Ameliorative effects of green tea extract from tannase digests on house dust mite antigen-induced atopic dermatitis-like lesions in NC/Nga mice

A two-sample Mendelian randomization study of mutual relations of six types of diets in atopic dermatitis

BACKGROUND

In the continuous endeavor to find safe and efficient treatments for Atopic Dermatitis (AD), there remains a considerable focus on dietary adjustments. Nevertheless, the limited availability of research and conflicting findings in the academic literature pose a hurdle in establishing conclusive recommendations.

METHOD

Mendelian randomization (MR) was applied to the most comprehensive genome-wide association studies (GWAS) data on tea intake (447 485), green tea intake (n = 64 949), flavored milk intake (n = 64 941), never eat eggs, dairy, wheat, sugar: Wheat products(n = 461 046), never eat eggs, dairy, wheat, sugar: Sugar or foods/drinks containing sugar (n = 461 046), never eat eggs, dairy, wheat, sugar: I eat all of the above (n = 461 046) and atopic dermatitis (n = 218 467). We used the inverse-variance weighted method (IVW) as the primary method.

RESULTS

The IVW analyses have demonstrated an increased tea intake was genetically associated with a reduced risk of AD (odds ratio [OR]: 0.646, 95% confidence interval [CI]: 0.430-0.968, p = 0.034). Furthermore, green tea intake was significantly negatively associated with AD (IVW OR: 0.986, 95% CI: 0.975-0.998; p = 0.024) in the IVW model. AD risk could be reduced by never eating wheat products (IVW OR: 8.243E-04, 95% CI: 7.223E-06-9.408E-02, p = 0.003). There was no association between never eating eggs, dairy, wheat, sugar: Sugar, or foods/drinks containing sugar, I eat all of the above and AD.

CONCLUSIONS

Our MR study suggests a causal relationship between tea intake, green tea intake, and the avoidance of eating wheat products with atopic dermatitis. Our findings recommend that preventing and managing atopic dermatitis may be achieved by never eating wheat products while increasing tea and green tea intake.

Potentialities of Tannase-Treated Green Tea Extract in Nutraceutical and Therapeutic Applications

Green tea has garnered widespread interest in the past decades due to its content of health-beneficial polyphenols and catechins, besides reportedly exhibiting activities for the prevention, and possibly treatment, of many modern-life-associated afflictions. Hence, the functional food potential of health-beneficial beverages such as green tea is widely and commercially promoted. Biotransformation of green tea extract using enzymes such as tannase ostensibly enhances its beneficial well-being properties and disease-preventing functionalities. The tannase-treated green tea catechins may exhibit enhanced, amongst others, antioxidant, anti-tumour, anti-wrinkle, anti-inflammatory, anti-obesity and anti-sarcopenia properties compared to native green tea extract. Nonetheless, the health benefits and therapeutic and toxicological effects associated with these compounds, before and after tannase treatment, present a scientific gap for detailed studies. Accordingly, the review surveys the literature from the late twentieth century until the year 2023 related to the aforementioned important aspects.

Effects of Echinocystic Acid on Atopic Dermatitis and Allergic Inflammation of the Skin and Lungs

BACKGROUND

Echinocystic acid (ECA), a pentacyclic triterpene enriched in various herbs, promotes anti-inflammatory and antioxidant activity; however, its therapeutic effects on atopic dermatitis (AD) or atopic march and the underlying mechanisms of action have not yet been fully elucidated.

PURPOSE

This study aimed to elucidate the effects and molecular mechanisms of ECA on AD and allergic inflammation.

METHODS

We evaluated the inhibitory effects of ECA using a house dust mite (HDM)-induced AD mouse model and human keratinocytes.

RESULTS

The results revealed that ECA improved AD symptoms by decreasing epidermal/dermal thickness, immune cell infiltration, and restoring skin barrier function, as well as an imbalanced immune response. In addition, repeated epicutaneous HDM challenges aggravated allergic inflammation in mice lungs, which was caused by the infiltration of immune cells and collagen deposition, whereas ECA alleviated these symptoms. Moreover, ECA suppressed the expression of T helper cell-derived cytokines, phosphorylation of extracellular signal-regulated kinase, and signal transducer and activator of transcription 1 in the skin and lungs of mice with HDM-induced AD, as well as inhibited the translocation of nuclear factor-κB in HaCaT keratinocytes.

CONCLUSION

This is the meaningful study to demonstrate that ECA improves allergic inflammation of the skin and lungs through recovery of the skin barrier, regulation of immune balance, and alleviation of lung inflammation, suggesting that ECA has therapeutic potential as an antiatopic and antiallergic agent that blocks the progression of AD to atopic march.

Ameliorative effects of epigallocatechin-3-gallate nanoparticles on 2,4-dinitrochlorobenzene induced atopic dermatitis: A potential mechanism of inflammation-related necroptosis

Atopic dermatitis (AD) is a common autoimmune and chronic inflammatory cutaneous disease with a relapsing-remitting course. Necroptosis is a regulated necrotic cell death mediated by receptor-interacting protein 1 (RIP1), receptor-interacting protein 3 (RIP3), and mixed lineage kinase domain-like pseudokinase (MLKL), which is activated by tumor necrosis factor-α (TNF-α). However, the mechanism and the role of necroptosis have not been delineated in AD progression. (-)-Epigallocatechin-3-gallate (EGCG), the main biological activity of tea catechin, is well known for its beneficial effects in the treatment of skin diseases. Here, PEG-PLGA-EGCG nanoparticles (EGCG-NPs) were formulated to investigate the bioavailability of EGCG to rescue cellular injury following the inhibition of necroptosis after AD. 2,4-dinitrochlorobenzene (DNCB) was used to establish AD mouse models. As expected, topically applied EGCG-NPs elicited a significant amelioration of AD symptoms in skin lesions, including reductions in the ear and skin thickness, dermatitis score, and scratching behavior, which was accompanied by redox homeostasis restored early in the experiment. In addition, EGCG-NPs significantly decreased the expression of inflammatory cytokines like TNF-α, interferon-γ (IFN-γ), interleukin-4 (IL-4), interleukin-6 (IL-6), and interleukin-17A (IL-17A) in a time-dependent manner than those of in AD group. As a result, the overexpression of RIP1, RIP3, and MLKL in the entire epidermis layers was dramatically blocked by EGCG-NPs, as well as the expression ofphosphorylated p38 (p-p38), extracellular signal-regulated kinase 1 (ERK1), and extracellular signal-regulated kinase 2 (ERK2). These findings promote that EGCG-NPs formulation represents a promising drug-delivery strategy for the treatment of AD by maintaining the balance of Th1/Th2 inflammation response and targeting necroptosis.

Skin Care Product Rich in Antioxidants and Anti-Inflammatory Natural Compounds Reduces Itching and Inflammation in the Skin of Atopic Dermatitis Patients

The atopic dermatitis (AD) complex pathogenesis mechanism reveals marked changes of certain signaling factors as well as some morphological alterations in the epidermis. Reduced resilience against environmental factors and oxidative stress often makes the treatment with corticosteroids or tacrolismus ointments indispensable. In view of the correlation between oxidative stress and AD pathological factors, antioxidants can be incorporated into AD management strategies. This study investigates a curly kale, apple and green tea-containing natural extract rich in antioxidants for its effects on signaling inflammatory molecules and skin barrier enhancement in human epidermal keratinocytes- (NHEKs) based cell assays. Furthermore, the skin penetration on porcine ears was measured ex vivo using Raman micro spectroscopy. Finally, in a double-blind half-side, placebo-controlled clinical study, the effects of a formulation containing this extract were analyzed for the influence of lesion severity, epidermal barrier function, and pruritus in mild to moderately AD patients. Summarizing our results: The extract reduces expression of inflammatory cytokines in keratinocytes and increases barrier-related molecules. The verum formulation with a very high antioxidant capacity used in AD patients with mild to moderate lesions reduces itching, local SCORAD, and improves barrier function and the hydration of skin lesions.

Immunomodulatory and Anti-inflammatory Effects of Asiatic Acid in a DNCB-Induced Atopic Dermatitis Animal Model

We examined the immunomodulatory and anti-inflammatory effects of asiatic acid (AA) in atopic dermatitis (AD). AA treatment (5–20 µg/mL) dose-dependently suppressed the tumor necrosis factor (TNF)-α level and interleukin (IL)-6 protein expression in interferon (IFN)-γ + TNF-α-treated HaCaT cells. The 2,4-dinitrocholrlbenzene (DNCB)-induced AD animal model was developed by administering two AA concentrations (30 and 75 mg/kg/d: AD + AA-L and AD + AA-H groups, respectively) for 18 days. Interestingly, AA treatment decreased AD skin lesions formation and affected other AD characteristics, such as increased ear thickness, lymph node and spleen size, dermal and epidermal thickness, collagen deposition, and mast cell infiltration in dorsal skin. In addition, in the DNCB-induced AD animal model, AA treatment downregulated the mRNA expression level of AD-related cytokines, such as Th1- (TNF-α and IL-1β and -12) and Th2 (IL-4, -5, -6, -13, and -31)-related cytokines as well as that of cyclooxygenase-2 and CXCL9. Moreover, in the AA treatment group, the protein level of inflammatory cytokines, including COX-2, IL-6, TNF-α, and IL-8, as well as the NF-κB and MAPK signaling pathways, were decreased. Overall, our study confirmed that AA administration inhibited AD skin lesion formation via enhancing immunomodulation and inhibiting inflammation. Thus, AA can be used as palliative medication for regulating AD symptoms.

Improved Anti-Inflammatory Effects of Liposomal Astaxanthin on a Phthalic Anhydride-Induced Atopic Dermatitis Model

Previously, we found that astaxanthin (AST) elicited an anti-inflammatory response in an experimental atopic dermatitis (AD) model. However, the use of AST was limited because of low bioavailability and solubility. We hypothesized that liposome formulation of AST could improve this. In this study, we compared the anti-inflammatory and anti-dermatotic effects of liposomal AST (L-AST) and free AST. We evaluated the effect of L-AST on a phthalic anhydride (PA)-induced animal model of AD by analyzing morphological and histopathological changes. We measured the mRNA levels of AD-related cytokines in skin tissue and immunoglobulin E concentrations in the serum. Oxidative stress and transcriptional activities of signal transducer and activator of transcription 3 (STAT3) and nuclear factor (NF)-κB were analyzed via western blotting and enzyme-linked immunosorbent assay. PA-induced dermatitis severity, epidermal thickening, and infiltration of mast cells in skin tissues were ameliorated by L-AST treatment. L-AST suppressed AD-related inflammatory mediators and the inflammation markers, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 in PA-induced skin conditions. Oxidative stress and expression of antioxidant proteins, glutathione peroxidase-1 (GPx-1) and heme oxygenase-1 (HO-1), were recovered by L-AST treatment in skin tissues from PA-induced mice. L-AST treatment reduced transcriptional activity of STAT3 and NF-κB in PA-induced skin tissues. Our results indicate that L-AST could be more effective than free AST for AD therapy.

Conjugated linoleic acid attenuates 2,4-dinitrofluorobenzene-induced atopic dermatitis in mice through dual inhibition of COX-2/5-LOX and TLR4/NF-κB signaling

Conjugated linoleic acid (CLA), commonly found in beef, lamb and dairy products, has been reported to exhibit anti-inflammatory and antipruritus effects and to inhibit the release of chemical mediators such as histamine and eicosanoid in laboratory rodents. The chief objective of the study is to assess the efficacy of CLA on atopic dermatitis (AD) in mice and to explore possible mechanisms with CLA treatments. To develop a new therapy for AD, the anti-AD potential of CLA was investigated by inducing AD-like skin lesions in mice using 2,4-dinitrofluorobenzene. We evaluated dermatitis severity; histopathological changes; serum levels of T helper (Th) cytokines (interferon-γ, interleukin-4); changes in protein expression by western blotting and immunohistochemistry staining for cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX), toll like receptor 4 (TLR-4), myeloid differentiation factor 88 (MyD88), nuclear factor-κB (NF-κB) and tumor necrosis factor α (TNF-α); and production of the proinflammatory lipid mediators, such as prostaglandin E₂ and leukotriene B4, in the skin lesions. Treatment with CLA ameliorated the development of AD-like clinical symptoms and effectively inhibited epidermal hyperplasia and infiltration of mast cells and CD4⁺ T cells in the AD mouse skin. Total serum immunoglobulin E levels and the expression levels of Th1/Th2 cytokines and lipid mediators in dorsal skin were dramatically suppressed by CLA. Furthermore, CLA down-regulated the expressions of COX-2, 5-LOX, TLR4, MyD88, NF-κB and TNF-α. Taken together, our findings demonstrate the potential usefulness of CLA as an anti-inflammatory dietary supplement or drug for the prevention and management of AD skin diseases by modulating the COX-2/5-LOX and TLR4/MyD88/NF-κB signaling pathways.

The role of kinin B1 and B2 receptors in the mouse model of oxazolone-induced atopic dermatitis

This study evaluated the role of kinin B₁ and B₂ receptors in the pre-clinical mouse model of oxazolone-induced atopic dermatitis. The B₁ R715 or B₂ HOE140 receptor antagonists were dosed at different schemes of treatment. After assessment of clinical lesion scores and pruritus, lesional skin samples were collected for histopathological analysis. The plasma extravasation and the expression of the metalloproteinase ADAMTS5 were also assessed. The immunopositivity for kinin receptors was evaluated in the skin, dorsal root ganglion (DRG), thoracic spinal cord and brain cortex sections. Marked upregulation of B₁ and B₂ receptors was observed in the skin of oxazolone-treated mice. The induction of atopic dermatitis led to a downregulation of both receptors in the DRG, without any alteration in the spinal cord and brain cortex. The repeated administration of HOE140 (50 nmol/kg; i.p.) partially inhibited the oxazolone-related pruritus, associated with a reduction of ADAMTS5 immunolabelling in the skin. Alternatively, R715 (438 nmol/kg; i.p.) produced a mild inhibition of plasma extravasation in oxazolone-challenged mice. Noteworthy, the repeated i.d. injection of R715 (30 nmol/site) or HOE140 (3 nmol/site) significantly reduced the histiocyte numbers, according to the histopathological analysis. Either B₁ or B₂ kinin antagonists, irrespective of the protocol of treatment, did not alter any other evaluated clinical or histological parameters. Data brings novel evidence about the role of kinin receptors in allergy-related conditions, such as atopic dermatitis. Further studies to test different protocols of treatment with kinin antagonists on in-depth cellular alterations underlying oxazolone-induced atopic dermatitis remain to be performed.