Globular adiponectin inhibits osteoblastic differentiation of vascular smooth muscle cells through the PI3K/AKT and Wnt/ß-catenin pathway.

Lipid metabolism is closely related to the improvement of vascular calcification (VC) in chronic kidney disease (CKD). Globular adiponectin (gAd) has been reported to be involved in the development of VC in CKD, but the detailed regulatory role remains unclear. The present study is aimed to investigate the biological function and the underlying regulation mechanism of gAd in the process of VC during CKD. Vascular smooth muscle cells (VSMCs) calcification was determined by Alizarin Red S staining. Protein signaling related with VC was tested by western blotting. The expression and intracellular localization of runt-related transcription factor 2 (Runx2) was detected by immunofluorescence and uraemic rat with VC was established by a two-step nephrectomy. Combined with the results of Alizarin Red S staining, we discovered that ß-glycerophosphate (ß-Gp)-induced the osteoblastic differentiation of VSMCs was significantly reversed by gAd treatment. Along with the VSMCs calcification and the increase of Runx2 in ß-Gp-exposed VSMCs, the activities of protein kinase B (AKT) and Wnt/ß-catenin pathway were enhanced, but that were counteracted by the exposure of gAd in rat and human VSMCs. After administration with agonists of the Wnt (SKL2001) and AKT (SC79), there appeared more osteoblastic differentiation and higher expression of Runx2 in gAd-treated VSMCs, but showing lower impact in the presence of SC79 than that in the presence of SKL2001. In the in vivo experiments, intravenous injection of gAd also significantly inhibited VC and Runx2 level in uraemic rat in a dose-dependent manner, possibly through regulating Wnt/ß-catenin pathway. This study demonstrates that gAd ameliorates osteoblastic differentiation of VSMCs possibly by blocking PI3K/AKT and Wnt/ß-catenin signaling transduction. The findings provide an important foundation for gAd in treating VC in kidney diseases.

Fast fixing and comprehensive identification to help improve real-time ligands discovery based on formaldehyde crosslinking, immunoprecipitation and SDS-PAGE separation.

BACKGROUND: Fast Fixation is necessary to study real-time protein-protein interactions under physiological conditions. Fast formaldehyde cross-linking can fix transient and weak protein interactions, thereby reducing the number of false negatives but producing great complexity. To reduce this complexity, immunoaffinity purification can Fish out complexes that include particular target proteins, but affinity-based co-purification has a limited capacity to eliminate nonspecific binding to beads and/or antibodies. To Filter out these complexes, SDS-PAGE is used to disrupt non-covalent bonds, thereby eliminating uncross-linked complexes and simultaneously providing molecular weight information for identification. RESULTS: We described a 4 F strategy to help improve real-time ligands discovery based on formaldehyde crosslinking, immunoprecipitation and SDS-PAGE separation: Fast Fix, Fish, and Filter, using albumin interactome as an example. The use of gel excision without staining makes this strategy comprehensive and sensitive. The target protein must be identified in the same slice as its ligands. The ligands must be identified in slices for the experimental group but not in the corresponding control slices. Only proteins that appear in the range of molecular weights equal to or greater than the sum of the proteins' theoretical molecular weights, together with the target, are considered ligands. In this study, 5 s of cross-linking with 10% formaldehyde was achieved in human blood. The use of this strategy identified 35 ligands for albumin. Comparison with four major previous studies of the albuminome revealed that 68.57% of the 35 ligands identified in our study were identified in these other studies. CONCLUSIONS: Fast cross-linking was achieved. The 4 F strategy can be used to identify real-time in situ interactions without prior intervention and to comprehensively identify ligands of particular target proteins with fewer false positives.

Differential protein expression in perfusates from metastasized rat livers.

BACKGROUND: Liver perfusates exhibit theoretical advantages regarding the discovery of disease biomarkers because they contain proteins that readily enter the blood-stream, and perfusion preserves the disease state in its natural context. The purpose of the study is to explore the value of liver perfusate proteome in the biomarker discovery of liver diseases. RESULTS: In this study, 86 differentially expressed proteins were identified in perfusates from isolated rat livers metastasized by Walker-256 tumor cells. Among these proteins, 27 were predicted to be secreted, and 59 were intracellular or membrane proteins. Most of the secretory proteins (70.4%) were decreased in metastasized liver perfusates. The main canonical ingenuity pathway to which these secretory proteins belonged was acute phase response, which indicated that the liver-associated immune reaction was damaged by the metastasis. In contrast, most of the intracellular or membrane proteins (86.4%) exhibited higher relative abundances in the metastasized liver perfusates. Some of these proteins, including Rpl21, Atic, Eif3s2, Echs1, Eps15 and Ywhab, have previously been reported to be involved in cancer genesis and progression. As a member of the 14-3-3 protein family, Ywhab plays a key role in cellular proliferation and oncogenic transformation and has been reported to be involved in the development of breast cancer. Its abundance was elevated by 3.5-fold in the metastasized perfusates. Validation by Western blotting revealed a 3.7-fold increase in the abundance of this protein in metastasized plasma. CONCLUSIONS: These results show that perfusate proteome can be used as an alternative initial resource for biomarker identification, which ultimately requires validation in serum.