Repetitive hypoxic preconditioning induces an immunosuppressed B cell phenotype during endogenous protection from stroke

Nancy L. Monson, Sterling B. Ortega, Sara J. Ireland, Anouk J M Meeuwissen, Ding Chen, Erik J. Plautz, Erin Shubel, Xiangmei Kong, Min K. Li, Laura H. Freriks, Ann M. Stowe

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21 Scopus citations

Abstract

Background: Repetitive hypoxic preconditioning (RHP) creates an anti-inflammatory phenotype that protects from stroke-induced injury for months after a 2-week treatment. The mechanisms underlying long-term tolerance are unknown, though one exposure to hypoxia significantly increased peripheral B cell representation. For this study, we sought to determine if RHP specifically recruited B cells into the protected ischemic hemisphere, and whether RHP could phenotypically alter B cells prior to stroke onset.Methods: Adult, male SW/ND4 mice received RHP (nine exposures over 2 weeks; 8 to 11 % O2; 2 to 4 hours) or identical exposures to 21 % O2 as control. Two weeks following RHP, a 60-minute transient middle cerebral artery occlusion was induced. Standard techniques quantified CXCL13 mRNA and protein expression. Two days after stroke, leukocytes were isolated from brain tissue (70:30 discontinuous Percoll gradient) and profiled on a BD-FACS Aria flow cytometer. In a separate cohort without stroke, sorted splenic CD19+ B cells were isolated 2 weeks after RHP and analyzed on an Illumina MouseWG-6 V2 Bead Chip. Final gene pathways were determined using Ingenuity Pathway Analysis. Student's t-test or one-way analysis of variance determined significance (P < 0.05).Results: CXCL13, a B cell-specific chemokine, was upregulated in post-stroke cortical vessels of both groups. In the ischemic hemisphere, RHP increased B cell representation by attenuating the diapedesis of monocyte, macrophage, neutrophil and T cells, to quantities indistinguishable from the uninjured, contralateral hemisphere. Pre-stroke splenic B cells isolated from RHP-treated mice had >1,900 genes differentially expressed by microarray analysis. Genes related to B-T cell interactions, including antigen presentation, B cell differentiation and antibody production, were profoundly downregulated. Maturation and activation were arrested in a cohort of B cells from pre-stroke RHP-treated mice while regulatory B cells, a subset implicated in neurovascular protection from stroke, were upregulated.Conclusions: Collectively, our data characterize an endogenous neuroprotective phenotype that utilizes adaptive immune mechanisms pre-stroke to protect the brain from injury post-stroke. Future studies to validate the role of B cells in minimizing injury and promoting central nervous system recovery, and to determine whether B cells mediate an adaptive immunity to systemic hypoxia that protects from subsequent stroke, are needed.

Original languageEnglish (US)
Article number22
JournalJournal of Neuroinflammation
Volume11
DOIs
StatePublished - Jan 31 2014

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Keywords

  • B cells
  • B10
  • CXCL13
  • Hypoxic preconditioning
  • Neuroprotection
  • Stroke

ASJC Scopus subject areas

  • Neuroscience(all)
  • Immunology
  • Neurology
  • Cellular and Molecular Neuroscience

Cite this

Monson, N. L., Ortega, S. B., Ireland, S. J., Meeuwissen, A. J. M., Chen, D., Plautz, E. J., Shubel, E., Kong, X., Li, M. K., Freriks, L. H., & Stowe, A. M. (2014). Repetitive hypoxic preconditioning induces an immunosuppressed B cell phenotype during endogenous protection from stroke. Journal of Neuroinflammation, 11, [22]. https://doi.org/10.1186/1742-2094-11-22