Validation of computer-assisted, pixel-based analysis of multiple-colour immunofluorescence histology

Sex-specific adipose tissue's dynamic role in metabolic and inflammatory response following peripheral nerve injury

Epidemiological data and research highlight increased neuropathy and chronic pain prevalence among females, spanning metabolic and normometabolic contexts, including murine models. Prior findings demonstrated diverse immune and neuroimmune responses between genders in neuropathic pain (NeP), alongside distinct protein expression in sciatic nerves. This study unveils adipose tissue's (AT) role in sex-specific NeP responses after peripheral nerve injury. Metabolic assessments, metabolomics, energy expenditure evaluations, AT proteomic analyses, and adipokine mobilization depict distinct AT reactions to nerve damage. Females exhibit altered lipolysis, fatty acid oxidation, heightened energy expenditure, and augmented steroids secretion affecting glucose and insulin metabolism. Conversely, male neuropathy prompts glycolysis, reduced energy expenditure, and lowered unsaturated fatty acid levels. Males' AT promotes regenerative molecules, oxidative stress defense, and stimulates peroxisome proliferator-activated receptors (PPAR-γ) and adiponectin. This study underscores AT's pivotal role in regulating gender-specific inflammatory and metabolic responses to nerve injuries, shedding light on female NeP susceptibility determinants.

Intraperitoneal transfer of wild-type bone marrow repopulates tissue macrophages in the Csf1r knockout rat without contributing to monocytopoiesis

Homozygous null mutation of the Csf1r gene (Csf1rko) in rats leads to the loss of most tissue macrophage populations and pleiotropic impacts on postnatal growth and organ maturation, leading to early mortality. The phenotype can be reversed by intraperitoneal transfer of WT BM cells (BMT) at weaning. Here, we used a Csf1r-mApple transgenic reporter to track the fate of donor-derived cells. Following BMT into Csf1rko recipients, mApple+ve cells restored IBA1+ tissue macrophage populations in every tissue. However, monocytes, neutrophils, and B cells in the BM, blood, and lymphoid tissues remained of recipient (mApple-ve ) origin. An mApple+ve cell population expanded in the peritoneal cavity and invaded locally in the mesentery, fat pads, omentum, and diaphragm. One week after BMT, distal organs contained foci of mApple+ve , IBA1-ve immature progenitors that appeared to proliferate, migrate, and differentiate locally. We conclude that rat BM contains progenitor cells that are able to restore, replace, and maintain all tissue macrophage populations in a Csf1rko rat directly without contributing to the BM progenitor or blood monocyte populations.

MNPmApp: An image analysis tool to quantify mononuclear phagocyte distribution in mucosal tissues

Mononuclear phagocytes (MNPs) such as dendritic cells and macrophages perform key sentinel functions in mucosal tissues and are responsible for inducing and maintaining adaptive immune responses to mucosal pathogens. Positioning of MNPs at the epithelial interface facilitates their access to luminally-derived antigens and regulates MNP function through soluble mediators or surface receptor interactions. Therefore, accurately quantifying the distribution of MNPs within mucosal tissues as well as their spatial relationship with other cells is important to infer functional cellular interactions in health and disease. In this study, we developed and validated a MATLAB-based tissue cytometry platform, termed "MNP mapping application" (MNPmApp), that performs high throughput analyses of MNP density and distribution in the gastrointestinal mucosa based on digital multicolor fluorescence microscopy images and that integrates a Monte Carlo modeling feature to assess randomness of MNP distribution. MNPmApp identified MNPs in tissue sections of the human gastric mucosa with 98 ± 2% specificity and 76 ± 15% sensitivity for HLA-DR+ MNPs and 98 ± 1% specificity and 85 ± 12% sensitivity for CD11c+ MNPs. Monte Carlo modeling revealed that mean MNP-MNP distances for both HLA-DR+ and CD11c+ MNPs were significantly lower than anticipated based on random cell placement, whereas MNP-epithelial distances were similar to randomly placed cells. Surprisingly, H. pylori infection had no significant impact on the number of HLA-DR and CD11c MNPs or their distribution within the gastric lamina propria. However, our study demonstrated that MNPmApp is a reliable and user-friendly tool for unbiased quantitation of MNPs and their distribution at mucosal sites.

Sex Differences in Neuropathy: The Paradigmatic Case of MetFormin

As a widely prescribed anti-diabetic drug, metformin has been receiving novel attention for its analgesic potential. In the study of the complex etiology of neuropathic pain (NeP), male and female individuals exhibit quite different responses characterized by higher pain sensitivity and greater NeP incidence in women. This "gender gap" in our knowledge of sex differences in pain processing strongly limits the sex-oriented treatment of patients suffering from NeP. Besides, the current investigation of the analgesic potential of metformin has not addressed the "gender gap" problem. Hence, this study focuses on metformin and sex-dependent analgesia in a murine model of NeP induced by chronic constriction injury of the sciatic nerve. We investigated sexual dimorphism in signaling pathways involved by 7 days of metformin administration, such as changes in AMP-activated protein kinase and the positive regulation of autophagy machinery, discovering that metformin affected in a sexually dimorphic manner the immunological and inflammatory response to nerve lesion. These effects were complemented by morphological and adaptive changes occurring after peripheral nerve injury. Altogether these data can contribute to explaining a number of potential mechanisms responsible for the complete recovery from NeP found in male mice, as opposed to the failure of long-lasting recovery in female animals.

Foot-and-mouth disease virus localisation on follicular dendritic cells and sustained induction of neutralising antibodies is dependent on binding to complement receptors (CR2/CR1)

Previous studies have shown after the resolution of acute infection and viraemia, foot-and-mouth disease virus (FMDV) capsid proteins and/or genome are localised in the light zone of germinal centres of lymphoid tissue in cattle and African buffalo. The pattern of staining for FMDV proteins was consistent with the virus binding to follicular dendritic cells (FDCs). We have now demonstrated a similar pattern of FMDV protein staining in mouse spleens after acute infection and showed FMDV proteins are colocalised with FDCs. Blocking antigen binding to complement receptor type 2 and 1 (CR2/CR1) prior to infection with FMDV significantly reduced the detection of viral proteins on FDCs and FMDV genomic RNA in spleen samples. Blocking the receptors prior to infection also significantly reduced neutralising antibody titres, through significant reduction in their avidity to the FMDV capsid. Therefore, the binding of FMDV to FDCs and sustained induction of neutralising antibody responses are dependent on FMDV binding to CR2/CR1 in mice.

Aging-Related Impairments to M Cells in Peyer's Patches Coincide With Disturbances to Paneth Cells

The decline in mucosal immunity during aging increases susceptibility, morbidity and mortality to infections acquired via the gastrointestinal and respiratory tracts in the elderly. We previously showed that this immunosenescence includes a reduction in the functional maturation of M cells in the follicle-associated epithelia (FAE) covering the Peyer’s patches, diminishing the ability to sample of antigens and pathogens from the gut lumen. Here, co-expression analysis of mRNA-seq data sets revealed a general down-regulation of most FAE- and M cell-related genes in Peyer’s patches from aged mice, including key transcription factors known to be essential for M cell differentiation. Conversely, expression of ACE2, the cellular receptor for SARS-Cov-2 virus, was increased in the aged FAE. This raises the possibility that the susceptibility of aged Peyer’s patches to infection with the SARS-Cov-2 virus is increased. Expression of key Paneth cell-related genes was also reduced in the ileum of aged mice, consistent with the adverse effects of aging on their function. However, the increased expression of these genes in the villous epithelium of aged mice suggested a disturbed distribution of Paneth cells in the aged intestine. Aging effects on Paneth cells negatively impact on the regenerative ability of the gut epithelium and could indirectly impede M cell differentiation. Thus, restoring Paneth cell function may represent a novel means to improve M cell differentiation in the aging intestine and increase mucosal vaccination efficacy in the elderly.

Fragmentation of tissue-resident macrophages during isolation confounds analysis of single-cell preparations from mouse hematopoietic tissues

Mouse hematopoietic tissues contain abundant tissue-resident macrophages that support immunity, hematopoiesis, and bone homeostasis. A systematic strategy to characterize macrophage subsets in mouse bone marrow (BM), spleen, and lymph node unexpectedly reveals that macrophage surface marker staining emanates from membrane-bound subcellular remnants associated with unrelated cells. Intact macrophages are not present within these cell preparations. The macrophage remnant binding profile reflects interactions between macrophages and other cell types in vivo. Depletion of CD169⁺ macrophages in vivo eliminates F4/80⁺ remnant attachment. Remnant-restricted macrophage-specific membrane markers, cytoplasmic fluorescent reporters, and mRNA are all detected in non-macrophage cells including isolated stem and progenitor cells. Analysis of RNA sequencing (RNA-seq) data, including publicly available datasets, indicates that macrophage fragmentation is a general phenomenon that confounds bulk and single-cell analysis of disaggregated hematopoietic tissues. Hematopoietic tissue macrophage fragmentation undermines the accuracy of macrophage ex vivo molecular profiling and creates opportunity for misattribution of macrophage-expressed genes to non-macrophage cells.

CXCR2 increases in ALS cortical neurons and its inhibition prevents motor neuron degeneration in vitro and improves neuromuscular function in SOD1G93A mice

Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease characterized by depletion of motor neurons (MNs), for which effective medical treatments are still required. Previous transcriptomic analysis revealed the up-regulation of C-X-C motif chemokine receptor 2 (CXCR2)-mRNA in a subset of sporadic ALS patients and SOD1G93A mice. Here, we confirmed the increase of CXCR2 in human ALS cortex, and showed that CXCR2 is mainly localized in cell bodies and axons of cortical neurons. We also investigated the effects of reparixin, an allosteric inhibitor of CXCR2, in degenerating human iPSC-derived MNs and SOD1G93A mice. In vitro, reparixin rescued MNs from apoptotic cell death, preserving neuronal morphology, mitochondrial membrane potential and cytoplasmic membrane integrity, whereas in vivo it improved neuromuscular function of SOD1G93A mice. Altogether, these data suggest a role for CXCR2 in ALS pathology and support its pharmacological inhibition as a candidate therapeutic strategy against ALS at least in a specific subgroup of patients.

Immunofluorescence-guided segmentation of three-dimensional features in micro-computed tomography datasets of human lung tissue

Micro-computed tomography (µCT) provides non-destructive three-dimensional (3D) imaging of soft tissue microstructures. Specific features in µCT images can be identified using correlated two-dimensional (2D) histology images allowing manual segmentation. However, this is very time-consuming and requires specialist knowledge of the tissue and imaging modalities involved. Using a custom-designed µCT system optimized for imaging unstained formalin-fixed paraffin-embedded soft tissues, we imaged human lung tissue at isotropic voxel sizes less than 10 µm. Tissue sections were stained with haematoxylin and eosin or cytokeratin 18 in columnar airway epithelial cells using immunofluorescence (IF), as an exemplar of this workflow. Novel utilization of tissue autofluorescence allowed automatic alignment of 2D microscopy images to the 3D µCT data using scripted co-registration and automated image warping algorithms. Warped IF images, which were accurately aligned with the µCT datasets, allowed 3D segmentation of immunoreactive tissue microstructures in the human lung. Blood vessels were segmented semi-automatically using the co-registered µCT datasets. Correlating 2D IF and 3D µCT data enables accurate identification, localization and segmentation of features in fixed soft lung tissue. Our novel correlative imaging workflow provides faster and more automated 3D segmentation of µCT datasets. This is applicable to the huge range of formalin-fixed paraffin-embedded tissues held in biobanks and archives.

Sexually Dimorphic Immune and Neuroimmune Changes Following Peripheral Nerve Injury in Mice: Novel Insights for Gender Medicine

Neuropathic pain (NeP) in humans is often a life-long condition with no effective therapy available. The higher incidence of female gender in NeP onset is worldwide reported, and although the cause is generally attributed to sex hormones, the actual mechanisms and the players involved are still unclear. Glial and immune cells take part in NeP development, and orchestrate the neuroimmune and inflammatory response, releasing pro-inflammatory factors with chemoattractant properties that activate resident immune cells and recruit immune cells from circulation. The neuro-immune crosstalk is a key contributor to pain hypersensitivity following peripheral nervous system injury. Our previous works showed that in spite of the fact that female mice had an earlier analgesic response than males following nerve lesion, the recovery from NeP was never complete, suggesting that this difference could occur in the very early stages after injury. To further investigate gender differences in immune and neuroimmune responses to NeP, we studied the main immune cells and mediators elicited both in plasma and sciatic nerves by peripheral nerve lesion. After injury, we found a different pattern of distribution of immune cell populations showing either a higher infiltration of T cells in nerves from females or a higher infiltration of macrophages in nerves from males. Moreover, in comparison to male mice, the levels of cytokines and chemokines were differently up- and down-regulated in blood and nerve lysates from female mice. Our study provides some novel insights for the understanding of gender-associated differences in the generation and perseveration of NeP as well as for the isolation of specific neurodegenerative mechanisms underlying NeP. The identification of gender-associated inflammatory profiles in neuropathy is of key importance for the development of differential biomarkers and gender-specific personalized medicine.

Stable colony-stimulating factor 1 fusion protein treatment increases hematopoietic stem cell pool and enhances their mobilisation in mice

Background

Prior chemotherapy and/or underlying morbidity commonly leads to poor mobilisation of hematopoietic stem cells (HSC) for transplantation in cancer patients. Increasing the number of available HSC prior to mobilisation is a potential strategy to overcome this deficiency. Resident bone marrow (BM) macrophages are essential for maintenance of niches that support HSC and enable engraftment in transplant recipients. Here we examined potential of donor treatment with modified recombinant colony-stimulating factor 1 (CSF1) to influence the HSC niche and expand the HSC pool for autologous transplantation.

Methods

We administered an acute treatment regimen of CSF1 Fc fusion protein (CSF1-Fc, daily injection for 4 consecutive days) to naive C57Bl/6 mice. Treatment impacts on macrophage and HSC number, HSC function and overall hematopoiesis were assessed at both the predicted peak drug action and during post-treatment recovery. A serial treatment strategy using CSF1-Fc followed by granulocyte colony-stimulating factor (G-CSF) was used to interrogate HSC mobilisation impacts. Outcomes were assessed by in situ imaging and ex vivo standard and imaging flow cytometry with functional validation by colony formation and competitive transplantation assay.

Results

CSF1-Fc treatment caused a transient expansion of monocyte-macrophage cells within BM and spleen at the expense of BM B lymphopoiesis and hematopoietic stem and progenitor cell (HSPC) homeostasis. During the recovery phase after cessation of CSF1-Fc treatment, normalisation of hematopoiesis was accompanied by an increase in the total available HSPC pool. Multiple approaches confirmed that CD48⁻CD150⁺ HSC do not express the CSF1 receptor, ruling out direct action of CSF1-Fc on these cells. In the spleen, increased HSC was associated with expression of the BM HSC niche macrophage marker CD169 in red pulp macrophages, suggesting elevated spleen engraftment with CD48⁻CD150⁺ HSC was secondary to CSF1-Fc macrophage impacts. Competitive transplant assays demonstrated that pre-treatment of donors with CSF1-Fc increased the number and reconstitution potential of HSPC in blood following a HSC mobilising regimen of G-CSF treatment.

Conclusion

These results indicate that CSF1-Fc conditioning could represent a therapeutic strategy to overcome poor HSC mobilisation and subsequently improve HSC transplantation outcomes.

Very Early Involvement of Innate Immunity in Peripheral Nerve Degeneration in SOD1-G93A Mice

Recent preclinical and clinical evidence suggest that immune system has a role in the progression and prognosis of Amyotrophic Lateral Sclerosis (ALS), but the identification of a clear mechanism and immune players remains to be elucidated. Here, we have investigated, in 30 and 60 days (presymptomatic) and 120 days (symptomatic) old SOD1-G93A mice, systemic, peripheral, and central innate and adaptive immune and inflammatory response, correlating it with the progression of the neurodegeneration in neuromuscular junction, sciatic nerves, and spinal cord. Surprisingly, we found a very initial (45-60 days) presence of IgG in sciatic nerves together with a gradual enhancement of A20/TNFAIP3 (protein controlling NF-κB signalling) and a concomitantly significant increase and activation of circulating mast cells (MCs) as well as MCs and macrophages in sciatic nerve and an enhancement of IL-6 and IL-10. This immunological frame coincided with a myelin aggregation. The 30-60 days old SOD1-G93A mice didn't show real elements of neuroinflammation and neurodegeneration in spinal cord. In 120 days old mice macrophages and monocytes are widely diffused in sciatic nerves, peripheral neurodegeneration reaches the tip, high circulating levels of TNFα and IL-2 were found and spinal cord exhibits clear signs of neural damage and infiltrating immune cells. Our results underpin a clear immunological disorder at the origin of ALS axonopathy, in which MCs are involved in the initiation and sustaining of inflammatory events. These data cannot be considered a mere epiphenomenon of motor neuron degeneration and reveal new potential selective immune targets in ALS therapy.

Accelerated onset of CNS prion disease in mice co-infected with a gastrointestinal helminth pathogen during the preclinical phase

Prion infections in the central nervous system (CNS) can cause extensive neurodegeneration. Systemic inflammation can affect the progression of some neurodegenerative disorders. Therefore, we used the gastrointestinal helminth pathogen Trichuris muris to test the hypothesis that a chronic systemic inflammatory response to a gastrointestinal infection would similarly affect CNS prion disease pathogenesis. Mice were injected with prions directly into the CNS and subsequently orally co-infected with T. muris before the onset of clinical signs. We show that co-infection with a low dose of T. muris that leads to the development of a chronic T helper cell type 1-polarized systemic immune response accelerated the onset of clinical prion disease. In contrast, co-infection with a high dose of T. muris that induces a T helper cell type 2-polarized immune response did not affect prion disease pathogenesis. The reduced survival times in mice co-infected with a low dose of T. muris on d 105 after CNS prion infection coincided with enhanced astrocyte activation in the brain during the preclinical phase. These data aid our understanding of how systemic inflammation may augment the progression of neurodegeneration in the CNS.

Sexual Dimorphism in Immune Development and in Response to Nutritional Intervention in Neonatal Piglets

Although sex disparity in immunological function and susceptibility to various inflammatory and infectious disease is recognized in adults, far less is known about the situation in young infants during immune development. We have used an outbred piglet model to explore potential early sex disparity underlying both mucosal immune development and systemic responses to novel antigen. Despite similarities in intestinal barrier function and therefore, presumably, antigen exposure, females had less CD172⁺ (Sirp-α) antigen presenting cells and expression of MHCIIDR at 28 days old compared to males, along with greater regulatory T-cell numbers. This suggests that, during infancy, females may have greater potential for local immune regulation than their male counterparts. However, females also presented with significantly greater systemic antibody responses to injected ovalbumin and dietary soya. Females also synthesized significantly more IgA in mesenteric lymph nodes, whereas males synthesized more in caecal mucosa, suggesting that plasma cells were retained within the MLN in females, but increased numbers of plasma cells circulated through to the mucosal tissue in males. Significant effects of inulin and Bifidobacterium lactis NCC2818 on the developing immune system were also sex-dependent. Our results may start to explain inconsistencies in outcomes of trials of functional foods in infants, as distinction between males and females is seldom made. Since later functionality of the immune system is highly dependent on appropriate development during infancy, stratifying nutritional interventions by sex may present a novel means of optimizing treatments and preventative strategies to reduce the risk of the development of immunological disorders in later life.

Impact of caloric restriction on peripheral nerve injury-induced neuropathic pain during ageing in mice

The incidence of peripheral neuropathy development and chronic pain is strongly associated with the arrival of senescence. The gradual physiological decline that begins after the mature stage produces myelin dysregulation and pathological changes in peripheral nervous system, attributed to reduction in myelin proteins expression and thinner myelin sheath. Moreover in elder subjects, when nerve damage occurs, the regenerative processes are seriously compromised and neuropathic pain (NeP) is maintained. We previously demonstrated that caloric restriction (CR) in adult (4 months) nerve-lesioned mice was able to facilitate remyelination and axons regeneration, to have anti-inflammatory action and to prevent NeP chronification. Here, we show CR therapeutic potential on nerve injury-induced neuropathy in mice at the beginning of the senescence (12 months). Long lasting decrease in hypersensitvity induced by peripheral nerve lesion and powerful reduction in proinflammatory circulating agents have been observed. Moreover, our results evidence that CR is able to counteract the ageing-related delay in axonal regeneration, enhancing Schwann cells proliferation and accelerating recovery processes. Differently from adults, it does not affect fibres myelination. In light of a continuous growth in elderly population and correlated health problems, including metabolic disorders, the prevalence of neuropathy is enhancing, generating a significant public cost and social concern. In this context energy depletion by dietary restriction can be a therapeutic option in NeP.

Antigen Sampling CSF1R-Expressing Epithelial Cells Are the Functional Equivalents of Mammalian M Cells in the Avian Follicle-Associated Epithelium

The follicle-associated epithelium (FAE) is a specialized structure that samples luminal antigens and transports them into mucosa-associated lymphoid tissues (MALT). In mammals, transcytosis of antigens across the gut epithelium is performed by a subset of FAE cells known as M cells. Here we show that colony-stimulating factor 1 receptor (CSF1R) is expressed by a subset of cells in the avian bursa of Fabricius FAE. Expression was initially detected using a CSF1R-reporter transgene that also label subsets of bursal macrophages. Immunohistochemical detection using a specific monoclonal antibody confirmed abundant expression of CSF1R on the basolateral membrane of FAE cells. CSF1R-transgene expressing bursal FAE cells were enriched for expression of markers previously reported as putative M cell markers, including annexin A10 and CD44. They were further distinguished from a population of CSF1R-transgene negative epithelial cells within FAE by high apical F-actin expression and differential staining with the lectins jacalin, PHA-L and SNA. Bursal FAE cells that express the CSF1R-reporter transgene were responsible for the bulk of FAE transcytosis of labeled microparticles in the size range 0.02-0.1 μm. Unlike mammalian M cells, they did not readily take up larger bacterial sized microparticles (0.5 μm). Their role in uptake of bacteria was tested using Salmonella, which can enter via M cells in mammals. Labeled Salmonella enterica serovar Typhimurium entered bursal tissue via the FAE. Entry was partially dependent upon Type III secretion system-1. However, the majority of invading bacteria were localized to CSF1R-negative FAE cells and in resident phagocytes that express the phosphatidylserine receptor TIM4. CSF1R-expressing FAE cells in infected follicles showed evidence of cell death and shedding into the bursal lumen. In mammals, CSF1R expression in the gut is restricted to macrophages which only indirectly control M cell differentiation. The novel expression of CSF1R in birds suggests that these functional equivalents to mammalian M cells may have different ontological origins and their development and function are likely to be regulated by different growth factors.

Discrimination of Prion Strain Targeting in the Central Nervous System via Reactive Astrocyte Heterogeneity in CD44 Expression

Prion diseases or transmissible spongiform encephalopathies are fatal, progressive, neurodegenerative, protein-misfolding disorders. Prion diseases may arise spontaneously, be inherited genetically or be acquired by infection and affect a variety of mammalian species including humans. Prion infections in the central nervous system (CNS) cause extensive neuropathology, including abnormal accumulations of misfolded host prion protein, vacuolar change resulting in sponge-like (spongiform) appearance of CNS tissue, neurodegeneration and reactive glial responses. Many different prion agent strains exist and these can differ based on disease duration, clinical signs and the targeting and distribution of the neuropathology in distinct brain areas. Reactive astrocytes are a prominent feature in the prion disease affected CNS as revealed by distinct morphological changes and upregulation of glial fibrillary acidic protein (GFAP). The CD44 antigen is a transmembrane glycoprotein involved in cell-cell interactions, cell adhesion and migration. Here we show that CD44 is also highly expressed in a subset of reactive astrocytes in regions of the CNS targeted by prions. Astrocyte heterogeneity revealed by differential CD44 upregulation occurs coincident with the earliest neuropathological changes during the pre-clinical phase of disease, and is not affected by the route of infection. The expression and distribution of CD44 was compared in brains from a large collection of 15 distinct prion agent strains transmitted to mice of different prion protein (Prnp) genotype backgrounds. Our data show that the pattern of CD44 upregulation observed in the hippocampus in each prion agent strain and host Prnp genotype combination was unique. Many mouse-adapted prion strains and hosts have previously been characterized based on the pattern of the distribution of the spongiform pathology or the misfolded PrP deposition within the brain. Our data show that CD44 expression also provides a reliable discriminatory marker of prion infection with a greater dynamic range than misfolded prion protein deposition, aiding strain identification. Together, our data reveal CD44 as a novel marker to detect reactive astrocyte heterogeneity during CNS prion disease and for enhanced identification of distinct prion agent strains.

Increased susceptibility to oral Trichuris muris infection in the specific absence of CXCR5+ CD11c+ cells

Trichuris muris is a natural mouse helminth pathogen which establishes infection specifically in the caecum and proximal colon. The rapid expulsion of T. muris in resistant mouse strains is associated with the induction of a protective T helper cell type 2 (Th2)‐polarized immune response. Susceptible mouse strains, in contrast, mount an inappropriate Th1 response to T. muris infection. Expression of the chemokine CXCL13 by stromal follicular dendritic cells attracts CXCR5‐expressing cells towards the B‐cell follicles. Previous studies using a complex in vivo depletion model have suggested that CXCR5‐expressing conventional dendritic cells (cDC) help regulate the induction of Th2‐polarized responses. Here, transgenic mice with CXCR5 deficiency specifically restricted to CD11c⁺ cells were used to determine whether the specific absence CXCR5 on CD11c⁺ cells such as cDC would influence susceptibility to oral T. muris infection by affecting the Th1/Th2 balance. We show that in contrast to control mice, those which lacked CXCR5 expression on CD11c⁺ cells failed to clear T. muris infection and developed cytokine and antibody responses that suggested a disturbed Th1/Th2 balance with enhanced IFN‐γ expression. These data suggest an important role of CXCR5‐expressing CD11c⁺ cells such as cDC in immunity to oral T. muris infection.

Effect of co-infection with a small intestine-restricted helminth pathogen on oral prion disease pathogenesis in mice

The early replication of some orally-acquired prion strains upon stromal-derived follicular dendritic cells (FDC) within the small intestinal Peyer’s patches is essential to establish host infection, and for the disease to efficiently spread to the brain. Factors that influence the early accumulation of prions in Peyer’s patches can directly influence disease pathogenesis. The host’s immune response to a gastrointestinal helminth infection can alter susceptibility to co-infection with certain pathogenic bacteria and viruses. Here we used the natural mouse small intestine-restricted helminth pathogen Heligmosomoides polygyrus to test the hypothesis that pathology specifically within the small intestine caused by a helminth co-infection would influence oral prion disease pathogenesis. When mice were co-infected with prions on d 8 after H. polygyrus infection the early accumulation of prions within Peyer’s patches was reduced and survival times significantly extended. Natural prion susceptible hosts such as sheep, deer and cattle are regularly exposed to gastrointestinal helminth parasites. Our data suggest that co-infections with small intestine-restricted helminth pathogens may be important factors that influence oral prion disease pathogenesis.

Mechanoporation is a potential indicator of tissue strain and subsequent degeneration following experimental traumatic brain injury

BACKGROUND

An increases in plasma membrane permeability is part of the acute pathology of traumatic brain injury and may be a function of excessive membrane force. This membrane damage, or mechanoporation, allows non-specific flux of ions and other molecules across the plasma membrane, and may ultimately lead to cell death. The relationships among tissue stress and strain, membrane permeability, and subsequent cell degeneration, however, are not fully understood.

METHODS

Fluorescent molecules of different sizes were introduced to the cerebrospinal fluid space prior to injury and animals were sacrificed at either 10 min or 24 h after injury. We compared the spatial distribution of plasma membrane damage following controlled cortical impact in the rat to the stress and strain tissue patterns in a 3-D finite element simulation of the injury parameters.

FINDINGS

Permeable cells were located primarily in the ipsilateral cortex and hippocampus of injured rats at 10 min post-injury; however by 24 h there was also a significant increase in the number of permeable cells. Analysis of colocalization of permeability marker uptake and Fluorojade staining revealed a subset of permeable cells with signs of degeneration at 24 h, but plasma membrane damage was evident in the vast majority of degenerating cells. The regional and subregional distribution patterns of the maximum principal strain and shear stress estimated by the finite element model were comparable to the cell membrane damage profiles following a compressive impact.

INTERPRETATION

These results indicate that acute membrane permeability is prominent following traumatic brain injury in areas that experience high shear or tensile stress and strain due to differential mechanical properties of the cell and tissue organization, and that this mechanoporation may play a role in the initiation of secondary injury, contributing to cell death.

Effects of caloric restriction on neuropathic pain, peripheral nerve degeneration and inflammation in normometabolic and autophagy defective prediabetic Ambra1 mice

There is a growing interest on the role of autophagy in diabetes pathophysiology, where development of neuropathy is one of the most frequent comorbidities. We have previously demonstrated that neuropathic pain after nerve damage is exacerbated in autophagy-defective heterozygous Ambra1 mice. Here, we show the existence of a prediabetic state in Ambra1 mice, characterized by hyperglycemia, intolerance to glucose and insulin resistance. Thus, we further investigate the hypothesis that prediabetes may account for the exacerbation of allodynia and chronic pain and that counteracting the autophagy deficit may relieve the neuropathic condition. We took advantage from caloric restriction (CR) able to exert a double action: a powerful increase of autophagy and a control on the metabolic status. We found that CR ameliorates neuropathy throughout anti-inflammatory and metabolic mechanisms both in Ambra1 and in WT animals subjected to nerve injury. Moreover, we discovered that nerve lesion represents, per se, a metabolic stressor and CR reinstates glucose homeostasis, insulin resistance, incomplete fatty acid oxidation and energy metabolism. As autophagy inducer, CR promotes and anticipates Schwann cell autophagy via AMP-activated protein kinase (AMPK) that facilitates remyelination in peripheral nerve. In summary, we provide new evidence for the role of autophagy in glucose metabolism and identify in energy depletion by dietary restriction a therapeutic approach in the fight against neuropathic pain.

Involvement of leptin signaling in the development of cannabinoid CB2 receptor-dependent mirror image pain

Neuropathic pain typically appears in a region innervated by an injured or diseased nerve and, in some instances, also on the contralateral side. This so-called mirror image pain is often observed in mice lacking CB2 receptors after sciatic nerve injury, but the underlying mechanisms for this phenotype largely remain unclear. Here we focused on peripheral leptin signaling, which modulates neuropathic pain development and interacts with the endocannabinoid system. Leptin production is induced at the site of nerve injury in CB2-deficient mice (CB2-KO) mice and wild type controls (WT). However, induction of leptin receptor expression was only observed in the injured nerve of CB2-KO mice. This was paralleled by a stimulation of the leptin receptor-downstream STAT3 signaling and an infiltration of F4/80-positive macrophages. Interestingly, an upregulation of leptin receptor expression STAT3 activity and macrophage infiltration was also observed on the non-injured nerve of CB2-KO mice thus reflecting the mirror image pain in CB2-KO animals. Importantly, perineurally-administered leptin-neutralizing antibodies reduced mechanical hyperalgesia, blocked mirror image pain and inhibited the recruitment of F4/80-positive macrophages. These results identify peripheral leptin signaling as an important modulator of CB2 signaling in neuropathic pain.

Minocycline plus N-acetylcysteine protect oligodendrocytes when first dosed 12 hours after closed head injury in mice

The mouse closed head injury (CHI) model of traumatic brain injury (TBI) produces widespread demyelination. Myelin content is restored by minocycline (MINO) plus n-acetylcysteine (NAC) or MINO alone when first dosed at 12 h after CHI. In a rat controlled cortical impact model of TBl, a first dose of MINO plus NAC one h after injury protects resident oligodendrocytes that induce remyelination. In contrast, MINO less effectively protects oligodendrocytes and remyelination is mediated by oligodendrocyte precursor cell proliferation and differentiation. MINO plus NAC or MINO alone is hypothesized to work similarly in the CHI model as in the controlled cortical impact model even when first dosed at 12-h post-CHI. We tested this hypothesis by examining the time course of the changes in the oligodendrocyte antigenic markers CC1, 2',3'-Cyclic-nucleotide 3'-phosphodiesterase and phospholipid protein between 2 and 14 days post-CHI in mice treated with saline, NAC, MINO or MINO plus NAC. CHI produced a long-lasting loss of these markers that was not altered by NAC treatment. In contrast, oligodendrocyte marker expression was maintained by MINO plus NAC between 2 and 14 days post-injury. MINO alone did not prevent the early loss of oligodendrocyte markers, but marker expression significantly increased by 14-days post-injury. These data suggest that MINO plus NAC or MINO alone when first dosed 12 h after CHI increase myelin content using similar mechanisms seen when first dosed 1 h after closed head injury. These data also suggest that drugs protect oligodendrocytes with a clinically useful therapeutic time window.

Experimental Stroke Differentially Affects Discrete Subpopulations of Splenic Macrophages

Changes to the immune system after stroke are complex and can result in both pro-inflammatory and immunosuppressive consequences. Following ischemic stroke, brain resident microglia are activated and circulating monocytes are recruited to the injury site. In contrast, there is a systemic deactivation of monocytes/macrophages that may contribute to immunosuppression and the high incidence of bacterial infection experienced by stroke patients. The manipulation of macrophage subsets may be a useful therapeutic strategy to reduce infection and improve outcome in patients after stroke. Recent research has enhanced our understanding of the heterogeneity of macrophages even within the same tissue. The spleen is the largest natural reservoir of immune cells, many of which are mobilized to the site of injury after ischemic stroke and is notable for the diversity of its functionally distinct macrophage subpopulations associated with specific micro-anatomical locations. Here, we describe the effects of experimental stroke in mice on these distinct splenic macrophage subpopulations. Red pulp (RP) and marginal zone macrophages (MZM) specifically showed increases in density and alterations in micro-anatomical location. These changes were not due to increased recruitment from the bone marrow but may be associated with increases in local proliferation. Genes associated with phagocytosis and proteolytic processing were upregulated in the spleen after stroke with increased expression of the lysosome-associated protein lysosomal-associated membrane proteins specifically increased in RP and MZM subsets. In contrast, MHC class II expression was reduced specifically in these populations. Furthermore, genes associated with macrophage ability to communicate with other immune cells, such as co-stimulatory molecules and inflammatory cytokine production, were also downregulated in the spleen after stroke. These findings suggest that selective splenic macrophage functions could be impaired after stroke and the contribution of macrophages to stroke-associated pathology and infectious complications should be considered at a subset-specific level. Therefore, optimal therapeutic manipulation of macrophages to improve stroke outcome is likely to require selective targeting of functionally and spatially distinct subpopulations.

Development of Immune Cells in the Intestinal Mucosa Can Be Affected by Intensive and Extensive Farm Environments, and Antibiotic Use

Epidemiological studies have demonstrated that exposure to farm environments during childhood can be linked to reductions in the incidence of immune disorders, but generating an appropriate model is difficult. 108 half-sibling piglets were born on either extensive (outdoor) or intensive (indoor) farms: at 1 day old, a subset of piglets from each litter were transferred to a high-hygiene isolator facility to create differences in rearing environment either during birth/first day or during the subsequent 56 days of life. Interactions between CD14, CD16, MHCIIDR, and capillary endothelium were assessed using four-color quantitative fluorescence immunohistology. Effects of birth and rearing environment on the antigen-presenting microenvironment of the proximal and distal jejunum (professional and stromal) were apparent at 5, 28, and 56 days after birth However, effects on CD4⁺CD25⁺Foxp3⁺ regulatory T-cells (T_regs) in the intestinal mucosa were apparent around weaning at 28 days but had disappeared by 56 days. These T_regs were reduced in the isolator piglets compared to their farm-reared siblings, but this effect was less marked in piglets born on the extensive farm and required administration of antibiotics. Our results suggest that there may be at least two windows of opportunity in which different farm environments were influencing immune development: one during the perinatal period (up to the first day of life), and one during later infancy. Furthermore, the differences on T_regs suggest that the effects of early life influences may be particularly critical around weaning.

The role of CSF1R-dependent macrophages in control of the intestinal stem-cell niche

Colony-stimulating factor 1 (CSF1) controls the growth and differentiation of macrophages.CSF1R signaling has been implicated in the maintenance of the intestinal stem cell niche and differentiation of Paneth cells, but evidence of expression of CSF1R within the crypt is equivocal. Here we show that CSF1R-dependent macrophages influence intestinal epithelial differentiation and homeostasis. In the intestinal lamina propria CSF1R mRNA expression is restricted to macrophages which are intimately associated with the crypt epithelium, and is undetectable in Paneth cells. Macrophage ablation following CSF1R blockade affects Paneth cell differentiation and leads to a reduction of Lgr5+ intestinal stem cells. The disturbances to the crypt caused by macrophage depletion adversely affect the subsequent differentiation of intestinal epithelial cell lineages. Goblet cell density is enhanced, whereas the development of M cells in Peyer's patches is impeded. We suggest that modification of the phenotype or abundance of macrophages in the gut wall alters the development of the intestinal epithelium and the ability to sample gut antigens.

Use of computer-assisted image analysis for semi-quantitative histology of the hepatopancreas in whiteleg shrimp Penaeus vannamei (Boone)

Despite the increasing use of novel molecular techniques in pathology, histology remains the standard method for monitoring tissue alterations and for assessing pathology. Histopathological evaluation is generally laborious and subjective with risk of discrepancies in semi-quantitative scoring between pathologists. In contrast, computer-assisted image analysis (CAIA) is potentially faster, more objective and thus suitable for routine screening. Limited research has been carried out on CAIA in crustacean histopathology, and the methods described were not fully automated. Therefore, the aim of this study was to develop CAIA in whiteleg shrimp (Penaeus vannamei) for the study of the hepatopancreas. Paraffin sections were immunohistochemically stained with monoclonal antibodies WSH8 against haemocytes and counterstained with Mayer's haematoxylin for detection of haemocytes and B-cell vacuoles, and modified toluidine blue protocol was used for detection of F-cells; frozen sections were stained with Oil Red O for detection of lipid droplets within R-cells. Visiopharm^® software was used to develop and validated protocols for the quantification of morphological parameters (areas of haemocyte infiltration, F-cells, B-cell vacuoles, lipid droplets and their ratios to total tissue area and total lumen area). These protocols enable the future use of CAIA for determination of the nutritional and pathological condition of this organ.

Streptococcus thermophilus NCIMB 41856 ameliorates signs of colitis in an animal model of inflammatory bowel disease

Treatment of inflammatory bowel disease (IBD) is mainly based on suppression of symptoms, often with numerous side effects. Trials of probiotics in IBD have frequently produced disappointing results. The majority of probiotics are unusual, since they do not require iron for growth, unlike many bacteria resident in the intestine. The IBD intestine is iron-rich due to bleeding and use of oral iron supplements; conventional probiotics would be rapidly outcompeted. We have evaluated an iron-responsive Streptococcus thermophilus strain for its potential to reduce signs of colitis. Efficacy of S. thermophilus was evaluated in the dextran sodium sulphate mouse model of colitis. Treated animals were given 1×108 cfu S. thermophilus per day and clinical observations were taken daily. At termination, gross and histopathological signs of disease, cellular infiltration, location of bacteria, and cytokine expression in the intestine were determined. S. thermophilus delayed onset of colitis and reduced clinical signs of disease, including bodyweight loss and gastrointestinal bleeding. It reduced bacterial translocation into the colonic tissue. Increased numbers of CD8+ intraepithelial lymphocytes were seen in control animals treated with S. thermophilus. S. thermophilus had no effect on gross pathology, histopathology or cytokine production in either colitic or control animals. We propose that S. thermophilus promotes maintenance of mucosal barrier function which reduces bacterial translocation, thereby reducing immune stimulation and associated inflammation. This allows mucosal healing, reducing gastrointestinal bleeding and weight loss. This could be studied as a locally-acting adjunct or alternative to current IBD treatments.

Prion disease pathogenesis in the absence of the commensal microbiota

Prion diseases are a unique group of transmissible, typically sub-acute, neurodegenerative disorders. During central nervous system (CNS) prion disease, the microglia become activated and are thought to provide a protective response by scavenging and clearing prions. The mammalian intestine is host to a large burden of commensal micro-organisms, especially bacteria, termed the microbiota. The commensal microbiota has beneficial effects on host health, including through the metabolism of essential nutrients, regulation of host development and protection against pathogens. The commensal gut microbiota also constitutively regulates the functional maturation of microglia in the CNS, and microglial function is impaired when it is absent in germ-free mice. In the current study, we determined whether the absence of the commensal gut microbiota might also affect prion disease pathogenesis. Our data clearly show that the absence of the commensal microbiota in germ-free mice did not affect prion disease duration or susceptibility after exposure to prions by intraperitoneal or intracerebral injection. Furthermore, the magnitude and distribution of the characteristic neuropathological hallmarks of terminal prion disease in the CNS, including the development of spongiform pathology, accumulation of prion disease-specific protein (PrP), astrogliosis and microglial activation, were similar in conventionally housed and germ-free mice. Thus, although the commensal gut microbiota constitutively promotes the maintenance of the microglia in the CNS under steady-state conditions in naïve mice, our data suggest that dramatic changes to the abundance or complexity of the commensal gut microbiota are unlikely to influence CNS prion disease pathogenesis.

Early intervention with Bifidobacterium lactis NCC2818 modulates the host-microbe interface independent of the sustained changes induced by the neonatal environment

Inflammatory and metabolic diseases can originate during early-life and have been correlated with shifts in intestinal microbial ecology. Here we demonstrate that minor environmental fluctuations during the early neonatal period had sustained effects on the developing porcine microbiota and host-microbe interface. These inter-replicate effects appear to originate during the first day of life, and are likely to reflect very early microbiota acquisition from the environment. We statistically link early systemic inflammation with later local increases in inflammatory cytokine (IL-17) production, which could have important enteric health implications. Immunity, intestinal barrier function, host metabolism and host-microbiota co-metabolism were further modified by Bifidobacterium lactis NCC2818 supplementation, although composition of the in situ microbiota remained unchanged. Finally, our robust model identified novel, strong correlations between urinary metabolites (eg malonate, phenylacetylglycine, alanine) and mucosal immunoglobulin (IgM) and cytokine (IL-10, IL-4) production, thus providing the possibility of the development of urinary ‘dipstick’ tests to assess non-accessible mucosal immune development and identify early precursors (biomarkers) of disease. These results have important implications for infants exposed to neonatal factors including caesarean delivery, antibiotic therapy and delayed discharge from hospital environments, which may predispose to the development of inflammatory and metabolic diseases in later life.

Oral Prion Disease Pathogenesis Is Impeded in the Specific Absence of CXCR5-Expressing Dendritic Cells

After oral exposure, the early replication of certain prion strains upon stromal cell-derived follicular dendritic cells (FDC) in the Peyer's patches in the small intestine is essential for the efficient spread of disease to the brain. However, little is known of how prions are initially conveyed from the gut lumen to establish infection on FDC. Our previous data suggest that mononuclear phagocytes such as CD11c⁺ conventional dendritic cells play an important role in the initial propagation of prions from the gut lumen into Peyer's patches. However, whether these cells conveyed orally acquired prions toward FDC within Peyer's patches was not known. The chemokine CXCL13 is expressed by FDC and follicular stromal cells and modulates the homing of CXCR5-expressing cells toward the FDC-containing B cell follicles. Here, novel compound transgenic mice were created in which a CXCR5 deficiency was specifically restricted to CD11c⁺ cells. These mice were used to determine whether CXCR5-expressing conventional dendritic cells propagate prions toward FDC after oral exposure. Our data show that in the specific absence of CXCR5-expressing conventional dendritic cells the early accumulation of prions upon FDC in Peyer's patches and the spleen was impaired, and disease susceptibility significantly reduced. These data suggest that CXCR5-expressing conventional dendritic cells play an important role in the efficient propagation of orally administered prions toward FDC within Peyer's patches in order to establish host infection.IMPORTANCE Many natural prion diseases are acquired by oral consumption of contaminated food or pasture. Once the prions reach the brain they cause extensive neurodegeneration, which ultimately leads to death. In order for the prions to efficiently spread from the gut to the brain, they first replicate upon follicular dendritic cells within intestinal Peyer's patches. How the prions are first delivered to follicular dendritic cells to establish infection was unknown. Understanding this process is important since treatments which prevent prions from infecting follicular dendritic cells can block their spread to the brain. We created mice in which mobile conventional dendritic cells were unable to migrate toward follicular dendritic cells. In these mice the early accumulation of prions on follicular dendritic cells was impaired and oral prion disease susceptibility was reduced. This suggests that prions exploit conventional dendritic cells to facilitate their initial delivery toward follicular dendritic cells to establish host infection.

Adrenergic-mediated loss of splenic marginal zone B cells contributes to infection susceptibility after stroke

Infection is a major complication of acute stroke and causes increased mortality and morbidity; however, current interventions do not prevent infection and improve clinical outcome in stroke patients. The mechanisms that underlie susceptibility to infection in these patients are unclear. Splenic marginal zone (MZ) B cells are innate-like lymphocytes that provide early defence against bacterial infection. Here we show experimental stroke in mice induces a marked loss of MZ B cells, deficiencies in capturing blood-borne antigen and suppression of circulating IgM. These deficits are accompanied by spontaneous bacterial lung infection. IgM levels are similarly suppressed in stroke patients. β-adrenergic receptor antagonism after experimental stroke prevents loss of splenic MZ B cells, preserves IgM levels, and reduces bacterial burden. These findings suggest that adrenergic-mediated loss of MZ B cells contributes to the infection-prone state after stroke and identify systemic B-cell disruption as a target for therapeutic manipulation.

Maternal exposure to low levels of corticosterone during lactation protects adult rat progeny against TNBS-induced colitis: A study on GR-mediated anti-inflammatory effect and prokineticin system

The early phase of life represents a critical period for the development of an organism. Interestingly, early life experiences are able to influence the development of the gastrointestinal tract and the reactivity to colonic inflammatory stress. We recently demonstrated that adult male rats exposed to low doses of corticosterone during lactation (CORT-nursed rats) are protected against experimental colitis induced by the intracolonic infusion of 2,4,6-trinitrobenzenesulfonic acid (TNBS). Based on these interesting results, we wanted to better investigate which cellular actors could be involved in the protection of CORT-nursed rats from TNBS-induced experimental colitis. Therefore, in the present work, we focused our attention on different factors implicated in GR-mediated anti-inflammatory effect. To address this issue, colonic tissues, collected from control and CORT-nursed healthy animals and from control and CORT-nursed colitic rats, were processed and the following inflammatory factors were evaluated: the expression of (i) glucocorticoid receptors (GR), (ii) glucocorticoid-induced leucine zipper (GILZ), (iii) phospho-p65NF-κB, (iv) the pro-inflammatory cytokines IL-1β and TNF-α, (v) the prokineticins PK2 and PK2L and (vi) their receptors PKR1 and PKR2. We found that adult CORT-nursed rats, in comparison to controls, showed increased expression of colonic GR and reduced expression of pro-inflammatory molecules (IL-1β, TNF-α, PK2 and PK2L) in response to inflammatory colitis. The observed changes were associated with an increase in GILZ colonic expression and with a reduction in phospo-p65NF-κB colonic expression.

Increased Abundance of M Cells in the Gut Epithelium Dramatically Enhances Oral Prion Disease Susceptibility

Many natural prion diseases of humans and animals are considered to be acquired through oral consumption of contaminated food or pasture. Determining the route by which prions establish host infection will identify the important factors that influence oral prion disease susceptibility and to which intervention strategies can be developed. After exposure, the early accumulation and replication of prions within small intestinal Peyer's patches is essential for the efficient spread of disease to the brain. To replicate within Peyer's patches, the prions must first cross the gut epithelium. M cells are specialised epithelial cells within the epithelia covering Peyer's patches that transcytose particulate antigens and microorganisms. M cell-development is dependent upon RANKL-RANK-signalling, and mice in which RANK is deleted only in the gut epithelium completely lack M cells. In the specific absence of M cells in these mice, the accumulation of prions within Peyer's patches and the spread of disease to the brain was blocked, demonstrating a critical role for M cells in the initial transfer of prions across the gut epithelium in order to establish host infection. Since pathogens, inflammatory stimuli and aging can modify M cell-density in the gut, these factors may also influence oral prion disease susceptibility. Mice were therefore treated with RANKL to enhance M cell density in the gut. We show that prion uptake from the gut lumen was enhanced in RANKL-treated mice, resulting in shortened survival times and increased disease susceptibility, equivalent to a 10-fold higher infectious titre of prions. Together these data demonstrate that M cells are the critical gatekeepers of oral prion infection, whose density in the gut epithelium directly limits or enhances disease susceptibility. Our data suggest that factors which alter M cell-density in the gut epithelium may be important risk factors which influence host susceptibility to orally acquired prion diseases.

c-Rel is dispensable for the differentiation and functional maturation of M cells in the follicle-associated epithelium

M cells reside within the follicle-associated epithelium (FAE) overlying the gut-associated lymphoid tissues. These unique phagocytic epithelial cells enable the mucosal immune system to sample antigens within the lumen of the intestine. The differentiation of M cells from uncommitted precursors in the FAE is dependent on the production of receptor activator of nuclear factor-κB ligand (RANKL) by subepithelial stromal cells. The ligation of a variety of cell surface receptors activates the nuclear factor-κB (NF-κB) family of transcription factors which in-turn induce the transcription of multiple target genes. RANKL-stimulation can stimulate the nuclear translocation of the NF-κB subunit c-Rel. We therefore used c-Rel-deficient mice to determine whether the differentiation and functional maturation of M cells in the Peyer's patches was dependent on c-Rel. Our data show that c-Rel-deficiency does not influence the expression of RANKL or RANK in Peyer's patches, or the induction of M-cell differentiation in the FAE. RANKL-stimulation in the differentiating M cells induces the expression of SpiB which is essential for their subsequent maturation. However, SpiB expression in the FAE was also unaffected in the absence of c-Rel. As a consequence, the functional maturation of M cells was not impaired in the Peyer's patches of c-Rel-deficient mice. Although our data showed that the specific expression of CCL20 and ubiquitin D in the FAE was not impeded in the absence of c-Rel, the expression of ubiquitin D was dramatically reduced in the B cell-follicles of c-Rel-deficient mice. Coincident with this, we also observed that the status of follicular dendritic cells in the B cell-follicles was dramatically reduced in Peyer's patches from c-Rel-deficient mice. Taken together, our data show that c-Rel is dispensable for the RANKL-mediated differentiation and functional maturation of M cells.

17beta-estradiol counteracts neuropathic pain: a behavioural, immunohistochemical, and proteomic investigation on sex-related differences in mice

Sex differences play a role in pain sensitivity, efficacy of analgesic drugs and prevalence of neuropathic pain, even if the underlying mechanisms are far from being understood. We demonstrate that male and female mice react differently to structural and functional changes induced by sciatic nerve ligature, used as model of neuropathic pain. Male mice show a gradual decrease of allodynia and a complete recovery while, in females, allodynia and gliosis are still present four months after neuropathy induction. Administration of 17β-estradiol is able to significantly attenuate this difference, reducing allodynia and inducing a complete recovery also in female mice. Parallel to pain attenuation, 17β-estradiol treated-mice show a functional improvement of the injured limb, a faster regenerative process of the peripheral nerve and a decreased neuropathy-induced gliosis. These results indicate beneficial effects of 17β-estradiol on neuropathic pain and neuronal regeneration and focuses on the importance of considering gonadal hormones also in clinical studies.

Innate Immune Response of the Pig Laryngeal Mucosa to Endotracheal Intubation

Objective

The aim of this study was to measure the effects of endotracheal intubation on innate immune response within the pig laryngeal mucosa.

Study Design

Prospective controlled basic science study.

Setting

The animal experiments and analyses were conducted at the University of Bristol.

Samples and Methods

Eighteen pigs, matched at the major histocompatibility complex (MHC), were used in the study. The pigs were divided into 9 pairs. One of each pair (9 pigs in total) was intubated with an endotracheal tube under general anesthesia for 90 minutes. Two days later, pinch biopsies were taken from the supraglottis (specifically the false cords) and subglottis of both pigs. The experiment was repeated 8 more times. Based on quantitative immunohistochemistry, percentage areas of positive staining for CD172a, CD163, MHC class II, CD14, and CD16 were calculated separately for the epithelium and lamina propria of each biopsy.

Results

Total areas of laryngeal mucosa (epithelium and lamina propria) expressing CD172a and coexpressing CD163 and CD172a were significantly reduced at 2 days following endotracheal intubation ( P = .039 and P = .037, respectively). MHC class II expression and MHC class II coexpression with CD172a were similarly reduced following intubation ( P = .003 and P = .005, respectively). In the supraglottis, MHC class II coexpression with CD16 and CD14 was also reduced following endotracheal intubation ( P = .037).

Conclusions

Our results indicate that endotracheal intubation reduces the number of innate immune cells within the upper airway mucosa. This may be an important first step in a cascade leading to chronic wound and scar formation causing airway stenosis.

Improving reliability of live/dead cell counting through automated image mosaicing

Cell counting is one of the basic needs of most biological experiments. Numerous methods and systems have been studied to improve the reliability of counting. However, at present, manual cell counting performed with a hemocytometer still represents the gold standard, despite several problems limiting reproducibility and repeatability of the counts and, at the end, jeopardizing their reliability in general. We present our own approach based on image processing techniques to improve counting reliability. It works in two stages: first building a high-resolution image of the hemocytometer's grid, then counting the live and dead cells by tagging the image with flags of different colours. In particular, we introduce GridMos (http://sourceforge.net/p/gridmos), a fully-automated mosaicing method to obtain a mosaic representing the whole hemocytometer's grid. In addition to offering more significant statistics, the mosaic "freezes" the culture status, thus permitting analysis by more than one operator. Finally, the mosaic achieved can thus be tagged by using an image editor, thus markedly improving counting reliability. The experiments performed confirm the improvements brought about by the proposed counting approach in terms of both reproducibility and repeatability, also suggesting the use of a mosaic of an entire hemocytometer's grid, then labelled trough an image editor, as the best likely candidate for the new gold standard method in cell counting.

Effects of age-related loss of P/Q-type calcium channels in a mice model of peripheral nerve injury

We analyzed the role of P/Q-type calcium channels in sciatic nerve regeneration after lesion induced by chronic constriction injury (CCI) in heterozygous null mutant mice lacking the CaV2.1α1 subunit of these channels (Cacna1a+/-). Compared with wild type, Cacna1a+/- mice showed an initial reduction of the CCI-induced allodynia, indicating a reduced pain perception, but they also evidenced a lack of recovery over time, with atrophy of the injured hindpaw still present 3 months after CCI when wild-type mice fully recovered. In parallel, Cacna1a+/- mice exhibited an early onset of age-dependent loss of P/Q-type channels, which can be responsible for the lack of functional recovery. Moreover, Cacna1a+/- mice showed an early age-dependent reduction of muscular strength, as well as of Schwann cells proliferation and sciatic nerve remyelination. This study demonstrates the important role played by P/Q-type channels in recovery from nerve injury and has important implications for the knowledge of age-related processes.

Effect of noradrenaline on the virulence properties of campylobacter species

Campylobacter species cause a spectrum of illnesses in humans. The type of illness and the outcome is dependent on the virulence of the infecting pathogen strain and host immune status. Acute stress can seriously compromise host immunity and increase susceptibility to infection. Noradrenaline (NA) is a stress hormone. Several studies have shown that it stimulated growth and increased the pathogenicity of organisms including E. coli and Campylobacter jejuni. However, the effect of NA on other Campylobacter species is unknown. We have examined the effect of NA on growth rate, motility, invasion of T84 epithelial cells, and colonisation of chickens by diverse Campylobacter species. Campylobacter cultures grown with NA had reduced lag phases, increased growth rates, and higher final optical densities than controls. The motility of Campylobacter was also significantly increased in the presence of noradrenaline. Some of the Campylobacter strains tested also showed increased invasion of T84 epithelial cells, greater breakdown of tight junctions, and an enhanced potential to colonise chickens. Our results show that noradrenaline-induced enhancement of virulence of Campylobacter can influence the outcome of infection.

Higher pain perception and lack of recovery from neuropathic pain in females: a behavioural, immunohistochemical, and proteomic investigation on sex-related differences in mice

In experimental and clinical pain studies, the sex of subjects was rarely taken into account, even if nociceptive inputs appear to be processed and modulated by partially distinct neural mechanisms in each sex. In this study we analysed, in male and female mice, behavioural and neuronal responses in developing, maintaining, and recovering from neuropathic pain. Experiments were carried out in adult CD1 mice by using Chronic Constriction Injury (CCI) as neuropathic pain model. We investigated the temporal trend of mechanical nociceptive threshold together with functional recovery of the injured paw, and the immunofluorescence staining of proteins associated with nerve injury and repair and with spinal gliosis, 7 and 121days after CCI. A proteomic analysis on proteins extracted from sciatic nerves was also performed. Male mice showed a gradual decrease of CCI-induced allodynia, the complete recovery occurring 81days after the sciatic nerve ligation. On the contrary, in female mice, allodynia was still present 121days after CCI. Sex-dependent differences also resulted from immunofluorescence experiments: in sciatic nerve, the expression of P0 and Neu200 is greater in neuropathic males than in neuropathic females, suggesting faster nerve regeneration. Proteomic analysis confirmed sex-related differences of proteins associated with nerve regenerative processes. In addition, the reactive gliosis induced by CCI at day 7, as revealed by colocalization of glial fibrillary acidic protein (astrocytes) and CD11b (microglia) with phosphorylated p38, disappeared 121 days after CCI in male but not in female mice. These results may have important therapeutic implications for the treatment of neuropathic pain.

Minocycline plus N-acetylcysteine synergize to modulate inflammation and prevent cognitive and memory deficits in a rat model of mild traumatic brain injury

Traumatic brain injury (TBI) differs in severity from severe to mild. This study examined whether a combination of the drugs minocycline (MINO) plus N-acetylcysteine (NAC) produces behavioral and histological improvements in a mild version of the controlled cortical impact model of TBI (mCCI). Following mCCI, rats acquired an active place avoidance task by learning the location of a stationary shock zone on a rotating arena. Rats acquired this task with a training protocol using a 10-minute intertrial interval. Mildly injured rats had an apparent deficit in long-term memory since they did not acquire the task when the intertrial interval was increased to 24 h. Mildly injured rats also had an apparent deficit in set shifting since, after successfully learning one shock zone location they did not learn the location of a second shock zone. MINO plus NAC synergistically limited these behavioral deficits in long-term memory and set shifting. mCCI also produced neuroinflammation at the impact site and at distal white matter tracts including the corpus callosum. At the impact site, MINO plus NAC attenuated CD68-expressing phagocytic microglia without altering neutrophil infiltration or astrocyte activation. The drugs had no effect on astrocyte activation in the corpus callosum or hippocampus. In the corpus callosum, MINO plus NAC decreased CD68 expression yet increased overall microglial activation as measured by Iba-1. MINO plus NAC acted synergistically to increase Iba-1 expression since MINO alone suppressed expression and NAC alone had no effect. Despite the known anti-inflammatory actions of the individual drugs, MINO plus NAC appeared to modulate, rather than suppress neuroinflammation. This modulation of neuroinflammation may underlie the synergistic improvement in memory and set-shifting by the drug combination after mCCI.

The functional maturation of M cells is dramatically reduced in the Peyer's patches of aged mice

The transcytosis of antigens across the follicle-associated epithelium (FAE) of Peyer's patches by microfold cells (M cells) is important for the induction of efficient immune responses to mucosal antigens. The mucosal immune response is compromised by ageing, but effects on M cells were unknown. We show that M-cell density in the FAE of aged mice was dramatically reduced. As a consequence, aged Peyer's patches were significantly deficient in their ability to transcytose particulate lumenal antigen across the FAE. Ageing specifically impaired the expression of Spi-B and the downstream functional maturation of M cells. Ageing also dramatically impaired C-C motif chemokine ligand 20 expression by the FAE. As a consequence, fewer B cells were attracted towards the FAE, potentially reducing their ability to promote M-cell maturation. Our study demonstrates that ageing dramatically impedes the functional maturation of M cells, revealing an important ageing-related defect in the mucosal immune system's ability to sample lumenal antigens.

Glycated albumin causes pancreatic β-cells dysfunction through autophagy dysfunction

Growing evidence suggests that advanced glycation end-products (AGEs) are cytotoxic to pancreatic β-cells. The aims of this study were to investigate whether glycated albumin (GA), an early precursor of AGEs, would induce dysfunction in pancreatic β-cells and to determine which kinds of cellular mechanisms are activated in GA-induced β-cell apoptosis. Decreased viability and increased apoptosis were induced in INS-1 cells treated with 2.5 mg/mL GA under 16.7mM high-glucose conditions. Insulin content and glucose-stimulated secretion from isolated rat islets were reduced in 2.5 mg/mL GA-treated cells. In response to 2.5 mg/mL GA in INS-1 cells, autophagy induction and flux decreased as assessed by green fluorescent protein-microtubule-associated protein 1 light chain 3 dots, microtubule-associated protein 1 light chain 3-II conversion, and SQSTM1/p62 in the presence and absence of bafilomycin A1. Accumulated SQSTM1/p62 through deficient autophagy activated the nuclear factor-κB (p65)-inducible nitric oxide synthase-caspase-3 cascade, which was restored by treatment with small interfering RNA against p62. Small interfering RNA treatment against autophagy-related protein 5 significantly inhibited the autophagy machinery resulting in a significant increase in iNOS-cleaved caspase-3 expression. Treatment with 500μM 4-phenyl butyric acid significantly alleviated the expression of endoplasmic reticulum stress markers and iNOS in parallel with upregulated autophagy induction. However, in the presence of bafilomycin A1, the decreased viability of INS-1 cells was not recovered. Glycated albumin, an early precursor of AGE, caused pancreatic β-cell death by inhibiting autophagy induction and flux, resulting in nuclear factor-κB (p65)-iNOS-caspase-3 cascade activation as well as by increasing susceptibility to endoplasmic reticulum stress and oxidative stress.

Overexpression of the Hedgehog signalling pathway in head and neck squamous cell carcinoma

BACKGROUND

Overexpression of the Hedgehog (HH) signalling pathway has been described in several malignancies and is associated with a poor prognosis. HH signalling blockade reduces tumour growth in vitro and in vivo. We aimed to determine whether head and neck squamous cell carcinomas (HNSCCs) express HH proteins in comparison to healthy mucosa.

PATIENTS AND METHODS

Formalin-fixed and paraffin-embedded tissue sections of 10 patients with HNSCC were stained with fluorescence-labelled antibodies for cytokeratin and HH proteins (SHH, PTCH1/2, SMO, Gli1-3) and photographs were taken with a laser scanning microscope. The pixel count and colour intensity were analysed in RGB (red/green/blue) colour mode, and expression levels were compared to healthy mucosa.

RESULTS

Image analysis in RGB mode provided objective evidence for the over-expression of HH signalling components in HNSCC, particularly with regard to the transcription factors Gli1 (10-fold) and SHH (5-fold) in comparison with healthy mucosa. The lowest levels were found for Gli3 in HNSCC.

CONCLUSIONS

We postulate pivotal roles of Gli1 and SHH expression in the carcinogenesis of HNSCC. HH pathway overexpression appears to be involved in the initiation of tumour growth and spread due to its stem cell-modulating properties. Detection of HH pathway components, and especially Gli1 and SHH, in HNSCC might offer a promising target for further anticancer research in HNSCC.

Dietary supplementation with Bifidobacterium lactis NCC2818 from weaning reduces local immunoglobulin production in lymphoid-associated tissues but increases systemic antibodies in healthy neonates

Weaning is associated with a major shift in the microbial community of the intestine, and this instability may make it more acquiescent than the adult microbiota to long-term changes. Modulation achieved through dietary interventions may have potentially beneficial effects on the developing immune system, which is driven primarily by the microbiota. The specific aim of the present study was to determine whether immune development could be modified by dietary supplementation with the human probiotic Bifidobacterium lactis NCC2818 in a tractable model of weaning in infants. Piglets were reared by their mothers before being weaned onto a solid diet supplemented with B. lactis NCC2818, while sibling controls did not receive supplementation. Probiotic supplementation resulted in a reduction in IgA (P<0·0005) and IgM (P<0·009) production by mucosal tissues but had no effect on IgG production (P>0·05). Probiotic-supplemented pigs had more mast cells than unsupplemented littermates (P<0·0001), although numbers in both groups were low. In addition, the supplemented piglets made stronger serum IgG responses to fed and injected antigens (P<0·05). The present findings are consistent with B. lactis NCC2818 reducing intestinal permeability induced by weaning, and suggest that the piglet is a valuable intermediate between rodent models and human infants. The results also strongly suggest that measures of the effect of probiotic supplementation on the immune system need to be interpreted carefully as proxy measures of health benefit. However, they are useful in developing an understanding of the mechanism of action of probiotic strains, an important factor in predicting favourable health outcomes of nutritional intervention.

Ablation of the cellular prion protein, PrPC, specifically on follicular dendritic cells has no effect on their maturation or function

Follicular dendritic cells (FDC) are situated in the primary follicles of lymphoid tissues where they maintain the structural integrity of the B-lymphocyte follicle, and help to drive immunoglobulin class-switch recombination, somatic hypermutation and affinity maturation during the germinal centre response. FDC can also provide a reservoir for pathogens that infect germinal centres including HIV and prions. FDC express high levels of the normal cellular form of the prion protein (PrP(C) ), which makes them susceptible to prion infection. The function of PrP(C) is uncertain and it is not known why FDC require such high levels of expression of a protein that is found mainly on cells of the central nervous system. In this study, the function of FDC was assessed in mice that had PrP(C) ablated specifically in their FDC. In mice with FDC-specific PrP(C) ablation, our analysis revealed no observable deficits in lymphoid follicle microarchitecture and FDC status. No effects on FDC ability to trap immune complexes or drive antigen-specific antibody responses and affinity maturation in B lymphocytes were observed. These data clearly demonstrate that PrP(C) expression is dispensable for the functional maturation of FDC and their ability to maintain antigen-specific antibody responses and affinity maturation.

IL-13 promotes collagen accumulation in Crohn's disease fibrosis by down-regulation of fibroblast MMP synthesis: a role for innate lymphoid cells?

Background

Fibrosis is a serious consequence of Crohn’s disease (CD), often necessitating surgical resection. We examined the hypothesis that IL-13 may promote collagen accumulation within the CD muscle microenvironment.

Methods

Factors potentially modulating collagen deposition were examined in intestinal tissue samples from fibrotic (f) CD and compared with cancer control (C), ulcerative colitis (UC) and uninvolved (u) CD. Mechanisms attributable to IL-13 were analysed using cell lines derived from uninvolved muscle tissue and tissue explants.

Results

In fCD muscle extracts, collagen synthesis was significantly increased compared to other groups, but MMP-2 was not co-ordinately increased. IL-13 transcripts were highest in fCD muscle compared to muscle from other groups. IL-13 receptor (R) α1 was expressed by intestinal muscle smooth muscle, nerve and KIR⁺ cells. Fibroblasts from intestinal muscle expressed Rα1, phosphorylated STAT6 in response to IL-13, and subsequently down-regulated MMP-2 and TNF-α-induced MMP-1 and MMP-9 synthesis. Cells with the phenotype KIR⁺CD45⁺CD56^+/−CD3⁻ were significantly increased in fCD muscle compared to all other groups, expressed Rα1 and membrane IL-13, and transcribed high levels of IL-13. In explanted CD muscle, these cells did not phosphorylate STAT6 in response to exogenous IL-13.

Conclusions

The data indicate that in fibrotic intestinal muscle of Crohn’s patients, the IL-13 pathway is stimulated, involving a novel population of infiltrating IL-13Rα1⁺, KIR⁺ innate lymphoid cells, producing IL-13 which inhibits fibroblast MMP synthesis. Consequently, matrix degradation is down-regulated and this leads to excessive collagen deposition.

Direct experimental evidence that early-life farm environment influences regulation of immune responses

BACKGROUND

  In mammals, early-life environmental variations appear to affect microbial colonization and therefore competent immune development, and exposure to farm environments in infants has been inversely correlated with allergy development. Modelling these effects using manipulation of neonatal rodents is difficult due to their dependency on the mother, but the relatively independent piglet is increasingly identified as a valuable translational model for humans. This study was designed to correlate immune regulation in piglets with early-life environment.

METHODS

  Piglets were nursed by their mother on a commercial farm, while isolator-reared siblings were formula fed. Fluorescence immunohistology was used to quantify T-reg and effector T-cell populations in the intestinal lamina propria and the systemic response to food proteins was quantified by capture ELISA.

RESULTS

  There was more CD4(+) and CD4(+) CD25(+) effector T-cell staining in the intestinal mucosa of the isolator-reared piglets compared with their farm-reared counterparts. In contrast, these isolator-reared piglets had a significantly reduced CD4(+) CD25(+) Foxp3(+) regulatory T-cell population compared to farm-reared littermates, resulting in a significantly higher T-reg-to-effector ratio in the farm animals. Consistent with these findings, isolator-reared piglets had an increased serum IgG anti-soya response to novel dietary soya protein relative to farm-reared piglets.

CONCLUSION

  Here, we provide the first direct evidence, derived from intervention, that components of the early-life environment present on farms profoundly affects both local development of regulatory components of the mucosal immune system and immune responses to food proteins at weaning. We propose that neonatal piglets provide a tractable model which allows maternal and treatment effects to be statistically separated.