The cellular basis of protease-activated receptor 2–evoked mechanical and affective pain
Shayne N. Hassler, Moeno Kume, Juliet M. Mwirigi, Ayesha Ahmad, Stephanie Shiers, Andi Wangzhou, Pradipta R. Ray, Serge N. Belugin, Dhananjay K. Naik, Michael D. Burton, Josef Vagner, Scott Boitano, Armen N. Akopian, Gregory Dussor, Theodore J. Price
Shayne N. Hassler, Moeno Kume, Juliet M. Mwirigi, Ayesha Ahmad, Stephanie Shiers, Andi Wangzhou, Pradipta R. Ray, Serge N. Belugin, Dhananjay K. Naik, Michael D. Burton, Josef Vagner, Scott Boitano, Armen N. Akopian, Gregory Dussor, Theodore J. Price
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Research Article Neuroscience

The cellular basis of protease-activated receptor 2–evoked mechanical and affective pain

Abstract

Protease-activated receptor 2 (PAR2) has long been implicated in inflammatory and visceral pain, but the cellular basis of PAR2-evoked pain has not been delineated. Although PAR2-evoked pain has been attributed to sensory neuron expression, RNA-sequencing experiments show ambiguous F2rl1 mRNA detection. Moreover, many pharmacological tools for PAR2 are nonspecific, acting also on the Mas-related GPCR family (Mrg) that are highly enriched in sensory neurons. We sought to clarify the cellular basis of PAR2-evoked pain. We developed a PAR2–conditional knockout mouse and specifically deleted PAR2 in all sensory neurons using the PirtCre mouse line. Our behavioral findings show that PAR2 agonist–evoked mechanical hyperalgesia and facial grimacing, but not thermal hyperalgesia, are dependent on PAR2 expression in sensory neurons that project to the hind paw in male and female mice. F2rl1 mRNA is expressed in a discrete population (~4%) of mostly small-diameter sensory neurons that coexpress the Nppb and IL31ra genes. This cell population has been implicated in itch, but our work shows that PAR2 activation in these cells causes clear pain-related behaviors from the skin. Our findings show that a discrete population of DRG sensory neurons mediate PAR2-evoked pain.

Authors

Shayne N. Hassler, Moeno Kume, Juliet M. Mwirigi, Ayesha Ahmad, Stephanie Shiers, Andi Wangzhou, Pradipta R. Ray, Serge N. Belugin, Dhananjay K. Naik, Michael D. Burton, Josef Vagner, Scott Boitano, Armen N. Akopian, Gregory Dussor, Theodore J. Price

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Figure 6

PAR2 agonists effectuate facial grimacing via PAR2+ sensory neurons.

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PAR2 agonists effectuate facial grimacing via PAR2+ sensory neurons. Mic...
Mice were injected with PAR2 agonists and grimacing was subsequently scored 1, 3, 5, 24, and 48 hours after hind paw injection. Baseline (BL) measures were obtained before administering 2AT, 48/80, or NE. When compared with F2rl1floxPirt+/+ mice, F2rl1floxPirtCre mice show decreased facial grimacing in response to 2AT (30 pmol) (A), 48/80 (6.5 nmol) (B), and NE (10 units) (C). Effect size is determined by calculating the cumulative difference between the value for each time point and the baseline value. *P < 0.05 compared with F2rl1floxPirt+/+ or F2rl1floxPirtCre groups. #P < 0.05 compared with baseline measures. n = 4 for F2rl1floxPirt+/+ and F2rl1floxPirtCre groups treated with 2AT and 48/80, n = 7 for F2rl1floxPirt+/+ and F2rl1floxPirtCre groups treated with NE. Data are expressed as mean ± SEM. Two-way ANOVA used for grimace score, with Holm-Šidák and Dunnett’s multiple comparisons: *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001; ##P < 0.01, ###P < 0.001, and ####P < 0.0001. Unpaired t test used for effect size: **P < 0.01, and ****P < 0.0001. Asterisks denote significant differences between genotypes. Pound signs denote significant differences versus BL as a function of time.