5-Methoxypsoralen increases the sensitivity of the retina to light in humans

Comparison of the effects of psoriasis and vitiligo on retina pigment epithelium thickness

PURPOSE

The purpose of the study was to compare Retinal Pigment Epithelium (RPE) thickness in patients with Psoriasis and Vitiligo.

MATERIALS AND METHODS

The right eyes of 67 Psoriasis and 65 Vitiligo patients and 71 healthy individuals were included in the study. The RPE thicknesses were analyzed with the Spectral Domain Optical Coherence Tomography after routine ophthalmological examinations (SD-OCT).

RESULTS

No statistically significant differences were detected when Psoriasis and Vitiligo patients were compared in terms of RPE levels (p= 0.033). When compared with the control group, no significant differences were found with Psoriasis patients, but a significant difference was detected with Vitiligo patients (p=0.515, p=0.001, respectively).

CONCLUSION

Although no changes were detected in RPE in Psoriasis, the decreased RPE thickness in Vitiligo may be an indicator of the effect of melanin loss on the posterior segment of the eye in Vitiligo. For this reason, measurement of RPE thickness with OCT can help in detecting the damage in Vitiligo patients.

Effect of oral photochemotherapy (8-methoxypsoralen + UVA) on the electrophysiologic function of retina

CONTEXT

Since we had observed electroretinographic (ERG) abnormalities in some patients undergoing photochemotherapy with normal eye examination, we decided to investigate the effects of this therapy on retinal function.

OBJECTIVE

To investigate the effects of oral photochemotherapy (8-methoxypsoralen + Ultraviolet-A) on electrophysiologic function of retina.

MATERIALS AND METHODS

Patients with vitiligo, psoriasis or eczema were enrolled. Patients with any abnormal eye exam or a positive drug or family history for retinal disease were excluded. Baseline standard ERG was provided with the RETIport32 device. The second ERG was performed 6 months after the first and at least 1 week after the last photochemotherapy session (mean number of sessions: 45 ± 11). The outcome measures were changes in rod response, standard combined response, single-flash cone response, 30-Hz flicker (N1-P1) and oscillatory potentials amplitudes.

RESULTS

Forty patients were enrolled; 20 of them (mean age: 31.1 ± 12 years) completed the study. The mean rod response b-wave amplitude decreased from 88.9 ± 47.5 to 86.4 ± 36.6 and standard combined response b-wave amplitude decreased from 266.52 to 261.85 µV (p = 0.422 and p = 0.968, respectively) and the standard combined response a-wave amplitude increased from 155.4 ± 40.0 at baseline to 165.1 ± 48.4 in the follow-up ERG (p = 0.092). The mean single-flash cone response a-wave amplitude decreased insignificantly in the follow-up ERG trace (34.5 ± 13.7 and 29 ± 15.4, respectively, p = 0.242). The mean single-flash cone response b-wave amplitude showed an insignificant increase (p = 0.087). The amplitudes of 30-Hz flicker wave and oscillatory potentials did not change significantly in the follow-up ERG (p = 0.551 and p = 0.739, respectively).

CONCLUSION

Since no significant change in ERG traces was observed, oral photochemotherapy seems safe for retinal electrophysiologic function.

Antidepressant effect of 5-methoxypsoralen: The melatonin synchronizer hypothesis

5-methoxypsoralen (5-MOP) stimulates pineal melatonin secretion, and a decrease in dark phase melatonin levels has been described in major depression. As exogenous melatonin has shown synchronizer properties, authors hypothesized that giving 5-MOP would have antidepressant properties. Twenty-six inpatients meeting the criteria of major depressive disorders were enrolled in a four-week, double blind trial of 5-MOP versus amitriptyline. Clinical improvement was identical in both treatment groups but biological changes were different in each group: 5-MOP patients showed an early nocturnal surge of melatonin levels that was maintained at the fourth treatment week, while melatonin levels remained unchanged in patients treated with amitriptyline.

Effects of benzopsoralen derivatives on HL60 and HeLa cells

The effect of 4-hydroxymethyl-6,7,8,9-tetrahydro-2H-benzofuro-[3,2-g]-1-benzo piran-2-one (compound 1) and 4-hydroxymethyl-2H-benzofuro-[3,2g]-1-benzopiran-2-one (compound 2), two new benzopsoralen derivatives, was tested on HL60 and HeLa cell lines in the dark and by UVA irradiation; 8-methoxypsoralen was used as a reference compound. The action of the compounds was evaluated by means of the neutral red uptake assay, by means of ultrastructure, morphometry and interaction with human erythrocytes membrane. In both HL60 and HeLa cell lines benzopsoralen derivatives showed more antiproliferative activity after UVA irradiation, however less than 8-methoxypsoralen. Compound 1 was more effective than compound 2 both in the dark and after UVA irradiation. The ultrastructure showed a morphological rank damage caused by these compounds: compound 2 induced slight modifications in the cytoplasm organization, compound 1 induced some vacuolizations and 8-methoxypsoralen generated plenty of vacuoles and an empty space around the nucleus. Morphometrical data in HL60 cells turned out to be in accordance with the different action mechanisms existing between 8-methoxypsoralen and the two benzopsoralen derivatives; in HeLa cells we noted an increase in the nuclear area induced by all the three compounds. Only compound 1 caused the formation of echinocytes both in the dark and after UVA irradiation, suggesting the involvement of a mechanism not strictly related to DNA interaction and singlet oxygen production.

Light treatment for seasonal affective disorder: theoretical considerations and clinical implications

The concept of seasonal affective disorder (SAD) includes any depression whose onset is related to a certain season. Reduced environmental light is hypothesized to be the main precipitating factor of winter depression. Light treatment is used to prevent the onset of depressive episodes and to reduce depressive symptoms in patients with depression during winter months. The mechanisms of action which lead to the well-documented antidepressant response are still unknown. Several hypotheses of the pathogenesis of SAD are discussed, and the clinical practice of light treatment is reviewed.

Melatonin decreases the amplitude of the b-wave of the human electroretinogram

In a double-blind placebo crossover study of 13 healthy volunteers, the pineal hormone melatonin (10 mg) was given at 4 pm, and the electroretinogram measured under conditions of dark and light adaptation. A significant diminution of b-wave amplitude was found under both photopic (delta = 5.4 microV, p < 0.05) and scotopic conditions (delta = 7.4 microV, p < 0.01). These data indicate that melatonin may transduce the dark signal at the level of the retina as well as the pineal. Acute administration of melatonin decreases sensitivity to light.