Expression Of Lipoprotein Receptor-related Protein Research Articles

Abstract 1374: Targeting CD47/SIRPɑ axis in urologic cancer triggers enhanced phagocytosis of tumor cell and induces tumor growth inhibition

Abstract Signal regulatory protein-α (SIRPα; CD172a or SHPS-1) is a transmembrane molecule that highly expressed on myeloid population. Binding of CD47 (integrin-associated protein, IAP) to SIRPα inhibits phagocytosis in macrophages, which acts as a mechanism of maintaining homeostasis. Tumor cells however, often time upregulate CD47 to evade immune response. Using publicly available dataset, we found that human prostate cancer cells upregulate expression of both CD47 and calreticulin, a “eat me” signal when engaged with Low density lipoprotein receptor-related protein 1 (LRP1). In addition, macrophages, monocytes and dendritic cells in human prostate cancer do have relatively high level of SIRPɑ and LRP1 expression. This finding provides the rationale of targeting CD47/SIRPɑ axis in prostate cancer to shift the balance between pro-phagocytosis and anti-phagocytosis signaling. We then moved to RM1 and B6Cap, two syngeneic prostate cancer models in immunocompetent mice. Significant tumor growth inhibition was seen in both models with anti SIRPɑ blocking antibody. Furthermore, we observed in vitro that CD47 or SIRPɑ blockage led to enhanced PC3 cell line phagocytosis by human monocyte derived macrophages (HMDMs). Same finding was found using mouse bone marrow derived macrophages (BMDMs). We then utilized ovalbumin expressing MB49 bladder cancer cell line and cocultured those with BMDMs. CD8+ T cell from OT1 mice exhibited higher expression of activation makers when cocultured BMDMs treated by either anti CD47 or SIRPɑ antibody, indicating that enhanced phagocytosis subsequently increases antigen cross presentation in macrophages. In summary, we identified that CD47 is overexpressed in human prostate cancer; blocking CD47/SIRPɑ did inhibit tumor growth through enhanced phagocytosis and antigen presentation. Citation Format: Fan Shen, Monali Praharaj, Alex J. Lee, Thomas R. Nirschl, Xiaoxu Wang. Targeting CD47/SIRPɑ axis in urologic cancer triggers enhanced phagocytosis of tumor cell and induces tumor growth inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1374.

Abstract 13109: Epigenetic Regulation and Function of Pleiotropic GWAS Locus LRP1 in Human Induced Pluripotent Stem Cells Derived Contractile Smooth Muscle Cells

Introduction: Spontaneous coronary artery dissection (SCAD) is an increasingly recognized cause of myocardial infarction in young and middle-aged women. A common genetic variant, rs11172113, located in LRP1 (low density lipoprotein receptor-related protein 1) first intron, was associated with several vascular diseases, including SCAD, and regulation of LRP1 expression in arterial tissues. However, the biological mechanisms through which rs11172113 influence LRP1 function in the context of non-atherosclerotic arterial lesions are not known. Hypothesis: We hypothesized that rs11172113 genotype affects LRP1 expression through specific mechanisms in contractile smooth muscle cells (SMCs), leading to alterations of their physiological function. Methods: We differentiated 4 human induced pluripotent stem cells (iPSCs) lines (2 males, 2 females) towards either contractile or synthetic SMCs using a recently optimized 24-day protocol. We performed RNA-Seq and ATAC-Seq at 6 time points during differentiation. We silenced LRP1 using siRNAs in differentiated SMCs and used CRISPR-Cas9 to induce deletions of the enhancer region containing rs11172113 or frame-shift indels in exons 2 or 5 of LRP1 in iPSCs. Results: iPSCs derived SMCs presented the expected morphology and expression of SMC markers. Transcriptomic analyses showed that contractile SMCs harbored SMC properties during late differentiation and resembled SMCs of artery tissue, whereas genes involved in cell stress were upregulated in synthetic SMCs at the end of differentiation. In particular, LRP1 expression and DNA accessibility at rs11172113 were higher in contractile SMCs. The deletion of rs11172113 enhancer region led to a decrease in the expression of LRP1 in both contractile and synthetic SMCs. LRP1 inactivation decreased the proliferation and increased the migration capacity of contractile SMCs. Detailed characterization of the influence of LRP1 on extracellular matrix maintenance and cellular contraction is ongoing. Conclusions: We confirmed rs11172113 to regulate LRP1 expression in iPSCs derived contractile SMCs. Our results support LRP1 influence on SMCs phenotype as a causal factor in the genetic susceptibility to SCAD and related vascular diseases.

Mutation of LRP1 in cardiac neural crest cells causes congenital heart defects by perturbing outflow lengthening

The recent recovery of mutations in vesicular trafficking genes causing congenital heart disease (CHD) revealed an unexpected role for the endocytic pathway. We now show that mice with a C4232R missense mutation in Low density lipoprotein receptor related protein 1 (LRP1) exhibit atrioventricular septal defects with double outlet right ventricle. Lrp1m/m mice exhibit shortened outflow tracts (OFT) and dysmorphic hypocellular cushions with reduced proliferation and increased apoptosis. Lrp1m/m embryonic fibroblasts show decreased cell motility and focal adhesion turnover associated with retention of mutant LRP1 in endoplasmic reticulum and reduced LRP1 expression. Conditional deletion of Lrp1 in cardiac neural crest cells (CNC) replicates the full CHD phenotype. Cushion explants showed defective cell migration, with gene expression analysis indicating perturbation of Wnt and other signaling pathways. Thus, LRP1 function in CNCs is required for normal OFT development with other cell lineages along the CNC migratory path playing a supporting role.

The low density receptor-related protein 1 plays a significant role in ricin-mediated intoxication of lung cells

Ricin, a highly lethal plant-derived toxin, is a potential biological threat agent due to its high availability, ease of production and the lack of approved medical countermeasures for post-exposure treatment. To date, no specific ricin receptors were identified. Here we show for the first time, that the low density lipoprotein receptor-related protein-1 (LRP1) is a major target molecule for binding of ricin. Pretreating HEK293 acetylcholinesterase-producer cells with either anti-LRP1 antibodies or with Receptor-Associated Protein (a natural LRP1 antagonist), or using siRNA to knock-down LRP1 expression resulted in a marked reduction in their sensitivity towards ricin. Binding assays further demonstrated that ricin bound exclusively to the cluster II binding domain of LRP1, via the ricin B subunit. Ricin binding to the cluster II binding domain of LRP1 was significantly reduced by an anti-ricin monoclonal antibody, which confers high-level protection to ricin pulmonary-exposed mice. Finally, we tested the contribution of LRP1 receptor to ricin intoxication of lung cells derived from mice. Treating these cells with anti-LRP1 antibody prior to ricin exposure, prevented their intoxication. Taken together, our findings clearly demonstrate that the LRP1 receptor plays an important role in ricin-induced pulmonary intoxications.

Effect of Zhenxin Xingshui Yizhi Fang on Aβ25-35 induced expression of related transporters in HBMEC cell model

Ethnopharmacological relevanceAβ (β-amyloid) deposition and abnormal transport were suggested to be risk factors for Alzheimer's disease (AD). Zhenxin Xingshui Yizhi Fang (XSF), an ancient prescription in traditional Chinese medicine, was first recorded in Qianjin Yifang for treating palpitation, hypnosia, amnesia. It is reported that XSF could improve mice learning memory ability, reduce the deposition of senile plaques in hippocampus of rat brain. In this study, the neuroprotective effect of XSF against Aβ25-35-induced apoptosis in cultured human brain microvascular endothelial cells (HBMEC) and its potential mechanism were investigated. Materials and methodsHBMEC cells were treated with Aβ25-35 to established neurotoxic cell model. After that, the cells were treated with 125, 250, 500 μg/mL XSF to observe the protective effect. The viability of HBMEC cells were evaluated by MTT assay, the Aβ25-35-induced apoptosis was characterized by Hoechst-33258 and the activity of cysteinyl aspartate specific proteinase-3. The expression level of Aβ1-42 in cells induced by Aβ25-35 was measured by human Aβ1-42 kit. Protein and mRNA expression levels of advanced glycation end products (RAGE), low density lipoprotein receptor-related protein 1 (LRP1), glucose transporter 1 and 3 (GLUT1 and GLUT3) were assayed by capillary electrophoresis immunoassay and quantitative real-time polymerase chain reaction analyses. ResultsIn Aβ25-35 induced neurotoxic cells, the percentage of apoptotic cells, the concentration of Aβ1-42 and CASPASE-3 activity, protein and mRNA expression levels of RAGE increased significantly, but that of LRP1, GLUT1 and GLUT3 significantly decreased. XSF could inhibit the apoptotic of cells, reduced the concentration of Aβ1-42 and CASPASE-3 expression, downregulate RAGE and upregulate LRP1, GLUT1 and GLUT3 expression. ConclusionThe results suggest that XSF can reduce the cytotoxicity of HBMEC induced by Aβ25-35, inhibit apoptosis, and regulate the transport of Aβ on BBB and energy metabolism disorder in HBMEC.

Omega-3 polyunsaturated fatty acids promote brain-to-blood clearance of β-Amyloid in a mouse model with Alzheimer’s disease

Amyloid-β (Aβ) plaques is one of the typical pathological hallmark of Alzheimer disease (AD). Accumulating evidence suggests that the imbalance between Aβ production and clearance leads to extracellular Aβ accumulation in the brain. It is reported that the blood–brain barrier (BBB) transport plays a predominant role in Aβ clearance from brain to blood. In the present study, we investigated dynamic alterations of BBB transport function in the early disease stage of AD using APPswe/PS1dE9 C57BL/6J (APP/PS1) transgenic mice. Our results showed that the expression of lipoprotein receptor-related protein 1 (LRP-1), a main efflux transporter of BBB, started to decrease at the age of 4 months old. Interestingly, supplementing with fish oil which is rich in omega-3 polyunsaturated fatty acids (PUFAs) significantly enhanced the expression level of LRP-1 and promoted Aβ clearance from the bran to circulation, as revealed by reduced soluble/insoluble Aβ levels and senile plaques in the brain parenchyma and a corresponding increase of Aβ levels in plasma. Besides, fish oil supplement significantly inhibited the NF-κB activation, reduced the expression of interleukin-1β and tumor necrosis factor-α, and suppressed the glial activation in APP/PS1 mice. The results of the study provide evidence that BBB transport function could be impaired at a very early disease stage, which might contribute to Aβ pathological accumulation in AD, and omega-3 PUFAs intervention could be an effective strategy for the prevention of the progression of AD through promoting Aβ clearance from brain-to-blood.

LRP1-upregulated nanoparticles for efficiently conquering the blood-brain barrier and targetedly suppressing multifocal and infiltrative brain metastases

Brain metastases present mostly multifocal, infiltrative and co-opting growth with the blood-brain barrier (BBB) remaining intact. The BBB, as the barrier of drug delivery to such lesions, is the major cause of the failure of systemic drug therapy and needs to be conquered. Angiopep-2 ligates the low density lipoprotein receptor related protein 1 (LRP1) on brain microvascular endothelial cells (BMECs) to drive transcytosis for BBB crossing. However, besides tight junction, low transcytosis is increasingly deemed to be a crucial factor in restricting BBB permeability. Herein, it is reported that statins-loaded Angiopep-2-anchored nanoparticles (S@A-NPs) can raise LRP1 expression to surmount the low transcytosis of BBB. We demonstrate that S@A-NPs can selectively heighten LRP1 expression on both BMECs and brain metastatic tumor cells, efficiently and self-promotingly penetrate through the BBB and target brain metastases through Angiopep-2 mediated endocytosis and statins induced LRP1 up-regulation. The systemic administration of S@A-NPs loaded with doxorubicin (S@A-NPs/DOX) observably lengthens median survival of mice bearing brain metastases. Due to the efficient BBB passing and brain metastasis targeting, S@A-NPs/DOX may serve as a potential approach for clinical management of brain metastases.

LRP1 promotes synthetic phenotype of pulmonary artery smooth muscle cells in pulmonary hypertension

Pulmonary hypertension (PH) is characterized by a thickening of the distal pulmonary arteries caused by medial hypertrophy, intimal proliferation and vascular fibrosis. Low density lipoprotein receptor-related protein 1 (LRP1) maintains vascular homeostasis by mediating endocytosis of numerous ligands and by initiating and regulating signaling pathways.Here, we demonstrate the increased levels of LRP1 protein in the lungs of idiopathic pulmonary arterial hypertension (IPAH) patients, hypoxia-exposed mice, and monocrotaline-treated rats. Platelet-derived growth factor (PDGF)-BB upregulated LRP1 expression in pulmonary artery smooth muscle cells (PASMC). This effect was reversed by the PDGF-BB neutralizing antibody or the PDGF receptor antagonist. Depletion of LRP1 decreased proliferation of donor and IPAH PASMC in a β1-integrin-dependent manner. Furthermore, LRP1 silencing attenuated the expression of fibronectin and collagen I and increased the levels of α-smooth muscle actin and myocardin in donor, but not in IPAH, PASMC. In addition, smooth muscle cell (SMC)-specific LRP1 knockout augmented α-SMA expression in pulmonary vessels and reduced SMC proliferation in 3D ex vivo murine lung tissue cultures.In conclusion, our results indicate that LRP1 promotes the dedifferentiation of PASMC from a contractile to a synthetic phenotype thus suggesting its contribution to vascular remodeling in PH.

Over-expression of low-density lipoprotein receptor-related Protein-1 is associated with poor prognosis and invasion in pancreatic ductal adenocarcinoma

BackgroundLow-density lipoprotein receptor-Related Protein-1 (LRP-1) has been reported to involve in tumor development. However, its role in pancreatic cancer has not been elucidated. The present study was designed to evaluate the expression of LRP-1 in Pancreatic Ductal Adenocarcinoma Cancer (PDAC) as well as its association with prognosis. MethodsHere, 478 pancreatic cancers were screened for suitable primary PDAC tumors. The samples were analyzed using qRT-PCR, western blotting, and Immunohistochemistry (IHC) staining as well as LRP-1 expression in association with clinicopathological features. ResultsThe relative LRP-1 mRNA expression was up-regulated in 82.3% (42/51) of the PDAC tumors and its expression (3.72 ± 1.25) was significantly higher than that in pancreatic normal margins (1.0 ± 0.23, P < 0.05). This up-regulation was stage dependent (P < 0.05). A similar pattern of LRP-1 protein expression was discovered (P < 0.05). The high expression of LRP-1 in the PDAC tissues was strongly correlated with the low survival time (P = 0.001), TNM classification (P = 0.001), low differentiations status (P = 0.001), lymphatic invasion (P = 0.01) and Perineural Invasion (PNI) status (P = 0.001). ConclusionsOur finding for the first time revealed that LRP-1 expression inversely associated with poor prognosis and PNI in PDAC tumor.

Overexpression of low density lipoprotein receptor-related protein 1 (LRP1) is associated with worsened prognosis and decreased cancer immunity in clear-cell renal cell carcinoma

AimClear-cell renal cell carcinoma (ccRCC) is characterized with underlying genetic disorders and the role of low density lipoprotein receptor-related protein 1 (LRP1) in ccRCC is unknown. MethodAn in silico exploratory analysis using multiple public genetic datasets was used to establish association between LRP1 expression and clinicopathological parameters. Associations of interest were validated using 155 ccRCC samples using immunohistochemistry. ResultsLRP1 was overexpressed in tumor compared with normal kidney tissue. Increased LRP1 expression in ccRCC was associated with advanced stage, grade and worsened overall survival and progression-free survival. Functional annotation indicated an immune-modulatory role of LRP1 in ccRCC. LRP1 expression was significantly correlated with expressions of PBRM1, SETD2, and KDM5C. Positive correlations between LRP1 and pro-angiogenic factors ERAP1, SCG2, STAB1, and RUNX1 were observed. LRP1 expression was positively correlated with PD-L2 level. Negative correlations between LRP1 and anti-angiogenic factors EMCN and IL18 were observed. LRP1 expression was not associated with microvessel density (MVD) yet was negatively correlated with tumor-infiltrating lymphocytes (TIL). ConclusionLRP1 is associated with worsened prognosis in ccRCC and is related to cancer immune modulation. LRP1-targeted therapy can be of therapeutic potential.

Long-term electroacupuncture stimulation prevents osteoporosis in ovariectomised osteopaenic rats through multiple signalling pathways.

The pathogenic mechanisms of postmenopausal osteoporosis (PMOP) development are complex and are related to multiple cellular signalling transduction pathways. The aim of this study was to compare the effects of electroacupuncture (EA) at GV4/GV6 versus BL20/BL23 on the bones in ovariectomised (OVX) rats to explore the pathways that mediate the effects of EA on bone. Forty female Sprague-Dawley rats were allocated to one of four groups (n=10 rats each) that received sham surgery (Sham group), OVX surgery only (OVX group), OVX surgery plus EA at GV4/GV6 (GV group) and OVX surgery plus EA at BL20/BL23 (BL group). Bone turnover markers osteocalcin (OC) and tartrate-resistant acid phosphatase 5b (TRACP 5b) were measured in serum, and bone mineral density (BMD) of the lumbar vertebrae and histomorphology of the femur were evaluated. Moreover, the expression of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) was detected by ELISA. The expression of lipoprotein receptor-related protein (LRP) 5, β-catenin, runt-related transcription factor (Runx) 2 involving Wnt/β-catenin signalling and p38, c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinases 1/2 involving mitogen-activated protein kinase signalling were determined by Western blotting. The two EA-treated groups demonstrated increased levels of OC and the BMD of lumbar vertebrae, decreased levels of TRACP 5b and improved bone microstructure in the femur, compared with the untreated OVX group (P<0.05). Histomorphology analysis showed that EA treatment significantly increased the values of the trabeculae (µm), trabecular area (%) and trabecular bone number (per mm) and reduced trabecular separation (mm), compared with the OVX group. In addition, the ratio of OPG to RANKL and LRP5, β-catenin and Runx2 expression were significantly upregulated, while the expression of phosphorylated (p)-p38 and p-JNK were downregulated in EA-treated groups compared with the OVX group. EA attenuates PMOP and it appears that the mechanism involves the regulation of multiple targets and pathways.

Suppression of Alzheimer's disease-related phenotypes by the heat shock protein 70 inducer, geranylgeranylacetone, in APP/PS1 transgenic mice via the ERK/p38 MAPK signaling pathway.

HSP70 overexpression has a remedying effect in neurodegenerative diseases. In Alzheimer's disease (AD), the suppressive effects of HSP70 overexpression on AD-related phenotypes and the underlying mechanisms are unknown. In the current study, the effect of geranylgeranylacetone (GGA), a non-toxic inducer of heat shock protein (HSP)-70 expression, on cognitive function and other pathological phenotypes were evaluated in APP/PS1 mice. It was observed that all doses of orally administered GGA (200, 400, and 800 mg/kg/day) improved cognitive deficit (P<0.05) and lowered the levels of amyloid-β (Aβ) peptide (P<0.05) in APP/PS1 mice. GGA treatment also increased the levels of low density lipoprotein receptor-related protein 1 (LRP-1) (P<0.05), while the levels of p-glycoprotein and receptor for advanced glycation end products were unaltered. Significant decreases in the levels of inflammatory cytokines, namely tumor necrosis factor-α, interleukin-1β and cyclooxygenase-2, were also observed in the GGA-treated mice (P<0.05). Subsequent treatment with the HSP70 inhibitor quercetin caused significant decreases in the levels of phosphorylated (p)-p38 mitogen-activated protein kinase (p38 MAPK) and p-extracellular signal-regulated protein kinases (ERK; P<0.05), indicating that ERK/p38 MAPK signaling in AD-related phenotypes may be suppressed by oral administration of GGA. Finally, in APP/PS1 mice treated with GGA+SB-203580 (p38 inhibitor) and GGA+PD98059 (ERK inhibitor), it was observed that orally administered GGA led to the activation of ERK/p38 MAPK signaling (P<0.05) and increased LRP-1 expression (P<0.05), which subsequently aided the clearance of Aβ40 and Aβ42 (P<0.05) and alleviated AD-related phenotypes. These results indicate that oral administration of GGA in APP/PS1 mice alleviates AD-related phenotypes by regulation of the ERK/p38 MAPK signaling pathway. Thus, GGA may be a potential therapeutic for the treatment of AD.

Interleukin-1β Regulates PCSK9 and LDL Receptor Expression together with de novo Cholesterol Synthesis in HepG2 Cells

Background and Aim : Chronic inflammation is associated with changes in lipid and cholesterol metabolism in the liver. A predominant finding is changes in surface LDL receptor (LDLR) expression at various stages of disease which may be associated with serum increases in LDL and therefore increased risk of developing atherosclerosis. At the same time, increased cholesterol accumulation has also been observed and linked to development of fatty liver. Methods : Here, we use the hepatoma cell line HepG2 as a model of highly active chronic inflammation and report on cytokine mediated changes in expression of proprotein convertase subtilisin/kexin type 9 (PCSK9), LDLR and low density lipoprotein receptor-related protein 1 (LRP-1) as well as expression of rate limiting enzymes in the cholesterol synthesis. Results : Overall, we observed a predominant role of Interleukin-1b (IL-1b) in reduction of PCSK9 accompanied by increased LDLR expression, whereas LRP-1 expression was not influenced. Key enzymes in cholesterol biosynthesis were all downregulated by IL-1b. Conclusion : In conclusion, we identify IL-1b as a key regulator of cholesterol metabolism.

Low Density Lipoprotein-Receptor Related Protein 1 Is Differentially Expressed by Neuronal and Glial Populations in the Developing and Mature Mouse Central Nervous System.

The low density lipoprotein-receptor related protein 1 (LRP1) is a large endocytic cell surface receptor that is known to interact with a variety of ligands, intracellular adaptor proteins and other cell surface receptors to regulate cellular behaviours ranging from proliferation to cell fate specification, migration, axon guidance, and lipid metabolism. A number of studies have demonstrated that LRP1 is expressed in the brain, yet it is unclear which central nervous system cell types express LRP1 during development and in adulthood. Herein we undertake a detailed study of LRP1 expression within the mouse brain and spinal cord, examining a number of developmental stages ranging from embryonic day 13.5 to postnatal day 60. We report that LRP1 expression in the brain peaks during postnatal development. On a cellular level, LRP1 is expressed by radial glia, neuroblasts, microglia, oligodendrocyte progenitor cells (OPCs), astrocytes and neurons, with the exception of parvalbumin+ interneurons in the cortex. Most cell populations exhibit stable expression of LRP1 throughout development; however, the proportion of OPCs that express LRP1 increases significantly from ~69% at E15.5 to ~99% in adulthood. We also report that LRP1 expression is rapidly lost as OPCs differentiate, and is absent from all oligodendrocytes, including newborn oligodendrocytes. While LRP1 function has been primarily examined in mature neurons, these expression data suggest it plays a more critical role in glial cell regulation–where expression levels are much higher.

The effect and mechanism of microRNA-21 on cis-dichlorodiamineplatinum resistance in lung cancer cell strain

To investigate the role of miR-21 on multidrug resistance (MDR) in non-small cell lung cancer(NSCLC)and to provide experimental and theoretical basis for MDR reversal. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) was used to determine the mRNA level of miR-21 both in the chemo-sensitivity cell strain A549 and the chemo-resistance cell strain A549/DDP (primary A549/DDP cells). The miR-21 interference sequence was synthesized and transfected into A549/DDP cells by liposome as the carrier. The miR-21 expression level was knocked down and the change of chemo-sensitivity of cells was detected. Effects of miR-21 on the cell apoptosis and cell cycle in miR-21-depleted A549/DDP cells were analyzed by flow cytometry to elucidate the involvement of miR-21 in MDR reversal in NSCLC. The expression of multidrug-resistant proteins Survivin, Cyclin D1, Epidermal growth factor receptor (EGFR), Multidrug resistance-associated protein1 (MRP1) and Lipoprotein receptor-related protein (LRP) were detected by Western blot. MiR-21 level in multidrug-resistant NSCLC cell line A549/DDP was (5.223±0.316) folds higher than that in A549 cell line (t=48.318, P<0.01). Knockdown of miR-21 in A549/DDP cells significantly reversed their sensitivity to cis-DDP, meanwhile, the value of half maximal inhibitory concentration was significantly decreased compared with control group transfected with empty vector ((22.2±1.2) and (48.6±3.2) μmol/L, t=5.608, P<0.01). Cell apoptosis rate in A549/DDP cell with knockdown of miR-21 was significantly increased compared with primary A549/DDP cell line ((27.7±1.1) % and (16.8±1.1) %, t=10.183, P<0.01). Cell cycle G0/G1 phase in A549/DDP cell with knockdown of miR-21 was significantly decreased compared with primary A549/DDP cell line ((37.5±1.2) % and (43.4±2.3) %, t=8.202, P<0.01). Compared with primary A549/DDP cell line, the expression of Survivin, Cyclin D1, EGFR, MRP1 and LRP in A549/DDP cell with knockdown of miR-21 were significantly decreased ((71.7±4.3)%, t=8.325, P<0.01; (69.4±4.5)%, t=5.162, P<0.01; (52.3±3.2)%, t=8.042, P<0.01; (60.6±4.2)%, t=6.641, P<0.01; (72.9±3.8)%, t=4.566, P<0.01, respectively). miR-21 silencing reverses the multidrug resistance in lung cancer cell via accelerating cell apoptosis and modulating multidrug resistance-related gene expression. miR-21 may be a potential therapeutic candidate in multidrug resistance patients with lung cancer.

Methotrexate and its therapeutic antagonists caffeine and theophylline, target a motogenic T-cell mechanism driven by thrombospondin-1 (TSP-1).

Methotrexate (MTX) is a widely used treatment for inflammatory diseases such as rheumatoid arthritis and psoriasis, based on the concept that it is immunosuppressive. Its mechanism of action, however, remains unclear, although it is thought to depend on adenosine. Caffeine and theophylline, which have several targets including adenosine receptors, have been shown to suppress the beneficial clinical effects of MTX. Here we show that MTX and caffeine and theophylline differentially affect a motogenic T-cell mechanism driven by endogenous thrombospondin-1 (TSP-1) and its receptor, low density lipoprotein receptor-related protein 1 (LRP1). MTX stimulated TSP-1 expression and the motogenic TSP-1/TSP-1 receptor mechanism in primary human T cells, hence mimicking IL-2 and CXCL12, which similar to MTX, dampen inflammatory disease. SiRNA-mediated gene silencing of TSP-1 and LRP1 inhibited this stimulatory effect. Caffeine and theophylline inhibited the TSP-1/TSP-1 receptor mechanism by inhibiting LRP1 expression. These results indicate that the effect of MTX on T cells is immunoregulatory rather than immunosuppressive, and suggest a pathway dependent on TSP-1/TSP-1 receptor interactions for the regulation of immune responses.

The lipid-lowering effect and possible mechanism of apobec-1 in nephrotic syndrome rabbits

Objective To observe the effect of liver acquired expression of apobec-1 on blood lipid metabolism, hepatic low density lipoprotein receptor (LDLR), and hepatic low density lipoprotein receptor related protein (LRP) in nephrotic syndrome(NS) rabbits and to explore the lipid-lowering effect and possible mechanism. Methods Thirty healthy ordinary level male new Zealand rabbits were randomly divided into 3 groups: sham operation group(n=10), NS group(n=10), and apobec-1 treatment group(n=10). Adaptive feeding was given for 1 week, then NS group and apobec-1 treatment group underwent left nephrectomy, and 1 week later, adriamycin (4 mg/kg) was used to construct the NS model by way of ear vein injection.In the 11th week after operation, apobec-1 recombinant adenovirus (1×1013 virus/kg) was injected through ear vein in apobec-1 treatment group.The 12th week after operation, all rabbits were sacrificed.Right kidney, liver, blood and 24 hour urine were collected.In 3 groups, 24 hour urinary protein(24UPr), albumin (Alb), blood urea nitrogen (BUN), creatinine (Cr), blood lipid were detected.Renal pathology was observed by means of HE staining.Expressions of liver LDLR, LRP were observed by using Western blot. Results (1) There were significant differences among the 3 groups in 24UPr(F=42.778, P=0.000), Alb(F=3.819, P=0.034), BUN (F=6.562, P=0.005), Cr (F=16.076, P=0.000), total cholesterol (TC) (F=17.531, P=0.000), total triglyceride (TG) (F=6.192, P=0.006), very low density lipoprotein (VLDL-C) (F=6.192, P=0.006), low density lipoprotein (LDL-C) (F=34.924, P=0.000) and apolipoprotein B100 (ApoB100) (F=5.180, P=0.012) and apolipoprotein B48 (ApoB48) (F=6.161, P=0.006). (2) Compared with the sham operation group, NS group showed that 24UPr, BUN, Cr, TC, TG, VLDL-C, LDL-C, ApoB100 increased, but Alb decreased, and there was statistical significance (all P<0.05). (3) Compared with NS group, apobec-1 treatment group showed that TC, TG, VLDL-C, LDL-C, ApoB100, ApoB48 decreased, and there were statistical significances(all P<0.05). (4) Compared with the sham operation group, apobec-1 treatment group showed that 24UPr, BUN, Cr increased, but Alb, apolipoprotein B48 (ApoB48) decreased, there were statistical significances(all P<0.05). (5)There were significant differences of hepatic protein expression among the 3 groups in LRP(F=44.180, P=0.000), LDLR(F=63.141, P=0.000). Compared with the sham operation group and NS group, apobec-1 treatment group showed that the expression of LRP was up-regulated (P<0.01, 0.05), while the expression of LDLR was down-regulated (all P<0.05). Conclusions When liver acquired expression of apobec-1 in NS, it could up-regulate LRP, accelerate the elimination of ApoB48-lipoproteins, and produce a certain lipid-lowering effect. Key words: Low density lipoprotein receptor; Low density lipoprotein receptor related protein; Nephrotic syndrome; apobec-1

Low density lipoprotein receptor-related protein 1 expression correlates with cholesteryl ester accumulation in the myocardium of ischemic cardiomyopathy patients

Our hypothesis was that overexpression of certain lipoprotein receptors might be related to lipid accumulation in the human ischemic myocardium. Intramyocardial lipid overload contributes to contractile dysfunction and arrhythmias in cardiomyopathy. Thus, the purpose of this study was to assess the effect of hypercholesterolemic LDL and hypertrigliceridemic VLDL dose on LRP1 expression in cardiomyocytes, as well as the potential correlation between LRP1 expression and neutral lipid accumulation in the left ventricle tissue from ischemic cardiomyopathy patients. Cell culture experiments include control and LRP1-deficient cardiomyocytes exposed to lipoproteins under normoxic and hypoxic conditions. Explanted hearts from 18 ICM patients and eight non-diseased hearts (CNT) were included. Low density lipoprotein receptor-related protein 1 (LRP1), very low density lipoprotein receptor (VLDLR) and low density lipoprotein receptor (LDLR) expression was analyzed by real time PCR and Western blotting. Cholesteryl ester (CE), triglyceride (TG) and free cholesterol (FC) content was assess by thin layer chromatography following lipid extraction. Western blotting experiments showed that protein levels of LRP1, VLDLR and HIF-1α were significantly upregulated in ischemic hearts. Immunohistochemistry and confocal microscopy analysis showed that LRP1 and HIF-1α were upregulated in cardiomyocytes of ICM patients. In vitro studies showed that VLDL, LDL and hypoxia exerted an upregulatory effect on LRP1 expression and that LRP1 played a major role in cholesteryl ester accumulation from lipoproteins in cardiomyocytes. Myocardial CE accumulation strongly correlated with LRP1 levels in ischemic hearts. Taken together, our results suggest that LRP1 upregulation is key for myocardial cholesterol ester accumulation in ischemic human hearts and that LRP1 may be a target to prevent the deleterious effects of myocardial cholesterol accumulation in ischemic cardiomyopathy.

The P2Y2 receptor regulates lipoprotein receptor‐related protein 1 expression in smooth muscle cells

Extracellular nucleotides exert various effects in the cardiovascular system. Uridine 5′‐triphosphate (UTP) regulates G‐protein‐coupled P2Y2 receptor (P2Y2R) activation which causes actin cytoskeletal reorganization. We isolated aortic smooth muscle cells (SMC) from wild‐type (WT) and P2Y2R−/− mice to investigate whether UTP and the P2Y2R modulate expression of low density lipoprotein receptor‐related protein 1 (LRP1) and low density lipoprotein receptor (LDLR). For LRP1 expression, cells were stimulated in the presence or absence of 100 μM UTP overnight. For LDLR mRNA expression, cells were transiently transfected for 24 h with cDNA encoding a hemagglutinin‐tagged WT P2Y2R or a mutant P2Y2R that does not bind filamin‐A (FLN‐A) and treated with 100 μM UTP overnight. Total RNA was isolated, reversed transcribed to cDNA, and mRNA abundance determined by RT‐PCR using the ΔCt method with GAPDH as a control gene. Results show SMC expressing the P2Y2R that lacks the FLN‐A binding domain exhibit 3‐fold lower LDLR expression than SMC expressing the WT P2Y2R. However, there was a 3‐fold increase in LRP1 mRNA expression in response to UTP in P2Y2R−/− SMC compared to WT. Actinomycin‐D (20 μg/ml) significantly reduced UTP‐induced LRP1 mRNA expression in P2Y2R−/− SMC (P &lt; 0.05). These results might indicate the presence of a P2Y4R in P2Y2R−/− SMC as a possible cause for the effect of UTP, which is being further investigated.

La hipoxia estimula la expresión del receptor LRP1 a través del factor de transcripción HIF-1α en células musculares lisas de pared vascular humana

ObjectiveHypoxia is considered a key factor in the progression of atherosclerotic lesions. Low density lipoprotein receptor-related protein 1 (LRP1) plays a pivotal role in the vasculature. The aims of this study were to investigate the effect of hypoxia on LRP1 expression and function in vascular smooth muscle cells (VSMC) and the role of hypoxia-inducible factor alpha (HIF-1α). Methods and resultsReal time PCR and Western blot analysis demonstrated that hypoxia (1% O2) time-dependently induced LRP1 mRNA (maximum levels at 1-2hours) and protein expression (maximum levels at 12-24hours). The delayed hypoxic upregulation of LRP1 protein versus mRNA may be explained by the long half-life of LRP1 protein. Luciferase assays demonstrated that hypoxia and HIF-1α over-accumulation induced LRP1 promoter activity and that two consensus HRE sites located at –1072/–1069 and –695/–692 participate in the induction. Chromatin immunoprecipitation showed the in vivo binding of HIF-1α to LRP1 promoter in hypoxic VSMC. Hypoxia effects on LRP1 protein expression were functionally translated into an increased cholesteryl ester (CE) accumulation from aggregated LDL (agLDL) uptake. The blockade of HIF-1α expression inhibited the upregulatory effect of hypoxia on LRP1 expression and agLDL-derived intracellular CE over-accumulation, suggesting that both LRP1 overexpression and CE over-accumulation in hypoxic vascular cells are dependent on HIF-1α. Immunohistochemical analysis showed the colocalization of LRP1 and HIF-1α in vascular cells of human advanced atherosclerotic plaques. ConclusionsHypoxia upregulates LRP1 expression and agLDL-derived intracellular CE accumulation in human VSMC through HIF-1α induction.