João P. Freitas

Anti‐ and pro‐oxidant effects of urate in copper‐induced low‐density lipoprotein oxidation

We recently reported that, depending on its concentration, urate is either a pro- or an antioxidant in Cu(2+)-induced low-density lipoprotein (LDL) oxidation. We also previously demonstrated an antioxidant synergy between urate and some flavonoids in the Cu(2+)-induced oxidation of diluted serum. As a result, the effect of the flavonoid quercetin on the Cu(2+)-induced oxidation of isolated LDL has been studied either in the presence or absence of urate. We demonstrate that, like urate, quercetin alone, at low concentration, exhibits a pro-oxidant activity. The pro-oxidant behavior depends on the Cu(2+) concentration but it is not observed at high Cu(2+) concentration. When compared with urate, the switch between the pro- and the antioxidant activities occurs at much lower quercetin concentrations. As for urate, the pro-oxidant character of quercetin is related to its ability to reduce Cu(2+) with the formation of semioxidized quercetin and Cu(+) with an expected yield larger than that obtained with urate owing to a more favorable redox potential. It is also shown that the pro-oxidant activity of urate can be inhibited by quercetin. An electron transfer between quercetin and semioxidized urate leading to the repair of urate could account for this observation as suggested by recently published pulse radiolysis data. It is anticipated that the interactions between quercetin-Cu(2+)-LDL and urate, which are tightly controlled by their respective concentration, determine the balance between the pro- and antioxidant behaviors. Moreover, as already observed with other antioxidants, it is demonstrated that quercetin alone behaves as a pro-oxidant towards preoxidized LDL.

Oxidative Stress in Adamantiades-Behçet’s Disease

Background: Adamantiades-Behçet’s disease is a chronic systemic disorder associating oral and genital ulcerative lesions with ocular and cutaneous manifestations. Previous publications report increased superoxide production by neutrophils and macrophages, increases in cytokines and malondialdehyde (MDA), as well as low levels of enzymatic antioxidant defenses. Aim: We looked for another marker of oxidative stress in Adamantiades-Behçet’s disease: the presence of clastogenic factors (CF) in patients’ plasma. In addition, we determined plasma endproducts of lipid peroxidation (MDA). Patients and Methods: We studied 20 patients and 20 controls. The clastogenic activity was evaluated by means of cytogenetic methods. This test (CF test) detects circulating prooxidants, due to their clastogenic effects after exposure of lymphocyte cultures of healthy persons to plasma ultrafiltrates from patients. The clastogenic prooxidants are lipid peroxidation products and cytokines, in particular TNF-α. Lipid peroxidation was evaluated by the Yagi method. Results: The CF test was positive in 18 out of 20 patients, while it was negative in all 20 control persons. The mean increase in chromosomal breaks was 10.6 ± 3.8 in cultures exposed to patients’ plasma and 1.3 ± 2.4 for cultures receiving control plasma (p <0.001). The clastogenic effect of patients’ plasma ultrafiltrates was significantly inhibited by superoxide dismutase (EC 1.15.1.1), suggesting an important role of the superoxide radical in the clastogenic pathway. Thiobarbituric-acid-reactive substances (expressed as nanomoles MDA per milliliter) were also significantly increased in these patients: 10.6 ± 3.2 for patients and 6.6 ± 1.4 for controls (p <0.001). Conclusion: The presence of CF in the plasma of patients, indicating the presence of circulating prooxidants with chromosome-damaging effects, confirms an oxidative stress in Adamantiades-Behçet’s disease. The anticlastogenic effect of superoxide dismutase in vitro suggests the implication of the superoxide radical. MDA levels were also significantly increased in patients.

Follow-Up of Exocrine Pancreatic Function in Type-1 Diabetes mellitus

In a previous study, mild to moderate exocrine pancreatic insufficiency, as measured by the secretin-pancreozymin test, was found in 23 (43%) of 53 patients with type-1 diabetes mellitus. Of these 53 patients, 20 (7 of whom initially had an abnormal secretin-pancreozymin test) were available for a follow-up examination 11 years later. Of the 7 patients with abnormal exocrine pancreatic function at the first test, 5 remained abnormal and 2 became normal, whereas of the 13 patients with initially normal pancreatic function the test result remained normal in 11 patients and became abnormal in 2. In these 2 groups the test result did not differ significantly between both tests. However, exocrine pancreatic function had returned to normal or had become abnormal in 2 patients, respectively, at the second test. In the 3 patients with exocrine pancreatic insufficiency at the first and second tests, the lipase level had not fallen below 10% or less than the normal level at which steatorrhea occurs and therapy is required. There was no significant correlation between the duration of the diabetes and the test results for both time points of investigation. The data suggest that mild to moderate exocrine pancreatic insufficiency found in type-1 diabetes is due to an early event in the course of the diabetes and does not progress. Therefore, this finding is of minor clinical importance and expensive pancreatic enzyme substitution will not be required.

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.

Cutaneous Manifestations of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a multiorgan autoimmune disease of unknown etiology with many clinical manifestations. The skin is one of the target organs most variably affected by the disease. The American College of Rheumatology (ACR) established 11 criteria as a classificatory instrument to operationalise the definition of SLE in clinical trials. They were not intended to be used to diagnose individuals and do not do well in that capacity. Cutaneous lesions account for four of these 11 revised criteria of SLE. Skin lesions in patients with lupus may be specific or nonspecific. This paper covers the SLE-specific cutaneous changes: malar rash, discoid rash, photosensitivity, and oral mucosal lesions as well as SLE nonspecific skin manifestations, their pathophysiology, and management. A deeper thorough understanding of the cutaneous manifestations of SLE is essential for diagnosis, prognosis, and efficient management. Thus, dermatologists should cooperate with other specialties to provide optimal care of SLE patient.

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

AIMS To evaluate the oxidative stress parameters before, during and after interferon treatment. PATIENTS/METHODS Twenty 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). RESULTS Compared 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. CONCLUSIONS The 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.

Lipid peroxidation in type 2 normolipidemic diabetic patients

Vascular complications, as a consequence of atherosclerosis, are the main causes of morbidity and mortality in diabetes. Low density lipoprotein (LDL) oxidation is accepted as a relevant pathogenic mechanism in atherogenesis. The aim of this work was to study the relationship between lipid peroxidation (LPO) and metabolic control. LPO was evaluated in 40 type 2 normolipidemic diabetic patients by measuring thiobarbituric acid reactive substances (TBARS), in the plasma, using malondialdehyde (MDA), end product of the oxidation of polyunsaturated fatty acids, as a standard. Fast blood glucose (FBG), serum total cholesterol (TC) and serum triglycerides (TG) were evaluated by routine methods. Fructosamine (FR) was measured by the nitroblue tetrazolium (NBT) colorimetric test. An elevated level of lipid peroxides (P < 0.001) was observed in the plasma of diabetic patients (4.51 +/- 1.29 nmol/ml) as compared to normal subjects (3.54 +/- 1.00 nmol/ml). Lipid peroxides did not correlate with the FR levels, nor with FBG, TC and TG. These results show an increase of LPO in type 2 normolipidemic diabetic patients. Probably the mechanism for higher lipid peroxide levels in diabetes is multifactorial. Our study supports the hypothesis of a role of oxidative stress in diabetes independently of the lipid serum content.

CLASTOGENIC FACTORS AS BIOMARKERS OF OXIDATIVE STRESS IN CHRONIC HEPATITIS C.

Background/Aims: Clastogenic factors (CFs) are composed of lipid peroxidation products, cytokines and other oxidants with chromosome-damaging properties. They are regularly observed after radiation exposure and in chronic inflammatory diseases, where they are supposed to be risk factors for carcinogenesis. It appeared of interest to investigate their presence in the plasma of patients with chronic hepatitis C. Methods: CFs are detected by chromosomal breakage studies. They were compared to malondialdehyde (MDA), total plasma thiols (t-SH), alanine aminotransferase (ALT), viral load and histological data. Results: CFs were increased in 19 of 20 patients, 16 had increased MDA levels and 15 had decreased t-SH levels. Mean values were significantly different from the 20 controls (p < 0.001). After the first 3 months of interferon treatment, all three markers showed significant improvement, but were not completely normalized. There was a positive correlation between CFs and necroinflammatory activity (p < 0.03), while MDA was correlated with fibrosis (p < 0.03). Viral load was correlated with necrosis and inflammation (p < 0.05). Conclusion: The presence of CFs in chronic hepatitis C confirms the occurrence of oxidative stress in this disease and could be useful in clinical trials for testing antioxidants. The CF test is a sensitive assay for the detection of oxidative stress and correlates with necroinflammatory activity.

Sensitivity to thimerosal and photosensitivity to piroxicam

17 patients allergic to thimerosal. with no previous history of photosensitivity or piroxicam ingestion. 2 patients with piroxicam‐induced photosensitivity, and 10 controls were patch or photopatch tested, with 1 or more of the following thimerosal, thiosalicylic acid, irradiated and non‐irradiated solutions of piroxicam alone, L‐cysteine alone and piroxicam plus l‐cysteine, and piroxicam in petrolatum, The results of the tests supported the hypothesis that there are cross reactions between thiosalicylic acid and piroxicam, a photosensitizer. The mechanism of the cross‐reactions may involve photoproduts of piroxicm and L‐cysteine, as patients allergic to thiosalicylic aid, who have positive photopatch tests to piroxicam, also had positive patch tests to the irradiated solution of piroxicam plus L., cysteine.

Hyaluronic Acid in Progressive Systemic Sclerosis

BACKGROUND The glycosaminoglycans metabolism is disturbed in progressive systemic sclerosis (PSS). Serum hyaluronic acid (HA) is elevated in this disease. OBJECTIVE This study was conducted to determine the HA plasma concentrations of patients with PSS according to the different stages of the disease. METHODS We studied 48 patients divided into three subgroups: subgroup 1 (n = 10), with skin compromise without evidence of other organ involvement; subgroup 2 (n = 21), with skin and esophagus involvement; subgroup 3 (n = 17), with skin, lung and other internal organ involvement. A radiometric assay was performed for quantification of HA. RESULTS Our results confirm the increase in plasma HA in patients with PSS. They also suggest that lung involvement is the main feature responsible for high plasma concentrations of HA. The plasma HA levels were elevated in patients compared to normals (p <0.001). Significant differences were observed between subgroups 1 and 3 (p <0.01) and between subgroups 2 and 3 (p <0.01). A positive correlation between disease severity scores and plasma HA values was observed (p <0.01). CONCLUSION An important elevation of HA plasma levels could be a serologic marker of disease severity, progression and degree of visceral involvement.