Counting strokes

ESTROGEN REPLACEMENT THERAPY FOR STROKE

Stroke is the third most common cause of death and severe disability among Western populations. Overall, the incidence of stroke is uniformly higher in men than in women. Stroke is rare in women during the reproductive years, and rapidly increases after menopause, strongly suggesting that estrogen (E2) plays an important role in the prevention of stroke. Ongoing studies are currently evaluating both the benefits and risks associated with E2 replacement therapy and hormone replacement therapy in stroke. Equally important is the role of E2 receptor (ER), as studies indicate that ER populations in several tissue sites may significantly change during stress and aging. Such changes may affect the patient's susceptibility to neurological disorders including stroke, and greatly affect the response to selective E2 receptor modulators (SERMs). Replacement therapies may be inefficient with low ER levels. The goal of this review paper is to discuss an animal model that will allow investigations of the potential therapeutic effects of E2 and its derivatives in stroke. We hypothesize that E2 neuroprotection is, in part, receptor mediated. This hypothesis is a proof of principle approach to demonstrate a role for specific ER subtypes in E2 neuroprotection. To accomplish this, we use a retroviral mediated gene transfer strategy that express subtypes of the ER gene in regions of the rat brain most susceptible to neuronal damage, namely the striatum and cortex. The animal model is exposed to experimental stroke conditions involving middle cerebral artery occlusion (MCAo) method, and eventually the extent of neuronal damage will be evaluated. A reduction in neuronal damage is expected when E2 is administered with specific ER subtypes. From this animal model, an optimal E2 dose and treatment regimen can be determined. The animal model can help identify potential E2-like therapeutics in stroke, and screen for beneficial or toxic additives present in commercial E2 preparations that are currently available. Such studies will be informative in designing drug therapies for stroke.

Matrix metalloproteinase-3 gene polymorphisms are associated with ischemic stroke

Stroke is a heterogeneous disease caused by different pathogenic mechanisms. Several candidate genes for stroke have been proposed, but few have been replicated. Matrix metalloproteinases (MMPs) are expressed following stroke. We investigated the association of single nucleotide polymorphisms (SNPs) of the MMP3 gene with stroke in the Korean population. This study included 186 stroke patients [116 ischemic stroke (IS) and 70 intracerebral hemorrhage (ICH)] and 668 age-matched control subjects (267 for IS and 401 for ICH). Three SNPs [rs520540 (Ala362Ala), rs602128 (Asp96Asp), and rs679620 (Lys45Glu)] in the coding region of MMP3 were selected and genotyped by direct sequencing. HelixTree, SNPAnalyzer, SNPStats, and Haploview version 4.2 were used to analyze genetic data. Multiple logistic regression models (codominant, dominant, and recessive models) were conducted to evaluate odds ratio, 95% confidence interval, and P value. Three SNPs in the MMP3 gene were significantly associated with IS (P<0.05). The genotype distribution of 3 SNPs differed between the IS and control subjects. However, there was no association of the SNPs between the ICH and control. In analysis of gender, 3 SNPs were also associated with IS in female group (P<0.05). These SNPs remained significantly associated with IS after the Bonferroni correction for multiple testing (P(c)<0.05). Haplotype analysis revealed that no haplotypes were associated with IS or ICH. Overall, the results of our study demonstrate an association of the MMP3 gene with development of IS, and no association of MMP3 with ICH.

Sensitivity to cerebral ischaemic insult in a rat model of stroke is determined by a single genetic locus

Ischaemic stroke is a complex disorder caused by a combination of genetic and environmental factors. Clinical and epidemiological studies have provided strong evidence for genetic influences in the development of human stroke and several mendelian traits featuring stroke have been described. The genetic analysis of the non-mendelian, common ischaemic stroke in humans is hindered by the late onset of the disease and the mode of inheritance, which is complex, polygenic and multifactorial. An important approach to the study of such polygenic diseases is the use of appropriate animal models in which individual contributing factors can be recognized and analysed. The spontaneously hypertensive stroke-prone rat (SHRSP) is an experimental model of stroke characterized by a high frequency of spontaneous strokes as well as an increased sensitivity to experimentally induced focal cerebral ischaemia. Rubattu et al. performed a genomewide screen in an F2 cross obtained by mating SHRSP and SHR, in which latency to stroke on Japanese rat diet was used as a phenotype. This study identified three major quantitative trait loci (QTLs), STR-1-3. Of these, STR-2 and 3 conferred a protective effect against stroke in the presence of SHRSP alleles and STR-2 co-localized with the genes encoding for atrial natriuretic and brain natriuretic factors. Our investigation was designed to identify the genetic component responsible for large infarct volumes in the SHRSP in response to a focal ischaemic insult by performance of a genome scan in an F2 cross derived from the SHRSP and the normotensive reference strain, WKY rat. We identified a highly significant QTL on rat chromosome 5 with a lod score of 16.6 which accounts for 67% of the total variance, co-localizes with the genes encoding atrial and brain natriuretic factor and is blood pressure independent.