Berberine Suppresses SASP Inflammation via RXRα/PPARγ/NEDD4 Axis in Atherosclerosis

Study Background and Research Question

Chronic inflammatory diseases such as atherosclerosis are increasingly recognized as being driven in part by the accumulation of senescent cells. These aging cells, through the senescence-associated secretory phenotype (SASP), secrete a range of pro-inflammatory factors that perpetuate tissue injury and dysfunction. Human carotid artery single-cell sequencing has revealed a preponderance of senescent foam cells within atherosclerotic plaques, highlighting the translational relevance of targeting SASP-related inflammation. While berberine (BBR) is known to possess anti-aging and anti-inflammatory properties, the molecular mechanisms by which it modulates atherosclerosis-associated cell senescence and inflammation remained insufficiently defined prior to this study. The key research question addressed is: How does berberine regulate inflammatory aging in atherosclerosis at the level of RXRα/PPARγ/NEDD4 signaling in macrophage-derived foam cells?

Key Innovation from the Reference Study

The pivotal innovation of Zheng et al. (Am. J. Chin. Med. 2025.53:251-283) lies in the identification of the RXRα/PPARγ/NEDD4 signaling axis as a central regulator of SASP-mediated inflammation in atherosclerotic plaques, and the demonstration that berberine exerts its anti-inflammatory effects via modulation of this pathway. The study integrates single-cell transcriptomics, in vivo mouse models, and targeted genetic knockdown approaches to causally link berberine’s anti-SASP action to this signaling cascade. Notably, the work shows that berberine-driven activation of RXRα and PPARγ, with subsequent upregulation of the E3 ubiquitin ligase NEDD4, promotes degradation of the pro-inflammatory GATA4/p62 complex, thereby curtailing SASP factor production in macrophage-derived foam cells.

Methods and Experimental Design Insights

The investigators employed a multi-tiered methodological approach. Initially, ApoE^-/- mice were fed a high-fat diet to induce atherosclerotic lesions, with BBR administered to assess effects on plaque morphology and systemic inflammation. In vitro, RAW264.7 macrophages and primary peritoneal macrophage-derived foam cells served as cellular models for SASP induction and intervention. Inflammatory proteins characteristic of SASP were quantified post-treatment. Smart-seq single-cell RNA sequencing analysis provided high-resolution pathway insights. Importantly, lentivirus-mediated macrophage-specific knockdown of RXRα in ApoE^-/- mice was performed to test the necessity of this nuclear receptor in mediating BBR’s anti-SASP effects. This combination of genetic, pharmacological, and transcriptomic approaches enabled precise dissection of pathway dependencies and outcomes.

Core Findings and Why They Matter

Key findings from the reference study include:

• Berberine reduced inflammation linked to SASP in both in vivo and in vitro models of atherosclerosis, decreasing pro-inflammatory cytokine production and altering plaque characteristics.
• Smart-seq analysis identified upregulation of RXRα and PPARγ, concurrent with increased NEDD4 transcription in BBR-treated foam cells. This axis was required for the observed anti-inflammatory effects.
• BBR promoted GATA4 binding to p62, facilitating their ubiquitination and subsequent degradation, which suppressed SASP factor secretion.
• Macrophage-specific knockdown of RXRα abolished berberine’s ability to activate PPARγ, increase NEDD4, and inhibit SASP, confirming the functional necessity of the RXRα/PPARγ/NEDD4 pathway.

These results provide mechanistic clarity on how modulation of nuclear receptor signaling and targeted protein degradation can attenuate inflammatory aging in vascular disease. The demonstration that RXRα-PPARγ heterodimer formation is a prerequisite for NEDD4-mediated effects also links transcriptional regulation to ubiquitin-proteasome dynamics in the context of SASP control.

Comparison with Existing Internal Articles

Recent internal reviews on PPARγ antagonists, especially T0070907: Precision PPARγ Antagonist for Signaling Dissection and T0070907: Precision PPARγ Antagonist for Pathway Dissection, have highlighted the importance of selective PPARγ modulation in dissecting adipogenesis, inflammation, and cell cycle regulation. These articles emphasize how potent PPARγ antagonists like T0070907 enable precise interrogation of the PPARγ/RXRα heterodimer and its downstream signaling, including transcriptional repression and co-repressor recruitment. The present study’s elucidation of the RXRα/PPARγ/NEDD4 axis as a regulatory node for SASP further rationalizes the use of selective PPARγ antagonists in workflow design, for instance, to block agonist-induced PPARγ transactivation or to model the impact of pathway inhibition on inflammatory phenotypes. The mechanistic links drawn here can therefore inform experimental designs that leverage T0070907 or similar agents to parse the relative contributions of PPARγ-dependent versus independent regulatory events.

Protocol Parameters

• Berberine dosing in atherosclerosis models: Administered to ApoE^-/- mice on a high-fat diet; typical durations range from several weeks, aligned with plaque development timelines as detailed in the reference study.
• In vitro SASP induction: RAW264.7 or primary macrophages exposed to pro-oxidant stimuli to model foam cell formation and senescence; BBR or pathway inhibitors/antagonists applied pre- or post-SASP induction.
• Lentiviral RXRα knockdown: Use of pLVCD68-shRNA targeting RXRα for macrophage-specific depletion in vivo, enabling pathway dependency testing.
• Single-cell transcriptomics: Smart-seq or equivalent platforms to resolve gene expression changes in response to pharmacological or genetic interventions.

Limitations and Transferability

While the study robustly demonstrates the anti-SASP effect of berberine via the RXRα/PPARγ/NEDD4 pathway in murine and cellular models, several limitations merit consideration. First, human validation beyond single-cell sequencing is limited; the translational fidelity of mouse models for human atherosclerosis, though strong in some respects, is not absolute. Second, while the RXRα/PPARγ/NEDD4 axis is necessary for BBR’s anti-inflammatory effect, the broader context of nuclear receptor crosstalk and potential pathway compensation in vivo remains to be fully mapped. Third, the study does not explore whether pharmacological PPARγ antagonists could mimic or modulate these effects, though the mechanistic rationale is established. Finally, off-target effects and the long-term safety of pathway manipulation, particularly in chronic disease settings, require further investigation.

Research Support Resources

For researchers aiming to interrogate the RXRα/PPARγ/NEDD4 signaling pathway or model SASP and inflammatory aging, highly selective chemical tools are essential. T0070907 (SKU A4301) is a well-characterized PPARγ antagonist with nanomolar affinity and specificity, suitable for dissecting PPARγ-dependent processes in both cellular and in vivo systems. Its utility in modulating transcriptional repression, adipogenesis inhibition, and cell cycle arrest has been detailed in several workflow-oriented reviews. When designing experiments to parse the role of PPARγ in SASP regulation or to evaluate the effects of pathway blockade, T0070907 provides a robust option for selective intervention. Protocols and storage guidance can be found in the product information. Researchers are encouraged to integrate such antagonists in parallel with genetic approaches to comprehensively map the contribution of PPARγ signaling to inflammatory phenotypes.