Role of phosphoinositide 3-kinase-Akt signaling pathway in the age-related cytokine dysregulation in splenic macrophages stimulated via TLR-2 or TLR-4 receptors

Akkermansia muciniphila attenuated lipopolysaccharide-induced acute lung injury by modulating the gut microbiota and SCFAs in mice

Gut microbiota are closely related to lipopolysaccharide (LPS)-induced acute lung injury (ALI). Akkermansia muciniphila (A. muciniphila) maintains the intestinal barrier function and regulates the balance of reduced glutathione/oxidized glutathione. However, it may be useful as a treatment strategy for LPS-induced lung injury. Our study aimed to explore whether A. muciniphila could improve lung injury by affecting the gut microbiota. The administration of A. muciniphila effectively attenuated lung injury tissue damage and significantly decreased the oxidative stress and inflammatory reaction induced by LPS, with lower levels of myeloperoxidase (MDA), enhanced superoxide dismutase (SOD) activity, decreased pro-inflammatory cytokine levels, and reduced macrophage and neutrophil infiltration. Moreover, A. muciniphila maintained the intestinal barrier function, reshaped the disordered microbial community, and promoted the secretion of short-chain fatty acids (SCFAs). A. muciniphila significantly downregulated the expression of TLR2, MyD88 and NF-kappa B (P < 0.05). Butyrate supplementation demonstrated a significant improvement in the inflammatory response (P < 0.05) and mitigation of histopathological damage in mice with ALI, thereby restoring the intestinal butyric acid concentration. In conclusion, our findings indicate that A. muciniphila inhibits the accumulation of inflammatory cytokines and attenuates the activation of the TLR2/Myd88/NF-κB pathway due to exerting anti-inflammatory effects through butyrate. This study provides an experimental foundation for the potential application of A. muciniphila and butyrate in the prevention and treatment of ALI.

Macrophages, Low-Grade Inflammation, Insulin Resistance and Hyperinsulinemia: A Mutual Ambiguous Relationship in the Development of Metabolic Diseases

Metabolic derangement with poor glycemic control accompanying overweight and obesity is associated with chronic low-grade inflammation and hyperinsulinemia. Macrophages, which present a very heterogeneous population of cells, play a key role in the maintenance of normal tissue homeostasis, but functional alterations in the resident macrophage pool as well as newly recruited monocyte-derived macrophages are important drivers in the development of low-grade inflammation. While metabolic dysfunction, insulin resistance and tissue damage may trigger or advance pro-inflammatory responses in macrophages, the inflammation itself contributes to the development of insulin resistance and the resulting hyperinsulinemia. Macrophages express insulin receptors whose downstream signaling networks share a number of knots with the signaling pathways of pattern recognition and cytokine receptors, which shape macrophage polarity. The shared knots allow insulin to enhance or attenuate both pro-inflammatory and anti-inflammatory macrophage responses. This supposedly physiological function may be impaired by hyperinsulinemia or insulin resistance in macrophages. This review discusses the mutual ambiguous relationship of low-grade inflammation, insulin resistance, hyperinsulinemia and the insulin-dependent modulation of macrophage activity with a focus on adipose tissue and liver.

A Mechanistic Exploratory Study on the Therapeutic Efficacy of Astragaloside IV Against Diabetic Retinopathy Revealed by Network Pharmacology

Purpose: Diabetic retinopathy (DR) is a serious complication of diabetes mellitus, which nearly happens to all the diabetic sufferers. This study aims to identify the preliminary molecular regulation involved in the therapeutic efficacy of astragaloside IV (AS- IV) for DR.

Methods: Diabetic rat models were established and treated with AS-IV. Optical coherence tomography (OCT) and Hematoxylin-eosin (HE) staining was employed to demonstrate the histopathological changes. The main targets of AS-IV were identified by searching from public databases of traditional Chinese medicine (GeneCards, PharmMapper and Swiss Target Prediction). Besides, disease targets of DR were also obtained by integrated data from GEO datasets and predicted from public databases. Protein-protein interaction (PPI) network was constructed by Cytoscape with overlapping genes and 10 core targets were selected, on which Gene Ontology (GO) along with Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were conducted. The interaction between AS-IV and these crucial genes were analyzed using molecular docking. RT-qPCR and western blot were used to verify the expression variation of core targets.

Results: OCT imaging and HE staining demonstrated that AS-IV administration significantly increased retinal thickness in diabetic rats, obviously alleviating DR induced histopathological changes as well as elevated blood glucose levels. 107 common targets of AS-IV and DR were determined after intersection. PPI network analysis filtered 10 hub genes potentially targeted by AS-IV, including VEGFA, CASP3, HIF1α, STAT3, CTNNB1, SRC, AKT1, EGFR, IL1β and IL6. Enrichment analysis indicated that these genes were mainly enriched in biological processes like T cell activation, epithelial cell proliferation and protein kinase B signaling, and involved in oxidative stress, apoptosis and inflammation-related pathways. The molecular docking prediction suggested that AS-IV exhibited stable binding to these core targets. In addition, mRNA levels of core targets in diabetic rats were differentially expressed before and after AS-IV treatment. Western blot further revealed that AS-IV treatment elevated DR-depressed protein levels of PI3K and AKT.

Conclusion: Our study elucidated the effect of AS-IV in attenuating retinopathy induced by diabetes in rats and preliminarily unveiled the therapeutic efficacy of AS-IV in the treatment of DR might be attributed to activation of PI3K-AKT signaling pathway.

Benznidazole Anti-Inflammatory Effects in Murine Cardiomyocytes and Macrophages Are Mediated by Class I PI3Kδ

Benznidazole (Bzl), the drug of choice in many countries for the treatment of Chagas disease, leads to parasite clearance in the early stages of infection and contributes to immunomodulation. In addition to its parasiticidal effect, Bzl inhibits the NF-κB pathway. In this regard, we have previously described that this occurs through IL-10/STAT3/SOCS3 pathway. PI3K pathway is involved in the regulation of the immune system by inhibiting NF-κB pathway through STAT3. In this work, the participation of PI3K in the immunomodulatory effects of Bzl in cardiac and immune cells, the main targets of Chagas disease, was further studied. For that, we use a murine primary cardiomyocyte culture and a monocyte/macrophage cell line (RAW 264.7), stimulated with LPS in presence of LY294002, an inhibitor of PI3K. Under these conditions, Bzl could neither increase SOCS3 expression nor inhibit the NOS2 mRNA expression and the release of NOx, both in cardiomyocytes and macrophages. Macrophages are crucial in the development of Chronic Chagas Cardiomyopathy. Thus, to deepen our understanding of how Bzl acts, the expression profile of M1-M2 macrophage markers was evaluated. Bzl inhibited the release of NOx (M1 marker) and increased the expression of Arginase I (M2 marker) and a negative correlation was found between them. Besides, LPS increased the expression of pro-inflammatory cytokines. Bzl treatment not only inhibited this effect but also increased the expression of typical M2-macrophage markers like Mannose Receptor, TGF-β, and VEGF-A. Moreover, Bzl increased the expression of PPAR-γ and PPAR-α, known as key regulators of macrophage polarization. PI3K directly regulates M1-to-M2 macrophage polarization. Since p110δ, catalytic subunit of PI3Kδ, is highly expressed in immune cells, experiments were carried out in presence of CAL-101, a specific inhibitor of this subunit. Under this condition, Bzl could neither increase SOCS3 expression nor inhibit NF-κB pathway. Moreover, Bzl not only failed to inhibit the expression of pro-inflammatory cytokines (M1 markers) but also could not increase M2 markers. Taken together these results demonstrate, for the first time, that the anti-inflammatory effect of Bzl depends on PI3K activity in a cell line of murine macrophages and in primary culture of neonatal cardiomyocytes. Furthermore, Bzl-mediated increase expression of M2-macrophage markers involves the participation of the p110δ catalytic subunit of PI3Kδ.

Network Pharmacology-Based Identification of Potential Targets of Lonicerae japonicae Flos Acting on Anti-Inflammatory Effects

Lonicerae japonicae flos (LJF) is widely used for the treatment of inflammation-related diseases in traditional Chinese medicine (TCM). To clarify the anti-inflammatory mechanism of LJF, 29 compounds with high content in LJF were selected for network pharmacology. Then, a comprehensive network pharmacology strategy was implemented, which involved compound-inflammation-target construction, protein-protein interaction (PPI) network analysis, and enrichment analysis. Finally, molecular docking and in vitro experiments were performed to verify the anti-inflammatory activity and targets of the key compound. As a result, 279 inflammation-associated proteins were identified, which are mainly involved in the AGE/RAGE signaling pathway in diabetic complications, the HIF-1 signaling pathway, the PI3K-AKT signaling pathway, and EGFR tyrosine kinase inhibitor resistance. A total of 12 compounds were linked to more than 35 targets, including apigenin, kaempferol, quercetin, luteolin, and ferulic acid. The results of molecular docking showed that AKT has the most binding activity, exhibiting certain binding activity with 10 compounds, including vanillic acid, protocatechuic acid, secologanic acid, quercetin, and luteolin; the results of qRT-PCR and WB confirmed that two key compounds, secologanic acid and luteolin, could significantly decrease the secretion of TNF-α and the AKT expression of RAW264.7 murine macrophages stimulated by LPS (lipopolysaccharide). These results demonstrate that the comprehensive strategy can serve as a universal method to illustrate the anti-inflammatory mechanisms of traditional Chinese medicine by identifying the pathways or targets.

Functional genomics of inflamm-aging and immunosenescence

The aging population is at a higher risk for age-related diseases and infections. This observation could be due to immunosenescence: the decline in immune efficacy of both the innate and the adaptive immune systems. Age-related immune decline also links to the concept of 'inflamm-aging,' whereby aging is accompanied by sterile chronic inflammation. Along with a decline in immune function, aging is accompanied by a widespread of 'omics' remodeling. Transcriptional landscape changes linked to key pathways of immune function have been identified across studies, such as macrophages having decreased expression of genes associated to phagocytosis, a major function of macrophages. Therefore, a key mechanism underlying innate immune cell dysfunction during aging may stem from dysregulation of youthful genomic networks. In this review, we discuss both molecular and cellular phenotypes of innate immune cells that contribute to age-related inflammation.

Long-term aerobic exercise training-induced anti-inflammatory response and mechanisms: Focusing on the toll-like receptor 4 signaling pathway

Toll-like receptor 4 (TLR-4), which regulate inflammatory reactions, has become a popular research topic in recent years. This article reviews the latest scientific evidence on the regulation of TLR-4 by regular aerobic exercise training. The literature shows that long-term regular aerobic exercise training can effectively attenuate the expression of TLR-4 in immune cells and regulate its downstream intracellular cascade, including the p38 and PI3K/Akt signaling pathways. This further reduces cytokines secretion by inflammatory cells, which enhances immune system. We consider that the scientific evidence that long-term aerobic exercise training improves the inflammatory response provides a reasonable basis for using aerobic exercise training as a treatment for patients.

Oxiracetam Offers Neuroprotection by Reducing Amyloid β-Induced Microglial Activation and Inflammation in Alzheimer's Disease

Background: Alzheimer's disease (AD) is characterized by amyloid beta (Aβ) accumulation in the brain, which triggers the activation of microglia; in turn, microglia release neuroinflammatory factors capable of damaging neurons. Thus, a therapeutic approach targeting this sustained microglia-induced inflammatory response deserves investigation. Here, we examined whether oxiracetam (ORC), a nootropic of the racetam family, can indirectly prevent Aβ-induced neurotoxicity by attenuating microglial activation.

Methods: Aβ42 oligomers were used to stimulate BV2 microglial cells, and the morphological changes and phagocytic capacity of BV2 cells were evaluated using fluorescence microscopy. We used quantitative reverse transcription polymerase chain reaction to assess the inhibitory effects of ORC on Aβ-induced mRNA levels of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α); enzyme-linked immunosorbent assay was used to examine the productions of these cytokines. We also assessed the mRNA level of inducible nitric oxide synthase and the production of nitric oxide (NO). The conditioned medium from BV2 cells was used to culture hippocampal HT22 cells to assess indirect toxicity using the MTT assay.

Results: ORC prevented the Aβ-induced activation of BV2 cells, as reflected by reduced morphological changes and phagocytic ability. In addition, ORC downregulated the expression of Aβ-induced cytokines (IL-1β, IL-6, and TNF-α) and the production of NO in BV2 cells. Furthermore, ORC protected HT22 cells from indirect damage evoked by Aβ-treated BV2 cell-conditioned medium, but not from direct Aβ-induced toxicity.

Conclusions: ORC suppressed the activation of BV2 cells, decreased the production of Aβ-induced inflammatory molecules and NO in BV2 cells, and protected HT22 cells against indirect toxicity mediated by Aβ-treated BV2 cell-conditioned medium. Thus, ORC may exert a protective role in AD through attenuating the damage caused by inflammation and oxidative stress.

High-mobility group box 1 protein participates in acute lung injury by activating protein kinase R and inducing M1 polarization

High-mobility group box 1 protein (HMGB1) is a crucial proinflammatory cytokine that contributes to acute lung injury (ALI). Macrophages are known to express the primary receptors (Toll-like receptor [TLR] 2, and TLR4) of HMGB1 for transmitting intracellular signals. Studies have revealed that double-stranded RNA activated protein kinase R (PKR), which is expressed in macrophages, participates in ALI by regulating macrophage polarization and proinflammatory cytokine release, and that PKR is normally activated by a subset of TLRs. The present study investigated whether HMGB1 engages in ALI by activating PKR in macrophages and inducing classically activated macrophage (M1) polarization via TLR2- and TLR4-mediated nuclear factor (NF)-κB signaling pathways. In an vivo mouse model of lipopolysaccharide (LPS)-induced ALI, anti-HMGB1, rHMGB1, LPS-RS (TLR2 and TLR4 antagonist), or C16 (PKR inhibitor) was administered to mice 2 h after LPS challenge or 1 h before LPS challenge. In vitro, bone marrow-derived macrophages from mice primed with LPS were stimulated with or without anti-HMGB1, rHMGB1, LPS-RS, or C16. Our studies revealed that rHMGB1 stimulation induced M1 polarization in ALI, and that anti-HMGB1 and C16 treatments had the opposite effect. Anti-HMGB1 and LPS-RS significantly inhibited LPS-induced PKR expression in macrophages; however, rHMGB1 administration increased PKR expression. These results indicate that HMGB1 participates in the pathogenesis of ALI by activating PKR in macrophages and inducing M1 polarization through TLR2- and TLR4-mediated NF-κB signaling pathways.

HMGB1 participates in LPS‑induced acute lung injury by activating the AIM2 inflammasome in macrophages and inducing polarization of M1 macrophages via TLR2, TLR4, and RAGE/NF‑κB signaling pathways

High mobility group box 1 (HMGB1), a crucial proinflammatory cytokine, was reported to activate the absent in melanoma 2 (AIM2) inflammasome, which are both essential in acute lung injury (ALI). However, their interaction mechanism has remained elusive. Macrophages are known to express the AIM2 inflammasome and the main receptors [receptor for advanced glycation end products (RAGE), Toll‑like receptor 2/4 (TLR‑2/TLR‑4)] of HMGB1 to transmit intracellular signals. The present study aimed to indicate whether HMGB1 participates in the process of lipopolysaccharides (LPS)‑induced ALI through activating the AIM2 inflammasome in macrophages, as well as inducing polarization of M1 macrophages via TLR2, TLR4 and RAGE/ nuclear factor‑κB (NF‑κB) signaling pathways. In an in vivo mouse model of LPS‑induced ALI, anti‑HMGB1, recombinant (r)HMGB1, LPS from Rhodobacter sphaeroides (LPS‑RS, TLR2/4 antagonist) or FPS‑ZM1 (RAGE antagonist) were administrated. In in vitro studies, bone marrow‑derived macrophages from mice primed with LPS were stimulated with or without anti‑HMGB1, rHMGB1, LPS‑RS, or FPS‑ZM1. The findings revealed that anti‑HMGB1, LPS‑RS and FPS‑ZM1 significantly decreased infiltration of inflammatory cells, wet‑to‑dry ratio, myeloperoxidase activity in the lung, the levels of cytokines, as well as macrophages and neutrophil infiltration in the bronchoalveolar lavage fluid. However, rHMGB1 aggravated the inflammatory response in ALI. Mechanistically, anti‑HMGB1, LPS‑RS and FPS‑ZM1 attenuated activation of TLR2, TLR4, and RAGE/NF‑κB signaling pathways and expression of the AIM2 inflammasome in macrophages. However, rHMGB1 enhanced their expression levels and induced polarization of M1 macrophages. These results indicated that HMGB1 could participate in the pathogenesis of ALI by activating the AIM2 inflammasome in macrophages, as well as inducing polarization of M1 macrophages through TLR2, TLR4 and RAGE/NF‑κB signaling pathways.

Regulation of autophagy as a therapy for immunosenescence-driven cancer and neurodegenerative diseases: The role of exercise

Aging is one of the risk factors for the development of low-grade inflammation morbidities, such as several types of cancer and neurodegenerative diseases, due to changes in the metabolism, hormonal secretion, and immunosenescence. The senescence of the immune system leads to improper control of infections and tissue damage increasing age-related diseases. One of the mechanisms that maintain cellular homeostasis is autophagy, a cell-survival mechanism, and it has been proposed as one of the most powerful antiaging therapies. Regular exercise can reestablish autophagy, probably through AMP-activated protein kinase activation, and help in reducing the age-related senescence diseases. Therefore, in this study, we discuss the effects of exercise training in immunosenescence and autophagy, preventing the two main age-related disease, cancer and neurodegeneration.

Long-term intake of phenolic compounds attenuates age-related cardiac remodeling

With the onset of advanced age, cardiac‐associated pathologies have increased in prevalence. The hallmarks of cardiac aging include cardiomyocyte senescence, fibroblast proliferation, inflammation, and hypertrophy. The imbalance between levels of reactive oxygen species (ROS) and antioxidant enzymes is greatly enhanced in aging cells, promoting cardiac remodeling. In this work, we studied the long‐term impact of phenolic compounds (PC) on age‐associated cardiac remodeling. Three‐month‐old Wistar rats were treated for 14 months till middle‐age with either 2.5, 5, 10, or 20 mg kg⁻¹ day⁻¹ of PC. PC treatment showed a dose‐dependent preservation of cardiac ejection fraction and fractional shortening as well as decreased hypertrophy reflected by left ventricular chamber diameter and posterior wall thickness as compared to untreated middle‐aged control animals. Analyses of proteins from cardiac tissue showed that PC attenuated several hypertrophic pathways including calcineurin/nuclear factor of activated T cells (NFATc3), calcium/calmodulin‐dependent kinase II (CAMKII), extracellular regulated kinase 1/2 (ERK1/2), and glycogen synthase kinase 3ß (GSK 3ß). PC‐treated groups exhibited reduced plasma inflammatory and fibrotic markers and revealed as well ameliorated extracellular matrix remodeling and interstitial inflammation by a downregulated p38 pathway. Myocardia from PC‐treated middle‐aged rats presented less fibrosis with suppression of profibrotic transforming growth factor‐ß1 (TGF‐ß1) Smad pathway. Additionally, reduction of apoptosis and oxidative damage in the PC‐treated groups was reflected by elevated antioxidant enzymes and reduced RNA/DNA damage markers. Our findings pinpoint that a daily consumption of phenolic compounds could preserve the heart from the detrimental effects of aging storm.

Noni (Morinda citrifolia L.) fruit juice reverses age-related decline in neural-immune interactions in the spleens of old F344 rats

ETHNOPHARMACOLOGICAL RELEVANCE

Various parts of the tropical plant, Morinda citrifolia L. (Noni), have been widely used in traditional medicine in South and Southeast Asia for several centuries. The therapeutic effects of the noni are believed to be mediated through several phytochemicals such as anthraquinones, iridoid, fatty acid glycosides, alcohols, etc.

AIM OF THE STUDY

The aim of the study is to investigate the effects of Morinda citrifolia fruit juice (noni fruit juice; NFJ) on neural-immune interactions through the involvement of intracellular signaling pathways both in vitro and in vivo in the splenic lymphocytes of young and old male F344 rats.

MATERIAL AND METHODS

In the in vitro study, splenocytes from young and old F344 rats were isolated and treated with 0.0001-1% concentrations of NFJ for a period of 24h, while in the in vivo study, old F344 rats were orally administered (5ml/kg body weight) with NFJ (5%, 10% and 20%) twice daily for 60 days. After the treatment period, concanavalin A (Con A)-induced lymphocyte proliferation, cytokines (IL-2, IFN-γ, IL-6, and TNF-α) production, expression of tyrosine hydroxylase (p-TH), nerve growth factor (NGF), m-TOR, IκB-α, p-NF-κB (p50 and p65), p-ERK, p-Akt, p-CREB and lipid peroxidation, protein carbonyl formation, nitric oxide (NO) production were examined in the splenocytes.

RESULTS

In vitro NFJ incubation of splenic lymphocytes increased Con A-induced lymphocyte proliferation, IL-2 and IFN-γ production, and expression of p-ERK, p-Akt, and p-CREB in young and old rats. In vivo treatment of old rats with NFJ increased lymphoproliferation, IL-2 and IFN-γ production, the expression of p-TH, NGF, and NO production, and suppressed IL-6 production, lipid peroxidation, protein carbonyl formation, and the expression of IκB-α and p-NF-κB (p50) in the splenocytes.

CONCLUSION

Taken together, these results suggest that Morinda citrifolia fruit juice enhanced neural-immune interactions and cell survival pathways while inhibiting inflammatory processes that may be useful in the treatment of age-associated diseases.

Advanced Age Alters Monocyte and Macrophage Responses

SIGNIFICANCE

With the growing population of baby boomers, there is a great need to determine the effects of advanced age on the function of the immune system. Recent Advances: It is universally accepted that advanced age is associated with a chronic low-grade inflammatory state that is referred to as inflamm-aging, which alters the function of both immune and nonimmune cells. Mononuclear phagocytes play a central role in both the initiation and resolution of inflammation in multiple organ systems and exhibit marked changes in phenotype and function in response to environmental cues, including the low levels of pro-inflammatory mediators seen in the aged.

CRITICAL ISSUES

Although we know a great deal about the function of immune cells in young adults and there is a growing body of literature focusing on aging of the adaptive immune system, much less is known about the impact of age on innate immunity and the critical role of the mononuclear phagocytes in this process.

FUTURE DIRECTIONS

In this article, there is a focus on the tissue-specific monocyte and macrophage subsets and how they are altered in the aged milieu, with the hope that this compilation of observations will spark an expansion of research in the field. Antioxid. Redox Signal. 25, 805-815.

Attenuation of exercise effect on inflammatory responses via novel role of TLR4/PI3K/Akt signaling in rat splenocytes

Moderate exercise diminishes proinflammation cytokine production in various types of immune cells, but the intracellular signaling pathways involved are not completely understood. Phosphoinositide 3-kinase (PI3K)/Akt, a crucial downstream protein of toll-like receptor 4 (TLR4), may modulate inflammation. The present study aimed to investigate the effects of exercises on lipopolysaccharide (LPS)-stimulated inflammatory response in splenocytes and to explore potential mechanisms of the PI3K/Akt pathway. Male rats were divided into sedentary and exercise groups. Animals in the exercise group underwent endurance training 30 min/day, 7 days/wk, at the speed of 20 m/min on a treadmill for 1 wk. Here, we showed that exercise 1) attenuated TLR4, 2) increased PI3K/phospho-Akt (p-Akt), and 3) diminished phospho-nuclear factor-κB (p-NF-κB) expression. In addition, administration of splenocytes isolated from trained rats with LPS in vitro showed 1) reduced tumor necrosis factor (TNF-α), interleukin 6 (IL-6), and nitric oxide secretion and 2) decreased splenocyte proliferation. The plasma corticosterone (CCS) level in the exercise group was higher than that in the sedentary group. We confirmed that CCS down-regulated TNF-α and IL-6 secretion in response to LPS in rat splenocytes. Dexamethasone also significantly attenuated LPS-evoked release of TNF-α and IL-6 in a dose-dependent manner. These findings suggested that exercise dampened the secretion of inflammation mediators probably through partial inhibition of TLR4 and p-NF-κB and activation of PI3K/p-Akt expression in the spleen.

Oxidative stress response and Nrf2 signaling in aging

Increasing oxidative stress, a major characteristic of aging, has been implicated in a variety of age-related pathologies. In aging, oxidant production from several sources is increased, whereas antioxidant enzymes, the primary lines of defense, are decreased. Repair systems, including the proteasomal degradation of damaged proteins, also decline. Importantly, the adaptive response to oxidative stress declines with aging. Nrf2/EpRE signaling regulates the basal and inducible expression of many antioxidant enzymes and the proteasome. Nrf2/EpRE activity is regulated at several levels, including transcription, posttranslation, and interactions with other proteins. This review summarizes current studies on age-related impairment of Nrf2/EpRE function and discusses the changes in Nrf2 regulatory mechanisms with aging.

Tollip is a critical mediator of cerebral ischaemia-reperfusion injury

Toll-like receptor (TLR) signalling plays an important role in regulating cerebral ischaemia-reperfusion (I/R) injury. Toll-interacting protein (Tollip) is an endogenous negative modulator of TLR signalling that is involved in several inflammatory diseases. Our previous study showed that Tollip inhibits overload-induced cardiac remodelling. However, the role of Tollip in neurological disease remains unknown. In the present study, we proposed that Tollip might contribute to the progression of stroke and confirmed this hypothesis. We found that Tollip expression was significantly increased in I/R-challenged brain tissue of humans, mice and rats in vivo and in primary neurons subjected to oxygen and glucose deprivation in vitro, indicating the involvement of Tollip in I/R injury. Next, using genetic approaches, we revealed that Tollip deficiency protects mice against I/R injury by attenuating neuronal apoptosis and inflammation, as demonstrated by the decreased expression of pro-apoptotic and pro-inflammatory genes and the increased expression of anti-apoptotic genes. By contrast, neuron-specific Tollip over-expression exerted the opposite effect. Mechanistically, the detrimental effects of Tollip on neuronal apoptosis and inflammation following I/R injury were largely mediated by the suppression of Akt signalling. Additionally, to further support our findings, a Tollip knockout rat strain was generated via CRISPR-Cas9-mediated gene inactivation. The Tollip-deficient rats were also protected from I/R injury, based on dramatic decreases in neuronal apoptosis and ischaemic inflammation through Akt activation. Taken together, our findings demonstrate that Tollip acts as a novel modulator of I/R injury by promoting neuronal apoptosis and ischaemic inflammation, which are largely mediated by suppression of Akt signalling.

PI3K inhibitors in inflammation, autoimmunity and cancer

The healthy immune system protects against infection and malignant transformation without causing significant damage to host tissues. Immune dysregulation results in diverse pathologies including autoimmune disease, chronic inflammatory disorders, allergies as well as immune deficiencies and cancer. Phosphoinositide 3-kinase (PI3K) signalling has been shown to be a key pathway in the regulation of the immune response and continues to be the focus of intense research. In recent years we have gained detailed understanding of PI3K signalling, and saw the development of potent and highly selective small molecule inhibitors, of which several are currently in clinical trials for the treatment of immune-related disorders and cancer. The role of PI3K signalling in the immune response has been the subject of detailed reviews; here we focus on relevant recent progress in pre-clinical and clinical development of PI3K inhibitors.

Role of B cell receptor signaling in IL-10 production by normal and malignant B-1 cells

B-1 cells are considered innate immune cells, which produce the majority of natural antibodies. B-1 cell responses to B cell receptor (BCR) and Toll-like receptor ligation are tightly regulated owing to the cross-reactivity to self-antigens. CD5 has been shown to play a major role in downregulation of BCR responses in B-1 cells. Here, we provide evidence for another mechanism by which BCR response is regulated in B-1 cells. B-1 cells, as well as their malignant counterpart, B cell chronic lymphocytic leukemia (B-CLL) cells, produce interleukin-10 (IL-10) constitutively. IL-10 secretion by normal B-1 cells downregulates their proliferation responses to BCR ligation. However, we found that CLL cells appear to be unique in not responding to IL-10-mediated feedback-suppressive effects in comparison to normal B-1 cells. In addition, we describe a novel role of the BCR signaling pathway in constitutive IL-10 secretion by normal and malignant B-1 cells. We found that inhibition of Src family kinases, spleen tyrosine kinase, Syk, or Bruton's tyrosine kinase reduces constitutive IL-10 production by both normal and malignant B-1 cells.

Bone marrow-derived macrophages from aged rats are more responsive to inflammatory stimuli

Background

Lipopolysaccharide (LPS) and interferon-γ (IFNγ) increase expression of tumour necrosis factor-α (TNFα) that characterizes the M1 activation state of macrophages. Whereas it is accepted that the immune system undergoes changes with age, there is inconsistency in the literature with respect to the impact of age on the response of macrophages to inflammatory stimuli. Here, we investigate the effect of age on the responsiveness of bone marrow-derived macrophages (BMDMs) to LPS and IFNγ. The context for addressing this question is that macrophages, which infiltrate the brain of aged animals, will encounter the neuroinflammatory environment that has been described with age.

Methods

Brain tissue, prepared from young and aged rats, was assessed for expression of inflammatory markers by PCR and for evidence of infiltration of macrophages by flow cytometry. BMDMs were prepared from the long bones of young and aged rats, maintained in culture for 8 days and incubated in the presence or absence of LPS (100 ng/ml) or IFNγ (50 ng/ml). Cells were harvested and assessed for mRNA expression of markers of M1 activation including TNFα and NOS2, or for expression of IFNγR1 and TLR4 by western immunoblotting. To assess whether BMDMs induced glial activation, mixed glial cultures were incubated in the presence of conditioned media obtained from unstimulated BMDMs of young and aged rats and evaluated for expression of inflammatory markers.

Results

Markers associated with M1 activation were expressed to a greater extent in BMDMs from aged rats in response to LPS and IFNγ, compared with cells from young rats. The increased responsiveness was associated with increases in IFNγ receptor (IFNγR) and Toll-like receptor 4 (TLR4). The data show that conditioned media from BMDMs of aged rats increased the expression of pro-inflammatory mediators in glial cells. Significantly, there was an age-related increase in macrophage infiltration into the brain, and this was combined with increased expression of IFNγ and the Toll-like receptor 4 agonist, high-mobility group protein B1 (HMGB1).

Conclusion

Exposure of infiltrating macrophages to the inflammatory microenvironment that develops in the brain with age is likely to contribute to a damaging cascade that negatively impacts neuronal function.

Anti-pneumococcal deficits of monocyte-derived macrophages from the advanced-age, frail elderly and related impairments in PI3K-AKT signaling

The advanced-age, frail elderly are especially vulnerable to developing pneumococcal infection and disease. Macrophages are critical mediators in the defence against Streptococcus pneumoniae at the upper respiratory tract, however, little is known of their anti-pneumococcal capacity in the elderly. Herein we demonstrate that monocyte-derived macrophages (MDMs) from the advanced-age, frail elderly produce less TNF, IL-6, IL-1β and IL-8 in response to heat-killed S. pneumoniae, which does not appear to be related to mRNA stability or decay. Furthermore, despite maintaining the ability to bind and phagocytose bacteria, MDMs from these individuals have a reduced capacity to kill S. pneumoniae. These defects parallel reduced PI3K-AKT signaling, which can significantly abrogate bacterial killing, but does not affect cytokine responses. Since macrophages are critical in the defence against S. pneumoniae, this study adds valuable insight into the susceptibility of the elderly to pneumococcal disease and highlights the PI3K-AKT signaling pathway as a potential therapeutic target.

Immunosenescence in monocytes, macrophages, and dendritic cells: lessons learned from the lung and heart

In the absence of an immune challenge, healthy, aged individuals have a significantly higher basal inflammatory state where circulating levels of cytokines, including IL-6, TNF-α and IL-1β, are elevated [1]. This progressive pro-inflammatory state, termed "inflamm-aging", affects the phenotype/function of cells present in the aged as well as renders the older individuals more susceptible to a poor prognosis after systemic insults. Although it is important to understand the mechanisms that underlie the progression of disease, most preclinical analyses of disease therapies are performed in young adult mice that have an intact, functional immune system. Oftentimes, this is not necessarily representative of the immune disposition in the aged, let alone diseased, aged. Herein, two distinct responses that are not only commonly associated with aging but that also have dendritic cells and/or monocytes and macrophages as key players are discussed: pulmonary infection and myocardial infarction. Although studies of pulmonary infection in the aged have progressed significantly, studies of monocytes and macrophages in inflammation and cardiac injury following ischemia in the aged have not been as forthcoming. Nonetheless, several elegant studies have established the dynamic role of monocytes and macrophages post infarction. These will be discussed in light of what is known with aging.

GSK3β and the control of infectious bacterial diseases

Glycogen synthase kinase 3β (GSK3β) has been shown to be a crucial mediator of the intensity and direction of the innate immune system response to bacterial stimuli. This review focuses on: (i) the central role of GSK3β in the regulation of pathogen-induced inflammatory responses through the regulation of pro- and anti-inflammatory cytokine production, (ii) the extensive ongoing efforts to exploit GSK3β for its therapeutic potential in the control of infectious diseases, and (iii) the increasing evidence that specific pathogens target GSK3β-related pathways for immune evasion. A better understanding of complex bacteria-GSK3β interactions is likely to lead to more effective anti-inflammatory interventions and novel targets to circumvent pathogen colonization and survival.

Impaired innate mucosal immunity in aged mice permits prolonged Streptococcus pneumoniae colonization

Streptococcus pneumoniae is a frequent asymptomatic colonizer of the nasopharyngeal niche and only occasionally progresses toward infection. The burden of pneumococcal disease is particularly high in the elderly, and the mechanisms behind this increased susceptibility are poorly understood. Here we used a mouse model of pneumococcal carriage to study immunosenescence in the upper respiratory tract (URT). Nasal mucosa-associated lymphoid tissue (NALT) showed increased expression of Toll-like receptor 1, interleukin-1β, NLRp3 inflammasome, and CCL2 in naive elderly compared to young animals. This suggests an increased proinflammatory expression profile in the NALT of aged mice at baseline. Simultaneously, we observed a more tolerogenic profile in respiratory epithelia of naive elderly compared to young adult mice with upregulation of the NF-κβ pathway inhibitor peroxisome proliferator-activated receptor gamma (PPARγ). After nasal instillation of pneumococci, pneumococcal colonization was prolonged in elderly mice compared to in young adults. The delay in clearance was associated with absent or delayed upregulation of a proinflammatory mediator(s) in the NALT, diminished influx of macrophages into the URT niche, and absent downregulation of PPARγ in respiratory epithelium, accompanied by diminished expression of cathelicidin (CRAMP) at the site of colonization. These findings suggest that unresponsiveness to pneumococcal challenge due to altered mucosal immune regulation is the key to increased susceptibility to disease in the elderly.

Immunosenescence and pneumococcal disease: an imbalance in host-pathogen interactions

Respiratory infections are among the most important causes of morbidity and mortality from infectious diseases worldwide. The most common causative bacterium, Streptococcus pneumoniae, frequently colonises the upper respiratory tract, where it resides mostly asymptomatically. Occasionally, however, S pneumoniae can cause severe disease such as pneumonia. Local host immunity is essential to control colonising pathogens by preventing overgrowth, spread, and invasion. However, age-related immune deficits in elderly people, known as immunosenescence, might contribute to increased disease burden. We review present knowledge about immunosenescence in the respiratory tract against Gram-positive bacteria, particularly S pneumoniae. We discuss the possible underdetection of pneumococcal colonisation in elderly people, and suggest changes to present surveillance methods to improve understanding of the relation between colonisation and disease. We conclude that present knowledge about alteration of host-pathogen interactions by immunosenescence in the respiratory tract is insufficient, and that research is needed to enable improved measures for prevention.

The adipokine/ceramide axis: key aspects of insulin sensitization

Until recently, sphingolipid physiology was primarily the domain of oncologists and immunologists. However, mounting evidence implicates ceramides and their derivatives in various aspects of metabolism via directly impacting the insulin receptor as well as modulating cell survival and proliferation. More recent observations suggest a strong link between a number of adipokines and ceramide catabolism. Here, we aim to briefly review the available data on the established metabolic effects of sphingolipids in various cell types and will discuss how adipokines exert a critical influence on the steady state levels of these lipid mediators.

Age-related defects in TLR2 signaling diminish the cytokine response by alveolar macrophages during murine pneumococcal pneumonia

Alveolar macrophages (AMs) are the first immune cells to respond to an invading pathogen and coordinate the inflammatory response within the lungs. Studies suggest that macrophages exhibit age-related deficiencies in Toll-like receptor (TLR) function; however, the impact of this dysfunction during pneumonia, the leading cause of infectious death in the elderly, and the underlying mechanisms responsible remain unclear. We examined disease severity in young, mature, and aged BALB/cBy mice following intratracheal infection with the Gram-positive bacteria Streptococcus pneumoniae (Spn). Both mature and aged mice failed to clear bacteria and as a result had increased mortality, tissue damage and vascular leakage. Early production of TNFα, IL-1β, and IL-6 during pneumonia declined with age and was associated with an inability of isolated AMs to respond to pneumococcal cell wall (CW) and ethanol-killed Spn ex vivo. Total levels of TLR1 were unaffected by age and TLR2 surface expression was slightly yet significantly increased on aged AMs suggesting that intracellular TLR signaling defects were responsible for the age-related decline in cytokine responsiveness. Following infection of isolated AMs with live Spn, a significant age-related decline in TLR2-induced phosphorylation of p65 NFκB, JNK and p38 MAPK, and an increase in ERK phosphorylation was observed by immunoblotting. These data are the first to demonstrate that TLR2-dependent recognition of Spn by aged AMs is impaired and is associated with a delayed pro-inflammatory cytokine response in vivo along with enhanced susceptibility to pneumococcal pneumonia.