Second Injury in the Cornea: The Role of Inflammatory Cytokines in Corneal Damage and Repair

Olopatadine enhances recovery of alkali-induced corneal injury in rats

AIMS

The alkali-induced corneal injury is an ocular emergency that required an immediate and effective management to preserve the normal corneal functions and transparency. Olopatadine is a fast, topically-effective anti-allergic drug, which exhibited potent anti-inflammatory and anti-angiogenic abilities in different allergic animals' models. Therefore, this study aimed to evaluate the therapeutic effect of olopatadine on alkali-induced corneal injury in rats.

MATERIALS AND METHODS

Corneal alkali injury (CI) induced in the right eyes of an eight-week-old male Wister rats, by application of 3 mm diameter filter-papers, soaked for 10 s in 1 N-NaOH, to the right eyes' corneal centers for 30 s, afterward, the filter paper removed, and the rat right eye rinsed with 20 ml normal saline. For treatment of CI, either 0.2% or 0.77% olopatadine applied topically daily for 14 days, starting immediately after the induction of CI.

KEY FINDINGS

Olopatadine, in the present work, effectively and dose-dependently enhanced the corneal healing after alkali application, with significant reduction of the corneal opacity and neovascularization scores, besides, it suppressed the augmented corneal IL-1β, VEGF, caspase-3 levels, and nuclear NF-κB immunohistochemical expression, meanwhile it abrogated the corneal histopathological changes, induced by alkali application.

SIGNIFICANCE

Olopatadine appears to be a potential treatment option for alkali-induced corneal injury.

Interleukin-6 participation in pathology of ocular diseases

Interleukin-6 (IL-6) is a multifunctional cytokine that affects a variety of cells in the body such as osteoclasts, hepatocytes, endothelial cells, epithelial cells, white and red blood cells and etc. Elevated levels of IL-6 have been detected in many ocular diseases. Studies show that IL-6 has a major role in the pathology of glaucoma, CRVO, macular edema, ocular neovascularization, posterior capsule opacity formation, keratitis, dry eye disease, allergic eye disease, ocular autoimmune disease, corneal chemical burn, ocular inflammation and so on. IL-6 does its effects through the classic or trans-signal pathways in cells. Blocking of IL-6 signal pathways via Tocilizumab or other chemicals and therapeutics will help to overcome complications related to ocular diseases.

Immunohistochemical study of matrix metalloproteinases-2 and -9, macrophage inflammatory protein-2 and tissue inhibitors of matrix metalloproteinases-1 and -2 in normal, purulonecrotic and fungal infected equine corneas

OBJECTIVE

Determine the effects of matrix metalloproteinases (MMPs)-2, -9, macrophage inflammatory protein-2 (MIP-2), tissue inhibitors of matrix metalloproteinase (TIMP)-1 and -2 by immunohistochemical expression in fungal affected and purulonecrotic corneas.

PROCEDURE

Paraffin-embedded equine corneal samples; normal (n = 9), fungal affected (FA; n = 26), and purulonecrotic without fungi (PN; n = 41) were evaluated immunohistochemically for MMP-2, -9, MIP-2, TIMP-1 and -2. The number of immunoreactive inflammatory cells was counted and statistics analyzed. Western blot was performed to detect MMP-2, MMP-9, TIMP-1 and TIMP-2 proteins.

RESULTS

Matrix metalloproteinases-2, -9, MIP-2, TIMP-1 and -2 immunoreactivity was identified in corneal epithelium of normal corneas, and in corneal epithelium, inflammatory cells, keratocytes, and vascular endothelial cells of both FA and PN samples. Inflammatory cell immunoreactivity was significantly higher in FA and PN samples than in the normal corneas. There was positive correlation between MMP-2 and MIP-2, MMP-9 and MIP-2, and MMP-9 and TIMP-1 in inflammatory cell immunoreactivity in FA samples. There was positive correlation between MMP-9 and MIP-2, MMP-9 and TIMP-2, MIP-2 and TIMP-1, and MIP-2 and TIMP-2 in inflammatory cell immunoreactivity in PN samples. Western blot confirmed the presence of all four proteins in equine corneal samples.

CONCLUSION

Increased immunoreactivity of MMP-2 and -9 in FA and PN samples is indirectly related to MIP-2 through its role in neutrophil chemo-attraction. Tissue inhibitors of matrix metalloproteinase-1 and TIMP-2 are up-regulated in equine purulonecrotic and fungal keratitis secondary to MMP-2 and MMP-9 expression. The correlation between MMPs -2 and -9, MIP-2, TIMPs -1 and -2 suggests that these proteins play a specific role in the pathogenesis of equine fungal keratitis.

Efficacy of early systemic betamethasone or cyclosporin A after corneal alkali injury via inflammatory cytokine reduction

PURPOSE

To evaluate the effects of early systemic administration of betamethasone or cyclosporin A (CsA) on inflammatory cytokine expression and corneal damage after alkali injury.

METHODS

Sixty-five Wistar rat corneas injured with 1N NaOH were divided into three groups: untreated, betamethasone-treated and CsA-treated. Both agents were administered systemically and daily during the first 7 days after injury. Interleukin (IL)-1alpha, -6 and -8 concentrations in the injured corneas were measured with ELISA at 2, 4 and 7 days after injury. Corneal damage was evaluated by scoring clinical findings.

RESULTS

In untreated injured corneas, IL-1alpha, -6 and -8 were markedly elevated during the 7-day period following injury. Both betamethasone and CsA significantly suppressed IL-1alpha and IL-8 at day 4. Only betamethasone significantly suppressed IL-6 at days 4 and 7. Both agents significantly reduced corneal opacity at day 4.

CONCLUSION

Early systemic administration of betamethasone or CsA after alkali injury may be of benefit by suppressing inflammatory cytokine expression in the cornea.

Interleukin-1 facilitates airway epithelial migration in response to injury

OBJECTIVE

To test the hypothesis that interleukin (IL)-1 plays a permissive role in respiratory epithelial cell migration and proliferation.

STUDY DESIGN

Primary cultures of porcine respiratory epithelial cells or tracheal organ explants were cultured in the presence or absence of function-blocking antibodies to IL-1. Areas of epithelial cell outgrowth were determined in control and antibody-treated organ explants daily for 4 days. At intervals, cultured cells were collected for cell counting and viability determination. Time course and dose-response curves were constructed for control and antibody-treated groups.

RESULTS

Interleukin-1 secretion into culture supernatants increased sharply from days 3 to 7. Outgrowths from tracheal explants were reduced by greater than 60% by single antibody treatment, and by over 90% by treatment with antibodies to both IL-1alpha and -1beta by day 4 of culture. Function-blocking antibodies to IL-1 significantly reduced cell number by day 7 of culture.

CONCLUSIONS

Interleukin-1 is produced by respiratory epithelial cells in culture during log phase growth and plays a permissive role in cell migration and proliferation.