Ion-Current-Based Temporal Proteomic Profiling of Influenza-A-Virus-Infected Mouse Lungs Revealed Underlying Mechanisms of Altered Integrity of the Lung Microvascular Barrier

Investigation of influenza-A-virus
(IAV)-infected lung proteomes
will greatly promote our understanding on the virus-host crosstalk.
Using a detergent-cocktail extraction and digestion procedure and
a reproducible ion-current-based method, we performed the first comprehensive
temporal analysis of mouse IAV infection. Mouse lung tissues at three
time points post-inoculation were compared with controls (n = 4/group), and >1600 proteins were quantified without
missing value in any animal. Significantly changed proteins were identified
at 4 days (n = 144), 7 days (n =
695), and 10 days (n = 396) after infection, with
low false altered protein rates (1.73–8.39%). Functional annotation
revealed several key biological processes involved in the systemic
host responses. Intriguingly, decreased levels of several cell junction
proteins as well as increased levels of tissue metalloproteinase MMP9
were observed, reflecting the IAV-induced structural breakdown of
lung epithelial barrier. Supporting evidence of MMP9 activation came
from immunoassays examining the abundance and phosphorylation states
of all MAPKs and several relevant molecules. Importantly, IAV-induced
MMP gelatinase expression was suggested to be specific to MMP9, and
p38 MAPK may contribute predominantly to MMP9 elevation. These findings
help to resolve the long-lasting debate regarding the signaling pathways
of IAV-induced MMP9 expression and shed light on the molecular mechanisms
underlying pulmonary capillary-alveolar leak syndrome that can occur
during influenza infection.