Abstract
Purpose :
Toll-like receptor (TLR) acting as lipopolysaccharide (LPS) sensor is involved in recognition of and response to endotoxin mediated infections. Their activation contributes to uveitis leading to stimulation of signaling events that include expressions of various cytokines such as TNF-α. The mainstay for the treatment is steroids, which are substrates for P-gp transporters, and on topical application, would be effluxed, leading to insufficient therapeutic levels in aqueous humor (AH). Hence, this study evaluated alternative P-gp sparing molecules that act via similar anti-inflammatory pathways to control inflammation.
Methods :
Topical dapsone and nimesulide (0.1%) were formulated aseptically and evaluated in endotoxin-induced uveitis (EIU) Wistar rat model in comparison with topical prednisolone (1%). Rats received 0.1 ml saline containing 200 µg LPS through hindpaw, with three times a day (TID) topical instillation of 10 µl vehicle, nimesulide, dapsone and prednisolone (Table 1) in their respective groups. 30 µl of AH was collected for protein extravasation analysis and TNF-α levels.
Results :
Results showed topical nimesulide significantly reduced AH TNF-α levels in EIU (Nimesulide) group (14.07±5.36 ng/ml) as compared to EIU (Vehicle) group (40.6±5.51 ng/ml). It also reduced protein leakage in AH of EIU (Nimesulide) group (8.37±2.87 mg/ml) as compared to control (18.48±2.13 mg/ml). The topical dapsone resulted in a significant decrease in total protein concentration of AH in EIU (Dapsone) group (11.44±0.93 mg/ml) when compared to EIU (Vehicle) group (22.5±2.06 mg/ml). Moreover, 0.1% dapsone topical instillation also decreased TNF-α levels in AH of EIU (Dapsone) group (18.4±2.26 ng/ml) when compared to EIU (Vehicle) group (26.49±3.66 ng/ml). While prednisolone administered (TID) in EIU showed non-significant reduction in total protein as well as TNF-α levels in AH.
Conclusions :
For the first time, sterile topical nimesulide and dapsone formulations were developed and were found to be effective in modulating TLR by reducing inflammatory markers (TNF-α) and vascular leakage in AH of rats when compared to prednisolone. Therefore, this study showed that molecules that are P-gp sparing could be a better option for targeting TNF-α pathway for their utility in uveitis.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.