TLR9-ERK-mTOR signaling is critical for autophagic cell death induced by CpG oligodeoxynucleotide 107 combined with irradiation in glioma cells

TLR9 and Glioma: Friends or Foes?

Toll-like receptor 9 (TLR9) is an intracellular innate immunity receptor that plays a vital role in chronic inflammation and in recognizing pathogenic and self-DNA in immune complexes. This activation of intracellular signaling leads to the transcription of either immune-related or malignancy genes through specific transcription factors. Thus, it has been hypothesized that TLR9 may cause glioma. This article reviews the roles of TLR9 in the pathogenesis of glioma and its related signaling molecules in either defending or promoting glioma. TLR9 mediates the invasion-induced hypoxia of brain cancer cells by the activation of matrix metalloproteinases (2, 9, and 13) in brain tissues. In contrast, the combination of the TLR9 agonist CpG ODN to radiotherapy boosts the role of T cells in antitumor effects. The TLR9 agonist CpG ODN 107 also enhances the radiosensitivity of human glioma U87 cells by blocking tumor angiogenesis. CpG enhances apoptosis in vitro and in vivo. Furthermore, it can enhance the antigen-presenting capacity of microglia, switch immune response toward CD8 T cells, and reduce the number of CD4CD25 Treg cells. CpG ODN shows promise as a potent immunotherapeutic drug against cancer, but specific cautions should be taken when activating TLR9, especially in the case of glioblastoma.

Quercetin Suppresses Human Glioblastoma Migration and Invasion via GSK3β/β-catenin/ZEB1 Signaling Pathway

High invasiveness is a biological and clinical characteristic of glioblastoma and predicts poor prognosis of patients. Quercetin, a natural flavonoid compound, exhibits anticancer activity. However, we have a limited understanding of the possible underlying mechanism of quercetin in glioblastoma. In this study, we investigated the anticancer effect of quercetin in human glioblastoma cells. Our results showed that quercetin markedly suppressed the viability of glioblastoma cells in vitro and in vivo, and significantly inhibited glioblastoma cell migration and invasion. Moreover, quercetin reversed EMT-like mesenchymal phenotype and reduced the expression levels of EMT-related markers. Furthermore, we found that quercetin suppressed GSK-3β/β-catenin/ZEB1 signaling in glioblastoma. Taken together, our results demonstrate that quercetin inhibited migration and invasion of human glioma cells by suppressing GSK3β/β-catenin/ZEB1 signaling. Our study provides evidence that quercetin is a promising therapeutic natural compound to treat glioblastoma.

LACpG10-HL Functions Effectively in Antibiotic-Free and Healthy Husbandry by Improving the Innate Immunity

Antibiotics are broadly restricted in modern husbandry farming, necessitating the need for efficient and low-cost immunomodulatory preparations in antibiotic-free and healthful farming. As is known to all, CpG oligonucleotides (CpG-ODNs, an effective innate immunostimulatory agent) recognized by TLR9 in mammals (while TLR21 in avians) could collaborate with some united agent to induce stronger immune responses, but the cost is prohibitively expensive for farmers. Here, considering the coordination between TLR2 and TLR9/TLR21, we firstly proposed the idea that the well-fermented Lactococcus lactis could be utilized as a CpG-plasmid carrier (LACpG10) to enhance the host’s innate immunity against pathogenic invasion. In the present study, after obtaining LACpG10-HL from homogenized and lyophilized recombinant strain LACpG10, we treated primary chicken lymphocytes, two cell lines (HD11 and IPEC-J2), and chickens with LACpG10-HL, CpG plasmids (pNZ8148-CpG10), and other stimulants, and respectively confirmed the effects by conducting qRT-PCR, bacterial infection assays, and a zoological experiment. Our data showed that LACpG10-HL could induce excellent innate immunity by regulating autophagy reactions, cytokine expression, and motivating PRRs. Interestingly, despite having no direct antiseptic effect, LACpG10-HL improved the antibacterial capacities of lymphocytes and enterocytes at the first line of defense. Most importantly, water-supplied LACpG10-HL treatment reduced the average adverse event rates, demonstrating that LACpG10-HL maintained its excellent immunostimulatory and protective properties under farming conditions. Our research not only contributes to revealing the satisfactory effects of LACpG10-HL but also sheds new light on a cost-effective solution with optimal immune effects in green, antibiotic-free, and healthful husbandry farming.

Toll-like receptors and toll-like receptor-targeted immunotherapy against glioma

Glioma represents a fast proliferating and highly invasive brain tumor which is resistant to current therapies and invariably recurs. Despite some advancements in anti-glioma therapies, patients’ prognosis remains poor. Toll-like receptors (TLRs) act as the first line of defense in the immune system being the detectors of those associated with bacteria, viruses, and danger signals. In the glioma microenvironment, TLRs are expressed on both immune and tumor cells, playing dual roles eliciting antitumoral (innate and adaptive immunity) and protumoral (cell proliferation, migration, invasion, and glioma stem cell maintenance) responses. Up to date, several TLR-targeting therapies have been developed aiming at glioma bulk and stem cells, infiltrating immune cells, the immune checkpoint axis, among others. While some TLR agonists exhibited survival benefit in clinical trials, it attracts more attention when they are involved in combinatorial treatment with radiation, chemotherapy, immune vaccination, and immune checkpoint inhibition in glioma treatment. TLR agonists can be used as immune modulators to enhance the efficacy of other treatment, to avoid dose accumulation, and what brings more interests is that they can potentiate immune checkpoint delayed resistance to PD-1/PD-L1 blockade by upregulating PD-1/PD-L1 overexpression, thus unleash powerful antitumor responses when combined with immune checkpoint inhibitors. Herein, we focus on recent developments and clinical trials exploring TLR-based treatment to provide a picture of the relationship between TLR and glioma and their implications for immunotherapy.

Molecular updates on berberine in liver diseases: Bench to bedside

Liver diseases are life-threatening illnesses and are the major cause of mortality and morbidity worldwide. These may include liver fibrosis, liver cirrhosis, and drug-induced liver toxicity. Liver diseases have a wide prevalence globally and the fifth most common cause of death among all gastrointestinal disorders. Several novel therapeutic approaches have emerged for the therapy of liver diseases that may provide better clinical outcomes with improved safety. The use of phytochemicals for the amelioration of liver diseases has gained considerable popularity. Berberine (BBR), an isoquinoline alkaloid of the protoberberine type, has emerged as a promising molecule for the treatment of gastrointestinal disorders. Accumulating studies have proved the hepatoprotective effects of BBR. BBR has been shown to modulate multiple signaling pathways implicated in the pathogenesis of liver diseases including Akt/FoxO2, PPAR-γ, Nrf2, insulin, AMPK, mTOR, and epigenetic pathways. In the present review, we have emphasized the important pharmacological activities and mechanisms of BBR in liver diseases. Further, we have reviewed various pharmacokinetic and toxicological barriers of this promising phytoconstituent. Finally, formulation-based novel approaches are also summarized to overcome the clinical hurdles for BBR.

Involvement of Cathepsins in Innate and Adaptive Immune Responses in Periodontitis

Periodontitis is an infectious disease whereby the chronic inflammatory process of the periodontium stimulated by bacterial products induces specific host cell responses. The activation of the host cell immune system upregulates the production of inflammatory mediators, comprising cytokines and proteolytic enzymes, which contribute to inflammation and bone destruction. It has been well known that periodontitis is related to systemic inflammation which links to numerous systemic diseases, including diabetes and arteriosclerosis. Furthermore, periodontitis has been reported in association with neurodegenerative diseases such as Alzheimer's disease (AD) in the brain. Regarding immune responses and inflammation, cathepsin B (CatB) plays pivotal role for the induction of IL-1β, cathepsin K- (CatK-) dependent active toll-like receptor 9 (TLR9) signaling, and cathepsin S (CatS) which involves in regulating both TLR signaling and maturation of the MHC class II complex. Notably, both the production and proteolytic activities of cathepsins are upregulated in chronic inflammatory diseases, including periodontitis. In the present review, we focus on the roles of cathepsins in the innate and adaptive immune responses within periodontitis. We believe that understanding the roles of cathepsins in the immune responses in periodontitis would help to elucidate the therapeutic strategies of periodontitis, thus benefit for reduction of systemic diseases as well as neurodegenerative diseases in the global aging society.

CpG Oligodeoxynucleotides Induces Apoptosis of Human Bladder Cancer Cells via Caspase-3-Bax/Bcl-2-p53 Axis

OBJECTIVE

To evaluate the anti-cancer effect of unmethylated cytosine-phosphorothioate-guanine (CpG)-containing oligodeoxynucleotides (ODNs) on human bladder cancer UM-UC-3 cells, our study was carried out.

METHODS

The viability of cells (UM-UC-3, T24 and SV-HUC-1) with CpG ODN treatments was examined by cell counting kit-8 (CCK-8) assay. Apoptosis and cell cycle phase were determined by flow cytometry analysis. Pre-apoptosis factors of caspase-3, p53, B-cell lymphoma 2 associated X protein (Bax) and anti-apoptosis factor of B-cell lymphoma 2 (Bcl-2) were detected by western blot.

RESULTS

Experimental results showed that the viability of human bladder cancer cells (UM-UC-3 and T24) with CpG ODN treatment was decreased and the viability of human normal urothelial cells (SV-HUC-1) with CpG ODN treatment was increased with time-dependance manner. Moreover, CpG ODN increased the apoptosis rate of UM-UC-3 cells and arrested more cells in G0G1 phase. Furthermore, the expression of caspase-3, p53 and Bax were increased and the expression of Bcl-2 was decreased with CpG ODN treatment on UM-UC-3 cells.

CONCLUSION

CpG ODN promoted the proliferation of normal urinary transitional epithelial cells (SV-HUC-1) and inhibited the cell viability of human bladder cancer cells (UM-UC-3 and T24) in vitro. CpG ODN induced the apoptosis of human bladder cancer (UM-UC-3) cells in a cascade progress via enhancing the expression of caspase-3, p53 and Bax, and inhibiting the expression of Bcl-2 with significant time-dependancy. CpG ODN inhibited cell cycle distribution of human bladder cancer (UM-UC-3) cells with more cells were arrested in G0G1 phase. This study suggested that the CpG ODN is the potential candidate on human bladder cancer.

Converging TLR9 and PI3Kgamma signaling induces sterile inflammation and organ damage

Toll-like receptor 9 (TLR9) and Phosphatidylinositol-3-kinase gamma (PI3Kγ) are very important effectors of the immune response, however, the importance of such crosstalk for disease development is still a matter of discussion. Here we show that PI3Kγ is required for immune responses in which TLR9 is a relevant trigger. We demonstrate the requirement of PI3Kγ for TLR9-induced inflammation in a model of CpG-induced pleurisy. Such requirement was further observed in inflammatory models where DNA sensing via TLR9 contributes to disease, such as silicosis and drug-induced liver injury. Using adoptive transfer, we demonstrate that PI3Kγ is important not only in leukocytes but also in parenchymal cells for the progression of inflammation. We demonstrate this crosstalk between TLR9 and PI3Kγ in vitro using human PBMCs. The inhibition of PI3Kγ in CpG-stimulated PBMCs resulted in reduction of both cytokine production and phosphorylated Akt. Therefore, drugs that target PI3Kγ have the potential to treat diseases mediated by excessive TLR9 signalling.

High-Frequency Repetitive Transcranial Magnetic Stimulation Mediates Autophagy Flux in Human Bone Mesenchymal Stromal Cells via NMDA Receptor-Ca2+-Extracellular Signal-Regulated Kinase-Mammalian Target of Rapamycin Signaling

Aim

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive and safe technique for treatment of central and peripheral nerve injury. In recent years, this technique has been widely used in clinic, and an increasing number of studies have reported its mechanisms. In this study, we investigated the mechanisms of rTMS-mediated autophagy flux in human bone mesenchymal stromal cells (BMSCs).

Methods

A frequency of 50 Hz was employed. Cells were divided into five groups: (1) normal, (2) sham, (3) 0.5 T, (4) 1.0 T, and (5) 1.5 T. Cells were stimulated for 20 min/day. The levels of p62, LC3-II/I, phosphorylated extracellular signal-regulated kinase (p-ERK), ERK, phosphorylated-AKT (p-AKT), AKT, phosphorylated mammalian target of rapamycin (p-mTOR), mTOR, phosphorylated protein kinase A (p-PKA), PKA, phosphorylated epidermal growth factor receptor (p-EGFR), EGFR, Nanog, Oct4, Sox2, and NMDA receptor (NMDAR1) were investigated by western blotting. Intracellular calcium (Ca²⁺) levels were quantified by flow cytometry. p62 and LC3 expression was also assessed by immunofluorescence analysis.

Results

In the 0.5 T group, rTMS increased the expression of LC3-II/I, p-ERK/ERK, and NMDAR1 and decreased the levels of p62 and p-mTOR/mTOR than in the normal group. The ratio of p-AKT/AKT, p-PKA/PKA, and p-EGFR/EGFR and the expression of Nanog, Oct4, and Sox2 remained unchanged. Immunofluorescence analysis revealed colocalization of p62 with LC3 puncta, and flow cytometry analysis displayed that Ca²⁺ levels were elevated. However, in the 1.0 and 1.5 T groups, no changes in the expression of these autophagy markers were observed.

Conclusion

In the 0.5 T group, high-frequency rTMS can induce autophagy through NMDAR–Ca²⁺–ERK–mTOR signaling in BMSCs. In the 1.0 and 1.5 T groups, autophagy is not activated.

Inhibition of Ctsk modulates periodontitis with arthritis via downregulation of TLR9 and autophagy

Objectives

The mechanisms underlying the effects of Toll‐like receptor 9 (TLR9) and autophagy on rheumatoid arthritis (RA)‐aggravated periodontitis are unclear. We aimed to explore a novel target, cathepsin K (Ctsk)‐mediated TLR9‐related autophagy, during the progress of periodontitis with RA.

Materials and Methods

DBA/J1 mouse model of periodontitis with RA was created by local colonization of Porphyromonas gingivalis (Pg) and injection of collagen. The expression of Ctsk was inhibited by adeno‐associated virus (AAV). Micro‐CT, immunohistochemistry (IHC), Western blot and quantitative real‐time polymerase chain reaction (qRT‐PCR) were used to detect the expression of TLR9‐related autophagy in periodontitis with RA. Small interfering RNA (siRNA) and CpG oligodeoxynucleotides (CpG ODN) were applied in macrophages. Western blot, immunofluorescence (IF) and qRT‐PCR were used to verify the in vivo results.

Results

RA can promote periodontitis bone destruction in the lesion area, while inhibiting Ctsk could effectively alleviate this effect. The infiltration of macrophages, TLR9, autophagy proteins (TFEB and LC3) and inflammatory cytokines increased in the periodontitis‐with‐RA group and was reduced by the inhibition of Ctsk in the periodontal region. Macrophage stimulation confirmed the in vivo results. With the activation of TLR9 by CpG ODN, inhibition of Ctsk could suppress both TLR9 downstream signalling proteins and autophagy‐related proteins.

Conclusions

This study advanced a novel role for Ctsk in TLR9 and autophagy to explain the interaction between periodontitis and RA.

Role of TFEB in autophagic modulation of ischemia reperfusion injury in mice kidney and protection by urolithin A

Kidney ischemia reperfusion injury (IRI) is an acute kidney injury associated with high number of mortality. We have examined the molecular mechanism and found that oxidative stress and hypoxia leads to induction of autophagy. In IRI induced autophagy, TFEB translocated to nucleus in response to IRI and induced a number of target genes of Coordinated Lysosomal Expression and Regulation (CLEAR) network. Real-time PCR analyses result showed IRI dependent increase in mRNA level to lysosomal hydrolases (Ctsa, Psap), lysosomal membranes (Lamp1), lysosomal acidification (Atp6ap1) non-lysosomal proteins involved in lysosomal biogenesis (M6pr, Nagpa) and autophagy (Becn1, VPS11). Overall, both lysosomal biogenesis and autophagy pathways were induced. Two key players of TFEB dependent proteins in autophagy, LAMP1 and BECN1 were verified by protein analyses. Pretreatment with urolithin A promoted autophagy and attenuated renal injury in kidney IRI and thus inverse relationship existed between TFEB-CLEAR pathway and kidney injury. Urolithin A also attenuated IRI induced pro-inflammatory cytokines TNFα, IL1β, MIP1α and MIP2 mRNA and associated kidney injury. Overall, our results explored the understanding of autophagy and CLEAR network to kidney IRI and those insights may help to develop new therapeutic strategies to protect against IRI.

Involvement of P2X7 Receptor in Proliferation and Migration of Human Glioma Cells

Previous studies have demonstrated that activation of P2X₇ receptors (P2X₇R) results in the proliferation and migration of some types of tumor. Here, we asked whether and how the activated P2X₇R contribute to proliferation and migration of human glioma cells. Results showed that the number of P2X₇R positive cells was increasing with grade of tumor. In U87 and U251 human glioma cell lines, both expressed P2X₇R and the expression was enhanced by 3′-O-(4-benzoylbenzoyl) ATP (BzATP), the agonist of P2X₇R, and siRNA. Our results also showed that 10 μM BzATP was sufficient to induce the proliferation of glioma cell significantly, while the cell proliferation reached the peak with 100 μM BzATP. Also, the migration of U87 and U251 cells was significantly increased upon BzATP treatment. However, the number of apoptotic cells of U87 and U251 was not significantly changed by BzATP. In addition, the expression of ERK, p-ERK, and proliferating cell nuclear antigen (PCNA) protein was increased in BzATP-treated U87 and U251 glioma cells. PD98059, an inhibitor of the MEK/ERK pathway, blocked the increased proliferation and migration of glioma cells activated by BzATP. These results suggest that ERK pathway is involved in the proliferation and migration of glioma cells induced by P2X₇R activation.

TLRs/NLRs: Shaping the landscape of host immunity

Innate immune system provides the first line of defense against pathogenic organisms. It has a varied and large collection of molecules known as pattern recognition receptors (PRRs) which can tackle the pathogens promptly and effectively. Toll-like receptors (TLRs) and NOD-like receptors (NLRs) are members of the PRR family that recognize pathogen associated molecular patterns (PAMPs) and play pivotal roles to mediate defense against infections from bacteria, fungi, virus and various other pathogens. In this review, we discuss the critical roles of TLRs and NLRs in the regulation of host immune-effector functions such as cytokine production, phagosome-lysosome fusion, inflammasome activation, autophagy, antigen presentation, and B and T cell immune responses that are known to be essential for mounting a protective immune response against the pathogens. This review may be helpful to design TLRs/NLRs based immunotherapeutics to control various infections and pathophysiological disorders.

Stimulating Innate Immunity to Enhance Radiation Therapy-Induced Tumor Control

Novel ligands that target Toll-like receptors and other innate recognition pathways represent a potent strategy for modulating innate immunity to generate antitumor immunity. Although many of the current clinically successful immunotherapies target adaptive T-cell responses, both preclinical and clinical studies suggest that adjuvants have the potential to enhance the scope and efficacy of cancer immunotherapy. Radiation may be a particularly good partner to combine with innate immune therapies, because it is a highly efficient means to kill cancer cells but may fail to send the appropriate inflammatory signals needed to act as an efficient endogenous vaccine. This may explain why although radiation therapy is a highly used cancer treatment, true abscopal effects-regression of disease outside the field without additional systemic therapy-are extremely rare. This review focuses on efforts to combine innate immune stimuli as adjuvants with radiation, creating a distinct and complementary approach from T cell-targeted therapies to enhance antitumor immunity.

ERK-dependent mTOR pathway is involved in berberine-induced autophagy in hepatic steatosis

Non-alcoholic fatty liver disease (NAFLD) is a burgeoning health problem and is considered as a hepatic manifestation of metabolic syndrome. Increasing evidence demonstrates that berberine (BBR), a natural plant alkaloid, is beneficial for obesity-associated NAFLD. However, the mechanisms about how BBR improves hepatic steatosis remain uncertain. Recently, some reports revealed that enhanced autophagy could decrease hepatic lipid accumulation. In this study, we first established a high-fed diet (HFD) mice model and oleate-palmitate-induced lipotoxicity hepatocytes to explore the association among BBR, autophagy and hepatic steatosis. Our data demonstrated that BBR had profound effects on improving hepatic lipid accumulation both in vivo and in vitro, and led to high autophagy flux. The molecular alterations proceeding these changes were characterized by inhibition of the ERK/mTOR pathway. These findings suggest an important mechanism for the positive effects of BBR on hepatic steatosis, and may provide new evidence for the clinical use of BBR in NAFLD.

The role of TLR9 in stress-dependent autophagy formation

Autophagy is a self-degradation process that is important for balancing energy sources at critical times in development and in response to nutrient stress. Recently, it was report that autophagy is controlled by recognizing conserved pattern recognition receptors (PRRs), including toll-like receptors (TLRs). However, the molecular mechanism of TLRs in autophagy is not well understood. In this study, we found that serum starvation-dependent autophagy was associated with TLR9 activation in the absence of CpG-ODN, which is a specific TLR9 ligand. TLR9 was not only elevated but also colocalized with LC3 during autophagy by serum starvation or CPG-ODN treatment; however, these events did not occur simultaneously during autophagosome accumulation. Autophagy was even induced upon TLR9 activation after inhibiting recruitment of initial autophagy components by 3-MA, a specific inhibitor of class III PI3-kinase. Our data suggested that TLR9 may be promptly induced and recruit autophagy components from the endosome to autophagosome in response to stress.

Crosstalk between autophagy and intracellular radiation response (Review)

Autophagy induced by radiation is critical to cell fate decision. Evidence now sheds light on the importance of autophagy induced by cancer radiotherapy. Traditional view considers radiation can directly or indirectly damage DNA which can activate DNA damage the repair signaling pathway, a large number of proteins participating in DNA damage repair signaling pathway such as p53, ATM, PARP1, FOXO3a, mTOR and SIRT1 involved in autophagy regulation. However, emerging recent evidence suggests radiation can also cause injury to extranuclear targets such as plasma membrane, mitochondria and endoplasmic reticulum (ER) and induce accumulation of ceramide, ROS, and Ca2+ concentration which activate many signaling pathways to modulate autophagy. Herein we review the role of autophagy in radiation therapy and the potent intracellular autophagic triggers induced by radiation. We aim to provide a more theoretical basis of radiation-induced autophagy, and provide novel targets for developing cytotoxic drugs to increase radiosensitivity.