Statins Reduce Cellular Respiration and Induce De‐differentiation of Myofibroblasts

Abstract

BackgroundFibroblast to myofibroblast trans‐differentiation with altered bioenergetics precedes cardiac fibrosis (CF). Promotion of de‐differentiation could mitigate CF‐related pathologies; however, no specific remedial therapeutics for CF is clearly defined. Therefore, we determined whether statins, a hypolipidemic class of drugs commonly prescribed in patients at risk of heart failure (HF), can alter cellular bioenergetics and de‐differentiate myofibroblasts.MethodsPrimary cultures of differentiated human ventricular fibroblasts (hVFs) were randomly subjected to in vitro statin treatment (n = 3–6). Differentiation status was determined by α‐smooth muscle actin (α‐SMA) expression while cellular respiration was measured by Seahorse Extracellular Flux Analyzer XF‐96, as oxygen consumption rate (OCR) at baseline and following application of each well with mitochondrial modulators: Oligomycin (1 μg/ml), FCCP (0.1 μM) and antimycin A (1 μg/ml), normalized to total protein. Data were analyzed by either unpaired t test or one‐Way Analysis of Variance.ResultsIn vitro treatment of already differentiated myofibroblasts for 72 hours with both lipophilic (atorvastatin, simvastatin) and hydrophilic (rosuvastatin) statins concentration – dependently reduced α‐SMA/α‐β‐tubulin expression, normalized to % maximal differentiation. The respective IC50 values were 729 ± 13 nM (atorvastatin), 3.6 ± 1 μM (rosuvastatin) and 185 ± 13 nM (simvastatin); n = 3 per concentration of each statin. Basal OCR was significantly decreased in the simvastatin‐treated hVFs vs the differentiated control hVFs (TGF) (0.144 ± 0.026 vs. 0.278 ± 0.104, p = 0.002). Simvastatin reduced the ATP‐linked (0.083 ± 0.018 vs. 0.160 ± 0.059, p = 0.01), the proton leak‐linked (0.017 ± 0.008 vs. 0.074 ± 0.041, p = 0.01) and the maximal (0.250 ± 0.031 vs. 0.501 ± 0.142, p<0.001) OCR, but did not significantly affect spare capacity or non‐mitochondrial OCR. The inhibitory effect of simvastatin on the mitochondrial OCR was reversed by geranylgeranyl pyrophosphate (GGPP, 20 μM ) which significantly increased the basal (0.193 ± 0.053, p = 0.020), the spare‐capacity (0.233 ± 0.091, p = 0.008), and the maximal (0.377 ± 0.131, p = 0.003) OCR, without any change in the non‐mitochondrial OCR. The simvastatin treatment of the differentiated hVFs in vitro reduced ECAR after addition of FCCP (0.066 ± 0.011 vs. 0.093 ± 0.010, p<0.001) and AA (0.056 ± 0.014 vs. 0.097 ± 0.008, p<0.001). GGPP reversed ECAR to a similar level as control differentiated hVFs (FCCP: 0.081 ± 0.015, p = 0.005; AA: 0.080 ± 0.014, p = 0.018). Both atorvastatin (100 nM, 300 nM) and rosuvastatin (300 nM, 1 μM) also increased the ADP/ATP ratio in these cells, confirming the pan‐statin effect of decreased bioenergetics during de‐differentiation. Therefore, statins altered hVF bioenergetics and de‐differentiated the myofibroblasts which involved GGPP‐sensitive mechanisms, reduced cellular respiration with potential activation of KATP channels, as GGPP supplementation or KATP‐channel inhibition by glibenclamide countered the de‐differentiation.ConclusionStatin induced de‐differentiation of myofibroblasts via GGPP‐sensitive signaling, lowered bioenergetics, and KATP channels.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.