Inhibition of lipopolysaccharide-induced microglia activation by calcitonin gene related peptide and adrenomedullin

Calcitonin gene-related peptide attenuated discogenic low back pain in rats possibly via inhibiting microglia activation

Discogenic low back pain (DLBP) is a multifactorial disease and associated with intervertebral disc degeneration. Calcitonin gene-related protein (CGRP) plays a critical role in pain processing, while the role in DLBP remains unclear. This study aims to investigate the anti-nociceptive role and related mechanisms of CGRP in DLBP. Here we established the DLBP rat and validated the model using histology and radiography. Minocycline, a microglial inhibitor, and CGRP were intrathecally injected and the behavioral test was performed to determine hyperalgesia. Further, BV2 microglial cells and microglial activation agent lipopolysaccharide (LPS) were employed for the in vitro experiment. We observed obvious lumbar intervertebral disc degeneration and hyperalgesia at 12 weeks postoperation in DLBP group, with significantly activated microglia in the spinal cord. CGRP treatment significantly inhibited the upregulation of proinflammatory cytokines and NLRP3/caspase-1 expression induced by LPS in BV2 cells, whereas treatment with CGRP alone had little effect on BV2 cells. The intrathecal injection of CGRP into DLBP rats relieved mechanical and thermal hyperalgesia, reverted the microglial activation and decreased the expression of NLRP3/caspase-1, similar to the effects produced by minocycline. Our results provide evidence that microglial activation in the spinal cord play a key role in hyperalgesia in DLBP rats. CGRP alleviates DLBP induced hyperalgesia and inhibits microglial activation in the spinal cord. Regulation of CGRP and microglial activation may provide a new strategy for ameliorating DLBP.

Nordalbergin Exerts Anti-Neuroinflammatory Effects by Attenuating MAPK Signaling Pathway, NLRP3 Inflammasome Activation and ROS Production in LPS-Stimulated BV2 Microglia

Microglia-associated neuroinflammation is recognized as a critical factor in the pathogenesis of neurodegenerative diseases; however, there is no effective treatment for the blockage of neurodegenerative disease progression. In this study, the effect of nordalbergin, a coumarin isolated from the wood bark of Dalbergia sissoo, on lipopolysaccharide (LPS)-induced inflammatory responses was investigated using murine microglial BV2 cells. Cell viability was assessed using the MTT assay, whereas nitric oxide (NO) production was analyzed using the Griess reagent. Secretion of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) was detected by the ELISA. The expression of inducible NO synthase (iNOS), cyclooxygenase (COX)-2, mitogen-activated protein kinases (MAPKs) and NLRP3 inflammasome-related proteins was assessed by Western blot. The production of mitochondrial reactive oxygen species (ROS) and intracellular ROS was detected using flow cytometry. Our experimental results indicated that nordalbergin ≤20 µM suppressed NO, IL-6, TNF-α and IL-1β production; decreased iNOS and COX-2 expression; inhibited MAPKs activation; attenuated NLRP3 inflammasome activation; and reduced both intracellular and mitochondrial ROS production by LPS-stimulated BV2 cells in a dose-dependent manner. These results demonstrate that nordalbergin exhibits anti-inflammatory and anti-oxidative activities through inhibiting MAPK signaling pathway, NLRP3 inflammasome activation and ROS production, suggesting that nordalbergin might have the potential to inhibit neurodegenerative disease progression.

A Whole-Genome Sequencing Study Implicates GRAMD1B in Multiple Sclerosis Susceptibility

While the role of common genetic variants in multiple sclerosis (MS) has been elucidated in large genome-wide association studies, the contribution of rare variants to the disease remains unclear. Herein, a whole-genome sequencing study in four affected and four healthy relatives of a consanguineous Italian family identified a novel missense c.1801T > C (p.S601P) variant in the GRAMD1B gene that is shared within MS cases and resides under a linkage peak (LOD: 2.194). Sequencing GRAMD1B in 91 familial MS cases revealed two additional rare missense and two splice-site variants, two of which (rs755488531 and rs769527838) were not found in 1000 Italian healthy controls. Functional studies demonstrated that GRAMD1B, a gene with unknown function in the central nervous system (CNS), is expressed by several cell types, including astrocytes, microglia and neurons as well as by peripheral monocytes and macrophages. Notably, GRAMD1B was downregulated in vessel-associated astrocytes of active MS lesions in autopsied brains and by inflammatory stimuli in peripheral monocytes, suggesting a possible role in the modulation of inflammatory response and disease pathophysiology.

Approaching the Gut and Nasal Microbiota in Parkinson's Disease in the Era of the Seed Amplification Assays

Parkinson's disease (PD) is a neurodegenerative disorder often associated with pre-motor symptoms involving both gastrointestinal and olfactory tissues. PD patients frequently suffer from hyposmia, hyposalivation, dysphagia and gastrointestinal dysfunctions. During the last few years it has been speculated that microbial agents could play a crucial role in PD. In particular, alterations of the microbiota composition (dysbiosis) might contribute to the formation of misfolded α-synuclein, which is believed to be the leading cause of PD. However, while several findings confirmed that there might be an important link between intestinal microbiota alterations and PD onset, little is known about the potential contribution of the nasal microbiota. Here, we describe the latest findings on this topic by considering that more than 80% of patients with PD develop remarkable olfactory deficits in their prodromal disease stage. Therefore, the nasal microbiota might contribute to PD, eventually boosting the gut microbiota in promoting disease onset. Finally, we present the applications of the seed amplification assays to the study of the gut and olfactory mucosa of PD patients, and how they could be exploited to investigate whether pathogenic bacteria present in the gut and the nose might promote α-synuclein misfolding and aggregation.

Redox and Calcium Alterations of a Müller Cell Line Exposed to Diabetic Retinopathy-Like Environment

Diabetic retinopathy (DR) is a common complication of diabetes mellitus and is the major cause of vision loss in the working-age population. Although DR is traditionally considered a microvascular disease, an increasing body of evidence suggests that neurodegeneration is an early event that occurs even before the manifestation of vasculopathy. Accordingly, attention should be devoted to the complex neurodegenerative process occurring in the diabetic retina, also considering possible functional alterations in non-neuronal cells, such as glial cells. In this work, we investigate functional changes in Müller cells, the most abundant glial population present within the retina, under experimental conditions that mimic those observed in DR patients. More specifically, we investigated on the Müller cell line rMC-1 the effect of high glucose, alone or associated with activation processes and oxidative stress. By fluorescence microscopy and cellular assays approaches, we studied the alteration of functional properties, such as reactive oxygen species production, antioxidant response, calcium homeostasis, and mitochondrial membrane potential. Our results demonstrate that hyperglycaemic-like condition per se is well-tolerated by rMC-1 cells but makes them more susceptible to a pro-inflammatory environment, exacerbating the effects of this stressful condition. More specifically, rMC-1 cells exposed to high glucose decrease their ability to counteract oxidative stress, with consequent toxic effects. In conclusion, our study offers new insights into Müller cell pathophysiology in DR and proposes a novel in vitro model which may prove useful to further investigate potential antioxidant and anti-inflammatory molecules for the prevention and/or treatment of DR.

Diphenylarsinic acid induced activation of MAP kinases, transcription factors, and oxidative stress-responsive factors and hypersecretion of cytokines in cultured normal human cerebellar astrocytes

Diphenylarsinic acid (DPAA) is a non-natural pentavalent organic arsenic and was detected in well water in Kamisu, Ibaraki, Japan in 2003. Individuals that had consumed this arsenic-contaminated water developed cerebellar symptoms such as myoclonus. We previously revealed that DPAA exposure in rats in vitro and in vivo specifically affected astrocytes rather than neurons among cerebellar cells. Here, we evaluated adverse effects of DPAA in cultured normal human cerebellar astrocytes (NHA), which were compared with those in normal rat cerebellar astrocytes (NRA) exposed to DPAA at 10 μM for 96 h, focusing on aberrant activation of astrocytes; increase in cell viability, activation of MAP kinases (ERK1/2, p38MAPK, and SAPK/JNK) and transcription factors (CREB, c-Jun, and c-Fos), upregulation of oxidative stress-responsive factors (Nrf2, HO-1, and Hsp70), and also hypersecretion of brain cytokines (MCP-1, adrenomedullin, FGF-2, CXCL1, and IL-6) as reported in NRA. While DPAA exposure at 10 μM for 96 h had little effect on NHA, a higher concentration (50 μM for 96 h) and longer exposure (10 μM for 288 h) induced similar aberrant activation. Moreover, exposure to DPAA at 50 μM for 96 h or 10 μM for 288 h in NHA induced hypersecretion of cytokines induced in DPAA-exposed NRA (MCP-1, adrenomedullin, FGF-2, CXCL1, and IL-6), and IL-8 besides into culture medium. These results suggested that aberrantly activated human astrocytes by DPAA exposure might play a pivotal role in the pathogenesis of cerebellar symptoms, affecting adjacent neurons, microglia, brain blood vessels, or astrocyte itself through these brain cytokines in human.

Gα13 Contributes to LPS-Induced Morphological Alterations and Affects Migration of Microglia

Microglia are the resident immune cells of the CNS that are activated in response to a variety of stimuli. This phenotypical change is aimed to maintain the local homeostasis, also by containing the insults and repair the damages. All these processes are tightly regulated and coordinated and a failure in restoring homeostasis by microglia can result in the development of neuroinflammation that can facilitate the progression of pathological conditions. Indeed, chronic microglia activation is commonly recognized as a hallmark of many neurological disorders, especially at an early stage. Many complex pathways, including cytoskeletal remodeling, are involved in the control of the microglial phenotypical and morphological changes that occur during activation. In this work, we focused on the small GTPase Gα13 and its role at the crossroad between RhoA and Rac1 signaling when microglia is exposed to pro-inflammatory stimulation. We propose the direct involvement of Gα13 in the cytoskeletal rearrangements mediated by FAK, LIMK/cofilin, and Rac1 during microglia activation. In fact, we show that Gα13 knockdown significantly inhibited LPS-induced microglial cell activation, in terms of both changes in morphology and migration, through the modulation of FAK and one of its downstream effectors, Rac1. In conclusion, we propose Gα13 as a critical factor in the regulation of morphological and functional properties of microglia during activation, which might become a target of intervention for the control of microglia inflammation.

A 3D Fiber-Hydrogel Based Non-Viral Gene Delivery Platform Reveals that microRNAs Promote Axon Regeneration and Enhance Functional Recovery Following Spinal Cord Injury

Current treatment approaches toward spinal cord injuries (SCI) have mainly focused on overcoming the inhibitory microenvironment that surrounds lesion sites. Unfortunately, the mere modulation of the cell/tissue microenvironment is often insufficient to achieve desired functional recovery. Therefore, stimulating the intrinsic growth ability of injured neurons becomes crucial. MicroRNAs (miRs) play significant roles during axon regeneration by regulating local protein synthesis at growth cones. However, one challenge of using miRs to treat SCI is the lack of efficient delivery approaches. Here, a 3D fiber-hydrogel scaffold is introduced which can be directly implanted into a spinal cord transected rat. This 3D scaffold consists of aligned electrospun fibers which provide topographical cues to direct axon regeneration, and collagen matrix which enables a sustained delivery of miRs. Correspondingly, treatment with Axon miRs (i.e., a cocktail of miR-132/miR-222/miR-431) significantly enhances axon regeneration. Moreover, administration of Axon miRs along with anti-inflammatory drug, methylprednisolone, synergistically enhances functional recovery. Additionally, this combined treatment also decreases the expression of pro-inflammatory genes and enhance gene expressions related to extracellular matrix deposition. Finally, increased Axon miRs dosage with methylprednisolone, significantly promotes functional recovery and remyelination. Altogether, scaffold-mediated Axon miR treatment with methylprednisolone is a promising therapeutic approach for SCI.

Adrenomedullin 2 attenuates LPS-induced inflammation in microglia cells by receptor-mediated cAMP-PKA pathway

Inflammation plays a critical role in the development of neurodegenerative diseases. Adrenomedullin 2 (AM2), a member of the calcitonin gene-related peptide family, has been known to have anti-inflammatory effects. Here, we evaluated the anti-inflammatory effects of AM2 in LPS-activated microglia and BV2 cells. The endogenous mRNA and protein expressions of AM2, calcitonin receptor-like receptor (CLR), receptor activity-modifying proteins (RAMPs) including RAMP1, RAMP2 and RAMP3 and the production of inflammatory mediators including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were detected by RT-PCR and Western blot. Our results revealed that LPS (1 μg/mL) significantly stimulated CLR, RAMP1, RAMP2 and RAMP3 protein expressions in BV2 microglia cells, but AM2 had a significant decrease. However, the mRNA levels of AM2, CLR, and RAMP1/2/3 were all markedly increased. LPS also induced obvious increases in mRNA and protein levels of the inflammatory mediators (TNF-α, IL-1β, COX2 and iNOS). More importantly, AM2 (10 nM) administration effectively inhibited the mRNA and protein expressions of these mediators induced by LPS and increased the cAMP content in LPS-stimulated BV2 cells. Furthermore, the antagonism with AM2 receptor antagonist IMD17-47, adrenomedullin (AM) receptor antagonist by AM22-52 or the inhibition of protein kinase A (PKA) activation by P1195 effectively prevented the inhibitory role of AM2 in LPS-induced production of the above inflammatory mediators. In conclusion, AM2 inhibits LPS-induced inflammation in BV2 microglia cells that may be mainly through AM receptor-mediated cAMP-PKA pathway. Our results indicate AM2 plays an important protective role in microglia inflammation, suggesting therapeutic potential for AM2 in neuroinflammation diseases caused by activated microglia.

Adrenomedullin: A vasoactive agent for sporadic and hereditary vascular cognitive impairment

Adrenomedullin (AM) is an endogenous peptide mainly secreted from endothelial cells, which has multiple physiological actions such as anti-inflammation, vasodilation, vascular permeability regulation and angiogenesis. Blood AM levels are upregulated in a variety of pathological states including sepsis, severe COVID-19, acute ischemic stroke and vascular cognitive impairment with white matter changes, likely serving as a compensatory biological defense response against infection and ischemia. AM is currently being tested in clinical trials for ulcerative colitis, Crohn's disease, severe COVID-19 for its anti-inflammatory properties and in ischemic stroke for its additional angiogenic action. AM has been proposed as a therapeutic option for vascular cognitive impairment as its arteriogenic and angiogenic properties are thought to contribute to a slowing of cognitive decline in mice after chronic cerebral hypoperfusion. As AM promotes differentiation of oligodendrocyte precursor cells into mature oligodendrocytes under hypoxic conditions, AM could also be used in the treatment of CADASIL, where reduced oxygen delivery is thought to lead to the death of hypoxia-prone oligodendrocytes. AM therefore holds potential as an innovative therapeutic drug, which may regenerate blood vessels, while controlling inflammation in cerebrovascular diseases.

Do the Bugs in Your Gut Eat Your Memories? Relationship between Gut Microbiota and Alzheimer's Disease

The human microbiota is composed of trillions of microbial cells inhabiting the oral cavity, skin, gastrointestinal (GI) tract, airways, and reproductive organs. The gut microbiota is composed of dynamic communities of microorganisms that communicate bidirectionally with the brain via cytokines, neurotransmitters, hormones, and secondary metabolites, known as the gut microbiota-brain axis. The gut microbiota-brain axis is suspected to be involved in the development of neurological diseases, including Alzheimer's disease (AD), Parkinson's disease, and Autism Spectrum Disorder. AD is an irreversible, neurodegenerative disease of the central nervous system (CNS), characterized by amyloid-β plaques, neurofibrillary tangles, and neuroinflammation. Microglia and astrocytes, the resident immune cells of the CNS, play an integral role in AD development, as neuroinflammation is a driving factor of disease severity. The gut microbiota-brain axis is a novel target for Alzheimer's disease therapeutics to modulate critical neuroimmune and metabolic pathways. Potential therapeutics include probiotics, prebiotics, fecal microbiota transplantation, and dietary intervention. This review summarizes our current understanding of the role of the gut microbiota-brain axis and neuroinflammation in the onset and development of Alzheimer's disease, limitations of current research, and potential for gut microbiota-brain axis targeted therapies.

Sumatriptan improves the locomotor activity and neuropathic pain by modulating neuroinflammation in rat model of spinal cord injury

OBJECTIVES

To investigate the therapeutic effects of sumatriptan in a rat model of spinal cord injury (SCI) and possible anti-inflammatory and analgesic mechanisms underlying this effect.

METHODS

Using an aneurysm mini-clip model of contusive SCI, T9-10 laminectomies were performed for 60 male rats. Animals were divided into six experimental groups (n = 10 per group) as follows: a minocycline administered positive control group, a saline-vehicle negative control group, a sham-operated group, and three experimental groups which received separate doses of sumatriptan (0.1, 0.3 and 1 mg/kg). Behavioural assessments were used to evaluate locomotor activity and neuropathic pain for 28 days. At the end of the study, spinal cord tissues were collected from sacrificed animals for histopathological analysis. Levels of calcitonin gene-related peptide (CGRP) and two pro-inflammatory cytokines (tumor necrosis factor [TNF]-α and interleukin [IL]-1β) were assessed by the enzyme-linked immunosorbent assay (ELISA).

RESULTS

Sumatriptan significantly (P < 0.001) improved the locomotor activity in SCI group. Sumatriptan was also more effective than the positive control, i.e. minocycline (0.3 mg/kg). Additionally, sumatriptan and minocycline similarly attenuated the mechanical and thermal allodynia in SCI (P < 0.001). TNF-α, IL-1β and CGRP levels in sumatriptan- and minocycline-treated groups significantly (P < 0.001) decreased compared to controls. Histopathological analysis also revealed a markedly improvement in hemorrhage followed by inflammatory cell invasion, neuronal vacuolation, and cyst formation in both sumatriptan- and minocycline-treated groups compared to control animals.

CONCLUSIONS

Sumatriptan improves functional recovery from SCI through its anti-inflammatory effects and reducing pro-inflammatory and pain mediators.

Phyllanthus amarus prevents LPS-mediated BV2 microglial activation via MyD88 and NF-κB signaling pathways

BACKGROUND

Phyllanthus amarus has been shown to attenuate lipopolysaccharide (LPS)-induced peripheral inflammation but similar studies in the central nervous system are scarce. The aim of the present study was to investigate the neuroprotective effects of 80% ethanol extract of P. amarus (EPA) in LPS-activated BV2 microglial cells.

METHODS

BV2 microglial cells c for 24 h, pre-treated with EPA for 24 h prior to LPS induction for another 24 h. Surface expression of CD11b and CD40 on BV2 cells was analyzed by flow cytometry. ELISA was employed to measure the production of pro-inflammatory mediators i.e. nitric oxide (NO) and tumor necrosis factor (TNF)-α. Western blotting technique was used to determine the expression of inducible nitric oxide synthase (iNOS), myeloid differentiation protein 88 (MYD88), nuclear factor kappa B (NF-κB), caspase-1, and mitogen activated protein kinase (MAPK).

RESULTS

Qualitative and quantitative analyses of the EPA using a validated ultra-high pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method indicated the presence of phyllanthin, hypophyllanthin, niranthin, ellagic acid, corilagin, gallic acid, phyltetralin, isolintetralin and geraniin. EPA suppressed the production of NO and TNFα in LPS-activated BV2 microglial cells. Moreover, EPA attenuated the expression of MyD88, NF-κB and MAPK (p-P38, p-JNK and p-ERK1/2). It also inhibited the expression of CD11b and CD40. EPA protected against LPS-induced microglial activation via MyD88 and NF-κB signaling in BV2 microglial cells.

CONCLUSIONS

EPA demonstrated neuroprotective effects against LPS-induced microglial cells activation through the inhibition of TNFα secretion, iNOS protein expression and subsequent NO production, inhibition of NF-κB and MAPKs mediated by adapter protein MyD88 and inhibition of microglial activation markers CD11b and CD40.

Involvement of 5-HT1B/1D receptors in the inflammatory response and oxidative stress in intestinal ischemia/reperfusion in rats

Acute mesenteric ischemia (AMI) is caused by an abrupt cessation of blood flow to the small intestine. Reperfusion is the return of blood flow to the ischemic bowel. Intestinal ischemia/reperfusion (I/R) leads to the formation of reactive oxygen species, local inflammatory response, and may lead to the patient's death. Pre-treatment of the intestinal may reduce the high mortality associated with AMI. 5-Hydroxytryptamine 1B (5-HT1B) and 5-HT1D receptors have anti-inflammatory and neuroprotective effects in different experimental studies. We aimed to investigate the potential involvement of these receptors in intestinal I/R injury. Firstly, we assessed the expression and localization of 5-HT1B and 5-HT1D receptors in the enteric nervous system using an immunofluorescence-based method. Intestinal I/R in rats was induced by 30 min occlusion of superior mesenteric artery and reperfusion for 2 h. Rats were randomly divided in different control and I/R groups (n = 6) receiving either vehicle, sumatriptan (5-HT1B/1D receptors agonist; 0.1 mg/kg), GR127,935 (5-HT1B/1D receptors antagonist; 0.1 mg/kg) and combination of sumatriptan (0.1 mg/kg) + GR127,935 (0.1 mg/kg) before determination of biochemical and histological parameters. In the enteric nervous system, 5-HT1B and 5-HT1D receptors were expressed 17% and 11.5%, respectively. Pre-treatment with sumatriptan decreased 5-hydroxytryptamine (5HT) level by 53%, and significantly decreased calcitonin gene-related peptide (CGRP) levels, lipid pereoxidation, neutrophil infiltration, and level of pro-inflammatory markers in the serum. Histopathologic studies also showed a remarkable decrease in intestinal tissue injury. These findings suggest that sumatriptan may inhibit intestinal injury induced by I/R through modulating the inflammatory response by activation of 5-HT1B/1D receptors.

Hispidulin Inhibits Neuroinflammation in Lipopolysaccharide-Activated BV2 Microglia and Attenuates the Activation of Akt, NF-κB, and STAT3 Pathway

Microglia, resident innate immune cells in central nervous system, regulates neuroinflammation and is associated with a variety of neuropathologies. The present study investigated the antineuroinflammatory effects of hispidulin (HPD), a naturally flavone compound, in lipopolysaccharide- (LPS-) stimulated BV2 microglia cells. The expression levels of nitric oxide (NO), reactive oxygen species (ROS), and pro-inflammatory factors were determined by the Griess method, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). Western blotting was used to measure various transcription factors such as Akt, nuclear factor-kappa B (NF-κB), and signal transducer and activator of transcription 3 (STAT3) activities. Our experimental results demonstrated that HPD increased cell viability and reduced apoptosis in LPS-treated BV2 microglia cells. Moreover, HPD significantly reduced the levels of NO, ROS, inducible nitric oxide synthase (iNOS), cyclooxygenase- (COX-) 2, tumor necrosis factor- (TNF-) α, interleukin- (IL-) 1β, IL-6, and prostaglandin E2 (PGE2) in a dose-dependent manner. Phosphorylation of NF-κB/IκB, Akt, and STAT3 proteins expression by HPD was suppressed in LPS-induced BV2 microglial cells. We concluded that HPD may inhibit neuroinflammatory responses by inhibiting NF-κB pathway activation and ROS formation. These results propose that HPD has potential as anti-inflammatory agents against microglia-mediated neuroinflammatory disorders.

PERK-mediated expression of peptidylglycine α-amidating monooxygenase supports angiogenesis in glioblastoma

PKR-like kinase (PERK) plays a significant role in inducing angiogenesis in various cancer types including glioblastoma. By proteomics analysis of the conditioned medium from a glioblastoma cell line treated with a PERK inhibitor, we showed that peptidylglycine α-amidating monooxygenase (PAM) expression is regulated by PERK under hypoxic conditions. Moreover, PERK activation via CCT020312 (a PERK selective activator) increased the cleavage and thus the generation of PAM cleaved cytosolic domain (PAM sfCD) that acts as a signaling molecule from the cytoplasm to the nuclei. PERK was also found to interact with PAM, suggesting a possible involvement in the generation of PAM sfCD. Knockdown of PERK or PAM reduced the formation of tubes by HUVECs in vitro. Furthermore, in vivo data highlighted the importance of PAM in the growth of glioblastoma with reduction of PAM expression in engrafted tumor significantly increasing the survival in mice. In summary, our data revealed PAM as a potential target for antiangiogenic therapy in glioblastoma.

Immunotherapy in sepsis - brake or accelerate?

Sepsis, a life threating syndrome characterized by organ failure after infection, is the most common cause of death in hospitalized patients. The treatment of sepsis is generally supportive in nature, involving the administration of intravenous fluids, vasoactive substances and oxygen plus antibiotics to eliminate the pathogen. No drugs have been approved specifically for the treatment of sepsis, and clinical trials of potential therapies have failed to reduce mortality - suggesting that new approaches are needed. Abnormalities in the immune response elicited by the pathogen, ranging from excessive inflammation to immunosuppression, contribute to disease pathogenesis. Although hundreds of immunomodulatory agents are potentially available, it remains unclear which patient benefits from which immune therapy at a given time point. Results indicate the importance of personalized therapy, specifically the need to identify the type of intervention required by each individual patient at a given point in the disease process. To address this issue will require using biomarkers to stratify patients based on their individual immune status. This article reviews recent and ongoing clinical investigations using immunostimulatory or immunosuppressive therapies against sepsis including non-pharmacological and novel preclinical approaches.

Inhibition of calcium-calmodulin-dependent phosphodiesterase (PDE1) suppresses inflammatory responses

A novel, potent, and highly specific inhibitor of calcium-calmodulin-dependent phosphodiesterases (PDE) of the PDE1 family, ITI-214, was used to investigate the role of PDE1 in inflammatory responses. ITI-214 dose-dependently suppressed lipopolysaccharide (LPS)-induced gene expression of pro-inflammatory cytokines in an immortalized murine microglial cell line, BV2 cells. RNA profiling (RNA-Seq) was used to analyze the impact of ITI-214 on the BV2 cell transcriptome in the absence and the presence of LPS. ITI-214 was found to regulate classes of genes that are involved in inflammation and cell migration responses to LPS exposure. The gene expression changes seen with ITI-214 treatment were distinct from those elicited by inhibitors of other PDEs with anti-inflammatory activity (e.g., a PDE4 inhibitor), indicating a distinct mechanism of action for PDE1. Functionally, ITI-214 inhibited ADP-induced migration of BV2 cells through a P2Y12-receptor-dependent pathway, possibly due to increases in the extent of cAMP and VASP phosphorylation downstream of receptor activation. Importantly, this effect was recapitulated in P2 rat microglial cells in vitro, indicating that these pathways are active in native microglial cells. These studies are the first to demonstrate that inhibition of PDE1 exerts anti-inflammatory effects through effects on microglia signaling pathways. The ability of PDE1 inhibitors to prevent or dampen excessive inflammatory responses of BV2 cells and microglia provides a basis for exploring their therapeutic utility in the treatment of neurodegenerative diseases associated with increased inflammation and microglia proliferation such as Parkinson's disease and Alzheimer's disease.

Lupeol inhibits LPS-induced neuroinflammation in cerebellar cultures and induces neuroprotection associated to the modulation of astrocyte response and expression of neurotrophic and inflammatory factors

In the central nervous system (CNS), neuroinflammation, especially that modulated by the cell response of astrocytes and microglia, is associated with damage to neurons in neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease and, Multiple Sclerosis. Lupeol is a dietary triterpene that has demonstrated biological activities as antioxidant. This study investigated the anti-inflammatory and neuroprotective effects of lupeol in an in vitro model of neuroinflammation in primary cerebellar cultures. Cultures were obtained from 6-day-old Wistar rats, subjected to inflammatory damage with lipopolysaccharide (LPS, 1 μg/mL) and treated with lupeol (0.1 μM). We observed, after a 48-hour treatment, through Fluorjade-B staining and immunocytochemistry (ICQ) for βIII-tubulin, that lupeol induced neuroprotection in cultures submitted to inflammatory damage. On the other hand, through ICQ for GFAP, it was possible to observe that lupeol modulated the astrocyte morphology for Bergmann glia-like phenotype and, especially for velate astrocyte-like phenotype, both phenotypes associated with the neuroprotective profile. Moreover, RT-qPCR analysis showed that lupeol induced the down-regulation of the mRNA expression for proinflammatory markers TNF, iNOS and NLRP3, as well as the production of nitric oxide (method of Greiss), which were up-regulated by LPS, and also induced up-regulation of the mRNA expression for arginase and IL-6 mRNA. In addition, lupeol induced up-regulation of mRNA expression for neurotrophins GDNF and NGF and also for the sonic hedgehog-Gli pathway. Together, these results lead to the conclusion that lupeol inhibits neuroinflammation in cerebellar cultures and induces neuroprotection associated with the modulation of astrocyte response and expression of neurotrophic and inflammatory factors.

Identification of new molecular targets for PET imaging of the microglial anti-inflammatory activation state

Microglia are potential targets for therapeutic intervention in neurological and neurodegenerative diseases affecting the central nervous system. In order to assess the efficacy of therapies aimed to reduce the tissue damaging activities of microglia and/or to promote the protective potential of these cells, suitable pre-clinical and clinical tools for the in vivo analysis of microglia activities and dynamics are required. The aim of this work was to identify new translational markers of the anti-inflammatory / protective state of microglia for the development of novel PET tracers.

Methods: New translational markers of the anti-inflammatory/protective activation state of microglia were selected by bioinformatic approaches and were in vitro and ex vivo validated by qPCR and immunohistochemistry in rodent and human samples. Once a viable marker was identified, a novel PET tracer was developed. This tracer was subsequently confirmed by autoradiography experiments in murine and human brain tissues.

Results: Here we provide evidence that P2RY12 expression increases in murine and human microglia following exposure to anti-inflammatory stimuli, and that its expression is modulated in the reparative phase of experimental and clinical stroke. We then synthesized a novel carbon-11 labeled tracer targeting P2RY12, showing increased binding in brain sections of mice treated with IL4, and low binding to brain sections of a murine stroke model and of a stroke patient.

Conclusion: This study provides new translational targets for PET tracers for the anti-inflammatory/protective activation state of microglia and shows the potential of a rationale-based approach. It therefore paves the way for the development of novel non-invasive methodologies aimed to monitor the success of therapeutic approaches in various neurological diseases.

Corylin inhibits LPS-induced inflammatory response and attenuates the activation of NLRP3 inflammasome in microglia

Background

Inflammation has been found to be associated with many neurodegenerative diseases, including Parkinson’s and dementia. Attenuation of microglia-induced inflammation is a strategy that impedes the progression of neurodegenerative diseases.

Methods

We used lipopolysaccharide (LPS) to simulate murine microglia cells (BV2 cells) as an experimental model to mimic the inflammatory environment in the brain. In addition, we examined the anti-inflammatory ability of corylin, a main compound isolated from Psoralea corylifolia L. that is commonly used in Chinese herbal medicine. The production of nitric oxide (NO) by LPS-activated BV2 cells was measured using Griess reaction. The secretion of proinflammatory cytokines including tumor necrosis factor (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) by LPS-activated BV2 cells was analyzed using enzyme-linked immunosorbent assay (ELISA). The expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase-activation and recruitment domain (ASC), caspase-1, IL-1β and mitogen-activated protein kinases (MAPKs) in LPS-activated BV2 cells was examined by Western blot.

Results

Our experimental results demonstrated that corylin suppressed the production of NO and proinflammatory cytokines by LPS-activated BV2 cells. In addition, corylin inhibited the expression of iNOS and COX-2, attenuated the phosphorylation of ERK, JNK and p38, decreased the expression of NLRP3 and ASC, and repressed the activation of caspase-1 and IL-1β by LPS-activated BV2 cells.

Conclusion

Our results indicate the anti-inflammatory effects of corylin acted through attenuating LPS-induced inflammation and inhibiting the activation of NLRP3 inflammasome in LPS-activated BV2 cells. These results suggest that corylin might have potential in treating brain inflammation and attenuating the progression of neurodegeneration diseases.

Calcitonin gene-related peptide decreases IL-1beta, IL-6 as well as Ym1, Arg1, CD163 expression in a brain tissue context-dependent manner while ameliorating experimental autoimmune encephalomyelitis

Activation states of immune cells (among them, the so-called pro- or anti-inflammatory states) influence the pathogenesis of multiple sclerosis (MS). The neuropeptide calcitonin gene-related peptide (CGRP) can exert a pro- or anti-inflammatory role in a context-dependent manner. In mice CGRP was found to attenuate the development of experimental autoimmune encephalomyelitis (EAE, a common MS animal model). We analyzed CGRP effects on the expression of cytokines and markers of activation states, as well as its intracellular cascade, following intrathecal administration during EAE immunization. Real Time quantitative-PCR (RT-PCR) showed that IL-1beta and IL-6 (associated to a pro-inflammatory state in EAE), but also Ym1 (also known as Chil3), Arg1 and CD163 (associated to an anti-inflammatory state in EAE) were decreased in the encephalon (devoid of cerebellum). In the cerebellum itself, IL-1beta and Ym1 were decreased. TNF-alpha (associated to a pro-inflammatory state in EAE), but also IL-10 (associated to another type of anti-inflammatory state) and BDNF were unchanged in these two regions. No changes were detected in the spinal cord. Additional tendencies toward a change (as revealed by RT-PCR) were again decreases: IL-10 in the encephalon and Arg1 in the spinal cord. CGRP decreased percentage of Ym1⁺/CD68⁺ immunoreactive cells and cell density of infiltrates in the cervical spinal cord pia mater. Instead, Ym1 in the underlying parenchyma and at thoracic and lumbar levels, as well as Arg1, were unchanged. In cultured microglia the neuropeptide decreased Ym1, but not Arg1, immunoreactivity. Inducible NOS (iNOS) was unchanged in spinal cord microglia and astrocytes. The neuropeptide increased the activation of ERK1/2 in the astrocytes of the spinal cord and in culture, but did not influence the activation of ERK1/2 or p38 in the spinal cord microglia. Finally, in areas adjacent to infiltration sites CGRP-treated microglia showed a larger ramification radius. In conclusion, CGRP-induced EAE amelioration was associated to a concomitant, context-dependent decrease in the expression of markers belonging to both pro- or anti-inflammatory activation states of immune cells. It can be hypothesized that CGRP-induced EAE attenuation is obtained through a novel mechanism that promotes down-regulation of immune cell activation that facilitates the establishment of a beneficial environment in EAE provided possibly also by other factors.

Necrotizing enterocolitis is associated with acute brain responses in preterm pigs

Background

Necrotizing enterocolitis (NEC) is an acute gut inflammatory disorder that occurs in preterm infants in the first weeks after birth. Infants surviving NEC often show impaired neurodevelopment. The mechanisms linking NEC lesions with later neurodevelopment are poorly understood but may include proinflammatory signaling in the immature brain. Using preterm pigs as a model for preterm infants, we hypothesized that severe intestinal NEC lesions are associated with acute effects on the developing hippocampus.

Methods

Cesarean-delivered preterm pigs (n = 117) were reared for 8 days and spontaneously developed variable severity of NEC lesions. Neonatal arousal, physical activity, and in vitro neuritogenic effects of cerebrospinal fluid (CSF) were investigated in pigs showing NEC lesions in the colon (Co-NEC) or in the small intestine (Si-NEC). Hippocampal transcriptome analysis and qPCR were used to assess gene expressions and their relation to biological processes, including neuroinflammation, and neural plasticity. Microglia activation was quantified by stereology. The neuritogenic response to selected proteins was investigated in primary cultures of hippocampal neurons.

Results

NEC development rapidly reduced the physical activity of pigs, especially when lesions occurred in the small intestine. Si-NEC and Co-NEC were associated with 27 and 12 hippocampal differentially expressed genes (DEGs), respectively. These included genes related to neuroinflammation (i.e., S100A8, S100A9, IL8, IL6, MMP8, SAA, TAGLN2) and hypoxia (i.e., PDK4, IER3, TXNIP, AGER), and they were all upregulated in Si-NEC pigs. Genes related to protection against oxidative stress (HBB, ALAS2) and oligodendrocytes (OPALIN) were downregulated in Si-NEC pigs. CSF collected from NEC pigs promoted neurite outgrowth in vitro, and the S100A9 and S100A8/S100A9 proteins may mediate the neuritogenic effects of NEC-related CSF on hippocampal neurons. NEC lesions did not affect total microglial cell number but markedly increased the proportion of Iba1-positive amoeboid microglial cells.

Conclusions

NEC lesions, especially when present in the small intestine, are associated with changes to hippocampal gene expression that potentially mediate neuroinflammation and disturbed neural circuit formation via enhanced neuronal differentiation. Early brain-protective interventions may be critical for preterm infants affected by intestinal NEC lesions to reduce their later neurological dysfunctions.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1201-x) contains supplementary material, which is available to authorized users.

Adrenomedullin, a Novel Target for Neurodegenerative Diseases

Neurodegenerative diseases represent a heterogeneous group of disorders whose common characteristic is the progressive degeneration of neuronal structure and function. Although much knowledge has been accumulated on the pathophysiology of neurodegenerative diseases over the years, more efforts are needed to understand the processes that underlie these diseases and hence to propose new treatments. Adrenomedullin (AM) is a multifunctional peptide involved in vasodilation, hormone secretion, antimicrobial defense, cellular growth, and angiogenesis. In neurons, AM and related peptides are associated with some structural and functional cytoskeletal proteins that interfere with microtubule dynamics. Furthermore, AM may intervene in neuronal dysfunction through other mechanisms such as immune and inflammatory response, apoptosis, or calcium dyshomeostasis. Alterations in AM expression have been described in neurodegenerative processes such as Alzheimer's disease or vascular dementia. This review addresses the current state of knowledge on AM and its possible implication in neurodegenerative diseases.

Adrenomedullin and Adrenomedullin-Targeted Therapy As Treatment Strategies Relevant for Sepsis

Sepsis remains a major medical challenge, for which, apart from improvements in supportive care, treatment has not relevantly changed over the last few decades. Vasodilation and vascular leakage play a pivotal role in the development of septic shock, with vascular leakage being caused by disrupted endothelial integrity. Adrenomedullin (ADM), a free circulating peptide involved in regulation of endothelial barrier function and vascular tone, is implicated in the pathophysiology of sepsis. ADM levels are increased during sepsis, and correlate with extent of vasodilation, as well as with disease severity and mortality. In vitro and preclinical in vivo data show that administration of ADM exerts anti-inflammatory, antimicrobial, and protective effects on endothelial barrier function during sepsis, but other work suggests that it may also decrease blood pressure, which could be detrimental for patients with septic shock. Work has been carried out to negate ADMs putative negative effects, while preserving or even potentiating its beneficial actions. Preclinical studies have demonstrated that the use of antibodies that bind to the N-terminus of ADM results in an overall increase of circulating ADM levels and improves sepsis outcome. Similar beneficial effects were obtained using coadministration of ADM and ADM-binding protein-1. It is hypothesized that the mechanism behind the beneficial effects of ADM binding involves prolongation of its half-life and a shift of ADM from the interstitium to the circulation. This in turn results in increased ADM activity in the blood compartment, where it exerts beneficial endothelial barrier-stabilizing effects, whereas its detrimental vasodilatory effects in the interstitium are reduced. Up till now, in vivo data on ADM-targeted treatments in humans are lacking; however, the first study in septic patients with an N-terminus antibody (Adrecizumab) is currently being conducted.

eIF4B phosphorylation at Ser504 links synaptic activity with protein translation in physiology and pathology

Neuronal physiology requires activity-driven protein translation, a process in which translation initiation factors are key players. We focus on eukaryotic initiation factor 4B (eIF4B), a regulator of protein translation, whose function in neurons is undetermined. We show that neuronal activity affects eIF4B phosphorylation and identify Ser504 as a phosphorylation site regulated by casein kinases and sensitive to the activation of metabotropic glutamate receptors. Ser504 phosphorylation increases eIF4B recruitment to the pre-initiation complex and influences eIF4B localization at synapses. Moreover, Ser504 phosphorylation modulates the translation of protein kinase Mζ. Therefore, by sensing synaptic activity, eIF4B could adjust translation to neuronal needs, promoting adaptive changes in synaptic plasticity. We also show that Ser504 phosphorylation is increased in vivo in a rat model of epilepsy during epileptogenesis i.e. when translation drives maladaptive synaptic changes. We propose eIF4B as a mediator between neuronal activity and translation, with relevance in the control of synaptic plasticity.

Neuropeptides and Microglial Activation in Inflammation, Pain, and Neurodegenerative Diseases

Microglial cells are responsible for immune surveillance within the CNS. They respond to noxious stimuli by releasing inflammatory mediators and mounting an effective inflammatory response. This is followed by release of anti-inflammatory mediators and resolution of the inflammatory response. Alterations to this delicate process may lead to tissue damage, neuroinflammation, and neurodegeneration. Chronic pain, such as inflammatory or neuropathic pain, is accompanied by neuroimmune activation, and the role of glial cells in the initiation and maintenance of chronic pain has been the subject of increasing research over the last two decades. Neuropeptides are small amino acidic molecules with the ability to regulate neuronal activity and thereby affect various functions such as thermoregulation, reproductive behavior, food and water intake, and circadian rhythms. Neuropeptides can also affect inflammatory responses and pain sensitivity by modulating the activity of glial cells. The last decade has witnessed growing interest in the study of microglial activation and its modulation by neuropeptides in the hope of developing new therapeutics for treating neurodegenerative diseases and chronic pain. This review summarizes the current literature on the way in which several neuropeptides modulate microglial activity and response to tissue damage and how this modulation may affect pain sensitivity.

Disruption of calcitonin gene-related peptide signaling accelerates muscle denervation and dampens cytotoxic neuroinflammation in SOD1 mutant mice

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease. Neuronal vacuolization and glial activation are pathologic hallmarks in the superoxide dismutase 1 (SOD1) mouse model of ALS. Previously, we found the neuropeptide calcitonin gene-related peptide (CGRP) associated with vacuolization and astrogliosis in the spinal cord of these mice. We now show that CGRP abundance positively correlated with the severity of astrogliosis, but not vacuolization, in several motor and non-motor areas throughout the brain. SOD1 mice harboring a genetic depletion of the βCGRP isoform showed reduced CGRP immunoreactivity associated with vacuolization, while motor functions, body weight, survival, and astrogliosis were not altered. When CGRP signaling was completely disrupted through genetic depletion of the CGRP receptor component, receptor activity-modifying protein 1 (RAMP1), hind limb muscle denervation, and loss of muscle performance were accelerated, while body weight and survival were not affected. Dampened neuroinflammation, i.e., reduced levels of astrogliosis in the brain stem already in the pre-symptomatic disease stage, and reduced microgliosis and lymphocyte infiltrations during the late disease phase were additional neuropathology features in these mice. On the molecular level, mRNA expression levels of brain-derived neurotrophic factor (BDNF) and those of the anti-inflammatory cytokine interleukin 6 (IL-6) were elevated, while those of several pro-inflammatory cytokines found reduced in the brain stem of RAMP1-deficient SOD1 mice at disease end stage. Our results thus identify an important, possibly dual role of CGRP in ALS pathogenesis.

Calcitonin Peptide Family Members Are Differentially Regulated by LPS and Inhibit Functions of Rat Alveolar NR8383 Macrophages

Members of the calcitonin peptide family—calcitonin gene-related peptide (CGRP), adrenomedullin (AM), and adrenomedullin2/intermedin (IMD)–exert modulatory effects upon monocytes and macrophages of various extrapulmonary origins. Utilizing the rat alveolar macrophage (AMφ) cell line NR8383, we here set out to determine to which extent these three peptides and their receptors are differentially regulated in AMφ and what specific effects they have on AMφ key functions. LPS treatment differentially up-regulated expression of the peptides and receptors. Among the three peptides, IMD mRNA content was lowest both in primary rat AMφ and NR8383 cells, whereas IMD peptide dominated in basal and LPS-stimulated secretion from NR8383 cells. Fcγ receptor-mediated phagocytosis and TNF-α production were inhibited by AM, IMD, and CGRP, whereas pro-IL-1β mRNA was slightly down-regulated exclusively by CGRP. Neither of these peptides affected IL-6 or IL-10 production. None increased intracellular calcium concentration, but AM significantly inhibited store-operated calcium entry. In conclusion, the rat AMφ cell line NR8383 is both a source and a target of the calcitonin peptide family members AM, IMD, and CGRP. Despite sharing proteins of the receptor complexes, AM, IMD, and CGRP each showed a characteristic pattern of effects and regulation, suggesting that these closely related peptides are not just redundant members of one common signaling pathway but act in concert by addressing parallel signaling cascades. Since peptide and receptor expression are up-regulated by LPS, these signaling pathways might act as inhibitory feedback mechanisms in pulmonary bacterial infection.

An intracellular adrenomedullin system reduces IL-6 release via a NF-kB-mediated, cAMP-independent transcriptional mechanism in rat thymic epithelial cells

Thymic epithelial cells (TECs) play a key role in the regulation of central immune tolerance by expressing autoantigens and eliminating self-reactive T cells. In a previous paper we reported that adrenomedullin (ADM) and its co-receptor protein RAMP2 are located intracellularly in newborn human thymic epithelial cells (TECs). This work has two main aims: (1) to examine the cellular localization of ADM and its receptor in TECs of adult Wistar rats to validate this animal model for the study of the ADM system and its function(s) in thymus; (2) to investigate the potential modulating effect of ADM on the NF-kB pathway, which is involved through the production of cytokines such as IL-6, in the maturation of T-lymphocytes and immunological tolerance. Our results show that, similarly to human newborn TECs, ADM is localized to the cytoplasm of adult rat TECs, and RAMP2 is expressed in the nucleus but not in the plasma membrane. Pretreatment of TECs for 4h with ADM significantly reduced lipopolysaccharide (LPS)-induced release of IL-6 (P<0.001) and expression of the p65 subunit of NF-kB, while doubled the expression of IkBα (P<0.001), the physiological inhibitor of NF-kB nuclear translocation. These effects were not mediated by activation of the cAMP pathway, a signalling cascade that is rapidly activated by ADM in cells that express plasma membrane RAMP2, but were the consequence of a reduction in the transcription of p65 (P<0.001) and an increase in the transcription of IkBα (P<0.05). On the basis of these findings we propose that in rat TECs ADM reduces IL-6 secretion by modulating NF-kB genes transcription through an interaction with a receptor localized to the nucleus. This may partly explain the protective effects of ADM in autoimmune diseases and points to the ADM system of TECs as a novel potential target for immunomodulating drugs.

Microglia-Induced Maladaptive Plasticity Can Be Modulated by Neuropeptides In Vivo

Microglia-induced maladaptive plasticity is being recognized as a major cause of deleterious self-sustaining pathological processes that occur in neurodegenerative and neuroinflammatory diseases. Microglia, the primary homeostatic guardian of the central nervous system, exert critical functions both during development, in neural circuit reshaping, and during adult life, in the brain physiological and pathological surveillance. This delicate critical role can be disrupted by neural, but also peripheral, noxious stimuli that can prime microglia to become overreactive to a second noxious stimulus or worsen underlying pathological processes. Among regulators of microglia, neuropeptides can play a major role. Their receptors are widely expressed in microglial cells and neuropeptide challenge can potently influence microglial activity in vitro. More relevantly, this regulator activity has been assessed also in vivo, in experimental models of brain diseases. Neuropeptide action in the central nervous system has been associated with beneficial effects in neurodegenerative and neuroinflammatory pathological experimental models. This review describes some of the mechanisms of the microglia maladaptive plasticity in vivo and how neuropeptide activity can represent a useful therapeutical target in a variety of human brain pathologies.

Purinergic Modulation of Spinal Neuroglial Maladaptive Plasticity Following Peripheral Nerve Injury

Modulation of spinal reactive gliosis following peripheral nerve injury (PNI) is a promising strategy to restore synaptic homeostasis. Oxidized ATP (OxATP), a nonselective antagonist of purinergic P2X receptors, was found to recover a neuropathic behavior following PNI. We investigated the role of intraperitoneal (i.p.) OxATP treatment in restoring the expression of neuronal and glial markers in the mouse spinal cord after sciatic spared nerve injury (SNI). Using in vivo two-photon microscopy, we imaged Ca(2+) transients in neurons and astrocytes of the dorsal horn of spinal cord at rest and upon right hind paw electrical stimulation in sham, SNI, and OxATP-treated mice. Neuropathic behavior was investigated by von Frey and thermal plantar test. Glial [glial fibrillary acidic protein (GFAP), ionized calcium-binding adaptor molecule 1 (Iba1)] and GABAergic [vesicular GABA transporter (vGAT) and glutamic acid decarboxylase 65/76 (GAD65/67)] markers and glial [glutamate transporter (GLT1) and GLAST] and neuronal amino acid [EAAC1, vesicular glutamate transporter 1 (vGLUT1)] transporters have been evaluated. In SNI mice, we found (i) increased glial response, (ii) decreased glial amino acid transporters, and (iii) increased levels of neuronal amino acid transporters, and (iv) in vivo analysis of spinal neurons and astrocytes showed a persistent increase of Ca(2+) levels. OxATP administration reduced glial activation, modulated the expression of glial and neuronal glutamate/GABA transporters, restored neuronal and astrocytic Ca(2+) levels, and prevented neuropathic behavior. In vitro studies validated that OxATP (i) reduced levels of reactive oxygen species (ROS), (ii) reduced astrocytic proliferation, (iii) increase vGLUT expression. All together, these data support the correlation between reactive gliosis and perturbation of the spinal synaptic homeostasis and the role played by the purinergic system in modulating spinal plasticity following PNI.

Ceruloplasmin potentiates nitric oxide synthase activity and cytokine secretion in activated microglia

BACKGROUND

Ceruloplasmin is a ferroxidase expressed in the central nervous system both as soluble form in the cerebrospinal fluid (CSF) and as membrane-bound GPI-anchored isoform on astrocytes, where it plays a role in iron homeostasis and antioxidant defense. It has been proposed that ceruloplasmin is also able to activate microglial cells with ensuing nitric oxide (NO) production, thereby contributing to neuroinflammatory conditions. In light of the possible role of ceruloplasmin in neurodegenerative diseases, we were prompted to investigate how this protein could contribute to microglial activation in either its native form, as well as in its oxidized form, recently found generated in the CSF of patients with Parkinson's and Alzheimer's diseases.

METHODS

Primary rat microglial-enriched cultures were treated with either ceruloplasmin or oxidized-ceruloplasmin, alone or in combination with lipopolysaccharide (LPS). Production of NO and expression of inducible nitric oxide synthase (iNOS) were evaluated by Griess assay and Western blot analysis, respectively. The productions of the pro-inflammatory cytokine IL-6 and the chemokine MIP-1α were assessed by quantitative RT-PCR and ELISA.

RESULTS

Regardless of its oxidative status, ceruloplasmin by itself was not able to activate primary rat microglia. However, ceruloplasmin reinforced the LPS-induced microglial activation, promoting an increase of NO production, as well as the induction of IL-6 and MIP-1α. Interestingly, the ceruloplasmin-mediated effects were observed in the absence of an additional induction of iNOS expression. The evaluation of iNOS activity in primary glial cultures and in vitro suggested that the increased NO production induced by the combined LPS and ceruloplasmin treatment is mediated by a potentiation of the enzymatic activity.

CONCLUSIONS

Ceruloplasmin potentiates iNOS activity in microglial cells activated by a pro-inflammatory stimulus, without affecting iNOS expression levels. This action might be mediated by the activation of a yet unknown Cp receptor that triggers intracellular signaling that cross-talks with the response elicited by LPS or other pro-inflammatory stimuli. Therefore, ceruloplasmin might contribute to pathological conditions in the central nervous system by exacerbating neuroinflammation.

Expression of inducible nitric oxide synthase (iNOS) in microglia of the developing quail retina

Inducible nitric oxide synthase (iNOS), which produce large amounts of nitric oxide (NO), is induced in macrophages and microglia in response to inflammatory mediators such as LPS and cytokines. Although iNOS is mainly expressed by microglia that become activated in different pathological and experimental situations, it was recently reported that undifferentiated amoeboid microglia can also express iNOS during normal development. The aim of this study was to investigate the pattern of iNOS expression in microglial cells during normal development and after their activation with LPS by using the quail retina as model. iNOS expression was analyzed by iNOS immunolabeling, western-blot, and RT-PCR. NO production was determined by using DAR-4M AM, a reliable fluorescent indicator of subcellular NO production by iNOS. Embryonic, postnatal, and adult in situ quail retinas were used to analyze the pattern of iNOS expression in microglial cells during normal development. iNOS expression and NO production in LPS-treated microglial cells were investigated by an in vitro approach based on organotypic cultures of E8 retinas, in which microglial cell behavior is similar to that of the in situ retina, as previously demonstrated in our laboratory. We show here that amoeboid microglia in the quail retina express iNOS during normal development. This expression is stronger in microglial cells migrating tangentially in the vitreal part of the retina and is downregulated, albeit maintained, when microglia differentiate and become ramified. LPS treatment of retina explants also induces changes in the morphology of amoeboid microglia compatible with their activation, increasing their lysosomal compartment and upregulating iNOS expression with a concomitant production of NO. Taken together, our findings demonstrate that immature microglial cells express iNOS during normal development, suggesting a certain degree of activation. Furthermore, LPS treatment induces overactivation of amoeboid microglia, resulting in a significant iNOS upregulation.

Relations between metabolic homeostasis, diet, and peripheral afferent neuron biology

It is well established that food intake behavior and energy balance are regulated by crosstalk between peripheral organ systems and the central nervous system (CNS), for instance, through the actions of peripherally derived leptin on hindbrain and hypothalamic loci. Diet- or obesity-associated disturbances in metabolic and hormonal signals to the CNS can perturb metabolic homeostasis bodywide. Although interrelations between metabolic status and diet with CNS biology are well characterized, afferent networks (those sending information to the CNS from the periphery) have received far less attention. It is increasingly appreciated that afferent neurons in adipose tissue, the intestines, liver, and other tissues are important controllers of energy balance and feeding behavior. Disruption in their signaling may have consequences for cardiovascular, pancreatic, adipose, and immune function. This review discusses the diverse ways that afferent neurons participate in metabolic homeostasis and highlights how changes in their function associate with dysmetabolic states, such as obesity and insulin resistance.

Expression and distribution of the adrenomedullin system in newborn human thymus

Adrenomedullin (AM) is a multifunctional peptide endowed with various biological actions mediated by the interaction with the calcitonin receptor-like receptor (CLR), which couples to the receptor activity-modifying proteins 2 or 3 (RAMP2 or RAMP3) to form the functional plasma membrane receptors AM1 and AM2, respectively. In this study, we investigated for the first time the expression and localization of AM, CLR, RAMP2 and RAMP3 in human thymic tissue from newborns and in primary cultures of thymic epithelial cells (TECs) and thymocytes. Immunohistochemical analysis of thymic tissue showed that both AM and RAMP2 are abundantly expressed in the epithelial cells of medulla and cortex, blood vessels and mastocytes. In contrast, RAMP3 could not be detected. In cultured TECs, double immunofluorescence coupled to confocal microscopy revealed that AM is present in the cytoplasmic compartment, whereas RAMP2 could be detected in the cytoplasm and nucleus, but not in the cell membrane. At variance with RAMP2, CLR was not only present in the nucleus and cytoplasm of TECs, but could also be detected in the cell membrane. The nuclear and cytoplasmic localizations of RAMP2 and CLR and the absence of RAMP2 in the cell membrane were confirmed by western-blot analysis performed on cell fractions. AM, RAMP2 and CLR could also be detected in thymocytes by means of double immunofluorescence coupled to confocal microscopy, although these proteins were not present in the whole thymocyte population. In these cells, AM and RAMP2 were detected in the cytoplasm, whereas CLR could be observed in the cytoplasm and the plasma membrane. In conclusion, our results show that the AM system is widely expressed in human thymus from newborns and suggest that both AM1 receptor components CLR and RAMP2 are not associated with the plasma membrane of TECs and thymocytes but are located intracellularly, notably in the nucleus.

Involvement of adrenomedullin in spinal glial activation following chronic administration of morphine in rats

BACKGROUND

Adrenomedullin (AM) belongs to the calcitonin gene-related peptide (CGRP) family. Our previous studies show that chronic exposure to morphine increases spinal AM bioactivity, contributing to the development and maintenance of morphine tolerance. This study investigated the possible involvement of AM in morphine-evoked gliosis.

METHODS

Real-time polymerase chain reaction was performed to determine interleukin-1β (IL-1β), IL-6 and tumour necrosis factor-α (TNF-α) mRNAs in the spinal dorsal horn and cultured sensory ganglion explants. Immunohistochemistry was performed to identify spinal microglia and astrocytes.

RESULTS

Repetitive intrathecal (i.t.) injection of morphine (20 μg) increased the expression of IL-1β, IL-6 and TNF-α mRNAs in the spinal dorsal horn. The co-administration of the selective AM receptor antagonist AM22-52 (36 μg) markedly attenuated chronic morphine-evoked increase in IL-1β and IL-6, but not TNF-α, mRNA levels. Exposure of cultured dorsal root ganglion (DRG) explants to morphine (3.3 μmol/L) for 6 days up-regulated IL-1β and IL-6 mRNA expressions. The depletion of AM gene using small interfering RNA (siRNA) approach abolished morphine-evoked increase in IL-1β and IL-6 syntheses in the cultured DRG. The blockade of AM receptors by i.t. AM22-52 also inhibited chronic morphine-evoked cell hypertrophy of microglia and astrocytes as well as an increase in OX-42 and GFAP (glial fibrillary acidic protein) immunoreactivities. Furthermore, the 6-day treatment with AM (10 μg, i.t.) induced morphological changes of microglia and astrocytes as well as an increase in IL-1β, IL-6 and TNF-α mRNA levels in the spinal dorsal horn.

CONCLUSION

The present study supports the idea that up-regulation of the pronociceptive mediator AM can recruit spinal glial cells, resulting in an increase in cytokines during chronic use of morphine.

Involvement of calcitonin gene-related peptide and receptor component protein in experimental autoimmune encephalomyelitis

Calcitonin Gene-Related Peptide (CGRP) inhibits microglia inflammatory activation in vitro. We here analyzed the involvement of CGRP and Receptor Component Protein (RCP) in experimental autoimmune encephalomyelitis (EAE). Alpha-CGRP deficiency increased EAE scores which followed the scale alpha-CGRP null>heterozygote>wild type. In wild type mice, CGRP delivery into the cerebrospinal fluid (CSF) 1) reduced chronic EAE (C-EAE) signs, 2) inhibited microglia activation (revealed by quantitative shape analysis), and 3) did not alter GFAP expression, cell density, lymphocyte infiltration, and peripheral lymphocyte production of IFN-gamma, TNF-alpha, IL-17, IL-2, and IL-4. RCP (probe for receptor involvement) was expressed in white matter microglia, astrocytes, oligodendrocytes, and vascular-endothelial cells: in EAE, also in infiltrating lymphocytes. In relapsing-remitting EAE (R-EAE) RCP increased during relapse, without correlation with lymphocyte density. RCP nuclear localization (stimulated by CGRP in vitro) was I) increased in microglia and decreased in astrocytes (R-EAE), and II) increased in microglia by CGRP CSF delivery (C-EAE). Calcitonin like receptor was rarely localized in nuclei of control and relapse mice. CGRP increased in motoneurons. In conclusion, CGRP can inhibit microglia activation in vivo in EAE. CGRP and its receptor may represent novel protective factors in EAE, apparently acting through the differential cell-specific intracellular translocation of RCP.

Adrenomedullin protects from experimental autoimmune encephalomyelitis at multiple levels

Adrenomedullin is a neuropeptide known for its cardiovascular activities and anti-inflammatory effects. Here, we investigated the effect of adrenomedullin in a model of experimental autoimmune encephalomyelitis (EAE) that mirrors chronic progressive multiple sclerosis. A short-term systemic treatment with adrenomedullin reduced clinical severity and incidence of EAE, the appearance of inflammatory infiltrates in spinal cord and the subsequent demyelination and axonal damage. This effect was exerted at multiple levels affecting both early and late events of the disease. Adrenomedullin decreased the presence/activation of encephalitogenic Th1 and Th17 cells and down-regulated several inflammatory mediators in peripheral lymphoid organs and central nervous system. Noteworthy, adrenomedullin inhibited the production by encephalitogenic cells of osteopontin and of Granulocyte Macrophage Colony-Stimulating Factor (GM-CSF), two critical cytokines in the development of EAE. At the same time, adrenomedullin increased the number of IL-10-producing regulatory T cells with suppressive effects on the progression of EAE. Furthermore, adrenomedullin generated dendritic cells with a semi-mature phenotype that impaired encephalitogenic responses in vitro and in vivo. Finally, adrenomedullin regulated glial activity and favored an active program of neuroprotection/regeneration. Therefore, the use of adrenomedullin emerges as a novel multimodal therapeutic approach to treat chronic progressive multiple sclerosis.

Astrocytes acquire resistance to iron-dependent oxidative stress upon proinflammatory activation

Background

Astrocytes respond to local insults within the brain and the spinal cord with important changes in their phenotype. This process, overall known as “activation”, is observed upon proinflammatory stimulation and leads astrocytes to acquire either a detrimental phenotype, thereby contributing to the neurodegenerative process, or a protective phenotype, thus supporting neuronal survival. Within the mechanisms responsible for inflammatory neurodegeneration, oxidative stress plays a major role and has recently been recognized to be heavily influenced by changes in cytosolic iron levels. In this work, we investigated how activation affects the competence of astrocytes to handle iron overload and the ensuing oxidative stress.

Methods

Cultures of pure cortical astrocytes were preincubated with proinflammatory cytokines (interleukin-1β and tumor necrosis factor α) or conditioned medium from lipopolysaccharide-activated microglia to promote activation and then exposed to a protocol of iron overload.

Results

We demonstrate that activated astrocytes display an efficient protection against iron-mediated oxidative stress and cell death. Based on this evidence, we performed a comprehensive biochemical and molecular analysis, including a transcriptomic approach, to identify the molecular basis of this resistance.

Conclusions

We propose the protective phenotype acquired after activation not to involve the most common astrocytic antioxidant pathway, based on the Nrf2 transcription factor, but to result from a complex change in the expression and activity of several genes involved in the control of cellular redox state.

Iron uptake in quiescent and inflammation-activated astrocytes: a potentially neuroprotective control of iron burden

Astrocytes play a crucial role in proper iron handling within the central nervous system. This competence can be fundamental, particularly during neuroinflammation, and neurodegenerative processes, where an increase in iron content can favor oxidative stress, thereby worsening disease progression. Under these pathological conditions, astrocytes undergo a process of activation that confers them either a beneficial or a detrimental role on neuronal survival. Our work investigates the mechanisms of iron entry in cultures of quiescent and activated hippocampal astrocytes. Our data confirm that the main source of iron is the non-transferrin-bound iron (NTBI) and show the involvement of two different routes for its entry: the resident transient receptor potential (TRP) channels in quiescent astrocytes and the de novo expressed divalent metal transporter 1 (DMT1) in activated astrocytes, which accounts for a potentiation of iron entry. Overall, our data suggest that at rest, but even more after activation, astrocytes have the potential to buffer the excess of iron, thereby protecting neurons from iron overload. These findings further extend our understanding of the protective role of astrocytes under the conditions of iron-mediated oxidative stress observed in several neurodegenerative conditions.

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Non-transferrin-bound iron (NTBI) is the main source of iron for astrocytes.

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TRPC channels represent an entry pathway for Fe^2 + in resting astrocytes.

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Activation process increases the competence of astrocytes to uptake iron.

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DMT1 expression accounts for potentiation of iron ingress in activated astrocytes.