Transforming Growth Factor Beta 1 Modulates the Functional Expression of the Neurokinin-1 Receptor in Human Keratocytes

• Published in: Current eye research 2016-08, Vol.41 (8), p.1035-1043
• Main Authors: Roux, Sandrine Le, Borbely, Gabor, Słoniecka, Marta, Backman, Ludvig J., Danielson, Patrik
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aged, 80 and over; anatomi; Blotting, Western; Cell Differentiation; Cell Proliferation; Cells, Cultured; Cornea; Corneal Keratocytes - cytology; Corneal Keratocytes - metabolism; cytokines; Female; Gene Expression Regulation; Human Anatomy; Humans; Immunohistochemistry; Male; Middle Aged; neuropeptides; Real-Time Polymerase Chain Reaction; Receptors, Neurokinin-1 - biosynthesis; Receptors, Neurokinin-1 - genetics; RNA - genetics; Signal Transduction; stroma; substance P; Transforming Growth Factor beta1 - biosynthesis; Transforming Growth Factor beta1 - genetics
• ISSN: 0271-3683; 1460-2202; 1460-2202
• DOI: 10.3109/02713683.2015.1088954

Purpose: Transforming growth factor beta 1 (TGF-β1) is a cytokine involved in a variety of processes, such as differentiation of fibroblasts into myofibroblasts. TGF-β1 has also been shown to delay the internalization of the neurokinin-1 receptor (NK-1 R) after its activation by its ligand, the neuropeptide substance P (SP). NK-1 R comprises two naturally occurring variants, a full-length and a truncated form, triggering different cellular responses. SP has been shown to affect important events in the cornea - such as stimulating epithelial cell proliferation - processes that are involved in corneal wound healing and thus in maintaining the transparency of the corneal stroma. An impaired signaling through NK-1 R could thus impact the visual quality. We hypothesize that TGF-β1 modulates the expression pattern of NK-1 R in human corneal stroma cells, keratocytes. The purpose of this study was to test that hypothesis. Methods: Cultures of primary keratocytes were set up with cells derived from healthy human corneas, obtained from donated transplantation graft leftovers, and characterized by immunocytochemistry and Western blot. Immunocytochemistry for TGF-β receptors and NK-1 R was performed. Gene expression was assessed with real-time polymerase chain reaction (qPCR). Results: Expression of TGF-β receptors was confirmed in keratocytes in vitro. Treating the cells with TGF-β1 significantly reduced the gene expression of NK-1 R. Furthermore, immunocytochemistry for NK-1 R demonstrated that it is specifically the expression of the full-length isotype of the receptor that is reduced after treatment with TGF-β1, which was also confirmed with qPCR using a specific probe for the full-length receptor. Conclusions: TGF-β1 down-regulates the gene expression of the full-length variant of NK-1 R in human keratocytes, which might impact its signaling pathway and thus explain the known delay in internalization after activation by SP seen with TGF-β1 treatment.