Acute Effect of Caffeine on the Synthesis of Pro-Inflammatory Cytokines in the Hypothalamus and Choroid Plexus during Endotoxin-Induced Inflammation in a Female Sheep Model.

This study was designed to determine the effect of acute caffeine (CAF) administration, which exerts a broad spectrum of anti-inflammatory activity, on the synthesis of pro-inflammatory cytokines and their receptors in the hypothalamus and choroid plexus (ChP) during acute inflammation caused by the injection of bacterial endotoxin-lipopolysaccharide (LPS). The experiment was performed on 24 female sheep randomly divided into four groups: control; LPS treated (iv.; 400 ng/kg of body mass (bm.)); CAF treated (iv.; 30 mg/kg of bm.); and LPS and CAF treated. The animals were euthanized 3 h after the treatment. It was found that acute administration of CAF suppressed the synthesis of interleukin (IL-1ß) and tumor necrosis factor (TNF)α, but did not influence IL-6, in the hypothalamus during LPS-induced inflammation. The injection of CAF reduced the LPS-induced expression of TNF mRNA in the ChP. CAF lowered the gene expression of IL-6 cytokine family signal transducer (IL6ST) and TNF receptor superfamily member 1A (TNFRSF1) in the hypothalamus and IL-1 type II receptor (IL1R2) in the ChP. Our study on the sheep model suggests that CAF may attenuate the inflammatory response at the hypothalamic level and partly influence the inflammatory signal generated by the ChP cells. This suggests the potential of CAF to suppress neuroinflammatory processes induced by peripheral immune/inflammatory challenges.

Hypothalamic-Pituitary Autoimmunity and Related Impairment of Hormone Secretions in Chronic Fatigue Syndrome.

CONTEXT: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a severe chronic illness that reduces the quality of life. A potential role of neuroendocrine autoimmune dysfunction has been hypothesized. OBJECTIVE: This work aims to investigate the occurrence of antipituitary (APA) and antihypothalamic (AHA) antibodies and possible related hypothalamic/pituitary dysfunctions in ME/CSF patients. METHODS: This is a case-control study conducted in a university hospital setting (Stanford, California, USA; and Naples, Italy). Thirty women with ME/CSF (group 1) diagnosed according to Fukuda, Canadian, and Institute of Medicine criteria, at Stanford University, were enrolled and compared with 25 age-matched healthy controls. APA and AHA were detected by immunofluorescence; moreover, we investigated hormonal secretions of anterior pituitary and respective target glands. APA and AHA titers both were assessed and the prevalence of pituitary hormone deficiencies was also investigated. RESULTS: Patients in group 1 showed a high prevalence of AHA (33%) and APA (56%) and significantly lower levels of adrenocorticotropin (ACTH)/cortisol, and growth hormone (GH) peak/insulin-like growth factor-1 (IGF-1) vs controls (all AHA/APA negative). Patients in group 1A (13 patients positive at high titers, ≥ 1:32) showed ACTH/cortisol and GH peak/IGF-1 levels significantly lower and more severe forms of ME/CFS with respect to patients in group 1B (7 positive at middle/low titers, 1:16-1:8) and 1C (10 antibody-negative patients). CONCLUSION: Both AHA and/or APA at high titers were associated with hypothalamic/pituitary dysfunction, suggesting that hypothalamic/pituitary autoimmunity may play an important role in the manifestations of ME/CFS, especially in its more severe forms.

Metformin reduces oxandrolone- induced depression-like behavior in rats via modulating the expression of IL-1ß, IL-6, IL-10 and TNF-α.

Oxandrolone (OXA) is an androgen and anabolic steroid (AAS) that is used to reverse weight loss associated with some medical conditions. One of the side effects of OXA is its potential to induce depressive symptoms. Growing evidence suggested that neuroinflammation and cytokines play crucial roles in sickness behavioral and associated mood disturbances. Previous studies showed that metformin attenuated neuroinflammation. This study investigated the potential protective role of metformin against OXA-induced depression-like behavior and neuroinflammation. Twenty- four Wistar male rats were randomly grouped into four groups: the control group (Control) received only vehicle; the oxandrolone group (OXA) received oxandrolone (0.28 mg/kg, i.p); the metformin group (MET) received metformin (100 mg/kg, i.p); and the oxandrolone / metformin group (OXA + MET) received both oxandrolone (0.28 mg/kg, i.p) and metformin (100 mg/kg, i.p). These treatments were administered for fourteen consecutive days. Behavioral tests to measure depression-like behavior were conducted before and after treatments. qRT-PCR was used to measure the relative expression of proinflammatory and anti-inflammatory cytokines in the hippocampus and hypothalamus. The results showed that oxandrolone induced depression-like behavior and dysregulated pro-/anti-inflammatory cytokines, while metformin attenuated these effects. These findings suggest that metformin is a potential treatment to reverse the depressive effects induced by oxandrolone that involve neuroinflammatory effects.

The role of inflammatory cytokines in anemia and gastrointestinal mucosal injury induced by foot electric stimulation.

Foot electrical stimulation (FES) has been considered as a classic stressor that can disturb homeostasis. Acute anemia was observed in the model induced by FES. The aim of this study was to explore the role of inflammatory cytokines underlying the acute anemia and gastrointestinal (GI) mucosal injury in the FES. Twenty-four male Kunming mice (20 ± 2 g) were randomly divided into control group and experimental group. The mice were placed in a footshock chamber that can generate 0.5 mA electrical impulse periodically for 0.5 h. After the process, red blood cell count, hemoglobin concentration and hematocrit, the levels of corticotropin releasing hormone (CRH) in serum and hypothalamus, and adrenocorticotropic hormone (ACTH) in serum and pituitary were detected separately. In addition, we investigated the expressions of inflammatory cytokines (IL-1, IL-6, TNF-α, iNOS, and IL-10) in the hypothalamus and duodenum by Polymerase Chain Reaction (PCR). Results showed that this FES model induced anemia, increased CRH and ACTH activity in the serum after the FES. Moreover, the expressions of IL-1ß, IL-6, TNF-α, and iNOS were significantly increased following the process, while IL-10 was not activated. These findings suggest that anemia, the inflammatory cytokines in the hypothalamus and duodenum of the mice in the model induced by FES is closely related to GI mucosal injury/bleeding. Taken together, these results underscore the importance of anemia, GI mucosal injury/bleeding and stress, future studies would be needed to translate these findings into the benefit of affected patients.

Enriched environment enhances NK cell maturation through hypothalamic BDNF in male mice.

Macroenvironmental factors, including a patient's physical and social environment, play a role in cancer risk and progression. Our previous preclinical studies have shown that the enriched environment (EE) confers anti-obesity and anti-cancer phenotypes that are associated with enhanced adaptive immunity and are mediated by brain-derived neurotrophic factor (BDNF). Natural killer (NK) cells have anti-cancer and anti-viral properties, and their absence or depletion is associated with inferior clinical outcomes. In this study, we investigated the effects of EE on NK cell maturation following their depletion. Mice living in EE displayed a higher proportion of NK cells in the spleen, bone marrow, and blood, compared to those living in the standard environment (SE). EE enhanced NK cell maturation in the spleen and was associated with upregulation of BDNF expression in the hypothalamus. Hypothalamic BDNF overexpression reproduced the EE effects on NK cell maturation in secondary lymphoid tissues. Conversely, hypothalamic BDNF knockdown blocked the EE modulation on NK cell maturation. Our results demonstrate that a bio-behavior intervention enhanced NK cell maturation and was mediated at least in part by hypothalamic BDNF.

Gut Hormone GIP Induces Inflammation and Insulin Resistance in the Hypothalamus.

The hypothalamus plays a critical role in controlling energy balance. High-fat diet (HFD) feeding increases the gene expression of proinflammatory mediators and decreases insulin actions in the hypothalamus. Here, we show that a gut-derived hormone, glucose-dependent insulinotropic polypeptide (GIP), whose levels are elevated during diet-induced obesity, promotes and mediates hypothalamic inflammation and insulin resistance during HFD-induced obesity. Unbiased ribonucleic acid sequencing of GIP-stimulated hypothalami revealed that hypothalamic pathways most affected by intracerebroventricular (ICV) GIP stimulation were related to inflammatory-related responses. Subsequent analysis demonstrated that GIP administered either peripherally or centrally, increased proinflammatory-related factors such as Il-6 and Socs3 in the hypothalamus, but not in the cortex of C57BL/6J male mice. Consistently, hypothalamic activation of IκB kinase-ß inflammatory signaling was induced by ICV GIP. Further, hypothalamic levels of proinflammatory cytokines and Socs3 were significantly reduced by an antagonistic GIP receptor (GIPR) antibody and by GIPR deficiency. Additionally, centrally administered GIP reduced anorectic actions of insulin in the brain and diminished insulin-induced phosphorylation of Protein kinase B and Glycogen synthase kinase 3ß in the hypothalamus. Collectively, these findings reveal a previously unrecognized role for brain GIP signaling in diet-induced inflammation and insulin resistance in the hypothalamus.

NAMPT and BMAL1 Are Independently Involved in the Palmitate-Mediated Induction of Neuroinflammation in Hypothalamic Neurons.

Obesity is a prominent metabolic disease that predisposes individuals to multiple comorbidities, including type 2 diabetes mellitus, cardiovascular diseases, and cancer. Elevated circulating levels of fatty acids contribute to the development of obesity, in part, by targeting the hypothalamus. Palmitate, the most abundant circulating saturated fatty acid, has been demonstrated to dysregulate NAMPT and circadian clock proteins, as well as induce neuroinflammation. These effects ultimately result in hypothalamic dysregulation of feeding behavior and energy homeostasis. NAMPT is the rate-limiting enzyme of the NAD+ salvage pathway and its expression is under the control of the circadian clock. NAD+ produced from NAMPT can modulate the circadian clock, demonstrating bidirectional interactions between circadian and metabolic pathways. Using NPY/AgRP-expressing mHypoE-46 neurons as well as the novel mHypoA-BMAL1-WT/F and mHypoA-BMAL1-KO/F cell lines, we studied whether there were any interactions between NAMPT and the core circadian clock protein BMAL1 in the palmitate-mediated induction of neuroinflammation. We report that palmitate altered Nampt, Bmal1, Per2 and the inflammatory genes Nf-κb, IκBα, Il-6, and Tlr4. Contrary to studies performed with peripheral tissues, the palmitate-mediated induction in Nampt was independent of BMAL1, and basal Nampt levels did not appear to exhibit rhythmic expression. Palmitate-induced downregulation of Bmal1 and Per2 was independent of NAMPT. However, NAMPT and BMAL1 were both involved in the regulation of Nf-κb, IκBα, Il-6, and Tlr4, as NAMPT inhibition resulted in the repression of basal Nf-κb and IκBα and normalized palmitate-mediated increases in Il-6, and Tlr4. On the other hand, BMAL1 deletion repressed basal Nf-κb, but increased basal Il-6. We conclude that NAMPT and BMAL1 do not interact at the transcriptional level in hypothalamic neurons, but are independently involved in the expression of inflammatory genes.

Cellular Contributors to Hypothalamic Inflammation in Obesity.

The hypothalamus is a crucial organ for the maintenance of appropriate body fat storage. Neurons in the hypothalamic arcuate nucleus (ARH) detect energy shortage or surplus via the circulating concentrations of metabolic hormones and nutrients, and then coordinate energy intake and expenditure to maintain energy homeostasis. Malfunction or loss of hypothalamic ARH neurons results in obesity. Accumulated evidence suggests that hypothalamic inflammation is a key pathological mechanism that links chronic overconsumption of a high-fat diet (HFD) with the development of obesity and related metabolic complications. Interestingly, overnutrition-induced hypothalamic inflammation occurs specifically in the ARH, where microglia initiate an inflammatory response by releasing proinflammatory cytokines and chemokines in response to excessive fatty acid flux. Upon more prolonged HFD consumption, astrocytes and perivascular macrophages become involved and sustain hypothalamic inflammation. ARH neurons are victims of hypothalamic inflammation, but they may actively participate in hypothalamic inflammation by sending quiescence or stress signals to surrounding glia. In this mini-review, we describe the current state of knowledge regarding the contributions of neurons and glia, and their interactions, to HFD-induced hypothalamic inflammation.

Antibodies Against Hypothalamus and Pituitary Gland in Childhood-Onset Brain Tumors and Pituitary Dysfunction.

Purpose: To detect the presence of antipituitary (APA) and antihypothalamus antibodies (AHA) in subjects treated for brain cancers, and to evaluate their potential association with pituitary dysfunction. Methods: We evaluated 63 patients with craniopharyngioma, glioma, and germinoma treated with surgery and/or radiotherapy and/or chemotherapy at a median age of 13 years. Forty-one had multiple pituitary hormone deficiencies (MPHD), six had a single pituitary defect. GH was the most common defect (65.1%), followed by AVP (61.9%), TSH (57.1%), ACTH (49.2%), and gonadotropin (38.1%). APA and AHA were evaluated by simple indirect immunofluorescence method indirect immunofluorescence in patients and in 50 healthy controls. Results: Circulating APA and/or AHA were found in 31 subjects (49.2%) and in none of the healthy controls. In particular, 25 subjects out of 31 were APA (80.6%), 26 were AHA (83.90%), and 20 were both APA and AHA (64.5%). Nine patients APA and/or AHA have craniopharyngioma (29%), seven (22.6%) have glioma, and 15 (48.4%) have germinoma. Patients with craniopharyngioma were positive for at least one antibody in 39.1% compared to 33.3% of patients with glioma and to 78.9% of those with germinoma with an analogous distribution for APA and AHA between the three tumors. The presence of APA or AHA and of both APA and AHA was significantly increased in patients with germinoma. The presence of APA (P = 0.001) and their titers (P = 0.001) was significantly associated with the type of tumor in the following order: germinomas, craniopharyngiomas, and gliomas; an analogous distribution was observed for the presence of AHA (P = 0.002) and their titers (P = 0.012). In addition, we found a significant association between radiotherapy and APA (P = 0.03). Conclusions: Brain tumors especially germinoma are associated with the development of hypothalamic-pituitary antibodies and pituitary defects. The correct interpretation of APA/AHA antibodies is essential to avoid a misdiagnosis of an autoimmune infundibulo-neurohypophysitis or pituitary hypophysitis in patients with germinoma.

Immune-mediated febrile response in female rats: Role of central hypothalamic mediators.

Lipopolysaccharide (LPS) induces fever through cytokines like receptor-activator of nuclear factor κB ligand (RANKL), triggering mediators like prostaglandins (PG), endothelin-1 (ET-1), corticotrophin-releasing factor (CRF), substance P (SP) and endogenous opioids. LPS-induced fever is reduced in females compared with males except in ovariectomized (OVX) females which show increased fever mediated by PG. The present study aimed to identify the mediators involved in fever in intact and OVX female rats. Fever was induced with LPS (50 µg/kg) intraperitoneally or CRF (2.5 µg), ET-1 (1 pg), morphine (10 µg) and SP (500 ng) intracerebroventricularly in sham-operated and OVX rats. The role of RANKL was evaluated with osteoprotegerin (OPG, 1 µg, intracerebroventricularly). Expression of RANK, CRFI/II, ETB, µ-opioid (MOR) and NK1 receptors was evaluated by confocal microscopy. Besides LPS, only morphine induced fever in OVX rats while all mediators induced fever in sham-operated animals. OPG abolished LPS-induced fever in OVX but not sham-operated animals. Overall, fever involves similar central mediators in cycling females and males but only morphine induced fever in OVX females. Importantly, RANK/RANKL participates in LPS-induced fever in OVX females, as in males but not in cycling females.

Green Tea Polyphenol (-)-Epigallocatechin Gallate (EGCG) Attenuates Neuroinflammation in Palmitic Acid-Stimulated BV-2 Microglia and High-Fat Diet-Induced Obese Mice.

Obesity is closely associated with neuroinflammation in the hypothalamus, which is characterized by over-activated microglia and excessive production of pro-inflammatory cytokines. The present study was aimed at elucidating the effects of (-)-epigallocatechin gallate (EGCG) on palmitic acid-stimulated BV-2 microglia and high-fat-diet-induced obese mice. The results indicated the suppressive effect of EGCG on lipid accumulation, pro-inflammatory cytokines (TNF-α, IL-6, and IL-1ß) release, and microglial activation in both cellular and high-fat-diet rodent models. These results were associated with lower phosphorylated levels of the janus kinase 2/signal transducers and activators of transcription 3 (JAK2/STAT3) signaling pathway. In conclusion, EGCG can attenuate high-fat-induced hypothalamic inflammation via inhibiting the JAK2/STAT3 signaling pathways in microglia.

Interleukin-6 Expression by Hypothalamic Microglia in Multiple Inflammatory Contexts: A Systematic Review.

Interleukin-6 (IL-6) is a unique cytokine that can play both pro- and anti-inflammatory roles depending on the anatomical site and conditions under which it has been induced. Specific neurons of the hypothalamus provide important signals to control food intake and energy expenditure. In individuals with obesity, a microglia-dependent inflammatory response damages the neural circuits responsible for maintaining whole-body energy homeostasis, resulting in a positive energy balance. However, little is known about the role of IL-6 in the regulation of hypothalamic microglia. In this systematic review, we asked what types of conditions and stimuli could modulate microglial IL-6 expression in murine model. We searched the PubMed and Web of Science databases and analyzed 13 articles that evaluated diverse contexts and study models focused on IL-6 expression and microglia activation, including the effects of stress, hypoxia, infection, neonatal overfeeding and nicotine exposure, lipopolysaccharide stimulus, hormones, exercise protocols, and aging. The results presented in this review emphasized the role of "injury-like" stimuli, under which IL-6 acts as a proinflammatory cytokine, concomitant with marked microglial activation, which drive hypothalamic neuroinflammation. Emerging evidence indicates an important correlation of basal IL-6 levels and microglial function with the maintenance of hypothalamic homeostasis. Advances in our understanding of these different contexts will lead to the development of more specific pharmacological approaches for the management of acute and chronic conditions, like obesity and metabolic diseases, without disturbing the homeostatic functions of IL-6 and microglia in the hypothalamus.

Short-Term High-Fat Diet Consumption Reduces Hypothalamic Expression of the Nicotinic Acetylcholine Receptor α7 Subunit (α7nAChR) and Affects the Anti-inflammatory Response in a Mouse Model of Sepsis.

Sepsis is one of the leading causes of death in hospitalized patients and the chronic and low-grade inflammation observed in obesity seems to worsen susceptibility and morbidity of infections. However, little is known with respect to a short-term high-fat diet (HFD) and its role in the development of sepsis. Here, we show for the first time, that short-term HFD consumption impairs early nicotinic acetylcholine receptor α7 subunit (α7nAChR)- mediated signaling, one of the major components of the cholinergic anti-inflammatory pathway, with a focus on hypothalamic inflammation and innate immune response. Mice were randomized to a HFD or standard chow (SC) for 3 days, and sepsis was subsequently induced by a lethal intraperitoneal (i.p.) injection of lipopolysaccharide (LPS) or by cecal ligation and puncture (CLP) surgery. In a separate experiment, both groups received LPS (i.p.) or LPS (i.p.) in conjunction with the selective α7nAChR agonist, PNU-282987 (i.p. or intracerebroventricular; i.c.v.), and were sacrificed 2 h after the challenge. Short-term HFD consumption significantly reduced the α7nAChR mRNA and protein levels in the hypothalamus and liver (p < 0.05). Immunofluorescence microscopy demonstrated lower cholinergic receptor nicotinic α7 subunit (α7nAChR)+ cells in the arcuate nucleus (ARC) (α7nAChR+ cells in SC = 216 and HFD = 84) and increased F4/80+ cells in the ARC (2.6-fold) and median eminence (ME) (1.6-fold), which can contribute to neuronal damage. Glial fibrillary acidic protein (GFAP)+ cells and neuronal nuclear antigen (NeuN)+ cells were also increased following consumption of HFD. The HFD-fed mice died quickly after a lethal dose of LPS or following CLP surgery (2-fold compared with SC). The LPS challenge raised most cytokine levels in both groups; however, higher levels of TNF-α (Spleen and liver), IL-1ß and IL-6 (in all tissues evaluated) were observed in HFD-fed mice. Moreover, PNU-282987 administration (i.p. or i.c.v.) reduced the levels of inflammatory markers in the hypothalamus following LPS injection. Nevertheless, when the i.c.v. injection of PNU-282987 was performed the anti-inflammatory effect was much smaller in HFD-fed mice than SC-fed mice. Here, we provide evidence that a short-term HFD impairs early α7nAChR expression in central and peripheral tissues, contributing to a higher probability of death in sepsis.

Maternal resistin predisposes offspring to hypothalamic inflammation and body weight gain.

Resistin promotes hypothalamic neuroinflammation and insulin resistance through Toll like receptor 4 (TLR4), this hormone is thought to be a link between obesity and insulin-resistance. Indeed, resistin plasma levels are higher in obese and insulin resistant subjects. However, the impact of maternal resistin on the predisposition of offspring to hypothalamic neuroinflammation is unknown. Here, female mice were treated with resistin during gestation/lactation periods, then hypothalamic neuroinflammation was investigated in male offspring at p28 and p90. At p28, resistin increased the expression of inflammation markers (IL6, TNFα and NFκB) and TLR4 in the hypothalamus and decreased both hypothalamic insulin and leptin receptors' expression. The hypothalamic up-regulation IL6, TNFα and TLR4 was sustained until p90 promoting most likely hypothalamic inflammation. Maternal resistin also increased IL6 and TNFα in the adipose tissue of offspring at p90 associated with a higher body weight gain. In contrast, liver and muscle were not affected. These findings reveal that the augmentation of maternal resistin during gestation and lactation promotes hypothalamic and adipose tissue inflammation of offspring as evidenced by sustained increase of inflammation markers from weaning to adulthood. Thus, maternal resistin programs offspring hypothalamic and adipose tissue inflammation predisposing then offspring to body weight gain.

Estrogen receptor beta and G protein-coupled estrogen receptor 1 are involved in the acute estrogenic regulation of arginine-vasopressin immunoreactive levels in the supraoptic and paraventricular hypothalamic nuclei of female rats.

The ovarian hormone 17ß-estradiol is known to regulate the release, expression and immunoreactivity of arginine-vasopressin (AVP) in the supraoptic and paraventricular hypothalamic nuclei of rodents. Previous studies have shown that estrogen receptor α is involved in the effects of chronic estradiol administration on arginine-vasopressin immunoreactivity in the female rat hypothalamus. In this study we have examined the effect of an acute administration of estradiol or specific agonists for estrogen receptors α, ß and G protein-coupled estrogen receptor 1 on the immunoreactivity of arginine-vasopressin in the hypothalamus of adult ovariectomized female rats. Acute estradiol administration resulted in a significant decrease in the number of arginine-vasopressin immunoreactive neurons in the supraoptic and paraventricular nuclei after 24 h. The effects of the specific estrogen receptors agonists suggest that the action of estradiol on arginine-vasopressin immunoreactivity is mediated in the supraoptic nucleus by G protein-coupled estrogen receptor 1 and in the paraventricular nucleus by both estrogen receptor ß and G protein-coupled estrogen receptor 1. Thus, in contrast to previous studies on the effect of chronic estrogenic treatments, the present findings suggest that estrogen receptor ß and G protein-coupled estrogen receptor 1 mediate the acute effects of estradiol on arginine-vasopressin immunoreactivity in the hypothalamus of ovariectomized rats.

Early life alcohol exposure primes hypothalamic microglia to later-life hypersensitivity to immune stress: possible epigenetic mechanism.

Growing evidence has shown that developmental alcohol exposure induces central nervous system inflammation and microglia activation, which may contribute to long-term health conditions, such as fetal alcohol spectrum disorders. These studies sought to investigate whether neonatal alcohol exposure during postnatal days (PND) 2-6 in rats (third trimester human equivalent) leads to long-term disruption of the neuroimmune response by microglia. Exposure to neonatal alcohol resulted in acute increases in activation and inflammatory gene expression in hypothalamic microglia including tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). Adults with neonatal alcohol pre-exposure (alcohol fed; AF) animals showed an exaggerated peripheral stress hormonal response to an immune challenge (lipopolysaccharides; LPS). In addition, there were significantly more microglia present in the hypothalamus of adult AF animals, and their hypothalamic microglia showed more cluster of differentiation molecule 11b (Cd11b) activation, TNF-α expression, and IL-6 expression in response to LPS. Interestingly, blocking microglia activation with minocycline treatment during PND 2-6 alcohol exposure ameliorated the hormonal and microglial hypersensitivity to LPS in AF adult animals. Investigation of possible epigenetic programming mechanisms by alcohol revealed neonatal alcohol decreased several repressive regulators of transcription in hypothalamic microglia, while concomitantly increasing histone H3 acetyl lysine 9 (H3K9ac) enrichment at TNF-α and IL-6 promoter regions. Importantly, adult hypothalamic microglia from AF animals showed enduring increases in H3K9ac enrichment of TNF-α and IL-6 promoters both at baseline and after LPS exposure, suggesting a possible epigenetic mechanism for the long-term immune disruption due to hypothalamic microglial priming.

The Role of Interleukin-10 in Mediating the Effect of Immune Challenge on Mouse Gonadotropin-Releasing Hormone Neurons In Vivo.

Immune challenge alters neural functioning via cytokine production. Inflammation has profound impact on the central regulation of fertility, but the mechanisms involved are not clearly defined. The anti-inflammatory cytokine interleukin (IL)-10 is responsible for balancing the immune response in the brain. To examine whether IL-10 has an effect on the function of the gonadotropin-releasing hormone (GnRH) neurons, we first examined the effect of immune responses with distinct cytokine profiles, such as the T cell-dependent (TD) and T cell-independent (TI) B-cell response. We investigated the effect of the TD and TI immune responses on ERK1/2 phosphorylation in GnRH neurons by administering fluorescein isothiocyanate/keyhole limpet hemocyanin (KLH-FITC) or dextran-FITC to female mice. Although dextran-FITC had no effect, KLH-FITC induced ERK1/2 phosphorylation in GnRH neurons after 6 d. KLH-FITC treatment increased the levels of IL-10 in the hypothalamus (HYP), but this treatment did not cause lymphocyte infiltration or an increase in the levels of proinflammatory cytokines. In IL-10 knock-out (KO) mice, KLH-FITC-induced ERK1/2 phosphorylation in the GnRH neurons was absent. We also showed that in IL-10 KO mice, the estrous cycle was disrupted. Perforated patch-clamp recordings from GnRH-GFP neurons, IL-10 immunohistochemistry, and in vitro experiments on acute brain slices revealed that IL-10 can directly alter GnRH neuron firing and induce ERK1/2 phosphorylation. These observations demonstrate that IL-10 plays a role in influencing signaling of GnRH neurons in the TD immune response. These results also provide the first evidence that IL-10 can directly alter the function of GnRH neurons and may help the maintenance of the integrity of the estrous cycle.

Diet-Induced Obesity Elicits Macrophage Infiltration and Reduction in Spine Density in the Hypothalami of Male but Not Female Mice.

Increasing prevalence in obesity has become a significant public concern. C57BL/6J mice are prone to diet-induced obesity (DIO) when fed high-fat diet (HFD), and develop chronic inflammation and metabolic syndrome, making them a good model to analyze mechanisms whereby obesity elicits pathologies. DIO mice demonstrated profound sex differences in response to HFD with respect to inflammation and hypothalamic function. First, we determined that males are prone to DIO, while females are resistant. Ovariectomized females, on the other hand, are susceptible to DIO, implying protection by ovarian hormones. Males, but not females, exhibit changes in hypothalamic neuropeptide expression. Surprisingly, ovariectomized females remain resistant to neuroendocrine changes, showing that ovarian hormones are not necessary for protection. Second, obese mice exhibit sex differences in DIO-induced inflammation. Microglial activation and peripheral macrophage infiltration is seen in the hypothalami of males, while females are protected from the increase in inflammatory cytokines and do not exhibit microglia morphology changes nor monocyte-derived macrophage infiltration, regardless of the presence of ovarian hormones. Strikingly, the anti-inflammatory cytokine IL-10 is increased in the hypothalami of females but not males. Third, this study posits a potential mechanism of obesity-induced impairment of hypothalamic function whereby obese males exhibit reduced levels of synaptic proteins in the hypothalamus and fewer spines in GnRH neurons, located in the areas exhibiting macrophage infiltration. Our studies suggest that inflammation-induced synaptic remodeling is potentially responsible for hypothalamic impairment that may contribute to diminished levels of gonadotropin hormones, testosterone, and sperm numbers, which we observe and corresponds to the observations in obese humans. Taken together, our data implicate neuro-immune mechanisms underlying sex-specific differences in obesity-induced impairment of the hypothalamic function with potential consequences for reproduction and fertility.

Autoimmune pituitary involvement in Prader-Willi syndrome: new perspective for further research.

The role of antipituitary antibodies in the pathophysiology of pituitary hormone deficiency has been increasingly elucidated over the last decade. Prader-Willi syndrome is a genetic disorder which includes hypothalamic/pituitary dysfunction as one of its main features. We looked for autoimmune pituitary involvement in 55 adults with Prader-Willi syndrome, discovering that about 30% of them have a positive titer of antipituitary antibodies. Although the presence of these autoantibodies could only be an "epiphenomenon", our results suggest that autoimmune mechanisms might contribute, at least in part, to the pituitary impairment of Prader-Willi syndrome, and in addition to genetically determined dysfunction of the central nervous system. This paper provides a new perspective on pituitary impairment in these patients, suggesting that the search for hypophisitis could be a reasonable and interesting field for further research.

Sex differences in effects of gestational polychlorinated biphenyl exposure on hypothalamic neuroimmune and neuromodulator systems in neonatal rats.

Polychlorinated biphenyls (PCBs) are ubiquitous in the environment and exposure to them is associated with immune, endocrine and neural dysfunction. Effects of PCBs on inflammation and immunity are best described in spleen and blood, with fewer studies on neural tissues. This is an important gap in knowledge, as molecules typically associated with neuroinflammation also serve neuromodulatory roles and interact with hormones in normal brain development. The current study used Sprague-Dawley rats to assess whether gestational PCB exposure altered hypothalamic gene expression and serum cytokine concentration in neonatal animals given an immune challenge. Dams were fed wafers containing a mixture of PCBs at an environmentally relevant dose and composition (20 µg/kg, 1:1:1 Aroclor 1242:1248:1254) or oil vehicle control throughout their pregnancy. One day old male and female offspring were treated with an inflammatory challenge (lipopolysaccharide, LPS, 50 µg/kg, sc) or saline vehicle control approximately 3.5 h prior to tissue collection. Across both basal and activated inflammatory states, PCB exposure caused greater expression of a subset of inflammatory genes in the hypothalamus and lower expression of genes involved in dopamine, serotonin, and opioid systems compared to oil controls. PCB exposure also altered reactions to inflammatory challenge: it reversed the normal decrease in Esr2 hypothalamic expression and induced an abnormal increase in IL-1b and IL-6 serum concentration in response to LPS. Many of these effects were sex specific. Given the potential long-term consequences of neuroimmune disruption, our findings demonstrate the need for further research.