A mouse SAP model was established by intraperitoneal (ip)
injections of 20 μg/kg
body weight caerulein. Pathological changes in the lung were observed by
hematoxylin and
eosin staining. Lung macrophages were isolated from bronchoalveolar lavage fluid. The quantity and purity of lung macrophages were detected by fluorescence-activated cell sorting and evaluated by real-time polymerase chain reaction (RT-PCR). They were treated with IL-4/IRF5 specific
siRNA (IRF5
siRNA) to reverse their polarization and were evaluated by detecting markers expression of M1/M2 using RT-PCR.
RESULTS: SAP associated
acute lung injury (ALI) was induced successfully by ip
injections of
caerulein, which was confirmed by histopathology. Lung macrophages expressed high levels of IRF5 as M1 phenotype during the early
acute pancreatitis stages. Reduction of IRF5 expression by IRF5
siRNA reversed the action of macrophages from M1 to M2 phenotype in vitro. The expressions of M1 markers, including IRF5 (S + IRF5
siRNA vs S + PBS, 0.013 ± 0.01 vs 0.054 ± 0.047, P < 0.01), TNF-α (S + IRF5
siRNA vs S + PBS, 0.0003 ± 0.0002 vs 0.019 ± 0.018, P < 0.001), iNOS (S + IRF5
siRNA vs S + PBS, 0.0003 ± 0.0002 vs 0.026 ± 0.018, P < 0.001) and
IL-12 (S + IRF5
siRNA vs S + PBS, 0.000005 ± 0.00004 vs 0.024 ± 0.016, P < 0.001), were decreased. In contrast, the expressions of M2 markers, including
IL-10 (S + IRF5
siRNA vs S + PBS, 0.060 ± 0.055 vs 0.0230 ± 0.018, P < 0.01) and Arg-1 (S + IRF5
siRNA vs S + PBS, 0.910 ± 0.788 vs 0.0036 ± 0.0025, P < 0.001), were increased. IRF5
siRNA could reverse the lung macrophage polarization more effectively than
IL-4.
CONCLUSION: