Regulation of connexin 43 by interleukin 1β in adult rat cardiac fibroblasts and effects in an adult rat cardiac myocyte: fibroblast co-culture model

Godfrey L Smith,Alexandra Riddell,Lisa Chilton,Lisa Mcarthur,Stuart A Nicklin

doi:10.1016/j.heliyon.2019.e03031

Godfrey L Smith, Alexandra Riddell + Show 3 more

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https://doi.org/10.1016/j.heliyon.2019.e03031

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Journal: Heliyon	Publication Date: Dec 30, 2019
Citations: 6	License type: cc-by

Affiliation: University of Glasgow, James Cook University

Abstract

Connexin 43 expression (Cx43) is increased in cardiac fibroblasts (CFs) following myocardial infarction. Here, potential mediators responsible for increasing Cx43 expression and effects of differential CF phenotype on cardiac myocyte (CM) function were investigated. Stimulating adult rat CFs with proinflammatory mediators revealed that interleukin 1β (IL-1β) significantly enhanced Cx43 levels through the IL-1β pathway. Additionally, IL-1β reduced mRNA levels of the myofibroblast (MF) markers: (i) connective tissue growth factor (CTGF) and (ii) α smooth muscle actin (αSMA), compared to control CFs. A co-culture adult rat CM:CF model was utilised to examine cell-to-cell interactions. Transfer of calcein from CMs to underlying CFs suggested functional gap junction formation. Functional analysis revealed contraction duration (CD) of CMs was shortened in co-culture with CFs, while treatment of CFs with IL-1β reduced this mechanical effect of co-culture. No effect on action potential rise time or duration of CMs cultured with control or IL-1β-treated CFs was observed. These data demonstrate that stimulating CFs with IL-1β increases Cx43 and reduces MF marker expression, suggesting altered cell phenotype. These changes may underlie the reduced mechanical effects of IL-1β treated CFs on CD of co-cultured CMs and therefore have an implication for our understanding of heterocellular interactions in cardiac disease.

Highlights

Cardiac myocytes (CMs) are responsible for cardiac contraction and are undoubtedly the most important cell type in the heart
As proinflammatory/profibrotic mediators are augmented in cardiac disease [29, 30, 31], the effect of a range of proteins, including Ang II, TGFβ1, interleukin 1β (IL-1β), IL-1α, TNFα, IL-6 and IL-6 in combination with the sIL-6R on Connexin 43 expression (Cx43) mRNA expression was examined in cardiac fibroblasts (CFs) (Figure 2)
Stimulation of CFs cultured in the absence of foetal bovine serum (FBS) with TGFβ1, IL-1β, IL-1α or IL-6 in combination with the sIL-6R induced a significant upregulation of Cx43 mRNA expression (RQ: 1.7 Æ 1.1 [P < 0.05], 10.2 Æ 3.1 [P < 0.001], 10.0 Æ 4.9 [P < 0.001] and 2.0 Æ 1.3 [P < 0.01] respectively; Figure 2A)

Summary

Introduction

Cardiac myocytes (CMs) are responsible for cardiac contraction and are undoubtedly the most important cell type in the heart. CFs proliferate in mass and undergo a phenotypic switch to become myofibroblasts (MFs) [1] These cells have a contractile phenotype, developing the expression of α-smooth muscle actin (αSMA), and secrete excessive volumes of ECM components, resulting in typical fibrosis seen after injury [2]. This contributes to cardiac dysfunction and dramatically increases the proarrhythmic potential of the heart, by creating structures that disrupt the conduction through the heart and predispose the conduction pathway to re-entry [3]. Electrical signals have been shown to propagate from one band of CMs to another when they were separated by CFs over distances of up to 300 μm in a culture model [12], demonstrating the ability of CFs to passively conduct electrical impulses

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