Cyclooxygenase-2 (cox-2) in the thick ascending limb: regulation and function.

In postnatal weeks 2–4, cyclooxygenase-2 (COX-2) is induced in the rat kidney cortex where it is critically involved in final stages of kidney development. We examined whether changes in circulating gluco- or mineralocorticosteroids or in their renal receptors regulate postnatal COX-2 induction. Plasma corticosterone concentration peaked at birth, decreased to low levels at days 3- 13, and increased to adult levels from day 22. Aldosterone peaked at birth and then stabilized at adult levels. Gluco- and mineralocorticoid receptor (GR and MR) mRNAs were expressed stably in kidney before, during, and after COX-2 induction. 11β-Hydroxysteroid dehydrogenase 2 was induced shortly after birth and was widely distributed in the whole collecting duct system in the suckling period and then returned to an adult pattern. Supplementation with corticosterone (20 mg·kg-1·day-1) or GR-specific dexamethasone (1 mg·kg-1·day-1) during low endogenous corticosterone suppressed renal COX-2 mRNA and protein and led to a restricted distribution of COX-2 immunolabeling. The ability of glucocorticoids to affect COX-2 was reflected in colocalization of GR-α and COX-2 immunoreactivity and mRNAs in thick ascending limb of Henle's loop. The MR antagonist potassium canrenoate (20 mg·kg-1·day-1) enhanced COX-2 expression from days 5 to 10, but low MR-specific concentrations of DOCA (1 mg·kg-1·day-1) had no effect on COX-2. Renomedullary interstitial cells expressed GR-α and COX-2. Dexamethasone suppressed COX-2 in these cells. Thus low plasma concentrations of corticosterone allowed for cortical and medullary COX-2 induction during postnatal kidney development. Increased circulating glucocorticoid in the postnatal period may damage late renal development through inhibition of COX-2.

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Cross talk between the intrarenal dopaminergic and cyclooxygenase-2 systems

AJP Renal Physiology ◽

10.1152/ajprenal.00240.2004 ◽

2005 ◽

Vol 288 (4) ◽

pp. F840-F845 ◽

Cited By ~ 22

Author(s):

Ming-Zhi Zhang ◽

Bing Yao ◽

James A. McKanna ◽

Raymond C. Harris

Keyword(s):

Salt Intake ◽

Enzyme Inhibitor ◽

Control Diet ◽

Sch 23390 ◽

Cyclooxygenase 2 ◽

High Salt ◽

Thick Ascending Limb ◽

Natriuretic Hormone ◽

Fluid Delivery ◽

Cox 2

In mammalian kidney, dopamine produced in the proximal tubule (PT) acts as an autocrine/paracrine natriuretic hormone that inhibits salt and fluid reabsorption in the PT. In high-salt-treated animals, PT dopamine activity increases and inhibits reabsorption, leading to increased salt and fluid delivery to the macula densa (MD) and subsequent natriuresis and diuresis. Regulated cyclooxygenase-2 (COX-2) in the MD represents another intrinsic system mediating renal salt and water homeostasis. Renal cortical COX-2 is inversely related to salt intake, and decreased extracellular NaCl stimulates COX-2 expression in cultured MD/cortical thick ascending limb cells. The current study investigated interactions between renal dopamine and cortical COX-2 systems. In rats fed a control diet, the dopamine precursor l-dihydroxyphenylalanine (l-DOPA) or the DA1 receptor agonist SKF-81297 suppressed cortical COX-2 expression. High salt suppressed cortical COX-2 expression, which was attenuated by inhibition of dopamine production with benserazide or the DA1 receptor antagonist, SCH-23390. In contrast, l-DOPA or the dopamine-metabolizing enzyme inhibitor entacapone suppressed low-salt-induced cortical COX-2 expression. Inhibition of PT reabsorption with the carbonic anhydrase inhibitor acetazolamide suppressed cortical COX-2 expression. In contrast, treatment with distally acting diuretics led to elevation of cortical COX-2. These results indicate that dopamine modulates renal cortical COX-2 expression by modifying PT reabsorption.

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Physiological regulation of cyclooxygenase-2 in the kidney

AJP Renal Physiology ◽

10.1152/ajprenal.2001.281.1.f1 ◽

2001 ◽

Vol 281 (1) ◽

pp. F1-F11 ◽

Cited By ~ 209

Author(s):

Raymond C. Harris ◽

Matthew D. Breyer

Keyword(s):

Nitric Oxide ◽

Water Deprivation ◽

Cyclooxygenase 2 ◽

Mitogen Activated Protein Kinase ◽

Angiotensin Converting Enzyme Inhibition ◽

Protein Kinase Activity ◽

Thick Ascending Limb ◽

Physiological Regulation ◽

Cox 2

In adult mammalian kidney, cyclooxygenase-2 (COX-2) expression is found in a restricted subpopulation of cells. The two sites of renal COX-2 localization detected in all species to date are the macula densa (MD) and associated cortical thick ascending limb (cTALH) and medullary interstitial cells (MICs). Physiological regulation of COX-2 in these cellular compartments suggests functional roles for eicosanoid products of the enzyme. COX-2 expression increases in high-renin states (salt restriction, angiotensin-converting enzyme inhibition, renovascular hypertension), and selective COX-2 inhibitors significantly decrease plasma renin levels, renal renin activity, and mRNA expression. There is evidence for negative regulation of MD/cTALH COX-2 by angiotensin II and by glucocorticoids and mineralocorticoids. Conversely, nitric oxide generated by neuronal nitric oxide synthase is a positive modulator of COX-2 expression. Decreased extracellular chloride increases COX-2 expression in cultured cTALH, an effect mediated by increased p38 mitogen-activated protein kinase activity, and, in vivo, a sodium-deficient diet increases expression of activated p38 in MD/cTALH. In contrast to COX-2 in MD/cTALH, COX-2 expression increases in MICs in response to a high-salt diet as well as water deprivation. Studies in cultured MICs have confirmed that expression is increased in response to hypertonicity and is mediated, at least in part, by nuclear factor-κB activation. COX-2 inhibition leads to apoptosis of MICs in response to hypertonicity in vitro and after water deprivation in vivo. In addition, COX-2 metabolites appear to be important mediators of medullary blood flow and renal salt handling. Therefore, there is increasing evidence that COX-2 is an important physiological mediator of kidney function.

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Prostaglandin E2 EP3 receptor regulates cyclooxygenase-2 expression in the kidney

AJP Renal Physiology ◽

10.1152/ajprenal.00634.2011 ◽

2012 ◽

Vol 303 (3) ◽

pp. F449-F457 ◽

Cited By ~ 12

Author(s):

Carlos P. Vio ◽

Mariana Quiroz-Munoz ◽

Catherina A. Cuevas ◽

Carlos Cespedes ◽

Nicholas R. Ferreri

Keyword(s):

Protein Expression ◽

Negative Feedback ◽

Fold Increase ◽

Treated Group ◽

Cyclooxygenase 2 ◽

Thick Ascending Limb ◽

Sprague Dawley ◽

Mrna Accumulation ◽

Cox 2 ◽

Ep3 Receptor

Cyclooxygenase-2 (COX-2) is constitutively expressed and highly regulated in the thick ascending limb (TAL). As COX-2 inhibitors (Coxibs) increase COX-2 expression, we tested the hypothesis that a negative feedback mechanism involving PGE2 EP3 receptors regulates COX-2 expression in the TAL. Sprague-Dawley rats were treated with a Coxib [celecoxib (20 mg·kg−1·day−1) or rofecoxib (10 mg·kg−1·day−1)], with or without sulprostone (20 μg·kg−1·day−1). Sulprostone was given using two protocols, namely, previous to Coxib treatment (prevention effect; Sulp7-Coxib5 group) and 5 days after initiation of Coxib treatment (regression effect; Coxib10-Sulp5 group). Immunohistochemical and morphometric analysis revealed that the stained area for COX-2-positive TAL cells (μm2/field) increased in Coxib-treated rats (Sham: 412 ± 56.3, Coxib: 794 ± 153.3). The Coxib effect was inhibited when sulprostone was used in either the prevention (285 ± 56.9) or regression (345 ± 51.1) protocols. Western blot analysis revealed a 2.1 ± 0.3-fold increase in COX-2 protein expression in the Coxib-treated group, an effect abolished by sulprostone using either the prevention (1.2 ± 0.3-fold) or regression (0.6 ± 0.4-fold vs. control, P < 0.05) protocols. Similarly, the 6.4 ± 0.6-fold increase in COX-2 mRNA abundance induced by Coxibs ( P < 0.05) was inhibited by sulprostone; prevention: 0.9 ± 0.3-fold ( P < 0.05) and regression: 0.6 ± 0.1 ( P < 0.05). Administration of a selective EP3 receptor antagonist, L-798106, also increased the area for COX-2-stained cells, COX-2 mRNA accumulation, and protein expression in the TAL. Collectively, the data suggest that COX-2 levels are regulated by a novel negative feedback loop mediated by PGE2 acting on its EP3 receptor in the TAL.

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Induction of Cyclooxygenase-2 in Thick Ascending Limb Cells by Adrenalectomy

Journal of the American Society of Nephrology ◽

10.1681/asn.v124649 ◽

2001 ◽

Vol 12 (4) ◽

pp. 649-658

Author(s):

CARLOS P. VIO ◽

SHAO-JIAN AN ◽

CARLOS CÉSPEDES ◽

JOHN C. MCGIFF ◽

NICHOLAS R. FERRERI

Keyword(s):

Protein Expression ◽

Renal Tissue ◽

Cyclooxygenase 2 ◽

Prostaglandin E ◽

Thick Ascending Limb ◽

Selective Marker ◽

Mrna Accumulation ◽

Cox 2 ◽

Morphologic Analysis ◽

Intact Rats

Abstract. Adrenalectomized (ADX) and sham-operated rats received either dexamethasone (DEX) or vehicle. Renal tissue was used for morphologic analysis, assessment of cyclooxygenase-2 (COX-2) protein expression and mRNA accumulation, and quantitation of COX-2 activity. In untreated or shamoperated rats, COX-2 protein was observed in a subset of tubular epithelial cells (<2%), which were located mainly in the cortex. All COX-2-positive cells also expressed Tamm-Horsfall glycoprotein, a highly selective marker for thick ascending limb (TAL) cells. After ADX, >30% of TAL cells expressed COX-2 in a manner consistent with recruitment of COX-2-positive TAL cells toward the medulla. Treatment of ADX rats with DEX reduced the number of COX-2-positive cells to that observed in sham-operated or intact rats. COX-2 mRNA accumulation was increased by ADX and partially attenuated by treatment with DEX. Western blot analysis of cortical microsomes revealed a substantial increase in COX-2 expression in ADX rats, compared with ADX/DEX-treated, sham-operated, or intact rats. The increase in COX-2 protein expression was associated with a twofold increase in prostaglandin E2 formation by cortical microsomes obtained from ADX rats, compared with sham-operated rats. It is concluded that ADX induces expression of enzymatically active COX-2, such that expression occurs in the cortical TAL and proceeds in a defined pattern toward the outer medullary TAL. It is suggested that ADX induces expression of TAL cells that, in the basal state, do not express COX-2 protein.

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Nitric oxide regulates renal cortical cyclooxygenase-2 expression

AJP Renal Physiology ◽

10.1152/ajprenal.2000.279.1.f122 ◽

2000 ◽

Vol 279 (1) ◽

pp. F122-F129 ◽

Cited By ~ 31

Author(s):

Hui-Fang Cheng ◽

Jun-Ling Wang ◽

Ming-Zhi Zhang ◽

James. A. McKanna ◽

Raymond C. Harris

Keyword(s):

Nitric Oxide ◽

Primary Cultures ◽

Cyclooxygenase 2 ◽

Macula Densa ◽

Thick Ascending Limb ◽

Salt Diet ◽

Nos Inhibitors ◽

Low Salt ◽

Cox 2 ◽

Arteriolar Tone

We have previously shown that cyclooxygenase-2 (COX-2) is localized to the cortical thick ascending limb of the loop of Henle (cTALH)/macula densa of the rat kidney, and expression increases in response to low-salt diet and/or angiotensin-converting enzyme (ACE) inhibition. Because of the localization of neuronal nitric oxide synthase (nNOS) to macula densa and surrounding cTALH, the present study investigated the role of nitric oxide (NO) in the regulation of COX-2 expression. For in vivo studies, rats were fed a normal diet, low-salt diet or low-salt diet combined with the ACE inhibitor captopril. In each group, one-half of them were treated with the nNOS inhibitors 7-nitroinidazole (7-NI) or S-methyl-thiocitrulline. Both of these NOS inhibitors inhibited increases in COX-2 mRNA and immunoreactive protein in response to low salt and low salt+captopril. For in vitro studies, COX-2 expression was studied in primary cultures of rabbit cTALH cells immunodisssected with Tamm-Horsfall antibody. Basal COX-2 immunoreactivity expression was stimulated by S-nitroso- N-acetyl-penicillamine (SNAP), an NO donor, and intracellular cGMP concentration. The cultured cells expressed immunoreactive nNOS, and 7-NI inhibited basal COX-2 immunoreactivity expression, which could be partially overcome by cGMP. In summary, these studies indicate that NO is a mediator of increased renal cortical COX-2 expression seen in volume depletion and suggest important interactions between the NO and COX-2 systems in the regulation of arteriolar tone and the renin-angiotensin system by the macula densa.

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Selective increase of cyclooxygenase-2 expression in a model of renal ablation

AJP Renal Physiology ◽

10.1152/ajprenal.1998.275.4.f613 ◽

1998 ◽

Vol 275 (4) ◽

pp. F613-F622 ◽

Cited By ~ 28

Author(s):

Jun-Ling Wang ◽

Hui-Fang Cheng ◽

Ming-Zhi Zhang ◽

James. A. McKanna ◽

Raymond C. Harris

Keyword(s):

Mesangial Cells ◽

Thick Ascending Limb ◽

Altered Expression ◽

Isolated Glomeruli ◽

Renal Ablation ◽

Cox 2 ◽

Collecting Tubules ◽

And Function ◽

Selective Increase ◽

Cox 1

Previous studies have suggested a possible role for prostaglandins (PGs) in mediating alterations in nephron structure and function ensuing after renal ablation. Two isoforms of cyclooxygenase (COX) have been described: constitutive (COX-1) and inducible (COX-2). We examined expression of these isoforms following subtotal renal ablation (5/6 ablation, RA) in rats. In renal cortex, COX-2 mRNA and immunoreactive protein (IP) increased progressively compared with sham-operated littermates. In contrast, there were no significant changes in COX-1 mRNA expression. In normal kidney, cortical COX-1 IP was immunolocalized predominantly to mesangial cells and collecting tubules, whereas COX-2 IP was found in a subset of cortical thick ascending limb of Henle’s loop (CTAL) cells in the region of the macula densa (MD). Following RA, significantly increased COX-2 IP was detected in the MD and surrounding CTAL cells. In addition, fainter immunoreactive COX-2 was detected in scattered visceral epithelial cells and mesangial cells of the glomerulus. Immunoblotting of isolated glomeruli demonstrated a selective increase of glomerular immunoreactive COX-2 expression following RA. No change of COX-1 expression was seen. To determine COX activity, isolated glomeruli were incubated with arachidonic acid and PGE2 measured by enzyme immunoassay (EIA). Compared with sham, glomeruli from 2 wk RA produced significantly more PGs. SC-58560, a selective COX-1 inhibitor, did not inhibit PG production in the remnant glomeruli at concentrations up to 10−4 M, whereas SC-58236, a relatively selective COX-2 inhibitor, significantly inhibited PG production by RA glomeruli. In preliminary studies, to define mechanisms of altered expression of glomerular COX-2, rat mesangial cells were incubated with serum from sham or 2 wk RA. There were significant increases in COX-2 expression in response to 2 wk RA serum. In summary, these results indicate selective increases in renal cortical COX-2 expression following renal ablation.

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Annexin A1 modulates macula densa function by inhibiting cyclooxygenase 2

AJP Renal Physiology ◽

10.1152/ajprenal.00704.2011 ◽

2012 ◽

Vol 303 (6) ◽

pp. F845-F854 ◽

Cited By ~ 4

Author(s):

S. Seidel ◽

H. Neymeyer ◽

T. Kahl ◽

T. Röschel ◽

K. Mutig ◽

...

Keyword(s):

Rat Kidney ◽

Juxtaglomerular Apparatus ◽

Inhibitory Effect ◽

Cyclooxygenase 2 ◽

Macula Densa ◽

Thick Ascending Limb ◽

Annexin A1 ◽

Glomerular Number ◽

Formyl Peptide ◽

Cox 2

Annexin A1 (ANXA1) exerts anti-inflammatory effects through multiple mechanisms including inhibition of prostaglandin synthesis. Once secreted, ANXA1 can bind to G protein-coupled formyl peptide receptors (Fpr) and activate diverse cellular signaling pathways. ANXA1 is known to be expressed in cells of the juxtaglomerular apparatus, but its relation to the expression of cyclooxygenase 2 (COX-2) in thick ascending limb and macula densa cells has not been elucidated. We hypothesized that ANXA1 regulates the biosynthesis of COX-2. ANXA1 abundance in rat kidney macula densa was extensively colocalized with COX-2 (95%). Furosemide, an established stimulus for COX-2 induction, caused enhanced expression of both ANXA1 and COX-2 with maintained colocalization (99%). In ANXA1-deficient mice, COX-2-positive cells were more numerous than in control mice (+107%; normalized to glomerular number; P < 0.05) and renin expression was increased (+566%; normalized to glomerular number; P < 0.05). Cultured macula densa cells transfected with full-length rat ANXA1 revealed downregulation of COX-2 mRNA (−59%; P < 0.05). Similarly, treatment with dexamethasone suppressed COX-2 mRNA in the cells (−49%; P < 0.05), while inducing ANXA1 mRNA (+56%; P < 0.05) and ANXA1 protein secretion. Inhibition of the ANXA-1 receptor Fpr1 with cyclosporin H blunted the effect of dexamethasone on COX-2 expression. These data show that ANXA1 exerts an inhibitory effect on COX-2 expression in the macula densa. ANXA1 may be a novel intrinsic modulator of renal juxtaglomerular regulation by inhibition of PGE2 synthesis.

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Cyclooxygenase-2 expression and function in the medullary thick ascending limb

AJP Renal Physiology ◽

10.1152/ajprenal.1999.277.3.f360 ◽

1999 ◽

Vol 277 (3) ◽

pp. F360-F368 ◽

Cited By ~ 22

Author(s):

Nicholas R. Ferreri ◽

Shao-Jian An ◽

John C. McGiff

Keyword(s):

Thick Ascending Limb ◽

Mrna Accumulation ◽

Medullary Thick Ascending Limb ◽

Dependent Inhibition ◽

Cox 2 ◽

Time Required ◽

Factor Α ◽

And Function ◽

Time Dependent Inhibition ◽

In Cells

The medullary thick ascending limb (MTAL) metabolizes arachidonic acid (AA) via cytochrome P-450 (CyP450)- and cyclooxygenase (COX)-dependent pathways. In the present study, we demonstrated that the COX-2-selective inhibitor, NS-398, prevented tumor necrosis factor-α (TNF)- and phorbol myristate acetate (PMA)-mediated increases in PGE2 production by cultured MTAL cells. Accumulation of COX-2, but not COX-1, mRNA increased when cells were challenged with TNF (1 nM) or PMA (1 μM). Pretreatment of cells for 30 min with actinomycin D (AcD, 1 μM) had little effect on COX-2 mRNA accumulation in unstimulated cells or in cells challenged with either TNF or PMA. Moreover, a posttranscriptional mechanism(s) appears to contribute significantly to COX-2 mRNA accumulation as pretreatment for 15 min with cycloheximide (CHX, 1 μM) caused a superinduction of COX-2 mRNA accumulation in unstimulated cells as well as in cells challenged with either TNF or PMA. Expression of COX-2 protein in unstimulated MTAL cells was attenuated by preincubation for 2 h with dexamethasone (Dex, 2 μM); however, Dex had little or no effect on COX-2 expression in cells challenged with either PMA or TNF. The time-dependent inhibition of86Rb uptake by MTAL cells challenged with TNF was diminished by pretreating cells with NS-398. These data suggest that TNF-mediated induction of COX-2 protein expression accounted for the lag-time required for this cytokine to inhibit 86Rb uptake in MTAL cells.

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