Abstract
Purpose :
There is an unmet clinical need for drug therapies for inherited retinal dystrophies (IRD). Broad-spectrum histone deacetylase inhibitors (HDACi) rescue vision in animal models of inherited blindness. Similar results in retinitis pigmentosa patients are highly controversial. We hypothesized that selective HDAC6 inhibitors (HDAC6i) can restore vision, with increased efficacy and safety. Secondly, we postulated that HDAC6i protects against oxidative damage, a hallmark of retinal degeneration.
Methods :
Zebrafish models of IRD, dying on edge (dye) and raifteirí (raf), were treated at 3 days post fertilization (dpf) with 100 µM Tubastatin A (TubA), 25 µM Bas-2 or 10 µM Tubacin (n = 12 dye and n = 48 raf). Visual function was assessed at 6 dpf using optokinetic response assays (OKR) to determine the efficacy of HDAC6i in restoring vision. Retinal morphology was analyzed by light and electron microscopy. ARPE-19 cells were incubated with increasing concentrations of H2O2 for 6 hours with or without 2-hour pre-incubation with 20 μM TubA. MTT assays were used to quantify cell number. Statistical analysis used are two-tailed Student’s T-test and Two-way ANOVA.
Results :
Vision was significantly restored in dye-/- treated with all three HDAC6i. TubA, Bas-2 and Tubacin treatment, respectively, resulted in increased visual function from 1-2 saccades/minute on average to 17 saccades/minute (p < 0.0001), 4 saccades/minute (p = 0.0002) or 5 saccades/minute (p < 0.0001). Vision was improved in TubA treated raf-/-, with an average of 2 saccades/minute (p = 0.0002) compared to vehicle controls (0.2 saccades/minute). Restoration of photoreceptor outer segment morphology was observed in TubA treated raf and dye mutants. In ARPE-19, TubA treatment was not cytotoxic. H2O2 reduced cell viability (25-45%) in a dose-dependent manner and this was attenuated by pre-incubation with TubA.
Conclusions :
Selective HDAC6i drugs offer new potential to uncover therapeutic targets for treatment of IRD. HDAC6i protects ARPE-19 cells from apoptosis induced by oxidative damage. Future experiments include elucidating HDAC6i mechanism of action in rescuing visual function and its role in protecting retinal cells from oxidative stress.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.