Mass drug administration of ivermectin, diethylcarbamazine, plus albendazole compared with diethylcarbamazine plus albendazole for reduction of lymphatic filariasis endemicity in Papua New Guinea: a cluster-randomised trial

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The Effects of Calcium Channel Blockers are not Related to their Chemical Structure in the Collar Model of the Rabbit

Placing a silicone collar around the rabbit carotid artery induces intimal thickening, an early stage in atherosclerosis and restenosis. We investigated whether treatment with oral pranidipine, a new potent, long-lasting dihydropyridine calcium channel blocker (CCB), inhibited collar-induced intimal thickening in addition to the changes in vascular reactivity usually observed in this model. Pranidipine treatment did not inhibit collar-induced intimal thickening. Placing the collar around the carotid artery resulted in the characteristic changes in vascular reactivity, such as increased sensitivity to 5-hydroxytryptamine. Treatment with Nω-nitro-l-arginine (100 μM) and pranidipine, however, did not affect collar-induced changes in vascular reactivity. From results of this and previous studies, we conclude that pranidipine does not prevent collar-induced intimal thickening or collar-induced changes in vascular reactivity. Not all CCBs prevent collar-induced intimal thickening, suggesting that the effects of these agents are not related to their chemical structure and/or their calcium channel-blocking actions.

Diverse effects of taurine on vascular response and inflammation in GSH depletion model in rabbits

OBJECTIVE

A reduction in GSH and an increase in free radicals are observed in inflammatory diseases, indicating oxidative stress. Taurine protects cells from the cytotoxic effects of inflammation. There have been limited studies to date evaluating the effect of taurine in oxidative stress-induced vascular dysfunction and its role in vascular inflammatory diseases. Therefore, we aimed to investigate the effect of taurine on the regulation of vascular tonus and vascular inflammatory markers in rabbit aortae and carotid arteries in oxidative stress-induced by GSH depletion.

MATERIALS AND METHODS

Rabbits were treated subcutaneously with buthionine sulfoximine (BSO), GSH-depleting compound and/or taurine. Cumulative concentration-response curves for acetylcholine (ACh), phenylephrine and 5-hydroxytriptamine (5-HT) were constructed with or without Nω-nitro-L-arginine (LNA) in the carotid artery and aorta rings. Immunohistochemical staining was performed for TNF-α and IL-1β.

RESULTS

BSO increased ACh-induced NO-dependent relaxations, phenylephrine-induced contractions in the carotid artery and 5-HT induced-contractions in both the carotid artery and the aorta. BSO decreased EDHF dependent relaxations only in the aorta. ACh-induced NO-dependent relaxations and augmented contractions were normalized by taurine. BSO increased TNF-α expressions in both carotid arteries and aortas, which were reversed by taurine. The BSO-induced increase in IL-1β was reversed by taurine only in aortae.

CONCLUSIONS

Treatment with BSO resulted in vascular reactivity changes and increased immunostaining of TNF-α in mainly carotid arteries in this model of oxidative stress. The effect of taurine on BSO-induced vascular reactivity changes varied depending on the vessel. The inhibition of the increase in TNF-α expression by taurine in both carotid arteries and aortae supports the proposal that taurine has a beneficial effect in the treatment of inflammatory diseases such as atherosclerosis.

Antioxidant enzyme activities and total nitrite/nitrate levels in the collar model. Effect of nicardipine

There is a large body of literature describing the causative role of oxidative stress mediated by increased levels of reactive oxygen species in the pathogenesis of cardiovascular disease such as atherosclerosis, hypertension, and restenosis after angioplasty. The positioning of a soft silicone collar around the rabbit carotid artery elicits intimal thickening. The findings from recent studies demonstrated that both intimal thickening and atherosclerosis lead to synthesis of inducible nitric oxide synthase, resulting in abundant amounts of nitric oxide. We investigated the effects of collaring and nicardipine treatment on the activities of antioxidant enzymes, superoxide dismutase and catalase, and total nitrite/nitrate levels, stable products of nitric oxide. Placing the collar increased the total nitrite/ nitrate levels and decreased superoxide dismutase activity in collared arteries. Treatment with nicardipine (20 mg/kg/day, s.c.) prevented enhanced nitric oxide degradation without affecting superoxide dismutase and catalase activities. Our results suggest that enhanced nitric oxide production and superoxide anion are generated in response to the collaring, resulting in oxidative stress within the segment in this model.

Effects of treatment with FK409, a nitric oxide donor, on collar-induced intimal thickening and vascular reactivity

Intimal thickening in arteries is considered a site of predilection for atherosclerosis. In a rabbit model of early atherosclerosis, a silastic collar was placed around the carotid artery, which resulted in the formation of intimal thickening. We investigated whether the oral application of FK409 ((+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide , 10 mg kg(-1) day(-1), p.o.), a nitric oxide donor, inhibited the collar-induced intimal thickening as well as accompanying reactivity changes in rabbit carotid artery. The intimal thickening was significantly inhibited by FK409. The collar treatment increased the pD2 value of 5-hydroxytryptamine (5-HT) whereas it decreased those of phenylephrine and acetylcholine and did not significantly alter that of nitroglycerine. Maximal contractile force development in response to potassium chloride (KCl), 5-HT and phenylephrine was decreased in collared arteries. The collar did not alter the maximal relaxant effects of acetylcholine and nitroglycerine. Despite the significant reduction of intimal thickening, FK409 treatment did not affect these collar-induced modifications in vascular reactivity.

Effects of nicardipine on collar-induced intimal thickening and vascular reactivity in the rabbit

The effects of nicardipine treatment on collar-induced intimal thickening and on accompanying reactivity changes in rabbit carotid artery have been investigated. Treatment for three weeks with subcutaneous nicardipine (20 mgkg(-1) per day) significantly inhibited the intimal thickening caused by perivascular application of a silicone rubber collar. Potassium chloride (KCl), phenylephrine and 5-hydroxytryptamine (5-HT) induced concentration-dependent contractions in both sham-operated and collared arteries. Collar-induced attenuation of maximum KCl-, phenylephrine- and 5-HT-induced contraction was not affected by nicardipine. Collaring caused the means of pD2 values (the negative logarithm of EC50 values, 50% effective concentration) of 5-HT and phenylephrine to increase and decrease, respectively. Nicardipine did not affect the altered sensitivity to these agonists. Neither collar implantation nor nicardipine treatment altered the pD2 values for acetylcholine- and nitroglycerine-induced relaxations. These results demonstrate that nicardipine inhibits collar-induced intimal thickening in rabbit carotid artery without affecting the accompanying changes in vascular reactivity, indicating a possible lack of association between the development of intimal thickening and altered reactivity.

Effect of verapamil on intimal thickening and vascular reactivity in the collared carotid artery of the rabbit

1. Intimal thickening is a common site for atherosclerosis. Therefore, we investigated whether the calcium entry blocker verapamil (10 mg kg-1 body weight day-1, s.c.) can retard intimal thickening and changes in vascular reactivity induced by a non-occlusive, silicone collar positioned around the left carotid artery of rabbits. The contralateral carotid artery was sham-operated and served as a control. 2. Verapamil and placebo (saline 0.1 ml kg-1, day-1, s.c.) treatments were initiated 7 days before placing the collar and lasted 3 weeks. Thereafter, segments were cut from collared and sham-treated arteries for histology and isometric tension recording. 3. The intima/media (I/M ratio increased after 14 days of collar treatment, but intimal thickening was not inhibited by verapamil (I/M ratio placebo 0.31 +/- 0.07, verapamil 0.32 +/- 0.09). 4. The collar decreased the capacity to develop force, as indicated by the response to a supramaximal concentration of KCl, decreased the sensitivity (pD2) to acetylcholine (ACh) and phenylephrine (Phe), but increased the sensitivity to 5-hydroxytryamine (5-HT). 5. Although verapamil did not affect intimal thickening, it normalized the hypersensitivity to 5-HT in collared arteries. 6. The contraction to the supramaximal concentration of KCl was not affected by verapamil. Verapamil decreased the Emax of ACh, but this was only seen in collar-treated arteries. Verapamil also decreased the sensitivity to ACh and Phe, in both sham- and collar-treated arteries. 7. We conclude that verapamil, without preventing thickening of the intima, can modify collar-induced changes in vascular reactivity.

The effect of cigarette smoke on the plasma piroxicam concentrations in rats

The plasma concentration of unchanged piroxicam has been determined at 15, 30, 60 and 90 min after 10 mg kg-1 oral administration of the drug to rats exposed to cigarette smoke or pretreated with phenobarbitone, 3,4-benzpyrene or ethanol. Plasma piroxicam concentrations decreased in rats pretreated with phenobarbitone, 3,4-benzpyrene and ethanol and in rats 24 h after exposure to cigarette smoke.

The effect of a single treatment with cigarette smoke on the blood levels and hemodynamic effects of propranolol in rats

The effect of a single treatment with cigarette smoke on the blood levels and hemodynamic effects of propranolol in rats was studied. Pentobarbital sleep time was not affected whereas zoxazolamine paralysis time was shortened 72% in rats, 24 h after the cigarette smoke exposure. The beta-adrenoceptor blocking effect of propranolol observed at 10 and 20 min time intervals was abolished in rats exposed to cigarette smoke 24 h after the exposure. The blood propranolol concentrations were decreased in rats pretreated with phenobarbital, 3,4-benzpyrene and ethanol as well as in cigarette smoke exposed rats. Among several factors that could influence propranolol metabolism, in this study, enzyme induction is suggested to be dominant.