Abstract
Purpose: :
Our previous data implicated protein kinase CK2 in retinal angiogenesis, and showed that in retina, CK2 immunostaining was observed primarily in astrocytes rather than in vascular endothelial cells. Also, in neovascularized mouse retinas, the staining for CK2 increased in astrocytes investing intraretinal vessels. The purpose was: 1) to study semi–quantitatively CK2 expression in cultured human astrocytes and endothelial cells; 2) to quantify CK2 subunit expression in the mouse oxygen–induced retinopathy (OIR).
Methods: :
CK2 α and α’ expression in cultured human brain and optic nerve head astrocytes, as well as in brain and retinal microvascular endothelial cells was examined by Western blotting and immunohistochemistry. mRNA levels of CK2 α, α’ and ß subunits were identified by quantitative RT–PCR (QPCR) in mouse normoxic and oxygen–treated retinas, and CK2α expression in mouse retinas was studied by Western blotting.
Results: :
The expression of CK2α and CK2α’ at the protein level was detected by Western blotting in all the cultured cells tested, though its level evaluated relative to ß–tubulin expression was higher in endothelial cells. Conversely, the latter showed weaker and more diffuse immunostaining for CK2α/α’ than cultured human astrocytes that showed bright perinuclear and fibrillar staining which co–distributed with that of GFAP suggesting association of CK2 with the cytoskeleton. By QPCR, the levels of CK2α, CK2α’ and CK2ß mRNAs in day P13 mouse OIR retinas were all 20–25% higher than in day P13 normoxic retinas, whereas in day P17 retinas, OIR samples showed a similar decrease for all CK2 subunits compared to normoxic samples. Western analyses of mouse retinal extracts did not show significant change in the amount of CK2α between normoxic and oxygen–treated retinas. Presumably, a lower turnover rate of CK2α subunit compared to its mRNA makes it difficult to detect changes in the net retinal amount of CK2α at the protein level.
Conclusions: :
CK2 expression was detected in human cultured astrocytes and endothelial cells, apparently in close association with the GFAP–containing cytoskeleton. Moderate increase in the mRNA levels of all three CK2 subunits was discovered in day P13 mouse OIR retinas coinciding with the onset of retinal neovascularization.
Keywords: astrocytes: optic nerve head • hypoxia • retinal neovascularization