Systemic photoprotection: a valuable addition to topical sun protection

Systemic sun protection is an interesting additional way to shield the at-risk group. A fern extract has shown promising results for this indication due to its strong antioxidant properties [1].

“Oral photoprotective agents do not substitute but complement conventional photoprotection,” said Prof. Salvador González Rodriguez (University of Alcala de Henares, Spain). An additional protection, in particular for high-risk groups, is necessary due to the limitations of topical sunscreens: they are re-applied to infrequently, the quantity of the applied product is usually too small, and they are subject to unnoticed removal by perspiration [2,3]. Although wearing protective clothing and applying a broad-spectrum, water-resistant sunscreen with a sun protection factor of at least 30 are still the most reliable methods of sun protection, this might not be sufficient for high-risk groups. “The problem with topical sunscreen is that there is no universal application; therefore, we also need a systemic protection,” said Prof. González Rodriguez.

The most promising results regarding oral sun protection come from an extract of a Central American fern plant, Polypodium leucotomos. Studies have shown photoprotective, immune-modulatory, and antioxidative properties of the fern extract [4]. Polypodium leucotomos is a powerful antioxidant due to its high content of phenolic compounds [5]. It not only inhibits the generation of reactive oxygen species (ROS) by ultraviolet (UV) light but also prevents UV-induced and ROS-induced DNA damage.

A study in healthy patients showed that the fern extract is an effective chemophotoprotector against PUVA-induced skin phototoxicity: skin treated with the fern extract revealed a significant numeric reduction of sunburn cells, preservation of Langerhans' cells, decrease of tryptase-positive mast cell infiltration, and decrease of vasodilation [6]. The extract also inhibits mitochondrial DNA damage induced by UVA, and matrix metalloproteinases (MMP)-1 expression induced by visible light and infrared radiation.

In addition, it blocks the photoisomerisation and photodecomposition of trans-urocanic acid to cis-urocanic acid, which partially affects Langerhans cells and mast cell degranulation, thereby contributing to UV-induced immunosuppression [7]. These cellular and molecular effects are reflected in inhibitions of carcinogenesis and photoaging.

In addition to its antioxidant activity, the fern extract bears promise in the treatment and prevention of photoaging due to its proven effects on extracellular matrix remodelling. The fern extract inhibits several MMPs by inducing elastin and different types of collagen; thus, promoting regeneration of the skin [8].

“I think that systemic photoprotection is of particular relevance in high-risk patients like lighter skin phototypes, patients with photodermatosis and photoaggravated dermatosis, pigmentation disorders patients, patients with a clinical history of skin cancer, and patients under phototherapy, as adjuvant treatment,” concluded Prof. González Rodriguez.

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   1. González Rodriguez S. D2T03.4D, EADV 2019, 9-13 Oct, Madrid, Spain.
   2. Diffey BL. J Am Acad Dermatol 2001;45:882-5.
   3. Péna Ortega M, et al. Piel 2004;19:179-83.
   4. Choudhry SZ, et al. J Drugs Dermatol 2014;13:148-53.
   5. Parrado C, et al. Int J Mol Sci 2016;17:pii:E1026.
   6. Middelkamp-Hup MA, et al. J Am Acad Dermatol 2004;50:41-9.
   7. El-Haj N, et al. Int J Dermatol 2015;54:362-6.
   8. Philips N, et al. Arch Dermatol Res 2009;301:487-95.

 



Posted on 9 October 201912 March 2021