Schistosome infection-derived Hepatic Stellate Cells are cellular source of prostaglandin D₂: role in TGF-β-stimulated VEGF production

Hepatic Stellate Cells (HSCs) play a crucial role in pathogenesis of liver inflammation and fibrosis. During chronic liver injury, HSCs lose vitamin A and transform into myofibroblastic cells. In schistosomal granulomas, these activated HSCs are called GR-HSCs. Schistosomal-triggered hepatic fibrogenesis has TGF-β as the most potent fibrogenic stimulus, that also controls gene expression of the angiogenic molecule VEGF in HSCs. COX-dependent production of prostaglandins (PGs) also play role in angiogenic processes. Besides angiogenic roles, prostanoids control immunomodulation of Schistosoma mansoni infection. Specifically, schistosoma-derived PGD2 has emerged as a key parasite regulator of immune defense evasion, while no role is still established to host PGD2. Therefore, the aim of this work is to investigate the ability of GR-HSCs to synthesize COX-derived PGD2 and a potential role of this prostanoid in VEGF production by GR-HSCs in vitro. Here, we confirmed that GR-HSCs express COX-2, which displayed perinuclear localization. While unstimulated GR-HSCs produce basal levels of PGD2, TGF-β stimulation besides increasing COX2- mRNA levels, enhanced synthesis/secretion of PGD2 in GR-HSCs supernatant. Moreover, GR-HSCs-derived PGD2 mediate VEGF production by TGF-β-stimulated GR-HSCs, since the pre-treatment with HQL-79, an inhibitor of hematopoietic PGD synthase inhibited both PGD2 synthesis and VEGF secretion by TGF-β-stimulated GR-HSCs. All together, our findings show an autocrine/paracrine activity of GR-HSCs-derived PGD2 on TGF-β-induced VEGF production by GR-HSCs, unveiling a role for PGD2 as important regulator of HSCs activation in hepatic granulomas from schistosome infected mice.

Schistosome apyrase SmATPDase1, but not SmATPDase2, hydrolyses exogenous ATP and ADP

Schistosomes are parasitic worms that can live in the bloodstream of their vertebrate hosts for many years. It has been proposed that the worms impinge on host purinergic signalling by degrading proinflammatory molecules like ATP as well as prothrombotic mediators like ADP. This capability may help explain the apparent refractoriness of the worms to both immune elimination and thrombus formation. Three distinct ectoenzymes, expressed at the host-exposed surface of the worm's tegument, are proposed to be involved in the catabolism of ATP and ADP. These are alkaline phosphatase (SmAP), phosphodiesterase (SmNPP-5), and ATP diphosphohydrolase (SmATPDase1). It has recently been shown that only one of these enzymes-SmATPDase1-actually degrades exogenous ATP and ADP. However, a second ATP diphosphohydrolase homolog (SmATPDase2) is located in the tegument and has been reported to be released by the worms. It is possible that this enzyme too participates in the cleavage of exogenous nucleotide tri- and di-phosphates. To test this hypothesis, we employed RNA interference (RNAi) to suppress the expression of the schistosome SmATPDase1 and SmATPDase2 genes. We find that only SmATPDase1-suppressed parasites are significantly impaired in their ability to degrade exogenously added ATP or ADP. Suppression of SmATPDase2 does not appreciably affect the worms' ability to catabolize ATP or ADP. Furthermore, we detect no evidence for the secretion or release of an ATP-hydrolyzing activity by cultured parasites. The results confirm the role of tegumental SmATPDase1, but not SmADTPDase2, in the degradation of the exogenous proinflammatory and prothrombotic nucleotides ATP and ADP by live intravascular stages of the parasite.

Upregulation of retinal dehydrogenase 2 in alternatively activated macrophages during retinoid-dependent type-2 immunity to helminth infection in mice

Although the vitamin A metabolite retinoic acid (RA) plays a critical role in immune function, RA synthesis during infection is poorly understood. Here, we show that retinal dehydrogenases (Raldh), required for the synthesis of RA, are induced during a retinoid-dependent type-2 immune response elicited by Schistosoma mansoni infection, but not during a retinoid-independent anti-viral immune response. Vitamin A deficient mice have a selective defect in T_H2 responses to S. mansoni, but retained normal LCMV specific T_H1 responses. A combination of in situ imaging, intra-vital imaging, and sort purification revealed that alternatively activated macrophages (AAMφ) express high levels of Raldh2 during S. mansoni infection. IL-4 induces Raldh2 expression in bone marrow-derived macrophages in vitro and peritoneal macrophages in vivo. Finally, in vivo derived AAMφ have an enhanced capacity to induce Foxp3 expression in CD4+ cells through an RA dependent mechanism, especially in combination with TGF-β. The regulation of Raldh enzymes during infection is pathogen specific and reflects differential requirements for RA during effector responses. Specifically, AAMφ are an inducible source of RA synthesis during helminth infections and T_H2 responses that may be important in regulating immune responses.

Vitamin A deficiency, a major global health concern, increases morbidity and death due to infectious diseases. For vitamin A to be utilized by the immune system, it must be metabolized into retinoic acid (RA), its active form. RA is a key determinant of T cell activity. However, its contribution to protective immunity during infection is poorly understood, as is the regulation of its synthesis in this context. We examined RA synthesis by immune cells responding to helminth infection and virus infection. While intestinal T cell responses were vitamin A-dependent during both infections, only T cell responses elicited by helminth infection were vitamin A-dependent in the liver. Consistent with this finding, the enzymes necessary for RA synthesis were expressed by inflammatory cells recruited to the liver during helminth, but not virus, infection. We identified alternatively-activated macrophages as a source of RA synthesis within immune cells responding to helminth infection and find that they can induce regulatory T cells. Our findings provide a better understanding of vitamin A utilization during infection and demonstrate that RA synthesis is an inducible component of protective immunity.

Structural basis for inhibition of cathepsin B drug target from the human blood fluke, Schistosoma mansoni

Schistosomiasis caused by a parasitic blood fluke of the genus Schistosoma afflicts over 200 million people worldwide. Schistosoma mansoni cathepsin B1 (SmCB1) is a gut-associated peptidase that digests host blood proteins as a source of nutrients. It is under investigation as a drug target. To further this goal, we report three crystal structures of SmCB1 complexed with peptidomimetic inhibitors as follows: the epoxide CA074 at 1.3 Å resolution and the vinyl sulfones K11017 and K11777 at 1.8 and 2.5 Å resolutions, respectively. Interactions of the inhibitors with the subsites of the active-site cleft were evaluated by quantum chemical calculations. These data and inhibition profiling with a panel of vinyl sulfone derivatives identify key binding interactions and provide insight into the specificity of SmCB1 inhibition. Furthermore, hydrolysis profiling of SmCB1 using synthetic peptides and the natural substrate hemoglobin revealed that carboxydipeptidase activity predominates over endopeptidolysis, thereby demonstrating the contribution of the occluding loop that restricts access to the active-site cleft. Critically, the severity of phenotypes induced in the parasite by vinyl sulfone inhibitors correlated with enzyme inhibition, providing support that SmCB1 is a valuable drug target. The present structure and inhibitor interaction data provide a footing for the rational design of anti-schistosomal inhibitors.

A cyclohexanecarboxamide derivative with inhibitory effects on Schistosoma mansoni cercarial serine protease and penetration of mice skin by the parasite

A cyclohexanecarboxamide derivative, N-phenyl-N-[1-(piperidine-1-carbonyl)cyclohexyl] benzamide (MNRC-5), was evaluated for its inhibitory effects on Schistosoma mansoni cercarial serine protease activity and cercarial penetration. MNRC-5 exerted an inhibitory effect on S. mansoni cercarial serine protease at serial concentrations of the specific chromogenic substrate Boc-Val-Leu-Gly-Arg-PNA for such enzyme family and the inhibitory coefficient (Ki) value was deduced. Moreover, topical treatment of mice tails with the most potent inhibitory concentration of MNRC-5 formulated in jojoba oil successfully blocked cercarial penetration as demonstrated by a significant reduction (75%; p < 0.05) in the recovered S. mansoni worms from treated mice in comparison to control ones whose tails were painted with jojoba oil base containing no MNRC-5. In addition, the IgM and IgG reactivities to crude S. mansoni cercarial, worm and egg antigens were generally lower in sera from treated infected mice than untreated infected mice. In conclusion, we report on a new serine protease inhibitor capable for blocking penetration of host skin by S. mansoni cercariae as measured by lowering worm burden and decrease in the levels of both IgM and IgG towards different bilharzial antigens upon topical treatment.

Schistosoma mansoni arginase shares functional similarities with human orthologs but depends upon disulphide bridges for enzymatic activity

Schistosome helminths constitute a major health risk for the human population in many tropical areas. We demonstrate for the first time that several developmental stages of the human parasite Schistosoma mansoni express arginase, which is responsible for the hydrolysis of l-arginine to l-ornithine and urea. Arginase activity by alternatively activated macrophages is an essential component of the mammalian host response in schistosomiasis. However, it has not been previously shown that the parasite also expresses arginase when it is in contact with the mammalian host. After cloning and sequencing the cDNA encoding the parasite enzyme, we found that many structural features of human arginase are well conserved in the parasite ortholog. Subsequently, we discovered that S. mansoni arginase shares many similar molecular, biochemical and functional properties with both human arginase isoforms. Nevertheless, our data also reveal striking differences between human and schistosome arginase. Particularly, we found evidence that schistosome arginase activity depends upon disulphide bonds by cysteines, in contrast to human arginase. In conclusion, we report that S. mansoni arginase is well adapted to the physiological conditions that exist in the human host.

Alpha-Glutathione S-transferase and serum aminotransferases in schistosomiasis mansoni patients with or without hepatitis C virus

The present study evaluated alpha-Glutathione-S-transferase as a biochemical marker for hepatocellular damage in schistosomiasis mansoni patients, with or without chronic hepatitis C (HCV) patients as compared to controls. Alpha GST, ALT and AST were assayed in sera of GI: 20 schistosomiasis mansoni patients with HCV, GII: 16 schistosomiasis mansoni patients without HCV, GIII: 19 pure HCV patients and GIV: 20 normal controls. The results showed that alpha-Glutathione-S-transferase was less sensitive and less specific but more accurate than ALT & AST as a liver affection marker in HCV patients.

Disruption of ERK signalling in Biomphalaria glabrata defence cells by Schistosoma mansoni: implications for parasite survival in the snail host

Biomphalaria glabrata is an intermediate snail host for the human blood fluke Schistosoma mansoni. To survive in B. glabrata, S. mansoni must suppress the snail's haemocyte-mediated defence response; the molecular mechanisms by which this is achieved remain largely unknown. We report here that S. mansoni excretory-secretory products (ESPs) attenuate phosphorylation of extracellular signal-regulated kinase (ERK) in haemocytes from a B. glabrata strain susceptible to S. mansoni. Whole S. mansoni sporocysts also impair ERK signalling in these cells. In striking contrast, ERK signalling in haemocytes from a B. glabrata strain refractory to schistosome infection is unaffected by ESPs or sporocysts. Effects of ESPs on ERK are similar in the presence or absence of snail plasma, thus ESPs seem to affect haemocytes directly. These findings reveal novel schistosome interference mechanisms; as ERK regulates various haemocyte defence reactions, we propose that disruption of ERK signalling in haemocytes facilitates S. mansoni survival within susceptible B. glabrata.

Cationic amino acid transporter-2 regulates immunity by modulating arginase activity

Cationic amino acid transporters (CAT) are important regulators of NOS2 and ARG1 activity because they regulate L-arginine availability. However, their role in the development of Th1/Th2 effector functions following infection has not been investigated. Here we dissect the function of CAT2 by studying two infectious disease models characterized by the development of polarized Th1 or Th2-type responses. We show that CAT2(-/-) mice are significantly more susceptible to the Th1-inducing pathogen Toxoplasma gondii. Although T. gondii infected CAT2(-/-) mice developed stronger IFN-gamma responses, nitric oxide (NO) production was significantly impaired, which contributed to their enhanced susceptibility. In contrast, CAT2(-/-) mice infected with the Th2-inducing pathogen Schistosoma mansoni displayed no change in susceptibility to infection, although they succumbed to schistosomiasis at an accelerated rate. Granuloma formation and fibrosis, pathological features regulated by Th2 cytokines, were also exacerbated even though their Th2 response was reduced. Finally, while IL-13 blockade was highly efficacious in wild-type mice, the development of fibrosis in CAT2(-/-) mice was largely IL-13-independent. Instead, the exacerbated pathology was associated with increased arginase activity in fibroblasts and alternatively activated macrophages, both in vitro and in vivo. Thus, by controlling NOS2 and arginase activity, CAT2 functions as a potent regulator of immunity.

Activity of liver microsomal enzymes during the chronic phase of murine schistosomiasis

The effects of schistosomiasis on microsomal enzymes were studied on post-infection day 90 when accumulated damage and fibrosis are most intense but granulomatous reaction around the eggs harbored in the liver is smaller than during the earlier phases. Swiss Webster (SW) and DBA/2 mice of either sex (N = 12 per sex per group) were infected with 100 Schistosoma mansoni cercariae on postnatal day 10 and killed on post-infection day 90. Cytochrome P-450 (CYP) concentration and alkoxyresorufin-O-dealkylases (EROD, MROD, BROD, and PROD), p-nitrophenol-hydroxylase (PNPH), coumarin-7-hydroxylase (COH), and UDP-glucuronosyltransferase (UGT) activities were measured in hepatic microsomes. Age-matched mice of the same sex and strain were used as controls. In S. mansoni-infected mice, CYP1A- and 2B-mediated activities (control = 100%) were reduced in SW (EROD: male (M) 36%, female (F) 38%; MROD: M 38%, F 39%; BROD: M 46%, F 19%; PROD: M 50%, F 28%) and DBA/2 mice (EROD: M 64%, F 58%; MROD: M 60%; BROD: F 49%; PROD: M 73%) while PNPH (CYP2E1) was decreased in SW (M 31%, F 38%) but not in DBA/2 mice. COH did not differ between infected and control DBA/2 and UGT, a phase-2 enzyme, was not altered by infection. In conclusion, chronic S. mansoni infection reduced total CYP content and all CYP-mediated activities evaluated in SW mice, including those catalyzed by CYP2E1 (PNPH), CYP1A (EROD, MROD) and 2B (BROD, PROD). In DBA/2 mice, however, CYP2A5- and 2E1-mediated activities remained unchanged while total CYP content and activities mediated by other CYP isoforms were depressed during chronic schistosomiasis.

Variation in expression of Biomphalaria glabrata SOD1: a potential controlling factor in susceptibility/resistance to Schistosoma mansoni

The snail Biomphalaria glabrata kills the blood fluke Schistosoma mansoni by a mechanism involving production of hydrogen peroxide, the enzymatic product of cytosolic Cu/Zn superoxide dismutase (SOD1). This enzyme exhibits higher activity in blood cells (hemocytes) from a predominantly resistant strain of B. glabrata than in hemocytes from a susceptible strain. Additionally, B. glabrata SOD1 polymorphisms have been associated with susceptibility/resistance to the parasite. To address the hypothesis that SOD1 transcription levels differ in accordance with variation at the SOD1 locus, quantitative PCR was performed using hemocyte-derived cDNA prepared from SOD1-genotyped snails. Here we report that individuals possessing the allele previously associated with resistance to S. mansoni express significantly higher levels of hemocyte SOD1 transcripts than individuals lacking this allele. A causal relationship between SOD1 expression and susceptibility/resistance to S. mansoni is supported by the correlation of transcript quantity with data (from a previous study) on the probability of infection.

Specific inhibitors of mitogen-activated protein kinase and PI3-K pathways impair immune responses by hemocytes of trematode intermediate host snails

To characterize molecular mechanisms regulating snail cellular immune responses, the contributions of mitogen-activated protein kinases (MAPKs) and phosphatidylinositol 3-kinase (PI3-K) were examined in hemocytes of the trematode intermediate host snails Biomphalaria glabrata and Lymnaea stagnalis. Simultaneous measurement of phagocytosis/encapsulation and H2O2 production by hemocytes in the presence or absence of specific signal transduction inhibitors was used to assess the role of extracellular-signal regulated kinases 1 and 2 (ERK1/2), p38, JNK and PI3-K. Hemocyte spreading was significantly reduced in a dose-dependent manner by the ERK inhibitor, PD098059, and by wortmannin, a potent PI3-K inhibitor. The JNK inhibitor, SP600125, and the p38 kinase inhibitor, SB203580, had no effect on hemocyte spreading. Sheep red blood cell phagocytosis was significantly impaired by PD098059, SP600125, and SB203580. Hydrogen peroxide production during phagocytosis was severely inhibited by PD098059. Additionally, PD098059, but not the other inhibitors, significantly impaired the cellular encapsulation of trematode larvae and H2O2 production during encapsulation. These results suggest that MAPK and PI3-K signal transduction pathways play a pivotal role in the immune responses of snail hemocytes. PI3-K and ERK appear to strongly regulate cell motility. ERK, JNK and p38 contribute to phagocytosis-mediated signal transduction. ERK also play a major role in oxidative burst activation and the encapsulation of trematode larvae by snail hemocytes.

DRUG-METABOLIZING ENZYMES AND PRAZIQUANTEL BIOAVAILABILITY IN MICE HARBORING SCHISTOSOMA MANSONI ISOLATES OF DIFFERENT DRUG SUSCEPTIBILITIES

The level of drug-metabolizing enzymes (cytochrome P450 [CYP450] and cytochrome b5 [cyt b5]) and the bioavailability of praziquantel (PZQ) were investigated in batches of mice infected with Schistosoma mansoni displaying either a decreased susceptibility to PZQ ("EE2" and "BANL"-isolates), or a normal susceptibility to the drug ("CD" isolate). Each batch was divided into 2 groups. The first group was further subdivided into 5 subgroups. Subgroups 1 to 4 were treated 7 wk postinfection (PI) with oral PZQ at 25, 50, 100, and 200 mg/kg for 5 consecutive days, whereas the fifth subgroup was administered the vehicle only as control. Animals were perfused 9 wk PI, and worms were counted to estimate PZQ ED50. CYP450 and cyt b5 were examined in hepatic microsomes of infected untreated mice and of infected mice treated with 25 and 200 mg/ kg PZQ. The second group was given PZQ 7 wk PI and was further subdivided into 11 subgroups, killed at 2, 5, 15, 30, 60, 90, 120, 150, 180, 240, and 360 min postdosing to study pharmacokinetic parameters of PZQ. Mice harboring S. mansoni isolates having higher PZQ ED50 (170.3 mg/kg for EE2 and 249.9 mg/kg for BANL vs. 82.96 mg/kg for CD) had higher levels of CYP450 and cyt b5, a PZQ Cmax decreased by 19-30% and area under the serum concentration-time curve0-6 hr decreased by 57-74%. Data suggest that S. mansoni isolates that are less sensitive to PZQ induce a lower inhibition of hepatic drug-metabolizing enzymes, with a consequently higher metabolic transformation of PZQ.

Efficacy of Citrus reticulata and Mirazid in treatment of Schistosoma mansoni

This work has been carried out to investigate the effect of Schistosoma mansoni infection on mice livers after treatment with the ethanolic extract of Citrus reticulata root or the oleo-resin extract from Myrrh of Commiphora molmol tree (Mirazid), as a new antishistosomal drug. Marker enzymes for different cell organelles were measured; succinate dehydrogenase (SDH); lactate dehydrogenase (LDH) and its isoenzymes; glucose-6-phosphatase (G-6-Pase); acid phosphatase (AP) and 5'- nucleotidase. Liver function enzymes; aspartate aminotransferase (AST); alanine aminotransferase (ALT), and alkaline phosphatase (ALP) were also estimated. Parasitological studies through ova count and worm burden will also be taken into consideration. The results showed a marked reduction in SDH, LDH, AST, and ALT enzyme activities and a significant increase in G-6-Pase, AP, 5'- nucleotidase, and ALP after S. mansoni infection. A noticeable alteration in LDH subunits were also noticed. Treatment with C. reticulata or Mirazid improved all the previous enzyme activities with a noticeable reduction in ova count and worm burden.

Manganese superoxide dismutase from Biomphalaria glabrata

The investigation of the response of Biomphalaria glabrata snails to Echinostoma paraensei (digenea) at 2 days post-exposure by suppression subtractive hybridization yielded a partial sequence of the anti-oxidant enzyme manganese superoxide dismutase (MnSOD). Full-length MnSOD (669nt) from M line and BS-90 strains of B. glabrata differed by one synonymous nucleotide replacement. B. glabrata has 1-4 MnSOD loci (Southern hybridization). Both snail strains expressed MnSOD at equal baseline levels (quantitative PCR). Susceptible snails increased expression of MnSOD following infection with E. paraensei or Schistosoma mansoni, and expression was reduced in the incompatible combination (BS-90 B. glabrata and S. mansoni). Thus, MnSOD did not determine resistance or susceptibility for these parasites, but expression of MnSOD is consistent with its involvement in a stress response of B. glabrata.

Localization of leucine aminopeptidase in the Schistosoma mansoni eggs and in liver tissue from infected mice

Infection with Schistosoma mansoni causes hepatic granuloma formation and fibrosis in response to parasite eggs. The present work localized the leucine aminopeptidase (LAP) in S. mansoni eggs and in liver tissue sections from infected mice. Fresh eggs and livers obtained from infected hamsters were processed and stained with the L-leucine-7-amino-trifluoromethyl-coumarin specific substrate. The L-argnine-7-amino-trifluoro-methylcoumarin and Bestatin (leucine aminopeptidase inhibitor) were used to test the LAP substrate specificity and reactivity. The staining pattern for that enzyme in the egg and liver tissue reflects that the leucine aminopeptidase is a major egg constituent distributed in nearly all the egg except the spine. The control substrates confirmed the substrate broad specificity of LAP. In conclusion, the LAP enzyme is a major egg antigen and the target antigen for the antipathology vaccine development studies.

Effect of artemether alone and in combination with grapefruit juice on hepatic drug-metabolising enzymes and biochemical aspects in experimental Schistosoma mansoni

Artemether is an efficacious antimalarial drug that also displays antischistosomal properties. Grapefruit juice increases the oral availability of a variety of the CYP3A4 substrates. This study was designed to evaluate the effect of repeated administration of grapefruit juice with artemether on the hepatic activities of cytochrome P-450 (CYP450) and cytochrome b5 (cyt b5), on the serum levels of some biochemical enzymes and antischistosome efficacy. Results showed that administration of grapefruit juice alone induced more inhibition in the hepatic activities of CYP450 and cyt b5 than that produced by Schistosoma mansoni infection. Moreover, it enhanced degeneration of eggs and accelerated healing of the pathological granulomatous lesions. Treatment of S. mansoni-infected mice with artemether at a total dose of 300 mg/kg resulted in total and female worm burden reductions of 66.7 and 90.1%, respectively, hence protecting the host from damage induced by schistosome eggs. Treatment of S. mansoni-infected mice with artemether at 150 mg/kg reduced the total and female worm numbers by 43.3 and 54.4%, respectively, thus somewhat ameliorating hepatic granulomatous lesions compared with the infected untreated group. This was associated with no change in the hepatic activities of CYP450 and cyt b5 and in the serum levels of total protein, albumin, globulin and alanine aminotransferase compared with the uninfected control group. Coadministration of grapefruit juice with the lower dose (150 mg/kg) of artemether eliminated eggs and granulomatous reactions. In this group, the inhibitory effects of grapefruit juice on CYP450 and cyt b5 were apparent but serum liver enzymes were unchanged compared with the uninfected control group. Coadministration of grapefruit juice with artemether achieved complete protection of the host from damage induced by schistosomal infection.

Superoxide dismutase expression and H2O2 production by hemocytes of the trematode intermediate host Lymnaea stagnalis (Gastropoda)

Snail hemocytes mobilise ROS-generating enzymes during oxidative burst similar to those of mammalian leukocytes. We report herein the identification of an inducible Cu/Zn superoxide dismutase, which converts O2- to H2O2, in hemocytes of the pond snail Lymnaea stagnalis. The deduced amino acid sequence with all characteristic residues (His44,46,61,69,78 and 118, Asp81, Cys55/144, Arg141 and the Greek Key loop region Glu119-Leu/Val142) includes an open reading frame of 155 AA. Changes in Cu/ZnSOD gene expression induced by stimulation with Zymosan or trematode larvae were examined in a time course. Activated hemocytes significantly up-regulate Cu/ZnSOD expression during 2-48 h upon stimulation with the maximal induction at 45 min during phagocytosis and at 12 h during encapsulations. This increase in Cu/ZnSOD expression paralleled the increasing production of hydrogen peroxide by hemocytes. Thus, intracellular or extracellular targets elicit an induced expression of Cu/ZnSOD and the generation of elevated amounts of hydrogen peroxide by L. stagnalis hemocytes, reflecting a significant activation of their host defense function.

IL-13 activates a mechanism of tissue fibrosis that is completely TGF-beta independent

Fibrosis is a characteristic feature in the pathogenesis of a wide spectrum of diseases. Recently, it was suggested that IL-13-dependent fibrosis develops through a TGF-beta1 and matrix metalloproteinase-9-dependent (MMP-9) mechanism. However, the significance of this pathway in a natural disorder of fibrosis was not investigated. In this study, we examined the role of TGF-beta in IL-13-dependent liver fibrosis caused by Schistosoma mansoni infection. Infected IL-13-/- mice showed an almost complete abrogation of fibrosis despite continued and undiminished production of TGF-beta1. Although MMP-9 activity was implicated in the IL-13 pathway, MMP-9-/- mice displayed no reduction in fibrosis, even when chronically infected. To directly test the requirement for TGF-beta, studies were also performed with neutralizing anti-TGF-beta Abs, soluble antagonists (soluble TGF-betaR-Fc), and Tg mice (Smad3-/- and TGF-betaRII-Fc Tg) that have disruptions in all or part of the TGF-beta signaling cascade. In all cases, fibrosis developed normally and with kinetics similar to wild-type mice. Production of IL-13 was also unaffected. Finally, several genes, including interstitial collagens, several MMPs, and tissue inhibitors of metalloprotease-1 were up-regulated in TGF-beta1-/- mice by IL-13, demonstrating that IL-13 activates the fibrogenic machinery directly. Together, these studies provide unequivocal evidence of a pathway of fibrogenesis that is IL-13 dependent but TGF-beta1 independent, illustrating the importance of targeting IL-13 directly in the treatment of infection-induced fibrosis.

Pivotal roles of the parasite PGD2 synthase and of the host D prostanoid receptor 1 in schistosome immune evasion

Prostaglandins (PG) are important modulators of immune and inflammatory responses. We recently demonstrated that the production of PGD(2) by the helminthic parasite Schistosoma mansoni inhibits the migration of epidermal Langerhans cells (LC) to the draining lymph nodes (DLN). Here, we identify the responsible parasite enzyme as being a 28-kDa glutathione-S-transferase (termed Sm28GST). Intradermal injection of Sm28GST in wild-type (WT), but not in D prostanoid receptor (DP) 1-deficient mice abrogates the departure of LC from the epidermis after TNF-alpha or FITC treatment. During infection, DP1 deficiency restores LC migration, but does not enhance the rate of T cell proliferation in the skin DLN. However, relative to WT mice, DLN cells from DP1-deficient infected mice produce dramatically less IFN-gamma and IL-10, but equal amount of IL-4. Interestingly, infected DP1-deficient mice develop a more Th2-biased humoral immune response, a significantly reduced parasitemia and a decreased egg-induced inflammatory response in the liver and intestines. Taken together, we propose that DP1 activation by the Sm28GST-derived PGD(2) could represent a strategy for the schistosome to evade host immune defenses. We also suggest that DP1 is important in the Th1/Th2 balance of the immune response and in inflammatory reactions during infection.

[Schistosomal portal hypertension: influence of the portal blood flow in serum levels of hepatic enzymes]

AIM

To evaluate relation between the portal blood flow and the laboratory hepatic screening in patients with schistosomal portal hypertension.

PATIENTS AND METHODS

Sixty-four patients with schistosomal portal hypertension had studied, being 19 not operated, 23 submitted to esophagogastric devascularization with splenectomy and 22 submitted to distal splenorenal shunt. Evaluated the laboratory hepatic screening through the dosage of albumin, aspartate aminotransferase, alanine aminotransferase, direct bilirubin and indirect bilirubin, alkaline phosphatase, gamma-glutamil transferase and prothrombin time. The portal flow was evaluated for Doppler. The results have been analyzed through linear regression, Pearson correlation coefficient, chi-square and one-way analysis of variance with Tukey's test.

RESULTS

It was proven that only gamma-glutamil transferase had significant correlation with the portal flow. In compare of the quartiles, also only gamma-glutamil transferase showed resulted significant, it was evidenced that the fourth quartile, that is bigger portal flow and formed in its majority for patients not operated, also was bigger average of gamma-glutamil transferase and significantly bigger value than first and the third quartiles.

CONCLUSIONS

1. The portal blood flow was bigger in patients that the serum level of GGT was bigger; 2. the gamma-glutamil transferase is the variable of the hepatic screening evaluation more representative of the portal flow influence in hepatic functional activity in patients with hepatosplenic schistosomiasis, and 3. probably, the different surgeries through hemodynamics modifications, are beneficial in to diminish the degree of cholestasis or in decrease the microssomal induction.

Cloning, expression and preliminary crystallographic studies of the potential drug target purine nucleoside phosphorylase from Schistosoma mansoni

The parasite Schistosoma mansoni, unlike its mammalian hosts, lacks the de novo pathway for purine biosynthesis and depends on salvage pathways for its purine requirements. The gene encoding one enzyme of this pathway, purine nucleoside phosphorylase from S. mansoni (SmPNP) was identified, fully sequenced and cloned into the bacterial expression vector pMAL c2G to produce a protein in fusion with maltose-binding protein. The recombinant fusion protein was expressed at high levels and was purified in a single step by amylose resin affinity chromatography. After factor Xa cleavage, SmPNP was purified using a cation-exchange column and crystallized by hanging-drop vapour diffusion using polyethylene glycol 1500 as precipitant in the presence of 20% glycerol in acetate buffer. The use of the non-detergent sulfobetaine 195 (NDSB 195) as an additive had a marked effect on the size of the resulting crystals. Two data sets were obtained, one from a crystal grown in the absence of NDSB 195 and one from a crystal grown in its presence. The crystals are isomorphous and belong to the space group P2(1)2(1)2(1). It is intended to use the structures in the discovery and development of specific inhibitors of SmPNP.

Biochemical changes after subchronic and chronic interaction of Schistosoma mansoni infection in Swiss albino mice with two specific compounds

In Egypt, infection with Schistosoma mansoni (S.m.) and residues of pesticides have been considered as major environmental pollutants that adversely affect health. Effects of diazinon (DZN) and/or praziquantel (PZQ) on the levels of plasma triiodothyronine (T3), thyroxine (T4), activities of brain acetylcholinesterase (AchE) and liver alanine aminotransferase (ALT) in addition to blood reduced glutathione (GSH) in healthy and S.m. infected mice were investigated after 9 and 17 weeks of either infection or intoxication with DZN. Triiodothyronine showed significant differences among the different treatments. The group of mice treated with PZQ showed the highest levels of T3 at both time intervals. Thyroxine level showed significant differences between the two time intervals. The lowest levels of T4 were observed in the infected-PZQ group at week 17. The maximum inhibition of brain AchE activity was noticed in DZN-PZQ treated group after 9 and 17 weeks. The different treatments significantly reduced the activities of liver ALT. The highest decrease was recorded in the infected-DZN-PZQ group at week 9. All treatments significantly lowered the levels of blood GSH after 9 weeks.

Changes in the expression of cytochrome P450 isozymes and related carcinogen metabolizing enzyme activities in Schistosoma mansoni-infected mice

Mixed-function oxidase enzymes metabolize most xenobiotic agents. Western blotting was used to investigate the effect of Schistosoma mansoni infection on the expression of various cytochrome P450 (CYP) isozymes and specific enzyme assays to study related metabolic functions in mouse liver microsomes. Male BK-TO mice were infected with 200 cercariae per mouse and their livers were assayed at 6, 15, 30 and 45 days post-infection (p.i.) and compared with appropriately matched controls. The expression of each of the CYP isozymes (1A1, 2B1/2, 2C6, and 4A) was either unaffected or transiently increased up to 30 days post-infection. By 45 days, a significant loss of signal was observed, particularly for CYP 1A1 and 2B1 /2 where no signal could be detected. Evidence supporting these findings was obtained from enzyme assays specific for particular CYP isozymes. The activity of ethoxyresorufin O-deethylase (CYP 1A1) was reduced by 97% and that of pentoxyresorufin O-depentylase (CYP 2B1 /2) by 96% at 45 days p.i. Similarly, the activity of ethoxycoumarin hydroxylase was progressively reduced over the period under study. It is believed that N-nitrosamines are activated principally by N-nitrosodimethylamine N-demethylase I which was significantly increased at both 30 and 45 days p.i. To further investigate metabolic competency following S. mansoni infection, the in vitro binding of benzo(a)pyrene metabolites to DNA was measured, using isolated liver microsomes to activate benzo(a)pyrene. Benzo(a)-pyrene-DNA adduct formation was markedly increased at 6,15 and 30 days with a maximum at 15 days, but decreased at 45 days p.i. It was concluded that S. mansoni infection changes the expression of different CYP isozymes and also the activity of phase I drug-metabolizing enzymes at different periods of infection and may thus change the liver's capacity to activate or detoxify many endogenous and exogenous compounds. Such alterations may also change the therapeutic actions of drugs that are primarily metabolized by the P450 system, when administered to patients with schistosomiasis.

Effects of carnosine on bilharzial infestation in hamsters: biochemical and histochemical studies

We tested the ability of carnosine to improve some liver disorders induced by Schistosoma mansoni parasite in hamsters (Mesocricetus auratus). Results indicate that parasitic infestation induced elevation in serum alkaline phosphatase, gamma-glutamyl transferase, aspartate aminotransferase and procollagen III peptide as a marker of liver fibrosis. Administration of carnosine (10 mg/day) for 15 days either concurrent with infection, 2 and 4 weeks post-infestation was effective in reducing differential worm burden. It was also effective in renormalizing blood glucose level depending on the time course. The most evident effect of carnosine was on serum procollagen III peptide level, which was lowered in infested groups treated with carnosine. Histopathological studies confirmed the potential use of carnosine for intervention in schistosomiasis.

[Serum gamma-glutamyltransferase alteration in hepatic schistosomiasis doesn't correlate with parasitic load and precedes ultrasound alterations]

BACKGROUND

Liver disorders are the major manifestations of schistosomiasis mansoni. Factors that account for increased concentrations of cholestasis-indicating enzymes in the hepatosplenic form of the disease are unknown.

OBJECTIVE

To assess the correlation between increased gamma-glutamyltransferase serum levels and both the parasitic load and ultrasound alterations in patients with schistosomiasis.

PATIENTS AND METHODS

Twenty-five patients with the chronic form of schistosomiasis were assessed for the presence or absence of increased enzymatic levels, for the parasitic load (low x medium/high) and for ultrasound parameters. Furthermore, analysis of prothrombin time and a platelet count were performed.

RESULTS

Of the 25 patients, 13 showed increased gamma-glutamyltransferase plasma levels. No significant correlation was found between increased gamma-glutamyltransferase levels and the parasitic load, or between increased enzyme levels and ultrasound alterations. Nor did the prothrombin index or the platelet count differ between the two groups (normal gamma-glutamyltransferase levels and increased gamma-glutamyltransferase levels).

CONCLUSION

The parasitic load explains no rise in gamma-glutamyltransferase plasma levels in patients with the chronic form of schistosomiasis, and conventional ultrasound is not a sensitive method to detect the alteration suggested by the increased enzyme level in those patients.

The effect of Nigella sativa oil against the liver damage induced by Schistosoma mansoni infection in mice

It has been reported that Nigella sativa oil possesses anticestode and antinematode actions. Besides, it produced a hepatoprotective effect in some models of liver toxicity. Therefore, our aim in this work was to study the effect of the Nigella oil (N.O) on Schistosomiasis mansoni infected mice. The oil was given in two dose levels (2.5 and 5 ml/kg, orally for two weeks) either alone or in combination with praziquantel (PZQ), the drug of choice for the treatment of schistosomiasis. Three aspects of drug action were investigated, the effect on Schistosomiasis mansoni infection, the effect on liver functions, and on redox state. The parasitological investigation included worm distribution, oogram pattern and ova count. Furthermore, liver granuloma diameters were measured. The biochemical parameters were the serum level of L-alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), alkaline phosphatase (AP), albumin (Alb) and total protein. Moreover, to assess the antioxidant capability of the Nigella oil, four parameters were studied, viz., liver lipid peroxide (LPD) and reduced glutathione (GSH) contents and the activity of the defence enzyme superoxide dismutase (SOD) and lactate dehydrogenase (LDH). When the oil was given alone, it reduced the number of S. mansoni worms in the liver and decreased the total number of ova deposited in both the liver and the intestine. Furthermore, it increased the number of dead ova in the intestinal wall and reduced the granuloma diameters markedly. When N.O was administered in combination with PZQ, the most prominent effect was a further lowering in the dead ova number over that produced by PZQ alone. Concerning the biochemical parameters, infection of mice with S. mansoni produced a pronounced elevation in the serum activity of ALT, GGT, with a slight increase in AP level. However, it tended to reduce serum albumin level. These changes were accompanied with an alteration in the liver contents of LPD and GSH along with a significant decline in the activity of the cytosolic SOD and LDH. Administration of Nigella sativa oil succeeded partially to correct the previous changes in ALT, GGT, AP activity, as well as the Alb content in serum. However, it failed in the liver to restore either LPD and GSH content or LDH and SOD activities to normal level. These results suggest that Nigella sativa oil may play a role against the alterations caused by S. mansoni infection, an effect which may be induced partly by improving the immunological host system and to some extent with its antioxidant effect.

Regulation of hepatic fibrosis and extracellular matrix genes by the th response: new insight into the role of tissue inhibitors of matrix metalloproteinases

Hepatic fibrosis is the hallmark of Schistosoma mansoni infection and often results in portal hypertension and bleeding from esophageal varices. The fibrotic process is highly dependent on type 2 cytokines, yet their role in the regulation of extracellular matrix remodeling genes remains largely unknown. Here, we examined the expression of matrix metalloproteases (MMP) -2, -3, -9, -12, and -13 and their inhibitors, tissue inhibitor of metalloproteases (TIMP) -1, -2, and -3, in the livers of infected mice and correlated their expression profiles with fibrosis and type 2 cytokine production. Expression of MMP-2, -3, -9, -12, and -13 and of TIMP-1 and -2 mRNA rapidly increased at the onset of egg laying in infected mice, while TIMP-3 was unchanged. Because TIMP are presumed to be important regulators of the extracellular matrix, and their expression correlated with the development of fibrosis, we studied their role in fibrogenesis by infecting TIMP-1- and TIMP-2-deficient mice. Strikingly, our data revealed no role for TIMP-1 or -2 in the fibrotic pathology induced by S. mansoni eggs. Because of these findings, we infected IL-10/IFN-gamma-deficient mice that develop an exaggerated fibrotic response to determine whether changes in type 2 cytokine dominance influence the pattern of MMP and TIMP expression. Fibrosis and type 2 cytokine production correlated with increased MMP-2/MMP-9 vs TIMP-1/TIMP-2 expression. These data, in addition to our knockout studies, demonstrate that TIMP-1/TIMP-2 play no essential role in fibrogenesis in schistosomiasis. Indeed, our findings suggest that inhibiting profibrotic cytokines or specific MMP may be a more effective strategy to ameliorate fibrotic pathology.

Differential regulation of nitric oxide synthase-2 and arginase-1 by type 1/type 2 cytokines in vivo: granulomatous pathology is shaped by the pattern of L-arginine metabolism

Type 2 cytokines regulate fibrotic liver pathology in mice infected with Schistosoma mansoni. Switching the immune response to a type 1-dominant reaction has proven highly effective at reducing the pathologic response. Activation of NOS-2 is critical, because type 1-deviated/NO synthase 2 (NOS-2)-deficient mice completely fail to control their response. Here, we demonstrate the differential regulation of NOS-2 and arginase type 1 (Arg-1) by type 1/type 2 cytokines in vivo and for the first time show a critical role for arginase in the pathogenesis of schistosomiasis. Using cytokine-deficient mice and two granuloma models, we show that induction of Arg-1 is type 2 cytokine dependent. Schistosome eggs induce Arg-1, while Mycobacterium avium-infected mice develop a dominant NOS-2 response. IFN-gamma suppresses Arg-1 activity, because type 1 polarized IL-4/IL-10-deficient, IL-4/IL-13-deficient, and egg/IL-12-sensitized animals fail to up-regulate Arg-1 following egg exposure. Notably, granuloma size decreases in these type-1-deviated/Arg-1-unresponsive mice, suggesting an important regulatory role for Arg-1 in schistosome egg-induced pathology. To test this hypothesis, we administered difluoromethylornithine to block ornithine-aminodecarboxylase, which uses the product of arginine metabolism, L-ornithine, to generate polyamines. Strikingly, granuloma size and hepatic fibrosis increased in the ornithine-aminodecarboxylase-inhibited mice. Furthermore, we show that type 2 cytokine-stimulated macrophages produce proline under strict arginase control. Together, these data reveal an important regulatory role for the arginase biosynthetic pathway in the regulation of inflammation and demonstrate that differential activation of Arg-1/NOS-2 is a critical determinant in the pathogenesis of granuloma formation.

Infection induces antibodies against the cercarial secretions, but not against the cercarial elastases of Schistosoma mansoni, Schistosoma haematobium, Schistosoma japonicum and Trichobilharzia ocellata

Cercarial secretions from different species of the parasite Schistosoma and from Trichobilharzia ocellata contain a proteolytic activity, cercarial elastase, which was demonstrated by a 30 kDa band in gelatin gels. Sera of patients infected with Schistosoma mansoni, Schistosoma haematobium or Schistosoma japonicum contain immunoglobulin G which react in ELISA with cercarial secretions from all schistosomes and cross-react among the different parasite species. In Western blots, however, infection sera from patients, as well as heavily infected mice or rabbits, did not react with a 30-kDa protein. Moreover, when sections from infected snails (Biomphalaria, Bulinus and Lymnaea) were analysed by immunofluorescence using the same infection sera, only the tegument of the developing cercariae was recognized, but not the acetabular glands. In contrast, when antisera against purified cercarial elastase from either S. mansoni or S. haematobium were tested with sections of infected Biomphalaria or Bulinus, fluorescence was strong in the preacetabular glands of the cercariae of either species, but undetectable with the tegument. Cross-reactivity of both antisera extended to T. ocellata-infected Lymnaea, but not to S. japonicum-infected Oncomelania. In conclusion, although immunization with purified cercarial elastase results in antibody production, the enzyme does not induce an apparent antibody response following natural infection.

Signal transduction events in human peripheral blood mononuclear cells stimulated by Schistosoma mansoni antigens

Activation of protein tyrosine kinases (PTKs) is a common step of T cell stimulation. However, the relationship between PTKs and activation of peripheral blood mononuclear cells (PBMC) from intestinal chronic schistosomiasis patients has not been explored yet. In this study, we investigated the participation of Lck and ZAP-70 protein tyrosine kinases (PTKs), as well as PLC-gamma1 and Shc proteins in PBMC activation by Schistosoma mansoni antigens. PBMC were stimulated with SEA (soluble egg antigen) or SWAP (soluble worm preparation), lysed, precipitated with specific antibodies and the level of tyrosine phosphorylation evaluated. Our results show that Lck and Shc were phosphorylated upon stimulation of the cells with SWAP, as well as with SEA. However, the phosphorylation level was more pronounced in SWAP than in SEA-stimulated cells. Phosphorylation of ZAP-70 was observed only in SWAP stimulated cells. Additionally, PLC-gamma1 phosphorylation was not observed in PBMC stimulated with SEA. Together, these results indicate that SEA and SWAP induce PBMC proliferation through distinct intracellular signaling pathways. Moreover, the weaker response of PBMC to SEA compared to SWAP stimulation suggests down-regulation of cells from intestinal chronic schistosomiasis patients to SEA, which may occur during immunomodulation to S. mansoni response.

Arginase expression in peritoneal macrophages and increase in circulating polyamine levels in mice infected with Schistosoma mansoni

We investigated the nitric oxide (NO) synthase and arginase pathways in resident peritoneal macrophages of mice infected with the tropical parasite Schistosoma mansoni. The two enzymes may have opposite effects, insofar as NO may be involved in the killing of the parasite whereas arginase may stimulate parasite growth via polyamine synthesis. We determined the effects of the infection on the expression and activity of the two enzymes in macrophages, before and after cytokine activation. Cells from infected mice expressed the hepatic type I arginase, whereas in control cells, the enzyme was expressed only after cytokine activation, as were NO synthase II and type II arginase in both groups of cells. Moreover, we found that in infected mice, arginase expression in macrophages was associated with a ten fold increase in the concentration of circulating ornithine-derived polyamines. This may be of pathological importance, since parasitic helminths are though to be dependent on their hosts for the uptake and interconversion of polyamines.

Effect of praziquantel treatment on the activities of some liver microsomal enzymes in mice infected with Schistosoma mansoni

One of the most commonly used drugs for clinical management of schistosomiasis is praziquantel (PZQ, CAS 55268-74-1). Now, PZQ is recognized, world wide, as a powerful therapeutic agent for the control of schistosomiasis. Previous studies have shown decreased activities of some of the microsomal drug-metabolizing enzymes in the livers of S. mansoni-infected mice. Consequently, this work was initiated in order to investigate the effect of PZQ treatment (in a total dose of 1000 mg/kg given on two consecutive days each of 500 mg/kg body weight) administered to mice with or without previous S. mansoni infection on selected liver microsomal drug-metabolizing enzymes. The effect of these factors on liver function was also studied. The drug was given orally seven weeks after infection with 80 Egyptian strains of S. mansoni cercariae/mouse. The activities of aminopyrine-N-demethylase, aniline hydroxylase and the hepatic glutathione content as well as the concentrations of gamma-glutamyl transferase were measured after different time intervals following the second dose of PZQ treatment. The results indicated a meaningful decrease in the activities of aminopyrine-N-demethylase and aniline hydroxylase and a high elevation in the concentrations of gamma-glutamyl transferase and the contents of hepatocellular glutathione in mice infected with S. mansoni compared with their corresponding control groups. After two weeks following the praziquantel treatment, there was an improvement in the activities of these enzymes towards the control values. Collectively, the present findings point to the importance of initiating more studies in this discipline and careful deliberation of results in order to fully understand the possible interactions of antibilharzial drugs with the liver microsomal drug-metabolizing enzymes.

Effect of Schistosoma mansoni infection and treatment on drug metabolizing enzymes

The effect of Schistosoma mansoni infection on drug-metabolizing enzymes was investigated before and after treatment of S. mansoni-infected male albino mice with the antibilharzial drug praziquantel (CAS 55268-74-1). The drug was given in a total dose of 1000 mg/kg, and was administered at 500 mg/kg of body weight for two consecutive days each of 500 mg/kg of body weight. The drug was given 49 days after infection with 80 Egyptian strains of S. mansoni cercariae/mouse. The hepatic content of cytochrome P-450, cytochrome b-5 and NADPH cytochrome P-450 reductase were determined at 4, 8, 24, 72 h, one and two weeks after the second dose of treatment. The enzymes were determined in the microsomal fraction after homogenization and ultracentrifugation at 105,000 x g. The results indicate a marked decrease of most enzymes in the infected groups compared to normal controls. Two weeks after treatment there was an improvement of the level of most enzymes towards the normal values. The levels of liver function tests were also improved. Concerning the oogram pattern, there was a rapid change even after 8 h after the second dose of treatment. It was concluded that the antibilharzial drug could be considered as a safe drug with a rapid onset of action.

Recombinant expression and localization of Schistosoma mansoni cathepsin L1 support its role in the degradation of host hemoglobin

Cysteine proteinases expressed by schistosomes appear to play key roles in the digestion of host hemoglobin, the principal source of amino acid nutrients utilized by these parasites. We have shown previously that the predominant cysteine proteinase activity in soluble extracts and excretory/secretory (ES) products of adults of Schistosoma mansoni and S. japonicum is cathepsin L-like in its substrate specificity. However, biochemical analysis of the cathepsin L activity in extracts and ES products of schistosomes has been complicated by the presence of at least two distinct forms of schistosome cathepsin L, termed SmCL1 and SmCL2. We now report the purification and enzyme characteristics of active, recombinant SmCL1 which was obtained by transforming Saccharomyces cerevisiae with an expression plasmid encoding the preproenzyme of SmCL1. Recombinant SmCL1 was secreted by the transformed yeast into the culture media from which it was purified by gel filtration and ion-exchange chromatography. The purified enzyme exhibited substrate specificity against synthetic peptidyl substrates (e.g., Boc-Val-Leu-Lys-NHMec and Z-Phe-Arg-NHMec; kcat/Km = 17.25 and 6.24 mM-1 s-1, respectively) and against gelatin and hemoglobin, characteristic of cathepsin L. Immunoblot analysis using antiserum raised against recombinant SmCL1 demonstrated that native SmCL1 of 33 kDa was present in ES products and soluble extracts of S. mansoni. Using this antiserum and thin tissue sections, we localized the native SmCL1 to the gastrodermis and to the tegument of adult schistosomes. Recombinant SmCL1 was capable of degrading human hemoglobin at pH 4.0 to 4.5 but not higher, suggesting that denaturation of hemoglobin by low pH, as found in the cecum of the adult schistosome, may be necessary for its catalysis by cathepsin L and other gut-associated proteinases. Together, these results support a role for SmCL1 in the degradation of host hemoglobin within the gut of the schistosome.

Different levels of Schistosoma mansoni infection induce changes in drug-metabolizing enzymes

Most carcinogens and xenobiotics are metabolized primarily by the mixed function oxidase system which includes cytochrome P450, cytochrome b5, NADPH-cytochrome c reductase and aryl hydrocarbon [benzo(a)pyrene] hydroxylase. The present study investigates the influence of infection with different levels of Schistosoma mansoni cercariae on the hepatic levels of reduced glutathione, glutathione S-transferase and glutathione reductase in addition to the enzymes of mixed function oxidase. Cercariae infection levels of 60, 120, 180, 300 and 600 per mouse increased: (i) the hepatic content of cytochrome P450 by 27%, 38%, 72%, 57%, 48% respectively; (ii) the aryl hydrocarbon hydroxylase activity by 44%, 64%, 76%, 90%, 51% respectively; and (iii) the hepatic level of reduced glutathione by 67%, 83%, 103%, 60%, 38% respectively. The cytochrome b5 content did not change at the lowest level of infection but increased at the other four levels by 45%, 76%, 49% and 38% respectively. The activity of glutathione S-transferase increased at the first three levels by 42%, 40%, 27% respectively and decreased at the last two levels by 28% and 52% respectively. On the other hand, the activity of glutathione reductase did not change at any level, whereas, NADPH-cytochrome c reductase activity decreased at the last two levels by 44% and 54%. The alterations in the activities of phase I & II of drug-metabolizing enzymes as a result of infection with different levels of S. mansoni may thus change the liver's capacity to detoxify many endogenous compounds and may also potentiate the deleterious effects of aromatic hydrocarbons, e.g. benzo(a)pyrene, upon the liver and probably other organs. Such alterations may also change the therapeutic actions of drugs that are primarily metabolized by the P450 system, when administered to patients with schistosomiasis.

Characterization of mouse mast cell protease-8, the first member of a novel subfamily of mouse mast cell serine proteases, distinct from both the classical chymases and tryptases

Using a recently developed PCR-based strategy, a cDNA encoding a novel mouse mast cell (MC) serine protease (MMCP-8) was isolated and characterized. The MMCP-8 mRNA contains an open reading frame of 247 amino acids (aa), divided into a signal sequence of 18 aa followed by a 2-aa activation peptide (Gly-Glu) and a mature protease of 227 aa. The mature protease has an M(r) of 25072, excluding post-translational modifications, a net positive charge of +12 and six potential N-glycosylation sites. MMCP-8 showed a high degree of homology with mouse granzyme B in the critical regions for determining substrate cleavage specificity, indicating that MMCP-8, similar to granzyme B, preferentially cleaves after Asp residues. A comparative analysis of the aa sequence of MMCP-8 with other hematopoietic serine proteases shows that it is more closely related to cathepsin G and T cell granzymes than to the MC chymases. We therefore conclude that MMCP-8 belongs to a novel subfamily of mouse MC proteases distinct from both the classical chymases and tryptases. Southern blot analysis of BALB/c genomic DNA indicated that only one MMCP-8 gene (or MMCP-8 like gene) is present in the mouse genome. Northern blot analysis of rodent hematopoietic cell lines revealed high levels of MMCP-8 mRNA in a mouse connective tissue MC-like tumor line. However, MMCP-8 mRNA could not be detected in mouse liver, intestine, lung or ears, indicating very low expression in normal tissues. Analysis of the expression of different MMCP in the tissues of Schistosoma mansoni-infected BALB/c mice showed a strong increase in MMCP-8 levels in the lungs but not in the intestines of infected animals, suggesting the presence of a novel subpopulation of MC in the lungs that expressed MMCP-8, either alone or in combination with MMCP-5 and carboxypeptidase A. The dramatic increase in MMCP-1 and MMCP-2 levels but not of MMCP-8 in the intestines of parasitized animals also shows that MMCP-8 is not expressed in mucosal MC in the mouse. This latter is in clear contrast to what has been observed in the rat where the MMCP-8 homologues, RMCP-8, -9 and -10, can be considered as true mucosal MC proteases.

The effect of dimethylnitrosamine on the activities of renal prenolsulfotransferase and arylsulfatases A and B in Schistosona mansoni infected mice

The activities of renal phenolsulfotransferase and arylsulfatases A and B were estimated in 400 male Swiss albino mice classified into four groups: Normal controls, Schistosoma mansoni infected group, Dimethylnitrosamine (DMN) treated group and infected treated group. The activity levels of the studied enzymes were significantly increased in all groups when compared with the control group, also the statistical analyses showed a high significant increase of the three enzymes levels in the infected treated group; when compared separately with treated or infected groups. It was concluded, therefore, that schistosomal infection is implicated in the development of kidney cancer which may arise from the pattern of hepatic mixed-function oxidase induction characterized for schistosomiasis and its temporal relationship with the procarcinogenic initiating events. Furthermore, the striking significant increase in the enzymatic activity levels of the acid hydrolases arylsulfatases due to the lesion of both cytotoxic effects of dimethylnitrosamine as well as pathological change of schistosomiasis which may play an active role in the initiation of the malignant process by detoxifying endogenous sulfated aromatic metabolites.

Schistosoma mansoni cercariae: stimulation of acetabular gland secretion is adapted to the chemical composition of mammalian skin

The chemical signals of mammalian skin that stimulate the secretion of acetabular gland contents of Schistosoma mansoni cercariae were determined by exposing cercariae to fractions of human and pig skin surface obtained by thin-layer chromatography. Postacetabular gland secretion was stimulated by hydrophilic skin extracts but was often combined with a secretion of preacetabular glands. Secretion of preacetabular glands, which contain enzymes for skin lysis, could be selectively stimulated with skin surface lipids. Two different mechanisms of lipid-stimulated preacetabular gland release could be distinguished. First, secretion in combination with penetration behavior and probably tegument transformation was stimulated by the fraction of free fatty acids. Second, secretion independent of penetration behavior and tegument transformation was exclusively stimulated by glucosylceramides and phospholipids, probably phosphatidylcholines. The secretion mechanisms seem to allow a continuous lysis of epidermal macromolecules during the skin passage of the cercariae. Free fatty acids occur in the uppermost skin layers and may stimulate the combination of the first response; phospholipids and glucosylceramides are restricted to deeper epidermal layers and may stimulate the enzyme secretion there. An active preacetabular gland release was also stimulated by toxic chemicals, which could suggest an emergency penetration program for impaired cercariae.

Evaluation of alkaline phosphatase immunoassay and comparison with other diagnostic methods in areas of low transmission of schistosomiasis

The alkaline phosphatase immunoassay (APIA) is an antibody detection technique which permits the diagnosis of schistosomiasis using a butanolic extract preparation from adult worms. APIA has demonstrated high sensitivity and specificity in previous reports with well characterized human sera. Its potential as a diagnostic tool for epidemiological surveillance was assessed in comparison with three other diagnostic tests: stool examination, ELISA with soluble egg antigen (SEA) and the circumoval precipitin test (COPT). APIA was 100% specific in an area without Schistosoma mansoni transmission and had 89% sensitivity in an endemic area where 69% of the infected subjects excreted less than 100 eggs g of faeces. It was found to be less sensitive in children under 5 years of age who were positive by the COPT test. APIA can be applied as an initial screening test, based on its high sensitivity, specificity, absence of cross-reactivity with intestinal parasites and the fact that it is a technique suitable for use in epidemiological surveillance.

Effect of schistosomal infection and its treatment on some key enzymes of glucose metabolism in mice livers

Three antischistosomal drugs, praziquantel (CAS 55268-74-1, EMBAY 8440, Prz), oxamniquine (CAS 21738-42-1, Oxa) and oltipraz (CAS 64224-21-1, Olt) were examined for their ability to reverse the disturbances in carbohydrate metabolism induced by Schistosoma mansoni (S. mansoni) infection. The infected mice were screened every 2 weeks for 16 weeks for their body and liver weights in addition to assessment of the activities of liver pyruvate kinase (PK), phosphofructokinase (PFK) (glycolysis), citrate synthase (CS) (Krebs' cycle) glycogen phosphorylase (GP) (glycogenolysis), glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) (hexose monophosphate shunt). Results of the study showed that infection with S. mansoni caused the following changes in mice livers: 1. significant increase in liver weights from the 6th week of infection, which coincided with schistosomal egg deposition, whereas body weights were reduced, 2. remarkable increase in the activities of PK and PFK from the 4th week of infection, 3. marked reduction in CS, GP, G6PDH and 6PGDH. These results lead to the conclusion that glycolysis is largely stimulated in the livers of infected mice on the expense of other metabolic pathways of glucose utilization. Administration of Prz to infected mice caused normalization of all measured enzyme activities almost from the 2nd week of infection, whereas liver and body weights were improved from the 10th week. Oxa was less effective in these regards while Olt was the least. These data support the selection of Prz as a drug of choice for S. mansoni infection.

Stem cell factor dependent hyperplasia of mucosal-type mast cells but not eosinophils in Schistosoma mansoni-infected rats

Stem cell factor (SCF) is a growth factor with multiple activities which acts on numerous cell types including primordial germ cells, haemopoietic stem cells, melanocytes and mast cells. SCF is critical for the development of the mast cell hyperplasia associated with infection with the intestinal parasites Nippostrongylus brasiliensis and Trichinella spiralis. In the present study we have assessed the role of SCF in the mast cell and eosinophil responses to Schistosoma mansoni in the rat by blocking its effects in vivo with polyclonal antibody to SCF. Rats treated with sheep anti-SCF antibody on days 21, 24, 27 and 30 of infection with S. mansoni showed a rapid decrease in serum concentrations of the mucosal mast cell-associated protease rat mast cell protease II (RMCP II) by day 24, compared with normal sheep IgG-treated controls. Similarly, the number of mucosal mast cells and RMCP II levels in both small intestine and liver were also significantly reduced by day 32 of infection. In contrast with the depeletion of mast cells and mast cell proteases, eosinophil numbers in liver or intestine did not change significantly after anti-SCF treatment compared with controls. These results confirm that mast cell survival and hyperplasia are dependent on the presence of SCF whilst demonstrating that the eosinophil recruitment to liver and intestine associated with S. mansoni infection is SCF-independent.

Circulating enzyme activities of collagen turnover and undulin in patients with various degrees of schistosomiasis and alcoholic liver cirrhosis

In contrast to alcoholic liver disease, schistosomiasis leads to presinusoidal hepatic fibrosis, which determines the prognosis of the disease. Since conventional liver function tests and liver biopsy provide little information about the dynamics of the fibrotic process, we measured the activities of two circulating enzymes of collagen turnover, namely serum galactosylhydroxylysyl-glucosyl-transferase and plasma prolidase activity, together with undulin, a novel extracellular matrix glycoprotein. The study encompassed 15 healthy control subjects. 69 patients with various stages of Schistosoma mansoni/hematobium infection [28 with early active infection and no organ involvement, 27 with hepatosplenic involvement, and 14 with complications of portal hypertension] and 16 patients with alcoholic liver cirrhosis. Liver biopsies were obtained from 30 schistosomal patients for histopathological grading. Serum galactosylhydroxylysyl-glucosyl-transferase was significantly increased in all clinical stages of schistosomiasis (p < 0.05), but normal in alcoholic cirrhosis. In contrast, plasma prolidase activity showed a significant increase only in early schistosomiasis (p < 0.01), but dropped to subnormal levels in advanced stages (p < 0.001). Undulin was highly elevated both in alcoholic patients and in all schistosomal groups (p < 0.001), and was capable of distinguishing between early and advanced schistosomal stages. We conclude that serum undulin may be a valuable non-invasive parameter for monitoring the course of schistosomal and alcoholic liver disease.

[Immunological aspects of the phenoloxidase enzymatic system of Schistosoma mansoni]

The phenol oxidase enzymatic system (EC 1.10.3.1, EC 1.10.3.2) is widespread in different species of the animal and vegetal kingdom. Despite its importance in the eggshell formation of the trematodes phenol oxidase (PO) has been little studied in these organisms, mainly in S. mansoni. This report presents the initial results concerning the immunization of rabbits with PO of S. mansoni and mushroom tyrosinase. The immunological analysis done by means of double immunodifusion (Ouchterlony) and immunoelectrophoresis techniques revealed some immunological identity between the PO of males and females. It was not seen cross reaction between the antisera against PO and tyrosinase, what suggests that the antigenic determinants of both enzymes are different in spite of their catalytic sites being similar, since they act over the same substrate. The results reported here represent a first step in way to obtain the PO isoenzymes in their pure form and should open new insights for further studies on the molecular mechanisms involved in the sclerotization process of the S. mansoni eggshell.

Lysyl oxidase cDNA of myofibroblast from mouse fibrotic liver

In order to study the regulation of lysyl oxydase (LO) in fibrosis, mRNAs were extracted from an enriched population of myofibroblasts (MF) isolated from liver of schistosomiasis infected mouse. Four mRNAs (5.5kb, 4.5kb, 2.4kb and 2.0kb) hybridizing with a LO cDNA probe were transcribed in fibrotic liver, but only the two largest mRNAs were found in MF. A cDNA library was constructed, allowing the cloning of twenty four cDNAs. The largest clone of 4689bp should correspond to the 5.5kb mRNA. Its sequence was essentially similar to the NIH-3T3 fibroblasts LO-ras recision gene (rrg4) cDNA, with the same exon/intron structure, but with some differences at the sites of initiation of transcription which were shown to occur mainly at -392 and -358 nucleotides before the putative start of translation. These two main sites of initiation did not explain the origin of the 4.5kb and 5.5kb mRNAs, and as no spliced variants were found among the 24 clones, some regulation should also involve the 3'end region.

Hepatic recruitment of mast cells occurs in rats but not mice infected with Schistosoma mansoni

The pathogenesis of infection with Schistosoma mansoni in rats is distinct from that in mice. Rats are non-permissive hosts and infection is terminated in the liver before egg laying commences whereas the parasites completes its life cycle in mice. Comparison of the mast cell responses in the two species reveals that a pronounced hepatic mastocytosis occurs in the rat and this is concomitant with the demise of the parasite. The majority of recruited hepatic mast cells contain the highly soluble granule chymase, rat mast cell protease-II, which is released systemically into blood during the period of parasite elimination. In contrast, very few mast cells are found in livers of parasitized mice and none contain the soluble granule chymase mouse mast cell protease-1. However, during egg deposition in the gut, an intraepithelial mastocytosis occurs in parasitized mice. These intraepithelial cells are typical mucosal mast cells as determined by their content of mouse mast cell protease-1. Recruitment of mucosal mast cells occurs in the intestinal lamina propria of infected rats soon after the parasites migrate to the liver. These findings suggest that mast cells of the mucosal phenotype are involved in the pathogenesis of the hepatic response to infection in the rat but that, in the mouse, mucosal mastocytosis is associated with intestinal sensitization by egg antigens.

Effect of praziquantel treatment on lipid peroxide levels and superoxide dismutase activity in tissues of healthy and Schistosoma mansoni infected mice

The elevated levels of lipid peroxide product as malondialdehyde (MDA) in plasma, liver, spleen, intestine and kidney of Schistosome-infected mice were differently ameliorated by treatment with praziquantel (EMBAY 8440, CAS 55268-74-1) (2 x 500 mg/kg body wt.) being nearly normalized in plasma and intestine, moderately improved in liver and slightly affected in spleen and kidney. However, the drug failed to affect the MDA levels in the different organs of healthy mice. Moreover, the increased hepatic superoxide dismutase (SOD) activity in infected mice was normalized while the decreased activities in the other tissues were further decreased than normal values in response to praziquantel treatment. Interestingly, in healthy mice, the drug similarly inhibited SOD activities in blood, spleen and kidney. The specificity of this action remains to be clarified. Possible explanations of these findings are given.

Transient expression of lysyl oxidase by liver myofibroblasts in murine schistosomiasis

BACKGROUND

Murine schistosomiasis provides an experimental model of reversible fibrosis. The lysyl oxidase catalyzes the first step of collagen and elastin enzymatic cross-linking and appears to be a crucial factor in stabilizing the neosynthesized extracellular matrix in the liver.

EXPERIMENTAL DESIGN

A cDNA probe encoding a portion of the murine lysyl oxidase was cloned, and antibodies were raised against the corresponding recombinant peptide expressed as a fusion protein. Both tools were used to examine the expression of the lysyl oxidase mRNAs and peptides, all within granulomas and cells extracted from infected liver.

RESULTS

Transient up-regulation of two dominant 4.5 kb and 5.5 kb transcripts was observed among four mRNAs hybridizing with the lysyl oxidase cDNA probe during the development of granulomas. An identical time course was obtained for alpha 1(I) procollagen messenger expression. The lysyl oxidase expression was observed in type I collagen producing cells mainly localized at the periphery of fibroinflammatory granulomas and it disappeared in late granulomas. The lysyl oxidase and type I collagen expressing cells, located within granulomas, exhibited the characteristics of myofibroblasts, as judged by their expression of alpha-smooth muscle actin and desmin and by their ultrastructural morphology. Four antigenically related peptides were immunopurified from an enriched preparation of myofibroblast-like cells extracted from infected mouse liver. Two of these peptides had the molecular weight of prolysyl oxidase (50,000) and activated lysyl oxidase (32,000). The two others (28,000 and 66,000) might correspond to cleavage product or dimeric form respectively.

CONCLUSIONS

This study demonstrates that the lysyl oxidase was transiently up-regulated at the transcriptional level parallely to alpha(1)I procollagen within developing granulomas. Myofibroblasts are involved in the expression of the lysyl oxidase which may be secreted as a proenzyme and an activated enzyme.