Genetic evidence points to deposition of amyloid-β (Aβ) as a causal factor for Alzheimer’s disease. Aβ generation is initiated when β-secretase (BACE1) cleaves the amyloid precursor protein. Starting ...with an oxazine lead 1, we describe the discovery of a thiazine-based BACE1 inhibitor 5 with robust Aβ reduction in vivo at low concentrations, leading to a low projected human dose of 14 mg/day where 5 achieved sustained Aβ reduction of 80% at trough level.
Abstract
The
CA
1‐projecting axons of
CA
3 pyramidal cells, called Schaffer collaterals, constitute one of the major information flow routes in the hippocampal formation. Recent anatomical studies ...have revealed the non‐random structural connectivity between
CA
3 and
CA
1, but little is known regarding the functional connectivity (i.e. how
CA
3 network activity is functionally transmitted downstream to the
CA
1 network). Using functional multi‐neuron calcium imaging of rat hippocampal slices, we monitored the spatiotemporal patterns of spontaneous
CA
3 and
CA
1 burst activity under pharmacological
GABA
ergic blockade. We found that spatially clustered
CA
3 activity patterns were transformed into layered
CA
1 activity sequences. Specifically, synchronized bursts initiated from multiple hot spots in
CA
3 ensembles, and
CA
1 neurons located deeper in the pyramidal cell layer were recruited during earlier phases of the burst events. The order of these sequential activations was maintained across the bursts, but the sequence velocity varied depending on the inter‐burst intervals. Thus,
CA
3 axons innervate
CA
1 neurons in a highly topographical fashion.
•GIRK channel function was crucial for opioid antinociception in oxaliplatin model.•Fentanyl did not obtain GIRK channel-related antinociception in oxaliplatin model.•Action site of GIRK channel was ...different between morphine and oxycodone.
It has begun to be understood that μ-opioid receptor (MOR) produces ligand-biased agonism, which contributes to differential physiological functions of MOR agonists. We previously demonstrated that in oxaliplatin-induced neuropathy in rats, morphine and oxycodone exhibited antinociceptive effects while antinociception of fentanyl was partial, and such different efficacies might result from the different level of Gi/o protein activation. Based on our background, to reveal further mechanism, we focused on the role of Gi/o protein-related downstream signaling, the G-protein inwardly rectifying K+1 (GIRK1) channel. The GIRK1 channel blocker tertiapin-Q (30pmol) was intracerebroventricularly (i.c.v.) or intrathecally (i.t.) administered to rats with oxaliplatin-induced neuropathy. The antinociception of systemic morphine (3mg/kg, subcutaneously (s.c.)) was suppressed only by pretreatment of i.t. tertiapin-Q, while supraspinal tertiapin-Q suppressed only the antinociception of systemic oxycodone (0.56mg/kg, s.c.). Partial antinocicpetion of fentanyl (0.017mg/kg, s.c.) was neither affected by i.c.v nor i.t. tertiapin-Q. These results demonstrated that GIRK1 channels differentially contribute to antinociceptive effects of MOR agonists, and that action site of GIRK1 channels is also different between morphine and oxycodone in oxaliplatin model. This study suggests the possibility that GIRK1 channels have a crucial role for antinociception of MOR agonists in oxaliplatin-induced neuropathy.
Background and Purpose
Oxycodone and morphine are μ‐opioid receptor agonists prescribed to control moderate‐to‐severe pain. Previous studies suggested that these opioids exhibit different analgesic ...profiles. We hypothesized that distinct mechanisms mediate the differential effects of these two opioids and investigated the role of G protein‐gated inwardly rectifying potassium (KIR3 also known as GIRK) channels in their antinociceptive effects.
Experimental Approach
Opioid‐induced antinociceptive effects were assessed in mice, using the tail‐flick test, by i.c.v. and intrathecal (i.t.) administration of morphine and oxycodone, alone and following inhibition of KIR3.1 channels with tertiapin‐Q (30 pmol per mouse, i.c.v. and i.t.) and KIR3.1‐specific siRNA. The antinociceptive effects of oxycodone and morphine were also examined after tertiapin‐Q administration in the mouse femur bone cancer and neuropathic pain models.
Key Results
The antinociceptive effects of oxycodone, after both i.c.v. and i.t. administrations, were markedly attenuated by KIR3.1 channel inhibition. In contrast, the antinociceptive effects of i.c.v. morphine were unaffected, whereas those induced by i.t. morphine were attenuated, by KIR3.1 channel inhibition. In the two chronic pain models, the antinociceptive effects of s.c. oxycodone, but not morphine, were inhibited by supraspinal administration of tertiapin‐Q.
Conclusion and Implications
These results demonstrate that KIR3.1 channels play a primary role in the antinociceptive effects of oxycodone, but not those of morphine, at supraspinal sites and suggest that supraspinal KIR3.1 channels are responsible for the unique analgesic profile of oxycodone.
The proinflammatory cytokine interleukin (IL)-1β is up-regulated in microglial cells surrounding amyloid plaques, leading to the hypothesis that IL-1β is a risk factor for Alzheimer's disease. ...However, we unexpectedly found that IL-1β significantly enhanced α-cleavage, indicated by increases in sAPPα and C83, but reduced β-cleavage, indicated by decreases in sAPPβ and Aβ40/42, in human neuroblastoma SK-N-SH cells. IL-1β did not significantly alter the mRNA levels of BACE1, ADAM-9, and ADAM-10, but up-regulated that of TACE by threefold. The proform and mature form of TACE protein were also significantly up-regulated. A TACE inhibitor (TAPI-2) concomitantly reversed the IL-1β-dependent increase in sAPPα and decrease in sAPPβ, suggesting that APP consumption in the α-cleavage pathway reduced its consumption in the β-cleavage pathway. IL-1Ra, a physiological antagonist for the IL-1 receptor, reversed the effects of IL-1β, suggesting that the IL-1β-dependent up-regulation of α-cleavage is mediated by the IL-1 receptor. IL-1β also induced this concomitant increase in α-cleavage and decrease in β-cleavage in mouse primary cultured neurons. Taken together we conclude that IL-1β is an anti-amyloidogenic factor, and that enhancement of its signaling or inhibition of IL-1Ra activity could represent potential therapeutic strategies against Alzheimer's disease.
Background and Purpose Oxycodone and morphine are mu -opioid receptor agonists prescribed to control moderate-to-severe pain. Previous studies suggested that these opioids exhibit different analgesic ...profiles. We hypothesized that distinct mechanisms mediate the differential effects of these two opioids and investigated the role of G protein-gated inwardly rectifying potassium (K sub(IR)3 also known as GIRK) channels in their antinociceptive effects. Experimental Approach Opioid-induced antinociceptive effects were assessed in mice, using the tail-flick test, by i.c.v. and intrathecal (i.t.) administration of morphine and oxycodone, alone and following inhibition of K sub(IR)3.1 channels with tertiapin-Q (30pmol per mouse, i.c.v. and i.t.) and K sub(IR)3.1-specific siRNA. The antinociceptive effects of oxycodone and morphine were also examined after tertiapin-Q administration in the mouse femur bone cancer and neuropathic pain models. Key Results The antinociceptive effects of oxycodone, after both i.c.v. and i.t. administrations, were markedly attenuated by K sub(IR)3.1 channel inhibition. In contrast, the antinociceptive effects of i.c.v. morphine were unaffected, whereas those induced by i.t. morphine were attenuated, by K sub(IR)3.1 channel inhibition. In the two chronic pain models, the antinociceptive effects of s.c. oxycodone, but not morphine, were inhibited by supraspinal administration of tertiapin-Q. Conclusion and Implications These results demonstrate that K sub(IR)3.1 channels play a primary role in the antinociceptive effects of oxycodone, but not those of morphine, at supraspinal sites and suggest that supraspinal K sub(IR)3.1 channels are responsible for the unique analgesic profile of oxycodone.
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A series of 2′,4′-dimethyl-4,5′-bithiazol-2-yl amino derivatives have been identified as selective TRPV4 antagonists that display inhibition potencies against 4α-phorbol ...12,13-didecanoate (4αPDD), well known as a TRPV4 selective agonist and/or a hypotonicity. In particular, 9-(6-((2′,4′-dimethyl-4,5′-bithiazol-2-yl)amino)nicotinoyl)-3-oxa-9-azabicyclo3.3.1nonan-7-one showed an analgesic effect in Freund’s Complete Adjuvant (FCA) induced mechanical hyperalgesia model in guinea pig (reported in Part 1). However, there are some concerns such as species differences and the need for higher plasma exposure to achieve target efficacy for evaluation by an in vivo pain model. In this Letter, we report the resolution of some of the problems by further optimizing the chemical scaffold.
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A novel series of 2′,4′-dimethyl-4,5′-bithiazol-2-yl amino derivatives were found by high throughput screening of the TRPV4 receptor, at which these compounds showed competitive ...antagonist potential against 4α-phorbol 12,13-didecanoate (4αPDD) as the selective TRPV4 agonist and showed excellent selectivity for TRPV1, N-type and L-type calcium ion channels, but poor ADME profile. In our SAR strategy, we found that the lead molecule 1 also having the unique 3-oxa-9-azabicyclo 3.3.1 nonan-7-one on the right part showed potent TRPV4 antagonist activity, good solubility at pH 6.8, good microsomal stability for human and better ADME profile including oral bioavailability. Moreover, compound 1 had an analgesic effect in Freund’s Complete Adjuvant (FCA) induced mechanical hyperalgesia model in guinea pig. In this letter, we report a lead optimization process to identify the lead compound 1 (Fig. 1).
Background and Purpose
We demonstrated previously that oxycodone has potent antinociceptive effects at supraspinal sites. In this study, we investigated changes in neuronal function and ...antinociceptive mechanisms of oxycodone at ventrolateral periaqueductal gray (
VLPAG
) neurons, which are a major site of opioid action, in a femur bone cancer (
FBC
) model with bone cancer‐related pain.
Experimental Approach
We characterized the supraspinal antinociceptive profiles of oxycodone and morphine on mechanical hypersensitivity in the
FBC
model. Based on the disinhibition mechanism underlying supraspinal opioid antinociception, the effects of oxycodone and morphine on
GABA
A
receptor‐mediated inhibitory postsynaptic currents (
IPSCs
) in
VLPAG
neurons were evaluated in slices from the
FBC
model.
Key Results
The supraspinal antinociceptive effects of oxycodone, but not morphine, were abolished by blocking
G
protein‐gated inwardly rectifying potassium1 (
K
ir
3.1) channels. In slices from the
FBC
model,
GABA
ergic synaptic transmission at
VLPAG
neurons was enhanced, as indicated by a leftward shift of the input–output relationship curve of evoked
IPSCs
, the increased paired‐pulse facilitation and the enhancement of miniature
IPSC
frequency. Following treatment with oxycodone and morphine,
IPSCs
were reduced in the
FBC
model, and the inhibition of presynaptic
GABA
release by oxycodone, but not morphine was enhanced and dependent on
K
ir
3.1 channels.
Conclusion and Implications
Our results demonstrate that
K
ir
3.1 channels are important for supraspinal antinociception and presynaptic
GABA
release inhibition by oxycodone in the
FBC
model. Enhanced
GABA
ergic synaptic transmission at
VLPAG
neurons in the
FBC
model is an important site of supraspinal antinociception by oxycodone via
K
ir
3.1 channel activation.
Accumulation of amyloid beta peptide (Abeta) in brain is a hallmark of Alzheimer's disease (AD). Inhibition of beta-site amyloid precursor protein (APP)-cleaving enzyme-1 (BACE1), the enzyme that ...initiates Abeta production, and other Abeta-lowering strategies are commonly tested in transgenic mice overexpressing mutant APP. However, sporadic AD cases, which represent the majority of AD patients, are free from the mutation and do not necessarily have overproduction of APP. In addition, the commonly used Swedish mutant APP alters APP cleavage. Therefore, testing Abeta-lowering strategies in transgenic mice may not be optimal. In this study, we investigated the impact of BACE1 inhibition in non-transgenic mice with physiologically relevant APP expression. Existing Abeta ELISAs are either relatively insensitive to mouse Abeta or not specific to full-length Abeta. A newly developed ELISA detected a significant reduction of full-length soluble Abeta 1-40 in mice with the BACE1 homozygous gene deletion or BACE1 inhibitor treatment, while the level of x-40 Abeta was moderately reduced due to detection of non-full-length Abeta and compensatory activation of alpha-secretase. These results confirmed the feasibility of Abeta reduction through BACE1 inhibition under physiological conditions. Studies using our new ELISA in non-transgenic mice provide more accurate evaluation of Abeta-reducing strategies than was previously feasible.
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