Masazumi Yamaguchi

Calpain inhibitor, SJA6017, reduces the rate of formation of selenite cataract in rats

Purposes. 1) To measure the amount of calpain inhibitor SJA6017 taken up by lenses of young rats after administration; and 2) To test efficacy of SJA6017 against selenite cataract in regard to amelioration of proteolysis of lens protein and prevention of lens nuclear opacity. Methods. Selenite nuclear cataracts were produced by subcutaneous injection of an overdose of sodium selenite to 16-day-old rats. SJA6017 was administered daily using intraperitoneal injections at 100 mg/kg body weight/day for 4 days. Lenses were observed and photographed by slit lamp biomicroscopy, and scored into one of three stages. Enucleated lenses were also scored into one of four stages and lens opacities in the nuclear region were quantified by image analysis. Proteolysis of crystallins was detected by SDS-PAGE. The amount of SJA6017 taken up by the lens was detected with a column switching HPLC system. Results. Nuclear cataracts were visible in 31% of the animals receiving only selenite, while the frequency of nuclear cataract in the Se+SJA6017 group was reduced to only 16%. This effect of SJA6017 was confirmed by densitometric analysis as a reduction in the density of the nucleus. Similar proteolytic changes of crystallins occurred at all stages of selenite cataract formation. The amount of SJA6017 in the lens was detected at the level of 0.03 µM. Conclusions. Systemic SJA6017 was taken up by the lens, and SJA6017 ameliorated in vivo selenite cataract formation. These studies are important because they partially validate the biochemical rationale for developing non-surgical, drug treatments for cataract prevention in man.

Molecular design to enhance the penetration into the retina via ocular instillation

To investigate the molecular design of drugs that have good penetration into the retina from anterior segment of the eye via ocular instillation, we optimized the length of methoxyethylene glycol chain (mEG) in the P3 region of an oral bioavailable calpain inhibitor SNJ-1945 (2) as a model compound. Modulation of the mEG length led to the optimal balance between hydrophilicity and lipophilicity and provided the compound with higher retinal exposure via ocular instillation. Incorporation of a mEG moiety would be a useful and convenient approach to attain high intraocular penetration.