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Regulation of C5aR expression and function: potential modulation by lipid-lowering drugs

Palmer, Elizabeth 2011. Regulation of C5aR expression and function: potential modulation by lipid-lowering drugs. PhD Thesis, Cardiff University.

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The pro-inflammatory anaphylatoxin C5a exerts its biological actions via the C5a receptor (C5aR), a G-protein-coupled-receptor (GPCR). Cholesterol, a crucial component of biological membranes, has previously been shown to regulate expression and function of numerous GPCRs. As statin therapy is widely used to reduce serum cholesterol levels, it was hypothesised that statins can exert anti-inflammatory effects by down regulation expression and/or function of the C5aR. This thesis first investigated how basal human C5aR expression was regulated. It was shown that the majority of the -2Kbp promoter region is dispensable for transcription of the C5aR and that the main regulatory domains are localised in the first 200 bp of the promoter region. Furthermore CCAAT and NFAT motifs are important for the transcriptional control of the human C5aR, however the transcription factors which bind to these sites could not be identified. A model system to measure C5aR expression and function was set up using two pro-monocytic U937 sub-cell lines, which demonstrated that dibutyryl-cyclic-AMP was the best inducer of the C5aR, but only in one of the cell lines. Induction of the C5aR made these cells more responsive to C5a induced intracellular calcium-release and IL-8 and MMP-9 secretion. Investigating possible effects of cholesterol and modulation of cholesterol on C5aR expression and function showed that statins did not affect expression and function of basal levels of C5aR in monocytes or U937 cells, but reduced induced C5aR expression. Concomitantly C5a induced release of intracellular calcium and secretion of IL-8 reduced, however C5a induced MMP-9 secretion increased. This reduction was due to inhibition of isoprenoid biosynthesis rather than inhibition of cholesterol biosynthesis. Using sucrose gradient floatation it was shown that the C5aR is unlikely to reside in a lipid raft region of the plasma membrane making it less likely to be susceptible to membrane cholesterol content.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Pharmacy
Subjects: R Medicine > RM Therapeutics. Pharmacology
ISBN: 9781303222733
Date of First Compliant Deposit: 30 March 2016
Last Modified: 01 Dec 2014 16:01

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