Psychoneuroimmunology: The new frontier in suicide research

Integrative Analyses of scRNA-seq, Bulk mRNA-seq, and DNA Methylation Profiling in Depressed Suicide Brain Tissues

BACKGROUND

Suicidal behaviors have become a serious public health concern globally due to the economic and human cost of suicidal behavior to individuals, families, communities, and society. However, the underlying etiology and biological mechanism of suicidal behavior remains poorly understood.

METHODS

We collected different single omic data, including single-cell RNA sequencing (scRNA-seq), bulk mRNA-seq, DNA methylation microarrays from the cortex of Major Depressive Disorder (MDD) in suicide subjects' studies, as well as fluoxetine-treated rats brains. We matched subject IDs that overlapped between the transcriptome dataset and the methylation dataset. The differential expression genes and differentially methylated regions were calculated with a 2-group comparison analysis. Cross-omics analysis was performed to calculate the correlation between the methylated and transcript levels of differentially methylated CpG sites and mapped transcripts. Additionally, we performed a deconvolution analysis for bulk mRNA-seq and DNA methylation profiling with scRNA-seq as the reference profiles.

RESULTS

Difference in cell type proportions among 7 cell types. Meanwhile, our analysis of single-cell sequence from the antidepressant-treated rats found that drug-specific differential expression genes were enriched into biological pathways, including ion channels and glutamatergic receptors.

CONCLUSIONS

This study identified some important dysregulated genes influenced by DNA methylation in 2 brain regions of depression and suicide patients. Interestingly, we found that oligodendrocyte precursor cells (OPCs) have the most contributors for cell-type proportions related to differential expression genes and methylated sites in suicidal behavior.

Levels of IL-6 are Associated with Lifetime Attempted Suicide in Alcohol Use Disorder Patients

Background

Patients with alcohol use disorder (AUD) have an increased risk of suicide. Neuroimmunological measures, such as cytokines, are shown to deviate in people with attempted suicide. Few studies have investigated this among AUD patients.

Patients and Methods

One-hundred and fourteen patients undergoing residential treatment for AUD were interviewed on lifetime suicide attempts (SA) along with several other background variables and clinical characteristics. Serum blood samples were drawn for analysis of cytokines.

Results

Thirty-one patients (27%) reported at least one SA. These patients had more symptoms of current affective disorders and more severe dependence. In bivariate analysis only IL-6 and IL-10 appeared to be associated with lifetime SA but without reaching statistical significance. In multivariate linear regression, adjusting for sex, nicotine use, somatic illness, and the use of anti-inflammatory drugs, IL-6 was associated to SA (p = 0.033).

Conclusion

The cytokine IL-6 has repeatedly been found to be associated with suicidality. The present study concurs with this role of IL-6 in a naturalistic observational study of AUD patients.

Nonmedical Social Determinants, Syndemic Conditions, and Suicidal Thoughts and Behaviors in a Treatment-seeking Community Sample: A Latent Class Analysis

OBJECTIVE

Knowledge gaps remain regarding whether syndemic conditions identify treatment-seeking individuals most at risk for suicidal thoughts and behaviors (STB). We employed latent class analysis to: (1) model treatment-seeking individuals' syndemic conditions, (2) examine latent classes across nonmedical social determinants, and (3) assess associations between class membership and STB.

METHOD

Participants were 982 individuals presenting at a community mental health clinic between October 2014 and February 2020. The three-step latent class analytic approach was used. Regression analyses were employed to examine nonmedical social determinants and STB outcomes associated with class membership.

RESULTS

Participants were aged 18 to >72 (75.8% White; 76.7% heterosexual; 53.7% cisgender woman; 73.8% earned ≥$20,000 annually). Latent class analysis resulted in a three-class solution. Participants in Class 1 were characterized by low probabilities across syndemic conditions. Class 2 was characterized by high probabilities of anxiety and depression. Class 3 was characterized by high probabilities of eating disorders, anxiety, and depression. Participants of color, sexual minority participants, cisgender women, and those experiencing financial distress were more likely to be in classes characterized by syndemic conditions. Classes characterized by syndemic conditions, relative to no syndemic conditions, were associated with greater risk of STB.

CONCLUSION

Findings confirm the concentrated clustering of co-occurring syndemic conditions among marginalized groups and highlight differing risks for those considering suicide or who have attempted suicide vs. those engaging in self-harm. Results underscore the need for resource allocation and multilevel interventions targeting syndemic conditions and suicidality for minority populations and those experiencing financial distress.

Editorial commentary on the special issue emerging psychoneuroimmunology research: Future leaders in focus

The theme of this BBI-Health special issue is to promote the research, creativity and forward-thinking of future key opinion leaders in the field of psychoneuroimmunology (PNI). We asked contributing researchers to identify new ideas and spaces for innovation to map out the future trajectory of our discipline. This special issue provides global and diverse views from early career investigators focused on science, society, and/or policy, with an emphasis on diversity in all its aspects. The common thread weaving through the articles contained in this special issue is that all authors were invited to consider the future of PNI while they were experiencing the global COVID-19 lockdowns that slowed down or even prevented them from access to their "hands-on" research. The contributors vary from Master level to assistant professors, and all have already significantly contributed to the field of PNI. Each contributor has provided a photograph and short biography alongside their written perspectives. We hope that you will enjoy learning about their visions for the future of PNI and will join us with enthusiasm as we watch our field grow through the advancement of their scientific careers.