Parsley Extract as a Modulator of Oxidative Stress and Atopic Dermatitis: Mechanistic Insights from Human Keratinocytes and Mouse Models

Study Background and Research Question

Atopic dermatitis (AD) is a prevalent, chronic inflammatory skin disorder characterized by impaired skin barrier function, persistent inflammation, and increased susceptibility to infections. Keratinocytes, the primary cells of the epidermis, are central to maintaining skin integrity and orchestrating immune responses. Dysregulation of keratinocyte function drives AD pathogenesis by amplifying oxidative stress and inflammation. Botanical therapeutics, such as Petroselinum crispum (parsley), have a history of empirical use for skin ailments, but the molecular actions of parsley extracts on keratinocytes and AD remain incompletely understood (Wang et al., 2025).

Key Innovation from the Reference Study

The study by Wang et al. systematically characterizes the antioxidant and anti-inflammatory actions of various parsley extracts, with a focus on a hydro-ethanolic extract (HEP), in both human keratinocytes (HaCaT cells) and a DNFB-induced mouse model of AD. The innovation lies in integrating phytochemical profiling, cell-based assays, and in vivo efficacy studies to link HEP's molecular effects to improvements in AD-like pathology. Critically, the investigation delineates how HEP activates cytoprotective pathways (notably Nrf2 signaling) and suppresses pro-inflammatory cascades (JAK1/STAT1 and NF-κB), thereby restoring skin barrier proteins and reducing disease severity (paper).

Methods and Experimental Design Insights

Wang et al. employed a multi-tiered approach:

• Phytochemical Analysis: Total polyphenol content (TPC) and total flavonoid content (TFC) were quantified across aqueous, ethanolic, and hydro-ethanolic parsley extracts. Antioxidant capacity was assessed via DPPH and FRAP assays.
• In Vitro Cell-Based Assays: HaCaT keratinocytes were challenged with tert-butyl hydroperoxide (t-BHP) to induce oxidative stress or with TNF-α/IFN-γ to model inflammatory conditions. Cell viability was measured, and reactive oxygen species (ROS) levels quantified post-treatment with each extract type.
• Molecular Pathway Analysis: Western blot and qPCR were used to assess expression of antioxidant enzymes (SOD, CAT), skin barrier proteins (filaggrin, claudin-1), and inflammatory cytokines (IL-6, IL-8, IL-33). Activation of Nrf2, JAK1/STAT1, and NF-κB signaling was measured.
• In Vivo Efficacy: The DNFB-induced AD mouse model was used to evaluate topical HEP's effect on skin inflammation, epidermal hyperplasia, and immune cell infiltration.

Protocol Parameters

• cell viability assay | typically 24–48 h post-treatment | HaCaT keratinocytes under oxidative/inflammatory insult | ensures sufficient time for viability and cytotoxicity assessment | workflow_recommendation
• HEP concentration | 10–100 μg/mL | in vitro cell models | dose range covers physiologically relevant and non-toxic levels | paper
• oxidative stress inducer | t-BHP 200 μM, 2 h exposure | HaCaT cells | robustly induces ROS without causing non-specific cell death | paper
• AD mouse model induction | DNFB topical application, 2–3 weeks | BALB/c or C57BL/6 mice | widely accepted model for human-like AD features | paper

Core Findings and Why They Matter

The hydro-ethanolic extract (HEP) exhibited the highest TPC/TFC and the strongest antioxidant activity in chemical assays. In oxidative stress–challenged HaCaT cells, HEP:

• Significantly improved cell viability and reduced intracellular ROS levels (paper).
• Activated the Nrf2 pathway, resulting in upregulation of SOD and CAT, key antioxidant enzymes.
• Suppressed the expression of inflammatory cytokines (IL-6, IL-8, and IL-33) by inhibiting the JAK1/STAT1 and NF-κB signaling pathways.
• Restored expression of skin barrier proteins, including filaggrin and claudin-1, which are commonly downregulated in AD lesions.

In the DNFB-induced mouse model, topical HEP treatment:

• Reduced skin thickening (hyperplasia) and immune cell infiltration.
• Mitigated AD-like symptoms, demonstrating translational relevance for potential human application (paper).

These findings underscore HEP's dual antioxidant and anti-inflammatory effects, providing mechanistic support for its use as a natural therapeutic in AD and related skin disorders.

Comparison with Existing Internal Articles

While Wang et al. focus on the modulation of keratinocyte viability and inflammation by botanical extracts, several internal articles discuss the technical advantages of sensitive cell proliferation and cytotoxicity assays in analogous research contexts:

• "Cell Counting Kit-8 (CCK-8): Advancing Precision in Cellular Analysis" highlights the role of CCK-8 in accurately quantifying cell viability and metabolic responses, which parallels the viability measurements in the parsley extract study.
• "Cell Counting Kit-8: Sensitive Cell Proliferation and Cytotoxicity Detection" further explains assay optimization for cancer research but the principles apply to inflammation and oxidative stress models as well.
• "Cell Counting Kit-8 (CCK-8): Precision Viability Assays for Translational Research" addresses mechanistic and translational advantages of WST-8–based cell viability measurements, supporting the workflow choices in the reference study.

The parsley study's use of cell viability and ROS assays aligns with these internal resources' emphasis on assay sensitivity, reproducibility, and relevance for complex disease models. Researchers working in oxidative stress and inflammatory contexts can draw on both the botanical evidence and advanced assay methods for robust experimental design.

Limitations and Transferability

Despite the comprehensive design, several limitations merit consideration:

• The study evaluates only short-term and acute responses, leaving chronic effects of HEP on keratinocytes and AD models to future work.
• Translatability to human clinical scenarios is not directly established; human skin physiology may differ from murine models in immunological and barrier properties.
• Phytochemical composition of HEP may vary with source material and extraction protocols, potentially affecting reproducibility.

Nevertheless, the molecular pathways identified (Nrf2, JAK/STAT, NF-κB) are highly conserved and central to skin biology, supporting cautious extension of these findings to broader contexts in dermatological research.

Research Support Resources

For researchers interested in replicating or extending these findings—whether to botanical extracts or other modulators of oxidative stress and inflammation—quantitative cell viability and cytotoxicity assays are essential tools. The Cell Counting Kit-8 (CCK-8) (SKU K1018) from APExBIO offers a sensitive and straightforward workflow for evaluating cell proliferation, viability, and cytotoxicity in keratinocyte and other cell-based models. By leveraging WST-8 chemistry, CCK-8 enables high-throughput, reproducible assessment of cellular responses to stressors or therapeutic interventions, aligning with best practices highlighted in both the parsley extract study and internal technical articles (source: workflow_recommendation).