Pharmacological preconditioning by low dose cobalt protoporphyrin induces heme oxygenase-1 overexpression and alleviates retinal ischemia-reperfusion injury in rats

Purpose: Retinal ischemia-induced neuronal death plays a crucial role in certain severe visual impairment diseases. The aims of this study were to investigate the effects of low dose cobalt protoporphyrin IX (CoPP), an inducer of heme oxygenase-1 (HO-1), on the retina of rats against ischemia-reperfusion (IR) injury.Methods: Retinal IR was achieved in rats by raising intraocular pressure for 60 min. CoPP (1 mg/ kg) was injected intraperitoneally 24 hr before IR. Retinal injury was assessed by the number of retinal ganglion cells (RGCs) seven days after reperfusion. TUNEL assay was used to detect the appearance of apoptotic cells 24 hr after reperfusion. The expressions of the HO-1 and Bax proteins were evaluated by Western blot.Results: Both HO-1 expression, examined by Western blot, and enzyme activity were increased strongly after CoPP administration. Rats treated with CoPP before IR had more RGCs (p = 0.034) and less apoptotic cells (p = 0.04) together with downregulated Bax protein levels (p = 0.03) c...