Hydration status regulates sodium flux and inflammatory pathways through epithelial sodium channel (ENaC) in the skin.
Although it is known that the inflammatory response that results from disruption of epithelial barrier function after injury results in excessive scarring, the upstream signals remain unknown. It has also been observed that epithelial disruption results in reduced hydration status and that the use of occlusive dressings that prevent water loss from wounds decreases scar formation. We hypothesized that hydration status changes sodium homeostasis and induces sodium flux in keratinocytes, which result in activation of pathways responsible for keratinocyte-fibroblast signaling and ultimately lead to activation of fibroblasts. Here, we demonstrate that perturbations in epithelial barrier function lead to increased sodium flux in keratinocytes. We identified that sodium flux in keratinocytes is mediated by epithelial sodium channels (ENaCs) and causes increased secretion of proinflammatory cytokines, which activate fibroblast via the cyclooxygenase 2 (COX-2)/prostaglandin E2 (PGE2) pathway. Similar changes in signal transduction and sodium flux occur by increased sodium concentration, which simulates reduced hydration, in the media in epithelial cultures or human ex vivo skin cultures. Blockade of ENaC, prostaglandin synthesis, or PGE2 receptors all reduce markers of fibroblast activation and collagen synthesis. In addition, employing a validated in vivo excessive scar model in the rabbit ear, we demonstrate that utilization of either an ENaC blocker or a COX-2 inhibitor results in a marked reduction in scarring. Other experiments demonstrate that the activation of COX-2 in response to increased sodium flux is mediated through the PIK3/Akt pathway. Our results indicate that ENaC responds to small changes in sodium concentration with inflammatory mediators and suggest that the ENaC pathway is a potential target for a strategy to prevent fibrosis.
Laboratory for Wound Repair and Regenerative Medicine, Department of Surgery/Plastic Surgery Division, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Wei
W
Xu
Laboratory for Wound Repair and Regenerative Medicine, Department of Surgery/Plastic Surgery Division, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Seok Jong
SJ
Hong
Department of Agricultural and Biological Engineering, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA.
Michael
M
Zeitchek
Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Garry
G
Cooper
Laboratory for Wound Repair and Regenerative Medicine, Department of Surgery/Plastic Surgery Division, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Shengxian
S
Jia
Laboratory for Wound Repair and Regenerative Medicine, Department of Surgery/Plastic Surgery Division, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Ping
P
Xie
Laboratory for Wound Repair and Regenerative Medicine, Department of Surgery/Plastic Surgery Division, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Hannan A
HA
Qureshi
Laboratory for Wound Repair and Regenerative Medicine, Department of Surgery/Plastic Surgery Division, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA; Department of Plastic Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Aimei
A
Zhong
Department of Agricultural and Biological Engineering, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA.
Marshall D
MD
Porterfield
Laboratory for Wound Repair and Regenerative Medicine, Department of Surgery/Plastic Surgery Division, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Robert D
RD
Galiano
Department of Physiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
D James
DJ
Surmeier
Laboratory for Wound Repair and Regenerative Medicine, Department of Surgery/Plastic Surgery Division, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA. Electronic address: tmustoe@nmh.org.
Thomas A
TA
Mustoe
D000818:Animals; D002450:Cell Communication / Q000502:physiology; D002478:Cells, Cultured; D002921:Cicatrix / Q000517:prevention & control; D018920:Coculture Techniques; D051546:Cyclooxygenase 2 / Q000378:metabolism; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000037:antagonists & inhibitors / Q000378:metabolism; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000378:metabolism*; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D023421:Models, Animal; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011817:Rabbits; D015398:Signal Transduction / Q000502:physiology*; D012867:Skin / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D012964:Sodium / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
D052246:Cyclooxygenase 2 Inhibitors; D053503:Epithelial Sodium Channels; D014867:Water; D012964:Sodium; D051546:Cyclooxygenase 2; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D015232:Dinoprostone