1. Metformin is an activator of AMP-activated protein kinase (AMPK). Recent studies suggest that pharmacological activation of AMPK inhibits cardiac hypertrophy. In the present study, we examined whether long-term treatment with metformin could attenuate ventricular hypertrophy in a rat model. The potential involvement of nitric oxide (NO) in the effects of metformin was also investigated. 2. Ventricular hypertrophy was established in rats by transaortic constriction (TAC). Starting 1 week after the TAC procedure, rats were treated with metformin (300 mg/kg per day, p.o.), N(G)-nitro-L-arginine methyl ester (L-NAME; 50 mg/kg per day, p.o.) or both for 8 weeks prior to the assessment of haemodynamic function and cardiac hypertrophy. 3. Cultured cardiomyocytes were used to examine the effects of metformin on the AMPK-endothelial NO synthase (eNOS) pathway. Cells were exposed to angiotensin (Ang) II (10⁻⁶ mol/L) for 24 h under serum-free conditions in the presence or absence of metformin (10⁻³ mol/L), compound C (10⁻⁶ mol/L), L-NAME (10⁻⁶ mol/L) or their combination. The rate of incorporation of [³H]-leucine was determined, western blotting analyses of AMPK-eNOS, neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) were undertaken and the concentration of NO in culture media was determined. 4. Transaortic constriction resulted in significant haemodynamic dysfunction and ventricular hypertrophy. Myocardial fibrosis was also evident. Treatment with metformin improved haemodynamic function and significantly attenuated ventricular hypertrophy. Most of the effects of metformin were abolished by concomitant L-NAME treatment. L-NAME on its own had no effect on haemodynamic function and ventricular hypertrophy in TAC rats. 5. In cardiomyocytes, metformin inhibited AngII-induced protein synthesis, an effect that was suppressed by the AMPK inhibitor compound C or the eNOS inhibitor L-NAME. The improvement in cardiac structure and function following metformin treatment was associated with enhanced phosphorylation of AMPK and eNOS and increased NO production. 6. The findings of the present study indicate that long-term treatment with metformin could attenuate ventricular hypertrophy induced by pressure overload via activation of AMPK and a downstream signalling pathway involving eNOS-NO.

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Protein disulfide isomerase 3 (PDIA3) is a chaperone protein that modulates the folding of newly synthesized glycoproteins, has isomerase and redox activity, and has been implicated in the pathogenesis of many diseases. However, the role of PDIA3 in pregnancy-associated diseases remains largely unknown. Our present study reveals a key role for PDIA3 in the biology of placental trophoblasts from women with preeclampsia (PE). Immunohistochemistry and Western blot analysis revealed that PDIA3 expression was decreased in villous trophoblasts from women with PE compared to normotensive pregnancies. Further, using a Cell Counting Kit-8 assay, flow cytometry, and 5-ethynyl-2’-deoxyuridine (EdU) staining, we found that siRNA-mediated PDIA3 knockdown significantly promoted apoptosis and inhibited proliferation in the HTR8/SVneo cell line, while overexpression of PDIA3 reversed these effects. Furthermore, RNA sequencing and Western blot analysis demonstrated that knockdown of PDIA3 inhibited MDM2 protein expression in HTR8 cells, concurrent with marked elevation of p53 and p21 expression. Conversely, overexpression of PDIA3 had the opposite effects. Immunohistochemistry and Western blot further revealed that MDM2 protein expression was downregulated and p21 was increased in trophoblasts of women with PE compared to women with normotensive pregnancies. Our findings indicate that PDIA3 expression is decreased in the trophoblasts of women with PE, and decreased PDIA3 induces trophoblast apoptosis and represses trophoblast proliferation through regulating the MDM2/p53/p21 pathway.