Biomedical subjects

J Nadler

Publications and source records attributed to J Nadler.

At least 37 records · Page 2Linked to original sources

PubMed1994

Evidence that pioglitazone increases intracellular free magnesium concentration in freshly isolated rat adipocytes.

Pioglitazone is one of a new class of oral agents being developed as antidiabetic agents which can increase insulin sensitivity, reduced blood pressure and improve abnormalities in lipid metabolism. The mechanism of action of pioglitazone is not known. Increasing evidence suggests that magnesium can play an important role in regulating glucose homeostasis and vascular tone. To clarify a potential mechanism of pioglitazone action we determined the effects of pioglitazone on intracellular free magnesium concentration in freshly isolated rat adipocytes. Concentrations of pioglitazone as low as 300 nM markedly increased the free magnesium concentration in the adipocytes. Pioglitazone action was selective for magnesium since intracellular free calcium concentration was not altered. These new data suggest that a potentially important mechanism explaining the metabolic and vascular actions of these new anti-diabetic agents is increasing free magnesium concentration in target tissues.

Adipocytes↗

PubMed1994

Role of specific isoforms of protein kinase C in angiotensin II and lipoxygenase action in rat adrenal glomerulosa cells.

Evidence indicates that the lipoxygenase (LO) pathway of arachidonic acid is a key mediator of angiotensin II (AII)-induced aldosterone synthesis in adrenal glomerulosa cells. Although protein kinase C (PKC) may play a role in AII action, the precise PKC isoforms involved and whether LO products can activate PKC is not clear. We therefore evaluated the effect of AII and LO products such as 12- and 15-hydroxyeicosatetraenoic acids (HETEs) on PKC activation in isolated rat adrenal glomerulosa cells. PKC activity was measured by the phosphorylation of a PKC specific peptide while the PKC isoforms were identified by Western immunoblotting using antibodies that recognize the alpha, beta, gamma or epsilon isoforms of PKC. Treatment of the cells for 15 min with AII (10[-8]M) or the LO products 12- or 15-HETE caused a marked increase in PKC activity in membrane fractions with reciprocal decreases in the cytosolic PKC activity. Rat glomerulosa cells expressed only the alpha, and epsilon isoforms of PKC. AII increased membrane bound levels of both PKC-alpha and -epsilon (1.9- and 1.5-fold, respectively), whereas the LO products predominantly activated PKC-epsilon. Reciprocal decreases in immunoreactive cytosolic PKC levels were seen. AII-induced aldosterone synthesis was blocked by H-7 and retinal as well as by a PKC-specific pseudosubstrate inhibitor, PKC(19-36). These results suggest that AII and LO pathway-induced actions in the adrenal glomerulosa may be mediated by specific PKC isoforms.

Angiotensin II↗

PubMed1994

Magnesium deficiency in alcoholism: possible contribution to osteoporosis and cardiovascular disease in alcoholics.

Magnesium (Mg) deficiency occurs frequently in chronic alcoholism and may contribute to the increased incidence of osteoporosis and cardiovascular disease seen in this population. Mg deficiency is primarily due to renal Mg-wasting and is exacerbated by dietary Mg deprivation, gastrointestinal losses with diarrhea or vomiting, as well as concomitant use of drugs such as diuretics and aminoglycosides. Osteoporosis is prevalent in the alcoholic population. Mg deficiency may contribute to increased bone loss by its effects on mineral homeostasis. In Mg depletion, there is often hypocalcemia due to impaired parathyroid hormone (PTH) secretion, as well as renal and skeletal resistance to PTH action. Serum concentrations of 1,25-vitamin D are also low. These changes are seen with even mild degrees of Mg deficiency and may contribute to the metabolic bone disease seen in chronic alcoholics. Hypomagnesemia in alcoholics may also contribute to increased cardiovascular disease by altering platelet function. Mg deficiency has been demonstrated to enhance platelet reactivity. In these studies, Mg was shown to inhibit platelet aggregation against various aggregation agents. Patients with Mg deficiency were shown to have increased platelet aggregation that was normalized with Mg therapy. The antiplatelet effect of Mg may be related to the finding that Mg inhibits the synthesis of thromboxane A2 and 12-hydroxyeicosatetraenoic acid, eicosanoids thought to be involved in platelet aggregation. Mg also inhibits the thrombin-induced Ca2+ influx in platelets, as well as stimulates synthesis of prostaglandin I2, the potent antiaggregatory eicosanoid. Therefore, Mg deficiency may increase platelet aggregation and cause increased hypertension and atherosclerotic cardiovascular disease in alcoholics.

Alcoholism↗

PubMed1994

Role of the lipoxygenase pathway in angiotensin II-induced vascular smooth muscle cell hypertrophy.

The 12-lipoxygenase pathway is a key mediator of angiotensin II (Ang II)-induced effects in the adrenal cortex. We also recently demonstrated that Ang II increases 12- and 15-lipoxygenase product levels in vascular smooth muscle cells. However, the relation between lipoxygenase activation and Ang II-induced vascular smooth muscle cell hypertrophy is not known. We studied the effects of Ang II and 12-lipoxygenase products on both total cell protein content and the levels of the matrix protein fibronectin in quiescent porcine aortic smooth muscle cells. Ang II-induced increases in cellular protein content were attenuated by the specific 12-lipoxygenase inhibitor baicalein; in contrast, the cyclooxygenase inhibitor ibuprofen had no effect. Direct addition of the 12-lipoxygenase product 12-S-hydroxyeicosatetraenoic acid increased total cell protein content. We have recently shown that porcine vascular smooth muscle cell growth is potentiated in high glucose (25 mmol/L) culture conditions. We observed that both Ang II and 12-S-hydroxyeicosatetraenoic acid induced a greater increase in protein content in cells cultured for two passages in high glucose. Furthermore, Ang II and 12-S-hydroxyeicosatetraenoic acid also markedly increased fibronectin levels in cells cultured in high glucose. These results suggest that 12-lipoxygenase activation plays a key role in Ang II-induced vascular smooth muscle cell hypertrophy. Furthermore, both Ang II and lipoxygenase effects are enhanced in cells cultured under hyperglycemic conditions.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1994

Effect of dopamine2 blockade on renal function under varied sodium intake.

This study explored the role of the dopamine-2 receptor (DA2) in the control of renal blood flow (RBF) and the influence of variations in sodium intake. These relationships have not been previously defined in man. Seven normotensive male subjects underwent a low dose dopamine (DA) infusion (1 microgram/kg.min) for 3 h, known to activate both DA1 and DA2 receptors. The effect of DA2 receptor on renal hemodynamics was studied using a relatively specific DA2 blocker [domperidone (DOM); 60 mg, orally] alone and with a DA infusion. Systemic and renal hemodynamics parameters were measured noninvasively. Urinary prostacyclin was measured in 3-h urine specimens, obtained during the DA infusion. The DA infusion increased RBF and prostacyclin during both normal and high salt diets, but this effect was attenuated on a low salt diet. DOM alone significantly reduced basal RBF during normal (1304 +/- 48 vs. 1175 +/- 45 mL/min.1.73 m2; P < 0.01) and low salt diets (1402 +/- 80 vs. 1220 +/- 101 mL/min.1.73 m2; P < 0.02), but was without effect during high sodium intake. DOM had no effect on prostacyclin excretion at any level of salt intake. These results suggest that both DA1 and DA2 are activated in renal vessels by DA, and that DA2 receptors play a role in the renal vasodilating action of DA. Changes in sodium balance alter the actions of the two receptors (DA1 and DA2) in a coordinated fashion in the regulation of RBF.

Adult↗

PubMed1994

Hypoaldosteronism.

Explore the source record for details and available documents.

Adrenal Gland Diseases↗

PubMed1993

Elevated glucose and angiotensin II increase 12-lipoxygenase activity and expression in porcine aortic smooth muscle cells.

The lipoxygenase (LO) pathway of arachidonate metabolism has been suggested to play a key role in atherosclerosis and in mediating several actions of angiotensin II (AII). However, the relationship between LO activation and factors linked to accelerated diabetic vascular disease such as hyperglycemia and AII is not known. We have investigated the effect of high glucose (HG; 25 mM) and AII on LO activity as well as LO protein and mRNA expression in porcine aortic vascular smooth muscle cells (PVSMCs). We observed that cells cultured in HG had significantly higher levels of the cell-associated LO products 12- and 15-hydroxyeicosatetraenoic acids (HETEs). AII added to cells grown in HG specifically further increased only cell-associated 12-HETE levels. Using immunoblot analysis and reverse transcriptase PCRs, we demonstrated the presence in PVSMCs of porcine leukocyte-type 12-LO protein and mRNA, respectively. Furthermore, the levels of both were markedly upregulated by AII as well as by HG. These studies suggest that enhanced 12-LO activity and expression are mechanisms for accelerated vascular disease produced by HG and AII in diabetes mellitus.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1993

Potential role of 12 hydroxyeicosatetraenoic acid in angiotensin II-induced calcium signal in rat glomerulosa cells.

Recent evidence suggests that 12 hydroxyeicosatetraenoic acid (12HETE), a product of the 12 lipoxygenase (LO) pathway of arachidonic acid metabolism, may have a role in mediating angiotensin II (AII)-induced aldosterone secretion. The present study examined the possible role of the 12 LO product 12HETE in AII-induced calcium ([Ca++]i) signals in rat glomerulosa cells. The addition of 12HETE to glomerulosa cells induced a dose-dependent (10(-6)-10(-8) M) rise in [Ca++]i levels that was sustained over 15 min. The effects of 12HETE on [Ca++]i were attenuated but not blocked by nifedipine (5 x 10(-6) M) and were preserved in a calcium-free medium, suggesting mobilization of intracellular calcium stores. Furthermore, the 12HETE-mediated rise in [Ca++]i was almost entirely abolished by dantrolene. In parallel, 12HETE reversed the inhibitory effect of nifedipine on AII-induced aldosterone secretion [AII (10(-9) M) - 36 +/- 7, AII + nifedipine (5 x 10(-6) M) - 13 +/- 2, AII + nifedipine + 12HETE (5 x 10(-8) M) - 27 +/- 4 ng/10(6) cells]. Dantrolene also inhibited AII-dependent aldosterone secretion (AII 10(-9) M - 75.8 +/- 5.6, AII + dantrolene 10(-6) M 45.5 +/- 8.8 ng/10(-6) cells), but this inhibition could not be reversed by 12HETE 10(-8) M (45.4 +/- 10.6 ng/10(6) cells). The LO blockers baicalein and BW755C inhibited the effect of AII on aldosterone production and on [Ca++]i in a parallel fashion. During LO blockade, the addition of 12HETE (10(-7) M) restored the AII-induced rise in [Ca++]i. Collectively, these observations suggest that activation of the LO pathway in the rat adrenal glomerulosa contributes to change in cytosolic calcium, which may be important for the steroidogenic effect of AII.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1992

Platelet-derived growth factor is a potent inhibitor of angiotensin II-induced aldosterone synthesis.

Platelet-derived growth factor (PDGF) is a potent mitogen for several cell types. In addition, PDGF has vasoconstrictive action and shares some signal transduction mechanisms with angiotensin II (AII). In the present study, we have examined the effects of PDGF on basal and AII-induced aldosterone synthesis in freshly isolated rat adrenal glomerulosa cells. Recombinant human PDGF-BB caused a dose-dependent inhibition of AII-induced aldosterone synthesis being effective at concentrations as low as 10(-12) M. We also investigated possible mechanisms of action of PDGF. We have previously reported that the 12-lipoxygenase (LO) pathway of arachidonic acid plays a key role in AII-induced aldosterone synthesis. We thus examined whether PDGF action is mediated by changes in 12-LO activation. PDGF, at the same doses that blocked AII-induced synthesis also significantly inhibited AII-induced increases in the 12-LO product, 12-hydroxyeicosatetraenoic acid (12-HETE) formation. Further, the addition of 12-HETE completely restored the stimulatory effect of AII during inhibition by PDGF. These results suggest that PDGF could act, at least in part, by inhibition of AII-induced 12-HETE formation. We also examined the role of diacylglycerol (DG) formation since we have previously reported that DG is the source of arachidonic acid for 12-HETE formation. We observed that both AII and PDGF stimulated [3H]arachidonic acid-labeled DG formation. However, PDGF did not alter AII-induced DG formation suggesting that PDGF action is not mediated by affecting AII-induced increases in DG.(ABSTRACT TRUNCATED AT 250 WORDS)

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1992

Angiotensin II regulates cytochrome P-450 steroid hydroxylase enzyme expression in human adrenal glomerulosa cells.

We have examined the regulation of cytochrome P-450 side chain cleavage enzyme (P-450SCC) and P-45011 beta (18) hydroxylase (P-450(11) beta) enzyme expression by angiotensin II (AII), the major regulator of aldosterone biosynthesis, in cultured human adrenal glomerulosa cells. We also examined the effect of lipoxygenase products of arachidonic acid on the expression of these enzymes since it has been previously shown that the 12-lipoxygenase pathway plays a key role in AII-induced aldosterone synthesis in rat and human adrenal glomerulosa cells. AII (10(-7) mol/L) induced a 3-fold stimulation of P-450SCC and over a 2-fold increase in P-450(11) beta protein expression. The 12-lipoxygenase product, 12-hydroxyeicosatetraenoic acid (12-HETE) caused a 2-fold increase in P-450(11) beta levels without altering P-450SCC levels. These results show for the first time that AII can directly increase the levels of P-450SCC and P-450(11) beta enzymes in glomerulosa cells. The results also suggest that 12-HETE may mediate long term effects of AII action by stimulating P-450(11) beta levels.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1992

Mechanism of angiotensin II-induced proliferation in bovine adrenocortical cells.

The peptide hormone angiotensin-II (AII) is a potent vasoconstrictor and major regulator of aldosterone synthesis. In addition, AII also has growth-promoting effects. We have recently shown that the lipoxygenase (LO) pathway of arachidonic acid plays a major role in AII-induced aldosterone synthesis in adrenal glomerulosa cells. The LO pathway is also involved in the vasopressor and renin-inhibitory effects of AII. However, the role of LO products in AII-induced mitogenic effects have not yet been investigated. In the present studies we have evaluated the role of the LO pathway in AII-induced proliferative responses in a bovine adrenocortical cell clone termed AC1 cells. In addition, the potential receptor type and mechanism of AII-induced proliferation was studied by evaluating the effect of specific nonpeptide type 1 and type 2 AII receptor antagonists and the role of protein kinase-C (PKC). AII-induced DNA synthesis was significantly attenuated by two structurally dissimilar LO inhibitors, baicalein and phenidone. In addition, the LO product 12-hydroxyeicosatetraenoic acid (12-HETE) itself caused a significant increase in DNA synthesis, suggesting that the 12-LO pathway in part plays a role in AII-mediated mitogenesis. AII-induced proliferative responses were blocked by the type 1 AII receptor antagonist. Both AII- and 12-HETE-induced increases in DNA synthesis were markedly inhibited by two PKC blockers, staurosporine and sangivamycin. Further, both AII and 12-HETE could activate PKC by translocating it from the cytosol to the membrane fraction, as determined by Western immunoblotting. These results suggest that both 12-LO activation and protein kinase-C have an important role in AII-induced adrenal cell proliferation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1991

Angiotensin II-induced aldosterone synthesis is potentiated by epidermal growth factor.

Epidermal growth factor (EGF) is a potent mitogen and has effects in several endocrine systems. We examined the effects of EGF on basal and angiotensin II (AII)-induced aldosterone synthesis in freshly isolated rat and cultured human adrenal glomerulosa cells. EGF alone caused a significant increase in basal aldosterone synthesis in both the rat and human cells. In addition, EGF caused a significant increase in AII-induced aldosterone secretion in both rat and cultured human cells during short and long term incubations. Further, we observed that the effect of EGF was highly specific to AII since it did not alter either potassium (8.7 mM) or ACTH (10(-10) M) mediated increases in aldosterone synthesis. We also investigated possible mechanisms of action of EGF. Since earlier studies showed that the lipoxygenase pathway of arachidonic acid plays a key role in mediating AII-induced aldosterone synthesis, we studied the effect of lipoxygenase inhibition in EGF action. We observed that the nonselective lipoxygenase blocker BW755c, which blocked AII-induced aldosterone synthesis, also inhibited EGF mediated increase in aldosterone synthesis. We also examined the effects of EGF on diacylglycerol (DG) formation since DG is an important second messenger in AII action. We found that EGF stimulated basal DG levels and also potentiated AII-induced DG formation, suggesting that EGF may potentiate AII-induced aldosterone synthesis via increases in DG. These results suggest that EGF may play an important role in aldosterone synthesis by acting as a specific positive modulator of AII action in the adrenal.

Adrenocorticotropic Hormone↗

PubMed1990

Key role of diacylglycerol-mediated 12-lipoxygenase product formation in angiotensin II-induced aldosterone synthesis.

We have shown earlier that the 12-lipoxygenase product of arachidonic acid (AA), 12-hydroxyeicosatetraenoic acid (12-HETE), plays an important role in mediating angiotensin II (AII)-induced aldosterone secretion (J. Clin. Invest. (1987) 80, 1763). In the present study, we have evaluated whether diacylglycerol (DG) is the source of arachidonic acid giving rise to this 12-HETE. Treatment of rat adrenal glomerulosa cells with a DG lipase inhibitor, RHC 80267, which prevents conversion of DG to AA and HETEs, blocked AII-induced aldosterone and 12-HETE formation. In contrast, a DG kinase inhibitor, R59022, which prevents conversion of DG to phosphatidic acid, potentiated AII-induced aldosterone and 12-HETE formation. These two inhibitors block DG metabolism which would be expected to lead to increased DG levels and protein kinase C activity and AII-induced steroidogenesis. However, only R59022 potentiated AII action while RHC 80267 was inhibitory. This suggests that conversion of DG to AA and 12-HETE is important for AII action. Further proof for this was obtained by measuring [3H]AA-labeled DG levels. The combination of the inhibitors significantly potentiated AII-induced DG formation even though this same combination was inhibitory on AII-induced aldosterone and 12-HETE. Thus, the inhibitory effect of RHC 80267 is due to blockade of AA release and not of DG formation. These results suggest that DG plays a dual role in AII action, both as an activator of protein kinase C and as a source of AA for 12-HETE formation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1990

Effect of dopamine on renal blood flow, prostaglandins, renin and electrolyte excretion in normal and hypertensive humans.

A low dose of dopamine (1 microgram/min/kg) infused for 3 h, which is without systemic hemodynamic effects in normal subjects, increased the renal blood flow and renal production of prostacyclin (PGI2). This action was blocked by metoclopramide as well as by either of two cyclooxygenase (CO) blockers, but effects were not altered by administration of the alpha 1 blocker prazosin. Much of the effect of dopamine (DA) is apparently via the DA1 receptor, since fenoldopam (0.1 microgram/min/kg) reproduced these actions. However, although fenoldopam increased glomerular filtration rate and urinary Na+, CO blockers were without effect. In contrast neither DA or fenoldopam infusions changed either renal blood flow or PGI2 in a group of patients with essential hypertension. Renin secretion was shown to be increased via DA1 receptor activation both in humans and rat renal tissue. The DA2 receptor may also play a role since domperidone can reduce renal blood flow.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1990

Simultaneous measurement of two major prostacyclin metabolites in urine.

We describe a combined HPLC-RIA technique to measure both major metabolites of prostacyclin (PGI2): 6-keto PGF1 alpha and 2,3-dinor-6 keto PGF1 alpha. The measurement of the former, which originates from renal blood vessels, and the latter, from systemic vessels and the liver, may provide a better overall evaluation of production than measurement of one metabolite. An aliquot of acidified urine with added 3H-labeled metabolites is adsorbed and then eluted from a C18 Bond-Elut column. The sample is then passed through an HPLC system by use of an isocratic solvent combination that separates the two metabolites from known prostaglandins. The purified metabolites are then quantified by RIA. Using a logit-log10 transform, one can measure between 12 and 250 pg of either metabolite, with high accuracy and precision (CVs of 12% for a low concentration and 7% for a high concentration). Reference values for apparently healthy subjects were, respectively, 107 (SD 45) and 171 (SD 69) ng/g creatinine for 6-keto PGF1 alpha and the dinor metabolite in men (n = 18) and 45 (SD 22) and 141 (SD 28) ng/g creatinine, respectively, in women (n = 15). Indomethacin in standard doses reduced both metabolite values by 50%. Intravenous administration of angiotensin II (5 ng/kg of body wt per minute) did not alter excretion rates, but equipressor doses of norepinephrine (0.1 microgram/kg per minute) increased the production of both metabolites (6-keto greater than dinor).

6-Ketoprostaglandin F1 alpha↗

PubMed1989

Hypotensive effects of the lipoxygenase inhibitor phenidone in two-kidney, one clip Goldblatt hypertension.

This study examined the role of the lipoxygenase (LO) pathway in the maintenance of hypertension in rats with two-kidney, one clip (2K,1C) Goldblatt hypertension. A single dose of the lipoxygenase blocker phenidone was injected intraperitoneally to 2K,1C rats during the early phase (14 days) of the development of hypertension (mean intraarterial blood pressure 137 +/- 3.9 mm Hg). Phenidone (60 mg/kg) markedly decreased arterial pressure to nadir levels of 58.9% of resting blood pressure. The maximal changes were observed 15 min after injection and the hypotensive response was sustained for at least 2 h. Plasma renin concentration (PRC) increased from 74.3 +/- 18.9 to 281.0 +/- 6.5 ng/mL/h after injection (P less than .05). Thus, the hypotensive effect of phenidone was not due to suppression of renin secretion but presumably due to inhibition of its effects. It is suggested that arachidonate metabolites of the LO pathway at the vascular bed may be involved in maintenance of high arterial pressure in 2K,1C renovascular hypertension in rat.

Animals↗

PubMed1989

A 12-lipoxygenase product of arachidonate metabolism is involved in angiotensin action on renin release.

Angiotensin II (AII) action is coupled to the hydrolysis of phospholipids resulting in the formation of arachidonic acid, the precursor of both prostaglandins, and hydroxyeicosatetraenoic acids (HETEs). Since 12-HETE is not only a major arachidonate lipoxygenase (LO) product in the kidney, but is also a potent inhibitor of renin release, we studied the role of AII on renin inhibition and 12-HETE formation using rat renal cortical slices and isolated juxtaglomerular-like cells. In both preparations, 12-HETE was produced in a basal state. AII significantly inhibited renin release (control 100 +/- 3%, AII (10(8) M) 79 + 4%, P less than 0.01) and stimulated 12-HETE formation in slices (control 106 +/- 6%, AII 10(-8) M 177 +/- 18%, P less than 0.01) and in an enriched juxtaglomular cell preparation (control 96 +/- 3%, AII 10(-8) M 130 +/- 6%, P less than 0.001). A specific cyclooxygenase blocker, meclofenomate, or 5-LO blocker, U60,257, did not alter basal or AII-induced renin inhibition or 12-HETE formation by slices. The LO blockers BW755c, at 10(-5) M, or baicalein, 10(-6) M, did not significantly alter basal renin or 12-HETE levels, but BW755c at 10(-4) M, significantly stimulated basal renin (131 +/- 4%) and decreased basal 12-HETE levels (72 +/- 5%). However, both BW755c and baicalein blunted AII-induced renin inhibition (AII, 10(-8) M 70 +/- 3%, AII + BW755c, 10(-5) M 85 +/- 4%, P less than 0.02, AII + baicalein, 10(-6) M, 90 +/- 4%, P less than 0.005) and AII mediated 12-HETE formation (AII, 10(-8) M 150 +/- 5%, AII + BW755c, 10(-5) M 117 +/- 8%, P less than 0.02, AII + baicalein, 10(-6) M 110 +/- 3%, P less than 0.005). These results suggest that AII inhibition of renin is not mediated by the cyclooxygenase or 5-LO pathway, but rather by the 12-LO pathway. These findings reveal a new action for 12-LO products which may play a pivotal role in stimulus secretion coupling of renin secretion.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed1989

Tumor necrosis factor and interleukin-1 are potent inhibitors of angiotensin-II-induced aldosterone synthesis.

Cytokines such as tumor necrosis factor (TNF) and interleukin-1 (IL-1), mediate many inflammatory and cellular responses. However, the effects of TNF and IL-1 on basal and angiotensin-II (AII)-stimulated aldosterone synthesis are not known. We studied the effect of recombinant and purified TNF and IL-1 on basal as well as AII-, ACTH-, and K+-induced aldosterone synthesis in isolated rat adrenal glomerulosa cells. Since we have previously shown that AII action is mediated by activation of the 12-lipoxygenase (12LO) pathway of arachidonic acid, we also evaluated the effects of these cytokines on the 12LO product 12-hydroxyeicosatetraenoic acid (12HETE) using a validated RIA technique. TNF at 2.5 and 5.0 ng/ml produced a dose-dependent inhibition of AII-induced aldosterone synthesis [AII, 39.0 +/- 3.3 ng/10(6) cells.h; AII plus TNF (5.0 ng/ml), 14.3 +/- 1.6; P less than 0.001 vs. AII; AII plus TNF (2.5 ng/ml), 24.7 +/- 3.2; P less than 0.01 vs. AII]. Similarly, TNF at 5.0 ng/ml also attenuated the stimulatory effect of ACTH (10(-9) M). However, K+-induced aldosterone synthesis was not altered. TNF also did not alter basal aldosterone levels. AII, as previously shown, stimulates 12HETE synthesis (basal, 608 +/- 114 pg/10(5) cells.h; versus AII, 1268 +/- 197; P less than 0.02). TNF at concentrations of 1.0-5.0 ng/ml produced a dose-dependent inhibition of AII stimulatory action on 12HETE synthesis [AII plus TNF (1.0 ng/ml), 650 +/- 26 pg, P less than 0.03 vs. AII; AII plus TNF (5.0 ng/ml), 390 +/- 46; P less than 0.01 vs. AII plus TNF (1.0 ng/ml)]. In addition, 12HETE at 10(-8) M completely restored the effects of AII during blockage by TNF. Purified human IL-1 (75% beta, 25% alpha) as well as recombinant human IL-1 beta at concentrations as low as 50 pg/ml inhibited AII-induced aldosterone synthesis. IL-1 beta did not alter ACTH- or K+-induced aldosterone synthesis and, in fact, had a tendency to potentiate ACTH effects. These results suggest that the cytokines TNF and IL-1 are potent inhibitors, particularly of AII action in the adrenal glomerulosa cell. Therefore, local or systemically produced TNF or IL-1 may be important negative modulators of aldosterone synthesis.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗