Abrogation of chronic rejection in rat model system involves modulation of the mTORC1 and mTORC2 pathways.
Academic Article
Overview
abstract
BACKGROUND: Current immunosuppressive regimens fail to avert chronic rejection (CR) of transplanted organs; however, selective targeting of actin-cytoskeletal regulators decreases T-cell motility and abrogates CR in rat model system. Administration of mutated class I major histocompatibility complex molecules or selective targeting of the RhoA pathway, which controls T-cell cytoskeletal activity, using Y27632 (a selective Rock1 inhibitor) resulted in reduced T-cell infiltration and abrogation of CR as judged from the neointimal index (13.9±19.7 vs. 45±37.5; P<0.001) and the number of affected vessels (30% vs. 60%; P<0.01). Here, we examined the role of mammalian target of rapamycin (mTOR) pathway in inhibition of CR. METHODS: A mutated class I major histocompatibility complex molecule that eliminates CR was delivered into ACI recipients of Wistar-Furth hearts at the time of transplantation with subtherapeutic cyclosporine (10 mg/kg on days 0-2). Controls included untreated and cyclosporine A-treated (10 mg/kg on days 0-2) heart allograft recipients. RESULTS: Western blotting and immunostaining showed that rat heart allografts with abolished CR exhibited down-regulation of the RAPA-sensitive mTORC1 components such as mTOR and Raptor and down-regulation of the RAPA-insensitive mTORC2 elements Rictor and Sin1. The mTOR regulator Deptor and its downstream target Rac1 were also inhibited. CONCLUSIONS: Abrogation of CR in rat model system involves modulation of two mTOR pathways: a RAPA-sensitive mTORC1 pathway regulating cellular proliferation and a RAPA-insensitive mTORC2 pathway regulating T-cell motility. Selective targeting of T-cell actin cytoskeletal pathways shows potential for pathway-targeted immunosuppression therapies.
