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Cytokine-initiated signal transduction in human myometrial cells
F Hertelendy1, R Romero, M Molnár
1Department of Obstetrics and Gynecology, St. Louis University School of Medicine, MO 63110-0250.
Insights
Interleukin-1 (IL-1) and tumor necrosis factor (TNF) bind to human myometrial cells, increasing cyclic AMP (cAMP) and prostaglandin production. These cytokines may activate adenylyl cyclase isoforms, elevating intracellular cAMP levels.
Area of Science:
- Reproductive biology
- Cellular signaling
- Immunology
Background:
- Interleukin-1 (IL-1) and tumor necrosis factor (TNF) are key inflammatory cytokines with diverse cellular effects.
- Human myometrial cells (HMC) play a critical role in uterine function and pregnancy.
- Understanding cytokine actions in HMC is crucial for reproductive health research.
Purpose of the Study:
- To investigate the binding characteristics of IL-1 in HMC.
- To elucidate the post-receptor signaling pathways activated by IL-1 and TNF in HMC.
- To examine the effects of IL-1 and TNF on intracellular signaling molecules like cAMP and prostaglandins in HMC.
Main Methods:
- Human myometrial cells (HMC) were cultured to assess cytokine binding and cellular responses.
- Radioiodinated IL-1 ([125I]IL-1) was used to characterize IL-1 binding kinetics.
- Cyclic AMP (cAMP), prostaglandin E2 (PGE2), and prostaglandin I2 (PGI2) production were measured.
- Membrane preparations were utilized for ADP-ribosylation assays and immunoblotting to study protein levels.
Main Results:
- HMC specifically bind [125I]IL-1 with a high affinity (apparent Kd of 2 x 10(-10) M).
- Incubation with IL-1 or TNF led to a time- and dose-dependent increase in cAMP accumulation and potentiated forskolin-stimulated cAMP production.
- Both cytokines significantly increased PGE2 and PGI2 production, independent of adenylyl cyclase activation.
- IL-1 treatment did not affect ADP-ribosylation or Gi protein levels, suggesting a distinct signaling mechanism.
Conclusions:
- IL-1 and TNF binding to HMC triggers intracellular signaling cascades.
- These cytokines likely activate specific isoforms of the catalytic component of adenylyl cyclase.
- The activation of adenylyl cyclase leads to increased intracellular cAMP levels in HMC.
Problem:
The objectives of this study were to evaluate interleukin-1 (IL-1) binding and some postreceptor actions of this cytokine and tumor necrosis factor (TNF) in human myometrial cells (HMC).
Method:
Monolayer cultures of HMC were used to characterize binding and to measure cyclic (c)AMP, prostaglandin (PG)E2, and PGI2 production. Membrane preparations were used to assess ADP-ribosylation and for immunoblotting.
Results:
HMC were found to specifically bind [125I]IL-1 with an apparent Kd of 2 x 10(-10) M. Incubation of HMC with IL-1 or TNF caused a time-dependent and dose-dependent accumulation of cAMP, as well as a significant potentiation of forskolin-promoted cAMP production. These cytokines also increase PGE2 and PGI2 output, independently of the activation of adenylyl cyclase. IL-1 treatment had no measurable effect either on cholera toxin-mediated and pertussis toxin-mediated ADP-ribosylation, or on the amount of Gi proteins, as assessed by immunoblotting using a polyclonal antibody.
Conclusions:
It is suggested that IL-1 and TNF may activate one or more isoforms of the catalytic component of adenylyl cyclase, raising intracellular cAMP.