Study On The Effect And Mechanism Of APDD-A2 In The Treatment Of Drug-resistant Acne

Acne is a chronic bacterial sebaceous gland inflammatory disease that usually develops on the face and upper trunk(front chest and back)of teenagers.It is characterized by the formation of acne,papules,nodules,pustules and cysts,which account for 35% to 90% of puberty infected persons.Acne can generally be divided into two main categories:non-inflammatory acne(open and closed acne)and inflammatory acne(papules,pustules,nodules and cysts).The pathogenesis of acne mainly undergoes four main pathophysiological processes:(ⅰ)inflammation caused by the release of inflammatory mediators into the skin;(ⅱ)changes in the keratinization process leading to keratinization;(ⅲ)increased sebum production under the control of androgens and Change;(ⅳ)Follicular colonization of Propionibacterium acnes.Among them,the overgrowth of Propionibacterium acnes is widely regarded as a key factor in the formation of acne.Propionibacterium acnes is a facultative gram-positive anaerobic bacteria that mainly exists in the sebaceous glands of hair follicles.It is a normal parasitic bacteria of the skin,the most abundant in the sebaceous glands of hair follicles.Propionibacterium acnes is known for producing many virulence factors,including the release of pro-inflammatory cytokines such as IL-1β,IL-8 and TNF-α from monocytes and keratinocytes,which are the main causes of acne formation.Antimicrobial resistance is a growing risk to global public health.Due to the widespread use of antibiotics,acne treatment has developed resistance.Therefore,there is an urgent need to discover and develop new therapeutic drugs with new targets and unique mechanisms of action of drug-resistant pathogens.And antimicrobial peptides(AMPs)therapy has multiple advantages such as rapid killing of invading pathogens,low development trend of bacterial resistance,and enhancement of host immunity,which has become a new treatment method.In this study,the minimum inhibitory concentration(MIC)was used to determine the antibacterial activity of peptides against P.acnes.It was observed that APDD-A2 has the best antibacterial effect on P.acnes and drug-resistant P.acnes,with a MIC value of 8μg /mL,the MIC values for Staphylococcus aureus and Bacillus subtilis are 32μg/mL and64μg/mL,respectively.The time-killing curve and dose-response curve of APDD-A2 were measured by the colony counting method,and it was found that the killing speed of APDD-A2 was better than clindamycin and was dose-dependent.Scanning electron microscopy and nucleic acid leakage experiments are used to explore the mode of action of P.acnes.The leakage of nucleic acid and the rupture of cell membranes can be observed.Therefore,the mode of action of APDD-A2 is to interfere with the integrity of the bacteria,thereby impairing permeability and Lead to leakage of bacterial contents.Further explore the stability and toxicity of APDD-A2 to determine the possibility of its preparation.APDD-A2 maintains a high degree of stability in 4-37℃,pH1-pH7 and acetonitrile,with little degradation.The CCK-8 method was used to evaluate the cytotoxicity of APDD-A2 to HaCaT and RAW264.7 cells,and it was found that its cytotoxicity and hemolytic activity were high(32μg/mL).Subsequent in vivo mouse LD50 experiments of the peptide were carried out to verify the toxicity of the peptide.80 mg/kg APDD-A2 was injected intraperitoneally,and the mice did not die.The ears of mice were injected with P.acnes and drug-resistant P.acnes to construct an animal model to evaluate the antimicrobial activity of APDD-A2 in vivo.It was found by HE staining that no swelling was observed in the ears of mice injected with PBS only,and erythema and swelling of the mouse ear skin were observed 8 hours after the injection of P.acnes.After using APDD-A2 on the upper epidermis of mouse ears,P.acnes-induced infiltrating inflammatory cells and a decrease in inflammation were observed.In summary,APDD-A2 has anti-drug-resistant P.acnes activity and has great potential for development.At the same time,it is also a clinical treatment for various skins caused by the widespread use of antibiotics to produce drug-resistant P.acnes.Illness provides an effective choice.