Myeloperoxidase-positive Neutrophils Research Articles

Xenogenous implanted dental follicle stem cells promote periodontal regeneration through inducing the N2 phenotype of neutrophils

BackgroundPeriodontal tissue loss is the main reason for tooth mobility and loss caused by periodontal disease. Dental follicle stem cells (DFSCs) have significant therapeutic potential in periodontal regeneration, which maybe mainly depends on their potent immunomodulatory capacity. Consequently, this study aims to elucidate the impact of implanted xenogenous DFSCs on innate immune responses during early and late stages in the periodontal defect repair period.MethodsTo trace and investigate the immunomodulation mechanisms of DFSCs in vivo, DFSCs were engineered (E-DFSCs) using lentiviral vectors expressing CD63-enhanced green fluorescent protein (CD63-EGFP) and β-Actin-mCherry protein (ACTB-mCherry) to exhibit green and red fluorescence. The biological characteristics and functions of E-DFSCs were verified by proliferation, differentiation, and co-culture experiments in vitro. In vivo, the periodontal regeneration capacity of E-DFSCs was detected by implantation of murine periodontal defect model, and the response of innate immune cells was detected at the 1st, 3rd, and 5th days (early stage) and 4th week (late stage) after implantation.ResultsIn vitro assessments showed that E-DFSCs retain similar properties to their non-engineered counterparts but exhibit enhanced macrophage immunomodulation capability. In mice models, four-week micro-CT and histological evaluations indicated that E-DFSCs have equivalent efficiency to DFSCs in periodontal defect regeneration. At the early stage of repair in mice periodontal defect, fluorescence tracking showed that implanted E-DFSCs might primarily activate endogenous cells through direct contact and indirect actions, and most of these cells are myeloperoxidase-positive neutrophils. Additionally, compared with the control group, the neutrophilic infiltration and conversion of N2-type were significantly increased in the E-DFSC group. At the late stage of defect regeneration, more M2-type macrophages, fewer TRAP + osteoclasts, and an upregulated OPG/RANKL ratio were detected in the E-DFSC group compared to the control group, which indicated that immune balance tilts towards healing and bone formation.ConclusionThe xenogenous implanted DFSCs can induce the N2 phenotype of neutrophils in the early stage, which can activate the innate immune mechanism of the host to promote periodontal tissue regeneration.

The potential of disulfiram as a drug to improve the prognosis after the onset of subarachnoid hemorrhage

Subarachnoid hemorrhage due to rupture of intracranial aneurysms has a poor outcome, making this disease being the social problem. Inflammation evoked by the increase in intracranial pressure and the clot in the subarachnoid space after the onset of SAH exacerbates neuronal death and vasospasm, resulting in the poor outcome and severe aftereffects. Here, FROUNT mediates CCR2 and CCR5 signaling as an intracellular molecule binding to these chemoattractant receptors which facilitate the migration of inflammatory cells, such as macrophages, in situ to trigger inflammation there. Animal model of subarachnoid hemorrhage was established in rats through intrathecal injection of autologous blood. The effect of the FROUNT inhibitor, disulfiram, on survival rate, neuronal death in hippocampus or vasospasm was then examined. The intrathecal administration of disulfiram significantly suppressed the infiltration of CD68-positive macrophages and myeloperoxidase-positive neutrophils toward the clot in the cistern in situ. In this condition, disulfiram ameliorated the death of animals after the onset of subarachnoid hemorrhage in rats. In addition, disulfiram suppressed both the two major events after subarachnoid hemorrhage, the neuronal death in hippocampus and vasospasm. The pharmacological inhibition of CCR2 and CCR5 signaling by disulfiram could thus be the therapeutic strategy to improve the outcome of subarachnoid hemorrhage.

SIRT1 downregulation in pneumonia is associated with an immature neutrophil response and increased disease severity.

Pneumonia remains a common complication in trauma patients. Sirtuin 1 (SIRT1) is an anti-inflammatory NAD + -dependent deacetylase that has been shown to reduce the severity of ARDS in polymicrobial sepsis. The impact of SIRT1 in acute pneumonia, however, remains unknown. We hypothesized that SIRT1 deletion in pneumonia would worsen the inflammatory response and clinical severity, and that increased SIRT1 expression would be protective. Ten- to 14-week-old male and female SIRT1 knockout (S1KO) mice, SIRT1 overexpressor (S1OE) mice, and their wildtype (WT) littermates underwent intra-tracheal inoculation with Pseudomonas aeruginosa . Rectal temperature was recorded, SIRT1 lung protein was quantified by western blotting, Sirt1 mRNA was measured by qPCR, and lung leukocyte subpopulations were analyzed by flow cytometry. Data were analyzed by one-way ANOVA using Prism software. Pneumonia created a functional SIRT1 knockdown in the lungs of WT mice by 4 hours, resulting in comparable SIRT1 levels and temperatures to the S1KO mice by 12 hours. Pneumonia also partially reduced SIRT1expression in S1OE mice, but S1OE mice still had improved thermoregulation 12 hours after pneumonia. In all groups, Sirt1 mRNA expression was not affected by infection. Sirtuin 1 deletion was associated with decreased neutrophil infiltration in the lung, as well as a shift toward a more immature neutrophil phenotype. SIRT1 deletion was also associated with decreased myeloperoxidase-positive neutrophils in the lungs following pneumonia, indicating decreased neutrophil activity. S1OE mice had no change in lung leukocyte subpopulations when compared to WT. Pneumonia creates a functional SIRT1 knockdown in mice. SIRT1 deletion altered the early inflammatory cell response to pneumonia, resulting in a neutrophil response that would be less favorable for bacterial clearance. Despite overexpression of SIRT1, S1OE mice also developed low SIRT1 levels and exhibited only minimal improvement. This suggests increasing SIRT1 transcription is not sufficient to overcome pneumonia-induced downregulation and has implications for future treatment options. Targeting SIRT1 through increasing protein stability may promote a more efficient inflammatory cell response to pneumonia, thereby preventing subsequent lung injury.

Abstract 15421: Mice Deficient in Endothelial Cell-Selective Adhesion Molecule Display Coronary Microvascular Rarefaction and Left Ventricle Diastolic Dysfunction

Coronary microvascular dysfunction and chronic inflammation play a role in the development of left ventricular diastolic dysfunction (LVDD) in heart failure with preserved ejection fraction (HFpEF). Endothelial cell-selective adhesion molecule (ESAM) is part of the endothelial cell junction complex, which plays a role in the maintenance of cell barrier function, inflammatory cell transmigration and angiogenesis. Here, we examined the role of ESAM in affecting coronary microvascular density and left ventricle diastolic function by employing mice with genetic deletion of ESAM (ESAM -/- ). Using echocardiography, we found that ESAM -/- mice display LVDD, as indicated by a significantly (p<0.05) reduced E/A ratio (E=early, A=late mitral inflow peak velocities), increased E/e’ ratio, isovolumic relaxation time and E wave deceleration time, with no change in the ejection fraction. Using an unbiased, automated tracing and 3D reconstruction of microvascular network revealed that ESAM -/- mice have a reduced coronary microvascular density, which was accompanied by myocardial accumulation of myeloperoxidase-positive neutrophils and elevated myocardial levels of inflammatory cytokines and chemokines. ESAM -/- mice exhibited a reduced endothelial sprout formation in the carotid artery, whereas in cultured endothelial cells siRNA-mediated ESAM knockdown impaired tube formation. Thus, ESAM deficiency in mice leads to coronary microvascular rarefaction, which likely via a myocardial hypoperfusion-related neutrophil accumulation and inflammatory mediator production impairs LV diastolic function.

Orally delivered perilla (Perilla frutescens) leaf extract effectively inhibits SARS-CoV-2 infection in a Syrian hamster model

On analyzing the results of cell-based assays, we have previously shown that perilla (Perilla frutescens) leaf extract (PLE), a food supplement and orally deliverable traditional Chinese medicine approved by the Taiwan Food and Drug Administration, effectively inhibits SARS-CoV-2 by directly targeting virions. PLE was also found to modulate virus-induced cytokine expression levels. In this study, we explored the anti-SARS-CoV-2 activity of PLE in a hamster model by examining viral loads and virus-induced immunopathology in lung tissues. Experimental animals were intranasally challenged with different SARS-CoV-2 doses. Jugular blood samples and lung tissue specimens were obtained in the acute disease stage (3−4 post-infection days). As expected, SARS-CoV-2 induced lung inflammation and hemorrhagic effusions in the alveoli and perivascular areas; additionally, it increased the expression of several immune markers of lung injury − including lung Ki67-positive cells, Iba-1-positive macrophages, and myeloperoxidase-positive neutrophils. Virus-induced lung alterations were significantly attenuated by orally administered PLE. In addition, pretreatment of hamsters with PLE significantly reduced viral loads and immune marker expression. A purified active fraction of PLE was found to confer higher antiviral protection. Notably, PLE prevented SARS-CoV-2-induced increase in serum markers of liver and kidney function as well as the decrease in serum high-density lipoprotein and total cholesterol levels in a dose-dependent fashion. Differently from lung pathology, monitoring of serum biomarkers in Syrian hamsters may allow a more humane assessment of the novel drugs with potential anti-SARS-CoV-2 activity. Our results expand prior research by confirming that PLE may exert an in vivo therapeutic activity against SARS-CoV-2 by attenuating viral loads and lung tissue inflammation, which may pave the way for future clinical applications.

HMGB1 Inhibitor Effectively Alleviates Psoriasis-Like Lesions and Inflammatory Cytokines in K14-VEGF Transgenic Mice

Objective: Anti-high-mobility group box 1 (HMGB1) is involved in the pathogenesis of many inflammatory and autoimmune diseases, including psoriasis. The present study aimed to investigate the therapeutic effects of HMGB1 monoclonal antibody (mAb) in keratin 14 (K14)-vascular endothelial growth factor (VEGF) transgenic homozygous mice. Methods: Twelve VEGF transgenic mice were randomly divided into two groups of six mice each: the anti-HMGB1 mAb group and the immune complex (IC) mAb group. The mice underwent intraperitoneal injection of anti-HMGB1 mAb or IC mAb once every 2 days for a total of three treatments. Compare the lesions on the ears of the mice and evaluate the severity of the lesions using the baseline and clinical scores on the last day of treatment. The changes in psoriasis-like lesions, cellular infiltration of T cells, dendritic cells, and neutrophils were detected by hematoxylin–eosin staining and immunohistochemistry. The mRNA expression of the inflammatory cytokines, including interleukin (IL)-6, tumor necrosis factor-α, interferon-γ, and IL-17 in the lesions were assessed by real-time quantitative polymerase chain reaction. The number of γ δ T cells in the lesions of two groups were detected by flow cytometry. The t test was used to compare their differences. Results: The anti-HMGB1 mAb effectively ameliorated the clinical skin lesions. The clinical scores in the anti-HMGB1 mAb group were lower than those in the IC mAb group (6.00 ± 0.52 vs. 10.83 ± 0.48, P < 0.001). Histopathologic changes and improvements in the K14-VEGF transgenic homozygous mice were evident after three treatments. The scores of mice in the anti-HMGB1 mAb group were significantly lower than those in the IC mAb group (3.25 ± 0.71 vs. 6.95 ± 0.83, P = 0.0033). The average epidermal thickness in the anti-HMGB1 mAb group was reduced by about 45% when compared with that in the IC mAb group (32.15 ± 7.08 vs. 64.69 ± 7.93, P = 0.0054). Moreover, anti-HMGB1 mAb also decreased the number of infiltrating CD3+ T cells, myeloperoxidase-positive neutrophils, and CD11c+ dendritic cells. The ratio of ear skin γ δ T cells was reduced in anti-HMGB1 mAb treated group. The mRNA expression of IL-6, tumor necrosis factor-α, interferon-γ, and IL-17 in the anti-HMGB1 mAb group were significantly reduced when compared with IC mAb group (0.36 ± 0.070 vs.1.98 ± 0.62, P = 0.0148; 6.43 ± 1.37 vs. 13.80 ± 1.33, P = 0.0006; 2.62 ± 0.83 vs. 7.77 ± 1.32, P = 0.0026; 4.69 ± 1.13 vs.11.41 ± 1.92, P = 0.0054). Conclusion: HMGB1 blockade (anti-HMGB1 mAb) reduced leukocyte infiltration and suppressed inflammatory cytokine expression in this K14-VEGF transgenic mouse model, markedly reducing the severity of the psoriasis-like lesions. HMGB1 blockade might serve as a potential target for the treatment of psoriasis.

Leptospiral meningoencephalitis in a raccoon dog.

Neuroleptospirosis is a rare disease caused by pathogenic Leptospira interrogans in humans; however, it has not been fully studied in animals. A young wild raccoon dog was found convulsing in the recumbent position and died the next day. Histologic examination revealed nonsuppurative meningoencephalitis in the cerebrum, cerebellum, midbrain, and medulla oblongata. The lesions consisted of mixed infiltrates of Iba1-positive macrophages and CD3-positive T cells, with a small number of CD79α-positive B cells and myeloperoxidase-positive neutrophils. In the frontal cortex, perivascular cuffs and adjacent microglial nodules were distributed diffusely, especially in the molecular layer. Glial nodules were comprised of Iba1- and myeloperoxidase-positive activated microglia. Immunohistochemistry revealed leptospires in mononuclear cell perivascular cuffs, but not in glial nodules. Neuroleptospirosis was accompanied by Leptospira-related nonsuppurative interstitial nephritis, pulmonary edema and hemorrhage, and coronary periarteritis, as well as Toxocara tanuki in the small intestine and nonspecific foreign-body granulomas in the lungs and stomach.

Bacterial Peptidoglycan and Leukocyte Reactivity in the Brain Following Ischaemic Stroke

It has recently been reported that bacteria found in the brain of neurodegenerative diseases, such as Alzheimer’s and amyotrophic lateral sclerosis, may cause neuroinflammation. Whilst infiltrating immune cells into brain are a key contributor to the pathophysiology of ischaemic stroke, whether or not this is due to the presence of bacteria within the brain remains to be determined. Therefore, the aim of this study was to establish whether peptidoglycan positive bacteria located within the ischaemic hemisphere post‐stroke attract infiltrating immune cells. To test this aim, C57BL6 male mice (8–12 weeks old) were subjected to either photothrombotic stroke (n=16), 0.5 h middle cerebral artery occlusion (MCAO, n=12) or sham surgery (n=12). Functional tests assessing motor function were conducted pre‐surgery, 24 h and/or 72 h post‐surgery. Infarct volume was assessed at 24 or 72 h post‐stroke via thionin staining and infiltrating immune cells within the brain were identified by immunofluorescence. Photothrombosis or MCAO caused significant functional impairment, as determined by the hanging wire and cylinder tests, compared to sham (P<0.05). Photothrombotic stroke caused cortical infarct damage whereas MCAO induced hypothalamic, thalamic, hippocampal and cortical infarct damage. Peptidoglycan immunoreactivity was observed within the infarct core of both ischaemic stroke models at 24 and 72 h post‐surgery. Whilst infiltrating myeloperoxidase‐positive neutrophils were located in close proximity with peptidoglycan‐positive cells at 24 h post‐stroke, F4/80‐positive macrophages were co‐localised with peptidoglycan‐positive cells at 72 h post‐stroke. Collectively, these data suggest that bacteria located in the infarct core following cerebral ischaemia may trigger an immune response, and thus could be a therapeutic target for stroke patients.

Infiltration by myeloperoxidase-positive neutrophils is an independent prognostic factor in breast cancer.

Myeloperoxidase (MPO) is an enzyme secreted by neutrophil granulocytes as a result of phagocytosis during inflammation. In colorectal cancer, tumour infiltration by MPO expressing cells has been shown to be independently associated with a favourable prognosis. In this study, we explored the role of MPO-positive cell infiltration and its prognostic significance in invasive breast cancer. We performed immunohistochemical staining for MPO on multiple tissue microarrays comprising a total of 928 human breast cancer samples with detailed clinical-pathological annotation and outcome data. MPO-positive cell infiltration (≥ 5 cells/tissue punch) was found in 150 (16%) of the 928 evaluable breast cancer cases. In univariate survival analyses, infiltration by MPO-positive cells was associated with a significantly better overall survival (p < 0.001). In subset univariate analyses, the infiltration by MPO-positive cells was associated with significantly better overall survival in the Luminal B/HER2-negative subtype (p = 0.005), the HER2 enriched subtype (p = 0.011), and the Triple Negative subtype (p < 0.001). In multivariate analysis, MPO expression proved to be an independent prognostic factor for improved overall survival (p < 0.001). This is the first study to show that infiltration of MPO-positive cells is an independent prognostic biomarker for improved overall survival in human breast cancer.

P241 - Infiltration by Myeloperoxidase positive neutrophils is an independent prognostic factor in breast cancer

P241 - Infiltration by Myeloperoxidase positive neutrophils is an independent prognostic factor in breast cancer

Acute (gangrenous) esophageal necrosis (black esophagus). A rare form of injury with specific histologic features and diverse clinical associations with a common pathogenesis

Acute esophageal necrosis (AEN) also known as black esophagus is a rare form of injury to the esophageal mucosa that complicates a variety of clinical conditions. It is characterized by circumferential black discoloration of the mucosa. There is little information relating to the histopathologic features and pathogenesis of this condition. In this study we describe the histopathologic features of six cases of AEN (3 autopsy and 3 biopsy cases) and compared the finding to 26 cases of ulcerated esophagitis. Cases and controls were assessed for type of necrosis, inflammatory cells, vascular thrombi, pigment deposits, granulation tissue and presence of viable mucosa. Cases were evaluated with histochemical stains for iron and microorganisms and immunohistochemical stains to inflammatory cells (myeloperoxidase, CD20, CD3 and CD163), squamous cells (pancytokeratin and p40) and muscle (smooth muscle actin). Most patients were males (60%) with an average age of 58 years. All specimens show the characteristic black discoloration of the mucosa. Microscopic examination revealed a distinct band of basophilic necrosis, Prussian blue-negative pigment deposits and fibrin thrombi in vessels. Myeloperoxidase-positive neutrophils were seen beneath the area of necrosis and CD163-positive macrophages throughout the esophagus. Basophilic necrosis was never seen in control cases. Only one control case showed intravascular thrombi and pigment deposits. We conclude that the combination of basophilic necrosis, intravascular thrombi and pigment deposits are diagnostic of AEN. We theorize that microvascular occlusion is the unifying lesion that explains the diversity of conditions associated with this disorder.

Aging alters the immunological response to ischemic stroke

The peripheral immune system plays a critical role in aging and in the response to brain injury. Emerging data suggest inflammatory responses are exacerbated in older animals following ischemic stroke; however, our understanding of these age-related changes is poor. In this work, we demonstrate marked differences in the composition of circulating and infiltrating leukocytes recruited to the ischemic brain of old male mice after stroke compared to young male mice. Blood neutrophilia and neutrophil invasion into the brain were increased in aged animals. Relative to infiltrating monocyte populations, brain-invading neutrophils had reduced phagocytic potential, and produced higher levels of reactive oxygen species and extracellular matrix-degrading enzymes (i.e., MMP-9), which were further exacerbated with age. Hemorrhagic transformation was more pronounced in aged versus young mice relative to infarct size. High numbers of myeloperoxidase-positive neutrophils were found in postmortem human brain samples of old (> 71 years) acute ischemic stroke subjects compared to non-ischemic controls. Many of these neutrophils were found in the brain parenchyma. A large proportion of these neutrophils expressed MMP-9 and positively correlated with hemorrhage and hyperemia. MMP-9 expression and hemorrhagic transformation after stroke increased with age. These changes in the myeloid response to stroke with age led us to hypothesize that the bone marrow response to stroke is altered with age, which could be important for the development of effective therapies targeting the immune response. We generated heterochronic bone marrow chimeras as a tool to determine the contribution of peripheral immune senescence to age- and stroke-induced inflammation. Old hosts that received young bone marrow (i.e., Young → Old) had attenuation of age-related reductions in bFGF and VEGF and showed improved locomotor activity and gait dynamics compared to isochronic (Old → Old) controls. Microglia in young heterochronic mice (Old → Young) developed a senescent-like phenotype. After stroke, aged animals reconstituted with young marrow had reduced behavioral deficits compared to isochronic controls, and had significantly fewer brain-infiltrating neutrophils. Increased rates of hemorrhagic transformation were seen in young mice reconstituted with aged bone marrow. This work suggests that age alters the immunological response to stroke, and that this can be reversed by manipulation of the peripheral immune cells in the bone marrow.

Class I histone deacetylase (HDAC) inhibitor CI-994 promotes functional recovery following spinal cord injury

Spinal cord injury (SCI) induces severe and long-lasting neurological disability. Accumulating evidence has suggested that histone deacetylase (HDAC) inhibitors exert neuroprotective effects against various insults and deficits in the central nervous system. In the present study, we assessed the effect of the class I HDAC inhibitor CI-994 in a mouse model of SCI. Following SCI, mice were treated with either dimethyl sulfoxide (control vehicle) or 1, 10, or 30 mg/kg CI-994. Level of acetylated histone H3 expression was increased in the motor cortex and spinal cord of 10 mg/kg CCI-994-treated mice after SCI. CI-994 increased histone H3 acetylation in the myeloperoxidase-positive neutrophils and CD68-positive microglia/macrophages in the spinal cord. Although it did not appear to contribute to corticospinal tract axonal reorganization, intraperitoneal injection of CI-994 promoted behavioral recovery following SCI. Furthermore, administration of CI-994 suppressed neutrophil accumulation, inflammatory cytokine expressions, and neuronal loss as early as 3 days following injury. Thus, our findings indicate that HDAC inhibitors may improve functional recovery following SCI, especially during the early stages of the disease.

Histamine drives severity of innate inflammation via histamine 4 receptor in murine experimental colitis.

Ulcerative colitis (UC) patients exhibit elevated histamine, but how histamine exacerbates disease is unclear since targeting histamine 1 receptor (H1R) or H2R is clinically ineffective. We hypothesized that histamine functioned instead through the other colon-expressed histamine receptor, H4R. In humans, UC patient biopsies exhibited increased H4R RNA and protein expression over control tissue, and immunohistochemistry showed that H4R was in proximity to immunopathogenic myeloperoxidase-positive neutrophils. To characterize this association further, we employed both the oxazolone (Ox)- and dextran sulfate sodium (DSS)-induced experimental colitis mouse models and also found upregulated H4R expression. Mast cell (MC)-derived histamine and H4R drove experimental colitis, as H4R−/− mice had lower symptom scores, neutrophil-recruitment mediators (colonic IL-6, CXCL1, CXCL2), and mucosal neutrophil infiltration than wild-type (WT) mice, as did MC-deficient KitW-sh/W-sh mice reconstituted with histidine decarboxylase–deficient (HDC−/−) bone marrow–derived MCs compared to WT-reconstituted mice; adaptive responses remained intact. Furthermore, Rag2−/−×H4R−/− mice had reduced survival, exacerbated colitis, and increased bacterial translocation than Rag2−/− mice, revealing an innate protective anti-bacterial role for H4R. Taken together, colonic MC-derived histamine initiates granulocyte infiltration into the colonic mucosa through H4R, suggesting alternative therapeutic targets beyond adaptive immunity for UC.

Human T-cell leukemia virus type 1 infects multiple lineage hematopoietic cells in vivo.

Human T-cell leukemia virus type 1 (HTLV-1) infects mainly CD4+CCR4+ effector/memory T cells in vivo. However, it remains unknown whether HTLV-1 preferentially infects these T cells or this virus converts infected precursor cells to specialized T cells. Expression of viral genes in vivo is critical to study viral replication and proliferation of infected cells. Therefore, we first analyzed viral gene expression in non-human primates naturally infected with simian T-cell leukemia virus type 1 (STLV-1), whose virological attributes closely resemble those of HTLV-1. Although the tax transcript was detected only in certain tissues, Tax expression was much higher in the bone marrow, indicating the possibility of de novo infection. Furthermore, Tax expression of non-T cells was suspected in bone marrow. These data suggest that HTLV-1 infects hematopoietic cells in the bone marrow. To explore the possibility that HTLV-1 infects hematopoietic stem cells (HSCs), we analyzed integration sites of HTLV-1 provirus in various lineages of hematopoietic cells in patients with HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) and a HTLV-1 carrier using the high-throughput sequencing method. Identical integration sites were detected in neutrophils, monocytes, B cells, CD8+ T cells and CD4+ T cells, indicating that HTLV-1 infects HSCs in vivo. We also detected Tax protein in myeloperoxidase positive neutrophils. Furthermore, dendritic cells differentiated from HTLV-1 infected monocytes caused de novo infection to T cells, indicating that infected monocytes are implicated in viral spreading in vivo. Certain integration sites were re-detected in neutrophils from HAM/TSP patients at different time points, indicating that infected HSCs persist and differentiate in vivo. This study demonstrates that HTLV-1 infects HSCs, and infected stem cells differentiate into diverse cell lineages. These data indicate that infection of HSCs can contribute to the persistence and spread of HTLV-1 in vivo.

Glycyrrhizin protects against focal cerebral ischemia via inhibition of T cell activity and HMGB1-mediated mechanisms.

BackgroundGlycyrrhizin (Gly) protects against brain injury induced by stroke. We studied whether Gly achieves its protection by inhibiting T cell activity and high-mobility group box 1 (HMGB1) release in the ischemic brain.MethodsStroke was induced by transient middle cerebral artery occlusion in rats and mice. Gly was injected intraperitoneally before or after stroke. We measured infarction, neuroinflammatory cells, gene expressions of interferon-γ (IFNγ), IL-4, and IL-10 in CD4 T cells, HMGB1 release, and T cell proliferation in cultured splenocytes.ResultsGly treatment reduced infarctions and neuroinflammation characterized by the infiltration of CD68-positive macrophages and myeloperoxidase-positive neutrophils, which corresponds to a reduction in the number of T cells and their subsets, CD4 and CD8 T cells, in the ischemic brain, as measured by flow cytometry. Unlike in wild-type animals, Gly did not offer protection in nude rats and severe combined immunodeficient (SCID) mice who had no T cells, while Gly reduced infarction in both nude rats and SCID mice whose T cells were reconstituted, suggesting that T cells should be the target of Gly. In addition, Gly administration inhibited T cell proliferation stimulated by ConA in in vitro assays and inhibited HMGB1 release from the ischemic brain. Furthermore, Gly attenuated gene expression of IFNγ, but not IL-4 and IL-10 in CD4 T cells. Lastly, HMGB1 promoted T cell proliferation stimulated by ConA, which was inhibited by the addition of Gly.ConclusionsGly blocks infarction by inhibiting IFNγ-mediated T cell activity, which is at least partly modulated by HMGB1 activity.

Dendritic cell immunoreceptor 1 alters neutrophil responses in the development of experimental colitis

BackgroundUlcerative colitis, an inflammatory bowel disease, is associated with the massive infiltration of neutrophils. Although the initial infiltration of neutrophils is beneficial for killing bacteria, it is presumed that persistent infiltration causes tissue damage by releasing antibacterial products as well as inflammatory cytokines. A murine C-type lectin receptor, dendritic cell immunoreceptor 1 (Dcir1), is expressed on CD11b+ myeloid cells, such as macrophages, dendritic cells and neutrophils. It was reported that Dcir1 is required to maintain homeostasis of the immune system to prevent autoimmunity, but it is also involved in the development of infectious disease resulting in the enhanced severity of cerebral malaria. However, the role of Dcir1 in intestinal immune responses during colitis remains unclear. In this study, we investigated the role of Dcir1 in intestinal inflammation using an experimental colitis model induced with dextran sodium sulfate (DSS).ResultsIn contrast to wild type (WT) mice, Dcir1−/− mice exhibited mild body weight loss during the course of DSS colitis accompanied by reduced colonic inflammation. Dcir1 deficiency caused a reduced accumulation of neutrophils in the inflamed colon on day 5 of DSS colitis compared with WT mice. Consistently, the production of a neutrophil-attracting chemokine, MIP-2, was also decreased in the Dcir1−/− colon compared with the WT colon on day 5. There were fewer myeloperoxidase-positive neutrophils in the inflamed colon of Dcir1−/− mice than in that of WT mice. Moreover, bone marrow neutrophils from Dcir1−/− mice produced less reactive oxygen species (ROS) by lipopolysaccharide stimulation than those from WT mice. This suggests that Dcir1 deficiency decreases the accumulation of tissue destructive neutrophils during DSS colitis.ConclusionDcir1 enhances the pathogenesis of DSS colitis by altering neutrophil recruitment and their functions.

Imaging Inflammation in Cerebrovascular Disease.

Imaging inflammation in large intracranial artery pathology may play an important role in the diagnosis of and risk stratification for a variety of cerebrovascular diseases. Looking beyond the lumen has already generated widespread excitement in the stroke community, and the potential to unveil molecular processes in the vessel wall is a natural evolution to develop a more comprehensive understanding of the pathogenesis of diseases, such as ICAD and brain aneurysms.

Heme Oxygenase-1 Gene Therapy Provides Cardioprotection Via Control of Post-Ischemic Inflammation: An Experimental Study in a Pre-Clinical Pig Model

BackgroundHeme oxygenase-1 (HO-1) is an inducible stress-responsive enzyme converting heme to bilirubin, carbon monoxide, and free iron, which exerts anti-inflammatory and antiapoptotic effects. Although efficient cardioprotection after HO-1 overexpression has been reported in rodents, its role in attenuating post-ischemic inflammation is unclear. ObjectivesThis study assessed the efficacy of recombinant adenoassociated virus (rAAV)-encoding human heme oxygenase-1 (hHO-1) in attenuating post-ischemic inflammation in a murine and a porcine ischemia/reperfusion model. MethodsMurine ischemia was induced by 45 min of left anterior descending occlusion, followed by 24 h of reperfusion and functional as well as fluorescent-activated cell sorting analysis. Porcine hearts were subjected to 60 min of ischemia and 24h of reperfusion before hemodynamic and histologic analyses were performed. ResultsHuman microvascular endothelial cells transfected with hHO-1 displayed an attenuated interleukin-6 and intercellular adhesion molecule 1 expression, resulting in reduced monocytic THP-1 cell recruitment in vitro. In murine left anterior descending occlusion and reperfusion, the post-ischemic influx of CD45+ leukocytes, Ly-6G+ neutrophils, and Ly-6Chigh monocytes was further exacerbated in HO-1-deficient hearts and reversed by rAAV.hHO-1 treatment. Conversely, in our porcine model of ischemia, the post-ischemic influx of myeloperoxidase-positive neutrophils and CD14+ monocytes was reduced by 49% and 87% after rAAV.hHO-1 transduction, similar to hHO-1 transgenic pigs. Functionally, rAAV.hHO-1 and hHO-1 transgenic left ventricles displayed a smaller loss of ejection fraction than control animals. ConclusionsWhereas HO-1 deficiency exacerbates post-ischemic cardiac inflammation in mice, hHO-1 gene therapy attenuates inflammation after ischemia and reperfusion in murine and porcine hearts. Regional hHO-1 gene therapy provides cardioprotection in a pre-clinical porcine ischemia/reperfusion model.

Gut bacteria require neutrophils to promote mammary tumorigenesis.

Recent studies suggest that gastrointestinal tract microbiota modulate cancer development in distant non-intestinal tissues. Here we tested mechanistic hypotheses using a targeted pathogenic gut microbial infection animal model with a predilection to breast cancer. FVB-Tg(C3-1-TAg)cJeg/JegJ female mice were infected by gastric gavage with Helicobacter hepaticus at three-months-of-age putting them at increased risk for mammary tumor development. Tumorigenesis was multifocal and characterized by extensive infiltrates of myeloperoxidase-positive neutrophils otherwise implicated in cancer progression in humans and animal models. To test whether neutrophils were important in etiopathogenesis in this bacteria-triggered model system, we next systemically depleted mice of neutrophils using thrice weekly intraperitoneal injections with anti-Ly-6G antibody. We found that antibody depletion entirely inhibited tumor development in this H. hepaticus-infected model. These data demonstrate that host neutrophil-associated immune responses to intestinal tract microbes significantly impact cancer progression in distal tissues such as mammary glands, and identify gut microbes as novel targets for extra-intestinal cancer therapy.