Photosensitized oxidation of the eye lens proteins, the crystallins, is thought to lead to protein crosslinks and high molecular weight aggregates. Such protein modifications may be important factors in the formation of lens opacities or cataracts. We focus attention here on type 2 photo-oxidation involving the reaction of singlet oxygen (1O2) with crystallins and some "control" proteins. We find that: (1) trp residues are oxidized to N-formyl kynurenine and related products, but this in itself does not lead to the production of high molecular weight protein aggregates of the protein; (2) tyr residues react with 1O2 but we do not detect dihydroxyphenylalanine or bityrosine nor are protein crosslinks formed as a result; (3) oxidation of his residues appears necessary for high molecular weight protein covalent aggregates to form. Proteins devoid of his, e.g. melittin or bovine pancreatic trypsin inhibitor, do not form high molecular weight products upon reaction with 1O2. Prior reaction and blocking of his inhibits the crosslinking reactions. (4) The oxidized protein is seen to be more acidic than the parent and has an altered tertiary structure. (5) Among the crystallins, reactivity towards 1O2 varies in the order gamma greater than beta greater than alpha and also gamma A/E greater than gamma D greater than gamma B crystallin.

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The aim of this study was to evaluate the long-term effects of lithium treatment on neonatal hypoxicischemic brain injury, inflammation, and neural stem/progenitor cell (NSPC) proliferation and survival. Nine-day-old male rats were subjected to unilateral hypoxia-ischemia (HI) and 2 mmol/kg lithium chloride was injected intraperitoneally immediately after the insult. Additional lithium injections, 1 mmol/kg, were administered at 24-hour intervals for 7 days. Animals were killed 6, 24, 72 hours, or 7 weeks after HI. Lithium reduced total tissue loss by 69%, from 89.4 ± 14.6 mm 3 in controls (n = 15) to 27.6 ± 6.2 mm 3 in lithium-treated animals (n = 14) 7 weeks after HI (P < 0.001). Microglia activation was inhibited by lithium treatment, as judged by Iba-1 and galectin-3 immunostaining, and reduced interleukin-1b and CCL2 levels. Lithium increased progenitor, rather than stem cell, proliferation in both nonischemic and ischemic brains, as judged by 5-bromo-2-deoxyuridine labeling 24 and 72 hours as well as by phospho-histone H3 and brain lipid-binding protein labeling 7 weeks after HI. Lithium treatment also promoted survival of newborn NSPCs, without altering the relative levels of neuronal and astroglial differentiation. In summary, lithium conferred impressive, morphological long-term protection against neonatal HI, at least partly by inhibiting inflammation and promoting NSPC proliferation and survival.

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