Metabolism of Docosahexaenoic Acid (DHA) Induces Pyroptosis in BV-2 Microglial Cells

Abstract

DHA is one of the most abundant fatty acids in the brain, largely present in stores of membrane phospholipids. It is readily released by the action of phospholipase A2 and is known to induce anti-inflammatory and neurotrophic effects. It is not thought to contribute to proinflammatory processes in the brain. In this study, an immortalized murine microglia cell line (BV-2) was used to evaluate the effect of DHA on neuroinflammatory cells. Pretreatment of BV-2 cells with low concentrations of DHA (30 µM) attenuates lipopolysaccharide-mediated inflammatory cytokine gene expression, consistent with known anti-inflammatory effects. However, higher (but still physiologically relevant) concentrations of DHA (200 µM) induce profound cell swelling and a reduction of viability. This is accompanied by increases in the expressions of inflammatory cytokine and lipoxygenase genes, activation of caspase-1 activity, and release of IL1β, indicating that cells were undergoing a proinflammatory cell death program known as pyroptosis. This process could be attenuated by pharmacological inhibition of 12-lipoxygenase (12-LOX, Alox12e), but not by inhibition of 5-LOX or 15-LOX. Cumulatively, these data demonstrate that DHA has an anti-inflammatory effect on microglial cells, but its metabolism by 12-LOX generates one or more products that activate a proinflammatory cell death program.

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Abbreviations

AA:

Arachidonic acid

CNS:

Central nervous system

DAMP:

Damage-associated molecular pattern

DHA:

Docosahexaenoic acid

DMEM:

Dulbecco’s modified Eagle’s medium

ETI:

Eicosatrienoic acid

LPS:

Lipopolysaccharide

MTT:

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide

PRR:

Pattern recognition receptor

PUFA:

Polyunsaturated fatty acid

SPM:

Specialized pro-resolving mediators

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Acknowledgements

The authors are grateful to Low Kay En and the Electron Microscopy Unit at the National University of Singapore for expert technical assistance with the scanning electron microscopy, and to Pabba Anubharath for expert technical assistance with the processing of time-lapse microscopy data. This work was supported by the Ministry of Education, Singapore (T1-2016 Sep-11, D.R.H.); the National Medical Research Council, Singapore (NMRC/CIRG/1410/2014, W.Y.O.); and the National University Health System (NUHSRO/2014/085/AF-Partner/01, D.R.H.).

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Correspondence to Deron R. Herr.

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The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary data 1 Time-lapse video microscopy of BV-2 cells treated with vehicle. Total video length: 4 hours. (MP4 31248 KB)

Supplementary data 2 Time-lapse video microscopy of BV-2 cells treated with 200 μM DHA. Total video length: 4 hours. (MP4 31238 KB)

Supplementary data 3 Time-lapse video microscopy of BV-2 cells treated with 200 μM cisplatin (CDDP). Total video length: 4 hours. (MP4 31222 KB)

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Srikanth, M., Chandrasaharan, K., Zhao, X. et al. Metabolism of Docosahexaenoic Acid (DHA) Induces Pyroptosis in BV-2 Microglial Cells. Neuromol Med 20, 504–514 (2018). https://doi.org/10.1007/s12017-018-8511-0

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Keywords

  • Neuroinflammation
  • Proptosis
  • Microglia
  • Docosahexaenoic acid (DHA)
  • Lipoxygenase
  • 12-LOX