The effects of tunicamycin on embryonic and new born murine lymphoid tissues

Most cells in multicellular organisms are in contact with a intricate meshwork of extracellular glycoproteins, proteoglycans as well as other components such as growth factors, chemokines and cytokines. Together, these components constitute the extracellular matrix. The extracellular matrix is a complex, dynamic and critical component of all tissues. It plays an active and complex role in regulating the morphogenesis, survival, migration, proliferation and metabolic functions of cells that contact it. Various amounts and types of glycoproteins, glycosaminoglycans and other components are present in extracellular matrices. The amount and type of these components vary considerably in different tissues and usually differ with the same tissue depending on the developmental stage. Cellular responses to the extracellular matrix seem to be mediated by the action of these macromolecules via their active sites (i.e. glycoconjugates). Tunicamycin, one of a group antibiotic, is widely used in cell biology for its ability to inhibit N-linked glycosylation of asparagine residues on proteins and to induce endoplasmic reticulum stress. In the present study, the effects of tunicamycin on developing murine thymus and spleen tissues at 16th, 17th and 18th gestational days and 1st and 3rd postnatal days were evaluated with three structural and physiological parameters: 1) alterations in glycosaminoglycans, 2) apoptosis and 3) alterations in laminin. with alcian blue/periodic acid-Schiff staining, it was shown that thymic and splenic microenvironments contained carboxylated glycosaminoglycans in all evaluated periods from control and tunicamycin treated groups. On the other hand, immunohistochemical analyses revealed that basement membranes and vessel walls of thymic and splenic tissues of control groups highly expressed laminin molecules whereas; these expressions were decreased in tunicamycin treated groups. In order to determine apoptotic effects of tunicamycin, TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling) assay was performed and it was found that apoptosis in developing thymus and spleen is strongly increased with tunicamycin treatments. In conclusion, during the lymphoid tissue development, glycosaminoglycan content of the extracellular matrix and the glycosylation status of extracellular glycoproteins (e.g. laminin) that mediate cell-extracellular matrix interactions are very important factors that seals the fate of cell physiology and morphogenesis.