Transcriptomics of Rat Striata 16 h after Gamma Knife Surgery: Distinct Bilateral Effects in the Un-irradiated Striatum

Gamma knife surgery (GKS) is used for treatment of various brain disorders. The effects of gamma irradiation to targeted and un-targeted regions were evaluated by monitoring gene expression changes in the unilateral irradiated (60 Gy) and contralateral un-irradiated striata in the rat. Striata of irradiated and control brains were dissected 16 h post-irradiation for analysis by rat whole genome 44K DNA oligo microarray. Results revealed 230 induced and 144 repressed genes in the irradiated striatum and 432 induced and 239 repressed genes in the un-irradiated striatum. The number of altered genes in un-irradiated striatum was more than that in irradiated striatum. Results of RT-PCR and western analyses suggested that gamma-irradiation caused cellular damage, including oxidative stress, in both striata of both hemispheres. Our present results indicate that unilateral irradiation during GKS produce bilateral effects as early as 16 h, the time-period analyzed, and these molecular changes in the un-irradiated striatum are ample proof. For the experiment, a total of four adult male Wistar rats were housed in acrylic cage at 24 ºC with tap water and laboratory chow ad libitum. The rats were anesthetized with pentobarbital (40 mg/kg intraperitoneally) and fixed in the Regis-Valliccioni frame (Neurospace, Neuilly, France). A central maximum dose of 60 Gy was administered (for 30 min) to the unilateral striatum with the Leksell gamma knife model C (Elekta Instrument AB) unit by means of 4-mm collimator. At 16 h post-irradiation, whole brains were rapidly removed and left and right striata were separated on ice according to the method of Glowinski and Iversen with some modifications. The irradiated and un-irradiated striata from irradiated rats and the ipsilateral and contralateral striata from control rats, respectively, were dissected from individual male rats and used for extraction of total RNA. Dye-swap or reverse labeling with Cy3 and Cy5 dyes procedure was applied followed by hybridization and wash processes, and the hybridized microarrays (G4131A) were scanned using a Standard protocol of Agilent DNA Microarray Scanner and data processing was done by Feature Extraction software Version 8.1 from Agilent Technologies.