Abstract
Polycyclic aromatic hydrocarbons are environmental pollutants known to be carcinogenic and immunotoxic. In intact cell assays, benzo[a]pyrene (B[a]P) disrupts Ca2+ homeostasis in both immune and nonimmune cells, but the molecular mechanism is undefined. In this study, B[a]P and five metabolites are examined for their ability to alter Ca2+ transport across microsomal membranes. Using a well-defined model system, junctional SR vesicles from skeletal muscle, we show that a single o-quinone metabolite of B[a]P, B[a]P-7,8-dione, can account for altered Ca2+ transport across microsomal membranes. B[a]P-7,8-dione induces net Ca2+ release from actively loaded vesicles in a dose-, time-, and Ca2+-dependent manner. In the presence of 5 μM extravesicular Ca2+, B[a]P-7,8-dione exhibited threshold and EC50 values of 0.4 and 2 μM, respectively, and a maximal release rate of 2 μmol of Ca2+ min-1 mg-1. The mechanism by which B[a]P-7,8-dione enhanced Ca2+ efflux was further investigated by measuring macroscopic fluxes and single RyR1 channels reconstituted in bilayer lipid membranes and direct measurements of SERCA catalytic activity. B[a]P-7,8-dione (≤ 20 μM) had no measurable effect on initial rates of Ca2+ accumulation in the presence of ruthenium red to block ryanodine receptor (RyR1), nor did it alter Ca2+-dependent (thapsigarginsensitive) ATPase activity. B[a]P-7,8-dione selectively altered the function of RyR1 in a time-dependent diphasic manner, first activating then inhibiting channel activity. Considering that RyR1 and its two alternate isoforms are broadly expressed in mammalian cells and their important role in Ca2+-signaling, the present results reveal a mechanism by which metabolic bioactivation of B[a]P may mediate RyR dysfunction of pathophysiological significance.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 506-513 |
| Number of pages | 8 |
| Journal | Molecular Pharmacology |
| Volume | 59 |
| Issue number | 3 |
| State | Published - 2001 |
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- Pharmacology
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A bioactive metabolite of benzo[a]pyrene, benzo[a]pyrene-7,8- dione, selectively alters microsomal Ca2+ transport and ryanodine receptor function. / Pessah, Isaac N; Beltzner, Chris; Burchiel, Scott W.; Sridhar, Gopishetty; Penning, Trevor; Feng, Wei.
In: Molecular Pharmacology, Vol. 59, No. 3, 2001, p. 506-513.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - A bioactive metabolite of benzo[a]pyrene, benzo[a]pyrene-7,8- dione, selectively alters microsomal Ca2+ transport and ryanodine receptor function
AU - Pessah, Isaac N
AU - Beltzner, Chris
AU - Burchiel, Scott W.
AU - Sridhar, Gopishetty
AU - Penning, Trevor
AU - Feng, Wei
PY - 2001
Y1 - 2001
N2 - Polycyclic aromatic hydrocarbons are environmental pollutants known to be carcinogenic and immunotoxic. In intact cell assays, benzo[a]pyrene (B[a]P) disrupts Ca2+ homeostasis in both immune and nonimmune cells, but the molecular mechanism is undefined. In this study, B[a]P and five metabolites are examined for their ability to alter Ca2+ transport across microsomal membranes. Using a well-defined model system, junctional SR vesicles from skeletal muscle, we show that a single o-quinone metabolite of B[a]P, B[a]P-7,8-dione, can account for altered Ca2+ transport across microsomal membranes. B[a]P-7,8-dione induces net Ca2+ release from actively loaded vesicles in a dose-, time-, and Ca2+-dependent manner. In the presence of 5 μM extravesicular Ca2+, B[a]P-7,8-dione exhibited threshold and EC50 values of 0.4 and 2 μM, respectively, and a maximal release rate of 2 μmol of Ca2+ min-1 mg-1. The mechanism by which B[a]P-7,8-dione enhanced Ca2+ efflux was further investigated by measuring macroscopic fluxes and single RyR1 channels reconstituted in bilayer lipid membranes and direct measurements of SERCA catalytic activity. B[a]P-7,8-dione (≤ 20 μM) had no measurable effect on initial rates of Ca2+ accumulation in the presence of ruthenium red to block ryanodine receptor (RyR1), nor did it alter Ca2+-dependent (thapsigarginsensitive) ATPase activity. B[a]P-7,8-dione selectively altered the function of RyR1 in a time-dependent diphasic manner, first activating then inhibiting channel activity. Considering that RyR1 and its two alternate isoforms are broadly expressed in mammalian cells and their important role in Ca2+-signaling, the present results reveal a mechanism by which metabolic bioactivation of B[a]P may mediate RyR dysfunction of pathophysiological significance.
AB - Polycyclic aromatic hydrocarbons are environmental pollutants known to be carcinogenic and immunotoxic. In intact cell assays, benzo[a]pyrene (B[a]P) disrupts Ca2+ homeostasis in both immune and nonimmune cells, but the molecular mechanism is undefined. In this study, B[a]P and five metabolites are examined for their ability to alter Ca2+ transport across microsomal membranes. Using a well-defined model system, junctional SR vesicles from skeletal muscle, we show that a single o-quinone metabolite of B[a]P, B[a]P-7,8-dione, can account for altered Ca2+ transport across microsomal membranes. B[a]P-7,8-dione induces net Ca2+ release from actively loaded vesicles in a dose-, time-, and Ca2+-dependent manner. In the presence of 5 μM extravesicular Ca2+, B[a]P-7,8-dione exhibited threshold and EC50 values of 0.4 and 2 μM, respectively, and a maximal release rate of 2 μmol of Ca2+ min-1 mg-1. The mechanism by which B[a]P-7,8-dione enhanced Ca2+ efflux was further investigated by measuring macroscopic fluxes and single RyR1 channels reconstituted in bilayer lipid membranes and direct measurements of SERCA catalytic activity. B[a]P-7,8-dione (≤ 20 μM) had no measurable effect on initial rates of Ca2+ accumulation in the presence of ruthenium red to block ryanodine receptor (RyR1), nor did it alter Ca2+-dependent (thapsigarginsensitive) ATPase activity. B[a]P-7,8-dione selectively altered the function of RyR1 in a time-dependent diphasic manner, first activating then inhibiting channel activity. Considering that RyR1 and its two alternate isoforms are broadly expressed in mammalian cells and their important role in Ca2+-signaling, the present results reveal a mechanism by which metabolic bioactivation of B[a]P may mediate RyR dysfunction of pathophysiological significance.
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M3 - Article
VL - 59
SP - 506
EP - 513
JO - Molecular Pharmacology
JF - Molecular Pharmacology
SN - 0026-895X
IS - 3
ER -