AbstractContrast-induced nephropathy (CIN) is a severe complication that can sometimes affect the kidneys of patients following angiographic procedures that involve the administration of iodinated contrast medium (CM) to aid visualisation of blood vessels in medical imaging. CIN represents around 12% of all hospital acquired acute renal injury cases, the third most common cause of acute renal injury. The incidence of CIN is highest amongst patients with pre-existing renal impairment. The underlying mechanisms responsible for CIN are still poorly understood and although the condition usually manifests as temporary and reversible acute renal failure, it nevertheless is associated with an increased financial burden on healthcare systems on account of extended hospital stays and increased morbidity and mortality.
In this study, the direct effect of CM exposure on a human endothelial cell line, EA.hy926, was explored using a novel in vitro cell model developed to mimic the in vivo setting in terms of CM delivery and exposure, considering clearance of CM over time. Pre-treatment with buthionine sulfoximine (BSO), a selective inhibitor of glutathione (GSH) biosynthesis, was used to mimic the dysfunctional endothelial cell state of those at greatest risk of developing CIN. Initial results revealed that direct exposure of CM was not toxic to EA.hy926 cells. The next step was to assess the effects of CM on endothelial dysfunction and, of all the parameters explored, the powerful vasoconstrictor, endothelin-1 (ET-1), was the only marker to significantly increase following exposure to CM, but only when GSH was depleted. These results demonstrated, for the first time, a significant increase in ET-1 levels in a GSH depleted EA.hy926 cell model, exposed to CM, which set the stage for exploring the effects of CM on plasma ET-1 levels in patients with chronic kidney disease (CKD) undergoing angiography.
Plasma and buffy coat cell samples were harvested from a previously conducted clinical study. This was a comprehensive 4-part trial aiming to assess the therapeutic potential of N-acetylcysteine (NAC) as an antioxidant therapy/prophylactic to lower the impact of CM infusion on renal function. The results obtained suggested that oral NAC treatment may prevent a CM-induced ET-1 increase in patients at risk of CIN. However, NAC had no impact on estimated glomerular filtration rate (eGFR), implying that ET-1 is not likely to be associated with the observed fall in eGFR.
To conclude, the key findings of this study were that whilst CM was found to be relatively benign, subtle effects were observed, particularly on ET-1 production in GSH depleted cells. Oxidative stress was not associated with clinical exposure to CM and NAC was unable to impact plasma oxygen radical antioxidant capacity. Whilst the primary outcome of this thesis is that CM is relatively benign and that pre-existing renal insufficiency is the principal risk factor for CIN, the potential for use of prophylactic ET-1 antagonists to prevent the condition emerged, particularly for patients with low baseline ET-1.
|Date of Award||31 Oct 2022|
|Sponsors||Interreg VA - Cross Border|
|Supervisor||Ian Megson (Supervisor), Andrew Treweeke (Supervisor) & James Cobley (Supervisor)|