Tanshinone ⅡA Attenuates Bleomycin-induced Pulmonary Fibrosis Via Modulating Angiotensin-converting Enzyme2/ANG-(1-7)

BackgroundIdiopathic pulmonary fibrosis (IPF), which lesions limit in lungs and causesdiffused fibrosis in the whole lungs. IPF gradually results in lung function damage andprogressive dyspnea, and finally respiratory and circulation failure. The pathogenesisof IPF is still unclear. Researchers found various humoral and cell factors participatedin the development of IPF, which mechanisms were still remain unknown. Because theprogressive lesions in lung tissue and the extreme dyspnea and deficiency of effectivetreatments, the mortality of IPF is very high. Most of the IPF patients are adults, whichmorbidity increases along with age growth. Recent years, due to the repeatedlyoccurrence of acute bronchitis, tumors, and mistaken of pesticides, the morbidity of IPF in child increases significantly. So far, the regular treatments of IPF can justrelieve the symptoms clinically and cannot halt the progressive of the disease or cure it.Therefore, the clinical research should focus on exploring the etiological factors andpathological mechanisms of IPF. It is urgent to seek effective and safe methods toinhibit inflammation and fibrosis during IPF.Tanshinone Ⅱ A (T Ⅱ A) is a liposoluble substance extracted from Salviamiltiorrhiza roots, which molecular formula is C18H12O3. TⅡA belongs to diterpenequinone compounds and possesses anti-bacteria, anti-inflammation, and hormone-likeeffects. Now Tanshinone ⅡA is usually used on kinds of diseases of infection,cardiovascular and nervous system, and dermal. Currently, it’s still not clear whetherTanshinone possesses protective effects on pulmonary fibrosis.Renin-aldosterone-aldosterone system (RAAS) is the main humoral regulatorysystem of human being, which plays key roles during development of IPF. Angiotensinconverting enzyme2(ACE2) is an important member of RAAS and a homologue ofangiotensin converting enzyme (ACE), which effects are different from ACE.AngiotensinⅡ (AngⅡ) is another important member of RAAS which is hydrolyzedfrom Angiotensin Ⅰ (Ang Ⅰ) by ACE, which plays important roles duringdevelopment of inflammation. ACE2could hydrolyze AngⅠ and AngⅡ into Ang(1-9) and Ang (1-7), and then attenuate inflammation induced by Ang Ⅱ. In thepresent study, we observed whether TⅡA exert protective effects on pulmonaryfibrosis and further explored the possible mechanisms underlying. The present studymay offer new theoretical evidences for treating pulmonary fibrosis clinically.Objectives1. Observe the protective effects of TⅡA on bleomycin induced pulmonary fibrosis.2. Further explore whether TⅡA attenuate bleomycin induced pulmonary fibrosisvia ACE-2/ANG-(1-7) axis. MethodsTo observe the effects of TⅡA on pulmonary fibrosis, male SD rats wererandomly assigned into control, bleomycin (BLM), and bleomycin plus TⅡA threegroups (n=10). Pulmonary fibrosis was induced by intratracheal injection of bleomycin.The bleomycin+TⅡA group was administrated TⅡA (25mg/kg/day) intraperitoneallyafter bleomycin was given for1hour. The control group was received intratrachealinjection of sterile saline (50μl).Lung coefficient analysis: After rats were anesthetized, sternotomy surgery wasperformed and lungs were taken out at7,14, and28days respectively. Lungs werethen cleaned with cold PBS solution and sipped by filter paper, the lung coefficientwas calculated. Histological analysis of lungs: Lung tissues were embedded in paraffinand cut into4μm slices. Hematoxylin and eosin staining (HE), Trichrome Masson’sstaining, and sirius red staining were performed. Observe the changes of pulmonaryparenchymal and interstitial tissues under a microscope. Expressions of ACE2,ANG-(1-7), and TGF-β were analyzed by immunochemical staining. Pretein levels ofACE-2and TGF-β were detected by WB assays, and mRNA levels of ACE-2andTGF-β were detected by RT-PCR analysis. ANG-(1-7) was analyzed by ELISA assays.ResultsBLM resulted in severe pulmonary fibrosis and alveolar inflammation; togetherwith significant elevation of transforming growth factor-β1(TGF-β1).Angiotensin-converting enzyme2(ACE-2) together with angiotensin-(1-7)[ANG-(1-7)] were both greatly reduced after BLM administration. TIIA treatmentnotably attenuated BLM induced pulmonary fibrosis and inflammation, decreasedexpression of TGF-β1and reversed ACE-2and ANG-(1-7) production in rat lungs.Thus we may draw the conclusion that TIIA may exert protective effects on BLMinduced pulmonary fibrosis in rats, and the ACE-2/ANG-(1-7) axis may ascribe tothose protective effects. Conclusions1. TIIA may exert protective effects on BLM induced pulmonary fibrosis.2. The ACE-2/ANG-(1-7) axis may answer for the protective effects of TIIA onBLM I nduced pulmonary fibrosis.