DEC2 Blocks the Effect of the ARNTL2/NPAS2 Dimer on the Expression of PER3 and DBP

Area of Science:

• Immunology
• Chronobiology
• Molecular Biology

Background:

• Rheumatoid arthritis (RA) exhibits circadian symptom variations, linked to disturbed clock gene expression.
• Clock genes like ARNTL2, NPAS2, and DEC2 are implicated in RA pathogenesis.
• Tumor necrosis factor (TNF) is a known potent inducer of these clock genes.

Purpose of the Study:

• To investigate the regulation of ARNTL2 and NPAS2 by TNF in human fibroblasts.
• To elucidate the downstream effects of TNF-induced ARNTL2 and NPAS2 on other clock gene expressions.
• To explore the role of NF-κB signaling in TNF-mediated regulation of these clock genes.

Main Methods:

• Primary human fibroblasts were stimulated with TNF.
• Gene expression and protein localization were analyzed using RT-qPCR and immunofluorescence staining.
• NF-κB pathway involvement was assessed using an IKK-2 inhibitor (IMD-0354) and transfection studies in HEK293 cells.

Main Results:

• TNF promoted nuclear localization of ARNTL2.
• TNF's effects on ARNTL2 and NPAS2 expression were mediated via NF-κB signaling, similar to DEC2.
• ARNTL2/NPAS2 dimers showed distinct regulatory effects on other clock genes (PER3, DBP) compared to ARNTL/NPAS2.

Conclusions:

• ARNTL2 and NPAS2 are regulated by TNF through NF-κB in fibroblasts.
• These genes exhibit unique regulatory roles in circadian component interactions.
• The findings suggest a role for ARNTL2 and NPAS2 in cellular circadian adaptation during inflammation.