BACKGROUND: Toll-like receptor (TLR) 2/4 might play important roles in mediating proinflammatory cytokine synthesis and release. And nitric oxide (NO) has been used to treat acute respiratory distress syndrome (ARDS). This study aimed to investigate the changes in TLR2/4 gene expression in the lungs of rats with acute lung injury (ALI) complicated by acute hemorrhage necrotizing pancreatitis (AHNP) and the effect of NO on the TLR2/4 gene expression.
METHODS: One hundred and ten SD male rats were randomly divided into sham-operated group (n=10), AHNP group (n=30), chloroquine-treated group (n=30), and L-Arg-treated group (n=40). The lungs were dissected for lung histological scoring, and bronchoalveolar lavages were harvested for lung injury indexing. TLR2/4 mRNA expression in the lungs was measured by RT-PCR.
RESULTS: TLR2/4mRNA was detected in the lungs with low values in the sham-operated group (0.016±0.210E-2, 0.112±0.750E-2), but it was markedly increased at 3 hours in the AHNP group (0.787±0.751E-2, 1.512±1.794E-2), peaking at 12 hours (1.113±6.141E-2, 2.957±2.620E-2; P<0.05 or P<0.01). When lung injuries were aggravated, TNF-α concentrations in the lungs were increased, but NO concentrations were decreased (P<0.05 or P<0.01). When TLR2/4mRNA was inhibited by CQ (3h: 0.313±5.491E-2, 0.005±1.419E-3; 6h: 0.488±7.442E-2, 0.010±1.518E-3; 12h: 0.883±8.911E-2, 0.024±2.760E-3; P<0.05 or P<0.01), lung injuries were relieved. NO concentrations in the lungs were increased but TNF-α concentrations were decreased (P<0.05 or P<0.01). When the rats with AHNP were treated with L-Arg, TLR2/4mRNA expression in the lungs could be effectively inhibited (50mg-T: 0.656±3.977E-2, 1.501±6.111E-2; 100mg-T: 0.260±0.891E-2, 0.732±5.135E-2; 200mg-T: 0.126±0.914E-2, 0.414±1.678E-2; 400mg-T: 0.091±0.399E-2, 0.287±0.176E-2; P<0.05 or P<0.01) and lung injuries were relieved. At the same time, NO concentrations in the lungs were markedly increased, but TNF-α concentrations were decreased (P<0.05 or P<0.01).
CONCLUSIONS: The expression of TLR2/4mRNA is increased in the lungs in rats with AHNP and lung injuries are aggravated. TLR2/4mRNA gene expression of the lungs of rats with AHNP could be markedly inhibited by NO, leading to the relief of lung injuries.