The emerging role of nuclear receptor coactivator 4 in health and disease: a novel bridge between iron metabolism and immunity.

Nuclear receptor coactivator 4 (NCOA4) has recently been recognized as a selective cargo receptor of ferritinophagy participating in ferroptosis. However, NCOA4 is also a coactivator that modulates the transcriptional activity of many vital nuclear receptors. Recent novel studies have documented the role of NCOA4 in healthy and pathogenic conditions via its modulation of iron- and non-iron-dependent metabolic pathways. NCOA4 exhibits non-ferritinophagic and iron-independent features such as promoting tumorigenesis and erythropoiesis, immunomodulation, regulating autophagy, and participating in DNA replication and mitosis. Full-length human-NCOA4 is composed of 614 amino acids, of which the N-terminal (1-237) contains nuclear-receptor-binding domains, while the C-terminal (238-614) principally contains a ferritin-binding domain. The exploration of the protein structure of NCOA4 suggests that NCOA4 possesses additional significant and complex functions based on its structural domains. Intriguingly, another three isoforms of NCOA4 that are produced by alternative splicing have been identified, which may also display disparate activities in physiological and pathological processes. Thus, NCOA4 has become an important bridge that encompasses interactions between immunity and metabolism. In this review, we outline the latest advances in the important regulating mechanisms underlying NCOA4 actions in health and disease conditions, providing insights into potential therapeutic interventions.

FASN regulates STING palmitoylation via malonyl-CoA in macrophages to alleviate sepsis-induced liver injury.

STING (stimulator of interferon genes) is a critical immunoregulatory protein in sepsis and is regulated by various mechanisms, especially palmitoylation. FASN (fatty acid synthase) is the rate-limiting enzyme to generate cellular palmitic acid (PA) via acetyl-CoA and malonyl-CoA and participates in protein palmitoylation. However, the mechanisms underlying the interaction between STING and FASN have not been completely understood. In this study, STING-knockout mice were used to confirm the pivotal role of STING in sepsis-induced liver injury. Metabolomics confirmed the dyslipidemia in septic mice and patients. The compounds library was screened, revealing that FASN inhibitors exerted a significant inhibitory effect on the STING pathway. Mechanically, the regulatory effect of FASN on the STING pathway was dependent on palmitoylation. Further experiments indicated that the upstream of FASN, malonyl-CoA inhibited STING pathway possibly due to C91 (palmitoylated residue) of STING. Overall, this study reveals a novel paradigm of STING regulation and provides a new perspective on immunity and metabolism.

The interaction between STING and NCOA4 exacerbates lethal sepsis by orchestrating ferroptosis and inflammatory responses in macrophages.

The discovery of STING-related innate immunity has recently provided a deep mechanistic understanding of immunopathy. While the detrimental effects of STING during sepsis had been well documented, the exact mechanism by which STING causes lethal sepsis remains obscure. Through single-cell RNA sequence, genetic approaches, and mass spectrometry, we demonstrate that STING promotes sepsis-induced multiple organ injury by inducing macrophage ferroptosis in a cGAS- and interferon-independent manner. Mechanistically, Q237, E316, and S322 in the CBD domain of STING are critical binding sites for the interaction with the coiled-coil domain of NCOA4. Their interaction not only triggers ferritinophagy-mediated ferroptosis, but also maintains the stability of STING dimers leading to enhanced inflammatory response, and reduces the nuclear localization of NCOA4, which impairs the transcription factor coregulator function of NCOA4. Meanwhile, we identified HET0016 by high throughput screening, a selective 20-HETE synthase inhibitor, decreased STING-induced ferroptosis in peripheral blood mononuclear cells from patients with sepsis and mortality in septic mice model. Our findings uncover a novel mechanism by which the interaction between STING and NCOA4 regulates innate immune response and ferroptosis, which can be reversed by HET0016, providing mechanistic and promising targets insights into sepsis.

Post-Translational Modifications of STING: A Potential Therapeutic Target.

Stimulator of interferon genes (STING) is an endoplasmic-reticulum resident protein, playing essential roles in immune responses against microbial infections. However, over-activation of STING is accompanied by excessive inflammation and results in various diseases, including autoinflammatory diseases and cancers. Therefore, precise regulation of STING activities is critical for adequate immune protection while limiting abnormal tissue damage. Numerous mechanisms regulate STING to maintain homeostasis, including protein-protein interaction and molecular modification. Among these, post-translational modifications (PTMs) are key to accurately orchestrating the activation and degradation of STING by temporarily changing the structure of STING. In this review, we focus on the emerging roles of PTMs that regulate activation and inhibition of STING, and provide insights into the roles of the PTMs of STING in disease pathogenesis and as potential targeted therapy.

Iron homeostasis and disorders revisited in the sepsis.

Sepsis is a life-threatening condition caused by a dysregulated host-response to inflammation, although it currently lacks a fully elucidated pathobiology. Iron is a crucial trace element that is essential for fundamental processes in both humans and bacteria. During sepsis, iron metabolism is altered, including increased iron transport and uptake into cells and decreased iron export. The intracellular sequestration of iron limits its availability to circulating pathogens, which serves as a conservative strategy against the pathogens. Although iron retention has been showed to have protective protect effects, an increase in labile iron may cause oxidative injury and cell death (e.g., pyroptosis, ferroptosis) as the condition progresses. Moreover, iron disorders are substantial and correlate with the severity of sepsis. This also suggests that iron may be useful as a diagnostic marker for evaluating the severity and predicting the outcome of the disease. Further knowledge about these disorders could help in evaluating how drugs targeting iron homeostasis can be optimally applied to improve the treatment of patients with sepsis. Here, we present a comprehensive review of recent advances in the understanding of iron metabolism, focusing on the regulatory mechanisms and iron-mediated injury in sepsis.

STING-dependent induction of lipid peroxidation mediates intestinal ischemia-reperfusion injury.

Stimulator of interferon genes (STING) is essential for the type I interferon response against DNA pathogens. Recent evidence has indicated that STING also plays a critical role in various diseases such as systemic lupus erythematous, nonalcoholic fatty liver disease, and cancer. However, the exact function and mechanism of STING in ischemia/reperfusion (I/R) injury, especially in the intestine, remains unknown. In the current study, we evaluated the contribution of STING to the intestinal I/R progression. The data indicate a robust STING activation, specifically in the reperfusion period, with the evidence of interferon response and NF-κB pathway activation. The intestinal I/R injury and distant organ damage was absent in STING-/- mice. Mechanically, this detrimental effect relies on excess level of lipid peroxidation, which was proved by the level of 4-hydroxynonenal (4-HNE) and the malondialdehyde (MDA). Additionally, bone marrow derived macrophage (BMDM) was stimulated with mtDNA or STING agonist showed a dose- and time-dependent lipid peroxidation and cell death, which could be reverse by STING-/- or pretreatment of lipid peroxidation inhibitor. Liproxstatin-1 could also ameliorate injury I/R induced multiple-organ damage. Similar results were also identified in the GSE96733 database, which indicated that STING activation was associated with the disbalance of lipid peroxidation and antioxidant system. Collectively, our results indicate a novel role for STING activation in the regulation of lipid peroxidation is closely associated with intestinal I/R injury, and that anti-lipid peroxidation is a unique and effective mechanistic approach for intestinal I/R injury and STING activation associated damage prevention and treatment.

[Status of diagnosis and management of acute appendicitis in 2017: a national multi-center retrospective study].

OBJECTIVE: To analyze the current status of diagnosis and management of acute appendicitis (AA) in China. METHODS: Questionnaire survey was used to retrospectively collect data of hospitalized patients with AA from 43 medical centers nationwide in 2017 (Sort by number of cases provided: Jinling Hospital of Medical School of Nanjing University, The First Affiliated Hospital of Xinjiang Medical University, Lu'an People's Hospital, Tengzhou Central People's Hospital, Dalian Central Hospital, The Affiliated Hospital of Xuzhou Medical University, Dongying People's Hospital, Jinjiang Hospital of Traditional Chinese Medicine, Huangshan Shoukang Hospital, Xuyi People's Hospital, Nanjing Jiangbei People's Hospital, Lanzhou 940th Hospital of PLA, Heze Municipal Hospital, The First College of Clinical Medical Science of China Three Gorges University, Affiliated Jiujiang Hospital of Nanchang University, The Second People's Hospital of Hefei, Affiliated Central Hospital of Shandong Zaozhuang Mining Group, The Third People's Hospital of Kunshan City, Xuzhou First People's Hospital, The 81st Group Army Hospital of PLA, Linyi Central Hospital, The General Hospital of Huainan Eastern Hospital Group, The 908th Hospital of PLA, Liyang People's Hospital, The 901th Hospital of Joint Logistic Support Force, The Third Affiliated Hospital of Chongqing Medical University, The Fourth Hospital of Jilin University, Harbin Acheng District People's Hospital, The First Affiliated Hospital of Zhengzhou University, Nanjing Luhe People's Hospital, Taixing Municipal People's Hospital, Baotou Central Hospital, The Affiliated Hospital of Nantong University, Linyi People's Hospital, The 72st Group Army Hospital of PLA, Zaozhuang Municipal Hospital, People's Hospital of Dayu County, Taixing City Hospital of Traditional Chinese Medicine, Suzhou Municipal Hospital, Beijing Guang'anmen Hospital, Langxi County Hospital of Traditional Chinese Medicine, Nanyang Central Hospital, The Affiliated People's Hospital of Inner Mongolia Medical University).The diagnosis and management of AA were analyzed through unified summary. Different centers collected and summarized their data in 2017 and sent back the questionnaires for summary. RESULTS: A total of 8 766 AA patients were enrolled from 43 medical centers, including 4 711 males (53.7%) with median age of 39 years and 958 (10.9%) patients over 65 years old. Of 8 776 patients, 5 677 cases (64.6%) received one or more imaging examinations, and the other 3 099 (35.4%) did not receive any imaging examination. A total of 1 858 (21.2%) cases received medical treatment, mainly a combination of nitroimidazoles (1 107 cases, 59.8%) doublet regimen, followed by a single-agent regimen of non-nitroimidazoles (451 cases, 24.4%), a nitroimidazole-free doublet regimen (134 cases, 7.2%), a triple regimen of combined nitroimidazoles (116 cases, 6.3%), nitroimidazole alone (39 cases, 2.1%) and nitroimidazole-free triple regimen (3 cases, 0.2%). Of the 6 908 patients (78.8%) who underwent surgery, 4 319 (62.5%) underwent laparoscopic appendectomy and 2589 (37.5%) underwent open surgery. Ratio of laparotomy was higher in those patients under 16 years old (392 cases) or over 65 years old (258 cases) [15.1%(392/2 589) and 10.0%(258/2 589), respectively, compared with 8.5%(367/4 316) and 8.0%(347/4 316) in the same age group for laparoscopic surgery, χ²=91.415, P<0.001; χ²=15.915,P<0.001]. Patients with complicated appendicitis had higher ratio of undergoing open surgery as compared to those undergoing laparoscopic surgery [26.7%(692/2 589) vs. 15.6%(672/4 316), χ²=125.726, P<0.001].The cure rates of laparoscopic and open surgery were 100.0% and 99.8%(2 585/2 589) respectively without significant difference (P=0.206). Postoperative complication rates were 4.5%(121/2 589) and 4.7%(196/4 316) respectively, and the difference was not statistically significant (χ²=0.065, P=0.799). The incidence of surgical site infection was lower (0.6% vs. 1.7%, χ²=17.315, P<0.001), and hospital stay was shorter [6(4-7) days vs. 6(5-8) days, U=4 384 348.0, P<0.001] in the laparoscopic surgery group, while hospitalization cost was higher (median 12 527 yuan vs. 9 342 yuan, U=2 586 809.0, P<0.001). CONCLUSIONS: The diagnosis of acute appendicitis is still clinically based, supplemented by imaging examination. Appendectomy is still the most effective treatment at present. Laparoscopic appendectomy has become the main treatment strategy, but anti-infective drugs are also very effective.

Released Mitochondrial DNA Following Intestinal Ischemia Reperfusion Induces the Inflammatory Response and Gut Barrier Dysfunction.

Ischemia-reperfusion (I/R) injury is a challenging clinical problem, especially injuries involving the gastrointestinal tract. Mitochondrial DNA (mtDNA) is released upon cell death and stress, and can induce the inflammatory response. We aimed to investigate the role of mtDNA in the pathogenesis of intestinal I/R. Intestinal I/R model was established with clamping of the superior mesenteric artery, and IEC-6 cells were incubated under hypoxia/reoxygenation (H/R) conditions to simulate I/R injury. Using in vitro models, H/R up-regulated oxidative stress, disrupted mitochondrial activity and the mitochondrial membrane potential, induced apoptosis and elevated the mtDNA levels in the supernatant of intestinal epithelial cells, and the co-culture of mtDNA with human primary dendritic cells significantly elevated TLR9-MyD88 expression and enhanced the production of inflammatory cytokines and chemokines. MtDNA was also released in a mouse model of intestinal I/R and was associated with the increased secretion of inflammatory cytokines and increased gut barrier injury compared with that of the sham group. We concluded that mtDNA contributes to I/R injury and may serve as a biomarker of intestinal I/R. We further suggest that oxidized mtDNA originated from IECs during intestinal I/R exacerbates the acute proinflammatory process by eliciting the production of proinflammatory cytokines and chemokines.

Effects of Changes in the Levels of Damage-Associated Molecular Patterns Following Continuous Veno-Venous Hemofiltration Therapy on Outcomes in Acute Kidney Injury Patients With Sepsis.

Background: We investigated the association of damage-associated molecular pattern (DAMP) removal with mortality in sepsis patients undergoing continuous veno-venous hemofiltration (CVVH). Methods: Circulating levels of DAMPs [mitochondrial DNA (mtDNA); nuclear DNA (nDNA); heat shock protein 70 (HSP70); and high mobility group box 1 (HMGB1)] and cytokines were measured at baseline, 6 and 12 h after initiation of CVVH. Urinary DNA levels were analyzed at baseline and end of CVVH. The expression of human leukocyte antigen (HLA)-DR was assayed at 0, 3, and 7 days after initiation of CVVH. Moreover, the effects of HSP70 and HMGB1 clearance on survival were analyzed. Results: We evaluated 43 patients with acute kidney injury (AKI) (33 sepsis patients). Twenty-two sepsis patients (67%) and three non-sepsis patients (30%) expired (P = 0.046). Significant reductions in the levels of circulating interleukin-6 (P = 0.046) and tumor necrosis factor-α (P = 0.008) were found in the sepsis group. The levels of mtDNA were increased (ND2, P = 0.035; D-loop, P = 0.003), whereas that of HSP70 was reduced (P = 0.000) in all patients during the first 12 h. The levels of DAMPs in the plasma were markedly increased after blood passage from the inlet through the dialyzer in survivor sepsis patients. The clearance rates of HSP70 and HMGB1 were good predictors of mortality [area under the curve (AUC) = 0.937, P = 0.000; AUC = 0.90, P = 0.001, respectively]. The level of HLA-DR was increased in response to higher HSP70 clearance (P = 0.006). Survival was significantly worse in groups with higher clearance rates of HSP70 and HMGB1 than the cut-off value (log-rank test: P = 0.000 for both). Higher HSP70 clearance was a significant independent predictor of mortality (odds ratio = 1.025, 95% confidence interval [CI]: 1.012-1.039, P = 0.000). The urinary nDNA (ß-globin) level before CVVH was an independent risk factor for the duration of CVVH in patients with sepsis (sRE = 0.460, 95% CI: 1.720-8.857, P = 0.005). Conclusion: CVVH removes inflammatory factors, reduces urinary DAMPs, and removes plasma DAMPs. However, survival decreases in response to higher HSP70 clearance.

Shifting trends in bacteriology and antimicrobial resistance among gastrointestinal fistula patients in China: an eight-year review in a tertiary-care hospital.

BACKGROUND: The purpose of this study was to determine the shifting trends in bacteriology and antimicrobial resistance of infectious specimens isolated from gastrointestinal (GI) fistula patients over eight years in China. METHODS: We retrospectively reviewed the microbial records of intra-abdominal specimens at a teaching hospital from 2008 to 2015. Study period was divided into the first half (2008-2011) and the second half (2012-2015). All isolates underwent antibiotic susceptibility testing by the micro dilution method. RESULTS: A total of 874 intra-abdominal isolates were consecutively collected from 502 GI fistula patients (mean age, 46.5 years, 71.1% male) during the study period. Patients in the second study period (2012-2015) were older (>65 years) and more likely to have experienced cancer. Over the entire study period, most infections were caused by E. coli (24.2%) and K. pneumonia (14.1%). There was a significant decrease in the proportion E. coli isolates that were extended- spectrum beta-lactamase (ESBL)-positive (P = 0.026). The proportion of E. coli resistant to imipenem increased from 14.3% in 2008-2011 to 25.9% in 2012-2015 (P = 0.037). Imipenem resistance prevalence was higher in ESBL-negative bacteria than ESBL-positive bacteria for both E. coli and K. pneumonia (P < 0.001). In Enterococcus, significant increase in resistance to ampicillin (P = 0.01) and moxifloxacin (P = 0.02) over time were observed. In Staphylococcus and fungi, rates of antibiotic resistance did not significantly change over the study period. CONCLUSIONS: Gram-negative bacteria predominated as causative agents of intra-abdominal infections in GI fistula patients, and there was an increase in levels of resistance to certain antibiotics, particularly carbapenems. Infection control and source control are important tools available to surgeons to prevent the emergence of antibiotic-resistant pathogens.