AJTMH HINARI
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Am. J. Trop. Med. Hyg., 79(3), 2008, pp. 372-377
Copyright © 2008 by The American Society of Tropical Medicine and Hygiene

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Rajendiran, S.
Right arrow Articles by Nambiar, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Rajendiran, S.
Right arrow Articles by Nambiar, S.
Related Collections
Right arrow Pathogenesis
Right arrow Dengue

Desialylation of Plasma Proteins in Severe Dengue Infection: Possible Role of Oxidative Stress

Soundravally Rajendiran, Hoti Sugeerappa Lakshamanappa*, Bobby Zachariah, AND Selvaraj Nambiar
Department of Molecular Biology and Bioinformatics, Vector Control Research Centre (VCRC), Pondicherry, India; Department of Biochemistry, Jawaharlal Institute of Postgraduate Medicine and Research, Pondicherry, India


ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Oxidative stress in dengue infection has been suggested. This study was carried out to explore the plasma protein oxidation and its sialic acid content in dengue infection. Thirty-two dengue hemorrhagic fever (DHF), 25 dengue shock syndrome (DSS), 29 dengue fever (DF), and 63 healthy controls were included in this study. The extent of carbonylation, sulphydryl content, and desialylation of plasma protein was estimated in acute phase sample. Significantly higher levels of protein carbonyls and lower levels of sialic acid and sulphydryl groups were found in DHF and DSS compared with DF using one-way analysis of variance. Regression analysis showed that desialylation is dependent on protein carbonyls in DHF/DSS. This study indicates that, in dengue infection, plasma proteins undergo increased levels of desialylation, which can be attributed to the oxidative stress. Future studies on sialylation status of endothelium and platelets can show light into the pathogenesis of the dengue infection.


INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Dengue is the most frequent arboviral infection, with > 100 million infections throughout the world annually, including 250,000–500,000 cases of dengue hemorrhagic fever (DHF) and 24,000 deaths.1,2 In most cases, dengue fever (DF) is self-limited. However, there is a risk of progressive development into DHF or dengue shock syndrome (DSS). DHF is a severe febrile disease characterized by abnormalities in hemostasis and increased vascular permeability, and severe progression may result in DSS. DSS is a form of hypovolemic shock that is associated clinically with hemoconcentration and that might lead to death if appropriate care is not given. Although DF is distinct from DHF/DSS by traditional classification, the various clinical manifestations after dengue virus infection show a continuum from mild to severe reactions, just as in many other viral diseases.

Sialic acid, a family of acetylated derivatives of neuraminic acid, is widely distributed in mammals. It usually occurs as a terminal component at the non-reducing end of carbohydrate chains of glycoproteins and glycolipids. In human plasma, a large quantity of sialic acid is found in orosomucoid, {alpha}1-antitrypsin, haptoglobin, ceruloplasmin, fibrinogen, complement proteins, and transferrin.3,4 For glycoproteins, glycan moieties are important integral parts both structurally and functionally.5 Sialic acid has been found to influence the glycoprotein function and its life span.6,7 Moreover, it was reported that non-reducing terminal sialic acid residues may be a target molecule of reactive oxygen species (ROS) and ROS specifically cleave and liberate them. An apparent link has been found between oxidative stress and sialic acid content of glycoproteins.8

The mechanisms involved in the pathogenesis of dengue virus infection, especially the manifestation of DHF/DSS, remain unresolved. In secondary DHF cases, higher viremia is observed, and antibody-dependent enhancement of viral entry into phagocytic cells has been hypothesized as the causative factor.9,10 However, the mechanism by which high vire-status induces DHF is not clear. Aberrant secretion of proinflammatory cytokines has been suggested as yet another risk factor for DHF/DSS.11 In dengue viral infection, prolonged activation of T cells and their apoptosis has been proposed as a cause of delayed viral clearance.12 Although the pathogenesis of dengue fever is not well understood, oxidative stress seems to play an important role.13

After viral entry, immune system activation takes place, and phagocytic and other cells produce ROS as a defense mechanism.13 There is now much evidence that oxidants play a complex role in viral diseases, starting from influences on host cell metabolism and less desired toxic effects on host tissue.14–16 Oxidants are highly unstable and react with nucleic acid, lipids, proteins, carbohydrate, or any other molecule, causing a cascade of chain reactions resulting in cellular damage. This process might cause loss of fluidity and production of protein and lipid peroxides, which leads to cell wall destruction. Protein carbonyls (PCs) are an established marker of protein oxidation.17 The PCs have been shown to be more susceptible for cross-linking and cleavage that undergo rapid proteolysis.18 Wide spectrum of antioxidant defense mechanisms inactivates and lies in balance with these oxidants. The protein-bound sulfhydryl group (PBSH) has an important role in antioxidant defense. Although mammalian erythrocytes are rich in glutatione (GSH), the concentration of GSH in extracellular content, especially in human plasma, is very low compared with the intracellular content.19 Most of the free sulfhydryl groups in human plasma are protein-bound amino acid residues, which have been suggested to contribute significantly to the antioxidant capacity of the human plasma.20

However, no information is available about the sialic acid content of plasma glycoproteins in the different clinical spectrum of dengue infection. Furthermore, the relation between bound sialic acid and oxidative changes in plasma proteins of patients with dengue has not been described.

Hence this work was carried out on dengue infection to look for 1) the sialic acid content of serum glycoproteins and 2) its relationship with markers of plasma protein oxidation.


MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Study design, patients, and controls. In Pondicherry town, South India, a dengue outbreak was reported for the first time in September 2003.21 Eighty-six dengue-infected adults (age range, 26–54 years; 48 men and 38 women) participated in the study. Sixty-three healthy subjects (age range, 23–55 years; 42 men and 21 women) were included as controls. Infected individuals were further classified into 29 DF, 32 DHF, and 25 DSS cases per the WHO grading system explained below. Normal controls were blood donors who were negative for both anti-dengue IgM and IgG antibodies. Written informed consent was obtained from all participants, and the study was approved by the ethical review committee of the institution.

Clinical definitions and dengue virus testing. A complete clinical history, laboratory tests, and other parameters pertaining to the diagnosis of dengue infection such as the tourniquet test, hematocrit, and platelet count (Sysmex-k-100 automated cell counter) carried out at local hospitals were recorded. Cases were classified according to the WHO grading system.22 Dengue infection was divided into classic DF, DHF, and DSS. DF was a mild self-limiting acute febrile illness. DHF was defined as fever with hemorrhagic manifestations, thrombocytopenia, and hemoconcentration or other signs of plasma leakage (equivalent to WHO classification DHF Grades I and II). DSS was defined as DHF criteria plus hypotension for the age or narrow pulse pressure (> 20 mm of Hg) or the clinical signs of shock, e.g., slow capillary filling, cold clammy skin (equivalent to DHF Grades III and IV). Thrombocytopenia was defined as a platelet count < 100,000/mm3 and hemoconcentration as a 20% increase in hematocrit above normal for age and sex. Serologic testing of blood samples for both IgM and IgG antidengue antibodies was undertaken using an ELISA kit (Novatech, Dietzenbach, Germany), as per the procedure described by the manufacturer. Multiplex reverse transcriptasepolymerase chain reaction (RT-PCR) was carried out, and the dengue 3 serotype was found to be responsible for this outbreak.23

Estimation of plasma sialic acid. Sialic acid content of plasma protein was measured by using the following modifications of Aminoff’s method.24 Briefly, 50 µL plasma was taken and diluted in distilled water (1:4). Serum proteins were precipitated by centrifuging with 125 µL of 5% TCA at 2,000 rpm for 5 minutes. Supernatant was discarded, and the sialic acid moieties of the protein pellet were hydrolyzed with 0.5 mL of 0.1 mol/L H2SO4 at 80°C for 60 minutes. To the hydrolysates, 250 µL of periodate reagent (25 mmol/L periodic acid in 0.125 mol/L H2SO4, pH 1.2) was added and incubated in a 37°C water bath for 30 minutes. Excess of periodate was reduced by 0.2 mL sodium arsenite (2% solution of sodium arsenite in 0.5 mol/L HCl). As soon as yellow color of liberated iodine started fading off, 2 mL of thiobarbituric acid (0.1 mol/L solution of 2-thiobarbituric acid in water, pH adjusted to 9.0 with NaOH) was added, and with a stopper, the tubes were incubated in a boiling water bath for 8 minutes. The tubes were cooled in ice water and extracted with 5 mL of acid butanol mixture (butan-1-ol containing 5% vol/vol in HCl); the separation of two phases was done by a short rapid centrifugation, and color intensity of butanol phase was measured spectrophotometrically at 549 nm. The sialic acid level was calculated using molar extinction coefficient (70.7 103 L/mol cm) and expressed in micrograms per milligram protein considering the molecular weight of sialic acid as 309.3. Total serum protein was measured by the Biuret method using a Ciba Corning 550 Express autoanalyzer (Ciba Corning Diagnostics, Oberlin, OH).

Assay of carbonylation of plasma protein. The assay was done according to the method of Levine and others.25 The millimolar extinction coefficient of the colored product is 22.01/mmol/cm at 366 nm. The carbonylated protein reacts with 2,4-dinitrophenyhydrazine (DNPH) to form a colored adduct of 2,4-dinitrophenylhydrazone. Plasma total protein was estimated by the biuret method using fully automated auto-analyzer 550 express plus (Ciba Corning Diagnostics).

Determination of protein-bound sulphydryl group content. Protein-bound sulphydryl group contents were determined according to the method of Sedlak and Lindsay.26 with 5, 5'-dithiobis 2-nitrobenzoic acid (DTNB) with minor modifications. Briefly, 200 µL plasma was taken and diluted in distilled water (1:4). Plasma proteins were precipitated by centrifuging with 500 µL of 5% TCA at 15,000 rpm for 3 minutes. Supernatant was discarded, and the protein pellet was mixed with 2 mL of 0.2 mol/L Tris-HCl buffer (pH 8.2)–20 mmol/L EDTA and 20 µL of 10 mmol/L DTNB and 0.15 mL of 5% SDS. Finally, absorbance was measured at 412 nm against a sample blank (without DTNB) and also corrected for a reagent blank (without sample). The absorbance readings were made 15 minutes after adding DTNB to test samples. The experimentally determined molar extinction coefficient was 13.1/mm/cm. Values are expressed in nmoles per milligram protein.

Statistical analysis. Data were analyzed using the statistical program SPSS for windows, version 13 (SPSS, Chicago, IL). Results are given as mean ± SD. The independent Student t test was used to determine the statistically significant difference between cases and controls. One-way ANOVA followed by a post hoc test Tukey HSD was used to find difference in the parameters studied within the clinical groups of dengue infection. The relationship between PCOs and bound sialic acid content was evaluated using linear regression. Results are expressed as regression coefficient (β). Clinical features between the different groups were compared by {chi}2 test for binary variables and Student t test or Mann-Whitney U test where appropriate. P < 0.05 was considered statistically significant.

Patients were bled between 3 and 5 days of onset of symptoms around defervescence. Blood samples were collected in a heparinized bottle, and separated plasma was stored at –70°C until analysis.


RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Table 1Go shows the clinical characteristics of dengue-infected patients included in this study. All patients presented with fever (100%). The mean (SD) duration of fever was 4.2 (1.1) days (range, 1–9 days). There were no significant differences in the duration of fever between the different clinical groups (P = 0.07). Duration of hospitalization was more in the DHF and DSS groups compared with the DF group (P < 0.001). Headache, arthralgia, and petechia were significantly more common in DHF in comparison to DF (P < 0.001), whereas hepatomegaly and clinical bleeding were significantly more frequent in DSS (P = 0.002). During hospitalization, hematocrit levels of the patients increased, and patients with shock (DSS) had significantly higher peaks of hematocrit compared with the DF and DHF groups (P < 0.001). The hematocrit values of DHF patients were higher than in DF patients (P < 0.001). The overall mean time (days) to reach the maximum hematocrit level after onset of fever was higher in DHF (4.9) and DSS (5.6) compared with DF (4.2) patients.


View this table:
[in this window]
[in a new window]

 
TABLE 1
Characteristics of patients with different clinical spectrum of dengue infection
 
The level of sialic acid residues, sulphydryl groups, and carbonyl content of plasma proteins in dengue-infected individuals and controls are shown in the Table 2Go. The levels of sialic acid residues and PBSH were found to be significantly (P < 0.001) decreased in dengue infection, whereas PCOs were significantly (P < 0.001) increased in these cases in comparison to control subjects. One-way ANOVA followed by a post hoc Tukey HSD test showed that a significant difference was observed with low bound sialic acid content and PBSH and high PCOs in all three clinical groups compared with controls (Table 3Go). Similar results were found in DHF and DSS cases compared with DF cases (P < 0.05). Between DHF and DSS, a significant difference was observed in bound sialic acid (P = 0.033) and PCOs levels (P < 0.001); however, no difference was found in PBSH content (P = 0.456). Linear regression analysis showed a significant negative association between protein carbonyls and bound sialic acid levels in DHF (β = –0.409, P < 0.001) and DSS (β = –0.508, P < 0.001; Figure 1Go). A positive correlation existed between sulphydryl groups and bound sialic acid levels among DSS (r = 0.450, P = 0.024).


View this table:
[in this window]
[in a new window]

 
TABLE 2
Mean and SD of protein-bound sialic acid, protein carbonyls, and protein-bound sulphydryl groups in dengue-infected individuals and controls
 

View this table:
[in this window]
[in a new window]

 
TABLE 3
Mean and SD of protein-bound sialic acid, protein carbonyls, and protein-bound SH group levels in DF, DHF, DSS, and controls
 

Figure 1
View larger version (18K):
[in this window]
[in a new window]

  		FIGURE 1. Association of protein carbonyls and protein-bound sialic acid levels in patients with DHF and DSS. Plasma protein carbonyls are plotted against protein-bound sialic acid levels for all patients with (A) DHF (β = –0.409, P < 0.001) and (B) DSS (β = –0.508, P < 0.001).

 

DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
Within recent years, there has been considerable interest and research in sialic acid and its role in health and diseases.27 Serum sialic acid is a marker of the acute-phase response. Acute-phase glycoproteins with sialic acid as a component of the oligosaccharide side chain being produced by the liver, stimulated by proinflammatory cytokines such as interleukin-6, interleukin-6 and tumor necrosis factor-{alpha}.28–32 These cytokines were found to be elevated in dengue infection, and their levels have been associated with severity of disease.11 However, C-reactive protein concentrations were not found to be different in dengue infection from controls and found to be lower than bacterial infection.32 Our research indicates that there is a significant decrease (P < 0.001) in plasma protein-bound sialic acid content in dengue patients compared with controls. This finding was also observed when patients with DF, DHF, and DSS were compared with controls. It was noted that the extent of desialylation was maximal in DSS, followed by DHF, and its levels were minimal in DF. There are several possible explanations for the decrease in sialic acid concentrations. It has been reported that ROS may specifically cleave terminal sialic acid residues.33 Liver dysfunction seen in dengue viral infection might lead to reduced synthesis and release of acute phase proteins.9 Aberrant coagulation and vascular leakage might also lead to loss of serum protein into third space.9

A recent report has shown increased oxidative stress in dengue infection and its association with disease severity.13 The altered levels of lipid peroxides and activity of antioxidant enzymes were studied to show oxidative stress.13,34 This study found increased levels of the protein carbonyls and reduced antioxidant capacity evaluated as sulphydryl group content of plasma proteins during early phase of dengue viral infection. This finding is consistent with another report of increased lipid peroxidation and lowered antioxidative serum capacity associated with dengue viral illness.13,34 The oxidation of protein-bound sulfhydryl groups is a direct indication of oxidative damage. Sulfhydryl groups are known to scavenge aqueous peroxyl radicals. In this study, a significant decrease in plasma protein-bound sulfhydryl groups on early days of illness showed that they may be one of the early antioxidant defenses to combat the peroxyl radical attack in dengue infection. However, the rest of the total antioxidant status needs to be studied to corroborate this result. The alteration of the redox markers indicates that these changes probably started before the onset of clinical symptoms, suggesting an early compromise of the oxidant/antioxidant balance.

From this study, oxidative stress–induced changes in plasma proteins were found to be more in severe dengue infection (DHF/DSS) compared with milder infection (DF). Also, the observations of the significant negative correlation between carbonyl and sialic acid content of plasma proteins among DHF/DSS cases probably indicated that oxidative stress was involved in enhanced desialylation of proteins in blood in dengue infection. The previous studies have shown that oxidative stress can cause desialylation of glycoproteins of serum protein, platelets, and low-density lipoprotein (LDL) particles.8,35,36 However, the exact mechanism is not clearly understood. Desialysed plasma proteins produced by oxidative damage are taken up by the liver, because it is a generalized mechanism of removal of asialoglycoproteins.37

In DHF/DSS, increased vascular permeability is suggested because of malfunction of endothelium rather than structural destruction.10,38 When endothelial cells are stimulated by cytokines, ROS generation can be detected, and this process has been reported in dengue infection.38,39 Several studies on the relationship between ROS and vascular dysfunction have been reported.40,41 These results suggest a higher severity of oxidative stress and desialylation of plasma proteins in DHF/DSS patients compared with mild dengue infection. Research studies have also indicated that vascular permeability is regulated by sialic acid moieties. The vascular endothelium carries a high concentration of sialic acid, and hence, extensive endothelial damage associated with severe dengue infection could account for its shedding into the circulation.28 Therefore, it raises the possibility of oxidative stress and associated glycoprotein changes in inducing endothelial dysfunction and vascular leakage, the pathognomonic features of severe dengue infection.

It has been shown that thrombocytopenia in dengue evolved from the increase in the destruction rate of peripheral platelets rather than their insufficient formation. Although the cause and mechanisms of peripheral platelet destruction are not very clear, it is suggested that this destruction is a result of some immunologic events depending on antibody activities.42,43 A study on malaria showed a negative relation between the thrombocyte counts and plasma lipid peroxidation and also with platelet malendialdehyde levels.44 Hence, it is worth studying whether glycosylation of the platelet membrane is reduced in dengue viral infection and oxidative stress and its relative contribution toward sialic acid content of platelets in explaining the pathogenesis of thrombocytopenia in dengue viral infection.

This study concluded that desialylation of plasma protein was found in dengue viral infection. The extent of desialylation was maximal in DSS, followed by DHF, and its severity was minimal in DF. Also the degree of desialylation was found to be associated with the extent of protein oxidation in severe dengue disease. Hence, future studies on the sialylation status of endothelial cells and platelets may shed some light into the pathogenesis of dengue viral infection.

Received December 29, 2007. Accepted for publication May 13, 2008.

Acknowledgments: The authors thank Dr. M. G. Sridhar, P. Sankar, Dr. Sajita Setia, and Smitha Mariano Koshy for kind help in manuscript preparation and the clinicians of JIPMER for providing a clinical description of patients.

* Address correspondence to S. L. Hoti, Department of Molecular Biology and Bioinformatics, Vector Control Research Centre (VCRC), Pondicherry, India. E-mail: hotigood{at}gmail.com Back

Authors’ addresses: Soundravally Rajendiran and S.L. Hoti, Department of Molecular Biology and Bioinformatics, Vector Control Research Centre (VCRC), Pondicherry, India, Tel: 00-91-9443602724, Fax: 91-413-227204, E-mail: hotigood{at}gmail.com. Bobby Zachariah and Selvaraj Nambiar, Department of Biochemistry, Jawaharlal Institute of Postgraduate Medicine and Research, Pondicherry, India.


REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Gubler DJ, 1998. Dengue and dengue hemorrhagic fever. Clin Microbiol Rev 11: 480–496.[Abstract/Free Full Text]
  2. Gibbons RV, Vaughn DW, 2002. Dengue: an escalating problem. BMJ 324: 1563–1566.[Free Full Text]
  3. Taniuchi K, Chifu K, Hayashi N, Nakamachi Y, Yamaguchi N, Miyamato Y, 1981. A new enzymatic method for the determination of sialic acid and its application as a marker of acute phase reactants. Kobe J Med Sci 27: 91–102.[Medline]
  4. Petren S, 1989. Vesterberg 0. The N-acetylneuraminic acid content of five forms of human transferrin. Biochim Biophys Acta 994: 161–165.[Medline]
  5. Nurden AT, George JN, Philips DR, 1986. Platelet membrane glycoproteins: their structure, function, and modification in disease. Philips DR, Shuman MA, eds. Biochemistry of Platelets. Orlando, FL: Academic Press, 160–212.
  6. Thornhill WB, Wu MB, Jiang X, Wu X, Morgan PT, Margiotta JF, 1996. Expression of Kv1.1 delayed rectifier potassium channels in Lec mutant Chinese hamster ovary cell lines reveals a role for sialidation in channel function. J Biol Chem 271: 19093–19098.[Abstract/Free Full Text]
  7. Murray RK, 1996. Glycoproteins. Murray RK, Granner DK, Mayes PA, Rodwell VW, eds. Harper’s Biochemistry. 24th edition. NJ: Prentice Hall, 651.
  8. Goswami K, Nandakumar DN, Koner BC, Bobby Z, Sen SK, 2003. Oxidative changes and desialylation of serum proteins in hyperthyroidism. Clin Chim Acta 337: 163–168.[Web of Science][Medline]
  9. Halstead SB, 1988. Pathogenesis of dengue. Challenges to molecular biology. Science 239: 476–481.[Abstract/Free Full Text]
  10. Kurane I, Takasaki T, 2001. Dengue fever and dengue haemorrhagic fever: challenges of controlling an enemy still at large. Rev Med Virol 11: 301–311.[Web of Science][Medline]
  11. Chatuverdi UC, Agarwal R, Elbishbishi EA, Mustafa AS, 2000. Cytokine cascade in dengue hemorrhagic fever: implications for pathogenesis. FEMS Immunol Med Microbiol 28: 183–188.[Web of Science][Medline]
  12. Mongkolsapaya J, Dejnirattisai W, Xu X, Vasanawathana S, Tangthawornchaikul N, Chairunsri A, Sawasdivorn S, Duangchinda T, Dong T, Rowland-Jones S, Yenchitsomanus P, McMichael A, Malasit P, Screaton G, 2003. Original antigenic sin and apoptosis in the pathogenesis of dengue hemorrhagic fever. Nat Med 9: 921–927.[Web of Science][Medline]
  13. Gil L, Martinez G, Tapanes R, Castro O, González D, Bernardo L, Vázquez S, Kourí G, Guzman M, 2004. Oxidative stress in adult dengue patients. Am J Trop Med Hyg 71: 652–657.[Abstract/Free Full Text]
  14. Peterhans E, Grob M, Burge T, Zanoni R, 1987. Virus-induced formation of reactive oxygen intermediates in phagocytic cells. Free Radic Res Commun 3: 39–46.[Medline]
  15. Sahnoun Z, Jamoussi K, Zeghal KM, 1997. Free radicals and antioxidants: human physiology, pathology and therapeutics aspects. Therapie 52: 251–270.[Web of Science][Medline]
  16. Yoshikawa T, 1996. Vascular dysfunction and free radicals. Free Radic Biol Med 2002; 33 : 425–426.
  17. Winter ML, Liehr JG, 1991. Free radical-induced carbonyl content in protein of estrogen-treated hamsters assayed by sodium boro [3H] hydride reduction. J Biol Chem 266: 14446–14450.[Abstract/Free Full Text]
  18. Wolff SP, Dean R, 1986. Fragmentation of protein by free radicals and its effect on their susceptibility to enzymic hydrolysis. Biochem J 234: 399–403.[Web of Science][Medline]
  19. Pantke U, Volk T, Schmutzler M, Kox WJ, Sitte N, Grune T, 1999. Oxidized proteins as a marker of oxidative stress during coronary heart surgery. Free Radic Biol Med 27: 1080–1086.[Web of Science][Medline]
  20. Wayner DDM, Burton GW, Ingold KU, Barclay LRC, Locke SJ, 1987. The relative contributions of vitamin E, urate, ascorbate, and proteins to the total peroxyl radical trapping antioxidant activity of human plasma. Biochim Biophys Acta 924: 408–419.[Medline]
  21. Hoti SL, Soundravally R, Rajendran G, Das LK, Ravi R, Das PK, 2006. Dengue and dengue haemorrhagic fever outbreaks in Pondicherry, South India, during 2003–2004: emergence of DENV-3. Dengue Bull 30: 42–50.
  22. World Health Organization, 1997. Dengue Haemorrhagic Fever: Diagnosis, Treatment, Prevention, and Control. Second edition. Geneva: World Health Organization.
  23. Lanciotti RS, Calisher CH, Gubler DJ, Chang G-J, Vorndam V, 1992. Rapid detection and typing of dengue viruses from clinical samples by using reverse transcriptase-polymerase chain reaction. J Clin Microbiol 30: 545–551.[Abstract/Free Full Text]
  24. Aminoff D, 1961. Methods for the quantitative estimation of N-acetylneuraminic acid and their application to hydrolysates of sialomucoids. Biochem J 81: 384–392.[Web of Science][Medline]
  25. Levine RL, Williams JA, Stadtman BR, Shacter E, 1994. Carbonyl assays for determination of oxidatively modified protein. Enzymology 233: 346–357.
  26. Sedlak J, Lindsay RH, 1968. Estimation of total, protein-bound, and nonprotein sulfhydryl groups in tissue with Ellman’s reagent. Anal Biochem 25: 192–205.[Web of Science][Medline]
  27. Lindberg G, Eklund GA, Gullberg B, Rastam L, 1991. Serum sialic acid concentration and cardiovascular mortality. BMJ 302: 143–146.[Abstract/Free Full Text]
  28. Taniuchi K, Chifu K, Hayashi N, Nakamachi Y, Yamaguchi N, Miyamoto Y, Doi K, Baba S, Uchida Y, Tsukada Y, Sugimori T, 1981. A new enzymatic method for the determination of sialic acid in serum and its application for a marker of acute phase reactants. Kobe J Med Sci 27: 91–102.[Medline]
  29. Pickup JC, Mattock MB, Chusney GD, Burt D, 1997. NIDDM as a disease of the innate immune system: association of acute phase reactants and interleukin-6 with metabolic syndrome X. Diabetologia 40: 1286–1292.[Web of Science][Medline]
  30. Kushner I, 1993. Regulation of the acute phase response by cytokines. Perspect Biol Med 36: 611–622.[Web of Science][Medline]
  31. Baumann H, Gauldie J, 1994. The acute phase response. Immunol Today 15: 74–80.[Web of Science][Medline]
  32. Juffrie M, Meer GM, Hack CE, Haasnoot K, Sutaryo X, Veerman AJ, Thijs LG, 2001. Inflammatory mediators in dengue virus infection in children: interleukin-6 and its relation to C-reactive protein and secretory phospholipase A2. Am J Trop Med Hyg 65: 70–75.[Abstract]
  33. Halliwell B, Gutteridge JM, 1990. Role of free radicals and catalytic metal ions in human disease: an overview. Methods Enzymol 186: 1–85.[Medline]
  34. Klassen P, Hans KB, Mazariegos M, Noel WS, Furst P, 2004. Classic dengue fever affects levels of circulating antioxidants. Nutrition 20: 542–547.[Web of Science][Medline]
  35. Goswami K, Koner BC, 2002. Level of sialic acid residues in Platelet proteins in diabetes, aging, and Hodgkin’s lymphoma: a potential role of free radicals in desialylation. Biochem Biophys Res Commun 297: 502–505.[Web of Science][Medline]
  36. Tanaka K, Tokumaru S, Kojo S, 1997. Possible involvement of radical reactions in desialylation of LDL. FEBS Lett 413: 202–204.[Web of Science][Medline]
  37. Bratosin D, Mazurier J, Tissier JP, Estaquier J, Huart JJ, Ameisen JC, Aminoff D, Montreuil J, 1998. Cellular and molecular mechanisms of senescent erythrocyte phagocytosis by macrophages. A review. Biochemie 80: 173–195.[Web of Science][Medline]
  38. Rothman AL, Ennis FA, 2000. Toga/flaviviruses: immunopathology. Cunningham MW, Fujinami RS, eds. Effects of Microbes on the Immune System. Philadelphia: Lippincott Williams and Wilkins, 473–490.
  39. Anderson R, Wang S, Osiowy C, Issekutz AC, 1997. Activation of endothelial cells via antibody-enhanced dengue virus infection of peripheral blood monocytes. J Virol 71: 4226–4232.[Abstract/Free Full Text]
  40. Granger DN, Rutili G, McCord J, 1981. Superoxide radicals in feline intestinal ischemia. Gastroenterology 81: 22–29.[Web of Science][Medline]
  41. Irani K, 2000. Oxidant signaling in vascular cell growth, death, and survival. Circ Res 87: 179–183.[Abstract/Free Full Text]
  42. Osu K, Inoves U, 2003. Correlation of increased platelet associated IgG and thrombocytopenia in dengue fever. J Med Virol 71: 259–264.[Web of Science][Medline]
  43. Schexneider KJ, Reedy EA, 2005. Thrombocytopenia in dengue fever. Current Hematol Resp 4: 145–148.
  44. Erela O, Vurala H, Aksoya N, Aslanb G, Ulukan M, 2001. Oxidative stress of platelets and thrombocytopenia in patients with vivax malaria. Clin Biochem 34: 341–344.[Web of Science][Medline]




This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Rajendiran, S.
Right arrow Articles by Nambiar, S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Rajendiran, S.
Right arrow Articles by Nambiar, S.
Related Collections
Right arrow Pathogenesis
Right arrow Dengue

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS