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Skin wound healing is a critical and complex biological process after trauma. This process is activated by signaling pathways of both epithelial and nonepithelial cells, which release a myriad of different cytokines and growth factors. Hepatocyte growth factor (HGF) is a cytokine known to play multiple roles during the various stages of wound healing. This study evaluated the benefits of HGF on reepithelialization during wound healing and investigated its mechanisms of action. Gross and histological results showed that HGF significantly accelerated reepithelialization in diabetic (DB) rats. HGF increased the expressions of the cell adhesion molecules β1-integrin and the cytoskeleton remodeling protein integrin-linked kinase (ILK) in epidermal cells in vivo and in vitro. Silencing of ILK gene expression by RNA interference reduced expression of β1-integrin, ILK, and c-met in epidermal cells, concomitantly decreasing the proliferation and migration ability of epidermal cells. β1 -Integrin can be an important maker of poorly differentiated epidermal cells. Therefore, these data demonstrate that epidermal cells become poorly differentiated state and regained some characteristics of epidermal stem cells under the role of HGF after wound. Taken together, the results provide evidence that HGF can accelerate reepithelialization in skin wound healing by dedifferentiation of epidermal cells in a manner related to the β1-integrin/ILK pathway. [ABSTRACT FROM AUTHOR]

Interleukin 6 (IL-6) influences the growth and survival of multiple myeloma (MM) cells via the activation of multiple signalling cascades. Although sphingosine kinase (SPHK) signalling is known to play important roles in the regulation of cell proliferation and apoptosis, the role of SPHK activation in IL-6 signalling and in the pathology of MM remains unclear. This study found that IL-6 activated SPHK in MM cells, which mediates the suppressive effects of IL-6 on MM cell apoptosis. Both MM cell lines and primary MM cells constitutively expressed SPHK, and treatment of MM cells with IL-6 resulted in activation of SPHK in a concentration-dependent manner. Specific inhibitors of the phosphatidylinositol-3 kinase and extracellular signal-regulated kinase/mitogen-activated protein kinase pathways blocked the IL-6-induced activation of SPHK. It was further demonstrated that IL-6-induced activation of SPHK inhibited dexamethasone-induced apoptosis of MM cells. IL-6 stimulation or retroviral-mediated overexpression of SPHK1 in MM cells resulted in increased intracellular SPHK activity and upregulation of myeloid cell leukaemia-1 (Mcl-1), leading to increased cell proliferation and survival. Conversely, inhibition of SPHK1 by small interfering RNA reduced IL-6-induced upregulation of Mcl-1 and blocked the suppressive effect of IL-6 on MM cell apoptosis. Taken together, these results delineate a key role for SPHK activation in IL-6-induced proliferation and survival of MM cells, and suggest that SPHK may be a potential new therapeutic target in MM. [ABSTRACT FROM AUTHOR]