Efeito da inibição do miR 196b na fase aguda da epileptogênese em modelo experimental de epilepsia do lobo temporal

Abstract

Epilepsy is a neurological disorder characterized by spontaneous and recurrent seizures. Temporal lobe epilepsy (TLE) is associated with a high rate (30-40%) of refractoriness to treatment with antiepileptic drugs (AEDs). The search for new therapeutic approaches is an urgent need. Manipulation of gene expression has been explored in the development of therapeutic interventions in many neuropathogenetic processes. In this sense, non-coding RNAs, such as microRNAs (miRs), are preferred targets due to the regulatory role they play in the reorganization of gene expression. Recently, we identified that miR 196b-5p has increased expression in the acute phase of epileptogenesis. In this work, we depleted miR-196b-5p levels to gain insights into the functional significance and therapeutic potential of this dysregulation. For this purpose, Wistar rats received, via the intracerebroventricular (ICV) route, the miR-196b-5p inhibitor (0.4 nmol/2μL) 24 hours before being submitted to Status Epilepticus induced by Lithium-Pilocarpine. We observed a significant depletion of miR-196-5p hippocampal levels. The effect of this depletion was evaluated in terms of molecular (expression of epileptogenesis markers and the SLC9A6 target), histochemical (marking of Fluoro-Jade positive neurons) and behavioral parameters (assessment of self-sustained seizures through latency, severity, and frequency). As a control group, wistar rats were used that received, via ICV, 2μL of phosphate saline buffer (PBS). The animals that received the miR-196b-5p inhibitor (0.4 nmol/2μL) did not show a significant change in the latency time for the onset of SE, as well as in the severity and frequency of seizures during 90 minutes of SE. Regarding the analysis of neurodegeneration, we did not observe a significant difference in Fluoro-Jade positive cells between the groups. Regarding epileptogenesis, we did not observe a significant difference in the expression of GFAP (astrogliosis), BDNF (neuroplasticity) and TNF-a (neuroinflammation) markers. The joint analysis of these data indicates that miR196 depletion does not have anticonvulsant and antiepileptogenic potential. On the other hand, we observed that animals administered the miR-196b-5p inhibitor (0.4 nmol/2μL) showed an even greater increase in the levels of neuropeptide Y (NPY) transcripts, indicating a possible regulatory role of miR- 196b about NPY. A decrease in the levels of miR 146a transcripts was also observed in animals administered the miR-196b-5p inhibitor (0.4 nmol/2μL), indicating a possible decrease in neuroinflammation. In conclusion, our data suggest that the LNAtype inhibitor is a useful tool for functional assays of miRs inhibition, however, the inhibition of miR-196b-5p, at the doses and times used here, did not alter the epileptogenic processes investigated.