Inflammation due to Chronic Alcohol Exposure Promotes Cardiac Atrophy and Dysfunction Resulting from Impaired Fibroblast‐Myocyte Crosstalk

Abstract

Alcoholic cardiomyopathy (ACM) is a cardiac disease caused by chronic heavy alcohol abuse. ACM is most notably a type of dilated cardiomyopathy (DCM), accounting for approximately 21–50% of all idiopathic non‐ischemic DCM cases in Western countries. ACM is typically characterized by left ventricular dilation and LV muscle wasting (atrophy), with diastolic and systolic dysfunction (ejection fraction < 40%) occurring in later stages. Previous studies in our lab have shown that chronic alcohol exposure prevents compensatory hypertrophy in both volume‐ and pressure‐overload models of heart failure. However, the mechanisms of alcohol‐induced cardiac atrophy and dysfunction are not clear. The purpose of this study was to investigate mechanisms of chronic alcohol‐induced cardiac remodeling and dysfunction. We also sought to determine the role of cardiac fibroblasts, which play a dynamic role in cardiac remodeling, in mediating these effects.Adult male Wistar rats were exposed to ethanol (EtOH) vapor inhalation for 16 weeks. Echocardiography was performed to assess terminal cardiac structure and function. Cardiac fibroblasts were isolated from the left ventricle (LV) for both ex vivo and in vitro analysis. Gene expression was determined by real‐time PCR and flow cytometry. Protein expression was determined via Western blot analysis. EtOH led to cardiac wall thinning and impaired systolic function, as evident by decreased LV wall thickness at diastole (LVPWd) and fractional shortening, respectively, Additionally, EtOH decreased mRNA levels of various contractile proteins including Acta1, Actc1, and Myh7. EtOH also increased mRNA and protein levels of LV inflammatory markers, TNF‐α and NF‐κB. Furthermore, EtOH induced increased activation of JNK and decreased mTOR activation, suggestive of decreased hypertrophic signaling and atrophy. EtOH led to myofibroblast activation as assessed by flow cytometry and led to ECM remodeling (increased collagen III content). EtOH increased Tnf and Il6 mRNA in cardiac fibroblasts ex vivo, and increased mRNA levels of several pro‐inflammatory cytokines and chemokines in vitro. Administration of conditioned media from EtOH‐treated fibroblasts decreased contractile protein mRNA levels and impaired Akt and mTOR signaling in differentiated H9C2 cardiomyocytes.Our results indicate that EtOH‐induced cardiac atrophy and dysfunction is associated with activation of inflammatory pathways. Furthermore, EtOH may induce a pro‐inflammatory cardiac fibroblast phenotype, leading to aberrant fibroblast‐myocyte cross‐talk.Support or Funding InformationFunding provided by the NIH/NIAAA 1R21AA022690 (JDG) and the Saving tiny Hearts Society (JDG).