Adaptation of acneic and non acneic strains of Cutibacterium acnes to sebum-like environment

The primary role of sebum in the pathophysiology of acne vulgaris and its therapeutic relevance in acne management

BACKGROUND

Sebum physiology and its contributions to acne vulgaris (AV) pathophysiology have been long debated. Within the pilosebaceous unit, androgens drive sebocyte production of sebum, comprising mono-, di-, and triglycerides (the latter converted to fatty acids); squalene; cholesterol; cholesterol esters; and wax esters. Upon release to the skin surface, human sebum has important roles in epidermal water retention, antimicrobial defenses, and innate immune responses.

AIMS

Alterations in sebum alone and with other pathogenic factors (inflammation, follicular hyperkeratinization, and Cutibacterium acnes [C. acnes] proliferation) contribute to AV pathophysiology. Androgen-driven sebum production, mandatory for AV development, propagates C. acnes proliferation and upregulates inflammatory and comedogenic cascades.

RESULTS

Some sebum lipids have comedogenic effects in isolation, and sebum content alterations (including elevations in specific fatty acids) contribute to AV pathogenesis. Regional differences in facial sebum production, coupled with patient characteristics (including sex and age), help exemplify this link between sebum alterations and AV lesion formation.

CONCLUSIONS

To date, only combined oral contraceptives and oral spironolactone (both limited to female patients), oral isotretinoin and topical clascoterone (cortexolone 17α-propionate) modulate sebum production in patients with AV. A better understanding of mechanisms underlying sebaceous gland changes driving AV development is needed to expand the AV treatment armamentarium.

In Vitro Biological Activities of Hesperidin-Related Compounds with Different Solubility

The biological activities of hesperidin-related compounds, such as hesperetin laurate (HTL), hesperetin (HT), hesperidin (HD), and hesperidin glucoside (HDG), were investigated in vitro. The compounds showed different hydrophobicities, and the octanol-water partition coefficient log P were 7.28 ± 0.06 for HTL, 2.59 ± 0.04 for HT, 2.13 ± 0.03 for HD, and -3.45 ± 0.06 for HDG, respectively. In the DPPH assay and β-carotene bleaching assay to determine antioxidant capacity, all compounds tested showed antioxidant activity in a concentration-dependent manner, although to varying degrees. HTL and HT showed similarly high activities compared to HD or HDG. HD and HDG did not show a significant difference despite the difference in solubility between the two. Cytotoxicity was high; in the order of hydrophobicity-HTL > HT > HD > HDL in keratinocyte HaCaT cells. All compounds tested showed reducing effects on cellular inflammatory mediators and cytokines induced by UV irradiation. However, HTL and HT effectively reduced nitric oxide (NO), tumor necrosis factor α (TNF-α), and interleukin-6 (IL-6) levels compared to HD and HDG. The inhibitory effects of hesperidin-related compounds on skin-resident microorganisms were evaluated by measuring minimum inhibitory concentration (MIC). HTL showed the highest inhibitory effects against Staphylococcus aureus, Cutibacterium acnes, Candida albicans, and Malassezia furfur, followed by HT, while HD and HDF showed little effect. In conclusion, the hydrophobicity of hesperidin-related compounds was estimated to be important for biological activity in vitro, as was the presence or absence of the sugar moiety.

Sebum Components Dampen the Efficacy of Skin Disinfectants against Cutibacterium acnes Biofilms

At Canadian Blood Services, despite the use of 2% chlorhexidine and 70% isopropyl alcohol (standard disinfectant, SD) prior to venipuncture, Cutibacterium acnes evades eradication and is a major contaminant of platelet concentrates (PCs). Since C. acnes forms bacterial aggregates known as biofilms in the sebaceous niches of the skin, this study aimed to assess whether sebum-like components impact disinfectant efficacy against C. acnes leading to its dominance as a PC contaminant. C. acnes mono-species and dual-species biofilms (C. acness and a transfusion-relevant Staphylococcus aureus isolate) were formed in the presence and absence of sebum-like components and exposed to SD, a hypochlorous acid-based disinfectant (Clinisept+, CP), or a combination of both disinfectants to assess disinfectant efficacy. Our data indicate that sebum-like components significantly reduce the disinfectant efficacy of all disinfectant strategies tested against C. acnes in both biofilm models. Furthermore, though none of the disinfectants led to bacterial eradication, the susceptibility of C. acnes to disinfectants was heightened in an isolate-dependent manner when grown in the presence of S. aureus. The reduction of skin disinfection efficacy in the presence of sebum may contribute to the overrepresentation of C. acnes as a PC contaminant and highlights the need for improved disinfection strategies.

Genome-scale metabolic modeling and in silico analysis of opportunistic skin pathogen Cutibacterium acnes

Cutibacterium acnes, one of the most abundant skin microbes found in the sebaceous gland, is known to contribute to the development of acne vulgaris when its strains become imbalanced. The current limitations of acne treatment using antibiotics have caused an urgent need to develop a systematic strategy for selectively targeting C. acnes, which can be achieved by characterizing their cellular behaviors under various skin environments. To this end, we developed a genome-scale metabolic model (GEM) of virulent C. acnes, iCA843, based on the genome information of a relevant strain from ribotype 5 to comprehensively understand the pathogenic traits of C. acnes in the skin environment. We validated the model qualitatively by demonstrating its accuracy prediction of propionate and acetate production patterns, which were consistent with experimental observations. Additionally, we identified unique biosynthetic pathways for short-chain fatty acids in C. acnes compared to other GEMs of acne-inducing skin pathogens. By conducting constraint-based flux analysis under endogenous carbon sources in human skin, we discovered that the Wood-Werkman cycle is highly activated under acnes-associated skin condition for the regeneration of NAD, resulting in enhanced propionate production. Finally, we proposed potential anti-C. acnes targets by using the model-guided systematic framework based on gene essentiality analysis and protein sequence similarity search with abundant skin microbiome taxa.

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.

Genomics of Invasive Cutibacterium acnes Isolates from Deep-Seated Infections

Cutibacterium acnes, formerly known as Propionibacterium acnes, is a commensal of the human pilosebaceous unit but also causes deep-seated infection, especially in the context of orthopedic and neurosurgical foreign materials. Interestingly, little is known about the role of specific pathogenicity factors for infection establishment. Here, 86 infection-associated and 103 commensalism-associated isolates of C. acnes were collected from three independent microbiology laboratories. We sequenced the whole genomes of the isolates for genotyping and a genome-wide association study (GWAS). We found that C. acnes subsp. acnes IA1 was the most significant phylotype among the infection isolates (48.3% of all infection isolates; odds ratio [OR] = 1.98 for infection). Among the commensal isolates, C. acnes subsp. acnes IB was the most significant phylotype (40.8% of all commensal isolates; OR = 0.5 for infection). Interestingly, C. acnes subsp. elongatum (III) was rare overall and did not occur at all in infection. The open reading frame-based GWAS (ORF-GWAS) did not show any loci with a strong signal for infection association (no P values of ≤0.05 after adjustment for multiple testing; no logarithmic OR [logOR] of ≥|2|). We concluded that all subspecies and phylotypes of C. acnes, possibly with the exception of C. acnes subsp. elongatum, are able to cause deep-seated infection given favorable conditions, most importantly related to inserted foreign material. Genetic content appears to have a small effect on the likelihood of infection establishment, and functional studies are needed to understand the individual factors contributing to deep-seated infections caused by C. acnes. IMPORTANCE Opportunistic infections emerging from human skin microbiota are of ever-increasing importance. Cutibacterium acnes, being abundant on the human skin, may cause deep-seated infections (e.g., device-associated infections). Differentiation between invasive (i.e., clinically significant) C. acnes isolates and sole contaminants is often difficult. Identification of genetic markers associated with invasiveness not only would strengthen our knowledge related to pathogenesis but also could open ways to selectively categorize invasive and contaminating isolates in the clinical microbiology lab. We show that in contrast to other opportunistic pathogens (e.g., Staphylococcus epidermidis), invasiveness is apparently a broadly distributed ability across almost all C. acnes subspecies and phylotypes. Thus, our work strongly supports an approach in which clinical significance is judged from clinical context rather than by detecting specific genetic traits.

Skin dysbiosis and Cutibacterium acnes biofilm in inflammatory acne lesions of adolescents

Acne vulgaris is a common inflammatory disorder affecting more than 80% of young adolescents. Cutibacterium acnes plays a role in the pathogenesis of acne lesions, although the mechanisms are poorly understood. The study aimed to explore the microbiome at different skin sites in adolescent acne and the role of biofilm production in promoting the growth and persistence of C. acnes isolates. Microbiota analysis showed a significantly lower alpha diversity in inflammatory lesions (LA) than in non-inflammatory (NI) lesions of acne patients and healthy subjects (HS). Differences at the species level were driven by the overabundance of C. acnes on LA than NI and HS. The phylotype IA1 was more represented in the skin of acne patients than in HS. Genes involved in lipids transport and metabolism, as well as potential virulence factors associated with host-tissue colonization, were detected in all IA1 strains independently from the site of isolation. Additionally, the IA1 isolates were more efficient in early adhesion and biomass production than other phylotypes showing a significant increase in antibiotic tolerance. Overall, our data indicate that the site-specific dysbiosis in LA and colonization by virulent and highly tolerant C. acnes phylotypes may contribute to acne development in a part of the population, despite the universal carriage of the microorganism. Moreover, new antimicrobial agents, specifically targeting biofilm-forming C. acnes, may represent potential treatments to modulate the skin microbiota in acne.

Proteomics as a tool to improve novel insights into skin diseases: what we know and where we should be going

Background

Biochemical processes involved in complex skin diseases (skin cancers, psoriasis, and wound) can be identified by combining proteomics analysis and bioinformatics tools, which gain a next-level insight into their pathogenesis, diagnosis, and therapeutic targets.

Methods

Articles were identified through a search of PubMed, Embase, and MEDLINE references dated to May 2022, to perform system data mining, and a search of the Web of Science (WoS) Core Collection was utilized to conduct a visual bibliometric analysis.

Results

An increased trend line revealed that the number of publications related to proteomics utilized in skin diseases has sharply increased recent years, reaching a peak in 2021. The hottest fields focused on are skin cancer (melanoma), inflammation skin disorder (psoriasis), and skin wounds. After deduplication and title, abstract, and full-text screening, a total of 486 of the 7,822 outcomes met the inclusion/exclusion criteria for detailed data mining in the field of skin disease tooling with proteomics, with regard to skin cancer. According to the data, cell death, metabolism, skeleton, immune, and inflammation enrichment pathways are likely the major part and hotspots of proteomic analysis found in skin diseases. Also, the focuses of proteomics in skin disease are from superficial presumption to depth mechanism exploration within more comprehensive validation, from basic study to a combination or guideline for clinical applications. Furthermore, we chose skin cancer as a typical example, compared with other skin disorders. In addition to finding key pathogenic proteins and differences between diseases, proteomic analysis is also used for therapeutic evaluation or can further obtain in-depth mechanisms in the field of skin diseases.

Conclusion

Proteomics has been regarded as an irreplaceable technology in the study of pathophysiological mechanism and/or therapeutic targets of skin diseases, which could provide candidate key proteins for the insight into the biological information after gene transcription. However, depth pathogenesis and potential clinical applications need further studies with stronger evidence within a wider range of skin diseases.

Acne, Microbiome, and Probiotics: The Gut–Skin Axis

The objective of this narrative review was to check the influence of the human microbiota in the pathogenesis of acne and how the treatment with probiotics as adjuvant or alternative therapy affects the evolution of acne vulgaris. Acne is a chronic inflammatory skin disease involving the pilosebaceous units. The pathogenesis of acne is complex and multifactorial involving genetic, metabolic, and hormonal factors in which both skin and gut microbiota are implicated. Numerous studies have shown the bidirectionality between the intestinal microbiota and skin homeostasis, a communication mainly established by modifying the immune system. Increased data on the mechanisms of action regarding the relevance of Cutibacterium acnes, as well as the importance of the gut–skin axis, are becoming known. Diverse and varied in vitro studies have shown the potential beneficial effects of probiotics in this context. Clinical trials with both topical and oral probiotics are scarce, although they have shown positive results, especially with oral probiotics through the modulation of the intestinal microbiota, generating an anti-inflammatory response and restoring intestinal integrity, or through metabolic pathways involving insulin-like growth factor I (IGF-1). Given the aggressiveness of some standard acne treatments, probiotics should continue to be investigated as an alternative or adjuvant therapy.

Cotton and Flax Textiles Leachables Impact Differently Cutaneous Staphylococcus aureus and Staphylococcus epidermidis Biofilm Formation and Cytotoxicity

Bacteria can bind on clothes, but the impacts of textiles leachables on cutaneous bacteria remain unknown. Here, we studied for the first time the effects of cotton and flax obtained through classical and soft ecological agriculture on the representatives S. aureus and S. epidermidis bacteria of the cutaneous microbiota. Crude flax showed an inhibitory potential on S. epidermidis bacterial lawns whereas cotton had no effect. Textile fiber leachables were produced in bacterial culture media, and these extracts were tested on S. aureus and S. epidermidis. Bacterial growth was not impacted, but investigation by the crystal violet technique and confocal microscopy showed that all extracts affected biofilm formation by the two staphylococci species. An influence of cotton and flax culture conditions was clearly observed. Flax extracts had strong inhibitory impacts and induced the formation of mushroom-like defense structures by S. aureus. Conversely, production of biosurfactant by bacteria and their surface properties were not modified. Resistance to antibiotics also remained unchanged. All textile extracts, and particularly soft organic flax, showed strong inhibitory effects on S. aureus and S. epidermidis cytotoxicity on HaCaT keratinocytes. Analysis of flax leachables showed the presence of benzyl alcohol that could partly explain the effects of flax extracts.

Microbiome and Probiotics in Acne Vulgaris—A Narrative Review

Acne vulgaris is a chronic disease characterised by the appearance of eruptions such as whiteheads, blackheads, pustules, papules, and cysts. Among factors that cause acne vulgaris are the abnormal keratinisation of the sebaceous canal, bacterial colonisation (Cutibacterium acnes), increased sebum production, genotypic factors, and hormonal disorders. Treatment is often long and tedious, and can lead to a reduction in quality of life and social isolation. The intestinal microbiota is greatly important in the formation of acne lesions. It is also responsible for the proper immunity of the organism. Acne is a disease that can be related to the condition of the digestive tract and its microbiome. Research shows that the use of probiotics may reduce skin eruptions. The probiotic supplementation and cosmetics markets are very dynamically developing. The use of internal supplementation and probiotic-containing cosmetics gives hope for the improvement of the skin condition of people with acne.

A Polylysine dendrigraft is able to differentially impact Cutibacterium acnes strains preventing acneic skin

With a view to reducing the impact of Cutibacterium acnes on acne vulgaris, it now appears interesting to modify the balance between acneic and non-acneic strains of C. acnes using moderate approach. In the present study, we identified that a G2 dendrigraft of lysine dendrimer (G2 dendrimer) was able to modify membrane fluidity and biofilm formation of a C. acnes acneic strain (RT5), whereas it appeared no or less active on a C. acnes non-acneic strain (RT6). Moreover, skin ex vivo data indicated that the G2 is able to decrease inflammation (IL1α and TLR2) and improve skin desquamation after of C. acnes acneic strains colonization. Then, in vivo data confirmed, after C. acnes quantification by metagenomic analysis, that the G2 cream after 28 days of treatment was able to increase the diversity of C. acnes strains versus placebo cream. Data showed also a modification of the balance expression between C. acnes phylotype IA1 and phylotype II abundances. Taken together, the results confirm the interest of using soft compounds in cosmetic product for modifying phylotype abundances as well as diversity of C. acnes strains could be a new strategy for prevent acne vulgaris outbreak.

Effects of Ulva sp. Extracts on the Growth, Biofilm Production, and Virulence of Skin Bacteria Microbiota: Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes Strains

Ulva sp. is known to be a source of bioactive compounds such as ulvans, but to date, their biological activity on skin commensal and/or opportunistic pathogen bacteria has not been reported. In this study, the effects of poly- and oligosaccharide fractions produced by enzyme-assisted extraction and depolymerization were investigated, for the first time in vitro, on cutaneous bacteria: Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes. At 1000 μg/mL, poly- and oligosaccharide fractions did not affect the growth of the bacteria regarding their generation time. Polysaccharide Ulva sp. fractions at 1000 μg/mL did not alter the bacterial biofilm formation, while oligosaccharide fractions modified S. epidermidis and C. acnes biofilm structures. None of the fractions at 1000 μg/mL significantly modified the cytotoxic potential of S. epidermidis and S. aureus towards keratinocytes. However, poly- and oligosaccharide fractions at 1000 μg/mL induced a decrease in the inflammatory potential of both acneic and non-acneic C. acnes strains on keratinocytes of up to 39.8%; the strongest and most significant effect occurred when the bacteria were grown in the presence of polysaccharide fractions. Our research shows that poly- and oligosaccharide Ulva sp. fractions present notable biological activities on cutaneous bacteria, especially towards C. acnes acneic and non-acneic strains, which supports their potential use for dermo-cosmetic applications.

Cutibacterium acnes as an Opportunistic Pathogen: An Update of Its Virulence-Associated Factors

Cutibacterium acnes is a member of the skin microbiota found predominantly in regions rich in sebaceous glands. It is involved in maintaining healthy skin and has long been considered a commensal bacterium. Its involvement in various infections has led to its emergence as an opportunist pathogen. Interactions between C. acnes and the human host, including the human skin microbiota, promote the selection of C. acnes strains capable of producing several virulence factors that increase inflammatory capability. This pathogenic property may be related to many infectious mechanisms, such as an ability to form biofilms and the expression of putative virulence factors capable of triggering host immune responses or enabling C. acnes to adapt to its environment. During the past decade, many studies have identified and characterized several putative virulence factors potentially involved in the pathogenicity of this bacterium. These virulence factors are involved in bacterial attachment to target cells, polysaccharide-based biofilm synthesis, molecular structures mediating inflammation, and the enzymatic degradation of host tissues. C. acnes, like other skin-associated bacteria, can colonize various ecological niches other than skin. It produces several proteins or glycoproteins that could be considered to be active virulence factors, enabling the bacterium to adapt to the lipophilic environment of the pilosebaceous unit of the skin, but also to the various organs it colonizes. In this review, we summarize current knowledge concerning characterized C. acnes virulence factors and their possible implication in the pathogenicity of C. acnes.

Development and characterization of a 3D in vitro model mimicking acneic skin

Acne is an inflammatory skin disease of the pilosebaceous unit, involving four essential factors: hyperseborrhoea combined to a modification of sebum composition, colonization by Cutibacterium (C.) acnes, hyperkeratinization and secreted inflammation. Understanding and mimicking compromised skin is essential to further develop appropriate therapeutic solutions. This study aimed to develop new in vitro 3D models mimicking acneic skin, by combining two main factors involved in the physiopathology, namely, altered sebum composition and C. acnes invasion. Normal human keratinocytes were first used to generate reconstructed human epidermis (RHE) that were then left untreated (control) or treated topically with a combination of both peroxidized squalene and C. acnes cultures. Once validated, this model considered relevant to mimic acneic skin, was further improved by using different phylotypes of C. acnes strains specifically isolated from healthy and acneic patients. While both phylotypes IB and II did not significantly alter RHE, C. acnes IA1 strains induce major acneic skin hallmarks such as hyperkeratinization, secreted inflammation and altered barrier function. Interestingly, these results are obtained independently of the origin of IA1 phylotypes (acneic vs. healthy patient), thus suggesting a role of the ecosystem in controlling C. acnes virulence in healthy skin. In conclusion, by combining two major factors involved in the physiopathology of acne, we (1) succeeded to design in vitro 3D models mimicking this skin disorder and (2) highlighted how C. acnes phylotypes can have an impact on epidermal physiology. These relevant models will be suitable for the substantiation of therapeutic molecules dedicated to acne treatment.

Antibiotic Resistance in Acne: Mechanisms, Complications and Management

Antibiotic resistance in acne was first observed in the 1970s, and since the 1980s has become a major concern in dermatologic daily practice. The mechanisms for this type of resistance include biofilm formation that promotes virulence and the transmission of resistant bacterial strains. Genetic mutations with modification of ribosomal RNA, alteration in efflux pumps, and enzymatic inactivation are able to create resistance to tetracyclines and macrolides. The state of art in acne treatment is no longer to use antimicrobials as monotherapy. There should be a time limit for its use plus the employment of non-antibiotic maintenance. Earlier initiation of oral isotretinoin therapy should be considered in patients with insufficient response to antimicrobials, severe acne, or a history of repeated antimicrobial use. A better understanding of acne pathogenesis, the subtypes of Propionibacterium (also known as Cutibacterium) acnes, homeostasis of the skin microbiota, and the mechanisms of antibiotic resistance would be useful in the selection of narrow-spectrum or species-specific antimicrobials, as well as the non-antimicrobial, anti-inflammatory treatment of acne. A number of novel treatments awaiting clinical proof may include the use of bacteriophages, natural or synthetic antimicrobial peptides, probiotics, and biofilm-targeting agents, as well as the reassessment of phototherapy.

Staphylococcus epidermidis and Cutibacterium acnes: Two Major Sentinels of Skin Microbiota and the Influence of Cosmetics

Dermatological and cosmetics fields have recently started to focus on the human skin microbiome and microbiota, since the skin microbiota is involved in the health and dysbiosis of the skin ecosystem. Amongst the skin microorganisms, Staphylococcus epidermidis and Cutibacterium acnes, both commensal bacteria, appear as skin microbiota sentinels. These sentinels have a key role in the skin ecosystem since they protect and prevent microbiota disequilibrium by fighting pathogens and participate in skin homeostasis through the production of beneficial bacterial metabolites. These bacteria adapt to changing skin microenvironments and can shift to being opportunistic pathogens, forming biofilms, and thus are involved in common skin dysbiosis, such as acne or atopic dermatitis. The current evaluation methods for cosmetic active ingredient development are discussed targeting these two sentinels with their assets and limits. After identification of these objectives, research of the active cosmetic ingredients and products that maintain and promote these commensal metabolisms, or reduce their pathogenic forms, are now the new challenges of the skincare industry in correlation with the constant development of adapted evaluation methods.

The Skin Microbiome: A New Actor in Inflammatory Acne

Our understanding of the role of Cutibacterium acnes in the pathophysiology of acne has recently undergone a paradigm shift: rather than C. acnes hyperproliferation, it is the loss of balance between the different C. acnes phylotypes, together with a dysbiosis of the skin microbiome, which results in acne development. The loss of diversity of C. acnes phylotypes acts as a trigger for innate immune system activation, leading to cutaneous inflammation. A predominance of C. acnes phylotype IA₁ has been observed, with a more virulent profile in acne than in normal skin. Other bacteria, mainly Staphylococcus epidermis, are also implicated in acne. S. epidermidis and C. acnes interact and are critical for the regulation of skin homeostasis. Recent studies also showed that the gut microbiome is involved in acne, through interactions with the skin microbiome. As commonly used topical and systemic antibiotics induce cutaneous dysbiosis, our new understanding of acne pathophysiology has prompted a change in direction for acne treatment. In the future, the development of individualized acne therapies will allow targeting of the pathogenic strains, leaving the commensal strains intact. Such alternative treatments, involving modifications of the microbiome, will form the next generation of ‘ecobiological’ anti-inflammatory treatments.

Lactobacillus paraplantarum THG-G10 as a potential anti-acne agent with anti-bacterial and anti-inflammatory activities

Cutibacterium acnes (formerly Propionibacterium acnes) is the main bacterium targeted for the prevention and medical treatment of acne vulgaris. Lactic acid bacteria (LAB) are a group of microorganisms classified by their ability to produce lactic acid through fermentation. Although the activities of LAB have been studied, their potential anti-acne effects are not well known. Here, Lactobacillus paraplantarum THG-G10, which has anti-bacterial activity against C. acnes, was isolated from traditional Kimchi in Republic of Korea. The anti-acne effects of dried cell-free supernatant of L. paraplantarum THG-G10 (DC-G10) were evaluated by determining its anti-microbial and anti-inflammatory activities. Anti-microbial activity was examined by a broth dilution assay: 25 mg/ml of DC-G10 inhibited the growth of C. acnes KCTC 5012 and KACC 1194; salicylic acid and benzoyl peroxide for acne treatment inhibited the growth of C. acnes KCTC 5012 and KACC 11946 at concentrations of 1.25 and 7.5 mg/ml, respectively; and tea tree oil inhibited the growth of C. acnes KCTC 5012 but not the growth of C. acnes KACC 11946 at 50 mg/ml. Anti-inflammatory activity was evaluated by a nitric oxide (NO) assay: only DC-G10 and ascorbic acid reduced LPS-induced NO production in RAW 264.7 cells in a dose-dependent manner. In addition, the toxicities of erythromycin, salicylic acid, benzoyl peroxide, tea tree oil, and DC-G10 were examined in HaCaT cells and normal human dermal fibroblasts (NHDFs). In these cells, the cytotoxic effects of DC-G10 were weaker than the effects of erythromycin, benzoyl peroxide, and ascorbic acid. Furthermore, scanning electron microscopy revealed that DC-G10 induces deleterious morphological changes in the bacterial cell membrane. These results demonstrate that DC-G10 may be an effective and safe treatment for acne vulgaris.

Acne and Stress: Impact of Catecholamines on Cutibacterium acnes

Cutibacterium acnes (former Propionibacterium acnes), is a bacterium characterized by high genomic variability, consisting of four subtypes and six major ribotypes. Skin is the largest neuroendocrine organ of the human body and many cutaneous hormones and neurohormones can modulate bacterial physiology. Here, we investigated the effect of catecholamines, i.e., epinephrine and norepinephrine, on two representative strains of C. acnes, of which the genome has been fully sequenced, identified as RT4 acneic and RT6 non-acneic strains. Epinephrine and norepinephrine (10^-6 M) had no impact on the growth of C. acnes but epinephrine increased RT4 and RT6 biofilm formation, as measured by crystal violet staining, whereas norepinephrine was only active on the RT4 strain. We obtained the same results by confocal microscopy with the RT4 strain, whereas there was no effect of either catecholamine on the RT6 strain. However, this strain was also sensitive to catecholamines, as shown by MATs tests, as epinephrine and norepinephrine affected its surface polarity. Flow cytometry studies revealed that epinephrine and norepinephrine are unable to induce major changes of bacterial surface properties and membrane integrity. Exposure of sebocytes to control or catecholamine-treated bacteria showed epinephrine and norepinephrine to have no effect on the cytotoxic or inflammatory potential of either C. acnes strains but to stimulate their effect on sebocyte lipid synthesis. Uriage thermal spring water was previously shown to inhibit biofilm production by C. acnes. We thus tested its effect after exposure of the bacteria to epinephrine and norepinephrine. The effect of the thermal water on the response of C. acnes to catecholamines depended on the surface on which the biofilm was grown. Finally, an in-silico study revealed the presence of a protein in the genome of C. acnes that shows homology with the catecholamine receptor of Escherichia coli and eukaryotes. This study suggests that C. acnes may play a role as a relay between stress mediators (catecholamines) and acne.

Adaptation of acneic and non acneic strains of Cutibacterium acnes to sebum-like environment

Cutibacterium acnes, former Proprionibacterium acnes, is a heterogeneous species including acneic bacteria such as the RT4 strain, and commensal bacteria such as the RT6 strain. These strains have been characterized by metagenomic analysis but their physiology was not investigated until now. Bacteria were grown in different media, brain heart infusion medium (BHI), reinforced clostridial medium (RCM), and in sebum like medium (SLM) specifically designed to reproduce the lipid rich environment of the sebaceous gland. Whereas the RT4 acneic strain showed maximal growth in SLM and lower growth in RCM and BHI, the RT6 non acneic strain was growing preferentially in RCM and marginally in SLM. These differences were correlated with the lipophilic surface of the RT4 strain and to the more polar surface of the RT6 strain. Both strains also showed marked differences in biofilm formation activity which was maximal for the RT4 strain in BHI and for the RT6 strain in SLM. However, cytotoxicity of both strains on HaCaT keratinocytes remained identical and limited. The RT4 acneic strain showed higher inflammatory potential than the RT6 non acneic strain, but the growth medium was without significant influence. Both bacteria were also capable to stimulate β‐defensine 2 secretion by keratinocytes but no influence of the bacterial growth conditions was observed. Comparative proteomics analysis was performed by nano LC‐MS/MS and revealed that whereas the RT4 strain only expressed triacylglycerol lipase, the principal C. acnes virulence factor, when it was grown in SLM, the RT6 strain expressed another virulence factor, the CAMP factor, exclusively when it was grown in BHI and RCM. This study demonstrates the key influence of growth conditions on virulence expression by C. acnesand suggest that acneic and non acneic strains are related to different environmental niches.