# Uncoupling caspase 8-mediated-apotosis from caspase 8-mediated-inflammation in glaucoma.

> **NIH NIH R21** · SCHEPENS EYE RESEARCH INSTITUTE · 2020 · $246,250

## Abstract

One important unanswered question in glaucoma is whether apoptosis of retinal ganglion cells (RGCs) and
axon degeneration are two separate events mediated by molecularly distinct pathways, or whether they are
linked and triggered through a common pathway. Answering this question is critical to developing effective
neuroprotective therapies that protect both axons and RGC somas. In support of the idea there are two distinct
pathways that mediate axon degeneration and RGC apoptosis, it was demonstrated that deletion of the pro-
apoptotic BAX gene blocked apoptosis of RGCs in a mouse model of glaucoma, but did not prevent axon
degeneration. There is accumulating evidence that axon degeneration is triggered by axon damage in the optic
nerve head, which precedes RGC apoptosis and is linked to microglial activation and neurotoxic inflammation.
Therefore, it is possible that blocking inflammation could prevent axon degeneration and subsequent death of
RGCs, leaving open the possibility that there is a shared pathway linking axon degeneration and RGC
apoptosis. In support of the idea that inflammation may be the shared pathway that links axon degeneration
and RGC apoptosis, our laboratory demonstrated previously that blocking the Fas/Fas ligand (FasL) signaling
pathway prevents axon degeneration and RGC apoptosis in both inducible and chronic mouse models of
glaucoma and this protection coincided with an inhibition of microglia activation and induction of inflammatory
mediators. However, since Fas triggers apoptotic and inflammatory pathways, the question remains as to
whether blocking inflammation alone would prevent axon degeneration and subsequent RGC apoptosis. The
challenge to resolving this issue is the inability to uncouple Fas-mediated inflammation from Fas-mediated
apoptosis. However, Fas signaling requires activation of caspase-8 for both apoptosis and inflammation and
recent studies examining the molecular mechanism of caspase-8 activation discovered an additional auto-
cleavage step that is required for the induction of caspase-8-mediated apoptosis but not required for induction
of caspase-8 mediated inflammation. Using this information, a mutant mouse was created (Casp8DA/DA) in
which a point mutation in the auto-cleavage site blocked caspase-8-mediated apoptosis, but did not block
caspase-8-mediated inflammation. We will use these mice to definitively determine how caspase-8-mediated
inflammation and/or apoptosis triggers axon degeneration and RGC apoptosis in glaucoma. We hypothesize
that elevated IOP triggers caspase-8-mediated inflammation that acts as a common pathway triggering axon
degeneration and RGC apoptosis. This hypothesis will be tested in two aims: (1) Determine whether caspase-
8-mediated apoptosis contributes to axon degeneration and death of RGCs in a microbead-induced mouse
model of glaucoma and (2) Demonstrate that Fas-mediated activation of microglia mediates neurotoxic
inflammation, axon degeneration, and death of RGCs ...

## Key facts

- **NIH application ID:** 9919567
- **Project number:** 5R21EY030276-02
- **Recipient organization:** SCHEPENS EYE RESEARCH INSTITUTE
- **Principal Investigator:** MEREDITH GREGORY-KSANDER
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $246,250
- **Award type:** 5
- **Project period:** 2019-05-01 → 2022-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9919567

## Citation

> US National Institutes of Health, RePORTER application 9919567, Uncoupling caspase 8-mediated-apotosis from caspase 8-mediated-inflammation in glaucoma. (5R21EY030276-02). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/9919567. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*