scholarly journals Cytochrome P-450 may link intracellular Ca2+ stores with plasma membrane Ca2+ influx

1991 ◽  
Vol 274 (1) ◽  
pp. 193-197 ◽  
Author(s):  
J Alvarez ◽  
M Montero ◽  
J García-Sancho
Keyword(s):  
Plasma Membrane ◽  
Aryl Hydrocarbon Hydroxylase ◽  
Plasma Membrane Permeability ◽  
Aryl Hydrocarbon ◽  
Oxygen Scavenging ◽  
Aryl Hydrocarbon Hydroxylase Activity ◽  
Cytochrome P 450 ◽  
Degree Of Filling ◽  
Ca2 Channels ◽  
Dependent Mechanism

We have studied the mechanism of the regulation of plasma membrane Ca2+ permeability by the degree of filling of the intracellular Ca2+ stores. Using Mn2+ as a Ca2+ surrogate for plasma membrane Ca2+ channels, we found that Mn2+ uptake by rat thymocytes is inversely related to the degree of filling of the intracellular Ca2+ stores. This store-dependent plasma membrane permeability is inhibited by oxygen scavenging, CO, imidazole antimycotics and other cytochrome P-450 inhibitors. The pattern of inhibition is similar to that reported previously for the inhibition of microsomal cytochrome P-450-mediated aryl hydrocarbon hydroxylase activity of lymphocytes. Several calmodulin antagonists, both phenothiazinic (trifluoperazine, fluphenazine and chlorpromazine) and dibenzodiazepinic (clozapine), accelerate Mn2+ uptake by cells with Ca2(+)-filled stores, and this effect is prevented by imidazole antimycotics. Our results suggest that cytochrome P-450 may be the link between the stores and the plasma membrane Ca2+ pathway. We propose a model in which this cytochrome, sited at the stores, stimulates plasma membrane Ca2+ influx. This stimulatory effect is, in turn, prevented by the presence of Ca2+ inside the stores, possibly via a calmodulin-dependent mechanism.

scholarly journals Control of plasma-membrane Ca2+ entry by the intracellular Ca2+ stores. Kinetic evidence for a short-lived mediator

1992 ◽  
Vol 288 (2) ◽  
pp. 519-525 ◽  
Author(s):  
M Montero ◽  
J Alvarez ◽  
J García-Sancho
Keyword(s):  
Plasma Membrane ◽  
Time Lag ◽  
Human Neutrophils ◽  
Half Time ◽  
Plasma Membrane Permeability ◽  
Steady State Levels ◽  
Clearance Kinetics ◽  
Cytochrome P 450 ◽  
Degree Of Filling ◽  
Ca2 Channels

We have studied the correlation between the degree of filling of the intracellular Ca2+ stores and the plasma-membrane permeability to Mn2+, a Ca2+ surrogate for plasma-membrane Ca2+ channels, in human neutrophils loaded with fura-2. Refilling of the stores of cells previously depleted of Ca2+ decreased the entry of Mn2+, but the magnitude of this effect depended on the refilling protocol. When refilling was allowed to proceed to steady-state levels by a 3 min incubation with different external Ca2+ concentrations (0.05-1 mM), almost complete inhibition of Mn2+ entry was observed at 40% of maximum refilling. In contrast, when different degrees of store refilling were attained by incubation with 1 mM-Ca2+ for short periods (10-40 s), inhibition of Mn2+ entry was smaller at comparable degrees of refilling. When quick refilling was allowed to proceed up to 40% (about 20 s at 37 degrees C) and then stopped at this level by removal of external Ca2+, the rate of Mn2+ uptake was high just after refilling and then decreased with time within the next few seconds (half-times approximately 7 s at 37 degrees C and approximately 20 s at 25 degrees C). We have proposed previously that the Ca2+ stores, when emptied of Ca2+, may generate a second messenger able to open the plasma-membrane Ca2+ channels by a mechanism involving cytochrome P-450. The results here are consistent with the existence of such a messenger and suggest that it is cleared from the cytoplasm with a half-time of about 7 s at 37 degrees C. In addition, inhibition of Mn2+ entry in cells with empty Ca2+ stores by cytochrome P-450 inhibitors showed a time lag consistent with the clearance kinetics proposed above.

scholarly journals Control of Ca2+ entry into HL60 and U937 human leukaemia cells by the filling state of the intracellular Ca2+ stores

1993 ◽  
Vol 289 (3) ◽  
pp. 761-766 ◽  
Author(s):  
S R Alonso-Torre ◽  
J Alvarez ◽  
M Montero ◽  
A Sanchez ◽  
J García-Sancho
Keyword(s):  
Plasma Membrane ◽  
Inositol Phosphate ◽  
Platelet Activating Factor ◽  
Membrane Receptors ◽  
Plasma Membrane Permeability ◽  
Prolonged Incubation ◽  
Differentiated Cells ◽  
Cytochrome P 450 ◽  
Filling State ◽  
Ca2 Channels

Differentiation of HL60 cells by treatment with dimethyl sulphoxide induces the expression of membrane receptors for N-formylmethionyl-leucyl-phenylalanine (fMLP) and for platelet-activating factor (PAF). In these cells both agonists produced an increase in the cytosolic Ca2+ concentration ([Ca2+]i) by release of Ca2+ from the intracellular stores, followed shortly by an acceleration of the entry of Ca2+ or Mn2+, used here as a Ca2+ surrogate for Ca2+ channels. Cytochrome P-450 inhibitors blocked the agonist-induced entry of Ca2+ or Mn2+ with no modification of Ca2+ release from the stores. Emptying the intracellular Ca2+ stores either by treatments inducing no inositol phosphate production, such as prolonged incubation in Ca(2+)-free medium or treatment with the Ca2+ ionophore ionomycin, increased the plasma-membrane permeability to Ca2+ and Mn2+. This Ca(2+)-store-regulated Mn2+ entry was inhibited by Ni2+ and by cytochrome P-450 inhibitors. Refilling of the Ca2+ stores by incubation in Ca(2+)-containing medium restored low Mn2+ permeability. The same mechanism is present and functional in non-differentiated cells, before expression of membrane receptors for fMLP and PAF. These results suggest that agonist-induced Ca2+ (Mn2+) entry is secondary to the emptying of the intracellular Ca2+ stores, which in turn activates plasma-membrane channels by a mechanism involving cytochrome P-450.

scholarly journals On the occurrence of cytochrome P-450 and aryl hydrocarbon hydroxylase activity in rat brain.

1977 ◽  
Vol 145 (6) ◽  
pp. 1607-1611 ◽  
Author(s):  
J A Cohn ◽  
A P Alvares ◽  
A Kappas
Keyword(s):  
Carbon Monoxide ◽  
Rat Brain ◽  
Specific Activity ◽  
Aryl Hydrocarbon Hydroxylase ◽  
Hydroxylase Activity ◽  
Difference Spectra ◽  
Aryl Hydrocarbon ◽  
Brain Microsomes ◽  
Aryl Hydrocarbon Hydroxylase Activity ◽  
Cytochrome P 450

The difference spectra of the carbon monoxide-complex of dithionite-reduced rat brain microsomes, compared with both reduced microsomes, alone, and the carbon monoxide-complex of oxidized microsomes, indicate the presence of small amounts of cytochrome P-450 in brain. As in liver, cytochrome P-450 in brain is degraded in vitro to its inactive form, cytochrome P-420 by methylmercury chloride. Aryl hydrocarbon hydroxylase activity is also present in rat brain microsomes and, at lower specific activity, in brain homogenates. This carcinogen metabolizing activity is increased four-fold in rats pretreated with 3-methylcholanthrene.

scholarly journals Agonist-induced Ca2+ influx into human platelets is secondary to the emptying of intracellular Ca2+ stores

1991 ◽  
Vol 280 (3) ◽  
pp. 783-789 ◽  
Author(s):  
M T Alonso ◽  
J Alvarez ◽  
M Montero ◽  
A Sanchez ◽  
J García-Sancho
Keyword(s):  
Plasma Membrane ◽  
Platelet Activating Factor ◽  
Human Platelets ◽  
Temperature Dependent ◽  
Plasma Membrane Permeability ◽  
Low Concentrations ◽  
Cytochrome P 450 ◽  
Filling State ◽  
Ca2 Channels ◽  
Stimulation Of

We have studied the relation between the filling state of the intracellular Ca2+ stores and the plasma-membrane permeability to Mn2+, used here as a Ca2+ surrogate for Ca2+ channels. Emptying of the intracellular Ca2+ stores either by incubation in Ca(2+)-free medium or by treatment with low concentrations of the Ca2+ ionophore ionomycin accelerated the influx of Mn2+. Refilling of the Ca2+ stores by incubation in Ca(2+)-containing medium restores low Mn2+ permeability. This Ca(2+)-store-regulated permeability was inhibited by Ni2+ and by cytochrome P-450 inhibitors. Stimulation of platelets with thrombin produced Ca2+ release from the intracellular stores, which was followed, after a temperature-dependent lag (2 s at 37 degrees C; 5 s at 18 degrees C), by an acceleration of Mn2+ influx. Cytochrome P-450 inhibitors prevented the thrombin-induced Mn2+ influx, with little effect on the Ca2+ mobilization from the intracellular stores. Ki values were similar to those estimated for inhibition of the store-regulated permeability in non-stimulated platelets. Similar results were found in platelets stimulated by platelet-activating factor or by ADP. We propose that agonist-induced Ca2+ (Mn2+) influx in platelets is secondary to the emptying of the intracellular Ca2+ stores. The activation of the plasma-membrane Ca2+ (Mn2+) pathway may take place by a mechanism involving microsomal cytochrome P-450, similar to that described previously in thymocytes [Alvarez, Montero & García-Sancho (1991) Biochem. J. 274, 193-197] and neutrophils [Montero, Alvarez & García-Sancho (1991) Biochem. J. 277, 73-79].

Pulmonary toxicity of 1,1-dichloroethylene: correlation of early changes with covalent binding

1986 ◽  
Vol 64 (2) ◽  
pp. 112-121 ◽  
Author(s):  
P. G. Forkert ◽  
V. Stringer ◽  
K. M. Troughton
Keyword(s):  
Structural Damage ◽  
Covalent Binding ◽  
Significant Inhibition ◽  
Clara Cells ◽  
Aryl Hydrocarbon Hydroxylase ◽  
Hydroxylase Activity ◽  
Aryl Hydrocarbon ◽  
Temporal Correlations ◽  
Aryl Hydrocarbon Hydroxylase Activity ◽  
Cytochrome P 450

Administration of a single intraperitoneal dose of 1,1-dichloroethylene (125 mg/kg,1,1-DCE) to mice resulted in bronchiolar injury with selective necrosis of Clara cells. Degenerative changes were manifest in Clara cells as early as 1 h following 1,1-DCE exposure, and were characterized by marked swelling of mitochondria and aggregation of chromatin against the nuclear membrane. Cell death was apparent at 2 h; by 8 h, areas of the bronchiolar epithelium were devoid of lining cells, and at 24 h, the majority of Clara cells were exfoliated. The residual epithelium consisted of flattened cells which formed a thin lining for the airway. Necrosis of Clara cells early in the course of 1,1-DCE exposure coincided with peak covalent binding of [14C] 1,1-DCE and significant depression of components of the pulmonary mixed-function oxidase system; cytochrome P-450 and aryl hydrocarbon hydroxylase activity were markedly reduced but not depleted. Liver damage involving centrilobular hepatocytes was observed at 24 h in 30% of treated animals, and coincided with significant inhibition of aryl hydrocarbon hydroxylase activity; cytochrome P-450 content, however, remained unchanged. While changes in the liver evoked by 1,1-DCE were less striking, the results in lung demonstrate positive temporal correlations between structural damage, peak covalent binding and disturbances of monooxygenase enzymes.

Effect of chronic cysteamine treatment on mouse liver aryl hydrocarbon hydroxylase activity

1988 ◽  
Vol 66 (11) ◽  
pp. 1433-1436 ◽  
Author(s):  
Theresa C. Peterson
Keyword(s):  
Nephropathic Cystinosis ◽  
Aryl Hydrocarbon Hydroxylase ◽  
Serum Aminotransferase ◽  
Aryl Hydrocarbon ◽  
Human Dose ◽  
Aryl Hydrocarbon Hydroxylase Activity ◽  
In Vivo Effects ◽  
Cytochrome P 450

Patients receive chronic cysteamine in the management of nephropathic cystinosis. In a previous report our results indicated that acute cysteamine treatment inhibited cytochrome P-450. Cysteamine (85 mg/kg i.p.) was administered daily to female Swiss mice for 1.5 and 8.5 months. Cysteamine treatment (8.5 months) did not affect hepatic microsomal aryl hydrocarbon hydroxylase (AHH) activity compared with controls. A small decrease in liver AHH activity was seen after 1.5 months of treatment with cysteamine. Liver histology, body weight, liver and spleen weights, and serum aminotransferase activity after chronic and subchronic treatment did not differ from controls. Chronic in vivo cysteamine treatment, unlike acute in vitro treatment did not decrease AHH activity. Incubation of isolated murine hepatocytes with cysteamine significantly inhibited AHH activity compared with controls. The inhibition occurred in a concentration-related manner, with 65% inhibition at 8.8 mM (1 mg/mL) (equivalent to the predicted plasma concentration using the maximally tolerable human dose), and 100% inhibition at 44 mM (5 mg/mL). The concentrations used in vitro were not cytotoxic. This suggests that chronic cysteamine treatment may not result in drug interactions and that in vitro results are not always good indicators of in vivo effects.

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