Abstract 700: Genetic Deletion Of Neutrophil Elastase Does Not Alter Lesions In Mice With Atherosclerosis Induced By Aav8-mediated Over-expression Of PCSK9

Introduction: Elevated circulating glucocorticoids are causally linked to increased cardiovascular disease. Atherosclerosis is a key cardiovascular pathology, yet the contribution of glucocorticoids underlying atherogenesis is unclear. Corticosteroid binding globulin (CBG) regulates glucocorticoid action through binding, thus controlling its systemic bioavailability. Cleavage of CBG by neutrophil elastase (NE) is proposed to enhance bioavailability of glucocorticoids by reducing its binding affinity. Strikingly, Apoe -/- mice lacking NE (ELA -/- ) display reduced atherosclerosis. Hypothesis: This investigation addresses the hypothesis that NE influences atherogenesis through CBG cleavage, increasing glucocorticoid bioavailability at sites of plaque development. Methods: Adult (8-12wk old) male C57BL/6J, ELA -/- and ELA +/+ mice were injected with AAV8-PCSK9 (IP; 1x10 12 vector genomes) and fed a western diet (21% fat; 0.21% cholesterol) for 18wks (N=10-13). Control mice received diet without viral injection (N=10). Results: In C57BL/6J mice, histological analysis of brachiocephalic arteries demonstrated lesion development with AAV8-PCSK9-treatment, in parallel with increased (P=0.015) circulating NE protein levels (58.0 ± 5.5ng/ml) compared to diet-control mice (NE levels 32.8 ± 6.2ng/ml). AAV8-PCSK9 treatment did not alter circulating glucocorticoids (Corticosterone AM levels P=0.94; AAV8-PCSK9 65 ± 16nM; Control 74 ± 36nM) but hepatic CBG (Serpina6) transcript levels were reduced (1-fold; P=0.01; AAV8-PCSK9 0.57 ± 0.04; Control 1.13 ± 0.20). Interestingly, no differences in lesion size (P=0.8539; 23.2 ± 2.5%) or collagen content (P=0.5156; 17.64 ± 5.6%), or in circulating glucocorticoid levels (corticosterone AM levels; P=0.36; 225 ± 59nM) were observed in ELA -/- mice compared to controls (lesion size 24.2 ± 6.3%; collagen 12 ± 5%; glucocorticoid levels 142 ± 29nM). Conclusions: In contrast to published data using Apoe -/- mice, these results demonstrate that NE does not influence lesion size in this model of atherosclerosis. This suggests that NE inhibition would not be a useful therapeutic target in atherosclerosis. Future studies will directly address the role of CBG in the development of atherosclerosis.