CELLULAR SENESCENCE IMPLICATED IN SEPSIS-INDUCED MUSCLE WEAKNESS AND AMELIORATED WITH METFORMIN.

ABSTRACT: Background: Sepsis is a life-threatening medical emergency, frequently complicated with intensive care unit-acquired weakness syndrome (ICU-AW). ICU-AW patients display flaccid weakness of the limbs, especially in the proximal limb muscles. However, little is known regarding its pathogenesis. Here, we aimed to identify the potential signaling pathway involved in ICU-AW regulation and identify a potential therapeutic drug for intervention. Methods: Both in vivo and in vitro septic mice were used. For the in vivo septic mice, either cecum ligation and puncture or intraperitoneal injection of LPS was conducted in mice. The body weight and muscle mass were then measured and recorded. Muscle strength was evaluated by limb grip strength test. The expression of proteins extracted from cells and muscles was checked through Western blot analysis. Quantitative reverse transcription-polymerase chain reaction was carried out to test the transcriptional level of genes. Senescence-associated ß-galactosidase (SA-ß-gal) staining and Sirius red for collagen staining were conducted. Metformin, as an antiaging agent, was then tested for any attenuation of sepsis-related symptoms. For in vitro sepsis modeling, myoblasts were treated with LPS, analyzed for senescence-related protein expression, and subsequently retested upon metformin treatment. Results: We found that both the weight and strength of muscle were dramatically reduced in cecum ligation and puncture- or LPS-induced septic mice. RNA-seq analysis revealed that various cellular senescent genes were involved in sepsis. In line with this, expression of senescence-related genes, p53 and p21 were both upregulated. Both SA-ß-gal and Sirius red for collagen staining were enhanced in tibialis anterior muscles. Notably, inhibition of p53 expression by siRNA prominently reduced the number of SA-ß-gal-positive myoblasts upon LPS treatment. This indicated sepsis-induced cellular senescence to be dependent on p53. Consistent with the function of metformin in antiaging, metformin attenuated cellular senescence in both murine myoblasts and skeletal muscles during sepsis. Muscle strength of septic mice was improved upon metformin treatment. Metformin intervention is therefore proposed as a potential therapeutic strategy for ICU-AW. Conclusion: Taken together, we revealed a previously unappreciated linkage between cellular senescence and sepsis-induced muscle weakness and propose metformin as a potential therapeutic drug for the treatment of ICU-AW.

Rab5a activates IRS1 to coordinate IGF-AKT-mTOR signaling and myoblast differentiation during muscle regeneration.

Rab5 is a master regulator for endosome biogenesis and transport while its in vivo physiological function remains elusive. Here, we find that Rab5a is upregulated in several in vivo and in vitro myogenesis models. By generating myogenic Rab5a-deficient mice, we uncover the essential roles of Rab5a in regulating skeletal muscle regeneration. We further reveal that Rab5a promotes myoblast differentiation and directly interacts with insulin receptor substrate 1 (IRS1), an essential scaffold protein for propagating IGF signaling. Rab5a interacts with IRS1 in a GTP-dependent manner and this interaction is enhanced upon IGF-1 activation and myogenic differentiation. We subsequently identify that the arginine 207 and 222 of IRS1 and tyrosine 82, 89, and 90 of Rab5a are the critical amino acid residues for mediating the association. Mechanistically, Rab5a modulates IRS1 activation by coordinating the association between IRS1 and the IGF receptor (IGFR) and regulating the intracellular membrane targeting of IRS1. Both myogenesis-induced and IGF-evoked AKT-mTOR signaling are dependent on Rab5a. Myogenic deletion of Rab5a also reduces the activation of AKT-mTOR signaling during skeletal muscle regeneration. Taken together, our study uncovers the physiological function of Rab5a in regulating muscle regeneration and delineates the novel role of Rab5a as a critical switch controlling AKT-mTOR signaling by activating IRS1.

Hsp90ß interacts with MDM2 to suppress p53-dependent senescence during skeletal muscle regeneration.

Cellular senescence plays both beneficial and detrimental roles in embryonic development and tissue regeneration, while the underlying mechanism remains elusive. Recent studies disclosed the emerging roles of heat-shock proteins in regulating muscle regeneration and homeostasis. Here, we found that Hsp90ß, but not Hsp90α isoform, was significantly upregulated during muscle regeneration. RNA-seq analysis disclosed a transcriptional elevation of p21 in Hsp90ß-depleted myoblasts, which is due to the upregulation of p53. Moreover, knockdown of Hsp90ß in myoblasts resulted in p53-dependent cellular senescence. In contrast to the notion that Hsp90 interacts with and protects mutant p53 in cancer, Hsp90ß preferentially bound to wild-type p53 and modulated its degradation via a proteasome-dependent manner. Moreover, Hsp90ß interacted with MDM2, the chief E3 ligase of p53, to regulate the stability of p53. In line with these in vitro studies, the expression level of p53-p21 axis was negatively correlated with Hsp90ß in aged mice muscle. Consistently, administration of 17-AAG, a Hsp90 inhibitor under clinical trial, impaired muscle regeneration by enhancing injury-induced senescence in vivo. Taken together, our finding revealed a previously unappreciated role of Hsp90ß in regulating p53 stability to suppress senescence both in vitro and in vivo.

Chimeric Antigen Receptor-T Cells with 4-1BB Co-Stimulatory Domain Present a Superior Treatment Outcome than Those with CD28 Domain Based on Bioinformatics.

BACKGROUND: The second-generation CD19-chimeric antigen receptor (CAR)-T co-stimulatory domain that is commonly used in clinical practice is CD28 or 4-1BB. Previous studies have shown that the persistence of CAR-T in the 4-1BB co-stimulatory domain appears to be longer. METHODS: The expression profile data of GSE65856 were obtained from GEO database. After data preprocessing, the differentially expressed genes (DEGs) between the mock CAR versus CD19-28z CAR T cells and mock CAR versus CD19-BBz CAR T cells were identified using the limma package. Subsequently, functional enrichment analysis of DEGs was performed using the DAVID tool. Then, the protein-protein international (PPI) network of these DEGs was visualized by Cytoscape, and the miRNA-target gene-disease regulatory networks were predicted using Webgestal. RESULTS: A total of 18 common DEGs, 6 CD19-28z specific DEGs and 206 CD19-BBz specific DEGs were identified. Among CD19-28z specific DEGs, down-regulated PAX5 might be an important node in the PPI network and could be targeted by miR-496. In CD19-BBz group, JUN was a hub node in the PPI network and involved in the regulations of miR520D - early growth response gene 3 (EGR3)-JUN and mi-R489-AT-rich interaction domain 5A (ARID5A)-JUN networks. CONCLUSION: The 4-1BB co-stimulatory domain might play in important role in the treatment of CAR-T via miR-520D-EGR3-JUN and miR489-ARID5A-JUN regulation network, while CD28 had a negative effect on CAR-T treatment.

Activation of AKT-mTOR Signaling Directs Tenogenesis of Mesenchymal Stem Cells.

Tendon repair is a clinical challenge because of the limited understanding on tenogenesis. The synthesis of type I collagen (Collagen I) and other extracellular matrix are essential for tendon differentiation and homeostasis. Current studies on tenogenesis focused mostly on the tenogenic transcriptional factors while the signaling controlling tenogenesis on translational level remains largely unknown. Here, we showed that mechanistic target of rapamycin (mTOR) signaling was activated by protenogenic growth factor, transforming growth factors beta1, and insulin-like growth factor-I. The expression of mTOR was upregulated during tenogenesis of mesenchymal stem cells (MSCs). Moreover, mTOR was downregulated in human tendinopathy tissues and was inactivated upon statin treatment. Both inhibition and depletion of AKT or mTOR significantly reduced type I collagen production and impaired tenogenesis of MSCs. Tendon specific-ablation of mTOR resulted in tendon defect and reduction of Collagen I. However, there is no evident downregulation of tendon associated collagens at the transcription level. Our study demonstrated that AKT-mTOR axis is a key mediator of tendon differentiation and provided a novel therapeutic target for tendinopathy and tendon injuries. Stem Cells 2018;36:527-539.

Knockdown of REGγ inhibits the proliferation and migration and promotes the apoptosis of multiple myeloma cells by downregulating NF-κB signal pathway.

OBJECTIVES: This study aimed to evaluate the effects of REGγ knockdown on the proliferation, apoptosis and migration of multiple myeloma (MM) cells, and reveal the potential regulatory mechanisms. METHODS: The expression of REGγ on myeloma cells of 28 MM patients was detected by Western blot. shRNA-REGγ-1 and shRNA-REGγ-2 were constructed to downregulate REGγ in RPMI-8226 cells. The proliferation, apoptosis and migration of transfected cells were analyzed by Cell Counting Kit 8 (CCK8), flow cytometry and transwell chamber, respectively. The expression of phosphorylated p65 (p-p65), p65, NF-kappa-B inhibitor ε (IkBε), matrix metalloproteinase 2 (MMP2), B-cell lymphoma xL (Bcl-xL) and X-linked inhibitor of apoptosis protein (XIAP) in transfected cells was detected by Western blot. Using cycloheximide (CHX), the half-life period of IkBε was detected by Western blot. RESULTS: The expression of REGγ was positive in myeloma cells. The proliferation and migration of RPMI-8226 cells were significantly inhibited by shRNA-REGγ-1/shRNA-REGγ-2, while the apoptosis rates were significantly increased (p < 0.05). The expression of p-p65 and IkBε was significantly reduced in RPMI-8226 cells transfected with shRNA-REGγ-1/shRNA-REGγ-2. The degradation of IkBε was significantly lower in RPMI-8226 cells transfected with shRNA-REGγ-1 than the control (longer half-life period). Besides, the expression of MMP2, Bcl-xL and XIAP in RPMI-8226 cells was significantly inhibited by shRNA-REGγ-1/shRNA-REGγ-2. DISCUSSION: Knockdown of REGγ may inhibit the proliferation and migration, and promote the apoptosis of RPMI-8226 cells possibly by downregulating NF-κB signal pathway.

[Allogeneic hematopoietic stem cell transplantation for the treatment of mucopolysaccharidosis type 1: a case report].

Mucopolysaccharidosis type I (MPS-I) is an inborn error of metabolism with progressive multisystem involvement. Hurler syndrome is the most severe form of MPS-I that causes progressive deterioration of the central nervous system with ensuing death. This study reported the therapeutic effect of allogeneic hematopoietic stem cell transplantation (allo-HSCT) on Hurler syndrome in one case. The patient was a 25-month-old boy. He underwent allo-HSCT. The donor was his elder sister whose HLA-B locus was not matching. The reduced-intensity of BuCy conditioning regimen in allo-HSCT for this patient was as follows: busulfan 3.7 mg/kg daily at 9 to 6 days before transplantation, cyclophosphamide 42.8 mg/kg daily at 5 to 2 days before transplantation, and rabbit antithymocyte globulin 3.5 mg/kg daily at 1, 3, 5, and 7 days before transplantation. Human granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (CD34+ cells 12.8 x10(6)/kg) were infused and cyclosporine (CSA), short-course methotrexate, daclizumab and mycophenolate mofetil (MMF) were administered to prevent graft-versus-host disease (GVHD). Complete donor-type engraftment was confirmed by Short Tandem Repeat-Polymerase Chain Reaction (STR-PCR) on day 14 after transplantation. Neutrophil and platelet engraftment occurred on days 11 and 19 after transplantation respectively. Only grade I regimen-related toxicity of live and gastrointestinal tract occurred. GVHD and graft failure were not observed. After transplantation, the clinical symptoms and the neurocognitive function were greatly improved in this patient. It was concluded that allo-HSCT was effective for the treatment of MPS-I. The reduced-intensity conditioning regimen was helpful to decrease the regimen-related toxicity. Sufficient immunosuppressive therapy and adequate hematopoietic stem cells infusion may be beneficial to the donor cell engraftment and reducing the incidence of graft failure and GVHD.