Microbe-induced Inflammation Research Articles

Infection induced inflammation impairs wound healing through IL-1β signaling

Wound healing is impaired by infection; however, how microbe-induced inflammation modulates tissue repair remains unclear. We took advantage of the optical transparency of zebrafish and a genetically tractable microbe, Listeria monocytogenes, to probe the role of infection and inflammation in wound healing. Infection with bacteria engineered to activate the inflammasome, Lm-Pyro, induced persistent inflammation and impaired healing despite low bacterial burden. Inflammatory infections induced il1b expression and blocking IL-1R signaling partially rescued wound healing in the presence of persistent infection. We found a critical window of microbial clearance necessary to limit persistent inflammation and enable efficient wound repair. Taken together, our findings suggest that the dynamics of microbe-induced tissue inflammation impacts repair in complex tissue damage independent of bacterial load, with a critical early window for efficient tissue repair.

Pulmonary Tuberculosis and Lung Cancer – Innate Immunity and the Evolutionary Links of Microbe-induced Inflammation with Cancer: A Case Series

Lung cancer is a chronic inflammatory disease. Postprimary tuberculosis (PPTb) is also a manifestation of chronic lung inflammation induced by Mycobacterium tuberculosis. Both acute and chronic inflammation are macrophage-mediated responses. Persistent lung lesions of both PPTb and lung cancer result from chronic nonresolving inflammation. Metabolic adaptation of macrophages through evolutionarily conserved pathways is termed as macrophage polarization. Progressive inflammation induced by microbes activates metabolic alterations in the tissue microenvironment and consequent tumorigenesis by M2-polarized macrophages. The M2 macrophages are poorly bactericidal, permitting intracellular microbial persistence. Both host and microbes undergo metabolic adaptations through hypoxia-inducible factor-induced gene induction. Three cases of PPTb progressing to lung cancer are presented. All cases were initially smear positive for acid-fast bacilli, and progressed to lung cancer while on antituberculosis treatment. Progressive lung inflammation in these cases induced by M. tuberculosis resulted in the progression of infection-induced inflammation to cancer. Smoking and diabetes were risk factors for progression to lung cancer.

Immune-checkpoint proteins, cytokines, and microbiome impact on patients with cervical insufficiency and preterm birth.

Microenvironmental factors, including microbe-induced inflammation and immune-checkpoint proteins that modulate immune cells have been associated with both cervical insufficiency and preterm delivery. These factors are incompletely understood. This study aimed to explore and compare interactions among microbiome and inflammatory factors, such as cytokines and immune-checkpoint proteins, in patients with cervical insufficiency and preterm birth. In particular, factors related to predicting preterm birth were identified and the performance of the combination of these factors was evaluated. A total of 220 swab samples from 110 pregnant women, prospectively recruited at the High-Risk Maternal Neonatal Intensive Care Center, were collected between February 2020 and March 2021. This study included 63 patients with cervical insufficiency receiving cerclage and 47 control participants. Endo- and exocervical swabs and fluids were collected simultaneously. Shotgun metagenomic sequencing for the microbiome and the measurement of 34 immune-checkpoint proteins and inflammatory cytokines were performed. First, we demonstrated that immune-checkpoint proteins, the key immune-regulatory molecules, could be measured in endocervical and exocervical samples. Secondly, we identified significantly different microenvironments in cervical insufficiency and preterm birth, with precise cervical locations, to provide information about practically useful cervical locations in clinical settings. Finally, the presence of Moraxella osloensis (odds ratio = 14.785; P = 0.037) and chemokine CC motif ligand 2 levels higher than 73 pg/mL (odds ratio = 40.049; P = 0.005) in endocervical samples were associated with preterm birth. Combining M. osloensis and chemokine CC motif ligand 2 yielded excellent performance for predicting preterm birth (area under the receiver operating characteristic curve = 0.846, 95% confidence interval = 0.733-0.925). Multiple relationships between microbiomes, immune-checkpoint proteins, and inflammatory cytokines in the cervical microenvironment were identified. We focus on these factors to aid in the comprehensive understanding and therapeutic modulation of local microbial and immunologic compositions for the management of cervical insufficiency and preterm birth.

Macrocyclic θ-defensins suppress tumor necrosis factor-α (TNF-α) shedding by inhibition of TNF-α–converting enzyme

Theta-defensins (θ-defensins) are macrocyclic peptides expressed exclusively in granulocytes and selected epithelia of Old World monkeys. They contribute to anti-pathogen host defense responses by directly killing a diverse range of microbes. Of note, θ-defensins also modulate microbe-induced inflammation by affecting the production of soluble tumor necrosis factor (sTNF) and other proinflammatory cytokines. Here, we report that natural rhesus macaque θ-defensin (RTD) isoforms regulate sTNF cellular release by inhibiting TNF-α-converting enzyme (TACE; also known as adisintegrin and metalloprotease 17; ADAM17), the primary pro-TNF sheddase. Dose-dependent inhibition of cellular TACE activity by RTDs occurred when leukocytes were stimulated with live Escherichia coli cells as well as numerous Toll-like receptor agonists. Moreover, the relative inhibitory potencies of the RTD isoforms strongly correlated with their suppression of TNF release by stimulated blood leukocytes and THP-1 monocytes. RTD isoforms also inhibited ADAM10, a sheddase closely related to TACE. TACE inhibition was abrogated by introducing a single opening in the RTD-1 backbone, demonstrating that the intact macrocycle is required for enzyme inhibition. Enzymologic analyses showed that RTD-1 is a fast binding, reversible, non-competitive inhibitor of TACE. We conclude that θ-defensin-mediated inhibition of pro-TNF proteolysis by TACE represents a rapid mechanism for the regulation of sTNF and TNF-dependent inflammatory pathways. Molecules with structural and functional features mimicking those of θ-defensins may have clinical utility as TACE inhibitors for managing TNF-driven diseases.

Inflammasome Activation by ATP Enhances Citrobacter rodentium Clearance through ROS Generation

Background: Nod-like receptor family, pyrin domain containing 3 (NLRP3) is an important cytosolic sensor of cellular stress and infection. Once activated, NLRP3 forms a multiprotein complex (inflammasome) that triggers the maturation and secretion of interleukin (IL)-1β and IL-18. We aimed to define the consequences of NLRP3 induction, utilizing exogenous adenosine triphosphate (ATP) as an inflammasome activator, to determine if inflammasome activation increases macrophage killing of Citrobacter rodentium and define mechanisms. Methods: Bacterial survival was measured using a gentamicin protection assay. Inflammasome activation or inhibition in mouse J774A.1 macrophages were assessed by measuring IL-1β; cytokines and reactive oxygen species (ROS) were measured by ELISA and DCFDA, respectively. Results: Activation of the inflammasome increased bacterial killing by macrophages and its inhibition attenuated this effect with no impact on phagocytosis or cell death. Furthermore, inflammasome activation suppressed pro-inflammatory cytokines during infection, possibly due to more effective bacterial killing. While the infection increased ROS production, this effect was reduced by inflammasome inhibitors, indicating that ROS is inflammasome-dependent. ROS inhibitors increased bacterial survival in the presence of ATP, suggesting that inflammasome-induced bacterial killing is mediated, at least in part, by ROS activity. Conclusion: Improving inflammasome activity during infection may increase bacterial clearance by macrophages and reduce subsequent microbe-induced inflammation.

Endogenous regulation of inflammatory pain by T-cell-derived opioids: when friend turns to foe.

Painful sensation is a hallmark of microbe-induced inflammation. This inflammatory pain is downregulated a few days after infection by opioids locally released by effector T lymphocytes generated in response to microbe-derived antigens. This review focuses on the endogenous regulation of inflammatory pain associated with adaptive T-cell response and puts in perspective the clinical consequences of the opioid-mediated analgesic activity of colitogenic T lymphocytes in inflammatory bowel disease.

Orbital Inflammation After Dental Procedures

This study reports 3 cases of acute orbital inflammation that occurred within 3 weeks of various dental procedures and offers a possible mechanism as to their cause. The charts of 3 patients were retrospectively examined. Clinical notes, laboratory testing, and imaging studies were reviewed. The cases involved a 36-year old woman, a 61-year-old woman, and a 44-year-old woman who developed acute dacryoadenitis after tooth extraction in the former case and after routine dental cleaning in the latter 2. All cases were initially treated with an oral steroid taper over 6 to 8 weeks. The first 2 cases resolved promptly and have remained quiescent. The last individual had recurrent symptoms prompting lacrimal gland biopsy that demonstrated chronic, nongranulomatous inflammation without monoclonality. The patient subsequently responded to periorbital steroid injection only to have a recurrent bout of inflammation after repeat dental cleaning. Another periorbital steroid injection resulted in resolution of inflammation. The authors propose that a subset of acute orbital inflammation may represent an autoimmune response triggered by dental manipulation. These cases are suggestive of an atypical variant of noninfectious, microbe-induced inflammation.

Synergistic Inflammation Is Induced by Blood Degradation Products with Microbial Toll‐Like Receptor Agonists and Is Blocked by Hemopexin

Detection of microbial components by immune cells via Toll-like receptors (TLRs) with subsequent induction of inflammation is essential for host defense. However, an overactive immune response can cause tissue damage and sepsis. The endogenous molecule hemoglobin and its derivative heme are often released into tissue compartments where there is infection in the presence of degrading blood. We found that hemoglobin synergizes with multiple TLR agonists to induce high levels of tumor necrosis factor and interleukin-6 from macrophages and that this synergy is independent of TLR4 and MyD88. In contrast, heme synergized with some but not all TLR agonists studied. Furthermore, the synergy of both hemoglobin and heme with lipopolysaccharide was suppressed by hemopexin, a plasma heme-binding protein. These studies suggest that hemoglobin and heme may substantially contribute to microbe-induced inflammation when bacterial or viral infection coexists with blood degradation and that hemopexin may play a role in controlling inflammation in such settings.

The role of Desulfovibrio desulfuricans lipopolysaccharides in modulation of periodontal inflammation through stimulation of human gingival fibroblasts

Objective Periodontitis is a destructive disease which is likely to be the result of the activities of different microbial complexes. Recently, sulphate-reducing bacteria (SRB) have been detected in the oral cavity, and they have been found to be common inhabitants of sites showing periodontal destruction. The aim of study was to evaluate the influence of endotoxins of Desulfovibrio desulfuricans bacteria on human gingival fibroblast HGF-1 line. Methods The immunological response of gingival fibroblasts was evaluated by determination of their IL-6 and IL-8 secretion upon treatement with D. desulfuricans intestinal and type strain LPS, sodium butyrate (NaB) and IL-1β. The amounts of cytokines were estimated by ELISA immunoassay. The influence of LPS and NaB on fibroblast proliferation was determined using the CyQUANT Cell Proliferation Assay Kit. Results No significant growth inhibition of cells exposed to LPS was observed, except for the culture growing in the presence of intestinal strain endotoxin at the highest concentration (100 μg/ml). The secretion of IL-6 and IL-8 by fibroblasts was increased by D. desulfuricans endotoxins. Cells stimulated with proinflammatory cytokine 1L-1β showed very high levels of both cytokines secretion. The release of IL-6 and IL-8 by cells in response to LPS and 1L-1β was modulated by butyric acid. Conclusions The observed response of gingival fibroblasts to stimulation by endotoxin suggests that D. desulfuricans can be involved in the pathogenesis of periodontitis. Moreover, butyrate present in the oral cavity seems to have immunoregulatory effect on cytokine production by gingival fibroblasts under physiological conditions and during microbe-induced inflammation.

SELECTIVE USE OF MEMBRANE CD14, BUT NOT SOLUBLE CD14 ANDINHIBITION BY SERUM IN THE INFLAMMATORY CYTOKINE RESPONSE INDUCED BY A NOVELTLR LIGAND (P. AERUGINOSA EXOENZYME S)

Background/Purpose: Soluble andmembrane CD14 (sCD14 and mCD14) bind microbial products, are toll-like receptor(TLR) coreceptors, and induce inflammation. Clinical relevance is demonstrated by a correlation of sCD14 levels with morbidity and mortality in inflammatory diseases. Moreover, P. aeruginosa induces damaging inflammation in the lungs of cysticfibrosis patients and its virulence is often attributed to the TLR2 and TLR4ligand exoenzyme S (ExoS). Because of the importance of the response of CD14 toTLR ligands and its potential for therapeutic manipulation, its role inExoS-induced inflammatory cytokines was investigated. Methods: The ability of ExoS to induce TNFand IL-6 cytokine production in cell lines that express TLR and either CD14 positive or negative was assessed (THP-1 or U373 cells, respectively). Recombinant CD14 or CD14 blocking agents were used to test the contribution ofmCD14 and sCD14. Results: Enhancing expression of mCD14 on THP-1 cells increased TNF production, which was abrogated by blocking or removing mCD14. Transfecting mCD14 into U373 cells demonstrated that mCD14 was required for binding ExoS and subsequent IL-6 production. Unlike TLR ligands that only stimulate one TLR, such as lipopolysaccharide, neither sCD14 nor serum enhanced production of cytokine in response to ExoS. Uniquely, serum inhibited ExoS induced TNF. Conclusion: This work demonstrates a fundamental difference in the requirement of ExoS and other TLR ligands for CD14, which must be considered when designing therapies to block microbe-induced inflammation. The presence of a potential therapeutic molecule in serum could help in the development of an ExoS neutralizing agent.

Effects of Porphyromonas gingivalis and Escherichia coli lipopolysaccharides on mononuclear phagocytes.

The mononuclear phagocyte plays an important role in the regulation of microbe-induced inflammation, in part through its ability to secrete mediators, particularly cytokines, in response to microorganisms and their products. To evaluate the effects of the microbial flora associated with chronic adult periodontitis on cytokine induction, lipopolysaccharide (LPS) from the periodontopathogen Porphyromonas gingivalis was used to stimulate naive and phorbol ester-primed U937 monocytic cells, as well as elutriated human peripheral blood monocytes. We assessed the effect of this LPS, in comparison to that of LPS from Escherichia coli, on cell proliferation, cytokine induction, and surface expression of the LPS receptor CD14. P. gingivalis LPS stimulated proliferation of U937 cells at concentrations of greater than 1 ng/ml, while E. coli LPS inhibited proliferation. Phorbol myristic acid (PMA)-treated U937 cells and elutriated monocytes responded to E. coli LPS activation by producing tumor necrosis factor alpha (TNF-alpha) mRNA and protein; however, P. gingivalis LPS induced greater numbers of TNF-alpha mRNA-positive cells and higher (P < 0.05) levels of protein than did E. coli LPS. Both cell types expressed interleukin-1 beta (IL-1beta) mRNA and protein in response to either LPS treatment. Compared with E. coli LPS, P. gingivalis LPS induced significantly (P < 0.05) higher numbers of IL-1 mRNA-positive U937 cells and elutriated monocytes, as well as production of significantly more (P < 0.05) IL-1 protein by the monocytes. The PMA-treated U937 cells and the monocytes produced high levels of IL-1 receptor antagonist mRNA and protein which were only marginally affected by the LPS preparations. While E. coli LPS induced expression of CD 14 on the surface of PMA-primed U937 cells and monocytes, P. gingivalis LPS exhibited a significantly (P < 0.05) greater ability to enhance receptor levels. Our results indicate that P. gingivalis LPS can activate the mononuclear phagocyte for proliferation, cytokine production, and CD14 expression, providing evidence for the potential of this bacterial component to act as a critical regulatory factor in the chronic inflammatory response associated with periodontitis.