sirolimus and Pterygium

Profibrotic activation is essential for pterygium development. In this study, we investigated the role of the mechanistic target of rapamycin (mTOR) in regulating TGF-β1-induced myofibroblastic responses in human pterygium fibroblasts (HPFs) and elucidated the relative contributions of mTOR signaling components.. HPFs were pretreated with the mTOR inhibitors rapamycin and Torin2, and TGF-β1-induced expression of profibrotic markers, including α-smooth muscle actin (α-SMA) and fibronectin, was evaluated. RNA interference-based approaches targeting raptor and rictor, regulatory subunits of mTOR complex 1 (mTORC1) and 2 (mTORC2), respectively, were used to determine the impact of each mTOR complex on HPFs. The contractile phenotype of HPFs was assessed by a collagen gel contraction assay.. The mTOR active-site inhibitor Torin2, which suppresses both mTORC1 and mTORC2 activity in HPFs, inhibited TGF-β1-induced expression of α-SMA and fibronectin. The allosteric inhibitor rapamycin only partially suppressed mTORC1 activity and exhibited a minimal effect on the induction of profibrotic markers. The induction of α-SMA and fibronectin in HPFs was abrogated by RNA interference-mediated knockdown of rictor but was only moderately affected by raptor knockdown. Akt inhibition mimicked the effect of Torin2 and rictor knockdown on myofibroblast differentiation of HPFs. mTOR inhibition potently reduced the contractile ability of HPFs in collagen gel contraction assays.. This study found that mTOR signaling promoted profibrotic activation of HPFs and confirmed the importance of the mTORC2-Akt axis in TGF-β1-induced myofibroblast differentiation. Therefore, our study may open up new avenues for the development of novel therapeutic strategies involving targeting of mTOR signaling to treat pterygium.

Topics: Actins; Adult; Aged; Blotting, Western; Cell Differentiation; Fibroblasts; Fibronectins; Flow Cytometry; Fluorescent Antibody Technique, Indirect; Humans; Mechanistic Target of Rapamycin Complex 2; Middle Aged; Myofibroblasts; Naphthyridines; Proto-Oncogene Proteins c-akt; Pterygium; Real-Time Polymerase Chain Reaction; RNA Interference; Signal Transduction; Sirolimus; Transforming Growth Factor beta1

The authors have previously shown that the growth of cultured fibroblasts obtained from primary pterygia was associated with an increase in cholesterol esterification, suggesting that alterations of cholesterol homeostasis may be involved in the development and progression of this disorder. This investigation was conducted to determine whether antiproliferative agents such as pioglitazone (PIO) and everolimus (EVE) may inhibit proteins involved in the cholesterol ester cycle and the proliferation of pterygium fibroblasts (PF).. Quiescent normal conjunctival fibroblasts and PFs were treated with or without inhibitors of cell proliferation (PIO and EVE) or with inhibitors of cholesterol esterification-progesterone (Pg) and Sandoz compound (SaH)-and then were stimulated to growth by 10% fetal calf serum (FCS). Cell proliferation was assessed by counting cells. Trypan blue uptake was used to determine cell viability. mRNA and protein levels were determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively.. PIO and EVE significantly abolished the increase in cholesterol esters, acyl-coenzyme A cholesterol acyltransferase (ACAT1), and multidrug resistance protein (MDR1) mRNA observed in growing cells. Each inhibitor upregulated ATP-binding cassette-A1 (ABCA1), neutral cholesterol ester hydrolase (NCEH) mRNA, and caveolin-1 expression in a manner similar to that of specific inhibitors of cholesterol esterification such as Pg and SaH.. Intracellular modifications of cholesterol homeostasis may be relevant to pterygium development. Moreover, antiproliferative agents such as PIO and EVE may represent a potential topical medication in the prevention and inhibition of pterygium growth at an early stage, probably by modulation of cholesterol ester metabolism.

Topics: Aged; Amides; ATP Binding Cassette Transporter, Subfamily B, Member 1; Caveolin 1; Cell Division; Cells, Cultured; Cholesterol; Cholesterol Esters; Enzyme Inhibitors; Everolimus; Female; Fibroblasts; Homeostasis; Humans; Hypoglycemic Agents; Immunosuppressive Agents; In Vitro Techniques; Male; Middle Aged; Organosilicon Compounds; Pioglitazone; Progesterone; Pterygium; RNA, Messenger; Sirolimus; Sterol O-Acyltransferase; Thiazolidinediones

To determine whether the fibrovascular proliferation observed in pterygium, may be, at least in part, mediated by an increased activity of cholesterol metabolism. The correlation between lipid metabolism and rate of growth was studied in human normal conjunctival (NCF) and primary pterygium fibroblasts (PFs) in primary culture. The expression of two proliferation markers (Ki-67 and p53) was evaluated by immunohistochemical staining techniques. Proliferation was evaluated by [(3)H]thymidine incorporation and by immunohistochemical assays. Lipid metabolism was evaluated by (14)C-oleate incorporated into cholesterol esters as well as by oil red O staining. Moreover, the cultures of pterygium fibroblasts were supplemented with two antiproliferative drugs in order to confirm the effective alterations in cholesterol metabolism related to proliferation. Immunohistochemistry of frozen sections from primary pterygium demonstrated an increased staining in Ki-67 and p53 compared with staining observed in normal conjunctiva. A dramatically increased activity of intracellular cholesterol metabolism was demonstrated in pterygium fibroblasts obtained from four different patients. This finding was confirmed by the reduction of cholesterol metabolism in pterygium fibroblasts treated with antiproliferative drugs. Collectively, these data support the hypothesis that alterations of cholesterol metabolism are involved in the development of pterygia. This finding may represent a target of new therapeutic approaches for treatment and prevention of pterygium.

Topics: Aged; Case-Control Studies; Cell Proliferation; Cell Separation; Cell Survival; Cells, Cultured; Cholesterol; Conjunctiva; Esters; Everolimus; Female; Fibroblasts; Humans; Lipid Metabolism; Male; Middle Aged; Pioglitazone; Pterygium; Sirolimus; Thiazolidinediones