Amy M.L. Quek

Oxidative damage in dengue fever

Oxidative stress may be important in the pathogenesis of dengue infection. Using accurate markers of oxidative damage, we assessed the extent of oxidative damage in dengue patients. The levels of hydroxyeicosatetraenoic acid products (HETEs), F(2)-isoprostanes (F(2)-IsoPs), and cholesterol oxidation products (COPs) were measured in 28 adult dengue patients and 28 age-matched study controls during the febrile, defervescent, and convalescent stages of infection. We compared the absolute and the percentage change in these markers in relation to key clinical parameters and inflammatory markers. The levels of total HETEs and total HETEs/arachidonate, total F(2)-IsoPs/arachidonate, and COPs/cholesterol were higher during the febrile compared to the convalescent level. Total HETEs correlated positively with admission systolic blood pressure (r=0.52, p<0.05), whereas an inverse relationship was found between 7beta-hydroxycholesterol and systolic and diastolic blood pressure (r=-0.61 and -0.59, respectively, p<0.01). The urinary F(2)-IsoP level was higher in urine during the febrile stage compared to the convalescent level. Despite lower total cholesterol levels during the febrile stage compared to convalescent levels, a higher percentage of cholesterol was found as COPs (7beta-, 24-, and 27-hydroxycholesterol). The levels of platelet-activating factor-acetylhydrolase activity, vascular cellular adhesion molecule-1, tumor necrosis factor-alpha, and high-sensitivity C-reactive protein were higher during the febrile stage compared to their convalescent levels (p<0.01). Markers of oxidative damage are altered during the various stages of dengue infection.

Oral zinc supplementation does not improve oxidative stress or vascular function in patients with type 2 diabetes with normal zinc levels

OBJECTIVE There is considerable controversy about what constitutes optimal zinc intakes in patients with type 2 diabetes mellitus. Several studies suggest that higher zinc intakes improve vascular function and decrease oxidative damage. We aimed to assess the effects of zinc supplementation using a range of reliable biomarkers of oxidative damage and vascular function in patients with type 2 diabetes. METHODS Forty male type 2 diabetic patients were supplemented either with 240 mg/day of zinc as zinc gluconate (n=20) or with placebo (n=20) for 3 months. Blood and spot urine samples were taken at baseline, days 3 and 7, months 1, 2 and 3 during supplementation and 1 month after cessation. Serum zinc, reliable biomarkers of oxidative damage (F(2)-isoprostanes, neuroprostanes, cholesterol oxidation products, allantoin) as well as hydroxyeicosatetraenoic acid products and vascular-related indices (augmentation index, pulse wave velocity and aortic pressure) were measured. RESULTS Despite significantly higher levels of serum zinc in the treatment group, markers of oxidative damage, levels of hydroxyeicosatetraenoic acid products and vascular indices were unchanged by zinc supplementation during the four-month study period. CONCLUSION Improving the zinc status in patients with type 2 diabetes with normal zinc levels did not have any impact on oxidative damage and vascular function, and such supplementation may not be generally beneficial in these individuals.

Markers of oxidative damage are not elevated in otherwise healthy individuals with the metabolic syndrome.

OBJECTIVE The role of oxidative damage in the pathogenesis of metabolic syndrome is poorly understood. RESEARCH DESIGN AND METHODS A detailed cross-sectional study was performed to assess the relationship between lipid oxidation products, γ-glutamyltransferase, high-sensitivity C-reactive protein (hs-CRP), and phospholipase activities with respect to the metabolic status in a cohort of otherwise healthy individuals. RESULTS A total of 179 individuals (87 men and 92 women) aged 43 ± 14 years (mean ± SD) participated in this study. There were no differences in the levels of plasma F2-isoprostanes, hydroxyeicosatetraenoic acids, cholesterol oxidation products, and phospholipase activities in individuals with features of metabolic syndrome. In multivariate analyses, serum hs-CRP was a consistent independent predictor of metabolic syndrome. CONCLUSIONS Minimal changes were observed in multiple markers of oxidative damage in a well-characterized cohort of individuals with features of metabolic syndrome.

Relationship between circulating vascular endothelial growth factor and its soluble receptors in adults with dengue virus infection: a case–control study

BACKGROUND We performed a case-control study to assess the relationship between vascular endothelial growth factor (VEGF) and its soluble receptors (sVEGFR-1 and 2) in adult patients with dengue fever (DF) and dengue hemorrhagic fever (DHF). METHODS We recruited 60 adult patients (34 DF and 26 DHF) with serologically-confirmed dengue infections, 10 patients with non-hemorrhagic infections, and 31 community-based healthy volunteers. The levels of VEGF, sVEGFR-1, and sVEGFR-2 were measured and the differences in these markers were compared using one-way analysis of variance (ANOVA), which was adjusted for multiple comparisons. RESULTS We observed lower VEGF levels in DF and DHF compared to study controls (p<0.01). sVEGFR-1 was higher in DHF than DF, whilst sVEGFR-2 was lower in DF and DHF compared to study controls (all p<0.01). In DHF, lower VEGF levels were observed in older patients. The use of a single marker, sVEGFR-1>350 pg/ml, was predictive of DHF. CONCLUSION The changes in VEGF and its soluble receptors highlight the importance of vascular permeability cytokines in the pathogenesis of DHF.

Products of 5-lipoxygenase and myeloperoxidase activities are increased in young male cigarette smokers

Abstract The significance of 5-lipoxygenase and myeloperoxidase activities has not been extensively studied among young male smokers. Leukotriene B4, 20-hydroxy-leukotriene B4, 20-carboxy-leukotriene B4 and 3-chlorotyrosine were measured in plasma and urinary samples of young male smokers at 8 hours following cigarette abstinence and an hour after cigarette smoking. Leukotriene B4 and 3-chlorotyrosine were determined in neutrophils isolated from these individuals. The levels of these markers were compared with those of age-matched controls. In vitro studies were performed to evaluate the production of leukotriene B4 and 3-chlorotyrosine from human neutrophils following exposure to nicotine and cotinine. Thirty male smokers (mean age, 27.4 years) and 28 male non-smokers (mean age, 28.7 years) were studied. Plasma levels of leukotriene B4, 20-carboxy-leukotriene B4 and 3-chlorotyrosine were higher in smokers than in non-smokers; leukotriene B4 and 20-carboxy-leukotriene B4 levels increased further an hour after cigarette smoking. Peripheral neutrophils isolated from smokers showed greater expressions of myeloperoxidase and 5-lipoxygenase activities compared with non-smokers, while plasma leukotriene B4 and 3-chlorotyrosine were correlated significantly with high-sensitivity C-reactive protein and plasma nicotine concentrations. Exposure of human neutrophils to nicotine and cotinine resulted in a higher production of leukotriene B4 and 3-chlorotyrosine. To conclude, leukotriene B4 and 3-chlorotyrosine levels are increased in young male cigarette smokers. These results suggest that cigarette smoking aggravates neutrophil-mediated inflammation by modulating the activities of myeloperoxidase and 5-lipoxygenase pathways.

Accurate targeting of botulinum toxin injections: how to and why.

Botulinum toxin (BTX), the exotoxin of the obligate anaerobe, Clostridium botulinum, is used to ameliorate pain and treat conditions associated with glandular, smooth and skeletal muscle overactivity. The benefits derived from the injection of BTX may be negated by unintended weakness of uninjected muscles. Performance of BTX injections may be facile, requiring only surface marking or clinical-localisation techniques but may be more technically demanding, necessitating the use of equipment, such as electromyography (EMG) or ultrasonography (U/S). Less often, endoscopic, fluoroscopic or computed tomographic (CT) guidance may be required. Despite evidence to support the efficacy of BTX injections in treating many conditions, there is no evidence to support the superiority of any one injection technique over needle localisation using surface anatomy. This is possibly due to the lack of well-designed controlled studies, that is, current studies are hampered by small patient numbers, lack of consistency of injection technique and the application of different rating scales. Intuitively, certain injection techniques are more suited to injection of specific muscles or conditions, for example, U/S or passive-monitoring EMG should be used to treat cervical dystonia, active-monitoring EMG applied for strabismus injections, whereas either active-monitoring EMG or endoscopy is indicated when giving BTX for spasmodic dysphonia. Finally, electrical-stimulation EMG or U/S (or a combination of both) would be most suitable when injecting the forearm muscles for spasticity or writers cramps.

Does Influenza A Infection Increase Oxidative Damage

Considerable data implicate oxidative damage in influenza pathogenesis. We examined temporal changes in oxidative damage using accurate biomarkers in an adult cohort with acute influenza infection and their relationships with clinical parameters. Clinical information and blood samples were collected during their acute illness and 3 months later. A fatigue questionnaire was administered 3 months following influenza infection. Thirty-five patients (mean age, 34 years) with polymerase chain reaction-confirmed influenza A infection were included; all patients returned for follow-up assessments. Adjusted levels of plasma F2-isoprostanes, total hydroxyeicosatetraenoic products (HETEs), 7β-hydroxycholesterol and 7-ketocholesterol, serum gamma-glutamyltransferase, and high-sensitivity C-reactive protein (hsCRP) were increased during the acute illness compared with age-matched controls. Despite clinical recovery, levels of these biomarkers remained higher at month 3 compared with controls. A proportion of patients had persistent symptoms such as fatigue (23%), myalgia (14%), and arthralgia (11%) at month 3. Patients with significant fatigue had higher baseline levels of plasma F2-isoprostanes, F4-neuroprostanes, and total HETEs compared to those without fatigue. By contrast, patients with persistent arthralgia and myalgia had higher baseline levels of serum hsCRP compared to those without these symptoms. Our observations lead to the hypothesis that oxidative damage participates in the pathogenesis of influenza infection and postinfectious fatigue.

Intravenous immunoglobulin may reduce relapse frequency in neuromyelitis optica

OBJECTIVES To evaluate the use of intravenous immunoglobulin (IVIG) in preventing relapses in patients with neuromyelitis optica (NMO) and its spectrum disorders (NMOSDs). METHODS Six NMO/NMOSD patients who were treated with IVIG induction dose followed by 2- to 3- monthly infusions were retrospectively identified. Annualized relapse rates (ARR) and Expanded Disability Status Scale (EDSS) pre- and post-IVIG were recorded. RESULTS Median number of relapses and median ARR significantly reduced from 8.0 to 1.0 and 0.75 to 0.15 (p<0.05) respectively. Median EDSS of 6.5 remained the same. Median duration of treatment was 4.0 years. CONCLUSION IVIG may be used to reduce the relapse frequency in patients with NMO/NMOSD.

Augmentation of 5-lipoxygenase activity and expression during dengue serotype-2 infection

BackgroundLeukotriene B4, a 5-lipoxygenase product of arachidonic acid with potent chemotactic effects on neutrophils, has not been assessed in dengue patients. In this study, plasma leukotriene B4 and serum high-sensitivity C-reactive protein levels were determined in adult patients during the febrile, convalescent and defervescent stages of dengue serotype-2 (DENV-2) infection, and compared with those of age--matched healthy and non-dengue febrile subjects. In vitro studies were performed to examine the effects of live and heat-inactivated DENV-2 on the activities and expression of 5-lipoxygenase in human neutrophils.ResultsPlasma leukotriene B4 was elevated during the febrile stages of dengue infection compared to levels during convalescence and in study controls. Plasma leukotriene B4 also correlated with serum high-sensitivity C-reactive protein in dengue patients (febrile, r = 0.91, p < 0.001; defervescence, r = 0.87, p < 0.001; convalescence, r = 0.87, p < 0.001). Exposure of human neutrophils to DENV-2 resulted in a significant rise in leukotriene B4; the extent of increase, however, did not differ between exposure to live and heat-inactivated DENV-2. Pre-incubation of either live or heat-inactivated DENV-2 resulted in reduced leukotriene B4 release by neutrophils, indicating that contact with dengue antigens (and not replication) triggers the neutrophil response. Production of leukotriene B4 was associated with an increase in 5-lipoxygenase expression in human neutrophils; addition of MK886 (a 5-lipoxygenase activating protein inhibitor) attenuated further increase in leukotriene B4 production.ConclusionThese findings provide important clinical and mechanistic data on the involvement of 5-lipoxygenase and its metabolites in dengue infection. Further studies are needed to elucidate the therapeutic implications of these findings.

Cyclooxygenase-1 Mediated Platelet Reactivity in Young Male Smokers

Background: The purpose of this study is to investigate the acute and chronic effects of cigarette smoking on cyclooxygenase- 1(COX-1)-mediated platelet reactivity among cigarette smokers. Methods: The levels of collagen-induced platelet aggregation, platelet COX-1 activity, and expressions were compared between smokers and age-matched nonsmokers. In smokers, the acute effects of cigarette smoking were assessed by repeating these measurements an hour after smoking. Results: Twenty-five smokers and age-matched nonsmokers (all men; mean age, 29 years) were studied. Collagen-induced platelet aggregation and plasma/urinary thromboxane B2 (TXB2) and 11-dehydroxythromboxane B2 levels were higher in cigarette smokers compared to nonsmokers. Greater expression of platelet COX-1 was observed in smokers than in nonsmokers. Among smokers, collagen-induced platelet aggregation correlated positively with platelet volume and circulating nicotine and cotinine concentrations. The levels of plasma/urinary TXB2 were significantly increased an hour after cigarette smoking. Conclusion: Cigarette smoking aggravates COX-1-mediated platelet reactivity in young, otherwise healthy, smoking men.