The protective role of transferrin in Müller glial cells after iron-induced toxicity.
OBJECTIVE
Transferrin (Tf) expression is enhanced by aging and inflammation in humans. We investigated the role of transferrin in glial protection.


METHODS
We generated transgenic mice (Tg) carrying the complete human transferrin gene on a C57Bl/6J genetic background. We studied human (hTf) and mouse (mTf) transferrin localization in Tg and wild-type (WT) C57Bl/6J mice using immunochemistry with specific antibodies. Müller glial (MG) cells were cultured from explants and characterized using cellular retinaldehyde binding protein (CRALBP) and vimentin antibodies. They were further subcultured for study. We incubated cells with FeCl(3)-nitrilotriacetate to test for the iron-induced stress response; viability was determined by direct counting and measurement of lactate dehydrogenase (LDH) activity. Tf expression was determined by reverse transcriptase-quantitative PCR with human- or mouse-specific probes. hTf and mTf in the medium were assayed by ELISA or radioimmunoassay (RIA), respectively.


RESULTS
mTf was mainly localized in retinal pigment epithelium and ganglion cell layers in retina sections of both mouse lines. hTf was abundant in MG cells. The distribution of mTf and hTf mRNA was consistent with these findings. mTf and hTf were secreted into the medium of MG cell primary cultures. Cells from Tg mice secreted hTf at a particularly high level. However, both WT and Tg cell cultures lose their ability to secrete Tf after a few passages. Tg MG cells secreting hTf were more resistant to iron-induced stress toxicity than those no longer secreted hTf. Similarly, exogenous human apo-Tf, but not human holo-Tf, conferred resistance to iron-induced stress on MG cells from WT mice.


CONCLUSIONS
hTf localization in MG cells from Tg mice was reminiscent of that reported for aged human retina and age-related macular degeneration, both conditions associated with iron deposition. The role of hTf in protection against toxicity in Tg MG cells probably involves an adaptive mechanism developed in neural retina to control iron-induced stress.
Inserm, U872, Paris, France. e-picard@idf.inserm.fr
Emilie
E
Picard
Isabelle
I
Fontaine
Laurent
L
Jonet
Florian
F
Guillou
Francine
F
Behar-Cohen
Yves
Y
Courtois
Jean-Claude
JC
Jeanny
D000818:Animals; D001059:Apoproteins / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D003470:Culture Media; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007501:Iron / Q000633:toxicity*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000187:drug effects; D014168:Transferrin / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
D001059:Apoproteins; D003470:Culture Media; D012333:RNA, Messenger; D014168:Transferrin; D007501:Iron