CCN1 is an opsonin for bacterial clearance and a direct activator of Toll-like receptor signaling

Stimulus-responsive hydrogels for diabetic wound management via microenvironment modulation

Diabetic wounds, a major complication of diabetes mellitus, pose a significant clinical challenge. The treatment of diabetic wounds requires comprehensive interventions tailored to their pathophysiological characteristics, such as recurring bacterial infection, persistent inflammation, excessive oxidative stress, and impaired angiogenesis. The development of stimulus-responsive hydrogel dressings offers new strategies for diabetic wound treatment. By responding to various physical and biochemical signals, these smart hydrogels enable real-time monitoring and precise modulation of the wound microenvironment to accelerate diabetic wound healing. In this review, we provide an overview of the disease characteristics of chronic diabetic wounds and introduce the current clinical treatment approaches. We summarize the cutting-edge applications of physical and biochemical signal-responsive hydrogels for diabetic wound treatment by modulating the wound microenvironment.

Akkermansia muciniphila Alleviates Porphyromonas gingivalis-induced Periodontal Disease by Enhancing Bacterial Clearance

This study is to investigate the role of Akkermansia muciniphila (Am) in enhancing immune defense against Porphyromonas gingivalis (Pg)-induced periodontal disease. Twenty C57BL/6 J mice received 50 µL of Pg suspension (1.5 × 109 CFU/mL) with or without 50 µL of Am suspension (1.5 × 109 CFU/mL) orally every 2 days for a total of 18 administrations to assess bone resorption and inflammation. Gingival cervical fluid and periodontal plaques were collected for microbiota analysis using 16S sequencing. THP-1 (a human leukemia monocytic cell line) differentiated macrophages were used to explore the underlying beneficial mechanisms of Am by evaluating gene expression, cytokine production, and phagocytosis activity. Am administration attenuated alveolar bone loss and reduced inflammation in Pg-induced periodontitis in mice. Microbiota analysis revealed that Am reduced bacterial load and modified the composition of periodontal microbiota. In THP-1 macrophages, Am enhanced the phagocytosis of Pg by restoring MyD88 protein levels. RNA sequencing and western blotting results showed that Am upregulated TLR2 and MyD88 expression while downregulating C5aR, indicating interference with the TLR2-C5aR-MyD88 interplay. Am enhances immune defense against Pg-induced periodontal disease by modulating the TLR2-C5aR-MyD88 signaling pathway. These findings suggest that Am could be a promising therapeutic option for managing periodontal disease.

ChNLRC4, a cytoplasmic pattern recognition receptor, activates the pyroptosis signaling pathway in Mollusca

NLR inflammasomes recognize pathogen-associated molecular patterns (PAMPs), triggering Caspase-1 activation and leading to gasdermin D (GSDMD)-mediated pyroptosis, a crucial immune response in mammals. The functional GSDME-mediated pyroptosis has been reported in invertebrates, yet the existence of an NLR-Caspase-GSDME axis mediating pyroptosis signaling cascades remains unclear. In this study, we reported an NLRC4 homolog named ChNLRC4, a pattern recognition receptor from the oyster Crassostrea hongkongensis that is able to bind to LPS and Lys-type PGN through its LRR domain. ChNLRC4 interacted with ChCaspase-1 through CARD-CARD domain homotypic interactions and enhanced ChCaspase-1 activity. Additionally, overexpression of ChNLRC4 promoted ChCaspase-1-mediated cleavage of ChGSDME, leading to pyroptosis in HEK293T cells. Furthermore, knockdown of chnlrc4 resulted in a significant reduction in the death rate of hemocytes, immune infiltration of hemocytes, cilium shedding, and bacterial clearance. Collectively, this study provides insight into the role of NLR within the pyroptosis signaling pathway in oysters.

Cooperation of TRADD- and RIPK1-dependent cell death pathways in maintaining intestinal homeostasis

Dysfunctional NF-κB signaling is critically involved in inflammatory bowel disease (IBD). We investigated the mechanism by which RIPK1 and TRADD, two key mediators of NF-κB signaling, in mediating intestinal pathology using TAK1 IEC deficient model. We show that phosphorylation of TRADD by TAK1 modulates RIPK1-dependent apoptosis. TRADD and RIPK1 act cooperatively to mediate cell death regulated by TNF and TLR signaling. We demonstrate the pathological evolution from RIPK1-dependent ileitis to RIPK1- and TRADD-co-dependent colitis in TAK1 IEC deficient condition. Combined RIPK1 inhibition and TRADD knockout completely protect against intestinal pathology and lethality in TAK1 IEC KO mice. Furthermore, we identify distinctive microbiota dysbiosis biomarkers for RIPK1-dependent ileitis and TRADD-dependent colitis. These findings reveal the cooperation between RIPK1 and TRADD in mediating cell death and inflammation in IBD with NF-κB deficiency and suggest the possibility of combined inhibition of RIPK1 kinase and TRADD as a new therapeutic strategy for IBD.

Multispecies synbiotics alleviate dextran sulfate sodium (DSS)-induced colitis: Effects on clinical scores, intestinal pathology, and plasma biomarkers in male and female mice

BACKGROUND

Inflammatory bowel disease (IBD) is characterized by recurrent inflammation of the gastrointestinal tract and has been linked to an imbalance in gut bacteria. Synbiotics, which combine probiotics and prebiotics, are emerging as potential IBD treatments.

AIM

To examine the effects of four synbiotic formulations on intestinal inflammation and peripheral biomarkers in a rodent IBD model of both sexes.

METHODS

Colitis was induced in male and female C57BL/6 mice using 1% dextran sulfate sodium (DSS). Concurrently, a non-exposed control group was maintained. Starting on day 4 post-induction, DSS-exposed mice received one of four synbiotic preparations (Synbio1-4 composed of lactic acid bacteria, Bifidobacterium and dietary fibres), an anti-inflammatory drug used to treat IBD (mesalazine), or placebo (water) until day 14. Clinical symptoms and body weight were monitored daily. Blood samples (taken on days -3, 4, and 14, relative to DSS introduction), were used to analyze plasma biomarkers. At the end of the study, intestinal tissues underwent histological and morphological evaluation.

RESULTS

Compared to placebo, the Synbio1-, 2- and 3-treated groups had improved clinical scores by day 14. Synbio1 was the only preparation that led to clinical improvements to scores comparable to those of controls. The Synbio1-and 3-treated groups also demonstrated histological improvements in the colon. Plasma biomarker analyses revealed significant Synbio1-induced changes in plasma IL17A, VEGFD, and TNFRSF11B levels that correlated with improved clinical or histological scores. Sex-stratified analyses revealed that most therapeutic-like effects were more pronounced in females.

CONCLUSION

Our findings underscore the potential therapeutic benefits of specific synbiotics for IBD management. However, further research is needed to validate these outcomes in human subjects.

Helicity-directed recognition of bacterial phospholipid via radially amphiphilic antimicrobial peptides

The fundamental differences in phospholipids between bacterial and mammalian cell membranes present remarkable opportunities for antimicrobial design. However, it is challenging to distinguish bacterial anionic phospholipid phosphatidylglycerol (PG) from mammalian anionic phosphatidylserine (PS) with the same net charge. Here, we report a class of radially amphiphilic α helix antimicrobial peptides (RAPs) that can selectively discriminate PG from PS, relying on the helix structure. The representative RAP, L10-MMBen, can direct the rearrangement of PG vesicles into a lamellar structure with its helix axis parallel to the PG membrane surface. The helical structure imparts both the thermodynamic and kinetic advantages of L10-MMBen/PG assembly, and the hiding of hydrophobic regions in RAPs is crucial for PG recognition. L10-MMBen exhibits high selectivity against bacteria depending on PG recognition, showing low in vivo toxicity and significant treatment efficacy in mice infection models. Our study introduces a helicity-direct bacterial phospholipid recognition paradigm for designing highly selective antimicrobial peptides.

Nanomechanics of CCN1-Mediated Staphylococcus aureus Phagocytosis

Phagocytosis is an essential mechanism of the human immune system where pathogens are eliminated by immune cells. The CCN1 protein plays an important role in the phagocytosis of Staphylococcus aureus by favoring the bridging of the αVβ3 integrin to the bacterial peptidoglycan (PG), through mechanical forces that remain unknown. Here, we employ single-molecule experiments to unravel the nanomechanics of the PG-CCN1-αVβ3 ternary complex. While CCN1 binds αVβ3 integrins with moderate force (∼60 pN), much higher binding strengths (up to ∼800 pN) are observed between CCN1 and PG. Notably, the strength of both CCN1-αVβ3 and CCN1-PG bonds is dramatically enhanced by tensile loading, favoring a model in which mechanical stress induces the exposure of cryptic integrin binding sites in CCN1 and multivalent binding between CCN1 lectin sites and monosaccharides along the PG glycan chains.

Cellular communication network factor 1 promotes retinal leakage in diabetic retinopathy via inducing neutrophil stasis and neutrophil extracellular traps extrusion

BACKGROUND

Diabetic retinopathy (DR) is a major cause of blindness and is characterized by dysfunction of the retinal microvasculature. Neutrophil stasis, resulting in retinal inflammation and the occlusion of retinal microvessels, is a key mechanism driving DR. These plugging neutrophils subsequently release neutrophil extracellular traps (NETs), which further disrupts the retinal vasculature. Nevertheless, the primary catalyst for NETs extrusion in the retinal microenvironment under diabetic conditions remains unidentified. In recent studies, cellular communication network factor 1 (CCN1) has emerged as a central molecule modulating inflammation in pathological settings. Additionally, our previous research has shed light on the pathogenic role of CCN1 in maintaining endothelial integrity. However, the precise role of CCN1 in microvascular occlusion and its potential interaction with neutrophils in diabetic retinopathy have not yet been investigated.

METHODS

We first examined the circulating level of CCN1 and NETs in our study cohort and analyzed related clinical parameters. To further evaluate the effects of CCN1 in vivo, we used recombinant CCN1 protein and CCN1 overexpression for gain-of-function, and CCN1 knockdown for loss-of-function by intravitreal injection in diabetic mice. The underlying mechanisms were further validated on human and mouse primary neutrophils and dHL60 cells.

RESULTS

We detected increases in CCN1 and neutrophil elastase in the plasma of DR patients and the retinas of diabetic mice. CCN1 gain-of-function in the retina resulted in neutrophil stasis, NETs extrusion, capillary degeneration, and retinal leakage. Pre-treatment with DNase I to reduce NETs effectively eliminated CCN1-induced retinal leakage. Notably, both CCN1 knockdown and DNase I treatment rescued the retinal leakage in the context of diabetes. In vitro, CCN1 promoted adherence, migration, and NETs extrusion of neutrophils.

CONCLUSION

In this study, we uncover that CCN1 contributed to retinal inflammation, vessel occlusion and leakage by recruiting neutrophils and triggering NETs extrusion under diabetic conditions. Notably, manipulating CCN1 was able to hold therapeutic promise for the treatment of diabetic retinopathy.

Advancements in understanding bacterial enteritis pathogenesis through organoids

Bacterial enteritis has a substantial role in contributing to a large portion of the global disease burden and serves as a major cause of newborn mortality. Despite advancements gained from current animal and cell models in improving our understanding of pathogens, their widespread application is hindered by apparent drawbacks. Therefore, more precise models are imperatively required to develop more accurate studies on host-pathogen interactions and drug discovery. Since the emergence of intestinal organoids, massive studies utilizing organoids have been conducted to study the pathogenesis of bacterial enteritis, revealing new mechanisms and validating established ones. In this review, we focus on the advancements of several bacterial pathogenesis mechanisms observed in intestinal organoid/enteroid models, exploring the host response and bacterial effectors during the infection process. Finally, we address the features that warrant additional investigation or could be enhanced in existing organoid models in order to guide future research endeavors.

Lesion-remote astrocytes govern microglia-mediated white matter repair

Spared regions of the damaged central nervous system undergo dynamic remodeling and exhibit a remarkable potential for therapeutic exploitation. Here, lesion-remote astrocytes (LRAs), which interact with viable neurons, glia and neural circuitry, undergo reactive transformations whose molecular and functional properties are poorly understood. Using multiple transcriptional profiling methods, we interrogated LRAs from spared regions of mouse spinal cord following traumatic spinal cord injury (SCI). We show that LRAs acquire a spectrum of molecularly distinct, neuroanatomically restricted reactivity states that evolve after SCI. We identify transcriptionally unique reactive LRAs in degenerating white matter that direct the specification and function of local microglia that clear lipid-rich myelin debris to promote tissue repair. Fueling this LRA functional adaptation is Ccn1 , which encodes for a secreted matricellular protein. Loss of astrocyte CCN1 leads to excessive, aberrant activation of local microglia with (i) abnormal molecular specification, (ii) dysfunctional myelin debris processing, and (iii) impaired lipid metabolism, culminating in blunted debris clearance and attenuated neurological recovery from SCI. Ccn1 -expressing white matter astrocytes are specifically induced by local myelin damage and generated in diverse demyelinating disorders in mouse and human, pointing to their fundamental, evolutionarily conserved role in white matter repair. Our findings show that LRAs assume regionally divergent reactivity states with functional adaptations that are induced by local context-specific triggers and influence disorder outcome. Astrocytes tile the central nervous system (CNS) where they serve vital roles that uphold healthy nervous system function, including regulation of synapse development, buffering of neurotransmitters and ions, and provision of metabolic substrates 1 . In response to diverse CNS insults, astrocytes exhibit disorder-context specific transformations that are collectively referred to as reactivity 2-5 . The characteristics of regionally and molecularly distinct reactivity states are incompletely understood. The mechanisms through which distinct reactivity states arise, how they evolve or resolve over time, and their consequences for local cell function and CNS disorder progression remain enigmatic. Immediately adjacent to CNS lesions, border-forming astrocytes (BFAs) undergo transcriptional reprogramming and proliferation to form a neuroprotective barrier that restricts inflammation and supports axon regeneration 6-9 . Beyond the lesion, spared but dynamic regions of the injured CNS exhibit varying degrees of synaptic circuit remodeling and progressive cellular responses to secondary damage that have profound consequences for neural repair and recovery 10,11 . Throughout these cytoarchitecturally intact, but injury-reactive regions, lesion-remote astrocytes (LRAs) intermingle with neurons and glia, undergo little to no proliferation, and exhibit varying degrees of cellular hypertrophy 7,12,13 . The molecular and functional properties of LRAs remain grossly undefined. Therapeutically harnessing spared regions of the injured CNS will require a clearer understanding of the accompanying cellular and molecular landscape. Here, we leveraged integrative transcriptional profiling methodologies to identify multiple spatiotemporally resolved, molecularly distinct states of LRA reactivity within the injured spinal cord. Computational modeling of LRA-mediated heterotypic cell interactions, astrocyte-specific conditional gene deletion, and multiple mouse models of acute and chronic CNS white matter degeneration were used to interrogate a newly identified white matter degeneration-reactive astrocyte subtype. We define how this reactivity state is induced and its role in governing the molecular and functional specification of local microglia that clear myelin debris from the degenerating white matter to promote repair.

Elucidation of the Tissue Distribution and Host Immunostimulatory Activity of Exogenously Administered Probiotic-Derived Extracellular Vesicles for Immunoadjuvant

Extracellular vesicles (EVs) are cell-derived nanoparticles that can be used as novel biomaterials. In the development of EVs-based therapeutic systems, it is essential to understand the in vivo fate of exogenously administered EVs and subsequent biological responses mediated by EVs. Although probiotics and microorganisms that modulate the host immune system also secrete EVs, their tissue distribution and biological reactions after administration to the host have not been sufficiently elucidated. In this study, we characterized EVs released from the probiotics Bifidobacterium longum (B-EVs) and Lactobacillus plantarum WCFS1 (L-EVs) in terms of tissue distribution and immune-activating capacity after intravenous and subcutaneous administration in mice. B-EVs and L-EVs exhibited particle sizes of approximately 100-160 nm and negative zeta potentials. These EVs contained peptidoglycan, DNA, and RNA as their cargoes. Intravenously administered B-EVs and L-EVs mainly accumulated in the liver and spleen. Furthermore, liver F4/80 and splenic CD169 macrophages took up the intravenously administered EVs. Subcutaneously administered B-EVs and L-EVs accumulated in the lymph nodes and were mainly located in the B-lymphocyte zone, indicating that exogenously administered probiotic-derived EVs showed a similar biodistribution, irrespective of the EVs-secreting cell type. Evaluation of EVs-mediated immune reactions demonstrated that intravenously administered EVs showed little activation potency. In contrast, subcutaneously administered B-EVs strongly increased the expression of inflammatory cytokine (TNF-α) and co-stimulatory molecules (CD40 and CD80) than L-EVs. These findings indicate that the subcutaneous administration of B-EVs is a useful strategy for the development of novel EVs-based immunotherapies.

Hepatocyte CYR61 polarizes profibrotic macrophages to orchestrate NASH fibrosis

Obesity is increasing worldwide and leads to a multitude of metabolic diseases, including cardiovascular disease, type 2 diabetes, nonalcoholic fatty liver disease, and nonalcoholic steatohepatitis (NASH). Cysteine-rich angiogenic inducer 61 (CYR61) is associated with the progression of NASH, but it has been described to have anti- and proinflammatory properties. We sought to examine the role of liver CYR61 in NASH progression. CYR61 liver-specific knockout mice on a NASH diet showed improved glucose tolerance, decreased liver inflammation, and reduced fibrosis. CYR61 polarized infiltrating monocytes promoting a proinflammatory/profibrotic phenotype through an IRAK4/SYK/NF-κB signaling cascade. In vitro, CYR61 activated a profibrotic program, including PDGFa/PDGFb expression in macrophages, in an IRAK4/SYK/NF-κB-dependent manner. Furthermore, targeted-antibody blockade reduced CYR61-driven signaling in macrophages in vitro and in vivo, reducing fibrotic development. This study demonstrates that CYR61 is a key driver of liver inflammation and fibrosis in NASH.

Antibiotic-Induced Recruitment of Specific Algae-Associated Microbiome Enhances the Adaptability of Chlorella vulgaris to Antibiotic Stress and Incidence of Antibiotic Resistance

Insights into the symbiotic relation between eukaryotic hosts and their microbiome lift the curtain on the crucial roles of microbes in host fitness, behavior, and ecology. However, it remains unclear whether and how abiotic stress shapes the microbiome and further affects host adaptability. This study first investigated the effect of antibiotic exposure on behavior across varying algae taxa at the community level. Chlorophyta, in particular Chlorella vulgaris, exhibited remarkable adaptability to antibiotic stress, leading to their dominance in phytoplankton communities. Accordingly, we isolated C. vulgaris strains and compared the growth of axenic and nonaxenic ones under antibiotic conditions. The positive roles of antibiotics in algal growth were apparent only in the presence of bacteria. Results of 16S rRNA sequencing further revealed that antibiotic challenges resulted in the recruitment of specific bacterial consortia in the phycosphere, whose functions were tightly linked to the host growth promotion and adaptability enhancement. In addition, the algal phycosphere was characterized with 47-fold higher enrichment capability of antibiotic resistance genes (ARGs) than the surrounding water. Under antibiotic stress, specific ARG profiles were recruited in C. vulgaris phycosphere, presumably driven by the specific assembly of bacterial consortia and mobile genetic elements induced by antibiotics. Moreover, the antibiotics even enhanced the dissemination potential of the bacteria carrying ARGs from the algal phycosphere to broader environmental niches. Overall, this study provides an in-depth understanding into the potential functional significance of antibiotic-mediated recruitment of specific algae-associated bacteria for algae adaptability and ARG proliferation in antibiotic-polluted waters.

CCN proteins: opportunities for clinical studies-a personal perspective

The diverse members of the CCN family now designated as CCN1(CYR61), CCN2 (CTGF), CCN3(NOV), CCN4(WISP1), CCN5(WISP2), CCN6(WISP3) are a conserved matricellular family of proteins exhibiting a spectrum of functional properties throughout all organs in the body. Interaction with cell membrane receptors such as integrins trigger intracellular signaling pathways. Proteolytically cleaved fragments (constituting the active domains) can be transported to the nucleus and perform transcriptional relevant functional activities. Notably, as also found in other protein families some members act opposite to others creating a system of functionally relevant checks and balances. It has become apparent that these proteins are secreted into the circulation, are quantifiable, and can serve as disease biomarkers. How they might also serve as homeostatic regulators is just becoming appreciated. In this review I have attempted to highlight the most recent evidence under the subcategories of cancer and non-cancer relevant that could lead to potential therapeutic approaches or ideas that can be factored into clinical advances. I have added my own personal perspective on feasibility.

Analysis of CCN Functions in Liver Regeneration After Partial Hepatectomy

The remarkable regenerative capability of the liver has long been appreciated. Upon significant loss of liver tissue, the remnant liver can grow rapidly to restore the original liver mass through a combination of hepatocyte proliferation and hypertrophy to maintain homeostasis. Experimentally, 2/3 partial hepatectomy in mice has been used extensively as a model to dissect the molecular mechanism of liver regeneration and the genetic networks involved. Herein, we describe the protocols for partial hepatectomy and analyses of pertinent CCN protein functions.

CCN Proteins (Cellular Communication Network Factors): Expanding Their Repertoire Toward a New Concept

I herein report the general structures and functions of CCN proteins and possible molecular mechanisms involved in the unique biological actions of this family of intercellular signaling regulators, which are considered matricellular proteins and were once referred to as "signal conductors" but have recently been renamed "Cellular Communication Network Factors." Their repertoire of functions beyond their role as matricellular proteins is also described to aid in future studies. Advanced research concerning their relevance to pathology is briefly introduced as well. The information provided in this chapter is expected to be useful for readers of subsequent chapters.

Cellular Senescence in Acute and Chronic Wound Repair

Cellular senescence, once thought an artifact of in vitro culture or passive outcome of aging, has emerged as fundamental to tissue development and function. The senescence mechanism importantly halts cell cycle progression to protect against tumor formation, while transiently present senescent cells produce a complex secretome (or SASP) of inflammatory mediators, proteases, and growth factors that guide developmental remodeling and tissue regeneration. Transiently present senescence is important for skin repair, where it accelerates extracellular matrix formation, limits fibrosis, promotes reepithelialization, and modulates inflammation. Unfortunately, advanced age and diabetes drive pathological accumulation of senescent cells in chronic wounds, which is perpetuated by a proinflammatory SASP, advanced glycation end-products, and oxidative damage. Although the biology of wound senescence remains incompletely understood, drugs that selectively target senescent cells are showing promise in clinical trials for diverse pathological conditions. It may not be long before senescence-targeted therapies will be available for the management, or perhaps even prevention, of chronic wounds.

Regulation of CyR61 expression and release by 3-mercaptopyruvate sulfurtransferase in colon cancer cells

Cysteine-rich angiogenic inducer 61 (CYR61, also termed CCN family member 1 or CCN1), is a matricellular protein encoded by the CYR61 gene. This protein has been implicated in the regulation of various cancer-associated processes including tumor growth, angiogenesis, tumor cell adhesion, migration, and invasion as well as the regulation of anticancer drug resistance. Hydrogen sulfide (H₂S) is a gaseous endogenous biological mediator, involved in the regulation of cellular bioenergetics, angiogenesis, invasion, and chemotherapeutic resistance in several types of cancer. H₂S is produced by three enzymes: cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current studies were set up to investigate if CBS or 3-MST regulates CyR61 in colon cancer cells in the context of the regulation of proliferation, migration, and survival. The study mainly utilized HCT116 cells, in which two of the principal H₂S-producing enzymes, CBS and 3-MST, are highly expressed. The H₂S donor GYY4137 and the polysulfide donor Na₂S₃ activated the CyR61 promoter in a concentration-dependent fashion. Aminooxyacetic acid (AOAA), a pharmacological inhibitor of CBS as well as HMPSNE: 2-[(4-hydroxy-6- methylpyrimidin-2-yl)sulfanyl]-1-(naphthalen-1-yl)ethan-1-one, a pharmacological inhibitor of 3-MST inhibited CyR61 mRNA expression. This effect was more pronounced in response to HMPSNE than to AOAA and occurred through the modulation of S1PR via ATF1 and CREB. CyR61 was found to play an active, but relatively minor role in maintaining colon cell proliferation. HMPSNE markedly suppressed the secretion/release of CyR61 from the colon cancer cells. Moreover, HMPSNE promoted colon cancer cell apoptosis; endogenously produced CyR61 was found to counteract this effect, at least in part via RhoA activation. Taken together, we conclude that the upregulation of 3-MST in cancer cells exerts cytoprotective effects and confers the cancer cells a more aggressive phenotype - at least in part via the modulation of CyR61 expression and release.

Cellular communication network factor 1-stimulated liver macrophage efferocytosis drives hepatic stellate cell activation and liver fibrosis

Following inflammatory injury in the liver, neutrophils quickly infiltrate the injured tissue to defend against microbes and initiate the repair process; these neutrophils are short lived and rapidly undergo apoptosis. Hepatic stellate cells (HSCs) are the principal precursor cells that transdifferentiate into myofibroblast-like cells, which produce a large amount of extracellular matrix that promotes repair but can also lead to fibrosis if the injury becomes chronic. The matricellular protein cellular communication network factor 1 (CCN1) acts as a bridging molecule by binding phosphatidylserine in apoptotic cells and integrin αv β3 in phagocytes, thereby triggering efferocytosis or phagocytic clearance of the apoptotic cells. Here, we show that CCN1 induces liver macrophage efferocytosis of apoptotic neutrophils in carbon tetrachloride (CCl4 )-induced liver injury, leading to the production of activated transforming growth factor (TGF)-β1, which in turn induces HSC transdifferentiation into myofibroblast-like cells that promote fibrosis development. Consequently, knock-in mice expressing a single amino acid substitution in CCN1 rendering it unable to bind αv β3 or induce efferocytosis are impaired in neutrophil clearance, production of activated TGF-β1, and HSC transdifferentiation, resulting in greatly diminished liver fibrosis following exposure to CCl4 . Conclusion: These results reveal the crucial role of CCN1 in stimulating liver macrophage clearance of apoptotic neutrophils, a process that drives HSC transdifferentiation into myofibroblastic cells and underlies fibrogenesis in chronic liver injury.

The matricellular protein SPARC induces inflammatory interferon-response in macrophages during aging

The risk of chronic diseases caused by aging is reduced by caloric restriction (CR)-induced immunometabolic adaptation. Here, we found that the matricellular protein, secreted protein acidic and rich in cysteine (SPARC), was inhibited by 2 years of 14% sustained CR in humans and elevated by obesity. SPARC converted anti-inflammatory macrophages into a pro-inflammatory phenotype with induction of interferon-stimulated gene (ISG) expression via the transcription factors IRF3/7. Mechanistically, SPARC-induced ISGs were dependent on toll-like receptor-4 (TLR4)-mediated TBK1, IRF3, IFN-β, and STAT1 signaling without engaging the Myd88 pathway. Metabolically, SPARC dampened mitochondrial respiration, and inhibition of glycolysis abrogated ISG induction by SPARC in macrophages. Furthermore, the N-terminal acidic domain of SPARC was required for ISG induction, while adipocyte-specific deletion of SPARC reduced inflammation and extended health span during aging. Collectively, SPARC, a CR-mimetic adipokine, is an immunometabolic checkpoint of inflammation and interferon response that may be targeted to delay age-related metabolic and functional decline.

Inhibition of KLF6 reduces the inflammation and apoptosis of type II alveolar epithelial cells in acute lung injury

BACKGROUND

The development of acute lung injury (ALI) into a severe stage leads to acute respiratory distress syndrome (ARDS). The morbidity and mortality of ALI and ARDS are very high. Objective: This study is aimed to explore the effect of Krüppel-like factor 6 (KLF6) on lipopolysaccharide (LPS)-induced type II alveolar epithelial cells in ALI by interacting with cysteine-rich angiogenic inducer 61 (CYR61).

MATERIAL AND METHODS

ALI mice model and LPS-induced type II alveolar epithelial cells were conducted to simulate ALI in vivo and in vitro. The messenger RNA (mRNA) and protein expression of KLF6 in lung tissues were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. Pathological changes in lung tissues were observed by hematoxylin and eosin (H&E) staining. The viability and KLF6 expression of A549 cells treated with different concentrations of LPS were detected by cell counting kit-8 (CCK-8) assay, RT-qPCR, and Western blot analysis. After indicated treatment, the viability and apoptosis of A549 cells were analyzed by CCK-8 and TUNEL assays, and the inflammation factors of A549 cells were detected by Enzyme-linked-immunosorbent serologic assay, RT-qPCR, and Western blot analysis. The combination of KLF6 and CYR61 was determined by chromatin immunoprecipitation (ChIP)-PCR and dual-luciferase reporter assay.

RESULTS

KLF6 expression was increased in lung tissues of ALI mice and LPS-induced A549 cells. Interference with KLF6 improved the viability, reduced the inflammatory damage, and promoted the apoptosis of LPS-induced A549 cells. In addition, KLF6 could bind to CYR61. Interference with KLF6 could decrease CYR61 expression in LPS-induced A549 cells. LPS also enhanced the TLR4/MYD88 signaling pathway, which was reversed by KLF6 interference. The above phenomena in LPS-induced A549 cells transfected with Si-KLF6 could be reversed by overexpression of CYR61.

CONCLUSION

Inhibition of KLF6 promoted the viability and reduced the inflammation and apoptosis of LPS-induced A549 cells, which was reversed by CYR61.

Therapeutic effects of the extract of Sancao Formula, a Chinese herbal compound, on imiquimod-induced psoriasis via cysteine-rich protein 61

OBJECTIVE

Psoriasis is a common chronic inflammatory skin disease that is prone to recurrence, and the proinflammatory factor, cysteine-rich protein 61 (Cyr61), is important in its pathophysiology. Long-term clinical practice has shown that Sancao Formula (SC), a Chinese herbal compound, is effective in the treatment of psoriasis, but the precise mechanism remains unknown. In this study, we investigate the mechanism by which SC extract alleviates imiquimod (IMQ)-induced psoriasis.

METHODS

The expression of Cyr61 in psoriatic lesions and normal healthy skin was detected using immunohistochemical analysis to investigate the biological role of Cyr61 in models of psoriatic inflammation. A psoriatic mouse model was established by topical application of IMQ, and the effect of topical application of SC extract was evaluated using the psoriasis area and severity index (PASI) score, hematoxylin-eosin staining, and histopathological features of the skin. Next, a HaCaT cell inflammation model was established using interferon-γ (IFN-γ), and the effect of SC extract on the mRNA and protein levels of Cyr61 and intercellular cell adhesion molecule-1 (ICAM-1) was confirmed using Western blot and quantitative real-time polymerase chain reaction analyses.

RESULTS

Immunohistochemical staining showed that the expression of Cyr61 in psoriatic lesions was higher than that in normal skin samples (78.26% vs 41.18%, P < 0.05), and the number of Cyr61-positive cells in psoriatic lesions was also significantly higher than in normal skin (18.66 ± 2.51 vs 4.33 ± 1.52, P < 0.05). Treatment in mice with IMQ-induced psoriasis showed that SC extract could significantly improve the inflammatory phenotype, PASI score (10.875 ± 0.744 vs 3.875 ± 0.582, P < 0.05), and pathological features compared with those in IMQ model group; SC treatment was also associated with decreased levels of Cyr61 and ICAM-1. In the IFN-γ-induced inflammatory cell model, the mRNA and protein levels of Cyr61 and ICAM-1 were upregulated, while the SC extract downregulated the levels of Cyr61 and ICAM-1.

CONCLUSION

The results provide a theoretical basis for the involvement of Cyr61 in the pathogenesis of psoriasis, and suggest that SC should be used to target Cyr61 for the prevention of psoriasis recurrence.

CCN1 Promotes Inflammation by Inducing IL-6 Production via α6β1/PI3K/Akt/NF-κB Pathway in Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease with unknown etiology. CCN1, an extracellular matrix-associated protein, is associated with carcinoma, inflammation, liver fibrosis, and even autoimmune diseases. However, the role that CCN1 plays in AIH has remained undetermined. In this study, expression of CCN1 in liver was detected by real-time PCR, western blot and immunohistochemistry (IHC). CCN1 level in serum was detected by ELISA. Diagnostic value of CCN1 was determined by receiver operating characteristic (ROC) curve analysis. CCN1 conditional knockout (CCN1^fl/flCre⁺) mice were generated by mating CCN1^fl/fl C57BL/6J and CAG-Cre-ERT C57BL/6J mice. Autoimmune hepatitis mice model was induced by concanavalin A (ConA). IKKα/β, IκBα, NF-κB p65 and Akt phosphorylation were determined by western blot. NF-κB p65 nuclear translocation was examined by immunofluorescence. Here, we found that CCN1 was over-expressed in hepatocytes of AIH patients. CCN1 level also increased in serum of AIH patients compared to healthy controls (HC). ROC curve analysis results showed that serum CCN1 was able to distinguish AIH patients from HD. In ConA induced hepatitis mice model, CCN1 conditional knockout (CCN1^fl/flCre⁺) attenuated inflammation by reducing ALT/AST level and IL-6 expression. In vitro, CCN1 treatment dramatically induced IL-6 production in LO2 cells. Moreover, the production of IL-6 was attenuated by CCN1 knockdown. Furthermore, we showed that CCN1 could activate IL-6 production via the PI3K/Akt/NF-κB signaling pathway by binding to α6β1 receptor. In summary, our results reveal a novel role of CCN1 in promoting inflammation by upregulation of IL-6 production in AIH. Our study also suggests that targeting of CCN1 may represent a novel strategy in AIH treatment.

Involvement of CCN1 Protein and TLR2/4 Signaling Pathways in Intestinal Epithelial Cells Response to Listeria monocytogenes

CCN1 is well studied in terms of its functions in injury repair, cell adhesion survival and apoptosis, bacterial clearance and mediation of inflammation-related pathways, such as the TLR2/4 pathways. However, the role of CCN1 protein and its interaction with TLR2/4 pathways in intestinal epithelial cells was not elucidated after Listeria monocytogenes infection. The results of this study confirm that L. monocytogenes infection induced intestinal inflammation and increased the protein expression of CCN1, TLR2, TLR4 and p38, which followed a similar tendency in the expression of genes related to the TLR2/4 pathways. In addition, organoids infected by L. monocytogenes showed a significant increase in the expression of CCN1 and the activation of TLR2/4 pathways. Furthermore, pre-treatment with CCN1 protein to organoids infected by L. monocytogenes could increase the related genes of TLR2/4 pathways and up-regulate the expression of TNF, and increase the count of pathogens in organoids, which indicates that the interaction between the CCN1 protein and TLR2/4 signaling pathways in intestinal epithelial cells occurred after L. monocytogenes infection. This study will provide a novel insight of the role of CCN1 protein after L. monocytogenes infection in the intestine.

N6-Methyladenosine Modification Profile in Bovine Mammary Epithelial Cells Treated with Heat-Inactivated Staphylococcus aureus

The symptoms of mastitis caused by Staphylococcus aureus (S. aureus) in dairy cows are not obvious and difficult to identify, resulting in major economic losses. N6-Methyladenosine (m6A) modification has been reported to be closely associated with the occurrence of many diseases. However, only a few reports have described the role of m6A modification in S. aureus-induced mastitis. In this study, after 24 h of treatment with inactivated S. aureus, MAC-T cells (an immortalized bovine mammary epithelial cell line) showed increased expression levels of the inflammatory factors IL-1β, IL-6, TNF-α, and reactive oxygen species. We found that the mRNA levels of METLL3, METLL14, WTAP, and ALKBH5 were also upregulated. Methylated RNA immunoprecipitation sequencing analysis revealed that 133 genes were m6A hypermethylated, and 711 genes were m6A hypomethylated. Biological functional analysis revealed that the differential m6A methylated genes were mainly related to oxidative stress, lipid metabolism, inflammatory response, and so on. In the present study, we also identified 62 genes with significant changes in m6A modification and mRNA expression levels. These findings elucidated the m6A modification spectrum induced by S. aureus in MAC-T cells and provide the basis for subsequent m6A research on mastitis.

Remodeling Chondroitin-6-Sulfate-Mediated Immune Exclusion Enhances Anti-PD-1 Response in Colorectal Cancer with Microsatellite Stability

Metastatic microsatellite-stable (MSS) colorectal cancer rarely responds to immune checkpoint inhibitors (ICI). Metabolism heterogeneity in the tumor microenvironment (TME) presents obstacles to antitumor immune response. Combining transcriptome (The Cancer Genome Atlas MSS colorectal cancer, n = 383) and digital pathology (n = 96) analysis, we demonstrated a stroma metabolism-immune excluded subtype with poor prognosis in MSS colorectal cancer, which could be attributed to interaction between chondroitin-6-sulfate (C-6-S) metabolites and M2 macrophages, forming the "exclusion barrier" in the invasive margin. Furthermore, C-6-S derived from cancer-associated fibroblasts promoted co-nuclear translocation of pSTAT3 and GLI1, activating the JAK/STAT3 and Hedgehog pathways. In vivo experiments with C-6-S-targeted strategies decreased M2 macrophages and reprogrammed the immunosuppressive TME, leading to enhanced response to anti-PD-1 in MSS colorectal cancer. Therefore, C-6-S-induced immune exclusion represents an "immunometabolic checkpoint" that can be exploited for the application of combination strategies in MSS colorectal cancer ICI treatment.

Proteome Profiling of RNF213 Depleted Cells Reveals Nitric Oxide Regulator DDAH1 Antilisterial Activity

RNF213 is a large, poorly characterized interferon-induced protein. Mutations in RNF213 are associated with predisposition for Moyamoya disease (MMD), a rare cerebrovascular disorder. Recently, RNF213 was found to have broad antimicrobial activity in vitro and in vivo, yet the molecular mechanisms behind this function remain unclear. Using mass spectrometry-based proteomics and validation by real-time PCR we report here that knockdown of RNF213 leads to transcriptional upregulation of MVP and downregulation of CYR61, in line with reported pro- and anti-bacterial activities of these proteins. Knockdown of RNF213 also results in downregulation of DDAH1, which we discover to exert antimicrobial activity against Listeria monocytogenes infection. DDAH1 regulates production of nitric oxide (NO), a molecule with both vascular and antimicrobial effects. We show that NO production is reduced in macrophages from RNF213 KO mice, suggesting that RNF213 controls Listeria infection through regulation of DDAH1 transcription and production of NO. Our findings propose a potential mechanism for the antilisterial activity of RNF213 and highlight NO as a potential link between RNF213-mediated immune responses and the development of MMD.

The Acari Hypothesis, II: Interspecies Operability of Pattern Recognition Receptors

Hypersensitivity to galactose-α-1,3-galactose (α-gal) is an informative example of a pathologic IgE-mediated process. By way of their saliva, ticks are able to sensitize humans to tick dietary elements that express α-gal. Mites, which along with ticks constitute the phyletic subclass Acari, feed on proteinaceous foodstuffs that represent most, if not all, human allergens. Given: (1) the gross nature of the pathophysiological reactions of allergy, especially anaphylaxis, (2) the allergenicity of acarian foodstuffs, and (3) the relatedness of ticks and mites, it has been hypothesized that human-acarian interactions are cardinal to the pathogenesis of allergy. In this report, a means by which such interactions contribute to that pathogenesis is proposed.

CYR61, regulated by miR-22-3p and MALAT1, promotes autophagy in HK-2 cell inflammatory model

Background

Renal tubular epithelial cells play an important role in renal function and are a major site of injury from inflammation. Emerging evidence suggests that CYR61 is involved in the regulation of autophagy. However, there are few studies on CYR61 in nephropathy and associated inflammation. This study aimed to clarify how CYR61 regulates autophagy in human renal epithelial cells while in an inflammatory state and regulates the upstream pathway of CYR61 levels.

Methods

The human renal tubular epithelial cells (HK-2) cell line treated by lipopolysaccharide (LPS) was used as an inflammatory model of human epithelial cells. Short hairpin RNA (shRNA) was used to down-regulate CYR61, and the changes in the transcription and expression levels of related molecules, as well as the morphological changes of HK-2 cells, were detected by quantitative real time-PCR (qRT-PCR), western blot (WB), and transmission electron microscopy. Either CYR61 or MALAT1 were up-regulated by overexpression vectors, or MALAT1 was down-regulated by miR-22-3p mimics. Subsequently, the levels of CYR61, MALAT1, related inflammatory factors, and autophagy factors were measured by qPCR, WB, and enzyme-linked immunosorbent assay (ELISA). Cell apoptosis was detected by flow cytometry and acridine-orange assay.

Results

We observed that down-regulation of CYR61 could down-regulate 1B-light chain 3 (LC3) level and inhibit autophagy in the LPS-induced inflammation model of HK-2 cells. The expression levels of CYR61, Beclin1, Atg5, LC3, interleukin 6 (IL-6), and tumor necrosis factor-α (TNF-α) were significantly increased by upregulating CYR61 or MALAT1 by overexpression vector, while the expression level of p62 was significantly decreased, intracellular reactive oxygen species (ROS) content was increased, and the proportion of autophagy and apoptosis was increased. The use of miR-22-3p mimics significantly reversed the changes induced by up-regulation of CYR61 or MALAT1 at the molecular and cellular levels.

Conclusions

Our data indicated that CYR61 positively regulates autophagy of HK-2 cells under an inflammatory state, and was negatively regulated by miR-22-3p, while miR-22-3p and MALAT1 were negatively regulated by each other.

Pattern recognition receptors in health and diseases

Pattern recognition receptors (PRRs) are a class of receptors that can directly recognize the specific molecular structures on the surface of pathogens, apoptotic host cells, and damaged senescent cells. PRRs bridge nonspecific immunity and specific immunity. Through the recognition and binding of ligands, PRRs can produce nonspecific anti-infection, antitumor, and other immunoprotective effects. Most PRRs in the innate immune system of vertebrates can be classified into the following five types based on protein domain homology: Toll-like receptors (TLRs), nucleotide oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs), C-type lectin receptors (CLRs), and absent in melanoma-2 (AIM2)-like receptors (ALRs). PRRs are basically composed of ligand recognition domains, intermediate domains, and effector domains. PRRs recognize and bind their respective ligands and recruit adaptor molecules with the same structure through their effector domains, initiating downstream signaling pathways to exert effects. In recent years, the increased researches on the recognition and binding of PRRs and their ligands have greatly promoted the understanding of different PRRs signaling pathways and provided ideas for the treatment of immune-related diseases and even tumors. This review describes in detail the history, the structural characteristics, ligand recognition mechanism, the signaling pathway, the related disease, new drugs in clinical trials and clinical therapy of different types of PRRs, and discusses the significance of the research on pattern recognition mechanism for the treatment of PRR-related diseases.

Immunology of Acute and Chronic Wound Healing

Skin wounds greatly affect the global healthcare system, creating a substantial burden on the economy and society. Moreover, the situation is exacerbated by low healing rates, which in fact are overestimated in reports. Cutaneous wounds are generally classified into acute and chronic. The immune response plays an important role during acute wound healing. The activation of immune cells and factors initiate the inflammatory process, facilitate wound cleansing and promote subsequent tissue healing. However, dysregulation of the immune system during the wound healing process leads to persistent inflammation and delayed healing, which ultimately result in chronic wounds. The microenvironment of a chronic wound is characterized by high quantities of pro-inflammatory macrophages, overexpression of inflammatory mediators such as TNF-α and IL-1β, increased activity of matrix metalloproteinases and abundance of reactive oxygen species. Moreover, chronic wounds are frequently complicated by bacterial biofilms, which perpetuate the inflammatory phase. Continuous inflammation and microbial biofilms make it very difficult for the chronic wounds to heal. In this review, we discuss the role of innate and adaptive immunity in the pathogenesis of acute and chronic wounds. Furthermore, we review the latest immunomodulatory therapeutic strategies, including modifying macrophage phenotype, regulating miRNA expression and targeting pro- and anti-inflammatory factors to improve wound healing.

Expression of Cyr61 is associated with clinical course in patients with Crohn's disease

BACKGROUNDS

Cysteine-rich angiogenic inducer 61 (Cyr61) is emerging as an important regulator of tissue homeostasis and wound repair. We aim to explore the colonic mucosal expression of Cyr61 and analyze the association between Cyr61 expression and clinical course in patients with Crohn's disease (CD).

METHODS

Endoscopic samples were identified from 83 CD patients with and 372 controls by searching pathological reports. Among them, age- and sex- matched 43 of each group by a propensity score were selected to compare Cyr61 expression by immunohistochemistry (IHC). IHC scores for Cyr61 expression of CD patients were divided into tertiles to evaluate the association with clinical course. We also measured the level of mRNA for Cyr 61 and proinflammatory genes in inflamed and noninflamed colonic mucosal lesions from CD patients.

RESULTS

The mean IHC scores for Cyr61 expression was higher in CD patients (86.5) than in controls (46.1, P < 0.001). In CD patients, the mean IHC scores for Cyr61 expression (68.3) was lower in patients with clinical recurrence than in patients without recurrence (92.2, P = 0.01). Cyr61 mRNA levels in inflamed mucosa were twofold higher than those in non-inflamed lesion (P > 0.05) and the mRNA levels of IL-6 and TLR-4 in inflamed mucosa were significantly higher than those in non-inflamed mucosa in CD patients (all P < 0.05). When CD patients were stratified into tertile groups according to IHC scores for Cyr61 expression, clinical recurrence rates tended to be lower in patients with high Cyr61 expression (P for trend = 0.02). Compared with tertile 1 of Cyr61 expression, tertile 3 of Cyr 61 expression was associated with reduced risk of clinical recurrence (OR 0.43, 95% CI 0.20-0.92) after adjustment for age, sex and CD activity index at the time of colonoscopy in CD patients (P = 0.03).

CONCLUSIONS

Cyr61 mucosal expression in CD patients was inversely associated with clinical course. Future study need to be considered to evaluate whether Cyr 61 may play a role in activating inflammatory responses and contributing to wound healing and tissue repair in patients with CD.

Somanath P, Zhang D. The Roles of CCN1/CYR61 in Pulmonary Diseases

CCN1 (cysteine-rich 61, connective tissue growth factor, and nephroblastoma-1), previously named CYR61 (cysteine-rich angiogenic inducer 61) belongs to the CCN family of matricellular proteins. CCN1 plays critical roles in the regulation of proliferation, differentiation, apoptosis, angiogenesis, and fibrosis. Recent studies have extensively characterized the important physiological and pathological roles of CCN1 in various tissues and organs. In this review, we summarize both basic and clinical aspects of CCN1 in pulmonary diseases, including acute lung injury (ALI), chronic obstructive pulmonary disease (COPD), lung fibrosis, pulmonary arterial hypertension (PAH), lung infection, and lung cancer. We also emphasize the important challenges for future investigations to better understand the CCN1 and its role in physiology and pathology, as well as the questions that need to be addressed for the therapeutic development of CCN1 antagonists in various lung diseases.

Integrins Control Vesicular Trafficking; New Tricks for Old Dogs

Integrins are transmembrane receptors that transduce biochemical and mechanical signals across the plasma membrane and promote cell adhesion and migration. In addition, integrin adhesion complexes are functionally and structurally linked to components of the intracellular trafficking machinery and accumulating data now reveal that they are key regulators of endocytosis and exocytosis in a variety of cell types. Here, we highlight recent insights into integrin control of intracellular trafficking in processes such as degranulation, mechanotransduction, cell–cell communication, antibody production, virus entry, Toll-like receptor signaling, autophagy, and phagocytosis, as well as the release and uptake of extracellular vesicles. We discuss the underlying molecular mechanisms and the implications for a range of pathophysiological contexts, including hemostasis, immunity, tissue repair, cancer, and viral infection.

Integrin adhesion complexes control polarized targeting of the intracellular trafficking machinery via microtubules.

Integrin adhesions are exocytic hubs for a variety of vesicles, including lytic and dense granules, lysosome-related organelles, and biosynthetic vesicles.

Integrin-dependent adhesion and signaling is required for degranulation of platelets and leukocytes and controls hemostasis and immunity.

Specialized adhesion complexes containing integrin αvβ5 and clathrin are sites of frustrated endocytosis and hubs for mechanotransduction.

Integrin control of endocytosis regulates Toll-like receptor signaling and autophagy in immune cells.

Integrins control intercellular communication and viral transfer through extracellular vesicles.