Date on Master's Thesis/Doctoral Dissertation

8-2022

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Degree Program

Pharmacology and Toxicology, PhD

Committee Chair

Song, Zhao-Hui

Committee Co-Chair (if applicable)

Hein, David

Committee Member

Hein, David

Committee Member

Ceresa, Brian

Committee Member

Freedman, Jonathan

Committee Member

Magnuson, David

Author's Keywords

cannabidiol ocular; pharmacology; pharmacokinetics

Abstract

Cannabidiol (CBD) is the most abundant non-psychotropic cannabinoid constituent of Cannabis sativa. CBD is potentially therapeutic for the eye through antioxidant, anti-inflammatory, and neuroprotective effects. However, the effect of CBD on intraocular pressure (IOP)- the major risk factor for glaucoma- is controversial and large variability exists in the literature. IOP is regulated through aqueous humor (AH) dynamics in trabecular meshwork (TM) tissues. Measurement of CBD in AH and correlation with effects on IOP would clarify what concentrations mediate changes to IOP. Therefore, the overall goal of this dissertation is to measure CBD in ocular tissues and correlate concentrations with ocular pharmacologic effects. Effects of CBD on AH outflow were measured in porcine anterior segment explants. Effects of CBD on TM contractility and Rho/ROCK signaling were assessed in vitro. Porcine AH CBD concentrations were measured following ocular topical application ex vivo. A cyclodextrin solution, cyclodextrin solution containing gellan gum (GG) which forms a hydrogel in situ, and a semifluorinated alkane (SFA) were used to apply CBD topically. Murine AH and serum were measured by LC-MS/MS, and porcine AH and cornea concentrations were measured by HPLC. IOP was assessed following intraperitoneal and topical administration in vivo. Corneal analgesia of topical CBD was assessed using an eye wiping test. CBD increased AH outflow ex vivo, decreased TM cell contractility and inhibited TM Rho/ROCK signaling in vitro. Intraperitoneal administration of CBD reached an AH Cmax of 71.55 ng/mL and decreased IOP lasting up to 4 hours. AH concentration of CBD time dependently increased following topical application ex vivo when applied in cyclodextrin vehicles but was localized to the cornea when applied in SFA. Topical CBD lowered IOP when applied in cyclodextrin containing vehicles and reduced corneal pain when applied in an SFA vehicle. Addition of GG increased AH concentrations (Cmax 1864 ng/mL) and extended IOP reduction (from 5 to 8 hours) relative to cyclodextrin-only formulations. We have determined that low micromolar CBD concentrations alter AH outflow and IOP, and vehicle chosen can localize CBD delivery. The results highlight the importance of not only vehicle but also tissue concentrations for CBD mediated pharmacologic effects.

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