Manganese porphyrin antioxidant alleviates particulate matter-induced allergic conjunctivitis

Abstract

Purpose : Particulate matter (PM) is a well-known trigger for the development of both acute and chronic forms of ocular surface disease. The purpose of this study was to evaluate the prototypic manganese porphyrin, manganese(III) tetrakis(1-methyl-4-pyridyl) porphyrin (Mn-TM-2-PyP), for its ability to protect against PM-induced damage.

Methods : Standardized Reference Material (SRM^® 2786) consisting of fine atmospheric particulate of < 4 µm diameter was obtained from NIST. Rabbit corneal epithelial (SIRC) cells were exposed to a dose range of PM (1 - 300 µg/ml) for 24 h. Cell viability and motility assays were performed to evaluate the effect of PM and the protective effect of Mn-TM-2-PyP. The pharmacologic efficacy of Mn-TM-2-PyP (0.05% in saline, BID for 10 d) was tested in PM-induced allergic conjunctivitis in New Zealand White rabbits and assessed by ophthalmic exams and corneal fluorescein staining.

Results : MTT assay revealed dose-dependent loss of cell viability in response to PM exposure with IC₅₀ of 13.6 µg/ml PM (n = 3 - 6), while lactate dehydrogenase (LDH) release increase dose-dependently with EC₅₀ of 149.1 µg/ml PM (n = 3 - 6). Mn-TM-2-PyP (0.005% and 0.05%; 30 min pre-treatment) protected against PM (100 µg/ml)-induced LDH release (n = 3, P < 0.05). Exposure to PM (200 µg/ml) for 24 h significantly reduced motility of SIRC cells in scratch assays. Scratches were 54.4 ± 2.4% of the original width in untreated cells, while the scratch remained at 79.8 ± 2.6% in PM-treated cells (P < 0.001). In contrast, Mn-TM-2-PyP improved PM-treated SIRC motility beyond the level in untreated cells with scratch widths at 42.0 ± 1.9% (P < 0.001). In vivo, 10 d treatment with Mn-TM-2-PyP completely resolved PM-induced hyperemia (n = 4, P < 0.001) and corneal pathology (n = 4, P < 0.001) when compared to saline-treated eyes. Mn-TM-2-PyP had no effect on tear volumes.

Conclusions : Mn-TM-2-PyP protected against PM-induced cytotoxicity and impairment in motility in vitro and PM-induced allergic conjunctivitis in vivo. These data corroborate previous studies that have suggested generation of cellular oxidative stress as underlying mechanism of the deleterious effects of PM on epithelial cells. Our data suggest that oxidative stress is an etiological contributor to PM-induced allergic conjunctivitis in rabbits and support future therapeutic development of antioxidants for PM-induced ocular surface disease.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.