Ascites from cirrhotic patients induces angiogenesis through the phosphoinositide 3-kinase/Akt signaling pathway

https://doi.org/10.1016/j.jhep.2005.01.035Get rights and content

Background/Aims

Ascites in patients with cirrhosis is associated with worsening of systemic hemodynamics. Thus, the aim of this study was to investigate the biological activity of ascites on endothelial cells.

Methods

Human umbilical vein endothelial cells (HUVECs) were used to investigate the angiogenic activity of ascites obtained from cirrhotic patients.

Results

Ascites-induced Akt activation, cell migration and tube formation in HUVECs. The pretreatment of HUVECs with the phosphatidylinositide 3-kinase (PI3-kinase) inhibitor LY294002, resulted in a decrease in chemotaxis and cell tube formation induced by ascites. Moreover, the inhibition of Akt activity in HUVECs by transduction of an inactive phosphorylation Akt mutant (AA-Akt), blocked tube formation. These angiogenic effects of ascites were also operative in vivo showing a PI3-kinase activation dependence in the angiogenesis induced by ascites. In addition, the preincubation of ascites with anti-fibronectin antibody led to a significant decrease in HUVECs migration, cell tube formation and in vivo angiogenesis.

Conclusions

These results confirm the novel concept that ascites is a bioactive fluid which can modify vascular properties through the activation of the PI3-kinase/Akt pathway in endothelial cells. Furthermore, our results demonstrated that this ascites-induced mechanism is mediated, at least in part, by fibronectin.

Introduction

Patients with cirrhosis exhibit a characteristic hyperdynamic circulatory syndrome with increased cardiac output and excessive vasodilation, mainly occurring in the splanchnic circulation. Aggravation of these complications marks the progression of compensated cirrhosis into the decompensated phase of the disease characterized by derangement of body fluid homeostasis which results in accumulation of ascites into the peritoneal cavity [1]. Because of its relatively simple composition [2], ascites has generally been considered to have little influence on the hemodynamic, and host defense abnormalities occurring in cirrhotic patients. This concept, however, has recently been challenged by several investigations describing significant amounts of proinflammatory cytokines, growth factors, vasoactive agents or extracellular matrix-forming proteins in ascites of cirrhotic patients [3], [4], [5], [6]. In addition, several studies have demonstrated that the cellular component of ascites might influence the concentration of these substances [7], [8], [9]. It is of interest that many of the substances found in ascites are able to activate the PI3-kinase/Akt signaling pathway. Akt signaling regulates endothelial NO production, cell migration, and survival in physiological conditions which are all cellular responses that contribute to angiogenesis and maturation of the vascular network. The correct adaptation of the vascular system to the activation of this signaling pathway is essential to maintain normal tissue function and homeostasis in response to physiological and pathophysiological stimuli, such as an increase in growth factors and cytokine concentration [10], [11], [12], [13], [14].

In this context, little is known about the pathophysiological adaptation of the endothelium to the presence of ascitic fluid and how these modifications produce long-term structural changes in the splanchnic vasculature. Here, we considered the hypothesis that, under proper stimulus, the production of these substances in the peritoneal cavity could, theoretically, regulate angiogenesis in the splanchnic vascular bed. Therefore, we undertook the present study to investigate the changes in molecular and cellular events caused by the exposure of human endothelial cells to ascites from cirrhotic patients.

Section snippets

Patients

The investigation was performed in ascites of 13 cirrhotic patients (9 women and 4 men). The etiology of cirrhosis was alcoholic in six subjects, HBsAg or hepatitis C antibody-associated in five, both alcoholic and viral in one and cryptogenic in one case. All patients had advanced liver cirrhosis: six belonged to Child-Pugh class B and seven to Child-Pugh class C. Patients developing spontaneous bacterial peritonitis and/or hepatocellular carcinoma were excluded from the study. Ascites from

Ascites activates Erk-1/2, JNK and Akt in endothelial cells

We propose as a working hypothesis that ascites from cirrhotic patients contains bioactive factors that may stimulate distinct intracellular signaling pathway in endothelial cells. To test this hypothesis, we examined phosphorylated and total Erk-1/2 mitogen-activated protein kinase (MAPK), c-Jun N-terminal protein kinase (JNK) MAPK, and Akt upon stimulation of endothelial cells with ascites. Stimulation of BAECs with ascites-induced time-dependent activation of Erk-1/2 MAPK and JNK MAPK which

Discussion

Here we demonstrated that ascites from cirrhotic patients is a bioactive fluid that induces time-dependent activation of Erk-1/2 MAPK, JNK MAPK and Akt signaling pathways in endothelial cells. In addition, we showed that ascites presents in vitro and in vivo angiogenic properties. By contrast, PD fluid lacked angiogenic properties although after long-term peritoneal dialysis the peritoneum of patients with end-stage renal failure undergoes histological changes that include increased

Acknowledgements

The authors thank Dr Kenneth Walsh for kindly providing the AA-Akt adenoviruses as well as Dr A Arañó (from the Centro de Investigación y Desarrollo Aplicado, S.A.L.) for his assistance with the CAM assay. We also thank the staff of Granja Bellavista S.C.P. for providing fertilized 4-day-old eggs and Dr T Doñate for her assistance with peritoneal dialysis patients.

This work was supported by grants from Dirección General de Investigación Científica y Técnica (SAF2001-2585 to M.M-R; and

References (29)

Cited by (12)

  • The Thalidomide renaissance

    2010, Gastroenterologie Clinique et Biologique
  • Pathophysiology of Portal Hypertension

    2015, PanVascular Medicine, Second Edition
  • The emerging roles of microvesicles in liver diseases

    2014, Nature Reviews Gastroenterology and Hepatology
View all citing articles on Scopus
View full text