Aggravation effects of JAK-STAT signaling pathway in retinal ischemia reperfusion injury

Background

Retinal ischemia reperfusion injury (RIRI) is a common pathological process of many retinal vascular diseases with comprehensive pathogenesis mechanism.Researches showed that apoptosis of retinal cells and nerve fiber loss is the finally common pathway of RIRI, and Janus kinase signal transducer and activator of transcription (JAK-STAT) pathway is a newly discovered signal transcript channel in recent years, which is involved in varieties of pathological processes.However, whether JAK-STAT pathway is associated with RIRI is still unelucidated.

Objective

This study was to investigate the time course of activation of JAK-STAT signal pathway and its significance during RIRI.

Methods

Forty clear adult male Sprague-Dawley rats were randomized into RIRI 6-hour, 12-hour, 24-hour and 48-hour groups.RIRI models were induced in lateral eyes of the rats by perfusing normal saline solution into the anterior chamber to elevate intraocular pressure (IOP) to 110 mmHg for 60 minutes and then allowing reperfusion, and the fellow eyes of the rats served as normal control group.The rats were sacrificed and the eyeballs were enucleated at 6, 12, 24 and 48 hours after reperfusion.The expressions of JAK2 and STAT3 protein (absorbance) in the retinas were located and detected by immunohistochemistry, and the relative expression levels of JAK2 and STAT3 mRNA in the retinas were detected by real-time fluorescence quantitative PCR.The use and care of the rats followed the ARVO Statement.

Results

Immunohistochemistry showed that JAK2 and STAT3 were faintly expressed in inner nuclear layer and retinal ganglion cells (RGCs) in the normal control group and strongly expressed in various RIRI groups.Significant differences were found in the expression intensities of JAK2 and STAT3 protein among the five groups (F=88.735, 96.625, both at P<0.01). Compared with the normal control group, the expression intensities of JAK2 and STAT3 were enhanced in RIRI groups, with the peak values in RIRI 12-hour group (JAK2: t=4.308, 5.559, 5.315, 4.726; all at P<0.01.STAT3: t=5.047, 7.843, 6.281, 4.887; all at P<0.01). The thickening of inner retinal layer, loosening of retinal tissue, vacuolus degeneration of cells and decrease of RGCs were seen in the RIRI eyes.The relative expressing levels of the JAK2 mRNA and STAT3 mRNA in the retinas were significantly different among the groups (F=111.239, 129.539; both at P<0.01), and the relative expressing levels of JAK2 mRNA and STAT3 mRNA in the retinas were significantly increased in RIRI 6-hour, 12-hour, 24-hour and 48-hour groups in comparison with the normal control group (JAK2 mRNA: t=3.504, 5.102, 4.679, 4.213; all at P<0.01.STAT3 mRNA: t=6.541, 8.787, 5.693, 5.898; all at P<0.01).

Conclusions

The retinal morphology appears to be abnormal and RGCs are evidently decreased in rat eyes with RIRI, and the expressions of JAK2 and STAT3 in the retinas are simultaneously up-regulated, indicating that JAK-STAT signal pathway is involved during the RIRI process.

Retina; Ischemia reperfusion injury; Signal transduction pathway; Retinal ganglion cells; Janus kinase signal transducer and activator of transcription; Rats, Sprague-Dawley