Pharmacological inhibition of Na+/K+-ATPase induces neurovascular degeneration and glial cell alteration in the rat retina

Koki Nagaoka; Yuki Kurauchi; Daiki Asano; Akane Morita; Kenji Sakamoto; Tsutomu Nakahara

doi:10.1016/j.exer.2022.109107

Pharmacological inhibition of Na⁺/K⁺-ATPase induces neurovascular degeneration and glial cell alteration in the rat retina

Exp Eye Res. 2022 Jul:220:109107. doi: 10.1016/j.exer.2022.109107. Epub 2022 May 11.

Authors

Koki Nagaoka¹, Yuki Kurauchi², Daiki Asano¹, Akane Morita¹, Kenji Sakamoto¹, Tsutomu Nakahara³

Affiliations

¹ Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan.
² Department of Chemico-Pharmacological Sciences, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oehonmachi, Chuo-ku, Kumamoto, 862-0973, Japan.
³ Department of Molecular Pharmacology, Kitasato University School of Pharmaceutical Sciences, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan. Electronic address: nakaharat@pharm.kitasato-u.ac.jp.

PMID: 35568201
DOI: 10.1016/j.exer.2022.109107

Abstract

Na⁺/K⁺-ATPase (NKA) plays an important role in ion homeostasis and neurotransmitter uptake. In the retina, multidirectional communications among neurons, glia, and blood vessels (that is, neuro-glio-vascular interaction) are crucial for maintaining tissue homeostasis. We investigated the role of NKA in the elements of neuro-glio-vascular unit in neonatal and adult rat retinas. Male Sprague-Dawley rats (1- and 8-week-old) were injected intravitreally with ouabain (20 nmol/eye), an inhibitor of NKA. Morphological changes in retinal neurons, glia, and blood vessels were examined. The intravitreal injection of ouabain decreased the number of cells in the ganglion cell layer, as well as the thicknesses of the inner plexiform and inner nuclear layers in neonatal and adult rats compared to age-matched controls. The ouabain-induced neuronal cell damage was partially prevented by D-(-)-2-amino-5-phosphonopentanoic acid, an antagonist of N-methyl-D-aspartic acid receptors. In the deep retinal vascular plexus of the ouabain-injected eyes, angiogenesis was delayed in neonatal rats, whereas capillary degeneration occurred in adult rats. The immunoreactivity of glutamine synthetase and vascular endothelial growth factor (VEGF) decreased in the retinas of neonatal and adult rats injected intravitreally with ouabain. The immunoreactivity of glial fibrillary acidic protein was enhanced in the retinas of ouabain-injected adult eyes. After the ouabain injection, CD45-positive leukocytes and Iba1-positive microglia increased in the inner retinal layer of neonatal rats, whereas they increased in the middle retinal layer of adult rats. These results suggest that the inhibition of NKA induces the degeneration of neuronal and vascular cells and alteration of glial cells in both neonatal and adult retinas. In addition to the direct effects of NKA inhibition, the disturbance of retinal glutamate metabolism and decreased VEGF expression may contribute to neurovascular degeneration. The activity of NKA is crucial for maintaining elements of neuro-glio-vascular unit in the retina.

Keywords: Endothelial cell; Glial cell; Na(+)/K(+)-ATPase; Neuronal cell; Retina.

MeSH terms

Adenosine Triphosphatases / metabolism
Adenosine Triphosphatases / pharmacology
Animals
Male
Neuroglia / metabolism
Ouabain* / metabolism
Ouabain* / pharmacology
Rats
Rats, Sprague-Dawley
Retina / metabolism
Vascular Endothelial Growth Factor A* / metabolism

Substances

Vascular Endothelial Growth Factor A
Ouabain
Adenosine Triphosphatases