Abstract
Lipopolysaccharide (LPS) stimulates cytoplasmic accumulation of pro-interleukin (IL)-1β. Activation of P2X7 receptors stimulates conversion of pro-IL-1β into mature IL-1β, which is then secreted. Because both LPS (in vivo) and IL-1β (in vitro) decrease vascular reactivity to contractile agents, we hypothesized the following: 1) P2X7 receptor activation contributes to LPS-induced vascular hyporeactivity, and 2) IL-1β mediates this change. Thoracic aortas were obtained from 12-week-old male C57BL/6 mice. The aortic rings were incubated for 24 h in Dulbecco's modified Eagle's medium, LPS, benzoylbenzoyl-ATP (BzATP; P2X7 receptor agonist), LPS plus BzATP, oxidized ATP (oATP; P2X7 receptor antagonist), or oATP plus LPS plus BzATP. After the treatment, the rings were either mounted in a myograph for evaluation of contractile activity or homogenized for IL-1β and inducible nitric-oxide synthase (iNOS) protein measurement. In endothelium-intact aortic rings, phenylephrine (PE)-induced contractions were not altered by incubation with LPS or BzATP, but they significantly decreased in aortic rings incubated with LPS plus BzATP. Treatment with oATP or IL-1ra (IL-1β receptor antagonist) reversed LPS plus BzATP-induced hyporeactivity to PE. In the presence of NG-nitro-l-arginine methyl ester or N-([3-(aminomethyl)phenyl]methyl)ethanimidamide (selective iNOS inhibitor), the vascular hyporeactivity induced by LPS plus BzATP on PE responses was not observed. BzATP augmented LPS-induced IL-1β release and iNOS protein expression, and these effects were also inhibited by oATP. Moreover, incubation of endothelium-intact aortic rings with IL-1β induced iNOS protein expression. Thus, activation of P2X7 receptor amplifies LPS-induced hyporeactivity in mouse endothelium-intact aorta, which is associated with IL-1β-mediated release of nitric oxide by iNOS.
Footnotes
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This study was supported by a grant from the National Institutes of Health (HL-74167).
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.107.135350.
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ABBREVIATIONS: LPS, lipopolysaccharide; IL, interleukin; NOS, nitric-oxide synthase; BzATP, benzoylbenzoyl-ATP; PE, phenylephrine; l-NAME, NG-nitro-l-arginine methyl ester; 1400W, N-([3-(aminomethyl)phenyl]methyl)ethanimidamide; oATP, oxidized ATP; IL-1ra, IL-1β receptor antagonist; DMEM, Dulbecco's modified Eagle's medium; iNOS, inducible NOS; ELISA, enzyme-linked immunoadsorbent assay.
- Received December 14, 2007.
- Accepted June 13, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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