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 increases SLC26A3 expression in inflamed intestine and reduces diarrheal severity in C57BL/6 mice with dextran-sodium-sulfate-induced colitis

Background Diarrhea is a common clinical feature of ulcerative colitis resulting from unbalanced intestinal fluid and salt absorption and secretion.The Cl-/HCO3-exchanger SLC26A3 is strongly expressed in the mid-distal colon and plays an essential role in colonic Cl-absorption and HCO3-secretion.Sic26a3 expression is up-regulated by lysophosphatidic acid （LPA） in vitro.Our study was designed to investigate the effects of LPA on SLC26A3 expression and the diarrheal phenotype in a mouse colitis model.Methods Colitis was induced in C57BL/6 mice by adding 4％ of dextran sodium sulfate （DSS） to the drinking water.The mice were assigned to LPA treatment DSS group,phosphate-buffered saline （PBS） treatment DSS group,DSS only group and untreated mice with a completely randomized design.Diarrhea severity was evaluated by measuring mice weight,disease activity index （DAI）,stool water content and macroscopic evaluation of colonic damage.The effect of LPA treatment on Sic26a3 mRNA level and protein expression in the different groups of mice was investigated by quantitative PCR and Western blotting.Results All mice treated with DSS lost weight,but the onset and severity of weight loss was attenuated in the LPA treatment DSS group.The increases in stool water content and the macroscopic inflammation score in LPA treatment DSS group were significantly lower compared to DSS control group or PBS treatment DSS group （（18.89±8.67）％ vs.（28.97±6.95）％ or （29.48±6.71）％,P=0.049,P=0.041,respectively and 2.67±0.81 vs.4.5±0.83 or 4.5±0.54,P=0.020,P=0.006,respectively）,as well as the increase in DAI （P=0.004,P=0.008,respectively）.LPA enema resulted in higher Slc26a3 mRNA and protein expression levels compared to PBS-treated and untreated DSS colitis mice.Conclusion LPA increases Slc26a3 expression in the inflamed intestine and reduces diarrhea severity in DSS-induced colitis,suggesting LPA might be a therapeutic strategy in the treatment of colitis associated diarrhea.

Electrochemically derived nanographene oxide activates endothelial tip cells and promotes angiogenesis by binding endogenous lysophosphatidic acid

Graphene oxide(GO)exhibits good mechanical and physicochemical characteristics and has extensive application prospects in bone tissue engineering.However,its effect on angiogenesis is unclear,and its potential toxic effects are heavily disputed.Herein,we found that nanographene oxide(NGO)synthesized by one-step water electrolytic oxidation is smaller and shows superior biocompatibility.Moreover,NGO significantly enhanced angiogenesis in calvarial bone defect areas in vivo,providing a good microenvironment for bone regeneration.Endothelial tip cell differentiation is an important step in the initiation of angiogenesis.We verified that NGO activates endothelial tip cells by coupling with lysophosphatidic acid(LPA)in serum via strong hydrogen bonding interactions,which has not been reported.In addition,the mechanism by which NGO promotes angiogenesis was systematically studied.NGO-coupled LPA activates LPAR6 and facilitates the formation of migratory tip cells via Hippo/Yes-associated protein(YAP)independent of reactive oxygen species(ROS)stimulation or additional complex modifications.These results provide an effective strategy for the application of electrochemically derived NGO and more insight into NGO-mediated angiogenesis.

Modulation of Na_v1.8 by Lysophosphatidic Acid in the Induction of Bone Cancer Pain

Given that lysophosphatidic acid（LPA） and the tetrodotoxin-resistant sodium channel Na_v1.8 are both involved in bone cancer pain, the present study was designed to investigate whether crosstalk between the LPA receptor LPA_1（also known as EDG2） and Na_v1.8 in the dorsal root ganglion（DRG） contributes to the induction of bone cancer pain. We showed that the EDG2 antagonist Ki16198 blocked the mechanical allodynia induced by intrathecal LPA in na？ve rats and attenuated mechanical allodynia in a rat model of bone cancer. EDG2 and Na_v1.8expression in L_（4-6）DRGs was upregulated following intrathecal or hindpaw injection of LPA. EDG2 and Na_v1.8expression in ipsilateral L_（4-6）DRGs increased with the development of bone cancer. Furthermore, we showed that EDG2 co-localized with Na_v1.8 and LPA remarkably enhanced Na_v1.8 currents in DRG neurons, and this was blocked by either a protein kinase C（PKC） inhibitor or a PKCe inhibitor. Overall, we demonstrated the modulation of Na_v1.8 by LPA in DRG neurons, and that this probably underlies the peripheral mechanism by which bone cancer pain is induced.

Crystal structures and biochemical studies of human lysophosphatidic acid phosphatase type 6

Lysophosphatidic acid(LPA)is an important bioac-tive phospholipid involved in cell signaling through G-protein-coupled receptors pathways.It is also involved in balancing the lipid composition inside the cell,and modulates the function of lipid rafts as an intermediate in phospholipid metabolism.Because of its involvement in these important processes,LPA degradation needs to be regulated as precisely as its production.Lysophospha-tidic acid phosphatase type 6(ACP6)is an LPA-specifi c acid phosphatase that hydrolyzes LPA to monoacylglyc-erol(MAG)and phosphate.Here,we report three crystal structures of human ACP6 in complex with malonate,L-(+)-tartrate and tris,respectively.Our analyses revealed that ACP6 possesses a highly conserved Rossmann-fold-like body domain as well as a less conserved cap domain.The vast hydrophobic substrate-binding pocket,which is located between those two domains,is suitable for ac-commodating LPA,and its shape is different from that of other histidine acid phosphatases,a fact that is consistent with the observed difference in substrate preferences.Our analysis of the binding of three molecules in the active site reveals the involvement of six conserved and crucial residues in binding of the LPA phosphate group and its catalysis.The structure also indicates a water-supplying channel for substrate hydrolysis.Our structural data are consistent with the fact that the enzyme is active as a monomer.In combination with additional mutagenesis and enzyme activity studies,our structural data provide important insights into substrate recognition and the mechanism for catalytic activity of ACP6.

Rho-associated protein kinase modulates neurite extension by regulating microtubule remodeling and vinculin distribution

Rho-associated protein kinase is an essential regulator of cytoskeletal dynamics during the process of neurite extension. However, whether Rho kinase regulates microtubule remodeling or the distri- bution of adhesive proteins to mediate neurite outgrowth remains unclear. By specifically modulat- ing Rho kinase activity with pharmacological agents, we studied the morpho-dynamics of neurite outgrowth. We found that lysophosphatidic acid, an activator of Rho kinase, inhibited neurite out- growth, which could be reversed by Y-27632, an inhibitor of Rho kinase. Meanwhile, reorganization of microtubules was noticed during these processes, as indicated by their significant changes in the soma and growth cone. In addition, exposure to lysophosphatidic acid led to a decreased mem- brane distribution of vinculin, a focal adhesion protein in neurons, whereas Y-27632 recruited vin- culin to the membrane. Taken together, our data suggest that Rho kinase regulates rat hippocampal neurite growth and microtubule formation via a mechanism associated with the redistribution of vinculin.

Reductive lipid nanoparticles loaded with vinorelbine inhibit chemotherapy-induced invasion of cancer cells by modulating ENPP2

Cancer is a predominant culprit behind worldwide death and accounts for up to 10 million deaths every year.Chemotherapy is the primary therapeutic method employed for cancer in clinical settings and is essential in controlling tumor progression.Despite the advances in this field,tumor invasion and metastasis during treatment remain a significant cause of treatment failure.Nevertheless,the underlying mechanisms involving such a disappointing phenomenon are still not fully elucidated.Vinorelbine(VNB)extends the lifespan of many cancer patients in the clinic as an emerging chemotherapy drug approved by Food and Drug Administration(FDA).However,VNB-induced tumor metastasis is still an intractable problem,which may be closely related to the abnormal oxidative stress generated during VNB-mediated treatment.Hence,the study aims to construct a reductive nanosystem loaded with VNB,called VNB-VNP,to improve cancer cure rates and reduce tumor metastasis.With the reductive component vitamin E,VNB-VNP can effectively reduce oxidative stress and significantly outperform free VNB in preventing tumor progression.The transcriptome analysis shows that VNB-VNP can alleviate the over-expression of ectonucleotide pyrophosphatase/phosphodiesterase 2(ENPP2),which may be the main reason why VNB-VNP can inhibit tumor invasion and metastasis.Overall,the research designs a new platform for VNB treatment,which demonstrates promising efficacy in inhibiting neoplastic progression and identifies a new mechanism associated with VNB-induced tumor metastasis,which may offer several valuable references for enhancing chemotherapy efficacy in clinical anti-tumor therapy.

Acupuncture stimulation of Yamen(GV 15), Fengfu(GV 16), Baihui(GV 20), Shuigou(GV 26) and Hegu(LI 4) reduces brain microglia activation in a traumatic brain injury rat model

OBJECTIVE: To evaluate the effect of acupuncture on neuroinflammation in traumatic brain injury(TBI) rats by stimulating Yamen(GV 15), Fengfu(GV16), Baihui(GV 20), Shuigou(GV 26) and Hegu(LI 4)acupoints and to investigate the mechanism underpinning this effect.METHODS: A TBI model was induced in SpragueDawley rats using Feeney's freefall impact method.Acupuncture to stimulate the Yamen(GV 15), Fengfu(GV 16), Baihui(GV 20), Shuigou(GV 26) and Hegu(LI 4) acupoints was performed on the TBI rats. After 3 consecutive days of acupuncture treatment, we investigated signal molecules, receptors and microglia related to neuroinflammation in brain tissue of the TBI rats and analyzed the possi-ble mechanism underlying the effect of acupuncture on neuroinflammation.RESULTS: After the acupuncture treatment, ionized calcium binding adaptor molecule 1(Iba1), a protein specific to microglia, was investigated. In the cortical layer of damaged brain tissue in TBI rats,the Iba1-positive area was 3.3% ± 0.9% in the rats that received acupuncture compared with 5.2% ±1.4% in the TBI rats that did not receive acupuncture, and the microglia were smaller with more slender protrusions in the acupuncture-treated rats.This result indicates that acupuncture can significantly reduce microglia activation in TBI rats. A possible mechanism for this effect is that acupuncture reduces the expression of autotaxin and lysophosphatidic acid. Together, these constitute the autotaxin-lysophosphatidic acid axis, which induces microglial activation in the brains of TBI rats. Acupuncture treatment may downregulate the expression of Lysophosphatidic acid(LPA) receptor(LPAR) 1 and LPAR2 on the microglial cytomembrane, which affects the microglia activation process.CONCLUSION: Acupuncture stimulating the Yamen(GV 15), Fengfu(GV 16), Baihui(GV 20),Shuigou(GV 26) and Hegu(LI 4) acupoints can effectively inhibit the development of neuroinflammation after TBI. One possible mechanism for this effect is that acupuncture downregulates LPA synthesis and affects the LPA-LPAR pathway by inhibiting LPAR1 and LPAR2, thereby inhibiting microglial activation and reducing neuroinflammation.

Bioactive lipids and cancer metastasis to bone

Bioactive lipids constitute a large family of molecules considered as inflammatory mediators.Among them,lysophosphatidic acid(LPA),sphingosine 1-phosphate(S1P),and eicosanoids(prostanoids such as PGE2 and leukotrienes such as LTB4,LTC4,and LTD4)play a central role in the pathophysiology of several inflammatory diseases.However,it has long been known that these bioactive lipids are also involved in cancer,mainly because of their ability to control the pro-inflammatory microenvironment of tumors as well as their ability to act directly on tumor cells promoting cell proliferation,migration,and survival.Recently,there has been increased interest in determining how these lipid mediators orchestrate tumor development and metastasis.Bone metastases result from a complex dialogue between tumor cells and bone cells.Recent findings demonstrate that all these bioactive lipids can profoundly affect bone metabolism by acting positively or negatively on both osteoblasts and osteoclasts.This review gives an overview of previous findings demonstrating direct involvement of LPA,S1P,and PGE2 in bone metastasis.This review also emphasizes the recent findings that characterize the activity of these bioactive lipids directly on bone cells and how these activities could be integrated into the complex molecular mechanisms leading to bone metastasis formation and progression.