Purpose: To investigate the (i) effect(s) of cholinergics on the expression and secretion of transforming growth factor (TGF)-beta(2) in human retinal pigment epithelium (RPE) and (ii) mechanism of action of atropine in the treatment of myopia.
Materials and methods: The RPE cell line, D407, was (i) treated with carbachol (10 microM), (ii) treated with atropine (10 nM-100 microM), or (iii) pre-treated with atropine (10 nM-100 microM) and then exposed to carbachol (10 microM). A no-treatment group served as control. Expression of TGF-beta(2), after stimulation at different time points (2, 4, 8, 16, 24, and 48 hr), was measured by RT-PCR and Western blot analysis. Secretion of TGF-beta(2) was determined by ELISA.
Results: Carbachol induced a time-dependent increase in the levels of TGF-beta(2) mRNA and protein in the cytoplasm (p < 0.001). ELISA assays showed a time-dependent increase in levels of TGF-beta(2) protein in the supernatant with carbachol treatment (p < 0.001). There was no change of TGF-beta(2) in the cytoplasm or supernatant with atropine alone (p > 0.05). The increased expression and secretion of TGF-beta(2) caused by carbachol were suppressed by atropine (in the range of 10 nM-100 microM) when compared to treatment with carbachol alone (p < 0.001). The stimulating effect of 10 microM carbachol was inhibited completely by 100 microM atropine.
Conclusions: In RPE cells, atropine inhibits the expression and secretion of TGF-beta(2) by blocking the muscarinic acetylcholine receptor (mAChR), which may control the development of myopia.