The Different Impact of VEGF-A and VEGF-D on Peritumoral Brain Edema

The study consisted of VEGF-A and VEGF-D levels analysis in the blood samples in patients with brain tumors. VEGF is a family of angiogenic factors. This study evaluated the association between VEGF-A and VEGF-D levels and the extent of peritumoral brain edema. The study group was divided into patients with moderate and severe edema based on the Stenih off scale and its modification for posterior foss a tumors. It was found that plasma VEGF-A level in patients with severe brain edema was significantly higher (Me = 25.42 pg/ml) than in patients with moderate brain edema (Me = 29.18 pg / ml) - U Mann-Whitney test, p = 0.0258. It was also found that VEGF-D plasma level in patients with severe brain edema was significantly lower (Me = 95.25 pg / ml) than in patients with moderate brain edema (Me = 183.57 pg / ml) - Mann-Whitney test, p = 0.0034. It was also found that the plasma concentration of VEGF-D in patients with better functional status was significantly higher (Me = 185.47pg / ml) than the concentration in patients with worse functional status (Me = 111.34pg / ml) - U Mann-Whitney test, p = 0.0428. The above results proved that VEGF-A and VEGF-D present omni directional association with peritumoral brain edema in patients with intracranial tumors. VEGF-A promotes the formation of peritumoral edema, while the relationship between VEGF-D and brain edema seems to be the opposite of VEGF-A.


Introduction
Vascular endothelial growth factor (VEGF) plays important role in tumor development and patophysiology [1]. It is main angiogenic factor and promotes new blood vessels formation and also causes the permeability of blood vessels and inconsequence edema [1,2]. In the literature it is also referred to as vascular permeability factor (VPF). Often in references it is named VEGF / VPF [1]. VEGF interacts via VEGFR1, VEGFR2, and VEGF3 receptors.
These are receptors with tyrosine kinase activity. VEGF belongs to the platelet-derived growth factors family [2]. The most important form is VEGF-A and has main biological activity in angiogenesis and vascular permeability [1,2]. The importance of VEGF-A in promoting brain edema in tumors has been reported by many authors [3]. VEGF-A causes blood-brain barrier (BBB) permeability and passage of fluid from blood vessels to brain tissue [3]. The main receptor responsible for VEGR-A activity is VEGFR2. The VEGF family also includes VEGF-B, VEGF-C, VEGF-D and Placenta Growth Factor (PIGF), other forms such as VEGF-E and VEGF-D in animal models and their role is not known [4]. In past decades, attention has been gained to the biological significance of VEGF-D as an equally important biologically important factor [5]. VEGF-D effects on the cell via the VEGFR3 receptor. VEGFR3 does not react with VEGF-A and this may indicate the different biological activity of VEGF-D and VEGF-A [4,5]. The exact biological significance of VEGF-D is still under investigation by many authors [4]. VEGF-A and VEGF-D are significantly described in the literature for the

Material and Methods
In order to conduct the research, the approval of the Bioethics   (Table 1).

Statistical Analysis
The statistical analysis was carried out using Stat Soft®

Results
It was found that plasma VEGF-A level in patients with severe brain edema was significantly higher (Me = 25.42 pg/ml) than in patients with moderate brain edema (Me = 29.18 pg / ml) -U Mann-Whitney test, p = 0.0258. It was also found that VEGF-D plasma level in patients with severe brain edema was significantly lower (Me = 95.25 pg / ml) than in patients with moderate brain edema (Me = 183.57 pg / ml) -Mann-Whitney test, p = 0.0034.
The results of VEGF-A and VEGF-D plasma levels associated with brain edema are both presented in (Table 2). (Figure 1) presents VEGF-A plasma level associated with brain edema and ( Figure   2). Presents this association regarding VEGF-D. It was also found that the plasma concentration of VEGF-D in patients with better functional status was significantly higher (Me = 185.47pg / ml) than the concentration in patients with worse functional status (Me = 111.34pg / ml) -U Mann-Whitney test, p = 0.0428. These results are presented in (Table 3) and (Figure 3).

Discussion
The effect of VEGF on brain edema formation is described in many references in the literature. VEFG-A, as the most common form of VEGF, has the best known mechanism of impact on brain edema and its clinical implications [1][2][3][4][5][6]. Gerstner el. [7] emphasizes that the most brain tumors over secrete VEGF-A [7]. Elevated level of VEGF-Aleads to anabnormally permeable tumor vasculature and allows fluid to leak from the intravascular space into the brain tissue [7]. It causes vaso geniccerebraledema and increased interstitial fluid pressure. According to Gerstner et al. Cerebraled emacause significant morbidity and mortality and isassociated with neurological condition [7]. Gerstner also emphasizes that VEGF-A is potential target in brain edema treatment because agents that block the VEGF-A path way are able to decrease vascular permeability by restoring the abnormal tumor vasculature to a morenormal state [7]. It coincides with the results of our study, where high levels of VEGF-A were associated with severe brain edema around the tumor. Wang et al. [8] based rat model emphasizes that VEGFis the major regulator of micro vascular permeability [8]. Acoording to Wang et al. BBB permeability was significantly increased following Volume 28-Issue 3 treatment with VEGF. It has also been well documented that VEGF expression is increased in various type of cells, including neurons, endo the lial cells, astrocytes, pial cells in rats [8].
VEGF-induced permeability depends on the VEGFR2-mediated endo the lialnitricoxidesynthase (eNOS) pathway by down regulating the expression of tight junction proteins [1][2][3][4]8]. In addition, the tight junction between endothelial cells is the key element in BBB permeability, and disruption of tight junctions leads to BBB breakdown on rat model [8]. Liu et al. [9] describes that VEGF has been implicated in the pathogenesis of brain edema formation after experimental subarachnoid hemorrhage (SAH) [9]. His study suggests that VEGF is involved in brain edema formation after SAH, and that anti-VEGF antibody an decrease BBB permeability, suppress brain edema formation, and improve functional outcome after 24 h of SAH [9]. In our study no association was found between VEGF-A and the patients clinical state of patients, also our study VEGF impact on peritumoral brain edema in cancer patients was described while Liu studied VEGF-A in brain edema after SAH. However, regarding association between VEGF and brain edema, our results are the same as Liu et al. [9] Carlson et al. [10], similarly to our study, examined VEGF-A in brain edema in tumor cases. Similarly to other authors Gerstner et al. [7][8][9] and like our study Carlson proved that VEGF-Ais a potent mediator of vascular permeability [10]. According to Carlson et al.

VEGF inhibition reduces edema and tumor burden in some patients
with malignantglioma, where as others show no response. The role of VEGF expression in edema production and the relationship to survivalis not well understood [10].
Carlson postulated that there are both VEGF-dependent and VEGF-independent pathways of edema production in gliomas and may explain whye demais not reduced in some patients following anti-VEGF treatment [10]. Although most references refer to the role of VEGF-A in brain edema and the literature data is consistent that VEGF increases brain edema by increasing vascular permeability [6][7][8][9][10], there are also reports on the role of VEGF-D in brain edema and vascular permeability. Our study showed that higher VEGF-D plasma levels were associated with less brain edema and better functional status. Schluter et al. [11] showed on mice model that in vivo VEGF-D supplementation via preserved the structural and functional integrity of retinal ganglion cells agains texcito toxicity and, additionally spared endothelial cells from degeneration [11]. Viral-mediated suppression of expression of the VEGF-D-binding receptor VEGFR3 in retinal ganglion cells revealed that VEGF-D exerts its protective capacity directly on retinal ganglion cells, while protection of endothelial cells is the result of upheld neuronalintegrity [11]. These findings suggest that VEGF-D supplementation might be a novel, clinically applicable approach for neuronal and vascular protection [11]. However, the study by potentially explain that such effect is due to increased protection and vascular integrity [11], moreover, Schluter shows that VEGF-D has a positive effect on neuronal integrity [11].
In our work, it has been shown that a higher concentration of VEGF-D is associated with a better clinical and functional state.
Von Moos [12] obtained different results in the subject of VEGF-D in vessel permeability. In her work, she examined VEGF-D levels in fluid overloaded patients treated by hemo dialysis. Fluid over load was defined by bio impedance analysis [12]. He study proved that fluid overload correlated positively with VEGF-D levels [12]. Von Moos also showed that VEGF-D is a potential over hydration and prognostic marker. People with high VEGF-D levels were in worse clinical condition and the prognosis was worse [12]. The results of von Moos are different from the results of our work.

Conclusion
VEGF-A and VEGF-D present omni directional association with peritumoral brain edema in patients with intracranial tumors.

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