An angiotensin-converting enzyme (ACE) polymorphism may mitigate the effects of angiotensin-pathway medications on posttraumatic stress symptoms

[Cognitive impairment in post-traumatic stress disorder]

Post-traumatic stress disorder (PTSD) is a common mental health disorder, with an incidence of up to 12.5% among primary care patients. Most often, PTSD is detected in combat veterans, victims of terrorist attacks and terror, but it can also be a consequence of traumatic brain injury and medical interventions. Impaired cognitive functioning is a key feature of PTSD, including attention deficits and reduced processing speed, executive dysfunction, and impairments in verbal learning and memory. Cognitive impairments in PTSD are significantly persistent and are largely similar in nature to neuropsychological impairments in neurodegenerative pathology. Possible pathogenetic mechanisms underlying PTSD are the development of neuroinflammation, oxidative stress and decreased production of neurotrophic factors. One of the promising areas of treatment is the use of Cerebrolysin, which has powerful neurotrophic and anti-inflammatory activity.

Assessment of the Genetic Characteristics of a Generation Born during a Long-Term Socioeconomic Crisis

BACKGROUND

A socioeconomic crisis in Russia lasted from 1991 to 1998 and was accompanied by a sharp drop in the birth rate. The main factor that influenced the refusal to have children during this period is thought to be prolonged social stress.

METHODS

comparing frequencies of common gene variants associated with stress-induced diseases among generations born before, after, and during this crisis may show which genes may be preferred under the pressure of natural selection during periods of increased social stress in urban populations.

RESULTS

In the "crisis" group, a statistically significant difference from the other two groups was found in rs6557168 frequency (p = 0.001); rs4522666 was not in the Hardy-Weinberg equilibrium in this group, although its frequency did not show a significant difference from the other groups (p = 0.118). Frequencies of VNTRs in SLC6A3 and MAOA as well as common variants rs17689918 in CRHR1, rs1360780 in FKBP5, rs53576 in OXTR, rs12720071 and rs806377 in CNR1, rs4311 in ACE, rs1800497 in ANKK1, and rs7412 and rs429358 in APOE did not differ among the groups.

CONCLUSIONS

a generation born during a period of prolonged destructive events may differ from the rest of the gene pool of the population in some variants associated with personality traits or stress-related disorders.

Sex-dependent effects of angiotensin II type 1 receptor blocker on molecular and behavioral changes induced by single prolonged stress

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that not only entails alterations in fear behavior and anxiety but also includes neuroendocrine dysfunctions involving the hypothalamic pituitary adrenal (HPA) axis and the renin-angiotensin system. Recent preclinical studies demonstrate that activation of the angiotensin type 1 receptor (AT1R) in the paraventricular region of the hypothalamus (PVR) promotes anxiety-like behaviors and enables microglia proliferation. An increase in microglia and anxiety-like behavior also occurs in the PTSD animal model single-prolonged stress (SPS). In the present study, we tested whether AT1Rs contribute to the effects of SPS on behavior and microglia in brain structures important for HPA axis regulation and fear behavior. To test this, male and female animals were exposed to SPS and then given the oral AT1R antagonist candesartan beginning one week later. Candesartan did not alter auditory fear conditioning or extinction in SPS-exposed male or female animals. However, we found that the male animals exposed to SPS showed increased anxiety-like behavior, which was reversed by candesartan. In contrast, neither SPS nor candesartan altered anxiety-like behavior in the female animals. At the molecular level, SPS increased the cellular expression of AT1Rs in the PVR of male animals and candesartan reversed this effect, whereas AT1Rs in the PVR of females were unaltered by either SPS or candesartan. Iba1-expressing microglia increased in the PVR after SPS exposure and was reversed by candesartan in both sexes suggesting that SPS stimulates AT1Rs to increase microglia in the PVR. Collectively, these results suggest that the contribution of AT1Rs to the molecular and behavioral effects of SPS is sex-dependent.

Psychological and biological mechanisms linking trauma with cardiovascular disease risk

Cardiovascular disease (CVD) is the leading cause of death and disability worldwide, and experiences of psychological trauma have been associated with subsequent CVD onset. Identifying key pathways connecting trauma with CVD has the potential to inform more targeted screening and intervention efforts to offset elevated cardiovascular risk. In this narrative review, we summarize the evidence for key psychological and biological mechanisms linking experiences of trauma with CVD risk. Additionally, we describe various methodologies for measuring these mechanisms in an effort to inform future research related to potential pathways. With regard to mechanisms involving posttraumatic psychopathology, the vast majority of research on psychological distress after trauma and CVD has focused on posttraumatic stress disorder (PTSD), even though posttraumatic psychopathology can manifest in other ways as well. Substantial evidence suggests that PTSD predicts the onset of a range of cardiovascular outcomes in trauma-exposed men and women, yet more research is needed to better understand posttraumatic psychopathology more comprehensively and how it may relate to CVD. Further, dysregulation of numerous biological systems may occur after trauma and in the presence of posttraumatic psychopathology; these processes of immune system dysregulation and elevated inflammation, oxidative stress, mitochondrial dysfunction, renin-angiotensin system dysregulation, and accelerated biological aging may all contribute to subsequent cardiovascular risk, although more research on these pathways in the context of traumatic stress is needed. Given that many of these mechanisms are closely intertwined, future research using a systems biology approach may prove fruitful for elucidating how processes unfold to contribute to CVD after trauma.

Involvement of the brain-heart axis in the link between PTSD and cardiovascular disease

Posttraumatic stress disorder (PTSD) has long been associated with a heightened risk of cardiovascular disease (CVD). A number of mechanisms have been implicated to underlie this brain-heart axis relationship, such as altered functioning of the autonomic nervous system and increased systemic inflammation. While neural alterations have repeatedly been observed in PTSD, they are rarely considered in the PTSD-CVD link. The brain-heart axis is a pathway connecting frontal and limbic brain regions to the brainstem and periphery via the autonomic nervous system and it may be a promising model for understanding CVD risk in PTSD given its overlap with PTSD neural deficits. We first provide a summary of the primary mechanisms implicated in the association between PTSD and CVD. We then review the brain-heart axis and its relevance to PTSD, as well as findings from PTSD trials demonstrating that a number of PTSD treatments have effects on areas of the brain-heart axis. Finally, we discuss sex considerations in the PTSD-CVD link. A critical next step in this study is to determine if PTSD treatments that affect the brain-heart axis (e.g., brain stimulation that improves autonomic function) also reduce the risk of CVD.

Antihypertensive drugs and brain function: mechanisms underlying therapeutically beneficial and harmful neuropsychiatric effects

A bidirectional relationship exists between hypertension and psychiatric disorders, including unipolar and bipolar depression, anxiety, post-traumatic stress disorder (PTSD), psychosis, schizophrenia, mania, and dementia/cognitive decline. Repurposing of antihypertensive drugs to treat mental disorders is thus being explored. A systematic knowledge of the mechanisms of action and clinical consequences of the use of antihypertensive agents on neuropsychiatric functions has not been achieved yet. In this article, we review the putative role of antihypertensive agents in psychiatric disorders, discuss the targets and mechanisms of action, and examine how and to what extent specific drug classes/molecules may trigger, worsen, or mitigate psychiatric symptoms. In addition, we review pharmacokinetics (brain penetration of drugs) and pharmacogenetics data that add important information to assess risks and benefits of antihypertensive drugs in neuropsychiatric settings. The scientific literature shows robust evidence of a positive effect of α1 blockers on PTSD symptoms, nightmares and sleep quality, α2 agonists on core symptoms, executive function and quality of life in Attention-Deficit/Hyperactivity Disorder, PTSD, Tourette's syndrome, and β blockers on anxiety, aggression, working memory, and social communication. Renin-angiotensin system modulators exert protective effects on cognition, depression, and anxiety, and the loop diuretic bumetanide reduced the core symptoms of autism in a subset of patients. There is no evidence of clear benefits of calcium channel blockers in mood disorders in the scientific literature. These findings are mainly from preclinical studies; clinical data are still insufficient or of anecdotal nature, and seldom systematic. The information herewith provided can support a better therapeutic approach to hypertension, tailored to patients with, or with high susceptibility to, psychiatric illness. It may prompt clinical studies exploring the potential benefit of antihypertensive drugs in selected patients with neuropsychiatric comorbidities that include outcomes of neuropsychiatric interest and specifically assess undesirable effects or interactions.

Involvement of the Renin-Angiotensin System in Stress: State of the Art and Research Perspectives

BACKGROUND

Along with other canonical systems, the renin-angiotensin system (RAS) has shown important roles in stress. This system is a complex regulatory proteolytic cascade composed of various enzymes, peptides, and receptors. Besides the classical (ACE/Ang II/AT1 receptor) and the counter-regulatory (ACE2/Ang-(1-7)/Mas receptor) RAS axes, evidence indicates that nonclassical components, including Ang III, Ang IV, AT₂ and AT₄, can also be involved in stress.

OBJECTIVE AND METHODS

This comprehensive review summarizes the current knowledge on the participation of RAS components in different adverse environmental stimuli stressors, including air jet stress, cage switch stress, restraint stress, chronic unpredictable stress, neonatal isolation stress, and post-traumatic stress disorder.

RESULTS AND CONCLUSION

In general, activation of the classical RAS axis potentiates stress-related cardiovascular, endocrine, and behavioral responses, while the stimulation of the counter-regulatory axis attenuates these effects. Pharmacological modulation in both axes is optimistic, offering promising perspectives for stress-related disorders treatment. In this regard, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are potential candidates already available since they block the classical axis, activate the counter-regulatory axis, and are safe and efficient drugs.

Insertion/deletion polymorphism at angiotensin-converting enzyme gene in PTSD individuals and their reciprocal effects on blood pressure

OBJECTIVES

The aim of the present study was to investigate relationships between insertion/deletion (I/D) polymorphism at angiotensin-converting enzyme gene (ACE) and post-traumatic stress disorder (PTSD), as well as their interactions on blood pressure.

METHODS

Variants of ACE I/D were identified by polymerase chain reaction method and verified by DNA sequencing. PTSD symptoms were assessed by the PTSD Checklist-Civilian Version (PCL-C) based on DSM-IV-TR criteria among high school students at 6 months after the 2008 Wenchuan earthquake.

RESULTS

Female subjects were found to have higher prevalence of PTSD and PCL-C scores than male counterparts in the II homozygotes (p = .038 for PTSD and p = .003 for PCL-C scores) and the ID heterozygotes (p = .000 for PTSD and p = .000 for PCL-C scores), but not in the DD homozygotes. Male subjects with the ID (p = .046) or the DD genotype (p = .039) had lower pulse pressure (PP) than the male II homozygotes, while the female II homozygotes had lower diastolic blood pressure (DBP) than the female DD homozygotes (p = .036). ACE I/D, PTSD, or PCL-C scores, as well as gender and BMI, were found to be the predictors of PP.

CONCLUSIONS

These results indicate that there are interactions of ACE I/D and PTSD, together with gender and BMI, on PP. This finding may be the additional explanation for the heterogeneous relationships between PTSD and blood pressure, and suggest psychiatry care and different medication strategies for patients with comorbidities of PTSD and hypertension and with different genotypes of ACE I/D.

Associations of trauma and posttraumatic stress disorder with aldosterone in women

BACKGROUND

Posttraumatic stress disorder (PTSD) has been associated with increased cardiovascular risk, however, underlying mechanisms have not been fully specified. PTSD is associated with stress-related hormones, including dysregulated glucocorticoid activity. Dysregulation of aldosterone, a mineralocorticoid activated by psychological stress and implicated in cardiovascular damage, may be a relevant pathway linking PTSD and cardiovascular risk. Few studies to date have evaluated the association between PTSD and aldosterone, none with repeated measures of aldosterone. We examined if trauma and PTSD were associated with altered aldosterone levels relative to women unexposed to trauma.

METHODS

The association of trauma exposure and chronic PTSD with plasma aldosterone levels was investigated in 521 middle-aged women in the Nurses' Health Study II. Aldosterone was assessed at two time points, 10-16 years apart, and trauma exposure and PTSD were also ascertained for both time points. Regarding exposure assessment, women were characterized based on a structured diagnostic interview as: having chronic PTSD (PTSD at both time points; n = 174); being trauma-exposed (trauma exposure at first time point but no PTSD; n = 174); and being unexposed (no trauma exposure at either time point; reference group for all analyses; n = 173). Linear mixed models examined associations of trauma and PTSD status with log-transformed aldosterone levels, adjusting for covariates and health-related variables that may confound or lie on the pathway between PTSD and altered aldosterone levels.

RESULTS

Across the sample, mean aldosterone concentration decreased over time. Adjusting for covariates, women with chronic PTSD had significantly lower aldosterone levels averaged over time, compared to women unexposed to trauma (β = - 0.08, p = 0.04). Interactions between trauma/PTSD group and time were not significant, indicating change in aldosterone over time did not differ by trauma/PTSD status. Post-hoc exploratory analyses suggested that menopausal status partially mediated the relationship between chronic PTSD status and aldosterone level, such that postmenopausal status explained 7% of the effect of PTSD on aldosterone.

CONCLUSIONS

These findings indicate that PTSD is associated with lower levels of aldosterone. Further work is needed to understand implications of this type of dysregulation in a key biological stress system for cardiovascular and other health outcomes previously linked with PTSD.

Randomized, Placebo-Controlled Trial of the Angiotensin Receptor Antagonist Losartan for Posttraumatic Stress Disorder

BACKGROUND

Evidence-based pharmacological treatments for posttraumatic stress disorder (PTSD) are few and of limited efficacy. Previous work suggests that angiotensin type 1 receptor inhibition facilitates fear inhibition and extinction, important for recovery from PTSD. This study tests the efficacy of the angiotensin type 1 receptor antagonist losartan, an antihypertensive drug, repurposed for the treatment of PTSD.

METHODS

A randomized controlled trial was conducted for 10 weeks in 149 men and women meeting DSM-5 PTSD criteria. Losartan (vs. placebo) was flexibly titrated from 25 to 100 mg/day by week 6 and held at highest tolerated dose until week 10. Primary outcome was the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) change score at 10 weeks from baseline. A key secondary outcome was change in CAPS-5 associated with a single nucleotide polymorphism of the ACE gene. Additional secondary outcomes included changes in the PTSD Checklist for DSM-5 and the Patient Health Questionnaire-9, and proportion of responders with a Clinical Global Impressions-Improvement scale of "much improved" or "very much improved."

RESULTS

Both groups had robust improvement in PTSD symptoms, but there was no significant difference on the primary end point, CAPS-5 measured as week 10 change from baseline, between losartan and placebo (mean change difference, 0.9, 95% confidence interval, -3.2 to 5.0). There was no significant difference in the proportion of Clinical Global Impressions-Improvement scale responders for losartan (58.6%) versus placebo (57.9%), no significant differences in changes in PTSD Checklist for DSM-5 or Patient Health Questionnaire-9, and no association between ACE genotype and CAPS-5 improvement on losartan.

CONCLUSIONS

At these doses and durations, there was no significant benefit of losartan compared with placebo for the treatment of PTSD. We discuss implications for failure to determine the benefit of a repurposed drug with strong a priori expectations of success based on preclinical and epidemiological data.

Examining Individual and Synergistic Contributions of PTSD and Genetics to Blood Pressure: A Trans-Ethnic Meta-Analysis

Growing research suggests that posttraumatic stress disorder (PTSD) may be a risk factor for poor cardiovascular health, and yet our understanding of who might be at greatest risk of adverse cardiovascular outcomes after trauma is limited. In this study, we conducted the first examination of the individual and synergistic contributions of PTSD symptoms and blood pressure genetics to continuous blood pressure levels. We harnessed the power of the Psychiatric Genomics Consortium-PTSD Physical Health Working Group and investigated these associations across 11 studies of 72,224 trauma-exposed individuals of European (n = 70,870) and African (n = 1,354) ancestry. Genetic contributions to blood pressure were modeled via polygenic scores (PGS) for systolic blood pressure (SBP) and diastolic blood pressure (DBP) that were derived from a prior trans-ethnic blood pressure genome-wide association study (GWAS). Results of trans-ethnic meta-analyses revealed significant main effects of the PGS on blood pressure levels [SBP: β = 2.83, standard error (SE) = 0.06, p < 1E-20; DBP: β = 1.32, SE = 0.04, p < 1E-20]. Significant main effects of PTSD symptoms were also detected for SBP and DBP in trans-ethnic meta-analyses, though there was significant heterogeneity in these results. When including data from the largest contributing study - United Kingdom Biobank - PTSD symptoms were negatively associated with SBP levels (β = -1.46, SE = 0.44, p = 9.8E-4) and positively associated with DBP levels (β = 0.70, SE = 0.26, p = 8.1E-3). However, when excluding the United Kingdom Biobank cohort in trans-ethnic meta-analyses, there was a nominally significant positive association between PTSD symptoms and SBP levels (β = 2.81, SE = 1.13, p = 0.01); no significant association was observed for DBP (β = 0.43, SE = 0.78, p = 0.58). Blood pressure PGS did not significantly moderate the associations between PTSD symptoms and blood pressure levels in meta-analyses. Additional research is needed to better understand the extent to which PTSD is associated with high blood pressure and how genetic as well as contextual factors may play a role in influencing cardiovascular risk.

Post-traumatic stress disorder and its association with stroke and stroke risk factors: A literature review

Stroke is a major cause of mortality and disability globally that has multiple risk factors. A risk factor that has recently gained more attention is post-traumatic stress disorder (PTSD). Literature searches were carried out for updated PTSD information and for the relationship between PTSD and stroke. The review was divided into two sections, one exploring PTSD as an independent risk factor for stroke, with a second concentrating on PTSD's influence on stroke risk factors. The study presents accumulating evidence that shows traumatic stress predicts stroke and is also linked to many major stroke risk factors. The review contributes knowledge to stroke aetiology and acts as a reference for understanding the relationship between PTSD and stroke. The information presented indicates that screening and identification of traumatic experience would be beneficial for directing stroke patients to appropriate psychological and lifestyle interventions. In doing so, the burden of stroke may be reduced worldwide.

Posttraumatic Stress Disorder Treatment Effects on Cardiovascular Physiology: A Systematic Review and Agenda for Future Research

Posttraumatic stress disorder (PTSD) is linked to both altered physiological functioning and poorer cardiovascular health outcomes, including an increased risk for cardiovascular disease and cardiovascular-related mortality. An important question is whether interventions for PTSD might ameliorate the risk for poorer health by improving cardiovascular physiological intermediaries. To begin to characterize the literature addressing this question, we conducted a systematic review of empirical studies examining the impact of PTSD interventions on cardiovascular physiological intermediaries, including blood pressure (BP), heart rate (HR), cardiac impedance, and subclinical atherosclerosis. Outcomes included both tonic (i.e., resting) cardiovascular functioning and cardiovascular reactivity (CVR). A total of 44 studies met the inclusion criteria. There was mixed evidence regarding whether PTSD treatment improved tonic cardiovascular functioning. There was stronger evidence that PTSD treatments reduced CVR to trauma-related stressors, particularly for higher-quality studies of cognitive behavioral interventions. No studies examined cardiac impedance or subclinical atherosclerosis. The studies had a high degree of heterogeneity in the populations sampled and interventions tested. Moreover, they generally included small sample sizes and lacked control conditions. Interventions for PTSD may improve cardiovascular physiological outcomes, particularly CVR to trauma cues, although additional methodologically rigorous studies are needed. We outline changes to future research that would improve the literature regarding this important question, including the more frequent use of control groups and larger sample sizes.

Transcriptomic Analysis of Mouse Brain After Traumatic Brain Injury Reveals That the Angiotensin Receptor Blocker Candesartan Acts Through Novel Pathways

Traumatic brain injury (TBI) results in complex pathological reactions, where the initial lesion is followed by secondary inflammation and edema. Our laboratory and others have reported that angiotensin receptor blockers (ARBs) have efficacy in improving recovery from traumatic brain injury in mice. Treatment of mice with a subhypotensive dose of the ARB candesartan results in improved functional recovery, and reduced pathology (lesion volume, inflammation and gliosis). In order to gain a better understanding of the molecular mechanisms through which candesartan improves recovery after controlled cortical impact injury (CCI), we performed transcriptomic profiling on brain regions after injury and drug treatment. We examined RNA expression in the ipsilateral hippocampus, thalamus and hypothalamus at 3 or 29 days post injury (dpi) treated with either candesartan (0.1 mg/kg) or vehicle. RNA was isolated and analyzed by bulk mRNA-seq. Gene expression in injured and/or candesartan treated brain region was compared to that in sham vehicle treated mice in the same brain region to identify genes that were differentially expressed (DEGs) between groups. The most DEGs were expressed in the hippocampus at 3 dpi, and the number of DEGs reduced with distance and time from the lesion. Among pathways that were differentially expressed at 3 dpi after CCI, candesartan treatment altered genes involved in angiogenesis, interferon signaling, extracellular matrix regulation including integrins and chromosome maintenance and DNA replication. At 29 dpi, candesartan treatment reduced the expression of genes involved in the inflammatory response. Some changes in gene expression were confirmed in a separate cohort of animals by qPCR. Fewer DEGs were found in the thalamus, and only one in the hypothalamus at 3 dpi. Additionally, in the hippocampi of sham injured mice, 3 days of candesartan treatment led to the differential expression of 384 genes showing that candesartan in the absence of injury had a powerful impact on gene expression specifically in the hippocampus. Our results suggest that candesartan has broad actions in the brain after injury and affects different processes at acute and chronic times after injury. These data should assist in elucidating the beneficial effect of candesartan on recovery from TBI.

Genome-wide meta-analysis, fine-mapping and integrative prioritization implicate new Alzheimer's disease risk genes

Genome-wide association studies have discovered numerous genomic loci associated with Alzheimer's disease (AD); yet the causal genes and variants are incompletely identified. We performed an updated genome-wide AD meta-analysis, which identified 37 risk loci, including new associations near CCDC6, TSPAN14, NCK2 and SPRED2. Using three SNP-level fine-mapping methods, we identified 21 SNPs with >50% probability each of being causally involved in AD risk and others strongly suggested by functional annotation. We followed this with colocalization analyses across 109 gene expression quantitative trait loci datasets and prioritization of genes by using protein interaction networks and tissue-specific expression. Combining this information into a quantitative score, we found that evidence converged on likely causal genes, including the above four genes, and those at previously discovered AD loci, including BIN1, APH1B, PTK2B, PILRA and CASS4.

The renin-angiotensin system in PTSD: a replication and extension

Prior observational studies have suggested that medications targeting the renin-angiotensin system, such as angiotensin-converting enzyme inhibitors (ACE-Is) and angiotensin receptor blockers (ARBs), may be associated with decreased PTSD symptoms. Given known sex differences in PTSD prevalence and cardiovascular disease, here we tested whether the effects of ACE-I/ARB status on PTSD differ by sex. We also expanded these observations with replication analyses in a large biorepository database. Participants in the initial sample included 840 trauma-exposed individuals recruited as part of the Grady Trauma Project. The Modified PTSD Symptom Scale (M-PSS) was administered and ACE-I/ARB status was determined by self-report. Replication analyses were conducted using a large biorepository database (Partners Healthcare Biobank, N = 116,389) with diagnoses and medication status based on available electronic health records. Among individuals treated with ACE-Is/ARBs in the initial sample, women had significantly higher M-PSS total and Re-experiencing severity compared to men (p's < 0.05). Analyses with the large biorepository sample robustly replicated the overall effects of ACE-I/ARB medication associated with lower rate of PTSD diagnosis (p < 0.001). We also demonstrated that this effect may be specific to the renin-angiotensin system as it did not replicate for beta-blockers, calcium channel blockers, or diuretics. When we examined more specific drug classes, results indicated that the ACE-I/ARB effect on PTSD may be driven more by ARBs (e.g., Losartan) than by ACE-Is. Post-hoc analyses indicated that racial differences may exist in these effects. Overall, our results replicate and extend prior observations that the renin-angiotensin system is associated with PTSD. Medications targeting this system may be worthy of further investigation for PTSD treatment. Our findings suggest that sex and race effects should be considered in future treatment research.

Limbic Neuropeptidergic Modulators of Emotion and Their Therapeutic Potential for Anxiety and Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is characterized by hypervigilance, increased reactivity to unpredictable versus predictable threat signals, deficits in fear extinction, and an inability to discriminate between threat and safety. First-line pharmacotherapies for psychiatric disorders have limited therapeutic efficacy in PTSD. However, recent studies have advanced our understanding of the roles of several limbic neuropeptides in the regulation of defensive behaviors and in the neural processes that are disrupted in PTSD. For example, preclinical studies have shown that blockers of tachykinin pathways, such as the Tac2 pathway, attenuate fear memory consolidation in mice and thus might have unique potential as early post-trauma interventions to prevent PTSD development. Targeting this pathway might also be beneficial in regulating other symptoms of PTSD, including trauma-induced aggressive behavior. In addition, preclinical and clinical studies have shown the important role of angiotensin receptors in fear extinction and the promise of using angiotensin II receptor blockade to reduce PTSD symptom severity. Additional preclinical studies have demonstrated that the oxytocin receptors foster accurate fear discrimination by facilitating fear responses to predictable versus unpredictable threats. Complementary human imaging studies demonstrate unique neural targets of intranasal oxytocin and compare its efficacy with well-established anxiolytic treatments. Finally, promising data from human subjects have demonstrated that a selective vasopressin 1A receptor antagonist reduces anxiety induced by unpredictable threats. This review highlights these novel promising targets for the treatment of unique core elements of PTSD pathophysiology.

Evaluation of an angiotensin Type 1 receptor blocker on the reconsolidation of fear memory

Inhibition of the angiotensin type 1 receptor (AT₁R) has been shown to decrease fear responses in both humans and rodents. These effects are attributed to modulation of extinction learning, however the contribution of AT₁R to alternative memory processes remains unclear. Using classic Pavlovian conditioning combined with radiotelemetry and whole-genome RNA sequencing, we evaluated the effects of the AT₁R antagonist losartan on fear memory reconsolidation. Following the retrieval of conditioned auditory fear memory, animals were given a single intraperitoneal injection of losartan or saline. In response to the conditioned stimulus (CS), losartan-treated animals exhibited significantly less freezing at 24 h and 1 week; an effect that was dependent upon memory reactivation and independent of conditioned cardiovascular reactivity. Using an unbiased whole-genome RNA sequencing approach, transcriptomic analysis of the basolateral amygdala (BLA) identified losartan-dependent differences in gene expression during the reconsolidation phase. These findings demonstrate that post-retrieval losartan modifies behavioral and transcriptomic markers of conditioned fear memory, supporting an important regulatory role for this receptor in reconsolidation and as a potential pharmacotherapeutic target for maladaptive fear disorders such as PTSD.

Dysregulation of inflammation, neurobiology, and cognitive function in PTSD: an integrative review

Compelling evidence from animal and human research suggest a strong link between inflammation and posttraumatic stress disorder (PTSD). Furthermore, recent findings support compromised neurocognitive function as a key feature of PTSD, particularly with deficits in attention and processing speed, executive function, and memory. These cognitive domains are supported by brain structures and neural pathways that are disrupted in PTSD and which are implicated in fear learning and extinction processes. The disruption of these supporting structures potentially results from their interaction with inflammation. Thus, the converging evidence supports a model of inflammatory dysregulation and cognitive dysfunction as combined mechanisms underpinning PTSD symptomatology. In this review, we summarize evidence of dysregulated inflammation in PTSD and further explore how the neurobiological underpinnings of PTSD, in the context of fear learning and extinction acquisition and recall, may interact with inflammation. We then present evidence for cognitive dysfunction in PTSD, highlighting findings from human work. Potential therapeutic approaches utilizing novel pharmacological and behavioral interventions that target inflammation and cognition also are discussed.

Posttraumatic stress disorder is associated with reduced vitamin D levels and functional polymorphisms of the vitamin D binding-protein in a population-based sample

OBJECTIVE

Low levels of vitamin D were found to be associated with different mental disorders. However, the role of vitamin D in the pathogenesis of PTSD is unclear. In this study, we aimed at investigating whether PTSD is linked to reduced vitamin D levels and vitamin D deficiency. Moreover, we sought to investigate the role of the vitamin D-binding protein (also group-specific component or Gc) by testing if two functional polymorphisms (rs4588 and rs7041) were associated with vitamin D levels and PTSD.

METHODS

Serum levels of total 25(OH)D were measured in a general-population sample of the Study of Health in Pomerania (SHIP-1). The number of traumatic events and status of PTSD were assessed using the PTSD module of the Structured Clinical Interview for the DSM-IV. Study participants were genotyped for rs4588 and rs7041. Associations of 25(OH)D levels and the genotypes with PTSD were tested in subjects with at least one traumatic event (n = 1653).

RESULTS

25(OH)D levels were inversely (OR: 0.96; p = 0.044) and vitamin D deficiency was positively (OR = 2.02; p = 0.028) associated with PTSD. Both polymorphisms of the Gc were associated with 25(OH)D levels and PTSD: Carriers of the CC-genotype of rs4588 showed significantly higher 25(OH)D levels (ß = 0.179, p < 0.001) and lower odds for PTSD (OR = 0.35; p = 0.023) compared to the AA-genotype. Likewise, carriers of the TT-allele of rs7041 showed lower 25(OH)D levels (-0.122; p < 0.001) and increased odds for PTSD (OR = 2.80; p = 0.015) compared to the GG-genotype.

CONCLUSIONS

Our results suggest that an altered vitamin D metabolism may be involved in the pathophysiology of PTSD. Also, genotypes of the Gc and thus Gc serum levels may impact on PTSD development over and above the effects of 25(OH)D. Our findings contribute to explain the associations of PTSD with different mental and physical disorders.

The bradykinin system in stress and anxiety in humans and mice

Pharmacological research in mice and human genetic analyses suggest that the kallikrein-kinin system (KKS) may regulate anxiety. We examined the role of the KKS in anxiety and stress in both species. In human genetic association analysis, variants in genes for the bradykinin precursor (KNG1) and the bradykinin receptors (BDKRB1 and BDKRB2) were associated with anxiety disorders (p < 0.05). In mice, however, neither acute nor chronic stress affected B1 receptor gene or protein expression, and B1 receptor antagonists had no effect on anxiety tests measuring approach-avoidance conflict. We thus focused on the B2 receptor and found that mice injected with the B2 antagonist WIN 64338 had lowered levels of a physiological anxiety measure, the stress-induced hyperthermia (SIH), vs controls. In the brown adipose tissue, a major thermoregulator, WIN 64338 increased expression of the mitochondrial regulator Pgc1a and the bradykinin precursor gene Kng2 was upregulated after cold stress. Our data suggests that the bradykinin system modulates a variety of stress responses through B2 receptor-mediated effects, but systemic antagonists of the B2 receptor were not anxiolytic in mice. Genetic variants in the bradykinin receptor genes may predispose to anxiety disorders in humans by affecting their function.

Angiotensin II Type 2 Receptor-Expressing Neurons in the Central Amygdala Influence Fear-Related Behavior

BACKGROUND

The renin-angiotensin system has been implicated in posttraumatic stress disorder; however, the mechanisms responsible for this connection and the therapeutic potential of targeting the renin-angiotensin system in posttraumatic stress disorder remain unknown. Using an angiotensin receptor bacterial artificial chromosome (BAC) and enhanced green fluorescent protein (eGFP) reporter mouse, combined with neuroanatomical, pharmacological, and behavioral approaches, we examined the role of angiotensin II type 2 receptor (AT₂R) in fear-related behavior.

METHODS

Dual immunohistochemistry with retrograde labeling was used to characterize AT₂R-eGFP⁺ cells in the amygdala of the AT₂R-eGFP-BAC reporter mouse. Pavlovian fear conditioning and behavioral pharmacological analyses were used to demonstrate the effects of AT₂R activation on fear memory in male C57BL/6 mice.

RESULTS

AT₂R-eGFP⁺ neurons in the amygdala were predominantly expressed in the medial amygdala and the medial division of the central amygdala (CeM), with little AT₂R-eGFP expression in the basolateral amygdala or lateral division of the central amygdala. Characterization of AT₂R-eGFP⁺ neurons in the CeM demonstrated distinct localization to gamma-aminobutyric acidergic projection neurons. Mice receiving acute intra-central amygdala injections of the selective AT₂R agonist compound 21 prior to tests for cued or contextual fear expression displayed less freezing. Retrograde labeling of AT₂R-eGFP⁺ neurons projecting to the periaqueductal gray revealed AT₂R-eGFP⁺ neuronal projections from the CeM to the periaqueductal gray, a key brain structure mediating fear-related freezing.

CONCLUSIONS

These findings suggest that CeM AT₂R-expressing neurons can modulate central amygdala outputs that play a role in fear expression, providing new evidence for a novel angiotensinergic circuit in the regulation of fear.

The effect of angiotensin AT1A inactivation on innate and learned fear responses in mice and its relationship to blood pressure

Angiotensin AT₁ receptors are implicated in behavioral and physiological processes associated with fear and stress. However, the precise role of AT₁ receptors in modulating fear-related behavior and its relation to their physiological effects remains unclear. Here, we examined innate and learned fear responses and their relationship to cardiovascular arousal in AT_1A receptor knockout (AT_1A^-/-) mice. Using synchronized video and blood pressure telemetry, we found that, in a novel test environment, AT_1A^-/- mice showed reduced neophobia but a similar rise in blood pressure, as compared to AT_1A^+/+ mice. In response to a discrete threat, footshock, both flight behavior and cardiovascular arousal were decreased in AT_1A^-/- mice. Reduced flight behavior was also observed in AT_1A^-/- mice in the elevated T-maze test. During fear conditioning, the immediate freezing response to the first shock, but not the rate of freezing acquisition was decreased in AT_1A^-/- mice. Likewise, AT_1A^-/- mice showed reduced freezing and pressor responses to the first re-exposure, but normal rate of freezing extinction over subsequent trials. Similarly, in the elevated T-maze, the rates of avoidance acquisition and escape learning remained unchanged in AT_1A^-/- mice. Finally, after re-exposure, AT_1A^-/- mice displayed altered c-Fos expression, compared to AT_1A^+/+ mice, in the hypothalamus and periaqueductal gray but not in fear-related limbic-cortical areas, nor in medullary nuclei that convey visceral afferent information. We conclude that AT_1A receptor knockout reduces innate fear responses, without affecting learning efficiency in mice. These effects are dissociable from cardiovascular effects and likely reflect altered neurotransmission in hypothalamic-midbrain defense regions.

Common pathways and communication between the brain and heart: connecting post-traumatic stress disorder and heart failure

Psychiatric illnesses and cardiovascular disease (CVD) contribute to significant overall morbidity, mortality, and health care costs, and are predicted to reach epidemic proportions with the aging population. Within the Veterans Administration (VA) health care system, psychiatric illnesses such as post-traumatic stress disorder (PTSD) and CVD such as heart failure (HF), are leading causes of hospital admissions, prolonged hospital stays, and resource utilization. Numerous studies have demonstrated associations between PTSD symptoms and CVD endpoints, particularly in the Veteran population. Not only does PTSD increase the risk of HF, but this relationship is bi-directional. Accordingly, a VA-sponsored conference entitled "Cardiovascular Comorbidities in PTSD: The Brain-Heart Consortium" was convened to explore potential relationships and common biological pathways between PTSD and HF. The conference was framed around the hypothesis that specific common systems are dysregulated in both PTSD and HF, resulting in a synergistic acceleration and amplification of both disease processes. The conference was not intended to identify all independent pathways that give rise to PTSD and HF, but rather identify shared systems, pathways, and biological mediators that would be modifiable in both disease processes. The results from this conference identified specific endocrine, autonomic, immune, structural, genetic, and physiological changes that may contribute to shared PTSD-CVD pathophysiology and could represent unique opportunities to develop therapies for both PTSD and HF. Some recommendations from the group for future research opportunities are provided.

Differential activation of the renin-angiotensin-aldosterone-system in response to childhood and adulthood trauma

OBJECTIVE

Previous evidence suggested lasting and cumulative effects of traumatization on the renin-angiotensin-aldosterone-system (RAAS). However, it is unclear whether traumas during childhood and those experienced in adulthood differentially impact the RAAS. In this study, we sought to investigate main and putative interactive effects of childhood and adulthood trauma on RAAS functioning.

METHODS

Plasma concentrations of renin and aldosterone were measured in a general population sample (n = 2016). Childhood trauma was assessed using the Childhood Trauma Questionnaire (CTQ), adulthood trauma was measured using the PTSD module of the Structured Clinical Interview of the DSM-IV. Linear regression models were calculated to assess the relations between childhood or adulthood traumatization with renin and aldosterone concentrations.

RESULTS

Exposure to (ß = 0.094; p = 0.01), severity of childhood trauma (ß = 0.004; p = 0.01) were associated with increased aldosterone, but not renin levels. Results were carried by all dimensions of abuse, while childhood neglect was not associated with altered RAAS activity. In contrast, adulthood traumas (ß = 0.113; p < 0.01) were significantly associated with increased renin concentrations. Subjects with PTSD (renin: ß = 0.345; p = 0.01; aldosterone: ß = 0.232; p = 0.04) and those who had been exposed to both childhood and adulthood trauma showed increases in renin (ß = 0.180; p < 0.01) and aldosterone (ß = 0.340; p < 0.01) levels.

DISCUSSION

These findings indicate that trauma is associated with differential alterations of the RAAS depending on the time of traumatization. Moreover, exposure to childhood or adulthood trauma may act synergistically on the RAAS, resulting in severe dysregulation of the RAAS. The results contribute to explain associations between trauma and enhanced risk for physical disease.

Stress-Induced Sensitization of Angiotensin II Hypertension Is Reversed by Blockade of Angiotensin-Converting Enzyme or Tumor Necrosis Factor-α

BACKGROUND

Post-traumatic stress disorder (PTSD) is characterized by a disordered stress response and associated with increased cardiovascular disease risk. The present study investigated whether angiotensin (Ang) II-elicited hypertensive response is sensitized in a model of PTSD and whether inhibition of angiotensin-converting enzyme (ACE) or tumor necrosis factor (TNF)-α prior to PTSD blocks this sensitization of Ang II hypertension.

METHODS

The resident-intruder paradigm was used to model PTSD. Each intruder rat (male Sprague-Dawley) was given normal drinking water or was pretreated with either an ACE inhibitor (captopril) or a TNF-α inhibitor (pentoxifylline) in the drinking water for 2 weeks. Subsequently, they were exposed to a different resident (male Long-Evans) for 2 hours on 3 days with each session separated by 1 day and then received a subcutaneous infusion of Ang II for 2 weeks.

RESULTS

The stressed rats had a significantly enhanced hypertensive response to the Ang II infusion (stressed Δ40.2 ± 3.9 mm Hg vs. unstressed Δ20.5 ± 4.5 mm Hg) and an upregulation of mRNA or protein expression of renin-angiotensin system (RAS) and proinflammatory cytokine (PIC) components and of a microglial marker in the lamina terminalis and hypothalamic paraventricular nucleus when compared with unstressed control rats. Both the sensitized hypertensive response and enhanced gene and protein expression were blocked by pretreatment with either ACE (Δ21.3 ± 3.9 mm Hg) or TNF-α inhibitor (Δ21.4 ± 2.6 mm Hg).

CONCLUSIONS

The results indicate that upregulation of the brain RAS and PICs produced by severe stress contributes to traumatic-induced sensitization of hypertensive response to Ang II, and disorders such as PTSD may predispose individuals to development of hypertension.

Recruitment of central angiotensin II type 1 receptor associated neurocircuits in carbon dioxide associated fear

Individuals with fear-associated conditions such as panic disorder (PD) and posttraumatic stress disorder (PTSD) display increased emotional responses to interoceptive triggers, such as CO₂ inhalation, that signal a threat to physiological homeostasis. Currently, effector systems and mechanisms underlying homeostatic modulation of fear memory are not well understood. In this regard, the renin angiotensin system (RAS), particularly the angiotensin receptor type 1 (AT1R), a primary homeostatic regulatory target, has gained attention. RAS polymorphisms have been reported in PD and PTSD, and recent studies report AT1R-mediated modulation of fear extinction. However, contribution of AT1Rs in fear evoked by the interoceptive threat of CO₂ has not been investigated. Using pharmacological, behavioral, and AT1R/ACE gene transcription analyses, we assessed central AT1R recruitment in CO₂-associated fear. CO₂ inhalation led to significant AT1R and ACE mRNA upregulation in homeostatic regulatory regions, subfornical organ (SFO) and paraventricular nucleus (PVN), in a temporal manner. Intracerebroventricular infusion of selective AT1R antagonist, losartan, significantly attenuated freezing during CO₂ inhalation, and during re-exposure to CO₂ context, suggestive of AT1R modulation of contextual fear. Regional Fos mapping in losartan-treated mice post-behavior revealed significantly attenuated labeling in areas regulating defensive behavior, contextual fear, and threat responding; such as, the bed nucleus of stria terminalis, dorsal periaqueductal gray, hypothalamic nuclei, hippocampus, and prefrontal areas such as the prelimbic, infralimbic, and anterior cingulate cortices. Sub-regions of the amygdala did not show CO₂-associated AT1R regulation or altered Fos labeling. Collectively, our data suggests central AT1R recruitment in modulation of fear behaviors associated with CO₂ inhalation via engagement of neurocircuits regulating homeostasis and defensive behaviors. Our data provides mechanistic insights into the interoceptive regulation of fear, relevant to fear related disorders such as PD and PTSD.

Associations of trauma exposure and post-traumatic stress disorder with the activity of the renin-angiotensin-aldosterone-system in the general population

BACKGROUND

Previous studies suggested that exposure to traumatic events during childhood and adulthood and post-traumatic stress disorder (PTSD) are associated with a dysregulation of different neuroendocrine systems. However, the activity of the renin-angiotensin-aldosterone-system (RAAS) in relation to trauma/PTSD has been largely neglected.

METHODS

Traumatization, PTSD, and plasma concentrations of renin and aldosterone were measured in 3092 individuals from the general population. Subgroups according to the status of traumatization ('without trauma'; 'trauma, without PTSD', 'PTSD') were formed and compared regarding renin and aldosterone concentrations. Additionally, we calculated the associations between the number of traumata, renin, and aldosterone concentrations. Finally, associations of PTSD with renin/aldosterone levels were controlled for the number of traumata ('trauma load').

RESULTS

Levels of renin, but not aldosterone, were increased in traumatized persons without PTSD (p = 0.02) and, even stronger, with PTSD (p &lt; 0.01). Moreover, we found a dose-response relation between the number of traumata and renin levels (β = 0.065; p &lt; 0.001). Regression analyses showed PTSD as a significant predictor of renin (β = 0.38; p &lt; 0.01). This effect was only slightly attenuated when controlled for trauma load (β = 0.32; p &lt; 0.01).

CONCLUSIONS

Our results suggest that traumatization has lasting and cumulative effects on RAAS activity. Finding elevated renin levels in PTSD independent from trauma load supports the concept of PTSD as a disorder with specific neuroendocrine characteristics. Alternatively, elevated renin levels in traumatized persons may increase the risk for developing PTSD. Our findings contribute to explain the relationship between traumatic stress/PTSD and physical disorders.

Theranostic pharmacology in PTSD: Neurobiology and timing

Recent reviews and treatment guidelines regard trauma-focused cognitive-behavior therapies as the treatments of choice for chronic post-traumatic stress disorder (PTSD). However, many patients do not engage in this treatment when it is available, drop out before completion, or do not respond. Medications remain widely used, alone and in conjunction with psychotherapy, although the limitations of traditional monoamine-based pharmacotherapy are increasingly recognized. This article will review recent developments in psychopharmacology for PTSD, with a focus on current clinical data that apply putative neurobiologic mechanisms to medication use-i.e., a theranostic approach. A theranostic approach however, also requires consideration of timing, pre, peri or post trauma in conjunction with underlying dynamic processes affecting synaptic plasticity, the HPA axis, hippocampal activation, PFC-amygdala circuitry and fear memory.

Estradiol modulation of the renin-angiotensin system and the regulation of fear extinction

Post-traumatic stress disorder (PTSD) is more prevalent in women than men, yet much remains to be determined regarding the mechanism underlying this sex difference. Clinical and preclinical studies have shown that low estradiol levels during extinction of fear conditioning in rodents (i.e., cue exposure therapy in humans) leads to poor extinction consolidation and increased fear during extinction recall. The renin-angiotensin system (RAS) is also associated with stress-related pathologies, and RAS antagonists can enhance extinction consolidation in males. However, less is known about how estradiol and the RAS converge to alter fear extinction consolidation in females. Since estradiol downregulates the RAS, we determined the role of surgically (via ovariectomy [OVX]) and pharmacologically (via the hormonal contraceptive [HC], levonorgestrel) clamping estradiol at low levels in female rats on fear-related behavior, serum estradiol and angiotensin II (Ang II) levels, and angiotensin II type I receptor (AT1R) binding in the brain. We then tested whether the AT1R antagonist losartan would alter fear-related behavior in an estradiol-dependent manner. We found that both OVX and HC treatment produced extinction consolidation deficits relative to intact female rats in proestrus (when estradiol levels are high), and that losartan treatment mitigated these deficits and reduced freezing. OVX, but not HC, altered AT1R ligand binding, though HC reduced estradiol and increased Ang II levels in plasma. These findings have significant clinical implications, indicating that administration of an AT1R antagonist, especially if estradiol levels are low, prior to an exposure therapy session may improve treatment outcomes in females.

Untangling PTSD and TBI: Challenges and Strategies in Clinical Care and Research

PURPOSE OF REVIEW

Traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) can result from similar injuries and can result in similar symptoms, such as problems with sleep, concentration, memory, and mood. Although PTSD and persistent sequelae due to a TBI (PST) have generally been viewed as pragmatically confounded but conceptually separable entities, we examine emerging evidence emphasizing the breadth of overlap in both clinical presentation and underlying pathophysiology between PST and PTSD.

RECENT FINDINGS

New evidence underscores the poor specificity of symptoms to etiology and emphasizes the potential, after both physical brain injury and traumatic stress, for changes in each of the three interacting systems that coordinate the body's response to the experience or expectation of major injury-the immune, endocrine, and neuromodulatory neurotransmitter systems. A view of PTSD and PST sharing common pathophysiologic elements related to the CNS response to acute injury or threat carries important implications for research and clinical care.

Relationship between Toxoplasma gondii seropositivity and acoustic startle response in an inner-city population

Toxoplasma gondii (TOXO) is a neuroinvasive protozoan parasite that induces the formation of persistent cysts in mammalian brains. It infects approximately 1.1million people in the United States annually. Latent TOXO infection is implicated in the etiology of psychiatric disorders, especially schizophrenia (SCZ), and has been correlated with modestly impaired cognition. The acoustic startle response (ASR) is a reflex seen in all mammals. It is mediated by a simple subcortical circuit, and provides an indicator of neural function. We previously reported the association of TOXO with slowed acoustic startle latency, an index of neural processing speed, in a sample of schizophrenia and healthy control subjects. The alterations in neurobiology with TOXO latent infection may not be specific to schizophrenia. Therefore we examined TOXO in relation to acoustic startle in an urban, predominately African American, population with mixed psychiatric diagnoses, and healthy controls. Physiological and diagnostic data along with blood samples were collected from 364 outpatients treated at an inner-city hospital. TOXO status was determined with an ELISA assay for TOXO-specific IgG. A discrete titer was calculated based on standard cut-points as an indicator of seropositivity, and the TOXO-specific IgG concentration served as serointensity. A series of linear regression models were used to assess the association of TOXO seropositivity and serointensity with ASR magnitude and latency in models adjusting for demographics and psychiatric diagnoses (PTSD, major depression, schizophrenia, psychosis, substance abuse). ASR magnitude was 11.5% higher in TOXO seropositive subjects compared to seronegative individuals (p=0.01). This effect was more pronounced in models with TOXO serointensity that adjusted for sociodemographic covariates (F=7.41, p=0.0068; F=10.05, p=0.0017), and remained significant when psychiatric diagnoses were stepped into the models. TOXO showed no association with startle latency (t=0.49, p=0.63) in an unadjusted model, nor was TOXO associated with latency in models that included demographic factors. After stepping in individual psychiatric disorders, we found a significant association of latency with a diagnosis of PTSD (F=5.15, p=0.024), but no other psychiatric diagnoses, such that subjects with PTSD had longer startle latency. The mechanism by which TOXO infection is associated with high startle magnitude is not known, but possible mechanisms include TOXO cyst burden in the brain, parasite recrudescence, or molecular mimicry of a host epitope by TOXO. Future studies will focus on the neurobiology underlying the effects of latent TOXO infection as a potential inroad to the development of novel treatment targets for psychiatric disease.

A Unique "Angiotensin-Sensitive" Neuronal Population Coordinates Neuroendocrine, Cardiovascular, and Behavioral Responses to Stress

Stress elicits neuroendocrine, autonomic, and behavioral responses that mitigate homeostatic imbalance and ensure survival. However, chronic engagement of such responses promotes psychological, cardiovascular, and metabolic impairments. In recent years, the renin-angiotensin system has emerged as a key mediator of stress responding and its related pathologies, but the neuronal circuits that orchestrate these interactions are not known. These studies combine the use of the Cre-recombinase/loxP system in mice with optogenetics to structurally and functionally characterize angiotensin type-1a receptor-containing neurons of the paraventricular nucleus of the hypothalamus, the goal being to determine the extent of their involvement in the regulation of stress responses. Initial studies use neuroanatomical techniques to reveal that angiotensin type-1a receptors are localized predominantly to the parvocellular neurosecretory neurons of the paraventricular nucleus of the hypothalamus. These neurons are almost exclusively glutamatergic and send dense projections to the exterior portion of the median eminence. Furthermore, these neurons largely express corticotrophin-releasing hormone or thyrotropin-releasing hormone and do not express arginine vasopressin or oxytocin. Functionally, optogenetic stimulation of these neurons promotes the activation of the hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes, as well as a rise in systolic blood pressure. When these neurons are optogenetically inhibited, the activity of these neuroendocrine axes are suppressed and anxiety-like behavior in the elevated plus maze is dampened. Collectively, these studies implicate this neuronal population in the integration and coordination of the physiological responses to stress and may therefore serve as a potential target for therapeutic intervention for stress-related pathology.SIGNIFICANCE STATEMENT Chronic stress leads to an array of physiological responses that ultimately rouse psychological, cardiovascular, and metabolic impairments. As a consequence, there is an urgent need for the development of novel therapeutic approaches to prevent or dampen deleterious aspects of "stress." While the renin-angiotensin system has received some attention in this regard, the neural mechanisms by which this endocrine system may impact stress-related pathologies and consequently serve as targets for therapeutic intervention are not clear. The present studies provide substantial insight in this regard. That is, they reveal that a distinct population of angiotensin-sensitive neurons is integral to the coordination of stress responses. The implication is that this neuronal phenotype may serve as a target for stress-related disease.

Polymorphisms at the F12 and KLKB1 loci have significant trait association with activation of the renin-angiotensin system

Background

Plasma coagulation Factor XIIa (Hageman factor; encoded by F12) and kallikrein (KAL or Fletcher factor; encoded by KLKB1) are proteases of the kallikerin-kinin system involved in converting the inactive circulating prorenin to renin. Renin is a key enzyme in the formation of angiotensin II, which regulates blood pressure, fluid and electrolyte balance and is a biomarker for cardiovascular, metabolic and renal function. The renin-angiotensin system is implicated in extinction learning in posttraumatic stress disorder.

Methods & Results

Active plasma renin was measured from two independent cohorts- civilian twins and siblings, as well as U.S. Marines, for a total of 1,180 subjects. Genotyping these subjects revealed that the carriers of the minor alleles at the two loci- F12 and KLKB1 had a significant association with reduced levels of active plasma renin. Meta-analyses confirmed the association across cohorts. In vitro studies verified digestion of human recombinant pro-renin by kallikrein (KAL) to generate active renin. Subsequently, the active renin was able to digest the synthetic substrate angiotensinogen to angiotensin-I. Examination of mouse juxtaglomerular cell line and mouse kidney sections showed co-localization of KAL with renin. Expression of either REN or KLKB1 was regulated in cell line and rodent models of hypertension in response to oxidative stress, interleukin or arterial blood pressure changes.

Conclusions

The functional variants of KLKB1 (rs3733402) and F12 (rs1801020) disrupted the cascade of enzymatic events, resulting in diminished formation of active renin. Using genetic, cellular and molecular approaches we found that conversion of zymogen prorenin to renin was influenced by these polymorphisms. The study suggests that the variant version of protease factor XIIa due to the amino acid substitution had reduced ability to activate prekallikrein to KAL. As a result KAL has reduced efficacy in converting prorenin to renin and this step of the pathway leading to activation of renin affords a potential therapeutic target.

Angiotensin type 1a receptors on corticotropin-releasing factor neurons contribute to the expression of conditioned fear

Although generally associated with cardiovascular regulation, angiotensin II receptor type 1a (AT1a R) blockade in mouse models and humans has also been associated with enhanced fear extinction and decreased post-traumatic stress disorder (PTSD) symptom severity, respectively. The mechanisms mediating these effects remain unknown, but may involve alterations in the activities of corticotropin-releasing factor (CRF)-expressing cells, which are known to be involved in fear regulation. To test the hypothesis that AT1a R signaling in CRFergic neurons is involved in conditioned fear expression, we generated and characterized a conditional knockout mouse strain with a deletion of the AT1a R gene from its CRF-releasing cells (CRF-AT1a R((-/-)) ). These mice exhibit normal baseline heart rate, blood pressure, anxiety and locomotion, and freeze at normal levels during acquisition of auditory fear conditioning. However, CRF-AT1a R((-/-)) mice exhibit less freezing than wild-type mice during tests of conditioned fear expression-an effect that may be caused by a decrease in the consolidation of fear memory. These results suggest that central AT1a R activity in CRF-expressing cells plays a role in the expression of conditioned fear, and identify CRFergic cells as a population on which AT1 R antagonists may act to modulate fear extinction.

Autonomic and inflammatory consequences of posttraumatic stress disorder and the link to cardiovascular disease

Stress- and anxiety-related disorders are on the rise in both military and general populations. Over the next decade, it is predicted that treatment of these conditions, in particular, posttraumatic stress disorder (PTSD), along with its associated long-term comorbidities, will challenge the health care system. Multiple organ systems are adversely affected by PTSD, and PTSD is linked to cancer, arthritis, digestive disease, and cardiovascular disease. Evidence for a strong link between PTSD and cardiovascular disease is compelling, and this review describes current clinical data linking PTSD to cardiovascular disease, via inflammation, autonomic dysfunction, and the renin-angiotensin system. Recent clinical and preclinical evidence regarding the role of the renin-angiotensin system in the extinction of fear memory and relevance in PTSD-related immune and autonomic dysfunction is also addressed.