Downregulation of nitric oxide accumulation by cyclooxygenase-2 induction and thromboxane A2 production in interleukin-1beta-stimulated rat aortic smooth muscle cells.

Abstract

BACKGROUND:

Cytokines from inflammatory cells do not produce nitric oxide, but stimulate the production of nitric oxide in vascular smooth muscle cells (VSMC). Thromboxane A2 (TXA2) has been believed to have a key role in atherosclerogenesis and post-angioplasty restenosis.

OBJECTIVE:

To determine whether cytokine-induced nitric oxide production is regulated by the TXA2/prostaglandin H2 (PGH2) receptor.

METHODS AND RESULTS:

We studied the interleukin-1beta (IL-1beta)-induced production of nitric oxide in rat VSMCs using the TXA2/PGH2 receptor antagonists, seratrodast and Bay-u3405, and an agonist, U-46619. Nitrite formation was measured colorimetrically. IL-1beta increased nitrite formation in a time-dependent manner. The nitrite concentration was 1.7 times greater in the presence of seratrodast than that without it. Nitrite accumulation was increased by Bay-u3405, but was decreased in the presence of U-46619, to 44% of that in its absence. Western and Northern blotting showed that seratrodast increased the levels of expression of inducible nitric oxide synthase (iNOS) protein and mRNA in a dose-dependent manner, whereas U-46619 decreased them. We speculated that VSMCs produced TXA2, thereby decreasing nitric oxide production; therefore we measured the accumulation of TXB2 using an enzyme immunoassay. Untreated VSMCs produced about 20 pg/mg protein of TXB2. This was increased by the addition of IL-1beta, to 152.1 +/- 43.0 pg/mg protein after a 24 h incubation; the expression of cyclooxygenase-2 (COX-2) protein was also increased, but there was no effect on the expression of COX-1 and TXA2 synthase. U-63557A, a TXA2 synthase inhibitor, increased the accumulation of nitrite to 1.3-fold that in its absence.

CONCLUSIONS:

These data suggest that the expression of iNOS and the production of nitric oxide are regulated by the TXA2/PGH2 receptor in IL-1beta-stimulated VSMCs. The endogenous production of TXA2 by the induction of COX-2 from IL-1beta-stimulated VSMCs probably downregulated the production of nitric oxide in VSMCs. TXA2/PGH2 receptor inhibitors may contribute to the reduction in formation of atherosclerosis in lesions with vascular injury by enhancing the production of nitric oxide by VSMCs.

• Authors: Takahiro Shiokoshi, Yoshinobu Ohsaki, Junichi Kawabe, Takayuki Fujino, Kenjiro Kikuchi
• Journal: Journal of hypertension (J Hypertens) Vol. 20 Issue 3 Pg. 455-61 (Mar 2002) ISSN: 0263-6352 [Print] England
• PMID: 11875313 (Publication Type: Journal Article)

Chemical References

• Benzoquinones
• Heptanoic Acids
• Interleukin-1
• Isoenzymes
• Membrane Proteins
• Prostaglandin Antagonists
• RNA, Messenger
• Receptors, Prostaglandin
• Receptors, Thromboxane
• Receptors, Thromboxane A2, Prostaglandin H2
• Nitric Oxide
• seratrodast
• Thromboxane A2
• 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid
• Nitric Oxide Synthase
• Nitric Oxide Synthase Type II
• Nos2 protein, rat
• Cyclooxygenase 1
• Cyclooxygenase 2
• Prostaglandin-Endoperoxide Synthases
• Ptgs1 protein, rat

Topics

• 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid (pharmacology)
• Animals
• Aorta (cytology, drug effects, metabolism)
• Benzoquinones (pharmacology)
• Cells, Cultured
• Cyclooxygenase 1
• Cyclooxygenase 2
• Down-Regulation
• Enzyme Induction (physiology)
• Heptanoic Acids (pharmacology)
• Interleukin-1 (pharmacology)
• Isoenzymes (metabolism)
• Male
• Membrane Proteins
• Muscle, Smooth, Vascular (cytology, drug effects, metabolism)
• Nitric Oxide (metabolism)
• Nitric Oxide Synthase (genetics, metabolism)
• Nitric Oxide Synthase Type II
• Prostaglandin Antagonists (pharmacology)
• Prostaglandin-Endoperoxide Synthases (metabolism)
• RNA, Messenger (metabolism)
• Rats
• Rats, Sprague-Dawley
• Receptors, Prostaglandin (agonists, antagonists & inhibitors)
• Receptors, Thromboxane (agonists, antagonists & inhibitors)
• Receptors, Thromboxane A2, Prostaglandin H2
• Thromboxane A2 (biosynthesis)