Proximal tubules from caspase-1-deficient mice are protected against hypoxia-induced membrane injury.
BACKGROUND
Caspase-1 is a proinflammatory caspase via activation of the cytokine IL-18. We have recently demonstrated that the caspase-1-mediated production of IL-18 plays a deleterious role in ischaemic acute renal failure (ARF) which is independent of neutrophils and CD4+ T cells. The role of caspase-1 in hypoxia-induced membrane injury of proximal tubules (PT) in vitro is unknown.


METHODS
Freshly isolated mouse PT exposed to 25 min of hypoxia were used to study the role of caspases, caspase-1 and IL-18 in hypoxia-induced membrane injury. Lactate dehydrogenase (LDH) release into the PT medium was used as a biochemical parameter of cell membrane damage. IL-18 was determined by enzyme-linked immunosorbent assay (ELISA) and immunoblotting.


RESULTS
PT pre-incubated with the novel pancaspase inhibitor IDN-8050 were protected; LDH release (%) was 35+/-3 in vehicle-treated hypoxic PT and 21+/-2 in IDN-8050-treated hypoxic PT (P<0.01, n=6). To investigate the mechanism of protection and examine the role of caspase-1 specifically, PT were isolated in parallel from wild-type and caspase-1- deficient (-/-) mice. PT from caspase-1-/-mice demonstrated less hypoxia-induced membrane injury. LDH release was 37+/-2 in wild-type hypoxic PT and 28+/-2 in caspase-1-/-hypoxic PT (P<0.01, n=12). IL-18 was detected in PT by immunoblotting and ELISA. PT pre-incubated with IL-18 binding protein, an inhibitor of IL-18, were not protected.


CONCLUSIONS
These studies demonstrate a deleterious effect of the proinflammatory caspase, caspase-1, on PT in vitro in the absence of inflammatory cells and vascular effects.
Edelstein
Charles L
CL
University of Colorado Health Science Center, Department of Internal Medicine, Denver, CO 80262, USA, and Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Kaohsiung Medical Center, Taiwan.
Hoke
Thomas S
TS
Somerset
Hilary
H
Fang
Wenfeng
W
Klein
Christina L
CL
Dinarello
Charles A
CA
Faubel
Sarah
S
D000818:Animals; D020170:Caspase 1 / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3 / Q000378:metabolism; D061945:Caspase Inhibitors; D015687:Cell Hypoxia / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology*; D005786:Gene Expression Regulation; D020382:Interleukin-18 / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000502:physiology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009569:Nitric Oxide / Q000502:physiology
D061945:Caspase Inhibitors; D020382:Interleukin-18; D009569:Nitric Oxide; D007770:L-Lactate Dehydrogenase; D053148:Caspase 3; D020170:Caspase 1