Degradation of crystallins from a psoriatic patient undergoing PUVA therapy

Comparative physico-chemical and spectroscopic analyses were carried out in human lens proteins obtained from extracts of normal, senile and PUVA cataracts. Mass recovery analysis reveals a large protein concentration loss in the PUVA cataract relative to the normal lens and senile cataract. This protein loss parallels an increase in the degraded polypeptide chains. However, the tryptophan content (2.1 mol/mol of 20 kDa protein subunit) and the apparent fluorescence quantum yield (phi f = 0.056) of the tryptophan residues which are believed to be involved in the development of UV-induced cataracts are unchanged after age-related alterations and/or in vivo photochemistry associated with psoralen (8MOP) photosensitized reactions.

Photosensitizing drugs and their possible role in enhancing ocular toxicity. Parker Heath memorial lecture

During the past decade there has been a considerable resurgence of interest in the photochemical effects of ultraviolet radiation capable of penetrating through the cornea (300-400 nm), on the intraocular tissues. The ocular lens and retina have received the most attention. The last few decades have also witnessed the development of a new therapeutic regimen, namely photosensitizing (phototherapy), in which the patients are given known photosensitizing agents and exposed to nonionizing radiation (ultraviolet, and on occasion, visible radiation). Such therapy has caused some ocular side effects, which in most cases could have been prevented. Drugs that are known photosensitizers and are capable of intraocular penetration through the blood-aqueous and blood-retina barrier are discussed with respect to their known or potential photosensitizing and/or phototoxic effects on intraocular tissues.

The role of sunlight in human cataract formation

This review summarizes and integrates new findings concerning the role of near-ultraviolet radiation, as is present in sunlight and common artificial light sources, in stimulating human and animal cataract formation. Epidemiological and basic research studies are summarized and critical statements concerning them are offered. Although certain questions still remain unanswered, the evidence that near-UV radiation does stimulate cataract formation is very strong. Avoidance of excessive exposure to near-ultraviolet light and the use of protective lenses that filter it out are suggested to prevent the enhancement of human cataract formation by near-UV light.

The lens and PUVA therapy

A study was made of patients, who were receiving PUVA therapy for psoriasis, to see if lens abnormalities occurred which could be due to the PUVA treatment. In a group of 42 patients there was only one eye of one patient, in which a very slight opacity was found which might possibly have developed during the therapy.

Allopurinol therapy and cataractogenesis in humans

Long-term ingestion of allopurinol, an antihyperuricemic agent used to treat gout, may be related to the development of lens opacities in relatively young patients (second to fifth decades of life). Cataracts obtained from three patients taking allopurinol were subjected to high-resolution phosphorescence spectroscopy. The characteristic allopurinol triplet was demonstrated in all three cataracts. Identical spectra were obtained for normal human lenses incubated in media containing 10(-3)M allopurinol and exposed to 1.2 mW/cm2 ultraviolet radiation for 16 hours; control lenses (irradiated without allopurinol) showed no allopurinol triplets. Similar data were obtained for lenses from rats given one dose of allopurinol and exposed to ultraviolet radiation overnight. These data provide evidence that allopurinol can be photobound in rat and human lenses and suggest its cataractogenic potential.

8-methoxypsoralen and long ultraviolet effects on the rat lens: experiments with high dosage

The effect of systemic 8-methoxypsoralen (8-MOP; 100 mg/kg daily) and subsequent long ultraviolet irradiation (UVA; 300 mJ/cm2; peak: 365 nm) on albino and pigmented rat eyes was studied in a 3-dimensional experimental set-up. While 8-MOP and UVA did not cause any ocular pathology when administered alone, a combined application of the two factors caused reversible corneal opacities, and irreversible iris devascularisation and cataracts. The irreversible changes were seen only in the albinos and accompanied by a significant decrease in lens wet weight. Phosphorescence and EPR spectroscopy demonstrated the formation of an 8-MOP-protein photoadduct in the animals treated with both 8-MOP and UVA. The results of this study emphasize the necessity of shielding the eyes of patients on photochemotherapy with protective spectacles.

Ocular kinetics of 8-methoxypsoralen. An experimental study with pigmented and albino rabbits without UVA-stimulation

Tritiated 8-methoxypsoralen (8-MOP), with radioactivity in the ring system, was injected into both pigmented rabbits and albino rabbits; at 0.5, 1, 2, 4, 6, and 24 h after 8-MOP injection the animals' plasma and ocular radioactivities were determined by liquid scintillation counting. The experiment was done without photostimulation but in incomplete darkness. The plasma radioactivity declined rapidly during the first hour, peak radioactivity occurring in the first samples of vascularized ocular structures taken 0.5 h after the injection. The radioactivity of these tissues generally declined rapidly and similarly in both animal groups. The 1, 2, and 4 h samples of pigmented animals formed an exception; in these the radioactivities in the iris-ciliary body and the retina-choroid of the pigmented animals showed increased activities that were statistically significant, and the plasma radioactivity was exceeded by two to three times. The radioactivities in the internal parts of the eye were lower than in the vascular parts. The radioactivity in the lens reached a peak in the specimens taken 1-2 h after injection and remained at the level of the plasma radioactivity for the rest of the 24 h.