acute ischemic stroke (AIS). We have assessed whether serum markers of inflammation and vascular integrity are associated with the severity of corneal nerve loss in patients with TIA and AIS. Corneal confocal microscopy (CCM) was performed to quantify corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD) and corneal nerve fiber length (CNFL) in 105 patients with TIA (n = 24) or AIS (n = 81) and age matched control subjects (n = 56). Circulating levels of IL-6, MMP-2, MMP-9, E-Selectin, P-Selectin and VEGF were quantified in patients within 48 h of presentation with a TIA or AIS. CNFL (P = 0.000, P = 0.000), CNFD (P = 0.122, P = 0.000) and CNBD (P = 0.002, P = 0.000) were reduced in patients with TIA and AIS compared to controls, respectively with no difference between patients with AIS and TIA. The NIHSS Score (P = 0.000), IL-6 (P = 0.011) and E-Selectin (P = 0.032) were higher in patients with AIS compared to TIA with no difference in MMP-2 (P = 0.636), MMP-9 (P = 0.098), P-Selectin (P = 0.395) and VEGF (P = 0.831). CNFL (r = 0.218, P = 0.026) and CNFD (r = 0.230, P = 0.019) correlated with IL-6 and multiple regression analysis showed a positive association of CNFL and CNFD with IL-6 (P = 0.041, P = 0.043). Patients with TIA and AIS have evidence of corneal nerve loss and elevated IL6 and E-selectin levels. Larger longitudinal studies are required to determine the association between inflammatory and vascular markers and corneal nerve fiber loss in patients with cerebrovascular disease.

Gamma subunit of complement component 8 is a neuroinflammation inhibitor

The complement system is part of the innate immune system that comprises several small proteins activated by sequential cleavages. The majority of these complement components, such as components 3a (C3a) and C5a, are chemotactic and pro-inflammatory. However, in this study, we revealed an inhibitory role of complement component 8 gamma (C8G) in neuroinflammation. In patients with Alzheimer's disease, who exhibit strong neuroinflammation, we found higher C8G levels in brain tissue, CSF, and plasma. Our novel findings also showed that the expression level of C8G increases in the inflamed mouse brain, and that C8G is mainly localized to brain astrocytes. Experiments using recombinant C8G protein and shRNA-mediated knockdown showed that C8G inhibits glial hyperactivation, neuroinflammation, and cognitive decline in acute and chronic animal models of Alzheimer's disease. Additionally, we identified sphingosine-1-phosphate receptor 2 (S1PR2) as a novel interaction protein of C8G and demonstrated that astrocyte-derived C8G interacts with S1PR2 to antagonize the pro-inflammatory action of S1P in microglia. Taken together, our results reveal the previously unrecognized role of C8G as a neuroinflammation inhibitor. Our findings pave the way towards therapeutic containment of neuroinflammation in Alzheimer's disease and related neurological diseases.

Circulating endothelial cell-derived extracellular vesicles mediate the acute phase response and sickness behaviour associated with CNS inflammation

Brain injury elicits a systemic acute-phase response (APR), which is responsible for co-ordinating the peripheral immunological response to injury. To date, the mechanisms responsible for signalling the presence of injury or disease to selectively activate responses in distant organs were unclear. Circulating endogenous extracellular vesicles (EVs) are increased after brain injury and have the potential to carry targeted injury signals around the body. Here, we examined the potential of EVs, isolated from rats after focal inflammatory brain lesions using IL-1β, to activate a systemic APR in recipient naïve rats, as well as the behavioural consequences of EV transfer. Focal brain lesions increased EV release, and, following isolation and transfer, the EVs were sequestered by the liver where they initiated an APR. Transfer of blood-borne EVs from brain-injured animals was also enough to suppress exploratory behaviours in recipient naïve animals. EVs derived from brain endothelial cell cultures treated with IL-1β also activated an APR and altered behaviour in recipient animals. These experiments reveal that inflammation-induced circulating EVs derived from endothelial cells are able to initiate the APR to brain injury and are sufficient to generate the associated sickness behaviours, and are the first demonstration that EVs are capable of modifying behavioural responses.

Predictors of 30-day mortality and 90-day functional recovery after primary intracerebral hemorrhage : hospital based multivariate analysis in 585 patients

OBJECTIVE

The purpose of this study was to identify independent predictors of mortality and functional recovery in patients with primary intracerebral hemorrhage (PICH) and to improve functional outcome in these patients.

METHODS

Data were collected retrospectively on 585 patients with supratentorial PICH admitted to the Stroke Unit at our hospital between 1st January 2004 and the 31st July 2008. Using multivariate logistic regression analysis, the associations between all selected variables and 30-day mortality and 90-day functional recoveries after PICH was evaluated.

RESULTS

Ninety-day functional recovery was achieved in 29.1% of the 585 patients and 30-day mortality in 15.9%. Age (OR=7.384, p=0.000), limb weakness (OR=6.927, p=0.000), and hematoma volume (OR=5.293, p=0.000) were found to be powerful predictors of 90-day functional recovery. Furthermore, initial consciousness (OR=3.013, p=0.014) hematoma location (lobar, OR=2.653, p=0.003), ventricular extension of blood (OR=2.077, p=0.013), leukocytosis (OR=2.048, p=0.008), alcohol intake (drinker, OR=1.927, p=0.023), and increased serum aminotransferase (OR=1.892, p=0.035) were found to be independent predictors of 90-day functional recovery after PICH. On the other hand, a pupillary abnormality (OR=4.532, p=0.000) and initial unconsciousness (OR=3.362, p=0.000) were found to be independent predictors of 30-day mortality after PICH.

CONCLUSION

The predictors of mortality and functional recovery after PICH identified during this analysis may assist during clinical decision-making, when advising patients or family members about the prognosis of PICH and when planning intervention trials.

A new model of cortical stroke in the rhesus macaque

Primate models are essential tools for translational research in stroke but are reportedly inconsistent in their ability to produce cortical infarcts of reproducible size. Here, we report a new stroke model using a transorbital, reversible, two-vessel occlusion approach in male rhesus macaques that produces consistent and reproducible cortical infarcts. The right middle cerebral artery (distal to the orbitofrontal branch) and both anterior cerebral arteries were occluded with vascular clips. Bilateral occlusion of the anterior cerebral artery was critical for reducing collateral flow to the ipsilateral cortex. Reversible ischemia was induced for 45, 60, or 90 mins (n=2/timepoint) and infarct volume and neurologic outcome were evaluated. The infarcts were located predominantly in the cortex and increased in size with extended duration of ischemia determined by T(2)-weighted magnetic resonance imaging . Infarct volume measured by 2,3,5-triphenyl tetrazolium chloride and cresyl violet staining corroborated magnetic resonance imaging results. Neurologic deficit scores worsened gradually with longer occlusion times. A subset of animals (n=5) underwent 60 mins of ischemia resulting in consistent infarct volumes primarily located to the cortex that correlated well with neurologic deficit scores. This approach offers promise for evaluating therapeutic interventions in stroke.

Blood cell-derived RANTES mediates cerebral microvascular dysfunction, inflammation, and tissue injury after focal ischemia-reperfusion

BACKGROUND AND PURPOSE

Although chemokines have been implicated in cardiovascular diseases, few studies have addressed the role of these inflammatory mediators in ischemic stroke. This study tested the hypothesis that RANTES (CCL5; regulated on activation, normal T-cell expressed and secreted) mediates the cerebral microvascular dysfunction, inflammation, and tissue injury induced by brain ischemia and reperfusion.

METHODS

After 60-minute middle cerebral artery occlusion and reperfusion, the adhesion of leukocytes and platelets in cerebral venules, infarct volume, and blood-brain barrier permeability were measured in wild-type mice (WT), RANTES-deficient mice (RANTES(-/-)), WT mice transplanted with RANTES(-/-) bone marrow (RANTES>WT), and control bone marrow chimeras (WT>WT). The concentration of RANTES and several cytokines was also measured by enzyme-linked immunosorbent assay and a cytometric bead array.

RESULTS

The enhanced leukocyte and platelet adhesion, increased blood-brain barrier permeability, and tissue infarction elicited in WT and WT>WT mice after middle cerebral artery occlusion and reperfusion were significantly blunted in RANTES(-/-) mice. Similar attenuation of the middle cerebral artery occlusion and reperfusion-induced responses were noted in RANTES>WT chimeras. Although RANTES deficiency did not alter the changes in tissue cytokine levels elicited by middle cerebral artery occlusion and reperfusion, plasma concentrations interleukin-6, interleukin-10, and interleukin-12 were all reduced.

CONCLUSIONS

These findings implicate blood cell-derived RANTES in the microvascular, inflammatory, and tissue injury responses of the brain to ischemia and reperfusion.

Oxidized low-density lipoprotein is present in astrocytes surrounding cerebral infarcts and stimulates astrocyte interleukin-6 secretion

Ischemic injury to brain is associated with both disruption of the blood-brain barrier and increased oxidative stress. Given the neurotoxicity associated with exposure to oxidized low-density lipoprotein (oxLDL) in vitro, we tested the hypothesis that oxLDL may be present in parenchymal cells of cerebrum after infarction and that oxLDL may influence the pathophysiology of cerebral infarction. Our results showed that the subacute phase of cerebral infarction in patients was characterized by the appearance of oxLDL epitopes in astrocytes, but not neurons or microglia, in the perinecrotic zone. We further demonstrated that minimally oxLDL was most effectively internalized by primary cultures of rat astrocytes, and that exposure to minimal oxLDL stimulated astrocyte interleukin-6 secretion but did not alter nitric oxide production. These results demonstrate for the first time that oxLDL is present in brain parenchyma of patients with ischemic infarction and suggest a potential mechanism by which oxLDL may activate innate immunity and thereby indirectly influence neuronal survival.

[Acute phase response after stroke: differences between ischemic stroke and intracerebral hemorrhage]

BACKGROUND

To evaluate differences in the temporal profile of acute phase response (APR) between ischemic stroke (IS) and intracerebral hemorrhage (ICH).

PATIENTS AND METHOD

We studied APR parameters (< 24 h and 3-5 day) in 88 consecutive patients (43 ICH and 45 IS). The increase/decrease of the parameters between both dates was analyzed.

RESULTS

Leukocyte increase (LI) and fibrinogen increase (FI) is significantly higher in ICH than in IS (p = 0.047 and p = 0.035).

CONCLUSIONS

APR temporal profile is different for ICH and IS.

Lack of interleukin-6 expression is not protective against focal central nervous system ischemia

BACKGROUND AND PURPOSE

Interleukin-6 (IL-6) appears to be involved in the inflammatory response associated with central nervous system (CNS) ischemia. Although IL-6 levels increase after stroke, it is not known whether IL-6 directly influences CNS ischemic injury. In this study, we used a focal reversible stroke model to investigate whether mice lacking IL-6 were protected against acute ischemic injury.

METHODS

We bred IL-6-deficient C57 black mice (I-129 IL-6 KO back-crossed with C57), including homozygous knockouts (IL-6 -/-), heterozygous littermates (IL-6 +/-), and normal littermates (IL-6 +/+). The status of all animals was confirmed by DNA sampling and polymerase chain reaction analysis. Reversible middle cerebral artery occlusion was produced by advancing a silicone-coated 8-0 filament into the internal carotid artery for 2 hours (experiment 1) or 45 minutes (experiment 2). At 24 hours, animals were evaluated on a 28-point clinical scale, blood and cerebrospinal fluid were obtained, and the brains were evaluated for infarct volume and IL-6 mRNA levels.

RESULTS

In experiment 1 (severe ischemia), no differences were seen in lesion size or neurological function between the groups: lesion volume was IL-6 -/- (n=15), 57+/-13 mm(3); IL-6 +/- (n=15), 58+/-23 mm(3); and IL-6 +/+ (n=15), 58+/-18 mm(3) (P=NS). ELISA testing confirmed very low to absent levels of IL-6 in the serum and cerebrospinal fluid of knockout animals. Brain mRNA levels of the other proinflammatory cytokines, including tumor necrosis factor-alpha, IL-1beta, and IL-1 receptor antagonist, were 50% lower in IL-6-deficient ischemic animals than in normal animals. In experiment 2 (mild ischemia), no differences were seen in lesion size or neurological function between the groups: lesion volume was IL-6 -/- (n=10), 16+/-8 mm(3); IL-6 +/- (n=10), 14+/-4 mm(3); and IL-6 +/+ (n=10), 19+/-12 mm(3) (P=NS).

CONCLUSIONS

In this study, infarct size and neurological function at 24 hours were not different in animals deficient in IL-6 after transient CNS ischemia. This suggests that IL-6 does not have a direct influence on acute ischemic injury. Further study investigating the role of IL-6 on long-term recovery after stroke is in progress.

Temporal modulation of cytokine expression following focal cerebral ischemia in mice

There is increasing evidence that the inflammatory response plays an important role in CNS ischemia. The murine model of focal ischemia, however, remains incompletely characterized. In this study we examined expression of several cytokines and the vascular adhesion molecule E-selectin, in order to characterize the molecular events following stroke in the C57BL/6J mouse. Using a multi-probe RNAse protection assay (RPA), mRNA for 19 cytokines was analyzed following permanent and transient occlusion of the middle cerebral artery in mice. In addition, samples from the same mice were analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR) to evaluate E-selectin mRNA expression levels. Several cytokine mRNAs showed a similar expression pattern in both permanent and transient CNS ischemia while others showed a temporal expression pattern that was dependent on the type of stroke. For both models, mRNA levels of TNFalpha rose early (4 h) followed by IL-6 (10-18 h) and a comparatively late increase (96 h) in TGFbeta1. IL-1alpha, IL-1beta and IL-1ra levels showed a model dependent shift in temporal expression. Reperfusion appeared to delay the induction of these cytokines. Temporal changes in cytokine mRNA expression in the mouse CNS occur following ischemic damage. Our findings demonstrate the utility and power of multi-probe RPA for evaluation of changes in cytokine mRNA levels. Moreover, this study is, to our knowledge the first to show temporal changes in cytokine mRNA in mouse cerebral ischemia, forming a basis for further exploration of the roles of these cytokines in modulating ischemic neuronal damage in this model.