Inflammation and caspase activation in long-term renal ischemia/reperfusion injury and immunosuppression in rats.
BACKGROUND
We have previously shown the long-term influence of renal ischemia/reperfusion (I/R) injury and immunosuppression on fibrotic genes and apoptosis in a rat model. For the first time, we have now investigated the effects of I/R and immunosuppression on inflammation and caspase activation.


METHODS
I/R injury was induced in the right kidney and the left was removed. Cyclosporin (CsA) (10 mg/kg), tacrolimus (0.2 mg/kg), rapamycin (1 mg/kg), or mycophenolate mofetil (MMF) (10 mg/kg) was then administered for 16 weeks. The effects of I/R and immunosuppressants on interstitial inflammation, interleukin (IL)-1beta expression, caspase-1 and caspase-3 activation, tubulointerstitial damage, and fibrosis were evaluated.


RESULTS
ED-1+ (a specific rat monocyte/macrophage marker) cells were mainly localized in the tubulointerstitium and periglomerular areas and increased in I/R group compared to controls (P < 0.01). This was further increased by CsA, but decreased by tacrolimus, rapamycin, or MMF (P < 0.05). The 17 kD active IL-1beta remained unchanged, but 35 kD IL-1beta precursor was decreased by rapamycin in comparison with I/R group (P < 0.05). The 45 kD or 20 kD caspase-1 was increased by I/R or CsA, respectively, and decreased by rapamycin (P < 0.05). The 24 kD caspase-3, which proved to be an active caspase-3 subunit, was increased in I/R and CsA groups and deceased by tacrolimus, rapamycin, or MMF (P < 0.05), but not 32 kD precursor or 17 kD active caspase-3. The activity data of caspase-1 and caspase-3 exhibited the same trend as Western blotting data. The staining of active caspase-3 was scattered in kidneys, mainly in tubular and interstitial areas, which was consistent with that of ED-1+ cells. There was a strong positive correlation between interstitial inflammation and 24 kD caspase-3 expression or caspase-3 activity (r = 0.814 or 0.484), all of which were also closely related with urinary protein (r = 0.537, 0.529, or 0.517), serum creatinine (r = 0.463, 0.573, or 0.539), tubulointerstitial damage (r = 0.794, 0.618, or 0.712) and fibrosis (r = 0.651, 0.567, or 0.469), all P < 0.01.


CONCLUSIONS
This study shows that the mechanisms of long-term I/R injury and immunosuppressants treatment include interstitial inflammation and caspase activation, most clearly demonstrated by the 24 kD active caspase-3.
Yang
Bin
B
Department of Infection, Immunity and Inflammation, University of Leicester, Leicester General Hospital, UK. by5@le.ac.uk
Jain
Sunjay
S
Pawluczyk
Izabella Z A
IZ
Imtiaz
Shehla
S
Bowley
Lee
L
Ashra
Shairbanu Y
SY
Nicholson
Michael L
ML
D000818:Animals; D017209:Apoptosis / Q000276:immunology; D020170:Caspase 1 / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002908:Chronic Disease; D016572:Cyclosporine / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D005109:Extracellular Matrix / Q000473:pathology; D005355:Fibrosis; D005921:Glomerulonephritis / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D007166:Immunosuppressive Agents / Q000276:immunology*; D007375:Interleukin-1 / Q000378:metabolism; D008297:Male; D009173:Mycophenolic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D020123:Sirolimus / Q000494:pharmacology; D016559:Tacrolimus / Q000494:pharmacology
D007166:Immunosuppressive Agents; D007375:Interleukin-1; D016572:Cyclosporine; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D020170:Caspase 1; D009173:Mycophenolic Acid; D020123:Sirolimus; D016559:Tacrolimus