Mechanisms of intestinal epithelial cell damage by Clostridiumperfringens

Clostridium perfringens, a Gram-positive bacterium, causes intestinal diseases in humans and livestock through its toxins, related to alpha toxin (CPA), beta toxin (CPB), C. perfringens enterotoxin (CPE), epsilon toxin (ETX), Iota toxin (ITX), and necrotic enteritis B-like toxin (NetB). These toxins disrupt intestinal barrier, leading to various cell death mechanisms such as necrosis, apoptosis, and necroptosis. Additionally, non-toxin factors like adhesins and degradative enzymes contribute to virulence by enhancing colonization and survival of C. perfringens. A vicious cycle of intestinal barrier breach, misregulated cell death, and subsequent inflammation is at the heart of chronic inflammatory and infectious gastrointestinal diseases. Understanding these mechanisms is essential for developing targeted therapies against C. perfringens-associated intestinal diseases.

Lamotrigine protects against cognitive deficits, synapse and nerve cell damage, and hallmark neuropathologies in a mouse model of Alzheimer’s disease

Lamotrigine (LTG) is a widely used drug for the treatment of epilepsy. Emerging clinical evidence suggests that LTG may improve cognitive function in patients with Alzheimer’s disease. However, the underlying molecular mechanisms remain unclear. In this study, amyloid precursor protein/presenilin 1 (APP/PS1) double transgenic mice were used as a model of Alzheimer’s disease. Five-month-old APP/PS1 mice were intragastrically administered 30 mg/kg LTG or vehicle once per day for 3 successive months. The cognitive functions of animals were assessed using Morris water maze. Hyperphosphorylated tau and markers of synapse and glial cells were detected by western blot assay. The cell damage in the brain was investigated using hematoxylin and eosin staining. The levels of amyloid-β and the concentrations of interleukin-1β, interleukin-6 and tumor necrosis factor-α in the brain were measured using enzyme-linked immunosorbent assay. Differentially expressed genes in the brain after LTG treatment were analyzed by high-throughput RNA sequencing and real-time polymerase chain reaction. We found that LTG substantially improved spatial cognitive deficits of APP/PS1 mice; alleviated damage to synapses and nerve cells in the brain; and reduced amyloid-β levels, tau protein hyperphosphorylation, and inflammatory responses. High-throughput RNA sequencing revealed that the beneficial effects of LTG on Alzheimer’s disease-related neuropathologies may have been mediated by the regulation of Ptgds, Cd74, Map3k1, Fosb, and Spp1 expression in the brain. These findings revealed potential molecular mechanisms by which LTG treatment improved Alzheimer’s disease. Furthermore, these data indicate that LTG may be a promising therapeutic drug for Alzheimer’s disease.

Exploring the Role of Staphylococcus aureus in Inflammatory Diseases

Staphylococcus aureus is a very common Gram-positive bacterium, and S. aureus infections play an extremely important role in a variety of diseases. This paper describes the types of virulence factors involved, the inflammatory cells activated, the process of host cell death, and the associated diseases caused by S. aureus. S. aureus can secrete a variety of enterotoxins and other toxins to trigger inflammatory responses and activate inflammatory cells, such as keratinocytes, helper T cells, innate lymphoid cells, macrophages, dendritic cells, mast cells, neutrophils, eosinophils, and basophils. Activated inflammatory cells can express various cytokines and induce an inflammatory response. S. aureus can also induce host cell death through pyroptosis, apoptosis, necroptosis, autophagy, etc. This article discusses S. aureus and MRSA (methicillin-resistant S. aureus) in atopic dermatitis, psoriasis, pulmonary cystic fibrosis, allergic asthma, food poisoning, sarcoidosis, multiple sclerosis, and osteomyelitis. Summarizing the pathogenic mechanism of Staphylococcus aureus provides a basis for the targeted treatment of Staphylococcus aureus infection.

A map of the spatial distribution and tumour-associated macrophage states in glioblastoma and grade-4 IDH-mutant astrocytoma

Tumour-associated macrophages (TAMs) abundantly infiltrate high-grade gliomas and orchestrate immune response, but their diversity in isocitrate dehydrogenase (IDH)-differential grade-4 gliomas remains largely unknown. This study aimed to dissect the transcriptional states, spatial distribution and clinicopathological significance of distinct monocyte-derived TAM (Mo-TAM) and microglia-derived TAM (Mg-TAM) clusters across glioblastoma-IDH-wildtype and astrocytoma-IDH-mutant-grade 4 (Astro-IDH-mut-G4). Single-cell RNA sequencing was performed on four cases of human glioblastoma and three cases of Astro-IDH-mut-G4. Cell clustering, single-cell regulatory network inference and gene set enrichment analysis were performed to characterize the functional states of myeloid clusters. Spatial distribution of TAM subsets was determined in human glioma tissues using multiplex immunostaining. The prognostic value of different TAM-cluster specific geneset was evaluated in the TCGA glioma cohort. Profiling and unbiased clustering of 24,227 myeloid cells from glioblastoma and Astro-IDH-mut-G4 identified 9 myeloid cell clusters including monocyte, six Mo/Mg-TAM subsets, dendritic cell, and proliferative myeloid cluster. Different Mo/Mg-TAM clusters manifest functional and transcriptional diversity controlled by specific regulons. Multiplex immunostaining of subset-specific markers identified spatial enrichment of distinct TAM clusters at peri-vascular/necrotic areas in tumour parenchyma or at tumour-brain interface. Glioblastoma harboured a substantially higher number of monocytes and Mo-TAM-inflammatory cluster, whereas Astro-IDH-mut-G4 was with higher proportion of TAM subset mediating antigen presentation. Glioblastomas with higher proportion of monocytes exhibited a mesenchymal signature, increased angiogenesis and worse patient outcome. Our findings provide insight into myeloid cell diversity and its clinical relevance in IDH-differential grade-4 gliomas, and may serve as a resource for immunotherapy development. This article is protected by copyright. All rights reserved.

Evaluation of the Anti-Inflammatory and Anti-Oxidative Effects of Therapeutic Human Lactoferrin Fragments

Chronic inflammation is considered a pressing health issue that needs resolving. Inflammatory disease such as inflammatory bowel disease requires a long-term medical regimen to prevent disease progression. Conventionally, lactoferrin is used to treat mild gastrointestinal tract and skin inflammation. Protease-digested lactoferrin fragments often exhibit improved therapeutic properties compared to full-length lactoferrin (flHLF). However, there are no studies on the use of protease-digested lactoferrin fragments to treat inflammation. Herein, we assess the anti-inflammatory properties of engineered recombinant lactoferrin fragments (rtHLF4, rteHLF1, and rpHLF2) on non-malignant colonic fibroblast cells and colorectal cancer cells. We found that rtHLF4 is 10 times more effective to prevent inflammation compared to flHLF. These results were investigated by looking into the reactive oxygen species (ROS) production, angiogenesis activity, and cellular proliferation of the treated cells. We have demonstrated in this study the anti-inflammatory properties of the flHLF and the various lactoferrin fragments. These results complement the anti-cancer properties of these proteins that were demonstrated in an earlier study.

N6-Methyladenosine Methylation Analysis of Long Noncoding RNAs and mRNAs in IPEC-J2 Cells Treated With Clostridium perfringens beta2 Toxin

Background

The n6-methyladenosine (m6A) modification is present widely in mRNAs and long non-coding RNAs (lncRNAs), and is related to the occurrence and development of certain diseases. However, the role of m6A methylation in Clostridium perfringens type C infectious diarrhea remains unclear.

Methods

Here, we treated intestinal porcine jejunum epithelial cells (IPEC-J2 cells) with Clostridium perfringens beta2 (CPB2) toxin to construct an in vitro model of Clostridium perfringens type C (C. perfringens type C) infectious diarrhea, and then used methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) to identify the methylation profiles of mRNAs and lncRNAs in IPEC-J2 cells.

Results

We identified 6,413 peaks, representing 5,825 m6A-modified mRNAs and 433 modified lncRNAs, of which 4,356 m6A modified mRNAs and 221 m6A modified lncRNAs were significantly differential expressed between the control group and CPB2 group. The motif GGACU was enriched significantly in both the control group and the CPB2 group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analysis showed that the differentially methylated modified mRNAs were mainly enriched in Hippo signaling pathway and Wnt signaling pathway. In addition, the target genes of the differentially m6A modified lncRNAs were related to defense response to virus and immune response. For example, ENSSSCG00000042575, ENSSSCG00000048701 and ENSSSCG00000048785 might regulate the defense response to virus, immune and inflammatory response to resist the harmful effects of viruses on cells.

Conclusion

In summary, this study established the m6A transcription profile of mRNAs and lncRNAs in IPEC-J2 cells treated by CPB2 toxin. Further analysis showed that m6A-modified RNAs were related to defense against viruses and immune response after CPB2 toxin treatment of the cells. Threem6A-modified lncRNAs, ENSSSCG00000042575, ENSSSCG00000048785 and ENSSSCG00000048701, were most likely to play a key role in CPB2 toxin-treated IPEC-J2 cells. The results provide a theoretical basis for further research on the role of m6A modification in piglet diarrhea.

Taraxacum mongolicum protects against Staphylococcus aureus-infected mastitis by exerting anti-inflammatory role via TLR2-NF-κB/MAPKs pathways in mice

ETHNOPHARMACOLOGICAL RELEVANCE

As a traditional Chinese medicine, Taraxacum mongolicum has been widely used for the prevention and treatment of a variety of inflammatory and infectious diseases, and also clinically used as a remedy for mastitis. However, the scientific rationale and mechanism behind its use on mastitis in vivo are still unclear.

AIM OF THE STUDY

This study aimed to investigate the protective effect and potential mechanism of Taraxacum mongolicum Hand.-Mazz. (T. mongolicum) on mastitis infected by Staphylococcus aureus (S. aureus).

MATERIALS AND METHODS

Female ICR mice were given intragastrically 2.5, 5 and 10 g/kg of T. mongolicum extract twice per day for 6 consecutive days, and infected with S. aureus via teat canal to induce mastitis. Pro-inflammatory cytokine tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) levels were determined by ELISA. Myeloperoxidase (MPO) activity and distribution were measured by reagent kit and immunohistochemistry. Histopathological changes of mammary gland tissues were observed by H&E staining. Toll-like receptor 2 (TLR2) expression, phosphorylations of related proteins in nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) signaling pathways were detected by western blot.

RESULTS

T. mongolicum decreased TNF-α, IL-6 and IL-1β levels, and reduced MPO activity and distribution in sera and mammary glands with S. aureus-infected mastitis. In addition, T. mongolicum effectively attenuated histopathological damages and cell necrosis of mammary gland tissues infected by S. aureus. Moreover, T. mongolicum inhibited the expression of TLR2, and the phosphorylations of inhibitor κBα (IκBα), p65, p38, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) proteins in mammary glands with S. aureus-infected mastitis.

CONCLUSIONS

This study suggests that T. mongolicum protects against S. aureus-infected mastitis by exerting anti-inflammatory role, which is attributed to the inhibition of TLR2-NF-κB/MAPKs pathways.

Psoriatic skin inflammation is promoted by c-Jun/AP-1-dependent CCL2 and IL-23 expression in dendritic cells

Toll‐like receptor (TLR) stimulation induces innate immune responses involved in many inflammatory disorders including psoriasis. Although activation of the AP‐1 transcription factor complex is common in TLR signaling, the specific involvement and induced targets remain poorly understood. Here, we investigated the role of c‐Jun/AP‐1 protein in skin inflammation following TLR7 activation using human psoriatic skin, dendritic cells (DC), and genetically engineered mouse models. We show that c‐Jun regulates CCL2 production in DCs leading to impaired recruitment of plasmacytoid DCs to inflamed skin after treatment with the TLR7/8 agonist Imiquimod. Furthermore, deletion of c‐Jun in DCs or chemical blockade of JNK/c‐Jun signaling ameliorates psoriasis‐like skin inflammation by reducing IL‐23 production in DCs. Importantly, the control of IL‐23 and CCL2 by c‐Jun is most pronounced in murine type‐2 DCs. CCL2 and IL‐23 expression co‐localize with c‐Jun in type‐2/inflammatory DCs in human psoriatic skin and JNK‐AP‐1 inhibition reduces the expression of these targets in TLR7/8‐stimulated human DCs. Therefore, c‐Jun/AP‐1 is a central driver of TLR7‐induced immune responses by DCs and JNK/c‐Jun a potential therapeutic target in psoriasis.

O-Vanillin Attenuates the TLR2 Mediated Tumor-Promoting Phenotype of Microglia

Malignant gliomas are primary brain tumors with poor prognoses. These tumors are infiltrated by brain intrinsic microglia and peripheral monocytes which promote glioma cell invasion. In our previous studies, we discovered that the activation of Toll-like receptor 2 (TLR2) on microglia/brain macrophages converts them into a protumorigenic phenotype through the induction of matrix metalloproteinases (MMP) 9 and 14. In the present study, we used in vitro and in situ microglia-glioma interaction experimental models to test the impact of a novel inhibitor of TLR 2, ortho vanillin (O-Vanillin) to block TLR2 mediated microglia protumorigenic phenotype. We demonstrate that O-Vanillin inhibits the TLR2 mediated upregulation of MMP 9, MMP 14, IL 6 and iNOS expression. Similarly, the glioma supernatant induced MMP 9 and MMP 14 expression in murine and human microglia is abrogated by O-Vanillin treatment. O-Vanillin is not toxic for microglia, astrocytes or oligodendrocytes. Glioma growth in murine brain slice cultures is significantly reduced after treatment with O-Vanillin, and this reduced glioma growth depends on the presence of microglia. In addition, we also found that O-Vanillin inhibited the glioma induced proliferation of murine primary microglia. In summary, O-Vanillin attenuates the pro-tumorigenic phenotype of microglia/brain macrophages and thus qualifies as a candidate for glioma therapy.

Expression of long pentraxin 3 in human nasal mucosa fibroblasts, tissues, and secretions of chronic rhinosinusitis without nasal polyps

Numerous studies have shown that microbiomes play an important role in the pathogenesis of chronic rhinosinusitis (CRS). In addition to a known short pentraxin, C-reactive protein, long pentraxin 3 (PTX3) belongs to pentraxin family which detects conserved microbial pentraxin motifs and mobilizes early defense against foreign invaders, but its participation in CRS remains unclear. In the present study, through an intensive screening, peptidoglycan (PGN) was selected as a main material to investigate the action mechanism of a cell wall component on CRS without nasal polyps (CRSsNP) nasal mucosa-derived fibroblasts and the PTX3 expression in human nasal mucosa tissue and discharge. The PGN not only enhanced PTX3 mRNA and protein production in cells but also caused marked PTX3 secretion into extracellular space. The pharmacological interventions indicated that the PTX3 induction was mediated mainly through toll-like receptor 2 (TLR2), phosphoinositide-phospholipase C (PI-PLC), protein kinase C (PKC), NF-κB, and cAMP response element binding protein (CREB), which was further confirmed by the observations that a direct PKC activator (phorbol ester) had a similar inductory effect on PTX3 expression/production and the siRNA interference knockdown of PKCμ/δ, NF-κB, and CREB compromised PTX3 production. Meanwhile, PTX3 was found to be overexpressed/produced in nasal mucosa and discharge/secretion of the CRSsNP patients. Collectively, we first demonstrated here that PGN enhances PTX3 expression and release in nasal fibroblasts through TLR2, PI-PLC, PKCμ/δ, NF-κB, and CREB signaling pathways. The PTX3 is overexpressed in nasal mucosa and discharge/secretion of CRSsNP patients, revealing its possible importance in CRSsNP development and progression. KEY MESSAGES: Long pentraxin 3 (PTX3) is highly expressed in nasal mucosa and discharge/secretion of patients of chronic rhinosinusitis without nasal polyps (CRSsNP). The bacteria cell wall component-peptidoglycan (PGN) causes PTX3 expression in CRSsNP nasal mucosa-derived fibroblasts, contributing to the PTX3 increase in tissues. PGN induces PTX3 expression through a previously known IκB/NF-κB and a novel PKCμ/δ and CREB signaling pathway. The PTX3 may be used as a biomarker for CRS.

Targets of immunomodulation in bacterial endophthalmitis

Bacterial infection of the posterior segment of the eye (endophthalmitis) leads to a robust host response that often results in irreversible damage to the layers of the retina, significant vision loss, and in some patients, enucleation of the globe. While a great deal of effort has gone into understanding the role of bacterial virulence factors in disease initiation and propagation, it is becoming increasingly clear that the host response to infection plays a major role in causing the damage associated with endophthalmitis. Researchers have identified the host receptors which detect infecting organisms and initiate the cascade of events that result in inflammation. This inflammation may damage nonregenerative tissues of the eye while attempting to clear the infection. Both Gram-positive and Gram-negative bacteria can cause endophthalmitis. These organisms initiate an immune response by activating toll-like receptor (TLR) pathways. Once an inflammatory response is initiated, the expression of immunomodulators, such as proinflammatory chemokines and cytokines, affect the recruitment of PMNs and other inflammatory cells into the eye. We and others have reported that knockout mice that do not express specific inflammatory pathways and molecules have an attenuated response to infection and retain significant retinal function. These findings suggest that host immune mediators are important components of the response to infections in the posterior segment of the eye, and the timing and level of their production may be related to the severity of the damage and the ultimate visual outcome. If that is the case, a better understanding of the complex and often redundant role of these pathways and inflammatory mediators may identify host molecules as potential anti-inflammatory therapeutic targets. This review highlights potential anti-inflammatory targets during acute inflammation in endophthalmitis, compares and contrasts those with findings in other models of ocular inflammation, and translates current immunomodulatory strategies for other types of infection and inflammation to this blinding disease. Given the poor visual outcomes seen in patients treated with antibiotics alone or in combination with corticosteroids, immunomodulation in addition to antibiotic therapy might be more effective in preserving vision than current regimens.

Implications of Probiotics on the Maternal-Neonatal Interface: Gut Microbiota, Immunomodulation, and Autoimmunity

Probiotics are being investigated for the treatment of autoimmune disease by re-balancing dysbiosis induced changes in the immune system. Pregnancy is a health concern surrounding autoimmune disease, both for the mother and her child. Probiotics for maternity are emerging on the market and have gained significant momentum in the literature. Thus far, evidence supports that probiotics alter the structure of the normal microbiota and the microbiota changes significantly during pregnancy. The interaction between probiotics-induced changes and normal changes during pregnancy is poorly understood. Furthermore, there is emerging evidence that the maternal gut microbiota influences the microbiota of offspring, leading to questions on how maternal probiotics may influence the health of neonates. Underpinning the development and balance of the immune system, the microbiota, especially that of the gut, is significantly important, and dysbiosis is an agent of immune dysregulation and autoimmunity. However, few studies exist on the implications of maternal probiotics for the outcome of pregnancy in autoimmune disease. Is it helpful or harmful for mother with autoimmune disease to take probiotics, and would this be protective or pathogenic for her child? Controversy surrounds whether probiotics administered maternally or during infancy are healthful for allergic disease, and their use for autoimmunity is relatively unexplored. This review aims to discuss the use of maternal probiotics in health and autoimmune disease and to investigate their immunomodulatory properties.

Temporal Effects of High Fishmeal Diet on Gut Microbiota and Immune Response in Clostridium perfringens-Challenged Chickens

Necrotic enteritis (NE) caused by Clostridium perfringens is responsible for huge financial losses in the poultry industry annually. A diet highly supplemented with fishmeal is one factor predisposing chickens to the development of clinical NE. However, the effects of fishmeal-rich diets on the gut microbiota and immune response in chickens with C. perfringens challenge over the long-term are not well-understood. Here, a chicken NE model was established in which chickens were fed high fishmeal diet and subsequently infected with C. perfringens (FM/CP). Two control groups of chickens, one that was not infected and had a high fishmeal feeding (FM) and another group only infected with C. perfringens with basic diets (CP), were used as comparators. We analyzed the gut microbiota and immune response of the three groups at the age of 20, 24 [1 day post-infection (dpi)] and 30 days (7 dpi) using 16S rDNA sequencing and real-time PCR, respectively. We found that the composition of the gut microbiota had significant shifted in both the CP and FM/CP groups, although the CP group did not have intestinal lesions. The structure of the gut microbiota in C. perfringens-challenged chickens, independent of a high fishmeal diet, had the tendency to return to their non-infection state if the chickens no longer received C. perfringens challenge. Gut microbiota variation with time in challenged chickens with high fishmeal diet feeding was superimposed upon that of non-infected chickens with high fishmeal feeding. For the immune response, the relative expression of IL-8 in the ileum was significantly higher in infected chickens independent of high fishmeal feeding than in non-infected chickens. However, the expression of alpha 1-acid glycoprotein (AGP) and serum amyloid A (SAA) genes in chicken liver were significantly increased in FM/CP compared to the other groups. In conclusion, high fishmeal feeding induced significant changes to the structure of chicken gut microbiota over time and such changes provided an opening for C. perfringens infection to progress to NE. The relative expression of AGP and SAA in liver tissue may be used as diagnostic biomarkers for poultry NE but such an indication requires further investigation.

Peptidoglycan induces bradykinin receptor 1 expression through Toll-like receptor 2 and NF-κB signaling pathway in human nasal mucosa-derived fibroblasts of chronic rhinosinusitis patients

Numerous studies have demonstrated that Gram-positive microbiomes play an important role in the pathogenesis and in the way of treatment of chronic rhinosinusitis (CRS). Kinins are inflammatory mediators and one of their receptors, namely bradykinin receptor 1 (BKR1 or B1R), is believed to be induced and involved in inflammation in pathophysiological conditions. In the present study, we investigated the effect of peptidoglycan (PGN), a major cell wall component of G(+) bacteria, on BKR expression and its signaling pathway in nasal fibroblasts from CRS without nasal polyp (CRSsNP). The PGN induced increases in B1R mRNA and protein production. The induction was abolished by the NF-κB and protein kinase A inhibitor. In parallel, the PGN treatment directly activated IκB/NF-κB signaling and CREB phosphorylation. Interestingly, a further analysis suggested no involvement of cAMP/PKA/CREB pathway in this induction. The B1R expression and IκB/NF-κB signaling pathway could be attenuated by Toll-like receptor-2 (TLR2) blocking/neutralizing Ab. In a functional assay, the addition of B1R selective agonist (Des-Arg¹⁰ -kallidin) to the fibroblasts after PGN stimulation led to an increase in CXCL8 release and p38 MAPK and ERK1/2 phosphorylation, which could be inhibited by the B1R antagonist. Taken together, our results revealed for the first time that PGN can increase B1R expression in human nasal mucosa-derived fibroblasts through TLR2 activation and NF-κB signaling pathway. This induction functionally leads to MAPKs activation and CXCL8 release upon B1R stimulation. Our results also suggest that a major component of G(+) bacteria can participate in B1R upregulation in nasal mucosa during CRSsNP progression.

Metformin attenuates the TLR4 inflammatory pathway in skeletal muscle of diabetic rats

AIMS

Inflammation induced by hyperglycemia triggers the toll-like receptor (TLR) pathway into cells. Our hypothesis was that metformin treatment attenuates the TLR signaling pathways triggered by inflammation in skeletal muscle of hypoinsulinemic/hyperglycemic STZ-induced rats. Thus, we examined TLR signaling under hypoinsulinemia and hyperglycemia conditions and its correlation with insulin resistance in muscle of diabetic rats treated with metformin.

METHODS

Ten-day diabetic rats were submitted to 7 days of saline (D group) or metformin (500 mg/kg once per day) (D + M group). The skeletal muscle was collected before the insulin tolerance test. Then, Western blotting analysis of skeletal muscle supernatant was probed with TLR4, TLR2, NF-κB, IκB, p-AMPK and p-JNK. TNF-α and CXCL1/KC content was analyzed by ELISA.

RESULTS

Metformin treatment increased whole-body insulin sensitivity. This regulation was accompanied by a parallel change of p-AMPK and by an inverse regulation of TLR4 and NF-κB contents in the soleus muscle (r = 0.7229, r = -0.8344 and r = -0.7289, respectively, Pearson correlation; p < 0.05). Metformin treatment increased IκB content when compared to D rats. In addition, metformin treatment decreased p-JNK independently of TLR2 signal in diabetic rats.

CONCLUSION

In summary, the results indicate a relationship between muscular TLR4, p-AMPK and NF-κB content and insulin sensitivity. The study also highlights that in situations of insulin resistance, such as in diabetic subjects, metformin treatment may prevent attenuation of activation of the inflammatory pathway.

Interleukin-6 in Allogeneic Stem Cell Transplantation: Its Possible Importance for Immunoregulation and As a Therapeutic Target

Allogeneic stem cell transplantation is associated with a high risk of treatment-related mortality mainly caused by infections and graft-versus-host disease (GVHD). GVHD is characterized by severe immune dysregulation and impaired regeneration of different tissues, i.e., epithelial barriers and the liver. The balance between pro- and anti-inflammatory cytokine influences the risk of GVHD. Interleukin-6 (IL-6) is a cytokine that previously has been associated with pro-inflammatory effects. However, more recent evidence from various autoimmune diseases (e.g., inflammatory bowel disease, rheumatoid arthritis) has shown that the IL-6 activity is more complex with important effects also on tissue homeostasis, regeneration, and metabolism. This review summarizes the current understanding of how pro-inflammatory IL-6 effects exerted during the peritransplant period shapes T-cell polarization with enhancement of Th17 differentiation and suppression of regulatory T cells, and in addition we also review and discuss the results from trials exploring non-selective IL-6 inhibition in prophylaxis and treatment of GVHD. Emerging evidence suggests that the molecular strategy for targeting of IL-6-initiated intracellular signaling is important for the effect on GVHD. It will therefore be important to further characterize the role of IL-6 in the pathogenesis of GVHD to clarify whether combined IL-6 inhibition of both trans- (i.e., binding of the soluble IL-6/IL-6 receptor complex to cell surface gp130) and cis-signaling (i.e., IL-6 ligation of the IL-6 receptor/gp130 complex) or selective inhibition of trans-signaling should be tried in the prophylaxis and/or treatment of GVHD in allotransplant patients.

Electroacupuncture Improves Cognitive Deficits through Increasing Regional Cerebral Blood Flow and Alleviating Inflammation in CCI Rats

Objective. To investigate the effect of EA on regional cerebral blood flow, cognitive deficits, inflammation, and its probable mechanisms in chronic cerebral ischemia (CCI) rats. Methods. Rats were assigned randomly into sham operation group (sham group) and operation group. For operation group, CCI model was performed using the permanent bilateral common carotid artery occlusion (BCCAO) method, and then rats were further randomly divided into model group and electroacupuncture (EA) group. 2/15 Hz low-frequency pulse electric intervention was applied at “Baihui” and “Dazhui” acupoints in EA group. Four weeks later, Morris water maze test was adopted to assess the cognitive function, using laser Doppler flowmetry to test changes of regional cerebral blood flow (rCBF); double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) to measure proinflammatory cytokines (IL-6, TNF-α, and IL-1β); western blot to test the protein expression quantities of proinflammatory cytokines, JAK2, and STAT3; and RT-PCR to test JAK2 mRNA and STAT3 mRNA in the hippocampus in each group. Results. Compared with the model group, learning and memory abilities and rCBF and IL-6 expression of the EA group enhanced markedly; IL-1β and JAK2 significantly decreased; TNF-α and STAT3 also declined, but the difference was not apparent. Conclusion. Our research suggests that EA can improve cognitive deficits which may be induced by increasing rCBF and anti-inflammatory effect.

Role of Transcription Factors in Pulmonary Artery Smooth Muscle Cells: An Important Link to Hypoxic Pulmonary Hypertension

Hypoxia, namely a lack of oxygen in the blood, induces pulmonary vasoconstriction and vasoremodeling, which serve as essential pathologic factors leading to pulmonary hypertension (PH). The underlying molecular mechanisms are uncertain; however, pulmonary artery smooth muscle cells (PASMCs) play an essential role in hypoxia-induced pulmonary vasoconstriction, vasoremodeling, and PH. Hypoxia causes oxidative damage to DNAs, proteins, and lipids. This damage (oxidative stress) modulates the activity of ion channels and elevates the intracellular calcium concentration ([Ca²⁺]_i, Ca²⁺ signaling) of PASMCs. The oxidative stress and increased Ca²⁺ signaling mutually interact with each other, and synergistically results in a variety of cellular responses. These responses include functional and structural abnormalities of mitochondria, sarcoplasmic reticulum, and nucleus; cell contraction, proliferation, migration, and apoptosis, as well as generation of vasoactive substances, inflammatory molecules, and growth factors that mediate the development of PH. A number of studies reveal that various transcription factors (TFs) play important roles in hypoxia-induced oxidative stress, disrupted PAMSC Ca²⁺ signaling and the development and progress of PH. It is believed that in the pathogenesis of PH, hypoxia facilitates these roles by mediating the expression of multiple genes. Therefore, the identification of specific genes and their transcription factors implicated in PH is necessary for the complete understanding of the underlying molecular mechanisms. Moreover, this identification may aid in the development of novel and effective therapeutic strategies for PH.

The intrinsic microglial clock system regulates interleukin-6 expression

Similar to neurons, microglia have an intrinsic molecular clock. The master clock oscillator Bmal1 modulates interleukin-6 upregulation in microglial cells exposed to lipopolysaccharide. Bmal1 can play a role in microglial inflammatory responses. We previously demonstrated that gliotransmitter ATP induces transient expression of the clock gene Period1 via P2X7 purinergic receptors in cultured microglia. In this study, we further investigated mechanisms underlying the regulation of pro-inflammatory cytokine production by clock molecules in microglial cells. Several clock gene transcripts exhibited oscillatory diurnal rhythmicity in microglial BV-2 cells. Real-time luciferase monitoring also showed diurnal oscillatory luciferase activity in cultured microglia from Per1::Luciferase transgenic mice. Lipopolysaccharide (LPS) strongly induced the expression of pro-inflammatory cytokines in BV-2 cells, whereas an siRNA targeting Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1), a core positive component of the microglial molecular clock, selectively inhibited LPS-induced interleukin-6 (IL-6) expression. In addition, LPS-induced IL-6 expression was attenuated in microglia from Bmal1-deficient mice. This phenotype was recapitulated by pharmacological disruption of oscillatory diurnal rhythmicity using the synthetic Rev-Erb agonist SR9011. Promoter analysis of the Il6 gene revealed that Bmal1 is required for LPS-induced IL-6 expression in microglia. Mice conditionally Bmal1 deficient in cells expressing CD11b, including microglia, exhibited less potent upregulation of Il6 expression following middle cerebral artery occlusion compared with that in control mice, with a significant attenuation of neuronal damage. These results suggest that the intrinsic microglial clock modulates the inflammatory response, including the positive regulation of IL-6 expression in a particular pathological situation in the brain, GLIA 2016. GLIA 2017;65:198-208.

mTORC1 mediates peptidoglycan induced inflammatory cytokines expression and NF-κB activation in macrophages

Peptidoglycan (PGN) is the major structural component of the bacterial cell wall, especially gram positive bacteria, which induces inflammatory responses. Mammalian target of rapamycin (mTOR) regulates the production of inflammatory cytokines induced by antigens, while the function of mTORC1 in peptidoglycan induced inflammatory response is unknown. This study aims to examine the role and the regulatory mechanism of mTOR signaling pathway in peptidoglycan induced cytokine expression in mouse macrophages. We observed that peptidoglycan upregulated the secretion of proinflammatory cytokines IL-6, TNF-α and anti-inflammatory cytokine IL-10 in a dose- and time-dependent manner. mTORC1 positively regulates IL-6 and TNF-α, but negatively regulates IL-10 secretion. mTORC1 regulates NF-κB p65 activation by degrading IκB-α in response to peptidoglycan. mTOR, NF-κB and STAT3 signaling pathways are involved in peptidoglycan induced inflammatory cytokines expression via a TLR1/TLR2-dependent mechanism in macrophages. Thus, mTORC1 pathway regulates the innate immune response to bacterial peptidoglycan.

Reprint of: Microglial toll-like receptors and Alzheimer's disease

Microglial activation represents an important pathological hallmark of Alzheimer's disease (AD), and emerging data highlight the involvement of microglial toll-like receptors (TLRs) in the course of AD. TLRs have been observed to exert both beneficial and detrimental effects on AD-related pathologies, and transgenic animal models have provided direct and credible evidence for an association between TLRs and AD. Moreover, analyses of genetic polymorphisms have suggested interactions between genetic polymorphisms in TLRs and AD risk, further supporting the hypothesis that TLRs are involved in AD. In this review, we summarize the key evidence in this field. Future studies should focus on exploring the mechanisms underlying the potential roles of TLRs in AD.

A tetramethoxychalcone from Chloranthus henryi suppresses lipopolysaccharide-induced inflammatory responses in BV2 microglia

Neuroinflammation underlies the pathogenesis and progression of neurodegenerative diseases. 2׳-hydroxy-4,3׳,4׳,6׳-tetramethoxychalcone (HTMC) is a known chalcone derivative isolated from Chloranthus henryi with anti-inflammatory activities in BV2 macrophages. However, its pharmacological effects on microglial cells have not been demonstrated. To this end, we examined the effects of HTMC on lipopolysaccharide (LPS)-induced inflammatory responses in BV2 microglial cells. HTMC concentration-dependently inhibited LPS-induced expression of inflammatory enzymes including inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), nitric oxide (NO) production, and the secretion of inflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. In addition, HTMC inhibited reactive oxygen species (ROS) production by reducing NADPH oxidase (Nox) 2 and Nox4 expression. In addition, HTMC interfered LPS-induced c-Jun N-terminal kinase 1/2 (JNK) phosphorylation in a time- and concentration-dependent manner. By inhibiting phosphorylation and nuclear translocation of Jun, HTMC suppressed LPS-induced activator protein-1 (AP-1) activation. Taken together, our data indicate that HTMC suppresses inflammatory responses in LPS-stimulated BV2 microglial cells by modulating JNK-AP-1 and NADPH oxidases-ROS pathways. HTMC represents a promising therapeutic agent for neurodegenerative and related aging-associated diseases.

Microglial toll-like receptors and Alzheimer's disease

Microglial activation represents an important pathological hallmark of Alzheimer's disease (AD), and emerging data highlight the involvement of microglial toll-like receptors (TLRs) in the course of AD. TLRs have been observed to exert both beneficial and detrimental effects on AD-related pathologies, and transgenic animal models have provided direct and credible evidence for an association between TLRs and AD. Moreover, analyses of genetic polymorphisms have suggested interactions between genetic polymorphisms in TLRs and AD risk, further supporting the hypothesis that TLRs are involved in AD. In this review, we summarize the key evidence in this field. Future studies should focus on exploring the mechanisms underlying the potential roles of TLRs in AD.

Inflammatory responses to a Clostridium perfringens type A strain and α-toxin in primary intestinal epithelial cells of chicken embryos

The causative pathogen of necrotic enteritis is the Gram-positive bacterium Clostridium perfringens. Its main cell wall component, peptidoglycan (PGN), can be recognized by Toll-like receptor 2 and nucleotide-binding oligomerization domain (NOD). Consequently, the immune response is initiated via activation of nuclear factor kappa B (NF-κB) signalling pathway. An in vitro study was conducted to investigate chicken intestinal inflammatory responses to C. perfringens type A and one of its virulence factors, α-toxin. In primary intestinal epithelial cells, C. perfringens as well as commercially available PGN and α-toxin challenge upregulated mRNA expression of interleukin (IL)-6, IL-8 and inducible nitric oxide synthase (iNOS) with a dosage-dependent manner at 3 h post infection (p.i.; P ≤ 0.001). Time-course effects of three stimulators at high concentration were further examined. C. perfringens infection elevated IL-6, IL-8 and iNOS levels from 1 h to 9 h p.i., while PGN treatment increased IL-6 and IL-8 expression at 1 h and 3 h p.i. (P < 0.05). Bacterial and PGN treatments induced NOD1 expression at 6 h p.i. and only bacterial infection boosted NF-κB p65 expression at 6 h and 9 h p.i. (P < 0.05). α-Toxin treatment upregulated IL-6 and IL-8 expression throughout infection, as well as iNOS, TNF-α and NF-κB p65 expression at later hours p.i. (P < 0.05). In conclusion, both C. perfringens and α-toxin challenge induced intense cytokine expression associated with NF-κB activation in chicken intestinal epithelial cells. The receptors for the recognition of PGN component of C. perfringens need further investigation.

Interlukin-18 Is a Pivot Regulatory Factor on Matrix Metalloproteinase-13 Expression and Brain Astrocytic Migration

The expression of matrix metalloproteinase-13 (MMP-13) has been shown to be elevated in some pathophysiological conditions and is involved in the degradation of extracellular matrix in astrocytes. In current study, the function of MMP-13 was further investigated. The conditioned medium (CM) collected from activated microglia increased interleukin (IL)-18 production and enhanced MMP-13 expression in astrocytes. Furthermore, treatment with recombinant IL-18 increased MMP-13 protein and mRNA levels in astrocytes. Recombinant IL-18 stimulation also increased the enzymatic activity of MMP-13 and the migratory activity of astrocytes, while administration of MMP-13 or pan-MMP inhibitors antagonized IL-18-induced migratory activity of astrocytes. In addition, administration of recombinant IL-18 to astrocytes led to the phosphorylation of JNK, Akt, or PKCδ, and treatment of astrocytes with JNK, PI3 kinase/Akt, or PKCδ inhibitors significantly decreased the IL-18-induced migratory activity. Taken together, the results suggest that IL-18-induced MMP-13 expression in astrocytes is regulated by JNK, PI3 kinase/Akt, and PKCδ signaling pathways. These findings also indicate that IL-18 is an important regulator leading to MMP-13 expression and cell migration in astrocytes.

Cobalt Protoporphyrin Upregulates Cyclooxygenase-2 Expression Through a Heme Oxygenase-Independent Mechanism

Cobalt protoporphyrin (CoPP) is a potent HO-1 inducer and generally known to be an antioxidant in various cell types. Little is known about the CoPP-induced cyclooxygenase-2 (COX-2) expression and its downstream signaling in microglial cells. In current study, CoPP caused concentration- and time-dependent increases in COX-2 expression in microglial cells. Furthermore, activation of apoptosis signal-regulating kinase (ASK) 1/MAP kinase involved in CoPP-induced COX-2 expression in microglia. CoPP also induced P2X7 receptor activation, and treatment of P2X7 inhibitors effectively reduced CoPP-induced COX-2 expression. Protein inhibitor of activated STAT (PIAS) 1 is reported to be involved in modulating anti-inflammatory response through negative regulation of transcription factors. Interestingly, treatment with CoPP markedly induced PIAS1 degradation which is regulated by PI3K, Akt, and glycogen synthase kinase 3α/β (GSK3α/β) signaling pathways. These results suggest that CoPP induces COX-2 expression through activating P2X7 receptors and ASK1/MAP kinases as well as PIAS1 degradation signaling pathways. Our study provides a new insight into the regulatory effect of CoPP on neuroinflammation in microglial cells.

TDP-43 activates microglia through NF-κB and NLRP3 inflammasome

Transactive response DNA-binding protein-43 (TDP-43) is a multifunctional nucleic acid binding protein present in ubiquitinated inclusions in tissues of patients with amyotrophic lateral sclerosis (ALS) and fronto-temporal lobar degeneration (FTLD). The ALS-associated mutations in the glycine-rich C-terminal domain of TDP-43 established a causal link between TDP-43 and disease, and conferred both loss- and gain-of-function properties in neurons. Since it has not been established whether these intra-neuronal changes are sufficient to cause ALS or whether non-cell autonomous neuronal-glial signaling could be involved, we investigated the extracellular effects of TDP-43 proteins on microglial activation and motoneuron toxicity. Wild-type, truncated 25kD C-terminal fragments, or mutant forms of TDP-43 all activated microglia and upregulated NOX2, TNF-α, and IL-1β, with WT forms being significantly less effective in activating microglia. This response to TDP-43 was mediated by its interaction with the microglial surface CD14 receptor and subsequent stimulation of the NF-κB and AP-1 pathways, as well as the intracellular inflammasome. At the cell surface, CD14 blocking antibodies suppressed microglial NF-κB activation and proinflammatory cytokine production mediated by TDP-43. Intracellularly, the NLRP3 inflammasome was induced and functional caspase-1 was produced augmenting the release of mature IL-1β. Further, TDP-43-mediated activation of microglia caused a proinflammatory cascade that was toxic to motoneurons. In the absence of microglia, TDP-43 was not toxic to motoneurons. The ability of TDP-43 to promote CD14-mediated activation of microglial NF-κB and AP-1 pathways, as well as the NLRP3 inflammasome, suggests the involvement of a non-cell autonomous proinflammatory signaling that enhances motoneuron injury, and may offer novel therapeutic targets in ALS.

TLR2 and AP-1/NF-kappaB are involved in the regulation of MMP-9 elicited by heat killed Listeria monocytogenes in human monocytic THP-1 cells

BACKGROUND

MMP-9 is crucial for a normal immune response, but excessive release of this enzyme leads to severe tissue damage. Listeria monocytogenes (LM) is an opportunistic food-borne pathogen causing listerosis, meningitis and sepsis. Heat killed Listeria monocytogenes (HKLM) activates immune system and leads production of cytokines and chemokines. However, nothing is known about the involvement of HKLM in MMP-9 regulation. Therefore we investigated the role of HKLM in the regulation of MMP-9 gene expression in THP-1 cells.

METHODS

Commercially available heat killed Listeria monocytogenes was used in this study. HKLM-induced MMP-9 expression was assessed with quantitative real-time qPCR and ELISA. Action of HKLM in different signaling pathways were studied by using THP-1-XBlue™ cells (THP-1-cells with NF-κB/AP-1 reporter construct), THP-1-XBlue™-defMyD cells (MyD88(-/-) THP-1 cells), anti-TLR2 mAb and pharmacological inhibitors. Phospho and total proteins were determined by Western blotting.

RESULTS

Increased MMP-9 production (mRNA: 395-Fold; Protein: 8141 pg/ml; P < 0.05) was observed in HKLM stimulated THP-1 cells as compared to the un-stimulated THP-1 cells. This production of MMP-9 was completely abrogated by anti-TLR2 blocking mAb (P = 0.0024). Furthermore, THP-1-XBlue™-defMyD cells were unable to produce MMP-9 in response to HKLM. HKLM- induced activation of NF-kappaB/AP-1 was also observed in THP-1-XBlue™ Cells. In addition, inhibitors of JNK (SP600125), MEK/ERK (U0126; PD98056), p38 MAPK (SB203580) and NF-kappaB (BAY 11-7085, Triptolide and Resveratrol) significantly suppressed (P < 0.05) HKLM-stimulated MMP-9 expression.

CONCLUSION

Our results indicate that HKLM activates TLR2 and NF-κB/AP-1 signaling pathways, leading to up-regulation of MMP-9 production in THP-1 cells. Thus, MMP-9 could be an appropriate therapeutic target to stop severe tissue damage caused by infection or chronic inflammation.

Peptidoglycan Induces the Production of Interleukin-8 via Calcium Signaling in Human Gingival Epithelium

The etiology of periodontal disease is multifactorial. Exogenous stimuli such as bacterial pathogens can interact with toll-like receptors to activate intracellular calcium signaling in gingival epithelium and other tissues. The triggering of calcium signaling induces the secretion of pro-inflammatory cytokines such as interleukin-8 as part of the inflammatory response; however, the exact mechanism of calcium signaling induced by bacterial toxins when gingival epithelial cells are exposed to pathogens is unclear. Here, we investigate calcium signaling induced by bacteria and expression of inflammatory cytokines in human gingival epithelial cells. We found that peptidoglycan, a constituent of gram-positive bacteria and an agonist of toll-like receptor 2, increases intracellular calcium in a concentration-dependent manner. Peptidoglycan-induced calcium signaling was abolished by treatment with blockers of phospholipase C (U73122), inositol 1,4,5-trisphosphate receptors, indicating the release of calcium from intracellular calcium stores. Peptidoglycan-mediated interleukin-8 expression was blocked by U73122 and 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester). Moreover, interleukin-8 expression was induced by thapsigargin, a selective inhibitor of the sarco/endoplasmic reticulum calcium ATPase, when thapsigargin was treated alone or co-treated with peptidoglycan. These results suggest that the gram-positive bacterial toxin peptidoglycan induces calcium signaling via the phospholipase C/inositol 1,4,5-trisphosphate pathway, and that increased interleukin-8 expression is mediated by intracellular calcium levels in human gingival epithelial cells.

Amitriptyline up-regulates connexin43-gap junction in rat cultured cortical astrocytes via activation of the p38 and c-Fos/AP-1 signalling pathway

BACKGROUND AND PURPOSE

Intercellular communication via gap junctions, comprised of connexin (Cx) proteins, allow for communication between astrocytes, which in turn is crucial for maintaining CNS homeostasis. The expression of Cx43 is decreased in post-mortem brains from patients with major depression. A potentially novel mechanism of tricyclic antidepressants is to increase the expression and functioning of gap junctions in astrocytes.

EXPERIMENTAL APPROACH

The effect of amitriptyline on the expression of Cx43 and gap junction intercellular communication (GJIC) in rat primary cultured cortical astrocytes was investigated. We also investigated the role of p38 MAPK intracellular signalling pathway in the amitriptyline-induced expression of Cx43 and GJIC.

KEY RESULTS

Treatment with amitriptyline for 48 h significantly up-regulated Cx43 mRNA, protein and GJIC. The up-regulation of Cx43 was not monoamine-related since noradrenaline, 5-HT and dopamine did not induce Cx43 expression and pretreatment with α- and β-adrenoceptor antagonists had no effect. Intracellular signalling involved p38 MAPK, as amitriptyline significantly increased p38 MAPK phosphorylation and Cx43 expression and GJIC were significantly blocked by the p38 inhibitor SB 202190. Furthermore, amitriptyline-induced Cx43 expression and GJIC were markedly reduced by transcription factor AP-1 inhibitors (curcumin and tanshinone IIA). The translocation of c-Fos from the cytosol and the nucleus of cortical astrocytes was increased by amitriptyline, and this response was dependent on p38 activity.

CONCLUSION AND IMPLICATION

These findings indicate a novel mechanism of action of amitriptyline through cortical astrocytes, and further suggest that targeting this mechanism could lead to the development of a new class of antidepressants.

Endothelin-1 driven proliferation of pulmonary arterial smooth muscle cells is c-fos dependent

Pulmonary hypertension (PH) is characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation leading to vascular remodeling. Although, multiple factors have been associated with pathogenesis of PH the underlying mechanisms are not fully understood. Here, we hypothesize that already very short exposure to hypoxia may activate molecular cascades leading to vascular remodeling. Microarray studies from lung homogenates of mice exposed to only 3h of hypoxia revealed endothelin-1 (ET-1) and connective tissue growth factor (CTGF) as the most upregulated genes, and the mitogen-activated protein kinase (MAPK) pathway as the most differentially regulated pathway. Evaluation of these results in vitro showed that ET-1 but not CTGF stimulation of human PASMCs increased DNA synthesis and expression of proliferation markers such as Ki67 and cell cycle regulator, cyclin D1. Moreover, ET-1 treatment elevated extracellular signal-regulated kinase (Erk)-dependent c-fos expression and phosphorylation of c-fos and c-jun transcription factors. Silencing of c-fos with siRNA abrogated the ET-1-induced proliferation of PASMCs. Expression and immunohistochemical analyses revealed higher levels of total and phosphorylated c-fos and c-jun in the vessel wall of lung samples of human idiopathic pulmonary arterial hypertension patents, hypoxia-exposed mice and monocrotaline-treated rats as compared to control subjects. These findings shed the light on the involvement of c-fos/c-jun in the proliferative response of PASMCs to ET-1 indicating that already very short hypoxia exposure leads to the regulation of mediators involved in vascular remodeling underlying PH.

Regulatory effects of fisetin on microglial activation

Increasing evidence suggests that inflammatory processes in the central nervous system that are mediated by microglial activation play a key role in neurodegeneration. Fisetin, a plant flavonol commonly found in fruits and vegetables, is frequently added to nutritional supplements due to its antioxidant properties. In the present study, treatment with fisetin inhibited microglial cell migration and ROS (reactive oxygen species) production. Treatment with fisetin also effectively inhibited LPS plus IFN-γ-induced nitric oxide (NO) production, and inducible nitric oxide synthase (iNOS) expression in microglial cells. Furthermore, fisetin also reduced expressions of iNOS and NO by stimulation of peptidoglycan, the major component of the Gram-positive bacterium cell wall. Fisetin also inhibited the enhancement of LPS/IFN-γ- or peptidoglycan-induced inflammatory mediator IL (interlukin)-1 β expression. Besides the antioxidative and anti-inflammatory effects of fisetin, our study also elucidates the manner in fisetin-induced an endogenous anti-oxidative enzyme HO (heme oxygenase)-1 expression. Moreover, the regulatory molecular mechanism of fisetin-induced HO-1 expression operates through the PI-3 kinase/AKT and p38 signaling pathways in microglia. Notably, fisetin also significantly attenuated inflammation-related microglial activation and coordination deficit in mice in vivo. These findings suggest that fisetin may be a candidate agent for the development of therapies for inflammation-related neurodegenerative diseases.

Molecular neuroimaging of post-injury plasticity

Nerve injury induces long-term changes in neuronal activity in the primary somatosensory cortex (S1), which has often been implicated as the origin of sensory dysfunction. However, the cellular mechanisms underlying this phenomenon remain unclear. C-fos is an immediate early gene, which has been shown to play an instrumental role in plasticity. By developing a new platform to image real-time changes in gene expression in vivo, we investigated whether injury modulates the levels of c-fos in layer V of S1, since previous studies have suggested that these neurons are particularly susceptible to injury. The yellow fluorescent protein, ZsYellow1, under the regulation of the c-fos promoter, was expressed throughout the rat brain. A fiber-based confocal microscope that enabled deep brain imaging was utilized, and local field potentials were collected simultaneously. In the weeks following limb denervation in adult rats (n=10), sensory stimulation of the intact limb induced significant increases in c-fos gene expression in cells located in S1, both contralateral (affected, 27.6±3 cells) and ipsilateral (8.6±3 cells) to the injury, compared to controls (n=10, 13.4±3 and 1.0±1, respectively, p value<0.05). Thus, we demonstrated that injury activates cellular mechanisms that are involved in reshaping neuronal connections, and this may translate to neurorehabilitative potential.

Anti-neuroinflammatory effects of the calcium channel blocker nicardipine on microglial cells: implications for neuroprotection

BACKGROUND/OBJECTIVE

Nicardipine is a calcium channel blocker that has been widely used to control blood pressure in severe hypertension following events such as ischemic stroke, traumatic brain injury, and intracerebral hemorrhage. However, accumulating evidence suggests that inflammatory processes in the central nervous system that are mediated by microglial activation play important roles in neurodegeneration, and the effect of nicardipine on microglial activation remains unresolved.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study, using murine BV-2 microglia, we demonstrated that nicardipine significantly inhibits microglia-related neuroinflammatory responses. Treatment with nicardipine inhibited microglial cell migration. Nicardipine also significantly inhibited LPS plus IFN-γ-induced release of nitric oxide (NO), and the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, nicardipine also inhibited microglial activation by peptidoglycan, the major component of the Gram-positive bacterium cell wall. Notably, nicardipine also showed significant anti-neuroinflammatory effects on microglial activation in mice in vivo.

CONCLUSION/SIGNIFICANCE

The present study is the first to report a novel inhibitory role of nicardipine on neuroinflammation and provides a new candidate agent for the development of therapies for inflammation-related neurodegenerative diseases.

Chloral hydrate-dependent reduction in the peptidoglycan-induced inflammatory macrophage response is associated with lower expression levels of toll-like receptor 2

The aim of this study was to investigate the effect and mechanism of action of chloral hydrate on the peptidoglycan (PGN)-induced inflammatory macrophage response. The effect of chloral hydrate on the production of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) by murine peritoneal macrophages with PGN-stimulation was investigated. In addition, RAW264.7 cells transfected with a nuclear factor-κB (NF-κB) luciferase reporter plasmid stimulated by PGN were used to study the effect of chloral hydrate on the levels NF-κB activity. Flow cytometry and western blotting were performed to investigate the expression levels of toll-like receptor 2 (TLR2) in the treated RAW264.7 cells. It was identified that chloral hydrate reduced the levels of IL-6 and TNF-α produced by the peritoneal macrophages stimulated with PGN. The levels of NF-κB activity of the RAW264.7 cells stimulated by PGN decreased following treatment with chloral hydrate, which was associated with a reduction in the expression levels of TLR2 and reduced levels of TLR2 signal transduction. These data demonstrate that chloral hydrate reduced the magnitude of the PGN-induced inflammatory macrophage response associated with lower expression levels of TLR2.

GDNF increases cell motility in human colon cancer through VEGF-VEGFR1 interaction

Glial cell line-derived neurotrophic factor (GDNF), a potent neurotrophic factor, has been shown to affect cancer cell metastasis and invasion. However, the molecular mechanisms underlying GDNF-induced colon cancer cell migration remain unclear. GDNF is found to be positively correlated with malignancy in human colon cancer patients. The migratory activities of two human colon cancer cell lines, HCT116 and SW480, were found to be enhanced in the presence of human GDNF. The expression of vascular endothelial growth factor (VEGF) was also increased in response to GDNF stimulation, along with VEGF mRNA expression and transcriptional activity. The enhancement of GDNF-induced cancer cell migration was antagonized by a VEGF-neutralizing antibody. Our results also showed that the expression of VEGF receptor 1 (VEGFR1) was increased in response to GDNF stimulation, whereas GDNF-induced cancer cell migration was reduced by a VEGFR inhibitor. The GDNF-induced VEGF expression was regulated by the p38 and PI3K/Akt signaling pathways. Treatment with GDNF increased nuclear hypoxia-inducible factor 1 α (HIF1α) accumulation and its transcriptional activity in a time-dependent manner. Moreover, GDNF increased hypoxia responsive element (HRE)-containing VEGF promoter transcriptional activity but not that of the HRE-deletion VEGF promoter construct. Inhibition of HIF1α by a pharmacological inhibitor or dominant-negative mutant reduced the GDNF-induced migratory activity in human colon cancer cells. These results indicate that GDNF enhances the migration of colon cancer cells by increasing VEGF-VEGFR interaction, which is mainly regulated by the p38, PI3K/Akt, and HIF1α signaling pathways.

Tanshinone IIA inhibits lipopolysaccharide-induced MUC1 overexpression in alveolar epithelial cells

The anti-inflammatory function of tanshinone IIA (TIIA), an active natural compound from Chinese herbal medicine Danshen, has been well recognized, and therefore TIIA has been widely used to treat various inflammatory conditions associated with cardiac and lung diseases. Mucin 1 (Muc1) plays important anti-inflammatory roles in resolution of acute lung inflammation. In this study, we investigated the effects of TIIA on LPS-induced acute lung inflammation, as well as its relationship to Muc1 expression in mouse lung and MUC1 in human alveolar epithelial cells. TIIA pretreatment significantly inhibited LPS-induced pulmonary inflammation in both Muc1 wild-type (Muc1(+/+)) and knockout (Muc1(-/-)) mice, as manifested by reduced neutrophil infiltration and reduced TNF-α and keratinocyte chemoattractant levels in bronchoalveolar lavage fluid. The inhibitory effects of TIIA on airway inflammation were associated with reduced expression of Muc1 in Muc1(+/+) mouse lung. Moreover, pretreatment with TIIA significantly inhibited LPS-induced MUC1 expression and TNF-α release in A549 alveolar epithelial cells. TNF-α upregulated MUC1 mRNA and protein expression in A549 cells, which was inhibited by pretreatment with TIIA. The LPS-induced MUC1 expression was blocked when A549 cells were transfected with siRNA targeting for TNF-α receptor 1. Furthermore, TIIA inhibited LPS-induced nuclear translocation of NF-κB and upregulation of Toll-like receptor 4 in A549 cells. Taken together, these results demonstrate that TIIA suppressed LPS-induced acute lung inflammation regardless of the presence of Muc1, and TIIA inhibited LPS- and TNF-α-induced MUC1/Muc1 expression in airway epithelial cells, suggesting that MUC1/Muc1 does not account for the mechanisms of the anti-inflammatory effects of TIIA in the airway.

Salmonella enhance chemosensitivity in tumor through connexin 43 upregulation

The use of preferentially replicating bacteria as oncolytic agents is one of the innovative approaches for the treatment of cancer. The capability of Salmonella to disperse within tumors and hence to delay tumor growth was augmented when combined with chemotherapy. This work is warranted to elucidate the underlying mechanism of antitumor effects by the combination therapy of Salmonella and cisplatin. The presence of functional gap junctions is highly relevant for the success of chemotherapy. Following Salmonella treatment, dose- and time-dependent upregulation of connexin 43 (Cx43) expressions were observed. Moreover, Salmonella significantly enhanced gap intercellular communication (GJIC), as revealed by the fluorescent dye scrape loading assay. To study the pathway underlying these Salmonella-induced effects, we found that Salmonella induced a significant increase in mitogen-activated protein kinases (MAPK) signaling pathways. The Salmonella-induced upregulation of Cx43 was prevented by treatment of cells with the phosphorylated p38 inhibitor, but not phosphorylated extracellular signal-regulated kinase (pERK) inhibitor or phosphorylated c-jun N terminal kinase (pJNK) inhibitor. Specific knockdown of Cx43 had an inhibitory effect on GJIC and resulted in a reduction of cell death after Salmonella and cisplatin treatment. Our results suggest that accumulation of Salmonella in tumor sites leads to increase Cx43 gap junction communication and enhances the combination of Salmonella and cisplatin therapeutic effects.

Interferon-α induces nitric oxide synthase expression and haem oxygenase-1 down-regulation in microglia: implications of cellular mechanism of IFN-α-induced depression

Substantiating evidence for the inflammation theory of depression is that interferon-alpha (IFN-α) induces clinical depression. Despite numerous researches on neurochemical and neuroendocrinological mechanisms from human and animal studies, the direct mechanisms of IFN-α at cellular levels are still lacking. In this study, we aimed to identify the cellular mechanisms for IFN-α-induced neuroinflammatory response with the murine BV-2 microglia cell line. IFN-α potently induced nitric oxide synthase (iNOS) and nitric oxide (NO) release and down-regulated haem oxygenase-1 (HO-1) expression, which could be dampened by Janus kinase 1 (JAK1) and c-Jun NH2-terminal kinase (JNK) inhibition, respectively. IFN-α activated JAK1, JNK, signal transducers and activators of transcription (STAT)1 and STAT3, but not extracellular signal-regulated kinases (ERK) and phosphoinositide 3 (PI3) kinase, signal pathways. The transfection with STAT1 and STAT3 siRNA also inhibited IFN-α-induced iNOS/NO expression and HO-1 down-regulation. The HO-1 activator, CoppIX, reversed iNOS/NO up-regulation and HO-1 down-regulation induced by IFN-α. On the other hand, a knockdown of HO-1 expression enhanced IFN-α-induced iNOS/NO expression. The effects of IFN-α-induced iNOS/NO up-regulation and HO-1 down-regulation in microglia are associated with JAK1/JNK/STAT1 and STAT3 signalling pathways. The different effects between IFN-α and IFN-γ on HO-1 regulation and ERK phosphorylation might provide a possible explanation of different risk in their induction of neuropsychiatric adverse effects in clinical and animal studies. The results from this study add the missing part of direct cellular mechanisms for IFN-α-induced depression.

Toll-like receptor 2 mediates peripheral nerve injury-induced NADPH oxidase 2 expression in spinal cord microglia

We have previously reported that NADPH oxidase 2 (Nox2) is up-regulated in spinal cord microglia after spinal nerve injury, demonstrating that it is critical for microglia activation and subsequent pain hypersensitivity. However, the mechanisms and molecules involved in Nox2 induction have not been elucidated. Previous studies have shown that Toll-like receptors (TLRs) are involved in nerve injury-induced spinal cord microglia activation. In this study, we investigated the role of TLR in Nox2 expression in spinal cord microglia after peripheral nerve injury. Studies using TLR knock-out mice have shown that nerve injury-induced microglial Nox2 up-regulation is abrogated in TLR2 but not in TLR3 or -4 knock-out mice. Intrathecal injection of lipoteichoic acid, a TLR2 agonist, induced Nox2 expression in spinal cord microglia both at the mRNA and protein levels. Similarly, lipoteichoic acid stimulation induced Nox2 expression and reactive oxygen species production in primary spinal cord glial cells in vitro. Studies on intracellular signaling pathways indicate that NF-κB and p38 MAP kinase activation is required for TLR2-induced Nox2 expression in glial cells. Conclusively, our data show that TLR2 mediates nerve injury-induced Nox2 gene expression in spinal cord microglia via NF-κB and p38 activation and thereby may contribute to spinal cord microglia activation.

Desipramine protects neuronal cell death and induces heme oxygenase-1 expression in Mes23.5 dopaminergic neurons

BACKGROUND

Desipramine is known principally as a tricyclic antidepressant drug used to promote recovery of depressed patients. It has also been used in a number of other psychiatric and medical conditions. The present study is the first to investigate the neuroprotective effect of desipramine.

METHODOLOGY/PRINCIPAL FINDINGS

Mes23.5 dopaminergic cells were used to examine neuroprotective effect of desipramine. Western blot, reverse transcription-PCR, MTT assay, siRNA transfection and electrophoretic mobility shift assay (EMSA) were carried out to assess the effects of desipramine. Desipramine induces endogenous anti-oxidative enzyme, heme oxygenase-1 (HO-1) protein and mRNA expression in concentration- and time-dependent manners. A different type of antidepressant SSRI (selective serotonin reuptake inhibitor), fluoxetine also shows similar effects of desipramine on HO-1 expression. Moreover, desipramine induces HO-1 expression through activation of ERK and JNK signaling pathways. Desipramine also increases NF-E2-related factor-2 (Nrf2) accumulation in the nucleus and enhances Nrf2-DNA binding activity. Moreover, desipramine-mediated increase of HO-1 expression is reduced by transfection with siRNA against Nrf2. On the other hand, pretreatment of desipramine protects neuronal cells against rotenone- and 6-hydroxydopamine (6-OHDA)-induced neuronal death. Furthermore, inhibition of HO-1 activity by a HO-1 pharmacological inhibitor, ZnPP IX, attenuates the neuroprotective effect of desipramine. Otherwise, activation of HO-1 activity by HO-1 activator and inducer protect 6-OHDA-induced neuronal death.

CONCLUSIONS/SIGNIFICANCE

These findings suggest that desipramine-increased HO-1 expression is mediated by Nrf2 activation through the ERK and JNK signaling pathways. Our results also suggest that desipramine provides a novel effect of neuroprotection, and neurodegenerative process might play an important role in depression disorder.

Developing connections amongst key cytokines and dysregulated germinal centers in autoimmunity

Systemic autoimmunity owing to overactivity of Tfh and dysregulated germinal centers has been described in mice and humans. Cytokines such as IL-21, IFN-γ, IL-6 and IL-17 are elevated in the plasma of mouse models of lupus, arthritis, and multiple sclerosis, and in subsets of patients with autoimmune disease. Monoclonal antibodies targeting these cytokines are entering clinical trials. While these cytokines exert pleiotropic effects on immune cells and organs, it is becoming clear that each and all of them can profoundly regulate Tfh numbers and/or function and induce or maintain the aberrant germinal center reactions that lead to pathogenic autoantibody formation. Here we review recent discoveries into the roles of IL-21, IFN-γ, IL-6, and IL-17 in germinal center responses and antibody-driven autoimmunity. These new insights used in conjunction with biomarkers of an overactive Tfh pathway may help stratify patients to rationalize the use of emerging monoclonal anti-cytokine antibody therapies.