Transcriptional Profiling of Lipopolysaccharide-Induced Acute Lung Injury

Abstract

Mortality associated with acute lung injury (ALI) induced by lipopolysaccharide (LPS) remains high in humans, warranting improved treatment and prevention strategies. ALI is characterized by the expression of proinflammatory mediators and extensive neutrophil influx into the lung, followed by severe lung damage. Understanding the pathogenesis of LPS-induced ALI is a prerequisite for designing better therapeutic strategies. In the present study, we used microarrays to gain a global view of the transcriptional responses of the lung to LPS in a mouse model of ALI that mimics ALI in humans. A total of 71 inflammation-associated genes were up-regulated in LPS-treated lungs, including a chemokine, LPS-induced CXC chemokine (LIX), whose role in the induction of ALI is unknown. Most of the inflammatory genes peaked at 2 h post-LPS treatment. Real-time reverse transcription-PCR confirmed the LPS-induced up-regulation of selected genes identified by microarray analysis, including LIX. The up-regulation of LIX, tumor necrosis factor alpha, and macrophage inflammatory protein 2 was confirmed at the protein level by enzyme-linked immunosorbent assays. To determine the role of LIX in the induction of ALI, we used both exogenous LIX and a LIX blocking antibody. Exogenous LIX alone elicited a neutrophil influx in the lungs, and the anti-LIX antibody attenuated the LPS-induced neutrophil accumulation in the lungs. Taken together, the results of our study demonstrate for the first time the temporal expression of inflammatory genes during LPS-induced ALI and suggest that early therapeutic intervention is crucial to attenuate lung damage. Moreover, we identified a role for LIX in the induction of ALI, and therefore LIX may serve as a novel therapeutic target for the minimization of ALI.

Toll/IL-1 Receptor Domain-Containing Adaptor Inducing IFN-β (TRIF)-Mediated Signaling Contributes to Innate Immune Responses in the Lung during Escherichia coli Pneumonia

“…5, E and J). In this context, we have demonstrated that LIX is predominantly produced by resident cells, i.e., alveolar type II cells after LPS challenge (25,26).…”

“…The induction of lung inflammation in a murine model by LPS aerosolization has been described in our previous studies (25)(26)(27)(28). Briefly, mice were exposed to 0.3 mg of LPS/ml in 0.9% saline by aerosolization for 20 min under a laminar flow hood by using a flow rate of 2 L/min.…”

“…A midventral incision was used to open the thoracic cavity, and the trachea was isolated and cannulated with a 20-gauge catheter. BALF was obtained from the whole lung to collect cells in the airspace and to obtain proteins for cytokine and chemokine detection, as described previously (25)(26)(27)(28). A total of 3.0 ml of BALF was retrieved from each mouse, and 0.5 ml of BALF was centrifuged and placed on glass cytospin slides, which were then stained by modified Wright-Giemsa staining (Diff-Quick; Fisher Scientific) to determine leukocyte subtypes based on their cellular and nuclear morphology.…”

“…Cytokine and chemokine levels were assessed in BALF or culture supernatants of bone marrow-derived macrophage (BMM) cultures using a cytokine-or chemokine-specific sandwich ELISA, as described in our earlier publications (25)(26)(27)(28). The minimum detection limit is 2 pg/ml cytokine or chemokine protein.…”

Functions and Regulation of NF-κB RelA during Pneumococcal Pneumonia

“…During acute pulmonary inflammation, the CXC chemokines KC, MIP-2, and LIX generate the chemotactic gradients that direct neutrophils from the vascular to the alveolar spaces (30,31,33,46). IL-6 is also expressed in the lungs and is required for maximal neutrophil recruitment and bacterial killing (25,47).…”