Hematological and parasitological effect of cyctein protease inhibitor on murine schistosomiasis

ABSTRACT

Cysteine protease enzyme [CP] is crucial for parasitic disease propagation, and inhibitors of such proteases are emerging with promising therapeutic uses in the treatment. This study was designed to evaluate the hematological and parasitological efficacy of one of the cysteine protease inhibitors [Sodium nitroprusside] that was administered alone as chemotherapy for murine schistosomiasis manosni in different schistosomal stages [shistosomula and mature worm]. Thirty mice were infected with 80 S. mansoni cercariae/mouse and were divided into 3 groups [10 mice each]. Group I Infected untreated mice Group II and III. Mice were intraperitoneally treated with 100 mg/kg of cysteine protease inhibitor for 10 consecutive days three and six weeks post infection. Eight weeks post infection all animals were sacrificed and subjected for assessment of cysteine protease protein expression in liver tissue samples using immunoblotting technique [Western blotting], parasitological criteria and EM examination of buffy coat bone marrow and worms. Expression of cysteine protease protein was detected at the expected molecular weight [28 kDa] in 9 of the 10 [90%] infected untreated mice. After treatment protein expression returned negative in the treated groups. A highly significant reduction in worm burden was observed in all groups treated with inhibitor in comparison to infected control group [p<0.001]. However the greatest reduction in the worm burden was observed in treated group 6 weeks post infection in comparison to 3 weeks post infection [P<0.05]. Also, treatment could reduce egg count when given early in infection or significantly decreased egg burden when given late in infection. As regards EM examination sodium nitroprusside treated mice 3 and 6 weeks post the infection revealed degenerated tegument with completely implanted and degenerated spines. In addition 6 weeks post infection treated Schistosoma mansoni male worms showed vaculation and necrosis of spermatocytes. Buffy coat examination of Schistosoma mansoni infected untreated mice showed the inability of the eosinophil to be degranulated, while both treated groups revealed degranulation. In addition the group treated six weeks post infection showed hypodense eosinophils with large number of cytoplasmic vacuoles which represent an activated phenotype. Also in latter group activated lymphocytes were detected with marked dilatation of the endoplasmic reticulum. Bone marrow examination of Schistosoma mansoni - treated mice revealed degranulated eosinophils and eosinophilic myelocytes with activated phenotype in addition to degranulated platelets. Our findings indicate that the cysteine protease secreted by the different stages S. mansoni plays a crucial role in attenuating effector functions of eosinophils as it decreases the eosinophil's responses and inhibit its activation to the parasite resulting in diminished degranulation and reduced generation of superoxide. So, it is preferable to give CPI at any time post infection, with frequent observation of platelets function and different coagulation tests