An antibody-drug conjugate targeting GPR56 demonstrates efficacy in preclinical models of colorectal cancer.

BACKGROUND: Long-term prognosis remains poor for colorectal cancer (CRC) patients with advanced disease due to treatment resistance. The identification of novel targets is essential for the development of new therapeutic approaches. GPR56, an adhesion GPCR, is highly expressed in CRC tumours and correlates with poor survival. Here, we describe the generation and preclinical evaluation of a novel ADC consisting of an anti-GPR56 antibody (10C7) conjugated with the DNA-damaging payload duocarmycin. METHODS: RNA-seq dataset analysis was performed to determine GPR56 expression in CRC subtypes. The specificity of binding, epitope mapping, and internalisation of 10C7 was examined. 10C7 was conjugated to payload and ADC cytotoxicity was assessed against a panel of CRC cell lines and tumour organoids. Antitumour efficacy was evaluated in xenograft models of CRC cell lines and patient-derived tumours. RESULTS: High GPR56 was shown to be associated with the microsatellite stable (MSS) subtype that accounts for 80-85% of CRC. GPR56 ADC selectively induced cytotoxicity in CRC cells and tumour organoids at low nanomolar potency in a GPR56-dependent manner and showed significant antitumour efficacy against GPR56-expressing xenograft models. CONCLUSIONS: This study provides the rationale for the future development of a GPR56-targeted ADC approach to potentially treat a large fraction of MSS CRC patients.

Ginsenoside Rb1 Blocks Ritonavir-Induced Oxidative Stress and eNOS Downregulation through Activation of Estrogen Receptor-Beta and Upregulation of SOD in Human Endothelial Cells.

We have previously shown that ritonavir (RTV), a highly active anti-retroviral therapy (HAART) drug, can cause endothelial dysfunction through oxidative stress. Several antioxidants including ginsenoside Rb1, a compound with antioxidant effect, can effectively block this side effect of RTV in endothelial cells. In the current study, we explored a mechanism by which ginsenoside Rb1 could protect these cells via binding of estrogen receptors (ERs). We found that several human endothelial cell lines differentially expressed ER-ß and had very low levels of ER-α. RTV treatment significantly increased the production of reactive oxygen species (ROS) and decreased the expression of endothelial nitric oxidase synthase (eNOS) and superoxide dismutase (SOD) in HUVECs, while Rb1 effectively blocked these effects of RTV. These effects of Rb1 were effectively inhibited by silencing ER-ß, indicating that ginsenoside Rb1 requires ER-ß for its antioxidant activity in inhibiting the deleterious effect of RTV in human endothelial cells. Furthermore, Rb1 specifically activated ER-ß transactivation activity by ER-ß luciferase reporter assay. Rb1 competitively bound to ER-ß, which was determined by the high sensitive fluorescent polarization assay.

Anti-tumor activity of camptothecin analog conjugate of a RSPO4-based peptibody targeting LGR4/5/6 in preclinical models of colorectal cancer.

Antibody-drug conjugates (ADCs) have emerged as a major modality of targeted cancer therapy, yet no ADC has been approved for colorectal cancer (CRC). LGR4/5/6 (leucine-rich repeat containing, G protein-coupled receptor 4, 5, 6) are three related receptors that are expressed at high levels together or alternately in nearly all cases of CRC. ADCs targeting LGR5 have been shown to have robust anti-tumor potency, but not all CRC cells express LGR5 and LGR5-positive tumor cells may lose LGR5 expression due to cancer cell plasticity. R-spondin 4 (RSPO4) is a natural protein ligand of LGR4/5/6 with high affinity for all three receptors. We fused a mutant form of RSPO4 that retains high affinity binding to LGR4/5/6 to IgG1 Fc to create a peptibody designated R462. Conjugation of R462 with a camptothecin analog (CPT2) at eight drugs per peptibody led to the synthesis of R462-CPT2 that showed highly potent cytotoxic activity in vitro in CRC cell lines expressing any of LG4/5/6. In cell line xenograft and PDX models of CRC, R462-CPT2 demonstrated robust anti-tumor effect. Importantly, R462-CPT2 showed no major adverse effect at therapeutically effective dose levels. These results strongly support the use of RSPO ligand drug-conjugates that target LGR4/5/6 simultaneously for the treatment of CRC.

Loss of LGR5 through Therapy-induced Downregulation or Gene Ablation Is Associated with Resistance and Enhanced MET-STAT3 Signaling in Colorectal Cancer Cells.

Leucine-rich repeat-containing, G protein-coupled receptor 5 (LGR5) is highly expressed in colorectal cancer and cancer stem cells (CSCs) that play important roles in tumor initiation, progression, and metastasis. Loss of LGR5 has been shown to enhance therapy resistance. However, the molecular mechanisms that mediate this resistance remain elusive. In this study, we demonstrate conversion of LGR5+ colorectal cancer cells to an LGR5- state in response to chemotherapy, LGR5- targeted antibody-drug conjugates (ADCs), or LGR5 gene ablation led to activation of STAT3. Further investigation revealed increased STAT3 activation occurred as a result of increased mesenchymal epithelial transition (MET) factor receptor activity. LGR5 overexpression decreased MET-STAT3 activity and sensitized colorectal cancer cells to therapy. STAT3 inhibition suppressed MET phosphorylation, while constitutively active STAT3 reduced LGR5 levels and increased MET activity, suggesting a potential feedback mechanism. Combination treatment of MET-STAT3 inhibitors with irinotecan or antibody-drug conjugates (ADCs) substantiated synergistic effects in colorectal cancer cells and tumor organoids. In colorectal cancer xenografts, STAT3 inhibition combined with irinotecan enhanced tumor growth suppression and prolonged survival. These findings suggest a mechanism by which drug-resistant LGR5- colorectal cancer cells acquire a survival advantage through activation of MET-STAT3 and provide rationale for new treatment strategies to target colorectal cancer.

Nanoparticle-Mediated Therapy with miR-198 Sensitizes Pancreatic Cancer to Gemcitabine Treatment through Downregulation of VCP-Mediated Autophagy.

Pancreatic ductal adenocarcinoma (PDAC) remains an extremely aggressive disease characterized by rapidly acquired multi-drug resistance, including to first-line chemotherapeutic agent gemcitabine. Autophagy is a process that is often exploited by cancer and is one of several intrinsic factors associated with resistance to gemcitabine. We have previously found that miR-198 acts as a tumor suppressor in PDAC through the targeting of factors including Valosin-containing protein (VCP). VCP has been reported to play an important role in autophagic flux. In this study, we investigated whether the repression of VCP through miR-198 administration disrupts the autophagy process and sensitizes PDAC cells to gemcitabine treatment in vitro. Moreover, we used LGA-PEI (LPNP) nanoparticles to effectively administer miR-198 to tumors in vivo, inducing tumor sensitization to gemcitabine and leading to a significant reduction in tumor burden and metastases and a concomitant downregulation of VCP expression and autophagy maturation. Our results indicate a potential therapeutic strategy for targeting gemcitabine resistant PDAC and establishes the use of LPNPs for effective therapeutic delivery of nucleic acids in vitro and in vivo.

Ginkgolic acid inhibits HIV protease activity and HIV infection in vitro.

BACKGROUND: Several HIV protease mutations, which are resistant to clinical HIV protease inhibitors (PIs), have been identified. There is a great need for second-generation PIs with different chemical structures and/or with an alternative mode of inhibition. Ginkgolic acid is a natural herbal substance and a major component of the lipid fraction in the nutshells of the Ginkgo biloba tree. The objective of this study was to determine whether ginkgolic acid could inhibit HIV protease activity in a cell free system and HIV infection in human cells. MATERIAL/METHODS: Purified ginkgolic acid and recombinant HIV-1 HXB2 KIIA protease were used for the HIV protease activity assay. Human peripheral blood mononuclear cells (PBMCs) were used for HIV infection (HIV-1SF162 virus), determined by a p24gag ELISA. Cytotoxicity was also determined. RESULTS: Ginkgolic acid (31.2 µg/ml) inhibited HIV protease activity by 60%, compared with the negative control, and the effect was concentration-dependent. In addition, ginkgolic acid treatment (50 and 100 µg/ml) effectively inhibited the HIV infection at day 7 in a concentration-dependent manner. Ginkgolic acid at a concentration of up to 150 µg/ml demonstrated very limited cytotoxicity. CONCLUSIONS: Ginkgolic acid effectively inhibits HIV protease activity in a cell free system and HIV infection in PBMCs without significant cytotoxicity. Ginkgolic acid may inhibit HIV protease through different mechanisms than current FDA-approved HIV PI drugs. These properties of ginkgolic acid make it a promising therapy for HIV infection, especially as the clinical problem of viral resistance to HIV PIs continues to grow.

Two Antibody-Guided Lactic-co-Glycolic Acid-Polyethylenimine (LGA-PEI) Nanoparticle Delivery Systems for Therapeutic Nucleic Acids.

We previously reported a new polymer, lactic-co-glycolic acid-polyethylenimine (LGA-PEI), as an improved nanoparticle (NP) delivery for therapeutic nucleic acids (TNAs). Here, we further developed two antibody (Ab)-conjugated LGA-PEI NP technologies for active-targeting delivery of TNAs. LGA-PEI was covalently conjugated with a single-chain variable fragment antibody (scFv) against mesothelin (MSLN), a biomarker for pancreatic cancer (PC), or a special Ab fragment crystallizable region-binding peptide (FcBP), which binds to any full Ab (IgG). TNAs used in the current study included tumor suppressor microRNA mimics (miR-198 and miR-520h) and non-coding RNA X-inactive specific transcript (XIST) fragments; green fluorescence protein gene (GFP plasmid DNA) was also used as an example of plasmid DNA. MSLN scFv-LGA-PEI NPs with TNAs significantly improved their binding and internalization in PC cells with high expression of MSLN in vitro and in vivo. Anti-epidermal growth factor receptor (EGFR) monoclonal Ab (Cetuximab) binding to FcBP-LGA-PEI showed active-targeting delivery of TNAs to EGFR-expressing PC cells.

A subset of cytotoxic effector memory T cells enhances CAR T cell efficacy in a model of pancreatic ductal adenocarcinoma.

In humans, the natural killer (NK) cell marker CD161 identifies several subsets of T cells, including a polyclonal CD8 αß T cell receptor-expressing subset with characteristic specificity for tissue-localized viruses. This subset also displays enhanced cytotoxic and memory phenotypes. Here, we characterized this unique T cell subset and determined its potential suitability for use in chimeric antigen receptor (CAR) T cell therapy. In mice, gene expression profiling among the CD161-equivalent CD8+ T cell populations (CD8+NK1.1+) revealed substantial up-regulation of granzymes, perforin, killer lectin-like receptors, and innate signaling molecules in comparison to CD8+NK1.1- T cells. Adoptive transfer of CD8+NK1.1+ cells from previously exposed animals offered substantially enhanced protection and improved survival against melanoma tumors and influenza infection compared to CD8+NK1.1- cells. Freshly isolated human CD8+CD61+ T cells exhibited heightened allogeneic killing activity in comparison to CD8+CD61- T cells or total peripheral blood mononuclear cells (PBMCs). To determine whether this subset might improve the antitumor efficacy of CAR T cell therapy against solid tumors, we compared bulk PBMCs, CD8+CD161-, and CD8+CD161+ T cells transduced with a human epidermal growth factor receptor-2 (HER2)-specific CAR construct. In vitro, CD8+CD161+ CAR-transduced T cells killed HER2+ targets faster and with greater efficiency. Similarly, these cells mediated enhanced in vivo antitumor efficacy in xenograft models of HER2+ pancreatic ductal adenocarcinoma, exhibiting elevated expression of granzymes and reduced expression of exhaustion markers. These data suggest that this T cell subset presents an opportunity to improve CAR T cell therapy for the treatment of solid tumors.

Mesothelin and TGF-α predict pancreatic cancer cell sensitivity to EGFR inhibitors and effective combination treatment with trametinib.

Clinical trials of EGFR inhibitors in combination with gemcitabine for the treatment of pancreatic ductal adenocarcinoma (PDAC) have generated mixed results partially due to the poorly defined effectiveness of EGFR inhibitors in PDAC. Here, we studied a panel of PDAC cell lines to compare the IC50s of the EGFR inhibitors gefitinib and cetuximab. We found that gefitinib induced biphasic inhibition in over 50% of PDAC cells, with the initial growth inhibition occurring at nanomolar concentrations and a second growth inhibition occurring outside the clinical range. In contrast to gefitinib, cetuximab produced a single phase growth inhibition in a subset of PDAC cells. Using this sensitivity data, we screened for correlations between cell morphology proteins and EGFR ligands to EGFR inhibitor sensitivity, and found that mesothelin and the EGFR ligand TGF-α have a strong correlation to gefitinib and cetuximab sensitivity. Analysis of downstream signaling pathways indicated that plc-γ1 and c-myc were consistently inhibited by EGFR inhibitor treatment in sensitive cell lines. While an inconsistent additive effect was observed with either cetuximab or gefitinib in combination with gemcitabine, the cell pathway data indicated consistent ERK activation, leading us to pursue EGFR inhibitors in combination with trametinib, a MEK1/2 inhibitor. Both cetuximab and gefitinib in combination with trametinib produced an additive effect in all EGFR sensitive cell lines. Our results indicate that mesothelin and TGF-α can predict PDAC sensitivity to EGFR inhibitors and a combination of EGFR inhibitors with trametinib could be a novel effective treatment for PDAC.

Identification of benzo(a)pyrene diol epoxide-binding DNA fragments using DNA immunoprecipitation technique.

Benzo(a)pyrene diol epoxide (BPDE), an active metabolite of the tobacco carcinogen benzo(a)pyrene, can induce p53 gene mutation, down-regulate retinoic acid receptor beta, and increase cyclooxygenase-2 expression in human epithelial cells. However, it remains unknown whether these effects are direct or indirect. To investigate the direct effects of BPDE on gene expression, we used our newly developed DNA immunoprecipitation technique to identify and clone BPDE-binding DNA fragments. A total of 67 fragments were sequenced and grouped into four categories after their sequences were blasted in the GenBank database: (a). 15 fragments matched known gene sequences; (b). 24 matched expressed sequence tag clones; (c). 22 matched genomic DNA of unknown genes; and (d). 6 clones did not show any homology with GenBank sequences known to date. The 67 fragments include DNA repair and apoptosis-related genes, zinc finger protein, cellular enzymes, expressed sequence tag clones, and CpG islands. These data further demonstrate that BPDE-induced gene alterations are important events in carcinogenesis and that the identification of the resulting clones may help us to better understand the mechanisms of BPDE-induced carcinogenesis.

New polymer of lactic-co-glycolic acid-modified polyethylenimine for nucleic acid delivery.

AIM: To develop an improved delivery system for nucleic acids. MATERIALS & METHODS: We designed, synthesized and characterized a new polymer of lactic-co-glycolic acid-modified polyethylenimine (LGA-PEI). Functions of LGA-PEI polymer were determined. RESULTS: The new LGA-PEI polymer spontaneously formed nanoparticles (NPs) with DNA or RNA, and showed higher DNA or RNA loading efficiency, higher or comparable transfection efficacy, and lower cytotoxicity in several cell types including PANC-1, Jurkat and HEK293 cells, when compared with lipofectamine 2000, branched or linear PEI (25 kDa). In nude mouse models, LGA-PEI showed higher delivery efficiency of plasmid DNA or miRNA mimic into pancreatic and ovarian xenograft tumors. LGA-PEI/DNA NPs showed much lower toxicity than control PEI NPs in mouse models. CONCLUSION: The new LGA-PEI polymer is a safer and more effective system to deliver DNA or RNA than PEI.

Chemo-immunotherapy mediates durable cure of orthotopic KrasG12D/p53-/- pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related death in the United States, exhibiting a five-year overall survival (OS) of only 7% despite aggressive standard of care. Recent advances in immunotherapy suggest potential application of immune-based treatment approaches to PDAC. To explore this concept further, we treated orthotopically established K-rasG12D/p53-/- PDAC tumors with gemcitabine and a cell-based vaccine previously shown to generate durable cell-mediated (TH1) immunity. Tumor progression was monitored by IVIS. The results indicated that the combination of chemotherapy and dendritic cell (DC) vaccination was effective in eliminating tumor, preventing metastasis and recurrence, and significantly enhancing OS. No animal that received the combination therapy relapsed, while mice that received gemcitabine-only or vaccine-only regimens relapsed and progressed. Analysis of circulating PBMC demonstrated that mice receiving the combination therapy exhibited significantly elevated levels of CD8+IFNγ+CCR7+NK1.1+ T-cells with significantly reduced levels of exhausted GITR+CD8+ T-cells after the cessation of treatment. Retro-orbital tumor re-challenge of surviving animals at six-months post-treatment demonstrated durable antitumor immunity only among mice that had received the combination therapy. CD8+ splenocytes derived from surviving mice that had received the combination therapy were sorted into NK1.1pos and NK1.1neg populations and adoptively transferred into naive recipients. Transfer of only 1,500 CD8+NK1.1pos T-cells was sufficient to mediate tumor rejection whereas transfer of 1,500 CD8+NK1.1neg T-cells imparted only minimal effects. The data suggest that addition of a TH1 DC vaccine regimen as an adjuvant to existing therapies can mediate eradication of tumors and offer durable protection against PDAC.

Overexpression of Semaphorin-3E enhances pancreatic cancer cell growth and associates with poor patient survival.

Semaphorin-3E (Sema3E) is a member of an axon guidance gene family, and has recently been reported to contribute to tumor progression and metastasis. However, its role in pancreatic cancer is yet unknown and uncharacterized. In this study, we showed that Sema3E is overexpressed in human pancreatic cancer, and that high Sema3E levels are associated with tumor progression and poor survival. Interestingly, we also observed Sema3E expression in the nucleus, even though Sema3E is reported to be a secreted protein. Overexpression of Sema3E in pancreatic cancer cells promoted cell proliferation and migration in vitro, and increased tumor incidence and growth in vivo. Conversely, knockout of Sema3E suppressed cancer cell proliferation and migration in vitro, and reduced tumor incidence and size in vivo. Moreover, Sema3E induced cell proliferation via acting through the MAPK/ERK pathway. Collectively, these results reveal an undiscovered role of Sema3E in promoting pancreatic cancer pathogenesis, suggesting that Sema3E may be a suitable prognostic marker and therapeutic target for pancreatic cancer.

Reduced 15S-lipoxygenase-2 expression in esophageal cancer specimens and cells and upregulation in vitro by the cyclooxygenase-2 inhibitor, NS398.

Alterations in arachidonic acid metabolism are involved in human carcinogenesis. Cyclooxygenase (COX) and lipoxygenase (LOX) are key enzymes in this metabolism. We analyzed the expression of 15S-lipoxygenase-2 (15-LOX-2) mRNA and protein in surgical specimens from normal (N=37) and malignant (63) esophageal tissues using in situ hybridization and immunohistochemistry (IHC), and in normal (1), premalignant (1), and malignant (5) esophageal cell lines using Northern and Western blotting. 15-LOX-2 was expressed in normal esophageal epithelial cells (EECs) at the highest levels, whereas an SV40-immortalized HET-1A line and three of five esophageal cancer cell lines failed to express it at detectable levels. 15-LOX-2 was detected in 76% (28/37) of the normal esophageal mucosae, but only in 46% (29/63) of the cancer specimens using IHC (P<.01). Transient transfection of 15-LOX-2 expression vectors into esophageal cancer cells significantly inhibited the proliferation of 15-LOX-2-negative cancer cells. The COX-2 inhibitor, NS398, induced 15-LOX-2 expression in esophageal cancer cells, which is associated with reduced cell viability. This study demonstrated that 15-LOX-2 expression is lost in esophageal cancers and that the induction of 15-LOX-2 can inhibit cancer cell proliferation. Further investigation of the effects of nonsteroidal anti-inflammatory drugs on 15-LOX-2 expression and apoptosis in esophageal cancer cells may be warranted.

Anti-human protein S antibody induces tissue factor expression through a direct interaction with platelet phosphofructokinase.

INTRODUCTION: Autoantibodies including anti-human protein S antibody (anti-hPS Ab) and anti-human protein C antibody (anti-hPC Ab) can be detected in patients with autoimmune diseases with hypercoagulability. The objective of the present study was to determine the effects and molecular pathways of these autoantibodies on tissue factor (TF) expression in human coronary artery endothelial cells (HCAECs). MATERIALS AND METHODS: HCAECs were treated with anti-hPS Ab or anti-hPC Ab for 3 hours. TF expression was measured by real-time PCR and Western blot. TF-mediated procoagulant activity was determined by a commercial kit. MAPK phosphorylation was analyzed by Bio-Plex luminex immunoassay and Western blot. The potential proteins interacting with anti-hPS Ab were studied by immunoprecipitation, mass spectrometry and in vitro pull-down assay. RESULTS: Anti-hPS Ab, but not anti-hPC Ab, specifically induced TF expression and TF-mediated procoagulant activity in HCAECs in a concentration-dependent manner. This effect was confirmed in human umbilical endothelial cells (HUVECs). ERK1/2 phosphorylation was induced by anti-hPS Ab treatment, while inhibition of ERK1/2 by U0216 partially blocked anti-hPS Ab-induced TF upregulation (P<0.05). In addition, anti-hPS Ab specifically cross-interacted with platelet phosphofructokinase (PFKP) in HCAECs. Anti-hPS Ab was able to directly inhibit PFKP activities in HCAECs. Furthermore, silencing of PFKP by PFKP shRNA resulted in TF upregulation in HCAECs, while activation of PFKP by fructose-6-phosphate partially blocked the effect of anti-hPS Ab on TF upregulation (P<0.05). CONCLUSIONS: Anti-hPS Ab induces TF expression through a direct interaction with PFKP and ERK1/2 activation in HCAECs. Anti-hPS Ab may directly contribute to vascular thrombosis in the patient with autoimmune disorders.

Roles of cardiovascular risk factors in endothelial nitric oxide synthase regulation: an update.

Cardiovascular disease remains the number one killer in the United States and many other countries. Each year, there are enormous research efforts on its pathogenesis, prevention and treatment led by scientists worldwide. One of the most significant research areas is the impact and mechanisms of existing or new cardiovascular risk factors on the vascular system. The current review provides the most updated research advances in the area of the regulation of the endothelial nitric oxide synthase-nitric oxide (eNOS-NO) system by several cardiovascular risk factors. There are many exciting discoveries made from the studies of several major cardiovascular risk factors such as hypertension, cigarette smoking, dyslipidemia and diabetes mellitus as well as emerging risk factors such as HIV infection, antiretroviral therapy, genomic variability, and cytokines. In general, cardiovascular risk factors could impair the eNOS-NO system with a variety of molecular mechanisms including decrease in NO bioavailability by excess reactive oxygen species, inhibition of eNOS expression and activity, and deficiency of eNOS cofactors. Special attention is paid to the impact of several new or emerging risk factors on cardiovascular disease and the eNOS-NO system. These mechanistic studies are clinically significant because they may lead towards new and effective strategies for the prevention and treatment of cardiovascular disease.

Resistin increases monolayer permeability of human coronary artery endothelial cells.

Resistin has been linked to obesity, insulin resistance, atherosclerosis, and the development of cardiovascular disease. Nevertheless, the effects and the molecular mechanisms of resistin on endothelial permeability, a key event in the development of atherosclerosis, inflammation, and vascular disease, are largely unknown. In order to determine the effect of resistin on endothelial permeability, human coronary artery endothelial cells (HCAECs) were treated with clinically relevant concentrations of resistin and the endothelial permeability was measured using the Transwell system with a Texas-Red-labeled dextran tracer. The permeability of HCAEC monolayers treated with resistin (80 ng/mL) was 51% higher than the permeability of control monolayers (P<0.05). The mRNA levels of tight junction proteins zonula occludens-1 (ZO-1) and occludin in resistin-treated cells were 37% and 42% lower, respectively, than the corresponding levels in untreated cells. The protein levels of these molecules in resistin-treated cells were significantly reduced by 35% and 37%, respectively (P<0.05), as shown by flow cytometry and Western blot analysis. Superoxide dismutase (SOD) mimetic MnTBAP effectively blocked the resistin-mediated reduction of ZO-1 and occludin levels in HCAECs. In addition, superoxide anion production was increased from 21% (untreated cells) to 55% (cells treated with 40 ng/mL resistin), and 64% (resistin, 80 mg/mL) (P<0.05). The natural antioxidant Ginkgolide A effectively inhibited resistin-induced increase in permeability and the increase in superoxide anion production in HCAECs. Furthermore, resistin treatment significantly activated p38 MAPK, but not ERK1/2. Pretreatment of HCAECs with a p38 inhibitor effectively blocked resistin-induced permeability. These results provide new evidence that resistin may contribute to the vascular lesion formation via increasing endothelial permeability through the mechanism of oxidative stress and the activation of p38 MAPK.

Lysophosphatidic acid causes endothelial dysfunction in porcine coronary arteries and human coronary artery endothelial cells.

AIM: The objective of this study was to determine the effects of lysophosphatidic acid (LPA) on endothelial functions and molecular alternations in both porcine coronary arteries and human coronary artery endothelial cells (HCAECs). METHODS AND RESULTS: The vessel rings and HCAECs were treated with clinically relevant concentrations of LPA for different times. Vasomotor reactivity was studied with a myograph tension system. LPA (10 and 50 µM) treatment for the vessel rings significantly reduced endothelium-dependent vasorelaxation in response to bradykinin (×10(-5)M) by 32% and 49%, respectively, compared with the control (P<0.05). LPA decreased endothelial nitric oxide synthase (eNOS) mRNA and immunoreactivity levels in the vessel rings. In HCAECs, LPA reduced eNOS mRNA, phospho-eNOS and total eNOS protein levels. In addition, superoxide anion levels in LPA-treated vessel rings and HCAECs were significantly increased by lucegenin-enhanced chemiluminescence assay and dihydroethidium staining, respectively. Mitochondrial membrane potential and ATP content in LPA-treated HCAECs were substantially decreased. The mRNA levels of reactive oxygen species generating enzymes NOX4 and p40(phox) were increased, while endogenous antioxidant enzyme superoxide dismutase 1 was decreased in response to LPA treatment in HCAECs. Furthermore, exogenous antioxidant molecule selenomethionine (SeMet) effectively reversed these LPA-induced effects in both porcine coronary arteries and HCAECs. CONCLUSIONS: LPA causes endothelial dysfunction by a mechanism associated with decreased eNOS expression and increased oxidative stress in porcine coronary arteries and HCAECs.