Dataset Information

Lipid phosphate phosphatase inhibitors locally amplify lysophosphatidic acid LPA1 receptor signalling in rat brain cryosections without affecting global LPA degradation.

ABSTRACT:

Background

Lysophosphatidic acid (LPA) is a signalling phospholipid with multiple biological functions, mainly mediated through specific G protein-coupled receptors. Aberrant LPA signalling is being increasingly implicated in the pathology of common human diseases, such as arteriosclerosis and cancer. The lifetime of the signalling pool of LPA is controlled by the equilibrium between synthesizing and degradative enzymatic activity. In the current study, we have characterized these enzymatic pathways in rat brain by pharmacologically manipulating the enzymatic machinery required for LPA degradation.

Results

In rat brain cryosections, the lifetime of bioactive LPA was found to be controlled by Mg2+-independent, N-ethylmaleimide-insensitive phosphatase activity, attributed to lipid phosphate phosphatases (LPPs). Pharmacological inhibition of this LPP activity amplified LPA1 receptor signalling, as revealed using functional autoradiography. Although two LPP inhibitors, sodium orthovanadate and propranolol, locally amplified receptor responses, they did not affect global brain LPA phosphatase activity (also attributed to Mg2+-independent, N-ethylmaleimide-insensitive phosphatases), as confirmed by Pi determination and by LC/MS/MS. Interestingly, the phosphate analog, aluminium fluoride (AlFx-) not only irreversibly inhibited LPP activity thereby potentiating LPA1 receptor responses, but also totally prevented LPA degradation, however this latter effect was not essential in order to observe AlFx--dependent potentiation of receptor signalling.

Conclusions

We conclude that vanadate- and propranolol-sensitive LPP activity locally guards the signalling pool of LPA whereas the majority of brain LPA phosphatase activity is attributed to LPP-like enzymatic activity which, like LPP activity, is sensitive to AlFx- but resistant to the LPP inhibitors, vanadate and propranolol.

SUBMITTER: Aaltonen N

PROVIDER: S-EPMC3418163 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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Publications

Lipid phosphate phosphatase inhibitors locally amplify lysophosphatidic acid LPA1 receptor signalling in rat brain cryosections without affecting global LPA degradation.

Aaltonen Niina N Lehtonen Marko M Varonen Katri K Goterris Gemma Arrufat GA Laitinen Jarmo T JT

BMC pharmacology 20120611

<h4>Background</h4>Lysophosphatidic acid (LPA) is a signalling phospholipid with multiple biological functions, mainly mediated through specific G protein-coupled receptors. Aberrant LPA signalling is being increasingly implicated in the pathology of common human diseases, such as arteriosclerosis and cancer. The lifetime of the signalling pool of LPA is controlled by the equilibrium between synthesizing and degradative enzymatic activity. In the current study, we have characterized these enzyma ...[more]

PMID: 22686545

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Project description:BACKGROUND:In the extracellular environment, lysophosphatidic acid (LPA) species are generated via autotaxin (ATX)-mediated hydrolysis of lysophospholipid precursors. Members of the LPA family are potent lipid mediators transmitting signals via six different G protein-coupled LPA receptors (LPAR1-6). The LPA signaling axis is indispensable for brain development and function of the nervous system; however, during damage of the central nervous system, LPA levels can increase and aberrant signaling events counteract brain function. Here, we investigated regulation of the ATX/LPA/LPAR axis in response to lipopolysaccharide-induced systemic inflammation in mice and potential neurotoxic polarization programs in LPA-activated primary murine microglia. METHODS:In vivo, LPAR1-6 expression was established by qPCR in whole murine brain homogenates and in FACS-sorted microglia. ELISAs were used to quantitate LPA concentrations in the brain and cyto-/chemokine secretion from primary microglia in vitro. Transcription factor phosphorylation was analyzed by immunoblotting, and plasma membrane markers were analyzed by flow cytometry. We used MAPK inhibitors to study signal integration by the JNK, p38, and ERK1/2 branches in response to LPA-mediated activation of primary microglia. RESULTS:Under acute and chronic inflammatory conditions, we observed a significant increase in LPA concentrations and differential regulation of LPAR, ATX (encoded by ENPP2), and cytosolic phospholipase A2 (encoded by PLA2G4A) gene expression in the brain and FACS-sorted microglia. During pathway analyses in vitro, the use of specific MAPK antagonists (SP600125, SB203580, and PD98059) revealed that JNK and p38 inhibition most efficiently attenuated LPA-induced phosphorylation of proinflammatory transcription factors (STAT1 and -3, p65, and c-Jun) and secretion of IL-6 and TNF?. All three inhibitors decreased LPA-mediated secretion of IL-1?, CXCL10, CXCL2, and CCL5. The plasma membrane marker CD40 was solely inhibited by SP600125 while all three inhibitors affected expression of CD86 and CD206. All MAPK antagonists reduced intracellular COX-2 and Arg1 as well as ROS and NO formation, and neurotoxicity of microglia-conditioned media. CONCLUSION:In the present study, we show that systemic inflammation induces aberrant ATX/LPA/LPAR homeostasis in the murine brain. LPA-mediated polarization of primary microglia via MAPK-dependent pathways induces features reminiscent of a neurotoxic phenotype.

Dataset Information

Lipid phosphate phosphatase inhibitors locally amplify lysophosphatidic acid LPA1 receptor signalling in rat brain cryosections without affecting global LPA degradation.

Background

Results

Conclusions

Publications

Lipid phosphate phosphatase inhibitors locally amplify lysophosphatidic acid LPA1 receptor signalling in rat brain cryosections without affecting global LPA degradation.

Similar Datasets

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