Effects of acute and repeated exposure to lipopolysaccharide on cytokine and corticosterone production during remyelination

Icaritin Promotes Myelination by Simultaneously Enhancing the Proliferation and Differentiation of Oligodendrocyte Precursor Cells

Myelin repair, which is known as remyelination, is critical to the treatment of neurodegenerative diseases, and myelination depends on not only the differentiation of oligodendrocyte precursor cells toward oligodendrocytes but also the renewal of oligodendrocyte precursor cells under pathological conditions. However, simultaneously promoting the differentiation and proliferation of oligodendrocyte precursor cells in lesions remains an unmet challenge and might affect demyelinating diseases. Kidney-tonifying herbs of traditional Chinese medicine (TCM) are effective in improving the symptoms of degenerative patients. However, herbs or compounds with dual functions are unverified. The purpose of this study was to find a kidney-tonifying TCM that synchronously improved the differentiation and proliferation of oligodendrocyte precursor cells under pathological conditions. Compounds with dual functions were screened from highly frequently used kidney-tonifying TCM, and the effects of the obtained compound on remyelination were investigated in an in vitro oligodendrocyte precursor cell differentiation model under pathological conditions and in demyelinating mice in vivo. The compound icaritin, which is an active component of Yin-Yang-Huo (the leaves of Epimedium brevicornu Maxim), demonstrated multiple effects on the remyelination process, including enhancing oligodendrocyte precursor cell proliferation, facilitating the differentiation of neural progenitor cells toward oligodendrocyte precursor cells and further toward oligodendrocytes, and maturation of oligodendrocytes under corticosterone- or glutamate-induced pathological conditions. Importantly, icaritin effectively rescued behavioral functions and increased the formation of myelin in a cuprizone-induced demyelination mouse model. The multiple effects of icaritin make it a promising lead compound for remyelination therapy.

Reaction of different cell types of the brain on neurotoxin cuprizone and hormone melatonin treatment in young and aging mice

Introduction

The brain myelin and neurons destruction in multiple sclerosis may be associated with the production of neuroinflammatory cells (macrophages, astrocytes, T-lymphocytes) of pro-inflammatory cytokines and free radicals. The age-associated changes of the above cells can influence on the response of nervous system cells to toxic damaging and regulatory factors of humoral/endocrine nature, in particular pineal hormone melatonin. The study aim was (1) to evaluate changes of the brain macrophages, astrocytes, T-cells, neural stem cells, neurons, and central nervous system (CNS) functioning in the neurotoxin cuprizone-treated mice of different age; and (2) to assess in such mice the effects of exogenous melatonin and possible courses of its action.

Methods

A toxic demyelination and neurodegeneration model was induced in 129/Sv mice aged 3-5 and 13-15 months by adding cuprizone neurotoxin to their food for 3 weeks. From the 8th day of the cuprizone treatment, melatonin was injected intraperitoneally at 6 p.m. daily, at a dose of 1 mg/kg. The brain GFPA + -cells were evaluated by immunohistochemical method, the proportion of CD11b+, CD3+CD11b+, CD3+, CD3+CD4+, CD3+CD8+, Nestin+-cells was determined via flow cytometry. Macrophage activity was evaluated by their ability to phagocytose latex beads Morphometric analysis of the brain neurons and the behavioral reactions ("open field" and rotarod tests) were performed. To assess the involvement of the bone marrow and thymus in the action of melatonin, the amount of granulocyte/macrophage colony-forming cells (GM-CFC), and blood monocytes and thymic hormone thymulin were evaluated.

Results and discussion

The numbers of the GFAP+-, CD3+-, CD3+CD4+, CD3+CD8+, CD11b+, CD3+CD11b+, Nestin+-cells and macrophages phagocytic latex beads and malondialdehyde (MDA) content were increased in the brain of young and aging mice under cuprizone influence. The proportion of undamaged neurons within the brain, motor, affective, and exploratory activities, and muscle tone decreased in mice of both ages. Introducing melatonin to mice of any age reduced the number of GFAP+-, CD3+- cells and their subpopulations, macrophage activation, and MDA content. At the same time, the percentage of brain neurons that were unchanged increased as the number of Nestin+ cells decreased. The behavioral responses were also improved. Besides, the number of bone marrow GM-CFC and the blood level of monocytes and thymulin increased. The effects of both neurotoxin and melatonin on the brain astrocytes, macrophages T-cells, and immune system organs as well as the structure and functioning of neurons were more pronounced in the young mice.

Conclusion

We have observed the involvement of the astrocytes, macrophages, T-cells, neural stem cells, and neurons in the brain reaction of mice different age after administration of neurotoxin cuprizone and melatonin. The brain cell composition reaction has the age features. The neuroprotective effects of melatonin in cuprizone-treated mice have been realized through an improvement of the brain cell composition and oxidative stress factors and functioning of bone marrow and thymus.

LPS tolerance prevents anxiety-like behavior and amygdala inflammation of high-fat-fed dams' adolescent offspring

Maternal high-fat diets (HFD) can generate inflammation in the offspring's amygdala, which can lead to anxiety-like behaviors. Conversely, lipopolysaccharide (LPS) tolerance can reduce neuroinflammation in the offspring caused by maternal high-fat diets. This study evaluated the combination of LPS tolerance and high-fat maternal diet on amygdala's inflammatory parameters and the anxiety-like behavior in adolescent offspring. Female pregnant Wistar rats received randomly a standard diet or a high-fat diet during gestation and lactation. On gestation days 8, 10, and 12, half of the females in each group were intraperitonially injected with LPS (0.1 mg.kg-1). After weaning, the male offspring (n = 96) were placed in individual boxes in standard conditions, and when 6 weeks-old, the animals underwent: Open-Field, Light/Dark Box, Elevated Plus-Maze, and Rotarod tests. When 50 days-old the offspring were euthanized and the amygdala removed for cytokine and redox status analysis. The offspring in the HFD group showed lower amygdala IL-10 levels, high IL-6/IL-10 ratio, and anxiety-like behaviors. These effects were attenuated in the HFD offspring submitted to LPS tolerance, which showed an anti-inflammatory compensatory response in the amygdala. Also, this group showed a higher activity of the enzyme catalase in the amygdala. In addition, receiving the combination of LPS tolerance and maternal HFD did not lead to anxiety-like behavior in the offspring. The results suggest that LPS tolerance attenuated amygdala inflammation through an anti-inflammatory compensatory response besides preventing anxiety-like behavior caused by the high-fat maternal diet.

Infection as an Environmental Trigger of Multiple Sclerosis Disease Exacerbation

Over the past several decades, significant advances have been made in identifying factors that contribute to the pathogenesis of multiple sclerosis (MS) and have culminated in the approval of some effective therapeutic strategies for disease intervention. However, the mechanisms by which environmental factors, such as infection, contribute to the pathogenesis and/or symptom exacerbation remain to be fully elucidated. Relapse frequency in MS patients contributes to neurological impairment and, in the initial phases of disease, serves as a predictor of poor disease prognosis. The purpose of this review is to examine the evidence that supports a role for peripheral infection in modulating the natural history of this disease. Evidence supporting a role for infection in promoting exacerbation in animal models of MS is also reviewed. Finally, a few mechanisms by which infection may exacerbate symptoms of MS and other neurological diseases are discussed. Those who comprise the majority of MS patients acquire approximately two upper-respiratory infections per year; furthermore, this type of infection doubles the risk for MS relapse, underscoring the contribution of this relationship as being potentially important and particularly detrimental.

Effect of honey bee venom on lewis rats with experimental allergic encephalomyelitis, a model for multiple sclerosis

Multiple sclerosis (MS) is a progressive and autoimmune neurodegenerative disease of the central nervous system (CNS). This disease is recognized through symptoms like inflammation, demyelination and the destruction of neurological actions. Experimental allergic encephalomyelitis (EAE) is a widely accepted animal model for MS. EAE is created in animals by injecting the tissue of myelin basic protein (MBP), CNS, or myelin oligodendrocyte glycoprotein (MOG) along with the adjuvant. EAE and MS are similar diseases. Honey Bee venom (Apis mellifera) contains a variety of low and high molecular weight peptides and proteins, including melittin, apamin, adolapin, mast cell degranulating peptide and phospholipase A2. Bee venom (BV) could exert anti-inflammatory and antinociceptive effects on the inflammatory reactions. The guinea pig spinal cord homogenate (GPSCH) is with the Complete Freund's Adjuvant (CFA), consisting of 1 mg/mL Mycobacterium tuberculosis. It was used for inducting EAE in Lewis rats for creating the MS model. The hematoxylin and eosin and luxol fast blue methods were used respectively in analyses of inflammation and detection of demyelination in the central nervous system. Furthermore, the ELISA and the high performance liquid chromatography (HPLC) were used for the assessment of tumor necrosis factor alpha (TNF-α) and nitrate in rats serum. In this study, we indicated that the treatment of EAE with Bee venom decreased the symptoms of clinical disorder, pathological changes, inflammatory cell infiltration, demyelination in the central nervous system, level of serum TNF-α, and the serum nitrates in rat EAE induced through GPSCH.

Lipopolysaccharide delays demyelination and promotes oligodendrocyte precursor proliferation in the central nervous system

Systemic infection can influence the course in many diseases of the central nervous system (CNS) such as multiple sclerosis (MS), yet the relationship between infection outside the CNS and potential damage and/or protection within the CNS is still not understood. Activation of microglia is a characteristic feature of most CNS autoimmune disorders, including MS, and both protective and degenerative functions of microglia have been proposed. Hence, we analyzed the effects of a systemic inflammatory reaction induced by peripheral treatment with lipopolysaccharide (LPS) on microglial reaction and cuprizone induced de- and remyelination. We found that LPS administration delayed demyelination, which was linked with inhibition of microglial proliferation and reduced numbers of activated microglia. The phenotype of microglia changed as an increase of Toll-like receptor 4 was found. During remyelination, LPS treatment delayed the onset of myelin protein re-expression, but later there was a beneficial effect via an increase of proliferating oligodendrocyte precursor cells (OPC) and mature oligodendrocytes. Moreover, the expression of ciliary neurotrophic factor was increased in response to LPS, a growth factor known to mediate OPC proliferation. Additional experiments showed that the time window to induce LPS effects was limited and associated with the presence of microglia. In conclusion, LPS delayed demyelination and caused beneficial effects on remyelination via increasing the proliferation of OPC. These differences seem to be an effect of LPS induced microglial modulation and indicate that exposure to certain infectious agents within a given time window may be beneficial in promoting tissue repair.

Differential sensitivity to endotoxin exposure in young and middle-age mice

Aging can have a profound effect on the neurobehavioral response to immune activation; aged subjects are predisposed to greater deficits in performance and cognitive function in conjunction with an exaggerated neuroinflammatory response. While increased reactivity to an immune insult has been well characterized in aged subjects, the alterations that may exist by middle-age have not been thoroughly investigated. The present study compared the reactions of young (4-month) and middle-age (12-month) male BALB/c mice to an acute or repeated lipopolysaccharide (LPS) challenge(s). The data suggest that in some respects middle-aged mice are more sensitive to endotoxin exposure, as they show enhanced weight loss, splenic cytokine levels, and c-fos expression in the brain following acute LPS administration compared to younger mice. However, acute LPS exposure led to comparable decreases in locomotor activity in young and middle-aged mice. Following repeated LPS administration both age groups showed diminished behavioral and neural reactions to the final LPS challenge, indicating tolerance development. However, the immune system of the middle-aged mice was still mildly responsive to the final LPS exposure, as splenic levels of IL-1beta were significantly elevated. Collectively, the data suggest that middle-age subjects are more sensitive to an immune insult.

Prenatal exposure to lipopolysaccharide results in cognitive deficits in age-increasing offspring rats

Studies have suggested that maternal infection/inflammation maybe a major risk factor for neurodevelopmental brain damage. In the present study, we evaluated the effects of prenatal exposure to a low level of inflammatory stimulation lipopolysaccharide (LPS) repeatedly on spatial learning and memory performances in rat offspring's lifetime. Sixteen pregnant Sprague-Dawley rats were randomly divided into two groups. The rats in the LPS group were treated i.p. with LPS (0.79 mg/kg) at gestation day 8, 10 and 12; meanwhile the rats in the control group were treated with saline. After delivery, the rat offspring at 3- (young), 10- (adult) and 20-mon-old (aged) were allocated. Spatial learning and memory abilities were tested by Morris water maze. The structure of hippocampal CA1 region was observed by light microscopy. The expression of synaptophysin (SYP) and glial fibrillary acidic protein (GFAP) in hippocampal CA1 region were measured by immunohistochemistry. Results showed that the rat offspring of LPS group needed longer escape latency and path-length in the Morris water maze and presented a significant neuron loss, decreased expression of SYP, increased expression of GFAP in CA1 region in histological studies. All these changes were more significant with the age increasing. These findings support the hypothesis that maternal systemic inflammation may alter the state of astrocytes in rat offspring for a long time, the alteration may affect neurons and synapse development in neural system, increase the neurons' vulnerability to environment especially as the age increasing, at last result in distinct learning and memory impairment.