Epigallocatechin Gallate Attenuates Hip Fracture-Induced Acute Lung Injury by Limiting Mitochondrial DNA (mtDNA) Release

Abstract

BACKGROUND To study the protective effects and explore the mechanism of epigallocatechingallate (EGCG) on the hip fracture-induced acute lung injury. MATERIAL AND METHODS Thirty male Sprague-Dawley (SD) rats were randomly divided into the control group, hip fracture group, and hip fracture + EGCG (10 mg/Kg) group. After 24 h, blood samples, bronchoalveolar lavage fluid (BALF), and lung tissue were collected. Serum mitochondrial DNA (mtDNA) was measured by RT-PCR and BALF was used to perform cytological analysis and enzyme-linked immunosorbent assay (ELISA) assay. Lung tissue was used to evaluate the injury level. RESULTS EGCG significantly reduced the hip fracture-induced high level of serum mtDNA (p<0.05). HE staining showed protective effects of EGCG. Lower lung injury score and wet/dry ratio were identified in the hip fracture + EGCG group than in the hip fracture group (p<0.05). We found significantly lower levels of infiltration of inflammatory cells and production of inflammatory cytokines in the BALF of the hip fracture + EGCG group than in the hip fracture group (p<0.05). CONCLUSIONS Our study found that EGCG had protective effects on hip fracture-induced acute lung injury and suggests that EGCG exerts its protective effects through limiting the release of mtDNA. Our results provide a novel pharmacological agent to attenuate hip fracture-induced acute lung injury, as well as a potential theory to better explain the anti-inflammatory property of EGCG.

Figure 1

EGCG attenuates hip fracture-induced elevated serum mtDNA level. Significantly increased mtDNA level in the hip fracture group (p<0.05). EGCG treatment significantly decreased mtDNA (p<0.05). * p<0.05 vs. control group, ^# p<0.05 vs. the hip fracture group, N=10.

Figure 2

EGCG attenuates hip fracture-induced acute lung injury. (A–C) HE staining images of 3 groups are shown. (D) The lung injury scores in the hip fracture group were much higher than in the control and hip fracture + EGCG groups. (E) The higher ratio in the hip fracture group than in the control and hip fracture + EGCG groups. * p<0.05 vs. control group, ^# p<0.05 vs. the hip fracture group, N=10.

Figure 3

EGCG attenuates hip fracture-induced inflammatory cells infiltration in the BALF. Rats with EGCG pre-treatment all showed decreased numbers of total cells, monocyte/macrophage number, and neutrophile number compared with the hip fracture group. * p<0.05 vs. control group, ^# p<0.05 vs. hip fracture group, N=10.

Figure 4

EGCG attenuates hip fracture-induced inflammatory cytokines production in the BALF. Significant increases of inflammatory cytokines (TNF-α and IL-6) are shown in the hip fracture group, and pre-treatment with EGCG significantly inhibited the production of inflammatory cytokines (p<0.05). * p<0.05 vs. control group, ^# p<0.05 vs. the hip fracture group, N=10.