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An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization
Published on: June 12, 2013
Individual variation of scavenger receptor expression in human macrophages with oxidized low-density lipoprotein is
Paula Martín-Fuentes1, Fernando Civeira, Delia Recalde
1Laboratorio de Investigación Molecular, Hospital Universitario Miguel Servet, Instituto Aragonés de Ciencias de la Salud, Paseo Isabel la Católica 103, 50009 Zaragoza, Spain. pmartin.iacs@aragon.es
Insights
Individual differences in macrophage scavenger receptor (SR) gene expression influence inflammatory responses to oxidized low-density lipoprotein (oxLDL). This suggests specific SRs, like CD36 and LOX-1, may drive more pro-inflammatory macrophage activation.
Area of Science:
- Immunology
- Cardiovascular Biology
- Cell Biology
Background:
- Atherosclerosis is an inflammatory disease driven by oxidized low-density lipoprotein (oxLDL).
- Scavenger receptors (SRs), including CD36, SR-A, and LOX-1, mediate oxLDL uptake by macrophages, leading to foam cell formation and inflammation.
- Interindividual variability in macrophage SR expression may explain differing inflammatory responses to oxLDL.
Purpose of the Study:
- To investigate if variations in macrophage SR gene expression determine inflammatory responses to oxLDL.
- To analyze the correlation between SR expression and inflammatory markers in human macrophages.
Main Methods:
- Macrophages were isolated from 18 healthy volunteers.
- Cells were incubated with oxLDL for 1, 3, 6, and 18 hours.
- Gene and protein expression of SRs (CD36, SR-A, LOX-1) and inflammatory molecules (IL-1beta, IL-8, PPARgamma, NF-kappaB) were quantified.
- Subjects were classified as high or low responders based on SR gene expression levels.
Main Results:
- Significant interindividual variability in CD36, SR-A, and LOX-1 gene expression was observed after 1 hour of oxLDL incubation.
- High and low responders exhibited distinct inflammatory response patterns.
- CD36 and LOX-1 gene expression positively correlated with IL-1beta; SR-A correlated with IL-8, PPARgamma, and NF-kappaB.
- A negative correlation was found between CD36 and SR-A protein levels after 18 hours.
- Findings were consistent across repeated sampling.
Conclusions:
- Macrophage SR gene expression profiles are highly variable among individuals.
- The type of SR expressed influences macrophage activation and inflammatory response to oxLDL.
- CD36 and LOX-1 are associated with a more pro-inflammatory macrophage phenotype compared to SR-A.
Abstract:
Atherosclerosis is an inflammatory disease in which oxidized low-density lipoprotein (oxLDL) plays important roles. Scavenger receptors (SR) CD36, SR-A, and LOX-1 uptake over 90% of the oxLDL leading to foam cell formation and secretion of inflammatory cytokines. To investigate whether the interindividual differences in macrophage SR gene expression could determine the inflammatory variability in response to oxLDL, we quantified the gene and protein expression of SR and inflammatory molecules from macrophages isolated from 18 volunteer subjects and incubated with oxLDL for 1, 3, 6, and 18 h. The individual gene expression profile of the studied SR at 1 h of incubation was highly variable, showing a wide fold-change range: CD36: -3.57-4.22, SR-A: -5.0-4.43, and LOX-1: -1.56-75.32. We identified subjects as high and low responders depending on whether their SR gene expression was above or below the median, showing a different inflammation response pattern. CD36 and LOX-1 gene expression correlated positively with IL-1beta; SR-A correlated negatively with IL-8 and positively with PPARgamma and NF-kappaBIotaA. These results were confirmed in the same subjects 3 mo after the first sampling. Furthermore, a negative correlation existed between CD36 and SR-A at protein level after 18 h of oxLDL incubation (R = -0.926, p = 0.024). These data would suggest that the type of SR could determine the macrophage activation: more proinflammatory when associated to CD36 and LOX-1 than when associated with SR-A.
