| 1. |
- Hagbom, Marie, et al.
(author)
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The 5-HT3 Receptor Affects Rotavirus-Induced Motility
- 2021
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In: Journal of Virology. - : AMER SOC MICROBIOLOGY. - 0022-538X .- 1098-5514. ; 95:15
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Journal article (peer-reviewed)abstract
- Rotavirus infection is highly prevalent in children, and the most severe effects are diarrhea and vomiting. It is well accepted that the enteric nervous system (ENS) is acti-vated and plays an important role, but knowledge of how rotavirus activates nerves within ENS and to the vomiting center is lacking. Serotonin is released during rotavirus infection, and antagonists to the serotonin receptor subtype 3 (5-HT3 receptor) can attenuate rotavi-rus-induced diarrhea. In this study, we used a 5-HT3 receptor knockout (KO) mouse model to investigate the role of this receptor in rotavirus-induced diarrhea, motility, electrolyte secretion, inflammatory response, and vomiting reflex. The number of diarrhea days (P= 0.03) and the number of mice with diarrhea were lower in infected 5-HT3 receptor KO than wild-type pups. In vivo investigation of fluorescein isothiocyanate (FITC)-dextran transit time showed that intestinal motility was lower in the infected 5-HT3 receptor KO compared to wild-type mice (P= 0.0023). Ex vivo Ussing chamber measurements of poten-tial difference across the intestinal epithelia showed no significant difference in electrolyte secretion between the two groups. Immediate early gene cFos expression level showed no difference in activation of the vomiting center in the brain. Cytokine analysis of the intestine indicated a low effect of inflammatory response in rotavirus-infected mice lack -ing the 5-HT3 receptor. Our findings indicate that the 5-HT3 receptor is involved in rotavi-rus-induced diarrhea via its effect on intestinal motility and that the vagus nerve signaling to the vomiting center occurs also in the absence of the 5-HT3 receptor. IMPORTANCE The mechanisms underlying rotavirus-induced diarrhea and vomiting are not yet fully understood. To better understand rotavirus pathophysiology, characterization of nerve signaling within the ENS and through vagal efferent nerves to the brain, which have been shown to be of great importance to the disease, is necessary. Serotonin (5-HT), a mediator of both diarrhea and vomiting, has been shown to be released from entero-chromaffin cells in response to rotavirus infection and the rotavirus enterotoxin NSP4. Here, we investigated the role of the serotonin receptor 5-HT3, which is known to be involved in the nerve signals that regulate gut motility, intestinal secretion, and signal transduction through the vagus nerve to the brain. We show that the 5-HT3 receptor is involved in rotavirus-induced diarrhea by promoting intestinal motility. The findings shed light on new treatment possibilities for rotavirus diarrhea.
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| 2. |
- Hellysaz, Arash
(author)
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Anatomical studies of the dopamine system in the hypothalamus and the pituitary gland
- 2018
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Doctoral thesis (other academic/artistic)abstract
- The hypothalamus is a small, evolutionarily conserved brain region, necessary for our survival as individuals and as a species. It collects various sensory inputs, process them to maintain homeostasis and to overcome stressors, and generates outputs that affect the autonomic nervous system, the endocrine system and somatomotor behaviors. Energy metabolism, fluid balance, thermoregulation, sleep, aggression and reproduction are examples of functions under direct and indirect hypothalamic control. The neurochemical basis for these regulations involve different neurotransmitters and neuromodulators. The catecholamine dopamine is highly associated with various hypothalamic functions and behaviors, and has early on been shown to be present in intrinsic hypothalamic populations as well as incoming axon terminals. It acts on two types of receptors, excitatory D1-type and inhibitory D2-type, of which both have been reported to be expressed in the hypothalamus. To increase our understanding of these circuitries, this thesis aims to investigate the dopamine system in the hypothalamus, and the structures closely related to its inputs and outputs, namely the circumventricular organs and the pituitary. Immunohistochemical methods were used to generate a comprehensive distribution map of dopamine’s two main receptors, D1 and D2, and the neurochemical identity of these dopamine-receptor expressing cells were characterized. While the D2 receptor was widely expressed, D1 expression was found to be sparse. The suprachiasmatic nucleus, however, showed the contrary expression pattern. The D2 receptor could be localized to parvocellular neurons as well as endocrine cells of the pituitary. Little evidence for dopamine receptor expression on the magnocellular neurons could, however, be observed. Evidence for D1 receptor expression was also found in the subcommissural organ and a sub-cluster of ependymal cells in the third ventricle. Tuberoinfundibular dopamine (TIDA) neurons, which release dopamine in the portal vessels and thereby inhibit lactotrophs and prolactin release, were investigated in greater detail with regards to modulatory input, and morphological features. Anatomical substrate for innervation by serotonin and hypocretin/orexin on TIDA cell body and dendrites was identified together with electrophysiological evidence for excitation and suppression by hypocretin/orexin and serotonin or selective serotonin reuptake inhibitors, respectively. Morphological studies of male mice and rat TIDA neurons were done on tissue section and marker filled neurons by means of immunohistochemistry. TIDA neurons were found to preferentially extend dendrites towards the third ventricle, possibly even into the ventricle. Axon terminals were found in the median eminence, but collateral branches oriented laterally could also be detected. An intermingling subcellular distribution of inhibitory and excitatory synapses, on somatic and dendritic level, was also identified. No significant differences could be observed in most morphological properties of mouse and rat TIDA neurons. However, rats exhibited a higher total number of TIDA neurons and a lower spine density than mice. Finally, the expression of three different calcium binding proteins, i.e. calbindin-D28k, calretinin and parvalbumin, were investigated within the arcuate nucleus. While both calbindin-D28k and calretinin could be detected in the arcuate nucleus, little evidence for parvalbumin expression was observed. None of the proteins were expressed in TIDA neurons or other investigated populations, except for proopiomelanocortin neurons that expressed both calbindin-D28k and calretinin. These neurons showed a rostrocaudal segregation of the two calcium binding proteins that resulted in two separate subpopulations. Overall, the studies presented in this thesis reveal a previously unappreciated abundance of dopaminergic involvement in the hypothalamic circuitries which will increase our understanding of mammalian homeostatic and endocrine control.
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| 3. |
- Hellysaz, Arash, 1982-, et al.
(author)
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Microbiota do not restrict rotavirus infection of colon
- 2023
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In: Journal of Virology. - : American Society for Microbiology. - 0022-538X .- 1098-5514. ; 97:11
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Journal article (peer-reviewed)abstract
- Rotavirus is associated with extensive infection of the small intestine, whereas colon is considered to be uninfected. Considering that almost all bacteria in the gut colonize the colon, we hypothesized that the microbiota may act as a physical barrier preventing rotavirus infection in the colon in vivo. To address this hypothesis, we used human and mice colonoids, and biopsies of different intestinal segments of untreated and antibiotic-treated adult and infant mice. Rotavirus quantification was performed by qPCR and volumetric 3D imaging of intestinal segments. By 3D imaging, we observed infection in all the small intestinal segments, most extensively in the ileum, with most limited number of infected cells in colon. Broad-spectrum antibiotic treatment yielded no significant change in infection in either ileum or colon of adults and mice pups, although there is a substantial decrease in microbial load. We also show that rotavirus can successfully infect and replicate in colonoids from both mice and humans. Collectively, our data, including novel 3D imaging of the gut, mouse, and human colonoids, conclude that microbiota does not affect rotavirus infection in colon.IMPORTANCEAlterations of the gut microbiome can have significant effects on gastrointestinal homeostasis leading to various diseases and symptoms. Increased understanding of rotavirus infection in relation to the microbiota can provide better understanding on how microbiota can be used for clinical prevention as well as treatment strategies. Our volumetric 3D imaging data show that antibiotic treatment and its consequent reduction of the microbial load does not alter the extent of rotavirus infection of enterocytes in the small intestine and that restriction factors other than bacteria limit the infection of colonocytes.
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| 4. |
- Hellysaz, Arash, et al.
(author)
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Rotavirus Downregulates Tyrosine Hydroxylase in the Noradrenergic Sympathetic Nervous System in Ileum, Early in Infection and Simultaneously with Increased Intestinal Transit and Altered Brain Activities
- 2022
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In: mBio. - : American Society for Microbiology. - 2161-2129 .- 2150-7511. ; 13:5
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Journal article (peer-reviewed)abstract
- Previous studies have investigated the mechanisms of rotavirus diarrhea mainly by focusing on intrinsic intestinal signaling. Although these observations are compelling and have provided important mechanistic information on rotavirus diarrhea, no information is available on how the gut communicates with the central nervous system (CNS) during rotavirus infection or on how this communication initiates sickness symptoms. While rotavirus diarrhea has been considered to occur only due to intrinsic intestinal effects within the enteric nervous system, we provide evidence for central nervous system control underlying the clinical symptomology. Our data visualize infection by large-scale three-dimensional (3D) volumetric tissue imaging of a mouse model and demonstrate that rotavirus infection disrupts the homeostasis of the autonomous system by downregulating tyrosine hydroxylase in the noradrenergic sympathetic nervous system in ileum, concomitant with increased intestinal transit. Interestingly, the nervous response was found to occur before the onset of clinical symptoms. In adult infected animals, we found increased pS6 immunoreactivity in the area postrema of the brain stem and decreased phosphorylated STAT5-immunoreactive neurons in the bed nucleus of the stria terminalis, which has been associated with autonomic control, including stress response. Our observations contribute to knowledge of how rotavirus infection induces gut-nerve-brain interaction early in the disease. IMPORTANCE Previous studies have investigated the mechanisms of rotavirus diarrhea mainly by focusing on intrinsic intestinal signaling. Although these observations are compelling and have provided important mechanistic information on rotavirus diarrhea, no information is available on how the gut communicates with the central nervous system (CNS) during rotavirus infection or on how this communication initiates sickness symptoms. We show that rotavirus infection presymptomatically disrupts the autonomic balance by downregulating the noradrenergic sympathetic nervous system in ileum, concomitant with increased intestinal transit and altered CNS activity, particularly in regions associated with autonomic control and stress response. Altogether, these observations reveal that the rotavirus-infected gut communicates with the CNS before the onset of diarrhea, a surprising observation that brings a new understanding of how rotavirus gives rise to sickness symptoms.
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| 5. |
- Hellysaz, Arash, et al.
(author)
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Rotavirus Sickness Symptoms: Manifestations of Defensive Responses from the Brain
- 2024
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In: Viruses. - : MDPI. - 1999-4915. ; 16:7
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Research review (peer-reviewed)abstract
- Rotavirus is infamous for being extremely contagious and for causing diarrhea and vomiting in infants. However, the symptomology is far more complex than what could be expected from a pathogen restricted to the boundaries of the small intestines. Other rotavirus sickness symptoms like fever, fatigue, sleepiness, stress, and loss of appetite have been clinically established for decades but remain poorly studied. A growing body of evidence in recent years has strengthened the idea that the evolutionarily preserved defensive responses that cause rotavirus sickness symptoms are more than just passive consequences of illness and rather likely to be coordinated events from the central nervous system (CNS), with the aim of maximizing the survival of the individual as well as the collective group. In this review, we discuss both established and plausible mechanisms of different rotavirus sickness symptoms as a series of CNS responses coordinated from the brain. We also consider the protective and the harmful nature of these events and highlight the need for further and deeper studies on rotavirus etiology.
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| 6. |
- Hellysaz, Arash, et al.
(author)
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Understanding the Central Nervous System Symptoms of Rotavirus : A Qualitative Review
- 2021
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In: Viruses. - : MDPI. - 1999-4915. ; 13:4
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Research review (peer-reviewed)abstract
- This qualitative review on rotavirus infection and its complications in the central nervous system (CNS) aims to understand the gut-brain mechanisms that give rise to CNS driven symptoms such as vomiting, fever, feelings of sickness, convulsions, encephalitis, and encephalopathy. There is substantial evidence to indicate the involvement of the gut-brain axis in symptoms such as vomiting and diarrhea. The underlying mechanisms are, however, not rotavirus specific, they represent evolutionarily conserved survival mechanisms for protection against pathogen entry and invasion. The reviewed studies show that rotavirus can exert effects on the CNS trough nervous gut-brain communication, via the release of mediators, such as the rotavirus enterotoxin NSP4, which stimulates neighboring enterochromaffin cells in the intestine to release serotonin and activate both enteric neurons and vagal afferents to the brain. Another route to CNS effects is presented through systemic spread via lymphatic pathways, and there are indications that rotavirus RNA can, in some cases where the blood brain barrier is weakened, enter the brain and have direct CNS effects. CNS effects can also be induced indirectly as a consequence of systemic elevation of toxins, cytokines, and/or other messenger molecules. Nevertheless, there is still no definitive or consistent evidence for the underlying mechanisms of rotavirus-induced CNS complications and more in-depth studies are required in the future.
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| 7. |
- Hellysaz, Arash, et al.
(author)
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Viral Gastroenteritis: Sickness Symptoms and Behavioral Responses
- 2023
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In: mBio. - : AMER SOC MICROBIOLOGY. - 2161-2129 .- 2150-7511. ; 14:2
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Journal article (other academic/artistic)abstract
- Viral infections have a major impact on physiology and behavior. The clinical symptoms of human rotavirus and norovirus infection are primarily diarrhea, fever, and vomiting, but several other sickness symptoms, such as nausea, loss of appetite, and stress response are never or rarely discussed. These physiological and behavioral changes can be considered as having evolved to reduce the spread of the pathogen and increase the chances of survival of the individual as well as the collective. The mechanisms underlying several sickness symptoms have been shown to be orchestrated by the brain, specifically, the hypothalamus. In this perspective, we have described how the central nervous system contributes to the mechanisms underlying the sickness symptoms and behaviors of these infections. Based on published findings, we propose a mechanistic model depicting the role of the brain in fever, nausea, vomiting, cortisol-induced stress, and loss of appetite.
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| 8. |
- Romanov, Roman A., et al.
(author)
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Molecular interrogation of hypothalamic organization reveals distinct dopamine neuronal subtypes
- 2017
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In: Nature Neuroscience. - : Nature Publishing Group. - 1097-6256 .- 1546-1726. ; 20:2, s. 176-188
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Journal article (peer-reviewed)abstract
- The hypothalamus contains the highest diversity of neurons in the brain. Many of these neurons can co-release neurotransmitters and neuropeptides in a use-dependent manner. Investigators have hitherto relied on candidate protein-based tools to correlate behavioral, endocrine and gender traits with hypothalamic neuron identity. Here we map neuronal identities in the hypothalamus by single-cell RNA sequencing. We distinguished 62 neuronal subtypes producing glutamatergic, dopaminergic or GABAergic markers for synaptic neurotransmission and harboring the ability to engage in task-dependent neurotransmitter switching. We identified dopamine neurons that uniquely coexpress the Onecut3 and Nmur2 genes, and placed these in the periventricular nucleus with many synaptic afferents arising from neuromedin S+ neurons of the suprachiasmatic nucleus. These neuroendocrine dopamine cells may contribute to the dopaminergic inhibition of prolactin secretion diurnally, as their neuromedin S+ inputs originate from neurons expressing Per2 and Per3 and their tyrosine hydroxylase phosphorylation is regulated in a circadian fashion. Overall, our catalog of neuronal subclasses provides new understanding of. hypothalamic organization and function.
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| 9. |
- Thörn Pérez, Carolina, et al.
(author)
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Adaptive Resetting of Tuberoinfundibular Dopamine (TIDA) Network Activity during Lactation in Mice
- 2020
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In: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 40:16, s. 3203-3216
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Journal article (peer-reviewed)abstract
- Giving birth triggers a wide repertoire of physiological and behavioral changes in the mother to enable her to feed and care for her offspring. These changes require coordination and are often orchestrated from the CNS, through as of yet poorly understood mechanisms. A neuronal population with a central role in puerperal changes is the tuberoinfundibular dopamine (TWA) neurons that control release of the pituitary hormone, prolactin, which triggers key maternal adaptations, including lactation and maternal care. Here, we used Ca2+ imaging on mice from both sexes and whole-cell recordings on female mouse TWA neurons in vitro to examine whether they adapt their cellular and network activity according to reproductive state. In the high-prolactin state of lactation, TIDA neurons shift to faster membrane potential oscillations, a reconfiguration that reverses upon weaning. During the estrous cycle, however, which includes a brief, but pronounced, prolactin peak, oscillation frequency remains stable. An increase in the hyperpolarization-activated mixed cation current, I-h, possibly through unmasking as dopamine release drops during nursing, may partially explain the reconfiguration of TIDA rhythms. These findings identify a reversible plasticity in hypothalamic network activity that can serve to adapt the darn for motherhood.
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