Novel Peptide Nanoparticle Biased Antagonist of CCR3 Blocks Eosinophil Recruitment and Airway Hyperresponsiveness

Background—Chemokine signaling through CCR3 is a key regulatory pathway for eosinophil recruitment into tissues associated with allergic inflammation and asthma. To date, none of the CCR3 antagonists have shown efficacy in clinical trials. One reason may be their unbiased mode of inhibition that prevents receptor internalization, leading to drug tolerance. Objective—We sought to develop a novel peptide nanoparticle CCR3 inhibitor (R321) with a biased mode of inhibition that would block G-protein signaling, but enable or promote receptor internalization. Methods—Self-assembly of R321 peptide into nanoparticles and peptide binding to CCR3 were analyzed by dynamic light scattering and NMR. Inhibitory activity on CCR3 signaling was assessed in vitro using flow cytometry, confocal microscopy, and western blot analysis in a CCR3+ eosinophil cell line and blood eosinophils. In vivo effects of R321 were assessed using a triple allergen mouse asthma model. Results—R321 self-assembles into nanoparticles and binds directly to CCR3, altering receptor function. IC50 values for eotaxin-induced chemotaxis of blood eosinophils are in the low nanomolar range. R321 inhibits only the early phase of ERK1/2 activation and not the late phase generally associated with β-arrestin recruitment and receptor endocytosis, promoting CCR3 internalization and degradation. In vivo, R321 effectively blocks eosinophil recruitment into the lungs and airways and prevents airway hyperresponsiveness in a mouse eosinophilic asthma model. Conclusions—R321 is a potent and selective antagonist of the CCR3 signaling cascade. Inhibition through a biased mode of antagonism may hold significant therapeutic promise by eluding the formation of drug tolerance

Rare Case of a Calcified Catheter-Related Sheath Embolizing to the Right Pulmonary Artery

Catheter-related sheaths, formerly known as “fibrin sheaths,” are the most common complications of central venous catheters. Although usually harmless, they can very rarely detach from the venous wall against which they were formed and embolize with effects ranging from subclinical embolisms to death. This rare occurrence has only been described a few times in the literature to date, and to our knowledge, the embolized sheath has never been directly visualized with CT. We report the case of catheter-related sheath embolization to the right pulmonary artery in a child, as confirmed on CT

Novel peptide nanoparticle–biased antagonist of CCR3 blocks eosinophil recruitment and airway hyperresponsiveness

Background—Chemokine signaling through CCR3 is a key regulatory pathway for eosinophil recruitment into tissues associated with allergic inflammation and asthma. To date, none of the CCR3 antagonists have shown efficacy in clinical trials. One reason may be their unbiased mode of inhibition that prevents receptor internalization, leading to drug tolerance. Objective—We sought to develop a novel peptide nanoparticle CCR3 inhibitor (R321) with a biased mode of inhibition that would block G-protein signaling, but enable or promote receptor internalization. Methods—Self-assembly of R321 peptide into nanoparticles and peptide binding to CCR3 were analyzed by dynamic light scattering and NMR. Inhibitory activity on CCR3 signaling was assessed in vitro using flow cytometry, confocal microscopy, and western blot analysis in a CCR3+ eosinophil cell line and blood eosinophils. In vivo effects of R321 were assessed using a triple allergen mouse asthma model. Results—R321 self-assembles into nanoparticles and binds directly to CCR3, altering receptor function. IC50 values for eotaxin-induced chemotaxis of blood eosinophils are in the low nanomolar range. R321 inhibits only the early phase of ERK1/2 activation and not the late phase generally associated with β-arrestin recruitment and receptor endocytosis, promoting CCR3 internalization and degradation. In vivo, R321 effectively blocks eosinophil recruitment into the lungs and airways and prevents airway hyperresponsiveness in a mouse eosinophilic asthma model. Conclusions—R321 is a potent and selective antagonist of the CCR3 signaling cascade. Inhibition through a biased mode of antagonism may hold significant therapeutic promise by eluding the formation of drug tolerance