A role for interleukin 17A in IBD-related neuroplasticity

Chronic Effects of the Sympathetic Nervous System in Inflammatory Models

The immune system is embedded in a network of regulatory systems to keep homeostasis in case of an immunologic challenge. Neuroendocrine immunologic research has revealed several aspects of these interactions over the past decades, e.g., between the autonomic nervous system and the immune system. This review will focus on evidence revealing the role of the sympathetic nervous system (SNS) in chronic inflammation, like colitis, multiple sclerosis, systemic sclerosis, lupus erythematodes, and arthritis with a focus on animal models supported by human data. A theory of the contribution of the SNS in chronic inflammation will be presented that spans these disease entities. One major finding is the biphasic nature of the sympathetic contribution to inflammation, with proinflammatory effects until the point of disease outbreak and mainly anti-inflammatory influence thereafter. Since sympathetic nerve fibers are lost from sites of inflammation during inflammation, local cells and immune cells achieve the capability to endogenously produce catecholamines to fine-tune the inflammatory response independent of brain control. On a systemic level, it has been shown across models that the SNS is activated in inflammation as opposed to the parasympathetic nervous system. Permanent overactivity of the SNS contributes to many of the known disease sequelae. One goal of neuroendocrine immune research is defining new therapeutic targets. In this respect, it will be discussed that at least in arthritis, it might be beneficial to support β-adrenergic and inhibit α-adrenergic activity besides restoring autonomic balance. Overall, in the clinical setting, we now need controlled interventional studies to successfully translate the theoretical knowledge into benefits for patients.

Structural Changes in the Nervous Fibers of the Colon Mucosa in Experimental Acute Colitis

Morphological, morphometric, and ultrastructural analysis of the nerve fibers in the colon mucosa was performed in C57BL/6 mice at various terms of development of acute colitis induced by dextran sodium sulphate. The nerve fibers were labeled with antibodies to pan-neuronal marker βIII-tubulin. The progression of inflammatory and ulcerative processes in the mucosa on days 3-5 was associated with hyperplasia and hypertrophy of nerve fibers that peaked on day 7 after colitis induction. Ultrastructural analysis at all terms of colitis development showed moderate degeneration of axons. Thus, hypertrophy and hyperplasia of the nervous fibers in colon mucosa in experimental acute colitis correlated with aggravation of the ulcerative process in the mucosa. These changes are determined by alteration of histoarchitectonics and regenerative processes in the mucosa.

A ropy exopolysaccharide producing strain Bifidobacterium longum subsp. longum YS108R alleviates DSS-induced colitis by maintenance of the mucosal barrier and gut microbiota modulation

B. longum has been reported to exert an alleviative effect on colitis, but the results also suggested significant differences among strains. Here in this study, we compared the effect of B. longum subsp. longum strains with different properties in EPS production on DSS-induced colitis. To investigate the alleviative effect of a ropy-exopolysaccharide (EPS) producing strain, Bifidobacterium longum subsp. longum YS108R, on experimental colitis, C57BL/6J mice (male, 6-8 weeks old) were randomly assigned to six groups (n = 8): normal control, DSS colitis and four DSS colitis groups orally administered with three B. longum subsp. longum strains (YS108R, C11A10B and HAN4-25) and B. animalis subsp. lactis BB12, respectively, in which YS108R produced ropy-EPS, C11A10B produced non-ropy-EPS, HAN4-25 did not produce EPS and BB12 was set as a positive control. Ropy-EPS producing strain YS108R could alleviate the symptoms and remit inflammation induced by DSS, in which YS108R could decrease the pro-inflammatory cytokine IL-6 and IL-17A levels after DSS challenge (from 102 ± 45.22 to 37.95 ± 20.33 pg mL-1 and from 22.14 ± 5.43 to 12.58 ± 2.74, p < 0.05), but another non-ropy-EPS producing strain C11A10B did not decrease the levels of these pro-inflammatory cytokines. Furthermore, YS108R could maintain the expression levels of genes related to the mucosal barrier, but strain HAN4-25, a non-EPS producer, was not able to maintain the expression levels of these genes after DSS challenge. Analysis of gut microbiota showed that DSS treatment significantly increased the relative abundance of Enterobacteriaceae and Peptostreptococcaceae (0.2623 ± 0.162 and 0.0512 ± 0.0361) and decreased the relative abundance of S24-7 (0.042 ± 0.0326); however, YS108R administration could decrease the relative abundance of Enterobacteriaceae and Peptostreptococcaceae to 0.0848 ± 0.0399 and 0.0032 ± 0.0047 and increase the relative abundance of S24-7 to 0.2625 ± 0.0566 (p < 0.05). The results showed that B. longum subsp. longum YS108R could alleviate DSS-induced colitis by modulating the inflammation related cytokines, maintenance of the normal mucosal barrier and reverting the change of microbiota.

Neuroimmune Communication in Health and Disease

The immune and nervous systems are tightly integrated, with each system capable of influencing the other to respond to infectious or inflammatory perturbations of homeostasis. Recent studies demonstrating the ability of neural stimulation to significantly reduce the severity of immunopathology and consequently reduce mortality have led to a resurgence in the field of neuroimmunology. Highlighting the tight integration of the nervous and immune systems, afferent neurons can be activated by a diverse range of substances from bacterial-derived products to cytokines released by host cells. While activation of vagal afferents by these substances dominates the literature, additional sensory neurons are responsive as well. It is becoming increasingly clear that although the cholinergic anti-inflammatory pathway has become the predominant model, a multitude of functional circuits exist through which neuronal messengers can influence immunological outcomes. These include pathways whereby efferent signaling occurs independent of the vagus nerve through sympathetic neurons. To receive input from the nervous system, immune cells including B and T cells, macrophages, and professional antigen presenting cells express specific neurotransmitter receptors that affect immune cell function. Specialized immune cell populations not only express neurotransmitter receptors, but express the enzymatic machinery required to produce neurotransmitters, such as acetylcholine, allowing them to act as signaling intermediaries. Although elegant experiments have begun to decipher some of these interactions, integration of these molecules, cells, and anatomy into defined neuroimmune circuits in health and disease is in its infancy. This review describes these circuits and highlights continued challenges and opportunities for the field.