Interleukin-6 in retinal ischemia reperfusion injury in rats.
OBJECTIVE
To study the role of interleukin (IL)-6 after retinal ischemia-reperfusion (I/R) injury in rats.


METHODS
Intraocular pressure of adult male Lewis albino rats was raised to create retinal ischemia for 1 hour. Retinal reperfusion was reestablished, and the animals were killed at various time points after the injury. Their eyes were enucleated and processed for immunohistochemistry to detect IL-6 and ED-1 (a marker of microglial/phagocytic cells), enzyme-linked immunosorbent assay (ELISA) of IL-6 protein, and semiquantitative real-time RT-PCR for IL-6 mRNA. The neuroprotective effect of IL-6 was evaluated by giving intravitreal injections of 150 or 300 ng rat recombinant IL-6 to eyes immediately after I/R injury and counting cresyl violet-stained retinal ganglion cell layer cells (RGCLCs) and fluorochrome-labeled retinal ganglion cells (RGCs) on flat preparations of retinas at 7 days.


RESULTS
IL-6-positive cells appeared after I/R injury in the inner plexiform layer (IPL) and the inner nuclear layer (INL). Their numbers were significantly higher 18 hours after the injury, and most of these cells were also ED-1 positive. ELISA showed noticeable increases in endogenous retinal IL-6 protein levels 8 hours after I/R injury. Semiquantitative real-time RT-PCR showed significant increases in endogenous retinal IL-6 mRNA levels between 2 and 18 hours. Exogenously added IL-6 prevented between 50% and 70% of RGC loss after I/R injury.


CONCLUSIONS
IL-6 is upregulated after retinal I/R injury, and its expression by microglia/phagocytic cells may protect RGC layer neurons from I/R injury. Exogenously added IL-6 protects the inner retina after I/R injury.
Sanchez
Ruben N
RN
Department of Ophthalmology, Doheny Eye Institute, University of Southern California, Keck School of Medicine, Los Angeles, California 90033, USA.
Chan
Candy K
CK
Garg
Sumit
S
Kwong
Jacky M K
JM
Wong
Micheline J
MJ
Sadun
Alfredo A
AA
Lam
Tim T
TT
D000818:Animals; D002452:Cell Count; D053331:Ectodysplasins; D004797:Enzyme-Linked Immunosorbent Assay; D007124:Immunoenzyme Techniques; D007267:Injections; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D011994:Recombinant Proteins; D015427:Reperfusion Injury / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control; D012162:Retinal Degeneration / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015854:Up-Regulation; D014822:Vitreous Body
D053331:Ectodysplasins; D015850:Interleukin-6; D008565:Membrane Proteins; D018696:Neuroprotective Agents; D012333:RNA, Messenger; D011994:Recombinant Proteins