Modulation of Human Hydrogen Sulfide Metabolism by Micronutrients, Preliminary Data

Background: Hydrogen sulfide (H2S) is a pivotal gasotransmitter networking with nitric oxide (NO) and carbon monoxide (CO) to regulate basic homeostatic functions. It is released by the alternative pathways of transulfuration by the enzymes Cystathionine Beta Synthase (CBS) and Cystathionine Gamma Lyase (CSE), and by Cysteine AminoTransferase (CAT)/ 3-Mercaptopyruvate Sulfur Transferase (3MPST). A non-enzymatic, intravascular release is also in place. We retrospectively investigated the possibility to modulate the endogenous H2S release and signaling in humans by a dietary manipulation with supplemented micronutrients (L-cystine, Taurine and pyridoxal 5-phopsphate/P5P). Methods: Patients referring for antiaging purposes underwent a 10-day supplementation. Blood was collected at baseline and after treatment and the metabolome was investigated by mass spectrometry to monitor the changes in the metabolites reporting on H2S metabolism and related pathways. Results: Data were available from 6 middle aged subjects (2 women). Micronutrients increased 3-mercaptopyruvate ( P = .03), reporting on the activity of CAT that provides the substrate for H2S release within mitochondria by 3MPST, decreased lanthionine ( P = .024), reporting the release of H2S from CBS, and had no significant effect of H2S release from CSE. This is compatible with a homeostatic balancing. We also recorded a strong increase of reporters of H2S-induced pathways including 5-MethylTHF ( P = .001) and SAME ( P = .022), reporting on methylation capacity, and of BH4 ( P = .021) and BH2 ( P = .028) reporting on nitric oxide metabolism. These activations may be explained by the concomitant induction of non-enzymatic release of H2S. Conclusions: Although the current evidences are weak and will need to be confirmed, the effect of micronutrients was compatible with an increase of the H2S endogenous release and signaling within the control of homeostatic mechanisms, further endorsing the role of feeding in health and disease. These effects might result in a H2S boosting effect in case of defective activity of pathologic origin, which should be checked in duly designed clinical trials.

Glutamatergic dysfunction leads to a hyper-dopaminergic phenotype through deficits in short-term habituation: a mechanism for aberrant salience.

Psychosis in disorders like schizophrenia is commonly associated with aberrant salience and elevated striatal dopamine. However, the underlying cause(s) of this hyper-dopaminergic state remain elusive. Various lines of evidence point to glutamatergic dysfunction and impairments in synaptic plasticity in the aetiology of schizophrenia, including deficits associated with the GluA1 AMPAR subunit. GluA1 knockout (Gria1-/-) mice provide a model of impaired synaptic plasticity in schizophrenia and exhibit a selective deficit in a form of short-term memory which underlies short-term habituation. As such, these mice are unable to reduce attention to recently presented stimuli. In this study we used fast-scan cyclic voltammetry to measure phasic dopamine responses in the nucleus accumbens of Gria1-/- mice to determine whether this behavioral phenotype might be a key driver of a hyper-dopaminergic state. There was no effect of GluA1 deletion on electrically-evoked dopamine responses in anaesthetized mice, demonstrating normal endogenous release properties of dopamine neurons in Gria1-/- mice. Furthermore, dopamine signals were initially similar in Gria1-/- mice compared to controls in response to both sucrose rewards and neutral light stimuli. They were also equally sensitive to changes in the magnitude of delivered rewards. In contrast, however, these stimulus-evoked dopamine signals failed to habituate with repeated presentations in Gria1-/- mice, resulting in a task-relevant, hyper-dopaminergic phenotype. Thus, here we show that GluA1 dysfunction, resulting in impaired short-term habituation, is a key driver of enhanced striatal dopamine responses, which may be an important contributor to aberrant salience and psychosis in psychiatric disorders like schizophrenia.

P043 Succinate receptor (SUCNR1) mediates leukocyte-endothelial cell interactions induced by TNFa

Background The Krebs cycle metabolite succinate contributes to inflammatory conditions like arthritis and colitis by activating its receptor SUCNR1. We aimed to analyze whether the succinate-SUCNR1 pathway contributes to the leukocyte-endothelial cell interactions that initiate the inflammatory response. Methods We evaluated leukocyte rolling and adhesion by intravital microscopy in cremaster venules of wild-type (WT) and Sucrn1−/− mice treated, 4h before, with succinate (1 Mm, intraescrotally), combined or not with the common pro-inflammatory cytokine TNFα (500 ng/mice, i.p.), or with their vehicles. We analyzed the activity of the NF-κB signaling pathway in endothelial cells (HUVEC) treated (4h) with succinate (0.5–1 mM) ± TNFα (20ng/ml), by detecting this transcription factor, its inhibitor iκBα, and their phosphorylated forms, by western blot. Results are expressed as mean±SEM (N≥6) and analyzed by ANOVA + Newman-Keuls test. Results In WT mice, succinate tended to induce leukocyte rolling and adhesion, and amplified the effects of TNFα on rolling. SUCNR1-deficient mice failed to increase leukocyte rolling in response to these treatments while showed an attenuated response to the effect of TNFα on leukocyte adhesion (Figure 1). Succinate treatment intensified the activation of the NF-κB pathway in HUVEC treated with TNFα, as shown by the increased IκBα phosphorylation, which allows its degradation, the reduced total IκBα, and the increased NF-κB/IκBα ratio (Figure 2). Conclusion Our results suggest that the endogenous release of succinate and the consequent stimulation of the SUCNR1 mediates the leukocyte-endothelial cell interactions induced by TNFα, and this pro-inflammatory activity may be related with an increased activation of the NF-κB signaling pathway in endothelial cells. Thus, the accumulation of succinate observed in various inflammatory diseases probably contributes to the initiation of the inflammatory focus by promoting the accumulation of leukocytes. Bibliography

Human endogenous oxytocin and its neural correlates show adaptive responses to social touch based on recent social context

Both oxytocin (OT) and touch are key mediators of social attachment. In rodents, tactile stimulation elicits endogenous release of OT, potentially facilitating attachment and other forms of prosocial behavior, yet the relationship between endogenous OT and neural modulation remains unexplored in humans. Using serial sampling of plasma hormone levels during functional neuroimaging, we show that contextual circumstances of social touch facilitate or inhibit not only current hormonal and brain responses, but also calibrate later responses. Namely, touch from a romantic partner enhanced subsequent OT release for touch from an unfamiliar stranger, yet OT responses to partner touch were dampened following stranger touch. Hypothalamus and dorsal raphe activation reflected plasma OT changes during the initial interaction. In the subsequent social interaction, OT modulation depended on the previous interaction, mediated by precuneus and parietal-temporal cortex pathways, including a region of medial prefrontal cortex that also covaried with plasma cortisol. These findings demonstrate that hormonal neuromodulation during successive human social interactions is adaptive to social context, and they point to mechanisms that flexibly calibrate receptivity in social encounters.

Noradrenaline Release from Locus Coeruleus Terminals in the Hippocampus Enhances Excitation-Spike Coupling in CA1 Pyramidal Neurons Via β-Adrenoceptors

Release of the neuromodulator noradrenaline signals salience during wakefulness, flagging novel or important experiences to reconfigure information processing and memory representations in the hippocampus. Noradrenaline is therefore expected to enhance hippocampal responses to synaptic input; however, noradrenergic agonists have been found to have mixed and sometimes contradictory effects on Schaffer collateral synapses and the resulting CA1 output. Here, we examine the effects of endogenous, optogenetically driven noradrenaline release on synaptic transmission and spike output in mouse hippocampal CA1 pyramidal neurons. We show that endogenous noradrenaline release enhances the probability of CA1 pyramidal neuron spiking without altering feedforward excitatory or inhibitory synaptic inputs in the Schaffer collateral pathway. β-adrenoceptors mediate this enhancement of excitation-spike coupling by reducing the charge required to initiate action potentials, consistent with noradrenergic modulation of voltage-gated potassium channels. Furthermore, we find the likely effective concentration of endogenously released noradrenaline is sub-micromolar. Surprisingly, although comparable concentrations of exogenous noradrenaline cause robust depression of slow afterhyperpolarization currents, endogenous release of noradrenaline does not, indicating that endogenous noradrenaline release is targeted to specific cellular locations. These findings provide a mechanism by which targeted endogenous release of noradrenaline can enhance information transfer in the hippocampus in response to salient events.

Infantile Iatrogenic Cushing Syndrome due to Topical Steroids

Cushing syndrome is an endocrinological disorder characterized by increased free plasma glucocorticoids level. It is either due to an excessive endogenous release of steroids (e.g., pituitary adenoma or adrenal hyperplasia) or exogenous administration of steroids. In children, iatrogenic Cushing syndrome is the most common form of Cushing syndrome occurring in this age group. The vast majority of cases are due to oral or parenteral preparation of steroids, which are commonly prescribed for pulmonary, hematological, renal, or autoimmune pathologies. Topical preparations can rarely cause Cushing syndrome in young children, and only a few cases were reported in the literature, where the patients were older than 5 months of age. In this report, we present a three-month-old girl who developed iatrogenic Cushing syndrome due to prolonged and inappropriate use of topical clobetasol cream for napkin dermatitis.

92 Intra-nasal oxytocin treatment does not attenuate the hypothalamo-pituitary-adrenal axis in beef heifers subjected to isolation stress or restraint and isolation stress

Changes in the physiological, psychological, and behavioral manifestations of stress are observed in association with increases in circulating oxytocin. Providing oxytocin intra-nasally attenuates stressor-induced hypothalamo-pituitary-adrenal (HPA) axis activation in humans and rodents. The present study was conducted to investigate effects of intra-nasal oxytocin supplementation on stressor-induced activation of the HPA axis in beef cattle. We hypothesized that oxytocin would attenuate activation of the HPA axis, ultimately decreasing plasma cortisol. Bos taurus heifers (n = 28) were blocked by bodyweight and randomly allocated to one of four treatment groups, in a 2 × 2 factorial arrangement: 1) Saline, isolated, standing, and unrestrained (S-IS, 0.015mL/kg BW 0.9% isotonic saline, n = 7); 2) Saline, isolated, and restrained (S-RIS; 0.015 ml/kg BW 0.9% isotonic saline; n = 7); 3) Oxytocin, IS (OXT-IS, 0.3 IU/kg BW oxytocin; n = 7); and 4) Oxytocin and isolated and restrained (OXT-RIS, 0.3 IU/kg BW oxytocin; n = 7). Oxytocin and saline were administered intra-nasally. Appropriate stressors were applied 30 minutes following intra-nasal treatment. Blood samples were collected directly following imposing the stressor, and every 10 minutes thereafter, for 2 h. Cortisol concentrations increased over time in animals exposed to restraint and isolation stress (P < 0.01) and decreased over time in animals exposed to isolation stress (P < 0.01). In the present study, oxytocin did not affect measured indicators of HPA axis activation. Greater plasma oxytocin concentrations were observed in restrained animals administered saline, compared with their standing counterparts administered oxytocin (P < 0.01), indicating some endogenous release of oxytocin in response to restraint stress. Overall, restraint stress increased cortisol and oxytocin in Bos taurus heifers compared with heifers subjected only to isolation. Finding a more intermediate stress model may allow for more precise detection of effects of oxytocin on the stress response.

Characteristics of Dissolved Organic Nitrogen in the Sediments of Six Water Sources in Taihu Lake, China

KCl-extractable sediment dissolved organic nitrogen (KS-DON) extracted from sediments near drinking water intakes of six drinking water sources in Taihu Lake in China was partitioned into hydrophobic and hydrophilic fractions and high/low molecular weight fractions. The results showed that the total dissolved nitrogen (TDN) contents of the extracts ranged from 67.78 to 128.27 mg/kg. KS-DON was the main TDN species, accounting for more than 50%, with NH4+-N and NO3−-N averaging 30% and 20%, respectively. The molecular weight fractions of <1 kDa accounted for almost half of KS-DON. Hydrophilic compounds accounted for more than 75% of KS-DON. Three fluorescence peaks were identified: soluble microbial byproducts (A); protein-like substances (B); and humic acid-like substances (C). It is concluded that the KS-DON in Taihu Lake sources has higher bioavailability and higher risk of endogenous release. Ecological dredging and establishment of constructed wetlands are possible measures to reduce the release of endogenous nitrogen.