Paulo Filipe

DIFFERENT EFFECTS OF THIOL AND NONTHIOL ACE INHIBITORS ON COPPER-INDUCED LIPID AND PROTEIN OXIDATIVE MODIFICATION

Differences among angiotensin-converting enzyme inhibitors (ACEI) in scavenging reactive oxygen species were described and mainly attributed to the presence or absence of a thiol group. Plasma constituents and red cells are known targets for oxidative damage. Transition metals, like copper, are well known catalizers of free radical generation. In the present study we compared the abilities of captopril (a thiol ACEI), enalaprilat, and lisinopril (two nonthiol ACEI) for inhibiting copper-induced thiobarbituric acid reactive substances (TBARS) formation and fluorescence generation in whole human plasma and low-density lipoprotein. The effects of those ACEI on copper/hydrogen peroxide-induced fluorescence development and electrophoretic mobility modification in albumin and on copper-induced TBARS formation and hemolysis in human red cells were also compared. Captopril was more effective than the two nonthiol ACEI in inhibiting plasma and LDL lipid peroxidation, but it was ineffective in inhibiting the albumin oxidative modification that was moderately inhibited by enalaprilat and lisinopril. On the contrary, the inhibitory effects of the three ACEI on copper-induced lipid peroxidation and hemolysis in red cell suspensions were more uniform. This as yet unreported red cell protective effect may deserve pharmacological evaluation. Our results show that captopril is a more effective antioxidant than the nonthiol ACEI in some systems. However, the nonthiol ACEI also have the ability to partially protect some targets against oxidative damage. These observations suggest that the presence of a thiol group in the ACEI structure is not the only determinant for the antioxidant properties.

Oxidative Stress in Chronic Hepatitis C: The Effect of Interferon Therapy and Correlation with Pathological Features

AIMSnTo evaluate the oxidative stress parameters before, during and after interferon treatment.nnnPATIENTS/METHODSnTwenty patients were treated with interferon a2b 5 MU, three times a week, subcutaneously, for 12 months. Liver biopsy was performed six months before treatment and at the six month follow-up. Chromosomal breakage studies were evaluated by the adjusted clastogenic score (ACS, normal value [nv] 1.1 +/- 2.4%). Plasma malondialdehyde (MDA) was measured according to the Yagi method (nv 6.6 +/- 1.4 nmol/mL) and total thiols using the Ellmans reagent (DTNB) (nv 9.8 +/- 1.3 micromol/g protein). A serum marker of fibrogenesis, the amino-terminal propeptide of Procollagen type III (PIIIP), was quantified by radioimmunoassay (nv 0.37 +/- 0.18 U/L).nnnRESULTSnCompared with reference samples, the plasma of patients before treatment showed an increase of ACS (9.2 +/- 3.2%, P<0.001); higher MDA values (12.6 +/- 2.7 nmol/mL, P<0.001) and total plasma sulfhydryl groups (t-SH) were decreased (6.3 +/- 1.1 micromol/g protein, P<0.001). During treatment and at the follow-up, a decrease in ACS was noticed in all patients (P<0.001), but without normalization; a decrease in MDA was seen, with progressive normalization until the end of the follow up only in sustained responders (P<0.003), while an increase of t-SH was seen, with progressive normalization until the end of follow up in all patients (P<0.005). A positive correlation of ACS with grading of inflammation was found (r=0.52, P<0.03) but not with fibrosis staging. In contrast, plasma MDA correlates with fibrosis staging (r=0.51, P<0.03) and with PIIIP (r=0.57, P<0.03) but without grading of inflammation.nnnCONCLUSIONSnThe present study confirmed the presence of oxidative stress in chronic hepatitis C patients. Interferon promotes a long term inhibition of oxidative stress with concomitant improvement of activity and fibrosis. In the management of chronic hepatitis C, adjuvant therapy with antioxidants could be useful.

Redox reactions of the urate radical/urate couple with the superoxide radical anion, the tryptophan neutral radical and selected flavonoids in neutral aqueous solutions

The kinetics of several processes involving the potential antioxidant role of urate in physiological systems have been investigated by pulse radiolysis. While the monoanionic urate radical, ·UH-, can be produced directly by oxidation with ·Br-2 or ·OH, it can also be generated by oxidation with the neutral tryptophan radical, ·Trp, with a rate constant of 2 × 107 M-1s-1. This radical, ·UH-, reacts with ·O-2 with a rate constant of 8 × 108 M-1s-1. Also, ·UH- is reduced by flavonoids, quercetin and rutin in CTAB micelles at rate constants of 6 × 106 M-1s-1 and 1 × 106 M-1s-1, respectively. These results can be of value by providing reference data useful in further investigation of the antioxidant character of urate in more complex biological systems.

Protective effects of a 21-aminosteroid against copper-induced erythrocyte and plasma lipid peroxidation.

The 21-aminosteroids, or lazaroids, are a novel class of antioxidant drugs designed to inhibit iron-dependent lipid peroxidation in biological lipid environments. They have been shown to be of therapeutic value in several animal models of traumatic, ischemic and hemorrhagic injury of the central nervous system. Our purpose was to evaluate the ability of 21-aminosteroids to protect human erythrocytes and plasma against oxidative damage in vitro. We found that the 21-aminosteroid U74500A inhibited erythrocyte and plasma lipid peroxidation. U74500A at 1 microM significantly reduced copper-induced and hydrogen peroxide-induced erythrocyte lipid peroxidation by 76.5 and 27.6%, respectively. The inhibition of erythrocyte lipid peroxidation was accompanied by an inhibition of hemolysis. Copper-induced plasma lipid peroxidation was also significantly reduced by as little as 1 microM U74500A. These results suggest that 21-aminosteroids may prove useful in preventive or therapeutic interventions in situations where erythrocyte or plasma components are subjected to oxidative stress and in situations related to copper-induced oxidative damage.

An Insight into the Mechanisms of the Phototoxic Response Induced by Cyamemazine in Cultured Fibroblasts and Keratinocytes

Abstract The phototoxicity of cyamemazine (CMZ, Tercian®), a neuroleptic of the phenothiazine family, has recently been reported in humans. CMZ has an absorbance maximum at 267 nm (molar absorptivity, 25u200a800 M−1 cm−1) but a weaker molar absorptivity in the ultraviolet A (UV-A) region. CMZ exhibits a fluorescence with maximum emission at 535 nm and a quantum yield of 0.11. CMZ is a powerful photosensitizing agent toward HS 68 human skin fibroblasts and NCTC 2544 keratinocytes. At a UV-A radiation dose of 10 J/cm2, innocuous to cells in the absence of CMZ, the LD50 (lethal dose corresponding to 50% killing) are 0.5 and 1 μM for the fibroblasts and the keratinocytes, respectively, after overnight incubation with the drug. Short incubation times do not significantly alter the LD50. The CMZ-induced phototoxicity is accompanied by lipid membrane peroxidation consistent with the amphiphilic character of this photosensitizer. Keratinocytes are an order of magnitude less sensitive to the photosensitized lipid peroxidation than fibroblasts. Microspectrofluorometry reveals that lysosomal membranes are major sites of CMZ incorporation into the two cell lines because a Forster-type resonance energy transfer process occurs from CMZ to LysoTracker Red DND99 (LTR), a specific fluorescent probe of lysosomal membranes. The CMZ-photosensitized destruction of LTR demonstrates that CMZ retains its photosensitizing capacity after its lysosomal uptake.

The inhibition of lipid peroxidation by cinnarizine. Possible implications to its therapeutic and side-effects.

Cinnarizine has antivasoconstrictor properties and improves red-cell deformability. Its major side-effects are the induction of extrapyramidal reactions. It is a calcium antagonist, but it was suggested that its effects may depend on other mechanisms, namely on antiperoxidant properties. We have studied these properties in different biological systems, intact red-cells included. The occurrence of lipid peroxidation was determined by the formation of 2-thiobarbituric acid reactive products. Cinnarizine was found to inhibit spontaneous lipid peroxidation in rat liver homogenates, copper-induced lipid peroxidation in human plasma and copper-induced and hydrogen peroxide-induced lipid peroxidation in human red-cells. In red-cells, the inhibition of lipid peroxidation is accompanied by the inhibition of hemolysis. Copper-induced red-cell lipid peroxidation is 85% inhibited by as little as 5 microM cinnarizine. The antioxidant activity of cinnarizine may contribute to explain some of the effects of this drug.

On the repair of oxidative damage to apoferritin: a model study with the flavonoids quercetin and rutin in aerated and deaerated solutions

Abstract Ferritin (Ft) impairment through •O2–, H2O2, and •OH production occurs in the cases of ketoses, diabetes mellitus, acute intermittent porphyria and tyrosinemia. In addition to •Trp and TyrO• radical production, ferrous iron liberation and Ft synthesis stimulation, site-specific oxidation reactions are induced leading to toxic iron accumulation in organs with high Ft content, for example, liver and brain. To elucidate the potential pathways to Ft recovery, repair of oxidative damage to horse spleen apoferritin (apoFt) and Ft by quercetin (QH) or rutin (RH) was studied in the presence and absence of oxygen. •Trp and TyrO• radicals were produced in pulse radiolysis through apoFt oxidation by •Br2– radicals. QH and RH bind to apoFt on eight sites with binding constants of ˜80,000 and ˜32,000 M−1, respectively. In deaerated solutions, a repair of apoFt radicals is observed involving both bound and free flavonoids. This repair occurs by a fast intra- and a slow inter-molecular electron transfer from bound and free flavonoids, respectively. With QH, the rate constants are 104 s–1 and 3.5 × 107 M–1 s–1 for the intra- and intermolecular repair reactions, respectively. Oxygen does not interfere with repair of apoFt or Ft by bound QH but inhibits 90% of Ft repair by RH. These results taken together indicate that flavonoid antioxidants may help alleviate Ft impairment in diseases involving an oxidative stress.

PIODERMA GANGRENOSO EM ASSOCIAÇÃO A HIDROSADENITE SUPURATIVA – UMA ASSOCIAÇÃO RARA MAS BEM DEFINIDA

Pyoderma gangrenosum (PG) and hidradenitis suppurativa (HS) are inflammatory diseases of unknown aetiology, which association is rare but well established. We describe the case of a 27-year-old female patient, with axillary and inguinal hidradenitis supurativa lesions since four years ago who developed a pyoderma gangrenosum lesion in her right leg. Treatment was instituted with systemic corticosteroids in inpatient setting. Afterwards, clindamycin and rifampicin were chosen followed by low dose isotretinoin with good response. The association of HS and PG can possibly have a common aetiology related to neutrophilic activity dysfunction. The description autossomic dominant syndrome PAPA (PG, acne and pyogenic arthritis) as well as PASH (PG, acne and HS), dermatos included in the spectrum of autoinflammatory diseases, promise a better comprehension of aetiopathogenesis of this association with possible diagnostic and therapeutic improvements.

FENÓMENO PROZONA EM SÍFILIS SECUNDÁRIA. A IMPORTÂNCIA DA COMUNICAÇÃO ENTRE O CLÍNICO E O LABORATÓRIO

The prozone phenomenon is defined as a falsely negative test due to very high titters of antibody, as high titters of antigen or antibody may prevent the formation of antigen-antibody complexes in laboratory tests of many diseases, like syphilis or brucellosis. We describe the case of a 27 year old caucasian male admitted in the emergency room with enlarged palpable lymph nodes and a skin eruption either suggestive of secondary syphilis or primary skin lymphoma. Since initial RPR screen was negative, he was admitted in ward with the latest hypothesis. Skin biopsies were suggestive of syphilis. The laboratory was then contacted to repeat the test under dillutional protocol, which enabled the test to be positive (VDRL 1/256 and TPHA positive). This case illustrates the importance of close contact with the laboratory in order to avoid false negative results, like those given in presence of prozone phenomenon.KEYWORDS – Syphilis, Cutaneous; Syphilis Serodiagnosis; False Negative Reactions.