Inflammation-related molecules in tears of patients with chronic ocular pain and dry eye disease

Analyze interleukin-1β, interleukin-6, and tumor necrosis factor-α levels in dry eye and the therapeutic effect of cyclosporine A

BACKGROUND

Dry eye is a common eye disease. Artificial tears supplements are widely used for the treatment of dry eyes. However, multiple adverse effects have been observed in patients receiving long-term treatment with artificial tears, which may affect the therapeutic effect.

AIM

To analyze the characteristics of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) levels in patients with dry eye and the therapeutic effect of artificial tears combined with cyclosporine A.

METHODS

A total of 124 dry eye patients treated at The First People’s Hospital of Xining from April 2020 to April 2022 were selected as the observation group, while 20 healthy individuals served as the control group during the same period. Levels of inflammatory markers, including IL-1β, IL-6, and TNF-α, were analyzed. The observation group was further divided into a study group and a control group, each consisting of 62 patients. The control group received artificial tears, whereas the study group received a combination of artificial tears and cyclosporine A. Inflammatory markers, Schirmer’s test (SIT), tear break-up time (TBUT), corneal fluorescein staining (CFS), National Eye Institute Visual Function Questionnaire-25 (NEI-VFQ-25) scores, and adverse events (AEs) were compared between the two groups.

RESULTS

The observation group exhibited significantly elevated serum levels of IL-1β, IL-6, and TNF-α in comparison to the healthy group. Following treatment, the study group demonstrated substantial reductions in IL-1β, IL-6, and TNF-α levels relative to the control group. Moreover, after treatment, the study group experienced a marked decrease in CFS scores and significant increases in both SIT and BUT levels when compared to the control group. Additionally, significant improvements were observed in the primary symptom of dry eye and secondary symptoms such as photophobia, foreign body sensation, fatigue, red eye, and burning sensation within the study group. Furthermore, post-treatment NEI-VFQ-25 scores across all dimensions exhibited significant enhancements in the study group compared to the control group (P < 0.05). It is noteworthy that significant AEs were reported in both groups throughout the treatment period.

CONCLUSION

Cyclosporine A combined with artificial tears is effective in treating dry eye, yielding enhanced outcomes by improving SIT and TBUT levels, reducing CFS scores, and ameliorating vision-related quality of life.

Neuropathic Corneal Pain: Tear Proteomic and Neuromediator Profiles, Imaging Features, and Clinical Manifestations

PURPOSE

To investigate the tear proteomic and neuromediator profiles, in vivo confocal microscopy (IVCM) imaging features, and clinical manifestations in neuropathic corneal pain (NCP) patients.

DESIGN

Cross-sectional study.

METHODS

A total of 20 NCP patients and 20 age-matched controls were recruited. All subjects were evaluated by corneal sensitivity, Schirmer test, tear break-up time, and corneal and ocular surface staining, Ocular Surface Disease Index and Ocular Pain Assessment Survey questionnaires were administered, as well as IVCM examinations for corneal nerves, microneruomas, and epithelial and dendritic cells. Tears were collected for neuromediator and proteomic analysis using enzyme-linked immunosorbent assay and data-independent acquisition mass spectrometry.

RESULTS

Burning and sensitivity to light were the 2 most common symptoms in NCP. A total of 188 significantly dysregulated proteins, such as elevated metallothionein-2, creatine kinases B-type, vesicle-associated membrane protein 2, neurofilament light polypeptide, and myelin basic protein, were identified in the NCP patients. The top 10 dysregulated biological pathways in NCP include neurotoxicity, axonal signaling, wound healing, neutrophil degradation, apoptosis, thrombin signaling mitochondrial dysfunction, and RHOGDI and P70S6K signaling pathways. Compared to controls, the NCP cohort presented with significantly decreased corneal sensitivity (P < .001), decreased corneal nerve fiber length (P = .003), corneal nerve fiber density (P = .006), and nerve fiber fractal dimension (P = .033), as well as increased corneal nerve fiber width (P = .002), increased length, total area and perimeter of microneuromas (P < .001, P < .001, P = .019), smaller corneal epithelial size (P = .017), and higher nerve growth factor level in tears (P = .006).

CONCLUSIONS

These clinical manifestations, imaging features, and molecular characterizations would contribute to the diagnostics and potential therapeutic targets for NCP.

Analysis of the mucosal chemokines CCL28, CXCL14, and CXCL17 in dry eye disease: An in vitro and clinical investigation

Mucosal chemokines have antimicrobial properties and play an important role in mucosal immunity. However, little is known about their expression on the ocular surface. This study aimed to analyze the expression of the mucosal chemokines CCL28, CXCL14 and CXCL17 in corneal and conjunctival epithelial cells under in vitro dry eye (DE) conditions, and in conjunctival samples from healthy subjects and DE patients. Human corneal epithelial cells (HCE) and immortalized human conjunctival epithelial cells (IM-HConEpiC) were incubated under hyperosmolar (400-500 mOsM) or inflammatory (TNF-α 25 ng/mL) conditions for 6 h and 24 h to measure CCL28, CXCL14, and CXCL17 gene expression by RT-PCR and their secretion by immunobead-based analysis (CCL28, CXCL14) and ELISA (CXCL17). Additionally, twenty-seven DE patients and 13 healthy subjects were included in this study. DE-related questionnaires (OSDI, mSIDEQ and NRS) evaluated symptomatology. Ocular surface integrity was assessed using vital staining. Tactile sensitivity was measured with Cochet-Bonnet esthesiometer, and mechanic and thermal (heat and cold) sensitivity using Belmonte's non-contact esthesiometer. Subbasal nerve plexus and dendritic cell density were analyzed by in vivo confocal microscopy. Conjunctival cells from participants were collected by impression cytology to measure mucosal chemokines gene expression by RT-PCR. Our results showed that HCE and IM-HConEpiC cells increased CCL28, CXCL14, and CXCL17 secretion under hyperosmolar conditions. The gene expression of CCL28 was significantly upregulated in conjunctival samples from DE patients. CCL28 expression correlated positively with symptomatology, corneal staining, heat sensitivity threshold, and dendritic cell density. CXCL14 expression correlated positively with age, ocular pain, conjunctival staining, tactile sensitivity, and image reflectivity. CXCL17 expression correlated positively with corneal staining. These results suggest that corneal and conjunctival epithelial cells could be a source of CCL28, CXCL14, and CXCL17 on the ocular surface and that CCL28 might be involved in DE pathogenesis.

Analysis of Clinical Characteristics and Neuropeptides in Patients with Dry Eye with and without Chronic Ocular Pain after FS-LASIK

INTRODUCTION

Chronic ocular pain, particularly prevalent in patients with dry eye disease and post-femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) surgery, presents with unclear clinical characteristics and an undefined pathogenesis. In this study, we aimed to compare clinical characteristics and tear neuropeptide concentrations in patients with dry eye disease (DED) with and without chronic ocular pain following FS-LASIK, and investigate correlations between ocular pain, clinical characteristics, and tear neuropeptide levels.

METHODS

Thirty-eight post-FS-LASIK patients with DED were assigned to two groups: those with chronic ocular pain and those without chronic ocular pain. Dry eye, ocular pain, and mental health-related parameters were evaluated using specific questionnaires and tests. The morphology of corneal nerves and dendritic cells (DCs) was evaluated by in vivo confocal microscopy. Function of corneal innervation was evaluated by corneal sensitivity. Concentrations of tear cytokines (interleukin [IL]-6, IL-23, IL-17A, and interferon-γ) and neuropeptides (α-melanocyte-stimulating hormone, neurotensin, β-endorphin, oxytocin, and substance P [SP]) were measured using the Luminex assay.

RESULTS

Most patients with chronic ocular pain experienced mild to moderate pain; the most common types included stimulated pain (provoked by wind and light), burning pain, and pressure sensation. More severe dry eye (P < 0.001), anxiety symptoms (P = 0.026), lower Schirmer I test values (P = 0.035), lower corneal nerve density (P = 0.043), and more activated DCs (P = 0.041) were observed in patients with ocular pain. Tear concentrations of SP and oxytocin were significantly higher in patients with ocular pain (P = 0.001, P = 0.021, respectively). Furthermore, significant correlations were observed among ocular pain severity, SP, and anxiety levels.

CONCLUSIONS

Patients with DED after FS-LASIK who have chronic ocular pain show more severe ocular and psychological discomfort and higher tear levels of neuropeptides. Furthermore, ocular pain severity is correlated with tear SP levels.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05600985.

Inflammation mechanism and anti-inflammatory therapy of dry eye

Dry eye is a widespread chronic inflammatory disease that causes fatigue, tingling, burning, and other symptoms. Dry eye is attributed to rheumatic diseases, diabetes, hormone disorders, and contact lenses, which activate inflammatory pathways: mitogen-activated protein kinases (MAPK) and nuclear factor-B (NF-κB), promote macrophage inflammatory cell and T cell activation, and inflammation factors. Clinicians use a combination of anti-inflammatory drugs to manage different symptoms of dry eye; some of these anti-inflammatory drugs are being developed. This review introduces the dry eye inflammation mechanisms and the involved inflammatory factors. We also elucidate the anti-inflammatory drug mechanism and the detection limits.

Pain and the biochemistry of fibromyalgia: patterns of peripheral cytokines and chemokines contribute to the differentiation between fibromyalgia and controls and are associated with pain, fat infiltration and content

Objectives

This explorative study analyses interrelationships between peripheral compounds in saliva, plasma, and muscles together with body composition variables in healthy subjects and in fibromyalgia patients (FM). There is a need to better understand the extent cytokines and chemokines are associated with body composition and which cytokines and chemokines differentiate FM from healthy controls.

Methods

Here, 32 female FM patients and 30 age-matched female healthy controls underwent a clinical examination that included blood sample, saliva samples, and pain threshold tests. In addition, the subjects completed a health questionnaire. From these blood and saliva samples, a panel of 68 mainly cytokines and chemokines were determined. Microdialysis of trapezius and erector spinae muscles, phosphorus-31 magnetic resonance spectroscopy of erector spinae muscle, and whole-body magnetic resonance imaging for determination of body composition (BC)-i.e., muscle volume, fat content and infiltration-were also performed.

Results

After standardizing BC measurements to remove the confounding effect of Body Mass Index, fat infiltration and content are generally increased, and fat-free muscle volume is decreased in FM. Mainly saliva proteins differentiated FM from controls. When including all investigated compounds and BC variables, fat infiltration and content variables were most important, followed by muscle compounds and cytokines and chemokines from saliva and plasma. Various plasma proteins correlated positively with pain intensity in FM and negatively with pain thresholds in all subjects taken together. A mix of increased plasma cytokines and chemokines correlated with an index covering fat infiltration and content in different tissues. When muscle compounds were included in the analysis, several of these were identified as the most important regressors, although many plasma and saliva proteins remained significant.

Discussion

Peripheral factors were important for group differentiation between FM and controls. In saliva (but not plasma), cytokines and chemokines were significantly associated with group membership as saliva compounds were increased in FM. The importance of peripheral factors for group differentiation increased when muscle compounds and body composition variables were also included. Plasma proteins were important for pain intensity and sensitivity. Cytokines and chemokines mainly from plasma were also significantly and positively associated with a fat infiltration and content index.

Conclusion

Our findings of associations between cytokines and chemokines and fat infiltration and content in different tissues confirm that inflammation and immune factors are secreted from adipose tissue. FM is clearly characterized by complex interactions between peripheral tissues and the peripheral and central nervous systems, including nociceptive, immune, and neuroendocrine processes.

Neurophysiology of corneal neuropathic pain and emerging pharmacotherapeutics

The altered activity generated by corneal neuronal injury can result in morphological and physiological changes in the architecture of synaptic connections in the nervous system. These changes can alter the sensitivity of neurons (both second-order and higher-order projection) projecting pain signals. A complex process involving different cell types, molecules, nerves, dendritic cells, neurokines, neuropeptides, and axon guidance molecules causes a high level of sensory rearrangement, which is germane to all the phases in the pathomechanism of corneal neuropathic pain. Immune cells migrating to the region of nerve injury assist in pain generation by secreting neurokines that ensure nerve depolarization. Furthermore, excitability in the central pain pathway is perpetuated by local activation of microglia in the trigeminal ganglion and alterations of the descending inhibitory modulation for corneal pain arriving from central nervous system. Corneal neuropathic pain may be facilitated by dysfunctional structures in the central somatosensory nervous system due to a lesion, altered synaptogenesis, or genetic abnormality. Understanding these important pathways will provide novel therapeutic insight.

TNF is a critical cytokine in age-related dry eye disease

Aging is a complex biological process that is characterized by low-grade inflammation, called inflammaging. Aging affects multiple organs including eye and lacrimal gland. Tumor necrosis factor (TNF) is a pleiotropic cytokine that participates in inflammation, activation of proteases such as cathepsin S, and formation of ectopic lymphoid organs. Using genetic and pharmacological approaches, we investigated the role of TNF in age-related dry eye disease, emphasizing the ocular surface and lacrimal gland inflammation. Our results show the increased protein and mRNA levels of TNF in aged lacrimal glands, accompanied by increased TNF, IL1β, IL-18, CCL5, CXCL1, IL-2, IL-2 receptor alpha (CD25), IFN-γ, IL-12p40, IL-17, and IL-10 proteins in tears of aged mice. Moreover, genetic loss of the Tnf-/- in mice decreased goblet cell loss and the development of ectopic lymphoid structures in the lacrimal gland compared to wild-type mice. This was accompanied by a decrease in cytokine production. Treatment of mice at an early stage of aging (12-14-month-old) with TNF inhibitor tanfanercept eye drops for eight consecutive weeks decreased cytokine levels in tears, improved goblet cell density, and decreased the marginal zone B cell frequency in the lacrimal gland compared to vehicle-treated animals. Our studies indicate that modulation of TNF during aging could be a novel strategy for age-related dry eye disease.

Tear Fluid Biomarkers and Quality of Life in People with Type 2 Diabetes and Dry Eye Disease

Dry eye disease (DED) can be extremely distressing and is common in type 2 diabetes (T2D). To investigate potential biomarkers of DED in T2D, panels of proteins in tears, alongside clinical signs and symptoms of DED, were assessed. Patients were classified into four groups: T2D + DED (n = 47), T2D-only (n = 41), DED-only (n = 17) and healthy controls (n = 17). All patients underwent the Ocular Surface Disease Index (OSDI) and Dry Eye-Related Quality of Life (DEQS) questionnaires, tear evaporation rate (TER), fluorescein tear break-up time (fTBUT), corneal fluorescein staining (CFS) and Schirmer 1 test assessments. Six metabolic proteins and 14 inflammatory cytokines were analyzed with multiplex bead analysis. Interleukin (IL)-6 and IL-8 concentrations in tears were significantly higher in the T2D + DED group, and these biomarkers were positively correlated with CFS. In addition, tear IL-6 was negatively correlated with fTBUT in the T2D + DED group. Clinical signs of DED in the T2D + DED group were similar to the DED-only group. The T2D + DED group had more patients with moderate and severe DED (versus the DED-only group), suggesting a different pathogenesis for DED in T2D versus DED-only. Therefore, IL-6 and IL-8 could potentially be diagnostic biomarkers of DED in T2D.

The protective effect of luteolin on the depression-related dry eye disorder through Sirt1/NF-κB/NLRP3 pathway

Luteolin has been reported to exhibit therapeutic effect on depressive-like behaviors in mice. Nevertheless, the therapeutic effect of luteolin on the depression-related dry eye disorder remains inconclusive. In this study, C57 mice were subjected to chronic unpredictable mild stress in a dry environment (relative humidity in the cage <40%). The behavioral test and phenol red cotton thread test were employed to select the mice with both dry eye and depression-like behavior. The mechanism of luteolin on depression-related dry eye disorder was assessed by the Sirt1 selective inhibitor EX-527. Luteolin alleviated depressive-like behaviors induced by CUMS, increased tear secretion and restored corneal defects in mice. The secretions of pro-inflammatory factors IL-1β, IL-6, IL-18 and TNF-α were decreased in hippocampi and corneal tissues by Luteolin treatment. Luteolin treatment up-regulated Sirt1 expression and down-regulated Ac-NF-κB, NLRP3, Ac-Caspase-1, GSDMD-N, Cleaved IL-1β, and Cleaved IL-18 expressions. In addition, the selective inhibition of Sirt1 could weaken the therapeutic effect of luteolin on depression-related dry eye disorder. The beneficial effect of luteolin through Sirt1/NF-κB/NLRP3 signaling pathway might be a therapeutic strategy for the depression-related dry eye disorder.

Role of ocular surface neurobiology in neuronal-mediated inflammation in dry eye disease

Inflammation is the consequence of dry eye disease regardless of its etiology. Several injurious or harmless processes to the ocular surface neurons promote ocular surface neurogenic inflammation, leading to the vicious cycle of dry eye disease. These processes include the regular release of neuromediators during the conduction of ocular surface sensations, hyperosmolarity-induced ocular surface neuronal damage, neuro-regenerative activities, and neuronal-mediated dendritic cell activities. Neurogenic inflammation appears to be the main culprit, instigating the self-perpetuating inflammation observed in patients with dry eye disease.