Differential expression of various cytokine receptors in the brain after stimulation with LPS in young and old mice

Dynamics of cachexia-associated inflammatory changes in the brain accompanying intra-abdominal fibrosarcoma growth in Wistar rats

Accumulated data indicate that inflammation affecting brain structures participates in the development of cancer-related cachexia. However, the mechanisms responsible for the induction and progression of cancer-related neuroinflammation are still not fully understood. Therefore, we studied the time-course of neuroinflammation in selected brain structures and cachexia development in tumor-bearing rats. After tumor cells inoculation, specifically on the 7th, 14th, 21st, and 28th day of tumor growth, we assessed the presence of cancer-associated cachexia in rats. Changes in gene expression of inflammatory factors were studied in selected regions of the hypothalamus, brain stem, and circumventricular organs. We showed that the initial stages of cancer growth (7th and 14th day after tumor cells inoculation), are not associated with cachexia, or increased expression of inflammatory molecules in the brain. Even when we did not detect cachexia in tumor-bearing rats by the 21st day of the experiment, the inflammatory brain reaction had already started, as we found elevated levels of interleukin 1 beta, interleukin 6, tumor necrosis factor alpha, and glial fibrillary acidic protein mRNA levels in the nucleus of the solitary tract. Furthermore, we found increased interleukin 1 beta expression in the locus coeruleus and higher allograft inflammatory factor 1 expression in the vascular organ of lamina terminalis. Ultimately, the most pronounced manifestations of tumor growth were present on the 28th day post-inoculation of tumor cells. In these animals, we detected cancer-related cachexia and significant increases in interleukin 1 beta expression in all brain areas studied. We also observed significantly decreased expression of the glial cell activation markers allograft inflammatory factor 1 and glial fibrillary acidic protein in most brain areas of cachectic rats. In addition, we showed increased expression of cluster of differentiation 163 and cyclooxygenase 2 mRNA in the hypothalamic paraventricular nucleus, A1/C1 neurons, and area postrema of cachectic rats. Our data indicate that cancer-related cachexia is associated with complex neuroinflammatory changes in the brain. These changes can be found in both hypothalamic as well as extrahypothalamic structures, while their extent and character depend on the stage of tumor growth.

The evolutionarily conserved miRNA-137 targets the neuropeptide hypocretin/orexin and modulates the wake to sleep ratio

The hypocretin (Hcrt, also known as orexin) neuropeptides regulate sleep and wake stability, and disturbances of Hcrt can lead to sleep disorders. MicroRNAs (miRNAs) are short noncoding RNAs that fine-tune protein expression levels, and miRNA-based therapeutics are emerging. We report a functional interaction between miRNA (miR-137) and Hcrt. We demonstrate that intracellular miR-137 levels in Hcrt neurons regulate Hcrt expression with downstream effects on wakefulness. Specifically, lowering of miR-137 levels increased wakefulness in mice. We further show that the miR-137:Hcrt interaction is conserved across mice and humans, that miR-137 also regulates sleep–wake balance in zebrafish, and that the MIR137 locus is genetically associated with sleep duration in humans. Together, our findings reveal an evolutionarily conserved sleep–wake regulatory role of miR-137.

Hypocretin (Hcrt), also known as orexin, neuropeptide signaling stabilizes sleep and wakefulness in all vertebrates. A lack of Hcrt causes the sleep disorder narcolepsy, and increased Hcrt signaling has been speculated to cause insomnia, but while the signaling pathways of Hcrt are relatively well-described, the intracellular mechanisms that regulate its expression remain unclear. Here, we tested the role of microRNAs (miRNAs) in regulating Hcrt expression. We found that miR-137, miR-637, and miR-654-5p target the human HCRT gene. miR-137 is evolutionarily conserved and also targets mouse Hcrt as does miR-665. Inhibition of miR-137 specifically in Hcrt neurons resulted in Hcrt upregulation, longer episodes of wakefulness, and significantly longer wake bouts in the first 4 h of the active phase. IL-13 stimulation upregulated endogenous miR-137, while Hcrt mRNA decreased both in vitro and in vivo. Furthermore, knockdown of miR-137 in zebrafish substantially increased wakefulness. Finally, we show that in humans, the MIR137 locus is genetically associated with sleep duration. In conclusion, these results show that an evolutionarily conserved miR-137:Hcrt interaction is involved in sleep–wake regulation.

IL-13Rα2 Status Predicts GB-13 (IL13.E13K-PE4E) Efficacy in High-Grade Glioma

High-grade gliomas (HGG) are devastating diseases in children and adults. In the pediatric population, diffuse midline gliomas (DMG) harboring H3K27 alterations are the most aggressive primary malignant brain tumors. With no effective therapies available, children typically succumb to disease within one year of diagnosis. In adults, glioblastoma (GBM) remains largely intractable, with a median survival of approximately 14 months despite standard clinical care of radiation and temozolomide. Therefore, effective therapies for these tumors remain one of the most urgent and unmet needs in modern medicine. Interleukin 13 receptor subunit alpha 2 (IL-13Rα2) is a cell-surface transmembrane protein upregulated in many HGGs, including DMG and adult GBM, posing a potentially promising therapeutic target for these tumors. In this study, we investigated the pharmacological effects of GB-13 (also known as IL13.E13K-PE4E), a novel peptide-toxin conjugate that contains a targeting moiety designed to bind IL-13Rα2 with high specificity and a point-mutant cytotoxic domain derived from Pseudomonas exotoxin A. Glioma cell lines demonstrated a spectrum of IL-13Rα2 expression at both the transcript and protein level. Anti-tumor effects of GB-13 strongly correlated with IL-13Rα2 expression and were reflected in apoptosis induction and decreased cell proliferation in vitro. Direct intratumoral administration of GB-13 via convection-enhanced delivery (CED) significantly decreased tumor burden and resulted in prolonged survival in IL-13Rα2-upregulated orthotopic xenograft models of HGG. In summary, administration of GB-13 demonstrated a promising pharmacological response in HGG models both in vitro and in vivo in a manner strongly associated with IL-13Rα2 expression, underscoring the potential of this IL-13Rα2-targeted therapy in a subset of HGG with increased IL-13Rα2 levels.

Neurotensin agonist PD 149163 modulates the neuroinflammation induced by bacterial endotoxin lipopolysaccharide in mice model

OBJECTIVE

The disruption of bidirectional communication between neuroendocrine and immune components by stressors leads to mental problems. The immunomodulation therapy of neuroinflammation-led psychiatric illness is an emerging area of research. Therefore, the present study aimed to evaluate immune modulation efficacy of PD 149163 (PD) against the lipopolysaccharide (LPS)-induced neuroinflammation.

MATERIALS AND METHODS

The Swiss albino mice (female/12 weeks) were divided into six groups (6 mice/group): (I) Control: 0.9% NaCl; (II) LPS: 1 mg/kg BW, for 5 days; (III) LPS + PD Low: LPS 1 mg/kg BW (for 5 days) after that PD 100 µg/kg BW (for 21 days); (IV) LPS + PD High: LPS 1 mg/kg BW (for 5 days) after that PD 300 µg/kg BW (for 21 days); (V) PD Low: PD 100 µg/kg BW (for 21 days); (VI) PD High: PD 300 µg/kg BW (for 21 days). All treatments were given intraperitoneal.

RESULTS

The LPS-induced weight loss (body and brain) was normalized to control after PD treatment. The PD enhanced superoxide dismutase (SOD) activity while decreased lipid hydroperoxide (LOOH) level altered in LPS-exposed mice. The significantly increased pro-inflammatory cytokines (IL-6 and TNF-α) in LPS exposure were also decreased by PD. Likewise, the LPS-induced HPA axis activation was stabilized by PD. In the hippocampus, the pyramidal cell layer thickness, pyramidal neurons number and size of CA1 and CA3 regions were reduced along with misalignment, shrinkage, and impairment of cytoarchitecture. In the co-treated group, the LPS-induced hippocampus disruption was reversed after PD exposure.

CONCLUSION

We suggested that the PD modulates the LPS-induced neuroinflammation and psychiatric illness in a dose-dependent manner.

Influence of peripheral lipopolysaccharide (LPS) on feed intake, body temperature and hypothalamic expression of neuropeptides involved in appetite regulation in broilers and layer chicks

1. This study examined the expression of genes related to appetite-regulating neuropeptides in the hypothalamus of broiler and layer chicks (Gallus gallus) after intraperitoneal (IP) injection of lipopolysaccharide (LPS). 2. Both broiler and layer chicks received (n = 10 per group) LPS at doses of 0 and 200 µg and feed intake was measured up to 6 h after injection. In a further experiment, (n = 8 per group) mRNA abundance of some hypothalamic neuropeptides was measured 2 h after injection. The rectal temperature of each chick was measured before and 2 h post-injection. 3. Feed intake was significantly decreased by LPS from 2 h after injection and thereafter, while the rectal temperature did not change. 4. LPS decreased the expression of appetite-enhancing neuropeptides: neuropeptide Y (NPY) and agouti-related peptide (AgRP) in broilers and, NPY in layer chicks. The expression of appetite-suppressing neuropeptides (corticotrophin-releasing factor (CRF), proopiomelanocortin (POMC) and, cocaine and amphetamine regulated-transcript (CART) was not changed in broilers, while CRF tended to decrease and POMC was significantly decreased in layers. The abundance of the cytokine tumour necrosis factor-alpha (TNF-α) did not change in broilers but was decreased in layers. 5. The findings indicated that the reduction in gene expression of hypothalamic appetite-enhancing neuropeptides NPY and AgRP is responsible for anorexia caused by LPS at a dose that did not influence body temperature.

Microglial and peripheral immune priming is partially sexually dimorphic in adolescent mouse offspring exposed to maternal high-fat diet

Background

Maternal nutrition is critical for proper fetal development. While increased nutrient intake is essential during pregnancy, an excessive consumption of certain nutrients, like fat, can lead to long-lasting detrimental consequences on the offspring. Animal work investigating the consequences of maternal high-fat diet (mHFD) revealed in the offspring a maternal immune activation (MIA) phenotype associated with increased inflammatory signals. This inflammation was proposed as one of the mechanisms causing neuronal circuit dysfunction, notably in the hippocampus, by altering the brain-resident macrophages—microglia. However, the understanding of mechanisms linking inflammation and microglial activities to pathological brain development remains limited. We hypothesized that mHFD-induced inflammation could prime microglia by altering their specific gene expression signature, population density, and/or functions.

Methods

We used an integrative approach combining molecular (i.e., multiplex-ELISA, rt-qPCR) and cellular (i.e., histochemistry, electron microscopy) techniques to investigate the effects of mHFD (saturated and unsaturated fats) vs control diet on inflammatory priming, as well as microglial transcriptomic signature, density, distribution, morphology, and ultrastructure in mice. These analyses were performed on the mothers and/or their adolescent offspring at postnatal day 30.

Results

Our study revealed that mHFD results in MIA defined by increased circulating levels of interleukin (IL)-6 in the mothers. This phenotype was associated with an exacerbated inflammatory response to peripheral lipopolysaccharide in mHFD-exposed offspring of both sexes. Microglial morphology was also altered, and there were increased microglial interactions with astrocytes in the hippocampus CA1 of mHFD-exposed male offspring, as well as decreased microglia-associated extracellular space pockets in the same region of mHFD-exposed offspring of the two sexes. A decreased mRNA expression of the inflammatory-regulating cytokine Tgfb1 and microglial receptors Tmem119, Trem2, and Cx3cr1 was additionally measured in the hippocampus of mHFD-exposed offspring, especially in males.

Conclusions

Here, we described how dietary habits during pregnancy and nurturing, particularly the consumption of an enriched fat diet, can influence peripheral immune priming in the offspring. We also found that microglia are affected in terms of gene expression signature, morphology, and interactions with the hippocampal parenchyma, in a partially sexually dimorphic manner, which may contribute to the adverse neurodevelopmental outcomes on the offspring.

Interferon-γ potentiates GABAA receptor-mediated inhibitory currents in rat hippocampal CA1 pyramidal neurons

The neural transmission and plasticity can be differentially modulated by various elements of the immune system. Interferon-γ (IFN-γ) is a "pro-inflammatory" cytokine mainly produced by T lymphocytes, activates its corresponding receptor and plays important roles under both homeostatic and inflammatory conditions. However, the impact of IFN-γ on the γ-aminobutyric acid (GABA)-mediated currents in the hippocampus, a major brain region involved in the cognitive function, has not been investigated. Here we detected abundant expression of both IFN-γ receptor subunit gene transcripts (Ifngr1 and Ifngr2) in the rat hippocampus by quantitative PCR. In addition, we pre-incubated rat hippocampal slices with IFN-γ (100 ng/ml) and recorded GABA-activated spontaneous and miniature postsynaptic inhibitory currents (sIPSCs and mIPSCs) and tonic currents in hippocampal CA1 pyramidal neurons by the whole-cell patch-clamp method. The pre-incubation with IFN-γ increased the frequency but not the mean amplitude, rise time or decay time of both sIPSCs and mIPSCs in hippocampal CA1 pyramidal neurons, suggesting a presynaptic effect of IFN-γ. Moreover, the GABA-activated tonic currents were enhanced by IFN-γ. In conclusion, the potentiation of GABAergic currents in hippocampal neurons by IFN-γ may contribute to the disturbed neuronal excitability and cognitive dysfunction during neuroinflammation.

Effect of Central Injection of Neostigmine on the Bacterial Endotoxin Induced Suppression of GnRH/LH Secretion in Ewes during the Follicular Phase of the Estrous Cycle

Induced by a bacterial infection, an immune/inflammatory challenge is a potent negative regulator of the reproduction process in females. The reduction of the synthesis of pro-inflammatory cytokine is considered as an effective strategy in the treatment of inflammatory induced neuroendocrine disorders. Therefore, the effect of direct administration of acetylcholinesterase inhibitor—neostigmine—into the third ventricle of the brain on the gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) secretions under basal and immune stress conditions was evaluated in this study. In the study, 24 adult, 2-years-old Blackhead ewes during the follicular phase of their estrous cycle were used. Immune stress was induced by the intravenous injection of LPS Escherichia coli in a dose of 400 ng/kg. Animals received an intracerebroventricular injection of neostigmine (1 mg/animal) 0.5 h before LPS/saline treatment. It was shown that central administration of neostigmine might prevent the inflammatory-dependent decrease of GnRH/LH secretion in ewes and it had a stimulatory effect on LH release. This central action of neostigmine is connected with its inhibitory action on local pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)α synthesis in the hypothalamus, which indicates the importance of this mediator in the inhibition of GnRH secretion during acute inflammation.

Role of Corticotropin Releasing Factor in the Neuroimmune Mechanisms of Depression: Examination of Current Pharmaceutical and Herbal Therapies

Approximately 3% of the world population suffers from depression, which is one of the most common form of mental disorder. Recent findings suggest that an interaction between the nervous system and immune system might be behind the pathophysiology of various neurological and psychiatric disorders, including depression. Neuropeptides have been shown to play a major role in mediating response to stress and inducing immune activation or suppression. Corticotropin releasing factor (CRF) is a major regulator of the hypothalamic pituitary adrenal (HPA) axis response. CRF is a stress-related neuropeptide whose dysregulation has been associated with depression. In this review, we summarized the role of CRF in the neuroimmune mechanisms of depression, and the potential therapeutic effects of Chinese herbal medicines (CHM) as well as other agents. Studying the network of CRF and immune responses will help to enhance our understanding of the pathogenesis of depression. Additionally, targeting this important network may aid in developing novel treatments for this debilitating psychiatric disorder.

Fish pituitary show an active immune response after in vitro stimulation with Vibrio bacterin

The pituitary is a central organ of the neuro-endocrine system in fish that plays critical roles in various physiological processes, including stress response and behavior. Although it is known that pituitary hormones can have a direct or indirect influence stimulating or suppressing the immune responses, whether there is a local immune response in the pituitary or what is the effect of the immune stimulus on the pituitary function in fish is unknown. With the aim to understand the interaction between the immune responses and the endocrine axes at the pituitary level, particularly the Hypothalamus-Pituitary-Interrenal (HPI) axis, pituitaries of rainbow trout (Oncorhynchus mykiss) were cultured in vitro, incubated with bacterin, or bacterin plus CRH, cortisol, human recombinant IL1β, or spleen medium for 3 h, and then genes involved in pro-inflammation (il1β, il8, tnfα1, ifnγ), anti-inflammation (tgfβ1b, il10), immune modulation (mhcIIa, c3, mif) and stress response (crhbp, pomca, pomcb, gr1) were tested. Data showed that, incubation with bacterin alone and bacterin plus recombinant IL1β or CRH, as well as medium from bacterin treated spleen caused significant up-regulation of pro-inflammatory genes il1β and il8, while down-regulated the anti-inflammatory gene tgfβ1b. Besides, recombinant IL1β plus bacterin or alone caused raise of mhcIIa and tnfa, respectively. On the contrary, just a slight or even no alteration was recorded in the expression of stress response genes including crhbp, pomca, pomcb and gr1 in the in vitro cultured trout pituitary following this stimulation. These results suggest a local immune gene equipment in the pituitary of fish, and the potential for fish pituitary to develop both innate and adaptive immune responses, whereas that immune stimulation was not able to evoke a significant endocrine stress response in vitro.

Hypothalamic Inflammation at a Crossroad of Somatic Diseases

Various hypothalamic nuclei function as central parts of regulators that maintain homeostasis of the organism. Recently, findings have shown that inflammation in the hypothalamus may significantly affect activity of these homeostats and consequently participate in the development of various somatic diseases such as obesity, diabetes, hypertension, and cachexia. In addition, hypothalamic inflammation may also affect aging and lifespan. Identification of the causes and mechanisms involved in the development of hypothalamic inflammation creates not only a basis for better understanding of the etiopathogenesis of somatic diseases, but for the development of new therapeutic approaches for their treatment, as well.

Neostigmine Attenuates Proinflammatory Cytokine Expression in Preoptic Area but Not Choroid Plexus during Lipopolysaccharide-Induced Systemic Inflammation

The study was designed to examine whether the administration of neostigmine (0.5 mg/animal), a peripheral inhibitor of acetylcholinesterase (AChE), during an immune/inflammatory challenge provoked by intravenous injection of bacterial endotoxin-lipopolysaccharide (LPS; 400 ng/kg)-attenuates the synthesis of proinflammatory cytokines in the ovine preoptic area (POA), the hypothalamic structure playing an essential role in the control of the reproduction process, and in the choroid plexus (CP), a multifunctional organ sited at the interface between the blood and cerebrospinal fluid in the ewe. Neostigmine suppressed (p < 0.05) LPS-stimulated synthesis of cytokines such as interleukin- (IL-) 1β, IL-6, and tumor necrosis factor (TNF) α in the POA, and this effect was similar to that induced by the treatment with systemic AChE inhibitor-donepezil (2.5 mg/animal). On the other hand, both AChE inhibitors did not influence the gene expression of these cytokines and their corresponding receptors in the CP. It was found that this structure seems to not express the neuronal acetylcholine (ACh) receptor subunit alpha-7, required for anti-inflammatory action of ACh. The mechanism of action involves inhibition of the proinflammatory cytokine synthesis on the periphery as well as inhibition of their de novo synthesis rather in brain microvessels and not in the CP. In conclusion, it is suggested that the AChE inhibitors incapable of reaching brain parenchyma might be used in the treatment of neuroinflammatory processes induced by peripheral inflammation.

Resveratrol modulates response against acute inflammatory stimuli in aged mouse brain

With upcoming age, the capability to fight against harmful stimuli decreases and the organism becomes more susceptible to infections and diseases. Here, the objective was to demonstrate the effect of dietary resveratrol in aged mice in potentiating brain defenses against LipoPolySaccharide (LPS). Acute LPS injection induced a strong proinflammatory effect in 24-months-old C57/BL6 mice hippocampi, increasing InterLeukin (Il)-6, Tumor Necrosis Factor-alpha (Tnf-α), Il-1β, and C-X-C motif chemokine (Cxcl10) gene expression levels. Resveratrol induced higher expression in those cytokines regarding to LPS. Oxidative Stress (OS) markers showed not significant changes after LPS or resveratrol, although for resveratrol treated groups a slight increment in most of the parameters studies was observed, reaching signification for NF-kB protein levels and iNOS expression. However, Endoplasmic Reticulum (ER) stress markers demonstrated significant changes in resveratrol-treated mice after LPS treatment, specifically in eIF2α, BIP, and ATF4. Moreover, as described, resveratrol is able to inhibit the mechanistic Target of Rapamycin (mTOR) pathway and this effect could be linked to (eIF2α) phosphorylation and the increase in the expression of the previously mentioned proinflammatory genes as a response to LPS treatment in aged animals. In conclusion, resveratrol treatment induced a different cellular response in aged animals when they encountered acute inflammatory stimuli.

Pathophysiological and behavioral effects of systemic inflammation in aged and diseased rodents with relevance to delirium: A systematic review

Delirium is a frequent outcome for aged and demented patients that suffer a systemic inflammatory insult. Animal models that reconstruct these etiological processes have potential to provide a better understanding of the pathophysiology of delirium. Therefore, we systematically reviewed animal studies in which systemic inflammation was superimposed on aged or diseased animal models. In total, 77 studies were identified. Aged animals were challenged with a bacterial endotoxin in 29 studies, 25 studies superimposed surgery on aged animals, and in 6 studies a bacterial infection, Escherichia coli (E. coli), was used. Diseased animals were challenged with a bacterial endotoxin in 15 studies, two studies examined effects of the cytokine IL-1β, and one study used polyinosinic:polycytidilic acid (poly I:C). This systematic review analyzed the impact of systemic inflammation on the production of inflammatory and neurotoxic mediators in peripheral blood, cerebrospinal fluid (CSF), and on the central nervous system (CNS). Moreover, concomitant behavioral and cognitive symptoms were also evaluated. Finally, outcomes of behavioral and cognitive tests from animal studies were compared to features and symptoms present in delirious patients.

Are the emergence of affective disturbances in neuropathic pain states contingent on supraspinal neuroinflammation?

Neuro-immune interactions contribute to the pathogenesis of neuropathic pain due to peripheral nerve injury. A large body of preclinical evidence supports the idea that the immune system acts to modulate the sensory symptoms of neuropathy at both peripheral and central nervous system sites. The potential involvement of neuro-immune interactions in the highly debilitating affective disturbances of neuropathic pain, such as depression, anhedonia, impaired cognition and reduced motivation has received little attention. This is surprising given the widely accepted view that sickness behaviour, depression, cognitive impairment and other neuropsychiatric conditions can arise from inflammatory mechanisms. Moreover, there is a set of well-described immune-to-brain transmission mechanisms that explain how peripheral inflammation can lead to supraspinal neuroinflammation. In the last 5years increasing evidence has emerged that peripheral nerve injury induces supraspinal changes in cytokine or chemokine expression and alters glial cell activity. In this systematic review, based on strong preclinical evidence, we advance the argument that the emergence of affective disturbances in neuropathic pain states are contingent on pro-inflammatory mediators in the interconnected hippocampal-medial prefrontal circuitry that subserve affective behaviours. We explore how dysregulation of inflammatory mediators in these networks may result in affective disturbances through a wide variety of neuromodulatory mechanisms. There are also promising results from clinical trials showing that anti-inflammatory agents have efficacy in the treatment of a variety of neuropsychiatric conditions including depression and appear suited to sub-groups of patients with elevated pro-inflammatory profiles. Thus, although further research is required, aggressively targeting supraspinal pro-inflammatory mediators at critical time-points in appropriate clinical populations is likely to be a novel avenue to treat debilitating affective disturbances in neuropathic conditions.

Uninephrectomy in Rats on a Fixed Food Intake Potentiates Both Anorexia and Circulating Cytokine Subsets in Response to LPS

Recent human studies have suggested that mild reduction in kidney function can alter immune response and increase susceptibility to infection. The role of mild reduction in kidney function in altering susceptibility to bacterial lipopolysaccharide (LPS) responses was investigated in uninephrectomized rats compared to Sham-operated controls rats 4 weeks after surgery. Throughout the 4 weeks, all rats were maintained under mild food restriction at 90% of ad libitum intake to ensure the same caloric intake in both groups. In comparison to Sham, uninephrectomy (UniNX) potentiated LPS-induced anorexia by 2.1-fold. The circulating anorexigenic cytokines granulocyte-macrophage colony stimulating factor, interferon-γ, tumor necrosis factor-α, and complement-derived acylation-stimulating protein were elevated after LPS in UniNX animals compared to Sham animals. Interleukin(IL)1β and IL6 pro-inflammatory cytokines were transiently increased. Anti-inflammatory cytokines IL4 and IL10 did not differ or had a tendency to be lower in UniNX group compared to Sham animals. LPS-induced anorexia was associated with increased anorexigenic neuropeptides mRNA for pro-opiomelanocortin, corticotrophin-releasing factor, and cocaine–amphetamine-regulated transcript in the hypothalamus of both Sham and UniNX groups, but at higher levels in the UniNX group. Melanocortin-4-receptor mRNA was markedly increased in the UniNX group, which may have contributed to the enhanced anorexic response to LPS of the UniNX group. In summary, UniNX potentiates pro-inflammatory cytokine production, anorexia, and selected hypothalamic anorexigenic neuropeptides in response to LPS.

The central role of hypothalamic inflammation in the acute illness response and cachexia

When challenged with a variety of inflammatory threats, multiple systems across the body undergo physiological responses to promote defense and survival. The constellation of fever, anorexia, and fatigue is known as the acute illness response, and represents an adaptive behavioral and physiological reaction to stimuli such as infection. On the other end of the spectrum, cachexia is a deadly and clinically challenging syndrome involving anorexia, fatigue, and muscle wasting. Both of these processes are governed by inflammatory mediators including cytokines, chemokines, and immune cells. Though the effects of cachexia can be partially explained by direct effects of disease processes on wasting tissues, a growing body of evidence shows the central nervous system (CNS) also plays an essential mechanistic role in cachexia. In the context of inflammatory stress, the hypothalamus integrates signals from peripheral systems, which it translates into neuroendocrine perturbations, altered neuronal signaling, and global metabolic derangements. Therefore, we will discuss how hypothalamic inflammation is an essential driver of both the acute illness response and cachexia, and why this organ is uniquely equipped to generate and maintain chronic inflammation. First, we will focus on the role of the hypothalamus in acute responses to dietary and infectious stimuli. Next, we will discuss the role of cytokines in driving homeostatic disequilibrium, resulting in muscle wasting, anorexia, and weight loss. Finally, we will address mechanisms and mediators of chronic hypothalamic inflammation, including endothelial cells, chemokines, and peripheral leukocytes.

Brain mechanisms of sympathetic activation in heart failure: Roles of the renin‑angiotensin system, nitric oxide and pro‑inflammatory cytokines (Review)

Patients with chronic heart failure (CHF) have an insufficient perfusion to the peripheral tissues due to decreased cardiac output. The compensatory mechanisms are triggered even prior to the occurrence of clinical symptoms, which include activation of the sympathetic nervous system (SNS) and other neurohumoral factors. However, the long‑term activation of the SNS contributes to progressive cardiac dysfunction and has toxic effects on the cardiomyocytes. The mechanisms leading to the activation of SNS include changes in peripheral baroreceptor and chemoreceptor reflexes and the abnormal regulation of sympathetic nerve activity (SNA) in the central nervous system (CNS). Recent studies have focused on the role of brain mechanisms in the regulation of SNA and the progression of CHF. The renin‑angiotensin system, nitric oxide and pro‑inflammatory cytokines were shown to be involved in the abnormal regulation of SNA in the CNS. The alteration of these neurohumoral factors during CHF influences the activity of neurons in the autonomic regions and finally increase the sympathetic outflow. The present review summarizes the brain mechanisms contributing to sympathoexcitation in CHF.

Assessment of in vivo antimalarial activities of some selected medicinal plants from Turkey

Resistant infections lead to increased necessity of searching novel drugs and drug combinations. The purpose of this paper was to investigate antimalarial properties of some selected medicinal plants that have been traditionally used in Turkey for antipyretic and analgesic purposes. Lavandula stoecheas subsp. cariensis, Phlomis nissolii, Phlomis bourgaei, Phlomis leucophracta, Centaurea hierapolitana, Centaurea polyclada, Centaurea lydia, Scrophularia cryptophila, Scrophularia depauperata, Scrophularia floribunda, Rubia davisiana, and Alkanna tinctoria subsp. subleiocarpa were investigated for their in vivo antimalarial activities in mice infected with Plasmodium yoelii. Two hundred fifty to 500 mg/kg doses of plant extracts were given to mice as a single daily dose for 4 days. P. nissolii water extract, C. lydia chloroform extract, S. cryptophila ethanol extract, and C. polyclada methanol extract showed antimalarial activity with reducing parasitaemia. The chemotherapeutic effects of plant extracts ranged between 13.5% and 66.91%. The chemosuppressions exerted by combined plant extracts of P. nissolii, S. cryptophila, and C. lydia with C. polyclada methanol extract were detected as 51.25%, 57.33%, and 58.33%, respectively. Investigation of cytotoxic activities against brine shrimps revealed that methanol extract of C. polycada, chloroform extract of C. lydia, and ethanol extract of S. cryptophila showed cytotoxic activities, while water extract of P. nissolii was not active against brine shrimps.

Proinflammatory cytokines, aging, and age-related diseases

Inflammation is a physiological process that repairs tissues in response to endogenous or exogenous aggressions. Nevertheless, a chronic state of inflammation may have detrimental consequences. Aging is associated with increased levels of circulating cytokines and proinflammatory markers. Aged-related changes in the immune system, known as immunosenescence, and increased secretion of cytokines by adipose tissue, represent the major causes of chronic inflammation. This phenomenon is known as "inflamm-aging." High levels of interleukin (IL)-6, IL-1, tumor necrosis factor-α, and C-reactive protein are associated in the older subject with increased risk of morbidity and mortality. In particular, cohort studies have indicated TNF-α and IL-6 levels as markers of frailty. The low-grade inflammation characterizing the aging process notably concurs at the pathophysiological mechanisms underlying sarcopenia. In addition, proinflammatory cytokines (through a variety of mechanisms, such as platelet activation and endothelial activation) may play a major role in the risk of cardiovascular events. Dysregulation of the inflammatory pathway may also affect the central nervous system and be involved in the pathophysiological mechanisms of neurodegenerative disorders (eg, Alzheimer disease).The aim of the present review was to summarize different targets of the activity of proinflammatory cytokines implicated in the risk of pathological aging.

Molecular mechanisms of cachexia in chronic disease

Cachexia is a metabolic syndrome that manifests with excessive weight loss and disproportionate muscle wasting. It is related to many different chronic diseases, such as cancer, infections, liver disease, inflammatory bowel disease, cardiac disease, chronic obstructive pulmonary disease, chronic renal failure and rheumatoid arthritis. Cachexia is linked with poor outcome for the patients. In this article, we explore the role of the hypothalamus, liver, muscle tissue and adipose tissue in the pathogenesis of this syndrome, particularly concentrating on the role of cytokines, hormones and cell energy-controlling pathways (such as AMPK, PI3K/Akt and mTOR). We also look at possible future directions for therapeutic strategies.

Astrocyte reactivity to unconjugated bilirubin requires TNF-α and IL-1β receptor signaling pathways

Jaundice and sepsis are common neonatal conditions that can lead to neurodevelopment sequelae, namely if present at the same time. We have reported that tumor necrosis factor (TNF)-α and interleukin (IL)-1β are produced by cultured neurons and mainly by glial cells exposed to unconjugated bilirubin (UCB). The effects of these cytokines are mediated by cell surface receptors through a nuclear factor (NF)-κB-dependent pathway that we have showed to be activated by UCB. The present study was designed to evaluate the role of TNF-α and IL-1β signaling on astrocyte reactivity to UCB in rat cortical astrocytes. Exposure of astrocytes to UCB increased the expression of both TNF-α receptor (TNFR)1 and IL-1β receptor (IL-1R)1, but not TNFR2, as well as their activation, observed by augmented binding of receptors' molecular adaptors, TRAF2 and TRAF6, respectively. Silencing of TNFR1, using siRNA technology, or blockade of IL-1β cascade, using its endogenous antagonist, IL-1 receptor antagonist (IL-1ra), prevented UCB-induced cytokine release and NF-κB activation. Interestingly, lack of TNF-α signal transduction reduced UCB-induced cell death for short periods of incubation, although an increase was observed after extended exposure; in contrast, inhibition of IL-1β cascade produced a sustained blockade of astrocyte injury by UCB. Together, our data show that inflammatory pathways are activated during in vitro exposure of rat cortical astrocytes to UCB and that this activation is prolonged in time. This supports the concept that inflammatory pathways play a role in brain damage by UCB, and that they may represent important pharmacological targets.

Hypothalamic mechanisms in cachexia

The role of nutrition and balanced metabolism in normal growth, development, and health maintenance is well known. Patients affected with either acute or chronic diseases often show disorders of nutrient balance. In some cases, a devastating state of malnutrition known as cachexia arises, brought about by a synergistic combination of a dramatic decrease in appetite and an increase in metabolism of fat and lean body mass. Other common features that are not required for the diagnosis include decreases in voluntary movement, insulin resistance, and anhedonia. This combination is found in a number of disorders including cancer, cystic fibrosis, AIDS, rheumatoid arthritis, renal failure, and Alzheimer's disease. The severity of cachexia in these illnesses is often the primary determining factor in both quality of life, and in eventual mortality. Indeed, body mass retention in AIDS patients has a stronger association with survival than any other current measure of the disease. This has led to intense investigation of cachexia and the proposal of numerous hypotheses regarding its etiology. Most authors suggest that cytokines released during inflammation and malignancy act on the central nervous system to alter the release and function of a number of neurotransmitters, thereby altering both appetite and metabolic rate. This review will discuss the salient features of cachexia in human diseases, and review the mechanisms whereby inflammation alters the function of key brain regions to produce stereotypical illness behavior. The paper represents an invited review by a symposium, award winner or keynote speaker at the Society for the Study of Ingestive Behavior [SSIB] Annual Meeting in Portland, July 2009.

Regulation of cytokine signaling and T-cell recruitment in the aging mouse brain in response to central inflammatory challenge

Aging is often accompanied by increased levels of inflammatory molecules in the organism, but age-related changes in the brain response to inflammatory challenges still require clarification. We here investigated in mice whether cytokine signaling and T-cell neuroinvasion undergo age-related changes. We first analyzed the expression of molecules involved in T-cell infiltration and cytokine signaling regulation in the septum and hippocampus of 2-3 months and 20- to 24-month-old mice at 4h after intracerebroventricular injections of tumor necrosis factor (TNF)-alpha or interferon-gammaversus saline injections. Transcripts of the chemokine CXCL9, intercellular adhesion molecule (ICAM)-1 and suppressor of cytokine signaling molecules (SOCS) 1 and 3 were increased in both age groups after cytokine injection; microglia-derived matrix metalloproteinase (MMP) 12 mRNA was induced in old mice also after control saline injections. Age-related changes in ICAM-1 protein expression and T-cell infiltration were then analyzed in mice of 3-4, 8-9 and 15-16 months at 48h after TNF-alpha injections. ICAM-1 immunoreactivity, and Western blotting in striatum, septum, hippocampus and hypothalamus showed progressive age-related enhancement of TNF-alpha-elicited ICAM-1 upregulation. Double immunofluorescence revealed ICAM-1 expression in microglia and astrocytic processes. CD3(+), CD4(+) and CD8(+) T-cells exhibited progressive age-related increases in brain parenchyma and choroid plexus after cytokine exposure. The findings indicate that the brain responses to inflammatory challenges are not only preserved with advancing age, but also include gradual amplification of ICAM-1 expression and T-cell recruitment. The data highlight molecular and cellular correlates of age-related increase of brain sensitivity to inflammatory stimuli, which could be involved in altered brain vulnerability during aging.

Brain cytokines as neuromodulators in cardiovascular control

1. The role of cytokines in cardiovascular control, especially in neurogenic hypertension, has received considerable attention during the past few years. Brain cytokines have been shown to exert profound effects on neuronal activity. Recently, a number of studies have shown that administration of pro-inflammatory cytokines or anti-inflammatory cytokines into the central nervous system has a significant impact on sympathetic outflow, arterial pressure and cardiac remodelling in experimental models of hypertension and heart failure. 2. Our objective in this review is to present a succinct account of the effect of cytokines on neuronal activity and their role in cardiovascular disease. Furthermore, we propose a hypothesis for a neuromodulatory role of cytokines in the neural control of cardiovascular function.

A role for natural regulatory T cells in the pathogenesis of experimental cerebral malaria

Cerebral malaria (CM) is a serious complication of Plasmodium falciparum infection that is responsible for a significant number of deaths in children and nonimmune adults. A failure to control blood parasitemia and subsequent sequestration of parasites to brain microvasculature are thought to be key events in many CM cases. Here, we show for the first time, to our knowledge, that CD4(+)CD25(+)Foxp3(+) natural regulatory T (Treg) cells contribute to pathogenesis by modulating immune responses in P. berghei ANKA (PbA)-infected mice. Depletion of Treg cells with anti-CD25 monoclonal antibody protected mice from experimental CM. The accumulation of parasites in the vasculature and brain was reduced in these animals, resulting in significantly lower parasite burdens compared with control animals. Mice lacking Treg cells had increased numbers of activated CD4(+) and CD8(+) T cells in the spleen and lymph nodes, but CD8(+) T-cell recruitment to the brain was selectively reduced in these mice. Importantly, a non-Treg-cell source of interleukin-10 was critical in preventing experimental CM. Finally, we show that therapeutic administration of anti-CD25 monoclonal antibody, even when blood parasitemia is established, can prevent disease, confirming a critical and paradoxical role for Treg cells in experimental CM pathogenesis.

Loss of the atypical inflammatory response in juvenile and aged rats

Epidemiological evidence indicates that the severity of many human neuropathologies is often age-related, and this also appears true in rodent models of human disease. In this study, we examined the inflammatory response within the brain to the archetypal pro-inflammatory cytokines interleukin-1beta (IL-1beta) or tumour necrosis factor-alpha (TNF-alpha). We assessed how the cerebral vasculature changes with age and whether any structural alterations are associated with altered cytokine sensitivities. Six hours after equivalent microinjections of IL-1beta or TNF-alpha, 3-week-old juvenile and 18-month-old aged rats displayed increased leucocyte recruitment, blood-brain barrier (BBB) breakdown, and a loss of specificity in the populations of leucocytes recruited when compared with the restricted profile observed in 2-month-old young adult rat brain. The expression of the tight junction protein claudin-1 was absent in those vessels where neutrophils were being actively recruited. To determine whether changes in the structure of the BBB might be responsible for the increased susceptibility observed at either end of the age spectrum, we compared the number of claudin-1 positive vessels in the unchallenged brain to the total number of vessels. Virtually all vessels in the young adult brain express claudin-1, but a significant proportion of vessels are claudin-1 negative in the juvenile rat brain. In the aged rat brain, the overall number of vessels is markedly reduced, but the majority of these still appear to be claudin-1 positive. The pattern of claudin-1 expression together with the change in vessel density indicates that the properties of the BBB change with age, and, despite similarities, the underlying cause of the heightened inflammatory response in the juvenile and in the aged brain is likely to differ. Indeed, the spatial characteristics of the cytokine-induced BBB breakdown are different at either end of the age spectrum. These studies identify two periods within the lifespan of a rat where susceptibility to pro-inflammatory mediators is dramatically increased.

Melatonin treatment in old mice enables a more youthful response to LPS in the brain

Melatonin modulates the expression of a number of genes related to inflammation and immunity. Declining levels of melatonin with age may thus relate to some of the changes in immune function that occur with age. mRNA expression levels in murine CNS were measured using oligonucleotide microarrays in order to determine whether a dietary melatonin supplement may modify age-related changes in the response to an inflammatory challenge. CB6F1 male mice were fed 40-ppm melatonin for 9 weeks prior to sacrifice at 26.5 months of age, and compared with age-matched untreated controls and 4.5-month-old controls. A subset of both young and old animals was injected i.p. with lipopolysaccharide (LPS). After 3 h, total RNA was extracted from whole brain (excluding brain stem and cerebellum), and individual samples were hybridized to Affymetrix Mouse 430-2.0 arrays. Data were analyzed in Dchip and GeneSpring. Melatonin treatment markedly altered the response in gene expression of older animals subjected to an LPS challenge. These changes in general, caused the response to more closely resemble that of young animals subjected to the same LPS challenge. Thus melatonin treatment effects a major shift in the response of the CNS to an inflammatory challenge, causing a transition to a more youthful mRNA expression profile.

Poly(ADP-ribose) polymerase-1 inhibition protects the brain against systemic inflammation

Poly(ADP-ribose) polymerase-1 (PARP-1) is involved in DNA repair, but its overactivation can induce cell death. Our aim was to investigate the role of PARP-1 in activation of programmed cell death processes in the brain during systemic inflammation. Our data indicated that lipopolysaccharide (1mg/kgb.w., i.p.)-evoked systemic inflammation enhanced PARP-1 activity in the mouse brain, leading to the lowering of beta-NAD(+) concentration, to translocation of apoptosis inducing factor from mitochondria to the nucleus, and to enhanced lipid peroxidation. Inhibitor of PARP-1, 3-aminobenzamide (30 mg/kgb.w., i.p.), protected the brain against prooxidative and cell death processes, suggesting involvement of PARP-1 in systemic inflammation-related processes in the brain.

Temporal expression of IL-1beta protein and mRNA in the brain after systemic LPS injection is affected by age and estrogen

Estrogen has been shown to suppress neural inflammation in vivo in response to intracerebral LPS injections or by intraparenchymal injections of NMDA. Using the latter approach, we have shown that estrogen suppresses inflammatory cytokine expression in lesioned ovariectomized young adult females but not reproductive senescent animals. However, in cultured microglia derived from either young or senescent animals, estrogen fails to suppress LPS-induced cytokine expression. These data suggest that estrogen's effects on the neural inflammatory response may result from its actions on blood-borne immune cells or its actions at the blood brain barrier or both. This hypothesis was directly tested here using a systemic injury model and comparing the neural inflammatory response in the olfactory bulb, which is protected by the blood brain barrier, and in the pituitary gland, which is incompletely protected by the blood brain barrier. Young and senescent Sprague-Dawley female rats were ovariectomized and replaced with either an estrogen or placebo pellet. Three weeks later, animals received a single i.p. injection of LPS (or vehicle) and were terminated 0.5, 2 or 3h later. Systemic injections of LPS increased IL-1beta expression in the liver in a time-dependent manner in young and senescent females. In young adults, LPS increased cytokine expression in both the bulb and the pituitary gland. However, estrogen treatment attenuated IL-1beta expression in the olfactory bulb but not in the pituitary gland. In senescent animals, estrogen completely suppressed IL-1beta expression in the bulb and the pituitary gland, while placebo-replaced animals responded normally. This age-related difference in cytokine induction by LPS was also seen in mRNA regulation, such that LPS induced IL-1beta mRNA in the olfactory bulb of young adults but not in the senescent female. Age and hormone effects on pituitary cytokines were also mirrored in plasma corticosterone (CORT) levels, such that estrogen treatment to senescent females attenuated LPS-induced CORT. These data suggest that the central inflammatory response to a systemic insult can be modulated by estrogen although the mechanism underlying the initiation of this response varies with reproductive age.

Effects of Icariin on Hypothalamic-Pituitary-Adrenal Axis Action and Cytokine Levels in Stressed Sprague-Dawley Rats

Icariin is one of the major active flavonoids constituents of Epimedium brevicornum MAXIM (Berberidaceae). Icariin and E. brevicornum have a wide range of pharmacological activities. Abnormality in the hypothalamic-pituitary-adrenal (HPA) axis is considered to be a key neurobilogical factor in major depression, and cytokines have a close relationship with the activation of the HPA axis. In the present study, the aim was to determine whether icariin possesses an antidepressant-like activity, and to explore the effects of icariin on the HPA axis and cytokine levels in chronic mild stress (CMS) model of depression in Sprague-Dawley rats. Icariin significantly increased the sucrose intake of CMS-treated rats from week 3. It not only attenuated the CMS-induced increases in serum corticotropin-releasing factor (CRF) and cortisol levels, but also reversed the abnormal levels of serum interleukin-6 (IL-6) and tumor-necrosis-factor alpha (TNF-alpha) to the normal in the stressed rats. These results suggested that icariin possessed an antidepressant-like property that was at least in part mediated by neuroendocrine and immune systems.

The use of melanocortin antagonists in cachexia of chronic disease

Cachexia is a wasting syndrome that frequently develops in the setting of chronic diseases including cancer, congestive heart failure, chronic obstructive pulmonary disease, AIDS, renal failure and liver failure. Loss of lean body mass is believed to be a significant factor contributing to morbidity and mortality in these chronic diseases; however, there are currently no treatments available that have proven to be effective in reversing the progressive loss of lean body mass in cachectic patients. Evidence from animal models suggests a compelling link between inflammation, the central melanocortin system and cachexia. This review summarises the current evidence supporting the role of the melanocortin 4 (MC4) receptor subtype in cachexia, and discusses the development and use of small-molecule MC4 antagonists, which have proved to be effective in preventing the loss of lean body mass in animal models of cachexia. MC4 antagonists represent an attractive therapeutic approach for cachexia that may attenuate the loss of lean body mass in cachectic patients.

Immune modulation of the hypothalamic-pituitary-adrenal (HPA) axis during viral infection

Compelling data has been amassed indicating that soluble factors, or cytokines, emanating from the immune system can have profound effects on the neuroendocrine system, in particular the hypothalamic- pituitary-adrenal (HPA) axis. HPA activation by cytokines (via the release of glucocorticoids), in turn, has been found to play a critical role in restraining and shaping immune responses. Thus, cytokine-HPA interactions represent a fundamental consideration regarding the maintenance of homeostasis and the development of disease during viral infection. Although reviews exist that focus on the bi-directional communication between the immune system and the HPA axis during viral infection (188,235), others have focused on the immunomodulatory effects of glucocorticoids during viral infection (14,225). This review, however, concentrates on the other side of the bi-directional loop of neuroendocrine-immune interactions, namely, the characterization of HPA axis activity during viral infection and the mechanisms employed by cytokines to stimulate glucocorticoid release.

Age-related decline of brain monoamines in mice is reversed to young level by Japanese herbal medicine

Young (3-month-old) and aged mice (18-month-old) were fed a diet containing Japanese herbal medicine (TJ-41 or TJ-48) for 5 months, and the effect of the herbal medicines were examined in terms of levels of monoamines and their metabolites in the brain of young and aged mice. In the aged mice, the levels of norepinepherine, serotonin and their metabolites in the brain were decreased in the cortex, hippocampus and hypothalamus. Feeding of diet containing TJ-48, but not TJ-41, enhanced the levels of some monoamines and their metabolites in the brains of aged mice, comparable to those of young mice. The results indicated that the improvement of levels of monoamines by Japanese herbal medicine was observed only in the aged mice, not in the young mice. The data have suggested the importance of the aged animals to see the effect of medicine on the functions of organs or systems.

Direct effects of interleukin-6 on liver progenitor oval cells in culture

Following acute injury, liver is usually regenerated from hepatocytes by a process that is dependent on interleukin (IL)-6. If this pathway is impaired, restoration of the liver mass and ultimately the survival of the animal are dependent on recruitment of cells from a precursor cell population, either a stem cell or an oval cell. Importantly, oval cells are also implicated in tumorigenesis. A carcinogenic choline-deficient ethionine supplemented (CDE) diet is capable of inducing substantial numbers of oval cells that we can isolate and utilize to identify cytokines, which affect oval cell proliferation and differentiation. Currently, a putative role of IL-6 in oval cell biology is suggested by the elevation of IL-6 in liver and serum of mice treated with a CDE diet and knockout mouse studies. Also, when IL-6 is injected into the peritoneal cavity of mice on the CDE diet, oval cell numbers are increased compared to mice on the CDE diet alone. We investigated the role of human IL-6 on p53 null immortalized murine oval cell lines (PIL), finding that they express transcripts for the IL-6 receptor and gp 130, STAT-3 is phosphorylated upon IL-6 stimulation, IL-6 induces IL-6 production, and proliferation is induced by IL-6. In addition, we show that mouse primary oval cells also express IL-6 receptor and gp 130 mRNA. These findings suggest that IL-6 directly stimulates oval cells and an autocrine mechanism may sustain oval cell proliferation.

Cytokines and major depression

In the research field of psychoneuroimmunology, accumulating evidence has indicated the existence of reciprocal communication pathways between nervous, endocrine and immune systems. In this respect, there has been increasing interest in the putative involvement of the immune system in psychiatric disorders. In the present review, the role of proinflammatory cytokines, such as interleukin (IL)-1, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma, in the aetiology and pathophysiology of major depression, is discussed. The 'cytokine hypothesis of depression' implies that proinflammatory cytokines, acting as neuromodulators, represent the key factor in the (central) mediation of the behavioural, neuroendocrine and neurochemical features of depressive disorders. This view is supported by various findings. Several medical illnesses, which are characterised by chronic inflammatory responses, e.g. rheumatoid arthritis, have been reported to be accompanied by depression. In addition, administration of proinflammatory cytokines, e.g. in cancer or hepatitis C therapies, has been found to induce depressive symptomatology. Administration of proinflammatory cytokines in animals induces 'sickness behaviour', which is a pattern of behavioural alterations that is very similar to the behavioural symptoms of depression in humans. The central action of cytokines may also account for the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity that is frequently observed in depressive disorders, as proinflammatory cytokines may cause HPA axis hyperactivity by disturbing the negative feedback inhibition of circulating corticosteroids (CSs) on the HPA axis. Concerning the deficiency in serotonergic (5-HT) neurotransmission that is concomitant with major depression, cytokines may reduce 5-HT levels by lowering the availability of its precursor tryptophan (TRP) through activation of the TRP-metabolising enzyme indoleamine-2,3-dioxygenase (IDO). Although the central effects of proinflammatory cytokines appear to be able to account for most of the symptoms occurring in depression, it remains to be established whether cytokines play a causal role in depressive illness or represent epiphenomena without major significance.

Cytokines and the aging brain – what we don't know might help us

Cognitive aspects of aging represent a grave challenge for our societal circumstances as members of the baby-boom generation spiral toward a collective 'senior moment'. In addition, age-related changes in the CNS can contribute to motor deficits and other somatic aberrations. Inflammation and its regulation by cytokines have been connected to many aspects of aging, and mechanisms addressed here provide a rationale for this. Nevertheless, a role for cytokines in normal aging of the human brain has not been confirmed, and it seems to be possible to ameliorate both cognitive decline and cytokine elevation via lifestyle choices. So ignorance of the brain should not prohibit development of successful strategies for delaying or avoiding neurological deficits.

Oral Administration with Papillomavirus Pseudovirus Encoding IL-2 Fully Restores Mucosal and Systemic Immune Responses to Vaccinations in Aged Mice

Infectious diseases are one of the major threats for the elderly because their immune system is often compromised, and vaccinations to prevent these infections are not effective. A major defect in their immune system seems to be the inability of T cells to produce IL-2. We used papillomavirus (PV) pseudoviruses (PSVs) as a model vaccine and a gene delivery vector to address how to enhance immune responses to vaccinations. We found that oral immunization with PV PSV induced minimal mucosal and systemic Abs and CTLs specific for the PSVs in aged mice compared with young adult mice. In addition, fewer specific Th cells were generated in the aged mice. When aged mice were immunized with PV PSVs encoding human IL-2, specific Th cells were generated, producing murine IL-2, IL-4, and IFN-gamma. Further, specific Abs and CTLs were induced, resulting in protection against mucosal viral challenge. Thus, this study provided a basis for clinical trials using PV PSVs encoding IL-2 for vaccination of the elderly.

Thymic generation and regeneration

The thymus is a complex epithelial organ in which thymocyte development is dependent upon the sequential contribution of morphologically and phenotypically distinct stromal cell compartments. It is these microenvironments that provide the unique combination of cellular interactions, cytokines, and chemokines to induce thymocyte precursors to undergo a differentiation program that leads to the generation of functional T cells. Despite the indispensable role of thymic epithelium in the generation of T cells, the mediators of this process and the differentiation pathway undertaken by the primordial thymic epithelial cells are not well defined. There is a lack of lineage-specific cell-surface-associated markers, which are needed to characterize putative thymic epithelial stem cell populations. This review explores the role of thymic stromal cells in T-cell development and thymic organogenesis, as well as the molecular signals that contribute to the growth and expansion of primordial thymic epithelial cells. It highlights recent advances in these areas, which have allowed for a lineage relationship amongst thymic epithelial cell subsets to be proposed. While many fundamental questions remain to be addressed, collectively these works have broadened our understanding of how the thymic epithelium becomes specialized in the ability to support thymocyte differentiation. They should also facilitate the development of novel, rationally based therapeutic strategies for the regeneration and manipulation of thymic function in the treatment of many clinical conditions in which defective T cells have an important etiological role.

Lewis hypothalamic cells constitutively and upon stimulation express higher levels of mRNA for pro-inflammatory cytokines and related molecules: comparison with inflammatory resistant Fischer rat hypothalamic cells

Endogenous hypothalamic pro-inflammatory cytokines modulate the hypothalamic-pituitary-adrenal (HPA) axis responses. To investigate whether hypothalamic IL-1beta, IL-6, and tumor necrosis factor-alpha (TNF-alpha) are associated with differential inflammatory susceptibilities between Lewis (LEW/N) and Fischer (F344/N) rats, mRNA levels of pro-inflammatory cytokines and related molecules in hypothalamic cell cultures of both strains were quantified by real-time polymerase chain reaction (PCR). In addition to IL-1beta, IL-6, TNF-alpha, and their receptors, LEW/N hypothalamic cells also transcribed more anti-inflammatory molecules, IL-1RII, IL-1RA, and transforming growth factor (TGFbeta1), than F334/N cells. Our findings suggest that a balance exists between transcripts for endogenous pro- and anti-inflammatory molecules in LEW/N rats that may allow them, under basal conditions, to maintain hypothalamic homeostasis and health. However, under stimulated conditions, this balance may be more easily perturbed toward chronic inflammation.

Age-related inflammatory cytokines and disease

Aging is associated with chronic low-grade increases in circulating levels of inflammatory markers. A wide range of environmental factors, including smoking, infections, and obesity, genetic factors, and the declining function of sex hormones may contribute to systemic low-grade inflammatory activity in older individuals. Age-associated disease may exacerbate this phenomenon. The multifunctional cytokines TNF-alpha and IL-6 have been associated with morbidity and mortality in the elderly. Evidence supports the direct role of TNF-alpha in the pathogeneses of atherosclerosis, type 2 DM, and AD in older individuals. Age-related increases in systemic levels of TNF-alpha could provide a unifying basis for these disorders. Furthermore, TNF-alpha induces a catabolic state that causes frailty. Circulating levels of IL-6 seem to be a strong risk factor for frailty in the elderly, which could reflect its association with increased production of TNF-alpha. IL-6 also may be a risk factor for thromboembolic complications. In healthy, elderly populations, high circulating levels of TNF-alpha and IL-6 predict mortality, independent of comorbidity, indicating that TNF-alpha and IL-6 cause morbidity and mortality. In cohorts of frail, older individuals, TNF-alpha and IL-6 also act as disease markers. Circulating levels of TNF-alpha seem to be the best predictor of mortality in frail, elderly populations with a high mortality rate, whereas IL-6 seems to be the strongest risk marker in healthy, elderly populations. This finding could reflect that in relatively healthy old populations the increase in circulating levels of IL-6 represent a systemic response to local proinflammatory activities; however, when age-related inflammatory diseases progress, levels of TNF-alpha increase in the circulation and become gradually a stronger risk marker than IL-6. In conclusion low-grade elevations in levels of circulating cytokines are strong independent risk factors of morbidity and mortality in the elderly, and lifestyle factors and comorbidities may modulate these levels. Exercise and dietary interventions may be possible strategies to decrease inflammatory activity and improve the health status of the elderly.