Suppression of collagen production in norepinephrine stimulated cardiac fibroblasts culture: differential effect of alpha and beta-adrenoreceptor antagonism

Human pluripotent stem cell-derived cardiac stromal cells and their applications in regenerative medicine

Coronary heart disease is one of the leading causes of death in the United States. Recent advances in stem cell biology have led to the development and engineering of human pluripotent stem cell (hPSC)-derived cardiac cells and tissues for application in cellular therapy and cardiotoxicity studies. Initial studies in this area have largely focused on improving differentiation efficiency and maturation states of cardiomyocytes. However, other cell types in the heart, including endothelial and stromal cells, play crucial roles in cardiac development, injury response, and cardiomyocyte function. This review discusses recent advances in differentiation of hPSCs to cardiac stromal cells, identification and classification of cardiac stromal cell types, and application of hPSC-derived cardiac stromal cells and tissues containing these cells in regenerative and drug development applications.

Proliferation in cardiac fibroblasts induced by β1-adrenoceptor autoantibody and the underlying mechanisms

Chronic sustained stimulation of β-adrenoceptor is closely related to cardiac fibrosis which is bad for cardiac function. Growing evidence showed that the high prevalence of β₁-adrenoceptor autoantibody (β₁-AA) in the sera of patients with various types of cardiovascular diseases decreased cardiac function. In the current study, we demonstrated that β₁-AA impaired the cardiac function evaluated by echocardiography and that β₁-AA triggered cardiac fibrosis in terms of increased expression of α-smooth muscle actin as the marker of myofibroblast and collagen deposition in a passive β₁-AA immunized mice model during 16 weeks. Further, we showed that β₁-AA activated β₁-AR/cAMP/PKA pathway and promoted proliferation in primary cardiac fibroblasts through specific binding to β₁-AR but not to β₂-AR. Moreover, β₁-AA was also likely to promote proliferation in cardiac fibroblasts through activating p38MAPK and ERK1/2 as p38MAPK inhibitor SB203580 and ERK1/2 inhibitor PD98059 partially reversed the proliferative effect. The persistent activating signalling of PKA and P38MAPK in 1 h induced by β₁-AA was associated with lacking agonist-induced desensitization phenomena. The conditioned medium from β₁-AA-stimulated cardiac fibroblasts induced cardiomyocyte apoptosis, which indicated that β₁-AA changed the secretion of cardiac fibroblasts contributing to cardiac injury. These findings will contribute to our understanding of the pathological mechanisms of β₁-AA.

A computational model of cardiac fibroblast signaling predicts context-dependent drivers of myofibroblast differentiation

Cardiac fibroblasts support heart function, and aberrant fibroblast signaling can lead to fibrosis and cardiac dysfunction. Yet how signaling molecules drive myofibroblast differentiation and fibrosis in the complex signaling environment of cardiac injury remains unclear. We developed a large-scale computational model of cardiac fibroblast signaling in order to identify regulators of fibrosis under diverse signaling contexts. The model network integrates 10 signaling pathways, including 91 nodes and 134 reactions, and it correctly predicted 80% of independent previous experiments. The model predicted key fibrotic signaling regulators (e.g. reactive oxygen species, tissue growth factor β (TGFβ) receptor), whose function varied depending on the extracellular environment. We characterized how network structure relates to function, identified functional modules, and predicted cross-talk between TGFβ and mechanical signaling, which was validated experimentally in adult cardiac fibroblasts. This study provides a systems framework for predicting key regulators of fibroblast signaling across diverse signaling contexts.

Meningeal norepinephrine produces headache behaviors in rats via actions both on dural afferents and fibroblasts

BACKGROUND

Stress is commonly reported to contribute to migraine although mechanisms by which this may occur are not fully known. The purpose of these studies was to examine whether norepinephrine (NE), the primary sympathetic efferent transmitter, acts on processes in the meninges that may contribute to the pain of migraine.

METHODS

NE was applied to rat dura using a behavioral model of headache. Primary cultures of rat trigeminal ganglia retrogradely labeled from the dura mater and of rat dural fibroblasts were prepared. Patch-clamp electrophysiology, Western blot, and ELISA were performed to examine the effects of NE. Conditioned media from NE-treated fibroblast cultures was applied to the dura using the behavioral headache model.

RESULTS

Dural injection both of NE and media from NE-stimulated fibroblasts caused cutaneous facial and hindpaw allodynia in awake rats. NE application to cultured dural afferents increased action potential firing in response to current injections. Application of NE to dural fibroblasts increased phosphorylation of ERK and caused the release of interleukin-6 (IL-6).

CONCLUSIONS

These data demonstrate that NE can contribute to pro-nociceptive signaling from the meninges via actions on dural afferents and dural fibroblasts. Together, these actions of NE may contribute to the headache phase of migraine.

The stimulatory effects of alpha1-adrenergic receptors on TGF-beta1, IGF-1 and hyaluronan production in human skin fibroblasts

Skin fibroblasts modulate tissue repair, wound healing and immunological responses. Adrenergic receptors (ARs) mediate important physiological functions, such as endocrine, metabolic and neuronal activity. In this study, the expression α1A-ARs in human skin fibroblasts is examined and verified. Regulatory effects of α1-agonist cirazoline on cell migration and the production of transforming growth factor β1 (TGF-β1), insulin-like growth factor 1 (IGF-1), hyaluronan (HA), fibronectin and procollagen type I carboxy-terminal peptide (PIP) by human skin fibroblasts are assessed and validated. α1A-AR mRNA and protein were found in human skin fibroblasts WS1. Exposure of cirazoline doubled skin fibroblast migration and the increase in cell migration was attenuated by α1-antagonist prazosin. TGF-β1 mRNA and production were enhanced after exposure to cirazoline and IGF-1 production was also increased after treatment with cirazoline. Exposure to cirazoline also enhanced HA and PIP production. The increases in TGF-β1, IGF-1, HA and PIP production were partially abolished in fibroblasts transfected with α1A-AR short interfering RNAs, indicating that α1A-ARs are involved in the cirazoline-induced increases in TGF-β1, IGF-1, HA and PIP production. Thus, α1A-ARs are stably expressed and stimulate cell migration and TGF-β1, IGF-1, HA and PIP production in human skin fibroblasts. Moreover, TGF-β1, IGF-1, HA and PIP production and the cell migration of human skin fibroblasts are possibly modulated by natural catecholamines produced by the endocrine system or sympathetic innervation, which could directly or indirectly participate in cytokine secretion, fibroblast migration and matrix production of wound healing in the skin.

Alpha1a-adrenoceptor genetic variant induces cardiomyoblast-to-fibroblast-like cell transition via distinct signaling pathways

The role of naturally occurring human α1a-Adrenergic Receptor (α1aAR) genetic variants associated with cardiovascular disorders is poorly understood. Here, we present the novel findings that expression of human α1aAR-247R (247R) genetic variant in cardiomyoblasts leads to transition of cardiomyoblasts into a fibroblast-like phenotype, evidenced by morphology and distinct de novo expression of characteristic genes. These fibroblast-like cells exhibit constitutive, high proliferative capacity and agonist-induced hypertrophy compared with cells prior to transition. We demonstrate that constitutive, synergistic activation of EGFR, Src and ERK kinases is the potential molecular mechanism of this transition. We also demonstrate that 247R triggers two distinct EGFR transactivation-dependent signaling pathways: 1) constitutive Gq-independent β-arrestin-1/Src/MMP/EGFR/ERK-dependent hyperproliferation and 2) agonist-induced Gq- and EGFR/STAT-dependent hypertrophy. Interestingly, in cardiomyoblasts agonist-independent hyperproliferation is MMP-dependent, but in fibroblast-like cells it is MMP-independent, suggesting that expression of α1aAR genetic variant in cardiomyocytes may trigger extracellular matrix remodeling. Thus, these novel findings demonstrate that EGFR transactivation by α1aAR-247R leads to hyperproliferation, hypertrophy and alterations in cardiomyoblasts, suggesting that these unique genetically-mediated alterations in signaling pathways and cellular function may lead to myocardial fibrosis. Such extracellular matrix remodeling may contribute to the genesis of arrhythmias in certain types of heart failure.

Matrix metalloproteinase-2 stimulates collagen-I expression through phosphorylation of focal adhesion kinase in rat cardiac fibroblasts

Collagen-I is thought to be the main component of the extracellular matrix in cardiac fibrosis, the accumulation of which occurs with excessive activation of matrix metalloproteinase-2 (MMP-2). MMP-2 degrades the extracellular matrix; however, the relative importance of MMP-2 to collagen-I synthesis in cardiac fibroblasts remains unclear. We investigated whether extracellular activation of MMP-2 regulates collagen-I synthesis and phosphorylation of focal adhesion kinase (FAK) in rat cardiac fibroblasts. Primary cultures of rat cardiac fibroblasts were incubated with purified active MMP-2 to determine whether extracellular MMP-2 affects collagen-I synthesis and FAK phosphorylation in cardiac fibroblasts. Exogenous MMP-2 significantly stimulated FAK (Tyr397) phosphorylation and induced collagen-I expression in a time-dependent manner. Simultaneous treatment with the FAK inhibitor PF573228 abolished exogenous MMP-2-enhanced FAK (Tyr397) phosphorylation and collagen-I expression. Cells were then stimulated with norepinephrine (NE) to investigate whether endogenous MMP-2 could also induce collagen-I expression through FAK (Tyr397) phosphorylation. NE-stimulated endogenous MMP-2 activation in conditioned medium was significantly attenuated by simultaneous treatment with the MMP inhibitor PD166793. Similarly, NE-induced FAK (Tyr397) phosphorylation and collagen-I expression were significantly inhibited by simultaneous treatment with PD166793 or PF573228. Furthermore, MMP-2 knockdown induced by small interfering RNA (siRNA) significantly abolished endogenous MMP-2 expression and activation. MMP-2 siRNA significantly abolished NE-induced FAK (Tyr397) phosphorylation and collagen-I expression. These findings suggest that the extracellular activation of MMP-2 accelerated collagen-I synthesis in rat cardiac fibroblasts and that FAK phosphorylation (Tyr397) plays a pivotal role in MMP-2-stimulated collagen-I synthesis.

The regulatory effect of norepinephrine on connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF) expression in cultured cardiac fibroblasts

BACKGROUND

Connective tissue growth factor (CTGF) and vascular endothelial cell growth factor (VEGF) have been implicated as important effectors during cardiac remodeling. This study tested the hypothesis that norepinephrine (NE) induces CTGF and VEGF gene and protein expression in cardiac fibroblasts (CF) and the CTGF/VEGF complex will have an effect on angiogenesis.

METHODS AND RESULTS

Rats CF were cultured in NE (0.01 to 100 μM) for 24h. CTGF and VEGF gene expression were measured by quantitative-PCR. CTGF protein and CTGF/VEGF complex were detected by Western blot. The effect of CTGF/VEGF complex on angiogenesis was detected by endothelial cell tube formation assay. VEGF antigen level, reactive oxygen species (ROS) production were measured by ELISA and DCFH-DiOxyQ assay respectively. NE at 0.01 μM up-regulated CTGF mRNA and secretory protein expression significantly whereas at 100 μM both gene and protein were down-regulated significantly when compared with controls. At 0.01 to 0.1 μM of NE, there was no change in VEGF gene and protein level. NE at 100 μM increased VEGF gene and antigen level and ROS production significantly when compared with controls. CTGF/VEGF complex was found to inhibit the angiogenesis of endothelial cells.

CONCLUSIONS

NE regulates CTGF and VEGF expression in a dose-dependent manner and via VEGF can induce angiogenesis. This work suggests NE may have an important role in ventricular remodeling.

Cardiac and neuroprotection regulated by α(1)-adrenergic receptor subtypes

Sympathetic nervous system regulation by the α(1)-adrenergic receptor (AR) subtypes (α(1A), α(1B), α(1D)) is complex, whereby chronic activity can be either detrimental or protective for both heart and brain function. This review will summarize the evidence that this dual regulation can be mediated through the different α(1)-AR subtypes in the context of cardiac hypertrophy, heart failure, apoptosis, ischemic preconditioning, neurogenesis, locomotion, neurodegeneration, cognition, neuroplasticity, depression, anxiety, epilepsy, and mental illness.