IL-1α, IL-1β, IL-6, and IL-8 secretion of human keratocytes following photodynamic inactivation (PDI) in vitro
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With increasing resistance of microorganisms to antibiotics, photodynamic inactivation (PDI) may also be a potential therapeutic option in infectious keratitis. As part of the inflammatory response in infectious keratitis, keratocytes produce various interleukins. The purpose of this study was to evaluate the potential anti-inflammatory effect of PDI, analyzing interleukin-1 alpha (IL-1α), interleukine-1 beta (IL-1β), interleukin-6 (IL-6), and interleukin-8 (IL-8) secretion of human keratocytes following PDI, in vitro.
Primary human keratocytes were isolated by digestion in collagenase A (1.0 mg/ml) from human corneal buttons, and cultured in DMEM/Ham’s F12 medium supplemented with 10 % FCS. Keratocyte cell cultures underwent illumination using red (670 nm) light for 13 min following exposure to 100 nM concentration of the photosensitizer chlorin e6 (Ce6) in the culture medium. Five and 24 hours after PDI, secretion of IL-1α, IL-1β, IL-6, and IL-8 was measured by enzyme-linked immunoabsorbent assay (ELISA).
The secretion of IL-1α was under the measurement limit in treated and untreated cell cultures 5 and 24 h after PDI. Compared to untreated controls, IL-6 and IL-8 secretion of keratocytes decreased (p < 0.05 and 0.0001) significantly 5 hours after PDI, whereas IL-1β secretion remained unchanged. Twenty-four hours after PDI, secretion of IL-1β, IL-6, and IL-8 did not differ significantly from untreated controls.
In the short term, PDI does not have an impact on IL-1α and IL-1β secretion of keratocytes, in vitro. Photodynamic inactivation inhibits IL-6 and IL-8 secretion of keratocytes transiently (5 h), which normalizes 24 h following treatment. Through the short-term impact of chlorine e6-PDI on IL-6 and IL-8 secretion, PDI may inhibit the inflammatory cascade in at least keratocyte cultures.
KeywordsPhotodynamic inactivation Human keratocytes Chlorin e6 IL-1α IL-1β IL-6 IL-8 Cell culture
We are thankful for the support of the China Scholarship Council (CSC) (J. Wang) and the Alexander von Humboldt Foundation (Dr. N. Szentmáry). This project was also supported by “Zentrales Innovationsprogram Mittelstand (ZIM)” of the German Federal Ministry of Economics and Technology (grant number: KF2152004MD0), Germany.
Conflict of interest
None of the authors have any financial conflict of interest.
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