Data Availability StatementThe data used to support the findings of this study are available from the corresponding author upon request

Data Availability StatementThe data used to support the findings of this study are available from the corresponding author upon request. (GPx4) was increased, and the levels of cluster of differentiation 1a (CD1A) were low. Moreover, the apoptosis of inflammatory cells was elevated. The production of phosphorylated extracellular signal-related kinase (p-ERK), phosphorylated c-Jun amino-terminal kinase (p-JNK), and phosphorylated mammalian Rabbit Polyclonal to OVOL1 target of rapamycin (p-mTOR) was low, and epidermal thickness was decreased. Besides, the expression levels of involucrin were measured by treating genistein, an active ingredient of Douchi extract, and palmitoylethanolamide (PEA), one SU9516 of the ECS agonists. The results showed that genistein had a better lipid barrier formation effect than PEA. In conclusion, HTD alleviates the symptoms of AD by maintaining skin homeostasis, improving skin barrier formation, and downregulating inflammation, through ECS intervention. 1. Introduction Atopic dermatitis (AD) is an inflammatory skin disease, highly relapsing, characterized by prorates, dryness, and erythematous eczema [1] and is also the initial stage of an atopic march that progresses to asthma and allergic rhinitis [2]. The pathogenesis of AD has not yet been elucidated and is thought to be caused by a combination of genetic, immunological, and environmental factors and skin barrier dysfunction [3]. Among them, skin barrier dysfunction has become the most important factor since the outside-inside hypothesis in the 1990s that damage to the skin barrier was the early mechanism of AD pathogenesis [4]. Levels of various keratinocyte differentiation markers, including filaggrin, involucrin, and loricrin, are low in AD lesions [5]. Moreover, levels of ceramide in stratum corneum (SC) are reduced [6]. Hallmarks of AD skin are epidermal hyperplasia resulting from increased epidermal proliferation and reduced differentiation [7] and spongiosis resulting from tissue remodeling [8]. These structural changes in the skin barrier disrupt skin homeostasis, preventing the skin from performing its normal barrier function. The endocannabinoid system (ECS) is usually a biological system composed of cannabinoids (CBs) that regulate appetite, pain sensation, mood, and memory [9]. Recently, it was revealed that an increase or decrease of the ECS tones is associated with the various pathological conditions [10]. Temporarily altered activity of ECS reduces the symptoms of the body’s compensatory response or slows disease progression. In other cases, activation of ECS can act as a pathogenic or reflect a defect in the body [11]. In particular, the ECS is usually associated with the regulation of cell growth, proliferation, immunity, and the inflammatory response involved in skin homeostasis [12]. Representative CBs, anandamide (N-arachidonoylethanolamine; AEA) and 2-arachidonoylglycerol (2-AG), which are produced locally in various cellular compartments of the skin, regulate the various cutaneous functions via binding to cannabinoid receptor type (CB)1 or CB2 [13]. In epidermal keratinocytes, activation of CB1 and CB2 suppresses cellular proliferation and differentiation [14], releases the inflammatory mediators [15], and induces apoptosis [16]. Additionally, CB1 suppresses the secretion of proinflammatory chemokines to help control skin inflammation [17]. In the hair follicle, activation of CB1 attenuates hair growth and proliferation, whereas promotes apoptosis and the regression phase [18]. In the sebaceous gland, activation of CB2 stimulates lipid formation and apoptosis [19]. Furthermore, various CBs inhibit sensory phenomena such as pain and itching via CB1 [20, 21]. ECS constitutively regulates the well-balanced proliferation and differentiation of skin cells, as well as immune and inflammatory responses. The fine-tuned changes in ECS might promote or alleviate skin diseases [13]. Therefore, the ECS is usually a microenvironmental control factor for maintaining skin homeostasis. Thus, the role of the ECS as a new therapeutic target for skin diseases has been highlighted [22]. In traditional Chinese medicine, inflammatory diseases such as asthma, rhinitis, and AD are thought to be due to heat syndrome [23]. Therefore, inflammatory diseases are treated with heat-clearing herbal medicine to remove the accumulated heat in the body [24]. Fetal heat is caused by changes in the microimmune environment that affect fetal survival, such as in Th2-skewed conditions. Thus, fetal heat manifests as a variety of diseases in newborns by disrupting the homeostasis of the fetus, of which AD is the most common [25]. In Korean medicine, Hataedock (HTD), herbal extracts that are orally administered to neonates and infants, was used to clear fetal heat to prevent inflammatory diseases. Our previous studies have shown that HTD mitigates AD development due to fetal heat and SU9516 controls Th2-skewed conditions [26, 27]. Moreover, our studies showed that lipid barrier formation in the epidermis is increased after the application of HTD [28]. Douchi (fermented Merr.), one of the most commonly used herbs in HTD, is usually SU9516 a kind of fermented soybean known as a herb that reduces heat by radiating the body heat [29]. Recently, many studies have been conducted on ECS modulators, especially soybean [30C32]. In particular, genistein,.