← All decks
Dermatology
Ultraviolet Radiation
Built from Dermatology, 5th Edition
What’s inside
11 sections · 99 slides
Overview
- Scope of this topic
UV Spectrum and Absorption
How sunlight's wavelengths reach the skin and what molecules absorb them
- What is ultraviolet light
- UVA1, UVA2, and the UVA/UVB cut-off
- The UV waveband sequence
- Depth of penetration of UV wavelengths into skin
- Why penetration depth matters
- Chromophores: how skin senses UV
- UV chromophores in skin
- UV absorption by chromophores and downstream signalling
- Absorption spectra and why they matter
Sunburn and Tanning
The short-term, visible effects of UV exposure on the skin
- What happens in sunburn
- Second-degree sunburn with blister formation
- How sunburn causes pain and inflammation
- Two kinds of tanning
- UVB tan versus UVA tan
- Tanning bed and sun-exposure sequelae
- Skin phototype and long-term risk
Effects on the Cutaneous Immune System
How UV light both triggers and suppresses immune responses
- A two-faced effect on immunity
- Innate immune activation by UV-induced DAMPs
- How UV switches on innate immunity
- Mechanisms of UV-induced immunosuppression
- How UV suppresses adaptive immunity
- The upside and downside of immunosuppression
- Sensors that trigger UV's immune effects
- UV and skin fibroblasts
Photoaging
The clinical, structural, and functional changes seen in chronically sun-exposed skin
- Photoaging versus intrinsic aging
- UVA and the dermal changes of photoaging
- Unilateral photoaging through a window
- How chronic inflammation ages the dermis
- Why photoaging is not simply reversible
UV-Induced Tumor Formation
How chronic UV exposure drives the development of skin cancer
- UV: a major skin cancer risk factor
- The photocarcinogenesis cascade
- The 'one-two punch' of photocarcinogenesis
- Chromothripsis: a fast route to cancer
- UVA is a real carcinogen too
- UV and melanoma
- Why melanoma favors intermittently sun-exposed skin
UV Induction of DNA Damage
How different UV wavelengths damage the DNA molecule
- DNA photoproducts: the core UV DNA lesion
- Formation of a thymine dimer
- Cyclobutane-pyrimidine dimers (CPDs)
- Formation of a 6,4-photoproduct
- 6,4-photoproducts
- 300 nm UVB reaches the basal epidermis more effectively than 290 nm
- The most effective wavelength in real skin
- Indirect DNA damage: photosensitized reactions
- Formation of the oxidative lesion 8-oxoG
- Oxidative DNA damage
- Action spectrum for dimer and oxidative DNA damage
- Which lesion matters most for mutations
Repair of UV-Induced DNA Damage
How cells detect and fix UV-damaged DNA, and what happens when repair fails
- Nucleotide excision repair (NER)
- Xeroderma pigmentosum
- The seven XP complementation groups
- Steps of nucleotide excision repair
- Two ways NER finds DNA damage
- From recognition to a repaired strand
- Reading the XP gene table
- Deficient DNA repair genes in xeroderma pigmentosum complementation groups
- Deficient DNA repair genes in xeroderma pigmentosum complementation groups (continued)
- Deficient DNA repair genes in xeroderma pigmentosum complementation groups (continued)
- XP variant: repair works, but replication fails
- Types of impaired function across disorders
- Types of impaired function in inherited disorders with abnormal DNA repair
- Base excision repair: fixing oxidative damage
- Cytokines that influence DNA repair
UV-Induced Mutations
How UV DNA damage becomes a permanent genetic mutation
- From DNA damage to mutation
- UV-signature CC to TT mutation
- Signature mutations of UV light
- Standard phototherapy and cancer risk
Mechanisms of UV-Based Phototherapy
How UV light is used deliberately to treat inflammatory and neoplastic skin disease
- Diseases treated with UV phototherapy
- UV's therapeutic toolkit
- Key components of the therapeutic mechanism of UV phototherapy
- Regulatory T cells and long remission
- Phototherapy in cutaneous T-cell lymphoma
- Phototherapy and the skin microbiome
- Phototherapy in fibrotic disease
- Systemic effects of phototherapy
Photoprotection
How skin defends itself against UV damage, and how sunscreens and other measures add protection
- The skin's own lines of defense
- Mechanisms that protect against photocarcinogenesis
- Eumelanin versus pheomelanin
- Adaptive and downregulated defenses
- UVA and sunscreen limitations
- Practical sun protection measures
- Understanding SPF
- What makes a good sunscreen
- Antioxidants in sunscreens: an open question
- DNA repair enzymes and oral agents
- The skin microbiome and UV protection
- Key takeaways
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Dermatology, 5th Edition (2-Volume Set)