An in vivo evaluation of the inflammatory effect of purified comedonal components in human skin

Final Report on the Safety Assessment of Squalane and Squalene

Squalane and Squalene have been identified as natural components of human sebum. Both ingredients are used in a variety of cosmetics at concentrations ranging from ≤0.1 to >50%. Animal studies indicate Squalene is slowly absorbed through the skin, while both compounds are poorly absorbed from the gastrointestinal tract. The acute animal toxicity of these ingredients by all routes is low. Both compounds are nonirritants to rabbit skin and eye at 100% concentration. Formulations containing Squalene indicate it is not a significant human skin irritant or sensitizer. Limited contact sensitization tests indicate Squalene is not a significant contact allergen or irritant. It is concluded that both Squalane and Squalene are safe as cosmetic ingredients in the present practices of use and concentration.

Post-acne scarring: a short review of its pathophysiology

The onset of acne is an expected phenomenon in adolescence. However, its arrival produces long-term psychological and physical sequelae for the individual. A review of available data illustrates the pathophysiological sequence of the advent of post-acne scarring from its humble beginnings as a microscopic comedone to its eventual devastating end point of indented or exophytic scars. Acne scarring shows many different forms and is explainable by the depth and severity of the antecedent inflammation and the ability of the individual to heal these lesions. Post-acne scarring is debilitating and socially disabling for many and is the avoidable outcome of untreated or inadequately treated acne. Treatment will depend on the resultant scar topography.

Inflammation in acne vulgaris

Recent findings suggest that an overly vigorous immune response to Propionibacterium acnes may be the fundamental problem in patients with inflammatory acne. These data and evidence for the antiinflammatory effects of acne medications are reviewed.

Acne-like chronic inflammatory activity of Propionibacterium acnes preparations in an animal model: correlation with ability to stimulate the reticuloendothelial system

The ability of strains and fractions of killed propionibacteria suspensions to produce chronic rat ear inflammation after intradermal injection of 70-micrograms aliquots was highly correlated with production of splenomegaly in the mouse after i.p. injection of 1.4 mg Propionibacterium acnes strains CN 6134, VPI 0009, ATCC 11828, and UCLA SC and N1 produced a 2- to 3-fold increase in rat ear thickness and a 5- to 7-fold increase in mouse spleen weight 15 days post injection. In contrast P. granulosum CN 5888, P. acnes UCLA 6S and periodated, acetylated, or 12-h cultures of VPI 0009 were inactive or weakly active as stimulators of chronic ear inflammation and splenomegaly. Active strains produced in the rat ear a transepidermal elimination response characterized by follicular encapsulation and the formation of secondary comedones. These effects correlated with persistence of phagocytized bacteria within macrophages. Furthermore, when rats were first immunized and then challenged with active strains of P. acnes, an increased sensitivity to low doses of P. acnes and a chronic exacerbation of inflammation was observed.

Antibody titers to Propionibacterium acnes cell wall carbohydrate in nodulocystic acne patients

In order to determine which structures in Propionibacterium acnes are most antigenic to severe acne patients, we studied the specificity of anti-P. acnes antibodies in serum from 15 nodulocystic acne patients and 5 normals. Complement fixation titers to P. acnes cell wall fractions were determined using guinea pig serum as a complement source. The mean titers of patients and normals to whole cells were 39.6 and 3 (p less than 0.1); to crude cell wall, 138 and 8 (p less than 0.01); and to protein and nucleic acid-free cell wall, 225 and 9.33 (p less than 0.001), respectively. The mean precipitin titer to P. acnes cytosol was 12.7 for patients and 0 for normals. Immunoelectrophoresis of cytosol from 8 P. acnes strains were developed with each of the 15 patient sera. A single broadly migrating anionic antigen was detected. The antigen was also present in P. acnes culture supernatants. Sephadex G-100 chromatography of cytosol revealed a single peak of antigenic reactivity at Mr = 100,000. Three patients' sera revealed a second weakly reacting antigen in the cytosol preparation. Twentyfold concentration of immunoglobulin from patient sera failed to reveal any other antigenic reactivities. The antigen was found to be resistant to nuclease, pronase, and lysozyme treatment; was precipitable with 70% ethanol; and was destroyed by sodium m-periodate--findings that are consistent with a carbohydrate structure.

Intradermal injection of Propionibacterium acnes: a model of inflammation relevant to acne

The intradermal injection of 140 micrograms of Propionibacterium acnes (CN 6134) into the ears of female Sprague-Dawley rats produced a chronic inflammation with formation of acneiform lesions. Inflammation was characterized by more than a doubling of ear thickness at 24 h and a peak of 3-4 times control levels at day 21. At 42 days post injection ears were still 3 times normal thickness. Histologically there was early polymorph accumulation giving way to macrophages and lymphocytes by day 7. Pilosebaceous follicles overlying the inflamed area lost their sebaceous glands and became hyperplastic cords of cells that grew down and encapsulated inflammatory loci. By day 9 many of these follicles had become secondary comedones. Three isolates of P. acnes from inflammatory acne lesions and 4 of 5 isolates from non-acne patients produced results similar to that of the strain CN 6134. In these cases the number of histologically evident secondary comedones was correlated with ear thickness. In contrast, samples of Streptococcus lactis, Escherichia coli B, and Staphylococcus epidermidis failed to produce this combination of chronic inflammation and high lesion count. Benzoyl peroxide, tetracycline, erythromycin, phenidone, naproxen, and cis and trans retinoic acid were inactive as inhibitors of P. acnes CN 6134-induced ear thickening. The corticosteroid fluocinolone acetonide produced dramatic suppression of inflammation, but upon cessation of treatment the ears returned to inflamed levels. The specificity for P. acnes, the formation of acneiform lesions, and the recalcitrance of the inflammation suggest our model is indeed relevant to acne.

Anti-P. acnes antibody in comedonal extracts

Extracts of comedonal material obtained from patients with acne vulgaris were analyzed for albumin, IgG, IgM, IgA, and anti-Propionibacterium acnes antibodies using immunodiffusion and anti-immunoglobulin hemagglutination tests. Extracts were obtained from comedones of patients with (1) comedonal, (2) papulopustular, (3) nodular-cystic, (4) "burned out" acne, (5) patients under oral tetracycline treatment, and (6) with pustules. In all comedonal extracts analyzed, albumin and IgG (ratio approximately 1:2.5) could be detected. IgM, IgA, and C3 could not be found in noninflamed comedones by the techniques used; pustules, however, contained all immunoglobulin classes and albumin in ratios found in serum as well as C3. The anti-P. acnes antibody activity in the comedonal extracts was associated with the IgG class. Immunofluorescence microscopical examination of material from single comedones obtained by the cyano-acrylate technique showed IgG antibody on rod-shaped bacteria. The amount of IgG and albumin in comedonal extracts from the various patient groups was not different. It is concluded that IgG (and antibody of the IgG class) in comedones is derived from the serum and selectively accumulated in the follicle by an unknown mechanism.

Chemotactic efficiency of various chemoattractants for polymorphonuclear leukocytes in inflammatory acne vulgaris

The chemoattractant efficiencies of a Propionibacterium acnes (P. acnes) cell wall preparation, a P. acnes culture supernatant, and a soluble comedonal extract in the presence and absence of autologous serum for polymorphonuclear leukocytes (PMNs) have been compared in the present study. It has been found that all three preparations have no or very little chemotactic activity for PMNs in the absence of serum. In the presence of autologous serum chemotactic factors is generated by all preparations via the alternative complement pathway. The relative efficiencies of the various preparations to induce chemotactic factor by the alternate complement pathway has been evaluated. Based on the bacterial numbers of the original preparations from which the test preparations had been derived the comedonal extract appears to be more efficient in generating chemotactic factor than the other preparations. It is concluded that in vivo generation of chemotactic factors occurs mainly via the alternate complement pathway activated by soluble comedonal factors diffusing through the follicular wall.

Delayed skin test reactivity to Propionibacterium acnes correlates with severity of inflammation in acne vulgaris

Propionibacterium acnes is the bacterial species most consistently isolated from acne lesions. Intradermal injection of a heat-killed suspension of P. acnes induced a delayed erythematous and often popular inflammatory reaction which was maximal after 24-48 h. This response was dose related and was probably mediated at least partly by immune mechanisms. In eighty-one subjects with acne of varying severity of the acne. These findings indicate that the host response to P. acnes is an important variable in determining the severity of inflammatory acne.

Polymorphonuclear leukocyte lysosomal release in response to Propionibacterium acnes in vitro and its enhancement by sera from inflammatory acne patients

Propionibacterium acnes cells were tested for the ability to trigger lysosomal hydrolase release from human polymorphonuclear leukocytes. Representative strains of P. acnes serotype I and II failed to stimulate lysosomal release in the absence of serum. P. acnes growth culture supernatants failed to trigger release under any test condition. Addition of fresh or heat-inactivated human serum resulted in lysosomal hydrolase release directly proportional to the number of P. acnes/PMN. Pooled sera from acne patients, with a high anti-P. acnes titer stimulated release to P. acnes. Preabsorption of this reagent with P. acnes cells reduced the anti-P. acnes titer and produced 93.37 +/- 11.49% inhibition of lysosomal enzyme release compared to unabsorbed anti-serum. Electron microscopy indicated that P. acnes was readily phagocytosed by PMNs when fresh or heated serum was present.

Cytotaxin production by comedonal bacteria (Propionibacterium acnes, Propionibacterium granulosum and Staphylococcus epidermidis)

The potential role of different species of comedonal bacteria as chemotactic stimuli in the inflammatory phase of acne vulgaris was investigated by comparing 12 strains of Staphylococcus epidermidis, 11 strains of Propionibacterium acnes, and 5 strains of P. granulosum for production of cytotaxin in vitro. Results indicated that not only were there marked differences in cytotaxin production between different strains of the same species grown under identical growth conditons, but there were often significant differences in cytotaxin activity of the same strain grown in different media. This finding is discussed in relation to development of inflammation in quiescent comedones in acne vulgaris.

Bacterial flora of comedones

Open comedones from thirty-eight patients with acne vulgaris on the face or back were compared for microbial flora. A total of eighty-three comedones from the face and sixty-three from the upper back were individually processed for quantitative bacterial analysis. The greatest difference between the flora of comedones at these two sites was that 44.6% of comedones from the back (compared to 9.6% from the face) harboured no aerobic cocci. The decreased prevalence of staphylococci in the lesions from the back reflects the relative absence of these organisms in isolated follicles from normal uninvolved skin of the back. The geometric mean count of anaerobes in comedones from the back was in the same range as the count found in isolated follicles in normal uninvolved skin in a previous study. This work supports the concept that the bacterial flora of comedones is an extension of the follicular flora and may be unrelated to the event of comedogenesis.

The chemoattractant properties of comedonal components

Acculation of clusters of polymorphonuclear leukocytes (PMN) along the periphery of the walls of comedones (predominantly of the closed variety), has been described as the first change marking the transition of quiescent, noninflamed lesions in acne, into inflammatory ones. The present study analyzed the chemoattractant properties of different comedonal components for human PMN in an effort to evaluate the potential significance of these substances in stimulating the chemotactic response of PMN in the initial phases of inflammatory acne. It was found that the lipids extracted from pooled comedones had chemotactic activity for PMN in vitro. Beyond that, all chemotactic activity in comedones was related to bacteria. Propionibacterium acnes produced low molecular weight, dialyzable, heat stable chemotactic factors which were released into culture medium during bacterial growth. In addition to the extracellular cytotaxins, P. acnes whole cells and other extracellular products were strong cytotaxigens and activated heat labile chemotactic factors in human and guinea pig serum.