SEARCH

SEARCH BY CITATION

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. References

Background

Whereas emollients are integral to the long-term management of atopic dermatitis (AD), the evidence for their efficacy in disease flares is limited.

Objective

We aimed to investigate the stand-alone efficacy of an emollient formulation with regard to improvement of the clinical symptoms, skin barrier function and reduction of pathogenic bacterial colonization in acute stage of AD.

Materials and methods

Twenty AD volunteers aged 12–65 years with symmetric, mild to moderately severe inflammatory lesions on the forearms/arms were recruited for the study. At inclusion, the forearms/arms of each volunteer were randomized to receive for 1 week either an o/w formulation containing licochalcone A (Glycyrrhiza Inflata root extract), decanediol, menthoxypropanediol and ω-6-fatty acids (emollient arm) or 1% hydrocortisone (HC arm); after 1 week, the application of the emollient and HC were discontinued and the volunteers applied a w/o emollient containing licochalcone A and ω-6-fatty acids on both arms for further 3 weeks. The outcomes included reduction of the clinical and itch severity, decrease in S.aureus colonization, improvement of the barrier function, skin hydration and skin tolerability assessed after 1 week (D7) and after 4 weeks (D28) respectively.

Results

In both arms, there was a significant decrease in the severity score, itch intensity, erythema and TEWL on D7 and D28 compared to baseline. In addition, emollient use resulted in pronounced decrease in S.aureus colonization and significant increase of skin hydration on D7. The comparison of the outcomes, based on percentage change from baseline, showed no significant differences between the emollient and HC arm at any time point.

Conclusions

The results of the study indicate that the 1-week stand-alone application of an emollient, tailored to target inflammation, pruritus, compromised barrier function and pathogenic bacterial colonization may offer benefit for the improvement of mild to moderately severe localized flares of AD.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. References

Atopic dermatitis (AD) is a chronic, relapsing and intensely pruritic inflammatory skin disease in result of a complex interplay of genetic, immunologic and environmental factors.[1-3] The disease occurs most frequently in infancy or early childhood and may persist throughout life in up to 40–60% of the cases. AD causes substantial physical and psychological discomfort for the patients and the affected families and may have considerable negative impact on life quality.[4]

The management of AD requires efficient control of the flares by treatment of the acute inflammatory symptoms along with restoration of the skin barrier homeostasis and avoidance of the relevant triggering or disease-aggravating factors.[5] Topical steroids and immunomodulators are first-line treatment of the disease flares, whereas the long-term management is based on the use of emollients that aim to improve skin hydration, maintain the barrier integrity, relieve pruritus and prevent new flares.[6-8] Although independent lines of research suggest that the use of emollients may result in enhanced therapeutic responses and improved outcomes, so far there has been limited evidenced-based proof concerning the stand-alone efficacy of emollients in acute stage of disease.[5, 6, 9] Therefore, in the present study, we investigated the effects of an o/w formulation containing licochalcone A (Glycyrrhiza Inflata root extract), decanediol (decylene glycol), menthoxypropanediol and ω-6-fatty acids with regard to reduction of the lesional severity, pruritus relief, improvement of the skin barrier function and reduction in pathogenic bacterial colonization in AD patients with mild to moderately severe disease flare.

Materials and methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. References

Study population

Twenty volunteers with mild to moderately severe AD aged 12–65 years (16 female and 4 male; median age 26.2 years), meeting the UK Working Party Criteria were enrolled in the study.[10] The inclusion criteria were defined as follows: (1) Presence of at least two inflammatory lesions of comparable clinical severity symmetrically on the forearms/arms; and (2) SCORAD intensity parameters (local SCORAD) in the test area greater than 4 and no greater than 8. Volunteers with SCORAD intensity parameters in the test area lesser than 4 and greater than 8 or with severe forms of AD as well as history for other skin or systemic diseases were not considered eligible for participation. The exclusion criteria were further defined as follows: (1) Treatment with topical or systemic corticosteroids, immunosuppressive agents, UV-light as well as topical or systemic antimicrobial agents in the last 2 weeks preceding the study; (2) Previously known or suspected delayed-type sensitization; (3) Pregnancy or lactation and (4) Participation in another study within the preceding 4 weeks.

The protocol was approved by the Ethics Committee of the University of Lübeck (Nr. 08-228). The study was performed according to the principles of the Declaration of Helsinki and all participants gave written informed consent/assent beforehand.

Study design

The study was a 4-week, prospective, randomized, investigator-blinded, controlled half-side comparison test. On recruitment, the forearms/arms of each volunteer were randomized to receive within the first week either an o/w formulation containing licochalcone A, decanediol, menthoxypropanediol and ω-6-fatty acids (AC formulation; study arm, respectively, further referred to as AC-AL or emollient arm) or 1% hydrocortisone (HC; study arm further referred to as HC-AL or hydrocortisone arm). After 1 week, the application of the AC formulation and HC were discontinued and the volunteers were asked to apply a w/o emollient containing licochalcone A and ω-6-fatty acids (referred to as AL) on both forearms/arms twice daily for further 3 weeks (Fig. 1). Monitoring of the outcome parameters was performed at baseline (D0), after 1 week (D7) and after 4 weeks (D28).

image

Figure 1. Study flow chart.

Download figure to PowerPoint

Outcomes and methods of assessment

The outcomes included reduction of the lesional severity and itch intensity, improvement of the skin barrier function, assessed by the changes in transepidermal water loss (TEWL) and stratum corneum hydration (capacitance), reduction in the lesional skin colonization with S.aureus and skin tolerability.

Clinical severity scoring and itch severity assessment

The clinical severity scoring was performed by assessment of the SCORAD intensity parameters in the test area (local SCORAD) taking into consideration the presence of erythema, exsudation, papulation, excoriations, lichenification and skin dryness on a 0–3 scale as previously described.[11]

The itch intensity was assessed by the volunteers using a visual analogue scale from 0 (no perceptible itch in the test area) to 10 (worst imaginable itch).

Assessment of erythema and skin barrier function

The non-invasive assessment of erythema, TEWL and skin hydration was performed on the volar surface of the forearms/arms. Erythema was measured with the skin Colorimeter CL400 and expressed in the L*a*b* system. TEWL was measured with the open chamber system (Tewameter TM300) and skin hydration was assessed by measuring capacitance (Corneometer CM825), all devices from Courage and Khazaka Electronics (Cologne, Germany). The assessment of erythema and TEWL was based on the average value of three consecutive measurements per field performed by the same observer; the assessment of skin hydration was based on the average value of five consecutive measurements per field. All measurements were performed under controlled environmental conditions (room temperature 20 ± 2°C; average relative humidity 40–45%) and according to the published guidelines.[12-16]

Quantification of lesional skin S.aureus colonization density

The assessment of lesional skin S.aureus colonization was performed according to a previously validated and published protocol.[17] The samples were collected by gently rubbing the skin with 1 mL eluant buffer solution for 1 min with the help of a teflon ring and spatula. After transferring the sample into 2 mL sterile Eppendorf tubes (Eppendorf, Hamburg, Germany), 100 μL of the original suspension as well as 1:10 and 1:100 dilutions of the same were plated in duplicate on RAPID-Staph agar (Bio-Rad, Munich, Germany) and the colonies were counted after 48-h cultivation at 37°C and 5% CO2.

Statistical analysis

Statistical analysis was performed using GraphPrism Version 4 (GraphPad Software Inc, San Diego, CA, USA). A P-value <0.05 was considered statistically significant. The changes in the severity score, pruritus intensity, erythema (a*-value), TEWL, capacitance and S.aureus counts for each study arm over time were analysed by repeated measures anova or Friedmann test for the respective parameter; for P-values less than 0.05 a post hoc test was performed. The differences between the study arms at baseline, after 1 week and after 4 weeks were analysed by unpaired t-test or Mann–Whitney test. In the respective tables and figures, the values are expressed as mean and standard error (SEM), except for the clinical severity score and itch intensity, expressed as median and interquartile range.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. References

Eighteen volunteers (14 female and 4 male, median age 26.5 years; median total SCORAD at inclusion 31.0) completed the study per protocol. Two volunteers were excluded from further participation within, respectively, the second and fourth study week because of worsening of the skin condition outside the test area that required topical treatment.

Significant reduction of the clinical severity score and itch intensity in result of stand-alone emollient use

The clinical severity score and itch intensity assessment at baseline (D0), after 1 week (D7) and after 4 weeks (D28) are presented in Table 1a.

Table 1. Clinical and non-invasive bioengineering assessment at baseline (D0), after 1 week (D7) and after 4 weeks (D28): (a) SCORAD intensity parameters (local SCORAD) and itch severity in the test area (median and interquartile range); (b) Lesional skin erythema (a*-value), transepidermal water loss (TEWL) and capacitance (mean ± SEM; n = 18).
(a)
 D0D7D28
Local SCORAD
AC-AL7.0 (5.0–8.0)3.5 (1.5–6.5)**4.0 (2.0–6.5)**
HC-AL6.5 (4.0–8.0)3.0 (2.0–4.5)***4.25 (2.5–6.0)**
Itch severity (VAS 0–10)
AC-AL3.5 (2.0–5.75)1.75 (0.0–4.0)**1.75 (0.0–3.5)**
HC-AL3.75 (2.25–5.25)1.0 (0.0–2.0)***1.5 (0.0–3.5)*
(b)
 D0D7D28
  1. *< 0.05, **< 0.01, ***< 0.001.

    Level of significance <0.05, compared to baseline.

    AC-AL-emollient arm; HC-AL-hydrocortisone arm; VAS-visual analogue scale; AU-arbitrary units.

a*-value/AU/
AC-AL16.47 ± 0.7114.73 ± 0.66*14.52 ± 0.64**
HC-AL16.28 ± 0.7513.71 ± 0.51**14.38 ± 0.64*
TEWL/g/m2/h/
AC-AL31.32 ± 3.5421.40 ± 3.09*20.45 ± 2.52**
HC-AL26.63 ± 2.7014.20 ± 0.85***21.24 ± 3.06*
Capacitance/AU/
AC-AL20.86 ± 2.5329.10 ± 3.97*27.44 ± 3.40
HC-AL22.40 ± 2.4524.56 ± 3.3828.38 ± 3.94

At the beginning of the study, there were no significant differences in the severity score between the study arms. The application of AC and HC within the first study week resulted in improvement of the skin condition in the test area (Fig. 2); on D7 the local SCORAD was significantly reduced compared to baseline (for arm AC-AL and HC-AL, respectively, < 0.01 and < 0.001). At the end of the study (D28), the severity score was still significantly decreased compared to baseline in both arms (< 0.01 for both, arm AC-AL and HC-AL). The reduction in the local SCORAD on D7 was −37.39% and −45.5% from baseline for, respectively, the emollient and HC arm; on D28, respectively, −31.74% and −31.98% (Fig. 3a). The differences between the study arms with regard to percentage change were not significant.

image

Figure 2. Clinical photographs of the test area at baseline (D0), after 1 week (D7) and after 4 weeks (D28): AC-AL-emollient arm; HC-AL-hydrocortisone arm.

Download figure to PowerPoint

image

Figure 3. Comparison of the outcomes, assessed as percentage change from baseline: (a) Clinical severity in the test area (local SCORAD); (b) Itch intensity. Mean ± SEM, normalized data (n = 18); AC-AL-emollient arm, HC-AL-hydrocortisone arm, VAS-visual analogue scale.

Download figure to PowerPoint

The assessment of itch intensity showed significant reduction in the visual analogue scale values for both study arms on D7 and D28 compared to baseline (Table 1a); on D28 there was no significant difference with regard to the outcome between the emollient and HC arm (Fig. 3b).

Significant decrease of erythema and TEWL as well as increase of skin hydration following stand-alone emollient application

The results from the non-invasive measurements of erythema (a*-value), TEWL and capacitance on D0, D7 and D28 are presented in Table 1b. At baseline, there were no significant differences in the measured parameters between the study arms.

The mean a*-values at the beginning of the study were 16.47 ± 0.71 and 16.28 ± 0.75 AU for, respectively, arm AC-AL and HC-AL. On D7 and D28, the a*-values were significantly reduced compared to baseline for both study arms (AC-AL:14.73 ± 0.66 and 14.52 ± 0.64 AU, respectively, < 0.05 and < 0.01 compared to D0; HC-AL: 13.71 ± 0.51 and 14.38 ± 0.64 AU, respectively, < 0.01 and < 0.05). The differences between the study arms assessed as percentage change from baseline on D7 and D28 were not significant (data not shown).

For both study arms, on D7 there was significant decrease in TEWL compared to baseline (AC-AL: on D0 and D7, 31.32 ± 3.54 and 21.40 ± 3.09 g/m2/h, < 0.05; HC-AL, respectively, 26.63 ± 2.70 and 14.20 ± 0.85 g/m2/h, < 0.001). On D28, the mean TEWL values for both arms were still significantly reduced compared to D0 (D28: arm AC-AL and HC-AL, 20.45 ± 2.52 and 21.24 ± 3.06 g/m2/h, respectively, < 0.01 and < 0.05 compared to D0; Fig. 4a). The comparison of TEWL assessed as percentage change from baseline throughout the study showed no significant differences between the study arms (Fig. 4b).

image

Figure 4. (a) Significant reduction in transepidermal water loss (TEWL) in the emollient as well as hydrocortisone arm after 1 week (D7) and after 4 weeks (D28) compared to baseline (D0). (b) Comparison of the outcomes, assessed as percentage change of baseline. Mean ± SEM (n = 18); level of significance <0.05, *P < 0.05, **P < 0.01, ***P < 0.001. AC-o/w formulation containing licochalcone A (Glycyrrhiza Inflata root extract), decanediol, menthoxypropanediol and ω-6-fatty acids, HC-1% hydrocortisone, AL-w/o formulation containing licochalcone A and ω-6-fatty acids.

Download figure to PowerPoint

The changes in skin hydration (capacitance) are shown in Fig. 5. The application of the emollient within the first study week resulted in significant increase in capacitance on D7 compared to baseline (D0 and D7, respectively, 20.86 ± 2.53 and 29.10 ± 3.97 AU, < 0.05), whereas the changes in the HC arm were not significant (D0: 22.40 ± 2.45 AU, D7: 24.56 ± 3.38 AU; > 0.05).

image

Figure 5. Skin hydration: significant increase in capacitance in the emollient arm on D7 compared to D0. Mean ± SEM (n = 18); level of significance <0.05, *P < 0.05. AC-o/w formulation containing licochalcone A (Glycyrrhiza Inflata root extract), decanediol, menthoxypropanediol and ω-6-fatty acids, HC-1% hydrocortisone, AL-w/o formulation containing licochalcone A and ω-6-fatty acids, AU-arbitrary units.

Download figure to PowerPoint

Reduced colonization of the skin lesions with S.aureus

The quantitative analysis of lesional skin S.aureus colonization throughout the study showed pronounced and consistent reduction in the bacterial counts on the emollient (AC-AL) arm (Fig. 6).

image

Figure 6. Lesional skin S.aureus colonization density at baseline (D0), after 1 week (D7) and after 4 weeks (D28). Mean ± SEM; level of significance <0.05. AC-AL-emollient arm, HC-AL-hydrocortisone arm.

Download figure to PowerPoint

Skin tolerability and amount of used steroid

The skin tolerability assessment data based on the reported subjective symptoms throughout the study are presented in Table 2. The average amount of used HC within the first study week was 6.03 g per volunteer.

Table 2. Skin tolerability assessment: Percentage (number) of volunteers reporting the respective symptom using a standardized questionnaire. AC-o/w formulation containing licochalcone A (Glycyrrhiza Inflata root extract), decanediol, menthoxypropanediol and ω-6-fatty acids, HC-1% hydrocortisone, AL- w/o formulation containing licochalcone A and ω-6-fatty acids; conform with the application, the data for AC and HC refer to D7 and for AL to D28 (n = 18)
SymptomACHCAL
Erythema5.6% (1/18)5.6% (1/18)0.0% (0/18)
Scaling0.0% (0/18)5.6% (1/18)0.0% (0/18)
Skin dryness5.6% (1/18)5.6% (1/18)0.0% (0/18)
Burning11.1% (2/18)16.7% (3/18)5.6% (1/18)
Stinging0.0% (0/18)0.0% (0/18)0.0% (0/18)
Skin tightness5.6% (1/18)5.6% (1/18)0.0% (0/18)
Itch22.2% (4/18)11.1% (2/18)5.6% (1/18)
Other0.0% (0/18)0.0% (0/18)5.6% (1/18)

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. References

In the present study, we have shown that the stand-alone application of an emollient, tailored to target inflammation, pruritus, compromised barrier function and pathogenic bacterial colonization is an efficient and safe approach for improvement of mild to moderately severe AD flares. As 1% HC, the 1-week twice daily application of AC lead to significant reduction in the severity of signs and symptoms, improvement of the skin barrier function and decrease in lesional skin S.aureus colonization density. There were no significant differences with respect to the time frame and the scale of exerted effects between the study arms; in addition to the efficacy of AC, the findings for comparable outcomes between the emollient (AC-AL) and hydrocortisone (HC-AL) arm at the end of the study suggest the steroid-sparing potential of the emollient regimen.

The efficacy of licochalcone A for improvement of the clinical manifestations of AD has been initially suggested by the findings of a controlled, randomized, investigator-blinded study in children with mild to moderately severe disease that showed significant reduction in SCORAD and lack of significant differences in the outcomes after 6-week twice daily application of a licochalcone A-based emollient compared to 1% HC.[18]

Licochalcone A is a reversely constructed chalcone specific for the Xynjiang licorice root Glycyrrhiza inflata, used in cosmetic formulations due to its potent anti-inflammatory and antioxidative properties.[19-21] Experimental studies have shown that licochalcone A-rich extracts from G. inflata and synthetic licochalcone A suppress the production of pro-inflammatory mediators and cytokines such as PGE2, LTB4, IL-6 and TNF-α in in vitro systems relevant to the skin such as dermal fibroblasts, granulocytes, dendritic cells and human skin equivalents.[22-24] The in vitro findings have been further confirmed by in vivo studies showing the efficacy of licochalcone A-containing formulations for reducing experimentally induced erythema, improvement of the inflammatory signs in patients with rosacea and recently – in mild to moderately severe inflammatory forms of acne.[24-26] The findings of the present study extend these observations and provide new evidence for the anti-inflammatory effects of licochalcone A in mild to moderately severe AD, on the basis of clinical assessment and non-invasive skin bioengineering methods.

Pruritus is a major diagnostic criterion and a cardinal symptom of AD.[10, 27, 28] Though the first-line anti-inflammatory agents such as topical steroids and calcineurin inhibitors are known to induce short-term improvement, the achievement of lasting relief is a challenge and a most important goal in disease management.[29, 30] The pathogenesis of itch related to AD involves numerous factors within the skin, nervous system and the environment and recent advances indicate a critical role for different thermosensitive members of the transient receptor potential (TRP) ion channels superfamily in the transmission and modulation of itch.[31-34] Independent lines of research provide evidence that both the generation and the alleviation of itch is temperature-dependent. Skin cooling and topical application of substances that induce a cooling sensation upon contact with the skin and mucosae such as menthol, eucalyptol or icilin have been shown to mitigate experimentally induced and disease-related itch.[34-37] The cooling sensation has been further shown to be mediated by the activation of TRPM8, a thermosensitive calcium-permeable channel expressed in the sensory neurons and activated by temperatures ≤28°C as well as cooling agents suggesting that TRPM8 may be a novel pharmacological target for the management of itch.[32, 34, 38-41] The findings of the study are consistent with this concept and provide initial in vivo evidence for pruritus relief in result of the use of an emollient containing methoxypropanediol, a TRPM8 agonist, in atopic skin.

A strong line of publications shows the positive correlation between S.aureus colonization density and AD severity.[42-44] Atopic skin provides a favourable environment for increased S.aureus adherence and proliferation attributed to distinct, interrelated pathomechanisms including compromised barrier integrity, altered sphingolipid metabolism[45-49] and expression of antimicrobial peptides,[50] upregulation of extracellular matrix adhesins[51, 52] as well as enhanced pathogen binding to areas of Th2-mediated inflammation.[44, 53] Earlier publications indicate that 30–60% of the S.aureus strains isolated from AD patients produce exotoxins with superantigen properties that exert potent disease-promoting effects while at the same time, contribute to induction of corticosteroid resistance and alter the therapeutic responses.[54-57]

In view of the relevance of S.aureus colonization for disease exacerbation and chronicity, the reduction in the bacterial density in result of emollient use is an important finding of our study. In addition to direct S.aureus targeting by decanediol, the active antimicrobial component of the AC formulation, the observed effects may have been further enhanced by the improvement of the compromised barrier conditions through reduction in the lesional severity, decrease in TEWL and increase in skin hydration.[58]

In the present investigation, HC was used as a reference for the effects exerted by the o/w formulation with respect to clinical outcomes, barrier function and pathogenic bacterial colonization. Independently of the study design, the formulation is in a strict sense an emollient and therefore, not meant as alternative to first-line topical medications intended to treat AD. The presented results, however, provide proof-of-principle that the stand-alone use of emollients may offer benefit from a clinical, laboratory and patient's perspective and exert a steroid-sparing effect that would equal the amount of used HC.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. References