Effects of dialyzer membrane on interleukin-1beta (IL-1beta) and IL-1beta-converting enzyme in mononuclear cells.
BACKGROUND
In vitro stimulation of mononuclear cells (peripheral blood mononuclear cells; PBMCs) with an endotoxin (lipopolysaccharide; LPS) revealed elevated cell-associated levels of interleukin-1beta (IL-1beta) in end-stage renal disease (ESRD) patients on Cuprophan hemodialysis (HD), suggesting a defect in the process of IL-1beta's release from activated cells. IL-1beta is initially synthesized as an inactive precursor called proIL-1beta. ProIL-1beta is processed into the biologically active mature form of IL-1beta (mIL-1beta) requiring the specific IL-1beta-converting enzyme (ICE).


METHODS
Using specific immunoassays (enzyme-linked immunosorbent assays), we measured cell-associated and extracellular proIL-1beta as well as mIL-1beta in LPS-stimulated PBMCs to test whether ICE-dependent processing of proIL-1beta and/or secretion of mIL-1beta was impaired in ESRD patients compared with healthy controls. PBMCs of healthy controls (N = 9), of ESRD patients on peritoneal dialysis (PD, N = 10), and of those patients on intermittent HD (N = 8) were studied. The same HD patients were studied three times with low-flux Cuprophan (GFS 12), low-flux polysulfon (F6 HPS), and high-flux polysulfon (F60S) in randomized order. PBMCs were separated from whole blood by Ficoll-Hypaque centrifugation and incubated in vitro for 18 hours in the presence LPS (10 ng/mL). Extracellular (PBMC culture supernatants) and cell-associated (cell lysates) levels of proIL-1beta and mIL-1beta were measured.


RESULTS
The total production (cell-associated plus extracellular) of LPS-induced IL-1beta (proIL-1beta plus mIL-1beta) was similar in healthy controls (25.96 +/- 0.84 ng/2.5 x 10(6) PBMC), PD patients (29.53 +/- 1.31 ng/2.5 x 106 PBMC), and in Cuprophan-treated HD patients (23.28 +/- 1.24 ng/2.5 x 10(6) PBMC). In normal controls, 43.6% of the total IL-1beta was processed into mIL-1beta, which was significantly more than that in PD patients (27.3%, P < 0.02) but was similar to that in Cuprophan-treated HD patients (37.1%). Comparing cell-associated and extracellular concentrations of mIL-1beta, PBMCs of normal controls secreted 82.2% of mIL-1beta; this was significantly more than that in PD patients (59.4%, P < 0.01) and that in Cuprophan HD patients (54.2%, P < 0.01). When HD patients were switched from Cuprophan to F6 HPS or F60S, neither total IL-1beta production nor processing of IL-1beta changed. However, secretion of mIL-1beta increased significantly with F6 HPS (80.6%, P < 0.01) as well as with F60S (76.6%, P < 0.02) compared with Cuprophan.


CONCLUSIONS
We conclude that the ability of PBMCs to produce IL-1beta in response to LPS is normal in PD patients as well as in HD patients. ICE-dependent processing of inactive proIL-1beta into biologically active mIL-1beta is reduced in PD patients, but not in HD patients. Secretion of mIL-1beta is impaired in PD and HD patients treated with Cuprophan. This impaired ability to secrete active mIL-1beta seems to be independent of ICE activity and is normalized when HD-patients are switched from Cuprophan to low- or high-flux polysulfon. Increased cell-associated levels of biologically active mIL-1beta in circulating PBMCs represent a state of inflammation that may contribute to chronic inflammatory diseases such as beta2-microglobulin amyloidosis. Replacement of Cuprophan by synthetic membranes normalizes PBMC function and reduces the state of inflammation in ESRD patients.
Linnenweber
S
S
Division of Nephrology, Medizinische Hochschule Hannover, Hannover, Germany.
Lonnemann
G
G
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D020170:Caspase 1 / Q000097:blood*; D002482:Cellulose / Q000031:analogs & derivatives*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D018836:Inflammation Mediators / Q000378:metabolism; D007375:Interleukin-1 / Q000097:blood*; D007676:Kidney Failure, Chronic / Q000097:blood / Q000276:immunology / Q000628:therapy; D007688:Kidneys, Artificial / Q000009:adverse effects; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D008297:Male; D008567:Membranes, Artificial; D008875:Middle Aged; D010530:Peritoneal Dialysis / Q000009:adverse effects*; D011108:Polymers; D006435:Renal Dialysis / Q000009:adverse effects*; D013450:Sulfones
D018836:Inflammation Mediators; D007375:Interleukin-1; D008567:Membranes, Artificial; D011108:Polymers; D013450:Sulfones; C017662:polysulfone P 1700; D002482:Cellulose; C009865:cuprammonium cellulose; D020170:Caspase 1