Effects of resveratrol on nucleotide degrading enzymes in streptozotocin-induced diabetic rats

AimsDiabetes mellitus is associated with platelet alterations that may contribute to the development of cardiovascular complications. The present study investigates the effects of resveratrol (RSV), an important compound with cardioprotective activities, on NTPDase, ecto-nucleotide pyrophosphatase/phosphodiesterase (E-NPP), 5′-nucleotidase and adenosine deaminase (ADA) activities in platelets from streptozotocin (STZ)-induced diabetic rats.Main methodsThe animals were divided into six groups (n = 8): control/saline; control/RSV 10 mg/kg; control/RSV 20 mg/kg; diabetic/saline; diabetic/RSV 10 mg/kg; diabetic/RSV 20 mg/kg. RSV was administered during 30 days and after this period the blood was collected for enzymatic assay.Key findingsThe results demonstrated that NTPDase, E-NPP and 5′-nucleotidase activities were significantly higher in the diabetic/saline group (P < 0.05) compared to control/saline group. Treatment with RSV significantly increased NTPDase, 5′-nucleotidase and E-NPP activities in the diabetic/RSV10 and diabetic/RSV20 groups (P < 0.05) compared to diabetic/saline group. When RSV was administered per se there was also an increase in the activities of these enzymes in the control/RSV10 and control/RSV20 groups (P < 0.05) compared to control/saline group. ADA activity was significantly increased in the diabetic/saline group (P < 0.05) compared to control/saline group. The treatment with RSV prevented this increase in the diabetic/RSV10 and diabetic/RSV20 groups. No significant differences in ADA activity were observed in the control/RSV10 and control/RSV20 compared to control/saline group.SignificanceThe present findings demonstrate alterations in nucleotide hydrolysis in platelets of STZ-induced diabetic rats and treatment with RSV was able to modulate adenine nucleotide hydrolysis, which may be important in the control of the platelet coagulant status in diabetes.     

Targeting Stat3 induces senescence in tumor cells and elicits prophylactic and therapeutic immune responses against breast cancer growth mediated by NK cells and CD4+ T cells

Aberrant Stat3 activation and signaling contribute to malignant transformation by promoting cell cycle progression, inhibiting apoptosis, and mediating tumor immune evasion. Stat3 inhibition in tumor cells induces the expression of chemokines and proinflammatory cytokines, so we proposed to apply Stat3-inhibited breast cancer cells as a source of immunogens to induce an antitumor immune response. Studies were performed in two murine breast cancer models in which Stat3 is activated: progestin-dependent C4HD cells and 4T1 cells. We immunized BALB/c mice with irradiated cancer cells previously transfected with a dominant-negative Stat3 vector (Stat3Y705F) in either a prophylactic or a therapeutic manner. Prophylactic administration of breast cancer cells transfected with Stat3Y705F (Stat3Y705F-breast cancer cells) inhibited primary tumor growth compared with administration of empty vector-transfected cells in both models. In the 4T1 model, 50% of the challenged mice were tumor free, and the incidence of metastasis decreased by 90%. In vivo assays of C4HD tumors showed that the antitumor immune response involves the participation of CD4(+) T cells and cytotoxic NK cells. Therapeutic immunization with Stat3Y705F-breast cancer cells inhibited tumor growth, promoted tumor cell differentiation, and decreased metastasis. Furthermore, inhibition of Stat3 activation in breast cancer cells induced cellular senescence, contributing to their immunogenic phenotype. In this work, we provide preclinical proof of concept that ablating Stat3 signaling in breast cancer cells results in an effective immunotherapy against breast cancer growth and metastasis. Moreover, our findings showing that Stat3 inactivation results in induction of a cellular senescence program disclose a potential mechanism for immunotherapy research.     

New occurrence of B chromosomes in Partamonahelleri (Friese, 1900) (Hymenoptera, Meliponini)

Cytogenetic analyses of the stingless bee Partamona helleri collected in the state of Bahia, Northeast Brazil revealed the chromosome numbers n = 18 in the haploid males and 2n = 35 in the diploid females. All karyotypes displayed one large acrocentric B chromosome, which differs from the minute B chromosomes previously described in the populations from southeastern Brazil. Giemsa staining, C-banding and DAPI/CMA(3) fluorochrome staining also revealed a remarkable interpopulational divergence regarding both the regular karyotype and the B chromosomes. The B chromosomes found in the samples from Jequié, Bahia, were entirely heterochromatic, while those found in Cravolandia, Bahia, displayed a euchromatic portion at the telomeric end of the long arm. CMA (3) labeling sites varied from seven to eight between the two localities in Bahia, due to the presence of an extra GC-rich block in the karyotype of the samples from Jequié. This is the first report of a large B chromosome in P. helleri and reveals the occurrence of a geographic differentiation within this species.     

Inhibition of bovine kidney low molecular mass phosphotyrosine protein phosphatase by uric acid

Uric acid inhibited 50% of the activity of bovine kidney low molecular mass phosphotyrosine protein phosphatase at concentrations of 1.0, 0.4, 1.3, and 0.2 mM, respectively for p-nitrophenyl phosphate (p-NPP), flavine mononucleotide, beta-naphthyl phosphate and tyrosine phosphate (Tyr-P) as substrates. The mixed type inhibition of p-NPP hydrolysis was fully reversible, with Kic and Kiu values of 0.4 and 1.1 mM, respectively; the inhibition by uric acid shifted the pH optimum from 5.0 to 6.5. When Tyr-P was the substrate, competitive inhibition was observed with a Ki value of 0.05 mM. Inhibition studies by uric acid in the presence of thiol compounds, and preincubation studies in the presence of inorganic phosphate suggest that the interaction of uric acid with the enzyme occurred at the active site, but did not involve SH residues, and that the mechanism of inhibition depended on the structure of the substrates.     

Increased cellular activity in rat insular cortex after water and salt ingestion induced by fluid depletion

Insular cortex (IC) receives inputs from multiple sensory systems, including taste, and from receptors that monitor body electrolyte and fluid balance and blood pressure. This work analyzed metabolic activity of IC cells after water and sodium ingestion induced by sodium depletion. Rats were injected with the diuretic furosemide (10 mg/kg body wt), followed 5 min later by injections of the angiotensin-converting enzyme inhibitor captopril (5 mg/kg body wt). After 90 min, some rats received water and 0.3 M NaCl to drink for 2 h while others did not. A third group had access to water and saline but was not depleted of fluids. All rats were killed for processing of brain tissue for Fos-immunoreactivity (Fos-ir). Nondepleted animals had weak-to-moderate levels of Fos-ir within subregions of IC. Fluid-depleted rats without fluid access had significantly increased Fos-ir in all areas of IC. Levels of Fos-ir were highest in fluid-depleted rats that drank water and sodium. Fos-ir levels were highest in anterior regions of IC and lowest in posterior regions of IC. These results implicate visceral, taste, and/or postingestional factors in the increased metabolic activity of cells in IC.     

Decolorization of synthetic dyes by solid state cultures of Lentinula (Lentinus) edodes producing manganese peroxidase as the main ligninolytic enzyme

The ability of the white-rot fungus Lentinula (Lentinus) edodes to decolorize several synthetic dyes was investigated using solid state cultures with corn cob as substrate. Cultures, containing amido black, congo red, trypan blue, methyl green, remazol brilliant blue R, methyl violet, ethyl violet and Poly R478 at 200 ppm, were completely decolorized after 18 days of incubation. Partial decolorization was observed in the cultures containing 200 ppm of brilliant cresyl blue and methylene blue. High manganese peroxidase activity (2600 U/g substrate), but very low lignin peroxidase (<10 U/g substrate) and laccase (<16 U/g substrate) activities were detected in the cultures. In vitro, the dye decolorization was markedly decreased by the absence of manganic ions and H2O2. These data suggest that manganese peroxidase appear to be the main responsible for the capability of L. edodes to decolorize synthetic dyes.     

Protective role of arginase in a mouse model of colitis

Arginase is the endogenous inhibitor of inducible NO synthase (iNOS), because both enzymes use the same substrate, l-arginine (Arg). Importantly, arginase synthesizes ornithine, which is metabolized by the enzyme ornithine decarboxylase (ODC) to produce polyamines. We investigated the role of these enzymes in the Citrobacter rodentium model of colitis. Arginase I, iNOS, and ODC were induced in the colon during the infection, while arginase II was not up-regulated. l-Arg supplementation of wild-type mice or iNOS deletion significantly improved colitis, and l-Arg treatment of iNOS(-/-) mice led to an additive improvement. There was a significant induction of IFN-gamma, IL-1, and TNF-alpha mRNA expression in colitis tissues that was markedly attenuated with l-Arg treatment or iNOS deletion. Treatment with the arginase inhibitor S-(2-boronoethyl)-l-cysteine worsened colitis in both wild-type and iNOS(-/-) mice. Polyamine levels were increased in colitis tissues, and were further increased by l-Arg. In addition, in vivo inhibition of ODC with alpha-difluoromethylornithine also exacerbated the colitis. Taken together, these data indicate that arginase is protective in C. rodentium colitis by enhancing the generation of polyamines in addition to competitive inhibition of iNOS. Modulation of the balance of iNOS and arginase, and of the arginase-ODC metabolic pathway may represent a new strategy for regulating intestinal inflammation.     

The RpoS sigma factor in the dissimilatory Fe(III)-reducing bacterium Geobacter sulfurreducens

Geobacter sulfurreducens RpoS sigma factor was shown to contribute to survival in stationary phase and upon oxygen exposure. Furthermore, a mutation in rpoS decreased the rate of reduction of insoluble Fe(III) but not of soluble forms of iron. This study suggests that RpoS plays a role in regulating metabolism of Geobacter under suboptimal conditions in subsurface environments.