NF-κB-Mediated Integrin-Linked Kinase Regulation in Angiotensin II-Induced Pro-fibrotic Process in Cardiac Fibroblasts

Aims: Cardiac fibrosis is a final outcome of many clinical conditions that lead to cardiac failure and is characterized by a progressive substitution of cellular elements by extracellular-matrix proteins, such as collagen type I, collagen type II, connective tissue growth factor (CTGF), etc. The aim of this study was to identify the mechanisms responsible for angiotensin II (Ang II)-stimulated cardiac fibrosis using rat neonatal cardiac fibroblasts. Main methods: Neonatal fibroblasts were transfected with I kappa B alpha mutant, constitutively active (ca) integrin-linked kinase (ILK), dominant negative of ILK and small interfering RNA (siRNA) of ILK in the presence and absence of Ang-II stimulation. The pro-fibrotic gene expression and protein levels were determined by quantitative real time PCR and western blotting using their specific probes and antibodies. NF-kappa B translocation was determined by immunocytochemistry and confocal microscopy images were analyzed. Key findings: Our results indicate that overexpression of ILK promotes a pro-fibrotic process by upregulating collagen type land CTGF genes via activation of nuclear factor-kappa B (NF-kappa B) in cardiac fibroblasts. Inactivation of either NF-kappa B by the super-repressor I kappa B alpha or ILK by siRNA significantly attenuates the pro-fibrotic process. Moreover, ILK overexpression triggers NF-kappa B-p65 translocation to the nucleus, and ILK inhibition prevents the translocation in cardiac fibroblasts stimulated with Ang II. Significance: Our data suggest that the Ang II-stimulated pro-fibrotic process is regulated by a complex mechanism involving crosstalk between ILK and NF-kappa B activation. This dual mechanism may play a critical role in the progression of cardiac fibrosis. (C) 2014 Elsevier Inc. All rights reserved.