Chronic Innate Immune Activation Research Articles

Control of innate immunity and lipid biosynthesis in neurodegeneration.

The cGAS-STING innate immunity pathway and the SREBP-activated cholesterol and fatty acid synthesis pathway are abnormally co-regulated in neurodegenerative disease. Activation of STING signaling occurs at the endoplasmic reticulum (ER) membrane with STING anchored by INSIG1 along with SREBP and the sterol-bound SREBP cleavage activating protein (SCAP) when sterols are in abundance. When sterols are low, the INSIG-dependent STING pathway is inactivated and the SREBP-SCAP complex is translocated to the Golgi where SREBP is cleaved and translocated to the nucleus to transactivate genes for cholesterol and fatty acid synthesis. Thus, there is inverse activation of STING vs. SREBP: when innate immunity is active, pathways for cholesterol and fatty acid synthesis are suppressed, and vice versa. The STING pathway is stimulated by foreign viral cytoplasmic nucleic acids interacting with the cyclic GMP-AMP synthase (cGAS) DNA sensor or RIG-I and MDA5 dsRNA sensors, but with neurodegeneration innate immunity is also activated by self-DNAs and double-stranded RNAs that accumulate with neuronal death. Downstream, activated STING recruits TBK1 and stimulates the transactivation of interferon stimulated genes and the autophagy pathway, which are both protective. However, chronic activation of innate immunity contributes to microglia activation, neuroinflammation and autophagy failure leading to neurodegeneration. STING is also a proton channel that when activated stimulates proton exit from STING vesicles leading to cell death. Here we review the salient features of the innate immunity and cholesterol and fatty acid synthesis pathways, observations of abnormal STING and SREBP signaling in neurodegenerative disease, and relevant therapeutic approaches.

PET Imaging of Innate Immune Activation Using 11C Radiotracers Targeting GPR84.

Chronic innate immune activation is a key hallmark of many neurological diseases and is known to result in the upregulation of GPR84 in myeloid cells (macrophages, microglia, and monocytes). As such, GPR84 can potentially serve as a sensor of proinflammatory innate immune responses. To assess the utility of GPR84 as an imaging biomarker, we synthesized 11C-MGX-10S and 11C-MGX-11Svia carbon-11 alkylation for use as positron emission tomography (PET) tracers targeting this receptor. In vitro experiments demonstrated significantly higher binding of both radiotracers to hGPR84-HEK293 cells than that of parental control HEK293 cells. Co-incubation with the GPR84 antagonist GLPG1205 reduced the binding of both radiotracers by >90%, demonstrating their high specificity for GPR84 in vitro. In vivo assessment of each radiotracer via PET imaging of healthy mice illustrated the superior brain uptake and pharmacokinetics of 11C-MGX-10S compared to 11C-MGX-11S. Subsequent use of 11C-MGX-10S to image a well-established mouse model of systemic and neuro-inflammation revealed a high PET signal in affected tissues, including the brain, liver, lung, and spleen. In vivo specificity of 11C-MGX-10S for GPR84 was confirmed by the administration of GLPG1205 followed by radiotracer injection. When compared with 11C-DPA-713-an existing radiotracer used to image innate immune activation in clinical research studies-11C-MGX-10S has multiple advantages, including its higher binding signal in inflamed tissues in the CNS and periphery and low background signal in healthy saline-treated subjects. The pronounced uptake of 11C-MGX-10S during inflammation, its high specificity for GPR84, and suitable pharmacokinetics strongly support further investigation of 11C-MGX-10S for imaging GPR84-positive myeloid cells associated with innate immune activation in animal models of inflammatory diseases and human neuropathology.

AIM/CD5L ameliorates autoimmune arthritis by promoting removal of inflammatory DAMPs at the lesions

The hallmark of autoimmune arthritis is the preceding autoantibody production and the following synovial inflammation with hyperplasia and tissue destruction of the joints. The joint inflammation is mediated not only by effector lymphocytes and auto-antibodies but also chronic activation of innate immunity, particularly promoted by the danger-associated molecular patterns (DAMPs). Here we show that apoptosis inhibitor of macrophage (AIM, also called CD5L) protein regulates arthritis by promoting removal of lesional DAMPs both physiologically and therapeutically. When the autoimmune arthritis was promoted by injecting a cocktail of anti-collagen antibodies without type-II collagen immunization, AIM-deficient (AIM−/−) mice exhibited more exacerbated and sustained swelling at multiple joints with greater synovial hyperplasia and bone erosion than wild-type mice. Administration of recombinant AIM (rAIM) reduced S100A8/9, a major DAMP known to be involved in arthritis progression, and decreased various inflammatory cytokines at the lesions in antibody-injected AIM−/− mice, leading to marked prevention of arthritis symptoms. In human rheumatoid arthritis (RA) patients, AIM was more activated via dissociating from IgM-pentamer in response to DAMPs-mediated inflammation both in serum and synovial fluid than in healthy individuals or non-autoimmune osteoarthritis patients, suggesting a disease-regulatory potency of AIM also in human RA patients. Thus, our study implied a therapeutic availability of rAIM to prevent arthritis symptoms targeting DAMPs.

Adult female acne: relevance and possible solutions

In recent years, there has been an increase in the proportion of AFA in the structure of acne incidence. The etiopathogenesis of the disease is multicomponent and has not been fully elucidated. It is assumed that hormonal factors and chronic activation of innate immunity are involved in the process against the background of genetic predisposition, which are stimulated by external environmental factors: daily stress, Western-style diet, tobacco use, hormonal drugs, cosmetics. The article presents a modern classification of the clinical course of AFA and scales for assessing the severity of the course of the disease: GEA (Global Acne Severity Scale) and AFAST (Adult Female Acne Scoring Tool). AFA is predominantly characterized by a mild or moderate course. Treatment requires a personalized approach with particular attention to the individual needs and characteristics of adult women. When choosing a topical therapy, the doctor should consider the less pronounced oiliness of the skin, the slow progression of the disease with the outcome in hyperpigmentation and scarring. Modern acne treatment regimens include systemic and topical therapy along with proper basic skin care. The most effective topical agents include retinoids, which can induce a specific biological response by binding and activating retinoic acid receptors. Comedonal and mild papulopustular acne are indications for adapalene monotherapy for acne in adult women. Adaklin (0.1% adapalene) cream is a highly effective first choice for the pathogenetic treatment of AFA. Rational mono- and combination therapy with adapalene is the key to successful external therapy of mild and moderate AFA and prevention of post-acne. The review provided up-to-date, evidence-based information on the clinical presentation, etiopathogenesis, and treatment of adult female acne (AFA).

Innate immune function during antineoplastic treatment is associated with 12-months survival in non-small cell lung cancer.

The immune system has proven to be a key player in the progression as well as containment of cancer with new treatment strategies based on immunotherapy targeting this interaction. Assessing immune function could reveal critical information about the immune response to therapeutic interventions, revealing predictive biomarkers for tailored care and precision medicine. We investigated immune function in 37 patients with inoperable non-small cell lung cancer (NSCLC) undergoing treatment with PD-L1 immune checkpoint inhibitor (ICI), chemotherapy (CT) or chemo-radiotherapy (CT/RT). Blood samples before (day 0) and during therapy (day 7, 21 and 80) were investigated by a standardized immunoassay, TruCulture®. Outcomes revealed a developing innate immune response induced by both immunotherapy and chemotherapy. NSCLC-patients displayed evidence of chronic innate immune activation and exhaustion prior to treatment. This pattern was particularly pronounced during treatment in patients dying within 12-months follow-up. Compared to treatment with CT, ICI demonstrated a higher ex vivo-stimulated release of proinflammatory cytokines. These preliminary findings may pave the way for tailored treatment and immune-monitoring.

Cellular resistance to an oncolytic virus is driven by chronic activation of innate immunity

The emergence of cellular resistances to oncolytic viruses is an underexplored process that could compromise the efficacy of cancer virotherapy. Here, we isolated and characterized B16 mouse melanoma cells that evolved resistance to an oncolytic vesicular stomatitis virus (VSV-D51). RNA-seq revealed that resistance was associated to broad changes in gene expression, which typically involved chronic upregulation of interferon-stimulated genes. Innate immunity activation was maintained in the absence of the virus or other infection signals, and conferred cross-resistance to wild-type VSV and the unrelated Sindbis virus. Furthermore, we identified differentially expressed genes with no obvious role in antiviral immunity, such as Mnda, Psmb8 and Btn2a2, suggesting novel functions for these genes. Transcriptomic changes associated to VSV resistance were similar among B16 clones and in some clones derived from the mouse colon carcinoma cell line CT26, suggesting that oncolytic virus resistance involves certain conserved mechanisms and is therefore a potentially predictable process.

CD36 expression intensity on different subpopulations of circulating monocytes depending on the extent of subclinical atherosclerosis

It is known that chronic activation of innate immunity and persistent low-intensity inflammation play a crucial role in the initiation and progression of atherosclerosis. It was found that atherogenic lipoproteins can act as inducers of the inflammatory response through ligand-receptor interaction with pattern-recognizing receptors of immunocompetent cells, such as CD36 (SR-B2) and Toll-like receptors. It is suggested that expression of CD36 on circulating monocytes may represent the burden of systemic atherosclerosis and, therefore, act as its diagnostic marker. The aim of the present study was to assess the intensity of CD36 expression on circulating monocytes of different subpopulations in patients without established cardiovascular disease (CVD) depending on the extent of subclinical atherosclerosis of peripheral arteries. One hundred patients without established atherosclerotic CVD, 49 (49.0%) men and 51 (51.0%) women, were included in the study. Monoclonal antibody conjugates were used to phenotype monocyte subpopulations. The expression of CD36 on CD14++CD16- monocytes (classical monocytes), CD14+CD16+ monocytes (intermediate monocytes), CD14+CD16++ monocytes (non-classical monocytes) was determined by the average fluorescence intensity. There was a statistically significant decrease in CD36 expression intensity on classical and non-classical monocytes with increasing number of vascular basins affected by atherosclerosis. A statistically significant decrease in CD36 expression intensity on classical and non-classical monocytes was found in the patients with two vascular beds lesions in comparison with patients with a single vascular bed lesion upon pairwise comparisons.

Intensity of CD36 expression by monocyte subpopulations and blood lipid spectrum parameters in patients without established atherosclerotic cardiovascular disease

Introduction. At the current stage of the study of atherosclerosis, it has been established that chronic activation of innate immunity, causing persistent low-intensity sterile inflammation, plays a crucial role at all stages of atherogenesis. Laboratory evaluation of signaling pathways associated with molecular patterns (DAMPs) in atherosclerosis and related to cardiovascular diseases (CVD) may contribute to the discovery of new diagnostic and prognostic markers. Objective: to study the relationship between lipid metabolism parameters and CD36 exposure to circulating monocytes in patientwithout established CVD. Material and methods . The study included 42 patients aged 40–64 years without established atherosclerotic CVD, 19 (45.2 %) men and 23 (54.7 %) women. Dyslipidemia was detected in 95.2 % of patients. The blood serum concentrations of total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, glucose, glycated hemoglobin, high-sensitivity C-reactive protein (hs-CRP), creatinine were determined with subsequent calculation of glomerular filtration rate. Phenotyping of circulating monocyte subpopulations was performed by flow cytometry on a Navios 6/2 device (Beckman Coulter, USA). Results and discussion . According to the results of correlation analysis, non-HDL cholesterol levels were inversely correlated with absolute ( r = –0.394; p = 0.013) and relative ( r = –0.432; p = 0.006) content of CD14 + CD16 ++ CD36 + TLR2 + monocytes. LDL cholesterol levels were also inversely correlated with the relative content of CD14 + CD16 + CD36 + TLR2 + monocytes ( r = –0.417; p = 0.018). According to correlation analysis, the level of non-HDL cholesterol inversely correlated with the intensity of CD36 expression on classical ( r = –0.650; p < 0.0001), intermediate ( r = –0.323; p = 0.045) and non classical ( r = –0.480; p = 0.002) monocytes. Also, CD36 expression intensity on classical ( r = –0.449; p = 0.004) and non-classical ( r = –0.382; p = 0.016) monocytes was inversely correlated with remnant cholesterol levels. In addition, increased non-HLA cholesterol levels were associated with decreased TLR2 expression on CD14 + CD16 ++ monocytes ( r = –0.381; p = 0.018). It should be noted that a decrease in CD36 expression on intermediate monocytes was also associated with an increase in hs-CRP ( r = –0.657; p = 0.003). Conclusion . In patients without established atherosclerotic CVD, an increase in cholesterol content of atherogenic lipoprotein fractions was associated with a decrease in the number of CD14 + CD16 ++ and CD14 + CD16 + monocytes co-expressing CD36 and TLR2 as well as with a decrease in CD36 expression on classical, intermediate and non-classical monocytes.

Hippo kinase loss contributes to del(20q) hematologic malignancies through chronic innate immune activation

AbstractHeterozygous deletions within chromosome 20q, or del(20q), are frequent cytogenetic abnormalities detected in hematologic malignancies. To date, identification of genes in the del(20q) common deleted region that contribute to disease development have remained elusive. Through assessment of patient gene expression, we have identified STK4 (encoding Hippo kinase MST1) as a 20q gene that is downregulated below haploinsufficient amounts in myelodysplastic syndrome (MDS) and myeloproliferative neoplasm (MPN). Hematopoietic-specific gene inactivation in mice revealed Hippo kinase loss to induce splenomegaly, thrombocytopenia, megakaryocytic dysplasia, and a propensity for chronic granulocytosis; phenotypes that closely resemble those observed in patients harboring del(20q). In a JAK2-V617F model, heterozygous Hippo kinase inactivation led to accelerated development of lethal myelofibrosis, recapitulating adverse MPN disease progression and revealing a novel genetic interaction between these 2 molecular events. Quantitative serum protein profiling showed that myelofibrotic transformation in mice was associated with cooperative effects of JAK2-V617F and Hippo kinase inactivation on innate immune-associated proinflammatory cytokine production, including IL-1β and IL-6. Mechanistically, MST1 interacted with IRAK1, and shRNA-mediated knockdown was sufficient to increase IRAK1-dependent innate immune activation of NF-κB in human myeloid cells. Consistent with this, treatment with a small molecule IRAK1/4 inhibitor rescued the aberrantly elevated IL-1β production in the JAK2-V617F MPN model. This study identified Hippo kinase MST1 (STK4) as having a central role in the biology of del(20q)-associated hematologic malignancies and revealed a novel molecular basis of adverse MPN progression that may be therapeutically exploitable via IRAK1 inhibition.

Chronic innate immune activation of TBK1 suppresses mTORC1 activity and dysregulates cellular metabolism

Three-prime repair exonuclease 1 knockout (Trex1-/-) mice suffer from systemic inflammation caused largely by chronic activation of the cyclic GMP-AMP synthase-stimulator of interferon genes-TANK-binding kinase-interferon regulatory factor 3 (cGAS-STING-TBK1-IRF3) signaling pathway. We showed previously that Trex1-deficient cells have reduced mammalian target of rapamycin complex 1 (mTORC1) activity, although the underlying mechanism is unclear. Here, we performed detailed metabolic analysis in Trex1-/- mice and cells that revealed both cellular and systemic metabolic defects, including reduced mitochondrial respiration and increased glycolysis, energy expenditure, and fat metabolism. We also genetically separated the inflammatory and metabolic phenotypes by showing that Sting deficiency rescued both inflammatory and metabolic phenotypes, whereas Irf3 deficiency only rescued inflammation on the Trex1-/- background, and many metabolic defects persist in Trex1-/-Irf3-/- cells and mice. We also showed that Leptin deficiency (ob/ob) increased lipogenesis and prolonged survival of Trex1-/- mice without dampening inflammation. Mechanistically, we identified TBK1 as a key regulator of mTORC1 activity in Trex1-/- cells. Together, our data demonstrate that chronic innate immune activation of TBK1 suppresses mTORC1 activity, leading to dysregulated cellular metabolism.

Chronic Activation of Innate Immunity Correlates With Poor Prognosis in Cancer Patients Treated With Oncolytic Adenovirus.

Despite many clinical trials conducted with oncolytic viruses, the exact tumor-level mechanisms affecting therapeutic efficacy have not been established. Currently there are no biomarkers available that would predict the clinical outcome to any oncolytic virus. To assess the baseline immunological phenotype and find potential prognostic biomarkers, we monitored mRNA expression levels in 31 tumor biopsy or fluid samples from 27 patients treated with oncolytic adenovirus. Additionally, protein expression was studied from 19 biopsies using immunohistochemical staining. We found highly significant changes in several signaling pathways and genes associated with immune responses, such as B-cell receptor signaling (P < 0.001), granulocyte macrophage colony-stimulating factor (GM-CSF) signaling (P < 0.001), and leukocyte extravasation signaling (P < 0.001), in patients surviving a shorter time than their controls. In immunohistochemical analysis, markers CD4 and CD163 were significantly elevated (P = 0.020 and P = 0.016 respectively), in patients with shorter than expected survival. Interestingly, T-cell exhaustion marker TIM-3 was also found to be significantly upregulated (P = 0.006) in patients with poor prognosis. Collectively, these data suggest that activation of several functions of the innate immunity before treatment is associated with inferior survival in patients treated with oncolytic adenovirus. Conversely, lack of chronic innate inflammation at baseline may predict improved treatment outcome, as suggested by good overall prognosis.

Light induces NLRP3 inflammasome activation in retinal pigment epithelial cells via lipofuscin-mediated photooxidative damage.

Photooxidative damage and chronic innate immune activation have been implicated in retinal pigment epithelium (RPE) dysfunction, a process that underlies blinding diseases such as age-related macular degeneration (AMD). To identify a potential molecular link between these mechanisms, we investigated whether lipofuscin-mediated phototoxicity activates the NLRP3 inflammasome in RPE cells in vitro. We found that blue light irradiation (dominant wavelength 448 nm, irradiance 0.8 mW/cm2, duration 6 h) of lipofuscin-loaded primary human RPE cells and ARPE-19 cells induced photooxidative damage, lysosomal membrane permeabilization (79.5 % of cells vs. 3.8 % in nonirradiated controls), and cytosolic leakage of lysosomal enzymes. This resulted in activation of the inflammasome with activation of caspase-1 and secretion of interleukin-1β (14.6 vs. 0.9 pg/ml in nonirradiated controls) and interleukin-18 (87.7 vs. 0.2 pg/ml in nonirradiated controls). Interleukin secretion was dependent on the activity of NLRP3, caspase-1, and lysosomal proteases cathepsin B and L. These results demonstrate that accumulation of lipofuscin-like material in vitro renders RPE cells susceptible to phototoxic destabilization of lysosomes, resulting in NLRP3 inflammasome activation and secretion of inflammatory cytokines. This new mechanism of inflammasome activation links photooxidative damage and innate immune activation in RPE pathology and may provide novel targets for therapeutic intervention in retinal diseases such as AMD.Key message• Visible light irradiation of lipofuscin-loaded RPE cells activates inflammasome.• Inflammasome activation results from lysosomal permeabilization and enzyme leakage.• Inflammasome activation induces secretion of inflammatory cytokines by RPE cells.• Photooxidative damage by visible light as new mechanism of inflammasome activation.• Novel link between hallmark pathogenetic features of retinal degenerative diseases.

Regulation of toll-like receptor signaling by the SF3a mRNA splicing complex.

The innate immune response plays a key role in fighting infection by activating inflammation and stimulating the adaptive immune response. However, chronic activation of innate immunity can contribute to the pathogenesis of many diseases with an inflammatory component. Thus, various negatively acting factors turn off innate immunity subsequent to its activation to ensure that inflammation is self-limiting and to prevent inflammatory disease. These negatively acting pathways include the production of inhibitory acting alternate proteins encoded by alternative mRNA splice forms of genes in Toll-like receptor (TLR) signaling pathways. We previously found that the SF3a mRNA splicing complex was required for a robust innate immune response; SF3a acts to promote inflammation in part by inhibiting the production of a negatively acting splice form of the TLR signaling adaptor MyD88. Here we inhibit SF3a1 using RNAi and subsequently perform an RNAseq study to identify the full complement of genes and splicing events regulated by SF3a in murine macrophages. Surprisingly, in macrophages, SF3a has significant preference for mRNA splicing events within innate immune signaling pathways compared with other biological pathways, thereby affecting the splicing of specific genes in the TLR signaling pathway to modulate the innate immune response.

Corticotrophin-Releasing Factor (CRF) and the urocortins are potent regulators of the inflammatory phenotype of human and mouse white adipocytes and the differentiation of mouse 3T3L1 pre-adipocytes.

Chronic activation of innate immunity takes place in obesity and initiated by the hypertrophic adipocytes which obtain a pro-inflammatory phenotype. The corticotrophin-releasing factor (CRF) family of neuropeptides and their receptors (CRF1 and CRF2) affect stress response and innate immunity. Adipose tissue expresses a complete CRF system. The aim of this study was to examine the role of CRF neuropeptides in the immune phenotype of adipocytes assessed by their expression of the toll-like receptor-4 (TLR4), the production of inflammatory cytokines IL-6, TNF-α and IL-1β, chemokines IL-8, monocyte attractant protein-1 (MCP-1) and of the adipokines adiponectin, resistin and leptin. Our data are as follows: (a) CRF, UCN2 and UCN3 are expressed in human white adipocytes as well as CRFR1a, CRFR2a and CRFR2b but not CRFR2c. 3T3L1 pre-adipocytes and differentiated adipocytes expressed both CRF1 and CRF2 receptors and UCN3, while UCN2 was detected only in differentiated adipocytes. CRF2 was up-regulated in mouse mature adipocytes. (b) CRF1 agonists suppressed media- and LPS-induced pre-adipocyte differentiation while CRF2 receptor agonists had no effect. (c) In mouse pre-adipocytes, CRF2 agonists suppressed TLR4 expression and the production of IL-6, CXCL1 and adiponectin while CRF1 agonists had no effect. (d) In mature mouse adipocytes LPS induced IL-6 and CXCL1 production and suppressed leptin. (e) In human visceral adipocytes LPS induced IL-6, TNF-α, IL-8, MCP-1 and leptin production and suppressed adiponectin and resistin. (f) In mouse mature adipocytes CRF1 and CRF2 agonists suppressed basal and LPS-induced production of inflammatory cytokines, TLR4 expression and adiponectin production, while in human visceral adipocytes CRF and UCN1 suppressed basal and LPS-induced IL-6, TNF-α, IL-8 and MCP-1 production. In conclusion, the effects of the activation of CRF1 and CRF2 may be significant in ameliorating the pro-inflammatory activity of adipocytes in obesity.

The HIV-1 protease inhibitor nelfinavir activates PP2 and inhibits MAPK signaling in macrophages: a pathway to reduce inflammation

The HIV-1 PI NFV has off-target effects upon host enzymes, including inhibition of the 20S proteasome, resulting in activation of PP1. HIV-1-associated monocyte/macrophage activation, in part a result of systemically elevated levels of microbial products including LPS, is associated with risk of mortality, independent of viremia or CD4 T cell loss. This study tested the hypothesis that activation of protein phosphatases by NFV would reduce activation of monocytes/macrophages through dephosphorylation of signal transduction proteins. NFV uniquely blocked LPS-induced production by human monocyte-derived macrophages of the inflammatory cytokines TNF and IL-6, as well as sCD14. Although NFV failed to modulate NF-κB, NFV treatment reduced phosphorylation of AKT and MAPKs. Inhibition of PP2 with okadaic acid blocked the anti-inflammatory effect of NFV, whereas the PP1 inhibitor calyculin A failed to counter the anti-inflammatory effects of NFV. For in vivo studies, plasma sCD14 and LPS were monitored in a cohort of 31 pediatric HIV-1 patients for over 2 years of therapy. Therapy, including NFV, reduced sCD14 levels significantly compared with IDV or RTV, independent of ΔLPS levels, VL, CD4 T cell frequency, or age. The hypothesis was supported as NFV induced activation of PP2 in macrophages, resulting in disruption of inflammatory cell signaling pathways. In vivo evidence supports that NFV may offer beneficial effects independent of antiviral activity by reducing severity of chronic innate immune activation in HIV-1 infection.

Extensive innate immune gene activation accompanies brain aging, increasing vulnerability to cognitive decline and neurodegeneration: a microarray study

BackgroundThis study undertakes a systematic and comprehensive analysis of brain gene expression profiles of immune/inflammation-related genes in aging and Alzheimer’s disease (AD).MethodsIn a well-powered microarray study of young (20 to 59 years), aged (60 to 99 years), and AD (74 to 95 years) cases, gene responses were assessed in the hippocampus, entorhinal cortex, superior frontal gyrus, and post-central gyrus.ResultsSeveral novel concepts emerge. First, immune/inflammation-related genes showed major changes in gene expression over the course of cognitively normal aging, with the extent of gene response far greater in aging than in AD. Of the 759 immune-related probesets interrogated on the microarray, approximately 40% were significantly altered in the SFG, PCG and HC with increasing age, with the majority upregulated (64 to 86%). In contrast, far fewer immune/inflammation genes were significantly changed in the transition to AD (approximately 6% of immune-related probesets), with gene responses primarily restricted to the SFG and HC. Second, relatively few significant changes in immune/inflammation genes were detected in the EC either in aging or AD, although many genes in the EC showed similar trends in responses as in the other brain regions. Third, immune/inflammation genes undergo gender-specific patterns of response in aging and AD, with the most pronounced differences emerging in aging. Finally, there was widespread upregulation of genes reflecting activation of microglia and perivascular macrophages in the aging brain, coupled with a downregulation of select factors (TOLLIP, fractalkine) that when present curtail microglial/macrophage activation. Notably, essentially all pathways of the innate immune system were upregulated in aging, including numerous complement components, genes involved in toll-like receptor signaling and inflammasome signaling, as well as genes coding for immunoglobulin (Fc) receptors and human leukocyte antigens I and II.ConclusionsUnexpectedly, the extent of innate immune gene upregulation in AD was modest relative to the robust response apparent in the aged brain, consistent with the emerging idea of a critical involvement of inflammation in the earliest stages, perhaps even in the preclinical stage, of AD. Ultimately, our data suggest that an important strategy to maintain cognitive health and resilience involves reducing chronic innate immune activation that should be initiated in late midlife.

Aging is associated with chronic innate immune activation and dysregulation of monocyte phenotype and function

Chronic inflammation in older individuals is thought to contribute to inflammatory, age-related diseases. Human monocytes are comprised of three subsets (classical, intermediate and nonclassical subsets), and despite being critical regulators of inflammation, the effect of age on the functionality of monocyte subsets remains to be fully defined. In a cross-sectional study involving 91 healthy male (aged 20-84 years, median 52.4) and 55 female (aged 20-82 years, median 48.3) individuals, we found age was associated with an increased proportion of intermediate and nonclassical monocytes (P = 0.002 and 0.04, respectively) and altered phenotype of specific monocyte subsets (e.g. increased expression of CD11b and decreased expression of CD38, CD62L and CD115). Plasma levels of the innate immune activation markers CXCL10, neopterin (P < 0.001 for both) and sCD163 (P = 0.003) were significantly increased with age. Whilst similar age-related changes were observed in both sexes, monocytes from women were phenotypically different to men [e.g. lower proportion of nonclassical monocytes (P = 0.002) and higher CD115 and CD62L but lower CD38 expression] and women exhibited higher levels of CXCL10 (P = 0.012) and sCD163 (P < 0.001) but lower sCD14 levels (P < 0.001). Monocytes from older individuals exhibit impaired phagocytosis (P < 0.05) but contain shortened telomeres (P < 0.001) and significantly higher intracellular levels of TNF both at baseline and following TLR4 stimulation (P < 0.05 for both), suggesting a dysregulation of monocyte function in the aged. These data show that aging is associated with chronic innate immune activation and significant changes in monocyte function, which may have implications for the development of age-related diseases.

Activation of innate immunity accelerates sialoadenitis in a mouse model for Sjögren’s syndrome‐like disease

Sjögren's syndrome is a chronic autoimmune disorder characterized by progressive lymphocytic infiltration within the salivary and lacrimal glands. This study was undertaken to investigate the effects of innate immunity activation on sialoadenitis in a mouse strain genetically susceptible for development of SS-like disease. Female New Zealand Black X New Zealand White F1 mice were repeatedly treated with toll-like 3 receptor agonist poly(I:C). Submandibular glands were investigated at different time points for sialoadenitis by immunohistochemistry and for gene expression of different chemokines by quantitative PCR. Submandibular gland-infiltrating cells were characterized by flow cytometry. Poly(I:C) treatment significantly upregulated the expression of multiple chemokines within the submandibular glands. The severity and incidence of sialoadenitis was considerably higher in poly(I:C)-treated mice. There was a preponderance of dendritic cells and NK cells in the initial inflammatory cell infiltrates, and these were followed by CD4+ T cells. Our data clearly demonstrate that systemic activation of innate immunity accelerates sialoadenitis in a mouse model for SS-like disease. These findings suggest that chronic activation of innate immunity can influence certain features of SS.

Repeated TLR9 stimulation results in macrophage activation syndrome–like disease in mice

Hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) are 2 similar diseases characterized by a cytokine storm, overwhelming inflammation, multiorgan dysfunction, and death. Animal models of HLH suggest that disease is driven by IFN-γ produced by CD8⁺ lymphocytes stimulated by persistent antigen exposure. In these models and patients with "primary" HLH, the antigen persists due to genetic defects, resulting in ineffective cytotoxic responses by CD8⁺ T cells and poor pathogen clearance. However, infectious triggers are often not identified in patients with MAS, and some patients with HLH or MAS lack defects in cytotoxic T cell killing. Herein, we show that repeated stimulation of TLR9 produced an HLH/MAS-like syndrome on a normal genetic background, without exogenous antigen. Like previous HLH models, TLR9-induced MAS was IFN-γ dependent; however, unlike other models, disease did not require lymphocytes. We further showed that IL-10 played a protective role in this model and that blocking IL-10 signaling led to the development of hemophagocytosis. IL-10 may therefore be an important target for the development of effective therapeutics for MAS. Our data provide insight into MAS-like syndromes in patients with inflammatory diseases in which there is chronic innate immune activation but no genetic defects in cytotoxic cell function.

Elevation of Soluble CD14 levels Supports Chronic Innate Immune Activation in Subjects with CVID, XLA, and SLE Compared to Healthy Subjects

Elevation of Soluble CD14 levels Supports Chronic Innate Immune Activation in Subjects with CVID, XLA, and SLE Compared to Healthy Subjects