CM1, a Chrysin Derivative, Protects from Endotoxin-Induced Lethal Shock by Regulating the Excessive Activation of Inflammatory Responses.

Sepsis, a leading cause of death worldwide, is a harmful inflammatory condition that is primarily caused by an endotoxin released by Gram-negative bacteria. Effective targeted therapeutic strategies for sepsis are lacking. In this study, using an in vitro and in vivo mouse model, we demonstrated that CM1, a derivative of the natural polyphenol chrysin, exerts an anti-inflammatory effect by inducing the expression of the ubiquitin-editing protein TNFAIP3 and the NAD-dependent deacetylase sirtuin 1 (SIRT1). Interestingly, CM1 attenuated the Toll-like receptor 4 (TLR4)-induced production of inflammatory cytokines by inhibiting the extracellular-signal-regulated kinase (ERK)/MAPK and nuclear factor kappa B (NF-κB) signalling pathways. In addition, CM1 induced the expression of TNFAIP3 and SIRT1 on TLR4-stimulated primary macrophages; however, the anti-inflammatory effect of CM1 was abolished by the siRNA-mediated silencing of TNFAPI3 or by the genetic or pharmacologic inhibition of SIRT1. Importantly, intravenous administration of CM1 resulted in decreased susceptibility to endotoxin-induced sepsis, thereby attenuating the production of pro-inflammatory cytokines and neutrophil infiltration into the lung compared to control mice. Collectively, these findings demonstrate that CM1 has therapeutic potential for diverse inflammatory diseases, including sepsis.

TNF in Human Tuberculosis: A Double-Edged Sword.

TNF, a pleiotropic proinflammatory cytokine, is important for protective immunity and immunopathology during Mycobacterium tuberculosis (Mtb) infection, which causes tuberculosis (TB) in humans. TNF is produced primarily by phagocytes in the lungs during the early stages of Mtb infection and performs diverse physiological and pathological functions by binding to its receptors in a context-dependent manner. TNF is essential for granuloma formation, chronic infection prevention, and macrophage recruitment to and activation at the site of infection. In animal models, TNF, in cooperation with chemokines, contributes to the initiation, maintenance, and clearance of mycobacteria in granulomas. Although anti-TNF therapy is effective against immune diseases such as rheumatoid arthritis, it carries the risk of reactivating TB. Furthermore, TNF-associated inflammation contributes to cachexia in patients with TB. This review focuses on the multifaceted role of TNF in the pathogenesis and prevention of TB and underscores the importance of investigating the functions of TNF and its receptors in the establishment of protective immunity against and in the pathology of TB. Such investigations will facilitate the development of therapeutic strategies that target TNF signaling, which makes beneficial and detrimental contributions to the pathogenesis of TB.

Expression of cytokines and co-stimulatory molecules in the Toxoplasma gondii-infected dendritic cells of C57BL/6 and BALB/c mice.

Toxoplasma gondii is an intracellular protozoan parasite which can infect most warm-blooded animals and humans. Among the different mouse models, C57BL/6 mice are more susceptible to T. gondii infection compared to BALB/c mice, and this increased susceptibility has been attributed to various factors, including T-cell responses. Dendritic cells (DCs) are the most prominent type of antigen-presenting cells and regulate the host immune response, including the response of T-cells. However, differences in the DC responses of these mouse strains to T. gondii infection have yet to be characterized. In this study, we cultured bone marrow-derived DCs (BMDCs) from BALB/c and C57BL/6 mice. These cells were infected with T. gondii. The activation of the BMDCs was assessed based on the expression of cell surface markers and cytokines. In the BMDCs of both mouse strains, we detected significant increases in the expression of cell surface T-cell co-stimulatory molecules (major histocompatibility complex (MHC) II, CD40, CD80, and CD86) and cytokines (tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-12p40, IL-1ß, and IL-10) from 3 h post-T. gondii infection. The expression of MHC II, CD40, CD80, CD86, IFN-γ, IL-12p40, and IL-1ß was significantly higher in the T. gondii-infected BMDCs obtained from the C57BL/6 mice than in those from the BALB/c mice. These findings indicate that differences in the activation status of the BMDCs in the BALB/c and C57BL/6 mice may account for their differential susceptibility to T. gondii.

SIRT1 Promotes Host Protective Immunity against Toxoplasma gondii by Controlling the FoxO-Autophagy Axis via the AMPK and PI3K/AKT Signalling Pathways.

Sirtuin 1 (SIRT1) regulates cellular processes by deacetylating non-histone targets, including transcription factors and intracellular signalling mediators; thus, its abnormal activation is closely linked to the pathophysiology of several diseases. However, its function in Toxoplasma gondii infection is unclear. We found that SIRT1 contributes to autophagy activation via the AMP-activated protein kinase (AMPK) and PI3K/AKT signalling pathways, promoting anti-Toxoplasma responses. Myeloid-specific Sirt1-/- mice exhibited an increased cyst burden in brain tissue compared to wild-type mice following infection with the avirulent ME49 strain. Consistently, the intracellular survival of T. gondii was markedly increased in Sirt1-deficient bone-marrow-derived macrophages (BMDMs). In contrast, the activation of SIRT1 by resveratrol resulted in not only the induction of autophagy but also a significantly increased anti-Toxoplasma effect. Notably, SIRT1 regulates the FoxO-autophagy axis in several human diseases. Importantly, the T. gondii-induced phosphorylation, acetylation, and cytosolic translocation of FoxO1 was enhanced in Sirt1-deficient BMDMs and the pharmacological inhibition of PI3K/AKT signalling reduced the cytosolic translocation of FoxO1 in BMDMs infected with T. gondii. Further, the CaMKK2-dependent AMPK signalling pathway is responsible for the effect of SIRT1 on the FoxO3a-autophagy axis and for its anti-Toxoplasma activity. Collectively, our findings reveal a previously unappreciated role for SIRT1 in Toxoplasma infection.

Fenofibrate Exerts Anticancer Effects on Human Cervical Cancer HeLa Cells via Caspase-Dependent Apoptosis and Cell Cycle Arrest.

OBJECTIVE: In the present study, we attempted to identify the effects of fenofibrate on human cervical cancer cells. METHODS: The cytotoxicity of fenofibrate in cervical cancer cells was determined by Cell Counting Kit-8. Immunoblotting assay was used to determine the protein expression of caspase-3, poly ADP-ribose polymerase cleavage, B-cell lymphoma 2 family protein expression, microtubule-associated protein 1A/1B-light chain 3 (LC3), as well as cyclins and cyclin-dependent kinases. Immunofluorescence imaging was used to determine the expression of cleaved caspase-3 and LC3. Flow cytometry was used to determine cell cycle and apoptosis. RESULTS: We first showed that fenofibrate treatment reduced cell viability in HeLa cervical cancer cells in a dose-dependent manner at 24 h and 48 h. Importantly, fenofibrate-induced cell death was mediated through cell cycle arrest in the G0-G1 phase and caspase-dependent apoptosis. Moreover, fenofibrate also induced autophagy activation in a dose-dependent manner and pharmacological inhibition of autophagy led to increase of sub-G1 phase and caspase-dependent cell death in HeLa cells. CONCLUSION: In conclusion, these data demonstrated that fenofibrate initially induced cell cycle arrest, followed by caspase-3-dependent cell death in cervical cancer HeLa cells. However, fenofibrate also induced autophagy activation, which is closely related to the survival of diverse cancer cells, thus reducing the anticancer effects of fenofibrate. Therefore, the combination of an autophagy inhibitor and fenofibrate might have the potential to become a new therapeutic strategy for cervical cancer.

Trichomonas vaginalis induces apoptosis via ROS and ER stress response through ER-mitochondria crosstalk in SiHa cells.

BACKGROUND: Trichomonas vaginalis causes lesions on the cervicovaginal mucosa in women; however, its pathogenesis remains unclear. We have investigated the involvement of the endoplasmic reticulum (ER) in the induction of apoptosis by T. vaginalis and its molecular mechanisms in human cervical cancer SiHa cells. METHODS: Apoptosis, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP), ER stress response and Bcl-2 family protein expression were evaluated using immunocytochemistry, flow cytometry, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-imidacarbocyanine iodide dye staining and western blotting. RESULTS: Trichomonas vaginalis induced mitochondrial ROS production, apoptosis, the ER stress response and mitochondrial dysfunction, such as MMP depolarization and an imbalance in Bcl-2 family proteins, in SiHa cells in a parasite burden- and infection time-dependent manner. Pretreatment with N-acetyl cysteine (ROS scavenger) or 4-phenylbutyric acid (4-PBA; ER stress inhibitor) significantly alleviated apoptosis, mitochondrial ROS production, mitochondrial dysfunction and ER stress response in a dose-dependent manner. In addition, T. vaginalis induced the phosphorylation of apoptosis signal regulating kinase 1 (ASK1) and c-Jun N-terminal kinases (JNK) in SiHa cells, whereas 4-PBA or SP600125 (JNK inhibitor) pretreatment significantly attenuated ASK1/JNK phosphorylation, mitochondrial dysfunction, apoptosis and ER stress response in SiHa cells, in a dose-dependent manner. Furthermore, T. vaginalis excretory/secretory products also induced mitochondrial ROS production, apoptosis and the ER stress response in SiHa cells, in a time-dependent manner. CONCLUSIONS: Trichomonas vaginalis induces apoptosis through mitochondrial ROS and ER stress responses, and also promotes ER stress-mediated mitochondrial apoptosis via the IRE1/ASK1/JNK/Bcl-2 family protein pathways in SiHa cells. These data suggest that T. vaginalis-induced apoptosis is affected by ROS and ER stress response via ER-mitochondria crosstalk.

FAF1 downregulation by Toxoplasma gondii enables host IRF3 mobilization and promotes parasite growth.

Fas-associated factor 1 (FAF1) has gained a reputation as a member of the FAS death-inducing signalling complex. However, the role of FAF1 in the immunity response is not fully understood. Here, we report that, in the human retinal pigment epithelial (RPE) cell line ARPE-19 cells, FAF1 expression level was downregulated by Toxoplasma gondii infection, and PI3K/AKT inhibitors reversed T. gondii-induced FAF1 downregulation. In silico analysis for the FAF1 promoter sequence showed the presence of a FOXO response element (FRE), which is a conserved binding site for FOXO1 transcription factor. In accordance with the finding, FOXO1 overexpression potentiated, whereas FOXO1 depletion inhibited intracellular FAF1 expression level. We also found that FAF1 downregulation by T. gondii is correlated with enhanced IRF3 transcription activity. Inhibition of PI3K/AKT pathway with specific inhibitors had no effect on the level of T. gondii-induced IRF3 phosphorylation but blocked IRF3 nuclear import and ISGs transcription. These results suggest that T. gondii can downregulate host FAF1 in PI3K/AKT/FOXO1-dependent manner, and the event is essential for IRF3 nuclear translocation to active the transcription of ISGs and thereby T. gondii proliferation.

Silver nanoparticles induce apoptosis via NOX4-derived mitochondrial reactive oxygen species and endoplasmic reticulum stress in colorectal cancer cells.

Aim: To investigate the anticancer mechanisms of silver nanoparticles (AgNPs) in colorectal cancer. Methods: Anticancer effects of AgNPs were determined in colorectal cancer HCT116 cells and xenograft mice using cellular and molecular methods. Results: AgNPs induced mitochondrial reactive oxygen species production, mitochondrial dysfunction and endoplasmic reticulum (ER) stress responses through NOX4 and led to HCT116 cell apoptosis. Pretreatment with DPI or 4-PBA significantly inhibited mitochondrial reactive oxygen species production, apoptosis, ER stress response, NOX4 expression and mitochondrial dysfunction in AgNP-treated HCT116 cells. AgNPs also significantly suppressed HCT116 cell-based xenograft tumor growth in nude mice by inducing apoptosis and ER stress responses. Conclusion: AgNPs exert anticancer effects against colorectal cancer via ROS- and ER stress-related mitochondrial apoptosis pathways.

The Role of PI3K/AKT Pathway and NADPH Oxidase 4 in Host ROS Manipulation by Toxoplasma gondii.

Dendritic cell is one of the first innate immune cell to encounter T. gondii after the parasite crosses the host intestinal epithelium. T. gondii requires intact DC as a carrier to infiltrate into host central nervous system (CNS) without being detected or eliminated by host defense system. The mechanism by which T. gondii avoids innate immune defense of host cell, especially in the dendritic cell is unknown. Therefore, we examined the role of host PI3K/AKT signaling pathway activation by T. gondii in dendritic cell. T. gondii infection or T. gondii excretory/secretory antigen (TgESA) treatment to the murine dendritic cell line DC2.4 induced AKT phosphorylation, and treatment of PI3K inhibitors effectively suppressed the T. gondii proliferation but had no effect on infection rate or invasion rate. Furthermore, it is found that T. gondii or TgESA can reduce H2O2-induced intracellular reactive oxygen species (ROS) as well as host endogenous ROS via PI3K/AKT pathway activation. While searching for the main source of the ROS, we found that NADPH oxidase 4 (NOX4) expression was controlled by T. gondii infection or TgESA treatment, which is in correlation with previous observation of the ROS reduction by identical treatments. These findings suggest that the manipulation of the host PI3K/AKT signaling pathway and NOX4 expression is an essential mechanism for the down-regulation of ROS, and therefore, for the survival and the proliferation of T. gondii.

Involvement of endoplasmic reticulum stress response and IRE1-mediated ASK1/JNK/Mcl-1 pathways in silver nanoparticle-induced apoptosis of human retinal pigment epithelial cells.

Silver nanoparticles (AgNPs) have cytotoxic effects on various human cell types. The endoplasmic reticulum (ER) is very sensitive to cytotoxic damage. Retina tissue is easily affected by internal and external stimuli. However, the effect of AgNPs on human retinal cells is not known. This study examined the effect of AgNPs on ER stress induction and their mechanism of action in human retinal pigment epithelium (RPE) ARPE-19 cells. We found that AgNPs significantly increased ARPE-19 cell cytotoxicity and stimulated caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavage, as well as mitochondrial membrane potential (MMP) depolarization, in ARPE-19 cells in a dose-dependent manner (0.2-5 µg/mL for 18 h). AgNPs (5 µg/mL for 18 h) induced several signature ER stress markers, as indicated by the upregulated expressions of CCAAT/enhancer-binding protein-homologous protein (CHOP), phosphorylated protein kinase RNA-like ER kinase (PERK), eukaryotic initiation factor 2α (eIF2α), and inositol-requiring protein 1 (IRE1), and cleaved activating transcription factor 6 (ATF6). AgNPs also activated ASK1 and JNK in ARPE-19 cells, and induced increases in Bax and Puma expressions, as well as a decrease in Mcl-1 expression. However, inhibition of the ER stress response by pretreatment with 4-PBA included apparently and dose-dependently reduced levels of p-PERK, p-IRE1, CHOP, cleaved ATF6, p-ASK1, p-JNK, cleaved caspase-3, procaspase-12, and MMP depolarization in AgNP-treated ARPE-19 cells; it also led to significantly increased Mcl-1 protein levels in a dose-dependent manner in ARPE-19 cells. Pretreatment with JNK inhibitor SP600125 significantly attenuated caspase-3 cleavage and MMP depolarization and increased Mcl-1 protein levels in AgNPs-treated ARPE-19 cells in a dose-dependent manner. Hence, our study demonstrated that AgNPs induced apoptosis in human RPE ARPE-19 cells by ER stress response and ER stress-dependent mitochondrial apoptosis via the IRE1/ASK1/JNK/Mcl-1 pathways.

Inflammasome and Mitophagy Connection in Health and Disease.

The inflammasome is a large intracellular protein complex that activates inflammatory caspase-1 and induces the maturation of interleukin (IL)-1ß and IL-18. Mitophagy plays an essential role in the maintenance of mitochondrial homeostasis during stress. Previous studies have indicated compelling evidence of the crosstalk between inflammasome and mitophagy. Mitophagy regulation of the inflammasome, or vice versa, is crucial for various biological functions, such as controlling inflammation and metabolism, immune and anti-tumor responses, and pyroptotic cell death. Uncontrolled regulation of the inflammasome often results in pathological inflammation and pyroptosis, and causes a variety of human diseases, including metabolic and inflammatory diseases, infection, and cancer. Here, we discuss how improved understanding of the interactions between inflammasome and mitophagy can lead to novel therapies against various disease pathologies, and how the inflammasome-mitophagy connection is currently being targeted pharmacologically by diverse agents and small molecules. A deeper understanding of the inflammasome-mitophagy connection will provide new insights into human health and disease through the balance between mitochondrial clearance and pathology.

VEGF Production Is Regulated by the AKT/ERK1/2 Signaling Pathway and Controls the Proliferation of Toxoplasma gondii in ARPE-19 Cells.

The retina is the primary site of Toxoplasma gondii infection in the eye, and choroidal neovascularization in ocular toxoplasmosis is one of the most important causes of visual impairment. Vascular endothelial growth factor (VEGF) is one of the key regulators of blood vessel development, however, little is known about the mechanisms of T. gondii-induced VEGF production in ocular toxoplasmosis. Here, we investigate the effect of T. gondii on VEGF production regulation in human retinal pigment epithelium ARPE-19 cells and attempted to unveil the underlying mechanism of this event by focusing on the interaction between parasite and the selected host intracellular signaling pathways. T. gondii infection increased the expression of VEGF mRNA and protein in ARPE-19 cells in parasite burden- and infection time-dependent manner. The proportional increase of VEGF upstream regulators, HIF-1α and HO-1, was also observed. T. gondii induced the activation of host p-AKT, p-ERK1/2, and p-p38 MAPK in ARPE-19 cells in a parasite-burden dependent manner. However, VEGF expression decreased after the pre-treatment with PI3K inhibitors (LY294002 and GDC-0941), ERK1/2 inhibitor (PD098059), and p38 MAPK inhibitor (SB203580), but not JNK inhibitor (SP600125), in a dose-dependent manner. The anti-VEGF agent bevacizumab or VEGF siRNA transfection prominently inhibited the activation of p-AKT and p-ERK1/2, but not p-p38 MAPK and JNK1/2 in T. gondii-infected ARPE-19 cells. Bevacizumab treatment or VEGF siRNA transfection significantly inhibited the proliferation of T. gondii tachyzoites in the host cell, dose-dependently, but not invasion of parasites. VEGF-receptor 2 (VEGF-R2) antagonist, SU5416, attenuated VEGF production and tachyzoite proliferation in T. gondii-infected ARPE-19 cells in a dose-dependent manner. Collectively, T. gondii prominently induces VEGF production in ARPE-19 cells, and VEGF and AKT/ERK1/2 signaling pathways mutually regulate each other in T. gondii-infected ARPE-19 cells, but not p38 MAPK and JNK1/2 signaling pathways. VEGF and VEGF-R2 control the parasite proliferation in T. gondii-infected ARPE-19 cells. From this study, we revealed the putative mechanisms for VEGF induction as well as the existence of positive feedback between VEGF and PI3K/MAPK signaling pathways in T. gondii-infected retinal pigment epithelium.

4-Hydroxybenzaldehyde Restricts the Intracellular Growth of Toxoplasma gondii by Inducing SIRT1-Mediated Autophagy in Macrophages.

Toxoplasma gondii is an intracellular protozoan parasite that infects approximately one third of the human popu- lation worldwide. Considering the toxicity and side effects of anti-toxoplasma medications, it is important to develop effec- tive drug alternatives with fewer and less severe off-target effects. In this study, we found that 4-hydroxybenzaldehyde (4- HBA) induced autophagy and the expression of NAD-dependent protein deacetylase sirtuin-1 (SIRT1) in primary murine bone marrow-derived macrophages (BMDMs). Interestingly, treatment of BMDMs with 4-HBA significantly reduced the number of macrophages infected with T. gondii and the proliferation of T. gondii in infected cells. This effect was impaired by pretreating the macrophages with 3-methyladenine or wortmannin (selective autophagy inhibitors) or with sirtinol or EX527 (SIRT1 inhibitors). Moreover, we found that pharmacological inhibition of SIRT1 prevented 4-HBA-mediated expres- sion of LC3-phosphatidylethanolamine conjugate (LC3-II) and the colocalization of T. gondii parasitophorous vacuoles with autophagosomes in BMDMs. These data suggest that 4-HBA promotes antiparasitic host responses by activating SIRT1- mediated autophagy, and 4-HBA might be a promising therapeutic alternative for the treatment of toxoplasmosis.

RM, a novel resveratrol derivative, attenuates inflammatory responses induced by lipopolysaccharide via selectively increasing the Tollip protein in macrophages: A partial mechanism with therapeutic potential in an inflammatory setting.

Although the novel resveratrol derivative RM has therapeutic potential for the treatment of inflammatory bowel disease, little is currently known regarding the manner whereby RM regulates excessive inflammatory responses. In this study, we initially investigated the molecular mechanisms underlying the anti-inflammatory effects induced by RM in Toll-like receptor (TLR)-activated macrophages. Upon stimulation with lipopolysaccharide, we found that RM-treated activated macrophages down-regulated the increase in pro-inflammatory cytokines (TNF-α, IL-6, IL-1ß, and IL-12p70), nitric oxide (NO) production, and activating interleukin-1 receptor-associated kinase 1 (IRAK-1) phosphorylation, mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signaling pathways. Interestingly, the TLR negative regulator Toll-interacting protein (Tollip) was selectively enhanced during RM stimulation in time- and dose-dependent manners. In response to knockdown of Tollip expression by RNA interference, RM-treated activated macrophages showed augmented expression of inflammatory mediators (pro-inflammatory cytokines, NO, inducible nitric oxidase, and cyclooxygenase-2, and surface molecules) and restored the expression of MAPK and NF-κB signals inhibited by RM treatment. Taken together, our findings indicate that RM has therapeutic potential for treating TLR-induced inflammatory diseases via the promotion of Tollip expression.

Omega-3 Polyunsaturated Fatty Acids Prevent Toxoplasma gondii Infection by Inducing Autophagy via AMPK Activation.

Omega-3 polyunsaturated fatty acids (ω3-PUFAs) have potential protective activity in a variety of infectious diseases, but their actions and underlying mechanisms in Toxoplasma gondii infection remain poorly understood. Here, we report that docosahexaenoic acid (DHA) robustly induced autophagy in murine bone marrow-derived macrophages (BMDMs). Treatment of T. gondii-infected macrophages with DHA resulted in colocalization of Toxoplasma parasitophorous vacuoles with autophagosomes and reduced intracellular survival of T. gondii. The autophagic and anti-Toxoplasma effects induced by DHA were mediated by AMP-activated protein kinase (AMPK) signaling. Importantly, BMDMs isolated from Fat-1 transgenic mice, a well-known animal model capable of synthesizing ω3-PUFAs from ω6-PUFAs, showed increased activation of autophagy and AMPK, leading to reduced intracellular survival of T. gondii when compared with wild-type BMDMs. Moreover, Fat-1 transgenic mice exhibited lower cyst burden in the brain following infection with the avirulent strain ME49 than wild-type mice. Collectively, our results revealed mechanisms by which endogenous ω3-PUFAs and DHA control T. gondii infection and suggest that ω3-PUFAs might serve as therapeutic candidate to prevent toxoplasmosis and infection with other intracellular protozoan parasites.

Dipenyleneiodonium Induces Growth Inhibition of Toxoplasma gondii through ROS Induction in ARPE-19 Cells.

Based on the reactive oxygen species (ROS) regulatory properties of diphenyleneiodonium (DPI), we investigated the effects of DPI on host-infected T. gondii proliferation and determined specific concentration that inhibit the intracellular parasite growth but without severe toxic effect on human retinal pigment epithelial (ARPE-19) cells. As a result, it is observed that host superoxide, mitochondria superoxide and H2O2 levels can be increased by DPI, significantly, followed by suppression of T. gondii infection and proliferation. The involvement of ROS in anti-parasitic effect of DPI was confirmed by finding that DPI effect on T. gondii can be reversed by ROS scavengers, N-acetyl-L-cysteine and ascorbic acid. These results suggest that, in ARPE-19 cell, DPI can enhance host ROS generation to prevent T. gondii growth. Our study showed DPI is capable of suppressing T. gondii growth in host cells while minimizing the un-favorite side-effect to host cell. These results imply that DPI as a promising candidate material for novel drug development that can ameliorate toxoplasmosis based on ROS regulation.

Therapeutic Potential of Gamma-Irradiated Resveratrol in Ulcerative Colitis via the Anti-Inflammatory Activity and Differentiation of Tolerogenic Dendritic Cells.

BACKGROUND/AIMS: New therapeutic strategies and the development of treatments against inflammatory bowel disease (IBD) require the initiation of immune tolerance and inhibition of excessive inflammation. Resveratrol, a polyphenolic compound, is a powerful immunosuppressor, but it can lead to apoptotic death of normal cells at high concentrations. When we induced a structural modification of resveratrol by gamma irradiation, we were able to investigate the potential tolerogenic and anti-inflammatory effect of a new radiolysis product (named γ-Res) during dendritic cell (DC) activation/differentiation. METHODS: The potential tolerogenic and anti-inflammatory effect of γ-Res were investigated by cytokine secretion, surface molecule expression, antigen uptake ability, antigen presenting ability, signaling pathway, and mixed lymphocyte reaction (MLR) assay using enzyme-linked immunosorbent assay (ELISA), western blot and flow cytometry. RESULTS: LPS-activated DCs treated with γ-Res exhibited alterations in their mature and functional statuses including a strongly inhibited cytokine production, surface molecule expression, antigen-presenting ability, and activated DC-induced T cell proliferation/activation. In addition, the DCs generated by the γ-Res treatment during DC differentiation induced a decreased surface molecule expression and increased IL-10 production without altering the levels of TNF-α and IL-12p70, thereby promoting the inhibition of T cell proliferation/activation and the induction of regulatory T cells via interaction with DCs in vitro. Furthermore, in the in vivo DSS-induced colitis model, γ-Res treatment conferred protective immunity with a decrease in IFN-γ+CD4+ and IL-17A+CD4+ T cells and imparted protection by reducing the disease activity and histological disease score and increasing the survival rate in dextran sulfate sodium (DSS)-induced colitis in mice. CONCLUSION: Thus, our results suggest that γ-Res may be an excellent candidate for use in IBD treatment.

Protective effects of a traditional herbal extract from Stellaria dichotoma var. lanceolata against Mycobacterium abscessus infections.

Stellaria dichotoma var. lanceolata (SdLv), a member of the Caryophyllaceae, is a traditional herbal medicine that has been used to treat fever, night sweats, and malaria in East Asia. Inflammation plays an essential role in both host defense and pathogenesis during infection by diverse intracellular pathogens. Herein, we showed that an herbal extract from SdLv effectively attenuated inflammatory responses from infection of Mycobacterium abscessus (Mab), but not Toxoplasma gondii (T. gondii). In primary murine macrophages, Mab infection resulted in the rapid activation of nuclear factor (NF)-κB and mitogen-activated protein kinase (MAPK), as well as in the generation of proinflammatory cytokines, such as tumor necrosis factor α and interleukin-6, which were all significantly inhibited by pretreatment with SdLv. However, herbal extracts from Bupleurum chinense DC. (Buch) or Bupleurum falcatum L. (Bufa) did not affect M. abs-induced activation of proinflammatory responses. Importantly, we demonstrated that generation of intracellular reactive oxygen species, which are important signaling intermediaries in the activation of NF-κB and the MAPK signaling pathway, was rapidly increased in Mab-infected macrophages, and this was effectively suppressed by pretreatment with SdLv, but not Buch and Bufa. We further found that the treatment of Buch and Bufa, but not SdLv, led to the activation of NF-κB and the MAPK signaling pathway and the generation of intracellular reactive oxygen species. Moreover, oral administration of SdLv significantly reduced lethality in Mab-infected mice. Collectively, these results suggest the possible use of SdLv as an effective treatment for Mab infection.

ESRRA (estrogen-related receptor α) is a key coordinator of transcriptional and post-translational activation of autophagy to promote innate host defense.

The orphan nuclear receptor ESRRA (estrogen-related receptor α) is a key regulator of energy homeostasis and mitochondrial function. Macroautophagy/autophagy, an intracellular degradation process, is a critical innate effector against intracellular microbes. Here, we demonstrate that ESRRA is required for the activation of autophagy to promote innate antimicrobial defense against mycobacterial infection. AMP-activated protein kinase pathway and SIRT1 (sirtuin 1) activation led to induction of ESRRA, which is essential for autophagosome formation, in bone marrow-derived macrophages. ESRRA enhanced the transcriptional activation of numerous autophagy-related (Atg) genes containing ERR response elements in their promoter regions. Furthermore, ESRRA, operating in a feed-forward loop with SIRT1, was required for autophagy activation through deacetylation of ATG5, BECN1, and ATG7. Importantly, ESRRA deficiency resulted in a decrease of phagosomal maturation and antimicrobial responses against mycobacterial infection. Thus, we identify ESRRA as a critical activator of autophagy via both transcriptional and post-translational control to promote antimicrobial host responses.

NADPH oxidase 4 is required for the generation of macrophage migration inhibitory factor and host defense against Toxoplasma gondii infection.

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (Nox) are an important family of catalytic enzymes that generate reactive oxygen species (ROS), which mediate the regulation of diverse cellular functions. Although phagocyte Nox2/gp91phox is closely associated with the activation of host innate immune responses, the roles of Nox family protein during Toxoplasma gondii (T. gondii) infection have not been fully investigated. Here, we found that T. gondii-mediated ROS production was required for the upregulation of macrophage migration inhibitory factor (MIF) mRNA and protein levels via activation of mitogen-activated protein kinase and nuclear factor-κB signaling in macrophages. Interestingly, MIF knockdown led to a significant increase in the survival of intracellular T. gondii in bone marrow-derived macrophages (BMDMs). Moreover, Nox4 deficiency, but not Nox2/gp91phox and the cytosolic subunit p47phox, resulted in enhanced survival of the intracellular T. gondii RH strain and impaired expression of T. gondii-mediated MIF in BMDMs. Additionally, Nox4-deficient mice showed increased susceptibility to virulent RH strain infection and increased cyst burden in brain tissues and low levels of MIF expression following infection with the avirulent ME49 strain. Collectively, our findings indicate that Nox4-mediated ROS generation plays a central role in MIF production and resistance to T. gondii infection.