Neuropeptide Y induces secretion of high-mobility group box 1 protein in mouse macrophage via PKC/ERK dependent pathway.

Despite increasing evidence highlighting the role of NPY in the modulation of inflammatory reaction, surprisingly little is known about the direct effects of NPY on the release of proinflammatory mediators. In the present work, we have evaluated the effects of NPY on the release of TNF-α, IL-1ß, IL-6 and HMGB1 mediators in peritoneal macrophages. Our results demonstrate for the first time that NPY can directly induce active HMGB1 release and cytoplasmic translocation, while the production of TNF-α, IL-1ß and IL-6 is not affected. PKC and ERK pathway inhibitors can abolish the promotive effect of NPY on HMGB1 secretion. Thus, our results indicate that NPY might impact on the innate immune system by directly potentiating the HMGB1 release from the macrophage.

Tanshinone IIA pretreatment attenuates hepatic ischemia-reperfusion.

Tanshinone IIA (Tan IIA), an active component derived from Salvia miltiorrhiza root, has been used to treat various ischemic cardiovascular and cerebrovascular diseases. However, its impact on hepatic ischemia/reperfusion (I/R) injury remains unclear. Here, we addressed this issue by using a 90-minute partial liver ischemia model. Mice were administered Tan IIA intragastrically for 3 days before ischemia and were assessed for liver damage 6-h after reperfusion. Tan IIA pretreatment significantly inhibited serum aminotransferases and proinflammatory cytokine levels along with reduced inflammatory infiltration and liver damage. Mechanistic studies revealed that Tan IIA suppressed TLR4 expression in nonparenchymal cells (NPCs) and induced heme oxygenase-1 (HO-1) production in both parenchymal and NPCs. Moreover, the phosphorylation of AKT and ERK1/2 in the liver was enhanced, while the phosphorylation of JNK, p38 and p65 was suppressed. These results suggest Tan IIA can suppress TLR4 signaling which then enhances HO-1 expression along with reduced proinflammatory cytokine expressions in the liver, and Tan IIA could be a useful candidate drug in clinic for prevention and treatment of hepatic I/R injury.

Corticosterone rapidly promotes respiratory burst of mouse peritoneal macrophages via non-genomic mechanism.

BACKGROUND: The immunomodulatory effects of glucocorticoids (GCs) have been described as bimodal. High concentration of GCs exerts immunosuppressive effects and low levels of GCs are immunopermissive. While the immunosuppressive mechanisms of GCs have been investigated intensely, the immunopermissive effects of GCs remain unclear. A lot of studies showed GCs could exert rapid non-genomic actions. We herein studied the rapid immunopromoting effects of GCs. METHODS: We observed the rapid (within 30 minutes) effects of corticosterone on respiratory burst of mouse peritoneal macrophages and studied their mechanisms. The superoxide anions were measured by cytochrome C reduction assay. Protein kinase C phosphorylation was measured by Western blotting and membrane fluidity was evaluated by fluorescence polarization measurement. RESULTS: The 10(-8) mol/L and 10(-7) mol/L corticosterone rapidly increased the superoxide anions production by macrophages, which were insensitive to GC-receptor antagonist, mifepristone, and protein-synthesis inhibitor, cycloheximide. Corticosterone coupled to bovine serum albumin was able to mimic the effects of corticosterone. The effects were independent of protein kinase C pathway and the change in membrane fluidity. CONCLUSIONS: The results indicate that corticosterone rapidly promote the superoxide anions production by mouse peritoneal macrophages may through non-genomic mechanisms. This study may contribute to understanding the effects of GCs under stress condition and the physiological significance of nongenomic effects of GCs.

Suppression of allograft rejection by Tim-1-Fc through cross-linking with a novel Tim-1 binding partner on T cells.

Engagement of T-cell immunoglobulin mucin (Tim)-1 on T cells with its ligand, Tim-4, on antigen presenting cells delivers positive costimulatory signals to T cells. However, the molecular mechanisms for Tim-1-mediated regulation of T-cell activation and differentiation are relatively poorly understood. Here we investigated the role of Tim-1 in T-cell responses and allograft rejection using recombinant human Tim-1 extracellular domain and IgG1-Fc fusion proteins (Tim-1-Fc). In vitro assays confirmed that Tim-1-Fc selectively binds to CD4(+) effector T cells, but not dendritic cells or natural regulatory T cells (nTregs). Tim-1-Fc was able to inhibit the responses of purified CD4(+) T cells that do not express Tim-4 to stimulation by anti-CD3/CD28 mAbs, and this inhibition was associated with reduced AKT and ERK1/2 phosphorylation, but it had no influence on nTregs. Moreover, Tim-1-Fc inhibited the proliferation of CD4(+) T cells stimulated by allogeneic dendritic cells. Treatment of recipient mice with Tim-1-Fc significantly prolonged cardiac allograft survival in a fully MHC-mismatched strain combination, which was associated with impaired Th1 response and preserved Th2 and nTregs function. Importantly, the frequency of Foxp3(+) cells in splenic CD4(+) T cells was increased, thus shifting the balance toward regulators, even though Tim-1-Fc did not induce Foxp3 expression in CD4(+)CD25(-) T cells directly. These results indicate that Tim-1-Fc can inhibit T-cell responses through an unknown Tim-1 binding partner on T cells, and it is a promising immunosuppressive agent for preventing allograft rejection.