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American Heart Association, Arteriosclerosis, Thrombosis, and Vascular Biology, 8(40), p. 1830-1837, 2020

DOI: 10.1161/atvbaha.120.314506

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SR-BI (Scavenger Receptor BI), Not LDL (Low-Density Lipoprotein) Receptor, Mediates Adrenal Stress Response—Brief Report

This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Abstract

Objective: Adrenal gland secretes stress-induced glucocorticoids (iGCs) to coping with stress. Previous study showed that SR-BI (scavenger receptor BI) null (SR-BI −/− ) mice failed to generate iGC in stress conditions, suggesting that SR-BI–mediated cholesterol uptake from HDL (high-density lipoprotein) is a key regulator for iGC production. However, the LDL (low-density lipoprotein)/LDLr (LDL receptor) pathway can also provide cholesterol for iGC synthesis, but rodents have limited LDL levels in circulation. Here, we generated SR-BI −/− ApoBtg (apolipoprotein B transgenic) mice with normal LDL levels in circulation to determine the relative contribution of the HDL/SR-BI and LDL/LDLr pathways to iGC production in stress conditions. Approach and Results: To obtain mouse models with normal LDL levels, SR-BI −/− mice were bred to ApoBtg mice. Then, the F1 SR-BI±ApoBtg mice were backcrossed to SR-BI −/− to obtain SR-BI −/− ApoBtg, SR-BI −/− ApoBwt (apolipoprotein B wild type), and SR-BI +/+ ApoBtg mice. We first examined the lipoprotein profile, which shows a 6.5-fold increase in LDL levels in SR-BI −/− ApoBtg mice compared with SR-BI −/− ApoBwt mice. Then, we induced stress with adrenocorticotropic hormone and cecal ligation and puncture. One hour after adrenocorticotropic hormone stimulation, SR-BI +/+ ApoBtg control mice produced iGC (14.9-fold), but both SR-BI −/− ApoBwt and SR-BI −/− ApoBtg showed no iGC production ( P <0.001). Three hours after cecal ligation and puncture treatment, SR-BI +/+ ApoBtg control mice showed iGC production (6.4-fold), but both SR-BI −/− ApoBwt and SR-BI −/− ApoBtg mice showed no iGC production ( P <0.001). Conclusions: SR-BI −/− ApoBtg mice fail to produce iGC in stress conditions even though with restored LDL levels in circulation. These findings clarify that the HDL/SR-BI, not LDL/LDLr, pathway is responsible for iGC production in stress conditions.