Biglycan Involvement in Heart Fibrosis: Modulation of Adenosine 2A Receptor Improves Damage in Immortalized Cardiac Fibroblasts

Cardiac fibrosis is a common pathological feature of different cardiovascular diseases, characterized by the aberrant deposition of extracellular matrix (ECM) proteins in the cardiac interstitium, myofibroblast differentiation and increased fibrillar collagen deposition stimulated by transforming growth factor (TGF)-beta activation. Biglycan (BGN), a small leucine-rich proteoglycan (SLRPG) integrated within the ECM, plays a key role in matrix assembly and the phenotypic control of cardiac fibroblasts. Moreover, BGN is critically involved in pathological cardiac remodeling through TGF-beta binding, thus causing myofibroblast differentiation and proliferation. Adenosine receptors (ARs), and in particular A(2AR), may play a key role in stimulating fibrotic damage through collagen production/deposition, as a consequence of cyclic AMP (cAMP) and AKT activation. For this reason, A(2AR) modulation could be a useful tool to manage cardiac fibrosis in order to reduce fibrotic scar deposition in heart tissue. Therefore, the aim of the present study was to investigate the possible crosstalk between A(2AR) and BGN modulation in an in vitro model of TGF-beta-induced fibrosis. Immortalized human cardiac fibroblasts (IM-HCF) were stimulated with TGF-beta at the concentration of 10 ng/mL for 24 h to induce a fibrotic phenotype. After applying the TGF-beta stimulus, cells were treated with two different A(2AR) antagonists, Istradefylline and ZM241385, for an additional 24 h, at the concentration of 10 mu M and 1 mu M, respectively. Both A(2AR) antagonists were able to regulate the oxidative stress induced by TGF-beta through intracellular reactive oxygen species (ROS) reduction in IM-HCFs. Moreover, collagen1a1, MMPs 3/9, BGN, caspase-1 and IL-1 beta gene expression was markedly decreased following A(2AR) antagonist treatment in TGF-beta-challenged human fibroblasts. The results obtained for collagen1a1, SMAD3, alpha-SMA and BGN were also confirmed when protein expression was evaluated; phospho-Akt protein levels were also reduced following Istradefylline and ZM241385 use, thus suggesting that collagen production involves AKT recruited by the A(2AR). These results suggest that A(2AR) modulation might be an effective therapeutic option to reduce the fibrotic processes involved in heart pathological remodeling.

Automated summary

Cardiac fibrosis is characterized by abnormal deposition of extracellular matrix proteins, myofibroblast differentiation, and collagen deposition stimulated by TGF-beta activation. Biglycan (BGN) plays a key role in matrix assembly and the control of cardiac fibroblast phenotype. Adenosine receptors (ARs), particularly A(2AR), may stimulate fibrotic damage through collagen production, and A(2AR) modulation could be an effective therapeutic option to reduce fibrotic processes in heart remodeling.