Effects of calcitonin gene-related peptide on aquaporin 1 and aquaporin 5 expressions in young rats with acute lung injury

Abstract

Objective To explore the effect of calcitonin gene-related peptide (CGRP) on expressions of aquaporin (AQP)1 and AQP 5 in young rats with acute lung injury(ALI) caused by lipopolysaccharide(LPS). Methods Eighty-four young rats were randomly divided into control group, ALI model group and CGRP group.The rats in ALI model group were given intraperitoneal injection of LPS (5 mg/kg)for 2, 6, 12, 24 hours; while the rats in CGRP group were given intraperitoneal CGRP (1 mg/kg) after 1 h injection of LPS.At 2 h, 6 h, 12 h and 24 h, all rats were sacrificed and lung tissues were obtained.The histopathological changes in lung tissues were evaluated by adopting hematoxylin-eosin staining, and wet/dry(W/D) was measured.The mRNA and protein levels of AQP1 and AQP5 in lung tissues were detected by adopting fluorogenic quantitative PCR(qPCR) and Western blot. Results Pathological stain showed that rats in control group had a normal lung tissue structure, and LPS made lung tissue edema, narrowing the alveolar cavity and inflammatory cell infiltration.CGRP attenuated the effect of LPS on rat′s lung.The W/D ratio of lung tissue was significantly higher than that in the control group, and CGRP reduced the W/D ratio of lung tissue.qPCR showed that the mRNA levels of AQP1 and AQP5 from rats in ALI group (0.009±0.001 and 0.055±0.006) decreased compared with those in the control group (0.035±0.002 and 0.167±0.006) and CGRP group (0.024±0.002 and 0.134±0.012) (all P<0.001). Western blot results showed after 24 h injection of LPS, both AQP1 and AQP5 levels from ALI group (0.397±0.041 and 0.215±0.029) were significantly lower than those in the control group (0.850±0.020 and 0.741±0.032) (all P<0.001), and their levels in CGRP group (0.593±0.065 and 0.461±0.039) were also lower than those in the control group, but higher than those in ALI group (all P<0.001). Conclusion CGRP can enhance AQP1 and AQP5 levels and reduce pulmonary edema, and it has a protective effect on rats with acute lung injury. Key words: Acute lung injury; Calcitonin gene-related peptide; Aquaporin