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Autotoxins secreted by roots into the soil can trigger rhizosphere microecological imbalances and affect root secretory properties resulting in conditions such as replanting disease. However, information on the effect of autotoxins on root secretion characteristics and regulation of the composition of rhizosphere microorganisms by altered root exudates is limited. In this study, autotoxin r-hydroxybenzoic acid (4-HBA) was added to the soil of potted grapevine seedlings, CO2 pulse-labeling, and DNA stable isotope probing were used to track the rhizosphere microbiome that assimilates root exudates. Bacterial and fungal microbiomes that assimilated plant-derived carbon were identified by high-throughput sequencing. Results showed that 4-HBA treatment altered bacterial and fungal communities in 13C-labeled organisms, with a lower abundance of beneficial bacteria (e.g., Gemmatimonas, Streptomyces, and Bacillus) and a higher abundance of potential pathogen fungi (e.g., Fusarium, Neocosmospora, Gibberella, and Fusicolla) by changing the composition of root exudates. The exogenous addition of upregulated compound mixtures of root exudates reduced the abundance of beneficial bacterial Bacillus and increased the abundance of potential pathogen fungi Gibberella. These results suggest that 4-HBA can alter root secretion properties and altered root exudates may enrich certain potential pathogens and reduce certain beneficial bacteria, thereby unbalancing the structure of the rhizosphere microbial community. [ABSTRACT FROM AUTHOR]

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Alfalfa (Medicago sativa) is a highly valuable perennial forage legume that suffers from autotoxicity, which decreases plant resistance, reduces soil fertility, causes serious soil-borne diseases, and promotes ecological imbalance. We evaluated the effects of autotoxicity on the seed germination of 22 alfalfa varieties, and then elucidated the oxidative damage and lipid peroxidation in two alfalfa varieties with contrasting autotoxicity tolerances. The technique for order of preference by similarity to ideal solution (TOPSIS) method was used to rank the germination of the 22 alfalfa varieties when exposed to six autotoxic concentrations (0, 0.025, 0.075, 0.125, 0.175, and 0.225 g∙mL−1). We found WL656HQ and 3105C to be autotoxicity-tolerant and autotoxicity-sensitive varieties, respectively. The germination index mainly affects the comprehensive allelopathic index of WL656HQ and 3105C, which were the simple vigor index and radicle length according to the random forest model, respectively. 3105C eliminates reactive oxygen species (ROS) via antioxidant enzymes and antioxidants under T1 (0.025 g∙mL−1), but the oxidative stress system and the oxidative scavenging system cannot maintain the balance under T2 (0.125 g∙mL−1), causing oxidative bursts. In comparison, WL656HQ used its oxidative scavenging system (peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR)) to maintain its redox dynamic balance by removing excess ROS at all concentrations. In conclusion, the positive and negative indicators of autotoxicity for the two varieties were ascorbate (ASA) and hydroxyl free radicals (OH•), and proline (Pro) and dehydroascrobate (DHA), respectively. The most sensitive autotoxic concentrations of 3105C and WL656HQ were T2 (0.125 g∙mL−1) and T1 (0.025 g∙mL−1), respectively.

Phenolics from root exudates or decaying residues are usually referred as autotoxins of several plant species. However, how phenolics affect soil microbial communities and their functional significances are poorly understood. Rhizosphere bacterial and fungal communities from cucumber (Cucumis sativus L.) seedlings treated with p-coumaric acid, an autotoxin of cucumber, were analyzed by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer amplicons. Then, feedback effects of the rhizosphere biota on cucumber seedlings were evaluated by inoculating non-sterilized and sterilized rhizosphere soils to sterilized background soils. p-Coumaric acid decreased the bacterial diversity of rhizosphere but increased fungal diversity and altered the compositions of both the bacterial and fungal communities. p-Coumaric acid increased the relative abundances of microbial taxa with phenol-degrading capability (such as Chaetomium, Humicola, and Mortierella spp.) and microbial taxa which contained plant pathogens (such as Fusarium spp.). However, p-coumaric acid inhibited the relative abundances of Lysobacter, Haliangium, and Gymnoascus spp., whose species can have pathogen-antagonistic and/or plant-growth-promoting effects. The positive effect of cucumber rhizosphere microbiota on cucumber seedling growth was reduced by p-coumaric acid. Overall, our results showed that, besides its direct phytotoxicity, p-coumaric acid can inhibit cucumber seedling growth through generating negative plant-soil microbial interactions. [ABSTRACT FROM AUTHOR]

Platelet activation initiates an upsurge in polyun­saturated (18:2 and 20:4) lysophosphatidic acid (LPA) production. The biochemical pathway(s) responsible for LPA production during blood clotting are not yet fully understood. Here we describe the purification of a phospholipase A1 (PLA1) from thrombin-activated human platelets using sequential chromatographic steps followed by fluorophosphonate (FP)-biotin affinity labeling and proteomics characterization that identified acyl-protein thioesterase 1 (APT1), also known as lysophospholipase A-I (LYPLA-I; accession code O75608) as a novel PLA1. Addition of this recombinant PLA1 significantly increased the production of sn-2-esterified polyunsaturated LPCs and the corresponding LPAs in plasma. We examined the regioisomeric preference of lysophospholipase D/autotaxin (ATX), which is the subsequent step in LPA production. To prevent acyl migration, ether-linked regioisomers of oleyl-sn-glycero-3-phosphocholine (lyso-PAF) were synthesized. ATX preferred the sn-1 to the sn-2 regioisomer of lyso-PAF. We propose the following LPA production pathway in blood: 1) Activated platelets release PLA1; 2) PLA1 generates a pool of sn-2 lysophospholipids; 3) These newly generated sn-2 lysophospholipids undergo acyl migration to yield sn-1 lysophospholipids, which are the preferred substrates of ATX; and 4) ATX cleaves the sn-1 lysophospholipids to generate sn-1 LPA species containing predominantly 18:2 and 20:4 fatty acids.

Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are second-generation lysophospholipid mediators that exert multiple biological functions through their own cognate receptors. They are both present in the blood stream, activate receptors with similar structures (endothelial differentiation gene receptors), have similar roles in the vasculature and are vasoactive. However, it is unclear whether these lysophospholipid mediators cross-talk downstream of each receptor. Here, we provide in vivo evidence that LPA signaling counteracted S1P signaling. When autotaxin (Atx), an LPA-producing enzyme, was overexpressed in zebrafish embryos by injecting atx mRNA, the embryos showed cardia bifida, a phenotype induced by down-regulation of S1P signaling. A similar cardiac phenotype was not induced when catalytically inactive Atx was introduced. The cardiac phenotype was synergistically enhanced when antisense morpholino oligonucleotides (MO) against S1P receptor (s1pr2/mil) or S1P transporter (spns2) was introduced together with atx mRNA. The Atx-induced cardia bifida was prominently suppressed when embryos were treated with an lpar1 receptor antagonist, Ki16425, or with MO against lpar1. These results provide the first in vivo evidence of cross-talk between LPA and S1P signaling. [ABSTRACT FROM AUTHOR]

Background & Aims: Pruritus is a disabling complication of cholestatic liver disorders. Its management remains challenging. Ultraviolet B (UVB) phototherapy has been successfully used to treat pruritus in other indications. Methods: This is an observational case series. The study population consists of 13 patients (10 females, mean age 52years) with pruritus due to different cholestatic liver disorders: PBC (n=4), PSC (n=2), drug-induced (n=3) and persistent cholestasis after liver transplantation (LT) (n=4). Serum alkaline phosphatase levels were: 686±363μ/L and serum bile acids levels: 147±15μmol/L. In all patients, conventional medical treatment had failed to control pruritus. Perception of pruritus was recorded by the visual analogue scale (VAS). Results: The mean follow-up was 3years. Ten patients (77%) had more than 60% reduction in perceived pruritus of which 4 had more than an 80% reduction. Median [25–75% percentiles] VAS score before and after treatment decreased from 8.0 [8.0–10] to 2.0 [1.5–2.1] (p <0.001). The mean number of irradiations required to obtain this effect was 26±17 (average duration of phototherapy: 8weeks). No significant changes in cholestatic serum markers were observed. Four patients (30%) needed an additional phototherapy course because of recurrent pruritus and in all of them again a marked improvement of pruritus was observed. The therapy was well tolerated, except in two patients who developed, during retreatment, pronounced erythema in one case and paresthesia in the other case. Conclusions: UVB phototherapy appears to be a promising and well tolerated treatment also for cholestasis-associated pruritus. [ABSTRACT FROM AUTHOR]

Abstract: We previously found that lysophosphatidic acid (LPA)-like activity eliciting Cl− currents in Xenopus oocytes is increased in rabbit aqueous humor (AH) following corneal freeze wounds. The purpose of this study was to examine whether actual levels of LPA in AH from wounded eyes are higher than those from control eyes, and to determine the sources and enzymatic pathways of AH LPA in control and wounded conditions. Lysophospholipase D (lysoPLD) activity was measured by the enzymatic determination of choline following incubation of AH samples with exogenous lysophosphatidylcholines (LPCs). The molecular species compositions of LPA and LPC in fresh and incubated AH were determined by liquid chromatography–tandem mass spectrometry. A high, but similar activity of lysoPLD in the samples from both control and freeze-wounded eyes was detected. Its enzymatic properties resemble those of plasma lysoPLD, identified as autotaxin. Levels of LPCs, predominant substrates of lysoPLD in AH, were several times higher in the AH samples from injured eyes than those from the control eyes. Our results suggest that lysoPLD is constitutively released from corneal tissues and/or ciliary body into the AH, with no injury-induced increase in release following freeze-wounding. They also suggest that wound-induced increases in LPA-like biological activity are due to linoleoyl species-rich molecular composition in AH from wounded eyes. A possible mechanism of the altered molecular composition is an increase in the AH concentrations of LPCs, linoleoyl species of which are preferentially converted to corresponding unsaturated LPA by the constitutively active lysoPLD. [Copyright &y& Elsevier]

Autotaxin (ATX) is lysophospholipase D, which converts lysophospholipids such as lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA), a bioactive lipid mediator with multiple biological roles. ATX is present in high concentrations in various biological fluids and is responsible for LPA production in these fluids. The plasma ATX level is altered in some patho-physiological conditions. Three splicing isoforms of ATX have been reported so far (ATXα, β and γ). In this study, we identified and characterized ATXδ, a novel alternative splice variant of ATX, which has a four-amino acid deletion in the L2 linker region of ATXβ. ATXδ was found to be the second major isoform following ATXβ and fully active. ATXβ and ATXδ showed similar divalent cation sensitivity and cell motility-stimulating activity. ATXβ and ATXδ are present in wide range of organism from fish to mammals. Among them, only ATXδ was found in Gallus gallus and Xenopus laevis, suggesting the indispensable role of the isoform. ATXδ was expressed in various human tissues with different expression patterns from that of ATXβ. These results show that ATXδ is a second major ATX isoform sharing similar biochemical characters with the major isoform, ATXβ, and is a potential biomarker. [ABSTRACT FROM PUBLISHER]

The aim of this study was to analyze changes in autotoxin (ATX) (both enzyme activity and gene expression), metalloproteinase- 9(MMP-9) and p53 antibodies (Abs) serum levels in breast cancer patients and to correlate their results with various clinical, pathological features of breast cancer. Sixty female breast cancer patients ( 42 with lymph node (LN) metastasis and 18 without LN metastasis) were included in this study and subjected to determination of ATX (both activity by colorimetric method and gene expression by RT-PCR) and both p53 Abs and MMP-9 by ELISA technique. Our results showed that there were statistically significant differences between breast cancer patients with and without LN metastasis in all the studied parameters except for p53 Abs. ATX (both activity and gene expression) and the serum levels of both MMP-9 and p53 Abs, were significantly different between different stages and grades of breast cancer patients with increasing activity and levels from stage I to IV and from grade I to III. Only ATX (both activity and expression) was significantly different between patients with tumor size less than or more than 5. There was a highly significant correlation between ATX activity and gene expression. In Conclusions: the present study suggested that ATX activity, MMP-9 and p53Abs could serve as useful and convenient prognostic and detection markers of metastasizing breast cancer. Also, ATX activity may be used as an index for increased ATX gene expression. [ABSTRACT FROM AUTHOR]

Secondary metabolites, for example capsaicin, are substances with no known direct function in basic metabolism, but can provide some important adaptive significance in protection against herbivory and/or microbial infection. Capsaicin, responsible for the heat sensation in chile pepper fruit, is only found in the genus Capsicum (chile peppers). Like the accumulation of capsaicinoids, germination of chile pepper seed has been observed to vary among genotypes. To test whether capsaicin could be a contributor to reduced seed germination, two no-heat cultivars, Keystone Resistant Giant and Pimiento L, were treated with capsaicin to determine its effect on germination. Seeds were treated with 0, 500, or 1500 ppm capsaicin. Capsaicin treatment resulted not only in reduced but also delayed germination. We determined that capsaicin can decrease chile pepper seed germination, and may be the cause of slow germination in some chile pepper cultivars. [ABSTRACT FROM AUTHOR]

Abstract: Ecto-nucleotide pyrophosphatases/phosphodiesterases (E-NPPs) are membrane-bound ecto-enzymes involved in the modulation of purinergic signaling. Important physiological roles related to brain development have been associated to purinergic neurotransmission. NPP1, two splice isoforms of NPP2, and NPP3 have already been identified in adult rat brain. However, there are no studies evaluating the mRNA expression of these NPP members during the brain development. The effort of the present study was to map NPP gene expression pattern in olfactory bulb, hippocampus, cerebral cortex, striatum, and cerebellum at crucial ages for rat development (7, 14, 21, 60, and 150 days old) by a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) strategy. Our results demonstrated an increase in the relative expression of NPP1 throughout the aging in all structures analyzed, except in hippocampus, where the higher expression has been detected in 14 days old rats. Both NPP2 isoforms have shown a similar pattern of expression among all structures. The relative expression of NPP3 decreased during the aging mainly on cerebellum, hippocampus, and olfactory bulb. Altogether, the different patterns of NPP gene expression during rat brain development reinforce the idea that each enzyme may play a distinct role on modulating the purinergic signaling throughout aging. [Copyright &y& Elsevier]

Abstract: Lysophosphatidic acid (LPA) is a lipid mediator with multiple biological actions. We have reported that LPA stimulates hepatic stellate cell proliferation and inhibits DNA synthesis in hepatocytes, suggesting that LPA might play some role in the liver. We have found that plasma LPA level and serum autotaxin (ATX) activity were increased in patients with chronic hepatitis C. However, the clinical significance of LPA and its synthetic enzyme, autotaxin (ATX), is still unclear. To determine whether the increase of plasma LPA level and serum ATX activity might be found generally in liver injury, we examined the possible modulation of them in the blood in rats with various liver injuries. Plasma LPA level and serum ATX activity were increased in carbon tetrachloride-induced liver fibrosis correlatively with fibrosis grade, in dimethylnitrosamine-induced acute liver injury correlatively with serum alanine aminotransferase level or in 70% hepatectomy as early as 3 h after the operation. Plasma LPA level was correlated with serum ATX activity in rats with chronic and acute liver injury. ATX mRNA in the liver was not altered in carbon tetrachloride-induced liver fibrosis. Plasma LPA level and serum ATX activity are increased in various liver injuries in relation to their severity. Whether increased ATX and LPA in the blood in liver injury is simply a result or also a cause of the injury should be further clarified. [Copyright &y& Elsevier]

In this study, we investigated the effects of long-term continuous cucumber cropping on phenolic acids in rhizosphere soil, as well as their link to soil chemical characteristics, enzyme activities, and microbiological activities, using rhizosphere soil from the 2nd, 6th, 10th, 14th, 18th, 20th, 24th, and 26th round of cucumber cultivation in solar greenhouse. The results showed that contents of phenolic acids increased significantly with increasing continuous cropping rounds. The increase amount per round of total phenolic acid was significantly higher in the early stage (0-2 rounds) and late stage (20-26 rounds) than middle stage (10-14 rounds) of continuous cropping. Soil nutrient contents were enriched, while invertase enzyme activity and microbial activities were decreased. Redundancy analysis showed that organic matter, total phosphorus, total nitrogen, available nitrogen, microbial biomass carbon and microbial metabolic entropy were main soil fertility factors correlating with the accumulation of phenolic acids. Results of structural equation model showed that soil phosphorus enrichment directly led to the accumulation of phenolic acids, and that nitrogen enrichment indirectly facilitated the accumulation of phenolic acids by altering the activity of microorganisms. As a result, proper nitrogen and phosphorus fertilizers application would reduce the accumulation of phenolic acids and alleviate the cucumber continuous cropping obstacles.

Alfalfa (Medicago sativa) is a highly valuable perennial forage legume that suffers from autotoxicity, which decreases plant resistance, reduces soil fertility, causes serious soil-borne diseases, and promotes ecological imbalance. We evaluated the effects of autotoxicity on the seed germination of 22 alfalfa varieties, and then elucidated the oxidative damage and lipid peroxidation in two alfalfa varieties with contrasting autotoxicity tolerances. The technique for order of preference by similarity to ideal solution (TOPSIS) method was used to rank the germination of the 22 alfalfa varieties when exposed to six autotoxic concentrations (0, 0.025, 0.075, 0.125, 0.175, and 0.225 g∙mL−1). We found WL656HQ and 3105C to be autotoxicity-tolerant and autotoxicity-sensitive varieties, respectively. The germination index mainly affects the comprehensive allelopathic index of WL656HQ and 3105C, which were the simple vigor index and radicle length according to the random forest model, respectively. 3105C eliminates reactive oxygen species (ROS) via antioxidant enzymes and antioxidants under T1 (0.025 g∙mL−1), but the oxidative stress system and the oxidative scavenging system cannot maintain the balance under T2 (0.125 g∙mL−1), causing oxidative bursts. In comparison, WL656HQ used its oxidative scavenging system (peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR)) to maintain its redox dynamic balance by removing excess ROS at all concentrations. In conclusion, the positive and negative indicators of autotoxicity for the two varieties were ascorbate (ASA) and hydroxyl free radicals (OH•), and proline (Pro) and dehydroascrobate (DHA), respectively. The most sensitive autotoxic concentrations of 3105C and WL656HQ were T2 (0.125 g∙mL−1) and T1 (0.025 g∙mL−1), respectively. [ABSTRACT FROM AUTHOR]

• 1000 μM of ρ-Hydroxybenzoic acid (4-HBA) had a significant allelopathic effect on seedling growth of grapevine.. • Verapamil (Vp, calcium channel inhibitor) hindered Ca2+ flow from the cell wall to the cytoplasm induced by 1000 μM of 4-HBA. • Vp and 4-HBA decreased the PAL activity and 4-HBA and salicylic acid (SA) content in root exudates. • DETC and 4-HBA decreased the PAL activity and 4-HBA content in root exudates. • Calcium and reactive oxygen signal transductions involved in regulation of root secretion under 4-HBA. ρ-Hydroxybenzoic acid (4-HBA) is a major autotoxin that can regulate grapevine secretion characteristics and cause replant disease. In our study, we aimed to investigate the involvement of various signal transduction pathways (calcium, Ca2+ and reactive oxygen species) in 4-HBA-induced grapevine root secretions. The roots of grapevine seedlings were treated with specific calcium channel inhibitor (Verapamil, Vp), and inhibitors of superoxide dismutase (SOD) (diethyldithiocarbamate, DETC) and NADPH oxidase (diphenylene iodonium, DPI). The distribution of Ca2+ in the root tip tissues was observed, and the phenylalanine ammonia-lyase (PAL) activity and phenolic acid content (ρ-Hydroxybenzoic acid and salicylic acid) in the secretions were measured. The results showed that 1000 μM of 4-HBA had a significant allelopathic effect on seedling growth, leading to Ca2+ flow from the cell wall to the cytoplasm, and that Vp hindered this process. The treatments with Vp and 4-HBA or DETC and 4-HBA decreased the PAL activity of roots and 4-HBA content in root exudates compared to the 4-HBA treatment. The salicylic acid (SA) content in root exudates decreased after co-treating with Vp and 4-HBA, DPI and 4-HBA. This result indicates that Ca2+ and SOD play major roles in 4-HBA induced root secretions. [ABSTRACT FROM AUTHOR]

Lysophosphatidic acid (LPA) functions through activation of LPA receptors (LPARs). LPA-LPAR signaling has been implicated in development of fibrosis. However, the role of LPA-LPAR signaling in development of diabetic nephropathy (DN) has not been studied. We examined whether BMS002, a novel dual LPAR1 and LPAR3 antagonist, affects development of DN in endothelial nitric oxide synthase-knockout db/db mice. Treatment of these mice with BMS002 from 8 to 20 weeks of age led to a significant reduction in albuminuria, similar to that observed with renin-angiotensin system inhibition (losartan plus enalapril). LPAR inhibition also prevented the decline in GFR observed in vehicle-treated mice, such that GFR at week 20 differed significantly between vehicle and LPAR inhibitor groups ( P <0.05). LPAR inhibition also reduced histologic glomerular injury; decreased the expression of profibrotic and fibrotic components, including fibronectin, α -smooth muscle actin, connective tissue growth factor, collagen I, and TGF- β ; and reduced renal macrophage infiltration and oxidative stress. Notably, LPAR inhibition slowed podocyte loss (podocytes per glomerulus ±SEM at 8 weeks: 667±40, n =4; at 20 weeks: 364±18 with vehicle, n =7, and 536±12 with LPAR inhibition, n =7; P <0.001 versus vehicle). Finally, LPAR inhibition minimized the production of 4-hydroxynonenal (4-HNE), a marker of oxidative stress, in podocytes and increased the phosphorylation of AKT2, an indicator of AKT2 activity, in kidneys. Thus, the LPAR antagonist BMS002 protects against GFR decline and attenuates development of DN through multiple mechanisms. LPAR antagonism might provide complementary beneficial effects to renin-angiotensin system inhibition to slow progression of DN., (Copyright © 2017 by the American Society of Nephrology.)

Introduction: Chronic pruritus occurs in 13% of the general population without age limitation. There is a high unmet need here as effective treatment options are still missing., Areas Covered: Clinical and experimental research during the past decade identified new mechanisms in chronic pruritus allowing the definition of a broad range of specific treatment targets for the first time. This refers specifically to inflammatory pruritic dermatoses, uremic and cholestatic pruritus. Targets identified are, for example, receptors for substance P, IL-31 and nerve growth factor. Search was made for current studies addressing these diseases and targets in the available clinical registration databases., Expert Opinion: The current pharmacological development is very promising especially for patients suffering from chronic pruritus in inflammatory dermatoses, chronic kidney diseases and hepatobiliary diseases. However, there are still several pruritic diseases in which neither mediators nor specific target populations (e.g., children) nor stages of diseases, have been identified; however, it can be assumed that within the next 10 years, major changes in the possibilities of antipruritic treatment will take place.

The role of the lysophospholipase D autotaxin (ATX) and lysophosphatidic acid (LPA) in cancer is emerging and represents two key players in regulating cancer progression. In this brief review, we will discuss some of our recent findings, which highlight a central role that LPA and its receptor plays in orchestrating melanoma-stroma interactions in the establishment of lung metastases. In particular, we evaluated not only the function of LPA receptors on tumor cells but also their role on host tissues and how they can influence melanoma growth and metastasis. Using the syngeneic B16F10 murine melanoma model, we made three key observations. First, our in vitro findings demonstrate that LPA receptors, specifically LPA 2 and LPA 5 expressed in B16F10 cells appear to have opposing roles in cell invasion; the former seems to be responsible for the high basal invasion rate of B16F10 cells while the latter is anti-invasive upon exogenous LPA stimulation. Second, we observed a profound reduction in the incidence of pulmonary melanoma metastasis in LPA 1 - and LPA 5 -knockout (KO) mice, respectively, when compared to wild-type (WT) mice. Third, no differences in terms of subcutaneous tumor growth between LPA 1 KO, LPA 5 KO and WT mice were observed. These findings suggest that LPA receptors exert different functions in melanoma cells versus host tissues in terms of invasion and metastasis.