Vascular Endothelial Growth Factor (VEGF-a) in Fabry disease: Association with cutaneous and systemic manifestations with vascular involvement

Abstract

Introduction

Fabry disease is an X-linked inherited metabolic disorder characterized by the deficiency of lysosomal α-galactosidase A enzyme. This leads to the accumulation, into lysosomes through the body, of glycosphingolipids, mainly Gb3. Skin involvement and progressive multi-organ failure are usually observed. Endothelium is the preferential target of the Gb3 storage that determines endothelial dysfunction and vasculopathy leading to the clinical manifestations of the disease. The serum levels of Vascular Endothelial Growth Factor-A (VEGF-A), a specific endothelial cell mitogen, were analyzed in Fabry patients to explore a possible association to the clinical manifestations with vascular involvement.

Methods

Thirty-five patients with a biochemical and genetic diagnosis of Fabry disease, along with an age–gender-matched healthy control group, were enrolled. Serum samples were collected and analyzed by ELISA. The genetic mutations, the specific organ dysfunction, and the cardiovascular risk factors such as dyslipidaemia, diabetes, smoking habits and hypertension were evaluated in Fabry patients.

Results

The mean serum level of VEGF-A in Fabry patients group was significantly higher than in the control group (P = 0.006). A statistical significant association, between VEGF-A levels and the skin manifestation including angiokeratomas, sweating abnormalities and Fabry Facies was found. An association was also found between high VEGF-A and specific GLA mutations, the male gender, the renal and neurological manifestations, the presence of eye vessels tortuosity, smoking habit and hypertension.

Conclusions

We detected increased VEGF-A levels in patients with Fabry disease compared to the controls, and we hypothesized that this could be a response to the vascular damage characterising this lysosomal disorder. However, further studies are necessary to clarify the role of VEGF-A in Fabry.

Introduction

Fabry disease (OMIM 301500, FD) is a rare X-linked lysosomal storage disorder (LSD) due to the insufficient activity of the α-galactosidase A (α-Gal A) enzyme [1]. Up to now, 665 mutations of the GLA gene have been identified [2], including point mutation (missense and nonsense), splicing mutations and gross mutations (deletions and insertions) [3]. The absent or reduced activity of α-Gal A enzyme leads to the accumulation of neutral glycosphingolipids, mainly globotryaosilceramide (Gb3), into lysosomes throughout the body [4]. Endothelial cells and smooth vascular muscle cells are the preferential target of this process [5]. The FD clinical manifestations are in part the result of the vascular damage induced by lipid storages, and they include skin signs and progressive multi-organ failure [6]. Angiokeratomas (AGK), the hallmark of the disease, are present in 66% of male and 36% of female Fabry patients [7] on the genitals, lumbosacral area, gluteal cleft and trunk around umbilicus on the lips, periungual areas and palms in both sexes. Other skin manifestations include teleangectasias, sweating abnormalities (hypohidrosis and less frequently hyperidrosis) and facial dysmorphia. The typical Fabry facies is characterized by recessed forehead, prominent supraorbital ridges, widened nasal bridge, bulbous nasal tip, full lips and coarse features with prognathism [8]. Systemic manifestations start early in life with gastrointestinal disturbances, acral pain in hands and feet and fever, cornea verticillata and conjunctival and retinal vessels tortuosity [9]. In adulthood, morbidity is mainly due to cardiovascular, renal and central nervous system involvement, specifically left ventricular hypertrophy, proteinuria (gradually progressing to end stage renal failure) and early strokes [10], [11]. Female patients usually show less severe clinical manifestations, due to random inactivation of X chromosome, but a significant proportion of women are as severely affected as males, and need to be treated [12]. Average life expectancy, previously reduced to 50–55 years in males and 70 years in females, has been increased thanks to regular infusions recombinant α-Galactosidase (rα-Gal A), the enzyme replacement therapy (ERT) [13], available since 2001. This is currently the primary treatment for Fabry patients since it has shown to significantly reduce glycosphingolipids storages in the endothelial cells in the skin and in several visceral organs therefore halting and even reverting the progression of the disease [14], [15], [16]. However, some patients, do not seem to respond to the treatment [17], [18]. Although multiple factors have been advocated, recent studies suggest that the deregulation of key mediators of endothelial function and altered endothelial pathways caused by intracellular Gb3 accumulation, may play a pivotal role [19], [20].

New therapeutic approaches are very high desirable and experimental trials are currently investigating the efficacy of an orally administered small chaperone molecule, 1-deoxygalactonojirimycin (DGJ or AT1001, GR181413A, migalastat hydrochloride, Amicus Therapeutics Inc., Cranbury, New Jersey, USA), for Fabry patients carrying alfa-galactosidase gene missense mutation leading to α-Gal A conformational defects. The DGJ is able to improve via binding and stabilization, the endogenous activity of natural α-Gal A in patients with responsive mutation and of rα-Gal A given by infusion [21], [22].

Vascular Endothelial Growth Factor A (VEGF-A) is a specific endothelial cells mitogen and the most important pro-angiogenic factor [23]. It is mainly expressed by endothelial cells, keratinocytes, podocytes, smooth vascular muscle cells, microglia, and osteoblasts. VEGF-A promotes endothelial cell proliferation and differentiation and it increases vascular permeability mediating endothelium-dependent vasodilation. Previous studies have showed high serum levels of VEGF-A in patients with different kidney [24], heart [25], cerebral [26] and skin angiogenesis and cutaneous disorders [27]. Aim of this study is to analyse the VEGF-A serum levels with the correlation to the cutaneous and the specific organ manifestation with vascular involvement in Fabry patients, in order to clarify the pathogenesis and vasculopaty of this lysosomal storage disorder.