Peripheral Inflammatory Response Research Articles

Inflammation triggers RNA transfer from blood cells to brain neurons.

The nervous and immune systems are the two most complex systems in the body. That complexity is amplified by the fact that each influences the other, as they constantly exchange messages in response to environmental and internal cues. The best known messages from immune cells are the cytokines, which trigger changes within neurons through well-established receptor-initiated cascades. But in a new study in this issue of PLOS Biology, Kirsten Ridder, Stefan Momma, and colleagues show that hematopoietic cells, which include the cells of the immune system, release messenger RNAs (mRNAs) and microRNAs (miRNAs) that are absorbed by neurons. This mechanism of signaling is elevated in response to inflammation, and the transferred RNAs have the potential to influence neuronal responses. Inflammation has recently been shown to drive an even more unexpected neuro–immune interaction—fusion of hematopoietic cells with Purkinje neurons of the cerebellum, in which the resulting cell contains both nuclei. The authors sought to determine whether less drastic transfers of genetic messages might be taking place as well. To do so, they relied on the Cre recombination system. In this system, a gene of interest is engineered to be flanked by target sequences (“lox” sequences) for the enzyme Cre recombinase. Enzymatic action rearranges the site and triggers expression of the gene within. Here, the authors used mice with a lox-flanked reporter gene in all tissues. The Cre recombinase gene, though, was introduced only to hematopoietic cells. Thus, any non-hematopoietic cells expressing the reporter gene must have picked up either the Cre recombinase gene, its mRNA, or the protein itself, from hematopoietic cells. The authors found that a small number of Purkinje neurons expressed the reporter, despite the absence of any double nuclei (ruling out cell fusion as described above and therefore gene transfer). So how were the neurons getting the message? Extracellular vesicles (EVs) have lately emerged as a significant vehicle for trafficking multiple kinds of molecules between cells, including proteins and mRNAs, so the authors isolated EVs from peripheral blood. When they analyzed the contents, they found the EVs contained Cre recombinase mRNA, but not the protein. In healthy mice, the number of Cre-recombined neurons was very low, far less than 1%. But when the authors triggered a peripheral inflammatory response that number jumped by several orders of magnitude, affecting an average of 6% of Purkinje neurons. Under such conditions of inflammation, several other types of brain neurons were also targeted, including those in the hippocampus, cortex, and substantia nigra. These results show that mRNA can be transferred from immune cells of the peripheral blood to neurons of the central nervous system via EVs. It remains to be seen whether other immune-derived mRNAs take advantage of the same means of transport to enter neurons. But known exosome passengers also include miRNAs, short non-coding RNAs that influence gene expression in many types of organisms. By excising single neurons, the authors showed that Cre-recombined neurons contained three miRNAs not found in non-recombined neurons; the same three were also present in exosomes isolated from blood in mice experiencing inflammation. These results suggest that the three miRNAs could derive from the same immune cells as the Cre recombinase. If that is so, this study indicates there is not only another medium of information exchange between the immune and nervous system but also a whole new type of message, and it suggests that the regulation of the nervous system by the immune system may be more extensive and intimate than previously appreciated. Purkinje neurons express a reporter gene upon uptake of RNA from hematopoietic extracellular vesicles. The number of these vesicle-targeted cells increases in response to inflammation. Ridder K, Keller S, Dams M, Rupp A-K, Schlaudraff J, et al. (2014) Extracellular Vesicle-Mediated Transfer of Genetic Information Between the Hematopoietic System and the Brain in Response to Inflammation. doi:10.1371/journal.pbio.1001874.

Inhibition of soluble tumor necrosis factor is therapeutic in Huntington's disease

Neuroinflammation is a common feature of many neurodegenerative diseases, including Huntington's disease (HD). HD is an autosomal dominant genetic disease caused by an expanded CAG repeat in exon 1 of the huntingtin (HTT) gene. Previous studies demonstrated that levels of several proinflammatory cytokines, including tumor necrosis factor (TNF)-α, were higher in the plasma and brain tissues of mice and patients with HD, suggesting that inflammation may contribute to HD progression. To evaluate the pathological role of TNF-α in HD pathogenesis, we blocked TNF-α signaling using a dominant negative inhibitor of soluble TNF-α (XPro1595). XPro1595 effectively suppressed the inflammatory responses of primary astrocytes-enriched culture isolated from a transgenic mouse model (R6/2) and human astrocytes-enriched culture derived from induced pluripotent stem cells (iPSCs) of HD patients evoked by lipopolysaccharide and cytokines, respectively. Moreover, XPro1595 protected the cytokine-induced toxicity of primary R6/2 neurons and human neurons derived from iPSCs of HD patients. To assess the beneficial effect of XPro1595 in vivo, an intracerebroventricular (i.c.v.) infusion was provided with an osmotic minipump. ELISA analyses showed that i.c.v. infusion of XPro1595 decreased elevated levels of TNFα in the cortex and striatum, improved motor function, reduced caspase activation, diminished the amount of mutant HTT aggregates, increased neuronal density and decreased gliosis in brains of R6/2 mice. Moreover, reducing the peripheral inflammatory response by a systemic injection of XPro1595 improved the impaired motor function of R6/2 mice but did not affect caspase activation. Collectively, our findings suggest that an effective and selective anti-inflammatory treatment targeting the abnormal brain inflammatory response is a potential therapeutic strategy for HD.

Activation of spinal NF-κB/p65 contributes to peripheral inflammation and hyperalgesia in rat adjuvant-induced arthritis.

It is known that noxious stimuli from inflamed tissue may increase the excitability of spinal dorsal horn neurons (a process known as central sensitization), which can signal back and contribute to peripheral inflammation. However, the underlying mechanisms have yet to be fully defined. A number of recent studies have indicated that spinal NF-κB/p65 is involved in central sensitization, as well as pain-related behavior. Thus, the aim of this study was to determine whether NF-κB/p65 can facilitate a peripheral inflammatory response in rat adjuvant-induced arthritis (AIA). Lentiviral vectors encoding short hairpin RNAs that target NF-κB/p65 (LV-shNF-κB/p65) were constructed for gene silencing. The spines of rats with AIA were injected with LV-shNF-κB/p65 on day 3 or day 10 after treatment with Freund's complete adjuvant (CFA). During an observation period of 20 days, pain-related behavior, paw swelling, and joint histopathologic changes were evaluated. Moreover, the expression levels of spinal tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), and cyclooxygenase 2 (COX-2) were assessed on day 14 after CFA treatment. The presence of peripheral inflammation in rats with AIA induced an increase in NF-κB/p65 expression in the spinal cord, mainly in the dorsal horn neurons and astrocytes. Delivery of LV-shNF-κB/p65 to the spinal cord knocked down the expression of NF-κB/p65 and significantly attenuated hyperalgesia, paw edema, and joint destruction. In addition, spinal delivery of LV-shNF-κB/p65 reduced the overexpression of spinal TNFα, IL-1β, and COX-2. These findings indicate that spinal NF-κB/p65 plays an important role in the initiation and development of both peripheral inflammation and hyperalgesia. Thus, inhibition of spinal NF-κB/p65 expression may provide a potential treatment to manage painful inflammatory disorders.

Perspectives on neuroinflammation and excitotoxicity: A neurotoxic conspiracy?

Emerging evidences underline the ability of several environmental contaminants to induce an inflammatory response within the central nervous system, named neuroinflammation. This can occur as a consequence of a direct action of the neurotoxicant to the CNS and/or as a response secondary to the activation of the peripheral inflammatory response. In both cases, neuroinflammation is driven by the release of several soluble factors among which pro-inflammatory cytokines. IL-1β and TNF-α have been extensively studied for their effects within the CNS and emerged for their role in the modulation of the neuronal response, which allow the immune response to integrate with specific neuronal functions, as neurotransmission and synaptic plasticity. In particular, it has been evidenced a potential detrimental link between these cytokines and the glutamatergic system that seems to be part of increased brain excitability and excitotoxicity occurring in different pathological conditions. Aim of this mini-review will be to present experimental evidence on the way IL-1β and TNF-α impact neurons, focusing on the glutamatergic signalling, to provide a perspective on novel pathways possibly involved in environmental contaminants neurotoxicity.

Abstract W MP46: Beyond the Brain: Stroke Induces Vascular Breakdown and Unique Profiles of Peripheral Inflammatory Response in the Eye and Spinal Cord

Ischemic stroke, a leading cause of death and long-term disability, has far-reaching effects across the CNS beyond the region of infarct. As extensions of the brain, neural networks of the eye and spinal cord are affected by cerebral ischemia through the transmission of inflammatory and degenerative changes. Although neuropathological effects of MCAO have been reported in both regions, the contribution of the peripheral inflammatory response to the evolution of injury in these CNS regions is unknown. We evaluated local glial responses, vascular integrity, leukocyte infiltration, and cytokine expression after stroke in the eye and spinal cord. Adult male C57Bl/6 WT or GFP+ bone marrow chimeric mice were subjected to 90-min MCAO or sham surgery (n=3-6). Imaging of the retinal vasculature was performed by ophthalmoscopy. At 8h, 24 and/or 36h, 72h and 7d post-stroke mice were perfused with PBS and sacrificed. Organs were harvested for immunohistochemistry, Evans blue extravasation, flow cytometry, and RT-qPCR. Early (8h) after MCAO, over four-fold increases in TNFα and IL-1β gene expression were observed in the ipsilateral eye relative to sham (4.64±1.21, 1±0.17; 11.03±7.75, 1±0.21). Microglial activation indicated by increased CD11b, CD45, and cell granularity at 36h was accompanied by an influx of peripheral leukocytes predominantly comprised of neutrophils (81%). In contrast to BBB breakdown which was highest at 24h, blood-retinal barrier breakdown peaked in the ipsilateral eye at 36h, shown by a twelve-fold increase in Evans blue concentration (sham, 24h, 36h: 0.16, 0.41, 1.95 ug/mg tissue wet weight). Similarly, major blood-spinal cord barrier breakdown occurred at 36h (0.32 vs 0.052 ug/mg). This was followed by a largely monocytic response with corresponding increases in TNFα, IL-1β, and IFNγ gene expression. Together, our data show robust unilateral peripheral inflammatory responses after stroke in CNS regions outside of the brain. In addition, blood-parenchymal barrier permeability peaks later in the eye and spinal cord than in the brain. Given the distinct time course and inflammatory components associated with each region, these findings may have wide implications for treatments attenuating CNS-wide inflammatory damage after stroke.

INMiND: getting to the bottom of neuroinflammation

INMiND: getting to the bottom of neuroinflammation

Oral gabapentin treatment accentuates nerve and peripheral inflammatory responses following experimental nerve constriction in Wistar rats

Gabapentin (GBP) is an anti-convulsive drug often used as analgesic to control neuropathic pain. This study aimed at evaluating whether oral GBP treatment could improve nerve inflammation response after sciatic nerve constriction in association with selected pain and motor spontaneous behavior assessments in Wistar rats. We evaluated nerve myeloperoxidase (MPO) and inflammatory cytokines on the 5th day post-injury, time in which nerve inflammation is ongoing. In addition, the role of GBP on carrageenan-induced paw edema and peritoneal cell migration was analyzed. GBP was given by gavage at doses of 30, 60 and 120mg/kg, 60min prior to chronic constriction of the sciatic nerve (CCSN) and during 5 days post-injury, 12/12h. CCSN animals treated with saline were used as controls and for behavioral and inflammation assessments untreated sham-operated rats were also used. On the 5th day, GBP (60 and 120mg/kg) alleviated heat-induced hyperalgesia and significantly increased delta walking scores in CCSN animals, the latter suggesting excitatory effects rather than sedation. GBP (60mg/kg) significantly increased nerve MPO, TNF-α, and IL-1β levels, comparing with the saline group. GBP (120mg/kg) reduced the anti-inflammatory cytokine IL-10 nerve levels compared with the CCSN saline group. Furthermore, GBP (60 and 120mg/kg) increased carrageenan-induced paw edema and peritoneal macrophage migration compared with the CCSN saline group. Altogether our findings suggest that GBP accentuates nerve and peripheral inflammatory response, however confirmed its analgesic effect likely due to an independent CNS-mediated mechanism, and raise some concerns about potential GBP inflammatory side effects in widespread clinical use.

Acetylcholinesterase Inhibitors Reduce Neuroinflammation and -Degeneration in the Cortex and Hippocampus of a Surgery Stress Rat Model

Exogenous stress like tissue damage and pathogen invasion during surgical trauma could lead to a peripheral inflammatory response and induce neuroinflammation, which can result in postoperative cognitive dysfunction (POCD). The cholinergic anti-inflammatory pathway is a neurohumoral mechanism that plays a prominent role by suppressing the inflammatory response. Treatments with acetylcholinesterase inhibitors enhance cholinergic transmission and may therefore act as a potential approach to prevent neuroinflammation. In the presence or absence of acetylcholinesterase inhibitors, adult Wistar rats underwent surgery alone or were additionally treated with lipopolysaccharide (LPS). Physostigmine, which can overcome the blood-brain barrier or neostigmine acting only peripheral, served as acetylcholinesterase inhibitors. The expression of pro- and anti-inflammatory cytokines in the cortex, hippocampus, spleen and plasma was measured after 1 h, 24 h, 3 d and 7 d using Real-Time PCR, western blot analysis or cytometric bead array (CBA). Fluoro-Jade B staining of brain slices was employed to elucidate neurodegeneration. The activity of acetylcholinesterase was estimated using a spectrofluorometric method. Surgery accompanied by LPS-treatment led to increased IL-1beta gene and protein upregulation in the cortex and hippocampus but was significantly reduced by physostigmine and neostigmine. Furthermore, surgery in combination with LPS-treatment caused increased protein expression of IL-1, TNF-alpha and IL-10 in the spleen and plasma. Physostigmine and neostigmine significantly decreased the protein expression of IL-1 and TNF-alpha. Neuronal degeneration and the activity of acetylcholinesterase were elevated after surgery with LPS-treatment and reduced by physostigmine and neostigmine. Along with LPS-treatment, acetylcholinesterase inhibitors reduce the pro-inflammatory response as well as neurodegeneration after surgery in the cortex and hippocampus. This combination may represent a tool to break the pathogenesis of POCD.

Evaluation of mean platelet volume, neutrophil/lymphocyte ratio and platelet/lymphocyte ratio in advanced stage endometriosis with endometrioma

We compared the preoperative values of mean platelet volume (MPV) and peripheral systemic inflammatory response (SIR) markers (neutrophil/lymphocyte ratio and platelet/lymphocyte ratio) between patients with advanced-stage (stage 3/4) endometriosis having endometrioma (OMA) and patients with a non-neoplastic adnexal mass other than endometrioma (non-OMA). Patients who underwent operations with the pre-diagnosis of infertility or adnexal mass and who underwent laparoscopic tubal ligation were included. Haemoglobin levels, leucocyte count, platelet count, neutrophil count and lymphocyte count were not significantly different between patients with advanced stage endometriosis having OMA, patients with non-OMA and patients in the control group (p=0.970, p=0.902, p=0.373, p=0.501 and p=0.463, respectively). Patients with stage 3/4 endometriosis having OMA, patients with non-OMA and control patients were also not significantly different in terms of MPV (p=0.836), neutrophil/lymphocyte ratio (NLR) (p=0.555) and platelet/lymphocyte ratio (PLR) (p=0.358). Preoperative cancer antigen 125 (Ca-125) levels were significantly higher in patients with OMA (p=0.006). Mean size of the OMAs was significantly lower than non-OMAs (p=0.000). It is very important to determine advanced stage endometriosis and OMAs during preoperative evaluation in order to inform patients and plan an appropriate surgical approach. We demonstrate that MPV, NLR and PLR values are not useful for this purpose in patients with advanced stage endometriosis that are proven to develop severe inflammation at either the cellular or molecular level.

Sustained inflammation 1.5 years post-stroke is not associated with depression in elderly stroke survivors

BackgroundDepression is common in elderly stroke survivors and has been associated with systemic inflammation. We aimed to investigate an elderly population of Swedish stroke patients for evidence of sustained peripheral inflammation 18 months post-stroke and to identify if inflammation is associated with post-stroke depression at 18 months post-stroke.MethodsThe Barthel Index was used to measure the level of impairment in activities of daily living at 3 days post-stroke. Serum concentrations of inflammation markers, ie, C-reactive protein and white cell count, were measured in 149 stroke patients (mean age 81 ± 5.33 years, 35% male) at 18 months post-stroke, and a comparison was made with an age-matched sample of elderly Swedish individuals who had not suffered a stroke. At the same visit, clinical depression was diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Third Edition-Revised criteria. Severity of depression was assessed using the Montgomery-Asberg Depression Rating Scale (MADRS).ResultsMean C-reactive protein and white cell count levels in stroke patients were significantly elevated at 18 months post-stroke compared with population probands. Disability scores were associated with MADRS depression scores, but C-reactive protein and white cell count were not.ConclusionWe found evidence for a sustained peripheral inflammatory response at 18 months post-stroke. C-reactive protein and white cell count were not associated with depression in this study.

A new treatment for neurogenic inflammation caused by EV71 with CR2-targeted complement inhibitor

BackgroundEnterovirus 71 (EV71), one of the most important neurotropic EVs, has caused death and long-term neurological sequelae in hundreds of thousands of young children in the Asia-Pacific region in the past decade. The neurological diseases are attributed to infection by EV71 inducing an extensive peripheral and central nervous system (CNS) inflammatory response with abnormal cytokine production and lymphocyte depletion induced by EV71 infection. In the absence of specific antiviral agents or vaccines, an effective immunosuppressive strategy would be valuable to alleviate the severity of the local inflammation induced by EV71 infection.Presentation of the hypothesisThe complement system plays a pivotal role in the inflammatory response. Inappropriate or excessive activation of the complement system results in a severe inflammatory reaction or numerous pathological injuries. Previous studies have revealed that EV71 infection can induce complement activation and an inflammatory response of the CNS. CR2-targeted complement inhibition has been proved to be a potential therapeutic strategy for many diseases, such as influenza virus-induced lung tissue injury, postischemic cerebral injury and spinal cord injury. In this paper, a mouse model is proposed to test whether a recombinant fusion protein consisting of CR2 and a region of Crry (CR2-Crry) is able to specifically inhibit the local complement activation induced by EV71 infection, and to observe whether this treatment strategy can alleviate or even cure the neurogenic inflammation.Testing the hypothesisCR2-Crry is expressed in CHO cells, and its biological activity is determined by complement inhibition assays. 7-day-old ICR mice are inoculated intracranially with EV71 to duplicate the neurological symptoms. The mice are then divided into two groups, in one of which the mice are treated with CR2-Crry targeted complement inhibitor, and in the other with phosphate-buffered saline. A group of mice deficient in complement C3, the breakdown products of which bind to CR2, are also infected with EV71 virus. The potential bioavailability and efficacy of the targeted complement inhibitor are evaluated by histology, immunofluorescence staining and radiolabeling.Implications of the hypothesisCR2-Crry-mediated targeting complement inhibition will alleviate the local inflammation and provide an effective treatment for the severe neurological diseases associated with EV71 infection.

Paeoniflorin Protects against Ischemia-Induced Brain Damages in Rats via Inhibiting MAPKs/NF-κB-Mediated Inflammatory Responses

Paeoniflorin (PF), the principal component of Paeoniae Radix prescribed in traditional Chinese medicine, has been reported to exhibit many pharmacological effects including protection against ischemic injury. However, the mechanisms underlying the protective effects of PF on cerebral ischemia are still under investigation. The present study showed that PF treatment for 14 days could significantly inhibit transient middle cerebral artery occlusion (MCAO)-induced over-activation of astrocytes and microglia, and prevented up-regulations of pro-inflamamtory mediators (TNFα, IL-1β, iNOS, COX2 and 5-LOX) in plasma and brain. Further study demonstrated that chronic treatment with PF suppressed the activations of JNK and p38 MAPK, but enhanced ERK activation. And PF could reverse ischemia-induced activation of NF-κB signaling pathway. Moreover, our in vitro study revealed that PF treatment protected against TNFα-induced cell apoptosis and neuronal loss. Taken together, the present study demonstrates that PF produces a delayed protection in the ischemia-injured rats via inhibiting MAPKs/NF-κB mediated peripheral and cerebral inflammatory response. Our study reveals that PF might be a potential neuroprotective agent for stroke.

Influence of apoptosis on the cutaneous and peripheral lymph node inflammatory response in dogs with visceral leishmaniasis

In canine visceral leishmaniasis (CVL), the abnormalities most commonly observed in clinical examination on the animals are lymphadenomegaly and skin lesions. Dogs are the main domestic reservoir for the protozoon Leishmania (L.) chagasi and the skin is the main site of contamination by the vector insect. Some protozoa use apoptosis as an immunological escape mechanism. The aim of this study was to correlate the presence of apoptosis with the parasite load and with the inflammatory response in the skin and lymph nodes of dogs naturally infected with Leishmania (L.) chagasi. Thirty-three dogs from the municipality of Araçatuba (São Paulo, Brazil) were used, an endemic area for CVL. Muzzle, ear and abdominal skin and the popliteal, subscapular, iliac and mesenteric lymph nodes of symptomatic (S), oligosymptomatic (O) and asymptomatic (A) dogs were analyzed histologically. The parasite load and percentage apoptosis were evaluated using an immunohistochemical technique. Microscopically, the lymph nodes presented chronic lymphadenitis and the skin presented plasmacytic infiltrate and granulomatous foci in the superficial dermis, especially in the ear and muzzle regions. The inflammation was most severe in group S. The parasite load and apoptotic cell density were also greatest in this group. The cause of the lymphoid atrophy in these dogs was correlated with T lymphocyte apoptosis, thus leaving the dogs more susceptible to CVL. The peripheral lymph nodes presented the greatest inflammatory response. Independent of the clinical picture, the predominant inflammatory response was granulomatous and plasmacytic, both in the skin and in the peripheral lymph nodes. The ear skin presented the greatest intensity of inflammation and parasite load, followed by the muzzle skin, in group S. The ear skin area presented a non-significant difference in cell profile, with predominance of macrophages, and a significant difference from group A to groups O and S. It was seen that in these areas, there were high densities of parasites and cells undergoing apoptosis, in group S. The association between apoptosis and parasite load was not significant in the lymph nodes, but in the muzzle regions and at the ear tips, a positive correlation was seen between the parasite load and the density of cells undergoing apoptosis. The dogs in group S had the highest parasite load and the greatest number of apoptotic cells, thus suggesting that the parasite had an immune evasion mechanism, which could be proven statistically in the skin.

Peripheral nerve inflammation in ALS mice: cause or consequence

Neuroinflammation is a prominent pathologic feature in the spinal cord of patients with amyotrophic lateral sclerosis (ALS), and is characterized by glial activation and infiltrating T cells.1 A similar inflammatory response is present in spinal cords of ALS mice1 and is preceded by evidence of a “dying back phenomenon” which includes motor axon degeneration and alterations of the neuromuscular junction.2 The presence of monocytes/macrophages surrounding the degenerating peripheral nerve fibers is an early event that occurs prior to the onset of clinical signs of motor weakness,3 and thus raises the question whether the peripheral nerve inflammatory response initiates, or is in response to, the neurodegenerative process. To address this question, we evaluated the time course of denervation and accompanying inflammatory responses in the lumbar spinal cord–sciatic nerve–gastrocnemius and the cervical spinal cord–phrenic nerve–diaphragm motor units of ALS mice, and found that denervation occurred prior to inflammation; also, both denervation and inflammation occurred earlier in the sciatic nerve motor unit than in the phrenic nerve motor unit. Therefore, peripheral nerve inflammation is probably not the cause of denervation, but rather a response to the neurodegenerative process.

Developmental neuroinflammation and schizophrenia

There is increasing interest in and evidence for altered immune factors in the etiology and pathophysiology of schizophrenia. Stimulated by various epidemiological findings reporting elevated risk of schizophrenia following prenatal exposure to infection, one line of current research aims to explore the potential contribution of immune-mediated disruption of early brain development in the precipitation of long-term psychotic disease. Since the initial formulation of the "prenatal cytokine hypothesis" more than a decade ago, extensive epidemiological research and remarkable advances in modeling prenatal immune activation effects in animal models have provided strong support for this hypothesis by underscoring the critical role of cytokine-associated inflammatory events, together with downstream pathophysiological processes such as oxidative stress, hypoferremia and zinc deficiency, in mediating the short- and long-term neurodevelopmental effects of prenatal infection. Longitudinal studies in animal models further indicate that infection-induced developmental neuroinflammation may be pathologically relevant beyond the antenatal and neonatal periods, and may contribute to disease progression associated with the gradual development of full-blown schizophrenic disease. According to this scenario, exposure to prenatal immune challenge primes early pre- and postnatal alterations in peripheral and central inflammatory response systems, which in turn may disrupt the normal development and maturation of neuronal systems from juvenile to adult stages of life. Such developmental neuroinflammation may adversely affect processes that are pivotal for normal brain maturation, including myelination, synaptic pruning, and neuronal remodeling, all of which occur to a great extent during postnatal brain maturation. Undoubtedly, our understanding of the role of developmental neuroinflammation in progressive brain changes relevant to schizophrenia is still in infancy. Identification of these mechanisms would be highly warranted because they may represent a valuable target to attenuate or even prevent the emergence of full-blown brain and behavioral pathology, especially in individuals with a history of prenatal complications such as in-utero exposure to infection and/or inflammation.

MRI signature in a novel mouse model of genetically induced adult oligodendrocyte cell death

Two general pathological processes contribute to multiple sclerosis (MS): acute inflammation and degeneration. While magnetic resonance imaging (MRI) is highly sensitive in detecting abnormalities related to acute inflammation both clinically and in animal models of experimental autoimmune encephalomyelitis (EAE), the correlation of these readouts with acute and future disabilities has been found rather weak. This illustrates the need for imaging techniques addressing neurodegenerative processes associated with MS. In the present work we evaluated the sensitivity of different MRI techniques (T(2) mapping, macrophage tracking based on labeling cells in vivo by ultrasmall particles of iron oxide (USPIO), diffusion tensor imaging (DTI) and magnetization transfer imaging (MTI)) to detect histopathological changes in a novel animal model making use of intrinsic, temporally and spatially controlled triggering of oligodendrocyte cell death. This mouse model allows studying the MRI signature associated to neurodegenerative processes of MS in the absence of adaptive inflammatory components that appear to be foremost in the EAE models. Our results revealed pronounced T(2) hyperintensities in brain stem and cerebellar structures, which we attribute to structural alteration of white matter by pronounced vacuolation. Brain areas were found devoid of significant macrophage infiltration in line with the absence of a peripheral inflammatory response. The significant decrease in diffusion anisotropy derived from DTI measures in these structures is mainly caused by a pronounced decrease in diffusivity parallel to the fiber indicative of axonal damage. Triggering of oligodendrocyte ablation did not translate into a significant increase in radial diffusivity. Only minor decreases in MT ratio have been observed, which is attributed to inefficient removal of myelin debris.

Anesthetic modulation of neuroinflammation in Alzheimer's disease

To summarize key studies and recent thought on the role of neuroinflammation in chronic neurodegeneration, and whether it can be modulated by anesthesia and surgery. A large and growing body of evidence shows that neuroinflammation participates in the development of neurodegeneration associated with Alzheimer's disease. Modulation may be possible early in the pathogenesis, and less so when cognitive symptoms appear. A dysfunctional hypoinflammatory response may permit accelerated damage due to other mechanisms in late disease. The peripheral inflammatory response elicited by surgery itself appears to provoke a muted neuroinflammatory response, which enhances ongoing neurodegeneration in some models. Anesthetics have both anti-inflammatory and proinflammatory effects depending on the drug and concentration, but in general, appear to play a small role in neuroinflammation. Human studies at the intersection of chronic neurodegeneration, neuroinflammation, and surgery/anesthesia are rare. The perioperative period has the potential to modulate the progression of chronic neurodegenerative diseases. The growing number of elderly having surgery, combined with the expanding life expectancy, indicates the potential for this interaction to have considerable public health implications, and call for further research, especially in humans.

Peripheral Tissue Trauma Triggers an Inflammatory Response Causing Intestinal Microvascular Serum Leak Which Disrupts Gastrointestinal Motility

Introduction: Combat and civilian trauma is the leading cause of death for individuals in the prime of their life. Gastrointestinal dysfunction plays a key role in the detrimental sequelae of trauma (systemic inflammatory response, feeding intolerance, reflux/aspiration pneumonia and bacterial overgrowth/dissemination through mucosal barrier failure), but the mechanisms through which peripheral tissue injury can induce these responses is unclear. Aims: To investigate the mechanism of trauma-induced gastrointestinal dysfunction in a precisely controllable non-narcotic, tissue-bone matrix (TBX) trauma model, which is known to reproducibly display significant gastrointestinal dysmotility. Methods: A non-narcotic murine tissue trauma model was constructed by the dorsal subcutaneous implantation of minced donor syngeneic tissue-bone matrix (TBX) precisely adjusted to 17.5% body weight and studied after 21 hrs. Inflammatory mediators in serum, fresh TBX and TBX wound fluid at 21hrs were measured by electrochemiluminescence detection and intestinal muscularis microvascular leak was microscopically quantified in whole-mounts after i.v. injection of FITC-dextran (70k MW). Gastrointestinal transit and jejunal circular muscle contractility was assessed after injection of normal mouse serum (i.p. 100μl q1h x 8). Results: Compared to normal serum, TNF α was only acutely elevated in fresh TBX fluid (1.1±0.01, 4.1±0.22 and 1.1±0.01 ng/ml) and IL 1β exhibited increased levels in both fresh TBX fluid and in TBX wound fluid (1.9±0.22, 107.6±1.45 and 92.2±6.12 ng/ml). Whereas, IL-6 (80.4±10.0, 158.5±4.08 and 26851.1±4883.39 ng/ml) and kerotinocyte chemokine (KC; 237.5±47.14, 110.4±1.59 and 9763.2±817.29 ng/ml) were significantly increased in the re-harvested TBX wound fluid after 21 hours of implantation. The systemic response to the implanted TBX resulted in significant serum elevations in IL-6, KC and IL-10 compared to control and sham surgical groups at 21 hrs (N=6 each), as well as causing significant intestinal muscularis microvascular leak. Interestingly, i.p. injections of normal serum into naive mice recapitulated the TBX-induced dysmotility causing delayed gastrointestinal transit (9.8±0.15 vs. 3.4±0.22) and a 49.5% suppression in bethanechol stimulated jejunal muscle strip contractility compared to saline injections (N=6). Conclusion: Peripheral tissue injury and consequent systemic inflammatory response cause intestinal muscularis microvascular leak and dysmotility, which can be recapitulated by intraperitoneal injection of exogenous normal serum. These novel findings demonstrate the key regulatory effect of intestinalmicrovascular leak on gastrointestinal motility in trauma.

Challenges towards MR imaging of the peripheral inflammatory response in the subacute and chronic stages of transient focal ischemia

Intravenous administration of iron oxide nanoparticles after experimental stroke has been shown to produce focal signal intensity changes in the ischemic boundary on MRI images. These changes have been attributed to the influx of iron-laden blood-borne macrophages, although it has been suggested that this effect might not always be completely specific to inflammatory cells. The aim of the present study was to investigate this phenomenon in a subacute time frame that is more relevant to the peripheral inflammatory response. Imaging experiments (T(2) -, T(2)*- and T(1) -weighted sequences) were acquired in Wistar rats 6 days after transient middle cerebral artery occlusion (MCAO). Animals were intravenously infused with different doses of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles (300, 600 or 1000 µmol Fe/kg), or saline and gadolinium, and imaged again 24 h later. Tissue was immediately processed for immunohistochemistry with the macrophage marker ED-1, in combination with Prussian blue for iron. Ischemic tissue exhibited a large increase in T(2) values, and overall contrast enhancement was apparent in the brain and surrounding muscle. In contrast with previous reports, there were no regions of focal signal intensity changes in the ischemic territory in any of the images, although a region of interest analysis revealed a trend towards iron accumulation in the ischemic hemisphere, particularly in the cortex of T(2)* images. However, histological examination revealed that, despite extensive ED-1-positive macrophage accumulation in the entire ischemic territory, none of these cells were Prussian blue positive, except in the meninges of one animal that received a high dose of USPIO nanoparticles. These results imply that the observed trend is a result of the presence of contrast agent in the blood, or meninges, and not iron-containing inflammatory cells.

The role of TLR2 in nerve injury‐induced neuropathic pain is essentially mediated through macrophages in peripheral inflammatory response

Activation of macrophages/microglia via toll-like receptors (TLRs) plays an important role in inflammation and host defense against pathogens. Pathogen-associated molecular patterns bind TLRs, thereby triggering NF-κB signaling and production of proinflammatory cytokines. Recent data suggest that nonpathogenic molecules resulting from trauma can also trigger inflammation via TLRs. We sought to determine whether peripheral nerve injury could induce the expression of TLR2 on the site of injury-damaged nerves and/or in the central nervous system and to investigate whether TLR2 is necessary for the development of nerve injury-induced neuropathic pain. We observed a significant increase in TLR2, IκB-α, and TNF-α mRNAs in damaged nerves. Increased inflammation-related molecules were found essentially on ED1(+) macrophages. Expression of both IκB-α and TNF-α in peripheral injured nerves was reduced in TLR2 deficient mice where the recruitment of ED1(+) cells is significantly impaired. Although after peripheral nerve injury, spinal microglia became highly activated showing an increase in Iba-1 immunoreactivity and an enlargement of their cell bodies, neither TLR2 mRNA nor IκB-α mRNA was detected in activated microglia. Nerve injury-evoked spinal microglial activation was not significantly altered in TLR2 KO mice. Paw withdrawal threshold and latency in response to mechanical and heat stimuli, respectively, decreased shortly after nerve lesion in wild type mice. In TLR2 KO mice, nerve injury-induced thermal hyperalgesia was completely abolished contrary to that seen in wild-type mice, whereas mechanical allodynia was partially reduced. We suggest that TLR2 is necessary for the development of neuropathic pain and its contribution is more important in thermal hypersensitivity than that of mechanical allodynia.