Pentoxifylline influences the autocrine function of organ cultured donor corneas and enhances endothelial cell survival

Abstract

Background/aims: Scientific interest in pentoxifylline has been reawakened owing to the recognised effects of this drug on immune functions, particularly its influence on cytokine production. In a previous study, the authors demonstrated that spiking of organ culture media with endotoxin elicited a marked enhancement in the release of IL-6 and IL-8 from corneal tissue and that these events coincided with degenerative changes in endothelial cells and a higher incidence of actual loss among this population. Since traces of donor derived endotoxin can be detected in up to 50% of corneal organ cultures, this substance may have a direct influence on graft viability or trigger inflammatory responses in the host. They, therefore, wished to ascertain whether supplementation of media with pentoxifylline improved endothelial cell survival in organ cultured donor corneas.

Methods: 12 fellow pairs of donor corneas were cultured for 20 days, with a change of medium on day 10: One of each pair was incubated in the absence, and the other in the presence, of pentoxifylline (25 microg/ml). Samples of medium were withdrawn at regular intervals during the course of incubation and screened for cytokines IL-6, IL-8, and prostaglandin E2 by ELISA. Endothelial cell morphology and numerical density were assessed on days 0, 10 and 20.

Results: Addition of pentoxifylline to organ culture media led to a significant improvement in endothelial cell survival. This drug also elicited a significant increase in the level of IL-6 and marginally suppressed that of IL-8 during the initial 10 day phase of incubation. During the second 10-20 day phase, the level of both IL-6 and IL-8 decreased significantly in the presence of pentoxifylline, the relation between these two cytokines being the inverse of that observed in the absence of the drug. No significant changes in the level of prostaglandin E2 were apparent.

Conclusion: The addition of pentoxifylline to organ culture media leads, ultimately, to a suppression of IL-6 and IL-8 secretion by corneal tissue. The potentially damaging effects of these cytokines are thereby quelled, as evidenced by the improvement in endothelial cell survival.

Figure 1

The percentage of endothelial cell loss incurred by 12 fellow pairs of donor corneas (I-XII) after 20 days of incubation. Cultures of left corneas (solid bars) were supplemented with 25 µg/ml of pentoxifylline; those of right ones (open bars) served as controls.

Figure 2

Levels of IL-6, IL-8, and prostaglandin E2 (PGE2) within the media of cultured corneas during the initial 10 day phase of incubation. Data pertaining to 17 fellow pairs are shown. Each box represents the mean (SD) of the final four ELISA measurements for each donor cornea. Media containing left corneas were spiked with 25 µg/l of pentoxifylline (solid boxes); those containing right ones served as controls (open boxes).

Figure 3

Levels of IL-6, IL-8, and prostaglandin E2 (PGE2) within the media of cultured corneas during the second 10 to 20 day phase of incubation. Data pertaining to 12 fellow pairs are shown. Each box represents the mean (SD) of the final four ELISA-measurements for each donor cornea. Media containing left corneas were spiked with 25 µg/l of pentoxifylline (solid boxes); those containing right ones served as controls (open boxes).