Comparative evaluation of six commercial adult toothpaste formulations reveals cytotoxicity and altered functions in a human oral melanocyte model: an in vitro study

This study aims to compare six commercial adult toothpaste (labeled as A, B, C, D, E, and F) for cytotoxicity and melanocyte function alterations in vitro using primary human epidermal melanocytes from a Caucasian donor (HEMn-LP cells) as a model of oral melanocytes. Cells were incubated with toothpaste extracts (50% w/v) in culture media at dilutions (1:25, 1:50, 1:100, 1:200, 1:500, 1:800, and 1:1000) for 24 h. MTS and LDH assays were used to assess cytotoxicity. The effects of noncytotoxic toothpaste concentrations on melanocyte functional endpoints were then examined using spectrophotometric methods. All toothpaste showed concentration-dependent cytotoxicity that was heterogeneous across toothpaste containing SLS detergent. IC50 values of cytotoxicity followed the order: A = E > C > B > D > F. To compare toothpaste, they were tested at 1:800 and 1:1000 dilutions that were noncytotoxic after 24 h. None of the toothpaste affected cellular melanin production. However, toothpaste A, C, and D suppressed tyrosinase activity at both dilutions, while toothpaste B suppressed tyrosinase activity only at 1:800 dilution. Toothpaste A, C, E, and F elevated ROS production at 1:800 dilution, with no change at 1:1000 dilution. Toothpaste has a heterogeneous effect on melanocytes. Toothpaste B, E, and F at 1:1000 dilution were the safest as they did not alter melanocyte functions at this dilution, although toothpaste F is the least cytotoxic of these. Future studies are necessary to expand these results in a physiological environment of oral tissue. The findings of this study provide novel insight into the biocompatibility studies of toothpaste on oral melanocytes. They can aid dental practitioners and consumers in selecting noncytotoxic toothpaste that do not contribute to ROS generation by melanocytes in the oral cavity or lead to cytotoxicity and impaired cellular function.

Toothpastes for children and their detergent contents affect molecular mechanisms of odontogenesis in zebrafish embryos

We aimed to evaluate how different types of toothpaste (TP) for children affected molecular mechanisms of odontogenesis in zebrafish embryos. Commercially available TPs were selected according to their detergent contents as the cocamidopropyl betaine (CAPB) containing TP (TP1) and sodium lauryl sulfate (SLS) containing TP (TP2). TP3 contained no detergent. Effects of SLS, and CAPB alone were also examined. TP and detergent concentrations affecting development were determined as 750 mg/L and 4 mg/L, respectively. Embryos were exposed to TP1, TP2, TP3, SLS, CAPB, and embryo medium (control) for 72 h post fertilization. Acetylcholinesterase (AChE) activity and oxidant-antioxidant parameters were analyzed spectrophotometrically. Expressions of tooth development genes were evaluated by reverse transcription PCR (RT-PCR). Intraocular distance, lower jaw, and ceratohyal cartilage length were displayed using Alcian Blue staining. axin2 and wnt10a expressions increased in SLS and TP2 groups. igf2a and eve1 expressions decreased in all groups except TP3. nrOb1 expression decreased in TP1, SLS, and CAPB groups. Oxidant-antioxidant balance was disturbed in all groups except TP3, evidenced by increased lipid peroxidation, nitric oxide. SLS, and CAPB groups were more affected in terms of AChE, glutathione-S-transferase, and superoxide dismutase; perturbations were observed in cartilage structures. Altered expression of tooth development gene axin2 correlated with wnt10a, and with changes in cartilage structures in SLS and TP2 groups. TP3 group presented no disruptions in oxidant-antioxidant balance. Our study shows the availability of externally developing zebrafish embryos in examining the effects of TP' contents on embryogenesis.

Allergies Come Clean: The Role of Detergents in Epithelial Barrier Dysfunction

PURPOSE OF REVIEW

The prevalence and incidence of allergic disease have been rising in Westernized countries since the twentieth century. Increasingly, evidence suggests that damage to the epithelium initiates and shapes innate and adaptive immune responses to external antigens. The objective of this review is to examine the role of detergents as a potential risk factor for developing allergic disease.

RECENT FINDINGS

Herein, we identify key sources of human detergent exposure. We summarize the evidence suggesting a possible role for detergents and related chemicals in initiating epithelial barrier dysfunction and allergic inflammation. We primarily focus on experimental models of atopic dermatitis, asthma, and eosinophilic esophagitis, which show compelling associations between allergic disease and detergent exposure. Mechanistic studies suggest that detergents disrupt epithelial barrier integrity through their effects on tight junction or adhesion molecules and promote inflammation through epithelial alarmin release. Environmental exposures that disrupt or damage the epithelium may account for the increasing rates of allergic disease in genetically susceptible individuals. Detergents and related chemical compounds represent possible modifiable risk factors for the development or exacerbation of atopy.

Combined effects of temperature rise and sodium lauryl sulfate in the Mediterranean mussel

Personal care products (PCPs) are those compounds used daily (e.g., soaps, shampoos, deodorants, and toothpaste), explaining their frequent detection in aquatic systems. Still, scarce information is available on their effects on inhabiting wildlife. Among the most commonly used PCPs is the surfactant Sodium Lauryl Sulfate (SLS). The present study investigated the influence of temperature (CTL 17 ºC vs 22 ºC) on the effects of SLS (0 mg/L vs 4 mg/L) in the mussel species Mytilus galloprovincialis. Mussels' general health status was investigated, assessing their metabolic and oxidative stress responses. Higher biochemical alterations were observed in SLS-exposed mussels and warming enhanced the impacts, namely in terms of biotransformation capacity and loss of redox homeostasis, which may result in consequences to population maintenance, especially if under additional environmental stressors. These results confirm M. galloprovincialis as an excellent bioindicator of PCPs pollution, and the need to consider actual and predicted climate changes.

COVID-19 Spotlights Connections between Disease and Multiple Lifestyle Factors

The SARS-CoV-2 virus (severe acute respiratory syndrome coronavirus 2), and the disease it causes (COVID-19), have had a profound impact on global human society and threaten to continue to have such an impact with newly emerging variants. Because of the widespread effects of SARS-CoV-2, understanding how lifestyle choices impact the severity of disease is imperative. This review summarizes evidence for an involvement of chronic, non-resolving inflammation, gut microbiome disruption (dysbiosis with loss of beneficial microorganisms), and impaired viral defenses, all of which are associated with an imbalanced lifestyle, in severe disease manifestations and post-acute sequelae of SARS-CoV-2 (PASC). Humans' physiological propensity for uncontrolled inflammation and severe COVID-19 are briefly contrasted with bats' low propensity for inflammation and their resistance to viral disease. This insight is used to identify positive lifestyle factors with the potential to act in synergy for restoring balance to the immune response and gut microbiome, and thereby protect individuals against severe COVID-19 and PASC. It is proposed that clinicians should consider recommending lifestyle factors, such as stress management, balanced nutrition and physical activity, as preventative measures against severe viral disease and PASC.

Influence of permeability enhancers on the paracellular permeability of metformin hydrochloride and furosemide across Caco-2 cells

Permeability enhancers can affect absorption of paracellularly transported drugs. This study aims to evaluate effects of permeability enhancers (chitosan, methyl-β -cyclodextrin, sodium caprate, sodium lauryl sulfate, etc.) on the permeability of paracellularly absorbed furosemide and metformin hydrochloride. Methyl thiazole tetrazolium bromide test was carried out to determine the drug concentrations in permeability study. Trans-epithelial electrical resistance (TEER) values determined to assess the integrity of tight junctions. Permeability enhancers were applied at different concentrations alone, in dual/triple combinations. Permeability was determined using human colorectal adenocarcinoma (Caco-2) cells (TEER > 400 Ω·cm²). Permeability enhancers have no significant effect (<2-fold; p > 0.05) on the permeability of furosemide (1.80 × 10^-5 ± 4.55 × 10^-7 cm/s); however, metformin permeability (1.36 × 10^-5 ± 1.25 × 10^-6 cm/s) increased significantly (p < 0.05) with 0.3% and 0.5% (w/v) chitosan (2.0- and 2.7-fold, respectively), 1% methyl-β -cyclodextrin (w/v) (3.5-fold), 10 and 20 µmol/L sodium caprate (2.2- and 2.8-fold, respectively), and 0.012% sodium lauryl sulfate (w/v) (1.9-fold). Furosemide permeability increased significantly (p < 0.05) with chitosan-sodium lauryl sulfate combination (1.7-fold), and all triple combinations (1.4- to 1.9-fold). Chitosan containing dual/triple combinations resulted in significant increase (p < 0.05) in metformin permeability (1.7 to 2.8-fold). All results indicated that absorption of furosemide and metformin can be improved by the combination of permeability enhancers. Therefore, it can be evaluated for the formulation of development strategies containing furosemide and metformin by the pharmaceutical industry.

Virucidal activity in vitro of mouthwashes against a feline coronavirus type II

Transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can occur through saliva and aerosol droplets deriving from the upper aerodigestive tract during coughing, sneezing, talking, and even during oral inspection or dental procedures. The aim of this study was to assess in vitro virucidal activity of commercial and experimental mouthwashes against a feline coronavirus (FCoV) strain. Commercial and experimental (commercial-based products with addition of either sodium dodecyl sulfate (SDS) or thymus vulgaris essential oil (TEO) at different concentrations) mouthwashes were placed in contact with FCoV for different time intervals, that is, 30 s (T30), 60 s (T60), and 180 s (T180); subsequently, the virus was titrated on Crandell Reese Feline Kidney cells. An SDS-based commercial mouthwash reduced the viral load by 5 log10 tissue culture infectious dose (TCID)₅₀ /50 µl at T30 while a cetylpyridinium (CPC)-based commercial mouthwash was able to reduce the viral titer of 4.75 log10 at T60. Furthermore, five experimental mouthwashes supplemented with SDS reduced the viral titer by 4.75-5 log10 according to a dose- (up to 4 mM) and time-dependent fashion.

How temperature rise will influence the toxic impacts of 17 α-ethinylestradiol in Mytilus galloprovincialis?

Pharmaceutical drugs are Contaminants of Emerging Concern (CECs) and are continuously discharged into the environment. As a result of human and veterinary use, these substances are reaching aquatic coastal systems, with limited information regarding the toxic effects of these compounds towards inhabiting organisms. Among CECs are pharmaceuticals like 17 α-ethinylestradiol (EE2), which is a synthetic hormone with high estrogenic potency. EE2 has been increasingly found in different aquatic systems but few studies addressed its potential toxicity to marine wildlife, in particular to bivalves. Therefore, the aim of the present study was to evaluate the influence of temperature (17 °C-control and 21 °C) on the potential effects of EE2 on the mussel Mytilus galloprovincialis. For this purpose, mussels were exposed to different concentrations of EE2 (5.0; 25.0; 125.0 and 625 ng/L), resembling low to highly polluted sites. Mussels exposed to each concentration were maintained under two temperatures, 17 and 21 °C, which represent actual and predicted warming conditions, respectively. After 28 days, oxidative stress status, metabolism related parameters, neurotoxicity and histopathological alterations were measured. The results obtained clearly showed an interactive effect of increased temperature and EE2, with limited antioxidant and biotransformation capacity when both stressors were acting together, leading to higher cellular damage. The combination of both stressors also enhanced mussels' metabolic capacity and neurotoxic effects. Nevertheless, loss of redox balance was confirmed by the strong decrease of the ratio between reduce glutathione (GSH) and oxidized glutathione (GSSG) in contaminated mussels, regardless the temperature. Histopathological indexes in contaminated mussels were significantly different from the control group, indicating impacts in gills and digestive glands of mussels due to EE2, with higher values observed at 21 °C. Overall, this study demonstrates that of EE2 represents a threat to mussels and predicted warming conditions will enhance the impacts, which in a near future might result in impairments at the population and community levels.

The influence of salinity on sodium lauryl sulfate toxicity in Mytilus galloprovincialis

The influence of salinity on the effects of sodium lauryl sulfate (SLS) was evaluated using the Mediterranean mussel Mytilus galloprovincialis, exposed for 28 days to SLS (control-0.0 and 4.0 mg/L) under three salinity levels (Control-30, 25 and 35). The effects were monitored using biomarkers related to metabolism and energy reserves, defence mechanisms (antioxidant and biotransformation enzymes) and cellular damage. The results revealed that non-contaminated mussels tended to maintain their metabolic capacity regardless of salinity, without activation of antioxidant defence strategies. On the contrary, although contaminated mussels presented decreased metabolic capacity at salinities 25 and 35, they were able to activate their antioxidant mechanisms, preventing cellular damage. Overall, the present findings indicate that SLS, especially under stressful salinity levels, might potentially jeopardize population survival and reproduction success since reduced metabolism and alterations on mussels' antioxidant mechanisms will impair their biochemical and, consequently, physiological performance.

Intracellular oxidative stress induced by calcium influx initiates the activation of phagocytosis in keratinocytes accumulating at S-phase of the cell cycle after UVB irradiation

BACKGROUND

Phagocytosis is an essential process that maintains cellular homeostasis. In the epidermis, the phagocytosis of melanosomes into keratinocytes is important to protect their DNA against damage from ultraviolet B (UVB) radiation. Furthermore, it is considered that UVB activates the phagocytosis by keratinocytes but the detailed mechanism involved is not fully understood.

OBJECTIVE

To clarify the mechanism of UVB-enhanced phagocytosis in keratinocytes, we investigated the relationship between the phagocytic ability of keratinocytes and the cell cycle stage of keratinocytes.

METHODS

The phagocytic ability of keratinocytes was evaluated using the incorporation of fluorescent beads after exposure to UVB or oxidative stress. S-phase was evaluated by BrdU incorporation and immunostaining of cyclin D1. Intracellular calcium levels of keratinocytes were measured using the probe Fluo-4AM.

RESULTS

The phagocytosis of fluorescent beads into keratinocytes was enhanced by UVB and also by oxidative stress. We found that keratinocytes exposed to UVB or oxidative stress were at S-phase of the cell cycle. Furthermore, keratinocytes synchronized to S-phase showed a higher phagocytic ability according to the increased intracellular ROS level. The UVB-enhanced phagocytosis and entrance into S-phase of keratinocytes was abolished by ascorbic acid, a typical antioxidant. Keratinocytes synchronized to S-phase and exposed to UVB or oxidative stress had increased levels of intracellular calcium and their enhanced phagocytic abilities were diminished by the calcium ion chelator BAPTA-AM.

CONCLUSION

Taken together, intracellular oxidative stress induced by intracellular calcium influx mediates the UVB-enhanced phagocytic ability of keratinocytes accumulating at S-phase of the cell cycle.

Toxicity Profiling of Biosurfactants Produced by Novel Marine Bacterial Strains

Surface active agents (SAAs), currently used in modern industry, are synthetic chemicals produced from non-renewable sources, with potential toxic impacts on humans and the environment. Thus, there is an increased interest for the identification and utilization of natural derived SAAs. As such, the marine environment is considered a promising source of biosurfactants with low toxicity, environmental compatibility, and biodegradation compared to their synthetic counterparts. MARISURF is a Horizon 2020 EU-funded project aiming to identify and functionally characterize SAAs, derived from a unique marine bacterial collection, towards commercial exploitation. Specifically, rhamnolipids produced by Marinobacter MCTG107b and Pseudomonas MCTG214(3b1) strains were previously identified and characterized while currently their toxicity profile was assessed by utilizing well-established methodologies. Our results showed a lack of cytotoxicity in in vitro models of human skin and liver as indicated by alamar blue and propidium iodide assays. Additionally, the use of the single gel electrophoresis assay, under oxidative stress conditions, revealed absence of any significant mutagenic/anti-mutagenic potential. Finally, both 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) cell-free assays, revealed no significant anti-oxidant capacity for neither of the tested compounds. Consequently, the absence of significant cytotoxicity and/or mutagenicity justifies their commercial exploitation and potential development into industrial end-user applications as natural and environmentally friendly biosurfactants.

Assessment of the different skin sensitization potentials of irritants and allergens as single substances and in combination using the KeratinoSens assay

BACKGROUND

People are exposed to mixtures containing allergens and irritants often causing contact dermatitis. Therefore, regulatory authorities require systematic information on the effects of mixtures on the sensitization threshold. In this study a moderate (cinnamal) and a weak (ethylene glycol dimethacrylate) allergen were combined with irritants covering different mechanisms of action (sodium dodecyl sulfate, salicylic acid, and α-pinene). For a systematic approach, the single substances were initially tested using the KeratinoSens assay. Thereafter, each allergen was combined with noncytotoxic concentrations of the irritants.

METHOD

The KeratinoSens assay was applied for the single substances according to OECD (Organisation for Economic Co-operation and Development) Test Guideline 442D. Based on these results, three noncytotoxic concentrations of the irritants were selected and applied simultaneously with 12 concentrations of the allergens to the KeratinoSens cells. Sensitization threshold and cytotoxicity were measured and compared with the individual testing.

RESULTS

The combinations of allergens and irritants differed from the effects of the single substances and lowered the sensitization threshold. The quantitative approach allowed a clear description of the changes which varied by factors between 1.1 and 10.3.

CONCLUSIONS

Overall, the allergen was the prominent compound in the mixture and its nature appeared to determine the degree of the response.

Pyridoxine (VB6 ) restores the down-regulation of serine palmitoyltransferase mRNA expression in keratinocytes cultured in highly oxidative conditions through enhancement of the intracellular antioxidant system

BACKGROUND

Pyridoxine (VB₆ ), which acts as a coenzyme in the biosynthesis of niacin, is formulated in pharmaceuticals to treat skin roughness. However, the mechanism of action of VB₆ is not known precisely.

OBJECTIVE

This study was conducted to clarify the influence of highly oxidative conditions on the expression of skin moisture-related mRNAs and to evaluate the preventive effects of VB₆ focusing on antioxidant behaviour.

METHODS

Intracellular levels of reactive oxygen species (ROS) in normal human epidermal keratinocytes (NHEKs) were determined using the 2',7'-dichlorofluorescein diacetate assay. Real-time PCR was employed to investigate the influence of higher oxidative conditions on the expression of mRNAs encoding serine palmitoyl transferase (SPT) and filaggrin, and to characterize the mechanism of the antioxidant effect of VB₆ . Intracellular glutathione was quantified using an assay based on the glutathione recycling system with 5,5'-dithiobis (2-nitrobenzoic acid) reagent and glutathione reductase. Carbonylated proteins (CPs) were semi-quantified by detecting aldehyde residues.

RESULTS

Treatment of NHEKs with BSO increased the level of intracellular CPs by interfering with intracellular glutathione synthesis. Further, treatment with BSO down-regulated the expression level of SPT mRNA, but VB₆ restored SPT mRNA expression in BSO-treated NHEKs. VB₆ decreased the level of intracellular CPs with or without BSO treatment in a dose-dependent manner. In addition, VB₆ increased levels of intracellular NADH/NADPH and glutathione through the activation of nuclear factor E2-related factor 2 (Nrf2) signalling.

CONCLUSION

These results suggest that highly oxidative conditions cause an impaired skin barrier function due to the down-regulation of SPT that results in skin roughness. VB₆ improved the down-regulation of SPT mRNA expression initiated by highly oxidative conditions by enhancing the intracellular antioxidant system.

In vivo Raman spectroscopy study on the stimulation mechanism of surfactant

BACKGROUND

Surfactant is widely used in skin care products and cleansers, while it may cause physical discomfort. In this study, in vivo Raman spectroscopy was used to explore surfactant irritation mechanism on skin, which was not found in literature.

METHODS

Sodium dodecyl sulfate (SDS) was chosen to represent surfactant. Research on the negative effect of SDS was undertaken by scanning the two states of the skin (without and with the contact of SDS), respectively, on six volunteers, by means of Raman technique and skin magnifier.

RESULTS

The damage to the surface of normal skin by SDS was visible from the photographs taken by skin magnifier, and the apparent damage matched the damage that was happening underneath the skin elucidated by Raman spectra. Compared to the normal skin, the inter-cellular lipids (ICL) lateral packing order of the damaged skin was significantly reduced in 2-12 μm of skin depth (P < 0.05), deeper than 12 μm was not detected. The skin depth of 0-2 μm could not be determined due to strong interference of SDS. Significant change in the secondary and tertiary structures of keratin was not found.

Complexes of Ectoine with the Anionic Surfactants as Active Ingredients of Cleansing Cosmetics with Reduced Irritating Potential

For many years, an increasing number of diagnosed atopy and skin problems have been observed. For people affected by the problem of atopy, the selection of skin care products, including cosmetics, is extremely important. Cleansing cosmetics, due to their ability to cause skin irritations and disturb the hydrolipidic barrier, can increase problems with atopic skin. New solutions to reduce the effects of these products on the skin are very important. In this work, the effect of ectoine on the properties of anionic surfactants was analyzed. Based on model systems, analysis of the effect of ectoine on the irritating effect of four anionic surfactants and their ability to solubilize model sebum was performed. Antioxidant activity was also evaluated, and cytotoxic studies were performed on cell cultures. It was shown that the addition of ectoine to the anionic surfactant solutions improves its safety of use. After introducing ectoine to the surfactant solution, a decrease of irritant potential (about 20%) and a decrease in the ability to solubilize of model sebum (about 10–20%) was noted. Addition of ectoine to surfactant solutions also reduced their cytotoxicity by up to 60%. The obtained results indicate that ectoine may be a modern ingredient that improves the safety of cleansing cosmetics.

Toxic impacts induced by Sodium lauryl sulfate in Mytilus galloprovincialis

Pharmaceuticals and personal care products (PPCPs) are continuously dispersed into the environment, as a result of human and veterinary use, reaching aquatic coastal systems and inhabiting organisms. However, information regarding to toxic effects of these compounds towards marine invertebrates is still scarce, especially in what regards to metabolic capacity and oxidative status alterations induced in bivalves after chronic exposure. In the present study, the toxic impacts of Sodium lauryl sulfate (SLS), an anionic surfactant widely used as an emulsifying cleaning agent in household and cosmetics, were evaluated in the mussel Mytilus galloprovincialis, after exposure for 28 days to different concentrations (0.0; 0.5; 1.0; 2.0 and 4.0 mg/L). For this, effects on mussels respitation rate, metabolic capacity and oxidative status were evaluated. The obtained results indicate a significant decrease on mussel's respiration rate after exposure to different SLS concentrations, an alteration that was accompanied by a decrease of bioconcentration factor along the increasing exposure gradient, especially at the highest exposure concentration. Nonetheless, the amount of SLS accumulated in organisms originated alterations in mussel's metabolic performance, with higher metabolic capacity up to 2.0 mg/L followed by a decrease at the highest tested concentration (4.0 mg/L). Mussels exposed to SLS revealed limited antioxidant defense mecanhisms but cellular damage was only observed at the highest exposure concentration (4.0 mg/L). In fact, up to 2.0 mg/L of SLS limited toxic impacts were observed, namely in terms of oxidative stress and redox balance. However, since mussel's respiration rate was greatly affected by the presence of SLS, the present study may highlight the potential threat of SLS towards marine bivalves, limiting their filtration capacity and, thus, affecting their global physiological development (including growth and reproduction) and ultimely their biochemical performance (afecting their defense capacity towards stressful conditons).

Sodium Lauryl Sulfate vs. Sodium Coco Sulfate. Study of the Safety of Use Anionic Surfactants with Respect to Their Interaction with the Skin

As a result of growing awareness, consumers are increasingly interested in products that are safe on the skin and environmentally-friendly. This is one of the most important reasons for the very rapid development of the natural cosmetics segment which has been observed for several years now. Among the most commonly used anionic surfactants of natural origin are sodium lauryl sulfate (SLS) and sodium coco sulfate (SCS). As there are no unambiguous reports on the safety of using SCS, in this study an attempt was made to evaluate the effect of SCS on the skin. The results of the determination of the skin irritation potential (zein value) indicate that the analyzed parameter is approximately 15 % lower in SCS than in SLS. SCS has a stronger ability to interact with epidermal lipids and cause their elution from the skin, which in turn may damage the protective epidermal barrier. The results obtained during the evaluation of the effect produced by the analyzed substances on the metabolism of human keratinocytes (HaCaT) show that after 4 h of incubation with the studied groups of compounds there was a significant decrease in cell proliferation. The highest decrease in cell metabolism was demonstrated for SLS.

Defensive Effects of a Unique Polysaccharide, Sacran, to Protect Keratinocytes against Extracellular Stimuli and Its Possible Mechanism of Action

Sacran, a polysaccharide isolated from the alga Aphanothece sacrum (Suizenji-nori), has unique physical and physiological characteristics. In a previous study, we reported that sacran improves skin conditions in individuals who suffer from atopic dermatitis (AD), focusing on its trapping function against extrinsic stimuli compared with hyaluronic acid (HA). First, we examined the penetration of sacran through stratum corneum (SC) with an impaired barrier function using immature reconstructed human epidermal equivalents. Sacran penetrates the SC to living cell layers of the epidermis, which suggested that sacran would attenuate adverse influences in keratinocytes caused by extracellular factors such as irritants or proinflammatory cytokines such as interleukin 1α (IL-1α). Sacran markedly reduced the cell damage induced by a nonionic detergent, sodium lauryl sulfate (SLS). Moreover, sacran restored the elevation of intracellular reactive oxygen species (ROS) levels stimulated by SLS and by IL-1α. These effects of sacran were superior to those of HA. In order to investigate the restoration effects of sacran, the influence of sacran on the physical properties of lipid bilayers was evaluated by measuring the order parameter using the ESR spin-labeling method. Because sacran failed to cause changes in the order parameters of liposomes and HaCaT keratinocytes, these results indicate that sacran does not interact with lipid bilayers although it restored changes in the order parameter caused by SLS. The sum of these results demonstrates that sacran reduces the influence of extracellular stimuli by its trapping effects. We conclude that the improving action of sacran is based on its trapping effect.

Development of an in vitro photosafety evaluation method utilizing intracellular ROS production in THP-1 cells

Photoreactive compounds that may experience exposure to ultraviolet (UV) radiation can lead to the intracellular production of reactive oxygen species (ROS), which may cause phototoxic and photoallergenic responses. Here, we developed a novel in vitro photosafety assay and investigated whether it could be used to predict phototoxicity and photosensitivity by measuring changes in intracellular ROS production. THP-1 cells that had previously taken up 5-(and-6)-carboxy-2',7'-difluorodihydrofluorescein diacetate (carboxy-H₂DFFDA), a ROS-sensitive fluorescent reagent, were exposed to photoreactive substances such as phototoxic and photoallergenic materials and then subjected to with UV-A irradiation (5 J/cm²). The fluorescence intensity was subsequently measured using a flow cytometer, and the intracellular ROS production was calculated. A statistically significant increase in ROS following treatment with photoreactive substances was observed in cells irradiated with UV-A. In contrast, no significant increase was observed for non-photoreactive substances in comparison to the control solution. Next, to confirm the impact of intracellular ROS on the photosensitive response, changes in CD86 and CD54 expression were measured following quencher addition during the photo human cell line activation test (photo h-CLAT). The results confirmed the reduction of CD86 and CD54 expression in response to photoallergenic substances following quencher addition. Together, these findings suggest that intracellular ROS production is involved in photosensitizing reactions. Therefore, we suggest that the developed method utilizing intracellular ROS production as an index may be useful as a novel in vitro evaluation tool for photoreactive substances.

Topical treatment with sacran, a sulfated polysaccharide from Aphanothece sacrum, improves corneocyte-derived parameters

Sacran, a polysaccharide isolated from Aphanothece sacrum (Suizenji-nori) alga, has unique characteristics in terms of its physiological properties and effects on the skin, and has recently become a focus of attention as a novel biomaterial. In a previous study, we reported the unique physical characteristics of sacran, which forms a gel-like film containing water in the presence of polyols. This film resists penetration by water and chemicals. We expected this unique physical characteristic to act as an artificial barrier upon the application of sacran to the skin. In the present study, we tested the efficacy of sacran application in healthy individuals who reported previous symptoms of dry or inflamed skin, to evaluate the potential benefits of sacran for skin care in patients with mild atopic dermatitis. Compared with placebo, sacran-containing serum did not significantly alter either the water content of the skin surface or transepidermal water loss. However, subjects using the serum showed improvements in corneocyte parameters including size, percentage of thick abrasion, ratio of SH to SS groups, ratio of interleukin (IL)-1 receptor antagonist to IL-1α, and carbonylated protein level. These results indicate that the sulfated polysaccharide sacran is an effective agent for improving or maintaining the skin conditions.