Tacrolimus inhibits intimal hyperplasia in arterialised veins in rats

Antibody-mediated rejection of arterialised venous allografts is inhibited by immunosuppression in rats

Objectives and Design

We determined in a rat model (1) the presence and dynamics of alloantibodies recognizing MHC complexes on quiescent Brown-Norway (BN) splenic cells in the sera of Lewis (LEW) recipients of Brown-Norway iliolumbar vein grafts under tacrolimus immunosuppression; and (2) the presence of immunoglobulins in the wall of acute rejected vein allografts.

Materials and Methods

Flow cytometry was used for the analysis of day 0, 14 and 30 sera obtained from Lewis recipients of isogeneic iliolumbar vein grafts (group A) or Brown-Norway grafts (group B, C) for the presence of donor specific anti-MHC class I and II antibodies. Tacrolimus 0.2 mg/kg daily was administered from day 1 to day 30 (group C). Histology was performed on day 30.

Results

Sera obtained preoperatively and on day 30 were compared in all groups. The statistically significant decrease of anti MHC class I and II antibody binding was observed only in allogenic non-immunosuppressed group B (splenocytes: MHC class I - day 0 (93%±7% ) vs day 30 (66%±7%), p = 0.02, MHC class II - day 0 (105%±3% ) vs day 30 (83%±5%), p = 0.003; B-cells: MHC class I - day 0 (83%±5%) vs day 30 (55%±6%), p = 0.003, MHC class II - day 0 (101%±1%) vs day 30 (79%±6%), p = 0.006; T-cells: MHC class I - day 0 (71%±7%) vs day 30 (49%±5%), p = 0.04). No free clusters of immunoglobulin G deposition were detected in any experimental group.

Conclusion

Arterialized venous allografts induce strong donor-specific anti-MHC class I and anti-MHC class II antibody production with subsequent immune-mediated destruction of these allografts with no evidence of immunoglobulin G deposition. Low-dose tacrolimus suppress the donor-specific antibody production.

The effects of preoperative immunosuppressive therapy on ischemia and reperfusion (I/R) injury in healthy rats

PURPOSE

Warm-ischemia-induced injuries might be encountered during renal transplants from cadavers and healthy donors. Toll-like receptors (TLR) in ischemia-reperfusion (I/R) injury are one of the indicators of intracellular injury pathways. The intensity of ischemic injury is directly proportionate to high TLR levels. To minimize the I/R injury, we investigated TLR2 and TLR4 levels on rats, which were pretreated with tacrolimus (FK506) before I/R.

METHODS

Eight Wistar albino rats in the study group were administered .01 mg/kg intramuscular tacrolimus. Administration to the study group was performed 24 and 1 h before warm ischemia. Eight rats in the control group were injected with 0.1 c.c. of distilled water. Blood samples were collected from the tail veins of all the rats on the first, second and third days. Expression levels of TLR2 and TLR4 genes were analyzed using the polymerase chain reaction method, to determine any significant difference between the control and study groups on the days when blood was taken.

RESULTS

TLR2 (p = 0.045) and TLR4 (p = 0.022) levels in the study group were found to be statistically, and significantly, lower than those in the control group, on the second day following warm-ischemia- and reperfusion-induced injury.

CONCLUSIONS

Administration of immunosuppressive drugs to healthy donor rats led to a statistically significant reduction in the expression levels of TLR2 and TLR4 in the early period. In light of the data obtained by this study, we hypothesize that a preoperative therapy on donors might have a role in preventing I/R injury.