The Innate Immunity in Alzheimer Disease- Relevance to Pathogenesis and Therapy.

The genetic, cellular, and molecular changes associated with Alzheimer disease provide evidence of immune and inflammatory processes involvement in its pathogenesis. These are supported by epidemiological studies, which show some benefit of long-term use of NSAID. The hypothesis that AD is in fact an immunologically mediated and even inflammatory pathological process may be in fact scientifically intriguing. There are several obstacles that suggest the need for more complex view, in the process of targeting inflammation and immunity in AD. In our previous studies we proposed a reliable methodology to assess innate immunity in Alzheimer patients and controls. The methodology is based on the phenomenon of human leukocytes being resistant to viral infection. The unspecific character of the resistance, dependent on interferons and tumor necrosis factor, and occurrence in cells ex vivo indicate that an in vivo mechanism of innate immunity may be involved. The above mentioned resistance could be estimated in a test based on peripheral blood leukocytes infection by vesicular stomachs virus.

Age- and disease-related innate immunity of human leukocytes ex vivo.

Two mechanisms of innate immunity, i.e. resistance to viral infection and the production of cytokines by leukocytes, were compared in blood isolated from four groups of donors: healthy young (19-35 years old), healthy elderly (over 60), elderly Alzheimer's disease (AD) patients, and elderly patients with alimentary tract cancer (CA). Peripheral blood leukocytes (PBLs) were isolated by gradient centrifugation in Gradisol G. The degree of resistance was calculated from the kinetics of vesicular stomatitis virus (VSV) replication in the PBLs. Cytokine (TNFα, IFNα, IFNγ, IL-12, and IL-10) levels were determined by ELISA. The antiviral resistance of the PBLs varied, but a difference was observed only between the young and elderly groups and not between the healthy elderly controls and those with AD or cancer. Differences observed in all the groups concerned the ability and intensity of cytokine production. The most impressive results were obtained for spontaneous TNF and IFNα release. While TNF was released spontaneously by the PBLs of the elderly CA patients and the young healthy group, it was usually undetected in the AD and only sometimes in the healthy elderly group. Leukocytes isolated from the elderly groups responded to VSV infection with more intense IFNα and IFNγ production than the younger group.

Flavones from root of Scutellaria baicalensis Georgi: drugs of the future in neurodegeneration?

Flavonoids are natural, plant-derived compounds which exert diverse biological activities, also valuable neuroprotective actions within the brain and currently are intensively studied as agents able to modulate neuronal function and to prevent age-related neurodegeneration. Among them, flavones isolated from Scutellaria baicalensis root exhibit strong neuroprotective effects on the brain and are not toxic in the broad range of tested doses. Their neuroprotective potential has been shown in both oxidative stress-induced and amyloid-beta and alpha-synuclein-induced neuronal death models. Baicalein, the main flavone present in Scutellaria baicalensis root, strongly inhibited aggregation of neuronal amyloidogenic proteins in vitro and induces dissolution of amyloid deposits. It exerts strong antioxidative and anti-inflammatory activities and also exhibits anti-convulsive, anxiolytic, and mild sedative actions. Importantly, baicalein, and also another flavone: oroxylin A, markedly enhanced cognitive and mnestic functions in animal models of aging brains and neurodegeneration. In the preliminary study, wogonin, another flavone from Scutellaria baicalensis root, has been shown to stimulate brain tissue regeneration, inducing differentiation of neuronal precursor cells. This concise review provides the main examples of neuroprotective activities of the flavones and reveals their potential in prevention and therapyof neurodegenerative diseases.

Production of cytokines and stimulation of resistance to viral infection in human leukocytes by Scutellaria baicalensis flavones.

Extracts of Scutellaria baicalensis display a wide spectrum of antiviral activity. It was of great interest to check the effect of baicalein and wogonin preparations on two important mechanisms of innate immunity: the secretion of cytokines and the natural resistance of human leukocytes to viral infection. To study the effect of S. baicalensis extracts on interferons (IFNs), tumor necrosis factor alpha (TNF-alpha), and interleukin (IL) production and virus replication, uninfected and vesicular stomatitis virus (VSV)-infected human peripheral blood leukocytes (PBLs) were used. Four pulverized preparations obtained from roots of Scutellaria and a Sigma-Aldrich preparation of purified baicalein were used in the study. RPMI extracts containing different amounts of baicalein and wogonin were used to study the effect on VSV replication in PBLs. PBLs express ex vivo individually differentiated cytokine-dependent resistance/innate immunity to viral infections. The degree of resistance was estimated on the basis of VSV replication in PBLs. The results obtained indicate that baicalein- and wogonin-containing extracts modulate cytokine production, that is inhibit IFN-alpha and IFN-gamma and stimulate TNF-alpha and IL (IL-12, IL-10) production. They also augment the resistance of PBLs to VSV. Extract from S. baicalensis containing baicalein and wogonin regulates the innate antiviral immunity by modulation of cytokine production and stimulation of human leukocyte resistance.

Effect of donepezil on innate antiviral immunity of human leukocytes.

BACKGROUND: The effect of donepezil on two mechanisms of innate immunity: leukocyte resistance to viral infection and cytokine production was studied. METHODS: The degree of natural resistance of human peripheral blood leukocytes (PBLs) was determined by studying the kinetics of vesicular stomatitis virus (VSV) replication. A titer of 0-1 log TCID(50) indicated complete resistance, 2-3 log partial resistance, and >4 lack of resistance. Cytokine levels were determined with use of ELISA test. NFkappaB activation was assayed by immunocytochemical staining. RESULTS: Preliminary study of VSV replication in the PBLs of Alzheimer's disease patients showed a high sensitivity to infection, except of PBL those under donepezil therapy. The PBL resistance stimulated us to study the effect of donepezil on innate immunity. Donepezil inhibited VSV replication in the leukocytes of healthy blood donors but influence on infection in L929 and A549 cells was not shown. The effect was dose dependent and individually differentiated. The production of TNFalpha and IFNs was reduced in infected leukocytes in a dose-dependent manner in the PBLs of the healthy blood donors and of AD patients. NFkappaB activation was also reduced by donepezil. CONCLUSIONS: Donepezil regulate two mechanisms of innate immunity of leukocytes: resistance to viruses and cytokine production.

Resistance of human leukocytes to vesicular stomatitis virus infection as one of the innate antiviral immune activities; participation of cell subpopulations.

Among reactions of innate immunity, resistance of human peripheral blood leukocytes (PBL) to viral infection seems important. The purpose of our study was to find, which of the subpopulations of PBL is the most responsible for the innate antiviral immunity of these cells. The innate immunity was measured by using the direct method of infection of leukocytes with vesicular stomatitis virus (VSV). The lack of VSV replication by infected leukocytes (0-1 log TCID50) was taken as an indicator for complete immunity; a low level of VSV (2-3 log) for partial immunity; and high VSV titer (more than 4 log) for no immunity. The resistance/innate immunity of whole PBL and subpopulations such as: adherent cells, fractions enriched in lymphocytes T, and lymphocytes B (separated on column with nylon wool), NK(+) and NK(-) (separated by microbeads activated cell sorting MACS) differ from each other. All fractions express higher resistance/innate immunity than the whole PBL. NK(+) cells were found the most resistant fraction of PBL to VSV infection. The results indicate that among the leukocytes in PBL the regulation mechanisms of innate immunity exist. The study on the mechanism of innate immunity regulation as well as the role of NK in innate immunity of PBL must be continued.

Cytokine production by human leukocytes with different expressions of natural antiviral immunity and the effect of antibodies against interferons and TNF-alpha.

INTRODUCTION: Two activities of innate antiviral immunity were studied: the resistance of human peripheral blood mononuclear cells (PMBCs) ex vivo to viral infection and the production of cytokines. MATERIALS AND METHODS: Samples of blood were taken from healthy blood donors and from persons with frequent infections of the upper respiratory system. PMBCs were isolated by gradient centrifugation. Vesicular stomatitis virus (VSV) was used as the indicatory virus to infect PMBCs. The cytokines: IFN, TNF, and IL-6 were titrated by biological methods and IL-10 by ELISA. RESULTS: Blood donors were divided for two groups: those with VSV-resistant and those with VSV-sensitive PMBCs and secretion of cytokines by them was compared. The resistant PMBCs produced more cytokines than the sensitive ones. A statistically significant difference, was found only in the case of the IFNs. To examine the contribution of IFNs and TNF in maintaining resistance, leukocytes from both groups were treated with specific anti-cytokine antibodies. The authors' previous study showed that the elimination of spontaneous IFN-alpha, IFN-beta, IFN-gamma, and TNF-alpha from resistant leukocytes resulted in increased VSV replication This indicates the important role of cytokines. In VSV-sensitive PMBCs, anti-IFN-alpha showed the opposite effect (decreased virus replication). In the absence of spontaneous IFN-alpha, disturbances in cytokine production were observed. CONCLUSIONS: Complete resistance of PMBC to VSV infection is accompanied by higher cytokine release, The paradoxical effect of anti-IFN-alpha on virus replication in leukocytes sensitive to viral infection may be attributed to changes in the cytokine profile balance, i.e. high TNF production by VSV-infected leukocytes and a complete reduction of IL-6 production.

Mechanisms of over-activated innate immune system regulation in autoimmune and neurodegenerative disorders.

Reactions of innate immunity include phagocytosis, the production and activity of cytokines, chemokines, and adhesion molecules, the killing of infected or changed cells by NK cells and complement activated by natural lectins, and the cytokine-dependent resistance of leukocytes to viral infection. All these mechanisms maintain innate immunity. Deficiency in this immunity is sometimes accompanied by frequent bacterial and viral infections. When innate immunity is permanently stimulated and the intensity of the reactions is stronger, these mechanisms may be directed against the host and subsequently stimulate acquired immunity (antibody and cellular immunity). A higher production of cytokines, oxidative stress, and a high production of NO accompany autoimmunity and neurodegeneration. The possible participation of innate immune receptors, cytokines, and other factors in the development of autoimmune and neurodegenerative diseases is discussed. The importance and possible role of blood-derived microglial cells in the prevention or elimination of amyloid deposits and plaque formation is described. A possible regulatory system, based on the presence of suppressors of cytokine signaling (SOCS), receptors of the Tyro-3 family, adenosine and adenosine phosphates, and IL-10, is reviewed. This review presents the mechanisms involved in the control of the innate immune response by microglia in the development of neurodegenerative disorders.

[Control of over-activated innate immunity]. / Mechanizmy kontroli odpornosci wrodzonej.

The basic reactions of innate immunity are reviewed. The mechanisms of innate immunity described are: phagocytosis, secretion and activity of cytokines, cytokine-dependent resistance of leukocytes to viral infections, the killing activity of NK cells independent on MHC, and killing by lectin-activated complement. Properly controlled, these mechanisms are responsible for maintaining homeostasis. Deficiency is frequently associated with the occurrence of infections or tumor diseases. On the other hand, over-activation is observed in autoimmunity, neurodegeneration, and inflammatory diseases. It is usually accompanied by elevated cytokine production, NO, oxidative stress, and the killing of cells. Therefore, the mechanisms which control the reactions of natural immunity are of importance for human and animal organisms. Natural mechanisms in human and animal organisms which mitigate these reactions are know. Among the mechanisms controlling innate immunity are cytokines (IL-10, TGFbeta), suppressors of cytokines signaling (SOCS), Tyro-3 receptors, and adenosine and adenosine phosphates. The possible participation of other mechanisms involved in controlling innate immunity are also considered.

Innate immunity: cells, receptors, and signaling pathways.

Essential differences between the innate and acquired branches of immunity are described. These differences concern the detection system (receptors and pathogen structures) and the cells engaged in both systems as well as the effectory mechanisms. In contrast to those of the acquired system, receptors of the innate system, which developed during evolution, recognize unchanged structures on large groups of pathogens (e.g. lipopolysaccharide in Gram-negative bacteria). Two lineages, natural killer (NK) and dendritic cells (DCs), play important roles in the innate system. Phenotypic and functional differentiation is observed among NKs and DCs, so each of their sublineages plays a different role in the innate system. Every lineage of cells of the innate immune system express different stimulatory and sometimes also inhibitory receptors on their surfaces (e.g. NK cells). Among the stimulatory are Toll-like receptors (TLRs), mannose and scavenger receptors, and the stimulatory receptors of NK cells. All TLRs show similarity in structure and in the kind of molecules involved in intracellular signaling. The immune reactions of the innate system involve cytokine-dependent resistance of cells against infection with pathogen, production of cytokines (tumor necrosis factor, interferons, interleukins, chemokines) and MHC-independent killing. Although these reactions protect the host from invasion by microorganisms, they can also be responsible for significant tissue damage or may stimulate the development of autoimmunity. Therefore innate immunity must be under rigorous control. The possible regulatory mechanisms of innate immunity are discussed.

[Mechanisms of innate immunity]. / Mechanizmy wrodzonej odpornosci.

Innate (natural) immunity differs from acquired immunity with respect to the detection systems (receptors and structures detected on pathogens), the cells engaged, and the nature of the mechanisms. Innate immunity is an ancient system, with similar structures in plants, invertebrates, and vertebrates are involved in the development of defense against pathogens. Toll-like receptor (TLR) structures are present in all organisms, and some mechanisms (i.e. complement activation) were also discovered in invertebrates and vertebrates. During infection, innate reactions develop before acquired immune reactions do. Natural immunity involves such reactions as the production of different cytokines, chemokines, and interleukins; the innate, cytokines-dependent nonspecific immunity of leukocytes; HLA-independent pathogen-killing cells, and phagocytosis. Such cytokines as interferons, the TNF family, and interleukines 12 and 18 participate in antiviral, antibacterial, antiprotozoan and anticancer natural immunity. NK cells, cytokines of the TNF family, and the complement system activated by lectins are engaged in the non-specific killing of infected or tumor cells. As over-activation of the innate system can be dangerous, the system must be submitted the strict control. The exact mechanism of this control system is not yet known, but there are several indications of its presence.

Age related natural antiviral non-specific immunity of human leukocytes.

BACKGROUND: The purpose of our study was to examine the dependence of innate antiviral immunity on age and sex in human leukocytes. MATERIAL/METHODS: Innate antiviral immunity was measured by using the direct method of infection of leukocytes with vesicular stomatitis virus (VSV), which was selected as the indicatory virus for detection of immunity. The lack of VSV replication by infected leukocytes (0-1 log TCID50) was taken as an indicator for complete immunity; a low level of VSV replication (2-3 log) for partial immunity; and a high VSV titer (4 or more log) for the no or very low immunity. RESULTS: The kinetics of VSV replication was studied in leukocytes isolated from 127 individuals ranging in a age from 0 to 89 years. Individual differentiation in the kinetics of VSV replication indicated differing degrees of innate immunity even in newborns. Age-related differences in natural immunity were observed: low immunity in newborns, highest in the age group 31-40, and reduced in the age group >60. Sex dependent innate immunity was shown in the group of aged persons, as innate immunity was higher in women than in men. CONCLUSIONS: Innate immunity of leukocytes develops to age 30-40, after which immunity is gradually reduced. Sex dependence was observed only in the group of elderly persons, where women expressed higher immunity; this is probably a reason for their statistically greater longevity.

Individual differentiation of innate antiviral immunity in humans; the role of endogenous interferons and tumor necrosis factor in the immunity of leukocytes.

The natural antiviral immunity of human lymphocytes, leukocytes from peripheral blood and whole-blood cultures was studied using the method of infection with two viruses belonging to different taxonomic groups, vesicular stomatitis virus (VSV) and encephalomyocarditis virus (EMCV). The kinetics of virus replication in the kinds of cultures and the dependence of culture infection on pre-infection incubation time were studied. When the cultures were infected immediately after preparation, most of them were found to be resistant to the viruses. However, when they were infected after several (1-5) days of incubation, VSV and EMCV multiplied in the cultures to high titers. The time of losing resistance was individually differentiated. The results indicate the presence of a non-specific antiviral immunity characteristic for individuals. The antiviral immunity of healthy donors was compared with that of people suffering from recurrent infections of the upper respiratory tract. This latter group expressed statistically significant lower innate immunity than healthy donors. However, there were no differences in interferon (IFN) and tumor necrosis factor (TNF) production between these groups. In order to examine the contribution of the endogenous IFNs and TNF-alpha in maintaining innate immunity, specific antibodies against IFN-alpha, IFN-beta, IFN-gamma and TNF-alpha were added to VSV-infected leukocytes resistant to infection. The antibodies reduced the antiviral resistance in 9 of 16 experiments. The results suggest that both endogenous interferons and TNF-alpha may participate in the constitution of innate immunity, though they are not the only mediators of it.