Induction of Neuronal PI3Kγ Contributes to Endoplasmic Reticulum Stress and Long-Term Functional Impairment in a Murine Model of Traumatic Brain Injury

  • Shan Liu
  • Rong Jin
  • Adam Y. Xiao
  • Rui Chen
  • Jarvis Li
  • Wei Zhong
  • Xiaozhou Feng
  • Guohong LiEmail author
Original Article


Phosphoinositide 3-kinase γ (PI3Kγ) expressed in immune cells is linked to neuroinflammation in several neurological diseases. However, the expression and role of PI3Kγ in preclinical traumatic brain injury (TBI) have not been investigated. In WT mice, we found that TBI induced rapid and extensive expression of PI3Kγ in neurons within the perilesional cortex and the ipsilateral hippocampal subfields (CA1, CA3), which peaked between 1 and 3 days and declined significantly 7 days after TBI. Intriguingly, the induction of neuronal PI3Kγ in these subregions of the brain spatiotemporally coincided with both the TBI-induced activation of the neuronal ER stress pathway (p-eIF2α, ATF4, and CHOP) and neuronal cell death (marked by TUNEL-positive neurons) 3 days after TBI. Further, we show that the absence of PI3Kγ in knockout mice profoundly reduced the TBI-induced activation of the ER stress pathway and neuronal cell death. White matter disruption is a better predictor of long-term clinical outcomes than focal lesion size. We show that PI3Kγ deficiency not only reduced brain tissue loss but also alleviated white matter injury (determined by axonal injury and demyelination) up to 28 days after TBI. Importantly, PI3Kγ-knockout mice exhibited greater functional recovery including forepaw use, sensorimotor balance and coordination, and spatial learning and memory up to 28 days after TBI. These results unveil a previously unappreciated role for neuronal PI3Kγ in the regulation of ER stress associated with neuronal cell death, white matter damage, and long-term functional impairment after TBI.

Key Words

PI3K gamma endoplasmic reticulum stress neurons white matter trauma 



This work was supported in part by National Institutes of Health grants NS089991 and NS088719 (Dr. Li) and the Louisiana State University Health Sciences Foundation Fund for Schumpert Endowed Chair (Guohong Li).

Required Author Forms

Disclosure forms provided by the authors are available with the online version of this article.

Authors’ Contributions

SL, RJ, WZ, and AYX performed the experiments and data analysis. SL contributed to manuscript writing. GL designed and supervised the study and wrote the manuscript.

Compliance with Ethical Standards

Conflict of Interest

The authors declare that they have no competing interests.

Supplementary material

13311_2019_748_Fig9_ESM.png (223 kb)
Suppl. Fig. 1

Schematic diagram showing the region of interests (ROIs) selected for image acquisition and quantitative analysis. CC: corpus callosum; EC: external capsule (PNG 222 kb)

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High resolution image (TIF 1.71 mb)
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Suppl. Fig. 2

Representative immunofluorescence images of PI3K p110γ (green) and Iba1 (a cell marker for microglia and macrophages, red) double staining and quantitative analysis of Iba1-positive cells in the ipsilateral perilesional cortex, CA1 and CA3 subfields of the dorsal hippocampus at 3 days after TBI. Scale bar = 50 μm; n = 5 per group, *p < 0.05 vs WT-Sham; #p < 0.05 vs WT-TBI (PNG 1.97 mb)

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High resolution image (TIF 18.9 mb)
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Suppl. Fig. 3

Representative immunofluorescence images of P-eIF2α (green) and NeuN (red) double staining in the ipsilateral perilesional cortex, hippocampal CA1 and CA3 subfields at 3 days after TBI. Scale bars = 100 μm (PNG 645 kb)

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High resolution image (TIF 5.60 mb)
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Suppl. Fig. 4

Representative immunofluorescence images showing the co-localization of PI3K p110γ (green) and CHOP (red) in neurons within the ipsilateral perilesional cortex, hippocampal CA1 and CA3 subfields at 3 days after TBI. Scale bars = 50 μm (PNG 1.79 mb)

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High resolution image (TIF 5.60 mb)
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Suppl. Fig. 5

A, Nissl staining shows brain sections (from bregma −0.2 to −3.8 mm with 0.4 mm interval) from a WT mouse and a KO mouse at 28 days after TBI. Red dotted area indicates tissue loss. B, The changes in body weight were measured before (day 0) and up to 28 days after TBI. n = 12 per group, *p < 0.05 vs WT-TBI (PNG 1.01 mb)

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High resolution image (TIF 10.3 mb)
13311_2019_748_MOESM6_ESM.pdf (59 kb)
ESM 1 (PDF 58 kb)
13311_2019_748_MOESM7_ESM.docx (41 kb)
ESM 2 (DOCX 41 kb)


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Copyright information

© The American Society for Experimental NeuroTherapeutics, Inc. 2019

Authors and Affiliations

  • Shan Liu
    • 1
  • Rong Jin
    • 1
  • Adam Y. Xiao
    • 2
  • Rui Chen
    • 3
  • Jarvis Li
    • 4
  • Wei Zhong
    • 1
  • Xiaozhou Feng
    • 5
  • Guohong Li
    • 1
    • 3
    Email author
  1. 1.Department of Neurosurgery and Neuroscience InstitutePenn State University Hershey Medical CenterHersheyUSA
  2. 2.Department of Molecular and Cellular PhysiologyLouisiana State University Health Sciences CenterShreveportUSA
  3. 3.Department of NeurosurgeryLouisiana State University Health Sciences CenterShreveportUSA
  4. 4.Hershey High SchoolHersheyUSA
  5. 5.Department of PharmacologyPenn State University Hershey Medical CenterHersheyUSA

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