RESUMEN
Thrombocytopenia is a major complication in hematopoietic-acute radiation syndrome (H-ARS) that increases the risk of mortality from uncontrolled hemorrhage. There is a great demand for new therapies to improve survival and mitigate bleeding in H-ARS. Thrombopoiesis requires interactions between megakaryocytes (MKs) and endothelial cells. 16, 16-dimethyl prostaglandin E2 (dmPGE2), a longer-acting analogue of PGE2, promotes hematopoietic recovery after total-body irradiation (TBI), and various angiotensin-converting enzyme (ACE) inhibitors mitigate endothelial injury after radiation exposure. Here, we tested a combination therapy of dmPGE2 and lisinopril to mitigate thrombocytopenia in murine models of H-ARS following TBI. After 7.75 Gy TBI, dmPGE2 and lisinopril each increased survival relative to vehicle controls. Importantly, combined dmPGE2 and lisinopril therapy enhanced survival greater than either individual agent. Studies performed after 4 Gy TBI revealed reduced numbers of marrow MKs and circulating platelets. In addition, sublethal TBI induced abnormalities both in MK maturation and in in vitro and in vivo platelet function. dmPGE2, alone and in combination with lisinopril, improved recovery of marrow MKs and peripheral platelets. Finally, sublethal TBI transiently reduced the number of marrow Lin-CD45-CD31+Sca-1- sinusoidal endothelial cells, while combined dmPGE2 and lisinopril treatment, but not single-agent treatment, accelerated their recovery. Taken together, these data support the concept that combined dmPGE2 and lisinopril therapy improves thrombocytopenia and survival by promoting recovery of the MK lineage, as well as the MK niche, in the setting of H-ARS.
Asunto(s)
16,16-Dimetilprostaglandina E2/uso terapéutico , Síndrome de Radiación Aguda/tratamiento farmacológico , Inhibidores de la Enzima Convertidora de Angiotensina/uso terapéutico , Plaquetas/efectos de los fármacos , Células Endoteliales/efectos de los fármacos , Trastornos Hemorrágicos/tratamiento farmacológico , Lisinopril/uso terapéutico , Megacariocitos/efectos de los fármacos , Trombocitopenia/tratamiento farmacológico , Trombopoyesis/efectos de los fármacos , Síndrome de Radiación Aguda/complicaciones , Animales , Plaquetas/efectos de la radiación , Médula Ósea/efectos de los fármacos , Médula Ósea/efectos de la radiación , Proteína C-Reactiva/análisis , Radioisótopos de Cesio , Evaluación Preclínica de Medicamentos , Células Endoteliales/efectos de la radiación , Endotelio Vascular/efectos de los fármacos , Endotelio Vascular/efectos de la radiación , Femenino , Rayos gamma/efectos adversos , Trastornos Hemorrágicos/etiología , Megacariocitos/efectos de la radiación , Ratones , Ratones Endogámicos C57BL , Selectina-P/análisis , Agregación Plaquetaria/efectos de los fármacos , Agregación Plaquetaria/efectos de la radiación , Factor Plaquetario 4/análisis , Traumatismos Experimentales por Radiación/tratamiento farmacológico , Traumatismos Experimentales por Radiación/etiología , Trombocitopenia/etiología , Trombopoyesis/efectos de la radiación , Irradiación Corporal Total , Factor de von Willebrand/análisisRESUMEN
PDZ domains are common 80- to 90-amino-acid regions named after the first three proteins discovered to share these domains: postsynaptic density 95, discs large, and zonula occludens. PDZ domain-containing proteins typically interact with the C-terminus of membrane receptors. Glutamate receptor interacting protein 1 (GRIP1), a seven-PDZ domain protein scaffold, regulates glutamate receptor surface expression and trafficking in neurons. We have found that human and mouse T cells also express GRIP1. T cell-specific GRIP1(-/-) mice >11 weeks old had prolonged cardiac allograft survival. Compared with wild-type T cells, in vitro stimulated GRIP1(-/-) T cells had decreased expression of activation markers and increased apoptotic surface marker expression. Surface expression of the strong T cell inhibitory molecule cytotoxic T lymphocyte antigen-4 (CTLA-4) was increased on GRIP1(-/-) T cells from mice >11 weeks old. CTLA-4 increases with T cell stimulation and its surface expression on GRIP1(-/-) T cells remained high after stimulation was removed, indicating a possible internalization defect in GRIP1-deficient T cells. CTLA-4-blocking antibody treatment following heart transplantation led to complete rejection in T cell GRIP1(-/-) mice, indicating that increased CTLA-4 surface expression contributed to the extended graft survival. Our data indicate that GRIP1 regulates T cell activation by regulating CTLA-4 surface expression.