The Role Of Proinflammation Cytokine Secretion Induced By Nuclear Translocation Of HIF-1? In H1N1 Infection-induced Severe Pneumonia

ObjectiveThe mortality of influenza A(HIN1)infection-induced severe pneumonia was correlation with the host inflammatory response.Hence,the control of over-secretion of inflammatory cytokines(cytokine storm)is considered to be a key measure to treat the severe pneumonia caused by HI N1 infection.It has been reported that hypoxia-inducible factor 1-alpha(HIF-la)is associated with the production of pro-inflammatory molecules,but whether HIF-1? participates in the acute inflammatory responses against H1N1 infection is still unclear.The aim of this study was to investigate the role of proinflammation cytokine secretion induced by nuclear translocation of HIF-1? in H1N1 infection-induced severe pneumonia and provides a new basis for the development of treating severe pneumonia caused by H1N1 infection.Methods1.To investigate the role of HIF-la in H1N1 infection,A549 and THP-1 cell lines infected with H1N1 virus.To investigate the influence of H1N1 infection on the expression of HIF-la,A549 and THP-1 cells were infected with H1N1 at different multiplicity of infection(MOI)values.Real-time quantitative RT-PCR and Western blot analysis were used to quantify the intracellular HIF-1? mRNA and protein levels,respectively.2.An immunofluorescence assay was used to confirm whether HIF-1? protein accumulated in the nucleus post-H1N1 infection.The nuclear and cytoplasmic HIF-1?protein levels were analyzed by Western blot to further confirm these observations.3.To investigate the role of HIF-1? nuclear accumulation in H1N1 infection-induced inflammation and cytokine secretion,cytokine secretion was determined during H1N1 infection with or without 2ME2.4.To investigate the effects of increasing HIF-1? nuclear accumulation,cells were infected with H1N1 and then incubated in a hypoxic condition of 1%O2 for 24 hours.Results1.H1N1 infection of A549 and THP-1 cells did not alter HIF-1? mRNA and total protein levels.2.H1N1 infection of A549 and THP-1 cells induced nuclear translocation of HIF-1?.3.Blocking the nuclear accumulation of HIF-1? reduced pro-inflammation cytokine secretion in both H1N1-infected A549 and THP-1 cells.4.Increasing HIF-1? nuclear accumulation by hypoxia condition led to enhanced pro-inflammatory cytokine secretion both in H1N1-infected A549 and THP-1 cells.ConclusionsH1N1 infection induced the nuclear translocation of HIF-1? without altering HIF-1? mRNA or total protein expression under normal oxygen concentrations,and HIF-1? nuclear accumulation enhanced the secretion of pro-inflammatory cytokines which,in vivo,could result in inflammation in the lung tissue.With inflammatory diffusion,micro-environmental hypoxia could be induced,which would strongly increase the level of HIF-1? and be one of the drivers of HIF-1? nuclear accumulation.Thus,an irreversible,vicious cycle would be created between H1N1 infection and inflammation,which may contribute to H1N1-induced,severe pneumonia.