MicroRNA-155 regulates monocyte chemokine and chemokine receptor expression in Rheumatoid Arthritis.

OBJECTIVE: To test the hypothesis that miR-155 regulates monocyte migratory potential via modulation of chemokine and chemokine receptor expression in RA, and thereby is associated with disease activity. METHODS: The miR-155 copy-numbers in monocytes from peripheral blood (PB) of healthy (n = 22), RA (n = 24) and RA SF (n = 11) were assessed by real time-PCR using synthetic miR-155 as a quantitative standard. To evaluate the functional impact of miR-155, human monocytes were transfected with control or miR-155 mimic, and the effect on transcript levels, and production of chemokines was evaluated by Taqman low-density arrays and multiplex assays. A comparative study evaluated constitutive chemokine receptor expression in miR-155-/- and wild-type murine (CD115 + Ly6C + Ly6G-) monocytes. RESULTS: Compared with healthy monocytes, the miR-155 copy-number was higher in RA, peripheral blood (PB) and SF monocytes (PB P < 0.01, and SF P < 0.0001). The miR-155 copy-number in RA PB monocytes was higher in ACPA-positive compared with ACPA-negative patients (P = 0.033) and correlated (95% CI) with DAS28 (ESR), R = 0.728 (0.460, 0.874), and with tender, R = 0.631 (0.306, 0.824) and swollen, R = 0.503 (0.125, 0.753) joint counts. Enforced-expression of miR-155 in RA monocytes stimulated the production of CCL3, CCL4, CCL5 and CCL8; upregulated CCR7 expression; and downregulated CCR2. Conversely, miR155-/- monocytes showed downregulated CCR7 and upregulated CCR2 expression. CONCLUSION: Given the observed correlations with disease activity, these data provide strong evidence that miR-155 can contribute to RA pathogenesis by regulating chemokine production and pro-inflammatory chemokine receptor expression, thereby promoting inflammatory cell recruitment and retention in the RA synovium.

Anti-Toll-like receptor 2 and 4 antibodies suppress inflammatory response in mice.

Toll-like receptors (TLRs) 2 and 4 recognize different endogenous and exogenous agonists and play a distinct role in infection and inflammation. However, their ultimate effect in a given infectious and inflammatory disease is less understood. We produced polyclonal anti-murine TLR2 and TLR4 antibodies and investigated their effect on cutaneous leishmaniasis and inflammatory arthritis. Administration of these antibodies to susceptible BALB/c mice, infected in the footpad with Leishmania major, reduced footpad swelling but not the parasite load compared with mice treated with control IgG. The antibodies synergistically reduced leishmanial-specific T-cell proliferation, T helper type 1 and type 2 cytokine production, specific IgG1 and IgG2a antibody synthesis, and T-cell receptor and co-stimulatory molecule expression on dendritic cells in infected mice. We then tested the effect of these antibodies on collagen-induced arthritis (CIA) in DBA/1 mice, a classic model of chronic inflammation. Both antibodies markedly suppressed the development of clinical parameters with concomitant reduction of pro-inflammatory cytokine production. These data therefore suggest that anti-TLR2 and 4 antibodies may have a synergistic therapeutic effect on inflammatory disease in vivo.

Genome-wide analysis reveals extensive functional interaction between DNA replication initiation and transcription in the genome of Trypanosoma brucei.

Identification of replication initiation sites, termed origins, is a crucial step in understanding genome transmission in any organism. Transcription of the Trypanosoma brucei genome is highly unusual, with each chromosome comprising a few discrete transcription units. To understand how DNA replication occurs in the context of such organization, we have performed genome-wide mapping of the binding sites of the replication initiator ORC1/CDC6 and have identified replication origins, revealing that both localize to the boundaries of the transcription units. A remarkably small number of active origins is seen, whose spacing is greater than in any other eukaryote. We show that replication and transcription in T. brucei have a profound functional overlap, as reducing ORC1/CDC6 levels leads to genome-wide increases in mRNA levels arising from the boundaries of the transcription units. In addition, ORC1/CDC6 loss causes derepression of silent Variant Surface Glycoprotein genes, which are critical for host immune evasion.

Liver and kidney structure and iron content in romanian brown bears (Ursus arctos) before and after hibernation.

The annual cycle of the brown bear (Ursus arctos) in the Carpathian Mountains (Romania) consists of an active period from April to November, and an inactive period (hibernation) of approximately 4-5 months between November and March. During hibernation, the brown bears sleep continually and do not feed or drink water. Analyses of liver and kidney of male brown bears showed that liver iron content was 3 times higher in bears at the end of hibernation than at the end of the active period. A possible trend towards a decrease in iron content was noted for the kidney. The presence of iron in the liver was confirmed by the presence of the Perls-positive granules in the cytoplasm of Kupffer cells, in other non-parenchymal cells and also in some hepatocytes. The hepatic veins of the bear liver samples obtained in early spring showed narrower lumens with pleated walls, compared to the normal outline of the hepatic veins in the liver from the bears sampled during autumn. Also in the early spring bears, the renal glomeruli were partially fibrosed. Renal glomerular fibrosis was sometimes observed in samples from the prehibernation period. The tissue iron values from the livers and kidneys of brown bears in early spring or autumn might provide useful data on iron metabolism under conditions of hibernation and accompanying starvation.

Enhanced Th1 response to Staphylococcus aureus infection in human lactoferrin-transgenic mice.

Lactoferrin (Lf) is an iron-binding protein of external secretions and neutrophil secondary granules with antimicrobial and immunomodulatory activities. To further define these properties of Lf, we have investigated the response to Staphylococcus aureus infection in transgenic mice carrying a functional human Lf gene. The transgenic mice cleared bacteria significantly better than congenic littermates, associated with a trend to reduced incidence of arthritis, septicemia, and mortality. We identified two pathways by which S. aureus clearance was enhanced. First, human Lf directly inhibited the growth of S. aureus LS-1 in vitro. Second, S. aureus-infected transgenic mice exhibited enhanced Th1 immune polarization. Thus, spleen cells from infected transgenic mice produced higher levels of TNF-alpha and IFN-gamma and less IL-5 and IL-10 upon stimulation ex vivo with the exotoxin toxic shock syndrome toxin-1 compared with congenic controls. To confirm that these effects of Lf transgene expression could occur in the absence of live bacterial infection, we also showed that Lf-transgenic DBA/1 mice exhibited enhanced severity of collagen-induced arthritis, an established model of Th1-induced articular inflammation. Higher levels of stainable iron in the spleens of transgenic mice correlated with human Lf distribution, but all other parameters of iron metabolism did not differ between transgenic mice and wild-type littermates. These results demonstrate that human Lf can mediate both antimicrobial and immunomodulatory activities with downstream effects on the outcome of immune pathology in infectious and inflammatory disease.