MAPK signaling pathways modulate IL-1β expression in human keratinocytes

Pseudomonas aeruginosa-Derived DnaJ Induces the Expression of IL-1β by Engaging the Interplay of p38 and ERK Signaling Pathways in Macrophages

As members of pathogen-associated molecular patterns, bacterial heat shock proteins (HSPs) are widely recognized for their role in initiating innate immune responses. This study aimed to examine the impact of DnaJ, a homolog of HSP40 derived from Pseudomonas aeruginosa (P. aeruginosa), on the regulation of IL-1β expression in macrophages. We demonstrated that DnaJ modulates macrophages to secrete IL-1β by activating NF-κB and MAPK signaling pathways. Specifically, ERK was identified as a positive mediator for IL-1β expression, while p38 acted as a negative mediator. These results suggest that the reciprocal actions of these two crucial MAPKs play a vital role in controlling IL-1β expression. Additionally, the reciprocal actions of MAPKs were found to regulate the activation of inflammasome-related molecules, including vimentin, NLRP3, caspase-1, and GSDMD. Furthermore, our investigation explored the involvement of CD91/CD40 in ERK signaling-mediated IL-1β production from DnaJ-treated macrophages. These findings emphasize the importance of understanding the signaling mechanisms underlying IL-1β induction and suggest the potential utility of DnaJ as an adjuvant for stimulating inflammasome activation.

Oxidative Stress in Dairy Cows: Insights into the Mechanistic Mode of Actions and Mitigating Strategies

This review examines several molecular mechanisms underpinning oxidative stress in ruminants and their effects on blood and milk oxidative traits. We also investigate strategies to alleviate or repair oxidative damages by improving animal immune functions using novel feed additives. Microbial pathogenic cells, feeding management, and body condition score were some of the studied factors, inducing oxidative stress in ruminants. The predominance of Streptococcus spp. (24.22%), Acinetobacter spp. (21.37%), Romboutsia spp. (4.99%), Turicibacter spp., (2.64%), Stenotrophomonas spp. (2.33%), and Enterococcus spp. (1.86%) was found in the microbiome of mastitis cows with a decrease of d-mannose and increase of xanthine:guanine ratio when Streptococcus increased. Diversity of energy sources favoring the growth of Fusobacterium make it a keystone taxon contributing to metritis. Ruminal volatile fatty acids rose with high-concentrate diets that decreased the ruminal pH, causing a lysis of rumen microbes and release of endotoxins. Moreover, lipopolysaccharide (LPS) concentration, malondialdehyde (MDA), and superoxide dismutase (SOD) activities increased in high concentrate cows accompanied by a reduction of total antioxidant capacity (T-AOC), glutathione peroxidase (GPx), and catalase (CAT) activity. In addition, albumin and paraoxonase concentrations were inversely related to oxidative stress and contributed to the protection of low-density and high-density lipoproteins against lipid peroxidation, protein carbonyl, and lactoperoxidase. High concentrate diets increased the expression of MAPK pro-inflammatory genes and decreased the expression of antioxidant genes and proteins in mammary epithelial tissues. The expression levels of NrF2, NQO1, MT1E, UGT1A1, MGST3, and MT1A were downregulated, whereas NF-kB was upregulated with a high-grain or high concentrate diet. Amino-acids, vitamins, trace elements, and plant extracts have shown promising results through enhancing immune functions and repairing damaged cells exposed to oxidative stress. Further studies comparing the long-term effect of synthetic feed additives and natural plant additives on animal health and physiology remain to be investigated.

Heparinoid suppresses Der p-induced IL-1β production by inhibiting ERK and p38 MAPK pathways in keratinocytes

Epidermal keratinocytes initiate skin inflammation by activating immune cells. The skin barrier is disrupted in atopic dermatitis (AD) and epidermal keratinocytes can be exposed to environmental stimuli, such as house dust mite (HDM) allergens. We showed previously that HDM allergens activate the NLRP3 inflammasome of keratinocytes, thereby releasing pro-inflammatory cytokines. Heparinoid is an effective moisturizer for atopic dry skin. However, a recent report showed that heparinoid treatment can improve inflammation of lichen planus. Therefore, we hypothesized that it acts on epidermal keratinocytes not only as a moisturizer, but also as a suppressant of the triggers of skin inflammation. We found that HDM allergen-induced interleukin (IL)-1β release from keratinocytes was inhibited significantly by heparinoid pretreatment without affecting cell viability. However, heparinoid did not affect caspase-1 release, suggesting that heparinoid did not affect HDM allergen-induced inflammasome activation. Heparinoid treatment not only decreased intracellular levels of pro-IL-1β, but also suppressed IL-1β messenger RNA (mRNA) expression in keratinocytes. Among the intracellular signalling pathways, the activation of extracellular signal-regulated kinase and p38 pathways, which are required for IL-1β expression in keratinocytes, was inhibited by heparinoid treatment. The inhibitory effect of heparinoid on IL-1β mRNA expression was also confirmed with living skin equivalents. Our results demonstrated that heparinoid suppresses the initiation of keratinocyte-mediated skin inflammation.

The aryl hydrocarbon receptor: a review of its role in the physiology and pathology of the integument and its relationship to the tryptophan metabolism

The aryl hydrocarbon receptor (AHR) is a cytosolic receptor for low molecular weight molecules, of which the most widely recognized ligand is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and the most widely recognized effect, chloracne. Adverse effects of manipulation were most recently and graphically demonstrated by the poisoning of Viktor Yushchenko during the Ukrainian presidential elections of 2004. However, recent research has revealed a receptor with wide-ranging, and at times, paradoxical actions. It was arguably among the first biological receptors to be utilized by dermatologists, dating from the time of topical tar preparations as a therapeutic agent. I provide a review outlining the role AHR plays in the development, cellular oxidation/antioxidation, responses to ultraviolet light, melanogenesis, epidermal barrier function, and immune regulation and its relationship to tryptophan metabolism. Finally, I will review the role of AHR in diseases of the integument.

Functions of the aryl hydrocarbon receptor in the skin

Among other functions, the skin serves as the barrier against the environment and provides vital protection from physical or chemical harm and from infection. Skin cells express the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor and sensor of environmental chemicals; at the same time, AHR ligands are abundant in skin from exogenous or endogenous sources. For example, solar radiation, in particular ultraviolet (UV) B, generates AHR ligands from tryptophan in the skin. Recent evidence has shown that AHR is involved in the (patho)physiology of skin including the regulation of skin pigmentation, photocarcinogenesis, and skin inflammation. We here provide a state-of-the-art summary of work which relates to the role of the AHR in (1) adaptive responses against environmental challenges such as UVB or topical chemicals and (2) intrinsic developmental roles for homeostasis of skin cells and (3) skin immunity. We also discuss the existing evidence that AHR antagonists or AHR ligands may be used for the prevention and/or treatment of skin disease.

Role of mitogen-activated protein kinase cascades in 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced apoptosis in neuronal pheochromocytoma cells

Mitogen-activated protein kinases (MAPKs) are involved in neuronal death caused by many cytotoxins. Conventional MAPKs consist of three family members: extracellular signal-regulated kinase-1/2 (ERK1/2), c-Jun N-terminal kinase (JNK) and p38. It has been originally shown that ERK1/2 is important for cell survival, whereas JNK and p38 are deemed stress responsive and thus involved in apoptosis. However, information describing the role of MAPKs in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced neurotoxicity is insufficient. The aim of this study was to identify the role of MAPK cascades in TCDD-induced neurotoxicity using differentiated pheochromocytoma (PC12) cells as a model for neuronal cells. Cell viability assay, terminal deoxynucleotidyl transferase dUTP nick-end labeling assay and flow cytometry analysis showed that TCDD attenuated cell viability with a dose- and time-dependent manner and significantly induced apoptosis in primary cortical neurons and PC12 cells. Western blot analysis indicated that TCDD markedly activated the expression of ERK1/2, JNK and p38 in TCDD-treated PC12 cells. Furthermore, PD98059 (ERK1/2 inhibitor), SP600125 (JNK inhibitor) and SB202190 (p38 inhibitor) notably blocked the effect of TCDD on cell apoptosis. Based on the findings above, it is concluded that the activation of MAPK signaling pathways may be associated with TCDD-mediated neuronal apoptosis.

A role for the aryl hydrocarbon receptor and the dioxin TCDD in rheumatoid arthritis

OBJECTIVE

Environmental factors are involved in RA pathogenesis and epidemiological studies have suggested that smoking is an environmental risk factor for RA. The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is one of the major toxic components in cigarettes. To clarify the biological effects of smoking in RA, we investigated the role of TCDD in RA pathogenesis.

METHODS

Human synovial tissue was obtained from RA and OA patients and aryl hydrocarbon receptor (AhR) expression in these tissues was evaluated using immunohistochemistry and real-time PCR. Expression of various cytokines was measured by real-time PCR following stimulation of RA synoviocytes with different concentrations of TCDD. To study the role of AhR, we treated RA synoviocytes with alpha-naphthoflavone, a known AhR antagonist. To evaluate which signal transduction pathways were stimulated by the TCDD-AhR interaction, we used inhibitors of nuclear factor-kappaB (NF-kappaB) and extra-cellular stimulus-activated kinase (ERK).

RESULTS

Higher AhR mRNA and protein levels were observed in RA synovial tissue than in OA tissue. TCDD up-regulated the expression of IL-1beta, IL-6 and IL-8 through binding to AhR, and this effect was transmitted via the NF-kappaB and ERK signalling cascades. AhR expression in synovial cells was up-regulated by TNF-alpha.

CONCLUSION

TNF-alpha activates AhR expression in RA synovial tissue, and that cigarette smoking and exposure to TCDD enhances RA inflammatory processes. TCDD induces inflammatory cytokines via its association with AhR, resulting in stimulation of the NF-kappaB and ERK signalling cascades. Thus TCDD exposure, such as smoking exacerbates RA pathophysiology.

Role of mitogen-activated protein kinases in aryl hydrocarbon receptor signaling

Human populations are increasingly exposed to a number of environmental pollutants such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls and dioxins. These compounds are activators of the aryl hydrocarbon receptor (AhR) that controls the expression of many genes including those for detoxification enzymes. The regulatory mechanisms of AhR are multi-factorial and include phosphorylation by various protein kinases. Significant progress in the research of mitogen-activated protein kinases (MAPKs) has been achieved in the last decade. Isolated reports have been published on the role of MAPKs in AhR functions and vice versa, with activation of MAPKs by AhR ligands. This mini-review summarizes current knowledge on the mutual interactions between MAPKs and AhR. The majority of studies has been done on cancer-derived cell lines that have impaired cell cycle regulation and lacks the complete detoxification apparatus. We emphasize the importance of the future studies that should be done on non-transformed cells to distinguish the role of MAPKs in cancer and normal cells. Primary cultures of human or rodent hepatocytes that are equipped with a fully functional biotransformation battery or xenobiotics-metabolizing extra-hepatic tissues should be the models of choice, as the results in our experiments confirm.

Activated stress response pathways within multicellular aggregates utilize an autocrine component

Multicellular aggregates (spheroids) of primary human foreskin fibroblasts (HFF-2) and a glioblastoma cell line (T98G) entered and exited from long term (2 weeks) metabolic arrest utilizing an autocrine response. Cytokine production (specifically IFN-gamma) activated a Gadd45alpha/p38 pathway that led to increased AP-1 (c-jun and ATF3) transcription factor levels, augmenting cytokine production in an autocrine fashion. Whereas HFF-2 aggregates were capable of surviving long term arrest and recovery during NF-kappaB inhibition independent of JNK activation, T98G aggregates were not. Such endogenous processes are not easily observed with adherent monolayer cell culturing systems, strongly suggesting that more emphasis needs to be placed on determining the operational signal transduction cascades within multicellular aggregates. Extracellular inputs such as spheroid formation, arrest, and regrowth as monolayers invoke intracellular signaling responses converging at the AP-1 transcription factor level. Variations in responses are both cell type and transformation state dependent and require an autocrine cytokine component. The data are discussed in relation to the wounding response and avascular tumor growth mechanisms.

Autocrine extracellular signal-regulated kinase activation in normal human keratinocytes is not interrupted by calcium triggering and is involved in the control of cell cycle at the early stage of calcium-induced differentiation

Normal human epidermal keratinocytes (NHEK) respond to the autocrine activated extracellular signal-regulated kinase (ERK) signaling pathway, which contributes to the survival of keratinocytes. However, during the condition of calcium-induced differentiation, how the autocrine ERK signaling is regulated and affected is poorly understood. The purpose of this study was to understand and to obtain clues to the possible function of the autocrine ERK activation during the calcium-induced differentiation of NHEK. We demonstrated that the autocrine activated ERK was not interrupted by calcium triggering and that it was sustained for at least one day after changing the medium. We also found that the autocrine ERK activation was associated with the expression of cyclin D1 and the cell cycle regulation at the early stage of calcium triggering by treating the cells with the mitogen-activated protein kinase inhibitor PD98059. However, the PD98059 treatment did not have a significant influence on the expression of involucrin and loricrin. In addition, we demonstrated that autocrine ERK activation was associated with protein kinase C and p38MAPK signaling. We suggest that the activation of autocrine ERK is not interrupted by calcium triggering and it might participate in cell growth during the early stage of calcium-induced differentiation in NHEK.

Bifunctional modulating effects of an indigo dimer (bisindigotin) to CYP1A1 induction in H4IIE cells

In this study, we measured and characterized the bifunctional effects of a newly identified natural compound-bisindigotin (SLY-1), isolated from leaf extracts of Isatis indigotica, to CYP1A1/EROD activities in H4IIE cells. The compound, SLY-1 (1muM) elicited a transitory and significant induction of CYP1A1 RNA/protein levels and EROD activities in the cells. Maximum levels of CYP1A1 expression and EROD induction were attained at 8 and 12h of post-treatment, respectively. Thereafter the induction decreased significantly. Similar profile of CYP1A2 and CYP1B1 mRNA induction was observed. In contrast TCDD elicited CYP1A1/EROD induction was persistent. The transitory effect by SLY-1 is most likely due to the clearance of SLY-1 by cellular metabolism. Taken together the observation indicated that SLY-1 is an Ah receptor agonist for CYP1A1/CYP1A2/CYP1B1/EROD induction. Interestingly in the TCDD/SLY-1 cotreatment study, although synergistic effects on CYP1A1 expression and EROD induction were observed at 4-8h, significant inhibitory effects to TCDD induced CYP1A1 protein and EROD activity were detected at 12-24h of post-treatment. Because there was no significant reduction of CYP1A1, CYP1A2 or CYP1B1 transcript levels between TCDD- and TCDD/SLY-1 treated cells, the data pointed to the translational and/or post-translational inhibitory effect. The cellular signal transduction system may be modulated following exposure to SLY-1. To investigate the possible mechanisms involved, various specific kinase inhibitors or activators (chelerythrin, PD98059, U0126, ZM336372, SB202190, PKA inhibitor PKI (6-22) amide, and dbcAMP) were used for the assessment. Chelerythrine, PD98059 or dbcAMP treatment in TCDD induced cells showed significant inhibitory effects on CYP1A1 mRNA/protein expressions and EROD activities. U0126 had no observable EROD inhibitory effect. ZM336372 or SB202190 showed inhibition only at EROD activities. The results indicated that the SLY-1 inhibitory effect was possibly not mediated by the cAMP/PKA, PKC or MEK pathways. Nevertheless our results indicate that SLY-1 is not only an inducer of the CYP1A1 system, but also a potent inhibitor of CYP1A1 enzyme.

Corticotropin-Releasing Hormone (CRH) Downregulates Interleukin-18 Expression in Human HaCaT Keratinocytes by Activation of p38 Mitogen-Activated Protein Kinase (MAPK) Pathway

It is generally accepted that corticotropin-releasing hormone (CRH) acts as the main coordinator of the central response to stress. Stress or an abnormal response to stressors has been found to modify the evolution of skin disorders, including psoriasis and atopic dermatitis. Nevertheless, the specific pathogenic role of stress remains unknown in skin diseases. Interleukin (IL)-18, a member of the IL-1 family, is a key mediator of peripheral inflammation and host defense responses, and is secreted by human keratinocytes. Here, we investigated the regulatory effect of CRH on expression of IL-18 in skin keratinocytes. Exposure of HaCaT cells to CRH resulted in a reduction of IL-18 mRNA transcripts and its production was in a concentration-dependent manner. In order to investigate whether the mitogen-activated protein kinase (MAPK) signaling pathway is involved in the downregulation of IL-18 production, cells were pre-treated with SB203580, an inhibitor of p38 MAPK, prior to the addition of CRH. This pre-treatment blocked the decrease in IL-18 production. In addition, CRH treatment induced rapid phosphorylation of p38 MAPK. SB203580 were able to inhibit CRH-induced p38 MAPK phosphorylation. CRH also inhibited production of IL-18 in human primary keratinocytes. These results suggest that CRH regulates IL-18 production through the MAPK signaling pathway in human keratinocytes.

Effects of TCDD in modulating the expression of Sertoli cell secretory products and markers for cell–cell interaction

Among different mammalian tissues, testis is found to be one of the most sensitive organs to TCDD exposure. In this study, primary Sertoli cell culture was established. The purity of the cultured cells was verified using 3beta-hydroxysteroid dehydrogenase, alkaline phosphatase as well as testosterone induction assays. Effects of TCDD in modulating the expression of CYP1A1, aromatase, secretory products (i.e. Mullerian inhibiting substance (MIS), 17beta-estradiol (E(2)) and lactate) and markers for cell-cell interaction (i.e. sertolin and testin) were then examined. Our data demonstrated that Sertoli cells exposed to 0.2-2000 pg/ml of TCDD showed a dose dependent induction of CYP1A1 mRNA. The minimal dose of activation was 2 pg/ml, which indicated that the cell was very sensitive to TCDD exposure. However, there was little or no detectable level CYP1A1 protein and EROD activities found. Dose-dependent inductions of aromatase transcript (200%) and E(2) (20%) secretion were measured. In addition there was a significant reduction (40%) of MIS mRNA. No detectable change in the level of secreted lactate was observed. Sertolin and testin, the gene makers for cell-cell interactions were differentially modulated upon TCDD treatment. Taken together, the results implicated that TCDD exposure might interfere with the normal Sertoli cell functions.