Natural Product Chemistry and Biological Research

Natural products are substances found in nature that have not been significantly modified by humans [...].

Lipid lowering and anti-ageing effects of edible flowers of Viola x wittrockiana Gams in a Caenorhabditis elegans obese model

Life expectancy has increased considerably in the last decades, clearing the way for preventive medicine. The ingestion of healthy foods or ingredients to improve health is gaining attention and edible flowers entail a promising source of bioactive compounds. The aim of this work was to study the anti-ageing and anti-obesity properties of an extract obtained from an edible flower Viola x wittrockiana though in vitro and in vivo methodologies with Caenorhabditis elegans as a model. The capacity to inhibit the enzymes α-glucosidase and lipase as well as to prevent advance glycation end-product (AGE) formation was tested in vitro. Caenorhabditis elegans was used as an obesity in vivo model to assess the effects of the extract on fat accumulation, development, progeny and health span. Viola flowers showed lower IC50 values in the α-glucosidase assay than the reference drug acarbose and exerted a higher inhibition of AGE formation than the reference substance aminoguanidine; the extract also showed pancreatic lipase inhibiting properties. Moreover, the extract lowered fat storage of C. elegans in a dose-dependent manner, up to 90.37% at the highest tested dose, and improved health span biomarkers such as lipofuscin accumulation and progeny availability. Our results demonstrate, for the first time, the anti-obesogenic and anti-ageing activity of Viola x wittrockiana flowers and their potential use as functional foods and nutraceuticals.

Radiographic and histopathological study of gastrointestinal dysmotility in lipopolysaccharide-induced sepsis in the rat

BACKGROUND

Sepsis is a highly incident condition in which a cascade of proinflammatory cytokines is involved. One of its most frequent consequences is ileus, which can increase mortality. Animal models such as that induced by systemic administration of lipopolysaccharide (LPS) are useful to deeply evaluate this condition. The effects of sepsis on the gastrointestinal (GI) tract have been explored but, to our knowledge, in vivo studies showing the motor and histopathological consequences of endotoxemia in an integrated way are lacking. Our aim was to study in rats the effects of sepsis on GI motility, using radiographic methods, and to assess histological damage in several organs.

METHODS

Male rats were intraperitoneally injected with saline or E. coli LPS at 0.1, 1, or 5 mg kg-1 . Barium sulfate was intragastrically administered, and X-rays were performed 0-24 h afterwards. Several organs were collected for organography, histopathology, and immunohistochemistry studies.

KEY RESULTS

All LPS doses caused gastroparesia, whereas changes in intestinal motility were dose-and time-dependent, with an initial phase of hypermotility followed by paralytic ileus. Lung, liver, stomach, ileum, and colon (but not spleen or kidneys) were damaged, and density of neutrophils and activated M2 macrophages and expression of cyclooxygenase 2 were increased in the colon 24 h after LPS 5 mg kg-1 .

CONCLUSIONS AND INFERENCES

Using radiographic, noninvasive methods for the first time, we show that systemic LPS causes dose-, time-, and organ-dependent GI motor effects. Sepsis-induced GI dysmotility is a complex condition whose management needs to take its time-dependent changes into account.

Antidiabetic and anti-obesity properties of a polyphenol-rich flower extract from Tagetes erecta L. and its effects on Caenorhabditis elegans fat storages

Diabetes mellitus (DM) is a metabolic disease characterized by a high blood sugar level that can cause severe complications to the organism or even death when not treated. However, certain dietary habits and foods may have beneficial effects on this condition. A polyphenolic-rich extract (containing hyperoside, isoquercitrin, quercetin, ellagic acid, and vanillic acid) of Tageres erecta L. (T. erecta) was obtained from yellow and orange flowers using an ethanolic Soxhlet extraction. These extracts were screened for antidiabetic and anti-obesity properties using in vitro and in vivo procedures. The capacity to inhibit the enzymes lipase and α-glucosidase, as well as the inhibition of advance glycation end-products (AGEs) was tested in vitro. Caenorhabditis elegans (C. elegans) was used as an obesity in vivo model to assess extracts effects on fat accumulation using the wild-type strain N2 and a mutant with no N3 fatty acid desaturase activity BX24. Extracts from both cultivars (yellow and orange) T. erecta presented in vitro inhibitory activity against the enzymes lipase and α-glucosidase, showing lower IC₅₀ values than acarbose (control). They also showed important activity in preventing AGEs formation. The polyphenol-rich matrices reduced the fat content of obese worms in the wild-type strain (N2) down to levels of untreated C. elegans, with no significant differences found between negative control (100% reduction) and both tested samples (p < 0.05). Meanwhile, the fat reduction was considerably lower in the BX24 mutants (fat-1(wa-9)), suggesting that N3 fatty acid desaturase activity could be partially involved in the T. erecta flower effect. Our findings suggested that polyphenols from T. erecta can be considered candidate bioactive compounds in the prevention and improvement of metabolic chronic diseases such as obesity and diabetes.

Flowers of Allium cepa L. as Nutraceuticals: Phenolic Composition and Anti-Obesity and Antioxidant Effects in Caenorhabditis elegans

Allium cepa L., commonly known as onion, is one of the most-consumed vegetables. The benefits of the intake of its bulb are well studied and are related to its high polyphenol content. The flowers of onions are also edible; however, there are no studies about their biological properties. Our aim was to determine the polyphenolic profile and assess the antioxidant and anti-obesity capacity of an ethanolic extract from fresh flowers of A. cepa. The phenolic constituents were identified through LC-DAD-ESI/MSn. For the anti-obesity potential, the inhibitory activity against digestive enzymes was measured. Several in vitro assays were carried out to determine the antioxidant capacity. A Caenorhabditis elegans model was used to evaluate the effect of the extract on stress resistance and fat accumulation. For the first time, kaempferol and isorhamnetin glucosides were identified in the flowers. The extract reduced fat accumulation in the nematode and had a high lipase and α- glucosidase inhibitory activity. Regarding the antioxidant activity, the extract increased the survival rate of C. elegans exposed to lethal oxidative stress. Moreover, the activities of superoxide dismutase and catalase were enhanced by the extract. Our results demonstrate, for the first time, the antioxidant and anti-obesity activity of onion flowers and their potential use as functional foods and nutraceuticals.

The Potential Role of Everlasting Flower (Helichrysum stoechas Moench) as an Antihypertensive Agent: Vasorelaxant Effects in the Rat Aorta

Helichrysum stoechas (L.) Moench (H. stoechas) is a medicinal plant traditionally used in the Iberian Peninsula to treat different disorders such as arterial hypertension. The aim of this study was to investigate the vascular effects of a polyphenolic methanolic extract of H. stoechas, which has high antioxidant activity, and its mechanism of action. Isometric myography studies were performed in an organ bath with rat aortic rings with intact endothelium. The H. stoechas extract produced vasorelaxation in the aortic rings that were precontracted by phenylephrine or KCl. L-NAME and Rp-8-Br-PET-cGMPS but not indomethacin or H-89; it also reduced the relaxant response evoked by H. stoechas extract on the phenylephrine-induced contractions. H. stoechas extract reduced the response to CaCl2 similar to verapamil and reduced the phenylephrine-induced contractions comparable with heparin. TRAM-34, apamin and glibenclamide reduced relaxation induced by the H. stoechas extract. The combination of L-NAME+TRAM-34+apamin almost completely inhibited the H. stoechas-induced effect. In conclusion, the relaxant effect of the H. stoechas extract is partially mediated by endothelium through the activation of the NO/PKG/cGMP pathway and the opening of Ca2+-activated K+ channels. Furthermore, the decrease in the cytosolic Ca2+ by the inhibition of Ca2+ influx through the L-type Ca2+ channels and by the reduction of Ca2+ release from the sarcoplasmic reticulum via the IP3 pathway is also involved.

Rock tea (Jasonia glutinosa (L.) DC.) polyphenolic extract inhibits triglyceride accumulation in 3T3-L1 adipocyte-like cells and obesity related enzymes in vitro

Jasonia glutinosa (L.) DC., also known in Spain as "té de roca" (rock tea, RT), is an endemic plant species of the Iberian Peninsula and Southern France. Traditionally, it is used in infusions, prepared with the flowering aerial parts, as a digestive and anti-inflammatory herbal tea. Despite the traditional knowledge of this plant as a digestive after meals, there are hardly any scientific studies that support its use. The aim of this study is to assess the effects of RT extract on physiological targets related to metabolic diseases such as obesity. For this purpose, enzyme inhibition bioassays of lipase, α-glucosidase and fatty acid amide hydrolase were carried out in cell-free systems. Similarly, adipocytes derived from 3T3-L1 cells were employed to study the effects of the extract on adipocyte differentiation and triglyceride (TG) accumulation. RT extract was able to inhibit lipase, α-glucosidase and fatty acid amide hydrolase. Furthermore, the extract displayed anti-adipogenic properties in a dose-dependent manner as it significantly reduced TG accumulation during adipocyte differentiation. These results may explain from a molecular perspective the beneficial effects of RT in the prevention of metabolic-associated disorders such as obesity, diabetes and related complications.

Conditional KCa3.1-transgene induction in murine skin produces pruritic eczematous dermatitis with severe epidermal hyperplasia and hyperkeratosis

Ion channels have recently attracted attention as potential mediators of skin disease. Here, we explored the consequences of genetically encoded induction of the cell volume-regulating Ca2+-activated KCa3.1 channel (Kcnn4) for murine epidermal homeostasis. Doxycycline-treated mice harboring the KCa3.1+-transgene under the control of the reverse tetracycline-sensitive transactivator (rtTA) showed 800-fold channel overexpression above basal levels in the skin and solid KCa3.1-currents in keratinocytes. This overexpression resulted in epidermal spongiosis, progressive epidermal hyperplasia and hyperkeratosis, itch and ulcers. The condition was accompanied by production of the pro-proliferative and pro-inflammatory cytokines, IL-β1 (60-fold), IL-6 (33-fold), and TNFα (26-fold) in the skin. Treatment of mice with the KCa3.1-selective blocker, Senicapoc, significantly suppressed spongiosis and hyperplasia, as well as induction of IL-β1 (-88%) and IL-6 (-90%). In conclusion, KCa3.1-induction in the epidermis caused expression of pro-proliferative cytokines leading to spongiosis, hyperplasia and hyperkeratosis. This skin condition resembles pathological features of eczematous dermatitis and identifies KCa3.1 as a regulator of epidermal homeostasis and spongiosis, and as a potential therapeutic target.

Antioxidant and Antiaging Effects of Licorice on the Caenorhabditis elegans Model

The causative relationship between oxidative stress and aging remains controversial, but it is a fact that many of the pathologies of age-related diseases are associated with oxidative stress. Phytochemicals may reduce damage from oxidative stress; the intake of these through diet could represent a strategy to lessen their pathological consequences. The popular and widely consumed licorice (Glycyrrhiza glabra) is a rich source of potential antioxidants. The aim of this study was to investigate whether licorice increases the oxidative stress resistance and lifespan of the animal model Caenorhabditis elegans. Licorice roots ethanolic extract showed in vitro antioxidant activity, with an IC₅₀ of 51.17 μg/mL using 2,2-diphenyl-1-picrylhydrazyl (DPPH) as free radical. C. elegans pretreated with licorice showed an increase of survival rate when exposed to the oxidant juglone, being this increase up to ∼33.56%. This pretreated population also showed an increase in lifespan of 14.28% at a concentration of 250 μg/mL. In conclusion, we suggest that licorice has a high antioxidant capability both in vitro and in vivo and that this activity may explain the observed extension of lifespan.

Jasonia glutinosa (L.) DC., a traditional herbal medicine, reduces inflammation, oxidative stress and protects the intestinal barrier in a murine model of colitis

Jasonia glutinosa (L.) DC., known as rock tea (RT), is traditionally used in Spain as a digestive due to its beneficial properties in bowel disorders. The pharmacological nature of these properties has not been established yet. The aim of this work was to evaluate the therapeutic utility of RT in experimental colitis and to identify chemical constituents with anti-inflammatory and/or anti-oxidative properties. RT extract was prepared with ethanol in a Soxhlet apparatus and analysed by HPLC-DAD. Superoxide radical scavenging properties, xanthine oxidase and lipoxygenase (5-LOX) inhibitory activity, and capability to lower nitric oxide (NO) and tumor necrosis factor α (TNF-α) levels were measured in cell-free and cell-based assays. In the 2.5%-dextran-sodium sulphate (DSS) injury-repair model of ulcerative colitis (UC), mice were daily treated with sulfasalazine (SSZ, as reference drug, 100 mg/kg bw), RT (5, 25 and 50 mg/kg bw, p.o.), or vehicle over 20 days. Colitis was scored daily. Colon samples were examined macroscopically and histopathologically. Protein levels of myeloperoxidase (MPO), interleukins 6, and 10 (IL-6, IL-10), inducible NO synthase (iNOS), and cyclooxygenase-2 (COX-2) were studied as markers of oxidative stress and inflammatory activity. The integrity of the apical epithelial layer was assessed by immunofluorescence staining of zonula ocludens-1 (ZO-1). Finally, intestinal contractility was also evaluated by isometric myography. Fifteen phenolic compounds and three pigments were identified and quantified, of which caffeoylquinic acids, and the flavonoid, quercetin-3-O-galactoside, were the most abundant. RT extract significantly scavenged superoxide radicals, inhibited 5-LOX activity, and lowered NO and TNF-α levels. DSS-treated mice receiving RT scored clinically lower than controls during the first 3 days of DSS treatment and during the recovery period. SSZ was less effective than RT. Anatomical and histological examination of colon samples revealed that RT significantly prevented colon shortening, increased colon thickness, and lowered the macroscopic damage score. RT also significantly prevented the increase of MPO activity, IL-6 levels, iNOS and COX-2 expression, the loss of ZO-1 apical expression, and normalized contractility disturbances. In conclusion, daily administration of RT showed therapeutic properties in the DSS-model of UC. The benefits of RT can likely be attributed to its anti-inflammatory and antioxidant phenolic and flavonoid constituents.

KCa3.1 Transgene Induction in Murine Intestinal Epithelium Causes Duodenal Chyme Accumulation and Impairs Duodenal Contractility

The epithelial intermediate-conductance calcium/calmodulin-regulated KCa3.1 channel is considered to be a regulator of intestine function by controlling chloride secretion and water/salt balance. Yet, little is known about the functional importance of KCa3.1 in the intestinal epithelium in vivo. Our objective was to determine the impact of epithelial-specific inducible overexpression of a KCa3.1 transgene (KCa3.1+) and of inducible suppression (KCa3.1−) on intestinal homeostasis and function in mice. KCa3.1 overexpression in the duodenal epithelium of doxycycline (DOX)-treated KCa3.1+ mice was 40-fold above the control levels. Overexpression caused an inflated duodenum and doubling of the chyme content. Histology showed conserved architecture of crypts, villi, and smooth muscle. Unaltered proliferating cell nuclear antigen (PCNA) immune reactivity and reduced amounts of terminal deoxynucleotide transferase mediated X-dUTP nick end labeling (TUNEL)-positive apoptotic cells in villi indicated lower epithelial turnover. Myography showed a reduction in the frequency of spontaneous propulsive muscle contractions with no change in amplitude. The amount of stool in the colon was increased and the frequency of colonic contractions was reduced in KCa3.1+ animals. Senicapoc treatment prevented the phenotype. Suppression of KCa3.1 in DOX-treated KCa3.1− mice caused no overt intestinal phenotype. In conclusion, inducible KCa3.1 overexpression alters intestinal functions by increasing the chyme content and reducing spontaneous contractions and epithelial apoptosis. Induction of epithelial KCa3.1 can play a mechanistic role in the process of adaptation of the intestine.

Pomegranate polyphenols and urolithin A inhibit α-glucosidase, dipeptidyl peptidase-4, lipase, triglyceride accumulation and adipogenesis related genes in 3T3-L1 adipocyte-like cells

ETHNOPHARMACOLOGICAL RELEVANCE

Pomegranate fruit is considered an antidiabetic medicine in certain systems of traditional medicine. In addition, pomegranate polyphenols are known as powerful antioxidants with beneficial effects such as the reduction of oxidative / inflammatory stress and the increase of protective signalling such as antioxidant enzymes, neurotrophic factors and cytoprotective proteins.

AIM OF THE STUDY

This work evaluates the effects of pomegranate juice, its main polyphenols known as ellagic acid and punicalagin, as well as its main metabolite urolithin A, on physiological and pharmacological targets of metabolic diseases such as obesity and diabetes.

MATERIALS AND METHODS

For this purpose, enzyme inhibition bioassays of lipase, α-glucosidase and dipeptidyl peptidase-4 were carried out in cell-free systems. Similarly, adipocytes derived from 3T3-L1 cells were employed to study the effects of ellagic acid, punicalagin and urolithin A on adipocyte differentiation and triglyceride (TG) accumulation.

RESULTS

Pomegranate juice, ellagic acid, punicalagin and urolithin A were able to inhibit lipase, α-glucosidase and dipeptidyl peptidase-4. Furthermore, all tested compounds but significantly the metabolite urolithin A displayed anti-adipogenic properties in a dose-dependent manner as they significantly reduced TG accumulation and gene expression related to adipocyte formation such as adiponectin, PPARγ, GLUT4, and FABP4 in 3T3-L1 adipocytes.

CONCLUSION

These results may explain from a molecular perspective the beneficial effects and traditional use of pomegranate in the prevention of metabolic-associated disorders such as obesity, diabetes and related complications.

Different mechanisms of actions of genistein, quercetin on spontaneous contractions of rabbit duodenum

Flavonoids are known to relax precontracted intestinal smooth muscle and delay intestinal transit or intestinal peristalsis. The aim of this study was to determine the effects of genistein and quercetin on spontaneous contractions of rabbit duodenum in vitro in an organ bath. Genistein and quercetin (0.1-10µM) reduced the amplitude of spontaneous contractions in the longitudinal and circular smooth muscle of rabbit duodenum, but they did not modify the frequency. Bay K8644 (L-type Ca2+ channel activator), apamin, charybdotoxin, and tetraetylammonium (K+ channel blockers) reverted the inhibition of amplitude of spontaneous contractions induced by genistein in longitudinal and circular smooth muscle. H-89 (protein kinase A inhibitor) antagonized the reduction of the amplitude of spontaneous contractions induced by quercetin in longitudinal and circular smooth muscle of duodenum, while 2,5-dideoxiadenosine (adenylyl cyclase inhibitor) reverted only the reduction of the amplitude in circular smooth muscle. In conclusion, genistein and quercetin reduce the spontaneous contractions in the duodenum by different mechanisms of actions. The effect of genistein would be mediated by Ca2+ and K+ channels, while the effect of quercetin would be mediated by cAMP and protein kinase A.

Vascular Reactivity Profile of Novel KCa 3.1-Selective Positive-Gating Modulators in the Coronary Vascular Bed

Opening of intermediate-conductance calcium-activated potassium channels (KC a 3.1) produces membrane hyperpolarization in the vascular endothelium. Here, we studied the ability of two new KC a 3.1-selective positive-gating modulators, SKA-111 and SKA-121, to (1) evoke porcine endothelial cell KC a 3.1 membrane hyperpolarization, (2) induce endothelium-dependent and, particularly, endothelium-derived hyperpolarization (EDH)-type relaxation in porcine coronary arteries (PCA) and (3) influence coronary artery tone in isolated rat hearts. In whole-cell patch-clamp experiments on endothelial cells of PCA (PCAEC), KC a currents evoked by bradykinin (BK) were potentiated ≈7-fold by either SKA-111 or SKA-121 (both at 1 μM) and were blocked by a KC a 3.1 blocker, TRAM-34. In membrane potential measurements, SKA-111 and SKA-121 augmented bradykinin-induced hyperpolarization. Isometric tension measurements in large- and small-calibre PCA showed that SKA-111 and SKA-121 potentiated endothelium-dependent relaxation with intact NO synthesis and EDH-type relaxation to BK by ≈2-fold. Potentiation of the BK response was prevented by KC a 3.1 inhibition. In Langendorff-perfused rat hearts, SKA-111 potentiated coronary vasodilation elicited by BK. In conclusion, our data show that positive-gating modulation of KC a 3.1 channels improves BK-induced membrane hyperpolarization and endothelium-dependent relaxation in small and large PCA as well as in the coronary circulation of rats. Positive-gating modulators of KC a 3.1 could be therapeutically useful to improve coronary blood flow and counteract impaired coronary endothelial dysfunction in cardiovascular disease.

Roles of Toll-Like Receptor 4, IκB Kinase, and the Proteasome in the Intestinal Alterations Caused by Sepsis

BACKGROUND

Lipopolysaccharide decreases intestinal contractility and induces the production of cytokines, which play an important role in the pathogenesis of sepsis.

AIM

The objective of the present study was to examine the role of Toll-like receptor 4, IκB kinase, and the proteasome in the intestinal alterations induced by lipopolysaccharide.

METHODS

Sepsis was induced in rabbits by intravenous injection of lipopolysaccharide. Contractility studies of rabbit duodenum were performed in an organ bath. Expressions of interleukin-1β, interleukin-6, interleukin-8, interleukin-10, IκB kinase-α, IκB kinase-β, IκB kinase-γ, and the proteasome mRNA were determined by RT-PCR on rabbit duodenum.

RESULTS

Neomycin and polymyxin B (Toll-like receptor 4 inhibitors), IKK NBD peptide (IκB kinase complex inhibitor), and MG-132 (proteasome inhibitor) blocked partially the effects of lipopolysaccharide on the acetylcholine-, prostaglandin E2-, substance P-, and KCl-induced contractions in the longitudinal and circular smooth muscle of rabbit duodenum. Lipopolysaccharide increased the mRNA expression of interleukin-6 and interleukin-8 in duodenal tissue, and this effect was partly reversed by neomycin, polymyxin B, IKK NBD peptide, and MG-132. IκB kinase-α, IκB kinase-β, IκB kinase-γ, and the proteasome mRNA expressions was not affected by lipopolysaccharide treatment.

CONCLUSIONS

Toll-like receptor 4, the IκB kinase complex, and the proteasome could be therapeutic targets in the treatment of sepsis symptoms in the intestine.

Bioactive properties of commercialised pomegranate (Punica granatum) juice: antioxidant, antiproliferative and enzyme inhibiting activities

Pomegranate juice exerts antioxidant and protective effects, antiproliferative activity in cancer cells and inhibits COX-2 and MAO-A.

A novel pan-negative-gating modulator of KCa2/3 channels, fluoro-di-benzoate, RA-2, inhibits endothelium-derived hyperpolarization-type relaxation in coronary artery and produces bradycardia in vivo

Small/intermediate conductance KCa channels (KCa2/3) are Ca(2+)/calmodulin regulated K(+) channels that produce membrane hyperpolarization and shape neurologic, epithelial, cardiovascular, and immunologic functions. Moreover, they emerged as therapeutic targets to treat cardiovascular disease, chronic inflammation, and some cancers. Here, we aimed to generate a new pharmacophore for negative-gating modulation of KCa2/3 channels. We synthesized a series of mono- and dibenzoates and identified three dibenzoates [1,3-phenylenebis(methylene) bis(3-fluoro-4-hydroxybenzoate) (RA-2), 1,2-phenylenebis(methylene) bis(3-fluoro-4-hydroxybenzoate), and 1,4-phenylenebis(methylene) bis(3-fluoro-4-hydroxybenzoate)] with inhibitory efficacy as determined by patch clamp. Among them, RA-2 was the most drug-like and inhibited human KCa3.1 with an IC50 of 17 nM and all three human KCa2 subtypes with similar potencies. RA-2 at 100 nM right-shifted the KCa3.1 concentration-response curve for Ca(2+) activation. The positive-gating modulator naphtho[1,2-d]thiazol-2-ylamine (SKA-31) reversed channel inhibition at nanomolar RA-2 concentrations. RA-2 had no considerable blocking effects on distantly related large-conductance KCa1.1, Kv1.2/1.3, Kv7.4, hERG, or inwardly rectifying K(+) channels. In isometric myography on porcine coronary arteries, RA-2 inhibited bradykinin-induced endothelium-derived hyperpolarization (EDH)-type relaxation in U46619-precontracted rings. Blood pressure telemetry in mice showed that intraperitoneal application of RA-2 (≤100 mg/kg) did not increase blood pressure or cause gross behavioral deficits. However, RA-2 decreased heart rate by ≈145 beats per minute, which was not seen in KCa3.1(-/-) mice. In conclusion, we identified the KCa2/3-negative-gating modulator, RA-2, as a new pharmacophore with nanomolar potency. RA-2 may be of use to generate structurally new types of negative-gating modulators that could help to define the physiologic and pathomechanistic roles of KCa2/3 in the vasculature, central nervous system, and during inflammation in vivo.

In vitro effect of calcium dobesilate on oxidative/inflammatory stress in human varicose veins

AIM

To determine whether calcium dobesilate can act in chronic venous insufficiency by similar antioxidant, anti-inflammatory mechanisms as in diabetic retinopathy.

METHODS

Calcium dobesilate was tested in vitro for its protective action against oxidative/inflammatory stress in human varicose veins. Varicose greater saphenous veins were obtained from 14 patients (11 men, 3 women) aged 53-65 years. Oxidative stress was induced exogenously in the vein segments, with the phenazine methosulphate (PMS)/NADH couple. Total antioxidant status (TAS) and malondialdehyde (MDA) contents were used as markers of oxidative stress.

RESULTS

Calcium dobesilate significantly prevented oxidative disturbances in the micromolar range. PMS/NADH-dependent TAS decrease was fully prevented with IC(50) = 11.4 ± 2.3 µmol/L (n = 6 veins), whereas MDA increase was fully prevented with IC(50) = (102 ± -3) µmol/L (n = 6 veins). Calcium dobesilate acted quali- and quantitatively like rutin, the reference compound. Comparison with pharmacokinetic data suggests that calcium dobesilate can act at therapeutic concentrations.

CONCLUSION

Calcium dobesilate protected human varicose veins against oxidative stress in vitro at levels that correspond to therapeutic concentrations. Further studies are required to investigate whether a similar action is found in varicose veins from patients orally treated with calcium dobesilate.

Contractile effect of tachykinins on rabbit small intestine

AIM

To study the role of the tachykinin receptors in spontaneous contractions of longitudinal and circular smooth muscle from rabbit small intestine and to determine the mechanism of action of Substance P (SP).

METHODS

Rabbit duodenum, jejunum and ileum segments were prepared. The spontaneous contractions of longitudinal and circular smooth muscle were recorded using a computer via an isometric force transducer. The specific agonists and antagonists of tachykinin receptors were added into the organ bath.

RESULTS

The agonists of tachykinin NK1 receptor (SP and [Sar9] SP), NK2 receptor (NKA and (β-Ala8)-NKA), and NK3 receptor (NKB and Senktide) all induced contractions in the small intestine. The contractions were diminished by NK1 receptor antagonist L-733,060, NK2 receptor antagonist GR-94800, and NK3 receptor antagonist SB 218795. Contractions caused by SP were also reduced by atropine, verapamil, PKC inhibitor staurosporine, and PLC inhibitor U73122.

CONCLUSION

Ttachykinin NK1, NK2, and NK3 receptors mediate the contractions of the smooth muscle in rabbit intestine. Furthermore, SP acts directly on smooth muscle cells through the tachykinin NK1 receptor.