What you see may not always be what you get – Bioavailability and extrapolation from in vitro tests

Are Prepubertal Gynaecomastia and Premature Thelarche Linked to Topical Lavender and Tea Tree Oil Use?

Various studies, conducted since 2007, have reported a total of eight boys with prepubertal gynaecomastia and four girls with premature thelarche following exposure to lavender and/or tree tea oil. All patients experienced regression of the breast tissue after they stopped using these oils. Both of these essential oils, and several of their constituents, have oestrogenic and antiandrogenic activity in vitro. However, limited dermal penetration of some of the components means that the in vitro findings cannot be extrapolated to the in vivo situation. There are unanswered questions as to how much lavender or tea tree oil was actually present in the skincare products used by the children and a lack of information about exposure to other agents. Furthermore, since both prepubertal gynaecomastia and premature thelarche often spontaneously regress, it cannot be concluded that the use of lavender and/or tree tea oil is the cause of the gynaecomastia and thelarche in these children.

TFOS Lifestyle: Impact of cosmetics on the ocular surface

In this report the use of eye cosmetic products and procedures and how this represents a lifestyle challenge that may exacerbate or promote the development of ocular surface and adnexal disease is discussed. Multiple aspects of eye cosmetics are addressed, including their history and market value, psychological and social impacts, possible problems associated with cosmetic ingredients, products, and procedures, and regulations for eye cosmetic use. In addition, a systematic review that critically appraises randomized controlled trial evidence concerning the ocular effects of eyelash growth products is included. The findings of this systematic review highlight the evidence gaps and indicate future directions for research to focus on ocular surface outcomes associated with eyelash growth products.

Tea tree oil extract causes mitochondrial superoxide production and apoptosis as an anticancer agent, promoting tumor infiltrating neutrophils cytotoxic for breast cancer to induce tumor regression

The antitumor activity of the tea tree oil (TTO) derived product, Melaleuca Alternifolia Concentrate (MAC) was characterized mechanistically at the molecular and cellular level. MAC was analyzed for its anticancer activity against human prostate (LNCaP) and breast (MCF-7) cancer cell lines growing in vitro. MAC (0.02-0.06% v/v) dose-dependently induced the intrinsic (mitochondrial) apoptotic pathway in both the LNCaP and MCF-7 cell lines, involving increased mitochondrial superoxide production, loss of mitochondrial membrane potential (MMP), caspase 3/7 activation, as well as the presence of TUNEL⁺ and cleaved-PARP⁺ cell populations. At concentrations of 0.01-0.04% v/v, MAC caused cell cycle arrest in the G_0/1-phase, as well as autophagy. The in vivo anticancer actions of MAC were examined as a treatment in the FVB/N c-Neu murine model for spontaneously arising breast cancers. Intratumoral MAC injections (1-4% v/v) significantly suppressed tumor progression in a dose-dependent manner and was associated with greater levels of tumor infiltrating neutrophils exhibiting anticancer cytotoxic activity. Induction of breast cancer cell death by MAC via the mitochondrial apoptotic pathway was also replicated occurring in tumors treated in vivo. In conclusion, our data highlights the potential for the Melaleuca-derived MAC product inducing anticancer neutrophil influx, supporting its application as a novel therapeutic agent.

Effects of Terpinen-4-ol on Meibomian Gland Epithelial Cells In Vitro

PURPOSE

Infestation with demodex mites has been linked to the development of chalazion, meibomian gland dysfunction, and blepharitis. An effective treatment is the eyelid application of terpinen-4-ol (T4O), a tea tree oil component. However, T4O is also known to be toxic to nonocular epithelial cells. We hypothesize that T4O toxicity also extends to human meibomian gland epithelial cells (HMGECs).

METHODS

Immortalized (I) HMGECs were cultured with varying concentrations (1.0%-0.001%) of T4O under proliferating or differentiating conditions up to 5 days. Experimental procedures included analyses of cell appearance, survival, P-Akt signaling, lysosome accumulation, and neutral lipid content.

RESULTS

Our findings show that T4O causes a dose- and time-dependent decrease in the cell survival of IHMGECs. After 15 minutes of exposure to 1% T4O, IHMGECs exhibited rounding, atrophy, and poor adherence. Within 90 minutes of such treatment, almost all cells died. Reducing the T4O concentration to 0.1% also led to a marked decrease in P-Akt signaling and cell survival of IHMGECs. Decreasing the T4O amount to 0.01% caused a slight, but significant, reduction in the IHMGEC number after 5 days of culture and did not influence the ability of these cells to differentiate.

CONCLUSIONS

T4O, even at levels 10-fold to 100-fold lower than demodicidal concentrations, is toxic to HMGECs in vitro.

Tea tree oil presents in vitro antitumor activity on breast cancer cells without cytotoxic effects on fibroblasts and on peripheral blood mononuclear cells

The purpose of this study was to investigate some possible mechanisms underlying the in vitro antitumor activity of tea tree oil (TTO) on human and mouse breast cancer cells (MCF-7 and 4T1, respectively) and its cytotoxicity on fibroblasts (HFF-1) and on peripheral blood mononuclear cells (PBMCs). TTO High-Resolution Gas Chromatography (HRGC) showed seventeen main constituents, such as Terpinen-4-ol, γ-Terpinene, and α-Terpinene. High TTO concentrations (≥ 600 μg/mL) showed a remarkable antitumor activity, decreasing cell viability and cell proliferation of MCF-7 and 4T1 cells. TTO at 300 μg/mL increased the number of MCF-7 cells in the early stages of apoptosis and increased the BAX/BCL-2 genes ratio. TTO, mainly at 300 μg/mL, decreased cell growth and arrested MCF-7 cells in the S phase of the cell cycle. Lower antitumor concentrations (≤300 μg/mL) evaluated in MCF-7 and 4T1 cells were not cytotoxic to PBMCs and HFF-1. Also, TTO (300 μg/mL) was able to induce cell proliferation in fibroblasts after 72 h, indicating non-cytotoxic effect in these cells. TTO exhibited in vitro antitumor effect on MCF-7 and 4T1 cells by decreasing cell viability and modulating apoptotic pathways and cell cycle arrestment of MCF-7 cells. In this sense, our study provides new perspectives on the potential use of TTO for the development of new alternative therapies to treat topically locally advanced breast cancer (LABC).

Antimicrobial activity, cytotoxicity and chemical analysis of lemongrass essential oil (Cymbopogon flexuosus) and pure citral

The aim of this study was to determine the antimicrobial effects of lemongrass essential oil (C. flexuosus) and to determine cytotoxic effects of both test compounds on human dermal fibroblasts. Antimicrobial susceptibility screening was carried out using the disk diffusion method. Antimicrobial resistance was observed in four of five Acinetobacter baumannii strains with two strains confirmed as multi-drug-resistant (MDR). All the strains tested were susceptible to both lemongrass and citral with zones of inhibition varying between 17 to 80 mm. The mean minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of citral (mic—0.14 % and mbc—0.3 % v/v) was lower than that of Lemongrass (mic—0.65 % and mbc—1.1 % v/v) determined using the microtitre plate method. Cell viability using human dermal fibroblasts (HDF; 106-05a) was determined following exposure to both compounds and a control (Grapeseed oil) using the XTT assay and the IC₅₀ determined at 0.095 % (v/v) for citral and 0.126 % (v/v) for lemongrass. Grapeseed oil had no effect on cell viability. Live cell imaging was performed using the LumaScope 500 imaging equipment and changes in HDF cell morphology such as necrotic features and shrinkage were observed. The ability of lemongrass essential oil (EO) and citral to inhibit and kill MDR A. baumannii highlights its potential for use in the management of drug-resistant infections; however, in vitro cytotoxicity does suggest further tests are needed before in vivo or ex vivo human exposure.

Modelling of Cr and Ni ions release during orthodontic treatment: in vitro and in vivo methods

The kinetics of metal ions release from orthodontic appliances in in vitro, in in vivo on pigs, and in vivo trials on patients (where hair samples were taken) was discussed. We have evaluated (by means of ICP-OES and ISO 17025) and compared the mass of Cr and Ni ions released. Not all the metal ions released from the appliance were transferred to hair tissue. The transfer factor was expressed as coefficient ω and evaluated as: ωCr(patients) 33.0%, ωCr(pigs) 17.2%, ωNi(patients) 49.8%, ωNi(pigs) 0.553%. The kinetics was described by a power function. Coefficient ω was used to combine the models: the in vitro and in vivo on animals on the one hand and the in vitro and in vivo on human on the other, which enabled the extrapolation of in vitro and translation of the results into in vivo conditions. The dose of metal ions released during orthodontic treatment was estimated.

Measuring human skin buffering capacity: an in vitro model

BACKGROUND/PURPOSE

It has been thought that skin possesses buffering capacity. This study measured the skin buffering capacity against two model solutions of acid and base at three concentrations with an in vitro system.

METHODS

Ten microliters of model base (sodium hydroxide--NaOH) and acid (hydrochloric acid--HCl) solutions at concentrations of 0.025, 0.05, and 0.1 N was applied to human cadaver skin (3.18 microL/cm(2)) placed onto glass diffusion cells. Phosphate-buffered saline (PBS) was used as a standard buffer solution. Deionized water served as the negative control, whereas untreated skin served as the blank control. Skin pH was read and recorded immediately following dosing (0 time), and at 10 and 30 min of post-dosing. After the 30 min of dosing, each skin, except untreated skin (blank control), was then washed by applying 1 cm(3) of deionized water. The pH on each washed skin was measured immediately following washing, and the pH measurement was repeated at 10 and 30 min of post-washing. Six replicates were conducted.

RESULTS

The pH values sharply significantly increased (P<0.05) immediately following dosing with NaOH at all concentrations (the highest concentration, caused the highest pH), and then decreased closely to baselines within 30 min post-application but still remained at significantly (P<0.05) higher values when compared with the blank control (untreated skin). HCl (acid) significantly (P<0.05) decreased skin pH immediately following dosing with all concentrations (the highest concentration, caused the lowest pH) and then restored rapidly to baseline. There was no significant difference in post-washing procedures on the skins that were pre-treated with the acid (HCI) solutions. However, with all base solutions (NaOH) pre-treated skin, pH values were significantly higher (P<0.05) at all time points post-washing. Furthermore, both PBS and water controls significantly elevated (P<0.05) the pH values following washing.

CONCLUSION

Skin pH and its buffering capacity can be measured on human cadaver skin in vitro, which may partially replicate the response of in vivo skin. Dose-response was noted; i.e. the higher concentration caused larger changes in skin pH. In addition, the restoration of skin pH is relatively faster with acid when compared with base treatment. Clinical implications are offered.