A Novel Second-Generation EP2 Receptor Antagonist Reduces Neuroinflammation and Gliosis After Status Epilepticus in Rats

Abstract

Prostaglandin-E 2 (PGE 2 ), an important mediator of inflammation, achieves its functions via four different G protein-coupled receptors (EP1, EP2, EP3, and EP4). We previously demonstrated that the EP2 receptor plays a proinflammatory and neurodegenerative role after status epilepticus (SE). We recently developed TG8-260 as a second-generation highly potent and selective EP2 antagonist. Here, we investigate whether TG8-260 is anti-inflammatory and combats neuropathology caused by pilocarpineinduced SE in rats. Adult male Sprague-Dawley rats were injected subcutaneously with pilocarpine (380-400 mg/kg) to induce SE. Following 60 min of SE, the rats were administered three doses of TG8-260 or vehicle and were allowed to recover. Neurodegeneration, neuroinflammation, gliosis, and blood-brain barrier (BBB) integrity were examined 4 days after SE. The results confirmed that pilocarpine-induced SE results in hippocampal neurodegeneration and a robust inflammatory response that persists days after SE. Furthermore, inhibition of the EP2 receptor by TG8-260 administered beginning 2 h after SE significantly reduced hippocampal neuroinflammation and gliosis but, in distinction to the earlier generation EP2 antagonist, did not mitigate neuronal injury or BBB breakdown. Thus, attenuation of neuroinflammation and gliosis is a common feature of EP2 inhibition following SE.

EP2 Antagonists (2011–2021): A Decade’s Journey from Discovery to Therapeutics

“…Continual efforts in medicinal chemistry and lead optimization to improve the drug-like properties of small-molecule EP2 antagonists 3 and 4 led to the discovery of a second-generation EP2 antagonist, TG8–260 ( 10 ). Unlike the first-generation EP2 antagonists (Figure A), compound 10 does not possess an acrylamide moiety; however, its structure was not fully disclosed until recently . Nonetheless, compound 10 was tested in a TR-FRET cAMP functional assay with a Schild K B of 13.2 nM and a water solubility of 238 μM.…”

“…Nonetheless, compound 10 was tested in a TR-FRET cAMP functional assay with a Schild K B of 13.2 nM and a water solubility of 238 μM. Strikingly, compound 10 showed a more than 500-fold selectivity to EP2 over other Gα s -coupled prostanoid receptors DP, EP4, and IP, which is a significant improvement compared to compounds 3 and 4 . With an intraperitoneal administration in C57BL/6 mice, compound 10 showed a terminal plasma half-life of 2.8 h and an extremely low brain penetration with a brain-to-plasma ratio of 0.02, which is ∼15- and 80-fold less than that of compounds 3 and 4 , respectively.…”

“…With an intraperitoneal administration in C57BL/6 mice, compound 10 showed a terminal plasma half-life of 2.8 h and an extremely low brain penetration with a brain-to-plasma ratio of 0.02, which is ∼15- and 80-fold less than that of compounds 3 and 4 , respectively. Interestingly, a 60 min episode of pilocarpine-induced SE in Sprague–Dawley rats was able to significantly increase the brain-to-plasma ratio of compound 10 from 0.03 to 0.05, suggesting that the SE-induced blood-brain barrier (BBB) opening facilitated its entry to the brain parenchyma . EP2 receptor inhibition by compound 10 administered in adult male Sprague–Dawley rats beginning 2 h after a pilocarpine-induced SE considerably reduced hippocampal neuroinflammation and gliosis (Table ).…”

“…EP2 receptor inhibition by compound 10 administered in adult male Sprague–Dawley rats beginning 2 h after a pilocarpine-induced SE considerably reduced hippocampal neuroinflammation and gliosis (Table ). However, SE-triggered neuronal injury and BBB breakdown were not mitigated by the treatment with compound 10 , suggesting that the lack of brain penetration prevented the compound from providing favorable beneficial effects like what the first-generation EP2 antagonists did in the pilocarpine model of seizures. Nevertheless, both first-generation (compound 4 ) and second-generation (compound 10 ) EP2 antagonists exhibited powerful anti-inflammatory activities following pilocarpine-induced SE.…”

Sleep Disruption Worsens Seizures: Neuroinflammation as a Potential Mechanistic Link

“…Therefore, prostaglandin receptors antagonists emerge as promising therapeutic agents to treat epilepsy [218,223,245]. Prostaglandin E2 (PGE2) is the most abundant, and pharmacological inhibition of its receptor, EP2, using novel selective antagonists has been shown to improve survival, weight recovery, cognitive deficits, and reduced neuroinflammation, gliosis, and neurodegeneration in various animal seizure models [250][251][252][253].…”