Genotoxin-producing induces tissue-specific types of DNA damage and DNA damage response outcomes.

Introduction: Typhoid toxin-expressing causes DNA damage in the intestinal mucosa , activating the DNA damage response (DDR) in the absence of inflammation. To understand whether the tissue microenvironment constrains the infection outcome, we compared the immune response and DDR patterns in the colon and liver of mice infected with a genotoxigenic strain or its isogenic control strain.

Methods: spatial transcriptomic and immunofluorescence have been used to assess DNA damage makers, activation of the DDR, innate immunity markers in a multiparametric analysis.

The crosstalk between DNA repair and immune responses.

In recent years, increasing evidence has highlighted the profound connection between DNA damage repair and the activation of immune responses. We spoke with researchers about their mechanistic interplays and the implications for cancer and other diseases.

Protocol for isolation of microbiota-derived membrane vesicles from mouse blood and colon.

Bacterial membrane vesicles have emerged as gadgets allowing remote communication between the microbiota and distal host organs. Here we describe a protocol for enriching vesicles from serum and colon that could widely be adapted for other tissues. We detail pre-clearing of serum or colon fluids using 0.

The gut microbiota prime systemic antiviral immunity via the cGAS-STING-IFN-I axis.

The microbiota are vital for immune homeostasis and provide a competitive barrier to bacterial and fungal pathogens. Here, we investigated how gut commensals modulate systemic immunity and response to viral infection. Antibiotic suppression of the gut microbiota reduced systemic tonic type I interferon (IFN-I) and antiviral priming.

Nuclear AIM2-Like Receptors Drive Genotoxic Tissue Injury by Inhibiting DNA Repair.

Radiation is an essential preparative procedure for bone marrow (BM) transplantation and cancer treatment. The therapeutic efficacy of radiation and associated toxicity varies from patient to patient, making it difficult to prescribe an optimal patient-specific irradiation dose. The molecular determinants of radiation response remain unclear.

Bacterial detection by NAIP/NLRC4 elicits prompt contractions of intestinal epithelial cell layers.

The gut epithelium serves to maximize the surface for nutrient and fluid uptake, but at the same time must provide a tight barrier to pathogens and remove damaged intestinal epithelial cells (IECs) without jeopardizing barrier integrity. How the epithelium coordinates these tasks remains a question of significant interest. We used imaging and an optical flow analysis pipeline to study the dynamicity of untransformed murine and human intestinal epithelia, cultured atop flexible hydrogel supports.

Chromatin-bound cGAS is an inhibitor of DNA repair and hence accelerates genome destabilization and cell death.

DNA repair via homologous recombination (HR) is indispensable for genome integrity and cell survival but if unrestrained can result in undesired chromosomal rearrangements. The regulatory mechanisms of HR are not fully understood. Cyclic GMP-AMP synthase (cGAS) is best known as a cytosolic innate immune sensor critical for the outcome of infections, inflammatory diseases, and cancer.

TUBE and UbiCRest assays for elucidating polyubiquitin modifications in protein complexes.

Ubiquitination is a reversible posttranslational modification that regulates nearly all cellular processes. The ubiquitin polypeptide is conjugated via its C-terminus to amine groups of lysine residues on target protein. Additionally, ubiquitins moieties can be conjugated in tandem to the initial ubiquitin via any of its internal lysine residues or N terminal methionine residue, resulting in the formation of polyubiquitin chains with distinct biophysical properties and biological functions.

Comet and micronucleus assays for analyzing DNA damage and genome integrity.

Detection of DNA damage in cells is fundamental for the study of DNA repair and genome-instability associated processes including carcinogenesis. Many studies often rely on cytotoxicity assays to estimate genotoxicity. However, measurements of cytotoxicity, a delayed outcome requiring high threshold genotoxicity to induce, does not provide information about the subtle, early genotoxic effects relevant for mechanistic understanding of DNA repair processes.

Biochemical and microscopic analysis of inflammasome complex formation.

Inflammasomes are multiprotein signaling platforms responsible for the maturation of pro-IL-1β and pro-IL-18 as well as the induction of an inflammatory cell death termed pyroptosis. Most inflammasomes consist of an upstream sensor, in most cases an adaptor protein (ASC) and inflammatory caspases such as caspase-1. Upon activation, sensor proteins oligomerize with adaptor proteins, forming large complexes called specks.

Hydrogen peroxide release by bacteria suppresses inflammasome-dependent innate immunity.

Hydrogen peroxide (HO) has a major function in host-microbial interactions. Although most studies have focused on the endogenous HO produced by immune cells to kill microbes, bacteria can also produce HO. How microbial HO influences the dynamics of host-microbial interactions is unclear.

The innate immune DNA sensor cGAS: A membrane, cytosolic, or nuclear protein?

Cyclic cGMP-AMP synthase (cGAS) alerts the innate immune system to the presence of foreign or damaged self-DNA inside the cell and is critical for the outcome of infections, inflammatory diseases, and cancer. Two studies now demonstrate that cGAS activation is regulated by differential subcellular localization through its non-enzymatic, N-terminal domain.

The deubiquitinase MYSM1 dampens NOD2-mediated inflammation and tissue damage by inactivating the RIP2 complex.

NOD2 is essential for antimicrobial innate immunity and tissue homeostasis, but require tight regulation to avert pathology. A focal point of NOD2 signaling is RIP2, which upon polyubiquitination nucleates the NOD2:RIP2 complex, enabling signaling events leading to inflammation, yet the precise nature and the regulation of the polyubiquitins coordinating this process remain unclear. Here we show that NOD2 signaling involves conjugation of RIP2 with lysine 63 (K63), K48 and M1 polyubiquitin chains, as well as with non-canonical K27 chains.

DNA damage-induced immune response: Micronuclei provide key platform.

DNA damage-induced activation of the cytoplasmic DNA sensor cGAS influences the outcome of infections, autoinflammation, and cancer. Recent studies by Harding et al. (2017.

Subversion of innate immune responses by Francisella involves the disruption of TRAF3 and TRAF6 signalling complexes.

The success of pathogens depends on their ability to circumvent immune defences. Francisella tularensis is one of the most infectious bacteria known. The remarkable virulence of Francisella is believed to be due to its capacity to evade or subvert the immune system, but how remains obscure.

Detection of a microbial metabolite by STING regulates inflammasome activation in response to Chlamydia trachomatis infection.

The innate immune system is a critical component of host defence against microbial pathogens, but effective responses require an ability to distinguish between infectious and non-infectious insult to prevent inappropriate inflammation. Using the important obligate intracellular human pathogen Chlamydia trachomatis; an organism that causes significant immunopathology, we sought to determine critical host and pathogen factors that contribute to the induction of inflammasome activation. We assayed inflammasome activation by immunoblotting and ELISA to detect IL-1β processing and LDH release to determine pyroptosis.

Fast type I interferon response protects astrocytes from flavivirus infection and virus-induced cytopathic effects.

Background: Neurotropic flaviviruses such as tick-borne encephalitis virus (TBEV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and Zika virus (ZIKV) are causative agents of severe brain-related diseases including meningitis, encephalitis, and microcephaly. We have previously shown that local type I interferon response within the central nervous system (CNS) is involved in the protection of mice against tick-borne flavivirus infection. However, the cells responsible for mounting this protective response are not defined.

Loss of the DNA Damage Repair Kinase ATM Impairs Inflammasome-Dependent Anti-Bacterial Innate Immunity.

The ATM kinase is a central component of the DNA damage repair machinery and redox balance. ATM dysfunction results in the multisystem disease ataxia-telangiectasia (AT). A major cause of mortality in AT is respiratory bacterial infections.

Type I Interferon response in olfactory bulb, the site of tick-borne flavivirus accumulation, is primarily regulated by IPS-1.

Background: Although type I interferons (IFNs)-key effectors of antiviral innate immunity are known to be induced via different pattern recognition receptors (PRRs), the cellular source and the relative contribution of different PRRs in host protection against viral infection is often unclear. IPS-1 is a downstream adaptor for retinoid-inducible gene I (RIG-I)-like receptor signaling. In this study, we investigate the relative contribution of IPS-1 in the innate immune response in the different brain regions during infection with tick-borne encephalitis virus (TBEV), a flavivirus that causes a variety of severe symptoms like hemorrhagic fevers, encephalitis, and meningitis in the human host.

Deubiquitinase MYSM1 Regulates Innate Immunity through Inactivation of TRAF3 and TRAF6 Complexes.

Pattern-recognition receptors (PRRs) including Toll-like receptors, RIG-I-like receptors, and cytoplasmic DNA receptors are essential for protection against pathogens but require tight control to avert inflammatory diseases. The mechanisms underlying this strict regulation are unclear. MYSM1 was previously described as a key component of epigenetic signaling machinery.

DNA damage primes the type I interferon system via the cytosolic DNA sensor STING to promote anti-microbial innate immunity.

Dysfunction in Ataxia-telangiectasia mutated (ATM), a central component of the DNA repair machinery, results in Ataxia Telangiectasia (AT), a cancer-prone disease with a variety of inflammatory manifestations. By analyzing AT patient samples and Atm(-/-) mice, we found that unrepaired DNA lesions induce type I interferons (IFNs), resulting in enhanced anti-viral and anti-bacterial responses in Atm(-/-) mice. Priming of the type I interferon system by DNA damage involved release of DNA into the cytoplasm where it activated the cytosolic DNA sensing STING-mediated pathway, which in turn enhanced responses to innate stimuli by activating the expression of Toll-like receptors, RIG-I-like receptors, cytoplasmic DNA sensors, and their downstream signaling partners.

Type I interferon protects mice from fatal neurotropic infection with Langat virus by systemic and local antiviral responses.

Unlabelled: Vector-borne flaviviruses, such as tick-borne encephalitis virus (TBEV), West Nile virus, and dengue virus, cause millions of infections in humans. TBEV causes a broad range of pathological symptoms, ranging from meningitis to severe encephalitis or even hemorrhagic fever, with high mortality. Despite the availability of an effective vaccine, the incidence of TBEV infections is increasing.

Bacteria induce prolonged PMN survival via a phosphatidylcholine-specific phospholipase C- and protein kinase C-dependent mechanism.

Polymorphonuclear leukocytes (PMNs) are essential for the human innate immune defense, limiting expansion of invading microorganisms. PMN turnover is controlled by apoptosis, but the regulating signaling pathways remain elusive, largely due to inherent differences between mice and humans that undermine use of mouse models for understanding human PMN biology. Here, we aim to elucidate signal transduction mediating survival of human peripheral blood PMNs in response to bacteria, such as Yersinia pseudotuberculosis, an enteropathogen that causes the gastro-intestinal disease yersiniosis, as well as Escherichia coli and Staphylococcus aureus.