Nicola Mascolo

FLAVONOIDS : OLD AND NEW ASPECTS OF A CLASS OF NATURAL THERAPEUTIC DRUGS

Flavonoids are natural products widely distributed in the vegetable kingdom and currently consumed in large amounts in the daily diet. Flavonoids are capable of modulating the activity of enzymes and affect the behaviour of many cell systems, suggesting that the compounds may possess significant antihepatotoxic, antiallergic, anti-inflammatory, antiosteoporotic and even antitumor activities. This review summarizes available data on these beneficial effects of flavonoids.

Cannabinoid CB1‐receptor mediated regulation of gastrointestinal motility in mice in a model of intestinal inflammation

We have studied the effect of cannabinoid agonists (CP 55,940 and cannabinol) on intestinal motility in a model of intestinal inflammation (induced by oral croton oil in mice) and measured cannabinoid receptor expression, endocannabinoids (anandamide and 2‐arachidonylglycerol) and anandamide amidohydrolase activity both in physiological and pathophysiological states. CP 55,940 (0.03 – 10 nmol mouse−1) and cannabinol (10 – 3000 nmol mouse−1) were more active in delaying intestinal motility in croton oil‐treated mice than in control mice. These inhibitory effects were counteracted by the selective cannabinoid CB1 receptor antagonist SR141716A (16 nmol mouse−1). SR141716A (1 – 300 nmol mouse−1), administered alone, increased intestinal motility to the same extent in both control and croton oil‐treated mice Croton oil‐induced intestinal inflammation was associated with an increased expression of CB1 receptor, an unprecedented example of up‐regulation of cannabinoid receptors during inflammation. High levels of anandamide and 2‐arachidonylglycerol were detected in the small intestine, although no differences were observed between control and croton oil‐treated mice; by contrast anandamide amidohydrolase activity increased 2 fold in the inflamed small intestine. It is concluded that inflammation of the gut increases the potency of cannabinoid agonists possibly by ‘up‐regulating’ CB1 receptor expression; in addition, endocannabinoids, whose turnover is increased in inflamed gut, might tonically inhibit intestinal motility.

Ethnopharmacologic investigation of ginger (Zingiber officinale)

An ethanolic extract of the rhizomes of Zingiber officinale was investigated for anti-inflammatory, analgesic, antipyretic, antimicrobial and hypoglycaemic activities. In rats, the extract reduced carrageenan-induced paw swelling and yeast-induced fever but was ineffective in suppressing the writhing induced by intraperitoneal acetic acid. The extract produced blood glucose lowering in rabbits. The growth of both Gram-positive and Gram-negative bacteria was significantly inhibited. A dose-dependent inhibition of prostaglandin release effect was observed using rat peritoneal leucocytes.

Inhibition of intestinal motility and secretion by flavonoids in mice and rats: Structure-activity relationships

Abstract— Intraperitoneal administration of some flavonoids (apigenin, flavone, kaempferol, morin, myricetin, naringin and rutin; 12·5–50 mg kg−1) significantly (P < 0·05–0·01) reduced small (28–69%) and large (83–134%) intestinal transit in mice. Other flavonoids (naringenin, silibinin, silymarin and taxifolin, 100–200 mg kg−1) reduced (23–41%; P < 0·5–0·01) intestinal transit at doses of 100–200 mg kg−1 while hesperitin, catechin and phloridzin (up to 200 mg kg−1) had no effect. This effect was antagonized by yohimbine (87–96%) and phentolamine (87–91%) but not by prazosin, propranolol, atropine, hexamethonium, mepyramine, cyproheptadine and naloxone. Yohimbine (92–96%) also antagonized the inhibitory effect of flavonols (12·5–50 mg kg−1) (P < 0·05–0·01) on intraluminal accumulation of fluid and diarrhoea induced by castor oil. By contrast, verapamil potentiated the flavonol effect. It is suggested that these effects, influenced by the structure of the molecules, are mediated by α2‐adrenergic receptors and calcium.

Nitric Oxide as a Modulator of Intestinal Water and Electrolyte Transport

The role of nitric oxide in intestinal fluid andelectrolyte secretion depends upon whether theconditions under study are physiological orpathophysiological. In physiological conditions,endogenous nitric oxide seems to be a proabsorptive molecule,based on the findings that nitric oxide synthaseinhibitors reverse net fluid absorption to net secretionin mice, rats, guinea pigs, rabbits, and dogs. This proabsorptive mode involves the enteric nervoussystem, the suppression of prostaglandin formation, andthe opening of basolateral K+ channels.However, in some pathophysiological states nitric oxidesynthase may be produced at higher concentrations thatare capable of evoking net secretion. Thus nitric oxidesynthase contributes to the diarrheal response intrinitrobenzene sulfonic acid-induced ileitis in guinea pigs and is the mediator of the laxative actionof several intestinal secretagogues including castoroil, phenolphthalein, bisacodyl, magnesium sulfate, bilesalts, senna, and cascara in the rat. Corresponding with the in vivo results, nitric oxide-donatingcompounds or nitric oxide itself stimulate chloridesecretion in the guinea pig and rat intestine in vitro.Exceptions are the diarrhea produced by bacterial enterotoxins in the rat, in which nitric oxideseems to have a proabsorptive role, and the mouse ileumin vitro, in which nitric oxide-donating compoundsproduce a net proabsorptive effect on basal ion transport. Several endogenous secretagogues(substance P, 5-hydroxytryptamine, interleukin-1beta),which are important mediators of the inflammatory boweldiseases, act, at least in part, through the liberation of nitric oxide. Clinical studies have shownthat nitric oxide is elevated in several inflammatorybowel diseases and other secretory conditions includingulcerative colitis, Crohns disease, toxic megacolon, diverticulitis, infectious gastroenteritis, andinfantile methemoglobinemia. However, the determinationof nitric oxide in secretory diarrhea per se does notgive conclusive information on the nitric oxide contribution to clinical secretorydiarrhea.

An endogenous cannabinoid tone attenuates cholera toxin-induced fluid accumulation in mice.

BACKGROUND & AIMS Cholera toxin (CT) is the most recognizable enterotoxin causing secretory diarrhea, a major cause of infant morbidity and mortality throughout the world. In this study, we investigated the role of the endogenous cannabinoid system (i.e., the cannabinoid receptors and their endogenous ligands) in CT-induced fluid accumulation in the mouse small intestine. METHODS Fluid accumulation was evaluated by enteropooling; endocannabinoid levels were measured by isotope-dilution gas chromatography mass spectrometry; CB(1) receptors were localized by immunohistochemistry and their messenger RNA (mRNA) levels were quantified by reverse-transcription polymerase chain reaction (PCR). RESULTS Oral administration of CT to mice resulted in an increase in fluid accumulation in the small intestine and in increased levels of the endogenous cannabinoid, anandamide, and increased expression of the cannabinoid CB(1) receptor mRNA. The cannabinoid receptor agonist CP55,940 and the selective cannabinoid CB(1) receptor agonist arachidonoyl-chloro-ethanolamide inhibited CT-induced fluid accumulation, and this effect was counteracted by the CB(1) receptor antagonist SR141716A, but not by the CB(2) receptor antagonist SR144528. SR141716A, per se, but not the vanilloid VR1 receptor antagonist capsazepine, enhanced fluid accumulation induced by CT, whereas the selective inhibitor of anandamide cellular uptake, VDM11, prevented CT-induced fluid accumulation. CONCLUSIONS These results indicate that CT, along with enhanced intestinal secretion, causes overstimulation of endocannabinoid signaling with an antisecretory role in the small intestine.

Phytotherapy and quality of herbal medicines.

The extensive use of plants as medicines has pointed out that herbal medicines are not as safe as frequently claimed. Therefore, it can be harmful to take herbal medicines without being aware of their potential adverse effects. A comprehensive surveillance system for monitoring the adverse effects of herbal medicines is now essential. Also knowledge of the correlation existing between the marker compounds and other ingredients that occur in plants is a necessary requirement for ensuring the efficacy and quality of the herbal medicines.

Excitatory transmission to the circular muscle of the guinea‐pig ileum: evidence for the involvement of cannabinoid CB1 receptors

1 The effect of cannabinoid drugs has been investigated on cholinergic and non‐adrenergic non‐cholinergic (NANC) contractile responses to the circular smooth muscle of guinea‐pig ileum elicited by electrical field stimulation (EFS). 2 The cannabinoid receptor agonist WIN 55,212‐2 (1–1000 nm) and the putative endogenous ligand anandamide (0.1–100 μm) both produced a concentration‐dependent inhibition of the cholinergic (9–57% and 1–51% inhibition) and NANC (9–55% and 2–57% inhibition) contractile responses. WIN 55,212‐2 and anandamide did not modify the contractions produced by exogenous acetylcholine or substance P. 3 Apamin (30 nm), a blocker of Ca2+‐activated K+ channels, reduced the inhibitory effect of WIN 55,212‐2 on cholinergic, but not NANC, contractile response. NG‐nitro‐l‐arginine methyl ester (100 μm), an inhibitor of nitric oxide synthase, or naloxone (1 μm), an opioid receptors antagonist, did not modify the inhibitory effect of WIN 55,212‐2 on both cholinergic and NANC contractions. 4 The inhibitory effects of WIN 55,212‐2 and anandamide on both cholinergic and NANC contractile response was competitively antagonized by the cannabinoid CB1 receptor antagonist SR 141716A (10–1000 nm). 5 In absence of other drugs, SR 141716A (1–1000 nm) enhanced cholinergic (1–45% increase) and NANC (2–38% increase) contractile responses elicited by electrical stimulation, but did not modify the contractions produced by acetylcholine or substance P. 6 It is concluded that activation of prejunctional cannabinoid CB1 receptors produces inhibition of cholinergic and NANC excitatory responses in the guinea‐pig circular muscle. The inhibition of cholinergic (but not NANC) transmission involves activation of apamin‐sensitive K+ channels. In addition, an endogenous cannabinoid ligand could inhibit cholinergic and NANC transmission in the guinea‐pig ileal circular muscle.

Dissociation of castor oil-induced diarrhoea and intestinal mucosal injury in rat : effect of NG-nitro-L-arginine methyl ester

1 Castor oil (2 ml orally) produced diarrhoea in rats 1–7 h after challenge, which was associated with gross damage to the duodenal and jejunal mucosa. 2 The injury was accompanied by release of acid phosphatase into the gut lumen, indicating cellular injury. 3 Intraperitoneal injection of the nitric oxide (NO) synthase inhibitor NG ‐nitro‐L‐arginine methyl ester (1‐NAME, 2.5–50 mg kg−1 twice), prevented the diarrhoea. The dose of 1‐NAME (50mg kg−1) completely blocked the diarrhoea but increased the release of acid phosphatase and worsened the gross damage. 4 The NO donating compound, isosorbide‐5‐mononitrate (IMN, 150 mg kg−1 twice) reversed the effects of 1‐NAME (50 mg kg1) on castor oil‐induced diarrhoea, gross damage and acid phosphatase release. 5 The apparent dissociation of the diarrhoeal and intestinal mucosal damaging effects of castor oil suggest that NO has a protective effect on the rat duodenal and jejunal mucosa, but that NO mediates, in part, the diarrhoea effect of this laxative.

The role of cannabinoid receptors in intestinal motility, defaecation and diarrhoea in rats

We have studied the effects of the cannabinoid receptor agonists (R)-(+)[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2, 3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (WIN 55,212-2, 0. 3-5 mg/kg, i.p.) and (-)-cis-3-[2-hydroxy-4-(1, 1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol) (CP 55,940, 0.03-1 mg/kg, i.p.), the cannabinoid CB(1) receptor antagonist (N-piperidin-1-yl)-5-(4-chlorophenyl)-1-2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716A, 0. 3-5 mg/kg, i.p.) and the cannabinoid CB(2) receptor antagonist N-[-(1S)-endo-1,3,3-trimethyl bicyclo [2.2.1] heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazo le- 3-carboxamide (SR144528, 1 mg/kg, i.p.) on intestinal motility, defaecation and castor-oil (1 ml/100 g rat, orally)-induced diarrhoea in the rat. SR141716A, but not SR144528, increased defaecation and upper gastrointestinal transit, while WIN 55,212-2 and CP 55,940 decreased upper gastrointestinal transit but not defaecation. WIN 55,212-3 (5 mg/kg), the less active enantiomer of WIN 55,212-2, was without effect. A per se non-effective dose of SR141716A (0.3 mg/kg), but not of SR144528 (1 mg/kg) or the opioid receptor antagonist, naloxone (2 mg/kg i.p.), counteracted the inhibitory effect of both WIN 55,212-2 (1 mg/kg) and CP 55,940 (0.1 mg/kg) on gastrointestinal motility. WIN 55,212-2 did not modify castor-oil-induced diarrhoea, while CP 55,940 produced a transient delay in castor-oil-induced diarrhoea at the highest dose tested (1 mg/kg), an effect counteracted by SR141715A (5 mg/kg). These results suggest that (i) intestinal motility and defaecation could be tonically inhibited by the endogenous cannabinoid system, (ii) exogenous activation of cannabinoid CB(1) receptors produces a reduction in intestinal motility in the upper gastrointestinal tract but not in defaecation, (iii) endogenous or exogenous activation of cannabinoid CB(2) receptors does not affect defaecation or intestinal motility and (iv) the cannabinoid receptor agonist, CP 55, 940, possesses a weak and transient antidiarrhoeal effect while the cannabinoid receptor agonist, WIN 55,212-2, does not possess antidiarrhoeal activity.