Preoptic Anterior Hypothalamus Research Articles

Effects of Guizhi and Erxian Decoction on menopausal hot flashes: insights from the gut microbiome and metabolic profiles.

To examine the influence of GED on the gut microbiota and metabolites using a bilateral ovariectomized (OVX) rat model. We tried to elucidate the underlying mechanisms of GED in the treatment of menopausal hot flashes. 16S rRNA sequencing, metabonomics, molecular biological analysis, and fecal microbiota transplantation (FMT) were conducted to elucidate the mechanisms by which GED regulates the gut microbiota. GED significantly reduced OVX-induced hot flashes and improved disturbances in the gut microbiota metabolites. Moreover, FMT validated that the gut microbiota can trigger hot flashes, while GED can alleviate hot flash symptoms by modulating the composition of the gut microbiota. Specifically, GED upregulated the abundance of Blautia, thereby increasing l(+)-ornithine levels for the treatment of menopausal hot flashes. Additionally, GED affected endothelial nitric oxide synthase and heat shock protein 70 (HSP70) levels in the hypothalamic preoptic area by changing the gut microbiota composition. Our study illuminated the underlying mechanisms by which GED attenuated the hot flashes through modulation of the gut microbiota and explored the regulatory role of the gut microbiota on HSP70 expression in the preoptic anterior hypothalamus, thereby establishing a foundation for further exploration of the role of the gut-brain axis in hot flashes.

1531-P: Preoptic Anterior Hypothalamus Estrogen Signaling Controls Energy and Temperature Homeostasis

An ovarian hormone, estrogen, has been shown to act on the preoptic anterior hypothalamus (POA) to modulate temperature and energy homeostasis. However, the underlying neural mechanism is still largely less known. Interestingly, we found that POA neurons express high levels of estrogen receptor α (ERα) and β (ERβ), and a subpopulation of POA neurons co-express ERα and ERβ (ERα/βPOA). We showed that ERα agonist stimulates ERα/βPOA neurons, whereas ERβ agonist inhibits ERα/βPOA neurons. Estrogen17β-estradiol (E2) showed mixed actions in the ERα/βPOA neurons, presumably caused by the counterbalance between ERα and ERβ. This dynamic counterbalance may lead to distinct effects of E2 in regulating temperature and energy balance depending on temperature or nutritional status. Consistently, chemogenetic activation of ERαPOA decreased food intake, brown adipose tissue (BAT) thermogenesis, and body temperature, mimicking warm-induced adaptation. Conversely, inhibition of ERβPOA neurons increases food intake, BAT thermogenesis, and body temperature, mimicking cold-induced adaptation. In conclusion, these results support a model that ERα/βPOA neurons service as an integrating center for the estrogenic regulation of temperature and energy homeostasis. Disclosure P.Luo: None. P.Xu: None. X.Yang: None. B.Feng: None. H.Ye: None. N.Antony: None. L.Carrillo-sáenz: None. V.C.Torres irizarry: None. B.T.Layden: Consultant; Bayer Inc. Y.He: None. Funding National Institutes of Health (R01DK123098, P30DK020595 to P.X.), (P20GM135002, R01DK129548 to Y.H.), (T32AA026577 to V.C.T.I.); American Heart Association (915789 to V.C.T.I.), (20POST35120600 to Y.H.); U.S. Department of Defense (W81XWH-20-1-0075 to P.X

Hyperthermia

There is scientific support for the concept of a temperature set point that is, maintenance of an optimal temperature for the metabolic processes that life depends on Nervous activity in the preoptic-anterior hypothalamus of the brain triggers heat losing (sweating, etc.) or heat generating (shivering and muscle contraction, etc.) activities through stimulation of the autonomic nervous system. The pre-optic anterior hypothalamus has been shown to contain warm sensitive, cool sensitive, and temperature insensitive neurons, to determine the body's temperature setpoint. As the temperature that these neurons are exposed to rises above 37 °C (99 °F), the rate of electrical discharge of the warm-sensitive neurons increases progressively. There is scientific support for the concept of a temperature set point that is, maintenance of an optimal temperature for the metabolic processes that life depends on Nervous activity in the preoptic-anterior hypothalamus of the brain triggers heat losing (sweating, etc.) or heat generating (shivering and muscle contraction, etc.) activities through stimulation of the autonomic nervous system. The pre-optic anterior hypothalamus has been shown to contain warm sensitive, cool sensitive, and temperature insensitive neurons, to determine the body's temperature setpoint. As the temperature that these neurons are exposed to rises above 37 °C (99 °F), the rate of electrical discharge of the warm-sensitive neurons increases progressively.

1390-P: FOXO1 Promotes Sexually Dimorphic Effects on Energy Balance in the Preoptic Anterior Hypothalamus

The preoptic anterior hypothalamus (POAH) , known as a thermointegrative center, modulates metabolic adaptation in response to temperature change, thus making it relevant for body weight homeostasis. Forkhead transcription factor O1 (FoxO1) plays an important role in mediating effects of leptin and insulin on metabolic homeostasis in the hypothalamus. However, the homeostatic role of FoxO1 in POAH has not been investigated. We found that FoxO1 specific deletion in the POAH neurons (FoxO1POAH-KO) prevented high fat diet-induced obesity (DIO) in female but not male mice. This female-specific protection was associated with increased lean mass, decreased fat mass, and upregulated thermogenesis in adipose tissues. The female FoxO1POAH-KO mice also showed improved insulin sensitivity and increased energy expenditure when exposed at room temperature (22 °C) or cold (6 °C) . Moreover, the FoxO1POAH-KO-induced protection against DIO in females was blunted by ovariectomy (OVX) , while 17β-estradiol supplementation after OVX failed to restore this protection, suggesting an estrogen-independent mechanism. Finally, mice with FoxO1 constitutively activated in the POAH neurons (FoxO1POAH-CA) significantly increased DIO in both sexes, further supporting an essential metabolic role of FoxO1POAH. Together, these findings indicate that FoxO1POAH is a crucial transcription factor that directs and coordinates control of energy balance, thermogenesis, and glucose homeostasis in female mice. Key words: FoxO1, POAH, sex difference. Disclosure P. Luo: None. H. Ye: None. T. Unterman: None. P. Xu: None. Funding P. Xu is supported by National Institutes of Health (R00DK1070 and R01DK123098) , Department of Defense (Innovative Grant W81XWH-19-PRMRP-DA) , and The University of Chicago Diabetes Research and Training Center (The Pilot and Feasibility Award DK020595) .

Molecular Characterization and Expression of Cytochrome P450 Aromatase in Atlantic Croaker Brain: Regulation by Antioxidant Status and Nitric Oxide Synthase During Hypoxia Stress.

We have previously shown that nitric oxide synthase (NOS, an enzyme) is significantly increased during hypoxic stress in Atlantic croaker brains and modulated by an antioxidant (AOX). However, the influence of NOS and AOX on cytochrome P450 aromatase (AROM, CYP19a1, an enzyme) activity on vertebrate brains during hypoxic stress is largely unknown. In this study, we characterized brain AROM (bAROM, CYP19a1b) cDNA in croaker and examined the interactive effects of hypoxia and a NOS-inhibitor or AOX on AROM activity. The amino acid sequence of croaker bAROM cDNA is highly homologous (76–80%) to other marine teleost bAROM cDNAs. Both real-time PCR and Northern blot analyses showed that bAROM transcript (size: ∼2.8 kb) is highly expressed in the preoptic-anterior hypothalamus (POAH). Hypoxia exposure (dissolved oxygen, DO: 1.7 mg/L for 4 weeks) caused significant decreases in hypothalamic AROM activity, bAROM mRNA and protein expressions. Hypothalamic AROM activity and mRNA levels were also decreased by pharmacological treatment with N-ethylmaleimide (NEM, an alkylating drug that modifies sulfhydryl groups) of fish exposed to normoxic (DO: ∼6.5 mg/L) conditions. On the other hand, treatments with Nω-nitro-L-arginine methyl ester (NAME, a competitive NOS-inhibitor) or vitamin-E (Vit-E, a powerful AOX) prevented the downregulation of hypothalamic AROM activity and mRNA levels in hypoxic fish. Moreover, NAME and Vit-E treatments also restored gonadal growth in hypoxic fish. Double-labeled immunohistochemistry results showed that AROM and NOS proteins are co-expressed with NADPH oxidase (generates superoxide anion) in the POAH. Collectively, these results suggest that the hypoxia-induced downregulation of AROM activity in teleost brains is influenced by neuronal NOS activity and AOX status. The present study provides, to the best of our knowledge, the first evidence of restoration of AROM levels in vertebrate brains by a competitive NOS-inhibitor and potent AOX during hypoxic stress.

Thermoregulatory dysfunction in Parkinson's disease

Thermoregulatory dysfunction is considered to be the least investigated among all the autonomic disorders in Parkinson disease. Pathophysiological mechanisms of this phenomena involve as central, as peripheric parts of nervous system. Dopamine deficiency in combination with peripheric autonomic dysfunction leads to temperature balance disturbance, which may be expressed by various clinical symptoms. Dopaminergic innervation of preoptic-anterior hypothalamus area plays a crucial role in thermoregulation function of central nervous system. Current thermoregulatory tests give possibility not only to reveal sudomotor and heat dissipation disorders in patients with Parkinson disease, but also to make differential diagnosis with other neurodegenerative disorders. Early detection and treatment of thermoregulatory dysfunction may improve quality of life in patients with Parkinson disease.

Early-Life m6A RNA Demethylation by Fat Mass and Obesity-Associated Protein (FTO) Influences Resilience or Vulnerability to Heat Stress Later in Life.

Early life heat stress leads to either resilience or vulnerability to a similar stress later in life. We have previously shown that this tuning of the stress response depends on neural network organization in the preoptic anterior hypothalamus (PO/AH) thermal response center and is regulated by epigenetic mechanisms. Here, we expand our understanding of stress response establishment describing a role for epitranscriptomic regulation of the epigenetic machinery. Specifically, we explore the role of N6-methyladenosine (m6A) RNA methylation in long-term response to heat stress. Heat conditioning of 3-d-old chicks diminished m6A RNA methylation in the hypothalamus, simultaneously with an increase in the mRNA levels of the m6A demethylase, fat mass and obesity-associated protein (FTO). Moreover, a week later, methylation of two heat stress-related transcripts, histone 3 lysine 27 (H3K27) methyltransferase, enhancer of zeste homolog 2 (EZH2) and brain-derived neurotrophic factor (BDNF), were downregulated in harsh-heat-conditioned chicks. During heat challenge a week after conditioning, there was a reduction of m6A levels in mild-heat-conditioned chicks and an elevation in harsh-heat-conditioned ones. This increase in m6A modification was negatively correlated with the expression levels of both BDNF and EZH2 Antisense "knock-down" of FTO caused an elevation of global m6A RNA methylation, reduction of EZH2 and BDNF mRNA levels, and decrease in global H3K27 dimethylation as well as dimethyl H3K27 level along BDNF coding region, and, finally, led to heat vulnerability. These findings emphasize the multilevel regulation of gene expression, including both epigenetic and epitranscriptomic regulatory mechanisms, fine-tuning the neural network organization in a response to stress.

Sexual behaviour of rams: male orientation and its endocrine correlates

The components of heterosexual behaviour in rams are reviewed as a basis for understanding partner preference behaviour. A small percentage of rams will not mate with oestrous females and if given a choice will display courtship behaviour towards another ram in preference to a female. Some of the endocrine profiles of these male-oriented rams differ from those of heterosexual controls. These differences include reduced serum concentrations of testosterone, oestradiol and oestrone, reduced capacity to produce testosterone in vitro, and reduced capacity to aromatize androgens in the preoptic-anterior hypothalamus of the brain. Our observation that aromatase activity is significantly lower in the preoptic-anterior hypothalamic area of male-oriented rams than in female-oriented rams may indicate an important neurochemical link to sexual behaviour that should be investigated. The defect in steroid hormone production by the adult testes of the male-oriented ram may represent a defect that can be traced to the fetal testes. If this contention is correct, partner preference behaviour of rams may also be traceable to fetal development and represent a phenomenon of sexual differentiation.

Estradiol Valerate and Remifemin ameliorate ovariectomy-induced decrease in a serotonin dorsal raphe–preoptic hypothalamus pathway in rats

Perimenopausal syndromes begin as ovarian function ceases and the most common symptoms are hot flushes. Data indicate that the projections of serotonin to hypothalamus may be involved in the mechanism of hot flushes. Therefore, the aim of this study is to investigate the potential role of the serotonin dorsal raphe–preoptic hypothalamus pathway for hot flushes in an animal model of menopause. We determined the changes in serotonin expression in the dorsal raphe (DR) and preoptic anterior hypothalamus (POAH) in ovariectomized rats. We also explored the therapeutical effects of estradiol valerate and Remifemin in this model. Eighty female Sprague-Dawley rats were randomly assigned to sham-operated (SHAM) group, ovariectomy (OVX) group with vehicle, ovariectomy with estradiol valerate treatment (OVX+E) group and ovariectomy with Remifemin (OVX+ICR) group. Serotonin expression was evaluated in the DR and POAH using immunofluorescence and quantified in the DR using an enzyme-linked immunosorbent assay (ELISA). Apoptosis was analyzed in the DR by TUNEL assay. The number of serotonin immunoreactive neurons and the level of serotonin expression in the DR decreased significantly following OVX compared to the SHAM group. No TUNEL-positive cells were detected in the DR in any group. In addition, following OVX, the number of serotonin-positive fibers decreased significantly in the ventromedial preoptic nucleus (VMPO), especially in the ventrolateral preoptic nucleus (VLPO). Treatment with either estradiol or Remifemin for 4 weeks countered the OVX-induced decreases in serotonin levels in both the DR and the hypothalamus, with levels in the treated rats similar to those in the SHAM group. A fluorescently labeled retrograde tracer was injected into the VLPO at the 4-week time point. A significantly lower percentage of serotonin with CTB double-labeled neurons in CTB-labeled neurons was demonstrated after ovariectomy, and both estradiol and Remifemin countered this OVX-induced decrease. We conclude that serotonin pathway is changed after ovariectomy, including the serotonin synthesis in DR and serotonin fibers in PO/AH, both E and Remifemin have an equivalent therapeutic effect on it.

Arginine vasotocin V1a2 receptor and GnRH-I co-localize in preoptic neurons of the sex changing grouper, Epinephelus adscensionis

The arginine vasotocin/vasopressin (AVT/AVP) and gonadotropin releasing hormone (GnRH) systems are known to control sexual behaviors and reproduction, respectively, in different vertebrate groups. However, a direct functional connection between these two neuroendocrine systems has not been demonstrated for any vertebrate species. Therefore, the objective of this research was to test the hypothesis that AVT acts on the GnRH system via an AVT V1a receptor in a sex changing grouper species, the rock hind, Epinephelus adscensionis. AVT V1a2 receptors were co-localized with GnRH-I on neurons in the preoptic anterior hypothalamus identifying a structural linkage between the AVT system and GnRH-I. Transcripts for avt, gnrh-I, and two AVT receptor subtypes (v1a1 and v1a2) were isolated and characterized for E. adscensionis and their expression was measured in males and females by q-RT-PCR. Translation of V1a-type cDNA sequences revealed two distinct forms of the AVT V1a receptor in E. adscensionis brain similar to those reported for other species. The observation of significantly higher gnrh-I mRNA in the POA+H of rock hind males as compared to females suggests differential regulation of the gnrh-I transcripts in the two sexes of this protogynous species. In male E. adscensionis, but not in females, a negative relationship was seen between plasma 11-ketotestosterone (11-KT) and the v1a1 receptor mRNA levels in the POA+H, while a positive trend was observed between 11-KT and v1a2 receptor mRNA levels, indicating that these receptor forms may be differentially regulated.

Profiles of reproduction-related mRNA expressions in hypothalamus of female mice with advancing age

To explore the effects of aging on the levels of reproduction-related mRNA genes including Gnrh, KISS1/KISS1r, estrogen receptor-alpha (ERα), estrogen receptor-beta (ERβ) and progesterone receptor (PR) in hypothalamus. Proestrus and metestrus in young (3-4 months) and middle-aged (10-11 months) female mice and diestrus in senile (18-19 months) female mice were observed. And the levels of related mRNA genes in preoptic area anterior hypothalamus (POA-AH) and medial basal hypothalamus (MBH) were determined by real-time polymerase chain reaction (RT-PCR). In middle-aged mice on proestrus, the level of Gnrh mRNA in POA-AH (0.896 ± 0.049) was significantly lower than that in young mice (1.228 ± 0.147, P = 0.049). The level of ERα mRNA in POA-AH decreased in young mice on proestrus whereas increased in middle-aged mice (0.432 ± 0.063 vs 0.603 ± 0.018, P = 0.016). The level of ERα mRNA of POA-AH, both in middle-aged mice (0.432 ± 0.063, P = 0.014) and senile mice (0.403 ± 0.145, P = 0.020) on diestrus, were significantly lower than that in young mice. The PR mRNA expression in middle-aged mice on proestrus (1.037 ± 0.037) was markedly lower than that in young mice (1.251 ± 0.081, P = 0.031) . In senile mice, the levels of Gnrh mRNA (1.520 ± 0.146, P = 0.004) and ERβ mRNA (1.572 ± 0.184, P = 0.011) increased in POA-AH compared with that in young mice on metestrus. Aging had no effect upon KISS1 and KISS1r mRNA levels in POA-AH. In contrast, KISS1 mRNA level of MBH in middle-aged (1.663 ± 0.398, P = 0.037) and senile (2.622 ± 0.454, P = 0.014) mice obviously increased compared with the young mice group. Higher levels of ERα mRNA and decreases of PR and Gnrh mRNA in POA-AH in middle-aged mice on proestrus may play an important role in declining reproductive function.

Functional interaction between HIV-gp120 and opioid system in the preoptic anterior hypothalamus

BackgroundRecently we found that fever (part of HIV-related wasting) is induced by the action of the human immunodeficiency virus-1 (HIV-1) envelope glycoprotein (gp120) in the preoptic anterior hypothalamus (POAH). As the opioid system plays a role in the pathogenesis of HIV-1, in the present study we sought to examine the capacity of the opioid system to regulate the febrile response induced by gp120. MethodsStainless steel cannulas were stereotactically into the POAH, and a biotelemetry system was used to monitor the body temperature (Tb changes). We examined the in vivo effects of naloxone as well as highly opioid-selective receptor antagonists, on gp120-induced fever. ResultsPretreatment with naloxone or the mu-opioid receptor-selective antagonist, cyclic d-Phe-Cys-Tyr-d-Trp-Arg-Thr-Pen-Thr-NH(2) (CTAP), significantly delayed the febrile response induced by gp120. In contrast, naltriben (NTB), a selective antagonist for the delta-2 opioid receptor, did not cause any effect on gp120-induced fever. ConclusionThese results (1) provide pharmacologic evidence of a functional in vivo interaction between the opioid system and this viral protein in the POAH and (2) show that mu-opioid receptors can regulate gp120-induced fever.

Effects of arginine vasopressin on firing activity and thermosensitivity of rat PO/AH area neurons

It is well known that the preoptic–anterior hypothalamus (PO/AH), containing temperature-sensitive and -insensitive neurons plays an important role in precise thermoregulatory responses. Previous in vivo studies suggest that the arginine vasopressin (AVP) is an important endogenous mediator in thermoregulation, since AVP and V1a vasopressin receptor antagonist can induce hypothermia and hyperthermia, respectively. In the present study, intracellular electrophysiological activity was recorded from temperature-sensitive and -insensitive neurons in rat PO/AH tissue slices, using a whole-cell patch clamp. By monitoring neuron’s changes of firing activity and thermosensitivity when perfused with AVP or V1a vasopressin receptor antagonist, we found that AVP increased the spontaneous firing rate in 65% of warm-sensitive neurons and decreased it in nearly 50% of cold-sensitive and temperature-insensitive neurons. These changes are due to the AVP enhancing the rise rate of depolarization prepotential in warm-sensitive neurons and reducing it in the other neurons. Moreover, AVP increased the thermosensitivity of warm-sensitive neurons while it decreased thermosensitivity of cold-sensitive and temperature-insensitive neurons. V1a vasopressin receptor participated in these responses. Since excited warm-sensitive neurons or inhibited cold-sensitive and temperature-insensitive neurons promote heat loss or suppress heat production and retention. These results that AVP excites warm-sensitive neurons and inhibits cold-sensitive and temperature-insensitive neurons suggest a probable mechanism of AVP-induced hypothermia.

Heat shock factor 1 regulates the expression of the TRPV1 gene in the rat preoptic‐anterior hypothalamus area during lipopolysaccharide‐induced fever

The TRPV1 cation channel is a member of the thermo-TRP family of ionic channels activated by noxious heat and various endogenous mediators. Expression of TRPV1 is widespread and includes hypothalamic neurons. The preoptic-anterior hypothalamus area (PO/AH) are required for regulation of body temperature, suggesting that resident thermosensitive TRPV1 channels may be involved in thermoregulation. Heat shock factor 1 (HSF1) is a ubiquitous heat-sensitive transcription factor that co-ordinates the genomic response to noxious heat, but it is not known whether TRPV1 expression is part of this adaptive mechanism. We therefore investigated whether HSF1 regulates TRPV1 transcription in response to lipopolysaccharide (LPS)-induced fever in rats. Expression of TRPV1 and nuclear translocation of HSF1 were transiently upregulated during LPS-induced fever, with temporal profiles that mirrored the rise and fall in body temperature. We used a series of luciferase reporter vectors encoding different spans of the TRPV1 gene 5'-flanking region to identify possible HSF1-binding sites. Reporter assays in transfected PC12 cells demonstrated that only TRPV1 promoters with the -1160 to -821 region drove reporter expression in response to heat shock. This region contains one putative heat shock-responsive element (HSE) for HSF1 binding at -919 to -910. Site-directed mutagenesis of this HSE abrogated reporter activity in response to heat shock, indicating that -919 to -910 contains the specific HSF1-binding sequence. In the PO/AH, electrophoretic mobility shift assay and chromatin immunoprecipitation assay analyses demonstrated that HSF1 is recruited to the HSE of the TRPV1 gene in PO/AH cells during LPS-induced fever, resulting in enhanced TRPV1 expression. Based on these findings, we conclude that HSF1 regulates TRPV1 gene expression in PO/AH of rats with LPS-induced fever.

Fasting of 3-day-old chicks leads to changes in histone H3 methylation status

Unfavorable nutritional conditions during early developmental periods may cause neuronal network remodeling in the hypothalamus, which influences subsequent adaptability to those same stressful conditions. Alterations in hypothalamic plasticity as a result of neuronal remodeling are achieved by variations in the repertoire of proteins expressed via gene transcriptional activation or repression, both of which are modulated by histone methylation status. This study demonstrates that fasting had a stimulatory effect on dimethylation and trimethylation of histone 3 at lysine 27 (H3K27) in preoptic/anterior hypothalamus (PO/AH) of 3-day-old chicks. The expression of enhancer of zeste 2 (EZH2), a H3K27-specific histone methyltransferase (HMT), was significantly increased by fasting in the paraventricular nucleus (PVN) and PO/AH, which is consistent with the upregulation of H3K27 dimethylation and trimethylation. Furthermore, in the PVN, corticotrophin-releasing hormone (CRH) mRNA expression was significantly inhibited, while mRNA expressions of thyrotropin-releasing hormone (TRH) and type 2 deiodinase (D2) were significantly stimulated by fasting. These findings highlight the potential role of H3K27 methylation status in early feed stress responses in chicks and may be indicative of an epigenetic mechanism for later adaptation to feed intake stress.

Central interleukin-10 attenuated lipopolysaccharide-induced changes in core temperature and hypothalamic glutamate, hydroxyl radicals and prostaglandin-E2

It has been documented that intravenous lipopolysaccharide (LPS) in rabbits causes fever accompanied by increased levels of extracellular glutamate, hydroxyl radicals, and prostaglandin E2 (PGE2) in the hypothalamus and circulating tumor necrosis factor-alpha (TNF-α). This investigation was to determine whether central interleukin-10 (IL-10) exerted its antipyresis by reducing changes in circulating TNF-α and extracellular glutamate, hydroxyl radicals and PGE2 in the hypothalamus. The microdialysis probes were stereotaxically and chronically implanted into the preoptic anterior hypothalamus of rabbit brain for determinating extracellular glutamate, hydroxyl radicals, and PGE2 in situ. It was found that systemically injected LPS (2μg/kg, intravenously) increased the levels of core temperature, and extracellular glutamate, hydroxyl radicals, and PGE2 in the hypothalamus accompanied by increased plasma levels of TNF-α. Pretreatment with IL-10 (10–100ng, intracerebroventricularly) 1h before intravenous LPS significantly reduced the LPS-induced changes in extracellular glutamate, hydroxyl radicals, and PGE2 in the hypothalamus and fever, but not the increased levels of TNF-α in rabbits. These findings suggested that directly injected IL-10 into the lateral cerebral ventricle 1h before intravenous LPS exerted its antipyresis by inhibiting the changes in extracellular glutamate, hydroxyl radicals and PGE2 in the hypothalamus during LPS fever in rabbits.

MiR-138 inhibits EZH2 methyltransferase expression and methylation of histone H3 at lysine 27, and affects thermotolerance acquisition

Thermotolerance acquisition involves neuronal network remodeling and, hence, alteration in the repertoire of expressed proteins. We have previously demonstrated the role of histone H3 methylation at lysine 27 (H3K27) by EZH2 methyltransferase in the regulation of gene expression during the critical period for the establishment of thermal control in chicks. Here we describe another level of biological regulation, demonstrating the inhibitory role of microRNAs (miRNAs) in the regulation of EZH2 expression in thermoregulatory system development and functioning. During heat conditioning in the critical period for the establishment of thermal control, a decrease in expression of the EZH2-targeting miR-138 occurred simultaneously with an increase in EZH2 levels in the preoptic anterior hypothalamus. Intracranial injection of miR-138 during the critical period led to a transient reduction in EZH2 levels, which was accompanied by a decrease in H3K27 methylation. Injection of miR-138 followed by heat conditioning also abolished EZH2 induction during heat conditioning. Moreover, this miR-138-induced inhibition of EZH2 during the critical period resulted in a long-term effect on EZH2 expression. A week after the treatment, the EZH2 protein levels in conditioned and in nonconditioned chicks were different from those in their saline-injected counterparts and the directions of change were opposite to each other. Finally, miR-138 injection during the critical period disrupted the establishment of thermoregulation, manifested as a defective body temperature response to heat. These data demonstrate a role for miRNAs in regulating the expression of histone-modifying enzymes, and thus emphasize the multilevel regulation mechanism which includes both epigenetic and miRNA regulatory mechanisms in neuronal network organization during the critical period of sensory development.

Cyclooxygenase‐2/microsomal prostaglandin E synthase‐1 complex in the preoptic‐anterior hypothalamus of the mouse: involvement through fever to intravenous lipopolysaccharide

Prostaglandin E₂ (PGE₂) is now well established as a central effector of pyrogen fever. However, questions remain on the source, local vs. blood-borne, of the compound for the early phase of the typically biphasic fever (Phases 1 and 2) to i.v. pyrogens. To verify the role of centrally formed PGE₂, we examined the cyclooxygenase (COX)/prostaglandin E synthase (PGES) complex through fever to i.v. lipopolysaccharide (LPS). Experiments were carried out in the conscious mouse and LPS effect was ascertained on all steps of expression - gene, protein, catalytic activity - of individual enzymes. The analysis was limited to the preoptic-anterior hypothalamus (AH/POA). We found upregulation of the COX2 transcript together with an upward trend for the mPGES1 transcript during Phase 1. Coincidentally, there was a progressive increase in COX2 and mPGES1 protein expression through Phases 1 and 2. Catalytic activity for COX1 and COX2 combined was instead enhanced only in Phase 2, while mPGES1 activity remained steady at an intrinsically high level. Other COX and PGES enzymes were not modified through either Phase, and COX2/mPGES1 changes subsided with fever defervescence. The findings confirm a key function of COX2 and mPGES1 for the synthesis of pyrogenic PGE₂ and, at the same time, document their early response to LPS. We conclude that locally formed PGE₂ in AH/POA is qualified for a role in the initiation of fever.

The interrelationship between sleep regulation and thermoregulation

The circadian distribution of vigilance states and body temperature changes are tightly coupled. The increase in heat loss at the end of the day is associated with increased ease to fall asleep. Experimental data show that warming the skin or the brain can increase sleep propensity, sleep consolidation, and the duration of sleep. Anatomical and neurophysiological studies show that the pre-optic-anterior-hypothalamus (POAH) is the main integrator of sleep and thermoregulatory information. It integrates information on vigilance states, body temperature, and environmental temperature and influences vigilance states and body temperature in response. Animals that display daily torpor may be a valuable model to investigate the relationship between sleep and thermoregulation. During torpor these animals seem to apply similar strategies and physiological processes as humans during entrance into sleep, but in a more extreme way, providing an excellent opportunity to investigate these processes in more detail. More systematic investigations are needed to further our understanding of the relationship between sleep and thermoregulation, and may provide the basis to treat sleep disturbances with thermal strategies.

Epigenetic control of translation regulation: Alterations in histone H3 lysine 9 post‐translation modifications are correlated with the expression of the translation initiation factor 2B (Eif2b5) during thermal control establishment

Thermal control set point is regulated by thermosensitive neurons of the preoptic anterior hypothalamus (PO/AH) and completes its development during postnatal critical sensory period. External stimuli, like increase in environmental temperature, influence the neuronal protein repertoire and, ultimately, cell properties via activation or silencing of gene transcription, both of which are regulated by the "histone code.''" Here, we demonstrated an increase in global histone H3 lysine 9 (H3K9) acetylation as well as H3K9 dimethylation in chick PO/AH during heat conditioning at the critical period of sensory development. In contrast to the global profile of H3K9 modifications, acetylation and dimethylation patterns of H3K9 at the promoter of the catalytic subunit of eukaryotic translation initiation factor 2B (Eif2b5) were opposite to each other. During heat conditioning, there was an increase in H3K9 acetylation at the Eif2b5 promoter, simultaneously with decrease in H3K9 dimethylation. These alterations coincided with Eif2b5 mRNA induction. Moreover, exposure to excessive heat during the critical period resulted in long-term effect on both H3K9 tagging at the Eif2b5 promoter and Eif2b5 mRNA expression. These data suggest a role for dynamic H3K9 post-translational modifications in global translation regulation during the thermal control establishment.