Dry eyes are caused by highly increased osmolarity of tear film,
inflammation, and apoptosis of the ocular surface. In this study, we investigated the effect of Polygonum cuspidatum (PCE) aqueous extract in in vivo and in vitro
dry eye models.
Dry eye was induced by excision of the lacrimal gland and hyperosmotic media. In vivo,
oral administration of PCE in exorbital lacrimal gland-excised rats recovered tear volume and Mucin4 (MUC4) expression by inhibiting corneal irregularity and expression of inflammatory
cytokines. In vitro, hyperosmotic media induced human corneal epithelial cell (
HCEC) cytotoxicity though increased
inflammation, apoptosis, and oxidative stress. PCE treatment significantly inhibited expression of
cyclooxygenase-2 and inflammatory
cytokines (
interleukin-6 and
tumor necrosis factor-α), and activation of NF-κB p65 in hyperosmolar stress-induced HCECs. Hyperosmolarity-induced increase in
Bcl-2-associated X protein (BAX) expression and activation of cleaved
poly (ADP-ribose) polymerase and
caspase 3 were attenuated in a concentration-dependent manner by PCE. PCE treatment restored anti-oxidative
proteins such as
heme oxygenase-1 (HO-1),
superoxide dismutase-1 (SOD-1), and
glutathione peroxidase (GPx) in hyperosmolar stress-induced HCECs. These data demonstrate that PCE prevents adverse changes in the ocular surface and tear fluid through inhibition of hyperosmolar stress-induced
inflammation, apoptosis, and oxidation, suggesting that PCE may have the potential to preserve eye health.