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The mechanisms by which nitric oxide affects mammary epithelial growth and differentiation

Franklyn F Bolander1

  • 1Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA.

Biochemical and Biophysical Research Communications
|April 25, 2003
PubMed

Insights

Nitric oxide (NO) stimulates mammary epithelial growth via Jun N-terminal kinase (JNK) and inhibits differentiation through extracellular signal-regulated kinase (ERK), utilizing distinct molecular pathways.

Area of Science:

  • Cell biology
  • Molecular endocrinology
  • Signal transduction

Background:

  • Prolactin is a key hormone regulating mammary gland development and function.
  • Nitric oxide (NO) is a signaling molecule with diverse physiological roles, including effects on cell growth and differentiation.
  • The precise molecular mechanisms by which NO influences prolactin-mediated mammary epithelial responses are not fully understood.

Purpose of the Study:

  • To elucidate the specific intracellular signaling pathways by which nitric oxide (NO) modulates prolactin-stimulated DNA synthesis and differentiation in mouse mammary epithelial cells.
  • To determine the involvement of Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and protein kinase G (PKG) in NO's actions.
  • To investigate the role of cyclic adenosine monophosphate (cAMP) in mediating NO's effects on mammary epithelial cells.

Main Methods:

  • Utilized specific pharmacological inhibitors targeting key signaling molecules such as JNK, ERK, and PKG.
  • Assessed the impact of NO and pathway inhibitors on prolactin-stimulated DNA synthesis.
  • Measured the accumulation of alpha-lactalbumin, a marker of differentiation, in response to prolactin and NO.
  • Investigated the role of cAMP by manipulating its levels and assessing NO's effects.

Main Results:

  • Nitric oxide (NO) significantly enhanced prolactin-stimulated DNA synthesis, an effect blocked by Jun N-terminal kinase (JNK) inhibitors via a protein kinase G (PKG)-independent pathway.
  • NO inhibited prolactin-induced differentiation, evidenced by reduced alpha-lactalbumin accumulation, an effect prevented by extracellular signal-regulated kinase (ERK) inhibitors and dependent on PKG.
  • While NO can increase cAMP levels by inhibiting phosphodiesterase 3, suppression of cAMP did not abolish NO's effects on DNA synthesis or differentiation, suggesting cAMP is not the primary mediator.

Conclusions:

  • Nitric oxide (NO) employs distinct molecular pathways to regulate mammary epithelial cell proliferation and differentiation.
  • NO stimulates mammary epithelial cell growth through the JNK signaling pathway.
  • NO inhibits mammary epithelial cell differentiation via the ERK signaling pathway, which is dependent on PKG.

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