Combined effects of interferon and steroid hormones on 2',5'-oligoadenylate synthetase activity in chronic lymphocytic leukemia cells

Molecular cloning and functional characterization of porcine 2',5'-oligoadenylate synthetase 1b and its effect on infection with porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome virus (PRRSV) has previously been shown to increase porcine 2'-5'-oligoadenylate synthase (OAS) 1a expression, but the specific role of porcine OAS1b (pOAS1b) in PRRSV replication remains unknown. In this study, we conducted sequence analysis of the porcine OAS1b gene and studied the effects of its overexpression or silencing on PRRSV replication. OAS1b, localized mainly in the cytoplasm, was found to contain conserved protein domains, such as the P-Loop and D-Box, indicating that its nucleotidyl transferase activity was complete and the antiviral effect depended on ribonuclease L (RNase L). OAS1b overexpression inhibited PRRSV replication, whereas small-interfering-RNA silencing of OAS1b resulted in increased virus titers. Additionally, OAS1b promoted expression of interferons as well as interferon-β promoter activity. These results lay the theoretical foundation for the development of new anti-PRRSV strategies.

Molecular Cloning and Identification of the 2'-5' Oligoadenylate Synthetase 2 Gene in Chinese Domestic Pigs Through Bioinformatics Analysis, and Determination of Its Antiviral Activity Against Porcine Reproductive and Respiratory Syndrome Virus Infection

An interferon-mediated antiviral protein, 2'-5' oligoadenylate synthetase 2, plays an important role in the antiviral response of interferons. In this study, 2'-5' oligoadenylate synthetase 2 genes were cloned from Chinese domestic pigs. Bioinformatics analysis revealed that the 2024-bp long open reading fame encodes 707 amino acids. There are two conserved regions in this protein: the nucleotidyltransferase domain, and the 2'-5' oligoadenylate synthetase domain (OAS). Genetic evolution analysis showed that the 2'-5' oligoadenylate synthetase 2 gene in domestic pigs is closely related to that of cattle. There are multiple antigenic sites, no signal peptide, and no transmembrane region in the gene, which is predicted to be a hydrophilic protein. Secondary structures were found to be mainly alpha helix-based; its tertiary structure is close to that of humans and cattle, but not that of mice. Tissue distribution results indicated that this protein is distributed in multiple organs, with high distribution in the liver; it is mainly localized in the cytoplasm. PRRSV infection, interferon-beta, and Poly(I: C) treatment all promoted 2'-5' oligoadenylate synthetase 2 gene expression. Overexpression and RNA silencing of porcine OAS2 inhibited and promoted PRRSV replication in cells, respectively. The inhibitory effect of porcine OAS2 was mainly dependent on RNase L, similar to what was predicted. This study has laid the foundation for future antiviral studies in pig, and provided a new way of preventing and treating PRRSV in the future.

Theoretical basis, experimental design, and computerized simulation of synergism and antagonism in drug combination studies

The median-effect equation derived from the mass-action law principle at equilibrium-steady state via mathematical induction and deduction for different reaction sequences and mechanisms and different types of inhibition has been shown to be the unified theory for the Michaelis-Menten equation, Hill equation, Henderson-Hasselbalch equation, and Scatchard equation. It is shown that dose and effect are interchangeable via defined parameters. This general equation for the single drug effect has been extended to the multiple drug effect equation for n drugs. These equations provide the theoretical basis for the combination index (CI)-isobologram equation that allows quantitative determination of drug interactions, where CI < 1, = 1, and > 1 indicate synergism, additive effect, and antagonism, respectively. Based on these algorithms, computer software has been developed to allow automated simulation of synergism and antagonism at all dose or effect levels. It displays the dose-effect curve, median-effect plot, combination index plot, isobologram, dose-reduction index plot, and polygonogram for in vitro or in vivo studies. This theoretical development, experimental design, and computerized data analysis have facilitated dose-effect analysis for single drug evaluation or carcinogen and radiation risk assessment, as well as for drug or other entity combinations in a vast field of disciplines of biomedical sciences. In this review, selected examples of applications are given, and step-by-step examples of experimental designs and real data analysis are also illustrated. The merging of the mass-action law principle with mathematical induction-deduction has been proven to be a unique and effective scientific method for general theory development. The median-effect principle and its mass-action law based computer software are gaining increased applications in biomedical sciences, from how to effectively evaluate a single compound or entity to how to beneficially use multiple drugs or modalities in combination therapies.