Phillygenin improves diabetic nephropathy by inhibiting inflammation and apoptosis via regulating TLR4/MyD88/NF-κB and PI3K/AKT/GSK3β signaling pathways.

Background: Phillygenin (PHI), a main bioactive compound found in the fruit of Forsythia suspensa, exhibits antiviral, antioxidant, anti-inflammatory, and antihypertensive activities. However, the molecular mechanisms underlying its effects on diabetic nephropathy (DN) remain unclear.

Purpose: To evaluate the therapeutic effects of PHI on DN and elucidate the molecular mechanisms involved.

Methods: Cell viability assays and RNA-seq analyses were performed to identify potential mechanisms through which PHI regulates HG-induced MPCs. The therapeutic efficacy of PHI was assessed in both DN cells and mouse models. Cytokine levels were measured using ELISA, while the expression levels of key signaling pathways, including TLR4/MyD88/NF-κB and PI3K/AKT/GSK3β along with downstream effectors were analyzed via immunoblotting, immunofluorescence, and immunohistochemical staining.

Results: PHI inhibited inflammatory responses and alleviated apoptosis by reducing the expression levels of IL-6, TNF-α, IL-1β, TLR4, MyD88, NF-κB, and cleaved caspase-3, while enhancing the phosphorylation of PI3K, AKT, GSK3β (Ser9), and pro-caspase-3 in MPCs under HG conditions in vitro. Additionally, in vivo experiments demonstrated that treatment with PHI (50 mg/kg) in db/db mice effectively improved renal function and attenuated kidney injury by reducing the urinary albumin-to-creatinine ratio (UACR), mitigating podocyte apoptosis, and inhibiting inflammatory via modulation of the TLR4/MyD88/NF-κB and PI3K/AKT/GSK3β signaling pathways.

Conclusion: PHI inhibits inflammation and apoptosis in vitro and alleviates diabetic kidney injury in db/db mice by interfering TLR4/MyD88/NF-κB and PI3K/AKT/GSK3β signaling pathways. Thus, this study reveals for the first time that PHI is a potential novel therapeutic agent for DN.