Effect of Ostertagia circumcincta excretory/secretory products on gastrin release in vitro

Abomasal dysfunction and cellular and mucin changes during infection of sheep with larval or adult Teladorsagia circumcincta

This is the first integrated study of the effects on gastric secretion, inflammation and fundic mucins after infection with L3 T. circumcincta and in the very early period following transplantation of adult worms. At 3 months-of-age, 20 Coopworth lambs were infected intraruminally with 35,000 L3; infected animals were killed on Days 5, 10, 15, 20 and 30 post-infection and 6 controls on either Day 0 or 30 post-infection. Another 15 Romney cross lambs received 10,000 adult worms at 4-5 months-of-age though surgically-implanted abomasal cannulae and were killed after 6, 12, 24 and 72 hours; uninfected controls were also killed at 72 hours. Blood was collected at regular intervals from all animals for measurement of serum gastrin and pepsinogen and abomasal fluid for pH measurement from cannulated sheep. Tissues collected at necropsy were fixed in Bouin's fluid for light microscopy, immunocytochemistry and mucin staining and in Karnovsky's fluid for electron microscopy. Nodules around glands containing developing larvae were seen on Day 5 p.i., but generalised effects on secretion occurred only after parasite emergence and within hours after transplantation of adult worms. After L3 infection, there were maximum worm burdens on Days 10-15 post-infection, together with peak tissue eosinophilia, inhibition of gastric acid secretion, hypergastrinaemia, hyperpepsinogenaemia, loss of parietal cells, enlarged gastric pits containing less mucin and increased numbers of mucous neck cells. After adult transplantation, serum pepsinogen was significantly increased after 9 hours and serum gastrin after 18 hours. Parallel changes in host tissues and the numbers of parasites in the abomasal lumen suggest that luminal parasites, but not those in the tissues, are key drivers of the pathophysiology and inflammatory response in animals exposed to parasites for the first time. These results are consistent with initiation of the host response by parasite chemicals diffusing across the surface epithelium, possibly aided by components of ES products which increased permeability. Parietal cells appear to be a key target, resulting in secondary increases in serum gastrin, pit elongation, loss of surface mucins and inhibition of chief cell maturation. Inflammation occurs in parallel, and could either cause the pathology or exacerbate the direct effects of ES products.

Proteomic analysis of excretory secretory products from Clonorchis sinensis adult worms: molecular characterization and serological reactivity of a excretory-secretory antigen-fructose-1,6-bisphosphatase

Clonorchis sinensis is a food-borne zoonotic parasite that resides in bile ducts and causes clonorchiasis, which may result in cholelithiasis, cholecystitis, hepatic fibrosis, and liver tumors. Although total excretory secretory products (ESP) of C. sinensis adults induce hepatic fibrosis in vivo in rats, the causative mechanism is not well understood. To study components of the ESP, C. sinensis culture medium was collected and analyzed using shotgun LC-MS/MS. We identified a total of 110 proteins, including glycometabolic enzymes (such as fructose-1,6-bisphosphatase (FBPase) and enolase), detoxification enzymes (such as glutamate dehydrogenase, dihydrolipoamide dehydrogenase and cathepsin B endopeptidase), and a number of RAB family proteins. To identify a potential causative agent for hepatic fibrosis, we expressed and purified a recombinant FBPase, a 1,041-bp gene product that encodes a 41.7-kDa protein with prototypical FBPase domains and that can form a tetramer with a molecular mass of 166.8 kDa. In addition, we found that FBPase is an antigen present in the ESP and in circulation. Immunofluorescence showed that FBPase localizes to the intestinal cecum and vitellarium in C. sinensis adults. Our results describe the components of the excretory secretory products from C. sinensis adult worms and suggest that FBPase may be an important antigen present in the ESP of C. sinensis and may lay the foundation for additional studies on the development of clonorchiasis-associated hepatic fibrosis.

Teladorsagia circumcincta: survival of adults in vitro is enhanced by the presence of a mammalian cell line

Adult Teladorsagia circumcincta survival and motility in vitro was examined in a range of different cell culture media, supplements and gas mixes. Under optimum conditions, worms survived for 14 days, exhibiting high motility for 9 days and egg production for 72 h. Optimum conditions involved co-culture of worms with a HeLa cell line in a supplemented cell medium (CEM) and an atmosphere containing 10% CO(2), 5% O(2) 85% N(2), 65% humidity at 37 degrees C. The incubation medium consisted of Minimum Essential Medium with 10% fetal calf serum, 1% non-essential amino acids, 1% glutamax and 1% penicillin-neomycin-streptomycin cocktail mix. Compared with optimum conditions, incubation in CEM alone, cell conditioned CEM, RPMI alone, Medium 199 alone, reduced CO(2) or O(2), or when cells were replaced with Escherichia coli, both survival and motility were reduced. Optimum conditions for adult T. circumcincta maintenance for culture, anthelmintic testing or generation of excretory/secretory products are described.

Abomasal bacteria produce an inhibitor of gastrin secretion in vitro

Previously, proliferating microflora transferred with abomasal nematodes, were suspected to be the source of the gastrin inhibitor in some parasite excretory/secretory products. Aerobic cultures in HBSS of abomasal fluid from uninfected sheep became inhibitory during the static growth phase, unless antibiotics were present. Basal gastrin secretion was reduced by up to 90%. Rumen fluid and incubates and medium in which Streptococcus bovis and ovine rumen Actinomycete spp. had been grown also contained the inhibitor. Unlike abomasal cultures, rumen fluid and incubates also reduced the measurement of gastrin standards. Rumen incubates were less potent after exposure to pH 2-3, suggesting that inactivation normally occurs in the unparasitised abomasum. Contaminating bacteria which generate the gastrin inhibitor in parasite ES products are probably rumen organisms which survive in the abomasum and proliferate during subsequent incubation. Significantly, rumen bacteria have been shown to be capable of affecting the secretory activity of the gastric mucosa.

Abomasal contents of parasitised sheep contain an inhibitor of gastrin secretion in vitro

Serum gastrin concentrations are typically elevated in parasitised sheep; however, in some animals serum gastrin concentrations may fall abruptly despite a very high abomasal pH. Although proliferating abomasal bacteria in culture generate a potent inhibitor of in vitro gastrin secretion, this inhibitor has not been detected in abomasal contents of unparasitised sheep. In sheep parasitised by O. circumcincta, all abomasal fluid samples of pH 5 and above were inhibitory to gastrin release in vitro. Inhibitory activity and abomasal pH were correlated in two separate experiments; the model best fitting the data being sigmoidal in each case, with zero activity at pH 3.6 and 4.6, respectively. There was no clear evidence that the presence of a gastrin inhibitor in the abomasal contents reduced the serum gastrin concentration in parasitised sheep. Serum gastrin was correlated with abomasal pH (log(10) serum gastrin concentrations conformed to log-linear sigmoidal models).

Effects of excretory/secretory products of Haemonchus contortus on cell vacuolation

Excretory/secretory (ES) products of the gastric nematode, Haemonchus contortus, have been implicated in the inhibition of gastric acid secretion which follows infection. Parietal cell vacuolation has been observed in abomasal sections from parasitised sheep, and ES prepared in vitro has been reported to cause vacuolation and to increase neutral red (NR) uptake in epithelial cell cultures. We have used the latter approach to examine, at the cellular level, the effects of ES prepared from L3 and adult nematodes. Both NR uptake and cellular vacuolation were increased following exposure to larval or adult ES products. ES preparations from adult worms induced more extensive vacuolation then those from L3 worms and, as with VacA treatment, adherent cells remained viable despite high levels of vacuolation. Whereas VacA-induced vacuolation resulted in NR uptake predominantly localised in vacuoles, this appeared not to be the case with ES-induced vacuolation, suggesting that different mechanisms might be involved. Both ES and VacA exposure was associated with an increased rate of cell detachment.

Excretory/secretory products of sheep abomasal nematode parasites cause vacuolation and increased neutral red uptake by HeLa cells

Excretory/secretory (ES) products of Ostertagia (Teladorsagia) circumcincta and Haemonchus contortus have been implicated in the inhibition of gastric acid secretion and vacuolation, and the loss of parietal cells associated with abomasal parasitism. Vacuolation of epithelial (HeLa) cells caused by adult O. circumcincta or L3 O. circumcincta or H. contortus ES products have been examined by differential interference contrast microscopy and by the neutral red uptake assay. ES products caused visible vacuolation of HeLa cells, and this effect was enhanced by 8 mM NH4Cl. Some parasite ES products caused a marked detachment of cells from the coverslip. At lower concentrations of ES products, neutral red uptake was usually increased above the control, but at higher concentrations of ES products, uptake was often decreased, probably because of cell detachment. Although generally consistent with direct observations of HeLa cell vacuolation by parasite chemicals, neutral red uptake was not a satisfactory quantitative assay.

The failure of Haemonchus contortus excretory/secretory products to stimulate gastrin secretion in vitro

Excretory/secretory (ES) products collected from exsheathed L3 or parasitic stages of Haemonchus contortus were tested in vitro for gastrin stimulatory properties using an ovine abomasal antral mucosal preparation. In addition, the motility of exsheathed L3 and parasites recovered on weeks 2, 6 and 8 post-infection was studied in water, saline, saline with glucose or ovine blood and in HBSS pH 2.5-7.4. Parasitic stages became immotile rapidly in water and HBSS pH 2.5, more slowly in HBSS pH 3.5, but nearly 100% remained motile for 48 h when blood was included in the medium. Exsheathed L3 motility was reduced only by water and HBSS pH 2.5, and then only in the second week of incubation. Gastrin secretion was not consistently increased by any of the parasite ES products tested in vitro, therefore, they probably do not stimulate the G cell directly to produce the hypergastrinaemia seen in parasitised sheep.

Excretory/secretory products of Haemonchus contortus inhibit aminopyrine accumulation by rabbit gastric glands in vitro

Abomasal parasites inhibit gastric acid secretion and reduce the number of acid secreting parietal cells either through physical contact with gastric tissue, the release of inhibitory excretory/secretory (ES) products or by initiating the host inflammatory response. To examine the role of parasite ES products, adult Haemonchus contortus were incubated in a medium based on Hank's balanced salt solution and three incubates were tested for the presence of inhibitors of acid secretion by dispersed rabbit gastric glands in vitro, using the intracellular accumulation of 14C-aminopyrine (AP) as an indirect measure of acid secretion. Acceptably sensitive rabbit preparations (80%) for testing ES products showed increased 14C-AP accumulation with either 10(-5) or 10(-4)M histamine. Sheep glands proved unsuitable as a test system as only two of six preparations responded weakly to histamine. Inhibitory activity was demonstrated in all the three parasite incubates, although responses varied quantitatively between tests, even with the same batch of incubate. In single tests, 16% ES products significantly reduced the 14C-AP ratio (P<0.05) of 10(-4)M histamine-stimulated glands (15 of 19 tests with Batch 1 and two of six with Batch 3). Even at 1 and 5%, ES products (Batch 2) were inhibitory for 10(-5)M histamine-stimulated glands: at 1% the mean reduction was 26.0% (range 7.8-54.8%, n=10), four of which were statistically significant and at 5% was 17.6% (range -15.3-53.8%, n=17), four of which were statistically significant. ES products were overall inhibitory (-12%, P<0.05), when tested on glands exposed to increasing histamine concentrations from 10(-6)M to 10(-3)M (which increased the 14C-AP ratio (P<0.001)). Responses by individual gland preparations differed (P<0.001). The active component(s) of the parasite ES products were less than 5000 molecular weight. Ammonium chloride, tested over the range of concentrations of ammonia present in worm incubates (0.2-1 mM, final concentrations in the gland incubations of 0.005-0.1 mM), had variable, but overall inhibitory effects on 10(-5)M histamine-stimulated glands (n=3). When tested with a range of histamine concentrations, 0.01 mM NH4Cl overall reduced the response by 8.6% (P<0.05)(n=4). The similarity of responses of rabbit glands to parasite ES products and to NH4Cl suggests that ammonia may be the small molecular weight ES product of adult H. contortus, which inhibited acid secretion in vitro.