Introduction: PQA-18 (prenylquinoline carboxy derivative 18) is a novel immunosuppressant that inhibits PAK-2 and suppresses cytokine production and macrophage (Mφ) differentiation/proliferation. The effect of PQA-18 was evaluated using a rat small intestine transplant model.
Methods: Male Dark Agouti (DA) (RT-1a) and Lewis (RT-1l) rats, 7 to 9 weeks old, were used as donors and recipients, respectively.  An approximately 15 cm ileal grafts from the donor was heterotopically transplanted to the recipient rats.  Recipients were administered PQA-18 (4 mg/kg/day) intraperitoneal injection from post-operative day1 (POD1) for two weeks.
(1) The survival time of the graft was compared between the non-administration group (ITx-g) and the PQA administered group (PQA-g).  The rejection was manifested by progressive stoma ischemia, necrosis and the development of an abdominal mass, based on our previous studies.
(2) At POD6, CD3 + T cells were separated from recipient mesenteric lymph nodes and mixed lymphocyte reaction (MLR) was performed.
(3) Further, the % of Mφ in the graft mesenteric lymph node (gMLN) and graft Peyer's patch (gPP) was measured by FACS.
(4) Bone marrow stem cells of Lewis rat were cultured with G-CSF for 4 days, with or without PQA-18, and the differentiation/proliferation of Mφ was also measured by FACS.
Results: (1) The graft survival time was prolonged from 7.0 ± 0.77 days in ITx-g (n = 9) to 10.7 ± 1.26 days in PQA-g (n = 10) (p <0.001).  However, there was no difference between the two groups in serum creatinine and BUN on POD10 and POD14, measured for the evaluation of renal function.
(2) MLR showed a suppression of T cell proliferation in PQA-g compared with ITx-g: 9.44 ± 1.21 vs 4.71 ± 0.55 (n = 4) (p <0.05), respectively.
(3) The % of Mφ in the graft was 60.55 ± 2.18% (ITx-g) vs 45.20 ± 3.20% (PQA-g)(n = 6) (p <0.01) for gMLN and 42.42 ± 3.61% (ITx-g) vs 29.8% ± 3.21% (PQA-g) (n = 6) for gPP (p <0.05).  In addition, the decreation of Mφ was observed in all cases of PQA-g.
(4) The % of Mφ differentiation was reduced in the dose dependent manner.  The group with 20μM of PQA-18 showed 5.01 ± 2.09% (n = 6), vs 14.45 ± 2.40% (control) (p <0.05).
Conclusion: PQA-18 significantly prolonged the survival of rat small intestinal grafts by suppressing the Mφ infiltration in the grafts and lymph nodes.