Abstract 513: Plasminogen And Lipoprotein(a) Competitively Interact To Modulate Macrophage Inflammation Via ATP-binding Cassette Transporter A1

Abstract

Lipoprotein (a) [Lp(a)] is an independent risk factor for cardiovascular disease (CVD) and resembles an LDL-like lipoprotein with the addition of apolipoprotein(a) (LPA). The LPA gene results from a duplication of the plasminogen gene ( PLG ) and the proteins share 88% amino acid sequence homology in their protease domains. We recently identified Lp(a) inhibits ATP-binding cassette transporter A1 (ABCA1)-dependent cholesterol efflux to PLG, and previous work demonstrates inhibition of cholesterol efflux is proinflammatory. We hypothesize that Lp(a) and PLG competitively modulate macrophage inflammation beyond cellular cholesterol regulation. In silico protein-protein interaction modeling unveiled candidate PLG-ABCA1 interaction sites which are distinct from ABCA1-APOA1 sites. Elicited peritoneal macrophages were collected from C57BL6/J mice and treated with vehicle, PLG, Lp(a), or both. Abca1, Nfkb1 , and Ccl2 gene expression was determined using qRT-PCR. PLG treatment increased Abca1 expression 1.8-fold compared to vehicle but did not affect Nfkb1 or Ccl2 expression. Addition of Lp(a) to PLG treatment inhibited PLG-dependent Abca1 upregulation. Lp(a) increased Nfkb1 and Ccl2 expression 1.4- and 2.0-fold, respectively. Addition of PLG to Lp(a) inhibited Lp(a)’s increase in Nfkb1 expression but had no effect on Ccl2 . THP-1 monocytes were differentiated to macrophages and treated with PLG, Lp(a), or both to determine whether they induced metabolic changes using Seahorse Analyzer. While PLG had no effect on metabolism, Lp(a) increased glycolysis 1.4-fold and glycolytic capacity 1.3-fold that was reduced when PLG and Lp(a) were used simultaneously. In ABCA1-expressing HEK293 cells, co-treatment using PLG and Lp(a) at equimolar concentrations resulted in 7.2-fold increase in STAT3 phosphorylation compared to ~3-fold increase elicited by each of PLG or Lp(a) treatment alone. These observations suggest Lp(a) independently promotes a glycolytic proinflammatory macrophage phenotype that can be inhibited by PLG. PLG and Lp(a) synergy activates ABCA1-dependent anti-inflammatory STAT3 signaling. PLG might be tapering Lp(a)-dependent macrophage inflammation which may ultimately reduce CVD risk in patients with high Lp(a) levels.