Transglutaminase 2 Accelerates Vascular Calcification in Chronic Kidney Disease

Abstract

Background: Transglutaminase 2 (TGM2) is a calcium-dependent enzyme that can cross-link nearly all extracellular matrix (ECM) proteins and can facilitate cell-ECM interaction through integrins. Given the importance of the ECM in vascular calcification we tested the hypothesis that increased TGM2 activity may accelerate vascular calcification in chronic kidney disease (CKD). Methods: We utilized thoracic aortas and vascular smooth muscle cells (VSMC) from the Cy/+ rat, a model of progressive CKD that develops arterial calcification on a normal phosphorus diet, compared to normal rats. Results: VSMC isolated from CKD rats had increased expression and activity of TGM2 compared to cells from normal rats. The increased calcification and expression of alkaline phosphatase activity observed in VSMC from CKD rats compared to normal was inhibited in a dose-dependent manner with the TGM inhibitors cystamine and Z006. Matrix vesicles (MV) from CKD rat VSMC also had increased TGM2 expression and the calcification of MV on type I collagen could be inhibited with cystamine and accelerated by exogenous cross-linking of fibronectin or type I collagen with TGM2. Finally, the calcification of aorta rings from CKD rats in ex vivo cultures was inhibited with TGM2 inhibitor. Conclusion: These data demonstrate a role of TGM2 in the pathogenesis of vascular calcification in CKD through enhancement of MV-ECM calcification.

The obligatory role of the actin cytoskeleton on inward remodeling induced by dithiothreitol activation of endogenous transglutaminase in isolated arterioles

“…Although the methods of activation and inhibition of transglutaminase used in our experiments have been used extensively in the past (1, 10, 17, 31, 37-39), a limitation of our study rests on the potential nonspecific effects of DTT and cystamine. Nonetheless, our results are consistent with an increasing body of evidence that indicates intracellular transglutaminase activation participates in vascular pathology (6,7,23,30). A better understanding of the pathways associated with transglutaminase-dependent cytoskeletal changes should provide new therapeutic avenues for controlling vascular remodeling and the adverse cardiovascular events associated with it.…”

Oligogalacturonic Acid Inhibits Vascular Calcification by Two Mechanisms

“…This observation is consistent with many other demonstrations in the literature showing that the in vivo effects of inhibitors are often less intense than those observed in vitro. 32 Taken as a whole, these results suggest that the decrease of VSMC and aortic ring calcification induced by DP8 is mainly related to the inhibition of osteogenic marker expression.…”

Transglutaminases: Expression in Kidney and Relation to Kidney Fibrosis

“…In a recent study based on a novel rat model of progressive CKD-MBD (Cy/+ rat) displaying arterial calcification on a normal phosphorus diet (Moe et al 2009), increased TG2 expression and activity was detected in Cy/+ rat-vascular smooth muscle cells and in pathological matrix vesicles ex vivo. Furthermore, the general TG inhibitor cystamine slowed down calcification in cells, matrix vesicles and aorta rings from the CKD rats (Chen et al 2013).…”

“…From all these investigations in experimental models of fibrosis (summarized in Table 11.1), it has become clear that TG2 serves as a crosslinker predominantly in Table 11.1 Studies of transglutaminase in CKD Experimental models Subtotal nephrectomy (SNx) in rat Johnson et al (1997Johnson et al ( , 1999Johnson et al ( , 2007 and Burhan et al (2011) Unilateral ureteric obstruction (UUO) in rat Chen et al (2005) Unilateral ureteric obstruction (UUO) in mouse Chen et al (2013) the interstitial space, and its action site is both tubular and glomerular with variations depending on the type of kidney damage.…”