Phenylalanine hydroxylase contributes to serotonin synthesis in mice

This is the final version. Available from the Federation of American Society of Experimental Biology via the DOI in this record.Serotonin is an important signaling molecule in the periphery and in the brain. The hydroxylation of tryptophan is the first and rate-limiting step of its synthesis. In most vertebrates, two enzymes have been described to catalyze this step, tryptophan hydroxylase (TPH) 1 and 2, with expression localized to peripheral and neuronal cells, respectively. However, animals lacking both TPH isoforms still exhibit about 10% of normal serotonin levels in the blood demanding an additional source of the monoamine. In this study, we provide evidence by the gain and loss of function approaches in in vitro and in vivo systems, including stable-isotope tracing in mice, that phenylalanine hydroxylase (PAH) is a third TPH in mammals. PAH contributes to serotonin levels in the blood, and may be important as a local source of serotonin in organs in which no other TPHs are expressed, such as liver and kidney.Saint Petersburg State University (SPbU)Bundesministerium für Bildung und Forschung (BMBF)Deutsches Zentrum für Herz-Kreislaufforschung (DZHK)Volkswagen Foundation (VolkswagenStiftung

Brainstem hypoxia contributes to the development of hypertension in the spontaneously hypertensive rat.

Systemic arterial hypertension has been previously suggested to develop as a compensatory condition when central nervous perfusion/oxygenation is compromised. Principal sympathoexcitatory C1 neurons of the rostral ventrolateral medulla oblongata (whose activation increases sympathetic drive and the arterial blood pressure) are highly sensitive to hypoxia, but the mechanisms of this O2 sensitivity remain unknown. Here, we investigated potential mechanisms linking brainstem hypoxia and high systemic arterial blood pressure in the spontaneously hypertensive rat. Brainstem parenchymal PO2 in the spontaneously hypertensive rat was found to be ≈15 mm Hg lower than in the normotensive Wistar rat at the same level of arterial oxygenation and systemic arterial blood pressure. Hypoxia-induced activation of rostral ventrolateral medulla oblongata neurons was suppressed in the presence of either an ATP receptor antagonist MRS2179 or a glycogenolysis inhibitor 1,4-dideoxy-1,4-imino-d-arabinitol, suggesting that sensitivity of these neurons to low PO2 is mediated by actions of extracellular ATP and lactate. Brainstem hypoxia triggers release of lactate and ATP which produce excitation of C1 neurons in vitro and increases sympathetic nerve activity and arterial blood pressure in vivo. Facilitated breakdown of extracellular ATP in the rostral ventrolateral medulla oblongata by virally-driven overexpression of a potent ectonucleotidase transmembrane prostatic acid phosphatase results in a significant reduction in the arterial blood pressure in the spontaneously hypertensive rats (but not in normotensive animals). These results suggest that in the spontaneously hypertensive rat, lower PO2 of brainstem parenchyma may be associated with higher levels of ambient ATP and l-lactate within the presympathetic circuits, leading to increased central sympathetic drive and concomitant sustained increases in systemic arterial blood pressure

CNS distribution, signalling properties and central effects of G-protein coupled receptor 4

Information on the distribution and biology of the G-protein coupled receptor 4 (GPR4) in the brain is limited. It is currently thought that GPR4 couples to Gs proteins and may mediate central respiratory sensitivity to CO2. Using a knock-in mouse model, abundant GPR4 expression was detected in the cerebrovascular endothelium and neurones of dorsal raphe, retro-trapezoidal nucleus locus coeruleus and lateral septum. A similar distribution was confirmed using RNAscope in situ hybridisation. In HEK293 cells, overexpressing GPR4, it was highly constitutively active at neutral pH with little further increase in cAMP towards acidic pH. The GPR4 antagonist NE 52-QQ57 effectively blocked GPR4-mediated cAMP accumulation (IC50 26.8 nM in HEK293 cells). In HUVEC which natively express GPR4, physiological acidification (pH 7.4-7.0) resulted in a cAMP increase by ∼55% which was completely prevented by 1 μM NE 52-QQ57. The main extracellular organic acid, L-lactic acid (LL; 1-10 mM), suppressed pH dependent activation of GPR4 in HEK293 and HUVEC cells, suggesting allosteric negative modulation. In unanaesthetised mice and rats, NE 52-QQ57 (20 mg kg-1) reduced ventilatory response to 5 and 10% CO2. In anaesthetised rats, systemic administration of NE 52-QQ57 (up to 20 mg kg-1) had no effect on hemodynamics, cerebral blood flow and blood oxygen level dependent responses. Central administration of NE 52-QQ57 (1 mM) in vagotomised anaesthetised rats did not affect CO2-induced respiratory responses. Our results indicate that GPR4 is expressed by multiple neuronal populations and endothelium and that its pH sensitivity is affected by level of expression and LL. NE 52-QQ57 blunts hypercapnic response to CO2 but this effect is absent under anaesthesia, possibly due to the inhibitory effect of LL on GPR4

Peripheral administration of lactate produces antidepressant-like effects.

In addition to its role as metabolic substrate that can sustain neuronal function and viability, emerging evidence supports a role for l-lactate as an intercellular signaling molecule involved in synaptic plasticity. Clinical and basic research studies have shown that major depression and chronic stress are associated with alterations in structural and functional plasticity. These findings led us to investigate the role of l-lactate as a potential novel antidepressant. Here we show that peripheral administration of l-lactate produces antidepressant-like effects in different animal models of depression that respond to acute and chronic antidepressant treatment. The antidepressant-like effects of l-lactate are associated with increases in hippocampal lactate levels and with changes in the expression of target genes involved in serotonin receptor trafficking, astrocyte functions, neurogenesis, nitric oxide synthesis and cAMP signaling. Further elucidation of the mechanisms underlying the antidepressant effects of l-lactate may help to identify novel therapeutic targets for the treatment of depression

Prevalence and intensity of dental caries and fluorosis in children of poltava city and its residential neighborhoods

Зростання захворюваності карієсом зубів у дітей є проблемою загального значення. За даними ВООЗ карієсом страждає більше ніж половина дітей шкільного віку всього світу (60-90%). Згідно даних літератури в останні роки спостерігається ріст захворюваності зубів і у дитячого населення нашої країни [1,2,3]. Причиною цього є як і погіршення соматичного здоров’я дітей внаслідок зниження імунітету, так і зниження соціально-економічного стану населення країни, відсутність адекватної спеціалізованої профілактики на державному рівні та невчасне лікування стоматологічної патології, руйнування системи планової санації.ми було оглянуто 270 учнів 1-4 класів Комунального закладу «Полтавська гімназія № 6» з поглибленим вивченням окремих предметів, де навчаються діти, що проживають в місті Полтава. Гімназія № 6, яка знаходиться у осередку історичної забудови, є одним із найстаріших загальноосвітніх закладів міста та згур- товує 1046 учнів.Згідно отриманих нами даних обстеження дітей гімназії № 6, яка знаходиться в центрі м. Полтава, гімназії с. Розсошенці, розташованої на межі м. Полтави та найбільш віддалених шкіл с. Щербані та с. Великий Тростянець, ми відзначили, що поширеність карієсу тимчасових зубів найвища в с. Розсошенці (66,54%), в гімназії міста Полтава та школах сіл Щер- бані та Великий Тростянець майже не відрізнялася і склала 52,59 % та 53,59 % відповідно (табл. 2, рис. 1). Інтенсивність карієсу тимчасових зубів згідно даних індексу кп чітко підтверджує, що потреба в стоматологічній санації для тимчасових зубів найвища в с. Розсошенці та становить 2,14±0,14 зуби, в м. Полтава 1,76±0,12 зубів, найнижчою в селах Щербані та Великий Тростянець 1,52±0,15. Нами встановлено, що поширеність карієсу за індексом кп+КПВ була найменшою у дітей гімназії № 6 м. Полтава та становила 61,85%. У школах сіл Розсошенці, Щербані та Великий Тростянець вона була на однаковому рівні – 72,05% та 71,89% відповідно.Рост заболеваемости кариесом зубов у детей является проблемой общего характера. Целью нашей работы было провести сравнительный анализ показателей кариеса и флюороза у детей младшей школы г. Полтава и пригорода, оценить необходимость санации полости рта. Осмотрено 695 детей 6-11 лет 3 учебных заведений г. Полтава и его пригорода. Определили распространенность и интенсивность кариеса временных и постоянных зубов и потребность в стоматологической санации, пораженность флюорозом. С помощью общепринятых методов официальной статистики проводили статистическую обработку результатов исследований. С помощью анализа полученных результатов обследования выявили наиболее тяжелую стоматологическую ситуацию пораженности флюорозом и кариесом постоянных зубов у детей, которые учились в школах пригорода г. Полтавы. Обнаруженная нами ситуация требует усиления как первичной так и вторичной профилактики именно в школах ближайшего пригорода.The growth in the incidence of dental caries in children is considered as a global challenge. The available reports have also demonstrated the rise of dental diseases in the paediatric population of Ukraine in the recent period. The findings of the survey on dental caries prevalence and intensity in children of Poltava city for 2014-2019 evidenced sizeable deterioration of the situation. Today on the territory of Ukraine there are 4 main geochemical provinces with different content of fluorine and its compounds. Poltava region is one of the most fluoride-contaminated, the fourth province, where the fluorine content in drinking water is more than 1.5-3.0 mg/l. The alkaline nature of the water of the Buchak-Kaniv aquifer with a large amount of sodium bicarbonate and chloride depositions promotes the ground water enrichment from water-bearing rocks and minerals into the water. The intensity and character of endemic of dental caries depends on the content of reactive forms of fluoride in drinking water. The aim of this study was to conduct a comparative analysis of caries and fluorosis indices in primary school children of Poltava city and the residential neighbourhoods and to assess their need in the dental sanitation. Within the regular dental checkups and satination we examined the 695 children aged 6-11 from three secondary schools of Poltava and its residential neighbourhoods (270 primary school pupils of Poltava Gymnasium № 6, 272 children from Rozsoshentsy Gymnasium and 153 children from Shcherbani Lyceum and its daughter setting in Trostyanets). To carry out the comparative analysis we determined the prevalence and intensity of dental caries in temporary and permanent teeth as well as we assessed the need in dental sanitation

Growth retardation and altered autonomic control in mice lacking brain serotonin

Serotonin synthesis in mammals is initiated by 2 distinct tryptophan hydroxylases (TPH), TPH1 and TPH2. By genetically ablating TPH2, we created mice (Tph2−/−) that lack serotonin in the central nervous system. Surprisingly, these mice can be born and survive until adulthood. However, depletion of serotonin signaling in the brain leads to growth retardation and 50% lethality in the first 4 weeks of postnatal life. Telemetric monitoring revealed more extended daytime sleep, suppressed respiration, altered body temperature control, and decreased blood pressure (BP) and heart rate (HR) during nighttime in Tph2−/− mice. Moreover, Tph2−/− females, despite being fertile and producing milk, exhibit impaired maternal care leading to poor survival of their pups. These data confirm that the majority of central serotonin is generated by TPH2. TPH2-derived serotonin is involved in the regulation of behavior and autonomic pathways but is not essential for adult life