Chemical inhibition of Src family kinases affects major LPS-activated pathways in primary human macrophages

Multiple roles of Lyn kinase in myeloid cell signaling and function

Lyn is an Src family kinase present in B lymphocytes and myeloid cells. In these cell types, Lyn establishes signaling thresholds by acting as both a positive and a negative modulator of a variety of signaling responses and effector functions. Lyn deficiency in mice results in the development of myeloproliferation and autoimmunity. The latter has been attributed to the hyper-reactivity of Lyn-deficient B cells due to the unique role of Lyn in downmodulating B-cell receptor activation, mainly through phosphorylation of inhibitory molecules and receptors. Myeloproliferation results, on the other hand, from the enhanced sensitivity of Lyn-deficient progenitors to a number of colony-stimulating factors (CSFs). The hyper-sensitivity to myeloid growth factors may also be secondary to poor inhibitory receptor phosphorylation, leading to impaired recruitment/activation of tyrosine phosphatases and reduced downmodulation of CSF signaling responses. Despite these observations, the overall role of Lyn in the modulation of myeloid cell effector functions is much less well understood, as often both positive and negative roles of this kinase have been reported. In this review, we discuss the current knowledge of the duplicitous nature of Lyn in the modulation of myeloid cell signaling and function.

Dasatinib inhibits recombinant viral antigen-specific murine CD4+ and CD8+ T-cell responses and NK-cell cytolytic activity in vitro and in vivo

OBJECTIVE

Dasatinib (BMS-354825) is a small molecule Src/Abl tyrosine kinase inhibitor approved for the treatment of chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia. Members of the Src family of kinases are involved in the induction of innate and adaptive immunity. The purpose of this study was to evaluate the inhibitory action of dasatinib on antigen-specific CD8(+) and CD4(+) T-cell function, as well as natural killer (NK) cell cytotoxicity.

MATERIALS AND METHODS

To assess dasatinib-mediated inhibition of antigen-specific T-cell proliferation, transgenic CD4(+) and CD8(+) T cells specific for ovalbumin were utilized. Endogenous CD4(+) and CD8(+) T-cell responses were determined following immunization of dasatinib-treated or control mice with a nonreplicating recombinant virus. Clearance of the RMA-S cells, a major histocompatibility complex (MHC) class I-deficient thymoma sensitive to NK-cell lysis, was analyzed in mice undergoing dasatinib treatment.

RESULTS

Dasatinib inhibited antigen-specific proliferation of murine CD4(+) and CD8(+) transgenic T cells in vitro and in vivo. Endogenous antigen-specific helper T-cell recall responses and induction of T-cell-mediated cytotoxicity following immunization with a nonreplicating recombinant virus were also inhibited. So to was the ability of NK cells to eliminate MHC class I-deficient cells in vivo.

CONCLUSIONS

These findings suggest that dasatinib has the potential to modulate the host immune response at clinical doses and highlights scope for off target applications, e.g., therapeutic immunosuppression in the context of autoimmune pathogenesis and allogeneic tissue transplantation.

Cell signalling in macrophages, the principal innate immune effector cells of rheumatoid arthritis

Rheumatoid arthritis is a multisystemic auto-inflammatory disease affecting up to 1% of the population and leading to the destruction of the joints. Evidence exists for the involvement of the innate as well as the adaptive immune systems in the pathology of the disease. The success of anti-tumour necrosis factor-alpha indicates the importance of pro-inflammatory mediators produced by innate immune cells in rheumatoid arthritis progression. Therefore, considerable efforts have been made in elucidating the signalling pathways leading to the expression of those mediators. This review will concentrate on the role of signalling pathways in innate immune cells in the context of rheumatoid arthritis.

Oligomannose-coated liposomes activate ERK via Src kinases and PI3K/Akt in J774A.1 cells

We have previously shown that liposomes coated with a neoglycolipid constructed from mannotriose and dipalmitoylphosphatidylethanolamine (Man3-DPPE) activate peritoneal macrophages to induce enhanced expression of co-stimulatory molecules and MHC class II. In this study, we investigated the signaling pathways activated by the Man3-DPPE-coated liposomes (OMLs) in a murine macrophage cell line, J774A.1. In response to OML stimulation, ERK among MAPKs was clearly and transiently phosphorylated in J774 cells. ERK phosphorylation was also induced by treatment of the cells with Man3-DPPE and Man3-BSA, but not by uncoated liposomes. In addition, rapid and transient phosphorylation of Akt and Src family kinases (SFKs) was observed in response to OMLs. OML-induced ERK phosphorylation was inhibited by specific inhibitors of PI3K and SFKs, and OML-induced Akt phosphorylation was inhibited by a inhibitor of SFKs. Therefore, OMLs may activate the PI3K/Akt pathway through phosphorylation of Src family kinases to induce ERK activation.

Src kinase-targeted anti-inflammatory activity of davallialactone from Inonotus xeranticus in lipopolysaccharide-activated RAW264.7 cells

BACKGROUND AND PURPOSE

Mushrooms are popular both as food and as a source of natural compounds of biopharmaceutical interest. Some mushroom-derived compounds such as beta-glucan have been shown to be immunostimulatory; this study explores the anti-inflammatory properties of hispidin analogues derived from the mushroom, Inonotus xeranticus. We sought to identify the molecular mechanism of action of these hispidin analogues by determining their effects on lipopolysaccharide (LPS)-mediated inflammatory responses in a macrophage cell line.

EXPERIMENTAL APPROACH

The production of inflammatory mediators was determined by Griess assay, reverse transcription-PCR and ELISA. The inhibitory effect of davalliactone on LPS-induced activation of signalling cascades was assessed by western blotting, immunoprecipitation and direct kinase assay.

KEY RESULTS

In activated RAW264.7 cells, davallialactone strongly downregulated LPS-mediated inflammatory responses, including NO production, prostaglandin E2 release, expression of proinflammatory cytokine genes and cell surface expression of co-stimulatory molecules. Davallialactone treatment did not alter cell viability or morphology. Davallialactone was found to exert its anti-inflammatory effects by inhibiting a signalling cascade that activates nuclear factor kappa B via PI3K, Akt and IKK, but not mitogen-activated protein kinases. Treatment with davallialactone affected the phosphorylation of these signalling proteins, but not their level of expression. These inhibitory effects were not due to the interruption of toll-like receptor 4 binding to CD14. In particular, davallialactone strongly inhibited the LPS-induced phosphorylation and kinase activity of Src, implying that Src may be a potential pharmacological target of davallialactone.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that davallialactone, a small molecule found in edible mushrooms, has anti-inflammatory activity. Davallialactone can be developed as a pharmaceutically valuable anti-Src kinase agent.