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MSC-secreted TGF-? regulates lipopolysaccharide-stimulated macrophage M2-like polarization via the Akt/FoxO1 pathway.

ABSTRACT: BACKGROUND:An uncontrolled inflammatory response is a critical pathophysiological feature of sepsis. Mesenchymal stem cells (MSCs) induce macrophage phenotype polarization and reduce inflammation in sepsis. MSC-secreted transforming growth factor beta (TGF-?) participated in the immune modulatory function of MSCs. However, the underlying mechanism of MSC-secreted TGF-? was not fully elucidated in regulation macrophage M2-like polarization. METHODS:The paracrine effects of MSCs on macrophage polarization were studied using a co-culture protocol with LPS-stimulated RAW264.7 cells/mouse peritoneal macrophages and MSCs. The effect of TGF-? in the co-culture system was blocked by the TGF-? receptor inhibitor. To determine the role of MSC-secreted TGF-?, we used recombinant TGF-? to culture with LPS-stimulated RAW264.7 cells. In addition, we employed antibody microarray analysis to determine the mechanisms of MSC secreted TGF-? on LPS-stimulated RAW264.7 cell/mouse peritoneal macrophage M2-like polarization. Furthermore, we used an Akt inhibitor and a FoxO1 inhibitor to inhibit the Akt/FoxO1 pathway. The nuclear translocation of FoxO1 was detected by Western blot. RESULTS:MSCs induced LPS-stimulated RAW264.7 cell/mouse peritoneal macrophage polarization towards the M2-like phenotype and significantly reduced pro-inflammatory cytokine levels via paracrine, which was inhibited by TGF-? receptor inhibitor. Furthermore, we found that MSC-secreted TGF-? enhanced the macrophage phagocytic ability. The antibody microarray analysis and Western blot verified that TGF-? treatment activated the Akt/FoxO1 pathway in LPS-stimulated macrophages, TGF-?-induced FoxO1 nuclear translocation and obviously expressed in the cytoplasm, the effects of TGF-? regulatory effects on LPS-stimulated macrophage were inhibited by pre-treatment with Akt inhibitor and FoxO1 inhibitor. CONCLUSIONS:TGF-? secreted by MSCs could skew LPS-stimulated macrophage polarization towards the M2-like phenotype, reduce inflammatory reactions, and improve the phagocytic ability via the Akt/FoxO1 pathway, providing potential therapeutic strategies for sepsis.

SUBMITTER: Liu F

PROVIDER: S-EPMC6878630 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Project description:BackgroundAfter surgery, wound recovery in diabetic patients may be disrupted due to delayed inflammation, which can lead to undesired consequences, and there is currently a lack of effective measures to address this issue. Mesenchymal stem cell (MSC)-derived exosomes (Exo) have been proven to be appropriate candidates for diabetic wound healing through the anti-inflammatory effects. In this study, we investigated whether melatonin (MT)-pretreated MSCs-derived exosomes (MT-Exo) could exert superior effects on diabetic wound healing, and we attempted to elucidate the underlying mechanism.MethodsFor the evaluation of the anti-inflammatory effect of MT-Exo, in vitro and in vivo studies were performed. For in vitro research, we detected the secreted levels of inflammation-related factors, such as IL-1?, TNF-? and IL-10 via ELISA and the relative gene expression of the IL-1?, TNF-?, IL-10, Arg-1 and iNOS via qRT-PCR and investigated the expression of PTEN, AKT and p-AKT by Western blotting. For in vivo study, we established air pouch model and streptozotocin (STZ)-treated diabetic wound model, and evaluated the effect of MT-Exo by flow cytometry, optical imaging, H&E staining, Masson trichrome staining, immunohistochemical staining, immunofluorescence, and qRT-PCR (?-SMA, collagen I and III).ResultsMT-Exo significantly suppressed the pro-inflammatory factors IL-1? and TNF-? and reduced the relative gene expression of IL-1?, TNF-? and iNOS, while promoting the anti-inflammatory factor IL-10 along with increasing the relative expression of IL-10 and Arg-1, compared with that of the PBS, LPS and the Exo groups in vitro. This effect was mediated by the increased ratio of M2 polarization to M1 polarization through upregulating the expression of PTEN and inhibiting the phosphorylation of AKT. Similarly, MT-Exo significantly promoted the healing of diabetic wounds by inhibiting inflammation, thereby further facilitating angiogenesis and collagen synthesis in vivo.ConclusionsMT-Exo could promote diabetic wound healing by suppressing the inflammatory response, which was achieved by increasing the ratio of M2 polarization to M1 polarization through activating the PTEN/AKT signalling pathway, and the pretreatment of MT was proved to be a promising method for treating diabetic wound healing.Graphical abstract: MT-Exo promotes diabetic wound healing by regulating M1 and M2 macrophage polarization.

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MSC-secreted TGF-? regulates lipopolysaccharide-stimulated macrophage M2-like polarization via the Akt/FoxO1 pathway.

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