Abstract
The acute-phase protein haptoglobin (Hpt) binds apolipoprotein A-I (ApoA-I) and impairs its action on lecithin-cholesterol acyltransferase, an enzyme that plays a key role in reverse cholesterol transport. We have previously shown that an ApoA-I mimetic peptide, P2a, displaces Hpt from ApoA-I, restoring the enzyme activity in vitro. The aim of this study was to evaluate whether P2a displaces Hpt from ApoA-I in vivo and whether this event leads to anti-inflammatory activity. Mice received subplantar injections of carrageenan. Paw volume was measured before the injection and 2, 4, 6, 24, 48, 72, and 96 h thereafter. At the same time points, concentrations of HDL cholesterol (C) and cholesterol esters (CEs) were measured by high-performance liquid chromatography, and Hpt and ApoA-I plasma levels were evaluated by enzyme-linked immunosorbent assay. Western blotting analysis for nitric-oxide synthase and cyclooxygenase (COX) isoforms was also performed on paw homogenates. CEs significantly decreased in carrageenan-treated mice during edema development and negatively correlated with the Hpt/ApoA-I ratio. P2a administration significantly restored the CE/C ratio. In addition, P2a displayed an anti-inflammatory effect on the late phase of edema with a significant reduction in COX2 expression coupled to an inhibition of prostaglandin E2 synthesis, implying that, in the presence of P2a, CE/C ratio rescue and edema inhibition were strictly related. In conclusion, the P2a effect is due to its binding to Hpt with consequent displacement of ApoA-I that exerts anti-inflammatory activity. Therefore, it is feasible to design drugs that, by enhancing the physiological endogenous protective role of ApoA-I, may be useful in inflammation-based diseases.
Footnotes
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
↵ The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- C
- cholesterol
- RCT
- reverse cholesterol transport
- HDL
- high-density lipoprotein
- ApoA-I
- apolipoprotein A-I
- LCAT
- lecithin-cholesterol acyltransferase
- Hpt
- haptoglobin
- CE
- cholesteryl ester
- BSA
- bovine serum albumin
- COX
- cyclooxygenase
- iNOS
- inducible nitric-oxide synthase
- PGE2
- prostaglandin E2
- P2as
- scramble peptide
- HPLC
- high-performance liquid chromatography
- ELISA
- enzyme-linked immunosorbent assay
- HDL-C
- unesterified and total cholesterol
- eNOS
- endothelial nitric-oxide synthase.
- Received October 24, 2011.
- Accepted December 12, 2011.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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