Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Sep 22:8:676.
doi: 10.3389/fphar.2017.00676. eCollection 2017.

Involvement of PPARγ in the Anticonvulsant Activity of EP-80317, a Ghrelin Receptor Antagonist

Chiara Lucchi  1 , Anna M Costa  1 , Carmela Giordano  1 , Giulia Curia  1 , Marika Piat  1 , Giuseppina Leo  1 , Jonathan Vinet  1 , Luc Brunel  2 , Jean-Alain Fehrentz  2 , Jean Martinez  2 , Antonio Torsello  3 , Giuseppe Biagini  1   4
Affiliations

Involvement of PPARγ in the Anticonvulsant Activity of EP-80317, a Ghrelin Receptor Antagonist

Chiara Lucchi et al. Front Pharmacol. .

Abstract

Ghrelin, des-acyl ghrelin and other related peptides possess anticonvulsant activities. Although ghrelin and cognate peptides were shown to physiologically regulate only the ghrelin receptor, some of them were pharmacologically proved to activate the peroxisome proliferator-activated receptor gamma (PPARγ) through stimulation of the scavenger receptor CD36 in macrophages. In our study, we challenged the hypothesis that PPARγ could be involved in the anticonvulsant effects of EP-80317, a ghrelin receptor antagonist. For this purpose, we used the PPARγ antagonist GW9662 to evaluate the modulation of EP-80317 anticonvulsant properties in two different models. Firstly, the anticonvulsant effects of EP-80317 were studied in rats treated with pilocarpine to induce status epilepticus (SE). Secondly, the anticonvulsant activity of EP-80317 was ascertained in the repeated 6-Hz corneal stimulation model in mice. Behavioral and video electrocorticographic (ECoG) analyses were performed in both models. We also characterized levels of immunoreactivity for PPARγ in the hippocampus of 6-Hz corneally stimulated mice. EP-80317 predictably antagonized seizures in both models. Pretreatment with GW9662 counteracted almost all EP-80317 effects both in mice and rats. Only the effects of EP-80317 on power spectra of ECoGs recorded during repeated 6-Hz corneal stimulation were practically unaffected by GW9662 administration. Moreover, GW9662 alone produced a decrease in the latency of tonic-clonic seizures and accelerated the onset of SE in rats. Finally, in the hippocampus of mice treated with EP-80317 we found increased levels of PPARγ immunoreactivity. Overall, these results support the hypothesis that PPARγ is able to modulate seizures and mediates the anticonvulsant effects of EP-80317.

Keywords: 6-Hz corneal stimulation; EP-80317; ghrelin; peroxisome proliferator-activated receptor gamma; pilocarpine; seizure; status epilepticus.

PubMed Disclaimer

Figures

FIGURE 1
FIGURE 1
ECoG analysis of seizure duration in the pilocarpine model. Representative epileptiform activity recorded from each treatment group is shown. In saline-treated and GW9662-treated rats, the seizure duration was similar to those of EP-80317 and GW9662+EP-80317 (GW+EP) groups. LFC, left frontal cortex; LOC, left occipital cortex; Ref, reference electrode; RFC, right frontal cortex; ROC, right occipital cortex.
FIGURE 2
FIGURE 2
Behavioral changes observed during repeated 6-Hz corneal stimulation. Seizure duration and severity are respectively illustrated in (A,B) for the various treatment groups. (A) The PPARγ activator EP-80317 significantly reduced the duration of seizures induced by the first 6-Hz corneal stimulation (∗p < 0.05, EP-80317 vs. saline in the first session of stimulation; Holm-Šídák test). Administering GW9662, a PPARγ blocker, counteracted this effect (GW+EP group). Note also that seizure duration significantly decreased in control mice at the third and fourth sessions (##p < 0.01, sessions three or four vs. session one in saline-treated mice; Holm-Šídák test). (B) The seizure severity, evaluated as the percentage of animals displaying postural loss during convulsions, was also significantly affected by EP-80317 (∗p < 0.05, EP-80317 vs. saline in the first session of stimulation; Fisher’s exact test).
FIGURE 3
FIGURE 3
Electrographic changes observed during repeated 6-Hz corneal stimulation. (A) Representative power spectra obtained at session one and four are illustrated for each treatment group. Note that powers of ictal activity did not significantly change going from first to fourth stimulation in mice treated with EP-80317, whereas clear alterations were present in all other groups. The inset on the right shows electrographic traces corresponding to power spectra of traces recorded by the occipital electrodes, after the fourth seizure induction. The gray color is for the first session; the black color is for the fourth session. (B) Mean power spectra of ictal events obtained through one or four separated 6-Hz corneal stimulation sessions. Histograms show that the power peak of ictal events significantly increased at the fourth session in saline-treated mice (##p < 0.01, session 4 vs. session 1; Holm-Šídák test) and in mice treated with GW9662 (#p < 0.05, session 4 vs. session 1), but not in mice treated with EP-80317 alone or in combination with GW9662 (GW+EP). Note also that the mean power peak of animals treated with EP-80317 was significantly lower than that of saline-treated mice, at the fourth stimulation (∗p < 0.05, EP-80317 vs. saline in the fourth session of stimulation).
FIGURE 4
FIGURE 4
PPARγ immunoreactivity in the hippocampal CA1 region of mice treated with saline or EP-80317 and exposed to different sessions of 6-Hz corneal stimulation. PPARγ immunoreactivity is illustrated in a representative unstimulated control (Ctrl) mouse and in mice treated with saline (Sal) or EP-80317 (EP) and respectively exposed to one (Sal-1, EP-1) or three (Sal-3, EP-3) different sessions of 6-Hz corneal stimulation. Note that PPARγ levels were significantly increased after the first session in EP-80317 mice only (°p < 0.05, EP-1 vs. Ctrl; Holm-Šídák test). Note also that PPARγ levels were significantly reduced in the third session of EP-80317 mice (##p < 0.01, EP-3 vs. EP-1). Scale bar: 100 μm.
FIGURE 5
FIGURE 5
PPARγ immunoreactivity in the hippocampal CA3 region of mice treated with saline or EP-80317 and exposed to different sessions of 6-Hz corneal stimulation. PPARγ immunoreactivity is illustrated in a representative unstimulated control (Ctrl) mouse and in mice treated with saline (Sal) or EP-80317 (EP) and respectively exposed to one (Sal-1, EP-1) or three (Sal-3, EP-3) different sessions of 6-Hz corneal stimulation. Note that PPARγ levels were significantly increased after the first session in EP-80317 mice only (∘∘∘p < 0.001, EP-1 vs. Ctrl; Holm-Šídák test). In EP-80317 mice, PPARγ levels were also significantly different from saline-treated mice (∗∗∗p < 0.001, EP-1 vs. Sal-1 in CA3). Note also that PPARγ levels were significantly reduced in the third session of EP-80317 mice (###p < 0.001, EP-3 vs. EP-1). Scale bar: 100 μm.
FIGURE 6
FIGURE 6
PPARγ immunoreactivity in the hilus of dentate gyrus (DH) of mice treated with saline or EP-80317 and exposed to different sessions of 6-Hz corneal stimulation. PPARγ immunoreactivity is illustrated in a representative unstimulated control (Ctrl) mouse and in mice treated with saline (Sal) or EP-80317 (EP) and respectively exposed to one (Sal-1, EP-1) or three (Sal-3, EP-3) different sessions of 6-Hz corneal stimulation. Note that PPARγ levels were significantly increased after the first session in EP-80317 mice only (∘∘∘p < 0.001, EP-1 vs. Ctrl; Holm-Šídák test). PPARγ levels were also significantly different from saline-treated mice (∗∗∗p < 0.001, EP-1 vs. Sal-1). Note also that PPARγ levels were significantly reduced in the third session of EP-80317 mice (###p < 0.001, EP-3 vs. EP-1). Scale bar: 100 μm.
FIGURE 7
FIGURE 7
Double immunofluorescence of interneurons expressing PPARγ. Photomicrographs illustrating co-labeling with glutamate decarboxylase 67 (GAD67, green) and PPARγ (red) in CA1 of a representative mouse are shown in top panels. Double immunofluorescence revealed the co-expression of GAD67 and PPARγ in some (arrows), but not all interneurons (arrowhead point to a PPARγ negative interneuron). Scale bar: 50 μm. Photomicrographs illustrating co-labeling of PPARγ (green) and parvalbumin (PV, red), somatostatin (SOM, red), or vasoactive intestinal peptide (VIP, red) in the hippocampus of mice exposed to repeated 6-Hz corneal stimulation are sequentially shown from the second row to bottom. Note that double immunofluorescence revealed the co-labeling of PPARγ/PV in CA3, PPARγ/SOM in the hilus of dentate gyrus (DH) (arrows), but not PPARγ/VIP in CA1 (arrowhead). Scale bar: 50 μm.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Adabi Mohazab R., Javadi-Paydar M., Delfan B., Dehpour A. R. (2012). Possible involvement of PPAR-gamma receptor and nitric oxide pathway in the anticonvulsant effect of acute pioglitazone on pentylenetetrazole-induced seizures in mice. Epilepsy Res. 101 28–35. 10.1016/j.eplepsyres.2012.02.015 - DOI - PubMed
    1. Aslan A., Yildirim M., Ayyildiz M., Güven A., Agar E. (2009). The role of nitric oxide in the inhibitory effect of ghrelin against penicillin-induced epileptiform activity in rat. Neuropeptides 43 295–302. 10.1016/j.npep.2009.05.005 - DOI - PubMed
    1. Bayliss J. A., Andrews Z. B. (2013). Ghrelin is neuroprotective in Parkinson’s disease: molecular mechanisms of metabolic neuroprotection. Ther. Adv. Endocrinol. Metab. 4 25–36. 10.1177/2042018813479645 - DOI - PMC - PubMed
    1. Biagini G., D’Arcangelo G., Baldelli E., D’Antuono M., Tancredi V., Avoli M. (2005). Impaired activation of CA3 pyramidal neurons in the epileptic hippocampus. Neuromol. Med. 7 325–342. 10.1385/NMM:7:4:325 - DOI - PubMed
    1. Biagini G., Torsello A., Marinelli C., Gualtieri F., Vezzali R., Coco S., et al. (2011). Beneficial effects of desacyl-ghrelin, hexarelin and EP-80317 in models of status epilepticus. Eur. J. Pharmacol. 670 130–136. 10.1016/j.ejphar.2011.08.020 - DOI - PubMed

LinkOut - more resources