TRPV1 SIGNALING FACILITATES AXONAL DEGENERATION OF CORNEAL SENSORY NERVES IN DRY EYE INDEPENDENTLY OF CD4+ T CELLS

PIZZANO, MANUELA; VEREERTBRUGGHEN, ALEXIA; CERNUTTO A; SABBIONE F; KEITELMAN I; SHIROMIZU CM; VERA AGUILAR, DOUGLAS; FEDERICO FUENTES; GIORDANO , M; TREVANI A; GALLETTI J

San Luis

Congreso; LXXI Reunión Anual de la Sociedad Argentina de Inmunología (SAI); 2023

Introduction: Corneal nerve damage causes the most clinically significantsymptoms in dry eye disease (DED) yet its pathophysiology remains poorlyunderstood. We have previously shown that type 1 immunity, and morespecifically, Th1 CD4+ T cells foster corneal neuropathy. Transient receptorpotential vanilloid-1 (TRPV1) channels abound in corneal nerve fibers andrespond to inflammation-derived ligands, which increase in DED. TRPV1overactivation promotes axonal degeneration in vitro but whether it contributes tocorneal neuropathy is unknown. Therefore, here we explored the role of TRPV1in DED-associated corneal nerve damage.Methods: Surgical DED was induced in TRPV1-deficient (TRPV1KO) and wildtype (wt) mice. Corneal nerve function was measured on days 0, 5, and 10 bymechanical and capsaicin sensitivity and eye-closing ratio as an indicator ofspontaneous pain. Nerve and epithelial morphology were assessed by confocalmicroscopy of corneal whole-mounts. Adoptive transfer of CD4+ T cells from bothstrains and pharmacological TRPV1 inhibition in wt mice were also evaluated.Gene expression was measured in the trigeminal ganglion by RT-qPCR.Results: wt and TRPV1KO mice developed comparable ocular desiccation andcorneal epithelial damage. Contrasting with wt mice, corneal mechanosensitivityin TRPV1KO mice did not worsen with disease progression. Capsaicin sensitivityincreased in wt mice with DED, and consistently, wt but not TRPV1KO mice withDED displayed signs of spontaneous pain. Wt mice with DED exhibited nervedegeneration throughout the corneal epithelium whereas TRPV1KO mice onlydeveloped a reduction in the most superficial nerve endings that failed topropagate to the deeper subbasal corneal nerves. Pharmacological blockade ofocular TRPV1 activity reproduced these findings in wt mice with DED. AlthoughTRPV1KO mice with DED had fewer pathogenic Th1 and Th17 CD4+ T cells inthe lymph nodes, conjunctival immune infiltration was comparable betweenstrains. Moreover, CD4+ T cells from wt and TRPV1KO mice with DED wereequally pathogenic when transferred into T cell-deficient mice, confirming thatTRPV1 activity in T cells is not involved in corneal neuropathy. Gene expressionof sensory channels TRPV1, TRPM8, and Piezo2 and pro-regenerative activatingtranscription factor 3 increased in the trigeminal ganglia of wt but not in TRPV1KOmice with DED. By contrast, TNF expression comparably increased in bothstrains.Conclusions: Although ocular desiccation is sufficient to trigger superficialcorneal nerve damage in DED, proximal propagation of axonal degenerationrequires TRPV1 signaling. Conversely, local inflammation sensitizes ocularTRPV1 channels, which are also involved in ocular pain, a key symptom of thedisease. Thus, corneal nerve TRPV1 overactivation constitutes a pathogenicevent in DED-associated corneal neuropathy and a potential therapeutic targetthat is independent of the effect of CD4+ T cells on corneal nerves.