A multiply charged tetracaine derivative blocks cyclic nucleotide-gated channels at subnanomolar concentrations

Cyclic nucleotide-gated (CNG) ion channels are central participants in sensory transduction, generating the electrical response to light in retinal photoreceptors and to odorants in olfactory receptors. They are expressed in many other tissues where their specific roles in signaling remain unclear. As is true for many other ion channels, there is a paucity of specific blockers needed to dissect the contributions of these channels to cell signaling. CNG channels are members of the superfamily of voltage-gated ion channels, and the local anesthetic tetracaine is known to block CNG channels in a manner that resembles the block of voltage-gated Na(+) channels. The amine in local anesthetics interacts with the charged selectivity filter of Na(+) channels, while the aromatic ring gets stuck in the inner cavity and has hydrophobic interactions with the residues lining that region. Here we have synthesized a derivative of tetracaine, 3-[(aminopropyl)amino]-N,N-dimethyl-N-(2-[[4-(butylamino)benzoyl]oxy]ethyl)propan-1-aminium acetate (APPA-tetracaine), that contains three positively charged amines at physiological pH instead of one. This compound blocked several different CNG channels in the picomolar to nanomolar concentration range at positive membrane potentials, making it several orders of magnitude more potent than tetracaine. In contrast, significant block of Na(+) channels by APPA-tetracaine required concentrations of hundreds of nanomolar. The results suggest that the highly charged moiety of APPA-tetracaine interacts strongly with the negative charge cluster in the selectivity filter of CNG channels. We propose that a variety of potent and specific ion channel blockers could be generated by expanding on traditional blocker structures to target the selectivity filters of other channels.     

In vivo pharmaco-proteomic analysis of hydroxyurea induced changes in the sickle red blood cell membrane proteome

Hydroxyurea (HU) is an effective drug for the treatment of sickle cell disease (SCD). The main clinical benefit of HU is thought to derive from its capacity to increase fetal hemoglobin (HbF) production. However, other effects leading to clinical benefit, such as improved blood rheology, have been suggested. In order to understand HU-induced changes at the proteomic level, we profiled sickle RBC membranes from of HU-treated and untreated patients. Our previous in vitro profiling studies on sickle RBC membranes identified a significant increase in predominantly anti-oxidant enzymes, protein repair and degradation components and a few RBC cytoskeletal proteins. In the present study, using 2D-DIGE (Two-Dimensional Difference In-Gel Electrophoresis) and tandem mass spectrometry, we detected 32 different proteins that significantly changed in abundance in the HU treatment group. The proteins that significantly increased in abundance were mostly membrane skeletal components involved in the regulation of RBC shape and flexibility, and those showing a significant decrease were components of the protein repair and degradation machinery. RBC palmitoylated membrane protein 55 (p55) is significantly increased in abundance at low (in vitro) and high (in vivo) concentrations of HU. Palmitoylated p55 may be an important target of HU-dependent regulation of the sickle RBC membrane, consistent with our earlier in vitro studies.     

Metal accumulation in two contiguous eutrophic peri-urban lakes,Chivero and Manyame,Zimbabwe

Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity.     

The antidepressant-like effect of Ocimum basilicum in an animal model of depression

We investigated the efficacy of Ocimum basilicum (OB) essential oils for treating depression related behavioral, biochemical and histopathological changes caused by exposure to chronic unpredictable mild stress (CUMS) in mice and to explore the mechanism underlying the pathology. Male albino mice were divided into four groups: controls; CUMS; CUMS plus fluoxetine, the antidepressant administered for pharmacological validation of OB; and CUMS plus OB. Behavioral tests included the forced swim test (FST), elevated plus-maze (EPM) and the open ?eld test (OFT); these tests were performed at the end of the experiment. We assessed serum corticosterone level, protein, gene and immunoexpression of brain-derived neurotropic factor (BDNF) and glucocorticoid receptors (GRs) as well as immunoexpression of glial fibrillary acidic protein (GFAP), Ki67, caspase-3 in the hippocampus. CUMS caused depression in the mice as evidenced by prolonged immobility in the FST, prolonged time spent in the open arms during the EPM test and reduction of open field activity in the OFT. OB ameliorated the CUMS induced depressive status. OB significantly reduced the corticosterone level and up-regulated protein and gene expressions of BDNF and GR. OB reduced CUMS induced hippocampal neuron atrophy and apoptosis, and increased the number of the astrocytes and new nerve cells. OB significantly increased GFAP-positive cells as well as BDNF and GR immunoexpression in the hippocampus.     

Preparation of soybean seed samples for FT-IR microspectroscopy

Typical preparation of seed samples for infrared (IR) microspectroscopy involves imbibition of the seed for varying time periods followed by cryosectioning. Imbibition, however, may initiate germination even at 4° C with associated changes in the chemistry of the sample. We have found that it is possible to section seeds that are sufficiently hard, such as soybeans, on a standard laboratory microtome without imbibition. The use of dry sectioning of unimbibed seeds is reported here, as well as a comparison of different mounting media and modes of analysis. Glycerol, Tissue-Tek, and ethanol were used as mounting media, and the quality of the resulting spectra was assessed. Ethanol was the preferred mountant, because it dried quickly with no residue and thus did not interfere with the spectrum of interest. Analysis in transmission mode using barium fluoride windows to hold the samples was compared with transmission-reflection analysis with sections mounted on special infrared-reflecting slides. The two modes of analysis performed well in different regions of the spectrum. The mode of analysis (transmission vs. transmission-reflection) should be based on the components of greatest interest in the sample.