Immune and inflammatory responses to stroke: good or bad?

The Role of immune and inflammatory mechanisms in ALS

Amyotrophic lateral sclerosis (ALS) is a severe progressive neurodegenerative disease. The cause is unknown, but genetic abnormalities have been identified in subjects with familial ALS and also in subjects with sporadic ALS. Environmental factors such as occupational exposure have been shown to be risk factors for the development of ALS. Patients differ in their clinical features and differ in the clinical course of disease. Immune abnormalities have been found in the central nervous system by pathological studies and also in the blood and CSF of subjects with ALS. Inflammation and immune abnormalities are also found in animals with a model of ALS due to mutations in the SOD1 gene. Previously it has been considered that immune abnormalities might contribute to the pathogenesis of disease. However more recently it has become apparent that an immune response can occur as a response to damage to the nervous system and this can be protective.

The Neuroprotective Effect of Genetic Mannose-binding Lectin Deficiency is not Sustained in the Sub-acute Phase of Stroke

INTRODUCTION

The complement cascade is a critical mediator of the inflammatory response following cerebral ischemia. Recent work has demonstrated that genetic-deficiency of Mannose-binding lectin(MBL) ameliorates reperfusion injury and improves outcome in the acute phase of stroke. The present study sought to further delineate the pathogenic role of MBL in stroke and to examine whether the neuroprotection associated with MBL-deficiency is sustained beyond the acute phase. We hypothesized that genetic MBL deficiency would suppress complement activation and ameliorate reperfusion injury in the acute phase, but that persistent inhibition of complement into the sub-acute phase would serve to abrogate this neuroprotective effect.

METHODS

The time-course and localization of post-ischemic cerebral MBL and C3 deposition were characterized using both Western-blot and immunohistochemistry. MBL-a/c null(MBL-KO) mice subjected to transient middle cerebral artery occlusion(MCAO) were then employed to investigate the histologic injury and functional outcome associated with genetic MBL deletion at both 24 hours and 7 days.

RESULTS

MBL-a/c rapidly deposit on ischemic endothelium and trigger downstream complement activation in the acute phase. Genetic deficiency of MBL abrogates C3 cleavage as well as the sub-acute accumulation of mononuclear cells in the ischemic region. Although MBL-KO mice demonstrate significantly improved outcome at 24 hours, the neuroprotective effect associated with genetic MBL deletion is not sustained.

CONCLUSIONS

Development of a successful anti-complement neuroprotective strategy will require carefully-tailored inhibition coupled with a greater understanding of the functional effects of complement activation during later phases of stroke recovery.

Levels of phosphorylated axonal neurofilament subunit H (pNfH) are increased in acute ischemic stroke

For the study of stroke outcomes, there is the need for measurements of severity of stroke damage. Phosphorylated neurofilament heavy protein (pNfH) levels are elevated in axonal injury. We have measured levels of pNfH in stroke and correlated these levels with measures of stroke severity. Blood samples were collected from 54 ischaemic stroke patients at day 1, week 1 (days 7-10) and weeks 3-6, and an ELISA was used to measure pNfH levels in each patient at each time-point. Serum pNfH levels were significantly elevated in stroke patients compared to healthy controls. The levels were low at day 1, higher at day 7 and reached a peak at week 3, the latest day that we assessed. Significant associations were found between the pNfH levels at week 3 and early and stroke severity, size and outcome. Blood pNfH levels that reflect the severity of ischaemic stroke, are correlated with outcome and rise during the weeks after stroke. This may be a useful measure of tissue damage in stroke.

Inflammation and gliosis in neurological diseases--clinical implications

The inflammatory reaction accompany all acute processes in the central nervous system (CNS), (as stroke or traumatic brain injury) and chronic neurodegenerative processes (as Parkinson's or Alzheimer's disease), and through the stage of cleaning of damage tissue, contribute to recovery and regeneration and eventually to restoration of the function. However many studies showed that inflammation in the CNS may be harmful because of an excessive vulnerability of the nervous tissue or impaired regulation. Manipulation of the inflammation is now one of the approaches in the treatment of the various diseases of the CNS.

Direct profiling of phospholipids and lysophospholipids in rat brain sections after ischemic stroke

Stroke, a deleterious cerebrovascular event, is caused by a critical reduction in the blood flow to the brain parenchyma that leads to brain injury and loss of brain functions. The inflammatory responses following ischemia often aggravate the neurological damage. Several pro-inflammatory mediators released after stroke are closely related to the metabolism of phospholipids. In this study we directly profiled the changes in phospholipids in the infarcted rat cerebral cortex 24 hours after middle cerebral artery occlusion (MCAO) using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Several phosphatidylcholine (PC) species and sphingomyelin (SM) were significantly decreased after infarction. The cationization pattern of the remaining PCs showed a prominent shift from a mostly potassiated or protonated form to a predominantly sodiated pattern. Stroke also elevated the lysophosphatidylcholines (LPCs) and heme in tissue. The isobaric pairs in PC and LPC classes were resolved by masses through their respective alkali metal adducts in the presence of CsCl. The major fatty acyl LPC species were also structurally confirmed by MALDI-MS/MS. Overall, the results described the changes in PC and LPC species in the infarcted rat cortex. The elevated tissue levels of LPCs and heme signify the ongoing pathological lipid breakdown and the state of parenchymal inflammation. The elevated LPC level in tissue suggests a means of intervention through lysophospholipid metabolism that could potentially benefit the management of stroke and other acute neurological injuries.

Cytokines and strokes of ill fortune

Incidence of Seizures in the Acute Phase of Stroke: A Population-based Study. Szaflarski JP, Rackley AY, Kleindorfer DO, Khoury J, Woo D, Miller R, Alwell K, Broderick JP, Kissela BM. Epilepsia 2008;49(6):974–981.

Purpose

The incidence of seizures within 24 h of acute stroke has not been studied extensively. We aimed to establish the incidence of acute poststroke seizures in a biracial cohort and to determine whether acute seizure occurrence differs by race/ethnicity, stroke subtype, and/or stroke localization.

Methods

We identified all stroke cases between July 1993 and June 1994 and in 1999 within the population of the Greater Cincinnati metropolitan region. Patients with a prior history of seizures/epilepsy were excluded from analysis.

Results

A total of 6044 strokes without a history of seizure(s) were identified; 190 (3.1%) had seizures within the first 24 h of stroke onset. Of ICH/SAH patients, 8.4% had a seizure within the first 24 h of stroke onset ( p ≤ 0.0001 vs all other stroke subtype). Of the patients with ischemic stroke, we observed higher incidence of seizures in cardioembolic versus small or large vessel ischemic ( p = 0.02) strokes. Patients with seizures experienced higher mortality than patients without seizures ( p < 0.001) but seizures were not an independent risk factor of mortality at 30 days after stroke. Independent risk factors for seizure development included hemorrhagic stroke, younger age, and prestroke Rankin score of ≥1. Race/ethnicity or localization of the ischemic stroke did not influence the risk for seizure development in the studied population.

Discussion

The overall incidence of acute seizures after stroke was 3.1%, with a higher incidence seen in hemorrhagic stroke, younger patients, and those presenting with higher prestroke Rankin scores. Acute seizures were associated with a higher mortality at 30 days after stroke.

Intravenous hMSCs improve myocardial infarction in mice because cells embolized in lung are activated to secrete the anti-inflammatory protein TSG-6

Quantitative assays for human DNA and mRNA were used to examine the paradox that intravenously (i.v.) infused human multipotent stromal cells (hMSCs) can enhance tissue repair without significant engraftment. After 2 x 10(6) hMSCs were i.v. infused into mice, most of the cells were trapped as emboli in lung. The cells in lung disappeared with a half-life of about 24 hr, but <1000 cells appeared in six other tissues. The hMSCs in lung upregulated expression of multiple genes, with a large increase in the anti-inflammatory protein TSG-6. After myocardial infarction, i.v. hMSCs, but not hMSCs transduced with TSG-6 siRNA, decreased inflammatory responses, reduced infarct size, and improved cardiac function. I.v. administration of recombinant TSG-6 also reduced inflammatory responses and reduced infarct size. The results suggest that improvements in animal models and patients after i.v. infusions of MSCs are at least in part explained by activation of MSCs to secrete TSG-6.