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Nuclear factor of activated T cells 5 (NFAT5)/Tonicity enhancer binding protein (TonEBP) is a transcription factor induced by hypertonic stress in the kidney. However, the function of NFAT5 in other organs has rarely been studied, even though it is ubiquitously expressed. Indeed, although NFAT5 was reported to be critical for heart development and function, its role in infectious heart diseases has remained obscure. In this study, we aimed to understand the mechanism by which NFAT5 interferes with infection of Coxsackievirus B3 (CVB3), a major cause of viral myocarditis. Our initial results demonstrated that although the mRNA level of NFAT5 remained constant during CVB3 infection, NFAT5 protein level decreased because the protein was cleaved. Bioinformatic prediction and verification of the predicted site by site-directed mutagenesis experiments determined that the NFAT5 protein was cleaved by CVB3 protease 2A at Glycine 503. Such cleavage led to the inactivation of NFAT5, and the 70-kDa N-terminal cleavage product (p70-NFAT5) exerted a dominant negative effect on the full-length NFAT5 protein. We further showed that elevated expression of NFAT5 to counteract viral protease cleavage, especially overexpression of a non-cleavable mutant of NFAT5, significantly inhibited CVB3 replication. Ectopic expression of NFAT5 resulted in elevated expression of inducible nitric oxide synthase (iNOS), a factor reported to inhibit CVB3 replication. The necessity of iNOS for the anti-CVB3 effect of NFAT5 was supported by the observation that inhibition of iNOS blocked the anti-CVB3 effect of NFAT5. In a murine model of viral myocarditis, we observed that treatment with hypertonic saline or mannitol solution upregulated NFAT5 and iNOS expression, inhibited CVB3 replication and reduced tissue damage in the heart. Taken together, our data demonstrate that the anti-CVB3 activity of NFAT5 is impaired during CVB3 infection due to 2A-mediated cleavage of NFAT5. Thus induction of NFAT5 by hypertonic agents may be a promising strategy for the development of anti-CVB3 therapeutics. [ABSTRACT FROM AUTHOR]

We previously demonstrated that coxsackievirus B3 (CVB3) infection upregulated heat shock protein 70 (Hsp70) and promoted CVB3 multiplication. Here, we report the underlying mechanism by which Hsp70 enhances viral RNA translation. By using an Hsp70-overexpressing cell line infected with CVB3, we found that Hsp70 enhanced CVB3 VP1 translation at two stages. First, Hsp70 induced upregulation of VP1 translation at the initiation stage via upregulation of internal ribosome entry site trans-acting factor lupus autoantigen protein and activation of eIF4E binding protein 1, a cap-dependent translation suppressor. Second, we found that Hsp70 increased CVB3 VP1 translation by enhancing translation elongation. This was mediated by the Akt-mammalian target of rapamycin complex 1 signal cascade, which led to the activation of eukaryotic elongation factor 2 via p70S6K- and cell division cycle protein 2 homolog (Cdc2)-mediated phosphorylation and inactivation of eukaryotic elongation factor 2 kinase. We also determined the position of Cdc2 in this signal pathway, indicating that Cdc2 is regulated by mammalian target of rapamycin complex 1. This signal transduction pathway was validated using a number of specific pharmacological inhibitors, short interfering RNAs (siRNAs) and a dominant negative Akt plasmid. Because Hsp70 is a central component of the cellular network of molecular chaperones enhancing viral replication, these data may provide new strategies to limit this viral infection. [ABSTRACT FROM AUTHOR]

Multidrug resistance (MDR) is a challenge for the treatment of cancer and the underlying molecular mechanisms remain elusive. The current study exposed MG63 osteosarcoma cells to increasing concentrations of vincristine (VCR) to establish four VCR-resistant MG63/VCR cell sublines (MG63/VCR1, 2, 3 and 4). The drug resistance indices (RI) of these sublines was detected with the CCK-8 assay and determined to be163, 476, 1,247, and 2,707-fold higher than that of parental cells, respectively. These sublines also exhibited cross-resistance to doxorubicin, paclitaxel and pirarubicin. With increased RI, the proliferative capacity of these sublines was gradually reduced and cell morphology was also altered, characterized by increased formation of pseudopodia and long cytoplasmic processes at opposite poles. However, the migration capacity and expression of certain drug resistance-associated genes were not in accordance with the increased RI; multidrug resistance protein 1 (MDR1) expression was significantly increased in these sublines compared with parental cells. However, in the highly resistant MG63/VCR3 and MG63/VCR4 cells, MDR-associated protein 1, topoisomerase II and LIM domain kinase 1 levels were significantly reduced compared with the moderately resistant MG63/VCR2 cells. Expression of glutathione S-transferase-⨅ mRNA was determined using reverse transcription-quantitative polymerase chain reaction and determined that it was not changed between MG63 and MG63/VCR cells. The data of the present study demonstrated that the molecular alterations of drug resistance may change with the degree of drug resistance. Taking cell morphology into consideration, the intratumor clonal and phenotypic heterogeneity may be responsible for drug resistance. These MG63/VCR sublines may be a valuable tool to assess drug resistance and the underlying mechanisms, and to identify novel drug resistance-associated genes or strategies to overcome MDR in human osteosarcoma. [ABSTRACT FROM AUTHOR]

Osteosarcoma is a type of malignant bone tumor with high metastasis and poor prognosis. Previous studies have demonstrated the involvement of LIM kinase 1 (LIMK1) in the proliferation of osteosarcoma cells. LIMK1 is over expressed in human osteosarcoma tissues and cell lines. To further study LIMK1-associated mechanisms, we used shRNA targeted to the LIMK1 gene to block its expression in the osteosarcoma cell lines MG63 and U2OS. Insulin promoted the proliferation of MG63 cells in a time- and dose-dependent manner, however, this insulin induced proliferation was significantly inhibited by transfection of shRNA targeted to the LIMK1 gene, as well as by the PI3K inhibitor LY294002, but not by the mitogen-activated protein kinase (MAPK) inhibitor PD98059. The level of cofilin phosphorylation was increased significantly following stimulation of insulin for 24 h, indicating the activation of LIMK1. MG63 cell proliferation was also significantly inhibited by 1,25-dihydroxy vitamin D3 (1,25(OH)2D3) in a time-dependent manner. Furthermore, 1,25(OH)2D3 negated the inhibitory effect of LIMK1 shRNA, indicating that LIMK1 is important in the inhibitory pathway of 1,25(OH)2D3. The present study confirms that LIMK1 is important in regulating osteosarcoma cell proliferation via the insulin/PI3K/LIMK1 signaling pathway, thus the development of gene therapy for osteosarcoma targeting LIMK1 is warranted. [ABSTRACT FROM AUTHOR]

A series of 1-halogenated sinomenine derivatives was designed and prepared. All synthesized derivatives were structurally confirmed by ESI-MS, PMR. The inhibition of the NF-κB pathway in vitro was evaluated with pNF-κB-luc cell lines. The derivatives 5b, 6a, 6c, and 7a inhibited NF-κB action with IC values lower than that of sinomenine. [ABSTRACT FROM AUTHOR]