Defense against Reactive Oxygen Species during Gastric Wound Repair is Mediated by the Cystine‐Glutamate xCT Transporter in Response to Injury
Authors: Teal Emma L , Chakrabarti Jayati L , Steele Nina , Hawkins Jennifer , Sundaram Nambirajan , Wang Jiang L , Helmrath Michael A , Diwan Tayyab L , Barrett Terry , Zavros Yana L 
Published: June 2021

Background/Hypothesis

Cluster‐of‐differentiation gene 44 (CD44) is an alternatively spliced cell surface protein. CD44 variant isoform 9 (CD44v9) has been shown to mediate gastric repair, but the precise mechanism is unknown. Reactive Oxygen Species (ROS) driven p38/MAPK signaling leads to increased caveolin‐1, and re‐direction of β‐catenin from the nucleus to the membrane where it decreases fundamental events contributing to repair such as cellular proliferation and migration. CD44v9 stabilizes the cystine‐glutamate transporter, xCT, which provides defense against ROS. Thus, we hypothesized that CD44v9 stabilizes the xCT transporter to potentiate defense against ROS to establish an environment conducive to efficient wound repair.

Methods

Acetic acid injury was induced in C57BL/6 (BL6) mice followed by vehicle, sulfasalazine (SSZ, an xCT inhibitor) or glutathione inhibitor (GSHinh). Acetic acid gastric injuries were induced in aged mice (>8 months) and animals were treated with p38 inhibitor. Mice were analyzed between days 1 to 30 post‐injury. A novel scratch‐wound assay generated from organoids derived from human stomachs and transferred to a gastric epithelial cell monolayer (huGEM) was treated with vehicle, SSZ or GSHinh.

Results

1) CD44v9 and xCT co‐expressing cells emerge at the ulcer margin: CD44v9/xCT co‐expressing cells emerged at the ulcer margin within 3‐days post‐injury. Compared to control mice, animals treated with SSZ or GSHinh showed impaired wound healing and loss of normal epithelial regeneration in response to injury. Western blots showed loss of activated β‐catenin, increased expression of caveolin‐1 that coincided with loss in repair in SSZ‐treated mice. FACS sorted CD44v9+ve cells from the ulcer margin expressed markers of EMT. 2) SSZ and GSHinh inhibited wound healing in huGEM scratch wound assays: HuGEM cultures exhibited a cellular composition reflective of primary gastric tissue that included the expression of parietal, chief, and mucous neck and pit cells. CD44v9/xCT co‐expressing cells emerged at the wound edge in huGEM cultures in response to a scratch wound. HuGEM cultures treated with SSZ or GSHinh exhibited significantly delayed wound closure. 3) p38 inhibitor rescues wound healing in vivo in the stomachs of aged mice: In human gastric biopsies, CD44v9, xCT, and activated β‐catenin was significantly decreased in elderly patients. Aged mice treated with p38 inhibitor displayed increased cellular proliferation, CD44v9 expression, and rescued repair when compared to aged vehicle controls.

Conclusion

CD44v9 and xCT emerge during gastric regeneration which may potentiate defense against ROS to allow for effective healing.

Support or Funding Information

R01 DK083402‐06A1

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.