Regulation of TNF-alpha by 1alpha,25-dihydroxyvitamin D3 in human macrophages from CAPD patients.
BACKGROUND
We have previously reported that 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] accumulates in the dialysis fluid of uremic patients treated by continuous ambulatory peritoneal dialysis (CAPD). It has been reported that this metabolite regulates the production of cytokines by monocytes/macrophages. Since tumor necrosis factor-alpha (TNF-alpha) initiates an inflammatory cascade during peritonitis, the aim of the present study was to investigate the effect of 1alpha, 25(OH)2D3 on the production of TNF-alpha by human peritoneal macrophages (HPMs).


METHODS
HPMs were obtained from patients on CAPD. Cells were incubated with various concentrations of 1alpha, 25(OH)2D3, 1alpha,24(S) dihydroxyvitamin D2 [1alpha,24(S)(OH)2D2] or 25-hydroxyvitamin D3 (25-OH-D3) for 16 hours. This was followed by lipopolysaccharide (LPS; 1 microg/mL) incubation for 2.5 to 6 hours. TNF-alpha protein production was determined by enzyme-linked immunosorbent assay. TNF-alpha mRNA was assayed by the reverse transcriptase-polymerase chain reaction procedure, using internal synthetic mRNA standards for quantitative results.


RESULTS
Incubation of HPMs with 1alpha,25(OH)2D3 prior to stimulation with LPS dose dependently inhibited the expression of TNF-alpha on both mRNA and protein levels. Similar results were obtained with the less calcemic vitamin D2 analogue 1alpha,24(S)(OH)2D2. Incubation of HPMs with 25-OH-D3 also revealed a down-regulation of TNF-alpha expression. Since this down-regulatory effect was blocked by ketoconazole, it is likely that this effect was caused by the conversion of 25-OH-D3 into 1alpha,25(OH)2D3 by HPMs.


CONCLUSIONS
1alpha,25(OH)2D3 has a potent inhibitory effect on the production of TNF-alpha by LPS-activated HPMs. We hypothesize that 1alpha, 25(OH)2D3 may constitute a regulatory mechanism that, by controlling the intensity of the inflammatory response of the peritoneum, will moderate tissue damage during peritonitis.
Cohen
M L
ML
Departments of Clinical Biochemistry and Nephrology, Faculty of Health Sciences, Ben-Gurion University of the Negev,Soroka Medical Center, Beer Sheva, Israel.
Douvdevani
A
A
Chaimovitz
C
C
Shany
S
S
D002112:Calcifediol / Q000378:metabolism; D002117:Calcitriol / Q000096:biosynthesis / Q000494:pharmacology*; D006801:Humans; D007676:Kidney Failure, Chronic / Q000473:pathology / Q000628:therapy; D008070:Lipopolysaccharides / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism*; D010531:Peritoneal Dialysis, Continuous Ambulatory; D012333:RNA, Messenger / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000378:metabolism
D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D014807:Vitamin D; D002117:Calcitriol; D002112:Calcifediol