TNF-alpha enhances intracellular glucocorticoid availability.

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Endocrinology

Background:

• Inflammation and corticosteroid action are closely linked.
• 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) regulates corticosteroid access to receptors.
• Understanding the regulation of 11beta-HSD2 is crucial for inflammatory response modulation.

Purpose of the Study:

• To investigate the effect of tumor necrosis factor-alpha (TNF-alpha) on 11beta-HSD2 activity in LLC-PK(1) cells.
• To elucidate the signaling pathways involved in TNF-alpha-mediated regulation of 11beta-HSD2.
• To understand how TNF-alpha influences the interaction between inflammation and corticosteroid action.

Main Methods:

• LLC-PK(1) cells were used to study NAD-dependent 11beta-HSD2 enzyme activity and mRNA expression.
• Cells were treated with TNF-alpha, phorbol myristate acetate (PMA), glucose, and specific inhibitors (GF-109203X, PD-098050, SB-202190, forskolin).
• Mitogen-activated protein kinases (MAPK) pathways (ERK, p38) and protein kinase A (PKA) were assessed.

Main Results:

• 11beta-HSD2 activity and mRNA were detected in differentiated LLC-PK(1) cells.
• TNF-alpha, PMA, and glucose concentration-dependently down-regulated 11beta-HSD2 activity and mRNA.
• TNF-alpha's effect was mediated via ERK and p38 MAPK pathways and reversed by PKA activation, unlike PMA and glucose effects.

Conclusions:

• TNF-alpha decreases 11beta-HSD2 activity in LLC-PK(1) cells.
• This reduction enhances glucocorticoid access to glucocorticoid receptors.
• The findings provide a mechanism by which TNF-alpha modulates inflammatory responses through corticosteroid action.