The role of free oxygen radicals in the expulsion of primary infections of Nippostrongylus brasiliensis

Effects of Dietary Taurine Supplementation to Gilts during Late Gestation and Lactation on Offspring Growth and Oxidative Stress

Simple Summary

Previous studies showed that gilts had elevated oxidative stress during late gestation and lactation, and could affect offspring growth. Taurine (Tau) is an important regulator of oxidative stress and possesses growth-enhancing properties. Our results suggested that taurine supplementation during late gestation and lactation of gilts increased growth performance in piglets through improved milk quality of gilts and intestinal morphology and barrier function of offspring.

Abstract

Birth is one of the most important events of animal production agriculture, as newborns are abruptly forced to adapt to environmental and nutritional disruptions that can lead to oxidative damage and delay in growth. Taurine (Tau) is an important regulator of oxidative stress and possesses growth-enhancing properties. In the present study, we investigated the effects of dietary Tau supplementation in gilts during late gestation and lactation on the growth performance of piglets by assessing intestinal morphology and barrier function, and oxidative stress status. Sixteen gilts were randomly allocated to the Con (basal diet) and Tau (basal diet with 1% Tau) groups from 75 d of gestation to weaning. Maternal dietary Tau supplementation significantly increased weaning weight and average daily gain weight in piglets. Piglets in the Tau group had higher villus height and villus height-to-crypt depth ratio (VCR), ZO-1 protein expression, and secretory immunoglobulin A (sIgA) content in the jejunum. Meanwhile, Tau bebeficial affected the milk quality of gilts, as indicated by decreased malondialdehyde (MDA) concentration and increased total superoxide dismutase (T-SOD), total antioxidative capability (T-AOC), glutathione peroxidase (GPx), and catalase (CAT) activity. Furthermore, Tau supplementation increased T-SOD activity in plasma and SOD2 protein expression in the jejunum in the piglets. In conclusion, this study provides evidence that dietary Tau supplementation to gilts improves growth performance in piglets, owing to improved intestinal morphology and barrier function, as well as inhibition of oxidative stress.

cDNA cloning and expression patterns of a peroxiredoxin, a catalase and a glutathione peroxidase from Haemonchus contortus

The range of antioxidant enzyme systems available to Haemonchus contortus for detoxification of hydrogen peroxide was investigated using cDNA cloning of candidate genes. PCR with primers based on conserved amino acid regions and spliced leader sequences was used to obtain full-length sequences for a 2-Cys peroxiredoxin, a catalase, and a selenium-independent glutathione peroxidase, indicating that H. contortus expresses a number of antioxidant systems with the potential to detoxify peroxide (nucleotide sequence data reported in this paper are available in the GenBank, EMBL and DDBJ databases under the accession numbers AY603335, AY603336 and AY603337). Quantitative PCR analysis comparing L3-stage larvae with adult worms showed significantly elevated peroxiredoxin levels in adults, equivalent catalase levels in the two stages, and significantly less glutathione peroxidase in adults, suggesting a significant role for peroxiredoxin in allowing the nematode to detoxify hydrogen peroxide encountered in the parasitic environment. Exposure of L4-stage worms to hydrogen peroxide in vitro (generated using glucose/glucose oxidase) caused no change in mRNA levels for each of the genes, though the exposed worms showed up to eightfold higher catalase activities. The lack of mRNA changes alongside increased catalase enzyme activity indicates that transcript level was not predictive of enzyme activity, suggesting that activity may be regulated in response to oxidative stress by a mechanism other than increased transcription.

Neural sarcocystosis in a straw-necked ibis (Carphibis spinicollis) associated with a Sarcocystis neurona-like organism and description of muscular sarcocysts of an unidentified Sarcocystis species

A Sarcocystis neurona-like parasite was associated with acute sarcocystosis in the brain of an ibis (Carphibis spinicollis). Numerous schizonts and merozoites were found extravascularly in encephalitic lesions. These schizonts reacted positively with anti-S. neurona and anti-S. falcatula polyclonal antibodies in an immunohistochemical test. Sarcocysts of an unidentified Sarcocystis species were present in the brain, heart, and skeletal muscles. Sarcocysts in skeletal muscles were microscopic, and the sarcocyst wall was up to 3 microm thick. The villar protrusions on the sarcocyst wall were up to 4.5 microm long, constricted at the base, and expanded laterally. Schizonts and sarcocysts distinct from those of S. falcatula.

Antibody-dependent cell-mediated cytotoxicity to newly excysted juvenile Fasciola hepatica in vitro is mediated by reactive nitrogen intermediates

Passive intraperitoneal transfer of sera from Fasciola hepatica-infected sheep, cattle or rats can protect naive rats from F. hepatica infection, suggesting a parasite killing mechanism within the peritoneal cavity that is dependent on the presence of parasite-specific antibody. We investigated antibody-dependent cell-mediated cytotoxicity by resident peritoneal lavage cell populations, containing large numbers of monocytes/macrophages, as a potential host resistance mechanism by which juvenile flukes could be killed within the peritoneal cavity of naive rats. Comparative studies were conducted using cell populations containing large numbers of monocytes/macrophages from sheep. The results demonstrate that monocyte/macrophage-rich lavage cell populations from rat and sheep differ substantially in their ability to generate nitric oxide. Only resident rat peritoneal lavage cells were able to mediate antibody-dependent cell-mediated cytotoxicity against newly excysted juvenile liver fluke. The mechanism of cytotoxicity was dependent on, and directly proportional to, the production of nitric oxide and required attachment of effector cells to the newly excysted juvenile liver fluke tegument, which occurred following the addition of sera from F. hepatica-infected animals. This is the first report demonstrating a mechanism of cell-mediated cytotoxicity to newly excysted juvenile liver fluke.

Cytokine regulation of host defense against parasitic gastrointestinal nematodes: lessons from studies with rodent models

Studies with rodents infected with Trichinella spiralis, Heligmosomoides polygyrus, Nippostronglyus brasiliensis, and Trichuris muris have provided considerable information about immune mechanisms that protect against parasitic gastrointestinal nematodes. Four generalizations can be made: 1. CD4+ T cells are critical for host protection; 2. IL-12 and IFN-gamma inhibit protective immunity; 3. IL-4 can: (a) be required for host protection, (b) limit severity of infection, or (c) induce redundant protective mechanisms; and 4. Some cytokines that are stereotypically produced in response to gastrointestinal nematode infections fail to enhance host protection against some of the parasites that elicit their production. Host protection is redundant at two levels: 1. IL-4 has multiple effects on the immune system and on gut physiology (discussed in this review), more than one of which may protect against a particular parasite; and 2. IL-4 is often only one of multiple stimuli that can induce protection. Hosts may have evolved the ability to recognize features that characterize parasitic gastrointestinal nematodes as a class as triggers for a stereotypic cytokine response, but not the ability to distinguish features of individual parasites as stimuli for more specific protective cytokine responses. As a result, hosts deploy a set of defense mechanisms against these parasites that together control infection by most members of that class, even though a specific defense mechanism may not be required to defend against a particular parasite and may even damage a host infected with that parasite.

Importance of interferon-gamma in protective immunity against Hymenolepis nana cysticercoids derived from challenge infection with eggs in BALB/c mice

The function of cytokines produced during Hymenolepis nana egg infection in mice in protective immunity against re-infection was examined. Treatment of mice with monoclonal antibody (MAb) against mouse interferon (IFN)-gamma caused suppression of protective immunity against H. nana re-infection when the MAb was injected intraperitoneally at a daily dose of 40.0 mg kg-1 during the effector phase of protective immunity. Although high levels of IFN-gamma, tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 beta were released into the intestinal tracts of the parasitised mice at challenge infection, there was almost no release of these cytokines in mice treated with the MAb. Daily administration of rolipram failed to suppress the protective immunity, even when 400 micrograms kg-1 of the agent was administered into mice during the effector phase of immunity. Treatment of mice with rolipram completely suppressed both TNF-alpha and IL-1 beta production in intestinal tracts, induced by H. nana challenge infection. However, endogenous IFN-gamma production in the intestine was scarcely affected by rolipram. These results strongly suggest that IFN-gamma is the most important (or essential) cytokine in protective immunity to H. nana re-infection, rather than TNF-alpha and IL-1 beta.

Immunological approaches for the control of fasciolosis

The immunological relationship between liver flukes and their mammalian hosts is being unravelled by in vivo and in vitro studies. Vaccine studies in cattle and sheep with purified antigens (fatty acid binding protein, FABP; glutathione S-transferase, GST; cathepsin L, CatL; hemoglobin) have shown that high reductions in worm burdens (31-72%) and egg production (69-98%) can be achieved, raising the realistic possibility that immunological control of Fasciola infection is a commercially achievable goal. Combination vaccines may also be feasible since a cocktail of CatL and hemoglobin elicits a significant 72% protection in cattle. Analysis of immune responses to Fasciola during infection in ruminants suggests that chronic infection correlates with a type 2 helper T cell response, implying that type 1 helper T cell responses are down-regulated in fasciolosis. Recent results studying the resistance of Indonesian Thin Tail (ITT) sheep to F. gigantica have shown that this breed exhibits high innate (or rapidly acquired) resistance to infection and acquires a higher level of resistance after a primary challenge. Initial studies suggest that the resistance of ITT sheep to F. gigantica may be determined by a major gene. Merino sheep also acquire resistance to F. gigantica. In contrast, ITT and Merino sheep do not exhibit resistance to F. hepatica. These results suggest that there are fundamental differences between these two species of Fasciola in the biology of their interaction with the sheep immune system. In vitro studies on immune mechanisms of killing of juvenile fluke have shown that juvenile larvae of F. hepatica are susceptible to antibody-dependent killing by activated rat macrophages in vitro which is mediated by nitric oxide. Future studies on the immune effector mechanisms expressed by resistant sheep which control infection by F. gigantica will lead to new knowledge which may allow the design of more effective vaccines for fasciolosis.

The early stages of Echinococcus granulosus development

The paper points out the essential aspects of host/parasite relationship during the development of oncospheres (ONC) of Echinococcus granulosus into an early cyst. Secretions of the penetration glands in the hatched ONC causes lysis of host tissue during penetration of the activated ONC. It also protects the parasite against the host's immune response while developing the laminated layer. The microvilli, compressed under the plasma membrane in the hatched ONC, are uplifted in the activated larvae; they increase in number and size and are substituted by short and truncated microtriches in metacestodes 3 days old. At that time appears the first lamination of the laminated layer that surrounds the metacestodes as an electron-dense matrix composed of fine microfibrillated material and remnants of sloughed microvilli. The second lamination appears by day 6-8 and is more electron-dense than the first one. The laminated layer is of parasite origin, formed of a series that emanates from the germinal membrane. It is suggested that Vg secretory vesicles, that are elaborated in the perikaryon of the germinal zone and continuously carried to the syncytium via the microtubular-cytoskeleton, are responsible for the laminated layer formation and are involved in initial evasion of the immune response of the host. The cyclical production of laminations could be necessary to create layers that can ultimately be sloughed off as the cyst grows and serve to divert the host cellular response to the parasite.

Novel sources of anthelmintics

The G-series of naturally occurring compounds from Eucalyptus species contain representatives that are endoperoxides and Mannich bases. Mannich bases have been shown to be effective in killing protozoa in vitro. Previous studies of the role of cells of the immune system reveal that helminth parasites are susceptible to free radical attack. A 3-year research project studied the anthelmintic potential of endoperoxides and/or Mannich bases derived from G-compounds. Results from 1 series of synthetic analogues which show a positive relationship between chemical structure and anthelmintic activity are reported here. A G-Mannich base with an aromatic ring side chain as well as a long aliphatic side chain was the most active analogue in the series with an LD 50 < 0.1 mM in an in vitro larval motility assay. This work showed that Mannich bases are a potential source of compounds for parasite control. More work on formulation and pharmacokinetics is required to advance these compounds to the threshold of commercial production.

Nippostrongylus brasiliensis: ability of plasma to prime free radical generation by leukocytes in response to adult worms not due to gamma-interferon or tumour necrosis factor

Plasma-borne factors prime leukocytes from both infected and uninfected rats for radical generation in response to N. brasiliensis. The concentration of these factors is increased following infection and reaches maximal levels on day 8 post-infection (p.i.) as demonstrated by the striking ability of plasma from infected rats to prime leukocytes from uninfected rats to produce free radicals in response to adult worms. The cytokines, gamma-interferon and tumour necrosis factor (TNF) can be detected in plasma during infection with a variety of organisms and several lines of immunological and pathophysiological evidence, including radical generation, weight loss, anaemia and diarrhoea, implicate generation of these proteins in response to infection with N. brasiliensis. We therefore investigated whether gamma-interferon and TNF were detectable in the plasma of rats infected with N. brasiliensis and whether the presence of these cytokines correlated with the ability of plasma to enhance radical generation in response to N. brasiliensis. However, gamma-interferon was not detected in the plasma of rats at any time after infection with N. brasiliensis and neutralizing monoclonal antibody to rat gamma-interferon had no effect on the ability of plasma to prime free radical generation. TNF was detected in the plasma of heavily-infected rats but only at very low levels (< 1 ng/ml), though copius in vivo synthesis of TNF could be induced by treatment of the infected rats with lipopolysaccharide (LPS). However, neither parasite-induced nor parasite plus LPS-induced plasma TNF correlated with the ability of plasma to enhance radical generation in response to N. brasiliensis.(ABSTRACT TRUNCATED AT 250 WORDS)

Echinococcus granulosus: the mechanism of oncosphere lysis by sheep complement and antibody

A heat-labile component of normal sheep serum (56 degrees C for 30 min but not 50 degrees C for 30 min) was able to lyse oncospheres in vitro. The degree of effect, and the proportion of oncospheres lysed, was related to the concentration of normal unheated sheep serum complement, or other sources of complement (rabbit, mouse) in the culture. Lower concentrations were required for lysis if the culture serum was obtained from sheep immune to E. granulosus infection. Heat inactivation of normal or immune sheep serum removed any lytic ability. No lysis occurred in any concentration of unheated foetal lamb serum. However, unheated foetal lamb serum was able to restore the lytic effect to heated normal or immune serum. This suggests that lysis in both immune and normal serum is antibody-dependent and complement-mediated. The lysis in normal serum would appear to be due to natural cross-reacting antibodies that can fix complement at the oncosphere surface. The complement lesion resulted in damage to the plasma membrane. This then peeled back, predisposing the oncosphere to osmotic destruction. The use of bleach to dissolve the embryophore caused damage to the plasma membrane similar to that caused by complement. Developing metacestodes at 3 days of age in vitro in immune serum were susceptible to the addition of complement at that time.

Effects of Plasmodium berghei (Apicomplexa) on Nippostrongylus brasiliensis (Nematoda) infection in the mouse, Mus musculus

Ova and free oxygen radical production and relative peripheral eosinophilia during single and concurrent infections in mice with P. berghei and N. brasiliensis were investigated. Prolonged helminth patent periods indicate that Nippostrongylus self-cure in concurrently infected mice was suppressed. Differential white blood cell determinations showed that the relative number of peripheral blood eosinophils steadily increased (P < or = 0.05) during a Nippostrongylus infection when compared to noninfected controls. Eosinophil levels in mice singly infected with P. berghei or concurrently infected with both parasites did not differ significantly from those of controls suggesting a suppression by Plasmodium of Nippostrongylus-induced eosinophilia. Generation of intestinal free oxygen radicals was indirectly assessed using the Thiobarbituric Acid Assay to measure malondialdehyde (MDA). Intestinal MDA levels were significantly elevated (P < or = 0.05) during single Plasmodium infections as well as concurrent infections while there was no change in MDA production during single Nippostrongylus infections. These results suggest suppression by Plasmodium of the immune response to Nippostrongylus, allowing prolonged patent periods. They also suggest that eosinophils play a role in self-cure while free oxygen radicals do not.

Immunological modulation and evasion by helminth parasites in human populations

Helminth parasites are highly prevalent in human communities in developing countries. In an endemic area an infected individual may harbour parasitic worms for most of his or her life, and the ability of these infections to survive immunological attack has long been a puzzle. But new techniques are starting to expose the diverse mechanisms by which these agents modulate or evade their hosts' defences, creating a dynamic interaction between the human immune system and the parasite population.

Fasciola hepatica: free radical generation by peritoneal leukocytes in challenged rodents

Free radical generation by peritoneal leukocytes from hosts able to develop resistance to reinfection with Fasciola hepatica (rats) was compared with that of hosts unable to develop resistance (mice). Free radical generation by rat leukocytes was 3.5 times higher per cell and 30 times higher per animal than radical production by mouse leukocytes. The capacity of peritoneal leukocytes to produce free radicals in response to adult fluke crude antigen was increased by the presence of host plasma and was quantitatively greater in challenged rats than in naive or primary infected rats. This was not the case for mice, in which cells from primary infected animals were equally as responsive as cells from challenged mice. Further experiments revealed that challenge infection in rats apparently caused the in vivo activation of peritoneal leukocytes and increased levels of unidentified factors in plasma and that both of these responses were involved in the initiation of free radical generation in response to F. hepatica. Dramatic increases in the number of eosinophils present in the peritoneal cavities of primary infected and challenged rats (but not mice) were observed but the role of eosinophils in the production of free radicals in response to F. hepatica remains to be determined.

Free radical generation and the course of primary infection with Nippostrongylus brasiliensis in congenitally athymic (nude) rats

The course of primary infections with Nippostrongylus brasiliensis was followed in nude (CBH/R nu/nu) and heterozygote (CBH/R nu/+) rats. In both nude and heterozygote rats peak egg production by N. brasiliensis occurred on days 7 and 8 post-infection. However, whereas in heterozygote rats egg production declined rapidly thereafter and ceased completely by day 14 post-infection, in nude rats high numbers of N. brasiliensis eggs were still seen on day 27 post-infection, when the experiment was terminated. In comparison with the nude rats, heterozygote rats had a 5-fold greater loss of weight by day 9 post-infection and a 4-fold higher incidence of diarrhoea. Furthermore, infected heterozygote rats became anaemic whereas uninfected rats and infected nude rats showed no evidence of anaemia. Free radical generation was measured in infected (9 days) and uninfected rats. Leucocytes from infected heterozygote rats were able to generate copious quantities of free radicals in response to N. brasiliensis whereas leucocytes from infected nude rats produced only slightly more free radicals than uninfected rats. Thus, worm rejection, weight loss, diarrhoea, anaemia and free radical generation in response to N. brasiliensis infection are all T-cell dependent events.

A role for protein kinase C in the production of free oxygen radicals in response to Nippostrongylus brasiliensis

The involvement of protein kinase C in the initiation of free oxygen radical generation by rat leukocytes in response to the nematode Nippostrongylus brasiliensis was investigated. Inhibitors of protein kinase C, trifluoperazine and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), inhibited free radical generation in response to N. brasiliensis in vitro. Neither inhibitor affected free radical generation by the cell-free xanthine/xanthine oxidase system, indicating that the agents did not scavenge free radicals; they also failed to affect leukocyte viability. Furthermore, activators of protein kinase C, the calcium ionophore A23187 and the diacylglycerol 1-oleoyl-2-acetyl-rac-glycerol (OAG), enhanced free radical generation by leukocytes in response to N. brasiliensis in vitro. Thus, protein kinase C apparently plays an important role in the initiation of free radical generation in response to N. brasiliensis; since free radicals may play a critical role in worm expulsion, this implies that protein kinase C may also be important in the rejection of N. brasiliensis from the small intestine of the rat.

Oxygen derived free radicals and the course of Eimeria vermiformis infection in inbred strains of mice

Free radical generation by peritoneal leukocytes from BALB/c and C57BL/6 mice was monitored for 18 days following infection with Eimeria vermiformis. Free radical generation occurred earlier and was quantitatively much greater in resistant BALB/c mice than in susceptible C57BL/6 mice, resistance being indicated by a much lower oocyst production and a shorter patent period of E. vermiformis. Plasma greatly enhanced free radical generation in response to a soluble antigen prepared from sporulated oocysts indicating the presence of plasma-borne factor(s) which enhance free radical generation in response to E. vermiformis.