Specific Irreversible Inhibitor Research Articles

Cost-Effectiveness of Zanubrutinib Versus Bendamustine and Rituximab in Patients With Untreated Chronic Lymphocytic Leukemia

Zanubrutinib, a potent and specific irreversible Bruton's tyrosine kinase inhibitor, has proven to be effective in untreated chronic lymphocytic leukemia (CLL), whether used alone or in combination with other therapies. Here, we compared the cost-effectiveness of zanubrutinib with bendamustine-rituximab (R-bendamustine) to determine its effectiveness as the first-line treatment for Chinese patients with untreated CLL. The evaluation utilized a partitioned survival model, constructed using TreeAge Pro 2011 software, incorporating data from SEQUOIA trial (NCT03336333). Transition probabilities were estimated from the reported survival probabilities in trials using parametric survival modeling. In this analysis, the quality-adjusted life years (QALYs), incremental cost-effectiveness ratio, and lifetime cost were calculated from the Chinese health care system perspective. Sensitivity analyses, including 1-way analysis and probabilistic sensitivity analysis, were carried out to explore the uncertainty of the modeling results. Additionally, several scenario analyses, including different zanubrutinib price calculation and 20-year time horizon, were evaluated. The findings revealed that zanubrutinib had an incremental cost-effectiveness ratio of $58,258.18 per additional QALYs gained compared with bendamustine-rituximab, with zanubrutinib being cost-effective only if its price was reduced by more than 30%. Research indicated that zanubrutinib achieved at least a 3.70% probability of cost-effectiveness at the threshold of $38,223.34/QALY. One-way sensitivity analysis revealed that the results were sensitive to the utility of progressed disease. The study highlighted the importance of considering the cost-effectiveness of zanubrutinib at its current price point for patients with untreated CLL in China, emphasizing the need for further assessment and potential pricing adjustments to enhance its economic viability in clinical practice.

Ornithine decarboxylase is involved in methyl jasmonate-regulated postharvest quality retention in button mushrooms (Agaricus bisporus).

In the present study, we investigated the role of ornithine decarboxylase (ODC) in the methyl jasmonate (MeJA)-regulated postharvest quality maintenance of Agaricus bisporus (J. E. Kange) Imbach button mushrooms by pretreating mushrooms with a specific irreversible inhibitor called α-difluoromethylornithine (DFMO) before exposure to MeJA vapor. Mushrooms were treated with 0 or 100 µmol L-1 MeJA or a combination of 120 µmol L-1 DFMO and 100 µmol L-1 MeJA, respectively, before storage at 4 °C for 21 days. Treatment with MeJA alone induced the increase in ODC activity whereas this effect was greatly suppressed by pretreatment with DFMO. α-Difluoromethylornithine strongly attenuated the effect of MeJA on decreasing cap opening, slowing the decline rate of soluble protein and total sugar, and accumulating total phenolics and flavonoids. α-Difluoromethylornithine pretreatment also counteracted the ability of MeJA to inhibit polyphenol oxidase and lipoxygenase activities, and malondialdehyde production, and to stimulate superoxide dismutase and catalase activities. It also largely downregulated MeJA-induced accumulation of free putrescine (Put). These results reveal that ODC is involved in MeJA-regulated postharvest quality retention of button mushrooms, and this involvement is likely to be associated with Put levels. © 2018 Society of Chemical Industry.

Coenzyme Q10 partially restores pathological alterations in a macrophage model of Gaucher disease

BackgroundGaucher disease (GD) is caused by mutations in the GBA1 gene which encodes lysosomal β-glucocerebrosidase (GCase). In GD, partial or complete loss of GCase activity causes the accumulation of the glycolipids glucosylceramide (GlcCer) and glucosylsphingosine in the lysosomes of macrophages.In this manuscript, we investigated the effects of glycolipids accumulation on lysosomal and mitochondrial function, inflammasome activation and efferocytosis capacity in a THP-1 macrophage model of Gaucher disease. In addition, the beneficial effects of coenzyme Q10 (CoQ) supplementation on cellular alterations were evaluated. Chemically-induced Gaucher macrophages were developed by differentiateing THP-1 monocytes to macrophages by treatment with phorbol 12-myristate 13-acetate (PMA) and then inhibiting intracellular GCase with conduritol B-epoxide (CBE), a specific irreversible inhibitor of GCase activity, and supplementing the medium with exogenous GlcCer. This cell model accumulated up to 16-fold more GlcCer compared with control THP-1 cells.ResultsChemically-induced Gaucher macrophages showed impaired autophagy flux associated with mitochondrial dysfunction and increased oxidative stress, inflammasome activation and impaired efferocytosis. All abnormalities were partially restored by supplementation with CoQ.ConclusionThese data suggest that targeting mitochondria function and oxidative stress by CoQ can ameliorate the pathological phenotype of Gaucher cells. Chemically-induced Gaucher macrophages provide cellular models that can be used to investigate disease pathogenesis and explore new therapeutics for GD.

Repeated oral administration of a cathepsin K inhibitor significantly suppresses bone resorption in exercising horses with evidence of increased bone formation and maintained bone turnover.

Our investigations evaluated the effect of VEL-0230, a highly specific irreversible inhibitor of cathepsin K (CatK). The objectives of our study were to determine whether repeated dosing of a CatK inhibitor (CatKI) produced a desired inhibition of the bone resorption biomarker (CTX-1), and document the effect of repeated dosing on bone homeostasis, structure, and dynamics of bone resorption and formation in horses. Twelve young exercising horses were randomized in a prospective, controlled clinical trial and received 4 weekly doses of a CatKI or vehicle. Baseline and poststudy nuclear scintigraphy, blood sampling and analysis of plasma bone biomarkers (CTX-1 and osteocalcin), poststudy bone fluorescent labeling, and bone biopsy were performed. Bone specimens were further processed for microcomputed tomography and bone histomorphometry. Each dose of this CatKI transiently inhibited plasma CTX-1 (reflecting inhibition of bone collagen resorption) and increased bone plasma osteocalcin concentrations, with no detectable adverse effect on normal bone turnover in the face of exercise. Bone morphology, density, and formation rate were not different between control and treated group. Further investigation of CatK inhibition in abnormal bone turnover is required in animals with bone diseases.

Myeloperoxidase Inhibition Increases Neurogenesis after Ischemic Stroke.

The relationship between inflammation and neurogenesis in stroke is currently not well understood. Focal ischemia enhances cell proliferation and neurogenesis in the neurogenic regions, including the subventricular zone (SVZ), dentate gyrus, as well as the non-neurogenic striatum, and cortex in the ischemic hemisphere. Myeloperoxidase (MPO) is a potent oxidizing enzyme secreted during inflammation by activated leukocytes, and its enzymatic activity is highly elevated after stroke. In this study, we investigated whether the inhibition of MPO activity by a specific irreversible inhibitor, 4-aminobenzoic acid hydrazide (ABAH) (MPO-/- mice) can increase neurogenesis after transient middle cerebral artery occlusion in mice. ABAH administration increased the number of proliferating bromodeoxyuridine (BrdU)-positive cells expressing markers for neural stems cells, astrocytes, neuroprogenitor cells (Nestin), and neuroblasts (doublecortin) in the ischemic SVZ, anterior SVZ, striatum, and cortex. MPO inhibition also increased levels of brain-derived neurotrophic factor, phosphorylation of cAMP response element-binding protein (Ser133), acetylated H3, and NeuN to promote neurogenesis in the ischemic SVZ. ABAH treatment also increased chemokine CXC receptor 4 expression in the ischemic SVZ. MPO-deficient mice treated with vehicle or ABAH both showed similar effects on the number of BrdU+ cells in the ischemic hemisphere, demonstrating that ABAH is specific to MPO. Taken together, our results underscore a detrimental role of MPO activity to postischemia neurogenesis and that a strategy to inhibit MPO activity can increase cell proliferation and improve neurogenesis after ischemic stroke.

Identification of a benzo imidazole thiazole derivative as the specific irreversible inhibitor of protein tyrosine phosphatase

Protein tyrosine phosphatases (PTPs) play key roles in many physiological processes, including cell proliferation, differentiation, immune responses and neural activities. Inappropriate regulation of the PTP activity could lead to human diseases, such as cancer or diabetes. Functional studies of PTP can be greatly facilitated by chemical probes that covalently label the active site of a PTP through an activity-dependent chemical reaction. Here, we characterize compound E4 as a new class of PTP activity probes. Compound E4 inactivate STEP in a time- and concentration-dependent fashion. Further study showed that compound E4 inhibits a series of PTPs in a time dependent manner, whereas it shows little or no inhibition toward metal dependent protein phosphatases. Collectively, this new identified covalent inhibitor of PTPs has the potential to be developed to an active site Cys directed PTP probes to study the active properties of the PTPs in cell signaling.

Myeloperoxidase Nuclear Imaging for Epileptogenesis.

To determine if myeloperoxidase (MPO) is involved in epileptogenesis and if molecular nuclear imaging can be used to noninvasively map inflammatory changes in epileptogenesis. The animal and human studies were approved by the institutional review boards. Pilocarpine-induced epileptic mice were treated with 4-aminobenzoic acid hydrazide (n = 46), a specific irreversible MPO inhibitor, or saline (n = 42). Indium-111-bis-5-hydroxytryptamide-diethylenetriaminepentaacetate was used to image brain MPO activity (n = 6 in the 4-aminobenzoic acid hydrazide and saline groups; n = 5 in the sham group) by using single photon emission computed tomography/computed tomography. The role of MPO in the development of spontaneous recurrent seizures was assessed by means of clinical symptoms and biochemical and histopathologic data. Human brain specimens from a patient with epilepsy and a patient without epilepsy were stained for MPO. The Student t test, one-way analysis of variance, and Mann-Whitney and Kruskal-Wallis tests were used. Differences were regarded as significant if P was less than .05. MPO and leukocytes increased in the brain during epileptogenesis (P < .05). Blocking MPO delayed spontaneous recurrent seizures (99.6 vs 142 hours, P = .016), ameliorated the severity of spontaneous recurrent seizures (P < .05), and inhibited mossy fiber sprouting (Timm index, 0.31 vs 0.03; P = .003). Matrix metalloproteinase activity was upregulated during epileptogenesis in an MPO-dependent manner (1.44 vs 0.94 U/mg, P = .049), suggesting that MPO acts upstream of matrix metalloproteinases. MPO activity was mapped during epileptogenesis in vivo in the hippocampal regions. Resected temporal lobe tissue from a human patient with refractory epilepsy but not the temporal lobe tissue from a patient without seizures demonstrated positive MPO immunostaining, suggesting high translational potential for this imaging technology. The findings of this study highlight an important role for MPO in epileptogenesis and show MPO to be a potential therapeutic target and imaging biomarker for epilepsy.

The Role of Butyrylcholinesterase in Beta‐Amyloid Formation in Neuroblastoma Cells

The progression of Alzheimer's disease (AD) correlates with changes in the level of cholinesterase activity, i.e., butyrylcholinesterase (BuChE) increases while acetylcholinesterase (AChE) decreases. The consequence is a decrease in the level of acetylcholine and loss of cognitive function. In addition, both enzymes are associated with neurotoxic β‐amyloid (Aβ) plaques. As such, butyrylcholinestersase inhibitors are a potential therapeutic to relieve the symptoms of AD. The BuChE specific irreversible inhibitor di‐n‐butyl 2‐chlorophenyl phosphate (DBPP) was tested for its effect on the formation of β‐amyloid and the amyloid precursor protein (APP) by ELISA and Western Blot analysis, respectively. Results of the ELISA assay showed an increase in Aβ‐40 and 42 concentration in neuroblastoma cells treated with 10‐5 M DBPP. In contrast lower. concentrations of 10‐6 M and 10‐8 M DBPP induced a lower concentration of Aβ‐40 and 42 when compared to the control.. Western Blot analysis of the cell lysate supernatant showed a decrease APP formation with 10‐5 DBPP. but little or no difference at the lower concentrations of inhibitor. Supported in part by CSUPERB and the CSULB Mini Grant Program.

Myeloperoxidase propagates damage and is a potential therapeutic target for subacute stroke.

Few effective treatment options exist for stroke beyond the hyperacute period. Radical generation and myeloperoxidase (MPO) have been implicated in stroke. We investigated whether pharmacologic reduction or gene deletion of this highly oxidative enzyme reduces infarct propagation and improves outcome in the transient middle cerebral artery occlusion mouse model (MCAO). Mice were treated with 4-aminobenzoic acid hydrazide (ABAH), a specific irreversible MPO inhibitor. Three treatment regimens were used: (1) daily throughout the 21-day observational period, (2) during the acute stage (first 24 hours), or (3) during the subacute stage (daily starting on day 2). We found elevated MPO activity in ipsilateral brain 3 to 21 days after ischemia. 4-Aminobenzoic acid hydrazide reduced enzyme activity by 30% to 40% and final lesion volume by 60% (P<0.01). The MPO-knockout (KO) mice subjected to MCAO also showed a similar reduction in the final lesion volume (P<0.01). The ABAH treatment or MPO-KO mice also improved neurobehavioral outcome (P<0.001) and survival (P=0.01), but ABAH had no additional beneficial effects in MPO-KO mice, confirming specificity of ABAH. Interestingly, inhibiting MPO activity during the subacute stage recapitulated most of the therapeutic benefit of continuous MPO inhibition, suggesting that MPO-targeted therapies could be useful when given after 24 hours of stroke onset.

Neuronal Nitric Oxide Synthase-Dependent Amelioration of Diastolic Dysfunction in Rats with Chronic Renocardiac Syndrome

We have recently described the chronic renocardiac syndrome (CRCS) in rats with renal failure, cardiac dysfunction and low nitric oxide (NO) availability by combining subtotal nephrectomy and transient low-dose NO synthase (NOS) inhibition. Cardiac gene expression of the neuronal isoform of NOS (nNOS) was induced. Hence, we studied the role of nNOS, in vivo cardiac function and β-adrenergic response in our CRCS model by micromanometer/conductance catheter. Left ventricular (LV) hemodynamics were studied during administration of dobutamine (dobu), the highly specific irreversible inhibitor of nNOS <smlcap>L</smlcap>-VNIO [<smlcap>L</smlcap>-N5-(1-Imino-3-butenyl)-ornithine], or both at steady state and during preload reduction. Rats with CRCS showed LV systolic dysfunction at baseline, together with prolonged diastolic relaxation and rightward shift of the end-systolic pressure-volume relationships. After <smlcap>L</smlcap>-VNIO infusion, diastolic relaxation of CRCS rats further prolonged. The time constant of active relaxation (tau) increased by 25 ± 6% from baseline (p < 0.05), and the maximal rate of pressure decrease was 36 ± 7% slower (p < 0.001). These variables did not change in controls. In our CRCS model, nNOS did not seem to affect systolic dysfunction. In summary, in this model of CRCS, blockade of nNOS further worsens diastolic dysfunction and <smlcap>L</smlcap>-VNIO does not influence inherent contractility and the response to dobu stress.

Determination of cathepsin G in endometrial tissue using a surface plasmon resonance imaging biosensor with tailored phosphonic inhibitor

ObjectiveCathepsin G is a serine peptidase whose physiological role is mainly associated with an early immune response, anti-microbial activity as well as platelet activation or hydrolysis of coagulation factors. In addition, since the activity of cathepsin G has been associated with the development of various pathological disorders, the measurement of its activity in patient samples is of high interest. Unfortunately, the usefulness of common immunological methods is limited, since they cannot distinguish between catalytically active and inactive protease. Study designHere we present the application of recently developed Surface Plasmon Resonance-based biosensor for the detection of active cathepsin G in human endometrium samples. The key element of the system is based on the irreversible binding of cathepsin G to its specific phosphonic-type inhibitor immobilized on the surface of the gold chip. The concentration of cathepsin G was measured in tissue samples from the group of patients with endometriosis as well as in the control group. ResultsThe level of cathepsin G ascertained in endometrium tissue samples was over twice as high for the group of patients suffering from endometriosis as compared to the control group, with the median values of 0.5pmol/mg and 0.2pmol/mg, respectively. ConclusionThe SPR sensor armed with a specific irreversible phosphonic inhibitor represents a highly useful tool for the determination of catalytically active cathepsin G concentration in endometrial tissue.

Thapsigargin Induces Apoptosis by Impairing Cytoskeleton Dynamics in Human Lung Adenocarcinoma Cells

The objective of this study was performed to investigate the effects of thapsigargin on apoptosis, actin cytoskeletal dynamics, and actin cytoskeletal proteins in human lung adenocarcinoma cell. Thapsigargin is a specific irreversible inhibitor of ER calcium-ATPase, which may promote ER stress by depletion of lumenal calcium stores and show potential to induce cell death. The effects of thapsigargin on the apoptosis in A549 cells were assayed by Hoechst staining. Moreover, the F-actin staining by Rhodamine-phalloidin and RhoA antibody for cytoskeleton organizations were applied to A549 cells. To confirm the impairment of cytoskeletal dynamics treated with thapsigargin, western blots were applied to analyze the protein levels of p-Cofilin-1 (Ser3), Cofilin-1, and pPaxillin (Tyr118), as well as RhoA and pS6 (S240/244). Results suggest that thapsigargin may induce cell death in A549 cells with a time- and dose-dependent manner. The F-actin fibers and RhoA signals are also reduced with a time- and dose-dependent manner by thapsigargin treatment. The phosphorylation forms of Cofilin-1 and paxillin are attenuated by 1 μM thapsigargin treatment for 24 h. These alternations may be caused by the inhibition of of mTORC1 activities (indicated by pS6 (Ser240/244)) and RhoA pathways after thapsigargin treatment. The present findings highlight important roles of calcium entry in cytoskeleton organization and apoptosis in human lung adenocarcinoma cells and will help to set a stage to the clinical treatment of cancer cell metastasis.

Investigations of the possible glycosylation of monoamine oxidase B from pig leucocytes.

Monoamine oxidase B (MAO B) from pig liver has been reported to be a sialoglycoprotein. However, when that enzyme from pig lymphocytes and granulocytes was separated by polyacrylamide gel electrophoresis after labelling with the specific irreversible inhibitor [3H]pargyline, staining with 1-ethyl-2-[3-(1-ethyl-naphtho [1,2d] thiazolin-2-ylidene)-2-methylpropenyl] naphtho [1,2d] thiazolium bromide ("Stains-all") failed to detect the presence of sialic acid residues. Treatment of the enzyme in disrupted lymphocytes and granulocytes, or in mitochondrial fractions prepared from them, with neuraminidase resulted in a decrease in MAO activity. However, after the enzyme was rendered soluble by treatment with octylglucoside, treatment with neuraminidase had no effect on the activity. These results indicate that sialic acid residues are not an intrinsic component of MAO B, although associated material containing such groups appears to affect the activity of the membrane-bound enzyme. The activities of membrane-bound preparations of MAO B from pig lymphocytes and granulocytes were unaffected by treatment with trypsin or beta-chymotrypsin. After the preparations had been rendered soluble by treatment with octylglucoside there was a decrease in the activity on treatment with beta-chymotrypsin, but trypsin treatment had no effect. Thus solubilization resulted in residues sensitive to cleavage by the former enzyme becoming accessible to it. Tryptic and chymotryptic peptides separated from the sodium dodecyl sulphate denatured enzymes by polyacrylamide gel electrophoresis revealed no differences between MAO B prepared from lymphocytes and granulocytes.

Proteolysis activity of IgM antibodies from rheumatoid arthritis patients' sera: evidence of atypical catalytic site

The IgM antibodies from rheumatoid arthritis (RA) patients' sera were screened for peptide hydrolyzing activity. Recovery of structurally intact IgM antibodies (Abs), in a single step, was achieved using a weak anion-exchange methacrylate monolith disk. The IgM Abs from patients' sera hydrolyzed the Pro-Phe-Arg-4-methyl-coumaryl-7-amide (PFR-MCA) substrate appreciably compared to the healthy donors. The apparent K(m) values of IgM Abs from patients' sera were between 0.4 and 0.7 mM. Furthermore, IgM Abs displayed 5 to 10-folds greater proteolysis activity than IgG Abs, recovered from the same pathological serum. The proteolysis activity, as a function, was found to be independent of IgM-RF titer value. Affinity labeling approach targeted at the catalytic site histidine was studied, using a specific irreversible inhibitor, N-α-tosyl-L-lysine chloromethyl ketone (TLCK). Despite modification of catalytic His, observation of serine protease like activity suggest presence of an atypical catalytic framework in a few pathological IgM Abs.

Purification and characterization of a novel extracellular protease from a halo‐alkaliphilic Bacillus sp. 17N‐1, active in polar organic solvents

A novel enzyme of molecular mass about 29 kDa was purified from the strain halo‐alkaliphilic Bacillus sp. 17N‐1 and designated protease‐B‐17N‐1. This enzyme is likely to be a cysteine protease; it was found active in media containing EDTAK2 and dithiothreitol, it maintained considerable activity at temperatures 14°C to 33°C and pH 6.50 to 8.50 with optimum k cat / Km and/or k cat values at pH 7.00 and 25°C. The activity of protease‐B‐17N‐1 was strongly affected by the specific irreversible inhibitor of cysteine proteases E‐64, while it remained unaffected by the 3,4‐dichloro‐isocoumarine, an irreversible inhibitor specific for serine proteases. Protease‐B‐17N‐1 retained full activity at 25°C after 30 min incubation at 8°C or at 33°C; moreover, it was found to be stable and active in the polar organic solvents DMSO and acetonitrile. The enzyme hydrolyzed the substrate Cbz‐FR‐pNA via Michaelis–Menten kinetics, while it showed insignificant activity for the substrate Suc‐AAA‐pNA. Valuable pKa s, rate constants, activation energies and other important features were estimated from the profiles of parameters k cat / Km , k cat and Km , versus pH, temperature, and [NaCl]. In addition, interesting results were obtained from the effect of different metallic ions and polar organic solvents on the Michaelis–Menten parameters of protease‐B‐17N‐1, showing that it performs catalysis via a (Cys)‐S−/(His)‐Im+H ion‐pair, as well as its industrial and biotechnological potential, respectively.

Mercury in canned tuna: The importance of selenium

To the Editor: The recent article by Gerstenberger et al. [1], reported the mercury (Hg) concentrations, but did not report the selenium (Se) contents of the tuna. Since methylmercury is, by biochemical definition, a highly specific irreversible inhibitor of Se-dependent enzymes [2], it is necessary to measure both Hg and Se to accurately assess risks associated with Hg exposures. The brain and neuroendocrine tissues depend upon Se-dependent enzymes to prevent and reverse oxidative damage that would otherwise accompany their high rates of oxygen consumption. Because the affinity of Hg for Se is approximately a million times higher than its affinity for sulfur [3], the Seenzymes are uniquely vulnerable to inhibition by high methylHg exposures. However, rather than impairing Se enzymes, eating ocean fish such as tuna that are known to provide far more Se than Hg actually enhances nutritional Se status, explaining why ocean fish consumption has repeatedly been shown to prevent, rather than contribute to Hg toxicity [2]. In contrast, consumption of meats of predatory whales and sharks that are known to contain far more Hg than Se has been shown to be hazardous. Current U.S. Environmental Protection Agency (U.S. EPA) risk criteria are based on a study of human Hg exposures that arose predominantly from eating pilot whale meats. Since pilot whale meats are virtually unique in having exceedingly high Hg to Se molar ratios (5:1), as well as Hg contents in excess of 3 ppm [4], this is clearly a food to avoid. In contrast, ocean fish are Se-rich and have Hg to Se molar ratios that are typically on the order of 1:5, which may explain why ocean fish consumption has been shown to counteract Hg toxicity from whale meat consumption [5]. Although blood Hg and blood Hg to Se molar ratios in children exposed in utero are highly correlated [6], relationships between Hg exposures and risk are most accurately predicted from the perspective of Hg to Se molar ratios. Therefore, the selenium-health benefit value (Se-HBV) is preferable since it incorporates both the relative and the absolute amounts of Se intake and Hg exposure in a single criterion. Health benefits are directly associated with positive Se-HBVs, whereas adverse health effects are directly proportional to negative Se-HBVs [2]. Since methylmercury is an enzyme inhibitor, its chemical reactions are clearly second order. Therefore, attempting to

Induction of cell death in neuroblastoma by inhibition of cathepsins B and L

A specific irreversible inhibitor of both cathepsins B and L, Fmoc-Tyr-Ala-CHN 2 (FYAD) induced apoptosis of neuroblastoma cells but not other tumor cells. Cysteine protease inhibitors that were not efficient inhibitors of both proteases did not cause death of any cell line tested. Apoptosis was preceded by accumulation of large electron dense vesicles and multivesicular bodies in the cytoplasm. Exposure of cells to the cathepsin D inhibitor, pepstatin, failed to rescue cells from FYAD-induced death. These results indicate that inhibition of cathepsins B and L may provide a unique mechanism for selectively inducing death of neuroblastoma with limited toxicity to normal cells and tissues.

Arachidonic acid-induced apoptosis in rat hepatoma AS-30D cells is mediated by reactive oxygen species.

Arachidonic acid at micromolar concentrations produced a drastic increase of the generation of reactive oxygen species (ROS) in rat hepatoma AS-30D cells cultivated in vitro along with an increase in the incidence of apoptotic cell death. Both processes were prevented by trolox, a water-soluble tocopherol derivative, and tempol, a known antioxidative agent. A synthetic hybrid of lipoic acid and trolox or preincubation with N-acetylcysteine were less effective. Preincubation of the cells with etomoxir, a known highly specific irreversible inhibitor of carnitine-palmitoyltransferase I, partly decreased the ROS formation induced by arachidonic acid but it did not affect the increase in apoptosis. Cumulatively, these results indicate that apoptosis induced in hepatoma cells by arachidonic acid is mediated by ROS. They also suggest that this effect is due to arachidonic acid as such and not to its mitochondrial oxidative metabolites.

Phenylalanine ammonia-lyase-mediated biosynthesis of 2-hydroxy-4-methoxybenzaldehyde in roots of Hemidesmus indicus

The fragrant rootstocks of Hemidesmus indicus are known to accumulate 2-hydroxy-4-methoxybenzaldehyde (MBALD), yet, the enzymatic route to this hydroxybenzoate is not known. Therefore, root organs of H. indicus hold promises to unravel the biosynthesis related to this phenolic fragrance. Chitosan treatment at 200mg/L concentration to the excised roots effectively increased phenolic accumulation in both the cortex and cork tissues reaching a peak after 24h treatment and decreasing thereafter. The activity of phenylalanine ammonia-lyase (PAL) enzyme in excised roots also increased upon chitosan elicitation, and the maximum specific activity was recorded after 12h of elicitation. Suppression of PAL in vivo by using a specific irreversible inhibitor aminooxyacetic acid (AOAA) resulted in the decrease in MBALD content, indicating its formation via phenylpropanoid pathway.

Secondary sphingolipid accumulation in a macrophage model of Gaucher disease

Glucosylceramide (GC) is a metabolic intermediate derived from the cellular turnover of membrane gangliosides and globosides. The catabolism of GC is impaired in Gaucher disease (GD) and consequently GC accumulates in affected cells leading to clinical manifestations of GD. The primary cell type affected in GD is the macrophage, and we investigated what effect excess GC has on the spatial coordination of other sphingolipids and phospholipids in a macrophage model of GD. A THP-1 macrophage model of GD was established by supplementation of the culture media with conduritol B epoxide, a specific irreversible inhibitor of acid β-glucosidase. This cell model accumulated up to 12-fold more GC compared with untreated cells. Sub-cellular fractionation showed that, initially, the primary site of GC accumulation was the lysosome but as more GC accumulated it distributed relatively evenly across the cell and was present in all sub-cellular fractions. We also observed secondary elevations in the concentrations of ceramide, di- and trihexosylceramide and phosphatidylglycerol, which all had similar sub-cellular distributions to that of GC, initially increasing in the lysosome and then throughout the sub-cellular compartments. Our results suggest that with excess GC accumulation, the pathway trafficking GC to the lysosome becomes saturated and GC as well as other sphingolipids are shunted to other parts of the cell. The presence of these sphingolipids at non-physiological concentrations is likely to interfere with other biochemical pathways outside the lysosome, leading to cell dysfunction and ultimately pathological mechanisms apparent in GD, such as macrophage activation.