Diabetes-induced disruption of gap junction pathways within the retinal microvasculature.
OBJECTIVE
Microvascular damage caused by diabetes is a leading cause of visual loss. Identifying events early in the course of diabetic retinopathy may help in understanding and, perhaps, preventing this disorder. The hypothesis that cell-to-cell communication within the retinal microvasculature may be affected soon after the onset of diabetes was tested.


METHODS
Streptozotocin was used to induce diabetes in rats. To assess cell-to-cell coupling the gap junction-permeant tracer, Neurobiotin, was delivered via patch pipettes into pericytes located on microvessels freshly isolated from the retinas of diabetic and control animals. Subsequently, immunohistochemical methods revealed the extent of the intercellular spread of the tracer. Electrophysiological methods were also used to detect intercellular communication.


RESULTS
In retinal microvessels of control rats, Neurobiotin spread hundreds of micrometers from the tracer-loaded pericytes. However, within days after the onset of diabetes, this cell-to-cell coupling was dramatically reduced. In contrast, microvessels of insulin-treated diabetic rats showed no significant loss of intercellular communication. Consistent with protein kinase C (PKC) playing a role in the diabetes-induced inhibition of gap junction pathways, exposure of microvessels to a PKC activator (phorbol myristate acetate) markedly reduced tracer coupling.


CONCLUSIONS
Within retinal microvessels there is extensive cell-to-cell coupling, which is markedly reduced soon after the onset of streptozotocin-induced diabetes. The closure of gap junction pathways disrupts the multicellular organization of retinal microvessels and may contribute to vascular dysfunction.
Oku
H
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Department of Ophthalmology and Visual Sciences, The University of Michigan, 1000 Wall Street, Ann Arbor, MI 48105, USA.
Kodama
T
T
Sakagami
K
K
Puro
D G
DG
D000818:Animals; D000968:Antimycin A / Q000031:analogs & derivatives* / Q000494:pharmacology; D001710:Biotin / Q000031:analogs & derivatives* / Q000378:metabolism; D002196:Capillaries / Q000378:metabolism / Q000473:pathology; D002450:Cell Communication / Q000187:drug effects; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000473:pathology*; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism / Q000473:pathology; D004594:Electrophysiology; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D007461:Iodoacetates / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D012171:Retinal Vessels / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007461:Iodoacetates; C070614:neurobiotin; C032456:antimycin; D000968:Antimycin A; D001710:Biotin; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate