824 Modulation of TLR3 protein in response to radiation in squamous cell lung carcinoma

BackgroundSquamous cell lung cancer (SCLC) is the second most common type of lung cancer. Treatment is complicated due to the lack of mutated molecular targets.1 Radiotherapy (RT) is commonly used to treat SCLC, but relapse and tumor progression are common. The combination of immunotherapy (IT) with RT can enhance the effect observed with RT alone.2 Effective combination of IT and RT requires an understanding of the pathways that synergize to enhance tumor cell kill in SCLC. Our lab has identified Toll-like receptor 3 (TLR3) as a molecule that is regulated by RT and can be targeted with IT. Toll-like receptors serve a crucial role against tumor cells by activating innate and adaptive immune responses that boost antitumor immunity.3 4 TLR3 is the only receptor whose molecular mechanism functions independent of MyD88, leading to NF-κB mediated apoptosis.5 We hypothesized that increased TLR3 expression would be associated with improved response to RT. We further hypothesized that RT can downregulate TLR3 and that this effect can be reversed with TLR3 agonists leading to enhanced tumor antigen recognition. We aim to use this data to formulate further studies using combined RT and IT.MethodsMouse (KLN205) and human (SW900) squamous cell carcinoma (SCC) cell lines were used to study the effect of radiation on TLR3 expression. Irradiation was performed using the gammacell 3000 elan irradiator. Cells were irradiated with 0, 5, 10 and 20 Gy. Protein extraction was performed 48 and 72 hours after RT. Protein extracts were analyzed by Western Blot. Further, TLR3 mRNA expression and 5-year overall survival of SCLC patients was obtained from public databases. Kaplan-Meier method was used to correlate between TLR3 mRNA expression and survival.ResultsIn vitro studies and western blot analysis demonstrated a decrease of TLR3 expression in response to increasing doses of radiation. This observation was consistent in mouse and human SCC cell lines. In silico analysis of SCLC patients who received RT showed that increased TLR3 mRNA expression was associated with improved overall survival and disease-free survival.ConclusionsOur findings point to an important role for TLR3 in SCLC. Combining RT with TLR3 agonists may enhance the tumor response to RT. Several complementary experiments are underway in our lab to use the TLR3 agonist, Poly I:C, which will allow a better understanding of the effect of RT on TLR3.ReferencesGeorge J, Lim SJ, Jang SJ, et al. Comprehensive genomic profiles of small cell lung cancer. Nature 2015;524:47–53.Darragh L, Oweida A, Karam SD. Overcoming resistance to combination radiation-immunotherapy: a focus on contributing pathways withing the tumor microenvironment. Frontiers in Immunology 2019;9:3154.Shcheblyakov D, Logunov DY, Tukhvatulin AI, et al. Toll-Like Receptors (TLRs): The Role in Tumor Progression. Acta Naturae 2010;2(3):21-9.Kawai T, Akira S. The role of pattern-recognition receptors in innate immunity: update on Toll-like receptors. Nat Immunol 2010;11:373–384.Bianchi F, Alexiadis S, Camiasaschi C, et al. TLR3 expression induces apoptosis in Human Non-Small-Cell Lung Cancer. Int J Mol Sci 2020 Feb;21(4):1440.

Expression of Toll-like receptors in emotiogenic structures of rat brain is changed under longterm alcohol consumption and ethanol withdrawal

Recent studies have provided strong evidence that long-term ethanol consumption leads to activation the mechanisms of neuroimmune signaling. Recently, much attention has been focused on the study of toll-like receptors (Toll-like receptors, TLRs), which play one of the key roles in the mechanisms of activation of the innate immune system in brain structures subsequently ethanol consumption. It is known that the activation of TLRs leads to the release of many proinflammatory cytokines with the resulting neuroinflammatory process. There are suggestions that TLRs may also be involved in the modulation of neurotransmitter systems of the brain, thereby contributing to the formation of pathological dependence on ethanol. The goal of our work was to study the level of expression the genes of TLRs (TLR3, TLR4, TLR7) and pro-inflammatory cytokine genes (IL-1β, CCL2) in the rat brain (amygdala, hippocampus, medial entorhinal cortex, striatum) under conditions of prolonged alcoholization and on different periods of alcohol withdrawal, which was previously not studied by researchers. Prolonged alcoholization of rats with ethanol did not lead to changes in levels mRNA of TLRs in the studied structures of the rat brain, with the exception of a small increase in the level of TLR3 mRNA in the hippocampus of prolonged alcoholized rats and a slight increase in the level of TLR3 mRNA in mEC. However, gene expression of TLRs undergoes changes in all the structures of the rat brain studied by us at different periods of alcohol withdrawal. The increased level of expression of both TLRs and proinflammatory genes in the period of alcohol withdrawal in the rat brain hippocampus deserves special attention, which indicates the presence of a persistent neuroinflammatory process in this brain structure in the period of alcohol withdrawal, which is probably supported with the participation of TLR-dependent signaling. The study of the mechanisms of inflammatory process activation by TLR-dependent signaling in different brain structures can open new targets for drug exposure. Such drugs can be used in the treatment of alcoholism.

Modulation of Mast Cell Toll-Like Receptor 3 Expression and Cytokines Release by Histamine

Background/Aims: As a major inflammatory molecule released from mast cell activation, histamine has been reported to regulate TLRs expression and cytokine production in inflammatory cells present in the microenvironment. In this study, we determined the ability of histamine to modulate TLRs expression and cytokine production in mast cells. Methods: HMC-1 and P815 cells were exposed to various concentrations of histamine in the presence or absence of histamine antagonist for 2, 6 or 16 h. The effect of histamine on the expression of TLR3 protein and mRNA was analyzed by flow cytometry、 RT-PCR and immunofluorescent microscopy. Furthermore, we also examined the effect of histamine on the secretion of MCP-1 and IL-13 from mast cells by ELISA. Results: The amplification of TLR3 mRNA and protein expression in mast cells was observed after incubation with histamine, which was accompanied by increasing secretion of IL-13 and MCP-1 via H1 receptor. The signaling pathways of PI3K/ Akt and Erk1/2/MAPK contributed to these induction effects. Conclusion: These results demonstrate that histamine up-regulates the expression of TLR3 and secretion of IL-13 and MCP-1 in mast cells, thus identifying a new mechanism for the histamine inducing allergic response.

Lactobacillus rhamnosus GG increases Toll-like receptor 3 gene expression in murine small intestine ex vivo and in vivo

Administration of Lactobacillus rhamnosus GG (LGG) has been reported to be therapeutically effective against acute secretory diarrhoea resulting from the structural and functional intestinal mucosal lesions induced by rotavirus infection; however, the underlying mechanisms remain to be completely elucidated. Because Toll-like receptor 3 (TLR3) plays a key role in the innate immune responses following the recognition of rotavirus, the present study examined whether LGG influences TLR3 gene expression in murine small intestine ex vivo and in vivo. We employed cultured intestinal organoids derived from small intestinal crypts as an ex vivo tissue model. LGG supplementation increased TLR3 mRNA levels in the intestinal organoids, as estimated by quantitative real-time polymerase chain reaction. Likewise, single and 7-day consecutive daily administrations of LGG increased TLR3 mRNA levels in the small intestine of C57BL/6N mice. The mRNA levels of other TLRs were not substantially altered both ex vivo and in vivo. In addition, LGG supplementation increased the mRNA levels of an antiviral type 1 interferon, interferon-α (IFN-α), and a neutrophil chemokine, CXCL1, upon stimulation with a synthetic TLR3 ligand, poly(I:C) in the intestinal organoids. LGG administration did not alter IFN-α and CXCL1 mRNA levels in the small intestine in vivo. Supplementation of other bacterial strains, Bifidobacterium bifidum and Lactobacillus paracasei, failed to increase TLR3 and poly(I:C)-stimulated CXCL1 mRNA levels ex vivo. We propose that upregulation of TLR3 gene expression may play a pivotal role in the therapeutic efficacy of LGG against rotavirus-associated diarrhoea. In addition, we demonstrated that intestinal organoids may be a promising ex vivo tissue model for investigating host-pathogen interactions and the antiviral action of probiotics in the intestinal epithelium.

Polymorphisms in Toll-like receptor 3 confer natural resistance to human herpes simplex virus type 2 infection

Lack of Toll-like receptor 3 (TLR3) functional activity predisposes children to human herpesvirus 1 (HSV-1) encephalitis. In this study, we have investigated whether there is any link between TLR3 and adult HSV-2 infection by studying genetic variations in TLR3. The frequency of four single-nucleotide polymorphisms (SNPs) in the TLR3 gene in 239 patients with genital HSV-2 infection and 162 healthy controls, as well as the impact of these variants on TLR3 gene-expression levels, were compared. Two SNPs in the TLR3 gene (rs13126816 and rs3775291) were associated with a reduced incidence of HSV-2 infection. The minor allelic variants at both rs13126816 and rs3775291 were more common among healthy HSV-2-seronegative subjects than among HSV-2-infected individuals. This was even more apparent in HSV-1-seronegative individuals. There was, however, no association between any of the four TLR3 SNPs and HSV-2 disease severity, as they were expressed at similar proportions in asymptomatic and symptomatic HSV-2-infected patients alike. Furthermore, when assessing TLR3 mRNA expression in a limited number of HSV-2-infected individuals, we found that individuals carrying the homozygous genotypes for the minor alleles had significantly higher levels of TLR3 mRNA expression in peripheral blood mononuclear cells in response to HSV-2 stimulation than individuals that were homozygous for the major allele variants. Taken together, these results suggest that genetic variations in TLR3 may affect the susceptibility to HSV-2 infection in humans.

p53 Regulates Toll-Like Receptor 3 Expression and Function in Human Epithelial Cell Lines

ABSTRACT Toll-like receptors (TLRs) are important sensors of microbial pathogens and mediators of innate immune responses. Although the signal transduction of TLRs is well elucidated, their basal regulation is largely unexplored. Here we show that the tumor suppressor p53 positively regulates the transcription of TLR3, a receptor for viral double-stranded RNA and poly(I-C), by binding to the p53 site in the TLR3 promoter. TLR3 expression was lower in HCT116 p53−/− cells than in HCT116 p53+/+ cells. Activation of p53 by 5-fluorouracil increased the TLR3 mRNA in epithelial cell lines with wild-type p53 but not in cell lines harboring mutant p53. Knockdown of p53 by small interfering RNA decreased the TLR3 expression. TLR3 mRNA was also lower in liver and intestine of p53−/− mice than in p53+/+ mice. Furthermore, the poly(I-C)-induced phosphorylation of IκB-α, nuclear translocation of NF-κB, and phosphorylation of interferon regulatory transcription factor 3, were drastically reduced in HCT116 p53−/− cells, indicating a dysregulation of the two signaling pathways governed by TLR3. Consequently, induction of interleukin-8 and beta interferon after poly(I-C) stimulation was impaired in HCT116 p53−/− cells. These results suggest that p53 influences TLR3 expression and function and highlight a role of p53 in innate immune response in epithelial cells.