Toll-like receptor 9 signaling mediates the anti-inflammatory effects of probiotics in murine experimental colitis

BACKGROUND & AIMS: We tested whether the attenuation of experimental colitis by live probiotic bacteria is due to their immunostimulatory DNA, whether toll-like receptor (TLR) signaling is required, and whether nonviable probiotics are effective. METHODS: Methylated and unmethylated genomic DNA isolated from probiotics (VSL-3), DNAse-treated probiotics and Escherichia coli (DH5 alpha) genomic DNA were administered intragastrically (i.g.) or subcutaneously (s.c.) to mice prior to the induction of colitis. Viable or gamma-irradiated probiotics were administered i.g. to wild-type mice and mice deficient in different TLR or in the adaptor protein MyD88, 10 days prior to administration of dextran sodium sulfate (DSS) to their drinking water and for 7 days thereafter. RESULTS: Intragastric and s.c. administration of probiotic and E. coli DNA ameliorated the severity of DSS-induced colitis, whereas methylated probiotic DNA, calf thymus DNA, and DNase-treated probiotics had no effect. The colitis severity was attenuated to the same extent by i.g. delivery of nonviable gamma-irradiated or viable probiotics. Mice deficient in MyD88 did not respond to gamma-irradiated probiotics. The severity of DSS-induced colitis in TLR2 and TLR4 deficient mice was significantly decreased by i.g. administration of gamma-irradiated probiotics, whereas, in TLR9-deficient mice, gamma-irradiated probiotics had no effect. CONCLUSIONS: The protective effects of probiotics are mediated by their own DNA rather than by their metabolites or ability to colonize the colon. TLR9 signaling is essential in mediating the anti-inflammatory effect of probiotics, and live microorganisms are not required to attenuate experimental colitis because nonviable probiotics are equally effective.     

The possible association between the presence of an MPO −463 G > A (rs2333227) polymorphism and cervical cancer risk

Purpose

The association between myeloperoxidase (MPO) polymorphism and the risk of cervical cancer is inconclusive. We performed a meta-analysis to clarify if a correlation exists between MPO polymorphism and the risk for developing cervical cancer.

Immunohistochemical and genetic evidence of myeloperoxidase involvement in multiple sclerosis

The myeloperoxidase enzyme (MPO) is expressed specifically in myeloid cells and catalyzes the formation of hypochlorous acid and other cytotoxic oxidants. We previously reported that two alleles of MPO exist which differ in promoter strength due to a base difference in an Alu-encoded hormone response element. The present study shows that the higher expressing MPO genotype is overrepresented in early onset multiple sclerosis in females, implicating MPO in this demyelinating disease. Contrary to the general conception that macrophages lack MPO, immunohistochemical analysis shows that MPO is present in microglia/macrophages in and around MS lesions as shown by colocalization with major histocompatibility antigens HLA-DR and phagocytized myelin. Also, MPO mRNA sequences are detected in cDNA derived from isolated human adult microglia. This is the first evidence that MPO is present in microglia/macrophages at MS lesions, that MPO gene expression occurs in microglia and that MPO plays a role in MS pathogenesis as shown by the allelic disequilibrium in early onset disease.     

Elevated activity and microglial expression of myeloperoxidase in demyelinated cerebral cortex in multiple sclerosis

Recent studies have revealed extensive cortical demyelination in patients with progressive multiple sclerosis (MS). Demyelination in gray matter lesions is associated with activation of microglia. Macrophages and microglia are known to express myeloperoxidase (MPO) and generate reactive oxygen species during myelin phagocytosis in the white matter. In the present study we examined the extent of microglial activation in the cerebral cortex and the relationship of microglial activation and MPO activity to cortical demyelination. Twenty-one cases of neuropathologically confirmed multiple sclerosis, with 34 cortical lesions, were used to assess microglial activation. HLA-DR immunolabeling of activated microglia was significantly higher in demyelinated MS cortex than control cortex and, within the MS cohort, was significantly greater within cortical lesions than in matched non-demyelinated areas of cortex. In homogenates of MS cortex, cortical demyelination was associated with significantly elevated MPO activity. Immunohistochemistry revealed MPO in CD68-positive microglia within cortical plaques, particularly toward the edge of the plaques, but not in microglia in adjacent non-demyelinated cortex. Cortical demyelination in MS is associated with increased activity of MPO, which is expressed by a CD68-positive subset of activated microglia, suggesting that microglial production of reactive oxygen species is likely to be involved in cortical demyelination.     

Phenotype for activated tissue macrophages in histiocytic necrotizing lymphadenitis

Macrophage polarization is divided into M1 and M2 type based on membrane receptors, cytokines, and chemokines. M1 expresses CD80, interleukin (IL)-6, IL-12, and chemokine receptor (CCR)7, while M2 expresses CD163, IL10, and chemokine ligand (CCL)22. The aim of the present study was to identify the properties of infiltrating tissue macrophages in histiocytic necrotizing lymphadenitis (HNL). Twenty patients with HNL were studied, and immunohistochemistry for CD68 (KP1), CD163, CCL22, CCR7, and CD123 was done, along with myeloperoxidase (MPO). To evaluate the phenotypes of tissue macrophages in HNL, the number of cells stained positively for CD163, CCL22, CCR7, CD123 and MPO concurrently with CD68 was counted, and the ratio was calculated for each antibody to CD68+ cells. There was a high rate of co-expression for CD163 (median, 78%) or CCL22 (80%) and a low rate for CCR7 (5%) in CD68+ cells. It is therefore conceivable that infiltration by M2 macrophages is dominant in HNL. Furthermore, some CD68+ tissue macrophages in HNL co-express MPO or CD123 (range, 5–80%; median, 23% and 40%, respectively). It is suggested that these characteristic tissue macrophages may be associated with the pathogenesis of HNL and that M2 macrophages may infiltrate to repair the lymphoid tissue injured by cytotoxic T cells in HNL.     

Complement Activation Is Involved in Renal Damage in Human Antineutrophil Cytoplasmic Autoantibody Associated Pauci-Immune Vasculitis

Objective  This study was to investigate the evidence for complement activation in renal biopsy specimens of patients with myeloperoxidase (MPO)-antineutrophil cytoplasmic autoantibody (ANCA)-associated pauci-immune vasculitis. Methods  Renal biopsy specimens from seven patients with MPO-ANCA positive pauci-immune necrotizing crescentic glomerulonephritis (NCGN) were used to detect the staining of membrane attack complex (MAC), C3d, C4d, mannose-binding lectin (MBL), factor B and factor P using immunohistochemistry and immunofluorescence. Renal tissue from seven patients with minimal change disease (MCD) and two normal renal tissue were used as controls. Results  MAC, C3d, factor B and factor P could be detected in glomeruli and small blood vessels with active vasculitis of patients with pauci-immune AAV, but not or scarcely in patients with MCD and in normal renal tissue. C3d and factor B co-localized with MAC, factor P colocalized with C3d. MBL and C4d were not detected in patients with AAV. Conclusion  The alternative pathway of the complement system is involved in renal damage of human pauci-immune AAV.     

Activity of antioxidant enzymes in the skin during surgical wounds

Full-thickness skin wounds (460 mm²) in rats were associated with increased blood chemiluminescence and neutrophil infiltration of the wound tissue and surrounding skin (recorded by myeloperoxidase activity). Activities of glutathione peroxidase and glutathione S-transferase in the skin and wound tissue increased on days 4 and 8. A correlation was revealed between activities of these enzymes and myeloperoxidase activity. Activities of myeloperoxidase and catalase increased in patient’s skin excised during plastic surgeries of more than 2.5 h duration. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 12, pp. 622–625, December, 2006     

Differential effect of oestrogen on post‐exercise cardiac muscle myeloperoxidase and calpain activities in female rats

The effects of oestrogen administration on 1 h post‐exercise cardiac muscle myeloperoxidase (MPO) and calpain activities were determined in female rats. Rats were ovariectomized and implanted for 2 weeks with either oestrogen (25 mg 17‐oestradiol) or placebo pellets or left with ovaries intact. Rats were then run for 1 h at 21 m min^–1, 12% grade, killed 1 h post‐exercise and cardiac muscle and blood samples were removed. Control animals from each group were killed without prior exercise. Serum oestrogen levels in the order of the highest to lowest were; ovariectomized oestrogen replaced rats > intact ovaries rats > ovariectomized placebo rats. Oestrogen induced significant (P < 0.05) elevations in cardiac MPO activity at rest and at 1 h post‐exercise in ovariectomized rats. No significant elevations in cardiac MPO activity were evident in placebo ovariectomized or normal ovary rats at rest or post‐exercise. Cardiac calpain activities were similar in all unexercised groups. Ovariectomized placebo and intact ovary rats had significantly (P < 0.05) elevated cardiac calpain activities 1 h post‐exercise while calpain activity was not significantly elevated in hearts from ovariectomized oestrogen rats. These results demonstrate that oestrogen supplementation in ovariectomized rats induces elevations in cardiac muscle MPO activities at rest and at 1 h post‐exercise. This is opposite to the effect of oestrogen in post‐exercise skeletal muscle and implies a greater neutrophil infiltration into cardiac muscle caused by oestrogen. This effect cannot be explained by changes in 1 h post‐exercise cardiac muscle calpain activity, the elevation of which was suppressed by oestrogen administration. Oestrogen influences cardiac calpain activity similarly to its effect in skeletal muscle. Thus, oestrogen administration to ovariectomized rats induces elevations in cardiac MPO activity while suppressing cardiac calpain activity.     

Study on Myeloperoxidase Role in Antituberculous Defense in the Context of Cytokine Activation

Myeloperoxidase (MPO), next to the NO synthase2 (NOS2), and NADPH oxidase, is the key enzyme of the oxidative burst responsible for the antimicrobial immunity. Because MPO participates in the eradication of Mycobacterium tuberculosis in the in vitro model and the extracellular enzyme may activate cells to cytokine synthesis, we investigated the changes in the enzyme concentration in serum of patients with active pulmonary tuberculosis (TB) and correlations between MPO and TNF-alpha, IFN-gamma, and IL-12. To our knowledge, our study is the first to indicate the involvement of MPO during active TB which manifested itself in the significant increase in serum concentration. The statistically significant elevation of TNF-alpha and IL-12 was also noticed in serum of the TB positive group. The statistical analysis revealed no correlation between the cytokine and MPO production in the studied cases. However, the increase in TNF-alpha and IL-12 serum concentration with simultaneous elevation of serum MPO in the group of the highest enzyme concentration may imply that correlation between the enzyme and the cytokines should not be excluded. Our study suggests possible involvement of MPO in the antituberculous, immunological response, and implies its connection with TNF-alpha and IL-12 activation.