Two isoforms of cyclooxygenase contribute to augmented endothelium-dependent contractions in femoral arteries of 1-year-old rats

Acta Pharmacol Sin. 2008 Feb;29(2):185-92. doi: 10.1111/j.1745-7254.2008.00749.x.

Abstract

Aim: The present experiments were designed to study the changes in endothelium-dependent contractions with aging.

Methods: The rat femoral arteries of 20-week and 1-year-old rats with and without endothelium were suspended in organ chambers to record isometric tension. The production of oxygen-derived free radicals in the endothelium was measured with 2,7o-dichlorodihydrofluorescein diacetate (DCF) using confocal microscopy. Protein presences were determined by Western blotting.

Results: In the arteries from the 1-year-old rats, endothelium-dependent relaxations to A23187 were reduced, but the endothelium-dependent contractions to A23187 (in the presence of Nomega-nitro-L-arginine methyl ester hydrochloride [L-NAME; an inhibitor of nitric oxide synthase]) were augmented, demonstrating endothelial dysfunction with aging. Indomethacin normalized the responses, suggesting that a cyclooxygenase (COX)-dependent contraction is prominent in aging. The endothelium-dependent contractions were also prevented by terutroban (a blocker of thromboxane-prostanoid receptors), confirming the activation of thromboxane-prostanoid receptors on vascular smooth muscle. Valeryl salicylate and NS-398 (preferential inhibitors of COX-1 and COX-2, respectively) partially reduced the response, indicating that both COX-1 and COX-2 are involved. Western blotting confirmed the upregulation of both isoforms in the arteries of the 1-year-old rats. In the presence of L-NAME, A23187 increased the DCF fluorescence in the endothelium, demonstrating that the production of oxygen-derived free radicals contributes to endothelium-dependent contractions. The activity of catalase was reduced in the arteries with endothelium of 1-year-old rats, indicating that hydrogen peroxide is the likely mediator of increased oxidative stress in the aging endothelium.

Conclusion: Endothelium-dependent contractions are augmented with aging. Oxidative stress potentiates the response, and both COX-1 and COX-2 are involved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Catalase / metabolism
  • Cyclooxygenase 1 / physiology*
  • Cyclooxygenase 2 / physiology*
  • Endothelium, Vascular / physiology*
  • Enzyme Inhibitors / pharmacology
  • Femoral Artery / physiology
  • Glutathione / metabolism
  • In Vitro Techniques
  • Muscle Contraction / drug effects
  • Muscle Contraction / physiology
  • Muscle, Smooth, Vascular / physiology*
  • NG-Nitroarginine Methyl Ester / pharmacology
  • Nitric Oxide Synthase Type III / antagonists & inhibitors
  • Rats
  • Rats, Sprague-Dawley
  • Reactive Oxygen Species / metabolism

Substances

  • Enzyme Inhibitors
  • Reactive Oxygen Species
  • Catalase
  • Nitric Oxide Synthase Type III
  • Cyclooxygenase 1
  • Cyclooxygenase 2
  • Glutathione
  • NG-Nitroarginine Methyl Ester