Mechanisms and Emerging Therapies for Treatment of Seizures in Pediatric Autoimmune Encephalitis and Autoinflammatory/Autoimmune-Associated Epilepsy

Herkinorin ameliorates neuronal damage in a pentylenetetrazol-induced epilepsy rat model through altering microglial and astrocytic activation by inhibiting PARP1 and NF-κB

BACKGROUND

Altered astrocytic and microglial functions have been shown to mediate inflammation and oxidative stress in epilepsy. Herkinorin, a novel mu opioid receptor (MOR) agonist, has a neuroprotective role in ischemic brain injury. In this report, we sought to explore the effects and mechanism of herkinorin in the treatment of epilepsy and neuronal damage.

METHODS

SH-SY5Y cells were treated with pentylenetetrazol (PTZ) and herkinorin. The viability, reactive oxygen species (ROS) release, and apoptosis of the cells were detected. A rat epilepsy model was induced via PTZ injection, and herkinorin was used for pretreatment. Immunofluorescence staining and immunohistochemistry were used to observe neuronal damage and microglial and astrocyte activation in the hippocampal CA1/3 region. Western blotting was used to determine the expression profiles of PARP1 and NF-κB.

RESULTS

PTZ substantially facilitated SH-SY5Y cell apoptosis, induced oxidative stress and promoted NLRP3-ASC-Caspase-1 inflammasome activation. Herkinorin attenuated SH-SY5Y cell damage mediated by PTZ and suppressed PARP1 and NF-κB. The activation of PARP1 by lipopolysaccharide (LPS) aggravated SH-SY5Y cell injury, and herkinorin treatment reversed these LPS-mediated effects. In in vivo experiments, herkinorin hampered epileptic seizures in rats and weakened PTZ-induced neuronal damage in the hippocampus. Moreover, herkinorin reduced PTZ-induced neuroinflammation, resulting in "M1" to "M2" polarization of microglia and "A1" to "A2" polarization of astrocytes. Moreover, herkinorin inhibited the expression of PARP1 and NF-κB phosphorylation in the hippocampus.

CONCLUSION

Herkinorin ameliorates PTZ-induced neuroinflammation in epileptic rats by inhibiting PARP1 and NF-κB and regulating microglial and astrocytic activation.

Is there a biochemical basis for purinergic P2X3 and P2X4 receptor antagonists to be considered as anti-seizure medications?

Patients with epilepsy require improved medications. Purinergic receptors were identified as late as 1976 and are slowly emerging as potential drug targets for the discovery of antiseizure medications. While compounds interacting with these receptors have been approved for use as medicines (e.g., gefapixant for cough) and continue to be explored for a number of diseases (e.g., pain, cancer), there have been no purinergic receptor antagonists that have been advanced for epilepsy. There are very few studies on the channel conducting receptors, P2X3 and P2X4, that suggest their possible role in seizure generation or control. However, the limited data available provides some compelling reasons to believe that they could be valuable antiseizure medication drug targets. The data implicating P2X3 and P2X4 receptors in epilepsy includes the role played by ATP in neuronal excitability and seizures, receptor localization, increased receptor expression in epileptic brain, the involvement of these receptors in seizure-associated inflammation, crosstalk between these purinergic receptors and neuronal processes involved in seizures (GABAergic and glutamatergic neurotransmission), and the significant attenuation of seizures and seizure-like activity with P2X receptor blockade. The discovery of new and selective antagonists for P2X3 and P2X4 receptors is ongoing, armed with new structural data to guide rational design. The availability of safe, brain-penetrant compounds will likely encourage the clinical exploration of epilepsy as a disease entity.