Enfermedad autoinmune: perturbación de la conversación entre la célula blanco (epitelial) y la matriz extracelular / Autoimmune disease: impaired cross-talk between epithelial cell and extracellular matrix

Glándulas salivales de pacientes con síndrome de Sjõgren presentan un aumento en la degradación de componentes de la lámina basal (LB, laminina y colágeno IV) y estroma (colágenos I y III y fibronectina). Estos cambios se correlacionan con un desbalance en la expresión y actividad de metaloproteinasas y sus inhibidores titulares (MMP/TIMP) que desorganiza la LB de acinos y ductos. Esta desorganización es concomitante a una sobreexpresión de lamininas -1 y -5 y a la degradación de nidógenos 1 y -2, que tienen como función establecer puentes de conexión entre laminina y colágeno IV. Cambios post-transcripcionales de la integrina alfa 6 beta 4 están correlacionados con una drástica redistribución de beta 4 en acinos con LB desorganizadas. Estos resultados sugieren que alteraciones en la adhesión célula-matriz y en la formación de contactos célula-célula pueden modificar la señalización de la integrina alfa 6 beta 4 induciendo muerte celular cuando hay una severa interrupción de la célula acinar con la LB.

Increased degradation of basal lamina (BL, laminin and type IV collagen) and stroma (type I and III collagens, and fibronectin) proteins have been observed in salivary glands of patients with Sjõgren’s syndrome. Such changes are associated with imbalanced expression and activity of extracellular matrix metalloproteinases and their tissue inhibitors (MMPs/TIMPs), which contribute to disorganization of the parenchyma basal lamina. Disorganization of the basal lamina is paralleled by an overexpression of laminin-1and -5 and the degradation of nidogens 1 and -2: linker proteins that help maintain the integrity of type IV collagen and laminin networks.Additionally, post-transcriptional changes in alpha 6 beta 4 integrin are associated with a dramatic redistribution of beta 4 in acini, particularly where perturbations in BL organization were apparent. These findings are taken to suggest that changes in acinar cell-matrix adhesion and cell-cell contact formation may alter alpha 6beta 4 integrin signaling, triggering cell death only when severe disruption of cell-BL attachment occurs.

Gangliosides enhance migration of mouse B16-melanoma cells through artificial basement membrane alone or in presence of laminin or fibronectin.

The migration of B16LuF1 cells, B16-melanoma cells of lower metastatic potential to lung was enhanced through artificial basement membrane in presence of gangliosides of B16LuF1 cells as well as gangliosides of B16-melanoma cells of higher metastatic potential to lung, namely, B16LuF5 and B16LuF10 cells. The same concentration (50 microM) of gangliosides of B16LuF1, B16LuF5 and B16LuF10 cells gradually increased the migration of B16LuF1 cells through basement membrane. Moreover, B16LuF10 cell gangliosides modified the migratory effect of laminin and fibronectin on B16LuF1 cells. Laminin alone increased migration of B16LuF1 cells whereas fibronectin alone decreased migration of the same cells. When B16LuF10 cell gangliosides were used in combination with fibronectin, gangliosides removed the migration inhibitory effect of fibronectin resulting in net enhancing effect. Gangliosides in association with laminin also increased the enhancing effect of laminin on migration of B16LuF1 cells. Thus, gangliosides showed additive enhancing effect when used in combination with laminin. However, effect of individual gangliosides were different. Out of six gangliosides isolated from B16LuF10 cells only two gangliosides corresponding to standard gangliosides GM2 and GM3 enhanced migration of B16LuF1 cells. The migration of B16LuF1 cells in presence of each of the remaining four gangliosides corresponding to GT1b, GD1b, GD1a and GM1 was not altered and was comparable to that of untreated control. Thus, gangliosides of B16 melanoma cells alone or in combination with laminin or fibronectin enhanced migration of B16 melanoma cells through artificial basement membrane, suggesting possible role of tumor gangliosides during invasion of metastatic tumor cells through basement membrane of the surrounding tissues in vivo.

Análisis de la distribución de los componentes de membrana basal laminina, fibronectina y colágeno IV en vasos sanguíneos de patología mamaria benigna y maligna / Analysis of the distribution of components in basal membrane laminin, fibronectin and type IV collagen in blood vessels of benign and malignant mammary pathology

Dentro de la compleja y aún poco comprendida biología de la formación de neovasos en tumores malignos se ha establecido que uno de los puntos restrictivos del proceso sería la precoz destrucción y remodelación que sufre la membrana basal perivascular, la cual estaría mediada por la activación de metalloproteinasas de matriz extracelular. Las diferencias en la cantidad y potencia de los distintos mediadores podrían traer como resultado un cambio en los patrones normales de distribución, cantidad y calidad de los componentes de membranas basales perivasculares en tejidos afectados por neoplasias respecto de lo que existe en la mama normal o en patologías benignas. Se estudiaron 118 piezas histológicas de patología mamaria entre 1990-2000. Se realizaron inmunomarcaciones con anticuerpos primarios antilaminina, fibronectina y colágeno de tipo IV para estudiar membrana basal perivascular. La cantidad de componentes de membrana basal de los vasos sanguíneos aumentan cuando una patología mamaria pasa de ser localizada a invasora y también a medida que se va perdiendo el grado de diferenciación histológica de las mismas. Las características moleculares de las membranas basales vasculares son diferentes en el tejido correspondiente a carcinomas mamarios invasores respecto de lo observado en tejido normal o en patologías sin disrupción de la membrana basal.

Heparan sulfate and control of cell division: adhesion and proliferation of mutant CHO-745 cells lacking xylosyl transferase

We have examined the role of cell surface glycosaminoglycans in cell division: adhesion and proliferation of Chinese hamster ovary (CHO) cells. We used both wild-type (CHO-K1) cells and a mutant (CHO-745) which is deficient in the synthesis of proteoglycans due to lack of activity of xylosyl transferase. Using different amounts of wild-type and mutant cells, little adhesion was observed in the presence of laminin and type I collagen. However, when fibronectin or vitronectin was used as substrate, there was an enhancement in the adhesion of wild-type and mutant cells. Only CHO-K1 cells showed a time-dependent adhesion on type IV collagen. These results suggest that the two cell lines present different adhesive profiles. Several lines of experimental evidence suggest that heparan sulfate proteoglycans play a role in cell adhesion as positive modulators of cell proliferation and as key participants in the process of cell division. Proliferation and cell cycle assays clearly demonstrate that a decrease in the amount of glycosaminoglycans does not inhibit the proliferation of mutant CHO-745 cells when compared to the wild type CHO-K1, in agreement with the findings that both CHO-K1 and CHO-745 cells take 8 h to enter the S phase

Insights into the physiological function of cellular prion protein

Prions have been extensively studied since they represent a new class of infectious agents in which a protein, PrPsc (prion scrapie), appears to be the sole component of the infectious particle. They are responsible for transmissible spongiform encephalopathies, which affect both humans and animals. The mechanism of disease propagation is well understood and involves the interaction of PrPsc with its cellular isoform (PrPc) and subsequently abnormal structural conversion of the latter. PrPc is a glycoprotein anchored on the cell surface by a glycosylphosphatidylinositol moiety and expressed in most cell types but mainly in neurons. Prion diseases have been associated with the accumulation of the abnormally folded protein and its neurotoxic effects; however, it is not known if PrPc loss of function is an important component. New efforts are addressing this question and trying to characterize the physiological function of PrPc. At least four different mouse strains in which the PrP gene was ablated were generated and the results regarding their phenotype are controversial. Localization of PrPc on the cell membrane makes it a potential candidate for a ligand uptake, cell adhesion and recognition molecule or a membrane signaling molecule. Recent data have shown a potential role for PrPc in the metabolism of copper and moreover that this metal stimulates PrPc endocytosis. Our group has recently demonstrated that PrPc is a high affinity laminin ligand and that this interaction mediates neuronal cell adhesion and neurite extension and maintenance. Moreover, PrPc-caveolin-1 dependent coupling seems to trigger the tyrosine kinase Fyn activation. These data provide the first evidence for PrPc involvement in signal transduction

Extracellular matrix molecules play diverse roles in the growth and guidance of central nervous system axons

Axon growth and guidance represent complex biological processes in which probably intervene diverse sets of molecular cues that allow for the appropriate wiring of the central nervous system (CNS). The extracellular matrix (ECM) represents a major contributor of molecular signals either diffusible or membrane-bound that may regulate different stages of neural development. Some of the brain ECM molecules form tridimensional structures (tunnels and boundaries) that appear during time- and space-regulated events, possibly playing relevant roles in the control of axon elongation and pathfinding. This short review focuses mainly on the recognized roles played by proteoglycans, laminin, fibronectin and tenascin in axonal development during ontogenesis

Moléculas de adhesión y su importancia en odontología: revisión de la literatura / Adhesion molecules and its importance in dentistry

En la actualidad se reconoce que las interacciones que se suceden entre las células entre sí y de éstas con los componentes de la matriz extracelular se producen por la intervención de las Moléculas de Adhesión. Las Moléculas de adhesión son glucoproteínas distribuidas en gran cantidad de células que le permiten al organismo realizar funciones tanto fisiológicas, como la adhesión entre las células epiteliales, como fisiopatológicas, por ejemplo la inflamación. Es por ello que se hace imperativo conocer estas familias, para así entender los procesos que se desarrollan en las diversas actividades, normales o patológicas, de la cavidad bucal

Expressäo de laminina no germe dental do primeiro molar de ratos em desenvolvimento / Expression of laminin in the germ of the first molar tooth of developing rats

A regulaçäo da diferenciaçäo e do desenvolvimento dos vários tecidos que formam o germe dental ainda näo está bem estabelecida. Tem-se atribuído à membrana basal e a seus componentes esse papel. O objetivo deste trabalho foi investigar a distribuiçäo de laminina no germe dental do primeiro molar de ratos, utilizando um anticorpo policlonal antilaminina. A análise imunohistoquímica mostrou que a lamina é expressa de forma contínua nas membranas basais dos epitélios interno e externo do orgäo do esmalte, nos pequenos vasos sangüíneos e nas fibrilas nervosas localizadas na papila e no folículo dentário de ratos recém-nascidos. Nas regiöes em que ocorreu diferenciaçäo de células mesenquimais em odontoblastos e de células do epitélio interno em ameloblastos, a expressäo de laminina näo foi mais observada. Essas mudanças sugerem que a expressäo de laminina na membrana basal está relacionada com a diferenciaçäo celular e com a secreçäo de matriz orgânica

Adhesion to laminin is down-regulated upon retinoic acid-induced F9 cell differentiation: a role for alpha6/beta1 integrin

F9 mouse teratocarcinoma cells have a high capacity to adhere to laminin and we identified alpha6/beta1 integrin as the principal laminin-binding protein present in these cells. F9 cells differentiated into parietal endoderm when monolayer cultures were treated with retinoic acid and dibutyryl cyclic AMP. In this process a decreased adherence to laminin was observed due to a lower expression of alpha6/beta1 integrin on the cell surface

Aspectos funcionais da glicosilacao de um receptor de laminina de melanoma murino / Functional aspects of the glycosylation in the receptor of laminin of murine melanoma

A interacao entre a laminina e gp120 140, uma proteina de celulas B16-F10, imunoquimicamente relacionada a alfa-6 beta-1 integrina, e dependente de oligossacaridios N-ligados presentes no receptor. Analise com lectinas de especificidades conhecidas permitiu concluir que gp120/140 e uma sialoglicoproteina, apresentando principalmente complexos antenarios, entre as estruturas N-ligadas. Ainda, foi possivel mostrar que gp120/140 apresenta residuos de alfa-galactose terminais. Por meio de tratamento com exoglicosidases, foi possivel mostrar que residuos alfa-gal presentes na cadeia alfa sao determinantes da interacao com laminina, em ensaios de ligand blotting. Estes residuos estao associados ao fenomeno de adesao celular. De outro lado, a cadeia beta-1, apresenta complexos tri- e tetra-antenarios, cuja sintese pode ser inibida indiretamente por swainsonina. Estes complexos parecem estar associados ao fenomeno de espalhamento celular. Mostrou-se ser possivel modular as funcoes de adesao e espalhamento mediadas por integrinas modificando-se o estado de glicolisacao de suas cadeias

Orquitis autoinmune experimental / Experimental autoimmune orchitis

A pesar de los numerosos trabajos realizados en el modelo de orquitis autoinmune experimental (OAE) aún existen varias incógnitas acerca de su patogenia. Clásicamente, la OAE se indujo en cobayos utilizando como antígenos, espermatozoides u homogenado testicular. Nuestro primer interés fue determinar si antígenos no espermáticos como los componentes extracelulares de la pared del túbulo seminífero, utilizados como inmunógenos, eran capaces de inducir un cuadro autoinmune testicular. Obtuvimos, a partir del testículo de la rataÑ a) una preparación rica en membranas basales del túbulos seminífero (STBM) y b) a partir del STBM, una fracción no relacionada al componente colágeno (D-STBM) que demostró poseer determinantes antigénicos comunes con la laminina, principal glicoproteína no colágena de las membranas basales. El 50% de las ratas inmunizadas con STBM, D-STBM o laminina, desarrolaron una lesión testicular moderada, multifocal, caracterizada por leves infiltrados intersticiales, alteraciones de las membranas basales del túbulo seminífero y de la célula de Sertoli, descamación del epitelio germinal y atrofia tubular. También se detectaron anticuerpos circulantes y una respuesta de inmunidad celular específica. A su vez, ratas inyectadas con un suero heterólogo anti-D-STBM desarrollaron una lesión similar. Por otra parte, se indujo una orquitis severa inmunizando ratas Wistar con un hmogenado testicular homólogo y adyuvantes y se estudiaron las poblaciones linfáticas de los ganglios...