Effect of lipoxin A4 on the Na+-K+-ATPase in alveolar type II epithelial cells of rats treated with endotoxin

Objective To study the protective role of pre-resolving mediator lipoxin A4(LXA4) in the NA+ -K+-ATPase in alveolar type Ⅱ (AT Ⅱ ) epithelial cells of rats exposed to lipopolysaccharide (LPS). Method The AT Ⅱ cells were isolated and purified, and divided randomly into control group (PBS), vehiculum (alcohol 0.7 μL/mL) group, LPS (1 μg/mL) group, LXA4(1/10 mol/mL) group and LPS (1 μg/mL LPS) + LXA4(1/10 mol/mL) group. After exposure to LPS and/or LXA4 for4 hours, NA+-K+ -ATPase and β1-subunits mRNA in AT Ⅱ epithelial cells were detected by using RT-PCR, and ATP, ADP, AMP, total adenine nucleotides (TAN) and energy charge (EC) were measured by using high performance liquid chromatography (HPLC), and then the activities of Na+-K+-ATPase were calculated accordingly. Results The NA+-K+-ATPase α-subunit and β-subunit mRNA were significantly decreased in LPS group ( P ＜ 0.05 vs. control group). However, the expressions of NA+ -K+-ATPase mRNA were significantly enhanced by application of LXA4 to AT Ⅱ epithelial cells exposed to LPS (P ＜0.05 vs. LPS group). The activities of NA+ -K+ -ATPase were enhanced in LPS group (P ＜0.05 vs. control group). Compared with control group and LPS group, the activities of NA+-K+-ATpase in LPS + LXA4 group were significantly increased (P ＜0.01 vs. control group; P ＜0.05 vs. LPS group). The EC of AT Ⅱ epithelial cells were higher in LPS group ( P ＜ 0.01 vs. control group). There were no significant differences in EC between control group and LPS + LXA4group(P ＞0.05). Conclusions The pro-resolving mediator LXA4 can enhance the expressions of NA + -K + -ATPase α-subunit and β-subunit mRNA, and the activities of NA + -K + -ATPase in AT Ⅱ epithelial cells or rats exposed to LPS, and ca also balance the metabolism of AT Ⅱ epithelial cells. These findings suggest that LXA4 plays an important role in lung edema clearance in lung injury induced by endotoxin, and the role is likely associated with the enhancement of the expressions of Na+ -K+ -AT-Pase α-subunit and β-subunit, and the activities of Na+ -K* -ATPase, maintaining the balance of metabolism of AT Ⅱ epithelial cells. Key words: Lipoxin A4 (LXA4);  Na+-K+-ATPase;  Alveolar type Ⅱ epithelial cells(AT Ⅱ ); Lipopolysaccharide (LPS)