The role of urinary PGE2 and renin-angiotensin-aldosterone system in the pathogenesis of essential hypertension

Pooled Analysis of Multiple Crossover Trials To Optimize Individual Therapy Response to Renin-Angiotensin-Aldosterone System Intervention

BACKGROUND AND OBJECTIVES

In the treatment of CKD, individual patients show a wide variation in their response to many drugs, including renin-angiotensin-aldosterone system inhibitors (RAASi). To investigate whether therapy resistance to RAASi can be overcome by uptitrating the dose of drug, changing the mode of intervention (with drugs from similar or different classes), or lowering dietary sodium intake, we meta-analyzed individual responses to different modes of interventions.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Randomized crossover trials were analyzed to assess correlation of individual responses to RAASi and nonsteroidal anti-inflammatory drugs (NSAIDs; n=395 patients). Included studies compared the antialbuminuric effect of uptitrating the dose of RAASi (n=10 studies) and NSAIDs (n=1), changing within the same class of RAASi (e.g., angiotensin-converting enzyme inhibition to angiotensin receptor blockers; n=5) or NSAIDs (n=1), changing from RAASi to NSAIDs (n=2), and changing from high to low sodium intake (n=5). A two-stage meta-analysis was conducted: Deming regression was conducted in each study to assess correlations in response, and individual study results were then meta-analyzed.

RESULTS

The albuminuria response to one dose of RAASi or NSAIDs positively correlated with the response to a higher dose of the same drug (r=0.72; 95% confidence interval [95% CI], 0.66 to 0.78), changes within the same class of RAASi or NSAIDs (r=0.54; 95% CI, 0.35 to 0.68), changes between RAASi and NSAIDs (r=0.44; 95% CI, 0.16 to 0.66), and changes from high to moderately low salt intake (r=0.36; 95% CI, 0.22 to 0.48). Results were similar when the individual systolic BP and potassium responses were analyzed, and were consistent in patients with and without diabetes.

CONCLUSIONS

Individuals who show a poor response to one dose or type of RAASi also show a poor response to higher doses, other types of RAASi or NSAIDs, or a reduction in dietary salt intake. Whether other drugs or drug combinations targeting pathways beyond the renin-angiotensin-aldosterone system and prostaglandins would improve the individual poor response requires further study.

Prostaglandin E2 modulation of blood pressure homeostasis: studies in rodent models

Hypertension is a well established risk factor for cardiovascular diseases such as stroke and is the leading cause of chronic kidney failure. Although a number of pharmacologic agents are available for the treatment of hypertension including agents that affect the renin-angiotensin-aldosterone system (RAAS), unmet needs in the treatment of hypertension suggest that identification of novel pharmacological targets would be an important healthcare goal. One potential target is prostaglandin E(2) (PGE(2)), a potent lipid mediator with a diverse and sometimes opposing range of biological effects. PGE(2) signals through four subtypes of G-protein coupled receptors designated EP1 through EP4. PGE(2) functions primarily as a vasodepressor; under certain conditions PGE(2) administration mediates vasopressor activity. This review focuses on the current understanding of the roles of PGE(2) receptors in vascular reactivity, hypertension and end-organ damage.

The role of prostaglandins in human hypertension

A large body of evidence supports the concept that prostaglandins (PG) are importantly involved in arterial pressure regulation. Various PGs, especially PGE2 and prostacyclin (PGI2) may influence blood pressure through control of vascular tone, sodium excretion, and renin release. Inhibition of PG synthesis by nonsteroidal antiinflammatory drugs (NSAID) augments the vasoconstrictor response to exogenous pressors such as angiotensin II, arginine vasopressin (AVP), and fludrocortisone. The acute administration of NSAID to either normotensive or untreated hypertensive subjects results in an increase in arterial pressure and peripheral resistance; long-term administration, however, is associated with little or no change in blood pressure, possibly because of a reduction in cardiac output. Although NSAID have little influence on blood pressure in normotensive subjects or untreated hypertensives, inhibition of PG synthesis blunts or abolishes the antihypertensive effect of most antihypertensive agents. NSAID antagonize the vasodepressor action of diuretics, beta-adrenoreceptor antagonists, vasodilators, and converting enzyme inhibitors. Consequently, potent NSAID should be used with caution, if at all, during treatment of hypertensive patients. Numerous studies have examined renal PG production in essential hypertension (EH). The majority have demonstrated reduced basal and stimulated urinary PGE2 excretion in EH compared to normotensive subjects, but there is substantial overlap. Nevertheless, renal PGE2 synthesis is significantly decreased in approximately one-third of patients with EH. A recent innovative approach to arterial pressure regulation has focused on dietary supplementation with polyunsaturated fatty acids (PUFA), especially linoleic acid and eicosapentaenoic acid. Several groups have demonstrated that long-term dietary supplementation with PUFA reduces blood pressure in both normotensive individuals and in patients with EH.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin excretion after furosemide in normal and low-renin essential hypertension

We examined the urinary excretion of prostaglandin (PG)E2 and PGF2 alpha before and 15 min after stimulation with the acutely vasodilating agent furosemide in 25 normotensive controls and 81 patients with essential hypertension (EH). After furosemide administration, PGE2 excretion was lower in patients with EH (P less than 0.02). Excretion rates of PGF2 alpha and of sodium, and urinary volume in hypertensive patients were not significantly different from the values found in normotensive controls. Patients with low-renin essential hypertension (LREH) had a significantly reduced excretion of both PGE2 and PGF2 alpha before and after administration of furosemide as compared to controls. The difference in PGF2 alpha excretion was also significant when LREH patients were compared to those with normal-renin essential hypertension (NREH). Patients with LREH were older and excreted less potassium than patients with NREH or normotensive controls. We conclude that the reduced PG excretion immediately after furosemide administration in patients with EH reflects a diminished capacity of the hypertensive kidney to generate prostaglandins which exert an overall vasodilating effect. Since renin secretion is under the control of renal PG formation, the decreased responsiveness of plasma renin activity (PRA) observed in patients with EH and predominantly in those with LREH may be the consequence of a decreased renal cortical PG generation. Alternatively, mechanisms that reduce both PRA and PG generation have to be considered.