Transglutaminase 2 expression in the salivary myoepithelial cells of mouse embryo

In vivo protein expression changes in mouse livers treated with dialyzed coffee extract as determined by IP-HPLC

Background

Coffee extract has been investigated by many authors, and many minor components of coffee are known, such as polyphenols, diterpenes (kahweol and cafestol), melanoidins, and trigonelline, to have anti-inflammatory, anti-oxidant, anti-angiogenic, anticancer, chemoprotective, and hepatoprotective effects. Therefore, it is necessary to know its pharmacological effect on hepatocytes which show the most active cellular regeneration in body.

Methods

In order to determine whether coffee extract has a beneficial effect on the liver, 20 C57BL/6J mice were intraperitoneally injected once with dialyzed coffee extract (DCE)-2.5 (equivalent to 2.5 cups of coffee a day in man), DCE-5, or DCE-10, or normal saline (control), and then followed by histological observation and IP-HPLC (immunoprecipitation high performance liquid chromatography) over 24 h.

Results

Mice treated with DCE-2.5 or DCE-5 showed markedly hypertrophic hepatocytes with eosinophilic cytoplasms, while those treated with DCE-10 showed slightly hypertrophic hepatocytes, which were well aligned in hepatic cords with increased sinusoidal spaces. DCE induced the upregulations of cellular proliferation, growth factor/RAS signaling, cellular protection, p53-mediated apoptosis, angiogenesis, and antioxidant and protection-related proteins, and the downregulations of NFkB signaling proteins, inflammatory proteins, and oncogenic proteins in mouse livers. These protein expression changes induced by DCE were usually limited to the range ± 10%, suggesting murine hepatocytes were safely reactive to DCE within the threshold of physiological homeostasis. DCE-2.5 and DCE-5 induced relatively mild dose-dependent changes in protein expressions for cellular regeneration and de novo angiogenesis as compared with non-treated controls, whereas DCE-10 induced fluctuations in protein expressions.

Conclusion

These observations suggested that DCE-2.5 and DCE-5 were safer and more beneficial to murine hepatocytes than DCE-10. It was also found that murine hepatocytes treated with DCE showed mild p53-mediated apoptosis, followed by cellular proliferation and growth devoid of fibrosis signaling (as determined by IP-HPLC), and subsequently progressed to rapid cellular regeneration and wound healing in the absence of any inflammatory reaction based on histologic observations.

Electronic supplementary material

The online version of this article (10.1186/s40902-018-0183-z) contains supplementary material, which is available to authorized users.

Variations in both TG1 and TG2 isozyme-specific in situ activities and protein expressions during mouse embryonic development

Transglutaminase (TG) is a family of enzymes that catalyzes cross-linking reactions among proteins. Using fluorescent-labeled highly reactive substrate peptides, we recently developed a system to visualize isozyme-specific in situ enzymatic activity. In the present study, we investigated the in situ activities of TG1 (skin-type) and TG2 (tissue-type) using whole mouse sections of various embryonic developmental stages and neonates. In each case, we also successfully used immunostaining of identical whole mouse sections for protein expression after detection of enzymatic activities. In general, the enzymatic activity was correlated with TG protein expression. However, in some tissues, TG protein expression patterns, which were inconsistent with the enzymatic activities, suggested that inactive TGs were produced possibly by self cross-linking or other modifications. Our method allowed us to simultaneously observe developmental variations in both TG isozyme-specific activities and protein levels in mouse embryonic and neonate tissues.

Antisense inhibition of transglutaminase 2 affects development of mouse embryo submandibular gland in organ culture

Tissue transglutaminase (TGase 2) has been implicated in numerous cellular functions, i.e., apoptosis, differentiation, extracellular matrix protein cross-linking and organogenesis. Earlier report of the strong transient expression of TGase 2 localized at the anchoring sites of muscle bundles of human embryo and recent findings of a similar transient expression of the TGase 2 in the salivary myoepithelial cells of mouse embryo indicated a definitive role of TGase 2 in the cytodifferentiation of myoepithelial cells. To understand functional role(s) of TGase 2 in the organogenesis of salivary gland, antisense inhibition of TGase 2 expression was performed in the organ culture of mouse embryo submandibular gland. The antisense of TGase 2 transfection tested using oral keratinocyte cell line, KB cells, elicited significant inhibition of cellular transglutaminase expression. The same antisense treatment of submandibular glands in organ culture also resulted in the suppression of cellular TGase 2 expression as indicated by weak immunoreaction against anti-TGase 2 in the myoepithelial cells of submandibular glands in contrast to strong reaction in those of the normal and sense-treated glands. Antisense to TGase 2 treatment induced retarded growth of salivary epithelium in 1 week and severe aberrant growth of salivary ducts and acini in 2 weeks and also expression of apoptotic inducer, Bax specifically localized in the myoepithelial cells, suggesting apoptotic state of myoepithelial cells. These data suggest that the antisense inhibition of TGase 2 expression affects the cytodifferentiation of ductal cells and myoepithelial cells, and resulted in severe retardation of tubuloalveolar structure formation of salivary gland.