Recognition of cytosolic DNA attenuates glucose metabolism and induces AMPK mediated energy stress response

Chemical and Biomolecular Strategies for STING Pathway Activation in Cancer Immunotherapy

The stimulator of interferon genes (STING) cellular signaling pathway is a promising target for cancer immunotherapy. Activation of the intracellular STING protein triggers the production of a multifaceted array of immunostimulatory molecules, which, in the proper context, can drive dendritic cell maturation, antitumor macrophage polarization, T cell priming and activation, natural killer cell activation, vascular reprogramming, and/or cancer cell death, resulting in immune-mediated tumor elimination and generation of antitumor immune memory. Accordingly, there is a significant amount of ongoing preclinical and clinical research toward further understanding the role of the STING pathway in cancer immune surveillance as well as the development of modulators of the pathway as a strategy to stimulate antitumor immunity. Yet, the efficacy of STING pathway agonists is limited by many drug delivery and pharmacological challenges. Depending on the class of STING agonist and the desired administration route, these may include poor drug stability, immunocellular toxicity, immune-related adverse events, limited tumor or lymph node targeting and/or retention, low cellular uptake and intracellular delivery, and a complex dependence on the magnitude and kinetics of STING signaling. This review provides a concise summary of the STING pathway, highlighting recent biological developments, immunological consequences, and implications for drug delivery. This review also offers a critical analysis of an expanding arsenal of chemical strategies that are being employed to enhance the efficacy, safety, and/or clinical utility of STING pathway agonists and lastly draws attention to several opportunities for therapeutic advancements.

A novel inactivated whole-cell Pseudomonas aeruginosa vaccine that acts through the cGAS-STING pathway

Pseudomonas aeruginosa infection continues to be a major threat to global public health, and new safe and efficacious vaccines are needed for prevention of infections caused by P. aeruginosa. X-ray irradiation has been used to prepare whole-cell inactivated vaccines against P. aeruginosa infection. However, the immunological mechanisms of X-ray-inactivated vaccines are still unclear and require further investigation. Our previous study found that an X-ray-inactivated whole-cell vaccine could provide protection against P. aeruginosa by boosting T cells. The aim of the present study was to further explore the immunological mechanisms of the vaccine. Herein, P. aeruginosa PAO1, a widely used laboratory strain, was utilized to prepare the vaccine, and we found nucleic acids and 8-hydroxyguanosine in the supernatant of X-ray-inactivated PAO1 (XPa). By detecting CD86, CD80, and MHCII expression, we found that XPa fostered dentritic cell (DC) maturation by detecting. XPa stimulated the cGAS-STING pathway as well as Toll-like receptors in DCs in vitro, and DC finally underwent apoptosis and pyroptosis after XPa stimulation. In addition, DC stimulated by XPa induced CD8⁺ T-cell proliferation in vitro and generated immunologic memory in vivo. Moreover, XPa vaccination induced both Th1 and Th2 cytokine responses in mice and reduced the level of inflammatory factors during infection. XPa protected mice in pneumonia models from infection with PAO1 or multidrug-resistant clinical isolate W9. Chronic obstructive pulmonary disease (COPD) mice immunized with XPa could resist PAO1 infection. Therefore, a new mechanism of an X-ray-inactivated whole-cell vaccine against P. aeruginosa infection was discovered in this study.

How immune-cell fate and function are determined by metabolic pathway choice: The bioenergetics underlying the immune response

Immune cells are highly dynamic in their response to the tissue environment. Most immune cells rapidly change their metabolic profile to obtain sufficient energy to engage in defensive or homeostatic processes. Such "immunometabolism" is governed through intermediate metabolites, and has a vital role in regulating immune-cell function. The underlying metabolic reactions are shaped by the abundance and accessibility of specific nutrients, as well as the overall metabolic status of the host. Here, we discuss how different immune-cell types gain a sufficient energy supply. We then explain how immune cells perform various functions under challenged conditions and expend energy to sustain homeostasis. Finally, we speculate on how the immune-cell metabolic profile might be modulated in health and disease, by manipulating nutrient availability. By such intervention, the recovery of patient with dysregulated immune system responses might be sped up and the fitness of an individual efficiently restored.

Electric field down-regulates CD9 to promote keratinocytes migration through AMPK pathway

Endogenous electric field (EF)-directed keratinocytes migration is known to play a key role in the wound re-epithelialization process. Although many molecules and signaling pathways are reported important for directional keratinocytes migration under EF, the underlying mechanism remains unclear. Our previous research found that CD9, a trans-membrane protein, is involved in wound re-epithelialization and CD9 downregulation contributes to keratinocytes migration. In this study, we observed the effect of EF on CD9 expression and keratinocytes migration. The keratinocytes migrated directionally toward the cathode and CD9 expression was down-regulated under EF (200mV/mm). In addition, CD9 overexpression reversed EF-induced migratory speed and the electrotactic response of keratinocytes. Also, we found that EF reduced AMP-activated protein kinase (AMPK) activity. Furthermore, AICAR, an AMPK activator, increased CD9 expression under EF, while compound C, an AMPK inhibitor, decreased CD9 expression in keratinocytes. Our results demonstrate that EF regulates CD9 expression and keratinocytes directional migration, in which AMPK pathway plays an important role.

Virus Control of Cell Metabolism for Replication and Evasion of Host Immune Responses

Over the last decade, there has been significant advances in the understanding of the cross-talk between metabolism and immune responses. It is now evident that immune cell effector function strongly depends on the metabolic pathway in which cells are engaged in at a particular point in time, the activation conditions, and the cell microenvironment. It is also clear that some metabolic intermediates have signaling as well as effector properties and, hence, topics such as immunometabolism, metabolic reprograming, and metabolic symbiosis (among others) have emerged. Viruses completely rely on their host's cell energy and molecular machinery to enter, multiply, and exit for a new round of infection. This review explores how viruses mimic, exploit or interfere with host cell metabolic pathways and how, in doing so, they may evade immune responses. It offers a brief outline of key metabolic pathways, mitochondrial function and metabolism-related signaling pathways, followed by examples of the mechanisms by which several viral proteins regulate host cell metabolic activity.

Regulating STING in health and disease

The presence of cytosolic double-stranded DNA molecules can trigger multiple innate immune signalling pathways which converge on the activation of an ER-resident innate immune adaptor named "STimulator of INterferon Genes (STING)". STING has been found to mediate type I interferon response downstream of cyclic dinucleotides and a number of DNA and RNA inducing signalling pathway. In addition to its physiological function, a rapidly increasing body of literature highlights the role for STING in human disease where variants of the STING proteins, as well as dysregulated STING signalling, have been implicated in a number of inflammatory diseases. This review will summarise the recent structural and functional findings of STING, and discuss how STING research has promoted the development of novel therapeutic approaches and experimental tools to improve treatment of tumour and autoimmune diseases.

G-rich DNA-induced stress response blocks type-I-IFN but not CXCL10 secretion in monocytes

Excessive inflammation can cause damage to host cells and tissues. Thus, the secretion of inflammatory cytokines is tightly regulated at transcriptional, post-transcriptional and post-translational levels and influenced by cellular stress responses, such as endoplasmic reticulum (ER) stress or apoptosis. Here, we describe a novel type of post-transcriptional regulation of the type-I-IFN response that was induced in monocytes by cytosolic transfection of a short immunomodulatory DNA (imDNA), a G-tetrad forming CpG-free derivative of the TLR9 agonist ODN2216. When co-transfected with cytosolic nucleic acid stimuli (DNA or 3P-dsRNA), imDNA induced caspase-3 activation, translational shutdown and upregulation of stress-induced genes. This stress response inhibited the type-I-IFN induction at the translational level. By contrast, the induction of most type-I-IFN-associated chemokines, including Chemokine (C-X-C Motif) Ligand (CXCL)10 was not affected, suggesting a differential translational regulation of chemokines and type-I-IFN. Pan-caspase inhibitors could restore IFN-β secretion, yet, strikingly, caspase inhibition did not restore global translation but instead induced a compensatory increase in the transcription of IFN-β but not CXCL10. Altogether, our data provide evidence for a differential regulation of cytokine release at both transcriptional and post-transcriptional levels which suppresses type-I-IFN induction yet allows for CXCL10 secretion during imDNA-induced cellular stress.