LPA Promotes T Cell Recruitment through Synthesis of CXCL13.

Lysophosphatidic acid (LPA) is a bioactive phospholipid playing an important role in various inflammatory diseases by inducing expression and secretion of many inflammatory cytokines/chemokines. Here we report in a murine air pouch model of inflammation that LPA induced CXCL13 secretion in a time-dependent manner and with exacerbation of the response when LPA was administered after a pretreatment with TNF-α, a key inflammatory cytokine. LPA mediates recruitment of leukocytes, including that of CD3(+) cells into unprimed and TNF-α-primed air pouches. CXCL13 neutralization using a blocking antibody injected into air pouches prior to administration of LPA into TNF-α-primed air pouches decreased CD3(+) cell influx. Our data highlight that LPA-mediated CXCL13 secretion plays a role in T cell recruitment and participates in regulation of the inflammatory response.

Topographic mapping of the glioblastoma proteome reveals a triple-axis model of intra-tumoral heterogeneity.

Glioblastoma is an aggressive form of brain cancer with well-established patterns of intra-tumoral heterogeneity implicated in treatment resistance and progression. While regional and single cell transcriptomic variations of glioblastoma have been recently resolved, downstream phenotype-level proteomic programs have yet to be assigned across glioblastoma's hallmark histomorphologic niches. Here, we leverage mass spectrometry to spatially align abundance levels of 4,794 proteins to distinct histologic patterns across 20 patients and propose diverse molecular programs operational within these regional tumor compartments. Using machine learning, we overlay concordant transcriptional information, and define two distinct proteogenomic programs, MYC- and KRAS-axis hereon, that cooperate with hypoxia to produce a tri-dimensional model of intra-tumoral heterogeneity. Moreover, we highlight differential drug sensitivities and relative chemoresistance in glioblastoma cell lines with enhanced KRAS programs. Importantly, these pharmacological differences are less pronounced in transcriptional glioblastoma subgroups suggesting that this model may provide insights for targeting heterogeneity and overcoming therapy resistance.

Differential Effects of Inhibitor Combinations on Lysophosphatidic Acid-Mediated Chemokine Secretion in Unprimed and Tumor Necrosis Factor-α-Primed Synovial Fibroblasts.

Lysophosphatidic acid (LPA) is a pleiotropic bioactive lysophospholipid involved in inflammatory mediator synthesis. Signaling through p38MAPK, ERK, Rho kinase, and MSK-CREB contributes to LPA-mediated IL-8 production in fibroblast-like synoviocytes (FLS) from rheumatoid arthritis (RA) patients. The study was undertaken to investigate how LPA activates MSKs and how signaling crosstalk between TNFα and LPA contributes to the super-production of cytokines/chemokines. RAFLS pretreated or not with TNFα were stimulated with LPA. Immunoblotting with phospho-antibodies monitored MSK activation. Cytokine/chemokine production was measured using ELISA and multiplex immunoassays. LPA induced MSK activation by signaling through ERK whereas p38MAPK, Rho kinase, NF-κB or PI3K contribute to IL-8 synthesis mainly via MSK-independent pathways. Priming with TNFα enhanced LPA-mediated MSK phosphorylation and cytokine/chemokine production. After priming with TNFα, inhibition of ERK or MSK failed to attenuate LPA-mediated IL-8 synthesis even if the MSK-CREB signaling axis was completely or partially inhibited. In TNFα-primed cells, inhibition of LPA-mediated cytokine/chemokine synthesis required a specific combination of inhibitors such as p38MAPK and ERK for IL-8 and IL-6, and Rho kinase and NF-κB for MCP-1. The ability of the signaling inhibitors to block LPA induced cytokine/chemokine synthesis is dependent on the inflammatory cytokinic environment. In TNFα-primed RAFLS the super-production of IL-8 and IL-6 induced by LPA occurs mainly via MSK-independent pathways, and simultaneous inhibition of at least two MAPK signaling pathways was required to block their synthesis. Since simultaneous inhibition of both the p38MAPK and ERK-MSK-CREB pathways are required to significantly reduce LPA-mediated IL-8 and IL-6 production in TNFα-preconditioned RAFLS, drug combinations targeting these two pathways are potential new strategies to treat rheumatoid arthritis.

Lysophosphatidic acid-induced IL-8 secretion involves MSK1 and MSK2 mediated activation of CREB1 in human fibroblast-like synoviocytes.

Lysophosphatidic acid (LPA) is a pleiotropic lipid mediator that promotes motility, survival, and the synthesis of chemokines/cytokines such as interleukin-8 (IL-8) and interleukin-6 by human fibroblast-like synoviocytes from patients with rheumatoid arthritis (RAFLS). In those cells LPA was reported to induce IL-8 secretion through activation of various signaling pathways including p38 mitogen-activated protein kinase (p38 MAPK), p42/44 MAPK, and Rho kinase. In addition to those pathways we report that mitogen- and stress-activated protein kinases (MSKs) known to be activated downstream of the ERK1/2 and p38 MAPK cascades and CREB are phosphorylated in response to LPA. The silencing of MSKs with small-interfering RNAs and the pharmacological inhibitor of MSKs SB747651A shows a role for both MSK1 and MSK2 in LPA-mediated phosphorylation of CREB at Ser-133 and secretion of IL-8 and MCP-1. Whereas CREB inhibitors have off target effects and increased LPA-mediated IL-8 secretion, the silencing of CREB1 with short hairpin RNA significantly reduced LPA-induced chemokine production in RAFLS. Taken together the data clearly suggest that MSK1 and MSK2 are the major CREB kinases in RAFLS stimulated with LPA and that phosphorylation of CREB1 at Ser-133 downstream of MSKs plays a significant role in chemokine production.