Ghrelin therapy mitigates bone marrow injury and splenocytopenia by sustaining circulating G-CSF and KC increases after irradiation combined with wound.

Background: Radiation injury combined wound (CI) enhances acute radiation syndrome and subsequently mortality as compared to radiation injury alone (RI). We previously reported that ghrelin (a 28-amino-acid-peptide secreted from the stomach) treatment significantly increased a 30-day survival, mitigated hematopoietic death, circulating white blood cell (WBC) depletion and splenocytopenia and accelerated skin-wound healing on day 30 after CI. Herein, we aimed to study the ghrelin efficacy at early time points after CI.

Methods: B6D2F1/J female mice were exposed to Co-γ-photon radiation at 9.5 Gy (LD) followed by a 15% total-body-surface-area skin wound. Several endpoints were measured at 4-5 h, days 1, 3, 7 and 15.

Results: Histological analysis of sternums on day 15 showed that CI induced more adipocytes and less megakaryocytes than RI. Bone marrow cell counts from femurs also indicated CI resulted in lower bone marrow cell counts on days 1, 7 and 15 than RI. Ghrelin treatment mitigated these CI-induced adverse effects. RI and CI decreased WBCs within 4-5 h and continued to decrease to day 15. Ghrelin treatment mitigated decreases in CI mice, mainly from all types of WBCs, but not RBCs, hemoglobin levels and hematocrit values. Ghrelin mitigated the CI-induced thrombocytopenia and splenocytopenia. CI increased granulocyte-colony stimulating factor (G-CSF) and keratinocyte chemoattractant (KC) in blood and bone marrow. Ghrelin therapy was able to enhance and sustain the increases in serum on day 15, probably contributed by spleen and ileum, suggesting the correlation between G-CSF and KC increases and the neutropenia mitigation. Activated caspase-3 levels in bone marrow cells were significantly mitigated by ghrelin therapy on days 3 and 15.

Conclusions: Our novel results are the first to suggest that ghrelin therapy effectively decreases hematopoietic death and splenocytopenia by sustaining circulating G-CSF and KC increases after CI. These results demonstrate efficacy of ghrelin as a radio-mitigator/therapy agent for CI.