Mitochondrial Complexes I and II Are More Susceptible to Autophagy Deficiency in Mouse beta-Cells

BACKGROUND: Damaged mitochondria are removed by autophagy. Therefore, impairment of autophagy induces the accumulation of damaged mitochondria and mitochondrial dysfunction in most mammalian cells. Here, we investigated mitochondrial function and the expression of mitochondrial complexes in autophagy-related 7 (Atg7)-deficient beta-cells. METHODS: To evaluate the effect of autophagy deficiency on mitochondrial function in pancreatic beta-cells, we isolated islets from Atg7(F/F):RIP-Cre+ mice and wild-type littermates. Oxygen consumption rate and intracellular adenosine 5'-triphosphate (ATP) content were measured. The expression of mitochondrial complex genes in Atg7-deficient islets and in beta-TC6 cells transfected with siAtg7 was measured by quantitative real-time polymerase chain reaction. RESULTS: Baseline oxygen consumption rate of Atg7-deficient islets was significantly lower than that of control islets (P<0.05). Intracellular ATP content of Atg7-deficient islets during glucose stimulation was also significantly lower than that of control islets (P<0.05). By Oxygraph-2k analysis, mitochondrial respiration in Atg7-deficient islets was significantly decreased overall, although state 3 respiration and responses to antimycin A were unaffected. The mRNA levels of mitochondrial complexes I, II, III, and V in Atg7-deficient islets were significantly lower than in control islets (P<0.05). Down-regulation of Atg7 in beta-TC6 cells also reduced the expression of complexes I and II, with marginal significance (P<0.1). CONCLUSION: Impairment of autophagy in pancreatic beta-cells suppressed the expression of some mitochondrial respiratory complexes, and may contribute to mitochondrial dysfunction. Among the complexes, I and II seem to be most vulnerable to autophagy deficiency.

Bone marrow stem/progenitor cell mobilization in C57BL/6J and BALB/c mice / 한국실험동물학회지

Bone marrow (BM) has been considered as a reservoir of stem/progenitor cells which are able to differentiate into ectodermal, endodermal, and mesodermal origins in vitro as well as in vivo. Following adequate stimulation, such as granulocyte stimulating factor (G-CSF) or AMD3100, BM resident stem/progenitor cells (BMSPCs) can be mobilized to peripheral blood. Several host-related factors are known to participate in this mobilization process. In fact, a significant number of donors are resistant to G-CSF induced mobilization protocols. AMD3100 is currently used in combination with G-CSF. However, information regarding host-related factors which may influence the AMD3100 directed mobilization is extremely limited. In this study, we were to get some more knowledge on the host-related factors that affect the efficiency of AMD3100 induced mobilization by employing in vivo mobilization experiments. As a result, we found that C57BL/6J mice are more sensitive to AMD3100 but less sensitive to G-CSF which promotes the proliferation of BMSPCs. We excluded S1P as one of the host related factor which influences AMD3100 directed mobilization because pre-treatment of S1P receptor antagonist FTY720 did not inhibit BMSPC mobilization. Further in vitro experiments revealed that BALB/c mice, compared to C57BL/6J mice, have less BMSPCs which migrate in response to host related factors such as sphingosine-1-phosphate (S1P) and to CXCL12. We conclude that AMD3100-directed mobilization depends on the number of BMSPCs rather than on the host-related factors. These results suggest that the combination of AMD3100 and G-CSF is co-operative and is optimal for the mobilization of BMSPCs.

Kinetics of IFN-gamma and IL-17 Production by CD4 and CD8 T Cells during Acute Graft-versus-Host Disease

Graft-versus-host disease (GVHD) is a fatal complication that occurs after allogeneic hematopoietic stem cell transplantation. To understand the dynamics of CD4 and CD8 T cell production of IFN-gamma and IL-17 during GVHD progression, we established a GVHD model by transplanting T cell-depleted bone marrow (TCD-BM) and purified T cells from B6 mice into irradiated BALB.B, creating an MHC-matched but minor histocompatibility (H) antigen-mismatched transplantation (B6 --> BALB.B GVHD). Transplantation-induced GVHD was confirmed by the presence of the appropriate compositional changes in the T cell compartments and innate immune cells in the blood and the systemic secretion of inflammatory cytokines. Using this B6 --> BALB.B GVHD model, we showed that the production of IFN-gamma and IL-17 by CD4 T cells preceded that by CD8 T cells in the spleen, mesenteric lymph node, liver, and lung in the BALB.B GVHD host, and Th1 differentiation predated Th17 differentiation in all organs during GVHD progression. Such changes in cytokine production were based on changes in cytokine gene expression by the T cells at different time points during GVHD development. These results demonstrate that both IFN-gamma and IL-17 are produced by CD4 and CD8 T cells but with different kinetics during GVHD progression.

Granulocyte-Derived Cationic Peptide Enhances Homing and Engraftment of Bone Marrow Stem Cells after Transplantation / 한국실험동물학회지

Current strategies to accelerate hematopoietic reconstitution after transplantation include transplantation of greater numbers of hematopoietic stem/progenitor cells (HSPCs) or ex vivo expansion of harvested HSPCs before transplant. However, the number of cells available for transplantation is usually low, and strategies to expand HSPCs and maintain equivalent engraftment capability ex vivo are limited. We noted that activated granulocyte-derived cationic peptides positively primed responsiveness of HSPCs to a CXCL12 gradient. Accordingly, we noted that accelerated homing/engraftment of beta-defensin-2, a well-known antimicrobial cationic peptide, primed bone marrow nucleated cells (BMNCs) compared to normal BMNCs after transplantation into lethally irradiated recipients. We envision that small cationic peptides, which primarily possess antimicrobial functions and are harmless to mammalian cells, could be applied to prime HSPCs before transplantation. This novel approach would be particularly important in cord blood transplantation, where the number of HSPCs available for transplantation is usually limited.