The Effect of Myrtacine and Celastrol-Enriched Extract on Cutibacterium acnes Extracellular Vesicles

Commensal bacteria interact with each other and their environment, secreting anti-microbial peptides, bacteriocins, and extracellular vesicles (EVs). Cutibacterium acnes (C. acnes), a commensal bacterium that plays a major role in acne, is classified into different phylotypes (IA₁, IA₂, IB, IC, II, and III), where overabundance of phylotype IA₁ relative to other phylotypes is found in acne lesions. EVs secreted by C. acnes phylotype IA₁ extracted from an acne lesion were previously found to induce a pro-inflammatory response in skin models. Here, we investigated the effects of Myrtus communis extract (Myrtacine) and Celastrol-enriched extract (CEE), anti-inflammatory ingredients, alone or in combination, on cutaneous innate immunity induced by C. acnes IA₁ EVs.

This study was conducted under preventive and modulating conditions: Myrtacine alone, CEE alone, or in combination were added to the culture medium either prior to (preventive) or after (modulating) incubation with C. acnes IA₁ EVs from healthy and acne skin in immortalized keratinocytes (HaCaT) and human skin explants. Then, regulation of β-defensin 2 (hBD2), interleukin (IL)-6, IL-8, IL-17α, and IL-36ɣ was assessed.

Preventive and modulating applications of Myrtacine and CEE significantly reduced expression of the five immune markers induced specifically by EVs from acne-derived C. acnes IA₁.

Our results show that C. acnes EVs may be a target of Myrtacine and CEE. They can down-modulate the pro-inflammatory activity induced by EVs derived from C. acnes IA₁ from acne skin, showing the interest of these ingredients at both preventive and modulating levels in the treatment of inflammatory acne.