Beta-adrenergic receptor blockade as a therapeutic approach for suppressing the renin-angiotensin-aldosterone system in normotensive and hypertensive subjects

Although beta-adrenergic-blocking drugs suppress the renin system (RAAS), plasma angiotensin II (Ang II) responses during beta-blockade have not been defined. This study quantifies the effects of beta-blockade on the RAAS and examines its impact on prorenin processing by measuring changes in the ratio of plasma renin activity (PRA) to total renin. In normotensive (N = 14) and hypertensive (N = 16) subjects, blood pressure (BP), heart rate, PRA, plasma prorenin, plasma total renin (prorenin + PRA), ratio of PRA to total renin (%PRA), plasma Ang II, and urinary aldosterone were measured before and after 1 week of beta-blockade. Plasma renin activity, Ang II, and urinary aldosterone levels were similar for normotensive and hypertensive subjects. Plasma renin activity correlated with Ang II. Total renin, which is proportional to (pro)renin gene expression, was lower in hypertensive subjects and was inversely related to BP. Beta-blockade decreased BP and heart rate in both groups, with medium- and high-renin hypertensive subjects responding more frequently than those with low renin. Beta-blockade consistently suppressed PRA, Ang II, and aldosterone. Total renin was unchanged, thus, %PRA fell. These results indicate that beta-blockers suppress plasma angiotensin II levels, in parallel with the marked reductions in PRA and urinary aldosterone levels in normotensive and hypertensive subjects. The suppression of Ang II levels was comparable to that produced during angiotensin converting enzyme (ACE) inhibition. However, by reducing prorenin processing to renin, beta-blockers do not stimulate renin secretion, unlike ACE inhibitors and Ang II receptor antagonists. This unique action of beta-blockers has important implications for the treatment of cardiovascular disease.

Reduced ferroxidase activity in the cerebrospinal fluid from patients with Parkinson's disease

Recent evidence suggest the implication of transition metals leading to overproduction of free radicals as a possible causal factor in the death of nigral cells associated to Parkinson's disease (PD). Iron depots in the basal ganglia of PD patients have been described; in addition, contents of nigral copper have been found decreased, while its concentration in cerebrospinal fluid (CSF) is raised, particularly the free form of the metal. To search for a possible link between altered copper concentrations and PD, we advanced the hypothesis that ferroxidase activity of ceruloplasmin is decreased in the CSF of PD patients. We studied 35 untreated PD patients, 14 L-3,4-dihydroxyphenylalanine (L-DOPA)-treated PD patients and 26 controls. Both CSF ferroxidase activity and CSF copper content were measured and correlated with the clinical stage of the disease. We found that untreated PD patients had a significant reduction of 40% in CSF ferroxidase while CSF copper was slightly increased as compared with both the values in L-DOPA-treated PD patients and controls. We also found that the fraction of copper linked to ferroxidase in untreated PD is inversely related to the clinical stage of the disease.

Characterization of cerebrospinal fluid antibody specificities in neurocysticercosis using phage display peptide library

To identify epitopes for antibodies present in cerebrospinal fluid (CSF) samples from two patients with confirmed neurocysticercosis, we used a phage peptide library that displayed random dodecapeptides as a fusion to the minor coat protein (pIII) of phage M13. To increase the specificity of selection, plates coated with anti-human Fc antibody were used in five rounds of biopanning. The DNA inserts of 30 selected clones were determined and the deduced amino acid sequences were analyzed. Sequence similarities between affinity-selected clones and three known T. solium and T. crassiceps proteins were encountered. Two phage clones have been shown to react in enzyme-linked immunosorbent assay with CSF samples from other patients with neurocysticercosis, and no reaction was observed with CSF samples from patients with other neurological disorders used as negative controls. Our results suggest that affinity selection of peptides from phage libraries using CSF samples from patients is an attractive tool for the development of novel reagents for a simple and sensitive immunodiagnostic test and for understanding the molecular mechanisms participating in the pathogenesis of neurocysticercosis.

Possible relationship between neurocysticercosis and hematological malignancies

BACKGROUND

Previous studies have shown an increased frequency of chromosomal abnormalities in lymphocytes from animals and humans with cysticercosis. Some reports have suggested an association between cancer and cysticercosis. The aim of this study was to investigate the possible association between neurocysticercosis and cancer.

METHODS

We designed a mortality rate study from the autopsy files of the Department of Pathology at the General Hospital of Mexico. A total of 1,271 autopsy files were reviewed. All files in which a malignant neoplasia was found during autopsy were selected as cases. Autopsies in which no malignant disease was found were used as controls. The odds ratio was determined between the frequency of neurocysticercosis in patients with any malignant neoplasia and that of the controls.

RESULTS

Neurocysticercosis was more frequent in cases with malignant hematological diseases (MHD) than in controls (p = 0.01). The odds ratio for this association was 3.54, with 95% confidence interval from 1.17-9.79.

CONCLUSIONS

Most human cancers arise from the interaction of a multiplicity of factors, including xenobiotics and endogenous constituents. Therefore, while it will be difficult to demonstrate that neurocysticercosis is a causal agent of malignant hematological diseases (MHD), it should be considered as a potential risk factor for cancer induction in countries where cysticercosis remains a public health problem.

Protective effect of pentoxifylline plus thalidomide against septic shock in mice

Mortality caused by septic shock in experimental animals is reduced by thalidomide, an inhibitor of tumour necrosis factor alpha. Another drug that could act on the pathophysiological mechanisms of septic shock is pentoxifylline, an inhibitor of platelet aggregation that increases the flexibility of the erythrocyte membrane and has fibrinolytic activity. We studied the effect of pentoxifylline alone and combined with thalidomide in septic shock; 97 NIH mice were injected with lipopolysaccharides of Salmonella abortus equi and D galactosamine. Animals were separated in 4 groups; group A (n = 20) was used as control, group B (n = 15) received thalidomide 50 mg/kg, group C (n = 20) received pentoxifylline 40 mg/kg, and group D (n = 15) received thalidomide plus pentoxifylline. Mortality was recorded every hour. Additionally, 5 animals from each group were sacrificed 8 h after the induction of septic shock for histological analysis of heart, lung, brain, kidney, small intestine, adrenal glands and liver. Microscopic findings were rated as absent, mild, moderate and severe damage. In control animals histological analysis showed intense haemorrhage and necrosis in all organs studied. When compared with controls, treatment with pentoxifylline plus thalidomide reduced mortality (P < 0.03). The tissue damage was less severe in animals from the groups that received pentoxifylline or pentoxifylline plus thalidomide (P < 0.05). Pentoxifylline seems to potentiate the beneficial effects of thalidomide, reducing mortality and attenuating the pathological changes produced by septic shock.

Protamine inhibits angiogenesis and growth of C6 rat glioma; a synergistic effect when combined with carmustine

Protamine inhibits angiogenesis and blocks endothelial, fibroblast and platelet growth factors. Human and experimental gliomas spread and grow in response to both paracrine and autocrine release of these factors. Our objective was to study the effect of protamine administration on cell proliferation, angiogenesis and tumoral growth of C6 glioma. Additionally, we compared the antitumoral effect of protamine with that of another inhibitor of angiogenesis, suramin, and investigated a potential synergistic antitumoral action of low doses of protamine combined with the antineoplastic carmustine. C6 glioma cells were implanted subcutaneously in Wistar rats. A highly malignant glioma developed in 80% of animals; when the tumour reached a diameter of 1.5 cm, either protamine, suramin, carmustine or protamine plus carmustine were administered in various doses. Tumour parameters were measured and compared between groups. In a dose-dependent manner, protamine reduced tumour volume (P < 0.001), mitotic index (P < 0.05), vascular density (P < 0.05) and cell viability (P < 0.005) of C6 glioma. An ultrastructural study demonstrated membranous inclusions in the cytoplasm of 28% of tumoral and endothelial cells of tumours from animals treated with protamine. The inhibition of tumoral growth produced by moderate doses of protamine was similar to that produced by toxic doses of suramin. The combination of protamine and carmustine had a synergistic curtailing effect on tumoral growth (P < 0.001). Our results indicate that protamine is an effective agent against glioblastoma; in non-toxic doses it could potentiate the antineoplastic effect of nitrosoureas for the treatment of glial tumours.

Nifurtimox plus pyrimethamine for treatment of murine toxoplasmosis

In the search for novel antitoxoplasmic agents, we evaluated the efficacy of nifurtimox (3-methyl-4[5'-nitrofurfurylidene-amino]-tetrahydroe-4H-1,4- thiazine-1,1-dioxide), an antiprotozoal drug effective against trypanosomiasis, in an experimental model of acute toxoplasmosis in mice. One hundred NIH mice were inoculated intraperitoneally, each with 2,614 RH tachyzoites of Toxoplasma gondii, and randomly allocated into 5 groups (n = 19-21). Animals from each group were orally treated for 10 days either with nifurtimox 25 mg/kg/day (NF1), nifurtimox 50 mg/kg/day (NF2), pyrimethamine 60 mg/kg/day (P), the combination nifurtimox 50 mg/kg/day plus pyrimethamine 60 mg/kg/day (NF2-P), or with corn oil (controls). Survival of mice was recorded daily for 1 mo after the experimental infection. Comparisons of cumulative mortality between groups were made applying the chi2 test. Mean survival time was longer in animals from P and NF2-P groups than those from NF1, NF2, and control groups. Cumulative mortality was less in mice from the NF2-P group (25%), than that in mice from the P (65%), the NF1 (100%), the NF2 (89%), or the control (95%) groups (P < 0.01). The doses of nifurtimox used in the present study were not significantly effective against murine toxoplasmosis. However, when combined with pyrimethamine, a strong anti-toxoplasma effect was obtained in comparison with survival rates associated with pyrimethamine or nifurtimox alone. It seems feasible that nifurtimox inhibits the replication of T. gondii tachyzoites similar to that of other protozoans, e.g., Trypanosoma and Leishmania. It will be important to determine if the reduction of mortality in mice treated with the nifurtimox-pyrimethamine combination results from summation or from synergism. Further studies on the toxic mechanisms exerted by nifurtimox on T. gondii seem warranted.

Colchicine, like methylprednisolone, decreases the perilesional fibrosis secondary to a chronic brain granuloma in cats

We studied the effects of long-term administration of colchicine on the fibrosis surrounding a granulomatous lesion previously induced by stereotactic injection of aluminum silicate into the brain parenchyma of cats. Every week the animals received a single i.m. injection of colchicine (0.25 mg), or methylprednisolone (4 mg), or saline solution (controls) for 6 months. The mean area of fibrosis in animals treated with colchicine or with methylprednisolone was smaller than that of control animals (P < 0.05). In controls, a dense capsule of procollagen and collagen fibers was found around the granuloma, and myelinated neurites were scarce, whereas in animals treated with colchicine or with methylprednisolone the capsule and fibers were thinner and more myelinated neurites remained. These changes were more evident in animals treated with colchicine. Our results suggest that chronic administration of colchicine or methylprednisolone limit the fibrosis and histological damage around a granulomatous lesion of the brain.

Pharmacokinetic optimisation of the treatment of neurocysticercosis

Neurocysticercosis is the most important parasitic infection of the nervous system. It is common in communities living in conditions with poor hygiene. Until the last 2 decades, there was no specific pharmacological treatment: surgery and corticosteroids were the only medical alternatives. The recent introduction of anticysticercal drugs, an isoquinoline (praziquantel) and a benzimidazole (albendazole), has dramatically changed the medical management of neurocysticercosis. Praziquantel is taken orally and undergoes extensive first pass hepatic biotransformation. Peak concentration in serum is reached after 1 to 2 hours and the elimination half-life is between 1 and 3 hours. Praziquantel permeates the blood-brain barrier, thus explaining its effectiveness on parenchymal brain cysticercosis. Plasma concentrations of the drug are increased when a high carbohydrate diet is administered. Cimetidine also increases the plasma concentration of praziquantel by inhibition of cytochrome P450. Bioavailability of the drug is markedly reduced when given jointly with antiepileptics or corticosteroids, specially carbamazepine, phenytoin or dexamethasone. The current schedule for neurocysticercosis treatment lasts 2 weeks at daily doses of 50 mg/kg. Recently, a new therapeutic scheme has been proposed that considers the pharmacokinetics of the drug. This regime lasts only 1 day and includes 3 dosages of 25 mg/kg at 2-hour intervals. This increases the time that the parasite is exposed to high drug concentrations. This therapeutic scheme has produced similar results to longer schemes, with the additional advantages of cost, length of usual treatments and reduction in total dose received (being one-tenth of the total dosage). Albendazole is considered by many as the drug of choice for treatment of neurocysticercosis. It is given orally and is rapidly and extensively metabolised to albendazole sulfoxide (ALBSO), which is considered to be the metabolite directly or indirectly responsible for both toxicity and efficacy outside the gastrointestinal tract. Concentrations of ALBSO are highly variable between individuals and it has a half-life of between 6 and 15 hours. It also crosses the blood-brain barrier. In patients with extrahepatic obstruction, the elimination process is prolonged and plasma concentration is increased. Fatty meals improve absorption. Concomitant administration of albendazole with dexamethasone or with praziquantel increases plasma concentration of ALBSO. Albendazole is administered in an 8 day course of 15 mg/kg per day in 2 divided doses 12 hours apart. This scheme, based on drug pharmacokinetics, has proven to be highly effective. Inflammation is a common accompaniment of neurocysticercosis; in many cases it is the aetiopathogen responsible for histological damage. Corticosteroid therapy is useful for preventing further tissue injury. Long term corticosteroid therapy can be accomplished with 50 mg of oral prednisone 3 times a week. Acute corticosteroid therapy includes brief courses with high dosages of intramuscular dexamethasone or intravenous methylprednisolone. Clinical decisions on cysticidal and anti-inflammatory treatments must be made with the information gathered by neuroimaging studies, either computed tomography or magnetic resonance, and by the analysis of cerebrospinal fluid.

Ultrastructural changes in limb distal nerves of rats with alcoholism and/or malnutrition before and after dietary correction

To study peripheral nerves changes in chronic alcoholism and in malnutrition, we examined ultrastructurally the distal nerve branches of the digits of rats treated with four different dietary schemes, as follows: controls (n = 22), fed standard rodent diet plus water ad libitum; alcoholism (n = 12), fed the standard diet and 2-12% ethanol in drinking water; malnutrition (n = 21), fed with corn tortillas instead of standard diet; and alcoholism and malnutrition combined (n = 22). After 10 months under these conditions, a proportion of animals from each group were sacrificed. The remaining rats of the malnutrition and alcoholism alone groups were deferred a standard diet. The combined alcohol + malnutrition group was subdivided into standard diet, malnutrition and ethanol. After a further 4 months under these new conditions, the animals were sacrificed. Ultrastructural examination of limb distal nerve branches showed that glycogen-like particles were more common in malnourished animals, whereas remyelinating axons were more numerous in ethanol-treated rats. Bands of regeneration were present in both groups, but were more common in animals treated with ethanol. These features decreased significantly when the respective nutritional factor was reversed. The results confirm that ethanol plays a definitive role in the development of alcoholic neuropathy and that malnutrition accentuates, the histopathological abnormalities.

Lack of therapeutic effect of colchicine on murine toxoplasmosis

In a previous report, we showed that addition of colchicine to cultures of glial cells infected with Toxoplasma gondii decreased the number of parasites by up to 80%. To provide support for potential therapeutic use of colchicine in toxoplasmosis, a murine model of T. gondii infection was used. Mice infected with pure RH T. gondii tachyzoites (from 2,233 to 25,000 parasites) were treated daily with either pyrimethamine (80 or 51 mg/kg), colchicine (10 mg/kg), pyrimethamine-colchicine, or vehicle (controls). Survival rates were lower in animals treated with colchicine (from 40% to 27%) and pyrimethamine-colchicine (from 73% to 41%) than in animals treated with pyrimethamine alone (from 100% to 73%). There was no extension of mean survival time in animals treated with colchicine compared to controls. These results demonstrate that colchicine does not improve the course of acute toxoplasmosis in mice, and it is detrimental rather than beneficial at the regimen tested.

Cysticercosis. Clinical classification based on imaging studies

Cysticercosis is a pleomorphic disease in which the diagnosis, treatment, and prognosis greatly vary in relation to the location, number, and stage of the lesions. A new classification is proposed that includes the information gathered by magnetic resonance imaging and computed tomography, supplemented by immunodiagnostic studies and clinical data. The different clinical entities produced by cysticercosis are grouped by the frequency and location of the parasites, including valuable data as the number and stage of the lesions as well as the degree of the inflammatory response from the host to the parasite. In this way, the disease can be individualized to define the reliability of diagnostic studies and to design specific therapeutic approaches that depend on the characteristics that the disease acquires in every location.

Pharmacokinetic study of praziquantel administered alone and in combination with cimetidine in a single-day therapeutic regimen

A brief therapeutic regimen of praziquantel, reduced to a single day, has been effective for treatment of neurocysticercosis. To study its pharmacokinetic characteristics, levels of praziquantel in plasma were determined for eight healthy volunteers after the administration of three oral doses of 25 mg/kg of body weight given at 2-h intervals, alone and with the simultaneous administration of cimetidine. Each volunteer received both regimens in a randomized crossover design. Blood samples were taken during a period of 12 h, and praziquantel concentration was measured by high-performance liquid chromatography. Levels of praziquantel in plasma remained above 300 ng/ml during a period of 12 h; they increased 100% when cimetidine was jointly administered. Compared with other regimens, the high levels obtained and the longer duration of action seem to be advantageous in prolonging the exposure of the parasites to the drug and support previous clinical experience showing that the treatment of neurocysticercosis with praziquantel can be reduced from 2 weeks to 1 day with the drug still retaining its cysticidal properties. Moreover, simultaneous administration of praziquantel and cimetidine could improve further the efficacy of the single-day therapy for cysticercosis and other parasitic diseases, such as schistosomiasis.

Intramedullary cysticercosis cured with drug treatment. A case report

STUDY DESIGN

A report of a patient with cervical intramedullary cysticercosis is presented.

OBJECTIVES

To report the first case of intramedullary. cysticercosis cured with drug management only, which supports the hypothesis that management with anthelmintics might be successfully used in this form of cysticercosis.

SUMMARY OF BACKGROUND DATA

Intramedullary cysticercosis is a rare manifestation of neurocysticercosis. Every treated patient reported to date has undergone surgery, frequently necessary for diagnosis. Since the anthelmintics praziquantel and albendazole were shown to be effective in parenchymal brain cysticercosis, these drugs have been considered potentially useful in patients with intramedullary cysticercosis. Nevertheless, no case yet had been reported to be cared with only medical therapy.

METHODS

The treatment of a patient who suffered multiple cysticercal reinfestations of the nervous system is presented.

RESULTS

The patient received prolonged treatment with albendazole because of superimposed cerebral reinfestations. During this treatment, she suffered acute paraparesis, and cervical magnetic resonance imaging showed cyst-like lesions with linear gadolinium enhancement and perilesional edema, indicative of dying cysticerci and inflammatory host reaction. Dexamethasone was added, and progressive neurologic improvement followed with complete resolution of intramedullary lesions.

CONCLUSIONS

A preoperative diagnostic suspicion of cysticercosis is important in patients with intramedullary cystic lesions because specific drug treatment is available. Treatment with anthelmintics, particularly albendazole, should be considered in patients with intramedullary cysticercosis before surgery. Corticosteroids may be added to the therapeutic regimen because this may reduce the perilesional edema and prevent neurologic deterioration during the course of anthelmintic treatment.

Could an aminoacridine interfere with the cellular mechanisms involved in the process of human immunodeficiency virus infection?

Immune activation and synthesis of nucleic acids participate in the course of infection by human immunodeficiency virus. Aminoacridines, formally used as antiparasitic drugs, but almost abandoned nowadays for therapeutic use, are strong deoxyribonucleic acid chemoprotectors and lysosome stabilizers. Theoretically, these actions within the cell and other peculiar pharmacological characteristics of aminoacridines, particularly quinacrine, could pose barriers to human immunodeficiency virus infection and replication.