Abstract
Purpose :
Several neurodegenerative diseases involve accumulation of misfolded tau, which leads to neurofibrillary tangle formation. Also, tau hyperacetylation promotes tau accumulation and aggregation. Here, we examined the levels and distribution of acetylated (Ac) and total tau in rat retinas following acoustic blast overpressure (ABO) exposure, relative to unexposed controls.
Methods :
Anesthetized adult male Long-Evans rats were subjected to ABO exposure, twice, with 1-mo. recovery between exposures. Eyes/retinas were harvested at 48 h post-2nd ABO exposure; non-exposed, age/sex-matched rats served as controls. Immunohistochemistry (IHC) was performed on cryosections of PFA-fixed eyes, probing with polyclonal antibodies (Abs) against Ac -tau (9AB or AC312) or a pan-tau rabbit mAb (EP2456Y). Average % IPL area occupied by pan-tau-labelling was calculated in thresholded z-stack images using ImageJ. Ab specificity was tested by Western blot (WB) analysis, using in vitro-acetylated recombinant rat tau (Ac-rat-tau) as a standard. Statistical analysis: Student’s t-test, with significance threshold P<0.05 (N=7/group).
Results :
IHC with Ac-tau Abs showed immunolabelling of nuclei within the GCL INL, ONL and RPE-choroid, and diffuse-to-punctate IPL labelling. A filamentous labelling pattern in the IPL and INL was evident using Ab AC312. However, pan-tau mAb EP2456Y labelled the inner retina, with a diffuse-to-punctate pattern in the GCL, IPL, and perinuclear labeling in the INL, consistent with prior studies. Tau puncta in the IPL varied in size and density. Thresholded image analysis of the IPL region revealed a ~2.8 fold increase in %Area occupied by pan-tau- labelled puncta in ABO-exposed retinas compared to controls. WB analysis revealed that both anti-Ac-tau Abs detected Ac-rat-tau, but not non-Ac-rat-tau. However, both Abs exhibited cross-reactivity with the catalytic domain of p300 acetyltransferase, required for tau acetylation in vitro. EP2456Y detected both Ac and non-Ac forms of tau, but not p300, and was tau-specific.
Conclusions :
Visual dysfunction following ABO exposure may be due, in part, to retinal tauopathy caused by tau accumulation, aggregation, and inclusion body formation. However, IHC results obtained using 9AB and AC312 anti-Ac-tau Abs should be interpreted with caution, due to potential cross-reactivity with p300.
This is a 2021 ARVO Annual Meeting abstract.