Genetic and environmental risk factors for atherosclerosis regulate transcription of phosphatase and actin regulating gene PHACTR1

Abstract

Background and aimsCoronary artery disease (CAD) risk is associated with non-coding genetic variants at the phosphatase and actin regulating protein 1(PHACTR1) gene locus. The PHACTR1 gene encodes an actin-binding protein with phosphatase regulating activity. The mechanism whereby PHACTR1 influences CAD risk is unknown. We hypothesized that PHACTR1 would be expressed in human cell types relevant to CAD and regulated by atherogenic or genetic factors.Methods and resultsUsing immunohistochemistry, we demonstrate that PHACTR1 protein is expressed strongly in human atherosclerotic plaque macrophages, lipid-laden foam cells, adventitial lymphocytes and endothelial cells. Using a combination of genomic analysis and molecular techniques, we demonstrate that PHACTR1 is expressed as multiple previously uncharacterized transcripts in macrophages, foam cells, lymphocytes and endothelial cells. Immunoblotting confirmed a total absence of PHACTR1 in vascular smooth muscle cells. Real-time quantitative PCR showed that PHACTR1 is regulated by atherogenic and inflammatory stimuli. In aortic endothelial cells, oxLDL and TNF-alpha both upregulated an intermediate length transcript. A short transcript expressed only in immune cells was upregulated in macrophages by oxidized low-density lipoprotein, and oxidized phospholipids but suppressed by lipopolysaccharide or TNF-alpha. In primary human macrophages, we identified a novel expression quantitative trait locus (eQTL) specific for this short transcript, whereby the risk allele at CAD risk SNP rs9349379 is associated with reduced PHACTR1 expression, similar to the effect of an inflammatory stimulus.ConclusionsOur data demonstrate that PHACTR1 is a key atherosclerosis candidate gene since it is regulated by atherogenic stimuli in macrophages and endothelial cells and we identify an effect of the genetic risk variant on PHACTR1 expression in macrophages that is similar to that of an inflammatory stimulus.

PHACTR1 Is a Genetic Susceptibility Locus for Fibromuscular Dysplasia Supporting Its Complex Genetic Pattern of Inheritance

“…Recent work on PHACTR1 regulation in atherosclerosis showed strong expression in human atherosclerotic plaque macrophages lipid-laden foam cells, adventitial lymphocytes and endothelial cells. [29] This group also describes the absence of PHACTR1 in SMCs of healthy and athesclerotic aortas, which is not supported by our immunostaining on medium-sized arteries using a different anti-body, though they have detected the expression of an intermediate transcript in SMCs. Further investigation is required to understand this discrepancy that might reflect PHACTR1 is much more abundantly expressed in macrophages from atherosclerotic plaques, where this population of cells is highly represented and biologically active, which is different from the FMD and healthy vessels without atherosclerosis.…”

A Genetic Variant Associated with Five Vascular Diseases Is a Distal Regulator of Endothelin-1 Gene Expression

“…The associated variants at 6p24 lie within the third intron of the gene encoding phosphatase and actin regulatory protein 1 ( PHACTR1 ), nominating PHACTR1 as the effector gene given its physical proximity. In support of this hypothesis, an association exists between risk genotype and PHACTR1 expression in arterial samples (Aguet et al, 2016; Beaudoin et al, 2015), and PHACTR1 function is linked with atherosclerosis-relevant phenotypes, such as angiogenesis (Jarray et al, 2011), extracellular matrix protein production (Jarray et al, 2015), and inflammation (Reschen et al, 2016) in vitro. Despite these data, the causal gene at the 6p24 locus remains uncertain.…”

Environmental exposures during pregnancy: Mechanistic effects on immunity

“…However, it is clear that prolonged or excessive inflammatory responses can induce considerable tissue damage (e.g., scarring and fibrosis) and can be highly detrimental to the host. Examples of common inflammatory diseases potentiated by environmental exposures include the following: atherosclerosis (Reschen, Lin, Chalisey, Soilleux, & O'Callaghan, 2016), Type II diabetes (Dendup, Feng, Clingan, & Astell-Burt, 2018), nonalcoholic fatty liver disease (Buzzetti, Pinzani, & Tsochatzis, 2016), cystic fibrosis (Schechter, 2011), chronic obstructive pulmonary disease (Wong, Magun, & Wood, 2016), inflammatory bowel diseases such as ulcerative colitis and Crohn's disease (Strober, Fuss, & Mannon, 2007), as well as neurodegenerative diseases like Alzheimer's and Parkinson's disease (Cannon & Greenamyre, 2011). Chronic (low-grade) inflammation can also induce genetic changes that potentially enable and stimulate carcinogenesis (Fedeles et al, 2015).…”