PDRN CareReactive Oxygen Species (ROS)
Dr. Sarah Chen
PhD, Molecular Biology
Reactive oxygen species (ROS) are chemically reactive molecules containing oxygen that are produced as natural byproducts of cellular metabolism and in response to environmental stressors [1].
Definition
Reactive oxygen species (ROS) are chemically reactive molecules containing oxygen that are produced as natural byproducts of cellular metabolism and in response to environmental stressors [1]. The term encompasses both free radicals β molecules with unpaired electrons such as superoxide anion (O2-) and hydroxyl radical (OH) β and non-radical oxidants such as hydrogen peroxide (H2O2) and singlet oxygen (1O2) [1]. At low concentrations, ROS serve essential signaling functions in cell proliferation, differentiation, and immune defense. At elevated concentrations, they overwhelm antioxidant defenses and inflict oxidative damage on DNA, proteins, lipids, and cellular organelles [1][2].
Types of ROS in Skin
Superoxide Anion (O2-)
The primary ROS produced by the mitochondrial electron transport chain during normal cellular respiration [1]. Superoxide is also generated by NADPH oxidase enzymes in immune cells during the respiratory burst against pathogens. While superoxide itself has limited reactivity, it serves as the precursor for more damaging ROS species.
Hydrogen Peroxide (H2O2)
Formed by the dismutation of superoxide (catalyzed by superoxide dismutase enzymes), hydrogen peroxide is a relatively stable, membrane-permeable oxidant [1]. It participates in cell signaling at low concentrations but causes oxidative damage at elevated levels. In the skin, H2O2 accumulates in the epidermis with aging due to declining catalase activity.
Hydroxyl Radical (OH)
The most reactive and damaging ROS species, generated from hydrogen peroxide through the Fenton reaction (catalyzed by iron or copper ions) [1]. Hydroxyl radicals react indiscriminately with virtually any biological molecule within nanoseconds of formation, making them impossible to scavenge enzymatically.
Singlet Oxygen (1O2)
An excited-state oxygen molecule generated primarily by UV-induced photosensitization reactions in the skin [2]. Endogenous photosensitizers (porphyrins, flavins, melanin precursors) absorb UV photon energy and transfer it to molecular oxygen, creating singlet oxygen that attacks nearby cellular components.
Sources of ROS in Skin
Exogenous Sources
- Ultraviolet radiation β The primary external driver, generating ROS through both direct photochemical reactions and photosensitization of endogenous chromophores [2][3]
- Air pollution β Particulate matter (PM2.5), ozone, and nitrogen oxides generate ROS upon contact with the skin surface [2]
- Infrared and visible light β Near-infrared radiation and high-energy visible (blue) light contribute to mitochondrial ROS generation [2]
- Cigarette smoke β Contains free radicals and pro-oxidant compounds that deplete cutaneous antioxidant reserves [2]
Endogenous Sources
- Mitochondrial respiration β Approximately 1 to 2 percent of oxygen consumed by mitochondria is converted to superoxide as electron transport chain leakage [1]
- Enzymatic activity β NADPH oxidases, xanthine oxidase, lipoxygenases, and cytochrome P450 enzymes produce ROS during their catalytic cycles [1]
- Inflammatory cells β Neutrophils and macrophages deliberately produce ROS via the respiratory burst to kill pathogens [1]
How ROS Damage Skin
DNA Damage
ROS generate oxidative DNA lesions including 8-oxo-7,8-dihydroguanine (8-oxoG), thymine glycol, and single-strand breaks [2]. Unrepaired oxidative DNA damage triggers cellular senescence, apoptosis, or β in the worst case β mutagenesis. Telomeric DNA is particularly vulnerable due to its guanine-rich repeat sequence [2].
Collagen Degradation
ROS activate the AP-1 and NF-kB transcription factor pathways, which upregulate matrix metalloproteinase (MMP) expression β enzymes that cleave collagen and elastin fibers [2][3]. Simultaneously, ROS suppress TGF-beta signaling, reducing new collagen synthesis. This dual mechanism β increased destruction plus decreased production β accelerates net collagen loss.
Lipid Peroxidation
ROS attack polyunsaturated fatty acids in cell membranes and the stratum corneum lipid matrix through chain-reaction peroxidation [2]. Lipid peroxidation compromises membrane integrity, disrupts barrier function, and generates reactive aldehyde byproducts (malondialdehyde, 4-hydroxynonenal) that further damage proteins and DNA.
Inflammatory Amplification
ROS activate NF-kB signaling, triggering production of pro-inflammatory cytokines (TNF-alpha, IL-1, IL-6) that recruit immune cells which produce additional ROS [2]. This positive feedback loop amplifies oxidative damage and sustains chronic low-grade inflammation (inflammaging).
PDRN and ROS-Mediated Damage
PDRN is not a direct antioxidant β it does not scavenge free radicals like vitamin C, vitamin E, or glutathione [4]. Instead, PDRN counteracts ROS damage through downstream protective mechanisms:
Breaking the ROS-Inflammation Cycle
PDRN's adenosine A2A receptor activation suppresses NF-kB-driven inflammatory signaling, interrupting the vicious cycle in which ROS trigger inflammation that generates more ROS [4]. By dampening this amplification loop, PDRN limits the total oxidative burden even without directly neutralizing free radicals.
DNA Repair Substrate Supply
PDRN provides purine and pyrimidine nucleotides through the salvage pathway, supplying the building blocks needed by base excision repair (BER) enzymes to correct oxidative DNA lesions [4][5]. Adequate nucleotide availability is essential for efficient repair of 8-oxoG and other ROS-induced DNA modifications.
Fibroblast Protection and Recovery
ROS exposure impairs fibroblast proliferation and collagen synthesis [2]. PDRN's A2A receptor-mediated stimulation of fibroblast activity counteracts these suppressive effects, helping maintain dermal matrix production despite ongoing oxidative challenge [4][5].
Clinical Implications
Understanding ROS biology clarifies PDRN's role in a comprehensive skincare approach [4][5]:
- Complementary defense β Topical antioxidants (vitamin C, niacinamide, resveratrol) prevent ROS damage; PDRN repairs damage that antioxidants fail to intercept
- Post-sun exposure β PDRN supports DNA repair and reduces inflammation after acute UV-generated ROS exposure
- Urban skin defense β In pollution-heavy environments, PDRN's anti-inflammatory action helps manage the chronic ROS burden from particulate matter
- Optimal protocol β Antioxidant serums in the morning (prevention), sunscreen (UV blocking), and PDRN morning and evening (repair and regeneration)
References
- [1]Schieber M, Bharthavaj N. ROS function in redox signaling and oxidative stress. Curr Biol. 2014;24(10):R453-R462. doi:10.1016/j.cub.2014.03.034
- [2]Rinnerthaler M, Bischof J, Streubel MK, Trost A, Richter K. Oxidative stress in aging human skin. Biomolecules. 2015;5(2):545-589. doi:10.3390/biom5020545
- [3]Masaki H. Role of antioxidants in the skin: anti-aging effects. J Dermatol Sci. 2010;58(2):85-90. doi:10.1016/j.jdermsci.2010.03.003
- [4]Squadrito F, Bitto A, Irrera N, et al.. Pharmacological Activity and Clinical Use of PDRN. Curr Pharm Des. 2017;23(27):3948-3957. doi:10.2174/1381612823666170516153716
- [5]Colangelo MT, Galli C, Gentile P. Polydeoxyribonucleotide: A Promising Biological Platform for Dermal Regeneration. Curr Pharm Des. 2020;26(17):2049-2056.