Identification of the intracellular signal-transduction pathways activated in retinal ischemia may be important in revealing novel pharmacological targets. To date, most studies have focused on identifying neuroprotective agents. The retinal blood vessels are key organs in circulatory failure, and this study was therefore designed to examine the retinal vasculature separately from the neuroretina.
Retinal ischemia was induced by elevating the intraocular pressure in porcine eyes, followed by 5, 12, or 20 h of reperfusion. Protein kinase C (PKC)α, PKCβ1, and PKCβ2 mRNA levels, and protein expression were determined using real-time PCR, western blot, and immunofluorescence staining techniques.
The retinal arteries could easily be dissected free and studied separately from the neuroretina in this porcine model. The PKCα, PKCβ1, and PKCβ2 mRNA levels tended to be lower in ischemia-reperfused than in sham-operated eyes in both the retinal arteries and the neuroretina. This was most prominent after 5 h, and less pronounced after 12 h and 20 h of reperfusion. Likewise, the protein levels of PKCα, PKCβ1, and PKCβ2 were slightly lower following ischemia-reperfusion when compared to sham-operated eyes. PKCα, PKCβ1, and PKCβ2 immunostaining were observed in bipolar cells of the neuroretina and in endothelial cells, and to a low extent in the smooth muscle layer, of the retinal arteries.
Retinal ischemia followed by reperfusion results in lower levels of PKC in both the neuroretina and retinal arteries. New targets for pharmacological treatment may be found by studying the retinal vasculature so as to identify the intracellular signal-transduction pathways involved in the development of injury following retinal circulatory failure.