Psychedelic N,N-Dimethyltryptamine and 5-Methoxy-N,N-Dimethyltryptamine Modulate Innate and Adaptive Inflammatory Responses through the Sigma-1 Receptor of Human Monocyte-Derived Dendritic Cells

Sigma-1 (sigmar-1) is an endoplasmic reticulum–associated chaperone receptor expressed in the central nervous system and in immune cells, and earlier studies in rodents implicated it in cell survival, neuronal differentiation and immunosuppression. Previous work has shown that sigmar-1 ligation can increase anti-inflammatory IL-10 and suppress pro-inflammatory mediators in vivo, and that endogenous indole alkaloids such as N,N-dimethyltryptamine (NN-DMT) and 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) bind sigmar-1. However, the role of sigmar-1 and its endogenous ligands in human myeloid immune cells, particularly monocyte-derived dendritic cells (moDCs), had not been characterised. Szabo and colleagues set out to determine whether NN-DMT and 5-MeO-DMT modulate inflammatory responses of human primary moDCs via the sigma-1 receptor. The study tested effects on innate cytokine responses to Toll-like and RIG-I–like receptor agonists and on subsequent moDC-driven CD4+ T-cell polarisation, and used gene-silencing and a selective sigmar-1 agonist to probe receptor dependence. The broader aim was to evaluate whether DMT–sigmar-1 signalling could represent a regulatory axis relevant to chronic inflammatory and autoimmune conditions affecting the CNS and peripheral tissues.

Human peripheral blood mononuclear cells were obtained from healthy donors; monocytes were isolated by positive selection with anti-CD14 microbeads and differentiated into monocyte-derived dendritic cells in serum-free AIMV medium with GM-CSF and IL-4. Autologous naive CD4+ T cells were isolated from the same donors for co-culture assays. The extracted text does not clearly report the final sample size or the number of donors used for every assay, though several experiments state replication across multiple donors. MoDCs were activated with pathogen-associated stimuli: bacterial lipopolysaccharide (LPS) and high-molecular-weight polyinosinic:polycytidylic acid (polyI:C) at working concentrations reported in the extraction as 500 ng/ml and 20 mg/ml respectively (the polyI:C concentration as extracted may be misformatted). Pretreatments with NN-DMT, 5-MeO-DMT and the selective sigmar-1 agonist PRE-084 were applied 1 hour prior to activation; the tryptamines and PRE-084 were used at a working concentration reported as 100 mM in the extracted text. Inactivated influenza A virus and heat-killed Escherichia coli were used as pathogen loads to assess antigen-driven T-cell responses; the precise inocula are reported in the extraction but the numerical formatting is unclear. Outcomes measured included gene expression by quantitative PCR (QPCR) using TaqMan assays with 36B4 as the normaliser, protein expression by Western blotting for OPRS1/sigmar-1 and β-actin, and cytokine concentrations in culture supernatants (IL-1β, IL-6, TNF-α, IL-8 and IL-10) by ELISA 24 hours after activation. Functional T-cell priming was assessed by ELISPOT detection of IFNγ (Th1) and IL-17 (Th17) producing CD4+ T cells after 4-day co-culture of activated moDCs with autologous naive CD4+ T cells. Gene-specific knockdown of SIGMAR1 was performed by electroporation of a mix of SIGMAR1 siRNAs (square-wave pulse, 500 V, 0.5 ms); silencing efficacy was checked by Western blot two days post-transfection. Statistical analyses used t-tests for two-group comparisons and one-way ANOVA with Bonferroni post hoc testing for multiple comparisons; data are presented as mean ± SEM.

Sigmar-1 expression was detected in primary human blood monocytes and increased during in vitro differentiation to monocyte-derived macrophages and moDCs, whereas sigmar-2 mRNA/protein were not detectable in the same donor samples. When moDCs were exposed to LPS or polyI:C, 24-hour measurements showed no significant change in sigmar-1 mRNA or protein expression relative to untreated controls across multiple donor experiments, indicating that these high-dose PRR stimuli did not alter sigmar-1 levels under the tested conditions. Pre-treatment (1 hour) with NN-DMT or 5-MeO-DMT produced clear anti-inflammatory shifts in moDC responses to both LPS and polyI:C. The authors report optimisation experiments that identified 100 mM DMT as the concentration that modulated TNF-α most effectively; the extraction notes that this concentration has been reported in prior in vivo studies. At the mRNA and protein levels, DMT pre-treatment strongly reduced expression and secretion of pro-inflammatory cytokines IL-1β, IL-6, TNF-α and the chemokine IL-8, while markedly increasing production of the anti-inflammatory cytokine IL-10. The two tryptamines produced similar modulatory patterns and a modest, non-significant increase in TGF-β was noted in some experiments. Functionally, DMT pre-treated, pathogen-loaded moDCs had a reduced capacity to prime naive autologous CD4+ T cells toward inflammatory Th1 (IFNγ-producing) and Th17 (IL-17-producing) phenotypes. This effect was observed with moDCs loaded with heat-killed E. coli and with inactivated influenza virus; in both models the numbers of IFNγ- and IL-17-secreting T cells measured by ELISPOT were significantly lower after DMT pre-treatment compared with pathogen-only moDCs. To examine receptor dependence, SIGMAR1 expression was knocked down by siRNA electroporation. The extracted text reports substantial reduction of sigmar-1 protein after silencing, but the exact percentage is unclear in the extraction. Sigmar-1 knockdown largely abrogated the effects of NN-DMT and 5-MeO-DMT on TNF-α suppression and IL-10 induction in both LPS- and polyI:C-activated moDCs. Similarly, the inhibitory effect of DMTs on moDC-driven Th1 and Th17 priming was diminished when sigmar-1 was silenced, though knockdown did not fully restore cytokine levels or T-cell priming to baseline, suggesting additional mechanisms may contribute. Finally, treatment with the selective sigmar-1 agonist PRE-084 reproduced the cytokine-modulatory profile of the DMTs (decreased TNF-α, increased IL-10), and these effects were reversed by sigmar-1 silencing, supporting a key role for sigmar-1 in the observed immunomodulation.

Szabo and colleagues interpret their findings as the first demonstration that NN-DMT and 5-MeO-DMT exert potent immunomodulatory effects on human monocyte-derived dendritic cells via the sigma-1 receptor. The authors emphasise that sigmar-1 is expressed in human monocytes and is upregulated during differentiation to macrophages and dendritic cells, and that activation of this receptor by endogenous or synthetic agonists reduces pro-inflammatory cytokines (IL-1β, IL-6, TNF-α, IL-8) while boosting IL-10 production. They further highlight that DMT pre-treatment of pathogen-activated moDCs impairs these cells’ capacity to initiate adaptive inflammatory responses, specifically reducing Th1 and Th17 polarisation. The discussion situates these results within prior murine studies that reported sigmar-1–mediated immunosuppression and increased IL-10, and proposes that the DMT–sigmar-1 axis may represent a previously underappreciated endogenous regulatory pathway for inflammation and immune homeostasis. The authors point out potential clinical relevance to chronic inflammatory and autoimmune diseases of the central nervous system and peripheral tissues, and to neuropsychiatric conditions in which neuroinflammation is implicated. Acknowledged uncertainties include the incomplete restoration of cytokine levels and T-cell priming after sigmar-1 knockdown, which the authors suggest indicates additional mechanisms of action. They note that dimethyltryptamines also bind serotonin receptors (notably 5-HT2A and 5-HT1A) and that serotonin signalling can modulate dendritic cell function; however, because experiments were performed in serum-free medium, the authors state that background serotonin in the culture is unlikely to account for the observed effects. Use of the selective sigmar-1 agonist PRE-084, whose effects were fully reversed by sigmar-1 silencing, is presented as further evidence that sigmar-1 is central to the immunomodulation seen in these experiments. In conclusion, the investigators propose that the DMT–sigmar-1 interaction may extend the biological role of dimethyltryptamines beyond neuromodulation and psychedelia to include regulation of innate and adaptive immunity, and they suggest the DMT–sigmar-1 axis as a candidate target for future pharmacotherapies of chronic inflammatory and autoimmune diseases. The extracted text does not report further experimental limitations or detailed translational next steps beyond these interpretations.