The viral mimetic polyinosinic:polycytidylic acid (poly I:C) induces cellular responses in primary cultures from rat brain sites with an incomplete blood-brain barrier

BGP-15 alleviates LPS-induced depression-like behavior by promoting mitophagy

The high prevalence of major depressive disorder (MDD) frequently imposes severe constraints on psychosocial functioning and detrimentally impacts overall well-being. Despite the growing interest in the hypothesis of mitochondrial dysfunction, the precise mechanistic underpinnings and therapeutic strategies remain unclear and require further investigation. In this study, an MDD model was established in mice using lipopolysaccharide (LPS). Our research findings demonstrated that LPS exposure induced depressive-like behaviors and disrupted mitophagy by diminishing the mitochondrial levels of PINK1/Parkin in the brains of mice. Furthermore, LPS exposure evoked the activation of the NLRP3 inflammasome, accompanied by a notable elevation in the concentrations of pro-inflammatory factors (TNF-α, IL-1β, and IL-6). Additionally, neuronal apoptosis was stimulated through the JNK/p38 pathway. The administration of BGP-15 effectively nullified the impact of LPS, corresponding to the amelioration of depressive-like phenotypes and restoration of mitophagy, prevention of neuronal injury and inflammation, and suppression of reactive oxygen species (ROS)-mediated NLRP3 inflammasome activation. Furthermore, we elucidated the involvement of mitophagy in BGP-15-attenuated depressive-like behaviors using the inhibitors targeting autophagy (3-MA) and mitophagy (Mdivi-1). Notably, these inhibitors notably counteracted the antidepressant and anti-inflammatory effects exerted by BGP-15. Based on the research findings, it can be inferred that the antidepressant properties of BGP-15 in LPS-induced depressive-like behaviors could potentially be attributed to the involvement of the mitophagy pathway. These findings offer a potential novel therapeutic strategy for managing MDD.

Norepinephrine Inhibits Lipopolysaccharide-Stimulated TNF-α but Not Oxylipin Induction in n-3/n-6 PUFA-Enriched Cultures of Circumventricular Organs

Sensory circumventricular organs (sCVOs) are pivotal brain structures involved in immune-to-brain communication with a leaky blood-brain barrier that detect circulating mediators such as lipopolysaccharide (LPS). Here, we aimed to investigate the potential of sCVOs to produce n-3 and n-6 oxylipins after LPS-stimulation. Moreover, we investigated if norepinephrine (NE) co-treatment can alter cytokine- and oxylipin-release. Thus, we stimulated rat primary neuroglial sCVO cultures under n-3- or n-6-enriched conditions with LPS or saline combined with NE or vehicle. Supernatants were assessed for cytokines by bioassays and oxylipins by HPLC-MS/MS. Expression of signaling pathways and enzymes were analyzed by RT-PCR. Tumor necrosis factor (TNF)α bioactivity and signaling, IL-10 expression, and cyclooxygenase (COX)2 were increased, epoxide hydroxylase (Ephx)2 was reduced, and lipoxygenase 15-(LOX) was not changed by LPS stimulation. Moreover, LPS induced increased levels of several n-6-derived oxylipins, including the COX-2 metabolite 15d-prostaglandin-J2 or the Ephx2 metabolite 14,15-DHET. For n-3-derived oxylipins, some were down- and some were upregulated, including 15-LOX-derived neuroprotectin D1 and 18-HEPE, known for their anti-inflammatory potential. While the LPS-induced increase in TNFα levels was significantly reduced by NE, oxylipins were not significantly altered by NE or changes in TNFα levels. In conclusion, LPS-induced oxylipins may play an important functional role in sCVOs for immune-to-brain communication.

LPS Primes Brain Responsiveness to High Mobility Group Box-1 Protein

High mobility group box (HMGB)1 action contributes to late phases of sepsis, but the effects of increased endogenous plasma HMGB1 levels on brain cells during inflammation are unclear. Here, we aimed to further investigate the role of HMGB1 in the brain during septic-like lipopolysaccharide-induced inflammation in rats (LPS, 10 mg/kg, i.p.). HMGB-1 mRNA expression and release were measured in the periphery/brain by RT-PCR, immunohistochemistry and ELISA. In vitro experiments with disulfide-HMGB1 in primary neuro-glial cell cultures of the area postrema (AP), a circumventricular organ with a leaky blood–brain barrier and direct access to circulating mediators like HMGB1 and LPS, were performed to determine the direct influence of HMGB1 on this pivotal brain structure for immune-to-brain communication. Indeed, HMGB1 plasma levels stayed elevated after LPS injection. Immunohistochemistry of brains and AP cultures confirmed LPS-stimulated cytoplasmatic translocation of HMGB1 indicative of local HMGB1 release. Moreover, disulfide-HMGB1 stimulation induced nuclear factor (NF)-κB activation and a significant release of interleukin-6, but not tumor necrosis factor α, into AP culture supernatants. However, only a few AP cells directly responded to HMGB1 with increased intracellular calcium concentration. Interestingly, priming with LPS induced a seven-fold higher percentage of responsive cells to HMGB1. We conclude that, as a humoral and local mediator, HMGB1 enhances brain inflammatory responses, after LPS priming, linked to sustained sepsis symptoms.

Inflammation-dependent ISG15 upregulation mediates MIA-induced dendrite damages and depression by disrupting NEDD4/Rap2A signaling

BACKGROUND

Maternal immune activation (MIA) is an independent risk factor for psychiatric disorders including depression spectrum in the offsprings, but the molecular mechanism is unclear. Recent studies show that interferon-stimulated gene-15 (ISG15) is involved in inflammation and neuronal dendrite development; here we studied the role of ISG15 in MIA-induced depression and the underlying mechanisms.

METHODS

By vena caudalis injecting polyinosinic: polycytidylic acid (poly I:C) into the pregnant rats to mimic MIA, we used AAV or lentivirus to introduce or silence ISG15 expression. Synaptic plasticity was detected by confocal microscope and Golgi staining. Cognitive performances of the offspring were measured by Open field, Forced swimming and Sucrose preference test.

RESULTS

We found that MIA induced depression-like behaviors with dendrite impairments in the offspring with ISG15 level increased in the offsprings' brain. Overexpressing ISG15 in the prefrontal cortex of neonatal cubs (P0) could mimic dendritic pathology and depressive like behaviors, while downregulating ISG15 rescued these abnormalities in the offsprings. Further studies demonstrated that MIA-induced upregulation of inflammatory cytokines promoted ISG15 expression in the offspring' brain which suppressed Rap2A ubiquitination via NEDD4 and thus induced Rap2A accumulation, while upregulating NEDD4 abolished ISG15-induced dendrite impairments.

CONCLUSIONS

These data reveal that MIA impedes offsprings' dendrite development and causes depressive like behaviors by upregulating ISG15 and suppressing NEDD4/Rap2A signaling. The current findings suggest that inhibiting ISG15 may be a promising intervention of MIA-induced psychiatric disorders in the offsprings.

The use of siRNA as a pharmacological tool to assess a role for the transcription factor NF-IL6 in the brain under in vitro and in vivo conditions during LPS-induced inflammatory stimulation

BACKGROUND

Studies with NF-IL6-deficient mice indicate that this transcription factor plays a dual role during systemic inflammation with pro- and anti-inflammatory capacities. Here, we aimed to characterize the role of NF-IL6 specifically within the brain.

METHODS

In this study, we tested the capacity of short interfering (si) RNA to silence the inflammatory transcription factor nuclear factor-interleukin 6 (NF-IL6) in brain cells under in vitro and in vivo conditions.

RESULTS

In cells of a mixed neuronal and glial primary culture from the rat area postrema (AP), short interfering RNA (siRNA) directed against NF-IL6 strongly reduced basal and lipopolysaccharide (LPS)-induced nuclear immunoreactivity of this transcription factor, with the strongest effect on astrocytes. The siRNA did not exert inflammatory effects in the primary culture as confirmed by unaltered levels of IL-6 in supernatants. In vivo, intracerebroventricular (i.c.v.) injections of fluorochrome labelled siRNA caused its appearance in relevant brain structures for fever induction pathways such as the vascular organ of lamina terminalis, the subfornical organ, the median preoptic nucleus (MnPO) and the AP in several cell types, including microglial cells. However, i.c.v. injections of siRNA per se caused signs of fever, anorexia and reduced locomotor activity, i.e. sickness behavior.

CONCLUSIONS

This approach was, thus, not suitable to characterize the role NF-IL6 in the brain in vivo, namely during experimentally induced systemic inflammation.

The blood-brain barrier in systemic inflammation

The blood-brain barrier (BBB) plays a key role in maintaining the specialized microenvironment of the central nervous system (CNS), and enabling communication with the systemic compartment. BBB changes occur in several CNS pathologies. Here, we review disruptive and non-disruptive BBB changes in systemic infections and other forms of systemic inflammation, and how these changes may affect CNS function in health and disease. We first describe the structure and function of the BBB, and outline the techniques used to study the BBB in vitro, and in animal and human settings. We then summarise the evidence from a range of models linking BBB changes with systemic inflammation, and the underlying mechanisms. The clinical relevance of these BBB changes during systemic inflammation are discussed in the context of clinically-apparent syndromes such as sickness behaviour, delirium, and septic encephalopathy, as well as neurological conditions such as Alzheimer's disease and multiple sclerosis. We review emerging evidence for two novel concepts: (1) a heightened sensitivity of the diseased, versus healthy, BBB to systemic inflammation, and (2) the contribution of BBB changes induced by systemic inflammation to progression of the primary disease process.

A distinct brain pathway links viral RNA exposure to sickness behavior

Sickness behaviors and metabolic responses to invading pathogens are common to nearly all types of infection. These responses evolved to provide short-term benefit to the host to ward off infection, but impact on quality of life, and when prolonged lead to neurodegeneration, depression, and cachexia. Among the major infectious agents, viruses most frequently enter the brain, resulting in profound neuroinflammation. We sought to define the unique features of the inflammatory response in the brain to these infections. We demonstrate that the molecular pathway defining the central response to dsRNA is distinct from that found in the periphery. The behavioral and physical response to the dsRNA mimetic poly I:C is dependent on signaling via MyD88 when it is delivered centrally, whereas this response is mediated via the TRIF pathway when delivered peripherally. We also define the likely cellular candidates for this MyD88-dependent step. These findings suggest that symptom management is possible without ameliorating protective antiviral immune responses.

Inflammatory transcription factors as activation markers and functional readouts in immune-to-brain communication

Immune-to-brain communication pathways involve humoral mediators, including cytokines, central modulation by neuronal afferents and immune cell trafficking to the brain. During systemic inflammation these pathways contribute to mediating brain-controlled sickness symptoms including fever. Experimentally, activation of these signaling pathways can be mimicked and studied when injecting animals with pathogen associated molecular patterns (PAMPS). One central component of the brain inflammatory response, which leads, for example, to fever induction, is transcriptional activation of brain cells via cytokines and PAMPS. We and others have studied the spatiotemporal activation and the physiological significance of transcription factors for the induction of inflammation within the brain and the manifestation of fever. Evidence has revealed a role of nuclear factor (NF)κB in the initiation, signal transducer and activator of transcription (STAT)3 in the maintenance and NF-interleukin (IL)6 in the maintenance or even termination of brain-inflammation and fever. Moreover, psychological stressors, such as exposure to a novel environment, leads to increased body core temperature and genomic NF-IL6-activation, suggesting a potential use of NF-IL6-immunohistochemistry as a multimodal brain cell activation marker and a role for NF-IL6 for differential brain activity. In addition, the nutritional status, as reflected by circulating levels of the cytokine-like hormone leptin, influence immune-to-brain communication and age-dependent changes in LPS-induced fever. Overall, transcription factors remain therapeutically important targets for the treatment of brain-inflammation and fever induction during infectious/non-infectious inflammatory and psychological stress. However, the exact physiological role and significance of these transcription factors requires to be further investigated.

Functional expression of P2 purinoceptors in a primary neuroglial cell culture of the rat arcuate nucleus

The arcuate nucleus (ARC) plays an important role in the hypothalamic control of energy homeostasis. Expression of various purinoceptor subtypes in the rat ARC and physiological studies suggest a modulatory function of P2 receptors within the neuroglial ARC circuitry. A differentiated mixed neuronal and glial microculture was therefore established from postnatal rat ARC, revealing neuronal expression of ARC-specific transmitters involved in food intake regulation (neuropeptide Y (NPY), proopiomelanocortin (POMC), tyrosine hydroxylase (TH)). Some NPYergic neurons cosynthesized TH, while POMC and TH expression proved to be mutually exclusive. Stimulation with the general purinoceptor agonists 2-methylthioadenosine-5'triphosphate (2-MeSATP) and ATP but not the P2X1/P2X3 receptor subtype agonist α,β-methyleneadenosine-5'triphosphate (α,β-meATP) induced intracellular calcium signals in ARC neurons and astrocytes. Some 5-10% each of 2-MeSATP responsive neurons expressed POMC, NYP or TH. Supporting the calcium imaging data, radioligand binding studies to hypothalamic membranes showed high affinity for 2-MeSATP, ATP but not α,β-meATP to displace [α-(35)S]deoxyadenosine-5'thiotriphosphate ([(35)S]dATPαS) from P2 receptors. Repetitive superfusion with equimolar 2-MeSATP allowed categorization of ARC cells into groups with a high or low (LDD) degree of purinoceptor desensitization, the latter allowing further receptor characterization. Calcium imaging experiments performed at 37°C vs. room temperature showed further reduction of desensitization. Agonist-mediated intracellular calcium signals were suppressed in all LDD neurons but only 25% of astrocytes in the absence of extracellular calcium, suggestive of metabotropic P2Y receptor expression in the majority of ARC astrocytes. The highly P2Y1-selective receptor agonists MRS2365 and 2-methylthioadenosine-5'diphosphate (2-MeSADP) activated 75-85% of all 2-MeSATP-responsive ARC astrocytes. Taking into consideration the high potency to dose-dependently stimulate ARC cells of the LDD group, the high affinity for rat P2X(1-3) and low affinity for rat P2X4, P2X7 and P2Y receptor subtypes except P2Y1 and P2Y13, the agonist 2-MeSATP primarily acted upon P2X2 and P2Y1 purinoceptors to trigger intracellular calcium signaling in ARC neurons and astrocytes.

Central mediators involved in the febrile response: effects of antipyretic drugs

Fever is a complex signal of inflammatory and infectious diseases. It is generally initiated when peripherally produced endogenous pyrogens reach areas that surround the hypothalamus. These peripheral endogenous pyrogens are cytokines that are produced by leukocytes and other cells, the most known of which are interleukin-1β, tumor necrosis factor-α, and interleukin-6. Because of the capacity of these molecules to induce their own synthesis and the synthesis of other cytokines, they can also be synthesized in the central nervous system. However, these pyrogens are not the final mediators of the febrile response. These cytokines can induce the synthesis of cyclooxygenase-2, which produces prostaglandins. These prostanoids alter hypothalamic temperature control, leading to an increase in heat production, the conservation of heat, and ultimately fever. The effect of antipyretics is based on blocking prostaglandin synthesis. In this review, we discuss recent data on the importance of prostaglandins in the febrile response, and we show that some endogenous mediators can still induce the febrile response even when known antipyretics reduce the levels of prostaglandins in the central nervous system. These studies suggest that centrally produced mediators other than prostaglandins participate in the genesis of fever. Among the most studied central mediators of fever are corticotropin-releasing factor, endothelins, chemokines, endogenous opioids, and substance P, which are discussed herein. Additionally, recent evidence suggests that these different pathways of fever induction may be activated during different pathological conditions.

Central mediators involved in the febrile response: effects of antipyretic drugs

Fever is a complex signal of inflammatory and infectious diseases. It is generally initiated when peripherally produced endogenous pyrogens reach areas that surround the hypothalamus. These peripheral endogenous pyrogens are cytokines that are produced by leukocytes and other cells, the most known of which are interleukin-1β, tumor necrosis factor-α, and interleukin-6. Because of the capacity of these molecules to induce their own synthesis and the synthesis of other cytokines, they can also be synthesized in the central nervous system. However, these pyrogens are not the final mediators of the febrile response. These cytokines can induce the synthesis of cyclooxygenase-2, which produces prostaglandins. These prostanoids alter hypothalamic temperature control, leading to an increase in heat production, the conservation of heat, and ultimately fever. The effect of antipyretics is based on blocking prostaglandin synthesis. In this review, we discuss recent data on the importance of prostaglandins in the febrile response, and we show that some endogenous mediators can still induce the febrile response even when known antipyretics reduce the levels of prostaglandins in the central nervous system. These studies suggest that centrally produced mediators other than prostaglandins participate in the genesis of fever. Among the most studied central mediators of fever are corticotropin-releasing factor, endothelins, chemokines, endogenous opioids, and substance P, which are discussed herein. Additionally, recent evidence suggests that these different pathways of fever induction may be activated during different pathological conditions.

Sickness: From the focus on cytokines, prostaglandins, and complement factors to the perspectives of neurons

Systemic inflammation leads to a variety of physiological (e.g. fever) and behavioral (e.g. anorexia, immobility, social withdrawal, depressed mood, disturbed sleep) responses that are collectively known as sickness. While these phenomena have been studied for the past few decades, the neurobiological mechanisms by which sickness occurs remain unclear. In this review, we first revisit how the body senses and responds to infections and injuries by eliciting systemic inflammation. Next, we focus on how peripheral inflammatory molecules such as cytokines, prostaglandins, and activated complement factors communicate with the brain to trigger neuroinflammation and sickness. Since depression also involves inflammation, we further elaborate on the interrelationship between sickness and depression. Finally, we discuss how immune activation can modulate neurons in the brain, and suggest future perspectives to help unravel how changes in neuronal functions relate to sickness responses.

Mechanisms of fever production and lysis: lessons from experimental LPS fever

Fever is a cardinal symptom of infectious or inflammatory insults, but it can also arise from noninfectious causes. The fever-inducing agent that has been used most frequently in experimental studies designed to characterize the physiological, immunological and neuroendocrine processes and to identify the neuronal circuits that underlie the manifestation of the febrile response is lipopolysaccharide (LPS). Our knowledge of the mechanisms of fever production and lysis is largely based on this model. Fever is usually initiated in the periphery of the challenged host by the immediate activation of the innate immune system by LPS, specifically of the complement (C) cascade and Toll-like receptors. The first results in the immediate generation of the C component C5a and the subsequent rapid production of prostaglandin E2 (PGE2). The second, occurring after some delay, induces the further production of PGE2 by induction of its synthesizing enzymes and transcription and translation of proinflammatory cytokines. The Kupffer cells (Kc) of the liver seem to be essential for these initial processes. The subsequent transfer of the pyrogenic message from the periphery to the brain is achieved by neuronal and humoral mechanisms. These pathways subserve the genesis of early (neuronal signals) and late (humoral signals) phases of the characteristically biphasic febrile response to LPS. During the course of fever, counterinflammatory factors, "endogenous antipyretics," are elaborated peripherally and centrally to limit fever in strength and duration. The multiple interacting pro- and antipyretic signals and their mechanistic effects that underlie endotoxic fever are the subjects of this review.

Central mediators involved in the febrile response induced by polyinosinic-polycytidylic acid: lack of involvement of endothelins and substance P

The present study evaluated the involvement of interleukin(IL)-1β, tumor necrosis factor-α (TNF-α), IL-6, interferon(IFN)-γ, prostaglandins of the E2 series, endothelins, substance P and opioids within the central nervous system in polyinosinic:polycytidylic acid (Poly I:C)-induced fever in rats. Poly I:C injection induced a febrile response which was reduced by intracerebroventricular administration of the antibodies against TNF-α, IL-6, or IFN-γ, or by IL-1 or μ receptor antagonists. Intraperitoneal injection of indomethacin or oral administration of celecoxib also reduced Poly I:C-induced fever. Poly I:C increased prostaglandin E2 levels in the cerebrospinal fluid of the animals which was also reduced by indomethacin. The intracerebroventricular injection of ETB or NK1 receptor antagonists did not alter Poly I:C-induced fever. These data suggest the involvement of IL-1β, TNF-α, IL-6, IFN-γ, prostaglandin E2, and opioids but not endothelins and substance P on Poly I:C-induced fever.

Intraperitoneal and subcutaneous injections of the TLR9 agonist ODN 1668 in rats: brain inflammatory responses are related to peripheral IL-6 rather than interferons

Subcutaneous or intraperitoneal administration of Toll-like receptor (TLR)-9 agonist, ODN 1668 caused moderate fever and anorexia. In comparison to stimulation of other intracellular TLRs, activation of TLR9 did not result in pronounced peripheral induction of interferons, but rather induced interleukin-6. Expression of cytokines (TNFα, IL-1β) and inducible forms of enzymes for prostaglandin E2 synthesis occurred in the brain, in conjunction with a moderate activation of the transcription factors STAT3 and NF-IL6 in brain endothelial cells. The lack of a septic-like state in ODN 1668-treated rats reinforces the therapeutic value of this drug.

Involvement of brain cytokines in zymosan-induced febrile response

This study compared the involvement of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) within the central nervous system (CNS) in the febrile response induced by zymosan (zym) and lipopolysaccharide (LPS). In addition, we investigated whether zym could activate important regions related to fever; namely, the vascular organ of the laminae terminalis (OVLT) and the median preoptic nucleus (MnPO). Intraperitoneal injection of zym (1, 3, and 10 mg/kg) induced a dose-related increase in core temperature. Zym (3 mg/kg) also reduced tail skin temperature, suggesting the activation of heat conservation mechanisms, as expected, during fever. LPS increased plasma levels of TNF-α measured at 1 h, IL-1β measured at 2 h, and IL-6 measured at 3 h after injection. Zym increased circulating levels of IL-6 but not those of TNF-α or IL-1β at the same time points. In addition, an intracerebroventricular injection of antibodies against TNF-α (2.5 μg) and IL-6 (10 μg) or the IL-1 receptor antagonist (160 ng) reduced the febrile response induced by zym and LPS. Zym (100 μg/ml) also increased intracellular calcium concentration in the OVLT and MnPO from rat primary neuroglial cultures and increased release of TNF-α and IL-6 into the supernatants of these cultures. Together, these results suggest that TNF-α, IL-1β, and IL-6 within the CNS participate in the febrile response induced by zym. However, the time course of release of these cytokines may be different from that of LPS. In addition, zym can directly activate the brain areas related to fever.

Chemokine ligand (CCL)-3 promotes an integrated febrile response when injected within pre-optic area (POA) of rats and induces calcium signaling in cells of POA microcultures but not TNF-α or IL-6 synthesis

Although studies have shown that chemokines are pyrogenic when injected into the brain, there are no data indicating which cell types and receptors in the CNS are employed by chemokines such as CCL3 (synonym: MIP-1α) to induce fever in rats. We aimed to study, whether CCL3 induces fever when injected directly into the thermoregulatory center within the pre-optic area (POA). Moreover, we investigated whether CCL3 activates cells from POA microcultures resulting in intracellular Ca++ mobilization and synthesis/release of TNF-α and IL-6. Microinjections of CCL3 into the POA induced a dose-dependent fever, which was accompanied by a decrease in tail skin temperature. The primary microcultures of the POA (from topographically excised rat pup brain tissue) were stimulated by bolus administrations of 100 μl CCL3 (0.1 or 0.01 μg) or sterile PBS as control. We evaluated the responses of 261 (30.89%) neurons, 346 (40.94%) astrocytes and 238 microglia cells (29.17%). Stimulation of rat POA microcultures with CCL3 was capable of inducing Ca++ signaling in 15.31% of all astrocytes and 5.75% of all neurons investigated. No cellular Ca++-signals were observed after overnight incubation of the cultures with antiCCR1 or antiCCR5 antibodies. CCL3 did not alter the release of the pyrogenic cytokines IL-6 or TNF-α into the supernatant of the cultures. In conclusion the present study shows for the first time that CCL-3 injected directly into the rat POA, evoked an integrated febrile response. In parallel this chemokine induces Ca++ signaling in astrocytes and neurons via both CCR1 and CCR5 receptors when administered to POA microcultures without stimulating the synthesis of TNF-α and IL-6. It is a possibility that CCL3-induced fever may occur via CCR1 and CCR5 receptors stimulation of astrocytes and neurons from POA.

Genome-wide effects of DNA methyltransferase inhibitor on gene expression in double-stranded RNA transfected porcine PK15 cells

Double-stranded RNA (dsRNA) is produced in host cells during viral replication. The effects of DNA demethylation on gene expression in dsRNA transfected swine cells are unclear. The study aims to profile the transcriptome changes which are induced by DNA methyltransferase inhibitor (Aza-CdR) in porcine PK15 cells transfected with viral-like dsRNA (Poly(I:C)). A total of 44, 76 and 952 differentially expressed genes (DEGs) were detected in the cells treated by Poly(I:C) plus Aza-CdR (P+A), Poly(I:C) (P) or Aza-CdR (A) alone compared to the controls (C). Immune response-related pathways are observed in the comparison of A vs. C and P vs. C, and the genes in the pathways were recovered in the comparison of (P+A) vs. C. GO analysis indicated that Aza-CdR has negative regulatory effects on viral reproduction. The results suggest that the stimulant of Poly(I:C) could be regressed by Aza-CdR. These observations provide new insights into the epigenetic regulatory effects on viral replication.

Interleukin-10 modulates the synthesis of inflammatory mediators in the sensory circumventricular organs: implications for the regulation of fever and sickness behaviors

Background

Whereas the role played by interleukin (IL)-10 in modulating fever and sickness behavior has been linked to it targeting the production of pro-inflammatory cytokines in the circulation, liver and spleen, it is not known whether it could directly target the local production of pro-inflammatory cytokines within the sensory circumventricular organs (CVOs) situated within the brain, but outside the blood–brain barrier. Using inactivation of IL-10, we, therefore, investigated whether IL-10 could modulate the synthesis of pro-inflammatory cytokines within the sensory CVOs, in particular the organum vasculosum laminae terminalis (OVLT) and area postrema (AP).

Findings

Primary OVLT and AP microcultures were established from topographically excised rat pup brain tissue. The microcultures were pretreated with either IL-10 antibodies (AB) (10 μl/350 μl medium) or phosphate-buffered saline (PBS) (10 μl/350 μl medium) before being incubated with lipopolysaccharide (LPS) (100 μg/ml) or PBS in complete medium for 6 h. Supernatants were removed from the microcultures after 6 h of incubation with LPS and used for the determination of IL-6 and tumor necrosis factor (TNF)-α. Pre-treating the OVLT and AP microcultures with IL-10 antibodies significantly enhanced the LPS-induced increase in TNF-α and IL-6 in the supernatant obtained from the microcultures.

Conclusions

Our results show for the first time that the LPS-induced release of pro-inflammatory cytokines in cells cultured from the AP and OVLT can be modulated in the presence of IL-10 antibodies. Thus, we have identified that the sensory CVOs may have a key role to play in both the initiation and modulation of neuroinflammation.