Evaluation of the neuroprotective mechanisms of 7,8-dihydroxyflavone and generation of sustained release nano/microparticles for improved ocular drug delivery

Flavia Messina¹, Andrea Cerquone Perpetuini², Husvinee Sundaramurthi¹, Ailis Moran³, Milton English⁴, Matthew Brooks⁴, Anand Swaroop⁴, Madhuri Dandamudi⁵, Alison L. Reynolds⁶, Niall O’Reilly⁷, Breandán N. Kennedy^3
1UCD - Conway Institute, ²Novartis, ³UCD - Conway Institute, ⁴National Eye Institute - NIH, ⁵WIT - PMBRC, ⁶UCD - School of Veterinary Medicine, ⁷WIT - PMBRC

Introduction/Background & aims 7,8-Dihydroxyflavone (7,8-DHF), a reported TrkB agonist, improves vision in the atp6voe1^ucd6 zebrafish model of inherited blindness [1]. Here, the mechanism by which 7,8-DHF restores vision is investigated and biodegradable nano/microparticles for 7,8-DHF ocular drug delivery are characterized.

Method/Summary of work 3 days post fertilized (dpf) sibling or atp6voe1^ucd6 larvae (n=5, N=3) were treated with 20-40 µM 7,8-DHF or 0.1% DMSO. Visual behaviour was assessed at 5 dpf by the optokinetic response assay (OKR) . For mechanistic analysis, 60 eyes of 5 dpf atp6voe1^ucd6 treated with 0.1% DMSO or 20 µM 7,8-DHF were analysed by RNAseq and differentially expressed genes/pathways identified using Cytoscape and gProfiler. PLGA nano/micro-particles incorporating 7,8-DHF were produced by single emulsion solvent evaporation, encapsulation efficiency analyzed by HPLC, and particle size or shape analysed by dynamic light scattering or scanning electron microscope.

Results/Discussion 20 µM 7,8-DHF rescues atp6voe1^ucd6 visual function (p= 0.04). RNAseq identified 15,662 genes of which 58 were down regulated and 213 up regulated by 7,8-DHF. Following gProfiler analyses, among the down-regulated processes are genes related to inflammation, among the up regulated processes are genes related to translation. 7,8-DHF PLGA nanoparticles show 59.14 ± 4.97 % drug encapsulation, mean size of 314 nm; the spherical microparticles of 3-30 µm display drug encapsulation of 72.92 ± 1.121%.

Conclusion(s) 7,8-DHF may rescue vision by decreasing inflammation in the eye. The biodegradable PLGA nano/microparticles display appropriate drug encapsulation and physiochemical properties. Future directions include characterization of efficacy and safety in biological systems.

Reference(s)

[1]. Daly C, Shine L, Heffernan T, et al. A Brain-Derived Neurotrophic Factor Mimetic Is Sufficient to Restore Cone Photoreceptor Visual Function in an Inherited Blindness Model. Sci Rep-uk. 2017;7(1):11320.