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Introduction: Current treatments for asthma help to alleviate clinical symptoms but do not cure the disease. In this study, we explored a novel therapeutic approach for the treatment of house dust mite allergen Der p 1induced asthma by aiming to eliminate specific population of B-cells involved in memory IgE response to Der p 1. Materials and Methods: To achieve this aim, we developed and evaluated two different proDer p 1-based fusion proteins; an allergen-toxin (proDer p 1-ETA) and an allergen-drug conjugate (ADC) (proDer p 1-SNAP-AURIF) against Der p 1 reactive hybridomas as an in vitro model for Der p 1 reactive human B-cells. The strategy involved the use of proDer p 1 allergen as a cell-specific ligand to selectively deliver the bacterial protein toxin Pseudomonas exotoxin A (ETA) or the synthetic small molecule toxin Auristatin F (AURIF) into the cytosol of Der p 1 reactive cells for highly efficient cell killing. Results: As such, we demonstrated recombinant proDer p 1 fusion proteins were selectively bound by Der p 1 reactive hybridomas as well as primary IgG1+ B-cells from HDM-sensitized mice. The therapeutic potential of proDer p 1-ETA' and proDer p 1-SNAP-AURIF was confirmed by their selective cytotoxic activities on Der p 1 reactive hybridoma cells. The allergen-toxin demonstrated superior cytotoxic activity, with IC50 values in the single digit nanomolar value, compared to the ADC. Discussions: Altogether, the proof-of-concept experiments in this study provide a promising approach for the treatment of patients with house dust mite-driven allergic asthma.
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Essentials peroxisome proliferator-activated receptor γ (PPARγ) agonists inhibit platelet function. PPARγ agonists negatively regulate outside-in signaling via integrin αIIbß3. PPARγ agonists disrupt the interaction of Gα13 with integrin ß3. This is attributed to an upregulation of protein kinase A activity. SUMMARY: Background Agonists for the peroxisome proliferator-activated receptor (PPARγ) have been shown to have inhibitory effects on platelet activity following stimulation by GPVI and GPCR agonists. Objectives Profound effects on thrombus formation led us to suspect a role for PPARγ agonists in the regulation of integrin αIIbß3 mediated signaling. Both GPVI and GPCR signaling pathways lead to αIIbß3 activation, and signaling through αIIbß3 plays a critical role in platelet function and normal hemostasis. Methods The effects of PPARγ agonists on the regulation of αIIbß3 outside-in signaling was determined by monitoring the ability of platelets to adhere and spread on fibrinogen and undergo clot retraction. Effects on signaling components downstream of αIIbß3 activation were also determined following adhesion to fibrinogen by Western blotting. Results Treatment of platelets with PPARγ agonists inhibited platelet adhesion and spreading on fibrinogen and diminished clot retraction. A reduction in phosphorylation of several components of αIIbß3 signaling, including the integrin ß3 subunit, Syk, PLCγ2, focal adhesion kinase (FAK) and Akt, was also observed as a result of reduced interaction of the integrin ß3 subunit with Gα13. Studies of VASP phosphorylation revealed that this was because of an increase in PKA activity following treatment with PPARγ receptor agonists. Conclusions This study provides further evidence for antiplatelet actions of PPARγ agonists, identifies a negative regulatory role for PPARγ agonists in the control of integrin αIIbß3 outside-in signaling, and provides a molecular basis by which the PPARγ agonists negatively regulate platelet activation and thrombus formation.