Exosome-associated lysophosphatidic acid signaling contributes to cancer pain

ABSTRACT

Pain associated with bone cancer remains poorly managed, and chemotherapeutic drugs used to treat cancer usually increase pain. The discovery of dual-acting drugs that reduce cancer and produce analgesia is an optimal approach. The mechanisms underlying bone cancer pain involve interactions between cancer cells and nociceptive neurons. We demonstrated that fibrosarcoma cells express high levels of autotaxin (ATX), the enzyme synthetizing lysophosphatidic acid (LPA). Lysophosphatidic acid increased proliferation of fibrosarcoma cells in vitro. Lysophosphatidic acid is also a pain-signaling molecule, which activates LPA receptors (LPARs) located on nociceptive neurons and satellite cells in dorsal root ganglia. We therefore investigated the contribution of the ATX-LPA-LPAR signaling to pain in a mouse model of bone cancer pain in which fibrosarcoma cells are implanted into and around the calcaneus bone, resulting in tumor growth and hypersensitivity. LPA was elevated in serum of tumor-bearing mice, and blockade of ATX or LPAR reduced tumor-evoked hypersensitivity. Because cancer cell-secreted exosomes contribute to hypersensitivity and ATX is bound to exosomes, we determined the role of exosome-associated ATX-LPA-LPAR signaling in hypersensitivity produced by cancer exosomes. Intraplantar injection of cancer exosomes into naive mice produced hypersensitivity by sensitizing C-fiber nociceptors. Inhibition of ATX or blockade of LPAR attenuated cancer exosome-evoked hypersensitivity in an ATX-LPA-LPAR-dependent manner. Parallel in vitro studies revealed the involvement of ATX-LPA-LPAR signaling in direct sensitization of dorsal root ganglion neurons by cancer exosomes. Thus, our study identified a cancer exosome-mediated pathway, which may represent a therapeutic target for treating tumor growth and pain in patients with bone cancer.

Exogenous oxygen is required for prostanoid induction under brain ischemia as evidence for a novel regulatory mechanism

Previously, we and others reported a rapid and dramatic increase in brain prostanoids (PG), including prostaglandins, prostacyclins, and thromboxanes, under ischemia that is traditionally explained through the activation of esterified arachidonic acid (20:4n6) release by phospholipases as a substrate for cyclooxygenases (COX). However, the availability of another required COX substrate, oxygen, has not been considered in this mechanism. To address this mechanism for PG upregulation through oxygen availability, we analyzed mouse brain PG, free 20:4n6, and oxygen levels at different time points after ischemic onset using head-focused microwave irradiation (MW) to inactivate enzymes in situ before craniotomy. The oxygen half-life in the ischemic brain was 5.32 ± 0.45 s and dropped to undetectable levels within 12 s of ischemia onset, while there were no significant free 20:4n6 or PG changes at 30 s of ischemia. Furthermore, there was no significant PG increase at 2 and 10 min after ischemia onset compared to basal levels, while free 20:4n6 was increased ∼50 and ∼100 fold, respectively. However, PG increased ∼30-fold when ischemia was followed by craniotomy of nonMW tissue that provided oxygen for active enzymes. Moreover, craniotomy performed under anoxic conditions without MW did not result in PG induction, while exposure of these brains to atmospheric oxygen significantly induced PG. Our results indicate, for the first time, that oxygen availability is another important regulatory factor for PG production under ischemia. Further studies are required to investigate the physiological role of COX/PG regulation through tissue oxygen concentration.

A shotgun metagenomic analysis of the fecal microbiome in humans infected with Giardia duodenalis

BACKGROUND

The mechanisms underlying the clinical outcome disparity during human infection with Giardia duodenalis are still unclear. In recent years, evidence has pointed to the roles of host factors as well as parasite's genetic heterogeneity as major contributing factors in the development of symptomatic human giardiasis. However, it remains contested as to how only a small fraction of individuals infected with G. duodenalis develop clinical gastrointestinal manifestations, whereas the majority of infected individuals remain asymptomatic. Here, we demonstrate that diversity in the fecal microbiome correlates with the clinical outcome of human giardiasis.

METHODS

The genetic heterogeneity of G. duodenalis clinical isolates from human subjects with asymptomatic and symptomatic giardiasis was determined using a multilocus analysis approach. We also assessed the genetic proximity of G. duodenalis isolates by constructing phylogenetic trees using the maximum likelihood. Total genomic DNA (gDNA) from fecal specimens was utilized to construct DNA libraries, followed by performing paired-end sequencing using the HiSeq X platform. The Kraken2-generated, filtered FASTQ files were assigned to microbial metabolic pathways and functions using HUMAnN 3.04 and the UniRef90 diamond annotated full reference database (version 201901b). Results from HUMAnN for each sample were evaluated for differences among the biological groups using the Kruskal-Wallis non-parametric test with a post hoc Dunn test.

RESULTS

We found that a total of 8/11 (72.73%) human subjects were infected with assemblage A (sub-assemblage AII) of G. duodenalis, whereas 3/11 (27.27%) human subjects in the current study were infected with assemblage B of the parasite. We also found that the parasite's genetic diversity was not associated with the clinical outcome of the infection. Further phylogenetic analysis based on the tpi and gdh loci indicated that those clinical isolates belonging to assemblage A of G. duodenalis subjects clustered compactly together in a monophyletic clade despite being isolated from human subjects with asymptomatic and symptomatic human giardiasis. Using a metagenomic shotgun sequencing approach, we observed that infected individuals with asymptomatic and symptomatic giardiasis represented distinctive microbial diversity profiles, and that both were distinguishable from the profiles of healthy volunteers.

CONCLUSIONS

These findings identify a potential association between host microbiome disparity with the development of clinical disease during human giardiasis, and may provide insights into the mechanisms by which the parasite induces pathological changes in the gut. These observations may also lead to the development of novel selective therapeutic targets for preventing human enteric microbial infections.

Inhibition of DAGLβ as a therapeutic target for pain in sickle cell disease

Sickle cell disease (SCD) is the most common inherited disease. Pain is a key morbidity of SCD and opioids are the main treatment but their side effects emphasize the need for new analgesic approaches. Humanized transgenic mouse models have been instructive in understanding the pathobiology of SCD and mechanisms of pain. Homozygous (HbSS) Berkley mice express >99% human sickle hemoglobin and several features of clinical SCD including hyperalgesia. Previously, we reported that the endocannabinoid 2-arachidonoylglycerol (2-AG) is a precursor of the pro-nociceptive mediator prostaglandin E2-glyceryl ester (PGE2-G) which contributes to hyperalgesia in SCD. We now demonstrate the causal role of 2-AG in hyperalgesia in sickle mice. Hyperalgesia in HbSS mice correlated with elevated levels of 2-AG in plasma, its synthesizing enzyme diacylglycerol lipase β (DAGLβ) in blood cells, and with elevated levels of PGE2 and PGE2-G, pronociceptive derivatives of 2-AG. A single intravenous injection of 2-AG produced hyperalgesia in non-hyperalgesic HbSS mice, but not in control (HbAA) mice expressing normal human HbA. JZL184, an inhibitor of 2-AG hydrolysis, also produced hyperalgesia in non-hyperalgesic HbSS or hemizygous (HbAS) mice, but did not influence hyperalgesia in hyperalgesic HbSS mice. Systemic and intraplantar administration of KT109, an inhibitor of DAGLβ, decreased mechanical and heat hyperalgesia in HbSS mice. The decrease in hyperalgesia was accompanied by reductions in 2-AG, PGE2 and PGE2-G in the blood. These results indicate that maintaining the physiological level of 2-AG in the blood by targeting DAGLβ may be a novel and effective approach to treat pain in SCD.

Connecting the Pipes: Agricultural Tile Drains and Elevated Imidacloprid Brain Concentrations in Juvenile Northern Leopard Frogs (Rana pipiens)

Neonicotinoids are neurotoxic insecticides and are often released into nearby wetlands via subsurface tile drains and can negatively impact nontarget organisms, such as amphibians. Previous studies have indicated that imidacloprid, a commonly used neonicotinoid, can cross the amphibian blood-brain barrier under laboratory conditions; however, little is known about the impact of low concentrations in a field-based setting. Here, we report aqueous pesticide concentrations at wetland production areas that were either connected or not connected to agricultural tile drains, quantified imidacloprid and its break down products in juvenile amphibian brains and livers, and investigated the relationship between imidacloprid brain concentration and brain size. Imidacloprid concentrations in brain and water samples were nearly 2.5 and 5 times higher at tile wetlands (brain = 4.12 ± 1.92 pg/mg protein; water = 0.032 ± 0.045 μg/L) compared to reference wetlands, respectively. Tile wetland amphibians also had shorter cerebellums (0.013 ± 0.001 mm), depicting a negative relationship between imidacloprid brain concentration and cerebellum length. The metabolite, desnitro-imidacloprid, had liver concentrations that were 2 times higher at tile wetlands (2 ± 0.3 μg/g). Our results demonstrate that imidacloprid can cross the amphibian blood-brain barrier under ecological conditions and may alter brain dimensions and provide insight into the metabolism of imidacloprid in amphibians.

A novel drug-like water-soluble small molecule Focal Adhesion Kinase (FAK) activator promotes intestinal mucosal healing

Non-steroidal anti-inflammatory drugs (NSAIDs) injure the proximal and distal gut by different mechanisms. While many drugs reduce gastrointestinal injury, no drug directly stimulates mucosal wound healing. Focal adhesion kinase (FAK), a non-receptor tyrosine kinase, induces epithelial sheet migration. We synthesized and evaluated a water-soluble FAK-activating small molecule, M64HCl, with drug-like properties. Monolayer wound closure and Western blots measured migration and FAK phosphorylation in Caco-2 ​cells, in vitro kinase assays established FAK activation, and pharmacologic tests assessed drug-like properties. 30 ​mg/kg/day M64HCl was administered in two murine small intestine injury models for 4 days. M64HCl (0.1-1000 ​nM) dose-dependently increased Caco-2 FAK-Tyr 397 phosphorylation, without activating Pyk2 and accelerated Caco-2 monolayer wound closure. M64HCl dose-responsively activates the FAK kinase domain vs. the non-salt M64, increasing the V_max of ATP-binding. Pharmacologic tests suggested M64HCl has drug-like properties and is enterally absorbed. M64HCl 25 ​mg/kg/day continuous infusion promoted healing of ischemic jejunal ulcers and indomethacin-induced small intestinal injury in C57Bl/6 mice. M64HCl-treated mice exhibited smaller ulcers 4 days after ischemic ulcer induction or indomethacin injury. Renal histology and plasma creatinine were normal. Mild hepatic inflammatory changes and ALT elevation were similar among M64HCl-treated mice and controls. M64HCl was concentrated in kidney and gastrointestinal mucosa and functional nephrectomy studies suggested predominantly urinary excretion. Little toxicity was observed in vitro or in single-dose mouse toxicity studies until >1000x higher than effective concentrations. M64HCl, a water-soluble FAK activator, promotes epithelial restitution and intestinal mucosal healing and may be useful to treat gut mucosal injury.

A model of painful vaso-occlusive crisis in mice with sickle cell disease

In order to better understand mechanisms underlying acute pain during vaso-occlusive crises (VOCs) in patients with sickle cell disease, Khasabova et al report on a clinically relevant model in mice where VOC is stimulated by exposure to cold. Cold exposure produces robust hyperalgesia, stasis, hypoxia, elevated heart rate, and increased levels of the endocannabinoid 2-AG and its synthesizing enzyme, DAGLβ, in plasma and blood cells, respectively. Blocking DAGLβ prevents the development of hyperalgesia. Collectively, these data point to 2-AG signaling as a targetable mediator of VOC pain.

Detection of imidacloprid and metabolites in Northern Leopard frog (Rana pipiens) brains

Neonicotinoids are a new type of highly water-soluble insecticide used in agricultural practices to eliminate pests. Neonicotinoids bind almost irreversibly to postsynaptic nicotinic acetylcholine receptors in the central nervous system of invertebrates, resulting in overstimulation, paralysis, and death. Imidacloprid, the most commonly used neonicotinoid, is often transported to nearby wetlands through subsurface tile drains and has been identified as a neurotoxin in several aquatic non-target organisms. The aim of the present study was to determine if imidacloprid could cross the blood-brain barrier in adult Northern Leopard frogs (Rana pipiens) following exposure to 0, 0.1, 1, 5, or 10 μg/L for 21 days. Additionally, we quantified the breakdown product of imidacloprid, imidacloprid-olefin, and conducted feeding trials to better understand how imidacloprid affects foraging behavior over time. Exposure groups had 12 to 313 times more imidacloprid in the brain relative to the control and breakdown products showed a dose-response relationship. Moreover, imidacloprid brain concentrations were approximately 14 times higher in the 10 μg/L treatment compared to the water exposure concentration, indicating imidacloprid can bioaccumulate in the amphibian brain. Reaction times to a food stimulus were 1.5 to 3.2 times slower among treatment groups compared to the control. Furthermore, there was a positive relationship between mean response time and log-transformed imidacloprid brain concentration. These results indicate imidacloprid can successfully cross the blood-brain barrier and bioaccumulate in adult amphibians. Our results also provide insights into the relationship between imidacloprid brain concentration and subsequent altered foraging behavior.

Thermal Decomposition of Anionic, Zwitterionic, and Cationic Polyfluoroalkyl Substances in Aqueous Film-Forming Foams

In this study, we investigated thermal decomposition mechanisms of cationic, zwitterionic, and anionic polyfluoroalkyl substances, including those present in aqueous film-forming foam (AFFF) samples. We present novel evidence that polyfluoroalkyl substances gave quantitative yields of perfluoroalkyl substances of different chain lengths during thermal treatment. The results support a radical-mediated transformation mechanism involving random-chain scission and end-chain scission, leading to the formation of perfluoroalkyl carboxylic acids such as perfluorooctanoic acid (PFOA) from certain polyfluoroalkyl amides and sulfonamides. Our results also support a direct thermal decomposition mechanism (chain stripping) on the nonfluorinated moiety of polyfluoroalkyl sulfonamides, resulting in the formation of perfluorooctanesulfonic acid (PFOS) and other structurally related polyfluoroalkyl compounds. Thermal decomposition of 8:2 fluorotelomer sulfonate occurred through end-chain scission and recombination reactions, successively yielding PFOS. All of the studied polyfluoroalkyl substances began to degrade at 200-300 °C, exhibiting near-complete decomposition at ≥400 °C. Using a high-resolution parent ion search method, we demonstrated for the first time that low-temperature thermal treatments of AFFF samples led to the generation of anionic fluoroalkyl substances, including perfluoroheptanesulfonamide, 8:2 fluorotelomer sulfonic acid, N-methyl perfluorooctane sulfonamide, and a previously unreported compound N-2-propenyl-perfluorohexylsulfonamide. This study provides key insights into the fate of polyfluoroalkyl substances in thermal processes.

Effect of granular activated carbon and other porous materials on thermal decomposition of per- and polyfluoroalkyl substances: Mechanisms and implications for water purification

Thermal treatment is routinely used to reactivate the spent granular activated carbon (GAC) from water purification facilities. It is also an integral part of sewage sludge treatment and municipal solid waste management. This study presents a detailed investigation of the fate of per- and polyfluoroalkyl substances (PFAS) and one PFAS alternative (GenX) in thermal processes, focusing on the effect of GAC. We demonstrate that the thermolysis of perfluoroalkyl carboxylic acids (PFCAs), including perfluorooctanoic acid (PFOA), and GenX can occur at temperatures of 150‒200 °C. Three temperature zones were discovered for PFOA, including a stable and nonvolatile zone (≤90 °C), a phase-transfer and thermal decomposition zone (90‒400 °C), and a fast decomposition zone (≥400 °C). The thermal decomposition began with the homolysis of a C‒C bond next to the carboxyl group of PFCAs, which formed unstable perfluoroalkyl radicals. Dual decomposition pathways seem to exist. The addition of a highly porous adsorbent, such as GAC or a copolymer resin, compressed the intermediate sublimation zone of PFCAs, changed their thermal decomposition pathways, and increased the decomposition rate constant by up to 150-fold at 250 °C. The results indicate that the observed thermal decomposition acceleration was linked to the adsorption of gas-phase PFCA molecules on GAC. The presence of non-activated charcoals/biochars with a low affinity for PFOA did not accelerate its thermal decomposition, suggesting that the π electron-rich, polyaromatic surface of charcoal/GAC played an insignificant role compared to the adsorbent's porosity. Overall, the results indicate that (1) substantial decomposition of PFCAs and GenX during conventional thermal GAC/sludge/waste treatment is very likely, and (2) the presence or addition of GAC or other highly porous materials can accelerate thermal PFAS decomposition and alter decomposition pathways.

Effects of Probiotic Supplementation on Short Chain Fatty Acids in the AppNL-G-F Mouse Model of Alzheimer's Disease

BACKGROUND

The intestinal microbiota and its metabolites, particularly short-chain fatty acids (SCFAs), have been implicated in immune function, host metabolism, and even behavior.

OBJECTIVE

This study was performed to investigate whether probiotic administration influences levels of intestinal microbiota and their metabolites in a fashion that may attenuate brain changes in a mouse model of Alzheimer's disease (AD).

METHODS

C57BL/6 wild-type (WT) mice were compared to AppNL-G-Fmice. The animals were treated with either vehicle or probiotic (VSL#3) for 8 weeks. Fecal microbiome analysis along with Aβ, GFAP, Iba-1, c-Fos, and Ki-67 immunohistochemistry was done. SCFAs were analyzed in serum and brains using UPLC-MS/MS.

RESULTS

Probiotic (VSL#3) supplementation for 2 months resulted in altered microbiota in both WT and AppNL-G-Fmice. An increase in serum SCFAs acetate, butyrate, and lactate were found in both genotypes following VSL#3 treatment. Propionate and isobutyrate were only increased in AppNL-G-Fmice. Surprisingly, VSL#3 only increased lactate and acetate in brains of AppNL-G-Fmice. No significant differences were observed between vehicle and VSL#3 fed AppNL-G-Fhippocampal immunoreactivities of Aβ, GFAP, Iba-1, and Ki-67. However, hippocampal c-Fos staining increased in VSL#3 fed AppNL-G-Fmice.

CONCLUSION

These data demonstrate intestinal dysbiosis in the AppNL-G-Fmouse model of AD. Probiotic VSL#3 feeding altered both serum and brain levels of lactate and acetate in AppNL-G-Fmice correlating with increased expression of the neuronal activity marker, c-Fos.

Discovery of Novel Small-Molecule FAK Activators Promoting Mucosal Healing

Gastrointestinal mucosal wounds are common to patients injured by factors as diverse as drugs, inflammatory bowel disease, peptic ulcers, and necrotizing enterocolitis. However, although many drugs are used to ameliorate injurious factors, there is no drug available to actually stimulate mucosal wound healing. Focal adhesion kinase (FAK), a nonreceptor tyrosine kinase, induces epithelial sheet migration and wound healing, making FAK a potential pharmacological target in this regard. In our previous research, we found a lead compound with drug-like properties, ZINC40099027, which promotes FAK phosphorylation, inducing mucosal healing in murine models. Herein we describe the design and optimization of a small library of novel FAK activators based on ZINC40099027 and their applications toward human intestinal epithelial wound closure and mouse ulcer healing.

Cyclooxygenase inhibition attenuates brain angiogenesis and independently decreases mouse survival under hypoxia

Although cyclooxygenase (COX) role in cancer angiogenesis has been studied, little is known about its role in brain angioplasticity. In the present study, we chronically infused mice with ketorolac, a non‐specific COX inhibitor that does not cross the blood–brain barrier (BBB), under normoxia or 50% isobaric hypoxia (10% O₂ by volume). Ketorolac increased mortality rate under hypoxia in a dose‐dependent manner. Using in vivo multiphoton microscopy, we demonstrated that chronic COX inhibition completely attenuated brain angiogenic response to hypoxia. Alterations in a number of angiogenic factors that were reported to be COX‐dependent in other models were assayed at 24‐hr and 10‐day hypoxia. Intriguingly, hypoxia‐inducible factor 1 was unaffected under COX inhibition, and vascular endothelial growth factor receptor type 2 (VEGFR2) and C‐X‐C chemokine receptor type 4 (CXCR4) were significantly but slightly decreased. However, a number of mitogen‐activated protein kinases (MAPKs) were significantly reduced upon COX inhibition. We conclude that additional, angiogenic factor‐independent mechanism might contribute to COX role in brain angioplasticity, probably including mitogenic COX effect on endothelium. Our data indicate that COX activity is critical for systemic adaptation to chronic hypoxia, and BBB COX is essential for hypoxia‐induced brain angioplasticity. These data also indicate a potential risk for using COX inhibitors under hypoxia conditions in clinics. Further studies are required to elucidate a complete mechanism for brain long‐term angiogenesis regulation through COX activity.

Intrathecal administration of Resolvin D1 and E1 decreases hyperalgesia in mice with bone cancer pain: Involvement of endocannabinoid signaling

Pain produced by bone cancer is often severe and difficult to treat. Here we examined effects of Resolvin D1 (RvD1) or E1 (RvE1), antinociceptive products of ω-3 polyunsaturated fatty acids, on cancer-induced mechanical allodynia and heat hyperalgesia. Experiments were performed using a mouse model of bone cancer produced by implantation of osteolytic ficrosarcoma into and around the calcaneus bone. Mechanical allodynia and heat hyperalgesia in the tumor-bearing paw were assessed by measuring withdrawal responses to a von Frey monofilament and to radiant heat applied on the plantar hind paw. RvD1, RvE1, and cannabinoid receptor antagonists were injected intrathecally. Spinal content of endocannabinoids was evaluated using UPLC-MS/MS analysis. RvD1 and RvE1 had similar antinociceptive potencies. ED_50s for RvD1 and RvE1 in reducing mechanical allodynia were 0.2 pg (0.53 fmol) and 0.6 pg (1.71 fmol), respectively, and were 0.3 pg (0.8 fmol) and 0.2 pg (0.57 fmol) for reducing heat hyperalgesia. Comparisons of dose-response relationships showed equal efficacy for reducing mechanical allodynia, however, efficacy for reducing heat hyperalgesia was greater for of RvD1. Using UPLC-MS/MS we determined that RvD1, but not RvE1, increased levels of the endocannabinoids Anandamide and 2-Arachidonoylglycerol in the spinal cord. Importantly, Resolvins did not alter acute nociception or motor function in naïve mice. Our data indicate, that RvD1 and RvE1 produce potent antiallodynia and antihyperalgesia in a model of bone cancer pain. RvD1 also triggers spinal upregulation of endocannabinoids that produce additional antinociception predominantly through CB2 receptors.

In Vivo Generation of PFOA, PFOS, and Other Compounds from Cationic and Zwitterionic Per- and Polyfluoroalkyl Substances in a Terrestrial Invertebrate (Lumbricus terrestris)

Perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS) are two environmentally persistent per- and polyfluoroalkyl substances (PFAS) that have been detected globally in human tissues and fluids. As part of a project investigating the indirect sources of PFOA/PFOS in the environment and engineered systems, this study is concerned with the mechanisms leading to their in vivo generation in terrestrial invertebrates. We demonstrate here the formation of PFOA and PFOS in earthworms (Lumbricus terrestris) from a group of four zwitterionic/cationic polyfluoroalkyl amides and sulfonamides. In bioaccumulation tests, the zwitterionic PFAS compounds were metabolized within 10 days to PFOA/PFOS at yields of 3.4-20.8 mol % by day 21 and several infrequently reported PFAS species for which chemical structures were determined using high-resolution mass spectrometry. Cationic PFAS, on the other hand, were found to be much less metabolizable in terms of the number (n = 2) and yields (0.9-5.1 mol %) of metabolites. Peak-shaped bioaccumulation profiles were frequently observed for the studied PFAS. Residual zwitterionic/cationic PFAS in earthworms were detected at the end of the elimination phase, indicating that not all zwitterionic/cationic PFAS molecules in vivo are available for enzymatic degradation. Finally, the relative importance of different exposure routes (i.e., waterborne and dietary exposure) was investigated.

Probiotics ameliorate intestinal pathophysiology in a mouse model of Alzheimer's disease

Evidence suggests that changes in intestinal microbiota may affect the central nervous system. However, it is unclear whether alteration of intestinal microbiota affects progression of Alzheimer's disease (AD). To understand this, wild-type control (C57BL/6) mice were compared with the App^NL-G-F model of disease. We used probiotic supplementation to manipulate the gut microbiota. Fecal samples were collected for microbiota profiling. To study brain and intestinal inflammation, biochemical and histological analyses were performed. Altered metabolic pathways were examined by quantifying eicosanoid and bile acid profiles in the brain and serum using ultraperformance liquid chromatography-tandem mass spectrometry. We observed that brain pathology was associated with intestinal dysbiosis and increased intestinal inflammation and leakiness in App^NL-G-F mice. Probiotic supplementation significantly decreased intestinal inflammation and gut permeability with minimal effect on amyloid-β, cytokine, or gliosis levels in the brain. Concentrations of several bile acids and prostaglandins were altered in the serum and brain because of AD or probiotic supplementation. Our study characterizes intestinal dysfunction in an AD mouse model and the potential of probiotic intervention to ameliorate this condition.

COX-2-derived prostaglandins as mediators of the deleterious effects of nicotine in chronic kidney disease

Tobacco smoking has been identified as a risk factor in the progression of chronic kidney disease (CKD). In previous studies, we showed that nicotine induces cyclooxygenase (COX)-2 expression in vivo and in vitro and that the administration of nicotine in vivo worsens the severity of renal injury in a model of subtotal renal ablation. In the present study, we tested the role of COX-2-derived prostaglandins on the deleterious effects of nicotine in CKD. Sham and 5/6 nephrectomy (5/6Nx) rats received tap water or nicotine (100 μg/mL) in the drinking water for 12 wk. Additional groups also systemically received the COX-2 inhibitor NS-398 (1.5 mg·kg^-1·day^-1 via osmotic minipump). The administration of nicotine worsened renal injury and proteinuria in 5/6Nx rats and increased proteinuria in sham rats. 5/6Nx rats had increased cortical production of the prostaglandins PGE₂, PGI₂, PGD₂, and PGF_2α and of thromboxane A₂. In these rats, nicotine reduced the production of all prostaglandins examined except thromboxane A₂. Treatment with the COX-2 inhibitor NS-398 resulted in complete inhibition of all prostaglandins studied and ameliorated renal injury and proteinuria in 5/6Nx rats on nicotine but not in 5/6 Nx rats on tap water. Nicotine also reduced the expression of megalin in all groups examined, and this was partially prevented by COX-2 inhibition. In the present study, we showed that in CKD, nicotine worsens renal injury at least in part by producing an imbalance in the production of prostaglandins. This imbalance in the production of prostaglandins likely plays a role in the deleterious effects of smoking on the progression of CKD.

Blood-Brain Barrier Is the Major Site for a Rapid and Dramatic Prostanoid Increase upon Brain Global Ischemia

We and others have demonstrated a rapid and dramatic increase in brain prostanoids upon decapitation-induced brain global ischemia and injury. However, the mechanism for this induction, including the cell types involved, are unknown. In the present study, we have validated and applied a pharmacological approach to inhibit prostanoid synthesis in the blood-brain barrier including endothelial cells. Our results indicate that a nonspecific cyclooxygenase (COX) inhibitor, ketorolac, does not pass the blood-brain barrier and does not enter red blood cells but penetrates endothelial cells. Ketorolac treatment did not affect basal prostanoid levels but completely prevented prostanoid induction upon global ischemia. These data indicate that basal prostanoids are synthesized in brain parenchyma cells, while inducible prostanoids are synthesized in the blood-brain barrier, most likely in endothelial cells. However, future studies with cell and COX isoform-specific gene ablation are needed to further validate this conclusion. These findings identify endothelial cells as a possible target for the development of pharmacological approaches to selectively attenuate inducible prostanoid pools without affecting basal levels under brain ischemia, trauma, surgery, and other related conditions.

Sorption and Desorption Mechanisms of Cationic and Zwitterionic Per- and Polyfluoroalkyl Substances in Natural Soils: Thermodynamics and Hysteresis

Sorption linearity and reversibility are implicit in models for the fate and transport of per- and polyfluoroalkyl substances (PFAS). In this study, however, we found that the sorption of cationic and zwitterionic PFAS in natural soils was highly nonlinear. The nonlinearity was so severe that it led to a variation in the coefficient of sorption by several orders of magnitude over the experimental concentration range. This implies a considerable increase in sorption as concentration falls in the natural environment. Sorption of cationic PFAS correlated strongly with the soil organic matter (SOM) content and was reversible in all soils. Sorption of zwitterionic PFAS, on the other hand, displayed concentration-dependent hysteresis in soils with a low SOM content. The irreversibility, which was associated with neither SOM, pore deformation, nor surface complexation, was likely caused by the entrapment of molecules in porous structures within inorganic components of soil aggregates. Furthermore, electrostatic interactions with negatively charged soil constituents and the hydrophobic effect were found to be major sorption driving forces for cationic/zwitterionic PFAS at low and high concentrations, respectively. The maximum electrostatic potential of PFAS ions, computed using density functional theory, was found to be a useful predictor of the sorption of ionic PFAS species.

Sterol Carrier Protein-2/Sterol Carrier Protein-x/Fatty Acid Binding Protein-1 Ablation Impacts Response of Brain Endocannabinoid to High-Fat Diet

Brain endocannabinoids (EC) such as arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) primarily originate from serum arachidonic acid (ARA), whose level is regulated in part by a cytosolic ARA-binding protein, that is, liver fatty acid binding protein-1 (FABP1), not expressed in the brain. Ablation of the Fabp1 gene (LKO) increases brain AEA and 2-AG by decreasing hepatic uptake of ARA to increase serum ARA, thereby increasing ARA availability for uptake by the brain. The brain also expresses sterol carrier protein-2 (SCP-2), which is also a cytosolic ARA-binding protein. To further resolve the role of SCP-2 independent of FABP1, mice ablated in the Scp-2/Scp-x gene (DKO) were crossed with mice ablated in the Fabp1 gene (LKO) mice to generate triple knock out (TKO) mice. TKO impaired the ability of LKO to increase brain AEA and 2-AG. While a high-fat diet (HFD) alone increased brain AEA, TKO impaired this effect. Overall, these TKO-induced blocks were not attributable to altered expression of brain proteins in ARA uptake, AEA/2-AG synthesis, or AEA/2-AG degrading enzymes. Instead, TKO reduced serum levels of free ARA and/or total ARA and thereby decreased ARA availability for uptake to the brain and downstream synthesis of AEA and 2-AG therein. In summary, Scp-2/Scp-x gene ablation in Fabp1 null (LKO) mice antagonized the impact of LKO and HFD on brain ARA and, subsequently, EC levels. Thus, both FABP1 and SCP-2 participate in regulating the EC system in the brain.

Microenvironment-sensing, nanocarrier-mediated delivery of combination chemotherapy for pancreatic cancer

Limited effectiveness of Raf and MEK inhibitors has impelled the interest to use the inhibitors of Extra-cellular Receptor Kinase (ERK) pathway in combination with Gemcitabine (GEM) in pancreatic cancer. However, off-target abundance of ERK receptors, challenging physico-chemical properties, and dose-limiting toxicity of the inhibitor has presented critical challenges towards fabricating this combination amenable for clinical translation. Herein we report a pharmaceutical nanoformulation of GEM and an ERK inhibitor (SCH 772984) co-stabilized within a pH-sensing nanocarrier (NC, with a hydrodynamic diameter of 161 ± 5.0 nm). The NCs were modularly derived from a triblock, self-assembling copolymer, and were chemically conjugated with GEM and encapsulated with SCH772984 at a loading content of 20.2% and 18.3%, respectively. Through pH-mediated unfolding of the individual blocks of the copolymer, the NCs were able to control the release of encapsulated drugs, traffic through cellular membranes, engage target receptors, suppress proliferation of pancreatic cancer cells, and accumulate at disease sites. Collectively our studies showed the feasibility of co-delivery of a combination chemotherapy consisting of GEM and an ERK inhibitor from a NC platform, which can sense and respond to tumor microenvironment of pancreatic cancer setting.

Synthesis of a novel brominated vinylic fatty acid with antileishmanial activity that effectively inhibits the Leishmania topoisomerase IB enzyme mediated by halogen bond formation

Many marine derived fatty acids, mainly from sponges, possess vinylic halogenated moieties (bromine or iodine) but their assessment as antileishmanial candidates remains elusive. In this work, we undertook the first total synthesis of a novel series of 2-allyl-3-halo-2-nonadecenoic acids, which preferentially inhibit the Leishmania DNA topoisomerase IB enzyme (LTopIB) over the human topoisomerase IB enzyme (hTopIB). The synthesis of 2-allyl-3-bromo-2E-nonadecenoic acid (1a) and 2-allyl-3-chloro-2E-nonadecenoic acid (2a) was achieved through a palladium catalyzed haloallylation of 2-nonadecynoic acid (2-NDA) using either allyl bromide or allyl chloride in the presence of PdCl2(PhCN)2 in 57–83 % overall yields. Among the new halogenated synthetic compounds, 1a was the most inhibitory of LTopIB with an EC50 = 7 μM, while the shorter chain analogs 2-allyl-3-bromo-2E-dodecenoic acid (1b) and 2-allyl-3-chloro-2E-dodecenoic acid (2b), synthesized from 2-dodecynoic acid, were not inhibitory of LTopIB (EC50 > 100 μM) resulting in the overall order of inhibition 1a > 2-NDA > 2a > > 1b ≅ 2b. The acids 1a and 2a inhibit LTopIB by a Gimatecan-independent mechanism. The enhanced LTopIB inhibition of 1a was computationally rationalized in terms of a halogen bond between the bromine in 1a and a DNA phosphate (binding energy = − 4.85 kcal/mol). Acid 1a also displayed preferential cytotoxicity towards Leishmania infantum amastigotes (EC50 = 2.5 μM) over L. infantum promastigotes (EC50 > 25 μM).

Plasma Unesterified Fatty-Acid Profile Is Dramatically and Acutely Changed under Ischemic Stroke in the Mouse Model

Although plasma biomarkers would facilitate rapid and accurate diagnosis of ischemic stroke for immediate treatment, no such biomarkers have been developed to date. In the present study, we tested our hypothesis that plasma unesterified fatty acids (FFA) are altered at early stages of acute ischemic stroke. Plasma was collected from mice 2 h after the permanent middle cerebral artery occlusion (pMCAo) onset, as well as from sham operated and control animals. After 2 h, pMCAo significantly changed the plasma FFA profile with the most dramatic 2- to 3-fold relative increase in very long n-3 and n-6 FFA including 20:4n-6, 22:4n-6, 22:5n-6, and 22:6n-3. Changes in the plasma FFA profile are consistent with FFA liberation from brain phospholipid hydrolyzed under ischemic insult. These results identify, for the first time, the plasma FFA profile as a potential biomarker for an early ischemic stroke within the therapeutic window for thrombolytic treatment. Further studies are required to confirm its specificity and sensitivity in clinical settings.

Scp-2/Scp-x ablation in Fabp1 null mice differentially impacts hepatic endocannabinoid level depending on dietary fat

Dysregulation of the hepatic endocannabinoid (EC) system and high fat diet (HFD) are associated with non-alcoholic fatty liver disease. Liver cytosol contains high levels of two novel endocannabinoid binding proteins-liver fatty acid binding protein (FABP1) and sterol carrier protein-2 (SCP-2). While Fabp1 gene ablation significantly increases hepatic levels of arachidonic acid (ARA)-containing EC and sex-dependent response to pair-fed high fat diet (HFD), the presence of SCP-2 complicates interpretation. These issues were addressed by ablating Scp-2/Scp-x in Fabp1 null mice (TKO). In control-fed mice, TKO increased hepatic levels of arachidonoylethanolamide (AEA) in both sexes. HFD impacted hepatic EC levels by decreasing AEA in TKO females and decreasing 2-arachidonoyl glycerol (2-AG) in WT of both sexes. Only TKO males on HFD had increased hepatic 2-AG levels. Hepatic ARA levels were decreased in control-fed TKO of both sexes. Changes in hepatic AEA/2-AG levels were not associated with altered amounts of hepatic proteins involved in AEA/2-AG synthesis or degradation. These findings suggested that ablation of the Scp-2/Scp-x gene in Fabp1 null mice exacerbated hepatic EC accumulation and antagonized the impact of HFD on hepatic EC levels-suggesting both proteins play important roles in regulating the hepatic EC system.

Identification of novel non-ionic, cationic, zwitterionic, and anionic polyfluoroalkyl substances using UPLC-TOF-MSE high-resolution parent ion search

Poly- and perfluoroalkyl substances (poly- and per-PFASs) are a large group of organic compounds that have become the target of investigation due to their widespread occurrence in the environment and biota, coupled with their known or suspected impacts on human health. Recent studies have shown that a significant portion of poly-PFASs remain unidentified. This study presents a time-of-flight mass spectrometry approach based on continuously interleaving scans at low and high collision energies (ToF-MS^E) for the rapid identification and characterization of unknown PFASs. The MS^E mode allowed for the simultaneous acquisition of full-spectrum accurate mass data of both parent and fragment ions in a single chromatographic run. Specific to PFASs, the hypothesis that PFASs can be selectively detected by the ToF-MS^E high-resolution parent-ion search (HRPIS) of their characteristic fragments was confirmed with certified standards of 24 poly- and per-PFAS. After being validated with these certified standards, the innovative HRPIS approach was applied to a group of commercial surfactants, which led to the identification of 47 new and 43 infrequently reported PFASs, including 40 non-ionic, 30 cationic, 15 zwitterionic, and five anionic compounds. It is envisaged that the results, especially the identification of new non-ionic PFASs, may provide important insights into the historical occupational and non-occupational exposure to PFASs from the production and application of these surfactants.

Inhibition of the Serotonin Transporter Is Altered by Metabolites of Selective Serotonin and Norepinephrine Reuptake Inhibitors and Represents a Caution to Acute or Chronic Treatment Paradigms

Previous studies of transgenic mice carrying a single isoleucine to methionine substitution (I172M) in the serotonin transporter (SERT) demonstrated a loss of sensitivity to multiple antidepressants (ADs) at SERT. However, the ability of AD metabolites to antagonize SERT was not assessed. Here, we evaluated the selectivity and potency of these metabolites for inhibition of SERT in mouse brain-derived synaptosomes and blood platelets from wild-type (I172 mSERT) and the antidepressant-insensitive mouse M172 mSERT. The metabolites norfluoxetine and desmethylsertraline lost the selectivity demonstrated by the parent compounds for inhibition of wild-type mSERT over M172 mSERT, whereas desvenlafaxine and desmethylcitalopram retained selectivity. Furthermore, we show that the metabolite desmethylcitalopram accumulates in the brain and that the metabolites desmethylcitalopram, norfluoxetine, and desvenlafaxine inhibit serotonin uptake in wild-type mSERT at potencies similar to those of their parent compounds, suggesting that metabolites may play a role in effects observed following AD administration in wild-type and M172 mice.

Fatty Acid Biosynthesis Inhibition Increases Reduction Potential in Neuronal Cells under Hypoxia

Recently, we have reported a novel neuronal specific pathway for adaptation to hypoxia through increased fatty acid (FA) biosynthesis followed by esterification into lipids. However, the biological role of this pathway under hypoxia remains to be elucidated. In the presented study, we have tested our hypothesis that activation of FA synthesis maintains reduction potential and reduces lactoacidosis in neuronal cells under hypoxia. To address this hypothesis, we measured the effect of FA synthesis inhibition on [Formula: see text]/NAD⁺ and [Formula: see text]/NADP⁺ ratios, and lactic acid levels in neuronal SH-SY5Y cells exposed to normoxic and hypoxic conditions. FA synthesis inhibitors, TOFA (inhibits Acetyl-CoA carboxylase) and cerulenin (inhibits FA synthase), increased [Formula: see text]/NAD⁺ and [Formula: see text]/NADP⁺ ratios under hypoxia. Further, FA synthesis inhibition increased lactic acid under both normoxic and hypoxic conditions, and caused cytotoxicity under hypoxia but not normoxia. These results indicate that FA may serve as hydrogen acceptors under hypoxia, thus supporting oxidation reactions including anaerobic glycolysis. These findings may help to identify a radically different approach to attenuate hypoxia related pathophysiology in the nervous system including stroke.

Fabp1 gene ablation inhibits high-fat diet-induced increase in brain endocannabinoids

The endocannabinoid system shifts energy balance toward storage and fat accumulation, especially in the context of diet-induced obesity. Relatively little is known about factors outside the central nervous system that may mediate the effect of high-fat diet (HFD) on brain endocannabinoid levels. One candidate is the liver fatty acid binding protein (FABP1), a cytosolic protein highly prevalent in liver, but not detected in brain, which facilitates hepatic clearance of fatty acids. The impact of Fabp1 gene ablation (LKO) on the effect of high-fat diet (HFD) on brain and plasma endocannabinoid levels was examined and data expressed for each parameter as the ratio of high-fat diet/control diet. In male wild-type mice, HFD markedly increased brain N-acylethanolamides, but not 2-monoacylglycerols. LKO blocked these effects of HFD in male mice. In female wild-type mice, HFD slightly decreased or did not alter these endocannabinoids as compared with male wild type. LKO did not block the HFD effects in female mice. The HFD-induced increase in brain arachidonic acid-derived arachidonoylethanolamide in males correlated with increased brain-free and total arachidonic acid. The ability of LKO to block the HFD-induced increase in brain arachidonoylethanolamide correlated with reduced ability of HFD to increase brain-free and total arachidonic acid in males. In females, brain-free and total arachidonic acid levels were much less affected by either HFD or LKO in the context of HFD. These data showed that LKO markedly diminished the impact of HFD on brain endocannabinoid levels, especially in male mice.

FABP-1 gene ablation impacts brain endocannabinoid system in male mice

Liver fatty acid-binding protein (FABP1, L-FABP) has high affinity for and enhances uptake of arachidonic acid (ARA, C20:4, n-6) which, when esterified to phospholipids, is the requisite precursor for synthesis of endocannabinoids (EC) such as arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG). The brain derives most of its ARA from plasma, taking up ARA and transporting it intracellularly via cytosolic fatty acid-binding proteins (FABPs 3,5, and 7) localized within the brain. In contrast, the much more prevalent cytosolic FABP1 is not detectable in the brain but is instead highly expressed in the liver. Therefore, the possibility that FABP1 outside the central nervous system may regulate brain AEA and 2-AG was examined in wild-type (WT) and FABP1 null (LKO) male mice. LKO increased brain levels of AA-containing EC (AEA, 2-AG), correlating with increased free and total ARA in brain and serum. LKO also increased brain levels of non-ARA that contain potentiating endocannabinoids (EC*) such as oleoyl ethanolamide (OEA), PEA, 2-OG, and 2-PG. Concomitantly, LKO decreased serum total ARA-containing EC, but not non-ARA endocannabinoids. LKO did not elicit these changes in the brain EC and EC* as a result of compensatory up-regulation of brain protein levels of enzymes in EC synthesis (NAPEPLD, DAGLα) or cytosolic EC chaperone proteins (FABPs 3, 5, 7, SCP-2, HSP70), or cannabinoid receptors (CB1, TRVP1). These data show for the first time that the non-CNS fatty acid-binding protein FABP1 markedly affected brain levels of both ARA-containing endocannabinoids (AEA, 2-AG) as well as their non-ARA potentiating endocannabinoids. Fatty acid-binding protein-1 (FABP-1) is not detectable in brain but instead is highly expressed in liver. The possibility that FABP1 outside the central nervous system may regulate brain endocannabinoids arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG) was examined in wild-type (WT) and FABP-1 null (LKO) male mice. LKO increased brain levels of arachidonic acid-containing endocannabinoids (AEA, 2-AG), correlating with increased free and total arachidonic acid in brain and serum. Read the Editorial Highlight for this article on page 371.

Brain 2-Arachidonoylglycerol Levels Are Dramatically and Rapidly Increased Under Acute Ischemia-Injury Which Is Prevented by Microwave Irradiation

The involvement of brain 2-arachidonoylglycerol (2-AG) in a number of critical physiological and pathophysiological regulatory mechanisms highlights the importance for an accurate brain 2-AG determination. In the present study, we validated head-focused microwave irradiation (MW) as a method to prevent postmortem brain 2-AG alterations before analysis. We compared MW to freezing to prevent 2-AG induction and estimated exogenous and endogenous 2-AG stability upon exposure to MW. Using MW, we measured, for the first time, true 2-AG brain levels under basal conditions, 30 s after brain removal from the cranium, and upon exposure to 5 min of brain global ischemia. Our data indicate that brain 2-AG levels are instantaneously and dramatically increased approximately 60-fold upon brain removal from the cranium. With 5 min of brain global ischemia 2-AG levels are also, but less dramatically, increased 3.5-fold. Our data indicate that brain tissue fixation with MW is a required technique to measure both true basal 2-AG levels and 2-AG alterations under different experimental conditions including global ischemia, and 2-AG is stable upon exposure to MW.

Novel Very Long-Chain α-Methoxylated Δ5,9 Fatty Acids from the Sponge Asteropus niger Are Effective Inhibitors of Topoisomerases IB

The novel fatty acids (2R,5Z,9Z)-2-methoxy-25-methyl-5,9-hexacosadienoic acid (1a) and (2R,5Z,9Z)-2-methoxy-24-methyl-5,9-hexacosadienoic acid (1b) were isolated in 80 % purity from the Caribbean sponge Asteropus niger by chloroform/methanol extraction followed by solvent partitioning and silica gel column chromatography. The compounds were characterized by utilizing a combination of gas chromatography-mass spectrometry, nuclear magnetic resonance, and circular dichroism. Acids 1a and 1b were not detected in the phospholipids (PtdCho and PtdIns) of the sponge, but rather as free FA and possibly in glycosylceramides. The mixtures of 1a and 1b displayed cytotoxicity towards THP-1 and HepG2 cells with EC50's between 41 and 35 μg/mL. Apoptosis was not the preferred mode of cell death induced by 1a-1b in the THP-1 cells. This implies other types of cytotoxicity mechanisms, such as membrane disruption and/or the inhibition (EC50 = 1.8 μg/mL) of the human topoisomerase IB enzyme (hTopIB), with a mechanism of inhibition different from the one displayed by camptothecin (CPT). In a separate experiment, the mixture of 1a and 1b also displayed cytotoxicity towards ex vivo mouse splenocytes infected with Leishmania infantum amastigotes (IC(50) = 0.17 mg/mL) and free living promastigotes (IC(50) = 0.34 mg/mL). It was also found that the FA were inhibitory of the Leishmania topoisomerase IB (LTopIB) with an EC(50) = 5.1 μg/mL. Taken together, 1a and 1b represent a new class of FA with potential as TopIB inhibitors that preferentially inhibit hTopIB over LTopIB.

Brain changes associated with thromboxane receptor antagonist SQ 29,548 treatment in a mouse model

The purpose of this study was to characterize behavioral and physiological effects of a selective thromboxane (TP) receptor antagonist, SQ 29,548, in the C57Bl/6 mouse model. At 6 months of age, male mice were given either sham or drug i.p. injections for 3 days at a dose of 2 mg/kg each day. On the day after the final injection, mice were subjected to behavioral testing before brain collection. Left hemisphere hippocampi were collected from all mice for protein analysis via Western blot. Right brain hemispheres were fixed and embedded in gelatin and then serially sectioned. The sections were immunostained with anti-c-Fos antibodies. Prostaglandin analysis was performed from remaining homogenized brain samples, minus the hippocampi. Injection of SQ 29,548 decreased selective brain prostaglandin levels compared with sham controls. This correlated with robust increases in limbic-region c-Fos immunoreactivity in the SQ 29,548-injected mice. However, drug-treated mice demonstrated no significant changes in relevant hippocampal protein levels compared with sham treatments, as determined from Western blots. Surprisingly, injection of SQ 29,548 caused mixed changes in parameters of depression and anxiety-like behavior in the mice. In conclusion, the results indicate that administration of peripheral TP receptor antagonists alters brain levels of prostanoids and influences neuronal activity, with only minimal alterations of behavior. Whether the drug affects neurons directly or through a secondary pathway involving endothelium or other tissues remains unclear.

Fatty acid biosynthesis from glutamate and glutamine is specifically induced in neuronal cells under hypoxia

Hypoxia is involved in many neuronal and non-neuronal diseases, and defining the mechanisms for tissue adaptation to hypoxia is critical for the understanding and treatment of these diseases. One mechanism for tissue adaptation to hypoxia is increased glutamine and/or glutamate (Gln/Glu) utilization. To address this mechanism, we determined incorporation of Gln/Glu and other lipogenic substrates into lipids and fatty acids in both primary neurons and a neuronal cell line under normoxic and hypoxic conditions and compared this to non-neuronal primary cells and non-neuronal cell lines. Incorporation of Gln/Glu into total lipids was dramatically and specifically increased under hypoxia in neuronal cells including both primary (2.0- and 3.0-fold for Gln and Glu, respectively) and immortalized cultures (3.5- and 8.0-fold for Gln and Glu, respectively), and 90% to 97% of this increase was accounted for by incorporation into fatty acids (FA) depending upon substrate and cell type. All other non-neuronal cells tested demonstrated decreased or unchanged FA synthesis from Gln/Glu under hypoxia. Consistent with these data, total FA mass was also increased in neuronal cells under hypoxia that was mainly accounted for by the increase in saturated and monounsaturated FA with carbon length from 14 to 24. Incorporation of FA synthesized from Gln/Glu was increased in all major lipid classes including cholesteryl esters, triacylglycerols, diacylglycerols, free FA, and phospholipids, with the highest rate of incorporation into triacylglycerols. These results indicate that increased FA biosynthesis from Gln/Glu followed by esterification may be a neuronal specific pathway for adaptation to hypoxia. We identified a novel neuronal specific pathway for adaptation to hypoxia through increased fatty acid biosynthesis from glutamine and glutamate (Gln/Glu) followed by esterification into lipids. All other non-neuronal cells tested demonstrated decreased or unchanged lipid synthesis from Gln/Glu under hypoxia. Incorporation of other lipogenic substrates into lipids was decreased under hypoxia in neuronal cells. We believe that this finding will provide a novel strategy for treatment of oxygen and energy deficient conditions in the neuronal system.

Eicosanoid post-mortem induction in kidney tissue is prevented by microwave irradiation

Previously, we, and others, have demonstrated a rapid and significant post-mortem increase in brain prostanoid (PG) levels analyzed without microwave fixation, and this is not the result of PG trapping or destruction in microwave-irradiated brain tissue. In the present study, we demonstrate a dramatic increase in kidney eicosanoid levels when analyzed without microwave fixation which was mainly accounted for by the 142-, 81-, and 62-fold increase in medullary 6-ketoPGF1α, PGE2, and PGF2α, levels, respectively, while PGD2 and TXB2 levels were increased ~7-fold. Whole kidney and cortex PG were also significantly increased in non-microwaved tissue, but at lesser extent. Arachidonic acid and the lipoxygenase products hydroxyeicosatetraenoic acids (HETE) were also induced in whole kidney, cortex, and medulla 1.5- to 5.5-fold depending upon tissue and metabolite. Cyclooxygenase inhibition with indomethacin decreased PG mass in non-microwaved tissue to basal levels, however HETE and arachidonic acid were not decreased. These data demonstrate the critical importance of kidney tissue fixation to limiting artifacts during kidney eicosanoid analysis.

A fast one-step extraction and UPLC-MS/MS analysis for E2/D 2 series prostaglandins and isoprostanes

Prostaglandins (PG) and isoprostanes (iso-PG) may be derived through cyclooxygenase or free radical pathways and are important signaling molecules that are also robust biomarkers of oxidative stress. Their quantification is important for understanding many biological processes where PG, iso-PG, or oxidative stress are involved. One of the common methods for PG and iso-PG quantifications is LC-MS/MS that allows a highly selective, sensitive, simultaneous analysis for prostanoids without derivatization. However, the currently used LC-MS/MS methods require a multi-step extraction and a long (within an hour) LC separation to achieve simultaneous separation and analysis of the major iso-PG. The developed and validated for brain tissue analysis one-step extraction protocol and UPLC-MS/MS method significantly increases the recovery of the PG extraction up to 95 %, and allows for a much faster (within 4 min) major iso-PGE2 and -PGD2 separation with 5 times narrower chromatographic peaks as compared to previously used methods. In addition, it decreases the time and cost of analysis due to the one-step extraction approach performed in disposable centrifuge tubes. All together, this significantly increases the sensitivity, and the time and cost efficiency of the PG and iso-PG analysis.

A rapid oxygen exchange on prostaglandins in plasma represents plasma esterase activity that is inhibited by diethylumbelliferyl phosphate with high affinity

RATIONALE

Fatty acids (FA) labeled with (18) O at the carboxyl group, including oxidized species (FA(18) O), are a useful, low-cost, and easy to prepare tool for quantitative and qualitative mass spectrometry (MS) analysis in biological systems. In addition, they are used to trace the fate of FAs in metabolic pathways including FA re-esterification and lipid remodeling pathways. Although a rapid (18) O exchange on FA(18) O in biological systems has been reported, the mechanism contributing to (18) O exchange has not been fully evaluated. This gap in knowledge limits the use of FA(18) O as a standard for MS and complicates data interpretation for FA metabolism in biological systems.

METHODS

In the present study we have addressed a number of possible mechanisms for a rapid (18) O exchange on prostaglandin E(2) (PGE(2) ) using rat plasma as a model. High-performance liquid chromatography coupled with electrospray ionization triple quadrupole MS in the multiple reaction monitoring mode was used for quantification.

RESULTS

The major mechanism for a rapid (18) O exchange on PGE(2) (18) O in rat plasma is PGE(2) processing with esterases, while FA re-esterification and non-enzymatic mechanisms do not significantly contribute to this phenomenon. In addition, we report a highly effective inhibition of (18) O exchange with diethylumbelliferyl phosphate that can be used to stabilize FA(18) O in biological samples.

CONCLUSIONS

These data indicate the necessity to consider esterase activity when FA(18) O are used to study FA metabolism, and the importance of esterase activity inhibition when FA(18) O are used as internal standards for MS analysis in biological systems. In addition, the results provide a rational for the development of new approaches to study esterase activities and affinity towards modified FA.

Baking reduces prostaglandin, resolvin, and hydroxy-fatty acid content of farm-raised Atlantic salmon (Salmo salar)

The consumption of seafood enriched in n-3 polyunsaturated fatty acids (PUFA) is associated with a decreased risk of cardiovascular disease. Several n-3 oxidation products from eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (22:6n-3) have known protective effects in the vasculature. It is not known whether the consumption of cooked seafood enriched in n-3 PUFA causes appreciable consumption of lipid oxidation products. We tested the hypothesis that baking Atlantic salmon (Salmo salar) increases the level of n-3 and n-6 PUFA oxidation products over raw salmon. We measured the contents of several monohydroxy-fatty acids (MHFA), prostanoids, and resolvins. Our data demonstrate that baking did not change the overall total levels of MHFA. However, baking resulted in selective regioisomeric loss of hydroxy fatty acids from arachidonic acid (20:4n-6) and EPA, while significantly increasing hydroxyl-linoleic acid levels. The contents of prostanoids and resolvins were reduced several-fold with baking. The inclusion of a coating on the salmon prior to baking reduced the loss of some MHFA but had no effect on prostanoid losses incurred by baking. Baking did not decrease n-3 PUFA contents, indicating that baking of salmon is an acceptable means of preparation that does not alter the potential health benefits of high n-3 seafood consumption. The extent to which the levels of MHFA, prostanoids, and resolvins in the raw or baked fish have physiologic consequence for humans needs to be determined.

LC/MS/MS method for analysis of E₂ series prostaglandins and isoprostanes

15-series prostaglandins (PGE₂s) and isoprostanes (isoPGE₂s) are robust biomarkers of oxidative stress, possess potent biological activity, and may be derived through cyclooxygenase or free radical pathways. Thus, their quantification is critical in understanding many biological processes where PG, isoPG, or oxidative stress are involved. LC/MS/MS methods allow a highly selective, sensitive, simultaneous analysis for prostanoids without derivatization. However, the LC/MS/MS methods currently used do not allow for simultaneous separation of the major brain PGE₂/D₂) and isoPGE₂ without derivatization and multiple HPLC separations. The developed LC/MS/MS method allows for the major brain PGE₂/PGD₂/isoPGE₂ such as PGE₂, entPGE₂, 8-isoPGE₂, 11β-PGE₂, PGD₂, and 15(R)-PGD₂ to be separated and quantified without derivatization. The method was validated by analyzing free and esterified isoPGE₂ in mouse brains fixed with head-focused microwave irradiation before or after global ischemia. Using the developed method, we report for the first time the esterified isoPGE₂ levels in brain tissue under basal conditions and upon global ischemia and demonstrate a nonreleasable pool of esterified isoPG upon ischemia. In addition, we demonstrated that PGE₂s found esterified in the sn-2 position in phospholipids are derived from a free radical nonenzymatic pathway under basal conditions. Our method for brain PG analysis provides a high level of selectivity to detect changes in brain PG and isoPG mass under both basal and pathological conditions.

Quantitative determination of free glycerol and myo-inositol from plasma and tissue by high-performance liquid chromatography

A high-performance liquid chromatographic method that accurately measures glycerol and myo-inositol from plasma and tissue is described. The method incorporates a pre-column derivatization reaction using aqueous extracts with benzoyl chloride as a modifying agent. The benzoylated derivatives are isolated by HPLC using reversed-phase gradient chromatography and quantified via absorbance detection at 231 nm. The benzoylated derivatives of glycerol and myo-inositol are well resolved from other known carbohydrates, internal standard and other contaminants encountered within samples and during incubation. The benzoylation of these analytes reach a maximum between 3.5 and 6 h of incubation and are stable for at least 24 days at 4 degrees C. The limit of quantization (LOQ) of glycerol was equal to 2.5 nmol/ml plasma and 6.4 nmol/g tissue and the LOQ of myo-inositol was 1.8 nmol/ml plasma and 3.6 nmol/g tissue. Incubation of known standards and samples with benzoyl chloride at 40 degrees C for 4 h showed fully benzoylated products as determined by mass spectral analysis. Calibration curves were linear between 2.7 and 174 nmol for glycerol and 1.4-89 nmol for myo-inositol. Comparison of tissue and plasma concentrations of glycerol and myo-inositol found using this method are in good agreement with other reported values using other techniques.

An improved LC-MS/MS procedure for brain prostanoid analysis using brain fixation with head-focused microwave irradiation and liquid-liquid extraction

High-performance liquid chromatography with tandem mass spectrometry detection (LC-MS/MS) allows a highly selective, sensitive, simultaneous analysis for prostanoids (PG) without derivatization. However, high chemical background noise reduces LC-MS/MS selectivity and sensitivity for brain PG analysis. Four common methods using different solvent systems for PG extraction were tested. Although these methods had the same recovery of PG, the modified acetone extraction followed by liquid/liquid purification had the greatest sensitivity. This method combined with hexane/2-propanol extraction permits the simultaneous analysis of other lipid molecules and PG in the same extract. We also determined that PG mass in brain powder stored at -80 degrees C was reduced 2- to 4- fold in 4 weeks; however, PG were stable for long periods (>3 months) in hexane/2-propanol extracts. PG mass was increased significantly when mice were euthanized by decapitation and the brains rapidly flash-frozen rather than euthanized using head-focused microwave irradiation. This reduction is not the result of PG trapping or destruction in microwave-irradiated brains, demonstrating its importance in limiting mass artifacts during brain PG analysis. Our improved procedure for brain PG analysis provides a reliable, rapid means to detect changes in brain PG mass under both basal and pathological conditions and demonstrates the importance of sample preparation in this process.

Brain prostaglandin formation is increased by alpha-synuclein gene-ablation during global ischemia

We have previously demonstrated that alpha-synuclein (Snca) gene ablation reduces brain arachidonic acid (20:4n-6) turnover rate in phospholipids through modulation of endoplasmic reticulum-localized acyl-CoA synthetase activity. Although 20:4n-6 is a precursor for prostaglandin (PG), Snca effect on PG levels is unknown. In the present study, we examined the effect of Snca ablation on brain PG level at basal conditions and following 30s of global ischemia. Brain PG were extracted with methanol, purified on C(18) cartridges, and analyzed by LC-MS/MS. We demonstrate, for the first time, that Snca gene ablation did not affect brain PG mass under normal physiological conditions. However, total PG mass and masses of individual PG were elevated approximately 2-fold upon global ischemia in the absence of Snca. These data are consistent with our previously observed reduction in 20:4n-6 recycling through endoplasmic reticulum-localized acyl-CoA synthetase in the absence of Snca, which may result in the increased 20:4n-6 availability for PG production in the absence of Snca during global ischemia and suggest a role for Snca in brain inflammatory response.

Brain neutral lipids mass is increased in alpha-synuclein gene-ablated mice

Because alpha-synuclein (Snca) has a role in brain lipid metabolism, we determined the impact that Snca deletion had on whole brain lipid composition. We analysed masses of individual phospholipid (PL) classes and neutral lipid mass as well as PL acyl chain composition in brains from wild-type and Snca-/- mice. Although total brain PL mass was not altered, cardiolipin and phosphatidylglycerol mass decreased 16% and 27%, respectively, in Snca-/- mice. In addition, no changes were observed in plasmalogen or polyphosphoinositide mass. In ethanolamine glycerophospholipids and phosphatidylserine, docosahexaenoic acid (22 : 6n-3) was decreased 7%, while 16 : 0 was increased 1.1-fold and 1.4-fold, respectively. Surprisingly, brain cholesterol, cholesteryl ester, and triacylglycerol mass were increased 1.1-fold, 1.6-fold, and 1.4-fold, respectively in Snca-/- mice. In isolated myelin, cholesterol mass was also increased 1.3-fold, but because there was also a net increase in myelin PL mass, the cholesterol to PL ratio was unaltered. No changes in the expression of cholesterogenic enzymes were observed, suggesting these did not account for the observed changes in cholesterol. These data extend our previous results in astrocytes and kinetic studies in vivo demonstrating a role for Snca in brain lipid metabolism and demonstrate a clear impact on brain neutral lipid metabolism.

α-Synuclein gene ablation increases docosahexaenoic acid incorporation and turnover in brain phospholipids

Previously, we demonstrated that ablation of alpha-synuclein (Snca) reduces arachidonate (20:4n-6) turnover in brain phospholipids through modulation of an endoplasmic reticulum-localized acyl-CoA synthetase (Acsl). The effect of Snca ablation on docosahexaenoic acid (22:6n-3) metabolism is unknown. In the present study, we examined the effect of Snca gene ablation on brain 22:6n-3 metabolism. We determined 22:6n-3 uptake and incorporation into brain phospholipids by infusing awake, wild-type and Snca-/- mice with [1-14C]22:6n-3 using steady-state kinetic modeling. In addition, because Snca modulates 20:4n-6-CoA formation, we assessed microsomal Acsl activity using 22:6n-3 as a substrate. Although Snca gene ablation does not affect brain 22:6n-3 uptake, brain 22:6n-3-CoA mass was elevated 1.5-fold in the absence of Snca. This is consistent with the 1.6- to 2.2-fold increase in the incorporation rate and turnover in ethanolamine glycerophospholipid, phosphatidylserine, and phosphatidylinositol pools. Increased 22:6n-3-CoA mass was not the result of altered Acsl activity, which was unaffected by the absence of Snca. While Snca bound 22:6n-3, Kd = 1.0 +/- 0.5 micromol/L, it did not bind 22:6n-3-CoA. These effects of Snca gene deletion on 22:6n-3 brain metabolism are opposite to what we reported previously for brain 20:4n-6 metabolism and are likely compensatory for the decreased 20:4n-6 metabolism in brains of Snca-/- mice.

Deposition of iron and beta-amyloid plaques is associated with cortical cellular damage in rabbits fed with long-term cholesterol-enriched diets

Hypercholesterolemia is a potential trigger of Alzheimer's disease, and is thought to increase brain levels of beta-amyloid (Abeta) and iron. However, animal models to address the mechanisms by which Abeta and iron accumulation may cause neuronal damage are poorly defined. To address this question, we fed adult rabbits a 1% cholesterol-enriched diet for 7 months. This diet was associated with increased regional deposition of both iron and Abeta peptide in the brain. Iron preferentially accumulated around Abeta plaques in the adjacent cortex, but was not found in the hippocampus. Co-localization of iron and Abeta was accompanied by apoptosis, DNA damage, blood-brain barrier (BBB) disruption, as well as dysregulation in the level of the iron-regulatory proteins, ferritin and heme-oxygenase-1. We further demonstrate that the cholesterol diet-induced apoptosis is mediated by the activation of the endoplasmic reticulum stress pathway, involving the down-regulation of the endoplasmic reticulum chaperones, calreticulin, grp78 and grp94, and the activation of the growth and arrest DNA damage protein, gadd153. Our results suggest that BBB damage and disturbances in iron metabolism may render the cortex more vulnerable than the hippocampus to the cholesterol-induced cellular stress.

Acyl-CoA synthetase activity links wild-type but not mutant alpha-synuclein to brain arachidonate metabolism

Because alpha-synuclein (Snca) has a role in brain lipid metabolism, we determined the impact that the loss of alpha-synuclein had on brain arachidonic acid (20:4n-6) metabolism in vivo using Snca-/- mice. We measured [1-(14)C]20:4n-6 incorporation and turnover kinetics in brain phospholipids using an established steady-state kinetic model. Liver was used as a negative control, and no changes were observed between groups. In Snca-/- brains, there was a marked reduction in 20:4n-6-CoA mass and in microsomal acyl-CoA synthetase (Acsl) activity toward 20:4n-6. Microsomal Acsl activity was completely restored after the addition of exogenous wild-type mouse or human alpha-synuclein, but not by A30P, E46K, and A53T forms of alpha-synuclein. Acsl and acyl-CoA hydrolase expression was not different between groups. The incorporation and turnover of 20:4n-6 into brain phospholipid pools were markedly reduced. The dilution coefficient lambda, which indicates 20:4n-6 recycling between the acyl-CoA pool and brain phospholipids, was increased 3.3-fold, indicating more 20:4n-6 was entering the 20:4n-6-CoA pool from the plasma relative to that being recycled from the phospholipids. This is consistent with the reduction in Acsl activity observed in the Snca-/- mice. Using titration microcalorimetry, we determined that alpha-synuclein bound free 20:4n-6 (Kd = 3.7 microM) but did not bind 20:4n-6-CoA. These data suggest alpha-synuclein is involved in substrate presentation to Acsl rather than product removal. In summary, our data demonstrate that alpha-synuclein has a major role in brain 20:4n-6 metabolism through its modulation of endoplasmic reticulum-localized acyl-CoA synthetase activity, although mutant forms of alpha-synuclein fail to restore this activity.

Uptake and metabolism of plasma-derived erucic acid by rat brain

We examined the ability of erucic acid (22:1n-9) to cross the blood-brain barrier (BBB) by infusing [14-14C]22:1n-9 (170 microCi/kg, iv and icv) into awake, male rats. [1-14C]arachidonic acid (20:4n-6) [intravenous (i.v.)] was the positive control. After i.v. infusion, 0.011% of the plasma [14-14C]22:1n-9 was extracted by the brain, compared with 0.055% of the plasma [1-14C]20:4n-6. The [14-14C]22:1n-9 was extensively beta-oxidized (60%), compared with 30% for [1-14C]20:4n-6. Although 20:4n-6 was targeted primarily to phospholipid pools, 22:1n-9 was targeted to cholesteryl esters, triglycerides, and phospholipids. When [14-14C]22:1n-9 was infused directly into the fourth ventricle of the brain [intracerebroventricular (i.c.v.)] for 7 days, 60% of the tracer entered the phospholipid pools, similar to the distribution observed for [1-14C]20:4n-6. This demonstrates plasticity in the ability of the brain to esterify 22:1n-9 in an exposure-dependent manner. In i.v. and i.c.v. infused rats, a significant amount of tracer found in the phospholipid pools underwent sequential rounds of chain shortening and was found as [12-14C]20:1n-9 and [10-14C]oleic acid. These results demonstrate for the first time that intact 22:1n-9 crosses the BBB, is incorporated into specific lipid pools, and is chain-shortened.

Mitochondrial lipid abnormality and electron transport chain impairment in mice lacking alpha-synuclein

The presynaptic protein alpha-synuclein, implicated in Parkinson disease (PD), binds phospholipids and has a role in brain fatty acid (FA) metabolism. In mice lacking alpha-synuclein (Snca-/-), total brain steady-state mass of the mitochondria-specific phospholipid, cardiolipin, is reduced 22% and its acyl side chains show a 51% increase in saturated FAs and a 25% reduction in essential n-6, but not n-3, polyunsaturated FAs. Additionally, 23% reduction in phosphatidylglycerol content, the immediate biosynthetic precursor of cardiolipin, was observed without alterations in the content of other brain phospholipids. Consistent with these changes, more ordered lipid head group and acyl chain packing with enhanced rotational motion of diphenylhexatriene (DPH) about its long axis were demonstrated in time-resolved DPH fluorescence lifetime experiments. These abnormalities in mitochondrial membrane properties were associated with a 15% reduction in linked complex I/III activity of the electron transport chain, without reductions in mitochondrial number, complex II/III activity, or individual complex I, II, III, or IV activity. Reduced complex I activity is thought to be a critical factor in the development of PD. Thus, altered membrane composition and structure and impaired complex I/III function in Snca-/- brain suggest a relationship between alpha-synuclein's role in brain lipid metabolism, mitochondrial function, and PD.