title: Dysregulated renin-angiotensin system contributes to acute lung injury caused by hind-limb ischemia-reperfusion in mice.
abstract: The mechanism of acute lung injury (ALI) following limb ischemia-reperfusion (LIR) is not yet clear. We speculate that the unbalanced expression of angiotensin-converting enzymes (ACE and ACE2) and angiotensins [Ang II and Ang-(1-7)] in the renin-angiotensin system (RAS) is a major cause of ALI. To prove this hypothesis, pathological changes, lung edema, and permeability of wild-type mice at different time points within 12 h of reperfusion after 2 h of hind-limb ischemia were first detected by morphological method, measurements of wet-to-dry weight ratio, and bronchoalveolar lavage fluid. Meanwhile, the changes of lung ACE/ACE2 mRNA and protein expression were surveyed by the methods of real-time reverse transcription-polymerase chain reaction, Western blotting, and immunohistochemistry. Angiotensin II/Ang-(1-7) levels in the blood serum and lung tissue were measured by enzyme-linked immunosorbent assay. Then the effects of ACE2 gene insertion and deletion on the previously mentioned parameters were investigated in the mice being exposed to hind-limb 2-h ischemia and 4-h reperfusion. The results revealed that lung injuries in the wild-type mice were gradually aggravated, and the expression of ACE in lung tissue was progressively increased, whereas that of ACE2 decreased within 12 h after LIR. Unexpectedly, both Ang II and Ang-(1-7) in the lung tissue were obviously increased after LIR, showing Ang-(1-7) higher than Ang II in the early stage of reperfusion but lower than Ang II at the late stage of reperfusion. Unlike local Ang II/Ang-(1-7) changes, circulating Ang-(1-7) became greatly descending, and Ang II was markedly ascending from the start of reperfusion, corresponding to local ACE/ACE2 unbalanced expression. ACE2 transgenosis improved the imbalance of ACE/ACE2 and Ang II/Ang-(1-7) expression and alleviated lung injuries, whereas ACE2 knockout further aggravated the imbalance of ACE/ACE2 and Ang II/Ang-(1-7) expression and made lung injuries more serious in the post-LIR mice. The results indicate that the dysregulation of local and circulating RAS with increased expression of ACE/Ang II and decreased expression of ACE2/Ang-(1-7) contribute to ALI caused by LIR in mice. Maintaining RAS homeostasis through upregulating ACE2 expression may lessen lung injury, which provides a new idea for the treatment of posttraumatic ALI.
authors.affiliation: *Department of Physiology, School of Basic Medical Science, and †International Education College, Hebei United University, Tangshan, People's Republic of China.
authors.forename: Li-Nan
authors.initials: LN
authors.lastname: Chen
authors.forename: Xiu-Hong
authors.initials: XH
authors.lastname: Yang
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Nissen
authors.forename: Yan-Yan
authors.initials: YY
authors.lastname: Chen
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Wang
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Wang
authors.forename: Jun-Ling
authors.initials: JL
authors.lastname: Gao
authors.forename: Lian-Yuan
authors.initials: LY
authors.lastname: Zhang
mesh_terms: D055371:Acute Lung Injury / Q000209:etiology* / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D000803:Angiotensin I / Q000096:biosynthesis / Q000097:blood / Q000235:genetics; D000085962:Angiotensin-Converting Enzyme 2; D000818:Animals; D005786:Gene Expression Regulation / Q000502:physiology; D005838:Genotype; D006614:Hindlimb / Q000098:blood supply*; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009929:Organ Size; D010446:Peptide Fragments / Q000096:biosynthesis / Q000097:blood / Q000235:genetics; D007703:Peptidyl-Dipeptidase A / Q000096:biosynthesis / Q000097:blood / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012084:Renin-Angiotensin System / Q000502:physiology*; D015427:Reperfusion Injury / Q000150:complications* / Q000235:genetics / Q000473:pathology / Q000503:physiopathology
chemical_list: D010446:Peptide Fragments; D012333:RNA, Messenger; D000803:Angiotensin I; D007703:Peptidyl-Dipeptidase A; C000705328:Ace2 protein, mouse; D000085962:Angiotensin-Converting Enzyme 2; C118790:angiotensin I (1-7)