antimicrobial peptide

Antimicrobial peptide can reduce acne infection in mice


Chances are you have experienced some form of acne, or know someone who has.   Also known as Propionibacterium acnes (P. acnes), these gram-positive bacteria drive the pathogenesis of what we commonly refer to as acne.  The bacteria aggregate in high numbers on the skin in areas such as hair follicles.  When bacteria density gets too high, the innate immune system reacts, resulting in a battery of proinflammatory signals and/or reactions.  Current treatments include both topical and oral antibiotics, but these therapies collectively have shown minimal efficacy at the expense of some side effects.  A recent study conducted by researchers from South Korea and Denver sought to explore the use of a novel and custom made antimicrobial peptide (AMPs) called P5.  AMPs have been previously shown to effectively kill bacterial pathogens while at the same time modulating host immunity.  The aim was to see if this tiny cationic peptide sequence could protect against P. acnes induced immune responses both in vitro and in vivo, and therefore present itself as a potential novel acne treatment. 

The researchers first demonstrated that P5 had antibacterial effects in vitro (administering the peptide to bacteria culture dishes).  In a follow-up in vitro experiment, P5 was shown to disrupt the morphology P. acnes, as displayed by scanning electron microscopy images.  P5 was also able to inhibit proinflammatory signals brought on by P. acnes, including reductions in cytokine signaling and toll-like receptor expression in human skin cells.  Furthermore, P5 reduced the expression of a gene responsible for regulating transcription of these inflammatory signals. 

In the in vivo experiments, mice were inoculated with P. acnes and split into two groups, either receiving the P5 AMP or a vehicle control intradermally (in the skin).  P. acnes growth was visibly reduced in the ears of mice when administered P5.  To demonstrate the effective quantitatively, the researchers measured ear thickness to record differences in swelling.  P5 was able to significantly reduced ear thickness in P. acnes mice that had been given P5.  Importantly, P5 alone– i.e., in mice without the P. acnes infection – did not have any effect on inflammation, suggesting the peptide’s role in modulating immunity specifically with P. acnes

Treating bacterial infections at the biological level using unique features of bacteria offers a promising technique to combat common maladies such as acne.  In fact, companies such as AOBiome are already utilizing unique methodologies, as their products are designed to help the skin microbiome.  In light of our previous discussions regarding misuse/overuse of antibiotics, this method could offer a much safer alternative toward treating acne.

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