Reversal of visual impairment in patients with retinis pigmentosa after administration of glutathione peroxidase enzyme

Ammannati P., Giordani R., Chimenti M.

glutathione peroxidase enzyme 

The glutathione peroxidase enzyme (GPX) administration effects have been studied in patients with retinitis pigmentosa (RP). RP at present is defined as a degenerative, progressive and irreversible one. It was found that in RP patients there was a decrease of GPX level in respect to normal subjects. Moreover in rabbits it was shown that retrobulbar administration of GPX prevents the abolition of the electroretinogram due to previous administration of an oxidant agent as AgNO. On the basis of the results obtained, it was hypothesized that a deficit of reducing enzyme of the pentose phosphate pathway may binder the regeneration of the pigment modified by the oxidation process due to light that hits the retina. This process can bring to a pathological increase of the epithelial pigmentation. It was decided to investigate the potential effect of the replacement therapy with GPX administration. The number of patients is 7636 and their cumulative data are reported. The treatment was administration of one I.U. of GPX in retrobulbar fat, for three consecutive days each month, for three consecutive months, in each eye. We measured the visual acuity, the peripheral retinal fields and ERG before and after therapy. After completion of therapy over the 90% of the patients showed a significant clinical improvement, confirmed by the measured parameters. The amelioration for visual acuity ranged from 1/10 (R.E.) to no variation (L.E.) to 68% in both eyes. ERG, extinct in about 98% the patients, presented an improvement from a normal morphology with a very reduced voltage to a normal voltage and morphology. These results have been stable for the 6 years of follow-up. The results support the hypothesis that a deficit of GPX may play an important role in the pathophysiology of RP. These results conduct to consider that the pentose phosphate pathway is essential for the retina correct metabolism and function.

Source: Atti della Fondazione "Giorgio Ronchi" 2 (2003): 187–195.

Publisher: Fondazione Giorgio Ronchi., Arcetri, Italia