CNI-1493 PROLONGS SURVIVAL AND REDUCES MYOCYTE LOSS, APOPTOSIS, AND INFLAMMATION DURING RAT CARDIAC ALLOGRAFT-REJECTION

Cytokines and cytotoxic agents, including nitric oxide (NO) released b y macrophages, play important roles during cardiac allograft rejection . Ln contrast to agents that suppress T-lymphocyte function, CNI-1493 is a multivalent guanlhydrazone compound that inhibits the synthesis a nd release of proinflammatory cytokines and NO from macrophages. This study investigated the effects of CNI-1493 on rejecting rat cardiac al lografts by using Lewis to Wistar-Furth heterotopic cardiac transplant s, CNI-1493 (2 mg/kg i.p., b.i.d.) or vehicle (water) was administered beginning the day before surgery. Rat cardiac allograft survival to c essation of heart brat, apoptosis of cardiac myocytes, degree of myoca rdial inflammation, and inducible nitric oxide synthase (iNOS) messeng er RNA (mRNA), protein, and enzyme activity were studied at days 1, 3, 5, and 7 after transplantation. Allograft survival was increased sign ificantly by 26% from 7.5 +/- 0.8 days in vehicle-treated rats (n = 6) to 9.5 +/- 1.2 days in CNI-1493-treated rats (n = 8, p < 0.05). Apopt otic cells per mm(2) myocardium decreased from 2.25 +/- 1.25 to 0.84 /- 0.49 at day 3 and 31.2 +/- 2.9 to 17.6 +/- 5.43 at day 5 after tran splantation with CNI-1493 treatment (p < 0.05). The number of apoptoti c myocytes and loss of cardiac muscle cells also decreased significant ly at day 5 in the treated animals (p < 0.05). The reduction of myocyt e loss at day 5 coincided with a significant decrease of the inflammat ory response and reduced macrophage influx (p < 0.05). Myocardial iNOS mRNA, protein, and enzyme levels increased during the course of allog raft rejection, and CNI-1493 did not significantly reduce iNOS express ion in the rejecting rat allograft. CNI-1493 prolongs allograft surviv al and reduces myocyte loss, apoptosis, and inflammation during rat ca rdiac allograft rejection. These effects of CNI-1493 appear to be unre lated to altered NO synthesis but may be related to effects of the dru g io inhibit macrophage synthesis of cytokines.