Vanessa Dorneles Torbitz

Association between DNA strand breakage and oxidative, inflammatory and endothelial biomarkers in type 2 diabetes

Evidence has been presented recently that type 2 diabetes patients have an increased level of DNA damage. This DNA damage could be associated with oxidative, inflammatory, and endothelial biomarkers and could represent a possible indication of injury in the endothelium and induction of inflammation in type 2 diabetes. To confirm this possible association, DNA strand breakage was evaluated by use of the comet assay and its association with oxidative, inflammatory, and endothelial biomarkers in type 2 diabetes patients. A case-control study (30 healthy controls and 32 subjects with type 2 diabetes) was performed to evaluate the association between DNA damage and NOx (nitrate/nitrite), interleukin-6 (IL-6), urinary albumin, fasting glucose, and glycated hemoglobin (HbA(1c)) levels. Type 2 diabetes patients presented higher DNA damage than control subjects, higher levels of IL-6 and urinary albumin, and lower NOx. Significant correlations between DNA damage and NOx (r=-0.303, p=0.016), IL-6 (r=0.845, p<0.001), urinary albumin (r=0.496, p<0.001), fasting glucose (r=0.449, p<0.001), and HbA(1c) (r=0.575, p<0.001) were reported. Our findings showed an increase of DNA damage in type 2 diabetes especially in those patients with poor glycemic control and associations among NOx, IL-6 and urinary albumin levels with DNA damage.

An Alternative Pathway Through the Fenton Reaction for the Formation of Advanced Oxidation Protein Products, a New Class of Inflammatory Mediators

The accumulation of advanced oxidation protein products (AOPPs) has been linked to several pathological conditions, and their levels are formed during oxidative stress as a result of reactions between plasma proteins and chlorinated oxidants produced by myeloperoxidase (MPO). However, it was suggested that the generation of this mediator of inflammation may also occur via an MPO-independent pathway. The aim of this study was to induce the formation of AOPPs in vitro through Fenton reaction and to investigate whether this generation could be counteracted by N-acetylcysteine (NAC) and fructose-1,6-bisphosphate (FBP). The complete Fenton system increased the AOPPs levels and both NAC and FBP were capable of inhibiting the formation of Fenton reaction-induced AOPPs. These data provide a new hypothesis about another pathway of AOPPs formation, as well as report that NAC and FBP may be good candidates to neutralize pro-inflammatory and pro-oxidant effects of AOPPs in several diseases.

Oxidative DNA damage is associated with inflammatory response, insulin resistance and microvascular complications in type 2 diabetes

Urinary markers of nucleic acid oxidation may be useful biomarkers in diabetes. It has been demonstrated that T2DM patients have an increased level of oxidative DNA damage; however, it is unclear whether increased DNA damage may be related to a greater degree of inflammation and insulin resistance. Thus, the aim of this present study was to investigate the relation of the impact of oxidative DNA damage, assessed by urinary 8-OHdG, on the levels of inflammatory cytokines, as well as insulin resistance. In addition, we also investigated the diagnostic ability of urinary 8-OHdG in the identification of microvascular complications in T2DM.A case-control study, enrolling 22 healthy controls and 54 subjects with T2DM, was performed to evaluate the relation between oxidative DNA damage and interleukin-6 (IL-6), IL-1,tumor necrosis factor-alpha (TNF-α), IL-10, and Homeostasis Model Assessment (HOMA-IR) index. T2DM patients presented higher urinary 8-OHdG, IL-6, IL-1, TNF-α levels and HOMA-IR, and lower IL-10 levels than control subjects. Moreover, urinary 8-OHdG levels were significantly higher in the group T2DM with microvascular complications when compared to the without complications. The areas under the curve for urinary 8-OHdG and urinary albumin were, respectively, 0.836 (P<0.001) and 0.786 (P=0.002). Thus, urinary 8-OHdG has a slightly higher ability to discriminate microvascular complications in T2DM compared with urinary albumin. It was also demonstrated that T2DM patients with higher median of urinary 8-OHdG had significantly elevated levels of IL-6, TNF-α and HOMA-IR, and decreased IL-10 levels. Our findings showed that T2DM patients with higher urinary 8-OHdG levels showed a greater inflammatory degree and higher insulin resistance. It is possible to speculate that T2DM patients present a cascade of events as increasing metabolic abnormalities such as insulin resistance and inflammatory activation, as well as increased ROS generation factors that may contribute directly to greater oxidative DNA damage.

Fructose-1,6-Bisphosphate and N-Acetylcysteine Attenuate the Formation of Advanced Oxidation Protein Products, a New Class of Inflammatory Mediators, In Vitro

The accumulation of advanced oxidation protein products (AOPP) has been linked to several pathological conditions. Previous studies have identified AOPP as a novel biomarker of oxidative damage to proteins and a novel class of mediator of inflammation. The aim of this study was to determine the effects of fructose-1,6-bisphosphate (FBP) and N-acetylcysteine (NAC) as well as the synergistic effect of both treatments on the formation of AOPP in vitro. For this purpose, we incubated the human serum albumin (HSA) with various hypochlorous acid (HOCl) concentrations to produce albumin-advanced oxidation protein products (HSA-AOPP). Both FBP and NAC were capable of inhibiting the formation of HOCl-induced AOPP in a concentration-dependent manner. The synergistic effect promoted by the association of these drugs showed to be more effective than when tested alone. Thus, both FBP and NAC may be good candidates to mitigate and neutralize pro-inflammatory and pro-oxidant effects of AOPP in several diseases.

Genoprotective and hepatoprotective effects of Guarana (Paullinia cupana Mart. var. sorbilis) on CCl4-induced liver damage in rats

Abstract Context: Several biological effects of Paullinia cupana (guarana) have been demonstrated, but little information is available on its effects on the liver. Objective: The current study was designed to evaluate the hepatoprotective and genoprotective effects of powder seeds from guarana on CCl4-induced liver injury in rats. Materials and methods: Male Wistar rats were pretreated with guarana powder (100, 300 and 600 mg/kg) or silymarin 100 mg/kg daily for 14 days before treatment with a single dose of CCl4 (50% CCl4, 1 mL/kg, intraperitoneally). Results: The treatment with CCl4 significantly increased the serum activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). In addition, CCl4 increased the DNA damage index in hepatocytes. Guarana in all concentrations was effective in decreasing the ALT and AST activities when compared with the CCl4-treated group. The treatment with guarana decreased DNA damage index when compared with the CCl4-treated group. In addition, the DNA damage index showed a significant positive correlation with AST and ALT. Discussion and conclusion: These results indicate that the guarana has hepatoprotective activity and prevents the DNA strand breakage in the CCl4-induced liver damage in rats.

Oxidative stress and inflammatory response biomarkers in dogs with mammary carcinoma

Mammary carcinoma is the most common cancer that affects dogs, and in many cases it leads to death. Thus, given the importance of this disease, to clarify its pathogenesis is an important measure. In this sense, the aim of this study was to investigate the levels of cytokines and nitric oxide (NO), oxidative and antioxidant status, as well as the activity of adenosine deaminase (ADA) and butyrylcholinesterase (BChE) in dogs diagnosed with mammary carcinoma. With this purpose, thirty-three (33) serum samples from female dogs with histopathological diagnosis of mammary carcinoma, without evidence of metastasis, were used (group B). The material was classified based on the degree of malignancy, as follows: subgroup B1 (low-grade malignancy; n=26) and subgroup B2 (high grade of malignancy; n=7). Serum samples from healthy females (group A; n=10) were used as negative control. Our results showed that levels of cytokines (TNF-α, INF-γ, IL-1, and IL-6), NOx (nitrite/nitrate), AOPP (protein oxidation), and FRAP (antioxidant power) were significantly (P<0.05) increased in dogs with mammary carcinoma (group B), when compared with group A. On the other hand, ADA activity was significantly decreased (P<0.05) in both subgroups B1 and B2, when compared with group A. BChE activity, however, was reduced (P<0.05) only in subgroup B2 when compared with group A and subgroup B1. Unlike other variables, NO, AOPP, and IFN-γ were influenced by the degree of tumor malignancy, i.e., their levels were even higher in subgroup B2. Therefore, based on these results, we can conclude that all variables investigated are related to the pathogenesis of this disease, since they were altered in dogs with mammary tumor. Additionally, we suggest that ADA activity had an anti-inflammatory effect on these tumor samples, probably in order to modulate the inflammatory response.

In Vitro Oxidation of Collagen Promotes the Formation of Advanced Oxidation Protein Products and the Activation of Human Neutrophils

The accumulation of advanced oxidation protein products (AOPPs) has been linked to several pathological conditions. Here, we investigated collagen as a potential source for AOPP formation and determined the effects of hypochlorous acid (HOCl)-treated collagen (collagen-AOPPs) on human neutrophil activity. We also assessed whether alpha-tocopherol could counteract these effects. Exposure to HOCl increased the levels of collagen-AOPPs. Collagen-AOPPs also stimulated the production of AOPPs, nitric oxide (NO), superoxide radicals (O2−), and HOCl by neutrophils. Collagen-AOPPs induced apoptosis and decreased the number of viable cells. Alpha-tocopherol prevented the formation of collagen-AOPPs, strongly inhibited the collagen-AOPP-induced production of O2− and HOCl, and increased the viability of neutrophils. Our results suggest that collagen is an important protein that interacts with HOCl to form AOPPs, and consequently, collagen-AOPP formation is related to human neutrophil activation and cell death.

In vitro oxidation of fibrinogen promotes functional alterations and formation of advanced oxidation protein products, an inflammation mediator.

Fibrinogen (FB) is a soluble blood plasma protein and is a key molecule involved in coagulation. Oxidative modification of proteins, such as the formation of advanced oxidation protein products (AOPP), a heterogeneous family of protein compounds structurally modified and derived from oxidative stress, may be associated with the pathophysiology of a number of chronic inflammatory diseases. Therefore, the aim of this study was to determine whether the formation of this mediator of inflammation occurs from FB and whether its generation is associated with structural changes. Results of the present study suggest that the oxidation of FB may provoke the formation of AOPP, which in turn, may promote functional alterations in FB, thus causing changes in its structural domains and increasing its procoagulant activity.

Oxidative stress by Haemonchus contortus in lambs: Influence of treatment with zinc edetate

The aim of the present study was to assess the effects of zinc edetate on the oxidative stress of lambs infected by Haemonchus contortus. Twenty-four lambs were allocated into four groups: Group I--uninfected animals; Group II--uninfected animals treated subcutaneously with zinc edetate; Group III--animals infected by H. contortus and Group IV--animals infected and treated. The oxidative stress index (OSI) and the eggs per gram of feces (EPG) were assessed after 10, 17, 24, 31 and 38 days post-infection. Based on the EPG and the quantity of adult H. contortus, the infection did not differ between groups III and IV. Zinc edetate reduced the OSI in Group IV in relation to Group I after 24 days post-infection, and in relation to group III after 31 days post-infection. Treatment with zinc edetate could help reduce the oxidative stress induced by H. contortus in lambs.

Fenton Reaction-Generated Advanced Oxidation Protein Products Induces Inflammation in Human Embryonic Kidney Cells.

Fenton reaction is a new mechanism able to generate advanced oxidation protein products (AOPPs) by exposing the human serum albumin to the Fenton system. Here, we characterized the effects of Fenton reaction-generated advanced oxidation protein products (AOPP-FR) on the gene transcription of the nuclear factor-κB (NF-κB), cyclooxygenase-2 (COX-2), and interleukin-6 (IL-6) in human embryonic kidney cells (HEK 293). To investigate the effects of AOPP-FR and AOPP-HOCl on transcription of inflammatory genes, the NF-κB, COX-2, and IL-6 luciferase promoter activities were analyzed. AOPP-FR and AOPP-HOCl were able to induce the activation of the gene transcription of NF-κB, COX-2, and IL-6 in HEK 293 cells. However, the effects of AOPP-FR were significantly higher than the effects of AOPP-HOCl in relation to COX-2 and IL-6. AOPP-FR induces the activation of the gene transcription of NF-κB, COX-2, and IL-6 and may represent a novel pathogenic mediator of inflammation in kidney.