[Effect of bortezomib on acute graft-versus-host disease in mice model and its mechanism]

To investigate the effect of bortezomib on prophylaxis of acute graft-versus-host disease (aGVHD) after mouse allogeneic-bone marrow transplantation (allo-BMT) and its mechanism.

C57BL/6 (H-2(b)) mice were used as donors and BALB/c (H-2d+) mice as recipients. After allo-BMT, the BALB/c mice were divided into 3 groups, ie. group A:BMT control, group B: BMT + early infusion of bortezomib (1 mg kg(-1) d(-1), day 0-3), group C: BMT + late infusion of bortezomib (1 mg kg(-1) d(-1), day 5-7). Clinical manifestations of aGVHD, pathohistological changes, survival rate and levels of recipients H-2(b) cells detected by flow cytometry in the recipient mice were observed. Monodirectional mixed lymphocyte culture (MLC) system was established ex vivo and different concentrations of bortezomib (0, 2, 4, 8 nmol/L) were added to the system. The viability of the cells was detected by CCK-8 assay and cells apoptosis by flow cytometry. The concentrations of IL-2, IFN-gamma, TNF-alpha in the supernatant were detected by enzyme-linked immunosorbent assay (ELISA).

The mice in group A developed typical aGVHD and all died of aGVHD within 3 weeks after transplantation, with a median survival time of (16.1 +/- 2.5) d. The symptoms of aGVHD was milder in group B than in group A, and the median survival time was significantly longer. The 60-day survival rate in group B was 70%, being significantly higher than that in other two groups(P<0.05). The mean value of donor-derived cell (H-2(b) cells) in group B was (98.1 +/- 1.1)% at 60 days. The symptoms of aGVHD was significantly severer in group C than in group A, and the median survival time was shorter. Bortezomib inhibited the cells viability in MLC system in a dose-dependent manner. After treated with 8 nmol/L bortezomib for 24 h, the inhibition ratio of cells viability was (41.4 +/- 6.0)%. The cell apoptosis rate increased gradually with bortezomib treatment for 12 h, 24 h and 36 h. After treated with 8 nmol/L bortezomib for 36 h, the apoptosis rate was (62.8 +/- 7.0)%. After treated for 24 h, the levels of IL-2, IFN-gamma and TNF-alpha in the supernatant were decreased.

Bortezomib administered immediately after allogeneic BMT can prevent aGVHD, improve the survival rate and have no influence of engraftment in the recipient mice. Delayed administration of bortezomib results in acceleration of aGVHD-induced mortality. Its mechanism maybe inhibition of the lymphocyte viability, increase of the cells apoptosis rate, and inhibition of secretion of IL-2, IFN-gamma, and TNF-alpha.