Abnormal Glucocorticoid Synthesis in the Lesional Skin of Erythematotelangiectatic Rosacea

Which factors influence Demodex proliferation? A retrospective pilot study highlighting a possible role of subtle immune variations and sebaceous gland status

Demodex folliculorum and brevis are commensal mites that live in low densities in human pilosebaceous follicles as part of the normal adult microbiota, but that give rise to demodicosis and, possibly, rosacea, when they proliferate excessively. This proliferation is favored by various factors, including age, marked immunosuppression, sebaceous gland hyperplasia, and hypervascularization-related factors. To study possible factors influencing mite proliferation, we explored the effects of different variables on Demodex densities (Dd) in a retrospective study of two groups of subjects selected on the basis of their clinical diagnosis: Demodex+, consisting of subjects with demodicosis or with centro-facial papulopustules suggesting rosacea (n = 844, mean Dd 263.5 ± 8.9 D/cm² ), and Demodex-, consisting of subjects with other facial dermatoses or healthy facial skin (n = 200, mean Dd 2.3 ± 0.4 D/cm² ). Demodex densities were measured using two consecutive standardized skin surface biopsies (SSSB1 [superficial] and SSSB2 [deep]) taken from the same facial site on each subject. In the Demodex+ group: the SSSB1 decreased with age in women (p = 0.004), and the SSSB2 increased with age in men (p = 0.001) (the pattern was similar for SSSB1 + 2, but not statistically significant); Dds were lower in those who had received cortisone (either topically or systemically); 13 subjects (1.5%) had known immunosuppression, 62 (7.3%) had hypothyroidism, and in 20 (3.6% of the women) there was a reported link with pregnancy; 78 of the subjects (9.2%) were part of a pair from the same family or household; when associated bacterial infection was suspected, Staphylococcus epidermidis was often isolated. Our results suggest close interactions between the mite, sebaceous gland size and function, and subtle variations of immune status. Potential factors influencing Demodex proliferation should be further investigated, including hypothyroidism, pregnancy, corticosteroid administration, Staphylococcus epidermidis, contagiousity, and genetic background.

The Pathogenic Role of Demodex Mites in Rosacea: A Potential Therapeutic Target Already in Erythematotelangiectatic Rosacea?

Rosacea is a common facial dermatosis but its definition and classification are still unclear, especially in terms of its links with demodicosis. Triggers of rosacea (ultraviolet light, heat, spicy foods, alcohol, stress, microbes) are currently considered to induce a cascading innate and then adaptive immune response that gets out of control. Recent histological and biochemical studies support the concept that this inflammatory response is a continuum, already present from the onset of the disease, even when no clinical signs of inflammation are visible. The Demodex mite is beginning to be accepted as one of the triggers of this inflammatory cascade, and its proliferation as a marker of rosacea; moreover, the papulopustules of rosacea can be effectively treated with topical acaricidal agents. Demodex proliferation appears to be a continuum process in rosacea, and may not be clinically visible at the onset of the disease. Molecular studies suggest that Demodex may induce tolerogenic dendritic cells and collaborate with vascular endothelial growth factor (VEGF) to induce T cell exhaustion and favor its own proliferation. These interactions among VEGF, Demodex, and immunity need to be explored further and the nosology of rosacea adapted accordingly. However, treating early rosacea, with only clinically visible vascular symptoms, with an acaricide may decrease early inflammation, limit potential flare-ups following laser treatment, and prevent the ultimate development of the papulopustules of rosacea. The effectiveness of this approach needs to be confirmed by prospective controlled clinical trials with long-term follow-up. Currently, the evidence suggests that patients with only vascular symptoms of rosacea should be carefully examined for the presence of follicular scales as signs of Demodex overgrowth or pityriasis folliculorum so that these patients, at least, can be treated early with an acaricidal cream.

TLR3 augments glucocorticoid-synthetic enzymes expression in epidermal keratinocytes; Implications of glucocorticoid metabolism in rosacea epidermis

BACKGROUND

While most skin diseases benefit from topical steroids, rosacea symptoms are exacerbated by topical steroids. In the rosacea pathogenesis, abnormal innate immune mechanisms including overexpression of the Toll-like receptor (TLR) have been proposed. However, the links between glucocorticoid metabolism and innate immunity in the epidermis have not been elucidated.

OBJECTIVE

In order to understand the pathology by which rosacea symptoms are exacerbated by steroids and environment stimuli, we examined the molecular links between the innate immune system and glucocorticoid synthesis in epidermis.

METHODS

We examined the expression of glucocorticoid-synthetic enzymes in rosacea skin. We stimulated epidermal keratinocytes by TLR ligands and examined the regulation of glucocorticoid-synthetic enzymes. We also employed siRNA and adenovirus vectors to knockdown and transduce TLR molecules, respectively.

RESULTS

Rosacea epidermis showed high HSD11B1 in the granular layer. Among TLR ligands, TLR3 ligand Poly(I:C) enhanced the expression of multiple glucocorticoid-synthetic enzymes including HSD11B1 and CYP11A1, and increased cortisol in the cultured media. Induction of HSD11B1 by Poly(I:C) was abolished by pretreatment with TLR3 siRNA. Transfection with an adenoviral vector incorporating TLR3 enhanced HSD11B1 and CYP11A1 protein expression by Poly(I:C). In addition, cell staining revealed increased expression of HSD11B1 and CYP11A1 proteins in the group transfected with TLR3 under the same conditions.

CONCLUSION

TLR3-stimulated epidermal keratinocytes and rosacea epidermis enhance the expression of glucocorticoid-synthetic enzymes, which would promote cortisol activation in the epidermis. The innate immunity modulates glucocorticoid-synthetic enzymes expression via the TLR3 pathway in epidermal keratinocytes.