Ampelopsis japonica Makino Extract Inhibits the Inflammatory Reaction Induced by Pathogen-Associated Molecular Patterns in Epidermal Keratinocytes

BACKGROUND: Keratinocytes are the major cells in epidermis, providing barrier components such as cornified cells through the sophisticated differentiation process. In addition, keratinocytes exerts their role as the defense cells via activation of innate immunity. It has been known that pathogen-associated molecular patterns (PAMPs) including double-strand RNA and nucleotides can provoke inflammatory reaction in keratinocytes. OBJECTIVE: The aim of this study is to evaluate the effect of Ampelopsis japonica Makino extract (AE) on PAMPs-induced inflammatory reaction of keratinocytes. METHODS: The effects of AE were determined using poly (I:C)-induced inflammation and imiquimod-induced psoriasiform dermatitis models. RESULTS: In cultured keratinocytes, AE significantly inhibited poly(I:C)-induced expression of inflammatory cytokines, such as interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor-α. AE significantly inhibited poly(I:C)-induced release of caspase-1 active form (p20), and down-regulated nuclear factor-κB signaling pathway. In imiquimod-induced psoriasiform dermatitis model, topical application of AE resulted in significant reduction of epidermal hyperplasia. CONCLUSION: These results suggest that AE may be a potential candidate for the treatment of skin inflammation.

Insight into the mechanisms regulating immune homeostasis in health and disease.

Innate and adaptive immune systems consist of cells and molecules that work together in concert to fight against microbial infection and maintain homeostasis. Hosts encounter microbes / exogenous pathogen-associated molecular patterns (PAMPs) and endogenous damage-associated molecular patterns (DAMPs) all the time and they must have proper mechanisms to counteract the danger such that appropriate responses (e.g., degree of inflammation and types of mediators induced) can be mounted in different scenarios. Increasing numbers of endogenous danger signals of host origin are being identified including, for example, uric acid and cholesterol crystals, high mobility group box1 (HMGB1) protein, oxidized LDL, vesicans, heat shock proteins (HSPs) and self DNA. Many of these endogenous ligands have been shown to be associated with inflammation-related diseases like atherosclerosis, gout and type 2 diabetes. Several DAMPs appear to have the ability to interact with more than one receptor. We are now beginning to understand how the immune system can distinguish infection from endogenous ligands elaborated following cellular insults and tissue damage. Appropriate responses to maintain the homeostatic state in health and disease depend largely on the recognition and response to these stimuli by germline encoded pattern-recognition receptors (PRRs) present on both immune and non-immune cells. These receptors are, for example, Toll-like receptors (TLRs), C-type lectin receptors (CLRs) and cytosolic receptors (e.g., RLRs, NLRs and some intracellular DNA sensors). Atypical PRR “danger” receptors, like the receptor for advanced glycation end products (RAGE) and their ligands have been identified. A proper response to maintain homeostasis relies on specific negative regulators and regulatory pathways to dampen its response to tissue injury while maintaining the capacity to eliminate infection and induce proper tissue repair. Moreover, some PRRs (e.g., TLR2,TLR4 and NLRP3) and atypical PRRs can recognize both PAMPs and DAMPs, either as single entities or after forming complexes (e.g., immune complexes, or DNA- HMGB1 and DNA-LL37 complexes), so there must be a mechanism to selectively depress or alleviate the inflammatory response to DAMPs, while leaving that of PAMPs intact. Excessive inflammatory responses can induce considerable tissue damage and can be highly detrimental to the host. For example, CD24 reacting with HMGB1 and HSPs has been implicated to function as negative regulator for RAGE. In this review, I will briefly overview the information on various host and microbial components and bring together the information to synthesize a model to explain how homeostasis can be maintained in states of health and disease. Understanding the molecular mechanisms by which the immune system functions under different scenarios will provide us with ways and means to design appropriate approaches, for example, to prevent or treat autoimmune and inflammatory diseases or the ability to design new drugs or formulate safe chemicals for vaccine adjuvants.

The Expression Pattern of Toll-like Receptor (TLR) and Cytokine Production to TLR Agonists in Human Retinal Pigment Epithelial Cells

Retinal pigment epithelium (RPE) constituting the outer blood-retina barrier plays an important role in ocular defense mechanism. Many studies reported that RPE participates in ongoing immune responses in the retina. However, the exact mechanism is still uncertain. Toll-like receptors (TLRs) participate in the recognition of pathogen-associated molecular patterns (PAMP), such as LPS, zymosan, lipoprotein, and dsRNA. The expression and function of TLRs in human RPE have not been established. In this study, we investigated TLRs expression in human fetal RPE and their recognition of PAMP to determine how human RPE participates in ocular defense mechanism against microbial component. RT-PCR and real time PCR revealed that TLR1 through 5 were constitutively expressed in human fetal RPE, and their expressions were slightly increased by LPS. We determined the TNF-alpha, IL-6, and IL-8 expression in human fetal RPE after treatment with LPS, zymosan, petidoglycan, or poly I:C. RT-PCR demonstrated that LPS and poly I:C treatment increased the production of TNF-alpha, IL-6, and IL-8 in human fetal RPE. LPS showed more potent effects on TNF-alpha and IL-8 production. Peptidoglycan and zymosan did not induce the production of TNF-alpha. CD14, the co-receptor of LPS was weakly expressed and functioned in recognizing LPS in human fetal RPE. These results suggest that human RPE may participate in ocular defense mechanism against microbial component through toll-like receptors.