Lysosomal enzymes of phagocytes and the mechanism of their release

Changes in the metabolic activity of macrophages under the influence of tick-borne encephalitis virus

The metabolic activity of macrophages infected with tick-borne encephalitis virus (TBEV) affecting the human nervous system has been studied for the first time. The penetration and reproduction of TBEV in the macrophages stimulated their oxygen metabolism, increasing the activity of NADPH-oxidase complex, as well as the mitochondrial enzymes lactate dehydrogenase, succinate dehydrogenase, and cytochrome oxidase. A wave-like change in the activity of these enzymes in the macrophages reflected the reaction of the cells to the penetration of the virus in the first period (within 3 h) and to the synthesis of the virus particles and their exit into the extracellular space in the second period (from 5 to 48 h). In the macrophages infected with TBEV, accumulation of NO metabolites was observed. In the late period of the examination (1-4 days), the activities of superoxide dismutase and lysosomal enzymes (nonspecific esterase and acid phosphatase) were detected. Thus, the early increase in the activity of the cell enzymes indicates the activation of the macrophages, and the subsequent increase in their activity corresponds to the enhanced synthetic activity of the macrophages.

Kupffer cell functions during intestinal amoebiasis in guinea pigs

Kupffer cells play an important role in all alimentary tract infections. Their role in intestinal amoebiasis is not clear. Hence, the present study examined Kupffer cell functions--phagocytic capacity and levels of a key lysosomal enzyme, N-acetyl-beta-glucosaminidase -- in guinea pigs infected with Entamoeba histolytica intracaecally. Animals were sacrificed on days 0, 3, 7, 14 and 21 post-infection. During intestinal amoebiasis the phagocytic capacity in Kupffer cells was depressed, whereas lysosomal enzyme levels were highly elevated. Maximum alteration in Kupffer cell functions was observed on the 14th post-infection day (P less than 0.01). Animals which survived until 21 days post-infection did not show any significant (P greater than 0.05) change in their Kupffer cell functions compared with controls and day zero values. Phagocytic capacity was inversely correlated with severity of caecal lesions. In contrast, enzyme levels were directly correlated with degree of caecal lesions. Similar trends were observed in blood monocytes. The depressed phagocytic capacity of mononuclear phagocytes and the increased enzyme release by these cells accompanying intestinal amoebic infection may contribute to the establishment of the infection and the tissue damage that accompanies it.

Role of lysosomal enzymes in tissue damage during hepatic amoebiasis. An experimental study

Two key lysosomal enzymes, N-acetyl-beta-glucosaminidase and beta-glucuronidase of Kupffer cells and blood monocytes were studied in guinea pigs infected intramesenterically with E. histolytica. The animals were sacrificed on days 0, 2, 5 and 8 post-infection. The enzyme levels in the cell lysate and supernatants of both Kupffer cells and blood monocytes were significantly higher (P less than 0.01) in the infected animals compared with the controls. This increase was more marked on the 5th and 8th days post infection (P less than 0.001). The alteration in enzyme levels was higher in Kupffer cells than in blood monocytes (P less than 0.05). The enzyme levels increased exponentially with the severity of the hepatic lesions. A direct correlation was observed between the enzyme levels and the severity of the hepatic lesions (P less than 0.01). Hence, the role of lysosomal enzymes, released by activated mononuclear phagocytic cells, in the pathogenesis of hepatic amoebiasis is postulated.

Role of beta-glucuronidase, a lysosomal enzyme, in the pathogenesis of intestinal amoebiasis: an experimental study

The role of beta-glucuronidase (BG), released by blood monocytes and Kupffer cells, in the pathogenesis of intestinal amoebiasis was studied. Guinea-pigs, infected intracaecally with Entamoeba histolytica, were killed 0, 3, 7, 14 and 21 d after infection. Enhanced levels of BG were observed in the cell lysates as well as supernatants of both blood monocytes and Kupffer cells in the infected animals, from the 3rd day after infection, as compared to those in controls. The rise in BG levels was more marked on 7 and 14 d after infection (P less than 0.001). The animal which survived for 21 d had lower levels of BG, though still significantly higher than those in controls (P less than 0.05). The animals with grade IV or V caecal scoring and on the verge of death had higher levels of beta-glucuronidase. A direct correlation was observed between the enzyme levels and severity of infection. It is postulated that acid hydrolases have a role in causing tissue damage during intestinal amoebiasis.

Lysosomal enzyme activities in polymorphonuclear leukocytes, macrophages, serum, and spleen of conventional, germ-free, and antigen-free Minnesota miniature swine

The activities of lysozyme, myeloperoxidase, and elastase were lower in PMNs and AMs from GF and AF Minnesota miniature piglets than in the leukocytes from their CONV counterparts. In the spleen and serum of gnotobiotic piglets only the levels of lysozyme were slightly reduced. Substantially depressed activities of these LEs were found also in PMNs from precolostral piglets in comparison with PMNs from their CONV mother. The bisassociation of GF piglets with Enterococcus liquefaciens and Escherichia coli caused an increase of LE activities in their AMs, spleens, and sera. Fewer LEs were released after phygocytic stimulation with zymosan from PMNs of GF, AF, and precolostral piglets than from PMNs of CONV animals of the same age. These data suggest that the antigenic-microbial stimulation is important for the development of normal lysosomal enzyme activities in PMNs and AMs from gnotobiotic animals.

Lysosomal enzymes and metabolic activity of polymorphonuclear leukocytes from patients with systemic lupus erythematosus and from experimental animals after levamisole treatment

The activity of beta-D-glucuronidase (BDG) was lowered and the activity of myeloperoxidase (MPO) was elevated in polymorphonuclear leukocytes (PMNs) of SLE patients compared with normal subjects. After levamisole treatment, the activities of BDG, MPO, and lysozyme rose in PMNs of SLE patients. A higher activity of lysozyme was also observed in peritoneal PMNs of rabbits after levamisole administration. During incubation of human phagocytizing and non-phagocytizing PMNs, no effects of levamisole at concentrations of 10(-3) to 10(-5) M were observed on the release of lysosomal enzymes. These concentrations of levamisole also did not influence INT reductase activity and production of superoxide by normal human PMNs in the presence of zymosan particles. These findings suggest that levamisole might have an effect on the actual level of lysosomal enzymes in PMNs rather than on their release.

Membrane receptors on human neutrophils in oral bacterial infections

Experiments were performed to examine the function of neutrophil membrane receptors in oral bacterial infections. For this purpose, Fc and C3b receptors on human peripheral blood neutrophils and exudate neutrophils obtained from subcutaneous abscesses were studied by using the rosette-forming method.