Pinoresinol diglucoside (PDG) attenuates cardiac hypertrophy via AKT/mTOR/NF-κB signaling in pressure overload-induced rats

Ethnopharmacological relevance: Pinoresinol diglucoside (PDG), the active compound extracted from Eucommia ulmoides, Styrax sp. and Forsythia suspensa, plays the roles in regulating hypertension, inflammation and oxidative stress.

Aims: Considering that hypertension and inflammation has been proved to contribute to cardiac remodeling, we tested the effects of PDG on cardiac hypertrophy (CM).

Methods: Male Sprague Dawley (SD) rats were used to construct hypertrophic rats by partial abdominal aortic constriction (AAC)-surgery. PDG solution (2 mg/ml) was used to treat AAC-induced rats by intraperitoneal injection at low dose (L-PDG, 2.5 mg/kg per day), medium dose (M-PDG, 5 mg/kg per day), and high dose (H-PDG, 7.5 mg/kg per day) for 3 weeks post AAC-surgery. CM was evaluated by the ratio of left ventricular weight to body weight ratio (LVW/BW), left ventricular wall thickness by H&E staining, and Collagen content deposit by Masson's staining. Further, isoproterenol (ISO) and phenylephrine (PE) were used to produce cellular models of CM in neonatal rat ventricular cardiomyocytes (NRVMs). PDG pre-treated NRVMs 2 h at low dose (L-PDG, 2.5 μg/ml), medium dose (M-PDG, 5 μg/ml), and high dose (H-PDG, 7.5 μg/ml) for 24 h with or without PE- and ISO-stimulation. CM was evaluated by the expressions of hypertrophic biomarkers. Next, the hypertrophic biomarkers and pro-inflammatory cytokines were measured using quantitative Real-Time PCR (qRT-PCR), the expressions of protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/transcription factor nuclear factor-kappa B (NF-kB) signaling pathway were determined by Western blotting.

Results: PDG treatment prevented cardiac histomorphology damages, decreased upregulations of hypertrophic biomarkers, and prevented fibrosis and inflammation after pressure overload resulting from AAC-surgery. Consistently, PDG remarkably inhibited the changes of cardiomyocyte hypertrophic biomarkers and inflammatory responses in cellular models of CM. Interestingly, PDG administration inhibited the activation of Akt/mTOR/NF-kB signaling pathway both in vivo and in vitro.

Conclusions: PDG prevents AAC-induced CM in vivo, PE- and ISO-induced CM in vitro. The Akt/mTOR/NF-kB signaling pathway could be the potential therapeutic target involved in the protection of PDG. These findings provide novel evidence that PDG might be a promising therapeutic strategy for CM.