Effects of autoantigen and dexamethasone treatment on expression of endothelial-monocyte activating polypeptide II and allograft-inflammatory factor-1 by activated macrophages and microglial cells in lesions of experimental autoimmune encephalomyelitis, neuritis and uveitis

Characterization of microglia/macrophage phenotypes in the spinal cord following intervertebral disc herniation

Dogs frequently suffer from traumatic spinal cord injury (SCI). Most cases of SCI have a favorable prognosis but 40-50% of dogs with paraplegia and absence of nociception do not regain ambulatory abilities, eventually leading to euthanasia. Microglia and infiltrating macrophages play a crucial role in inflammatory process after SCI. However, little is known about microglia/macrophage phenotypes representing a potential target for future therapeutic strategies. In the present study, the microglia/macrophage phenotype was characterized by immunohistochemistry in the morphologically unaltered canine spinal cord (10 control dogs) and during acute and subacute SCI (1-4 and 5-10 days post injury, 9 and 8 dogs, respectively) using antibodies directed against IBA1, MAC387, MHC-II, lysozyme, EGR2, myeloperoxidase, CD18, CD204 and lectin from Griffonia simplicifolia (BS-1). The expression of these markers was also analyzed in the spleen as reference for the phenotype of histiocytic cells. Histological lesions were absent in controls. In acute SCI, 4 dogs showed mild to moderate hemorrhages, 2 dogs bilateral gray matter necrosis and 6 dogs mild multifocal axonal swellings and myelin sheath dilation. One dog with acute SCI did not show histological alterations except for few dilated myelin sheaths. In subacute SCI, variable numbers of gitter cells, axonal changes and dilated myelin sheaths were present in all dogs and large areas of tissue necrosis in 2 dogs. Neuronal chromatolysis was found in 3 dogs with acute and subacute SCI, respectively. In control dogs, microglia/macrophage constitutively expressed IBA1 and rarely other markers. In acute SCI, a similar marker expression was found except for an increase in MAC387-positive cells in the spinal cord white matter due to an infiltration of few blood-borne macrophages. In subacute SCI, increased numbers of microglia/macrophages expressed CD18, CD204 and MHC-II in the gray matter SCI indicating enhanced antigen recognition, processing and presentation as well as cell migration and phagocytosis during this stage. Interestingly, only CD204-positive cells were upregulated in the white matter, which might be related to gray-white matter heterogeneity of microglia as previously described in humans. The present findings contribute to the understanding of the immunological processes during SCI in a large animal model for human SCI.

Capd Peritonitis Induces the Production of a Novel Peptide, Daintain/Allograft Inflammatory Factor-1

← Objectives

To study the occurrence of a novel macrophage-derived peptide, daintain/allograft inflammatory factor-1 (AIF-1), in dialysate from continuous ambulatory peritoneal dialysis (CAPD) patients at commencement and after a follow-up period of therapy and during peritonitis. In addition, we studied peptide production in response to bacterial stimulation of monocytes and macrophages.

← Design

Peritoneal fluid and supernatants from cells stimulated with different bacteria were analyzed for daintain/AIF-1.

← Patients and Setting

Peritoneal fluid was obtained from 5 patients at commencement of CAPD therapy and during 8 weeks follow-up, and from 14 patients (10 males, 4 females) during CAPD peritonitis and during the noninfected steady state. All patients were admitted to the Karolinska Hospital. A human monocyte cell-line, THP-1 was differentiated to macrophages, and both monocytes and macrophages were stimulated with live and heat-inactivated Escherichia coli, Staphylococcus aureus, and S. epidermidis Cells were also stimulated with interleukin (IL)-1β and interferon gamma (IFNγ). Daintain/AIF-1 was analyzed with radioimmunoassay technique and IL-8 with enzyme immunoassay technique.

← Results

An increased production of daintain/AIF-1 was observed in the first spent dialysate in the newly started CAPD patients, with a decrease during the follow-up period ( p < 0.05). During peritonitis, the first spent dialysate revealed significantly higher levels of daintain/AIF-1 (3.9 ng/mL) compared to the noninfected state (0.8 ng/mL), with production normalizing after 9 – 12 days. Bacterial stimulation with E. coli, S. aureus or S. epidermidi sinduced higher daintain/AIF-1 response in monocytes compared to macrophages ( p < 0.05). Live bacteria induced higher production of the peptide compared to heat-inactivated bacteria ( p < 0.05). Interleukin-1β and IFNγ were used to stimulate monocytes and macrophages; however, no daintain/AIF-1 production was found, although increased IL-8 levels were detected.

← Conclusion

CAPD peritonitis induces a high and prominent daintain/AIF-1 response. Bacteria are able to induce a response of the peptide from monocytes and macrophages, and it is likely that the virulent parts of the bacteria are heat-labile structures. The early rise in daintain/AIF-1 might be used as a marker of CAPD peritonitis.

Extracellular allograft inflammatory factor-1 (AIF-1) potentiates Th1 cell differentiation and inhibits Treg response in human peripheral blood mononuclear cells from normal subjects

We identified the presence of AIF-1 (allograft inflammatory factor-1) in human peripheral blood mononuclear cells (PBMCs) from normal subjects by immunocytological methods. After isolation of different types of mononuclear cells by FACS (Fluorescence-activated cell sorting) with >95% purity, we studied the transcript levels of AIF-1 using qPCR. We observed the following order of AIF-1 mRNA expression in mononuclear cells: T-lymphocytes ˃ Monocytes ˃ B-lymphocytes ˃ NK. After T cell expansion of isolated PBMCs using anti-CD3-CD28 magnetic beads (Dynabeads®), AIF-1 increased intracellularly in the presence of brefeldin A; this finding, along with an increase in the medium in the absence of the drug, suggests that AIF-1 is processed in the Golgi apparatus and may be secreted extracellularly. In another set of experiments, interleukin-12 and anti-interleukin-4 were added to PBMCs during T cell expansion to promote Th1 polarization and to inhibit Th2 differentiation. In this case, the presence of 6 nM of rhAIF-1 (recombinant human AIF-1) increased the mRNA expression of interferon-ϒ and interleukin-2. In the same set of experiments, the incubation of PBMCs with rhAIF-1 (6 nM) promoted the decrease of mRNA expression of IL-10 and TGF-β, along with the decrease of CD25 and Foxp3 proteins. Furthermore, extracellular rhAIF-1 (6 nM) increased the survival of naive and effector T cells during Th1 polarization by inhibition of apoptosis, without causing changes in cell cycle rate and in retinoblastoma-cyclin-dependent kinase (Rb-CDK) activation. Taken together, rhAIF-1 treatment of PBMCs potentiates Th1 response and inhibits functionally suppressive CD25 + Foxp3 + Treg, which suggests an important immunomodulatory role in governing T cell response.

Role of allograft inflammatory factor-1 in the regulation of inflammation and oxidative stress in primary peritoneal mesothelial cells

Peritoneal dialysis (PD) is often used to treat patients with end stage renal disease, and its long-term complications include excessive inflammation and oxidative stress. Allograft inflammatory factor 1 (AIF-1), as a cytoplasmic protein, is originally identified from infiltrating macrophages, and it was associated with inflammation in the cells other than macrophages, such as endothelial cells and vascular smooth muscle cells. To clarify the molecular mechanisms of AIF-1-modulated pathological changes in the peritoneum during PD, we first detected the AIF-1 expression in peritoneal tissues from PD mice. Results revealed that the pro-fibrotic stimulation caused AIF-1 upregulation and triggered inflammation in peritoneal tissues, and that AIF-1 co-expressed with pan-cytokeratin (a marker of peritoneal mesothelial cells). We next treated primary mouse peritoneal mesothelial cells (pan-cytokeratin and intercellular adhesion molecule 1 positive cells) with 50 or 100 ng/mL recombinant AIF-1, and evaluated the direct effects of AIF-1 on these cells in vitro. We found that exogenous AIF-1 treatment induced inflammation and oxidative stress in mesothelial cells. Apart from the augmented IL-6 and TNF-α secretion, the level of ROS was upregulated and the activity of anti-oxidative SOD was reduced in cells exposed to AIF-1. Moreover, AIF-1 simulation triggered the activation of NF-κB pathway-enhanced the conversion of IκB to phosphorylated IκB and promoted the translocation of NF-κB p65 from cytoplasm into nucleus. Additionally, AIF-1-evoked inflammation in peritoneal mesothelial cells was attenuated by the addition of NF-κB inhibitor (BAY 11-7082). In brief, this study provides us novel information to understand the molecular regulation mechanisms of AIF-1 in peritoneal fibrosis.

AIF-1 gene does not confer susceptibility to Behçet's disease: Analysis of extended haplotypes in Sardinian population

BACKGROUND

Behçet's disease (BD) is a polygenic immune-mediated disorder characterized by a close association with the HLA-B*51 allele. The HLA region has a strong linkage disequilibrium (LD) and carries several genetic variants (e.g. MIC-A, TNF-α genes) identified as associated to BD because of their LD with HLA-B*51. In fact, the HLA-B*51 is inherited as part of extended HLA haplotypes which are well preserved in patients with BD. Sardinian population is highly differentiated from other Mediterranean populations because of a distinctive genetic structure with very highly preserved HLA haplotypes.

PATIENTS AND METHODS

In order to identify other genes of susceptibility to BD within the HLA region we investigated the distribution of human Allograft Inflammatory Factor-1 (AIF-1) gene variants among BD patients and healthy controls from Sardinia. Six (rs2736182; rs2259571; rs2269475; rs2857597; rs13195276; rs4711274) AIF-1 single nucleotide polymorphisms (SNPs) and related extended haplotypes have been investigated as well as their LD within the HLA region and with HLA-B*51. Overall, 64 BD patients, 43 HLA-B*51 positive healthy controls (HC) and 70 random HC were enrolled in the study.

RESULTS

HLA-B*51 was the only allele with significantly higher frequency (pc = 0.0021) in BD patients (40.6%) than in HC (9.8%). The rs2259571T AIF-1 variant had a significantly reduced phenotypic, but not allelic frequency in BD patients (72.1%; pc = 0.014) compared to healthy population (91.3%). That was likely due to the LD between HLA-B*51 and rs2259571G (pc = 9E-5), even though the rs2259571G distribution did not significantly differ between BD patients and HC.

CONCLUSION

No significant difference in distribution of AIF-1 SNPs haplotypes was observed between BD patients and HC and between HLA-B*51 positive BD patients and HLA-B*51 positive HC. Taken together, these results suggest that AIF-1 gene is not associated with susceptibility to BD in Sardinia.

Neuro-immune lessons from an annelid: The medicinal leech

An important question that remains unanswered is how the vertebrate neuroimmune system can be both friend and foe to the damaged nervous tissue. Some of the difficulty in obtaining responses in mammals probably lies in the conflation in the central nervous system (CNS), of the innate and adaptive immune responses, which makes the vertebrate neuroimmune response quite complex and difficult to dissect. An alternative strategy for understanding the relation between neural immunity and neural repair is to study an animal devoid of adaptive immunity and whose CNS is well described and regeneration competent. The medicinal leech offers such opportunity. If the nerve cord of this annelid is crushed or partially cut, axons grow across the lesion and conduction of signals through the damaged region is restored within a few days, even when the nerve cord is removed from the animal and maintained in culture. When the mammalian spinal cord is injured, regeneration of normal connections is more or less successful and implies multiple events that still remain difficult to resolve. Interestingly, the regenerative process of the leech lesioned nerve cord is even more successful under septic than under sterile conditions suggesting that a controlled initiation of an infectious response may be a critical event for the regeneration of normal CNS functions in the leech. Here are reviewed and discussed data explaining how the leech nerve cord sensu stricto (i.e. excluding microglia and infiltrated blood cells) recognizes and responds to microbes and mechanical damages.

Immortalization of primary microglia: a new platform to study HIV regulation in the central nervous system

The major reservoirs for HIV in the CNS are in the microglia, perivascular macrophages, and to a lesser extent, astrocytes. To study the molecular events controlling HIV expression in the microglia, we developed a reliable and robust method to immortalize microglial cells from primary glia from fresh CNS tissues and commercially available frozen glial cells. Primary human cells, including cells obtained from adult brain tissue, were transformed with lentiviral vectors expressing SV40 T antigen or a combination of SVR40 T antigen and hTERT. The immortalized cells have microglia-like morphology and express key microglial surface markers including CD11b, TGFβR, and P2RY12. Importantly, these cells were confirmed to be of human origin by sequencing. The RNA expression profiles identified by RNA-seq are also characteristic of microglial cells. Furthermore, the cells demonstrate the expected migratory and phagocytic activity, and the capacity to mount an inflammatory response characteristic of primary microglia. The immortalization method has also been successfully applied to a wide range of microglia from other species (macaque, rat, and mouse). To investigate different aspects of HIV molecular regulation in CNS, the cells have been superinfected with HIV reporter viruses and latently infected clones have been selected that reactive HIV in response to inflammatory signals. The cell lines we have developed and rigorously characterized will provide an invaluable resource for the study of HIV infection in microglial cells as well as studies of microglial cell function.

Allograft inflammatory factor-1 in grass carp (Ctenopharynogodon idella): Expression and response to cadmium exposure

Allograft Inflammatory Factor-1 (AIF-1) is an inflammation responsive protein that is mainly produced by immunocytes. As a pro-inflammatory cytokine, AIF-1 is a key moderator in host immune defense reaction. However, the inflammatory properties of AIF-1 in freshwater fish still hasn't been clearly elucidated. In the present study, AIF-1 was identified from grass carp (Ctenopharynogodon idella). It's transcript was found in all examined tissues including brain, spleen, kidney, liver, heart, while a relative low level in red muscle, gill, thymus, white muscle, intestine and fin. Furthermore, AIF-1 transcription and expression level decreased in spleen and didn't change a lot in kidney with cadmium induction, respectively. The result indicated that grass carp AIF-1 might be involved in cadmium-induced stress.

Neuropeptide Y protects cerebral cortical neurons by regulating microglial immune function

Neuropeptide Y has been shown to inhibit the immunological activity of reactive microglia in the rat cerebral cortex, to reduce N-methyl-D-aspartate current (I_NMDA) in cortical neurons, and protect neurons. In this study, after primary cultured microglia from the cerebral cortex of rats were treated with lipopolysaccharide, interleukin-1β and tumor necrosis factor-α levels in the cell culture medium increased, and mRNA expression of these cytokines also increased. After primary cultured cortical neurons were incubated with the lipopolysaccharide-treated microglial conditioned medium, peak I_NMDA in neurons increased. These effects of lipopolysaccharide were suppressed by neuropeptide Y. After addition of the neuropeptide Y Y1 receptor antagonist BIBP3226, the effects of neuropeptide Y completely disappeared. These results suggest that neuropeptide Y prevents excessive production of interleukin-1β and tumor necrosis factor-α by inhibiting microglial reactivity. This reduces I_NMDA in rat cortical neurons, preventing excitotoxicity, thereby protecting neurons.

The leech nervous system: a valuable model to study the microglia involvement in regenerative processes

Microglia are intrinsic components of the central nervous system (CNS). During pathologies in mammals, inflammatory processes implicate the resident microglia and the infiltration of blood cells including macrophages. Functions of microglia appear to be complex as they exhibit both neuroprotective and neurotoxic effects during neuropathological conditions in vivo and in vitro. The medicinal leech Hirudo medicinalis is a well-known model in neurobiology due to its ability to naturally repair its CNS following injury. Considering the low infiltration of blood cells in this process, the leech CNS is studied to specify the activation mechanisms of only resident microglial cells. The microglia recruitment is known to be essential for the usual sprouting of injured axons and does not require any other glial cells. The present review will describe the questions which are addressed to understand the nerve repair. They will discuss the implication of leech factors in the microglial accumulation, the identification of nerve cells producing these molecules, and the study of different microglial subsets. Those questions aim to better understand the mechanisms of microglial cell recruitment and their crosstalk with damaged neurons. The study of this dialog is necessary to elucidate the balance of the inflammation leading to the leech CNS repair.

Identification of expressed genes in cDNA library of hemocytes from the RLO-challenged oyster, Crassostrea ariakensis Gould with special functional implication of three complement-related fragments (CaC1q1, CaC1q2 and CaC3)

A SMARTer™ cDNA library of hemocyte from Rickettsia-like organism (RLO) challenged oyster, Crassostrea ariakensis Gould was constructed. Random clones (400) were selected and single-pass sequenced, resulted in 200 unique sequences containing 96 known genes and 104 unknown genes. The 96 known genes were categorized into 11 groups based on their biological process. Furthermore, we identified and characterized three complement-related fragments (CaC1q1, CaC1q2 and CaC3). Tissue distribution analysis revealed that all of three fragments were ubiquitously expressed in all tissues studied including hemocyte, gills, mantle, digestive glands, gonads and adductor muscle, while the highest level was seen in the hemocyte. Temporal expression profile in the hemocyte monolayers reveled that the mRNA expression levels of three fragments presented huge increase after the RLO incubation at 3 h and 6 h in post-challenge, respectively. And the maximal expression levels at 3 h in post-challenge are about 256, 104 and 64 times higher than the values detected in the control of CaC1q1, CaC1q2 and CaC3, respectively.

Mutations in zebrafish lrp2 result in adult-onset ocular pathogenesis that models myopia and other risk factors for glaucoma

The glaucomas comprise a genetically complex group of retinal neuropathies that typically occur late in life and are characterized by progressive pathology of the optic nerve head and degeneration of retinal ganglion cells. In addition to age and family history, other significant risk factors for glaucoma include elevated intraocular pressure (IOP) and myopia. The complexity of glaucoma has made it difficult to model in animals, but also challenging to identify responsible genes. We have used zebrafish to identify a genetically complex, recessive mutant that shows risk factors for glaucoma including adult onset severe myopia, elevated IOP, and progressive retinal ganglion cell pathology. Positional cloning and analysis of a non-complementing allele indicated that non-sense mutations in low density lipoprotein receptor-related protein 2 (lrp2) underlie the mutant phenotype. Lrp2, previously named Megalin, functions as an endocytic receptor for a wide-variety of bioactive molecules including Sonic hedgehog, Bone morphogenic protein 4, retinol-binding protein, vitamin D-binding protein, and apolipoprotein E, among others. Detailed phenotype analyses indicated that as lrp2 mutant fish age, many individuals—but not all—develop high IOP and severe myopia with obviously enlarged eye globes. This results in retinal stretch and prolonged stress to retinal ganglion cells, which ultimately show signs of pathogenesis. Our studies implicate altered Lrp2-mediated homeostasis as important for myopia and other risk factors for glaucoma in humans and establish a new genetic model for further study of phenotypes associated with this disease.

Complex genetic inheritance, including variable penetrance and severity, underlies many common eye diseases. In this study, we present analysis of a zebrafish mutant, bugeye, which shows complex inheritance of multiple ocular phenotypes that are known risk factors for glaucoma, including high myopia, elevated intraocular pressure, and up-regulation of stress-response genes in retinal ganglion cells. Molecular genetic analysis revealed that mutations in low density lipoprotein receptor-related protein 2 (lrp2) underlie the mutant phenotypes. Lrp2 is a large transmembrane protein expressed in epithelia of the eye. It facilitates transport and clearance of multiple secreted bioactive factors through receptor-mediated endocytosis. Glaucoma, a progressive blinding disorder, usually presents in adulthood and is characterized by optic nerve damage followed by ganglion cell death. In bugeye/lrp2 mutants, ganglion cell death was significantly elevated, but surprisingly moderate, and therefore they do not model this endpoint of glaucoma. As such, bugeye/lrp2 mutants should be considered valuable as a genetic model (A) for buphthalmia, myopia, and regulated eye growth; (B) for identifying genes and pathways that modify the observed ocular phenotypes; and (C) for studying the initiation of retinal ganglion cell pathology in the context of high myopia and elevated intraocular pressure.

AIF-1 expression regulates endothelial cell activation, signal transduction, and vasculogenesis

Endothelial cell (EC) activation plays a key role in vascular inflammation, thrombosis, and angiogenesis. Allograft inflammatory factor-1 (AIF-1) is a cytoplasmic, calcium-binding, inflammation-responsive scaffold protein that has been implicated in the regulation of inflammation. The expression and function of AIF-1 in EC is uncharacterized, and the purpose of this study was to characterize AIF-1 expression and function in ECs. AIF-1 expression colocalized with CD31-positive ECs in neointima of inflamed human arteries but not normal arteries. AIF-1 is detected at low levels in unstimulated EC, but expression can be increased in response to serum and soluble factors. Stable transfection of AIF-1 small interfering RNA (siRNA) in ECs reduced AIF-1 protein expression by 73% and significantly reduced EC proliferation and migration (P < 0.05 and 0.001). Rescue of AIF-1 expression restored both proliferation and migration of siRNA-expressing ECs, and AIF-1 overexpression enhanced both of these activities, suggesting a strong association between AIF-1 expression and EC activation. Activation of mitogen-activated protein kinase p44/42 and PAK1 was significantly reduced in siRNA ECs challenged with inflammatory stimuli. Reduction of AIF-1 expression did not decrease EC tube-like structure or microvessel formation from aortic rings, but overexpression of AIF-1 did significantly increase the number and complexity of these structures. These data indicate that AIF-1 expression plays an important role in signal transduction and activation of ECs and may also participate in new vessel formation.

Increased smooth muscle cell activation and neointima formation in response to injury in AIF-1 transgenic mice

OBJECTIVE

Allograft Inflammatory Factor-1 (AIF-1) is a calcium binding scaffold protein which is rapidly induced in vascular smooth muscle cells (VSMCs) in response to injury and inflammation. A transgenic mouse in which AIF-1 expression was driven by a VSMC-specific SM22alpha promoter was generated to establish a direct relationship between AIF-1 expression and intimal hyperplasia.

METHODS AND RESULTS

Morphological analysis of partially ligated carotid artery demonstrate a significant increase in neointimal area of AIF-1 Tg versus wild-type mice (569+/-64 um versus 256+/-49 um, P=0.004). Immunohistochemistry using antibody to the proliferation marker Ki-67 show a significantly greater number of proliferating cells in the AIF-1 Tg lesion compared with wild-type arteries (10.6%+/-1.0 versus 3.6%+/-.9, P=0.0007). AIF-1 Tg arteries also had a greater number of cells with activated signal transduction kinase p38 (55.4%+/-7.0 versus 22.6%+/-5.4, P=0.002) and PAK1 (67.5%+/-6.7 versus 35.3%+/-10.2, P=0.02) compared with wild-type. Cultured VSMCs explanted from AIF-1 Tg proliferate (55.5+/-3.6x10(3) versus 37.2+/-2.0x10(3) cells/mL, P=0.0001) and migrate more rapidly (39.2+/-3.2 versus 17.1+/-1.5 VSMCs per HPF, P=0.0003) than wild-type, and have significantly greater levels of activated p38 and PAK1 than did VSMCs from wild-type littermates (P<0.05).

CONCLUSIONS

These data indicate that AIF-1 expression results in increased signal transduction, neointimal formation, and VSMC proliferation in injured mouse carotid arteries.

Identification of differentially expressed genes in lipopolysaccharide-stimulated yellow grouper Epinephelus awoara spleen

A subtracted cDNA library from lipopolysaccharide (LPS)-stimulated Epinephelus awoara spleen was constructed using the suppression subtractive hybridization (SSH). Random clones (209) were selected and sequenced. After assembling, 36 contigs and 56 singlets (accession numbers: EB410743-EB410834) were finally obtained, some of which were immune-related genes. A reverse transcription-polymerase chain reaction (RT-PCR) analysis of the expression patterns of eight transcripts showed that seven of them were up-regulated after 24 h of LPS stimulation. Furthermore, full-length cDNAs of homologues of defender against cell death 1 (DAD1) and allograft inflammatory factor-1 (AIF-1) were obtained by RACE-PCR.

Allograft inflammatory factor-1 and its immune regulation

The allograft inflammatory factor-1 (AIF-1) is a 17 kDa interferon-gamma (IFN-gamma) inducible Ca(2+)-binding EF-hand protein that is encoded within the HLA class III genomic region. Three proteins including ionized Ca(2+)-binding adaptor 1, microglia response factor-1, and daintain are identical with AIF-1. The expression of AIF-1 was mostly limited to the monocyte/macrophage lineage, and augmented by cytokines such as IFN-gamma. It was assumed that AIF-1 was a novel molecule involved in inflammatory responses, allograft rejection, as well as the activation and function of macrophages. However, it has been reported that AIF-1 is also expressed in macrophages and microglial cells in autoimmune diseases such as experimental autoimmune encephalomyelitis, neuritis and uveitis models, suggesting that AIF-1 may play a pivotal role in autoimmunity. In the present manuscript, the genomic and functional characteristics of AIF-1 family proteins as well as their immune regulatory effects are reviewed.

Dexamethasone attenuates early expression of three molecules associated with microglia/macrophages activation following rat traumatic brain injury

Corticosteroids have been used in the treatment of human traumatic brain injury (TBI), which is a leading cause of death and disability, but their efficiency is still a matter of debate. Dexamethasone was considered to delay post-traumatic inflammation and retard neuronal degeneration, resulting in attenuation of secondary injury following experimental TBI. In a rat TBI model, we have investigated the effects of dexamethasone on expression patterns of markers of inflammatory activation of microglia/macrophages by immunohistochemistry. Endothelial-monocyte activating polypeptide II (EMAP-II), P2X4 receptor (P2X4R) and allograft-inflammatory factor-1 (AIF-1) were reported to be associated with the activation of microglia/macrophages post central nervous system (CNS) injury and may play roles in inflammatory cascades of secondary brain damage. Dexamethasone significantly suppressed the accumulation of EMAP-II(+), P2X4R(+) or AIF(+) cells at Day-1 and 2 post-brain-trauma but not on Days 4 and 6, which is in accordance with the reported short- but not long-term protective effects of dexamethasone in TBI. These findings indicate a rather rapid but transient anti-inflammatory effect of dexamethasone in TBI.

Potential roles of allograft inflammatory factor-1 in the pathogenesis of hemangiomas

Hemangiomas are benign tumors of the vascular endothelium and are the most common tumors of infancy. These tumors are characterized by an initial phase of rapid proliferation in the first months of life, which is followed, in most cases, by spontaneous slow involution. Despite their high prevalence, their detailed pathogenesis remains unknown. Recent studies suggest that immunity responses, inflammatory cells and their precursors, myeloid cells, play important roles in the growth and involution of hemangiomas. The allograft inflammatory factor-1 is a powerful gene that is involved in several kinds of inflammatory response-related diseases. Studies also show that it is implicated in angiogenesis, proliferation and differentiation of stem cells, and development of tumors. Taken all these evidences into consideration, we hypothesize that allograft inflammatory factor-1 plays potential roles in pathogenesis, proliferation and involution of hemangioma. Investigating the role of allograft inflammatory factor-1 in the proliferation and involution of hemangioma will lead to a better understanding of pathogenesis of this lesion. Furthermore, the subtle regulation of allograft inflammatory factor-1 in the involution of hemangiomas will help design a new anti-angiogenic therapy for some tumors.

Expression of allograft inflammatory factor-1 in kidneys: A novel molecular component of podocyte

Our comprehensive gene expression profiles of the kidneys in an anti-glomerular basement membrane (GBM) nephritis model using DNA arrays revealed that allograft inflammatory factor-1 (AIF-1) was one of the highly expressed genes. Here, we explored the pathological significance of AIF-1 expression in the kidneys. The expression pattern of AIF-1 mRNA and protein in the kidneys of normal and diseased rats, such as anti-GBM nephritis and puromycin aminonucleoside nephrosis, was investigated by in situ hybridization, immunohistochemistry, and immunoelectron microscopy. Furthermore, the expression of AIF-1 in human kidneys and urinary sediments was examined. AIF-1 was expressed at both mRNA and protein levels in podocytes of normal and diseased rats, and in infiltrating cells in anti-GBM nephritis kidneys. The expression of AIF-1 in podocytes was constitutive; positive in podocytes of both normal and diseased rats. In humans, AIF-1 was expressed in podocytes and infiltrating inflammatory cells, similarly. Moreover, it was detected in urinary podocytes from patients with immunoglobulin A nephropathy. These data document for the first time that AIF-1, a constitutively expressed protein in rat and human podocytes, is a novel molecular component of podocytes, and that the upregulation of AIF-1 in an anti-GBM nephritis model may mainly be a consequence of its expression in infiltrating cells.

Inhibition of AIF-1 expression by constitutive siRNA expression reduces macrophage migration, proliferation, and signal transduction initiated by atherogenic stimuli

Allograft inflammatory factor-1 (AIF-1) is a cytoplasmic, calcium-binding, inflammation-responsive scaffold protein. Several studies have reported increased AIF-1 expression in activated macrophages and have implicated AIF-1 as a marker of activated macrophages. However, the function of AIF-1 in macrophages and the mechanism whereby it participates in macrophage activation are unknown at this time. Immunohistochemical analysis colocalized AIF-1 expression with CD68-positive macrophages in atherosclerotic human coronary arteries. Subsequent experiments were designed to determine a role for AIF-1 in macrophage activation in response to atherogenic stimuli. Stimulation of human and murine macrophages with oxidized LDL significantly increased AIF-1 expression above basal levels. Stable transfection of AIF-1 small interfering RNA (siRNA) in macrophages reduced AIF-1 protein expression by 79% and reduced macrophage proliferation by 52% ( P < 0.01). Inhibition of proliferation was not due to induction of apoptosis. Sequences that did not knock down AIF-1 expression had no effect on proliferation. AIF-1 siRNA expression reduced macrophage migration by 60% ( P < 0.01). Both proliferation and migration of siRNA-expressing macrophages could be restored by adenoviral expression of AIF-1 ( P < 0.001 and 0.005, respectively), suggesting a tight association between AIF-1 expression and macrophage activation. Phosphorylation of Akt, p44/42 MAPK, and p38 kinase were significantly reduced in siRNA macrophages challenged with oxidized LDL ( P < 0.05). Phosphorylation of p38 kinase was significantly inhibited in siRNA macrophages stimulated with T lymphocyte conditioned medium ( P < 0.05). These data indicate that AIF-1 mediates atherogenesis-initiated signaling and activation of macrophages.

Warm ischemia-induced alterations in oxidative and inflammatory proteins in hepatic Kupffer cells in rats

The aim of the study was to investigate the impact of ischemia/reperfusion injury on the proteome of Kupffer cells. Lean Zucker rats (n = 6 each group) were randomized to 75 min of warm ischemia or sham operation. After reperfusion for 8 h, Kupffer cells were isolated by enzymatic perfusion and density gradient centrifugation. Proteins were tryptically digested into peptides and differentially labeled with iTRAQ (isobaric tags for relative and absolute quantitation) reagent. After fractionation by cation exchange chromatography, peptides were identified by mass spectrometry (ESI-LC-MS/MS). Spectra were interrogated against the Swiss-Prot database and quantified using ProteinProspector. The results for heat shock protein 70 and myeloperoxidase were validated by ELISA. Quantitative information for more than 1559 proteins was obtained. In the ischemia group proteins involved in inflammation were significantly up-regulated. The ratio for calgranulin B in the ischemia/sham group was 1.81 +/- 0.97 (p < 0.0001), for complement C3 the ratio was 1.81 +/- 0.49 (p < 0.0001), and for myeloperoxidase the ratio was 1.30 +/- 0.32. Myeloperoxidase was only recently documented in Kupffer cells. The antioxidative proteins Cu,Zn-superoxide dismutase (1.34 +/- 0.19; p < 0.001) and catalase (1.23 +/- 0.43; p < 0.001) were also elevated. In conclusion, ischemia/reperfusion injury induces alterations in the Kupffer cell proteome. Isotope ratio mass spectrometry is a powerful tool to investigate these reactions. The ability to simultaneously monitor several pathways involved in reperfusion stress may result in important mechanistic insight and possibly new treatment options.

Expression of allograft inflammatory factor-1 and haeme oxygenase-1 in brains of rats infected with the neurotropic Borna disease virus

Experimental infection of Lewis rats with Borna disease virus (BDV) causes an immune-mediated nonpurulent meningoencephalitis. Viral persistence in the central nervous system is accompanied by mononuclear infiltrates, activated monocytic/microglial cells and reactive astrocytes. The immune-mediated process was further characterized by expression analysis of allograft inflammatory factor-1 (AIF-1), a novel marker of monocyte/microglial activation and of glial fibrillary acid protein (GFAP) between day 3 and day 50 post infection (p.i.). Potential neuroprotective effects of these cells were studied by the induction of haeme oxygenase-1 (HO-1), a defensive molecule against oxidative stress in various brain insults. In BDV-infected rat brains, mononuclear infiltrates and AIF-1 expression increased up to day 28 p.i. During early time points p.i., AIF-1 expression was mainly found in inflammatory lesions and adjacent brain parenchyma. Already 24 days p.i., a widespread upregulation of AIF-1 was observed which declined only moderately beyond day 28 p.i. HO-1 induction was maximal between days 18 and 28 p.i. Increased amounts of GFAP-positive astrocytes were present beyond 24 days p.i. Viral antigen expression increased simultaneously to the inflammatory reaction and persisted up to 50 days p.i. Widespread upregulation of AIF-1 indicates an early, long-lasting microglial activation, which might be involved in the immunesurveillance of the immune-mediated inflammatory events. The early peak of HO-1 most likely represents a neuroprotective, anti-inflammatory response by invading monocytes, microglial cells and astrocytes during the formation of encephalitic lesions and acute viral replication.

Expression of allograft inflammatory factor-1 in T lymphocytes: a role in T-lymphocyte activation and proliferative arteriopathies

Allograft inflammatory factor (AIF)-1 is a cytoplasmic, calcium-binding protein whose expression in transplanted human hearts correlates with rejection and development of coronary artery vasculopathy (CAV). AIF-1 is constitutively expressed in monocytes/macrophages, but its expression in human lymphocytes has not been described. After immunohistochemical analysis of human coronary arteries with CAV, we identified AIF-1 expression in CD3-positive lymphocytes. AIF-1 was differentially expressed in peripheral blood mononuclear cells and in the T-lymphoblastoid MOLT-4 cell line exposed to various cytokines, suggesting a role for AIF-1 in T-lymphocyte activation. To determine AIF-1 function, MOLT-4 cells were stably transduced by AIF-1 retrovirus. Overexpression of AIF-1 in these cells led to a 238% increase in cell number compared to empty vector controls. AIF-1 polymerized nonmuscle actin and MOLT-4 cells overexpressing AIF-1 migrated 95% more rapidly than empty vector controls. Primary human vascular smooth muscle cells cultured in conditioned media from AIF-1-transduced MOLT-4 cells proliferated 99% more rapidly than vascular smooth muscle cells cultured in conditioned media from empty vector-transduced MOLT-4 cells. These data indicate that AIF-1 is expressed in activated T lymphocytes, that its expression enhances activation of lymphocytes, and that AIF-1 expression in activated lymphocytes may have important ramifications for activation of adjacent arterial vascular smooth muscle cells and development of CAV.

Spinal cord injury induction of lesional expression of profibrotic and angiogenic connective tissue growth factor confined to reactive astrocytes, invading fibroblasts and endothelial cells

OBJECT

The glial scar composed of astrogliosis and extracellular matrix deposition represents a major impediment to axonal regeneration. The authors investigated the role of a novel profibrotic and angiogenic peptide connective tissue growth factor (CTGF [Hcs24/IGFBP-r2P]) in glial scar formation following spinal cord injury (SCI) in rats.

METHODS

The effects of SCI on CTGF expression during glial scar maturation 1 day to 1 month post-SCI were investigated using fluorescein-activated cell sorter (FACS) immunohistochemical analysis; these findings were compared with those obtained in sham-operated (control) spinal cords. The CTGF-positive cells accumulated at the spinal cord lesion site (p < 0.0001) corresponding to areas of glial scar formation. In the perilesional rim, CTGF expression was confined to invading vimentin-positive, glial fibrillary acidic protein (GFAP)-negative fibroblastoid cells, endothelial and smooth-muscle cells of laminin-positive vessels, and GFAP-positive reactive astrocytes. The CTGF-positive astrocytes coexpressed the activation-associated intermediate filaments nestin, vimentin (> 80%), and mesenchymal scar component fibronectin (50%).

CONCLUSIONS

The restricted accumulation of CTGF-reactive astrocytes and CTGF-positive fibroblastoid cells lining the laminin-positive basal neolamina suggests participation of these cells in scar formation. In addition, perilesional upregulation of endothelial and smooth-muscle CTGF expression points to a role in blood-brain barrier function modulating edema-induced secondary damage.

Lesional accumulation of P2X4 receptor+ macrophages in rat CNS during experimental autoimmune encephalomyelitis

P2X(4) receptor (P2X(4)R) is an ion channel gated by ATP. Here we report the presence and distribution of P2X(4)R by immunohistochemical analysis of the rat CNS. In normal control rats, P2X(4)R was expressed by perivascular cells, but not found on parenchymal monocytic cells. We further investigated P2X(4)R expression in experimental autoimmune encephalomyelitis. P2X(4)R(+) cells were mainly identified as infiltrative macrophages in CNS lesions. In the diseased brain, P2X(4)R(+) leukocytic cells were not only found in the direct vicinity of the inflammatory infiltrate, but widespread distribution was seen in the parenchyma. In experimental autoimmune encephalomyelitis spinal cord, the number of P2X(4)R(+) cells was much higher than in brain. P2X(4)R(+) macrophage accumulation reached the maximal levels around day 14 correlating to the clinical severity of experimental autoimmune encephalomyelitis, and this upregulation lasted until the recovery stage of the disease. This implicates a role of P2X(4)R in the inflammatory process of the CNS. In addition, bromodeoxyuridine immunohistochemistry was employed to demonstrate cell proliferation. Only few bromodeoxyuridine+/P2X(4)R+ monocytes/macrophages were observed in both the diseased brain and spinal cord. In conclusion, this is the first demonstration that P2X(4)R presents in autoimmune-lesioned CNS. Consequently, P2X(4)R might be a valuable marker to dissect the local monocyte heterogeneity in autoimmune disease.

Selection of recombinant phages binding to pathological endothelial and tumor cells of rat glioblastoma by in-vivo display

Pathological endothelial cells are attractive targets to selectively abrogate tumor growth. However, only a few cell surface molecules to address the endothelium of pathological blood vessels are known, but it could be anticipated that many more molecular addresses associated with abnormal endothelial function and proliferation could serve as potential candidates for development of drug delivery agents. To obtain a library of peptides mediating binding of recombinant M13 phages to endothelium of experimental rat brain tumors, in-vivo display of a combinatorial heptapeptide and a splenocyte M13 library was used. Phage clones were selected that bind to rat brain tumor endothelium in-vivo and phage proteins detected in tissues by immunohistochemistry. Some of the recombinant phages diffused or were transported far into the surrounding tumor tissue, where they persisted for several days. Sequence analysis of insertion peptides revealed surprising similarities to angiogenic and anti-angiogenic factors or matrix and guidance molecules that appear to be involved in glioblastoma pathology. In-vivo phage display of recombinant M13 phages is a tool to select peptides targeting pathological endothelium. Insertion peptides, their corresponding cellular proteins and ligands might have a variety of applications in providing molecular tools for targeting tumor vascular beds with diagnostic probes and therapeutic substances and might open new opportunities for treating frequently fatal glial tumors.

Expression of allograft inflammatory factor-1 in mouse uterus and poly(I:C)-induced fetal resorption

PROBLEM

To investigate whether the allograft inflammatory factor-1 (AIF-1) is expressed and plays a role in the reproductive system.

METHOD OF STUDY

AIF-1 expression was examined in uteri of non-pregnant and pregnant mice by Northern blot analysis, RT-PCR and immunohistochemistry.

RESULTS

The expression of AIF-1 varied during the estrous cycle with a peak at estrus. After the insemination, the expression of AIF-1 mRNA diminished gradually and again increased in the pre-implantation or implantation period in allogeneic or syngeneic pregnancy, respectively. Enhanced expressions of AIF-1, tumor necrosis factor-alpha (TNF-alpha) and nitric oxide synthase 2 (NOS2) mRNA were observed in the embryos of resorption-prone pregnancy injected with poly(I:C).

CONCLUSIONS

This study demonstrated for the first time that AIF-1 was expressed in uterus. The expression level was associated with the population size of macrophage and varied during the estrous cycle and the pregnancy period. The augmented expression of AIF-I with concomitant expressions of TNF-alpha and NOS2 mRNA in poly(I:C)-injected mice suggests a correlation between AIF-1 production and fetal resorption.

The allograft inflammatory factor-1 in Creutzfeldt-Jakob disease brains

The allograft inflammatory factor-1 (AIF-1) is a 17-kDa IFN-gamma inducible Ca(2+)-binding EF-hand protein that is encoded within the HLA class III genomic region and is involved in immune dysfunction and smooth muscle cell activation. We used immunohistochemistry double labelling experiments to analyse the spatial distribution and cell-type-specific localization of AIF-1 in the brains of patients who died as a result of sporadic Creutzfeldt-Jakob disease (CJD) and neuropathologically unaltered controls. Significantly more AIF-1 immunoreactive macrophages/microglial cells and, interestingly, neurones were observed in CJD patients compared to controls. Western blotting confirmed more prominent AIF-1 immunoreactive bands of approximately 50 kDa in four CJD patients compared to three controls. Chaotropic SDS-PAGE of the recombinant AIF-1 resulted in almost complete reduction of the 50 kDa band and mass spectrometry revealed only AIF-1-specific tryptic protein fragments suggesting that trimerized AIF-1 is the predominant form in vivo. Finally, we analysed mechanisms of neuronal AIF-1 induction. Following H2O2 challenge, a model of general cell stress, we observed the gradual induction of AIF-1 and, more interestingly, release to the supernatant of SKNSH neurones. Parallel reverse transcriptase polymerase chain reaction and sequencing was used to confirm AIF-1 mRNA expression.

AIF-1 is an actin-polymerizing and Rac1-activating protein that promotes vascular smooth muscle cell migration

Development of vascular restenosis is a multifaceted process characterized by migration and proliferation of vascular smooth muscle cells (VSMCs), resulting in loss of lumen diameter. Characterization of proteins that mediate this process is essential in our understanding of the pathogenesis of arterial injury. Allograft inflammatory factor-1 (AIF-1) is a cytoplasmic, calcium-binding protein that is expressed in VSMCs by allograft and balloon angioplasty injury. AIF-1 is not present in cultured human VSMCs but is induced by cytokines, and overexpression of AIF-1 results in increased VSMC growth and cell-cycle gene expression. To characterize AIF-1 modulatory effects in primary human VSMCs, AIF-1-interacting proteins were identified by an AIF-1/glutathione S transferase fusion protein affinity assay. MALDI-TOF mass spectrophotometric amino analysis identified actin as an AIF-1 interacting protein. This interaction was verified by coimmunoprecipitation. This is a functional interaction, because AIF-1 binds to and polymerizes F-actin in vitro. In unstimulated VSMCs, AIF-1 colocalizes with F-actin but translocates to lamellipodia on stimulation with platelet-derived growth factor. VSMCs stably transduced with AIF-1 retrovirus migrate 2.6-fold more rapidly (85.1+/-2.9 versus 225.5+/-16.6; P<0.001) in response to platelet-derived growth factor versus control cells. AIF-1 colocalizes with Rac1, and AIF-1-transduced VSMCs show a constitutive and enhanced activation of Rac1, providing a mechanism for the increased migration. These data indicate that AIF-1 binds and polymerizes F actin and also regulates Rac1 activity and VSMC migration. Considering the AIF-1 expression pattern in injured arteries, this suggests that AIF-1 may be involved in the cytoskeletal signaling network leading to vascular remodeling.

Accumulation of the proinflammatory cytokine endothelial-monocyte-activating polypeptide II in ramified microglial cells in brains of Borna virus infected Lewis rats

Borna disease virus (BDV) infection of adult Lewis rats induces a severe and often fatal neurologic disease characterized by a massive mononuclear meningo-encephalitis, and activation of microglial cells. Therefore, we analyzed expression of endothelial monocyte activating polypeptide II (EMAP II) by immunohistology as a marker for activation of microglial cells in BDV infected rat brains. EMAP II is a chemotactic peptide, inducing activation of macrophages and endothelial cells, and is considered a proinflammatory mediator of the innate immune system. An up to 30-fold increase in numbers of EMAP II+ microglial cells and a massive expression by infiltrating macrophages at perivascular inflammatory foci was observed in infected brains, with a maximum on day 25 after infection. These results provide evidence that EMAP II contributes to immune responses in inflammatory processes caused by viral infections.

Allograft inflammatory factor-1 expression correlates with cardiac rejection and development of cardiac allograft vasculopathy

BACKGROUND

Standard morphological features of endomyocardial biopsy specimens do not necessarily correlate with the efficacy of immunotherapy or development of cardiac allograft vasculopathy (CAV). We hypothesized that expression of allograft inflammatory factor-1 (AIF-1), a cytokine-inducible, calcium-binding protein associated with vascular smooth muscle cell proliferation, would be associated with allograft rejection and development of CAV.

METHODS AND RESULTS

A total of 157 endomyocardial biopsy specimens from 26 patients with heart transplants were examined for expression of AIF-1 mRNA by semiquantitative reverse transcription-polymerase chain reaction. A significant relation was found between the International Society for Heart and Lung Transplantation rejection grade and expression of AIF-1 (P<0.001). The calculated odds ratio indicates that a biopsy has 2.5 times the chance of AIF-1 expression per grade of rejection. The relative concentrations of AIF-1 and GAPDH mRNA were calculated and the resulting ratios indicated that the amount of AIF-1 mRNA expression is relative to the rejection grade (P<0.02). In grade 1 biopsy specimens, AIF-1 was localized to infiltrating immune cells. In grade 3 biopsy specimens, AIF-1 was observed in immune cells and myocytes. AIF-1 is expressed in vascular and immune cells in coronary arteries with CAV, and persistent expression of AIF-1 in the allograft correlates with development of CAV (P<0.002).

CONCLUSIONS

Expression of AIF-1 in cardiac allografts correlates with rejection, and the amount of AIF-1 expressed correlates with the severity of rejection. AIF-1 is expressed in coronary arteries with CAV, and persistent expression of AIF-1 in the cardiac allograft is associated with development of CAV.

Expression of EMAP-II by activated monocytes/microglial cells in different regions of the rat hippocampus after trimethyltin-induced brain damage

Endothelial monocyte-activating polypeptide-II (EMAP-II), a novel cytokine with proinflammatory and antiangiogenic properties, has previously been shown to be expressed by activated monocytes/microglial cells in the rat brain and was therefore considered a useful marker to stage microglial activation in inflammatory lesions. The aim of the present immunohistochemical study was to investigate expression of EMAP-II in the rat hippocampus after intoxication with the organotin compound trimethyltin (TMT). Administration of this neurotoxicant is known to produce brain damage mainly affecting the hippocampal formation, with severe neuronal cell loss being observed predominantly in regions CA-1 and CA-3. The maximum severity of TMT-induced brain damage is observed 21 days after a single ip administration. In this well-characterized model of neurodegeneration, activated microglial cells have been described to occur mainly in the early stages of TMT-induced neurotoxicity. Following TMT intoxication, we observed a significant increase in EMAP-II(+) monocytes/microglial cells in the CA-1 and the CA-3 regions. The CA-2 region, however, was largely spared. While appearance of single EMAP-II(+) microglial cells was observed already after 5 days, EMAP-II immunoreactivity reached its maximum after 21 days and persisted in some of the rats up to 35 days. These findings show a close correlation to the temporal and spatial pattern of neuronal damage described in the rat hippocampus after TMT administration previously. Thus, upregulation of EMAP-II by activated monocytes/microglial cells may serve as a sensitive marker of neurotoxic lesions in the rat brain.

Effects of malnutrition on the expression of daintain/AIF-1 in the gut mucosa of pigs

The allograft inflammatory factor (AIF-1/daintain) is a hormone-like peptide produced by activated monocytic cells in a variety of traumatic, inflammatory and degenerative lesions. Gut-derived AIF-1 has been shown to modulate insulin production and to attenuate autoimmune diabetes. As the localization of this gastrointestinal peptide in the porcine duodenum is not known and the pig is a convenient model for the study of nutritional modulation of the mucosal immune compartment, we have localized expression of AIF-1 by immunohistology in the duodenum of either malnourished (energy and protein supply 50% of demands, n = 5) or optimally fed pigs (n = 5). AIF-1 macrophages were predominantly located at the villus tip. The number of positively stained cells per high-power field was significantly (P < or = 0.001) higher in the malnourished pigs (74.6 +/- 2.44; least square means +/- SEM) compared to optimally fed pigs (32.56 +/- 1.99). It is likely that the effect in malnourished pigs can be explained by a more pronounced antigen contact of macrophages due to loss of epithelial integrity. Thus, AIF-1 is a novel marker for the study of the nutritional regulation of the mucosal immune system of the pig. AIF-1 expression in the duodenum was further validated by polymerase chain reaction and sequencing. Surprisingly, we detected a slight deviation from the original sequence (probably representing an allelic variation) and an AIF-1 splice variant, previously not known to occur in pigs.

The allograft inflammatory factor-1 family of proteins

The allograft inflammatory factor-1 (AIF-1) is a 17 kDa interferon-gamma-inducible Ca(2+)-binding EF-hand protein that is encoded within the HLA class III genomic region. Three proteins are probably identical with AIF-1 termed Iba1 (ionized Ca(2+)-binding adapter), MRF-1 (microglia response factor) and daintain. Considerable but not complete sequence identity with AIF-1 has been described for IRT-1 (interferon-responsive transcript), BART-1 (balloon angioplasty-responsive transcript), and other, yet unassigned alternatively spliced variants. In this review, genomic and functional characteristics of AIF-1-related proteins are summarized and a common nomenclature is proposed.

AIF-1 expression defines a proliferating and alert microglial/macrophage phenotype following spinal cord injury in rats

Microglial cells are among the first and dominant cell types to respond to CNS injury. Following calcium influx, microglial activation leads to a variety of cellular responses, such as proliferation and release of cytotoxic and neurotrophic mediators. Allograft inflammatory factor-1, AIF-1 is a highly conserved EF-handed, putative calcium binding peptide, associated with microglia activation in the brain. Here, we have analyzed the expression of AIF-1 following spinal cord injury at the lesion site and at remote brain regions. Following spinal cord injury, AIF-1+ cells accumulated in parenchymal pan-necrotic areas and perivascular Virchow-Robin spaces. Subsequent to culmination at day 3--a situation characterized by infiltrating blood borne macrophages and microglia activation--AIF-1+ cell numbers decreased until day 7. In remote areas of Wallerian degeneration and delayed neuronal death, a more discrete and delayed activation pattern of AIF-1+ microglia/macrophages reaching maximum levels at day 14 was observed. There was a considerable match between AIF-1+ cells and PCNA (proliferating cell nuclear antigen) or Ki-67+ labeled cells. AIF-1 expression preceded the expression of ED1, thus indicating a pre-phagocytic role. It appears that AIF-1+ microglia/macrophages are among the earliest cells to respond to spinal cord injury. Our results suggest a role of AIF-1 in the initiation of the early microglial response leading to activation and proliferation essential for the acute response to CNS injury. AIF-1 might modulate microgliosis influencing the efficacy of tissue debris removal, myelin degradation, recruitment of oligodendrocytes and re-organisation of the CNS architecture.

Overexpression of allograft inflammatory factor-1 promotes proliferation of vascular smooth muscle cells by cell cycle deregulation

Allograft inflammatory factor-1 (AIF-1) is not present in normal arteries, but its expression is induced in vascular smooth muscle cells (VSMCs) in several models of arterial injury. The proliferation of VSMCs is a major component of neointimal hyperplasia in many arteriopathies, and the purpose of this study was to determine the role of AIF-1 in the growth of VSMCs. Transfection and constitutive expression of AIF-1 in a primary and a rat VSMC line results in enhanced growth of those cells as measured by cell number and is proportional to the amount of AIF-1 expressed. Constitutive expression of AIF-1 results in a shorter cell cycle, as measured by flow cytometry, and aberrant expression of cell cycle proteins, as determined by Western blot. AIF-1 overexpression also permits growth of these cells in serum-reduced media. Collectively, these data suggest that AIF-1 may participate in the progression of vascular proliferative disease on the basis of its ability to regulate the growth of VSMCs.

Suppression of allograft rejection in the sponge Suberites domuncula by FK506 and expression of genes encoding FK506-binding proteins in allografts

Porifera (sponges) are, evolutionarily, the oldest metazoan phylum. Recent molecular data suggest that these animals possess molecules similar to and homologous with those of the innate and adaptive immune systems of higher Metazoa. Applying the biological system of parabiosis and the technique of differential display of mRNA, two cDNAs encoding putative FK506-binding proteins were isolated. FK506 is successfully used in clinics as a drug to prevent allograft rejection and is toxic to Suberites domuncula cells in vitro at doses above 100ng ml−1. Autograft fusion of transplants from S. domuncula was not affected by FK506. Allograft non-fusion was not affected by FK506 at toxic doses; however, at the non-toxic dose of 20ng ml−1, the allografts fused with each other. It is shown that at the attachment zone in untreated and (particularly drastic) in FK506-treated allografts, expression of the genes encoding the FK506-binding proteins is upregulated. These data indicate that the drug FK506 suppresses allograft rejection in S. domuncula, most probably via interaction with expression of the gene coding for the FK506-binding proteins.

A cofactor of tRNA synthetase, p43, is secreted to up-regulate proinflammatory genes

An auxiliary factor of mammalian multi-aminoacyl-tRNA synthetases, p43, is thought to be a precursor of endothelial monocyte-activating polypeptide II (EMAP II) that triggers proinflammation in leukocytes and macrophages. In the present work, however, we have shown that p43 itself is specifically secreted from intact mammalian cells, while EMAP II is released only when the cells are disrupted. Secretion of p43 was also observed when its expression was increased. These results suggest that p43 itself should be a real cytokine secreted by an active mechanism. To determine the cytokine activity and active domain of p43, we investigated tumor necrosis factor (TNF) and interleukin-8 (IL-8) production from human monocytic THP-1 cells treated with various p43 deletion mutants. The full length of p43 showed higher cytokine activity than EMAP II, further supporting p43 as the active cytokine. p43 was also shown to activate MAPKs and NFkappaB, and to induce cytokines and chemokines such as TNF, IL-8, MCP-1, MIP-1alpha, MIP-1beta, MIP-2alpha, IL-1beta, and RANTES. Interestingly, the high level of p43 was observed in the foam cells of atherosclerotic lesions. Therefore, p43 could be a novel mediator of atherosclerosis development as well as other inflammation-related diseases.

Heme oxygenase-1 in lesions of rat experimental autoimmune encephalomyelitis and neuritis

The enzyme heme oxygenase-1 (HO-1) is reducing heme to the gaseous mediator carbon monoxide, to iron and the antioxidant biliverdin. The inducible expression of HO-1 is considered a protective cellular mechanism against reactive oxygen intermediates. Further, carbon monoxide (CO) is a regulator of cGMP synthesis, of NO-synthetases and cyclooxygenases, thereby indirectly modulating reactive processes. Here we report expression of HO-1 in rat experimental autoimmune encephalomyelitis (EAE) and neuritis (EAN). With both models, similar results were obtained: HO-1 was localized predominantly to infiltrating, monocytic, but only rarely to ramified microglial cells or astrocytes surrounding the inflammatory lesions. Prominent expression by monocytic cells was seen from day 11 after immunization correlating with the development of neurologic disease. Further, local expression is persistent for long after cessation of neurologic signs. Thus, HO-1 could be considered a factor in the formation and resolution of inflammatory autoimmune lesions of the nervous system.

Endothelial monocyte-activating polypeptide II, a tumor-derived cytokine that plays an important role in inflammation, apoptosis, and angiogenesis

The interactions between a tumor and its surrounding environment are complex and characterized by a variety of factors. Tumors produce a number of proteins that enable them to recruit a vascular supply, invade into surrounding tissues, and metastasize to distant sites. The host, in turn, responds to these signals by producing its own repertoire of molecules that may either assist or prevent the actions of the tumor. A thorough understanding of this relationship is critical to the development of novel anti-cancer therapies. The tumor-derived cytokine endothelial monocyte-activating polypeptide II (EMAP-II) has profound effects on the tumor as well as on host response. These effects target the inflammatory cascade as well as the processes involved in angiogenesis. In this review the authors describe the current understanding of the role of EMAP-II in inflammation, apoptosis, and angiogenesis and use this molecule to illustrate the complex interactions that occur in the tumor microenvironment.

Augmented expression of daintain/allograft inflammatory factor-1 is associated with clinical disease: dynamics of daintain/allograft inflammatory factor-1 expression in spleen, peripheral nerves and sera during experimental autoimmune neuritis

Experimental autoimmune neuritis (EAN) is an animal model of Guillain-Barré syndrome, characterized by inflammation and demyelination of the peripheral nervous system (PNS). Daintain/allograft inflammatory factor-1 (daintain/AIF-1) is a novel interferon-gamma-inducible protein expressed by macrophages during organ specific autoimmune diseases. To study the involvement of daintain/AIF-1 in EAN we induced EAN in Lewis rats by immunizing with bovine PNS myelin (BPM) and complete Freund's adjuvant (CFA). The expression of daintain/AIF-1 was examined in the spleen, peripheral nerves and sera during the course of EAN by immunohistochemistry and radioimunoassay (RIA). The expression of daintain/AIF-1 in the spleen and in the sciatic nerves peaked at the preclinical stage (day 7 post immunization (p.i.)) and at the height (day 15 p.i.) of clinical EAN, consistent with a disease promoting role for daintain/AIF-1. Daintain/AIF-1 expressing cells represented a subset of ED1+ or CD11b/c+ mononuclear cells. A significant increase of daintain/AIF-1-like immunoreactivity in sera occurred at the preclinical stage of EAN. Taken together, these data indicate that daintain/AIF-1 may play a proinflammatory role in the pathogenesis of EAN.

The cytokine portion of p43 occupies a central position within the eukaryotic multisynthetase complex

Multicellular eukaryotes contain a macromolecular assembly of nine aminoacyl-tRNA synthetase activities and three auxiliary proteins. One of these, p43, is the precursor of endothelial monocyte-activating polypeptide II (EMAP II), an inflammatory cytokine involved in apoptotic processes. As a step toward understanding this paradoxical association, the EMAP II portion of p43 has been localized within the rabbit reticulocyte multisynthetase complex. Immunoblot analysis demonstrates strong reaction of anti-EMAP II antiserum with p43, as well as cross-reactivity with isoleucyl-tRNA synthetase. Electron microscopic images of immunocomplexes show two antibody binding sites. The primary site is near the midpoint of the multisynthetase complex at the intersection of the arms with the base. This site near the lower edge of the central cleft is assigned to the C-terminal cytokine portion of p43. The secondary site of antibody binding is in the base of the particle and maps the location of isoleucyl-tRNA synthetase. These data allow refinement of the three-domain model of polypeptide distribution within the multisynthetase complex. Moreover, the central location of p43/EMAP II suggests a role for this polypeptide in optimizing normal function and in rapid disruption of essential cellular machinery when apoptosis is signaled.