calpain and Anemia

The anaemia associated with visceral leishmaniasis is accompanied by altered Ca(2+) homeostasis and degradation of the cytoskeletal and integral proteins of the erythrocytic membrane. In the present study, such changes were followed in hamsters that were anaemic as the result of their experimental infection with Leishmania donovani. At each stage of the infection, the blood concentration of haemoglobin was found to be negatively correlated with the concentration of Ca(2+) (R(2) = 0.91), the percentage of erythrocytes with Heinz bodies (R(2) = 0.98) and thiol depletion (R(2) = 0.96) in the erythrocytes. Calpain (Ca(2+)-activated protease; EC 3.4.22.17) and its natural inhibitor calpastatin are known to regulate the catabolism of membrane structural proteins. Densitometric scanning of SDS-PAGE gels showed that erythrocytic membranes from infected hamsters contained less calpain and calpastatin than those from control animals. The level of calpain autolysis was found to increase as the infection progressed. The addition of purified calpain (from control hamsters) to erythrocyte ghosts caused greater degradation of the membranes of erythrocytes from infected animals than of the corresponding membranes from control animals. Calpastatin from the control hamsters was more effective, at inhibiting calpain-induced membrane proteolysis, than calpastatin from the infected animals. The results indicate that the Ca(2+)-activated protease and its inhibitor are involved in the degradation of erythrocytic membranes observed during visceral leishmaniasis.

Topics: Anemia; Animals; Calcium; Calcium-Binding Proteins; Calpain; Cricetinae; Cysteine Proteinase Inhibitors; Disease Models, Animal; Electrophoresis, Polyacrylamide Gel; Erythrocyte Membrane; Heinz Bodies; Leishmania donovani; Leishmaniasis, Visceral; Membrane Proteins; Mesocricetus; Protease Inhibitors; Sulfhydryl Compounds

A 34,000-dalton inhibitor of calpain (Ca2+-dependent cysteine proteinase) was found in the cytosol of anemic rat liver. When phenylhydrazine hydrochloride was continuously administered to rats, a 280,000-dalton calpain inhibitor that existed originally in the liver gradually disappeared within two weeks and, concomitantly, a 34,000-dalton inhibitor appeared. The purified 34,000-dalton inhibitor resembles 280,000-dalton inhibitor in that both are heat-stable proteins and do not inhibit papain and trypsin. Unlike the protomers of a 280,000-dalton inhibitor, 34,000-dalton inhibitor does not show any sign of self-association.

Topics: Anemia; Animals; Calpain; Liver; Male; Molecular Weight; Phenylhydrazines; Protease Inhibitors; Rats; Rats, Inbred Strains; Tissue Extracts