Supplementary MaterialsSupplementary Information 41467_2020_15930_MOESM1_ESM. trauma exposure. Prefrontal-limbic TSPO availability in the PTSD group was negatively associated with PTSD symptom severity and was significantly lower than in controls. Higher C-reactive protein levels were also associated with lower prefrontal-limbic TSPO availability and PTSD severity. An independent postmortem study found no differential gene expression in 22 LY294002 manufacturer PTSD vs. 22 controls, but showed lower relative expression of and microglia-associated genes and in a female PTSD subgroup. These findings suggest that peripheral immune activation in PTSD is usually associated with deficient brain microglial activation, challenging prevailing LY294002 manufacturer hypotheses positing neuroimmune activation as central to stress-related pathophysiology. and other microglia-associated genes that may be differentially expressed in relation to PTSD, to better understand what is likely a complex conversation of TSPO with other molecules to produce PTSD-related neuroimmune system alterations. This study presents the first known evidence that, contrary to our hypothesis, lower prefrontal-limbic TSPO availability is usually significantly associated with greater PTSD symptom severity, and is significantly lower in individuals with a diagnosis of PTSD compared to controls. We confirm the association of peripheral inflammation, as measured by plasma CRP levels, with PTSD severity, and demonstrate that TSPO availability is usually negatively associated with CRP. In an impartial sample of postmortem brain, we also report evidence of lower expression levels of and microglia-associated genes, and Genotype17 HAB, 9 MAB18 HAB, 5 MAB0.32Ethnicity (%)0.32??African American6 (23)9 (39)??Asian/Pacific Islander1 (4)1 (4)??Caucasian12 (46)9 (39)??Hispanic7 (27)4 (17)Clinical CharacteristicsPTSD severity??CAPS-IV (analyses were conducted LY294002 manufacturer among PTSD subgroups stratified by median of total symptom severity around the CAPS. In the high-severity PTSD compared to control group (but not in low-severity vs. control), [11C]PBR28 expression was non-significantly lower in prefrontal cortex BA11 (?1.66-fold lower (0.16), expression was investigated, based on evidence of sex effects on TSPO availability in the present and previous PET analyses40 and of sex effects on gene Rabbit polyclonal to baxprotein expression in the brain in preclinical studies41. There was a significant effect of sex (expression in BA11 in PTSD relative to controls, and a non-significant interaction effect (expression in within-group, female vs. male comparisons also suggested an conversation. Gene expression was significantly higher in female relative to male controls (BA11: 2.60-fold higher (0.10), expression was significantly lower relative to female controls (expression in males with PTSD compared to male controls in either region. Exploratory analyses examined expression of microglia-associated genes,?and (BA11: (BA11: expression was significantly lower in prefrontal cortical areas in females with PTSD relative to female controls (BA11: ?1.60-fold lower (0.03), in BA11 (?1.60-fold lower (0.06), genes was lower in areas comprising the prefrontal cortex in a postmortem brain sample.a In females with PTSD (expression was significantly lower in BA11 (?2.30-fold lower (0.10), expression was not significantly lower in PTSD (significantly lower in BA11 (?1.60-fold (0.03), was significantly lower in BA11 (?1.60-fold (0.06), and in BA25 in the female subgroup, and for in BA11 in PTSD vs. controls combined across sex. Mann-Whitney U assessments were used to assess differences in fold change. Displayed values are shown as fold change (?log2(ddand genes in prefrontal cortical tissue from females but not males with PTSD, providing convergent evidence of compromised microglial function potentially representing an overall neuroimmune suppression. Compromised microglial function could contribute meaningfully to the pathophysiology of PTSD, particularly compromised cortico-limbic connectivity42,43. Microglia have been implicated in the immunologic regulation of synaptic plasticity in part through production of neurotrophic factors such as IGF-1 and BDNF44,45, and in a neuroprotective response in rodent models of spinal cord injury, with selective microglial depletion exacerbating neurodegeneration and motor impairment45. Adding to this is a growing consensus that higher TSPO levels do not simply represent neuroinflammatory M1-type microglial activation, but rather that TSPO likely LY294002 manufacturer represents a dynamically-regulated balance between microglial M1- and M2-type activation says. For instance, observations of M1-predominant activation did not result in any increase in TSPO in in vitro human microglia cell culture46, while TSPO overexpression was associated with M2-predominant activation and reduced pro-inflammatory cytokine production in rodent microglial cells47. Furthermore, direct viral overexpression of brain TSPO prior to a footshock stressor promoted a neuroprotective function and ameliorated the ensuing PTSD-like behaviors in rodents34. Thus, we surmise that lower TSPO availability in association with PTSD severity may.