Lipoxin A4 (LXA4) Reduces Alkali-Induced Corneal Inflammation and Neovascularization and Upregulates a Repair Transcriptome

Bufalin Regulates STAT3 Signaling Pathway to Inhibit Corneal Neovascularization and Fibrosis After Alkali Burn in Rats

PURPOSE

Bufalin (BU) is a bioactive ingredient extracted from the skin and parotid venom glands of Bufo raddei, which can effectively inhibit angiogenesis. The aim of this study was to investigate whether BU could affect corneal neovascularization (CoNV).

METHODS

A rat CoNV model (right eye) was constructed by administration of NaOH, and the left eye served as a control. Corneal damage scores of rats were detected. Hematoxylin & eosin, TUNEL, and Masson staining examined pathological changes, apoptosis, and fibrosis of corneal tissues. Immunohistochemistry and western blotting assessed the expression of proteins.

RESULTS

BU intervention resulted in a significant reduction in corneal inflammatory cells, repair of corneal epithelial hyperplasia, significant reduction in stromal edema, and reduction in vascular proliferation. BU can inhibit corneal neovascularization.

CONCLUSION

This study demonstrated that BU inhibits CoNV, fibrosis, and inflammation by modulating the STAT3 signaling pathway, elucidating the intrinsic mechanism of its protective effect. BU has great potential in the treatment of CoNV caused by corneal alkali burns.

Lipoxin A4 (LXA4) as a Potential Drug for Diabetic Retinopathy

The purpose of this review is to propose that lipoxin A4 (LXA4), derived from arachidonic acid (AA), a potent anti-inflammatory, cytoprotective, and wound healing agent, may be useful to prevent and manage diabetic retinopathy (DR). LXA4 suppresses inappropriate angiogenesis and the production of pro-inflammatory prostaglandin E2 (PGE2), leukotrienes (LTs), 12-HETE (12-hydroxyeicosatetraenoic acid), derived from AA by the action of 12-lioxygenase (12-LOX)) interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), as well as the expression of NF-κB, inducible NO (nitric oxide) synthase (iNOS), cyclooxygenase-2 (COX-2), intracellular adhesion molecule-1 (ICAM-1), and vascular endothelial growth factor (VEGF)-factors that play a role in DR. Thus, the intravitreal injection of LXA4 may form a new approach to the treatment of DR and other similar conditions such as AMD (age-associated macular degeneration) and SARS-CoV-2-associated hyperinflammatory immune response in the retina. The data for this review are derived from our previous work conducted in individuals with DR and from various publications on LXA4, inflammation, and DR.

Inhibition of Experimental Corneal Neovascularization by the Tight Junction Protein ZO-1

Purpose: To explore the effects of the tight junction protein zonula occludens 1 (ZO-1) on experimental corneal neovascularization (CNV). Methods: CNV models were established in the left eyes of BALB/c mice using NaOH. Anti-ZO-1 neutralizing antibody was topically applied to the burnt corneas after modeling thrice a day for 1 week. CD31 expression was analyzed to calculate the ratio of CNV number to area using a corneal whole-mount fluorescent immunohistochemical assay. Messenger ribonucleic acid (mRNA) and protein expression levels of ZO-1, vascular endothelial growth factor (VEGF), interleukin (IL)-1β, IL-6, IL-8, IL-18, monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor alpha (TNF-α), phosphorylated protein kinase C (pPKC), and clusterin in burned corneas were detected by reverse transcriptase polymerase chain reaction (PCR) and western blot analyses. Infiltration of neutrophils, macrophages, and progenitor cells was examined by flow cytometry. Results: CNV was obviously greater in 45 s than in 15 s alkali injury group. In another experiment, CNV was obviously greater in the ZO-1 antibody group than in the vehicle-treated group. Corneal mRNA and protein expression levels of VEGF, IL-1β, IL-6, IL-8, IL-18, and MCP-1 were significantly higher in the ZO-1 antibody group than in the control group. Infiltration of neutrophils, macrophages, and progenitor cells was significantly greater in the ZO-1 antibody group than in the control group. TNF-α expression was much higher in 45 s than in 15 s alkali injury group. However, protein expression of pPKC and clusterin was much lower in 45 s than in 15 s alkali injury group. Conclusions: Anti-ZO-1 neutralizing antibody-treated mice exhibited enhanced alkali-induced CNV through enhanced intracorneal infiltration of progenitor and inflammatory cells.

A new R,R-RvD6 isomer with protective actions following corneal nerve injury

The transparent cornea is the most densely innervated tissue in the body, primarily by sensory nerves originating from the trigeminal ganglia (TG). Damage to corneal nerves reduces sensitivity and tear secretion and results in dry eye. Consequently, ocular pain, for which no satisfactory therapies exist, arises in many cases. Treatment of injured corneas with pigment epithelium-derived factor (PEDF) combined with docosahexaenoic acid (DHA) stimulates nerve regeneration in models of refractive surgery, which damages nerves. The mechanism involves the synthesis of a stereoisomer of resolvin D6 (R,R-RvD6) formed after incorporating DHA into membrane lipids. Activation of a PEDF receptor (PEDF-R) with phospholipase activity releases DHA to synthesize the new resolvin isomer, which is secreted via tears. Topical treatment of mice corneas with R,R-RvD6 shows higher bioactivity in regenerating nerves and increasing sensitivity compared to PEDF+DHA. It also stimulates a transcriptome in the TG that modulates genes involved in ocular pain. Our studies suggest an important therapeutic role for R,R-RvD6 in regenerating corneal nerves and decreasing pain resulting from dry eye.

A moderate dosage of prostaglandin E2-mediated annexin A1 upregulation promotes alkali-burned corneal repair

Corneal alkali burn remains a clinical challenge in ocular emergency, necessitating the development of effective therapeutic drugs. Here, we observed the arachidonic acid metabolic disorders of corneas induced by alkali burns and aimed to explore the role of Prostaglandin E2 (PGE2), a critical metabolite of arachidonic acid, in the repair of alkali-burned corneas. We found a moderate dosage of PGE2 promoted the alkali-burned corneal epithelial repair, whereas a high dosage of PGE2 exhibited a contrary effect. This divergent effect is attributed to different dosages of PGE2 regulating ANXA1 expression differently. Mechanically, a high dosage of PGE2 induced higher GATA3 expression, followed by enhanced GATA3 binding to the ANXA1 promoter to inhibit ANXA1 expression. In contrast, a moderate dosage of PGE2 increased CREB1 phosphorylation and reduced GATA3 binding to the ANXA1 promoter, promoting ANXA1 expression. We believe PGE2 and its regulatory target ANXA1 could be potential drugs for alkali-burned corneas.