Role of the IL-33-ST2 axis in sepsis

Medicinal evaluation and molecular docking study of osajin as an anti-inflammatory, antioxidant, and antiapoptotic agent against sepsis-associated acute kidney injury in rats

Despite efforts to find effective drugs for sepsis-associated acute kidney injury (SA-AKI), mortality rates in patients with SA-AKI have not decreased. Our study evaluated the protective effects of isoflavone osajin (OSJ) on SA-AKI in rats by targeting inflammation, oxidative stress, and apoptosis, which represent the cornerstones in the pathophysiological mechanism of SA-AKI. Polymicrobial sepsis was induced in rats via the cecal ligation and puncture (CLP) technique. Markers of oxidative stress were evaluated in kidney tissues using biochemical methods. The expression of interleukin-33 (IL-33), 8-hydroxydeoxyguanosine (8-OHdG), caspase-3, and kidney injury molecule-1 (KIM-1) was evaluated as indicators of inflammation, DNA damage, apoptosis, and SA-AKI respectively in the kidney tissues using immunohistochemical and immunofluorescent detection methods. The CLP technique significantly (p < 0.001) increased lipid peroxidation (LPO) levels and significantly (p < 0.001) decreased the activities of superoxide dismutase and catalase in kidney tissues. In the renal tissues, strong expression of IL-33, 8-OHdG, caspase-3, and KIM-1 was observed with severe degeneration and necrosis in the tubular epithelium and intense interstitial nephritis. In contrast, the administration of OSJ significantly (p < 0.001) reduced the level of LPO, markedly improved biomarkers of antioxidant status, decreased the levels of serum creatinine and urea, lowered the expression of IL-33, 8-OHdG, caspase-3, and KIM-1 and alleviated changes in renal histopathology. A promising binding score was found via a molecular docking investigation of the OSJ-binding mode with mouse IL-33 (PDB Code: 5VI4). Therefore, OSJ protects against SA-AKI by suppressing the IL-33/LPO/8-OHdG/caspase-3 pathway and improving the antioxidant system.

IL-33 Signaling Inhibition Leads to a Preeclampsia-Like Phenotype in Pregnant Rats

PROBLEM

Preeclampsia (PE) is a hypertensive pregnancy disorder that is a leading cause of maternal and fetal morbidity and mortality characterized by maternal vascular dysfunction, oxidative stress, chronic immune activation, and excessive inflammation. No cure exists beyond delivery of the fetal-placental unit and the mechanisms driving pathophysiology are not fully understood. However, aberrant immune responses have been extensively characterized in clinical studies and shown to mediate PE pathophysiology in animal studies. One pathway that may mediate aberrant immune responses in PE is deficiencies in the IL-33 signaling pathway. In this study, we aim to investigate the impact of IL-33 signaling inhibition on cNK, TH17, and TReg populations, vascular function, and maternal blood pressure during pregnancy.

METHOD OF STUDY

In this study, IL-33 signaling was inhibited using two different methods: intraperitoneal administration of recombinant ST2 (which acts as a decoy receptor for IL-33) and administration of a specific IL-33 neutralizing antibody. Maternal blood pressure, uterine artery resistance index, renal and placental oxidative stress, cNK, TH17, and TReg populations, various cytokines, and pre-proendothelin-1 levels were measured.

RESULTS

IL-33 signaling inhibition increased maternal blood pressure, uterine artery resistance, placental and renal oxidative stress. IL-33 signaling inhibition also increased placental cNK and TH17 and renal TH17 cells while decreasing placental TReg populations. IL-33 neutralization increased circulating cNK and TH17s and decreased circulating TRegs in addition to increasing pre-proendothelin-1 levels.

CONCLUSIONS

Data presented in this study demonstrate a role for IL-33 signaling in controlling vascular function and maternal blood pressure during pregnancy possibly by mediating innate and adaptive immune inflammatory responses, identifying the IL-33 signaling pathway as a potential therapeutic target for managing preeclampsia.

Emerging roles of lactate in acute and chronic inflammation

Traditionally, lactate has been considered a 'waste product' of cellular metabolism. Recent findings have shown that lactate is a substance that plays an indispensable role in various physiological cellular functions and contributes to energy metabolism and signal transduction during immune and inflammatory responses. The discovery of lactylation further revealed the role of lactate in regulating inflammatory processes. In this review, we comprehensively summarize the paradoxical characteristics of lactate metabolism in the inflammatory microenvironment and highlight the pivotal roles of lactate homeostasis, the lactate shuttle, and lactylation ('lactate clock') in acute and chronic inflammatory responses from a molecular perspective. We especially focused on lactate and lactate receptors with either proinflammatory or anti-inflammatory effects on complex molecular biological signalling pathways and investigated the dynamic changes in inflammatory immune cells in the lactate-related inflammatory microenvironment. Moreover, we reviewed progress on the use of lactate as a therapeutic target for regulating the inflammatory response, which may provide a new perspective for treating inflammation-related diseases.

Serum interleukin-33 and soluble suppression of tumorigenicity 2 in pediatric leukemia with febrile neutropenia

The purpose of this study was to evaluate the association between interleukin-33 (IL-33) and its receptor Soluble Suppression of Tumorigenicity-2 (sST2) levels and bacterial infections during febrile neutropenia (FN) in pediatric patients with acute lymphoblastic leukemia (ALL). In this prospective, case-control study, participants were divided into 3 groups: ALL patients with FN (Group A), ALL patients without neutropenia and fever (Group B), and healthy children without infection and chronic disease (Group C). There were 30 cases in each group. Blood samples for IL-33 and sST2 have been drawn from patients in Group A before the initiation of treatment and on days 1 and 5 of treatment, and from patients in Groups B and C at initiation. At admission, mean IL-33 level (39.02 ± 26.40 ng/L) in Group B and mean sST2 level (185.3 ± 371.49 ng/ml) in Group A were significantly higher than the other groups (p = 0.038, p < 0.001, respectively). No difference was observed in the mean IL-33 and sST2 levels in the 5-day follow-up of patients in Group A (p = 0.82, p = 0.86, respectively). IL-33 and sST2 levels were not associated with fever duration, neutropenia duration or length of hospitalization. While C-reactive protein (CRP) was significantly higher in patients with positive blood culture (p = 0.021), IL-33 (p = 0.49) and sST2 (p = 0.21) levels were not associated with culture positivity.  Conclusion: IL-33 and sST2 levels were not found valuable as diagnostic and prognostic markers to predict bacterial sepsis in patients with FN. What is Known: • Neutropenic patients are at high risk of serious bacterial and viral infections, but the admission symptom is often only fever. • Febrile neutropenia has a high mortality rate if not treated effectively. What is New: • Febrile neutropenia is not only caused by bacterial infections. Therefore, new biomarkers should be identified to prevent overuse of antibiotics. • Specific biomarkers are needed to diagnose bacterial sepsis in the early phase of febrile neutropenia.

Endothelial cell dynamics in sepsis-induced acute lung injury and acute respiratory distress syndrome: pathogenesis and therapeutic implications

Sepsis, a prevalent critical condition in clinics, continues to be the leading cause of death from infections and a global healthcare issue. Among the organs susceptible to the harmful effects of sepsis, the lungs are notably the most frequently affected. Consequently, patients with sepsis are predisposed to developing acute lung injury (ALI), and in severe cases, acute respiratory distress syndrome (ARDS). Nevertheless, the precise mechanisms associated with the onset of ALI/ARDS remain elusive. In recent years, there has been a growing emphasis on the role of endothelial cells (ECs), a cell type integral to lung barrier function, and their interactions with various stromal cells in sepsis-induced ALI/ARDS. In this comprehensive review, we summarize the involvement of endothelial cells and their intricate interplay with immune cells and stromal cells, including pulmonary epithelial cells and fibroblasts, in the pathogenesis of sepsis-induced ALI/ARDS, with particular emphasis placed on discussing the several pivotal pathways implicated in this process. Furthermore, we discuss the potential therapeutic interventions for modulating the functions of endothelial cells, their interactions with immune cells and stromal cells, and relevant pathways associated with ALI/ARDS to present a potential therapeutic strategy for managing sepsis and sepsis-induced ALI/ARDS.

IL-33 supplementation improves uterine artery resistance and maternal hypertension in response to placental ischemia

Preeclampsia (PE), a leading cause of maternal/fetal morbidity and mortality, is a hypertensive pregnancy disorder with end-organ damage that manifests after 20 wk of gestation. PE is characterized by chronic immune activation and endothelial dysfunction. Clinical studies report reduced IL-33 signaling in PE. We use the Reduced Uterine Perfusion Pressure (RUPP) rat model, which mimics many PE characteristics including reduced IL-33, to identify mechanisms mediating PE pathophysiology. We hypothesized that IL-33 supplementation would improve blood pressure (BP), inflammation, and oxidative stress (ROS) during placental ischemia. We implanted intraperitoneal mini-osmotic pumps infusing recombinant rat IL-33 (1 µg/kg/day) into normal pregnant (NP) and RUPP rats from gestation day 14 to 19. We found that IL-33 supplementation in RUPP rats reduces maternal blood pressure and improves the uterine artery resistance index (UARI). In addition to physiological improvements, we found decreased circulating and placental cytolytic Natural Killer cells (cNKs) and decreased circulating, placental, and renal TH17s in IL-33-treated RUPP rats. cNK cell cytotoxic activity also decreased in IL-33-supplemented RUPP rats. Furthermore, renal ROS and placental preproendothelin-1 (PPET-1) decreased in RUPP rats treated with IL-33. These findings demonstrate a role for IL-33 in controlling vascular function and maternal BP during pregnancy by decreasing inflammation, renal ROS, and PPET-1 expression. These data suggest that IL-33 may have therapeutic potential in managing PE.NEW & NOTEWORTHY Though decreased IL-33 signaling has been clinically associated with PE, the mechanisms linking this signaling pathway to overall disease pathophysiology are not well understood. This study provides compelling evidence that mechanistically links reduced IL-33 with the inflammatory response and vascular dysfunction observed in response to placental ischemia, such as in PE. Data presented in this study submit the IL-33 signaling pathway as a possible therapeutic target for the treatment of PE.

A biomarker for bacteremia in pregnant women with acute pyelonephritis: soluble suppressor of tumorigenicity 2 or sST2

Objective: Sepsis is a leading cause of maternal death, and its diagnosis during the golden hour is critical to improve survival. Acute pyelonephritis in pregnancy is a risk factor for obstetrical and medical complications, and it is a major cause of sepsis, as bacteremia complicates 15-20% of pyelonephritis episodes in pregnancy. The diagnosis of bacteremia currently relies on blood cultures, whereas a rapid test could allow timely management and improved outcomes. Soluble suppression of tumorigenicity 2 (sST2) was previously proposed as a biomarker for sepsis in non-pregnant adults and children. This study was designed to determine whether maternal plasma concentrations of sST2 in pregnant patients with pyelonephritis can help to identify those at risk for bacteremia.Study design: This cross-sectional study included women with normal pregnancy (n = 131) and pregnant women with acute pyelonephritis (n = 36). Acute pyelonephritis was diagnosed based on a combination of clinical findings and a positive urine culture. Patients were further classified according to the results of blood cultures into those with and without bacteremia. Plasma concentrations of sST2 were determined by a sensitive immunoassay. Non-parametric statistics were used for analysis.Results: The maternal plasma sST2 concentration increased with gestational age in normal pregnancies. Pregnant patients with acute pyelonephritis had a higher median (interquartile range) plasma sST2 concentration than those with a normal pregnancy [85 (47-239) ng/mL vs. 31 (14-52) ng/mL, p < .001]. Among patients with pyelonephritis, those with a positive blood culture had a median plasma concentration of sST2 higher than that of patients with a negative blood culture [258 (IQR: 75-305) ng/mL vs. 83 (IQR: 46-153) ng/mL; p = .03]. An elevated plasma concentration of sST2 ≥ 215 ng/mL had a sensitivity of 73% and a specificity of 95% (area under the receiver operating characteristic curve, 0.74; p = .003) with a positive likelihood ratio of 13.8 and a negative likelihood ratio of 0.3 for the identification of patients who had a positive blood culture.Conclusion: sST2 is a candidate biomarker to identify bacteremia in pregnant women with pyelonephritis. Rapid identification of these patients may optimize patient care.

NLRP3 inhibition improves maternal hypertension, inflammation, and vascular dysfunction in response to placental ischemia

Preeclampsia (PE) is a pregnancy-specific hypertensive disorder with end-organ damage that presents after 20 wk of gestation. PE pathophysiology often includes vascular dysfunction and increased inflammation that continues to damage patient health even after PE resolves. Currently, there is no cure for PE beyond delivery of the fetal-placental unit. Previous clinical studies have identified elevated placental NLRP3 expression in patients with PE and suggest NLRP3 as a potential therapeutic target. In this study, we examined the effect of NLRP3 inhibition on PE pathophysiology in the reduced uterine perfusion pressure (RUPP) model rat using MCC950 (20 mg/kg/day) or esomeprazole (3.5 mg/kg/day). We hypothesized that increased NLRP3 in response to placental ischemia impairs anti-inflammatory IL-33 signaling to induce T-helper 17 cell (TH17) and cytolytic NK cell (cNK) activation, which is known to mediate oxidative stress and vascular dysfunction leading to maternal HTN and intrauterine growth restriction. RUPP rats had significantly higher placental NLRP3 expression, maternal blood pressure, fetal reabsorption rate, vascular resistance, oxidative stress, cNKs and TH17s, and decreased IL-33 compared with normal pregnant (NP) rats. NLRP3 inhibition, with either treatment, significantly reduced placental NLRP3 expression, maternal blood pressure, fetal reabsorption rates, vascular resistance, oxidative stress, cNK, and TH17 populations in RUPP rats. Based on our findings, NLRP3 inhibition reduces PE pathophysiology and esomeprazole may be a potential therapeutic for PE treatment.

Inhibition of osteoclastogenesis by interleukin-33 administration in the periodontal ligament under mechanical loading

BACKGROUND AND OBJECTIVES

The molecular mechanisms mediating external root resorption are poorly understood. Interleukin-33 (IL-33) expression increased remarkably in the periodontal ligament (PDL) under orthodontic loading. The IL-33-driven responses are delicately cell type- and tissue context-dependent. It is unknown how IL-33 act on osteoclastogenesis in the context of root surface. This study aimed to investigate the effect of IL-33 on osteoclastogenesis in the PDL under mechanical loading.

MATERIALS AND METHODS

C57BL/6J mice were treated with injections of phosphate buffer saline (PBS) or recombinant mouse IL-33 (rmIL-33, 6 μl, 30 μg/ml), and subjected to models of orthodontic tooth movement. Tartrated resistant acid phosphates (TRAP)-positive cells and IL-33 expressions were examined in the PDL. IL-33 release from human PDL cells (hPDLCs) was detected by ELISA. Cementoblast-like (OCCM-30) cells were cultured in the presence of rmIL-33 to examine the release of osteoclast-regulatory proteins. The effects of rmIL-33 on osteoclastogenesis were examined in vitro in cultures of bone marrow macrophages (BMMs) and in BMMs-OCCM-30 cocultures. Expressions of osteoclast-specific or -related genes and proteins were investigated in BMMs-OCCM-30 cocultures treated with or without rmIL-33, in the presence or absence of granulocyte-macrophage colony-stimulating factor (GM-CSF) neutralizing antibody.

RESULTS

Interleukin-33 expressions were upregulated in the PDL under orthodontic loading. Static compressive force enhanced expression and release of IL-33 from hPDLCs. Administration of rmIL-33 resulted in reduced number of TRAP-positive cells in the PDL, and inhibited osteoclast differentiation from BMMs in vitro. OCCM-30 cells had varied osteoprotegerin (OPG) / receptor activator for nuclear factor-κB ligand (RANKL) secretion and increased release of GM-CSF under rmIL-33 stimulation. Treatment with rmIL-33 in BMMs-OCCM-30 cocultures resulted in inhibited differentiation and decreased activity of osteoclasts, and these effects were partially reversed by GM-CSF neutralizing antibody.

CONCLUSIONS

Interleukin-33 inhibits osteoclastogenesis in the PDL under orthodontic loading. The anti-osteoclastogenic effects were mediated partly by directly affecting osteoclast precursors and partly by cementoblast-mediated release of GM-CSF.

Pushing the frontiers of military medical excellence: updates, progress and future needs

Since its establishment in 2014, Military Medical Research has come a long way in becoming a premier journal for scientific articles from various different specialties, with a special emphasis on topics with military relevance. The field of military medicine may be obscure, and may not be readily encountered by the typical clinician on a day-to-day basis. This journal aims not only to pursue excellence in military research, but also keep current with the latest advancements on general medical topics from each and every specialty. This editorial serves to recap and synthesize the existing progress, updates and future needs of military medical excellence, discussing foremostly the unique traits of literature published in this journal, and subsequently presenting the discourse regarding wartime and peacetime medicine, the role of the military in a public health emergency, as well as wound healing and organ regeneration. Special attention have been devoted to military topics to shed light on the effects of Chemical, Biological, Radiological and Explosive (CBRE) warfare, environmental medicine and military psychiatry, topics which rarely have a chance to be discussed elsewhere. The interconnectedness between military combat and soldier physical and mental well-being is intricate, and has been distorted by pandemics such as coronavirus disease 2019 (COVID-19). This journal has come a long way since its first article was published, steadily contributing to the existing knowledge pool on general medical topics with a military slant. Only with continuous research and sharing, can we build upon the work of the scientific community, with hopes for the betterment of patient care.

Celastrol mitigates inflammation in sepsis by inhibiting the PKM2-dependent Warburg effect

BACKGROUND

Sepsis involves life-threatening organ dysfunction and is caused by a dysregulated host response to infection. No specific therapies against sepsis have been reported. Celastrol (Cel) is a natural anti-inflammatory compound that shows potential against systemic inflammatory diseases. This study aimed to investigate the pharmacological activity and molecular mechanism of Cel in models of endotoxemia and sepsis.

METHODS

We evaluated the anti-inflammatory efficacy of Cel against endotoxemia and sepsis in mice and macrophage cultures treated with lipopolysaccharide (LPS). We screened for potential protein targets of Cel using activity-based protein profiling (ABPP). Potential targets were validated using biophysical methods such as cellular thermal shift assays (CETSA) and surface plasmon resonance (SPR). Residues involved in Cel binding to target proteins were identified through point mutagenesis, and the functional effects of such binding were explored through gene knockdown.

RESULTS

Cel protected mice from lethal endotoxemia and improved their survival with sepsis, and it significantly decreased the levels of pro-inflammatory cytokines in mice and macrophages treated with LPS (P < 0.05). Cel bound to Cys424 of pyruvate kinase M2 (PKM2), inhibiting the enzyme and thereby suppressing aerobic glycolysis (Warburg effect). Cel also bound to Cys106 in high mobility group box 1 (HMGB1) protein, reducing the secretion of inflammatory cytokine interleukin (IL)-1β. Cel bound to the Cys residues in lactate dehydrogenase A (LDHA).

CONCLUSION

Cel inhibits inflammation and the Warburg effect in sepsis via targeting PKM2 and HMGB1 protein.

Interleukin-33/ Suppression of Tumorigenicity 2 in Renal Fibrosis: Emerging Roles in Prognosis and Treatment

Chronic kidney disease (CKD) is a major public health problem that affects more than 10% of the population worldwide and has a high mortality rate. Therefore, it is necessary to identify novel treatment strategies for CKD. Incidentally, renal fibrosis plays a central role in the progression of CKD to end-stage renal disease (ESRD). The activation of inflammatory pathways leads to the development of renal fibrosis. In fact, interleukin-33 (IL-33), a newly discovered member of the interleukin 1 (IL-1) cytokine family, is a crucial regulator of the inflammatory process. It exerts pro-inflammatory and pro-fibrotic effects via the suppression of tumorigenicity 2 (ST2) receptor, which, in turn, activates other inflammatory pathways. Although the role of this pathway in cardiac, pulmonary, and hepatic fibrotic diseases has been extensively studied, its precise role in renal fibrosis has not yet been completely elucidated. Recent studies have shown that a sustained activation of IL-33/ST2 pathway promotes the development of renal fibrosis. However, with prolonged research in this field, it is expected that the IL-33/ST2 pathway will be used as a diagnostic and prognostic tool for renal diseases. In addition, the IL-33/ST2 pathway seems to be a new target for the future treatment of CKD. Here, we review the mechanisms and potential applications of the IL-33/ST2 pathway in renal fibrosis; such that it can help clinicians and researchers to explore effective treatment options and develop novel medicines for CKD patients.

IL-33 and Soluble ST2 Are Associated With Recurrent Spontaneous Abortion in Early Pregnancy

Normal pregnancy is related to the successful transition from type 1 cellular immunity to type 2 cellular immunity. Therefore, this study aimed to investigate whether there is abnormal expression of cytokines in the process of inducing Recurrent spontaneous abortion (RSA). Interleukin (IL)-33 is a new member of the IL-1 family, and ST2, as IL-33’s receptor, induced the production of type 2 cytokines. In this study, blood samples were collected from 19 non-pregnant women of normal childbearing age, 28 normal pregnant women, and 33 women with RSA. The serum concentrations of IL-33 and ST2 were detected by flow cytometry. Our results showed that the serum concentrations of IL-33 and ST2 in the RSA group were significantly higher than those in the healthy control group (IL-33: P < 0.05; ST2: P < 0.0001), and IL-33 and ST2 had a higher level in the process of RSA predictive value. In addition, this study initially found that the serum concentrations of IL-33 and ST2 were not significantly correlated with the number of weeks of pregnancy, and there was a lower correlation between IL-33 and ST2 during RSA. This result may be related to the small number of cases. This study is the first time to correlate the changes in serum concentrations of IL-33 and ST2 with RSA, which may be a novel biomarker for the prediction and treatment of RSA.

Expression and clinical significance of IL-33 and its receptor ST2 in children with obstructive sleep apnea syndrome

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is characterized by a majority population of respiratory sleep disorders, which consists of simple snoring as well as increased upper airway resistance syndrome. Adenoid hypertrophy has been suggested as the main cause of OSAS in children. The role of interleukin-33 (IL-33) and its receptor suppressor of tumorigenicity 2 (ST2) in a variety of pediatric allergic diseases has been confirmed. We hypothesized that IL-33/ST2 path way might play a pivotal role in the pathogenesis of adenoid hypertrophy-associated OSAS in children.

METHODS

A total of 40 children undergoing adenoidectomy due to OSAS in the Otolaryngology of Tianjin Children's Hospital were selected as the study participants. The quantity of IL-33 and ST2 positive cells in adenoids was detected by immunohistochemical (IHC) streptavidin-peroxidase conjugate (SP) method.

RESULTS

The IL-33 positive cells were mainly distributed in the submucosa epithelium and vascular endothelium, and expressed in the nucleus and cytoplasm. Meanwhile, ST2 positive cells were primarily observed in the mucosa and expressed in the nucleus and cytoplasm, with a little expression of intercellular substance. There was a positive correlation between the proportion of adenoids in the posterior nostril diameter and the number of IL-33 positive cells. The expression of IL-33 in adenoids was positively correlated with the level of ST2 (r=0.809, P=0.000). The expression of IL-33 in adenoids was positively correlated with the level of eosinophil granulocyte (r=0.859, P=0.000). Moreover, the expression of ST2 in adenoids was positively correlated with the level of eosinophil granulocyte (r=0.814, P=0.000). The number of IL-33 positive cells was significantly higher in the moderate hypoxemia group than that in the mild hypoxemia group (P<0.05). There was no significant difference in the number of ST2 positive cells between the moderate hypoxemia group and mild hypoxemia group (P>0.05).

CONCLUSIONS

Both IL-33 and its receptor ST2 were expressed in adenoids of OSAS children. The severity of airway obstruction caused by adenoid hypertrophy was positively correlated with the expression of IL-33.

IL-33/ST2 Axis Plays a Protective Effect in Streptococcus pyogenes Infection through Strengthening of the Innate Immunity

Group A Streptococcus (GAS) causes invasive human diseases with the cytokine storm. Interleukin-33 (IL-33)/suppression of tumorigenicity 2 (ST2) axis is known to drive TH2 response, while its effect on GAS infection is unclear. We used an air pouch model to examine the effect of the IL-33/ST2 axis on GAS-induced necrotizing fasciitis. GAS infection induced IL-33 expression in wild-type (WT) C57BL/6 mice, whereas the IL-33- and ST2-knockout mice had higher mortality rates, more severe skin lesions and higher bacterial loads in the air pouches than those of WT mice after infection. Surveys of infiltrating cells in the air pouch of GAS-infected mice at the early stage found that the number and cell viability of infiltrating cells in both gene knockout mice were lower than those of WT mice. The predominant effector cells in GAS-infected air pouches were neutrophils. Absence of the IL-33/ST2 axis enhanced the expression of inflammatory cytokines, but not TH1 or TH2 cytokines, in the air pouch after infection. Using in vitro assays, we found that the IL-33/ST2 axis not only enhanced neutrophil migration but also strengthened the bactericidal activity of both sera and neutrophils. These results suggest that the IL-33/ST2 axis provided the protective effect on GAS infection through enhancing the innate immunity.

Diverse Roles of Cellular Senescence in Skeletal Muscle Inflammation, Regeneration, and Therapeutics

Skeletal muscle undergoes vigorous tissue remodeling after injury. However, aging, chronic inflammatory diseases, sarcopenia, and neuromuscular disorders cause muscle loss and degeneration, resulting in muscular dysfunction. Cellular senescence, a state of irreversible cell cycle arrest, acts during normal embryonic development and remodeling after tissue damage; when these processes are complete, the senescent cells are eliminated. However, the accumulation of senescent cells is a hallmark of aging tissues or pathological contexts and may lead to progressive tissue degeneration. The mechanisms responsible for the effects of senescent cells have not been fully elucidated. Here, we review current knowledge about the beneficial and detrimental effects of senescent cells in tissue repair, regeneration, aging, and age-related disease, especially in skeletal muscle. We also discuss how senescence of muscle stem cells and muscle-resident fibro-adipogenic progenitors affects muscle pathologies or regeneration, and consider the possibility that immunosenescence leads to muscle pathogenesis. Finally, we explore senotherapy, the therapeutic targeting of senescence to treat age-related disease, from the standpoint of improving muscle regeneration.

Role of the IL-33/ST2 receptor axis in ovarian cancer progression

Ovarian cancer remains a significant health problem for women in the world due to its diagnosis at advanced stages of disease and the high mortality rate of patients. To date, ovarian cancer is frequently treated with tumor reduction surgery followed by platinum/paclitaxel-based chemotherapy; however, most patients eventually develop relapsed disease. The mRNA expression levels of interleukin-33 (IL-33) and the suppressor of tumorigenicity 2 (ST2) receptor are significantly upregulated in ovarian cancer tissues and metastatic tumor lesions. In addition, IL-33 and ST2 expression has been associated with a poor overall survival in patients with epithelial ovarian cancer. The IL-33 receptor ST2 is expressed as both a membrane-anchored receptor (ST2L) activated by IL-33, and as a soluble variant that exhibits anti-inflammatory properties. In the present review, the functions of the IL-33/ST2L axis in cells and their aberrant expression levels in ovarian cancer were discussed. In addition, targeting their expression as a novel strategy for the control of ovarian cancer progression was emphasized.

Association of the systemic host immune response with acute hyperglycemia in mechanically ventilated septic patients

Hyperglycemia during sepsis is associated with increased organ dysfunction and higher mortality. The role of the host immune response in development of hyperglycemia during sepsis remains unclear. We performed a retrospective analysis of critically ill adult septic patients requiring mechanical ventilation (n = 153) to study the relationship between hyperglycemia and ten markers of the host injury and immune response measured on the first day of ICU admission (baseline). We determined associations between each biomarker and: (1) glucose, insulin, and c-peptide levels at the time of biomarker collection by Pearson correlation; (2) average glucose and glycemic variability in the first two days of ICU admission by linear regression; and (3) occurrence of hyperglycemia (blood glucose>180mg/dL) by logistic regression. Results were adjusted for age, pre-existing diabetes mellitus, severity of illness, and total insulin and glucocorticoid dose. Baseline plasma levels of ST2 and procalcitonin were positively correlated with average blood glucose and glycemic variability in the first two days of ICU admission in unadjusted and adjusted analyses. Additionally, higher baseline ST2, IL-1ra, procalcitonin, and pentraxin-3 levels were associated with increased risk of hyperglycemia. Our results suggest associations between the host immune response and hyperglycemia in critically ill septic patients particularly implicating the interleukin-1 axis (IL-1ra), the interleukin-33 axis (ST2), and the host response to bacterial infections (procalcitonin, pentraxin-3).

Interleukin-33 improves local immunity during Gram-negative pneumonia by a combined effect on neutrophils and inflammatory monocytes

Pneumonia represents a major health care burden and Gram‐negative bacteria provide an increasing therapeutic challenge at least in part through the emergence of multidrug‐resistant strains. IL‐33 is a multifunctional cytokine belonging to the IL‐1 family that can affect many different cell types. We sought here to determine the effect of recombinant IL‐33 on the host response during murine pneumonia caused by the common Gram‐negative pathogen Klebsiella pneumoniae. IL‐33 pretreatment prolonged survival for more than 1 day during lethal airway infection and decreased bacterial loads at the primary site of infection and distant organs. Postponed treatment with IL‐33 (3 h) also reduced bacterial growth and dissemination. IL‐33‐mediated protection was not observed in mice deficient for the IL‐33 receptor component IL‐1 receptor‐like 1. IL‐33 induced a brisk type 2 response, characterized by recruitment of type 2 innate lymphoid cells to the lungs and enhanced release of IL‐5 and IL‐13. However, neither absence of innate lymphoid cells or IL‐13, nor blocking of IL‐5 impacted on IL‐33 effects in mice infected with Klebsiella. Likewise, IL‐33 remained effective in reducing bacterial loads in mice lacking B, T, and natural killer T cells. Experiments using antibody‐mediated cell depletion indicated that neutrophils and inflammatory monocytes were of importance for antibacterial defense. The capacity of IL‐33 to restrict bacterial growth in the lungs was strongly reduced in mice depleted of both neutrophils and inflammatory monocytes, but not in mice selectively depleted of either one of these cell types. These results suggest that IL‐33 boosts host defense during bacterial pneumonia by a combined effect on neutrophils and inflammatory monocytes. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Goeckerman Regimen Reduces Alarmin Levels and PASI Score in Paediatric Patients with Psoriasis

BACKGROUND

Psoriasis is a chronic systemic inflammatory disease with (extra-)cutaneous manifestations. Inflammation is associated with cellular stress and tissue damage which lead to the release of alarmins (signals of danger). Goeckerman regimen (GR) is a highly efficacious treatment consisting of the application of pharmaceutical crude tar and UVB light exposure. The reduction of inflammatory processes in the skin is accompanied by changes in the levels of inflammatory markers - alarmins (HMBG-1, S100A7, S1000A8, S100A9, S100A12, IL-17, IL-22, and IL-33).

METHODS

The alarmin levels in sera of 19 paediatric patients with psoriasis were determined before and after GR using commercial ELISA kits. The Psoriasis area severity index (PASI) was used to determine the disease severity.

RESULTS

GR reduced both PASI and the levels of all measured alarmins. The levels of S100A7, S100A9, IL-22, IL-33, and HMGB-1 were significantly decreased. Positive correlations between IL-22 and PASI, between S100A9 and IL-17, S100A9 and IL-22, and a negative correlation between S100A8 and IL-33 were found.

CONCLUSIONS

Goeckerman regimen is a very effective, safe and low-cost therapy. We confirmed, it modulates the immune system reactivity, ameliorates the severity of the disease and reduces the levels of alarmins reflecting the presence and intensity of inflammation.

Novel Biomarkers in Patients with Chronic Kidney Disease: An Analysis of Patients Enrolled in the GCKD-Study

Background: Chronic kidney disease (CKD) and cardiovascular diseases (CVD) often occur concomitantly, and CKD is a major risk factor for cardiovascular mortality. Since some of the most commonly used biomarkers in CVD are permanently elevated in patients with CKD, novel biomarkers are warranted for clinical practice. Methods: Plasma concentrations of five cardiovascular biomarkers (soluble suppression of tumorigenicity (sST2), growth differentiation factor 15 (GDF-15), heart-type fatty acid-binding protein (H-FABP), insulin-like growth factor-binding protein 2 (IGF-BP2), and soluble urokinase plasminogen activator receptor) were analyzed by means of enzyme-linked immunosorbent assay (ELISA) in 219 patients with CKD enrolled in the German Chronic Kidney Disease (GCKD) study. Results: Except for sST2, all of the investigated biomarkers were significantly elevated in patients with CKD (2.0- to 4.4-fold increase in advanced CKD (estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73 m² body surface area (BSA)) and showed a significant inverse correlation with eGFR. Moreover, all but H-FABP and sST2 were additionally elevated in patients with micro- and macro-albuminuria. Conclusions: Based on our findings, sST2 appears to be the biomarker whose diagnostic performance is least affected by decreased renal function, thus suggesting potential viability in the management of patients with CVD and concomitant CKD. The predictive potential of sST2 remains to be proven in endpoint studies.

Effect of interleukin-33 on cementoblast-mediated cementum repair during orthodontic tooth movement

OBJECTIVE

This study aims to uncover the role of interleukin-33 on cementoblast-mediated cementum repair.

METHODS

6-8-week-old C57BL/6 mice were used to establish the model of orthodontic tooth movement. Interleukin-33 and suppression of tumorigenicity2 (ST2) expressions were immunohistochemically detected in the periodontal tissue. In vitro, cementoblast-like (OCCM-30) cells were cultured in the presence of recombinant mouse interleukin-33 protein (rmIL-33) at a 1-14 d time frame. ST2 expressions were immunofluorescently labeled and quantitatively examined. The effects of interleukin-33 on cementoblast differentiation, mineralization and proliferation were examined by alkaline phosphatase, alizarin red staining and cell counting kit-8, respectively. To further clarify the effect of interleukin-33 on cementogenesis-related protein expressions, runt-related transcription factor 2 (RUNX2), osterix, osteopontin, bone sialoprotein(BSP), osteocalcin, osteoprotegerin (OPG) and receptor activator of NF-КB ligand (RANKL) expressions were examined by western blot.

RESULTS

Orthodontic load of high magnitude induces external apical root resorption, and increases interleukin-33 expression in the periodontal tissue of mice. Cells in the cementum express ST2. Interleukin-33 initially down-regulates but later recovers ST2 mRNA and protein levels in OCCM-30 cells. Interleukin-33 abates cementoblast differentiation and mineralization, and suppresses RUNX2, osterix, BSP and osteopontin expressions in OCCM-30 cells at the later stage of the culture period. Interleukin-33 enhances RANKL expression, and reduces the ratio of OPG/RANKL in OCCM-30 cells.

CONCLUSION

Orthodontic load of high magnitude induces interleukin-33 expression in the periodontal tissue. Interleukin-33 has a negative effect on cementogenesis via suppressing cementoblast differentiation, mineralization and cementogenesis-related protein expressions.

Interleukin-33 activates and recruits natural killer cells to inhibit pulmonary metastatic cancer development

Increasing evidence suggests that IL-33 plays an important role in regulating tumor development. However, conflicting results, obtained from numerous studies, have highlighted the divergent functions of IL-33. The detailed mechanisms by which IL-33 modulates tumor development merit further investigation. Here, we report that IL-33 administration can effectively inhibit the development of pulmonary metastasis of breast cancer in a mouse. In our model, IL-33 promotes the production of TNF-α by macrophages, which increases IL-33 specific receptor (ST2) expression on natural killer (NK) cells and is pivotal in IL-33-induced NK cell activation. IL-33 treatment also facilitates the production of CCL5 in the lung by eosinophils and CD8⁺ T cells, which mediates the recruitment of NK cells to the tumor microenvironment. The systemic activation and local recruitment of NK cells result in potent tumor rejection in the lung. Our study reports a novel mechanism for the IL-33-meditated suppression of metastatic cancer and provides potential therapeutic strategies for targeting metastatic tumor.

Type 2 innate lymphoid cells participate in IL-33-stimulated Th2-associated immune response in chronic obstructive pulmonary disease

The aim of the present study was to investigate the roles of type 2 innate lymphoid cells (ILC2s) and interleukin-33 (IL-33) in chronic obstructive pulmonary disease (COPD). Serum and peripheral blood mononuclear cells (PBMCs) were isolated from healthy controls and COPD patients. ILC2 cells from the peripheral blood of COPD patients were stimulated with IL-33 or neutralizing ST2 antibody+IL-33 in vitro. The cell viability was assessed using a Cell Counting Kit-8 assay. ELISA was used to detect serum IL-33 and the levels of IL-4, IL-5, IL-6, IL-13 and soluble ST2 (sST2) in the culture supernatant. The percentage of ILC2 cells was measured by flow cytometry. The mRNA expression levels of GATA binding protein 3 (GATA3), RAR-related orphan receptor (ROR)α, ST2 and prostaglandin D2 receptor 2 (CRTH2) were detected by reverse transcription-quantitative PCR. It was revealed that IL-33, IL-5, IL-6 and IL-13 were significantly elevated in peripheral blood of patients with COPD. The proportion of ILC2s in peripheral blood of COPD patients was significantly increased, and the expression of RORA and CRTH2 was increased. The proportion of ST2⁺ ILC2 cells was significantly increased. After 48 h of IL-33 stimulation in vitro, the ratio of linage^-CD45⁺CD127⁺CRTH2⁺ cells reached a maximum. In addition, the viability of ILC2 cells, the expression levels of RORA, GATA3, ST2 and CRTH2 mRNA and the cytokines IL-4, IL-6, IL-5, IL-13 and sST2 were significantly increased. These effects were abrogated by treatment with anti-ST2. In conclusion, IL-33 is upregulated in the serum of patients with COPD and the proportion of ILC2s among the PBMCs is increased. IL-33 may promote the proliferation of ILC2 cells and secrete type 2 T-helper cell cytokines to participate in the immune response in COPD.

Elevations in Circulating sST2 Levels Are Associated With In-Hospital Mortality and Adverse Clinical Outcomes After Blunt Trauma

BACKGROUND

Soluble suppression of tumorigenicity 2 (sST2), a decoy receptor for interleukin (IL)-33, has emerged as a novel biomarker in various disease processes. Recent studies have elucidated the role of the sST2/IL-33 complex in modulating the balance of Th1/Th2 immune responses after tissue stress. However, the role of sST2 as a biomarker after traumatic injury remains unclear. To address this, we evaluated serum sST2 correlations with mortality and in-hospital adverse outcomes as endpoints in blunt trauma patients.

METHODS

We retrospectively analyzed clinical and biobank data of 493 blunt trauma victims 472 survivors (mean age: 48.4 ± 0.87; injury severity score [ISS]: 19.6 ± 0.48) and 19 nonsurvivors (mean age: 58.8 ± 4.5; ISS: 23.3 ± 2.1) admitted to the intensive care unit. Given the confounding impact of age on the inflammatory response, we derived a propensity-matched survivor subgroup (n = 19; mean age: 59 ± 3; ISS: 23.4 ± 2) using an IBM SPSS case-control matching algorithm. Serial blood samples were obtained from all patients (3 samples within the first 24 h and then once daily from day [D] 1 to D5 after injury). sST2 and twenty-nine inflammatory biomarkers were assayed using enzyme-linked immunosorbent assay and Luminex, respectively. Two-way analysis of variance on ranks was used to compare groups (P < 0.05). Spearman rank correlation was performed to determine the association of circulating sST2 levels with biomarker levels and in-hospital clinical outcomes.

RESULTS

Circulating sST2 levels of the nonsurvivor cohort were statistically significantly elevated at 12 h after injury and remained elevated up to D5 when compared either to the overall 472 survivor cohort or a matched 19 survivor subcohort. Admission sST2 levels obtained from the first blood draw after injury in the survivor cohort correlated positively with admission base deficit (correlation coefficient [CC] = 0.1; P = 0.02), international normalized ratio (CC = 0.1, P = 0.03), ISS (CC = 0.1, P = 0.008), and the average Marshall multiple organ dysfunction score between D2 and D5 (CC = 0.1, P = 0.04). Correlations with ISS revealed a positive correlation of ISS with plasma sST2 levels across the mild ISS (CC = 0.47, P < 0.001), moderate ISS (CC = 0.58, P < 0.001), and severe ISS groups (CC = 0.63, P < 0.001). Analysis of biomarker correlations in the matched survivor group over the initial 24 h after injury showed that sST2 correlates strongly and positively with IL-4 (CC = 0.65, P = 0.002), IL-5 (CC = 0.57, P = 0.01), IL-21 (CC = 0.52, P = 0.02), IL-2 (CC = 0.51, P = 0.02), soluble IL-2 receptor-α (CC = 0.5, P = 0.02), IL-13 (CC = 0.49, P = 0.02), and IL-17A (CC = 0.48, P = 0.03). This was not seen in the matched nonsurvivor group. sST2/IL-33 ratios were significantly elevated in nonsurvivors and patients with severe injury based on ISS ≥ 25.

CONCLUSIONS

Elevations in serum sST2 levels are associated with poor clinical trajectories and mortality after blunt trauma. High sST2 coupled with low IL-33 associates with severe injury, mortality, and worse clinical outcomes. These findings suggest that sST2 could serve as an early prognostic biomarker in trauma patients and that sustained elevations of sST2 could contribute to a detrimental suppression of IL-33 bioavailability in patients with high injury severity.

A conceptual time window-based model for the early stratification of trauma patients

Progress in the testing of therapies targeting the immune response following trauma, a leading cause of morbidity and mortality worldwide, has been slow. We propose that the design of interventional trials in trauma would benefit from a scheme or platform that could support the identification and implementation of prognostic strategies for patient stratification. Here, we propose a stratification scheme based on defined time periods or windows following the traumatic event. This 'time-window' model allows for the incorporation of prognostic variables ranging from circulating biomarkers and clinical data to patient-specific information such as gene variants to predict adverse short- or long-term outcomes. A number of circulating biomarkers, including cell injury markers and damage-associated molecular patterns (DAMPs), and inflammatory mediators have been shown to correlate with adverse outcomes after trauma. Likewise, several single nucleotide polymorphisms (SNPs) associate with complications or death in trauma patients. This review summarizes the status of our understanding of the prognostic value of these classes of variables in predicting outcomes in trauma patients. Strategies for the incorporation of these prognostic variables into schemes designed to stratify trauma patients, such as our time-window model, are also discussed.

Forebrain Cholinergic Signaling Regulates Innate Immune Responses and Inflammation

The brain regulates physiological functions integral to survival. However, the insight into brain neuronal regulation of peripheral immune function and the neuromediator systems and pathways involved remains limited. Here, utilizing selective genetic and pharmacological approaches, we studied the role of forebrain cholinergic signaling in the regulation of peripheral immune function and inflammation. Forebrain-selective genetic ablation of acetylcholine release and vagotomy abolished the suppression of serum TNF by the centrally-acting cholinergic drug galantamine in murine endotoxemia. Selective stimulation of acetylcholine action on the M1 muscarinic acetylcholine receptor (M1 mAChR) by central administration of the positive allosteric modulator benzyl quinolone carboxylic acid (BQCA) suppressed serum TNF (TNFα) levels in murine endotoxemia. This effect was recapitulated by peripheral administration of the compound. BQCA also improved survival in murine endotoxemia and these effects were abolished in M1 mAChR knockout (KO) mice. Selective optogenetic stimulation of basal forebrain cholinergic neurons innervating brain regions with abundant M1 mAChR localization reduced serum TNF in endotoxemic mice. These findings reveal that forebrain cholinergic neurons regulate innate immune responses and inflammation, suggesting the possibility that in diseases associated with cholinergic dysfunction, including Alzheimer's disease this anti-inflammatory regulation can be impaired. These results also suggest novel anti-inflammatory approaches based on targeting forebrain cholinergic signaling in sepsis and other disorders characterized by immune dysregulation.

Interleukin-33 contributes to ILC2 activation and early inflammation-associated lung injury during abdominal sepsis

Sepsis is defined as infection with organ dysfunction due to a dysregulated immune response. The lung is one of the most vulnerable organs at the onset of sepsis. Interleukin (IL)-33 can be released by injured epithelial and endothelial cells in the lung and regulate immune activation and infiltration. Therefore, we postulated that IL-33 would contribute to the immune response in the lung during sepsis. Using the cecal ligation and puncture (CLP) sepsis model, we show here that IL-33 contributes significantly to both sepsis-induced inflammation in the lung and systemic inflammatory response in the early phase of sepsis. Despite the higher intra-peritoneal bacterial burden, the absence of IL-33 resulted in less infiltration of neutrophils and monocytes into the lungs in association with lower circulating, lung and liver cytokine levels as well as reduced lung injury at 6 h after sepsis. IL-33 was required for the upregulation of IL-5 in type 2 Innate Lymphoid Cells (ILC2), while IL-5 neutralization suppressed neutrophil and monocyte infiltration in the lungs during CLP sepsis. This reduction in leukocyte infiltration in IL-33-deficient mice was reversed by administration of recombinant IL-5. These results indicate that IL-33 plays a major role in the local inflammatory changes in the lung, in part, by regulating IL-5 and this axis contributes to lung injury early after the onset of sepsis.

IL-33 attenuates mortality by promoting IFN-γ production in sepsis

OBJECTIVE AND DESIGN

Sepsis remains a major clinical problem with high morbidity and mortality. Interleukin (IL)-33 is a recently described member of the IL-1 family that is widely expressed and functions as a new inflammatory mediator. IL-33 has been reported to protect sepsis, but the underlying mechanisms are not well-elucidated.

MATERIALS AND METHODS

We measured the interferon gamma (IFN-γ) production in septic mice after IL-33 treatment.

RESULTS

IL-33 treatment enhanced the IFN-γ level in blood and promoted mice's survival, so the protective effects of IL-33 depend on IFN-γ. The IL-33 treatment also promoted both γδ T cells and NK cells in septic mice.

CONCLUSION

Our data showed that IL-33 attenuates mortality by promoting IFN-γ production in sepsis.

IL-33/ST2 axis affects the polarization and efferocytosis of decidual macrophages in early pregnancy

PROBLEM

To explore whether IL-33/ST2 axis modulates the polarization and efferocytosis of decidual macrophages (dMφs).

METHOD OF STUDY

The phenotype characteristics of dMφs from both normal pregnant women and recurrent spontaneous abortion (RSA) patients were determined by real-time polymerase chain reaction (RT-PCR) and flow cytometry (FCM). Then, the efferocytosis and expression of IL-33 and its receptor (ST2) in dMφs were analyzed by FCM. Finally, the effects of sST2, a decoy receptor for IL-33 that inhibits the IL-33/ST2 signaling pathway, on the polarization and efferocytosis of dMφs and human macrophage cell line U937 were investigated.

RESULTS

Compared with normal pregnancy, dMφs from RSA patients presented a M1 phenotype with high secretion of IL-33, whereas the expression of ST2 decreased. However, dMφs from RSA patients possessed a more powerful efferocytosis ability to clear the apoptotic decidual stromal cells (DSCs) compared with dMφs from normal pregnancy patients. Treatment with recombinant human sST2 led to the up-regulation of M1 bias and efferocytosis ability of both normal dMφs and U937.

CONCLUSION

This study indicates that IL-33 secreted by dMφs promotes M2 bias at the feto-maternal interface, and as a result, RSA might attribute to the disturbance of IL-33/ST2 axis and the enhancement of efferocytosis of dMφs subsequently.

RIP3 AND pMLKL promote necroptosis-induced inflammation and alter membrane permeability in intestinal epithelial cells

BACKGROUND

Necroptosis is an inflammatory form of programmed cell death requiring receptor-interacting protein kinase 3 (RIP3) and mixed lineage kinase domain-like protein (MLKL).

AIMS

The aim of this study is to examine in depth in vitro and ex vivo the contribution of necroptosis to intestinal inflammation.

METHODS

In vitro: we used an intestinal cell line, HCT116RIP3, produced in our laboratory and overexpressing RIP3. Ex vivo: intestinal mucosal biopsies were taken from patients with inflammatory bowel disease (IBD) (20 with Crohn's disease; 20 with ulcerative colitis) and from 20 controls.

RESULTS

RIP3-induced necroptosis triggers MLKL activation, increases cytokine/alarmin expression (IL-8, IL-1β, IL-33, HMGB1), NF-kBp65 translocation and NALP3 inflammasome assembly. It also affects membrane permeability by altering cell-cell junctional proteins (E-cadherin, Occludin, Zonulin-1). Targeting necroptosis through Necrostatin-1 significantly reduces intestinal inflammation in vitro and in cultured intestinal explants from IBD.

CONCLUSION

We show for the first time in vitro and ex vivo that RIP3-driven necroptosis seriously affects intestinal inflammation by increasing pMLKL, activating different cytokines and alarmins, and altering epithelial permeability. The inhibition of necroptosis causes a significant decrease of all these effects. These data strongly support the view that targeting necroptosis may represent a promising new option for the treatment of inflammatory enteropathies.

Immune Activation in Sepsis

Sepsis is caused by a dysregulated host response to infection. Immune responses determine the characteristics of sepsis. The body's protection against infection involves danger signal surveillance and recognition from nonself, effector functions in response to sensing danger signals, homeostatic regulation, and generation of immunologic memory. During sepsis, the immune system is activated by pathogen-associated and host-derived molecular patterns. Detecting these molecular patterns generates multisystem responses. Impaired organ function remote to the site of infection is the unifying feature. The processes by which an appropriate response to a microbial invader change from adaptive to maladaptive and dysregulated remain unclear.

Emerging Roles of IL-33/ST2 Axis in Renal Diseases

Renal diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD), have a great impact on health care systems worldwide. Similar to cardiovascular diseases, renal diseases are inflammatory diseases involving a variety of cytokines. Primary causes of renal injury include ischemia, uremic toxins, bacteremia, or nephrotoxicity. Inflammation represents an important component following kidney injury. Interleukin (IL)-33 is a member of the IL-1 cytokine family, which is widely expressed in epithelial barrier tissues and endothelial cells, and mediates both tissue inflammation and repair responses. IL-33 is released as a nuclear alarmin in response to tissue damage and triggers innate and adaptive immune responses by binding to its receptor, suppression of tumorigenicity 2 (ST2). Recent evidence from clinical and experimental animal studies indicates that the IL-33/ST2 axis is involved in the pathogenesis of CKD, renal graft injury, systemic lupus nephritis, and AKI. In this review, we discuss the pathological and tissue reparative roles of the IL-33/ST2 pathway in different types of renal diseases.