Toxoplasma gondii provoked rapid and sustained nuclear translocation of signal transducer and activator of transcription (STAT) 6, a central mediator of interleukin (IL)-4, in macrophage-differentiated human acute monocytic leukemia cells without exogenous IL-4 in western blot and immunofluorescence assay. Phosphorylation of STAT6 occurred immediately after the entry of T. gondii and only by live tachyzoites, not by killed or soluble extract. It was impeded by Janus kinase (JAK) 3 inhibitor and small interfering RNA (siRNA) of STAT6. It induced expression of IL-4 responsive genes such as IL-4R, CD40, and CD23. It also mediated expression of two large clusters of C-C chemokine ligands (CCLs) and serine protease inhibitors (SERPINs) in microarray of T. gondii-infected macrophages. CCL1, 2, 8, 13, and 22 and SPINT2, SERPINB3, B4, and B13 were increased by the infection and inhibited by the treatment of JAK3 inhibitor and siRNA-mediated STAT6 silencing, which suggested the expression was governed by STAT6 activation. Secreting those CCLs, T. gondii-infected macrophages may attract more monocytes and Th2 cells of CCR3 and CCR4 to enrich the Th2 environment nearby the infected macrophages, and induced SERPINs may participate in protection from intracellular damages produced by activated lysosomal enzymes and in the inhibition of caspase activity to block the apoptosis. This suggests that T. gondii exploits cytokine cross-regulation through STAT6 activation to obviate various toxoplasmacidal reactions by interferon-gamma.
The hepatitis C virus (HCV) is a major causative agent of chronic hepatitis and hepatocellular carcinoma. The development of alternative antiviral therapies is warranted because current treatments for the HCV infection affect only a limited number of patients and lead to significant toxicities. The HCV genome is exclusively present in the RNA form; therefore, ribozyme strategies to target certain HCV sequences have been proposed as anti-HCV treatments. In this study, we determined which regions of the internal ribosome entry site (IRES) of HCV are accessible to ribozymes by employing an RNA mapping strategy that is based on a trans-splicing ribozyme library. We then discovered that the loop regions of the domain IIIb of HCV IRES appeared to be particularly accessible. Moreover, to verify if the target sites that were predicted to be accessible are truly the most accessible, we assessed the ribozyme activities by comparing not only the trans-splicing activities in vitro but also the trans-cleavage activities in cells of several ribozymes that targeted different sites. The ribozyme that could target the most accessible site identified by mapping studies was then the most active with high fidelity in cells as well as in vitro. These results demonstrate that the RNA mapping strategy represents an effective method to determine the accessible regions of target RNAs and have important implications for the development of various antiviral therapies which are based on RNA such as ribozyme, antisense, or siRNA.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.