Increased alcohol self-administration following repeated Toll-like receptor 3 agonist treatment in male and female rats

Toll-like receptor (TLR) signaling may play an important role in the involvement of the neuroimmune system in the development and maintenance of alcohol use disorder. In the present study we administered TLR3 agonist poly(I:C) in male and female Long-Evans rats to determine whether TLR3 agonism can increase alcohol consumption in a daily 15% alcohol operant self-administration paradigm. We found few effects when poly(I:C) was given every-other-day at 0.3 or 1.0 mg/kg, however when instead 1.0 mg/kg was given on consecutive days alcohol intake increased in the days following injections specifically in females. Furthermore, in a second experiment we found that this effect only emerged when rats had a history of multiple poly(I:C) injections. In the final experiment the dose was increased to 3.0 mg/kg on consecutive days which resulted in significant reductions on injection days in females that were not accompanied by subsequent increases. The dose was increased to 9 mg/kg for one final pair of injections which led to reductions in intake in both males and females but only increased subsequent alcohol consumption in males. Overall, poly(I:C) was able to increase subsequent alcohol consumption in both sexes, with females being sensitive to lower doses than males both in terms of changes in alcohol consumption and general locomotor reduction. These findings show that TLR3 agonism may be involved in driving increased alcohol consumption and add to the body of work identifying the neuroimmune system as a potential therapeutic target for AUD.

Alzheimer’s Disease, Sleep Disordered Breathing, and Microglia: Puzzling out a Common Link

Sleep Disordered Breathing (SDB) and Alzheimer’s Disease (AD) are strongly associated clinically, but it is unknown if they are mechanistically associated. Here, we review data covering both the cellular and molecular responses in SDB and AD with an emphasis on the overlapping neuroimmune responses in both diseases. We extensively discuss the use of animal models of both diseases and their relative utilities in modeling human disease. Data presented here from mice exposed to intermittent hypoxia indicate that microglia become more activated following exposure to hypoxia. This also supports the idea that intermittent hypoxia can activate the neuroimmune system in a manner like that seen in AD. Finally, we highlight similarities in the cellular and neuroimmune responses between SDB and AD and propose that these similarities may lead to a pathological synergy between SDB and AD.

EMBRIOGENESIS OF NEURONAL ELENENTS (GLIOBLASTS AND GABAA RECEPTORS) IN THE HUMAN BRAIN NEUROIMMUNE SYSTEM UNDER PRENATAL ALCOHOL EXPOSURE

Exposure to alcohol causes imbalances in neuroimmune function and impaired brain development. Alcohol activates the innate immune signaling pathways in the brain. Neuroimmune molecules expressed and secreted by glial cells of the brain (microglia, oligodendroglia) alter the function of neurons and further stimulate the development of alcoholic behavior. Various signaling pathways and brain cells are involved in the transmission of neuroimmune signals. Glial cells are the main sources of immune mediators in the brain, which respond to and release immune signals in the central nervous system. The aim of this study was to study neuronal elements: morphometric parameters of glioblasts, synaptic structures and properties of synaptosomal GABAA-benzodiazepine receptors of the neuroimmune system in the embryogenesis of the human brain under perinatal exposure to alcohol. Changes in glioblasts in the brain tissue of human embryos and fetuses were revealed under conditions of chronic prenatal alcoholization with an increase in gestational age compared with control subgroups: a significant increase in the average number of glioblasts, the length of the perimeters of presynaptic terminal structures, postsynaptic density, presynaptic terminal regions were significantly less (p < 0.01) in the study group than in the control comparison group. Exposure to ethanol leads to a decrease in the affinity of GABAA-benzodiazepine receptors, which affects neuronal plasticity associated with the development and differentiation of progenitor cells (glioblasts and neuroblasts) during embryogenesis of the human brain and leads to suppression of GABAergic function in the brain. This causes a disruption in the interconnection of embryonic cells in the brain, leads to excessive apoptosis due to the activation of glial cells of the nervous tissue, disruption of neuroimmune function in the developing brain, changes in neuronal circuits, as well as a change in the balance of excitatory and inhibitory effects, which affects the functional activity in the central nervous system. Glial activation is a compensatory reaction caused by neuroplastic changes aimed at adapting the developing brain of the embryo and fetus under conditions of neurotoxicity and hypoxia under the influence of prenatal alcoholization of the maternal organism and the effect of ethanol on the fetus. The dynamics of changes in glial elements and receptor activity in the nervous tissue of human embryos and fetuses under conditions of prenatal exposure to alcohol indicates a more pronounced effect of alcohol on the earliest stages of human embryo development, which is of great practical importance in planning pregnancy and the inadmissibility of alcoholization of the mother in order to avoid negative consequences in offspring.

Regulating Systems in Neuroimmunology

Neuroimmunology is the study of the interaction between the immune system and nervous system during development, homeostasis, and disease states. Descriptions of neuroinflammatory diseases dates back centuries. However, in depth scientific investigation in the field began in the late 19th century and continues into the 21st century. Contrary to prior dogma in the field of neuroimmunology, there is immense reciprocal crosstalk between the brain and the immune system throughout development, homeostasis, and disease states. Proper neuroimmune functioning is necessary for optimal health, as the neuroimmune system regulates vital processes including neuronal signaling, synapse pruning, and clearance of debris and pathogens within the central nervous system. Perturbations in optimal neuroimmune functioning can have detrimental consequences for the host and underlie a myriad of physical, cognitive, and behavioral abnormalities. As such, the field of neuroimmunology is still relatively young and dynamic and represents an area of active research and discovery.

Neuroinflammation in Late-Onset Schizophrenia: Viewing from the Standpoint of the Microglia Hypothesis

Schizophrenia develops mainly in adolescence, but late-onset schizophrenia (LOS) is not uncommon. According to the international consensus, schizophrenia which develops over 40 years old is called LOS and psychosis which develops over 60 years old is called very late-onset schizophrenia-like psychosis (VLOS). Compared to early-onset schizophrenia (EOS) that develops before the age of 40 years, LOS and VLOS are reported to be more common in women, and there are clinically clear differences such as less involvement of genetic factors than EOS. This review outlines the abnormalities of the neuroimmune system in the pathophysiology of LOS, especially focusing on the role of microglia.

Serotonin Pathway in Neuroimmune Network

Once considered merely as a neurotransmitter, serotonin (5-HT) now enjoys a renewed reputation as an interlocutor in the dense and continuous dialogue between neuroendocrine and immune systems. In the last decades, a role has been depicted for serotonin and its derivatives as modulators of several immunological events, due to the expression of specific receptors or enzymes controlling 5-HT metabolism in diverse immune cell types. A growing body of evidence suggests that the effects of molecules belonging to the 5-HT pathways on the neuroimmune communication may be relevant in the clinical outcome of autoimmune/inflammatory pathologies of the central nervous system (CNS), such as multiple sclerosis, but also in Alzheimer’s disease, or in mood disorders and major depression. Moreover, since the predominance of 5-HT is produced by enterochromaffin cells of the gastrointestinal tract, where 5-HT and its derivatives are important mucosal signalling molecules giving rise to the so-called “brain-gut axis”, alterations in brain-gut communication are also involved in the pathogenesis and pathophysiology of several psychiatric and neurologic disorders. Here we illustrate how functional interactions between immune and neuronal cells are crucial to orchestrate tissue homeostasis and integrity, and the role of serotonin pathway components as pillars of the neuroimmune system.

HMGB1gene expression changes in the striatum and amigdal of the rat's brain under alcoholization and ethanol withdrawal

Intracellular signaling mediated by the HMGB1 protein, an agonist of TLRs, is considered as a possible target for the correction of pathologies of the neuroimmune system, however, the expression level of the Hmgb1 gene has not been previously studied in various brain structures of rats exposed to prolonged alcoholization followed by ethanol withdrawal. The study showed that long-term use of ethanol caused to an increase in the level of Hmgb1 mRNA in the striatum of rat brain. Alcohol withdrawal changed the level Hmgb1 mRNA in the striatum and amygdala on the 1st and 14th day. The data obtained may indicate that in different structures of the brain there are multidirectional changes in the molecular mechanisms of the neuroimmune response with prolonged use of ethanol and its withdrawal.