cytochalasin-d and Cataract

The relation between cataract and calpain proteolysis of lens fodrin was studied in two systems: elevated glucose (55.6 mM, diabetic model), and cytochalasin D (CD, 10(-2) mM, actin depolymerization-induced opacity model). Glucose treatment (48 h) caused a visible opaque layer and enzyme leakage, with a concomitant accumulation of ([Ca2+]i) around the lens equatorial cortex. CD caused both earlier and greater opacity and enzyme leakage than glucose. Lens fodrin digestion occurred in parallel with the timing and extent of calcium elevation. A calpain inhibitor peptide (CIP, 10(-2) mM) reduced the proteolysis of fodrin, opacity, and enzyme leakage in glucose-treated lenses but only partially retarded them in CD-treated lenses. These results suggest a mechanism in which calpain proteolysis of fodrin is a critical event in lens damage during opacification of cortical cataract.

Topics: Amino Acid Sequence; Animals; Calcium; Calpain; Carrier Proteins; Cataract; Culture Techniques; Cysteine Proteinase Inhibitors; Cytochalasin D; Fluoresceins; Fluorescent Dyes; Glucose; Glycoproteins; L-Lactate Dehydrogenase; Lens Cortex, Crystalline; Lens, Crystalline; Microfilament Proteins; Molecular Sequence Data; Organic Chemicals; Pyridinium Compounds; Rats

The effect of cytochalasin D (CD), an actin monomer-stabilizer, has been studied on cataract development in rat lenses. Cataractogenesis was induced by incubating the rat lenses in medium 199 (M199) containing 10(-5) M CD; by the end of 24 h, lenses first developed a visible opacity. The increased lactate dehydrogenase (LDH) activity in the culture medium, leakage of lens cytosolic proteins into the culture medium and observable development of opacity through a dissection microscope were correlated with cell damage associated with cataract formation. Non-denaturing polyacrylamide gel electrophoresis was used to separate three lens LDH isoenzymes. The effect of 1 mM vitamin C (VC) in reducing LDH leakage was also examined. The protective effect of VC on CD-initiated cataractous lenses is significant. This suggest that a portion of the opacity and lens damage may involve oxidative damage to the membrane-cytoskeleton complex which is started by CD, but partially prevented by VC

Topics: Animals; Ascorbic Acid; Cataract; Culture Media; Cytochalasin D; Electrophoresis, Polyacrylamide Gel; Female; Isoenzymes; L-Lactate Dehydrogenase; Lens, Crystalline; Nitroblue Tetrazolium; Organ Culture Techniques; Rats; Rats, Wistar