Racial Discrimination, Neural Connectivity, and Epigenetic Aging Among Black Women.

Importance: Racial discrimination increases the risk of adverse brain health outcomes, potentially via neuroplastic changes in emotion processing networks. The involvement of deep brain regions (brainstem and midbrain) in these responses is unknown. Potential associations of racial discrimination with alterations in deep brain functional connectivity and accelerated epigenetic aging, a process that substantially increases vulnerability to health problems, are also unknown. Objective: To examine associations of racial discrimination with brainstem and midbrain resting-state functional connectivity (RSFC) and DNA methylation age acceleration (DMAA) among Black women in the US. Design, Setting, and Participants: This cohort study was conducted between January 1, 2012, and February 28, 2015, and included a community-based sample of Black women (aged ≥18 years) recruited as part of the Grady Trauma Project. Self-reported racial discrimination was examined in association with seed-to-voxel brain connectivity, including the locus coeruleus (LC), periaqueductal gray (PAG), and superior colliculus (SC); an index of DMAA (Horvath clock) was also evaluated. Posttraumatic stress disorder (PTSD), trauma exposure, and age were used as covariates in statistical models to isolate racial discrimination-related variance. Data analysis was conducted between January 10 and October 30, 2023. Exposure: Varying levels of racial discrimination exposure, other trauma exposure, and posttraumatic stress disorder (PTSD). Main Outcomes and Measures: Racial discrimination frequency was assessed with the Experiences of Discrimination Scale, other trauma exposure was evaluated with the Traumatic Events Inventory, and current PTSD was evaluated with the PTSD Symptom Scale. Seed-to-voxel functional connectivity analyses were conducted with LC, PAG, and SC seeds. To assess DMAA, the Methylation EPIC BeadChip assay (Illumina) was conducted with whole-blood samples from a subset of 49 participants. Results: This study included 90 Black women, with a mean (SD) age of 38.5 (11.3) years. Greater racial discrimination was associated with greater left LC RSFC to the bilateral precuneus (a region within the default mode network implicated in rumination and reliving of past events; cluster size k = 228; t85 = 4.78; P < .001, false discovery rate-corrected). Significant indirect effects were observed for the left LC-precuneus RSFC on the association between racial discrimination and DMAA (ß [SE] = 0.45 [0.16]; 95% CI, 0.12-0.77). Conclusions and Relevance: In this study, more frequent racial discrimination was associated with proportionately greater RSFC of the LC to the precuneus, and these connectivity alterations were associated with DMAA. These findings suggest that racial discrimination contributes to accelerated biological aging via altered connectivity between the LC and default mode network, increasing vulnerability for brain health problems.

Moral injury, race-related stress and post-traumatic stress disorder in a trauma-exposed Black population.

BACKGROUND: Race-related stress (RRS) is an unrecognized source of moral injury (MI)-or the emotional and/or spiritual suffering that may emerge after exposure to events that violate deeply held beliefs. Additionally, MI has not been explored as a mechanism of risk for post-traumatic stress disorder (PTSD) in trauma-exposed civilians. We examined relations among exposure to potentially morally injurious events (moral injury exposure, MIE), related distress (moral injury distress, MID), and RRS in Black Americans. Potential indirect associations between RRS and PTSD symptoms via MID were also examined. METHODS: Black Americans (n = 228; 90.4% female; Mage = 31.6 years. SDage = 12.8 years) recruited from an ongoing study of trauma completed measures assessing civilian MIE and MID, RRS, and PTSD. Bivariate correlations were conducted with MIE and MID, and mediation analysis with MID, to examine the role of MI in the relationship between RRS and PTSD symptom severity. RESULTS: MIE was significantly correlated with cultural (r = 0.27), individual (r = 0.29), and institutional (r = 0.25) RRS; MID also correlated with cultural (r = 0.31), individual (r = 0.31), and institutional (r = 0.26) RRS (ps < 0.001). We found an indirect effect of RRS on PTSD symptoms via MID (ß = 0.10, p < 0.005). CONCLUSIONS: All types of RRS were associated with facets of MI, which mediated the relationship between RRS and current PTSD symptoms. MI may be a potential mechanism through which RRS increases the risk for PTSD in Black individuals.

C-reactive protein moderates associations between racial discrimination and ventromedial prefrontal cortex activation during attention to threat in Black American women.

Prior research has shown that racial discrimination (RD) impacts activation in threat network regions, including the ventromedial prefrontal cortex (vmPFC) and middle occipital cortex during attention to threat-relevant stimuli. However, little is known about the biological mechanisms that may modulate these effects; inflammation may be a pathway linking RD and threat network activation. As such, the current study aimed to explore whether systemic inflammation, measured by C-reactive protein (CRP) levels, may moderate the relationship between RD and activation in the vmPFC and middle occipital cortex during attention to threat. Blood samples for inflammatory marker (CRP) assays were obtained from forty Black American women (mean [SD] age, 39.93 [9.97] years; range, 22-58 years) recruited from an ongoing trauma study; participants also viewed threat-relevant stimuli as part of an attention task during fMRI. We found that CRP moderated the relationship between RD and vmPFC activation during attention to threat, such that participants with relatively higher concentrations of CRP ( ≥ 23.97 mg/L) demonstrated significant positive associations between RD and vmPFC activation [ß = 0.18, CI (0.04, 0.32), t = 2.65, p = 0.01]. No significant associations were observed for participants who showed moderate (10.89 mg/L) or low (0.20 mg/L) CRP concentrations. CRP did not moderate the relationship between RD and middle occipital cortex activation. Our data present a mechanism through which RD may influence immune system activation and, in turn, threat network activation. Inflammation may contribute to brain health vulnerabilities in Black Americans via its effects on threat circuits; this merits further investigation in large-scale studies.

Indirect Effects of Racial Discrimination on Health Outcomes Through Prefrontal Cortical White Matter Integrity.

BACKGROUND: Racial discrimination is consistently associated with adverse health outcomes and has been linked to structural decrements in brain white matter. However, it is unclear whether discrimination-related neuroplastic changes could indirectly affect health outcomes. Our goal was to evaluate indirect associations of racial discrimination on health outcomes through white matter microstructure in a sample of trauma-exposed Black women. METHODS: A trauma study in an urban hospital setting recruited 79 Black women who received a history and physical examination to assess medical disorders (compiled into a summed total of disorder types). Participants reported on experiences of racial discrimination and underwent diffusion tensor imaging; fractional anisotropy values were extracted from white matter pathways previously linked to racial discrimination (corpus callosum, including the body and genu; anterior cingulum bundle; and superior longitudinal fasciculus) and entered into mediational models. RESULTS: Indirect effects of racial discrimination on medical disorders through left anterior cingulum bundle fractional anisotropy were significant (ß = 0.07, SE = 0.04, 95% CI [0.003, 0.14]) after accounting for trauma and economic disadvantage. Indirect effects of racial discrimination on medical disorders through corpus callosum genu fractional anisotropy were also significant (ß = 0.08, SE = 0.04, 95% CI [0.01, 0.16]). CONCLUSIONS: Racial discrimination may increase risk for medical disorders via neuroplastic effects on microstructural integrity of stress-sensitive prefrontal white matter tracts. Racial discrimination-related changes in these tracts may affect health behaviors, which, in turn, influence vulnerability for medical disorders. These data highlight the connections between racial discrimination, prefrontal white matter connections, and incidence of medical disorders in Black Americans.

Medial orbitofrontal neurotrophin systems integrate hippocampal input into outcome-specific value representations.

In everyday life, we mentally represent possible consequences of our behaviors and integrate specific outcome values into existing knowledge to inform decisions. The medial orbitofrontal cortex (MO) is necessary to adapt behaviors when outcomes are not immediately available-when they and their values need to be envisioned. Nevertheless, neurobiological mechanisms remain unclear. We find that the neuroplasticity-associated neurotrophin receptor tropomyosin receptor kinase B (TrkB) is necessary for mice to integrate outcome-specific value information into choice behavior. This function appears attributable to memory updating (and not retrieval) and the stabilization of dendritic spines on excitatory MO neurons, which led us to investigate inputs to the MO. Ventral hippocampal (vHC)-to-MO projections appear conditionally necessary for value updating, involved in long-term aversion-based value memory updating. Furthermore, vHC-MO-mediated control of choice is TrkB dependent. Altogether, we reveal a vHC-MO connection by which specific value memories are updated, and we position TrkB within this functional circuit.