15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and Acute-Kidney-Injury

Neutral endopeptidase (NEP: EC 3.4.24.11) is involved in the degradation of peptides such as atrial natriuretic peptide, angiotensin II (AngII), and endothelin-1 (ET-1). In this study we propose that NEP inhibition provides protection in glycerol-induced acute renal failure (ARF). Renal vascular responses were evaluated in ARF rats where ARF was induced by injecting 50% glycerol in candoxatril, a NEP inhibitor (30 mg/kg, orally; for 3 weeks) pretreated rats. AngII and U46619 (a TxA2 mimetic) vasoconstriction was increased (2- to 4-fold) in ARF while ET-1 vasoconstriction was surprisingly reduced (23+/-3%; p<0.05). In ARF, candoxatril paradoxically enhanced ET-1 response (60+/-20%; p<0.05) but reduced AngII vasoconstriction (51+/-11%; p<0.05) without affecting U46619 response. However, candoxatril treatment was without effect on plasma ET-1 and TxB2 levels in ARF. Candoxatril reduced plasma AngII by 34+/-4% (p<0.05) in ARF which was approximately 3.5-fold higher compared to control. Candoxatril doubled the nitrite excretion in control but was without effect on proteinuria or nitrite excretion in ARF. Candoxatril enhanced Na+ and creatinine excretion in ARF by 73+/-9% and 33+/-2%, respectively. These results suggest that NEP inhibition may confer protection in glycerol-induced ARF by stimulating renal function but without a consistent effect on renal production and renal vascular responses to endogenous vasoconstrictors.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acute Kidney Injury; Administration, Oral; Angiotensin II; Animals; Antihypertensive Agents; Creatinine; Endothelin-1; Indans; Kidney; Male; Natriuresis; Neprilysin; Nitrates; Propionates; Proteinuria; Rats; Rats, Sprague-Dawley; Thromboxane A2; Vasoconstriction; Vasoconstrictor Agents

Peroxisome proliferator-activated receptor gamma (PPARgamma), a nuclear transcription factor, modulates vascular responses to angiotensin II (AII) or thromboxane A(2) (TxA(2)) via regulation of their gene/receptor. Increased vasoconstriction and deteriorating renal function in glycerol-induced acute renal failure (ARF) may be attributed to down-regulation of PPARgamma. In this study, we investigated the effect of ciglitazone (CG), a PPARgamma inducer, on AII and TxA(2) production and activity in glycerol-induced ARF. Vascular responses to AII or 9,11-dideoxy-11alpha,9alpha-epoxymethano prostaglandin F(2alpha) (U46619), a TxA(2) mimetic, were determined in preglomerular vessels following induction of ARF with glycerol. Renal damage and function were assessed in CG-treated (9 nmol/kg for 21 days) rats. PPARgamma protein expression and activity, which were significantly lower in ARF rats, were enhanced by CG (26 and 30%). CG also increased PPARgamma mRNA by 67 +/- 6%, which was reduced in ARF. In ARF, there was significant tubular necrosis and apoptosis, a 5-fold increase in proteinuria and a 2-fold enhancement in vasoconstriction to AII and U46619. CG reduced proteinuria (49 +/- 3%), enhanced Na(+) (124 +/- 35%) and creatinine excretion (92 +/- 25%), markedly diminished tubular necrosis, and reduced ARF-induced increase in AII (40 +/- 3%) and TxA(2) (39 +/- 2%) production, the attending increase in vasoconstriction to AII (36 +/- 2%) and U46619 (50 +/- 11%), and the increase in angiotensin receptor-1 (AT(1)) (23 +/- 3%) or thromboxane prostaglandin (TP) receptor (13 +/- 1%). CG reduced free radical generation by 55 +/- 14% while elevating nitrite excretion (65 +/- 13%). Our results suggest that enhanced activity of AII and TxA(2), increased AT(1) or TP receptor expression, and renal injury in glycerol-induced ARF are consequent to down-regulation of PPARgamma gene. CG ameliorated glycerol-induced effects through maintaining PPARgamma gene.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acute Kidney Injury; Angiotensin II; Animals; Creatinine; Dinoprost; Gene Expression; Glycerol; Hypoglycemic Agents; Kidney Glomerulus; Male; Nitric Oxide; Nitrites; PPAR gamma; Proteinuria; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Receptors, Thromboxane A2, Prostaglandin H2; Renal Artery; Sodium; Thiazolidinediones; Thromboxane A2; Thromboxane B2; Vasoconstriction

Peroxisome proliferator activated receptor-gamma (PPAR-gamma), a nuclear transcription factor, modulates angiotensin II (AII) or thromboxane A(2) (TxA(2)) response in the vasculature via transcriptional regulation of their gene or receptor expression. Increased AII or TxA(2) vasoconstriction and deteriorating renal function observed in glycerol-induced acute renal failure (ARF) may be attributed to a down-regulated PPAR-gamma expression/activity probably via an increased free radical generation. In this study, we investigated the effect of PPAR-gamma induction in glycerol-induced ARF by examining renal vascular reactivity to AII and TxA(2) and by renal expression/activity of PPAR-gamma. Vascular responses to AII or U46619, a TxA(2) mimetic were determined in rat isolated perfused kidney following induction of ARF with glycerol (50%, v/v, i.m.). Extent of renal damage and function were assessed with or without pre-treatment with ciglitazone (9 nmol kg(-1) x 21 days), a PPAR-gamma inducer. In ARF, vasoconstriction was enhanced to AII (three-fold; p<0.05) and U46619 (82%; p<0.05). Ciglitazone reduced AII and U46619 vasoconstriction by 59+/-1% (p<0.05) and 56+/-1% (p<0.05), respectively. Ciglitazone reduced proteinuria (38+/-3%) which was two-fold higher in ARF. Similarly, ciglitazone enhanced Na(+) excretion by 1.5 times while reducing BUN by 49+/-6%. On the contrary, ciglitazone did not change plasma creatinine which was significantly higher in ARF rats. Ciglitazone reduced free radical generation by 30+/-3% while elevating nitrite excretion approximately 2-fold. PPAR-gamma expression and activity were significantly lower in ARF rats and ciglitazone enhanced PPAR-gamma protein expression and activity by 45+/-3% and 52+/-4%, respectively. Data from this study suggest that reduced PPAR-gamma expression and activity may be involved in the pathology of glycerol-induced ARF and induction of PPAR-gamma by ciglitazone confers protection through reduced AII and TxA(2) vasoconstriction and/or enhanced renal function via reducing free radical generation.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acute Kidney Injury; Angiotensin II; Animals; Ascorbic Acid; Clofibrate; Down-Regulation; Free Radicals; Glycerol; Kidney; Male; Nitric Oxide; Nitriles; PPAR gamma; Rats; Rats, Sprague-Dawley; Renal Circulation; Thiazolidinediones; Thromboxane A2; Vasoconstriction

Angiotensin II and endothelin-1, major endogenous vasoconstrictors in acute renal failure (ARF), can modulate the effects of each other. This study aimed to evaluate the interaction between these vasoconstrictors in glycerol-induced ARF by evaluating their effects in the isolated perfused kidney in the presence of their respective antagonists. In ARF, angiotensin II (2.5-25 ng) caused an increase in perfusion pressure. Saralasin, 1 microM, a nonselective angiotensin receptor antagonist, reduced these responses by 61+/- 6% (p < 0.05). Surprisingly, SQ29548, 1 microM, a selective PGH2 /thromboxane A2 receptor blocker, also reduced angiotensin II responses (62 +/- 4%; p < 0.05). BQ610 1 microM, an ETA -selective receptor antagonist, was without effect, but BQ788 1 microM, an ETB -selective antagonist, attenuated the response by 70 +/- 4% (p < 0.05). In ARF, in contrast to angiotensin II, vasoconstriction by endothelin-1 (5-25 ng) was diminished. Saralasin further attenuated endothelin-1 response by 65 +/- 2% (p < 0.05), whereas SQ29548 was without effect. BQ788 reduced the responses by 67 +/- 7% (p < 0.05), whereas BQ610 was without effect (42 +/- 30%; p > 0.05). BQ610 and BQ788 combination further reduced vasoconstriction by 89 +/- 3% (p < 0.05). Responses to U46619 were not changed in ARF. However, saralasin and BQ788, but not BQ610, attenuated its vasoconstrictor action. We conclude that vascular responses in ARF may be attributed to enhanced responses to angiotensin II through activation of ETB and/or PGH2 /thromboxane A2 receptors. We also suggest that the vasoconstrictor response to endothelin-1 in ARF is predominantly ETB receptor-mediated.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Acute Kidney Injury; Angiotensin II; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Glycerol; In Vitro Techniques; Male; Perfusion; Rats; Rats, Sprague-Dawley; Vasoconstriction; Vasoconstrictor Agents