The vicious cycle governing the brain–immune system relationship in neurodegenerative diseases

Circulating cytotoxic immune cell composition, activation status and toxins expression associate with white matter microstructure in bipolar disorder

Patients with bipolar disorder (BD) show higher immuno-inflammatory setpoints, with in vivo alterations in white matter (WM) microstructure and post-mortem infiltration of T cells in the brain. Cytotoxic CD8+ T cells can enter and damage the brain in inflammatory disorders, but little is known in BD. Our study aimed to investigate the relationship between cytotoxic T cells and WM alterations in BD. In a sample of 83 inpatients with BD in an active phase of illness (68 depressive, 15 manic), we performed flow cytometry immunophenotyping to investigate frequencies, activation status, and expression of cytotoxic markers in CD8+ and tested for their association with diffusion tensor imaging (DTI) measures of WM microstructure. Frequencies of naïve and activated CD8+ cell populations expressing Perforin, or both Perforin and Granzyme, negatively associated with WM microstructure. CD8+ Naïve cells negative for Granzyme and Perforin positively associates with indexes of WM integrity, while the frequency of CD8+ memory cells negatively associates with index of WM microstructure, irrespective of toxins expression. The resulting associations involve measures representative of orientational coherence and myelination of the fibers (FA and RD), suggesting disrupted oligodendrocyte-mediated myelination. These findings seems to support the hypothesis that immunosenescence (less naïve, more memory T cells) can detrimentally influence WM microstructure in BD and that peripheral CD8+ T cells may participate in inducing an immune-related WM damage in BD mediated by killer proteins.

Vital role for primary healthcare providers: urgent need to educate the community about daily nutritional self-care to support immune function and maintain health

The importance of self-care to improve health and social well-being is well recognised. Nevertheless, there remains a need to encourage people to better understand how their body works, and how to keep it healthy. Because of its important role, part of this understanding should be based on why the immune system must be supported. This highly complex system is essential for defending against pathogens, but also for maintaining health throughout the body by preserving homeostasis and integrity. Accordingly, the immune system requires active management for optimal functioning and to reduce the risk of chronic diseases. In addition to regular exercise, healthy sleeping patterns, cultivating mental resilience, adequate nutrition through healthy and diverse dietary habits is key to the daily support of immune function. Diet and the immune system are closely intertwined, and a poor diet will impair immunity and increase the risk of acute and chronic diseases. To help elucidate the roles of primary healthcare providers in supporting individuals to engage in self-care, an international group of experts reviewed the evidence for the roles of the immune system in maintaining health and for nutrition in daily immune support, and discussed implications for population health and clinical practice.

Immunoception: the insular cortex perspective

To define the systemic neuroimmune interactions in health and disease, we recently suggested immunoception as a term that refers to the existence of bidirectional functional loops between the brain and the immune system. This concept suggests that the brain constantly monitors changes in immune activity and, in turn, can regulate the immune system to generate a physiologically synchronized response. Therefore, the brain has to represent information regarding the state of the immune system, which can occure in multiple ways. One such representation is an immunengram, a trace that is partially stored by neurons and partially by the local tissue. This review will discuss our current understanding of immunoception and immunengrams, focusing on their manifestation in a specific brain region, the insular cortex (IC).

Choroid plexus volume is enlarged in clinically isolated syndrome patients with optic neuritis

OBJECTIVES

We investigated choroid plexus (CP) volume in patients presenting with optic neuritis (ON) as a clinically isolated syndrome (CIS), compared to a cohort with established relapsing-remitting multiple sclerosis (RRMS) and healthy controls (HCs).

METHODS

Three-dimensional (3D) T1, T2-FLAIR and diffusion-weighted sequences were acquired from 44 ON CIS patients at baseline, 1, 3, 6 and 12 months after the onset of ON. Fifty RRMS patients and 50 HCs were also included for comparison.

RESULTS

CP volumes was larger in both ON CIS and RRMS groups compared to HCs, but not significantly different between ON CIS and RRMS patients (analysis of covariance (ANCOVA) adjusted for multiple comparisons). Twenty-three ON CIS patients who converted to clinically definite MS (MS) demonstrated CP volume similar to RRMS patients, but significantly larger compared to HCs. In this sub-group, CP volume was not associated with the severity of optic nerve inflammation or long-term axonal loss, not with brain lesion load. A transient increase of CP volume was observed following an occurrence of new MS lesions on brain magnetic resonance imaging (MRI).

INTERPRETATION

Enlarged CP can be observed very early in a disease. It transiently reacts to acute inflammation, but not associated with the degree of tissue destruction.

Ageing-Induced Decline in Primary Myeloid Cell Phagocytosis Is Unaffected by Optineurin Insufficiency

Optineurin is a ubiquitin-binding adaptor protein involved in multiple cellular processes, including innate inflammatory signalling. Mutations in optineurin were found in amyotrophic lateral sclerosis, an adult-onset fatal neurodegenerative disease that targets motor neurons. Neurodegeneration results in generation of neuronal debris, which is primarily cleared by myeloid cells. To assess the role of optineurin in phagocytosis, we performed a flow cytometry-based phagocytic assay of apoptotic neuronal debris and E. coli bioparticles in bone marrow-derived macrophages (BMDMs), and primary neonatal microglia from wild-type (WT) and optineurin-insufficient (Optn^470T) mice. We found no difference in phagocytosis efficiency and the accompanying cytokine secretion in WT and Optn^470T BMDMs and microglia. This was true at both steady state and upon proinflammatory polarization with lipopolysaccharide. When we analysed the effect of ageing as a major risk factor for neurodegeneration, we found a substantial decrease in the percentage of phagocytic cells and proinflammatory cytokine secretion in BMDMs from 2-year-old mice. However, this ageing-induced phagocytic decline was unaffected by optineurin insufficiency. All together, these results indicate that ageing is the factor that perturbs normal phagocytosis and proinflammatory cytokine secretion, but that optineurin is dispensable for these processes.