Tonsillar IgA1 as a possible source of hypoglycosylated IgA1 in the serum of IgA nephropathy patients.

BACKGROUND: There are many reports of incompletely glycosylated O-linked oligosaccharides on the IgA1 hinge region in certain IgA nephropathy patients. In addition, other reports have noted a relationship between tonsillectomy and IgA nephropathy. METHODS: Immunoglobulins from extracts of tonsillectomized tissue and other sources were analysed by isoelectric focusing (IEF) and by enzyme-linked immunosorbent assay (ELISA). RESULTS: The IEF profile of tonsillar IgA differed from that of serum IgA and it was enriched in cationic IgA. However, extracts from tonsillitis controls and IgA nephropathy patients exhibited profiles that were very similar. Enzymatic removal of sialic acid induced a shift of the peaks to the cathode side. The profiles of IgA from treated tonsillar extract and treated serum were closely overlapped. In addition, asialo Galbeta1,3GalNAc was clearly present in cationic IgA from tonsillar extract and in aberrant IgA1 from serum following enzymatic transfer of sialic acid to IgA1. Serum IgA also contained partly sialylated IgA1. Quantitative analysis of IgA and IgG in the extracts indicated that IgA was significantly higher, whereas IgG was significantly lower in IgA nephropathy patients. CONCLUSIONS: We found that the IgA1 produced in tonsillar tissue differed from serum IgA1. Furthermore, an overproduction of asialo IgA1 resulted from the disordered balance between IgA- and IgG-producing cells in the tonsils from the IgA nephropathy patient. Although it is unclear how such asialo IgA1 molecules are transferred from tonsil tissue to serum, a tonsillar source may produce a few micrograms of aberrant IgA1 that then appears in serum.     

FcgammaRIIa-131R allele and FcgammaRIIIa-176V/V genotype are risk factors for progression of IgA nephropathy.

BACKGROUND: Fcgamma receptors (FcgammaRs) may play an important role in positive and negative regulation of immune cell responses and immune complex (IC) clearance. Mesangial IgG deposition and circulating IgG/IgA-IC in sera are observed in patients with IgA nephropathy (IgAN). Therefore, the pathological roles of IgG-IC in IgAN have been discussed. On the other hand, several studies have identified FcgammaR polymorphisms (FcgammaRIIa, FcgammaRIIIa and FcgammaRIIIb) that determine susceptibility to autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. The objective of the present study was to clarify whether FcgammaR polymorphisms influence susceptibility to IgAN, clinical features or severity in patients with IgAN. METHODS: Japanese patients with IgAN (n = 124) and healthy controls (n = 100) were genotyped for FcgammaR polymorphisms (FcgammaRIIa-131H or R, FcgammaRIIIa-176F or V and FcgammaRIIIb-NA1 or -NA2). The genotyping of these polymorphisms was performed using allele-specific polymerase chain reaction (PCR) methods. Associations among FcgammaR polymorphisms and susceptibility, age of onset, levels of serum immunoglobulins, intensity of glomerular IgG deposition and pathological severity were analysed. RESULTS: These three FcgammaR polymorphisms showed no significant differences in genotype and allele frequencies between the IgAN patients and healthy controls. Each FcgammaR polymorphism had no influence on age of onset, serum levels of IgG and glomerular IgG deposition in IgAN. However, FcgammaRIIa-131R (R/R or H/R) or FcgammaRIIIa-176V homozygous carriers (V/V) showed significantly more severe injury than FcgammaRIIa-131H homozygous (H/H) (P < 0.03) or FcgammaRIIIa-176F carriers (F/F or F/V) (P < 0.03), respectively. CONCLUSION: The present study shows that polymorphisms of FcgammaRIIa and FcgammaRIIIa influence the severity of IgAN in Japanese patients but not the incidence, suggesting that IgG-IC may play important roles in the progression and prognosis of this disease via FcgammaRs.     

Cytoskeletal protein expression and regenerative markers in schistosomal nephropathy.

BACKGROUND: Progression of renal diseases is related to the abnormal regulation of cellular and extracellular matrix turnover. Other factors in addition to schistosomal antigens may be relevant to the progression of schistosomal nephropathy (SN). The validity of markers of fibroblastic differentiation, alpha smooth muscle actin (alphaSMA), and vimentin, as well as the regenerative activity (PCNA/apoptosis index) in determination of progression of SN in comparison to other forms of non-schistosomal nephropathy (non-SN) is investigated. METHODS: Three groups were included; group I pure SN (n=16), group II a diverse group of non-schistosomal patients with comparable pathologic changes on renal biopsy (n=40) and a control group (n=5). Immunohistochemical staining of myofibroblasts (alphaSMA and vimentin) and proliferating cells (PCNA) and histomorphometric analysis was done. In situ end labelling (ISEL) of DNA was used to evaluate apoptosis. RESULTS: No differences in the patterns of distribution of positivity of the different studied markers were observed between the different nephropathy groups. Both alphaSMA and vimentin were detected in glomerular mesangial, tubular epithelial, interstitial inflammatory fibroblast-like cells and occasionally endothelial cells. PCNA and apoptotic cells were detected in tubular epithelial and interstitial cells with paucity of positive cells in the glomerulus. Significant positive correlations were detected in group I between glomerular sclerosis and interstitial markers including interstitial alphaSMA (r=0.609, P=0.001), interstitial vimentin (r=0.812, P=0.00) and interstitial apoptosis (r=0.733, P=0.001). On the other hand, glomerulosclerosis in group II showed significant positive correlations with predominantly the glomerular markers; glomerular alphaSMA (r=0.475, P=0.002), glomerular apoptosis (r=0.684, P=0.00) and glomerular PCNA (r=0.691, P=0.00). Interstitial fibrosis correlated significantly with interstitial markers in group I including interstitial alphaSMA (r=0.837, P=0.00) interstitial vimentin (r=0.929, P=0.00), interstitial apoptosis (r=0.807, P=0.00) and interstitial PCNA (r=0.617, P=0.01), while in group II it correlated with both interstitial and glomerular markers. In addition, the tubulo-interstitial ratio was significantly higher in group I in comparison with group II (P=0.024), with no difference between groups II and III. CONCLUSIONS: Although SN may start as glomerulopathy associated with increased mesangial cellularity, the interstitial rather than the glomerular markers of myofibroblastic differentiation and those of cell turnover are playing a crucial role in late stages of schistosomal, but not in non-schistosomal nephropathies.     

Podocyte injury induced by mesangial-derived cytokines in IgA nephropathy

Background. We have previously documented that human mesangialcell (HMC)-derived tumour necrosis factor- (TNF-) is an importantmediator involved in the glomerulo-tubular communication inthe development of interstitial damage in IgA nephropathy (IgAN).With the strategic position of podocytes, we further examinedthe function of podocytes in IgAN. Methods. Podocyte markers were examined in renal tissues byimmunofluorescence. In vitro experiments were conducted withpodocytes cultured with polymeric IgA (pIgA) or conditionedmedium prepared from HMC incubated with pIgA (IgA–HMCconditioned medium). Results. Glomerular immunostaining for nephrin or ezrin wassignificantly weaker in patients with IgAN. The immunostainingof IgA and nephrin was distinctly separate with no co-localization.In vitro experiments revealed no effect of pIgA on the expressionof these podocyte proteins as IgA from IgAN patients did notbind to podocytes. In contrast, IgA conditioned medium preparedfrom IgAN patients down-regulated the expression of these podocyteproteins as well as other podocyte markers (podocin and synaptopodin)in cultured podocytes. The mRNA expression of nephrin, erzin,podocin but not synaptopodin correlated with the degree of proteinuriaand creatinine clearance. The down-regulation was reproduciblein podocytes cultured with TNF- or transforming growth factor-β(TGF-β) at concentration comparable to that in the IgA–HMCconditioned medium. The expression of these podocyte proteinswas restored partially with a neutralizing antibody againstTNF- or TGF-β and fully with combination of both antibodies. Conclusion. Our finding suggests podocyte markers are reducedin IgAN. An in vitro study implicates that humoral factors (predominantlyTNF- and TGF-β) released from mesangial cells are likelyto alter the glomerular permeability in the event of proteinuriaand tubulointerstitial injury in IgAN.     

Alphav integrin regulates TNF-alpha-induced nitric oxide synthesis in rat mesangial cells--possible role of osteopontin.

BACKGROUND: Tumour necrosis factor-alpha (TNF-alpha) induces nitric oxide (NO) synthesis in rat mesangial cells (MCs). We previously demonstrated that osteopontin (OP), a matrix protein that mainly interacts with the alphav integrin family, increased time-dependently by TNF-alpha stimulation at gene and protein levels. The regulation of NO synthesis by integrins or matrix proteins is unclear. METHODS: We examined whether integrin, especially alphav integrin, regulates NO synthesis in rat MCs and whether OP, an alphav integrin ligand, has an effect on TNF-alpha-induced NO synthesis. Furthermore, OP and inducible NO synthase (iNOS) gene expression was examined by Northern blotting. RESULTS: TNF-alpha increased NO synthesis in MCs in a time-dependent manner. Synthetic GRGDSP peptide, which is known to inhibit various integrins that interact with RGD-containing extracellular matrices, increased TNF-alpha-induced NO levels in a dose-dependent manner. Cyclical RGD peptide, the specific inhibitor of alphav integrin, also exhibited a dose-dependent effect of increasing NO levels, while GRGESP peptide, which has very low affinity to integrins, had no effect. In addition, NO synthesis was found to be significantly reduced when MCs were plated on OP-coated dishes compared to type I or IV collagen-coated dishes. Furthermore, anti-OP antibody increased NO synthesis in MCs. iNOS mRNA levels were increased by TNF-alpha, and were abruptly diminished after OP mRNA was significantly induced. CONCLUSIONS: The present study demonstrated the involvement of alphav integrin in TNF-alpha-induced NO synthesis in rat MCs, and the possible role of OP was suggested in the mechanism. TNF-alpha and extracellular matrices can co-operate to regulate the behaviour of MCs at least partly through NO synthesis, which may participate in the course of glomerular diseases.     

Hypoxia reduces the expression and anti-inflammatory effects of peroxisome proliferator-activated receptor-gamma in human proximal renal tubular cells.

BACKGROUND: Peroxisome proliferator-activated receptor (PPAR)-gamma may counteract tissue fibrosis via its anti-inflammatory actions, while hypoxia, a new pro-fibrotic factor, reportedly modifies PPAR-gamma expression. However, the effects of hypoxia on the expression and anti-inflammatory actions of PPAR-gamma have yet remained to be clarified in renal tubular cells. METHODS: Confluent human proximal renal tubular epithelial cells (HPTECs) were exposed to hypoxia (1% O2) and/or TNF-alpha at 10 ng/ml for up to 48 h. The cells were incubated with PPAR-gamma agonists, 15d-PGJ2 or pioglitazone, for 30 min before stimulation. Precise amounts of PPAR-gamma and MCP-1 mRNA and protein were measured by TaqMan quantitative PCR and immunoblot or ELISA, respectively. RESULTS: A cDNA array analysis identified PPAR-gamma as one of the hypoxia-affected genes in HPTECs. Hypoxia reduced mRNA levels of PPAR-gamma at 24 and 48 h and protein levels at 6 and 48 h. Knockout of hypoxia-inducible factor-1alpha (HIF-1alpha) with its dominant negative form did not block the hypoxia-induced reduction in PPAR-gamma expression. PPAR-gamma's activation with 15d-PGJ2 or pioglitazone reduced basal and TNF-alpha-stimulated MCP-1 expression at mRNA and protein levels at 24 h under normoxia. MCP-1 reduction rates at basal mRNA and protein levels were slightly but significantly lower during hypoxia than normoxia (9 vs 69% and 36 vs 42%, respectively, for 15d-PGJ2, and 0 vs 34% and 12 vs 21%, respectively, for pioglitazone). Finally, a specific inhibitor for PPAR-gamma, GW9662, weakened the MCP-1-decreasing effect of 15d-PGJ2 by about 30%, under basal conditions, while it abolished the effect of pioglitazone almost completely. CONCLUSIONS: Hypoxia-induced loss of function of PPAR-gamma reduces anti-inflammatory effects of PPAR-gamma activation, possibly modulating inflammatory responses in the diseased kidney.     

Rosiglitazone ameliorates cisplatin-induced renal injury in mice.

BACKGROUND: Inflammatory mechanisms may play an important role in the pathogenesis of cisplatin nephrotoxicity. Agonists of the peroxisome proliferator-activated receptor-gamma (PPARgamma), such as rosiglitazone, have been recently demonstrated to regulate inflammation by modulating the production of inflammatory mediators and adhesion molecules. The purpose of this study was to examine the protective effects of rosiglitazone on cisplatin nephrotoxicity and to explore the mechanism of its renoprotection. METHODS: Mice were treated with cisplatin with or without pre-treatment with rosiglitazone. Renal functions, histological findings, aquaporin 2 (AQP2) and adhesion molecule expression, macrophage infiltration and tumour necrosis factor-alpha (TNF-alpha) levels were investigated. The effect of rosiglitazone on nuclear factor (NF)-kappaB activity and on viability was examined using cultured human kidney (HK-2) cells. RESULTS: Rosiglitazone significantly decreased both the damage to renal function and histological pathology after cisplatin injection. Pre-treatment with rosiglitazone reduced the systemic levels of TNF-alpha and down-regulated adhesion molecule expression in addition to the infiltration of inflammatory cells after cisplatin administration. Rosiglitazone restored the decreased AQP2 expression after cisplatin treatment. Pre-treatment with rosiglitazone blocked the phosphorylation of the p65 subunit of NF-kappaB in cultured HK-2 cells. Rosiglitazone had a protective effect via a PPARgamma-dependent pathway in cisplatin-treated HK-2 cells. CONCLUSION: These results showed that pre-treatment with rosiglitazone attenuates cisplatin-induced renal damage through the suppression of TNF-alpha overproduction and NF-kappaB activation.     

Role of alpha-adducin DNA polymorphisms in the genetic predisposition to diabetic nephropathy.

BACKGROUND: There is substantial evidence for genetic susceptibility to diabetic nephropathy. In particular, genes that predispose to hypertension in the general population may confer susceptibility to nephropathy in patients with diabetes. A Gly460Trp variant in the alpha-adducin gene has been associated with essential hypertension. Our aim was to screen the alpha-adducin gene for polymorphisms and to determine if any variants predisposed patients with diabetes to nephropathy. A secondary objective was to assess for association between the Gly460Trp variant and hypertension. METHODS: The exons of the alpha-adducin gene were resequenced in 30 individuals. Selected variants were then genotyped in 155 patients with type 1 diabetes and nephropathy (cases) and 216 persons with type 1 diabetes but no evidence of nephropathy (controls) from Northern Ireland and in 95 cases and 118 controls from the Irish Republic. RESULTS: Eleven polymorphisms were detected, of which six were novel and three caused amino-acid substitutions. The Gly460Trp and a novel Ser617Cys polymorphism were in strong linkage disequilibrium (D' = 0.98). Neither the genotype nor allele frequencies for the Gly460Trp polymorphism (P = 0.89 and 0.93 respectively) or the Ser617Cys polymorphism (P = 0.46 and 0.76) were significantly different between cases and controls when the Northern Ireland and Irish Republic sample groups were combined. Carriage of the 460Trp allele was not significantly associated with systolic or diastolic blood pressure in either the cases (P = 0.48 and 0.06, respectively) or in the controls (P = 0.50 and 0.94, respectively). CONCLUSIONS: Variation in the alpha-adducin gene does not play a major role in the development of nephropathy in persons with type 1 diabetes in the Irish population. Furthermore, the Gly460Trp variant was not associated with hypertension in this population.     

Polymorphisms of the tumour necrosis factor alpha gene at position -308 and TNFd microsatellite in primary IgA nephropathy.

BACKGROUND: The development of glomerular inflammation in immunoglobulin A nephropathy (IgAN) has been associated with various cytokines, including tumour necrosis factor alpha (TNFalpha). A biallelic polymorphism in the promoter region of the TNFalpha gene (TNFA), at position -308, has been described (TNFA-1 and TNFA-2) and is associated with increased TNFalpha production for the TNFA-2 allele. Another microsatellite polymorphism has been described for TNFd, which is functional and associated with increased production of TNFalpha for the d3 allele. METHODS: We have studied these two polymorphisms in 242 Caucasian patients with biopsy-proven IgAN (169 male, 73 female), who were followed from 1990 to 1999, and in 210 appropriate local Caucasian controls (133 male, 77 female) for comparison of genotypes and allelic distribution. RESULTS: The respective frequencies of A1/A1, A1/A2 and A2/A2 TNFA genotypes were 76.4, 22.3 and 1.3% in IgAN vs 78.1, 19.5 and 2.4% in controls (P=NS). For TNFd, the frequencies of the respective genotypes d3/d3, d3/non-d3 and non-d3/non-d3 were significantly different (chi(2)=12.30, P=0.002, Pc=0.013) with an increased frequency of the low-producer genotype non-d3/non-d3 in IgAN patients (24 vs 12%). The combination of TNFA and TNFd polymorphisms demonstrated that compared with controls, patients with non-A2 and non-d3 alleles (low producers) were more common (18 vs 9%; P=0.006). In the genotype/clinical phenotype correlations, we could not demonstrate significant differences between the different subgroups of patients. However, high-producer TNFalpha patients (A2 and d3 alleles) had more chronic renal failure than others (36.6 vs 22.9%) at last follow-up and their survival without chronic renal failure (Kaplan-Meier) was lower. Nevertheless, TNFalpha polymorphisms were not an independent risk factor for the progression of the disease. CONCLUSIONS: TNFA and TNFd polymorphisms seem to influence the occurrence or initiation of the disease, but do not play a significant role, if any, in the progression of IgA nephritis.     

Increased levels of alpha-defensin (-1, -2 and -3) in type 1 diabetic patients with nephropathy.

OBJECTIVE: Diabetic nephropathy is associated with low-grade inflammation and activation of the complement system. Defensins, as part of the innate immune system, may play a regulatory role in the complement cascade and may also augment the production of proinflammatory cytokines. The aim of this study was therefore to elucidate whether alpha-defensin is associated with diabetic nephropathy, low-grade inflammation and lipid profiles. RESEARCH DESIGN AND METHODS: Data were obtained from 189 patients with type 1 diabetes selected from the FinnDiane Study. Patients were divided into three groups according to their albumin excretion rate (AER) in three consecutive overnight or 24-h urine collections: normoalbuminuria (AER <20 microg/min or <30 mg/24 h), microalbuminuria (20 200 microg/min or >300 mg/24 h). Alpha-defensin was determined by a novel, solid-phase radioimmunoassay (RIA) based on a monoclonal antibody, which recognizes alpha-defensin isoforms 1-3. RESULTS: Total serum alpha-defensin (-1, -2 and -3) concentrations were higher (P < 0.001) in patients with macroalbuminuria compared to micro- and normoalbuminuria, but no difference was observed between normoalbuminuria and microalbuminuria. In multiple linear regression analysis alpha-defensin was associated with systolic blood pressure (P = 0.032), HDL-cholesterol (P = 0.013), total cholesterol (P = 0.008), age (P = 0.001) and estimated glomerular filtration rate (P = 0.001), but not with low-grade inflammatory markers. CONCLUSIONS; Serum alpha-defensin (-1, -2 and -3) concentrations are increased in type 1 diabetic patients with diabetic nephropathy.     

Association between tumour necrosis factor-alpha G-308A polymorphism and risk of nephropathy in obese Chinese type 2 diabetic patients.

BACKGROUND: The G-308A polymorphism in the promoter region of the tumor necrosis factor alpha (TNF-alpha) gene has been reported to be associated with insulin resistance and obesity, both of which may increase the risk of diabetic nephropathy. We hypothesized that this polymorphism might interact with obesity to affect development of diabetic nephropathy. METHODS: A consecutive cohort of 1281 Chinese type 2 diabetic patients was enrolled for analysis. Genotyping of TNF-alpha G-308A polymorphism was performed using a PCR-based RFLP method with NcoI digestion. The mean value of the albumin creatinine ratio (ACR) of a random spot urine sample and a timed urinary collection was used to determine albuminuric status. Diabetic nephropathy was defined as serum creatinine > or =150 micromol/L and/or mean ACR > or =25 mg/mmol. Obesity was defined as body mass index > or =25 kg/m2 using Asian criteria. RESULTS: The G-308A polymorphism was not associated with either obesity or nephropathy. Clinical characteristics were similar between GG and GA/AA genotype carriers. Amongst the obese patients, GG genotype carriers had a higher median (interquartile range) urinary ACR [3.16 (0.70, 59.10) vs 1.28 (0.48, 12.28) mg/mmol; p = 0.01] and albumin excretion rate [38.7 (12.1, 620.3) vs 21.4 (8.9, 224.0) microg/min, p = 0.03] than GA/AA carriers. On multiple logistic regression analysis, compared with non-obese GA/AA carriers, obese subjects with the GG genotype had a 2.5-fold increased risk (95% CI: 1.04-6.03; P = 0.04) of nephropathy after adjustment for confounding factors. Other independent factors for diabetic nephropathy included male sex, systolic blood pressure, triglycerides (logarithmically transformed value), and the presence of cardiovascular and microvascular complications. CONCLUSION: Our findings suggest that the GG genotype of TNF-alpha G-308A polymorphism or a genetic variant in close linkage disequilibrium may interact with obesity to increase the risk of nephropathy in Chinese Type 2 diabetic patients. Apart from the need for replication of these results, functional studies are required to clarify its significance.     

Polymeric IgA increases the synthesis of macrophage migration inhibitory factor by human mesangial cells in IgA nephropathy.

BACKGROUND: It has been suggested that polymeric IgA (pIgA) or IgA immune complexes play a significant pathogenic role in IgA nephropathy (IgAN). Macrophage migration inhibitory factor (MIF) shares many activities with other pro-inflammatory cytokines. In human glomerulonephritis, including IgAN, glomerular expression of MIF is found to correlate with progressive renal injury. We hypothesized that deposition of pIgA within the kidney may lead to enhanced synthesis of MIF by mesangial cells. METHODS: In this study we examined the effect of pIgA and monomeric IgA (mIgA) from randomly selected patients with IgAN in clinical quiescence on the gene expression and protein synthesis of MIF in cultured human mesangial cells (HMC). RESULTS: Both pIgA and mIgA from IgAN patients or matched healthy controls increased MIF gene expression and protein synthesis in a dose-dependent fashion. The magnitude of MIF protein induction by pIgA (100 microg/ml) was similar to that of tumour necrosis factor-alpha (TNF-alpha) at 10 pg/ml. In all subjects, the induction of MIF was higher for pIgA when compared with mIgA (P < 0.01). Furthermore, the up-regulation of MIF synthesis by either pIgA or mIgA was significantly higher in IgAN patients than in healthy controls (P < 0.05). Similarly, pIgA and mIgA were able to induce TNF-alpha gene expression and protein synthesis in mesangial cells. Incubation of mesangial cells with neutralizing antibody to TNF-alpha reduced the MIF synthesis induced by pIgA. CONCLUSION: We demonstrate that pIgA is capable of inducing MIF and TNF-alpha production in HMC, which may play a major pathogenic role in IgAN. Induction of MIF can be partially blocked by neutralizing antibody to TNF-alpha, suggesting the possibility that up-regulation of MIF synthesis in HMC is mediated via an amplifying proinflammatory loop involving TNF-alpha.     

T gamma/delta lymphocytes in renal transplant recipients.

T gamma/delta lymphocytes are able to perform allospecific cytotoxicity and natural killer cytotoxicity in vitro. However, very little is known about their function in vivo. To investigate the possible involvement of T gamma/delta lymphocytes in the immune response to renal allografts, fine-needle aspiration biopsies and peripheral blood of 15 renal transplant recipients were studied during the first 4 weeks after transplantation. In addition peripheral blood of patients before transplantation, half a year and one year after transplantation was studied. No increase in the percentage of T gamma/delta lymphocytes in the fine-needle aspiration biopsies, including those taken during acute rejection episodes, was found. A significant decrease in the percentage of T gamma/delta lymphocytes was observed in peripheral blood after transplantation. We conclude that T gamma/delta lymphocytes seem to play no major role in the immune response to renal allografts.     

Plasma concentrations of alpha-melanocyte-stimulating hormone are elevated in patients on chronic haemodialysis.

BACKGROUND: Clinical and/or laboratory signs of systemic inflammation occur frequently in patients undergoing long-term haemodialysis. It is likely, therefore, that a compensatory release of endogenous anti-inflammatory molecules occurs to limit host reactions. The aim of the present research was to determine if the potent anti-inflammatory peptide alpha-melanocyte-stimulating hormone (alpha-MSH), a pro-opiomelanocortin derivative, is increased in plasma of haemodialysis patients. Because endotoxin and cytokines induce alpha-MSH in vivo and in vitro, we also measured plasma concentrations of endotoxin, interleukin-6 (IL-6), and tumour necrosis factor alpha (TNF-alpha), and the two circulating products of activated monocytes, nitric oxide (NO) and neopterin. METHODS: Thirty-five chronic haemodialysis patients, 20 patients with chronic renal failure not yet on dialysis, and 35 normal controls were included in the study. In the haemodialysis group, blood samples were obtained before and at the end of a dialysis session. Plasma alpha-MSH was measured using a double antibody radioimmunoassay, and IL-6, TNF-alpha, and neopterin using specific enzyme-linked immunosorbent assays. Plasma nitrites were determined by a colorimetric method, and endotoxin with the quantitative chromogenic LAL (limulus amoebocyte lysate) method. RESULTS: Mean plasma alpha-MSH was higher in haemodialysis patients than in control subjects, with the peptide concentrations being particularly elevated in dialysed patients with detectable endotoxin. High alpha-MSH concentrations were observed in the pre-dialysis samples, with no substantial change at the end of the dialysis session. Plasma concentrations of IL-6, TNF-alpha, neopterin, and NO were generally elevated in chronic haemodialysis patients and there was a negative correlation between circulating alpha-MSH and IL-6. In patients with renal failure not yet on dialysis, mean plasma alpha-MSH was similar to that of normal subjects. CONCLUSIONS: alpha-MSH is increased in the circulation of chronic haemodialysis patients and particularly so in case of detectable endotoxaemia. Reduction of renal clearance is unlikely to contribute to the observed rise of the peptide because alpha-MSH concentration is not increased in patients with chronic renal failure who are not yet on dialysis. It is likely that dialysis-associated endotoxaemia, directly and/or through cytokine release, enhances the production of the anti-inflammatory mediator alpha-MSH that limits host reactions.