The free radical scavenger S-PBN significantly prolongs DSG-mediated graft survival in experimental xenotransplantation.
BACKGROUND
Nitrones such as 2-sulfo-phenyl-N-tert-butyl nitrone (S-PBN) are known to trap and stabilize free radicals and to reduce inflammation. Recently, S-PBN was shown to reduce infiltration of T lymphocytes and the expression of adhesion molecules on the endothelium in experimental traumatic brain injury. We hypothesized that S-PBN could reduce infiltration of T lymphocytes during cell-mediated xenograft rejection and thereby increase graft survival. The concordant mouse-to-rat heart transplantation model was used to test the hypothesis. In this model, grafts undergo acute humoral xenograft rejection (AHXR) almost invariably on day 3 and succumb to cell-mediated rejection on approximately day 8 if AHXR is inhibited by treatment with 15-deoxyspergualin (DSG).


METHODS
Hearts from Naval Medical Research Institute (NMRI) mice were transplanted to the neck vessels of Lewis rats. Recipients were treated with S-PBN (n=9), DSG (n=9), S-PBN and DSG in combination (n=10) or left untreated (n=9) for survival studies. S-PBN was given daily intraperitoneally at a dose of 150 mg/kg body weight (BW) on day -1 to 30, and DSG was given daily intraperitoneally at a dose of 10 mg/kg BW on day -1 to 4 and 5 mg/kg BW on day 5 to 21. Nine additional recipients were given S-PBN only on days -1 and 0 in combination with continuous DSG treatment. Grafts were monitored until they stopped beating. Additional recipients were treated with S-PBN (n=5), DSG (n=5), S-PBN and DSG in combination (n=6) or left untreated (n=5) for morphological, immunohistochemical and flow cytometry analyses on days 2 and 6 after transplantation.


RESULTS
S-PBN treatment in combination with DSG resulted in increased median graft survival compared to DSG treatment alone (14 vs. 7 days; P=0.019). Lower number of T lymphocytes on day 6 (P=0.019) was observed by ex vivo propagation and flow cytometry when combining S-PBN with DSG, whereas immunohistochemical analyses demonstrated a significant reduction in the number of infiltrated CD4+, but not TCR+, cells. S-PBN treatment alone had no impact on graft survival compared to untreated rats (3 vs. 3 days). No differences were seen in ICAM-1 and VCAM-1 expression or in morphology between the groups.


CONCLUSIONS
The combination of S-PBN and DSG treatment increases xenograft survival. The main effect of S-PBN appears to be in direct connection with the transplantation. Because of its low toxicity, S-PBN could become useful in combination with other immunosuppressants to reduce cell-mediated xenograft rejection.
Department of Surgical Sciences, Section of Transplantation Surgery, Uppsala University, Uppsala, Sweden.
Ali-Reza
AR
Biglarnia
Cecilia
C
Emanuelsson
My
M
Quach
Fredrik
F
Clausen
Erik
E
Larsson
Mårten K J
MK
Schneider
Gunnar
G
Tufveson
Tomas
T
Lorant
D000818:Animals; D021461:Animals, Outbred Strains; D001557:Benzenesulfonates / Q000494:pharmacology*; D004359:Drug Therapy, Combination; D016166:Free Radical Scavengers / Q000494:pharmacology*; D006084:Graft Rejection / Q000276:immunology / Q000378:metabolism; D006085:Graft Survival / Q000187:drug effects* / Q000276:immunology; D006146:Guanidines / Q000494:pharmacology*; D016027:Heart Transplantation / Q000379:methods*; D007166:Immunosuppressive Agents / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D008198:Lymph Nodes / Q000166:cytology / Q000276:immunology; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D051379:Mice; D051381:Rats; D011917:Rats, Inbred Lew; D013154:Spleen / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D020858:Tissue and Organ Harvesting / Q000379:methods; D014183:Transplantation, Heterologous / Q000379:methods*; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
D001557:Benzenesulfonates; D016166:Free Radical Scavengers; D006146:Guanidines; D007166:Immunosuppressive Agents; D019010:Vascular Cell Adhesion Molecule-1; C094272:N-tert-butyl-(2-sulfophenyl)nitrone; D018799:Intercellular Adhesion Molecule-1; C037258:gusperimus