Electroacupuncture ameliorates endotoxin-induced acute lung injury in rabbits by regulating heme oxygenase-1 expression to improve mitochondrial dynamics

Abstract

Background: Electroacupuncture (EA) mitigates endotoxin-induced acute lung injury (ALI) during bacterial sepsis, but the mechanisms are unclear. This study aimed to investigate the potential mechanisms of EA improving endotoxin-induced ALI. Methods: Endotoxin-induced ALI was established by lipopolysaccharide (LPS) administration. Electroacupuncture was started 5 days before LPS administration and non-acupoint EA (punctured at non-acupoints with shallow insertion and no electrical stimulation) was used as the control treatment. In addition, hemin was applied to active HO-1 and ZnPP to suppress HO-1. Briefly, 70 rabbits were divided into seven treatment groups: untreated control (C), LPS, LPS + EA, LPS + non-acupoint EA, LPS + EA + hemin, LPS + EA + ZnPP, and LPS + EA + ZnPP + hemin. Lung samples were collected at 6 h after LPS administration for analysis of tissue injury (edema, inflammation, hemorrhage, necrosis), oxidative stress, mitochondrial membrane potential (MMP), respiratory control ratio (RCR), ATP production, and changes in expression of mitochondrial fusion and fission markers. Results: Electroacupuncture alleviated LPS-induced lung injury and mitochondria dysfunction as indicated by decreasing wet/dry tissue weight ratio, lung injury score, ROS production, and suppressing expression of mitochondrial fission proteins. Furthermore, EA also increased ATP content, mitochondrial membrane potential, respiratory control ratio, and expressions of mitochondrial fusion proteins (LPS + EA group vs. LPS group). These effects of EA were further enhanced by pretreatment with hemin (LPS + EA + hemin group) but suppressed by Znpp-IX (LPS + EA + ZnPP and LPS + EA + ZnPP + hemin groups). Conclusions: Electroacupuncture protects against endotoxin-induced ALI by upregulating heme oxygenase-1 expression, thereby preserving the balance between mitochondrial fusion and fission. Keywords: Heme oxygenase-1, Electroacupuncture, Lung injury, Mitochondrial dynamics