Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0349506 (photosensitivity)
 4,145 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activity of haem synthetase, the enzyme which chelates iron to protoporphyrin to form haem, was measured in cultured skin fibroblasts of children with protoporphyria and their parents from three families. In each family, one parent had deficient haem synthetase activity (3-0-11-1 pmol protohaem formed/mg protein/h) when compared to values in eight non-porphyric controls (means 24-9, range 13-7-51-5). The level of activity in the three parents was similar to that in their affected children. In two families the parent with deficient activity was also thought to be the carrier of the abnormal gene, as judged from a history of photosensitivity and analysis of erythrocyte protoporphyrin concentrations, but in the third family the pattern of inheritance could not be determined from these criteria. The activity of delta-aminolaevulinic acid synthetase was normal in cultured fibroblasts from the protoporphyric children and their parents, excluding a generalised defect in haem-pathway enzymes. These results support the premise that deficient haem synthetase activity, inherited in an autosomal dominant patter, is the primary defect in protoporphyria.
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PMID:Inheritance in protoporphyria. Comparison of haem synthetase activity in skin fibroblasts with clinical features. 5 42

The photodermatosis in erythropoietic protoporphyria (EPP) is caused by the accumulation of photosensitizing protoporphyrin (PP) in the skin, due to a defect in ferrochelatase, the enzyme that inserts ferrous iron into PP to form heme. Hydroxyl radical (.OH) and singlet oxygen generation with subsequent lipid peroxidation are thought to play a major role in the pathogenesis of the photodermatosis in EPP. Hydrogen peroxide (H2O2) can generate .OH in the Haber-Weiss as well as the Fenton reaction, and is thus a potentially harmful intermediate in the photoreduction of O2. The use of oxyradical scavengers, such as beta-carotene, has been reported to be beneficial in the treatment of EPP photodermatosis. In this study, N-acetylcysteine (NAC) 1800 mg/day was used for 3 reasons: (i) its -SH groups directly scavenge H2O2; (ii) ferrochelatase can be activated by sulfhydryl groups; (iii) NAC was reported to upregulate the glutathione redox system, which is a major endogenous anti-oxidant system. However, in a double-blind crossover placebo controlled study on 6 EPP patients, we could neither demonstrate an effect through photosensitivity tests, nor on light hypersensitivity as reported by the patients. This dosage of NAC could not increase reduced glutathione and did not affect the red blood cell PP content nor the excretion of PP in the feces. Neither were adverse effects observed. We conclude that the oral administration of NAC, in the relatively low dose used here, is not effective in the treatment of photodermatosis in EPP.
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PMID:Protoporphyrin photosensitivity cannot be attenuated by oral N-acetylcysteine. 134 25

A 28-year-old man who had suffered from erythropoietic protoporphyria since infancy was referred because of worsening photosensitivity. Conventional therapy with beta-carotene, terfenadine and topical sunscreens was ineffective or not tolerated, and he was treated with transfusions of washed packed cells. Unexpectedly, his photosensitivity deteriorated further, his whole blood protoporphyrin levels doubled and he developed abnormal liver function tests. This is the first report of such an adverse response to blood transfusion therapy for erythropoietic protoporphyria and may have been related to subclinical hepatitis or the increased iron load associated with blood transfusion.
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PMID:Erythropoietic protoporphyria, transfusion therapy and liver disease. 146 96

The formation and disappearance of a photosensitive species during the reaction of reduced cytochrome c oxidase (putatively a3II.O2), EC 1.9.3.1, has been followed by (a) mixing a3II.CO with O2 in a stopped flow apparatus; (b) initiating the oxygen-oxidase reaction by removing CO with a laser flash; (c) probing the reaction mixture for photosensitivity with a second laser flash. Photosensitivity appears in the reaction mixture after the first laser flash, reaches a maximum after 50-60 microseconds ([O2] greater than 100 microM), and disappears in a further 50-100 microseconds. The kinetics can be represented by the scheme [formula: see text]. In species B, O2 is associated with the protein, possibly CuB, but not with the heme. Species C is the photosensitive a3II.O2 complex, and in D, a3 iron has been oxidized. The formation of species C is responsible for the rapid phase of absorbance change in the oxidase-oxygen reaction. The rate of reaction with oxygen approaches the limit of 35,000 s-1 at high oxygen. Nitric oxide, however, reacts with FeII oxidase with a rate of 1 x 10(8) M-1 s-1, which is accurately maintained up to an observed rate of 10(5) s-1. In flash photolysis experiments, approximately half of the photodissociated nitric oxidase recombines in a biphasic geminate reaction with rates of 1 x 10(8) s-1 and 1 x 10(7) s-1.
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PMID:Studies of the primary oxygen intermediate in the reaction of fully reduced cytochrome oxidase. 165 79

Porphyria cutanea tarda (PCT) is a disorder of heme synthesis characterized by (a) a diminished activity of uroporphyrinogen decarboxylase biochemically and (b) cutaneous lesions secondary to a delayed type of photosensitivity clinically. A human immunodeficiency virus (HIV)-infected patient with PCT is reported and the world literature is reviewed. To date, 17 HIV-seropositive men with PCT have been described. The initial appearance of PCT occurred before or concurrent with the diagnosis of HIV infection in 71% of these individuals (12 men). The median age at onset of PCT was 36 years (range of 20 to 69 years); the median age for the detection of HIV infection was 35 years (range of less than 20 to 71 years). All of these patients had elevated levels of urine porphyrins and blisters on their dorsal hands. Abnormal liver function tests, erosions, hyperpigmentation, hypertrichosis, and skin fragility were also present in some of the men. Polycythemia, serologic evidence of increased iron stores, scarring, milia, and sclerodermoid changes were rarely observed. Successful therapeutic approaches for PCT in men with HIV infection included (a) elimination of PCT-precipitating agents, (b) avoidance of sun exposure, and (c) periodic phlebotomy. Multiple hypotheses for an etiologic role of the HIV and/or an HIV-associated infection, directly or indirectly, in the pathogenesis of PCT in HIV-seropositive men have been suggested.
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PMID:Porphyria cutanea tarda in human immunodeficiency virus-seropositive men: case report and literature review. 175 38

The role of iron in the mechanism of photosensitivity due to uroporphyrin was investigated. There is frequently increased levels of Fe in the serum from patients with porphyria cutanea tarda, where the photosensitivity is due to uroporphyrin. It has been reported that H2O2 has a major role in the uroporphyrin induced photosensitivity. Hence we examined the hypothesis that Fe would catalyze the production of OH from H2O2 and the OH thus formed may have a significant role in the uroporphyrin photosensitivity. This was examined by studying the effects of the Fe chelating compound deferoxamine in an in vitro system. Our results show that deferoxamine inhibited the uroporphyrin photosensitivity, but not the photosensitivity due to protoporphyrin. This indicates that Fe may play a role in the uroporphyrin photosensitization in the skin, by accelerating the formation of OH, which may be a major reactive species responsible for the photosensitization in porphyria cutanea tarda.
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PMID:Role of iron in the photosensitization by uroporphyrin. 181 50

"Opaque" physical sunscreens are important for photoprotection of individuals with visible light and UV-A photosensitivity such as those with porphyria, drug photoallergy, and polymorphous light eruption. Diffuse spectral transmittance of various thicknesses of opaque sunscreen formulations were measured from 350- to 800-nm range using a spectrophotometer equipped with an integrating sphere. Transmission through 20% zinc oxide paste was high and decreased minimally despite large increases in the sunscreen layer thickness. Adding a visible light absorber such as iron oxide to scattering sunscreens, however, substantially lowered transmittance below that predicted by the product of the transmittances for each component alone. Opaque sunscreens protected against hematoporphyrin derivative photosensitization of albino guinea pig skin; these results were quantitatively consistent with the in vitro findings. Poor photoprotection against visible light is obtained with white paste sunscreens, even if thick layers are applied. The addition of pigments to such sunscreens, however, greatly enhances photoprotection and cosmetic acceptability.
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PMID:Efficiency of opaque photoprotective agents in the visible light range. 155 Mar 79

The cutaneous porphyrias are disorders of heme biosynthesis in which excessive formation of porphyrins, secondary to partial enzyme deficiencies, produces photosensitization. There are five main types: porphyria cutanea tarda (PCT); variegate porphyria (VP); hereditary coproporphyria (HC); erythropoietic protoporphyria (EPP); and congenital erythropoietic porphyria (CEP). They can be differentiated by measuring heme precursors in urine, feces, erythrocytes, and plasma. VP, HC, EPP, and one form of PCT (type II) are autosomal dominant conditions with low clinical penetrance. The autosomal recessive prophyrias (CEP and homozygous counterparts of type II PCT, VP, and HC) are rare disorders. The skin lesions in PCT (the commonest cutaneous porphyria), VP, HC, and CEP are similar: mechanical fragility, subepidermal bullae, hypertrichosis, and pigmentation. EPP is characterized by acute photosensitivity without these lesions. Acute attacks of porphyria may occur in VP and HC but not in other cutaneous porphyrias. Liver disease is an uncommon, potentially fatal, complication of EPP. PCT is commonly associated with chronic liver disease, is often caused by alcohol and usually mild. PCT can be treated by repeated venesection to deplete iron stores or with low-dose chloroquine. Treatment of the other cutaneous porphyrias is largely symptomatic; accumulation of beta-carotene in the skin is particularly effective in EPP.
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PMID:The cutaneous porphyrias. 220 45

Erythropoietic protoporphyria, caused by an inherited deficiency of ferrochelatase, results in increased free protoporphyrin concentrations in erythrocytes and plasma. Cutaneous photosensitivity is the primary clinical manifestation, but in some patients, protoporphyrin accumulation in the liver may lead to fatal hepatic failure. No treatment exists for this lethal complication. We report the case of a patient with erythropoietic protoporphyria and abnormal results of liver function tests in whom oral iron therapy led to a substantial decrease in free erythrocyte and stool protoporphyrin levels with return of liver function to normal. Iron therapy should be considered for preventing potentially fatal hepatic failure in patients with erythropoietic protoporphyria.
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PMID:Iron therapy for hepatic dysfunction in erythropoietic protoporphyria. 371 7

The anticancer drug, bleomycin, has recently been shown to be light-sensitive by a number of research groups. This photosensitivity extends to its complexes with iron(II), copper(II), cobalt(III) and DNA. Nicking of DNA by photoactivated bleomycin occurs at lower concentrations than under dark conditions. Phototreatment of a bleomycin/dopamine beta-hydroxylase mixture leads to extensive irreversible inhibition of the enzyme. The implications of this drug's photoreactivity are discussed.
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PMID:Photoactivity of bleomycin. 619 4


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