Correction to: Deleterious Effects of VEGFR2 and RET Inhibition in a Preclinical Model of Parkinson's Disease.

The authors found a terrible mistake in the manuscript. The legends from the Fig. 5 and 6 are interchanged. The Fig. 5 should be appeared with the legend from the Fig. 6 and Fig. 6 should be appeared with the legend from the Fig. 5.

Deleterious Effects of VEGFR2 and RET Inhibition in a Preclinical Model of Parkinson's Disease.

Neurotrophic factors (NTFs) are a promising therapeutic option for Parkinson's disease (PD). They exert their function through tyrosine kinase receptors. Our goal was to assess the effects of administering a selective tyrosine kinase inhibitor (vandetanib) that blocks VEGFR2 and RET receptors in a preclinical model of PD. Rats underwent intrastriatal injections of 6-hydroxydopamine (6-OHDA). Two weeks later, the rats received 30 mg/kg vandetanib or saline orally. The effects were assessed using the rotational behavioral test, tyrosine hydroxylase (TH) immunohistochemistry, and western blot. In 6-OHDA-lesioned rats, motor symptoms were almost undetectable, but morphological and biochemical changes were significant. Vandetanib treatment, combined with the presence of 6-OHDA lesions, significantly increased behavioral impairment and morphological and biochemical changes. Therefore, after vandetanib treatment, the TH-immunopositive striatal volume, the percentage of TH+ neurons, and the extent of the axodendritic network in the substantia nigra decreased. Glial fibrillary acidic protein-positivity significantly decreased in the striatum and substantia nigra in the vandetanib-treated group. In addition, p-Akt and p-ERK 1/2 levels were significantly lower and caspase-3 expression significantly increased after vandetanib administration. In conclusion, we demonstrate for the first time the deleterious effect of a tyrosine kinase inhibitor on the dopaminergic system, supporting the beneficial and synergistic effect of NTFs reported in previous papers.

Effects of VEGF administration or neutralization on the BBB of developing rat brain.

We investigated the effects of exogenous Vascular Endothelial Growth Factor VEGF combined with an enriched environment on BBB integrity after a minimal trauma induced during the first days of the critical visual period in rats, when peak levels of endogenous VEGF secretion are reached. VEGF was administered using osmotic mini-pumps placed in middle cortical layers of P18 Long-Evansrats. Tissue changes were evaluated using conventional histology. BBB integrity was shown by immunohistochemistry techniques for EBA and GluT-1. Mini-pump implantation produced a wider cavity in anti-VEGF infused rats. In VEGF-infused rats there was a damaged region around the cannula that was smaller in rats raised in an enriched environment (EE). The administration of VEGF induced a high concentration of plasma proteins in the neuropil around the point of cannula placement and a high inflammatory reaction. VEGF-infused rats raised in an EE showed a lower degree of extravasation and better tissue preservation. Anti-VEGF administration produced a lower protein expression profile and more widespread deterioration of tissue. Double immunofluorescence for EBA and GluT-1 showed that the administration of VEGF preserves the tissue, which remains present but not fully functional. In contrast, a combination of VEGF administration and an EE partially protects the functionally damaged tissue with a higher preservation of BBB integrity.

The role of eNOS in vascular permeability in ENU-induced gliomas.

Brain edema in gliomas is an epiphenomenon related to blood-brain-barrier (BBB) breakdown in which endothelial nitric oxide synthase (eNOS) plays a key role. When induced by vascular endothelial growth factor (VEGF), eNOS synthesizes nitric oxide that increases vascular permeability. We investigated the relationship between eNOS, VEGF and BBB dysfunction in experimental gliomas.Tumors were produced in Sprague-Dawley rats by transplacentary administration of Ethylnitrosourea (ENU). Immunoexpression of eNOS and VEGF(165) was studied to identify locations of vascular permeability. BBB permeability was evaluated using gadolinium and intravital dyes and BBB integrity by endothelial barrier antigen (EBA), glucose transporter-1 (GluT-1) and occludin immunostaining. Low grade gliomas displayed constitutive eNOS expression in endothelial cells and in VEGF-positive astrocytes surrounding vessels. Malignant gliomas overexpressed eNOS in aberrant vessels and displayed numerous adjacent reactive astrocytes positive for VEGF. Huge dilated vessels inside tumors and glomeruloid vessels on the periphery of the tumor showed strong immunopositivity for eNOS and a lack of occludin and EBA staining in several vascular sections. BBB dysfunction on these aberrant vessels caused increased permeability as shown by Gadolinium contrast enhancement and intravital dye extravasation.These findings support the central role of eNOS in intra- and peritumoral edema in ENU-induced gliomas.

Microvascular adaptive changes in experimental endogenous brain gliomas.

Glioma growth depends on microvascular adaptation and angiogenesis. Our study focused on the structural changes that occur in the microvasculature to adapt to glioma growth. Vascular morphology, morphometry and permeability studies were performed in induced rat gliomas. Tumours were identified by magnetic resonance imaging and histopathology. Blood brain barrier integrity was examined by EBA and GluT-1 immunostaining and correlated with vascular permeability for gadolinium and intravital dyes. VEGF165 immunoexpression was also analyzed. Tumours were grouped in microtumours (6.69+/-0.99 mm3) displaying a homogeneous T2-w hyperintense signal corresponding to low-grade gliomas, and macrotumours (900.79+/-332.39 mm3) showing gadolinium contrast enhancement, intravital dye extravasation and histopathological features of high-grade gliomas. Results show that the microvascular network becomes aberrant as we move from micro to macrotumours. Vessel density decreases, whereas the relative area occupied by the vascular network increases. Microtumours display homogeneous angioarchitecture composed of simple and mildly dilated vessels similar to normal tissue. Macrotumours show different patterns, following a gradient from the neoangiogenic border to the hypoxic core. The tumour core contains scarce, huge, dilated vessels with some profiles co-expressing GluT-1 and VEGF165, the peripheral tissue shows light dilated vessels co-expressing EBA and GluT-1, and the border area displays glomeruloid vessels strongly positive for VEGF. Glucose uptake was maintained for some vascular endothelial sections in areas where BBB function was lost. In conclusion, during development of gliomas the microvasculature becomes aberrant, undergoing a sequence of adaptive changes which involve the distribution and permeability of vessels. This explains the disturbances of blood flow and the increased permeability.

VEGF immunopositivity related to malignancy degree, proliferative activity and angiogenesis in ENU-induced gliomas.

Growth of solid tumors is highly dependent on angiogenesis. During tumor development, neoplastic cells switch to an angiogenic phenotype, playing a significant role in the expression of the vascular endothelial growth factor (VEGF). Seventy-two brain gliomas were induced in Sprague Dawley rats by prenatal exposure to ethylnitrosourea (ENU). Screening and location of tumors was carried out using magnetic resonance imaging (MRI). Conventional histology and immunocytochemistry for antibodies against glial fibrillary acidic protein (GFAP), S-100, NF, oligodendrocyte Ab-2, Ki-67, and VEGF165 were performed. The proliferation index (PI) was calculated from the Ki-67 labeling index, and the concentration of VEGF165 was quantified by enzyme-linked immunosorbent assay (ELISA). In vivo identification of macro- and microtumor appears to be useful to lead morphological and biochemical studies. Histopathology allows us to identify microtumors as classic oligodendrogliomas (CO; mean PI of 6.01 +/- 2.8%) and macrotumors as anaplastic oligodendrogliomas (AO; mean PI of 14.06 +/- 5%). Classic oligodendrogliomas show scarce VEGF165 expression whereas anaplastic ones display VEGF165 protein level 100-fold increased respect to CO. Astrocytes, neoplastic, and endothelial cells show differential immunostaining patterns from the border to the core of neoplasm. Positive structures for VEGF and their distribution vary according to PI increase. Anaplastic gliomas displaying VEGF-positive intratumor capillaries correspond to the highest PI values. To identify the "angiogenic switch," we propose the glioma stage characterized by VEGF immunopositive neoplastic cells inside the tumor and positive endothelial cells surrounding it.

Role of VEGF in an experimental model of cortical micronecrosis.

Vascular endothelial growth factor (VEGF) is a major mediator in angiogenesis and vascular permeability. In central nervous system (CNS) it plays a pivotal role as: 1. inductor of endothelial cell proliferation, migration and inhibition of apoptosis, and 2. mediator of vascular permeability and subsequently of brain edema. This ubiquitous epiphenomenon is a major complication in several CNS pathologies, including head trauma and stroke. After brain injury the expression of VEGF is increased contributing to disruption of the blood brain barrier (BBB). VEGF increase the permeability of BBB via the synthesis/release of nitric oxide and subsequent activation of soluble guanylate cyclase. The immunohistochemistry shows an increase of stained astrocytes and endothelial cells around cortical micronecrosis. VEGF immunopositivity distribution shows some correspondence with the blood brain barrier breakdown following a cortical micronecrosis.