Immunomodulatory activity of Melaleuca alternifolia concentrate (MAC): Inhibition of LPS-induced NF-κB activation and cytokine production in myeloid cell lines

Tea Tree Oil: Properties and the Therapeutic Approach to Acne-A Review

Acne vulgaris is an inflammatory dermatological pathology that affects mostly young people. However, it can also appear in adulthood, mainly in women. It has a high psychosocial impact, not only at the time of active lesions but also due to the consequences of lesions such as scarring and hyperpigmentation. Several factors are involved in the physiopathology of acne and the constant search for active ingredients is a reality, namely phytotherapeutic ingredients. Tea tree oil is an essential oil extracted from Melaleuca alternifolia (Maiden & Betch) Cheel with known antibacterial, anti-inflammatory, and antioxidant properties, making it a candidate for the treatment of acne. This review aims to describe the various properties of tea tree oil that make it a possible ingredient to use in the treatment of acne and to present several human studies that have evaluated the efficacy and safety of using tea tree oil in the treatment of acne. It can be concluded that tea tree oil has good antibacterial, anti-inflammatory, and antioxidant properties that result in a decrease in the number of inflammatory lesions, mainly papules, and pustules. However, given the diversity of study designs, it is not possible to draw concrete conclusions on the efficacy and safety of this oil in the treatment of acne.

Intratumoral pro-oxidants promote cancer immunotherapy by recruiting and reprogramming neutrophils to eliminate tumors

Neutrophils have recently gained recognition for their potential in the fight against cancer. Neutrophil plasticity between the N1 anti-tumor and N2 pro-tumor subtypes is now apparent, as is the ability to polarize these individual subtypes by interventions such as intratumoral injection of various agents including bacterial products or pro-oxidants. Metabolic responses and the production of reactive oxygen species (ROS) such as hydrogen peroxide act as potent chemoattractants and activators of N1 neutrophils that facilitates their recruitment and ensuing activation of a toxic respiratory burst in tumors. Greater understanding of the precise mechanism of N1 neutrophil activation, recruitment and regulation is now needed to fully exploit their anti-tumor potential against cancers both locally and at distant sites. This systematic review critically analyzes these new developments in cancer immunotherapy.

Intracellular Replication Inhibitory Effects of Tea Tree Oil on Vesicular Stomatitis Virus and Anti-inflammatory Activities in Vero Cells

Viral disease management has been proven difficult, and there are no broadly licensed vaccines or therapeutics. Vesicular stomatitis virus (VSV) is an active pathogen of wild ungulates and livestock; its infection frequently caused irreversible vesicles on the tongue or other positions, leading to enormous economic loss. Tea tree oil (TTO) has been shown to be a popular remedy for many skin diseases owing to its antibacterial, antipruritic, and anti-inflammatory effects. However, the potential effect of TTO on VSV proliferation and the corresponding inflammatory response in cells remain unclear. In this study, methyl thiazolyl tetrazolium assay was used to evaluate the cell viability of TTO, and cytotoxic concentration 50 (CC50) was calculated. Then, fluorescence observation, reverse transcription-quantitative polymerase chain reaction, Western blot (WB), and flow cytometry (FCM) assay were used to evaluate the antiviral effect of TTO against VSV under three manners of pre-infection before medication, co-administration, pretreatment before infection at safe doses to Vero cells. Meanwhile, the mRNA expressions of interleukin 8, tumor necrosis factor α, and ISG56 in cells were also detected. The results showed that the maximum safe concentration of TTO to Vero cells was 0.063% and the CC50 is 0.32%. Most notably, TTO dose-dependently inhibited the VSV GFP fluorescence generation and restrained the replication of VSV in gene and protein levels regardless of the treatment modes. Based on the results of the FCM, effective concentration 50 of TTO against VSV is 0.019%. Similarly, the mRNA expression of the above cytokines induced by viral infection was also remarkably curbed. These findings suggest that TTO emerged blocking, prophylaxis, and treatment action against VSV replication and suppressed the related inflammation in Vero cells. This study provides a novel potential for TTO fighting against viral infection and anti-inflammatory activities in Vero cells.

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.

Therapeutic Potential of Melaleuca alternifolia Essential Oil in New Drug Delivery Systems

Medicinal plants produce secondary metabolites with special biological activities, which may be used as new therapeutic alternatives. For instance, tea tree essential oil (TTO) was shown to exert antimicrobial, antifungal, anthelmintic, antiviral, anti-tumor and anti-inflammatory activities. Due to their thermal instability, active principles can be easily degraded by physicochemical processes; therefore, they must be protected to increase their time of action and improve their controlled release. The aim of this review is to discuss formulations incorporating encapsulated TTO as the active ingredient. Micro and nanoencapsulated systems proved to be more thermostable than TTO and to exert better antimicrobial, antifungal, antiparasitic and larvicidal effects. Nanoencapsulation also reduced oil toxicity. Emulsified and hybrid systems developed by various methods showed improved repellent, antibacterial, antifungal and anti-inflammatory activities, thereby proving promising for the pharmaceutical industry. Liposomal formulations produced by hydration of lipid films exhibited constant rate of terpinen-4-ol release. In addition, their incorporation into biomaterials, such as sponges, nanofibers and films, showed great potential for treating infections. Mainly due to the advantages of their incorporation into new drug delivery systems over conventional formulations, there is an interest in the development of systems containing TTO as a pharmaceutical ingredient of plant origin.

Immunomodulatory Activities of Selected Essential Oils

Recently, the application of herbal medicine for the prevention and treatment of diseases has gained increasing attention. Essential oils (EOs) are generally known to exert various pharmacological effects, such as antiallergic, anticancer, anti-inflammatory, and immunomodulatory effects. Current literature involving in vitro and in vivo studies indicates the potential of various herbal essential oils as suitable immunomodulators for the alternative treatment of infectious or immune diseases. This review highlights the cellular effects induced by EOs, as well as the molecular impacts of EOs on cytokines, immunoglobulins, or regulatory pathways. The results reviewed in this article revealed a significant reduction in relevant proinflammatory cytokines, as well as induction of anti-inflammatory markers. Remarkably, very little clinical study data involving the immunomodulatory effects of EOs are available. Furthermore, several studies led to contradictory results, emphasizing the need for a multiapproach system to better characterize EOs. While immunomodulatory effects were reported, the toxic potential of EOs must be clearly considered in order to secure future applications.

S100A8 facilitates cholangiocarcinoma metastasis via upregulation of VEGF through TLR4/NF‑κB pathway activation

A growing body of evidence indicates that S100 calcium-binding protein A8 (S100A8) is frequently overexpressed in malignant tumor tissues and regulates tumor progression; however, the role of S100A8 in cholangiocarcinoma (CCA) remains unclear. The present study demonstrated that the protein expression of S100A8 was significantly higher in pathological tissues compared with adjacent normal tissues from patients with CCA. In addition, S100A8 expression was significantly associated with differentiation, lymph node metastasis and poor prognosis in patients following surgical resection of CCA. Furthermore, both in vitro and in vivo experiments revealed that overexpression of S100A6 promoted, while S100A8 knockdown attenuated, the migration and metastasis of CCA cells. Of note, the present results indicated that S100A8 promoted the CCA tumor cell-induced migration of vascular endothelial cells. Finally, S100A8 was demonstrated to positively regulate the expression of vascular endothelial growth factor (VEGF) in CCA cells, which was mediated by activation of the Toll-like receptor 4 (TLR4)/NF-κB pathway. In conclusion, the present study demonstrated that S100A8 had an important role in facilitating CCA cell migration and metastasis via upregulation of VEGF expression by activating the TLR4/NF-κB pathway. These findings may provide a novel target for CCA treatment.

Antrolone, a Novel Benzoid Derived from Antrodia cinnamomea, Inhibits the LPS-Induced Inflammatory Response in RAW264.7 Macrophage Cells by Balancing the NF-κB and Nrf2 Pathways

Antrodia cinnamomea, a medicinal mushroom, has previously demonstrated anti-inflammatory activity, although the specific compound responsible for the effect remains unclear. The present study was designed to investigate the anti-inflammatory property of antrolone, a novel benzoid derived from A. cinnamomea mycelium, and to clarify the underlying mechanisms of action. To this end, murine macrophage RAW264.7 cells were treated with antrolone (0.1–30[Formula: see text][Formula: see text]M) 30[Formula: see text]min prior to stimulation with lipopolysaccharides (LPS, 0.1[Formula: see text][Formula: see text]g/ml) for 24[Formula: see text]h. Cell viability, nitric oxide (NO) and prostaglandin E2 (PGE2) production, levels of pro-inflammatory cytokines and chemokines, and the signaling pathways involved in the inflammatory cascades were then investigated. Our results show that antrolone significantly decreased LPS-induced NO, PGE2, pro-inflammatory cytokine, and keratinocyte chemoattractant CXCL1 (KC) production and reduced levels of the proteins inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2). These effects were independent of the effect of antrolone on macrophage cytotoxicity. Moreover, antrolone significantly inhibited the activation of the NF[Formula: see text]B, MAPK, and AKT pathways, while it increased nuclear factor erythroid-2-related factor (Nrf2) and heme oxygenase-1 (HO-1) levels. Our findings suggest that antrolone exhibits potent anti-inflammatory activity and may, therefore, be a lead compound for the development of an anti-inflammatory drug.

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).

Can the tea tree oil (Australian native plant: Melaleuca alternifolia Cheel) be an alternative treatment for human demodicosis on skin?

Australian tea tree oil (TTO) and its extract terpinen-4-ol (T4O) are found to be effective in moderating demodex-related diseases. Their possible effects are lowering the mite counts, relieving the demodex-related symptoms and modulating the immune system especially the inflammatory response. This review summarizes the topical treatments of TTO and T4O in human demodicosis, their possible mechanism of actions, side-effects and potential resistance in treating this condition. Although current treatments other than TTO and T4O are relatively effective in controlling the demodex mite population and the related symptoms, more research on the efficacy and drug delivery technology is needed in order to assess its potential as an alternative treatment with minimal side-effect profile, low toxicity and low risk of demodex resistance.

Melaleuca alternifolia Induces Heme Oxygenase-1 Expression in Murine RAW264.7 Cells through Activation of the Nrf2-ARE Pathway

Melaleuca alternifolia concentrate (MAC) is the refined essential oil of the Australian native plant Melaleuca alternifolia. MAC has been reported to suppress the production of pro-inflammatory cytokines in both murine RAW264.7 macrophages and human monocytes stimulated with lipopolysaccharide (LPS). However, the mechanisms involved in this effect remain unclear. This study aims to delineate the molecular mechanisms that drive the anti-inflammatory activity of MAC and its active component, terpinen-4-ol, in macrophages. The effects of MAC on RAW264.7 cells were studied using western blotting, real-time PCR, an electrophoretic mobility shift assay (EMSA), and NF-[Formula: see text]B luciferase reporter assays. Our results showed that MAC significantly increased both the mRNA and protein levels of heme oxygenase-1 (HO-1) via p38 and JNK MAPK activation. In addition, we showed that MAC significantly increased the activation and nuclear translocation of NF-E2-related factor 2 (Nrf2), a key transcription factor regulating HO-1 induction. MAC was also associated with significant inhibition of iNOS expression, NO production, and NF-[Formula: see text]B activation. HO-1 was required for these anti-inflammatory effects as tin protoporphyrin IX (SnPPIX), an HO-1 inhibitor, abolished the effects of MAC on LPS-induced iNOS, NO, and NF-[Formula: see text]B activation. Our results indicate that MAC induces HO-1 expression in murine macrophages via the p38 MAPK and JNK pathways and that this induction is required for its anti-inflammatory activity.

Melaleuca alternifolia and its application against dental plaque and periodontal diseases: A systematic review

This is a systematic review of clinical and laboratory studies evaluating the effect of Melaleuca alternifolia on periodontopathogens, dental plaque, gingivitis, periodontitis, and inflammatory responses. The PubMed, Cochrane, Web of science, Bireme, Lilacs, Prospero, Open Grey, and Clinical Trials databases were searched to identify potentially eligible studies through October 2016. Of 1,654 potentially eligible studies, 25 were included in the systematic review. Their methodology was evaluated through the Cochrane Handbook for clinical studies and the GRADE system for in vivo/in vitro studies. Although clinical studies must be interpreted with caution due to methodological limitations, laboratory studies have found promising results. In vitro evidences showed that M. alternifolia has bactericidal and bacteriostatic effects against the most prevalent periodontopathogens. Clinical studies found comparable effects to chlorhexidine 0.12% in reducing gingival inflammation, although the antiplaque effect was lower. M. alternifolia also showed antioxidant properties, which are beneficial to the host, allied to the reduction on immune-inflammatory responses to pathogens. This systematic review suggests that the M. alternifolia has potential anti-inflammatory and antimicrobial properties, which can be easily applied to the periodontal tissues. However, further clinical trials are needed to elucidate the clinical relevance of its application.

The in vitro and in vivo antiviral properties of combined monoterpene alcohols against West Nile virus infection

West Nile Virus (WNV) is a mosquito-borne flavivirus that can cause neuroinvasive disease in humans and animals for which no therapies are currently available. We studied an established combination of monoterpene alcohols (CMA) derived from Melaleuca alternifolia, against WNV infection. The in vitro results show that CMA exhibits virucidal activity, as well as reduces the viral titres and percentage of infected cells. The antiviral mechanism of action of CMA was studied. We found that CMA did not alter the intracellular pH, neither induced apoptosis, but did induce cell cycle arrest in the G0/G1-phase although that was not the antiviral mechanism. Furthermore, we tested CMA in vivo using IRF 3(-)(/)(-)/7(-/-)mice and it was found that CMA treatment significantly delayed morbidity due to WNV infection, reduced the loss of body weight and reduced the viral titres in brain. These findings suggest that CMA could be a therapeutic agent against WNV infection.

In vitro effects of plant essential oils on non-specific immune parameters of red drum, Sciaenops ocellatus L

Phytochemicals such as plant essential oils (EOs) have been reported to favour various activities in the innate immune system of fish. Thus, the aim of this study was to verify the in vitro effect of three different plant EOs (Ocimum americanum, Cymbopogon flexuosus and Melaleuca alternifolia) on non-specific immune parameters and erythrocyte osmotic fragility of red drum, Sciaenops ocellatus. Concentrations of each plant EO evaluated in preparations of head-kidney macrophages, blood leucocytes and blood plasma were as follows: 0.0 (control), 1.0, 2.0, 4.0, 8.0, and 16.0 μg/ml. Red drum head-kidney macrophages significantly increased extracellular superoxide anion production when exposed (20 h) to O. americanum EO (1.0-8.0 μg/ml) and C. flexuosus EO (2.0 and 4.0 μg/ml). The respiratory burst of blood leucocytes (NBT test) significantly increased in all concentrations when compared to the respective control group, for all EOs. At the highest concentration (16.0 μg/ml), C. flexuosus EO significantly inhibited the haemolytic activity of complement system in red drum blood after 1 h exposure. None of the tested concentrations significantly altered plasma lysozyme activity or erythrocyte osmotic fragility after exposing (1 h) red drum whole blood to each EO. This study demonstrated that these plant EOs are capable of triggering superoxide anion production in red drum leucocytes (head-kidney macrophages and/or blood leucocytes). In vivo studies are warranted to address their potential as immunostimulants in the diet of red drum and other aquacultured species.