Abstract
Purpose :
Precedent literatures indicate that endoplasmic reticulum (ER) stress plays a contributory role in the development of chronic GVHD (cGVHD) in various organs. However, its effects on the eyelids and ocular surface in cGVHD have not been fully investigated. Herein, we aimed to elucidate the relationship between ER stress and ocular GVHD by using the ER stress suppressor 4-phenylbutyric acid (PBA).
Methods :
Allogeneic bone marrow transplantation (BMT) from B10.D2. to BALB/c mice was used to create a chronic GVHD (cGVHD) mouse model. As a non-cGVHD control, syngeneic BMT was conducted by transplanting donor cells from BALB/c mice into BALB/c mice. The cGVHD mice were treated with PBA or vehicle by intraperitoneal injection. The injections were conducted once a day from Day 10 to Day 27 after BMT. To confirm the efficacy of topical PBA administration, 2% PBA eye drops, or vehicle were administered to cGVHD mice twice a day from Day 7 to Day 27 after BMT.
Results :
Topographical results showed that the meibomian gland (MG) area in the vehicle-treated cGVHD mice were significantly decreased compared to syngeneic control. The intraperitoneally PBA-treated (PBAip) group retained a significantly larger MG area compared to vehicle-treated cGVHD mice. Immunohistochemical analysis using the inflammatory cell marker CD45 and the myofibroblast marker α-SMA showed that inflammation and pathological fibrosis of the eyelid tissue were significantly reduced in the PBAip group compared to the vehicle-treated group. The results using immunoblotting showed that the expression of the unfold protein response (UPR) markers GRP78, p-IRE1α, pPERK, and ATF6 were significantly elevated in the vehicle group compared to the syngeneic control and PBAip group. Corneal fluorescein staining score was significantly lower in the PBA eye drops-treated group compared to the vehicle group. The results of whole-mount immunohistochemistry showed that the number of leukocyte marker CD45, T cell marker CD4, macrophage marker F4/80 positive cells were significantly attenuated in PBA eye drops-treated group compared to the vehicle group.
Conclusions :
ER stress response was promoted in the eyelids of cGVHD mice. ER stress suppressor PBA attenuated the severity of ocular GVHD. These findings suggest that the ER stress suppressor PBA has a potential for therapeutic application in ocular GVHD.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.