Carboxymethyl beta-glucan binds to corneal epithelial cells and increases cell adhesion to laminin and resistance to oxidative stress.
OBJECTIVE
Polysaccharides are frequently used as viscoelastic agents to improve pharmacokinetics of ophthalmic preparations. Recently, polysaccharides from yeast cell walls such as beta-glucans have emerged as bioactive molecules endowed with immunomodulatory and cytoprotective properties. In this study, we investigated the effects of carboxymethyl beta-glucan (CMG), a water-soluble derivative of yeast beta-glucan, on cultured rabbit corneal epithelial cells.


METHODS
We developed a fluorescein-labeled CMG to visualize its binding to corneal cells by means of digital microscopy and image deconvolution. The effects of CMG on adhesion and survival of corneal epithelial cells exposed to noxious stimuli were also studied.


RESULTS
CMG binds defined regions scattered throughout the body of corneal cells, suggesting binding specificity. Tridimensional reconstruction of fluorescence shows that binding is localized mainly at the plasma and nuclear membranes. Interestingly, CMG binding is highly represented at the level of focal adhesion of cells spreading onto laminin. Accordingly, CMG promotes adhesion of corneal epithelial cells to laminin without affecting their proliferation rate. CMG also protects cells from oxidative stress-dependent cell death, being ineffective in preventing ultraviolet B cytotoxicity.


CONCLUSIONS
Data show that CMG dynamically binds to corneal epithelial cells, promoting cell adhesion and resistance to oxidative stress.
Porcu
Marco
M
Department of Pharmacology, University of Florence, Florence, Italy.
Guarna
Francesco
F
Formentini
Laura
L
Faraco
Giuseppe
G
Fossati
Silvia
S
Mencucci
Rita
R
Rapizzi
Emilio
E
Menchini
Ugo
U
Moroni
Flavio
F
Chiarugi
Alberto
A
D000818:Animals; D002448:Cell Adhesion / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D019573:Epithelium, Corneal / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D005456:Fluorescent Dyes; D006861:Hydrogen Peroxide / Q000633:toxicity; D007797:Laminin / Q000378:metabolism*; D018384:Oxidative Stress; D011817:Rabbits; D012441:Saccharomyces cerevisiae / Q000737:chemistry; D047071:beta-Glucans / Q000378:metabolism*
D005456:Fluorescent Dyes; D007797:Laminin; D047071:beta-Glucans; C029933:carboxymethyl-beta-1,3-glucan; D006861:Hydrogen Peroxide