Filaricidal activity of Daniellia oliveri and Psorospermum febrifugum extracts.

BACKGROUND: Drugs currently used for controlling onchocerciasis and lymphatic filariasis (LF) are mainly microfilaricidal, with minimal or no effect on the adult worms. For efficient management of these diseases, it is necessary to search for new drugs with macrofilaricidal activities that can be used singly or in combination with existing ones. Daniellia oliveri and Psorospermum febrifugum are two plants commonly used in the local management of these infections in Bambui, a township in the North West Region of Cameroon, but there is currently no documented scientific evidence to support their claimed anthelmintic efficacy and safety. The aim of this study was to provide evidence in support of the search for means to eliminate these diseases by screening extracts and chromatographic fractions isolated from these plants for efficacy against the parasitic roundworms Onchocerca ochengi and Brugia pahangi. METHODS: The viability of O. ochengi adult worms was assessed using the MTT/formazan assay. Fully confluent monkey kidney epithelial cells (LLC-MK2) served as the feeder layer for the O. ochengi microfilariae (mfs) assays. Viability of the mfs was assessed by microscopic examination for mean motility scoring (relative to the negative control) every 24 h post addition of an extract. The Worminator system was used to test the effects of the extracts on adult B. pahangi motility, and mean motility units were determined for each worm. Cytotoxicity of the active extracts on N27 cells was assessed using the MTS assay. RESULTS: Extracts from D. oliveri and P. febrifugum were effective against the adult roundworms O. ochengi and B. pahangi. Interestingly, extracts showing macrofilaricidal activities against O. ochengi also showed activity against O. ochengi mfs. The hexane stem bark extract of D. oliveri (DOBHEX) was more selective for adult O. ochengi than for mfs, with a half maximal and 100% inhibitory concentration (IC50 and IC100, respectively) against adult O. ochengi of 13.9 and 31.3 µg/ml, respectively. The in vitro cytotoxicity of all active extracts on N27 cells showed selective toxicity for parasites (selectivity index > 1). Bioassay-guided fractionation of the extracts yielded fractions with activity against adult B. pahangi, thus confirming the presence of bioactive principles in the plant extracts. CONCLUSIONS: Our study supports the use of D. oliveri and P. febrifugum in the traditional treatment of onchocerciasis and LF. The further purification of active extracts from these plants could yield lead compounds for filarial drug discovery and development.

Retinoic acid receptor gamma 2 interactions with vitamin D response elements.

The vitamin D receptor (VDR) typically binds DNA in a heterodimer complex with the retinoid X receptor (RXR) to direct repeat sequences separated by three base pairs, or vitamin D response elements (VDREs). A modified yeast one-hybrid screen was utilized to search for partner proteins capable of associating with the VDR on a repressor VDRE. Screening of a HeLa cell cDNA library revealed that retinoic acid receptor gamma 2 (RARgamma2) could specifically interact with VDREs, either in the presence or absence of the VDR. Importantly, the A-domain of RARgamma2 appeared to be crucial for this interaction as evidenced by the inability of RARgamma1 to affect reporter gene activity. Transfection data in COS-7 cells revealed the combination of both receptor ligands strongly attenuated transcriptional activation from an enhancer VDRE when RARgamma2 was co-transfected into these cells with the VDR. Furthermore, a VDR/RARgamma2 complex was detected in the mobility shift assay from nuclear extracts of transfected cells. Thus, the data highlight the novel ability of RARgamma2 to interact with VDREs and impact vitamin D activity, which would allow for additional fine-tuning of a transcriptional response depending on ligand availability and expression profile of these nuclear receptors in a given cell type.

Use and indication of vitamin D and vitamin D analogues in patients with renal bone disease.

Vitamin D plays a pivotal role in the pathogenesis and treatment of renal bone disease. Vitamin D levels decline in the early phase of renal failure, however, through a compensatory mechanism parathyroid hormone (PTH) stimulates the production of 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3), calcitriol) to return it to normal circulating concentrations. Nevertheless, resistance to calcitriol is observed and may be related to the decreased presence of the heterodimeric, DNA-binding partner for the vitamin D receptor protein. In end-stage kidney disease (ESKD) the circulating levels of calcitriol are invariably low. The indications of vitamin D therapy are the replacement of the missing hormone vs suppression of hyperparathyroidism (HPT) requiring daily low-dose oral vs intermittent 'pulse' or oral administration. However, this therapy must be accompanied by careful patient monitoring to avoid hypercalcaemia and low bone turnover. Low bone turnover is not merely a histologic entity, but a clinical condition associated with a high risk of extraosseous calcifications, in particular in the cardiovascular system, leading to increased morbidity. Thus, determination of bone turnover in patients with ESKD is essential. Bone biopsy is the gold standard to assess bone turnover, however, it is not always available and nephrologists rely on PTH levels. The intact PTH assay measures PTH(1-84) and large C-PTH fragments, which may antagonize the PTH(1-84) effects on bone. An assay that measures exclusively PTH(1-84) has recently become available and a calculated PTH(1-84)/C-PTH fragment ratio has been shown to be the best predictor of bone turnover in patients with ESKD not treated with vitamin D or with other medications known to affect bone metabolism. 1,25-dihydroxy-22-oxavitamin D(3) (22-oxacalcitriol, OCT) is a vitamin D analogue that could control serum PTH concentrations without deleterious effects on bone.