The in vitro effect of prolactin on the growth, motility and expression of prolactin receptors in larvae of Toxocara canis

Growth hormone stimulates the in vitro development and establishment of Haemonchus contortus in sheep

The physiologic increase in some sex hormones has been associated with an increase in the parasite load caused by Haemonchus contortus in ewes, especially prolactin. In lambs that are especially susceptible to hemonchosis, the levels of sex hormones are low; in contrast, the levels of another pituitary hormone, growth hormone (GH), which is structurally very similar to prolactin, are high. In this study, the in vitro and in vivo effects of GH on H. contortus larvae development and establishment were evaluated. The addition of 20 ng/mL GH for 5 and 10 days to cultures of H. contortus larvae induced an enlargement (p<0.01) and an L3/L4 molting rate (p<0.03) greater than that of untreated larvae or those treated with other concentrations of the hormone. Flow cytometry showed that 3.8% of the largest and most complex cells of newly obtained larvae of H. contortus were positive for the GH receptor, and by immunofluorescence with confocal microscopy, it was observed that these receptors are located in the intestinal region larvae. In the in vivo assay, the administration of recombinant GH to gonadectomized lambs produced an increase in FEC (p<0.03), the number of female adult worms in the abomasum (p<0.05) and the levels of specific antibodies (p<0.04) in relation to the control lambs; however, it did not affect the fertility of H. contortus females. Although many factors affect the development and implantation of H. contortus in the abomasum of sheep, the results of this study strongly suggest that GH participates in the development and establishment of the parasite in sheep, mainly in young sheep.

Transcriptome and metabolome analyses reveal gender-specific expression genes in sea cucumber (Holothuria leucospilota)

The sea cucumber Holothuria leucospilota, a nutritive and commercial marine species, has a high protein and low lipid content. To date, the mechanisms underlying gender determination and differentiation in sea cucumbers remain unclear. Identifying gender-specific molecular markers is an effective method of revealing the genetic basis of gender determination and differentiation. The inability to distinguish between male and female individuals causes reproductive efficiency to decline in aquaculture. In this study, we used the gonads of the sea cucumber H. leucospilota as samples to conduct the experiment. The differentially abundant metabolites (DAMs) detected by liquid chromatography-mass spectrometry were enriched in pathways associated with prolactin metabolism, insulin metabolism, hypoxia-inducible factor-1 signaling, and calcium signaling. At the transcriptome level, Illumina sequencing was performed on H. leucospilota, demonstrating that gender-specific expression genes were enriched in the retinoic acid-inducible gene I-like receptor signaling pathway, C-type lectin receptor signaling pathway, alpha-linolenic acid metabolism, and ether lipid metabolism by the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. By analyzing the common pathways between DAMs and differentially expressed genes, we found that gender-related genes of H. leucospilota were mostly enriched in the necroptosis pathway and the cysteine and methionine metabolism pathways. According to the common pathways, uch-sc1 and uch-sc2 are male-specific expression genes, and uch-sc3 and bhmt are female-specific expression genes at the mRNA level. These results provide information on gender differences in H. leucospilota.

Toxocara: Seroprevalence in Mexico

In Mexico, toxocariasis, like some other parasitosis in humans, is not a disease of conventional surveillance or immediate notification. Seroprevalence studies are scarce, six dealing with paediatric populations and eight dealing with adults; the reports were only from four states in Mexico. There were 1596 children, and the seroprevalence was 13.8%. In the case of adults, there were 1827 subjects, and seroprevalence was 4.7%. There is a significant positive association between seroprevalence and the paediatric population P<0.0001 (OR, 3.285; 95% CI, 2.541-4.279). It is advisable to perform competitive ELISAs and add another diagnostic test, such as Western blot or the detection of circulating antigens to reduce diagnostic uncertainty. This neglected parasitosis can be confused with retinoblastoma. Therefore, there is a risk of ocular enucleation. It is necessary to sensitise the authorities of the Ministry of Health and decision-makers, to provide economic support for epidemiological surveillance of this zoonotic parasite.

Comparative bioinformatic analysis suggests that specific dauer-like signalling pathway components regulate Toxocara canis development and migration in the mammalian host

Background

Toxocara canis is quite closely related to Ascaris suum but its biology is more complex, involving a phase of arrested development (diapause or hypobiosis) in tissues as well as transplacental and transmammary transmission routes. In the present study, we explored and compared dauer-like signalling pathways of T. canis and A. suum to infer which components in these pathways might associate with, or regulate, this added complexity in T. canis.

Methods

Guided by information for Caenorhabditis elegans, we bioinformatically inferred and compared components of dauer-like signalling pathways in T. canis and A. suum using genomic and transcriptomic data sets. In these two ascaridoids, we also explored endogenous dafachronic acids (DAs), which are known to be critical in regulating larval developmental processes in C. elegans and other nematodes, by liquid chromatography-mass spectrometry (LC-MS).

Results

Orthologues of C. elegans dauer signalling genes were identified in T. canis (n = 55) and A. suum (n = 51), inferring the presence of a dauer-like signalling pathway in both species. Comparisons showed clear differences between C. elegans and these ascaridoids as well as between T. canis and A. suum, particularly in the transforming growth factor-β (TGF-β) and insulin-like signalling pathways. Specifically, in both A. suum and T. canis, there was a paucity of genes encoding SMAD transcription factor-related protein (daf-3, daf-5, daf-8 and daf-14) and insulin/insulin-like peptide (daf-28, ins-4, ins-6 and ins-7) homologues, suggesting an evolution and adaptation of the signalling pathway in these parasites. In T. canis, there were more orthologues coding for homologues of antagonist insulin-like peptides (Tc-ins-1 and Tc-ins-18), an insulin receptor substrate (Tc-ist-1) and a serine/threonine kinase (Tc-akt-1) than in A. suum, suggesting potentiated functional roles for these molecules in regulating larval diapause and reactivation. A relatively conserved machinery was proposed for DA synthesis in the two ascaridoids, and endogenous Δ4- and Δ7-DAs were detected in them by LC-MS analysis. Differential transcription analysis between T. canis and A. suum suggests that ins-17 and ins-18 homologues are specifically involved in regulating development and migration in T. canis larvae in host tissues.

Conclusion

The findings of this study provide a basis for functional explorations of insulin-like peptides, signalling hormones (i.e. DAs) and related nuclear receptors, proposed to link to development and/or parasite-host interactions in T. canis. Elucidating the functional roles of these molecules might contribute to the discovery of novel anthelmintic targets in ascaridoids.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3265-y) contains supplementary material, which is available to authorized users.

Progesterone in vitro increases growth, motility and progesterone receptor expression in third stage larvae of Toxocara canis

The in vitro effect of progesterone in T. canis larvae on their enlargement and motility were evaluated, together to the possible presence of progesterone receptors (PRs). T. canis larvae were cultured in RPMI-1640 with different concentrations of progesterone (0, 20, 40, 80, 400 and 800 ng/mL). Enlargement and increases in motility were dependent on the concentration only from 0 to 80 ng/mL (p < 0.05). The mean percentage of PR + cells in newly obtained larvae as measured by flow cytometry was 8.16 ± 0.4. The number of PR + cells increased depending on concentration from 0 to 80 ng/mL (p < 0.001). Cells obtained from larvae stimulated at any of the studied hormone concentrations showed greater mean fluorescence intensity when compared to non-stimulated cells. Additionally, the expression and location of PR + cells were determined in the larvae. The sequence of an amplicon (420-bp) obtained by PCR from T. canis larvae showed 100% homology with a gene fragment that codes for the PR of the dog. PR + cells were immunolocated using confocal microscopy in the intestinal region of the larvae that had been recently obtained. The results of this study show that T. canis larvae can recognize and respond to the presence of progesterone through a molecule possibly able to bind it. Since we previously observed a similar response to prolactin, we suggest that both hormones could participate sequentially in the reactivation of T. canis larvae in pregnant bitches.

Prolactin as immune cell regulator in Toxocara canis somatic larvae chronic infection

Toxocariasis is a zoonotic disease produced by ingestion of larval Toxocara spp. eggs. Prolactin (PRL) has been considered to have an important role in Toxocara canis infection. Recent evidence has found that PRL directly can increase parasite growth and differentiation of T. canis The present study, evaluated the effect of high PRL levels on the immune system's response and parasites clearance in chronic infection. Our results showed that hyperprolactinemia did not affect the number of larvae recovered from several tissues in rats. Parasite-specific antibody production, showed no difference between the groups. Lung tissue presented eosinophilic granulomas typical of a chronic infection in all the experimental groups. Flow cytometry analysis was made in order to determine changes in the percentage of innate and adaptive immune cell subpopulations in the spleen, peripheric (PLN) and mesenteric (MLN) lymphatic nodes. The results showed a differential effect of PRL and infection on different immune compartments in the percent of total T cells, T helper cells, T cytotoxic cells, B cells, NK cells, and Tγδ cells. To our knowledge, for the first time it is demonstrated that PRL can have an immunomodulatory role during T. canis chronic infection in the murine host.

Progesterone inhibits the in vitro L3/L4 molting process in Haemonchus contortus

We evaluated the direct effects of progesterone on the morphology, maturation and behavior of Haemonchus contortus larvae in vitro. The presence and location of possible progesterone receptors in these larvae were also determined. The addition of 8ng/mL of progesterone to larval cultures over 10days reduced larval enlargement, while the addition of 160ng/mL of the hormone increased the enlargement. Up to 62% and 65% of the H. contortus larvae molted from third-stage larvae (L3) to fourth-stage larvae (L4) when cultured in RPMI-1640 media without hormone for 5 and 10days, respectively. The addition of different progesterone concentrations (1, 8, 16, 80 and 160ng/mL) to the larval cultures significantly inhibited the molting process within the same periods. The addition of 8ng/mL or higher progesterone concentrations to the cultures significantly increased larval motility (p<0.05) compared with unstimulated larvae. Flow cytometry showed the expression of progesterone receptors (P4-R) in 15% of the cells from newly isolated H. contortus larvae. When the larvae were cultured for 5days in the presence of the hormone, the percentage of P₄-R+ cells remained the same. In contrast, unstimulated larvae showed a significant reduction in the number of P₄-R+ cells. Using confocal microscopy, a greater concentration of P₄-Rs was immunolocated in the anterior portion of the alimentary tract of the larvae, suggesting that the cells in this region are targeted by the hormone. The results of the present study show that H. contortus larvae have possible P₄-Rs and respond to this hormone by inhibiting their molting process, thereby suggesting the participation of progesterone in the larval arrest phenomenon.