Abstract
The Gram-positive bacterium Cutibacterium acnes (previously Propionibacterium acnes), plays an important role in the pathogenesis and progression of the dermatological skin disorder acne vulgaris. The methanolic extract of Helichrysum odoratissimum (L.) Sweet (HO-MeOH) was investigated for its ability to target bacterial growth and pathogenic virulence factors associated with acne progression. The gas chromatography–mass spectrometry (GC-MS) analysis of HO-MeOH identified α-humulene (3.94%), α-curcumene (3.74%), and caryophyllene (8.12%) as major constituents, which correlated with previous reports of other Helichrysum species. The HO-MeOH extract exhibited potent antimicrobial activity against C. acnes (ATCC 6919) with a minimum inhibitory concentration (MIC) of 7.81 µg/ml. It enhanced the antimicrobial activity of benzoyl peroxide (BPO). The extract showed high specificity against C. acnes cell aggregation at sub-inhibitory concentrations, preventing biofilm formation. Mature C. acnes biofilms were disrupted at a sub-inhibitory concentration of 3.91 µg/ml. At 100 µg/ml, HO-MeOH reduced interleukin-1α (IL-1α) cytokine levels in C. acnes-induced human keratinocytes (HaCaT) by 11.08%, highlighting its potential as a comedolytic agent for the treatment of comedonal acne. The extract exhibited a 50% inhibitory concentration (IC50) of 157.50 µg/ml against lipase enzyme activity, an enzyme responsible for sebum degradation, ultimately causing inflammation. The extract’s anti-inflammatory activity was tested against various targets associated with inflammatory activation by the bacterium. The extract inhibited pro-inflammatory cytokine levels of IL-8 by 48.31% when compared to C. acnes-induced HaCaT cells at 7.81 µg/ml. It exhibited cyclooxygenase-II (COX-II) enzyme inhibition with an IC50 of 22.87 µg/ml. Intracellular nitric oxide (NO) was inhibited by 40.39% at 7.81 µg/ml when compared with NO production in lipopolysaccharide (LPS)-induced RAW264.7 cells. The intracellular NO inhibition was potentially due to the 2.14 fold reduction of inducible nitric oxide synthase (iNOS) gene expression. The HO-MeOH extract exhibited an IC50 of 145.45 µg/ml against virulent hyaluronidase enzyme activity, which is responsible for hyaluronan degradation and scar formation. This study provides scientific validation for the traditional use of H. odoratissimum as an ointment for pimples, not only due to its ability to control C. acnes proliferation but also due to its inhibitory activity on various targets associated with bacterial virulence leading to acne progression.
Highlights
Acne vulgaris (AV) is a chronic inflammatory skin disorder of the pilosebaceous, localized on the face, chest, and back
This study provides scientific validation for the traditional use of H. odoratissimum as a possible treatment for acne, based on direct antimicrobial effects as well as the inhibition of key targets in the pathogenic processes associated with the opportunistic pathogen, C. acnes in the progression of this skin disorder
The study identified the potent antimicrobial activity of the methanolic extract of H. odoratissimum against C. acnes and the anti-biofilm activity of this extract affecting the initial step of bacterial adhesion
Summary
Acne vulgaris (AV) is a chronic inflammatory skin disorder of the pilosebaceous, localized on the face, chest, and back. Glycerol is used as a nutrient source for the C. acnes bacterium, and the free fatty acids arrange themselves between keratinocytes, increasing bacterial cell adhesion, and enhancing biofilm formation within the pilosebaceous unit (Falcocchio et al, 2006). It is, an important target to consider when testing extracts or compounds for anti-acne activity. C. acnes results in the production of nitric oxide (NO) through chemotaxis and activation of neutrophil cells These increased levels of NO production within the pilosebaceous follicles causes irritation and rupture of the follicular wall, leading to the formation of inflammatory lesions (Portugal et al, 2007). Hyaluronidases act by completely degrading HA into disaccharides or by degradation
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