Expression of defensin antimicrobial peptides in the peritoneal cavity of patients on peritoneal dialysis.
OBJECTIVE
To investigate the expression and regulation of defensins in the peritoneal cavity of peritoneal dialysis (PD) patients.


METHODS
The presence of defensins in the peritoneal cavity was assessed using reverse transcription polymerase chain reaction (RT-PCR). In vivo defensin expression was analyzed in human peritoneal membrane biopsies and in peritoneal cavity leukocytes isolated from spent dialysate. Defensin expression in vitro was assessed in cultured human peritoneal mesothelial cells (HPMC) and confirmed with PCR Southern blot and DNA sequencing. The effect of tumor necrosis factor alpha (TNFalpha) and epidermal growth factor (EGF) on beta2 defensin expression in HPMC was analyzed by Northern blot analysis and RT-PCR respectively.


RESULTS
Both alpha and beta classes of defensins are expressed in the peritoneal cavity of PD patients. Messenger RNA for the alpha-defensin human neutrophil peptide 3 and for beta-defensin-1 (hbetaD-1) were found in preparations containing predominantly peritoneal leukocytes, whereas beta-defensin-2 (hbetaD-2) is expressed by HPMC. HPMC isolated from different individuals displayed variability in both basal hbetaD-2 expression and in response to stimulation by TNFalpha. Conversely, EGF consistently downregulated the level of hbetaD-2 message in HPMC.


CONCLUSIONS
Alpha- and beta-defensins are expressed in the peritoneal cavity, and hbetaD-2 is the main defensin present in the peritoneal membrane. Variable levels of expression of hbetaD-2 by mesothelial cells were seen, with evidence of regulation by cytokines and growth factors. This provides evidence for a previously unknown mechanism of innate immunity at that site.
Zarrinkalam
K H
KH
Department of Renal Medicine, Royal Adelaide Hospital, South Australia, Australia.
Leavesley
D I
DI
Stanley
J M
JM
Atkins
G J
GJ
Faull
R J
RJ
D001483:Base Sequence; D015152:Blotting, Northern; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000502:physiology; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010529:Peritoneal Cavity / Q000502:physiology*; D010530:Peritoneal Dialysis / Q000009:adverse effects; D010538:Peritonitis / Q000209:etiology; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D023084:alpha-Defensins / Q000096:biosynthesis* / Q000235:genetics; D023083:beta-Defensins / Q000096:biosynthesis* / Q000235:genetics
C106641:DEFB4A protein, human; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D023084:alpha-Defensins; D023083:beta-Defensins; D004815:Epidermal Growth Factor