Uterine Muscle as a Target of Polychlorinated Biphenyls

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Uterine Muscle as a Target of Polychlorinated
Biphenyls

• Rita Loch Caruso, Ph.D.
• Toxicology Program
• School of Public Health
• University of Michigan

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Childbirth
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Parturition
Preterm Birth (11.6)
Prolonged Labor (0.8)
Complications
Postmaturity (7.2)
Dysfunctional Labor (2.8)
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Human Pregnancy
Myometrium
Drawing by M. Brodel, from Williams, Am. J.
Obstet. Gynecol, 131, 1927
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Parturition
Fetal / Maternal Signal(s)
Coordinated, Forceful Sustained Myometrial
Oscillatory Contractions
Parturition
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A Mechanistic-based Approach for Assessing
Potential Chemical Hazards to Parturition
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Contraction-Promoting Signals
estrogen
Cell Relaxation
oxytocin
prostaglandins
Cell Contraction
stretch
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PCBs and Parturition

• Exposure to PCBs is associated with decreased
  gestation length in humans
• The PCB mixture Aroclor 1248 induces spontaneous
  abortion in monkeys
• Several PCB mixtures and congeners exhibit
  estrogen-like activity

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PCB Residues in Tissues Sampled From Women During
Parturition
Data are expressed as ppm of extracted lipids.
From Polishuk et al., Environ. Res. 13278, 1977.
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Uterine Anatomy
Human
Rat
Endometrium
Myometrium
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Uterine Contractility Measurement
Isometric Force Transducer
Uterine Segment
Organ Bath
Polygraph
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Aroclor 1242 Stimulates Uterine Contraction
Bae, J. et al. Environ. Health Perspect. 109275,
2001
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Aroclor 1242 Stimulates Uterine Contraction
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Microbial Dechlorination of Aroclor 1242
Auto1242 (control)
HR1242 (incubated with microbes)
2,4-CB/2,5-CB
2,2'-CB/2,6-CB
Difference between Auto1242 and HR1242
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Microbial Dechlorination Increases Uterotonicity
of Aroclor 1242
Bae, J. et al. Environ. Health Perspect. 109275,
2001
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Microbial Dechlorination of Aroclor 1254
Auto1242 (control)
2,2',4-CB
HR1242 (incubated with microbes)
2,2',4,4'-CB
Difference between Auto1242 and HR1242
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Microbial Dechlorination Increases Uterotonicity
of Aroclor 1254
Bae, J. et al. Environ. Health Perspect. 109275,
2001
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Structure
PCB
Abbreviation
Cl
Cl
3,3',4,4'-CB
3,4-TCB
Cl
Cl
Cl
Cl
3,3',4,4',5'-CB
3,4-PCB
Cl
Cl
Cl
Cl
Cl
2,4-TCB
2,2',4,4'-CB
Cl
Cl
Cl
Cl
2,2',4,4',5,5'-CB
HCB
Cl
Cl
Cl
Cl
Cl
2,4,6-CB
2,4,6-TCB
Cl
Cl
Cl
4-OH-2',4',6'-CB
4-OH-TCB
OH
Cl
Cl
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PCB Congener Uterotonicity
Tsai, Webb, and Loch-Caruso. Reprod. Toxicol.
1021-28, 1996.
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Ortho- and Para-Substituted PCB Congeners
DMSO
2-MCB
2,2'-DCB
2,4-DCB
2,4'-DCB
30 uM
60 uM
100 uM
Pretreatment
Tsuneto et al., unpublished
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Intracellular Calcium Increases Stimulate Uterine
Muscle Cell Contraction
Calcium
Calmodulin
Calcium-Calmodulin
Myosin Light Chain Kinase
Actin Myosin
Actomyosin-P
Myosin Light Chain Phosphatase
Cell Relaxation
Cell Contraction
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Mechanisms of Intracellular Calcium Increase
IP3
PIP2
RR
Ca2
SR
VOCC
Nifedipine
Thapsigargin Ryanodine
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Aroclor 1242 Does Not Increase Inositol
Phosphate Release
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Aroclor 1242 Increases Intracellular Calcium
Bae et al. Toxicol. Appl. Pharmacol. 155261, 1999
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Aroclor 1242 Requires Calcium for Uterotonicity
Aroclor 1242 (A1242)
Carbachol (CCH)
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Inhibition of Voltage-Operated Calcium Channels
Prevents Aroclor 1242 Stimulation
Aroclor 1242 (A1242)
Carbachol (CCH)
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Aroclor 1242 stimulation is not inhibited by
thapsigargin or ryanodine pretreatment
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Prostaglandins Stimulate Uterine Contraction
Phospholipids
Phospholipase
Arachidonic Acid
Cyclooxygenase
Eicosanoids (Prostaglandins F2? E2)
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• Aroclor 1242 releases large amounts of
  arachidonic acid that is not significantly
  metabolized
• Aroclor 1242 inhibits prostaglandin synthesis

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PLA2 Inhibitors Prevent Aroclor 1242 Uterotonicity
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Aroclor 1242 Mechanism
Ca2
Ca2
VOCC
Arachidonic acid
?
PLA2
Aroclor 1242
VOCC Voltage operated Ca2 channels PLA2
Phospholipase A2
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Hypothesis Long-term exposure to estrogenic
PCBs promotes uterine contraction by an estrogen
receptor-mediated mechanism.
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4-Hydroxy-2',4',6'-Trichlorobiphenyl Increases
Oxytocin-induced Contraction Frequency
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1 ?M 4-OH-TCB
1 ?M 4-OH-TCB Tamoxifen
Tamoxifen
Frequency (cycles/min)
5
Control
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Tsai et al. Biol Reprod. 56341, 1997
0 0.1 1 100 1000
Oxytocin (nM)
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17?-Estradiol Increases Oxytocin-induced
Contraction Frequency
10 nM estradiol
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10 nM estradiol tamoxifen
Tamoxifen
Frequency (cycles/min)
5
Control
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Tsai et al. Biol Reprod. 56341, 1997
0 0.1 1 100 1000
Oxytocin (nM)
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4-OH-2',4',6'-TCB Mechanism
OT
OTR
4-OH-TCB
Ca2
4-OH-TCB 4-hydroxy-2',4',6'-trichlorobiphenyl ER
Estrogen receptor OT Oxytocin OTR Oxytocin
Receptor
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Acknowledgments
Dr. R. Clinton Webb Dr. Ed Stuenkel Dr. Marc
Peters-Golden Dr. Mei-Ling Tsai Dr. Jeehyeon
Bae Taeko Tsuneta

• Superfund Basic Research Program
• University of Michigan

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