Ciglitazone-Induced Lenticular Opacities in Rats: In Vivo and Whole Lens Explant Culture Evaluation

Abstract

The cataractogenic potential of the thiazolidinedione ciglitazone (CIG) was investigated in vivo and in vitro. In the rat, CIG caused a dose-dependent (30 -300 mg/kg/day) increase in incidence and severity of nuclear cataract formation during a 3-month nonclinical safety assessment study. Potential mechanisms of toxicity were surveyed using whole rat lens explants exposed to CIG with or without various inhibitors of cataract formation. In vitro, CIG caused a concentration-(0.375-30 M) and time-dependent (3-24 h) change in biochemical [ATP content or mitochondrial reduction of the tetrazolium dye 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) and reduced glutathione (GSH) content] and morphometric (lens wet weight and clarity) markers of damage. Within 3 h of exposure, 7.5 M CIG decreased lens ATP content 37 Ϯ 7% (percentage of difference from control, p Ͻ 0.05). After 24 h of exposure, lens ATP content, MTT reduction, and GSH content declined 57 Ϯ 5, 30 Ϯ 28, and 42 Ϯ 8%, respectively. Lens wet weight increased 17 Ϯ 4% with a concomitant decrement in lens clarity. Pretreating lenses with the mitochondrial calcium uniport inhibitor ruthenium red (RR) partially or fully protected lenses from toxicity. In contrast, the antioxidant dithiothreitol, aldose reductase inhibitor sorbinil, and selective cell-permeable calpain inhibitors [calpain II inhibitor and (2S,3S)-trans-epoxysuccinyl-L-leucylamido-3-methylbutane ethyl ester (E64d)] were ineffective in providing protection under the present testing conditions. Early and selective changes in lenticular ATP content and the partial or full protective effect of RR suggest that alterations in lens bioenergetics may play an important role in CIG-induced cataract formation. Lens explant cultures were successfully used to select two thiazolidinediones that lacked cataractogenic activity when evaluated in 3-month rat safety assessment studies.

Light-responsive nanoparticle depot to control release of a small molecule angiogenesis inhibitor in the posterior segment of the eye

“…Adult Sprague-Dawley rats were euthanized by CO 2 asphyxiation followed by exsanguination, and their eyes were enucleated and stored at 4 °C in Belzer UW cold preservation media (Bridge to Life), supplemented with 100 μg/mL penicillin (Invitrogen), 100 μg/mL streptomycin (Invitrogen), and 200 μg/mL d-glutamine (Invitrogen) following published protocols [26, 27]. Lenses were then carefully dissected from the globes and incubated in 4 mL Media 199 (Invitrogen) supplemented with 1% w/v of penicillin (100 μg/mL) and streptomycin (100 μg/mL) pre-incubated in 5% CO 2 atmosphere at 37 °C for 24 h. Non-cloudy lenses were either exposed to 10 min of UV light (365 nm, 12 mW/cm 2 ) or left unirradiated.…”

The mechanisms of calcium homeostasis and signalling in the lens

“…In the lens, mitochondrial Ca 2þ signalling has not been specifically investigated. However, interestingly and contrary to what might be anticipated, the blocker of the Ca 2þ uniporter, ruthenium red, inhibited lens opacification in organ cultured rat lenses exposed to the cataractogenic compound ciglitazone (Aleo et al, 2005). The role of mitochondria in modulating Ca 2þ dynamics in lens cells, particularly in relation to cataractogenesis, certainly warrants further investigation.…”

Mechanism of Thiazolidinedione-Dependent Cell Death in Jurkat T Cells

“…They suggest that ATP depletion, in combination with an apoptotic stimulus, initiates a switch from apoptosis to necrosis. Recently, a concentration-and time-dependent ATP depletion after ciglitazone treatment was found in explanted Sprague-Dawley rat lenses (Aleo et al, 2005), whereas we observed ATP depletion in Jurkat P Ϫ cells. In line with reports in rat hepatocytes (Haskins et al, 2001), troglitazone and the combination of rotenone/TTFA did not significantly reduce the ATP content.…”