Diminished cytotoxic gene expression in rat cardiac transplants with low-dose cyclosporine/methotrexate combination therapy.
We have previously shown that administration of a combination low-dose cyclosporine (CsA) (1.0 mg/kg/day)/methotrexate (MTX) (450 micrograms/kg/wk) treatment significantly increases the survival of rat cardiac allografts, and may therefore potentially serve as an alternative immunosuppressive therapy designed to promote transplant survival while minimizing high-dose CsA side effects. In contrast to high-dose CsA, low-dose CsA/MTX treatment does not appear to alter IL-2 gene expression, since similar patterns of IL-2 gene transcripts were found in both low-dose CsA/MTX-treated and untreated control allografts on days 1 through 8 posttransplantation (post-tx). The mechanism(s) by which low dose CsA/MTX therapy increases the time of allograft survival remains to be elucidated. The aim of the present study was to determine the effects of low-dose CsA/MTX on the expression of the cytotoxic cytokines, TNF alpha, TNF beta, or lymphotoxin (LT), and the serine proteases HF and C11 (granzymes A and B, respectively) in rat cardiac allografts during rejection. RNA blot analysis showed significant suppression of TNF alpha, LT, HF, and C11 gene expression on days 1 through 8 post-tx in cardiac allografts from low-dose CsA/MTX-treated recipients compared with untreated allograft controls. TNF protein levels in cardiac allografts from low-dose CsA/MTX-treated recipients were also found to be significantly reduced on days 1 through 8 post-tx when compared with time-matched untreated allograft controls (P < or = 0.001). We conclude that low-dose CsA/MTX treatment, while effective in prolonging cardiac transplant survival, appears to act at the mRNA level to downregulate cytotoxic cytokine gene expression. Such trials aimed at evaluating low-dose combination therapy may afford new insight into mechanisms underlying improvement in immunosuppressive treatment.
Pizarro
T T
TT
Department of Cell Biology, Neurobiology, and Anatomy, Stritch School of Medicine, Loyola University Chicago, Maywood, Illinois 60153.
Malinowska
K
K
Kovacs
E J
EJ
Clancy
J
J
Robinson
J A
JA
Piccinini
L A
LA
D000818:Animals; D015152:Blotting, Northern; D002478:Cells, Cultured; D016572:Cyclosporine / Q000008:administration & dosage / Q000627:therapeutic use*; D016207:Cytokines / Q000378:metabolism*; D003602:Cytotoxicity, Immunologic / Q000235:genetics*; D015342:DNA Probes; D004359:Drug Therapy, Combination; D005260:Female; D015870:Gene Expression; D006084:Graft Rejection / Q000188:drug therapy / Q000378:metabolism*; D016027:Heart Transplantation; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000627:therapeutic use*; D009206:Myocardium / Q000378:metabolism; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011914:Rats, Inbred BN; D011917:Rats, Inbred Lew; D012697:Serine Endopeptidases / Q000378:metabolism*; D014184:Transplantation, Homologous
D016207:Cytokines; D015342:DNA Probes; D012333:RNA, Messenger; D016572:Cyclosporine; D012697:Serine Endopeptidases; D008727:Methotrexate