Phorbol ester increases mitochondrial cholesterol content in NCI H295R cells

Area of Science:

• Endocrinology
• Molecular Biology
• Cellular Physiology

Background:

• Steroidogenesis initiates with cholesterol mobilization to the inner mitochondrial membrane.
• Angiotensin II (AngII) stimulates aldosterone secretion by promoting mitochondrial cholesterol transport.
• The role of protein kinase C (PKC) in this cholesterol mobilization pathway remains unclear.

Purpose of the Study:

• To investigate the involvement of the protein kinase C (PKC) pathway in mediating cholesterol mobilization for steroidogenesis.
• To determine if PKC activation influences mitochondrial cholesterol content and aldosterone secretion.
• To examine the effect of atrial natriuretic peptide (ANP) on AngII- and PMA-stimulated cholesterol mobilization.

Main Methods:

• Human adrenocortical carcinoma cells were utilized for experiments.
• Cells were treated with phorbol 12-myristate 13-acetate (PMA), a PKC activator, or left untreated.
• Mitochondrial cholesterol content and aldosterone secretion were measured.

Main Results:

• PMA treatment significantly increased mitochondrial cholesterol content, similar to AngII.
• PMA also stimulated aldosterone secretion.
• Atrial natriuretic peptide (ANP) inhibited mitochondrial cholesterol accumulation induced by both AngII and PMA.

Conclusions:

• Protein kinase C (PKC) activation plays a role in cholesterol mobilization to mitochondria, thereby influencing steroid production.
• These findings suggest PKC is a key mediator in the regulation of steroidogenesis.
• ANP's inhibitory effect on steroidogenesis may be mediated by its ability to reduce cholesterol mobilization.