High levels of serum prolactin protect against diabetic retinopathy by increasing ocular vasoinhibins.
OBJECTIVE
Increased retinal vasopermeability (RVP) occurs early in diabetes and is crucial for the development of sight-threatening proliferative diabetic retinopathy (DR). The hormone prolactin (PRL) is proteolytically processed to vasoinhibins, a family of peptides that inhibit the excessive RVP related to DR. Here, we investigate the circulating levels of PRL in association with DR in men and test whether increased circulating PRL, by serving as a source of ocular vasoinhibins, can reduce the pathological RVP in diabetes.


METHODS
Serum PRL was evaluated in 40 nondiabetic and 181 diabetic men at various stages of DR. Retinal vasoinhibins were measured in rats rendered hyperprolactinemic by placing two anterior pituitary grafts under the kidney capsule and in PRL receptor-null mice. RVP was determined in hyperprolactinemic rats subjected to the intraocular injection of vascular endothelial growth factor (VEGF) or made diabetic with streptozotocin.


RESULTS
The circulating levels of PRL increased in diabetes and were higher in diabetic patients without retinopathy than in those with proliferative DR. In rodents, hyperprolactinemia led to vasoinhibin accumulation within the retina; genetic deletion of the PRL receptor prevented this effect, indicating receptor-mediated incorporation of systemic PRL into the eye. Hyperprolactinemia reduced both VEGF-induced and diabetes-induced increase of RVP. This reduction was blocked by bromocriptine, an inhibitor of pituitary PRL secretion, which lowers the levels of circulating PRL and retinal vasoinhibins.


CONCLUSIONS
Circulating PRL influences the progression of DR after its intraocular conversion to vasoinhibins. Inducing hyperprolactinemia may represent a novel therapy against DR.
Arnold
Edith
E
Neurobiology Institute, National University of Mexico (UNAM), Campus UNAM-Juriquilla, Juriquilla, Queretaro, Mexico.
Rivera
José C
JC
Thebault
Stéphanie
S
Moreno-Páramo
Daniel
D
Quiroz-Mercado
Hugo
H
Quintanar-Stéphano
Andrés
A
Binart
Nadine
N
Martínez de la Escalera
Gonzalo
G
Clapp
Carmen
C
D000818:Animals; D015415:Biomarkers / Q000097:blood; D018797:Cell Cycle Proteins / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000503:physiopathology; D003930:Diabetic Retinopathy / Q000097:blood / Q000473:pathology / Q000517:prevention & control*; D006801:Humans; D006966:Hyperprolactinemia / Q000097:blood; D008297:Male; D051379:Mice; D008875:Middle Aged; D011388:Prolactin / Q000097:blood*; D051381:Rats; D017208:Rats, Wistar; D042461:Vascular Endothelial Growth Factor A
D015415:Biomarkers; D018797:Cell Cycle Proteins; D042461:Vascular Endothelial Growth Factor A; C510089:Vash1 protein, mouse; D011388:Prolactin
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