Early JNJ-46356479 mGluR2 positive allosteric modulation attenuated adolescent apoptotic alterations in a postnatal ketamine-induced mouse model of schizophrenia

The glutamatergic hypothesis of schizophrenia proposes that an excess of glutamate promotes excitotoxicity and aberrant synaptic pruning by increasing apoptosis in dendritic spines [1]. We have previously observed that treatment with the metabotropic glutamate receptor 2 (mGluR2) positive allosteric modulator JNJ-46356479 (JNJ), which reduces presynaptic glutamate release, improves cognitive and neuromolecular alterations in a murine model of schizophrenia induced by postnatal ketamine (KET) exposure [2]. In the present study, we evaluated whether early treatment limited to adolescence of the animal with JNJ or clozapine (CLZ) could modulate brain levels of pro- and anti-apoptotic proteins at this developmental stage. This effect had previously been observed after pharmacological treatment during adulthood [3] and is of particular interest for understanding the developmental timing of intervention and its potential impact on early molecular alterations associated with the model.

Twenty-four C57BL/6J mice exposed to KET (30 mg/kg) or saline on postnatal days (PND) 7, 9 and 11 were treated with JNJ, CLZ (10 mg/kg) or vehicle from PND 35 to PND 60, corresponding to the adolescent period in mice. Hippocampal (HPC) and prefrontal cortex (PFC) tissue was obtained, and caspase-3, Bax and Bcl-2 protein levels were quantified by Western blotting using standard protein extraction and immunodetection protocols. All samples were processed under identical laboratory conditions to minimize variability, ensure consistency across experimental groups and maintain methodological rigor throughout the experimental workflow and downstream analyses.

After statistical analysis, differences between study groups were observed in caspase-3, Bax, and Bcl-2 protein levels. Postnatal KET exposure increased caspase-3 and Bax levels in the HPC and reduced Bcl-2 levels in the PFC, indicating a shift toward a pro-apoptotic profile. Adolescent treatment with JNJ or CLZ partially restored these deficits: reducing caspase-3 and Bax levels in the HPC and increasing Bcl-2 levels in the PFC. In addition, significant positive correlations were found between caspase-3 levels in the HPC and PFC (r = 0.503) and between caspase-3 and Bax levels in the PFC (r = 0.534), while a significant negative correlation was found between caspase-3 and Bcl-2 levels in the HPC (r = -0.545). These findings suggest coordinated regulation of apoptotic signaling across brain regions involved in cognitive and executive processing.

Early modulation of the glutamatergic system, particularly through mGluR2 targeting with the positive allosteric modulator JNJ, could attenuate the aberrant pro-apoptotic state, supporting its potential as an early intervention to reduce the effects of excess glutamate during key developmental stages and its relationship with altered synaptic pruning and disease progression [4]. These results further support the relevance of targeting glutamatergic signaling during specific developmental windows and reinforce the importance of evaluating early pharmacological interventions in translational models of schizophrenia. Overall, these findings provide additional support for the involvement of apoptotic pathways in this model and their modulation by glutamatergic-targeted treatments, suggesting a relevant link between aberrant neurotransmission and cell survival mechanisms.

References

1. Uno, Y., & Coyle, J. T. (2019). Glutamate hypothesis in schizophrenia. Psychiatry and clinical neurosciences, 73(5), 204–215. https://doi.org/10.1111/pcn.12823
2. Olivares-Berjaga, D., Martínez-Pinteño, A., Rodríguez, N., Mas, S., Morén, C., Parellada, E., & Gassó, P. (2025). Effectiveness of positive allosteric modulators of metabotropic glutamate receptor 2/3 (mGluR2/3) in animal models of schizophrenia. Translational psychiatry, 15(1), 11. https://doi.org/10.1038/s41398-024-03194-2
3. Olivares-Berjaga, D., Martínez-Pinteño, A., Rodríguez, N., Madero, S., Prohens, L., Martínez-Serrano, I., Mas, S., Morén, C., Parellada, E., & Gassó, P. (2024). Effects of the PAM of mGluR2, JNJ-46356479, on brain apoptotic protein levels in a mouse model of schizophrenia. Progress in neuro-psychopharmacology & biological psychiatry, 131, 110955. https://doi.org/10.1016/j.pnpbp.2024.110955
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