Blockage of NLRP3 inflammasome activation ameliorates acute inflammatory injury and long-term cognitive impairment induced by necrotizing enterocolitis in mice

Chromatin as alarmins in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe gastrointestinal disease primarily affecting premature neonates, marked by poorly understood pro-inflammatory signaling cascades. Recent advancements have shed light on a subset of endogenous molecular patterns, termed chromatin-associated molecular patterns (CAMPs), which belong to the broader category of damage-associated molecular patterns (DAMPs). CAMPs play a crucial role in recognizing pattern recognition receptors and orchestrating inflammatory responses. This review focuses into the realm of CAMPs, highlighting key players such as extracellular cold-inducible RNA-binding protein (eCIRP), high mobility group box 1 (HMGB1), cell-free DNA, neutrophil extracellular traps (NETs), histones, and extracellular RNA. These intrinsic molecules, often perceived as foreign, have the potential to trigger immune signaling pathways, thus contributing to NEC pathogenesis. In this review, we unravel the current understanding of the involvement of CAMPs in both preclinical and clinical NEC scenarios. We also focus on elucidating the downstream signaling pathways activated by these molecular patterns, providing insights into the mechanisms that drive inflammation in NEC. Moreover, we scrutinize the landscape of targeted therapeutic approaches, aiming to mitigate the impact of tissue damage in NEC. This in-depth exploration offers a comprehensive overview of the role of CAMPs in NEC, bridging the gap between preclinical and clinical insights.

Upregulation of Nrf2 signaling: A key molecular mechanism of Baicalin's neuroprotective action against diabetes-induced cognitive impairment

BACKGROUND AND AIM

Diabetes-associated cognitive impairment (DCI) is a prevalent complication of diabetes. However, there is a lack of viable strategies for preventing and treating DCI. This study aims to explore the efficacy of baicalin (Bai) in attenuating DCI and elucidating the underlying mechanisms.

EXPERIMENTAL PROCEDURE

GK rats fed a high-fat and high-glucose diet were utilized to investigate the therapeutic potential of Bai. Cognitive function was assessed using the Morris water maze and novel object recognition tests. To gain insight into the molecular mechanisms underlying Bai's neuro-protective effects, co-cultured BV2/HT22 cells were established under high-glucose (HG) stimulation. The modes of action of Bai were subsequently confirmed in vivo using the DCI model in db/db mice.

KEY RESULTS

Bai restored cognitive and spatial memory and attenuated neuron loss, along with reducing expressions of Aβ and phosphorylated Tau protein in diabetic GK rats. At the cellular level, Bai exhibited potent antioxidant and anti-inflammatory effects against HG stimulation. These effects were associated with the upregulation of Nrf2 and supressed Keap1 levels. Consistent with these in vitro findings, similar mechanisms were observed in db/db mice. The significant neuroprotective effects of Bai were abolished when co-administered with ATRA, a Nrf2 blocker, in db/db mice, confirming that KEAP1-Nrf2 signaling pathway was responsible for the observed effect.

CONCLUSIONS AND IMPLICATIONS

Bai demonstrates a great therapeutic potential for attenuating DCI. The antioxidant defense and anti-inflammatory actions of Bai were mediated through the KEAP1-Nrf2 axis. These findings advance our understanding of potential treatment approaches for DCI, a common complication associated with diabetes.

Subventricular zone stem cell niche injury is associated with intestinal perforation in preterm infants and predicts future motor impairment

Brain injury is highly associated with preterm birth. Complications of prematurity, including spontaneous or necrotizing enterocolitis (NEC)-associated intestinal perforations, are linked to lifelong neurologic impairment, yet the mechanisms are poorly understood. Early diagnosis of preterm brain injuries remains a significant challenge. Here, we identified subventricular zone echogenicity (SVE) on cranial ultrasound in preterm infants following intestinal perforations. The development of SVE was significantly associated with motor impairment at 2 years. SVE was replicated in a neonatal mouse model of intestinal perforation. Examination of the murine echogenic subventricular zone (SVZ) revealed NLRP3-inflammasome assembly in multiciliated FoxJ1+ ependymal cells and a loss of the ependymal border in this postnatal stem cell niche. These data suggest a mechanism of preterm brain injury localized to the SVZ that has not been adequately considered. Ultrasound detection of SVE may serve as an early biomarker for neurodevelopmental impairment after inflammatory disease in preterm infants.

NLRP3 activation in macrophages promotes acute intestinal injury in neonatal necrotizing enterocolitis

BACKGROUND

Macrophages are involved in various immune inflammatory disease conditions. This study aimed to investigate the role and mechanism of macrophages in regulating acute intestinal injury in neonatal necrotizing enterocolitis (NEC).

METHODS

CD68, nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing 3 (NLRP3), cysteine aspartate-specific protease-1 (caspase-1), and interleukin-1β (IL-1β) in paraffin sections of intestinal tissues from NEC and control patients were detected with immunohistochemistry, immunofluorescence, and western blot. Hypertonic pet milk, hypoxia and cold stimulation were used to establish a mouse (wild type and Nlrp3-/-) model of NEC. The mouse macrophage (RAW 264.7) and rat intestinal epithelial cell-6 lines were also cultured followed by various treatments. Macrophages, intestinal epithelial cell injuries, and IL-1β release were determined.

RESULTS

Compared to the gut "healthy" patients, the intestinal lamina propria of NEC patients had high macrophage infiltration and high NLRP3, caspase-1, and IL-1β levels. Furthermore, in vivo, the survival rate of Nlrp3-/- NEC mice was dramatically improved, the proportion of intestinal macrophages was reduced, and intestinal injury was decreased compared to those of wild-type NEC mice. NLRP3, caspase-1, and IL-1β derived from macrophages or supernatant from cocultures of macrophages and intestinal epithelial cells also caused intestinal epithelial cell injuries.

CONCLUSIONS

Macrophage activation may be essential for NEC development. NLRP3/caspase-1/IL-1β cellular signals derived from macrophages may be the underlying mechanism of NEC development, and all these may be therapeutic targets for developing treatments for NEC.

Evaluation of white matter microstructural alterations in premature infants with necrotizing enterocolitis

Background

Preterm infants with necrotizing enterocolitis (NEC) are at high risk of adverse neurodevelopmental outcomes. The aim of this study was to explore the value of diffusion tensor imaging (DTI) combined with serum C-reactive protein (CRP) and procalcitonin (PCT) in evaluating alterations of white matter (WM) microstructure in preterm infants with NEC.

Methods

A retrospective cross-sectional study was conducted in which all participants were consecutively enrolled at The Third Affiliated Hospital of Zhengzhou University from June 2017 and October 2021. Data from 30 preterm infants with NEC [mean gestational age at birth 31.41±1.15 weeks; mean age at magnetic resonance imaging (MRI) 37.53±3.08 weeks] and 40 healthy preterm infants with no NEC were recorded (mean gestational age at birth 32.27±2.09 weeks; mean age at MRI 37.15±3.23 weeks). WM was used to obtain the fractional anisotropy (FA) and mean diffusivity (MD) values of the regions of interest (ROIs). Additionally, serum levels of CRP and PCT were determined. Spearman correlation analysis was performed between the WM-derived parameters, CRP level, and the PCT serum index.

Results

Preterm infants with NEC had reduced FA values and elevated MD values in WM regions [posterior limbs of the internal capsule (PLIC), lentiform nucleus (LN), frontal white matter (FWM)] compared to the control group (P<0.05). Additionally, the FA of the PLIC was negatively correlated with serum CRP (r=-0.846; P<0.05) and PCT (r=-0.843; P<0.05). Meanwhile, the MD of PLIC was positively correlated with serum CRP (r=0.743; P<0.05) and PCT (r=0.743; P<0.05, respectively). The area under the curve (AUC) of FA and MD combined with CRP and PCT in the diagnosis of WM microstructure alterations with NEC was 0.968, representing a considerable improvement in predicted efficacy over single indicators, including FA [AUC: 0.938; 95% confidence interval (CI): 0.840-0.950], MD (AUC: 0.807; 95% CI: 0.722-0.838), CRP (AUC: 0.867; 95% CI: 0.822-0.889), and PCT (AUC: 0.706; 95% CI: 0.701-0.758).

Conclusions

WM can noninvasively and quantitatively assess the WM microstructure alterations in preterm infants with NEC. WM combined with serum CRP and PCT demonstrated superior performance in detecting and evaluating WM microstructure alterations in preterm infants with NEC.

New insights into intestinal macrophages in necrotizing enterocolitis: the multi-functional role and promising therapeutic application

Necrotizing enterocolitis (NEC) is an inflammatory intestinal disease that profoundly affects preterm infants. Currently, the pathogenesis of NEC remains controversial, resulting in limited treatment strategies. The preterm infants are thought to be susceptible to gut inflammatory disorders because of their immature immune system. In early life, intestinal macrophages (IMφs), crucial components of innate immunity, demonstrate functional plasticity and diversity in intestinal development, resistance to pathogens, maintenance of the intestinal barrier, and regulation of gut microbiota. When the stimulations of environmental, dietary, and bacterial factors interrupt the homeostatic processes of IMφs, they will lead to intestinal disease, such as NEC. This review focuses on the IMφs related pathogenesis in NEC, discusses the multi-functional roles and relevant molecular mechanisms of IMφs in preterm infants, and explores promising therapeutic application for NEC.

A key role for NLRP3 signaling in preterm labor and birth driven by the alarmin S100B

Preterm birth remains the leading cause of neonatal morbidity and mortality worldwide. A substantial number of spontaneous preterm births occur in the context of sterile intra-amniotic inflammation, a condition that has been mechanistically proven to be triggered by alarmins. However, sterile intra-amniotic inflammation still lacks treatment. The NLRP3 inflammasome has been implicated in sterile intra-amniotic inflammation; yet, its underlying mechanisms, as well as the maternal and fetal contributions to this signaling pathway, are unclear. Herein, by utilizing a translational and clinically relevant model of alarmin-induced preterm labor and birth in Nlrp3-/- mice, we investigated the role of NLRP3 signaling by using imaging and molecular biology approaches. Nlrp3 deficiency abrogated preterm birth and the resulting neonatal mortality induced by the alarmin S100B by impeding the premature activation of the common pathway of labor as well as by dampening intra-amniotic and fetal inflammation. Moreover, Nlrp3 deficiency altered leukocyte infiltration and functionality in the uterus and decidua. Last, embryo transfer revealed that maternal and fetal Nlrp3 signaling contribute to alarmin-induced preterm birth and neonatal mortality, further strengthening the concept that both individuals participate in the complex process of preterm parturition. These findings provide novel insights into sterile intra-amniotic inflammation, a common etiology of preterm labor and birth, suggesting that the adverse perinatal outcomes resulting from prematurity can be prevented by targeting NLRP3 signaling.

Role of the gut-microbiota-metabolite-brain axis in the pathogenesis of preterm brain injury

Brain injury, a common complication in preterm infants, includes the destruction of the key structural and functional connections of the brain and causes neurodevelopmental disorders; it has high morbidity and mortality rates. The exact mechanism underlying brain injury in preterm infants is unclear. Intestinal flora plays a vital role in brain development and the maturation of the immune system in infants; however, detailed understanding of the gut microbiota-metabolite-brain axis in preterm infants is lacking. In this review, we summarise the key mechanisms by which the intestinal microbiota contribute to neurodevelopment and brain injury in preterm infants, with special emphasis on the influence of microorganisms and their metabolites on the regulation of neurocognitive development and neurodevelopmental risks related to preterm birth, infection and neonatal necrotising enterocolitis (NEC). This review provides support for the development and application of novel therapeutic strategies, including probiotics, prebiotics, synbiotics, and faecal bacteria transplantation targeting at brain injury in preterm infants.

What animal model should I use to study necrotizing enterocolitis?

Unfortunately, we are all too familiar with the statement: "Necrotizing enterocolitis remains the leading cause of gastrointestinal surgical emergency in preterm neonates". It's been five decades since the first animal models of necrotizing enterocolitis (NEC) were described. There remains much investigative work to be done on identifying various aspects of NEC, ranging from the underlying mechanisms to treatment modalities. Experimental NEC is mainly focused on a rat, mouse, and piglet models. Our aim is to not only highlight the pros and cons of these three main models, but to also present some of the less-used animal models that have contributed to the body of knowledge about NEC. Choosing an appropriate model is essential to conducting effective research and answering the questions asked. As such, this paper reviews some of the variations that come with each model.

The Application of Nanoparticle-Based Imaging and Phototherapy for Female Reproductive Organs Diseases

Various female reproductive disorders affect millions of women worldwide and bring many troubles to women's daily life. Let alone, gynecological cancer (such as ovarian cancer and cervical cancer) is a severe threat to most women's lives. Endometriosis, pelvic inflammatory disease, and other chronic diseases-induced pain have significantly harmed women's physical and mental health. Despite recent advances in the female reproductive field, the existing challenges are still enormous such as personalization of disease, difficulty in diagnosing early cancers, antibiotic resistance in infectious diseases, etc. To confront such challenges, nanoparticle-based imaging tools and phototherapies that offer minimally invasive detection and treatment of reproductive tract-associated pathologies are indispensable and innovative. Of late, several clinical trials have also been conducted using nanoparticles for the early detection of female reproductive tract infections and cancers, targeted drug delivery, and cellular therapeutics. However, these nanoparticle trials are still nascent due to the body's delicate and complex female reproductive system. The present review comprehensively focuses on emerging nanoparticle-based imaging and phototherapies applications, which hold enormous promise for improved early diagnosis and effective treatments of various female reproductive organ diseases.

The role of neutrophil extracellular traps in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) continues to be one of the most common causes of mortality and morbidity in preterm infants. Although not fully elucidated, studies suggest that prematurity, formula feeding, imbalanced vascular supply, and altered bacterial colonization play major roles in the pathogenesis of NEC. NEC is characterized by increased cytokine release and leukocyte infiltration. Recent data from preterm infants and animal models of NEC suggest that neutrophil extracellular traps (NETs) are released in intestinal tissue. The contribution of NETs in the pathogenesis and/or prevention/treatment of this disease continues to be controversial. Here, we review the available data on NETs release in NEC in human patients and in different NEC models, highlighting their potential contribution to pathology and resolution of inflammation. Here, we review the available data on NETs release in NEC in human patients and the different NEC models, highlighting their potential contribution to pathology or resolution of inflammation.

Bifidobacterium: Host-Microbiome Interaction and Mechanism of Action in Preventing Common Gut-Microbiota-Associated Complications in Preterm Infants: A Narrative Review

The development and health of infants are intertwined with the protective and regulatory functions of different microorganisms in the gut known as the gut microbiota. Preterm infants born with an imbalanced gut microbiota are at substantial risk of several diseases including inflammatory intestinal diseases, necrotizing enterocolitis, late-onset sepsis, neurodevelopmental disorders, and allergies which can potentially persist throughout adulthood. In this review, we have evaluated the role of Bifidobacterium as commonly used probiotics in the development of gut microbiota and prevention of common diseases in preterm infants which is not fully understood yet. The application of Bifidobacterium as a therapeutical approach in the re-programming of the gut microbiota in preterm infants, the mechanisms of host-microbiome interaction, and the mechanism of action of this bacterium have also been investigated, aiming to provide new insights and opportunities in microbiome-targeted interventions in personalized medicine.

Eugenol Alleviates TGEV-Induced Intestinal Injury via Suppressing ROS/NLRP3/GSDMD-Dependent Pyroptosis

Transmissible gastroenteritis virus (TGEV), a coronavirus, is one of the main causative agents of diarrhea in piglets and significantly impacts the global swine industry. Pyroptosis is involved in the pathogenesis of coronavirus, but its role in TGEV-induced intestinal injury has yet to be fully elucidated. Eugenol, an essential plant oil, plays a vital role in antiviral innate immune responses. We demonstrate the preventive effect of eugenol on TGEV infection. Eugenol alleviates TGEV-induced intestinal epithelial cell pyroptosis and reduces intestinal injury in TGEV-infected piglets. Mechanistically, eugenol reduces the activation of NLRP3 inflammasome, thereby inhibiting TGEV-induced intestinal epithelial cell pyroptosis. In addition, eugenol scavenges TGEV-induced reactive oxygen species (ROS) increase, which in turn prevents TGEV-induced NLRP3 inflammasome activation and pyroptosis. Overall, eugenol protects the intestine by reducing TGEV-induced pyroptosis through inhibition of NLRP3 inflammasome activation, which may be mediated through intracellular ROS levels. These findings propose that eugenol may be an effective strategy to prevent TGEV infection.

Mitochondrial Epigenetics Regulating Inflammation in Cancer and Aging

Inflammation is a defining factor in disease progression; epigenetic modifications of this first line of defence pathway can affect many physiological and pathological conditions, like aging and tumorigenesis. Inflammageing, one of the hallmarks of aging, represents a chronic, low key but a persistent inflammatory state. Oxidative stress, alterations in mitochondrial DNA (mtDNA) copy number and mis-localized extra-mitochondrial mtDNA are suggested to directly induce various immune response pathways. This could ultimately perturb cellular homeostasis and lead to pathological consequences. Epigenetic remodelling of mtDNA by DNA methylation, post-translational modifications of mtDNA binding proteins and regulation of mitochondrial gene expression by nuclear DNA or mtDNA encoded non-coding RNAs, are suggested to directly correlate with the onset and progression of various types of cancer. Mitochondria are also capable of regulating immune response to various infections and tissue damage by producing pro- or anti-inflammatory signals. This occurs by altering the levels of mitochondrial metabolites and reactive oxygen species (ROS) levels. Since mitochondria are known as the guardians of the inflammatory response, it is plausible that mitochondrial epigenetics might play a pivotal role in inflammation. Hence, this review focuses on the intricate dynamics of epigenetic alterations of inflammation, with emphasis on mitochondria in cancer and aging.

Bench to bedside - new insights into the pathogenesis of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of death and disability from gastrointestinal disease in premature infants. Recent discoveries have shed light on a unifying theorem to explain the pathogenesis of NEC, suggesting that specific treatments might finally be forthcoming. A variety of experiments have highlighted how the interaction between bacterial signalling receptors on the premature intestine and an abnormal gut microbiota incites a pro-inflammatory response in the intestinal mucosa and its underlying endothelium that leads to NEC. Central amongst the bacterial signalling receptors implicated in NEC development is the lipopolysaccharide receptor Toll-like receptor 4 (TLR4), which is expressed at higher levels in the premature gut than in the full-term gut. The high prenatal intestinal expression of TLR4 reflects the role of TLR4 in the regulation of normal gut development, and supports additional studies indicating that NEC develops in response to signalling events that occur in utero. This Review provides new evidence explaining the pathogenesis of NEC, explores new findings indicating that NEC development has origins before birth, and discusses future questions and opportunities for discovery in this field.

A selective inhibitor of the NLRP3 inflammasome as a potential therapeutic approach for neuroprotection in a transgenic mouse model of Huntington’s disease

Background

Huntington’s disease (HD) is a neurodegenerative disorder caused by the expansion of the CAG repeat in the huntingtin (HTT) gene. When the number of CAG repeats exceeds 36, the translated expanded polyglutamine-containing HTT protein (mutant HTT [mHTT]) interferes with the normal functions of many cellular proteins and subsequently jeopardizes important cellular machineries in major types of brain cells, including neurons, astrocytes, and microglia. The NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome, which comprises NLRP3, ASC, and caspase-1, is involved in the activation of IL-1β and IL-18 and has been implicated in various biological functions. Although the existence of the NLRP3 inflammasome in the brain has been documented, the roles of the NLRP3 inflammasome in HD remain largely uncharacterized. MCC950 is a highly selective and potent small-molecule inhibitor of NLRP3 that has been used for the treatment of several diseases such as Alzheimer’s disease. However, whether MCC950 is also beneficial in HD remains unknown. Therefore, we hypothesized that MCC950 exerts beneficial effects in a transgenic mouse model of HD.

Methods

To evaluate the effects of MCC950 in HD, we used the R6/2 (B6CBA-Tg[HDexon1]62Gpb/1J) transgenic mouse model of HD, which expresses exon 1 of the human HTT gene carrying 120 ± 5 CAG repeats. Male transgenic R6/2 mice were treated daily with MCC950 (10 mg/kg of body weight; oral administration) or water for 5 weeks from the age of 7 weeks. We examined neuronal density, neuroinflammation, and mHTT aggregation in the striatum of R6/2 mice vs. their wild-type littermates. We also evaluated the motor function, body weight, and lifespan of R6/2 mice.

Results

Systematic administration of MCC950 to R6/2 mice suppressed the NLRP3 inflammasome, decreased IL-1β and reactive oxygen species production, and reduced neuronal toxicity, as assessed based on increased neuronal density and upregulation of the NeuN and PSD-95 proteins. Most importantly, oral administration of MCC950 increased neuronal survival, reduced neuroinflammation, extended lifespan, and improved motor dysfunction in R6/2 mice.

Conclusions

Collectively, our findings indicate that MCC950 exerts beneficial effects in a transgenic mouse model of HD and has therapeutic potential for treatment of this devastating neurodegenerative disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02419-9.

Down-expression of the NLRP3 inflammasome delays the progression of diabetic retinopathy

The investigation aimed to evaluate the effects of Mcc950, an inhibitor of the NLRP3 inflammasome, on diabetic retinopathy (DR) mice. The general physiological condition of each group of mice was recorded. Retinal blood vessels were stained for observation of the density of blood vessels, and retinas were used for further morphological examination and fluorescent staining after the intravitreal injection of Mcc950. Mcc950 partially reversed hyperglycemia-induced vascular damage and had reduced histological changes compared to DR mice. IL-1β production in mice retinas in the diabetic model (DM) group increased, but pretreatment with Mcc950 significantly reversed these changes. Additionally, Mcc950 engineered reduced FITC dextran extravasation and vascular leakage. Therefore, it played an apparent protective role in DR and could be a new treatment strategy for DR.

Mechanism of Baicalein in Brain Injury After Intracerebral Hemorrhage by Inhibiting the ROS/NLRP3 Inflammasome Pathway

Intracerebral hemorrhage (ICH) is a devastating subtype of stroke with high disability/mortality. Baicalein has strong anti-inflammatory activity. This study aims to explore the mechanism of baicalein on brain injury after ICH. The model of brain injury after ICH was established by collagenase induction, followed by the evaluation of neurological severity, brain water content, the degenerated neurons, neuronal apoptosis, and reactive oxygen species (ROS). The ICH model was treated with baicalein or silencing NLRP3 to detect brain injury. The expression of NLRP3 inflammasome was detected after treatment with ROS scavenger. The expressions of oxidative stress markers and inflammatory factors were detected, and the levels of components in NLRP3 inflammasome were detected. Baicalein reduced the damage of nervous system, lesion surface, brain water content, and apoptosis. Baicalein inhibited malondialdehyde and increased IL-10 by inhibiting ROS in brain tissue after ICH. Baicalein inhibited the high expression of NLRP3 inflammasome in ICH. ROS scavenger inhibited the NLRP3 inflammatory response by inhibiting ROS levels. Silencing NLRP3 alleviated the brain injury after ICH by inhibiting excessive oxidative stress and inflammatory factors. Overall, baicalein alleviated the brain injury after ICH by inhibiting ROS and NLRP3 inflammasome.