[show abstract][hide abstract] ABSTRACT: Influenza A virus (IAV) is one of the most common infectious pathogens in humans. Since the IVA genome does not have the processing protease for the viral hemagglutinin (HA) envelope glycoprotein precursors, entry of this virus into cells and infectious organ tropism of IAV are primarily determined by host cellular trypsin-type HA processing proteases. Several secretion-type HA processing proteases for seasonal IAV in the airway, and ubiquitously expressed furin and pro-protein convertases for highly pathogenic avian influenza (HPAI) virus, have been reported. Recently, other HA-processing proteases for seasonal IAV and HPAI have been identified in the membrane fraction. These proteases proteolytically activate viral multiplication at the time of viral entry and budding. In addition to the role of host cellular proteases in IAV pathogenicity, IAV infection results in marked upregulation of cellular trypsins and matrix metalloproteinase-9 in various organs and cells, particularly endothelial cells, through induced pro-inflammatory cytokines. These host cellular factors interact with each other as the influenza virus-cytokine-protease cycle, which is the major mechanism that induces vascular hyperpermeability and multiorgan failure in severe influenza. This mini-review discusses the roles of cellular proteases in the pathogenesis of IAV and highlights the molecular mechanisms of upregulation of trypsins as effective targets for the control of IAV infection. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.
Biochimica et Biophysica Acta 07/2011; 1824(1):186-94. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: Influenza A virus (IAV) infection markedly up-regulates ectopic trypsins in various organs, viral envelope glycoprotein processing proteases, which are pre-requisites for virus entry and multiplication. We investigated the pathological roles of trypsin up-regulation in the progression of IAV-induced myocarditis, cytokine induction, and viral replication in the hearts, and also investigated the protective effects of trypsin inhibitor on cardiac dysfunction in vivo and selective knockdown of trypsin on IAV-induced cellular damage in cardiomyoblasts.
The relationship of the expression among IAV RNA, trypsins, matrix metalloproteinase (MMP)-9, MMP-2, pro-inflammatory cytokines interleukin (IL)-6, IL-1β, and tumour necrosis factor-α was analysed in mice hearts and cardiomyoblasts after IAV infection. The severity of myocarditis was most noticeable during Day 6-9 post-infection, along with peak expression of viral RNA, trypsins, particularly trypsin₂, MMPs, and cytokines. Cardiac ATP levels were the lowest at Day 9. Up-regulated trypsins, viral protein, and tissue-injured loci in the myocardium were closely localized. Trypsin inhibitor aprotinin treatment in vivo and selective trypsin₁- and trypsin₂-knockdown, particularly the latter, in H9c2 cardiomyoblasts significantly suppressed viral replication, up-regulation of MMPs, and production of active MMP-9 and cytokines, resulting in marked protection against cellular damage, ATP depletion, and apoptosis. IAV infection-induced cardiac dysfunction monitored by echocardiography was improved significantly by aprotinin treatment.
IAV-induced trypsins, particularly trypsin₂, in the myocardium trigger acute viral myocarditis through stimulation of IAV replication, proMMP-9 activation, and cytokine induction. These results suggest that up-regulation of trypsins is one of the key host pathological findings in IAV-induced myocarditis.
Cardiovascular research 11/2010; 89(3):595-603. · 5.80 Impact Factor
[show abstract][hide abstract] ABSTRACT: Severe influenza is characterized by cytokine storm and multiorgan failure with edema. The aim of this study was to define the impact of the cytokine storm on the pathogenesis of vascular hyperpermeability in severe influenza.
Weanling mice were infected with influenza A WSN/33(H1N1) virus. The levels of proinflammatory cytokines, tumor necrosis factor (TNF) alpha, interleukin (IL) 6, IL-1beta, and trypsin were analyzed in the lung, brain, heart, and cultured human umbilical vein endothelial cells. The effects of transcriptional inhibitors on cytokine and trypsin expressions and viral replication were determined.
Influenza A virus infection resulted in significant increases in TNF-alpha, IL-6, IL-1beta, viral hemagglutinin-processing protease trypsin levels, and viral replication with vascular hyperpermeability in lung and brain in the first 6 days of infection. Trypsin upregulation was suppressed by transcriptional inhibition of cytokines in vivo and by anti-cytokine antibodies in endothelial cells. Calcium mobilization and loss of tight junction constituent, zonula occludens-1, associated with cytokine- and trypsin-induced endothelial hyperpermeability were inhibited by a protease-activated receptor-2 antagonist and a trypsin inhibitor.
The influenza virus-cytokine-protease cycle is one of the key mechanisms of vascular hyperpermeability in severe influenza.
The Journal of Infectious Diseases 10/2010; 202(7):991-1001. · 5.85 Impact Factor
[show abstract][hide abstract] ABSTRACT: Severe influenza is characterized by cytokine storm and multi-organ failure with edema. We found that the "influenza virus-cytokine-trypsin/MMP-9 cycle" in the endothelial cells is one of the key mechanisms of vascular hyperpermeability, the major pathogen of multi-organ failure. Upregulated TNF-alpha, IL-6 and IL-beta induce ectopic pancreatic trypsin and pro-MMP-9 in the endothelial cells and in various organs. Trypsin mediates the viral hemagglutinin processing, which is crucial for viral entry and multicycles of replication. In addition, trypsin is the most potent pro-MMP-9 convertase to form active MMP-9 and both proteases synergistically destruct matrix around blood vessels. In addition upregulated trypsin triggers through its receptor, PAR-2, the modification of cellular functions, such as increase in calcium mobilization and mitochondrial membrane permeability, suppression of ATP generation and loss of tight junction constituent, zonula occludens-1. High risk patients who have impaired mitochondrial fuel utilization will easy get into energy crisis, resulting in vascular hyperpermeability in severe influenza.
Nippon rinsho. Japanese journal of clinical medicine 08/2010; 68(8):1565-73.
[show abstract][hide abstract] ABSTRACT: Severe influenza is characterized clinicopathologically by multiple organ failure, although the relationship amongst virus and host factors that influence this morbid outcome and the underlying mechanisms of action remain unclear. The present study identified marked upregulation of matrix metalloproteinase (MMP)-9 and pro-inflammatory cytokine tumor necrosis factor alpha (TNF-alpha) in various organs after intranasal infection of influenza A WSN virus. MMP-9 and TNF-alpha were upregulated in the lung, the site of initial infection, as well as in the brain and heart. The infection-induced MMP-9 upregulation was inhibited by anti-TNF-alpha antibodies and by anti-oxidative reagents pyrrolidine dithiocarbamate and N-acetyl-L-cysteine, which inhibit activation of nuclear factor kappa B (NF-kappaB), as well as by nordihydroguaiaretic acid, which inhibits activation of activator protein 1 (AP-1). In addition, MMP-9 upregulation via TNF-alpha was also suppressed by inhibitors of mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinase 1/2 and p38, and partly by a c-Jun N-terminal kinase inhibitor. These results indicated that the influenza-induced MMP-9 upregulation in various organs is mediated through MAPK-NF-kappaB- and/or AP-1-dependent mechanisms. Strategies that neutralize TNF-alpha as well as inhibitors of MAPK-NF-kappa B- and/or AP-1-dependent pathways may be useful for suppressing the MMP-9 effect and thus preventing multiple organ failure in severe influenza.
The Journal of Medical Investigation 02/2010; 57(1-2):26-34.
[show abstract][hide abstract] ABSTRACT: Influenza A virus (IAV) is one of the most common infectious pathogens in humans and causes considerable morbidity and mortality. The recent spread of highly-pathogenic avian IAV H5N1 viruses has reinforced the importance of pandemic preparedness. In the pathogenesis of IAV infection, cellular proteases play critical roles in the process of viral entry into cells that subsequently leads to tissue damage in the infected organs. Since there are no processing protease for the viral membrane fusion glycoprotein hemagglutinin precursor (HA(0)) in IAV, entry of the virus into cells is determined primarily by the host cellular HA(0) processing proteases that proteolytically activate membrane fusion activity. HA(0) of seasonal human IAV has the consensus cleavage site motif Q(E)-T/X-R and is selectively processed by at least seven different trypsin-type processing proteases identified to-date in animal model experiments using mouse-adapted IAV or gene expression system in MDCK cells. As is the case for the highly pathogenic avian influenza (HPAI) A virus, endoproteolytic processing of the HA(0) occurs through ubiquitous cellular processing proteases, which selectively recognize the multi-basic consensus cleavage site motifs, such as R-X-K/R-R, and K-X-K/R-R. The cleavage enzymes for the R-X-K/R-R motif, but not K-X-K/R-R motif, have been reported to be furin and pro-protein convertase (PC)5/6 in the trans-Golgi network. Here we report new members of type II transmembrane serine proteases of the cell membrane, mosaic serine protease large form (MSPL) and its splice variant TMPRSS13, which recognize and cleave both R-X-K/R-R and K-X-K/R-R motifs without calcium. Furthermore, IAV infection significantly up-regulates a latent ectopic pancreatic trypsin, one of the potent HA processing proteases, and pro-matrix metalloprotease-9, in various organs. These proteases may synergistically damage the blood-brain barrier in the brain and basement membrane of blood vessels in various organs, resulting in severe edema and multiple organ failure. In this review, we discuss these proteases as new drug target molecules for IAV treatment acting by inhibition of IAV multiplication and prevention of multiple organ failure, other than anti-viral agents, viral neuraminidase inhibitors.
Journal of molecular and genetic medicine: an international journal of biomedical research 02/2008; 3(1):167-75.