Cyclooxygenase-2 Modulates Glycosaminoglycan Production in the Skin During Salt Overload

Abstract

Sodium (Na +) can accumulate in the skin tissue, sequestered by negatively charged glycosaminoglycans (GAGs). During dietary salt overload, the amount and charge density of dermal GAG molecules-e.g., hyaluronic acid (HA) and chondroitin sulfate (CS)increases; however, the regulation of the process is unknown. Previously, it has been demonstrated that the level of cyclooxygenase-2 (COX-2) activity and the content of prostaglandin E2 (PGE2) are elevated in the skin due to high-salt consumption. A link between the COX-2/PGE2 system and GAG synthesis was also suggested. We hypothesized that in dermal fibroblasts (DFs) high-sodium concentration activates the COX-2/PGE2 pathway and also that PGE2 increases the production of HA. Our further aim was to demonstrate that the elevation of the GAG content is ceased by COX-2 inhibition in a salt overloaded animal model. For this, we investigated the messenger RNA (mRNA) expression of COX-2 and HA synthase 2 enzymes as well as the PGE2 and HA production of DFs by real-time reverse transcription PCR (qRT-PCR) and ELISA, respectively. The results showed that both high-sodium concentration and PGE2 treatment increases HA content of the media. Sodium excess activates the COX-2/PGE2 pathway in DFs, and COX-2 inhibition decreases the synthesis of HA. In the animal experiment, the HA-and CS disaccharide content in the skin of male Wistar rats was measured using high performance liquid chromatography-mass spectrometry (HPLC-MS). In the skin of rats receiving high-salt diet, the content of both HA-and monosulfated-CS disaccharides increased, whereas COX-2 inhibition blocked this overproduction. In conclusion, high-salt environment could induce GAG production of DFs in a COX-2/PGE2-dependent manner. Moreover, the COX-2 inhibition resulted in a decreased skin GAG content of the salt overloaded rats. These data revealed a new DF-mediated regulation of GAG synthesis in the skin during salt overload.

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“…These results suggest that increased local salt concentration could directly influence the dermal ECM production of DF cells. Our recent study demonstrated that high salt environment increases the prostaglandin E2 production of DFs, that has been shown to inhibit the DF's collagen expression in an autocrine TGF-β/Smad pathway-dependent manner, which gives a possible explanation for our present results [10,56].…”

“…However, several previous human and animal studies demonstrated that sodium is stored in the skin in both free and inactive forms [2][3][4][5][6][7][8][9]. In addition, our previous study demonstrated that dermal fibroblasts are important mediators of skin sodium storage [10].…”

High salt diet impairs dermal tissue remodeling in a mouse model of IMQ induced dermatitis

“…For real-time PCR measurements DF cells were seeded into 96-well plates (Sarstedt, Nümbrecht, Germany) at a density of 10 4 cells/well (n = 6 well/treatment group) and were subjected to culture medium with normal (Control; 150 mmol/L) or high sodium concentration (NaCl; 200 mmol/L) with or without recombinant human TGF-ß (1 nmol/L) (Thermo Fisher Scientific). The additional sodium concentration was determined as previously described [ 10 ]. Vehicle treated cells served as controls.…”

“…However, several previous human and animal studies demonstrated that sodium is stored in the skin in both free and inactive forms [ 2 – 9 ]. In addition, our previous study demonstrated that dermal fibroblasts are important mediators of skin sodium storage [ 10 ].…”

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“…For real-time PCR measurements DF cells were seeded into 96-well plates (Sarstedt, Nu ¨mbrecht, Germany) at a density of 10 4 cells/well (n = 6 well/treatment group) and were subjected to culture medium with normal (Control; 150 mmol/L) or high sodium concentration (NaCl; 200 mmol/ L) with or without recombinant human TGF-ß (1 nmol/L) (Thermo Fisher Scientific). The additional sodium concentration was determined as previously described [10]. Vehicle treated cells served as controls.…”