Dicarbonyl stress in endothelial cells alters mitochondrial protein homeostasis

Introduction and open questions Methylglyoxal-derived hydroimidazolone (MG-H1) is formed in a reaction of the reactive dicarbonyl Methylglyoxal (MG) with arginine residues of proteins leading to misfolding, aggregation and loss of-function of the protein. Heat shock proteins (Hsp) mediate refolding and disaggregation of misfolded proteins.

We questioned the effect of MG on mouse cardiac endothelial cells and whether the loss of the stress-inducible Hsp70 (Hspa1a/Hspa1b) in a double knockout cell line (Hspa1a/Hspa1b KO) leads to reduced MG tolerance.

Methods mRNA was measured by qPCR and protein levels were measured by immunofluorescence. The data for the KO cells was obtained from three independent Hspa1a/Hspa1b KO cell clones.

Results After treatment with 500 µM MG, Hspa1a/Hspa1b was up-regulated on the mRNA level and on the protein level in wild-type cells (WT). The two mitochondrial chaperones Hspa9 and Hspd1 were induced after 500 µM MG treatment on the mRNA level and on the protein level, both in WT and even stronger in KO cells. The mitochondrial fission protein Drp1 was increased on the mRNA level after 500 µM MG treatment in WT as well as in KO cells.

Conclusion In WT and Hspa1a/Hspa1b KO cells, MG treatment lead to an up-regulation of Drp1, indicating increased mitochondrial fission and disturbance of mitochondrial homeostasis. As a compensatory mechanism, expression of the mitochondrial heat shock proteins Hspa9 and Hspd1 was significantly induced. In Hspa1a/Hspa1b KO cells, these changes were even stronger, indicating pronounced MG-induced mitochondrial stress in the absence of stress-inducible Hsp70.

Publication History

Article published online:
19 August 2021