alpha2-Macroglobulin induces glial fibrillary acidic protein expression mediated by low-density lipoprotein receptor-related protein 1 in Müller cells.
OBJECTIVE
Although it is known that Müller cells express the glial fibrillary acidic protein (GFAP) in response to acute retinal damage, the regulatory mechanism is not completely understood. α(2)-Macroglobulin (α(2)M) and its receptor, low-density lipoprotein receptor-related protein 1 (LRP1), have also been found in injured retinas. Herein, the authors examined the involvement of the α(2)M/LRP1 system in GFAP expression in Müller cells using in vitro and in vivo experimental models.


METHODS
Using Western blot analysis and immunocytochemistry, the authors evaluated the effect of α(2)M* on GFAP expression in the Müller cell line MIO-M1, which constitutively expresses LRP1. Intracellular signaling pathways activated by α(2)M* were examined by Western blot analysis. The effect of α(2)M* on GFAP expression in the mouse retina was examined by intravitreal microinjection of α(2)M* in mouse eyes.


RESULTS
These data demonstrate that α(2)M* induced GFAP expression in the MIO-M1 cell line, which was selectively blocked by RAP, an antagonist of LRP1 binding ligands. In addition, α(2)M* induced JAK/STAT pathway activation, determined by STAT3 phosphorylation (p-STAT3), which was also blocked by RAP. Finally, the authors showed that GFAP was expressed in the retinas of mice, preferentially in Müller cells at 3 and 6 days after a single intravitreal α(2)M* injection, whereas p-STAT3 staining increased at day 1 in both the ganglion cell layer and the inner nuclear layer.


CONCLUSIONS
These results demonstrate that α(2)M* induces GFAP expression in retinal Müller cells through LRP1, which could be mediated by JAK/STAT pathway activation.
Barcelona
Pablo F
PF
Centro de Investigaciones en Bioquímica Clínica e Inmunología-CONICET, Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina.
Ortiz
Susana G
SG
Chiabrando
Gustavo A
GA
Sánchez
Maria C
MC
D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D053612:Janus Kinases / Q000378:metabolism; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D009457:Neuroglia / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011973:Receptors, LDL / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D014746:Vimentin / Q000378:metabolism; D000511:alpha-Macroglobulins / Q000494:pharmacology*
D005904:Glial Fibrillary Acidic Protein; D026503:Low Density Lipoprotein Receptor-Related Protein-1; C486645:Lrp1 protein, mouse; D011973:Receptors, LDL; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D025521:Tumor Suppressor Proteins; D014746:Vimentin; D000511:alpha-Macroglobulins; D053612:Janus Kinases