Chlamydia pneumoniae burden in carotid arteries is associated with upregulation of plaque interleukin-6 and elevated C-reactive protein in serum

Document Type

Article

Abstract

OBJECTIVE: Chlamydia pneumoniae (Cpn) infection of vascular smooth muscle cells increases interleukin-6 (IL-6) secretion in vitro. In vivo, IL-6 stimulates liver C-reactive protein (CRP) production. Because serum levels of IL-6 and CRP are independent risk factors for stroke and myocardial infarction (MI), we investigated whether Cpn burden in carotid plaques might provide a link between plaque IL-6 expression and elevated serum levels of IL-6 and CRP. METHODS AND RESULTS: Consecutive patients undergoing elective carotid endarterectomy were studied. Serum levels of CRP and IL-6 were measured before surgery. Immunohistochemistry and real-time quantitative (k)RT-PCR were used to detect Cpn and the expression of IL-6 within carotid plaques. Cpn mRNA was present in 19 (37%) of 51 patients, suggesting viable infections. These patients had evidence for infection by PCR and immunohistochemistry. The Cpn burden, measured by real-time quantitative (k)-PCR using the number of organisms normalized against the number of eukaryotic cells in the tissue, was associated with plaque expression of IL-6 (Spearman R=0.55; P<0.0001), which was associated with serum levels of IL-6 (R=0.56; P<0.0001) and CRP (R=0.80; P<0.0001). CONCLUSIONS: IL-6 secretion in atherosclerotic plaques infected with Cpn could explain elevated serum inflammatory markers in individuals at risk for stroke and MI.

Medical Subject Headings

Aged; Aged, 80 and over; Biomarkers (blood); C-Reactive Protein (metabolism); Carotid Arteries (immunology, microbiology); Carotid Artery Diseases (epidemiology, immunology, microbiology); Chlamydophila Infections (complications, epidemiology, immunology); Chlamydophila pneumoniae (isolation & purification); Endarterectomy, Carotid; Female; Humans; Immunohistochemistry; Interleukin-6 (blood, genetics); Male; Middle Aged; Reverse Transcriptase Polymerase Chain Reaction; Risk Factors; Up-Regulation (immunology); Vasculitis (epidemiology, immunology, microbiology)

Publication Date

10-8-2005

Publication Title

Arteriosclerosis, thrombosis, and vascular biology

E-ISSN

1524-4636

Volume

25

Issue

12

First Page

2648

Last Page

53

PubMed ID

16210572

Digital Object Identifier (DOI)

10.1161/01.ATV.0000189157.88630.d1

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