The activation of IL-8 receptors in cultured guinea pig Müller glial cells is modified by signals from retinal pigment epithelium.
Interleukin 8 (IL-8, CXCL8) is a pro-inflammatory chemokine which attracts neutrophils to sites of inflammation via an activation of the G-protein-coupled receptors, CXCR1 and CXCR2. However, both IL-8 and IL-8 receptors are widely expressed in various tissues and cell types, and have been suggested to be involved in other functions such as angiogenesis, tumor growth, or brain pathology. We examined the expression of IL-8 and IL-8 receptors in highly enriched primary cultures of guinea pig Muller glial cells. Immunoreactivity for CXCL8, CXCR1 and CXCR2 was observed in all cultured Muller cells. The expression of CXCL8 was confirmed by PCR, and the secretion of the CXCL8 protein from Muller cells was revealed by ELISA. Western blots showed prominent bands at approximately 40 kDa by using antibodies specific for human CXCR1 and CXCR2, and the expression of a putative CXCR2 receptor in Muller cells was confirmed by PCR. Furthermore, cultured Muller cells responded to application of recombinant human IL-8 with an increase of the cytosolic Ca(2+) concentration. If supernatants of cultured human retinal pigment epithelium (RPE) cells were applied to the Muller cell cultures, no obvious changes were observed in the CXCL8, CXCR1 and CXCR2 expression but (i) Muller cell proliferation was stimulated, and (ii) there was an increased number of CXCL8-responsive Muller cells and the amplitudes of the evoked calcium responses were enhanced. It is concluded that Muller glial cells may participate in the inflammatory response(s) of the retina during ocular diseases, and that this contribution may be modified by interactions with RPE cells.
Malgorzata Goczalik
Iwona
I
Paul-Flechsig-Institute for Brain Research, University of Leipzig, Jahnallee 59, D-04109 Leipzig, Germany.
Raap
Maik
M
Weick
Michael
M
Milenkovic
Ivan
I
Heidmann
Jördis
J
Enzmann
Volker
V
Wiedemann
Peter
P
Reichenbach
Andreas
A
Francke
Mike
M
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002452:Cell Count / Q000379:methods; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D003952:Diagnostic Imaging / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D016209:Interleukin-8 / Q000378:metabolism / Q000494:pharmacology; D007668:Kidney / Q000378:metabolism; D009414:Nerve Growth Factors; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism*; D010857:Pigment Epithelium of Eye / Q000187:drug effects / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D023062:Receptors, Interleukin-8A / Q000235:genetics / Q000378:metabolism*; D023063:Receptors, Interleukin-8B / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000166:cytology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000378:metabolism; D013997:Time Factors; D014746:Vimentin / Q000378:metabolism
C020932:11-cis-retinal-binding protein; D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D005904:Glial Fibrillary Acidic Protein; D016209:Interleukin-8; D009414:Nerve Growth Factors; D012333:RNA, Messenger; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; D014746:Vimentin; D000255:Adenosine Triphosphate; D005974:Glutamate-Ammonia Ligase; D002118:Calcium