Inhibition of Polyinosinic-Polycytidylic Acid-Induced Acute Pulmonary Inflammation and NF-κB Activation in Mice by a Banana Plant Extract.

NF-κB activation is pivotal for the excess inflammation causing the critical condition and mortality of respiratory viral infection patients. This study was aimed to evaluate the effect of a banana plant extract (BPE) on suppressing NF-κB activity and acute lung inflammatory responses in mice induced by a synthetic double-stranded RNA viral mimetic, polyinosinic-polycytidylic acid (poly (I:C)). The inflammatory responses were analyzed by immunohistochemistry and HE stains and ELISA. The NF-κB activities were detected by immunohistochemistry in vivo and immunofluorescence and Western blot in vitro. Results showed that BPE significantly decreased influx of immune cells (neutrophils, lymphocytes, and total WBC), markedly suppressed the elevation of pro-inflammatory cytokines and chemokines (IL-6, RANTES, IFN-γ, MCP-1, keratinocyte-derived chemokine, and IL-17), and restored the diminished anti-inflammatory IL-10 in the bronchoalveolar lavage fluid (BALF) of poly (I:C)-stimulated mice. Accordingly, HE staining revealed that BPE treatment alleviated poly (I:C)-induced inflammatory cell infiltration and histopathologic changes in mice lungs. Moreover, immunohistochemical analysis showed that BPE reduced the pulmonary IL-6, CD11b (macrophage marker), and nuclear NF-κB p65 staining intensities, whilst restored that of IL-10 in poly (I:C)-stimulated mice. In vitro, BPE antagonized poly(I:C)-induced elevation of IL-6, nitric oxide, reactive oxygen species, NF-κB p65 signaling, and transient activation of p38 MAPK in human lung epithelial-like A549 cells. Taken together, BPE ameliorated viral mimic poly(I:C)-induced acute pulmonary inflammation in mice, evidenced by reduced inflammatory cell infiltration and regulation of both pro- and anti-inflammatory cytokines. The mechanism of action might closely associate with NF-κB signaling inhibition.

Persistence of Hepatitis B Virus DNA and the Tempos between Virion Secretion and Genome Maturation in a Mouse Model.

Hepatitis B virus (HBV) core protein (HBc) accumulates frequent mutations in natural infection. Wild-type HBV is known to secrete predominantly virions containing mature DNA genome. However, a frequent naturally occurring HBc variant, I97L, changing from an isoleucine to a leucine at amino acid 97, exhibited an immature secretion phenotype in culture, which preferentially secretes virions containing immature genomes. In contrast, mutant P130T, changing from a proline to a threonine at amino acid 130, exhibited a hypermaturation phenotype by accumulating an excessive amount of intracellular fully mature DNA genome. Using a hydrodynamic delivery mouse model, we studied the in vivo behaviors of these two mutants, I97L and P130T. We detected no naked core particles in all hydrodynamically injected mice. Mutant I97L in mice exhibited pleiotropic phenotypes: (i) excessive numbers of serum HBV virions containing immature genomes, (ii) significantly reduced numbers of intracellular relaxed-circle and single-stranded DNAs, and (iii) less persistent intrahepatic and secreted HBV DNAs than wild-type HBV. These pleiotropic phenotypes were observed in both immunocompetent and immunodeficient mice. Although mutant P130T also displayed a hypermaturation phenotype in vivo, it cannot efficiently rescue the immature virion secretion of mutant I97L. Unexpectedly, the single mutant P130T exhibited in vivo a novel phenotype in prolonging the persistence of HBV genome in hepatocytes. Taken together, our studies provide a plausible rationale for HBV to regulate envelopment morphogenesis and virion secretion via genome maturity, which is likely to play an important role in the persistence of viral DNA in this mouse model.IMPORTANCE Chronic infection with human hepatitis B virus (HBV) could lead to cirrhosis and hepatoma. At present, there is no effective treatment to eradicate the virus from patients. HBV in chronic carriers does not exist as a single homogeneous population. The most frequent naturally occurring mutation in HBV core protein occurs at amino acid 97, changing an isoleucine to leucine (I97L). One dogma in the field is that only virions containing a mature genome are preferentially secreted into the medium. Here, we demonstrated that mutant I97L can secrete immature genome in mice. Although viral DNA of mutant I97L with immature genome is less persistent than wild-type HBV in time course experiments, viral DNA of mutant P130T with genome hypermaturation, surprisingly, is more persistent. Therefore, virion secretion regulated by genome maturity could influence viral persistence. It remains an open issue whether virion secretion could be a drug target for HBV therapy.

Nucleic acid chaperone activity associated with the arginine-rich domain of human hepatitis B virus core protein.

UNLABELLED: Hepatitis B virus (HBV) DNA replication occurs within the HBV icosahedral core particles. HBV core protein (HBc) contains an arginine-rich domain (ARD) at its carboxyl terminus. This ARD domain of HBc 149-183 is known to be important for viral replication but not known to have a structure. Recently, nucleocapsid proteins of several viruses have been shown to contain nucleic acid chaperone activity, which can facilitate structural rearrangement of viral genome. Major features of nucleic acid chaperones include highly basic amino acid residues and flexible protein structure. To test the nucleic acid chaperone hypothesis for HBc ARD, we first used the disassembled full-length HBc from Escherichia coli to analyze the nucleic acid annealing and strand displacement activities. To exclude the potential contamination of chaperones from E. coli, we designed synthetic HBc ARD peptides with different lengths and serine phosphorylations. We demonstrated that HBc ARD peptide can behave like a bona fide nucleic acid chaperone and that the chaperone activity depends on basic residues of the ARD domain. The loss of chaperone activity by arginine-to-alanine substitutions in the ARD can be rescued by restoring basic residues in the ARD. Furthermore, the chaperone activity is subject to regulation by phosphorylation and dephosphorylation at the HBc ARD. Interestingly, the HBc ARD can enhance in vitro cleavage activity of RNA substrate by a hammerhead ribozyme. We discuss here the potential significance of the HBc ARD chaperone activity in the context of viral DNA replication, in particular, at the steps of primer translocations and circularization of linear replicative intermediates. IMPORTANCE: Hepatitis B virus is a major human pathogen. At present, no effective treatment can completely eradicate the virus from patients with chronic hepatitis B. We report here a novel chaperone activity associated with the viral core protein. Our discovery could lead to a new drug design for more effective treatment against hepatitis B virus in the future.

HBV maintains electrostatic homeostasis by modulating negative charges from phosphoserine and encapsidated nucleic acids.

Capsid assembly and stability of hepatitis B virus (HBV) core protein (HBc) particles depend on balanced electrostatic interactions between encapsidated nucleic acids and an arginine-rich domain (ARD) of HBc in the capsid interior. Arginine-deficient ARD mutants preferentially encapsidated spliced viral RNA and shorter DNA, which can be fully or partially rescued by reducing the negative charges from acidic residues or serine phosphorylation of HBc, dose-dependently. Similarly, empty capsids without RNA encapsidation can be generated by ARD hyper-phosphorylation in insect, bacteria, and human hepatocytes. De-phosphorylation of empty capsids by phosphatase induced capsid disassembly. Empty capsids can convert into RNA-containing capsids by increasing HBc serine de-phosphorylation. In an HBV replicon system, we observed a reciprocal relationship between viral and non-viral RNA encapsidation, suggesting both non-viral RNA and serine-phosphorylation could serve as a charge balance buffer in maintaining electrostatic homeostasis. In addition, by comparing the biochemistry assay results between a replicon and a non-replicon system, we observed a correlation between HBc de-phosphorylation and viral replication. Balanced electrostatic interactions may be important to other icosahedral particles in nature.

MicroRNA-22 can reduce parathymosin expression in transdifferentiated hepatocytes.

Pancreatic acinar cells AR42J-B13 can transdifferentiate into hepatocyte-like cells permissive for efficient hepatitis B virus (HBV) replication. Here, we profiled miRNAs differentially expressed in AR42J-B13 cells before and after transdifferentiation to hepatocytes, using chip-based microarray. Significant increase of miRNA expression, including miR-21, miR-22, and miR-122a, was confirmed by stem-loop real-time PCR and Northern blot analyses. In contrast, miR-93, miR-130b, and a number of other miRNAs, were significantly reduced after transdifferentiation. To investigate the potential significance of miR-22 in hepatocytes, we generated cell lines stably expressing miR-22. By 2D-DIGE, LC-MS/MS, and Western blot analyses, we identified several potential target genes of miR-22, including parathymosin. In transdifferentiated hepatocytes, miR-22 can inhibit both mRNA and protein expression of parathymosin, probably through a direct and an indirect mechanism. We tested two computer predicted miR-22 target sites at the 3' UTR of parathymosin, by the 3' UTR reporter gene assay. Treatment with anti-miR-22 resulted in significant elevation of the reporter activity. In addition, we observed an in vivo inverse correlation between miR-22 and parathymosin mRNA in their tissue distribution in a rat model. The phenomenon that miR-22 can reduce parathymosin protein was also observed in human hepatoma cell lines Huh7 and HepG2. So far, we detected no major effect on several transdifferentiation markers when AR42J-B13 cells were transfected with miR-22, or anti-miR-22, or a parathymosin expression vector, with or without dexamethasone treatment. Therefore, miR-22 appears to be neither necessary nor sufficient for transdifferentiation. We discussed the possibility that altered expression of some other microRNAs could induce cell cycle arrest leading to transdifferentiation.