Vascular Endothelial Growth Factor and Nitric Oxide Serum Levels in Arterial Hypertension

The associations between serum VEGF, bFGF and endoglin levels with microvessel density and expression of proangiogenic factors in malignant and benign ovarian tumors

AIM OF THE STUDY

To investigate whether serum levels of VEGF, bFGF and endoglin correlate with tumor VEGF and bFGF expression or microvessel density (MVD) in ovarian cancer.

PATIENTS AND METHODS

Forty five patients with epithelial ovarian cancers (EOCs) and 38 patients with benign ovarian tumors (BOTs) were included into the study. Serum levels of VEGF, bFGF and endoglin were assessed using ELISA. The expression of VEGF and bFGF in tumor samples were evaluated using ELISA of supernatants obtained from tumor homogenization. MVD was analyzed using immunohistochemistry with antibodies against CD31, CD34 and CD105.

RESULTS

Serum VEGF levels were significantly higher in EOCs than in BOTs (436.6pg/ml [19.67-2860] vs 295.5pg/ml [123-539], P=0.025). Serum endoglin levels were lowered in the group EOCs when compared to BOTs (33,720g/ml [12,220-73,940] vs 42,390pg/ml [19,380-56,910], P=0.015). There were no differences in bFGF levels between studied groups. EOCs have significantly higher CD105 MVD (25 vessels/mm2 [0-57] vs 6 vessels/mm2 [0-70], P<0.001) and tumor VEGF (405.9pg/mg protein [0-3000] vs 2.225 [0-634.7], P<0.001) expression than BOTs, while, bFGF expression was higher in BOTs than in EOCs (2076pg/mg protein [668.1-8718] vs 847.3pg/mg protein [188.9-8333], P=0.003). In patients with EOCs we have observed negative correlation between serum VEGF concentration and its tissue expression (r Spearman=-0.571, P=0.0261), and serum VEGF concentration correlated positively with CD34-MVD (r Spearman=0.545, P=0.0289). In a multiple regression analysis we have observed only the negative correlation between serum VEGF and CD105-MVD (r=-0.5288, P=0.0427).

CONCLUSIONS

Serum VEGF is a useful marker for prediction of ovarian cancer MVD and tumor VEGF expression.

Polymorphisms in VEGFA gene affect the antihypertensive responses to enalapril

PURPOSE

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor that affects blood pressure by promoting vasodilation mediated by nitric oxide. Angiotensin-converting enzyme inhibitors (ACEi) up-regulate the VEGF expression; thus, genetic polymorphisms in the VEGFA gene could affect the antihypertensive responses to these drugs.

METHODS

Hypertensive patients (n = 102) were prospectively treated only with the ACEi enalapril for 60 days. We compared the effect of VEGFA polymorphisms on changes in blood pressure after enalapril treatment. In addition, multiple linear regression analysis was carried out to assess the effect of covariates on blood pressure. Genotypes for g.-2578C>A (rs699947), g.-1154G>A (rs1570360), and g.-634G>C (rs2010963) VEGFA polymorphisms were determined, and haplotype frequencies were estimated.

RESULTS

Individuals carrying the CA and AA genotypes for the g.-2578C>A polymorphism and the AGG haplotype showed more intense decrease in blood pressure in response to enalapril 20 mg/day. A multiple linear regression analysis showed that the AA genotype for the g.-2578C>A polymorphism and the AGG haplotype are associated with more intense decrease in blood pressure in response to enalapril 20 mg/day, while the CC genotype for the g.-2578C>A polymorphism and the CGG haplotype are associated with the opposite effect.

CONCLUSIONS

These findings suggest that polymorphisms in VEGFA gene may affect the antihypertensive responses to enalapril.

VEGF is indirectly associated with NO production and acutely increases in response to hyperglycaemia(1)

BACKGROUND

Increased levels of vascular endothelial growth factor (VEGF) have been observed in patients with metabolic syndrome (MetS). Nitric oxide (NO) formation is reduced in MetS, but its relationship to VEGF production remains poorly defined. We evaluated the association between VEGF/NO synthesis and insulin sensitivity in obese subjects and investigated the secretory response of VEGF to an acute elevation of glucose.

MATERIALS AND METHODS

Seven healthy normal-weight subjects, seven obese subjects without MetS and seven obese subjects with MetS were recruited. Anthropometry, body composition and cardiometabolic functions (blood pressure, glucose, insulin, triglycerides, total cholesterol, HDL-C and VEGF) were measured, and a novel stable isotope method was used to assess in vivo rates of NO production. A frequent sampling intravenous glucose tolerance test was performed to study the dynamics of VEGF release.

RESULTS

Fasting VEGF levels were significantly higher in the two obese groups compared to the control group (P for trend = 0·02), but the difference was not significant after adjustment for age. Vascular endothelial growth factor levels were associated with systolic blood pressure (ρ = 0·54; P = 0·01) and NO production (ρ = -0·44; P = 0·04). Vascular endothelial growth factor levels increased in response to acute hyperglycaemia in normal-weight and obese subjects (P < 0·001).

CONCLUSIONS

Vascular endothelial growth factor levels rapidly increase during hyperglycaemia and are inversely related to NO production at steady state. The potential link between the acute secretion of VEGF and atherosclerotic risk in subjects with poorly controlled glycaemia as well as the potential of lowering elevated VEGF levels by increasing NO production and/or availability warrants further investigation.

Functional VEGF haplotypes affect the susceptibility to hypertension

We examined whether vascular endothelial growth factor (VEGF) polymorphisms (C-2578A, G-1154A and G-634C) are associated with hypertension, response to antihypertensive therapy and nitric oxide (NO) formation. Substudy 1 compared the distribution of VEGF genotypes and haplotypes in 178 patients with arterial hypertension (100 whites and 78 blacks) and 186 healthy controls (115 whites and 71 blacks). Substudy 2 compared the distribution of VEGF markers in 82 patients with controlled hypertension, 89 patients with resistant hypertension and 101 normotensive (NT) patients. In substudy 3, plasma nitrite/nitrate (NOx) levels were determined (chemiluminescence assay) in 64 NT subjects and 48 hypertensive (HTN) subjects, and the distribution of VEGF markers was compared in subjects having low NOx with subjects having high NOx. Although the substudy 1 showed no differences in genotypes or allele distributions for the three VEGF polymorphisms between NT and HTN subjects, the 'C-A-G' haplotype was more common in white NT subjects than in the white HTN subjects, and the 'C-A-C' haplotype was more frequent in black and white HTN subjects than in black and white NT subjects. The substudy 2 showed similar results, with no differences between responsive and resistant HTN subjects. The substudy 3 showed that the 'C-A-G' haplotype, which had a protective effect against hypertension, was significantly more common in subjects with higher NOx concentrations than in subjects with lower NOx concentrations. VEGF haplotypes are associated with hypertension, and the haplotype associated with normotension was more common in subjects with increased NO formation, possibly offering a mechanistic clue for our findings.

Management of hypertension in angiogenesis inhibitor-treated patients

BACKGROUND

Hypertension (HTN) is one of the most frequent side-effects of systemic inhibition of vascular endothelial growth factor (VEGF) signaling. Its incidence and severity are dependent on the type of drugs, dose, and schedule used. The recognition of this side-effect is an important issue because poorly controlled HTN could lead to serious cardiovascular events. On another hand, HTN induced by anti-VEGF agents maybe a predictive factor of oncologic response. Knowledge of this clinical toxicity and/or therapeutic target or novel biomarker of drug activity can aid clinicians choosing the optimal and least toxic regimen suitable for an individual patient.

METHODS

A Medline search was carried out using the following criteria: (i) all Medline listings as of 1 January 2000 with abstracts, (ii) English language, and (iii) Humans. The following phrases were used to query the database: ('hypertension', OR 'blood pressure') AND ('anti-VEGF' OR 'VEGF inhibition' OR 'bevacizumab' OR 'sunitinib' OR 'sorafenib' OR 'VEGF Trap'). The references of each article identified were carefully reviewed for additional reference.

RESULTS

Lifestyle modification should be encouraged. However, these nonpharmacologic strategies are not always suitable to patients with altered performance status related to metastatic cancer necessitating early drug intervention. Only one randomized study showed a beneficial effect of a calcium channel blocker use to prevent or minimize HTN secondary to antiangiogenic therapy. Nitrates looks as effective in controlling such side-effect.

CONCLUSIONS

No clear recommendation for an antihypertensive agent can be made in this context because there is a lack of controlled studies addressing the subject. Blood pressure-lowering drugs should be individualized to the patient's clinical circumstances and angiogenic inhibitors should be withheld only from patients who experienced hypertensive crisis.