DIO2 modifies inflammatory responses in chondrocytes.

Area of Science:

• Cell Biology
• Molecular Biology
• Immunology

Background:

• Selenium is known to neutralize inflammatory responses in chondrocytes, the cells responsible for maintaining cartilage.
• The precise molecular mechanisms underlying selenium's anti-inflammatory actions remain incompletely understood.
• Selenoproteins, such as Iodothyronine Deiodinase-2 (DIO2), Glutathione Peroxidase-1 (GPX1), and Thioredoxin Reductase-1 (TR1), are crucial for cellular function.

Purpose of the Study:

• To investigate the specific roles of DIO2, GPX1, and TR1 in mediating selenium's anti-inflammatory effects in human chondrocytes.
• To elucidate the molecular pathways through which selenoprotein knockdown influences inflammatory gene expression.

Main Methods:

• Primary human chondrocytes were treated with small interfering ribonucleic acid (siRNA) to specifically reduce the expression of DIO2, GPX1, and TR1.
• Cells were subsequently stimulated with interleukin-1β (IL-1β) to mimic inflammatory conditions.
• Gene expression levels of key inflammatory mediators (COX2, IL-1β) and nuclear receptors (LXRα/β) were quantified using quantitative Real Time-Polymerase Chain Reaction (qRT-PCR).

Main Results:

• Knockdown of DIO2, but not GPX1 or TR1, significantly increased both basal and IL-1β-induced cyclooxygenase-2 (COX2) gene expression.
• Suppression of DIO2 markedly enhanced IL-1β-induced IL-1β gene expression, indicating a pro-inflammatory effect.
• Downregulation of DIO2 led to a significant decrease in Liver X receptor alpha (LXRα) expression, while LXRβ expression remained unaffected.

Conclusions:

• The selenoprotein DIO2 plays a critical role in suppressing inflammatory responses in chondrocytes.
• Reduced DIO2 expression promotes inflammation by upregulating key mediators like IL-1β and COX2.
• Decreased LXRα expression following DIO2 suppression suggests that the LXRα pathway may be an upstream target mediating DIO2's anti-inflammatory effects.