Chagasin is a Trypanosoma cruzi protein that was recently characterized as a tight-binding inhibitor of papain-like cysteine proteases (CPs). Considering that parasite virulence and morphogenesis depend on the endogenous activity of lysosomal CPs of the cruzipain family, we sought to determine whether chagasin and cruzipain interact in the living cell. Ultrastructural studies showed that chagasin and cruzipain both localize to the Golgi complex and reservosomes (lysosome-like organelles), whereas free chagasin was found in small intracellular vesicles, suggesting that chagasin trafficking pathways might intersect with those of cruzipain. Taking advantage of the fact that sodium dodecyl sulphate and β-mercaptoethanol prevent binding between the isolated proteins but do not dismantle preformed cruzipain-chagasin complexes, we obtained direct evidence that chagasin-cruzipain complexes are indeed formed in epimastigotes. Chagasin transfectants (fourfold increase in CP inhibitory activity) displayed low rates of differentiation (metacyclogenesis) and exhibited increased resistance to a synthetic CP inhibitor. These phenotypic changes were accompanied by a drastic reduction of soluble cruzipain activity and by upregulated secretion of cruzipain-chagasin molecular complexes. Analysis of six T. cruzi strains revealed that expression levels of cruzipain and chagasin are variable, but the molar ratios are fairly stable (∼50:1) in most strains, with the exception of the G strain (5:1), which is poorly infective. On the same vein, we found that trypomastigotes overexpressing chagasin are less infective than wild-type parasites in vitro. The deficiency of chagasin overexpressers is caused by lower activity of membrane-associated CPs, because membranes recovered from wild-type trypomastigotes restored infectivity and this effect was nullified by the CP inhibitor E-64. In summary, our studies suggest that chagasin regulates the endogenous activity of CP, thus indirectly modulating proteolytic functions that are essential for parasite differentiation and invasion of mammalian cells.

The anticonvulsant activity of the racemate and enantiomers of linalool have been evaluated. Pretreatment of the mice with ( S)-(+)-, ( R)-(-)- and rac-linalool increased the latency of convulsions significantly in the PTZ model. Only rac-linalool had an effect at the dose of 200 mg/kg. The enantiomers and their racemic mixture were effective in inhibiting the convulsant effect of PTZ at the dose of 300 mg/kg. The linalools presented pharmacological activity close to that of diazepam. In the PIC seizure model, ( R)-(-)-linalool and rac-linalool presented activity at the dose of 200 mg/kg, but the rac-linalool was more potent than ( R)-(-)-linalool; ( S)-(+)-linalool had no effect at this dose. On the other hand, at the dose of 300 mg/kg this enantiomer was effective, but less potent than ( R)-(-)-linalool and rac-linalool. In the MES model, linalools decreased the convulsion time of the mice in the doses of 200 and 300 mg/kg. rac-Linalool presented maximum effect at 300 mg/kg. Surprisingly, it increased significantly the convulsion time at a dose of 100 mg/kg. Using the parameter of tonic hind convulsions, only ( R)-(-)-linalool produced protection from tonic extension at the dose of 200 mg/kg. When the (+)- and (-)-enantiomers, and rac-linalool were administered at the dose of 300 mg/kg they were also effective in preventing tonic convulsions induced by transcorneal electroshock in the animals. The (+)- and (-)-forms were equipotent and the rac-linalool was more effective than phenytoin. We have demonstrated that the two enantiomers have similar qualitative anticonvulsant activity, but show different potencies.

SummaryICP is a chagasin-family natural tight binding inhibitor of Clan CA, family C1 cysteine peptidases (CPs). We investigated the role of ICP in Trypanosoma brucei by generating bloodstream form ICP-deficient mutants (Dicp). A threefold increase in CP activity was detected in lysates of Dicp, which was restored to the levels in wild type parasites by re-expression of the gene in the null mutant. Dicp displayed slower growth in culture and increased resistance to a trypanocidal synthetic CP inhibitor. More efficient exchange of the variant surface glycoprotein (VSG) to procyclin during differentiation from bloodstream to procyclic form was observed in Dicp, a phenotype that was reversed in the presence of synthetic CP inhibitors. Furthermore, we showed that degradation of anti-VSG IgG is abolished when parasites are pretreated with synthetic CP inhibitors, and that parasites lacking ICP degrade IgG more efficiently than wild type. In addition, Dicp reached higher parasitemia than wild type parasites in infected mice, suggesting that ICP modulates parasite infectivity. Taken together, these data suggest that CPs of T. brucei bloodstream form play a role in surface coat exchange during differentiation, in the degradation of internalized IgG and in parasite infectivity, and that their function is regulated by ICP.

α,β-Epoxy-carvone (EC) is a monoterpene found in the essential oils of many species of plants. It can also be obtained by organic synthesis. EC exerts a depressant effect on the central nervous system and is also known to have anticonvulsant, antimicrobial and antioxidant effects. The present study investigated the antinociceptive and anti-inflammatory effects of EC. Intraperitoneal administration of EC at doses of 100, 200 or 300 mg/kg promoted a significant antinociceptive effect, as shown in the acetic acid-induced abdominal writhing test. EC also provoked a reduction in formalin-induced nociception in the first (300 mg/kg) and second phases (200 and 300 mg/kg). In the hot-plate test, an increase in response latency was found at 30 min (at 100, 200 and 300 mg/kg), and at 60 and 120 min (at 300 mg/kg) following administration of EC, an effect that was reversed by naloxone. Intraperitoneal administration of EC (300 mg/kg) inhibited the increased vascular permeability provoked by acetic acid. These findings suggest that EC inhibited the acute inflammatory reaction, with a pronounced peripheral and central antinociceptive effect in mice that is probably associated with activation of the opioidergic system, which appears to play a role in the antinociceptive activity induced by EC.

Chagas disease and visceral leishmaniasis are two neglected tropical diseases responsible for numerous deaths around the world. For both, current treatments are largely inadequate, resulting in a continued need for new drug discovery. As both kinetoplastid parasites are incapable of de novo purine synthesis, they depend on purine salvage pathways that allow them to acquire and process purines from the host to meet their demands. Purine nucleoside analogues therefore constitute a logical source of potential antiparasitic agents. Earlier optimization efforts of the natural product tubercidin (7deazaadenosine) involving modifications to the nucleobase 7-position and the ribofuranose 3′-position led to analogues with potent anti-Trypanosoma brucei and anti-Trypanosoma cruzi activities. In this work, we report the design and synthesis of pyrazolo [3,4-d]pyrimidine nucleosides with 3′-and 7-modifications and assess their potential as anti-Trypanosoma cruzi and antileishmanial agents. One compound was selected for in vivo evaluation in an acute Chagas disease mouse model.

We have evaluated the roles of key amino acids to the action of the natural inhibitor chagasin of papain-family cysteine peptidases. A W93A substitution decreased inhibitor affinity for human cathepsin L 100-fold, while substitutions of T31 resulted in 10–100-fold increases in the Ki for cruzipain of Trypanosoma cruzi. A T31A/T32A double mutant had increased affinity for cathepsin L but not for cruzipain, while the T31-T32 deletion drastically affected inhibition of both human and parasite peptidases. These differential effects reflect the occurrence of direct interactions between chagasin and helix 8 of cathepsin L, interactions that do not occur with cruzipain.

Five bis-arylimidamides were assayed as anti- agents by ,, and approaches. None were considered to be pan-assay interference compounds. They had a favorable pharmacokinetic landscape and were active against trypomastigotes and intracellular forms, and in combination with benznidazole, they gave no interaction. The most selective agent (28SMB032) tested led to a 40% reduction in parasitemia (0.1 mg/kg of body weight/5 days intraperitoneally) but without mortality protection. target fishing suggested DNA as the main target, but ultrastructural data did not match.

Selective sentinel lymphadenectomy dissection has been demonstrated to have high predictive value for axillary staging in breast cancer patients. Preoperative lymphoscintigraphy can localize and facilitate the harvesting of sentinel lymph nodes (SNLs) with a high success rate. The failure rate of selective sentinel lymphadenectomy ranges between 2% and 8%. Details of the failures were seldom addressed. This study analyzes the causes of failure to harvest SLNs in spite of positive preoperative lymphoscintigraphy. From November 1997 through November 2000, 201 female patients with histologically confirmed and operable breast carcinoma underwent selective sentinel lymphadenectomy at the University of California, San Francisco (UCSF) Carol Franc Buck Breast Care Center. Among these patients, 183 (91%) received preoperative lymphoscintigraphy to identify axillary lymph nodes. The causes of failure to harvest the SLNs in this group of patients despite successful preoperative lymphoscintigraphy were analyzed. In our series, the failure rate of SLN identification was 7.0% (14/201). The failure rate for our first year was 11.1% (6/54), second year 9.1% (7/77), and third year 1.4% (1/70). The incidence of failure in spite of positive preoperative lymphoscintigraphy was 3.5% (6/170). The shine-through effect of the primary injection site and failure to visualize a blue lymph node were the main reasons for technical failure. Most of these cases occurred during our learning curve of the procedure. The possibility of failure to get the SLN should be explained to patients before surgery. Axillary lymph node dissection (ALND) should be done if selective SLN dissection is not successful.