A novel cytoprotective peptide protects mesenchymal stem cells against mitochondrial dysfunction and apoptosis induced by starvation via Nrf2/Sirt3/FoxO3a pathway.

BACKGROUND: Mesenchymal stem cell (MSC) has been widely explored in the past decade as a cell-based treatment for various diseases. However, poor survival of adaptively transferred MSCs limits their clinical therapeutic potentials, which is largely ascribed to the nutrient starvation. In this study, we determined whether a novel kidney protective peptide CHBP could protect MSCs against starvation and invested the underlying mechanisms. METHODS: MSCs were subjected to serum deprivation and CHBP of graded concentrations was administered. Cell viability and apoptosis were detected by CCK-8, Annexin V/PI assay and Hoechst staining. ROS generation, mitochondrial membrane potential indicated by JC-1 and mitochondrial mass were measured by flow cytometry. The location of cytochrome c within cells was observed under fluorescence microscopy. Expressions of Nrf2, Sirt3, and FoxO3a were analyzed by western blot. In addition, preconditioning MSCs with CHBP was applied to test the possible protection against starvation. Finally, the effect of CHBP on the differentiation and self-renewal capacity of MSCs was also examined. RESULTS: CHBP improved cell viability and suppressed apoptosis in a dose dependent manner. Starvation resulted in the mitochondrial dysfunction and treatment of CHBP could alleviate mitochondrial stress by diminishing oxidative injury of ROS, restoring mitochondrial membrane potential and maintaining mitochondrial membrane integrity. Importantly, Nrf2/Sirt3/FoxO3a pathway was activated by CHBP and Sirt3 knockdown partially abolished the protection of CHBP. Moreover, MSCs pretreated with CHBP were more resistant to starvation. Under normal condition, CHBP exerted little effects on the differential and self-renewal capacity of MSCs. CONCLUSIONS: The present study demonstrated the efficient protection of CHBP upon MSCs against starvation-induced mitochondrial dysfunction and apoptosis and indicated possible involvement of Nrf2/Sirt3/FoxO3a pathway in the protective effect.

Erythropoietin protects against rhabdomyolysis-induced acute kidney injury by modulating macrophage polarization.

Erythropoietin (EPO) is a well-known hormone that is clinically used for the treatment of anemia. Very recently, an increasing body of evidence showed that EPO could still regulate bioactivities of macrophages. However, the details about the immunomodulatory effect of EPO on macrophages are not fully delineated, particularly in the setting of renal damages. Therefore, in the present study, we determined whether EPO could exert an impact on the dynamics of macrophages in a well-established model of rhabdomyolysis-induced acute kidney injury and explored the potential mechanisms. EPO was found to ameliorate kidney injuries by reducing macrophages recruitment and promoting phenotype switch toward M2 macrophages in vivo. It was also confirmed that EPO could directly suppress pro-inflammatory responses of M1 macrophages and promote M2 marker expression in vitro. Data indicated the possible involvement of Jak2/STAT3/STAT6 pathway in the augmentation of EPO on M2 polarization. These results improved the understanding of the immunoregulatory capacity of EPO on macrophages, which might optimize the therapeutic modalities of EPO.

Protective effects of cyclic helix B peptide on aristolochic acid induced acute kidney injury.

BACKGROUND: Aristolochic acid (AA) injuries remain a serious condition associated with acute renal dysfunction. Herein, the effect and mechanism of a novel tissue protective peptide, cyclic helical B-peptide (CHBP) derived from erythropoietin, were investigated in a mice model. METHODS: Mice were randomly divided into four groups, receiving the following treatments (1: saline; 2: AA 10mg/kg; 3: AA 10mg/kg +CHBP 4nmol/kg; 4: AA 10mg/kg +CHBP 8nmol/kg). RESULTS: Blood urea nitrogen and serum creatinine was increased by AA but decreased by CHBP in a dose-dependent fashion. CHBP also significantly improved renal tubular injury and inflammatory infiltration, which was gradually increased by AA. Apoptotic cells, infiltrating inflammatory cells, and active caspase-3+ cells were greatly reduced by CHBP. In addition, CHBP inhibited caspase-3, 9 and improved bcl-2, bcl-xl protein expression in vivo. CONCLUSION: Taken together, we demonstrated, for the first time, that CHBP effectively improved renal function and tissue damage caused by AA, which maybe through reducing caspase-3 activation, apoptosis, and inflammation.