Sex-specific association of depression and a haplotype in leukotriene A4 hydrolase gene

Montelukast induces beneficial behavioral outcomes and reduces inflammation in male and female rats

Background

Accumulative data links inflammation and immune dysregulation to the pathophysiology of mental disorders; little is known regarding leukotrienes’ (LTs) involvement in this process. Circumstantial evidence suggests that treatment with leukotriene modifying agents (LTMAs) such as montelukast (MTK) may induce adverse neuropsychiatric events. Further methodic evaluation is warranted.

Objective

This study aims to examine behavioral effects, as well as inflammatory mediator levels of chronic MTK treatment in male and female rats.

Methods

Depression-like phenotypes were induced by exposing male and female rats to a chronic unpredictable mild stress (CUMS) protocol for four weeks. Thereafter, rats were treated (intraperitoneally) once daily, for two weeks, with either vehicle (dimethyl sulfoxide 0.2 ml/rat) or 20 mg/kg MTK. Following treatment protocols, behavioral tests were conducted and brain regions were evaluated for inflammatory mediators including tumor necrosis factor (TNF)-α, interleukin (IL)-6 and prostaglandin (PG) E2.

Results

Overall, MTK did not invoke negative behavioral phenotypes (except for an aggression-inducing effect in males). Numerous positive behavioral outcomes were observed, including reduction in aggressive behavior in females and reduced manic/hyperactive-like behavior and increased sucrose consumption (suggestive of antidepressant-like effect) in males. Furthermore, in control males, MTK increased IL-6 levels in the hypothalamus and TNF-α in the frontal cortex, while in control females it generated a robust anti-inflammatory effect. In females that were subjected to CUMS, MTK caused a prominent reduction in TNF-α and IL-6 in brain regions, whereas in CUMS-subjected males its effects were inconsistent.

Conclusion

Contrary to prior postulations, MTK may be associated with select beneficial behavioral outcomes. Additionally, MTK differentially affects male vs. female rats in respect to brain inflammatory mediators, plausibly explaining the dissimilar behavioral phenotypes of sexes under MTK treatment.

The Role of Sex in Genetic Association Studies of Depression

Depression is the most common mental illness in the U.S. affecting nearly 40 million adults age 18 years and older. Depression has both genetic and environmental influences. In addition, women are more likely to be affected by depression than men. However, the relationship between genes and depression is complex and may be influenced by sex. Understanding the genetic basis of sex-specific differences for depression has the potential to lead to new biological understanding of the etiology of depression in females compared to males and to promote the development of novel and more effective pharmacotherapies. This review examines the role of sex in genetic associations with depression for both genome-wide association and candidate gene studies. While the genetic association signals of depression differ by sex, the role of sex in the heritability of depression is complex and warrants further investigation.

How Does Mental Health Impact Women's Heart Health?

From adolescence until old age, women are more vulnerable to common mental disorders (CMDs; depression and anxiety) than men at all stages of the life course. By middle age, women who have clinical depression are at twice the risk of having an incident cardiovascular disease (CVD) than those without. This has important implications for the way we prevent, identify and treat both CMDs and coronary heart disease in women. In this paper, we discuss the various genetic, biological, ethnic/racial, and psychological pathways by which women's vulnerability to CMDs elevate their CVD risk and recovery from a cardiac event. We review the evidence from trials that have, to date, failed to show that treating depression can reduce or delay the onset or recurrence of CVD events, especially for female patients. We discuss the value of lifestyle-based therapies for treating depression, to which women may be more responsive, and finish by discussing how population-based approaches including risk factor assessment could be tailored to consider these factors.

Paradoxical Effect of LTB4 on the Regulation of Stress-Induced Corticosterone Production

Depression is a mental illness with a complex and multifactorial etiology, which has been associated with stress and inflammation. Infections, autoimmune diseases, envenomation, and trauma induce an inflammatory response that is characterized by increasing levels of circulating cytokines (e.g., IL-1β) and lipid mediators [e.g., PGE₂ and leukotrienes B₄ (LTB₄)]. Recently, we showed that LTB₄ production by the 5-lipoxygenase (5-LO) pathway regulates IL-1β and PGE₂ release, reducing tissue damage in a model of sterile inflammation. Since IL-1β and PGE₂ increase in serum of stressed patients and potentially trigger depression, we used an animal model of chronic unpredictable stress (CUS) to investigate the potential impact of LTB₄ over depression-like symptoms. At basal conditions, 5-LO deficiency (Alox5^−/−) reduces the preference for sucrose, while inducing a higher immobilization time on the tail suspension test when compared 129sv. Moreover, Alox5^−/− mice present increased caspase-1 expression and elevated levels of IL-1β, IL-17 and PGE₂ in the spleen, with increasing corticosterone levels in the frontal cortex but reducing systemic levels. Compared to 129sv mice, CUS induced higher levels of systemic, frontal cortex and hippocampal corticosterone, and also reduced sucrose preference, increased levels of splenic IL-1β, IL-17 and PGE₂ and reduced levels of LTB₄. Interestingly, CUS exposure did not alter the reduced sucrose preference shown by Alox5^−/− mice but greatly enhanced splenic PGE₂ production. Compared to Alox5^−/− mice at basal conditions, CUS exposure also increased levels of systemic corticosterone, which remained lower than those of CUS-129sv animals. We also observed that treatment with LTB₄ decreased caspase-1 expression and systemic levels of corticosterone in CUS-Alox5^−/− mice but there was no significant impact on the reduced sucrose preference. Our results demonstrate that LTB₄ controls the hypothalamic-pituitary-adrenal (HPA) axis by regulating levels of systemic corticosterone associated with the repression of caspase-1 expression and production of inflammatory mediators. One limitation of our study is that 129sv and Alox5^−/− mice were not littermates, not sharing, therefore, the same intra-uterine and preweaning environment. Even so, taken together our results indicate that 5-LO activity is critical for the regulation of stress-induced symptoms, suggesting that the Alox5^−/− mouse could be a natural model of corticosterone-independent reduced reward sensitivity.

Genetic Contributions of Inflammation to Depression

This paper describes the effects of immune genes genetic variants and mRNA expression on depression's risk, severity, and response to antidepressant treatment, through a systematic review on all papers published between 2000 and 2016. Our results, based largely on case-control studies, suggest that common genetic variants and gene-expression pathways are involved in both immune activation and depression. The most replicated and relevant genetic variants include polymorphisms in the genes for interleukin (IL)-1β, IL-6, IL-10, monocyte chemoattractant protein-1, tumor necrosis factor-alpha, C-reactive protein, and phospholipase A2. Moreover, increased blood cytokines mRNA expression (especially of IL-1β) identifies patients that are less likely to respond to conventional antidepressants. However, even for the most replicated findings there are inconsistent results, not only between studies, but also between the immune effects of the genetic variants and the resulting effects on depression. We find evidence that these discrepant findings may be explained, at least in part, by the heterogeneity of the depression immunophenotype, by environmental influences and gene × environment interactions, and by the complex interfacing of genetic variants with gene expression. Indeed, some of the most robust findings have been obtained in patients developing depression in the context of treatment with interferon-alpha, a widely used model to mimic depression in the context of inflammation. Further 'omics' approaches, through GWAS and transcriptomics, will finally shed light on the interaction between immune genes, their expression, and the influence of the environment, in the pathogenesis of depression.

Anti-Inflammatory Activity of Natural Products

This article presents highlights of the published literature regarding the anti-inflammatory activities of natural products. Many review articles were published in this regard, however, most of them have presented this important issue from a regional, limited perspective. This paper summarizes the vast range of review and research articles that have reported on the anti-inflammatory effects of extracts and/or pure compounds derived from natural products. Moreover, this review pinpoints some interesting traditionally used medicinal plants that were not investigated yet.

Behavioral, emotional and neurobiological determinants of coronary heart disease risk in women

Women have more of the stress-related behavioral profile that has been linked to cardiovascular disease than men. For example, women double the rates of stress-related mental disorders such as depression and posttraumatic stress disorder (PTSD) than men, and have higher rates of exposure to adversity early in life. This profile may increase women's long-term risk of cardiometabolic conditions linked to stress, especially coronary heart disease (CHD). In addition to having a higher prevalence of psychosocial stressors, women may be more vulnerable to the adverse effects of these stressors on CHD, perhaps through altered neurobiological physiology. Emerging data suggest that young women are disproportionally susceptible to the adverse effects of stress on the risk of cardiovascular disease, both in terms of initiating the disease as well as worsening the prognosis in women who have already exhibited symptoms of the disease. Women's potential vulnerability to psychosocial stress could also help explain their higher propensity toward abnormal coronary vasomotion and microvascular disease compared with men.

Prevalence of undiagnosed depression among persons with hypertension and associated risk factors: a cross-sectional study in urban Nepal

Background

Despite an increasing number of studies exploring prevalence of depression among hypertensive patients in high income countries, limited data is available from low and middle income countries, particularly Nepal. Our aim was to investigate the prevalence of undiagnosed (sub clinical) depression and associated risk factors among hypertensive patients attending a tertiary health care clinic in Nepal.

Methods

The study was based on a cross-sectional study design, with 321 hypertensive patients attending the Out-Patient Department of a central hospital in Nepal. Blood measure was recorded via a mercury column sphygmomanometer. Depression levels were assessed using the Beck Depression Inventory-Ia (BDI) scale. Demographics and risk factors were assessed.

Result

The proportion of participants with undiagnosed depression was 15%. Multivariable analyses demonstrated an increase in BDI scores with increased aging. Approximately a 1 point increase in the BDI score was observed for each additional decade of aging in hypertensive patients. Additional factors associated with increased risk of depression included being female (4.28 point BDI score increase), smoking (5.61 point BDI score increase), being hypertensive with no hypertensive medication (4.46 point BDI score increase) and being illiterate (4.46 point BDI score increase).

Conclusions

Among persons with hypertension in outpatient settings in Nepal, demographic (age, sex, education), behavioural (smoking,) and adherence factors (anti-hypertensive medication) were associated with undiagnosed depression. Screening programs in Nepal may assist early intervention in hypertensive patients with sub clinical depression.

Evolutionary aspects of lipoxygenases and genetic diversity of human leukotriene signaling

Leukotrienes are pro-inflammatory lipid mediators, which are biosynthesized via the lipoxygenase pathway of the arachidonic acid cascade. Lipoxygenases form a family of lipid peroxidizing enzymes and human lipoxygenase isoforms have been implicated in the pathogenesis of inflammatory, hyperproliferative (cancer) and neurodegenerative diseases. Lipoxygenases are not restricted to humans but also occur in a large number of pro- and eucaryotic organisms. Lipoxygenase-like sequences have been identified in the three domains of life (bacteria, archaea, eucarya) but because of lacking functional data the occurrence of catalytically active lipoxygenases in archaea still remains an open question. Although the physiological and/or pathophysiological functions of various lipoxygenase isoforms have been studied throughout the last three decades there is no unifying concept for the biological importance of these enzymes. In this review we are summarizing the current knowledge on the distribution of lipoxygenases in living single and multicellular organisms with particular emphasis to higher vertebrates and will also focus on the genetic diversity of enzymes and receptors involved in human leukotriene signaling.

Permutation Tests in the Educational and Behavioral Sciences

Over the past two decades, permutation tests (PTs) have received much attention in the educational and behavioral sciences. The aim of this article is to review the theoretical developments of PTs, the active areas in the educational and behavioral research using PTs, and the types of analysis under which PTs have been applied. We obtained 224 published articles, which included 141 theoretical articles and 83 application articles. After scrutinizing each article, we are happy to see that (1) some researchers began to advocate introducing PTs into basic statistics training; (2) computing load for PTs may be reduced dramatically by some intelligent algorithms; (3) PTs began to be applied in new areas such as studies on the relationship between brain and behavior and the relationship between gene and behavior; (4) besides simple types of analysis such as independent two-group comparison, PTs can also be carried out under more complex situations such as multivariate analysis. However, we should also notice that PTs are still mostly used for simple analyses (e.g., randomness analysis).

Sex and age differences in the association of depression with obstructive coronary artery disease and adverse cardiovascular events

Background

Young women with coronary heart disease have high rates of depression and a higher risk of adverse events than men of similar age. Whether depression has a higher prognostic value in this group than in men and older women is not known. Our objective was to assess whether depression in young women is associated with higher risk of coronary artery disease (CAD) and adverse outcomes compared with similarly aged men and older women.

Methods and Results

We examined 3237 patients undergoing coronary angiography for evaluation of CAD and followed them for 2.9 years (median). Depressive symptoms were assessed with the Patient Health Questionnaire (PHQ)‐9, and CAD burden was dichotomized based on its presence or absence. After multivariable adjustment for CAD risk factors, depressive symptoms predicted CAD presence in women aged ≤55 years (odds ratio=1.07 95% confidence interval [CI] 1.02 to 1.13 per 1 point increase in PHQ‐9 score), but not in men aged ≤55 years or women aged >55 years. Depressive symptoms also predicted increased risk of death in women aged ≤55 years (adjusted hazard ratio=1.07, 95% CI 1.02 to 1.14, per 1 point increase in PHQ‐9 score), but not in men aged ≤55 years and women aged >55 years, with P=0.02 for the depression‐sex interaction and P=0.02 for depression‐sex‐age interaction.

Conclusions

Among patients with suspected or established CAD, depressive symptoms are associated with increased risk of death, particularly in young women. This group may be especially vulnerable to the adverse cardiovascular effects of depression.

Central genomic regulation of the expression of oestrous behaviour in dairy cows: a review

The expression of oestrous behaviour in Holstein Friesian dairy cows has progressively decreased over the past 50 years. Reduced oestrus expression is one of the factors contributing to the current suboptimal reproductive efficiency in dairy farming. Variation between and within cows in the expression of oestrous behaviour is associated with variation in peripheral blood oestradiol concentrations during oestrus. In addition, there is evidence for a priming role of progesterone for the full display of oestrous behaviour. A higher rate of metabolic clearance of ovarian steroids could be one of the factors leading to lower peripheral blood concentrations of oestradiol and progesterone in high-producing dairy cows. Oestradiol acts on the brain by genomic, non-genomic and growth factor-dependent mechanisms. A firm base of understanding of the ovarian steroid-driven central genomic regulation of female sexual behaviour has been obtained from studies on rodents. These studies have resulted in the definition of five modules of oestradiol-activated genes in the brain, referred to as the GAPPS modules. In a recent series of studies, gene expression in the anterior pituitary and four brain areas (amygdala, hippocampus, dorsal hypothalamus and ventral hypothalamus) in oestrous and luteal phase cows, respectively, has been measured, and the relation with oestrous behaviour of these cows was analysed. These studies identified a number of genes of which the expression was associated with the intensity of oestrous behaviour. These genes could be grouped according to the GAPPS modules, suggesting close similarity of the regulation of oestrous behaviour in cows and female sexual behaviour in rodents. A better understanding of the central genomic regulation of the expression of oestrous behaviour in dairy cows may in due time contribute to improved (genomic) selection strategies for appropriate oestrus expression in high-producing dairy cows.

Leukotriene haplotype × diet interaction on carotid artery hypertrophy and atherosclerosis in American Indians: the Strong Heart Family Study

OBJECTIVE

Gene × diet interaction plays an important role in atherosclerosis, an inflammatory disorder. Leukotrienes are the most potent inflammatory mediators, and genetic variants encoding leukotriene genes have been implicated in atherosclerosis. This study tests nutrigenetic interaction of a previously defined leukotriene haplotype on carotid artery hypertrophy and atherosclerosis in American Indians.

METHODS

This study included 3402 American Indians participating in the Strong Heart Family Study (SHFS). Carotid artery measurements, including intima-media thickness (IMT), vascular mass, and plaque, were assessed using ultrasound. Eleven tagSNPs in the leukotriene A4 hydrolase (LTA4H) gene were genotyped in all subjects. Main haplotype effect and haplotype × diet interaction were examined by generalized estimating equation, adjusting for known risk factors.

RESULTS

There was no significant main effect of haplotype or diet on any of the carotid artery measures. However, a previously defined LTA4H haplotype, called HapE, significantly interacted with dietary intake of n-3 and n-6 fatty acids on both IMT (P(HapE × n3) = 0.018, P(HapE × n6) = 0.040) and vascular mass (P(HapE × n3) = 0.012, P(HapE × n6) = 0.018), but not plaque. The direction of this nutrigenetic interaction on IMT was consistent with that reported in a recent study of Caucasian twins.

CONCLUSION

Dietary intake of polyunsaturated fatty acids significantly modifies the effect of a leukotriene haplotype on carotid artery hypertrophy but not atherosclerosis in American Indians, independent of established cardiovascular risk factors. Replication of nutrigenetic interaction in two distinct ethnic groups suggests the robustness and generalizability of our findings to diverse populations.

The role of immune genes in the association between depression and inflammation: a review of recent clinical studies

The role for dysregulation of the immune system in the pathogenesis of depressive disorder is well established, and emerging research suggests the role of an underlying genetic vulnerability. The purpose of this review is to summarize the existing literature on the genetic variants involved in neurobiological pathways associated with both immune activation and depression. Using PubMed, Scopus, The Cochrane Library, Embase, Ovid of Medline, PsycINFO and ISI web of Knowledge, we selected 52 papers which are relevant for this literature review. Findings across the literature suggest that functional allelic variants of genes for interleukin-1beta (IL)-1β, tumor necrosis factor-alpha (TNF-α) and C-reactive protein (CRP), as well as genetic variations affecting T-cell function, may increase the risk for depression. Moreover, single nucleotide polymorphisms (SNPs) in the IL-1β, IL-6 and IL-11 genes, and in those regulating T-cell function may be associated with reduced responsiveness to antidepressant therapy. There is also some evidence indicative of a role of genetic variants of the enzymes, Cyclo-oxygenase2 (COX-2) and Phospholipase2 (PLA2), in the aetiology of depression. Finally, SNPs in genes related to the serotonin pathway may play a fundamental role in the shared genetic liability to both immune activation and depressive symptoms. Our review confirms that genetic variants influence the biological mechanisms by which the innate immune system contributes to the development of depression. However, future studies are necessary to identify the molecular mechanisms underlying these associations.

The involvement of 5-lipoxygenase activating protein in anxiety-like behavior

The 5-lipoxygenase is an enzyme widely expressed in the central nervous system, where its activity is dependent on the presence the 5-lipoxygenase activating protein (FLAP) for the formation of leukotrienes, potent bioactive lipid mediators. Emerging evidence has shown that the FLAP/leukotriene pathway may play a role in neuropsychiatric disease contexts. In this study we investigated whether genetic deficiency of FLAP (FLAPKO) modulated some behavioral aspects in mice, and if this effect was age-dependent. While we observed that FLAPKO mice at 3 and 6 months of age did not different from wild type animals in the elevated plus maze, at 12 months of age they manifested a significant increase in anxiety-like behavior. By contrast, we observed no differences between FLAPKO mice and their controls at any of the three ages considered when they were tested for working memory in the Y maze paradigm. Additionally, while we found that cFOS protein and message levels were reduced in the brains of animals lacking FLAP, no changes for other transcription factors were detected. Taken together our findings suggest a novel role for FLAP in the pathogenesis of anxiety-like behavior. Future studies of FLAP neurobiology may be attractive for development of anxiolytic therapeutics.

Cardiovascular disease, psychosocial factors, and genetics: the case of depression

Psychosocial factors are associated with cardiovascular disease, but little is known about the role of genetics in this relationship. Focusing on the well-studied phenotype of depression, current data show that there are shared genetic factors that may give rise to both depression and CVD, and these genetic risks appear to be modified by gender. This pleiotropic effect suggests that a single pathway, when perturbed, gives rise to the dual phenotypes of CVD and depression. The data also suggest that women contribute disproportionately to the depression-CVD comorbidity, and this unbalanced contribution is attributable, in part, to genetic factors. While the underlying biology behind this relationship is unclear, recent data support contributions from inflammatory or serotonergic pathways toward the comorbidity between CVD and depression. Even without knowledge of a specific mechanism, epidemiological observations offer new directions to explain the relationship between depression and CVD that have both research and clinical applications.

Leukotriene A4 hydrolase haplotype, diet and atherosclerosis: a twin study

OBJECTIVE

Atherosclerosis is an inflammatory process resulting from the interaction between genetic and environmental factors. Leukotrienes are inflammatory mediators generated from arachidonic acid, and genetic polymorphisms involved in leukotriene metabolism are implicated in atherosclerosis. The objectives of this study are to examine whether genetic variants in key leukotriene enzymes are associated with atherosclerosis, and whether dietary intake of competing leukotriene substrates modifies the effect of leukotriene variants on atherosclerosis.

METHODS

Atherosclerosis was assessed by common carotid intima-media thickness (IMT) using ultrasound. Sequence variants within arachidonate 5-lipoxygenase activating protein (ALOX5AP) and leukotriene A4 hydrolase (LTA4H) genes were analyzed with 32 single nucleotide polymorphisms (SNPs) in 169 Caucasian twin pairs from the Vietnam Era Twin Registry. The associations between genetic polymorphisms and carotid atherosclerosis, and gene × diet interactions were examined by generalized estimating equation controlling for potential confounders.

RESULTS

A six-SNP haplotype in LTA4H, designated HapE, was significantly associated with carotid IMT after adjusting for known coronary risk factors. Twins carrying HapE had a much lower IMT compared to twins not carrying (695 μm vs. 750 μm, p = 0.0007). Moreover, dietary intake of polyunsaturated fatty acids strongly augmented the cardioprotective effect of HapE among those with this haplotype but not those without, suggesting a haplotype × diet interaction (interaction P(HapE×n-3) = 0.03, P(HapE×n-6) = 0.015).

CONCLUSION

We identified a novel leukotriene haplotype that appears to be protective toward subclinical atherosclerosis. This association is modified by dietary intake of polyunsaturated fatty acids.

Knockout of 5-lipoxygenase results in age-dependent anxiety-like behavior in female mice

Background

The enzyme 5-lipoxygenase (5LO) has been implicated in a variety of neurological and psychiatric disorders including anxiety. Knockout of 5LO has previously been shown to alter anxiety-like behavior in mice at a young age but the effect of 5LO knockout on older animals has not been characterized.

Methodology/Principal Findings

Here we used the elevated plus maze behavioral paradigm to measure anxiety-like behavior in female mice lacking 5LO (5LO-KO) at three different ages. Adolescent 5LO-KO animals did not significantly differ from wild-type (WT) animals in anxiety-like behavior. However, adult and older mice exhibited increased anxiety-like behavior compared to WT controls.

Conclusions

These results indicate that 5LO plays a role in the development of the anxiety-like phenotype in an age-dependent manner in female mice. Future work should further investigate this interaction as 5LO may prove to be an important molecular target for the development of novel anxiolytic therapies.

Gene expression patterns in four brain areas associate with quantitative measure of estrous behavior in dairy cows

BACKGROUND

The decline noticed in several fertility traits of dairy cattle over the past few decades is of major concern. Understanding of the genomic factors underlying fertility, which could have potential applications to improve fertility, is very limited. Here, we aimed to identify and study those genes that associated with a key fertility trait namely estrous behavior, among genes expressed in four bovine brain areas (hippocampus, amygdala, dorsal hypothalamus and ventral hypothalamus), either at the start of estrous cycle, or at mid cycle, or regardless of the phase of cycle.

RESULTS

An average heat score was calculated for each of 28 primiparous cows in which estrous behavior was recorded for at least two consecutive estrous cycles starting from 30 days post-partum. Gene expression was then measured in brain tissue samples collected from these cows, 14 of which were sacrificed at the start of estrus and 14 around mid cycle. For each brain area, gene expression was modeled as a function of the orthogonally transformed average heat score values using a Bayesian hierarchical mixed model. Genes whose expression patterns showed significant linear or quadratic relationships with heat scores were identified. These included genes expected to be related to estrous behavior as they influence states like socio-sexual behavior, anxiety, stress and feeding motivation (OXT, AVP, POMC, MCHR1), but also genes whose association with estrous behavior is novel and warrants further investigation.

CONCLUSIONS

Several genes were identified whose expression levels in the bovine brain associated with the level of expression of estrous behavior. The genes OXT and AVP play major roles in regulating estrous behavior in dairy cows. Genes related to neurotransmission and neuronal plasticity are also involved in estrous regulation, with several genes and processes expressed in mid-cycle probably contributing to proper expression of estrous behavior in the next estrus. Studying these genes and the processes they control improves our understanding of the genomic regulation of estrous behavior expression.