sphingosine-kinase and Hypertrophy

Cardiac fibrosis and myocyte hypertrophy are hallmarks of the cardiac remodelling process in cardiomyopathies such as heart failure (HF). Dyslipidemia or dysregulation of lipids contribute to HF. The dysregulation of high density lipoproteins (HDL) could lead to altered levels of other lipid metabolites that are bound to it such as sphingosine-1- phosphate (S1P). Recently, it has been shown that S1P and its analogue dihydrosphingosine-1-phosphate (dhS1P) are bound to HDL in plasma. The effects of dhS1P on cardiac cells have been obscure. In this study, we show that extracellular dhS1P is able to increase collagen synthesis in neonatal rat cardiac fibroblasts (NCFs) and cause hypertrophy of neonatal cardiac myocytes (NCMs). The janus kinase/signal transducer and activator (JAK/STAT) signalling pathway was involved in the increased collagen synthesis by dhS1P, through sustained increase of tissue inhibitor of matrix metalloproteinase 1 (TIMP1). Extracellular dhS1P increased phosphorylation levels of STAT1 and STAT3 proteins, also caused an early increase in gene expression of transforming growth factor-β (TGFβ), and sustained increase in TIMP1. Inhibition of JAKs led to inhibition of TIMP1 and TGFβ gene and protein expression. We also show that dhS1P is able to cause NCM hypertrophy through S1P-receptor-1 (S1PR1) signalling which is opposite to that of its analogue, S1P. Taken together, our results show that dhS1P increases collagen synthesis in cardiac fibroblasts causing fibrosis through dhS1P-JAK/STAT-TIMP1 signalling.

Topics: Animals; Animals, Newborn; Biomarkers; Cell Differentiation; Collagen; Fibroblasts; Gene Expression Regulation; Hypertrophy; Janus Kinases; Lysophospholipids; Matrix Metalloproteinase 2; Models, Biological; Myocardium; Myocytes, Cardiac; Oxadiazoles; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Rats, Sprague-Dawley; RNA, Messenger; Signal Transduction; Smad2 Protein; Sphingosine; STAT Transcription Factors; Thiophenes; Time Factors; Tissue Inhibitor of Metalloproteinase-1; Transforming Growth Factor beta

Topics: Adipocytes; Animals; Gene Knockout Techniques; Hypertrophy; Lipolysis; Male; Mice; Non-alcoholic Fatty Liver Disease; Phosphotransferases (Alcohol Group Acceptor)

Pulmonary hypertension (PH) is a serious condition that affects mainly young and middle-aged women, and its etiology is poorly understood. A prominent pathological feature of PH is accumulation of macrophages near the arterioles of the lung. In both clinical tissue and the SU5416 (SU)/athymic rat model of severe PH, we found that the accumulated macrophages expressed high levels of leukotriene A4 hydrolase (LTA4H), the biosynthetic enzyme for leukotriene B4 (LTB4). Moreover, macrophage-derived LTB4 directly induced apoptosis in pulmonary artery endothelial cells (PAECs). Further, LTB4 induced proliferation and hypertrophy of human pulmonary artery smooth muscle cells. We found that LTB4 acted through its receptor, BLT1, to induce PAEC apoptosis by inhibiting the protective endothelial sphingosine kinase 1 (Sphk1)-endothelial nitric oxide synthase (eNOS) pathway. Blocking LTA4H decreased in vivo LTB4 levels, prevented PAEC apoptosis, restored Sphk1-eNOS signaling, and reversed fulminant PH in the SU/athymic rat model of PH. Antagonizing BLT1 similarly reversed established PH. Inhibition of LTB4 biosynthesis or signal transduction in SU-treated athymic rats with established disease also improved cardiac function and reopened obstructed arterioles; this approach was also effective in the monocrotaline model of severe PH. Human plexiform lesions, one hallmark of PH, showed increased numbers of macrophages, which expressed LTA4H, and patients with connective tissue disease-associated pulmonary arterial hypertension exhibited significantly higher LTB4 concentrations in the systemic circulation than did healthy subjects. These results uncover a possible role for macrophage-derived LTB4 in PH pathogenesis and identify a pathway that may be amenable to therapeutic targeting.

Topics: Animals; Apoptosis; Cell Proliferation; Eicosanoids; Endothelial Cells; Familial Primary Pulmonary Hypertension; Female; Humans; Hypertension, Pulmonary; Hypertrophy; Leukotriene B4; Macrophage Activation; Macrophages; Myocytes, Smooth Muscle; Nitric Oxide Synthase Type III; Phosphotransferases (Alcohol Group Acceptor); Pulmonary Artery; Rats; Signal Transduction

Sphingosine kinase 1 (SphK1) pathway is critical in the pathogenesis of diabetic nephropathy. Recently, we found that berberine suppressed the activation of SphK1 pathway in diabetic kidney, protecting against diabetic nephropathy. The potential molecular mechanism, however, is still unknown. Here, we showed that berberine prevented the expression of α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1) and fibronectin (FN) in mesangial cells cultured by high glucose. Furthermore, berberine suppressed the activation of SphK1 pathway via inhibition of the activity and expression of SphK1 in mesangial cells cultured by high glucose. Surprisingly, berberine blocked the increased activity and expression of SphK1 in mesangial cells transfected by wild type SphK1 under normal glucose condition. However, berberine had no inhibitory effect on the recombinant human SphK1 protein. Finally, berberine markedly attenuated the high glucose-induced activator protein-1 (AP-1) activity in mesangial cells. Altogether, these data not only demonstrate that berberine is an important agent against diabetic nephropathy through inhibition of SphK1/AP-1 pathway, but also indicate that the inhibition of SphK1/AP-1 by berberine is independent of ambient glucose concentration.

Topics: Actins; Animals; Berberine; Cells, Cultured; Diabetic Nephropathies; Dose-Response Relationship, Drug; Down-Regulation; Fibronectins; Glucose; Humans; Hypertrophy; Mesangial Cells; Phosphotransferases (Alcohol Group Acceptor); Protein Kinase Inhibitors; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Signal Transduction; Transcription Factor AP-1; Transfection; Transforming Growth Factor beta1

Sphingosine 1-phosphate (S1P) mediates a number of cellular responses, including growth and proliferation. Skeletal muscle possesses the full enzymatic machinery to generate S1P and expresses the transcripts of S1P receptors. The aim of this work was to localize S1P receptors in rat skeletal muscle and to investigate whether S1P exerts a trophic action on muscle fibers. RT-PCR and Western blot analyses demonstrated the expression of S1P(1) and S1P(3) receptors by soleus muscle. Immunofluorescence revealed that S1P(1) and S1P(3) receptors are localized at the cell membrane of muscle fibers and in the T-tubule membranes. The receptors also decorate the nuclear membrane. S1P(1) receptors were also present at the neuromuscular junction. The possible trophic action of S1P was investigated by utilizing the denervation atrophy model. Rat soleus muscle was analyzed 7 and 14 days after motor nerve cut. During denervation, S1P was continuously delivered to the muscle through a mini osmotic pump. S1P and its precursor, sphingosine (Sph), significantly attenuated the progress of denervation-induced muscle atrophy. The trophic effect of Sph was prevented by N,N-dimethylsphingosine, an inhibitor of Sph kinase, the enzyme that converts Sph into S1P. Neutralization of circulating S1P by a specific antibody further demonstrated that S1P was responsible for the trophic effects of S1P during denervation atrophy. Denervation produced the down regulation of S1P(1) and S1P(3) receptors, regardless of the presence of the receptor agonist. In conclusion, the results suggest that S1P acts as a trophic factor of skeletal muscle.

Topics: Animals; Antibodies; Cell Enlargement; Cell Membrane; Disease Models, Animal; Enzyme Inhibitors; Hypertrophy; Infusion Pumps, Implantable; Lysophospholipids; Male; Muscle Denervation; Muscle, Skeletal; Muscular Atrophy; MyoD Protein; Myogenin; Myosin Heavy Chains; Neuromuscular Junction; Nuclear Envelope; Phosphotransferases (Alcohol Group Acceptor); Rats; Rats, Wistar; Receptors, Lysosphingolipid; RNA, Messenger; Sciatic Nerve; Sphingosine; Time Factors