LPS-induced lung inflammation is linked to increased epithelial permeability: role of MLCK

The respiratory system is directly exposed to low levels of lipopolysaccharide (LPS), present as a contaminant on airborne particles. In cystic fibrosis, the prevailing data identify structural changes of the airway epithelium, as well as tight junction dilatation. This study was aimed at determining the contribution of myosin light chain kinase to maintaining airway epithelium barrier integrity in the lung inflammatory response to LPS in rats. The effects of the selective myosin light chain kinase inhibitor, 5-iodonaphthalene-1-sulphonyl-homopiperazine (ML-7), were evaluated: 1) on pulmonary inflammation and airway epithelium barrier permeability alterations induced by intra-tracheal LPS from Pseudomonas aeruginosa; and 2) on levels of the phosphorylated form of the myosin light chain, which is increased in a human airway epithelial cell line (NCI-H292) and tracheal tissue after LPS exposure. The results show that LPS increased airway epithelium barrier paracellular permeability and lung inflammation, and that pre-treatment with ML-7 inhibited both effects. This effect of ML-7 was associated with the inhibition of phosphorylated myosin light chain in both NCI-H292 cells and tracheal tissue. The data, obtained using in vivo and in vitro approaches, demonstrate a key role for myosin light chain kinase in lung inflammation, and suggest that myosin light chain kinase could be a potential target for novel drugs intended for relief of lung injury.

Beneficial effect of trimebutine and N-monodesmethyl trimebutine on trinitrobenzene sulfonic acid-induced colitis in rats

The use of local anesthetics, such as lidocaine, has been proposed in the treatment of distal ulcerative colitis. Trimebutine maleate (TMB) displays a local anesthetic activity higher than that of lidocaine in rabbit corneal reflex. TMB and nor-TMB its main metabolite in human show similar affinity to that of bupivacaine toward sodium channel labeled by [3H]batrachotoxin and block sodium currents in sensory neurons from rat dorsal root ganglia. The aim of this study was to evaluate the effects of TMB and nor-TMB in comparison to lidocaine and bupivacaine in a rat model of acute colonic inflammation induced by trinitrobenzene sulfonic acid (TNBS). A single intracolonic instillation of TNBS (50 mg/kg dissolved in ethanol 30%) led to early plasma extravasation then macroscopic damage (hyperemia and necrosis), increased colonic weight and tissular MPO, a marker of neutrophilic infiltration. Local administration of TMB at dose of 3 to 60 mg/kg, 30 min before, 24 and 48 h after colitis induction, significantly reduced the severity of colitis. Nor-TMB (1, 3, 10, 30 mg/kg) as well as lidocaine (1, 3, 10 mg/kg) dose-dependently reduced colitis while bupivacaine at 10 mg/kg did not affect it significantly. In contrast systemic administration of TMB, nor-TMB and lidocaine at 10 mg/kg had no significant effect. Furthermore, local administration of TMB (30 mg/kg) and lidocaine (10 mg/kg) significantly reduced plasmatic extravasation. In conclusion, intracolonic treatment with TMB and nor-TMB improved acute experimental TNBS-induced colitis in rat and these effects could be explained by their local anesthetic activity.

Antidiarrhoeal properties of a novel sigma ligand (JO 2871) on toxigenic diarrhoea in mice: mechanisms of action

BACKGROUND AND AIMS

Sigma ligands display antisecretory activity against various secretagogues, suggesting antidiarrhoeal properties. In this study, we evaluated: (i) the antidiarrhoeal effect of JO 2871, a high affinity sigma ligand, in three models of toxigenic diarrhoea in mice; and (ii) the site and mechanism of action of this compound.

METHODS

Faeces were collected after toxin or vehicle administration in male DBA2 or NMRI mice. Diarrhoea was determined by cumulative stool weight (mg) over a 120 minute period. Diarrhoea was induced by intravenous administration of Salmonella enteriditis lipopolysaccharide (LPS), or oral administration of Escherichia coli heat stable (E coli-sta) or Clostridium difficile toxins. Two sigma ligands, igmesine and JO 2871, were administered either orally or intravenously, 60 and 30 minutes before the toxins, respectively. JO 2871 was also given orally 30 minutes after E coli-sta. In addition, JO 2871 was administered intracerebroventricularly five minutes before LPS and E coli-sta. BMY 14802 (1000 microg/kg orally), a sigma receptor antagonist, or cyclosomatostatin (CSS 1 microg/kg intravenously), a somatostatin antagonist, were given five minutes prior to JO 2871 in LPS, E coli-sta, and C difficile toxin treated mice. Gastric emptying and intestinal transit were evaluated after oral JO 2871 and BMY 14802 and intravenous CSS.

RESULTS

Stool weight measured 120 minutes after administration of the toxins was significantly increased. Oral JO 2871 and igmesine dose dependently inhibited toxigenic diarrhoea in all models. ED(50) values obtained using JO 2871 (1-20 microg/kg) were more than 40 times lower than those obtained with igmesine. Oral JO 2871 given after E coli-sta also inhibited diarrhoea in a dose dependent manner (ED(50) 50 microg/kg). Both sigma ligands were active by the intravenous route on LPS and E coli-sta induced stool weight increases. JO 2871 administered intracerebroventricularly failed to block this effect at any dose tested. Both BMY 14802 and CSS reversed the antidiarrhoeal effect of oral JO 2871. JO 2871, BMY 14802, and CSS did not affect transit parameters.

CONCLUSIONS

JO 2871 exerts a potent oral antidiarrhoeal effect, acting peripherally through sigma sites and somatostatin release.

Pregabalin (CI-1008) inhibits the trinitrobenzene sulfonic acid-induced chronic colonic allodynia in the rat

In human, digestive disorders are often associated with visceral pain. In these pathologies, visceral pain threshold is decreased indicating a visceral hypersensitivity. Pregabalin [CI-1008; S-(+)-3-isobutylgaba] presents antihyperalgesic actions in inflammatory somatic pain models. This study was designed to evaluate 1) the effect of injection of TNBS into the colon on visceral pain threshold, and 2) the antihyperalgesic effect of pregabalin on TNBS-induced chronic colonic allodynia. A significant decrease in the colonic pain threshold was observed in trinitrobenzene sulfonic acid (TNBS)-treated animals (17.8 +/- 1.27 versus 43.4 +/- 1.98 mm Hg). Pregabalin (30-200 mg/kg s.c.) and morphine (0.1-1 mg/kg s.c.) showed a dose-related inhibition of TNBS-induced colonic allodynia. Pregabalin did not inhibit the colonic inflammatory effect of TNBS. In normal conditions (control animals), morphine (0.3 mg/kg s.c.) significantly increased the colonic pain threshold, whereas pregabalin (200 mg/kg s.c.) did not modify the colonic pain threshold. Pregabalin suppressed the TNBS-induced colonic allodynia but did not modify the colonic threshold in normal conditions. The ability of pregabalin to block the chronic colonic allodynia indicates that it is effective in abnormal colonic hypersensitivity, suggesting a possible effect in chronic pain in irritable bowel syndrome.

Antinociceptive effect of pregabalin in septic shock-induced rectal hypersensitivity in rats

Pregabalin [S-(+)-3-isobutylgaba] is a novel compound under development for its analgesic, anxiolytic, and anticonvulsant properties, and its interaction with the alpha(2)delta-subunit of voltage-dependent Ca(2+) channels. In this study, we investigate the antinociceptive activity of pregabalin in a rat model of delayed visceral hyperalgesia induced by i.p. lipopolysaccharide (LPS) administration. LPS (Escherichia coli, serotype O111:B4) leads to a delayed lowering threshold (9-12 h) of abdominal contractions in response to rectal distension (RD) in awake rats surgically prepared for electromyography of abdominal muscles. This allodynic effect of LPS was blocked by morphine (0.3 mg/kg s.c.), and the action of morphine was antagonized by naloxone (2.5 mg/kg s.c.). A single i.p. (10, 30 mg/kg) and oral (1, 3, 10 and 30 mg/kg) treatment of pregabalin dose dependently suppressed LPS-induced rectal hypersensitivity. When administered 2 h before RD (but preceded 12 h by LPS injection), the oral dose of 10 mg/kg was effective both in the allodynic response induced by LPS and in the intensity of the nociceptive response related to RD. Pretreatment by either naloxone or bicuculline (a GABA(A) antagonist, 0.5 mg/kg i.p.) did not affect the antiallodynic effect of pregabalin. We conclude that pregabalin is a therapeutic candidate in the treatment of gut hypersensitivity not acting through GABA(A) and opiate receptors.

[Mass treatment of onchocerciasis in 1996]

Mass treatment of onchocerciasis has changed radically in the last 20 years. With implementation of the Onchocerciasis Control Programme (OCP), use of insecticides to control vector larvae has been effective but has not been extended to all infected areas due to the cost. The consequences of this problem have been lessened thanks to ivermectin, an effective drug that can be administered in a single yearly dose. Although ivermectin does not appear to induce major side-effects, surveillance is necessary after administration in polyparasitized subjects living in zones where loaiasis is present and in hypermicrofilaremic subjects. To assist in the fight against onchocerciasis, ivermectin is distributed free of charge through the Mectizan Foundation by Merck Laboratories. Inexpensive community distribution programs with active participation of the populations at risk have demonstrated their usefulness. The results of mass treatment through the Mectizan Foundation have been excellent. Non-governmental organizations and in particular the Organization for the Prevention of Blindness (OPB) have become increasingly involved in the fight against onchocerciasis. The campaign conducted by the OPB in Mali, Senegal and Guinea illustrate this involvement. The role of non-governmental organizations expanded greatly with the implementation of the APOC programme supported by the World Bank.

Gastrointestinal functional bowel disorders: new therapies

Present therapies for functional gastrointestinal disorders are symptomatic and mainly treat altered bowel habits. New therapies are focused on nerve-gut communication dysfunction: 5-HT3 antagonists and 5-HT4 agonists have demonstrated activity in clinical trials. Promising targets for upper gut dysmotility drugs are motilin and cholecystokinin A receptors. Tachykinins, calcitonin gene-related peptide or glutamate antagonists are the most relevant candidates for visceral pain.

Neuropeptide Y and sigma receptor agonists act through a common pathway to stimulate duodenal alkaline secretion in rats

Neuropeptide Y (NPY) has been shown to mimic the effects of some sigma receptor agonists in the brain and to possess the same proabsorptive effect as these agonists in the isolated mouse jejunum. The aim of present study was to investigate the effect of NPY on duodenal alkaline secretion in the rat and to define its mode of action. NPY (0.01 to 3 micrograms/kg i.v.) induced a dose-related increase in duodenal bicarbonate secretion, the maximal effect being obtained at 1 micrograms/kg. This response was significantly inhibited by the i.v. administration of haloperidol, BMY 14802, devazepide, hexamethonium, tetrodotoxin and by bilateral truncal vagotomy, but not by SCH 23390, sulpiride, prazosin or atropine, whereas i.c.v. devazepide had no effect. This pharmacological profile is identical to that reported for sigma receptor agonists. The results suggest that NPY and sigma ligands act through a common pathway to stimulate duodenal alkaline secretion in the rat.

Effects of a new sigma ligand, JO 1784, on cysteamine ulcers and duodenal alkaline secretion in rats

BACKGROUND

The ulceroprotective effects of JO 1784 [(+)-N-cyclopropyl-methyl-N-methyl-1,4-diphenyl-1-ethyl-but-3-en-1-yl amine, hydrochloride], a new specific and highly selective sigma ligand, were examined in rats.

METHODS

Different models of gastric ulcers (4-hour restraint stress, aspirin, ethanol, and taurocholate) and cysteamine-induced duodenal ulcers were used. The gastric acid secretion (4-hour Shay rat preparation) and the duodenal bicarbonate secretion were also studied.

RESULTS

JO 1784 elicited a potent protection against duodenal ulcers but had a weaker protective effect on any of the gastric ulceration models tested. It displayed no gastric antisecretory activity but induced a dose-dependent stimulation of duodenal bicarbonate secretion. Haloperidol, hexamethonium, tetrodotoxin, bivagotomy (but not atropine), and the intravenous but not intracerebroventricular administration of devazepide, a cholecystokinin A antagonist, inhibited the stimulatory effect of JO 1784.

CONCLUSION

These results show that JO 1784, a selective sigma ligand, is a potent protector of the duodenal mucosa. This activity may be related to its stimulating effect on bicarbonate secretion, which is driven through a complex nervous mechanism involving muscarinic synapses, vagal afferent fibers, and peripheral cholecystokinin receptors. This drug might open a new specific way in the treatment of duodenal ulcers.

Central and peripheral effects of prostaglandin E2 and enprostil on exocrine pancreatic secretion in rats

Prostaglandin E2 (PGE2) has been reported to exert some centrally mediated effects on intestinal motility and secretion and on gastric secretion, but it is not known whether such central effects exist on pancreatic secretion. The central and peripheral effects of PGE2 and enprostil, a long-acting, potent PGE2 analogue, were studied in conscious and anesthetized rats fitted with pancreatic fistulae. In chronically implanted, conscious rats, PGE2 inhibited the secretion of fluid, bicarbonate, and total protein in the pancreatic juice, both after i.v. or intracerebroventricular (icv) injections. The maximal inhibition was similar after both injection procedures (about 45% for fluid and bicarbonate and 60% for protein), but the potency of PGE2 was three to 10 times greater by the icv than the i.v. route. Enprostil also inhibited pancreatic secretion in a dose-related way. The maximal inhibition was larger than after PGE2 injection (about 70% for fluid and bicarbonate and 90% for protein). The potency of enprostil was five to 10 times lower by the icv than by the i.v. route. The diversion of gastric secretion suppressed the effect of icv PGE2 on fluid and bicarbonate output but not on protein and did not change the effect of enprostil on all the variables of pancreatic secretion. Adrenergic antagonists did not suppress the effect of icv PGE2 or enprostil on pancreatic secretion. In anesthetized rats, i.v. PGE2 inhibited hormone-stimulated protein secretion but did not change fluid and bicarbonate output, while i.v. enprostil inhibited cholecystokinin-stimulated fluid, bicarbonate, and protein output in the pancreatic juice.(ABSTRACT TRUNCATED AT 250 WORDS)

[Orbital and ocular tumors in the Republic of Mali]

Analysing 82 cases of oculo-orbital tumours in Malian patients, the authors find the classical features characterizing ocular carcinoma in Africa, i.e. early arising, development, late request for treatment. They stress on the age of the patients at the occasion of the first request for treatment in case of retinoblastoma, and notice the special frequency of squamous cell carcinoma with conjunctival or limbic localization.

Growth-hormone releasing factor does not antagonize somatostatin effects on pancreatic and gastric secretions

The effect of human GRF 44 upon somatostatin-inhibited pancreatic and gastric secretions was studied in rats with chronic fistulas. GRF did not show any antagonist action of somatostatin on these gastro-intestinal organs. GRF alone had a small inhibitory effect on gastric acid output.

[An Ota's naevus in a West African child (author's transl)]

Report of a case of Ota's naevus fuscocaeruleus ophtalmomaxillaris in an african child. The authors are not aware of a previous report of this deformity in Africa (South of the Sahara). They review the clinical and histological features of this naevus and describe in this case a pigmentary infiltration of corneal stroma.

[Corneal sensibility in 57 black Africans. A study based on 113 biomicroscopically normal ocular globes (author's transl)]

This study of the corneal sensitivity in 57 sahelian black Africans with a biomicroscopically normal cornea demonstrated that most of them (80,8 p. 100) had a normal corneal esthesia. The others (19,2 p. 100) having an hypoesthesia are older than the average age of this group and have a lower sociocultural status.

[Late aspects of palpebral anthrax (author's transl)]

Report of 5 cases of palpebral anthrax treated after the acute phase, in a cicatricial or precicatricial stade. The authors recommend to delay plastic surgery up to three months and to select total skin graft for upper eye-lid and pediculed skin flap for lower eye-lid.

(-)Eburnamonine in vascular lesions of the fundus of the eye (with 1 color plate)

Using photographs of the fundus of the eye after injection of fluorescein and treatment by (-)eburnamonine the authors show the vasodilatation effect of the drug and the unquestionable appearance of circulation flow in the right middle nasal artery which was previously reduced to a silver thread-like aspect.