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The optimal exercise intensity to improve endothelial function remains unclear, as well as whether the addition of hypoxia could potentiate this function. Therefore, the aim of this study was to compare the effects of different exercise intensities in normoxia and hypoxia on vascular reactivity and nitric oxide (NO) bioavailability in mice. C57BL/6 mice underwent treadmill running three times per week, for 4 weeks at either low, maximal or supramaximal intensity in normoxia or hypoxia (inspire oxygen fraction = 0.13). Vascular reactivity and expression of genes and proteins involved in NO production/bioavailability were assessed in aorta using isolated vessel tension experiments, RT-qPCR and western blot, respectively. Circulating NO metabolites and pro-/antioxidant markers were measured. Hypoxic exercise improved both acetylcholine-induced vasorelaxation and phenylephrine-induced vasoconstriction compared to normoxic exercise, independently of intensity. In hypoxia, a higher acetylcholine-induced vasorelaxation was observed with high intensities (supramaximal and maximal) compared to low intensity. Exercise protocols modulated endothelial nitric oxide synthase (eNOS) and α1-adrenergic receptor (α 1 -AR) mRNA level, but not superoxide dismutase 3 (SOD3) and p47phox. No significant differences were observed for protein expression of α 1 -AR, total eNOS, phosphorylated eNOS, SOD isoforms and p47phox. However, plasma SOD and catalase activities were significantly increased in hypoxic supramaximal compared to hypoxic low intensity, while concentration of nitrotyrosine significantly decreased. The latter was also observed in hypoxic maximal and supramaximal compared to the same intensities in normoxia. Hypoxic high-intensity exercise increases NO bioavailability and improves vascular function, opening promising clinical perspectives for cardiovascular disease prevention.

Aim The tools that have been used to assess the function of the vagus nerve lack specificity. This could explain discrepancies about the role of vagal gut‐brain signalling in long‐term control of energy balance. Here we use a validated approach to selectively ablate sensory vagal neurones that innervate the gut to determine the role of vagal gut‐brain signalling in the control of food intake, energy expenditure and glucose homoeostasis in response to different diets. Methods Rat nodose ganglia were injected bilaterally with either the neurotoxin saporin conjugated to the gastrointestinal hormone cholecystokinin (CCK), or unconjugated saporin as a control. Food intake, body weight, glucose tolerance and energy expenditure were measured in both groups in response to chow or high‐fat high‐sugar (HFHS) diet. Willingness to work for fat or sugar was assessed by progressive ratio for orally administered solutions, while post‐ingestive feedback was tested by measuring food intake after an isocaloric lipid or sucrose pre‐load. Results Vagal deafferentation of the gut increases meal number in lean chow‐fed rats. Switching to a HFHS diet exacerbates overeating and body weight gain. The breakpoint for sugar or fat solution did not differ between groups, suggesting that increased palatability may not drive HFHS‐induced hyperphagia. Instead, decreased satiation in response to intra‐gastric infusion of fat, but not sugar, promotes hyperphagia in CCK‐Saporin‐treated rats fed with HFHS diet. Conclusions We conclude that intact sensory vagal neurones prevent hyperphagia and exacerbation of weight gain in response to a HFHS diet by promoting lipid‐mediated satiation.

Aim NG2 cells in the brain are comprised of pericytes and NG2 glia and play an important role in the execution of cerebral hypoxia responses, including the induction of erythropoietin (EPO) in pericytes. Oxygen‐dependent angiogenic responses are regulated by hypoxia‐inducible factor (HIF), the activity of which is controlled by prolyl 4‐hydroxylase domain (PHD) dioxygenases and the von Hippel‐Lindau (VHL) tumour suppressor. However, the role of NG2 cells in HIF‐regulated cerebral vascular homeostasis is incompletely understood. Methods To examine the HIF/PHD/VHL axis in neurovascular homeostasis, we used a Cre‐loxP‐based genetic approach in mice and targeted Vhl, Epo, Phd1, Phd2, Phd3 and Hif2a in NG2 cells. Cerebral vasculature was assessed by immunofluorescence, RNA in situ hybridization, gene and protein expression analysis, gel zymography and in situ zymography. Results Vhl inactivation led to a significant increase in angiogenic gene and Epo expression. This was associated with EPO‐independent expansion of capillary networks in cortex, striatum and hypothalamus, as well as pericyte proliferation. A comparable phenotype resulted from the combined inactivation of Phd2 and Phd3, but not from Phd2 inactivation alone. Concomitant PHD1 function loss led to further expansion of the neurovasculature. Genetic inactivation of Hif2a in Phd1/Phd2/Phd3 triple mutant mice resulted in normal cerebral vasculature. Conclusion Our studies establish (a) that HIF2 activation in NG2 cells promotes neurovascular expansion and remodelling independently of EPO, (b) that HIF2 activity in NG2 cells is co‐controlled by PHD2 and PHD3 and (c) that PHD1 modulates HIF2 transcriptional responses when PHD2 and PHD3 are inactive.

Aim Skeletal muscles are distributed throughout the body, presenting a variety of sizes, shapes and functions. Here, we examined whether muscle regeneration and atrophy occurred homogeneously throughout the body in mouse models. Methods Acute muscle regeneration was induced by a single intramuscular injection of cardiotoxin in adult mice. Chronic muscle regeneration was assessed in mdx mice. Muscle atrophy in different muscles was evaluated by cancer cachexia, ageing and castration mouse models. Results We found that, in the cardiotoxin‐injected acute muscle injury model, head muscles slowly regenerated, while limb muscles exhibited a rapid regeneration and even overgrowth. This overgrowth was also observed in limb muscles alone (but not in head muscles) in mdx mice as chronic injury models. We described the body region–specific decline in the muscle mass in muscle atrophy models: cancer cachexia‐induced, aged and castrated mice. The positional identities, including gene expression profiles and hormone sensitivity, were robustly preserved in the ectopically engrafted satellite cell‐derived muscles in the castrated model. Conclusion Our results indicate that positional identities in muscles should be considered for the development of efficient regenerative therapies for muscle weakness, such as muscular dystrophy and age‐related sarcopenia.

Aim High‐altitude pulmonary oedema (HAPE) is a non‐cardiogenic pulmonary oedema that can occur during rapid ascent to a high‐altitude environment. Classically, HAPE has been described as a condition resulting from a combination of pulmonary vasoconstriction and hypertension. Inflammation has been described as important in HAPE, although as a side effect of pulmonary oedema rather than as a causative factor. In this study, we aim to understand the role of hypoxic response in myeloid cells and its involvement in pathogenesis of HAPE. Methods We have generated a conditional deletion in mice of the von Hippel‐Lindau factor (VHL) in myeloid cells to determine the effect of a deregulated hypoxic response in pulmonary oedema. Results The deletion of VHL in pulmonary myeloid cells gave rise to pulmonary oedema, increased pulmonary vascular permeability and reduced performance during exertion. These changes were accompanied by reduced stroke volume in the left ventricle. Conclusion In this model, we show that a deregulated myeloid cell hypoxic response can trigger some of the most important symptoms of HAPE, and thus mice with a deletion of VHL in the myeloid lineage can function as a model of HAPE.

Aim To identify microRNAs (miRs) involved in the regulation of skeletal muscle mass. For that purpose, we have initially utilized an in silico analysis, resulting in the identification of miR‐29c as a positive regulator of muscle mass. Methods miR‐29c was electrotransferred to the tibialis anterior to address its morphometric and functional properties and to determine the level of satellite cell proliferation and differentiation. qPCR was used to investigate the effect of miR‐29c overexpression on trophicity‐related genes. C2C12 cells were used to determine the impact of miR‐29c on myogenesis and a luciferase reporter assay was used to evaluate the ability of miR‐29c to bind to the MuRF1 3′UTR. Results The overexpression of miR‐29c in the tibialis anterior increased muscle mass by 40%, with a corresponding increase in fibre cross‐sectional area and force and a 30% increase in length. In addition, satellite cell proliferation and differentiation were increased. In C2C12 cells, miR‐29c oligonucleotides caused increased levels of differentiation, as evidenced by an increase in eMHC immunostaining and the myotube fusion index. Accordingly, the mRNA levels of myogenic markers were also increased. Mechanistically, the overexpression of miR‐29c inhibited the expression of the muscle atrophic factors MuRF1, Atrogin‐1 and HDAC4. For the key atrogene MuRF1, we found that miR‐29c can bind to its 3′UTR to mediate repression. Conclusions The results herein suggest that miR‐29c can improve skeletal muscle size and function by stimulating satellite cell proliferation and repressing atrophy‐related genes. Taken together, our results indicate that miR‐29c might be useful as a future therapeutic device in diseases involving decreased skeletal muscle mass.

Aim This study aimed to explore the molecular mechanisms for the parietal cell loss and fundic hyperplasia observed in gastric mucosa of mice lacking the carbonic anhydrase 9 (CAIX). Methods We assessed the ability of CAIX‐knockout and WT gastric surface epithelial cells to withstand a luminal acid load by measuring the pH i of exteriorized gastric mucosa in vivo using two‐photon confocal laser scanning microscopy. Cytokines and claudin‐18A2 expression was analysed by RT‐PCR. Results CAIX‐knockout gastric surface epithelial cells showed significantly faster pH i decline after luminal acid load compared to WT. Increased gastric mucosal IL‐1β and iNOS, but decreased claudin‐18A2 expression (which confer acid resistance) was observed shortly after weaning, prior to the loss of parietal and chief cells. At birth, neither inflammatory cytokines nor claudin‐18 expression were altered between CAIX and WT gastric mucosa. The gradual loss of acid secretory capacity was paralleled by an increase in serum gastrin, IL‐11 and foveolar hyperplasia. Mild chronic proton pump inhibition from the time of weaning did not prevent the claudin‐18 decrease nor the increase in inflammatory markers at 1 month of age, except for IL‐1β. However, the treatment reduced the parietal cell loss in CAIX‐KO mice in the subsequent months. Conclusions We propose that CAIX converts protons that either backflux or are extruded from the cells rapidly to CO 2 and H2O, contributing to tight junction protection and gastric epithelial pH i regulation. Lack of CAIX results in persistent acid backflux via claudin‐18 downregulation, causing loss of parietal cells, hypergastrinaemia and foveolar hyperplasia.

In recent years, most of the manuscripts published as a regular paper in ACTA Physiologica are based on animal experiments. As the mouse is the workhorse of physiologic research, most of the papers would not exist without animal experiments. All authors willing to submit manuscripts to ACTA Physiologica are expected to follow the 3R principle to reduce, refine, and replace animal experiments. 1 Most of the major research funding bodies in Europe require that the projects funded by them take full account of the 3Rs principle. It is a major issue for much of the public who are concerned about animal welfare and the need to avoid causing unnecessary or unjustified suffering. Applying the 3R strategy in physiologic research is not without difficulties but it is possible.

The present paper deals with a fundamental issue in neuroscience: the inter-neuronal communication. The paper gives a brief account of our previous and more recent theoretical contributions to the subject and also reports new recent data that support some aspects of our proposal on two major modes of communication in the central nervous system: the wiring and the volume transmission. There exist two competing theories on inter-neuronal communication: the neuron doctrine and the theory of the diffuse nerve network, supported by Cajal and Golgi, respectively (see their respective Nobel Lectures). The present paper gives a brief account of a view on inter-neuronal communication in the brain, the volume and wiring transmission concept that to a great extent reconcile these two theories. Thus, the theory of volume and wiring transmission are summarized and its recent developments that allow to extend these two modes of communication from the cellular network to the molecular network level is also briefly illustrated. The explanatory value of this broadened view is further enhanced by our recent proposal on the existence of a Global Molecular Network enmeshing the entire central nervous system. It may be interesting to note that also the Global Molecular Network theory is reminiscent of the old reticular theory of Apathy. Finally, the so-called 'tide hypothesis' for diffusion of signals in the brain is briefly discussed and its possible extension to the molecular level is for the first time introduced. Early indirect evidence supporting volume transmission in the brain was the discovery of transmitter-receptor mismatches. Thus, as an experimental part of the present paper a new approach to evaluate transmitter-receptor mismatches is given and evidence for inter-relationships between temperature micro-gradients and mismatches is provided.

Voltage-gated Ca 2+ channels (Cav) are highly expressed in the adrenal chromaffin cells of mammalian species. Besides shaping action potential waveforms, they are directly involved in the excitation-secretion coupling underlying catecholamine release and, possibly, control other Ca 2+ -dependent events that originate near the membrane. These functions are shared by a number of Cav channel types (L, N, P/Q, R and T) which have different structure-function characteristics and whose degree of expression changes remarkably among mammalian species. Understanding precisely the functioning of each voltage-gated Ca 2+ channels is a crucial task that helps clarifying the Ca 2+ -dependent mechanisms controlling exocytosis during physiological and pathological conditions.In this paper, we focus on classical and new roles that L- and T-type channels play in the control of chromaffin cell excitability and neurotransmitter release. Interestingly, L-type channels are shown to be implicated in the spontaneous autorhythmicity of chromaffin cells, while T-type channels, which are absent in adult chromaffin cells, are coupled with secretion and can be recruited following long-term ;8-adrenergic stimulation or chronic hypoxia. This suggests that like other cells, adrenal chromaffin cells undergo effective remodelling of membrane ion channels and cell functioning during prolonged stress conditions.