Ml. Cohen et al., Regulation of TNF-alpha by 1 alpha,25-dihydroxyvitamin D-3 in human macrophages from CAPD patients, KIDNEY INT, 59(1), 2001, pp. 69-75
Background We have previously reported that 1 alpha ,25-dihydroxyvitamin D-
3 [1 alpha ,25(OH)(2)D-3] accumulates in the dialysis fluid of uremic patie
nts treated by continuous ambulatory peritoneal dialysis (CAPD). It has bee
n reported that this metabolite regulates the production of cytokines by mo
nocytes/macrophages. Since tumor necrosis factor-alpha (TNF-alpha) initiate
s an inflammatory cascade during peritonitis, the aim of the present study
was to investigate the effect of 1 alpha ,25(OH)(2)D-3 on the production of
TNF-alpha by human peritoneal macrophages (HPMs).
Methods. HPMs were obtained from patients on CAPD. Cells were incubated wit
h various concentrations of 1 alpha ,25(OH)(2)D-3, 1 alpha ,24(S) dihydroxy
vitamin D-2 [1 alpha ,24(S)(OH)(2)D-2] Or 25-hydroxyvitamin D-3 (25-OH-D-3)
for 16 hours. This was followed by lipopolysaccharide (LPS; 1 mug/mL) incu
bation for 2.5 to 6 hours. TNF-alpha protein production was determined by e
nzyme-linked immunosorbent assay. TNF-alpha mRNA was assayed by the reverse
transcriptase-polymerase chain reaction procedure, using internal syntheti
c mRNA standards for quantitative results.
Results. Incubation of HPMs with 1 alpha ,25(OH)(2)D-3 prior to stimulation
with LPS dose dependently inhibited the expression of TNF-alpha on both mR
NA and protein levels. Similar results were obtained with the less calcemic
vitamin D-2 analogue 1 alpha ,24(S)(OH)(2)D-2. Incubation of HPMs with 25-
OH-D-3 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-D-3 into 1 alpha ,25(OH)(2)D-
3 by HPMs.
Conclusions. 1 alpha ,25(OH)(2)D-3 has a potent inhibitory effect on the pr
oduction of TNF-alpha by LPS-activated HPMs. We hypothesize that 1 alpha ,2
5(OH)(2)D-3 may constitute a regulatory mechanism that, by controlling the
intensity of the inflammatory response of the peritoneum, will moderate tis
sue damage during peritonitis.