Store-Operated Calcium Entry in Peripheral Blood Mononuclear Cells as a Translational Biomarker of CNS Plasticity: A Mechanistic Hypothesis for Neuroplastogen Drug Programs
Abstract
Background: Psychedelic and neuroplastogen drug development programs require biomarkers capable of bridging intracellular pharmacology to clinically interpretable endpoints. Existing peripheral approaches, most notably plasma BDNF measurement, have demonstrated inconsistent results, with meta-analytic evidence reporting only a small, statistically marginal effect size in ketamine responders (SMD 0.26, 95% CI 0.03–0.48, p = 0.02) and no consistent correlation with symptom reduction. Critically, the peripheral biomarker field for neuropsychiatric disorders is characterised by high heterogeneity and systematic effect size inflation, placing a high evidential bar on any new candidate.
Hypothesis: We propose that store-operated calcium entry (SOCE), measured in patient-derived PBMCs using validated flow cytometric methods, may serve as a mechanistically specific pharmacodynamic readout of systemic 5-HT2A receptor engagement. We further propose that repeated sub-threshold 5-HT2A engagement produces oscillatory Ca2+ signals that engage the Ca2+-calcineurin-NFAT transcriptional feedback loop, progressively shifting the ORAI1:ORAI2 expression ratio and increasing thapsigargin-evoked SOCE amplitude as a cumulative readout of prior receptor engagement.
Bipolar Disorder Precedent: Critically, the logic of this assay has a direct published precedent in peripheral lymphocyte-derived cells. Thapsigargin-evoked SOCE is significantly elevated in lymphoblastoid cells from bipolar I disorder patients versus controls, and is attenuated by chronic lithium and valproate treatment but not by lamotrigine — providing drug-specific pharmacodynamic discrimination via peripheral lymphocyte SOCE. This body of evidence validates the principle that thapsigargin-SOCE in peripheral lymphocyte-derived cells reflects CNS disease state and is sensitive to mechanistically relevant psychotropic drug action.
Proposed Methodology: Thapsigargin-based passive ER store depletion followed by extracellular calcium readdition, measured by Indo-1 AM flow cytometry in freshly isolated human PBMCs, with cell-subset resolution using standard lymphocyte surface markers and companion ORAI1:ORAI2 mRNA quantification by qRT-PCR in sorted CD4+ naive T cells.
Implications: SOCE dynamics in patient-derived PBMCs represent a mechanistically grounded, technically validated, and currently underexplored candidate for exploratory pharmacodynamic endpoint development in neuroplastogen programs — particularly non-hallucinogenic programs where the psychedelic experience can no longer serve as a proxy for target engagement.