Berberine Suppresses SASP Inflammation via RXRα/PPARγ/NEDD4 Axis

Study Background and Research Question

Atherosclerosis remains a leading cause of cardiovascular morbidity, with the chronic accumulation of senescent cells within vascular plaques driving persistent inflammation and tissue remodeling. Senescent cells, characterized by DNA damage, mitochondrial dysfunction, and a pro-inflammatory secretome known as the senescence-associated secretory phenotype (SASP), contribute substantially to disease progression. However, the molecular mechanisms governing SASP in atherosclerotic plaques—particularly the interplay between metabolic nuclear receptors and ubiquitin ligases—have not been fully elucidated. The reference study (American Journal of Chinese Medicine, 2025) addresses this gap by investigating how berberine (BBR), a bioactive plant alkaloid, modulates SASP-driven inflammation through the RXRα/PPARγ/NEDD4 signaling axis in macrophage-derived foam cells.

Key Innovation from the Reference Study

The central innovation of this work lies in its demonstration that berberine inhibits SASP-related inflammation in atherosclerosis by orchestrating a signaling cascade involving the retinoid X receptor alpha (RXRα), peroxisome proliferator-activated receptor gamma (PPARγ), and the E3 ubiquitin ligase NEDD4. Notably, the study provides mechanistic evidence that berberine not only activates RXRα and PPARγ but also upregulates NEDD4, leading to enhanced ubiquitination and degradation of the GATA4/p62 complex—a regulatory node critical for SASP protein production. By delineating this pathway, the research highlights a potential therapeutic target for mitigating vascular inflammation and cellular aging in atherosclerotic disease.

Methods and Experimental Design Insights

The study employed a multi-tiered experimental approach integrating in vivo and in vitro models. ApoE-deficient mice fed a high-fat diet were used to model atherosclerotic plaque formation and subjected to berberine treatment. Changes in plaque morphology and systemic blood chemistry were analyzed to assess berberine’s impact at the organismal level. Complementary in vitro studies utilized RAW264.7 macrophages and peritoneal macrophage-derived foam cells, enabling the dissection of SASP protein production and pathway activation in relevant cellular contexts. Smart-seq single-cell transcriptomic analysis provided granularity on pathway activation in response to berberine, highlighting changes in gene expression signatures linked to RXRα, PPARγ, and NEDD4. The functional necessity of RXRα in this pathway was probed using lentivirus-mediated macrophage-specific knockdown in vivo, clarifying the receptor’s indispensability for berberine’s anti-inflammatory effects. Protein-protein interactions and ubiquitination dynamics were assessed by immunoprecipitation and Western blot, with particular attention to the GATA4/p62 axis.

Core Findings and Why They Matter

Several key findings emerged from the study:

• Berberine treatment significantly reduced SASP-associated markers and inflammation within atherosclerotic plaques in ApoE^-/- mice (reference study).
• Single-cell sequencing revealed that berberine upregulates RXRα and PPARγ activity in macrophage-derived foam cells, leading to increased transcription of the E3 ligase NEDD4.
• The elevated NEDD4 promotes ubiquitination and degradation of the GATA4/p62 complex, thereby suppressing the production of SASP proteins.
• Knockdown of RXRα in plaque macrophages abrogated the anti-inflammatory effects of berberine, confirming the centrality of RXRα/PPARγ/NEDD4 signaling in SASP modulation.

These results collectively demonstrate that pharmacological modulation of the RXRα/PPARγ/NEDD4 axis can attenuate chronic inflammation associated with cellular senescence in atherosclerosis. The findings underscore the importance of nuclear receptor signaling and post-translational protein modification in controlling pro-inflammatory cellular phenotypes within vascular lesions.

Comparison with Existing Internal Articles

The mechanistic insights from this study align closely with prior internal reviews. For instance, the article "Berberine Modulates RXRα/PPARγ/NEDD4 to Suppress SASP in Atherosclerosis" highlights the importance of transcriptional and ubiquitin-mediated regulation in foam cell inflammation. Similarly, the overview at "Berberine Suppresses SASP Inflammation via RXRα/PPARγ/NEDD4 Axis" contextualizes the anti-inflammatory potential of targeting this pathway, particularly in the context of age-related vascular remodeling. The reference study advances these earlier frameworks by providing direct in vivo evidence for pathway dependency and by mapping the sequence of molecular events from berberine exposure to SASP suppression. Moreover, the findings complement the broader literature on PPARγ antagonists such as T0070907, which have been applied to dissect PPARγ-dependent transcriptional regulation and inflammatory signaling in diverse cellular models (see internal review). While T0070907 is primarily used as a PPARγ antagonist, the current study demonstrates the utility of PPARγ activation in suppressing inflammation, underscoring the nuanced, context-dependent roles of this nuclear receptor in vascular biology.

Limitations and Transferability

Despite its strengths, the study’s findings should be interpreted in light of several limitations. First, while murine models recapitulate key features of human atherosclerosis, differences in immune cell composition and metabolic regulation may limit direct translation. Second, the reliance on lentiviral knockdown to demonstrate RXRα’s role, while robust, does not exclude contributions from additional nuclear receptors or coregulators in the observed anti-inflammatory effect. Finally, the study focuses on berberine’s impact within the context of foam cell-driven SASP; whether similar mechanisms operate in other cell types or disease contexts remains to be established.

Protocol Parameters

• Berberine treatment in vivo: ApoE^-/- mice fed high-fat diet; berberine administered at 100 mg/kg/day by oral gavage for 8 weeks, monitoring plaque morphology and systemic inflammation.
• Cell culture for SASP analysis: RAW264.7 or peritoneal macrophage-derived foam cells exposed to berberine (10–40 µM, 24–48 h) prior to SASP marker evaluation.
• RXRα knockdown: Lentivirus-mediated shRNA delivery targeting RXRα in plaque macrophages, with confirmation by immunoblot and qPCR.
• Pathway inhibitor controls: Inclusion of PPARγ antagonists such as T0070907 or RXRα pathway inhibitors to validate specificity of berberine-induced effects in cell-based assays.
• Ubiquitination assays: Immunoprecipitation of GATA4/p62 followed by Western blot for ubiquitin and SASP markers.

Research Support Resources

For researchers seeking to further dissect the PPARγ signaling pathway or to model the effects of pathway inhibition in adipogenesis, inflammation, or cell cycle regulation, T0070907 (SKU A4301) from APExBIO offers a potent and selective antagonist tool. With an IC50 of 1 nM, T0070907 enables high-specificity modulation of PPARγ-dependent transcription, and has been widely used in studies of adipogenesis inhibition, cell cycle G2/M arrest, and PPARγ/RXRα heterodimer modulation. Application of such pathway-selective modulators can complement approaches described in the reference study, providing mechanistic contrast between activation and inhibition of PPARγ signaling.