Vascular Endothelial Growth Factor (VEGF) isoform expression and activity in human and murine lung injury.

Andrew R L Medford,Lynne Armstrong,Kathleen M Gillespie,Terry D Tetley,Ann B Millar,Berendine Van Zyl,Kay M Uppington,Sofia I H Godinho,Samantha K Douglas,Nassif B N Ibrahim

doi:10.1186/1465-9921-10-27

Abstract

BackgroundThe properties of vascular endothelial growth factor (VEGF) as a potent vascular permogen and mitogen have led to investigation of its potential role in lung injury. Alternate spliced VEGF transcript generates several isoforms with potentially differing functions. The purpose of this study was to determine VEGF isoform expression and source in normal and ARDS subjects and investigate the expression and regulation of VEGF isoforms by human alveolar type 2 (ATII) cells.MethodsVEGF protein expression was assessed immunohistochemically in archival normal and ARDS human lung tissue. VEGF isoform mRNA expression was assessed in human and murine lung tissue. Purified ATII cells were cultured with proinflammatory cytokines prior to RNA extraction/cell supernatant sampling/proliferation assay.Measurements and Main ResultsVEGF was expressed on alveolar epithelium, vascular endothelium and alveolar macrophages in normal and ARDS human lung tissue. Increases in VEGF expression were detected in later ARDS in comparison to both normal subjects and early ARDS (p < 0.001). VEGF121, VEGF165 and VEGF189 isoform mRNA expression increased in later ARDS (p < 0.05). The ratio of soluble to cell-associated isoforms was lower in early ARDS than normal subjects and later ARDS and also in murine lung injury. ATII cells constitutionally produced VEGF165 and VEGF121 protein which was increased by LPS (p < 0.05). VEGF165 upregulated ATII cell proliferation (p < 0.001) that was inhibited by soluble VEGF receptor 1 (sflt) (p < 0.05).ConclusionThese data demonstrate that changes in VEGF isoform expression occur in ARDS which may be related to their production by and mitogenic effect on ATII cells; with potentially significant clinical consequences.

Highlights

Functional and physical failure of the alveolar capillary membrane is a pivotal event in the development of lung injury, exemplified by the acute respiratory distress syndrome (ARDS)[1]
Human vascular endothelial growth factor (VEGF) lung expression and quantification in normal, early and late ARDS Human VEGF expression was noted on alveolar epithelium and macrophages with weaker endothelial expression in all human tissue sections
We found that alveolar type epithelial (ATII) cells constitutively express mRNA for all the three main VEGF isoforms: VEGF121, VEGF165 and VEGF189 (Figure 4a)

Summary

Introduction

Functional and physical failure of the alveolar capillary membrane is a pivotal event in the development of lung injury, exemplified by the acute respiratory distress syndrome (ARDS)[1]. Observational data show plasma VEGF levels rise and intrapulmonary (ie, measurable in the epithelial lining fluid (ELF) obtained by broncho-alveolar lavage) levels fall in the early stages of lung injury with normalization of both during recovery[7,8]. These changes in intrapulmonary VEGF have been confirmed in ARDS but have been observed in other conditions in which alveolar injury may occur, such as high-altitude pulmonary oedema [9,10,11]. The purpose of this study was to determine VEGF isoform expression and source in normal and ARDS subjects and investigate the expression and regulation of VEGF isoforms by human alveolar type 2 (ATII) cells

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Results

Conclusion