A low-molecular-weight soluble protein from bovine lingual epithelium. II. Purification and characterization

Expression of receptor for advanced glycation end products during rat tongue carcinogenesis by 4-nitroquinoline 1-oxide and effect of a selective cyclooxygenase-2 inhibitor, etodolac

OBJECTIVES

The expression of a receptor for advanced glycation end products (RAGE) in lesions developed during rat tongue carcinogenesis by 4-nitroquinoline 1-oxide (4-NQO) and the effect of a selective cyclooxygenase-2 inhibitor, etodolac, were investigated.

METHODS

The tongue lesions were induced in Fischer 344 rats given 20-30 ppm 4-NQO in their drinking water for 12 weeks and then fed the basal diet containing 150 and 300 ppm of etodolac for 16 weeks, respectively.

RESULTS

The incidence of carcinomas in the 4-NQO-alone group was 100%. Etodolac significantly reduced the incidences of carcinomas to 66.7% (p < 0.05) and 50% (p < 0.01) at doses of 150 and 300 ppm, respectively. RAGE protein was immunohistochemically expressed in dysplastic cells and cancer cells of dysplasias and carcinomas. Etodolac significantly decreased the stainability of RAGE protein in dysplasias (p < 0.02) and carcinomas (p < 0.01). The expression of RAGE mRNA analyzed by RT-PCR was clearly detected in carcinomas developing in the 4-NQO-alone group. In carcinomas developing in the etodolac-treated group, RAGE mRNA expression significantly decreased (p < 0.03).

CONCLUSIONS

These results indicate that RAGE is involved in rat tongue carcinogenesis by 4-NQO and suggest that the chemopreventive effect exerted by etodolac is partly related to the inhibition of RAGE expression.

Identification of a new non-neuronal cell type in rat olfactory epithelium

We have examined adult and embryonic rat olfactory epithelia by immunohistochemical techniques using the monoclonal antibody 1A-6, which was raised against embryonic rat olfactory epithelia. A heretofore unidentified cell type, reactive with the monoclonal antibody 1A-6, was observed scattered within the epithelium. The 1A-6 reactivity of these cells is most intense on the microvilli projecting from the luminal cell surfaces. For several reasons, we believe these cells are not neurons but a distinct subpopulation of supporting cells or some other sort of non-neuronal cells. (1) They have no identifiable axonal process, are not reactive with an antibody against olfactory marker protein, and are not in juxtaposition with trigeminal axons. (2) They survive ablation of the olfactory bulb. (3) Their nuclei lie within the supporting cell layer, and they resemble supporting cells morphologically and in their [3H]thymidine birthdating and turnover characteristics. However, the 1A-6-positive cells fail to react with the general supporting cell-specific monoclonal antibody SUS-1 [see Hempstead J. L. and Morgan J. I. (1983) Brain Res. 188, 289-295] a finding which suggests that they are not typical supporting cells. Immunoreactivity to 1A-6 is developmentally regulated. Immunohistochemical preparations of almost all tissues we examined showed widespread reactivity in the embryo but a much more restricted pattern in the adult. In the olfactory epithelium of the fetus, the luminal surfaces of all cells, including supporting cells and olfactory receptor cells and cilia, are reactive, while in the adult only the non-neuronal cell subpopulation shows this reactivity. We also found that during the reconstitution of olfactory epithelium which occurs in response to olfactory bulbectomy-induced neuronal degeneration, fetal patterns of 1A-6 reactivity are not re-expressed, i.e. the only 1A-6-positive cells are the non-neuronal cells seen in unperturbed adult olfactory epithelium. Preliminary biochemical analyses of membrane fractions from E19 brain and from adult olfactory mucosa indicate that the 1A-6 reactivity is associated with two bands, having molecular weights of 42,000 and 46,000 on Western blots.

Immunohistochemical localization of guanine nucleotide-binding proteins in rat olfactory epithelium during development

It has recently been proposed that guanine nucleotide (GTP)-binding proteins (G-proteins) are involved in transducing stimuli in olfactory receptor neurons. If this is the case, G-proteins should be expressed when receptor cells first generate action potentials in response to odorants, i.e. in the rat fetus on the 16th embryonic day (E16). We have done an immunohistochemical study to determine when the alpha- and beta-subunits of the stimulatory G-protein (Gs), are expressed in developing rat olfactory epithelium. The 3 primary antisera used were monospecific polyclonal antibodies generated in rabbits by immunization with synthetic peptides, the amino acid sequences of which matched a portion of the alpha- or beta-subunits of stimulatory G-protein. Both subunits were present in olfactory axons at E15 and in olfactory receptor cell cilia at E16, the day when cilia first sprout in these cells. As development progressed and more cilia grew, most were immunoreactive with antisera to both subunits. Examination of specimens with electron microscopic immunocytochemistry confirmed the localization. Not all cilia on a given olfactory cell were stained, in either fetal or juvenile specimens. The observation that G-proteins are expressed in cilia when action potentials are first demonstrated supports the hypothesis that G-proteins are involved in signal transduction in olfactory receptor cells.

Derivation of Langerhans cell granules from cytomembrane

OKT6 monoclonal antibody has been shown to react selectively with Langerhans cell (LC) cytomembrane in human skin. Taking advantage of this property, we examined the stainability of LC granules with OKT6 using immunoperoxidase method at the ultrastructural level. It was found that the delimiting membranes of LC granules, both attached to the cytomembrane and in the cytoplasm, were specifically stained in the epidermal sheet. These findings suggest that LC granules are derived from invagination of LC cytomembrane and retain T6 antigen. We employed two new methods: one is promotion of endocytosis by incubating the epidermal sheet in tissue culture medium with OKT6 at 4 degrees C and further incubation without OKT6 at 37 degrees C, and the other is the use of saponin to facilitate penetration of the secondary antibody through the cytomembrane of LC. In the LC cytoplasm only the delimiting membrane of the granule was stained; other membranous organelles, such as mitochondria and rough endoplasmic reticulum, did not react.