TRPA1 inhibition reduces ocular pain and corneal neurogenic inflammation in a mouse model of dry eye disease

Dry eye disease (DED) is characterized by neurosensory abnormalities, complicating the management of ocular pain, and is further worsened by significant ocular inflammation. Although multiple inflammatory pathways contribute to DED, the role of neurogenic inflammation, particularly through transient receptor potential ankyrin-1 (TRPA1) nociceptors, which are expressed in the cornea nerve fibers, remains underexplored. This study investigates the involvement of TRPA1 in ocular pain and neurogenic inflammation in chronic DED. To explore this, multi-unit extracellular recordings were used to monitor ciliary nerve activity in naive mice after exposure to the TRPA1 antagonist (HC-030031). An in vivo DED model was then created by surgically removing the extraorbital and Harderian lacrimal glands in mice. HC-030031 was topically applied twice daily from day 7 to day 21 post-surgery. Corneal sensitivity and integrity were evaluated, followed by immunohistology, flow cytometry, and mRNA expression analyses in the cornea. Electrophysiological recordings showed that while HC-030031 did not affect spontaneous corneal nerve activity, but it significantly reduced responses to thermal, mechanical, and chemical stimuli. Behavioral tests indicated that HC-030031 reversed corneal mechanical hypersensitivity and alleviated ocular discomfort associated with DED. Additionally, it promoted corneal nerve regeneration, decreased substance P, and reduced inflammation in the cornea. Specifically, it lowered immune cell infiltration and the expression of inflammatory genes such as Ccl2 and Il1Β in the cornea. These findings highlight the key role of TRPA1 nociceptors in modulating corneal neurosensory abnormalities and neurogenic inflammation in DED.