129X1/SvJ mouse strain has a novel defect in inflammatory cell recruitment

Intramuscular IL-10 Administration Enhances the Activity of Myogenic Precursor Cells and Improves Motor Function in ALS Mouse Model

Amyotrophic Lateral Sclerosis (ALS) is the most common adult motor neuron disease, with a poor prognosis, a highly unmet therapeutic need, and a burden on health care costs. Hitherto, strategies aimed at protecting motor neurons have missed or modestly delayed ALS due to a failure in countering the irreversible muscular atrophy. We recently provided direct evidence underlying the pivotal role of macrophages in preserving skeletal muscle mass. Based on these results, we explored whether the modulation of macrophage muscle response and the enhancement of satellite cell differentiation could effectively promote the generation of new myofibers and counteract muscle dysfunction in ALS mice. For this purpose, disease progression and the survival of SOD1G93A mice were evaluated following IL-10 injections in the hindlimb skeletal muscles. Thereafter, we used ex vivo methodologies and in vitro approaches on primary cells to assess the effect of the treatment on the main pathological signatures. We found that IL-10 improved the motor performance of ALS mice by enhancing satellite cells and the muscle pro-regenerative activity of macrophages. This resulted in delayed muscle atrophy and motor neuron loss. Our findings provide the basis for a suitable adjunct multisystem therapeutic approach that pinpoints a primary role of muscle pathology in ALS.

Boosting the peripheral immune response in the skeletal muscles improved motor function in ALS transgenic mice

Monocyte chemoattractant protein-1 (MCP1) is one of the most powerful pro-inflammatory chemokines. However, its signalling is pivotal in driving injured axon and muscle regeneration.

Anti-GD2 synergizes with CD47 blockade to mediate tumor eradication

The disialoganglioside GD2 is overexpressed on several solid tumors, and monoclonal antibodies targeting GD2 have substantially improved outcomes for children with high-risk neuroblastoma. However, approximately 40% of patients with neuroblastoma still relapse, and anti-GD2 has not mediated significant clinical activity in any other GD2+ malignancy. Macrophages are important mediators of anti-tumor immunity, but tumors resist macrophage phagocytosis through expression of the checkpoint molecule CD47, a so-called 'Don't eat me' signal. In this study, we establish potent synergy for the combination of anti-GD2 and anti-CD47 in syngeneic and xenograft mouse models of neuroblastoma, where the combination eradicates tumors, as well as osteosarcoma and small-cell lung cancer, where the combination significantly reduces tumor burden and extends survival. This synergy is driven by two GD2-specific factors that reorient the balance of macrophage activity. Ligation of GD2 on tumor cells (a) causes upregulation of surface calreticulin, a pro-phagocytic 'Eat me' signal that primes cells for removal and (b) interrupts the interaction of GD2 with its newly identified ligand, the inhibitory immunoreceptor Siglec-7. This work credentials the combination of anti-GD2 and anti-CD47 for clinical translation and suggests that CD47 blockade will be most efficacious in combination with monoclonal antibodies that alter additional pro- and anti-phagocytic signals within the tumor microenvironment.

MicroRNA-210 Promotes Bile Acid-Induced Cholestatic Liver Injury by Targeting Mixed-Lineage Leukemia-4 Methyltransferase in Mice

BACKGROUND AND AIMS

Bile acids (BAs) are important regulators of metabolism and energy balance, but excess BAs cause cholestatic liver injury. The histone methyltransferase mixed-lineage leukemia-4 (MLL4) is a transcriptional coactivator of the BA-sensing nuclear receptor farnesoid X receptor (FXR) and epigenetically up-regulates FXR targets important for the regulation of BA levels, small heterodimer partner (SHP), and bile salt export pump (BSEP). MLL4 expression is aberrantly down-regulated and BA homeostasis is disrupted in cholestatic mice, but the underlying mechanisms are unclear.

APPROACH AND RESULTS

We examined whether elevated microRNA-210 (miR-210) in cholestatic liver promotes BA-induced pathology by inhibiting MLL4 expression. miR-210 was the most highly elevated miR in hepatic SHP-down-regulated mice with elevated hepatic BA levels. MLL4 was identified as a direct target of miR-210, and overexpression of miR-210 inhibited MLL4 and, subsequently, BSEP and SHP expression, resulting in defective BA metabolism and hepatotoxicity with inflammation. miR-210 levels were elevated in cholestatic mouse models, and in vivo silencing of miR-210 ameliorated BA-induced liver pathology and decreased hydrophobic BA levels in an MLL4-dependent manner. In gene expression studies, SHP inhibited miR-210 expression by repressing a transcriptional activator, Kruppel-like factor-4 (KLF4). In patients with primary biliary cholangitis/cirrhosis (PBC), hepatic levels of miR-210 and KLF4 were highly elevated, whereas nuclear levels of SHP and MLL4 were reduced.

CONCLUSIONS

Hepatic miR-210 is physiologically regulated by SHP but elevated in cholestatic mice and patients with PBC, promoting BA-induced liver injury in part by targeting MLL4. The miR-210-MLL4 axis is a potential target for the treatment of BA-associated hepatobiliary disease.

Distinct Tumor Microenvironments Are a Defining Feature of Strain-Specific CRISPR/Cas9-Induced MPNSTs

The tumor microenvironment plays important roles in cancer biology, but genetic backgrounds of mouse models can complicate interpretation of tumor phenotypes. A deeper understanding of strain-dependent influences on the tumor microenvironment of genetically-identical tumors is critical to exploring genotype-phenotype relationships, but these interactions can be difficult to identify using traditional Cre/loxP approaches. Here, we use somatic CRISPR/Cas9 tumorigenesis approaches to determine the impact of mouse background on the biology of genetically-identical malignant peripheral nerve sheath tumors (MPNSTs) in four commonly-used inbred strains. To our knowledge, this is the first study to systematically evaluate the impact of host strain on CRISPR/Cas9-generated mouse models. Our data identify multiple strain-dependent phenotypes, including changes in tumor onset and the immune microenvironment. While BALB/c mice develop MPNSTs earlier than other strains, similar tumor onset is observed in C57BL/6, 129X1 and 129/SvJae mice. Indel pattern analysis demonstrates that indel frequency, type and size are similar across all genetic backgrounds. Gene expression and IHC analysis identify multiple strain-dependent differences in CD4+ T cell infiltration and myeloid cell populations, including M2 macrophages and mast cells. These data highlight important strain-specific phenotypes of genomically-matched MPNSTs that have implications for the design of future studies using similar in vivo gene editing approaches.

Frontline Science: Rev-Erbα links blue light with enhanced bacterial clearance and improved survival in murine Klebsiella pneumoniae pneumonia

The wavelength of light is a critical determinant of light's capacity to entrain adaptive biological mechanisms, such as enhanced immune surveillance, that precede and prepare us for the active circadian day, a time when the risk of encountering pathogen is highest. Light rich in the shorter wavelength visible blue spectrum maximally entrains these circadian rhythms. We hypothesized that exposure to blue light during sepsis will augment immunity and improve outcome. Using a clinically relevant Klebsiella pneumoniae acute lower respiratory tract infection model, we show that blue spectrum light shifts autonomic tone toward parasympathetic predominance and enhances immune competence, as characterized by accelerated pathogen clearance that is accompanied by reduced alveolar neutrophil influx, inflammation, and improved survival. Blue light functioned through an optic-cholinergic pathway and expansion of splenic Ccr2⁺ monocytes to increase control of the infection and improve survival. The "keystone" mediating these effects is the circadian clock protein Rev-Erbα, and biochemical activation with Rev-Erbα agonist SR9009 enhanced mononuclear cell phagocytosis in vitro and recapitulated the enhanced pathogen elimination in vivo observed with blue light. These findings underscore the potential therapeutic value of blue light and modulating Rev-Erbα to enhance host immunity against infection.

The Vitamin D Binding Protein and Inflammatory Injury: A Mediator or Sentinel of Tissue Damage?

Neutrophils are the most abundant type of white blood cell in most mammals including humans. The primary role of these cells is host defense against microbes and clearance of tissue debris in order to facilitate wound healing and tissue regeneration. The recruitment of neutrophils from blood into tissues is a key step in this process and is mediated by numerous different chemoattractants. The neutrophil migratory response is essential for host defense and survival, but excessive tissue accumulation of neutrophils is observed in many inflammatory disorders and strongly correlates with disease pathology. The vitamin D binding protein (DBP) is a circulating multifunctional plasma protein that can significantly enhance the chemotactic activity of neutrophil chemoattractants both in vitro and in vivo. Recent in vivo studies using DBP deficient mice showed that DBP plays a larger and more central role during inflammation since it induces selective recruitment of neutrophils, and this cofactor function is not restricted to C5a, as prior in vitro studies indicated, but can enhance chemotaxis to many chemoattractants. DBP also is an extracellular scavenger for actin released from damaged/dead cells and formation of DBP-actin complexes is an immediate host response to tissue injury. Recent in vitro evidence indicates that DBP bound to G-actin, and not free DBP, functions as an indirect but essential cofactor for neutrophil migration. DBP-actin complexes always will be formed regardless of what initiated an inflammation, since release of actin from damaged cells is a common feature in all types of injury and DBP is abundant and ubiquitous in all extracellular fluids. Indeed, these complexes have been detected in blood and tissue fluids from both humans and experimental animals following various forms of injury. The published data strongly supports the premise that DBP-actin complexes are the functional neutrophil chemotactic cofactor that enhances neutrophil chemotaxis in vitro and augments neutrophilic inflammation in vivo. This review will assess the fundamental role of DBP in neutrophilic inflammation and injury.

Engineered bacteria can function in the mammalian gut long-term as live diagnostics of inflammation

Bacteria can be engineered to function as diagnostics or therapeutics in the mammalian gut but commercial translation of technologies to accomplish this has been hindered by the susceptibility of synthetic genetic circuits to mutation and unpredictable function during extended gut colonization. Here, we report stable, engineered bacterial strains that maintain their function for 6 months in the mouse gut. We engineered a commensal murine Escherichia coli strain to detect tetrathionate, which is produced during inflammation. Using our engineered diagnostic strain, which retains memory of exposure in the gut for analysis by fecal testing, we detected tetrathionate in both infection-induced and genetic mouse models of inflammation over 6 months. The synthetic genetic circuits in the engineered strain were genetically stable and functioned as intended over time. The durable performance of these strains confirms the potential of engineered bacteria as living diagnostics.

Immune response in peripheral axons delays disease progression in SOD1G93A mice

Background

Increasing evidence suggests that the immune system has a beneficial role in the progression of amyotrophic lateral sclerosis (ALS) although the mechanism remains unclear. Recently, we demonstrated that motor neurons (MNs) of C57SOD1^G93A mice with slow disease progression activate molecules classically involved in the cross-talk with the immune system. This happens a lot less in 129SvSOD1^G93A mice which, while expressing the same amount of transgene, had faster disease progression and earlier axonal damage. The present study investigated whether and how the immune response is involved in the preservation of motor axons in the mouse model of familial ALS with a more benign disease course.

Methods

First, the extent of axonal damage, Schwann cell proliferation, and neuromuscular junction (NMJ) denervation were compared between the two ALS mouse models at the disease onset. Then, we compared the expression levels of different immune molecules, the morphology of myelin sheaths, and the presence of blood-derived immune cell infiltrates in the sciatic nerve of the two SOD1G93A mouse strains using immunohistochemical, immunoblot, quantitative reverse transcription PCR, and rotating-polarization Coherent Anti-Stokes Raman Scattering techniques.

Results

Muscle denervation, axonal dysregulation, and myelin disruption together with reduced Schwann cell proliferation are prominent in 129SvSOD1^G93A compared to C57SOD1^G93A mice at the disease onset, and this correlates with a faster disease progression in the first strain. On the contrary, a striking increase of immune molecules such as CCL2, MHCI, and C3 was seen in sciatic nerves of slow progressor C57SOD1^G93A mice and this was accompanied by heavy infiltration of CD8⁺ T lymphocytes and macrophages. These phenomena were not detectable in the peripheral nervous system of fast-progressing mice.

Conclusions

These data show for the first time that damaged MNs in SOD1-related ALS actively recruit immune cells in the peripheral nervous system to delay muscle denervation and prolong the lifespan. On the contrary, the lack of this response has a negative impact on the disease course.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0732-2) contains supplementary material, which is available to authorized users.

The role of different strain backgrounds in bacterial endotoxin-mediated sensitization to neonatal hypoxic-ischemic brain damage

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Strain background plays a role in the response to hypoxia–ischemia.

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LPS sensitizes the immature brain to hypoxia–ischemia across several mouse strains.

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Vehicle injection may induce immune response and sensitization to hypoxia–ischemia.

Genetic background is known to influence the outcome in mouse models of human disease, and previous experimental studies have shown strain variability in the neonatal mouse model of hypoxia–ischemia. To further map out this variability, we compared five commonly used mouse strains: C57BL/6, 129SVJ, BALB/c, CD1 and FVB in a pure hypoxic–ischemic setup and following pre-sensitization with lipopolysaccharide (LPS).

Postnatal day 7 pups were subjected to unilateral carotid artery occlusion followed by continuous 30 min 8% oxygen exposure at 36 °C. Twelve hours prior, a third of the pups received a single intraperitoneal LPS (0.6 μg/g) or a saline (vehicle) administration, respectively; a further third underwent hypoxia–ischemia alone without preceding injection. Both C57BL/6 and 129SVJ strains showed minimal response to 30 min hypoxia–ischemia alone, BALB/c demonstrated a moderate response, and both CD1 and FVB revealed the highest brain damage. LPS pre-sensitization led to substantial increase in overall brain infarction, microglial and astrocyte response and cell death in four of the five strains, with exception of BALB/c that only showed a significant effect with terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). Saline administration prior to hypoxia–ischemia resulted in an increase in inflammatory-associated markers, particularly in the astroglial activation of C57BL/6 mice, and in combined microglial activation and neuronal cell loss in FVB mice. Finally, two of the four strongly affected strains – C57BL/6 and CD1 – revealed pronounced contralateral astrogliosis with a neuroanatomical localization similar to that observed on the occluded hemisphere.

Overall, the current findings demonstrate strain differences in response to hypoxia–ischemia alone, to stress associated with vehicle injection, and to LPS-mediated pre-sensitization, which partially explains the high variability seen in the neonatal mouse models of hypoxia–ischemia. These results can be useful in future studies of fetal/neonatal response to inflammation and reduced oxygen–blood supply.

Cyclosporine A Treatment Inhibits Abcc6-Dependent Cardiac Necrosis and Calcification following Coxsackievirus B3 Infection in Mice

Coxsackievirus type B3 (CVB3) is a cardiotropic enterovirus. Infection causes cardiomyocyte necrosis and myocardial inflammation. The damaged tissue that results is replaced with fibrotic or calcified tissue, which can lead to permanently altered cardiac function. The extent of pathogenesis among individuals exposed to CVB3 is dictated by a combination of host genetics, viral virulence, and the environment. Here, we aimed to identify genes that modulate cardiopathology following CVB3 infection. 129S1 mice infected with CVB3 developed increased cardiac pathology compared to 129X1 substrain mice despite no difference in viral burden. Linkage analysis identified a major locus on chromosome 7 (LOD: 8.307, P<0.0001) that controlled the severity of cardiac calcification and necrosis following infection. Sub-phenotyping and genetic complementation assays identified Abcc6 as the underlying gene. Microarray expression profiling identified genotype-dependent regulation of genes associated with mitochondria. Electron microscopy examination showed elevated deposition of hydroxyapatite-like material in the mitochondrial matrices of infected Abcc6 knockout (Abcc6-/-) mice but not in wildtype littermates. Cyclosporine A (CsA) inhibits mitochondrial permeability transition pore opening by inhibiting cyclophilin D (CypD). Treatment of Abcc6 -/- mice with CsA reduced cardiac necrosis and calcification by more than half. Furthermore, CsA had no effect on the CVB3-induced phenotype of doubly deficient CypD-/-Abcc6-/- mice. Altogether, our work demonstrates that mutations in Abcc6 render mice more susceptible to cardiac calcification following CVB3 infection. Moreover, we implicate CypD in the control of cardiac necrosis and calcification in Abcc6-deficient mice, whereby CypD inhibition is required for cardioprotection.

Vitamin D-binding protein as a biomarker of active disease in acute intermittent porphyria

Acute intermittent porphyria (AIP) is an autosomal dominant metabolic disorder caused by a deficiency of hepatic porphobilinogen deaminase (PBGD). The disease is characterized by life threatening acute neurovisceral attacks. The aim of this study was to identify metabolites secreted by the hepatocytes that reflect differential metabolic status in the liver and that may predict response to the acute attack treatment. Plasma vitamin D binding protein (VDBP) from a mouse model of AIP displayed an abnormal migration in 2D-electrophoresis that is efficiently recovered upon gene therapy leading to liver specific over-expression of the PBGD protein. The change in VDBP mobility results from a differential isoelectric point suggesting a post-translational modification that takes place preferably in the liver. Liquid chromatography-mass spectrometry (LC-MS) analysis of human samples before and after glycosidase treatment revealed glycosylated plasma VDBP specifically in patients with recurrent attacks of AIP. Glycosylated VDBP recovered normal values in three severely afflicted AIP patients submitted to therapeutic liver transplantation. Our findings suggest that post-translational modification of VDBP might be considered as a promising biomarker to study and monitor the liver metabolic status in patients with AIP.

SIGNIFICANCE

We describe an increased glycosylation of VDBP in porphyric livers. Normal glycosylation was recovered upon liver gene therapy in a mouse model of porphyria or after liver transplantation in severely afflicted patients with AIP. Moreover, quantification of glycosylated VDBP by our ELISA immunoassay or LC-MS protocol in patients undergoing PBGD-gene therapy (www.aipgene.org) may be used as a marker indicating improvement or normalization of the patient's hepatic metabolism. This article is part of a Special Issue entitled: HUPO 2014.

Quantitative Trait Loci and Candidate Genes for Neutrophil Recruitment in Sterile Inflammation Mapped in AXB-BXA Recombinant Inbred Mice

Neutrophil recruitment (NR) to sites of sterile inflammation plays a key role in tissue damage and healing potential of lesions characteristic to non-infectious inflammatory diseases. Previous studies suggested significant genetic control of neutrophil survival, function, and migration in inflammatory responses to endogenous and exogenous stimuli. We have mapped the murine genome for quantitative trait loci (QTLs) harbouring genetic determinants that regulate NR in SI using a murine model of chemically-induced peritonitis. NR was quantified in 16 AXB-BXA recombinant inbred strains and their progenitors, A/J (A) and C57BL/6J (B). A continuous distribution of NR was found among the strains, with parent B showing higher NR and parent A showing lower NR (3.0-fold difference, p=0.05). Within the progeny strains, a 5.5-fold difference in NR was observed between the lowest, BXA1, and the highest responders AXB19 (p<0.001). This data was analyzed using GeneNetwork, which linked NR to one significant QTL on chromosome 12 (Peritoneal Neutrophil Recruitment 1, PNR1) and two suggestive QTLs (PNR2, PNR3) on chromosomes 12 and 16 respectively. Sixty-four candidate genes within PNR1 were cross-referenced with currently published data, mRNA expression from two NR microarrays, and single nucleotide polymorphism analysis. The present study brings new light into the genetics of NR in response to cell injury and highlights potential candidate genes Hif1α, Fntb, and Prkch and their products for further studies on neutrophil infiltration and inflammation resolution in sterile inflammation.

Oncogenic c-Myc-induced lymphomagenesis is inhibited non-redundantly by the p19Arf-Mdm2-p53 and RP-Mdm2-p53 pathways

The multifaceted oncogene c-Myc plays important roles in the development and progression of human cancer. Recent in vitro and in vivo studies have shown that the p19Arf-Mdm2-p53 and the ribosomal protein (RP)-Mdm2-p53 pathways are both essential in preventing oncogenic c-Myc-induced tumorigenesis. Disruption of each pathway individually by p19Arf deletion or by Mdm2(C305F) mutation, which disrupts RP-Mdm2 binding, accelerates Eμ-myc transgene-induced pre-B/B-cell lymphoma in mice at seemingly similar paces with median survival around 10 and 11 weeks, respectively, compared to 20 weeks for Eμ-myc transgenic mice. Because p19Arf can inhibit ribosomal biogenesis through its interaction with nucleophosmin (NPM/B23), RNA helicase DDX5 and RNA polymerase I transcription termination factor (TTF-I), it has been speculated that the p19Arf-Mdm2-p53 and the RP-Mdm2-p53 pathways might be a single p19Arf-RP-Mdm2-p53 pathway, in which p19Arf activates p53 by inhibiting RP biosynthesis; thus, p19Arf deletion or Mdm2(C305F) mutation would result in similar consequences. Here, we generated mice with concurrent p19Arf deletion and Mdm2(C305F) mutation and investigated the compound mice for tumorigenesis in the absence and the presence of oncogenic c-Myc overexpression. In the absence of Eμ-myc transgene, the Mdm2(C305F) mutation did not elicit spontaneous tumors in mice, nor did it accelerate spontaneous tumors in mice with p19Arf deletion. In the presence of Eμ-myc transgene, however, Mdm2(C305F) mutation significantly accelerated p19Arf deletion-induced lymphomagenesis and promoted rapid metastasis. We found that when p19Arf-Mdm2-p53 and RP-Mdm2-p53 pathways are independently disrupted, oncogenic c-Myc-induced p53 stabilization and activation is only partially attenuated. When both pathways are concurrently disrupted, however, c-Myc-induced p53 stabilization and activation are essentially obliterated. Thus, the p19Arf-Mdm2-p53 and the RP-Mdm2-p53 are non-redundant pathways possessing similar capabilities to activate p53 upon c-Myc overexpression.

M2 kupffer cells promote hepatocyte senescence: an IL-6-dependent protective mechanism against alcoholic liver disease

Alcoholic liver disease is a predominant cause of liver-related mortality in Western countries. The early steps of alcohol-induced steatosis and liver injury involve several mechanisms, including inflammation and oxidative stress. The inflammatory process is initiated by polarization of Kupffer cells toward a proinflammatory M1 phenotype, and we recently found that promoting anti-inflammatory M2 Kupffer cell polarization protects against alcohol-induced hepatocyte steatosis and apoptosis. Alcohol-induced oxidative stress is a potential trigger of senescence, and senescent cells exhibit characteristic functional resistance to apoptosis. We sought to evaluate induction of hepatocyte senescence as an early protective mechanism against alcoholic liver disease. Combining in vivo and in vitro studies, we show that M2 macrophages trigger hepatocyte senescence and enhance alcohol-induced hepatocyte senescence, as indicated by increased β-galactosidase activity, elevated CDKN1A mRNA expression, and induction of nuclear p21. We identify IL-6 as the mediator of M2-induced hepatocyte senescence. Senescent hepatocytes display characteristic resistance to apoptosis but also to steatosis, thus arguing for an early protective effect against alcoholic liver disease. These findings further suggest that pharmacologic interventions targeting M2 polarization during the early stages of alcoholic liver disease may represent an attractive strategy for the limitation of inflammation, hepatocyte apoptosis, and steatosis.

Circulating complexes of the vitamin D binding protein with G-actin induce lung inflammation by targeting endothelial cells

This study investigated the actin scavenger function of the vitamin D binding protein (DBP) in vivo using DBP null (-/-) mice. Intravenous injection of G-actin into wild-type (DBP+/+) and DBP-/- mice showed that contrary to expectations, DBP+/+ mice developed more severe acute lung inflammation. Inflammation was restricted to the lung and pathological changes were clearly evident at 1.5 and 4h post-injection but were largely resolved by 24h. Histology of DBP+/+ lungs revealed noticeably more vascular leakage, hemorrhage and thickening of the alveolar wall. Flow cytometry analysis of whole lung homogenates showed significantly increased neutrophil infiltration into DBP+/+ mouse lungs at 1.5 and 4h. Increased amounts of protein and leukocytes were also noted in bronchoalveolar lavage fluid from DBP+/+ mice 4h after actin injection. In vitro, purified DBP-actin complexes did not activate complement or neutrophils but induced injury and death of cultured human lung microvascular endothelial cells (HLMVEC) and human umbilical vein endothelial cells (HUVEC). Cells treated with DBP-actin showed a significant reduction in viability at 4h, this effect was reversible if cells were cultured in fresh media for another 24h. However, a 24-h treatment with DBP-actin complexes showed a significant increase in cell death (95% for HLMVEC, 45% for HUVEC). The mechanism of endothelial cell death was via both caspase-3 dependent (HUVEC) and independent (HLMVEC) pathways. These results demonstrate that elevated levels and/or prolonged exposure to DBP-actin complexes may induce endothelial cell injury and death, particularly in the lung microvasculature.

Neutrophil recruitment to the lung in both C5a- and CXCL1-induced alveolitis is impaired in vitamin D-binding protein-deficient mice

Knowledge of how neutrophils respond to chemotactic signals in a complex inflammatory environment is not completely understood. Moreover, even less is known about factors in physiological fluids that regulate the activity of chemoattractants. The vitamin D-binding protein (DBP) has been shown to significantly enhance chemotaxis to complement activation peptide C5a using purified proteins in vitro, and by ex vivo depletion of DBP in physiological fluids, but this function has not been determined in vivo. DBP null ((-/-)) mice were used to investigate how a systemic absence of this plasma protein affects leukocyte recruitment in alveolitis models of lung inflammation. DBP(-/-) mice had significantly reduced (~50%) neutrophil recruitment to the lungs compared with their wild-type DBP(+/+) counterparts in three different alveolitis models, two acute and one chronic. The histology of DBP(-/-) mouse lungs also showed significantly less injury than wild-type animals. The chemotactic cofactor function of DBP appears to be selective for neutrophil recruitment, but, in contrast to previous in vitro results, in vivo DBP can enhance the activity of other chemoattractants, including CXCL1. The reduced neutrophil response in DBP(-/-) mice could be rescued to wild-type levels by administering exogenous DBP. Finally, in inflammatory fluids, DBP binds to G-actin released from damaged cells, and this complex may be the active chemotactic cofactor. To our knowledge, results show for the first time that DBP is a significant chemotactic cofactor in vivo and not specific for C5a, suggesting that this ubiquitous plasma protein may have a more significant role in neutrophil recruitment than previously recognized.

Simple assays for measuring innate interactions with fungi

In recent decades, there has been a steady rise in immunocompromised populations and consequently a dramatic increase in the clinical relevance of normally non-pathogenic and commensal fungi such as Aspergillus fumigatus and Candida albicans. Understanding how these fungi interact with the host immune system is important for the development of immunotherapeutic approaches. Here, we describe a number of methods which have been developed to investigate the interactions of fungi with host leukocytes in vitro, including measuring fungal binding and induction of cytokines, phagocytosis, the respiratory burst, and fungal killing.

Immunological responses and actin dynamics in macrophages are controlled by N-cofilin but are independent from ADF

Dynamic changes in the actin cytoskeleton are essential for immune cell function and a number of immune deficiencies have been linked to mutations, which disturb the actin cytoskeleton. In macrophages and dendritic cells, actin remodelling is critical for motility, phagocytosis and antigen presentation, however the actin binding proteins, which control antigen presentation have been poorly characterized. Here we dissect the specific roles of the family of ADF/cofilin F-actin depolymerizing factors in macrophages and in local immune responses.

Macrophage migration, cell polarization and antigen presentation to T-cells require n-cofilin mediated F-actin remodelling. Using a conditional mouse model, we show that n-cofilin also controls MHC class II-dependent antigen presentation. Other cellular processes such as phagocytosis and antigen processing were found to be independent of n-cofilin. Our data identify n-cofilin as a novel regulator of antigen presentation, while ADF on the other hand is dispensable for macrophage motility and antigen presentation.

Vitamin D binding protein and monocyte response to 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D: analysis by mathematical modeling

Vitamin D binding protein (DBP) plays a key role in the bioavailability of active 1,25-dihydroxyvitamin D (1,25(OH)₂D) and its precursor 25-hydroxyvitamin D (25OHD), but accurate analysis of DBP-bound and free 25OHD and 1,25(OH)₂D is difficult. To address this, two new mathematical models were developed to estimate: 1) serum levels of free 25OHD/1,25(OH)₂D based on DBP concentration and genotype; 2) the impact of DBP on the biological activity of 25OHD/1,25(OH)₂D in vivo. The initial extracellular steady state (eSS) model predicted that 50 nM 25OHD and 100 pM 1,25(OH)₂D), <0.1% 25OHD and <1.5% 1,25(OH)₂D are ‘free’ in vivo. However, for any given concentration of total 25OHD, levels of free 25OHD are higher for low affinity versus high affinity forms of DBP. The eSS model was then combined with an intracellular (iSS) model that incorporated conversion of 25OHD to 1,25(OH)₂D via the enzyme CYP27B1, as well as binding of 1,25(OH)₂D to the vitamin D receptor (VDR). The iSS model was optimized to 25OHD/1,25(OH)₂D-mediated in vitro dose-responsive induction of the vitamin D target gene cathelicidin (CAMP) in human monocytes. The iSS model was then used to predict vitamin D activity in vivo (100% serum). The predicted induction of CAMP in vivo was minimal at basal settings but increased with enhanced expression of VDR (5-fold) and CYP27B1 (10-fold). Consistent with the eSS model, the iSS model predicted stronger responses to 25OHD for low affinity forms of DBP. Finally, the iSS model was used to compare the efficiency of endogenously synthesized versus exogenously added 1,25(OH)₂D. Data strongly support the endogenous model as the most viable mode for CAMP induction by vitamin D in vivo. These novel mathematical models underline the importance of DBP as a determinant of vitamin D ‘status’ in vivo, with future implications for clinical studies of vitamin D status and supplementation.

Adam17-dependent shedding limits early neutrophil influx but does not alter early monocyte recruitment to inflammatory sites

TNF-α-converting enzyme (TACE, herein denoted as Adam17) proteolytically sheds several cell-surface inflammatory proteins, but the physiologic importance of the cleavage of these substrates from leukocyte subsets during inflammation is incompletely understood. In this study, we show that Adam17-null neutrophils have a 2-fold advantage in their initial recruitment during thioglycollate-induced peritonitis, and they roll slower and adhere more readily in the cremaster model than wild-type neutrophils. Although CD44 and ICAM-1 are both in vitro substrates of Adam17, their surface levels are not altered on Adam17-null neutrophils. In contrast, L-selectin levels are elevated up to 10-fold in Adam17-null circulating neutrophils, and their accelerated peritoneal influx, slower rolling, and increased adhesion in the cremaster muscle are dependent on L-selectin. Analysis of mixed chimeras shows that enhanced L-selectin levels and accelerated influx were both cell-intrinsic properties of neutrophils lacking Adam17. In contrast, Adam17-null monocytes display no acceleration of infiltration into the peritoneum in spite of elevated L-selectin surface levels, and their peritoneal influx was independent of L-selectin. Therefore, our data demonstrate substrate and myeloid cell-type specificity of Adam17-mediated cleavage of its substrates, and show that neutrophils and monocytes use distinct mechanisms for infiltration of tissues.

Binding of the Staphylococcus aureus leucotoxin LukM to its leucocyte targets

The range of leucocytes susceptible to the leucotoxin LukM/F', a two-component pore-forming toxin of Staphylococcus aureus causing mastitis in ruminants, had not been defined. We used fluorescent-labeled LukM to investigate the binding of this toxin to bovine cells and to identify its cellular targets among bovine, human and murine leucocytes. LukM bound to bovine blood neutrophils from all the individuals tested with similar affinity, with an apparent dissociation constant (Kd) of 1.81 ± 0.14 nM and 13 3100 ± 506 binding sites. The amount of LukM bound to bovine neutrophils did not depend on the presence of the complementary component LukF', suggesting that the binding of LukM to its ligand does not depend on the formation of pore-forming oligomers, and that the number of bound LukM molecules corresponds to the number of available cell membrane ligands. Other staphylococcal class S components of bipartite leucotoxins (HlgA, HlgC, LukE, LukS-PV) were inefficient competitors of LukM for the binding to bovine neutrophils, indicating that LukM has a distinct ligand on target cells. Bovine blood neutrophils bound slightly more LukM than did milk neutrophils, and much more than did ovine and caprine blood neutrophils. Bovine monocytes and milk macrophages readily bound LukM, whereas blood lymphocytes did not. Human neutrophils bound little LukM and were resistant to LukM/F' at the highest tested concentration (40 nM). Murine neutrophils bound LukM and were susceptible to the toxicity of LukM/F', exhibiting flattening and nucleus alteration beginning at 0.3 nM concentration. Among murine peritoneal exudate cells, T lymphocytes (CD3+) and monocytes/macrophages (F4/80+) bound LukM, whereas binding to B lymphocytes (CD19+) was not detected. These results indicate that cells of the myeloid lineage are the main targets of LukM/F' in dairy ruminants, and that resident or inflammatory migrated phagocytes are susceptible to this toxin.

FAN stimulates TNF(alpha)-induced gene expression, leukocyte recruitment, and humoral response

Factor associated with neutral sphingomyelinase activation (FAN) is an adaptor protein that constitutively binds to TNF-R1. Microarray analysis was performed in fibroblasts derived from wild-type or FAN knockout mouse embryos to evaluate the role of FAN in TNF-induced gene expression. Approximately 70% of TNF-induced genes exhibited lower expression levels in FAN-deficient than in wild-type fibroblasts. Of particular interest, TNF-induced expression of cytokines/chemokines, such as IL-6 and CXCL-2, was impaired in FAN-deficient cells. This was confirmed by real time RT-PCR and ELISA. Upon i.p. TNF or thioglycollate injection, neutrophil recruitment into the peritoneal cavity was reduced by more than 50% in FAN-deficient mice. Nevertheless, FAN-deficient animals did not exhibit an increased susceptibility to different microorganisms including bacteria and parasites, indicating that FAN is not essential for pathogen clearance. Specific Ab response to BSA was substantially impaired in FAN-deficient mice and this was associated with a reduced content of leukocytes in the spleen of BSA-challenged FAN-deficient mice as compared with their wild-type counterparts. Altogether, our results indicate the involvement of FAN in TNF-induced gene expression and leukocyte recruitment, contributing to the establishment of the specific immune response.

Transglutaminases and disease: lessons from genetically engineered mouse models and inherited disorders

The human transglutaminase (TG) family consists of a structural protein, protein 4.2, that lacks catalytic activity, and eight zymogens/enzymes, designated factor XIII-A (FXIII-A) and TG1-7, that catalyze three types of posttranslational modification reactions: transamidation, esterification, and hydrolysis. These reactions are essential for biological processes such as blood coagulation, skin barrier formation, and extracellular matrix assembly but can also contribute to the pathophysiology of various inflammatory, autoimmune, and degenerative conditions. Some members of the TG family, for example, TG2, can participate in biological processes through actions unrelated to transamidase catalytic activity. We present here a comprehensive review of recent insights into the physiology and pathophysiology of TG family members that have come from studies of genetically engineered mouse models and/or inherited disorders. The review focuses on FXIII-A, TG1, TG2, TG5, and protein 4.2, as mice deficient in TG3, TG4, TG6, or TG7 have not yet been reported, nor have mutations in these proteins been linked to human disease.

Strain and model dependent differences in inflammatory cell recruitment in mice

OBJECTIVE AND DESIGN

The objective of this study was to determine genetic differences in inflammation in these distinct inbred mouse strains.

METHODS

Peritoneal leukocyte recruitment, matrix metalloproteinases and cytokines were quantified in A/J, 129/svJ, C57BL/6J, using thioglycollate or biomaterial implants as inflammatory stimuli.

RESULTS

In response to thioglycollate, A/J had significant decreases compared to C57BL/6J in both neutrophil (86 %) and macrophage (62 %) recruitment, and 129/svJ had a significant (43 %) decrease compared to C57BL/6J in macrophage recruitment. The reduced leukocyte recruitment corresponded to reduced matrix metalloproteinase-9. In the bioimplant model, 129/svJ had a 2-fold increase in neutrophil and macrophage recruitment compared to C57BL/6J, and the increased leukocyte recruitment corresponded to elevated cytokines, monocyte inhibitory protein-2 and monocyte chemoattractant protein-1, in the lavage compared to the values for C57BL/6J.

CONCLUSION

Not only was leukocyte recruitment strain dependent, but the three strains had marked differences in metalloproteinases and cytokine response. In addition, there were model specific differences in the metalloproteinase and cytokine response to the two inflammatory stimuli. Thus, inflammatory cell recruitment is genetically determined and stimulus specific and may determine the susceptibility to complex diseases.

Auf1/Hnrnpd-deficient mice develop pruritic inflammatory skin disease

Mice lacking heterogenous nuclear ribonuclear protein D (Hnrnpd), also known as Auf1, a regulator of inflammatory cytokine mRNA stability, develop chronic dermatitis with age that is characterized by pruritus and excoriations. Histological analysis showed marked epidermal acanthosis and spongiosis, neovascularization, and elevated number of inflammatory cells, including T cells, macrophages, neutrophils, mast cells, and eosinophils. Hnrnpd-deficient (Hnrnpd(tm1Rjsc)) mice with dermatitis display elevated serum IgE levels. Lesions in Hnrnpd(tm1Rjsc) mice were associated with a shift towards a Th(2) immune environment. Evaluation of T-cell-mediated skin inflammation by assaying contact hypersensitivity indicated an increased response in Hnrnpd(tm1Rjsc) mice. T cells and macrophages from Hnrnpd(tm1Rjsc) mice demonstrate a number of abnormalities associated with dermatitis, including increased IL2, tumor-necrosis factor-alpha (TNFalpha), and IL1beta production. Finally, many features of spontaneous dermatitis could be recapitulated in experimentally induced lesions by subcutaneous injection of CCL27 and TNF in unaffected Hnrnpd(tm1Rjsc) mice. Collectively, these data highlight the importance of HNRNPD and proper regulation of mRNA stability in the intricate processes of leukocyte recruitment and inflammatory activation within the skin.

Increased susceptibility of complement factor B/C2 double knockout mice and mannan-binding lectin knockout mice to systemic infection with Candida albicans

Candida albicans is the major cause of systemic fungal infections in immunocompromised patients. We investigated the susceptibility of mice deficient in complement factor B and C2 (Bf/C2-/-), C1q (C1qa-/-), and mannan-binding lectin (MBL)-A (MBL-A) and MBL-C (MBL-A/C-/-) to systemic infection with C. albicans. Animals were infected i.p. with 10(8)C. albicans blastoconidia and monitored for mortality. Bf/C2-/- mice showed high mortality (over 90%) within the study period of 3 weeks. In contrast, mortality in C1qa-/- mice was below 15% whereas that of MBL-A/C-/- mice was 40% (P<0.001). Intravenous infection of mice with 8x10(5) blastoconidia resulted in the same trend with Bf/C2-/- mice being highly susceptible compared to the other strains. Histology of kidney sections of infected Bf/C2-/- mice showed widespread mycelia confirming the high CFU counts from cultured tissue homogenates. In C1qa-/-, MBL-A/C-/- and wild type C57BL/6 mice hyphal growth was limited. However, massive inflammatory infiltration was apparent, which was not seen in Bf/C2-/- mice. The ability of the mouse sera to opsonize C. albicans was determined by quantification of phagocytosis of C. albicans by peritoneal phagocytes. Whilst phagocytosis mediated by Bf/C2-/- mouse serum was low (10.6%), more phagocytosis could be seen in MBL-A/C-/- (19.9%), C1qa-/- mice (23.9%) and wild type mice (29%). Deficiency of classical pathway activation has only a low impact whereas the lectin pathway contributes to the host defence against candidosis. The more pronounced lack of complement activation in Bf/C2-/- mice leads to uncontrolled infection due to an opsonophagocytic defect.

Epithelial cells remove apoptotic epithelial cells during post-lactation involution of the mouse mammary gland

Following the cessation of lactation, the mammary gland undergoes a physiologic process of tissue remodeling called involution in which glandular structures are lost, leaving an adipose tissue compartment that takes up a much larger proportion of the tissue. A quantitative morphometric analysis was undertaken to determine the mechanisms for clearance of the epithelial cells during this process. The involution process was set in motion by removal of pups from 14-day lactating C57BL/6 mice. Within hours, milk-secreting epithelial cells were shed into the glandular lumen. These cells became apoptotic, exhibiting exposure of phosphatidylserine residues on their surfaces, activation of effector caspase-3, staining for caspase-cleaved keratin 18, loss of internal organellar structure, and nuclear breakdown, but minimal blebbing or generation of apoptotic bodies. Clearance of residual milk and the shed epithelial cells was rapid, with most of the removal occurring in the first 72 h. Intact apoptotic epithelial cells were engulfed in large numbers by residual viable epithelial cells into spacious efferosomes. This process led to essentially complete involution within 4 days, at which point estrous cycling recommenced. Macrophages and other inflammatory cells did not contribute to the clearance of either residual milk or apoptotic cells, which appeared to be due entirely to the epithelium itself.

Induced prion protein controls immune-activated retroviruses in the mouse spleen

The prion protein (PrP) is crucially involved in transmissible spongiform encephalopathies (TSE), but neither its exact role in disease nor its physiological function are known. Here we show for mice, using histological, immunochemical and PCR-based methods, that stimulation of innate resistance was followed by appearance of numerous endogenous retroviruses and ensuing PrP up-regulation in germinal centers of the spleen. Subsequently, the activated retroviruses disappeared in a PrP-dependent manner. Our results reveal the regular involvement of endogenous retroviruses in murine immune responses and provide evidence for an essential function of PrP in the control of the retroviral activity. The interaction between PrP and ubiquitous endogenous retroviruses may allow new interpretations of TSE pathophysiology and explain the evolutionary conservation of PrP.

Genetic analysis of hyperoxic acute lung injury survival in reciprocal intercross mice

Acute lung injury (ALI) and its most severe presentation, acute respiratory distress syndrome, represent a full spectrum of a complex and devastating illness, with associated mortality that still hovers around 30-40%. Even supplemental O2, a routine and necessary therapy for such patients, paradoxically causes lung injury. The detrimental effects of O2 have established hyperoxic ALI (HALI) as a conventional model to study neonatal and adult forms of respiratory distress syndromes in experimental animals. To confront the high ALI mortality problem quite differently, we recently identified a mouse model (sensitive C57BL/6J and resistant 129X1/SvJ mice) to assess the genetic complexity of HALI and to identify genes affecting strain survival differences. Segregation analysis of 840 F2 mice generated from all four possible intercrosses between C57BL/6J and 129X1/SvJ mice demonstrated that survival time is a quantitative trait with decreased penetrance, and significant sex, cross, and parent-of-origin effects. Quantitative trait locus (QTL) analyses of the total F2 population identified three highly significant (named Shali1, Shali2 and Shali3, for Survival to hyperoxic acute lung injury) and one significant (Shali4) linkage. Analysis of F2 subpopulations further identified a male-specific QTL (Shali5). QTL allelic comparisons supported cross and sex effects and were consistent with imprinting. Genome-wide pairwise analysis predicted additive gene-gene interactions between the QTLs and also revealed a significant epistatic interaction with an otherwise unlinked region. QTL results confirmed that both parental strains contribute dominant resistance alleles to their offspring to determine individual HALI susceptibility.

The arthritis severity quantitative trait loci Cia4 and Cia6 regulate neutrophil migration into inflammatory sites and levels of TNF-alpha and nitric oxide

Neutrophils are required for the development of arthritis, and their migration into the synovial tissue coincides with the onset of clinical disease. Synovial neutrophil numbers also correlate with rheumatoid arthritis disease activity and severity. We hypothesized that certain arthritis severity genes regulate disease via the regulation of neutrophil migration into the joint. This hypothesis was tested in the synovial-like air pouch model injected with carrageenan using arthritis-susceptible DA and arthritis-resistant F344 rats. DA had nearly 3-fold higher numbers of exudate neutrophils compared with F344 (p < 0.001). Five DA.F344(QTL) strains congenic for severity loci and protected from autoimmune arthritis were studied. Only DA.F344(Cia4) (chromosome 7) and DA.F344(Cia6) (chromosome 8) congenics had significantly lower exudate neutrophil counts compared with DA. TNF-alpha levels were 2.5-fold higher in DA exudates as compared with F344 exudates, and that difference was accounted for by the Cia4 locus. Exudate levels of NO, a known inhibitor of neutrophil chemotaxis, were higher in F344, compared with DA, and that difference was accounted for by Cia6. This is the first time that non-MHC autoimmune arthritis loci are found to regulate three central components of the innate immune response implicated in disease pathogenesis, namely neutrophil migration into an inflammatory site, as well as exudate levels of TNF-alpha and NO. These observations underscore the importance of identifying the Cia4 and Cia6 genes, and suggest that they should generate useful novel targets for development of new therapies.

Gene expression response of the rat small intestine following oral Salmonella infection

Data on the molecular response of the intestine to the food-borne pathogen Salmonella are derived from in vitro studies, whereas in vivo data are lacking. We performed an oral S. enteritidis infection study in Wistar rats to obtain insight in the in vivo response in time. Expression profiles of ileal mucosa (IM) and Peyer's patches (PP) were generated using DNA microarrays at days 1, 3, and 6 postinfection. An overview of Salmonella-regulated processes was obtained and confirmed by quantitative real-time PCR on pooled and individual samples. Salmonella-induced gene expression responses in vivo are fewer and smaller than observed in vitro, and the response develops over a longer period of time. Few effects are seen at day 1 and mainly occur in IM, suggesting the mucosa as the primary site of invasion. Later, a bigger response is observed, especially in PP. Decreased expression of anti-microbial peptides genes (in IM at day 1) suggests inhibition of this process by Salmonella. Newly identified target processes are carbohydrate transport (increased expression in IM at day 1) and phase I and phase II detoxification (decreased expression at days 3 and 6). Increase of cytokine and chemokine expression occurs at later time points, both in PP and IM. Pancreatitis-associated protein, lipocalin 2, and calprotectin, potential inflammatory marker proteins, showed induced expression from day 3 onward. We conclude that the in vivo gene expression response of the ileum to Salmonella differs to a large extent from the response seen in vitro.

The arthritis severity quantitative trait locus Cia7 regulates neutrophil migration into inflammatory sites

Neutrophils are required for the development of arthritis in rodents, and are the predominant cell in the synovial fluid of active rheumatoid arthritis. We hypothesized that neutrophil migration into the inflammed joint is genetically regulated. In addition, this genetic regulation would be accounted for by one of the arthritis loci that we have previously identified in an intercross between arthritis-susceptible DA and arthritis-resistant ACI rats studied for collagen-induced arthritis. We used the synovial-like air pouch model injected with carrageenan, and tested DA, ACI, and four congenic strains. ACI exudates had a significantly lower number of neutrophils compared with DA. Transfer of DA alleles at Cia7 into the ACI background, as in ACI.DA(Cia7) congenics, was enough to increase exudate neutrophil numbers to levels identical to DA, and this locus accounted for the difference between parental strains. None of the other congenic intervals explained the differences in exudate neutrophil counts. In conclusion, we have identified a novel function for Cia7, and determined that it regulates neutrophil migration into a synovial-like inflammatory site. Our data revealed no intrinsic defect in neutrophil responses to chemotactic agents, and suggest that Cia7 regulates an as yet unidentified factor central to neutrophil recruitment into inflammed tissues.

Basso Mouse Scale for locomotion detects differences in recovery after spinal cord injury in five common mouse strains

Genetically engineered mice are used extensively to examine molecular responses to spinal cord injury (SCI). Inherent strain differences may confound behavioral outcomes; therefore, behavioral characterization of several strains after SCI is warranted. The Basso, Beattie, Bresnahan Locomotor Rating Scale (BBB) for rats has been widely used for SCI mice, but may not accurately reflect their unique recovery pattern. This study's purpose was to develop a valid locomotor rating scale for mice and to identify strain differences in locomotor recovery after SCI. We examined C57BL/6, C57BL/10, B10.PL, BALB/c, and C57BL/6x129S6 F1 strains for 42 days after mild, moderate, and severe contusive SCI or transection of the mid thoracic spinal cord. Contusions were created using the Ohio State University electromagnetic SCI device which is a displacement-driven model, and the Infinite Horizon device, which is a force-driven model. Attributes and rankings for the Basso Mouse Scale for Locomotion (BMS) were determined from frequency analyses of seven locomotor categories. Mouse recovery differed from rats for coordination, paw position and trunk instability. Disagreement occurred across six expert raters using BBB (p < 0.05) but not BMS to assess the same mice. BMS detected significant differences in locomotor outcomes between severe contusion and transection (p < 0.05) and SCI severity gradations resulting from displacement variations of only 0.1 mm (p < 0.05). BMS demonstrated significant face, predictive and concurrent validity. Novice BMS raters with training scored within 0.5 points of experts and demonstrated high reliability (0.92-0.99). The BMS is a sensitive, valid and reliable locomotor measure in SCI mice. BMS revealed significantly higher recovery in C57BL/10, B10.PL and F1 than the C57BL/6 and BALB/c strains after moderate SCI (p < 0.05). The differing behavioral response to SCI suggests inherent genetic factors significantly impact locomotor recovery and must be considered in studies with inbred or genetically engineered mouse strains.

Nogo-A-deficient mice reveal strain-dependent differences in axonal regeneration

Nogo-A, a membrane protein enriched in myelin of the adult CNS, inhibits neurite growth and regeneration; neutralizing antibodies or receptor blockers enhance regeneration and plasticity in the injured adult CNS and lead to improved functional outcome. Here we show that Nogo-A-specific knock-outs in backcrossed 129X1/SvJ and C57BL/6 mice display enhanced regeneration of the corticospinal tract after injury. Surprisingly, 129X1/SvJ Nogo-A knock-out mice had two to four times more regenerating fibers than C57BL/6 Nogo-A knock-out mice. Wild-type newborn 129X1/SvJ dorsal root ganglia in vitro grew a much higher number of processes in 3 d than C57BL/6 ganglia, confirming the stronger endogenous neurite growth potential of the 129X1/SvJ strain. cDNA microarrays of the intact and lesioned spinal cord of wild-type as well as Nogo-A knock-out animals showed a number of genes to be differentially expressed in the two mouse strains; many of them belong to functional categories associated with neurite growth, synapse formation, and inflammation/immune responses. These results show that neurite regeneration in vivo, under the permissive condition of Nogo-A deletion, and neurite outgrowth in vitro differ significantly in two widely used mouse strains and that Nogo-A is an important endogenous inhibitor of axonal regeneration in the adult spinal cord.

An interaction between genetic factors and gender determines the magnitude of the inflammatory response in the mouse air pouch model of acute inflammation

The widely used mouse air pouch model of acute inflammation is inducible in a variety of inbred strains, but the potential influence of genetic background and gender on inflammation severity has never been examined. We directly compared the degree of inflammation induced in the air pouch model across four commonly utilized inbred strains in both male and female mice. We then applied an in silico mapping method to identify loci potentially associated with determining inflammation severity for each gender. Air pouches were induced by subcutaneous injection 3 (3 cc) and 5 (1.5 cc) days prior to the experiment. 4h after carrageenan injection, exudates were retrieved and leukocyte concentration quantified using a hemocytometer. The in silico mapping method was applied as described below. The strain order for mean leukocyte count/mL in inflamed exudates differed between genders. In males, the order was C57BL/6J > BALB/cByJ > DBA/2J > DBA/1J, while in females the order was BALB/cByJ > DBA/2J > C57BL/6J > DBA/1J. The difference in inflammation severity between genders reached significance only in C57BL/6J mice. Independent in silico analysis based on phenotypic data from male versus female mice identified distinct sets of loci as potentially associated with the exudate count reached. We conclude that the degree of inflammation induced in the mouse air pouch model of inflammation is strain-specific and, therefore, genetically based, and the pattern of interstrain differences is altered in male relative to female mice. The loci identified by in silico mapping likely contain genes with differential roles in determining this phenotype between genders.

Comparative analysis of lesion development and intraspinal inflammation in four strains of mice following spinal contusion injury

Susceptibility to neuroinflammatory disease is influenced in part by genetics. Recent data indicate that survival of traumatized neurons is strain dependent and influenced by polygenic loci that control resistance/susceptibility to experimental autoimmune encephalomyelitis (EAE), a model of CNS autoimmune disease. Here, we describe patterns of neurodegeneration and intraparenchymal inflammation after traumatic spinal cord injury (SCI) in mice known to exhibit varying degrees of EAE susceptibility [EAE-resistant (r) or EAE-susceptible (s) mice]. Spinal cords from C57BL/6 (EAE-s), C57BL/10 (EAE-r), BALB/c (EAE-r), and B10.PL (EAE-s) mice were prepared for stereological and immunohistochemical analysis at 6 hours or 3, 7, 14, 28, or 42 days following midthoracic (T9) spinal contusion injury. In general, genetic predisposition to EAE predicted the magnitude of intraparenchymal inflammation but not lesion size/length or locomotor recovery. Specifically, microglia/macrophage activation, recruitment of neutrophils and lymphocytes, and de novo synthesis of MHC class II were greatest in C57BL/6 mice and least in BALB/c mice at all times examined. However, lesion volume and axial spread of neurodegeneration were similar in C57BL/6 and BALB/c mice and were significantly greater than in C57BL/10 or B10.PL mice. Strains with marked intraspinal inflammation also developed the most intense lesion fibrosis. Thus, strain-dependent neuroinflammation was observed after SCI, but without a consistent relationship to EAE susceptibility or lesion progression. Only in C57BL/6 mice was the magnitude of intraspinal inflammation predictive of secondary neurodegeneration, functional recovery, or fibrosis.

Abnormal anterior chamber associated immune deviation (ACAID) in 129-strain mice

PURPOSE

To characterize anterior chamber immune deviation (ACAID) in 129-strain and mixed 129-strain mice.

METHODS

ACAID was assayed using standard protocols with herpes simplex-1 (HSV-1) and trinitrophenol-hapten-spleen cells (TNP-spleen) in C57B1/6, 129P2, 129X1, and intercrossed strains. Systemic tolerance induction was assayed using an ultraviolet light skin tolerance protocol to 2,-4,6-trinitro-l-chlorobenzene (TNCB).

RESULTS

129X1 and C57Bl/6xl29Xl Fl mice did not show ACAID to HSV-1. C57Bl/6xl29P2 mice did not show ACAID to TNP-spleen. C57Bl/6xl29P2 mice did show normal peripheral immune deviation to TNCB. (C57Bl/6xl29Xl) x C57B1/6 N2 backcrossed mice showed a bimodal ACAID response to HSV-1 suggesting a single dominant allele in the 129X1 background responsible for suppressing ACAID.

CONCLUSION

ACAID to multiple antigens is significantly reduced in 129-strain mice and their outcrossed progeny. Since 129-strain embryonic stem cells are widely used to generate knockout and transgenic mice, care must be taken to extensively backcross resultant strains in order to assess the effect of particular genes on ACAID.

Lower macrophage recruitment and atherosclerosis resistance in FVB mice

The aim of this study was to compare some aspects of cholesterol accretion and cholesterol efflux in cellular components of the aortic wall derived from mice resistant or susceptible to atherosclerosis, FVB or C57BL, respectively. Cholesterol efflux, from cholesterol loaded smooth muscle cells or elicited macrophages, to apo A-I or HDL was similar in the two strains under basal conditions, and after cAMP or LXR upregulation. Recruitment of peritoneal macrophages, 3 days after thioglycollate injection, was 65% lower in FVB than in C57BL mice, commensurate with a 40% reduction in MCP-1 in peritoneal lavage. In additional three atherosclerosis resistant strains, NZB, A/J and 129(SvJ), macrophage recruitment was reduced to a similar extent despite high MCP-1 levels. Since impaired macrophage recruitment in CCR2(-/-) or MCP-1(-/-) C57BL mice was reported to reduce atherosclerosis, it seems plausible that in some mouse strains reduction in macrophage mobilization could contribute to atherosclerosis resistance.

Genetic approaches to autonomic dysreflexia

Autonomic dysreflexia is a potentially life-threatening condition in which episodic hypertension occurs after injuries above the mid-thoracic segments of the spinal cord. Despite the seriousness of this condition, little is known of the molecular mechanisms that lead to its development. The completed sequencing of the mouse genome, its dense genetic map, and the large repository of engineered and spontaneous mouse mutants, make the mouse an ideal model organism in which to study the molecular mechanisms underlying autonomic dysreflexia. We subjected two wild-type strains of mice, 129Sv and C57BL/6, and one spontaneous mouse mutant, Wallerian degeneration slow (Wld s), to spinal cord transection and clip-compression injury. We found that the incidence of autonomic dysreflexia is greatly reduced, compared to spinal cord-transected wild-type mice, in Wld s mice after both injury paradigms and in 129Sv and C57BL/6 that have undergone the clip-compression injury. We also found that the amplitude of the dysreflexic response was greater in cord-compressed 129Sv than in C57BL/6 mice. These results implicate axonal degeneration as an important source of signals that trigger the development of autonomic dysreflexia and are discussed in the context of mouse genetics, interstrain differences and possible molecular mechanisms underlying autonomic dysreflexia after spinal cord injury.

Impact of genetic background on nephropathy in diabetic mice

With the goal of identifying optimal platforms for developing better models of diabetic nephropathy in mice, we compared renal effects of streptozotocin (STZ)-induced diabetes among five common inbred mouse strains (C57BL/6, MRL/Mp, BALB/c, DBA/2, and 129/SvEv). We also evaluated the renal consequences of chemical and genetic diabetes on the same genetic background (C57BL/6). There was a hierarchical response of blood glucose level to the STZ regimen among the strains (DBA/2 > C57BL/6 > MRL/MP > 129/SvEv > BALB/c). In all five strains, males demonstrated much more robust hyperglycemia with STZ than females. STZ-induced diabetes was associated with modest levels of albuminuria in all of the strains but was greatest in the DBA/2 strain, which also had the most marked hyperglycemia. Renal structural changes on light microscopy were limited to the development of mesangial expansion, and, while there were some apparent differences among strains in susceptibility to renal pathological changes, there was a significant positive correlation between blood glucose and the degree of mesangial expansion, suggesting that most of the variability in renal pathological abnormalities was because of differences in hyperglycemia. Although the general character of renal involvement was similar between chemical and genetic diabetes, Akita mice developed more marked hyperglycemia, elevated blood pressures, and less variability in renal structural responses. Thus, among the strains and models tested, the DBA/2 genetic background and the Akita (Ins2(+/C96Y)) model may be the most useful platforms for model development.

Enhanced axonal growth into a spinal cord contusion injury site in a strain of mouse (129X1/SvJ) with a diminished inflammatory response

After injury in the adult central nervous system, invading and intrinsic cells contribute to the formation of a lesion site that is refractory to axonal growth. To test the hypothesis that the inflammatory response to trauma dictates the extent of axonal growth after spinal cord injury, the time course of lesion evolution was compared in two mouse strains with contrasting cellular responses to peripheral inflammatory challenge. Adult C57Bl/6 and 129X1/SvJ mice received identical contusion injuries to the mid-thoracic spinal cord and were allowed to recover for 6 hours to 9 weeks. Both strains responded with a rapid, transient increase in chemokine expression, but the magnitude of this early response was slightly reduced in the 129X1/SvJ mice. Morphological indicators of inflammation were similar during the first week postinjury. After 7 days postinjury, however, the cellular responses differed between strains. The C57Bl/6 lesion core was chronically occupied by macrophages, devoid of astrocytes, and contained few axonal profiles. In contrast, as the macrophage density decreased a network of astrocytic processes and axons of central and peripheral origin invaded the center of the lesion site in 129X1Sv/J mice. Growth of axons in the 129X1Sv/J mice was accompanied by increased extravascular laminin in the lesion core and a reduced expression of chondroitin sulfate proteoglycan glycosaminoglycan sidechains in the periphery of the lesion. These results demonstrate that the diminished chronic inflammatory response in 129X1/SvJ mice is associated with enhanced cellular repair and increased axonal growth after spinal cord injury.

Antibody-mediated glomerulonephritis in mice: the role of endotoxin, complement and genetic background

Antibody-mediated glomerulonephritis in man may be exacerbated by infection and this effect may be mediated by bacterial endotoxin. There is evidence supporting a role for endotoxin in heterologous nephrotoxic nephritis in rats, but the role of endotoxin in this model in mice has not previously been explored. Previous data in mice on the role of complement in this model are conflicting and this may be due to the mixed genetic background of mice used in these studies. We used the model of heterologous nephrotoxic nephritis in mice and explored the role of endotoxin, complement and genetic background. In this study we show a synergy between antibody and endotoxin in causing a neutrophil influx. We also show that C1q-deficient mice have an increased susceptibility to glomerular inflammation but this is seen only on a mixed 129/Sv x C57BL/6 genetic background. On a C57BL/6 background we did not find any differences in disease susceptibility when wildtype, C1q, factor B or factor B/C2 deficient mice were compared. We also demonstrate that C57BL/6 mice are more susceptible to glomerular inflammation than 129/Sv mice. These results show that endotoxin is required in this model in mice, and that complement does not play a major role in glomerular inflammation in C57BL/6 mice. C1q may play a protective role in mixed-strain 129/Sv x C57BL/6 mice, but the data may also be explained by systematic bias in background genes, as there is a large difference in disease susceptibility between C57BL/6 and 129/Sv mice.

Autonomic dysreflexia after spinal cord transection or compression in 129Sv, C57BL, and Wallerian degeneration slow mutant mice

To study plasticity of central autonomic circuits that develops after spinal cord injury (SCI), we have characterized a mouse model of autonomic dysreflexia. Autonomic dysreflexia is a condition in which episodic hypertension occurs after injuries above the midthoracic segments of the spinal cord. As synaptic plasticity may be triggered by axonal degeneration, we investigated whether autonomic dysreflexia is reduced in mice when axonal degeneration is delayed after SCI. We subjected three strains of mice, Wld(S), C57BL, and 129Sv, to either spinal cord transection (SCT) or severe clip-compression injury (CCI). The Wld(S) mouse is a well-characterized mutant that exhibits delayed Wallerian degeneration. The CCI model is an injury paradigm in which significant the axonal degeneration is due to secondary events and therefore delayed relative to the time of the initial injury. We herein demonstrate that the incidence of autonomic dysreflexia is reduced in Wld(S) mice after SCT and in all mice after CCI. To determine if differences in afferent arbor sprouting could explain our observations, we assessed changes in the afferent arbor in each mouse strain after both SCT and CCI. We show that independent of the type of injury, 129Sv mice but not C57BL or Wld(S) mice demonstrated an increased small-diameter CGRP-immunoreactive afferent arbor after SCI. Our work thus suggests a role for Wallerian degeneration in the development of autonomic dysreflexia and demonstrates that the choice of mouse strain and injury model has important consequences to the generalizations that may be drawn from studies of SCI in mice.

The enigmatic role of the hemochromatosis protein (HFE) in iron absorption

The HFE gene, a member of the class-I transplantation antigen gene family, is responsible for hereditary hemochromatosis, one of the most common inherited diseases in individuals of European descent. Patients exhibit predictable changes in iron homeostasis, including elevations in both transferrin saturation and serum ferritin levels. A subset of patients progress to overt clinical sequelae, resulting from iron overload. A hallmark of the disease is increased absorption of iron by the intestine. Although the HFE protein appears to modulate the function of the transferrin receptor in vitro, its precise role in vivo remains obscure. With multiple cell types involved in iron metabolism, the function of HFE is likely to be complex.

Absence of CCR8 does not impair the response to ovalbumin-induced allergic airway disease

Interaction of chemokines with their specific receptors results in tight control of leukocyte migration and positioning. CCR8 is a chemokine receptor expressed mainly in CD4(+) single-positive thymocytes and Th2 cells. We generated CCR8-deficient mice (CCR8(-/-)) to study the in vivo role of this receptor, and describe in this study the CCR8(-/-) mouse response in OVA-induced allergic airway disease using several models, including an adoptive transfer model and receptor-blocking experiments. All CCR8(-/-) mice developed a pathological response similar to that of wild-type animals with respect to bronchoalveolar lavage cell composition, peripheral blood and bone marrow eosinophilia, lung infiltrates, and Th2 cytokine levels in lung and serum. The results contrast with a recent report using one of the OVA-induced asthma models studied here. Similar immune responses were also observed in CCR8(-/-) and wild-type animals in a different model of ragweed allergen-induced peritoneal eosinophilic inflammation, with an equivalent number of eosinophils and analogous increased levels of Th2 cytokines in peritoneum and peripheral blood. Our results show that allergic diseases course without critical CCR8 participation, and suggest that further work is needed to unravel the in vivo role of CCR8 in Th2-mediated pathologies.