Lysophosphatidic Acid Inhibits Apoptosis Induced by Cisplatin in Cervical Cancer Cells

Autotaxin-Lysophosphatidate Axis: Promoter of Cancer Development and Possible Therapeutic Implications

Autotaxin (ATX) is a member of the ectonucleotide pyrophosphate/phosphodiesterase (ENPP) family; it is encoded by the ENPP2 gene. ATX is a secreted glycoprotein and catalyzes the hydrolysis of lysophosphatidylcholine to lysophosphatidic acid (LPA). LPA is responsible for the transduction of various signal pathways through the interaction with at least six G protein-coupled receptors, LPA Receptors 1 to 6 (LPAR1-6). The ATX-LPA axis is involved in various physiological and pathological processes, such as angiogenesis, embryonic development, inflammation, fibrosis, and obesity. However, significant research also reported its connection to carcinogenesis, immune escape, metastasis, tumor microenvironment, cancer stem cells, and therapeutic resistance. Moreover, several studies suggested ATX and LPA as relevant biomarkers and/or therapeutic targets. In this review of the literature, we aimed to deepen knowledge about the role of the ATX-LPA axis as a promoter of cancer development, progression and invasion, and therapeutic resistance. Finally, we explored its potential application as a prognostic/predictive biomarker and therapeutic target for tumor treatment.

Metabolomic Profiles in Patients with Cervical Cancer Undergoing Cisplatin and Radiation Therapy

This study was aimed to evaluate endogenous metabolic changes before and after cisplatin and radiation therapy in patients with cervical cancer via untargeted metabolomic analysis using plasma samples. A total of 13 cervical cancer patients were enrolled in this study. Plasma samples were collected from each patient on two occasions: approximately one week before therapy (P1) and after completion of cisplatin and radiation therapy (P2). Of the 13 patients, 12 patients received both cisplatin and radiation therapy, whereas one patient received radiation therapy alone. The samples were analyzed using the Ultimate 3000 coupled with Q ExactiveTM Focus Hybrid Quadrupole-OrbitrapTM mass spectrometry (Thermo Fisher Scientific, Waltham, MA, USA). Chromatographic separation utilized a Kinetex C18 column 2.1×100 mm (2.6 μm) (Phenomenex, Torrance, CA, USA), and the temperature was maintained at 40°C. Following P2, there were statistically significant increases in the concentrations of indoxyl sulfate, phenylacetylglutamine, Lysophosphatidyethanolamine (LysoPE) (18:1), and indole-3-acetic acid compared with the concentrations observed at P1. Specifically, in the human papillomavirus (HPV) noninfection group, indoxyl sulfate, LysoPE (18:1), and phenylacetylglutamine showed statistically significant increases at P2 compared with P1. No significant changes in metabolite concentrations were observed in the HPV infection group. Indoxyl sulfate, LysoPE (18:1), phenylacetylglutamine, and indole-3-acetic acid were significantly increased following cisplatin and radiation therapy.

Lysophosphatidic acid is associated with oocyte maturation by enhancing autophagy via PI3K-AKT-mTOR signaling pathway in granulosa cells

BACKGROUND

Folliculogenesis is a complex network of interacting cellular signals between somatic cells and oocytes. Many components in ovarian follicular fluid (FF) dynamically change during folliculogenesis and play a positive role in oocyte maturation. Previous studies have reported that lysophosphatidic acid (LPA) promotes cumulus cell expansion, oocyte nuclear maturation, and in vitro maturation of oocytes.

RESULTS

Initially, the expression of LPA was raised in matured FF significantly (P < 0.0001). Then, 10 μM LPA treated for 24 h in human granulosa cells (KGNs) aggravated cell proliferation, with increased autophagy, and reduced apoptosis. Meanwhile, we demonstrated that LPA mediated cell function through the PI3K-AKT-mTOR signaling pathway as PI3K inhibitor (LY294002) significantly prevented LPA-induced AKT, mTOR phosphorylation and autophagy activation. Such results were also verified by immunofluorescence staining and flow cytometry. In addition, an autophagy inhibitor 3 methyladenine (3MA) could also alleviate the effects of LPA, by activating apoptosis through PI3K-AKT-mTOR pathways. Finally, we found blockade with Ki16425 or knockdown LPAR1, alleviated LPA mediated autophagy activation in KGNs, suggesting that LPA enhances autophagy through activation of the LPAR1 and PI3K-AKT-mTOR signaling pathways.

CONCLUSION

This study demonstrates that increased LPA activated PI3K-Akt-mTOR pathway through LPAR1 in granulosa cells, suppressing apoptosis by enhancing autophagy, which might play a role in oocyte maturation in vivo.

Fatty acid metabolism: A new therapeutic target for cervical cancer

Cervical cancer (CC) is one of the most common malignancies in women. Cancer cells can use metabolic reprogramming to produce macromolecules and ATP needed to sustain cell growth, division and survival. Recent evidence suggests that fatty acid metabolism and its related lipid metabolic pathways are closely related to the malignant progression of CC. In particular, it involves the synthesis, uptake, activation, oxidation, and transport of fatty acids. Similarly, more and more attention has been paid to the effects of intracellular lipolysis, transcriptional regulatory factors, other lipid metabolic pathways and diet on CC. This study reviews the latest evidence of the link between fatty acid metabolism and CC; it not only reveals its core mechanism but also discusses promising targeted drugs for fatty acid metabolism. This study on the complex relationship between carcinogenic signals and fatty acid metabolism suggests that fatty acid metabolism will become a new therapeutic target in CC.

Autotaxin and Lysophosphatidic Acid Signalling: the Pleiotropic Regulatory Network in Cancer

Autotaxin, also known as ecto-nucleotide pyrophosphatase/phosphodiesterase family member 2, is a secreted glycoprotein that plays multiple roles in human physiology and cancer pathology. This protein, by converting lysophosphatidylcholine into lysophosphatidic acid, initiates a complex signalling cascade with significant biological implications. The article outlines the autotaxin gene and protein structure, expression regulation and physiological functions, but focuses mainly on the role of autotaxin in cancer development and progression. Autotaxin and lysophosphatidic acid signalling influence several aspects of cancer, including cell proliferation, migration, metastasis, therapy resistance, and interactions with the immune system. The potential of autotaxin as a diagnostic biomarker and promising drug target is also examined.

KAI1/CD82 gene and autotaxin-lysophosphatidic acid axis in gastrointestinal cancers

The KAI1/CD82 gene inhibits the metastasis of most tumors and is remarkably correlated with tumor invasion and prognosis. Cell metabolism dysregulation is an important cause of tumor occurrence, development, and metastasis. As one of the important characteristics of tumors, cell metabolism dysregulation is attracting increasing research attention. Phospholipids are an indispensable substance in the metabolism in various tumor cells. Phospholipid metabolites have become important cell signaling molecules. The pathological role of lysophosphatidic acid (LPA) in tumors was identified in the early 1990s. Currently, LPA inhibitors have entered clinical trials but are not yet used in clinical treatment. Autotaxin (ATX) has lysophospholipase D (lysoPLD) activity and can regulate LPA levels in vivo. The LPA receptor family and ATX/lysoPLD are abnormally expressed in various gastrointestinal tumors. According to our recent pre-experimental results, KAI1/CD82 might inhibit the migration and metastasis of cancer cells by regulating the ATX-LPA axis. However, no relevant research has been reported. Clarifying the mechanism of ATX-LPA in the inhibition of cancer metastasis by KAI1/CD82 will provide an important theoretical basis for targeted cancer therapy. In this paper, the molecular compositions of the KAI1/CD82 gene and the ATX-LPA axis, their physiological functions in tumors, and their roles in gastrointestinal cancers and target therapy are reviewed.

Lysophosphatidic acid protects cervical cancer HeLa cells from apoptosis induced by doxorubicin hydrochloride

Cervical cancer is one of the most common types of gynecological tumors. Lysophosphatidic acid (LPA), as a bioactive lipid medium, plays an important role in numerous physiological and pathophysiological processes, including the stimulation of cell migration and tumor cell invasion. LPA is increased in the plasma of patients with cervical cancer. Doxorubicin hydrochloride (DOX) is used as a first-line drug in the treatment of cervical cancer in clinics, however, the effect and molecular mechanism of LPA on DOX-induced apoptosis in cervical cancer cells remain unclear. Therefore, the present study aimed to explore the effect and underlying molecular mechanism of LPA on DOX-induced apoptosis in cervical cancer cells. HeLa cells were treated as a control group or with LPA (10 µmol/l), DOX (4 µmol/l) or LPA (10 µmol/l) + DOX (4 µmol/l) for 24 h. Using transmission electron microscopy the results demonstrated that LPA reduced cell death and the degree of chromatin aggregation in DOX-induced HeLa cells. Reverse transcription-quantitative PCR demonstrated that LPA significantly downregulated caspase-3 mRNA expression levels in DOX-induced HeLa cells. Moreover, western blotting demonstrated that LPA significantly reduced caspase-3 and cleaved caspase-3 protein expression levels in DOX-induced HeLa, C33A and SiHa cells. Furthermore, flow cytometry demonstrated that LPA may prevent apoptosis in DOX-induced HeLa cells (P<0.05). Using dichloro-dihydro-fluorescein diacetate assay, it was demonstrated that LPA significantly reduced the intracellular ROS levels induced by DOX. In summary, the present study indicated that LPA may protect HeLa cells from apoptosis induced by DOX. These findings have provided experimental evidence that LPA may be a potential therapeutic target for the treatment of cervical cancer.

Novel Insight into the Potential Role of Acylglycerophosphate Acyltransferases Family Members on Triacylglycerols Synthesis in Buffalo

Acylglycerophosphate acyltransferases (AGPATs) are the rate-limiting enzymes for the de novo pathway of triacylglycerols (TAG) synthesis. Although AGPATs have been extensively explored by evolution, expression and functional studies, little is known on functional characterization of how many members of the AGPAT family are involved in TAG synthesis and their impact on the cell proliferation and apoptosis. Here, 13 AGPAT genes in buffalo were identified, of which 12 AGPAT gene pairs were orthologous between buffalo and cattle. Comparative transcriptomic analysis and real-time quantitative reverse transcription PCR (qRT-PCR) further showed that both AGPAT1 and AGPAT6 were highly expressed in milk samples of buffalo and cattle during lactation. Knockdown of AGPAT1 or AGPAT6 significantly decreased the TAG content of buffalo mammary epithelial cells (BuMECs) and bovine mammary epithelial cells (BoMECs) by regulating lipogenic gene expression (p < 0.05). Knockdown of AGPAT1 or AGPAT6 inhibited proliferation and apoptosis of BuMECs through the expression of marker genes associated with the proliferation and apoptosis (p < 0.05). Our data confirmed that both AGPAT1 and AGPAT6 could regulate TAG synthesis and growth of mammary epithelial cells in buffalo. These findings will have important implications for understanding the role of the AGPAT gene in buffalo milk performance.

Targeting lysophosphatidic acid receptor with Ki16425 impedes T cell lymphoma progression through apoptosis induction, glycolysis inhibition, and activation of antitumor immune response

Lysophosphatidic acid (LPA) is a small phospholipid that acts as an extracellular lipid mediator. It promotes cancer progression by altering a wide array of cellular processes, including apoptosis, survival, angiogenesis, invasion, and migration through binding with its cognate receptors. Intriguingly, our previous study showed that in vitro treatment of LPA induced survival of T lymphoma cells. Hence, the present investigation was designed to investigate the antitumor potential of Ki16425, an antagonist of LPA receptors, against T cell lymphoma. Our in vitro results showed inhibition of LPA-mediated survival and metabolic activity of T lymphoma cells by Ki16425. Further, in vivo experimental findings indicated the tumor retarding potential of Ki16425 against T cell lymphoma through apoptosis induction, glycolysis inhibition, and immunoactivation. The administration of Ki16425 triggered apoptosis by down-regulating the expression of Bcl2 and up-regulating p53, Bax, cleaved caspase-3, and Cyt c expression. Further, Ki16425 suppressed glycolytic activity with concomitantly decreased expression of GLUT3 and MCT1. Moreover, we also noticed an elevated level of NO and iNOS in tumor cells after Ki16425 administration which might also be responsible for apoptosis induction and suppressed glycolysis. Additionally, we observed an increased population of total leukocytes, lymphocytes, and monocytes along with increased thymocytes count and IL-2 and IFN-γ levels. Besides, we observed amelioration of tumor-induced kidney and liver damages by Ki16425. Taken together, this is the first study that demonstrates that LPA receptors could be potential future therapeutic targets for designing promising therapeutic strategies against T cell lymphoma.

CG11426 gene product negatively regulates glial population size in the Drosophila eye imaginal disc

Glial cells play essential roles in the nervous system. Although glial populations are tightly regulated, the mechanisms regulating the population size remain poorly understood. Since Drosophila glial cells are similar to the human counterparts in their functions and shapes, rendering them an excellent model system to understand the human glia biology. Lipid phosphate phosphatases (LPPs) are important for regulating bioactive lipids. In Drosophila, there are three known LPP-encoding genes: wunen, wunen-2, and lazaro. The wunens are important for germ cell migration and survival and septate junction formation during tracheal development. Lazaro is involved in phototransduction. In the present study, we characterized a novel Drosophila LPP-encoding gene, CG11426. Suppression of CG11426 increased glial cell number in the eye imaginal disc during larval development, while ectopic CG11426 expression decreased it. Both types of mutation also caused defects in axon projection to the optic lobe in larval eye-brain complexes. Moreover, CG11426 promoted apoptosis via inhibiting ERK signaling in the eye imaginal disc. Taken together, these findings demonstrated that CG11426 gene product negatively regulates ERK signaling to promote apoptosis for proper maintenance of the glial population in the developing eye disc.

Dysregulation of lysophospholipid signaling by p53 in malignant cells and the tumor microenvironment

The TP53 gene has been widely studied for its roles in cell cycle control, maintaining genome stability, activating repair mechanisms upon DNA damage, and initiating apoptosis should repair mechanisms fail. Thus, it is not surprising that mutations of p53 are the most common genetic alterations found in human cancer. Emerging evidence indicates that dysregulation of lipid metabolism by p53 can have a profound impact not only on cancer cells but also cells of the tumor microenvironment (TME). In particular, intermediates of the sphingolipid and lysophospholipid pathways regulate many cellular responses common to p53 such as cell survival, migration, DNA damage repair and apoptosis. The majority of these cellular events become dysregulated in cancer as well as cell senescence. In this review, we will provide an account on the seminal contributions of Prof. Lina Obeid, who deciphered the crosstalk between p53 and the sphingolipid pathway particularly in modulating DNA damage repair and apoptosis in non-transformed as well as transformed cells. We will also provide insights on the integrative role of p53 with the lysophosphatidic acid (LPA) signaling pathway in cancer progression and TME regulation.

Lysophosphatidic acid promotes survival of T lymphoma cells by altering apoptosis and glucose metabolism

Lysophosphatidic acid (LPA) is a bioactive lipid, which plays an indispensable role in various physiological and pathological processes. Moreover, an elevated level of LPA has been observed in malignancies of different origins and implicated in their progression via modulation of proliferation, apoptosis, invasion and metastasis. Interestingly, few recent reports suggest a pivotal role of LPA-modulated metabolism in oncogenesis of ovarian cancer. However, little is understood regarding the role of LPA in the development and progression of T cell malignancies, which are considered as one of the most challenging neoplasms for clinical management. Additionally, mechanisms underlying the LPA-dependent modulation of glucose metabolism in T cell lymphoma are also not known. Therefore, the present study was undertaken to explore the role of LPA-altered apoptosis and glucose metabolism on the survival of T lymphoma cells. Observations of this investigation suggest that LPA supports survival of T lymphoma cells via altering apoptosis and glucose metabolism through changing the level of reactive species, namely nitric oxide and reactive oxygen species along with expression of various survival and glucose metabolism regulatory molecules, including hypoxia-inducible factor 1-alpha, p53, Bcl2, and glucose transporter 3, hexokinase II, pyruvate kinase muscle isozyme 2, monocarboxylate transporter 1, pyruvate dehydrogenase kinase 1. Taken together' the results of the present investigation decipher the novel mechanisms of LPA-mediated survival of T lymphoma cells via modulation of apoptosis and glucose metabolism.

Lipid Phosphate Phosphatases and Cancer

Lipid phosphate phosphatases (LPPs) are a group of three enzymes (LPP1–3) that belong to a phospholipid phosphatase (PLPP) family. The LPPs dephosphorylate a wide spectrum of bioactive lipid phosphates, among which lysophosphatidate (LPA) and sphingosine 1-phosphate (S1P) are two important extracellular signaling molecules. The LPPs are integral membrane proteins, which are localized on plasma membranes and intracellular membranes, including the endoplasmic reticulum and Golgi network. LPPs regulate signaling transduction in cancer cells and demonstrate different effects in cancer progression through the breakdown of extracellular LPA and S1P and other intracellular substrates. This review is intended to summarize an up-to-date understanding about the functions of LPPs in cancers.

Interfering Human Papillomavirus E6/E7 Oncogenes in Cervical Cancer Cells Inhibits the Angiogenesis of Vascular Endothelial Cells via Increasing miR-377 in Cervical Cancer Cell-Derived Microvesicles

Background

The dysregulation of the human papillomavirus 18 E6 and E7 oncogenes plays a critical role in the angiogenesis of cervical cancer (CC), including the proliferation, migration, and tube formation of vascular endothelial cells. Interfering E6/E7 increases the number of CC cell-derived microvesicles (CC-MVs). Additionally, microRNAs (miRNAs) can modulate CC angiogenesis and can be encapsulated in MVs.

Objective

We aim to investigate whether E6/E7 affects CC angiogenesis via regulating miRNAs in CC-MVs.

Methods

CC-MVs were isolated from a CC cell line (HeLa) which were transfected with small interfering RNAs (siRNAs) against E6/E7 or co-transfected with miR-377 mimics/inhibitors. The expression of several miRNAs in CC-MVs was detected using quantitative real-time PCR. After co-incubating CC-MVs with human umbilical vein endothelial cells (HUVECs), cell proliferation, migration, and tube formation of HUVECs were determined using cell counting kit-8, transwell, and tube formation assays, respectively.

Results

MiR-377 was increased in E6/E7-interfering CC-MVs. Overexpressing miR-377 in CC-MVs suppressed HUVEC proliferation, migration, and tube formation. LPAR2, the cell surface G protein-coupled receptor, was the downstream target of miR-377 in HUVECs. The co-transfection of E6/E7 siRNAs and miR-377 inhibitors in CCs negated the effect of E6/E7 siRNAs on the elevation of miR-377 in CC-MVs. In HUVECs, the co-transfection of E6/E7 siRNAs and miR-377 inhibitors restored the LPAR2 expression which was reduced by the E6/E7 siRNA transfection. Meanwhile, miR-377 mimic reduced LPAR2 expression and inhibited HUVEC proliferation, migration, and tube formation, while such response was negated by LPAR2 overexpression.

Conclusion

Interfering E6/E7 increased miR-377 in CC-MVs, and overexpressing miR-377 in CC-MVs inhibited angiogenesis of HUVECs via reducing LPAR2.

Role of the autotaxin-lysophosphatidate axis in the development of resistance to cancer therapy

Autotaxin (ATX) is a secreted enzyme that hydrolyzes lysophosphatidylcholine to produce lysophosphatidate (LPA), which signals through six G-protein coupled receptors (GPCRs). Signaling through LPA is terminated by its degradation by a family of three lipid phosphate phosphatases (LPPs). LPP1 also attenuates signaling downstream of the activation of LPA receptors and some other GPCRs. The ATX-LPA axis mediates a plethora of activities such as cell proliferation, survival, migration, angiogenesis and inflammation, which perform an important role in facilitating wound healing. This wound healing response is hijacked by cancers where there is decreased expression of LPP1 and LPP3 and increased expression of ATX. This maladaptive regulation of LPA signaling also causes chronic inflammation, which has been recognized as one of the hallmarks in cancer. The increased LPA signaling promotes cell survival and migration and attenuates apoptosis, which stimulates tumor growth and metastasis. The wound healing functions of increased LPA signaling also protect cancer cells from effects of chemotherapy and radiotherapy. In this review, we will summarize knowledge of the ATX-LPA axis and its role in the development of resistance to chemotherapy and radiotherapy. We will also offer insights for developing strategies of targeting ATX-LPA axis as a novel part of cancer treatment. This article is part of a Special Issue entitled Lysophospholipids and their receptors: New data and new insights into their function edited by Susan Smyth, Viswanathan Natarajan and Colleen McMullen.

Restoration of Mal overcomes the defects of apoptosis in lung cancer cells

BACKGROUND AND AIMS

Cancer is one of the life-threatening diseases of human beings; the pathogenesis of cancer remains to be further investigated. Toll like receptor (TLR) activities are involved in the apoptosis regulation. This study aims to elucidate the role of Mal (MyD88-adapter-like) molecule in the apoptosis regulation of lung cancer (LC) cells.

METHODS

The LC tissues were collected from LC patients. LC cells and normal control (NC) cells were isolated from the tissues and analyzed by pertinent biochemical and immunological approaches.

RESULTS

We found that fewer apoptotic LC cells were induced by cisplatin in the culture as compared to NC cells. The expression of Fas ligand (FasL) was lower in LC cells than that in NC cells. FasL mRNA levels declined spontaneously in LC cells. A complex of FasL/TDP-43 was detected in LC cells. LC cells expressed less Mal than NC cells. Activation of Mal by lipopolysaccharide (LPS) increased TDP-43 expression in LC cells. TDP-43 formed a complex with FasL mRNA to prevent FasL mRNA from decay. Reconstitution of Mal or TDP-43 restored the sensitiveness of LC cells to apoptotic inducers.

CONCLUSIONS

LC cells express low Mal levels that contributes to FasL mRNA decay through impairing TDP-43 expression. Reconstitution of Mal restores sensitiveness of LC cells to apoptosis inducers that may be a novel therapeutic approach for LC treatment.

Targeting Lysophosphatidic Acid in Cancer: The Issues in Moving from Bench to Bedside

Since the clear demonstration of lysophosphatidic acid (LPA)'s pathological roles in cancer in the mid-1990s, more than 1000 papers relating LPA to various types of cancer were published. Through these studies, LPA was established as a target for cancer. Although LPA-related inhibitors entered clinical trials for fibrosis, the concept of targeting LPA is yet to be moved to clinical cancer treatment. The major challenges that we are facing in moving LPA application from bench to bedside include the intrinsic and complicated metabolic, functional, and signaling properties of LPA, as well as technical issues, which are discussed in this review. Potential strategies and perspectives to improve the translational progress are suggested. Despite these challenges, we are optimistic that LPA blockage, particularly in combination with other agents, is on the horizon to be incorporated into clinical applications.

Lysophosphatidic acid enhances neointimal hyperplasia following vascular injury through modulating proliferation, autophagy, inflammation and oxidative stress

Lysophosphatidic acid (LPA), which is one of the intermediate products of membrane phospholipid metabolism, is a bioactive phospholipid that possesses diverse activities. In the present study, the effects of LPA on neointimal formation following vascular injury were investigated. A carotid artery balloon injury model was employed in the present study, and following vascular injury, rats received an intraperitoneal injection of 1 mg/kg LPA. Subsequently, histopathological alterations were assessed by hematoxylin and eosin staining, the expression levels of proliferating cell nuclear antigen (PCNA) were detected by immunohistochemistry, apoptosis was assessed via a terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, and the expression levels of apoptosis-associated and autophagy-associated proteins were detected by western blotting. In addition, inflammatory and oxidative stress-associated factors were assessed by reverse transcription-quantitative polymerase chain reaction or corresponding kits. The results of the present study demonstrated that LPA enhanced vascular injury-induced neointimal hyperplasia. LPA further elevated the expression levels of PCNA in the injured carotid artery tissues. LPA exhibited no effect on apoptosis in carotid artery tissues, whereas it modulated autophagy in the injured carotid artery tissues. Furthermore, LPA enhanced vascular injury-induced inflammation and oxidative stress. The present study demonstrated that LPA may enhance neointimal hyperplasia following vascular injury by modulating proliferation, autophagy, inflammation and oxidative stress, but not apoptosis. Furthermore LPA may contribute to the pathology of atherosclerosis and may be considered a promising therapeutic target for the treatment of atherosclerosis.

Expression of factors involved in apoptosis and cell survival is correlated with enzymes synthesizing lysophosphatidic acid and its receptors in granulosa cells originating from different types of bovine ovarian follicles

BACKGROUND

Lysophosphatidic acid (LPA) regulates reproductive processes in the cow. Ovarian granulosa cells play a pivotal role in follicle growth and development. Nevertheless, the role of LPA in the local regulation of granulosa cell function in different follicle categories in the bovine ovary has not been investigated.

METHODS

Ovarian follicles were divided into healthy, transitional and atretic categories. The expression levels of AX, PLA2, LPARs and factors involved in apoptosis and cell survival processes in granulosa cells in different types of follicles were measured by real-time PCR. The correlations between the expression levels of AX, PLA2, LPARs and the examined factors were measured. The immunolocalization of AX, PLA2 and LPARs in different ovarian follicles was examined by immunohistochemistry. Statistical analyses were conducted in GraphPad using a one-way ANOVA followed by the Kruskal-Wallis multiple comparison test or a correlation analysis followed by Pearson's test.

RESULTS

The expression levels of AX, PLA2 and LPARs, with the major role of LPAR2 and PLA2, were found in the granulosa cells originating from different follicle types. The expression levels of the factors involved in cell apoptosis (TNFα and its receptors, FAS, FASL, CASP3, CASP8, β-glycan, and DRAK2) were significantly higher in the granulosa cells of the atretic follicles compared to the healthy follicles. A number of correlations between LPARs, AX, PLA2 and factors associated with apoptosis were observed in the atretic but not in the healthy follicles. A greater expression of the factors involved in differentiation and proliferation in the granulosa cells (DICE1 and SOX2) was found in the healthy follicles in comparison with the atretic. A number of correlations between LPARs, AX, PLA2 and the factors associated with cell survival were observed in the healthy but not in the atretic follicles.

CONCLUSIONS

Granulosa cells are the target of LPA action and the source of LPA synthesis in the bovine ovarian follicle. We suggest that the participation of LPA in apoptosis in the atretic follicles mainly occurs through the regulation of TNF-α-dependent and caspase-induced pathways. In the transitional follicles, LPA might influence the inhibins to shift the balance between the number of healthy and atretic follicles. In the healthy follicle type, LPA, acting via LPAR1, might regulate MCL1 and estradiol-stimulating ERβ mRNA expression, leading to the stimulation of anti-apoptotic processes in the granulosa cells and their differentiation and proliferation.

Lysophosphatidic Acid Pretreatment Attenuates Myocardial Ischemia/Reperfusion Injury in the Immature Hearts of Rats

The cardioprotection of the immature heart during cardiac surgery remains controversial due to the differences between the adult heart and the newborn heart. Lysophosphatidic acid (LPA) is a small bioactive molecule with diverse functions including cell proliferation and survival via its receptor: LPA₁–LPA₆. We previously reported that the expressions of LPA₁ and LPA₃ in rat hearts were much higher in immature hearts and then declined rapidly with age. In this study, we aimed to investigate whether LPA signaling plays a potential protective role in immature hearts which had experienced ischemia/reperfusion (I/R) injury. The results showed that in Langendorff-perfused immature rat hearts (2 weeks), compared to I/R group, LPA pretreatment significantly enhanced the cardiac function, attenuated myocardial infarct size and CK-MB release, decreased myocardial apoptosis and increased the expression of pro-survival signaling molecules. All these effects could be abolished by Ki16425, an antagonist to LPA₁ and LPA₃. Similarly, LPA pretreatment protected H9C2 from hypoxia-reoxygenation (H/R) induced apoptosis and necrosis in vitro. The mechanisms underlying the anti-apoptosis effects were related to activation of the phosphatidylinositol 3-kinase (PI3K)/protein kinas B (AKT) signaling pathways as well as phosphorylation of the downstream effector of AKT, glycogen synthase kinase 3 beta (GSK3β), through LPA₁ and/or LPA₃. What's more, we found that LPA preconditioning increased glucose uptake of H9C2 subjected to H/R by the activation of AMP-Activated Protein Kinase (AMPK) but not the translocation of GLUT4. In conclusion, our study indicates that LPA is a potent survival factor for immature hearts against I/R injuries and has the potential therapeutic function as a cardioplegia additive for infantile cardiac surgery.

MCL-1 is the key target of adjuvant chemotherapy to reverse the cisplatin-resistance in NSCLC

Cisplatin is one of the most effective chemotherapeutic agents for the treatment of lung cancer. However, the acquired resistance occurred in cancer cells limits the clinical application of cisplatin. MCL-1, which is an important member in the pro-survival Bcl-2 family, plays a critical role in multidrug resistance (MDR). The aim of the present study is to investigate the value of Pan-Bcl-2 inhibitor as sensitizer for the chemotherapy of cisplatin-resistant non-small cell lung cancer (NSCLC) cells. We found the obatoclax but not the ABT-737 significantly decreased the IC50 (half maximal inhibitory concentration) of cisplatin in cisplatin-resistant NSCLC cells. Furthermore, we demonstrated that the mechanism of obatoclax-promoted cell death induced by cisplatin was dependent on the inhibition of MCL-1, which couldn't be inhibited by ABT-737 but is the target of obatoclax. Moreover, inhibition of MCL-1 recovered the function of NOXA and BAK in cisplatin-resistant NSCLC cells, leading to the promotion of mitochondrial apoptosis induced by cisplatin. Interestingly, our date indicated the obatoclax also reversed the cross-resistance in cisplatin-resistant NSCLC cells. Therefore, we demonstrated that the targeted therapy with MCL-1 inhibitors, such as obatoclax, may represent a novel strategy for cancer therapy.

G-Protein-Coupled Lysophosphatidic Acid Receptors and Their Regulation of AKT Signaling

A hallmark of G-protein-coupled receptors (GPCRs) is their ability to recognize and respond to chemically diverse ligands. Lysophospholipids constitute a relatively recent addition to these ligands and carry out their biological functions by activating G-proteins coupled to a large family of cell-surface receptors. This review aims to highlight salient features of cell signaling by one class of these receptors, known as lysophosphatidic acid (LPA) receptors, in the context of phosphatidylinositol 3-kinase (PI3K)-AKT pathway activation. LPA moieties efficiently activate AKT phosphorylation and activation in a multitude of cell types. The interplay between LPA, its receptors, the associated Gαi/o subunits, PI3K and AKT contributes to the regulation of cell survival, migration, proliferation and confers chemotherapy-resistance in certain cancers. However, detailed information on the regulation of PI3K-AKT signals induced by LPA receptors is missing from the literature. Here, some urgent issues for investigation are highlighted.