CXCL8 enhances the angiogenic activity of umbilical cord blood-derived outgrowth endothelial cells in vitro.

OECs (outgrowth endothelial cells), also known as late-EPCs (late-endothelial progenitor cells), have a high proliferation potential in addition to in vitro tube formation capability. In ischaemic animal models, injected OECs were integrated into regenerating blood vessels and improved neovascularization. Previous reports have demonstrated the expression of CXCL8 to be up-regulated in ischaemic tissues. It has also been documented that CXCL8 stimulates the angiogenic activity of mature ECs (endothelial cells). Therefore, it has been suggested that CXCL8 plays an important role in neovascularization in ischaemic tissues. However, it is still uncertain whether CXCL8 also stimulates the angiogenic activity of OECs. This study evaluated the effects of CXCL8 on the angiogenic activity of OECs in vitro. OECs were isolated from human UCB (umbilical cord blood)-derived mononuclear cells. Phenotypes of the OECs were assessed by flow cytometry, immunostaining, and real-time RT (reverse transcription)-PCR. The effects of CXCL8 on OECs were investigated by transwell migration assay and capillary tube formation assay on Matrigel. The OEC clones isolated from UCB expressed OEC phenotypes. In addition, CXCL8 receptors (CXCR1 and CXCR2) were expressed on these OEC clones. CXCL8 significantly stimulated the transwell migration and capillary tube formation of OECs. Neutralizing antibody against CXCR2, but not CXCR1, abolished a transwell migration of OECs induced by CXCL8, suggesting the involvement of CXCL8/CXCR2 axis in transwell migration. These results demonstrate that CXCL8 stimulates the angiogenic activity of UCB-derived OECs in vitro.

Marginal expression of CXCR4 on c-kit(+)Sca-1 (+)Lineage (-) hematopoietic stem/progenitor cells.

Stromal cell-derived factor 1 (SDF-1) and its receptor CXCR4 are the key regulatory molecules of hematopoietic stem cell (HSC) migration and engraftment to the bone marrow (BM) microenvironment. However, the significance of the ligand-receptor complex on HSC in steady-state BM is not clear. There is currently a lack of information as to how CXCR4 is expressed on HSCs. We herein demonstrate that c-kit(+)Sca-1(+)Lineage(-) (KSL) cells freshly isolated from BM expressed very low to undetectable levels of CXCR4. Two hours of incubation at 37 degrees C quickly up-modulated the receptor expression on KSL cells. Protein synthesis was not required for this early stage up-regulation, thus suggesting the emergence of intracellularly pooled receptors to the cell surface. However, protein synthesis was involved at the later stage of up-regulation. The up-regulated CXCR4 was functional, as evidenced by the fact that the incubated KSL cells more efficiently migrated to the SDF-1 gradient in vitro. Therefore, although KSL cells are able to express functional CXCR4, the receptors are only marginally expressed in the steady-state BM microenvironment. These observations therefore indicate the limited role of the SDF-1-CXCR4 axis on HSC functionality in a static BM environment.

Cytokine-dependent modification of IL-12p70 and IL-23 balance in dendritic cells by ligand activation of Valpha24 invariant NKT cells.

CD1d-restricted invariant NKT (iNKT) cells play crucial roles in various types of immune responses, including autoimmune diseases, infectious diseases and tumor surveillance. The mechanisms underlying their adjuvant functions are well understood. Nevertheless, although IL-4 and IL-10 production characterize iNKT cells able to prevent or ameliorate some autoimmune diseases and inflammatory conditions, the precise mechanisms by which iNKT cells exert immune regulatory function remain elusive. This study demonstrates that the activation of human iNKT cells by their specific ligand alpha-galactosylceramide enhances IL-12p70 while inhibiting the IL-23 production by monocyte-derived dendritic cells, and in turn down-regulating the IL-17 production by memory CD4(+) Th cells. The ability of the iNKT cells to regulate the differential production of IL-12p70/IL-23 is mainly mediated by a remarkable hallmark of their function to produce both Th1 and Th2 cytokines. In particular, the down-regulation of IL-23 is markedly associated with a production of IL-4 and IL-10 from iNKT cells. Moreover, Th2 cytokines, such as IL-4 and IL-13 play a crucial role in defining the biased production of IL-12p70/IL-23 by enhancement of IL-12p70 in synergy with IFN-gamma, whereas inhibition of the IFN-gamma-promoted IL-23 production. Collectively, the results suggest that iNKT cells modify the IL-12p70/IL-23 balance to enhance the IL-12p70-induced cell-mediated immunity and suppress the IL-23-dependent inflammatory pathologies. These results may account for the long-appreciated contrasting beneficial and adverse consequence of ligand activation of iNKT cells.

H11 has dose-dependent and dual hypertrophic and proapoptotic functions in cardiac myocytes.

We have shown previously that H11, a serine/threonine kinase, is up-regulated in a heart subjected to ischaemia/reperfusion. In the present study, we have characterized the cellular function of H11, using neonatal rat cardiac myocytes. Although transduction of adenovirus harbouring H11 at low doses increased the cell size, at higher doses it induced apoptosis in cardiac myocytes. Apoptosis was not observed when adenovirus harbouring H11-KI (kinase-inactive mutant of H11) was used, suggesting that the proapoptotic effect of H11 is kinase-dependent. The hypertrophic effect of H11 at high doses was unmasked when apoptosis was inhibited by the caspase inhibitor DEVD-CHO, suggesting that H11 stimulates both hypertrophy and apoptosis in parallel. H11-KI induced hypertrophy even at high doses, indicating that H11 stimulates hypertrophy through kinase-independent mechanisms. H11-KI activated Akt, and cardiac hypertrophy induced by H11-KI was blocked by LY294002, an inhibitor of phosphoinositide 3-kinase. Co-immunoprecipitation analyses indicated that H11 interacts with the alpha subunit of CK2 (casein kinase 2). Overexpression of H11 decreased the kinase activity of CK2. DRB (5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole), an inhibitor of CK2, mimicked the effect of H11, whereas DRB and H11 failed to exhibit additive effects on apoptosis, suggesting that H11 and DRB utilize a common mechanism to induce apoptosis, namely inhibition of CK2. In summary, H11 is a dual-function kinase in cardiac cells: it induces hypertrophy at low doses through kinase-independent activation of Akt, whereas it causes apoptosis at high doses through protein kinase-dependent mechanisms, in particular by physical interaction with and subsequent inhibition of CK2.

H11 kinase is a novel mediator of myocardial hypertrophy in vivo.

By subtractive hybridization, we found a significant increase in H11 kinase transcript in large mammalian models of both ischemia/reperfusion (stunning) and chronic pressure overload with hypertrophy. Because this gene has not been characterized in the heart, the goal of the present study was to determine the function of H11 kinase in cardiac tissue, both in vitro and in vivo. In isolated neonatal rat cardiac myocytes, adenoviral-mediated overexpression of H11 kinase resulted in a 37% increase in protein/DNA ratio, reflecting hypertrophy. A cardiac-specific transgene driven by the alphaMHC-promoter was generated, which resulted in an average 7-fold increase in H11 kinase protein expression. Transgenic hearts were characterized by a 30% increase of the heart weight/body weight ratio, by the reexpression of a fetal gene program, and by concentric hypertrophy with preserved contractile function at echocardiography. This phenotype was accompanied by a dose-dependent activation of Akt/PKB and p70(S6) kinase, whereas the MAP kinase pathway was unaffected. Thus, H11 kinase represents a novel mediator of cardiac cell growth and hypertrophy.

Reduction in the extent of atherosclerosis in apolipoprotein E-deficient mice induced by electroporation-mediated transfer of the human plasma platelet-activating factor acetylhydrolase gene into skeletal muscle.

The effect of increasing the activity of plasma platelet-activating factor (PAF) acetylhydrolase (AH) (PAF-AH) on the progression of atherosclerosis in apolipoprotein E-deficient (apoE(-/-)) mice was examined by gene delivery to skeletal muscle. The expression vector pcDNA3.1 containing either human PAF-AH cDNA (pcDNA/PAF-AH) or green fluorescent protein cDNA (pcDNA/GFP) was introduced into the skeletal muscle of both hind legs of 6-week-old apoE(-/-) mice by electroporation. The activity of PAH-AH in plasma was significantly increased 4-16 weeks after electroporation of apoE(-/-) mice with 120 microg of pcDNA/PAF-AH; the maximal (2.5-fold) increase was apparent after 8 weeks. The mean thickness of the aortic wall, determined by 160 measurements in each mouse, was significantly reduced in apoE(-/-) mice 8-16 weeks after exposure to pcDNA/PAF-AH compared with that in corresponding control animals that received pcDNA/GFP. These results suggest that the electrotransfer of the plasma PAF-AH gene to skeletal muscle reduces the extent of atherosclerosis in apoE(-/-) mice.