The metabolic switch can be activated in a recombinant strain of Streptomyces lividans by a low oxygen transfer rate in shake flasks.

BACKGROUND: In Streptomyces, understanding the switch from primary to secondary metabolism is important for maximizing the production of secondary metabolites such as antibiotics, as well as for optimizing recombinant glycoprotein production. Differences in Streptomyces lividans bacterial aggregation as well as recombinant glycoprotein production and O-mannosylation have been reported due to modifications in the shake flask design. We hypothetized that such differences are related to the metabolic switch that occurs under oxygen-limiting conditions in the cultures. RESULTS: Shake flask design was found to affect undecylprodigiosin (RED, a marker of secondary metabolism) production; the RED yield was 12 and 385 times greater in conventional normal Erlenmeyer flasks (NF) than in baffled flasks (BF) and coiled flasks (CF), respectively. In addition, oxygen transfer rates (OTR) and carbon dioxide transfer rates were almost 15 times greater in cultures in CF and BF as compared with those in NF. Based on these data, we obtained respiration quotients (RQ) consistent with aerobic metabolism for CF and BF, but an RQ suggestive of anaerobic metabolism for NF. CONCLUSION: Although the metabolic switch is usually related to limitations in phosphate and nitrogen in Streptomyces sp., our results reveal that it can also be activated by low OTR, dramatically affecting recombinant glycoprotein production and O-mannosylation and increasing RED synthesis in the process.

Gender-associated differential expression of cytokines in specific areas of the brain during helminth infection.

Intraperitoneal infection with Taenia crassiceps cysticerci in mice alters several behaviors, including sexual, aggressive, and cognitive function. Cytokines and their receptors are produced in the central nervous system (CNS) by specific neural cell lineages under physiological and pathological conditions, regulating such processes as neurotransmission. This study is aimed to determine the expression patterns of cytokines in various areas of the brain in normal and T. crassiceps-infected mice in both genders and correlate them with the pathology of the CNS and parasite counts. IL-4, IFN-γ, and TNF-α levels in the hippocampus and olfactory bulb increased significantly in infected male mice, but IL-6 was downregulated in these regions in female mice. IL-1ß expression in the hippocampus was unaffected by infection in either gender. Our novel findings demonstrate a clear gender-associated pattern of cytokine expression in specific areas of the brain in mammals that parasitic infection can alter. Thus, we hypothesize that intraperitoneal infection is sensed by the CNS of the host, wherein cytokines are important messengers in the host-parasite neuroimmunoendocrine network.

Helminth infection alters mood and short-term memory as well as levels of neurotransmitters and cytokines in the mouse hippocampus.

UNLABELLED: Helminthic infections are important causes of morbidity and mortality in many developing countries, where children bear the greatest health burden. The ability of parasites to cause behavioral changes in the host has been observed in a variety of host-parasite systems, including the Taenia crassiceps-mouse model. In murine cysticercosis, mice exhibit a disruption in the sexual, aggressive and avoidance predator behaviors. OBJECTIVE: The present study was conducted to characterize short-term memory and depression-like behavior, as well as levels of neurotransmitters and cytokines in the hippocampus of cysticercotic male and female mice. METHODS: Cytokines were detected by RT-PCR and neurotransmitters were quantified by HPLC. RESULTS: Chronic cysticercosis infection induced a decrease in short-term memory in both male and female mice, having a more pronounced effect in females. Infected females showed a significant increase in forced swimming tests with a decrease in immobility. In contrast, male mice showed an increment in total activity and ambulation tests. Serotonin levels decreased by 30% in the hippocampus of infected females whereas noradrenaline levels significantly increased in infected males. The hippocampal expression of IL-4 increased in infected female mice, but decreased in infected male mice. CONCLUSION: Our study suggests that intraperitoneal chronic infection with cysticerci in mice leads to persistent deficits in tasks dependent on the animal's hippocampal function. Our findings are a first approach to elucidating the role of the neuroimmune network in controlling short-term memory and mood in T. crassiceps-infected mice.

Regulation of intestinal immune response by selective removal of the anterior, posterior, or entire pituitary gland in Trichinella spiralis infected golden hamsters.

The influence of anterior pituitary hormones on the gastrointestinal tract of humans and animals has been previously reported. Hypophysectomy (HYPOX) in the rat causes atrophy of the intestinal mucosa, and reduction of gastric secretion and intestinal absorption, as well as increased susceptibility to bacterial and viral infections. However, to our knowledge, no findings have been published concerning the immune response following HYPOX during worm infection, particularly that which is caused by the nematode Trichinella spiralis. The aim of this work was to analyze the effects of total or partial HYPOX on colonization of T. spiralis in the intestinal lumen, together with duodenal and splenic cytokine expression. Our results indicate that 5 days post infection, only neurointermediate pituitary lobectomy (NIL) reduces the number of intestinally recovered T. spiralis larvae. Using semiquantitative inmunofluorescent laser confocal microscopy, we observed that the mean intensity of all tested Th1 cytokines was markedly diminished, even in the duodenum of infected controls. In contrast, a high level of expression of these cytokines was noted in the NIL infected hamsters. Likewise, a significant decrease in the fluorescence intensity of Th2 cytokines (with the exception of IL-4) was apparent in the duodenum of control and sham infected hamsters, compared to animals with NIL surgeries, which showed an increase in the expression of IL-5 and IL-13. Histology of duodenal mucosa from NIL hamsters showed an exacerbated inflammatory infiltrate located along the lamina propria, which was related to the presence of the parasite. We conclude that hormones from each pituitary lobe affect the gastrointestinal immune responses to T. spiralis through various mechanisms.

Tamoxifen treatment in hamsters induces protection during taeniosis by Taenia solium.

Human neurocysticercosis by Taenia solium is considered an emergent severe brain disorder in developing and developed countries. Discovery of new antiparasitic drugs has been recently aimed to restrain differentiation and establishment of the T. solium adult tapeworm, for being considered a central node in the disease propagation to both pigs and humans. Tamoxifen is an antiestrogenic drug with cysticidal action on Taenia crassiceps, a close relative of T. solium. Thus, we evaluated the effect of tamoxifen on the in vitro evagination and the in vivo establishment of T. solium. In vitro, tamoxifen inhibited evagination of T. solium cysticerci in a dose-time dependent manner. In vivo, administration of tamoxifen to hamsters decreased the intestinal establishment of the parasite by 70%, while recovered tapeworms showed an 80% reduction in length, appearing as scolices without strobilar development. Since tamoxifen did not show any significant effect on the proliferation of antigen-specific immune cells, intestinal inflammation, and expression of Th1/Th2 cytokines in spleen and duodenum, this drug could exert its antiparasite actions by having direct detrimental effects upon the adult tapeworm. These results demonstrate that tamoxifen exhibits a strong cysticidal and antitaeniasic effect on T. solium that should be further explored in humans and livestock.

A new MAP kinase protein involved in estradiol-stimulated reproduction of the helminth parasite Taenia crassiceps.

MAP kinases (MAPK) are involved in the regulation of cellular processes such as reproduction and growth. In parasites, the role of MAPK has been scarcely studied. Here, we describe the participation of an ERK-like protein in estrogen-dependent reproduction of the helminth parasite Taenia crassiceps. Our results show that 17beta-estradiol induces a concentration-dependent increase in the bud number of in vitro cultured cysticerci. If parasites are also incubated in presence of an ERK-inhibitor, the stimulatory effect of estrogen is blocked. The expression of ERK-like mRNA and its corresponding protein was detected in the parasite. The ERK-like protein was over-expressed by all treatments. Nevertheless, a strong induction of phosphorylation of this protein was observed only in response to 17beta-estradiol. Cross-contamination by host cells was discarded by flow cytometry analysis. Parasite cells expressing the ERK-like protein were exclusively located at the subtegument tissue by confocal microscopy. Finally, the ERK-like protein was separated by bidimensional electrophoresis and then sequenced, showing the conserved TEY activation motif, typical of all known ERK 1/2 proteins. Our results show that an ERK-like protein is involved in the molecular signalling during the interaction between the host and T. crassiceps, and may be considered as target for anti-helminth drugs design.

Neuroimmunoendocrine modulation in the host by helminth parasites: a novel form of host-parasite coevolution?

Helminth parasites have evolved diverse molecular mechanisms that facilitate their establishment, growth and reproduction inside an immunologically hostile environment. Thus, the physiological interactions during the course of the immune response to helminths are complex. Infection induces antigen-specific recognition by the immune system, which is consequently charged with the responsibility of marshalling the appropriate effector responses necessary to destroy the parasite, or at the very least inhibit its progression. Obviously, the immune system should accomplish this task while minimizing collateral damage to the host. As our understanding of the neuroendocrine system grows, it has become increasingly clear that this complex network of neurotransmitters, hormones, and cytokines plays an important role in mediating immunity. Helminths present an especially complex relationship between pathogen and these physiological systems, with hormonally dependent host factors such as sex and age correlated with parasite success. On top of the effect that this particular type of parasites may have on the invaded host, recent experimental evidence suggests that helminth parasites not only actively evade immune response, but are also able to exploit the hormonal microenvironment within their host to favor their establishment, growth and reproduction. This complex strategy of host-parasite relationship is much better exemplified by two helminth parasites: the trematode Schistosoma mansoni and the cestode Taenia crassiceps that respond to adrenal steroids and sexual steroids, respectively. Understanding how the host endocrine system can under certain circumstances favor the establishment of a parasitic infection opens interesting perspectives into the host-parasite relationship field.

Immune sexual dimorphism: effect of gonadal steroids on the expression of cytokines, sex steroid receptors, and lymphocyte proliferation.

The aims of this study were, first, to explore the differences in the expression of Th1/Th2 cytokines and of steroid receptors in spleen of intact and gonadectomized mice of both sexes; second, to evaluate the effect of estradiol (E2), progesterone (P4) and testosterone (T) on cytokine production and lymphocyte proliferation, and third, to determine the percentage of spleen cell subpopulations in both sexes. Results indicated dimorphic expression of IFN-gamma and IL-4, which was affected by gonadectomy. CD4+ T lymphocytes were the most frequent type of cell in the spleen, followed by B lymphocytes (CD19+). Interestingly, there was no dimorphic pattern of cell subtypes, and gonadectomy had no effect. Regarding lymphocyte proliferation, E2 inhibited both cells of male (19.51%) and female (24.62%). P4 diminished lymphocyte proliferation by 22% in cells of female and had no effect on cells of male. It is very interesting to note that the sex steroid receptors mRNA was highly expressed in all splenocytes, and that this expression was dimorphic. However, flow cytometry analysis confirmed that only expression of progesterone receptor was dimorphic. This dimorphic pattern was, however, only seen in lymphocytes. Present evidence indicates that sex steroids are capable of affecting crucial immune system functions dimorphically.

Separable putative polyadenylation and cleavage motifs in Trichomonas vaginalis mRNAs.

3' Untranslated region processing and polyadenylation in Trichomonas vaginalis was analyzed by 3' rapid amplification of cDNA ends and sequence analysis of T. vaginalis mRNAs. A putative polyadenylation signal with the sequence UAAA was found 11-30 nucleotides upstream from the cleavage site. The motif pyrimidine( downward arrow)(A)(0-3)AAUU is proposed to be the cleavage site for polyadenylation of transcripts. This potential sequence defining the cleavage site for polyadenylation in eukaryotes is a novel finding. As in other eukaryotes, runs of several U's downstream from the cleavage site were identified. A working hypothesis is proposed which couples the UAA translation stop codon with the signaling for the 3'end processing of transcripts in this early divergent parasitic protozoa.