Inhibition of Interleukin-1-α-Induced Nitric Oxide Synthase in Vascular Smooth Muscle and Full Reversal of Interleukin-1-α-Induced Hypotension by Nω-Amino-L-arginine

• Published in: JNCI : Journal of the National Cancer Institute 1992-07, Vol.84 (13), p.1008-1016
• Main Authors: Kilbourn, Robert G., Gross, Steven S., Lodato, Robert F., Adams, James, Levi, Roberto, Miller, Langdon L., Lachman, Lawrence B., Griffith, Owen W.
• Format: Article
• Language: English
• Subjects: Amino Acid Oxidoreductases - antagonists & inhibitors; Amino Acid Oxidoreductases - biosynthesis; Amino Acid Oxidoreductases - drug effects; Animals; Arginine - analogs & derivatives; Arginine - pharmacology; Arginine - therapeutic use; Biological and medical sciences; Cell Division - drug effects; Dogs; Drug toxicity and drugs side effects treatment; Enzyme Induction - drug effects; Humans; Hypotension - chemically induced; Hypotension - drug therapy; Interleukin-1 - adverse effects; Interleukin-1 - antagonists & inhibitors; Medical sciences; Mice; Muscle, Smooth, Vascular - drug effects; Muscle, Smooth, Vascular - enzymology; Nitric Oxide Synthase; Pharmacology. Drug treatments; Rats; Rats, Inbred F344; Toxicity: cardiovascular system; Tumor Cells, Cultured - cytology; Tumor Cells, Cultured - drug effects; Vascular Resistance - drug effects
• ISSN: 0027-8874; 1460-2105
• DOI: 10.1093/jnci/84.13.1008

Background: Interleukin-1-α (IL-1) is a cytokine with potentially therapeutic immunoproliferative and tumori-cidal activities. Preliminary clinical studies suggest that use of IL-1 may be restricted by dose-limiting hypotension. Purpose: The purpose of this study was to investigate the role of nitric oxide (NO) as a possible mediator of this hypotension. Methods: Cytokine-treated rat aortic smooth muscle cells were assayed for nitrite production, a stable breakdown product of nitric oxide. Nitric oxide synthase from smooth muscle cells was partially characterized in cytosol preparations using a novel Fe2+-myoglobin method to test for nitric oxide production. To determine the role of NO on the immunorestorative and antineoplastic activity of IL-1, Nω-amino-L-arginine (NAA) or Nω-monomethyl-L-arginine (NMA), inhibitors of nitric oxide synthase, were added to either cultures of IL-1-dependent T cells or A375 melanoma cells exposed to IL-1. To investigate the effects of NAA in vivo, pentobarbital anesthetized dogs, which were made hypotensive by administration of IL-1, received a single intravenous bolus dose of NAA. The effects of NAA were then reversed by the administration of L-arginine. Results: Our results show that cultured IL-1-activated rat aortic smooth muscle cells synthesize nitric oxide, a potent vasodilator. Induction of nitric oxide synthase is augmented by interferon-7 and blocked by IL-1 receptor antagonist and by inhibitors of RNA or protein synthesis. Nitric oxide synthesis by IL-1-activated smooth muscle cells is inhibited by NAA, NMA, and Nω-nitro-L-arginine (NNA) with ED50 (i.e., effective dose for 50% inhibition) values of 20, 60, and 1000 μM, respectively; this rank order of inhibition is characteristic of an agonist-unregulated, inducible isoform of nitric oxide synthase. In smooth muscle cells, inhibition of NO synthesis by NAA is reversed by excess L-arginine. Consistent with the induction of unregulated NO- synthesis in vascular smooth muscle in vivo, administration of IL-1 (50 μg/kg) to dogs caused a 33.5% decrease in systemic vascular resistance and a 28% decrease in blood pressure within 3 hours. Subsequent administration of NAA (20 mg/ kg) rapidly and completely reversed the hypotension and increased systemic vascular resistance; these effects of NAA were reversed by L-arginine. Neither the immunoproliferative nor the tumoricidal activity of IL-1 was diminished by NAA. Conclusions: Our results indicate that (a) vascular smooth mu