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The biological chemistry of hydrogen sulfide (H2S) with physiologically important heme proteins is in the focus of redox biology research. In this study, we investigated the interactions of lactoperoxidase (LPO) with H2S in the presence and absence of molecular dioxygen (O2) or hydrogen peroxide (H2O2). Under anaerobic conditions, native LPO forms no heme-H2S complex upon sulfide exposure. However, under aerobic conditions or in the presence of H2O2 the formation of both ferrous and ferric sulfheme (sulfLPO) derivatives was observed based on the appearances of their characteristic optical absorptions at 638 nm and 727 nm, respectively. Interestingly, we demonstrate that LPO can catalytically oxidize H2S by H2O2 via intermediate formation of relatively short-lived ferrous and ferric sulfLPO derivatives. Pilot product analyses suggested that the turnover process generates oxidized sulfide species, which include sulfate S O 4 2 - and inorganic polysulfides ( H S x - ; x = 2-5). These results indicated that H2S can serve as a non-classical LPO substrate by inducing a reversible sulfheme-like modification of the heme porphyrin ring during turnover. Furthermore, electron paramagnetic resonance data suggest that H2S can act as a scavenger of H2O2 in the presence of LPO without detectable formation of any carbon-centered protein radical species, suggesting that H2S might be capable of protecting the enzyme from radical-mediated damage. We propose possible mechanisms, which explain our results as well as contrasting observations with other heme proteins, where either no sulfheme formation was observed or the generation of sulfheme derivatives provided a dead end for enzyme functions.

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ABSTRACT: Despite the reported effects of smokeless tobacco (ST) on the periodontium and high prevalence of ST use in rural populations and in males studies on this specific topic are limited. The purpose of this cross-sectional investigation was to measure lipid peroxidation (as an end product of oxidative stress) end product i.e. Malondialdehyde (MDA) in saliva of patients with gingivitis, chronic periodontitis and to assess the influence of smokeless tobacco on Salivary Malondialdehyde (S-MDA). Total 30 patients with gingivitis, 30 with chronic periodontitis and 30 Smokeless Tobacco Chewers with Chronic Periodontitis and 30 periodontally healthy subjects were included in the study. Plaque Index (PI), Gingival Index (GI), Probing Pocket Depth (PD), and Clinical Attachment Loss (CAL) were recorded followed by stimulated Saliva sample collection. Salivary MDA Levels were assessed by UV Spectrophotometry. There was a statistically significant increase in the salivary MDA levels in gingivitis, chronic periodontitis and in smokeless tobacco chewers with chronic periodontitis when compared with healthy group. Higher salivary MDA levels in gingivitis group, chronic periodontitis, and smokeless tobacco chewers with chronic periodontitis reflects increasedoxygen radical activity during periodontal inflammation.

RESUMEN: A pesar de los efectos reportados del tabaco sin humo (TS) sobre el periodonto y la alta prevalencia del uso de TS en poblaciones rurales y en hombres, los estudios sobre este tema específico son limitados. El propósito de esta investigación transversal fue medir el producto final de la peroxidación lipídica (como producto final del estrés oxidativo), es decir, malondialdehído (MDA) en la saliva de pacientes con gingivitis, periodontitis crónica y evaluar la influencia del tabaco sin humo en el malondialdehído salival (S-MDA). Se incluyeron en el estudio un total de 30 pacientes con gingivitis, 30 con periodontitis crónica y 30 masticadores de tabaco sin humo con periodontitis crónica y 30 sujetos periodontalmente sanos. Se registraron el índice de placa (PI), el índice gingival (GI), la profundidad de la bolsa de sondeo (PD) y la pérdida de adherencia clínica (CAL), seguidos de la recogida de muestras de saliva estimuladas. Los niveles de MDA en saliva se evaluaron mediante espectrofotometría UV. Hubo un aumento estadísticamente significativo en los niveles de MDA en saliva en gingivitis, periodontitis crónica y en masticadores de tabaco sin humo con periodontitis crónica en comparación con el grupo sano. Los niveles más altos de MDA en saliva en el grupo de gingivitis, periodontitis crónica y masticadores de tabaco sin humo con periodontitis crónica reflejan un aumento de la actividad de los radicales de oxígeno durante la inflamación periodontal.

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The lateral preoptic area (LPO) is connected with limbic structures involved in physiological and behavioral responses to stress. Accordingly, exposure to stressors stimuli activates neurons within the LPO. In spite of these evidence, an involvement of the LPO on cardiovascular and neuroendocrine adjustments during aversive threats has not yet been investigated. Therefore, in the present study we tested the hypothesis that the LPO is involved in the control of cardiovascular and neuroendocrine responses to acute restraint stress in rats. Bilateral microinjection of the nonselective synaptic blocker CoCl2 (0.1nmol/100nl) into the LPO did not affect basal values of either arterial pressure, heart rate, tail skin temperature, or plasma corticosterone concentration. However, LPO treatment with CoCl2 enhanced the tachycardiac response and the increase in plasma corticosterone concentration caused by restraint stress. Conversely, LPO synaptic blockade decreased restraint-evoked pressor response. Sympathetic-mediated cutaneous vasoconstriction during restraint stress was not affected by LPO pharmacological treatment. These findings indicate an inhibitory influence of LPO on tachycardiac and plasma corticosterone responses evoked during aversive threats. Additionally, data suggest that LPO plays a facilitatory influence on stress-evoked pressor response.

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This work sought to ascertain survival and possible changes in levels of glycogen, triglycerides, total lipids, cholesterol, protein, and lipid peroxidation in gills, liver, and muscle of bullfrog tadpoles (Lithobates catesbeianus) exposed to low concentrations of atrazine (2.5 µg L(-1)), glyphosate (18 µg L(-1)), and quinclorac (0.025 µg L(-1)) at laboratorial conditions. Tadpoles showed a reduction of glycogen and triglyceride in all organs and an increase in lipid peroxidation (LPO) compared with control animals. Total lipid in gills and muscle increased in exposure to atrazine, and gills alone in exposure to glyphosate, but decreased in gills, liver, and muscle after quinclorac. Cholesterol increased in gills and liver after atrazine, in gills and muscle after glyphosate, and decreased in liver after quinclorac. Total protein in gills decreased after exposure to all herbicides, increased in muscle after atrazine, and in liver and muscle after quinclorac. These findings show that at concentrations of these herbicides tested can lead to an increase in energy expenditure to maintain homeostasis and survival of these animals despite the increase in lipid peroxidation levels in all organs analyzed. Responses observed can be one of the factors responsible for the decline in the number of amphibians around the world.

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This study aimed to investigate the beneficial effect of diphenyl diselenide (PhSe)2 on paraquat (PQ) induced alterations in rats liver. Adult male Wistar rats received (PhSe)2 at 10 mg kg(-1), by oral administration (p.o.), during five consecutive days. Twenty-four hours after the last (PhSe)2 dose, rats received PQ at 15 mg kg(-1), in a single intraperitoneally injection (i.p.). Seventy-two hours after PQ exposure, animals were sacrificed by decapitation for blood and liver samples obtainment. Histological alterations induced by PQ exposure, such as inflammatory cells infiltration and edema, were prevented by (PhSe)2 administration. Moreover, (PhSe)2 prevented hepatic lipid peroxidation (LPO) induced by PQ and was effective in reducing the myeloperoxidase (MPO) activity in liver, which was enhanced by PQ exposure. (PhSe)2 also was effective in protecting against the reduction in ascorbic acid and non-protein thiols (NPSH) levels induced by PQ. The inhibition of glutathione S-transferase (GST) activity, in rats exposed to PQ, was normalized by (PhSe)2 pre-treatment, whereas the inhibition of catalase (CAT) activity was not prevented by (PhSe)2. The serum alkaline phosphatase (ALP) inhibition, induced by PQ administration, was also prevented by (PhSe)2 pre-treatment. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were not modified by PQ and/or (PhSe)2 administration. Therefore, (PhSe)2 pre-treatment was effective in protecting against the hepatic alterations induced by PQ in rats. This protective effect can involve the antioxidant and anti-inflammatory properties of (PhSe)2.

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Numerous functions have been attributed to the Edinger-Westphal nucleus (EW), including those related to feeding behavior, pain control, alcohol consumption and the stress response. The EW is thought to consist of two parts: one controls accommodation, choroidal blood flow and pupillary constriction, primarily comprising cholinergic cells and projecting to the ciliary ganglion; and the other would be involved in the non-ocular functions mentioned above, comprising peptide-producing neurons and projecting to the brainstem, spinal cord and prosencephalic regions. Despite the fact that the EW is well known, its connections have yet to be described in detail. The aim of this work was to produce a map of the hypothalamic sources of afferents to the EW in the rat. We injected the retrograde tracer Fluoro-Gold into the EW, and using biotinylated dextran amine, injected into afferent sources as the anterograde control. We found retrogradely labeled cells in the following regions: subfornical organ, paraventricular hypothalamic nucleus, arcuate nucleus, lateral hypothalamic area, zona incerta, posterior hypothalamic nucleus, medial vestibular nucleus and cerebellar interpositus nucleus. After injecting BDA into the paraventricular hypothalamic nucleus, lateral hypothalamic area and posterior hypothalamic nucleus, we found anterogradely labeled fibers in close apposition to and potential synaptic contact with urocortin 1-immunoreactive cells in the EW. On the basis of our findings, we can suggest that the connections between the EW and the hypothalamic nuclei are involved in controlling stress responses and feeding behavior.

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