Human allograft arterial injury is ameliorated by sirolimus and cyclosporine and correlates with suppression of interferon-gamma.

BACKGROUND: Chronic allograft dysfunction may result from arterial injury, manifest as transplant arteriosclerosis (TA). This represents an important factor limiting long-term outcomes after heart and kidney transplantation; a relationship between acute allograft arterial injury and TA has been suggested. We have used SCID/bg mice bearing transplanted human artery, inoculated with allogeneic human PBMC to study arteriopathy in human vessels. Earlier work demonstrated arteriopathy similar to that observed clinically, and identified interferon-gamma as a mediator of the process. This study evaluated whether sirolimus (SRL), with cyclosporine A (CsA) or alone, affects TA, and examined possible mechanisms of action. METHODS: CB17/SCID/bg mice were transplanted with human arteries replacing the abdominal aorta; reconstituted with allogeneic human PBMC. Controls received vehicle alone for comparison with mice given CsA (5 mg/kg/d), SRL (0.1 or 0.5 mg/kg/d), or CsA (5 mg/kg/d) plus SRL (0.1 mg/kg/d). Transplant arteries were examined 28 days later by histology and immunohistochemistry; circulating human interferon-gamma was evaluated by ELISA, and intragraft interferon-gamma mRNA by qRT-PCR. RESULTS: The characteristic TA was modestly reduced by CsA or low-dose SRL, but eliminated by combination CsA plus SRL or higher dose SRL alone. Circulating interferon-gamma was reduced by CsA, but inhibition was dramatic with SRL alone or combined with CsA. Intragraft interferon-gamma and HLA-DR expression were moderately reduced by CsA or SRL, and eliminated with combined CsA plus SRL. CONCLUSIONS: SRL plus CsA prevented allograft arteriopathy, correlating with suppression of intragraft interferon-gamma, suggesting that SRL effects may result from anti-inflammatory consequences from inhibiting interferon-gamma.

Amelioration of human allograft arterial injury by atorvastatin or simvastatin correlates with reduction of interferon-gamma production by infiltrating T cells.

BACKGROUND: Graft arteriosclerosis (GA) is an important factor limiting long-term outcomes after organ transplantation. We have used a chimeric humanized mouse system to model this arteriopathy in human vessels, and found that the morphologic and functional changes of experimental GA are interferon (IFN)-gamma dependent. This study evaluated whether 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, described as inhibitors of IFN-gamma production, affect GA in our model. METHODS: C.B.-17 severe combined immunodeficiency-beige mice were transplanted with human artery segments as aortic interposition grafts and inoculated with allogeneic human peripheral blood mononuclear cells (PBMCs) or replication-deficient adenovirus encoding human IFN-gamma. Transplant arteries were analyzed from recipients treated with vehicle vs. atorvastatin or simvastatin at different doses. The effects of statins on T-cell alloresponses to vascular endothelial cells were also investigated in vitro. RESULTS: Graft arteriosclerosis-like arteriopathy induced by PBMCs was reduced by atorvastatin at 30 mg/kg/day or simvastatin at 100 mg/kg/day that correlated with decreased graft-infiltrating CD3+ T cells. Circulating IFN-gamma was also reduced, as were graft IFN-gamma and IFN-gamma-inducible chemokine transcripts and graft human leukocyte antigen-DR expression. Graft arteriosclerosis directly induced by human IFN-gamma in the absence of human PBMCs was also reduced by atorvastatin, but only at the highest dose of 100 mg/kg/day. Finally, atorvastatin decreased the clonal expansion and production of interleukin-2, but not IFN-gamma, by human CD4+ T cells in response to allogeneic endothelial cells in coculture. CONCLUSIONS: Our results suggest that a benefit of statin administration in transplantation may include amelioration of GA primarily by inhibiting alloreactive T-cell accumulation and consequent IFN-gamma production and secondarily through suppression of the arterial response to IFN-gamma.