Protective effects of hydrogen sulfide on portal hypertensive vasculopathy in rabbits by activating AKT-NF-κB pathway.

The role of hydrogen sulfide (H2S) in portal hypertension (PH)-induced esophagus-gastric junction vascular lesions in rabbits was observed. The rabbit PH models were established. The animals were randomly divided into the following groups: normal, PH, PH+sodium hydrosulfide (PH+S), PH+propargylglycine (PH+PPG). The plasma H2S levels, apoptosis of esophageal-gastric junction vascular smooth muscle cells, and the expression of nuclear transcription factor-κB (NF-κB), p-AKT, IκBa and Bcl-2 were detected. The cystathionine γ lyase (cystathionine-gamma-splitting enzyme, CSE) in the junction vascular tissue was measured. The results showed that the plasma H2S levels and the CSE expression levels had statistically significant difference among different groups (P<0.05). As compared with PH group, plasma H2S levels were declined obviously (11.9±4.2 vs. 20.6±4.5, P<0.05), and CSE expression levels in the junction vascular tissue were notably reduced (1.7±0.6 vs. 2.8±0.8, P<0.05), apoptosis rate of vascular smooth muscle cells per unit area was significantly decreased (0.10±0.15 vs. 0.24±0.07, P<0.05), and the expression levels of p-AKT and NF-κB were significantly decreased (2.31±0.33 vs. 3.04±0.38, P<0.05; 0.33±0.17 vs. 0.51±0.23, P<0.05), however, IκBa and Bcl-2 expression increased obviously (5.57±0.17 vs. 3.67±0.13, P<0.05; 0.79±0.29 vs. 0.44±0.36, P<0.05) in PH+PPG group. As compared with PH group, H2S levels were notably increased (32.7±7.3 vs. 20.6±4.5, P<0.05), the CSE levels in the junction vascular tissue were significantly increased (6.3±0.7 vs. 2.8±0.8, P<0.05), apoptosis rate of vascular smooth muscle cells per unit area was significantly increased (0.35±0.14 vs. 0.24±0.07, P<0.05), and the expression levels of p-AKT and NF-κB were significantly increased (4.29±0.49 vs. 3.04±0.38, P<0.05; 0.77±0.27 vs. 0.51±0.23, P<0.05), yet IκBa and Bcl-2 expression decreased significantly (3.23±0.24 vs. 3.67±0.13, P<0.05; 0.31±0.23 vs. 0.48±0.34, P<0.05) in PH+S group. It is concluded that esophagus-gastric junction vascular lesions happen under PH, and apoptosis of smooth muscle cells is declined. H2S can activate NF-κB by the p-AKT pathway, leading to the down-regulation of Bcl-2, eventually stimulating apoptosis of vascular smooth muscle cells, easing PH. H2S/CSE system may play an important role in remission of PH via the AKT-NF-κB pathway.

Propolis enhances the effectiveness of praziquantel in experimental schistosomiasis: biochemical and histopathological study.

Despite the wide current use of praziquantel (PZQ) in treatment of schistosomiasis, low cure rates have been recorded in many studies. The aim of this study was directed to evaluate the curative effect of propolis (Pps) alone or in combination with PZQ on biochemical, immunological, parasitological, and histological changes associated with experimental schistosomiasis in mice. Schistosoma mansoni-infected mice were divided into two experimental sets, each with four subgroups: (i) untreated, (ii) treated with Pps/day p.o for 4 weeks, (iii) treated with PZQ p.o 2 × 500 mg/kg bd wt, and (iv) treated with Pps + PZQ as in group ii and iii; all treatments started on the 8th week postinfection, in addition to uninfected group as control for the previous groups. Treatment of infected mice with Pps, although failed to eradicate the worm, significantly reduced the hepatic granuloma number, their lymphocytic infiltration and aggregation, hepatic and splenic myeloperoxidase (MPO) activity and plasma, and liver and thymus nitric oxide (NOx) levels together with normalization of plasma proteins and alleviation of oxidative stress in the examined tissues as evidenced by reduction of malondialdehyde (MDA) and normalization of glutathione (GSH). Promising results were obtained when Pps was given in combination with PZQ, where the anti-schistosomal activity of PZQ was markedly potentiated with complete alleviation and amelioration of the histological and biochemical alteration associated with schistosomiasis. This study highlights the potential usefulness of Pps as an adjunct to PZQ in schistosomiasis.

Effects of pentoxifylline during Schistosoma mansoni infection in Swiss mice: an analysis of worm burden, fecundity and liver histopathology.

The short-term effects of pentoxifylline (PTX) on granulomatous lesions during Schistosoma mansoni infection in Swiss mice were evaluated. Drug administration was initiated 42 and 140 days post-infection (DPI) for the acute and chronic infection groups, respectively. Treatment was carried out daily with 200 mg/kg (subcutaneous route) of the drug for five consecutive days. Recovery of parasites and tissues was performed at 49 DPI and 147 DPI, respectively. Liver histological analysis showed a decrease in the inflammatory reaction and fibrous content of the granulomas studied, and a significant reduction (P < 0.001) in their mean diameter was observed in the groups of rodents treated with PTX in acute and chronic infection, when compared to their respective control groups. However, no alteration in the number of S. mansoni recovered from the portal system was observed, and egg-laying kinetics was not notably modified by PTX treatment, and the immature stage distribution of S. mansoni eggs showed minor intrinsic variations with no statistical differences in the parameter second-stage/female/g among untreated mice and treated mice in acute and chronic infections, respectively, when evaluated by intestinal oograms. Data obtained indicate probable immunomodulatory effects of PTX in murine schistosomiasis both in acute and chronic infection.

Remodeling of hepatic vascular changes after specific chemotherapy of schistosomal periportal fibrosis

Hepatosplenic schistosomiasis was the first human disease in which the possibility of extensive long standing hepatic fibrosis being degraded and removed has been demonstrated. When such changes occurred, the main signs of portal hypertension (splenomegaly, esophageal varices) progressively disappeared, implying that a profound vascular remodeling was concomitantly occurring. Hepatic vascular alterations associated with advanced schistosomiasis have already been investigated. Obstruction of the intrahepatic portal vein branches, plus marked angiogenesis and compensatory hyperplasia and hypertrophy of the arterial tree are the main changes present. However, there are no data revealing how these vascular changes behave during the process of fibrosis regression. Here the mouse model of pipestem fibrosis was used in an investigation about these vascular alterations during the course of the infection, and also after treatment and cure of the disease. Animals representing the two polar hepatic forms of the infection were included: (1) "isolated granulomas" characterized by isolated periovular granulomas sparsely distributed throughout the hepatica parenchyma; and (2) 'pipestem fibrosis' with periovular granulomas and fibrosis being concentrated within portal spaces, before and after treatment, were studied by means of histological and vascular injection-corrosion techniques. Instances of widespread portal vein obstruction of several types were commonly found in the livers of the untreated animals. These obstructive lesions were soon repaired, and completely disappeared four months following specific treatment of schistosomiasis. Treatment was accomplished by the simultaneous administration of praziquantel and oxamniquine. The most impressive results were revealed by the technique of injection of colored masses into the portal system, followed by corrosion in strong acid. The vascular lesions of non-treated pipestem fibrosis were represented...

Cytokine production associated with periportal fibrosis during chronic schistosomiasis mansoni in humans.

Volunteers living in an area where schistosomiasis mansoni is endemic were subjected to ultrasound examination and classified into groups according to the levels of fibrosis diagnosed, namely, absence of indications of fibrosis (group 0), incipient fibrosis (group 1), and moderate/severe fibrosis (group 2). Peripheral blood mononuclear cells (PBMC) collected from the volunteers were stimulated with soluble antigens from adult schistosomes or from schistosome eggs, and the production of the cytokines gamma interferon, tumor necrosis factor alpha, transforming growth factor beta (TGF-beta), interleukin-4 (IL-4), IL-10, and IL-13 was determined. Potential associations of the level of fibrosis with age, sex, intensity of infection, and cytokine production were investigated between the three groups. Univariate analysis identified associations of age (>50), gender (male), and absence of eggs/g of feces with moderate/severe fibrosis and an association of intensity of infection (>100 eggs) with incipient fibrosis. When cytokine production in PBMC cultures stimulated by soluble egg antigens was categorized as low or high, significant differences in the distribution of IL-13 levels were established between groups 0 and 2. No significant differences were detected between the groups in the cytokines produced by PBMC cultures stimulated with soluble antigens from adult schistosomes. When all variables were tested in multivariate analyses, only IL-13 was strongly associated with fibrosis (odds ratio = 5.8; 95% confidence interval [CI] = 1.1 to 30.5). While high levels of TGF-beta appeared to be associated with protection against fibrosis, the strength of the association was low.

Remodeling of hepatic vascular changes after specific chemotherapy of schistosomal periportal fibrosis.

Hepatosplenic schistosomiasis was the first human disease in which the possibility of extensive long standing hepatic fibrosis being degraded and removed has been demonstrated. When such changes occurred, the main signs of portal hypertension (splenomegaly, esophageal varices) progressively disappeared, implying that a profound vascular remodeling was concomitantly occurring. Hepatic vascular alterations associated with advanced schistosomiasis have already been investigated. Obstruction of the intrahepatic portal vein branches, plus marked angiogenesis and compensatory hyperplasia and hypertrophy of the arterial tree are the main changes present. However, there are no data revealing how these vascular changes behave during the process of fibrosis regression. Here the mouse model of pipestem fibrosis was used in an investigation about these vascular alterations during the course of the infection, and also after treatment and cure of the disease. Animals representing the two polar hepatic forms of the infection were included: (1) "isolated granulomas" characterized by isolated periovular granulomas sparsely distributed throughout the hepatica parenchyma; and (2) 'pipestem fibrosis' with periovular granulomas and fibrosis being concentrated within portal spaces, before and after treatment, were studied by means of histological and vascular injection-corrosion techniques. Instances of widespread portal vein obstruction of several types were commonly found in the livers of the untreated animals. These obstructive lesions were soon repaired, and completely disappeared four months following specific treatment of schistosomiasis. Treatment was accomplished by the simultaneous administration of praziquantel and oxamniquine. The most impressive results were revealed by the technique of injection of colored masses into the portal system, followed by corrosion in strong acid. The vascular lesions of non-treated pipestem fibrosis were represented in the plastic casts by considerable diminution of the fine peripheral portal vein radicles, plus dilatation of periportal collaterals. Four months after treatment, this last picture appeared replaced by tufts of newly interwoven vessels formed along the main portal vein branches, disclosing a strong angiomatoid reparative change. Understanding about the cellular elements at play during fibro-vascular repairing changes of hepatic schistosomiasis represents a matter of considerable scientific and conceptual importance. At present time one may only speculate about the participation of some type of natural stem-cell capable of restoring the diseased liver back to normal once the cause of the disorder has been eliminated.

A fatty acid binding protein from Fasciola hepatica induced protection in C57/BL mice from challenge infection with Schistosoma bovis.

Three strains of mice (NMRI, C57/BL, BALB/c) were each immunized with a 12 kDa purified, native Fasciola hepatica fatty acid binding protein (Fh12) and challenged percutaneously with Schistosoma bovis cercariae. C57/BL mice immunized with Fh12 had significant reductions in S. bovis worm burden recoveries (96 and 87% reductions over controls in two separate experiments). When using NMRI or BALB/c mice, Fh12 alone or in Freund's adjuvant failed to induce significant protection against S. bovis. In C57/BL mice vaccinated against Fh 12, antibodies to the IgG2a isotype, but not to the IgG1 isotype, increased by 2 weeks after the second immunization and remained high through 8 weeks of S. bovis infection. Antibodies to S. bovis increased after 4 weeks of infection. Regarding cytokine production by spleen mononuclear cells, C57/BL mice vaccinated with Fh12 in adjuvant, and having the highest protective response against challenge infection with S. bovis, had an increase of IFN-gamma production with Concanavalin A but no increase of IL-4 in similarly stimulated cells. These results suggest that the protection obtained in this group of mice is mediated by a Th1 immune response.

Schistosoma mansoni: the immune response against cercarial glycocalyx.

Schistosoma mansoni cercarial glycocalyx was separated and purified by Sephacryl-300 SR. It was found to stimulate the humoral immune response in mice injected with it. Antiglycoalyx antibodies raised in CD/1 mice were found to be cytotoxic to schistosomula in vitro. But conversely, no protective effect was demonstrated in vivo. Eosinophil-mediated cytotoxicity was found to have no effector function in the murine immune response against schistosomes. A monoclonal antiglycocalyx IgM was prepared during our study. It was found to have no cytotoxic effect on schistosomules in vitro. However, it was found to have an inhibitory activity blocking the cytotoxic effect of other antiglycocalyx isotypes in the immune mouse. The contradiction between the result of antiglycocalyx antibody-mediated cytotoxicity obtained in vivo and that obtained in vitro is in itself revealing and suggests that the effect is crucially dependent upon factors as yet poorly understood.

Developmental differences determine larval susceptibility to nitric oxide-mediated killing in a murine model of vaccination against Schistosoma mansoni.

A persistent paradox in our understanding of protective immunity against Schistosoma mansoni infection in animals vaccinated with attenuated parasites has been that attrition of challenge parasites occurs during migration through the lungs in vivo, although parasites recovered from the lungs appear to be relatively resistant to cytotoxic effector mechanisms in vitro. We have compared the susceptibilities of different stages of larvae to killing by nitric oxide (NO), which was previously shown to be involved in the larvicidal function of cytokine-activated cytotoxic effector cells. Lung-stage larvae obtained 1 week after infection were not killed in vitro by NO generated either by a chemical NO donor or by activated cells. In contrast, parasites obtained from the portal system of control mice or from the lungs of vaccinated mice 2.5 weeks following challenge infection were killed by NO. As previously shown for mammalian cell targets, the effects of NO in susceptible larval stages may involve enzymes required for aerobic energy metabolism, since similar cytotoxicity was demonstrated by chemical inhibitors of the citric acid cycle or mitochondrial respiration. Taken together with previous observations of enhanced Th1 activity and expression of NO synthase in the lungs of vaccinated mice at 2.5 weeks after challenge infection, these observations elucidate the immune mechanism of vaccine-induced resistance to S. mansoni infection. Moreover, they suggest that conversion to a less metabolically active state may allow pathogens to escape the effects of the important effector molecule NO.

Natural history of Schistosoma mansoni infection in mice: egg production, egg passage in the feces, and contribution of host and parasite death to changes in worm numbers.

Mice, C57Bl/6N (B6) and BALB/cAnN (BALB), infected with Schistosoma mansoni were examined 8-26 weeks postinfection (PI) to estimate the fecundity of the worms and the contribution of death of worms and the death of heavily infected mice to the decrease in worm numbers in chronic infections. Portal worms were recovered by perfusion and the lungs were examined for parasites shunted from the portal circulation. Animals that died were more heavily infected than those that survived. Between eight and 12 weeks PI, this loss of worms resulted in a net decrease of approximately 19% of worm pairs in surviving BALB mice, but of only 4% in B6 mice. Loss of portal worms to the lungs after the eighth week of infection was 9-13% of portal worms in BALB mice and 3-4% in B6 mice. The estimated rates of egg production by S. mansoni decreased slightly with time in both strains of mice. At 12 and 20 weeks PI, tissue eggs per worm pair and eggs passed in the feces per worm pair often decreased as the intensity of infection increased. We do not consider the loss of worms in the murine host relevant to most infections in humans because of the high intensity of infection relative to body size in mice and the high frequency of severe portal obstruction in murine infections.

Characterization of the murine model of schistosomal hepatic periportal fibrosis ('pipestem' fibrosis).

During mild (one to two pairs of worms) and prolonged (23 weeks or more) mouse infections with Schistosoma mansoni, but not with S. japonicum, periovular granulomas and fibrosis were seen to be preferentially located along periportal tissues. This caused fibrotic expansion of the portal spaces on a background of normal-looking hepatic parenchyma, a picture mimicking 'clay pipestem fibrosis' seen in human patients with advanced schistosomiasis. The model was reproduced in outbred and in several strains of inbred mice, and their main characteristics were studied and compared to the human counterpart. A balanced consideration of the similarities and differences between the murine model and human pipestem fibrosis is needed for the adequate utilization of this simple, reproducible and inexpensive experimental model.

Asexually proliferous tetrathyridia of Mesocestoides sp. in the hepatic portal system of the prairie rattlesnake (Crotalus viridis viridis).

A female prairie rattlesnake (Crotalus viridis viridis) was gastric intubated with 250 tetrathyridia of Mesocestoides sp. The snake was killed 12 wk postinfection; a portion of the liver was examined histologically for evidence of tetrathyridia. Five tetrathyridia were seen in two hepatic portal triad vessels. We propose that a blood-borne metastasis of tetrathyridia in reptiles and rodents may occur.

Schistosoma mansoni: evoluçäo de vermes oriundos de cercárias irradiadas a nível de sistema porta, no camundongo / Schistosoma mansoni: development of worms from cercaria irradiated at the porta system level, in mice

Oito grupos de camundongos albinos (Mus musculus), näo isogênicos, foram infectados transcutaneamente com cerca de 450 cercárias (das cepas LE e SJ do S. mansoni), irradiadas com 3 Krad, 20 Krad e 40 Krad de radiaçäo gama proveniente de cobalto-60, e näo irradiados (grupos-controle). Os vermes provenientes de carcárias irradiadas com 20 e 40 Krad só foram encontrados em quantidades insignificantes no sistema porta. Verificou-se que os vermes irradiados com 3 Krad, que alcançam o sistema porta, mostram nítido retardo no desenvolvimento evolutivo quando comparados com os grupos-controles näo irradiados. Os vermes da cepa SJ (irradiados ou näo) têm evoluçäo mais lenta do que os da cepa LE

Schistosoma mansoni: aspectos quantitativos da evoluçäo de cercárias irradiadas a nível da pele, pulmöes e sistema porta, em camundongos / Schistosoma mansoni: quantitative aspects of the development of irradiated cercariae in the skin, lungs and portal system, in mice

Foi estudada a migraçäo do Schistosoma mansoni (cepas LE e SJ) em oito grupos de camundongos albinos (Mus musculus) näo isogênicos, infectados transcutaneamente com cerca de 450 cercárias näo irradiadas (grupos controles e irradiadas com 3 Krad, e 40 Krad de radiaçäo gama proveniente de cobalto-60. Na pele, observou-se uma diminuiçäo progressiva das taxas de recuperaçäo em funçäo do tempo e, nos pulmöes e sistema porta, verificou-se uma relaçäo inversa significativa entre as taxas de recuperaçäo total e as doses de irradiaçäo. A dose de 20 Krad praticamente impede a migraçäo dos parasitos, de ambas as cepas, dos pulmöes até o sistema porta, enquanto a de 40 Krd praticamente impede a migraçäo dos mesmos da pele para os pulmöes

Migration of the schistosomula of Schistosoma mansoni in mice vaccinated with radiation-attenuated cercariae, and normal mice: an attempt to identify the timing and site of parasite death.

The migration of the schistosomula of Schistosoma mansoni labelled with [75Se]methionine, has been followed from the skin to the hepatic portal system. Parasites were detected in all mouse tissues by compressed organ autoradiography. Two separate experiments were performed to track parasites in normal mice, and in mice previously vaccinated with irradiated cercariae. In normal mice, the profile of numbers of autoradiographic foci detected in the skin, lungs, systemic and splanchnic organs was described with time post-infection. The distribution of parasites to systemic organs, following exit from the lungs, paralleled the fractional distribution of cardiac output. Accumulation of schistosomula in the hepatic portal system was complete by day 21 post-infection. Only 2-3 passes of parasites around the vascular system would be required to produce the hepatic portal population. No significant decline in total foci was detected in the first 12 days post-infection. The majority of parasite elimination appeared to occur in the lungs as late as day 21, with lesser proportions in the systemic organs and skin infection site. The pattern of migration in vaccinated mice was similar to that in normal animals. One difference observed was the longer duration of stay in the skin; however, the majority of parasites eventually reached the lungs. The systemic phase of migration occurred on a reduced scale, as did accumulation of parasites in the hepatic portal system. The decline in total foci in vaccinated mice commenced approximately 7 days earlier than in normal mice and proceeded to a lower end-point. Again the majority of parasite elimination appeared to occur in the lungs with lesser proportions in the systemic organs and skin infection site. It is suggested that resistance to reinfection in vaccinated mice has two additive components which combine to retard the migration of schistosomula within the vasculature, preventing them from reaching the hepatic protal system.