Interaction between NO and COX pathways in retinal cells exposed to elevated
glucose and retina of diabetic rats.
Authors Du Y, Sarthy VP, Kern TS
Submitted By Submitted Externally on 10/1/2015
Status Published
Journal American journal of physiology. Regulatory, integrative and comparative physiology
Year 2004
Date Published 10/1/2004
Volume : Pages 287 : R735 - 41
PubMed Reference 15371279
Abstract A nonselective inhibitor of cyclooxygenase (COX; high-dose aspirin) and a
relatively selective inhibitor of inducible nitric oxide synthase (iNOS;
aminoguanidine) have been found to inhibit development of diabetic retinopathy
in animals, raising a possibility that NOS and COX play important roles in the
development of retinopathy. In this study, the effects of hyperglycemia on
retinal nitric oxide (NO) production and the COX-2 pathway, and the
interrelationship of the NOS and COX-2 pathways in retina and retinal cells,
were investigated using a general inhibitor of NOS [N(G)-nitro-l-arginine methyl
ester (l-NAME)], specific inhibitors of iNOS [l-N(6)-(1-iminoethyl)lysine
(l-NIL)] and COX-2 (NS-398), and aspirin and aminoguanidine. In vitro studies
used a transformed retinal Müller (glial) cell line (rMC-1) and primary bovine
retinal endothelial cells (BREC) incubated in 5 and 25 mM glucose with and
without these inhibitors, and in vivo studies utilized retinas from
experimentally diabetic rats (2 mo) treated or without aminoguanidine or
aspirin. Retinal rMC-1 cells cultured in high glucose increased production of NO
and prostaglandin E(2) (PGE(2)) and expression of iNOS and COX-2. Inhibition of
NO production with l-NAME or l-NIL inhibited all of these abnormalities, as did
aminoguanidine and aspirin. In contrast, inhibition of COX-2 with NS-398 blocked
PGE(2) production but had no effect on NO or iNOS. In BREC, elevated glucose
increased NO and PGE(2) significantly, whereas expression of iNOS and COX-2 was
unchanged. Viability of rMC-1 cells or BREC in 25 mM glucose was significantly
less than at 5 mM glucose, and this cell death was inhibited by l-NAME or NS-398
in both cell types and also by l-NIL in rMC-1 cells. Retinal homogenates from
diabetic animals produced significantly greater than normal amounts of NO and
PGE(2) and of iNOS and COX-2. Oral aminoguanidine and aspirin significantly
inhibited all of these increases. The in vitro results suggest that the
hyperglycemia-induced increase in NO in retinal Müller cells and endothelial
cells increases production of cytotoxic prostaglandins via COX-2. iNOS seems to
account for the increased production of NO in Müller cells but not in
endothelial cells. We postulate that NOS and COX-2 act together to contribute to
retinal cell death in diabetes and to the development of diabetic retinopathy
and that inhibition of retinopathy by aminoguanidine or aspirin is due at least
in part to inhibition of this NO/COX-2 axis.

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