powerpoint presentation · erythrasma - c. minutissimum trichomycosis - c. tenuis
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Structure and Function of the Skin:
Cancer, Immunity and Inflammation
The Cutaneous Microbiome
Heidi H. Kong, MD, MHSc, FAAD
Dermatology Branch
DISCLOSURE OF RELATIONSHIPS WITH INDUSTRY
Heidi H Kong, MD, MHSc, FAAD
C010: Structure and Function of the Skin: Cancer, Immunity and
Inflammation
The Cutaneous Microbiome
DISCLOSURES
No relevant conflicts to disclose
The Skin Microbiome
Complex host-microbial interactions
Host
Host defense
e.g. AMPs
Microbes
Commensal/Pathogen
Culturing/Sequencing
Skin
Microbes
Host
The Skin Microbiome
Skin
Microbes
Host
Physiology
Cornified keratinocytes
Temperature, pH, lipids
Immunology
Adaptive
Innate Toll-like receptors,
Antimicrobial peptides, etc.
Jalian, HR and Kim, J. 2008. Chapter 9 “Antimicrobial Peptides” In: Gaspari, AA, Tyring, SK, eds. Clinical and Basic
Immunodermatology. Guildford, United Kingdom: Springer (London).
Antimicrobial peptides
1200+ identified
Widespread distribution (plants & animals)
Ancient lineage
Broad spectrum
Grouped based on amino acid
composition (10-50 a.a.), size,
conformational structure
Antimicrobial peptides
Proposed Mechanism of action:
Cationic antimicrobial peptides associate with
negatively charged bacterial membrane
Leads to pores in the microbial membrane with
subsequent osmotic lysis and microbial cell deathJalian, HR and Kim, J. 2008. Chapter 9 “Antimicrobial Peptides” In: Gaspari, AA, Tyring, SK, eds. Clinical and Basic
Immunodermatology. Guildford, United Kingdom: Springer (London).
Ganz T. 2003. Nat Rev Immunol 3, 710-720.
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Jalian, HR and Kim, J. 2008. Chapter 9 “Antimicrobial Peptides” In: Gaspari, AA, Tyring, SK, eds. Clinical and Basic
Immunodermatology. Guildford, United Kingdom: Springer (London).
Many antimicrobial peptides have chemotactic properties
Jalian, HR and Kim, J. 2008. Chapter 9 “Antimicrobial Peptides” In: Gaspari, AA, Tyring, SK, eds. Clinical and Basic
Immunodermatology. Guildford, United Kingdom: Springer (London).
LL-37 (in blue) is found in keratinocytes, follicular epithelium, eccrine glands and neutrophils.
Granulysin (in yellow) is produced predominantly by T cells
LL-37 (cathelicidin) and granulysin expression in skin
LL-37:
- Chemotaxis
- Angiogenesis
- Wound healing
Granulysin:
- Chemotaxis
- Cytotoxic to tumor
cells
- Anti-inflammatory
- Graft rejection
Jalian, HR and Kim, J. 2008. Chapter 9 “Antimicrobial Peptides” In: Gaspari, AA, Tyring, SK, eds. Clinical and Basic
Immunodermatology. Guildford, United Kingdom: Springer (London).
• HNPs (in tan) are found in azurophilic granules of neutrophils
• HBDs (in magenta) are produced by keratinocytes and macrophages
HNPs (Human neutrophil peptides [α-defensins]) and HBD
(human β-defensin) expression in skin
HNPs:
- Increase TNFα & IL-1
in S. aureus activated
monocytes
HBD:
- Chemotaxis of T
cells & dendritic cells
- hBD-3 strengthens
epidermal tight
junction barrier
Jalian, HR and Kim, J. 2008. Chapter 9 “Antimicrobial Peptides” In: Gaspari, AA, Tyring, SK, eds. Clinical and Basic
Immunodermatology. Guildford, United Kingdom: Springer (London).
• RNAse 7 (in orange) is present in keratinocytes in the epidermis
• Dermcidin (in red) is found predominantly in sweat glands
• Psoriasin (in green) is found in keratinocytes, sebocytes and in follicular epithelium
RNAse 7, Dermcidin, and Psoriasin expression in skin
RNAse 7:
- Potent activity against
Enterococcus faecium
Dermcidin:
- Primary sweat AMP
Psoriasin:
- Most abundant AMP in skin
- Chemotaxis
- Induced by E. coli flagellin
Jalian, HR and Kim, J. 2008. Chapter 9 “Antimicrobial Peptides” In: Gaspari, AA, Tyring, SK, eds. Clinical and Basic
Immunodermatology. Guildford, United Kingdom: Springer (London).
Antimicrobial and immunomodulatory properties
Ong, PY, et al. 2002. N Engl J Med 347(15): 1151-1160.
AMPs are differentially expressed in psoriasis &
atopic dermatitis
HBD2 LL-37
Psoriasis PsoriasisNormal Normal
Chronic AD Chronic ADAcute AD Acute AD
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Reviewed in: Charles L Bevins & Fu-Tong Liu. 2007. Nat Med 13, 904 – 906.
Cathelicidin variant peptides induced by stratum corneum tryptic
enzyme (SCTE), which is increased in rosacea, promotes
enhanced pro-inflammatory responses
Skin diseases are associated with specific bacteria,
antimicrobial peptides and TLRs
Gallo, RL and Nakatsuji, T. 2011. J Invest Dermatol 131: 1974-1980.
Humans microbes are complex and multi-faceted
Microbes are more often considered pathogenic
Mycobacterium tuberculosis
Herpes simplex virus
Microbes perform functions important for human health
Vitamin synthesis
Development and activity of immune system
Inhibition of skin colonization by pathogens
Bacteria commonly found on skin
Duality of skin bacteria
Commensal vs pathogenic microbe
Staphylococcus epidermidis
Staphylococcus aureus
Corynebacterium spp.
Propionibacterium acnes
DNA sequencing is a powerful microscope for
microbial identification
Sequencing instrumentKong. Trends Molec Med. 2011
Collect superficial skin sample
Isolate DNA
Amplify DNA with primers
(bacteria = 16S rRNA gene)
DNA sequencing/analysis
Pipeline for skin microbiome studies
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Duality of skin microbes: commensal vs pathogen
Staphylococcus epidermidis
Major skin inhabitant
Frequent cause of nosocomial infections
Produce antibacterial products
Bacteriocins, Enzymes (Esp, a serine protease),
Phenol soluble modulins, etc.
Iwase et al. Nature 2010
Lai et al. J Invest Dermatol 2010
S. epidermidis produces antimicrobial products &
promotes host defense against pathogens via TLR2
Gallo RL, Nakatsuji T. J Invest Dermatol 2011.
S. epidermidis
phenol soluble modulins/
Skin injury releases host dsRNA activating TLR3 in keratinocytes.
S. epidermidis lipoteichoic acid (LTA) inhibits excess inflammation
via TLR2-dependent mechanism.
Gallo RL, Nakatsuji T. J Invest Dermatol 2011.
S. epidermidis can inhibit excess P. acnes-induced inflammation
P. acnes
miR-143
Wang Y et al. Appl Microbiol Biotechnol 2014.
Xia et al. J Invest Dermatol 2016.
TLR2
S. epidermidis
lipoteichoic acid
(LTA) inhibits excess
P. acnes-induced
inflammation via miR-
143/TLR2 interaction.
Naik S et al. Science 2012.
Skin commensals tune skin-resident T cells
Mouse model of leishmania
infection
In germ-free mice:
Reduced local skin inflammation and
effector T cell response
Adding S. epidermidis restores
immunity
SPF
GF
GF + S. epidermidis
In mice, neonatal skin exposure to commensal
can lead to immune tolerance
Scharschmidt T et al. Immunity 2015.
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Well-known pathogen
Self-limited to invasive infections
Atopic dermatitis
Job’s/AD Hyper IgE syndrome (STAT3 mutation)
Asymptomatic nasal colonization
20% permanently colonized
30-50% transiently colonized
S. aureus preferentially hemolyzes human blood to utilize iron from human hemoglobin as a nutrient
http://staphylococcusaureustreatment.com/images/staphylococcus_aureus_treatment_2.jpg
Duality of skin microbes: commensal vs pathogen
Staphylococcus aureus
Pishchany et al. Cell Host Microbe. 2010
Interactions with host & other bacteria
Hemolysins
Affinity for human hemoglobin
Phenol-soluble modulins
High levels produced by CA-MRSA
Streptococci very sensitive to PSMs (may partially explain CA-MRSA dominance)
Bacteriocins
http://staphylococcusaureustreatment.com/images/staphylococcus_aureus_treatment_2.jpg
Joo et al. J Biol Chem 2011
Duality of skin microbes: commensal vs pathogen
Staphylococcus aureus
Children with atopic dermatitisAge-matched controls
Kong, Oh…Segre. Genome Res 2012.
Staphylococcus spp increase during AD flares
Nakatsuji T et al. Sci Transl Med 2017
Commensal staphylococci can produce AMPs to
selectively kill S. aureus
Diphtheroids
Part of normal skin flora
C. accolens, C. pseudodiphtheriticum
Can release antipneumococcal free fatty acids from skin lipids
As a pathogen
Systemic infections
Immunocompromised patients, skin barrier defects
Erythrasma - C. minutissimum
Trichomycosis - C. tenuis
http://www.life.umd.edu/classroom/bsci424/Images/PathogenImages/CorynebacteriumGramStainChineseLetters.jpg
Bomar L et al. mBio 2016.
Zawar V. J Dermatol Case Rep. 2011
Duality of skin microbes: commensal vs pathogen
Corynebacterium spp.
Predominant skin inhabitant in oily sites
Breaks down sebum into fatty acids
Products active against bacteria, yeast & molds
Associated with
Folliculitis
Systemic infections
Acne
Many different strains of P. acnes in healthy vs acne pts
Possible therapeutic targets
http://microbewiki.kenyon.edu/images/thumb/6/61/P_acnes.jpg/250px-P_acnes.jpg
Duality of skin microbes: commensal vs pathogen
Propionibacterium acnes
Liu J et al. ISME J 2015.
Tomida S. et al. mBio. 2013.
Fitz-Gibbon S et al. J Invest Dermatol 2013.