Cupping alleviates lung injury through the adenosine/A(2B)AR pathway

BACKGROUND: Acute lung injury (ALI) is a serious condition. Inflammation plays a crucial role in the pathogenesis of ALI. Cupping, as a part of traditional Chinese medicine, is still a popular complementary and alternative therapy for a variety of ailments including respiratory diseases. However, reliable scientific data about cupping therapy are scarce. Adenosine, a purine nucleoside produced under metabolic stress by the action of extracellular ectonucleotidases (i.e. CD39 and CD73), can attenuate ALI through the A(2B)AR receptor. The aim of this study was to investigate the protective effect of cupping in a rat model of ALI and the role of adenosine in it. METHODS: Male adult rats were subjected to ALI by intratracheal LPS instillation (0.3 mg/kg). Immediately after intratracheal LPS instillation, vacuum pressure was applied to a sanitized plastic bell cup on the back of the rat by suction for 10 min. Pulmonary injury and inflammation were assessed at 4 h after LPS challenge. The role of adenosine and A(2B)AR in cupping's protection after LPS instillation were evaluated. RESULTS: Cupping alleviated LPS-induced lung injury, reduced inflammation and inhibited NF-kB activation in rats. Cupping upregulated CD39 and CD73 mRNA expression of the skin tissue at the cupping site and increased circulating levels of adenosine. Administration of PSB1115, a specific adenosine A(2B)AR receptor antagonist, abolished cupping's beneficial effects in LPS-induced ALI. CONCLUSIONS: Cupping attenuates lung inflammation and injury through the adenosine/A(2B)AR pathway. The current study provides evidence-based information about cupping therapy in ALI.