A systematic review of natural products for skin applications: Targeting inflammation, wound healing, and photo-aging

BACKGROUND

Every day the skin is constantly exposed to several harmful factors that induce oxidative stress. When the cells are incapable to maintain the balance between antioxidant defenses and reactive oxygen species, the skin no longer can keep its integrity and homeostasis. Chronic inflammation, premature skin aging, tissue damage, and immunosuppression are possible consequences induced by sustained exposure to environmental and endogenous reactive oxygen species. Skin immune and non-immune cells together with the microbiome are essential to efficiently trigger skin immune responses to stress. For this reason, an ever-increasing demand for novel molecules capable of modulating immune functions in the skin has risen the level of their development, particularly in the field of natural product-derived molecules.

PURPOSE

In this review, we explore different classes of molecules that showed evidence in modulate skin immune responses, as well as their target receptors and signaling pathways. Moreover, we describe the role of polyphenols, polysaccharides, fatty acids, peptides, and probiotics as possible treatments for skin conditions, including wound healing, infection, inflammation, allergies, and premature skin aging.

METHODS

Literature was searched, analyzed, and collected using databases, including PubMed, Science Direct, and Google Scholar. The search terms used included "Skin", "wound healing", "natural products", "skin microbiome", "immunomodulation", "anti-inflammatory", "antioxidant", "infection", "UV radiation", "polyphenols", "polysaccharides", "fatty acids", "plant oils", "peptides", "antimicrobial peptides", "probiotics", "atopic dermatitis", "psoriasis", "auto-immunity", "dry skin", "aging", etc., and several combinations of these keywords.

RESULTS

Natural products offer different solutions as possible treatments for several skin conditions. Significant antioxidant and anti-inflammatory activities were reported, followed by the ability to modulate immune functions in the skin. Several membrane-bound immune receptors in the skin recognize diverse types of natural-derived molecules, promoting different immune responses that can improve skin conditions.

CONCLUSION

Despite the increasing progress in drug discovery, several limiting factors need future clarification. Understanding the safety, biological activities, and precise mechanisms of action is a priority as well as the characterization of the active compounds responsible for that. This review provides directions for future studies in the development of new molecules with important pharmaceutical and cosmeceutical value.

Potential of omega-3 and conjugated fatty acids to control microglia inflammatory imbalance elicited by obesogenic nutrients

High-fat diet-induced obesity detrimentally affects brain function by inducing chronic low-grade inflammation. This neuroinflammation is, at least in part, likely to be mediated by microglia, which are the main immune cell population in the brain. Microglia express a wide range of lipid-sensitive receptors and their activity can be modulated by fatty acids that cross the blood-brain barrier. Here, by combining live cell imaging and FRET technology we assessed how different fatty acids modulate microglia activity. We demonstrate that the combined action of fructose and palmitic acid induce Ikβα degradation and nuclear translocation of the p65 subunit nuclear factor kB (NF-κB) in HCM3 human microglia. Such obesogenic nutrients also lead to reactive oxygen species production and LynSrc activation (critical regulators of microglia inflammation). Importantly, short-time exposure to omega-3 (EPA and DHA), CLA and CLNA are sufficient to abolish NF-κB pathway activation, suggesting a potential neuroprotective role. Omega-3 and CLA also show an antioxidant potential by inhibiting reactive oxygen species production, and the activation of LynSrc in microglia. Furthermore, using chemical agonists (TUG-891) and antagonists (AH7614) of GPR120/FFA4, we demonstrated that omega-3, CLA and CLNA inhibition of the NF-κB pathway is mediated by this receptor, while omega-3 and CLA antioxidant potential occurs through different signaling mechanisms.

Unraveling the hepatoprotective effects of blueberries in a hypercaloric diet-induced rat model of prediabetes by metabolomic and transcriptomic approaches

Background

We previously described protective effects of blueberry juice (BJ) against hepatic steatosis evolution in a hypercaloric diet-induced rat model of prediabetes; however, the underlying mechanisms, are still scarcely explored. Herein, we aim to elucidate the molecular pathways underpinning BJ hepatoprotection on the dysmetabolism evolution in a rat model of prediabetes.

Methods

A rat model of evolutive prediabetes [Male Wistar rats, 8 weeks old] was developed by ingestion of a high-sucrose (HSu, 35%) diet for 9 weeks (W9), supplemented with a high-fat diet (HF, 60%) for further 14 weeks (HSuHF, W23), vs control with standard diet. Half of the animals (n = 10/group) daily received BJ (25g/Kg BW, orally) between W9 and W23. Along with metabolic characterization, BJ effects on serum and hepatic metabolic surrogates were elucidated using a 1H NMR based metabolomic approach. Moreover, the liver expression of genes (RT-PCR) involved in insulin signaling, lipid metabolism, inflammatory response and mitochondrial respiration was also explored. Values are means ± S.E.M (ANOVA followed by post-hoc tests).

Results

HSuHF+BJ rats restored hepatic levels of betaine and tend to recover the depletion of glutathione content found in HSuHF animals’ livers. Moreover, BJ positively affected the hepatic mRNA expression of key enzymes and mediators involved in fatty acid oxidation, insulin signalling, inflammatory response, as well as mitochondrial respiratory chain-related genes, which were all downregulated (P < 0.05) in HSuHF animals’ livers.

Conclusions

Altogether, these molecular findings contribute to explain the mechanisms by which BJ elicits protection against hepatic steatosis and mitochondrial dysfunction induced by hypercaloric diets in the frame of prediabetes evolution.

Increasing phenolic and aromatic compounds extraction and maximizing liking of lemon verbena (Aloysia triphylla) infusions through the optimization of steeping temperature and time

Herbal infusions are a new emerging trend among consumers, appearing in the market in many different forms. Due to intense competition, the commercial success of herbal infusions largely depends on flavour. The identification of the best combinations of steeping time and water temperature for the preparation of Aloysia triphylla infusions using a central composite design and response surface methodology was performed. The procedure aimed to maximize its antioxidant activity, phenolic and aromatic compounds, and consumers' liking of the infusions. The antioxidant activity and phenolic content were evaluated using the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid radical cation) method and the Folin-Ciocalteu procedure. The analysis of aromatic compounds was performed based on the method of terpenic compounds. Sensory evaluation encompassed overall liking using a 9-point hedonic scale. Antioxidant activity and extraction of most phenolic compounds was higher for longer steeping times and higher temperatures, with some presenting a contrasting effect due to degradation at higher temperatures for longer steeping times. Results for terpenic compounds showed similar contrasting patterns. Based on the quadratic response surface, it was possible to predict the maximum overall liking for lemon verbena infusions prepared by brewing for 6 min at 96 ℃. Under such conditions, extraction of bioactive compounds was kept at a high level, close to the maximum attainable, while reducing the extraction of bitter compounds. These results are considered of great importance for the development of premium infusions from organic lemon verbena leaves.

Insight into antibiotics removal: Exploring the photocatalytic performance of a Fe3O4/ZnO nanocomposite in a novel magnetic sequential batch reactor

The purpose of this research was the preparation and photocatalytic evaluation of a novel nanocomposite (NC) based on Fe₃O₄/ZnO, to eliminate four persistent antibiotics in surface waters: sulfamethoxazole, trimethoprim, erythromycin and roxithromycin. Prior to the operation of the photocatalytic reactor, the influence of pH (3-9), catalyst concentration (50-800 mg L^-1), oxidant dose (0-100 mg L^-1) and concentration of different targets (10-100 μg L^-1) on the catalytic efficiency was evaluated. The analysis of reaction kinetics showed that degradation processes of the four antibiotics followed a pseudo-first-order kinetic model. Antibiotics adsorption onto the nanocomposite surface depended on their electrostatic nature and played an important role when decreasing the initial concentration of antibiotics. In this context, kinetic rates were higher at lower initial levels of organic pollutants, which is a favourable effect from a practical application perspective. On the other hand, a synergistic effect of the available Fe in the nanocomposite was found, contributing to the oxidation of antibiotics by photo-Fenton as a secondary reaction. Then, a magnetic photocatalytic reactor was operated under optimal conditions. The enhanced photonic efficiency of Fe₃O₄/ZnO in the system, as well as the ease of the magnetic separation and catalyst reusability, indicate the viability of this reactor configuration.

A diversity profile from the staphylococcal community on atopic dermatitis skin: a molecular approach

AIMS

The aim of this study was to determine the biodiversity of the skin staphylococcal community from patients with atopic dermatitis (AD) and superantigen (SAg) detection from Staphylococcus aureus isolates.

METHODS AND RESULTS

In this study, we developed a novel multiplex PCR that allows the identification and discrimination of bacteria belonging to the Staphylococcus genus both Staph. aureus and coagulase-negative Staphylococcus - Staph. capitis, Staph. epidermidis, Staph. haemolyticus and Staph. hominis isolated from the skin of patients with AD. In addition, a multiplex PCR assay that allows the rapid screening of the 19 genes that encode staphylococcal enterotoxins (SEs), SE-like toxins and toxic shock syndrome toxin-1 was also performed and applied in Staph. aureus isolates. The microflora of the skin of patients with AD was dominated by Staph. aureus (69 isolates, 35·6%) followed by Staph. epidermidis (59 isolates, 30·4%) species. The SElM and SElN genes were the most frequently detected in our study (15 isolates, 71·4%), followed by SEG and SElO (14 isolates, 66·7%).

CONCLUSIONS

Our molecular-based approach successfully identified the staphylococcal microflora that was relatively specific to patients with AD. Considering skin colonization and expression of virulence factors, the Staph. aureus may play a relevant role in AD pathophysiology.

SIGNIFICANCE AND IMPACT OF THE STUDY

This ability to classify disease-related microbial species provides new insights into the relevance of those microbes in human disorders.

Antimicrobial activity of wild mushroom extracts against clinical isolates resistant to different antibiotics

AIMS

This work aimed to screen the antimicrobial activity of aqueous methanolic extracts of 13 mushroom species, collected in Bragança, against several clinical isolates obtained in Hospital Center of Trás-os-Montes and Alto Douro, Portugal.

METHODS AND RESULTS

Microdilution method was used to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). MIC results showed that Russula delica and Fistulina hepatica extracts inhibited the growth of gram-negative (Escherichia coli, Morganella morganni and Pasteurella multocida) and gram-positive (Staphylococcus aureus, MRSA, Enterococcus faecalis, Listeria monocytogenes, Streptococcus agalactiae and Streptococcus pyogenes) bacteria. A bactericide effect of both extracts was observed in Past. multocida, Strep. agalactiae and Strep. pyogenes with MBC of 20, 10 and 5 mg ml⁻¹, respectively. Lepista nuda extract exhibited a bactericide effect upon Past. multocida at 5 mg ml⁻¹ and inhibited Proteus mirabilis at 20 mg ml⁻¹. Ramaria botrytis extract showed activity against Enterococcus faecalis and L. monocytogenes, being bactericide for Past. multocida, Strep. agalactiae (MBCs 20 mg ml⁻¹) and Strep. pyogenes (MBC 10 mg ml⁻¹). Leucopaxillus giganteus extract inhibited the growth of E. coli and Pr. mirabilis, being bactericide for Past. multocida, Strep. pyogenes and Strep. agalactiae.

CONCLUSIONS

Fistulina hepatica, R. botrytis and R. delica are the most promising species as antimicrobial agents.

SIGNIFICANCE AND IMPACT OF THE STUDY

Mushroom extracts could be an alternative as antimicrobials against pathogenic micro-organisms resistant to conventional treatments.

Effect of stress on acid dissolution of enamel

OBJECTIVES

This study was designed to measure the dissolution of buccal enamel of extracted teeth exposed to acid with or without simultaneous cyclic occlusal loading.

METHODS

Twenty mandibular premolars were mounted in pairs in a servohydraulic testing machine, and immersed in 1% lactic acid (pH 4.5) or water. One tooth of each pair was subjected to cyclic loading (100 N at 2 Hz for 200,000 cycles), with the load applied at 45 degrees to the tooth axis on the buccal incline of the buccal cusp. The second tooth of each pair was immersed in acid but not subjected to load. Control teeth were immersed in water, with one tooth of each pair undergoing cyclic loading. Impressions of the teeth were taken before and after exposure to acid and occlusal loading, and a profiling system was used to measure the depth and volume loss of enamel on the buccal surface.

RESULTS

The depth of enamel dissolved ranged from approximately 50-200 microm. In certain locations teeth undergoing cyclic loading during acid exposure showed greater volumetric loss than teeth not subjected to load. Loaded teeth showed a complex pattern of enamel dissolution; volumetric loss in the cervical third was greater than in the middle third, and was much greater in the mesiobuccal segment (under tension) than in the distobuccal segment (under compression). Unloaded teeth showed greater volumetric loss in the cervical third than in the middle third, with a uniform pattern of enamel dissolution from mesiobuccal to distobuccal aspects.

SIGNIFICANCE

Enamel dissolution is increased significantly in sites subjected to cyclic tensile load.

Semiconservative and unscheduled DNA synthesis on mammalian cells and its modification by glyoxylic compounds

The interaction of glyoxal and four other glyoxylic compounds with semiconservative DNA synthesis and with unscheduled DNA synthesis induced by 25-G X-rays on TC-SV40 hamster cells has been studied. Both syntheses were evaluated by measuring the incorporation of [3H-methyl]-thymidine into the newly synthetized DNA. The unscheduled DNA synthesis amounts to 4% of semiconservative synthesis. The modification of both syntheses by the glyoxylic compounds was tested using the products at non-toxic concentrations for the cells. All the glyoxals inhibited semiconservative DNA synthesis and potentiated unscheduled DNA synthesis at rather similar levels. These effects have been compared with the radiosensitizing activity of these glyoxals in the same TC-SV40 cells and no relationship could be established.