Narrowband ultraviolet B (NB-UVB) phototherapy is a commonly used treatment for various skin diseases, including vitiligo, psoriasis, eczema, and photodermatoses. While effective, prolonged use of NB-UVB carries significant adverse effects, notably inducing skin aging, inflammation, and reduced cell viability. The core mechanism behind this damage is the generation of reactive oxygen species (ROS), such as hydroxyl radicals and superoxide anions. This oxidative stress leads to DNA damage, cellular apoptosis, and the enhanced activity of matrix metalloproteinases (MMPs), which degrade collagen and accelerate premature aging.
To counteract these multi-faceted damages, researchers sought a multi-target approach, leading to the development of a polyherbal mixture for topical application. Polyherbal formulations are advantageous because they utilize different bioactive molecules acting through distinct mechanisms, offering multiple therapeutic effects and potential synergistic benefits, often requiring smaller amounts of individual components. This study specifically focused on combining three well-known herbs with established anti-photoaging properties and histories of safe topical use: Zingiber officinale (ZH), Garcinia mangostana (GE), and Centella asiatica (CAEw). The goal was to develop a formulation that could reduce the adverse effects after NB-UVB exposure in human keratinocytes.
Methods
The extracts (ZH, GE, and CAEw) were prepared to yield high levels of specific biomarkers: compound D, α-mangostin, and asiaticoside, respectively. The extracts were characterized for total phenolic and flavonoid content, along with antioxidant (DPPH, superoxide anion scavenging) and anti-collagenase activities. Optimal polyherbal mixture ratios were screened for efficacy in enhancing the viability of NB-UVB-exposed (120 mJ/cm2) HaCaT keratinocytes. The final selection, the ZH:GE:CAEw (1:1:1) mixture, was then evaluated for its ability to reduce intracellular ROS, inhibit apoptosis, and modulate the gene expression of pro-inflammatory (COX-2, iNOS) and aging-related (MMP-1, MMP-9) markers using qPCR.
Key Findings
• The optimal ratio determined for mitigating damage in NB-UVB-exposed HaCaT cells was the ZH:GE:CAEw (1:1:1) mixture.
• Post-treatment with 100 μg/mL of the 1:1:1 polyherbal mixture significantly increased cell viability from 62.3% to 80.1%.
• The 100 μg/mL polyherbal mixture effectively decreased intracellular ROS by 63.6%.
• The mixture significantly downregulated the mRNA expression of inflammatory genes (COX-2 and iNOS) and collagen-degrading enzymes (MMP-1 and MMP-9), allowing their expression to return to the level observed in non-irradiated cells.
• Although the formulation enhanced cell viability and reduced ROS, it did not reduce cell apoptosis induced by NB-UVB irradiation. This suggests that the increase in viable cells is due to proliferation and potentially beneficial apoptotic removal of damaged cells.
• The polyherbal mixture achieved these effects at lower concentrations of individual extracts (e.g., 33.3 μg/mL each in the 100 μg/mL total dose) compared to the concentrations required for single extracts to achieve a comparable effect, highlighting the advantage of the combination.
This research successfully developed a novel polyherbal formulation (ZH, GE, and CAEw in a 1:1:1 ratio) that demonstrates multi-target photoprotective efficacy in human keratinocytes against NB-UVB-induced damage. The novelty of this research lies both in the specific combination of these three herbs for post-UVB exposure treatment and the efficiency of the formulation. The mixture effectively attenuated damage by enhancing viable cell proliferation, reducing intracellular ROS, and providing anti-inflammatory and anti-photoaging activities by downregulating COX-2, iNOS, MMP-1, and MMP-9 expression. Crucially, the formulation maintained efficacy while reducing the required dosage of individual extracts, potentially lowering unwanted effects and production costs.
The findings have significant future implications for developing a topical product aimed at mitigating oxidative stress and premature skin aging associated with NB-UVB phototherapy. However, further work is necessary to elucidate the full molecular mechanisms and, most importantly, to conduct in vivo efficacy and toxicity studies to confirm safety and performance outside of the HaCaT cell model, particularly considering the potential for biphasic dose responses observed in other phytochemicals.
Link to the study: https://www.mdpi.com/2079-9284/12/6/241#
