Prevention of early islet graft failure by selective inducible nitric oxide synthase inhibitors after pig to nude rat intraportal islet transplantation.
BACKGROUND
Clinical and experimental data indicate that early failure of intraportally grafted islets is caused by inflammation including secretion of cytokines and nitric oxide. Direct inducible nitric oxide synthase suppression may avoid detrimental effects associated with steroid administration. We compared the efficiency of selective and unselective inducible nitric oxide synthase inhibitors with dexamethasone to suppress nitric oxide generation after intraportal islet xenotransplantation into nude rats.


METHODS
Nonfasting serum glucose levels were daily evaluated after intraportal transplantation of 4000 freshly isolated pig islets into diabetic nude rats (85 mg/kg streptozotocin) either sham-treated with saline (n=21) or continuously infused for 7 days with L-NG-monomethyl-arginine (n=7), S-methyl-isothiourea (n=15), or S-(2-aminoethyl)-isothiourea (n=19) in a dosage of 240, 100, or 50 mg/kg/day, respectively. Dexamethasone was injected i.p. twice as a daily bolus of 20 mg/kg (n=10) starting 1 day pretransplant. The nitrate/nitrite serum level was quantified colorimetrically 0, 24, and 48 hr posttransplant.


RESULTS
Saline treatment partially resulted in graft function (4/21) throughout the observation period (21 days). L-NG-monomethyl-arginine-treated rats showed sustained hyperglycemia (0/7) not different from diabetic controls. Normoglycemia was observed after treatment with dexamethasone (6/10, P<0.05 versus saline and L-NG-monomethyl-arginine), S-methyl-isothiourea (10/15, P<0.01), or S-(2-aminoethyl)-isothiourea (15/19, P<0.001). Graft function was associated with complete suppression of nitric oxide generation after S-methyl-isothiourea and S-(2-aminoethyl)-isothiourea treatment (P<0.001 versus saline) and partial suppression after dexamethasone treatment (P<0.05).


CONCLUSIONS
Our observation of long-term function of xenogeneic islets in an inflammatory environment without interference of reactive T cells revealed the potency of highly selective isothioureas to completely suppress inducible nitric oxide synthase making reduction of islet-toxic immunosuppression feasible.
Brandhorst
D
D
Third Medical Department, Justus-Liebig-University, Giessen, Germany.
Brandhorst
H
H
Zwolinski
A
A
Nahidi
F
F
Bretzel
R G
RG
D000818:Animals; D003864:Depression, Chemical; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006085:Graft Survival / Q000187:drug effects; D016381:Islets of Langerhans Transplantation / Q000276:immunology; D008099:Liver / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D011169:Portal Vein / Q000601:surgery; D051381:Rats; D011917:Rats, Inbred Lew; D011923:Rats, Nude; D013552:Swine; D014183:Transplantation, Heterologous / Q000276:immunology
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat