Mast cells instruct keratinocytes to produce thymic stromal lymphopoietin: Relevance of the tryptase/protease-activated receptor 2 axis.

BACKGROUND: Thymic stromal lymphopoietin (TSLP) promotes TH2 inflammation and is deeply intertwined with inflammatory dermatoses like atopic dermatitis. The mechanisms regulating TSLP are poorly defined. OBJECTIVE: We investigated whether and by what mechanisms mast cells (MCs) foster TSLP responses in the cutaneous environment. METHODS: Ex vivo and in vivo skin MC degranulation was induced by compound 48/80 in wild-type protease-activated receptor 2 (PAR-2)- and MC-deficient mice in the presence or absence of neutralizing antibodies, antagonists, or exogenous mouse MC protease 6 (mMCP6). Primary human keratinocytes and murine skin explants were stimulated with lysates/supernatants of human skin MCs, purified tryptase, or MC lysate diminished of tryptase. Chymase and histamine were also used. TSLP was quantified by ELISA, real-time quantitative PCR, and immunofluorescence staining. RESULTS: Mas-related G protein-coupled receptor X2 (Mrgprb2) activation elicited TSLP in intact skin, mainly in the epidermis. Responses were strictly MC dependent and relied on PAR-2. Complementarily, TSLP was elicited by tryptase in murine skin explants. Exogenous mMCP6 could fully restore responsiveness in MC-deficient murine skin explants. Conversely, PAR-2 knockout mice were unresponsive to mMCP6 while displaying increased responsiveness to other inflammatory pathways, such as IL-1α. Indeed, IL-1α acted in concert with tryptase. In primary human keratinocytes, MC-elicited TSLP generation was likewise abolished by tryptase inhibition or elimination. Chymase and histamine did not affect TSLP production, but histamine triggered IL-6, IL-8, and stem cell factor. CONCLUSION: MCs communicate with kerationocytes more broadly than hitherto suspected. The tryptase/PAR-2 axis is a crucial component of this cross talk, underlying MC-dependent stimulation of TSLP in neighboring kerationocytes. Interference specifically with MC tryptase may offer a treatment option for disorders initiated or perpetuated by aberrant TSLP, such as atopic dermatitis.

Olive-Oil-Derived Polyphenols Effectively Attenuate Inflammatory Responses of Human Keratinocytes by Interfering with the NF-κB Pathway.

SCOPE: Extra virgin olive oil (EVOO) is rich in phenolic compounds, including hydroxytyrosol (HTy) and hydroxytyrosyl acetate (HTy-Ac), which have presented multiple beneficial properties. Their impact on inflammatory responses in human keratinocytes and modes of action have not been addressed yet. METHODS AND RESULTS: Primary human keratinocytes are pretreated with HTy-Ac or HTy for 30 min and stimulated with IL-1ß or Toll-like receptor 3 ligand (TLR3-l). Thymic stromal lymphopoietin (TSLP), measured by ELISA, is attenuated by both polyphenols in a dose-dependent manner. The expression of several inflammation-related genes, including distinct TSLP isoforms and IL-8, are assessed by quantitative RT-PCR and likewise inhibited by HTy-Ac/HTy. Mechanistically, EVOO phenols counteracts IκB degradation and translocation of NF-κB to the nucleus, a transcription factor of essential significance to TSLP and IL-8 transcriptional activity; this is evidenced by immunoblotting. Accordingly, NF-κB recruitment to critical binding sites in the TSLP and IL-8 promoter is impeded in the presence of HTy-Ac/HTy, as demonstrated by chromatin immunoprecipitation. Promoter reporter assays finally reveal that the neutralizing effect on NF-κB induction has functional consequences, resulting in reduced NF-κB-directed transcription. CONCLUSION: EVOO phenols afford protection from inflammation in human keratinocytes by interference with the NF-κB pathway.

A review of molecular mechanisms in the development of hepatocellular carcinoma by aflatoxin and hepatitis B and C viruses.

Aflatoxins are food-borne secondary fungal metabolites that are hepatotoxic, hepatocarcinogenic, and mutagenic. Urinary and serum biomarkers are more efficient in reflecting dietary exposure to aflatoxin B1 (AFB1) than other methods such as food sampling and dietary questionnaires. Chronic infection of the hepatitis B virus (HBV) and dietary exposure to AFB1 are the major risk factors in a multifactorial etiology of hepatocellular carcinogenesis, raising the possibility of a synergistic interaction between 2 agents. These effects are due to the formation of DNA and protein adducts and lipid peroxidation. Most patients with hepatocellular carcinoma and HBV infection had prevalent GC → TA transversion mutation at the third position of codon 249 of the p53 gene. The HBx protein of HBV also promotes cell cycle progression, increases the expression of telomerase reverse transcriptase, inactivates negative growth regulators, and binds to and inhibits the expression of p53 (antiapoptotic activity) and other tumor suppressor genes and senescence-related factors. Some reports also evidence the role of hepatitis C virus in the pathogenesis of HCC. Inhibitors of AFB1 adducts are found to be potent chemoprotective agents against AFB1-induced HCC. This review focuses on the interaction of aflatoxin, HBV, and hepatitis C virus in the development of HCC.