Skin Lipid Structure Lec 2

Question 1

What is in the lipid barrier?

Answer 1

intercellular lipids surrounding corneocytes, it is multilamellar and anchored covalently to corneocyte, has ceramides, cholesterol, fatty acids in a 1:1:1 ratio, and has a broad narrow broad pattern.

Question 2

Epidermal Lipids

Answer 2

covalently-bound lipids, attached to 𝛃-sheet on Cell Envelope that surrounds dead corneocytes. They are attached to involucrin protein in envelope, and 𝛚-Hydroxy ceramides and fatty acids.

Question 3

What is the process of lipid processing in the epidermis?

Answer 3

The intercellular lipids are primarily generated from exocytosis of lipid-containing granules called lamellar bodies during the terminal differentiation of the epidermal keratinocytes. The lipid granules originate from the golgi. This primarily occurs at the granular layer/stratum corneum interface.

Question 4

Where are phospholipids found?

Answer 4

In basal and granular cells. not tolerated in stratum corneum.

Question 5

What happens when covalently bound ceramides are reduced with UV exposure?

Answer 5

TEWL (trans epidermal water loss) is increased.

Question 6

Metabolic Activity in the stratum corneum

Answer 6

Conversion of phospholipids to fatty acids and glucosyl ceramides to ceramides, hydrolysis of desmosomes to slough off SC, conversion of cholesterol sulfate to cholesterol, and filaggrin to NMF.

Question 7

Pro-barrier lipids for barrier function

Answer 7

Glycolipids, free sterols, and phospholipids

Question 8

Catabolic enzymes for desquamation

Answer 8

acid phosphatase, proteases, lipases, and glycosides.

Question 9

pH of skin

Answer 9

~5.0 in upper layers as it is dehydrated, ~7.3 in more hydrated lower layers.

Question 10

What happens when the conversion of glucosyl ceramides to cerimides is inhibited?

Answer 10

The barrier is disrupted.

Question 11

Friberg Model

Answer 11

combined all epidermal and surface lipids in proportions found in skin plus 32% water. This made a milky emulsion. Then they adjusted to skin pH of 5.

Question 12

Key findings in friberg model

Answer 12

The structure is liquid crystalline, could be lamellar or haxagonal structure but multese crosses were sen. These results suggest that a fatty acid/soap is the basis of the layered structure.

Question 13

How do lipids in SC exist?

Answer 13

in phases, and the individual lipids can move around depending on hydration/dehydration

Question 14

Requirements of actual lipid structure

Answer 14

Flexibility to mechanical stress, barrier to water transport, barrier to penetration of foreign substances, resistance to environmental insults, resistance to phase separation, and resiliency when challenged.

Question 15

Lamellar phases of Stratum Corneum

Answer 15

Can be LC, gel, or Orthorhombic Crystal, but double bonds are not conducive to Orth, so there is a mixture. At room temp, more OC, but less at 32 degrees, as well as more OC at bottom of SC

Question 16

What is required for formation of the LLP (long lamellar phase)?

Answer 16

Ceramide 1 with linoleic acid extension

Question 17

What is required for formation of SLP (short lamellar phase)?

Answer 17

Fatty acid

Question 18

What stabilizes the LLP and SLP from phase separation?

Answer 18

Cholesterol

Question 19

Wertz/Downing Stacked Monolayer Model

Answer 19

ceramides open up depending on amount of dehydration to form the different “layers”

Question 20

Forsling Domain mosaic Models

Answer 20

Coexistence of a gel domain surrounded by liquid crystalline grain borders

Question 21

Norlen Single Gel Phase Model

Answer 21

In the presence of water, ceramide does not exhibit splayed chains, and the phase is swelled.

Question 22

Lipids in Atopic skin

Answer 22

Contain reduced amounts of reduced FAs and ceramide-1. The barrier is amorphous and too liquid because the barrier lipid is too fluid.

Question 23

Ichthyosis

Answer 23

Reduction in free FA and ceramide-1, consistant with tendency to be enriched in hexagonal packing, with too fluid lipids.