Immunohistochemical localization of metallothionein in the developing teeth of cadmium-injected rats

The effect of cadmium exposition on the structure and mechanical properties of rat incisors

Alterations in the structure and mechanical properties of teeth in adult Wistar rats exposed to cadmium were investigated. Analyses were conducted on two sets of incisors from female and male specimens, that were intoxicated with cadmium (n = 12) or belonged to the control (n = 12). The cadmium group was administered with CdCl2 dissolved in drinking water with a dose of 4mg/kgbw for 10 weeks. The oral intake of cadmium by adult rats led to the range of structural changes in enamel morphology and its mechanical features. A significant increase of cadmium levels in the teeth in comparison to the control, a slight shift in the colour and reduction of pigmented enamel length, higher surface irregularity, a decrease of hydroxyapatite crystals size in the c-axis and simultaneous increase in pigmented enamel hardness were observed. The extent of these changes was sex-dependent and was more pronounced in males.

Zinc and Metallothionein in the Development and Progression of Dental Caries

Chronic oxidative stress and reactive oxygen species (ROS) in oral cavity as well as acidic pH on dental enamel surface due to the metabolic activities of bacterial plaque are the major contributors in the development and progression of dental caries. Along with other factors, deposition or dissolution Ca and Mg mostly determines the re- or demineralization of dental enamel. Zn plays an important role for both Ca and Mg bioavailability in oral cavity. Metallothionein (MT), a group of small molecular weight, cysteine-rich proteins (~ 7 kDa), is commonly induced by ROS, bacterial infection, and Zn. In the current review, we evaluated MT at the junction between the progression of dental caries and its etiologies that are common in MT biosynthesis.

Immunohistochemical localization of metallothionein in dental pulp after cavity preparation of rat molars

OBJECTIVE

Metallothionein (MT) is an intracellular cysteine-rich protein associated with cell proliferation and differentiation. Our objective was to examine immunohistochemically the localization of MT in the rat dental pulp after cavity preparation.

STUDY DESIGN

Cavities were prepared on the upper first molars of 9 rats. Specimens were collected at 1, 3, and 5 days after cavity preparation, and paraffin sections were made. For double-immunohistochemical staining, anti-MT monoclonal antibody (E9) and anti-proliferating cell nuclear antigen (PCNA) monoclonal antibody (PC10) were applied.

RESULTS

At 3 days after cavity preparation, some odontoblasts corresponding to the cavity, many pulp cells, and some endothelial cells in the pulp under the cavity showed both MT- and PCNA-positive immunostainings.

CONCLUSION

Metallothionein was detected in the dental pulp after pulp injury, and it is likely that MT is closely related to the proliferation of newly differentiating odontoblasts and angiogenesis during the healing process.

Salivary proteins and cytokines in drug-induced gingival overgrowth

Little is known about the involvement of saliva in gingival overgrowth (GO). It was hypothesized that, in this situation, the composition of saliva is altered. Thus, proteins, albumin, cytokines, and growth factors in whole and glandular saliva were investigated. Differences between glandular and gingival contributions to the composition of saliva were explored in patients medicated with cyclosporin who exhibited GO (responders), those without GO (non-responders), and non-medicated subjects (controls). In whole saliva, interleukin-1alpha (IL-1alpha), IL-6, IL-8, epidermal growth factor (EGF), nerve growth factor (NGF), and albumin were detected, but in glandular saliva only EGF and NGF were identified. Albumin and IL-6 differed significantly between responders and controls, although the overall profile of salivary proteins remained unchanged. Thus, inflammatory cytokines and albumin are confined to whole saliva and are associated with GO, whereas its content of EGF and NGF appears unaffected by cyclosporin.

Localization of metallothionein (MT) and expression of MT isoforms induced by cadmium in rat dental pulp

We investigated the induction of metallothionein (MT) by cadmium (Cd) in the dental pulp of rat incisors. Time-course studies of MT mRNA expression after single Cd injection were observed by Northern-blot analysis. The isoform-specific expressions of MT mRNAs (MT-I, MT-II and MT-III) were observed using the reverse transcriptase-polymerase chain reaction (RT-PCR) method. Both MT-I and MT-II mRNA levels increased within 3 h, peaked at 3 h and then decreased. These findings demonstrated that MT-I and MT-II mRNA were rapidly induced by Cd in dental pulp. MT-III mRNA was constitutively expressed in rat dental pulp, but the expression level did not change by Cd treatment. The localization of MT protein in Cd-treated rat dental pulp was determined by immunohistochemical staining using anti-MT antibody against MT-I and MT-II. MT protein was localized in the specific cell type of odontoblasts (secretory odontoblasts and resting odontoblasts). In conclusion, it is likely that stained MT in the immunohistochemical study should be MT-I and/or MT-II. Furthermore, MT-I and/or MT-II in Cd-treated rat dental pulp was localized in odontoblasts, in which accumulation of Cd were reported. The cell-specific synthesis of MT may be associated with its metal storage and detoxification role in dental tissues.

Cadmium induces expression of metallothionein in rat dental pulp

Metallothionein (MT) is a metalloprotein with high affinity for certain heavy metals. In the present study, the ability of cadmium (Cd) to induce the synthesis of MT in dental pulp was investigated. Rats were injected subcutaneously with CdCl2 (1.5 mg Cd/kg) daily for 7 days. Expression of the MT gene was demonstrated by reverse transcription polymerase chain-reaction techniques. The results indicate that Cd induced MT in dental pulp of rat incisor and this may be involved in the cellular defense mechanism against Cd toxicity.