Upregulation of Cortical COX-2 in Salt-Sensitive Hypertension: Role of Angiotensin II and Reactive Oxygen Species

Am J Physiol Renal Physiol. 2008 Feb;294(2):F385-92. doi: 10.1152/ajprenal.00302.2007. Epub 2007 Dec 19.

Abstract

Salt-sensitive (SS) hypertension is a vascular diathesis characterized by reduced cardiovascular and renal nitric oxide bioavailability and local upregulation of ANG II. We have demonstrated that rats infused with ANG II manifest increased cortical cyclooxygenase (COX)-2 expression and activity via NADPH oxidase-derived reactive oxygen species (ROS). In the present studies we used Dahl salt-sensitive (DS) rats to test the hypothesis that hypertensive SS rats have increased cortical COX-2 upregulation, which is mediated by ANG II and ROS. DS rats were placed on either a normal-salt diet (0.5% NaCl) or a high-salt diet (4% NaCl) for 6 wk and treated with either the ANG II type 1 (AT1) receptor blocker candesartan (Can, 10 mg.kg(-1).day(-1)) or the SOD mimetic tempol (1 mmol/l). Hypertensive SS rats had a twofold increase in the cortical expression of COX-2 as assessed by Western blot. These changes in COX-2 expression were accompanied by a 10-fold increase in COX-2 mRNA expression and a 2-fold increase in the urinary excretion of PGE2. Treatment with either the AT1 receptor blocker Can or the SOD mimetic tempol did not reduce blood pressure but resulted in significant reductions in the cortical expression of COX-2 and the urinary excretion of PGE2. In conclusion, we have demonstrated that local activation of the renin-angiotensin system, via increased ROS generation, mediates COX-2 upregulation in hypertensive SS rats. These studies unveil novel mechanistic pathways that may play a role in the pathogenesis of hypertensive renal injury.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amlodipine / pharmacology
  • Angiotensin II / physiology*
  • Angiotensin II Type 1 Receptor Blockers / pharmacology
  • Animals
  • Antihypertensive Agents / pharmacology
  • Antioxidants / pharmacology
  • Benzimidazoles / pharmacology
  • Blood Pressure / drug effects
  • Cyclic N-Oxides / pharmacology
  • Cyclooxygenase 1 / metabolism
  • Cyclooxygenase 2 / genetics
  • Cyclooxygenase 2 / metabolism*
  • Dinoprostone / urine
  • Gene Expression / drug effects
  • Hypertension / metabolism*
  • Kidney Cortex / metabolism*
  • Kidney Medulla / metabolism
  • Male
  • Membrane Proteins / metabolism
  • Rats
  • Rats, Inbred Dahl
  • Reactive Oxygen Species / metabolism*
  • Sodium Chloride, Dietary / pharmacology
  • Spin Labels
  • Tetrazoles / pharmacology
  • Up-Regulation / drug effects
  • Up-Regulation / physiology*

Substances

  • Angiotensin II Type 1 Receptor Blockers
  • Antihypertensive Agents
  • Antioxidants
  • Benzimidazoles
  • Cyclic N-Oxides
  • Membrane Proteins
  • Reactive Oxygen Species
  • Sodium Chloride, Dietary
  • Spin Labels
  • Tetrazoles
  • Angiotensin II
  • Amlodipine
  • Cyclooxygenase 1
  • Cyclooxygenase 2
  • Ptgs1 protein, rat
  • Ptgs2 protein, rat
  • Dinoprostone
  • candesartan
  • tempol