Principles of early drug discovery Hughes, JP; Rees, S; Kalindjian, SB ...
British journal of pharmacology,
March 2011, Letnik:
162, Številka:
6
Journal Article
Recenzirano
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Developing a new drug from original idea to the launch of a finished product is a complex process which can take 12–15 years and cost in excess of $1 billion. The idea for a target can come from a ...variety of sources including academic and clinical research and from the commercial sector. It may take many years to build up a body of supporting evidence before selecting a target for a costly drug discovery programme. Once a target has been chosen, the pharmaceutical industry and more recently some academic centres have streamlined a number of early processes to identify molecules which possess suitable characteristics to make acceptable drugs. This review will look at key preclinical stages of the drug discovery process, from initial target identification and validation, through assay development, high throughput screening, hit identification, lead optimization and finally the selection of a candidate molecule for clinical development.
The effects of an intravitreal or subretinal injection of soluble or aggregated forms of Abeta(1-42) on retinal nestin-immunoreactivity (-IR) and glial fibrillary acidic protein (GFAP)-IR in ...astrocytes and Müller glial cells and the integrity of the blood-retinal barrier (BRB) were tested in the in vivo rat vitreal-retinal model. Retinas were exposed for 1, 2, 3, 5 or 30 days. We present novel data demonstrating that aggregated Abeta(1-42) up-regulates nestin-IR in astrocytes and Müller cells, with a graded response directly related to the length of pre-injection aggregation time. Similar results were obtained with GFAP-IR, but the signal was weaker. An intravitreal injection of aggregated Abeta(1-42) led to VEGF-IR up-regulation, particularly in the GCL and to a lesser extent in the INL. VEGFR1-IR (Flt1) was also increased, particularly in Müller cells and this was accompanied by marked leakage of albumin into the retinal parenchyma of the injected eye, but not in the contralateral eye.
A novel human G protein-coupled receptor named AXOR12, exhibiting 81% homology to the rat orphan receptor GPR54, was cloned
from a human brain cDNA library. Heterologous expression of AXOR12 in ...mammalian cells permitted the identification of three
surrogate agonist peptides, all with a common C-terminal amidated motif. High potency agonism, indicative of a cognate ligand,
was evident from peptides derived from the gene KiSS-1 , the expression of which prevents metastasis in melanoma cells. Quantitative reverse transcriptase-polymerase chain reaction
was used to study the expression of AXOR12 and KiSS-1 in a variety of tissues. The highest levels of expression of AXOR12
mRNA were observed in brain, pituitary gland, and placenta. The highest levels of KiSS-1 gene expression were observed in placenta and brain. A polyclonal antibody raised to the C terminus of AXOR12 was generated
and used to show localization of the receptor to neurons in the cerebellum, cerebral cortex, and brainstem. The biological
significance of these expression patterns and the nature of the putative cognate ligand for AXOR12 are discussed.
The signaling pathways that mediate the ability of NGF to support survival of dependent neurons are not yet completely clear. However previous work has shown that the c-Jun pathway is activated after ...NGF withdrawal, and blocking this pathway blocks neuronal cell death. In this paper we show that over-expression in sympathetic neurons of phosphatidylinositol (PI) 3-kinase or its downstream effector Akt kinase blocks cell death after NGF withdrawal, in spite of the fact that the c-Jun pathway is activated. Yet, neither the PI 3-kinase inhibitor LY294002 nor a dominant negative PI 3-kinase cause sympathetic neurons to die if they are maintained in NGF. Thus, although NGF may regulate multiple pathways involved in neuronal survival, stimulation of the PI 3-kinase pathway is sufficient to allow cells to survive in the absence of this factor.
The aim of this study was to develop a rapid and accurate high throughput method of screening multiple genes across a single sample set to detect changes in gene expression in the dorsal root ...ganglion (DRG) following partial sciatic nerve ligation in the rat. Using Taqman quantitative RT-PCR, we show that expression of a number of genes, including galanin, vasointestinal peptide and neuropeptide Y are rapidly increased 24 h post-operation in the DRGs on the ligated side only. Other genes tested, including vanilloid receptor-1, substance P, galanin receptor-2 and housekeeping genes did not alter. Analysis of the expression of ASIC4 showed a small difference in expression at 7 days post ligation. By applying a statistical method for analysis of multiple variables, partial least squares, we show that the expression change of ASIC4 was significantly altered on the ligated side even though the change was small. This method will allow us to rapidly identify changes in expression of candidate genes that may be involved in adaptive responses in the DRG due to nerve injury.
Cytochrome c has been shown to play a role in cell-free models of apoptosis. During NGF withdrawal-induced apoptosis of intact rat superior cervical ganglion (SCG) neurons, we observe the ...redistribution of cytochrome c from the mitochondria to the cytoplasm. This redistribution is not inhibited by the caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone (ZVADfmk) but is blocked by either of the neuronal survival agents 8-(4-chlorophenylthio)adenosine 3′:5′-cyclic monophosphate (CPT-cAMP) or cycloheximide. Moreover, microinjection of SCG neurons with antibody to cytochrome c blocks NGF withdrawal-induced apoptosis. However, microinjection of SCG neurons with cytochrome c does not alter the rate of apoptosis in either the presence or absence of NGF. These data suggest that cytochrome c is an intrinsic but not limiting component of the neuronal apoptotic pathway.
Vertebrate T cells express either an alpha beta or gamma delta T cell receptor (TCR). The developmental relatedness of the two cell types is unresolved. alpha beta + T cells respond to specific ...pathogens by collaborating with immunoglobulin-producing B cells in distinct lymphoid organs such as the spleen and Peyer's patches. The precise influence of alpha beta + T cells on B cell development is poorly understood. To investigate the developmental effects of alpha beta + T cells on B cells and gamma delta + T cells, mice homozygous for a disrupted TCR alpha gene were generated. The homozygotes showed elimination of alpha beta + T cells and the loss of thymic medullae. Despite this, gamma delta + T cells developed in normal numbers, and there was an increase in splenic B cells.
Cerebellar granule neurons can be maintained in culture in a medium containing high serum and depolarising levels of KCl. When serum is removed and the KCl levels lowered from 25 to 5 mM, the cells ...undergo apoptosis. Apoptosis can be prevented by inhibitors of transcription or translation, suggesting a need for macromolecular synthesis in the apoptotic process. Using quantitative reverse transcription-polymerase chain reaction the levels of mRNA for a range of genes postulated to be important in apoptosis have been examined. Elevated levels of caspase 3, c-Jun, and Fas ligand were found, in addition to a corresponding increase in c-Jun protein and activation of caspase-3. These results suggest that cerebellar granule neurons upregulate components of both death receptor-mediated and the mitochondrial-mediated death pathways.
In order to study the involvement of caspases in neuronal cell death, we have examined the effects of the viral caspase inhibitor p35 and peptide caspase inhibitors on sympathetic neurons isolated ...from the superior cervical ganglion (SCG). In these neurons, apoptosis can be induced by the withdrawal of nerve growth factor (NGF) and also by the addition of the kinase inhibitor staurosporine. p35 has been shown to be a broad spectrum inhibitor of the caspase family and promotes the survival of SCG neurons withdrawn from NGF. We show that p35 is also protective when apoptosis is induced by staurosporine. In addition, p35 inhibits a number of the morphological features associated with apoptosis, such as nuclear condensation, TUNEL labelling, and externalisation of phosphatidylserine. The tri-peptide caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp (O-methyl)-fluoromethylketone (zVAD-fmk) was effective at inhibiting NGF withdrawal-induced and staurosporine-induced apoptosis of SCG neurons. Two other peptide inhibitors, acetyl-Tyr-Val-Ala-Asp-aldehyde (Ac-YVAD-CHO) and acetyl-Asp-Glu-Ala-Asp-aldehyde (Ac-DEVD-CHO), also inhibited apoptosis induced by both means when microinjected into SCG neurons but peptides derived from the caspase cleavage site in p35 were not protective. We present data to suggest that apoptosis induced by separate death stimuli can result either in the activation of distinct caspases or in differences in the time of activation of the family members.
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