Caspases, Bcl-2 proteins and apoptosis in autosomal-dominant polycystic kidney disease.
BACKGROUND
Apoptosis is a characteristic feature of human autosomal-dominant polycystic kidney disease (ADPKD). The Han:Sprague-Dawley (SPRD) rat model closely resembles human ADPKD and presents an opportunity to investigate the apoptotic pathway in the pathogenesis of this disease.


METHODS
Han:SPRD rats were studied during the early stages of ADPKD (newborn, 2 and 6 weeks old). Apoptotic cells were detected by the TUNEL (Tdt-mediated dUTP nick end-labeling) assay. Caspase-3 activity was measured using the fluorescent substrate DEVD-AMC and cleavage of poly (ADP-ribose) polymerase [PARP]. Expression of pro- and anti-apoptotic B-cell lymphoma (Bcl-2) proteins was detected on Western blot analysis.


RESULTS
TUNEL (+) cells, caspase-3 activity and caspase-mediated PARP breakdown were significantly increased in 2-week-old heterozygous (Cy/+) and homozygous (Cy/Cy) rat kidneys compared to normal littermate controls. In Cy/+ rat kidneys, decreased expression of anti-apoptotic Bcl-XL coincided with increased caspase-3 activity at 2 weeks of age while expression of Bcl-2, another anti-apoptotic protein, increased at 6 weeks of age. In Cy/Cy rat kidneys, decreased expression of Bcl-XL and increased expression of Bcl-2 was present at 2 weeks of age. Pro-apoptotic Bax and Bad expression was unchanged at 2 weeks of age in both Cy/+ and Cy/Cy rat kidneys.


CONCLUSIONS
Activation of caspase-3 and dysregulation of the balance between pro- and anti-apoptotic Bcl-2 family members, specifically a down-regulation of anti-apoptotic Bcl-XL, correlates with increased apoptosis in polycystic Han:SPRD rat kidneys.
Ecder
Tevfik
T
Department of Medicine, University of Colorado School of Medicine, Denver, Colorado 80262, USA.
Melnikov
Vyacheslav Y
VY
Stanley
Melinda
M
Korular
Didem
D
Lucia
M Scott
MS
Schrier
Robert W
RW
Edelstein
Charles L
CL
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007668:Kidney / Q000473:pathology / Q000503:physiopathology; D008297:Male; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D016891:Polycystic Kidney, Autosomal Dominant / Q000473:pathology / Q000503:physiopathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D051381:Rats; D051020:bcl-X Protein
C494813:Bcl2l1 protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases