Accuracy, discriminative properties and reliability of a human ESC-based in vitro toxicity assay to distinguish teratogens responsible for neural tube defects.

The poor correlation of developmental toxicity studies in animals with human outcome data has emphasized the need for complementary assays based on human cells and tissues. As neural tube defects represent an important proportion of congenital malformations, we evaluated here the accuracy of a human embryonic stem cell (hESC)-based assay to predict chemically induced disruption of neural tube formation. As teratogenic compounds, we used cyclopamine (CPA), valproic acid (VPA), ochratoxin A (OTA) and mycophenolic acid (MMF), all suspected or known inducers of human neural tube defects, as well as theophylline and saccharin as negative control compounds. We analyzed their effects on the ability of hES cells to give rise to neural precursors (expressing specific marker Nestin), to form neural tube-like structures (rosettes), and to express specific markers (Sox1, Otx2, Lix1, EvI1, Rspo3) during rosette formation. The results showed that various effects of the selected compounds on early neural development could be specifically revealed in vitro through related alterations of neurogenic differentiation of hESC. Furthermore, it was possible to discriminate toxicants acting at different time points during embryonic development and, therefore, responsible for distinct adverse effects on neural tube formation. By comparing four different hESC lines, we observed a significant (up to fivefold) variability of the line-dependent response to toxicants. We highlight at least two sources of variability: one related to the heterogeneity of hESC lines in culture (stemness/commitment profiles); the second to possible genetically determined differences in individual sensitivity to teratogens.

Cyclopamine: from cyclops lambs to cancer treatment.

In the late 1960s, the steroidal alkaloid cyclopamine was isolated from the plant Veratrum californicum and identified as the teratogen responsible for craniofacial birth defects including cyclops in the offspring of sheep grazing on mountain ranges in the western United States. Cyclopamine was found to inhibit the hedgehog (Hh) signaling pathway, which plays a critical role in embryonic development. More recently, aberrant Hh signaling has been implicated in several types of cancer. Thus, inhibitors of the Hh signaling pathway, including cyclopamine derivatives, have been targeted as potential treatments for certain cancers and other diseases associated with the Hh signaling pathway. A brief history of cyclopamine and cyclopamine derivatives investigated for the treatment of cancer is presented.

Hypotensive effect and toxicology of total alkaloids and veratramine from roots and rhizomes of Veratrum nigrum L. in spontaneously hypertensive rats.

Total alkaloids (VTA) and veratramine of Veratrum nigrum L. were tested for hypotensive effect using spontaneously hypertensive rats (SHR). Acute toxicities were also evaluated. There was a dose-dependent reduction in blood pressure and heart rate after a single ingestion (1.0 to 4.0 mg/kg, intragastric administration) of VTA. A single oral ingestion (0.56 to 2.24 mg/kg) of veratramine, the major component of VTA, dose-dependently decreased blood pressure and heart rate, suggesting that veratramine was involved in the hypotensive effect of VTA in SHR. The hypotensive effects of VTA and veratramine are directly positively correlated with the dosage. Side effects were not obvious.

Useful plants of dermatology. VIII. The false hellebore (Veratrum californicum).

Plants have and continue to provide medicine with an abundance of pharmacologically interesting and useful chemicals. In recent years, cyclopamine, a steroidal alkaloid isolated from Veratrum californicum, has been instrumental in dissecting the sonic hedgehog pathway. This brief report outlines cyclopamine's discovery with discussion of its potential application to clinical dermatology.

A preliminary assessment of the toxic and mutagenic potential of steroidal alkaloids in transgenic mice.

Impregnated CD2 transgenic mice, which contain multiple copies of a lambda gt10lacZ construct integrated into the genome of each cell, were given a predetermined estimated maximum tolerated dose of several steroidal alkaloids: Solanum glycoalkaloids from potato, alpha-chaconine and alpha-solanine; aglycones, solanidine and solasodine, and a Veratrum alkaloid, jervine. Observations were made of dams and foetuses for indications of toxicity and/or terata; some dam livers and foetuses were assayed for mutagenicity using the lacZ gene. Other dams were gavaged with a single dose of 75 mg all-trans-retinol/kg to serve as a reference teratogen. Unexpectedly, this level of retinol was not clearly teratogenic. The results of both positive and non-positive selection systems showed that the mutation frequencies in the livers of the dams dosed with alpha-chaconine, alpha-solanine and solanidine were three to four times higher than historically normal in the livers of this transgenic mouse strain.