Synergism between vascular endothelial growth factor and placental growth factor contributes to angiogenesis and plasma extravasation in pathological conditions

Vascular endothelial growth factor (VEGF) stimulates angiogenesis by activating VEGF receptor-2 (VEGFR-2). The role of its homolog, placental growth factor (PlGF), remains unknown. Both VEGF and PlGF bind to VEGF receptor-1 (VEGFR-1), but it is unknown whether VEGFR-1, which exists as a soluble or a membrane-bound type, is an inert decoy or a signaling receptor for PlGF during angiogenesis. Here, we report that embryonic angiogenesis in mice was not affected by deficiency of PlGF (Pgf-/-). VEGF-B, another ligand of VEGFR-1, did not rescue development in Pgf-/- mice. However, loss of PlGF impaired angiogenesis, plasma extravasation and collateral growth during ischemia, inflammation, wound healing and cancer. Transplantation of wild-type bone marrow rescued the impaired angiogenesis and collateral growth in Pgf-/- mice, indicating that PlGF might have contributed to vessel growth in the adult by mobilizing bone-marrow-derived cells. The synergism between PlGF and VEGF was specific, as PlGF deficiency impaired the response to VEGF, but not to bFGF or histamine. VEGFR-1 was activated by PlGF, given that anti-VEGFR-1 antibodies and a Src-kinase inhibitor blocked the endothelial response to PlGF or VEGF/PlGF. By upregulating PlGF and the signaling subtype of VEGFR-1, endothelial cells amplify their responsiveness to VEGF during the 'angiogenic switch' in many pathological disorders.

Spiroindolones, a potent compound class for the treatment of malaria

Recent reports of increased tolerance to artemisinin derivatives--the most recently adopted class of antimalarials--have prompted a need for new treatments. The spirotetrahydro-beta-carbolines, or spiroindolones, are potent drugs that kill the blood stages of Plasmodium falciparum and Plasmodium vivax clinical isolates at low nanomolar concentration. Spiroindolones rapidly inhibit protein synthesis in P. falciparum, an effect that is ablated in parasites bearing nonsynonymous mutations in the gene encoding the P-type cation-transporter ATPase4 (PfATP4). The optimized spiroindolone NITD609 shows pharmacokinetic properties compatible with once-daily oral dosing and has single-dose efficacy in a rodent malaria model.

Deletion of the hypoxia-response element in the vascular endothelial growth factor promoter causes motor neuron degeneration

Hypoxia stimulates angiogenesis through the binding of hypoxia-inducible factors to the hypoxia-response element in the vascular endothelial growth factor (Vegf) promotor. Here, we report that deletion of the hypoxia-response element in the Vegf promotor reduced hypoxic Vegf expression in the spinal cord and caused adult-onset progressive motor neuron degeneration, reminiscent of amyotrophic lateral sclerosis. The neurodegeneration seemed to be due to reduced neural vascular perfusion. In addition, Vegf165 promoted survival of motor neurons during hypoxia through binding to Vegf receptor 2 and neuropilin 1. Acute ischemia is known to cause nonselective neuronal death. Our results indicate that chronic vascular insufficiency and, possibly, insufficient Vegf-dependent neuroprotection lead to the select degeneration of motor neurons.

A recombinant blood-stage malaria vaccine reduces Plasmodium falciparum density and exerts selective pressure on parasite populations in a phase 1-2b trial in Papua New Guinea

The malaria vaccine Combination B comprises recombinant Plasmodium falciparum ring-infected erythrocyte surface antigen and 2 merozoite surface proteins (MSP1 and MSP2) formulated in oil-based adjuvant. A phase 1-2b double-blind, randomized, placebo-controlled trial in 120 children (5-9 years old) in Papua New Guinea demonstrated a 62% (95% confidence limits: 13%, 84%) reduction in parasite density in children not pretreated with sulfadoxine-pyrimethamine. Vaccinees had a lower prevalence of parasites carrying the MSP2-3D7 allelic form (corresponding to that in the vaccine) and a higher incidence of morbid episodes associated with FC27-type parasites. These results demonstrate functional activity of Combination B against P. falciparum in individuals with previous malaria exposure. The specific effects on parasites with particular msp2 genotypes suggest that the MSP2 component, at least in part, accounted for the activity. The vaccine-induced selection pressure exerted on the parasites and its consequences for morbidity strongly argue for developing vaccines comprising conserved antigens and/or multiple components covering all important allelic types.

Mycobacterium tuberculosis lineage 4 comprises globally distributed and geographically restricted sublineages

Generalist and specialist species differ in the breadth of their ecological niches. Little is known about the niche width of obligate human pathogens. Here we analyzed a global collection of Mycobacterium tuberculosis lineage 4 clinical isolates, the most geographically widespread cause of human tuberculosis. We show that lineage 4 comprises globally distributed and geographically restricted sublineages, suggesting a distinction between generalists and specialists. Population genomic analyses showed that, whereas the majority of human T cell epitopes were conserved in all sublineages, the proportion of variable epitopes was higher in generalists. Our data further support a European origin for the most common generalist sublineage. Hence, the global success of lineage 4 reflects distinct strategies adopted by different sublineages and the influence of human migration.

Cell type specific upregulation of vascular endothelial growth factor in an MCA-occlusion model of cerebral infarct

Vascular endothelial growth factor (VEGF) is an endothelial cell specific mitogen that has been implicated in hypoxia-mediated angiogenesis under physiological and pathological conditions. We used the middle cerebral artery occlusion model (MCAO) in the rat to investigate VEGF mRNA and protein localization, and VEGFR-1 mRNA and VEGFR-2 mRNA expression in cerebral ischemia. By nonradioactive in situ hybridization we observed upregulation of VEGF mRNA and VEGFR-1 mRNA, but not of VEGFR-2 mRNA in the hemisphere ipsilateral to MCA occlusion. VEGF mRNA was upregulated in the periphery of the ischemic area commencing 3 hours (h) after onset of MCAO, reached a peak after 24 h, and remained expressed at lower levels until 7 days (d) after MCAO. Double labelling experiments revealed that the majority of VEGF expressing cells in the penumbra and within the infarct were immunoreactive for Ox-42, Iba-1, and Ed1, but not for GFAP and neurofilament proteins, suggesting that microglial cells/macrophages are the major cell type expressing VEGE Since VEGF was also expressed in Ox-42 immunoreactive cells distant from the infarct (e.g. in the corpus callosum and hippocampus), activated microglial cells expressing VEGF may migrate towards the ischemic stimulus. VEGF protein was also detected on capillaries within the peri-ischemic area, suggesting that VEGF produced and secreted by microglial cells/macrophages binds to its receptors on nearby vascular endothelial cells and initiates an angiogenic response which counterbalances tissue hypoxia. Accordingly, apoptosis of neuroectodermal cells in the penumbra was highly depressed after the onset of angiogenesis. The spatial and temporal correlation between the induction of angiogenesis with VEGF and VEGFR-1 expression suggests that the ischemic upregulation of VEGF represents a physiological response of the brain to counterbalance hypoxia/ischemia in order to protect neuroectodermal tissue.

Single-Dose Tafenoquine to Prevent Relapse of Plasmodium vivax Malaria

BACKGROUND

Treatment of Plasmodium vivax malaria requires the clearing of asexual parasites, but relapse can be prevented only if dormant hypnozoites are cleared from the liver (a treatment termed "radical cure"). Tafenoquine is a single-dose 8-aminoquinoline that has recently been registered for the radical cure of P. vivax.

METHODS

This multicenter, double-blind, double-dummy, parallel group, randomized, placebo-controlled trial was conducted in Ethiopia, Peru, Brazil, Cambodia, Thailand, and the Philippines. We enrolled 522 patients with microscopically confirmed P. vivax infection (>100 to <100,000 parasites per microliter) and normal glucose-6-phosphate dehydrogenase (G6PD) activity (with normal activity defined as ≥70% of the median value determined at each trial site among 36 healthy male volunteers who were otherwise not involved in the trial). All patients received a 3-day course of chloroquine (total dose of 1500 mg). In addition, patients were assigned to receive a single 300-mg dose of tafenoquine on day 1 or 2 (260 patients), placebo (133 patients), or a 15-mg dose of primaquine once daily for 14 days (129 patients). The primary outcome was the Kaplan-Meier estimated percentage of patients who were free from recurrence at 6 months, defined as P. vivax clearance without recurrent parasitemia.

RESULTS

In the intention-to-treat population, the percentage of patients who were free from recurrence at 6 months was 62.4% in the tafenoquine group (95% confidence interval [CI], 54.9 to 69.0), 27.7% in the placebo group (95% CI, 19.6 to 36.6), and 69.6% in the primaquine group (95% CI, 60.2 to 77.1). The hazard ratio for the risk of recurrence was 0.30 (95% CI, 0.22 to 0.40) with tafenoquine as compared with placebo (P<0.001) and 0.26 (95% CI, 0.18 to 0.39) with primaquine as compared with placebo (P<0.001). Tafenoquine was associated with asymptomatic declines in hemoglobin levels, which resolved without intervention.

CONCLUSIONS

Single-dose tafenoquine resulted in a significantly lower risk of P. vivax recurrence than placebo in patients with phenotypically normal G6PD activity. (Funded by GlaxoSmithKline and Medicines for Malaria Venture; DETECTIVE ClinicalTrials.gov number, NCT01376167 .).

Strategies for detection of Plasmodium species gametocytes

Carriage and density of gametocytes, the transmission stages of malaria parasites, are determined for predicting the infectiousness of humans to mosquitoes. This measure is used for evaluating interventions that aim at reducing malaria transmission. Gametocytes need to be detected by amplification of stage-specific transcripts, which requires RNA-preserving blood sampling. For simultaneous, highly sensitive quantification of both, blood stages and gametocytes, we have compared and optimized different strategies for field and laboratory procedures in a cross sectional survey in 315 5-9 yr old children from Papua New Guinea. qRT-PCR was performed for gametocyte markers pfs25 and pvs25, Plasmodium species prevalence was determined by targeting both, 18S rRNA genes and transcripts. RNA-based parasite detection resulted in a P. falciparum positivity of 24.1%; of these 40.8% carried gametocytes. P. vivax positivity was 38.4%, with 38.0% of these carrying gametocytes. Sensitivity of DNA-based parasite detection was substantially lower with 14.1% for P. falciparum and 19.6% for P. vivax. Using the lower DNA-based prevalence of asexual stages as a denominator increased the percentage of gametocyte-positive infections to 59.1% for P. falciparum and 52.4% for P. vivax. For studies requiring highly sensitive and simultaneous quantification of sexual and asexual parasite stages, 18S rRNA transcript-based detection saves efforts and costs. RNA-based positivity is considerably higher than other methods. On the other hand, DNA-based parasite quantification is robust and permits comparison with other globally generated molecular prevalence data. Molecular monitoring of low density asexual and sexual parasitaemia will support the evaluation of effects of up-scaled antimalarial intervention programs and can also inform about small scale spatial variability in transmission intensity.

Expression of angiopoietin-1, angiopoietin-2, and tie receptors after middle cerebral artery occlusion in the rat

Vascular endothelial growth factor (VEGF), a key regulator of vasculogenesis and embryonic angiogenesis, was recently found to be up-regulated in an animal model of stroke. Unlike VEGF, angiopoietin (Ang)-1 and -2, their receptor tie-2, and the associated receptor tie-1 exert their functions at later stages of vascular development, i.e., during vascular remodeling and maturation. To assess the role of the angiopoietin/tie family in ischemia-triggered angiogenesis we analyzed their temporal and spatial expression pattern after middle cerebral artery occlusion (MCAO) using in situ hybridization and immunohistochemistry. Ang-1 mRNA was constitutively expressed in a subset of glial and neuronal cells with no apparent change in expression after MCAO. Ang-2 mRNA was up-regulated 6 hours after MCAO and was mainly observed in endothelial cell (EC) cord tips in the peri-infarct and infarct area. Up-regulation of both Ang-2 and VEGF coincided with EC proliferation. Interestingly, EC proliferation was preceded by a transient period of EC apoptosis, correlating with a change in VEGF/Ang-2 balance. Our observation of specific stages of vascular regression and growth after MCAO are in agreement with recent findings suggesting a dual role of Ang-2 in blood vessel formation, depending on the availability of VEGF.

Identification and differentiation of Leishmania species in clinical samples by PCR amplification of the miniexon sequence and subsequent restriction fragment length polymorphism analysis

We recently developed a new PCR-restriction fragment length polymorphism (RFLP)-based assay using the miniexon sequence from the genus Leishmania. Here we report the application of this new genotyping method to naturally infected clinical samples for the differentiation of New and Old World Leishmania species. Of the newly developed assay and four currently applied diagnostic tests (i.e., in vitro cultivation, serology, and two other molecular assays using either the small subunit-internal transcribed spacer sequence or a repetitive genomic sequence), the miniexon assay showed the highest sensitivity, 89.7%, compared to 70.6, 57.1, 51.7, and 79.3%, respectively. Species differentiation was robust and reliable compared with that by two other Leishmania genotyping techniques. The assay provides a valuable tool for the identification of Leishmania directly from clinical samples and enables determination of the infecting species by a facile technique with high discrimination power. Since Leishmania causes a broad spectrum of diseases distinguished by different parasite and host factors, detection and characterization of the infecting species is crucial for the confirmation of a diagnosis as well as the establishment of the clinical prognosis and the initiation of an adequate therapeutic approach. The miniexon PCR-RFLP assay will facilitate such determination and might improve diagnosis and treatment of leishmaniasis.

Differential expression of var gene groups is associated with morbidity caused by Plasmodium falciparum infection in Tanzanian children

The var gene family of Plasmodium falciparum encodes the variant surface antigen Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1). PfEMP1 is considered an important pathogenicity factor in P. falciparum infection because it mediates cytoadherence to host cell endothelial receptors. var genes can be grouped into three major groups, A, B, and C, and the conserved var genes, var1-4, according to sequence similarities in coding and noncoding upstream regions. Using real-time quantitative PCR in a study conducted in Tanzania, the var transcript abundances of the different var gene groups were compared among patients with severe, uncomplicated, and asymptomatic malaria. Transcripts of var group A and B genes were more abundant in patients with severe malaria than in patients with uncomplicated malaria. In general, the transcript abundances of var group A and B genes were higher for children with clinical malaria than for children with asymptomatic infections. The var group C and var1-like transcript abundances were similar between the three sample groups. A transcript abundance pattern similar to that for var group A was observed for var2csa and var3-like genes. These results suggest that substantial and systematic differences in var gene expression exist between different clinical presentations.

Premunition in Plasmodium falciparum infection: insights from the epidemiology of multiple infections

Epidemiological studies of multiple clone infections by Plasmodium falciparum in highly endemic areas have demonstrated age dependence in both the multiplicity of infection and the relationships between this multiplicity and the risk of acute illness. We hypothesize that, in infants, host defence against blood-stage infections with P. falciparum relies mainly on fever and cytokine activities, and the infections are of short duration. In older children, a high multiplicity of infection is characteristic of low-level chronic parasitaemia. This appears to confer cross-protection against newly inoculated parasites, via partially genotype-specific responses which are short-term, lasting little longer than the infections themselves. This has important implications for our understanding of immunity against P. falciparum, its ecological niche, and the epidemiological impact of interventions against it.

Age- and mental health-related circadian rhythms of plasma levels of melatonin, prolactin, luteinizing hormone and follicle-stimulating hormone in man

Circadian changes in plasma levels of melatonin, prolactin, LH and FSH were studied in four groups: seven healthy young men, six elderly men, six elderly women and six elderly demented patients (two men and four women). The daily activities of the subjects were synchronous and blood samples were taken every 4 h. The 24-h mean concentrations of prolactin in plasma were the same in all groups, whereas those of LH and FSh were twice as high in the elderly as in the young men and eight and 23 times higher respectively in the elderly women. The 24-h mean plasma levels of melatonin in the elderly were half those in the young, but were not influenced by the sex or mental condition of the subjects. A statistically significant circadian rhythm for melatonin was defined in the four groups, for prolactin in all groups except the elderly men and for LH only in the demented patients and in the young men. No circadian rhythm could be detected for FSH in any of the four groups. The acrophases of melatonin and prolactin ranged between 02.30 and 04.00 h, those of LH (when a rhythm was validated) clustered around 01.00 h. The circadian rhythms of plasma levels of melatonin, prolactin and LH are not modified in old age nor in dementia. A positive correlation has been demonstrated in young men between melatonin and LH and between melatonin and prolactin, but no such correlation could be found in the elderly.

The use of PCR genotyping in the assessment of recrudescence or reinfection after antimalarial drug treatment

In the past, assessment of drug efficacy against Plasmodium falciparum malaria has been performed by microscopy, screening for parasites in blood smears. However, in areas of high endemicity, reappearing parasites might be derived from new inoculations and could be classified falsely as treatment failures. Recently, a number of studies have used polymerase chain reaction (PCR) analysis of detectable parasites after drug administration to discriminate new infections from true recrudescence. The feasibility, high sensitivity and high resolution of this technique proves that it will be practical and highly valuable in studies on both drug resistance and vaccine efficacy as well as the testing of novel antimalarial drugs. In this article, Georges Snounou and Hans-Peter Beck discuss the uncertainties in the interpretation of data inherent to the technical limitations of the PCR technique, and the constraints imposed by the biology of the parasite. They suggest that although genotyping can provide strong evidence for differentiating between true recrudescence and reinfection, it must be interpreted with caution. They also propose strategies that might help minimize these uncertainties.

Molecular neuropathology of human mesial temporal lobe epilepsy

With the recent progress in surgical treatment modalities, human brain tissue from patients with intractable focal epilepsies will increasingly become available for studies on the molecular pathology, electrophysiological changes and pathogenesis of human focal epilepsies. An inherent problem for studies on human temporal lobe epilepsy (TLE) is the lack of suitable controls. Strategies to alleviate this obstacle include the use of human post mortem samples, hippocampus from experimental animals and, in particular, the comparative analysis of surgical specimens from patients with Ammon's horn sclerosis (AHS) and with focal temporal lesions but anatomically preserved hippocampal structures. In this review we focus on selected aspects of the molecular neuropathology of TLE: (1) the potential impact of persisting calretinin-immunoreactive neurons with Cajal-Retzius cell morphology, (2) astrocytic tenascin-C induction and redistribution as potential regulator of aberrant axonal sprouting and (3) alterations of Ca2+ -mediated hippocampal signalling pathways. The diverse and complex changes described so far in human TLE specimens require a systematic interdisciplinary approach to distinguish primary, epileptogenic alterations and secondary, compensatory mechanisms in the pathogenesis of human temporal lobe epilepsies.

etramps, a new Plasmodium falciparum gene family coding for developmentally regulated and highly charged membrane proteins located at the parasite-host cell interface

After invasion of erythrocytes, the human malaria parasite Plasmodium falciparum resides within a parasitophorous vacuole and develops from morphologically and metabolically distinct ring to trophozoite stages. During these developmental phases, major structural changes occur within the erythrocyte, but neither the molecular events governing this development nor the molecular composition of the parasitophorous vacuole membrane (PVM) is well known. Herein, we describe a new family of highly cationic proteins from P. falciparum termed early transcribed membrane proteins (ETRAMPs). Thirteen members were identified sharing a conserved structure, of which six were found only during ring stages as judged from Northern and Western analysis. Other members showed different stage-specific expression patterns. Furthermore, ETRAMPs were associated with the membrane fractions in Western blots, and colocalization and selective permeabilization studies demonstrated that ETRAMPs were located in the PVM. This was confirmed by immunoelectron microscopy where the PVM and tubovesicular extensions of the PVM were labeled. Early expressed ETRAMPs clearly defined separate PVM domains compared with the negatively charged integral PVM protein EXP-1, suggesting functionally different domains in the PVM with an oppositely charged surface coat. We also show that the dynamic change of ETRAMP composition in the PVM coincides with the morphological changes during development. The P. falciparum PVM is an important structure for parasite survival, and its analysis might provide better understanding of the requirements of intracellular parasites.

Analysis of multiple Plasmodium falciparum infections in Tanzanian children during the phase III trial of the malaria vaccine SPf66

In the first phase III efficacy trial of the malaria vaccine SPf66 in Africa, MOIs in SPf66- and placebo-vaccinated children were analyzed by polymerase chain reaction-restriction fragment length polymorphism of the Plasmodium falciparum merozoite surface antigen 2 (MSA2). MOIs were significantly reduced in asymptomatic vaccine recipients compared with those in asymptomatic placebo recipients; however, no differences were observed among symptomatic children in the vaccine and control groups. These results show that immunization with SPf66 modulates the course of naturally occurring infections, as reflected by reduced MOIs. In placebo recipients, however, there was a significant negative correlation between numbers of infecting genotypes, as identified by MSA2, and morbidity. Asymptomatic placebo recipients had an average of 5 concurrent infections, whereas children with clinical cases had an average of 3.4 infections. These data provide further evidence that premunition from concurrent infections is important in immunity against clinical malaria. No such effect of multiple infections was found in the vaccinated group.

Virulence of malaria is associated with differential expression of Plasmodium falciparum var gene subgroups in a case-control study

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a major pathogenicity factor in falciparum malaria that mediates cytoadherence. PfEMP1 is encoded by approximately 60 var genes per haploid genome. Most var genes are grouped into 3 subgroups: A, B, and C. Evidence is emerging that the specific expression of these subgroups has clinical significance. Using field samples from children from Papua New Guinea with severe, mild, and asymptomatic malaria, we compared proportions of transcripts of var groups, as determined by quantitative polymerase chain reaction. We found a significantly higher proportion of var group B transcripts in children with clinical malaria (mild and severe), whereas a large proportion of var group C transcripts was found in asymptomatic children. These data from naturally infected children clearly show that major differences exist in var gene expression between parasites causing clinical disease and those causing asymptomatic infections. Furthermore, parasites forming rosettes showed a significant up-regulation of var group A transcripts.

Evidence for an excitonic insulator phase in 1T-TiSe2

We present a new high-resolution angle-resolved photoemission study of 1T-TiSe2 in both its room-temperature, normal phase and its low-temperature, charge-density wave phase. At low temperature the photoemission spectra are strongly modified, with large band renormalizations at high-symmetry points of the Brillouin zone and a very large transfer of spectral weight to backfolded bands. A calculation of the theoretical spectral function for an excitonic insulator phase reproduces the experimental features with very good agreement. This gives strong evidence in favor of the excitonic insulator scenario as a driving force for the charge-density wave transition in 1T-TiSe2.

Evidence relating human verbal memory to hippocampal N-methyl-D-aspartate receptors

Studies in rodents and nonhuman primates have linked the activity of N-methyl-D-aspartate (NMDA) receptors within the hippocampus to animals' performance on memory-related tasks. However, whether these receptors are similarly essential for human memory is still an open question. Here we present evidence suggesting that hippocampal NMDA receptors, most likely within the CA1 region, do participate in human verbal memory processes. Words elicit a negative event-related potential (ERP) peaking around 400 ms within the anterior mesial temporal lobe (AMTL-N400). Ketamine, an NMDA-receptor antagonist, reduces the amplitude of the AMTL-N400 (in contrast to other hippocampal potentials) on initial presentation, eliminates the typical AMTL-N400 amplitude reduction with repetition, and leads to significant memory impairment. Of the various hippocampal subfields, only the density of CA1 neurons correlates with the word-related ERPs that are reduced by ketamine. Altogether, our behavioral, anatomical, and electrophysiological results indicate that hippocampal NMDA receptors are involved in human memory.

Diagnostic genotyping of Old and New World Leishmania species by PCR-RFLP

We have designed a new genotyping scheme for molecular diagnosis of the different Leishmania species pathogenic to humans. This scheme is based on PCR amplified sequences from the gene for the spliced leader RNA (mini-exon). This target was selected because it is present as tandem repeats (100 to 200 copies) in the genus Leishmania and other kinetoplastida, but is absent from the mammalian hosts and the sandfly vectors. The exon is highly conserved, whereas the intron and non-transcribed spacer region vary in size and sequence among different species. Thus, it was possible to amplify DNA from both Old and New World pathogenic Leishmania complexes using a single pair of primers deriving from the conserved region of the mini-exon tandem repeat. Species identification was performed by digesting mini-exon PCR products with one or two different restriction enzymes. Restriction fragment length polymorphism (RFLP) generated species-specific patterns of bands visualized in agarose gels, which allowed to differentiate each species unequivocally.

Molecular and functional changes in voltage-dependent Na(+) channels following pilocarpine-induced status epilepticus in rat dentate granule cells

Status epilepticus (S.E.) is known to lead to a large number of changes in the expression of voltage-dependent ion channels and neurotransmitter receptors. In the present study, we examined whether an episode of S.E. induced by pilocarpine in vivo alters functional properties and expression of voltage-gated Na(+) channels in dentate granule cells (DGCs) of the rat hippocampus. Using patch-clamp recordings in isolated DGCs, we show that the voltage-dependent inactivation curve is significantly shifted toward depolarizing potentials following S.E. (half-maximal inactivation at -43.2+/-0.6 mV) when compared with control rats (-48.2+/-0.8 mV, P<0.0001). The voltage-dependent activation curve is significantly shifted to more negative potentials following S.E., with half-maximal activation at -28.6+/-0.8 mV compared with -25.8+/-0.9 mV in control animals (P<0.05). The changes in voltage dependence resulted in an augmented window current due to increased overlap between the activation and inactivation curve. In contrast to Na(+) channel voltage-dependence, S.E. caused no changes in the kinetics of fast or slow recovery from inactivation. The functional changes were accompanied by altered expression of Na(+) channel subunits measured by real-time reverse transcription-polymerase chain reaction in dentate gyrus microslices. We investigated expression of the pore-forming alpha subunits Na(v)1.1-Na(v)1.3 and Na(v)1.5-Na(v)1.6, in addition to the accessory subunits beta(1) and beta(2). The Na(v)1.2 and Na(v)1.6 subunit as well as the beta(1) subunit were persistently down-regulated up to 30 days following S.E. The beta(2) subunit was transiently down-regulated on the first and third day following S.E. These results indicate that differential changes in Na(+) channel subunit expression occur in concert with functional changes. Because coexpression of beta subunits is known to robustly shift the voltage dependence of inactivation in a hyperpolarizing direction, we speculate that a down-regulation of beta-subunit expression may contribute to the depolarizing shift in the inactivation curve following S.E.

Differential inhibitory effects of garlic-derived organosulfur compounds on cholesterol biosynthesis in primary rat hepatocyte cultures

Using primary rat hepatocyte cultures, the potency of several garlic-derived organosulfur compounds to inhibit cholesterol biosynthesis in toto as well as at early and late steps of this metabolic pathway was compared. Concerning early steps, allicin significantly inhibited incorporation of [14C]acetate into nonsaponifiable neutral lipids already at concentrations as low as 10 microM, while diallyl disulfide and allyl mercaptan were effective above 100 microM only. Likewise, inhibition in response to the two vinyl-dithiins started at 500 microM. If [14C]acetate was replaced by [14C]mevalonate, inhibition due to allicin, diallyl disulfide, and allyl mercaptan disappeared suggesting that HMGCoA-reductase was the target of inhibition. In contrast, for the vinyl-dithiins a stimulation of mevalonate incorporation was found. Concerning the late step, the potency to exert accumulation of lanosterol presumably by inhibiting lanosterol 14 alpha-demethylase decreased in the order allicin > diallyl disulfide > allyl mercaptan = 1,3-vinyl-dithiin >> 1,2-vinyldithiin, the effect of the latter compound being close to zero. With respect to the total inhibition of [14C]acetate labeling of cholesterol, the half-maximal effective concentration-value of allicin was determined to be 17 +/- 2 microM compared to 64 +/- 7 microM for diallyl disulfide and to 450 +/- 20 microM for allyl mercaptan. Cytotoxicity as determined by the lactate dehydrogenase leakage assay was slightly higher for the two vinyl-dithiins than for diallyl disulfide and allyl mercaptan, but was apparent only at concentrations higher than 10 mM and, consequently, was irrelevant for the effects described. These results demonstrate that different garlic-derived organosulfur compounds interfere differently with cholesterol biosynthesis and, thus, may provoke multiple inhibition of this metabolic pathway in response to garlic consumption. The fact that allicin was the most effective inhibitor argues against the possibility that its degradation products, namely diallyl disulfide or allyl mercapatan, might mediate its effects, a possibility that might be true, however, in the case of the vinyl-dithiins.