Heterocellular Contact Can Dictate Arterial Function

Abstract

Rationale: Resistance arteries and conduit arteries rely upon different relative contributions of endothelial derived hyperpolarization (EDH) versus nitric oxide (NO) to achieve dilatory heterocellular signaling. Anatomically, resistance arteries use myoendothelial junctions (MEJs), endothelial cell (EC) projections that make contact with smooth muscle cells (SMCs). Conduit arteries have very few to no MEJs. Objective: Determine if the presence of MEJs in conduit arteries can alter heterocellular signaling. Methods and Results: We previously demonstrated that plasminogen activator inhibitor-1 (PAI-1) can regulate formation of MEJs. Thus, we applied pluronic gel containing PAI-1 directly to conduit arteries (carotid arteries, CAs) to determine if this could induce formation of MEJs. We found a significant increase in EC projections resembling MEJs that correlated with increased biocytin dye transfer from ECs to SMCs. Next, we used pressure myography to investigate whether these structural changes were accompanied by a functional change in vasodilatory signaling. Interestingly, PAI-1-treated CAs underwent a switch from a conduit to resistance artery vasodilatory profile via diminished NO signaling, and increased EDH signaling in response to the endothelium-dependent agonists Ach and NS309. Following PAI-1 application, we also found a significant increase in carotid expression of endothelial alpha globin, a protein predominantly expressed in resistance arteries. Carotids from mice with PAI-1, but lacking alpha globin (Hba1 −/−), demonstrated that L-NAME, an inhibitor of NO signaling, was able to prevent arterial relaxation.

Unbiased proteomics identifies plasminogen activator inhibitor-1 as a negative regulator of endothelial nitric oxide synthase

“…S7). These data are consistent with a recent study demonstrating that delivery of recombinant PAI-1 to carotid arteries induces myoendothelial junction formation, reduces NO signaling, and enhances endothelial-derived hyperpolarization signaling (45). Moreover, recent studies suggest that PAI-1 is not only a critical marker and mediator of senescence (46,47), but that it is intimately linked to aging (48), and individuals with a null mutation in PAI-1 have a longer lifespan (49).…”

“…Pressure Myography of Cannulated Arteries. As described previously (45,66), third order mesenteric arteries were removed, cannulated, and pressurized to 60 mmHg. Arteries were washed with a Ca 2+ -free Krebs-Hepes solution to obtain maximal passive diameter of the vessels.…”

Mechanisms underlying selective coupling of endothelial Ca2+ signals with eNOS vs. IK/SK channels in systemic and pulmonary arteries

“…6A), suggesting that regulation of eNOS activity, rather than its expression, underlies the differential contribution of eNOS in PAs and MAs. Because Hbα has been shown to interact with eNOS and scavenge NO, thereby limiting NO bioavailability (Straub et al 2012;Keller et al 2016;Shu et al 2019), we hypothesized that Hbα limits the role of eNOS-NO signalling in MAs. Immunostaining studies showed minimal expression of Hbα in ECs from PAs but confirmed strong expression and localization of Hbα at MEPs in MAs (Fig.…”

“…HbαX, a peptide that inhibits the interaction of Hbα with eNOS, (Straub et al 2014;Keller et al 2016;Shu et al 2019), was used to determine whether Hbα-eNOS interactions limit the role of eNOS in MAs; Scr X was used as a control. Both HbαX and Scr X possess a tat tag, which has previously been shown to render these peptides cell permeable (Straub et al 2014;Keller et al 2016;Shu et al 2019). Strikingly, MAs treated with HbαX were capable of constricting in response to L-NNA, suggesting that Hbα and eNOS normally interact in these arteries and that disruption of Hbα-eNOS interactions with HbαX disinhibited TRPV4 EC -eNOS signalling.…”

Endothelium-Dependent Hyperpolarization (EDH) in Diabetes: Mechanistic Insights and Therapeutic Implications

“…Endothelial stimulation with agonists or by shear stress increases the intracellular calcium concentrations, which in turn generates endothelial hyperpolarization through the opening of small (SK Ca ) and intermediate conductance (IK Ca ) Ca 2+ -activated K + channels [2,3,4,5,7]. Then, in a number of arteries in which MEGJs exist, the endothelium-dependent hyperpolarization (EDH) spreads to adjacent smooth muscle cells via MEGJs, leading to vasorelaxation [2,3,4,5,8,9]. Although the intracellular Ca 2+ release from the endoplasmic reticulum (ER) and the subsequent activation of the SK Ca and IK Ca channels is an initial step for the generation of EDH [3,4,7], the Ca 2+ influx through endothelial nonselective cation channels of the transient receptor potential (TRP) family after ER calcium depletion also contributes to the generation of EDH via the downstream activation of SK Ca and IK Ca channels (Figure 1) [2,3,4,5,10,11,12].…”