N-terminal rather than full-length osteopontin or its C-terminal fragment is associated with carotid-plaque inflammation in hypertensive patients

Talya Wolak, Neta Sion-Vardi, Victor Novack, Georg Greenberg, Gabriel Szendro, Tanya Tarnovscki, Ori Nov, Ilan Shelef, Esther Paran, Assaf Rudich

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Background Hypertensive patients develop carotid atherosclerotic plaques with enhanced inflammation. Full-length osteopontin (OPN-FL), a multifunctional protein whose levels are elevated in association with atherosclerosis, is cleaved by thrombin and matrix metalloproteinases to form a C-terminal and a putatively biologically active N-terminal fragment (OPN-C, OPN-N, respectively). We conducted a study to examine whether plaque inflammation in hypertensive patients corresponds to the expression of OPN or of its cleaved forms or both. Methods We collected 42 carotid plaques from 41 consecutive hypertensive patients during carotid endarterectomy. Plaque tissue was used to measure matrix metalloproteinase-12 (MMP-12) and OPN proteins, and for the classification of plaques as showing low-or high-degree inflammation through histological and immunohistochemical evaluation. Results Fifteen highly inflamed plaques and 27 plaques with characteristics of low-grade inflammation were collected. Moderate to heavy staining for OPN characterized 87% of the plaques with high-degree inflammation but only 44% of those with low-degree inflammation, corresponding to the percentages of plaques that were heavily stained for the macrophage marker CD68 (93% versus 26%, respectively, P < 0.01). Western blot analysis showed that the abundance of OPN-FL and OPN-C was comparable in the two groups. However, the abundance of OPN-N was significantly greater in the highly inflamed plaques (median, 3.8 (range, 0.8-7.3) vs. median, 0.9 (range, 0.2-1.5); P = 0.017, respectively). The abundance of MMP-12 was significantly greater in the high-than in the low-degree plaque inflammation group (4.8 (range 1.9-8.8) vs. 1.1 (range 0.3-1.4), respectively; P = 0.03). Conclusions The N-terminal fragment of osteopontin, rather than OPN-FL or OPN-C, is associated with carotid plaque inflammation in hypertensive patients. Future studies should assess whether targeting OPN cleavage could present a new approach to preventing high-risk carotid plaques.

Original languageEnglish
Pages (from-to)326-333
Number of pages8
JournalAmerican Journal of Hypertension
Volume26
Issue number3
DOIs
StatePublished - 1 Mar 2013
Externally publishedYes

Keywords

  • OPN-N
  • blood pressure
  • carotid plaque
  • hypertension
  • inflammation
  • osteopopontin

ASJC Scopus subject areas

  • Internal Medicine

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