Estrogen memory effect in human hepatocytes during repeated cell division without hormone.

Area of Science:

• Endocrinology
• Cell Biology
• Molecular Biology

Background:

• Sex steroids can induce persistent changes in target tissues, affecting subsequent hormonal responses.
• The mechanism of propagating these altered characteristics during cell division, especially without hormonal stimulation, remains unclear.

Purpose of the Study:

• To investigate the effects of estrogen on serum apolipoprotein synthesis in the human hepatocarcinoma cell line HepG2.
• To examine how transient estrogen exposure induces long-lasting changes in cellular response and whether these changes are inherited.

Main Methods:

• Utilized the HepG2 human hepatocarcinoma cell line as an in vitro model.
• Administered low concentrations of estrogen for 24 to 48 hours.
• Quantitatively correlated cellular memory effects with the induction and propagation of a nuclear estrogen-binding protein.

Main Results:

• Transient estrogen treatment resulted in long-lasting alterations in cellular response kinetics to subsequent estrogen stimulation.
• A moderate-affinity, nuclear, type II estrogen receptor-like protein was induced and propagated.
• These changes and altered nuclear protein composition were inherited by daughter cells for over ten generations in the absence of estrogen.

Conclusions:

• Transient estrogen exposure induces a "memory effect" in HepG2 cells, altering their responsiveness to hormonal stimuli.
• This cellular memory is linked to the induction and inheritance of specific nuclear estrogen-binding proteins.
• Estrogen-induced changes in cellular characteristics and nuclear composition can be epigenetically propagated across multiple cell divisions.