Influence of Pityrosporum species in the generation of free fatty acids in human surface lipids

Stratum corneum dysfunction in dandruff

Synopsis

Dandruff is characterized by a flaky, pruritic scalp and affects up to half the world’s population post-puberty. The aetiology of dandruff is multifactorial, influenced by Malassezia, sebum production and individual susceptibility. The commensal yeast Malassezia is a strong contributory factor to dandruff formation, but the presence of Malassezia on healthy scalps indicates that Malassezia alone is not a sufficient cause. A healthy stratum corneum (SC) forms a protective barrier to prevent water loss and maintain hydration of the scalp. It also protects against external insults such as microorganisms, including Malassezia, and toxic materials. Severe or chronic barrier damage can impair proper hydration, leading to atypical epidermal proliferation, keratinocyte differentiation and SC maturation, which may underlie some dandruff symptoms. The depleted and disorganized structural lipids of the dandruff SC are consistent with the weakened barrier indicated by elevated transepidermal water loss. Further evidence of a weakened barrier in dandruff includes subclinical inflammation and higher susceptibility to topical irritants. We are proposing that disruption of the SC of the scalp may facilitate dandruff generation, in part by affecting susceptibility to metabolites from Malassezia. Treatment of dandruff with cosmetic products to directly improve SC integrity while providing effective antifungal activity may thus be beneficial.

Résumé

Les pellicules se caractérisent par un cuir chevelu prurigineux, squameux, et affectent jusqu’à la moitié de la population post-pubertaire du monde. L’étiologie des pellicules est multifactorielle, influencée par Malassezia, par la production de sébum, et par la susceptibilité individuelle. La levure commensale Malassezia est un facteur fortement contributif à la formation de pellicules, mais la présence de Malassezia aussi sur les cuirs chevelus sains indique que Malassezia seule n’est pas une cause suffisante. Un stratum corneum (SC) sain forme une barrière protectrice pour empêcher la perte d’eau et maintenir l’hydratation du cuir chevelu. Il protège également contre les agressions externes tels les micro-organismes, y compris Malassezia, ou des substances toxiques. Des dommages aigus ou chroniques au niveau de la barrière peuvent nuire à une bonne hydratation, conduisant à des effets atypiques de la prolifération épidermique, de la différenciation des kératinocytes, et de la maturation du SC, ce qui peut expliquer une partie des symptômes des pellicules. L’appauvrissement et la désorganisation des lipides structurels d’un stratum corneum sujet aux pellicules sont compatibles avec la notion d’une barrière affaiblie telle qu’indiquée par une perte d’eau transépidermique élevée. Une preuve supplémentaire d’une barrière affaiblie dans les cas des pellicules est fournie par un niveau d’inflammation infraclinique et une plus grande susceptibilité aux irritants topiques. Nous proposons que la perturbation du SC du cuir chevelu facilite la production de pellicules, en partie en augmentant la sensibilité aux métabolites de Malassezia. Le traitement des pellicules avec des produits cosmétiques pour améliorer directement l’intégrité du SC, tout en offrant une activité antifongique efficace peut donc être bénéfique.

Seborrheic dermatitis

Seborrheic dermatitis is present in 1% to 3% of immunocompetent adults, and is more prevalent in men than in women. Seborrheic dermatitis may be seen in conjunction with other skin diseases, such as rosacea, blepharitis or ocular rosacea, and acne vulgaris. Malassezia yeasts have been associated with seborrheic dermatitis. Abnormal or inflammatory immune system reactions to these yeasts may be related to development of seborrheic dermatitis. Treatment modalities for seborrheic dermatitis include keratolytic agents, corticosteroids, and more recently, antifungal agents. Antifungal agents do not carry a risk of skin atrophy or telangiectasia with prolonged use, and it is more prudent to consider antifungals than corticosteroid preparations. The wide range of antifungal formulations available (creams, shampoos, or oral) provides safe, effective, and flexible treatment options for seborrheic dermatitis.

Immunology of diseases associated with Malassezia species

Malassezia species are members of the human cutaneous commensal flora, in addition to causing a wide range of cutaneous and systemic diseases in suitably predisposed individuals. Studies examining cellular and humoral immune responses specific to Malassezia species in patients with Malassezia-associated diseases and healthy controls have generally been unable to define significant differences in their immune response. The use of varied antigenic preparations and strains from different Malassezia classifications may partly be responsible for this, although these problems can now be overcome by using techniques based on recent work defining some important antigens and also a new taxonomy for the genus. The finding that the genus Malassezia is immunomodulatory is important in understanding its ability to cause disease. Stimulation of the reticuloendothelial system and activation of the complement cascade contrasts with its ability to suppress cytokine release and downregulate phagocytic uptake and killing. The lipid-rich layer around the yeast appears to be pivotal in this alteration of phenotype. Defining the nonspecific immune response to Malassezia species and the way in which the organisms modulate it may well be the key to understanding how Malassezia species can exist as both commensals and pathogens.

Synthesis and antibacterial evaluation of novel water-soluble organic peroxides

A set of new water-soluble organic peroxides has been synthesized and evaluated for in vitro antibacterial activity as part of an effort to develop new antibacterial agents for the treatment of acne vulgaris. The water solubility of these new dialkyl peroxides and peroxyesters was achieved by incorporating either a quaternary ammonium group or a polyethylene glycol moiety. These peroxides are effective against both gram-positive and gram-negative bacteria and have a prolonged activity compared to that of benzoyl peroxide and other peroxide-type antiseptic agents. Among them 4-[[(tert-butylperoxy)carbonyl]benzyl]triethylammonium chloride and [10-(tert-butylperoxy)decyl]trimethylammonium bromide have the broadest antimicrobial spectrums. We have shown that the oxidizing properties of the dioxy group of these compounds are responsible for their antibacterial activities.

Phospholipase activity in Malassezia furfur pathogenic strains

The lipophilic dimorphic yeast Malassezia furfur is a common skin commensal and the aetiological agent of pityriasis versicolor. A source of lipids is essential for its growth, and there are already demonstrations of in vitro lipase and lipoxygenase production. In eight wild strains, isolated from patients with pityriasis versicolor, we showed a phospholipase activity using a medium containing egg yolk emulsion as the only source of lipids; in this medium M. furfur grows and produces a phospholipase zone. Adding manganese sulphate, an unspecific inhibitor of phospholipase activity, M. furfur does not grow, because the lipophilic fungus cannot utilize the egg yolk as a source of fatty acids. Adding Tween 60 to the same medium, M. furfur also grows in presence of manganese sulphate.

Skin surface lipids in HIV-positive patients with and without seborrheic dermatitis

BACKGROUND

Seborrheic dermatitis (SD) is a frequent complication of infection with the human immunodeficiency virus (HIV). Most studies examining the cause of SD have concentrated on the roles of Pityrosporum ovale and sebaceous lipids. Previous studies of skin surface lipid from patients with SD have produced conflicting results, with some authors reporting an abnormal lipid composition and others finding little or no abnormality.

METHODS

The composition of skin surface lipid was studied in 15 HIV-positive and 10 HIV-negative men with SD, in 14 HIV-positive men without SD, and in 16 unaffected controls. Total lipids were extracted from unaffected forehead skin into petroleum ether and separated into lipid classes by thin layer chromatography. The lipid classes were quantitated by densitometry after charring with sulfuric acid.

RESULTS

Patients, HIV-positive with SD, had significantly lower proportions of free fatty acid (FFA) and higher levels of triglyceride than normal controls. Patients, HIV-positive without SD, had a significantly increased proportion of FFA compared to HIV-positive patients with SD. Patients with SD, both HIV-positive and HIV-negative, had a similar pattern of skin surface lipid. Levels of FFA were lower and those of triglyceride higher than in the patients unaffected by SD, whether HIV-positive or not. There was no significant difference found between groups in free cholesterol, wax esters, and squalene.

CONCLUSIONS

Abnormalities of skin surface lipid composition may play a part in the development of SD in both HIV-positive and HIV-negative men.

Lipase of Malassezia furfur: some properties and their relationship to cell growth

Lipase activity of Malassezia furfur, detected with alpha-naphthyl palmitate as a substrate, appeared to be associated with the insoluble fraction of the organism. Profiles of M. furfur lipase were similar to those of Candida cylindracea lipase. The pH optimum of the lipase was acidic, pH 5.0, which is very similar to skin surface pH. The enzyme activity was strongly activated by a lipase activator, sodium taurocholate (STC). Addition of STC to the culture medium activated cell growth in a dose-dependent manner and induced hyphae production. These results suggest that M. furfur lipase plays an important role in cell growth.

An immunological study in patients with seborrhoeic dermatitis

The humoral and cellular immune-status was studied in 30 patients with seborrhoeic dermatitis. Increased frequencies of natural killer cells were found in 46% of patients. Furthermore, subnormal mitogen stimulation responses were demonstrated in 13 patients, whereas two individuals were found to have very high numbers of activated T lymphocytes in peripheral blood. Higher-than-normal total serum IgG and IgA was observed in 14 and 11 patients, respectively. For nine of 12 patients with skin lesions, dermal perivascular cell infiltrates were seen. The majority of the infiltrating cells reacted with anti-CD4 antibodies. HLA-DR-expressing keratinocytes were found in two biopsies. The study suggests that patients with seborrhoeic dermatitis may have depressed T-cell function. This could have a bearing on their susceptibility to the Pityrosporum ovale-associated dermatitis. The very high frequencies of activated T cells observed in the peripheral blood of two otherwise healthy seborrhoeic individuals suggests that intermittent systemic immune activation may occur. Seborrhoeic dermatitis is a common skin disease. It can be diagnosed by its characteristic red to yellow-brown lesions covered with greasy scales distributed in areas with a high number of sebaceous glands, such as the scalp, face and upper trunk. There is an association between seborrhoeic dermatitis and the lipophilic yeast Pityrosporum ovale but its exact aetiological role is not known. The yeast is a member of the normal cutaneous flora but also the aetiological agent of pityriasis versicolor and Pityrosporum folliculitis. P. ovale can activate complement via the direct and alternative pathways. This may play some part in the induction of inflammation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acne vulgaris. Pathogenesis and treatment

Acne vulgaris is a multifactorial disease involving abnormalities in follicular keratinization, sebum production, proliferation of Propionibacterium acnes, and inflammation. Treatment is directed toward reversing these underlying pathogenic factors. Therapeutic options include topical comedolytics, topical and systemic antibiotics, hormonal manipulations, and oral retinoids.

Skin surface lipids in HIV sero-positive and HIV sero-negative patients affected with seborrheic dermatitis

Skin surface lipids of patients affected with seborrheic dermatitis both HIV sero-negative (C group) and HIV sero-positive (B group) have been studied by capillary Gas chromatography-Mass spectrometry (GC-MS) in comparison with normal age matched controls (A group) to determine whether, among the three groups of individuals, there were qualitative and quantitative changes in lipid class composition and in the fatty acid and alcohol components of lipid fractions. With regard to percent composition of skin surface lipid fractions, no significant differences were found between HIV sero-positive and HIV sero-negative patients with seborrheic dermatitis. The observed significant reduction of total lipids (micrograms/sq cm) in the sites affected with the disease in comparison with controls was associated with a slight but significant decrease of squalene (P less than 0.05) and with a corresponding increase of cholesterol and cholesterol esters (P less than 0.05). These abnormalities in lipid fractions and total lipids were not observed in the uninvolved skin of subjects with seborrheic dermatitis. Fatty acid and alcohol patterns of skin lipid fractions were not significantly different among the three groups of individuals.

Pityriasis versicolor and Pityrosporum ovale. Morphogenetic and ultrastructural considerations

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been performed on skin material of patients with pityriasis versicolor who were orally treated with itraconazole. Before as well as after therapy, variously sized spherical structures were observed on the surface of the keratinocytes with SEM. TEM examination revealed Pityrosporum ovale, predominantly in its mycelial phase, inside keratinocytes. The spherules as observed by SEM appeared to be amorphous, lipid-like droplets originating from the inside of the keratinocytes. The cytoplasm of the keratinocytes was at least partly occupied by the same amorphous material. It is therefore suggested that P. ovale penetrates the keratinocyte where degradation of the normal keratinous content to amorphous material takes place. This newly formed lipidic substrate may be an essential nutritive factor. The lipidified state of the stratum corneum persisted for at least 3 weeks after eradication of the fungus by itraconazole. It is speculated that the presence of large quantities of this lipid-like material might be the cause of hypopigmentation because it may constitute an ultraviolet light block.

Lipoxygenase activity of Pityrosporum in vitro and in vivo

Lipid peroxidation has been investigated both in cultures of Pityrosporum supplemented with different lipid classes and in skin surface lipids from patients affected with pityriasis versicolor. Thin-layer chromatography (TLC) and 2 spectrophotometric methods were used: the indirect thiobarbituric acid test and the direct N,N-diethyl-1,4-phenylene-diammonium sulfate (DEPD) test. The coupling of the DEPD test with the TLC technique performed by different eluent systems allowed the detection of the specific lipoperoxides deriving from the oxidation of the different lipid classes. In the cultures, Pityrosporum was capable of peroxidating not only unsaturated free fatty acids, but also unsaturated triglycerides, cholesterol, and squalene. A similar lipid peroxidation was observed in patients with pityriasis versicolor in skin lipids from areas positive for fungal hyphae and spores and fluorescent under the UV lamp (366 nm). The lipoperoxide values were significantly higher (p less than 0.05) than in skin lipids from normal controls. Hyphae and spore-negative areas of patients with pityriasis versicolor, whether apparently normal or achromic, showed no evidence of a significant lipid peroxidation and neither did skin areas of patients with pityriasis alba. Though further investigations are necessary, it seems reasonable to suggest, in analogy with other biologic systems, that the presence in skin lipids of a significant amount of highly reactive and cytotoxic lipoperoxides may play a role in the pathogenesis of skin alterations in pityriasis versicolor, including damage to melanocytes and resulting achromia.

Seborrhoeic dermatitis and Pityrosporum orbiculare: treatment of seborrhoeic dermatitis of the scalp with miconazole-hydrocortisone (Daktacort), miconazole and hydrocortisone

Seventy patients (36 males and 34 females) with seborrhoeic dermatitis of the scalp were treated in a double-blind controlled study, for a maximum of 6 weeks, with 2% miconazole base and 1% hydrocortisone (Daktacort), 2% miconazole base, or 1% hydrocortisone. Patients who were cured were treated with the same formulation prophylactically twice monthly for 3 months or until recurrence. Nineteen of 21 patients were cured in the Daktacort group, 15 of 22 in the miconazole group and 17 of 24 in the hydrocortisone group. The number of cultured Pityrosporum orbiculare was significantly lower in all groups after treatment, but in the hydrocortisone group was still significantly higher than in the two other groups. After 3 months of prophylactic treatment, both Daktacort (16 of 19 patients clear) and miconazole (10 of 15 patients clear) were significantly better than hydrocortisone (3 of 17 patients clear) (P less than 0.01). The numbers of P. orbiculare remained low in the Daktacort and miconazole groups and also significantly lower than in the hydrocortisone-treated group (P less than 0.01). In patients with recurrence, the numbers returned to pre-treatment levels. This study demonstrates the aetiological significance of the Pityrosporum yeasts in seborrhoeic dermatitis. Both Daktacort and miconazole were effective in treatment and as prophylactic agents.

Essential fatty acids and acne

Acne is characterized by hyperkeratosis of the follicular epithelium, leading to horny impactions that may lie dormant as open or closed comedones or may cause inflammation of the follicle. Although persons with acne have consistently been observed to have elevated levels of sebum secretion, no mechanism relating sebum secretion rates to comedogenesis is known. Acne patients have also been shown to have low levels of linoleic acid in their skin surface lipids. To explain this observation, the hypothesis is advanced that the linoleate concentration in human sebum depends on the quantity of linoleic acid present in each sebaceous cell at the commencement of its differentiation and on the extent to which this initial charge is diluted by subsequent endogenous lipid synthesis in each sebaceous cell. A corollary hypothesis holds that low concentrations of linoleate in sebum impose a state of essential fatty acid deficiency on the cells of the follicular epithelium and induce the characteristic response of hyperkeratosis. Both hypotheses could hold, without there being a systemic deficiency of linoleic acid, simply as the result of elevated lipogenesis in individual sebaceous cells.

Pityrosporum folliculitis: a common disease of the young and middle-aged

Fifty-one patients, thirty-nine women and twelve men, with Pityrosporum folliculitis are described. This investigation clearly demonstrates that Pityrosporum folliculitis is a real entity. The diagnosis is based primarily on the clinical picture, direct microscopy, histopathology, and the effect of antimycotic treatment. The typical patient is a woman of 30 years with itching follicular papules and pustules localized to the upper trunk or upper arms. Direct microscopy reveals round yeast cells and sometimes even hyphae. In biopsy specimens, abundant round budding yeast cells and occasionally hyphae are seen in a dilated follicle. Yeast growth is obtained only on lipid-enriched media. Twenty-five patients were treated with selenium sulfide shampoo, twelve with 50% propylene glycol in water, and ten with topical econazole cream with good results. Cure or marked improvement was seen after 3 to 4 weeks, but symptoms and lesions recurred if treatment was not continued intermittently. Predisposing factors such as occlusion and greasy skin are probably important, and future studies should focus on fungal hypersensitivity, quantitative variations in the number of Pityrosporum orbiculare, lipid composition of the skin, and extended epidemiologic data.

The Pityrosporon yeasts. Their role as pathogens

P. orbiculare (P. ovale), a member of the normal human cutaneous flora, is also an opportunistic pathogen, and the association with tinea versicolor is well-documented. Recently, the Pityrosporon yeasts have been associated with several other diseases. That Pityrosporon folliculitis is a separate disease is now documented. The association with CRP and with some cases of psoriasis and seborrheic dermatitis seem probable but are not yet fully proven. Reports show that P. orbiculare (P. ovale) are involved not only in dermatologic diseases, again indicating that the organisms are not "harmless" saprophytes. Because of our awareness of this association, more cases of systemic infections with Pityrosporon yeasts may be reported.

Characterization of chemical stimuli for the penetration of Schistosoma mansoni cercariae. I. Effective substances, host specificity

The stimulation of penetration of Schistosoma mansoni cercariae into agar was studied. This depends exclusively on chemical triggers whose specificity is analyzed in experiments with 230 chemicals. Only aliphatic hydrocarbon chains which have a polar as well as a nonpolar end group are effective. The effectiveness of saturated substances is limited, at pH 7.0, to chain lengths between 10 and 15 carbon atoms. Unsaturated substances are active at longer chain lengths. Their effectiveness is increased by the number of double bonds in the cis position, and these should not be placed too close to the nonpolar end of the chain. As well as double bonds, halogens, hydroxyl groups, and methyl side chains are equally effective. All penetration stimulating substances kill cercariae in free water, and the appropriate chemicals cause this lethality at very low concentrations. It is shown that the host recognition pattern at the stage of penetration is especially adapted to invasion of the human skin.

Characteristic gamma-lactone odor production of the genus Pityrosporum

Mass spectrometric-gas chromatographic analysis of culture headspaces revealed that members of the genous Pityrosporum produce volatile gamma-lactones during growth on lipid-containing media. Representative members of other yeast genera found on humans failed to produce these compounds. Addition of lecithin, oleic acids, triolein, or human sebum to the culture media stimulated gamma-lactone production by Pityrosporum species. All yeasts tested produced isopentanol and phenylethanol. Production of gamma-lactones may serve as a valuable characteristic in the identification of organisms of the genus Pityrosporum.

Induction of hyphae in cultures of Pityrosporum by cholesterol and cholesterol esters

The effect of cholesterol and cholesterol esters on Pityrosporum cultures has been studied. A mixture of 0.25% to 2.0% of cholesterol:cholesteryl stearate:glyceryl monostearate (2.0:1.5:2.0) added to Bacto Yeast Morphology Agar plus oleic acid was able to induce hyphae in cultures of both Pityrosporum orbiculare and P. ovale. This result is discussed with respect to the cholesterol effect on cell membranes and to the occurrence of cholesterol and cholesterol esters in the scaling patches of Pityriasis versicolor.

Octadecadienoic acids in the skin surface lipids of acne patients and normal subjects

Measurements were made of the proportions of octadeca-5,8-dienoic acid and octadeca-9,12-dienoic acid in the scalp surface lipids of 6 normal subjects, 5 subjects with slight acne, and 9 subjects with severe acne. The group averages for the delta5,8 isomer were: 0.74, 0.85, and 0.61% and for the delta9,12 isomer were 0.56, 0.27, and 0.19%, respectively. The differences in the levels of the delta9,12 isomer between the normal subjects and the groups with slight and with severe acne were statistically significant (p less than 0.02 and 0.001), respectively) but there was no significant difference in the content of the delta5,8 compound. The ratio of the delta5,8/delta9,12 isomers showed no correlation with the rate of sebum production in 12 subjects.

The localization and distribution of gram-positive cocci in normal skin and in lesions of acne vulgaris

The localization of gram-positive cocci in the normal skin and in the lesions of acne vulgaris was investigated using fluorescein-labeled antiserum raised to gram-positive, coagulase-negative cocci. The cocci were found in 10 of 19 specimens from normal facial skin and in 3 of 11 specimens from the normal skin of the rest of the body. The bacteria were found mostly in the openings of follicles, but in 6 of 10 facial skin specimens, they were also present deeply in the lumina of the dilated sebaceous follicles near the sebaceous glands. Cocci were found in 5 of 6 noninflammatory acne comedones. In inflammatory acne they were demonstrated not only in the follicular canals but also sparsely in the infiltrate surrounding the follicles.

Skin lipids: their biochemical uniqueness

Two key words characterize the uniqueness of skin lipids: complexity and perversity. Each suggests a function. Complexity manifests itself in the large number and variety of both saturated and unsaturated fatty chains synthesized by human skin. Functionally, this allows each individual to have a distinct odor or chemical fingerprint. Perversity manifests itself when one compares the lipids synthesized by skin with those synthesized by internal tissues. For example, skin makes odd instead of only even chains, branched instead of only straight chains, free instead of only esterified acids, places double bonds in unusual positions in the fatty chains, extends chains to extreme lengths, and accumulates intermediates in the synthesis of a biologically valuable compound such as cholesterol. Functionally, these products may pose metabolic problems to potential pathogens and thus contribute to the survival of only compatible microorganisms.