Inhibition of autophagy inhibits the conversion of cardiac fibroblasts to cardiac myofibroblasts

Abstract

The incidence of heart failure with concomitant cardiac fibrosis is very high in developed countries. Fibroblast activation in heart is causal to cardiac fibrosis as they convert to hypersynthetic cardiac myofibroblasts. There is no known treatment for cardiac fibrosis. Myofibroblasts contribute to the inappropriate remodeling of the myocardial interstitium, which leads to reduced cardiac function and ultimately heart failure. Elevated levels of autophagy have been linked to stress-induced ventricular remodeling and other cardiac diseases. Previously, we had shown that TGF-β1 treatment of human atrial fibroblasts both induced autophagy and enhanced the fibrogenic response supporting a linkage between the myofibroblast phenotype and autophagy. We now demonstrate that with in vitro culture of primary rat cardiac fibroblasts, inhibition of autophagy represses fibroblast to myofibroblast phenoconversion. Culturing unpassaged cardiac fibroblasts for 72 hours on plastic tissue culture plates is associated with elevated α-smooth muscle actin (α-SMA) expression. This activation parallels increased microtubule-associated protein 1A/1B-light chain 3 (LC-3β II) protein expression. Inhibition of autophagy with bafilomycin-A1 (Baf-A1) and chloroquine (CQ) in cardiac fibroblasts significantly reduces α-SMA and extracellular domain A fibronectin (ED-A FN) protein vs untreated controls. Myofibroblast cell migration and contractility were significantly reduced following inhibition of autophagy. These data support the possibility of a causal link between cardiac fibroblast-to-myofibroblast phenoconversion and autophagy.

Autophagy and the unfolded protein response promote profibrotic effects of TGF-β1 in human lung fibroblasts

“…Araya et al (3) recently showed that insufficient activation of autophagy may underpin cyclin-dependent kinase inhibitor 1 (p21)-regulated senescence in airway epithelial cells from IPF donors. Autophagy inhibition has also been associated with myofibroblast phenoconversion (21), a response associated with increased synthesis of extracellular matrix (ECM) proteins in response to transforming growth factor-␤ 1 (TGF-␤ 1 ) (3). Reduced levels of autophagy markers are evident in whole lung cell from IPF patients, although no specific mechanism for this has been definitively identified (41,43).…”

MicroRNA‐30c suppresses the pro‐fibrogenic effects of cardiac fibroblasts induced by TGF‐β1 and prevents atrial fibrosis by targeting TGFβRII

“…First, we observed that miR‐30c mimic significantly inhibited CF proliferation at 24, 48 and 72 hours with or without TGF‐β1 via CCK‐8 assay compared with that in negative control group (Figure 2B). In addition, the overexpressing miR‐30c attenuated the differentiation of CFs into myofibroblasts as indicated by decreased the levels of vimentin and α‐smooth muscle actin (α‐SMA) (Figure 2C–E), which is a reliable and classic marker for the myofibroblast 33, 34, 35. Furthermore, our result demonstrated that a miR‐30c mimic inhibited CF stimulated with or without TGF‐β1 migration via transwell migration assay (Figure 2F,G).…”

“…62,63 During cardiac fibrosis, CFs underwent phenotypic transition to myofibroblasts marked by increased a-SMA, which is a reliable and classic marker for the myofibroblast. [33][34][35] In addition to the enhancement of contractility, myofibroblasts characteristically demonstrate increased migratory activity. 64 CF proliferation, migration and differentiation are important factors in cardiac fibrosis.…”

Autophagy is involved in the sclerotic phase of systemic sclerosis

“…It has previously been reported that autophagy is activated in BLMtreated mouse lung 21 -23) , which is consistent with the present results of BLMinduced LC3 -positive puncta in the mouse skin. Furthermore, previous studies that conducted knockdown experiments of core Atg genes, Atg5 or Atg7, as well as pharmacological experiments using autophagy inhibitors (chloroquine and 3 -methyladenine), reported positive roles of autophagy in liver fibrosis 24) and the transdifferentiation of cardiac myofibroblasts 25) . Hydroxychloroquine, also an autophagy inhibitor, reduced the metabolic activity and suppressed cell proliferation of human fibroblasts 26) .…”