Experts Q&A
We discussed with Dr. Rached Ismail, PhD Lecturer specialized on Skin Microbiota at the University Rouen Normandie (CBSA Laboratory) and David Suissa, CEO and founder of BYOME LABS - an innovative biotech start-up specializing in microbiome testing and analysis for the cosmetics industry.
Together, they shed light on the intricate relationship between UV rays, the skin microbiome, and photoaging, and how skincare innovations can make a difference.
What is the link between UV rays, oxidative stress, and the balance of the skin microbiome?
David: UV rays induce oxidative stress by generating free radicals that attack the lipids, proteins, and DNA of skin cells, weakening the skin barrier. A healthy microbiome indirectly helps protect the skin from UV rays by strengthening the skin barrier and modulating inflammatory processes. In fact, when the skin microbiome is healthy and balanced, it plays a protective role by producing compounds that help shield the skin from UV rays. It helps maintain a functional skin barrier and participates in regulating inflammatory processes through the production of organic acids or free fatty acids, which can neutralize free radicals. This collaboration between a balanced microbiome and skin cells helps limit the harmful effects of UV radiation and preserve the skin's integrity. Therefore, a healthy microbiome is an essential ally in protecting the skin against external aggressions.
Rached: Being a part of the exposome, an imbalanced skin microbiome could not perform its functions of UV protection and immune system modulation. In addition, UV rays induce the production of reactive oxygen species that could exacerbate skin pigmentation, roughness and wrinkles, which are signs of skin aging. However, depending on its composition, the skin microbiota could limit or increase these markers of skin aging.
Thus, maintaining an balanced skin microbiota could limit skin aging process.
Does UV rays have an impact on the skin microbiome and how does UV-induced oxidative stress affect the balance of the skin microbiome?
Rached: Studies on the effect of UV rays on the skin microbiota still remain nascent and the literature on the impacts of UV rays and solar radiation on the skin microbiome is limited especially for the fungi, archaea and virus members of the skin microbiome.
Although, we know that UV rays can alter the composition of the bacterial microbiome and thus lead to dysbiosis. These impacts may be associated with compromised skin barrier function and activation of the immune system.
How does an imbalanced skin microbiome contribute to photoaging and reduce the skin’s ability to defend against UV rays?
David: Ultraviolet (UV) rays deeply alter the skin environment by generating oxidative stress, cellular damage, and inflammation. These disruptions change the conditions that favor the balance of the skin microbiome, leading to an imbalance known as dysbiosis. Dysbiosis refers to a change in the microbial composition of the skin, with a reduction in certain beneficial bacteria, such as Lactobacillus crispatus, and a proliferation of others, such as cyanobacteria.
This imbalance impairs the skin’s ability to control oxidative stress and modulate inflammation, thus accelerating the degradation of collagen and elastin. As a result, the skin becomes more vulnerable to photoaging, characterized by wrinkles, pigmentation spots, and skin sagging. Studies suggest that the composition of the microbiome changes with age, underscoring the importance of a balanced microbiome in preserving skin health and youthfulness.
Rached: An imbalance in the skin microbiome may result in dysbiosis of the skin barrier function and a decline in the quality of ceramides, which play a crucial role in maintaining skin hydration. This imbalance could also trigger an increase in inflammation due to oxidative stress. Additionally, UV rays reduce the population of protective strains of the microbiota, such as Staphylococcus epidermidis, which contributes to skin barrier homeostasis by producing protective ceramides through the synthesis of shingomyelinase.
Can strengthening the skin barrier and using pre-, pro-, or postbiotics help maintain a balanced microbiome and prevent photoaging?
David: Prebiotics, probiotics, and postbiotics are ingredients that work synergistically to nourish or repopulate the skin microbiome, thus promoting its balance and rebalancing it when disrupted. Prebiotics are specific nutrients that nourish the beneficial microorganisms already present on the skin, encouraging their growth (for example, promoting the development of S. epidermidis, which
stimulates keratinocyte proliferation and
intercellular junctions). Probiotics, on the other hand, are live or inactivated microorganisms introduced to strengthen the microbial flora and restore balance in case of dysbiosis. Finally, postbiotics are active metabolites produced by microorganisms, such as enzymes or peptides, that directly act on the skin to enhance its defense functions.
These three types of biotics strengthen the skin barrier and regulate inflammation, thus contributing to improving the skin’s resilience against external aggressions, including the long-term effects of UV rays, and preventing the signs of photoaging.
Rached: Maintaining a balanced microbiota could reduce the effects of photoaging by limiting pigmentation, loss of hydration, inflammation, …
What role do certain microorganisms in the skin microbiome play in protecting against UV damage, and how can cosmetic formulations enhance these natural defenses?
David: Certain bacteria in the skin microbiome, such as Staphylococcus epidermidis or Cutibacterium acnes, can produce bioactive metabolites (e.g., propionic acid) that support the skin's natural defenses by modulating inflammation and contributing to the neutralization of free radicals. For example, S. epidermidis secretes an enzyme essential for the production of ceramides, which are necessary for maintaining a high hydration level. However, hydration quickly decreases during prolonged sun exposure. Additionally, many strains have the ability to produce antimicrobial peptides that regulate opportunistic pathogen populations on damaged and dehydrated skin. This interaction between a balanced microbiome and skin cells helps reduce the harmful effects of UV rays, such as cellular damage and inflammation,
thus preserving skin integrity. On the other hand, dysbiosis, marked by an imbalance between beneficial bacteria and opportunistic species, can compromise the skin’s defense mechanisms, worsening the effects of UV radiation and accelerating photoaging. Cosmetic formulations enriched with pre-, pro-, or postbiotics can help restore the microbiome's balance. They support beneficial microorganisms, strengthen the skin barrier, and enhance the skin's ability to defend against oxidative stress and external aggressions.