Hemangiopoietin inhibits apoptosis of MO7e leukemia cells through phosphatidylinositol 3-kinase-AKT pathway

Recombinant hemangiopoietin promotes cell adhesion and binds heparin in its multimeric form

Hemangiopoietin (HAPO) is a novel growth factor stimulating the proliferation of hematopoietic and endothelial progenitor cells in vitro and in vivo. The native protein is a 294‑amino acid multimodular protein. The N‑terminus constitutes of two somatomedin B (SMB) homology domains that contain 14 cysteines. The central region is a putative heparin‑binding domain (pHBD) and the C‑terminus contains mucin‑like repeats. In the present study, we demonstrated that prokaryotic recombinant human HAPO (rhHAPO) self‑associates into a multimeric form with a mass weight of ~129 kDa, suggesting a homologous tetramer. rhHAPO in its multimeric form was found to be more stable and more potent in promoting HESS‑5 cell adhesion. Multimeric rhHAPO had a higher affinity to heparin compared with its dimeric form, although there was no significant conformational change. C‑terminal repeats-truncated rhHAPO (rhHAPOΔmucin) was also found to be assembled into a multimer, while deletion of pHBD (rhHAPOΔmucin‑pHBD) caused the protein to remain in a dimeric form, demonstrating that SMB domains participate in self‑aggregation of the molecule and that the pHBD region promotes the tetramerization.

Production of bioactive human hemangiopoietin in Escherichia coli

To devise an efficient approach for production of human hemangiopoietin (hHAPO), the gene of hHAPO was synthesized and subcloned into the pSUMO vector with a SUMO tag at the N-terminus. The expression construct was then transformed into the expression strain E. coli BL21(DE3). The fusion protein was expressed in soluble form and identified by SDS-PAGE and Western blotting. The fusion protein was purified to 90% purity by metal chelate chromatography with a yield of 45 mg per liter fermentation culture. The SUMO tag was removed by cleavage with SUMO protease at room temperature for 1 h, and the hHAPO was then re-purified by the metal chelate chromatography. Finally, about 21 mg hHAPO was obtained from 1 liter of fermentation culture with no less than 95% purity. The recombinant hHAPO significantly stimulated the proliferation of human umbilical vein endothelial cells.

Hemangiopoietin supports animal survival and accelerates hematopoietic recovery of chemotherapy-suppressed mice

OBJECTIVE

To determine if recombinant human hemangiopoietin (HAPO), a novel growth factor for primitive cells of hematopoietic and endothelial cell lineages, accelerates hematopoietic reconstitution after high-dose chemotherapy in vivo in mice.

METHODS

Male Balb/c mice after treatment of 5-fluorouracil were subcutaneously injected with HAPO or its dilution for consecutive 10 d. Their survival and body weight together with peripheral blood were routinely tested. At day 7 and 14, the numbers of bone marrow (BM) cells as well as colony-forming units (CFU) after in vitro colony culture were counted. The peripheral blood CFU and the percentage of CD34+ CD117+ cells in BM were analyzed. Transwell chamber was used for cell migratory assay.

RESULTS

HAPO at different doses significantly increased the survival rate and body weight, with an optimal effect in the HAPO 10 microg/d group. The number of BM cells and the percentage of CD34+ CD117+ cells were also increased after HAPO administration. The number of granulocyte/macrophage CFU and granulocyte, erythroid, macrophage and megakaryocyte CFU in BM after HAPO treatment was greater than that from the HAPO dilution group. More circulating CFU could be observed after injection of HAPO. In addition, this novel cytokine had a chemotactic effect on the hematopoietic stem/progenitor cells.

CONCLUSION

HAPO improves animal survival and accelerates hematopoietic reconstitution of mice after high-dose chemotherapy.

Lovastatin protects mesenchymal stem cells against hypoxia- and serum deprivation-induced apoptosis by activation of PI3K/Akt and ERK1/2

Cell therapy with bone marrow-derived mesenchymal stem cells (MSCs) has been shown to have great promises in cardiac repair after myocardial infarction. However, poor viability of transplanted MSCs in the infracted heart has limited the therapeutic efficacy. Our previous studies have shown in vitro that rat MSCs undergo caspase-dependent apoptosis in response to hypoxia and serum deprivation (Hypoxia/SD). Recent findings have implicated statins, an established class of cholesterol-lowering drugs, enhance the survival of cells under various conditions. In this study, we investigated the effect of lovastatin on rat MSCs apoptosis induced by Hypoxia/SD, focusing in particular on regulation of mitochondrial apoptotic pathway and the survival signaling pathways. We demonstrated that lovastatin (0.01-1 microM) remarkably prevented MSCs from Hypoxia/SD-induced apoptosis through inhibition of the mitochondrial apoptotic pathway, leading to attenuation of caspase-3 activation. The loss of mitochondrial membrane potential and cytochrome-c release from mitochondria to cytosol were significantly inhibited by lovastatin. Furthermore, the antiapoptotic effect of lovastatin on mitochondrial apoptotic pathway was effectively abrogated by both PI3K inhibitor, LY294002 and ERK1/2 inhibitor, U0126. The phosphorylations of Akt/GSK3 beta and ERK1/2 stimulated by lovastatin were detected. The activation of ERK1/2 was inhibited by a PI3K inhibitor, LY294002, but U0126, a ERK1/2 inhibitor did not inhibit phosphorylation of Akt and GSK3 beta. These data demonstrate that lovastatin protects MSCs from Hypoxia/SD-induced apoptosis via PI3K/Akt and MEK/ERK1/2 pathways, suggesting that it may prove a useful therapeutic adjunct for transplanting MSCs into damaged heart after myocardial infarction.