Increased Lacrimal Fluid Level of HMGB1 in Vernal Keratoconjunctivitis

Role of Damage-Associated Molecular Patterns (DAMPs/Alarmins) in Severe Ocular Allergic Diseases

Severe ocular allergic diseases, such as atopic keratoconjunctivitis and vernal keratoconjunctivitis, cause severe allergic inflammation in the conjunctiva and corneal epithelial damage, resulting in visual disturbances. The involvement of damage (danger)-associated molecular patterns (DAMPs/alarmins) in the pathogenesis of these diseases has been recognized. Alarmins released from damaged corneal epithelial cells or eosinophils play a critical role in the induction of corneal lesions, vicious loop of corneal injury, and exacerbation of conjunctival allergic inflammation. Alarmins in the conjunctiva also play an essential role in the development of both allergic inflammation, based on the acquired immune system, and type 2 inflammation by innate immune responses in the ocular surface. Therefore, alarmins may be a potentially important therapeutic target in severe refractory ocular allergic diseases.

Understanding Vernal Keratoconjunctivitis: Beyond Allergic Mechanisms

Vernal keratoconjunctivitis (VKC) is a chronic, recurrent, inflammatory disease of the cornea and conjunctiva mostly affecting boys in prepubertal age. VKC recurrence is characterized by intense symptoms of itching, redness, and photophobia associated with corneal damage, impairment of visual function, and quality of life. The pathogenesis of VKC has not yet been completely understood, and it is still controversial. In fact, VKC is considered an ocular allergic disease due to the involvement of immunoglobulin E, eosinophils, and mast cells, and of a lymphocyte T-helper type 2 reaction. However, approximately half of VKC patients have negative allergological history and testing, suggesting that other pathogenic mechanisms participate in VKC development and severity. Specifically, evidence suggests that genetic, endocrine, neuronal factors and an imbalance of innate immunity are involved in the pathogenesis of VKC. The purpose of this review is to summarize evidence on the pathogenic role of innate immunity, neuroimmune reaction, and hormonal changes in VKC. Increasing understanding of the pathogenic mechanisms behind VKC may lead to the identification of novel biomarkers for diagnosis and/or potential therapeutic targets in order to improve the management of this challenging condition.

Glycyrrhizin micelle as a genistein nanocarrier: Synergistically promoting corneal epithelial wound healing through blockage of the HMGB1 signaling pathway in diabetic mice

The purpose of this study was to explore the feasibility of targeting the HMGB1 signaling pathway to treat diabetic keratopathy with a dipotassium glycyrrhizinate-based micelle ophthalmic solution encapsulating genistein (DG-Gen), and to evaluate whether these dipotassium glycyrrhizinate (DG) micelles could synergistically enhance the therapeutic effect of encapsulated genistein (Gen). An optimized DG-Gen ophthalmic solution was fabricated with a Gen/DG weight of ratio 1:15, and this formulation featured an encapsulation efficiency of 98.96 ± 0.82%, and an average particle size of 29.50 ± 2.05 nm. The DG-Gen ophthalmic solution was observed to have good in vivo ocular tolerance and excellent in vivo corneal permeation, and to remarkably improve in vitro antioxidant activity. Ocular topical application of the DG-Gen ophthalmic solution significantly prompted corneal re-epithelialization and nerve regeneration in diabetic mice, and this efficacy might be due to the inhibition of HMGB1 signaling through down-regulation of HMGB1 and its receptors RAGE and TLR4, as well as inflammatory factor interleukin (IL)-6 and IL-1β. In conclusion, these data showed that HMGB1 signaling is a potential regulation target for the treatment of diabetic keratopathy, and novel DG-micelle formulation encapsulating active agents such as Gen could synergistically cause blockage of HMGB1 signaling to prompt diabetic corneal and nerve wound healing.

Expression profiles and potential corneal epithelial wound healing regulation targets of high-mobility group box 1 in diabetic mice

As a damage-associated molecular pattern molecule, high-mobility group box 1 protein (HMGB1) is involved in diabetes and its complications. However, the role of HMGB1 in diabetic keratopathy is not yet understood. The purpose of this study was to investigate the potential roles of HMGB1 in the development of diabetic keratopathy as well as potential strategies to block HMGB1 in order to prompt epithelial wound healing and nerve regeneration in diabetic corneas. The results demonstrated that diabetic keratopathy developed in mice over the duration of the diabetic condition with typical symptoms, including damaged ocular surfaces and corneal nerves. The diabetic corneas had significantly increased protein expression levels of HMGB1 and its receptors-the receptor for advanced glycation end products (RAGE) and toll-like receptor 4 (TLR4)-compared to the age-matched normal corneas (P < 0.05). Corneal HMGB1 levels significantly increased during the corneal wound healing process of the diabetic mice, peaking on the first day after the wound was created and then decreasing to the unwounded level on the seventh day. Exogenous HMGB1 peptide significantly retarded wound and nerve healing, while glycyrrhizin (an HMGB1 inhibitor) significantly prompted wound and nerve healing. Further, the western blot results confirmed that RAGE and TLR4 were also involved in corneal wound and nerve healing. In conclusion, these data showed that HMGB1 and its related receptors are highly involved in the development of diabetic keratopathy. This finding indicates that the blockage of HMGB1 might serve as a strategy to prompt diabetic corneal and nerve wound healing.

The performance of the alarmin HMGB1 in pediatric diseases: From lab to clinic

INTRODUCTION

The ubiquitously expressed nonhistone nuclear protein high-mobility group box protein 1 (HMGB1) has different functions related to posttranslational modifications and cellular localization. In the nucleus, HMGB1 modulates gene transcription, replication and DNA repair as well as determines chromosomal architecture. When the post-transcriptional modified HMGB1 is released into the extracellular space, it triggers several physiological and pathological responses and initiates innate immunity through interacting with its reciprocal receptors (i.e., TLR4/2 and RAGE). The effect of HMGB1-mediated inflammatory activation on different systems has received increasing attention. HMGB1 is now considered to be an alarmin and participates in multiple inflammation-related diseases. In addition, HMGB1 also affects the occurrence and progression of tumors. However, most studies involving HMGB1 have been focused on adults or mature animals. Due to differences in disease characteristics between children and adults, it is necessary to clarify the role of HMGB1 in pediatric diseases.

METHODS AND RESULTS

Through systematic database retrieval, this review aimed to first elaborate the characteristics of HMGB1 under physiological and pathological conditions and then discuss the clinical significance of HMGB1 in the pediatric diseases according to different systems.

CONCLUSIONS

HMGB1 plays an important role in a variety of pediatric diseases and may be used as a diagnostic biomarker and therapeutic target for new strategies for the prevention and treatment of pediatric diseases.

Vernal Keratoconjunctivitis: an update focused on clinical grading system

Introduction

Vernal keratoconjunctivitis (VKC) is a severe disease with a prevalence of < 1 case out of 10,000 in Europe, which occurs mainly in pediatric age and is characterized by a severe and often bilateral chronic inflammation of the ocular surface. The diagnosis is generally confirmed by the finding at the ocular examination of conjunctival hyperemia, papillary hypertrophy in the tarsal conjunctiva, giant papillae, papillae in the limbus region.

Objective

Aim of this review is to provide an updated overview on the disease focused on clinical grading system, searching papers published in the last decade on VKC in scientific databases.

Results

Currently there are no standardized criteria for diagnosis of VKC and there is no uniformity to define disease severity, which makes difficult to diagnose and treat the disease.

Conclusions

Given the wide overlap of the symptoms of VKC with the allergic conjunctivitis, criteria of probable, possible or improbable diagnosis are needed, providing pediatricians with parameters useful for deciding whether to drive the patient to the ophthalmologist for diagnostic confirmation.