The innate immune sensor NLRC3 attenuates Toll-like receptor signaling via modification of the signaling adaptor TRAF6 and transcription factor NF-κB.

Several members of the NLR family of sensors activate innate immunity. In contrast, we found here that NLRC3 inhibited Toll-like receptor (TLR)-dependent activation of the transcription factor NF-κB by interacting with the TLR signaling adaptor TRAF6 to attenuate Lys63 (K63)-linked ubiquitination of TRAF6 and activation of NF-κB. We used bioinformatics to predict interactions between NLR and TRAF proteins, including interactions of TRAF with NLRC3. In vivo, macrophage expression of Nlrc3 mRNA was diminished by the administration of lipopolysaccharide (LPS) but was restored when cellular activation subsided. To assess biologic relevance, we generated Nlrc3(-/-) mice. LPS-treated Nlrc3(-/-) macrophages had more K63-ubiquitinated TRAF6, nuclear NF-κB and proinflammatory cytokines. Finally, LPS-treated Nlrc3(-/-) mice had more signs of inflammation. Thus, signaling via NLRC3 and TLR constitutes a negative feedback loop. Furthermore, prevalent NLR-TRAF interactions suggest the formation of a 'TRAFasome' complex.

NLRC3, a member of the NLR family of proteins, is a negative regulator of innate immune signaling induced by the DNA sensor STING.

Stimulator of interferon genes (STING, also named MITA, MYPS, or ERIS) is an intracellular DNA sensor that induces type I interferon through its interaction with TANK-binding kinase 1 (TBK1). Here we found that the nucleotide-binding, leucine-rich-repeat-containing protein, NLRC3, reduced STING-dependent innate immune activation in response to cytosolic DNA, cyclic di-GMP (c-di-GMP), and DNA viruses. NLRC3 associated with both STING and TBK1 and impeded STING-TBK1 interaction and downstream type I interferon production. By using purified recombinant proteins, we found NLRC3 to interact directly with STING. Furthermore, NLRC3 prevented proper trafficking of STING to perinuclear and punctated region, known to be important for its activation. In animals, herpes simplex virus 1 (HSV-1)-infected Nlrc3(-/-) mice exhibited enhanced innate immunity and reduced morbidity and viral load. This demonstrates the intersection of two key pathways of innate immune regulation, NLR and STING, to fine tune host response to intracellular DNA, DNA virus, and c-di-GMP.

Stimulator of interferon genes (STING) is an essential proviral host factor for human rhinovirus species A and C.

Human rhinoviruses (RVs) are positive-strand RNA viruses that cause respiratory tract disease in children and adults. Here we show that the innate immune signaling protein STING is required for efficient replication of members of two distinct RV species, RV-A and RV-C. The host factor activity of STING was identified in a genome-wide RNA interference (RNAi) screen and confirmed in primary human small airway epithelial cells. Replication of RV-A serotypes was strictly dependent on STING, whereas RV-B serotypes were notably less dependent. Subgenomic RV-A and RV-C RNA replicons failed to amplify in the absence of STING, revealing it to be required for a step in RNA replication. STING was expressed on phosphatidylinositol 4-phosphate (PI4P)-enriched membranes and was enriched in RV-A16 compared with RV-B14 replication organelles isolated in isopycnic gradients. The host factor activity of STING was species-specific, as murine STING (mSTING) did not rescue RV-A16 replication in STING-deficient cells. This species specificity mapped primarily to the cytoplasmic, ligand-binding domain of STING. Mouse-adaptive mutations in the RV-A16 2C protein allowed for robust replication in cells expressing mSTING, suggesting a role for 2C in recruiting STING to RV-A replication organelles. Palmitoylation of STING was not required for RV-A16 replication, nor was the C-terminal tail of STING that mediates IRF3 signaling. Despite co-opting STING to promote its replication, interferon signaling in response to STING agonists remained intact in RV-A16 infected cells. These data demonstrate a surprising requirement for a key host mediator of innate immunity to DNA viruses in the life cycle of a small pathogenic RNA virus.

The mitochondrial proteins NLRX1 and TUFM form a complex that regulates type I interferon and autophagy.

The mitochondrial protein MAVS (also known as IPS-1, VISA, and CARDIF) interacts with RIG-I-like receptors (RLRs) to induce type I interferon (IFN-I). NLRX1 is a mitochondrial nucleotide-binding, leucine-rich repeats (NLR)-containing protein that attenuates MAVS-RLR signaling. Using Nlrx1(-/-) cells, we confirmed that NLRX1 attenuated IFN-I production, but additionally promoted autophagy during viral infection. This dual function of NLRX1 paralleled the previously described functions of the autophagy-related proteins Atg5-Atg12, but NLRX1 did not associate with Atg5-Atg12. High-throughput quantitative mass spectrometry and endogenous protein-protein interaction revealed an NLRX1-interacting partner, mitochondrial Tu translation elongation factor (TUFM). TUFM interacted with Atg5-Atg12 and Atg16L1 and has similar functions as NLRX1 by inhibiting RLR-induced IFN-I but promoting autophagy. In the absence of NLRX1, increased IFN-I and decreased autophagy provide an advantage for host defense against vesicular stomatitis virus. This study establishes a link between an NLR protein and the viral-induced autophagic machinery via an intermediary partner, TUFM.

Role of inflammasomes in the pathogenesis of periodontal disease and therapeutics.

Inflammasomes are a group of multimolecular intracellular complexes assembled around several innate immune proteins. Recognition of a diverse range of microbial, stress and damage signals by inflammasomes results in direct activation of caspase-1, which subsequently induces the only known form of secretion of active interleukin-1ß and interleukin-18. Although the importance of interleukin-1ß in the periodontium is not questioned, the impact of inflammasomes in periodontal disease and its potential for therapeutics in periodontology is still in its very early stages. Increasing evidence in preclinical models and human data strongly implicate the involvement of inflammasomes in a number of inflammatory, autoinflammatory and autoimmune disorders. Here we review: (a) the currently known inflammasome functions, (b) clinical/preclinical data supporting inflammasome involvement in the context of periodontal and comorbid diseases and (c) potential therapies targeting inflammasomes. To clarify further the inflammasome involvement in periodontitis, we present analyses of data from a large clinical study (n = 5809) that measured the gingival crevicular fluid-interleukin-1ß and grouped the participants based on current periodontal disease classifications. We review data on 4910 European-Americans that correlate 16 polymorphisms in the interleukin-1B region with high gingival crevicular fluid-interleukin-1ß levels. We show that inflammasome components are increased in diseased periodontal tissues and that the caspase-1 inhibitor, VX-765, inhibits ~50% of alveolar bone loss in experimental periodontitis. The literature review further supports that although patients clinically present with the same phenotype, the disease that develops probably has different underlying biological pathways. The current data indicate that inflammasomes have a role in periodontal disease pathogenesis. Understanding the contribution of different inflammasomes to disease development and distinct patient susceptibility will probably translate into improved, personalized therapies.

Diagnostic utility of surgical lung biopsies in elderly patients with indeterminate interstitial lung disease.

BACKGROUND AND OBJECTIVE: Idiopathic pulmonary fibrosis (IPF) is increasingly diagnosed by clinical and computed tomography (CT) criteria; however, surgical lung biopsy (SLB) may still be required in patients who lack definite CT features of usual interstitial pneumonia (UIP). We reviewed a cohort of elderly patients who underwent SLB, to evaluate the benefit of SLB in diagnosing idiopathic interstitial pneumonia (IIP). METHODS: We searched the pathology records of Mayo Clinic for ambulatory patients at least 75 years old, who underwent SLB between 2000 and 2012 for indeterminate IIP. Histologic slides were reviewed and clinical data were extracted from the record. RESULTS: A total of 55 patients (35 male) were enrolled. Median (interquartile range) age was 77 (76-80) years. Forced vital capacity was 70 (61-76)% and diffusing capacity of the lungs for carbon monoxide was 48 (42-54)% of predicted. In total, 37 (67%) patients had IPF, including 61% of those with HRCT findings inconsistent with UIP. Thirty-day mortality was 10% and 90-day mortality was 15%. CONCLUSION: The high mortality rate of SLB complicates the risk-benefit analysis in elderly patients with IIP. The expected value of the SLB is probably highest when the HRCT features are inconsistent with UIP, due to the frequent (39%) retrieval of patterns other than UIP.

Identifying the presence of clinically significant hepatic involvement in hereditary haemorrhagic telangiectasia using a simple clinical scoring index.

BACKGROUND & AIMS: Though hepatic involvement is common in patients with hereditary haemorrhagic telangiectasia (HHT), symptomatic liver disease is rare but potentially fatal without liver transplantation. Factors associated with clinically significant liver disease in patients with HHT are unknown. METHODS: In this prospective cohort study, we included consecutive patients from 2001 to 2011 with definite HHT, who underwent systematic protocol screening including contrast-enhanced hepatic CT and/or abdominal ultrasound. Using a multivariable logistic regression model, we developed a simple clinical scoring index to identify the presence of symptomatic liver disease (cardiac failure, portal hypertension, or biliary disease) or 'at-risk' liver disease (asymptomatic patients, with hepatic bruit, abnormal liver biochemistry, or elevated cardiac index). RESULTS: Of 316 patients with definite HHT, 171 patients (54.1%; age 53.4 ± 15.2 y, 101 females) had hepatic involvement on imaging. Twenty-nine patients had symptomatic liver disease (22 patients with high-output heart failure); 45 patients were 'at-risk' for liver disease. Using multivariable logistic regression analysis, we derived a score using age, gender, hemoglobin and alkaline phosphatase at presentation which could accurately distinguish patients with clinically significant liver involvement from patients with no or incidental liver lesions (c-statistic=0.80). A score <3 indicated low risk (<5%) and score >6 indicated high risk (>80%) of harboring clinically significant liver disease in HHT. CONCLUSIONS: A simple scoring system can distinguish patients at low, moderate, and high risk of harboring clinically significant liver disease. With validation, this score may be used to identify patients for individualized screening and enrollment in clinical trials.

Hepatopulmonary syndrome: favorable outcomes in the MELD exception era.

UNLABELLED: Hepatopulmonary syndrome (HPS) is a pulmonary vascular disorder occurring as a consequence of advanced liver disease, characterized by hypoxemia due to intrapulmonary vascular dilatations. HPS independently increases mortality, regardless of the cause or severity of liver disease. Liver transplantation (LT) improves survival in HPS. We present the largest consecutive series of HPS patients specifically addressing long-term survival relative to the degree of hypoxemia and the era in which LT was conducted. We evaluated 106 HPS patients at the Mayo Clinic from 1986 through 2010. Survival was assessed using Kaplan-Meier methodology. LT was accomplished in 49 HPS patients. Post-LT survival (1, 3, 5, and 10 years) did not differ between groups based on baseline partial pressure of arterial oxygen (PaO2 ) obtained at the time of HPS diagnosis. Improvements in overall survival at 1, 3, and 5 years post-LT in those HPS patients transplanted after January 1 2002 (n = 28) (92%, 88%, and 88%, respectively) as compared with those transplanted prior to that time (n = 21) (71%, 67%, and 67%, respectively) did not reach statistical significance (5-year P = 0.09). Model for Endstage Liver Disease (MELD) exception to facilitate LT was granted to 21 patients since January 1 2002 with post-LT survival of 19/21 patients and one wait-list death. CONCLUSION: Long-term outcome after LT in HPS is favorable, with a trend towards improved survival in the MELD exception era since 2002 as compared to earlier HPS transplants. Survival after LT was not associated with PaO2 levels at the time of HPS diagnosis. (HEPATOLOGY 2012).

Porphyromonas gingivalis mediates inflammasome repression in polymicrobial cultures through a novel mechanism involving reduced endocytosis.

The interleukin (IL)-1ß-processing inflammasome has recently been identified as a target for pathogenic evasion of the inflammatory response by a number of bacteria and viruses. We postulated that the periodontal pathogen, Porphyromonas gingivalis may suppress the inflammasome as a mechanism for its low immunogenicity and pathogenic synergy with other, more highly immunogenic periodontal bacteria. Our results show that P. gingivalis lacks signaling capability for the activation of the inflammasome in mouse macrophages. Furthermore, P. gingivalis can suppress inflammasome activation by another periodontal bacterium, Fusobacterium nucleatum. This repression affects IL-1ß processing, as well as other inflammasome-mediated processes, including IL-18 processing and cell death, in both human and mouse macrophages. F. nucleatum activates IL-1ß processing through the Nlrp3 inflammasome; however, P. gingivalis repression is not mediated through reduced levels of inflammasome components. P. gingivalis can repress Nlrp3 inflammasome activation by Escherichia coli, and by danger-associated molecular patterns and pattern-associated molecular patterns that mediate activation through endocytosis. However, P. gingivalis does not suppress Nlrp3 inflammasome activation by ATP or nigericin. This suggests that P. gingivalis may preferentially suppress endocytic pathways toward inflammasome activation. To directly test whether P. gingivalis infection affects endocytosis, we assessed the uptake of fluorescent particles in the presence or absence of P. gingivalis. Our results show that P. gingivalis limits both the number of cells taking up beads and the number of beads taken up for bead-positive cells. These results provide a novel mechanism of pathogen-mediated inflammasome inhibition through the suppression of endocytosis.

Feasibility and Efficacy of a Non-Opioid Based Pain Management After Medical Thoracoscopy.

BACKGROUND: Prescription opioids are a major cause of the opioid epidemic. Despite the minimally invasive nature of medical thoracoscopy (MT), data on the efficacy of non-opioid-based pain control after MT is lacking. The purpose of this study is to assess the feasibility and efficacy of a non-opioid-based pain management strategy in patients who underwent MT. METHODS: We performed a retrospective analysis of all patients who underwent MT in the Mayo Clinic (Minnesota and Arizona) outpatient setting. We assessed their pain level and the need for analgesia post-MT from August 1, 2019, to May 24, 2021. RESULTS: Forty patients were included. In the first 24 hours, 5/40 (12.5%) reported no pain. Twenty-eight patients out of 40 (70%) reported minor pain (pain scale 1-3), and 7/40 (17.5%) reported moderate pain (pain scale 4-6). No patients reported severe pain. Twenty-two out of 35 patients who experienced discomfort (63%) required acetaminophen, 6/35 patients (17%) required nonsteroidal anti-inflammatory drug, and 7/35 patients (20%) did not require analgesia. Of the 7 patients who had moderate pain, 5 (71%) reported that the moderate pain improved to mild at 72 hours post-MT. Zero patients required opioids, and none reported contacting any provider to manage the pain post-MT. Fourteen patients (78%) who had both parietal pleural biopsies and tunneled pleural catheter placed reported minor pain, 3 patients (17%) reported moderate pain, and 1 patient (6%) experienced no discomfort. CONCLUSION: MT is well-tolerated by patients with non-opioid-based pain management strategy as needed if there is no absolute contraindication.

Construction and characterization of a derivative of Neisseria gonorrhoeae strain MS11 devoid of all opa genes.

To better understand the role of Opa in gonococcal infections, we created and characterized a derivative of MS11 (MS11Δopa) that had the coding sequence for all 11 Opa proteins deleted. The MS11Δopa bacterium lost the ability to bind to purified lipooligosaccharide (LOS). While nonpiliated MS11Δopa and nonpiliated Opa-expressing MS11 cells grew at the same rate, nonpiliated MS11Δopa cells rarely formed clumps of more than four bacteria when grown in broth with vigorous shaking. Using flow cytometry analysis, we demonstrated that MS11Δopa produced a homogeneous population of bacteria that failed to bind monoclonal antibody (MAb) 4B12, a MAb specific for Opa. Opa-expressing MS11 cells consisted of two predominant populations, where ∼85% bound MAb 4B12 to a significant level and the other population bound little if any MAb. Approximately 90% of bacteria isolated from a phenotypically Opa-negative colony (a colony that does not refract light) failed to bind MAb 4B12; the remaining 10% bound MAb to various degrees. Piliated MS11Δopa cells formed dispersed microcolonies on ME180 cells which were visually distinct from those of piliated Opa-expressing MS11 cells. When Opa expression was reintroduced into MS11Δopa, the adherence ability of the strain recovered to wild-type levels. These data indicate that Opa contributes to both bacterium-bacterium and bacterium-host cell interactions.

Prevalence of spontaneous portosystemic shunts in patients with portopulmonary hypertension and effect on treatment.

BACKGROUND & AIMS: We documented the frequency of large spontaneous portosystemic shunts in patients with moderate or severe portopulmonary hypertension (POPH) and determined the association between large shunts and response to treatment. METHODS: We performed a retrospective case-control study of data from patients with mild (mean pulmonary artery pressure [MPAP], 25-35 mm Hg; n = 18), moderate (MPAP, 35-50 mm Hg; n = 45), and severe POPH (MPAP, >50 mm Hg; n = 16). Data were compared with those from controls (normal echocardiography with estimated right ventricular systolic pressure, <35 mm Hg; n = 122). Spontaneous portosystemic shunts greater than 10 mm in diameter, identified by computed tomography or magnetic resonance, were classified as large. Response to treatment at 6 months was defined by right ventricular systolic pressure or MPAP as significant (<35 mm Hg), partial (35-50 mm Hg), or no response (>50 mm Hg). RESULTS: The frequency of spontaneous shunts did not differ significantly between groups of subjects with severe (n = 14 of 16), moderate (n = 38 of 45), or mild POPH (n = 11 of 18) or normal echocardiograms (controls, n = 86 of 122) (P = .77). Large shunts were associated with severe (14 of 16) and moderate POPH (32 of 45), compared with mild POPH (6 of 18) or controls (30 of 122) (P < .01). In 13 patients with severe POPH, large shunts were associated with lack of response to treatment in 90% (8 of 9) or partial response in 50% (2 of 4). Among 27 patients with moderate POPH, large shunts were associated with no response to treatment in 13 of 19 (68%) and a partial response in 2 of 6 (33%). CONCLUSIONS: Large spontaneous portosystemic shunts are associated significantly with moderate and severe POPH, and with lack of response to treatment.

Hereditary hemorrhagic telangiectasia and risks for adverse pregnancy outcomes.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular dysplasia characterized by epistaxis, mucocutaneous telangiectasias, and arteriovenous malformations (AVM) in the brain, lung, liver, gastrointestinal tract, or spine. While pregnant women with HHT are known to have increased risks due to pulmonary AVMs, little is known about any increased risk for fetal birth defects or other adverse pregnancy outcomes. To investigate potential increased risk, individuals with a clinical diagnosis of HHT were asked to complete a survey composed of four sections: demographics, personal history of HHT, personal history of birth defects (modeled after state registries), and reproductive history. A total of 226 participants reported outcomes of 560 pregnancies, as well as self-reported personal history of birth defects. Of the 560 pregnancies, 450 (80.4%) resulted in 457 live births and 63 (13.8%) were pre-term. Of the 110 pregnancy losses, 80 (72.7%) were first trimester and five were stillborn. Anomalies considered to be medically or cosmetically significant were reported in 17 babies (3.7%). The presence of significant anomalies was not significantly associated with whether the baby had an HHT diagnosis (P=0.55) or the gender of the parent with HHT (P=0.32). Four liveborn babies and one stillborn had a cerebral AVM or hemorrhage in the perinatal period. Prevalence of uterine hemorrhage, pre-eclampsia, placental abnormalities, low-birth weight, and infertility did not appear increased over the general population. These data provide some reassurance that HHT does not lead to an appreciable increased risk for birth defects or other adverse pregnancy outcomes.

Neisseria gonorrhoeae-induced transactivation of EGFR enhances gonococcal invasion.

Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection gonorrhoea, adheres to and invades into genital epithelial cells. Here, we investigate host components that are used by the bacteria for their entry into epithelial cells. We found that gonococcal microcolony formation on the surface of HEC-1-B cells disrupted the polarized, basolateral distribution of both epidermal growth factor receptor (EGFR) and ErbB2, a related family member, and induced their accumulation under the microcolonies at the apical membrane. Gonococcal infection increased EGFR and ErbB2 phosphorylation. The EGFR kinase inhibitor, AG1478, reduced gonococcal invasion by 80%, but had no effect on adherence or the recruitment of EGFR and ErbB2 to the microcolonies. Gonococcal inoculation upregulated the mRNA levels of several ligands of EGFR. Prevention of EGFR ligand shedding by blocking matrix metalloproteinase activation reduced gonococcal invasion without altering their adherence, while the addition of the EGFR ligand, HB-EGF, was able to restore invasion to 66% of control levels. These data indicate that N. gonorrhoeae modulates the activity and cellular distribution of host EGFR, facilitating their invasion. EGFR activation does not appear to be due to direct gonococcal binding to EGFR, but instead by its transactivation by gonococcal induced increases in EGFR ligands.

Complications of Endobronchial Valve Placement for Bronchoscopic Lung Volume Reduction: Insights From the Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE).

BACKGROUND: Patients with advanced emphysema experience breathlessness due to impaired respiratory mechanics and diaphragm dysfunction. Bronchoscopic lung volume reduction (BLVR) is a minimally invasive bronchoscopic procedure done to reduce hyperinflation and air trapping, promoting atelectasis in the targeted lobe and allowing improved respiratory mechanics. Real-world data on safety and complications outside of clinical trials of BLVR are limited. METHODS: We queried the US Food and Drug Administrations (FDA) Manufacturers and User Device Experience database from May 2019 to June 2020 for reports involving BLVR with endobronchial valve (EBV) placement. Events were reviewed for data analysis. RESULTS: We identified 124 cases of complications during BLVR with EBV implantation. The most-reported complication was pneumothorax (110/124, 89%), all of which required chest tube placement. A total of 54 of these cases (54/110, 49%) were complicated by persistent air leak requiring additional interventions. Repeat bronchoscopy was needed to remove the valves in 28 patients, 12 were discharged with a Heimlich valve, and 10 had an additional pleural catheter placed. The other complications of BLVR with EBV placement included respiratory failure (6/124, 5%), pneumonia (4/124, 3%), hemoptysis (2/124, 1.6%), valve migration (1/124, 1%), and pleural effusion (1/124, 1%). A total of 14 deaths were reported during that year. CONCLUSION: Pneumothorax is the most-reported complication for BLVR with EBV placement, and in 65% of cases, pneumothorax is managed without removing valves. Importantly, 14 deaths were reported during that timeframe. Further studies are needed to estimate the true magnitude of the complications associated with BLVR.