muramidase and Chagas-Disease

Lysozymes have been described in invertebrates as digestive or immune molecules. We report here the characterization of two novel c-type lysozymes, RpLys-A (EU250274) and RpLys-B (EU250275), isolated from the fat body and digestive tract of immune stimulated Rhodnius prolixus, a major vector of Chagas disease. Transcriptional profiles indicate that the temporal and spatial expression patterns of these two peptides are very different. RpLys-A is expressed predominantly in the midgut after ingestion of Trypanosoma cruzi in a bloodmeal, or after injection of bacteria into the hemocoel. RpLys-B is expressed primarily in the fat body after bacterial injection. Phylogenetic alignments indicate that RpLys-A aligns best with molecules from other hemipterans whose major expression is found in the intestinal tract whereas RpLys-B aligns best with mosquito and tick molecules whose expression is found principally in hemocytes and fat body and whose role has been described as immune-related. These data suggest a differential compartmentalized role of two closely related molecules; one for immunity in the hemocoel and the other for digestion in the midgut.

Topics: Amino Acid Sequence; Animals; Base Sequence; Chagas Disease; Escherichia coli; Feeding Behavior; Host-Parasite Interactions; Humans; Micrococcus luteus; Molecular Sequence Data; Muramidase; Phylogeny; Promoter Regions, Genetic; Rhodnius; Sequence Alignment; Sequence Analysis, DNA; Time Factors; Trypanosoma cruzi

The release of beta-glucuronidase and lysozyme from human polymorphonuclear leukocytes (PMN) engaged in phagocytosis and lysis of Trypanosoma cruzi epimastigotes was studied in the presence or absence of chagasic serum. Lysosomal enzyme release was enhanced when parasites were sensitized with serum from a chronic Chagas' patient, increased up to 3 hr of incubation at 28 C, and depended on the PMN:parasite ratio. The release of lysosomal enzymes was determined by the presence of 2 mM cyanide, 2 microM azide, 3 mM amobarbital, and 1 mM phenylbutazone. These drugs inhibited the killing of sensitized T. cruzi by interfering with the oxidative microbicidal mechanisms of PMN without affecting the uptake of the parasites. Lysosomal enzyme release occurred in the presence of cyanide and azide, indicating that in these cases the enzymatic release was unrelated to the killing of the parasites. Amobarbital and phenylbutazone, which stabilize PMN membranes, inhibited the release of beta-glucuronidase and lysozyme by PMN. The addition of 10 micrograms/ml of cytochalasin B inhibited the phagocytosis and killing of sensitized T. cruzi by PMN but increased the enzymatic release by effector cells. Since cytochalasin B did not affect the close contact between PMN and parasites, it appears that the enzymes released to the extracellular milieu were not toxic to noningested parasites. Furthermore, the lysosomal enzymes did not lyse bystander unsensitized parasites. Therefore, the release of lysosomal enzymes during the interaction of T. cruzi epimastigotes and PMN seems to be related to the triggering event of the phagocytic process and does not bear a cause-effect relationship with parasite death.

Topics: Amobarbital; Azides; Chagas Disease; Cyanides; Cytochalasin B; Glucuronidase; Humans; Muramidase; Neutrophils; Phagocytosis; Phenylbutazone; Trypanosoma cruzi