beta-Catenin activity negatively regulates bacteria-induced inflammation

A Protective Role of Canonical Wnt/β-Catenin Pathway in Pathogenic Bacteria-Induced Inflammatory Responses

Inflammation is a complex host defensive response against various disease-associated pathogens. A baseline extent of inflammation is supposed to be tightly associated with a sequence of immune-modulated processes, resulting in the protection of the host organism against pathogen invasion; however, as a matter of fact is that an uncontrolled inflammatory cascade is the main factor responsible for the host damage, accordingly suggesting a significant and indispensable involvement of negative feedback mechanism in modulation of inflammation. Evidence accumulated so far has supported a repressive effect of the canonical Wnt/β-catenin pathway on microbial-triggered inflammation via diverse mechanisms, although that consequence is dependent on the cellular context, types of stimuli, and cytokine environment. It is of particular interest and importance to comprehend the precise way in which the Wnt/β-catenin pathway is activated, due to its essential anti-inflammatory properties. It is assumed that an inflammatory milieu is necessary for initiating and activating this signaling, implying that Wnt activity is responsible for shielding tissues from overwhelming inflammation, thus sustaining a balanced physiological condition against bacterial infection. This review gathers the recent efforts to elucidate the mechanistic details through how Wnt/β-catenin signaling modulates anti-inflammatory responses in response to bacterial infection and its interactions with other inflammatory signals, which warrants further study for the development of specific interventions for the treatment of inflammatory diseases. Further clinical trials from different disease settings are required.

The inhibitory effect of Gremlin-2 on adipogenesis suppresses breast cancer cell growth and metastasis

BACKGROUND

Gremlin-1 (GREM1) and Gremlin-2 (GREM2) are bone morphogenetic protein antagonists that play important roles in organogenesis, tissue differentiation, and tissue homeostasis. Although GREM1 has been reported to be involved in promoting various cancers, little has been reported about effects of GREM2 on cancer. Recently, it has been reported that GREM2 can inhibit adipogenesis in adipose-derived stromal/stem cells. However, as an inhibitor of adipogenesis, the role of GREM2 in cancer progression is not well understood yet.

METHODS

Pre-adipocyte 3T3-L1 cells overexpressing mock or Grem2 were established using a lentiviral transduction system and differentiated into adipocytes-mock and adipocytes-Grem2, respectively. To investigate the effect of adipocyte-Grem2 on breast cancer cells, we analyzed the proliferative and invasion abilities of spheroids using a 3D co-culture system of breast cancer cells and adipocytes or conditioned medium (CM) of adipocytes. An orthotopic breast cancer mouse model was used to examine the role of adipocytes-Grem2 in breast cancer progression.

RESULTS

Grem2 overexpression suppressed adipogenesis of 3T3-L1 cells. Proliferative and invasion abilities of spheroids formed by co-culturing MTV/TM-011 breast cancer cells and adipocytes-Grem2 were significantly reduced compared to those of spheroids formed by co-culturing MTV/TM-011 cells and adipocytes-mock. Compared to adipocytes-mock, adipocytes-Grem2 showed decreased mRNA expression of several adipokines, notably IL-6. The concentration of IL-6 in the CM of these cells was also decreased. Proliferative and invasive abilities of breast cancer cells reduced by adipocytes-Grem2 were restored by IL-6 treatment. Expression levels of vimentin, slug, and twist1 in breast cancer cells were decreased by treatment with CM of adipocytes-Grem2 but increased by IL-6 treatment. In orthotopic breast cancer mouse model, mice injected with both MTV/TM-011 cells and adipocytes-Grem2 showed smaller primary tumors and lower lung metastasis than controls. However, IL-6 administration increased both the size of primary tumor and the number of metastatic lung lesions, which were reduced by adipocytes-Grem2.

CONCLUSIONS

Our study suggests that GREM2 overexpression in adipocytes can inhibit adipogenesis, reduce the expression and secretion of several adipokines, including IL-6, and ultimately inhibit breast cancer progression.

Pro-inflammatory role of Wnt/β-catenin signaling in endothelial dysfunction

Background

Endothelial dysfunction is a critical component of both atherosclerotic plaque formation and saphenous vein graft failure. Crosstalk between the pro-inflammatory TNF-α-NFκB signaling axis and the canonical Wnt/β-catenin signaling pathway potentially plays an important role in regulating endothelial dysfunction, though the exact nature of this is not defined.

Results

In this study, cultured endothelial cells were challenged with TNF-α and the potential of a Wnt/β-catenin signaling inhibitor, iCRT-14, in reversing the adverse effects of TNF-α on endothelial physiology was evaluated. Treatment with iCRT-14 lowered nuclear and total NFκB protein levels, as well as expression of NFκB target genes, IL-8 and MCP-1. Inhibition of β-catenin activity with iCRT-14 suppressed TNF-α-induced monocyte adhesion and decreased VCAM-1 protein levels. Treatment with iCRT-14 also restored endothelial barrier function and increased levels of ZO-1 and focal adhesion-associated phospho-paxillin (Tyr118). Interestingly, inhibition of β-catenin with iCRT-14 enhanced platelet adhesion in cultured TNF-α-stimulated endothelial cells and in an ex vivo human saphenous vein model, most likely via elevating levels of membrane-tethered vWF. Wound healing was moderately retarded by iCRT-14; hence, inhibition of Wnt/β-catenin signaling may interfere with re-endothelialisation in grafted saphenous vein conduits.

Conclusion

Inhibition of the Wnt/β-catenin signaling pathway with iCRT-14 significantly recovered normal endothelial function by decreasing inflammatory cytokine production, monocyte adhesion and endothelial permeability. However, treatment of cultured endothelial cells with iCRT-14 also exerted a pro-coagulatory and moderate anti-wound healing effect: these factors may affect the suitability of Wnt/β-catenin inhibition as a therapy for atherosclerosis and vein graft failure.

Protective effect of berberine against LPS-induced injury in the intestine: a review

Sepsis is a systemic inflammatory condition caused by an unbalanced immunological response to infection, which affects numerous organs, including the intestines. Lipopolysaccharide (LPS; also known as endotoxin), a substance found in Gram-negative bacteria, plays a major role in sepsis and is mostly responsible for the disease's morbidity and mortality. Berberine is an isoquinoline alkaloid found in a variety of plant species that has anti-inflammatory properties. For many years, berberine has been used to treat intestinal inflammation and infection. Berberine has been reported to reduce LPS-induced intestinal damage. The potential pathways through which berberine protects against LPS-induced intestinal damage by inhibiting NF-κB, suppressing MAPK, modulating ApoM/S1P pathway, inhibiting COX-2, modulating Wnt/Beta-Catenin signaling pathway, and/or increasing ZIP14 expression are reviewed.Abbreviations: LPS, lipopolysaccharide; TLR, Toll-like receptor; MD-2, myeloid differentiation factor 2; CD14, cluster of differentiation 14; LBP, lipopolysaccharide-binding protein; MYD88, myeloid differentiation primary response 88; NF-κB, nuclear factor kappa light-chain enhancer of activated B cells; MAPK, mitogen-activated protein kinase; IL, interleukin; TNFα, tumor necrosis factor-alpha; Caco-2, cyanocobalamin uptake by human colon adenocarcinoma cell line; MLCK, myosin light-chain kinase; TJ, tight junction; IκBα, nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha; IBS, irritable bowel syndrome; ERK, extracellular signal-regulated kinase; JNK, c-Jun N-terminal kinase (JNK; GVB, gut-vascular barrier; ApoM, apolipoprotein M; S1P, sphingosine-1-phosphate; VE-cadherin, vascular endothelial cadherin; AJ, adherens junction; PV1, plasmalemma vesicle-associated protein-1; HDL, high-density lipoprotein; Wnt, wingless-related integration site; Fzd, 7-span transmembrane protein Frizzled; LRP, low-density lipoprotein receptor-related protein; TEER, transendothelial/transepithelial electrical resistance; COX-2, cyclooxygenase-2; iNOS, inducible nitric oxide synthase; IGF, insulin-like growth factor; IGFBP, insulin-like growth factor-binding protein; ZIP, Zrt-Irt-like protein; PPAR, peroxisome proliferator-activated receptors; p-PPAR, phosphorylated-peroxisome proliferator-activated receptors; ATF, activating transcription factors; SOD, superoxide dismutase; GSH-Px, glutathione peroxidase; SARA, subacute ruminal acidosis; IPEC-J2, porcine intestinal epithelial cells; ALI, acute lung injury; ARDS, acute respiratory distress syndrome.

Huoxin pill prevents excessive inflammation and cardiac dysfunction following myocardial infarction by inhibiting adverse Wnt/β‑catenin signaling activation

BACKGROUND

Myocardial infarction (MI) is the most common cause of cardiac injury, resulting in widespread and irreversible damage to the heart. The incidence of MI gives rise to the excessive production of inflammatory cytokines that further promotes myocardial dysfunction. Wnt/β-catenin signaling pathway is adversely activated during MI and plays an important role in the modulation of the inflammatory response following tissue injury. Huoxin pill (HXP) is a Traditional Chinese Medicine formulation that has been long used in the treatment of cardiovascular diseases, however its mechanisms of cardioprotection remain unclear.

METHODS

We performed murine models of MI in order to model myocardial ischemic damage and examine the effect and underlying mechanism of HXP in protecting against myocardial ischemic injury. We further constructed conditional cardiomyocyte-specific β-catenin knockout mice and induced surgical MI in order to better understand the role of Wnt/β-catenin signaling following myocardial infarction in the adult heart.

RESULTS

HXP administration strongly protected against cardiac ischemic injury, improved cardiac function, and markedly decreased the expression of pro-inflammatory cytokines following MI. Nuclear activation of β‑catenin resulted in significantly increased nuclear translocation and activation of NF-κB. In contrast, cardiomyocyte-specific deletion of β-catenin decreased NF-κB activation and exhibited beneficial effects following ischemic injury. Hence, HXP protected against MI-induced ischemic injury and excessive inflammatory response via inhibiting Wnt/β‑catenin signaling.

CONCLUSIONS

Our study elucidated the role of HXP in protecting against ischemic myocardial injury via preventing MI-induced inflammatory response, which was mediated by its ability to inhibit adverse Wnt/β‑catenin signaling activation. Thus, our study provides the basis for the implementation of HXP as an effective therapeutic strategy in protecting against myocardial ischemic diseases.

Gut-derived metabolites influence neurodevelopmental gene expression and Wnt signaling events in a germ-free zebrafish model

BACKGROUND

Small molecule metabolites produced by the microbiome are known to be neuroactive and are capable of directly impacting the brain and central nervous system, yet there is little data on the contribution of these metabolites to the earliest stages of neural development and neural gene expression. Here, we explore the impact of deriving zebrafish embryos in the absence of microbes on early neural development as well as investigate whether any potential changes can be rescued with treatment of metabolites derived from the zebrafish gut microbiota.

RESULTS

Overall, we did not observe any gross morphological changes between treatments but did observe a significant decrease in neural gene expression in embryos raised germ-free, which was rescued with the addition of zebrafish metabolites. Specifically, we identified 354 genes significantly downregulated in germ-free embryos compared to conventionally raised embryos via RNA-Seq analysis. Of these, 42 were rescued with a single treatment of zebrafish gut-derived metabolites to germ-free embryos. Gene ontology analysis revealed that these genes are involved in prominent neurodevelopmental pathways including transcriptional regulation and Wnt signaling. Consistent with the ontology analysis, we found alterations in the development of Wnt dependent events which was rescued in the germ-free embryos treated with metabolites.

CONCLUSIONS

These findings demonstrate that gut-derived metabolites are in part responsible for regulating critical signaling pathways in the brain, especially during neural development. Video abstract.

Astragalus polysaccharides and astragaloside IV alleviate inflammation in bovine mammary epithelial cells by regulating Wnt/β-catenin signaling pathway

The Wnt/β-catenin signaling regulates cell renewal and repair and is closely associated with inflammation. Astragalus polysaccharides (APS) and astragaloside IV (AS-IV), which are the main active substances extracted from Radix Astragali, protect cells by regulating Wnt signaling in cells, exerting antiinflammatory, antioxidant, and antistress effects. However, the mechanisms by which APS and AS-IV interact with Wnt signaling to achieve their therapeutic effects in bovine mammary epithelial cells (BMECs) are not understood. In this study, we used lipopolysaccharide (LPS)-stimulated BMECs as an in vitro model of inflammation to investigate the effects of APS and AS-IV on Wnt signaling in inflamed BMECs. Drug concentrations were screened using the CCK-8 method, the effect on protein expression was analyzed using immunoblotting, the effect on inflammatory factors using enzyme-linked immunosorbent assay, and the effect on oxidative factors using enzyme labeling and flow cytometry. LPS activated the expression of inflammatory and oxidative factors in cells and inhibited Wnt/β-catenin signaling. APS and AS-IV antagonized the inhibitory effect of LPS, protecting BMECs. They inhibited the expression of the IL-6, IL-8, and TNF-α inflammatory factors, and that of the MDA oxidative factor, and activated Wnt signaling in LPS-stimulated BMECs. Silencing of β-catenin abolished the protective effect of APS and AS-IV against LPS-stimulated BMECs. Thus, APS and AS-IV mediate protective effects in inflammatory BMECs model through activation of the Wnt signaling pathway. Wnt signaling pathway is one of the targets of the inhibitory effects of APS and AS-IV on inflammation.

Gut Microbiota Interact With the Brain Through Systemic Chronic Inflammation: Implications on Neuroinflammation, Neurodegeneration, and Aging

It has been noticed in recent years that the unfavorable effects of the gut microbiota could exhaust host vigor and life, yet knowledge and theory are just beginning to be established. Increasing documentation suggests that the microbiota-gut-brain axis not only impacts brain cognition and psychiatric symptoms but also precipitates neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). How the blood-brain barrier (BBB), a machinery protecting the central nervous system (CNS) from the systemic circulation, allows the risky factors derived from the gut to be translocated into the brain seems paradoxical. For the unique anatomical, histological, and immunological properties underpinning its permeable dynamics, the BBB has been regarded as a biomarker associated with neural pathogenesis. The BBB permeability of mice and rats caused by GM dysbiosis raises the question of how the GM and its metabolites change BBB permeability and causes the brain pathophysiology of neuroinflammation and neurodegeneration (NF&ND) and brain aging, a pivotal multidisciplinary field tightly associated with immune and chronic systemic inflammation. If not all, gut microbiota-induced systemic chronic inflammation (GM-SCI) mainly refers to excessive gut inflammation caused by gut mucosal immunity dysregulation, which is often influenced by dietary components and age, is produced at the interface of the intestinal barrier (IB) or exacerbated after IB disruption, initiates various common chronic diseases along its dispersal routes, and eventually impairs BBB integrity to cause NF&ND and brain aging. To illustrate the immune roles of the BBB in pathophysiology affected by inflammatory or "leaky" IB resulting from GM and their metabolites, we reviewed the selected publications, including the role of the BBB as the immune barrier, systemic chronic inflammation and inflammation influences on BBB permeability, NF&ND, and brain aging. To add depth to the bridging role of systemic chronic inflammation, a plausible mechanism indispensable for BBB corruption was highlighted; namely, BBB maintenance cues are affected by inflammatory cytokines, which may help to understand how GM and its metabolites play a major role in NF&ND and aging.

Enterotoxigenic Bacteroides fragilis activates IL-8 expression through Stat3 in colorectal cancer cells

Background

Enterotoxigenic Bacteroides fragilis (ETBF) has been implicated in colorectal carcinogenesis through the actions of its toxin, B. fragilis toxin (BFT). Studies on colorectal cell lines have shown that treatment with BFT causes disruption of E-cadherin leading to increased expression of the pro-inflammatory cytokine, IL-8. Stat3 activation has also been associated with ETBF-related colitis and tumour development. However, a link between E-cadherin, IL-8 and Stat3 has not been investigated in the context of ETBF infection.

Results

We found that co-culture of HT-29 and HCT116 colorectal cell lines with ETBF, had a similar effect on activation of IL8 gene and protein expression as treatment with purified BFT. Inhibition of Stat3 resulted in a decrease in IL-8 gene and protein expression in response to ETBF in both cell lines. A reduction in E-cadherin expression in response to ETBF treatment was not restored by blocking Stat3.

Conclusion

We found that treatment of colorectal cancer cell lines with live cultures of ETBF had the equivalent effect on IL-8 expression as the use of purified toxin, and this may be a more representative model of ETBF-mediated colorectal carcinogenesis. IL-8 gene and protein expression was mediated through Stat3 in HT-29 and HCT116 cells, whereas disruption of E-cadherin appeared to be independent of Stat3 signalling.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-022-00489-x.

Neuroinflammation in Schizophrenia: The Key Role of the WNT/β-Catenin Pathway

Schizophrenia is a very complex syndrome involving widespread brain multi-dysconnectivity. Schizophrenia is marked by cognitive, behavioral, and emotional dysregulations. Recent studies suggest that inflammation in the central nervous system (CNS) and immune dysfunction could have a role in the pathogenesis of schizophrenia. This hypothesis is supported by immunogenetic evidence, and a higher incidence rate of autoimmune diseases in patients with schizophrenia. The dysregulation of the WNT/β-catenin pathway is associated with the involvement of neuroinflammation in schizophrenia. Several studies have shown that there is a vicious and positive interplay operating between neuroinflammation and oxidative stress. This interplay is modulated by WNT/β-catenin, which interacts with the NF-kB pathway; inflammatory factors (including IL-6, IL-8, TNF-α); factors of oxidative stress such as glutamate; and dopamine. Neuroinflammation is associated with increased levels of PPARγ. In schizophrenia, the expression of PPAR-γ is increased, whereas the WNT/β-catenin pathway and PPARα are downregulated. This suggests that a metabolic-inflammatory imbalance occurs in this disorder. Thus, this research’s triptych could be a novel therapeutic approach to counteract both neuroinflammation and oxidative stress in schizophrenia.

Wnt signaling pathway in cancer immunotherapy

Wnt/β-catenin signaling is a highly conserved pathway that regulates cell proliferation, differentiation, apoptosis, stem cell self-renewal, tissue homeostasis, and wound healing. Dysregulation of the Wnt pathway is intricately involved in almost all stages of tumorigenesis in various cancers. Through direct and/or indirect effects on effector T cells, T-regulatory cells, T-helper cells, dendritic cells, and other cytokine-expressing immune cells, abnormal activation of Wnt/β-catenin signaling benefits immune exclusion and hinders T-cell-mediated antitumor immune responses. Activation of Wnt signaling results in increased resistance to immunotherapies. In this review, we summarize the process by which Wnt signaling affects cancer and immune surveillance, and the potential for targeting the Wnt-signaling pathway via cancer immunotherapy.

Transcription Factor-7-Like-2 (TCF7L2) in Atherosclerosis: A Potential Biomarker and Therapeutic Target

Transcription factor-7-like-2 (TCF7L2), a vital member of the T-cell factor/lymphoid enhancer factor (TCF/LEF) family, plays an important role in normal human physiological and pathological processes. TCF7L2 exhibits multiple anti-atherosclerotic effects through the activation of specific molecular mechanisms, including regulation of metabolic homeostasis, macrophage polarization, and neointimal hyperplasia. A single-nucleotide substitution of TCF7L2, rs7903146, is a genetic high-risk factor for type 2 diabetes and indicates susceptibility to cardiovascular disease as a link between metabolic disorders and atherosclerosis. In this review, we summarize the anti-atherosclerosis effect and novel mechanisms underlying the function of TCF7L2 to elucidate its potential as an anti-atherosclerosis biomarker and provide a novel therapeutic target for cardiovascular diseases.

Glycogen Synthase Kinase-3: A Focal Point for Advancing Pathogenic Inflammation in Depression

Increasing evidence indicates that the host immune response has a monumental role in the etiology of major depressive disorder (MDD), motivating the development of the inflammatory hypothesis of depression. Central to the involvement of chronic inflammation in MDD is a wide range of signaling deficits induced by the excessive secretion of pro-inflammatory cytokines and imbalanced T cell differentiation. Such signaling deficits include the glutamatergic, cholinergic, insulin, and neurotrophin systems, which work in concert to initiate and advance the neuropathology. Fundamental to the communication between such systems is the protein kinase glycogen synthase kinase-3 (GSK-3), a multifaceted protein critically linked to the etiology of MDD and an emerging target to treat pathogenic inflammation. Here, a consolidated overview of the widespread multi-system involvement of GSK-3 in contributing to the neuropathology of MDD will be discussed, with the feed-forward mechanistic links between all major neuronal signaling pathways highlighted.

Nuclear factor-kappa B (NF-κB) in pathophysiology of Parkinson disease: Diverse patterns and mechanisms contributing to neurodegeneration

Parkinson's disease (PD), the most common movement disorder, comprises several pathophysiologic mechanisms including misfolded alpha-synuclein aggregation, inflammation, mitochondrial dysfunction, and synaptic loss. Nuclear Factor-Kappa B (NF-κB), as a key regulator of a myriad of cellular reactions, is shown to be involved in such mechanisms associated with PD, and the changes in NF-κB expression is implicated in PD. Alpha-synuclein accumulation, the characteristic feature of PD pathology, is known to trigger NF-κB activation in neurons, thereby propagating apoptosis through several mechanisms. Furthermore, misfolded alpha-synuclein released from degenerated neurons, activates several signaling pathways in glial cells which culminate in activation of NF-κB and production of pro-inflammatory cytokines, thereby aggravating neurodegenerative processes. On the other hand, NF-κB activation, acting as a double-edged sword, can be necessary for survival of neurons. For instance, NF-κB activation is necessary for competent mitochondrial function and deficiency in c-Rel, one of the NF-κB proteins, is known to propagate DA neuron loss via several mechanisms. Despite the dual role of NF-κB in PD, several agents by selectively modifying the mechanisms and pathways associated with NF-κB, can be effective in attenuating DA neuron loss and PD, as reviewed in this paper.

Inflammation and Wnt Signaling: Target for Immunomodulatory Therapy?

Wnt proteins comprise a large family of highly conserved glycoproteins known for their role in development, cell fate specification, tissue regeneration, and tissue homeostasis. Aberrant Wnt signaling is linked to developmental defects, malignant transformation, and carcinogenesis as well as to inflammation. Mounting evidence from recent research suggests that a dysregulated activation of Wnt signaling is involved in the pathogenesis of chronic inflammatory diseases, such as neuroinflammation, cancer-mediated inflammation, and metabolic inflammatory diseases. Recent findings highlight the role of Wnt in the modulation of inflammatory cytokine production, such as NF-kB signaling and in innate defense mechanisms as well as in the bridging of innate and adaptive immunity. This sparked the development of novel therapeutic treatments against inflammatory diseases based on Wnt modulation. Here, we summarize the role and function of the Wnt pathway in inflammatory diseases and focus on Wnt signaling as underlying master regulator of inflammation that can be therapeutically targeted.

Lactic Acid Bacteria Isolated From Korean Kimchi Activate the Vitamin D Receptor-autophagy Signaling Pathways

BACKGROUND

Probiotic lactic acid bacteria (LAB) have been used in the anti-inflammation and anti-infection process of various diseases, including inflammatory bowel disease (IBD). Vitamin D receptor (VDR) plays an essential role in pathogenesis of IBD and infectious diseases. Previous studies have demonstrated that the human VDR gene is a key host factor to shape gut microbiome. Furthermore, intestinal epithelial VDR conditional knockout (VDRΔIEC) leads to dysbiosis. Low expressions of VDR is associated with impaired autophagy, accompanied by a reduction of ATG16L1 and LC3B. The purpose of this study is to investigate probiotic effects and mechanism in modulating the VDR-autophagy pathways.

METHODS

Five LAB strains were isolated from Korean kimchi. Conditional medium (CM) from these strains was used to treat a human cell line HCT116 or intestinal organoids to measure the expression of VDR and autophagy. Mouse embryonic fibroblast (MEF) cells with or without VDR were used to investigate the dependence on the VDR signaling. To test the role of LAB in anti-inflammation, VDR+/+ organoids were treated with 121-CM before infection with Salmonella enterica serovar Enteritidis. In vivo, the role of LAB in regulating VDR-autophagy signaling was examined using LAB 121-CM orally administrated to VDRLoxp and VDRΔIEC mice.

RESULTS

The LAB-CM-treated groups showed higher mRNA expression of VDR and its target genes cathelicidin compared with the control group. LAB treatment also enhanced expressions of Beclin-1 and ATG16L1 and changed the ratio of LC3B I and II, indicating the activation of autophagic responses. Furthermore, 121-CM treatment before Salmonella enterica serovar Enteritidis infection dramatically increased VDR and ATG16L1 and inhibited the inflammation. Administration of 121-CM to VDRLoxp and VDRΔIEC mice for 12 and 24 hours resulted in an increase of VDR and LC3B II:I ratio. Furthermore, we identified that probiotic proteins P40 and P75 in the LAB-CM contributed to the anti-inflammatory function by increasing VDR.

CONCLUSIONS

Probiotic LAB exert anti-inflammation activity and induces autophagy. These effects depend on the VDR expression. Our data highlight the beneficial effects of these 5 LAB strains isolated from food in anti-infection and anti-inflammation.

Vitamin D Receptor Protects Against Dysbiosis and Tumorigenesis via the JAK/STAT Pathway in Intestine

BACKGROUND & AIMS

Vitamin D exerts regulatory roles via vitamin D receptor (VDR) in mucosal immunity, host defense, and inflammation involving host factors and microbiome. Human Vdr gene variation shapes the microbiome and VDR deletion leads to dysbiosis. Low VDR expression and diminished vitamin D/VDR signaling are observed in colon cancer. Nevertheless, how intestinal epithelial VDR is involved in tumorigenesis through gut microbiota remains unknown. We hypothesized that intestinal VDR protects mice against dysbiosis via modulating the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway in tumorigenesis.

METHODS

To test our hypothesis, we used an azoxymethane/dextran sulfate sodium-induced cancer model in intestinal VDR conditional knockout (VDR^ΔIEC) mice, cell cultures, stem cell-derived colonoids, and human colon cancer samples.

RESULTS

VDR^ΔIEC mice have higher numbers of tumors, with the location shifted from the distal to proximal colon. Fecal microbiota analysis showed that VDR deletion leads to a bacterial profile shift from normal to susceptible carcinogenesis. We found enhanced bacterial staining in mouse and human tumors. Microbial metabolites from VDR^ΔIEC mice showed increased secondary bile acids, consistent with observations in human CRC. We further identified that VDR protein bound to the Jak2 promoter, suggesting that VDR transcriptionally regulated Jak2. The JAK/STAT pathway is critical in intestinal and microbial homeostasis. Fecal samples from VDR^ΔIEC mice activate the STAT3 signaling in human and mouse organoids. Lack of VDR led to hyperfunction of Jak2 in response to intestinal dysbiosis. A JAK/STAT inhibitor abolished the microbiome-induced activation of STAT3.

CONCLUSIONS

We provide insights into the mechanism of VDR dysfunction leading to dysbiosis and tumorigenesis. It indicates a new target: microbiome and VDR for the prevention of cancer.

JAK3 restrains inflammatory responses and protects against periodontal disease through Wnt3a signaling

Homeostasis between pro- and anti- inflammatory responses induced by bacteria is critical for the maintenance of health. In the oral cavity, pro-inflammatory mechanisms induced by pathogenic bacteria are well-established; however, the anti-inflammatory responses that act to restrain innate responses remain poorly characterized. Here, we demonstrate that infection with the periodontal pathogen Porphyromonas gingivalis enhances the activity of Janus kinase 3 (JAK3) in innate immune cells, and subsequently phospho-inactivates Nedd4-2, an ubiquitin E3 ligase. In turn, Wingless-INT (Wnt) 3 (Wnt3) ubiquitination is decreased, while total protein levels are enhanced, leading to a reduction in pro-inflammatory cytokine levels. In contrast, JAK3 or Wnt3a inhibition robustly enhances nuclear factor kappa-light-chain-enhancer of activated B cells activity and the production of pro-inflammatory cytokines in P. gingivalis-stimulated innate immune cells. Moreover, using gain- and loss-of-function approaches, we demonstrate that downstream molecules of Wnt3a signaling, including Dvl3 and β-catenin, are responsible for the negative regulatory role of Wnt3a. In addition, using an in vivo P. gingivalis-mediated periodontal disease model, we show that JAK3 inhibition enhances infiltration of inflammatory cells, reduces expression of Wnt3a and Dvl3 in P. gingivalis-infected gingival tissues, and increases disease severity. Together, our results reveal a new anti-inflammatory role for JAK3 in innate immune cells and show that the underlying signaling pathway involves Nedd4-2-mediated Wnt3a ubiquitination.

Local Wnt3a treatment restores bone regeneration in large osseous defects after surgical debridement of osteomyelitis

Impaired bone homeostasis caused by osteomyelitis provokes serious variations in the bone remodeling process, thereby involving multiple inflammatory cytokines to activate bone healing. We have previously established a mouse model for post-traumatic osteomyelitis and studied bone regeneration after sufficient debridement. Moreover, we could further characterize the postinfectious inflammatory state of bony defects after debridement with elevated osteoclasts and decreased bone formation despite the absence of bacteria. In this study, we investigated the positive effects of Wnt-pathway modulation on bone regeneration in our previous established mouse model. This was achieved by local application of Wnt3a, a recombinant activator of the canonical Wnt-pathway. Application of Wnt3a could enhance new bone formation, which was verified by histological and μ-CT analysis. Moreover, histology and western blots revealed enhanced osteoblastogenesis and downregulated osteoclasts in a RANKL-dependent manner. Further analysis of Wnt-pathway showed downregulation after bone infections were reconstituted by application of Wnt3a. Interestingly, Wnt-inhibitory proteins Dickkopf 1 (DKK1), sclerostin, and secreted frizzled protein 1 (sFRP1) were upregulated simultaneously to Wnt-pathway activation, indicating a negative feedback for active form of Beta-catenin. In this study, we could demonstrate enhanced bone formation in defects caused by post-traumatic osteomyelitis after Wnt3a application. KEY MESSAGES: Osteomyelitis decreases bone regeneration Wnt3a restores bone healing after infection Canonical Wnt-pathway activation with negative feedback.

Salmonella Enteritidis Effector AvrA Suppresses Autophagy by Reducing Beclin-1 Protein

Autophagy is a cellular process to clear pathogens. Salmonella enterica serovar Enteritidis (S.E) has emerged as one of the most important food-borne pathogens. However, major studies still focus on Salmonella enterica serovar Typhimurium. Here, we reported that AvrA, a S. Enteritidis effector, inhibited autophagy to promote bacterial survival in the host. We found that AvrA regulates the conversion of LC3 I into LC3 II and the enrichment of lysosomes. Beclin-1, a key molecular regulator of autophagy, was decreased after AvrA expressed strain colonization. In S.E-AvrA--infected cells, we found the increases of protein levels of p-JNK and p-c-Jun and the transcription level of AP-1. AvrA-reduction of Beclin-1 protein expression is through the JNK pathway. The JNK inhibitor abolished the AvrA-reduced Beclin-1 protein expression. Moreover, we identified that the AvrA mutation C186A abolished its regulation of Beclin-1 expression. In addition AvrA protein was found interacted with Beclin-1. In organoids and infected mice, we explored the physiologically related effects and mechanism of AvrA in reducing Beclin-1 through the JNK pathway, thus attenuating autophagic responses. This finding not only indicates an important role of S. Enteritidis effector in reducing host protein as a strategy to suppress autophagy, but also suggests manipulating autophagy as a new strategy to treat infectious diseases.

COX-2 mediated crosstalk between Wnt/β-catenin and the NF-κB signaling pathway during inflammatory responses induced by Haemophilus parasuis in PK-15 and NPTr cells

Haemophilus parasuis infection causes typical acute systemic inflammation in pigs, is characterized by fibrinous polyserositis inflammation, and results in great economic losses to the swine industry worldwide. However, the molecular details of how the host modulates the acute inflammatory response induced by H. parasuis are largely unknown. In previous studies, we found that H. parasuis high-virulence strain SH0165 infection induced the activation of both Wnt/β-catenin and NF-κB signaling in PK-15 and NPTr cells. In this study, we found that the activation of NF-κB, a central hub in inflammatory signaling, was impeded by the Wnt/β-catenin pathway during H. parasuis infection. In contrast, blocking NF-κB activity had no effect on the Wnt/β-catenin pathway during H. parasuis infection. Furthermore, we found that the inhibitory effect of β-catenin on NF-κB activity was mediated by its target gene, pig cyclooxygenase-2 (COX-2). Therefore, we demonstrated that H. parasuis infection activates the canonical Wnt/β-catenin signaling pathway, which leads to decreased NF-κB activity, reducing the acute inflammatory response in pigs. Additionally, the data provide a possible perspective for understanding the anti-inflammatory role of Wnt/β-catenin in pigs during bacterial infection.

GSK3 and miRNA in neural tissue: From brain development to neurodegenerative diseases

MicroRNAs (miRs) are small RNAs modulating gene expression and creating intricate regulatory networks that are dysregulated in many pathological states, including neurodegenerative disorders. In silico analyses denote a multifunctional kinase glycogen synthase kinase-3 (GSK3) as a putative target of numerous miRs identified in neural tissue. GSK3 is engaged in almost all aspects of neuronal development and functioning. Moreover, there is an autoregulatory feedback between GSK3 and miRNAs as the kinase can influence biogenesis of miRs. Members of the miR-GSK3 axes might thus represent convenient therapeutic targets in neuropathologies that display its abnormal regulation. This review summarizes the present knowledge about direct interactions of GSK3 and miRs in brain, and their putative roles in pathogenesis of neurodegenerative and neuropsychiatric disorders. This article is part of a Special Issue entitled: GSK-3 and related kinases in cancer, neurological and other disorders edited by James McCubrey, Agnieszka Gizak and Dariusz Rakus.

TLR4 induced Wnt3a-Dvl3 restrains the intensity of inflammation and protects against endotoxin-driven organ failure through GSK3β/β-catenin signaling

BACKGROUND

Accumulating evidence suggests a regulatory role of Wnt proteins in innate immune responses. However, the effects of Wnt3a signaling on TLR4-mediated inflammatory responses are controversial and the signaling crosstalk between TLR4 and Wnt3a remains uncertain.

METHODS

Gain- and Loss- of function approaches were utilized to determine the function of Wnt3a signaling in TLR4-mediated inflammatory responses. Cytokine production at protein and mRNA levels and phosphorylation of signaling molecules were measured by ELISA, qRT-PCR, and Western Blot, respectively. Endotoxemia mouse model was employed to assess the effect of Wnt3a on systemic inflammatory cytokine levels and neutrophil infiltration.

RESULTS

LPS stimulation leads to an increase of Wnt3a expression and its downstream molecule, Dvl3, in primary monocytes. Inhibition or silence of Wnt3a or Dvl3 significantly increases the production of pro-inflammatory cytokines (IL-12, IL-6, TNFα), robustly reduces β-catenin accumulation, and enhances the phosphorylation of NF-κB P65 and its DNA binding activity. These results were confirmed by multiple gain- and loss- of function approaches including specific siRNA and ectopic expression of Dvl3, GSK3β, and β-catenin in monocytes. Moreover, in vivo relevance was established in a murine endotoxin model, in which Wnt3a inhibition enhances the inflammatory responses by augmenting the systemic pro-inflammatory cytokine levels and neutrophil infiltration.

CONCLUSIONS

TLR4 activation promotes Wnt3a-Dvl3 signaling, which acts as rheostats to restrain the intensity of inflammation through regulating GSK3β-β-catenin signaling and NF-κB activity.

GENERAL SIGNIFICANCE

Wnt3a-Dvl3-β-catenin signaling axis could be a potential interventional target for manipulating the direction and intensity of inflammatory responses.

Functions of the WNT Signaling Network in Shaping Host Responses to Infection

It is well-established that aberrant WNT expression and signaling is associated with developmental defects, malignant transformation and carcinogenesis. More recently, WNT ligands have emerged as integral components of host responses to infection but their functions in the context of immune responses are incompletely understood. Roles in the modulation of inflammatory cytokine production, host cell intrinsic innate defense mechanisms, as well as the bridging of innate and adaptive immunity have been described. To what degree WNT responses are defined by the nature of the invading pathogen or are specific for subsets of host cells is currently not well-understood. Here we provide an overview of WNT responses during infection with phylogenetically diverse pathogens and highlight functions of WNT ligands in the host defense against infection. Detailed understanding of how the WNT network orchestrates immune cell functions will not only improve our understanding of the fundamental principles underlying complex immune response, but also help identify therapeutic opportunities or potential risks associated with the pharmacological targeting of the WNT network, as currently pursued for novel therapeutics in cancer and bone disorders.

Intestinal epithelial HMGB1 inhibits bacterial infection via STAT3 regulation of autophagy

Extracellular HMGB1 (high mobility group box 1) is considered as a damage-associated molecular pattern protein. However, little is known about its intracellular role. We studied the mechanism whereby intestinal epithelial HMGB1 contributes to host defense, using cell culture, colonoids, conditional intestinal epithelial HMGB1-knockout mice with Salmonella-colitis, il10-/- mice, and human samples. We report that intestinal HMGB1 is an important contributor to host protection from inflammation and infection. We identified a physical interaction between HMGB1 and STAT3. Lacking intestinal epithelial HMGB1 led to redistribution of STAT3 and activation of STAT3 post bacterial infection. Indeed, Salmonella-infected HMGB1-deficient cells exhibited less macroautophagy/autophagy due to decreased expression of autophagy proteins and transcriptional repression by activated STAT3. Then, increased p-STAT3 and extranuclear STAT3 reduced autophagic responses and increased inflammation. STAT3 inhibition restored autophagic responses and reduced bacterial invasion in vitro and in vivo. Moreover, low level of HMGB1 was correlated with reduced nuclear STAT3 and enhanced p-STAT3 in inflamed intestine of il10-/- mice and inflammatory bowel disease (IBD) patients. We revealed that colonic epithelial HMGB1 was directly involved in the suppression of STAT3 activation and the protection of intestine from bacterial infection and injury. Abbreviations: ATG16L1: autophagy-related 16-like 1 (S. cerevisiae); DAMP: damage-associated molecular pattern; HBSS: Hanks balanced salt solution; HMGB1: high mobility group box 1; IBD: inflammatory bowel disease; IL1B/Il-1β: interleukin 1 beta; IL10: interleukin 10; IL17/IL-17: interleukin 17; MEFs: mouse embryonic fibroblasts; STAT3: signal transducer and activator of transcription 3; TLR: toll-like receptor; TNF/TNF-α: tumor necrosis factor.

Intestinal Epithelial Cells Exposed to Bacteroides fragilis Enterotoxin Regulate NF-κB Activation and Inflammatory Responses through β-Catenin Expression

The Bacteroides fragilis enterotoxin (BFT), a virulence factor of enterotoxigenic B. fragilis (ETBF), interacts with intestinal epithelial cells and can provoke signals that induce mucosal inflammation. Although β-catenin signaling is reported to be associated with inflammatory responses and BFT is known to cleave E-cadherin linked with β-catenin, little is known about the β-catenin-mediated regulation of inflammation in ETBF infection. This study was conducted to investigate the role of β-catenin as a cellular signaling intermediate in the induction of proinflammatory responses to stimulation of intestinal epithelial cells with BFT. Expression of β-catenin in intestinal epithelial cells was reduced relatively early after stimulation with BFT and then recovered to normal levels relatively late after stimulation. In contrast, phosphorylation of β-catenin in BFT-exposed cells occurred at high levels early in stimulation and decreased as time passed. Concurrently, late after stimulation the nuclear levels of β-catenin were relatively higher than those early after stimulation. Suppression of β-catenin resulted in increased NF-κB activity and interleukin-8 (IL-8) expression in BFT-stimulated cells. However, suppression or enhancement of β-catenin expression neither altered the phosphorylated IκB kinase α/β complex nor activated activator protein 1 signals. Furthermore, inhibition of glycogen synthase kinase 3β was associated with increased β-catenin expression and attenuated NF-κB activity and IL-8 expression in BFT-exposed cells. These findings suggest the negative regulation of NF-κB-mediated inflammatory responses by β-catenin in intestinal epithelial cells stimulated with BFT, resulting in attenuation of acute inflammation in ETBF infection.

Bacterial Manipulation of Wnt Signaling: A Host-Pathogen Tug-of-Wnt

The host-pathogen interface is a crucial battleground during bacterial infection in which host defenses are met with an array of bacterial counter-mechanisms whereby the invader aims to make the host environment more favorable to survival and dissemination. Interestingly, the eukaryotic Wnt signaling pathway has emerged as a key player in the host and pathogen tug-of-war. Although studied for decades as a regulator of embryogenesis, stem cell maintenance, bone formation, and organogenesis, Wnt signaling has recently been shown to control processes related to bacterial infection in the human host. Wnt signaling pathways contribute to cell cycle control, cytoskeleton reorganization during phagocytosis and cell migration, autophagy, apoptosis, and a number of inflammation-related events. Unsurprisingly, bacterial pathogens have evolved strategies to manipulate these Wnt-associated processes in order to enhance infection and survival within the human host. In this review, we examine the different ways human bacterial pathogens with distinct host cell tropisms and lifestyles exploit Wnt signaling for infection and address the potential of harnessing Wnt-related mechanisms to combat infectious disease.

β-Catenin stabilization in NOD dendritic cells increases IL-12 production and subsequent induction of IFN-γ-producing T cells

Dendritic cells (DC) from diabetes-prone NOD mice and patients with type 1 diabetes (T1D) produce excess IL-12 that drives development of β-cell-destroying IFN-γ-producing T cells. The molecular mechanisms that control IL-12 production in T1D are unclear. In this study, we report that β-catenin, a multifunctional protein involved in inflammation, is dramatically increased in DC from NOD mice. We further investigated the mechanisms leading to accumulation of β-catenin in NOD DC and its role in the inflammatory pathogenic responses associated with T1D. Hyperphosphorylation of β-catenin at a stabilizing residue, serine 552, mediated by activation of Akt, appears to lead to β-catenin accumulation in NOD DC. Elevated β-catenin in DC correlated with IL-12 production and induction of IFN-γ-producing CD4 cells. On the one hand, knockdown/inhibition of β-catenin significantly reduced NOD DC production of IL-12 and their ability to induce IFN-γ-producing CD4 cells. On the other hand, overexpression of β-catenin in control DC resulted in increased IL-12 production and induction of IFN-γ-production in T cells. Additionally, we found that β-catenin inhibitors decreased NF-κB activation in NOD DC and IFN-γ production by NOD T cells in vivo. These data strongly suggest that accumulation of β-catenin in DC from NOD mice drives IL-12 production, and consequently, development of pathogenic IFN-γ-producing T cells. Targeting the defect responsible for β-catenin accumulation and subsequent overproduction of pro-inflammatory cytokines by NOD DC could be an effective therapeutic strategy for the prevention and/or treatment of T1D.

Secreted frizzled-related protein 2 promotes the osteo/odontogenic differentiation and paracrine potentials of stem cells from apical papilla under inflammation and hypoxia conditions

Objectives

Mesenchymal stem cell (MSC)‐based dental tissue regeneration is a potential treatment method in future, while inflammation and hypoxia niche will affect MSC‐mediated tissue regeneration. In this research, we intended to investigate the influence and mechanism of secreted frizzled‐related protein 2(SFRP2) on MSC function under inflammation and hypoxia conditions.

Material and methods

Stem cells from apical papilla (SCAPs) were used in this study. The alkaline phosphatase (ALP) activity, Alizarin Red S staining, scratch‐simulated wound migration and transwell chemotaxis assay were used to evaluate the functions of SFRP2. The Western blot, real‐time RT‐PCR and ChIP assays were used to evaluate the mechanism of SFRP2.

Results

Under inflammation and hypoxia conditions, the over‐expression of SFRP2 could enhance the osteo/odontogenic differentiation ability. Mechanismly, SFRP2 inhibited canonical Wnt/β‐catenin signalling pathway and then inhibited the target genes of nuclear factor kappa B (NFkB) signalling pathway. Inflammation or hypoxia conditions could promote the expression of lysine demethylase 2A (KDM2A) and repress SFRP2 transcription through decreasing histone methylation in the SFRP2 promoter. Besides, proteomic analysis showed that SFRP2 promoted SCAPs to secret more functional cytokines, which improve the migration, chemotaxis and osteo/odontogenic ability of MSCs.

Conclusions

Our discoveries revealed that SFRP2 enhanced the osteo/odontogenic differentiation and paracrine potentials of SCAPs under hypoxia and inflammation conditions and provided a potential cytokine for promoting tissue regeneration in hypoxia and inflammatory niche.

Minocycline attenuates ethanol-induced cell death and microglial activation in the developing spinal cord

Developmental exposure to ethanol may cause fetal alcohol spectrum disorders (FASD), and the immature central nervous system (CNS) is particularly vulnerable to ethanol. In addition to vulnerability in the developing brain, we previously showed that ethanol also caused neuroapoptosis, microglial activation, and neuroinflammation in the spinal cord. Minocycline is an antibiotic that inhibits microglial activation and alleviates neuroinflammation. We sought to determine whether minocycline could protect spinal cord neurons against ethanol-induced damage. In this study, we showed that minocycline significantly inhibited ethanol-induced caspase-3 activation, microglial activation, and the expression of pro-inflammatory cytokines in the developing spinal cord. Moreover, minocycline blocked ethanol-induced activation of glycogen synthase kinase 3 beta (GSK3β), a key regulator of microglial activation. Meanwhile, minocycline significantly restored ethanol-induced inhibition of protein kinase B (AKT), mammalian target of the rapamycin (mTOR), and ERK1/2 signaling pathways, which were important pro-survival signaling pathways for neurons. Together, minocycline may attenuate ethanol-induced damage to the developing spinal cord by inhibiting microglial activation/neuroinflammation and by restoring the pro-survival signaling.

Macrophages as a Source and Recipient of Wnt Signals

Macrophages are often viewed through the lens of their core functions, but recent transcriptomic studies reveal them to be largely distinct across tissue types. While these differences appear to be shaped by their local environment, the key signals that drive these transcriptional differences remain unclear. Since Wnt signaling plays established roles in cell fate decisions, and tissue patterning during development and tissue repair after injury, we consider evidence that Wnt signals both target and are affected by macrophage functions. We propose that the Wnt gradients present in developing and adult tissues effectively shape macrophage fates and phenotypes. We also highlight evidence that macrophages, through an ability to dispatch Wnt signals, may couple tissue debridement and matrix remodeling with stem cell activation and tissue repair.

Imbalance of autophagy and apoptosis in intestinal epithelium lacking the vitamin D receptor

Apoptosis and autophagy are dynamic processes that determine the fate of cells. Vitamin D receptor (VDR) deficiency in the intestine leads to abnormal Paneth cells and impaired autophagy function. Here, we will elucidate the mechanisms of the intestinal epithelial VDR regulation of autophagy and apoptosis. We used in vivo VDR^lox and VDR^∆IEC mice and ex vivo organoids generated from small intestine and colon tissues. We found that VDR deficiency induced more apoptotic cells and significantly increased cell death in the small intestine and colon of VDR^∆IEC mice. The proapoptotic protein B-cell lymphoma 2 (BCL-2) associated X protein (Bax) was enhanced, whereas autophagy related 16 like 1 (ATG16L1) and Beclin-1 were decreased in the intestines of VDR^ΔIEC mice. Apoptosis induced by Bax reduced autophagy by decreasing Beclin-1. Physical interactions between Beclin-1 and Bcl-2 were increased in the VDR-deficient epithelia from mice. The growth of VDR^∆IEC organoids was significantly slower with fewer Paneth cells than that of VDR^+/+ organoids. The expression levels of Beclin-1 and lysozyme were decreased in VDR^∆IEC organoids. Bacterial endotoxin levels were high in the serum from VDR^∆IEC mice and made mice susceptible to colitis. In the organoids and colitis IL-10^-/- mice, vitamin D₃ treatment increased VDR and ATG16L1 protein expression levels, which activated autophagic responses. In summary, intestinal epithelial VDR regulates autophagy and apoptosis through ATG16L1 and Beclin-1. Our studies provide fundamental insights into the tissue-specific function of VDR in modulating the balance between autophagy and apoptosis.-Lu, R., Zhang, Y.-G., Xia, Y., Sun, J. Imbalance of autophagy and apoptosis in intestinal epithelium lacking the vitamin D receptor.

Minocycline Preserves the Integrity and Permeability of BBB by Altering the Activity of DKK1-Wnt Signaling in ICH Model

Disruption of the blood-brain barrier (BBB) and subsequent neurological deficits are the most severe consequence of intracerebral hemorrhage (ICH). Minocycline has been wildly used clinically as a neurological protective agent in clinical practice. However, the underlying mechanisms by which minocycline functions remain unclear. Therefore, we assessed the influence of minocycline on BBB structure, neurological function, and inflammatory responses in a collagenase-induced ICH model, and elucidated underlying molecular mechanisms as well. Following a single injection of collagenase VII-S into the basal ganglia, BBB integrity was assessed by Evans blue extravasation while neurological function was assessed using an established neurologic function scoring system. Minocycline treatment significantly alleviated the severity of BBB disruption, brain edema, and neurological deficits in ICH model. Moreover, minocycline decreased the production of inflammatory mediators including TNF, IL-6, and MMP-9, by microglia. Minocycline treatment decreased DKK1 expression but increased Wnt1, β-catenin and Occludin, a phenomenon mimicked by DKK1 silencing. These data suggest that minocycline improves the consequences of ICH by preserving BBB integrity and attenuating neurologic deficits in a DKK1-related manner that involves enhancement of the Wnt1-β-catenin activity.

Controlling Nuclear NF-κB Dynamics by β-TrCP-Insights from a Computational Model

The canonical nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway regulates central processes in mammalian cells and plays a fundamental role in the regulation of inflammation and immunity. Aberrant regulation of the activation of the transcription factor NF-κB is associated with severe diseases such as inflammatory bowel disease and arthritis. In the canonical pathway, the inhibitor IκB suppresses NF-κB’s transcriptional activity. NF-κB becomes active upon the degradation of IκB, a process that is, in turn, regulated by the β-transducin repeat-containing protein (β-TrCP). β-TrCP has therefore been proposed as a promising pharmacological target in the development of novel therapeutic approaches to control NF-κB’s activity in diseases. This study explores the extent to which β-TrCP affects the dynamics of nuclear NF-κB using a computational model of canonical NF-κB signaling. The analysis predicts that β-TrCP influences the steady-state concentration of nuclear NF-κB, as well as changes characteristic dynamic properties of nuclear NF-κB, such as fold-change and the duration of its response to pathway stimulation. The results suggest that the modulation of β-TrCP has a high potential to regulate the transcriptional activity of NF-κB.

Multidisciplinary Roles of LRRFIP1/GCF2 in Human Biological Systems and Diseases

Leucine Rich Repeat of Flightless-1 Interacting Protein 1/GC-binding factor 2 (LRRFIP1/GCF2) cDNA was cloned for a transcriptional repressor GCF2, which bound sequence-specifically to a GC-rich element of epidermal growth factor receptor (EGFR) gene and repressed its promotor. LRRFIP1/GCF2 was also cloned as a double stranded RNA (dsRNA)-binding protein to trans-activation responsive region (TAR) RNA of Human Immunodeficiency Virus-1 (HIV-1), termed as TAR RNA interacting protein (TRIP), and as a binding protein to the Leucine Rich Repeat (LRR) of Flightless-1(Fli-1), termed as Flightless-1 LRR associated protein 1 (FLAP1) and LRR domain of Flightless-1 interacting Protein 1 (LRRFIP1). Subsequent functional studies have revealed that LRRFIP1/GCF2 played multiple roles in the regulation of diverse biological systems and processes, such as in immune response to microorganisms and auto-immunity, remodeling of cytoskeletal system, signal transduction pathways, and transcriptional regulations of genes. Dysregulations of LRRFIP1/GCF2 have been implicated in the causes of several experimental and clinico-pathological states and the responses to them, such as autoimmune diseases, excitotoxicity after stroke, thrombosis formation, inflammation and obesity, the wound healing process, and in cancers. LRRFIP1/GCF2 is a bioregulator in multidisciplinary systems of the human body and its dysregulation can cause diverse human diseases.

Lack of Vitamin D Receptor Leads to Hyperfunction of Claudin-2 in Intestinal Inflammatory Responses

BACKGROUND

Vitamin D3 and vitamin D receptor (VDR) are involved in the pathogenesis of inflammatory bowel disease (IBD) and bacterial infection. Claudin-2 is a junction protein that mediates paracellular water transport in epithelia. Elevation of Claudin-2 is associated with active IBD. However, VDR involved in epithelial junctions under inflammation and infection remains largely unknown. We investigated the mechanisms on how VDR and Claudin-2 are related in inflamed states.

METHODS

Using cultured VDR-/- enteroids, human intestinal epithelial cells, VDR-/- mice with Salmonella- or DSS-colitis, and human IBD samples, we investigated the mechanisms how VDR and Claudin-2 are related in inflamed states.

RESULTS

After Salmonella infection had taken place, we observed significantly enhanced Claudin-2 and an increased bacterial invasion and translocation. A lack of VDR regulation led to a robust increase of Claudin-2 at the mRNA and protein levels post-infection. In DSS-treated VDR-/- mice, Claudin-2 was significantly increased. Location and quantification of Claudin-2 protein in the mouse colons treated with DSS also confirmed these results. Inflammatory cytokines were significantly higher in the serum and mRNA levels in intestine, which are known to increase Claudin-2. Furthermore, in inflamed intestine of ulcerative colitis patients, VDR expression was low and Claudin-2 was enhanced. Mechanistically, we identified the enhanced Claudin-2 promoter activity through the binding sites of NF-κB and STAT in inflamed VDR-/- cells.

CONCLUSIONS

Our studies have identified a new role for intestinal epithelial VDR in regulating barrier functions in the context of infection and inflammation.

How are the expression patterns of gut antimicrobial peptides modulated by human gastrointestinal diseases? A bridge between infectious, inflammatory, and malignant diseases

The human gut barrier is the tissue exposed to the highest load of microorganisms, harbouring 100 trillion bacteria. In addition, the gut's renewal rate outruns that of any other human tissue. Antimicrobial peptides (AMPs) are highly optimized defense molecules in the intestinal barrier optimized to maintain gastrointestinal homeostasis. Alterations in AMPs activity can lead to or result from human gastrointestinal diseases. In this review, unique, conserved, or otherwise regular alterations in the expression patterns of human AMPs across gastrointestinal inflammatory and infectious diseases were analyzed for pattern elucidation. Human gastrointestinal diseases are associated with alterations in gut AMPs' expression patterns in a peptide-specific, disease-specific, and pathogen-specific way, modulating human gastrointestinal functioning. Across diseases, there is a (i) marked reduction in otherwise constitutively expressed AMPs, leading to increased disease susceptibility, and a (ii) significant increase in the expression of inducible AMPs, leading to tissue damage and disease severity. Infections and inflammatory conditions are associated with altered gene expression in the gut, whose patterns may favour cellular metaplasia, mucosal dysfunction, and disease states. Altered expression of AMPs can thus thrive disease severity and evolution since its early stages. Nevertheless, the modulation of AMP expression patterns unveils promising therapeutic targets.

Lactobacillus plantarum IS-10506 activates intestinal stem cells in a rodent model

This study investigated the probiotic effect of Lactobacillus plantarum IS-10506 in activating and regenerating leucine-rich repeat-containing G-protein-coupled receptor (Lgr)5- and B lymphoma Moloney murine leukaemia virus insertion region (Bmi)1-expressing intestinal stem cells in rodents following Escherichia coli serotype 055:B5 lipopolysaccharide (LPS) exposure. Male Sprague-Dawley rats (n=64) were randomised into control (KN), LPS (KL), probiotic + LPS (KL-Pr), and sequential probiotic + LPS + probiotic (KPR-7L) groups. Microencapsulated L. plantarum IS-10506 (2.86×10¹⁰ cfu/day) was administered via a gastric tube once daily for up to 7 days, and LPS (250 ng/kg body weight) was administered via a gastric tube on the first day of the experiment to all but the KN group. On day 3, 4, 6, and 7, four rats per group were sacrificed, and Lgr5, Bmi1, extracellular signal-regulated kinase (ERK), and β-catenin expression in the ileum was assessed by immunohistochemistry. LPS treatment reduced Lgr5 (P≤0.05) and Bmi1 (P=0.000) levels in intestinal epithelial cells, whereas probiotic treatment increased levels of Lgr5 (KPR-7L, P=0.008) and Bmi1 (KL-Pr, P=0.008; and KPR-7L, P=0.000). Lgr5 expression was upregulated in the KL-Pr group on day 3, 4, 6, and 7 (P=0.056). Additionally, ERK levels were elevated in Bmi1- and Lgr5-expressing cells in rats treated with probiotics (KL-Pr and KPR-7L), whereas β-catenin levels were increased in Lgr5-expressing cells from KPR-7L rats and in Bmi1-expressing cells from KL-Pr and KPR-7L rats on day 3 and 4. These results demonstrated that the probiotic L. plantarum IS-10506 activated intestinal stem cells to counter inflammation and might be useful for maintaining intestinal health, especially when used as a prophylactic agent.

Myeloid β-Catenin Deficiency Exacerbates Atherosclerosis in Low-Density Lipoprotein Receptor-Deficient Mice

Supplemental Digital Content is available in the text.

Objective—

The Wnt/β-catenin signaling is an ancient and evolutionarily conserved pathway that regulates essential aspects of cell differentiation, proliferation, migration and polarity. Canonical Wnt/β-catenin signaling has also been implicated in the pathogenesis of atherosclerosis. Macrophage is one of the major cell types involved in the initiation and progression of atherosclerosis, but the role of macrophage β-catenin in atherosclerosis remains elusive. This study aims to investigate the impact of β-catenin expression on macrophage functions and atherosclerosis development.

Approach and Results—

To investigate the role of macrophage canonical Wnt/β-catenin signaling in atherogenesis, we generated β-catenin^ΔmyeLDLR^−/− mice (low-density lipoprotein receptor–deficient mice with myeloid-specific β-catenin deficiency). As expected, deletion of β-catenin decreased macrophage adhesion and migration properties in vitro. However, deficiency of β-catenin significantly increased atherosclerotic lesion areas in the aortic root of LDLR^−/− (low-density lipoprotein receptor–deficient) mice without affecting the plasma lipid levels and atherosclerotic plaque composition. Mechanistic studies revealed that β-catenin can regulate activation of STAT (signal transducer and activator of transcription) pathway in macrophages, and ablation of β-catenin resulted in STAT3 downregulation and STAT1 activation, leading to elevated macrophage inflammatory responses and increased atherosclerosis.

Conclusions—

This study demonstrates a critical role of myeloid β-catenin expression in atherosclerosis by modulating macrophage inflammatory responses.

Infection with enteric pathogens Salmonella typhimurium and Citrobacter rodentium modulate TGF-beta/Smad signaling pathways in the intestine

Salmonella and Citrobacter are gram negative, members of Enterobacteriaceae family that are important causative agents of diarrhea and intestinal inflammation. TGF-β1 is a pleiotropic multifunctional cytokine that has been implicated in modulating the severity of microbial infections. How these pathogens alter the TGF-β1 signaling pathways in the intestine is largely unknown. Streptomycin-pretreated C57BL/6J mouse model colonized with S. typhimurium for 8 hours (acute) and 4 days (chronic) infection and FVB/N mice infected with C. rodentium for 6 days were utilized. Results demonstrated an increase in TGF-β1 receptor I expression (p<0.05) in S. typhimurium infected mouse ileum at both acute and chronic post-infection vs control. This was associated with activation of Smad pathways as evidenced by increased phosphorylated (p)-Smad2 and p-Smad3 levels in the nucleus. The inhibitory Smad7 mRNA levels showed a significant up regulation during acute phase of Salmonella infection but no change at 4d post-infection. In contrast to Salmonella, infection with Citrobacter caused drastic downregulation of TGF receptor I and II concomitant with a decrease in levels of Smad 2, 3, 4 and 7 expression in the mouse colon. We speculate that increased TGF-β1 signaling in response to Salmonella may be a host compensatory response to promote mucosal healing; while C. rodentium decreases TGF-β1 signaling pathways to promote inflammation and contribute to disease pathogenesis. These findings increase our understanding of how enteric pathogens subvert specific aspects of the host-cellular pathways to cause disease.

Beta-catenin promotes macrophage-mediated acute inflammatory response after myocardial infarction

Regulatory mechanisms for acute inflammatory responses post myocardial infarction (MI) have yet to be fully understood. In particular, the mechanisms by which cardiac macrophages modulate MI-induced myocardial inflammation remains unclear. In this study, using a mouse MI model, we showed that β-catenin-mediated signaling was activated in cardiac macrophages post-MI, especially in Ly-6C-positive proinflammatory macrophages. Using a RAW264.7-based β-catenin reporter cell line, we confirmed the presence of active β-catenin and its downstream signaling in cardiac macrophages after MI. Moreover, lentivirus-mediated inducible expression of constitutively active β-catenin revealed that β-catenin plays a role in promoting the inflammatory response by RAW264.7 cells. Depletion of endogenous macrophages and adoptive transfer of active β-catenin-expressing RAW264.7 cells resulted in enhancement of acute myocardial inflammation in recipient mice after MI, as demonstrated by elevated levels of lymphocyte infiltrates and increased expression of proinflammatory cytokines. However, infarct volume, myocardial tissue repair, and left ventricle function were not influenced by the expression of active β-catenin in the adoptive transfer assay. Our research has demonstrated that β-catenin-mediated signaling is important for cardiac macrophages to modulate post-MI inflammatory responses. These findings may be valuable for developing novel therapeutic strategies for MI.

β-Catenin Directs Nuclear Factor-κB p65 Output via CREB-Binding Protein/p300 in Human Airway Smooth Muscle

β-Catenin is a multifunctional protein that apart from its role in proliferative and differentiation events, also acts upon inflammatory processes, mainly via interaction with nuclear factor-κB (NF-κB). However, there is still controversy as to whether β-catenin facilitates or represses NF-κB output. Insights into the molecular mechanisms underlying the interaction between β-catenin and NF-κB have highlighted the cofactors CREB-binding protein (CBP) and p300 as important candidates. Here, we hypothesized that the interaction of β-catenin with CBP/p300 directs NF-κB output. Using human airway smooth muscle (ASM) cells, we found that β-catenin is essential in interleukin -1β (IL-1β)-mediated expression of interleukin-6 (IL-6) by promoting nuclear translocation of the p65 subunit of NF-κB. These effects were independent from WNT pathway activation or other factors that promote β-catenin signaling. In the nucleus, inhibition of either the CBP- or p300-β-catenin interaction could regulate NF-κB output, by enhancing (CBP inhibition) or inhibiting (p300 inhibition) IL-1β-induced expression of IL-6, respectively. Acetylation of p65 by p300 likely underlies these events, as inhibition of the p300-β-catenin interaction diminished levels of acetylated p65 at lysine 310, thereby reducing p65 transcriptional activity. In conclusion, β-catenin is a critical component of NF-κB-mediated inflammation in human ASM, affecting transcriptional output by interacting with the nuclear cofactors CBP and p300. Targeting β-catenin may be an alternative strategy to treat airway inflammation in patients with airway disease, such as asthma.

Revisiting asthma therapeutics: focus on WNT signal transduction

Asthma is a complex disease of the airways that develops as a consequence of both genetic and environmental factors. This interaction has highlighted genes important in early life, particularly those that control lung development, such as the Wingless/Integrase-1 (WNT) signalling pathway. Although aberrant WNT signalling is involved with an array of human conditions, it has received little attention within the context of asthma. Yet it is highly relevant, driving events involved with inflammation, airway remodelling, and airway hyper-responsiveness (AHR). In this review, we revisit asthma therapeutics by examining whether WNT signalling is a valid therapeutic target for asthma.

Presence of Salmonella AvrA in colorectal tumor and its precursor lesions in mouse intestine and human specimens

Evidence directly supporting an association between Salmonella infection and colorectal cancer in human subjects is sparse. It has been well recognized that Salmonella infection increases the risk of gallbladder cancer. AvrA, a bacterial protein from Salmonella enterica, plays a crucial role in establishing chronic infection. To our knowledge, the presence of the bacterial AvrA has never been studied in human samples. Here, we demonstrated the presence and cellular localization of AvrA in inflamed, colorectal tumor and its precursor lesions, using both animal experimental infection models and human clinical specimens. We performed a newly developed AvrA serological assay and to determine the presence of anti-Salmonella AvrA antibody in chronic infected mouse serum samples. Further, we tested the presence of AvrA gene in healthy human fecal samples, in order to advance etiological studies of Salmonella AvrA in human population. Our study suggests a potential role of this bacterial protein in human colorectal cancer. Moreover, our new serological assay may serve a useful tool to identify individuals at increased risk for colorectal cancer.