Understanding the modulations of glycero-lysophospholipids in an elastase-induced murine emphysema model.

BACKGROUND: Increasing evidence indicates that bioactive lipid mediators are involved in chronic obstructive pulmonary disease (COPD) pathogenesis. Recently, glycero-lysophospholipids, such as lysophosphatidic acid (LysoPA) and lysophosphatidylserine (LysoPS), have been recognized as significant inflammation-related lipid mediators. However, their association with COPD remains unclear. METHODS: We used an elastase-induced murine emphysema model to analyze the levels of lysophospholipids and diacyl-phospholipids in the lungs. Additionally, we assessed the expression of LysoPS-related genes and published data on smokers. RESULTS: In the early phase of an elastase-induced murine emphysema model, the levels of LysoPS and its precursor (phosphatidylserine [PS]) were significantly reduced, without significant modulations in other glycero-lysophospholipids. Additionally, there was an upregulation in the expression of lysoPS receptors, specifically GPR34, observed in the lungs of a cigarette smoke-exposed mouse model and the alveolar macrophages of human smokers. Elastase stimulation induces GPR34 expression in a human macrophage cell line in vitro. CONCLUSIONS: Elastase-induced lung emphysema affects the LysoPS/PS-GPR34 axis, and cigarette smoking or elastase upregulates GPR34 expression in alveolar macrophages. This novel association may serve as a potential pharmacological target for COPD treatment.

Identification of novel biomarkers of hepatocellular carcinoma by high-definition mass spectrometry: Ultrahigh-performance liquid chromatography quadrupole time-of-flight mass spectrometry and desorption electrospray ionization mass spectrometry imaging.

RATIONALE: Hepatocellular carcinoma (HCC) is a highly malignant disease for which the development of prospective or prognostic biomarkers is urgently required. Although metabolomics is widely used for biomarker discovery, there are some bottlenecks regarding the comprehensiveness of detected features, reproducibility of methods, and identification of metabolites. In addition, information on localization of metabolites in tumor tissue is needed for functional analysis. Here, we developed a wide-polarity global metabolomics (G-Met) method, identified HCC biomarkers in human liver samples by high-definition mass spectrometry (HDMS), and demonstrated localization in cryosections using desorption electrospray ionization MS imaging (DESI-MSI) analysis. METHODS: Metabolic profiling of tumor (n = 38) and nontumor (n = 72) regions in human livers of HCC was performed by an ultrahigh-performance liquid chromatography quadrupole time-of-flight MS (UHPLC/QTOFMS) instrument equipped with a mixed-mode column. The HCC biomarker candidates were extracted by multivariate analyses and identified by matching values of the collision cross section and their fragment ions on the mass spectra obtained by HDMS. Cryosections of HCC livers, which included both tumor and nontumor regions, were analyzed by DESI-MSI. RESULTS: From the multivariate analysis, m/z 904.83 and m/z 874.79 were significantly high and low, respectively, in tumor samples and were identified as triglyceride (TG) 16:0/18:1(9Z)/20:1(11Z) and TG 16:0/18:1(9Z)/18:2(9Z,12Z) using the synthetic compounds. The TGs were clearly localized in the tumor or nontumor areas of the cryosection. CONCLUSIONS: Novel biomarkers for HCC were identified by a comprehensive and reproducible G-Met method with HDMS using a mixed-mode column. The combination analysis of UHPLC/QTOFMS and DESI-MSI revealed that the different molecular species of TGs were associated with tumor distribution and were useful for characterizing the progression of tumor cells and discovering prospective biomarkers.

Increased serum mitochondrial creatine kinase activity as a risk for hepatocarcinogenesis in chronic hepatitis C patients.

Serum mitochondrial creatine kinase (MtCK) activity was reportedly increased in cirrhotic patients although less prominent than that in hepatocellular carcinoma (HCC) patients. To elucidate the clinical significance of serum MtCK activity in chronic liver disease, 171 chronic hepatitis C patients were enrolled. Serum MtCK activity in study subjects was correlated with serum albumin, platelet counts, liver stiffness values and serum aspartate and alanine aminotransferase. In mouse fibrotic liver induced by bile duct ligation, ubiquitous MtCK mRNA and protein expressions were significantly enhanced and its immunoreactivity was increased, predominantly in hepatocytes. During the mean follow-up period of 2.7 years, HCC developed in 21 patients, in whom serum MtCK activity was significantly higher than that in patients without HCC development. Multivariate Cox regression analysis revealed that higher serum MtCK activity was a risk for HCC development. A cutoff value of MtCK for the prediction of HCC development was determined as 9.0 U/L on receiver operating characteristics analysis, where area under receiver operating characteristics curve was 0.754, with a sensitivity of 61.9%, a specificity of 92.8% and a high negative predictive value of 94.2%. Cumulative incidence of HCC was significantly higher in patients with serum MtCK activity of >9.0 U/L compared to those with serum MtCK activity of ≤ 9.0 U/L even in patients with elevated liver stiffness value, >15 kPa. In conclusion, serum MtCK activity may be increased correlatively with the stage of liver fibrosis and hepatocellular damage. Increased serum MtCK activity is an independent risk for hepatocarcinogenesis in chronic hepatitis C patients.

High ubiquitous mitochondrial creatine kinase expression in hepatocellular carcinoma denotes a poor prognosis with highly malignant potential.

We previously reported the increased serum mitochondrial creatine kinase (MtCK) activity in patients with hepatocellular carcinoma (HCC), mostly due to the increase in ubiquitous MtCK (uMtCK), and high uMtCK mRNA expression in HCC cell lines. We explored the mechanism(s) and the relevance of high uMtCK expression in HCC. In hepatitis C virus core gene transgenic mice, known to lose mitochondrial integrity in liver and subsequently develop HCC, uMtCK mRNA and protein levels were increased in HCC tissues but not in non-tumorous liver tissues. Transient overexpression of ankyrin repeat and suppressor of cytokine signaling box protein 9 (ASB9) reduced uMtCK protein levels in HCC cells, suggesting that increased uMtCK levels in HCC cells may be caused by increased gene expression and decreased protein degradation due to reduced ASB9 expression. The reduction of uMtCK expression by siRNA led to increased cell death, and reduced proliferation, migration and invasion in HCC cell lines. Then, consecutive 105 HCC patients, who underwent radiofrequency ablation with curative intent, were enrolled to analyze their prognosis. The patients with serum MtCK activity >19.4 U/L prior to the treatment had significantly shorter survival time than those with serum MtCK activity ≤ 19.4 U/L, where higher serum MtCK activity was retained as an independent risk for HCC-related death on multivariate analysis. In conclusion, high uMtCK expression in HCC may be caused by hepatocarcinogenesis per se but not by loss of mitochondrial integrity, of which ASB9 could be a negative regulator, and associated with highly malignant potential to suggest a poor prognosis.

Alzheimer's disease manifests abnormal sphingolipid metabolism.

Introduction: Alzheimer's disease (AD) is associated with disturbed metabolism, prompting investigations into specific metabolic pathways that may contribute to its pathogenesis and pathology. Sphingolipids have garnered attention due to their known physiological impact on various diseases. Methods: We conducted comprehensive profiling of sphingolipids to understand their possible role in AD. Sphingolipid levels were measured in AD brains, Cerad score B brains, and controls, as well as in induced pluripotent stem (iPS) cells (AD, PS, and control), using liquid chromatography mass spectrometry. Results: AD brains exhibited higher levels of sphingosine (Sph), total ceramide 1-phosphate (Cer1P), and total ceramide (Cer) compared to control and Cerad-B brains. Deoxy-ceramide (Deoxy-Cer) was elevated in Cerad-B and AD brains compared to controls, with increased sphingomyelin (SM) levels exclusively in Cerad-B brains. Analysis of cell lysates revealed elevated dihydroceramide (dhSph), total Cer1P, and total SM in AD and PS cells versus controls. Multivariate analysis highlighted the relevance of Sph, Cer, Cer1P, and SM in AD pathology. Machine learning identified Sph, Cer, and Cer1P as key contributors to AD. Discussion: Our findings suggest the potential importance of Sph, Cer1P, Cer, and SM in the context of AD pathology. This underscores the significance of sphingolipid metabolism in understanding and potentially targeting mechanisms underlying AD.

Development of an advanced liquid chromatography-tandem mass spectrometry measurement system for simultaneous sphingolipid analysis.

Mass spectrometry-based lipidomics approaches offer valuable tools for the detection and quantification of various lipid species, including sphingolipids. The present study aimed to develop a new method to simultaneously detect various sphingolipid species that applies to diverse biological samples. We developed and validated a measurement system by employing a single-column liquid chromatography-mass spectrometry system utilizing a normal-phase separation mode with positive ionization. The measurement system provided precision with a coefficient of variant below 20% for sphingolipids in all types of samples, and we observed good linearity in diluted serum samples. This system can measure the following sphingolipids: sphingosine 1-phosphate (S1P), sphingosine (Sph), dihydroS1P (dhS1P), dihydroSph (dhSph), ceramide 1-phosphate (Cer1P), hexosylceramide (HexCer), lactosylceramide (LacCer), dh-ceramide, deoxy-ceramide, deoxy-dh-ceramide, and sphingomyelin (SM). By measuring these sphingolipids in cell lysates where S1P lyase expression level was modulated, we could observe significant and dynamic modulations of sphingolipids in a comprehensive manner. Our newly established and validated measurement system can simultaneously measure many kinds of sphingolipids in biological samples. It holds great promise as a valuable tool for laboratory testing applications to detect overall modulations of sphingolipids, which have been proposed to be involved in pathogenesis processes in a series of elegant basic research studies.

Cerebrospinal Fluid Lysophosphatidylcholine Species for Distinguishing Narrowing of the Lumbar Spine.

BACKGROUND: Reoperation, sometimes multiple, is common with progressively worse outcomes in patients with degenerative lumbar spine diseases. Lysophosphatidylcholine (LPC), a precursor of lysophosphatidic acid, in the cerebrospinal fluid (CSF) is a possible biomarker for neuropathic pain and discriminating neuropathic pain caused by lumbar spinal canal stenosis (LSCS) from other etiologies. This study aimed to explore this possible use of LPC species in the CSF. METHODS: Patients with LSCS (n = 137) and persistent spinal pain syndrome (n = 22) were subjected in this multi-site observational study. The CSF was collected by lumbar puncture. Using liquid chromatography-tandem mass spectrometry, we measured 6 LPC species, (16:0), (18:0), (18:1), (18:2), (20:4), and (22:6), in the CSF. We compared the LPC values between the groups and determined the cutoff levels that could efficiently discriminate the groups with high accuracy. RESULTS: The levels of all measured LPC species were significantly higher in the LSCS group than the persistent spinal pain syndrome group. Four LPC species demonstrated more than 0.80 area under the curve obtained from the receiver operating characteristic curve analysis. Although the specificity of cutoff levels for the 6 LPC species was low to moderate, their sensitivity was consistently high. CONCLUSIONS: The existing diagnostic protocols combining physical examinations and morphological imaging studies for lumbar spinal pain have limited sensitivity. Measuring LPC species in the CSF is a promising objective laboratory test and could be suitable for detecting the presence of lumbar spinal stenosis and can help indications for surgery.

Sphingosine kinase 2 and p62 regulation are determinants of sexual dimorphism in hepatocellular carcinoma.

OBJECTIVE: Hepatocellular carcinoma (HCC) is the third leading cause of cancer mortality, and its incidence is increasing due to endemic obesity. HCC is sexually dimorphic in both humans and rodents with higher incidence in males, although the mechanisms contributing to these correlations remain unclear. Here, we examined the role of sphingosine kinase 2 (SphK2), the enzyme that regulates the balance of bioactive sphingolipid metabolites, sphingosine-1-phosphate (S1P) and ceramide, in gender specific MASH-driven HCC. METHODS: Male and female mice were fed a high fat diet with sugar water, a clinically relevant model that recapitulates MASH-driven HCC in humans followed by physiological, biochemical cellular and molecular analyses. In addition, correlations with increased risk of HCC recurrence were determined in patients. RESULTS: Here, we report that deletion of SphK2 protects both male and female mice from Western diet-induced weight gain and metabolic dysfunction without affecting hepatic lipid accumulation or fibrosis. However, SphK2 deficiency decreases chronic diet-induced hepatocyte proliferation in males but increases it in females. Remarkably, SphK2 deficiency reverses the sexual dimorphism of HCC, as SphK2-/- male mice are protected whereas the females develop liver cancer. Only in male mice, chronic western diet induced accumulation of the autophagy receptor p62 and its downstream mediators, the antioxidant response target NQO1, and the oncogene c-Myc. SphK2 deletion repressed these known drivers of HCC development. Moreover, high p62 expression correlates with poor survival in male HCC patients but not in females. In hepatocytes, lipotoxicity-induced p62 accumulation is regulated by sex hormones and prevented by SphK2 deletion. Importantly, high SphK2 expression in male but not female HCC patients is associated with a more aggressive HCC differentiation status and increased risk of cancer recurrence. CONCLUSIONS: This work identifies SphK2 as a potential regulator of HCC sexual dimorphism and suggests SphK2 inhibitors now in clinical trials could have opposing, gender-specific effects in patients.

Cdc6 protein activates p27KIP1-bound Cdk2 protein only after the bound p27 protein undergoes C-terminal phosphorylation.

In mammalian cells Cdk2 activity during the G(1)-S transition is mainly controlled by p27(KIP1). Although the amount and subcellular localization of p27 influence Cdk2 activity, how Cdk2 activity is regulated during this phase transition still remains virtually unknown. Here we report an entirely new mechanism for this regulation. Cdc6 the AAA+ ATPase, known to assemble prereplicative complexes on chromosomal replication origins and activate p21(CIP1)-bound Cdk2, also activated p27-bound Cdk2 in its ATPase and cyclin binding motif-dependent manner but only after the p27 bound to the Cdk2 was phosphorylated at the C terminus. ROCK, which mediates a signal for cell anchorage to the extracellular matrix and activates the mTORC1 cascade as well as controls cytoskeleton assembly, was partly responsible for C-terminal phosphorylation of the p27. In vitro reconstitution demonstrated ROCK (Rho-associated kinase)-mediated phosphorylation of Cdk2-bound p27 at the C terminus and subsequent activation of the Cdk2 by Cdc6.

Cdc6 protein obstructs apoptosome assembly and consequent cell death by forming stable complexes with activated Apaf-1 molecules.

Cdc6 is the bifunctional AAA+ ATPase that assembles prereplicative complexes on origins of replication and activates p21(CIP1)- or p27(KIP1)-bound Cdk2. During the G(1)-S transition, the Cdc6 gene essential for chromosomal replication is activated by the E2F transcriptional factor. Paradoxically, Apaf-1 encoding the central component of the apoptosome is also activated at the same time and by E2F. Consequently, genes for antipodal life and death are regulated in the same manner by the same transcriptional factor. Here we report a striking solution to this paradox. Besides performing prereplicative complex assembly and Cdk2 activation, Cdc6 obstructed apoptosome assembly by forming stable complexes very likely with a monomer of cytochrome c-activated Apaf-1 molecules. This function depended on its own ATPase domain but not on the cyclin-binding motif. In proliferating rodent fibroblasts, Cdc6 continued to block apoptosome assembly induced by a non-cytochrome c or some other mechanism, suppressing seemingly unintended apoptosis when promoting cell proliferation. Thus, Cdc6 is an AAA+ ATPase with three functions, all working for life.

Successive phosphorylation of p27(KIP1) protein at serine-10 and C terminus crucially controls its potency to inactivate Cdk2.

During the G(1)-S transition, the activity of Cdk2 is regulated by its association with p27(KIP1), which in rodent fibroblasts undergoes phosphorylation mainly at serine 10, threonine 187, and C-terminal threonine 197 by KIS, Cdk2, and Pim or ROCK, respectively. Recently Cdc6 the AAA+ ATPase, identified initially to assemble pre-replicative complexes on origins of replication and later to activate p21(CIP1)-inactivated Cdk2, was found also to activate p27-bound Cdk2 but only after the bound p27 is C-terminally phosphorylated. On the other hand, the biological significance of the serine 10 phosphorylation remains elusive aside from its involvement in the stability of p27 itself. We report here that serine 10 phosphorylation is required for efficient C-terminal phosphorylation of its own by PIM and ROCK kinases and critically controls the potency of p27 as a Cdk2 inhibitor. In vitro, PIM1 and active ROCK1 efficiently phosphorylated free as well as Cdk2-bound p27 but only when the p27 was phosphorylated at Ser-10 in advance. Consistently, a Ser-10 nonphosphorylatable mutant p27 protein was not phosphorylated at the C terminus in vivo. Furthermore, when double-phosphorylated, free p27 was no longer a potent inhibitor of Cdk2, and Cdk2-bound p27 could be removed by Cdc6 to reactivate the Cdk2. Thus, phosphorylation at these two sites crucially controls the potency of this CDK inhibitor in two distinct modes.

Apolipoprotein M bound sphingosine 1-phosphate suppresses NETosis through activating S1P1 and S1P4.

The pleiotropic effects of high-density lipoprotein (HDL), including its protective properties against sepsis, are attributed to the sphingosine 1-phosphate and apolipoprotein M (ApoM) that are carried on the lipoproteins. In this study, we attempted to elucidate the possible mechanisms underlying the sepsis coagulopathic state by considering the modulation of NETosis. Our results revealed that in a lipopolysaccharide-induced sepsis mouse model, the levels of NETosis markers, such as plasma DNA and histone, were elevated in ApoM-knockout (KO) mice and attenuated in ApoM-overexpressing mice. In ApoM-KO mice, the survival rate decreased and the occurrence rates of coagulopathy and organ injury increased following the administration of histone. Treatment with a conditioned medium of ApoM-overexpressing cells attenuated the observed NETosis in HL-60S cells that differentiated into neutrophils and were inhibited through the suppression of S1P1 or S1P4. The attenuation of PKCδ and PKCα/ß by S1P1 and S1P4 activation may also be involved. In ApoM-overexpressing mice, coagulopathy and organ injuries were attenuated following an injection of histone; these effects were partially inhibited by S1P1, 3, S1P4, or S1P1 antagonists. Furthermore, the exogenous administration of ApoM protected ApoM-KO mice that were challenged with histone from developing NETosis. In conclusion, the ApoM/S1P axis protects against NETosis through the attenuation of PKC activation by S1P1 and S1P4. The development of drugs targeting the ApoM/S1P axis may be beneficial for the treatment of pathological conditions involving uncontrolled NETosis, such as sepsis.

The Lysophospholipase PNPLA7 Controls Hepatic Choline and Methionine Metabolism.

The in vivo roles of lysophospholipase, which cleaves a fatty acyl ester of lysophospholipid, remained unclear. Recently, we have unraveled a previously unrecognized physiological role of the lysophospholipase PNPLA7, a member of the Ca2+-independent phospholipase A2 (iPLA2) family, as a key regulator of the production of glycerophosphocholine (GPC), a precursor of endogenous choline, whose methyl groups are preferentially fluxed into the methionine cycle in the liver. PNPLA7 deficiency in mice markedly decreases hepatic GPC, choline, and several metabolites related to choline/methionine metabolism, leading to various symptoms reminiscent of methionine shortage. Overall metabolic alterations in the liver of Pnpla7-null mice in vivo largely recapitulate those in methionine-deprived hepatocytes in vitro. Reduction of the methyl donor S-adenosylmethionine (SAM) after methionine deprivation decreases the methylation of the PNPLA7 gene promoter, relieves PNPLA7 expression, and thereby increases GPC and choline levels, likely as a compensatory adaptation. In line with the view that SAM prevents the development of liver cancer, the expression of PNPLA7, as well as several enzymes in the choline/methionine metabolism, is reduced in human hepatocellular carcinoma. These findings uncover an unexplored role of a lysophospholipase in hepatic phospholipid catabolism coupled with choline/methionine metabolism.

Modulations of bioactive lipids and their receptors in postmortem Alzheimer's disease brains.

Background: Analyses of brain samples from Alzheimer's disease (AD) patients may be expected to help us improve our understanding of the pathogenesis of AD. Bioactive lipids, including sphingolipids, glycerophospholipids, and eicosanoids/related mediators have been demonstrated to exert potent physiological actions and to be involved in the pathogenesis of various human diseases. In this cross-sectional study, we attempted to elucidate the associations of these bioactive lipids with the pathogenesis/pathology of AD through postmortem studies of human brains. Methods: We measured the levels of glycerophospholipids, sphingolipids, and eicosanoids/related mediators in the brains of patients with AD (AD brains), patients with Cerad score B (Cerad-b brains), and control subjects (control brains), using a liquid chromatography-mass spectrometry method; we also measured the mRNA levels of specific receptors for these bioactive lipids in the same brain specimens. Results: The levels of several species of sphingomyelins and ceramides were higher in the Cerad-b and AD brains. Levels of several species of lysophosphatidic acids (LPAs), lysophosphatidylcholine, lysophosphatidylserine, lysophosphatidylethanolamine (LPE), lysophosphatidylinositol, phosphatidylcholine, phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol, and phosphatidylglycerol were especially high in the Cerad-b brains, while those of lysophosphatidylglycerol (LPG) were especially high in the AD brains. Several eicosanoids, including metabolites of prostaglandin E2, oxylipins, metabolites of epoxide, and metabolites of DHA and EPA, such as resolvins, were also modulated in the AD brains. Among the lipid mediators, the levels of S1P2, S1P5, LPA1, LPA2, LPA6, P2Y10, GPR174, EP1, DP1, DP2, IP, FP, and TXA2r were lower in the AD and/or Cerad-b brains. The brain levels of ceramides, LPC, LPI, PE, and PS showed strong positive correlations with the Aß contents, while those of LPG showed rather strong positive correlations with the presence of senile plaques and neurofibrillary tangles. A discriminant analysis revealed that LPG is especially important for AD and the LPE/PE axis is important for Cerad-b. Conclusions: Comprehensive lipidomics, together with the measurement of lipid receptor expression levels provided novel evidence for the associations of bioactive lipids with AD, which is expected to facilitate future translational research and reverse translational research.

Sphingosine 1-phosphate lyase facilitates cancer progression through converting sphingolipids to glycerophospholipids.

BACKGROUND: In addition to potent agonist properties for sphingosine 1-phosphate (S1P) receptors, intracellularly, S1P is an intermediate in metabolic conversion pathway from sphingolipids to glycerolysophospholipids (glyceroLPLs). We hypothesized that this S1P metabolism and its products might possess some novel roles in the pathogenesis of cancer, where S1P lyase (SPL) is a key enzyme. METHODS: The mRNA levels of sphingolipid-related and other cancer-related factors were measured in human hepatocellular carcinoma (HCC), colorectal cancer, and esophageal cancer patients' tumours and in their adjacent non-tumour tissues. Phospholipids (PL) and glyceroLPLs were measured by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). In-vitro experiments were performed in Colon 26 cell line with modulation of the SPL and GPR55 expressions. Xenograft model was used for determination of the cancer progression and for pharmacological influence. RESULTS: Besides high SPL levels in human HCC and colon cancer, SPL levels were specifically and positively linked with levels of glyceroLPLs, including lysophosphatidylinositol (LPI). Overexpression of SPL in Colon 26 cells resulted in elevated levels of LPI and lysophosphatidylglycerol (LPG), which are agonists of GPR55. SPL overexpression-enhanced cell proliferation was inhibited by GPR55 silencing. Conversely, inhibition of SPL led to the opposite outcome and reversed by adding LPI, LPG, and metabolites generated during S1P degradation, which is regulated by SPL. The xenograft model results suggested the contribution of SPL and glyceroLPLs to tumour progression depending on levels of SPL and GPR55. Moreover, the pharmacological inhibition of SPL prevented the progression of cancer. The underlying mechanisms for the SPL-mediated cancer progression are the activation of p38 and mitochondrial function through the LPI, LPG-GPR55 axis and the suppression of autophagy in a GPR55-independent manner. CONCLUSION: A new metabolic pathway has been proposed here in HCC and colon cancer, SPL converts S1P to glyceroLPLs, mainly to LPI and LPG, and facilitates cancer development.

Inhibition of autotaxin activity ameliorates neuropathic pain derived from lumbar spinal canal stenosis.

Lumbar spinal canal stenosis (LSS) or mechanical compression of dorsal root ganglion (DRG) is one of the causes of low back pain and neuropathic pain (NP). Lysophosphatidic acid (LPA) is a potent bioactive lipid mediator that is produced mainly from lysophosphatidylcholine (LPC) via autotaxin (ATX) and is known to induce NP via LPA1 receptor signaling in mice. Recently, we demonstrated that LPC and LPA were higher in cerebrospinal fluid (CSF) of patients with LSS. Based on the possible potential efficacy of the ATX inhibitor for NP treatment, we used an NP model with compression of DRG (CD model) and investigated LPA dynamics and whether ATX inhibition could ameliorate NP symptoms, using an orally available ATX inhibitor (ONO-8430506) at a dose of 30 mg/kg. In CD model, we observed increased LPC and LPA levels in CSF, and decreased threshold of the pain which were ameliorated by oral administration of the ATX inhibitor with decreased microglia and astrocyte populations at the site of the spinal dorsal horn projecting from injured DRG. These results suggested possible efficacy of ATX inhibitor for the treatment of NP caused by spinal nerve root compression and involvement of the ATX-LPA axis in the mechanism of NP induction.

Suppression of sphingosine 1-phosphate lyase retards the liver regeneration in mice after partial hepatectomy.

BACKGROUND: Liver regeneration is an extremely complicated process that is regulated by a number of signaling pathways. Sphingosine 1-phosphate (S1P), a potent bioactive lipid mediator playing crucial roles in various cellular responses through its receptors, has been attracting attention in the fields of hepatology, where S1P lyase (SPL), an irreversibly degrading enzyme of S1P, reportedly has a stimulatory role in growth of hepatocellular carcinoma (HCC). AIM OF THE STUDY: To examine whether SPL might play a stimulatory role in liver regeneration. METHOD: Using in-vivo siRNA technology, we inhibited SPL expression. Seventy percent of the liver was resected in mice as partial hepatectomy (PH). Liver tissue samples were collected and mRNA expression level of the SPL, IHC of the proliferating cell nuclear antigen (PCNA), protein levels of various proliferation factors and lipid measurements were performed in different groups. RESULTS: The mRNA levels of SPL increased in PH mice on the third day after PH surgery. When we suppressed the expression of SPL by in-vivo siRNA, we observed a significant decline of the PCNA positive cell numbers. Furthermore, the Cyclin D1 expressions and phosphorylation of ERK also were decreased in the siSPL injected PH group. CONCLUSION: We verified the importance of the SPL in liver regeneration, using the mice PH model. SPL might be a potential target to facilitate liver regeneration.

Possible involvement of PS-PLA1 and lysophosphatidylserine receptor (LPS1) in hepatocellular carcinoma.

Lysophosphatidylserine (LysoPS) is a lysophospholipid, its generating enzyme, phosphatidylserine-specific phospholipase A1 (PS-PLA1), reportedly plays roles in stomach and colon cancers. Here, we examined the potential roles of LysoPS in hepatocellular carcinoma (HCC). The ninety-seven HCC patients who underwent surgical treatment were enrolled in this study and approved by the institutional review board. Among LysoPS-related enzymes and receptors, increased PS-PLA1 or LysoPS receptor 1 (LPS1) mRNA was observed in HCC tissues compared to non-HCC tissues. PS-PLA1 mRNA in HCC was associated with no clinical parameters, while LPS1 mRNA in HCC was correlated inversely with tumor differentiation. Furthermore, higher serum PS-PLA1 was observed in HCC patients compared to healthy control and correlated with PS-PLA1 mRNA in non-HCC tissues and with serum AST or ALT. Additionally, serum levels of PS-PLA1 were higher in HCC patients with HCV-related liver injury than in those with HBV or non-HBV-, non-HCV-related liver diseases. In conclusion, among LysoPS-related enzymes and receptors, PS-PLA1 and LPS1 mRNA were increased in HCC. Based on the correlation between the serum PS-PLA1 and the mRNA level of PS-PLA1 in non-HCC tissues, the liver may be the main source of serum PS-PLA1, and serum PS-PLA1 levels may be a useful marker for liver injury.

Alteration of the lysophosphatidic acid and its precursor lysophosphatidylcholine levels in spinal cord stenosis: A study using a rat cauda equina compression model.

Cauda equina compression (CEC) is a major cause of neurogenic claudication and progresses to neuropathic pain (NP). A lipid mediator, lysophosphatidic acid (LPA), is known to induce NP via the LPA1 receptor. To know a possible mechanism of LPA production in neurogenic claudication, we determined the levels of LPA, lysophosphatidylcholine (LPC) and LPA-producing enzyme autotaxin (ATX), in the cerebrospinal fluid (CSF) and spinal cord (SC) using a CEC as a possible model of neurogenic claudication. Using silicon blocks within the lumbar epidural space, we developed a CEC model in rats with motor dysfunction. LPC and LPA levels in the CSF were significantly increased from day 1. Importantly, specific LPA species (16:0, 18:2, 20:4) were upregulated, which have been shown to produce by ATX detected in the CSF, without changes on its level. In SC, the LPC and LPA levels did not change, but mass spectrometry imaging analysis revealed that LPC was present in a region where the silicon blocks were inserted. These results propose a model for LPA production in SC and CSF upon neurogenic claudication that LPC produced locally by tissue damages is converted to LPA by ATX, which then leak out into the CSF.