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Inducing Acute Lung Injury in Mice by Direct Intratracheal Lipopolysaccharide Instillation
Published on: July 6, 2019
CXCR2 inhibition suppresses hemorrhage-induced priming for acute lung injury in mice
Joanne L Lomas-Neira1, Chun-Shiang Chung, Patricia S Grutkoski
1Aldrich 227, Rhode Island Hospital, 593 Eddy Street, Providence, RI 02903, USA. AAYALA@LIFESPAN.org
Abstract:
Polymorphonuclear neutrophil (PMN) extravasation/sequestration in the lung and a dysregulated inflammatory response characterize the pathogenesis of acute lung injury (ALI). Previously, we have shown that hemorrhage (Hem) serves to prime PMN such that subsequent septic challenge [cecal ligation and puncture (CLP)] produces a pathological, inflammatory response and consequent lung injury in mice. Keratinocyte-derived chemokine (KC) and macrophage inflammatory protein-2 (MIP-2) are murine CXC chemokines found elevated in the lungs and plasma following Hem/CLP and have been reported by others to share a common receptor (CXCR2). Based on these data, we hypothesize that blockade of CXCR2 immediately following Hem would suppress KC and MIP-2 priming of PMN, thereby reducing the inflammatory injury observed following CLP. To assess this, Hem mice (90 min at 35+/-5 mmHg) were randomized to receive 0, 0.4, or 1 mg antileukinate (a hexapeptide inhibitor of CXCRs) in 100 microl phosphate-bufferd saline (PBS)/mouse subcutaneously, immediately following resuscitation (Ringer's lactate-4x drawn blood volume). Twenty-four hours post-Hem, mice were subjected to CLP and killed 24 h later. The results show that blockade of CXCR2 significantly (P<0.05, Tukey's test) reduced PMN influx, lung protein leak, and lung-tissue content of interleukin (IL)-6, KC, and MIP-2 and increased tissue IL-10 levels. Plasma IL-6 was significantly decreased, and IL-10 levels increased in a dose-dependent manner compared with PBS-treated mice. A differential effect was observed in plasma levels of KC and MIP-2. KC showed a significant reduction at the 0.4 mg antileukinate dose. In contrast, plasma MIP-2 was significantly elevated at both doses compared with the PBS-treated controls. Together, these data demonstrate that blockade of CXCR2 signaling attenuates shock-induced priming and ALI observed following Hem and subsequent septic challenge in mice.
Insights
Blocking CXCR2 signaling effectively reduces lung inflammation and injury following hemorrhage and sepsis in mice. This targeted approach mitigates polymorphonuclear neutrophil infiltration and inflammatory markers, offering a potential therapeutic strategy for acute lung injury.
Area of Science:
- Immunology
- Pathophysiology
- Pharmacology
Background:
- Acute lung injury (ALI) involves polymorphonuclear neutrophil (PMN) lung sequestration and dysregulated inflammation.
- Hemorrhage (Hem) primes PMNs, exacerbating lung injury during subsequent septic challenge (cecal ligation and puncture - CLP).
- Keratinocyte-derived chemokine (KC) and macrophage inflammatory protein-2 (MIP-2) are elevated post-Hem/CLP and signal through CXCR2.
Purpose of the Study:
- To investigate if blocking CXCR2 immediately after hemorrhage can prevent PMN priming.
- To determine if CXCR2 blockade reduces inflammatory response and lung injury following subsequent septic challenge.
- To evaluate the efficacy of antileukinate, a CXCR2 inhibitor, in a murine model of shock and sepsis.
Main Methods:
- Mice underwent hemorrhage (90 min at 35+/-5 mmHg) followed by resuscitation.
- Hemorrhaged mice received subcutaneous antileukinate (0, 0.4, or 1 mg) or PBS immediately post-resuscitation.
- Mice were subjected to CLP 24 hours post-hemorrhage and assessed 24 hours later for lung injury markers.
Main Results:
- CXCR2 blockade significantly reduced PMN influx, lung protein leak, and levels of IL-6, KC, and MIP-2 in lung tissue.
- Tissue IL-10 levels were increased following CXCR2 blockade.
- Plasma IL-6 decreased and IL-10 increased dose-dependently; plasma KC reduced at 0.4 mg, while plasma MIP-2 increased at both doses.
Conclusions:
- Blockade of CXCR2 signaling effectively attenuates shock-induced PMN priming and subsequent acute lung injury in a murine model.
- Targeting CXCR2 presents a promising therapeutic strategy for mitigating inflammatory lung injury in conditions involving hemorrhage and sepsis.
- The study demonstrates the critical role of CXCR2 in mediating inflammatory responses following combined hemorrhagic shock and sepsis.
