Molecular targets of the antiinflammatory Harpagophytum procumbens (devil's claw): inhibition of TNFα and COX-2 gene expression by preventing activation of AP-1.

Harpagophytum procumbens (Hp) is often used in the supportive treatment of inflammatory and degenerative diseases of the skeletal system. Although the clinical efficacy in osteoarthritis has been demonstrated in clinical trials, the molecular target(s) of Hp are unclear. This study quantified the effects of the ethanol Hp extract (60% v/v ethanol, sole active ingredient of Pascoe®-Agil), on the expression and release of the major pro-inflammatory mediators in LPS-stimulated human monocytes and the intracellular signalling pathways involved in inflammation. The Hp extract dose-dependently inhibited the release of TNFα as well as that of interleukin (IL)-6, IL-1ß and prostaglandin E2 (PGE2). The Hp prevented TNFα and IL-6 mRNA expression in human monocytes and cyclooxygenase-2 (COX-2) in RAW 264.7 cells. Furthermore, the Hp extract inhibited LPS-stimulated AP-1-mediated gene transcription activity and binding to the AP-1 response elements. The extract had no effect on the LPS-induced binding of nuclear factor-κB in RAW 264.7 cells, on LPS-induced degradation of IκBα or on LPS-induced activation of mitogen-activated protein kinases (MAPK), p38MAPK and JNK in human monocytes. The data indicate that a standardized ethanol Hp extract inhibits induction of pro-inflammatory gene expression, possibly by blocking the AP-1 pathway. This is novel evidence of a possible mechanism of action of this antiinflammatory drug.

Assessment of a dry extract from milk thistle (Silybum marianum) for interference with human liver cytochrome-P450 activities.

The effect of a standardised dry extract from Silybum marianum (HEPAR-PASC®) on the enzyme kinetics of cytochrome-P450 isoenzymes (CYP) was investigated with primary human hepatocytes and human liver microsomes in order to assess the potential for drug-drug interactions. A cytotoxic effect on hepatocytes was observed at concentrations at and above 50 µg/ml. The EC(50) value was calculated to be 72.0 µg/ml. Therefore, the chosen test concentrations for CYP induction on human hepatocytes were 50, 10, and 1.5 µg/ml, which allowed for interpretation of the clinical significance of the data with a range of 50-1-fold c(max) at maximal recommended doses. No induction was observed at the lowest concentration of 1.5 µg/ml, which is close to c(max). The extract did not induce CYP 3A4 at any of the tested concentrations. A low or marginal induction of 1A2, 2B6, and 2E1 at the maximum concentration of 50 µg/ml was observed. CYP inhibition on human microsomes was tested at concentrations of 150, 15, and 1.5 µg/ml. No or minor CYP inhibition was observed for all CYPs tested at the lowest concentration of 1.5 µg/ml, i.e. CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4. At concentrations of 15 and 150 µg/ml the extract significantly inhibited CYP 2B6, 2C8, 2C9, 2C19, 2E1, and 3A4. In these cases, K(i) values were determined. All K(i) values exceeded c(max) by at least a factor of 10-fold. According to FDA regulations 1>c(max)/K(i)>0.1 indicates, that drug-drug interactions are possible for CYPs 2C8, and 2C9, but not likely, and are remote for CYPs 2C19, 2D6, and 3A4.

Anxiolytic activity of a phytochemically characterized Passiflora incarnata extract is mediated via the GABAergic system.

The purpose of this research was to assess the anxiolytic properties of a phytochemically characterized commercial extract from Passiflora incarnata (PI; Passifloraceae) in the elevated plus maze test in mice. Using an HPLC method, the flavonoids homoorientin, orientin, vitexin, and isovitexin were identified as major compounds. Following oral administration, the extract exerted an anxiolytic effect that was comparable to diazepam (1.5 mg/kg) at a dose of 375 mg/kg and exhibited a U-shaped dose-response curve. In addition, antagonism studies using the GABA (A)/benzodiazepine receptor antagonist flumazenil and the 5-HT (1A)-receptor antagonist WAY-100 635 were conducted. The active dose was effectively antagonized by flumazenil, but not by WAY-100 635. This study is the first demonstration of the IN VIVO, GABA-mediated anxiolytic activity of an HPLC- characterized extract of Passiflora incarnata.

Rationale and impact of vitamin C in clinical nutrition.

PURPOSE OF REVIEW: The impact of vitamin C on oxidative stress-related diseases is moderate because of its limited oral bioavailability and rapid clearance. Parenteral administration can increase the benefit of vitamin C supplementation as is evident in critically ill patients. The aim here is to assess recent evidence of the clinical benefit and underlying effects of parenteral vitamin C in conditions of oxidative stress. RECENT FINDINGS: In critically ill patients and after severe burns, the rapid restoration of depleted ascorbate levels with high-dose parenteral vitamin C may reduce circulatory shock, fluid requirements and oedema. SUMMARY: Oxidative stress is associated with reduced ascorbate levels. Ascorbate is particularly effective in protecting the vascular endothelium, which is especially vulnerable to oxidative stress. The restoration of ascorbate levels may have therapeutic effects in diseases involving oxidative stress. The rapid replenishment of ascorbate is of special clinical significance in critically ill patients who experience drastic reductions in ascorbate levels, which may be a causal factor in the development of circulatory shock. Supraphysiological levels of ascorbate, which can only be achieved by the parenteral and not by the oral administration of vitamin C, may facilitate the restoration of vascular function in the critically ill patient.

Functional screening of traditional antidepressants with primary cortical neuronal networks grown on multielectrode neurochips.

We optimized the novel technique of multielectrode neurochip recordings for the rapid and efficient screening of neuroactivity. Changes in the spontaneous activity of cultured networks of primary cortical neurons were quantified to evaluate the action of drugs on the firing dynamics of complex network activity. The multiparametric assessment of electrical activity changes caused by psychoactive herbal extracts from Hypericum, Passiflora and Valeriana, and various combinations thereof revealed a receptor-specific and concentration-dependent inhibition of the firing patterns. The spike and burst rates showed significant substance-dependent effects and significant differences in potency. The effects of specific receptor blockades on the inhibitory responses provided evidence that the herbal extracts act on gamma-amino butyric acid (GABA) and serotonin (5-HT) receptors, which are recognized targets of pharmacological antidepressant treatment. A biphasic effect, serotonergic stimulation of activity at low concentrations that is overridden by GABAergic inhibition at higher concentrations, is apparent with Hypericum alone and the triple combination of the extracts. The more potent neuroactivity of the triple combination compared to Hypericum alone and the additive effect of Passiflora and Valeriana suggest a synergy between constituent herbal extracts. The extracts and their combinations affected the set of derived activity parameters in a concomitant manner suggesting that all three constituent extracts and their combinations have largely similar modes of action. This study also demonstrates the sensitivity, selectivity and robustness of neurochip recordings for high content screening of complex mixtures of neuroactive substances and for providing multiparametric information on neuronal activity changes to assess the therapeutic potential of psychoactive substances.

Gastric perception thresholds are low and sensory neuropeptide levels high in helicobacter pylori-positive functional dyspepsia.

BACKGROUND AND AIMS: In functional dyspepsia (FD) decreased perception levels can be shown on gastric distension. Substance P (SP) and calcitonin gene-related peptide (CGRP) are involved in the sensitization of afferent neuronal pathways due to chronic inflammation. The role of Helicobacter pylori-induced gastric mucosal inflammation in the pathogenesis of FD is controversial. The aim of this study was to assess whether FD patients have altered mucosal concentrations of CGRP and SP, and to investigate whether this is associated with visceral hypersensitivity or H. pylori infection. METHODS: Gastrointestinal symptoms, H. pylori status, perception thresholds at gastric balloon distension, and gastric mucosal concentrations of CGRP and SP were determined in 13 FD patients and 18 healthy controls (HC). RESULTS: In H. pylori-positive FD patients discomfort and pain thresholds on gastric distension were lower compared to other groups. Antral mucosal levels of CGRP and SP were higher in H. pylori-positive subjects. In FD significantly negative correlations between discomfort and pain thresholds and antral mucosal concentrations of CGRP and SP were observed. CONCLUSIONS: In FD low perception thresholds on gastric distension are associated with high levels of CGRP and SP in the antrum, suggesting that sensory neuropeptides are involved in FD pathophysiology.

Brain-derived neurotrophic factor (BDNF) contributes to neuronal dysfunction in a model of allergic airway inflammation.

Brain-derived neurotrophic factor (BDNF) is a candidate molecule for mediating functional neuronal changes in allergic bronchial asthma. Recently, enhanced production of BDNF during allergic airway inflammation caused by infiltrating T-cells and macrophages as well as by resident airway epithelial cells has been described. It was the aim of this study to investigate the effect of enhanced BDNF levels on lung function and airway inflammation in a mouse model of allergic inflammation. Ovalbumin-sensitised BALB/c mice were challenged in two consecutive allergen challenges. Prior to the challenge, the mice were treated with either anti-BDNF antibodies or isotype-matched control antibodies. Airway responsiveness to methacholine, capsaicin and electric field stimulation, as well as airway inflammation and chronic airway obstruction 1 week after the last allergen challenge were assessed. Anti-BDNF blocked enhanced reactivity in response to capsaicin, but not airway smooth muscle hyper-reactivity in vivo. Furthermore, persistent airway obstruction, as observed 1 week after the last allergen challenge, was to a large extent prevented by anti-BDNF treatment. In vitro, BDNF and anti-BDNF treatment had a profound effect on local neuronal hyper-reactivity, as shown by electric field stimulation experiments. In contrast, neither BDNF nor anti-BDNF treatment affected airway inflammation. Our data indicate that development of allergen-induced neuronal hyper-reactivity in mice is partially mediated by BDNF. British Journal of Pharmacology (2004) 141, 431-440. doi:10.1038/sj.bjp.0705638

Immunohistochemical detection of the calcitonin receptor-like receptor protein in the microvasculature of rat endothelium.

Calcitonin-gene-related peptide and adrenomedullin have similar and potent vascular effects, which appear to be mediated by the G protein-coupled calcitonin receptor-like (CRL) receptor. Using immunohistochemical and Western blot analyses, we have obtained novel evidence that CRL receptor is expressed in the rat vascular endothelium using an antibody to rat CRL receptor that we have raised and fully characterised. These results are an important basis for further studies aimed at determining the so far ill-defined functional significance of the extensive distribution of CRL receptor in the vascular endothelium.

Virokinin, a bioactive peptide of the tachykinin family, is released from the fusion protein of bovine respiratory syncytial virus.

Tachykinins, an evolutionary conserved family of peptide hormones in both invertebrates and vertebrates, are produced by neuronal cells as inactive preprotachykinins that are post-translationally processed into different neuropeptides such as substance P, neurokinin A, and neurokinin B. We show here that furin-mediated cleavage of the bovine respiratory syncytial virus fusion protein results in the release of a peptide that is converted into a biologically active tachykinin (virokinin) by additional post-translational modifications. An antibody directed to substance P cross-reacted with the C terminus of mature virokinin that contains a classical tachykinin motif. The cellular enzymes involved in the C-terminal maturation of virokinin were found to be present in many established cell lines. Virokinin is secreted by virus-infected cells and was found to act on the tachykinin receptor 1 (TACR1), leading to rapid desensitization of this G protein-coupled receptor as shown by TACR1-green fluorescent protein conjugate translocation from the cell surface to endosomes and by co-internalization of the receptor with beta-arrestin 1-green fluorescent protein conjugates. In vitro experiments with isolated circular muscle from guinea pig stomach indicated that virokinin is capable of inducing smooth muscle contraction by acting on the tachykinin receptor 3. Tachykinins and their cognate receptors are present in the mammalian respiratory tract, where they have potent effects on local inflammatory and immune processes. The viral tachykinin-like peptide represents a novel form of molecular mimicry, which may benefit the virus by affecting the host immune response.

Expression and distribution of the calcitonin receptor-like receptor in the developing rat heart.

During ontogenesis the 52 amino acid peptide adrenomedullin is first expressed in the heart and it is essential for normal cardiovascular development. Recent work suggests that most adrenomedullin effects are conveyed via the calcitonin receptor-like receptor (CRLR) in combination with appropriate receptor activity-modifying proteins (RAMPs). Here, we investigated the expression of these components during the development of the rat heart, focusing on the period of coronary vascular development. Using RT-PCR, transcripts for CRLR, RAMP1 and RAMP2 were detected at all stages from E 14 to adulthood. The distribution of CRLR was investigated by immunohistochemistry, and endothelial cells and their precursors identified with monoclonal antibodies against RECA-1 and flk-1. On E 14, intense CRLR immunoreactivity was observed in endothelial cells of the large vessels and the endocardial cushions at the AV-junction. Small CRLR immunoreactive cell clusters were located in the wall of the outflow tract and subepicardially in the ventricular wall. On E 16, tubes of CRLR immunoreactive cells formed a subepicardial plexus, from which they penetrated radially towards the trabecular network and entered at E 18. Smooth muscle cells of coronary arteries gained a moderate CRLR immunoreactivity at E 20 which persisted at this intensity up to P 8 and then decreased. At the same time, CRLR immunoreactivity of endothelial cells in coronary arteries vanished while those of coronary veins still exhibited intense CRLR immunoreactivity. These data suggest multiple functions of the adrenomedullin/CRLR signaling pathway in cardiac development, among which the most prominent appears to be the early outgrowth and proliferation of the immature endothelial cells of the coronary vasculature.

Alternative splicing in single cells dissected from complex tissues: separate expression of prepro-tachykinin A mRNA splice variants in sensory neurones.

Tachykinins play an important role in peripheral inflammatory diseases and disorders of the CNS. Most members of the tachykinin family are generated by alternative post-transcriptional splicing of the prepro-tachykinin (PPT) A gene. Here, we examined the simultaneous expression of PPT-A splice variants in individual neurones of the nodose ganglion. In extracts of ganglia, the expression of the four PPT-A mRNA splice variants and their four encoded peptides was shown by RT-PCR and combined HPLC and radioimmunoassay respectively. In order to examine prepro-tachykinin A expression in individual cells, single neurones were isolated from the ganglia using laser-assisted microdissection and processed for RT-PCR. Some 31.9% of the neurones investigated expressed a specific PPT-A transcript. Each individual neurone was found to express only a single splice variant. This is the first study to analyse the differential expression of PPT-A splice variants at the single-cell level. In view of the large number of alternatively spliced genes in the human genome and the resulting profound physiological effects, including several diseases, the technique described here is useful for isolating cells without possible confounding effects of dissociated neuronal cultures. For PPT-A, the results indicate that alternative post-transcriptional splicing determines the tachykinergic phenotype and may therefore have important functional implications.

Leptin receptor expression in nodose ganglion cells projecting to the rat gastric fundus.

Recent studies suggest that in addition to adipocytes the chief cells of the gastric fundic mucosa are a site of leptin production. In order to assess the possible role of vagal afferent neurons in transmitting leptin signals from the stomach to the brain, leptin receptor (OB-R) expression was investigated in rat nodose ganglion cells and their projection to the stomach determined by retrograde tracing. Reverse transcription-polymerase chain reaction combined with laser-assisted cell picking revealed that large and small diameter neurons express both the long (OB-Rb) and short (OB-Ra) splice variants of the OB-R. OB-R like immunoreactivity was detected in the perikarya of approximately 8% of nodose ganglion neurons. Tracing studies revealed that a significant proportion (15%) of the immunopositive neurons projected to the gastric fundus. These findings suggest that leptin may use a neural route to relay its message from peripheral sites of leptin synthesis such as the gastric fundus to the brain.