Apolipoprotein B of low-density lipoprotein impairs nitric oxide-mediated endothelium-dependent relaxation in rat mesenteric arteries

Associations between maternal mid-pregnancy apolipoprotein A-1, apolipoprotein B, apolipoprotein B/apolipoprotein A-1 ratio and preterm birth

BACKGROUND AND AIMS

Elevated lipid levels during pregnancy have been shown to be related to the risk of preterm birth. Despite the importance of apolipoprotein (Apo) in lipid metabolism and transportation, evidence regarding apolipoprotein levels during pregnancy and preterm birth is still limited. Therefore, we aim to investigate the associations between maternal ApoA-1, ApoB, ApoB/ApoA-1 ratio and preterm birth.

MATERIALS AND METH

Data were extracted from the information system of Guangdong Women and Children Hospital. Lipoprotein levels were tested using Beckman Coulter AU5800 in mid-pregnancy at a median gestational age of 18 w. Maternal serum ApoB, ApoA-1 and ApoB/ApoA-1 ratio were categorized into tertiles. Logistic regression models were performed to evaluate the odds ratios and 95% confidence intervals for preterm birth.

RESULTS

A total of 5,986 maternal-newborn pairs were included in this study. The rate of preterm birth was 5.7% (n = 344). The multivariate-adjusted ORs (95% CI) of preterm birth were 1.51 (1.06, 2.10) for individuals with high ApoB (>90th), 0.63 (0.38, 0.99) for those with low ApoB (<10th), and 1.64 (1.18, 2.24) for those with high ApoB/ApoA-1 (>90th). Subgroup analyses showed that the association of ApoB and preterm birth was only significant among women with pre-pregnancy BMI 18.5-24 kg/m² (OR = 1.36, 95% CI: 1.12-1.65), age at delivery ≥ 35 years (OR = 1.43, 95% CI: 1.12-1.83).

CONCLUSION

Elevated maternal ApoB level and ApoB/ApoA-1 ratio during mid-pregnancy were related to increased risk of preterm birth. Monitoring maternal serum apolipoprotein levels may help to identify the high-risk population of preterm birth.

Sorafenib not only impairs endothelium-dependent relaxation but also promotes vasoconstriction through the upregulation of vasoconstrictive endothelin type B receptors

As a VEGF-targeting agent, sorafenib has been used to treat a number of solid tumors but can easily lead to adverse vascular effects. To elucidate the underlying mechanism, rat mesenteric arteries were subjected to organ cultured in the presence of different concentrations of sorafenib (0, 3, 6 and 9 mg/L) with or without inhibitors (U0126, 10-5 M; SB203580, 10-5 M; SP200126, 10-5 M) of MAPK kinases, and then acetylcholine- or sodium nitroprusside-induced vasodilation and sarafotoxin 6c-induced vasoconstriction were monitored by a sensitive myograph. The NO synthetases, the nitrite levels, the endothelial marker CD31,the ETB and ETA receptors and the phosphorylation of MAPK kinases were studied. Next, rats were orally administrated by sorafenib for 4 weeks (7.5 and 15 mg/kg/day), and their blood pressure, plasma ET-1, the ETB and ETA receptors and the phosphorylation of MAPK kinases in the mesenteric arteries were investigated. The results showed that sorafenib impairs endothelium-dependent vasodilation due to decreased NO levels and the low expression of eNOS and iNOS. Weak staining for CD31 indicated that sorafenib induced endothelial damage. Moreover, sorafenib caused the upregulation of vasoconstrictive ETB receptors, the enhancement of ETB receptor-mediated vasoconstriction and the activation of JNK/MAPK. Blocking the JNK, ERK1/2 and p38/MAPK signaling pathways by using the inhibitors significantly abolished ETB receptor-mediated vasoconstriction. Furthermore, it was observed that the oral administration of sorafenib caused an increase in blood pressure and plasma ET-1, upregulation of the ETB receptor and the activation of JNK in the mesenteric arteries. In conclusion, sorafenib not only impairs endothelium-dependent vasodilatation but also enhances ETB receptor-mediated vasoconstriction, which may be the causal factors for hypertension and other adverse vascular effects in patients treated with sorafenib.

Enhanced Endothelin A and B Receptor Expression and Receptor-Mediated Vasoconstriction in Rat Mesenteric arteries after Lipopolysaccharide Challenge

During organ culture of intact vessels, endothelin receptors (ETRs) were upregulated in vascular smooth muscle cells (VSMCs) by various stimuli, but whether inflammation alters ETR expression in vivo remains unclear. We aimed to explore the effects of lipopolysaccharide (LPS) challenge on ETR expression in the VSMC in vivo. Male Sprague-Dawley rats received a single intraperitoneal injection of LPS (5 mg/kg body weight) or normal saline (NS) for 6 hrs. The function and expression of ETR type A (ET_A) and type B (ET_B) were evaluated in the mesenteric arteries without endothelium, by using myograph system, real-time quantitative PCR, Western blot, and immunohistochemical staining, respectively. Serum tumor necrosis factor-α (TNF-α) level was assessed by using enzyme-linked immunosorbent assay. The results showed that, compared to control (NS) group, LPS treatment potently enhanced the vasoconstriction mediated by ET_A or ET_B in rat mesenteric artery, with elevated maximum effects. ET_A and ET_B expressions in the VSMC were increased at both mRNA and protein levels after LPS treatment, paralleled with activation of the NF-κB pathway and augmented serum TNF-α level. Conclusively, in the rat model of immediate systemic inflammation induced by LPS, ET_A and ET_B expressions were increased in the mesenteric arterial VSMC, paralleled with enhanced receptor-mediated vasoconstriction and activation of the NF-κB pathway. Our data has for the first time demonstrated the upregulation of ETRs in VSMCs by LPS-induced immediate inflammation in vivo.

Neuroprotective Properties of Linagliptin: Focus on Biochemical Mechanisms in Cerebral Ischemia, Vascular Dysfunction and Certain Neurodegenerative Diseases

Linagliptin is a representative of dipeptidyl peptidase 4 (DPP-4) inhibitors which are registered and used effectively in a treatment of diabetes mellitus type 2. They increase the levels of active forms of endogenous incretins such as GLP-1 and GIP by inhibiting their enzymatic decomposition. Scientific reports suggest beneficial effects of linagliptin administration via immunological and biochemical pathways involved in neuroprotective processes of CNS. Linagliptin’s administration leads to a decrease in the concentration of proinflammatory factors such as: TNF-α, IL-6 and increases the number of anti-inflammatory patrolling monocytes CX3CR1^bright. Significant reduction in Aβ42 level has been associated with the use of linagliptin implying potential application in Alzheimer’s disease. Linagliptin improved vascular functions by increasing production of nitric oxide (NO) and limiting concentration of apolipoprotein B. Linagliptin-induced decrease in macrophages infiltration may provide improvement in atheromatous plaque stabilization. Premedication with linagliptin increases neuron’s survival after stroke and augments neuronal stem cells proliferation. It seems to be connected with SDF-1α/CXCR4 signaling pathway. Linagliptin prevented abnormal proliferation and migration of rat brain microvascular endothelial cells in a state of hypoperfusion via SIRT1/HIF-1α/VEGF pathway. The article presents a summary of the studies assessing neuroprotective properties of linagliptin with special emphasis on cerebral ischemia, vascular dysfunction and neurodegenerative diseases.

Regulation and role of endoglin in cholesterol-induced endothelial and vascular dysfunction in vivo and in vitro

Our objective was to investigate the effect of cholesterol [hypercholesterolemia and 7-ketocholesterol (7K)] on endoglin (Eng) expression and regulation with respect to endothelial or vascular dysfunction in vivo and in vitro. In vivo experiments were performed in 2-mo-old atherosclerosis-prone apolipoprotein E-deficient/LDL receptor-deficient (ApoE^-/-/LDLR^-/-) female mice and their wild-type C57BL/6J littermates. In in vitro experiments, human aortic endothelial cells (HAECs) were treated with 7K. ApoE^-/-/LDLR^-/- mice developed hypercholesterolemia accompanied by increased circulating levels of P-selectin and Eng and a disruption of NO metabolism. Functional analysis of the aorta demonstrated impaired vascular reactivity, and Western blot analysis revealed down-regulation of membrane Eng/Smad2/3/eNOS signaling in ApoE^-/-/LDLR^-/- mice. 7K increased Eng expression via Krüppel-like factor 6 (KLF6), liver X nuclear receptor, and NF-κB in HAECs. 7K-induced Eng expression was prevented by the treatment with 2-hydroxypropyl-β-cyclodextrin; 8-{[5-chloro-2-(4-methylpiperazin-1-yl) pyridine-4-carbonyl] amino}-1-(4-fluorophenyl)-4, 5-dihydrobenzo[g]indazole-3-carboxamide; or by KLF6 silencing. 7K induced increased adhesion and transmigration of monocytic human leukemia promonocytic cell line cells and was prevented by Eng silencing. We concluded that hypercholesterolemia altered Eng expression and signaling, followed by endothelial or vascular dysfunction before formation of atherosclerotic lesions in ApoE^-/-/LDLR^-/- mice. By contrast, 7K increased Eng expression and induced inflammation in HAECs, which was followed by an increased adhesion and transmigration of monocytes via endothelium, which was prevented by Eng inhibition. Thus, we propose a relevant role for Eng in endothelial or vascular dysfunction or inflammation when exposed to cholesterol.-Vicen, M., Vitverova, B., Havelek, R., Blazickova, K., Machacek, M., Rathouska, J., Najmanová, I., Dolezelova, E., Prasnicka, A., Sternak, M., Bernabeu, C., Nachtigal, P. Regulation and role of endoglin in cholesterol-induced endothelial and vascular dysfunction in vivo and in vitro.

Apolipoprotein B vs non-high-density lipoprotein cholesterol: Association with endothelial hemostatic markers and carotid intima-media thickness

BACKGROUND

Both apolipoprotein B (apoB) and non-high-density lipoprotein cholesterol (non-HDL-C) are accepted as alternative risk factors or targets for lipid-lowering therapy, which correlate more strongly with cardiovascular events than low-density lipoprotein cholesterol.

OBJECTIVE

The aim of this cross-sectional study was to evaluate the differences in plasma levels of plasminogen activator inhibitor-1 (PAI-1) and of von Willebrand factor (vWF) as endothelial hemostatic markers and carotid intima-media thickness (C-IMT) as a morphologic marker for atherosclerotic vascular disease among dyslipidemic individuals with apoB levels higher, estimated or lower based on regression equation of apoB vs non-HDL-C.

METHODS

A total of 594 dyslipidemic subjects without atherosclerotic manifestation were divided into 3 groups (according to tertiles of apoB levels above, within, and below the line of identity): H-apoB (n = 200), E-apoB (n = 194), and L-apoB (n = 200). PAI-1, vWF, C-IMT and lipids, anthropometric parameters, markers of insulin resistance, and inflammation were measured. Differences in variables between groups were analyzed using analysis of variance.

RESULTS

There was a strong association between apoB and non-HDL-C. The correlations of apoB and of non-HDL-C with markers of endothelial damage and C-IMT were very similar. Despite these facts, individuals with higher apoB levels had significantly higher levels of PAI-1 compared with individuals with estimated (P < .05) or lower apoB (P < .001). There were no significant differences in vWF, C-IMT, markers of insulin resistance, obesity, and inflammation.

CONCLUSION

Individuals with apoB higher than predicted by non-HDL-C had significantly higher levels of PAI-1, which may contribute to the increased risk of future atherothrombotic events.

GPR55 agonist lysophosphatidylinositol and lysophosphatidylcholine inhibit endothelial cell hyperpolarization via GPR-independent suppression of Na+-Ca2+ exchanger and endoplasmic reticulum Ca2+ refilling

Lysophosphatidylinositol (LPI) and lysophosphatidylcholine (LPC) are lipid signaling molecules that induce endothelium-dependent vasodilation. In addition, LPC suppresses acetylcholine (Ach)-induced responses. We aimed to determine the influence of LPC and LPI on hyperpolarizing responses in vitro and in situ endothelial cells (EC) and identify the underlying mechanisms. Using patch-clamp method, we show that LPI and LPC inhibit EC hyperpolarization to histamine and suppress Na⁺/Ca²⁺ exchanged (NCX) currents in a concentration-dependent manner. The inhibition is non-mode-specific and unaffected by intracellular GDPβS infusion and tempol, a superoxide dismutase mimetic. In excised mouse aorta, LPI strongly inhibits the sustained and the peak endothelial hyperpolarization induced by Ach, but not by SKA-31, an opener of Ca²⁺-dependent K⁺ channels of intermediate and small conductance. The hyperpolarizing responses to consecutive histamine applications are strongly reduced by NCX inhibition. In a Ca²⁺-re-addition protocol, bepridil, a NCX inhibitor, and KB-R7943, a blocker of reversed NCX, inhibit the hyperpolarizing responses to Ca²⁺-re-addition following Ca²⁺ stores depletion. These finding indicate that LPC and LPI inhibit endothelial hyperpolarization to Ach and histamine independently of G-protein coupled receptors and superoxide anions. Reversed NCX is critical for ER Ca²⁺ refilling in EC. The inhibition of NCX by LPI and LPC underlies diminished endothelium-dependent responses and endothelial dysfunction accompanied by increased levels of these lipids in the blood.

Hydrogen sulfide inhibits development of atherosclerosis through up-regulating protein S-nitrosylation

Hydrogen sulfide (H₂S) is an important gaseous signaling molecule that serves many important regulatory roles in physiological and pathophysiological conditions. H₂S exerts an anti-atherosclerotic effect through mediating the biological functions of nitric oxide (NO). However, its mechanism of action is unclear. The purpose of this study is to explore the effect mechanism of H₂S on the development of atherosclerosis with regard to protein S-nitrosylation. A total of 45 male apoE^-/- mice were randomly divided into three groups. Atherosclerosis was induced by Western diet (21% fat and 0.15% cholesterol) with/without administration of a H₂S donor (NaHS) or an endogenous cystathionine γ-lyase inhibitor (d, l-propargylglycine) for 12 weeks. After 12 weeks, plasma lipid and plasma NO levels were measured. Aortic gross lesion area and histopathological features of aortic lesion were determined. Additionally, the level of S-nitrosylated proteins in vascular smooth muscle cells (VSMCs) was detected using immunofluorescence in aorta. Rat VSMCs were performed in an in vitro experiment. Inducible nitric oxide synthase (iNOS) protein expression, NO generation, protein S-nitrosylation, and cell proliferation and migration were measured. We found that H₂S significantly reduced the aortic atherosclerotic lesion area (P=0.006) and inhibited lipid and macrophage accumulation (P=0.004, P=0.002) and VSMC proliferation (P=0.019) in apoE^-/- mice. H₂S could up-regulate levels of plasma NO and protein S-nitrosylation in aorta VSMCs. However, d, l- propargylglycine had the opposite effect, increasing the lesion area and the content of lipids and macrophages in the lesions of apoE^-/- mice and down-regulating plasma NO levels and protein S-nitrosylation in aorta VSMCs. In vitro experiments, H₂S could significantly reverse the reduction of iNOS expression and NO generation induced by oxidized low-density lipoprotein in VSMCs. Moreover, H₂S could increase the protein S-nitrosylation level of VSMCs in a dose-dependent manner, and the effect could be inhibited by iNOS inhibitors. In addition, proliferation and migration of VSMCs could be inhibited by H₂S in a dose-dependent manner, which could be blocked by an iNOS inhibitor or protein S-nitrosylation removal agent. Our data suggest that H₂S could inhibit the development of atherosclerosis by up-regulating plasma NO and protein S-nitrosylation, thereby inhibiting the proliferation and migration of VSMCs.

Overview of Antagonists Used for Determining the Mechanisms of Action Employed by Potential Vasodilators with Their Suggested Signaling Pathways

This paper is a review on the types of antagonists and the signaling mechanism pathways that have been used to determine the mechanisms of action employed for vasodilation by test compounds. Thus, we exhaustively reviewed and analyzed reports related to this topic published in PubMed between the years of 2010 till 2015. The aim of this paperis to suggest the most appropriate type of antagonists that correspond to receptors that would be involved during the mechanistic studies, as well as the latest signaling pathways trends that are being studied in order to determine the route(s) that atest compound employs for inducing vasodilation. The methods to perform the mechanism studies were included. Fundamentally, the affinity, specificity and selectivity of the antagonists to their receptors or enzymes were clearly elaborated as well as the solubility and reversibility. All the signaling pathways on the mechanisms of action involved in the vascular tone regulation have been well described in previous review articles. However, the most appropriate antagonists that should be utilized have never been suggested and elaborated before, hence the reason for this review.

Pretreatment with β-Boswellic Acid Improves Blood Stasis Induced Endothelial Dysfunction: Role of eNOS Activation

Vascular endothelial cells play an important role in modulating anti-thrombus and maintaining the natural function of vascular by secreting many active substances. β-boswellic acid (β-BA) is an active triterpenoid compound from the extract of boswellia serrate. In this study, it is demonstrated that β-BA ameliorates plasma coagulation parameters, protects endothelium from blood stasis induced injury and prevents blood stasis induced impairment of endothelium-dependent vasodilatation. Moreover, it is found that β-BA significantly increases nitric oxide (NO) and cyclic guanosine 3’, 5’-monophosphate (cGMP) levels in carotid aortas of blood stasis rats. To stimulate blood stasis-like conditions in vitro, human umbilical vein endothelial cells (HUVECs) were exposed to transient oxygen and glucose deprivation (OGD). Treatment of β-BA significantly increased intracellular NO level. Western blot and immunofluorescence as well as immunohistochemistry reveal that β-BA increases phosphorylation of enzyme nitric oxide synthase (eNOS) at Ser1177. In addition, β-BA mediated endothelium-dependent vasodilatation can be markedly blocked by eNOS inhibitor L-NAME in blood stasis rats. In OGD treated HUEVCs, the protective effect of β-BA is attenuated by knockdown of eNOS. In conclusion, the above findings provide convincing evidence for the protective effects of β-BA on blood stasis induced endothelial dysfunction by eNOS signaling pathway.

Apolipoprotein B, the villain in the drama?

Low-density lipoprotein (LDL) is the major atherogenic lipoprotein and the primary target of lipid-lowering therapy for treating ischemic cardiovascular disease. Apolipoprotein B (apoB), an important structural component of LDL, plays a key role in cholesterol transport and removal in vascular wall. On the other hand, under pathological process, apoB interacts with the arterial wall to initiate the cascade of events that leads to atherosclerosis. However, interactions between apoB and vascular wall remain to be determined. Here, we address a pathological role of apoB per se and whole LDL particle in dysfunction of vascular endothelium and smooth muscle cells i.e. decreased endothelium-dependent vasodilation and increased receptor-mediated vasoconstriction. We intend to discuss: i) how apoB is responsible for the deleterious effects of LDL in the development of ischemic cardiovascular disease; ii) why vaccine based on peptides derived from apoB-100 is a promising therapy for treating ischemic cardiovascular disease, and iii) direct inhibition of apoB production should be a better therapeutic option than simple LDL-cholesterol lowering therapy in the patients with severe hypercholesterolemia at high cardiovascular risk with statin intolerance. In conclusion, apoB, but not cholesterol, plays a major role in LDL-induced dysfunction of endothelium, suggesting that direct apoB-targeting agents might be a promising therapy for the treatment of ischemic cardiovascular disease.