Journal of Cerebral Blood Flow and Metabolism

Adenoviruses have been proposed as potential vectors for gene therapy in the central nervous system, but there are no reports of their use in the treatment of a brain disease. Because central administration of interleukin-1 receptor antagonist protein (IL-1ra) reduces ischemic brain damage, we determined whether a recombinant adenovirus vector carrying the human IL-1ra cDNA (Ad.RSV IL-1ra) could be used to ameliorate brain injury in permanent focal ischemia. Groups of six rats received intraventricular injections of Ad.RSV IL-1ra or a control adenovirus containing the Escherichia coli β-galactosidase gene (Ad.RSV lacZ). Histochemical staining for β-galactosidase 5 days after virus injection indicated that transgene expression was confined primarily to the cells lining the ventricle. The concentrations of IL-1ra were fivefold to 50-fold higher in the Ad.RSV IL-1ra-injected animals, achieving levels of 9.1 ± 3.3 ng/g in brain and 23.7 ± 22.5 ng/ml in CSF. In these animals, cerebral infarct volume resulting from 24 h of permanent middle cerebral artery occlusion was reduced 64%. These studies demonstrate that adenoviral vectors can be used to deliver genes that attenuate brain injury.

Mười phút thiếu máu hoàn toàn đã được tạo ra trên 11 con chó bằng cách thắt tạm thời động mạch chủ. Ngay trước khi xảy ra thiếu máu, những con chó này đã nhận được nimodipine, một loại thuốc chẹn kênh canxi mới, với liều 10 μg kg⁻¹, tiêm tĩnh mạch, sau đó được truyền với liều 1 μg kg⁻¹ phút⁻¹ trong 2 giờ. Lưu lượng máu não và chuyển hóa sau thiếu máu được đo trong 120 phút ở sáu con chó. Khả năng phục hồi thần kinh được đánh giá sau 48 giờ thiếu máu ở năm con chó. Kết quả được so sánh với các nhóm kiểm soát đã được xác định trước đó. Nimodipine gần như làm gấp đôi lưu lượng máu não trong giai đoạn hạ huyết áp sau thiếu máu, so với những con chó không được điều trị (khoảng 45% so với 25% giá trị kiểm soát trước khi thiếu máu), nhưng không có ảnh hưởng đáng kể đến chuyển hóa. Nimodipine cũng cải thiện khả năng phục hồi thần kinh. Bốn trong số năm con chó được điều trị có tình trạng bình thường và một con bị tổn thương nhẹ, trong khi sáu trong số bảy con chó đối chứng bị tổn thương nặng hoặc đã chết. Điều này cho thấy trạng thái hạ huyết áp muộn xảy ra sau thiếu máu não hoàn toàn có thể góp phần vào tổn thương thần kinh cuối cùng, và rằng nimodipine mang lại tác dụng bảo vệ tiềm năng.

The neuroprotective effects of 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo( f)quinoxaline (NBQX), GYKI 52466, and MK-801 were tested following severe forebrain ischemia. Wistar rats were subjected to 10 min of normothermic ischemia and reperfused for 7 days. Necrotic hippocampal CA₁ neurons were counted and expressed as a percentage (mean ± SD). In Experiment 1, saline-treated rats sustained 81 ± 20% damage to dorsal CA₁. Rats given NBQX 30 mg/kg i.p. x 3 lost 21 ± 27% (p < 0.01). Neither MK-801 1 mg i.p. x 3 alone, nor in combination with the cytoprotective dose of NBQX protected CA₁, with 83 ± 18 and 54 ± 34% damage, respectively (NS). Giving NBQX 90 mg/kg i.v. did not protect cells (94 ± 5%) and resulted in nephrotoxicity. In Experiment 2, rats were given saline or three doses of NBQX 30 mg/kg i.p. immediately at reperfusion (RP) or after a 6-, 12-, or 24-h delay. Saline-treated rats suffered 79 ± 16% injury. NBQX given immediately resulted in 17 ± 17% injury, and even if treatment was delayed by either 6 or 12 h, there was marked protection with only 27 ± 32 and 25 ± 17% injury, respectively (all p < 0.01). Delaying the initiation of treatment to 24 h was not successful, resulting in 50 ± 28% injury (NS). In Experiment 3, saline-treated rats lost 81 ± 19% of CA₁ cells, while those given GYKI 52466 10 mg/kg i.p. x 5 starting immediately following RP lost 80 ± 14%. Blocking α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors with NBQX postischemia is highly efficacious, indicating that delayed degeneration of CA₁ cells is AMPA rather than N-methyl-d-aspartate (NMDA) receptor-linked and is reversible for CA₁ cells for at least 12 h.

Reactive astrocytes influence not only the severity of brain injury, but also the capacity of brain to reshape itself with learning. Mechanisms responsible for astrogliosis remain unknown but might be best studied in vitro, where improved access and visualization permit application of modern molecular and cellular techniques. We have begun to explore whether gliosis might be studied in hippocampal organotypic cultures (HOTCs), where potential cell-to-cell interactions are preserved and the advantages of an in vitro preparation are still realized. Following HOTC exposure to N-methyl-D-aspartate (NMDA), dose-dependent changes occurred in the optical density (OD) values for the astrocytic immunohistochemical [immunostaining (IS)] markers glial fibrillary acidic protein (GFAP) and vimentin. Exposure of HOTCs to NMDA (10 μ M) caused selective death in the CA₁ hippocampal region and the dentate gyrus. It also significantly increased GFAP IS and vimentin IS OD values in these regions. Increased GFAP IS and vimentin IS OD values were also seen in CA₃, a hippocampal region that displayed no cell death. Light microscopic examination revealed hypertrophied GFAP and vimentin IS cells, characteristic of reactive astrocytes. Cellular proliferation, as assessed by proliferating cell nuclear antigen IS, was also significantly increased in all three of these hippocampal regions. In contrast, exposure of HOTCs to a noninjurious level of NMDA (1 μ M) caused only minor changes in GFAP IS and vimentin IS OD values but a significantly reduced cellular proliferation in all HOTC regions. These results show that reactive astrocytosis from excitotoxic injury of HOTC parallels changes seen in vivo after global ischemia. Furthermore, since resting astroglia within HOTCs are also similar to their counterparts in vivo, HOTCs may be used to examine mechanisms by which these cells are transformed into reactive species within tissue that resembles intact brain.

Hemodynamic and cerebrovascular factors are crucially involved in secondary damage after traumatic brain injury (TBI). With magnetic resonance imaging, this study aimed to quantify regional cerebral blood flow (CBF) by arterial spin labeling and cerebral blood volume by using an intravascular contrast agent, during 14 days after lateral fluid-percussion injury (LFPI) in rats. Immunohistochemical analysis of vessel density was used to evaluate the contribution of vascular damage. Results show widespread ipsilateral and contralateral hypoperfusion, including both the cortex and the hippocampus bilaterally, as well as the ipsilateral thalamus. Hemodynamic unrest may partly be explained by an increase in blood vessel density over a period of 2 weeks in the ipsilateral hippocampus and perilesional cortex. Furthermore, three phases of perilesional alterations in CBF, progressing from hypoperfusion to normal and back to hypoperfusion within 2 weeks were shown for the first time in a rat TBI model. These three phases were similar to hemodynamic fluctuations reported in TBI patients. This makes it feasible to use LFPI in rats to study mechanisms behind hemodynamic changes and to explore novel therapeutic approaches for secondary brain damage after TBI.

Recent data suggest that repairing the cerebral vasculature after traumatic brain injury (TBI) may help to improve functional recovery. The Wnt/β-catenin signaling pathway promotes blood vessel formation during vascular development, but its role in vascular repair after TBI remains elusive. In this study, we examined how the cerebral vasculature responds to TBI and the role of Wnt/β-catenin signaling in vascular repair. We induced a moderate controlled cortical impact in adult mice and performed vessel painting to visualize the vascular alterations in the brain. Brain tissue around the injury site was assessed for β-catenin and vascular markers. A Wnt transgenic mouse line was utilized to evaluate Wnt gene expression. We report that TBI results in vascular loss followed by increases in vascular structure at seven days post injury (dpi). Immature, non-perfusing vessels were evident in the tissue around the injury site. β-catenin protein expression was significantly reduced in the injury site at 7 dpi. However, there was an increase in β-catenin expression in perilesional vessels at 1 and 7 dpi. Similarly, we found increased number of Wnt-GFP-positive vessels after TBI. Our findings suggest that Wnt/β-catenin expression contributes to the vascular repair process after TBI.

Aerobic activity has been shown highly beneficial to brain health, yet much uncertainty still surrounds the effects of exercise on the functioning of cerebral microvasculature. This study used two-photon fluorescence microscopy to examine cerebral hemodynamic alterations as well as accompanying geometric changes in the cortical microvascular network following five weeks of voluntary exercise in transgenic mice endogenously expressing tdTomato in vascular endothelial cells to allow visualization of microvessels irrespective of their perfusion levels. We found a diminished microvascular response to a hypercapnic challenge (10% FiCO₂) in running mice when compared to that in nonrunning controls despite commensurate increases in transcutaneous CO₂ tension. The flow increase to hypercapnia in runners was 70% lower than that in nonrunners (p = 0.0070) and the runners’ arteriolar red blood cell speed changed by only half the amount seen in nonrunners (p = 0.0085). No changes were seen in resting hemodynamics or in the systemic physiological parameters measured. Although a few unperfused new vessels were observed on visual inspection, running did not produce significant morphological differences in the microvascular morphometric parameters, quantified following semiautomated tracking of the microvascular networks. We propose that voluntary running led to increased cortical microvascular efficiency and desensitization to CO₂ elevation.

Cortical spreading depression (CSD) and depolarization waves are associated with dramatic failure of brain ion homeostasis, efflux of excitatory amino acids from nerve cells, increased energy metabolism and changes in cerebral blood flow (CBF). There is strong clinical and experimental evidence to suggest that CSD is involved in the mechanism of migraine, stroke, subarachnoid hemorrhage and traumatic brain injury. The implications of these findings are widespread and suggest that intrinsic brain mechanisms have the potential to worsen the outcome of cerebrovascular episodes or brain trauma. The consequences of these intrinsic mechanisms are intimately linked to the composition of the brain extracellular microenvironment and to the level of brain perfusion and in consequence brain energy supply. This paper summarizes the evidence provided by novel invasive techniques, which implicates CSD as a pathophysiological mechanism for this group of acute neurological disorders. The findings have implications for monitoring and treatment of patients with acute brain disorders in the intensive care unit. Drawing on the large body of experimental findings from animal studies of CSD obtained during decades we suggest treatment strategies, which may be used to prevent or attenuate secondary neuronal damage in acutely injured human brain cortex caused by depolarization waves.

The local cerebral metabolic rate for glucose was determined in 26 regions of the brain in 31 healthy subjects who underwent resting fluorodeoxyglucose positron emission tomography. Intercorrelations among the 26 regional measures were accepted as reliable at p < 0.01 (r > 0.45), uncorrected for the number of measures. From the matrix two apparently separate functional metabolic systems were identified: (1) a superior system involving the superior and middle frontal gyri, the inferior parietal lobule, and the occipital cortex; and (2) an inferior system involving the inferior frontal, Broca's, and posterior temporal regions. Evidence is presented to suggest that the superior system is involved in visual processing, memory recognition, and decision making, while the inferior system seems to at least participate in language-related functions.

Local CMRGlc values were determined for 13 regions in each hemisphere from tomographs of patients with Alzheimer's, Huntington's, and Parkinson's diseases who were studied using [¹⁸F]fluorodeoxyglucose with positron emission computed tomography. Intercorrelations among the 26 regional measures were calculated for each disease state and for normal controls, and were accepted as reliable at p < 0.01, uncorrected for the number of comparisons. The number of reliable correlations was found to be decreased in Parkinson's and Huntington's diseases, two primarily subcortical disorders, and increased in Alzheimer's disease, a primarily cortical disorder. The changes suggest that one role of the basal ganglia involves coordinating or pacing the ability of cortical brain regions to function as a unit.