Mucina y Enfermedad Periodontal / Mucin and periodontal disease

La enfermedad periodontal (EP) es una patología que afecta principalmente los tejidos que rodean a la pieza dentaria (PD) y se caracteriza, en la mayoría de los casos, por una exposición bacteriana que favorece una respuesta destructiva e inflamatoria del huésped, que conduce a la pérdida de inserción periodontal de la PD, provocando una marcada reabsorción ósea y la posible pérdida de las PD. El diagnóstico de EP implica evaluaciones clínicas y radiográficas, en la actualidad se están realizando diversas investigaciones para evaluar posibles compuestos en los fluidos orales a través de lo cual puede ser posible evaluar la presencia y gravedad de estas enfermedades, como así también el riesgo en los pacientes. Hay evidencias de la interacción de macromoléculas salivales, como las mucinas, con microorganismos específicos. De esta manera las mucinas, junto con otros productos de la saliva, ayudan a modular tanto el número como el tipo de proliferación de ciertos organismos y provocar la disminución de otros. La revisión de la literatura actual concluye que las mucinas salivales pueden servir como un parámetro bioquímico de la inflamación del periodonto (AU)

Periodontal disease (PD) is a pathology that mainly affects the tissues surrounding the tooth (PD) and is characterized, in most cases, by a bacterial exposure that favors a destructive and inflammatory response of the host, which leads to the loss of periodontal insertion of the PD, causing a marked bone resorption and the possible loss of the PD. The diagnosis of PD involves clinical and radiographic evaluations, at present several investigations are being carried out to evaluate possible compounds in oral fluids through which it may be possible to evaluate the presence and severity of these diseases, as well as the risk in patients. There is evidence of the interaction of salivary macromolecules, such as mucins, with specific microorganisms. In this way, mucins, together with other saliva products, help modulate both the number and type of proliferation of certain organisms and cause the decrease of others. The review of the current literature concludes that salivary mucins can serve as a biochemical parameter of inflammation of the periodontium (AU)

Mucinas salivales: estructura química, mecanismos de liberación y participación en la defensa no inmunológica de la cavidad bucal / Salivary mucins: chemical structure, release mechanisms and participation in the non-immunological defense of the oral cavity

En este artículo se describen: 1) las características físico-químicas de las mucinas salivales, denominadas MG1 y MG2. 2) El mecanismo de secreción por estimulación simpática y parasimpática. 3) La distinta participación de MG1 y MG2 tanto en la actividad deglutoria como en los mecanismos de defensa de la cavidad bucal, en relación con sus propiedades físico-químicas. 4) El rol de las mucinas salivales en la protección de la mucosa del tracto gastrointestinal. 5) La relación entre las mucinas saliales y las patologías de la cavidad bucal.(AU)

Mucinas salivales: estructura química, mecanismos de liberación y participación en la defensa no inmunológica de la cavidad bucal / Salivary mucins: chemical structure, release mechanisms and participation in the non-immunological defense of the oral cavity

En este artículo se describen: 1) las características físico-químicas de las mucinas salivales, denominadas MG1 y MG2. 2) El mecanismo de secreción por estimulación simpática y parasimpática. 3) La distinta participación de MG1 y MG2 tanto en la actividad deglutoria como en los mecanismos de defensa de la cavidad bucal, en relación con sus propiedades físico-químicas. 4) El rol de las mucinas salivales en la protección de la mucosa del tracto gastrointestinal. 5) La relación entre las mucinas saliales y las patologías de la cavidad bucal.

Trypanosoma cruzi surface mucins: host-dependent coat diversity.

The surface of the protozoan parasite Trypanosoma cruzi is covered in mucins, which contribute to parasite protection and to the establishment of a persistent infection. Their importance is highlighted by the fact that the approximately 850 mucin-encoding genes comprise approximately 1% of the parasite genome and approximately 6% of all predicted T. cruzi genes. The coordinate expression of a large repertoire of mucins containing variable regions in the mammal-dwelling stages of the T. cruzi life cycle suggests a possible strategy to thwart the host immune response. Here, we discuss the expression profiling of T. cruzi mucins, the mechanisms leading to the acquisition of mucin diversity and the possible consequences of a mosaic surface coat in the interplay between parasite and host.

Infection by Trypanosoma cruzi metacyclic forms deficient in gp82 but expressing a related surface molecule, gp30.

Trypanosoma cruzi metacyclic trypomastigotes invade and replicate in the gastric mucosal epithelium after oral infection. In this study we analyzed the process of infection by T. cruzi isolates deficient in the expression of gp82, the metacyclic stage-specific surface glycoprotein implicated in target cell entry in vitro and in promoting mucosal infection in mice after oral challenge. Mice infected by the oral route with metacyclic forms of gp82-deficient isolate 569 or 588 developed patent parasitemia but at greatly reduced levels compared to those infected with the gp82-expressing isolate CL. Metacyclic forms of both isolates expressed gp30, a surface glycoprotein detectable by monoclonal antibody (MAb) 3F6 directed to gp82. Otherwise, the gp82-deficient isolates displayed a surface profile similar to that of the CL isolate and also entered epithelial HeLa cells in a manner inhibitable by MAb 3F6 and dependent on the parasite signal transduction that involved the activation of protein tyrosine kinase and Ca(2+) mobilization from thapsigargin-sensitive stores. Like gp82, gp30 triggered the host cell Ca(2+) response required for parasite internalization. Purified gp30 and the recombinant gp82 inhibited HeLa cell invasion of metacyclic forms of isolates 569 and 588 by approximately 90 and approximately 70%, respectively. A cell invasion assay performed in the presence of gastric mucin, mimicking the in vivo infection, showed an inhibition of 70 to 75% in the internalization of gp82-deficient isolates but not of the CL isolate. The recombinant gp82 exhibited an adhesive capacity toward gastric mucin much higher than that of gp30. Taken together, our findings indicate that target cell entry of metacyclic trypomastigotes can be mediated either by gp82 or gp30 but that efficient mucosal infection depends on the expression of gp82.

Glycosylphosphatidylinositol-anchored mucin-like glycoproteins from Trypanosoma cruzi bind to CD1d but do not elicit dominant innate or adaptive immune responses via the CD1d/NKT cell pathway.

It has been proposed that self and protozoan-derived GPI anchors are natural ligands of CD1d. In this study, we investigated the ability of GPI anchors from Trypanosoma cruzi to bind to CD1d and mediate activation of NKT cells. We observed that GPI-anchored mucin-like glycoproteins (GPI mucins), glycoinositolphospholipids (GIPLs), and their phosphatidylinositol moieties bind to rCD1d and inhibit the stimulation of a NKT hybridoma by the alpha-galactosylceramide-CD1 complex. However, these GPI anchors and related structures were unable to activate NKT cells in vitro or in vivo. We found that high titers of Ab anti-GPI mucins, but not anti-GIPLs, were detected in sera from wild-type as well as in TAP1(-/-), CD1d(-/-), and MHC class II(-/-) mice after immunization. However, T-dependent anti-GPI mucin Ab isotypes, such as IgG1, IgG2a, IgG2b, and IgG3, were absent on MHC class II(-/-), but were conserved in CD1d(-/-) and TAP1(-/-) mice. Furthermore, we found that CD1d(-/-) mice presented a robust cytokine as well as anti-GPI mucins and anti-GIPL Ab responses, upon infection with T. cruzi parasites. These results indicate that, despite binding to CD1d, GPI mucins and related structures expressed by T. cruzi appear not to evoke dominant CD1d-restricted immune responses in vivo. In contrast, MHC class II is critical for the production of the major Ig G isotypes against GPI mucins from T. cruzi parasites.

Acidic pH and increasing [Ca(2+)] reduce the swelling of mucins in primary cultures of human cervical cells.

BACKGROUND: Cervical mucus is a heterogeneous mixture of water, ions and mucins that form a hydrophilic polymer gel. Mucins, the main components of mucus, are condensed inside secretory granules and swell to become a hydrogel after exocytosis. Using human cervical secretory cell primary cultures, the effect of [Ca(2+)] and [H(+)] on the swelling velocity of mucin granules was investigated in vitro. METHODS AND RESULTS: Immunocytochemistry demonstrated that estrogen and progesterone receptors were expressed in cultured secretory cells along with mucins type 1, 4, 5AC and 5B. Exocytosis of secretory cells, recorded by videomicroscopy, showed that during swelling, the radius of the secretory granule matrix followed first-order kinetics. An increase in extracellular [Ca(2+)] from 1 to 4 mmol/l or a reduction in pH from 7.4 to 6.5 was seen to produce a significant decrease in the velocity of swelling of the secretory granule matrix. CONCLUSIONS: The inverse relationship observed between the diffusion of the granular matrix and the extracellular [Ca(2+)] or [H(+)] suggested that changes in cation concentration might drastically affect the swelling characteristics of mucins and provide a control mechanism for the observed viscoelastic properties of mucus.

Trypanosoma cruzi surface mucin TcMuc-e2 expressed on higher eukaryotic cells induces human T cell anergy, which is reversible.

Chagas' disease is a chronic, debilitating, multisystemic disorder that affects millions of people in Latin America. The protozoan parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, has a large number of O-glycosylated Thr/Ser/Pro-rich mucin molecules on its surface (TcMuc). These mucins are the main acceptors of sialic acid and have been suggested to play a role on various host-parasite interactions, such as adhesion to macrophages, protection from complement lysis, and immunomodulation of the immune response mounted by the host. To observe the immunologic effect obtained by the heterologous expression of a TcMuc gene in higher eukaryotic cells exposed to xenogeneic lymphocytes, we developed a strategy based on the transfection of a known T. cruzi mucin gene (TcMuc-e2) into Vero cells. In contrast to the brisk proliferation and activation of human lymphocytes observed at 3, 4, and 5 days induced by normal Vero cells, neither proliferation nor significant activation of human lymphocytes was observed with TcMuc-e2-transfected Vero cells. This TcMuc-e2 mucin-induced suppression of T cell response can be reversed by the addition of exogenous IL-2. In addition it was demonstrated that the immunosuppressive reaction was not related to the induction of an important degree of apoptosis in human lymphocytes. Posttranslational modification are required for the inhibitory effect that TcMuc-e2 exerts when transfected to Vero cells. O-glycosylation and sialylation are required to obtain the immunomodulatory effect as assessed by O-sialoglycoprotease and neuraminidase treatments. These results are consistent with other studies showing that surface glycoconjugates from T. cruzi and mammalian cells can induce an inhibition of the immune response.

Mucin-like molecules form a negatively charged coat that protects Trypanosoma cruzi trypomastigotes from killing by human anti-alpha-galactosyl antibodies.

In the presence of sialic acid donors Trypanosoma cruzi acquires up to 10(7) sialic acid residues on its surface, in a reaction catalyzed by its unique trans-sialidase. Most of these sialic acid residues are incorporated into mucin-like glycoproteins. To further understand the biological role of parasite sialylation, we have measured the amount of mucin in this parasite. We found that both epimastigote and trypomastigote forms have the same number of mucin molecules per surface area, although trypomastigotes have less than 10% of the amount of glycoinositol phospholipids, the other major surface glycoconjugate of T. cruzi. Based on the estimated surface area of each mucin, we calculated that these molecules form a coat covering the entire trypomastigote cell. The presence of the surface coat is shown by transmission electron microscopy of Ruthenium Red-stained parasites. The coat was revealed by binding of antibodies isolated from Chagasic patients that react with high affinity to alpha-galactosyl epitopes present in the mucin molecule. When added to the trypomastigote, these antibodies cause an extensive structural perturbation of the parasite coat with formation of large blebs, ultimately leading to parasite lysis. Interestingly, lysis is decreased if the mucin coat is heavily sialylated. Furthermore, addition of MgCl2 reverses the protective effect of sialylation, suggesting that the sialic acid negative charges stabilize the surface coat. Inhibition of sialylation by anti-trans-sialidase antibodies, found in immunized animals, or human Chagasic sera, also increase killing by anti-alpha-galactosyl antibodies. Therefore, the large amounts of sialylated mucins, forming a surface coat on infective trypomastigote forms, have an important structural and protective role.

Glycoconjugates isolated from Trypanosoma cruzi but not from Leishmania species membranes trigger nitric oxide synthesis as well as microbicidal activity in IFN-gamma-primed macrophages.

In the present study, we investigated the role of glycosylphosphatidylinositol-anchored mucin-like glycoproteins (GPI-mucins) from Trypanosoma cruzi trypomastigotes in triggering the synthesis of nitric oxide as well as the microbicidal activity in murine macrophages. Our results show that GPI-mucins isolated from trypomastigote membranes are potent inducers of nitric oxide synthesis by IFN-gamma-primed macrophages, even at concentrations as low as 10 ng/ml. Our data also indicate the important role of glycosylphosphatidylinositol anchors from GPI-mucins as the second signal responsible for induction of nitric oxide synthesis by macrophages. To further investigate the role of these parasite molecules in inducing parasiticidal function, we cultured macrophages in the presence or absence of trypomastigote GPI-mucins and/or IFN-gamma and then infected these cells with either Leishmania spp. or T. cruzi. IFN-gamma was sufficient to induce microbial activity in macrophages infected with T. cruzi trypomastigotes. In contrast, killing of different species of Leishmania was further enhanced when macrophages exposed to IFN-gamma were also costimulated with trypomastigote-derived GPI-mucins. Our results also indicate that different glycolipids obtained from Leishmania major or Leishmania donovani (i.e., lipophosphoglycans or glycoinositolphospholipids) were unable to potentiate nitric oxide synthesis and/or microbicidal activity displayed by IFN-gamma-primed macrophages.