Mediation mediation of laser trabeculoplasty-induced matt metalloproteinase expression by IL-1 beta and TNF alpha

PURPOSE. Laser trabeculoplasty of the anterior uveal region of the trabecul ar meshwork induces sustained matrix metalloproteinase expression within th e juxtacanalicular region of the meshwork. Studies were conducted to test t he hypothesis that a factor mediates this response and to identify the fact or. METHODS. Human anterior segment organ cultures were subjected to laser trea tment using standard clinical parameters and were returned to culture for 8 hours. The resultant 8-hour-conditioned culture medium was then tested for factor activity by evaluating its ability to produce two typical trabecula r responses to laser treatment, that is, to induce stromelysin expression o r to trigger cell division, when applied to fresh organ cultures or to cell cultures. Confocal immunohistochemistry of the laser-treated organ culture s and western immunoblot analysis of the conditioned medium were used to ev aluate changes in potential candidates for the factor activity. The ability of the interleukin (IL)-1 receptor antagonist (IL-1ra)- and of tumor necro sis factor alpha (TNF alpha)- blocking antibodies to eliminate the stromely sin induction was evaluated. RESULTS. Medium conditioned for 8 hours induced typical trabecular cell div ision in anterior segment organ cultures. Medium conditioned for 8 hours, b ut not for 30 minutes, induced typical increases in stromelysin expression in these organ cultures and in cell cultures, After 8 hours, both trabecula r cells in laser-treated organ cultures and in the conditioned medium conta ined elevated levels of IL-1 beta and TNF alpha. Thr laser-treated organ cu ltures contained elevated levels of IL-1 alpha, but it was not secreted int o the medium. The ability of conditioned media to induce stromelysin expres sion was partially blocked by either the IL-1ra- or the TNF alpha-blocking antibody. CONCLUSIONS. Laser trabeculoplasty induces the expression and secretion of both IL-1 beta and TNF alpha within the first 8 hours after treatment. Thes e cytokines then mediate increased trabecular stromelysin expression. Putat ively, this initiates remodeling of the juxtacanalicular extracellular matr ix, a likely sire for the aqueous outflow resistance, and thus restores nor mal outflow facility.