Dimethylarginine metabolism during acute and chronic rejection of rat renal allografts.
BACKGROUND
Dimethylarginines are inhibitors of NO synthesis and are involved in the pathogenesis of vascular diseases. In this study, we ask the question if asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA) levels change during fatal and reversible acute rejection, and contribute to the pathogenesis of chronic vasculopathy.


METHODS
The Dark Agouti to Lewis rat strain combination was used to investigate fatal acute rejection. Fischer 344 kidneys were transplanted to Lewis rats to study reversible acute rejection episode and the process of chronic rejection. Isograft recipients and untreated Lewis rats were used as controls. l-arginine derivatives were determined by HPLC, and ADMA-metabolizing enzymes were studied by quantitative RT-PCR and western blotting.


RESULTS
Renal transplantation transiently increased dimethylarginine levels independent of acute rejection. ADMA plasma levels did not importantly differ between recipients undergoing fatal or reversible acute rejection, whereas SDMA was even lower in recipients of Fisher 344 grafts. In comparison to isograft recipients, ADMA and SDMA levels were slightly elevated during reversible, but not during the process of chronic rejection. Increased dimethylarginine levels, however, did not block NO synthesis. Interestingly, protein methylation, but not ADMA degradation, was increased in allografts.


CONCLUSIONS
Our data do not support the concept that renal allografts are protected from fatal rejection by dimethylarginines. Dimethylarginines may play a role in triggering chronic rejection, but a contribution to vascular remodelling itself is improbable. In contrast, differential arginine methylation of yet unknown proteins by PRMT1 may be involved in the pathogenesis of acute and chronic rejection.
Zakrzewicz
Dariusz
D
Department of Medicine II, University of Giessen Lung Center, Aulweg 123, D-35392 Giessen, Germany.
Zakrzewicz
Anna
A
Wilker
Sigrid
S
Boedeker
Rolf-Hasso
RH
Padberg
Winfried
W
Eickelberg
Oliver
O
Grau
Veronika
V
D000208:Acute Disease; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism; D015153:Blotting, Western; D002908:Chronic Disease; D006084:Graft Rejection; D007124:Immunoenzyme Techniques; D007674:Kidney Diseases / Q000378:metabolism* / Q000473:pathology / Q000628:therapy*; D016030:Kidney Transplantation; D008297:Male; D009566:Nitrates / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism; D011484:Protein-Arginine N-Methyltransferases / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014184:Transplantation, Homologous
D009566:Nitrates; D009573:Nitrites; D012333:RNA, Messenger; C487735:dimethylarginine; D001120:Arginine; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; C541817:PRMT1 protein, rat; D011484:Protein-Arginine N-Methyltransferases