Azelaic acid: its uptake and mode of action in Staphylococcus epidermidis NCTC 11047

Molecular mechanisms of microbiome modulation by the eukaryotic secondary metabolite azelaic acid

Photosynthetic eukaryotes, such as microalgae and plants, foster fundamentally important relationships with their microbiome based on the reciprocal exchange of chemical currencies. Among these, the dicarboxylate metabolite azelaic acid (Aze) appears to play an important, but heterogeneous, role in modulating these microbiomes, as it is used as a carbon source for some heterotrophs but is toxic to others. However, the ability of Aze to promote or inhibit growth, as well as its uptake and assimilation mechanisms into bacterial cells are mostly unknown. Here, we use transcriptomics, transcriptional factor coexpression networks, uptake experiments, and metabolomics to unravel the uptake, catabolism, and toxicity of Aze on two microalgal-associated bacteria, Phycobacter and Alteromonas, whose growth is promoted or inhibited by Aze, respectively. We identify the first putative Aze transporter in bacteria, a 'C4-TRAP transporter', and show that Aze is assimilated through fatty acid degradation, with further catabolism occurring through the glyoxylate and butanoate metabolism pathways when used as a carbon source. Phycobacter took up Aze at an initial uptake rate of 3.8×10-9 nmol/cell/hr and utilized it as a carbon source in concentrations ranging from 10 μM to 1 mM, suggesting a broad range of acclimation to Aze availability. For growth-impeded bacteria, we infer that Aze inhibits the ribosome and/or protein synthesis and that a suite of efflux pumps is utilized to shuttle Aze outside the cytoplasm. We demonstrate that seawater amended with Aze becomes enriched in bacterial families that can catabolize Aze, which appears to be a different mechanism from that in soil, where modulation by the host plant is required. This study enhances our understanding of carbon cycling in the oceans and how microscale chemical interactions can structure marine microbial populations. In addition, our findings unravel the role of a key chemical currency in the modulation of eukaryote-microbiome interactions across diverse ecosystems.

Cosmeceutical Aptitudes of Azelaic Acid

BACKGROUND

Azelaic acid (AZA) is a white crystalline dicarboxylic acid naturally found in grains, rye and barley. AZA has substantial biological and therapeutic abilities (viz a viz) its anti-inflammatory, anti-oxidant, anti-keratinizing, anti-microbial properties, etc. which contribute to its applicability in the management of mild to harsh dermatological complications (acne, rosacea, dermatitis, hyper-pigmentation, carcinomas, etc.). AZA has shown its effectiveness against varied non-inflammatory and inflammatory lesions by normalizing the hyper-keratinization statie and attenuating the increased levels of microbial content. Topically AZA, either alone or in conjunction with other active moieties, has proved to be effective in preventing acne and several other hyper-pigmentary conditions.

OBJECTIVES

Chronic applicability of AZA has been evidenced with the effects like itching, burning, stinging, redness, etc. To deal with the former issues, research is being conducted to substitute the conventional formulations with novel preparations (liposome's, niosomes, micro sponges, lipid nanocarriers, etc.), which could enhance the overall pharmaceutical and pharmacological profile of the drug.

CONCLUSION

This article is an attempt to highlight the basic physiochemical properties of AZA, its physiological role (especially in dermatology), various commercial preparations and recent novel approaches that are in research with an aim to augment the therapeutic and safety profile of AZA.

Azelaic acid: Properties and mode of action

Acne is a common skin disorder that can be problematic for adults as well as for adolescents. It has several key pathophysiological features such as follicular hyperkeratosis, elevated Propionibacterium acnes proliferation, and reactive inflammation, all of which should be targeted for an optimal outcome. Azelaic acid (AzA) has profound anti-inflammatory, antioxidative effects, and is bactericidal against a range of Gram-negative and Gram-positive microorganisms as well, including antibiotic-resistant bacterial strains. In addition, AzA's antikeratinizing effects are inhibitory toward comedones. AzA is effective overall in targeting multiple causes of acne and has been proven to be well tolerated in numerous clinical trials.

Azelaic acid (15% gel) in the treatment of acne rosacea

In December of 2002, the FDA approved azelaic acid 15% gel for the topical treatment of inflammatory papules and pustules of mild to moderate rosacea. Azelaic acid is a saturated dicarboxylic acid, which is naturally occurring and has been used in the treatment of rosacea, acne, and melasma. The 15% gel has a high efficacy and is generally well tolerated, with the local irritation (burning, stinging, itching, and scaling) being typically mild and transient. Azelaic acid 15% gel is considered effective and safe as a therapy for inflammatory papulo-pustular rosacea and is suitable for use on all skin types.

Evaluation of the antibacterial efficacy of diesters of azelaic acid

A number of diesters of the topical dermatosis treatment azelaic (nonanedioic) acid were prepared and tested for antibacterial effect. Two esters, bis-[(hexanoyloxy)methyl] nonanedioate and especially bis-[(butanoyloxy)methyl] nonanedioate showed promising activity against acne related bacteria in vitro. No activity of azelaic acid was detected in Mueller Hinton II agar at pH 7.3 when using the agar diffusion method, whereas both esters gave zones of growth inhibition. At pH 5.6, activity of azelaic acid was detected. At this pH, the zones of inhibition and MIC values obtained with azelaic acid were smaller than those of bis-[(butanoyloxy)methyl] nonanedioate for all test organisms. A preparation for topical use containing 20% (w/w) bis-[(butanoyloxy)methyl] nonanedioate, and the commercially available Skinoren (20% (w/w) azelaic acid), were compared for antibacterial effect against cutaneous bacteria using contact plate analyses of the skin. Though Skinoren was usually most effective, the differences were not statistically significant. Furthermore, bacteria surviving contact with the topical preparations were invariably more sensitive to the ester than to azelaic acid upon subculturing onto agar (pH 5.6) containing either preparation at 0.2-0.7 mg/ml. This might indicate that other factors, such as the composition of the cream base, mitigate the antibacterial activity of the ester. It is proposed that the pharmacological and microbiological properties of bis-[(butanoyloxy)methyl] nonanedioate are worthy of further study based on an extended screening of acne sufferers.

Mechanisms for the transport of alpha,omega-dicarboxylates through the mitochondrial inner membrane

alpha,omega-Dicarboxylates have antibacterial properties, have been used in the treatment of hyperpigmentary disorders, are active against various melanoma cell lines, and can also undergo beta-oxidation. Little, however, is known about their transport. In this paper, we examine the mitochondrial transport of alpha, omega-dicarboxylates ranging from oxalate (DC2) to sebacate (DC10). DC2-DC10 are transported by the inner membrane anion channel (IMAC). DC6-DC10 are also transported by an electroneutral mechanism that appears to reflect transport of the acid through the lipid bilayer. At 37 degrees C and pH 7.0, DC10 is transported very rapidly at 3 micromol/min.mg, and respiring mitochondria swell in the K+ salts of these acids. This transport mechanism is probably the major pathway by which the longer dicarboxylates enter cells, bacteria, and mitochondria. We also demonstrate that DC5-DC10 can also be transported by an electroneutral mechanism mediated by tributyltin, a potent inhibitor of IMAC. The mechanism appears to involve electroneutral exchange of a TBT-dicarboxylate-H complex for TBT-OH. Finally, we present evidence that of all the dicarboxylates tested only DC2-DC4 can be transported by the classical dicarboxylate carrier.

Follicular concentrations of azelaic acid after a single topical application

Follicular concentrations of azelaic acid (AzA) were determined in vivo using a rapid, non-invasive method, after a single topical application of 20% (w/w) AzA cream, in order to establish whether the in vitro antimicrobial effects observed in previous studies are relevant in vivo. Preweighed amounts of 20% (w/w) AzA cream were applied over demarcated areas on the forehead and back of nine young adults, and samples were taken over a period of 5 h. AzA was removed from the skin surface by washing with acetone, and follicular casts were collected using cyanacrylate gel. The samples were centrifuged to remove particulate matter, and the supernatants derivatized for analysis by HPLC. Although the results showed wide-ranging variability, the follicular concentration increased as the amount present on the surface declined. The maximum follicular concentrations of AzA attained ranged from 7.5 to 52.5 ng (micrograms of follicular casts)-1 and 0.5 to 23.4 ng (micrograms of follicular casts)-1 in samples taken from the back and forehead, respectively. Assuming an average density of follicular material of 0.9 g ml-1, the mean maximum follicular concentration attained on the back was between 36 and 251 mmol/l, and on the forehead was between 2 and 112 mmol/l, and indicates that the concentration of AzA attained in follicular casts after a single topical application is comparable with the concentration required to inhibit the growth of Propionibacterium acnes and Staphylococcus epidermidis, in vitro.

Azelaic acid. A review of its pharmacological properties and therapeutic efficacy in acne and hyperpigmentary skin disorders

Azelaic acid is a naturally occurring saturated dicarboxylic acid which, on topical application (usually as a 20% cream), has been shown to be effective in the treatment of comedonal acne and inflammatory (papulopustular, nodular and nodulocystic) acne, as well as various cutaneous hyperpigmentary disorders characterised by hyperactive/abnormal melanocyte function, including melasma and, possibly, lentigo maligna. In addition, azelaic acid has an antiproliferative and cytotoxic effect on the human malignant melanocyte, and preliminary findings indicate that it may arrest the progression of cutaneous malignant melanoma. The mechanism of this selective cytotoxic action of azelaic acid is unclear, but may possibly be related to its inhibition of mitochondrial oxidoreductase activity and DNA synthesis. In controlled studies, topical azelaic acid demonstrated comparable anti-acne efficacy to topical tretinoin, benzoyl peroxide, erythromycin and oral tetracycline, while in patients with melasma azelaic acid proved at least as effective as topical hydroquinone. On topical application azelaic acid is well tolerated, with adverse effects apparently limited to a generally mild and transient local cutaneous irritation. Thus, topical azelaic acid, employed either as monotherapy or in combination with other treatments, is likely to prove of value in the management of acne and several hyperpigmentary disorders, most notably melasma.