Suowen Xu

Cardiovascular actions and therapeutic potential of tanshinone IIA

Tanshinone IIA (TS), a pharmacologically active component isolated from the rhizome of the Chinese herb Salvia miltiorrhiza Bunge (Danshen), has been clinically used in Asian countries for the prevention and treatment of coronary heart disease. Recently, the pharmacological properties of TS in the cardiovascular system have attracted great interest. Emerging experimental studies and clinical trials have demonstrated that TS prevents atherogenesis as well as cardiac injury and hypertrophy. In atherosclerosis, TS acts by inhibiting LDL oxidation, monocyte adhesion to endothelium, smooth muscle cell migration and proliferation, macrophage cholesterol accumulation, proinflammatory cytokine expression and platelet aggregation. TS has some activity and potential to stabilize atherosclerotic plaques. The cardioprotective effects of TS are mainly related to its anti-oxidant and anti-inflammatory actions. In this review, we focus on the protective effects and the mechanism of action of TS in the cardiovascular system, and provide a novel perspective on clinical use of TS.

LOX-1 in atherosclerosis: biological functions and pharmacological modifiers

Lectin-like oxidized LDL (oxLDL) receptor-1 (LOX-1, also known as OLR-1), is a class E scavenger receptor that mediates the uptake of oxLDL by vascular cells. LOX-1 is involved in endothelial dysfunction, monocyte adhesion, the proliferation, migration, and apoptosis of smooth muscle cells, foam cell formation, platelet activation, as well as plaque instability; all of these events are critical in the pathogenesis of atherosclerosis. These LOX-1-dependent biological processes contribute to plaque instability and the ultimate clinical sequelae of plaque rupture and life-threatening tissue ischemia. Administration of anti-LOX-1 antibodies inhibits atherosclerosis by decreasing these cellular events. Over the past decade, multiple drugs including naturally occurring antioxidants, statins, antiinflammatory agents, antihypertensive and antihyperglycemic drugs have been demonstrated to inhibit vascular LOX-1 expression and activity. Therefore, LOX-1 represents an attractive therapeutic target for the treatment of human atherosclerotic diseases. This review aims to integrate the current understanding of LOX-1 signaling, regulation of LOX-1 by vasculoprotective drugs, and the importance of LOX-1 in the pathogenesis of atherosclerosis.

Berberine attenuates lipopolysaccharide-induced extracelluar matrix accumulation and inflammation in rat mesangial cells: involvement of NF-κB signaling pathway.

BACKGROUND Our previous studies demonstrated that berberine could improve the renal function in rats and mice with diabetic nephropathy (DN) and inhibit extracellular matrix (ECM) component, fibronectin (FN) expression in rat mesangial cells (MCs) cultured under high glucose. However, the molecular mechanisms have not been fully elucidated. OBJECTIVE To explore the potential mechanisms of berberine in the treatment of DN, we investigated the effects of berberine on lipopolysaccharide (LPS)-induced nuclear factor-kappa B (NF-κB) activation and its downstream inflammatory mediators, such as intercellular adhesion molecule-1 (ICAM-1), transforming growth factor-beta 1 (TGF-β1), inducible nitric oxide synthase (iNOS) and fibronectin (FN) protein expression in rat MCs. METHOD Cell proliferation was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The activation of NF-κB was detected by Western blot and confocal microscopy. The protein levels of ICAM-1, TGF-β1, iNOS and FN in rat MCs were detected by Western blot. RESULTS Our results revealed that berberine significantly suppressed LPS-induced cell proliferation and inhibited LPS-induced NF-κB nuclear translocation in MCs, as well as protein expression of ICAM-1, TGF-β1, iNOS and FN. CONCLUSION Berberine significantly repressed LPS-induced cell proliferation and FN expression in rat MCs through inhibiting the activation of NF-κB signaling pathway and protein expression of its downstream inflammatory mediators. The ameliorative effects of berberine on DN might be associated with this inhibition effect on NF-κB signaling pathway which was independent of its hypoglycemic effect.

Tanshinone II-A inhibits oxidized LDL-induced LOX-1 expression in macrophages by reducing intracellular superoxide radical generation and NF-κB activation.

Lectin-like oxidized LDL (oxLDL) receptor-1 (LOX-1), a novel scavenger receptor highly expressed in human and experimental atherosclerotic lesions, is responsible for the uptake of oxLDL in vascular cells. We demonstrated previously that Tanshinone II-A (Tan), a pharmacologically active compound extracted from the rhizome of the Chinese herb Salvia miltiorrhiza Bunge, inhibits atherogenesis in hypercholesterolemic rats, rabbits, and apolipoprotein-E deficient (ApoE⁻/⁻) mice. However, the precise mechanism by which Tan protects against atherogenesis remains to be elucidated. Therefore, we hypothesized that Tan can suppress the uptake of oxLDL by diminishing the expression of LOX-1 via suppression of NF-κB signaling pathway, thereby contributing to reduced macrophage foam cell formation. In cultured murine macrophages, oxLDL induced LOX-1 expression at the mRNA and protein levels, was abrogated by addition of Tan or pyrrolidinedithiocarbamic acid ammonium salt (PDTC), a widely used inhibitor of NF-κB, suggesting the involvement of NF-κB. Tan also reduced LOX-1 expression in atherosclerotic lesions of ApoE⁻/⁻ mice fed a high cholesterol diet. Mechanistically, Tan suppressed the nuclear translocation of NF-κB P65 subunit and phosphorylation of IκB-α induced by oxLDL. Electrophoretic mobility shift assay (EMSA) demonstrated that Tan inhibited the nuclear protein binding to NF-κB consensus sequence. Functionally, we observed that Tan inhibited DiI-oxLDL uptake by macrophages in a fashion similar to that produced by LOX-1 neutralizing antibody. Our current findings reveal a novel mechanism by which Tan protects against atherogenesis and shed new light on the potential therapeutic application of Tan to the treatment and prevention of atherosclerotic cardiovascular diseases.

Cryptotanshinone Suppressed Inflammatory Cytokines Secretion in RAW264.7 Macrophages through Inhibition of the NF-κB and MAPK Signaling Pathways

Cryptotanshinone (CTS), a major constituent extracted from the medicinal herb Salvia miltiorrhiza Bunge, has well-documented antioxidative and anti-inflammatory effects. In the present study, the pharmacological effects and underlying molecular mechanisms of CTS on lipopolysaccharide (LPS)-induced inflammatory responses were investigated. By enzyme-linked immunosorbent assay, we observed that CTS reduced significantly the production of proinflammatory mediators (tumor necrosis factor-α and interleukin-6) induced by LPS in murine macrophage-like RAW264.7 cells. Mechanistically, CTS inhibited markedly the phosphorylation of mitogen-activated protein kinases (MAPKs), including ERK1/2, p38MAPK, and JNK, which are crucially involved in regulation of proinflammatory mediator secretion. Moreover, immunofluorescence and western blot analysis indicated that CTS abolished completely LPS-triggered nuclear factor-κB (NF-κB) activation. Taken together, these data implied that NF-κB and MAPKs might be the potential molecular targets for clarifying the protective effects of CTS on LPS-induced inflammatory cytokine production in macrophages.

Berberine ameliorates renal injury in diabetic C57BL/6 mice: Involvement of suppression of SphK–S1P signaling pathway

Berberine (BBR) was previously found to have beneficial effects on renal injury in experimental diabetic rats. However, the mechanisms underlying the effects are not fully understood. Sphingosine kinase-Sphingosine 1-phosphate (SphK-S1P) signaling pathway has been implicated in the pathogenesis of diabetic nephropathy (DN). The aim of this study was to investigate the effects of BBR on renal injury and the activation of SphK-S1P signaling pathway in alloxan-induced diabetic mice with nephropathy. Alloxan-induced diabetic mice were treated orally with BBR (300 mg/kg/day) or vehicle for 12 weeks. BBR inhibited the increases in fasting blood glucose, kidney/body weight ratio, blood urea nitrogen, serum creatinine and 24-h albuminuria in diabetic mice. It also prevented renal hypertrophy, TGF-beta1 synthesis, FN and Col IV accumulation. Moreover, BBR down-regulated the elevated staining, activity and levels of mRNA and protein of SphK1, and S1P production as well. These findings suggest that the inhibitory effect of BBR on the activation of SphK-S1P signaling pathway in diabetic mouse kidney is a novel mechanism by which BBR partly exerts renoprotective effects on DN.

Tanshinone II-A attenuates and stabilizes atherosclerotic plaques in apolipoprotein-E knockout mice fed a high cholesterol diet.

Tanshinone II-A (Tan), a bioactive diterpene isolated from Salvia miltiorrhiza Bunge (Danshen), possesses anti-oxidant and anti-inflammatory activities. The present study investigated whether Tan can decrease and stabilize atherosclerotic plaques in Apolipoprotein-E knockout (ApoE(-/-)) mice maintained on a high cholesterol diet (HCD). Six week-old mice challenged with a HCD were randomly assigned to 4 groups: (a) C57BL/6J; (b) ApoE(-/-); (c) ApoE(-/-)+Tan-30 (30 mg/kg/d); (d) ApoE(-/-)+Tan-10 (10mg/kg/d). After 16 weeks of intervention, Tan treated mice showed decreased atherosclerotic lesion size in the aortic sinus and en face aorta. Furthermore, immunohistochemical analysis revealed that Tan rendered the lesion composition a more stable phenotype as evidenced by reduced necrotic cores, decreased macrophage infiltration, and increased smooth muscle cell and collagen contents. Tan also significantly reduced in situ superoxide anion production, aortic expression of NF-κB and matrix metalloproteinase-9 (MMP-9). In vitro treatment of RAW264.7 macrophages with Tan significantly suppressed oxidized LDL-induced reactive oxygen species production, pro-inflammatory cytokine (IL-6, TNF-α, MCP-1) expression, and MMP-9 activity. Tan attenuates the development of atherosclerotic lesions and promotes plaque stability in ApoE(-/-) mice by reducing vascular oxidative stress and inflammatory response. Our findings highlight Tan as a potential therapeutic agent to prevent atherosclerotic cardiovascular diseases.

Targeting hydrogen sulfide as a promising therapeutic strategy for atherosclerosis.

Physiological concentrations of nitric oxide (NO) and carbon monoxide (CO) have multiple protective effects in the cardiovascular system. Recent studies have implicated hydrogen sulfide (H2S) as a new member of vasculoprotective gasotransmitter family, behaving similarly to NO and CO. H2S has been demonstrated to inhibit multiple key aspects of atherosclerosis, including atherogenic modification of LDL, monocytes adhesion to the endothelial cells, macrophage-derived foam cell formation and inflammation, smooth muscle cell proliferation, neointimal hyperplasia, vascular calcification, and thrombogenesis. H2S also decreases plasma homocysteine levels in experimental animal models. In the human body, H2S production is predominantly catalyzed by cystathionine-β-synthase (CBS) and cystathionine γ-lyase (CSE). CSE is the primary H2S-producing enzyme in the vasculature. Growing evidence suggests that atherosclerosis is associated with vascular CSE/H2S deficiency and that H2S supplementation by exogenous H2S donors (such as NaHS and GYY4137) attenuates, and H2S synthesis suppression by inhibitors (such as D, L-propargylglycine) aggravates the development of atherosclerotic plaques. However, it remains elusive whether CSE deficiency plays a causative role in atherosclerosis. A recent study (Circulation. 2013; 127: 2523-2534) demonstrates that decreased endogenous H2S production by CSE genetic deletion accelerates atherosclerosis in athero-prone ApoE-/- mice, pinpointing that endogenously produced H2S by CSE activation may be of benefit in the prevention and treatment of atherosclerosis. This study will facilitate the development of H2S-based pharmaceuticals with therapeutic applications in atherosclerosis-related cardiovascular diseases.

Tanshinone IIA attenuates atherosclerosis in ApoE−/− mice through down-regulation of scavenger receptor expression

This study is designed to investigate the protection of tanshinone IIA (TSIIA) against atherosclerosis in apolipoprotein E deficient (ApoE(-/-)) mice and to explore the mechanisms by focusing on the expressions of scavenger receptors, scavenger receptor-A (SR-A) and CD36. The in vivo study demonstrated that TSIIA (10-90mg/kg) inhibited the atherosclerotic lesions, down-regulated the CD68 protein expression in lesion and decreased the contents of cholesterol in aortas of ApoE(-/-) mice. In addition, TSIIA reduced the serum levels of oxidized LDL (oxLDL) and down-regulated the mRNA expression of CD36, SR-A and peroxisome proliferator-activated receptor gamma (PPARγ) in aortas. The in vitro study showed that TSIIA (0.1-10μM) decreased cholesterol level and DiI-oxLDL uptake in mouse peritoneal macrophages treated with oxLDL (50μg/ml). In addition, TSIIA down-regulated the mRNA and protein expression of CD36 but not that of SR-A in oxLDL treated macrophages. TSIIA also down-regulated the mRNA expression of PPARγ in oxLDL treated macrophages. Furthermore, TSIIA reduced the mRNA expression of CD36 in macrophages treated with PPARγ agonist 15d-PGJ(2) (2μM) or troglitazone (50μM), whereas both 15d-PGJ(2) (0.5-1.5μM) and troglitazone (5-20μM) dose-dependently abolished the down-regulation of CD36 expression by TSIIA in oxLDL treated macrophages. These results suggest that TSIIA attenuates the atherosclerotic lesion in ApoE(-/-) mice, which might be attributed to the properties of both anti-oxidation and down-regulation of scavenger receptors. Furthermore, antagonism of PPARγ might be involved in the down-regulation of CD36 by TSIIA.

Roles of transcriptional corepressor RIP140 and coactivator PGC-1α in energy state of chronically infarcted rat hearts and mitochondrial function of cardiomyocytes

Transcriptional coactivator PPARγ coactivator-1α (PGC-1α) and corepressor receptor-interacting protein 140 (RIP140) are opposing-functional regulators in maintaining energy balance of most metabolic tissues and cells. However, the relative contributions of both factors to energy metabolism in cardiomyocytes remain largely unknown. Herein, we reported that the relative protein levels of RIP140/PGC-1α were up-regulated in the failing hearts after chronic myocardial infarction (MI), and correlated negatively with the energy state index phosphocreatine (PCr)/ATP ratios. Real-time PCR analysis revealed that mRNA expressions of estrogen related receptor α (ERRα), peroxisome proliferate activated receptor α and β (PPARα, PPARβ), nuclear respiratory factor 1 (NRF1) and their target genes were repressed by RIP140 and induced by PGC-1α in a dose dependent manner in neonatal rat cardiomyocytes. We also observed that overexpression of RIP140 through adenovirus delivery can abrogate the PGC-1α-mediated induction of mitochondrial membrane potential elevation and mitochondrial biogenesis, and activate both autophagy and apoptosis pathways. We conclude that RIP140 and PGC-1α exert antagonistic role in regulating cardiac energy state and mitochondrial biogenesis.