RESUMEN

BACKGROUND: Glaucoma is a leading cause of blindness, affecting retinal ganglion cells (RGCs) and their axons. By 2040, it is likely to affect 110 million people. Neuroinflammation, specifically through the release of proinflammatory cytokines by M1 microglial cells, plays a crucial role in glaucoma progression. Indeed, in post-mortem human studies, pre-clinical models, and ex-vivo models, RGC degeneration has been consistently shown to be linked to inflammation in response to cell death and tissue damage. Recently, Rho kinase inhibitors (ROCKis) have emerged as potential therapies for neuroinflammatory and neurodegenerative diseases. This study aimed to investigate the potential effects of three ROCKis (Y-27632, Y-33075, and H-1152) on retinal ganglion cell (RGC) loss and retinal neuroinflammation using an ex-vivo retinal explant model. METHODS: Rat retinal explants underwent optic nerve axotomy and were treated with Y-27632, Y-33075, or H-1152. The neuroprotective effects on RGCs were evaluated using immunofluorescence and Brn3a-specific markers. Reactive glia and microglial activation were studied by GFAP, CD68, and Iba1 staining. Flow cytometry was used to quantify day ex-vivo 4 (DEV 4) microglial proliferation and M1 activation by measuring the number of CD11b+, CD68+, and CD11b+/CD68+ cells after treatment with control solvent or Y-33075. The modulation of gene expression was measured by RNA-seq analysis on control and Y-33075-treated explants and glial and pro-inflammatory cytokine gene expression was validated by RT-qPCR. RESULTS: Y-27632 and H-1152 did not significantly protect RGCs. By contrast, at DEV 4, 50 µM Y-33075 significantly increased RGC survival. Immunohistology showed a reduced number of Iba1+/CD68+ cells and limited astrogliosis with Y-33075 treatment. Flow cytometry confirmed lower CD11b+, CD68+, and CD11b+/CD68+ cell numbers in the Y-33075 group. RNA-seq showed Y-33075 inhibited the expression of M1 microglial markers (Tnfα, Il-1ß, Nos2) and glial markers (Gfap, Itgam, Cd68) and to reduce apoptosis, ferroptosis, inflammasome formation, complement activation, TLR pathway activation, and P2rx7 and Gpr84 gene expression. Conversely, Y-33075 upregulated RGC-specific markers, neurofilament formation, and neurotransmitter regulator expression, consistent with its neuroprotective effects. CONCLUSION: Y-33075 demonstrates marked neuroprotective and anti-inflammatory effects, surpassing the other tested ROCKis (Y-27632 and H-1152) in preventing RGC death and reducing microglial inflammatory responses. These findings highlight its potential as a therapeutic option for glaucoma.

Asunto(s)

Fármacos Neuroprotectores , Piridinas , Células Ganglionares de la Retina , Quinasas Asociadas a rho , Animales , Piridinas/farmacología , Quinasas Asociadas a rho/metabolismo , Quinasas Asociadas a rho/antagonistas & inhibidores , Fármacos Neuroprotectores/farmacología , Ratas , Células Ganglionares de la Retina/efectos de los fármacos , Células Ganglionares de la Retina/patología , Células Ganglionares de la Retina/metabolismo , Enfermedades Neuroinflamatorias/tratamiento farmacológico , Enfermedades Neuroinflamatorias/metabolismo , Retina/efectos de los fármacos , Retina/patología , Retina/metabolismo , Amidas/farmacología , 1-(5-Isoquinolinesulfonil)-2-Metilpiperazina/análogos & derivados , 1-(5-Isoquinolinesulfonil)-2-Metilpiperazina/farmacología , Ratas Sprague-Dawley , Neuroprotección/efectos de los fármacos , Neuroprotección/fisiología , Microglía/efectos de los fármacos , Microglía/metabolismo , Microglía/patología , Inhibidores de Proteínas Quinasas/farmacología , Masculino , Traumatismos del Nervio Óptico/tratamiento farmacológico , Traumatismos del Nervio Óptico/patología , Traumatismos del Nervio Óptico/metabolismo , Isoquinolinas , Sulfonamidas

RESUMEN

Introduction: Damage to the corneal nerves can result in discomfort and chronic pain, profoundly impacting the quality of life of patients. Development of novel in vitro method is crucial to better understand corneal nerve regeneration and to find new treatments for the patients. Existing in vitro models often overlook the physiology of primary sensory neurons, for which the soma is separated from the nerve endings. Methods: To overcome this limitation, our novel model combines a compartmentalized microfluidic culture of trigeminal ganglion neurons from adult mice with live-imaging and automated 3D image analysis offering robust way to assess axonal regrowth after axotomy. Results: Physical axotomy performed by a two-second aspiration led to a reproducible 70% axonal loss and altered the phenotype of the neurons, increasing the number of substance P-positive neurons 72 h post-axotomy. To validate our new model, we investigated axonal regeneration after exposure to pharmacological compounds. We selected various targets known to enhance or inhibit axonal regrowth and analyzed their basal expression in trigeminal ganglion cells by scRNAseq. NGF/GDNF, insulin, and Dooku-1 (Piezo1 antagonist) enhanced regrowth by 81, 74 and 157%, respectively, while Yoda-1 (Piezo1 agonist) had no effect. Furthermore, SARM1-IN-2 (Sarm1 inhibitor) inhibited axonal regrowth, leading to only 6% regrowth after 72 h of exposure (versus 34% regrowth without any compound). Discussion: Combining compartmentalized trigeminal neuronal culture with advanced imaging and analysis allowed a thorough evaluation of the extent of the axotomy and subsequent axonal regrowth. This innovative approach holds great promise for advancing our understanding of corneal nerve injuries and regeneration and ultimately improving the quality of life for patients suffering from sensory abnormalities, and related conditions.

RESUMEN

Part of the lacrimal functional unit, the cornea protects the ocular surface from numerous environmental aggressions and xenobiotics. Toxicological evaluation of compounds remains a challenge due to complex interactions between corneal nerve endings and epithelial cells. To this day, models do not integrate the physiological specificity of corneal nerve endings and are insufficient for the detection of low toxic effects essential to anticipate Toxicity-Induced Dry Eye (TIDE). Using high-content imaging tool, we here characterize toxicity-induced cellular alterations using primary cultures of mouse trigeminal sensory neurons and corneal epithelial cells in a compartmentalized microfluidic chip. We validate this model through the analysis of benzalkonium chloride (BAC) toxicity, a well-known preservative in eyedrops, after a single (6h) or repeated (twice a day for 15 min over 5 days) topical 5.10-4% BAC applications on the corneal epithelial cells and nerve terminals. In combination with high-content image analysis, this advanced microfluidic protocol reveal specific and tiny changes in the epithelial cells and axonal network as well as in trigeminal cells, not directly exposed to BAC, with ATF3/6 stress markers and phospho-p44/42 cell activation marker. Altogether, this corneal neuroepithelial chip enables the evaluation of toxic effects of ocular xenobiotics, distinguishing the impact on corneal sensory innervation and epithelial cells. The combination of compartmentalized co-culture/high-content imaging/multiparameter analysis opens the way for the systematic analysis of toxicants but also neuroprotective compounds.

Asunto(s)

Síndromes de Ojo Seco , Microfluídica , Animales , Ratones , Córnea , Compuestos de Benzalconio/toxicidad , Conservadores Farmacéuticos/toxicidad , Síndromes de Ojo Seco/inducido químicamente , Síndromes de Ojo Seco/diagnóstico

RESUMEN

Dry eye disease (DED) is a multifactorial disorder in which the eyes respond to minor stimuli with abnormal sensations, such as dryness, blurring, foreign body sensation, discomfort, irritation, and pain. Corneal pain, as one of DED's main symptoms, has gained recognition due to its increasing prevalence, morbidity, and the resulting social burden. The cornea is the most innervated tissue in the body, and the maintenance of corneal integrity relies on a rich density of nociceptors, such as polymodal nociceptor neurons, cold thermoreceptor neurons, and mechano-nociceptor neurons. Their sensory responses to different stimulating forces are linked to the specific expression of transient receptor potential (TRP) channels. TRP channels are a group of unique ion channels that play important roles as cellular sensors for various stimuli. These channels are nonselective cation channels with variable Ca2+ selectivity. TRP homologs are a superfamily of 28 different members that are subdivided into 7 different subfamilies based on differences in sequence homology. Many of these subtypes are expressed in the eye on both neuronal and non-neuronal cells, where they affect various stress-induced regulatory responses essential for normal vision maintenance. This article reviews the current knowledge about the expression, function, and regulation of TRPs in ocular surface tissues. We also describe their implication in DED and ocular pain. These findings contribute to evidence suggesting that drug-targeting TRP channels may be of therapeutic benefit in the clinical setting of ocular pain.

RESUMEN

PURPOSE: To study changes in the subbasal nerve plexus by In vivo confocal microscopy (IVCM) in Sjögren's Syndrome (SS) with or without associated Small Fiber Neuropathy (SFN), in order to prevent diagnostic delay. METHODS: Seventy-one patients with SS, including 19 with associated SFN, 20 healthy volunteers and 20 patients with Meibomian gland dysfunction (MGD) were included in this retrospective case-control study. IVCM was used to investigate subbasal nerve plexus density and morphology. RESULTS: Corneal sensitivity as evaluated with the Cochet-Bonnet aesthesiometer was significantly reduced in the SS group versus the control group (P = 0.026) and the MGD group (P = 0.037). The number of inflammatory cells was significantly increased in the SS group to 86.2 ± 82.1 cells/mm2 compared to the control group (P < 0.001). The density of the subbasal nerve plexus was significantly reduced to 16.7 ± 6.5 mm/mm2 in the SS group compared to the control group (P < 0.005) and the MGD group (P = 0.042). The tortuosity of the nerves in the SS group was significantly increased compared to the control group (P < 0.001) and the MGD group (P = 0.025). The average number of subbasal nerve plexus neuromas was significantly increased in the SS group compared to the control group (P = 0.001), with a significant increase in the average number of neuromas in SS patients with associated SFN compared to SS patients without SFN (P = 0.008). CONCLUSION: IVCM can be useful to detect corneal nerve changes in SS patients and may allow earlier diagnosis of the disease and to consider new therapeutic approaches.

Asunto(s)

Neuroma , Síndrome de Sjögren , Neuropatía de Fibras Pequeñas , Estudios de Casos y Controles , Córnea/inervación , Diagnóstico Tardío , Humanos , Microscopía Confocal , Neuroma/complicaciones , Nervio Oftálmico , Estudios Retrospectivos , Síndrome de Sjögren/complicaciones , Síndrome de Sjögren/diagnóstico , Neuropatía de Fibras Pequeñas/complicaciones

RESUMEN

The functional imaging within the trigeminal ganglion (TG) is highly challenging due to its small size and deep localization. This study combined a methodological framework able to dive into the rat trigeminal nociceptive system by jointly providing 1) imaging of the TG blood vasculature at microscopic resolution, and 2) the measurement of hemodynamic responses evoked by orofacial stimulations in anesthetized rats. Despite the small number of sensory neurons within the TG, functional ultrasound imaging was able to image and quantify a strong and highly localized hemodynamic response in the ipsilateral TG, evoked not only by mechanical or chemical stimulations of corneal nociceptive fibers, but also by cutaneous mechanical stimulations of the ophthalmic and maxillary orofacial regions using a von Frey hair. The in vivo quantitative imaging of the TG's vasculature using ultrasound localization microscopy combined with in toto labelling reveals particular features of the vascularization of the area containing the sensory neurons, that are likely the origin of this strong vaso-trigeminal response. This innovative imaging approach opens the path for future studies on the mechanisms underlying changes in trigeminal local blood flow and evoked hemodynamic responses, key mechanisms for the understanding and treatment of debilitating trigeminal pain conditions.

Asunto(s)

Microscopía , Ganglio del Trigémino , Animales , Cara , Ratas , Ratas Sprague-Dawley , Ganglio del Trigémino/diagnóstico por imagen , Ultrasonografía

RESUMEN

The cornea, an anterior ocular tissue that notably serves to protect the eye from external insults and refract light, requires constant epithelium renewal and efficient healing following injury to maintain ocular homeostasis. Although several key cell populations and molecular pathways implicated in corneal wound healing have already been thoroughly investigated, insufficient/impaired or excessive corneal wound healing remains a major clinical issue in ophthalmology, and new avenues of research are still needed to further improve corneal wound healing. Because of its implication in numerous cellular/tissular homeostatic processes and oxidative stress, there is growing evidence of the role of Hedgehog signaling pathway in physiological and pathological corneal wound healing. Reviewing current scientific evidence, Hedgehog signaling and its effectors participate in corneal wound healing mainly at the level of the corneal and limbal epithelium, where Sonic Hedgehog-mediated signaling promotes limbal stem cell proliferation and corneal epithelial cell proliferation and migration following corneal injury. Hedgehog signaling could also participate in corneal epithelial barrier homeostasis and in pathological corneal healing such as corneal injury-related neovascularization. By gaining a better understanding of the role of this double-edged sword in physiological and pathological corneal wound healing, fascinating new research avenues and therapeutic strategies will undoubtedly emerge.

Asunto(s)

Lesiones de la Cornea , Epitelio Corneal , Córnea/metabolismo , Lesiones de la Cornea/metabolismo , Epitelio Corneal/metabolismo , Proteínas Hedgehog/metabolismo , Humanos , Cicatrización de Heridas/fisiología

RESUMEN

BACKGROUND: Glaucoma is a blinding degenerative neuropathy in which the death of retinal ganglion cells (RGCs) causes progressive loss of visual field and eventually vision. Neuroinflammation appears to be a key event in the progression and spread of this disease. Thus, microglial immunomodulation represents a promising therapeutic approach in which mesenchymal stem cells (MSCs) might play a crucial role. Their neuroprotective and regenerative potentials have already raised hope in animal models. Yet no definitive treatment has been developed, and some safety concerns have been reported in human trials. In the present study, we investigated the neuroprotective and immunomodulatory properties as well as the safety of MSCs in an ex vivo neuroretina explant model. METHODS: Labeled rat bone marrow MSCs were placed in coculture with rat retinal explants after optic nerve axotomy. We analyzed the neuroprotective effect of MSCs on RGC survival by immunofluorescence using RBPMS, Brn3a, and NeuN markers. Gliosis and retinal microglial activation were measured by using GFAP, CD68, and ITGAM mRNA quantification and GFAP, CD68, and Iba1 immunofluorescence stainings. We also analyzed the mRNA expression of both 'M1' or classically activated state inflammatory cytokines (TNFα, IL1ß, and IL6), and 'M2' or alternatively activated state microglial markers (Arginase 1, IL10, CD163, and TNFAIP6). RESULTS: The number of RGCs was significantly higher in retinal explants cultured with MSCs compared to the control group at Day 7 following the optic nerve axotomy. Retinal explants cultured with MSCs showed a decrease in mRNA markers of gliosis and microglial activations, and immunostainings revealed that GFAP, Iba1, and CD68 were limited to the inner layers of the retina compared to controls in which microglial activation was observed throughout the retina. In addition, MSCs inhibited the M1 phenotype of the microglia. However, edema of the explants was observed in presence of MSCs, with an increase in fibronectin labeling at the surface of the explant corresponding to an epiretinal membrane-like phenotype. CONCLUSION: Using an ex vivo neuroretina model, we demonstrated a neuroprotective and immunomodulatory effect of MSCs on RGCs. Unfortunately, the presence of MSCs also led to explant edema and epiretinal membrane formation, as described in human trials. Using the MSC secretome might offer the beneficial effects of MSCs without their potential adverse effects, through paracrine signaling.

Asunto(s)

Células Madre Mesenquimatosas , Células Ganglionares de la Retina , Animales , Modelos Animales de Enfermedad , Inmunomodulación , Células Madre Mesenquimatosas/metabolismo , Neuroprotección/fisiología , Ratas , Retina/metabolismo , Células Ganglionares de la Retina/metabolismo

RESUMEN

INTRODUCTION: Sensitive eyes are commonly reported by patients, but there are very few epidemiological studies on this disorder. The aim of this study was the evaluation of the self-reported frequency of sensitive eyes and the association with sensitive skin. METHODS: A survey was performed on a representative sample of the population aged more than 18 years in five different countries (Brazil, China, France, Russia, and the USA). All participants answered a questionnaire on sociodemographic characteristics; skin phototype; eye color; tobacco consumption; exposure to sunlight, air pollution, or having pets; and sleep disorders. The presence of sensitive eyes, eyelids, or skin and their triggering factors were assessed with specific questions. RESULTS: A total of 10,743 individuals (5,285 men and 5,458 women) were included in the study. Among them, 48.2% reported having sensitive skin and 46.0% reported having sensitive eyes. Sensitive eyes were more frequently reported by women (46.5%) than men (39.4%) in all countries, with the exception of China. The presence of sensitive eyes was more frequent if skin was very sensitive. More than half of subjects with sensitive eyes declared that their triggering factors were exposure to sunlight, dust, touch pad screens, or computer screens or dry air. They were more exposed to pollution and tobacco. Their phototype (including eye color) was lighter. DISCUSSION/CONCLUSION: This large study shows that self-declared sensitive eyes are very frequent and commonly associated with sensitive skin. Triggering factors of sensitive eyes are more specific.

Asunto(s)

Enfermedades de la Piel , China/epidemiología , Femenino , Francia/epidemiología , Humanos , Masculino , Piel , Luz Solar

RESUMEN

The 21st century has seen a steadily increasing social awareness of animal suffering, with increased attention to ethical considerations. Developing new integrated approaches to testing and assessment (IATA) strategies is an Organisation for Economic Co-operation and Development (OECD) goal to reduce animal testing. Currently, there is a lack of alternative models to test for ocular surface toxicity (aside from irritation) in lieu of the Draize eye irritation test (OECD guideline No. 405) performed in rabbits. Five alternative in vitro or ex vivo methods have been validated to replace this reference test, but only in combination. However, pathologies like Toxicity-Induced Dry Eye (TIDE), cataract, glaucoma, and neuropathic pain can occur after exposure to a pharmaceutical product or chemical and therefore need to be anticipated. To do so, new models of lacrimal glands, lens, and neurons innervating epithelia are required. These models must take into account real-life exposure (dose, time, and tear film clearance). The scientific community is working hard to develop new, robust, alternative, in silico, and in vitro models, while attempting to balance ethics and availability of biological materials. This review provides a broad overview of the validated methods for analyzing ocular irritation and those still used by some industries, as well as promising models that need to be optimized according to the OECD. Finally, we give an overview of recently developed innovative models, which could become new tools in the evaluation of ocular surface toxicity within the scope of IATAs.

Asunto(s)

Alternativas a las Pruebas en Animales , Irritantes , Animales , Ojo , Irritantes/toxicidad , Organización para la Cooperación y el Desarrollo Económico , Conejos , Pruebas de Toxicidad/métodos

RESUMEN

Background: This study aimed to compare the corneal nerve structural abnormalities detected using in vivo confocal microscopy (IVCM) in patients with neuropathic corneal pain (NCP) secondary to primary meibomian gland dysfunction (MGD) or autoimmune dry eye (AIDE). Methods: A two-stage retrospective nested case-control study was conducted. First, data from patients with either MGD or AIDE were assessed, selecting only cases with no corneal pain (VAS = 0) or severe pain (VAS ≥ 8). Ocular signs and symptoms of the 238 selected patients were compared between painful and painless cases. Next, painful patients with no corneal damage (Oxford score ≤ 1) were selected within each study group, defining the cases with NCP (i.e., "pain without stain"). IVCM images from all groups were compared with prospectively-recruited healthy controls, focusing on dendritiform cell density and nerve abnormalities (density, tortuosity, microneuromas). Results: AIDE patients had more ocular signs/symptoms than MGD patients. Compared with healthy controls, AIDE-related NCP patients showed increased nerve tortuosity and number of neuromas, whereas MGD-related NCP patients had reduced nerve density and increased number, perimeter, and area of microneuromas. Microneuromas were also observed in healthy controls. Furthermore, a higher number of microneuromas was found in MGD-related NCP compared to AIDE-related NCP or painless MGD. Conclusions: MGD-related NCP was associated with significantly more corneal nerve abnormalities than AIDE-related NCP or healthy controls. Although IVCM can be useful to detect NCP-related corneal nerve changes in such patients, the diagnosis of dry eye disease-related NCP will require an association of several IVCM-based criteria without relying solely on the presence of microneuromas.

RESUMEN

The action potential of most vertebrate neurons initiates in the axon initial segment (AIS) and is then transmitted to the soma where it is regenerated by somatodendritic sodium channels. For successful transmission, the AIS must produce a strong axial current, so as to depolarize the soma to the threshold for somatic regeneration. Theoretically, this axial current depends on AIS geometry and Na+ conductance density. We measured the axial current of mouse retinal ganglion cells using whole cell recordings with post hoc AIS labeling. We found that this current is large, implying high Na+ conductance density, and carries a charge that covaries with capacitance so as to depolarize the soma by ∼30 mV. Additionally, we observed that the axial current attenuates strongly with depolarization, consistent with sodium channel inactivation, but temporally broadens so as to preserve the transmitted charge. Thus, the AIS appears to be organized so as to reliably backpropagate the axonal action potential.NEW & NOTEWORTHY We measured the axial current produced at spike initiation by the axon initial segment of mouse retinal ganglion cells. We found that it is a large current, requiring high sodium channel conductance density, which covaries with cell capacitance so as to ensure a ∼30 mV depolarization. During sustained depolarization the current attenuated, but it broadened to preserve somatic depolarization. Thus, properties of the initial segment are adjusted to ensure backpropagation of the axonal action potential.

Asunto(s)

Potenciales de Acción/fisiología , Axones/fisiología , Cuerpo Celular/fisiología , Dendritas/fisiología , Células Ganglionares de la Retina/fisiología , Animales , Animales Recién Nacidos , Ratones , Ratones Endogámicos C57BL , Canales de Sodio/fisiología

RESUMEN

BACKGROUND: Dry eye disease (DED) is a multifactorial disease of the ocular surface accompanied by neurosensory abnormalities. Here, we evaluated the effectiveness of transient receptor potential vanilloid-1 (TRPV1) blockade to alleviate ocular pain, neuroinflammation, and anxiety-like behavior associated with severe DED. METHODS: Chronic DED was induced by unilateral excision of the Harderian and extraorbital lacrimal glands of adult male mice. Investigations were conducted at 21 days after surgery. The mRNA levels of TRPV1, transient receptor potential ankyrin-1 (TRPA1), and acid-sensing ion channels 1 and 3 (ASIC1 and ASIC3) in the trigeminal ganglion (TG) were evaluated by RNAscope in situ hybridization. Multi-unit extracellular recording of ciliary nerve fiber activity was used to monitor spontaneous and stimulated (cold, heat, and acid) corneal nerve responsiveness in ex vivo eye preparations. DED mice received topical instillations of the TRPV1 antagonist (capsazepine) twice a day for 2 weeks from d7 to d21 after surgery. The expression of genes involved in neuropathic and inflammatory pain was evaluated in the TG using a global genomic approach. Chemical and mechanical corneal nociception and spontaneous ocular pain were monitored. Finally, anxiety-like behaviors were assessed by elevated plus maze and black and white box tests. RESULTS: First, in situ hybridization showed DED to trigger upregulation of TRPV1, TRPA1, ASIC1, and ASIC3 mRNA in the ophthalmic branch of the TG. DED also induced overexpression of genes involved in neuropathic and inflammatory pain in the TG. Repeated instillations of capsazepine reduced corneal polymodal responsiveness to heat, cold, and acidic stimulation in ex vivo eye preparations. Consistent with these findings, chronic capsazepine instillation inhibited the upregulation of genes involved in neuropathic and inflammatory pain in the TG of DED animals and reduced the sensation of ocular pain, as well as anxiety-like behaviors associated with severe DED. CONCLUSION: These data provide novel insights on the effectiveness of TRPV1 antagonist instillation in alleviating abnormal corneal neurosensory symptoms induced by severe DED, opening an avenue for the repositioning of this molecule as a potential analgesic treatment for patients suffering from chronic DED.

Asunto(s)

Capsaicina/análogos & derivados , Córnea , Síndromes de Ojo Seco/metabolismo , Dolor/etiología , Canales Catiónicos TRPV/antagonistas & inhibidores , Animales , Capsaicina/farmacología , Síndromes de Ojo Seco/complicaciones , Masculino , Ratones , Ratones Endogámicos C57BL , Síndrome

RESUMEN

The cornea is the most densely innervated and sensitive tissue in the body. The cornea is exclusively innervated by C- and A-delta fibers, including mechano-nociceptors that are triggered by noxious mechanical stimulation, polymodal nociceptors that are excited by mechanical, chemical, and thermal stimuli, and cold thermoreceptors that are activated by cooling. Noxious stimulations activate corneal nociceptors whose cell bodies are located in the trigeminal ganglion (TG) and project central axons to the trigeminal brainstem sensory complex. Ocular pain, in particular, that driven by corneal nerves, is considered to be a core symptom of inflammatory and traumatic disorders of the ocular surface. Ocular surface injury affecting corneal nerves and leading to inflammatory responses can occur under multiple pathological conditions, such as chemical burn, persistent dry eye, and corneal neuropathic pain as well as after some ophthalmological surgical interventions such as photorefractive surgery. This review depicts the morphological and functional changes of corneal nerve terminals following corneal damage and dry eye disease (DED), both ocular surface conditions leading to sensory abnormalities. In addition, the recent fundamental and clinical findings of the importance of peripheral and central neuroimmune interactions in the development of corneal hypersensitivity are discussed. Next, the cellular and molecular changes of corneal neurons in the TG and central structures that are driven by corneal nerve abnormalities are presented. A better understanding of the corneal nerve abnormalities as well as neuroimmune interactions may contribute to the identification of a novel therapeutic targets for alleviating corneal pain.

RESUMEN

Dry eye disease (DED) is commonly associated with ocular surface inflammation and pain. In this study, we evaluated the effectiveness of repeated instillations of transient receptor potential melastatin 8 (TRPM8) ion channel antagonist M8-B on a mouse model of severe DED induced by the excision of extra-orbital lacrimal and Harderian glands. M8-B was topically administered twice a day from day 7 until day 21 after surgery. Cold and mechanical corneal sensitivities and spontaneous ocular pain were monitored at day 21. Ongoing and cold-evoked ciliary nerve activities were next evaluated by electrophysiological multi-unit extracellular recording. Corneal inflammation and expression of genes related to neuropathic pain and inflammation were assessed in the trigeminal ganglion. We found that DED mice developed a cold allodynia consistent with higher TRPM8 mRNA expression in the trigeminal ganglion (TG). Chronic M8-B instillations markedly reversed both the corneal mechanical allodynia and spontaneous ocular pain commonly associated with persistent DED. M8-B instillations also diminished the sustained spontaneous and cold-evoked ciliary nerve activities observed in DED mice as well as inflammation in the cornea and TG. Overall, our study provides new insight into the effectiveness of TRPM8 blockade for alleviating corneal pain syndrome associated with severe DED, opening a new avenue for ocular pain management.

Asunto(s)

Antiinflamatorios/farmacología , Síndromes de Ojo Seco/tratamiento farmacológico , Hiperalgesia/tratamiento farmacológico , Neuralgia/tratamiento farmacológico , Ácidos Nicotínicos/farmacología , Canales Catiónicos TRPM/genética , Tiofenos/farmacología , Administración Oftálmica , Animales , Antiinflamatorios/uso terapéutico , Receptor 1 de Quimiocinas CX3C/genética , Receptor 1 de Quimiocinas CX3C/metabolismo , Quimiocina CCL2/genética , Quimiocina CCL2/metabolismo , Frío , Córnea/efectos de los fármacos , Córnea/metabolismo , Córnea/fisiopatología , Modelos Animales de Enfermedad , Síndromes de Ojo Seco/complicaciones , Síndromes de Ojo Seco/genética , Síndromes de Ojo Seco/metabolismo , Potenciales Evocados Somatosensoriales/efectos de los fármacos , Ganglios Parasimpáticos/efectos de los fármacos , Ganglios Parasimpáticos/metabolismo , Ganglios Parasimpáticos/fisiopatología , Regulación de la Expresión Génica , Glándula de Harder/cirugía , Hiperalgesia/etiología , Hiperalgesia/genética , Hiperalgesia/metabolismo , Interleucina-18/genética , Interleucina-18/metabolismo , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Aparato Lagrimal/cirugía , Masculino , Ratones , Ratones Endogámicos C57BL , Neuralgia/etiología , Neuralgia/genética , Neuralgia/metabolismo , Prostaglandina-E Sintasas/genética , Prostaglandina-E Sintasas/metabolismo , Canales Catiónicos TRPM/antagonistas & inhibidores , Canales Catiónicos TRPM/metabolismo , Ganglio del Trigémino/efectos de los fármacos , Ganglio del Trigémino/metabolismo , Ganglio del Trigémino/fisiopatología

RESUMEN

Corneal pain is considered to be a core symptom of ocular surface disruption and inflammation. The management of this debilitating condition is still a therapeutic challenge. Recent evidence supports a role of the opioid system in the management of corneal nociception. However, the functional involvement of the mu opioid receptor (MOR) underlying this analgesic effect is not known. We first investigated the expression of the MOR in corneal nerve fibers and trigeminal ganglion (TG) neurons in control mice and a mouse model of corneal inflammatory pain. We then evaluated the anti-nociceptive and electrophysiological effects of DAMGO ([D-Ala2,N-Me-Phe4,Gly5-ol] enkephalin), a MOR-selective ligand. MOR immunoreactivity was detected in corneal nerve fibers and primary afferent neurons of the ophthalmic branch of the TG of naive mice. MOR expression was significantly higher in both structures under conditions of inflammatory corneal pain. Topical ocular administration of DAMGO strongly reduced both the mechanical (von Frey) and chemical (capsaicin) corneal hypersensitivity associated with inflammatory ocular pain. Repeated instillations of DAMGO also markedly reversed the elevated spontaneous activity of the ciliary nerve and responsiveness of corneal polymodal nociceptors that were observed in mice with corneal pain. Finally, these DAMGO-induced behavioral and electrophysiological responses were totally blunted by the topical application of naloxone methiodide, an opioid receptor antagonist. Overall, these results provide evidence that topical pharmacological MOR activation may constitute a therapeutic target for the treatment of corneal pain and improve corneal nerve function to alleviate chronic pain.

Asunto(s)

Analgésicos Opioides/farmacología , Encefalina Ala(2)-MeFe(4)-Gli(5)/farmacología , Dolor Ocular/tratamiento farmacológico , Receptores Opioides mu/agonistas , Administración Oftálmica , Analgésicos Opioides/administración & dosificación , Animales , Córnea/efectos de los fármacos , Córnea/inervación , Córnea/patología , Enfermedades de la Córnea/tratamiento farmacológico , Enfermedades de la Córnea/patología , Modelos Animales de Enfermedad , Encefalina Ala(2)-MeFe(4)-Gli(5)/administración & dosificación , Inflamación/tratamiento farmacológico , Inflamación/patología , Masculino , Ratones , Ratones Endogámicos C57BL

RESUMEN

Wallerian degeneration (WD) is a process of autonomous distal degeneration of axons upon injury. Macrophages (MPs) of the peripheral nervous system (PNS) are the main cellular agent controlling this process. Some evidence suggests that resident PNS-MPs along with MPs of hematogenous origin may be involved, but whether these two subsets exert distinct functions is unknown. Combining MP-designed fluorescent reporter mice and coherent anti-Stokes Raman scattering (CARS) imaging of the sciatic nerve, we deciphered the spatiotemporal choreography of resident and recently recruited MPs after injury and unveiled distinct functions of these subsets, with recruited MPs being responsible for efficient myelin stripping and clearance and resident MPs being involved in axonal regrowth. This work provides clues to tackle selectively cellular processes involved in neurodegenerative diseases.

Asunto(s)

Macrófagos/inmunología , Degeneración Walleriana/diagnóstico por imagen , Degeneración Walleriana/inmunología , Animales , Axones/fisiología , Modelos Animales de Enfermedad , Femenino , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Vaina de Mielina/fisiología , Microscopía Óptica no Lineal , Remielinización/genética , Nervio Ciático/diagnóstico por imagen , Nervio Ciático/inmunología , Nervio Ciático/lesiones , Transcriptoma

RESUMEN

Glaucoma is one of the leading causes of irreversible blindness in the world and remains a major public health problem. To date, incomplete knowledge of this disease's pathophysiology has resulted in current therapies (pharmaceutical or surgical) unfortunately having only a slowing effect on disease progression. Recent research suggests that glaucomatous optic neuropathy is a disease that shares common neuroinflammatory mechanisms with "classical" neurodegenerative pathologies. In addition to the death of retinal ganglion cells (RGCs), neuroinflammation appears to be a key element in the progression and spread of this disease. Indeed, early reactivity of glial cells has been observed in the retina, but also in the central visual pathways of glaucoma patients and in preclinical models of ocular hypertension. Moreover, neuronal lesions are not limited to retinal structure, but also occur in central visual pathways. This review summarizes and puts into perspective the experimental and clinical data obtained to date to highlight the need to develop neuroprotective and immunomodulatory therapies to prevent blindness in glaucoma patients.

Asunto(s)

Glaucoma/fisiopatología , Inflamación/complicaciones , Enfermedades del Nervio Óptico/fisiopatología , Animales , Modelos Animales de Enfermedad , Humanos

RESUMEN

The nervous and immune systems communicate with one another and jointly influence functional responses. To highlight the many advances on this hot topic, Brain, Behavior, and Immunity conceptualized a Special Issue entitled "Dialing in the Dialogue Between Inflammation and the Brain." Recent advances and exciting developments in understanding communication pathways between the brain and the immune system during both physiological and pathological insults are highlighted.

Asunto(s)

Encéfalo , Inflamación , Humanos , Sistema Inmunológico