Simvastatin reduces lipoprotein-associated phospholipase A2 in lipopolysaccharide-stimulated human monocyte-derived macrophages through inhibition of the mevalonate-geranylgeranyl pyrophosphate-RhoA-p38 mitogen-activated protein kinase pathway

Research Advance of Chinese Medicine in Treating Atherosclerosis: Focus on Lipoprotein-Associated Phospholipase A2

As a serious cardiovascular disease, atherosclerosis (AS) causes chronic inflammation and oxidative stress in the body and poses a threat to human health. Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a member of the phospholipase A2 (PLA2) family, and its elevated levels have been shown to contribute to AS. Lp-PLA2 is closely related to a variety of lipoproteins, and its role in promoting inflammatory responses and oxidative stress in AS is mainly achieved by hydrolyzing oxidized phosphatidylcholine (oxPC) to produce lysophosphatidylcholine (lysoPC). Moreover, macrophage apoptosis within plaque is promoted by localized Lp-PLA2 which also promotes plaque instability. This paper reviews those researches of Chinese medicine in treating AS via reducing Lp-PLA2 levels to guide future experimental studies and clinical applications related to AS.

Urocortin participates in LPS-induced apoptosis of THP-1 macrophages via S1P-cPLA2 signaling pathway

There is little literature showing the effect of urocortin (UCN) on macrophage apoptosis. The underlying mechanism is also unclear. This work was to investigate the involvement of UCN in the regulation of LPS-induced macrophage apoptosis and hence in the prevention from the atherosclerotic lesion development through targeting PLA2. Flow cytometry analysis showed that cell apoptosis was increased by more than 50% after LPS treatment in human THP-1 macrophage. Lp-PLA2 and cPLA2 were found to mediate LPS-induced macrophage apoptosis and NF-κB differentially influenced the expression of Lp-PLA2 and cPLA2. However, the reverse regulation of the expression of Lp-PLA2 and cPLA2 by NF-κB suggested that NF-κB may not be a key target for regulating macrophage apoptosis. Interestingly, we found that the approximate three folds upregulation of cPLA2 was in line with the induction of S1P formation and cell apoptosis by LPS. Inversely, LPS obviously decreased UCN expression by about 50% and secretion by about 25%. Both the enzyme inhibitor and knockdown expression of cPLA2 could completely abolish LPS-induced cell apoptosis. In addition, suppression of S1P synthesis by Sphk1 inhibitor PF-543 reduced the expression of cPLA2 and cell apoptosis but at the same time restored the normal level of UCN in cell culture supernatant. Furthermore, addition of exogenous UCN also reversed LPS-induced expression of cPLA2 and apoptosis. Taken together, UCN may be the reverse regulator of LPS-S1P-cPLA2-apoptosis pathway, thereby contributing to the prevention from the formation of unstable plaques.

Lipoprotein-Associated Phospholipase A2 is Linked with Poor Cardio-Metabolic Profile in Patients with Ischemic Stroke: A Study of Effects of Statins

Objectives

The objective of the study is to investigate the effects of statins on the lipoprotein-associated phospholipase A2 (Lp-PLA2) mass in patients with ischemic stroke.

Materials and Methods

A total number of 59 patient ages 43-69 years with cerebral stroke compared to 39 healthy controls that matching the age and body weight. The patients were divided into 32 patients on statins therapy assigned as statins users and 27 patients, not on statins therapy assigned as nonstatins users. Anthropometric and biochemical measurements were done including lipid profile and inflammatory biomarkers.

Results

Stroke patients on statins therapy showed a comparable low of Lp-PLA (29.82 ± 3.19 IU/mL) to nonstatins user stroke patients (15.58 ± 5.73 IU/mL). Lp-PLA2 mass levels were positively correlated with body mass index, blood pressure changes, total cholesterol, triglyceride, and very low-density lipoprotein and stroke risk (SR) percentage.

Conclusions

Patients on statins with ischemic stroke had low levels of Lp-PLA2 mass levels compared to nonstatins user with ischemic stroke. Lp-PLA2 mass levels were higher in men than women and correlated with lipid profile and SR in patients with ischemic stroke.

Lipoprotein-associated phospholipase A2: The story continues

Inflammation is thought to play an important role in the pathogenesis of vascular diseases. Lipoprotein-associated phospholipase A2 (Lp-PLA2) mediates vascular inflammation through the regulation of lipid metabolism in blood, thus, it has been extensively investigated to identify its role in vascular inflammation-related diseases, mainly atherosclerosis. Although darapladib, the most advanced Lp-PLA2 inhibitor, failed to meet the primary endpoints of two large phase III trials in atherosclerosis patients cotreated with standard medical care, the research on Lp-PLA2 has not been terminated. Novel pathogenic, epidemiologic, genetic, and crystallographic studies regarding Lp-PLA2 have been reported recently, while novel inhibitors were identified through a fragment-based lead discovery strategy. More strikingly, recent clinical and preclinical studies revealed that Lp-PLA2 inhibition showed promising therapeutic effects in diabetic macular edema and Alzheimer's disease. In this review, we not only summarized the knowledge of Lp-PLA2 established in the past decades but also emphasized new findings in recent years. We hope this review could be valuable for helping researchers acquire a much deeper insight into the nature of Lp-PLA2, identify more potent and selective Lp-PLA2 inhibitors, and discover the potential indications of Lp-PLA2 inhibitors.

Current Insights into the Biological Action of Squalene

Squalene is a triterpenic compound found in a large number of plants and other sources with a long tradition of research since it was first reported in 1926. Herein a systematic review of studies concerning squalene published in the last 8 years is presented. These studies have provided further support for its antioxidant, anti-inflammatory, and anti-atherosclerotic properties in vivo and in vitro. Moreover, an antineoplastic effect in nutrigenetic-type treatments, which depends on the failing metabolic pathway of tumors, has also been reported. The bioavailability of squalene in cell cultures, animal models, and in humans has been well established, and further progress has been made in regard to the intracellular transport of this lipophilic molecule. Squalene accumulates in the liver and decreases hepatic cholesterol and triglycerides, with these actions being exerted via a complex network of changes in gene expression at both transcriptional and post-transcriptional levels. Its presence in different biological fluids has also been studied. The combination of squalene with other bioactive compounds has been shown to enhance its pleiotropic properties and might lead to the formulation of functional foods and nutraceuticals to control oxidative stress and, therefore, numerous age-related diseases in human and veterinary medicine.

Community-based statins and advanced carotid plaque: Role of CD163 positive macrophages in lipoprotein-associated phospholipase A2 activity in atherosclerotic plaque

BACKGROUND AND AIMS

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂), an enzymatic inflammatory biomarker primarily bound to low-density lipoprotein cholesterol, is associated with an approximate twofold increased risk of cardiovascular disease and stroke. Despite indications that circulating Lp-PLA₂ is sensitive to statins, it remains largely unknown whether statin usage exerts local effects on Lp-PLA₂ expression at the site of atheromatous plaque.

METHODS

Carotid plaques (n = 38) were prospectively collected from symptomatic (n = 18) and asymptomatic (n = 20) patients with (n = 20) or without (n = 18) documented statin history. In all cases, endarterectomy was performed where the primary stenosis was removed in an undisturbed manner. Serial cryosections of the presenting lesion were assessed histologically for macrophages, Lp-PLA₂, and cell death (apoptotic index).

RESULTS

Symptomatic lesions exhibited less calcification, with greater inflammation characterized by increased expression of CD68⁺ and CD163⁺ macrophage subsets, and Lp-PLA₂. Symptomatic plaques also exhibited greater necrotic core area and increased apoptosis, as compared with asymptomatic lesions. In contrast, statin treatment did not appear to influence any of these parameters, except for the extent of apoptosis, which was less in statin treated as compared with statin naïve lesions. Overall, Lp-PLA₂ expression correlated positively with necrotic core area, CD68⁺ and CD163⁺ macrophage area, and cell death. Finally, in vitro assays and dual immunofluorescence staining confirmed CD163-expressing monocytes/macrophages are also a major source of Lp-PLA₂.

CONCLUSIONS

Statin treatment has no effect on local atherosclerotic lesion Lp-PLA2 activity, therefore, the addition of anti-inflammatory treatments to further decrease macrophage Lp-PLA₂ expression in atherosclerotic lesions may reduce lesional inflammation and cell death, and prevent necrotic core expansion and lesion progression.

Comparison of the effect of rosuvastatin versus rosuvastatin/ezetimibe on markers of inflammation in patients with acute myocardial infarction

Statins lower low-density lipoprotein cholesterol (LDL-C) and high-sensitivity C-reactive protein (hsCRP), and the addition of ezetimibe to statins further reduces LDL-C and hsCRP. Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a potentially important pathogenic factor participating in the progression of atherosclerosis. The aim of current study was to investigate how the addition of ezetimibe to rosuvastatin treatment affects reductions in LDL-C, hsCRP and Lp-PLA2 in patients with acute myocardial infarction (AMI). A total of 135 patients were enrolled in the study within 24 h of AMI, and were randomized to receive 10 mg rosuvastatin or 10 mg rosuvastatin plus 10 mg ezetimibe daily. HsCRP, Lp-PLA2, total cholesterol (TC), triglycerides (TG), LDL-C and high-density lipoprotein cholesterol (HDL-C) were determined at baseline and after 1, 3, 6 and 12 months of treatment. The addition of ezetimibe to rosuvastatin led to greater reduction of LDL-C compared with rosuvastatin monotherapy (from 3.00 to 1.19 mmol/l vs. 2.93 to 1.49 mmol/l, respectively; P<0.05), as well as reduced levels of hsCRP (from 5.15 to 0.68 mg/l vs. 4.33 to 1.49 mg/l, respectively; P<0.05) and Lp-PLA2 (from 333.13 to 79.07 mg/l vs. 327.95 to 123.62 mg/l, respectively; P<0.05). A positive association was identified between reductions of Lp-PLA2 and the changes of LDL-C (r=0.367; P=0.002). However, no significant correlation was observed between changes in Lp-PLA2 and hsCRP (r=0.264; P=0.512). The values of hsCRP and Lp-PLA2 appeared to increase during the first week after randomization, but dropped steeply to a lower level and remained stable thereafter. In conclusion, the addition of ezetimibe to rosuvastatin was demonstrated to further reduce LDL-C, hsCRP and Lp-PLA2 compared with rosuvastatin monotherapy in patients with AMI.

Alendronate Attenuates Spinal Microglial Activation and Neuropathic Pain

Many derivatives of bisphosphonates, which are inhibitors of bone resorption, have been developed as promising agents for painful pathologies in patients with bone resorption-related diseases. The mechanism for pain relief by bisphosphonates remains uncertain. Studies have reported that bisphosphonates could reduce central neurochemical changes involved in the generation and maintenance of bone cancer pain. In this study, we hypothesized that bisphosphonates would inhibit spinal microglial activation and prevent the development of hyperalgesia caused by peripheral tissue injury. We investigated the effects of alendronate (a nitrogen-containing bisphosphonate) on the development of neuropathic pain and its role in modulating microglial activation in vivo and in vitro. Intrathecal and intraperitoneal administration of alendronate relieved neuropathic pain behaviors induced by chronic constriction sciatic nerve injury. Alendronate also significantly attenuated spinal microglial activation and p38 mitogen-activated protein kinase (MAPK) phosphorylation without affecting astrocytes. In vitro, alendronate downregulated phosphorylated p38 and phosphorylated extracellular signal regulated kinase expression in lipopolysaccharide-stimulated primary microglia within 1 hour, and pretreatment with alendronate for 12 and 24 hours decreased the expression of inflammatory cytokines (tumor necrosis factor α, and interleukins 1β and 6). These findings indicate that alendronate could effectively relieve chronic constriction sciatic nerve injury-induced neuropathic pain by at least partially inhibiting the activation of spinal microglia and the p38 MAPK signaling pathway.

PERSPECTIVE

Alendronate could relieve neuropathic pain behaviors in animals by inhibiting the activation of spinal cord microglia and the p38 MAPK cell signaling pathway. Therapeutic applications of alendronate may be extended beyond bone metabolism-related disease.

Synergistic effects of colchicine combined with atorvastatin in rats with hyperlipidemia

Background

Inflammation and endothelial dysfunction is implicated in the atherosclerosis initiation and progression in the setting of hyperlipidemia. Colchicine is a potent anti-inflammatory agent and whether colchicine combined with atorvastatin has synergistic effects on inflammation amelioration and endothelial function improvement is unknown.

Methods

Hyperlipidemic rat model was produced by high-fat and high-cholesterol diet for 6 weeks. Rats with normal diet were served as shame group. In hyperlipidemic group, normal saline, atorvastatin (10 mg/kg body weight/day), colchicines (0.5 mg/kg body weight/day), or atorvastatin combined with colchicines (same dosages) were prescribed for 2 weeks. Serum levels of lipid profile, C-reactive protein (CRP), liver enzyme, lipoprotein associated phospholipase A2 (Lp-PLA2) and nitric oxide (NO) production were serially assessed.

Results

Before the beginning of the study, all laboratory variables were comparable among each group. After 6 weeks of hyperlipidemic model production, serum levels of cholesterols, CRP and Lp-PLA2 were significantly increased when compared to sham group, whereas NO production was reduced. With 2 weeks of colchicine therapy, serum levels of CRP and Lp-PLA2 were decreased and NO production was enhanced in the colchicine group in a lipid-lowering independent manner. Added colchicine into atorvastatin therapy further improved NO production and decreased CRP and Lp-PLA2 levels, indicating a potential synergism of colchicine and atorvastatin.

Conclusion

Colchicine combined with atorvastatin may have stronger protective effects on improving endothelial function and ameliorating inflammation in rats with hyperlipidemia.

Effect of 24 weeks of statin therapy on systemic and vascular inflammation in HIV-infected subjects receiving antiretroviral therapy

BACKGROUND

Human immunodeficiency virus (HIV)-infected individuals are at increased risk of cardiovascular disease (CVD) due in part to inflammation. Statins decrease inflammation in the general population, but their effect during HIV infection is largely unknown.

METHODS

This is an ongoing randomized, double-blinded, placebo-controlled trial to evaluate the effect of statin therapy on inflammatory markers during HIV infection. Subjects received rosuvastatin 10 mg daily or placebo for 24 weeks. Subjects were receiving stable (>12 weeks) antiretroviral therapy and had a low-density lipoprotein (LDL) cholesterol level of ≤130 mg/dL and evidence of heightened immune activation or inflammation. This was a prespecified interim analysis.

RESULTS

A total of 147 subjects were enrolled (78% were male, 70% were black, and the median age was 47 years). By 24 weeks, LDL cholesterol levels had decreased in the statin group, compared with an increase in the placebo group (-28% vs +3.8%; P < .01). A 10% reduction in the lipoprotein-associated phospholipase A2 (Lp-PLA2) level was seen in the statin group, compared with a 2% reduction in the placebo group (P < .01). In multivariable regression, receipt of statin treatment and having a nadir CD4(+) T-cell count of ≤100 cell/µL were the only statistically significant predictors of a decrease in Lp-PLA2 level. Markers of systemic inflammation did not change significantly between groups.

CONCLUSIONS

Twenty-four weeks of rosuvastatin therapy significantly decreased the level of Lp-PLA2, a vascular-specific, inflammatory enzyme that predicts cardiovascular events in the general population. Statins may hold promise as a means of attenuating CVD risk in HIV-infected individuals by decreasing Lp-PLA2 levels.

Changes in lipoprotein-Associated phospholipase A2 activity predict coronary events and partly account for the treatment effect of pravastatin: results from the Long-Term Intervention with Pravastatin in Ischemic Disease study

Background

Lipoprotein‐associated phospholipase A2 (Lp‐PLA₂) levels are associated with coronary heart disease (CHD) in healthy individuals and in patients who have had ischemic events.

Methods and Results

The Long‐term Intervention with Pravastatin in Ischemic Disease (LIPID) study randomized 9014 patients with cholesterol levels of 4.0 to 7.0 mmol/L to placebo or pravastatin 3 to 36 months after myocardial infarction or unstable angina and showed a reduction in CHD and total mortality. We assessed the value of baseline and change in Lp‐PLA₂ activity to predict outcomes over a 6‐year follow‐up, the effect of pravastatin on Lp‐PLA₂ levels, and whether pravastatin treatment effect was related to Lp‐PLA₂ activity change. Lp‐PLA₂ was measured at randomization and 1 year, and levels were grouped as quartiles. The prespecified end point was CHD death or nonfatal myocardial infarction. Baseline Lp‐PLA₂ activity was positively associated with CHD events (P<0.001) but not after adjustment for 23 baseline factors (P=0.66). In 6518 patients who were event free at 1 year, change in Lp‐PLA₂ was a significant independent predictor of subsequent CHD events after adjustment for these risk factors, including LDL cholesterol and LDL cholesterol changes (P<0.001). Pravastatin reduced Lp‐PLA₂ by 16% compared with placebo (P<0.001). After adjustment for Lp‐PLA₂ change, the pravastatin treatment effect was reduced from 23% to 10% (P=0.26), with 59% of the treatment effect accounted for by changes in Lp‐PLA₂. Similar reductions in treatment effect were seen after adjustment for LDL cholesterol change.

Conclusion

Reduction in Lp‐PLA₂ activity during the first year was a highly significant predictor of CHD events, independent of change in LDL cholesterol, and may account for over half of the benefits of pravastatin in the LIPID study.

Simvastatin inhibits lipopolysaccharide-induced osteoclastogenesis and reduces alveolar bone loss in experimental periodontal disease

BACKGROUND AND OBJECTIVE

Statins are inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase and have anti-inflammatory effects independent of cholesterol lowering. Recent clinical studies have indicated that statin intake has a beneficial effect on periodontal disease. However, the underlying mechanisms have not been well understood. In the current study, we employed a rat model with lipopolysaccharide (LPS)-induced periodontal disease and determined the effect of simvastatin, a commonly prescribed statin, on osteoclastogenesis, gingival inflammation and alveolar bone loss.

MATERIAL AND METHODS

Sprague-Dawley rats were injected with Aggregatibacter actinomycetemcomitans LPS in periodontal tissue three times per week for 8 wk and part of the rats with LPS injection were also given simvastatin via gavage. After the treatments, the rat maxillae were scanned by microcomputed tomography and the images were analyzed to determine alveolar bone loss. To explore the underlying mechanisms, the effect of simvastatin on osteoclastogenesis and gingival expression of proinflammatory cytokines were also determined by tartrate-resistant acid phosphatase staining and real-time polymerase chain reaction assays, respectively.

RESULTS

Results showed that LPS treatment markedly increased bone loss, but administration of simvastatin significantly alleviated the bone loss. Results also showed that LPS treatment stimulated osteoclastogenesis and the expression of inflammatory cytokines, but simvastatin significantly modulates the stimulatory effect of LPS on osteoclastogenesis and cytokine expression.

CONCLUSION

This study demonstrated that simvastatin treatment inhibits LPS-induced osteoclastogenesis and gingival inflammation and reduces alveolar bone loss, indicating that the intake of simvastatin may hinder the progression of periodontal disease.

The elevation of apoB in hypercholesterolemic patients is primarily attributed to the relative increase of apoB/Lp-PLA₂

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) is a risk factor of cardiovascular disease. Plasma Lp-PLA₂ is mainly associated with apolipoprotein (apo)B-containing lipoproteins, primarily with low density lipoproteins (LDLs). Importantly, only a proportion of circulating lipoproteins contain Lp-PLA₂. We determined the plasma levels of Lp-PLA₂-bound apoB (apoB/Lp-PLA₂) in patients with primary hypercholesterolemia. The effect of simvastatin therapy was also addressed. The plasma apoB/Lp-PLA₂ concentration in 50 normolipidemic controls and 53 patients with primary hypercholesterolemia at baseline and at 3 months posttreatment with simvastatin (40 mg/day) was determined by an enzyme-linked immunosorbent assay. The concentration of the apoB-containing lipoproteins that do not bind Lp-PLA₂ [apoB/Lp-PLA₂⁻] was calculated by subtracting the apoB/Lp-PLA₂ from total apoB. The apoB/Lp-PLA₂ levels were 3.6-fold higher, while apoB/Lp-PLA₂⁻ were 1.3-fold higher in patients compared with controls. After 3 months of simvastatin treatment apoB/Lp-PLA₂ and apoB/Lp-PLA₂⁻ levels were reduced by 52% and 33%, respectively. The elevation in apoB-containing lipoproteins in hypercholesterolemic patients is mainly attributed to the relative increase in the proatherogenic apoB/Lp-PLA₂, while simvastatin reduces these particles to a higher extent compared with apoB/Lp-PLA₂⁻. Considering that Lp-PLA₂ is proatherogenic, the predominance of apoB/Lp-PLA₂ particles in hypercholesterolemic patients may contribute to their higher atherogenicity and incidence of cardiovascular disease.

Reduction of platelet cytosolic phospholipase A2 activity by atorvastatin and simvastatin: biochemical regulatory mechanisms

Statins have demonstrated effects beyond reducing cholesterol level that may contribute to their clinical benefit, including effects on platelet biochemistry and function.

OBJECTIVES

To explore and compare the antiplatelet effect of two lipophilic statins (atorvastatin and simvastatin) and one hydrophilic statin (pravastatin) concerning: a) collagen-induced platelet aggregation and thromboxane A2 (TXA2) synthesis; b) the additive effect of statins on TXA2 synthesis in platelets treated with a submaximally effective concentration of aspirin and c) the biochemical mechanisms involved.

METHODS AND RESULTS

Washed human platelets were incubated with statins (1-20μM), and stimulated with collagen (1μg/ml) or arachidonic acid (AA) (200μM) and TXB2 was quantified by ELISA. Incubation with simvastatin or atorvastatin reduced (36.2% and 31.0%, respectively) collagen-induced TXB2 synthesis (p<0.05) and platelet aggregation (p<0.001), whereas pravastatin had no effects. Simultaneous incubation with a submaximally effective concentration of aspirin (1μM) and atorvastatin or simvastatin significantly increased the inhibition of TXB2 synthesis by aspirin by 4.4- and 4.1-fold, respectively. Statins did not affect AA-induced TXB2 synthesis, excluding an effect on COX-1/TXA2 synthase activities. Atorvastatin and simvastatin concentration-dependently inhibited the collagen-induced increase in cytosolic calcium and the kinetics of cPLA2 phosphorylation. Lipophilic statins reduced phosphorylation of both ERK1/2 and p38 MAPK, which regulate cPLA2 phosphorylation and calcium movement.

CONCLUSION

We report for the first time a direct downregulation by atorvastatin and simvastatin of platelet cPLA2 activity through effects on calcium and MAPK, which reduce collagen-induced TXA2 synthesis. These mechanisms might contribute to their beneficial effects, even in aspirin-treated patients.