Heat shock protein B1 is a key mediator of prolactin-induced beta-cell cytoprotection against oxidative stress

Maintaining islet cell viability in vitro, although challenging, appears to be a strategy for improving the outcome of pancreatic islet transplantation. We have shown that prolactin (PRL) leads to beta-cell cytoprotection against apoptosis, an effect mediated by heat shock protein B1 (HSPB1). Since the role of HSPB1 in beta-cells is still unclear and the hormone concentration used is not compatible with clinical applications because of all the side effects displayed by the hormone in other tissues, we explored the molecular mechanisms by which HSPB1 mediates beta-cell cytoprotection. Lysates from PRL- and/or cytokine-treated MIN6 beta-cells were subjected to HSPB1 immunoprecipitation followed by identification through mass spectrometry. PRL-treated cells presented an enrichment of several proteins co-precipitating with HSPB1. Of note were oxidative stress resistance-, protein degradation- and carbohydrate metabolism-related proteins. Wild type, HSPB1 silenced or overexpressing MIN6 cells were exposed to menadione and hydrogen peroxide and analysed for several oxidative stress parameters. HSPB1 knockdown rendered cells more sensitive to oxidative stress and led to a reduced antioxidant capacity, while prolactin induced an HSPB1-mediated cytoprotection against oxidative stress. HSPB1 overexpression, however, led to opposite effects. PRL treatment, HSPB1 silencing or overexpression did not change the expression nor activities of antioxidant enzymes, it also did not lead to a modulation of total glutathione levels nor G6PD expression. However, HSPB1 levels are related to a modulation of GSH/GSSG ratio, G6PD activity and NADPH/NADP ⁺ ratio. We have shown that HSPB1 is important for pro-survival effects against oxidative stress-induced beta-cell death. These results are in accordance with PRL-induced enrichment of HSPB1-interacting proteins related to protection against oxidative stress. Finally, our results outline the need of further studies investigating the importance of HSPB1 for beta-cell viability, since this could lead to the mitigation of beta-cell death through the up-regulation of an endogenous protective pathway.

Identification of urate hydroperoxide in neutrophils: A novel pro-oxidant generated in inflammatory conditions

Uric acid is the final product of purine metabolism in humans and is considered to be quantitatively the main antioxidant in plasma. In vitro studies showed that the oxidation of uric acid by peroxidases, in presence of superoxide, generates urate free radical and urate hydroperoxide. Urate hydroperoxide is a strong oxidant and might be a relevant intermediate in inflammatory conditions. However, the identification of urate hydroperoxide in cells and biological samples has been a challenge due to its high reactivity. By using mass spectrometry, we undoubtedly demonstrated the formation of urate hydroperoxide and its corresponding alcohol, hydroxyisourate during the respiratory burst in peripheral blood neutrophils and in human leukemic cells differentiated in neutrophils (dHL-60). The respiratory burst was induced by phorbol myristate acetate (PMA) and greatly increased oxygen consumption and superoxide production. Both oxygen consumption and superoxide production were further augmented by incubation with uric acid. Conversely, uric acid significantly decreased the levels of HOCl, probably because of the competition with chloride by the catalysis of myeloperoxidase. In spite of the decrease in HOCl, the overall oxidative status, measured by GSH/GSSG ratio, was augmented in the presence of uric acid. In summary, the present results support the formation of urate hydroperoxide, a novel oxidant in neutrophils oxidative burst. Urate hydroperoxide is a strong oxidant and alters the redox balance toward a pro-oxidative environment. The production of urate hydroperoxide in inflammatory conditions could explain, at least in part, the harmful effect associated to uric acid.

Uric acid disrupts hypochlorous acid production and the bactericidal activity of HL-60 cells

Uric acid is the end product of purine metabolism in humans and is an alternative physiological substrate for myeloperoxidase. Oxidation of uric acid by this enzyme generates uric acid free radical and urate hydroperoxide, a strong oxidant and potentially bactericide agent. In this study, we investigated whether the oxidation of uric acid and production of urate hydroperoxide would affect the killing activity of HL-60 cells differentiated into neutrophil-like cells (dHL-60) against a highly virulent strain (PA14) of the opportunistic pathogen Pseudomonas aeruginosa. While bacterial cell counts decrease due to dHL-60 killing, incubation with uric acid inhibits this activity, also decreasing the release of the inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF- α). In a myeloperoxidase/Cl^-/H₂O₂ cell-free system, uric acid inhibited the production of HOCl and bacterial killing. Fluorescence microscopy showed that uric acid also decreased the levels of HOCl produced by dHL-60 cells, while significantly increased superoxide production. Uric acid did not alter the overall oxidative status of dHL-60 cells as measured by the ratio of reduced (GSH) and oxidized (GSSG) glutathione. Our data show that uric acid impairs the killing activity of dHL-60 cells likely by competing with chloride by myeloperoxidase catalysis, decreasing HOCl production. Despite diminishing HOCl, uric acid probably stimulates the formation of other oxidants, maintaining the overall oxidative status of the cells. Altogether, our results demonstrated that HOCl is, indeed, the main relevant oxidant against bacteria and deviation of myeloperoxidase activity to produce other oxidants hampers dHL-60 killing activity.

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Uric acid decreased microbicide activity and release of cytokines by dHL-60 cells.

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Uric acid decreased HOCl in cells and in the myeloperoxidase/Cl^-/H₂O₂ system.

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Uric acid induces a pro-oxidant redox imbalance.

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HOCl is crucial for Pseudomonas aeruginosa killing by dHL-60.

Blood pressure measurement in hemodialysis: The importance of the measurement technique

Systemic arterial hypertension contributes to the high cardiovascular morbidity in hemodialysis (HD) patients, but the accuracy of blood pressure (BP) measurement in this population has not been well studied. To evaluate the agreement between BP measurement using the routine measurement technique (usual method) and the technique recommended by the VII Joint (standard method). This cross-sectional study enrolled 124 patients in a single center who had undergone dialysis for more than three months and were 18 years of age or older. The BP was verified at the start of dialysis by the nursing team (usual method) and by the researchers (standard method). The agreement between the systolic and diastolic BP (SBP and DBP) measurements was tested by the Bland-Altman analysis. A difference in BP measurement higher than ±5 mm Hg was considered clinically significant. The studied group had a mean age of 53.2 years. The average difference between routine and standard BP measurement was -6 mm Hg for SBP (limits of agreement: -40.1-28 mm Hg; P <0.001) and -5.6 mm Hg for DBP (limits of agreement: -33.1-21.8 mm Hg; P <0.001). A clinically significant difference in BP measured by both methods was observed in 69.4% of the patients for SBP and in 61.3% for DBP. The disagreement between the results of different BP measurement methods in HD patients was significant and the BP was underestimated using the usual BP method. BP measurement standardization should be encouraged to avoid errors in diagnosis and therapy.

Relaxin affects cell organization and early and late stages of spermatogenesis in a coculture of rat testicular cells

Relaxin and its receptor RXFP1 are co-expressed in Sertoli cells, and relaxin can stimulate proliferation of Sertoli cells. In this study, we investigated a role of relaxin in spermatogenesis, using a short-term culture of testicular cells of the rat that allowed differentiation of spermatogonia to spermatids. Sertoli, germ, and peritubular myoid cells were the predominant cell types in the culture. Sertoli and germ cells expressed RXFP1. Cultures were incubated without (control) or with 0.5% fetal bovine serum (FBS) or 100 ng/mL H2 relaxin (RLN) for 2 days. Cell organization, number, and differentiation were analyzed after 2 (D2), 5 (D5) or 8 (D8) days of culturing. Although the proportion of germ cells decayed from D2 to D5, the relative contribution of HC, 1C, 2C, and 4C germ cell populations remained constant in the control group during the whole culture. RLN did not affect the proportion of germ cell populations compared with control, but increased gene and/or protein expression of the undifferentiated and differentiated spermatogonia markers PLZF and c-KIT, and of the post-meiotic marker Odf2 in D5. RLN favored organization of cells in tubule-like structures, the arrangement of myoid cells around the tubules, arrangement of c-KIT-positive spermatogonia at the basal region of the tubules, and expression of the cell junction protein β-catenin close to the plasma membrane region. Knockdown of relaxin with small interfering RNA (siRNA) reduced expression of β-catenin at the cell junctions, and shifted its expression to the nucleus. We propose that relaxin may affect spermatogenesis by modulating spermatogonial self renewal and favoring cell contact.

Intensity and physiological responses to the 6-minute walk test in middle-aged and older adults: a comparison with cardiopulmonary exercise testing

The 6-minute walk test (6MWT) is a simple field test that is widely used in clinical settings to assess functional exercise capacity. However, studies with healthy subjects are scarce. We hypothesized that the 6MWT might be useful to assess exercise capacity in healthy subjects. The purpose of this study was to evaluate 6MWT intensity in middle-aged and older adults, as well as to develop a simple equation to predict oxygen uptake (V˙O2) from the 6-min walk distance (6MWD). Eighty-six participants, 40 men and 46 women, 40-74 years of age and with a mean body mass index of 28±6 kg/m², performed the 6MWT according to American Thoracic Society guidelines. Physiological responses were evaluated during the 6MWT using a K4b2 Cosmed telemetry gas analyzer. On a different occasion, the subjects performed ramp protocol cardiopulmonary exercise testing (CPET) on a treadmill. Peak V˙O2 in the 6MWT corresponded to 78±13% of the peak V˙O2 during CPET, and the maximum heart rate corresponded to 80±23% of that obtained in CPET. Peak V˙O2 in CPET was adequately predicted by the 6MWD by a linear regression equation: V˙O2 mL·min^-1·kg^-1 = -2.863 + (0.0563×6MWD_m) (R²=0.76). The 6MWT represents a moderate-to-high intensity activity in middle-aged and older adults and proved to be useful for predicting cardiorespiratory fitness in the present study. Our results suggest that the 6MWT may also be useful in asymptomatic individuals, and its use in walk-based conditioning programs should be encouraged.

Cobalt chloride induces metaphase when topically applied to larvae and pupae of the stingless bee Melipona scutellaris (Hymenoptera, Apidae, Meliponini)

In order to optimize preparations of bee metaphases, we tested cobalt chloride, which has been used as a metaphase inducer in other organisms, such as hamsters and fish. Four microliters of 65 mM cobalt chloride aqueous solution was topically applied to larval and pupal stages of the stingless bee Melipona scutellaris. The cerebral ganglion was removed after treatment and prepared for cytogenetic analysis. Identically manipulated untreated individuals were used as controls. The number of metaphases was increased 3-fold in treated individuals compared to controls. The micronucleus test showed no mutagenic effects of cobalt chloride on M. scutellaris cells. We concluded that cobalt chloride is a metaphase-inducing agent in M. scutellaris, thus being useful for cytogenetic analyses.

The effect of the Rochagan on radiolabeling with (99m)Tc

Radionuclides are used in nuclear medicine by variety of diagnostic procedures. The labeling of red blood cells (RBC) with (99m)Tc is a current method applied in clinical nuclear medicine. Drugs can alter this labeling and modify the disposition of the radiopharmaceuticals. The influence of Rochagan on the labeling of blood constituents with (99m)Tc was reported. Samples of blood were incubated with different concentrations of Rochagan (0%; 6.25%; 12.5%; 25%; 50%; 100%). Stannous chloride and (99m)Tc (3.7MBq/mL) were added. Plasma (P) and (RBC) were isolated and precipitated with thricloroacetic acid 5%. The insoluble (IF) and soluble fractions (SF) were separated. The %ATI in RBC, IF-P and IF-RBC were calculated. The %ATI on RBC decreased significantly (p<0.05) from control to all concentrations of Rochagan, respectively: 90.15 + or - 0.14(control) to 70.80 + or - 4.21; to 64.36 + or - 0.33; to 57.30 + or - 1.56; to 50.28 + or - 2.71; to 42.41 + or - 2.24; on IF-RBC, respectively: 84.70 + or - 0.87(control) to 67.16 + or - 4.38; to 63.63 + or - 2.92; to 59.02 + or - 3.17; to 43.75 + or - 1.00; to 24.15 + or - 0.94 and also on IF-P, respectively: 83.46 + or - 1.09(control) to 50.90 + or - 3.36; to 35.46 + or - 4.13; to 35.78 + or - 2.31; to 28.74 + or - 3.09; to 19.66 + or - 1.34. The analyses were performed by T-Student and Mann Whitney tests, p<0.05. This effect was probably due to products present in Rochagan that may complex with ions or have a direct/indirect effect on intracellular stannous ion concentration.

Biosensing hydrogen peroxide utilizing carbon paste electrodes containing peroxidases naturally immobilized on coconut (Cocus nucifera L.) fibers

A novel unmediated hydrogen peroxide biosensor based on the incorporation of fibrous tissue of coconut fruit in carbon paste matrix is presented. Cyclic voltammetry and amperometry were utilized to characterize the main electrochemical parameters and the performance of this new biosensor under different preparation and operation conditions. The resulting H2O2-sensitive biosensors respond rapidly (7 s to attain 90% of the signal), was operated at -0.15 V, presented linear response between 2.0x10(-4) and 3.4x10(-3) mol L(-1), the detection limit was estimated as 4.0x10(-5) mol L(-1). Its operation potential was situated between -0.2 and 0.1 V and the best pH was determined as 5.2. Electrodes containing 5% (w/w) of coconut fiber presented the best signal and their lifetime was extended to 3 months. The apparent Michaelis-Menten constant KM(app) and Vmax were estimated to be 8.90 mmol L(-1) and 6.92 mmol L(-1) microA(-1), respectively. The results obtained for determination of hydrogen peroxide in four pharmaceutical products (antiseptic solution, contact lenses cleaning solution, hair coloring cream and antiseptic dental rinse solution) were in agreement with those obtained by the spectrophotometric method. An additional advantage of these biosensors is the capacity to measure hydrogen peroxide even in samples with relatively low pH. To demonstrate the enzymatic activity of the coconut tissue, a very simple way was created during this work. Coconut fibers were immersed in H2O2 solution between two glass slides. Sequential images were taken to show the rapid generation of O2, attesting the high activity of the enzymes.

Schistosoma mansoni: continuous variation in susceptibility of the vector snail of schistosomiasis, Biomphalaria tenagophila I. Self-fertilization-lineage

Mascara, D., Kawano, T., Magnanelli, A. C., Silva, R. P. S., Sant' Anna, O. A., and Morgante, J. S. 1999. Schistosoma mansoni: continuous variation in susceptibility of the vector snail of schistosomiasis, Biomphalaria tenagophila I. Self-Fertilization-Lineage. Experimental Parasitology 93, 133-141. Artificial selection of Biomphalaria tenagophila snails for susceptibility to infection by Schistosoma mansoni (Brazilian SJ strain) was carried out from natural populations. After five self-fertilization generations, two lineages were isolated and were designated as SUSC (highly susceptible 93-100%) and RES (nonsusceptible 5-0%). Length of the prepatent period, cercarial production, and mortality of the hosts in postexposure were determined in all generations (F(1)-F(8)) and were analyzed as quantitative traits related to host susceptibility. Distribution patterns of frequencies were observed within snail families (samples derived from one F(0) snail), these traits showing a significant influence by selection applied to susceptibility. The multiple quantitative classes were described in terms of continuous variation. During the selection of SUSC lineage, classes with higher values of prepatent length and lower cercarial production were eliminated, and the heritability calculated for these two traits was 0.811 and 0.709, respectively. Experimental results were correlated with an increase in the level of susceptibility in the generations selected and are discussed in relation to inheritance patterns as well as the quantitative variation of susceptibility.