Inhibition of cyclooxygenase-1 and cyclooxygenase-2 impairs Trypanosoma cruzi entry into cardiac cells and promotes differential modulation of the inflammatory response.

The intracellular protozoan parasite Trypanosoma cruzi is the etiologic agent of Chagas disease, a serious disorder that affects millions of people in Latin America. Cell invasion by T. cruzi and its intracellular replication are essential to the parasite's life cycle and for the development of Chagas disease. Here, we present evidence suggesting the involvement of the host's cyclooxygenase (COX) enzymes during T. cruzi invasion. Pharmacological antagonists for COX-1 (aspirin) and COX-2 (celecoxib) caused marked inhibition of T. cruzi infection when rat cardiac cells were pretreated with these nonsteroidal anti-inflammatory drugs (NSAIDs) for 60 min at 37°C before inoculation. This inhibition was associated with an increase in the production of NO and interleukin-1ß and decreased production of transforming growth factor ß (TGF-ß) by cells. Taken together, these results indicate that COX-1 more than COX-2 is involved in the regulation of anti-T. cruzi activity in cardiac cells, and they provide a better understanding of the influence of TGF-ß-interfering therapies on the innate inflammatory response to T. cruzi infection and may represent a very pertinent target for new therapeutic treatments of Chagas disease.

Molecular cloning of a Trypanosoma cruzi cell surface casein kinase II substrate, Tc-1, involved in cellular infection.

In this work, we report the cloning and characterization of the first cell surface casein kinase II (CKII) substrate (Tc-1) of Trypanosoma cruzi, the causative agent of Chagas' disease. Analysis of the gene sequence revealed a 1,653-bp open reading frame coding for 550 amino acid residues. Northern blot analysis showed a 4.5-kb transcript that is expressed in invasive trypomastigotes but not in noninvasive epimastigote forms of T. cruzi. Southern blot analysis indicates that Tc-1 is a single-copy gene. At the amino acid level, Tc-1 displayed 95% and 99% identity to two hypothetical proteins recently reported by the T. cruzi genome project. Analysis of the translated amino acid sequence indicates that the Tc-1 gene has a putative transmembrane domain with multiple cytoplasmic and extracellular CKII phosphosites. Exogenous human CKII was able to phosphorylate serine residues on both recombinant Tc-1 and Tc-1 of intact trypomastigotes. This phosphorylation was inhibited by the CKII inhibitors heparin and 4,5,6,7,-tetrabromo-2-azabenzimidazole. Immunoblots of solubilized trypomastigotes, epimastigotes, and amastigotes probed with anti-recombinant Tc-1 immunoglobulin G revealed a 62-kDa protein that is expressed only in infective trypomastigotes. Immunoprecipitation of labeled surface proteins of trypomastigotes indicated that the 62-kDa protein is a surface protein, and we found that the protein is uniformly distributed on the surface of trypomastigotes by direct immunofluorescence. Antibodies to Tc-1 effectively blocked trypomastigote invasion of host cells and consequently reduced parasite load. Preincubation of either trypomastigotes or myoblasts with CKII inhibitors blocked T. cruzi infection. Thus, for the first time, we describe a cell surface CKII substrate of a protozoan parasite that is phosphorylated by human CKII and that is involved in cellular infection.

Responsive microtubule dynamics promote cell invasion by Trypanosoma cruzi.

The American trypanosome, Trypanosoma cruzi, can invade non-phagocytic cell types by a G-protein-mediated, calcium-dependent mechanism, in which the cell's natural puncture repair mechanism is usurped in order to recruit lysosomes to the parasite/host cell junction or 'parasite synapse.' The fusion of lysosomes necessary for construction of the nascent parasitophorous vacuole is achieved by directed trafficking along microtubules. We demonstrate altered host cell microtubule dynamics during the initial stages of the entry process involving de novo microtubule polymerization from the cytoplasmic face of the parasite synapse which appears to serve as a secondary microtubule organizing centre. The net result of these dynamic changes to the host cell's microtubule cytoskeleton is the development of the necessary infrastructure for transport of lysosomes to the parasite synapse.

Effects of cannabinoid treatment on Chagas disease pathogenesis: balancing inhibition of parasite invasion and immunosuppression.

Trypanosoma cruzi invades heart cells via a calcium-dependent, G protein-mediated mechanism, leading to severe cardiac inflammation considered by some to be autoimmune in nature. Cannabinoids inhibit calcium flux and G protein signalling; as potent immunosuppressive agents, they are effective in the treatment of autoimmune disease but contraindicated for the treatment of infections. We compared the action of the synthetic cannabinoid R(+)WIN55,212 and its inactive isomer S(-)WIN55,212 on cardiac myoblast invasion: R(+)WIN55,212 inhibited invasion by over 85%. We then tested for efficacy in modulating pathogenesis in mice by assaying parasite burden in heart and blood, cellular and humoral immunity to parasite and self antigens, and mortality. R(+)WIN55,212 significantly reduced cardiac inflammation but led to considerably increased parasitaemia. Cardiac parasitosis and mortality were not significantly different in treatment and control groups. We conclude that cannabinoids can block cardiac cell puncture repair mechanisms, thereby inhibiting trypanosome invasion as predicted by the mode of drug action, but, also inhibit immune cell effector functions, offsetting the benefit of inhibition parasite cell invasion. Refined use of cannabinoids may prove therapeutic in the future, but our results raise concern about the effect of cannabis use on those chronically infected by T. cruzi and on heart cell homeostasis generally.