The mucosal surfaces of both eyes are immunologically linked by a neurogenic inflammatory reflex involving TRPV1 and substance P

Abstract

Immunological interdependence between the two eyes has been reported for the cornea and the retina but not for the ocular mucosal surface. Intriguingly, patients frequently report ocular surface-related symptoms in the other eye after unilateral ocular surgery. Here we show how unilateral eye injuries in mice affect the mucosal immune response of the opposite ocular surface. We report that, despite the lack of lymphatic cross-drainage, a neurogenic inflammatory reflex in the contralateral conjunctiva is sufficient to increase, first, epithelial nuclear factor kappa B signaling, then, dendritic cell maturation, and finally, expansion of effector, instead of regulatory, T cells in the draining lymph node, leading to disrupted ocular mucosal tolerance. We also show that damage to ocular surface nerves is required. Using pharmacological inhibitors and agonists, we identified transient receptor potential vanilloid 1 (TRPV1) channel as the receptor sensing tissue damage in the injured eye and substance P released in the opposite ocular surface as the effector of the sympathetic response. Finally, blocking either step prevented subsequent ocular allergic reactions in the opposite eye in a unilateral corneal alkali burn model. This study demonstrates that both ocular surfaces are immunologically linked and suggests potential therapeutic targets for intervention.

Transient tear hyperosmolarity disrupts the neuroimmune homeostasis of the ocular surface and facilitates dry eye onset

“…For nuclear factor (NF)jB p65 quantification, the samples were processed as described previously. 27 For dendritic cell (DC) quantification, samples were incubated overnight at 4°with 2Á5 ug/ml Alexa Fluor 488 anti-mouse I-A/I-E antibody (#107616, BioLegendA), washed twice, and finally incubated with 1 lM ToPro-3 (ThermoFisher Scientific) for 30 min at 4°for nuclear staining. For corneal nerve staining, samples were incubated with 20 mM EDTA at 37°for 1 hr, then incubated overnight at 4°in PBS + Triton X-100 0Á3% + BSA 1% in the presence of 2Á5 ug/ml Alexa Fluor 488 anti-tubulin b3 antibody (#801203, BioLegend), washed twice, and finally labelled with ToPro-3 as for DC quantification.…”

“…For NF-jB p65 quantification, image acquisition and analysis were performed as described previously. 27 For corneal nerve and conjunctival DC image acquisition, a Z-stack scan (0Á5-1 µm step size) was performed from the superficial epithelium to the corneal stroma (one central and three peripheral corneal scans) or the conjunctival lamina propria (threeÀfive non-overlapping scans per sample). For all image analyses, IMAGEJ software was used (http://imagej.nih.gov/ ij/ provided by the National Institutes of Health, Bethesda, MD) by a masked observer.…”

“…Moreover, we have previously shown that this receptor is involved in another model of ocular surface immune disruption. 27 Therefore, we tested its role in THO signalling by adding the instillation of a TRPV1 antagonist along with hypertonic saline. As shown in Fig.…”

“…[24][25][26] Besides, the cornea is densely innervated, and regulatory neuroimmune crosstalk is crucial for ocular surface homeostasis. [27][28][29] Corneal intraepithelial nerves terminate as free nerve endings interspersed between the apical squamous epithelial cells, almost in direct contact with the tear film. 30 In a DED model, desiccating stress rapidly induces a break in the apical corneal epithelial barrier, 31 along with structural and functional alterations in corneal intraepithelial nerves.…”

Allergen-induced dendritic cell migration is controlled through Substance P release by sensory neurons

“…One potential allergen sensor is the sensory nervous system, which is highly 20 concentrated in barrier epithelia, broadly responsive to many different stimuli, and directly activated in vitro by diverse enzymatically active allergens such as bee venom, house dust mites, and papain (Chen and Lariviere, 2010;Reddy and Lerner, 2010;Serhan et al, 2019;Talbot et al, 2016;Trier et al, 2019;Veiga-Fernandes and Mucida, 2016). Sensory neurons have been shown to be closely associated with Langerhans cells in the human epidermis and activation of corneal sensory neurons can lead to DC activation in the contralateral eye (Guzman et al, 2018;Hosoi et al, 1993). Based on this, we hypothesized a two-step model for allergen activation of DCs wherein allergens 5 activate sensory neurons leading to their local release of neuropeptides (Step 1), which then act upon local DCs to promote their migration (Step 2) to the dLN where they can activate naïve T cells to promote Th2 differentiation.…”