KG LEONG1,2, E OZOLS1,2, J KANELLIS1,2, J LILES3, DJ NIKOLIC-PATERSON1,2, FY MA1,2.
1Department of Nephrology, Monash Medical Centre, Clayton, Victoria; 2Centre for Inflammatory Diseases, Monash University, Clayton, Victoria; 3Gilead Sciences, Foster City, CA, USA.
Aim: To determine whether cyclophilin (Cyp) inhibition can prevent renal ischaemia/reperfusion (I/R) injury.
Background: Cyclophilins are a family of enzymes which regulate protein folding. Of these enzymes CypD is an essential component of the mitochondrial permeability membrane pore (mPTP). During acute cellular injury, such as that occurring in I/R injury, the mPTP facilitates mitochondrial release of cytochrome c and calcium ions causing cell damage and cell death. We investigated whether a novel cyclophilin inhibitor (CYPi), which does not block calcineurin function, could prevent anticipated renal I/R injury.
Methods: Mice were anaesthetised with ketamine/xylazine and bilateral renal ischaemia (17min at 37 degrees) induced using non-traumatic vascular clamps and animals killed 24hr after reperfusion. Controls were sham operated. Renal I/R injury studies were performed in C57BL/6J mice (n=10/group) which were treated with 30mg/kg/BID CYPi or vehicle by oral gavage starting 1 hour prior to surgery.
Results: Renal I/R injury caused acute renal failure at day 1 in WT mice (179.0±19.1umol/L vs 12.2±1.4umol/L serum creatinine (sCr) in sham control; P<0.001). CYPi caused substantial protection from renal failure (sCr 36.4±6.7umol/L; P<0.001 vs vehicle). Scoring of PAS stained sections found that the percentage of tubules exhibiting damage in the outer medulla was reduced from 73.0±3.7% in vehicle to 46.7±14.8% in CYPi treated; P<0.001). Apoptotic tubular cells in the vehicle I/R group (11.4±3.2 TUNEL+ cells/mm2) was reduced with CYPi treatment (4.3±0.9 TUNEL+ cells/mm2; P<0.001). In addition, CYPi treatment reduced macrophage infiltration and TNF-α mRNA levels (both P<0.01 vs vehicle).
Conclusions: Cyclophilin inhibition prevented anticipated I/R-induced acute renal failure by suppressing tubular apoptosis and necrosis.