Jung W. Lee

Preventive effects of pyrroloquinoline quinone on formation of cataract and decline of lenticular and hepatic glutathione of developing chick embryo after glucocorticoid treatment

When 0.25 mumol of hydrocortisone succinate sodium (HC) was administered to 15-day-old fertile eggs, almost all lenses of chick embryos treated with HC for 48 hr were classified as cataract stage IV-V (95%). A triple application of potassium pyrroloquinoline quinone (PQQ) (1.25 mumol/egg) at 3, 10 and 20 hr after HC treatment showed a preventive effect against the HC-induced cataract formation (I:45%, II:25%, III: 30%). PQQ also prevented the decline of GSH in the lens caused by HC. The decline of GSH in liver 24 hr after HC administration was prevented by PQQ. These data indicate that PQQ can modify HC-induced effects and that the preventive effect of PQQ against HC-induced decline of hepatic GSH seemed to influence HC-induced events in lens.

The alteration of lipid peroxide in glucocorticoid-induced cataract of developing chick embryos and the effect of ascorbic acid

The level of lipid peroxide (LPO) in glucocorticoid-induced cataractous lenses was measured by using thiobarbituric acid. When 0.25 mumol of hydrocortisone hemisuccinate sodium (HC) were administered to 15-day-old chick embryos, the level of LPO in the lens increased to approximately 1.4-fold of the control level at 24 to 48 hr after HC treatment. However, the level returned to the control level by 96 hr with the disappearance of opacity in the lens. A triple application of ascorbic acid (20 mumol/egg) at 3, 10 and 20 hr after HC treatment prevented cataract formation and elevation in the level of LPO in 60% of the lenses. In 40% of the eggs treated with HC plus ascorbic acid, the results were no different than HC alone. Treatment with prednisolone hemisuccinate sodium (0.25 mumol/egg) produced an elevation in the level of LPO in the lens but that with cortisone hemisuccinate sodium or cortexolone hemisuccinate sodium did not change the level of LPO in the lens. The phenomena of the cataract formation and the elevation of LPO in the lens caused by HC seemed to be related to each other and due to its glucocorticoid activities.

Preventive effect of ascorbic acid against glucocorticoid-induced cataract formation of developing chick embryos

Glucocorticoid administration to developing chick embryos is known to promote cataract formation with a decreasing level of glutathione in the lens. To gain further understanding of this process, the level of ascorbic acid, a biological antioxidant, in the lenses was measured during the course of glucocorticoid treatment. When 0.25 mumol of hydrocortisone hemisuccinate sodium (HC) were administered to 15-day-old chick embryos, the level of ascorbic acid in the lens began to decline after 30 hr and became around 40% of the control value at 48 hr after HC treatment. At this time about 90% of the lenses showed opacity in the nuclear region. However, the level of ascorbic acid in the cataractous lens recovered to the control level at 96 hr, a time when the lens has recovered from cataract formation. A triple application of ascorbic acid (20 mumol/egg) at 3, 10 and 20 hr after HC treatment significantly prevented lens opacification. The administration of ascorbic acid prevented the decline of ascorbic acid content and partially that of glutathione content in the lens caused by HC.

Alteration of hepatic lipidperoxide levels during cataract formation caused by glucocorticoids in developing chick embryos

The level of hepatic lipidperoxides in chick embryos was determined during cataract formation resulting from glucocorticoid treatment. When 15 day old chick embryos were administered 0.25 mumol of hydrocortisone acetate their hepatic lipidperoxide level, determined by thio-barbituric acid, increased after a lag time of 20 hr and reached approximately 8-fold of control at 48 hr after the treatment. These studies indicate that the peroxidation of lipid in tissues should be considered in elucidating mechanisms of action or adverse effects of glucocorticoids.

Preventive effect of isocitrate on glucocorticoid-induced cataract formation of developing chick embryo

Glucocorticoid-induced cataract formation appears to proceed via oxidation or peroxidation steps possibly caused by multiple activities of glucocorticoid in the living system. Attempts were made to modify GC-induced metabolic changes and prevent cataract formation using intermediates of the citric acid cycle. The compounds were applied to the embryos at 3, 10 and 20 hr after the administration of hydrocortisone succinate sodium (HC:0.25 mumol/egg) to 15-day-old eggs. At 48 hr after HC treatment the lenses were classified and analyzed. Almost all lenses were classified as stage IV-V (greater than 94%). However, the application of sodium isocitrate (IC:15 mumol/egg) which was the most potent among several intermediates tested showed a significant preventive effect against cataract formation. The administration of IC prevented the decline of GSH, the elevations of LPO and reduced the marked elevation of glucose in the lens caused by HC. The IC treatment also diminished the elevation of LPO in blood and liver. The above effects by IC on HC-induced events may be due to the action of IC in preventing the early decline of hepatic GSH caused by HC. Possibly IC was utilized as an intermediate of the citric acid cycle and a substrate for isocitrate dehydrogenase in cytosol to modify GC-induced metabolic changes.

Elevation of glucose in ocular compartments of developing chick embryos with glucocorticoid-induced cataract.

When 15-day-old developing chick embryos were administered hydrocortisone hemisuccinate sodium (HC:0.25 mumol per egg) the concentration of glucose in both the aqueous humor and the vitreous body began to increase significantly after 3 hr and reached 24.4 +/- 0.3 mM and 22.3 +/- 0.9 mM, respectively, at 48 hr. Thereafter, the levels decreased to the control by 100 hr. During the treatment period, the glucose concentration of the control aqueous humor and vitreous body remained at approximately 7.5 mM and 4.3 mM, respectively. These changes in glucose after HC administration were quite different from that of the lens in regard to the extent of increase and the lag time required to produce glucose accumulation. By in vitro and in ovo experiments, it was found that the environment surrounding lens, medium and ocular fluids, greatly influenced the level of lenticular glucose rather than any changes metabolic activities in the lens. A glucose threshold of near 15 mM in milieu was required to promote the accumulation glucose in the lens.

GLUCOCORTICOID-INDUCED CATARACT OF THE DEVELOPING CHICK EMBRYO-PREVENTION BY PROPYLENE GLYCOL

When 0.25 mumol of hydrocortisone succinate sodium (HC) was administered to 15-day-old hens fertile eggs, almost all lenses of the embryos became cataractous with stages IV-V (> 90%) 48 h after the treatment. However, a triple application of propylene glycol (1.5 mmol/egg) at 3, 10 and 20 h after HC treatment effectively prevented the HC-induced cataract formation (I: 84%, II: 12%, III: 4%, IV-V: 0%) and repressed the decline of glutathione and the elevation of lipid peroxide in the lens caused by HC. Propylene glycol is metabolized to lactate and pyruvate producing NADH and is known to possess protective activities against X-ray irradiation. These properties have modified the HC-induced effects and decreased the production of oxidative stress in ovo, protecting the lens from losing its transparency after HC administration. Furthermore, a marked elevation of glucose in cataractous lenses noted after HC administration was not directly involved in opacification of the lenses.