Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.3.1 (NADPH oxidase)
 11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In afferent arteriolar vascular smooth muscle cells, ANG II induces a rise in cytosolic Ca(2+) ([Ca(2+)](i)) via inositol trisphosphate receptor (IP(3)R) stimulation and by activation of the adenine diphosphate ribose (ADPR) cyclase to form cyclic ADPR, which sensitizes the ryanodine receptor (RyR) to Ca(2+). We hypothesize that ANG II stimulation of NAD(P)H oxidases leads to the formation of superoxide anion (O(2)-*, which, in turn, activates ADPR cyclase. Afferent arterioles were isolated from rat kidney with the magnetized microsphere and sieving technique and loaded with fura-2 to measure [Ca(2+)](i). ANG II rapidly increased [Ca(2+)](i) by 124 +/- 12 nM. In the presence of apocynin, a specific inhibitor of NAD(P)H oxidase assembly, the [Ca(2+)](i) response was reduced to 35 +/- 5 nM (P < 0.01). Tempol, a superoxide dismutase mimetic, did not alter the [Ca(2+)](i) response to ANG II at a concentration of 10(-4) M (99 +/- 12 nM), but 10(-3) M tempol reduced the response to 32 +/- 3 nM (P < 0.01). The addition of nicotinamide, an inhibitor of ADPR cyclase, to apocynin or tempol (10(-3) M) resulted in no further inhibition. Measurement of superoxide production with the fluorescent probe tempo 9-AC showed that ANG II caused an increase of 48 +/- 20 arbitrary units; apocynin or diphenyl iodonium (an inhibitor of flavoprotein oxidases) inhibited the response by 94%. Hydrogen peroxide (H(2)O(2)) was studied at physiological (10(-7) M) and higher concentrations. In the presence of H(2)O(2) (10(-7) M), neither baseline [Ca(2+)](i) nor the response to ANG II was altered (125 +/- 15 nM), whereas H(2)O(2) (10(-6) and 10(-5) M) inhibited the [Ca(2+)](i) response to ANG II by 35 and 46%, respectively. We conclude that ANG II rapidly activates NAD(P)H oxidases of afferent arterioles, leading to the formation of O(2)-*, which then stimulates ADPR cyclase to form cADPR. cADPR, by sensitizing the RyR to Ca(2+), augments the Ca(2+) response (calcium-induced calcium release) initiated by activation of the IP(3)R.
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PMID:Angiotensin II, reactive oxygen species, and Ca2+ signaling in afferent arterioles. 1594 49

It is unknown if endothelin-A and -B receptors (ET(A)R and ET(B)R) activate the production of superoxide via NAD(P)H oxidase and subsequently stimulate the formation of cyclic adenine diphosphate ribose (cADPR) in afferent arterioles. Vessels were isolated from rat kidney and loaded with fura 2. Endothelin-1 (ET-1) rapidly increased cytosolic Ca(2+) concentration ([Ca(2+)](i)) by 303 nM. The superoxide dismutase mimetic tempol, the NAD(P)H oxidase inhibitor apocynin, and nicotinamide, an inhibitor of ADPR cyclase, diminished the response by approximately 60%. The ET(B)R agonist sarafotoxin 6c (S6c) increased peak [Ca(2+)](i) by 117 nM. Subsequent addition of ET-1 in the continued presence of S6c caused an additional [Ca(2+)](i) peak of 225 nM. Neither nicotinamide or 8-bromo- (8-Br) cADPR nor apocynin decreased the [Ca(2+)](i) response to S6c, but inhibited the subsequent [Ca(2+)](i) response to ET-1. The ET(B)R blockers BQ-788 and A-192621 prevented the S6c [Ca(2+)](i) peak and reduced the ET-1 response by more than one-half, suggesting an ET(B)R/ET(A)R interaction. In contrast, the ET(A)R blocker BQ-123 had no effect on the S6c [Ca(2+)](i) peak and obliterated the subsequent ET-1 response. ET-1 immediately stimulated superoxide formation (measured with TEMPO-9-AC, 68 arbitrary units) that was inhibited 95% by apocynin or diphenyl iodonium. S6c or IRL-1620 increased superoxide by 8% of that caused by subsequent ET-1 addition. We conclude that ET(A)R activation of afferent arterioles increases the formation of superoxide that accounts for approximately 60% of subsequent Ca(2+) signaling. ET(B)R activation appears to result in only minor increases in superoxide production. Nicotinamide and 8-Br-cADPR results suggest that ET-1 (and primarily ET(A)R) causes the activation of vascular smooth muscle cell-ADPR cyclase.
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PMID:Endothelin-A and -B receptors, superoxide, and Ca2+ signaling in afferent arterioles. 1678 36

The ubiquitous tripeptide glutathione (GSH) is an essential factor in many biological processes, thus its depletion has a major impact on cell function and survival. In this study, we examined regulation of GSH in cardiomyocytes under chronic oxidative stress elicited by myocardial infarction (MI). Cardiac dysfunction was induced in rats by coronary artery ligation, and experiments were conducted in myocytes isolated from non-infarcted left ventricle and septum after 6-8 weeks. Fluorescence microscopy studies using the probe monochlorobimane showed that [GSH] in myocytes from post-MI hearts was 42% less than in sham control hearts (P < 0.05). However, depleted GSH levels were normalized after 5-6 h by an insulin mimetic (bis-peroxovanadium-1,10-phenanthroline, bpV(phen); 10 micromol l(-1)) or by exogenous pyruvate (5 mmol l(-1)). The increase in [GSH] by bpV(phen) was partly inhibited by buthionine sulphoximine (BSO; 50 micromol l(-1)), a blocker of GSH synthesis, and by 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU; 100 micromol l(-1)), an inhibitor of glutathione disulphide reductase. By comparison, the effect of pyruvate was not altered by BSO but was completely blocked by BCNU. Studies using inhibitors of signalling cascades indicated that upregulation of [GSH] by bpV(phen) in myocytes from post-MI hearts was mediated by mitogen activated protein kinase/extracellular signal-regulated kinase kinase 1/2 and p38 mitogen-activated protein kinase but not by phosphatidylinositol 3-kinase. The effect of pyruvate was not altered by any kinase inhibitor tested. In cells loaded with the probe TEMPO-9-AC to monitor superoxide anion, baseline fluorescence was 2.3-fold greater in post-MI myocytes than in sham control myocytes (P < 0.05) and was markedly decreased by diphenyleneiodonium (30 micromol l(-1)), an inhibitor of NADPH oxidase, exogenous GSH (10 mmol l(-1)) or bpV(phen). In parallel studies, [GSH] in post-MI myocytes was also normalized by diphenyleneiodonium or exogenous GSH. These data show that GSH is differentially regulated by receptor tyrosine kinase-dependent and -independent agonists that maintain functional GSH levels necessary to neutralize excess generation of reactive oxygen species in the failing heart.
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PMID:Glutathione homeostasis in ventricular myocytes from rat hearts with chronic myocardial infarction. 1939 62