The molecular mechanisms of the effect of Dexamethasone and Cyclosporin A on TLR4 /NF-κB signaling pathway activation in oral lichen planus

NF-κB in biology and targeted therapy: new insights and translational implications

NF-κB signaling has been discovered for nearly 40 years. Initially, NF-κB signaling was identified as a pivotal pathway in mediating inflammatory responses. However, with extensive and in-depth investigations, researchers have discovered that its role can be expanded to a variety of signaling mechanisms, biological processes, human diseases, and treatment options. In this review, we first scrutinize the research process of NF-κB signaling, and summarize the composition, activation, and regulatory mechanism of NF-κB signaling. We investigate the interaction of NF-κB signaling with other important pathways, including PI3K/AKT, MAPK, JAK-STAT, TGF-β, Wnt, Notch, Hedgehog, and TLR signaling. The physiological and pathological states of NF-κB signaling, as well as its intricate involvement in inflammation, immune regulation, and tumor microenvironment, are also explicated. Additionally, we illustrate how NF-κB signaling is involved in a variety of human diseases, including cancers, inflammatory and autoimmune diseases, cardiovascular diseases, metabolic diseases, neurological diseases, and COVID-19. Further, we discuss the therapeutic approaches targeting NF-κB signaling, including IKK inhibitors, monoclonal antibodies, proteasome inhibitors, nuclear translocation inhibitors, DNA binding inhibitors, TKIs, non-coding RNAs, immunotherapy, and CAR-T. Finally, we provide an outlook for research in the field of NF-κB signaling. We hope to present a stereoscopic, comprehensive NF-κB signaling that will inform future research and clinical practice.

Dynamic changes of Th1/Th2/Th17 cytokines and hBD-2/3 in erosive oral lichen planus patients saliva before and after prednisone acetate treatment

Objective

This study aimed to investigate the expression of T helper 1 (Th1)/Th2/Th17- related cytokines and human beta defensins 2 and 3 (hBD-2 and -3) in the saliva of patients with erosive oral lichen planus (EOLP) and to explore their role in the pathogenesis of EOLP and the effects of glucocorticoids on EOLP.

Methods

A total of 30 patients with EOLP and 20 age- and sex-matched healthy individuals were included in this study. The patients were treated with prednisone at a dose of 0.4 mg/(kg·d) for 1 week and examined before and after treatment. Unstimulated whole saliva samples were collected to determine the levels of cytokines (interleukin 1 beta [IL-1β], tumour necrosis factor alpha [TNF]-α, interferon gamma [IFN-γ], IL-4, IL-6, IL-10 and IL-17) by cytometric bead array and those of hBD-2 and -3 b y enzyme-linked immunosorbent assay. In addition, oral rinse samples were collected to detect Candida load.

Results

The levels of salivary IL-1β, IL-6, hBD-2 and hBD-3 were higher and the IFN-γ/IL-4 and IL-1β/IL-6 ratios were lower in patients with EOLP than in healthy individuals. In patients with EOLP, hBD-2 levels were positively correlated with IFN-γ levels and negatively correlated with IL-17 levels, whereas hBD-3 levels were negatively correlated with IL-17 and IL-10 levels. In addition, the prevalence of EOLP was positively correlated with IL-6 levels and negatively correlated with the IFN-γ/IL-4 ratio. The levels of IL-1β, TNF-α, IFN-γ, IL-6, hBD-2 and hBD-3 and the IFN-γ/IL-4 ratio decreased after treatment with prednisone for 1 week. The levels of IL-6, hBD-2 and hBD-3 were significantly higher in EOLP patients than in healthy individuals; while TNF-α levels and the IFN-γ/IL-4 ratio were significantly lower in EOLP patients than in healthy individuals. Furthermore, the oral counts of Candida spp. (colony forming unit [CFU]) were negatively correlated with TNF-α levels. Numerical Rating Scale(NRS) and Sign scores decreased in EOLP patients after treatment. Approximately 80 % of patients were effectively treated. Salivary TNF-α levels were significantly higher in the treatment-ineffective group than in the treatment-effective group before treatment with prednisone, and differences in salivary IL-6 levels before and after treatment were significantly higher in the treatment-effective group than in the treatment-ineffective group.

Conclusions

High expression of IL-1β, IL-6, hBD-2 and Th1/Th2 imbalance in saliva may be associated with the pathogenesis of EOLP. IFN-γ/IL-4 balance may serve as a protective factor for EOLP. Glucocorticoids significantly alleviate the symptoms of EOLP and inhibit the expression of Th1/Th2 cytokines.

Network Pharmacology and Molecular Docking Analysis Exploring the Mechanism of Tripterygium wilfordii in the Treatment of Oral Lichen Planus

Background: Oral lichen planus (OLP) is an infrequent autoimmune disease of the oral mucosa, which affects up to 2% of the world population. An investigation of Tripterygium wilfordii's mechanism of action for treating OLP was conducted, and a theoretical basis was provided for improving current treatment regimens. Materials and Methods: We used a network pharmacological approach to gain insight into the molecular mechanism of Tripterygium wilfordii in the treatment of OLP. Then, potential protein targets between Tripterygium wilfordii and OLP were analyzed through a drug-target network. This was followed by KEGG enrichment analysis and Gene Ontology (GO) classification. Finally, for molecular docking, AutoDock Vina was used. Results: A protein-protein interaction (PPI) network was constructed by analyzing the common targets of a total of 51 wilfordii-OLP interactions from different databases. The GO and KEGG enrichment analyses showed that the treatment of OLP with Tripterygium wilfordii mainly involves lipopolysaccharide response, bacterial molecular response, positive regulation of cytokine production, and leukocyte proliferation, and the signaling pathways mainly include the AGE-RAGE, NF-κB, Toll-like receptor, IL-17, HIF-1, and TNF signaling pathways. The molecular docking results showed that β-sitosterol, kaempferol, hederagenin, and triptolide have a higher affinity for AKT1, TNF, CASP3, and PTGS2, respectively. Based on the CytoNCA analysis of common targets, 19 key targets, including AKT1, TNF, VEGFA, STAT3, CXCL8, PTGS2, TP53, and CASP3, and their connections were identified. Conclusions: Preliminarily, this study reveals that Tripterygium wilfordii interferes with OLP by interacting with multiple targets through multiple accesses, as validated by molecular docking.

E. coli LPS/TLR4/NF-κB Signaling Pathway Regulates Th17/Treg Balance Mediating Inflammatory Responses in Oral Lichen Planus

Oral lichen planus (OLP) is a chronic inflammatory autoimmune disease mediated by T cells. The imbalance of microflora has potential impacts on the onset and development of OLP, but the mechanism is still unclear. Here, we investigated the effects of Escherichia coli (E. coli) lipopolysaccharide (LPS) simulating the microbial enrichment state of OLP on T cell immune functions in vitro. Effect of E. coli LPS on the viability of T cell using CCK8 assay. After E. coli LPS pretreatment, the expression of the toll-like receptor 4 (TLR4), nuclear factor-kappa B p65 (NF-κB p65), cytokines, retinoic acid-related orphan receptor γt (RORγt), and forkhead box p3 (Foxp3) in the peripheral blood of OLP patients and normal controls (NC) were assessed using quantitative RT-PCR (qRT-PCR), western blot, and enzyme-linked immunosorbent assay (ELISA). Finally, Th17 and Treg cells were detected by flow cytometry. We found that the TLR4/NF-κB pathway was activated and the expression of interleukin (IL)-6 and IL-17 was increased in both groups after E. coli LPS stimulation. CC chemokine ligand (CCL)20 and CC chemokine receptor (CCR)4 expression was increased in OLP after E. coli LPS treatment, while no difference was found in CCR6 and CCL17 expression of both groups. Moreover, E. coli LPS treatment enhanced the proportion of Th17 cells, Th17/Treg ratio, and RORγt/Foxp3 ratio in OLP. In conclusion, E. coli LPS regulated Th17/Treg balance to mediate the inflammatory responses of OLP through the TLR4/NF-κB pathway in vitro, indicating that oral microbiota dysbiosis affected the chronic inflammatory state of OLP.

Updates on immunological mechanistic insights and targeting of the oral lichen planus microenvironment

Oral lichen planus (OLP) is a chronic immune inflammatory disease that is an oral potentially malignant disorder (OPMD), occurs in the oral mucosa and affects approximately 0.5% to 4% of the general population. There are usually five types of OLP: reticular/papular, plaque-like, atrophic/erythematous, erosive/ulcerative, and bullous. Furthermore, the chance of causing oral squamous cell carcinoma (OSCC) is 1.4%. Although the etiology of OLP is still unknown, accumulating evidence supports that immune dysregulation may play a vital role in the pathogenesis of OLP, especially the massive production of various inflammatory cells and inflammatory mediators. In this review, we focus on the relationship between OLP and its immune microenvironment. We summarize current developments in the immunology of OLP, summarizing functional cell types and crucial cytokines in the OLP immune microenvironment and the underlying mechanisms of key signaling pathways in the OLP immune microenvironment. We highlight the application potential of targeted immune microenvironment therapy for OLP.

Expression and Significance of TNF-α and NF-κB/p65 in Cutaneous Lichen Planus

Purpose

The purpose of this study was to explore the expression of TNF-α and NF-κB/p65 in Lichen planus skin lesions and their correlation with the pathogenesis of Lichen planus.

Patients and Methods

The case group consisted of 30 individuals diagnosed with LP based on clinical and histopathologic examination. The control group consisted of 10 individuals from an Orthopedic Department with normal skin. TNF-α and NF-κB/p65 expression in skin tissue samples was detected by immunohistochemistry.

Results

The immunohistochemical results showed that TNF-α and NF-κB/p65 expression levels were significantly higher in LP skin lesions than normal skin tissues (P ≤ 0.05). Positive TNF-α staining mainly occurred in the cytoplasm of keratinocytes of the stratum granulosum, stratum spinosum, and stratum basale in the epidermis and lymphocytes in the superficial dermis. Positive NF-κB/p65 staining mainly occurred in the nucleus and cytoplasm of keratinocytes of the stratum spinosum and stratum basale in the epidermis and lymphocytes in the superficial dermis.

Conclusion

TNF-α and NF-κB/p65 are overexpressed in cutaneous LP. The two are positively correlated in LP, suggesting that they both play essential roles in the pathogenesis of LP.

TLR4 Expression in Ex-Lichenoid Lesions—Oral Squamous Cell Carcinomas and Its Surrounding Epithelium: The Role of Tumor Inflammatory Microenvironment

Toll-like receptors (TLRs) regulate innate and adaptive immune responses. Moreover, TLRs can induce a pro-survival and pro-proliferation response in tumor cells. This study aims to investigate the expression of TLR4 in the epithelium surrounding oral squamous cell carcinomas (OSCC) in relation to its inflammatory microenvironment. This study included 150 human samples: 30 normal oral control (NOC), 38 non-lichenoid epithelium surrounding OSCC (NLE-OSCC), 28 lichenoid epithelium surrounding OSCC (LE-OSCC), 30 OSCC ex-non oral lichenoid lesion (OSCC Ex-NOLL), and 24 OSCC ex-oral lichenoid lesion (OSCC Ex-OLL). TLR4 expression was investigated by immunohistochemistry and the percentage of positive cells was quantified. In addition, a semiquantitative analysis of staining intensity was performed. Immunohistochemical analysis revealed that TLR4 is strongly upregulated in LE-OSCC as compared to normal control epithelium and NLE-OSCC. TLR4 expression was associated with the inflammatory environment, since the percentage of positive cells increases from NOC and NLE-OSCC to LE-OSCC, reaching the highest value in OSCC Ex–OLL. TLR4 was detected in the basal third of the epithelium in NLE-OSCC, while in LE-OSCC, TLR4 expression reached the intermediate layer. These results demonstrated that an inflammatory microenvironment can upregulate TLR4, which may boost tumor development.

Inflammatory and immune-related factor Caspase 1 contributes to the development of oral lichen planus

OBJECTIVE

In this study, we aimed at underlying the potential regulatory mechanism and overall biological functions of caspase 1 (CASP1) in oral lichen planus (OLP).

DESIGN

Buccal mucosa tissue samples were gained from healthy subjects or patients diagnosed with OLP. Immunochemical staining was applied to detect CASP1 in OLP tissues. Lipopolysaccharide (LPS) was used to construct OLP in vitro models. Cell counting kit-8 (CCK-8) and flow cytometry assay were applied to detecte cell viability and apoptosis.

RESULTS

The upregulation of CASP1 in OLP has been identified through comprehensive bioinformatics analysis and verified in clinical samples. In OLP tissues, inflammation-related factors, including tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6, and IL-18, were elevated and positively correlated with CASP1. In HaCaT cells, LPS stimulation induced CASP1 upregulation, suppressed cell viability, facilitated cell apoptosis, and elevated the levels of TNF-α, IL-1β, IL-6, and IL-18; silencing of CASP1 attenuated LPS-induced damages to HaCaT cells. Pearson's correlation analysis identified that 45 immune-related genes were positively correlated with CASP1; these 45 genes were enriched in the immune system process, associated with combined immunodeficiency, and spleen-specific and CD56 + NK cell-specific. PPI network among CASP1 and correlated immune-related factors was constructed, and CASP1 was positively correlated with RAC2, CYBB, and ARHGDIB. In HaCaT cells, LPS stimulation induced RAC2, CYBB, and ARHGDIB expression, whereas knocking down CASP1 attenuated LPS-induced increases in RAC2, CYBB, and ARHGDIB.

CONCLUSION

CASP1 is upregulated in OLP tissues. Knockdown of CASP1 in HaCaT cells could protect HaCaT cells from LPS-induced inflammatory injury. Comprehensive bioinformatics indicates that the interaction of CASP1 with RAC2, CYBB, and ARHGDIB, might be the potential molecular mechanism.

The presence of Prevotella melaninogenica within tissue and preliminary study on its role in the pathogenesis of oral lichen planus

OBJECTIVE

Oral lichen planus (OLP) is a chronic inflammatory disease that occurs in the oral mucosa with characteristic white striations lesions, recurrent erosions, and pains. The etiology and pathogenesis of OLP are still unclear.

MATERIALS AND METHODS

We analyzed the bacterial community structure of buccal mucosa in patients with OLP and normal controls by high-throughput sequencing. Fluorescence in situ hybridization (FISH) was used to detect Prevotella melaninogenica (P. melaninogenica) in 13 OLP samples and 10 controls. The amounts of P. melaninogenica in OLP buccal mucosa and the expression of inflammatory cytokines in co-culture of mouse-derived macrophages with P. melaninogenica were detected by RT-qPCR.

RESULTS

The P. melaninogenica was more abundant in OLP than in healthy controls, and the differences were significant at the level of the phylum, family, genus, and species (p < .05). FISH showed that P. melaninogenica can invade the epithelium and even the lamina propria of OLP, while no invasion was found in the normal mucosa. Prevotella melaninogenica can adhere to and invade macrophages and then activate the transcription of IL-1β, IL-6, and TNF-α in NF-κB signaling pathway.

CONCLUSION

Prevotella melaninogenica may be involved in the pathogenic process of OLP, and its specific mechanism deserves further study.

High-level laser therapy versus scalpel surgery in the treatment of oral lichen planus: a randomized control trial

OBJECTIVE

To compare the clinical effectiveness of various types of high-level laser therapy (HLLT) toward scalpel excision for the surgical treatment of erosive oral lichen planus (OLP).

MATERIALS AND METHODS

The total number of 128 individuals were enrolled in the study. The 35 did not meet the inclusion criteria due to malignancy signs and presence of diabetes mellitus. In total, 8 were lost to follow-up, and 10 were excluded from the analysis, due to analgesics intake. This way 75 patients with the erosive form of OLP were analyzed in three intervention groups (Er:YAG, n = 19; Nd:YAG, n = 15; Er:YAG + Nd:YAG combination, n = 20) and one control group with scalpel excision (n = 21). The therapy effectiveness has been assessed based on the comparison of salivary interleukin (IL)-1β, IL-6 and interferon (IFN)-γ preoperative levels to 14, 30 days, and 2 years postoperation, as well as pain level and time of epithelization.

RESULTS

All HLLT groups demonstrated a significantly (p > 0.05) higher IL-1β, IL-6, IFNγ and pain level reduction and quicker epithelization toward the control group on the 30th day, except Nd:YAG in case of IFNγ level. The highest IL-1β, IFNγ and pain level reduction and quicker epithelization on the 30th day was observed in Er:YAG group, followed by Er:YAG + Nd:YAG combination, Nd:YAG respectively. However no significant difference was observed between the HLLT groups with regard to IL-6 level reduction. After a 2-year follow-up, no significant difference was observed between all study groups with regard to all variables.

CONCLUSION

HLLT yields a superior clinical outcome compared to the scalpel excision for the surgical treatment of oral lichen planus, whereby the Er:YAG has been proposed as the most effective laser type at the end of the first postoperative month.

CLINICAL RELEVANCE

For the surgical treatment of erosive OLP the Er:YAG laser may be a preferable treatment option compared to Nd:YAG and scalpel surgery.

TRIAL REGISTRATION

The present trial was registered retrospectively in the German Clinical Trials Register, as a member of WHO international clinical trials registry platform, on the 18.03.2020 with the following number: DRKS00020986.

Quercetin protects human oral keratinocytes from lipopolysaccharide-induced injury by downregulating microRNA-22

BACKGROUND

Quercetin exerts anti-inflammatory effects, but whether it can benefit patients with the chronic inflammatory disease of oral lichen planus (OLP), which is a common chronic mucocutaneous disorder with an immune-mediated pathogenesis, is unclear. The present research examined the impacts of quercetin in a cell-based OLP model in which human oral keratinocytes (HOKs) were treated with lipopolysaccharide (LPS).

METHODS

Effects of quercetin on viability, proliferation, and apoptosis of HOKs were assessed using the Cell Counting Kit-8 assay, Western blotting, and flow cytometry, respectively. Effects of treatment on levels of microRNA-22 (miR-22) were measured using stem-loop reverse transcription polymerase chain reaction, while levels of proteins and phosphorylation in the PI3K/AKT and JAK1/STAT3 cascades were analyzed by Western blot.

RESULTS

Quercetin mitigated LPS-induced reduction in HOK viability and elevation of apoptosis. It also weakened LPS-induced upregulation of miR-22. Quercetin treatment led to significantly higher levels of p-PI3K, p-AKT, p-JAK1, and p-STAT3. These effects of quercetin were enhanced when miR-22 was knocked down and partly reversed when miR-22 was overexpressed.

CONCLUSION

Quercetin can mitigate LPS-induced injury in HOKs by downregulating miR-22, thereby activating PI3K/AKT and JAK1/STAT3 cascades.

Metal nanoparticles-induced activation of NLRP3 inflammasome in human oral keratinocytes is a possible mechanism of oral lichenoid lesions

The NLRP3 inflammasome has been implicated in the pathogenesis of various inflammatory diseases and is activated by particulate stimulants. Oral epithelial keratinocytes are frequently exposed to metal nanoparticles. In this study, we examined the effects of gold, silver, and palladium nanoparticles, which are frequently used for dental metal alloys on cell proliferation, cytotoxicity, autophagy, lysosomal functions, and NLRP3 inflammasome activation using the immortalized human oral keratinocyte cell line RT-7. The metal nanoparticles were agglomerated in the membrane vesicles in RT-7 cells and suppressed cell proliferation and increased lactate dehydrogenase activity as well as the proportion of apoptotic cells. Silver and palladium nanoparticles induced autophagy and lysosomal dysfunctions and all metal nanoparticles tested triggered the secretion of IL-1β through caspase-1 activation. Furthermore, the epithelium obtained from patients with oral lichenoid lesions (OLLs) had robust NLRP3, ASC, caspase-1, and IL-1β-positive keratinocytes and cDNA microarray showed significant elevation in the mRNA levels of NLRP3. These results suggest that internalized metal nanoparticles in oral mucosal epithelial cells activate the NLRP3 inflammasome through the induction of lysosomal damage and autophagy dysfunction. This process may be involved in the pathogenesis of OLL and suggest its potential as an alternative target for OLL therapy.

Monomethyl fumarate alleviates sepsis-induced hepatic dysfunction by regulating TLR-4/NF-κB signalling pathway

AIMS

Sepsis is a potentially fatal illness that can lead to impairment of multiple organs such as liver. The condition is deeply associated with oxidative stress and inflammation. Monomethyl fumarate (MMF) has manifested antioxidant and immunomodulatory properties. The aim of current study was to evaluate protective effects of MMF in sepsis-induced hepatic dysfunction.

MAIN METHODS

Sepsis was induced by cecal ligation and puncture (CLP). Wistar rats were assigned to one of sham, CLP, CLP + dexamethasone (as positive control of inflammation) and CLP + MMF groups. Levels of serum IL-1β, IL-6, IL-10, AST, ALT and γ‑GT were quantified. Furthermore, Hepatic levels of GSH and MDA and mRNA expression of TNF and NFKBIA along with hepatic protein level of TLR-4 were assessed. Also, histopathological study of liver was carried out to evaluate hepatic injuries.

KEY FINDINGS

Septic rats demonstrated risen levels of IL-1β, IL-6, IL-10, AST, ALT and γ‑GT, while treatment with dexamethasone or MMF attenuated these levels. Moreover, enhancements in protein level of TLR-4 and mRNA levels of TNF and NFKBIA were observed in CLP rats. These elevations were mitigated in CLP-induced rats that were treated with either dexamethasone or MMF. Treatment with dexamethasone or MMF also shifted sepsis-induced disturbance in the levels of GSH and MDA towards sham levels. Hepato-protective effects of dexamethasone and MMF were further confirmed by histopathological observations.

SIGNIFICANCE

Our findings imply that MMF alleviates sepsis-induced hepatic dysfunction by mitigating the inflammatory and oxidative state and this effect is at least partly mediated by the inhibition of TLR-4/NF-κB signalling pathway.

Immunohistopathological characterization and the impact of topical immunomodulatory therapy in oral chronic graft-versus-host disease: A pilot study

OBJECTIVE

To characterize the immunohistopathological features of oral chronic graft-versus-host disease (cGVHD), and the impact of topical immunomodulatory therapy on the infiltrating cells.

MATERIAL AND METHODS

Paired oral cGVHD biopsies obtained before (n = 12) and 1 month after treatment (n = 12) with topical dexamethasone (n = 8) or tacrolimus (n = 4) were characterized by immunohistochemistry using a panel of CD1a, CD3, CD4, CD8, CD20, CD31, CD62E, CD103, CD163, c-kit, and FoxP3. Controls included acute GVHD (aGVHD; n = 3), oral lichen planus (OLP; n = 5), and normal tissues (n = 5).

RESULTS

Oral cGVHD specimens prior to treatment were mainly characterized by basal cell squamatization, lichenoid inflammation, sclerosis, apoptosis, and lymphocytic exocytosis. The infiltrating cells in oral cGVHD primarily consisted of CD3+ , CD4+ , CD8+ , CD103+ , CD163+ , and FoxP3+ cells, which were higher than in normal tissues. Topical dexamethasone or tacrolimus reduced neutrophilic exocytosis, basal cell squamatization, and lichenoid inflammation in oral cGVHD, and dexamethasone reduced the number of CD4+ and CD103+ cells.

CONCLUSION

The high expression of CD3, CD4, CD8, CD103, CD163, and FoxP3 confirms that oral cGVHD is largely T-cell-driven with macrophage participation. The impact of topical immunomodulatory therapy was variable, reducing histological inflammatory features, but with a weak clinicopathological correlation. Topical dexamethasone reduced the expression of CD4 and CD103, which may offer novel therapeutic targets.

Ashwagandha root extract exerts anti‑inflammatory effects in HaCaT cells by inhibiting the MAPK/NF‑κB pathways and by regulating cytokines

A paste composed of the boiled leaves and roots of the Ashwagandha plant is used to cure ulcer and swelling in Ayurvedic medicine. However, the effects of the hot water extract of Ashwagandha roots (ASH‑WEX), which is also used in Ayurveda, on skin have not been fully elucidated. Therefore, the present study investigated the anti‑inflammatory activity of ASH‑WEX on skin, by using the human keratinocyte cell line HaCaT. The results indicated that ASH‑WEX significantly inhibited mRNA expression of inflammatory cytokines, including interleukin (IL)‑8, IL‑6, tumor necrosis factor (TNF‑α), IL‑1β and IL‑12, and promoted the mRNA expression of the anti‑inflammatory cytokine transforming growth factor (TGF)‑β1 in HaCaT cells. In addition, ASH‑WEX inhibited the lipopolysaccharide‑induced phosphorylation of p38 and c‑Jun N‑terminal kinase, as well as the nuclear translocation of nuclear factor (NF)‑κB p65. Downregulation of TNF‑α mRNA and upregulation of TGF‑β1 mRNA were also observed in vivo following ASH‑WEX treatment of mouse skin. In conclusion, the present study demonstrated that the anti‑inflammatory effect of ASH‑WEX may be due to its ability to suppress the NF‑κB and mitogen‑activated protein kinase pathways, and to modulate cytokine expression. These results suggest that ASH‑WEX can potentially protect against skin inflammation.

Porphyromonas gingivalis lipopolysaccharide induces over production of CC chemokine ligand 2 via toll-like receptor-4 in oral lichen planus

BACKGROUND

We recently reported that the CC chemokine ligand 2 (CCL2)-CC receptor 2 (CCR2) axis was involved in the pathogenesis of oral lichen planus (OLP). However, the exact mechanism for the high expression of CCL2 in OLP specimens is not clear. Therefore, this study was designed to investigate the potential role of the toll-like receptor 4 (TLR-4) pathway in overproduction of CCL2 in OLP lesions.

METHODS

Immunohistochemical staining and real-time RT-PCR were used to detect TLR-4, CCL2, and CCR2 expression in OLP lesions. Then, gingival epithelial cells from OLP lesions were established and treated with Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS). CCL2 expression in epithelial cells was determined by Western blotting and real-time RT-PCR. In some experiments, TAK-242, a specific inhibitor of TLR-4, was used to block the TLR-4 pathway before cells were stimulated with LPS.

RESULTS

We found that TLR-4 was significantly increased in the epithelium of OLP specimens, compared with controls. Moreover, LPS can induce the over production of CCL2 in epithelial cells of OLP, in vitro. TAK-242 effectively eliminated the increase in CCL2 expression induced by LPS by blocking the TLR-4/NF-κB pathway. In addition, we again confirmed that expression of CCL2 and CCR2 was increased in OLP specimens.

CONCLUSION

Increased TLR-4 expression contributes to the upregulated expression of CCL2 in the epithelium of OLP lesions, which suggests that oral bacteria participate in the pathogenesis of OLP via the TLR-4 pathway.

Semaphorin4D Drives CD8+ T-Cell Lesional Trafficking in Oral Lichen Planus via CXCL9/CXCL10 Upregulations in Oral Keratinocytes

Chemokine-mediated CD8⁺ T-cell recruitment is an essential but not well-established event for the persistence of oral lichen planus (OLP). Semaphorin 4D (Sema4D)/CD100 is implicated in immune dysfunction, chemokine modulation, and cell migration, which are critical aspects for OLP progression, but its implication in OLP pathogenesis has not been determined. In this study, we sought to explicate the effect of Sema4D on human oral keratinocytes and its capacity to drive CD8⁺ T-cell lesional trafficking via chemokine modulation. We found that upregulations of sSema4D in OLP tissues and blood were positively correlated with disease severity and activity. In vitro observation revealed that Sema4D induced C-X-C motif chemokine ligand 9/C-X-C motif chemokine ligand 10 production by binding to plexin-B1 via protein kinase B-NF-κB cascade in human oral keratinocytes, which elicited OLP CD8⁺ T-cell migration. We also confirmed using clinical samples that elevated C-X-C motif chemokine ligand 9/C-X-C motif chemokine ligand 10 levels were positively correlated with sSema4D levels in OLP lesions and serum. Notably, we determined matrix metalloproteinase-9 as a new proteolytic enzyme for the cleavage of sSema4D from the T-cell surface, which may contribute to the high levels of sSema4D in OLP lesions and serum. Our findings conclusively revealed an amplification feedback loop involving T cells, chemokines, and Sema4D-dependent signal that promotes OLP progression.

TLR1-10, NF-κB and p53 expression is increased in oral lichenoid disease

Toll-like receptors (TLRs) and nuclear factor-κB (NF-κB) in keratinocytes play an important role in dermatological autoimmune diseases. Tumour suppressor protein p53 regulates TLR expression. The aim of this study was to compare the expression of TLR1-TLR10, p53 and NF-κB in patients with oral lichenoid disease (OLD) with healthy mucosa. Oral mucosal biopsies from 24 patients with OLD and 26 healthy controls (HC) were analysed for the expression of TLR1-TLR10, NF-κB and p53 by immunohistochemistry. The expression of all TLRs was increased in OLD epithelia compared to HC samples and the difference was significant in TLR1, TLR3, TLR4, TLR5, TLR6 and TLR7. In the basement membrane zone, the immunoreactivity of TLR5 was significantly more intense in OLD compared to HC. In the intermediate layer, the immunoreactivity of NF-κB was significantly stronger in OLD, whereas the staining for p53 was more intense in all layers of OLD compared to HC samples. In OLD, a positive correlation between TLR2 and NF-κB in the basal layer and between TLR5, p53 and NF-κB in the intermediate layers was discovered. The expression of TLRs, p53 and NF-κB is increased in OLD, which may play a role in the pathogenesis of this chronic immune-mediated mucosal disease.

The caspase-1 inhibitor CARD18 is specifically expressed during late differentiation of keratinocytes and its expression is lost in lichen planus

BACKGROUND

CARD18 contains a caspase recruitment domain (CARD) via which it binds to caspase-1 and thereby inhibits caspase-1-mediated activation of the pro-inflammatory cytokine interleukin (IL)-1β.

OBJECTIVES

To determine the expression profile and the role of CARD18 during differentiation of keratinocytes and to compare the expression of CARD18 in normal skin and in inflammatory skin diseases.

METHODS

Human keratinocytes were induced to differentiate in monolayer and in 3D skin equivalent cultures. In some experiments, CARD18-specific siRNAs were used to knock down expression of CARD18. CARD18 mRNA levels were determined by quantitative real-time PCR, and CARD18 protein was detected by Western blot and immunofluorescence analyses. In situ expression was analyzed in skin biopsies obtained from healthy donors and patients with psoriasis and lichen planus.

RESULTS

CARD18 mRNA was expressed in the epidermis at more than 100-fold higher levels than in any other human tissue. Within the epidermis, CARD18 was specifically expressed in the granular layer. In vitro CARD18 was strongly upregulated at both mRNA and protein levels in keratinocytes undergoing terminal differentiation. In skin equivalent cultures the expression of CARD18 was efficiently suppressed by siRNAs without impairing stratum corneum formation. Epidermal expression of CARD18 was increased after ultraviolet (UV)B irradiation of skin explants. In skin biopsies of patients with psoriasis no consistent regulation of CARD18 expression was observed, however, in lesional epidermis of patients with lichen planus, CARD18 expression was either greatly diminished or entirely absent whereas in non-lesional areas expression was comparable to normal skin.

CONCLUSIONS

Our results identify CARD18 as a differentiation-associated keratinocyte protein that is altered in abundance by UV stress. Its downregulation in lichen planus indicates a potential role in inflammatory reactions of the epidermis in this disease.

Protein Carbonylation in Human Smokers and Mammalian Models of Exposure to Cigarette Smoke: Focus on Redox Proteomic Studies

SIGNIFICANCE

Oxidative stress is one mechanism whereby tobacco smoking affects human health, as reflected by increased levels of several biomarkers of oxidative stress/damage isolated from tissues and biological fluids of active and passive smokers. Many investigations of cigarette smoke (CS)-induced oxidative stress/damage have been carried out in mammalian animal and cellular models of exposure to CS. Animal models allow the investigation of many parameters that are similar to those measured in human smokers. In vitro cell models may provide new information on molecular and functional differences between cells of smokers and nonsmokers. Recent Advances: Over the past decade or so, a growing number of researches highlighted that CS induces protein carbonylation in different tissues and body fluids of smokers as well as in in vivo and in vitro models of exposure to CS.

CRITICAL ISSUES

We review recent findings on protein carbonylation in smokers and models thereof, focusing on redox proteomic studies. We also discuss the relevance and limitations of these models of exposure to CS and critically assess the congruence between the smoker's condition and laboratory models.

FUTURE DIRECTIONS

The identification of protein targets is crucial for understanding the mechanism(s) by which carbonylated proteins accumulate and potentially affect cellular functions. Recent progress in redox proteomics allows the enrichment, identification, and characterization of specific oxidative protein modifications, including carbonylation. Therefore, redox proteomics can be a powerful tool to gain new insights into the onset and/or progression of CS-related diseases and to develop strategies to prevent and/or treat them. Antioxid. Redox Signal. 26, 406-426.

Modulation of Human Immune Response by Fungal Biocontrol Agents

Although the vast majority of biological control agents is generally regarded as safe for humans and environment, the increased exposure of agriculture workers, and consumer population to fungal substances may affect the immune system. Those compounds may be associated with both intense stimulation, resulting in IgE-mediated allergy and immune downmodulation induced by molecules such as cyclosporin A and mycotoxins. This review discusses the potential effects of biocontrol fungal components on human immune responses, possibly associated to infectious, inflammatory diseases, and defective defenses.

Intermittent Hypoxia and Unsaturated Aldehydes: Effects on Oral Epithelial Wound Healing

Obstructive sleep apnea (OSA) is a highly prevalent sleep breathing disorder characterized by intermittent hypoxia (IH), leading to blood hypoxemia, hypercapnia, and sleep fragmentation. Studies on the effects of OSA on oral epithelial tissue healing are limited. Smoking is considered a risk factor for OSA through the exposure to chemically active toxins, present in the smoke. Acrolein is the most chemically active unsaturated aldehyde, impairing a variety of biological processes. The aim of this study was to determine the effect of IH on oral epithelial tissue healing, with and without acrolein. HaCaT cells were wounded by a cross-scratch made in the cell cultures, considered as time zero. Then, cells were exposed to 28 IH cycles (5-20% oxygen) during 12 h using the BioSpherix OxyCycler-C42 system. Control cells were maintained in normoxic conditions or in sustained hypoxia (SH) (5% oxygen) for the same durations, after which all cells were maintained for additional 12 h in normoxia. The migrating abilities of cells were measured after 24 h by calculating the percent of the residual cross-scratch area. In parallel experiments, 25 μM acrolein were added to each treatment. We found that the scratch closure was the slowest under IH. After 24 h, the residual scratch area in the IH treated cells was 29.5 ± 13.4% of the initial area, while in normoxia and SH it was 9.2 ± 5.8% and 10.3 ± 11.3%, respectively (p < 0.01 for both vs. IH). Adding acrolein further attenuated the migratory ability in IH as compared to normoxia and SH. We conclude that IH delays the healing process of oral epithelial tissue by slowing the cells' migratory abilities. The healing might be further attenuated by chemically active unsaturated aldehydes such as acrolein.

Apocynin inhibits Toll-like receptor-4-mediated activation of NF-κB by suppressing the Akt and mTOR pathways

Microbial product lipopolysaccharide has been shown to be involved in the pathogenesis of inflammatory skin diseases. Apocynin has demonstrated to have an anti-inflammatory effect. However, the effect of apocynin on the Toll-like receptor-4-dependent activation of Akt, mammalian target of rapamycin (mTOR), and nuclear factor (NF)-κB pathway, which is involved in productions of inflammatory mediators in keratinocytes, has not been studied. Using human keratinocytes, we investigated the effect of apocynin on the inflammatory mediator production in relation to the Toll-like receptor-4-mediated-Akt/mTOR and NF-κB pathways, which regulates the transcription genes involved in immune and inflammatory responses. Apocynin, Akt inhibitor SH-5, Bay 11-7085 and N-acetylcysteine each attenuated the lipopolysaccharide-induced production of cytokines, PGE₂, and chemokines, changes in the levels of Toll-like receptor-4, p-Akt, mTOR, and NF-κB, and production of reactive oxygen species in keratinocytes. The results show that apocynin appears to attenuate the lipopolysaccharide-stimulated production of inflammatory mediators in keratinocytes by suppressing the Toll-like receptor-4-mediated activation of the Akt, mTOR, and NF-κB pathways. The effect of apocynin appears to be attributed to its inhibitory effect on the production of reactive oxygen species. Apocynin appears to attenuate the microbial product-mediated inflammatory skin diseases.

Cathepsin K expression is increased in oral lichen planus

BACKGROUND

Oral lichen planus (OLP) is an idiopathic T-cell-mediated mucosal inflammatory disease. Cathepsin K (Cat K) is one of the lysosomal cysteine proteases. It is involved in many pathological conditions, including osteoporosis and cancer. The expression and role of Cat K in OLP are unknown.

METHODS

Twenty-five oral mucosal specimens diagnosed histopathologically as OLP and fourteen healthy controls (HC) were used to study the immunohistochemical (IHC) expression of Cat K. Colocalization of Cat K with CD1a, Melan-A, CD68, CD45, mast cell tryptase (MCT), and Toll-like receptors (TLRs) 4 and 9 were studied using double IHC and/or immunofluorescence (IF) staining. Expression of Cat K was also evaluated in OLP tissue samples before and after topical tacrolimus treatment.

RESULTS

Cat K was expressed in a higher percentage of cells in the epithelial zone, and the staining intensity was stronger in the stroma in OLP compared to controls (P < 0.001). In OLP, Cat K was present mostly in melanocytes and macrophages and sporadically in basal keratinocytes, endothelial cells, and extracellularly. Cat K was found also in some fibroblasts in HC and OLP samples. Coexpression of Cat K and TLRs 4 and 9 was seen in some dendritic cells (presumably melanocytes) and macrophages. In OLP, tacrolimus treatment reduced the expression of Cat K in the epithelium but increased it in the stroma.

CONCLUSIONS

These results suggest that Cat K is involved in the pathogenesis of OLP. Cat K possibly takes part in the modulation of matrix molecules and cellular receptors.

The Activation of NF-κB in Infiltrated Mononuclear Cells Negatively Correlates with Treg Cell Frequency in Oral Lichen Planus

Oral lichen planus (OLP) is a T cell-mediated chronic inflammatory mucosal disease with persistent accumulation of T cells in the lamina propria. Nuclear factor-kappa B (NF-κB) is a major regulator of immune responses, and NF-κB-dependent cytokines and pro-inflammatory mediators can be detected in higher levels in the saliva and serum from patients with OLP. CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells play an important role in the prevention of autoimmune pathology by regulating the immune response. To explore the correlation between NF-κB p65 activation and accumulation of Treg cells in patients with OLP, 40 ethnic Chinese patients with OLP and 10 healthy volunteers were recruited. The nuclear expression of NF-κB p65 in infiltrated mononuclear cells and Treg cells in the OLP lesion and the normal oral mucosa (NOM) was analyzed by immunohistochemistry assay. Our results showed that both the nuclear expression of NF-κB p65 and the number of Foxp3(+) Treg were higher in the OLP lesions. Furthermore, the frequency of Treg cells was negatively correlated with NF-κB nuclear expression in subepithelial lymphocytic infiltrate of the OLP lesion. This finding provides a new insight into the pathogenesis of OLP and may contribute to novel therapeutic strategies for the treatment of OLP by modulating the immune system.

miR-125b inhibits keratinocyte proliferation and promotes keratinocyte apoptosis in oral lichen planus by targeting MMP-2 expression through PI3K/Akt/mTOR pathway

Oral lichen planus (OLP) is a chronic inflammatory mucosal disease that involves the degeneration of keratinocytes. However, the etiology and mechanisms of OLP pathogenesis have not been fully elucidated. In this study, we used keratinocytes HaCaT stimulated with lipopolysaccharide (LPS) to mimic a local OLP immune environment, and investigated the regulatory role of miR-125b in keratinocyte proliferation and apoptosis under OLP conditions. Immunohistochemical analysis and quantitative real-time PCR (qRT-PCR) assay showed that MMP-2 expression was up-regulated and miR-125b expression was down-regulated in both OLP mucosa tissues and LPS-incubated HaCaT cells. Western blot analysis indicated that miR-125b overexpression suppressed LPS-induced MMP-2 expression in HaCaT cells. Molecularly, our results confirmed that MMP-2 is a target gene of miR-125b in HaCaT cells. The effect of miR-125b on cell proliferation was revealed by CCK-8 assay, BrdU assay and cell cycle analysis, which illustrated that miR-125b overexpression impeded LPS-induced HaCaT cell proliferation. Flow cytometry analysis further demonstrated that miR-125b overexpression promoted HaCaT cell apoptosis. Moreover, these effects were involved in PI3K/Akt/mTOR activation, as miR-125b overexpression inhibited LPS-enhanced expression of p-Akt and p-mTOR proteins. Taken together, these data confirm that miR-125b might inhibit keratinocyte proliferation and promote keratinocyte apoptosis in OLP pathogenesis by targeting MMP-2 through PI3K/Akt/mTOR pathway.

Possible alternative therapies for oral lichen planus cases refractory to steroid therapies

Oral lichen planus (OLP) is a chronic inflammatory disorder with a multifactorial etiopathogenesis. Immune dysregulation plays a critical role in the development and progression of this disease. Patients' lives may be affected by pain caused by atrophic-erosive lesions. Given the obscure etiology, treatment is usually symptomatic. Topical steroids remain the mainstay of management. However, their therapeutic benefits are not always evident. There are substantial data on the possible therapeutic strategies that are effective in OLP cases refractory to steroids. This review provides an overview of the current approaches for the management of steroid-refractory OLP. The miscellaneous treatment regimens include tacrolimus, pimecrolimus, thalidomide, low-level laser therapy, photodynamic therapy, and surgical excision. Some results obtained from these studies were promising. However, further studies, especially randomized controlled trials with strict inclusion and exclusion criteria and larger sample sizes, are required for the evaluation of the long-term safety and efficacy of these therapies.

Sesquiterpene lactone parthenolide attenuates production of inflammatory mediators by suppressing the Toll-like receptor-4-mediated activation of the Akt, mTOR, and NF-κB pathways

Microbial product lipopolysaccharide has been shown to be involved in the pathogenesis of inflammatory skin diseases. Parthenolide present in extracts of the herb feverfew has demonstrated an anti-inflammatory effect. However, the effect of parthenolide on the Akt/mTOR and NF-κB pathway activation-induced productions of inflammatory mediators in keratinocytes has not been studied. Using human keratinocytes, we investigated the effect of parthenolide on the inflammatory mediator production in relation to the Toll-like receptor-4-mediated-Akt/mTOR and NF-κB pathways, which regulate the transcription genes involved in immune and inflammatory responses. Parthenolide, Akt inhibitor, Bay 11-7085, and N-acetylcysteine each attenuated the lipopolysaccharide-induced production of IL-1β and PGE2, increase in the levels of cyclooxygenase, formation of reactive oxygen species, increase in the levels of Toll-like receptor-4, and activation of the Akt/mTOR and NF-κB in keratinocytes. The results show that parthenolide appears to attenuate the lipopolysaccharide-stimulated production of inflammatory mediators in keratinocytes by suppressing the Toll-like receptor-4-mediated activation of the Akt, mTOR, and NF-κB pathways. The activation of signaling transduction pathways appear to be regulated by reactive oxygen species. Parthenolide appears to attenuate the microbial product-mediated inflammatory skin diseases.

Anti-inflammatory effects of astaxanthin in the human gingival keratinocyte line NDUSD-1

Oral lichen planus is a chronic inflammatory disease that affects the mucous membrane of the oral cavity and can contribute to the development of other diseases. Inflammation in oral lichen planus is a T-cell-mediated autoimmune disease that acts through cytotoxic CD8⁺ T cells to trigger apoptosis of keratinocytes. However, the specific cause of oral lichen planus remains unknown and no effective medical treatment has yet been established. Astaxanthin is a carotenoid pigment with capacity for anti-inflammatory and anti-oxidant activities. In this study, we evaluated whether astaxanthin could be used to improve the pathology of oral lichen planus by reducing inflammation. In particular, the anti-inflammatory effects of astaxanthin on the chronic inflammation caused by lipopolysaccharide derived from Escherichia coli O55 in human gingival keratinocytes (NDUSD-1) were evaluated. Following astaxanthin treatment, localization of nuclear factor κB/p65 and the level of inflammatory cytokines (interleukin-6, tumor necrosis factor-α) tended to decrease, and cell proliferation significantly increased in vitro. These results suggest that astaxanthin could be useful for improving chronic inflammation such as that associated with oral lichen planus.

Oxidative damage in keratinocytes exposed to cigarette smoke and aldehydes

Cigarette smoke (CS) is a significant environmental source of human exposure to chemically active saturated (acetaldehyde) and α,β-unsaturated aldehydes (acrolein) inducing protein carbonylation and dysfunction. The exposure of oral tissues to environmental hazards is immense, especially in smokers. The objectives of the current study were to examine the effect of aldehydes originating from CS on intracellular proteins of oral keratinocytes and to observe the antioxidant response in these cells. Intracellular protein carbonyl modification under CS, acrolein and acetaldehyde exposure in the HaCaT keratinocyte cell line, representing oral keratinocytes was examined by Western blot. Possible intracellular enzymatic dysfunction under the above conditions was examined by lactate dehydrogenase (LDH) activity assay. Oxidative stress response was investigated, by DCF (2,7-dichlorodihydrofluorescein) assay and GSH (glutathione) oxidation. Intracellular protein carbonyls increased 5.2 times after CS exposure and 2.7 times after exposure to 1 μmol of acrolein. DCF assay revealed an increase of fluorescence intensity 3.2 and 3.1 times after CS and acrolein exposure, respectively. CS caused a 72.5% decrease in intracellular GSH levels compared to controls. Activity of intracellular LDH was preserved. α,β-Unsaturated aldehydes from CS are capable of intracellular protein carbonylation and have a role in intracellular oxidative stress elevation in keratinocytes, probably due to the reduction in GSH levels.

Inflammation-related cytokines in oral lichen planus: an overview

Cytokines are powerful mediators which play a central role in both innate and adapted immune responses. Aberrant productions of cytokines may lead to the onset of immune deficiency, allergy or autoimmunity, which are involved in the mechanisms of various immune-mediated inflammatory diseases. Oral lichen planus (OLP) is a chronic inflammation disease affecting the oral mucosa with unknown aetiology. Previous studies have described the abnormal expression patterns of various inflammation-related cytokines, such as IL-1, 2, 4, 5, 6, 8, 10, 12, 17, 18, TGF-β, IFN-γ and TNF-α, in lesions, saliva, serum and peripheral blood mononuclear cells from patients with OLP, which may reflect the immune dysregulation status and emerge as central players in the immunopathogenesis of OLP. Besides, the gene polymorphisms of several cytokines such as IFN-γ, TNF-α, IL-4, IL-10 have been found to be involved in the susceptibility of OLP. In this review, we gave a brief introduction of the characteristics and biological functions of these inflammation-related cytokines and summarized for the first time the current knowledge on the involvement of inflammation-related cytokines in OLP. Further research on the exact roles of these cytokines will aid the understanding of the pathogenesis and the identification of novel therapeutic approaches of OLP.

TNF receptor-associated factor 6 regulates proliferation, apoptosis, and invasion of glioma cells

Tumor necrosis factor receptor-associated factor 6 (TRAF6), which plays an important role in inflammation and immune response, is an essential adaptor protein for the NF-κB (nuclear factor κB) signaling pathway. Recent studies have shown that TRAF6 played an important role in tumorigenesis and invasion by suppressing NF-κB activation. However, up to now, the biologic role of TRAF6 in glioma has still remained unknown. To address the expression of TRAF6 in glioma cells, four glioma cell lines (U251, U-87MG, LN-18, and U373) and a non-cancerous human glial cell line SVG p12 were used to explore the protein expression of TRAF6 by Western blot. Our results indicated that TRAF6 expression was upregulated in human glioma cell lines, especially in metastatic cell lines. To investigate the role of TRAF6 in cell proliferation, apoptosis, invasion, and migration of glioma, we generated human glioma U-87MG cell lines in which TRAF6 was either overexpressed or depleted. Subsequently, the effects of TRAF6 on cell viability, cell cycle distribution, apoptosis, invasion, and migration in U-87MG cells were determined with 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyl tetrazolium bromide (MTT) assay, flow cytometry analysis, transwell invasion assay, and wound-healing assay. The results showed that knockdown of TRAF6 could decrease cell viability, suppress cell proliferation, invasion and migration, and promote cell apoptosis, whereas overexpression of TRAF6 displayed the opposite effects. In addition, the effects of TRAF6 on the expression of phosphor-NF-κB (p-p65), cyclin D1, caspase 3, and MMP-9 were also probed. Knockdown of TRAF6 could lower the expression of p-p65, cyclin D1, and MMP-9, and raise the expression of caspase 3. All these results suggested that TRAF6 might be involved in the potentiation of growth, proliferation, invasion, and migration of U-87MG cell, as well as inhibition of apoptosis of U-87MG cell by abrogating activation of NF-κB.

Effect of TRAF6 on the biological behavior of human lung adenocarcinoma cell

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is a unique adaptor protein of the tumor necrosis factor receptor-associated factor family that mediates both tumor necrosis factor receptor and interleukin-1 receptor/Toll-like receptor signaling. A recent study showed that TRAF6 played an important role in tumorigenesis and invasion through activation of nuclear factor kappa B (NF-κB). However, the biological role of TRAF6 remains unknown in lung cancer up to now. To address the expression of TRAF6 in lung cancer cells, four lung cancer cell lines (A549, HCC827, NCI-H292, and 95-D) and human bronchial epithelial cells were used to detect the expression of TRAF6 protein by western blotting. Results indicated that TRAF6 displayed an upregulation in human lung cancer cell lines. To investigate the effects of TRAF6 on the biological behavior of human lung adenocarcinoma cell, we generated human lung adenocarcinoma A549 cell line in which TRAF6 was depleted. The results showed that downregulation of TRAF6 could decrease cell viability, suppress cell proliferation and invasion, and promote cell apoptosis. At the same time, we explored the effects of TRAF6 on the expression of the following proteins: phosphor-NF-κB (p-p65), cyclin D1, caspase-3, and matrix metalloproteinase 9 (MMP9). Downregulation of TRAF6 could decrease the expression of p-p65, cyclin D1, and MMP9 and increase the expression of caspase-3. All these results suggested that TRAF6 might be involved in the potentiation of growth, proliferation, and invasion of A549 cell line, as well as the inhibition of A549 cell apoptosis by the activation of NF-κB. To make a long story short, the overexpression of TRAF6 might be related to the tumorigenesis and invasion of lung cancer.