探討基質金屬蛋白酵素9於流感病毒感染中之角色與調控

Abstract

A型流感病毒在全球造成嚴重的感染，甚至造成重症患者死亡；而不同的流感病毒株在臨床症狀上亦有所不同。為瞭解流感病毒致病機轉，我們以A/WSN/33 (H1N1)及A/Panama-like (H3N2)兩種不同的A型流感病毒株以氣管內注射感染C57BL/6小鼠並且比較其肺部免疫病理現象。與Panama-like病毒株相比，WSN病毒株感染之小鼠有較嚴重的肺臟損傷及細胞浸潤，同時伴隨更高量的活性氧物種 (Reactive oxygen species) 及活性氮 (Reactive Nitrogen Species) 的產生。若小鼠因NCF1缺陷而無法產生超氧化物，則會減輕流感病毒造成的肺臟損傷。更有趣的是，我們發現僅有WSN病毒株感染可在肺臟中誘發高量的基質金屬蛋白酵素9 (Matrix Metalloproteinase-9)，而Panama-like病毒株則無此現象，並且NCF1缺陷也會減少該蛋白酵素的產生。 基質金屬蛋白酵素9可降解胞外基質並且參與肺部組織的病理變化。目前已知嗜中性球與肺泡巨噬細胞為肺部內基質金屬蛋白酵素9之產生細胞。我們以氣管注射的方式使小鼠感染WSN病毒株，證實嗜中性球與肺泡巨噬細胞都會產生基質金屬蛋白酵素9，然而該酵素在嗜中性球的表現持續且不受調控。與嗜中性球不同，流感病毒與類鐸受體7之促效劑可引發巨噬細胞產生基質金屬蛋白酵素9並且受到MALT1蛋白之調控。另外，肺泡巨噬細胞產生的基質金屬蛋白酵素9是透過NF-κB 而非AP-1訊息傳導途徑調控。流感病毒與類鐸受體7之促效劑會使巨噬細胞內MALT1蛋白活化並且進一步降解NF-κB的負調控蛋白CYLD，但是不影響RelB蛋白。透過MALT1抑制劑的實驗，我們證實了CYLD蛋白減少是由於類鐸受體7之促效劑活化MALT1蛋白所致。有趣的是，在流感病毒感染的MALT1缺失小鼠的肺臟中，不止是基質金屬蛋白酵素9產生較少，同時TNF與IL-6也較少。與正常小鼠相較，MALT1缺失小鼠感染A型流感病毒時有較少的體重下降以及較高的存活率，可見基質金屬蛋白酵素9在流感病毒引發疾病嚴重程度中扮演重要的角色。我們的研究首度證實MALT1調控肺泡巨噬細胞基質金屬蛋白酵素9的產生，並且證明MALT1與流感病毒引發的疾病嚴重度相關。

Influenza A virus (IAV) infection causes significant morbidity and mortality worldwide. Infection by different strains of IAV presents different clinical pictures. We infected C57BL/6 mice intratracheally with influenza A/WSN/33 (H1N1) and A/Panama-like (H3N2) viruses and compared their immunopathologies in the lungs. There was more severe lung pathology accompanied by massive myeloid cell infiltration in mice infected by WSN virus than by Panama-like virus. WSN virus infection also induced production of reactive oxygen and nitrogen species (ROS/RNS). Neutrophil cytosolic factor 1 (NCF1, phox47) deficiency ameliorated lung pathology in infected mice. Interestingly, infection by WSN virus but not by Panama-like virus induced high levels of matrix metalloproteinase-9 (MMP-9), and NCF1 deficiency ablated MMP-9 expression in the lungs. MMP-9 degrades extracellular matrix and is involved in the pathology of pulmonary diseases. Both neutrophils and alveolar macrophages are known to be MMP-9 producers in the lungs. In mice intratracheally infected by WSN virus, both neutrophils and alveolar macrophages produced MMP-9. Neutrophils constitutively expressed MMP-9 and its production was not regulated. Production of MMP-9 by macrophages stimulated with IAV or Toll-like receptor 7 (TLR7) agonist was regulated by mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1). In addition, MMP-9 production in alveolar macrophages was mediated by NF-κB but not by AP-1. IAV- and TLR7 agonist-induced activation of MALT1 resulted in reduction of the level of cylindromatosis (CYLD), a negative regulator of NF-κB, but not RelB in macrophages. By using MALT1 inhibitor, we demonstrated TLR7 agonist-induced reduction of CYLD was MALT1 activity-dependent. Interestingly, MALT1 deficiency not only reduced the level of MMP-9, but also that of TNF and IL-6 in the lungs after infection. MALT1-deficient mice sustained less body weight loss and longer survival after IAV infection compared to WT mice. We demonstrated a novel role of MALT1 in MMP-9 production by alveolar macrophages and revealed the correlation between MALT1 and the severity of influenza infection.