Cleaved caspase 3 is not detected in optic nerve of TNF-α injected eyes. Immunoblot of optic nerve (Optic N) extracts stained for caspase-3 (top), cleaved caspase-3 (middle), and TUJ1 (bottom) as a loading control. Samples are collected from optic nerves 3 d after TNF-α or PBS injection (lanes 1–4). These samples were also used for Fig. 2, I and J. Because cleaved caspse-3 is not detected in TNF-α–injected optic nerves, cultured DRG neurons were incubated with either DMSO (lane 5) or 100 nM bortezomib (BTZ, lane 6) for 18 h as a positive control (Geisler et al., 2019a).