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Sepsis by using Cecal Ligation and Single Puncture Causes Alveolar Space Enlargement in LPA2 Knockout Mice

Yutong Zhao*, Panfeng Fu, Jing Zhao, Rachel K. Mialki, Jianxin Wei, Longshuang Huang, Jerold Chun, Adriana S. Leme, Steven D. Shapiro and Viswanathan Natarajan

Lysophosphatidic acid (LPA) plays a dual-function in lung inflammatory diseases. LPA receptors contribute to the pathogenesis of asthma, acute lung injury, and fibrosis. Here, we investigate the role of LPA receptor type 2 (LPA2) in sepsis-induced lung inflammation and injury. Sepsis was induced using cecal ligation and single puncture (CLP) with 27 gauge needle. Plasma interleukin-6 (IL-6) and KC levels were elevated in septic wild type and LPA2-/- mice, while septic LPA2-/- mice reduces plasma KC, not IL-6 levels, compared to septic wild type mice. Bronchoalveolar lavage (BAL) KC levels increased in septic wild type and LPA2-/- mice, while the sepsis had no effect on BAL IL-6 levels, protein leak, and inflammatory cell infiltration in the lungs in wild type and LPA2-/- mice. Hematoxylin and eosin (H&E) staining revealed that septic LPA2-/- mice aggravated alveolar space enlargement. Western blotting analysis of lung tissues demonstrate that the level of cortactin, an F-actin binding protein, was decreased in septic LPA2-/- mice, when compared to wild type mice. The level of immunoglobulin G (IgG) in BAL fluids significantly increased in septic LPA2-/- mice, when compared to septic wild type mice and sham mice. Furthermore, we found that sham and septic LPA2-/- mice increased surfactant proteins B, C, and D (SP-B, SP-C, and SP-D) expression in lungs, while SP-A levels in lungs was decreased in sham and septic LPA2-/- mice. These results suggest LPA2 may regulate cortactin and surfactant protein expression in the lung. LPA2 and its downstream signaling may play a protective role against sepsis induced emphysema like disease.