Exploring the Anti-Acne Potential of Impepho [Helichrysum odoratissimum (L.) Sweet] to Combat Cutibacterium acnes Virulence

Abstract

The Gram-positive bacterium <i>Cutibacterium acnes</i> (previously <i>Propionibacterium acnes</i>), plays an important role in the pathogenesis and progression of the dermatological skin disorder acne vulgaris. The methanolic extract of <i>Helichrysum odoratissimum</i> (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 <i>α</i>-humulene (3.94%), <i>α</i>-curcumene (3.74%), and caryophyllene (8.12%) as major constituents, which correlated with previous reports of other <i>Helichrysum</i> species. The HO-MeOH extract exhibited potent antimicrobial activity against <i>C. acnes</i> (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 <i>C</i>. <i>acnes</i> cell aggregation at sub-inhibitory concentrations, preventing biofilm formation. Mature <i>C</i>. <i>acnes</i> 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 <i>C</i>. <i>acnes</i>-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 <i>C</i>. <i>acnes</i>-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 <i>H. odoratissimum</i> as an ointment for pimples, not only due to its ability to control <i>C</i>. <i>acnes</i> proliferation but also due to its inhibitory activity on various targets associated with bacterial virulence leading to acne progression.