Chronic psychological stress impairs germinal center response by repressing miR-155

B cells and the stressed brain: emerging evidence of neuroimmune interactions in the context of psychosocial stress and major depression

The immune system has emerged as a key regulator of central nervous system (CNS) function in health and in disease. Importantly, improved understanding of immune contributions to mood disorders has provided novel opportunities for the treatment of debilitating stress-related mental health conditions such as major depressive disorder (MDD). Yet, the impact to, and involvement of, B lymphocytes in the response to stress is not well-understood, leaving a fundamental gap in our knowledge underlying the immune theory of depression. Several emerging clinical and preclinical findings highlight pronounced consequences for B cells in stress and MDD and may indicate key roles for B cells in modulating mood. This review will describe the clinical and foundational observations implicating B cell-psychological stress interactions, discuss potential mechanisms by which B cells may impact brain function in the context of stress and mood disorders, describe research tools that support the investigation of their neurobiological impacts, and highlight remaining research questions. The goal here is for this discussion to illuminate both the scope and limitations of our current understanding regarding the role of B cells, stress, mood, and depression.

Stress-induced immunosuppression affecting immune response to Newcastle disease virus vaccine through "miR-155-CTLA-4" pathway in chickens

MiR-155 and CTLA-4 are important factors involved in the regulation of immune function. However, there is no report about their involvement in function regulation of stress-induced immunosuppression affecting immune response. In this study, the chicken model of stress-induced immunosuppression affecting immune response (simulation with dexamethasone and immunization with Newcastle disease virus (NDV) attenuated vaccine) was established, then the expression characteristics of miR-155 and CTLA-4 gene were analyzed at several key time points during the processes of stress-induced immunosuppression affecting NDV vaccine immune response at serum and tissue levels. The results showed that miR-155 and CTLA-4 were the key factors involved in stress-induced immunosuppression and NDV immune response, whose functions involved in the regulation of immune function were different in different tissues and time points, and 2 day post immunization (dpi), 5dpi and 21dpi were the possible key regulatory time points. CTLA-4, the target gene of miR-155, had significant game regulation relationships between them in various tissues, such as bursa of Fabricius, thymus and liver, indicating that miR-155-CTLA-4 pathway was one of the main mechanisms of their involvement in the regulations of stress-induced immunosuppression affecting NDV immune response. This study can lay the foundation for in-depth exploration of miR-155-CTLA-4 pathway involved in the regulation of immune function.

The emerging role non-coding RNAs in B cell-related disorders

Long non-coding RNAs and microRNAs have recently attained much attention regarding their role in the development of B cell lineage as well as participation in the lymphomagenesis. These transcripts have a highly cell type specific signature which endows them the potential to be used as biomarkers for clinical situations. Aberrant expression of several non-coding RNAs has been linked with B cell malignancies and immune related disorders such as rheumatoid arthritis, systemic lupus erythematous, asthma and graft-versus-host disease. Moreover, these transcripts can alter response of immune system to infectious conditions. miR-7, miR-16-1, miR-15a, miR-150, miR-146a, miR-155, miR-212 and miR-132 are among microRNAs whose role in the development of B cell-associated disorders has been investigated. Similarly, SNHG14, MALAT1, CRNDE, AL133346.1, NEAT1, SMAD5-AS1, OR3A4 and some other long non-coding RNAs participate in this process. In the current review, we describe the role of non-coding RNAs in B cell malignancies.

Immune-microbiome interplay and its implications in neurodegenerative disorders

The neurodegeneration and its related CNS pathologies need an urgent toolbox to minimize the global mental health burden. The neuroimmune system critically regulates the brain maturation and survival of neurons across the nervous system. The chronic manipulated immunological drive can accelerate the neuronal pathology hence promoting the burden of neurodegenerative disorders. The gut is home for trillions of microorganisms having a mutual relationship with the host system. The gut-brain axis is a unique biochemical pathway through which the gut residing microbes connects with the brain cells and regulates various physiological and pathological cascades. The gut microbiota and CNS communicate using a common language that synchronizes the tuning of immune cells. The intestinal gut microbial community has a profound role in the maturation of the immune system as well as the development of the nervous system. We have critically summarised the clinical and preclinical reports from the past a decade emphasising that the significant changes in gut microbiota can enhance the host susceptibility towards neurodegenerative disorders. In this review, we have discussed how the gut microbiota-mediated immune response inclines the host physiology towards neurodegeneration and indicated the gut microbiota as a potential future candidate for the management of neurodegenerative disorders.

Stress-induced immunosuppression increases levels of certain circulating miRNAs and affects the immune response to an infectious bursal disease virus vaccine in chickens

Stress-induced immunosuppression can affect the immune effect of vaccine. However, the mechanism of stress-induced immunosuppression affecting immune response to infectious bursal disease virus (IBDV) vaccine in chicken is still unclear. In this study, thirteen IBDV related circulating miRNAs were selected to study their expressions, possible functions and mechanisms in dexamethasone (Dex)-induced immunosuppressed chicken vaccinated with IBDV attenuated vaccine. The experiment aimed to explore the relationship between the expressions of IBDV related circulating miRNAs and stress-induced immunosuppression. The quantitative real-time PCR (qRT-PCR) results showed that Dex-induced immunosuppression could induce the differential expressions of the candidate serum circulating miRNAs, especially on the 2nd, 5th, 7th and 28th day after dexamethasone treatment. Dex-induced immunosuppression could affect the immune response to the IBDV vaccine, which was possibly achieved by partially regulating the differential expressions of the IBDV related circulating miRNAs. Bioinformatics analysis showed that the candidate miRNAs could regulate the immune function mainly through targeting genes (such as CREB1 and MAPK1) in TGF-β and MAPK signaling pathways. This study can provide a preliminary reference for further studying the function and mechanism of circulating miRNAs in immune regulation.

Glucocorticoid circadian rhythms in immune function

Adrenal glucocorticoid (GC) hormones are important regulators of energy metabolism, brain functions, and the immune system. Their release follows robust diurnal rhythms and GCs themselves serve as entrainment signals for circadian clocks in various tissues. In the clinics, synthetic GC analogues are widely used as immunosuppressive drugs. GC inhibitory effects on the immune system are well documented and include suppression of cytokines and increased immune cell death. However, the circadian dynamics of GC action are often neglected. Synthetic GC medications fail to mimic complex GC natural rhythms. Several recent publications have shown that endogenous GCs and their daily concentration rhythms prepare the immune system to face anticipated environmental threats. That includes migration patterns that direct specific cell population to organs and tissues best exemplified by the rhythmic expression of chemoattractants and their receptors. On the other hand, chronotherapeutic approaches may benefit the treatment of immunological diseases such as asthma. In this review, we summarise our current knowledge on the circadian regulation of GCs, their role in innate and adaptive immune functions and the implications for the clinics.

Silencing MicroRNA-155 Attenuates Kainic Acid-Induced Seizure by Inhibiting Microglia Activation

OBJECTIVE(S)

Neuroinflammation is an important contributor to the development of seizures and epilepsy. Micro-RNA-155 (miR-155) plays a critical role in immunity and -inflammation. This study aims to explore the function of miR-155 and miR-155-mediated inflammation in epilepsy.

METHODS

About 8-week-old male C57BL/6 mice were administered an intraperitoneal injection (i.p.) of kainic acid (KA) (15 mg/kg) or saline. The mice in the KA group developing acute seizure were further subjected to intracerebroventricular injection (i.c.v.) of antagomir negative control (NC) or miR-155 antagomir. Animal behavior was observed according to Racine's scale, and electroencephalographs were recorded. Primary microglia were cultured and treated with antagomir NC or antagomir. Whole-cell electrophysiological recording was conducted to detect the spontaneous EPSCs and IPSCs in the neurons treated with different conditioned medium from those microglia. miR-155 were detected by qRT-PCR in those models, as well as in the brain or blood from epileptic patients and healthy controls.

RESULTS

miR-155 was abundantly expressed in glial cells compared with neurons, and its expression was markedly elevated in the brain of epilepsy patients and KA-induced seizure mice. Silencing miR-155 attenuated KA-induced seizure, abnormal electroencephalography, proinflammatory cytokine expression, and microglia morphology change. Moreover, conditioned media from KA-treated microglia impaired neuron excitability, whereas conditioned media from KA and miR-155 antagomir co-treated microglia had no such effects. Finally, miR-155 levels were significantly higher in the blood of epilepsy patients than those of healthy controls.

CONCLUSION(S)

These findings demonstrate that aberrant upregulation of miR-155 contributes to epileptogenesis through inducing microglia neuroinflammation.