Altered Expression of Angiotensinogen and Mediators of Angiogenesis in Ileal Crohn’s Disease
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Georgia E. Hume1,2, James D. Doecke3, Ning Huang1, Elizabeth V. Fowler1, Ian S. Brown4, Lisa A. Simms1, Graham L. Radford-Smith1,2
1) QIMR Berghofer Medical Research Institute and University of Queensland School of Medicine, Herston Campus, Brisbane,
2) Department of Gastroenterology, Royal Brisbane ,nd Women’s Hospital, Brisbane,
3) Health National Research Flagship, CSIRO Mathematics, Information and Statistics, RBWH Herston,
4) Envoi Pathology, Herston, Brisbane, Queensland, Australia
Background & Aims: Angiotensin II (AII) is a powerful splanchnic vasoconstrictor with pro-inflammatory and pro-fibrotic properties. Angiotensin converting enzyme (ACE) inhibitors and AII Receptor Antagonists (ARBs) are therapeutic in animal models of colitis. The aim of this case-control study is to determine the expression of angiotensinogen and related genes in human ileal Crohn’s disease.
Methods: Using quantitative real-time polymerase chain reaction (RT-PCR), we measured mRNA expression levels of angiotensinogen (AGT), hypoxia inducible factor (HIF)1α and melanoma cell adhesion molecule (MCAM; CD146) in 101 human samples (69 biopsy, 12 resection) from affected ileum (inflamed CD cases, n=36) and unaffected ileum (non-inflamed CD cases, n=45 and controls, n=20). Immunohistochemistry for angiotensinogen was also performed. The study was of case-control design in a tertiary care setting.
Results: Ileal expression of AGT was lower in CD cases compared to controls (p<0.0001), in inflamed CD samples (p=0.017) and current smokers (p=0.02). HIF1α expression was lower in non-inflamed CD biopsy samples than controls (p=0.006). The presence of disease-associated NOD2 variants was associated with increased expression of markers of angiogenesis (HIF1α p=0.009; MCAM p=0.007) in inflamed CD samples. Angiotensinogen immunohistochemical staining supported the quantitative RT-PCR expression findings.
Conclusions: Angiotensinogen expression is down regulated in human ileal CD, particularly in the presence of inflammation and current cigarette smoking, implicating the mesenteric vasculature and mucosal hypoxia as co-factors in ileal CD pathogenesis. A novel reduction in HIF1α expression in non-inflamed ileal mucosa in CD patients was also demonstrated.
Key words: Crohn’s disease – renin-angiotensin-aldosterone-system – angiogenesis – angiotensinogen.
Abbrevations: AI: angiotensin I; AII: angiotensin II; ACE: Angiotensin Converting Enzyme; AGT: angiotensinogen; ARB: Angiotensin II receptor Antagonists; AT1: Angiotensin type 1; AT2: Angiotensin type 2: AT-6: Angiotensinogen-6; ATG16L1: Autophagy-related 16-like 1; CD: Crohn’s disease; CTGF: Connective Tissue Growth Factor; ECM: Extracellular matrix; HIF-1: Hypoxia inducible factor-1; IBD: Inflammatory Bowel Disease; IBDU: Inflammatory Bowel Disease, type unclassified; MCAM: Melanoma Cell Adhesion Molecule; mRNA: Messenger RNA; NOD: Nucleotide-binding oligomerisation domain; NF-κB: Nuclear Factor-κB; NSAIDs: Non-Steroidal Anti-Inflammatory Drugs; PCR: Polymerase Chain Reaction; RAAS: Renin-angiotensin-aldosterone system; RT-PCR: Real Time Polymerase Chain Reaction; SNP: Single Nucleotide Polymorphism; TGF-β: Transforming Growth Factor-β; TNBS: Trinitrobenzene sulfonic acid; TNF: Tumour Necrosis Factor; UC: Ulcerative colitis; UPR: Unfolded protein response; VEGF: Vascular Endothelial Growth Factor.