The role of IL18-607C>A and IL18-137G>C promoter polymorphisms in antidepressant treatment phenotypes: A preliminary report

Association of Single Nucleotide Polymorphisms of Cytokine Genes with Depression, Schizophrenia and Bipolar Disorder

Immune gene variants are known to be associated with the risk of psychiatric disorders, their clinical manifestations, and their response to therapy. This narrative review summarizes the current literature over the past decade on the association of polymorphic variants of cytokine genes with risk, severity, and response to treatment for severe mental disorders such as bipolar disorder, depression, and schizophrenia. A search of literature in databases was carried out using keywords related to depressive disorder, bipolar disorder, schizophrenia, inflammation, and cytokines. Gene lists were extracted from publications to identify common genes and pathways for these mental disorders. Associations between polymorphic variants of the IL1B, IL6, and TNFA genes were the most replicated and relevant in depression. Polymorphic variants of the IL1B, IL6, IL6R, IL10, IL17A, and TNFA genes have been associated with schizophrenia. Bipolar disorder has mainly been associated with polymorphic variants of the IL1B gene. Interestingly, the IL6R gene polymorphism (rs2228145) was associated with all three diseases. Some cytokine genes have also been associated with clinical presentation and response to pharmacotherapy. There is also evidence that some specific polymorphic variants may affect the expression of cytokine genes. Thus, the data from this review indicate a link between neuroinflammation and severe mental disorders.

The Impact of BDNF, NTRK2, NGFR, CREB1, GSK3B, AKT, MAPK1, MTOR, PTEN, ARC, and SYN1 Genetic Polymorphisms in Antidepressant Treatment Response Phenotypes

This study aimed to investigate the influence of genetic variants in neuroplasticity-related genes on antidepressant treatment phenotypes. The BDNF-TrkB signaling pathway, as well as the downstream kinases Akt and ERK and the mTOR pathway, have been implicated in depression and neuroplasticity. However, clinicians still struggle with the unpredictability of antidepressant responses in depressed patients. We genotyped 26 polymorphisms in BDNF, NTRK2, NGFR, CREB1, GSK3B, AKT, MAPK1, MTOR, PTEN, ARC, and SYN1 in 80 patients with major depressive disorder treated according to the Texas Medical Algorithm for 27 months at Hospital Magalhães Lemos, Porto, Portugal. Our results showed that BDNF rs6265, PTEN rs12569998, and SYN1 rs1142636 SNP were associated with treatment-resistant depression (TRD). Additionally, MAPK1 rs6928 and GSK3B rs6438552 gene polymorphisms were associated with relapse. Moreover, we found a link between the rs6928 MAPK1 polymorphism and time to relapse. These findings suggest that the BDNF, PTEN, and SYN1 genes may play a role in the development of TRD, while MAPK1 and GSK3B may be associated with relapse. GO analysis revealed enrichment in synaptic and trans-synaptic transmission pathways and glutamate receptor activity with TRD-associated genes. Genetic variants in these genes could potentially be incorporated into predictive models of antidepressant response.

Genomic profile in association with sport-type, sex, ethnicity, psychological traits and sport injuries of elite athletes: review and future perspectives

In the last few years, some inherited determinants have been associated with elite athletic performance, but its polygenic trait character has limited the correct definition of elite athlete's genomic profile. This qualitative descriptive study aims to summarise the current understanding about genetic and epigenetic factors in elite athletes, as well as their genomic profile in association with sport-type, sex, ethnicity, psychological traits and sport injuries. A narrative review of the literature across a broad cross-section of the elite athletes' genomic profile was undertaken. Elite performance relies on rare gene variants within a great interface between molecular, cellular and behavioural sport-related phenotypes and the environment, which is still poorly understood. ACTN3 rs1815739 and ACE I/D polymorphisms appear to be associated to specific sprint phenotypes and influence the athletic status, i.e., the rs1815739 variant is more influential to 200-m performance and the ACE ID polymorphism is more involved in the longer, 400-m sprint performance. Generally, athletes show endurance-based sports characteristics or power-based sports characteristics, but some studies have reported some genes associations to both sports-based characteristics. Furthermore, genetic studies with larger cohorts of single-sport athletes might be preferable than studies combining athletes of different sports, given the existence of distinct athlete profiles and sport demands. Athletic performance may be influenced by the serotonergic pathway and the potential injury risk (namely stress fracture) might be associated to a genetic predisposition associated to the mechanical loading from the intense physical exercise. The study of gene variants associated to sex and ethnicity-related to athletic performance needs further investigation. The combination of genome-wide association studies addressing the genetic architecture of athletes and the subsequent replication and validation studies might for additional genetic data is mandatory.

The cytokine network in the pathogenesis of major depressive disorder. Close to translation?

Major depressive disorder (MDD) is a common condition that afflicts the general population across a broad spectrum of ages and social backgrounds. MDD has been identified by the World Health Organization as a leading cause of disability worldwide. Approximately 30% of patients are poor responsive to standard of care (SOC) treatment and novel therapeutic approaches are warranted. Since chronic inflammation, as it is often observed in certain cancers, type 2 diabetes, psoriasis and chronic arthritis, are accompanied by depression, it has been suggested that immunoinflammatory processes may be involved in the pathogenesis of MDD. Cytokines are a group of glycoproteins secreted from lymphoid and non-lymphoid cells that orchestrate immune responses. It has been suggested that a dysregulated production of cytokines may be implicated in the pathogenesis and maintenance of MDD. On the basis of their functions, cytokines can be subdivided in pro-inflammatory and anti-inflammatory cytokines. Since abnormal blood and cerebrospinal fluid of both pro and anti-inflammatory cytokines are altered in MDD, it has been suggested that abnormal cytokine homeostasis may be implicated in the pathogenesis of MDD and possibly to induction of therapeutic resistance. We review current data that indicate that cytokines may represent a useful tool to identify MDD patients that may benefit from tailored immunotherapeutic approaches and may represent a potential tailored therapeutic target.

Plasma levels of Interleukin 18 but not amyloid-β or Tau are elevated in female depressive patients

BACKGROUND

Depression is associated with inflammation and Alzheimer's disease (AD). However, detailed molecular mechanisms linking mood, neuroinflammation and AD remain unclear. Although changes in peripheral inflammatory factors such as Interleukin 18 (IL18), and AD-associated amyloid-β (Aβ) peptides have been linked to depression, a solid relationship between these factors in depressive disorder has yet to be established. This study aims to further determine whether plasma IL18, Aβ40, Aβ42, and the AD-associated tangle component Tau, as well as IL18 single nucleotide polymorphisms (SNPs) may be biomarkers for depression.

METHODS

We measured plasma IL18, Aβ40, Aβ42, and Tau in 64 depressive patients and 75 healthy controls, and characterized genotypes of three IL18 SNPs (rs187238, rs1946518 and rs1946519) in these subjects. Comparisons between depressive patients and controls were carried out in males, in females or in combination. Regression analyses were conducted to examine the correlation between these parameters.

RESULTS

We found that none of the plasma levels of IL18, Aβ40, Aβ42, and Tau, the ratio of Aβ42/Aβ40, and the genotypes of IL18 SNPs were significantly different between combined depressive patients and combined healthy controls, or between male depressive patients and male controls. However, IL18 levels were less in females than in males in healthy people and were significantly increased in female depressive patients compared to female controls. Moreover, IL18 and standardized IL18 were correlated with standardized Aβ42/Aβ40 ratio and standardized Tau in depressive patients.

CONCLUSIONS

Plasma IL18 may be a potential biomarker for depression in women.

Interleukin-18 levels in the hippocampus and behavior of adult rat offspring exposed to prenatal restraint stress during early and late pregnancy

Exposure to maternal stress during prenatal life is associated with an increased risk of neuropsychiatric disorders, such as depression and anxiety, in offspring. It has also been increasingly observed that prenatal stress alters the phenotype of offspring via immunological mechanisms and that immunological dysfunction, such as elevated interleukin-18 levels, has been reported in cultures of microglia. Prenatal restraint stress (PRS) in rats permits direct experimental investigation of the link between prenatal stress and adverse outcomes. However, the majority of studies have focused on the consequences of PRS delivered in the second half of pregnancy, while the effects of early prenatal stress have rarely been examined. Therefore, pregnant rats were subjected to PRS during early/middle and late gestation (days 8-14 and 15-21, respectively). PRS comprised restraint in a round plastic transparent cylinder under bright light (6500 lx) three times per day for 45 minutes. Differences in interleukin-18 expression in the hippocampus and in behavior were compared between offspring rats and control rats on postnatal day 75. We found that adult male offspring exposed to PRS during their late prenatal periods had higher levels of anxiety-related behavior and depression than control rats, and both male and female offspring exhibited higher levels of depression-related behavior, impaired recognition memory and diminished exploration of novel objects. Moreover, an elevated level of interleukin-18 was observed in the dorsal and ventral hippocampus of male and female early- and late-PRS offspring rats. The results indicate that PRS can cause anxiety and depression-related behaviors in adult offspring and affect the expression of interleukin-18 in the hippocampus. Thus, behavior and the molecular biology of the brain are affected by the timing of PRS exposure and the sex of the offspring. All experiments were approved by the Animal Experimentation Ethics Committee at Kunming Medical University, China (approval No. KMMU2019074) in January 2019.

NLRP3 inflammasome-driven pathways in depression: Clinical and preclinical findings

Over the past three decades, an intricate interaction between immune activation, release of pro-inflammatory cytokines and changes in brain circuits related to mood and behavior has been described. Despite extensive efforts, questions regarding when inflammation becomes detrimental or how we can target the immune system to develop new therapeutic strategies for the treatment of psychiatric disorders remain unresolved. In this context, novel aspects of the neuroinflammatory process activated in response to stressful challenges have recently been documented in major depressive disorder (MDD). The Nod-like receptor pyrin containing 3 inflammasome (NLRP3) is an intracellular multiprotein complex responsible for a number of innate immune processes associated with infection, inflammation and autoimmunity. Recent data have demonstrated that NLRP3 activation appears to bridge the gap between immune activation and metabolic danger signals or stress exposure, which are key factors in the pathogenesis of psychiatric disorders. In this review, we discuss both preclinical and clinical evidence that links the assembly of the NLRP3 complex and the subsequent proteolysis and release of the pro-inflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18) in chronic stress models and patients with MDD. Importantly, we also focus on the therapeutic potential of targeting the NLRP3 inflammasome complex to improve stress resilience and depressive symptoms.

IL6-174G > C genetic polymorphism influences antidepressant treatment outcome

BACKGROUND

Major depressive disorder is a condition associated with dysregulated cytokine levels; among these, IL6. Furthermore, genetic variations within cytokine genes have been proposed to predict antidepressant treatment outcome.

OBJECTIVES

This study aims to evaluate the role of IL6-174G > C and IL6R D358A A > C functional polymorphisms in antidepressant treatment phenotypes, specifically remission, relapse, and treatment resistant depression (TRD).

METHODS

The referred polymorphisms were genotyped in 80 MDD patients followed at Hospital Magalhães Lemos, Portugal, within a period of 27 months.

RESULTS

It was found that patients carrying IL6-174 GC genotype present a protection towards the development of TRD (OR = 0.242; 95% CI = 0.068-0.869; p = .038), when compared with GG genotype. Additionally, carriers of IL6-174 CC genotype remit earlier than patients with IL6-174 GG/GC genotypes, with a median time to remission of 6 weeks for CC carriers and 15 weeks for GG or GC carriers (p = .030, Log-rank test). No association was found between IL6R D358A genetic polymorphism and any of the treatment phenotypes evaluated.

CONCLUSIONS

The IL6-174G > C polymorphism influences antidepressant treatment outcome in this sub-set of MDD patients, providing a putative mechanistic link for the dysregulated IL-6 levels described in the literature in patients with TRD.