A G protein-associated ERK pathway is involved in LPS-induced proliferation and a PTK-associated p38 MAPK pathway is involved in LPS-induced differentiation in resting B cells

Proteomic changes of CD4+/CD25+/forkhead box p3+ regulatory T cells in a 30-day rat model of sepsis survival

Sepsis is defined as life threatening organ dysfunction arising from a dysregulated host response to infection. The outcomes of sepsis include early mortality, delayed mortality and recovery, and depend on the inflammatory response. Previous studies have demonstrated that regulatory T cells (Tregs) are important in determining the outcome of sepsis, as their suppressive function serves a role in maintaining immune homeostasis. However, Treg-mediated immunosuppression during the course of sepsis remains unclear and little is known about the survival of patients following diagnosis. Studying the survivors of sepsis may explain the mechanisms of natural recovery. Therefore, a 30-day rat model of sepsis survival was established in the current study. Cluster of differentiation CD4⁺/CD25⁺/forkhead box p3⁺ Tregs were isolated from the blood and spleens of rats undergoing cecal ligation and puncture or sham surgery, using flow cytometry. Proteomic analysis was performed using nano high-performance liquid chromatography-mass spectrometry. Several different biological pathways associated with uncommon differentially-expressed proteins were identified in the blood and spleen survivor and sham groups. Extracellular-regulated kinase/mitogen-activated protein kinase, as well as integrin and actin cytoskeletal pathway elements, including Ras-related protein 1b, talin 1 and filamin A, were associated with Tregs in the blood. Pathway elements associated with cell cycle regulators in the B-cell translocation gene family of proteins, tumor necrosis factor receptor superfamily member 4, Hippo signaling, P70-S6 kinase 1, phosphatidylinositol 3-kinase/protein kinase B signaling and 1,25-dihydroxyvitamin D3 biosynthesis were associated with Tregs from the spleen including phosphatase 2A activator regulatory factor 4, histone arginine methyltransferase, CD4, major histocompatibility complex class I antigens, 14-3-3 protein θ and nicotinamide adenine dinucleotide phosphate cytochrome P450 reductase. These results explain the mechanism by which Tregs naturally recover and indicates that Tregs in the blood and spleen vary. Differentially-expressed proteins serving a role in these pathways provide additional insight for the identification of new targets for the diagnosis and treatment of sepsis.

Umbilical cord mesenchymal stem cells suppress B-cell proliferation and differentiation

Mesenchymal stem cells (MSCs) may be obtained from umbilical cord as an abundant and noninvasive source. However, the immunomodulatory properties of umbilical cord-MSCs (UC-MSCs) were poorly studied. In this study, we aimed to investigate the effects of UC-MSCs on B-cell proliferation and differentiation. UC-MSCs were found to suppress the proliferation of B cells isolated from murine spleen. Moreover, UC-MSCs markedly suppressed B-cell differentiation as shown by the decreased number of CD138+cells and reduced levels of IgM and IgG production in coculture. As revealed by transwell experiments, soluble factors produced by UC-MSCs might be involved in mediating B-cell suppression. The Blimp-1 mRNA expression was suppressed whereas the PAX-5 mRNA expression was induced in coculture. Finally, UC-MSCs modified the phosphorylation pattern of Akt and p38 pathways, which were involved in B-cell proliferation and differentiation. These results may further support the potential therapeutic use of UC-MSCs in treating autoimmune disorders.

Immunostimulatory effects of Uncaria perrottetii (A. Rich.) Merr. (Rubiaceae) vinebark aqueous extract in Balb/C mice

AIMS OF THE STUDY

Crude extract of Uncaria perrottetii (A. Rich.) Merr. vinebark was evaluated for its immunomodulating activity in Balb/C mice. Initially, the immunomodulatory potential of the plant extract was evaluated using in vitro immune response assays at different concentrations of the plant extract (10 μg/mL, 20 μg/mL, 50 μg/mL and 100 μg/mL). Using the optimum concentration determined in the in vitro assays, the protective effect of the plant extract was assessed against drug-induced immunosuppression in vivo.

MATERIALS AND METHODS

For the in vivo experiment, thirty-six (36) mice were divided into 3 groups of 12 mice each: (1) cyclophosphamide drug-induced (30 mg/kg BW) immunosuppressed mice (Cy group) served as the positive control; (2) Uncaria perrottetii extract and Cy-treated mice (U+Cy); and (3) PBS-injected mice as the negative control group [(-) CTRL].

RESULTS

The optimum concentration was determined to be 50 μg/mL in the in vitro assays. At this concentration, Uncaria perrottetii extract stimulated peritoneal phagocyte activation, produced a significant increase in the activity of phagocytic cells from the spleen and promoted splenic cellular proliferation with or without lipopolysaccharide (LPS) when compared with the PBS-treated cells (negative control). Moreover, cells treated with 50 μg/mL of Uncaria perrottetii increased macrophage respiratory burst activity that was comparable to that of the phorbol myristate acetate-stimulated splenic macrophages. In all immune assays undertaken in the in vivo experiment, the Cy-treated mice showed significantly lower response when compared with the PBS-treated mice. Significant improvement in peritoneal cell activation, phagocytic activity and cellular proliferation was exhibited by the U+Cy-treated mice when compared with Cy-injected mice. The extract from Uncaria perrottetii also significantly enhanced respiratory burst and plasma lysozyme activity compared with the Cy-injected mice.

CONCLUSIONS

Based on the results of both in vitro and in vivo trials, Uncaria perrottetii extract has immunopotentiating activities on the innate immunity of Balb/C mice and the extract could potentially reverse the immunosuppressive effects of Cy. However, the potential of the plant as source of bioactive products and metabolites for drug development still has to be fully investigated.

Rac/ROS-related protein kinase C and phosphatidylinositol-3-kinase signaling are involved in a negative regulating cascade in B cell activation by antibody-mediated cross-linking of MHC class II molecules

In addition to their essential role in antigen presentation, MHC class II molecules have been widely described as receptors associated with signal transduction involved in regulating B cell function. However, their precise function and mechanism in signal transduction are not yet fully elucidated. Our previous studies demonstrated that cross-linking of MHC class II molecules led to the inhibition of resting B cell activation in which various signal molecules were involved. Especially, Rac-associated ROS-dependent MAP kinases, including ERK1/2 and p38, are involved in MHC class II-associated negative signal transduction in the phorbol 12, 13-dibutyrate (PDBU)-treated, but not LPS-treated, resting B cell line, 38B9. In this study, we further illustrated that PKC regulates downstream signal molecules, including MAP kinases and NF-kappaB in PDBU-stimulated resting B cells, together with Rac and ROS. In addition, we found that phosphatidylinositol 3-kinase (PI3K)-dependent activation of ERK/p38 MAP kinases was associated with the signaling procedure in PDBU-induced B cell activation. Collectively, Rac/ROS-related PKC and PI3K signaling are involved in a negative regulation cascade through the cross-linking of MHC class II molecules by anti-MHC class II antibodies in resting B cells.

Differential involvement of PKC-dependent MAPKs activation in lipopolysaccharide-induced AP-1 expression in human tracheal smooth muscle cells

Lipopolysaccharide (LPS) has been shown to up-regulate the expression of vascular cell adhesion molecule (VCAM)-1 which contributes to the occurrence of airway inflammatory diseases. Genetic analysis reveals the existence of activator protein-1 (AP-1) binding site on VCAM-1 promoter region. However, the role of AP-1 in LPS-induced VCAM-1 expression in human tracheal smooth muscle cells (HTSMCs) is not known. Here, we show that LPS increased VCAM-1 expression and adhesiveness of HTSMCs through AP-1, since pretreatment with an AP-1 inhibitor tanshinone attenuated LPS-induced VCAM-1 expression and leukocytes adhesion. The implication of AP-1 in LPS-induced VCAM-1 expression was confirmed by animal studies showing that pretreatment of mice with tanshinone attenuated LPS-induced VCAM-1 mRNA expression in airway tissues and accumulation of leukocytes in bronchoalveolar lavage. By using the pharmacological inhibitors and transfection with siRNA of PKC, p42, p38, or JNK2, LPS-induced expression of c-Fos was mediated through protein kinase C (PKC), p42/p44 MAPK and p38 MAPK. While, c-Jun expression was mediated through PKC and mitogen-activated protein kinases (MAPKs, p42/p44 MAPK, p38 MAPK and JNK) in HTSMCs. Pretreatment with the inhibitors of PKCs or MAPKs attenuated LPS-stimulated nuclear translocation and VCAM-1 promoter binding abilities of AP-1, which attenuated promoter activity and gene expression of VCAM-1 and the adhesiveness between HTSMCs and leukocytes. These results indicated that differential regulation of AP-1 through PKCs-dependent MAPKs activation plays central roles in LPS-induced VCAM-1 expression. The altered modulation of this axis with inhibitors or siRNAs may contribute to the improvement of airway inflammatory diseases.

A small compound that inhibits lipopolysaccharide-induced tumor necrosis factor-alpha production

Lipopolysaccharide (LPS) is critically involved in the inflammatory responses via generation of several pro-inflammatory cytokines. Since tumor necrosis factor-alpha (TNF-alpha) is one of the major pro-inflammatory cytokines which is induced by LPS treatment, the development of molecules capable of modulating LPS-induced TNF-alpha production is an issue of concern. We identified a novel synthetic compound that inhibits LPS-induced TNF-alpha production in human peripheral blood mononuclear cells (PBMCs). The active compound SM-7409 inhibited LPS-induced TNF-alpha production in a concentration-dependent manner, showing maximal activity at 5 microM. SM-7409 inhibited LPS-induced TNF-alpha mRNA transcript accumulation and protein expression. We also found that SM-7409 strongly inhibits LPS-induced extracellular signal-regulated protein kinase activity in PBMCs. Moreover, we found that SM-7409 strongly inhibits the LPS-induced other pro-inflammatory cytokines, such as interleukin (IL)-1beta and IL-8 in PBMCs. SM-7409 also dramatically inhibits the LPS-induced TNF-alpha production in neutrophils. Taken together, our results demonstrate that SM-7409 is a synthetic compound that inhibits LPS-induced TNF-alpha production, and thus SM-7409 should be useful for the development of chemotherapies targeting LPS-mediated inflammatory responses.