Preclinical and clinical study on type 3 metabotropic glutamate receptors in Parkinson's disease

Luisa Di Menna^#¹, Marika Alborghetti^#^{2

3}, Maria Ilenia De Bartolo^#⁴, Marina Borro³, Giovanna Gentile³, Manuela Zinni⁵, Matteo Bologna^{2

4}, Carolina Cutrona², Giovanna D'Errico¹, Tiziana Imbriglio¹, Domenico Bucci¹, Sara Merlo⁶, Roxana Paula Ginerete¹, Rosamaria Orlando¹, Federica Carrillo⁷, Giorgio Fortunato⁷, Milena Cannella¹, Maria Angela Sortino⁸, Julien Pansiot⁵, Olivier Baud^{5

9

10}, Ferdinando Nicoletti^{1

11}, Valeria Bruno^{1

11}, Maurizio Simmaco³, Francesco Ernesto Pontieri³, Edoardo Bianchini^{3

12}, Domiziana Rinaldi³, Amalia de Curtis¹³, Giovanni De Gaetano¹³, Licia Iacoviello^{13

14}, Teresa Esposito^{1

7}, Alfredo Berardelli^{15

16}, Giuseppe Battaglia^{1

11}

Affiliations

¹ Department of Molecular Pathology, IRCCS Neuromed, Pozzilli, Italy.
² Departments of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
³ Neuroscience, Mental Health, and Sensory Organs Clinical Neurophysiology, Sapienza University of Rome, Rome, Italy.
⁴ Department of Clinical Neurophysiology, IRCCS Neuromed, Pozzilli, Italy.
⁵ Inserm UMR1141 NeuroDiderot, Université Paris Cité, Paris, France.
⁶ Department of Drug and Health Sciences, University of Catania, Catania, Italy.
⁷ Institute of Genetics and Biophysics, Adriano Buzzati-Traverso, National Research Council, Naples, Italy.
⁸ Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy.
⁹ Department of Neonatal Medicine, Cochin-Port Royal Hospital, FHU PREMA, AP-HP Centre, Paris, France.
¹⁰ Université Paris Cite, CRESS, Obstetrical Perinatal and Pediatric Epidemiology Research Team, EPOPE, French Institute for Medical Research and Health INSERM, INRAE, 75014, Paris, France.
¹¹ Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy.
¹² AGEIS, Université Grenoble Alpes, 38000, Grenoble, France.
¹³ Department of Epidemiology and Prevention, IRCCS Neuromed, 86077, Pozzilli, Italy.
¹⁴ Department of Medicine and Surgery, LUM University, 70010, Casamassima, Bari, Italy.
¹⁵ Departments of Human Neurosciences, Sapienza University of Rome, Rome, Italy. alfredo.berardelli@uniroma1.it.
¹⁶ Department of Clinical Neurophysiology, IRCCS Neuromed, Pozzilli, Italy. alfredo.berardelli@uniroma1.it.

^# Contributed equally.

PMID: 39755677
PMCID: PMC11700162
DOI: 10.1038/s41531-024-00860-6

Preclinical and clinical study on type 3 metabotropic glutamate receptors in Parkinson's disease

Luisa Di Menna et al. NPJ Parkinsons Dis. 2025.

. 2025 Jan 4;11(1):9.

doi: 10.1038/s41531-024-00860-6.

Authors

Affiliations

¹ Department of Molecular Pathology, IRCCS Neuromed, Pozzilli, Italy.
² Departments of Human Neurosciences, Sapienza University of Rome, Rome, Italy.
³ Neuroscience, Mental Health, and Sensory Organs Clinical Neurophysiology, Sapienza University of Rome, Rome, Italy.
⁴ Department of Clinical Neurophysiology, IRCCS Neuromed, Pozzilli, Italy.
⁵ Inserm UMR1141 NeuroDiderot, Université Paris Cité, Paris, France.
⁶ Department of Drug and Health Sciences, University of Catania, Catania, Italy.
⁷ Institute of Genetics and Biophysics, Adriano Buzzati-Traverso, National Research Council, Naples, Italy.
⁸ Department of Biomedical and Biotechnological Sciences, University of Catania, Catania, Italy.
⁹ Department of Neonatal Medicine, Cochin-Port Royal Hospital, FHU PREMA, AP-HP Centre, Paris, France.
¹⁰ Université Paris Cite, CRESS, Obstetrical Perinatal and Pediatric Epidemiology Research Team, EPOPE, French Institute for Medical Research and Health INSERM, INRAE, 75014, Paris, France.
¹¹ Department of Physiology and Pharmacology, Sapienza University of Rome, Rome, Italy.
¹² AGEIS, Université Grenoble Alpes, 38000, Grenoble, France.
¹³ Department of Epidemiology and Prevention, IRCCS Neuromed, 86077, Pozzilli, Italy.
¹⁴ Department of Medicine and Surgery, LUM University, 70010, Casamassima, Bari, Italy.
¹⁵ Departments of Human Neurosciences, Sapienza University of Rome, Rome, Italy. alfredo.berardelli@uniroma1.it.
¹⁶ Department of Clinical Neurophysiology, IRCCS Neuromed, Pozzilli, Italy. alfredo.berardelli@uniroma1.it.

^# Contributed equally.

PMID: 39755677
PMCID: PMC11700162
DOI: 10.1038/s41531-024-00860-6

Abstract

Metabotropic glutamate (mGlu) receptors are candidate drug targets for therapeutic intervention in Parkinson's disease (PD). Here we focused on mGlu3, a receptor subtype involved in synaptic regulation and neuroinflammation. mGlu3^-/- mice showed an enhanced nigro-striatal damage and microglial activation in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Expression of genes encoding anti-inflammatory proteins and neuroprotective factors was reduced in the striatum of MPTP-treated mGlu3^-/- mice. We also examined polymorphic variants of GRM3 (the mGlu3 receptor encoding gene) in 723 PD patients and 826 healthy controls. Two GRM3 haplotypes were associated with PD, and gene variants correlated with motor and non-motor signs. Interestingly, PD patients carrying each of the two haplotypes showed an impaired cortical plasticity in the paired associated stimulation paradigm of magnetic transcranial stimulation. These findings suggest that mGlu3 receptors are neuroprotective in mouse models of parkinsonism and shape mechanisms of cortical plasticity in PD.

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Conflict of interest statement

Competing interests: The authors declare no competing interests.

Figures

**Fig. 1. Amplification of MPTP-induced nigro-striatal degeneration in mice lacking mGlu3 receptors.**
An illustration of the experimental protocol is shown in (A); DA and DOPAC levels in the striatum of wild-type, mGlu2^−/− or mGlu3^−/− treated with saline or MPTP (10 mg/kg, s.c., every other day) is shown in (B) and (C), respectively. Values are means + S.E.M. Number of mice per group: wild-type saline = 20 for DA and DOPAC; wild-type MPTP = 24 for DA and DOPAC; mGlu2^−/− saline or MPTP = 17 for DA and DOPAC; mGlu3^−/− saline = 17 for DA and DOPAC; mGlu3^−/− MPTP = 22 for DA and 19 for DOPAC. Significant difference vs. the respective groups treated with saline (*) or vs. wild-type mice treated with MPTP (#). Two-way ANOVA + Fisher LSD). DA levels: genotype, F_2,111 = 7.333; p = 0.001; treatment, F_1,111 = 176; p = <0.001; interaction, F_2,111 = 4.083; p = 0.019. Wild-type, MPTP vs. saline, p < 0.001; mGlu2^−/−, MPTP vs. saline, p < 0.001; mGlu3^−/−, MPTP vs. mGlu3^−/− saline, p < 0.001; mGlu2^−/− MPTP vs. wild-type MPTP, p = 0.01; mGlu3^−/− MPTP vs. wild-type MPTP, p = 0.019; mGlu2^−/− MPTP vs. mGlu3^−/− MPTP, p < 0.001; DOPAC levels: genotype, F_2,108 = 3.658; p = 0.029; treatment, F_1,108 = 119.2; p = <0.001; interaction, F_2,108 = 7.52; p = <0.001; Wild-type, MPTP vs. saline, p < 0.001; mGlu2^−/−, MPTP vs. saline, p < 0.001; mGlu3^−/−, MPTP vs. saline, p < 0.001; mGlu2^−/− MPTP vs. wild-type MPTP, p = 0.023; mGlu3^−/− MPTP vs. wild-type MPTP, p = 0.08; mGlu2^−/− MPTP vs. mGlu3^−/− MPTP, p < 0.001. Representative images of TH⁺ and Nissl-stained cells in the SNpc at low and high magnifications are shown in (D). Stereological cell counting of TH⁺ and Nissl-stained neurons in the SNpc of wild-type, mGlu2^−/− or mGlu3^−/− treated with saline or MPTP is shown in (E) and (F), respectively, where values are means + S.E.M. Number of mice per group: wild-type saline or MPTP = 6; mGlu2^−/− = 5 for saline and 6 for MPTP; mGlu3^−/− saline or MPTP = 5. Significant difference vs. the respective groups treated with saline (*) or vs. wild-type mice treated with MPTP (#) (Two-way ANOVA + Fisher LSD); TH⁺ cells: genotype, F_2,27 = 6.072; p = 0.007; treatment, F_2,27 = 17.45; p < 0.001; interaction, F_2,27 = 3.23; p = 0.05. Wild-type, MPTP vs. saline, p = 0.025; mGlu2^−/−, MPTP vs. saline, p = 0.522; mGlu3^−/−, MPTP vs. saline, p < 0.001; mGlu2^−/− MPTP vs. wild-type MPTP, p = 0.062; mGlu3^−/− MPTP vs. wild-type MPTP, p = 0.019; mGlu2^−/− MPTP vs. mGlu3^−/− MPTP, p < 0.001. Nissl-stained cells: genotype, F_2,27 = 10.02; p < 0.001; treatment, F_2,27 = 51.58; p < 0.001; interaction, F_2,27 = 7.55; p = 0.002. Wild-type, MPTP vs. saline, p < 0.001; mGlu2^−/−, MPTP vs. saline, p = 0.259; mGlu3^−/−, MPTP vs. saline, p < 0.001; mGlu2^−/− MPTP vs. wild-type MPTP, p = 0.002; mGlu3^−/− MPTP vs. wild-type MPTP, p = 0.013; mGlu2^−/− MPTP vs. mGlu3^−/− MPTP, p < 0.001.

**Fig. 2. Density of CD11b⁺ cells in the SNpc of wild-type, mGlu2^−/− and mGlu3^−/− mice challenged with MPTP.**
Representative images of CD11b⁺ cells in the SNpc of the three genotypes are shown in (A). Cell density is shown in (B) where values are means + S.E.M. Number of mice per group: wild-type saline and MPTP = 5; mGlu2^−/− saline = 13; mGlu2^−/− MPTP = 4; mGlu3^−/− saline = 12; mGlu3^−/− MPTP = 11. Significant difference vs. the respective saline (*) or vs. wild-type mice treated with MPTP (#). Two-way ANOVA + Fisher LSD; genotype, F_2,44 = 6.918; p = 0.002; treatment, F_1,44 = 15.334; p < 0.001; interaction, F_2,44 = 6.229; p = 0.004. Wild-type, MPTP vs. saline, p = 0.102; mGlu2^−/−, MPTP vs. saline, p = 0.833; mGlu3^−/−, MPTP vs. saline, p < 0.001; mGlu2^−/− MPTP vs. wild-type MPTP, p = 0.202; mGlu3^−/− MPTP vs. wild-type MPTP, p = 0.005; mGlu2^−/− MPTP vs. mGlu3^−/− MPTP, p < 0.001.

Fig. 3. Expression of genes encoding anti-inflammatory and pro-inflammatory proteins or neurotrophic factors of the TGF-β superfamily in the striatum of wild-type, mGlu2^−/− or mGlu3^−/− mice treated with saline or MPTP.
mRNA levels were normalized by levels of the housekeeping (either β-actin or GAPDH) and analysed by ΔΔCt using as reference values those obtained in wild-type mice treated with saline. Values are means + S.E.M. of 6-10 mice per group. p < 0.05 vs. the respective groups treated with saline (*), vs. the respective values of wild-type mice (#), or vs. the respective values of mGlu2^−/− mice (§) (Two-way ANOVA + Fisher’s LSD). Anti-inflammatory markers (A): Il-4: genotype, F_2,50 = 0.694; p < 0.504; treatment: F_1,50 = 8.741; p = 0.005; interaction: F_2,50 = 3.26; p = 0.046. Il4ra: genotype, F_2,50 = 27.307; p < 0.001; treatment: F_1,50 = 3.25; p = 0.077; interaction: F_2,50 = 8.84; p = 0.01. Mrc1: genotype, F_2,50 = 17.167; p < 0.001; treatment: F_1,50 = 0.059; p = 0.809; interaction: F_2,50 = 1.405; p = 0.255. Trem2: genotype, F_2,35 = 28.88; p < 0.0001; treatment: F_1,35 = 1.538; p = 0.223; interaction: F_2,35 = 0.217; p = 0.806. Arg-1: genotype, F_2,35 = 3.425; p = 0.0438; treatment: F_1,35 = 2.215; p = 0.145; interaction: F_2,35 = 0.064; p = 0.938. Il13: genotype, F_2,34 = 3.431; p = 0.0439; treatment: F_1,34 = 0.576; p = 0.453; interaction: F_2,34 = 1.532; p = 0.231. Socs-1: genotype, F_2,32 = 2.73; p = 0.0804; treatment: F_1,32 = 0.102; p = 0.752; interaction: F_2,32 = 0.704; p = 0502. Socs-3: genotype, F_2,35 = 7.811; p = 0.0016; treatment: F_1,35 = 0.0235; p = 0.879; interaction: F_2,35 = 0.403; p = 0.671. Pro-inflammatory markers (B): Ptgs2: genotype, F_2,50 = 0.761; p = 0.473; treatment: F_1,50 = 157; p = 0.694; interaction: F_2,50 = 0.12; p = 0.887. Nos2: genotype, F_2,35 = 3.56; p = 0.039; treatment: F_1,35 = 0.877; p = 0.355; interaction: F_2,35 = 0.949; p = 0.397. Il-6: genotype, F_2,50 = 87.78; p < 0.001; treatment: F_1,50 = 0.042; p = 0.837; interaction: F_2,50 = 3.684; p = 0.032. Il-1b: genotype, F_2,34 = 1.391; p = 0.263; treatment: F_1,34 = 1.325; p = 0.258; interaction: F_2,34 = 3.386; p = 0.046. Tnfa: genotype, F_2,34 = 4.377; p = 0.0204; treatment: F_1,34 = 9.687; p = 0.0037; interaction: F_2,34 = 6.599; p = 0.0038Bin 1: genotype, F_2,35 = 5.323; p = 0.0096; treatment: F_1,35 = 1.916; p = 0.175; interaction: F_2,35 = 1.974; p = 0.154. P2rx7: genotype, F_2,35 = 1.152; p = 0.3276; treatment: F_1,35 = 0.2736; p = 0.604; interaction: F_2,35 = 0.4779; p = 0.624. P2ry12: genotype, F_2,34 = 1.413; p = 0.2572; treatment: F_1,34 = 1.073; p = 0.308; interaction: F_2,34 = 0.5925; p = 0.5585; Cd86: genotype, F_2,50 = 16.102; p < 0.001; treatment: F_1,50 = 2.136; p = 0.15; interaction: F_2,50 = 6.79; p = 0.002. Trophic factors (C): Gdnf: genotype, F_2,50 = 21.573; p < 0.001; treatment: F_1,50 = 16.384; p < 0.001; interaction: F_2,50 = 3.565; p = 0.036. Tgfb: genotype, F_2,50 = 19.467; p < 0.001; treatment: F_1,50 = 0.0625; p = 0.804; interaction: F_2,50 = 20.95; p < 0.001.

**Fig. 4. *GRM3* gene haplotypes associated with Parkinson’s disease.**
Motor and non-motor phenotypes of patients affected by PD are shown in (A); HeY = Hoehn and Yahr disease stage (from 1 to 5); RBD = rapid eye movement sleep behavioural disorder; FOG = freezing of gait. *GRM3* gene structure (adapted from Ensambl) and position of polymorphic variants is shown in (B). The two haplotypes which were found to be significantly associated with PD (1 and 2) are shown in (C).

**Fig. 5. *GRM3* gene variants associated with motor and non-motor symptoms in patients affected by Parkinson’s disease.**
SNP single nucleotide polymorphism, RBD rapid eye movement sleep behavioural disorder, NMS non-motor symptoms, NMSS NMS scale.

**Fig. 6. *GRM3* gene variant associated with Parkinson’s disease in the cohort of patients available for wide exome sequencing (WES).**
Motor and non-motor phenotypes of patients affected by PD available for WES analysis are shown in (A); HeY = Hoehn and Yahr disease stage (from 1 to 5); RBD rapid eye movement sleep behavioural disorder, FOG freezing of gait. The *GRM3* variant significantly associated with PD in this cohort of patients is shown in (B).

**Fig. 7. *GRM3* gene variants associated with motor and non-motor symptoms of Parkinson’s disease in the cohort of patients available for wide exome sequencing (WES).**
SNP single nucleotide polymorphism, MDS-UPDRS Movement Disorder Society – Unified Parkinson’s Disease Rating Scale, RBD rapid eye movement sleep behavioural disorder, NMS non-motor symptoms.

**Fig. 8. Plasticity of primary motor cortex in patients affected by Parkinson’s disease carrying the GRM3 haplotypes or the wild-type genotype, and healthy controls.**
(A) Course of MEPs after the PAS protocol in the abductor pollicis brevis in PD patients without the haplotypes (dotted line); in PD patients with the haplotype (dashed line) and in healthy controls (solid line). The y-axis shows MEP amplitudes (mV). The x-axis shows measurements at the four time points: before PAS (T0) and 5 min (T1), 15 min (T2) and 30 min (T3) after PAS. A significantly reduced response after PAS was found in MEP recorded at T2 in PD carrying the haplotypes compared to PD with the wild-type genotype (U = 14.4, p = 0.013) and healthy controls (U = −15.127, p = 0.001). (B) Representative plots showing the MEP waveform in the three groups at the various time points.

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References

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Preclinical and clinical study on type 3 metabotropic glutamate receptors in Parkinson's disease

Affiliations

Preclinical and clinical study on type 3 metabotropic glutamate receptors in Parkinson's disease

Authors

Affiliations

Abstract

Conflict of interest statement

Figures

References

Grants and funding

LinkOut - more resources

Full Text Sources