Calcitonin potentiates oxygen-glucose deprivation-induced neuronal death

Trophic factors in the carotid body

The aim of the present study is to provide a review of the expression and action of trophic factors in the carotid body. In glomic type I cells, the following factors have been identified: brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, artemin, ciliary neurotrophic factor, insulin-like growth factors-I and -II, basic fibroblast growth factor, epidermal growth factor, transforming growth factor-alpha and -beta1, interleukin-1beta and -6, tumour necrosis factor-alpha, vascular endothelial growth factor, and endothelin-1 (ET-1). Growth factor receptors in the above cells include p75LNGFR, TrkA, TrkB, RET, GDNF family receptors alpha1-3, gp130, IL-6Ralpha, EGFR, FGFR1, IL1-RI, TNF-RI, VEGFR-1 and -2, ETA and ETB receptors, and PDGFR-alpha. Differential local expression of growth factors and corresponding receptors plays a role in pre- and postnatal development of the carotid body. Their local actions contribute toward producing the morphologic and molecular changes associated with chronic hypoxia and/or hypertension, such as cellular hyperplasia, extracellular matrix expansion, changes in channel densities, and neurotransmitter patterns. Neurotrophic factor production is also considered to play a key role in the therapeutic effects of intracerebral carotid body grafts in Parkinson's disease. Future research should also focus on trophic actions on carotid body type I cells by peptide neuromodulators, which are known to be present in the carotid body and to show trophic effects on other cell populations, that is, angiotensin II, adrenomedullin, bombesin, calcitonin, calcitonin gene-related peptide, cholecystokinin, erythropoietin, galanin, opioids, pituitary adenylate cyclase-activating polypeptide, atrial natriuretic peptide, somatostatin, tachykinins, neuropeptide Y, neurotensin, and vasoactive intestinal peptide.

In vitro neuronal cytotoxicity of latex and nonlatex orthodontic elastics

Although the toxicity of many dental materials has been thoroughly investigated, the toxicity of orthodontic elastic materials has not been extensively tested. We evaluated the neurotoxicity of 3 latex and 3 nonlatex orthodontic elastics in murine cerebral cortical cell cultures. Standard-sized pieces of each material from 3 manufacturers (American, Masel, and GAC) were placed on culture well inserts, allowing the material to be exposed to the culture bathing media without causing physical disruption of the cells. Cell death was quantified by assaying the release of the cytosolic enzyme lactate dehydrogenase. Exposure of cortical cultures to the nonlatex elastics did not cause significant neuronal death, but exposure to each of the latex elastics resulted in significant neuronal death. The neuronal death induced by each of the latex elastics was blocked by adding the metal chelator, EDTA (calcium disodium ethylenediaminetetraacetate). Because many latexes use zinc-containing compounds in the prevulcanization process, and the death induced had characteristics similar to zinc-induced neuronal death, it seems likely that the toxicity of latex elastics was mediated by zinc release. Because ingestion of zinc is not a health risk, the results suggest that, in spite of the finding that latex elastics have higher in vitro cytotoxicity than nonlatex elastics, the use of latex elastics in orthodontics is acceptable.

Calcitonin receptor gene and breast cancer: quantitative analysis with laser capture microdissection

There is a growing body of evidence indicating that calcitonin (CT) and its receptor (CTR) is involved in cell growth, differentiation and tissue development. Using laser capture microdissection (LCM) and real-time reverse transcription polymerase chain reactions (RT-PCR), we have investigated CTR mRNA expression in 60 primary breast cancers, including 14 pairs of matched cancers and unaffected ductal epithelia from the same patients. Our results demonstrate that CTR mRNA was constantly expressed in normal ductal epithelium and in breast cancer. In the 14 cases where matched samples were available, a decrease in CTR mRNA expression was found in 9 breast cancers (64.3%), an increased CTR expression in 2 cases (14.3%) and no significant change in 3 cases (21.4%). In 60 cases of primary breast cancers, decreased CTR expression was found in 44 (73.3%), increased CTR expression was detected in 10 cases (16.7%) and no change was observed in 6 cases (10%). Decreased CTR expression was found more often in cases with lymph node metastasis (p = 0.0498) and lymphatic invasion (p = 0.0179). Also there was a decreased CTR expression in cases with an extensive intraductal component (p = 0.0543) and a high nuclear grade (p = 0.1934), although this was not statistically significant. Overall, we conclude that CTR mRNA was constantly expressed in unaffected ductal epithelium, whereas decreased CTR mRNA expression was frequently found in breast cancers, particularly in cases with lymph node metastasis and lymphatic invasion. These results suggest that CTR might be of great potential significance in breast cancer progression.

In vitro neurotoxic evaluation of root-end-filling materials

Root-end-filling materials have been tested for toxicity on several cell types, but their toxicity has not been tested on neurons. In this study we evaluated the neurotoxicity in murine cerebral cortical cell cultures of four commonly used root-end-filling materials: mineral trioxide aggregate, amalgam, Super EBA, and Diaket. Standardized amounts of each material were placed on culture-well inserts, allowing the material to be exposed to the culture bathing media without causing physical disruption of the cells. Cell death was quantified by assaying release of the cytosolic enzyme lactate dehydrogenase. Exposure of cortical cultures to freshly mixed or 7-day-old MTA did not cause significant neuronal death, whereas exposure to freshly mixed or 7-day-old amalgam, Super EBA, and Diaket resulted in significant neuronal death (p < .05). Thus, each material, except for mineral trioxide aggregate, can induce neurotoxicity, even when allowed to set thoroughly.

Neurotoxicity of dental amalgam is mediated by zinc

The use of dental amalgam is controversial largely because it contains mercury. We tested whether amalgam caused toxicity in neuronal cultures and whether that toxicity was caused by mercury. In this study, we used cortical cell cultures to show for the first time that amalgam causes nerve cell toxicity in culture. However, the toxicity was not blocked by the mercury chelator, 2,3-dimercaptopropane-1-sulphonate (DMPS), but was blocked by the metal chelator, calcium disodium ethylenediaminetetraacetate (CaEDTA). DMPS was an effective mercury chelator in this system, since it blocked mercury toxicity. Of the components that comprise amalgam (mercury, zinc, tin, copper, and silver), only zinc neurotoxicity was blocked by CaEDTA. These results indicate that amalgam is toxic to nerve cells in culture by releasing zinc. While zinc is known to be neurotoxic, ingestion of zinc is not a major concern because zinc levels in the body are tightly regulated.