L-carnitine partially restores adherens junction integrity and promotes wound healing in human corneal epithelial cells exposed to hyperosmolar stress

Abstract

Disruption of tear film homeostasis and increased osmolarity are key features of dry eye disease (DED), leading to inflammation, epithelial barrier dysfunction, and ocular surface damage. Adherens junctions, primarily composed of cadherins and catenins, are essential for maintaining epithelial integrity and modulating signaling pathways that regulate cell proliferation and migration. This study investigates the effects of hyperosmolarity on adherens junction proteins and wound healing, as well as the therapeutic potential of L-carnitine (LCAR) in mitigating these effects. To induce hyperosmolar stress, telomerase-immortalized human corneal epithelial cells (hTCEpi) were treated with 70, 90, and 120 mM NaCl, resulting in final osmolarities of approximately 450, 490, and 550 mOsM, respectively. LCAR supplementation (200 mM) was evaluated as a potential osmoprotective therapy. Hyperosmolarity caused a dose-dependent reduction in trans-epithelial resistance (TER), with a 30–69 % decline across treatment groups, along with significantly impaired cell migration. Adherens junction proteins (E-cadherin, β-catenin, and p120-catenin) were downregulated, while α-catenin was upregulated. Notably, L-carnitine treatment alleviated these effects, significantly restoring TER and adherens junction protein levels to near-normal. These findings demonstrate that hyperosmolarity impairs corneal epithelial barrier function and delays wound healing by altering adherens junction complex. Our results highlight the potential of L-carnitine as a therapeutic agent to restore epithelial barrier integrity and mitigate hyperosmolarity-induced damage in DED.