In a recent study published within the PNAS Journal, a gaggle of researchers investigated the role of micro-ribonucleic acid (miRNA) miR-335-5p as a possible therapeutic goal for epilepsy by regulating neuronal excitability through the modulation of voltage-gated sodium channels (VGSCs).

Study: MicroRNA-335-5p suppresses voltage-gated sodium channel expression and will be a goal for seizure control. Image Credit: SewCreamStudio/Shutterstock.com

Background

Epilepsy affects thousands and thousands of people worldwide, and current antiseizure medications (ASMs) goal VGSCs. Nonetheless, some types of epilepsy, like Dravet syndrome, are treatment-resistant resulting from lack of VGSC function. To develop higher therapies, researchers are exploring miRNAs that regulate gene expression.

MiRNAs can control VGSC expression, making them attractive therapeutic targets. Triangulating miRNA datasets and studying miRNA alterations attributable to effective ASMs could reveal potential therapeutic miRNAs for epilepsy.

Cannabidiol (CBD), approved for treatment-resistant epilepsy, is an example of an efficient ASM with an unknown mechanism of motion, arising the necessity for further investigation.

In regards to the study

The study focused on investigating epilepsy using animal models. Animals were kept in controlled conditions with a 12-hour light-dark cycle, proper temperature, and humidity, with food and water freely available.

The researchers used two epilepsy models: the PPS model of temporal lobe epilepsy (TLE) in rats and the pentylenetetrazol (PTZ) model in mice. For the perforant path stimulation (PPS) model, electrodes were implanted, and seizures were induced using paired-pulse stimuli. For the PTZ model, mice received a convulsant dose of PTZ to trigger seizures.

Various treatments were administered to analyze their effects on epilepsy. They modulated miRNA through antisense oligonucleotide “antimir” injections and viral particles expressing specific miRNAs. Moreover, they administered CBD, a compound derived from cannabis, to check its potential effects on epilepsy.

The researchers analyzed miRNA and mRNA expression within the brain tissues of the animals. In addition they identified miRNA-target interactions and performed pathway enrichment analyses to grasp the molecular mechanisms involved in epilepsy.

Finally, ex vivo electrophysiological recordings and sodium currents (INa) recordings in human-induced pluripotent stem cell-derived neurons were conducted to check the results of miRNA manipulation.

All experimental procedures, resembling the European Communities Council Directive (2010/63/EU), adhered to moral guidelines.

Study results

This study focused on miR-335-5p as a possible therapeutic goal for treatment-resistant epilepsy. They used a triangulation approach, combining data from different datasets to discover miRNAs relevant to epilepsy.

MiR-335-5p stood out because it was consistently altered in rat hippocampal subfields, human plasma samples, and after treatment with CBD in mice.

To raised understand the functional role of miR-335-5p, the researchers investigated its targets. They found that miR-335-5p regulates several genes encoding for VGSCs, including sodium voltage-gated channel alpha subunit 1 (SCN1A), sodium voltage-gated channel alpha subunit 2 (SCN2A), and sodium voltage-gated channel alpha subunit 3 (SCN3A), that are crucial for neuronal excitability.

Pathway enrichment evaluation revealed that most of the targets of miR-335-5p are involved in pathways related to neuronal excitability, further supporting its potential role in epilepsy.

The authors used human induced pluripotent stem cell (iPSC)-derived neurons to validate the findings in human brain-relevant models. Inhibition of miR-335-5p in these neurons resulted in an upregulation of VGSCs, confirming the regulatory role of miR-335-5p in human neuronal excitability.

Further, inhibiting miR-335-5p increased seizure susceptibility, while overexpressing miR-335-5p using viral vectors reduced seizure severity and increased survival in response to seizures induced by PTZ.

Researchers found that the behavioral tests showed no opposed effects of miR-335-5p modulation on cognition or naturalistic behavior in mice, indicating its potential safety as a therapeutic goal.

Discussion

On this study, researchers utilized a mix of model-based, drug-altered, and human epilepsy biomarker datasets to discover miRNAs that regulate neuronal excitability, which may very well be relevant for seizure control.

Their approach, generally known as triangulation, led them to give attention to miR-335-5p, a miRNA primarily present in the brain. This approach provided additional miRNA targets for epilepsy treatment in comparison with other methods.

MiR-335-5p was not initially considered a number one candidate when only animal model miRNA profiles were examined, underscoring the importance of including human data and diverse sources of miRNA profiling. Interestingly, miR-335-5p levels appeared to differ amongst different models, which could also be related to temporal and activity-dependent changes in miRNA expression.

The researchers found that miR-335-5p plays a task in regulating the expression of VGSCs, that are crucial for neuronal excitability.

Inhibiting miR-335-5p increased VGSC levels and pyramidal neuron excitability in mice while overexpressing it had the alternative effect, reducing seizure severity. These findings suggest that miR-335-5p may very well be a possible therapeutic goal for modulating neuronal excitability in epilepsy.

Furthermore, the study demonstrated that miR-335-5p modulation didn’t adversely affect cognition or natural behavior in mice, indicating its potential safety as a therapeutic approach.

Conclusions

To summarize, researchers found that targeting miR-335-5p could potentially develop recent treatments for epilepsy, because it could influence VGSCs and fine-tune neuronal excitability, providing a bidirectional effect that is perhaps helpful in numerous types of epilepsy.

Nonetheless, further research is required to grasp the total extent of miR-335-5p’s role and its potential as a therapeutic strategy for epilepsy and other neurological disorders.