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Chapter 6: Extrinsic Aging

Leslie S. Baumann; Edmund M. Weisberg

INTRODUCTION

SUMMARY POINTS

What’s Important?

  1. The AhR signaling pathway is turned on by ozone and other pollutants and results in increased production of MMPs.

  2. The common deletion in mitochondria occurs in photoaged skin and is associated with decreased mitochondrial function.

  3. There is much overlap with intrinsic aging; therefore, reading Chapter 5 will provide useful supplemental information.

What’s New?

  1. The ECM components are broken down with sun exposure and other extrinsic insults resulting in changes in fibroblast activity.

  2. Pollution from traffic is a major cause of skin aging.

  3. Infrared and visible light can age skin.

What’s Coming?

  1. Knowledge on genetic expression and epigenetic methylation changes in sun-exposed vs. non-sun-exposed skin will increase.

  2. Studies on mitochondria and how to improve autophagy and mitochondrial function in aged skin are ongoing.

  3. It is still not possible to upregulate elastin levels in the skin by any means. Studies are ongoing to try and find ways to increase the quantity of mature elastin fibers that are bound to a microfibrillar backbone in the skin.

Since the end of the 19th century, dermatologists have discussed the notion that sunlight contributes to premature aging.1 However, tanning beds remain popular and the majority of people continue to avoid consistent daily sun protection. In addition, in the last 15 years, studies have shown that environmental influences such as pollution also play an important role in skin aging. The rise in popularity of vaping will likely impart deleterious effects to the skin of some individuals, also, but it is too early to know if the effects of this new technology will engender cutaneous aging as does traditional smoking of tobacco products.

The consequences to the skin from sun and environmental exposure are readily apparent when one compares the exposed skin of the face, hands, or neck to the unexposed skin of the buttocks, inner thighs, or inner arms (Fig. 6-1). This damage can be highlighted by using a Wood’s lamp, blue light, or an ultraviolet (UV) camera system, rendering the epidermal pigment component more noticeable (Figs. 6-2, 6-3, and 6-4). Showing such results to patients can prove useful in convincing them of the havoc that environmental exposures have wreaked on their skin.

FIGURE 6-1

Comparing the sun-exposed surface of the forearm to the non-sun-exposed surface demonstrates the sun’s ability to cause skin changes.

A photograph compares the sun-exposed dorsal surface of the forearm that appears dark, to the non-exposed ventral surface, which is lighter.
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FIGURE 6-2

Facial skin of 25-year-old with normal lens. Sun damage is barely visible.

A photograph of the face of a 25-year-old female patient with a normal lens, with barely visible sun damage.
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FIGURE 6-3

Photoaging is accentuated by using UV light.

A photograph of the face of the same patient, in figure 2, using UV light accentuates the photoaging.
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FIGURE 6-4

Photoaging as seen under blue light.

A photograph of the face of a female patient using blue light accentuates the photoaging.
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Although the sun is not the sole source or cause of ...

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