ALLOTRAP1258 INHIBITS CHRONIC REJECTION BY DIRECT EFFECTS ON SMOOTH MUSCLE CELLS.

Abstract

182 The rationally designed peptide, Allotrap 1258, has been described for its immunomodulatory activity both in vitro and in vivo. We analyzed the effect of Allotrap 1258 in a chronic rejection model using C57BL/10 (B10;H2b) donors and C3H(H2k) recipients. Allotrap1258 was administered i.p. to abdominal aortic transplant recipients at 0.1, 0.5 or 2.5 mg/kg every other day after transplantation. Grafts were analyzed on days 10 and 30. Allotrap1258 therapy resulted in a marked inhibition of vascular intimal thickening and media necrosis on day 30, but did not influence adventitial cellular inflammation. Inhibition of arteriosclerosis of aortic allografts was associated with a decreased production of specific complement-dependent cytotoxic antibodies. Although the mechanism of chronic rejection is unclear, it is believed to be due to increased apoptosis/necrosis followed by replication of the smooth muscle cell layer. Therefore, we analyzed the effects of peptide treatment on a rat smooth muscle cell line (A-10). Cell proliferation was measured as 3H-TdR uptake over 6 h. Allotrap1258 was added to cells either 18 or 24 h prior to 3H-TdR addition or simultaneously. Addition of Allotrap1258 inhibited cell proliferation irrespective of the time of addition. Inhibition was dose dependent with an 80% inhibition at 100 uM. Incubation of Allotrap1258 with various 51Cr-labelled cells showed no cytotoxicity. The effect of Allotrap1258 on apoptosis was studied following induction of apoptosis by TNFα. Apoptosis, monitored by ELISA quantiation of DNA fragments, was inhibited by Allotrap 1258 in a dose dependent fashion. (IC50=10 uM). Taken together, these data demonstrate that Allotrap1258 inhibits smooth muscle cell proliferation and TNFα induced apoptosis. This activity may contribute to the prevention of chronic allograft rejection by this novel immunomodulatory peptide. (Table)Table