VEGF receptor antagonist Cyclo-VEGI reduces inflammatory reactivity and vascular leakiness and is neuroprotective against acute excitotoxic striatal insult

Vascular endothelial growth factor associated dissimilar cerebrovascular phenotypes in two different mouse models of Alzheimer's Disease

Vascular perturbations and cerebral hypometabolism are emerging as important components of Alzheimer's disease (AD). While various in vivo imaging modalities have been designed to detect changes of cerebral perfusion and metabolism in AD patients and animal models, study results were often heterogenous with respect to imaging techniques and animal models. We therefore evaluated cerebral perfusion and glucose metabolism of two popular transgenic AD mouse strains, TgCRND8 and 5xFAD, at 7 and 12 months-of-age under identical conditions and analyzed possible molecular mechanisms underlying heterogeneous cerebrovascular phenotypes. Results revealed disparate findings in these two strains, displaying important aspects of AD progression. TgCRND8 mice showed significantly decreased cerebral blood flow and glucose metabolism with unchanged cerebral blood volume (CBV) at 12 months-of-age whereas 5xFAD mice showed unaltered glucose metabolism with significant increase in CBV at 12 months-of-age and a biphasic pattern of early hypoperfusion followed by a rebound to normal cerebral blood flow in late disease. Finally, immunoblotting assays suggested that VEGF dependent vascular tone change may restore normoperfusion and increase CBV in 5xFAD.

String Vessel Formation is Increased in the Brain of Parkinson Disease

BACKGROUND

String vessels are collapsed basement membrane without endothelium and have no function in circulation. String vessel formation contributes to vascular degeneration in Alzheimer disease. By comparing to age-matched control cases we have recently reported endothelial degeneration in brain capillaries of human Parkinson disease (PD).

OBJECTIVE

Current study evaluated changes of basement membrane of capillaries, string vessel formation and their association with astrocytes, blood-brain-barrier integrity and neuronal degeneration in PD.

METHODS

Brain tissue from human cases of PD and age-matched controls was used. Immunohistochemical staining for collagen IV, GFAP, NeuN, tyrosine hydroxylase, fibrinogen and Factor VIII was evaluated by image analysis in the substantia nigra, caudate nucleus and middle frontal gyrus.

RESULTS

While the basement-membrane-associated vessel density was similar between the two groups, the density of string vessels was significantly increased in the PD cases, particularly in the substantia nigra. Neuronal degeneration was found in all brain regions. Astrocytes and fibrinogen were increased in the caudate nuclei of PD cases compared with control cases.

CONCLUSIONS

Endothelial degeneration and preservation of basement membrane result in an increase of string vessel formation in PD. The data may suggest a possible role for cerebral hypoperfusion in the neuronal degeneration characteristic of PD, which needs further investigation. Elevated astrocytosis in the caudate nucleus of PD cases could be associated with disruption of the blood-brain barrier in this brain region.

The role of vascular endothelial growth factor and vascular endothelial growth inhibitor in clinical outcome of traumatic brain injury

OBJECTIVES

Tumor necrosis factor superfamily-15 (TNFSF15) also known as vascular endothelial growth inhibitor (VEGI) is a cytokine that modulates anti-angiogenesis and inflammation. Vascular endothelial growth factor (VEGF) promotes angiogenesis and vascular permeability following traumatic brain injury (TBI). The balance of VEGF and VEGI may play a key role in the maintenance of vascular and immune system homeostasis in the brain. However, the dynamic changes of circulating VEGF and VEGI after traumatic brain injury (TBI) and the correlation between plasma VEGF and plasma VEGI remains obscure. In this study, we were to investigate whether circulating VEGF and VEGI can be used as prognostic markers for patients with TBI.

PATIENTS AND METHODS

A prospective clinical study was conducted in two neurosurgical intensive care units of Tianjin Medical University General Hospital and Tianjin Huanhu Hospital (Tianjin, China). 40 patients and 30 healthy controls were recruited. The recruited subjects were aged over 18 with randomized gender and GCS. 1mL of blood was withdrawn on 1, 4, 7, 14, and 21days after TBI. Blood samples were centrifuged at 3000rpm and the supernatants were used to measure VEGF and VEGI by ELISA kit.

RESULTS

1) Circulating VEGF in TBI patients was decreased on the 1st day after TBI, then climbed up on the 4th day, reaching a maximum level on the14th day after TBI, as compared to normal controls. VEGF level returned to normal level on 21th day after TBI. 2) Circulating VEGI in TBI patients was decreased on the 1st and 4th day after TBI, then climbed up on the 7th day after TBI, reaching a maximum level on 14th day after TBI, as compared to normal controls. VEGI levels declined to normal level on 21th day after TBI. 3) There was a significant positive correlation between circulating VEGF and VEGI. 4) However, TBI patients whose conditions had improved exhibited lower VEGF levels 7days after TBI when compared to TBI patients whose condition had deteriorated. Survivors exhibited higher VEGI levels 7days after TBI when compared to non-survivors. 5)TBI patients whose condition had improved exhibited higher VEGI levels when compared to TBI patients whose condition had deteriorated 21days after TBI. Patients with mild TBI exhibited higher VEGI levels than those with moderate and severe TBI 21days after TBI. 6) A lower rate of recovery and higher hospital mortality were found in patients with VEGF/VEGI ratio≥2.366 as compared to those with VEGF/VEGI ratio<2.366 7days after TBI.

CONCLUSIONS

1) VEGF level positively correlates with VEGI after TBI. 2) The elevation of VEGF exhibits an adverse effect from 4 to 14days after TBI while it has an advantageous effect from 14 to 21days after TBI. Increasing VEGI levels are beneficial in recovery after TBI. Controlling the ratio of VEGF/VEGI may benefit the clinical outcome following TBI.

Age-Dependent Resistance to Excitotoxicity in Htt CAG140 Mice and the Effect of Strain Background

Mouse strain background can influence vulnerability to excitotoxic neuronal cell death and potentially modulate phenotypes in transgenic mouse models of human disease. Evidence supports a contribution of excitotoxicity to the selective death of medium spiny neurons in Huntington's disease (HD). Here, we assess whether strain differences in excitotoxic vulnerability influence striatal cell death in a knock-in mouse model of HD. Previous studies that evaluated resistance to excitotoxic lesions in several mouse models of HD had variable outcomes. In the present study, we directly compare one model on two different background strains to test the contribution of strain to excitotoxicity-mediated neurodegeneration. Mice of the FVB/N strain, which are highly vulnerable to excitotoxicity, become extremely resistant to quinolinic acid-induced striatal neurodegeneration with age, when carrying a huntingtin (Htt) allele expressing a HD transgene (CAG140). The resistance is much greater than the age-dependent resistance that has been previously reported in YAC128 mice. By 12 months of age, both heterozygous and homozygous FVB.CAG140 mice displayed virtually complete resistance to quinolinic acid-induced striatal neurodegeneration. A similar resistance develops in CAG140 mice on a C57BL/6N background although the effect size is smaller because C57BL/6N mice are already resistant due to genetic background. In a direct comparison with the YAC128 mice, FVB.CAG140 mice have greater resistance. FVB.CAG140 mice are also resistant to neurodegeneration following kainic acid-induced status epilepticus suggesting the existence of a common cellular mechanism that provides protection against multiple types of excitotoxic insult. These findings establish FVB.CAG140 mice as a useful model to investigate the cellular and molecular mechanisms that confer neuroprotection against excitotoxicity.

VEGI attenuates the inflammatory injury and disruption of blood-brain barrier partly by suppressing the TLR4/NF-κB signaling pathway in experimental traumatic brain injury

Acute traumatic brain injury (TBI) tends to cause the over-activation of inflammatory response and disruption of blood brain barrier (BBB), associating with long-term cognitive and behavioral dysfunction. Vascular endothelial growth inhibitor (VEGI), as a suppressor in the angiogenesis specifically by inducing apoptosis in proliferating endothelial cells, has been applied to different diseases, especially the tumors. But rare study had been done in the field of brain injury. So in this study, we investigated the effects and mechanisms associated with VEGI-induced neuroprotection following CNS injury in mice TBI models. We demonstrated that the VEGI treatment reduced the contusion brain tissue loss, the permeation of inflammatory cells (MPO(+)) and the activation of microglia (Iba-1(+)). The treatment up-regulated the tight junction proteins (CLN5, ZO-1 and OCLN), which are vital importance for the integrity of the blood brain barrier (BBB), the B-cell lymphoma 2 (Bcl-2) cell survival factors, while down-regulated the expression of TLR4, NF-κB and inflammatory cytokines (IL-1β, TNF-α, iNOS). The treatment also decreased the expression of reactive astrocytes (GFAP(+)), as well as the VEGF, and lowered the permeability of Evens Blue (EB). These findings suggested that the VEGI-treatment could alleviate the post-traumatic excessive inflammatory response, and maintain the stability of blood vessels, remitting the secondary brain damage.

Spermine improves recognition memory deficit in a rodent model of Huntington's disease

Huntington's disease (HD) is a progressive neurodegenerative disorder associated with motor and cognitive impairment. Intrastriatal administration of quinolinic acid (QA) causes neurodegeneration, glial proliferation and cognitive impairment in animals, which are similar to these seen in human HD. Since polyamines improve memory in cognitive tasks, we now tested if the post-training intrastriatal administration of spermine, an agonist of the polyamine site at the NMDA receptor, reverses the deficits in the object recognition task induced by QA. Bilateral striatal injections of QA (180 or 360 nmol/site) caused object recognition impairment, neuronal death and reactive astrogliosis. A single injection of spermine (0.1 and 1 nmol/site), 5 days after QA injection, reversed QA-induced impairment of object recognition task. Spermine (0.1 nmol/site) also inhibited QA-induced reactive astrogliosis measured by a semi-quantitative determination of GFAP immunolabelling, but did not alter neuronal death, measured by a semi-quantitative determination of fluoro-Jade C staining. These results suggest that polyamine binding sites may be considered a novel therapeutic target to prevent reactive astrogliosis and mnemonic deficits in HD.

Thalidomide inhibition of vascular remodeling and inflammatory reactivity in the quinolinic acid-injected rat striatum

Effects of thalidomide administration on vascular remodeling, gliosis and neuronal viability have been studied in excitotoxin-injected rat striatum. Intrastriatal injection of quinolinic acid (QUIN) caused time-dependent changes (durations of 6 h, 1 and 7 d post-injection) in vascular remodeling. QUIN excitotoxic insult was associated with increased numbers of vessels (laminin or collagen IV markers) demonstrating considerable abnormalities in morphology, including short fragments and vascular loops. Non-lesioned striatum, with injection of phosphate buffer solution (PBS) as a vehicle, showed no evidence for vascular remodeling. A maximal extent of vascular remodeling was measured at 1 d post-QUIN and was correlated with marked increases in microgliosis (ED1 marker) and astrogliosis (glial fibrillary acidic protein [GFAP] marker) relative to control PBS injection. Double staining of laminin with ED1 and GFAP demonstrated areas of close association of glial cells with blood vessels. Treatment of QUIN-injected animals with the anti-inflammatory compound, thalidomide significantly inhibited vascular remodeling (by 43%) and reduced microgliosis (by 33%) but was ineffective in modifying extents of astrogliosis. Intrastriatal QUIN injection was associated with a marked loss of striatal neurons relative to non-lesioned control with thalidomide treatment exhibiting a significant degree of neuroprotection (24% recovery) against QUIN-induced neurotoxicity. These results suggest close links between microglial-mediated inflammatory responses and vascular remodeling, with inflammatory reactivity associated with, and contributing to, neuronal damage in excitotoxically-lesioned striatum.