Genomic DNA released by dying cells induces the maturation of APCs

Acute Inflammation in Tissue Healing

There are well-established links between acute inflammation and successful tissue repair across evolution. Innate immune reactions contribute significantly to pathogen clearance and activation of subsequent reparative events. A network of molecular and cellular regulators supports antimicrobial and tissue repair functions throughout the healing process. A delicate balance must be achieved between protection and the potential for collateral tissue damage associated with overt inflammation. In this review, we summarize the contributions of key cellular and molecular components to the acute inflammatory process and the effective and timely transition toward activation of tissue repair mechanisms. We further discuss how the disruption of inflammatory responses ultimately results in chronic non-healing injuries.

Evolutionary Origins of Metabolic Reprogramming in Cancer

Metabolic changes that facilitate tumor growth are one of the hallmarks of cancer. These changes are not specific to tumors but also take place during the physiological growth of tissues. Indeed, the cellular and tissue mechanisms present in the tumor have their physiological counterpart in the repair of tissue lesions and wound healing. These molecular mechanisms have been acquired during metazoan evolution, first to eliminate the infection of the tissue injury, then to enter an effective regenerative phase. Cancer itself could be considered a phenomenon of antagonistic pleiotropy of the genes involved in effective tissue repair. Cancer and tissue repair are complex traits that share many intermediate phenotypes at the molecular, cellular, and tissue levels, and all of these are integrated within a Systems Biology structure. Complex traits are influenced by a multitude of common genes, each with a weak effect. This polygenic component of complex traits is mainly unknown and so makes up part of the missing heritability. Here, we try to integrate these different perspectives from the point of view of the metabolic changes observed in cancer.

Role of RAGE and its ligand HMGB1 in the development of COPD

Smoking is a well-established risk factor for chronic obstructive pulmonary disease (COPD). Chronic lung inflammation continues even after smoking cessation and leads to COPD progression. To date, anti-inflammatory therapies are ineffective in improving pulmonary function and COPD symptoms, and new molecular targets are urgently needed to deal with this challenge. The receptor for advanced glycation end-products (RAGE) was shown to be relevant in COPD pathogenesis, since it is both a genetic determinant of low lung function and a determinant of COPD susceptibility. Moreover, RAGE is involved in the physiological response to cigarette smoke exposure. Since innate and acquired immunity plays an essential role in the development of chronic inflammation and emphysema in COPD, here we summarized the roles of RAGE and its ligand HMGB1 in COPD immunity.

Inflammasome activation as a link between obesity and thyroid disorders: Implications for an integrated clinical management

Obesity is strongly associated with chronic low-grade inflammation. Obese patients have an increased risk to develop thyroid autoimmunity and to became hypothyroid, suggesting a pathogenetic link between obesity, inflammation and autoimmunity. Moreover, type 2 diabetes and dyslipidemia, also characterized by low-grade inflammation, were recently associated with more aggressive forms of Graves' ophthalmopathy. The association between obesity and autoimmune thyroid disorders may also go in the opposite direction, as treating autoimmune hyper and hypothyroidism can lead to weight gain. In addition, restoration of euthyroidism by L-T4 replacement therapy is more challenging in obese athyreotic patients, as it is difficult to maintain thyrotropin stimulation hormone (TSH) values within the normal range. Intriguingly, pro-inflammatory cytokines decrease in obese patients after bariatric surgery along with TSH levels. Moreover, the risk of thyroid cancer is increased in patients with thyroid autoimmune disorders, and is also related to the degree of obesity and inflammation. Molecular studies have shown a relationship between the low-grade inflammation of obesity and the activity of intracellular multiprotein complexes typical of immune cells (inflammasomes). We will now highlight some clinical implications of inflammasome activation in the relationship between obesity and thyroid disease.

Mitochondria and Mitochondrial DNA: Key Elements in the Pathogenesis and Exacerbation of the Inflammatory State Caused by COVID-19

Background and Objectives. The importance of mitochondria in inflammatory pathologies, besides providing energy, is associated with the release of mitochondrial damage products, such as mitochondrial DNA (mt-DNA), which may perpetuate inflammation. In this review, we aimed to show the importance of mitochondria, as organelles that produce energy and intervene in multiple pathologies, focusing mainly in COVID-19 and using multiple molecular mechanisms that allow for the replication and maintenance of the viral genome, leading to the exacerbation and spread of the inflammatory response. The evidence suggests that mitochondria are implicated in the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which forms double-membrane vesicles and evades detection by the cell defense system. These mitochondrion-hijacking vesicles damage the integrity of the mitochondrion’s membrane, releasing mt-DNA into circulation and triggering the activation of innate immunity, which may contribute to an exacerbation of the pro-inflammatory state. Conclusions. While mitochondrial dysfunction in COVID-19 continues to be studied, the use of mt-DNA as an indicator of prognosis and severity is a potential area yet to be explored.

Decellularization protocol-dependent damage-associated molecular patterns in rat uterus scaffolds differentially affect the immune response after transplantation

Scaffolds derived from decellularized tissue possess many advantages for bioengineering applications, including for novel infertility treatments. However, the decellularization process results in allogenic-independent damage-associated molecular patterns (DAMPs). This field is poorly studied, in particular for uterus bioengineering applications. An increased knowledge concerning the immune system activation after transplantation of decellularized tissue will enable safer construct development and thereby accelerate translation from research to clinic. We therefore transplanted rat uterus scaffolds produced by three different decellularization protocols based on Triton X-100 (P1 and P2) or sodium deoxycholate (P3) in a syngeneic animal model and assessed the immune response towards DAMPs exposed by the decellularization process. Biopsies were retrieved on day 5, 15, and 30 post transplantation and immunohistochemistry-stained CD45+ (leucocytes), CD4+ (T-cells), CD8a+ (cytotoxic T-cells), CD22+ (B-cells), NCR1+ (NK-cells), CD68+ (pan-macrophages), and CD163+ (M2 macrophages) cells within the grafts were quantified. The gene expression for interferon γ, interleukin (IL)-1β, IL-2, IL-6, and tumor necrosis factor (TNF) eotaxin-2, RANTES, MCP-1, MIP-1α, MIP-3α, IL-8 were also measured. Scaffolds from P1 induced a rapid cell infiltration after transplantation, presumably induced by DNA-based DAMPs. However, this response was only transient. Protocol 3 derived scaffolds induced an early pro-inflammatory cytokine response at the transcript level which remained high throughout the study. This response may be caused by the stronger decellularization detergent that could expose more extracellular matrix-related DAMPs. However, earlier proteomics analysis also identified significantly more abundant heat shook proteins-related DAMPs in this scaffold type. Protocol 2 caused the least immunogenic scaffolds and should thus be the future focus for in vivo uterus bioengineering applications.

Tumor necrosis: A synergistic consequence of metabolic stress and inflammation

Tumor necrosis is a common histological feature and poor prognostic predictor in various cancers. Despite its significant clinical implications, the mechanism underlying tumor necrosis remains largely unclear due to lack of appropriate pre-clinical modeling. We propose that tumor necrosis is a synergistic consequence of metabolic stress and inflammation, which lead to oxidative stress-induced cell death, such as ferroptosis. As a natural consequence of tumor expansion, tumor cells are inevitably stripped of vascular supply, resulting in deprivation of oxygen and nutrients. The resulting metabolic stress has commonly been considered the cause of tumor necrosis. Recent studies found that immune cells, such as neutrophils, when recruited to tumors, can directly trigger ferroptosis in tumor cells, suggesting that immune cells can be involved in amplifying tumor necrosis. This article will discuss potential mechanisms underlying tumor necrosis development and its impact on tumor progression as well as the immune response to tumors.

Immune response after allogeneic transplantation of decellularized uterine scaffolds in the rat

Data on how the immune system reacts to decellularized scaffolds after implantation is scarce and difficult to interpret due to many heterogeneous parameters such as tissue-type match, decellularization method and treatment application. The engraftment of these scaffolds must prove safe and that they remain inert to the recipient's immune system to enable successful translational approaches and potential future clinical evaluation. Herein, we investigated the immune response after the engraftment of three decellularized scaffold types that previously showed potential to repair a uterine injury in the rat. Protocol (P) 1 and P2 were based on Triton-X100 and generated scaffolds containing 820 ng mg^-1and 33 ng mg^-1donor DNA per scaffold weight, respectively. Scaffolds obtained with a sodium deoxycholate-based protocol (P3) contained 160 ng donor DNA per mg tissue. The total number of infiltrating cells, and the population of CD45⁺leukocytes, CD4⁺T-cells, CD8a⁺cytotoxic T-cells, CD22⁺B-cells, NCR1⁺NK-cells, CD68⁺and CD163⁺macrophages were quantified on days 5, 15 and 30 after a subcutaneous allogenic (Lewis to Sprague Dawley) transplantation. Gene expression for the pro-inflammatory cytokines INF-γ, IL-1β, IL-2, IL-6 and TNF were also examined. P1 scaffolds triggered an early immune response that may had been negative for tissue regeneration but it was stabilized after 30 d. Conversely, P3 initiated a delayed immune response that appeared negative for scaffold survival. P2 scaffolds were the least immunogenic and remained similar to autologous tissue implants. Hence, an effective decellularization protocol based on a mild detergent was advantageous from an immunological perspective and appears the most promising for futurein vivouterus bioengineering applications.

Aquaporin-3 is involved in NLRP3-inflammasome activation contributing to the setting of inflammatory response

Inflammasomes are large immune multiprotein complexes that tightly regulate the production of the pro-inflammatory cytokines, being dependent on cell regulatory volume mechanisms. Aquaporins (AQPs) are protein channels that facilitate the transport of water and glycerol (aquaglyceroporins) through membranes, essential for cell volume regulation. Although these membrane proteins are highly expressed in monocytes and macrophages, their role in the inflammatory process is still unclear. Here, we investigated the role of aquaglyceroporin AQP3 in NLRP3-inflammasome activation by complementary approaches based either on shRNA silencing or on AQP3 selective inhibition. The latter has been achieved using a reported potent gold-based inhibitor, Auphen. AQP3 inhibition or silencing partially blocked LPS-priming and decreased production of IL-6, proIL-1β, and TNF-α, suggesting the possible involvement of AQP3 in macrophage priming by Toll-like receptor 4 engagement. Moreover, AQP3-dependent cell reswelling increased IL-1β release through caspase-1 activation. NLRP3-inflammasome activation induced by reswelling, nigericin, and ATP was also blocked when AQP3 was inhibited or silenced. Altogether, these data point towards AQPs as potential players in the setting of the inflammatory response.

Cytosolic Ca2+ transients during pulsed focused ultrasound generate reactive oxygen species and cause DNA damage in tumor cells

Mechanical forces from non-ablative pulsed focused ultrasound (pFUS) generate pro-inflammatory tumor microenvironments (TME), marked by increased cytokines, chemokines, and trophic factors, as well as immune cell infiltration and reduced tumor growth. pFUS also causes DNA damage within tumors, which is a potent activator of immunity and could contribute to changes in the TME. This study investigated mechanisms behind the mechanotransductive effects of pFUS causing DNA damage in several tumor cell types. Methods: 4T1 (murine breast tumor), B16 (murine melanoma), C6 (rat glioma), or MDA-MB-231 (human breast tumor) cells were sonicated in vitro (1.1MHz; 6MPa PNP; 10ms pulses; 10% duty cycle; 300 pulses). DNA damage was detected by TUNEL, apoptosis was measured by immunocytochemistry for cleaved caspase-3. Calcium, superoxide, and H₂O₂ were detected by fluorescent indicators and modulated by BAPTA-AM, mtTEMPOL, or Trolox, respectively. Results: pFUS increased TUNEL reactivity (range = 1.6-2.7-fold) in all cell types except C6 and did not induce apoptosis in any cell line. All lines displayed cytosolic Ca²⁺ transients during sonication. pFUS increased superoxide (range = 1.6-2.0-fold) and H₂O₂ (range = 2.3-2.8-fold) in all cell types except C6. BAPTA-AM blocked increased TUNEL reactivity, superoxide and H₂O₂ formation, while Trolox also blocked increased TUNEL reactivity increased after pFUS. mtTEMPOL allowed H₂O₂ formation and did not block increased TUNEL reactivity after pFUS. Unsonicated C6 cells had higher baseline concentrations of cytosolic Ca²⁺, superoxide, and H₂O₂, which were not associated with greater baseline TUNEL reactivity than the other cell lines. Conclusions: Mechanotransduction of pFUS directly induces DNA damage in tumor cells by cytosolic Ca²⁺ transients causing formation of superoxide and subsequently, H₂O₂. These results further suggest potential clinical utility for pFUS. However, the lack of pFUS-induced DNA damage in C6 cells demonstrates a range of potential tumor responses that may arise from physiological differences such as Ca²⁺ or redox homeostasis.

Huoxue Jiedu Huayu Recipe Ameliorates Mesangial Cell Pyroptosis in Contralateral Kidney of UUO Rats

Objectives

To observe the effects of the Huoxue Jiedu Huayu Recipe (HJHR) on pyroptosis of glomerular mesangial cells in the contralateral unobstructed kidney (CK) of unilateral ureteral obstruction (UUO) rats.

Methods

Sprague-Dawley rats were randomly divided into 4 groups: sham group, UUO group (10 days of left ureter ligation), UUO treated with eplerenone (EPL) (UUO + EPL) group, and UUO treated with HJHR (UUO + HJHR) group. The CKs of all rats were collected for studies.

Results

Cell pyroptosis and macrophage infiltration was found in contralateral glomeruli, and nucleotide-binding oligomerization domain-like pyrin domain containing protein 3 (NLRP3) and interleukin (IL)-1β expression was upregulated in the CK of UUO rats. All of these changes were inhibited by HJHR and eplerenone. To determine how aldosterone (Aldo) activated the mineralocorticoid receptor (MR) and then induced mesangial cell pyroptosis with NLRP3-caspase-1-IL-1β pathway, human mesangial cells (HMCs) were treated with HJHR and eplerenone, which were examined to detect the expression of NLRP3 inflammasome-associated proteins following treatment with Aldo.

Conclusion

These results suggest that HJHR and eplerenone suppressed HMC pyroptosis via the MR/NLRP3 pathway.

DAMPs in Unilateral Ureteral Obstruction

Damage-associated molecular patterns (DAMPs) are released from tubular and interstitial cells in the kidney after unilateral ureteral obstruction (UUO). DAMPs are recognized by pattern recognition receptors (PRRs), which mediate the initiation of an immune response and the release of inflammatory cytokines. The animal model of UUO is used for various purposes. UUO in adult mice serves as a model for accelerated renal fibrosis, which is a hallmark of progressive renal disease. UUO in adult mice enables to study cell death, inflammation, and extracellular matrix deposition in the kidney. Neonatal UUO is a model for congenital obstructive nephropathies. It studies inflammation, apoptosis, and interstitial fibrosis in the neonatal kidney, when nephrogenesis is still ongoing. Following UUO, several DAMPs as well as DAMP receptors are upregulated. In adult UUO, soluble uric acid is upregulated and activates the NOD-like receptor family, pyrin domain containing-3 (NLRP3) inflammasome, which promotes fibrosis, apoptosis, and reactive oxygen species (ROS) injury. Further DAMPs associated with UUO are uromodulin, members of the IL-1 family, and necrotic cell DNA, all of which promote sterile inflammation. In neonatal UUO, the receptor for advanced glycation endproducts (RAGE) is highly upregulated. RAGE is a ligand for several DAMPs, including high mobility group box 1 (HMGB1) and S100 proteins, which play an important role in renal fibrosis. Additionally, necroptosis is an important mechanism of cell death, besides apoptosis, in neonatal UUO. It is highly inflammatory due to release of cytokines and specific DAMPs. The release and recognition of DAMPs initiate sterile inflammation, which makes them good candidates to develop and improve diagnostic and therapeutic strategies in renal fibrosis and congenital obstructive nephropathies.

Associations between NLRC4 Gene Polymorphisms and Autoimmune Thyroid Disease

Background

Many studies have shown that NLRC4 inflammasome polymorphisms are associated with a variety of autoimmune diseases, but the associations between NLRC4 polymorphisms and autoimmune thyroid diseases (AITDs) are unclear. Our research was aimed at identifying the correlations between NLRC4 polymorphisms and AITDs.

Methods

Hi-SNP high-throughput genotyping technology was used for detecting four single-nucleotide polymorphisms (SNPs) of NLRC4 in 1005 AITDs patients (including 629 Graves' disease and 376 Hashimoto's thyroiditis) and 781 healthy controls.

Results

Compared with healthy controls, the allele frequencies and genotype distribution of rs385076 were statistically related to AITDs (P = 0.016 and P = 0.048, respectively) and Hashimoto's thyroiditis (P = 0.022 and P = 0.046, respectively). Before adjusting for age and gender, rs385076 and AITDs had a significant association in three models of allele model, dominant model, and homozygous model. After adjusting for age and gender, in the above three models, there is still a clear relationship between them. Before adjusting for age and gender, there were prominent discrepancy between rs385076 and Hashimoto's thyroiditis in the allele model (OR = 0.81, 95% CI 0.67-0.97; P = 0.021) and the dominant model (OR = 0.73, 95% CI 0.57-0.94; P = 0.014), after adjusting for age and gender, rs385076 and Hashimoto's thyroiditis were significantly related to allele model, dominant model, and homozygous model. However, rs455060, rs212704, and rs675712 were not related to AITDs in our study.

Conclusion

NLRC4 rs385076 was found to have a significant association with Hashimoto's thyroiditis for the first time. It laid a foundation for the disclosure of the pathogenesis of AITDs, and provided a possible treatment prospect for HT.

Pathological role of excessive DNA as a trigger of keratinocyte proliferation in psoriasis

Psoriasis is characterized by excessive growth and aberrant differentiation of epidermal keratinocytes due to persistent inflammation. However, the underlying mechanism that triggers immune activation in psoriasis is not clear. In this study, we explored excessive DNA as a potential trigger of psoriasis using cultured human keratinocytes and psoriatic skin tissues. We demonstrated that human genomic DNA fragments induced tumour necrosis factor (TNF)-α expression, hyperproliferation and over-expression of heparin-binding epidermal-like growth factor (HB-EGF) and transforming growth factor (TGF)-α, accompanied by defective expression of keratins 1 and 10 in cultured normal human epidermal keratinocytes, which have a similar phenotype to that of keratinocytes in psoriatic skin lesions. In psoriatic lesions, we found high levels of double-stranded (ds)DNA fragments, accompanying keratinocytes expressing Ki-67, HB-EGF and TNF-α. In addition, we showed that 1,25-dihydroxyvitamin D₃ inhibited genomic DNA fragment-induced TNFA and interleukin-1β (IFNB) expression in human keratinocytes, and an intact function of cathelicidin anti-microbial peptide (CAMP) was required for this effect. These results suggest that excessive dsDNA fragments probably act as a risk factor for immune activation in psoriasis, and the active form of vitamin D can prevent genomic DNA-mediated skin inflammation via CAMP.

Innate Immune-Modulatory Activity of Prunella vulgaris in Thyrocytes Functions as a Potential Mechanism for Treating Hashimoto's Thyroiditis

Prunella vulgaris (PV), a perennial herb, has been used to treat thyroid diseases in China for over 2,000 years. In particular, its therapeutic effect has been described for Hashimoto's thyroiditis, including reducing titers autoantibodies against thyroid peroxidase and thyroglobulin of and T helper 17 (Th17) cells. However, the underlying mechanism for how PV exerts such effects has not been investigated. We examined the effects of PV on innate immune activation, which is thought to be one of the triggers for the development of autoimmune diseases, including Hashimoto's thyroiditis. In cultured thyrocytes, PV reduced mRNA levels of inflammatory cytokines that were originally induced as a result of innate immune activation initiated by transfection of double-stranded DNA (dsDNA) or dsRNA. PV suppressed activation of nuclear factor κB (NF-κB) and interferon regulatory factor 3 (IRF3), and suppressed corresponding promoter activation, which were initially activated by dsDNA or dsRNA. PV also suppressed the mRNA levels of molecules responsible for antigen processing and presentation, and PV protected thyrocytes from apoptosis induced by dsDNA and dsRNA. Additionally, PV suppressed the expression of genes involved in iodide uptake and oxidation. Taken together, these results suggest that PV exerts its protective effect on thyrocytes by suppressing both innate and adaptive immune responses and cell death. PV may also protect cells from iodide-associated oxidative injury. This report is among the first to identify the mechanisms to explain PV's beneficial effects in Hashimoto's thyroiditis.

Essential Role of Host Double-Stranded DNA Released from Dying Cells by Cationic Liposomes for Mucosal Adjuvanticity

Infectious disease remains a substantial cause of death. To overcome this issue, mucosal vaccine systems are considered to be a promising strategy. Yet, none are approved for clinical use, except for live-attenuated mucosal vaccines, mainly owing to the lack of effective and safe systems to induce antigen-specific immune responses in the mucosal compartment. We have reported that intranasal vaccination of an antigenic protein, with cationic liposomes composed of 1,2-dioleoyl-3-trimethylammonium-propane and 3β-[N-(N′,N′-dimethylaminoethane)-carbamoyl], induced antigen-specific mucosal and systemic antibody responses in mice. However, precise molecular mechanism(s) underlying the mucosal adjuvant effects of cationic liposomes remain to be uncovered. Here, we show that a host double-stranded DNA (dsDNA), released at the site of cationic liposome injection, plays an essential role for the mucosal adjuvanticity of the cationic liposome. Namely, we found that nasal administration of the cationic liposomes induced localized cell death, at the site of injection, resulting in extracellular leakage of host dsDNA. Additionally, in vivo DNase I treatment markedly impaired OVA-specific mucosal and systemic antibody production exerted by cationic liposomes. Our report reveals that host dsDNA, released from local dying cells, acts as a damage-associated molecular pattern that mediates the mucosal adjuvant activity of cationic liposomes.

Triggers of Autoimmunity: The Role of Bacterial Infections in the Extracellular Exposure of Lupus Nuclear Autoantigens

Infections are considered important environmental triggers of autoimmunity and can contribute to autoimmune disease onset and severity. Nucleic acids and the complexes that they form with proteins—including chromatin and ribonucleoproteins—are the main autoantigens in the autoimmune disease systemic lupus erythematosus (SLE). How these nuclear molecules become available to the immune system for recognition, presentation, and targeting is an area of research where complexities remain to be disentangled. In this review, we discuss how bacterial infections participate in the exposure of nuclear autoantigens to the immune system in SLE. Infections can instigate pro-inflammatory cell death programs including pyroptosis and NETosis, induce extracellular release of host nuclear autoantigens, and promote their recognition in an immunogenic context by activating the innate and adaptive immune systems. Moreover, bacterial infections can release bacterial DNA associated with other bacterial molecules, complexes that can elicit autoimmunity by acting as innate stimuli of pattern recognition receptors and activating autoreactive B cells through molecular mimicry. Recent studies have highlighted SLE disease activity-associated alterations of the gut commensals and the expansion of pathobionts that can contribute to chronic exposure to extracellular nuclear autoantigens. A novel field in the study of autoimmunity is the contribution of bacterial biofilms to the pathogenesis of autoimmunity. Biofilms are multicellular communities of bacteria that promote colonization during chronic infections. We review the very recent literature highlighting a role for bacterial biofilms, and their major components, amyloid/DNA complexes, in the generation of anti-nuclear autoantibodies and their ability to stimulate the autoreactive immune response. The best studied bacterial amyloid is curli, produced by enteric bacteria that commonly cause infections in SLE patients, including Escherichia coli and Salmonella spps. Evidence suggests that curli/DNA complexes can trigger autoimmunity by acting as danger signals, molecular mimickers, and microbial chaperones of nucleic acids.

Cancer Metabolism Drives a Stromal Regenerative Response

The metabolic reprogramming associated with malignant transformation has led to a growing appreciation of the nutrients required to support anabolic cell growth. Less well studied is how cancer cells satisfy those demands in vivo, where they are dispersed within a complex microenvironment. Tumor-associated stromal components can support tumor growth by providing nutrients that supplement those provided by the local vasculature. These non-malignant stromal cells are phenotypically similar to those that accumulate during wound healing. Owing to their immediate proximity, stromal cells are inevitably affected by the metabolic activity of their cancerous neighbors. Until recently, a role for tumor cell metabolism in influencing the cell fate decisions of neighboring stromal cells has been underappreciated. Here, we propose that metabolites consumed and released by tumor cells act as paracrine factors that regulate the non-malignant cellular composition of a developing tumor by driving stromal cells toward a regenerative response that supports tumor growth.

Nucleic Acid Sensing in Mammals and Plants: Facts and Caveats

The accumulation of nucleic acids in aberrant compartments is a signal of danger: fragments of cytosolic or extracellular self-DNA indicate cellular dysfunctions or disruption, whereas cytosolic fragments of nonself-DNA or RNA indicate infections. Therefore, nucleic acids trigger immunity in mammals and plants. In mammals, endosomal Toll-like receptors (TLRs) sense single-stranded (ss) or double-stranded (ds) RNA or CpG-rich DNA, whereas various cytosolic receptors sense dsDNA. Although a self/nonself discrimination could favor targeted immune responses, no sequence-specific sensing of nucleic acids has been reported for mammals. Specific immune responses to extracellular self-DNA versus DNA from related species were recently reported for plants, but the underlying mechanism remains unknown. The subcellular localization of mammalian receptors can favor self/nonself discrimination based on the localization of DNA fragments. However, autoantibodies and diverse damage-associated molecular patterns (DAMPs) shuttle DNA through membranes, and most of the mammalian receptors share downstream signaling elements such as stimulator of interferon genes (STING) and the master transcription regulators, nuclear factor (NF)-κB, and interferon regulatory factor 3 (IRF3). The resulting type I interferon (IFN) response stimulates innate immunity against multiple threats-from infection to physical injury or endogenous DNA damage-all of which lead to the accumulation of eDNA or cytoplasmatic dsDNA. Therefore, no or only low selective pressures might have favored a strict self/nonself discrimination in nucleic acid sensing. We conclude that the discrimination between self- and nonself-DNA is likely to be less strict-and less important-than assumed originally.

The allosteric activation of cGAS underpins its dynamic signaling landscape

Cyclic G/AMP synthase (cGAS) initiates type-1 interferon responses against cytosolic double-stranded (ds)DNA, which range from antiviral gene expression to apoptosis. The mechanism by which cGAS shapes this diverse signaling landscape remains poorly defined. We find that substrate-binding and dsDNA length-dependent binding are coupled to the intrinsic dimerization equilibrium of cGAS, with its N-terminal domain potentiating dimerization. Notably, increasing the dimeric fraction by raising cGAS and substrate concentrations diminishes duplex length-dependent activation, but does not negate the requirement for dsDNA. These results demonstrate that reaction context dictates the duplex length dependence, reconciling competing claims on the role of dsDNA length in cGAS activation. Overall, our study reveals how ligand-mediated allostery positions cGAS in standby, ready to tune its signaling pathway in a switch-like fashion.

The human immune system protects the body from various threats such as damaged cells or invading microbes. Many of these threats can move molecules of DNA, which are usually only found within a central compartment in the cell known as the nucleus, to the surrounding area, the cytoplasm.

An enzyme called cGAS searches for DNA in the cytoplasm of human cells. When DNA binds to cGAS it activates the enzyme to convert certain molecules (referred to as ‘substrates’) into another molecule (the ‘signal’) that triggers various immune responses to protect the body against the threat. To produce the signal, two cGAS enzymes need to work together as a single unit called a dimer.

The length of DNA molecules in the cytoplasm of cells can vary widely. It was initially thought that DNA molecules of any length binding to cGAS could activate the enzyme to a similar degree, but later studies demonstrated that this is not the case. However, it remains unclear how the length of the DNA could affect the activity of the enzyme, or why some of the earlier studies reported different findings.

Hooy and Sohn used biochemical approaches to study the human cGAS enzyme. The experiments show that cGAS can form dimers even when no DNA is present. However, when DNA bound to cGAS, the enzyme was more likely to form dimers. Longer DNA molecules were better at promoting cGAS dimers to form than shorter DNA molecules. The binding of substrates to cGAS also made it more likely that the enzyme would form dimers. These findings suggest that inside cells cGAS is primed to trigger a switch-like response when it detects DNA in the cytoplasm.

The work of Hooy and Sohn establishes a simple set of rules to predict how cGAS might respond in a given situation. Such information may aid in designing and tailoring efforts to regulate immune responses in human patients, and may provide insight into why the body responds to biological threats in different ways.

Point-of-care treatment of focal cartilage defects with selected chondrogenic mesenchymal stromal cells-An in vitro proof-of-concept study

Due to the poor self-healing capacities of cartilage, innovative approaches are a major clinical need. The use of in vitro expanded mesenchymal stromal cells (MSCs) in a 2-stage approach is accompanied by cost-, time-, and personnel-intensive good manufacturing practice production. A 1-stage intraoperative procedure could overcome these drawbacks. The aim was to prove the feasibility of a point-of-care concept for the treatment of cartilage lesions using defined MSC subpopulations in a collagen hydrogel without prior MSC monolayer expansion. We tested 4 single marker candidates (MSCA-1, W4A5, CD146, CD271) for their effectiveness of separating colony-forming units of ovine MSCs via magnetic cell separation. The most promising surface marker with regard to the highest enrichment of colony-forming cells was subsequently used to isolate a MSC subpopulation for the direct generation of a cartilage graft composed of a collagen type I hydrogel without the propagation of MSCs in monolayer. We observed that separation with CD271 sustained the highest enrichment of colony-forming units. We then demonstrated the feasibility of generating a cartilage graft with an unsorted bone marrow mononuclear cell fraction and with a characterized CD271 positive MSC subpopulation without the need for a prior cell expansion. A reduced volume of 6.25% of the CD271 positive MSCs was needed to achieve the same results regarding chondrogenesis compared with the unseparated bone marrow mononuclear cell fraction, drastically reducing the number of nonrelevant cells. This study provides a proof-of-concept and reflects the potential of an intraoperative procedure for direct seeding of cartilage grafts with selected CD271 positive cells from bone marrow.

Cytidine-phosphate-guanosine oligodeoxynucleotides in combination with CD40 ligand decrease periodontal inflammation and alveolar bone loss in a TLR9-independent manner

Local administration of toll-like receptor 9 (TLR9), agonist cytidine-phosphate-guanosine oligodeoxynucleotide (CpG ODNs), and CD40 ligand (CD40L) can decrease ligature-induced periodontal inflammation and bone loss in wild type (WT) mouse.

Elevated intragraft expression of innate immunity and cell death-related markers is a risk factor for adverse graft outcome

BACKGROUND

Molecules of the innate immune response are increasingly recognized as important mediators in allograft injury during and after kidney transplantation. We therefore aimed to establish the relationship between the expression of these genes at implantation, during an acute rejection (AR) and on graft outcome.

METHODS

A total of 19 genes, including Toll like receptors (TLRs), complement components and regulators, and apoptosis-related genes were analyzed at the mRNA level by qPCR in 123 biopsies with acute rejection and paired pre-transplantation tissue (n = 75).

RESULTS

Before transplantation, relative mRNA expression of BAX:BCL2 ratio (apoptosis marker) and several complement genes was significantly higher in tissue samples from deceased donors compared to living donors. During AR, TLRs and complement genes showed an increased expression compared to pre-transplant conditions, whereas complement regulators were decreased. A relatively high TLR4 expression level and BAX:BCL2 ratio during AR in the deceased donor group was associated with adverse graft outcome, independently of clinical risk factors.

CONCLUSIONS

Complement- and apoptosis-related gene expression is elevated in deceased donor transplants before transplantation. High BAX:BCL2 ratio and TLR4 expression during AR may reflect enhanced intragraft cell death and immunogenic danger signals, and pose a risk factor for adverse graft outcome.

Regulation of Tumor Progression by Programmed Necrosis

Rapidly growing malignant tumors frequently encounter hypoxia and nutrient (e.g., glucose) deprivation, which occurs because of insufficient blood supply. This results in necrotic cell death in the core region of solid tumors. Necrotic cells release their cellular cytoplasmic contents into the extracellular space, such as high mobility group box 1 (HMGB1), which is a nonhistone nuclear protein, but acts as a proinflammatory and tumor-promoting cytokine when released by necrotic cells. These released molecules recruit immune and inflammatory cells, which exert tumor-promoting activity by inducing angiogenesis, proliferation, and invasion. Development of a necrotic core in cancer patients is also associated with poor prognosis. Conventionally, necrosis has been thought of as an unregulated process, unlike programmed cell death processes like apoptosis and autophagy. Recently, necrosis has been recognized as a programmed cell death, encompassing processes such as oncosis, necroptosis, and others. Metabolic stress-induced necrosis and its regulatory mechanisms have been poorly investigated until recently. Snail and Dlx-2, EMT-inducing transcription factors, are responsible for metabolic stress-induced necrosis in tumors. Snail and Dlx-2 contribute to tumor progression by promoting necrosis and inducing EMT and oncogenic metabolism. Oncogenic metabolism has been shown to play a role(s) in initiating necrosis. Here, we discuss the molecular mechanisms underlying metabolic stress-induced programmed necrosis that promote tumor progression and aggressiveness.

Intralesional rose bengal in melanoma elicits tumor immunity via activation of dendritic cells by the release of high mobility group box 1

Intralesional (IL) therapy is under investigation to treat dermal and subcutaneous metastatic cancer. Rose bengal (RB) is a staining agent that was originally used by ophthalmologists and in liver function studies. IL injection of RB has been shown to induce regression of injected and uninjected tumors in murine models and clinical trials. In this study, we have shown a mechanism of tumor-specific immune response induced by IL RB. In melanoma-bearing mice, IL RB induced regression of injected tumor and inhibited the growth of bystander lesions mediated by CD8⁺ T cells. IL RB resulted in necrosis of tumor cells and the release of High Mobility Group Box 1 (HMGB1), with increased dendritic cell (DC) infiltration into draining lymph nodes and the activation of tumor-specific T cells. Treatment of DC with tumor supernatants increased the ability of DCs to stimulate T cell proliferation, and blockade of HMGB1 in the supernatants suppressed DC activity. Additionally, increased HMGB1 levels were measured in the sera of melanoma patients treated with IL RB. These results support the role of IL RB to activate dendritic cells at the site of tumor necrosis for the induction of a systemic anti-tumor immune response.

Iron Handling in Tumor-Associated Macrophages-Is There a New Role for Lipocalin-2?

Carcinogenesis is a multistep process. Besides somatic mutations in tumor cells, stroma-associated immunity is a major regulator of tumor growth. Tumor cells produce and secrete diverse mediators to create a local microenvironment that supports their own survival and growth. It is becoming apparent that iron acquisition, storage, and release in tumor cells is different from healthy counterparts. It is also appreciated that macrophages in the tumor microenvironment acquire a tumor-supportive, anti-inflammatory phenotype that promotes tumor cell proliferation, angiogenesis, and metastasis. Apparently, this behavior is attributed, at least in part, to the ability of macrophages to support tumor cells with iron. Polarization of macrophages by apoptotic tumor cells shifts the profile of genes involved in iron metabolism from an iron sequestering to an iron-release phenotype. Iron release from macrophages is supposed to be facilitated by ferroportin. However, lipid mediators such as sphingosine-1-phosphate, released form apoptotic tumor cells, upregulate lipocalin-2 (Lcn-2) in macrophages. This protein is known to bind siderophore-complexed iron and thus, may participate in iron transport in the tumor microenvironment. We describe how macrophages handle iron in the tumor microenvironment, discuss the relevance of an iron-release macrophage phenotype for tumor progression, and propose a new role for Lcn-2 in tumor-associated macrophages.

Identification, molecular evolution of toll-like receptors in a Tibetan schizothoracine fish (Gymnocypris eckloni) and their expression profiles in response to acute hypoxia

Hypoxia plays an important role in regulating a variety of physiological responses as well as in pathological situations, but to date the roles of Toll-like receptors (TLRs) in fish in response to hypoxia are still poorly understood. Here, we sequenced the transcriptome of G. eckloni and identified the members of TLR family by scanning transcriptome, and then investigated the expression profiles of a complete set of TLRs in G. eckloni in response to acute hypoxia (4 h at DO = 0.3 ± 0.1 mg/L). The de novo-assembled transcriptome consisted of a total of 162,235 transcripts, further clustered into 110,231 unigenes. Based on the transcriptome, a total of 18 TLRs were identified in G. eckloni, and of them three TLRs (TLR5, TLR8 and TLR22) possessed two distinct paralogous genes. The duplicated genes of TLR22 were discovered for the first time in cyprinid fish, but did not origin from a recent duplication event. Of them TLR22b may be specific for schizothoracine fish, at least for G. eckloni. Phylogenetic analysis supported the classification of TLRs into six families as in other vertebrates but was partly different from the previous study. The sliding window analysis showed strong signals of positive selection in TLR2, TLR 4, TLR 5a, TLR 7, TLR 19, TLR 20, TLR 21, TLR 22a and TLR 22b, but most codons under positive selection were located in the putative LRR regions. The mRNA expression of most TLRs in head kidney, spleen and gill decreased significantly or remained unchanged under acute hypoxia, whereas acute hypoxia increased expressions of TLR2 and TLR3 in head kidney, of TLR8a, TLR12 and TLR19 in spleen, and of TLR1 in gill, suggesting tissues-specific expressions of TLRs play important roles in mediating innate immune responses for host defense against tissue damages or physiological changes induced by hypoxia.

Five-year disease-free survival among stage II-IV breast cancer patients receiving FAC and AC chemotherapy in phase II clinical trials of Panagen

BACKGROUND

We report on the results of a phase II clinical trial of Panagen (tablet form of fragmented human DNA preparation) in breast cancer patients (placebo group n = 23, Panagen n = 57). Panagen was administered as an adjuvant leukoprotective agent in FAC and AC chemotherapy regimens. Pre-clinical studies clearly indicate that Panagen acts by activating dendritic cells and induces the development of adaptive anticancer immune response.

METHODS

We analyzed 5-year disease-free survival of patients recruited into the trial.

RESULTS

Five-year disease-free survival in the placebo group was 40 % (n = 15), compared with the Panagen arm - 53 % (n = 51). Among stage III patients, disease-free survival was 25 and 52 % for placebo (n = 8) and Panagen (n = 25) groups, respectively. Disease-free survival of patients with IIIB + C stage was as follows: placebo (n = 6)-17 % vs Panagen (n = 18)-50 %.

CONCLUSIONS

Disease-free survival rate (17 %) of patients with IIIB + C stage breast cancer receiving standard of care therapy is within the global range. Patients who additionally received Panagen demonstrate a significantly improved disease-free survival rate of 50 %. This confirms anticancer activity of Panagen.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02115984 from 04/07/2014.

Contamination of DNase Preparations Confounds Analysis of the Role of DNA in Alum-Adjuvanted Vaccines

Aluminum salt (alum) adjuvants have been used for many years as adjuvants for human vaccines because they are safe and effective. Despite its widespread use, the means by which alum acts as an adjuvant remains poorly understood. Recently, it was shown that injected alum is rapidly coated with host chromatin within mice. Experiments suggested that the host DNA in the coating chromatin contributed to alum's adjuvant activity. Some of the experiments used commercially purchased DNase and showed that coinjection of these DNase preparations with alum and Ag reduced the host's immune response to the vaccine. In this study, we report that some commercial DNase preparations are contaminated with proteases. These proteases are responsible for most of the ability of DNase preparations to inhibit alum's adjuvant activity. Nevertheless, DNase somewhat reduces responses to some Ags with alum. The effect of DNase is independent of its ability to cleave DNA, suggesting that alum improves CD4 responses to Ag via a pathway other than host DNA sensing.

Gut mucosal DAMPs in IBD: from mechanisms to therapeutic implications

Endogenous damage-associated molecular patterns (DAMPs) are released during tissue damage and have increasingly recognized roles in the etiology of many human diseases. The inflammatory bowel diseases (IBD), ulcerative colitis (UC) and Crohn's disease (CD), are immune-mediated conditions where high levels of DAMPs are observed. DAMPs such as calprotectin (S100A8/9) have an established clinical role as a biomarker in IBD. In this review, we use IBD as an archetypal common chronic inflammatory disease to focus on the conceptual and evidential importance of DAMPs in pathogenesis and why DAMPs represent an entirely new class of targets for clinical translation.

Naked DNA in cells: An inducer of major histocompatibility complex molecules to evoke autoimmune responses?

The major histocompatibility complex (MHC) is the exclusive chaperone that presents intracellular antigens, either self or foreign to T cells. Interestingly, aberrant expression of MHC molecules has been reported in various autoimmune target tissues such as thyroid follicular cells in Grave’s disease. Herein, we review the discovery of an unexpected effect of cytosolic double-stranded DNA (dsDNA), despite its origins, to induce antigen processing and presenting genes, including MHC molecules, in non-immune cells. Moreover, we highlight several recent studies that suggest cell injury endows thyroid epithelial cells with a phenotype of mature antigen presenting cells by inducing multiple antigen processing and presenting genes via releasing genomic DNA fragments into the cytosol. We discuss the possibility that such cytosolic dsDNA, in naked form without binding to histone proteins, might be involved in the development of cell damage-triggered autoimmune responses. We also discuss the possible molecular mechanism by which cytosolic dsDNA can induce MHC molecules. It is reasonable to speculate that cytosolic dsDNA-induced MHC class I is partially due to an autocrine/paracrine effect of type I interferon (IFN). While the mechanism of cytosolic dsDNA-induced MHC class II expression appears, at least partially, distinct from that mediated by IFN-γ. Further in-depth are required to clarify this picture.

Titanium ions form particles that activate and execute interleukin-1β release from lipopolysaccharide-primed macrophages

BACKGROUND AND OBJECTIVE

Peri-implantitis is a destructive inflammatory process characterized by destruction of the implant-supporting bone. Inflammasomes are large intracellular multiprotein complexes that play a central role in innate immunity by activating the release of proinflammatory cytokines. Although inflammasome activation has previously been linked to periodontal inflammation, there is still no information on a potential association with peri-implantitis. The aim of this study was to examine cytotoxic and proinflammatory effects, including inflammasome activation, of metals used in dental implants, in an in vitro model, as well as from clinical tissue samples.

MATERIAL AND METHODS

Human macrophages were exposed to different metals [titanium (Ti), cobalt, chromium and molybdenum] in a cell-culture assay. Cytotoxicity was determined using the neutral red uptake assay. Cytokine secretion was quantified using an ELISA, and the expression of genes of various inflammasome components was analysed using quantitative PCR. In addition, the concentrations of interleukin-1β (IL-1β) and Ti in mucosal tissue samples taken in the vicinity of dental implants were determined using ELISA and inductively coupled plasma mass spectrometry, respectively.

RESULTS

Ti ions in physiological solutions stimulated inflammasome activation in human macrophages and consequently IL-1β release. This effect was further enhanced by macrophages that have been exposed to lipopolysaccharides. The proinflammatory activation caused by Ti ions disappeared after filtration (0.22 μm), which indicates an effect of particles. Ti ions alone did not stimulate transcription of the inflammasome components. The Ti levels of tissue samples obtained in the vicinity of Ti implants were sufficiently high (≥ 40 μm) to stimulate secretion of IL-1β from human macrophages in vitro.

CONCLUSION

Ti ions form particles that act as secondary stimuli for a proinflammatory reaction.

Excessive Cytosolic DNA Fragments as a Potential Trigger of Graves' Disease: An Encrypted Message Sent by Animal Models

Graves' hyperthyroidism is caused by autoantibodies directed against the thyroid-stimulating hormone receptor (TSHR) that mimic the action of TSH. The establishment of Graves' hyperthyroidism in experimental animals has proven to be an important approach to dissect the mechanisms of self-tolerance breakdown that lead to the production of thyroid-stimulating TSHR autoantibodies (TSAbs). "Shimojo's model" was the first successful Graves' animal model, wherein immunization with fibroblasts cells expressing TSHR and a major histocompatibility complex (MHC) class II molecule, but not either alone, induced TSAb production in AKR/N (H-2^k) mice. This model highlights the importance of coincident MHC class II expression on TSHR-expressing cells in the development of Graves' hyperthyroidism. These data are also in agreement with the observation that Graves' thyrocytes often aberrantly express MHC class II antigens via mechanisms that remain unclear. Our group demonstrated that cytosolic self-genomic DNA fragments derived from sterile injured cells can induce aberrant MHC class II expression and production of multiple inflammatory cytokines and chemokines in thyrocytes in vitro, suggesting that severe cell injury may initiate immune responses in a way that is relevant to thyroid autoimmunity mediated by cytosolic DNA signaling. Furthermore, more recent successful Graves' animal models were primarily established by immunizing mice with TSHR-expressing plasmids or adenovirus. In these models, double-stranded DNA vaccine contents presumably exert similar immune-activating effect in cells at inoculation sites and thus might pave the way toward successful Graves' animal models. This review focuses on evidence suggesting that cell injury-derived self-DNA fragments could act as Graves' disease triggers.

The Pathogenesis of Hashimoto's Thyroiditis: Further Developments in our Understanding

Hashimoto's thyroiditis (HT) is part of a spectrum of thyroid autoimmune conditions and this review provides an update on the latest developments in the field. HT has a genetic predisposition with a number of immune-related and thyroid-specific genes conferring disease susceptibility. However, disentangling genes with protective and predisposing effect is a complex process that requires further work. The recent increase in the incidence of HT implicates environmental factors in disease pathogenesis including improved hygiene, increased dietary iodine intake, new treatment modalities and chemical agents. Additional unmodifiable predisposing factors include stress, climate, age and gender. Both cellular and humoral immunity play a role in HT pathogenesis. Defects in T regulatory cells and increased activation of follicular helper T cells may have a role in disease initiation/perpetuation. Infiltrating lymphocytes can be directly cytotoxic to thyroid follicular cells (TFC) or may affect cell viability/function indirectly through cytokine production, which alters TFC integrity and modulates their metabolic and immune function. Thyroid peroxidase and thyroglobulin antibodies are present in the majority of HT patients and help with management decisions. Antibodies against the sodium iodide symporter and pendrin are present in a minority with little known about their clinical relevance. In addition to immune cells, recent work has identified DNA fragments, generated following cell death, and micro RNA as potential factors in HT pathogenesis. Despite the large number of studies, the mechanistic pathways in HT are still not fully understood and further work is required to enhance our knowledge and identify novel preventative and therapeutic clinical targets.

Antitumor immunity by magnetic nanoparticle-mediated hyperthermia

Magnetic nanoparticle-mediated hyperthermia (MNHT) generates heat to a local tumor tissue of above 43°C without damaging surrounding normal tissues. By applying MNHT, a significant amount of heat-shock proteins is expressed within and around the tumor tissues, inducing tumor-specific immune responses. In vivo experiments have indicated that MNHT can induce the regression of not only a local tumor tissue exposed to heat, but also distant metastatic tumors unexposed to heat. In this article, we introduce recent progress in the application of MNHT for antitumor treatments and summarize the mechanisms and processes of its biological effects during antitumor induction by MNHT. Several clinical trials have been conducted indicating that the MNHT system may add a promising and novel approach to antitumor therapy.

Results of multicenter double-blind placebo-controlled phase II clinical trial of Panagen preparation to evaluate its leukostimulatory activity and formation of the adaptive immune response in patients with stage II-IV breast cancer

Background

We performed a multicenter, double-blind, placebo-controlled, phase II clinical trial of human dsDNA-based preparation Panagen in a tablet form. In total, 80 female patients with stage II-IV breast cancer were recruited.

Methods

Patients received three consecutive FAC (5-fluorouracil, doxorubicin and cyclophosphamide) or AC (doxorubicin and cyclophosphamide) adjuvant chemotherapies (3 weeks per course) and 6 tablets of 5 mg Panagen or placebo daily (one tablet every 2–3 hours, 30 mg/day) for 18 days during each chemotherapy course. Statistical analysis was performed using Statistica 6.0 software, and non-parametric analyses, namely Wilcoxon-Mann–Whitney and paired Wilcoxon tests. To describe the results, the following parameters were used: number of observations (n), median, interquartile range, and minimum-maximum range.

Results

Panagen displayed pronounced leukostimulatory and leukoprotective effects when combined with chemotherapy. In an ancillary protocol, anticancer effects of a tablet form of Panagen were analyzed. We show that Panagen helps maintain the pre-therapeutic activity level of innate antitumor immunity and induces formation of a peripheral pool of cytotoxic CD8+ perforin + T-cells. Our 3-year follow-up analysis demonstrates that 24% of patients who received Panagen relapsed or died after the therapy, as compared to 45% in the placebo cohort.

Conclusions

The data collected in this trial set Panagen as a multi-faceted “all-in-one” medicine that is capable of simultaneously sustaining hematopoiesis, sparing the innate immune cells from adverse effects of three consecutive rounds of chemotherapy and boosting individual adaptive immunity. Its unique feature is that it is delivered via gastrointestinal tract and acts through the lymphoid system of intestinal mucosa. Taken together, maintenance of the initial levels of innate immunity, development of adaptive cytotoxic immune response and significantly reduced incidence of relapses 3 years after the therapy argue for the anticancer activity of Panagen.

Trial registration

ClinicalTrials.gov NCT02115984 from 04/07/2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1142-z) contains supplementary material, which is available to authorized users.

Primary sterile necrotic cells fail to cross-prime CD8(+) T cells

Necrotic cells are known to activate the innate immune system and trigger inflammation by releasing damage associated molecular patterns (DAMPs). However, how necrotic cells influence the induction of antigen-specific CD8(+) T cell-mediated adaptive immune responses under sterile conditions, in the absence of pathogen associated molecular patterns (PAMPs), remains poorly understood. Here, we examined antigen-specific CD8(+) T-cell responses to primary sterile necrotic tumor cells both in vitro and in vivo. We found that primary necrotic cells alone fail to generate CD8(+) T cell-dependent immune responses toward cell-associated antigens. We show that necrotic cells trigger CD8(+) T-cell immunity only in the presence of PAMPs or analogs, such as p(dI-dC) and/or unmethylated CpG DNA. The electroporation of tumor cells with these PAMPs prior to necrosis induction triggered antigen-specific CD8(+) T-cell responses through a TLR9/MyD88-dependent pathway. In addition, we found that necrotic cells contain factors that can block the cross-priming of CD8(+) T cells even under non-sterile conditions and can serve as a possible mechanism of immunosuppression. These results suggest that antigen-specific CD8(+) T-cell responses to primary necrotic tumor cells can be induced in the presence of PAMPs and thus have a substantial impact on the development of antitumor vaccination strategies.

Self DNA from lymphocytes that have undergone activation-induced cell death enhances murine B cell proliferation and antibody production

Systemic lupus erythematosus (SLE) is characterized by prominent autoinflammatory tissue damage associated with impaired removal of dying cells and DNA. Self DNA-containing immune complexes are able to activate both innate and adaptive immune responses and play an important role in the maintenance and exacerbation of autoimmunity in SLE. In this study, we used DNA from lymphocytes that have undergone activation-induced cell death (ALD-DNA) and analyzed its role on the activation and differentiation of B cells from normal BALB/c mice as well as lupus-prone MRL^+/+ and MRL/lpr mice. We found that ALD-DNA directly increased the expression of costimulatory molecules and the survival of naïve B cells in vitro. Although ALD-DNA alone had little effect on the proliferation of naïve B cells, it enhanced LPS-activated B cell proliferation in vitro and in vivo. In addition, ALD-DNA increased plasma cell numbers and IgG production in LPS-stimulated cultures of naïve B cells, in part via enhancing IL-6 production. Importantly, B cells from lupus mice were hyperresponsive to ALD-DNA and/or LPS relative to normal control B cells in terminal plasma cell differentiation, as evidenced by increases in CD138⁺ cell numbers, IgM production, and mRNA levels of B lymphocyte-induced maturation protein-1 (Blimp-1) and the X-box binding protein 1 (XBP1). Furthermore, ALD-DNA enhanced CD40-activated naïve B cell proliferation. Collectively, these data indicate that self DNA can serve as a DAMP (damage-associated molecular pattern) that cooperates with signals from both innate and adaptive immunity to promote polyclonal B cell activation, a common characteristic of autoimmune diseases.

Cross Talk Between Vascular Smooth Muscle Cells and Monocytes Through Interleukin-1β/Interleukin-18 Signaling Promotes Vein Graft Thickening

Objective—

Interleukin (IL)-1β and IL-18 are key proinflammatory cytokines that play important roles in the pathophysiology of vein graft remodeling. However, the mechanism of IL-1β/IL-18 production and its role in the development of graft remodeling remain unclear.

Approach and Results—

IL-1β/IL-18 were rapidly expressed in venous interposition grafts. Vascular smooth muscle cell (VSMC) death and monocytic inflammasome activation occurred in grafted veins. Necrotic VSMCs induced the expression of IL-1β, IL-18, and other inflammasome-associated proteins in monocytes, which was partially inhibited by their antagonist, recombinant IL-1ra-Fc-IL-18bp. Activated monocytes stimulated proliferation of VSMCs by activating cell growth–related signaling molecules (AKT, STAT3, ERK1/2, and mTOR [AKT/protein kinase B, signal transducer and activator of transcription 3, extracellular signal-regulated kinase 1/2, mammalian target of rapamycin]) and increasing production of platelet-derived growth factor-bb; these effects were suppressed by IL-1ra-Fc-IL-18bp. Activated monocytes also promoted migration of VSMCs, which was independent of IL-1β/IL-18 signaling. Importantly, administration of IL-1ra-Fc-IL-18bp inhibited activation of cell growth–related signaling molecules, VSMC proliferation, and vein graft thickening in vivo.

Conclusions—

Our work identified an interaction among necrotic VSMCs, monocytes, and viable VSMCs through IL-1β/IL-18 signaling, which might be exploited as a therapeutic target in vein graft remodeling.

Rose Bengal acetate photodynamic therapy (RBAc-PDT) induces exposure and release of Damage-Associated Molecular Patterns (DAMPs) in human HeLa cells

The new concept of Immunogenic Cell Death (ICD), associated with Damage Associated Molecular Patterns (DAMPs) exposure and/or release, is recently becoming very appealing in cancer treatment. In this context, PhotoDynamic Therapy (PDT) can give rise to ICD and to immune response upon dead cells removal. The list of PhotoSensitizers (PSs) able to induce ICD is still short and includes Photofrin, Hypericin, Foscan and 5-ALA. The goal of the present work was to investigate if Rose Bengal Acetate (RBAc), a powerful PS able to trigger apoptosis and autophagy, enables photosensitized HeLa cells to expose and/or release pivotal DAMPs, i.e. ATP, HSP70, HSP90, HMGB1, and calreticulin (CRT), that characterize ICD. We found that apoptotic HeLa cells after RBAc-PDT exposed and released, early after the treatment, high amount of ATP, HSP70, HSP90 and CRT; the latter was distributed on the cell surface as uneven patches and co-exposed with ERp57. Conversely, autophagic HeLa cells after RBAc-PDT exposed and released HSP70, HSP90 but not CRT and ATP. Exposure and release of HSP70 and HSP90 were always higher on apoptotic than on autophagic cells. HMGB1 was released concomitantly to secondary necrosis (24 h after RBAc-PDT). Phagocytosis assay suggests that CRT is involved in removal of RBAc-PDT generated apoptotic HeLa cells. Altogether, our data suggest that RBAc has all the prerequisites (i.e. exposure and/or release of ATP, CRT, HSP70 and HSP90), that must be verified in future vaccination experiments, to be considered a good PS candidate to ignite ICD. We also showed tha CRT is involved in the clearance of RBAc photokilled HeLa cells. Interestingly, RBAc-PDT is the first cancer PDT protocol able to induce the translocation of HSP90 and plasma membrane co-exposure of CRT with ERp57.

Responses of macrophages to the danger signals released from necrotic cells

The immune system maintains homeostasis by recognizing and responding to cell death caused by various stresses. The immune response is considered to be elicited by 'danger signals' released from necrotic cells. However, the identity of the danger signals remains elusive. In this study, we focused on the expression of chemokines by macrophages stimulated with necrotic cells. In mouse bone-marrow-derived macrophages, the chemokine monocyte chemoattractant protein (MCP)-3 was induced at both the mRNA and protein levels in response to heat-killed murine cells. The induction of MCP-3 was also observed in MyD88-deficient macrophages, indicating that Toll-like receptors and the IL-1 receptor are not involved in this response. Consistent with this observation, the activation of NF-κB was not detected in RAW264.7 macrophages stimulated with necrotic cells. Treatments with proteinase K, DNaseI or RNaseA did not affect the ' STIMULATING ACTIVITY': of necrotic cells. In contrast, treatment with apyrase, which removes phosphates from nucleoside tri- and di-phosphates, abolished the inducing activity. Purified UDP at 30 µM concentration elicited similar induction of MCP-3 in RAW264.7 macrophages. Small interfering RNA-mediated knock-down of the UDP receptor P2Y6 in RAW264.7 cells significantly reduced the induction of MCP-3 in response to necrotic cells, but not its induction by lipopolysaccharide. Furthermore, ectopic expression of the P2Y6 receptor in HEK293 cells conferred responsiveness to necrotic cells. These results suggest that UDP released by necrotic cells plays a critical role as an endogenous danger signal and that P2Y6 is required for the induction of MCP-3 in response to necrotic cells.

UVB radiation illuminates the role of TLR3 in the epidermis

UV radiation poses a significant risk to human health. The mechanisms that help repair UV-damaged cells have recently been more clearly defined with the observation that Toll-like receptor 3 can sense self RNA released from necrotic keratinocytes following UV damage. TLR3 activation in the skin induces inflammation and increases expression of genes involved in skin barrier repair. Activation of TLR2 in the skin by commensal microbial products prevents excessive inflammation by blocking downstream TLR3 signaling. This review highlights how UV damage induced inflammation in the skin is propagated by host products and regulated by host inhabitants.

Peptidases released by necrotic cells control CD8+ T cell cross-priming

Cross-priming of CD8+ T cells and generation of effector immune responses is pivotal for tumor immunity as well as for successful anticancer vaccination and therapy. Dead and dying cells produce signals that can influence Ag processing and presentation; however, there is conflicting evidence regarding the immunogenicity of necrotic cell death. We used a mouse model of sterile necrosis, in which mice were injected with sterile primary necrotic cells, to investigate a role of these cells in priming of CD8+ T cells. We discovered a molecular mechanism operating in Ag donor cells that regulates cross-priming of CD8+ T cells during primary sterile necrosis and thereby controls adaptive immune responses. We found that the cellular peptidases dipeptidyl peptidase 3 (DPP-3) and thimet oligopeptidase 1 (TOP-1), both of which are present in nonimmunogenic necrotic cells, eliminated proteasomal degradation products and blocked Ag cross-presentation. While sterile necrotic tumor cells failed to induce CD8+ T cell responses, their nonimmunogenicity could be reversed in vitro and in vivo by inactivation of DPP-3 and TOP-1. These results indicate that control of cross-priming and thereby immunogenicity of primary sterile necrosis relies on proteasome-dependent oligopeptide generation and functional status of peptidases in Ag donor cells.

Molecular determinants of sterile inflammation

Necrotic cell death alerts the acquired immune system to activate naïve T cells even in the absence of non-self derived molecules (e.g. pathogens). In addition, sterile necrosis leads to innate immune-mediated acute inflammation. The dying cells still represent a threat to the body that should be eliminated by the host immune response. Although the inflammatory response plays important roles in protecting the host and repairing tissues, it can also cause the collateral damage to normal tissues that underlies disease pathogenesis. Tissue resident macrophages recognize the danger signals released from necrotic cells via the pattern recognition receptors and secrete IL-1 that results in acute neutrophilic inflammation. This article will review our current knowledge especially focusing on the role of IL-1 in the sterile necrotic cell death induced inflammation.

DNA vaccines: a simple DNA sensing matter?

Since the introduction of DNA vaccines two decades ago, this attractive strategy has been hampered by its low immunogenicity in humans. Studies conducted to improve the immunogenicity of DNA vaccines have shown that understanding the mechanism of action of DNA vaccines might be the key to successfully improving their immunogenicity. Our current understanding is that DNA vaccines induce innate and adaptive immune responses in two ways: (1) encoded protein (or polypeptide) antigen(s) by the DNA plasmid can be expressed in stromal cells (i.e., muscle cells) as well as DCs, where these antigens are processed and presented to naïve CD4 or CD8 T cells either by direct or cross presentation, respectively; and (2) the transfected DNA plasmid itself may bind to an un-identified cytosolic DNA sensor and activate the TBK1-STING pathway and the production of type I interferons (IFNs) which function as an adjuvant. Recent studies investigating double-stranded cytosolic DNA sensor(s) have highlighted new mechanisms in which cytosolic DNA may release secondary metabolites, which are in turn recognized by a novel DNA sensing machinery. Here, we discuss these new metabolites and the possibilities of translating this knowledge into improved immunogenicity for DNA vaccines.

Heme oxygenase-1 expression protects the heart from acute injury caused by inducible Cre recombinase

The protective effect of heme oxygenase-1 (HO-1) expression in cardiovascular disease has been previously demonstrated using transgenic animal models in which HO-1 is constitutively overexpressed in the heart. However, the temporal requirements for protection by HO-1 induction relative to injury have not been investigated, but are essential to employ HO-1 as a therapeutic strategy in human cardiovascular disease states. Therefore, we generated mice with cardiac-specific, tamoxifen (TAM)-inducible overexpression of a human HO-1 (hHO-1) transgene (myosin heavy chain (MHC)-HO-1 mice) by breeding mice with cardiac-specific expression of a TAM-inducible Cre recombinase (MHC-Cre mice), with mice containing an hHO-1 transgene preceded by a floxed-stop signal. MHC-HO-1 mice overexpress HO-1 mRNA and the enzymatically active protein following TAM administration (40 mg/kg body weight on 2 consecutive days). In MHC-Cre controls, TAM administration leads to severe, acute cardiac toxicity, cardiomyocyte necrosis, and 80% mortality by day 3. This cardiac toxicity is accompanied by a significant increase in inflammatory cells in the heart that are predominantly neutrophils. In MHC-HO-1 mice, HO-1 overexpression ameliorates the depression of cardiac function and high mortality rate observed in MHC-Cre mice following TAM administration and attenuates cardiomyocyte necrosis and neutrophil infiltration. These results highlight that HO-1 induction is sufficient to prevent the depression of cardiac function observed in mice with TAM-inducible Cre recombinase expression by protecting the heart from necrosis and neutrophil infiltration. These findings are important because MHC-Cre mice are widely used in cardiovascular research despite the limitations imposed by Cre-induced cardiac toxicity, and also because inflammation is an important pathological component of many human cardiovascular diseases.

Sterile inflammation in the liver and pancreas

The ability of tissue injury to result in inflammation is a well-recognized phenomenon and is central to a number of common liver and pancreatic diseases including alcoholic steatohepatitis and pancreatitis, as well as drug-induced liver injury, non-alcoholic steatohepatitis, and pancreatitis from other causes. The requirements of extracellular damage-associated molecules and a cytosolic machinery labeled the inflammasome have been established in in vitro culture systems and in vivo disease models. This has provided a generic insight into the pathways involved, and the challenge now is to understand the specifics of these mechanisms in relation to the particular insults and organs involved. One reason for the excitement in this field is that a number of therapeutic candidates such a toll-like receptor antagonists and interleukin-1R antagonists are either approved or in clinical trials for other indications.

Innate Immune Signaling by, and Genetic Adjuvants for DNA Vaccination

DNA vaccines can induce both humoral and cellular immune responses. Although some DNA vaccines are already licensed for infectious diseases in animals, they are not licensed for human use because the risk and benefit of DNA vaccines is still controversial. Indeed, in humans, the immunogenicity of DNA vaccines is lower than that of other traditional vaccines. To develop the use of DNA vaccines in the clinic, various approaches are in progress to enhance or improve the immunogenicity of DNA vaccines. Recent studies have shown that immunogenicity of DNA vaccines are regulated by innate immune responses via plasmid DNA recognition through the STING-TBK1 signaling cascade. Similarly, molecules that act as dsDNA sensors that activate innate immune responses through STING-TBK1 have been identified and used as genetic adjuvants to enhance DNA vaccine immunogenicity in mouse models. However, the mechanisms that induce innate immune responses by DNA vaccines are still unclear. In this review, we will discuss innate immune signaling upon DNA vaccination and genetic adjuvants of innate immune signaling molecules.

Traditional biochemical assays for studying toll-like receptor 9

Understanding the mechanistic basis of receptor activation and regulation can offer therapeutic targets for disease treatment. Evidence is emerging for a role of the normally foreign responsive Toll-like receptors (TLRs) in the development of autoimmunity through response to self-patterns. Regulatory mechanisms governing this class of receptors are poorly understood, and failures within this system likely contribute to development of autoimmunity. In this article, we review biochemical assays used to study one of the self-pattern responsive TLRs, TLR9, and suggest that these studies are critical for development of new targets for autoimmune therapies.

Innate immune response after adenoviral gene delivery into skin is mediated by AIM2, NALP3, DAI and mda5

Methods for human skin gene therapy requires efficient and stable introduction of genes into skin cells. Transient cutaneous gene therapy is an attractive approach in the treatment of skin diseases. The ‘Achilles heel’ of adenoviral gene therapy is its immunogenicity and many aspects of adenovirus induced cutaneous immune reaction still remain unanswered, particularly the role of keratinocytes. Therefore, human keratinocytes were transfected with adenoviral DNA and cytokine expression was analyzed. Moreover, adenoviral transduction of full-skin was performed ex vivo and in vivo. We observed cytokine induction after cytoplasmatic internalization of adenoviral DNA into epidermal cells. Inhibition of AIM2, NALP3, DAI or mda5 downregulated the cytokine response. Transduction of immunocompetent mice led to a detectable transgene expression for 12 days. Re-application of the vector led to a decrease in intensity and duration of transgene expression limited to 4 days and an increased cytokine expression. In contrast, immunodeficient mice showed a reduced expression of cytokines after DNA internalization. AIM2, NALP3, DAI and mda5 are essential in the induction of an innate immune response towards adenoviral DNA. This immune reaction leads to a decrease in transduction efficiency of the vector after re-application and modulation of these receptor systems stabilizes transgene expression.