Abstract
Abstract: :
Purpose: Previously, the chelating agents - picolinic acid (PA) and its analog fusaric acid were compared with EDTA as a method of inhibiting Posterior Capsular Opacification (PCO) using CHO cells as a model (ARVO, 2001). In this study, we continue the testing in pig lens epithelial cells. Picolinic acid and three analogs which cover the entire range of toxicity, were tested over the following concentrations: fusaric acid (1-100µg/mL), picolinic acid (10-1000µg/ml), dipicolinic acid (30-3000µg/ml), and nicotinic acid (100-5000µg/ml). Method: Pig eyes obtained from the local abattoir were dissected, leaving the posterior portion of the lens capsule attached to a portion of the sclera by the ciliary body. The dissected lens capsule was submersed in MEM eagle media with 10% fetal calf serum containing gentamycin, penicillin, streptomycin and amphotericin B. Media was changed every three days, and the lens epithelial cells were allowed to grow to confluency. The lens cells were trypsinized and the resultant cells were plated in tissue culture dishes. The attached cells were grown and subsequently tested according to the method used by Senderoff et al. (IOVS Vol 31 #12 pp2572-2578, 1990). Cell counts were performed, and were expressed as a percentage of the treated cell counts with respect to untreated or control cell counts. From plots of the percentage cell count versus concentration, the IC50 (i.e. concentration at which treated cell counts are 50% of the control) was established, and this was used as a measure of toxicity. Results: The IC50 were as follows: 5.6 µg/ml for fusaric acid, 55.3µg/ml for picolinic acid, 185µg/ml for dipicolinic acid and 539 µg/ml for nicotinic acid. The IC50 results obtained from pig lens epithelial cells are in the same range as values obtained from similar experiments performed in CHO cells. Conclusion: Picolinic acid has been shown to be an effective chelator of transition metals, most significantly, iron and zinc, which are important metals in proteins involved in cell replication. These analogs vary in their ability to inhibit cell growth in relation to (a) how well they chelate, and (b) how effectively they cross the cell membrane. Their effectiveness on lens epithelial cells in vitro enhances the possibility of using these agents in vivo for PCO applications.
Keywords: 390 drug toxicity/drug effects • 522 posterior capsular opacification (PCO) • 523 proliferation