Current Neurovascular Research - Volume 5, Issue 3, 2008

Haptoglobin (Hp) 2-2 phenotype has been associated with peripheral and coronary artery disease and risk of vascular complications in diabetic patients, but any association of Hp polymorphism with cerebrovascular disease has not been explored so far. We aimed to study Hp polymorphism in a sample of 124 patients with a rather homogeneous type of cerebrovascular disease, namely first symptomatic lacunar stroke due to small vessel disease, in comparison with a large (n=918) control group. Hp phenotypes were determined using starch gel electrophoresis. Hp1 allele frequency was significantly higher in patients than in controls (0.480 vs. 0.395, p<0.05), mainly due to a lower Hp2-2 phenotype frequency (25.0 vs. 36.3 %; OR 0.59; 95%CI 0.38-0.90; p<0.05). This was even more pronounced in younger (≤60 years) patients (Hp1 allele frequency 0.539). Concomitant asymptomatic lacunar lesions were present in 82 patients, extensive white matter lesions in 47 patients. The association between Hp1 and lacunar stroke suggests that Hp may serve different functions depending on the pathological processes in various types of vascular disease in different organs. The association between Hp1 and lacunar stroke may relate to blood-brain barrier dysfunction, to the association between hypertension and cerebral small vessel disease, or a special dependence of small vessel wall integrity on Hp2-2 related angiogenic potential. The presence of concomitant signs of cerebral small vessel disease weakened the association between Hp1 and lacunar stroke, which could reflect a difference in underlying vascular pathophysiology in which Hp phenotype may play a different role.

Focus upon therapeutic strategies that intersect between pathways that govern cellular metabolism and cellular survival may offer the greatest impact for the treatment of a number of neurodegenerative and metabolic disorders, such as diabetes mellitus. In this regard, we investigated the role of a Drosophila nicotinamidase (DN) in mammalian SHSY5Y neuronal cells during oxidative stress. We demonstrate that during free radical exposure to nitric oxide generators DN neuronal expression significantly increased cell survival and blocked cellular membrane injury. Furthermore, DN neuronal expression prevented both apoptotic late DNA degradation and early phosphatidylserine exposure that may serve to modulate inflammatory cell activation in vivo. Nicotinamidase activity that limited nicotinamide cellular concentrations appeared to be necessary for DN neuroprotection, since application of progressive nicotinamide concentrations could abrogate the benefits of DN expression during oxidative stress. Pathways that involved sirtuin activation and SIRT1 were suggested to be vital, at least in part, for DN to confer protection through a series of studies. First, application of resveratrol increased cell survival during oxidative stress either alone or in conjunction with the expression of DN to a similar degree, suggesting that DN may rely upon SIRT1 activation to foster neuronal protection. Second, the overexpression of either SIRT1 or DN in neurons prevented apoptotic injury specifically in neurons expressing these proteins during oxidative stress, advancing the premise that DN and SIRT1 may employ similar pathways for neuronal protection. Third, inhibition of sirtuin activity with sirtinol was detrimental to neuronal survival during oxidative stress and prevented neuronal protection during overexpression of DN or SIRT1, further supporting that SIRT1 activity may be necessary for DN neuroprotection during oxidative stress. Implementation of further work to elucidate the cellular mechanisms that govern nicotinamidase activity in mammalian cells may offer novel avenues for the treatment of disorders tied to oxidative stress and cellular metabolic dysfunction.

Intracerebral hemorrhage (ICH) was widely believed to be a monophasic event whereby cell death occurs from the initial space-occupying effects of the hematoma. However, we now know that secondary degenerative events contribute to delayed cell death, functional impairment and clinical deterioration. In three experiments, we further characterized the long-term maturation of injury in the collagenase model of striatal ICH in rat. First, we quantified the volume of tissue lost from 7 to 60 days showing that tissue loss more than doubled over this time. As the volume of tissue lost does not distinguish gray from white matter damage, gold chloride staining was used in a second experiment in ICH rats that survived 7 or 60 days. The mid-sagittal area of the corpus callosum significantly declined (22%) over this period, whereas the hippocampal and anterior commissures were not affected. A third experiment used the Golgi-Cox stain to examine dendritic arborization of peri-hematoma and contralateral medium spiny neurons of the striatum. We found an early and sustained increase in dendritic arborization in the non-lesioned hemisphere, whereas there was initial atrophy of peri-hematoma striatal neurons that eventually recovered to normal. These findings show that tissue loss, including white matter atrophy, continues over extended periods after ICH making it a potential target for cytoprotective agents. Finally, the dendritic alterations in both ipsi- and contralateral striatal neurons likely influence spontaneous recovery and are potential targets to further improve it.

Transforming growth factor2 (TGFβ2) is a prototypic member of a large superfamily of multifunctional cytokines, and its potential mechanisms of the neuroprotective activity in ischemic stroke and subcellular compartmentalization are largely unknown. The present study investigated TGF-β2 protein expression in hippocampal neuronal cells after transient forebrain ischemia (TFI). TFI was induced in male adult gerbils with bilateral occlusion of both common carotid arteries for 10 minutes. With immunohistochemical methods we observe the expression of TGF-β2 and morphological alternation in Golgi appratus (GA) in different postischemic periods and sham-operation (6 hours, 1, 3 and 7 days). In addition, the subcellular localization of TGF-β2 is determined in trans-Golgi network (TGN) by doublelabeling confocal immunofluorographs with TGN38.The results showed that TGF-β2 persistent express in the ischemic animals and it peaks at 3 days, then decreased 7 days postocclusion. No significant alterations to the GA were noted at the point of 6 hours,1 and 3 days following TFI, but there are a few neurons in which the GA lost the normal network-like configuration and its elements decreased in cortical cells from gerbils survived 7 days postocclusion. In addition, TGF-β2 was colocalized with TGN38 in the TGN after TFI .Taken together, this result suggested that TGF-β2 protein expression increased in neurons after ischemia, which may represent an endogenous adaptative response of the brain damage and its secretion via GA after ischemia is supposed to be beneficial for GA . Furthermore, fragmentation of GA is not common phenomenon in the ischemia, but intact GA structural of neurons is beneficial for cell survival.

Monocytes adhere and transmigrate through a blood-brain barrier (BBB) during a normal immune patrol and after pathological events. It is well established that the transmigration of monocytes through the BBB is stimulated by soluble amyloidβ. The aim of the present study was to explore if aggregated amyloidβ added to the basolateral side of a BBB may modulate the adhesion and migration of primary rat monocytes through a monolayer of rat brain capillary endothelial cells (BCEC). Monocytes were freshly isolated from rat blood by negative magnetic selection and applied to the apical side of a fully confluent BCEC-monolayer with or without pre-treatment with soluble or aggregated amyloidβ. Aggregation was performed by incubation of amyloidβ(1-42) for 2 weeks in acidic medium at 37°C. The monocytes adhered at the apical side of a BCEC-monolayer within 30-90 min (approx. 1,500 cells/well), and transmigrated to the basolateral side within 18 hours (approx. 40,000 cells/well), when stimulated with 1 ng/ml monocyte chemotactic protein-1. Soluble amyloidβ(1-42) (100 ng/ml) significantly enhanced the adhesion and migration of monocytes after 90 min, which was modulated by antibodies against platelet-endothelial cell adhesion molecule-1, intracellular adhesion molecule-1, receptor for advanced glycosylation end products and low density lipoprotein-related protein-1 but not vascular cell adhesion molecule-1. Addition of aggregated amyloidβ(1-42) to the basolateral side potentiated the transmigration of monocytes. In conclusion, aggregated amyloidβ(1-42) stimulates the transmigration of monocytes through a BBB, which is of importance in Alzheimers disease.

The heme oxygenase (HO) enzymes catalyze the rate-limiting step of heme breakdown, and may accelerate oxidative injury to neurons exposed to heme or hemoglobin. HO-1 and HO-2 are activated in vitro by the phosphatidylinositol 3-kinase (PI3K)/Akt and protein kinase C (PKC)/CK2 pathways, respectively. The present study tested the hypotheses that CK2, PKC, and PI3K inhibitors would reduce both HO activity and neuronal vulnerability to hemoglobin in murine cortical cultures. Oxidative cell injury was quantified by LDH release and malondialdehyde assays. HO activity was assessed by carbon monoxide assay. Consistent with prior observations, treating primary cortical cultures with hemoglobin for 16h resulted in release of approximately half of neuronal LDH and a seven-fold increase in malondialdehyde. Both endpoints were significantly reduced by the CK2 inhibitors 4,5,6,7-tetrabromobenzotriazole (TBB) and 2-dimethyl-amino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT), and by the PKC inhibitor GF109203X; the PI3K inhibitors LY294002 and wortmannin had no effect. None of these inhibitors altered basal HO activity. The 1.9-fold activity increase observed after hemoglobin treatment was largely prevented by LY294002 and LY303511, a structural analog of LY294002 that does not inhibit PI3K activity. It was not reduced by wortmannin, TBB or GF109203X. These results suggest that the protective effect of CK2 and PKC inhibitors in this model is not dependent on reduction in HO activity. In this culture system that expresses both HO-1 and HO-2, HO activity does not appear to be primarily regulated by the PKC/CK2 or PI3K pathways.

There is significant evidence to suggest that a dysfunctional blood-brain barrier [BBB] may contribute to the pathogenesis of some Alzheimer's disease [AD] lesions. An indicator for this could be diminished capillary vascular endothelial growth factor [VEGF] and / or endothelial nitric oxide synthase [eNOS] activity in AD brains. Cortical samples were taken from the superior temporal and calcarine cortices of ten confirmed AD and ten non-demented comparison brains. Contiguous coronal sections were stained using immunohistochemistry techniques to stain for tau protein, beta- amyloid [Aβ] n-termini [40 & 42], VEGF and eNOS. Standardized regions of cortex were randomly selected. Areas of ten contiguous field-diameters of comparable and full cortical widths were observed in each section and the densities of neurofibrillary tangles [NFTs], senile plaques [SPs] and Aβ, VEGF and eNOS positive capillaries were recorded. In both AD cortices there were significant inverse correlations found between both VEGF and eNOS-positive microvessels and the presence of NFTs, and each of the amyloid isoforms in SPs and amyloid-positive capillaries [p < 0.01]. In addition there was a significant positive correlation between VEGF and eNOS densities in both cortices [p< 0.01].These results suggest that diminished VEGF and eNOS activity in particularly lesion prone regions of AD brains may contribute to the pathogenesis of NFT and / or SP lesions.

Following brain lesions, the gliovascular basal lamina undergoes destruction and the gliovascular connections ‘decouple’. Laminin receptors, as dystroglycan, are essential in these processes. The present study compares the immunoreactivities of β-dystroglycan, glial fibrillary acidic protein (GFAP), and laminin following stab wounds in adult rats. In intact brain the vessels were immunopositive to β-dystroglycan, whereas the laminin of their basal lamina proved to be unavailable to immunoreactions. Following stab wound, however, the adjacent vessels lost their immunopositvity to β-dystroglycan, whereas immunopositivity to laminin became detectable in them. In an advanced stage of glial reaction the territory of GFAP immunopositive reactive astrocytes coincided with the area where vessels lost their immunopositivity to β-dystroglycan. When glial reaction regressed, the β-dystroglycan immunopositivity re-appeared, and laminin immunopositivity became undetectable again. Post-lesional disappearance of vascular β-dystroglycan immunostaining was described earlier, and was attributed to the cleavage of β-dystroglycan by matrix metalloproteinases as a mechanism of the decoupling of the gliovascular connections. Our results, which were obtained in a different type of lesion support that the loss of vascular β-dystroglycan immunopositivity is a general phenomenon following cerebral lesions, and an indirect marker of gliovascular decoupling. For the first time coincidences were presented between vascular immunonegativity to β-dystroglycan, glial reaction and detectability of laminin. Manifestation of laminin immunoreactivity also indicates gliovascular decoupling. Coincidence between glial reaction and lack of vascular β-dystroglycan suggests mutual enhancement between them. The observations may have clinico-pathologic importance since similar investigations may help to follow the progression and regression of post-lesion processes.