Neuroprotective effects of crocin against oxidative stress induced by ischemia/reperfusion injury in rat retina.

AIMS: Crocin, a pharmacologically active component of Crocus sativus L. (saffron), has been reported to be useful in the treatment of oxidative stress injury. In the present study, we investigated the antioxidative effect of crocin and the change of the ERK signaling pathway on rat retina induced by ischemia/reperfusion (IR) injury.

METHODS: Crocin was pretreated 30 min before and once daily after retinal IR injury by intraperitoneal injection. The retinal morphological damage was observed by hematoxylin and eosin (HE) staining. The number of retinal ganglion cells (RGCs) was counted by Brn-3a immunofluorescence staining. The antiapoptotic effect of crocin was determined by detecting cleaved caspase-3 protein levels by means of Western blot and immunohistochemical analysis. Furthermore, retinas were also used for the determination of malondialdehyde (MDA) levels, glutathione (GSH) levels, total superoxide dismutase (T-SOD), and reactive oxygen species (ROS). The phosphorylated ERK (p-ERK) protein level was determined by Western blot and immunohistochemical analysis.

RESULTS: Our results showed that crocin treatment (50 mg/kg) significantly inhibited the decrease of retinal thickness through HE staining and protected RGCs from decreasing. Compared with the IR + vehicle group, crocin treatment significantly decreased cleaved caspase-3 and p-ERK protein expression by Western blot analysis and immunohistochemistry. Immunohistochemical staining for cleaved caspase-3 and p-ERK in the retinal sections showed positive cells were present in the RGC layer and inner nuclear layer after IR injury. Similarly, crocin (50 mg/kg) treatment also significantly increased the level of activity of GSH, enhanced the activity of T-SOD, and decreased the activity level of ROS and MDA after IR injury.

CONCLUSIONS: These findings demonstrated that crocin treatment could notably protect the retina from damage induced by IR. It might be related to crocin antioxidant and antiapoptotic properties in the retina.