June 2020
Volume 61, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2020
Mitochondrial abnormality in astrocytes leads to optic nerve degeneration: a mechanism mediated by CXCL14
Author Affiliations & Notes
  • Meysam Yazdankhah
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Emily G. Boxi
    Neurology, The Johns Hopkins University, Maryland, United States
  • Stacey L Hose
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Nadezda A Stepicheva
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Joseph Weiss
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Sayan Ghosh
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Peng Shang
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Haitao Liu
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Christopher Scott Fitting
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
  • Ming-Wen Hu
    Wilmer Eye Institute, The Johns Hopkins University, Maryland, United States
  • Jiang Qian
    Wilmer Eye Institute, The Johns Hopkins University, Maryland, United States
  • Peter Calabresi
    Neurology, The Johns Hopkins University, Maryland, United States
  • J. Samuel Zigler
    Wilmer Eye Institute, The Johns Hopkins University, Maryland, United States
  • Debasish Sinha
    Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
    Wilmer Eye Institute, The Johns Hopkins University, Maryland, United States
  • Footnotes
    Commercial Relationships   Meysam Yazdankhah, None; Emily G. Boxi, None; Stacey Hose, None; Nadezda Stepicheva, None; Joseph Weiss, None; Sayan Ghosh, None; Peng Shang, None; Haitao Liu, None; Christopher Fitting, None; Ming-Wen Hu, None; Jiang Qian, None; Peter Calabresi, None; J. Samuel Zigler, None; Debasish Sinha, None
  • Footnotes
    Support  This work was supported by Knights Templar Eye Foundation grant to MY (2018-2020), Research to Prevent Blindness (Unrestricted grant to Ophthalmology, University of Pittsburgh) and University of Pittsburgh start-up funds to DS.
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 2791. doi:
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      Meysam Yazdankhah, Emily G. Boxi, Stacey L Hose, Nadezda A Stepicheva, Joseph Weiss, Sayan Ghosh, Peng Shang, Haitao Liu, Christopher Scott Fitting, Ming-Wen Hu, Jiang Qian, Peter Calabresi, J. Samuel Zigler, Debasish Sinha; Mitochondrial abnormality in astrocytes leads to optic nerve degeneration: a mechanism mediated by CXCL14. Invest. Ophthalmol. Vis. Sci. 2020;61(7):2791.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Neuroinflammation is a common feature of most optic nerve (ON) disorders. To unravel the mechanisms of how astrocytes contribute to ON neuroinflammation, we have developed a rat model where two separate mutations act synergistically to produce severe ON degeneration. One mutation is in the Cryba1 gene that is crucial for lysosomal function and is expressed only in astrocytes in ON. The other mutation is in the Bckdk gene that is crucial for mitochondrial function and is expressed in all cell types. This study reveals the key role of mitophagy in astrocytes in the homeostasis of ON.

Methods : ONs were dissected from wild type, both single mutants, and double mutant (DM) rats at postnatal days 21 (P21) and P120. Primary astrocyte cultures from ONs were subjected to scRNA-seq, immunostaining, and blotting. Live cell imaging was used to measure mitochondrial membrane potential (MMP), mitochondrial reactive oxidative stress (mitoROS) and mitophagy flux. Urolithin A (UA) was used to induce mitophagy in DM astrocytes.

Results : Immunoblotting and staining revealed severe ON degeneration associated with inflammation in DM ONs compared to other genotypes at P120, but not at P21. RNA-seq data showed that CXCL14 was the most up-regulated gene in the ON of P120 DM rats. scRNA-seq analysis on mixed primary cultures of glial cells showed that astrocytes are the main source of CXCL14 production in DM ONs. Overexpression of CXCL14 in cultured DM astrocytes is associated with elevation of mitoROS and reduction of MMP. Moreover, the number of fragmented mitochondria (required for mitophagy) was significantly increased, but mitophagy flux was inhibited in DM astrocytes relative to other genotypes. Stimulation of mitophagy flux by UA in DM astrocytes led to significant reductions in AKT/mTORC1 activation, the number of fragmented mitochondria and the level of mitoROS generation. Interestingly, mitophagy induction by UA led to reduction of CXCL14 expression in DM astrocytes, indicating a role of dysfunctional mitochondria in CXCL14 expression.

Conclusions : Astrocytes are the only cells in DM ON where the function of both mitochondria and lysosomes is impaired. Defective mitophagy in DM astrocytes leads to accumulation of dysfunctional mitochondria, which in turn, promotes recruitment of immune cells into ON through upregulated CXCL14 expression.

This is a 2020 ARVO Annual Meeting abstract.

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