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In this study, we using the in vivo destabilization of the medial meniscus (DMM) mouse model to investigate the role of bone morphogenetic protein 5 (BMP5) in osteoarthritis (OA) progression mediated via chondrocyte senescence and apoptosis. BMP5 expression was significantly higher in knee articular cartilage tissues of OA patients and DMM model mice than the corresponding controls. The Osteoarthritis Research Society International scores based on histological staining of knee articular cartilage sections were lower in DMM mice where BMP5 was knocked down in chondrocytes than the corresponding controls 4 weeks after DMM surgery. DMM mice with BMP5-deficient chondrocytes showed reduced levels of matrix-degrading enzymes such as MMP13 and ADAMTS5 as well as reduced cartilage destruction. BMP5 knockdown also decreased chondrocyte apoptosis and senescence by suppressing the activation of p38 and ERK MAP kinases. These findings demonstrate that BMP5 silencing inhibits chondrocyte senescence and apoptosis as well as OA progression by downregulating activity in the p38/ERK signaling pathway.

A switch from autophagy to apoptosis is implicated in chondrocytes during the osteoarthritis (OA) progression with currently unknown mechanism(s). In this study we utilized a flow fluid shear stress (FFSS) model in cultured chondrocytes and a unilateral anterior crossbite (UAC) animal model. We found that both FFSS and UAC actively induced endoplasmic reticulum stress (ERS) in the temporomandibular joints (TMJ) chondrocytes, as demonstrated by dramatic increases in expression of HSPA5, p-EIF2AK3, p-ERN1 and ATF6. Interestingly, both FFSS and UAC activated not only pro-death p-EIF2AK3-mediated ERS-apoptosis programs but also pro-survival p-ERN1-mediated autophagic flux in chondrocytes. Data from FFSS demonstrated that MTORC1, a downstream of p-ERN1, suppressed autophagy but promoted p-EIF2AK3 mediated ERS-apoptosis. Data from UAC model demonstrated that at early stage both the p-ERN1 and p-EIF2AK3 were activated and MTORC1 was inhibited in TMJ chondrocytes. At late stage, MTORC1-p-EIF2AK3-mediated ERS apoptosis were predominant, while p-ERN1 and autophagic flux were inhibited. Inhibition of MTORC1 by TMJ local injection of rapamycin in rats or inducible ablation of MTORC1 expression selectively in chondrocytes in mice promoted chondrocyte autophagy and suppressed apoptosis, and reduced TMJ cartilage loss induced by UAC. In contrast, MTORC1 activation by TMJ local administration of MHY1485 or genetic deletion of Tsc1 , an upstream MTORC1 suppressor, resulted in opposite effects. Collectively, our results establish that aberrant mechanical loading causes cartilage degeneration by activating, at least in part, the MTORC1 signaling which modulates the autophagy and apoptosis programs in TMJ chondrocytes. Thus, inhibition of MTORC1 provides a novel therapeutic strategy for prevention and treatment of OA. Abbreviations : ACTB: actin beta; ATF6: activating transcription factor 6; BECN1: beclin 1; BFL: bafilomycin A 1 ; CASP12: caspase 12; CASP3: caspase 3; DAPI: 4',6-diamidino-2-phenylindole; DDIT3: DNA-damage inducible transcript 3; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; ER: endoplasmic reticulum; ERS: endoplasmic reticulum stress; ERN1/IRE1: endoplasmic reticulum to nucleus signaling 1; FFSS: flow fluid shear stress; HSPA5/GRP78/BiP: heat shock protein 5; LAMP2: lysosome-associated membrane protein 2; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin complex 1; OA: osteoarthritis; PRKAA1/2/AMPK1/2: protein kinase, AMP-activated, alpha 1/2 catalytic subunit; RPS6: ribosomal protein S6; Rapa: rapamycin; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TG: thapsigargin; TMJ: temporomandibular joints; TSC1/2: tuberous sclerosis complex 1/2; UAC: unilateral anterior crossbite; UPR: unfolded protein response; XBP1: x-box binding protein 1.

Background: Targeting protein for Xklp2 (TPX2) is a microtubule-associated protein involved in targeting the motor protein Xklp2 to microtubules. TPX2 overexpression plays a key role in the progression of human cancers. But the underlying mechanism remains unclear., Aims: This study aimed to investigate the effects and mechanisms of TPX2 on the cell cycle, apoptosis, and epithelial-mesenchymal transition (EMT) in hepatocellular carcinoma (HCC)., Methods: The tissue TPX2 mRNA and protein were assessed by quantitative reverse transcriptase PCR and immunoblot. Cell proliferation, cell cycle, apoptosis, and invasion were determined by CCK-8, FACS, TdT-UTP nick end-labeling, and transwell assays. Immunoblotting was performed to detect the expression of target proteins., Results: TPX2 was highly expressed in tumor tissues compared with non-tumoral tissues, and TPX2 overexpression was positively correlated with poor prognosis. Knockdown TPX2 effectively reduced cell growth, G2/M arrest, induced apoptosis and cell death, and inhibited EMT. Mechanistically, in the TPX2-siRNA-treated groups, cell-cycle-related proteins cyclin A1, cyclin B1, cyclin E1, and cdk4 were up-regulated, while cyclin D1, cdk2, and p21 proteins were down-regulated. Cell-apoptosis-related proteins Bax, p53, caspase-3, and caspase-8 levels were increased. EMT-related proteins E-cadherin was up-regulated, while N-cadherin, β-catenin, MMP-9, MMP-2, and Slug were down-regulated. We also found that knockdown TPX2 in HCC cell lines caused a significant decrease in the level of p-Akt and p-ERK which are important signaling pathways in tumor formation., Conclusions: TPX2 expression is associated with proliferation, apoptosis, and EMT in hepatocellular carcinoma cell and patients.

Acute myeloid leukemia (AML) is a common disorder in the elderly. Although remarkable progress has been made over recent decades, the outcome remains poor. Thus, the development of a more effective method to overcome this problem is necessary. In this study, we aimed to investigate the synergistic cytotoxic effect of low-dose arsenic trioxide (As2O3) combined with aclacinomycin A (ACM) on the human AML cell lines KG-1a and HL-60, and to clarify the underlying mechanism. Results showed that As2O3 combined with ACM exerted a synergistic cytotoxic effect by activation of the apoptosis pathway. Additionally, we found that the combination treatment decreased Bcl-2, c-IAP and XIAP expression but increased SMAC and caspase-3 expression more significantly than the single drug treatments. Furthermore, combination index (CI) values were < 1 in all matched combination groups. Additional evaluation of As2O3 combined with ACM as a potential therapeutic benefit for AML seems warranted.

Most of breast cancers are resistant to mammalian target of rapamycin complex 1 (mTORC1) inhibitors rapamycin and rapalogs. Recent studies indicate mTORC2 is emerging as a promising cancer therapeutic target. In this study, we compared the inhibitory effects of targeting mTORC1 with mTORC2 on a variety of breast cancer cell lines and xenograft. We demonstrated that inhibition of mTORC1/2 by mTOR kinase inhibitors PP242 and OSI-027 effectively suppress phosphorylation of Akt (S473) and breast cancer cell proliferation. Targeting of mTORC2 either by kinase inhibitors or rictor knockdown, but not inhibition of mTORC1 either by rapamycin or raptor knockdown promotes serum starvation- or cisplatin-induced apoptosis. Furthermore, targeting of mTORC2 but not mTORC1 efficiently prevent breast cancer cell migration. Most importantly, in vivo administration of PP242 but not rapamycin as single agent effectively prevents breast tumor growth and induces apoptosis in xenograft. Our data suggest that agents that inhibit mTORC2 may have advantages over selective mTORC1 inhibitors in the treatment of breast cancers. Given that mTOR kinase inhibitors are in clinical trials, this study provides a strong rationale for testing the use of mTOR kinase inhibitors or combination of mTOR kinase inhibitors and cisplatin in the clinic.

The mammalian focal adhesion proteins Pinch1/2 activate integrins and promote cell-extracellular matrix adhesion and migration; however, their roles in adipose tissue and metabolism are unclear. Here we find that high-fat diet (HFD) feeding dramatically increases expression of Pinch1/2 proteins in white adipose tissue (WAT) in mice. Furthermore, expression of Pinch1 is largely upregulated in WAT in leptin-deficient ob/ob type 2 diabetic mice and obese humans. While mice with loss of Pinch1 in adipocytes or global Pinch2 do not display any notable phenotypes, deleting Pinch1 in adipocytes and Pinch2 globally significantly decreases body weight and WAT mass, but not brown adipose tissue mass, in HFD-fed, but not normal chow diet-fed, mice. Pinch loss ameliorates HFD-induced glucose intolerance and fatty liver. After HFD challenge, Pinch loss slightly but significantly accelerates energy expenditure. While Pinch loss decreases adipocyte size and alters adipocyte size distribution, it greatly accelerates cell apoptosis primarily in epididymal WAT and to a lesser extent in subcutaneous WAT. In vitro studies demonstrate that Pinch loss accelerates adipocyte apoptosis by activating the Bim/Caspase-8 pathway. In vivo, genetic ablation of Caspase-8 expression in adipocytes essentially abolishes the ameliorating effects of Pinch deficiency on obesity, glucose intolerance, and fatty liver in mice. Thus, we demonstrate a previously unknown function of Pinch in control of adipose mass, glucose, and fat metabolism via modulation of adipocyte apoptosis. We may define a novel target for the prevention and treatment of metabolic diseases, such as obesity and diabetes. [ABSTRACT FROM AUTHOR]