Nitrosative stress uncovers potent β₂-adrenergic receptor-linked vasodilation further enhanced by blockade of clathrin endosome formation

Abstract

This study investigated the effect of sodium nitroprusside (SNP) preexposure on vasodilation via the β-adrenergic receptor (BAR) system. SNP was used as a nitrosative/oxidative proinflammatory insult. Small arterioles were visualized by intravital microscopy in the hamster cheek pouch tissue (isoflurane, n = 45). Control dilation to isoproterenol (EC: 10 mol/l) became biphasic as a function of concentration after 2 min of exposure to SNP (10 M), with increased potency at picomolar dilation uncovered and decreased efficacy at the micromolar dilation. Control dilation to curcumin was likewise altered after SNP, but only the increased potency at a low dose was uncovered, whereas micromolar dilation was eliminated. The picomolar dilations were blocked by the potent BAR-2 inverse agonist carazolol (10 mol/l). Dynamin inhibition with dynasore mimicked this effect, suggesting that SNP preexposure prevented BAR agonist internalization. Using HeLa cells transfected with BAR-2 tagged with monomeric red fluorescent protein, exposure to 10-10 mol/l curcumin resulted in internalization and colocalization of BAR-2 and curcumin (FRET) that was prevented by oxidative stress (10 mol/l CoCl), supporting that stress prevented internalization of the BAR agonist with the micromolar agonist. This study presents novel data supporting that distinct pools of BARs are differentially available after inflammatory insult. NEW & NOTEWORTHY Preexposure to an oxidative/nitrosative proinflammatory insult provides a "protective preconditioning" against future oxidative damage. We examined immediate vasoactive and molecular consequences of a brief preexposure via β-adrenergic receptor signaling in small arterioles. Blocked receptor internalization with elevated reactive oxygen levels coincides with a significant and unexpected vasodilation to β-adrenergic agonists at picomolar doses.

Agonistic autoantibodies against ß2-adrenergic receptor influence retinal microcirculation in glaucoma suspects and patients

“…To the best of our knowledge, the exact molecular pathway mediated by β2-AR in retinal vessels is still elusive. It was reported that in ischemia the behavior of β2-AR varied: whereas a subgroup was internalized, a second group showed an alternate desensitization that finally caused an increase in affinity [ 46 ]. This in vitro observation supports our hypothesis of a link between β2-agAAb (via β2-AR) and impaired retinal microcirculation in glaucoma eyes.…”

Reactive Vasodilation Predicts Mortality in Primary Systemic Light-Chain Amyloidosis

“…On the contrary, recent experimental evidence indicates that nitrotyrosine may induce unexpected vasodilatory response to β-adrenergic agonists through blocking of β2 adrenergic receptor internalization at nerve endings. 56 Interestingly, CPT may induce vasodilation through stimulation of postjunctional β2 adrenoceptors 51 and could, therefore, be enhanced by increased NTY local concentrations. Thus, the effect of local concentrations of NTY on paradoxical vasodilation by CPT observed in our AL population should be further explored.…”

Activation of Gαq sequesters specific transcripts into Ago2 particles

“…One of these confirmed partners is the Promoter of RNA-induced silencing, C3PO 24 , 25 , which is inhibited by PLCβ1 binding 3 , 26 – 28 . In recent work, we characterized the proteins bound to cytosolic PLCβ1 in undifferentiated PC12 cells and found roughly 30% of bound proteins are identified as stress granules proteins, including Ago2, PABPC, eIF5a and G3BP1 4 , 29 . These studies showed that reducing the cytosolic level of PLCβ1 either by down-regulation, osmotic stress or Gαq activation allowed for the release of bound proteins and promoted the formation of stress granules.…”