Endothelial cells (ECs) of healthy arteries express high levels of connexin40 (Cx40), but this expression is lost in ECs overlying atherosclerotic plaques. Low/oscillatory shear stress observed in bends and bifurcations of arteries is known to be atherogenic partly through activation of the pro-inflammatory NFκB pathway in ECs.

Here, we investigate the relation between shear stress, Cx40 and NFκB.

Shear stress-modifying casts were placed around the right common carotid artery of mice expressing eGFP controlled by the Cx40 promoter. We found that Cx40 expression is down-regulated in regions of oscillatory shear stress (0.45±0.13, p=0.04), but is conserved in regions of high and low laminar shear stress (1.45±0.48 and 0.85±0.11, N=8) by en face immunofluorescence on Cx40^+/eGFP mice. Using a high-throughput phage display, we retrieved a consensus binding motif for the intracellular regulatory C-terminus of Cx40 (Cx40CT), i.e. HS[I,L,V][K,R]. One of the retrieved peptides (HSLRPEWRMPGP) showed a 58.3% homology with amino acids 5 to 16 of IκBα, a member of the protein family that inhibit the nuclear translocation of NFκB. In vitro binding of this peptide was confirmed by crosslinking and by en face proximity ligation assay targeting IκBα and Cx40 on rat carotid arteries. Nuclear translocation of NFκB in mouse ECs in response to activation by TNFα was enhanced after reduction of Cx40 with siRNA. Transfection of Cx40 or Cx40CT in HeLa cells demonstrated that Cx40CT was sufficient for inhibition of TNFα-induced of NFκB nuclear translocation. Finally, we observed an exaggarated induction of atherosclerotic plaques by LLSS or OSS in Apoe^−/− mice with endothelial-specific deletion of Cx40.

In conclusion, our data show a novel functional interaction between IκBα and Cx40 that may be relevant for the control of NFκB activation by shear stress in development of atherosclerotic disease.

The author hereby declares no conflict of interest