Lyn regulates inflammatory responses in Klebsiella pneumoniae infection via the p38/NF‐κB pathway

Abstract

Klebsiella pneumoniae is one of the most common pathogens in nosocomial infections and is becoming increasingly multidrug-resistant. However, the underlying molecular pathogenesis of this bacterium remains elusive, limiting the therapeutic options. Understanding the mechanism of its pathogenesis may facilitate the development of antibacterial therapeutics. Here, we show that Lyn, a pleiotropic Src tyrosine kinase, is involved in host defense against K. pneumoniae (Kp) by regulating phagocytosis process and simultaneously downregulating inflammatory responses. Using acute infection mouse models, we observed that lyn−/− mice were more susceptible to Kp with increased mortality and severe lung injury compared with wild-type mice. Kp infected-lyn−/− mice exhibited elevated inflammatory cytokines (IL-6 and TNF-α), and increased superoxide in the lung and other organs. In addition, the phosphorylation of p38 and NF-κB p65 subunit increased markedly in response to Kp infection in lyn−/− mice. We also demonstrated that the translocation of p65 from cytoplasm to nuclei increased in cultured murine lung epithelial cells by Lyn siRNA knockdown. Furthermore, lipid rafts clustered with activated Lyn and accumulated in the site of Kp invasion. Taken together, these findings revealed that Lyn may participate in host defense against Kp infection through the negative modulation of inflammatory cytokines.

DNA Repair Interacts with Autophagy To Regulate Inflammatory Responses to Pulmonary Hyperoxia

“…O 2 tension in cell culture medium below was 647 ± 9 mmHg determined as described (20). After bronchoalveolar lavage (BAL), the trachea and lung were obtained for cell biology assays or fixed in 10% formalin for histological analysis (21, 22). …”

“…The fixed tissue samples were processed for obtaining standard hematoxylin and eosin (H&E) staining and examined for differences in morphology post infection (21, 22). …”

A novel chemosynthetic peptide with ß-sheet motif efficiently kills Klebsiella pneumoniae in a mouse model

“…After anesthesia with 40 mg/kg ketamine, mice were instilled with 1×10 5 (four mice/group) colony-forming units (CFUs) of Kp by intranasal instillation, and sacrificed when they were moribund. 19,20 Survival was determined using Kaplan-Meier curve. After bronchoalveolar lavage (BAL), the lung was excised for homogenization or fixed in 10% formalin.…”

“…[18][19][20]29,30 Western blotting Lung tissues were lysed and homogenized in a radioimmunoprecipitation assay containing a protease inhibitor cocktail (Sigma, St Louis, MO, USA). The supernatants were collected and the protein concentration was quantitated.…”

“…19 Although the distribution of the bacteria in the enterocelia was somewhat variable, the infected mice exhibited much wider dissemination of bioluminescence in the area of thoracic cavity 4 hours postinfection with in vivo dynamic analysis using an IVIS XRII 200 biophotonic imager. However, the dissemination areas in infected mice were more constrained and only localized in one lung in IK8L-treated mice than those of sham-treated mice ( Figure 1A).…”