A citrus polymethoxy flavonoid, nobiletin inhibits sebum production and sebocyte proliferation, and augments sebum excretion in hamsters

Acne vulgaris is characterized by excess sebum production, and apart from all-trans retinoic acid (atRA) or 13-cis retinoic acid (13-cisRA), there are few effective agents for acne therapy that directly suppresses sebaceous lipogenesis. In this study, we demonstrated that topical application of a citrus polymethoxy flavonoid, nobiletin, to hamster auricles decreased skin surface triacylglycerols (TG) level and the size of sebaceous glands along with inhibition of diacylglycerol acyltransferase (DGAT)-dependent TG synthesis and sebocyte proliferation. The inhibitory actions were similar to that observed with atRA and 13-cisRA in hamster sebocytes. The antilipogenic and antiproliferative actions of nobiletin were also reproduced in UVB (5.4 kJ/m2)-irradiated hamsters, which showed aberrant enhancement of sebum accumulation and sebaceous enlargement. Furthermore, nobiletin, but not 13-cisRA, augmented sebum excretion along with increases in intracellular cAMP level, protein kinase A (PKA) activation, and apoptosis-independent phosphatidylserine (PS) externalization in cell membrane. These phenomena were reproduced by forskolin and inhibited by a PKA inhibitor, H-89. These results provide early evidence that nobiletin is an effective candidate for acne therapy through mechanisms that include the inhibition of DGAT-dependent TG synthesis and sebocyte proliferation, and the progression of apoptosis-independent and PS-externalization-dependent sebum excretion by PKA activation.     

The effect of trimethoprim-sulphamethoxazole on sebum excretion rate and biochemistry in acne vulgaris

SUMMARY.— The sebum excretion rate and skin surface liquid composition were determined before and after 1 and 2 months of therapy in patients taking a trimethoprim-sulphamethoxazole combination for acne vulgaris. Trimethoprim-sulphamethoxazole caused a significant reduction in skin surface free fatty acid and a significant rise in skin surface triglyceride after 1 and 2 mionths of therapy. There were no significant changes in sebum excretion rate, squalene or wax ester.     

SEBUM EXCRETION RATE AND BIOCHEMISTRY IN PATIENTS WITH ACNE VULGARIS TREATED BY ORAL FENFLURAMINE

SUMMARY.— Six patients with acne vulgaris were given oral fenfluramine. There was no clinical improvement in the acne vulgaris.
The sebum excretion rate and skin surface lipid composition were also investigated. There were no significant changes in either the sebum excretion rate or sebum biochemistry after 1, 2 and 3 months of therapy.     

Investigation of the mechanism of action of 2% fusidic acid lotion in the treatment of acne vulgaris

We describe the results of a single-centre, double-blind, vehicle-controlled, parallel group study on the quantitative effects of 2% fusidic acid lotion (Fucidin® lotion) in facial acne vulgaris. The trial was completed by 52 patients aged 15–25 years with mild to moderate acne who had been randomized to either Fucidin® Lotion (n= 25) or its base (n= 27). Primary outcome measures included colony counts of Propionibacterium acnes and microcoecaceae and measurements of skin surface lipid free tatty acids and sebum excretion rate. Clinical assessment was based on the acne grade, count of inflamed and non-inflamed lesions and evidence of a primary irritant dermatitis. There was a variable hut gradual reduction in lesion counts with the maximum improvement at 12 weeks for inflamed lesions, where the reduction was 19·9% for fusidic acid and 247% for the placebo. The non-inflamed lesions decreased by 10·8% in the fusidic acid group and increased by 15·9% in the placebo group; this difference was not statistically significant. Although the fusidic acid reduced the micrococcaceae count by 1 log cycle, inferring adequate compliance, there was no reduction in the counts of P. acnes, surface free fatty acids or sebum excretion rate. This study has failed to explain the mechanism of action of topical fusidic acid.     

13-cis Retinoic acid induces apoptosis and cell cycle arrest in human SEB-1 sebocytes

Isotretinoin (13-cis retinoic acid (13-cis RA)) is the most potent inhibitor of sebum production, a key component in the pathophysiology of acne, yet its mechanism of action remains largely unknown. The effects of 13-cis RA, 9-cis retinoic acid (9-cis RA), and all-trans retinoic acid (ATRA) on cell proliferation, apoptosis, and cell cycle proteins were examined in SEB-1 sebocytes and keratinocytes. 13-cis RA causes significant dose-dependent and time-dependent decreases in viable SEB-1 sebocytes. A portion of this decrease can be attributed to cell cycle arrest as evidenced by decreased DNA synthesis, increased p21 protein expression, and decreased cyclin D1. Although not previously demonstrated in sebocytes, we report that 13-cis RA induces apoptosis in SEB-1 sebocytes as shown by increased Annexin V-FITC staining, increased TUNEL staining, and increased cleaved caspase 3 protein. Furthermore, the ability of 13-cis RA to induce apoptosis cannot be recapitulated by 9-cis RA or ATRA, and it is not inhibited by the presence of a retinoid acid receptor (RAR) pan-antagonist AGN 193109. Taken together these data indicate that 13-cis RA causes cell cycle arrest and induces apoptosis in SEB-1 sebocytes by a RAR-independent mechanism, which contributes to its sebosuppressive effect and the resolution of acne.     

Quantitative analysis of skin surface lipids using a sebumeter method. Random lipid levels on the skin surface during therapy with 13-cis-retinoic acid, minocycline hydrochloride and UVA rays

The Sebumeter method used in this study for quantitative analysis of skin surface lipids differs from previous techniques in simple handling and quick practicability and is therefore helpful in the clinical routine. Sebumetrical measurements carried out on healthy persons revealed symmetrical distribution of skin surface lipids. The highest levels were found on the forehead; young people generally showed higher values than older persons. During therapy with 13-cis retinoic acid on acne patients for 6 months (0.5 mg/kg daily), we found reduction of the random level in the first month, particularly in the forehead region. During therapy with minocycline on 3 acne patients for 3 months (2 X 50 mg daily), there was no variation of the random level observed. UVA irradiation on the face for 10 minutes daily (0.55 J/cm2/min) over a period of 3 weeks resulted in continuous reduction of the random level in most of the tested persons; a small part of them reacted by fluctuating values.     

THE EFFECT OF CLINDAMYCIN IN ACNE-A CLINICAL AND LABORATORY INVESTIGATION

Summary.— Skin surface lipid composition and sebum excretion rate were determined before and after one and 2 months of therapy in patients taking clindamycin for severe acne vulgaris. All patients showed marked clinical improvement. Clindamycin produced a significant reduction in skin surface free fatty acids and a significant reciprocal increase in skin surface triglycerides after one and 2 months of therapy. There was no significant change in the sebum excretion rate. These results support the hypothesis that free fatty acids are important in the pathogenesis of acne vulgaris.     

In situ hybridization analysis of CRABP II expression in sebaceous follicles from 13-cis retinoic acid-treated acne patients

The aim of this study was to investigate the effects of 13-cis retinoic acid treatment on cellular retinoic acid binding protein II (CRABP II) mRNA expression in sebaceous follicles from acne patients, using in situ hybridization. Biopsies were taken from uninvolved skin areas in close juxtaposition to inflamed comedos before therapy, and at 2–4 or 14-16 weeks of treatment. Paraffin sections were used for in situ hybridization study with riboprobes transcribed from human CRABP II cDNA. After oral treatment with l 3-cis retinoic acid, sebaceous glands were reduced in size and atrophic, and the ratio of sebum-free to fully differentiated (sebum-producing) sebocytes was dramatically increased. The CRABP II expression in the sebaceous gland, and to some extent in infundtbular structures, was strongly increased compared with the level of expression in the epidermis. The maximum signal was always found in layers of suprabasal sebocytes lacking lipid droplets. but never in the basal layers. These findings indicate a selective activity of 13-cis retinoic acid on CRABP II mRNA expression in the sebaceous glands of acne patients.     

THE EFFECT OF PROLONGED TOPICAL APPLICATION OF AN ANTICHOLINERGIC AGENT ON THE SEBACEOUS GLANDS

SUMMARY.— The application of a topical anticholinergic agent (poldine methyl -methosulphate) to the forehead skin of 10 patients with mild acne vulgaris twice daily for 4 weeks produced a small but significant reduction in sebum excretion. This is compatible with the suggestion that the control of sebum secretion may have a cholinergic component, but the effect is small.     

Topical azelaic acid and the treatment of acne: a clinical and laboratory comparison with oral tetracycline

Topical azelaic acid and oral tetracycline were compared in a 6-month double-blind study for treatment of acne vulgaris in 45 male subjects with clinical acne. Their acne was graded, inflamed or non-inflamed, lesions were counted and the density of their skin microflora was measured. Both treatments were of benefit and produced only a few minor side-effects. Although oral tetracycline was more effective than azelaic acid, the differences were only just significant. The average reduction in numbers of cutaneous micrococcaceae and Propionibacterium sp. with azelaic acid treatment was 224 and 30-fold, respectively. In a separate group of 11 male subjects with physiological acne the effect of azelaic acid on sebum excretion rate was assessed, and little change was detected.     

The effect of marked inhibition of sebum production with 13cis-retinoic acid on skin surface lipid composition

Sebum production and skin surface lipid composition have been measured during the oral treatment with 13cis-retinoic acid of a group of patients with severe cystic acne. Two hundred and thirty-eight paired samples have been analyzed and compared. A marked, drug-induced decrease in sebum production was accompanied by a decrease in the concentration of wax esters, a slight decrease in the squalene concentration and in increase in the cholesterol concentration in the skin surface lipids. These changes were consonant with changes in the relative contributions of sebum and epidermal lipid to the surface film, except that at very low levels of sebum production there might be preferential preservation of squalene synthesis.     

Skin lipids in 13-cis-retinoic acid therapy of acne

The study presents clinical data and results of skin sebum (SER) determinations during 13-cis-retinoic acid treatment in 15 patients suffering from severe conglobate and cystic acne. The striking clinical improvement was mostly accompanied by decreased SER as well as changes in the composition of the skin surface lipids. While the sebaceous gland lipids were generally reduced, the epidermal lipids showed irregular tendencies. Despite of good therapy effects, 3 patients showed increased SER. This indicates that other mechanisms than those of sebum suppression may be responsible for the treatment success. Sebum suppression and modulation are important and valuable aspects for documentation as well as for elucidation of the working mechanism of 13-cis-retinoic acid.     

Photodynamic therapy for acne vulgaris: a pilot study of the dose-response and mechanism of action

Acne vulgaris does not always respond to conventional therapy. Photodynamic therapy (PDT) has been proposed as a treatment option. The aim of this study was to determine the optimal light dose for effective PDT treatment of acne and to investigate whether PDT reduces sebum excretion and the amount of Propionibacterium acnes. Fifteen patients (9 men, 6 women, age range 16-44 years, mean age 25 years) with mild to severe acne were enrolled in an open, unblinded study. Aminolaevulinic acid cream (20% in Unguentum Merck) was applied on two circular areas 3 h before PDT. The areas of investigation were irradiated with red light (635 nm) from a Waldman PDT 1200 lamp. Ten patients with facial acne were treated with a light dose of 50 J/cm(2) on the right cheek and 30 J/cm(2) on the left cheek. Five patients with acne on their back were treated either with 50 J/cm(2) or with 70 J/cm(2). Clinical follow-up was performed for at least 10 weeks. In the patients with facial acne, sebum excretion was determined before PDT and at every follow-up visit. The amount of P. acnes was measured in a skin surface biopsy using a cyano-acrylate polymer to extract the content of the sebaceous follicles. In 9 patients with facial acne the improvement of lesions was the same for the two light doses. According to the patients' own assessment, 8 improved after PDT (p=0.02). No difference was found between the two doses in patients with acne on the back. Hyperpigmentation was more common at higher doses of light, and pain was experienced more often by the patients when higher doses were used. No significant reduction in P. acnes or sebum excretion was found at any time after PDT. It is concluded that PDT could be an alternative treatment of acne lesions. The lowest possible light dose should be used for minimal side-effects. Other mechanisms of action for PDT than eradication of P. acnes and sebosuppression should be considered.     

Influence of oral metronidazole on the endocrine milieu and sebum excretion rate.

As part of a study of the mechanism of metronidazole's efficacy in the treatment of acne and rosacea, its effects on the endocrine milieu and sebum excretion rate were assessed. Thirteen healthy males received oral metronidazole treatment (500 mg/day) for 4 weeks. Serum sex hormone levels were determined in all 13 subjects and the sebum excretion rate was determined in seven of them, before and after treatment. We measured serum levels of estrone (E1), estradiol (E2), total testosterone (T), free testosterone (FT), dihydrotestosterone (DHT), dehydroepiandrosterone sulfate (DHEA-S), and sex hormone-binding globulin (SHBG). There were no significant changes in E1, T, FT, DHT, or SHBG levels, but E2 and DHEA-S levels decreased significantly after treatment. In all seven subjects in whom the sebum excretion rates were determined, the amount of facial skin surface lipids decreased significantly after treatment. These results suggest that metronidazole exerts its clinical effects through suppressing the sebum excretion by a mechanism other than anti-androgenic action.     

THE EFFECTS OF A 2-NAPHTHOL PEELING PASTE ON SEBACEOUS GLANDS REMOTE FROM ITS SITE OF APPLICATION

Summary— The sebum excretion rate and chemical composition of sebum from the foreheads of 4 young men with acne vulgaris were changed markedly when a 2-naphthol paste was applied to other skin sites. The excretion rate, free fatty acid content and wax ester content fell but the triglyceride content increased. Recurrence of acne on stopping treatment was associated with an increase in wax ester content and a decrease in triglyceride content but little change in excretion rate and free fatty acid content.     

Arotinoid Ro 13-6298 and etretin: two new retinoids inferior to isotretinoin in sebum suppression and acne treatment

Thirty patients have been treated with either etretin, the main derivative of etretinate, or arotinoid Ro 13-6298, a polyaromatic retinoid, or isotretinoin. Sebum production was measured before and during the treatments. While no change was observed in the patients treated with etretin, a reduction of 33% of the sebum excretion rate was observed for those treated with arotinoid Ro 13-6298 but only after long treatment periods of 20 to 30 weeks. The sebum excretion rate decreased by 92% in the patients treated with isotretinoin. Four patients suffering from severe nodulocystic acne were treated with arotinoid Ro 13-6298 for 2-5 months without improvement. Substantial improvement, however, resulted after a subsequent treatment with isotretinoin; sebum production decreased markedly as well. This study suggests that neither etretin nor arotinoid Ro 13-6298 will replace isotretinoin in the treatment of severe nodulocystic acne.     

A double-blind study of the effects of 13-cis-retinoic acid on acne, sebum excretion rate and microbial population

Forty-eight acne patients were treated orally with 13-cis-retinoic acid in a double-blind dose response study. There was a marked clinical improvement with a concomitant reduction in sebum excretion rate (SER) and production rate of free fatty acids (FFA). Microbial numbers decreased significantly; the decrease in propionibacteria was greater than that of aerobic bacteria. The decline in micro-organisms occurred after the reduction in sebum and FFA production. This suggests that the effect of the drug upon micro-organisms is secondary to the change in sebum excretion but it is nevertheless an important factor in the resolution of the acne.     

5% Aluminium chloride hexahydrate and sebum excretion rate

The present study was designed to assess whether 5% aluminium chloride hexahydrate in absolute alcohol exerted any effect on sebaceous gland excretory activity. Eleven acne patients controlled with long-term antibiotics applied active and placebo solutions in a double-blind trial. The sebum excretion rate was measured on two control visits and thereafter at fortnightly intervals for a further 6 weeks. Patients preferred the 'active' solution, many claiming increased dryness of their skin. However, neither the 'active' nor 'placebo' solution had a significant demonstrable effect on sebum excretion rate. The beneficial effect of topical aluminium chloride hexahydrate is therefore assumed to be due to factors other than an alteration in sebum excretion.     

VARIATIONS IN SKIN SURFACE LIPID COMPOSITION AND SEBUM EXCRETION RATE WITH DIFFERENT SAMPLING TECHNIQUES II

Summary.— The technique of Sellotape stripping was used to investigate the role of the stratum corneum in modifying sebum excretion rate and skin surface lipid composition.
All experiments were performed on the forehead. The stratum corneum influences the rate of sebum excretion as Sellotape stripping produced a significant increase in sebum excretion rate, but this effect was abolished by systemic antibiotics.
Skin surface lipid composition, when sampled by absorbent papers, was not influenced by Sellotape stripping, but when sampled by an ether-soaked sponge after Sellotape stripping, had a lessened epidermal lipid contribution. Thus the stratum corneum modifies skin surface lipid composition when sampled by an organic solvent.
Absorbent papers may be preferable to other sampling techniques on the forehead in the investigation of the role of sebaceous biochemical factors in the pathogenesis of acne vulgaris.     

Can sebum reduction predict acne outcome?

Sebum excretion has generally been accepted as an important factor in the development of acne vulgaris. However, the relationship of sebum excretion and acne outcome has not yet been clearly demonstrated quantitatively. The objective of this analysis was to explore the correlation of sebum and acne by combining data from studies of various acne treatments that have demonstrated effects on both sebum excretion and acne outcome. Acne measures included total lesion count, inflammatory lesion count and acne severity grade. For each acne measure, data were pooled and analysed at the 3‐ and 4‐month endpoints, when sebum reduction has generally equilibrated and efficacy in acne is approaching the maximum effect for most treatments. A linear model was used to describe the percentage reduction in each acne measure as a function of percentage reduction in sebum excretion. Slope values were similar for the three acne parameters and all were significantly different from zero (P < 0·025), suggesting a significant correlation of sebum and acne. The projected sebum reduction required to achieve 50% reduction in acne measures ranged from 30% to 50%. The results shown here suggest that the collective data across multiple studies may provide a useful generalization of the association of sebum reduction and acne outcome. As the relationship apparently remains consistent regardless of the treatment, it can be inferred that extrapolation to novel exploratory treatments may be valid.