Quercetin increases bioavailability of nitric oxide in the jejunum of euglycemic and diabetic rats and induces neuronal plasticity in the myenteric plexus.

Considering the antioxidant, neuroprotective, inflammatory and nitric oxide modulatory actions of quercetin, the aim of this study was to test the effect of quercetin administration in drinking water (40 mg/day/rat) on neuronal nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), overall population of myenteric neurons (HuC/D) and nitric oxide (NO) levels in the jejunal samples from diabetic rats. Male Wistar rats were distributed into four groups (8 rats per group): euglycemic (E), euglycemic administered with quercetin (E+Q), diabetic (D) and diabetic administered with quercetin (D+Q). Rats were induced to diabetes with streptozotocin (35mg/kg/iv) and, after 120 days, the proximal jejunum were collected and processed for immunohistochemical (VIP, nNOS and HuC/D) and chemiluminescence (quantification of tissue NO levels) techniques. Diabetes mellitus reduced the number of nNOS-IR (immunoreactive) (p <0.05) and HuC/D-IR (p <0.001) neurons, however, promoted an increased morphometric area of nNOS-IR neurons (p <0.001) and VIP-IR varicosities (p <0.05). In D+Q group, neuroplasticity effects were observed on HuC/D-IR neurons, accompanied by a reduction of cell body area of neurons nNOS- and VIP-IR varicosities (p <0.05). The NO levels were increased in the E+Q (p <0.05) and D+Q group (p <0.001) compared to the control group. In conclusion, the results showed that quercetin supplementation increased the bioavailability of NO in the jejunum in euglycemic and mitigate the effects of diabetes on nNOS-IR neurons and VIP-IR varicosities in the myenteric plexus of diabetic rats.

Supplementation with l-glutathione improves oxidative status and reduces protein nitration in myenteric neurons in the jejunum in diabetic Rattus norvegicus.

Diabetes mellitus is a syndrome with multiple etiologies, characterized by chronic hyperglycemia that increases the production of reactive oxygen species and decreases antioxidant defenses. The present study evaluated oxidative stress parameters and protein nitration in myenteric neurons in the jejunum in diabetic rats supplemented with l-glutathione. Rats (90 days of age) were distributed into four groups (n = 6/group): normoglycemic (N), normoglycemic supplemented with l-glutathione (NGT), diabetic (D), and diabetic supplemented with l-glutathione (DGT). At 210 days of age, the animals were sacrificed, and the jejunum was collected, washed, and subjected to various procedures: tert-butyl hydroperoxide chemiluminescence (CL), determination of total antioxidant capacity (TAC), determination of catalase activity, quantification of nitric oxide (NO), and double-labeling of HuC/D-immunoreactive myenteric neurons and nitrotyrosine (3-NT). Diabetes increased oxidative stress in the jejunum in the D group, reflected by increases in lipid peroxidation, TAC, catalase activity, and NO. The D group exhibited an increase in the percentage of myenteric neurons that were double-labeled with 3-NT. Supplementation with l-glutathione did not cause differences in the average CL curves between the D and DGT groups, but reductions of TAC and catalase activity were observed. Supplementation with l-glutathione promoted a reduction of neurons that contained 3-NT in the DGT group. Diabetes mellitus promoted oxidative stress in the jejunum, and supplementation with l-glutathione improved oxidative status by preventing protein nitration in myenteric neurons in diabetic animals that received supplementation.

Correlation of TGF-ß1 and oxidative stress in the blood of patients with melanoma: a clue to understanding melanoma progression?

TGF-ß1 and oxidative stress are involved in cancer progression, but in melanoma, their role is still controversial. Our aim was to correlate plasma TGF-ß1 levels and systemic oxidative stress biomarkers in patients with melanoma, with or without disease metastasis, to understand their participation in melanoma progression. Thirty patients were recruited for melanoma surveillance, together with 30 healthy volunteers. Patients were divided into two groups: Non-metastasis, comprising patients with tumor removal and no metastatic episode for 3 years; and Metastasis, comprising patients with a metastatic episode. The plasmatic cytokines TGF-ß1, IL-1 ß, and TNF-α were analyzed by ELISA. For oxidative stress, the following assays were performed: malondialdehyde (MDA), advanced oxidation protein products (AOPP) levels, total radical-trapping antioxidant parameter (TRAP) and thiol in plasma, and lipid peroxidation, SOD and catalase activity and GSH in erythrocytes. Patients with a metastatic episode had less circulating TGF-ß1 and increased TRAP, thiol, AOPP and lipid peroxidation levels. MDA was increased in both melanoma groups, while catalase, GSH, and IL-1ß was decreased in Non-metastasis patients. Significant negative correlations were observed between TGF-ß1 levels and systemic MDA, and TGF-ß1 levels and systemic AOPP, while a positive correlation was observed between TGF-ß1 levels and erythrocyte GSH. Lower levels of TGF-ß1 were related to increased oxidative stress in Metastasis patients, reinforcing new evidence that in melanoma TGF-ß1 acts as a tumor suppressor, inhibiting tumor relapse. These findings provide new knowledge concerning this cancer pathophysiology, extending the possibilities of investigating new therapies based on this evidence.

Systemic oxidative profile after tumor removal and the tumor microenvironment in melanoma patients.

This study highlights the systemic oxidative changes in patients submitted to primary cutaneous melanoma removal. Cutaneous melanoma is highly aggressive and its incidence is increasing worldwide. We evaluated systemic oxidative stress (OS) and 3-nitrotyrosine (3-NT) expression in melanoma tissue in relation to the Breslow thickness in patients under surveillance. Forty-three patients with cutaneous melanoma and 50 healthy volunteers were recruited. Patients were divided into two groups according to the tumor's Breslow thickness: T1/T2 (<2 mm) and T3/T4 (≥2 mm). Systemic OS and inflammatory mediators were evaluated in plasma, and the 3-NT expression was analyzed via immunohistochemistry. Compared with the controls, the patients had lower blood levels of reduced glutathione, higher malondialdehyde and thiol levels, and a higher total radical-trapping antioxidant parameter to uric acid ratio. The C-reactive protein and γ-glutamyl transpeptidase were increased only in the T3/T4 group. High levels of 3-NT were present only in T3/T4 patients. Our data suggested that a correlation exists between the Breslow thickness and a systemic pro-oxidant status, and that oxidative changes induced by the melanoma remain in the microenvironment post-surgery, demonstrating a role for oxygen species in melanoma.