Transglutaminase 2 regulates endothelial cell calcification via IL-6-mediated autophagy

Area of Science:

• Cardiovascular Biology
• Cellular and Molecular Medicine
• Biochemistry

Background:

• Endothelial cell (EC) calcification is a key marker of atherosclerotic calcification and intimal calcification.
• ECs are implicated in atherogenesis and may act as osteoprogenitor cells initiating intimal calcification.
• The precise mechanism of transglutaminase 2 (TG2)-mediated EC calcification remains unclear despite its known roles in cellular processes.

Purpose of the Study:

• To elucidate the molecular mechanism by which TG2 regulates endothelial cell calcification.
• To investigate the role of TG2 in activating signaling pathways and modulating autophagy in ECs.
• To explore the link between TG2, inflammation, and calcification in endothelial cells.

Main Methods:

• TG2 gene manipulation (overexpression/silencing) using siRNA and adenovirus vectors.
• Analysis of gene and protein expression (RT-PCR, Western Blot), TG2 activity (5-BP assay), and autophagy levels (LC3 assay, electron microscopy).
• Assessment of EC calcification (Alizarin Red S staining, calcium assay) and IL-6 levels (ELISA) under calcifying conditions.

Main Results:

• Calcifying medium (CM) increased TG2 activity and expression, activating the NF-κB pathway and inducing IL-6 autocrine signaling.
• IL-6 activated the JAK2/STAT3 pathway, suppressing autophagy and promoting EC calcification.
• TG2 was found to form complexes with NF-κB components, linking TG2 to autophagy inhibition and EC calcification.

Conclusions:

• TG2 plays a critical role in promoting endothelial cell calcification through the NF-κB and IL-6/JAK2/STAT3 signaling pathways.
• Inhibition of autophagy by TG2 signaling contributes to endothelial cell calcification and potentially EndMT.
• Understanding this TG2-mediated mechanism provides novel insights into the pathogenesis of atherosclerosis and vascular calcification.