Selective cyclooxygenase 2 inhibitor induces indefinite survival of fully allogeneic cardiac grafts and generates CD4+ regulatory cells.

Background: Selective inhibition of cyclooxygenase 2 has been reported to have not only anti-inflammatory effects but also effects on the immune response. We investigated ability of a cyclooxygenase 2 inhibitor to inhibit alloimmune response in a murine cardiac transplantation model.

Methods: CBA (H2(k)) mice underwent transplantation of C57BL/10 (H2(b)) hearts. On the day of transplantation, the recipients received either no treatment or single administration of aspirin (a cyclooxygenase 1 and 2 inhibitor) or the selective cyclooxygenase 2 inhibitor NS-398. Naive CBA mice (secondary recipients) underwent adoptive transfer of splenocytes from treated mice with long-surviving grafts (primary recipients) to determine whether regulatory cells developed after NS-398 treatment. Histologic, cell-proliferation, and cytokine studies were also performed.

Results: Untreated CBA mice rejected C57BL/10 cardiac grafts acutely (median survival time, 8 days). The majority of recipients given aspirin rejected their grafts within 20 days (median survival time, 11 days). In mice given NS-398, the majority of the grafts survived indefinitely (median survival time, >100 days). Secondary CBA recipients given CD4+ splenocytes from primary CBA recipients treated with NS-398 also had indefinite survival of C57BL/10 hearts (median survival time, >60 days). Graft acceptance and proliferative hyporesponsiveness were also confirmed by the histologic and cell-proliferation studies, respectively. Production of interleukin 4 and 10 from splenocytes of the recipients treated with NS-398 were significantly higher than that from untreated recipients.

Conclusions: In our model administration of cyclooxygenase 2 inhibitor induced indefinite survival of fully mismatched cardiac grafts and generated CD4+ regulatory cells. Cyclooxygenase 2 inhibitor could warrant consideration for use as an immunomodulating agent in clinical transplantation.