Human skin buffering capacity: an overview

Levin, Jacquelyn; Maibach, Howard I.

doi:10.1111/j.1600-0846.2007.00271.x

Cited by 59 publications

(50 citation statements)

References 34 publications

(75 reference statements)

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“…aureus (7, 9). It is well established that the pH of the skin is slightly acidic (34) and so the effect of pH on C6H sensitivity was tested (Fig. 1A).…”

Section: Resultsmentioning

confidence: 99%

Bactericidal Activity of the Human Skin Fatty Acid cis -6-Hexadecanoic Acid on Staphylococcus aureus

Cartron

England

Chiriac

et al. 2014

Antimicrob Agents Chemother

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Human skin fatty acids are a potent aspect of our innate defenses, giving surface protection against potentially invasive organisms. They provide an important parameter in determining the ecology of the skin microflora, and alterations can lead to increased colonization by pathogens such as Staphylococcus aureus. Harnessing skin fatty acids may also give a new avenue of exploration in the generation of control measures against drug-resistant organisms. Despite their importance, the mechanism(s) whereby skin fatty acids kill bacteria has remained largely elusive. Here, we describe an analysis of the bactericidal effects of the major human skin fatty acid cis-6-hexadecenoic acid (C6H) on the human commensal and pathogen S. aureus. Several C6H concentration-dependent mechanisms were found. At high concentrations, C6H swiftly kills cells associated with a general loss of membrane integrity. However, C6H still kills at lower concentrations, acting through disruption of the proton motive force, an increase in membrane fluidity, and its effects on electron transfer. The design of analogues with altered bactericidal effects has begun to determine the structural constraints on activity and paves the way for the rational design of new antistaphylococcal agents.

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“…aureus (7, 9). It is well established that the pH of the skin is slightly acidic (34) and so the effect of pH on C6H sensitivity was tested (Fig. 1A).…”

Section: Resultsmentioning

confidence: 99%

Bactericidal Activity of the Human Skin Fatty Acid cis -6-Hexadecanoic Acid on Staphylococcus aureus

Cartron

England

Chiriac

et al. 2014

Antimicrob Agents Chemother

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“…In postmenopausal compared with premenopausal woman the pH increased from 4.7 to 5.0. Well documented are an increased SC pH and a reduced buffer capacity in the elderly …”

Section: Ph Of the Healthy Skinmentioning

confidence: 99%

pH in nature, humans and skin

Proksch

2018

The Journal of Dermatology

393

273

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The pH plays an important physiological role in nature and humans. pH varies from 1 to 8 in human organs with tight regulation in blood and epithelia of barrier organs. The physiological pH of the stratum corneum is 4.1-5.8 and several mechanisms contribute to its formation: filaggrin degradation, fatty acid content, sodium-hydrogen exchanger (NHE1) activation and melanosome release. First, the acidic pH of the stratum corneum was considered to present an antimicrobial barrier preventing colonization (e.g. by Staphylococcus aureus and Malassezia). Later on, it was found that the pH influences skin barrier function, lipid synthesis and aggregation, epidermal differentiation and desquamation. Enzymes of ceramide metabolism (e.g. β-glucocerebrosidase or acid sphingomyelinase) as well as proteases (e.g. chymotryptic enzyme or cathepsin D linked to epidermal differentiation and desquamation) are regulated by the pH. Experimental disruption of the physical barrier leads to an increase of pH, returning to normal levels only after many hours. Inflammatory skin diseases and diseases with an involvement of the epidermis exhibit a disturbed skin barrier and an increased pH. This is known for atopic dermatitis, irritant contact dermatitis, ichthyosis, rosacea and acne, but also for aged and dry skin. Normalizing the pH by acidification through topical treatment helps to establish a physiological microbiota, to repair skin barrier, to induce epidermal differentiation and to reduce inflammation.

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“…The pH of the skin surface can range from 4.5 to 6.5, and the skin surface can contain a substantial amount of water (Fluhr et al, 2012). Lactic acid and amino acids can contribute to the buffering capacity (i.e., maintaining pH in a narrow range) of the surface of the skin (Levin and Maibach, 2008). Only the neutral form of nicotine readily passes through the stratum corneum; data from excised pig skin indicates monoprotonated nicotine passes through skin fifty times slower than neutral nicotine (Nair et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

Measurements of dermal uptake of nicotine directly from air and clothing

et al. 2016

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In this preliminary study, we have investigated whether dermal uptake of nicotine directly from air or indirectly from clothing can be a meaningful exposure pathway. Two participants wearing only shorts and a third participant wearing clean cotton clothes were exposed to environmental tobacco smoke (ETS), generated by mechanically “smoking” cigarettes, for three hours in a chamber while breathing clean air from head-enveloping hoods. The average nicotine concentration (420 μg/m3) was comparable to the highest levels reported for smoking sections of pubs. Urine samples were collected immediately before exposure and 60 hour post-exposure for bare-skinned participants. For the clothed participant, post-exposure urine samples were collected for 24 hour. This participant then entered the chamber for another three-hour exposure wearing a hood and clothes, including a shirt that had been exposed for five days to elevated nicotine levels. The urine samples were analyzed for nicotine and two metabolites—cotinine and 3OH-cotinine. Peak urinary cotinine and 3OH-cotinine concentrations for the bare-skinned participants were comparable to levels measured among non-smokers in hospitality environments before smoking bans. The amount of dermally absorbed nicotine for each bare-skinned participant was conservatively estimated at 570 μg, but may have been larger. For the participant wearing clean clothes, uptake was ~20 μg, and while wearing a shirt previously exposed to nicotine, uptake was ~80 μg. This study demonstrates meaningful dermal uptake of nicotine directly from air or from nicotine-exposed clothes. The findings are especially relevant for children in homes with smoking or vaping

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Human skin buffering capacity: an overview

Cited by 59 publications

References 34 publications

Bactericidal Activity of the Human Skin Fatty Acid cis -6-Hexadecanoic Acid on Staphylococcus aureus

Bactericidal Activity of the Human Skin Fatty Acid cis -6-Hexadecanoic Acid on Staphylococcus aureus

pH in nature, humans and skin

Measurements of dermal uptake of nicotine directly from air and clothing

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