Triggering receptor expressed on myeloid cells 2 (TREM2) is a membrane receptor on myeloid cells and plays an important role in the body's immune defense. Recently, TREM2 has received extensive attention from researchers, and its activity has been found in Alzheimer's disease, neuroinflammation, and traumatic brain injury. The appearance of TREM2 is usually accompanied by changes in apolipoprotein E (ApoE), and there has been a lot of research into their structure, as well as the interaction mode and signal pathways involved in them. As two molecules with broad and important roles in the human body, understanding their correlation may provide therapeutic targets for certain diseases. In this article, we reviewed several diseases in which TREM2 and ApoE are synergistically involved in the development. We further discussed the positive or negative effects of the TREM2-ApoE pathway on nervous system immunity and inflammation.
Humans ; Alzheimer Disease/metabolism* ; Apolipoproteins E/genetics* ; Microglia/metabolism* ; Myeloid Cells/metabolism* ; Signal Transduction ; Neuroinflammatory Diseases

OBJECTIVETo clarify the differential expression of the genes related to the lipid metabolism in the early stage of atherosclerosis in the young LDLR-/- mice of different ages.

METHODSA RT-PCR assay was used to analyse the gene expression patterns in the livers of LDLR-/- mice and wild type (WT) mice from 14 to 90 days. The characteristics of early lipid deposition in intima were evaluated using biochemical and pathological techniques.

RESULTSIn LDLR-/- mice, when compared to WT mice, the mRNA level of the apolipoprotein A IV (apoA IV), fatty acid translocase (Fat/CD36) and carnitine palmitoyl transferase I (CPT I) changed prominently at the age of 14-days (P < 0.05). At 30 days, the mRNA level of apolipoprotein A I (apoA I) was up regulated, but apolipoprotein F (apoF), CD36 and CPT I were down regulated (P < 0.05). At 60 days, the mRNA levels of apoA I, CPT I and liver X receptor alpha (LXRalpha) were up regulated, but apoA IV was down regulated (P < 0.05). At 90 days, the level of the apoA I was higher, but the expression of the apoA IV, apoF and acyl-coenzymeA oxidase 1 (ACOX1) were down regulated (P < 0.05), whereas the expression of apolipoprotein A V (apoA V), apolipoprotein E (apoE), peroxidase proliferator-activated receptor alpha (PPARalpha) and angiopoietin-like protein 3 (angptl 3) had no significant changes (P > 0.05). The serum levels of TC (P < 0.05), TG (P < 0.05) and LDLC (P < 0.05) in LDLR-/- mice were significantly higher than those in wild type mice with the same age.

CONCLUSIONSThe mRNA levels of the apoA I, apoA IV, apoF, FAT/CD36, CPT I, ACOX1 and LXRalpha of the LDLR-/- mice were significantly changed compared to the WT mice. The genes may be of some relevance to the complicated lipid metabolism network, and have effect in the early stage of atherogenesis.

Animals ; Apolipoprotein A-I ; genetics ; metabolism ; Apolipoproteins A ; genetics ; metabolism ; Apolipoproteins E ; genetics ; metabolism ; Gene Expression ; Lipid Metabolism ; Liver ; metabolism ; Liver X Receptors ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Knockout ; Orphan Nuclear Receptors ; genetics ; metabolism ; RNA, Messenger ; metabolism ; Receptors, LDL ; deficiency

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease featuring progressive cognitive impairment. Although the etiology of late-onset AD remains unclear, the close association of AD with apolipoprotein E (APOE), a gene that mainly regulates lipid metabolism, has been firmly established and may shed light on the exploration of AD pathogenesis and therapy. However, various confounding factors interfere with the APOE-related AD risk, raising questions about our comprehension of the clinical findings concerning APOE. In this review, we summarize the most debated factors interacting with the APOE genotype and AD pathogenesis, depict the extent to which these factors relate to APOE-dependent AD risk, and discuss the possible underlying mechanisms.
Alzheimer Disease/pathology* ; Apolipoprotein E4/genetics* ; Apolipoproteins E/genetics* ; Genotype ; Humans ; Lipid Metabolism ; Neurodegenerative Diseases ; Risk Factors

OBJECTIVE: To study the role of apolipoprotein E (APOE) in regulating endometrial cancer metastasis and explore the signaling pathway in the regulatory mechanism. METHODS: Human endometrial cancer cell line HEC-1B was transfected with a control siRNA (siCtrl) or a specific siRNA targeting APOE (siAPOE) or with either pEGFP-N1 plasmid or an APOEoverexpressing plasmid. The changes in migration, proliferation, apoptosis and cell cycle of the transfected cells were examined using wound healing assay, Transwell migration assay, MTT assay, flow cytometry, and Hoechst staining. The activity of the ERK/MMP9 signaling pathway in the transfected cells was assessed using RT-qPCR and Western blotting. The expression level of APOE in clinical specimens of endometrial cancer tissues were detected using immunohistochemistry and its correlation with differentiation of endometrial cancer tissues was analyzed. RESULTS: Wound healing assay and Transwell migration assay showed that compared with those in siCtrl group, HEC-1B cells transfected with siAPOE showed significantly reduced migration ability (P < 0.05), whereas APOE overexpression significantly promoted the migration of the cells (P < 0.05). Neither APOE knockdown nor overexpression produced significant effects on HEC-1B cell proliferation as shown by MTT assay and flow cytometry. Hoechst staining revealed that transfection with siAPOE did not significantly affect apoptosis of HEC-1B cells. APOE knockdown obviously reduced and APOE overexpression enhanced ERK phosphorylation and MMP9 expression in HEC-1B cells (P < 0.05). Treatment with U0126 partially reversed the effects of APOE overexpression on ERK phosphorylation, migration and MMP9 expression in HEC-1B cells (P < 0.05). APOE is highly expressed in clinical samples of endometrial cancer tissues as compared with the adjacent tissues. CONCLUSION APOE is highly expressed in endometrial cancer tissues to promote cancer cell migration by enhancing ERK phosphorylation and MMP9 expression.
Female ; Humans ; Matrix Metalloproteinase 9/metabolism* ; Cell Line, Tumor ; Signal Transduction ; Endometrial Neoplasms/genetics* ; Cell Proliferation ; Apoptosis ; Cell Movement ; RNA, Small Interfering ; Apolipoproteins E ; Apolipoproteins/pharmacology*

The work was aimed to investigate the differential expressions of lipid metabolism related genes in the early stage of atherosclerosis in the young apolipoprotein E deficient (apoE(-/-)) mice at different ages with normal chow diet. The genotypes of mice were identified by using multiplex polymerase chain reaction (multi-PCR) analysis. The semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and real-time quantitative RT-PCR were used to analyze the expressions of lipid metabolism related genes in the liver of apoE(-/-) and age-matched wild type (WT) mice of 14-day old, 1-month old, 2-month old, 3-month old. The serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) contents were assayed using COD-PAP and GPO-PAP methods. The serum apolipoprotein B100 (apoB100) content was quantitated by immune turbidimetry. The hearts were perfusion-fixed in 4% formaldehyde, infiltrated with 30% gum sucrose for 24 h at 4 °C, and embedded in OCT compound. The aortic sinus tissues were serially sectioned at -15 °C, stained with Sudan IV, and counterstained with light green. The results were shown as follows. Compared with that in WT mice, the mRNA levels of apoA I and apoA IV in apoE(-/-) mice aged from 14-day old to 3-month old changed prominently (P<0.05), with apoA I up-regulated and apoA IV down-regulated. At the age of 1 month, the expression of apoB100 in apoE(-/-) mice was higher than that in WT mice (P<0.05). The expression of apoA V was up-regulated (P<0.05) and there was obvious lipid deposition in the aortic intima in apoE(-/-) mice at the age of 2 months. The expressions of fatty acid translocase (Fat/CD36) and angiopoietin-like protein 3 (Angptl 3) in apoE(-/-) mice were higher than those in WT mice at the age of 3 months (P<0.05), while the expressions of peroxisome proliferator-activated receptor α (PPARα), liver X receptor α (LXRα), carnitine palmitoyl transferase I (CPT I) and acyl coenzyme A oxidase 1 (ACOX1) showed no significant changes. The serum TC, TG, LDL-C and HDL-C contents in apoE(-/-) mice aged from 14-day old to 3-month old were higher than those in age-matched WT mice. apoE(-/-) mice showed a marked increase in serum apoB100 content, consistent with the trend of serum LDL-C content and apoB100 mRNA content in the liver. The results suggest that the mRNA expressions of apoA I, apoA IV, apoA V, apoB100 and Angptl 3 in apoE(-/-) mice change significantly compared with those in WT mice, and these genes might be relevant to the complicated lipid metabolism network, and involved in the early stage of atherogenesis.
Animals ; Apolipoprotein A-I ; metabolism ; Apolipoprotein B-100 ; blood ; Apolipoproteins A ; metabolism ; Apolipoproteins E ; genetics ; Atherosclerosis ; genetics ; Gene Expression ; Lipid Metabolism ; genetics ; Lipoproteins, HDL ; blood ; Lipoproteins, LDL ; blood ; Liver ; metabolism ; Mice ; Mice, Knockout ; Triglycerides ; blood

OBJECTIVETo investigate if inflammatory stress enhances liver lipid accumulation via SREBPs mediated dysregulation of low density protein receptor (LDLr) expression in apolipoprotein E, scavenger receptors class A and CD36 triple knockout (ApoE/SRA/CD36 KO) mice.

METHODS16 Male ApoE/SRA/CD36 KO mice were subcutaneously injected with 0.5 ml 10% casein or PBS. The mice were fed a Western diet (Harlan, TD88137) containing 21% fat and 0.15% of cholesterol for 14 weeks. Animals were sacrificed and blood samples were collected. The serum amyloid A (SAA), IL-6, total cholesterol (TC), LDL and high density protein (HDL) were assayed. The lipid accumulation in liver was evaluated by Oil Red O staining. The mRNA and protein expression of SREBP-2, SREBPs cleavage activating protein (SCAP) and LDLr were analyzed by Real-Time Polymerase Chain Reaction (RT-PCR) and immunohistochemistry staining.

RESULTSBlood levels of SAA [(26.60+/-3.24) ng/ml vs (14.35+/-1.73) ng/ml, P < 0.01] and IL-6 [(36.37+/-2.20) pg/ml vs (18.02+/-4.87) pg/ml, P < 0.01] were higher, while TC [(7.72+/-1.70) mmol/L vs (13.23+/-3.61)mmol/L, P less than 0.01], LDL-cholesterol [(2.94+/-0.44) mmol/L vs (9.28+/-3.66) mmol/L, P less than 0.01] and HDL cholesterol [(2.24+/-0.63) mmol/L vs (4.13+/-0.42) mmol/L, P less than 0.01] were lower in inflamed mice compared to controls. ORO staining showed that lipid accumulation in the liver was more extensive in inflamed group despite lower blood lipid levels. Meanwhile, Real Time PCR data showed inflammation induced the expression of LDLr (4.56 fold), SCAP (3.14 fold) and SREBP-2 (14.72 fold) in liver. Immunohistochemical staining also indicated increased proteins expression in the liver, which was consistent with mRNA data.

CONCLUSIONSInflammation causes lipid accumulation in liver via disrupting SREBP-2 and LDLr expression.

Animals ; Apolipoproteins E ; genetics ; Cholesterol, LDL ; metabolism ; Fatty Liver ; metabolism ; Inflammation ; metabolism ; Liver ; metabolism ; Male ; Mice ; Mice, Knockout ; Receptors, LDL ; metabolism ; Sterol Regulatory Element Binding Protein 2 ; metabolism

OBJECTIVETo explore if PPARgamma agonist rosiglitazone could enhance the anti-atherosclerotic effects of mouse peroxisome proliferator-activated receptor gamma1 (PPARgamma1) gene transfer in apolipoprotein-knock out mice.

METHODSAdult ApoE-knock out mice were fed a Western-diet for 20-weeks and then injected with PBS, Ad. PPARgamma1 (5 x 10(8)pfu) or Ad. GFP (5 x 10(8)pfu) via jugular vein. Another group of mice were intervened with rosiglitazone (dissolved in 0.5% cellulose acetate, 4 mg.kg(-1).d(-1), per gavage) 1 week before Ad. PPARgamma1 injection (n = 10, each group). Two weeks later, the lipid core and plaque composition were characterized with oil red O staining and Movat method respectively. The expression of PPARgamma, SM-actin, MOMA-2, MMP-9/TIMP-1, CD40/CD40L and TF antigens in aortic roots and plaques among four groups were compared semi-quantitatively using immunohistochemical technology.

RESULTSAll parameters were similar between AdGFP and PBS groups (P > 0.05). The area of plaque were significantly decreased and oil red O staining area significantly increased in AdPPARgamma1 [(0.86 +/- 0.12) mm(2), (150 +/- 35) x 10(3) microm(2)] and AdPPARgamma1 + RO [(0.79 +/- 0.15) mm(2), (270 +/- 49) x 10(3) microm(2)] treated mice compared with AdGFP group [(0.98 +/- 0.17) mm(2), (80 +/- 21) x 10(3) microm(2)] all P < 0.05. Elastic fiber, collagen and proteoglycan in plaques were also significantly increased in AdPPARgamma1 and AdPPARgamma1 + RO groups. Upregulation of PPARgamma, SM-actin, TIMP-1 antigen activity and downregulation of MOMA-2, MMP-9, CD40/CD40L and TF antigen activity in AdPPARgamma1 and most significantly in AdPPARgamma1 + RO group were observed (P < 0.05).

CONCLUSIONAnti-atherosclerotic effects of PPARgamma1 gene transfer in ApoE-knock out mice could be enhanced by PPARgamma agonist rosiglitazone.

Animals ; Apolipoproteins E ; deficiency ; genetics ; Atherosclerosis ; genetics ; Gene Transfer Techniques ; Male ; Mice ; Mice, Knockout ; PPAR gamma ; agonists ; genetics ; metabolism ; Peroxisome Proliferator-Activated Receptors ; metabolism ; Thiazolidinediones ; pharmacology ; Transfection

OBJECTIVES: Plasma lipid profiles and Apolipoprotein E (ApoE) are established risk factors for cardiovascular disease (CVD). The knowledge of lipid profile may estimate the potential victims of cardiovascular disease before its initiation and progression and offers the opportunity for primary prevention. The most common ApoE polymorphism has been found to influence plasma lipid concentrations and its correlation with CVD has been extensively investigated in the last decade. METHODS: The ApoE polymorphism and its influence on plasma lipid were investigated in healthy woman workers. The information on confounding factors was obtained through a self-administered questionnaire and ApoE polymorphism was investigated using PCR. RESULTS: The relative frequencies of alleles E2, E3 and E4 for the study population (n=305) were 0.127, 0.750 and 0.121, respectively. ApoE polymorphism was associated with variations in plasma HDL-cholesterol lipid profile. In order to estimate the independent effects of alleles E2 and E4, as compared with E3, on lipid profile, multiple regression was performed after adjustment for confounding variables such as age, BMI, blood pressure, education status, insulin, fasting glucose, HOMA-IR, menopause. ApoE2 had a negative association with HDL cholesterol and ApoE4 had a positive association with LDL cholesterol. CONCLUSIONS: This study identified that the ApoE and CVD risk factors contribute to the lipid profiles, similar to other studies. The analysis including dietary intake and other gene in further studies may help to identify clear effects on lipid profiles as risk factor for CVD.
Adult ; Apolipoproteins E/blood/*genetics/metabolism ; Cardiovascular Diseases/epidemiology/prevention & control ; Cholesterol, HDL/genetics ; Female ; *Genotype ; Humans ; Lipid Metabolism/*genetics ; Polymerase Chain Reaction ; Primary Prevention

The lifelong exposure of antigens and stressors results in chronic oxidative stress situation in the organism. The free radicals and reactive oxygen species (ROS) with high reactivity produced by our cells under oxidative stress will cause oxidative damage in biomolecules. The oxidative damage leads to the releases of both damage-associated-molecular patterns (DAMPs) and intracellular cytokines. DAMPs activate pathogen recognition receptors (PRRs) and non-PRRs. Intracellular cytokines activate signalling pathways downstream of PRRs. Activation of these receptors results in the upregulation of cytokines and chemokines, which are released to recruit and activate additional inflammatory cells and cause the systemic and chronic sterile inflammation. The regulatory system, especially immune systems play an important role in homeostasis maintenance in the organism. The cells of immune systems are very vulnerable to oxidative damage. Once the homeostasis is destroyed, an imbalance between inflammatory and anti-inflammatory networks will occur. Genetic factor also is an important factor of oxi-inflamm-aging and age-related diseases. Many genes are involved in oxidative stress, inflammation process, and the genomic variations within most of these genes might produce different effects on oxi-inflamm-aging. The polymorphism of ApoE genes can affect the antioxidant and immunomodulatory/anti-inflammatory properties of the organism. ApoE genotype-phenotype is associated with the progress and prognosis of oxi-inflamm-aging, age-related diseases as well. Anti-inflammation together with regulation of the expression of ApoE might be an efficient method against oxi-inflamm-aging. Based on our previous studies, the progresses in these areas are reviewed.
Aging ; Animals ; Antioxidants ; metabolism ; Apolipoproteins E ; genetics ; Cytokines ; metabolism ; Homeostasis ; Humans ; Inflammation ; genetics ; Oxidative Stress ; Reactive Oxygen Species ; metabolism ; Signal Transduction

Inflammation has been shown to play an important role in the progression of Alzheimer's disease (AD). Recent epidemical study indicates that the incidence of AD in some populations is substantially influenced by the gene polymorphisms of the inflammation mediators. Meanwhile, an ensured risk factor, the ApoE epsilon4 allele is also reported to directly promote inflammation. Accordingly, it appears that an individual genetic background has partly determined his predisposition for AD by the extent of the inflammation response to the chronic stimulus by beta-amyloid peptide (Abeta) deposits and other antigen stressor in the elderly. Hence we present a hypothesis that the inflammation genotypes may contribute to AD susceptibility. This may provide a new orientation both for future identification of individuals at risk and for personalized medication.
Alzheimer Disease ; complications ; genetics ; Apolipoproteins E ; genetics ; Cytokines ; genetics ; metabolism ; Genetic Predisposition to Disease ; Humans ; Immunity, Innate ; Inflammation ; etiology ; genetics ; Risk Factors