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. 2021 Jan;87(1):129-139.
doi: 10.1111/bcp.14370. Epub 2020 Jun 2.

Development of AITC-induced dermal blood flow as a translational in vivo biomarker of TRPA1 activity in human and rodent skin

Victory Joseph  1 , Xiaoying Yang  2 , Simon S Gao  3 , Justin Elstrott  1 , Robby M Weimer  1 , Wiebke Theess  4 , Cory Thrasher  5 , Nand Singh  6 , Joseph Lin  4 , Rebecca N Bauer  7
Affiliations
Free article

Development of AITC-induced dermal blood flow as a translational in vivo biomarker of TRPA1 activity in human and rodent skin

Victory Joseph et al. Br J Clin Pharmacol. 2021 Jan.
Free article

Abstract

Background and purpose: Develop a translational assay of Transient Receptor Potential Ankyrin 1 (TRPA1) activity for use as a preclinical and clinical biomarker.

Experimental approach: Allyl isothiocyanate (AITC), capsaicin or citric acid were applied to ears of wildtype and Trpa1-knock out (Trpa1 KO) rats, and changes in dermal blood flow (DBF) were measured by laser speckle contrast imaging. In humans, the DBF, pain and itch responses to 5-20% AITC applied to the forearm were measured and safety was evaluated. Reproducibility of the DBF, pain and itch responses to topically applied 10% and 15% AITC were assessed at two visits separated by 13-15 days. DBF changes were summarized at 5-minute intervals as areas under the curve (AUC) and maxima. Intraclass correlation coefficient (ICC) was calculated to assess arm-arm and period-period reproducibility.

Key results: AITC- and citric acid-induced DBF were significantly reduced in Trpa1 KO rats compared to wildtype (90 ± 2% and 65 ± 11% reduction, respectively), whereas capsaicin response did not differ. In humans, each AITC concentration significantly increased DBF compared to vehicle with the maximal increase occurring 5 minutes post application. Ten percent and 15% AITC were selected as safe and effective stimuli. AUC from 0 to 5 minutes was the most reproducible metric of AITC-induced DBF across arms (ICC = 0.92) and periods (ICC = 0.85). Subject-reported pain was more reproducible than itch across visits (ICC = 0.76 vs 0.17, respectively).

Conclusion and implications: AITC-induced DBF is a suitable target engagement biomarker of TRPA1 activity for preclinical and clinical studies of TRPA1 antagonists.

Keywords: TRPA1; allyl isothiocyanate; biomarker; laser speckle contrast imaging; neurogenic inflammation; pharmacodynamic.

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References

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