Transfection of tubule cells with Fas ligand causes leukocyte apoptosis.
BACKGROUND
Since the Fas/Fas Ligand (FasL) interaction is recognized as a major pathway of apoptosis in immune cells, we hypothesized that selective expression of FasL by tubular cells (TC) may promote the resolution of interstitial inflammation by inducing apoptosis of infiltrating immune cells. In this study, the effect of FasL transfection of rat TC on apoptosis of leukocytes was examined.


METHODS
Rat tubule cells (NRK52E) were transfected with plasmids constructed using human and rat FasL (hFasL and rFasL). The propensity of activated, transfected TC to undergo apoptosis was examined. Similarly, the effects of FasL transfection on apoptosis of Jurkat cells and activated leukocytes were assessed directly following co-culture for 12 hours and in a cell insert system intended to assess the effects of soluble FasL. Fas and FasL expression was assessed by flow cytometry and apoptosis was examined using Annexin V staining and the TUNEL method.


RESULTS
Expression of FasL in TC was increased after FasL transfection. Transfected TC showed no detectable increase in apoptosis following lipopolysaccharide (LPS) or tumor necrosis factor-alpha (TNF-alpha) activation. Jurkat cell apoptosis was increased ninefold and eightfold after co-culture with TC transfected with hFasL and rFasL, respectively (67.0 +/- 12.1% and 60.1 +/- 8.8% vs. 6.7 +/- 1.8% with un-transfected TC, P < 0.01). Similarly, apoptosis of activated leukocytes was increased fourfold by co-culture (26.8 +/- 4.9% vs. 6.7 +/- 2.0% with untransfected TC, P < 0.01). Leukocyte apoptosis also was increased in an insert culture system (18.2 +/- 4.4% vs. 5.8 +/- 2.3% with un- transfected TC, P < 0.01). No increase of TC apoptosis was detected in any of the co-culture experiments.


CONCLUSIONS
Enhanced expression of FasL by TC is capable of inducing apoptosis of activated leukocytes, without evidence for increased susceptibility to apoptosis of the transfected cells themselves. This suggests a potential role for this approach in the limitation and resolution of renal tubulointerstitial inflammation.
Wang
Yiping
Y
Department of Renal Medicine, The University of Sydney at Westmead Hospital, Sydney, New South Wales, Australia. Yiping_Wang@wsahs.nsw.gov.au
Yi
Shounan
S
Tay
Yuet-Ching
YC
Feng
Ximin
X
Wang
Yang
Y
Kairaitis
Lukas
L
Harris
David C H
DC
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D053222:Fas Ligand Protein; D006801:Humans; D019169:Jurkat Cells / Q000502:physiology; D007684:Kidney Tubules / Q000166:cytology / Q000502:physiology*; D007962:Leukocytes / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000502:physiology*; D051381:Rats; D014162:Transfection
C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505662:Faslg protein, rat; D008562:Membrane Glycoproteins