Mitochondrial-Targeted Antioxidant-Encapsulating Nanoparticles as a Promising Therapeutic Strategy in Regulating Outflow Resistance

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Neurodegenerative diseases, including glaucoma, substantially alter quality of life of the affected Veteran. Glaucoma remains a leading cause of irreversible blindness. Currently affecting over 60 million individuals, this insidious optic neuropathy is characterized by a gradual loss of RGC neurons and is projected to impact nearly 80 million people by the year 2020. The prevalence of primary open angle glaucoma (POAG), the most common form of glaucoma, is approximately 1.86%, or nearly 2 million individuals, 45 years of age and older in the US. Despite being an extraordinarily significant socioeconomic burden to the DVA, the treatment of US Veterans with POAG remains limited and palliative. Current treatment options are restricted to non-specific interventions aimed at lowering intraocular pressure (IOP), a poorly-understood hallmark of POAG. For many glaucomatous Veterans, however, pharmacological and surgical management of IOP remains clinically refractive. The development of targeted therapeutic strategies directed at the cause of elevated IOP is critical for the advanced management of glaucomatous Veterans. In healthy eyes, IOP is maintained through balanced production and outflow of aqueous humor (AH). Increased resistance to AH outflow through the trabecular meshwork/juxtacanalicular tissue (TM/JCT) is a major contributor of aberrant elevation of IOP in POAG. The molecular mechanisms responsible for elevated IOP remain elusive, but most likely involve aberrant expression and signaling of transforming growth factor-β2 (TGF-β2). Numerous studies demonstrate that TGF-β2, a multifunctional cytokine that promotes TM cell contractility and increased extracellular matrix (ECM) synthesis and deposition within the TM, is markedly elevated in the AH of patients with POAG. While the cellular origin of TGF-β2 is unclear, we reported that human TM cells constitutively express and secrete active TGF-β2, highlighting the TM as a viable targetable source of active TGF-β2. Whereas the development of selective TGF-β2 downstream signaling pathway inhibitors continues to be the focus of intense investigations, targeted disruption of constitutive TGF-β2 expression and release from the TM represents an underexploited therapeutic strategy for the management of IOP in POAG. Numerous studies also report elevated levels of oxidative stress markers in AH of POAG patients, along with altered expression of antioxidant defenses in the TM. Selective oxidative damage to TM mitochondria (Mt) elicits TM cell dysfunction. Mt-generated reactive oxygen species (ROS) are required for TGF-β induced gene expression. Here, we present unpublished findings demonstrating Mt-targeted antioxidants significantly attenuate expression and release of TGF-β2 from cultured human TM cells. Collectively, a penultimate role of Mt-generated ROS in TGF-β2 mediated decreases in outflow facility and increased IOP in POAG begins to emerge. Hypothesis: Targeted disruption of constitutive TGF-β2 expression or signaling within the TM/JCT with mitochondrial-targeted antioxidant-encapsulating nanoparticles will increase outflow facility and lower IOP. The hypothesis of this study will be tested with the following three Specific Aims using a combination of ex vivo and in vitro established experimental approaches: Aim 1 will determine, ex vivo, whether perfusing human or porcine anterior segments with mitochondrial-targeted antioxidant-encapsulating nanoparticles will protect against experimentally induced decreases in outflow facility. Aim 2 will determine, ex vivo, whether perfusing human or porcine anterior segments with mitochondrial-targeted antioxidant-encapsulating nanoparticles will alter TM tissue integrity, endogenous TGF-β2 expression, or TGF-β2 mediated changes in ECM composition. Aim 3 will elucidate the mechanism(s) by which mitochondrial-targeted antioxidant-encapsulating nanoparticles alter TGF-β2 expression or TGF-β2 mediated changes in ECM composition in cultured human TM cells. Successful completion of the proposed study will serve as a critical first step toward developing this technology for the management of Veterans with POAG.