Biomedical subjects

H Yoo

Publications and source records attributed to H Yoo.

At least 37 records · Page 2Linked to original sources

PubMed1999

Antisense pharmacodynamics: critical issues in the transport and delivery of antisense oligonucleotides.

This review critically examines current understanding of the kinetics and biodistribution of antisense oligonucleotides, both at the cellular level and at the level of the intact organism. The pharmacodynamic relationships between biodistribution and the ultimate biological effects of antisense agents are considered. The problems and advantages inherent in the use of delivery systems are discussed in the light of further enhancing in vivo pharmacological actions of oligonucleotides.

Animals↗

PubMed1999

PAMAM dendrimers as delivery agents for antisense oligonucleotides.

PURPOSE: To investigate the potential use of PAMAM dendrimers for the delivery of antisense oligonucleotides into cells under conditions that mimic the in vivo environment. METHODS: We used HeLa cells stably transfected with plasmid pLuc/705 which has a luciferase gene interrupted by a human beta-globin intron mutated at nucleotide 705, thus causing incorrect splicing. An antisense oligonucleotide overlapping the 705 splice site, when delivered effectively, corrects splicing and allows luciferase expression. The ability of dendrimers to deliver oligonucleotides to HeLa Luc/705 cells was evaluated in the absence or presence of serum. RESULTS: PAMAM dendrimers formed stable complexes with oligonucleotides that had modest cytotoxicity and showed substantial delivery activity. The dose of the oligonucleotide, the charge ratio of oligonucleotide to dendrimer, and the size (generation) of the dendrimers were all critical variables for the antisense effect. The physical properties of dendrimer/oligonucleotide complexes were further investigated using sedimentation and gel electrophoresis methods. Effective oligonucleotide/generation 5 dendrimer complexes were macromolecular rather than particulate in nature, and were not sedimented at 100,000 RPM. Compared to other types of delivery agents, PAMAM dendrimers were more effective in delivering oligonucleotides into the nucleus of cells in the presence of serum proteins. CONCLUSIONS: Our results suggest that PAMAM dendrimers form nonparticulate delivery complexes that function in the presence of serum proteins and thus may be suited for in vivo therapeutic applications.

Blood Proteins↗

PubMed1999

Jugular foramen schwannomas: surgical approaches and outcome of treatment.

Twelve cases of schwannomas of the jugular foramen that involved surgery in our department between 1983 and 1997 are described. Eight were women and 4 were men (mean age, 40 years), and the duration of their symptoms, the most predominant of which were hearing loss and tinnitus, ranged from 1 month to 20 years (median, 8.5 months). Depending on their radiological and surgical features, tumors were classified as type A, a tumor primarily at the cerebellopontine angle with minimal enlargement of the jugular foramen (n = 5); type B, a tumor primarily at the jugular foramen with or without intracranial extension (n = 4); type C, a primarily extracranial tumor with extension into the jugular foramen (n = 0); or type D, a dumbbell tumor with both intracranial and extracranial components (n = 3). A retrosigmoid suboccipital craniectomy (RSSOC) was performed for type A tumors; for types B and D, the RSSOC or staged infratemporal fossa approach (ITFA)/RSSOC was used. Total removal was achieved in 6 cases, near total removal in 3, and subtotal removal in 3. The most common complication was lower cranial nerve dysfunction (n = 5). The follow-up period ranged from 6 to 173 (mean, 48) months, and there was no recurrence. Two patients showed regrowth of the tumor after subtotal resection, however. In 1 of these, the residual tumor had progressed within 12 months of initial surgery, it was again resected and linac radiosurgery was successful. In the other, the residual mass had progressed within 8 months of initial surgery, and the pathological report indicated malignant peripheral nerve sheath tumor. Conclusively, type A tumors could be totally resected with the retrosigmoid approach alone. For type B and D tumors, however, combined ITFA and retrosigmoid approach showed the better results. In spite of our limited data, cases showing adhesion to critical structures can be managed by subtotal or near total resection followed by radiosurgery to reduce postoperative complications.

Journal Article↗

PubMed1999

RNA-Stimulated ATPase and RNA helicase activities and RNA binding domain of hepatitis G virus nonstructural protein 3.

Hepatitis G virus (HGV) nonstructural protein 3 (NS3) contains amino acid sequence motifs typical of ATPase and RNA helicase proteins. In order to examine the RNA helicase activity of the HGV NS3 protein, the NS3 region (amino acids 904 to 1580) was fused with maltose-binding protein (MBP), and the fusion protein was expressed in Escherichia coli and purified with amylose resin and anion-exchange chromatography. The purified MBP-HGV/NS3 protein possessed RNA-stimulated ATPase and RNA helicase activities. Characterization of the ATPase and RNA helicase activities of MBP-HGV/NS3 showed that the optimal reaction conditions were similar to those of other Flaviviridae viral NS3 proteins. However, the kinetic analysis of NTPase activity showed that the MBP-HGV/NS3 protein had several unique properties compared to the other Flaviviridae NS3 proteins. The HGV NS3 helicase unwinds RNA-RNA duplexes in a 3'-to-5' direction and can unwind RNA-DNA heteroduplexes and DNA-DNA duplexes as well. In a gel retardation assay, the MBP-HGV/NS3 helicase bound to RNA, RNA/DNA, and DNA duplexes with 5' and 3' overhangs but not to blunt-ended RNA duplexes. We also found that the conserved motif VI was important for RNA binding. Further deletion mapping showed that the RNA binding domain was located between residues 1383 and 1395, QRRGRTGRGRSGR. Our data showed that the MBP-HCV/NS3 protein also contains the RNA binding domain in the similar domain.

Adenosine Triphosphatases↗

PubMed1998

Basilar papilla explants: a model to study hair cell regeneration-repair and protection.

Explants of basilar papillae from 6-7 days posthatch chicks were cultured in growth medium for a period of 1-8 days. Hair cells were counted following staining of stereocilia bundles with FITC-phalloidin, and the percentage of hair cell survival was determined by comparison to control (i.e. uncultured) specimens. Hair cell integrity was evaluated by scanning electron microscopy. Although previous studies have utilized organotypic culture of the basilar papilla to assess cell proliferation and ototoxicity, viability and integrity of hair cells was documented for periods of up to only 2 3 days. Our results demonstrate substantive auditory hair cell viability for a period of 7 days in vitro. We describe a pattern of natural hair cell loss in organotypic culture that progresses along a proximal-distal, abneural-neural gradient, mimicking the pattern of hair cell loss that occurs following ototoxic insult to the chick basilar papilla in vivo and the pattern we observed during a 48-h period of exposure of basilar papilla explants to an ototoxic dose of neomycin. Our results provide an important quantitative step for the use of organotypic culture of the chick basilar papilla as a purposeful model to investigate the process of hair cell regeneration-repair in the avian auditory system.

Animals↗

PubMed1996

alpha-Trinositol: a functional (non-receptor) neuropeptide Y antagonist in vasculature.

Neuropeptide Y is a sympathetic co-neurotransmitter released with noradrenaline upon sympathetic nerve stimulation. This study describes the ability of a synthetic inositol phosphate, alpha-trinositol(D-myo-inositol 1,2,6-triphosphate; PP 56) to antagonize vasoconstrictor responses to neuropeptide Y in-vitro as well as in-vivo. In human and guinea-pig isolated arteries alpha-trinositol potently (10 nM to 1 microM extracellular concentration) suppressed the constriction evoked by neuropeptide Y alone, the potentiation by neuropeptide Y of noradrenaline-evoked constriction, and the neuropeptide Y-induced inhibition of relaxation. Moreover, in the pithed (areflexive) rat, a non-adrenergic portion of the pressor response to preganglionic sympathetic nerve stimulation was sensitive to alpha-trinositol. As studied in the recently cloned human (vascular-type) Y1 receptor, the action of alpha-trinositol does not occur through antagonism at the neuropeptide Y recognition site nor does it induce allosteric changes of this receptor. However, we found alpha-trinositol to inhibit the rise in intracellular Ca2+ as well as inositol triphosphate concentrations induced by neuropeptide Y. It is, therefore, proposed that alpha-trinositol represents a non-receptor, but yet selective antagonist of neuropeptide Y in vasculature, opening up the possibility to investigate involvement of neuropeptide Y in sympathetic blood pressure control and in cardiovascular disorders.

Adrenergic alpha-Antagonists↗

PubMed1995

Identification of a brain- and reproductive-organs-specific gene responsive to DNA damage and retinoic acid.

We have identified and sequenced a new gene from human cells that is responsive to DNA damage and retinoic acid treatment, and it is highly expressed in brain and reproductive organs (BRE). This BRE gene encodes an mRNA of 1.7-1.9 kb, with an open reading frame of 1,149 bp, and gives rise to a deduced polypeptide of 383 amino acid residues. Treatment of fibroblast cell with UV and 4-nitroquinoline-1-oxide caused more than 90% and 50% decreases in BRE mRNA, respectively. Similar decreases in BRE expression were observed in RA-treatment of the brain glioma cell U-251 and the promyelocytic cell HL-60. Decrease in BRE mRNA was also observed in a squamous carcinoma cell, 1483, that showed X-ray resistance and has a more aggressive tumorigenic phenotype, but BRE expression was unchanged in cells after growth inhibition. These data indicate that BRE is a house-keeping gene and it may play a role in homeostatis or in certain pathways of differentiation in cells of neural, epithelial and germ line origins.

Amino Acid Sequence↗

PubMed1995

Effects of some novel D-myo-inositol-phosphate derivatives on binding and sympathetic transmission.

The vascular effects of myo-inositol and a series of D-myo-inositol phosphate derivatives: D-myo inositol-1-monophosphate (Ins[1]P1), D-myo-inositol-2-monophosphate (Ins[2]P1), D-myo-inositol-1, 2-biphosphate (Ins[1,2,6]P2), D-myo-inositol-1,2,6-trisphosphate (Ins[1,2,6]P3, alpha-trinositol; PP56), D-myo-inositol-1,2,5,6-tetraphosphate (Ins[1,2,5,6]P4), and D-myo-inositol-1,2,3,4,5,6-hexa-phosphate (InsP6, phytic acid) were studied in binding assays in rat heart membranes, in vitro in isolated guinea pig basilar artery, and in vivo in pithed rats. In binding assays in rat heart membranes, Ins[1,2,6]P3, Ins[1,2,5,6]P4, and InsP6 displaced the binding of [3H] alpha-trinositol [3H]Ins[1,2,6]P3). In the isolated guinea pig basilar artery, Ins[1,2]P2 and Ins[1,2,6]P3 inhibited the contractile effects of exogenous neuropeptide Y (NPY) in the concentration range of 10(-8)-10(-6) M. In pithed Sprague-Dawley rats, Ins[1,2,6]P3 inhibited the NPY-induced pressor response in the dose range [2 mg/kg (3.8 mumol/kg) combined with an infusion of 20 mg/kg/h (38 mumol/kg/h) for 30 min] in which no inhibitory effects on the pressor responses were elicited by preganglionic nerve stimulation (PNS) or a bolus injection of phenylephrine (Phe). Ins[1,2]P2 had only slight NPY inhibitory effects in vivo. We conclude that selected inositol derivatives may inhibit the vasopressor effects to NPY in vitro and in vivo. In particular, Ins[1,2,6]P3, which most readily inhibited the NPY-induced pressor response in vivo, may represent a new class of synthetic nonpeptide drugs, which may inhibit the vascular effects of NPY without binding to the NPY receptor itself.

Analysis of Variance↗

PubMed1995

Activity-wheel running attenuates suppression of natural killer cell activity after footshock.

We studied whether voluntary running in an activity wheel moderates splenic natural killer (NK) cell cytotoxicity after footshock. Young (50-day) male Fischer 344 rats were randomly assigned to 1) sedentary (n = 16) or 2) activity-wheel (n = 16) groups that each received controllable or uncontrollable footshock on 2 consecutive days or 3) a sedentary home-cage control group (n = 8). Spleens and trunk blood were collected 30 min after the second footshock session. Cytotoxicity was determined by a standard 4-h 51Cr release assay. Percentages of OX6+ (B), OX8+ [T suppressor/cytotoxic (Ts/c)], W3/25+ (T helper), Thy-1.1 (Pan T cell marker), and 5C6+ (NK) cells were determined by flow cytometry. Plasma adrenocorticotropic hormone, corticosterone, and prolactin concentrations were measured by radioimmunoassay as modulators of NK activity. Percentage of specific lysis after footshock was approximately 52% of control values for sedentary animals compared with approximately 96% of control values for activity-wheel animals. The groups did not differ in percentages of NK or Ts/c cells. We conclude that voluntary activity-wheel running protects against the suppression of splenic NK activity induced by footshock. This protective effect of wheel running is not explained by an elevation in baseline NK activity; increased percentages of splenic NK or Ts/c cells; or plasma levels of adrenocorticotropic hormone, corticosterone, and prolactin.

Adrenocorticotropic Hormone↗

PubMed1994

Characterization of specific binding sites for alpha-trinositol (D-myo-inositol 1,2,6-trisphosphate) in rat tissues.

Alfa-trinositol (or D-myo-inositol 1,2,6-trisphosphate) was recently found to, e.g., inhibit agonist-induced vasoconstriction and display antiinflammatory properties. However, its mechanism of action is unknown, although effects on Ca2+ fluxes, perhaps by interfering with endogenous inositol phosphate(s), have been suggested. Here we describe the existence of specific [3H]alpha-trinositol binding sites and compare these with binding sites for naturally occurring inositol phosphates. For this purpose we developed a tritiated analog of alpha-trinositol and used it in a centrifugation binding assay on extensively washed membranes from rat tissues. The degree of specific [3H] alpha-trinositol binding was markedly increased as a result of the many wash steps, indicating the existence of endogenous binding inhibitor(s). A single population of [3H] alpha-trinositol binding sites, displaying a KD of 159 nM and a Bmax of 71 pmol/mg protein, was present in cardiac membranes assayed at pH 7.4. Similar binding site densities were detected also in liver > lung > brain. The relative density of [3H] alpha-trinositol sites in cardiac membranes was 8-fold higher than [3H]Ins(1,4,5)P3 but 2-fold and 4-fold lower than [3H]Ins(1,3,4,5)P4 and [3H]InsP6 binding sites, respectively. Competition binding studies indicated the ability of Ins(1,3,4,5)P4 and InsP6, but not Ins(1,4,5)P3, to potently displace [3H] alpha-trinositol binding. Conversely, unlabelled alpha-trinositol showed relatively low potency vs. [3H]InsP6, but the novel inositol phosphate was virtually equipotent with Ins(1,3,4,5)P4 in inhibiting [3H]Ins(1,3,4,5)P4 binding. Finally, analyses of binding at different pH and ionic conditions revealed differences between alpha-trinositol and the three other previously studied inositol phosphates, although distinct similarities between alpha-trinositol and Ins(1,3,4,5)P4 were again observed.

Animals↗

PubMed1993

A proposed bovine neuropeptide Y (NPY) receptor cDNA clone, or its human homologue, confers neither NPY binding sites nor NPY responsiveness on transfected cells.

Receptors with seven transmembrane domains (7TM) constitute a large family of structurally and functionally related proteins which respond to various types of ligands. We describe here the cloning and expression of a human 7TM receptor, denoted hFB22 (human Fetal Brain 22), which is the homologue (92% amino acid identity) of a bovine receptor (LCR1) reported by others to bind neuropeptide Y (NPY) with a pharmacological profile of the Y3 receptor subtype. However, upon expression in COS1 (confirmed by Northern analysis), COS7 or CHO-K1 cells, the hFB22 receptor did not confer specific 125I-Bolton-Hunter-NPY, 3H-propionyl-NPY or 125I-peptide YY (PYY) binding sites, in either intact cells or in membrane preparations. Similarly, cells transfected with the corresponding bovine clone (LCR1) did not show specific NPY/PYY binding exceeding that resulting from endogenous binding sites; mock-transfected COS7 cells, used frequently for heterologous expression of receptors, were found to have endogenous specific 125I-NPY binding sites (Bmax = 112 fmol/mg protein; Kd = 0.25 nM). Moreover, the hFB22 transfected cells, when compared to control transfected cells, did not display de novo NPY- or PYY-induced second messenger responses, i.e., (1) inhibition of forskolin-stimulated cAMP accumulation or (2) 45Ca2+ influx. The presence of hFB22 mRNA was detected in several human neuroblastoma cell lines, none of which was found to express Y3-like NPY binding sites. hFB22 displays 39% amino acid sequence identity (in the transmembrane regions) to the human interleukin-8 receptor, and 32-36% amino acid identity to the human receptors of angiotensin II, bradykinin, and n-formylpeptide, but only 23% amino acid identity to the previously described human NPY/PYY receptor of the Y1 receptor subtype. Our results show that hFB22 and LCR1 do not encode NPY receptors, and their true ligand(s) remains to be identified.

Amino Acid Sequence↗

PubMed1993

Antisense oligodeoxynucleotides to NMDA-R1 receptor channel protect cortical neurons from excitotoxicity and reduce focal ischaemic infarctions.

The excitatory amino acid, L-glutamate, acting through its N-methyl-D-aspartate (NMDA) receptor, may contribute to neuronal death following cerebral vascular occlusion. In support of this hypothesis, NMDA receptor antagonists reduce the volume of infarction produced by occlusion of the middle cerebral artery in vivo and attenuate Ca2+ influx and neuronal death elicited by L-glutamate or NMDA in vitro. A complementary DNA coding for a major component of the NMDA receptor channel complex, a single protein of M(r) 105.5K (NMDA-R1), has been isolated from rat brain. Here we demonstrate that inhibition of the synthesis of NMDA-R1 by treatment with antisense oligodeoxynucleotides selectively reduces the expression of NMDA receptors, prevents the neurotoxicity elicited by NMDA in vitro and reduces the volume of the focal ischaemic infarction produced by occlusion of the middle cerebral artery in the rat.

Animals↗

PubMed1993

Mitogenic effects of ATP on vascular smooth muscle cells vs. other growth factors and sympathetic cotransmitters.

The sympathetic nervous system has been shown to exert a trophic influence on vascular smooth muscle cells (VSMC). Therefore, we studied the growth-regulating effects of the sympathetic cotransmitters ATP, neuropeptide Y (NPY), and norepinephrine (NE). ATP in concentrations of 1-100 microM greatly increased the incorporation of [3H]thymidine in VSMC from rat aorta and vena cava. ATP also increased cell number and total protein content. The maximal effect on [3H]thymidine incorporation was greater than for epidermal growth factor (20 ng/ml) or insulin (1 microgram/ml) and approximately one-half that of 10% fetal calf serum. The potency series of other nucleotides and analogues of ATP was ATP > beta, gamma-methyleneATP (AMP-PCP) > ADP > adenosine > alpha, beta- methyleneATP (AMP-CPP) > 2-methylthioATP, indicating involvement of a P2 receptor, however, it does not meet proposed pharmacological criteria of either the P2x or P2y subclass. Several proposed P2 receptor antagonists were without effect. The effect of ATP could be mediated by a "nucleotide receptor," since UTP also stimulated [3H]thymidine incorporation. In our model, there was a strong correlation between the mitogenic effects of ATP, AMP-CPP, AMP-PCP, and UTP and their ability to stimulate influx of extracellular Ca2+ (Ca2+o). Moreover, the mitogenic effect of ATP was increased by high concentrations of Ca2+o. Taken together with data showing the lack of involvement of several other second-messenger systems, this indicates a critical role for Ca2+o in mediating the mitogenic effects of ATP. Amiloride, known to inhibit the action of several growth factors, also inhibited ATP-induced mitogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1993

Preenhanced computed tomographic findings in brain death.

A patient complying with the clinical criteria for brain death was studied by preenhanced computed tomography (CT). Preenhanced CT showed apparent increased density at the base of the brain along the course of the major arterial vessels, and abnormally dense-appearing deep venous structures, like those of contrast-enhanced CT. There was a diffuse decrease in brain density with a poorly delineated ventricular system. These CT findings were very characteristic. CT as a non-invasive method seems to be valuable in the diagnosis of brain death. The relevant literature is reviewed and mechanisms showing those CT findings are discussed.

Brain Death↗

PubMed1992

A novel inositol phosphate selectively inhibits vasoconstriction evoked by the sympathetic co-transmitters neuropeptide Y (NPY) and adenosine triphosphate (ATP).

Postganglionic sympathetic nerves release norepinephrine (NE) as their primary neurotransmitter at vascular and other targets. However, much evidence supports involvement of additional messengers, co-transmitters, which are co-released with NE upon sympathetic nerve stimulation and thereby contribute to their actions, e.g., vasoconstriction. Two such putative co-transmitters, neuropeptide Y (NPY) and adenosine triphosphate (ATP) have been of particular interest since they fulfill several neurotransmitter criteria. Importantly, hitherto it has been difficult to antagonize vasoconstriction evoked by either NPY or ATP with agents that are devoid of intrinsic activity. The present study describes the ability of a novel inositol phosphate, D-myo-inositol 1,2,6-trisphosphate (Ins[1,2,6]P3; PP-56) to in vitro potently block vasoconstrictor responses elicited by NPY and ATP, but not by NE, as studied in guinea-pig isolated basilar artery. The action of Ins[1,2,6]P3 does not seem to occur through antagonism at NPY- or ATP-receptor recognition sites, labeled by 125I-peptide YY and 35S-gamma-ATP, respectively, in membranes of rat cultured vena cava vascular smooth muscle cells. However, it does involve inhibition of the influx of Ca2+ induced by either co-transmitter in these same vena cava cells. It is proposed that Ins[1,2,6]P3 may be a useful functional antagonist of non-adrenergic component(s) of the vasoconstrictor response to sympathetic nerve stimulation.

Adenosine Triphosphate↗

PubMed1992

Alterations in expression and structure of the DNA repair gene XRCC1.

The repair-associated gene XRCC1 was previously cloned by complementing the hamster mutant EM9, which has a high rate of spontaneous SCE and hypersensitivity to DNA damaging agents. In analyzing XRCC1 gene expression, similar levels of steady-state mRNA were found in normal cells, Bloom's syndrome cells with altered SCE, and in squamous carcinoma cells with differential X-ray sensitivity. An EcoRI restriction fragment-length polymorphism previously identified in XRCC1 did not correlate with the repair phenotypes of these cells. The mRNA of XRCC1 decreased to 20-40% after treatment of cells with a DNA damaging agent. XRCC1 also showed tissue specific expression in rats. The mRNA levels were high in testis (7-8 fold), ovary (3-4 fold) and brain (4-5 fold), when compared with those in intestine, liver and spleen (1-2 fold). These data and the high levels of XRCC1 protein detected in testis indicate that XRCC1 may play an important role in DNA processing during meiogenesis and recombination in germ cells.

Amino Acid Sequence↗

PubMed1992

Cloning and functional expression of a human neuropeptide Y/peptide YY receptor of the Y1 type.

Neuropeptide Y (NPY) and peptide YY (PYY) are structurally related peptides that primarily function as neurotransmitter and gastrointestinal hormone, respectively. Previous functional and binding data have indicated the existence of at least three distinct receptor types, Y1, Y2, and Y3, for NPY and/or PYY in mammals. We describe here a human Y1 cDNA clone, hY1-5, isolated from a fetal brain library. The human Y1 receptor consists of 384 amino acids and has seven putative transmembrane domains like other members of the G-protein-coupled superfamily of receptors. In the region spanning the transmembrane domains, the Y1 receptor displays 29% sequence identity to human tachykinin receptors, but it only shows 21% and 23% homology with proposed bovine (LCR1) and Drosophila (PR4) NPY receptor clones, respectively. Northern blot analysis of a human neuroblastoma cell line, SK-N-MC, previously used by many investigators as a model system for studies on the Y1 receptor, revealed a single 3.5-kilobase mRNA species. Reverse transcriptase-polymerase chain reaction analysis indicated expression also in human cultured vascular smooth muscle cells, supporting the view that the Y1 receptor is associated with NPY/PYY-evoked vasoconstriction. When expressed in COS1 cells, hY1-5 conferred specific 125I-PYY binding sites with displacement patterns characteristic of the Y1 receptor, i.e. PYY greater than or equal to NPY greater than or equal to [Leu31,Pro34]NPY much greater than NPY2-36 greater than C2NPY greater than pancreatic polypeptide greater than NPY13-36 greater than NPY18-36. Moreover, in the Y1 receptor-transfected COS1 cells, but not in type 1 angiotensin II receptor-transfected control cells, NPY and PYY accelerated 45Ca2+ influx and inhibited forskolin-stimulated cAMP accumulation, both phenomena being characteristic of the mammalian Y1 receptor.

Amino Acid Sequence↗

PubMed1992

In vitro toxicology of fumonisins and the mechanistic implications.

The effects of fumonisins B1(FB1), B2(FB2), and the backbone of fumonisin B1 remaining after hydrolysis of the tricarballylic groups with base (HFB1) on sphingolipid biosynthesis were studied in both primary rat hepatocytes and pig kidney epithelial cells (LLC-PK1). Fumonisins were potent inhibitors of sphingolipid biosynthesis in hepatocytes (IC50 of FB1 = 0.1 microM), but overt toxicity was not observed. In renal cells, fumonisins also inhibited sphingosine biosynthesis (IC50 for FB1 = 35 microM), and caused decreased cell proliferation as well. Higher doses (greater than or equal to 70 microM) killed renal cells after exposure for 3 days. The inhibition of de novo sphingolipid biosynthesis was specific, and appeared to be at the site of ceramide synthase, which catalyzes the formation of dihydroceramide or ceramide by the addition of the amide-linked fatty acid to sphinganine or sphingosine. These results may account for the ability of fumonisins to cause equine leucoencephalomalacia and to promote tumor formation.

Animals↗