Mast Cell Numbers of Rat Lungs in an Acute Model of Fat Embolism Are Reduced by Aliskiren and Losartan but Not by Captopril

Abstract

IntroductionFat embolism (FE) induced by iv injection of triolein (T) causes vasculitis, septal inflammation and fibrosis in rat lungs at 48 hrs that is mitigated by two drugs acting on the renin‐angiotensin system (RAS): captopril and losartan (1). The histopathological changes found at this time are also ameliorated by treatment with the renin inhibitor aliskiren as the associated increase in mast cell numbers (2). This study examines whether captopril and losartan also prevent the increase in mast cell number at this time.MethodsSprague‐Dawley rats (280–300g) were treated with 0.2 ml iv (T) n=31 or saline n=7. One hour later 0.2 ml of saline (n=7) ip, aliskiren (50 mg/kg n=6), (100 mg/kg n=6), captopril (150 mg/kg n=6) or losartan (10 mg/kg n=6) were given. Saline treated rat (n=7) receive ip, one hour later, the same dose of saline. 48 hours later all the rats were necropsied after isofluorane anesthesia, lungs fixed in 10% formalin and H&E stained for morphology, Masson trichrome for fibrosis and CD 117 for mast cells. Two pathologists unaware of slides identity took at random 10 photographs of all the slides at 400× and separately counted the mast cells.ResultsAs previously reported, 48 hours after triolein the lungs showed severe histopathological damage that was prevented by all three of the RAS drugs (1–3) and was associated with an increase in the number of mast cells (3). Aliskiren treatment reduced their numbers confirming previous findings (3,4). A significant reduction was also induced by losartan but not by captopril despite its protective effects on lung histopathology.ConclusionsMast cells may be involved in the pathological damage found after FE as suggested by their increase in number in the lungs after T and their reduction during protective treatment with aliskiren. Aliskiren and losartan also reduced their number. However, the lack of effect of captopril on mast cell number at this acute time period may suggest that some other pathways are involved in the time course of mast cell recruitment, such as angiotensin (1–7).Support or Funding InformationSupported by the Catherine T Geldmacher Foundation, St. Louis, MOThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.