Retransplantation in a patient with cystic fibrosis

A patient with cystic fibrosis is described who requested a third lung transplant. The medical and ethical issues involved are discussed.

Autosomal dominant Alport syndrome linked to the type IV collage alpha 3 and alpha 4 genes (COL4A3 and COL4A4)

Alport syndrome is a hereditary nephritis that may lead to end-stage renal disease (ESRD) in young adult life and is often associated with sensorineural deafness and/or ocular abnormalities. The majority of families are X-linked due to mutations in the COL4A5 gene at Xq22. Autosomal forms of the disease are also recognized with recessive disease, having been shown to be due to mutations in the COL4A3 and COL4A4 genes on chromosome 2. Familial benign haematuria has also been mapped to this region in some families.

Paraoxonase polymorphisms are not associated with cardiovascular risk in renal transplant recipients

Paraoxonase (PON1) gene variants have been identified as risk factors for cardiovascular disease (CVD). There are two common PON1 polymorphisms at position 55 (Leu-Met change) and 192 (Gln-Arg change) of the amino acid chain. Leucine at position 55 and arginine at position 192 have been associated with increased cardiovascular risk. The increased prevalence of CVD in renal transplant recipients can be only partly explained by the increased prevalence of conventional risk factors.

Autosomal dominant Alport syndrome caused by a COL4A3 splice site mutation

Alport syndrome (AS) is a clinically and genetically heterogeneous renal disorder, predominantly affecting the type IV collagen alpha 3/alpha 4/alpha 5 network of the glomerular basement membrane (GBM). AS can be caused by mutations in any of the three genes encoding these type IV collagen chains. The majority of AS families (85%) are X-linked (XL-AS) involving mutations in the COL4A5 gene. Mutations in the COL4A3 and COL4A4 genes cause autosomal recessive AS (AR-AS), accounting for approximately 14% of the cases. Recently, autosomal dominant AS (AD-AS) was linked to the COL4A3/COL4A4 locus in a large family.

Allele resolution of HLA-A using oligonucleotide probes in a two-stage typing strategy

High-resolution polymerase chain reaction using sequence-specific oligonucleotide probes (PCR-SSOP) typing methods for HLA-A identification have been established. The four systems, which operate independently of each other, are intended for use as secondary typing systems following HLA-A identification with a medium-resolution PCR-SSOP technique. The systems, all using digoxigenin-labelled probes, are based on group specific amplifications for resolution of: i) HLA-A*29 & -A*33; ii) HLA-A*24 & -A*30; and iii) HLA-A*26, -A*25, -A*11, -A*34, -A*66 and -A*68 alleles, respectively. The fourth system, for the detection of HLA-A*02 alleles, is a modification of a previously reported PCR-SSOP subtyping system. The methods have been applied to individuals from the local bone marrow registry and HLA-A allele frequencies for the Northern Ireland population have been established.

Regulation of erythropoietin gene expression depends on two different oxygen-sensing mechanisms

Erythropoietin (Epo), a glycoprotein hormone produced principally in the fetal kidney and in the adult liver in response to hypoxia, is the prime regulator of growth and differentiation in erythroid progenitor cells. The regulation of Epo gene expression is not fully understood, but two mechanisms have been proposed. One involves the participation of a heme protein capable of reversible oxygenation and the other depends on the intracellular concentration of reactive oxygen species (ROS), assumed to be a function of pO2. We have investigated the production of Epo in response to three stimuli, hypoxia, cobalt chloride, and the iron chelator desferrioxamine, in Hep3B cells. As expected, hypoxia caused a marked rise in Epo production. When the cells were exposed to the paired stimuli of hypoxia and cobalt no further increase was found. In contrast, chelation of iron under hypoxic conditions markedly enhanced Epo production, suggesting that the two stimuli act by separate pathways. The addition of carbon monoxide inhibited hypoxia-induced Epo production, independent of desferrioxamine concentration. Taken together these data support the concept that pO2 and ROS are sensed independently.

Erythropoietin production:evidence for multiple oxygen sensing pathways

The production of erythropoietin (Epo), the glycoprotein hormone which controls red blood cell formation, is regulated by feedback mechanisms sensing tissue oxygenation. The mechanism of the putative oxygen sensor has yet to be elucidated. There is evidence that at least two pathways participate in hypoxia signal transduction. One appears to involve a specific haem protein, and a second implicates reactive oxygen species (ROS). Iron catalyses the generation of intracellular ROS and therefore alters the cellular redox state. We have investigated the effect of modulating intracellular iron content on Epo production in Hep 3B cells. Iron chelation stimulates Epo production at 20% O2 and enhances Epo production at 1% O2, but it has no additive effect on cobalt-induced Epo production. Excess molar iron inhibited Epo production in response to hypoxia, desferrioxamine (DFO) and cobalt chloride and inhibited the DFO-enhancing effect of hypoxia-induced Epo production. We found that sulphydryl oxidising agents exert a differential inhibitory effect on hypoxia-induced versus DFO-induced Epo production, providing further evidence that multiple pathways of oxygen sensing exist.

Up-regulation of the endothelial cell adhesion molecule intercellular adhesion molecule-1 (ICAM-1) by autoantibodies in autoimmune vasculitis

Autoimmune vasculitis is characterized by the presence of autoantibodies, particularly anti-neutrophil cytoplasmic antibodies (ANCA) and anti-nuclear antibodies (ANA), in patient sera. These autoantibodies have an incompletely understood role in development of vascular injury. The expression or up-regulation of cell adhesion molecules is an early phase in the development of an inflammatory vascular lesion. Autoantibody-positive sera from patients with vasculitis were assessed for their ability to modulate adhesion molecule expression by human umbilical vein endothelial cells (HUVEC). Autoantibody-positive serum samples from 11 out of 21 patients with primary vasculitis produced substantial up-regulation of ICAM-1 on HUVEC. Autoantibody-negative samples did not produce adhesion molecule up-regulation. Up-regulation of adhesion molecules on HUVEC was observed with samples positive for ANA, a phenomenon not previously reported. Preincubation of the sera with purified antigens recognized by ANCA failed to block this activation. In addition, MoAbs to ANCA antigens were ineffective at inducing ICAM-1 up-regulation, suggesting that activation is independent of the molecular specificity of the antibody. This capacity of ANCA- and ANA-positive sera to up-regulate adhesion molecules on endothelial cells may be a factor in the vessel wall inflammation seen in ANCA-associated vasculitis.

Plasma glutathione peroxidase activity is reduced in haemodialysis patients

Cardiovascular disease is the major cause of morbidity and mortality in patients with end-stage renal failure. Increased free radical production and antioxidant depletion may contribute to the greatly increased risk of atherosclerosis in these patients. Glutathione peroxidase (GPX) is an important antioxidant, the plasma form of which is synthesized mainly in the kidney (eGPX). The aim of this study was to assess the activity of eGPX in patients with end-stage renal failure on haemodialysis. Venous blood was collected from 87 haemodialysis patients immediately prior to and after dialysis and from 70 healthy controls. Serum eGPX activity was measured using hydrogen peroxide as substrate and immunoreactivity determined by ELISA. eGPX activity was significantly reduced in dialysis patients when compared to controls (106 +/- 2.7 and 281 +/- 3.6 U/l respectively, p <0.001). Following haemodialysis, eGPX activity rose significantly to 146 +/- 3.8 U/l, p <0.001, although remaining below control values (p <0.005). Immunoreactive eGPX, however, was similar in all groups (pre-dialysis 14.10 +/- 1.26 microg/ml, post-dialysis 14.58 +/- 1.35 microg/ml, controls 15.20 +/- 1.62 microg/ml, p = NS). A decrease was observed in the specific activity of eGPX in patients when compared to controls (8.81 +/- 1.14, 10.71 +/- 1.54 and 21.97 +/- 1.68 U/mg respectively, p <0.0001). eGPX activity is impaired in patients undergoing haemodialysis and so may contribute to atherogenesis in renal failure.