Regulation and Effect of the Chemokine CXCL8/IL8 on Cell Viability and Cell Death of Human Trabecular Cells

Abstract

Purpose: : Several cytokines have been reported to play an essential role in ocular inflammation. It is suggested that the proinflammatory effect of cytokines such as IL1β and TNFα may be mediated via chemokines such as CXCL8/IL8. IL1β has been shown to be released after laser trabeculoplasty. The objectives of this study were to investigate, on the one hand, the effect of IL1β on the expression and release of CXCL8/IL8, and on the other hand, the effect of CXCL8/IL8 on trabecular cell viability and cell death under basal and stimulated conditions.

Methods: : HTM3 cells (from a glaucomatous patient) or HTM5 (non-glaucomatous) were grown in culture medium, for 24h. Cells were then incubated or not with 0.005% benzalkonium chloride (BAC) solution for 15 minutes and for 2, 12 or 24h in culture medium containing various concentrations of IL1β, TNFα or CXCL8/IL8 (1 to 500ng/ml). Cell viability and apoptosis were determined by cytofluorimetry using Neutral Red Uptake assay and YOPRO-1 determination. Furthermore, RT-PCR and Elisa kits were used to measure for CXCL8/IL8 mRNA and release.

Results: : IL1β and TNFα increased the expression of CXCL8/IL8 mRNA. Furthermore, IL1β stimulated the release of CXCL8/IL8 in a time and dose-dependent manner. CXCL8/IL8 had no effect on cell viability and cell death under basal conditions but potentiated in a dose and time-dependent way trabecular cell death induced by 0.005% BAC. We observed that the cell death induced by CXCL8/IL8 was linked to an apoptotic process.

Conclusions: : We report that proinflammatory cytokines may act via chemokines on trabecular cells. The fact that CXCL8/IL8 can potentiate BAC-induced apoptosis suggests that chemokines may play a role following exposure to topical preservatives in the human trabecular meshwork inflammation of glaucomatous treated eyes.KEY WORDSTrabecular meshwork, chemokines, inflammation.

Keywords: trabecular meshwork • inflammation • cytokines/chemokines