Research in the Department of Nephrology


Research in the department covers both the clinical and basic science aspects of nephrology from blood pressure management in patients to isolated single cells. The main research interests of the department are:


Anaemia and erythropoiesis

 The anaemia of chronic renal failure is multifactorial in origin and accounts for a considerable amount of morbidity in patients with the disease. Treatment of anaemia has improved considerably over the last decade since the introduction of recombinant erythropoietin (EPO) which is the kidney-derived hormone responsible for red blood cell production in the bone marrow. Our research focuses on two main areas related to anaemia:

Inhibition of erythropoiesis in uraemia and inflammation
We have shown that some cytokines, particularly those produced during infection or inflammation, can affect the response to EPO in patients with chronic renal failure. Similarly, erythropoiesis is inhibited in uraemia and can be restored by blocking certain cytokines, namely interferon-gamma and tumour necrosis factor-alpha. We are using cellular and molecular approaches to elucidate the mechanism of this effect.

Cross-talk in cytokine signalling pathways
EPO binds to and induces homodimerization of its receptor (EPO-R) followed by autophosphorylation of JAK2. Activated JAK2 then phosphorylates the EPO-R on several tyrosines which act as docking sites for signalling intermediates such as STAT5 and PI-3-kinase. The relative contribution of intermediates to EPO signal transduction is still unresolved and there is considerable functional redundancy. Our current work focuses on intermediates in the JAK-STAT pathway and we are investigating the possibility of cross-talk between different signalling molecules activated by EPO and cytokines such as interferon-gamma. Additionally, we are studying the expression and role of novel genes in response to cytokines and uraemia.

The vascular endothelium and hypertension

Cardiac energetics in CRF

Renal bone disease

Reactive oxygen species and inflammation
Idiopathic membranous nephropathy (IMN) is the commonest form of glomerulonephritis (GN), which presents with the nephrotic syndrome and heavy proteinuria in adults. Approximately 40% of cases will progress to end stage renal failure over a five to ten year period. The pathogenesis of the disease is largely unknown, although it is immune mediated and there is indirect evidence to suggest the involvement of reactive oxygen species (ROS).
Our group is focusing upon the role of ROS in glomerular damage, using a variety of analytical methodologies. The novel use of Electron Spin Resonance (ESR) Spectroscopy, with the spin trap DBNBS, (dibromo nitrosobenzene sulphonate) is being applied to study long lived radical adducts in tissue cortex samples in several in vivo GN models. Other complimentary methods are also being investigated, such as isoprostane, nitrotyrosine and malondialdehyde (MDA) analysis. An analytical HPLC (high performance liquid chromatography) method, for measurement of MDA, an indicator of lipid peroxidation, has been developed and validated, with a significant improvement in specificity and HPLC column life.
We have shown that MDA levels were significantly raised in patients with CRF due to GN, regardless of serum creatinine, which suggests that there is oxidative injury independent of any possible MDA retention due to renal impairment.

Mechanisms of hyperglycaemia induced proximal tubular injury
Diabetic nephropathy (DN) is the leading cause of end-stage renal disease (ESRD) in the western world. Approximately 30-40% of patients with type I and 15% with type II diabetes mellitus develop ESRD and require dialysis. However, despite numerous studies, the pathophysiology is DN is unknown. We have demonstrated that hyperglycaemia causes a three-fold increase in the expresion of an inducible isoform of cytochrome P450 (cyp450 2E1), promotes apoptosis and stimulates the release of ROS in a porcine proximal tubular cell line (LLC-PK1). Our current studies are centered around the role of reactive oxygen species (ROS) and nitric oxide (NO) in mediating proximal tubular damage in hyperglycaemic conditions. The possibility that the inducible isoform of cyp450 is a source of ROS/NO is also under investigation.

Calpain activity in uraemia

Dr Anne Dawnay's Group

Advanced glycation end-products
The vascular complications which commonly occur with ageing are rapidly accelerated in patients with diabetes and in those with chronic renal failure and especially so in both. There is increasing evidence to suggest that the accumulation of advanced glycation end-products (AGEs) as a result of increased production (due to hyperglycaemia) or decreased clearance (due to renal failure) may play a significant role. We have been working on an alternative hypothesis for the accumulation of AGEs in renal failure (currently funded by the MRC and National Kidney Research Fund) involving excessive accumulation of oxoaldehydes such as methylglyoxal, glyoxal and 3-deoxyglucosone which are known intermediates in AGE formation and more reactive than glucose by several orders of magnitude. We have recently shown for the first time that serum glyoxal and methylglyoxal concentrations increase as renal function declines and that the activity of their detoxifying enzymes, glyoxalases I and II, and the product D-lactate also increase together with a reduction in the cofactor GSH. We have shown in in vitro studies that similar pathological concentrations of oxoaldehydes are able to generate AGEs. The reasons for the elevation of methylglyoxal and glyoxal are the subject of future work but the four-fold increase in their concentrations may contribute substantially to increased de novo AGE formation in renal failure with consequent detrimental effects on the vasculature. In parallel with our work on sources of AGEs in renal failure, we have also been working on AGE formation in patients with renal failure treated by peritoneal dialysis. Loss of function of the peritoneal membrane with increasing duration of treatment is not uncommon and histologically the membrane shows diabetiform changes. This suggested that the high concentrations of glucose in peritoneal dialysis fluids (present to osmotically remove fluid from patients) were causing excessive AGE formation in the peritoneum and impairing its function. However peritoneal dialysis fluid contains glucose degradation products (such as the oxoaldehydes glyoxal, methylglyoxal, 3-deoxyglucosone) formed during heat sterilisation in the manufacturing stage. Although present at concentrations several orders of magnitude lower than that of glucose, we were the first group to demonstrate that they made a more significant contribution to AGE formation in peritoneal dialysis fluid than glucose per se. We have also been investigating AGE formation in a novel peritoneal dialysis fluid containing glucose polymer rather than glucose with characterisation of the products by mass spectrometry.

Endogenous ouabain
The existence of an endogenous digitalis-like inhibitor of sodium potassium ATPase was first suggested many years ago. More recently it was reported that the cardenolide ouabain, previously thought to occur only in plants, was also of endogenous origin in mammals. We have developed an immunoassay for ouabain as a means of studying this controversial compound for comparison with bioactivity measurements ex vivo (using inhibition of red cell rubidium uptake) and for investigating endogenous sources. We have demonstrated ACTH stimulated ouabain release from the intact perfused rat adrenal gland and are currently purifying sufficent quantities for analysis by capillary electrophoresis.

Last updated 11 May 1999