LAMP2 Knockout Cell Lysate

The anti-inflammatory activity of melatonin (MT) has been well documented; however, little is known regarding endogenously occurring MT in this respect, especially for large animals. In the current study, we created a MT-enriched animal model (goats) overexpressing the MT synthetase gene Aanat. The responses of these animals to lipopolysaccharide (LPS) stimulation were systematically studied. It was found that LPS treatment exacerbated the inflammatory response in wild-type (WT) goats and increased their temperature to 40 degrees C. In addition, their granulocyte counts were also significantly elevated. In contrast, these symptoms were not observed in transgenic goats with LPS treatment. The rescue study with MT injection into WT goats who were treated with LPS confirmed that the protective effects in transgenic goats against LPS were attributed to a high level of endogenously produced MT. The proteomic analysis in the peripheral blood mononuclear cells (PBMCs) isolated from the transgenic animals uncovered several potential mechanisms. MT suppressed the lysosome formation as well as its function by downregulation of the lysosome-associated genes Lysosome-associated membrane protein 2 (LAMP2), Insulin-like growth factor 2 receptor (IGF2R), and Arylsulfatase B (ARSB). A high level of MT enhanced the antioxidant capacity of these cells to reduce the cell apoptosis induced by the LPS. In addition, the results also uncovered previously unknown information that showed that MT may have protective effects on some human diseases, including tuberculosis, bladder cancer, and rheumatoid arthritis, by downregulation of these disease-associated genes. All these observations warranted further investigations.

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.