Cardiac troponin I autoantibody induces myocardial dysfunction by PTEN signaling activation.

BACKGROUND: The objective of the current study was to study the molecular mechanism(s) underlying cardiac troponin I autoantibody (cTnIAAb) binding to cardiomyocyte and resultant myocardial damage/dysfunction. METHODS: cTnIAAb was purified from serum of 10 acute myocardial infarction (AMI) patients with left ventricular remodeling. Recombinant human cTnI was used to generate three mouse-derived monoclonal anti-cTnI antibodies (cTnImAb1, cTnImAb2, and cTnImAb3). The target proteins in cardiac myocyte membrane bound to cTnImAb and effect of cTnIAAb and cTnImAb on apoptosis and myocardial function were determined. FINDINGS: We found that cTnIAAb/cTnImAb1 directly bound to the cardiomyocyte membraneα-Enolase (ENO1) and triggered cell apoptosis via increased expression of ENO1 and Bax, decreased expression of Bcl2, subsequently activating Caspase8, Caspase 3, phosphatase and tensin homolog (PTEN) while inhibiting Akt activity. This cTnIAAb-ENO1-PTEN-Akt signaling axis contributed to increased myocardial apoptosis, myocardial collagen deposition, and impaired systolic dysfunction. INTERPRETATION: Results obtained in this study indicate that cTnIAAb is involved in the process of ventricular remodeling after myocardial injury. FUND: The National Natural Science Foundation of China (Grant#: 81260026).

Mesenchymal stem cell-based NK4 gene therapy in nude mice bearing gastric cancer xenografts.

Mesenchymal stem cells (MSCs) have been recognized as promising delivery vehicles for gene therapy of tumors. Gastric cancer is the third leading cause of worldwide cancer mortality, and novel treatment modalities are urgently needed. NK4 is an antagonist of hepatocyte growth factor receptors (Met) which are often aberrantly activated in gastric cancer and thus represent a useful candidate for targeted therapies. This study investigated MSC-delivered NK4 gene therapy in nude mice bearing gastric cancer xenografts. MSCs were transduced with lentiviral vectors carrying NK4 complementary DNA or enhanced green fluorescent protein (GFP). Such transduction did not change the phenotype of MSCs. Gastric cancer xenografts were established in BALB/C nude mice, and the mice were treated with phosphate-buffered saline (PBS), MSCs-GFP, Lenti-NK4, or MSCs-NK4. The tropism of MSCs toward gastric cancer cells was determined by an in vitro migration assay using MKN45 cells, GES-1 cells and human fibroblasts and their presence in tumor xenografts. Tumor growth, tumor cell apoptosis and intratumoral microvessel density of tumor tissue were measured in nude mice bearing gastric cancer xenografts treated with PBS, MSCs-GFP, Lenti-NK4, or MSCs-NK4 via tail vein injection. The results showed that MSCs migrated preferably to gastric cancer cells in vitro. Systemic MSCs-NK4 injection significantly suppressed the growth of gastric cancer xenografts. MSCs-NK4 migrated and accumulated in tumor tissues after systemic injection. The microvessel density of tumor xenografts was decreased, and tumor cellular apoptosis was significantly induced in the mice treated with MSCs-NK4 compared to control mice. These findings demonstrate that MSC-based NK4 gene therapy can obviously inhibit the growth of gastric cancer xenografts, and MSCs are a better vehicle for NK4 gene therapy than lentiviral vectors. Further studies are warranted to explore the efficacy and safety of the MSC-based NK4 gene therapy in animals and cancer patients.

Enhancement by interleukin-1ß of AMPA and NMDA receptor-mediated currents in adult rat spinal superficial dorsal horn neurons.

BACKGROUND: Proinflammatory cytokine interleukin-1ß (IL-1ß) released from spinal microglia plays an important role in the maintenance of acute and chronic pain states. However, the cellular basis of this action remains poorly understood. Using whole-cell patch-clamp recordings, we examined the action of IL-1ß on AMPA- and NMDA-receptor-mediated currents recorded from substantia gelatinosa (SG) neurons of adult rat spinal cord slices which are key sites for regulating nociceptive transmission from the periphery. RESULTS: AMPA- and NMDA-induced currents were increased in peak amplitude by IL-1ß in a manner different from each other in SG neurons. These facilitatory actions of IL-1ß were abolished by IL-1 receptor (IL-1R) antagonist (IL-1ra), which by itself had no detectable effects on AMPA- and NMDA-induced currents. The AMPA- but not NMDA-induced current facilitated by IL-1ß was recovered to control level 30 min after IL-1ß washout and largely depressed in Na+-channel blocker tetrodotoxin-containing or nominally Ca2+-free Krebs solution. Minocycline, a microglia inhibitor, blocked the facilitatory effect of IL-1ß on AMPA- but not NMDA-induced currents, where minocycline itself depressed NMDA- but had not any effects on AMPA-induced currents. CONCLUSIONS: IL-1ß enhances AMPA and NMDA responses in SG neurons through IL-1R activation; the former but not latter action is reversible and due to an increase in neuronal activity in a manner dependent on extracellular Ca2+ and minocycline. It is suggested that AMPA and NMDA receptors are positively modulated by IL-1ß in a manner different from each other; the former but not latter is mediated by a neurotransmitter released as a result of an increase in neuronal activity. Since IL-1ß contributes to nociceptive behavior induced by peripheral nerve or tissue injury, the present findings also reveal an important cellular link between neuronal and glial cells in the spinal dorsal horn.

Reduced expression of PTEN and increased PTEN phosphorylation at residue Ser380 in gastric cancer tissues: a novel mechanism of PTEN inactivation.

AIM: PTEN is a tumor suppressor gene in different cancers. This study was to determine the protein expression of PTEN and phosphorylation of PTEN (p-PTEN) at residue Ser380 in different histology specimens of gastric tissues. METHODS: A total of 179tissue specimens of normal gastric mucosa, chronic gastritis, intestinal metaplasia, dysplasia, and gastric cancer were recruited for immunohistochemical analysis of PTEN and p-PTEN expression. Four gastric cancer AGS, MKN-45, MKN-28, and SGC-7901 cell lines and a non-cancerous gastric GES-1 cell line were used to detect expression of PTEN and p-PTEN protein using Western blot. RESULTS: Expression level of PTEN protein was significantly decreased in gastric cancer tissues compared to normal gastric mucosa, chronic gastritis, intestinal metaplasia and dysplasia (P<0.05). In contrast, p-PTEN protein level was significantly increased in intestinal metaplasia, dysplasia and gastric cancer compared to normal gastric mucosa and chronic gastritis (P<0.05). However, there was no any association of PTEN and p-PTEN expression with clinicopathological characteristics from gastric cancer patients. Moreover, the ratio of p-PTEN and PTEN was higher in gastric cancer cell lines than that of the non-malignant cells. CONCLUSIONS: This study demonstrated that aberrant expression of PTEN and p-PTEN at residue Ser380 was early event that could contribute to gastric carcinogenesis, and that PTEN phosphorylation at residue Ser380 could be a mechanism for PTEN inactivation.

VPS35 haploinsufficiency increases Alzheimer's disease neuropathology.

VPS35, a major component of the retromer complex, is important for endosome-to-Golgi retrieval of membrane proteins. Although implicated in Alzheimer's disease (AD), how VPS35 regulates AD-associated pathology is unknown. In this paper, we show that hemizygous deletion of Vps35 in the Tg2576 mouse model of AD led to earlier-onset AD-like phenotypes, including cognitive memory deficits, defective long-term potentiation, and impaired postsynaptic glutamatergic neurotransmission in young adult age. These deficits correlated well with an increase of ß-amyloid peptide (Aß) level in the mutant hippocampus. We further demonstrate that VPS35 is predominantly expressed in pyramidal neurons of young adult hippocampus and interacts with BACE1, a protease responsible for Aß production. Loss of VPS35 function in the mouse hippocampus increased BACE1 activity. Suppression of VPS35 expression in culture decreased BACE1 trans-Golgi localization but enriched it in endosomes. These results demonstrate an essential role for VPS35 in suppression of AD neuropathology and in inhibition of BACE1 activation and Aß production by promoting BACE1 endosome-to-Golgi retrieval.

Regulation of heterochromatin remodelling and myogenin expression during muscle differentiation by FAK interaction with MBD2.

Focal adhesion kinase (FAK), a major cell adhesion-activated tyrosine kinase, has an important function in cell adhesion and migration. Here, we report a new signalling of FAK in regulating chromatin remodelling by its interaction with MBD2 (methyl CpG-binding protein 2), underlying FAK regulation of myogenin expression and muscle differentiation. FAK interacts with MBD2 in vitro, in myotubes, and in isolated muscle fibres. Such an interaction, increased in myotubes exposed to oxidative stress, enhances FAK nuclear localization. The nuclear FAK-MBD2 complexes alter heterochromatin reorganization and decrease MBD2 association with HDAC1 (histone deacetylase complex 1) and methyl CpG site in the myogenin promoter, thus, inducing myogenin expression. In line with this view are observations that blocking FAK nuclear localization by expressing dominant negative MBD2 or suppression of FAK expression by its miRNA in C2C12 cells attenuates myogenin induction and/or impairs muscle-terminal differentiation. Together, these results suggest an earlier unrecognized role of FAK in regulating chromatin remodelling that is important for myogenin expression and muscle-terminal differentiation, reveal a new mechanism of MBD2 regulation by FAK family tyrosine kinases, and provide a link between cell adhesion and chromatin remodelling.

Netrin-1 mediates neuronal survival through PIKE-L interaction with the dependence receptor UNC5B.

Netrins, a family of secreted molecules, have critical functions in axon guidance and cell migration during neuronal development. In addition to its role as a chemotropic molecule, netrin-1 also acts as a survival factor. Both UNC5 (that is, UNC5A, UNC5B, UNC5C or UNC5D) and DCC are transmembrane receptors for netrin-1 (Refs 8, 9). In the absence of netrin-1, DCC and UNC5 act as dependence receptors and trigger apoptosis. However, how netrin-1 suppresses the apoptotic activity of the receptors remains elusive. Here we show that netrin-1 induces interaction of UNC5B with the brain-specific GTPase PIKE-L. This interaction triggers the activation of PtdIns-3-OH kinase signalling, prevents UNC5B's pro-apoptotic activity and enhances neuronal survival. Moreover, this process relies strongly on Fyn because PIKE-L is tyrosine phosphorylated in response to netrin-1, and the netrin-1-mediated interaction of UNC5B with PIKE-L is inhibited in Fyn-null mice. Thus, PIKE-L acts as a downstream survival effector for netrin-1 through UNC5B in the nervous system.

Retrograde regulation of motoneuron differentiation by muscle beta-catenin.

Synapse formation requires proper interaction between pre- and postsynaptic cells. In anterograde signaling, neurons release factors to guide postsynaptic differentiation. However, less is known about how postsynaptic targets retrogradely regulate presynaptic differentiation or function. We found that muscle-specific conditional knockout of beta-catenin (Ctnnb1, also known as beta-cat) in mice caused both morphologic and functional defects in motoneuron terminals of neuromuscular junctions (NMJs). In the absence of muscle beta-catenin, acetylcholine receptor clusters were increased in size and distributed throughout a wider region. Primary nerve branches were mislocated, whereas secondary or intramuscular nerve branches were elongated and reduced in number. Both spontaneous and evoked neurotransmitter release was reduced at the mutant NMJs. Furthermore, short-term plasticity and calcium sensitivity of neurotransmitter release were compromised in beta-catenin-deficient muscle. In contrast, the NMJ was normal in morphology and function in motoneuron-specific beta-catenin-deficient mice. Taken together, these observations indicate a role for muscle beta-catenin in presynaptic differentiation and function, identifying a previously unknown retrograde signaling in the synapse formation and synaptic plasticity.