Overexpression of lysosomal acid lipase and other proteins in atherosclerosis

A Form of Metabolic-Associated Fatty Liver Disease Associated with a Novel LIPA Variant

BACKGROUND

The LIPA gene on chromosome 10q23.31 contains 10 exons and encodes lipase A, the lysosomal acid lipase (LAL) containing 399 amino acids. Pathogenic variants in the LIPA result in autosomal recessive Wolman disease and cholesteryl ester storage disease (CESD). Here, we report a novel missense variant (NM_001127605.3:c.928T>A, p.Trp310Arg) of LIPA in an Iranian family with fatty liver disease identified by whole-exome sequencing and confirmed by Sanger sequencing.

METHODS

A 28-year-old woman referred with lean NASH cirrhosis and extremely high cholesterol levels. Fatty liver disease was found in six of her family members using vibration-controlled transient elastography (VCTE). Baseline routine laboratory tests were performed and whole-exome sequencing and confirmation by Sanger sequencing were done.

RESULTS

The index case had severe dyslipidemia and cirrhosis despite a body mass index of 21.09 kg/m2 . Six other family members had dyslipidemia and fatty liver or cirrhosis. A homozygous missense variant (NM_001127605.3:c.928T>A, p.Trp310Arg) of LIPA which caused LAL-D was found to be associated with fatty liver disease and/or cirrhosis.

CONCLUSION

A homozygous missense variant (NM_001127605.3:c.928T>A, p.Trp310Arg) of the LIPA gene which caused LAL-D was found to be associated with dyslipidemia, fatty liver disease and/or cirrhosis in six members of an Iranian family. These results should be confirmed by functional studies and extending the study to at least three families.

Serine Hydrolases in Lipid Homeostasis of the Placenta-Targets for Placental Function?

The metabolic state of pregnant women and their unborn children changes throughout pregnancy and adapts to the specific needs of each gestational week. These adaptions are accomplished by the actions of enzymes, which regulate the occurrence of their endogenous substrates and products in all three compartments: mother, placenta and the unborn. These enzymes determine bioactive lipid signaling, supply, and storage through the generation or degradation of lipids and fatty acids, respectively. This review focuses on the role of lipid-metabolizing serine hydrolases during normal pregnancy and in pregnancy-associated pathologies, such as preeclampsia, gestational diabetes mellitus, or preterm birth. The biochemical properties of each class of lipid hydrolases are presented, with special emphasis on their role in placental function or dysfunction. While, during a normal pregnancy, an appropriate tonus of bioactive lipids prevails, dysregulation and aberrant signaling occur in diseased states. A better understanding of the dynamics of serine hydrolases across gestation and their involvement in placental lipid homeostasis under physiological and pathophysiological conditions will help to identify new targets for placental function in the future.

Lysosomal acid lipase gene single nucleotide polymorphism and pulmonary tuberculosis susceptibility

BACKGROUND

The factors that predispose to pulmonary tuberculosis (PTB) are not fully understood, However. Gene polymorphisms have been associated with PTB development.

OBJECTIVES

In this study, we investigated the relationship between LIPA gene polymorphisms and a predisposition to pulmonary tuberculosis caused by Mycobacterium tuberculosis.

METHODS

A total of 202 cases of PTB and 218 healthy controls (HCS) were included in this study. Analyses were done under allelic, homozygous, and heterozygous, dominant, recessive models, and were used to calculate values, odds ratios (ORs), and 95% confidence intervals (CIs) for assessing the association between single nucleotide polymorphisms (SNPs) and disease risk. Genotyping was conducted using the real time polymerase chain reaction with high resolution melting curve analysis.

RESULTS

When comparing PTB patients with healthy controls (HCS), significant associations with disease development were observed for both SNPs rs1051338 and rs7922269. Analysis was done based on models of genetic inheritance in man that is co-dominant, recessive and dominant models. Rs1051338, the heterozygous (AC vs. AA) P: 0.001, OR: 1.998, 95% CI: 1.312-3.042 and homozygous (CC vs. AA) P: < 0.001, OR: 4.078, 95% CI: 2.134-7.796 Co-dominant associated with increased risk for the disease. Under recessive (CC vs. AA + AC), P: 0.001, OR: 2.829: 95% CI: 1.543-5.185 and dominant model (AC + CC vs. AA) P: < 001, OR: 2.331, 95% CI: 1.564-3.474 the genotypes distribution increased the individual risk, plus its alleles distribution (P: < 0.001, OR: 2.004, 95% CI: 1.505-2.669). Considering SNP rs7922269 mutation significantly increased pulmonary tuberculosis risk as was observed in the homozygous GG vs. TT (P: 0.003, OR: 3.162, 95% CI: 1.431-6.989); heterozygous GT vs. TT (P: < 0.001, OR: 1.2.259, 95% CI: 1.503-3.394); dominant model (GT + GG vs. TT; P: < 0.001, OR: 2.061, 95% CI: 1.402-3.032) and the allele G (P: < 0.001, OR: 1.829, 95% CI:1.361-2.458), however no significant association was observed in the Recessive model (GG vs. TT + GT; P: 0.057, OR: 2.568, 95% CI: 0.965-4.432).

CONCLUSION

The findings of our study strengthen the hypothesis that LIPA rs1051338 and rs7922269 polymorphism associated with increased risk for pulmonary Tb in a sample of northern Chinese population.

An overview of deregulated lipid metabolism in nonalcoholic fatty liver disease with special focus on lysosomal acid lipase

Obesity and type 2 diabetes are frequently complicated by excess fat accumulation in the liver, which is known as nonalcoholic fatty liver disease (NAFLD). In this context, liver steatosis develops as a result of the deregulation of pathways controlling de novo lipogenesis and fat catabolism. Recent evidences suggest the clinical relevance of a reduction in the activity of lysosomal acid lipase (LAL), which is a key enzyme for intracellular fat disposal, in patients with NAFLD. In this review, we provided a comprehensive overview of the critical steps in hepatic fat metabolism and alterations in these pathways in NAFLD, with a special focus on lipophagy and LAL activity. During NAFLD, hepatic fat metabolism is impaired at several levels, which is significantly contributed to by impaired lipophagy, in which reduced LAL activity may play an important role. For further research and intervention in NAFLD, targeting LAL activity may provide interesting perspectives.

Abemaciclib induces atypical cell death in cancer cells characterized by formation of cytoplasmic vacuoles derived from lysosomes

In the cell cycle, the G₁ /S transition is controlled by the cyclin-dependent kinase (CDK) 4/6-cyclin D complex. Constitutive activation of CDK4/6 dysregulates G₁ /S transition, leading to oncogenic transformation. We found that 3 CDK4/6 inhibitors, abemaciclib, ribociclib, and palbociclib, exerted a cytocidal effect as well as a cytostatic effect at the G₁ phase in cancer cell lines, including A549 human non-small cell lung cancer cells. Among these inhibitors, abemaciclib exhibited the most potent cytotoxic effect. The cell-death phenotype induced by abemaciclib, which entailed formation of multiple cytoplasmic vacuoles, was not consistent with apoptosis or necroptosis. Abemaciclib blocked autophagic flux, resulting in accumulation of autophagosomes, however vacuole formation and cell death induced by abemaciclib were independent of autophagy. In addition, methuosis, a cell-death phenotype characterized by vacuole formation induced by excessive macropinocytosis, was excluded because the vacuoles did not incorporate fluorescent dextran. Of note, both formation of vacuoles and induction of cell death in response to abemaciclib were inhibited by vacuolar-type ATPase (V-ATPase) inhibitors such as bafilomycin A1 and concanamycin A. Live-cell imaging revealed that the abemaciclib-induced vacuoles were derived from lysosomes that expanded following acidification. Transmission electron microscopy revealed that these vacuoles contained undigested debris and remnants of organelles. Cycloheximide chase assay revealed that lysosomal turnover was blocked by abemaciclib. Furthermore, mTORC1 inhibition along with partial lysosomal membrane permeabilization occurred after abemaciclib treatment. Together, these results indicate that, in cancer cells, abemaciclib induces a unique form of cell death accompanied by swollen and dysfunctional lysosomes.

Association Between LOX-1, LAL, and ACAT1 Gene Single Nucleotide Polymorphisms and Carotid Plaque in a Northern Chinese Population

Objective: Carotid atherosclerosis is one of the major risk factors for ischemic stroke. The presence of carotid plaque has been widely used to assess the risk of clinical atherosclerotic disease. Lectin-type oxidized LDL (low-density lipoprotein) receptor 1 (LOX-1), lysosomal acid lipase (LAL), and acyl-CoA:cholesterol acyltransferase 1 (ACAT1) are important for lipid accumulation in atherosclerosis. The objective of this study was to investigate the relationship between single nucleotide polymorphisms (SNPs) in the LOX-1, LAL, and ACAT1 genes and the presence of carotid plaque in a Northern Chinese population. Methods: Three polymorphisms in LOX-1 (rs1050286), LAL (rs11203042), and ACAT1 (rs11576517) were identified and genotyped in 215 patients with carotid plaque and 252 controls using the polymerase chain reaction with high-resolution melting analysis. Results: The LOX-1 (rs1050286) AA and LAL (rs11203042) TT genotypes were significantly associated with increased risk of carotid plaque, whereas a ACAT1 (rs11576517) TT genotype was shown to be protective against carotid plaque in a Northern Chinese population (p < 0.05). Even after the Bonferroni correction, the LAL (rs11203042) TT genotype (odds ratio = 3.838, 95% confidence interval = 1.748-8.426, p < 0.001) was still associated with an increased risk for carotid plaque. Conclusions: These results suggest that the LAL (rs11203042) TT genotype is associated with increased risk for carotid plaque in a Northern Chinese population, and that the LOX-1 (rs1050286) AA genotype shows a nonstatistically significant trend towards association. However, no association was found between the ACAT1 (rs11576517) polymorphisms and carotid plaque presence.

Persistent dyslipidemia in treatment of lysosomal acid lipase deficiency

BACKGROUND

Lysosomal acid lipase deficiency (LALD) is an autosomal recessive inborn error of lipid metabolism characterized by impaired lysosomal hydrolysis and consequent accumulation of cholesteryl esters and triglycerides. The phenotypic spectrum is diverse, ranging from severe, neonatal onset failure to thrive, hepatomegaly, hepatic fibrosis, malabsorption and adrenal insufficiency to childhood-onset hyperlipidemia, hepatomegaly, and hepatic fibrosis. Sebelipase alfa enzyme replacement has been approved by the Food and Drug Administration for use in LALD after demonstrating dramatic improvement in transaminitis and dyslipidemia with initiation of enzyme replacement therapy.

METHODS

A chart review was performed on 2 patients with childhood-onset, symptomatic LALD with persistent dyslipidemia despite appropriate enzyme replacement therapy to identify biological pathways and risk factors for incomplete response to therapy.

RESULTS

Two patients with attenuated, symptomatic LALD had resolution of transaminitis on enzyme replacement therapy without concomitant effect on dyslipidemia despite dose escalation and no evidence of antibody response to enzyme.

CONCLUSION

Enzyme replacement therapy does not universally resolve all complications of LALD. Persistent dyslipidemia remains a clinically significant issue, likely related to the complex metabolic pathways implicated in LALD pathogenesis. We discuss the possible mechanistic basis for this unexpected finding and the implications for curative LALD therapy.

Lysosomal Acid Lipase in Lipid Metabolism and Beyond

Lysosomal acid lipase (LAL), encoded by the lipase A ( LIPA) gene, hydrolyzes cholesteryl esters and triglycerides to generate free fatty acids and cholesterol in the cell. The essential role of LAL in lipid metabolism has been confirmed in mice and human with LAL deficiency. In humans, loss-of-function mutations of LIPA cause rare lysosomal disorders, Wolman disease and cholesteryl ester storage disease, in which LAL enzyme-replacement therapy has shown significant benefits in a phase 3 clinical trial. Recent studies have revealed the regulatory role of lipolytic products of lysosomal lipid hydrolysis in catabolic, anabolic, and signaling pathways. In vivo studies in mice with knockout of Lipa highlight the systemic impact of Lipa deficiency on metabolic homeostasis and immune cell function. Genome-wide association studies and functional genomic studies have identified LIPA as a risk locus for coronary heart disease, but the causal variants and mechanisms remain to be determined. Future studies will continue to focus on the role of LAL in the crosstalk between lipid metabolism and cellular function in health and diseases including coronary heart disease.

Role of Myeloperoxidase Oxidants in the Modulation of Cellular Lysosomal Enzyme Function: A Contributing Factor to Macrophage Dysfunction in Atherosclerosis?

Low-density lipoprotein (LDL) is the major source of lipid within atherosclerotic lesions. Myeloperoxidase (MPO) is present in lesions and forms the reactive oxidants hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN). These oxidants modify LDL and have been strongly linked with the development of atherosclerosis. In this study, we examined the effect of HOCl, HOSCN and LDL pre-treated with these oxidants on the function of lysosomal enzymes responsible for protein catabolism and lipid hydrolysis in murine macrophage-like J774A.1 cells. In each case, the cells were exposed to HOCl or HOSCN or LDL pre-treated with these oxidants. Lysosomal cathepsin (B, L and D) and acid lipase activities were quantified, with cathepsin and LAMP-1 protein levels determined by Western blotting. Exposure of J774A.1 cells to HOCl or HOSCN resulted in a significant decrease in the activity of the Cys-dependent cathepsins B and L, but not the Asp-dependent cathepsin D. Cathepsins B and L were also inhibited in macrophages exposed to HOSCN-modified, and to a lesser extent, HOCl-modified LDL. No change was seen in cathepsin D activity or the expression of the cathepsin proteins or lysosomal marker protein LAMP-1. The activity of lysosomal acid lipase was also decreased on treatment of macrophages with each modified LDL. Taken together, these results suggest that HOCl, HOSCN and LDL modified by these oxidants could contribute to lysosomal dysfunction and thus perturb the cellular processing of LDL, which could be important during the development of atherosclerosis.

Association and interaction of APOA5, BUD13, CETP, LIPA and health-related behavior with metabolic syndrome in a Taiwanese population

Increased risk of developing metabolic syndrome (MetS) has been associated with the APOA5, APOC1, BRAP, BUD13, CETP, LIPA, LPL, PLCG1, and ZPR1 genes. In this replication study, we reassessed whether these genes are associated with MetS and its individual components independently and/or through complex interactions in a Taiwanese population. We also analyzed the interactions between environmental factors and these genes in influencing MetS and its individual components. A total of 3,000 Taiwanese subjects were assessed in this study. Metabolic traits such as waist circumference, triglyceride, high-density lipoprotein (HDL) cholesterol, systolic and diastolic blood pressure, and fasting glucose were measured. Our data showed a nominal association of MetS with the APOA5 rs662799, BUD13 rs11216129, BUD13 rs623908, CETP rs820299, and LIPA rs1412444 single nucleotide polymorphisms (SNPs). Moreover, APOA5 rs662799, BUD13 rs11216129, and BUD13 rs623908 were significantly associated with high triglyceride, low HDL, triglyceride, and HDL levels. Additionally, we found the interactions of APOA5 rs662799, BUD13 rs11216129, BUD13 rs623908, CETP rs820299, LIPA rs1412444, alcohol consumption, smoking status, or physical activity on MetS and its individual components. Our study indicates that the APOA5, BUD13, CETP, and LIPA genes may contribute to the risk of MetS independently as well as through gene-gene and gene-environment interactions.

From Loci to Biology: Functional Genomics of Genome-Wide Association for Coronary Disease

Genome-wide association studies have provided a rich collection of ≈ 58 coronary artery disease (CAD) loci that suggest the existence of previously unsuspected new biology relevant to atherosclerosis. However, these studies only identify genomic loci associated with CAD, and many questions remain even after a genomic locus is definitively implicated, including the nature of the causal variant(s) and the causal gene(s), as well as the directionality of effect. There are several tools that can be used for investigation of the functional genomics of these loci, and progress has been made on a limited number of novel CAD loci. New biology regarding atherosclerosis and CAD will be learned through the functional genomics of these loci, and the hope is that at least some of these new pathways relevant to CAD pathogenesis will yield new therapeutic targets for the prevention and treatment of CAD.

Lysosomal Acid Lipase Activity Is Reduced Both in Cryptogenic Cirrhosis and in Cirrhosis of Known Etiology

Lysosomal acid lipase deficiency (LAL-d) is a rare autosomal recessive disease in which LAL activity is almost absent, with consequent massive microvesicular steatosis evolving to cirrhosis and liver failure. We aimed to determine LAL-activity, and to investigate the most common single nucleotide polymorphism (SNP) affecting the LIPA gene and responsible for 50–70% of LAL-d cases (rs116928232 c.894G>A), in patients with cryptogenic cirrhosis. Sixty-three patients with cryptogenic cirrhosis, 88 cirrhotics of known etiology, and 97 healthy subjects were enrolled. LAL-activity was determined in dried-blood-spot (DBS). The c.894G>A mutation was analyzed by pyrosequencing method in SNP mode. LAL-activity was severely reduced in patients with cryptogenic cirrhosis with respect to healthy subjects [0.62 (0.44–0.86) Vs 0.96 (0.75–1.25) nmol/spot/h, p<0.001)], but it was also reduced in known-etiology cirrhotics [0.54 (0.42–0.79) nmol/spot/h, p<0.001 Vs healthy subjects; p = 0.5 Vs cryptogenic cirrhotics]. Fourteen percent of cryptogenic cirrhotics and 20% of known-etiology cirrhotics showed a LAL-activity in the range of heterozygous carriers of LIPA gene mutations (0.15–0.40 nmol/spot/h). However, none of the subjects with reduced LAL-activity carried the c.894G>A SNP except for one patient with HCV cirrhosis. By multivariate analysis, LAL-activity was not associated with age, sex, liver enzymes, liver function or lipid parameters, while it was independently associated with white blood cell (β = 0.2; p<0.01) and platelet (β = 0.4; p<0.001) counts and with the condition of cirrhosis (β = -0.2; p = 0.04).

Development of a selective activity-based probe for glycosylated LIPA

Loss of LIPA activity leads to diseases such as Wolman's Disease and Cholesterol Ester Storage Disease. While it is possible to measure defects in LIPA protein levels, it is difficult to directly measure LIPA activity in cells. In order to measure LIPA activity directly we developed a LIPA specific activity based probe. LIPA is heavily glycosylated although it is unclear how glycosylation affects LIPA activity or function. Our probe is specific for a glycosylated form of LIPA in cells, although it labels purified LIPA regardless of glycosylation.

Does Lysosomial Acid Lipase Reduction Play a Role in Adult Non-Alcoholic Fatty Liver Disease?

Lysosomal Acid Lipase (LAL) is a key enzyme involved in lipid metabolism, responsible for hydrolysing the cholesteryl esters and triglycerides. Wolman Disease represents the early onset phenotype of LAL deficiency rapidly leading to death. Cholesterol Ester Storage Disease is a late onset phenotype that occurs with fatty liver, elevated aminotransferase levels, hepatomegaly and dyslipidaemia, the latter characterized by elevated LDL-C and low HDL-C. The natural history and the clinical manifestations of the LAL deficiency in adults are not well defined, and the diagnosis is often incidental. LAL deficiency has been suggested as an under-recognized cause of dyslipidaemia and fatty liver. Therefore, LAL activity may be reduced also in non-obese patients presenting non-alcoholic fatty liver disease (NAFLD), unexplained persistently elevated liver transaminases or with elevation in LDL cholesterol. In these patients, it could be indicated to test LAL activity. So far, very few studies have been performed to assess LAL activity in representative samples of normal subjects or patients with NAFLD. Moreover, no large study has been carried out in adult subjects with NAFLD or cryptogenic cirrhosis.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.

Single nucleotide polymorphisms within LIPA (Lysosomal Acid Lipase A) gene are associated with susceptibility to premature coronary artery disease. a replication in the genetic of atherosclerotic disease (GEA) Mexican study

AIM

The rs1412444 and rs2246833 polymorphisms within the LIPA gene were recently found to be significantly associated with coronary artery disease (CAD) in genome-wide association studies in Caucasian and Asian populations. The aim of the present study was to replicate this association in an independent population with a different genetic background.

METHODS

The rs1412444 and rs2246833 polymorphisms of the LIPA gene were genotyped by 5' exonuclease TaqMan genotyping assays in a sample of 899 Mexican patients with premature CAD, 270 individuals with subclinical atherosclerosis, and 677 healthy unrelated controls. Haplotypes were constructed after linkage disequilibrium analysis.

RESULTS

Under recessive and additive models, the rs1412444 T and rs2246833 T alleles were associated with an increased risk of premature CAD when compared to controls adjusting for age, gender, BMI, and total cholesterol (OR = 1.53, PRec = 0.0013 and OR = 1.34, PAdd = 5 × 10(-4) for rs1412444 and OR = 1.45, PRec = 0.0039 and OR = 1.28, PAdd = 0.0023 for rs2246833). The effect of the two polymorphisms on various metabolic cardiovascular risk factors was analyzed in premature CAD and controls (CAC score = 0). The T alleles in both polymorphisms after adjusting for age, gender, BMI, and medication were associated with hypo-α-lipoproteinemia, hypercholesterolemia, hypertriglyceridemia, metabolic syndrome, and type 2 diabetes mellitus using recessive and additive models. The polymorphisms were in strong linkage disequilibrium and, based on SNP functional prediction software, only the rs1412444 polymorphism seemed to be functional.

CONCLUSIONS

These results indicate that the rs1412444 and rs2246833 of the LIPA gene are shared susceptibility polymorphisms for CAD among different ethnicities.

Inhibition of endoplasmic reticulum stress and atherosclerosis by 2-aminopurine in apolipoprotein e-deficient mice

We previously reported that the apolipoprotein (apo) B48-carrying lipoproteins obtained from apoE knockout (apoE^−/−) mice, so called E⁻/B48 lipoproteins, transformed mouse macrophages into foam cells and enhanced the phosphorylation of eukaryotic translation initiation factor 2α (eIF-2α). Furthermore, the eIF-2α phosphorylation inhibitor, 2-aminopurine (2-AP), attenuated E⁻/B48 lipoprotein-induced foam cell formation. The present report studied the effect of 2-AP on atherosclerosis in apoE^−/− mice. Our results showed that the level of food intake, bodyweight, plasma cholesterol, and triglycerides was comparable in apoE^−/− mice treated with or without 2-AP. However, the mean size of atherosclerotic lesions in the aorta sinus as well as the surface area of the entire aorta of 2-AP-treated apoE^−/− mice were reduced by about 55% and 39%, respectively, compared to samples from untreated control apoE^−/− mice. In addition, the 2-AP-treated apoE^−/− mice showed a significant decrease in glucose-regulated protein 78 (GRP78) and phosphorylated eIF-2α in their aortic samples as compared to levels in untreated control apoE^−/− mice. These observations suggest that endoplasmic reticulum stress is a causal mechanism for the development of atherosclerosis in apoE^−/− mice and that therapeutic strategies can be developed for using eIF-2α phosphorylation inhibitors, such as 2-AP, to prevent or treat atherosclerosis.

Molecular studies on coronary artery disease-a review

Coronary artery disease (CAD) remains the major cause of mortality and morbidity in the entire world population. The conventional risk factors of CAD include hypertension, hyperlipidemia, diabetes mellitus, family history, smoking etc. These factors contribute only 50 % of the total risk of CAD. For providing a complete risk assessment in CAD, it is mandatory to have well-planned clinical, biochemical and genetic studies in patients with CAD and subjects who are at risk of developing CAD. In this review an attempt is made to critically evaluate the conventional and emerging risk factors which predispose the individual to CAD. Specifically, the molecular basis of CAD including high oxidative stress, low antioxidant status and increased DNA damage are covered. A comprehensive and multifactorial approach to the problem is the better way to reduce the morbidity and mortality of the disease.

Positive correlation between variants of lipid metabolism‑related genes and coronary heart disease

Four gene variants related to lipid metabolism (including the rs562338 and rs503662 variants of the APOB gene, the rs7767084 variant of the LPA gene and the rs2246942 variant of the LIPA gene) have been shown to be associated with coronary heart disease (CHD). The aim of the present study was to assess their association with CHD in the Han Chinese population and to assess the contribution of these gene variants to CHD. Using the standardized coronary angiography method, we enrolled 290 CHD patients and 193 non-CHD patients as non-CHD controls from Lihuili Hospital (Ningbo, China). In addition, we recruited 330 unrelated healthy volunteers as healthy controls from the Xi Men Community (Ningbo, China). Our results demonstrated that the rs503662 and rs562338 variants of the APOB gene were extremely rare in the Han Chinese population (minor allele frequency <1%). Genotype rs2246942-GG of the LIPA gene was associated with an increased risk of CHD [CHD cases versus healthy controls: P=0.04; odds ratio (OR)=1.63; 95% confidence interval (CI)=1.02–2.60). Genotype rs7767084-CC of the LPA gene was identified as a protective factor against CHD in females (CHD cases versus non-CHD controls: P=0.04, OR=0.21; CHD cases versus healthy controls: P=0.02, OR=0.21). The results of our meta-analysis indicated that rs7767084 was not associated with a high risk of CHD (P=0.83; combined OR=0.93; 95% CI=0.47–1.85). In the present study, two single nucleotide polymorphisms (SNPs) of genes involved in lipid metabolism (rs2246942 and rs7767084) were identified to be significantly associated with CHD in the Han Chinese population. Specifically, rs2246942-GG of the LIPA gene was a risk factor for CHD, while rs7767084-CC of the LPA gene was a protective factor against CHD in females. However, our meta-analysis indicated that rs7767084 is not associated with a higher risk of CHD.

Inhibition of lysosomal function in macrophages incubated with elevated glucose concentrations: a potential contributory factor in diabetes-associated atherosclerosis

OBJECTIVE

People with diabetes have an elevated risk of atherosclerosis. The accumulation of lipid within macrophage cells in the artery wall is believed to arise via the uptake and subsequent processing of modified low-density lipoproteins (LDL) via the endo-lysosomal system. In this study the effects of prolonged exposure to elevated glucose upon macrophage lysosomal function was examined to determine whether this contributes to modulated protein catabolism.

METHODS

Human monocytes were isolated from white-cell concentrates and differentiated, in vitro, into monocyte-derived macrophages over 11 days in medium containing 5-30 mmol/L glucose. Murine macrophage-like J774A.1 cells were incubated similarly. Lysosomal cathepsin (B, D, L and S) and acid lipase activities were assessed using fluorogenic substrates; cathepsin protein levels were examined by Western blotting. Lysosomal numbers were examined using the lysomotropic fluorescent dye LysoTracker DND-99, measurement of aryl sulfatase activity, and quantification of lysosome-associated membrane glycoprotein-1 (LAMP-1) by Western blotting.

RESULTS

Exposure to elevated glucose, but not mannitol, resulted in a concentration-dependent decrease in the activity, and to a lesser extent protein levels, of four lysosomal cathepsins. Acid lipase activity was also significantly reduced. Arysulfatase activity, LAMP-1 levels and lysosomal numbers were also decreased at the highest glucose concentrations, though to a lesser extent.

CONCLUSION

Long term exposure of human and murine macrophage cells to elevated glucose levels result in a depression of lysosomal proteolytic and lipase activities. This may result in decreased clearance and cellular accumulation of (lipo)proteins and contribute to the accumulation of modified proteins and lipids in diabetes-associated atherosclerosis.

A genome-wide association study identifies LIPA as a susceptibility gene for coronary artery disease

BACKGROUND

eQTL analyses are important to improve the understanding of genetic association results. We performed a genome-wide association and global gene expression study to identify functionally relevant variants affecting the risk of coronary artery disease (CAD).

METHODS AND RESULTS

In a genome-wide association analysis of 2078 CAD cases and 2953 control subjects, we identified 950 single-nucleotide polymorphisms (SNPs) that were associated with CAD at P<10(-3). Subsequent in silico and wet-laboratory replication stages and a final meta-analysis of 21 428 CAD cases and 38 361 control subjects revealed a novel association signal at chromosome 10q23.31 within the LIPA (lysosomal acid lipase A) gene (P=3.7×10(-8); odds ratio, 1.1; 95% confidence interval, 1.07 to 1.14). The association of this locus with global gene expression was assessed by genome-wide expression analyses in the monocyte transcriptome of 1494 individuals. The results showed a strong association of this locus with expression of the LIPA transcript (P=1.3×10(-96)). An assessment of LIPA SNPs and transcript with cardiovascular phenotypes revealed an association of LIPA transcript levels with impaired endothelial function (P=4.4×10(-3)).

CONCLUSIONS

The use of data on genetic variants and the addition of data on global monocytic gene expression led to the identification of the novel functional CAD susceptibility locus LIPA, located on chromosome 10q23.31. The respective eSNPs associated with CAD strongly affect LIPA gene expression level, which was related to endothelial dysfunction, a precursor of CAD.

LAMP-2 gene expression in peripheral leukocytes is increased in patients with coronary artery disease

BACKGROUND

Coronary artery disease (CAD) is a common complex disease that is caused by interaction between genetic and environmental factors. Accumulating evidence indicates that foam cells in the atherosclerotic plaques exhibit the characteristics of lysosomal storage diseases, namely lysosomal accumulation of indigested materials. In patients with lysosomal storage diseases, lysosomal accumulation of lipids and cholesterols in atherosclerotic plaque cells has been observed. However, the roles of lysosomal hydrolases and proteins in the pathogenesis of atherosclerosis and CAD remain unclear.

HYPOTHESIS

Lysosomal hydrolases and proteins may be involved in the pathogenesis of atherosclerosis and CAD by affecting lipid and cholesterol metabolism.

METHODS

Expression levels of LAMP-2, a lysosomal membrane marker gene, in the peripheral leukocytes of CAD patients (n = 134) and age- and sex-matched healthy controls (n = 80) were examined at transcription and protein levels with reverse transcriptase-polymerase chain reaction and Western blot analyses, respectively. The results were compared between CAD patients and healthy controls.

RESULTS

LAMP-2 gene expression and LAMP-2 protein levels were significantly increased in the peripheral leukocytes of CAD patients, compared with healthy controls. Furthermore, multivariate logistic regression analyses revealed that CAD is significantly associated with LAMP-2 gene expression levels (odds ratio [OR] 8.84, 95% confidence interval [CI]: 2.15-36.40, P = 0.003) or LAMP-2 protein levels (OR 2.03, 95% CI: 1.15-3.59, P = 0.015).

CONCLUSIONS

In CAD patients, LAMP-2 gene expression in the peripheral leukocytes was significantly increased than were controls, which indicates lysosomal accumulation. These data suggest that insufficient lysosomal hydrolases and proteins may lead to abnormal lipid and cholesterol metabolism, which cause initiation and progression of atherosclerosis and CAD.

Apolipoprotein E-Deficient Lipoproteins Induce Foam Cell Formation by Activation of PERK-EIF-2α Signaling Cascade

Transformation of macrophages into foam cells by apolipoprotein (Apo) E-deficient, ApoB48-containing (E(-)/B48) lipoproteins has been shown to be associated with increased phosphorylation of eukaryotic initiation factor-2α (eIF-2α). The present report examined the causal relationship between eIF-2α phosphorylation and lipid accumulation in macrophages induced by E(-)/B48 lipoproteins. E(-)/B48 lipoproteins increased eIF-2α phosphorylation and cholesterol ester accumulation, while lipoprotein degradation decreased and lysosomal acid lipase and cathepsin B mRNA translation was inhibited in mouse peritoneal macrophages (MPMs). These responses were overcome by overexpression of a nonphosphorylatable eIF-2α mutant in MPMs. Incubation of MPMs with E(-)/B48 lipoproteins also increased the phosphorylation of RNA-dependent protein kinase-like endoplasmic reticulum kinase (PERK), but not other eIF-2α kinases. Overexpression of a nonphosphorylatable PERK mutant inhibited PERK and eIF-2α phosphorylation, and alleviated cholesterol ester accumulation induced by E(-)/B48 lipoproteins. PERK is an eIF-2α kinase activated by endoplasmic reticulum (ER) stress. Taken together, findings from this report suggest that induction of ER stress, i.e., activation of the PERK-eIF2α signaling cascade, is a mechanism by which E(-)/B48 lipoproteins down-regulate lysosomal hydrolase synthesis, inhibit lysosomal lipoprotein degradation, and increase intracellular lipoprotein and cholesterol ester accumulation, resulting in foam cell formation.

Proteomics of the lysosome

Defects in lysosomal function have been associated with numerous monogenic human diseases typically classified as lysosomal storage diseases. However, there is increasing evidence that lysosomal proteins are also involved in more widespread human diseases including cancer and Alzheimer disease. Thus, there is a continuing interest in understanding the cellular functions of the lysosome and an emerging approach to this is the identification of its constituent proteins by proteomic analyses. To date, the mammalian lysosome has been shown to contain approximately 60 soluble luminal proteins and approximately 25 transmembrane proteins. However, recent proteomic studies based upon affinity purification of soluble components or subcellular fractionation to obtain both soluble and membrane components suggest that there may be many more of both classes of protein resident within this organelle than previously appreciated. Discovery of such proteins has important implications for understanding the function and the dynamics of the lysosome but can also lead the way towards the discovery of the genetic basis for human diseases of hitherto unknown etiology. Here, we describe current approaches to lysosomal proteomics and data interpretation and review the new lysosomal proteins that have recently emerged from such studies.

2-Aminopurine inhibits lipid accumulation induced by apolipoprotein E-deficient lipoprotein in macrophages: potential role of eukaryotic initiation factor-2alpha phosphorylation in foam cell formation

We previously reported that apolipoprotein (Apo) E-deficient, ApoB48-containing (E(-)/B48) lipoproteins inhibited expression of lysosomal hydrolase and transformed mouse peritoneal macrophages (MPMs) into foam cells. The present study examined the effect of 2-aminopurine (2-AP), an inhibitor of eukaryotic initiation factor (eIF)-2alpha phosphorylation, on E(-)/B48 lipoprotein-induced changes in gene expression and foam cell formation. Our data demonstrated that E(-)/B48 lipoproteins enhanced phosphorylation of eIF-2alpha in macrophages. Incubation of MPMs with E(-)/B48 lipoproteins inhibited the translation efficiency of mRNAs encoding lysosomal acid lipase, cathepsin B, and cation-dependent mannose 6 phosphate receptor, with a parallel reduction in the level of these proteins. Addition of 2-AP to the culture media alleviated the suppressive effect of E(-)/B48 lipoproteins on lysosomal hydrolase mRNA translation, increased macrophage degradation of E(-)/B48 lipoproteins, and inhibited foam cell formation. Transfection of MPMs with a nonphosphorylatable eIF-2alpha mutant also attenuated the suppressive effect of E(-)/B48 lipoproteins on expression of lysosomal acid lipase, associated with a reduced accumulation of cellular cholesterol esters. This is the first demonstration that ApoE-deficient lipoproteins inhibit lysosomal hydrolase synthesis and transform macrophages into foam cells through induction of eIF-2alpha phosphorylation.

Atherosclerosis: a redox-sensitive lipid imbalance suppressible by cyclopentenone prostaglandins

Disorders concerning the metabolism of plasma and intracellular lipids are hallmarks of atherosclerosis. However, failures in proper control of intracellular cholesterol balance, rather than simple cholesterol overloading due to augmented uptake, could fuel atherogenesis. Therefore, the understanding of atherosclerosis-associated lipid alterations, which feed an inflammatory microenvironment in the arterial wall, requires the meticulous investigation of several aspects of lipid synthesis, uptake and export from cells. In this regard, the presence of reactive cysteines in transcription factors and key enzymes of lipid metabolism may dictate cholesterol accumulation, and therefore the progression of vascular disease. The strong inhibitory effect of cysteine-reactant anti-inflammatory cyclopentenone prostaglandins (CP-PGs) over atherosclerosis progression in vivo (LipoCardium technology) symbolizes a new concept of atherosclerosis and its treatment. Results from this laboratory and those from other research groups have unraveled a novel facet in prostaglandin research in that CP-PGs may act as redox signals that guide lipid metabolism in atherosclerosis. By modifying enzymes (e.g., HMG-CoA reductase, ACAT and cholesteryl ester hydrolases) and transcription factors (e.g., NF-kappaB and Keap1) involved in inflammation and lipid metabolism, CP-PGs (especially those of A-series) induce pivotal changes in glutathione and lipid metabolism that completely arrest atherosclerosis progression. Hence, pharmacological manipulation of lipid metabolism by CP-PGs may be a novel and invaluable strategy for treating atherosclerosis. Also, a better understanding of why CP-PGs do not resolve inflammation physiologically may explain many unsolved questions and yield insights into atherogenesis and its termination.