Subcellular localization of proflavine derivative and induction of oxidative stress—In vitro studies

Acridines have been studied for several decades because of their numerous biological effects, especially anticancer activity. Recently, cytotoxicity of novel acridine derivatives, 3,6-bis((1-alkyl-5-oxo-imidazolidin-2-yliden)imino)acridine hydrochlorides (AcrDIMs), was confirmed for leukemic cell lines [Bioorg. Med. Chem. 2011, 19, 1790]. The mechanism of action of the most cytotoxic hexyl-AcrDIM was studied in this paper focusing attention on a subcellular distribution of the drug. Accumulation of hexyl-AcrDIM in mitochondria was confirmed after labeling mitochondria with MitoRED using ImageStream Imaging Flow Cytometer. The derivative significantly decreased intracellular ATP level (reduction of ATP level was decreased by vitamin E), and induced oxidative stress (ROS production detected by DHE assay) as well as cell cycle arrest in the S-phase (flow cytometry analysis) already after short-time incubation and induction of apoptosis. Cytotoxicity of hexyl-AcrDIM is closely connected with induction of oxidative stress in cells.     

Design,synthesis and evaluation of novel heterodimers of donepezil and huperzine fragments as acetylcholinesterase inhibitors

Four series of novel heterodimers comprised of donepezil and huperzine A (HupA) fragments were designed, synthesized, and evaluated in search of potent acetylcholinesterase (AChE) inhibitors as potential therapeutic treatment for Alzheimer’s disease. Heterodimers comprised of dimethoxyindanone (from donepezil), hupyridone (from HupA), and connected with a multimethylene linker, were identified as potent and selective inhibitors of AChE. Diastereomeric heterodimers (RS,S)-17b (with a tetramethylene linker) exhibited the highest potency of inhibition towards AChE with an IC₅₀ value of 9 nM and no detectable inhibitory effect on butyrylcholinesterase at 1 mM.     

Differential responses by two closely related native fishes to restoration actions

Globally, river degradation has decimated freshwater fish populations. To help reverse this trend in a southeastern Australia river, we used multiple restoration actions, including reintroduction of instream woody habitat, riparian revegetation, removal of a weir hindering fish movement, fencing out livestock, and controlling riparian weeds. We monitored the responses of native fish at the segment scale (20 km) and reach scale (0.3 km) over 7 years to assess the effectiveness of the different restoration strategies. Two closely related species, Murray cod Maccullochella peeli and trout cod Maccullochella macquariensis, increased at the restored segment compared with the control segment. However, inherent differences between river segments and low sample size hampered assessment of the mechanisms responsible for segment‐scale changes in fish abundance. In contrast, at the reach scale, only M. peeli abundance significantly increased in reaches supplemented with wood. These differential responses by 2 closely related fish species likely reflect species‐specific responses to increased habitat availability and enhanced longitudinal connectivity when the weir improved passage around a fishway. Changes in M. peeli abundance in segments supplemented with and without wood suggest an increase in carrying capacity and not simply a redistribution of individuals within the segment, facilitated the observed expansion. Our findings confirm the need to consider individual fish species' habitat preferences carefully when designing restoration interventions. Further, species‐specific responses to restoration actions provide waterway managers with precise strategies to target fish species for recovery and the potential to predict fish outcomes based on ecological preferences.     

Modulating biochemical perturbations during 72-hour machine perfusion of kidneys: role of preservation solution

This study documents renal biochemistry during hypothermic machine perfusion of kidneys. It is intended to demonstrate that a comprehensive evaluation of organ viability during ex-vivo preservation is needed to increase the number of organs available for transplantation and to reduce the current renal discard rate. Porcine kidneys were hypothermically machine perfused for 72 h with either Unisol-UHK or Belzer-Machine Perfusion Solution, (Belzer-MPS). Renal perfusate samples were periodically collected and biochemically analyzed. Significant differences were measured in the renal metabolic activity between the two experimental groups while similar values for traditional parameters such as renal flow rate and vascular resistance values were recorded. The effluent of UHK perfused kidneys showed strong metabolites and NH(4)(+) dynamics (P<0.05 vs. baseline), while the Belzer-MPS kidneys metabolic activity led to little or no change of the effluent biochemistry relative to baseline.     

O-fucosylation is required for ADAMTS13 secretion

ADAMTS13 is a plasma metalloproteinase that cleaves von Willebrand factor to smaller, less thrombogenic forms. Deficiency of ADAMTS13 activity in plasma leads to thrombotic thrombocytopenic purpura. ADAMTS13 contains eight thrombospondin type 1 repeats (TSR), seven of which contain a consensus sequence for the direct addition of fucose to the hydroxyl group of serine or threonine. Mass spectral analysis of tryptic peptides derived from human ADAMTS13 indicate that at least six of the TSRs are modified with an O-fucose disaccharide. Analysis of [(3)H]fucose metabolically incorporated into ADAMTS13 demonstrated that the disaccharide has the structure glucose-beta1,3-fucose. Mutation of the modified serine to alanine in TSR2, TSR5, TSR7, and TSR8 reduced the secretion of ADAMTS13. Mutation of more than one site dramatically reduced secretion regardless of the sites mutated. When the expression of protein O-fucosyltransferase 2 (POFUT2), the enzyme that transfers fucose to serines in TSRs, was reduced using siRNA, the secretion of ADAMTS13 decreased. A similar outcome was observed when ADAMTS13 was expressed in a cell line unable to synthesize the donor for fucose addition, GDP-fucose. Although overexpression of POFUT2 did not affect the secretion of wild-type ADAMTS13, it did increase the secretion of the ADAMTS13 TSR1,2 double mutant but not that of ADAMTS13 TSR1-8 mutant. Together these findings indicate that O-fucosylation is functionally significant for secretion of ADAMTS13.     

The roles of cyclin-dependent kinase 5 in dendrite and synapse development

Since the isolation of cyclin-dependent kinase 5 (Cdk5), this proline-directed serine/threonine kinase has been demonstrated as an important regulator of neuronal migration, neuronal survival and synaptic functions. Recently, a number of players implicated in dendrite and synapse development have been identified as Cdk5 substrates. Neurite extension, synapse and spine maturation are all modulated by a myriad of extracellular guidance cues or trophic factors. Cdk5 was recently demonstrated to regulate signaling downstream of some of these extracellular factors, in addition to modulating Rho GTPase activity, which regulates cytoskeletal dynamics. In this communication, we summarize our existing knowledge on the pathways and mechanisms through which Cdk5 affects dendrite, synapse and spine development.     

RCAN1-1L is overexpressed in neurons of Alzheimer's disease patients

At least two different isoforms of RCAN1 mRNA are expressed in neuronal cells in normal human brain. Although RCAN1 mRNA is elevated in brain regions affected by Alzheimer's disease, it is not known whether the disease affects neuronal RCAN1, or if other cell types (e.g. astrocytes or microglia) are affected. It is also unknown how many protein isoforms are expressed in human brain and whether RCAN1 protein is overexpressed in Alzheimer's disease. We explored the expression of both RCAN1-1 and RCAN1-4 mRNA isoforms in various cell types in normal and Alzheimer's disease postmortem samples, using the combined technique of immunohistochemistry and in situ hybridization. We found that both exon 1 and exon 4 are predominantly expressed in neuronal cells, and no significant expression of either of the exons was observed in astocytes or microglial cells. This was true in both normal and Alzheimer's disease brain sections. We also demonstrate that RCAN1-1 mRNA levels are approximately two-fold higher in neurons from Alzheimer's disease patients versus non-Alzheimer's disease controls. Using western blotting, we now show that there are three RCAN1 protein isoforms expressed in human brain: RCAN1-1L, RCAN1-1S, and RCAN1-4. We have determined that RCAN1-1L is expressed at twice the level of RCAN1-4, and that there is very minor expression of RCAN1-1S. We also found that the RCAN1-1L protein is overexpressed in Alzheimer's disease patients, whereas RCAN1-4 is not. From these results, we conclude that RCAN1-1 may play a role in Alzheimer's disease, whereas RCAN1-4 may serve another purpose.