Investigating the impact of aging and hyperlipidaemia on metformin cardioprotection against carfilzomib-induced cardiotoxicity in vivo
Authors: Psarrakou G , Chatzistefanou M , Efentakis P , Varela A , Papanagnou E.D , Nikolaou P.E , Tsoumani M , Davos C.H , Kastritis E , Trougakos I.P , Dimopoulos M.A , Terpos E , Andreadou I 
Published: November 2020

Abstract

Background
Carfilzomib (Cfz) is an irreversible proteasome inhibitor, indicated for the treatment of Multiple Myeloma (MM); however, is associated with cardiotoxicity in humans. Metformin (Met) has been suggested as a prophylactic therapy against Cfz-induced cardiotoxicity in mice.

Purpose
Considering that MM is an elderly disease, manifested in presence of cardiovascular comorbidities, we investigated the cardioprotective effect of Met against Cfz-cardiomyopathy on the age- or hyperlipidaemia-burdened myocardium in vivo.

Methods
Aging model: Male C57BL/6 mice, 15-month old, were randomized into: 1. Control (N/S 0.9%), 2. Met (140 mg/kg, po), 3. Cfz (8mg/kg, ip) and 4. Cfz+Met (8 and 140 mg/kg respectively) (n=5–7/group). Hyperlipidaemic model: ApoE−/− male mice, 20-weeks old were randomized into: 1. Control (N/S 0.9%), 2. Met (140 mg/kg, po), 3. Cfz (8mg/kg, ip) and 4. Cfz+Met (8 and 140 mg/kg respectively) (n=6/group). Cfz was administered every 48 hours and Met every 24 hours for 6 days. At baseline and at the end of treatments mice underwent echocardiography. Proteasomal activity and molecular signaling mechanisms were assessed in myocardial tissue and in peripheral blood mononuclear cells (PBMCs).

Results
Aging model: Proteasome activity was significantly reduced in myocardial tissue of aged vs young mice (P&lt;0.05). Cfz-treated mice showed an additional decrease in proteasomal activity compared to Control (P&lt;0.05) and Met (P&lt;0.01) groups, in heart and PBMCs. A significant fractional shortening (FS%) reduction was observed in Cfz group vs controls at day 6 (29.90±1.7 vs 37.60±0.2, respectively, P&lt;0.05) while Met in both Met and Cfz+Met groups maintained FS% vs controls (34.88±1.6, 33.20±0.6 vs 37.60±0.2, respectively, P=NS). By investigating molecular signaling pathways involved in cardioprotection, we observed that Cfz led to a decrease of Akt and AMPKα phosphorylation (P&lt;0.05 vs Control), whereas Cfz+Met co-administration restored Akt and AMPKα phosphorylation and upregulated t-eNOS and t-Akt (P&lt;0.05 vs Control). Hyperlipidaemic model: In ApoE−/− mice, no significant reduction of myocardial proteasomal activity was observed, whilst PBMCs proteasomal activity was decreased compared to controls (P&lt;0.05). Cfz treated ApoE−/− mice exhibited a reduction of myocardial (P&lt;0.01 in Cfz and P&lt;0.001 in Cfz+Met) and PBMCs' proteasome activity (P&lt;0.001) vs controls. Interestingly, Cfz, Met as well as the combination led to a decrease in FS% versus controls (44.00±1.2, 42.33±0.92, 42.33±1.0 vs 47.50±0.72 respectively, P&lt;0.05).

Conclusions
Our results demonstrate that Met retains its prophylactic potency against Cfz-induced cardiotoxicity in aged mice and activates cardioprotective signaling molecules. In the ApoE−/− mice, Met failed to exert cardioprotection against Cfz induced cardiomyopathy. Therefore, the monitoring of the cardiovascular burden seems to be of outmost importance in managing Cfz cardiac adverse effects.

Funding Acknowledgement
Type of funding source: Private company. Main funding source(s): Amgen