Apolipoprotein E isoform-dependent dendritic recovery of hippocampal neurons following activation of innate immunity

Background  

Innate immune activation, including a role for cluster of differentiation 14/toll-like receptor 4 co-receptors (CD14/TLR-4) co-receptors, has been implicated in paracrine damage to neurons in several neurodegenerative diseases that also display stratification of risk or clinical outcome with the common alleles of the apolipoprotein E gene (APOE): APOE2, APOE3, and APOE4. Previously, we have shown that specific stimulation of CD14/TLR-4 with lipopolysaccharide (LPS) leads to greatest innate immune response by primary microglial cultures from targeted replacement (TR) APOE4 mice and greatest p38MAPK-dependent paracrine damage to neurons in mixed primary cultures and hippocampal slice cultures derived from TR APOE4 mice. In contrast, TR APOE2 astrocytes had the highest NF-kappaB activity and no neurotoxicity. Here we tested the hypothesis that direct activation of CD14/TLR-4 in vivo would yield different amounts of paracrine damage to hippocampal sector CA1 pyramidal neurons in TR APOE mice.     

Association between variations in the <Emphasis Type="Italic">TLR4</Emphasis>gene and incident type 2 diabetes is modified by the ratio of total cholesterol to HDL-cholesterol

Background  

Toll-like receptor 4 (TLR4), the signaling receptor for lipopolysaccharides, is an important member of the innate immunity system. Since several studies have suggested that type 2 diabetes might be associated with changes in the innate immune response, we sought to investigate the association between genetic variants in the TLR4 gene and incident type 2 diabetes.     

APOE genotype-specific differences in the innate immune response

Apolipoprotein-E protein is an endogenous immunomodulatory agent that affects both the innate and the adaptive immune responses. Since individuals with the APOE4 gene demonstrate worsened pathology and poorer outcomes in many neurological disorders, we examined isoform-specific differences in the response of microglia, the primary cellular component of the brain's innate immune response, in detail. Our data demonstrate that microglia derived from APOE4/4 targeted replacement mice demonstrate a pro-inflammatory phenotype that includes altered cell morphology, increased NO production associated with increased NOS2 mRNA levels, and higher pro-inflammatory cytokine production (TNFα, IL-6, IL12p40) compared to microglia derived from APOE3/3 targeted replacement mice. The effect is gene dose-dependent and increases with the number of APOE4 gene alleles. The APOE genotype-specific immune profile observed in the microglial immune response is also observed in the cortex of aged APOE3/3 and APOE4/4 mice treated with lipopolysacchride (LPS) and in peripheral (peritoneal) macrophages. To determine if APOE4's action resulted from an isoform-specific difference in effective levels of the apolipoproteins, we generated mice expressing only a single allele of APOE3. Immune-stimulated macrophages from APOE3/0 mice demonstrated an increased inflammatory response compared to APOE3/3 mice, but less than in APOE4/4 mice. These data suggest that inhibition of inflammation depends upon the dose of apoE3 protein available and that apoE4 protein may alter inflammation partly by dose effects and partly by being qualitatively different than apoE3. Overall, these data emphasize the important role of apolipoprotein E and of the APOE genotype on the immune responses that are evident in most, if not all, neurological disease.     

Inhibition of CD1d‐mediated antigen presentation by the transforming growth factor‐β/Smad signalling pathway

CD1d‐mediated lipid antigen presentation activates a subset of innate immune lymphocytes called invariant natural killer T (NKT) cells that, by virtue of their potent cytokine production, bridge the innate and adaptive immune systems. Transforming growth factor (TGF‐β) is a known immune modulator that can activate the mitogen‐activated protein kinase p38; we have previously shown that p38 is a negative regulator of CD1d‐mediated antigen presentation. Several studies implicate a role for TGF‐β in the activation of p38. Therefore, we hypothesized that TGF‐β would impair antigen presentation by CD1d. Indeed, a dose‐dependent decrease in CD1d‐mediated antigen presentation and impairment of lipid antigen processing was observed in response to TGF‐β treatment. However, it was found that this inhibition was not through p38 activation. Instead, Smads 2, 3 and 4, downstream elements of the TGF‐β canonical signalling pathway, contributed to the observed effects. In marked contrast to that observed with CD1d, TGF‐β was found to enhance MHC class II‐mediated antigen presentation. Overall, these results suggest that the canonical TGF‐β/Smad pathway negatively regulates an important arm of the host's innate immune responses – CD1d‐mediated lipid antigen presentation to NKT cells.     

Effects of three consecutive days exercise on lymphocyte DNA damage in young men

Intense exercise affects the immune system. This study examines effects of three consecutive days of 1 h high-intensity exercise on lymphocyte counts, oxidative DNA damage, and apoptosis in young untrained (n = 8, 23.8 ± 3.2 years; UT) and endurance-trained (n = 8, 21.1 ± 3.7 years; TR) subjects. The subjects performed cycle ergometer exercise at 75% _boxclose_2 \dot{V}{\text{O}}_{2\max } 1 h daily for three consecutive days (exercise session). Blood samples were collected before exercise on the first day of the exercise session (day 1, D1) and at 24 h after the session (day 4, D4). Total lymphocyte counts, a lymphocyte oxidative DNA damage index using Comet assay with human 8-oxoguanine DNA glycosylase, oxidative stress markers, and apoptosis markers were measured. Lymphocyte counts at D1 in TR were significantly lower than in UT. Lymphocyte counts in TR changed little at D4 (from 1,988 ± 475 to 1,854 ± 363 cell/μl), but the lymphocyte counts in UT decreased significantly at D4 (from 2,583 ± 564 to 1,911 ± 528 cell/μl, P < 0.05). Lymphocyte oxidative DNA damage increased concomitantly with exercise sessions in both the groups (UT, from 31.3 ± 17.5 to 48.9 ± 15.7%; TR, from 21.9 ± 5.2 to 62.1 ± 12.5%, P < 0.05). Although no change was found in apoptosis markers over time, Annexin-V⁺ cells decreased in TR (effect size D = 0.8 is large). Three consecutive days of 1 h exercise decreased lymphocyte counts with increased lymphocyte oxidative DNA damage in UT. Lymphocyte counts remained unchanged irrespective of increased oxidative DNA damage in TR. Decreased lymphocyte apoptosis might prevent the decrease of lymphocytes in TR.     

The D9N,N291S and S447X variants in the lipoprotein lipase (LPL) gene are not associated with Type III Hyperlipidemia

Background  

Type III hyperlipidemia (Type III HLP) is associated with homozygosity for the ε2 allele of the APOE gene. However only about 10% of ε2 homozygotes develop Type III HLP and it is assumed that additional genetic and/or environmental factors are required for its development. Common variants in the LPL gene have been proposed as likely genetic co-factors.     

Toll-like receptor 4-dependent upregulation of cytokines in a transgenic mouse model of Alzheimer's disease

Background  

Aβ deposits in the brains of patients with Alzheimer's disease (AD) are closely associated with innate immune responses such as activated microglia and increased cytokines. Accumulating evidence supports the hypothesis that innate immune/inflammatory responses play a pivotal role in the pathogenesis of AD: either beneficial or harmful effects on the AD progression. The molecular mechanisms by which the innate immune system modulates the AD progression are not well understood. Toll-like receptors (TLRs) are first-line molecules for initiating the innate immune responses. When activated through TLR signaling, microglia respond to pathogens and damaged host cells by secreting chemokines and cytokines and express the co-stimulatory molecules needed for protective immune responses to pathogens and efficient clearance of damaged tissues. We previously demonstrated that an AD mouse model homozygous for a destructive mutation of TLR4 has increases in diffuse and fibrillar Aβ deposits as well as buffer-soluble and insoluble Aβ in the brain as compared with a TLR4 wild-type AD mouse model. Here, we investigated the roles of TLR4 in Aβ-induced upregulation of cytokines and chemokines, Aβ-induced activation of microglia and astrocytes and Aβ-induced immigration of leukocytes.     

Impaired Pneumovax-23<Emphasis Type="Italic">-</Emphasis>Induced Monocyte-Derived Cytokine Production in Patients with Common Variable Immunodeficiency

Introduction  

Streptococcus pneumoniae is one of the most common infectious pathogens in common variable immunodeficiency (CVID). Both innate and adaptive immune response appears to play a role in defense against S. pneumoniae. In mice, it has been established that TLR2 and macrophages-derived cytokines (IL-6, TNF-α) play a crucial role in defense against S. pneumoniae. In humans, monocyte/macrophage-derived cytokines in response to S. pneumoniae have not been studied. Patients with CVID respond poorly to Pneumovax-23 (containing all capsular polysaccharides) vaccination.     

Influenza-Induced Production of Interferon-Alpha is Defective in Geriatric Individuals

Background  

The majority of deaths (90%) attributed to influenza are in person’s age 65 or older. Little is known about whether defects in innate immune responses in geriatric individuals contribute to their susceptibility to influenza.     

Cloning and characterization of deer mouse (Peromyscus maniculatus) cytokine and chemokine cDNAs

Background  

Sin Nombre virus (SNV) establishes a persistent infection in the deer mouse, Peromyscus maniculatus. A strong antibody response occurs in response to SNV infection, but the role of the innate immune response is unclear. To address this issue, we have initiated an effort to identify and characterize deer mouse cytokine and chemokine genes. Such cytokines and chemokines are involved in various aspects of immunity, including the transition from innate to adaptive responses, type I and type II responses, recruitment of leukocytes to sites of infection, and production of mature cells from bone marrow progenitors.     

Does gamma-aminobutyric acid (GABA) influence the development of chronic inflammation in rheumatoid arthritis?

Background  

Recent studies have demonstrated a role for spinal p38 MAP kinase (MAPK) in the development of chronic inflammation and peripheral arthritis and a role for GABA in the inhibition of p38 MAPK mediated effects. Integrating these data suggests that GABA may play a role in downregulating mechanisms that lead to the production of proinflammatory agents such as interleukin-1, interleukin-6, and matrix metalloproteinase 3 – agents implicated in the pathogenesis of rheumatoid arthritis (RA). Genetic studies have also associated RA with members of the p38 MAPK pathway.     

Association study of functional genetic variants of innate immunity related genes in celiac disease

Background  

Recent evidence suggest that the innate immune system is implicated in the early events of celiac disease (CD) pathogenesis. In this work for the first time we have assessed the relevance of different proinflammatory mediators typically related to innate immunity in CD predisposition.     

Associations between cytotoxic T lymphocyte-associated antigen-4 polymorphisms and serum tumor necrosis factor-α and interferon-γ levels in patients with chronic hepatitis B virus infection

Background  

Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) polymorphism, which may affect host immune response including cytokines production, is thought to be associated with hepatitis B virus (HBV) infection. This study investigated the associations between CTLA4 polymorphism and serum tumor necrosis factor (TNF)-α and interferon (IFN)-γ levels in patients with chronic HBV infection.     

Modulation of Inflammasome Activity for the Treatment of Auto-inflammatory Disorders

Introduction  

The innate immune system orchestrates inflammatory responses to microorganisms or danger-associated molecular patterns generated, for example, by the deposition of uric acid in the joints of gout patients. The innate immune system comprises multiple germ-line encoded receptors, of which the nucleotide-binding domain and leucine-rich repeat containing receptors (NLRs) are crucial for the maturation of pro-inflammatory cytokines. NLRs oligomerize to form large multi-protein complexes termed inflammasomes that generate active caspase-1 fragments leading to the cleavage and secretion of mature cytokines such as IL-1β and IL-18.     

Sequencing of DC-SIGN promoter indicates an association between promoter variation and risk of nasopharyngeal carcinoma in cantonese

Background  

The dendritic cell-specific intercellular adhesion molecule 3 grabbing non-integrin (DC-SIGN) is an important pathogen recognition receptor of the innate immune system. DC-SIGN promoter variants play important role in the susceptibility to various infectious diseases. Nasopharyngeal carcinoma (NPC) is a malignancy that is common in southern China and whether DC-SIGN promoter variants have effects on susceptibility to NPC is still unknown. The aim of this study is to ascertain the potential involvement of DC-SIGN promoter single nucleotide polymorphisms (SNPs) in NPC susceptibility.     

A novel p38α MAPK inhibitor suppresses brain proinflammatory cytokine up-regulation and attenuates synaptic dysfunction and behavioral deficits in an Alzheimer's disease mouse model

Background  

An accumulating body of evidence is consistent with the hypothesis that excessive or prolonged increases in proinflammatory cytokine production by activated glia is a contributor to the progression of pathophysiology that is causally linked to synaptic dysfunction and hippocampal behavior deficits in neurodegenerative diseases such as Alzheimer's disease (AD). This raises the opportunity for the development of new classes of potentially disease-modifying therapeutics. A logical candidate CNS target is p38α MAPK, a well-established drug discovery molecular target for altering proinflammatory cytokine cascades in peripheral tissue disorders. Activated p38 MAPK is seen in human AD brain tissue and in AD-relevant animal models, and cell culture studies strongly implicate p38 MAPK in the increased production of proinflammatory cytokines by glia activated with human amyloid-beta (Aβ) and other disease-relevant stressors. However, the vast majority of small molecule drugs do not have sufficient penetrance of the blood-brain barrier to allow their use as in vivo research tools or as therapeutics for neurodegenerative disorders. The goal of this study was to test the hypothesis that brain p38α MAPK is a potential in vivo target for orally bioavailable, small molecules capable of suppressing excessive cytokine production by activated glia back towards homeostasis, allowing an improvement in neurologic outcomes.     

The APOE4 genotype alters the response of microglia and macrophages to 17beta-estradiol

The apolipoprotein E4 (APOE4) gene is a well-known risk factor for Alzheimer's disease (AD) and other neurological disorders. Post-menopausal women with AD who express at least one APOE4 gene have more severe neuropathology and worsened cognitive scores than their non-expressing counterparts. Since 17β-estradiol down-regulates inflammation as part of its neuroprotective role, we examined the effect of 17β-estradiol on the response of microglia to immune activation as a function of APOE genotype. Our data show that the anti-inflammatory activity of 17β-estradiol is significantly reduced in APOE4 targeted replacement mice compared to APOE3 mice. A significant interaction between APOE genotype and the response to 17β-estradiol was observed for NO and cytokine production by immune activated microglia. The genotype specific effect was not restricted to brain macrophages since peritoneal macrophages from APOE4 ovariectomized mice also demonstrated a significant difference in 17β-estradiol responsiveness. ERβ protein levels in APOE4 microglia were higher than APOE3 microglia, suggesting a difference in post-translational protein regulation in the presence of the APOE4 gene. Overall, our data indicate that the APOE genotype may be a critical component in assessing the effectiveness of 17β-estradiol's action and may impact the neuroprotective role of 17β-estradiol and of hormone replacement therapy on brain function when the APOE4 gene is expressed.     

The variation of AkT/TSC1-TSC1/mTOR signal pathway in hepatocytes after partial hepatectomy in rats

Objective

The aim of this study was to investigate the role and regulatory mechanisms of Akt/TSC1-TSC2/mTOR signal pathway on the hepatocyte growth and proliferation after partial hepatectomy in rats.

Methods

We used the animal model of 70% hepatectomy, separated and cultivated hepatocytes. According to the different time points after partial hepatectomy, it could be grouped into 0 h, 2 h, 6 h, 24 h and 72 h. According to the different kinds of specific inhibitor in the nutritive medium after the separation of hepatocytes, it could be grouped into Triciribine (TR), Rapamycin (RA) and Control (CO). We investigated ³H-Leucine incorporation into protein, the cross section areas of hepatocytes, and detected cell cycle through FCM. The expressions of phosphorylated protein TSC2 and mTOR were observed.

Results

(1) The content of phosphorylated protein TSC2 in group CO began to increase at 2 h and got to the peak at 6 h but declined at 24 h. The content of phosphorylated protein TSC2 in group RA had the same variation with that of phosphorylated protein TSC2 in group CO. (2) At the time point of 0 h, 2 h, 6 h and 24 h after operation, the incorporation efficiency of ³H-Leucine in groups RA and TR was different from that in group CO in statistics (P < 0.01). (3) It could be seen that the cross section areas of hepatocytes in groups RA and TR were different from that in group CO in statistics at 2 h and 6 h after operation (P < 0.05). (4) Comparing with the other two inhibitor groups (TR and RA), the number of cells during the period of G₀/G₁ in group CO became fewer, while the number of cells during the period of S and G₂/M grew obviously (referring to Fig. 8). After operation, each time point was different from the inhibitor groups obviously (P < 0.05 or P < 0.01). The peak declined greatly at 24 h and 72 h after operation.

Conclusions

These data strongly suggest the effects of Akt/TSC1-TSC2/mTOR signal pathway on hepatocyte growth, protein synthesis and cell cycle, and prove its contribution to liver regeneration.     

Tumor-infiltrating macrophages and dendritic cells in human colorectal cancer: relation to local regulatory T cells, systemic T-cell response against tumor-associated antigens and survival

Introduction  

Although systemic T-cell responses against tumor antigens and tumor infiltration by T cells have been investigated in colorectal cancer (CRC), the initiation of spontaneous immune responses in situ is not well understood. Macrophages and dendritic cells (DC) play an important role as a link between innate and adaptive immune response. The aim of the present study was to analyze macrophage and DC infiltration in CRC and to investigate whether there is a correlation to systemic T-cell response, regulatory T cell (Treg) infiltration, and survival.     

Role of NOD2 in regulating the immune response to Aspergillus fumigatus

Background  

The nucleotide-binding oligomerization domain-2 (NOD2) is a type of intracellular receptor recognizing the cell wall molecules of bacteria and inducing the innate immune response. Its role in defense against fungal infection remains uncertain. We thus investigated the role of the NOD2/RIP2 pathway in host responses to Aspergillus fumigatus (Af) in RAW264.7 cells.