Alaskan Bog Blueberry (Vaccinium uliginosum) Extract as an Innovative Topical Approach to Prevent UV-Induced Skin Damage

Gut-derived wild blueberry phenolic acid metabolites modulate extrinsic cutaneous damage

As the first line of defense, the skin is equipped with various physiological mechanisms positioned to prevent incoming oxidative damage from numerous environmental insults. With persistent exposure to the environment, understanding ways to augment the skin defenses is paramount in protecting from premature aging. In this study, we investigated the ability of five dietary phenolic metabolites, typically found in the bloodstream after wild blueberry consumption, to successfully defend the skin from UV light exposure in a novel ex vivo co-culture model of human skin explants and primary endothelial cells. Skin explants, placed in transwell inserts, were exposed to UV, and subsequently co-cultured with endothelial cells. When the endothelial cells had been pretreated with the bioactive metabolites at physiological concentrations (hippuric acid 3000 nM, isoferulic acid 1000 nM, salicylic acid 130 nM, benzoic acid 900 nM, α-hydroxyhippuric acid 400 nM) cutaneous damage was prevented on the co-cultured with UV-challenged skin explants. Co-culture with non-pretreated endothelial cells did not protect skin explants. Specifically, the pretreatment was able to reduce skin lipid peroxidation (measured as 4-hydroxynonenal protein adducts), and pro-inflammatory enzymes such as cyclooxygenase 2 (COX-2) and NADPH oxidase 4 (NOX-4). Furthermore, pretreatment with the metabolites prevented UV-induced release of inflammatory cytokines such as IL-1β and IL-8 as well as nitric oxides (NO) levels. In addition, the metabolites showed an impressive ability to prevent the loss of cutaneous structural proteins including involucrin and collagen type 1. Of note, endothelial cells cultured with UV exposed skin explants exhibited increased oxidative stress demonstrated by heme oxygenase-1 (HO-1) up-regulation which was significantly prevented in the metabolite treated models. These findings highlight the ability of dietary polyphenolic metabolites to improve cutaneous defenses against extrinsic stressors.

Tension as a key factor in skin responses to pollution

Being the more apparent organ exposed to the outdoor stressors, the effect of pollution on the skin has been widely studied in the last few decades. Although UV light is known as the most aggressive stressor to which our cutaneous tissue is daily exposed, other components of the tropospheric pollution have also shown to affect skin health and functionality. Among them, ozone has been proven to be one of the most toxic due to its high reactivity with the epidermal lipids. Studying the cutaneous effect of pollution in a laboratory setting presents challenges, therefore it becomes critical to employ appropriate and tailored models that aim to answer specific questions. Several skin models are available nowadays: in vitro models (2D cell lines and 3D cutaneous tissues), ex vivo skin explants and in vivo approaches (animals and humans). Although in the last 20 years researchers developed skin models that closely resemble human skin (3D cutaneous tissues), ex vivo skin explants still remain one of the best models to study cutaneous responses. Unfortunately, one important cutaneous property that is not present in the traditional ex vivo human skin explants is the physiological tension, which has been shown to be a cardinal player in skin structure, homeostasis, functional properties and responses to external stimuli. For this reason, in this study, to confirm and further comprehend the harmful mechanism of ozone exposure on the integumentary system, we have performed experiments using the state of art in cutaneous models: the innovative TenSkin™ model in which ex vivo human skin explants are cultured under physiologically relevant tension during the whole experimental procedure. Specifically, we were interested in corroborating previous findings showing that ozone exposure modulates the expression of cutaneous antimicrobial peptides (AMPs). The present work demonstrates that cutaneous exposure to ozone induces AMPs gene and protein levels (CAMP/LL-37, hBD2, hBD3) and that the presence of tension can further modulate their expression. In addition, different responses between tension and non-tension cultured skin were also observed during the evaluation of OxInflammatory markers [cyclooxygenase-2 (COX2), aryl hydrocarbon receptor (AhR), matrix-metallo-proteinase 9 (MMP9) and 4-hydroxy-nonenal (4HNE)]. This current study supports our previous findings confirming the ability of pollution to induce the cutaneous expression of AMPs via redox signaling and corroborates the principle that skin explants are a good and reliable model to study skin responses even though it underlines the need to holistically consider the role of skin tension before extrapolating the data to real life.

Blueberry Supplementation and Skin Health

Environmental stressors such as air pollutants, ozone, and UV radiation are among the most noxious outdoor stressors affecting human skin and leading to premature skin aging. To prevent the extrinsic aging, the skin is equipped with an effective defensive system. However, cutaneous defense mechanisms can be overwhelmed through chronic exposure to environmental pollutants. Recent studies have suggested that the topical usage of natural compounds, such as blueberries, could be a good strategy to prevent skin damage from the environment. Indeed, blueberries contain bioactive compounds found to induce an active skin response against the environmental noxious effects. In this review, results from recent studies on this topic are discussed in order to build the argument for blueberries to possibly be an effective agent for skin health. In addition, we hope to highlight the need for further research to elucidate the mechanisms behind the use of both topical application and dietary supplementation with blueberries to bolster cutaneous systems and defensive mechanisms.

Curcuma aromatica and Curcuma comosa Extracts and Isolated Constituents Provide Protection against UVB-Induced Damage and Attenuate Matrix Metalloproteinase-1 Expression in HaCaT Cells

Ultraviolet-B (UVB) exposure is one of the primary extrinsic factors causing skin photoaging. It stimulates inflammatory responses and arrests the cell cycle. Matrix metalloproteinase-1 (MMP-1) secreted by keratinocytes is one of the important extracellular matrixes to attenuate UVB-induced skin aging via collagen degradation. Curcuma aromatica (CA) and Curcuma comosa (CC), the herbaceous plants in the Zingiberaceae family, are commonly used in Thai traditional women’s medicines. The present work was aimed to investigate the potential of the CA and CC extracts and their isolated compounds to attenuate UVB-induced MMP-1 and cell cycle arrest in HaCaT keratinocytes. Total phenolic contents and antioxidant capacities of the extracts were determined. CC extract contains more phenolic components and provides more potent antioxidant activities than CA extract. HaCaTs were pretreated with the extracts or their isolated constituents 1–4 for 24 h and then repeatedly exposed to UVB at 100 mJ/cm2 10 times. Both extracts and compounds 1–4 effectively reduce UVB-induced MMP-1 levels in HaCaT cells and restore cell cycle arrest. This is the first report on the potential of CA and CC extracts in reducing UVB-induced MMP-1 expression and regulating cell proliferation in HaCaT cells. Thus, CA and CC extracts might be used as alternative natural agents to prevent UVB-induced skin photoaging.