This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

Background PCSK9 rs505151 and rs11591147 polymorphisms are identified as gain- and loss-of-function mutations, respectively. The effects of these polymorphisms on serum lipid levels and cardiovascular risk remain to be elucidated.MethodsIn this meta-analysis, we explored the association of PCSK9 rs505151 and rs11591147 polymorphisms with serum lipid levels and cardiovascular risk by calculating the standardized mean difference (SMD) and odds ratios (OR) with 95% confidence intervals (CI).ResultsPooled results analyzed under a dominant genetic model indicated that the PCSK9 rs505151 G allele was related to higher levels of triglycerides (SMD: 0.14, 95% CI: 0.02 to 0.26, P = 0.021, I2 = 0) and low-density lipoproteins cholesterol (LDL-C) (SMD: 0.17, 95% CI: 0.00 to 0.35, P = 0.046, I2 = 75.9%) and increased cardiovascular risk (OR: 1.50, 95% CI: 1.19 to 1.89, P = 0.0006, I2 = 48%). The rs11591147 T allele was significantly associated with lower levels of total cholesterol (TC) and LDL-C (TC, SMD: -0.45, 95% CI: -0.57 to −0.32, P = 0.000, I2 = 0; LDL-C, SMD: -0.44, 95% CI: -0.55 to −0.33, P = 0.000, I2 = 0) and decreased cardiovascular risk (OR: 0.77, 95% CI: 0.60 to 0.98, P = 0.031, I2 = 59.9) in Caucasians.ConclusionsThis study indicates that the variant G allele of PCSK9 rs505151 confers increased triglyceride (TG) and LDL-C levels, as well as increased cardiovascular risk. Conversely, the variant T allele of rs11591147 protects carriers from cardiovascular disease susceptibility and lower TC and LDL-C levels in Caucasians. These findings provide useful information for researchers interested in the fields of PCSK9 genetics and cardiovascular risk prediction not only for designing future studies, but also for clinical and public health applications.

Background: Endothelial dysfunction enhances vascular inflammation, which initiates pulmonary arterial hypertension (PAH) pathogenesis, further induces vascular remodeling and right ventricular failure. Activation of inflammatory caspases is an important initial event at the onset of pyroptosis. Studies have shown that caspase-1–mediated pyroptosis has played a crucial role in the pathogenesis of PAH. However, the role of caspase-11, another inflammatory caspase, remains to be elucidated. Therefore, the purpose of this study was to clarify the role of caspase-11 in the development of PAH and its mechanism on endothelial cell function. Methods: The role of caspase-11 in the progression of PAH and vascular remodeling was assessed in vivo. In vitro, the effect of caspase-4 silencing on the human pulmonary arterial endothelial cells pyroptosis was determined. Results: We confirmed that caspase-11 and its human homolog caspase-4 were activated in PAH animal models and TNF (tumor necrosis factor)-α–induced human pulmonary arterial endothelial cells. Caspase-11 −/− relieved right ventricular systolic pressure, right ventricle hypertrophy, and vascular remodeling in Sugen-5416 combined with chronic hypoxia mice model. Meanwhile, pharmacological inhibition of caspase-11 with wedelolactone exhibited alleviated development of PAH on the monocrotaline-induced rat model. Moreover, knockdown of caspase-4 repressed the onset of TNF-α–induced pyroptosis in human pulmonary arterial endothelial cells and inhibited the activation of pyroptosis effector GSDMD (gasdermin D) and GSDME (gasdermin E). Conclusions: These observations identified the critical role of caspase-4/11 in the pyroptosis pathway to modulate pulmonary vascular dysfunction and accelerate the progression of PAH. Our findings provide a potential diagnostic and therapeutic target in PAH.

Endothelial cell senescence is regarded as a vital characteristic of cardiovascular diseases. Elevated palmitate (PA) is an independent risk factor of cardiovascular diseases, but its role in endothelial cell senescence is currently unknown. During the course of studying the prosenescent role of PA, we discovered a key role of dsRNA-dependent protein kinase [protein kinase R (PKR)] in endothelial senescence. Exposure of human umbilical vein endothelial cells (HUVECs) to PA-induced cell senescence is characterized by increased levels of senescence-associated β-galactose glucosidase activity, excessive production of reactive oxygen species production, impaired cellular proliferation, and G phase arrest. This phenomenon is associated with an increase of PKR autophosphorylation and decreased activity of sirtuin 1 (Sirt1), a pivotal antisenescent factor. PKR inactivation by PKR siRNA or its phosphorylation inhibitor 2-aminopurine significantly attenuated PA-induced HUVEC senescence by reversing Sirt1 activity and its downstream signaling. Moreover, to study the regulatory mechanism between PKR and Sirt1, we found that PKR promotes JNK activation to inhibit Sirt1 activity and that this effect could be reversed by the JNK inhibitor SP600125. These findings provide evidence that PKR mediates PA-induced HUVEC senescence by inhibiting Sirt1 signaling. Our study provides novel insights into the actions and mechanisms of PKR in endothelial senescence. NEW & NOTEWORTHY This study first provides a novel observation that dsRNA-dependent protein kinase (PKR) mediates palmitate-induced sirtuin 1 inactivation and subsequent human umbilical vein endothelial cell senescence. Most importantly, these new findings will provide a potential therapeutic strategy to improve free fatty acid-induced endothelial senescence by targeting PKR in cardiovascular diseases.

Endothelial inflammation plays an important role in hyperhomocysteinemia (HHcy)-associated vascular diseases. High mobility group box 1 (HMGB1) is a pro-inflammatory danger molecule produced by endothelial cells. However, whether HMGB1 is involved in vascular endothelial inflammation of HHcy is poorly understood. Neuropilin-1 (NRP1) mediates inflammatory response and activates mitogen-activated protein kinases (MAPKs) pathway that has been reported to be involved in regulation of HMGB1. The aim of this study was to determine the alteration of HMGB1 in HHcy, and the role of NRP1 in regulation of endothelial HMGB1 under high homocysteine (Hcy) condition. In the present study, we first observed that the plasma level of HMGB1 was elevated in HHcy patients and an experimental rat model, and increased HMGB1 was also observed in the thoracic aorta of an HHcy rat model. HMGB1 was induced by Hcy accompanied with upregulated NRP1 in vascular endothelial cells. Overexpression of NRP1 promoted expression and secretion of HMGB1 and endothelial inflammation; knockdown of NRP1 inhibited HMGB1 and endothelial inflammation induced by Hcy, which partially regulated through p38 MAPK pathway. Furthermore, NRP1 inhibitor ATWLPPR reduced plasma HMGB1 level and expression of HMGB1 in the thoracic aorta of HHcy rats. In conclusion, our data suggested that Hcy requires NRP1 to regulate expression and secretion of HMGB1. The present study provides the evidence for inhibition of NRP1 and HMGB1 to be the novel therapeutic targets of vascular endothelial inflammation in HHcy in the future. NEW & NOTEWORTHY This study shows for the first time to our knowledge that the plasma level of high mobility group box 1 (HMGB1) is elevated in hyperhomocysteinemia (HHcy) patients, and homocysteine promotes expression and secretion of HMGB1 partially regulated by neuropilin-1 in endothelial cells, which is involved in endothelial inflammation. Most importantly, these new findings will provide a potential therapeutic strategy for vascular endothelial inflammation in HHcy.

ObjectiveIncreasing evidence suggested that endoplasmic reticulum (ER) stress contributes to insulin resistance, which plays an important role in the development of type 2 diabetes mellitus (T2DM). Accumulation of endogenous nitric oxide synthase (NOS) inhibitor, asymmetric dimethylarginine (ADMA), is associated with insulin resistance, T2DM, and diabetic cardiovascular complications, although the mechanisms have not been elucidated. This study was to determine whether elevated endogenous ADMA is involved in hepatic ER stress of type 2 diabetic rats, verify their causal relationship, and elucidate the potential mechanism underlying ADMA induced ER stress in rat hepatocytes.MethodsImmunoglobulin binding protein (Bip) transcription, eukaryotic initiation factor 2α kinase (eIF2α) phosphorylation, X box-binding protein-1 (XBP-1) mRNA splicing and C/EBP homologues protein (CHOP) expression were measured to reflect ER stress. Contents of ADMA and nitrite/nitrate as well as activities or expression of NOS and dimethylarginine dimethylaminohydrolase (DDAH) were detected to show the changes in DDAH/ADMA/NOS/NO pathway. The lipid peroxidation product malondialdehyde content and antioxidant enzyme superoxide dismutase activity were analyzed to evaluate oxidative stress.ResultsER stress was provoked in the liver of type 2 diabetic rats, as expressed by increases of Bip transcription, eIF2α phosphorylation, XBP-1 splicing and CHOP expression, all of which were in parallel with the elevation of serum ADMA, suppression of NO generation, NOS and DDAH activities in the liver. Exposure of hepatocytes to ADMA or hydrogen peroxide also induced ER stress, which was associated with the inhibition of NO production and increase of oxidative stress. Treatment of hepatocytes with antioxidant pyrrolidine dithiocarbamate not only decreased ADMA-induced oxidative stress and inhibition of NO production but also reduced ADMA-triggered ER stress.ConclusionsThese results indicate that increased endogenous ADMA contributes to hepatic ER stress in type 2 diabetic rats, and the mechanism underlying ADMA-induced ER stress may relate to oxidative stress via NOS uncoupling.

Aims: Mitochondrial dysfunction plays important roles in the development of diabetes. Elevated nitric oxide (NO) synthase inhibitor asymmetric dimethylarginine (ADMA) has been shown to be closely related to diabetes. But the relationship between them in diabetes has not been determined. This study was to explore the role of ADMA in hepatic mitochondrial dysfunction and its potential mechanisms in diabetic rats and hepatocytes. Methods: Respiratory enzymes activities, mitochondrial transmembrane potential and ATP content were measured to evaluate mitochondrial function. The copy number ratio of mitochondrial gene to nuclear gene was used to represent mitochondrial biogenesis. The activity of superoxide dismutase and malondialdehyde content were detected to reflect oxidative stress. Furthermore, changes in ADMA and NO contents, uncoupling protein 2 (UCP2) and peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) transcriptions were determined. Results: Elevated ADMA levels in serum of diabetic rats were found to be associated with hepatic mitochondrial dysfunction reflected by reductions of respiratory enzyme activities, mitochondrial membrane potential and ATP contents. Similar mitochondrial dysfunction also occurred in ADMA-treated hepatocytes. The mitochondrial dysfunction observed in diabetic rats or hepatocytes was accompanied with suppressions of mitochondrial biogenesis, PGC-1α transcription and NO synthesis as well as enhances of UCP 2 transcription and oxidative stress. These effects of ADMA could be attenuated by treatments with antioxidant or NO donor. Conclusions: These results indicate that elevated endogenous ADMA contributes to hepatic mitochondrial dysfunction in diabetic rats, and underlying mechanisms may be related to the suppression of mitochondrial biogenesis and mitochondrial uncoupling via inhibiting NO synthesis and enhancing oxidative stress.

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