Pro-inflammatory cytokine release in keratinocytes is mediated through the MAPK signal-integrating kinases

Anti-inflammatory Capacity of a Medicinal herb extract, Anemarrhena asphodeloides, on In vivo and In vitro models-induced atopic dermatitis

Anemarrhena asphodeloides (AA) Bunge, a rhizomatous plant from the Liliaceae family, is traditionally utilized to manage inflammatory conditions. Nevertheless, its impact on atopic dermatitis (AD) and the associated molecular pathways have not yet been fully explored. This study explored the therapeutic effects of AA on AD both in vivo, using 2,4-dinitrofluorobenzene-induced NC/Nga mice, and in vitro, with tumor necrosis factor-α/interferon-γ-stimulated HaCaT keratinocytes. Topical application of AA ointment on the dorsal skin notably alleviated AD symptoms and skin lesions, enhanced the dermatitis score, and improved parameters such as the rate of trans-epidermal water loss, epidermal thickness, mast cell infiltration, systemic IgE levels, and cytokine expression. Furthermore, AA treatment significantly reduced serum levels of thymic stromal lymphopoietin (TSLP) and locally suppressed mRNA expression of thymus and activation-regulated chemokine (TARC) along with other relevant cytokines in affected skin. Both in vivo and in vitro applications of AA curtailed TSLP levels by inhibiting the expression of signal transducer and activator of transcription 6, a key regulator of pruritus and an initiator of mitogen-activated protein kinase signaling pathways. Additionally, AA affected the expression of tumor necrosis factor-like weak inducer of apoptosis/fibroblast growth factor-inducible 14, a pathway of interest in the study of cutaneous inflammatory diseases. Collectively, these findings propose that AA holds potential as an effective therapeutic agent for treating AD-induced skin inflammation.

Kahweol Inhibits Pro-Inflammatory Cytokines and Chemokines in Tumor Necrosis Factor-α/Interferon-γ-Stimulated Human Keratinocyte HaCaT Cells

Atopic dermatitis (AD), marked by intense itching and eczema-like lesions, is a globally increasing chronic skin inflammation. Kahweol, a diterpene that naturally occurs in coffee beans, boasts anti-inflammatory, antioxidative, and anti-cancer properties. This research explores the anti-inflammatory action of kahweol on HaCaT human keratinocytes stimulated by tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), focusing on key signal transduction pathways. Our results demonstrate that kahweol markedly reduces the production of IL-1β, IL-6, C-X-C motif chemokine ligand 8, and macrophage-derived chemokine in TNF-α/IFN-γ-activated HaCaT cells. Furthermore, it curtails the phosphorylation of key proteins in the mitogen-activated protein kinase (MAPK) pathways, including c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p38. Additionally, kahweol impedes the phosphorylation and nuclear translocation of the NF-κB p65 subunit and constrains its DNA-binding capability. It also hampers the phosphorylation, nuclear translocation, and DNA-binding activities of signal transducer and activator of transcription 1 (STAT1) and STAT3. Collectively, these findings suggest that kahweol hinders the generation of cytokines and chemokines in inflamed keratinocytes by inhibiting the MAPK, NF-κB, and STAT cascades. These insights position kahweol as a promising agent for dermatological interventions, especially in managing inflammatory skin conditions such as AD.

Discovery of D25, a Potent and Selective MNK Inhibitor for Sepsis-Associated Acute Spleen Injury

Mitogen-activated protein kinase-interacting protein kinases (MNKs) and phosphorylate eukaryotic initiation factor 4E (p-eIF4E) play a critical role in regulating mRNA translation and protein synthesis associated with the development of cancer, metabolism, and inflammation. This study undertakes the modification of a 4-(3-(piperidin-4-yl)-1H-pyrazol-5-yl)pyridine structure, leading to the discovery of 4-(3-(piperidin-4-yl)-1H-pyrazol-5-yl)-1H-pyrrolo[2,3-b]pyridine (D25) as a potent and selective MNK inhibitor. D25 demonstrated inhibitory activity, with IC50 values of 120.6 nM for MNK1 and 134.7 nM for MNK2, showing exceptional selectivity. D25 inhibited the expression of pro-inflammation cytokines in RAW264.7 cells, such as inducible NO synthase, cyclooxygenase-2, and interleukin-6 (IL-6). In the lipopolysaccharide-induced sepsis mouse model, D25 significantly reduced p-eIF4E in spleen tissue and decreased the expression of tumor necrosis factor α, interleukin-1β, and IL-6, and it also reduced the production of reactive oxygen species, resulting in improved organ injury caused by inflammation. This suggests that D25 may provide a potential treatment for sepsis and sepsis-associated acute spleen injury.

Translation-Dependent Skin Hyperplasia Is Promoted by Type 1/17 Inflammation in Psoriasis

BACKGROUND

Psoriasis vulgaris (PV) is a chronic skin inflammatory disease and characterized by aberrant epidermal hyperplasia. The molecule eukaryotic initiation factor (eIF) 4E controls translation initiation of certain protein synthesis and determines cell cycle or differentiation fate.

OBJECTIVE

To determine the role of eIF4E in keratinocytes abnormal differentiation in the context of psoriasis.

METHODS

The expression of eIF4E in psoriatic skin lesions and normal skin from human subjects was examined by western blot and immunohistochemistry. In a murine model of psoriasis-like dermatitis that is induced by topical imiquimod, 4EGI-1 was used to inhibit eIF4E activities. To measure murine skin eIF4E and keratinocytes differentiation, immunofluorescence and western blot assays were conducted. Normal human epidermal keratinocytes (NHEK) were isolated, cultured, and stimulated with cytokines including TNF-α, IFN-γ, and IL-17A, respectively. Immunofluorescence and western blot were performed to test eIF4E and effect of 4EGI-1 in a co-culture system.

RESULTS

Compared with healthy controls, skin lesions from patients with PV exhibited a higher expression of eIF4E, which was positively correlated with the epidermal thickness. This expression pattern of eIF4E was replicated by the imiquimod-induced murine model. Skin hyperplasia and eIF4E activities in the murine model were attenuated by the administration of 4EGI-1. Both IFN-γ and IL-17A, rather than TNF-α, are sufficient to induce NHEK abnormal differentiation. This effect can be disrupted by 4EGI-1.

CONCLUSION

eIF4E plays a crucial role in keratinocytes abnormal differentiation driven by type 1/17 inflammation in the context of psoriasis. The initiation of abnormal translation provides an alternative treatment target for psoriasis.

Anti-Inflammatory Effects of Ellagic Acid on Keratinocytes via MAPK and STAT Pathways

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is characterized by an impaired skin barrier and intense itchiness, which decreases the individual’s quality of life. No fully effective therapeutic agents have prevailed for AD due to an insufficient grasp of the complex etiology. Ellagic acid (EA), a natural compound, has anti-inflammatory properties in chronic diseases. The effects of EA on AD have not yet been explored. The present study investigated the effects of EA on TNF-α/IFN-γ-stimulated HaCaT keratinocytes and house dust mite-induced AD-like skin lesions in NC/Nga mice. Treatment with EA suppressed inflammatory responses in keratinocytes by regulating critical inflammatory signaling pathways, such as mitogen-activated protein kinases and signal transducers and activators of transcription. In vivo studies using a DfE-induced AD mouse model showed the effects of EA administration through ameliorated skin lesions via decremented histological inflammatory reactions. These results suggest that EA could be a potential therapeutic alternative for the treatment of AD by inhibiting inflammatory signaling pathways.

Suppressed microRNA-195-5p expression in mycosis fungoides promotes tumor cell proliferation

BACKGROUND

Several cancers, including mycosis fungoides (MF), have reported dysregulation of miR-195-5p. miR-195-5p plays a role in cell cycle regulation in several malignant diseases.

OBJECTIVES

This study aimed to investigate: (a) the expression level of miR-195-5p in lesional MF skin biopsies and (b) the potential regulatory roles of miR-195-5p in MF.

METHODS

Quantitative real-time polymerase chain reaction (RT-qPCR) was used to determine miR-195-5p expression in MF skin biopsies and cell lines. The effect of miR-195-5p and ADP-ribosylation factor-like protein 2 (ARL2) on cell cycle and apoptosis was measured by flow cytometry assays. Changes in ARL2 expression were determined by RT-qPCR and Western blotting (WB).

RESULTS

We found lower expression levels of miR-195-5p in lesional skin from MF patients compared with non-lesional MF skin and skin from healthy volunteers. Additionally, miR-195-5p showed lower expression levels in the skin from patients with disease progression compared with patients with stable disease. In vitro studies showed that overexpression of miR-195-5p induced a cell cycle arrest in G0G1. Using microarray analysis, we identified several genes that were regulated after miR-195-5p overexpression. The most downregulated gene after miR-195-5p mimic transfection was ARL2. RT-qPCR and WB analyses confirmed downregulation of ARL2 following transfection with miR-195-5p mimic. Lastly, transfection with siRNA against ARL2 also induced a G0G1 arrest.

CONCLUSION

Upregulation of miR-195-5p in MF inhibits cycle arrest by downregulation of ARL2. miR-195-5p may thus function as a tumor suppressor in MF and low miR-195-5p expression in lesional MF skin may promote disease progression.

Deeping in the Role of the MAP-Kinases Interacting Kinases (MNKs) in Cancer

The mitogen-activated protein kinase (MAPK)-interacting kinases (MNKs) are involved in oncogenic transformation and can promote metastasis and tumor progression. In human cells, there are four MNKs isoforms (MNK1a/b and MNK2a/b), derived from two genes by alternative splicing. These kinases play an important role controlling the expression of specific proteins involved in cell cycle, cell survival and cell motility via eukaryotic initiation factor 4E (eIF4E) regulation, but also through other substrates such as heterogeneous nuclear ribonucleoprotein A1, polypyrimidine tract-binding protein-associated splicing factor and Sprouty 2. In this review, we provide an overview of the role of MNK in human cancers, describing the studies conducted to date to elucidate the mechanism involved in the action of MNKs, as well as the development of MNK inhibitors in different hematological cancers and solid tumors.

Neuroprotective Effect of Dioscin on the Aging Brain

Our previous works have shown that dioscin, a natural product, has various pharmacological activities, however, its role in brain aging has not been reported. In the present study, in vitro H₂O₂-treated PC12 cells and in vivo d-galactose-induced aging rat models were used to evaluate the neuroprotective effect of dioscin on brain aging. The results showed that dioscin increased cell viability and protected PC12 cells against oxidative stress through decreasing reactive oxygen species (ROS) and lactate dehydrogenase (LDH) levels. In vivo, dioscin markedly improved the spatial learning ability and memory of aging rats, reduced the protein carbonyl content and aging cell numbers, restored the levels of superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GSH-Px), malondialdehyde (MDA) and nitric oxide synthase (NOS) in brain tissue, and reversed the histopathological structure changes of nerve cells. Mechanism studies showed that dioscin markedly adjusted the MAPK and Nrf2/ARE signalling pathways to decrease oxidative stress. Additionally, dioscin also significantly decreased inflammation by inhibiting the mRNA or protein levels of TNF-α, IL-1β, IL-6, CYP2E1 and HMGB1. Taken together, these results indicate that dioscin showed neuroprotective effect against brain aging via decreasing oxidative stress and inflammation, which should be developed as an efficient candidate in clinical to treat brain aging in the future.

Regulation of gingival epithelial cytokine response by bacterial cyclic dinucleotides

BACKGROUND

Cyclic dinucleotides (cyclic di-guanosine monophosphate (c-di-GMP) and cyclic di-adenosine monophosphate (c-di-AMP)) and lipopolysaccharides (LPS) are pathogen-associated molecular patterns (PAMPs). Individual impacts of PAMPs on immune system have been evaluated, but simultaneous actions of multiple PAMPs have not been studied.

OBJECTIVE

Examination the effects of cyclic dinucleotides and Porphyromonas gingivalis LPS on gingival epithelial cytokine response.

METHODS

Human gingival keratinocytes (HMK) were incubated with 1, 10, and 100 µM concentrations of c-di-GMP and c-di-AMP, either in the presence or absence of P. gingivalis LPS. Intra- and extracellular levels of interleukin (IL)-1β, IL-8, IL-1Ra, monocyte chemoattractant protein (MCP)-1, and vascular endothelial growth factor (VEGF), were measured using the Luminex technique.

RESULTS

LPS decreased extracellular IL-8 levels, while the presence of c-di-AMP inhibited this effect. Incubating HMK cells with c-di-AMP (alone or with LPS) elevated the extracellular level of MCP-1. Extracellular VEGF level increased when cells were incubated with LPS and c-di-GMP together, or with c-di-AMP alone. LPS and c-di-AMP suppressed intracellular IL-1β levels. The c-di-AMP elevated intracellular levels of IL-1Ra.

CONCLUSION

c-di-AMP and, to a lesser extent, c-di-GMP regulate keratinocyte cytokine response, either as an aggregator or as a suppressor of LPS, depending on the cytokine type.

Fas/FasL pathway and cytokines in keratinocytes in atopic dermatitis - Manipulation by the electromagnetic field

BACKGROUND

Atopic dermatitis (AD) is one of the most frequent skin diseases. Changes of the keratinocytes functionality play a major role in the development of AD. For example, activation of the Fas (CD95)/FasL (CD178) pathway in AD does not lead to extensive apoptosis in skin. Binding of the Fas receptor to its protein ligand-FasL, which are present on the (AD)-modified keratinocytes, should result in the sequential induction of cell death, but there is no evidence of extensive apoptosis of these cells. This suggests that non-apoptotic mechanism of Fas/FasL pathway is commonly encountered, although not examined in the case of AD, phenomenon. An electromagnetic field, which was used to influence cultured cells in this study, can modulate proliferation, apoptosis, differentiation, and metabolism in various cells.

OBJECTIVE

Here, we evaluate the possibility to manipulate the immune activation of AD keratinocytes and their response to the electromagnetic field, which was not tested before.

METHODS

Keratinocytes isolated from the skin of healthy subjects (n = 20) and patients with atopic dermatitis (n = 20) as well as HaCaT and PCS-200-010 cell were exposed to the 900 MHz electromagnetic field for 60 minutes. Cytometric analysis of viability, Fas/FasL, p-ERK, p-p38 and p-JNK expression and Luminex analysis of cytokine concentration were performed in two-time points: 4 and 24 hours after the exposition.

RESULTS

This research has shown upregulated Fas, FasL, p-ERK, p-p38, and p-JNK expression along with increased cytokine secretion (IL-1β, IL-4, IL-8, IL-10, IL-12p70, IL-13, IL-17A, IL-31 and TNFα) by keratinocytes derived from the skin of patients with the AD when compared with healthy control. Exposure of keratinocyte cultures obtained from AD patients to EMF resulted in a decrease of 1β, IL-4, IL-10, IL-12, I L-13, IL-17, IL-31 and TNFα levels. Keratinocytes derived from the skin of AD patients are characterized by elevated Fas and FasL expression when compared to healthy control.

CONCLUSION

Apoptotic and nonapoptotic activation of the Fas/FasL-dependent signaling pathway may play a significant role in the pathogenesis of AD, by adjusting the local cytokine and chemokine environment at the site of inflammation. Moreover, the electromagnetic field exhibits strong immunomodulatory effects on AD-modified keratinocytes.

Markers of protein synthesis are increased in fetal membranes and myometrium after human labour and delivery

Preterm birth remains one of the leading causes of neonatal death. Inflammation and maternal infection are two of the leading aetiological factors for preterm birth. Labour is associated with increased production of proinflammatory cytokines, chemokines and prolabour mediators in human gestational tissues. In non-gestational tissues, synthesis of proinflammatory and prolabour mediators is regulated by components of the protein synthesis machinery. Therefore, in the present study we investigated the effect of human labour on the expression of three protein synthesis markers, namely eukaryotic elongation factor 2 kinase (EEF2K), mitogen-activated protein kinase interacting protein kinase 1 (MKNK1) and eukaryotic translation initiation factor 4E (EIF4E), and their role in regulating inflammation in human gestational tissues. In fetal membranes and myometrium, EEF2K expression was significantly lower, whereas MKNK1 expression was significantly higher withterm and preterm labourcompared to term nolabour. In contrast, EIF4E expression did not change in fetal membranes or myometrium with labour. In primary myometrial cells, loss-of-function studies using specific chemical inhibitors of EEF2K (A484954) and MKNK1 (CGP57380) demonstrated that MKNK1, but not EEF2K, was required for polyinosinic-polycytidylic acid (poly(I:C); a viral double-stranded RNA mimetic) and interleukin (IL)-1β-induced production of IL6, C-X-C motif chemokine ligand 8 (CXCL8), prostaglandin-endoperoxide synthase 2 (PTGS2) and prostaglandin F2α. In conclusion, spontaneous term and preterm labour is associated with decreased EEF2K and increased MKNK1 expression in fetal membranes and myometrium. Moreover, MKNK1 is involved in the genesis of proinflammatory and prolabour mediators that is mediated by inflammation or infection. However, further studies are required to elucidate the role of EEF2K in human labour.

The human IL-17A/F heterodimer regulates psoriasis-associated genes through IκBζ

Antagonists of IL-17A and its receptor have proven to be highly effective in the treatment of psoriasis. However, many of the underlying molecular mechanisms involved in the pathogenesis of psoriasis are still to be determined. IκBζ (encoded by the NFKBIZ gene) plays a key role in the development of psoriasis by mediating IL-17A- and IL-17F-driven effects. Both IL-17A and IL-17F expression are increased in lesional psoriatic skin. IL-17A/A and IL-17F/F homodimers as well as the IL-17A/F heterodimer signal through the same receptors. The aim of this study was to characterize the role of the IL-17A/F heterodimer in the regulation of NFKBIZ expression and in the regulation of selected psoriasis-associated genes. We demonstrated that IL-17A/F stimulation of human keratinocytes significantly induced NFKBIZ expression. Moreover, silencing IκBζ by siRNA revealed that IκBζ is a key regulator of IL-17A/F-inducible psoriasis-associated genes, including CCL20, DEFB4, IL-8, CHI3L1 and S100A7. In addition, IL-17A/F-induced NFKBIZ expression was mediated by a mechanism involving the p38 MAPK and NF-κB signalling pathways. In conclusion, we present IκBζ as a novel key regulator of IL-17A/F-driven effects in psoriasis. Thus, antagonists to IL-17A/F or IκBζ may present a targeted approach for treating psoriasis.

IL-17F regulates psoriasis-associated genes through IκBζ

Psoriasis is a common chronic inflammatory and immune-mediated skin disease. Antagonists of TNF-α and, recently, IL-17 have proven to be highly effective in the treatment for psoriasis; however, the molecular mechanisms involved in the pathogenesis of psoriasis are poorly understood. Recently, we presented evidence that IκBζ is a key regulator in the development of psoriasis through its role in mediating IL-17A-driven effects. Like IL-17A, IL-17F is produced by a variety of immune cells, and the expression of IL-17F is increased in psoriatic skin. The purpose of this study was to characterize the role of IL-17F in the regulation of IκBζ expression and to investigate whether IL-17F regulates psoriasis-associated genes in human keratinocytes through IκBζ. Here, we demonstrate that IL-17F stimulation induces IκBζ expression at both the mRNA and the protein levels in normal human keratinocytes. Moreover, silencing IκBζ by siRNA revealed that IκBζ is a key regulator of specific IL-17F-inducible psoriasis-associated genes and proteins, including DEFB4/hBD2, S100A7, CCL20, IL-8 and CHI3L1. In addition, IL-17F-induced IκBζ expression is mediated by a mechanism involving the p38 MAPK and NF-κB signalling pathways, as shown by the clear reduction in IL-17F-mediated expression of IκBζ during chemical inhibition of these two signalling pathways. In summary, we present IκBζ as a novel key regulator of IL-17F-driven effects in psoriasis. Thus, antagonists to IκBζ could potentially provide a more targeted approach for treating psoriasis as well as for treating the other inflammatory and immune-mediated diseases for which IL-17-targeting drugs have recently been approved.

Protein phosphatase 2Cδ/Wip1 regulates phospho-p90RSK2 activity in lesional psoriatic skin

Objectives

P90 ribosomal S6 kinase (RSK) 1 and 2 are serine/threonine protein kinases believed to mediate proliferation and apoptosis via the extracellular signal-regulated kinases (ERK1/2) signaling pathway. Macrophage migration inhibitory factor (MIF) and epidermal growth factor (EGF) are activators of this pathway and are elevated in the serum of patients with psoriasis compared with healthy controls. Studies on COS-7 cell cultures have shown that protein phosphatase 2Cδ (PP2Cδ) decreases the activity of RSK2 following EGF stimulation. We therefore hypothesize that PP2Cδ regulates RSK2 activity in psoriasis.

Methods

In paired biopsies from nonlesional (NL) and lesional (L) skins, we analyzed the level of RSK1, 2 phosphorylation and the expression of PP2Cδ isoforms, integrin-linked kinase-associated serine/threonine phosphatase (ILKAP) and wild-type p53-induced phosphatase 1 (Wip1) by Western blotting, immunofluorescence and coimmunoprecipitation with monoclonal antibody for RSK2. The induction of Wip1 by MIF or EGF was studied in cultured normal human keratinocytes.

Results

The protein level of RSK1, 2 phosphorylated at T573/T577 was significantly increased in L compared with NL psoriatic skin, while phosphorylation at S380/S386 was reduced in L compared with NL psoriatic skin when assayed by Western blotting and immunofluorescence microscopy. ILKAP expression was significantly higher in L than in NL skin, whereas Wip1 was expressed in similar amounts but showed increased coimmunoprecipitation with RSK2 in L compared with NL psoriatic skin. In cultured normal human keratinocytes stimulated with MIF, Wip1 phosphorylation and Wip1 expression were increased after 24 hours, but not when costimulated with dimethyl fumarate (DMF). The increased coimmunoprecipitation of Wip1 with RSK2 was significantly induced by EGF or MIF activation at 24 hours and could be significantly inhibited by DMF or the ERK1/2 inhibitor PD98059.

Conclusion

The complex formation of Wip1 with RSK2 indicates a direct interaction reducing P-RSK2 (S386) activation in L skin and indicates that Wip1 has a role in the pathogenesis of psoriasis.

STAT2 is involved in the pathogenesis of psoriasis by promoting CXCL11 and CCL5 production by keratinocytes

The JAK/STAT signaling pathway is suggested to play an important role in the pathogenesis of psoriasis, and recently JAK/STAT inhibitors have shown promising results in psoriasis treatment. The present study aimed to characterize the role of STAT2 in psoriasis. We demonstrated an increased expression of STAT2 and an increased level of phosphorylated/activated STAT2 in lesional compared with nonlesional psoriatic skin. Gene silencing of STAT2 by siRNA in human keratinocytes revealed that upon IFNα stimulation CXCL11 and CCL5 were the only two cytokines, among 102 analyzed, found to be regulated through a STAT2-dependent mechanism. Moreover, the regulation of CXCL11 and CCL5 depended on IRF9, but not on STAT1 and STAT6. The CXCL11 and CCL5 expression was increased in lesional compared with nonlesional psoriatic skin, and analysis demonstrated positive correlation between the expression of CXCL11 and IFNγ and between the expression of CCL5 and IFNγ in lesional psoriatic skin. In contrast, no correlation between the expression of CXCL11 and IL-17A and the expression of CCL5 and IL-17A in lesional psoriatic skin was found. Our data suggest that STAT2 plays a role in the psoriasis pathogenesis by regulating the expression of CXCL11 and CCL5, and thereby attracting IFNγ-producing immune cells to the skin.

TRIM21 is important in the early phase of inflammation in the imiquimod-induced psoriasis-like skin inflammation mouse model

Tripartite motif-containing protein 21 (TRIM21) regulates pro-inflammatory cytokines and type I interferons and acts as an autoantigen in certain autoimmune diseases, but TRIM21 has not been investigated in psoriasis. It has been suggested that TRIM21 may have a dual function; in the early phase of inflammation, it may function as a stimulator; but upon immune stimulation, its ubiquitinating mode of action may shift from stabilization to degradation of IRF3 causing inhibition of the immune responses. The imiquimod (IMQ)-induced psoriasis-like mouse model displays features similar to those of human psoriasis. However, chronicity is lacking in this model. We investigated whether the role of TRIM21 in psoriasis was pro-inflammatory or anti-inflammatory. We hypothesized that a shift of the TRIM21-ubiquitinating mode of action may explain the lack of chronicity in the IMQ-induced psoriasis-like mouse model. We showed that TRIM21 expression is increased in lesional psoriatic skin and in the early phase of IMQ-induced inflammation both in vitro and in vivo. Surprisingly, inflammation was significantly less pronounced in TRIM21 knockout mice than in wild-type mice as shown by ear thickness measured at days 8, 9 and 10 after treatment start, by spleen weight as a marker of systemic effect of IMQ at 10 days after treatment start and by expression of IL-12p40 at days 3 and 10 after treatment start and IL-17A at day 3 after treatment start. Therefore, induction of TRIM21 expression cannot explain the lack of chronicity in the IMQ-induced psoriasis-like skin inflammation mouse model.

The MNK-1/eIF4E pathway as a new therapeutic pathway to target inflammation and remodelling in asthma

Therapeutic targets in asthma are reduction of airway inflammation and remodelling, the latter is not affected by available drugs. Here we present data that inhibition of MAPK-activated protein kinase (MNK)-1 reduces inflammation and remodelling. MNK-1 regulates protein expression by controlling mRNA stability, nuclear export and translation through the eukaryotic initiation factor 4E (eIF4E). Airway smooth muscle cells were derived from asthmatic and non-asthmatic donors. Cells were pre-treated with CGP57380 (MNK-1 inhibitor) or MNK-1 siRNA, before TNF-α stimulation. Cytokine and protein expression was analysed by ELISA, real time PCR and immunoblotting. Proliferation was monitored by cell counts. TNF-α activated MNK-1 phosphorylation between 15 and 30min. and subsequently eIF4E between 15 and 60min. EIF4E activity was inhibited by CGP57380 dose-dependently. Inhibition of MNK-1 by CGP57380 or MNK-1 siRNA significantly reduced TNF-α induced CXCL10 and eotaxin mRNA expression and secretion, but had no effect on IL-8. However, CXCL10 mRNA stability or NF-κB activity were not affected by MNK-1 inhibition. Furthermore, eIF4E was detected in the cytosol and the nucleus, but TNF-α did not affected its export from the nucleus. Cytokine array assessment showed that in addition to eotaxin and CXCL10, asthma relevant GRO α and RANTES were down-regulated by MNK-1 inhibition. In addition, MNK-1 inhibition significantly reduced FCS and PDGF-BB induced cell proliferation. We are the first to report that MNK-1 controls chemokine secretion and proliferation in human airway smooth muscle cells. Therefore we suggest that MNK-1 inhibition may present a new target to limit inflammation and remodelling in asthmatic airways.

Transcriptional analysis of left-sided colitis, pancolitis, and ulcerative colitis-associated dysplasia

BACKGROUND

It is unknown why patients with extensive ulcerative colitis (UC) have a higher risk of colorectal cancer compared with patients with left-sided UC. This study characterizes the inflammatory processes in left-sided UC, pancolitis, and UC-associated dysplasia at the transcriptional level to identify potential biomarkers and transcripts of importance for the carcinogenic behavior of chronic inflammation.

METHODS

The Affymetrix GeneChip Human Genome U133 Plus 2.0 was applied on colonic biopsies from UC patients with left-sided UC, pancolitis, dysplasia, and controls. Reverse transcription polymerase chain reaction and immunohistochemistry were performed for validating selected transcripts in the initial cohort and in 2 independent cohorts of patients with UC. Microarray data were analyzed by principal component analysis, and reverse transcription polymerase chain reaction and immunohistochemistry data by the Wilcoxon's rank-sum test.

RESULTS

The principal component analysis results revealed separate clusters for left-sided UC, pancolitis, dysplasia, and controls. Close clustering of dysplastic and pancolitic samples indicated similarities in gene expression. Indeed, 101 and 656 parallel upregulated and downregulated transcripts, respectively, were identified in specimens from dysplasia and pancolitis. Validation of selected transcripts hereof identified insulin receptor alpha (INSRA) and MAP kinase interacting serine/threonine kinase 2 (MKNK2) with an enhanced expression in dysplasia compared with left-sided UC and controls, whereas laminin γ2 (LAMC2) was found with a lower expression in dysplasia compared with the remaining 3 groups.

CONCLUSIONS

This study demonstrates pancolitis and left-sided UC as distinct inflammatory processes at the transcriptional level, and identifies INSRA, MKNK2, and LAMC2 as potential critical transcripts in the inflammation-driven preneoplastic process of UC.

A genome-wide small interfering RNA (siRNA) screen reveals nuclear factor-κB (NF-κB)-independent regulators of NOD2-induced interleukin-8 (IL-8) secretion

NOD2 encodes an intracellular multidomain pattern recognition receptor that is the strongest known genetic risk factor in the pathogenesis of Crohn disease (CD), a chronic relapsing inflammatory disorder of the intestinal tract. NOD2 functions as a sensor for bacterial cell wall components and activates proinflammatory and antimicrobial signaling pathways. Here, using a genome-wide small interfering RNA (siRNA) screen, we identify numerous genes that regulate secretion of the proinflammatory cytokine IL-8 in response to NOD2 activation. Moreover, many of the identified IL-8 regulators are linked by protein-protein interactions, revealing subnetworks of highly connected IL-8 regulators implicated in processes such as vesicle formation, mRNA stability, and protein ubiquitination and trafficking. A TNFα counterscreen to induce IL-8 secretion in an NOD2-independent manner reveals that the majority of the identified regulators affect IL-8 secretion irrespective of the initiating stimuli. Using immortalized macrophages, we validate the ubiquitin protease, USP8, and the endosomal sorting protein, VPS28, as negative regulators of NOD2-induced cytokine secretion. Interestingly, several genes that affect NOD2-induced IL-8 secretion are present in loci associated with CD risk by genome-wide association studies, supporting a role for the NOD2/IL-8 pathway, and not just NOD2, in the pathogenesis of CD. Overall, this screen provides a valuable resource in the advancement of our understanding of the genes that regulate the secretion of IL-8.

Cytokine regulation by MAPK activated kinase 2 in keratinocytes exposed to sulfur mustard

Uncontrolled inflammation contributes to cutaneous damage following exposure to the warfare agent bis(2-chloroethyl) sulfide (sulfur mustard, SM). Activation of the p38 mitogen activated protein kinase (MAPK) precedes SM-induced cytokine secretion in normal human epidermal keratinocytes (NHEKs). This study examined the role of p38-regulated MAPK activated kinase 2 (MK2) during this process. Time course analysis studies using NHEK cells exposed to 200μM SM demonstrated rapid MK2 activation via phosphorylation that occurred within 15 min. p38 activation was necessary for MK2 phosphorylation as determined by studies using the p38 inhibitor SB203580. To compare the role of p38 and MK2 during SM-induced cytokine secretion, small interfering RNA (siRNA) targeting these proteins was utilized. TNF-α, IL-1β, IL-6 and IL-8 secretion was evaluated 24h postexposure, while mRNA changes were quantified after 8h. TNF-α, IL-6 and IL-8 up regulation at the protein and mRNA level was observed following SM exposure. IL-1β secretion was also elevated despite unchanged mRNA levels. p38 knockdown reduced SM-induced secretion of all the cytokines examined, whereas significant reduction in SM-induced cytokine secretion was only observed with TNF-α and IL-6 following MK2 knockdown. Our observations demonstrate potential activation of other p38 targets in addition to MK2 during SM-induced cytokine secretion.

The Role of Mitogen-Activated Protein Kinase-Activated Protein Kinases (MAPKAPKs) in Inflammation

Mitogen-activated protein kinase (MAPK) pathways are implicated in several cellular processes including proliferation, differentiation, apoptosis, cell survival, cell motility, metabolism, stress response and inflammation. MAPK pathways transmit and convert a plethora of extracellular signals by three consecutive phosphorylation events involving a MAPK kinase kinase, a MAPK kinase, and a MAPK. In turn MAPKs phosphorylate substrates, including other protein kinases referred to as MAPK-activated protein kinases (MAPKAPKs). Eleven mammalian MAPKAPKs have been identified: ribosomal-S6-kinases (RSK1-4), mitogen- and stress-activated kinases (MSK1-2), MAPK-interacting kinases (MNK1-2), MAPKAPK-2 (MK2), MAPKAPK-3 (MK3), and MAPKAPK-5 (MK5). The role of these MAPKAPKs in inflammation will be reviewed.

Translational control of human neutrophil responses by MNK1

A growing number of inflammatory and immune processes in vivo have been shown to be influenced by neutrophil-derived cytokines. Whereas the underlying transcriptional mechanisms are increasingly well understood, the translational regulation of this neutrophil response remains largely unexplored. Here, we show that the MNK1, which participates in translational control in several cell types, is activated in response to physiological neutrophil agonists (LPS, TNF-α) in the cytoplasmic and nuclear compartments. With the use of various pharmacological inhibitors, we found that MNK1 activation takes place downstream of the TAK1-p38 MAPK axis in neutrophils, whereas the MEK/ERK, JNK, PI3K, and PKC pathways are not involved. Pharmacological blockade of MNK1, as well as overexpression experiments, established that cytokine protein synthesis (but not gene expression) is under the control of MNK1 in neutrophils. Likewise, MNK1 inhibition reversed the antiapoptotic effect of LPS and TNF-α in neutrophils, and this was accompanied by a decreased expression of the antiapoptotic protein Mcl-1. Thus, MNK1 appears to be an important regulator of neutrophil responses. Although MNK1 inhibition did not affect protein recruitment to mRNA caps, it decreased the phosphorylation of molecules implicated in translation initiation control, such as S6K, S6, and hyperphosphorylated 4E-BP1. These molecular targets of MNK1 are shared with those of PI3K in neutrophils, and accordingly, MNK1 inhibition partially impaired the belated PI3K/Akt activation elicited by LPS or TNF in these cells. Given the importance of neutrophils and their products in numerous chronic inflammatory disorders, MNK1 could represent an attractive therapeutic target.

Mnk1 and 2 are dispensable for T cell development and activation but important for the pathogenesis of experimental autoimmune encephalomyelitis

T cell development and activation are usually accompanied by expansion and production of numerous proteins that require active translation. The eukaryotic translation initiation factor 4E (eIF4E) binds to the 5' cap structure of mRNA and is critical for cap-dependent translational initiation. It has been hypothesized that MAPK-interacting kinase 1 and 2 (Mnk1/2) promote cap-dependent translation by phosphorylating eIF4E at serine 209 (S209). Pharmacologic studies using inhibitors have suggested that Mnk1/2 have important roles in T cells. However, genetic evidence supporting such conclusions is lacking. Moreover, the signaling pathways that regulate Mnk1/2 in T cells remain unclear. We demonstrate that TCR engagement activates Mnk1/2 in primary T cells. Such activation is dependent on Ras-Erk1/2 signaling and is inhibited by diacylglycerol kinases α and ζ. Mnk1/2 double deficiency in mice abolishes TCR-induced eIF4E S209 phosphorylation, indicating their absolute requirement for eIF4E S209 phosphorylation. However, Mnk1/2 double deficiency does not affect the development of conventional αβ T cells, regulatory T cells, or NKT cells. Furthermore, T cell activation, in vivo primary and memory CD8 T cell responses to microbial infection, and NKT cell cytokine production were not obviously altered by Mnk1/2 deficiency. Although Mnk1/2 deficiency causes decreased IL-17 and IFN-γ production by CD4 T cells following immunization of mice with myelin oligodendrocyte glycoprotein peptide in complete Freund's adjuvant, correlating with milder experimental autoimmune encephalomyelitis scores, it does not affect Th cell differentiation in vitro. Together, these data suggest that Mnk1/2 has a minimal role in T cell development and activation but may regulate non-T cell lineages to control Th1 and Th17 differentiation in vivo.

Melatonin suppresses proinflammatory mediators in lipopolysaccharide-stimulated CRL1999 cells via targeting MAPK, NF-κB, c/EBPβ, and p300 signaling

Melatonin is an indoleamine secreted by the pineal gland as well as a plant-derived product that exerts potential anti-inflammatory properties, but the mechanisms of action remain unclear. Here, we investigated the roles of melatonin in regulation of proinflammatory mediators and identified the underlying mechanisms in human vascular smooth muscle (VSM) cell line CRL1999 stimulated by lipopolysaccharide (LPS). We found that treatment with melatonin significantly inhibited the production and expression of TNF-α and interleukin (IL)-1β, cyclooxygenase-2 (COX-2), inducible nitric oxide synthase, prostaglandin E(2) (PGE2), and nitric oxide (NO) in a dose-dependent manner. Moreover, we also found that the suppression of proinflammatory mediators by melatonin was mediated through inhibition of MAPK, NF-κB, c/EBPβ, and p300 signaling in LPS-stimulated CRL1999 cells. Treatment with melatonin markedly inhibited phosphorylation of ERK1/2, JNK, p38 MAPK, IκB-α, and c/EBPβ, blocked binding of NF-κB and c/EBPβ to promoters, and suppressed p300 histone acetyltransferase (HAT) activity and p300 HAT-mediated NF-κB acetylation. Transfection with an ERK-, IκB-, or c/EBPβ-specific siRNA or pretreatment with an ERK-, p38 MAPK-, or p300-selective inhibitor considerably abrogated the melatonin-mediated inhibition of proinflammatory mediators. Conversely, exogenous overexpression of a constitutively active p300, but not its HAT mutant, effectively reversed the melatonin-mediated inhibitions. Collectively, these results indicate that melatonin suppresses proinflammatory mediators by simultaneously targeting the multiple signaling such as ERK/p38 MAPK, c/EBPβ, NF-κB, and p300, in LPS-stimulated VSM cell line CRL1999, and suggest that melatonin is a potential candidate compound for the treatment of proinflammatory disorders.

Mnk Kinases in Cytokine Signaling and Regulation of Cytokine Responses

The kinases Mnk1 and Mnk2 are activated downstream of the p38 MAPK and MEK/ERK signaling pathways. Extensive work over the years has shown that these kinases control phosphorylation of the eukaryotic initiation factor 4E (eIF4E) and regulate engagement of other effector elements, including hnRNPA1 and PSF. Mnk kinases are ubiquitously expressed and play critical roles in signaling for various cytokine receptors, while there is emerging evidence that they have important functions as mediators of pro-inflammatory cytokine production. In this review the mechanisms of activation of MNK pathways by cytokine receptors are addressed and their roles in diverse cytokine-dependent biological processes are reviewed. The clinical-translational implications of such work and the relevance of future development of specific MNK inhibitors for the treatment of malignancies and auto-immune disorders are discussed.

Mnk Kinases in Cytokine Signaling and Regulation of Cytokine Responses

The kinases Mnk1 and Mnk2 are activated downstream of the p38 MAPK and MEK/ERK signaling pathways. Extensive work over the years has shown that these kinases control phosphorylation of the eukaryotic initiation factor 4E (eIF4E) and regulate engagement of other effector elements, including hnRNPA1 and PSF. Mnk kinases are ubiquitously expressed and play critical roles in signaling for various cytokine receptors, while there is emerging evidence that they have important functions as mediators of pro-inflammatory cytokine production. In this review the mechanisms of activation of MNK pathways by cytokine receptors are addressed and their roles in diverse cytokine-dependent biological processes are reviewed. The clinical-translational implications of such work and the relevance of future development of specific MNK inhibitors for the treatment of malignancies and auto-immune disorders are discussed.

CCL27 expression is regulated by both p38 MAPK and IKKβ signalling pathways

The skin-specific chemokine CCL27 is believed to play a pivotal role in establishing the inflammatory infiltrate characteristic for common inflammatory skin diseases. Through binding to the chemokine receptor 10 (CCR10), CCL27 mediates inflammation by promoting lymphocyte migration into the skin. Little is known about the regulation of CCL27 gene expression. The purpose of our study was to investigate the regulation of the IL-1β-induced CCL27 gene expression in normal human keratinocytes (NHEK). Preincubation of NHEK with the inhibitory κB (IκB) kinase (IKK) inhibitor, SC-514, or the p38 mitogen-activated protein kinase (MAPK) inhibitor, SB202190, revealed a profound reduction in both CCL27 mRNA and CCL27 protein expression indicating the significance of these pathways in the regulation of CCL27 expression. Furthermore, the impact of inhibitors of mitogen- and stress-activated kinase 1 (MSK1) or the mitogen-activated protein kinase-interacting kinases (Mnk1+2), downstream kinases of p38 MAPK, on IL-1β-induced CCL27 expression in NHEK were investigated. We identified seven NF-κB binding elements upstream from the CCL27 gene start codon using electrophoretic mobility shift assay (EMSA). Supershift analyses demonstrated the involvement of the p50/p65 NF-κB heterodimer. We conclude that IL-1β-induced CCL27 gene expression in NHEK is regulated through the p38 MAPK/MSK1/Mnk1+2 as well as the IKKβ/NF-κB signalling pathways.

Fungal allergen β-glucans trigger p38 mitogen-activated protein kinase-mediated IL-6 translation in lung epithelial cells

In addition to immune cells, airway epithelial cells can contribute to and shape the immune response in the lung by secreting specific cytokines. IL-6 is a key factor in determining the effector fate of CD4(+) T cells. Here we show that under basal conditions, the IL-6 gene is already highly expressed in lung epithelial cells, but not in immune cells resident in the lung. However, upon exposure of the lungs to fungal allergens, the direct contact of β-glucans present in the fungus cell wall with lung epithelial cells is sufficient to trigger the rapid synthesis and secretion of IL-6 protein. This posttranscriptional regulation of IL-6 in response to fungal extracts is mediated by the p38 mitogen-activated protein kinase pathway. The inhalation of β-glucans with a nonallergenic antigen is sufficient to provide an adjuvant effect that leads to mucous hyperplasia in the airways. Thus, β-glucans may constitute a common determinant of the fungal and plant-derived allergens responsible for some of the pathological features in allergic asthma.

IL-1 signalling determines the fate of skin grafts expressing non-self protein in keratinocytes

Although IL-1 is a known inflammatory cytokine during pathogen infection, the role of IL-1 in skin graft rejection, particularly where foreign antigen is expressed exclusively in keratinocytes, is less understood. Here, we use a syngeneic skin graft system, where antigens are expressed in epithelial cells via either a keratin 14 or keratin 5 promoter, to explore the role of IL-1 in graft rejection and induction of epithelial antigen-specific effector CD8(+) T-cell function. Keratin 5 ovalbumin (K5mOVA) transgenic skin grafts destined for rejection demonstrated increased expression of IL-1beta and its receptors compared to K14 HPV16 E7 transgenic grafts that do not reject spontaneously. Rejection of OVA grafts lacking the IL-1 receptor (IL-1R1) was delayed and associated with decreased numbers of antigen-specific CD8 T cells. In contrast, K14E7 grafts survived on immunocompetent, syngeneic recipients with decreased graft levels of IL-1beta and IL-1R1 and 2. However, in the absence of the IL-1 receptor antagonist, IL-1Ra, skin grafts were spontaneously rejected and an E7-specific CD8 T-cell response was primed. Thus, expression of the HPV16E7 oncoprotein in epithelial cells prevents IL-1beta-associated skin graft rejection and induction of antigen-specific CD8 T-cell responses. Enhancing IL-1beta signalling, via blocking of the IL-1 receptor antagonist, may represent an alternative strategy for treatment of HPV16E7-associated cancers.

The role of mitogen- and stress-activated protein kinase 1 and 2 in chronic skin inflammation in mice

Mitogen- and stress-activated protein kinase 1 and 2 (MSK1/2) are two kinases phosphorylated by both ERK1/2 and p38 MAPK. Recently, MSK1 and 2 have been reported to act as negative regulators of acute inflammation. In this study, we investigated the role of MSK1/2 in chronic skin inflammation using an oxazolone-induced allergic contact dermatitis model in MSK1/2 knockout mice and wild-type mice. MSK1/2 knockout mice were demonstrated to have significantly increased inflammation compared with wild-type mice. This was measured by an increased ear thickness, elevated infiltration of neutrophils in the skin and increased inflammatory histological changes. Furthermore, we found significantly elevated levels of the proinflammatory cytokines Tumor necrosis factor-α (TNF-α), IL-1β and IL-6 at both mRNA and protein levels in MSK1/2 knockout mice compared with wild-type mice after oxazolone treatment. In addition, the mRNA expression of the chemokine Thymus and activation regulated chemokine (TARC) was demonstrated to be significantly elevated in oxazolone-treated MSK1/2 knockout mice compared with wild-type mice. The increased expression of TARC was paralleled by increased infiltration of cells positive for the TARC receptor, CCR4, in the dermis of MSK1/2 knockout mice. Our results indicate that MSK1/2 are involved in the activation of feedback mechanisms that dampen oxazolone-induced skin inflammation.

Cell cycle progression or translation control is not essential for vesicular stomatitis virus oncolysis of hepatocellular carcinoma

The intrinsic oncolytic specificity of vesicular stomatitis virus (VSV) is currently being exploited to develop alternative therapeutic strategies for hepatocellular carcinoma (HCC). Identifying key regulators in diverse transduction pathways that define VSV oncolysis in cancer cells represents a fundamental prerequisite to engineering more effective oncolytic viral vectors and adjusting combination therapies. After having identified defects in the signalling cascade of type I interferon induction, responsible for attenuated antiviral responses in human HCC cell lines, we have now investigated the role of cell proliferation and translation initiation. Cell cycle progression and translation initiation factors eIF4E and eIF2Bε have been recently identified as key regulators of VSV permissiveness in T-lymphocytes and immortalized mouse embryonic fibroblasts, respectively. Here, we show that in HCC, decrease of cell proliferation by cell cycle inhibitors or siRNA-mediated reduction of G(1) cyclin-dependent kinase activities (CDK4) or cyclin D1 protein expression, do not significantly alter viral growth. Additionally, we demonstrate that translation initiation factors eIF4E and eIF2Bε are negligible in sustaining VSV replication in HCC. Taken together, these results indicate that cellular proliferation and the initiation phase of cellular protein synthesis are not essential for successful VSV oncolysis of HCC. Moreover, our observations indicate the importance of cell-type specificity for VSV oncolysis, an important aspect to be considered in virotherapy applications in the future.

Differential regulation of CHOP translation by phosphorylated eIF4E under stress conditions

Cells respond to environmental stress by inducing translation of a subset of mRNAs important for survival or apoptosis. CHOP, a downstream transcriptional target of stress-induced ATF4, is also regulated translationally in a uORF-dependent manner under stress. Low concentration of anisomycin induces CHOP expression at both transcriptional and translational levels. To study specifically the translational aspect of CHOP expression, and further clarify the regulatory mechanisms underlying stress-induced translation initiation, we developed a CMV promoter-regulated, uORF^chop-driven reporter platform. Here we show that anisomycin-induced CHOP expression depends on phosphorylated eIF4E/S209 and eIF2α/S51. Contrary to phospho-eIF2α/S51, phospho-eIF4E/S209 is not involved in thapsigargin-induced CHOP expression. Studies using various kinase inhibitors and mutants uncovered that both the p38MAPK-Mnk and mTOR signaling pathways contribute to stress-responsive reporter and CHOP expression. We also demonstrated that anisomycin-induced translation is tightly regulated by partner binding preference of eIF4E. Furthermore, mutating the uORF sequence abolished the anisomycin-induced association of chop mRNA with phospho-eIF4E and polysomes, thus demonstrating the significance of this cis-regulatory element in conferring on the transcript a stress-responsive translational inducibility. Strikingly, although insulin treatment activated ERK-Mnk and mTOR pathways, and consequently eIF4E/S209 phosphorylation, it failed to induce phospho-eIF2α/S51 and reporter translation, thus pinpointing a crucial determinant in stress-responsive translation.

Complex regulation and function of the inflammatory smooth muscle cell phenotype in atherosclerosis

Vascular smooth muscle cell (SMC) phenotypic modulation plays a key role in atherosclerosis and is classically defined as a switch from a 'contractile' phenotype to a 'synthetic' phenotype, whereby genes that define the contractile SMC phenotype are suppressed and proliferation and/or migratory mechanisms are induced. There is also evidence that SMCs may take on a 'proinflammatory' phenotype, whereby SMCs secrete cytokines and express cell adhesion molecules, e.g. IL-8, IL-6, and VCAM-1, respectively, which may functionally regulate monocyte and macrophage adhesion and other processes during atherosclerosis. Factors that drive the inflammatory phenotype are not limited to cytokines but also include hemodynamic forces imposed on the blood vessel wall and intimate interaction of endothelial cells with SMCs, as well as changes in matrix composition in the vessel wall. However, it is critical to recognize that our understanding of the complex interaction of these multiple signal inputs has only recently begun to shed light on mechanisms that regulate the inflammatory SMC phenotype, primarily through models that attempt to recreate this environment ex vivo. The goal of this review is to summarize our current knowledge in this area and identify some of the key unresolved challenges and questions requiring further study.

Candida albicans phospholipomannan triggers inflammatory responses of human keratinocytes through Toll-like receptor 2

The Toll-like receptors (TLRs) play an important role in the recognition of Candida albicans components and activation of innate immunity. Phospholipomannan (PLM), a glycolipid, is expressed at the surface of C. albicans cell wall, which acts as a member of the pathogen-associated molecular patterns family. In this study, we sought to clarify whether C. albicans-native PLM could induce an inflammation response in human keratinocytes and to determine the underlying mechanisms. Exposure of cultured human primary keratinocytes to PLM led to the increased gene expression and secretion of proinflammatory cytokines (IL-6) and chemokines (IL-8). PLM hydrolysed with beta-d-mannoside mannohydrolase failed to induce gene expression and secretion of IL-6 and IL-8. PLM up-regulated the mRNA and protein levels of TLR2, whereas the mRNA level of TLR4 was not altered. Keratinocytes challenged with PLM resulted in the activation of NF-kappaB and mitogen-activated protein kinase (MAPKs) including p38. Anti-TLR2 neutralizing antibody, NFkappaB and p38MAPK inhibitors blocked the PLM-induced secretion of IL-6, IL-8 in keratinocytes, but no such effect was observed in pretreatment with anti-TLR4-neutralizing antibody and lipopolysaccharide inhibitor (polymyxin B). These data suggest C. albicans-native PLM may contribute to the inflammatory responses of cutaneous candidiasis in the TLR2-NF-kappaB and p38MAPK signalling pathway dependent manner.