Findings From a National Survey of Older US Adults on Patient Willingness to Use Telehealth Services: Cross-Sectional Survey.

BACKGROUND: Telehealth (telemedicine and telepharmacy) services increase access to patient services and ensure continuity of care. However, few studies have assessed factors that influence patients' willingness to use telehealth services, and we sought to investigate this. OBJECTIVE: This study aims to examine respondents' (aged between 45 and 75 years) willingness to use telehealth services (telepharmacy and telemedicine) and the correlates of the willingness to use telehealth services. METHODS: We administered a cross-sectional national survey of 1045 noninstitutionalized US adults aged between 45 and 75 years in March and April 2021. Multiple logistic regression analyses were used to identify demographic and health service use correlates of self-reported willingness to use telehealth services. RESULTS: Overall willingness to use telemedicine was high (674/1045, 64.5%). Adults aged 55 years and older were less willing to use telemedicine (aged between 55 and 64 years: odds ratio [OR] 0.61, 95% CI 0.42-0.86; aged 65 years or older: OR 0.33, 95% CI 0.22-0.49) than those younger than 55 years. Those with a regular provider (OR 1.01, 95% CI 1-1.02) and long travel times (OR 1.75, 95% CI 1.03-2.98) were more willing to use telemedicine compared to those without a regular provider and had shorter travel times, respectively. Willingness to use telemedicine services increased from 64.5% (674/1045) to 83% (867/1045) if the service was low-cost or insurance-covered, was with their existing health care provider, or was easy-to-use. Overall willingness to use telepharmacy was 76.7% (801/1045). Adults aged older than 55 years were less willing to use telepharmacy (aged between 55 and 64 years: OR 0.57, 95% CI 0.38-0.86; aged 65 years or older: OR 0.24, 95% CI 0.15-0.37) than those younger than 55 years. Those who rated pharmacy service quality higher were more willing to use telepharmacy (OR 1.06, 95% CI 1.03-1.09) than those who did not. CONCLUSIONS: Respondents were generally willing to use telehealth (telemedicine and telepharmacy) services, but the likelihood of their being willing to use telehealth decreased as they were older. For those initially unwilling (aged 55 years or older) to use telemedicine services, inexpensive or insurance-covered services were acceptable.

A Thermoresponsive Chitosan/ß-Glycerophosphate Hydrogel for Minimally Invasive Treatment of Critical Limb Ischaemia.

A reduction in blood supply to any limb causes ischaemia, pain and morbidity. Critical limb ischaemia is the most serious presentation of peripheral vascular disease. One in five patients with critical limb ischaemia will die within six months of diagnosis and one in three will require amputation in this time. Improving blood flow to the limb, via the administration of angiogenic agents, could relieve pain and avoid amputation. Herein, chitosan is combined with ß-glycerophosphate to form a thermoresponsive formulation (chitosan/ß-GP) that will flow through a syringe and needle at room temperature but will form a gel at body temperature. The chitosan/ß-GP hydrogel, with or without the angiogenic molecule desferrioxamine (DFO), was injected into the mouse hind limb, following vessel ligation, to test the ability of the formulations to induce angiogenesis. The effects of the formulations were measured using laser Doppler imaging to determine limb perfusion and CD31 staining to quantify the number of blood vessels. Twenty-eight days following induction of ischaemia, the chitosan/ß-GP and chitosan/ß-GP + 100 µM DFO formulations had significantly (p < 0.001 and p < 0.05, respectively) improved blood flow in the ischaemic limb compared with an untreated control. Chitosan/ß-GP increased vessel number by 1.7-fold in the thigh of the ischaemic limb compared with an untreated control, while chitosan/ß-GP + 100 µM DFO increased vessel number 1.8-fold. Chitosan/ß-GP represents a potential minimally invasive treatment for critical limb ischaemia.

Cannabidiol Reverses Deficits in Hippocampal LTP in a Model of Alzheimer's Disease.

Here we demonstrate for the first time that cannabidiol (CBD) acts to protect synaptic plasticity in an in vitro model of Alzheimer's disease (AD). The non-psycho active component of Cannabis sativa, CBD has previously been shown to protect against the neurotoxic effects of beta amyloid peptide (Aß) in cell culture and cognitive behavioural models of neurodegeneration. Hippocampal long-term potentiation (LTP) is an activity dependent increase in synaptic efficacy often used to study cellular mechanisms related to memory. Here we show that acute application of soluble oligomeric beta amyloid peptide (Aß1-42) associated with AD, attenuates LTP in the CA1 region of hippocampal slices from C57Bl/6 mice. Application of CBD alone did not alter LTP, however pre-treatment of slices with CBD rescued the Aß1-42 mediated deficit in LTP. We found that the neuroprotective effects of CBD were not reversed by WAY100635, ZM241385 or AM251, demonstrating a lack of involvement of 5HT1A, adenosine (A2A) or Cannabinoid type 1 (CB1) receptors respectively. However in the presence of the PPARγ antagonist GW9662 the neuroprotective effect of CBD was prevented. Our data suggests that this major component of Cannabis sativa, which lacks psychoactivity may have therapeutic potential for the treatment of AD.

A Rational Design of a Selective Inhibitor for Kv1.1 Channels Prevalent in Demyelinated Nerves That Improves Their Impaired Axonal Conduction.

K+ channels containing Kv1.1 α subunits, which become prevalent at internodes in demyelinated axons, may underlie their dysfunctional conduction akin to muscle weakness in multiple sclerosis. Small inhibitors were sought with selectivity for the culpable hyper-polarizing K+ currents. Modeling of interactions with the extracellular pore in a Kv1.1-deduced structure identified diaryldi(2-pyrrolyl)methane as a suitable scaffold with optimized alkyl ammonium side chains. The resultant synthesized candidate [2,2'-((5,5'(di-p-topyldiaryldi(2-pyrrolyl)methane)bis(2,2'carbonyl)bis(azanediyl)) diethaneamine·2HCl] (8) selectively blocked Kv1.1 channels (IC50 ≈ 15 µM) recombinantly expressed in mammalian cells, induced a positive shift in the voltage dependency of K+ current activation, and slowed its kinetics. It preferentially inhibited channels containing two or more Kv1.1 subunits regardless of their positioning in concatenated tetramers. In slices of corpus callosum from mice subjected to a demyelination protocol, this novel inhibitor improved neuronal conduction, highlighting its potential for alleviating symptoms in multiple sclerosis.

A stimuli responsive liposome loaded hydrogel provides flexible on-demand release of therapeutic agents.

Lysolipid-based thermosensitive liposomes (LTSL) embedded in a chitosan-based thermoresponsive hydrogel matrix (denoted Lipogel) represents a novel approach for the spatiotemporal release of therapeutic agents. The entrapment of drug-loaded liposomes in an injectable hydrogel permits local liposome retention, thus providing a prolonged release in target tissues. Moreover, release can be controlled through the use of a minimally invasive external hyperthermic stimulus. Temporal control of release is particularly important for complex multi-step physiological processes, such as angiogenesis, in which different signals are required at different times in order to produce a robust vasculature. In the present work, we demonstrate the ability of Lipogel to provide a flexible, easily modifiable release platform. It is possible to tune the release kinetics of different drugs providing a passive release of one therapeutic agent loaded within the gel and activating the release of a second LTSL encapsulated agent via a hyperthermic stimulus. In addition, it was possible to modify the drug dosage within Lipogel by varying the duration of hyperthermia. This can allow for adaption of drug dosing in real time. As an in vitro proof of concept with this system, we investigated Lipogels ability to recruit stem cells and then elevate their production of vascular endothelial growth factor (VEGF) by controlling the release of a pro-angiogenic drug, desferroxamine (DFO) with an external hyperthermic stimulus. Initial cell recruitment was accomplished by the passive release of hepatocyte growth factor (HGF) from the hydrogel, inducing a migratory response in cells, followed by the delayed release of DFO from thermosensitive liposomes, resulting in a significant increase in VEGF expression. This delayed release could be controlled up to 14days. Moreover, by changing the duration of the hyperthermic pulse, a fine control over the amount of DFO released was achieved. The ability to trigger the release of therapeutic agents at a specific timepoint and control dosing level through changes in duration of hyperthermia enables sequential multi-dose profiles. STATEMENT OF SIGNIFICANCE: This paper details the development of a heat responsive liposome loaded hydrogel for the controlled release of pro-angiogenic therapeutics. Lysolipid-based thermosensitive liposomes (LTSLs) embedded in a chitosan-based thermoresponsive hydrogel matrix represents a novel approach for the spatiotemporal release of therapeutic agents. This hydrogel platform demonstrates remarkable flexibility in terms of drug scheduling and sequencing, enabling the release of multiple agents and the ability to control drug dosing in a minimally invasive fashion. The possibility to tune the release kinetics of different drugs independently represents an innovative platform to utilise for a variety of treatments. This approach allows a significant degree of flexibility in achieving a desired release profile via a minimally invasive stimulus, enabling treatments to be tuned in response to changing symptoms and complications.

Simvastatin treatment preserves synaptic plasticity in AßPPswe/PS1dE9 mice.

Epidemiological evidence suggests that chronic treatment with simvastatin may protect against the development of Alzheimer's disease (AD), but as yet it is unclear how this effect is mediated. Extensive data also indicates that the amyloid ß-protein (Aß) plays a central role in the disease process, and it has been suggested that the protective effects of simvastatin may be mediated by reducing Aß production or by counteracting the toxic effects of Aß. Accordingly, using the AßPPswe/PS1dE9 mouse model of AD, we investigated the effects of simvastatin on long-term potentiation (LTP), amyloid biology, and two key kinases involved in Aß-mediated toxicity. Since burgeoning data indicate that both fibrillar and non-fibrillar forms of Aß play a prominent role in AD pathogenesis, we were careful to investigate the effects of simvastatin on three biochemically distinct pools of Aß. In untreated AßPPswe/PS1dE9 mice, there was a dramatic and significant increase in the levels of water-soluble Aß between 6 and 8 months, but this remained constant between 8 and 18 months. In contrast, the concentrations of detergent-soluble and formic acid (FA)-soluble Aß species increased across all ages examined, thus demonstrating that while amyloid deposition continued, the levels of water-soluble Aß remained relatively constant. LTP was normal at 6 months, but was significantly impaired at 8 and 18 months. Importantly, a diet supplemented with 0.04% simvastatin for one month (at 7 months) positively affected synaptic plasticity in AßPPswe/PS1dE9 mice and did not significantly alter levels of water-soluble, detergent-soluble, or FA-soluble Aß, but did increase phosphorylation of both Akt and GSK-3, while tau and tau phosphorylation were unaltered. These results indicate that the protective effects of simvastatin may be mediated by maintaining signaling pathways that help to protect and rescue LTP.

Mesenchymal stem cells to augment therapeutic angiogenesis in hind-limb ischemia models: how important is their source?

Murine models of hind-limb ischemia are frequently used to assess interventions aimed at improving therapeutic angiogenesis in critical limb ischemia. Much of the current focus of angiogenesis lies with mesenchymal stem cells (MSCs). Important considerations when using these models include the strain of mouse, because some strains recover from ischemia more rapidly than others, and the MSC source. MSCs derived from certain strains generate increased levels of growth factors such as vascular endothelial growth factor. This may significantly affect the limb?s ability to generate collateral vessels.

Amyloid-ß nanotubes are associated with prion protein-dependent synaptotoxicity.

Growing evidence suggests water-soluble, non-fibrillar forms of amyloid-ß protein (Aß) have important roles in Alzheimer's disease with toxicities mimicked by synthetic Aß(1-42). However, no defined toxic structures acting via specific receptors have been identified and roles of proposed receptors, such as prion protein (PrP), remain controversial. Here we quantify binding to PrP of Aß(1-42) after different durations of aggregation. We show PrP-binding and PrP-dependent inhibition of long-term potentiation (LTP) correlate with the presence of protofibrils. Globular oligomers bind less avidly to PrP and do not inhibit LTP, whereas fibrils inhibit LTP in a PrP-independent manner. That only certain transient Aß assemblies cause PrP-dependent toxicity explains conflicting reports regarding the involvement of PrP in Aß-induced impairments. We show that these protofibrils contain a defined nanotubular structure with a previously unidentified triple helical conformation. Blocking the formation of Aß nanotubes or their interaction with PrP might have a role in treatment of Alzheimer's disease.

Importance of strict patient selection criteria for combined carotid endarterectomy and coronary artery bypass grafting.

BACKGROUND: Management of patients with severe concomitant carotid and coronary disease remains controversial. We report our experience of combined carotid endarterectomy (CEA) and coronary artery bypass surgery (CABG) over a fifteen year period using strict patient selection criteria. METHODS: From 1st January 1995 to December 31st 2009 165 patients underwent combined CABG/CEA procedures at the Mater Hospital. Mean age was 68.2 years (range 43-88) and 127 (77%) were male. Fifty-three (32%) had symptomatic carotid disease. Indications for combined procedures were the presence of symptomatic >70% or asymptomatic >80% internal carotid artery stenosis in a patient requiring urgent CABG because of either unstable angina, recent MI, severe triple vessel disease or severe Left Anterior Descending or Left Main Stem stenosis. RESULTS: Thirty-day stroke and death rate was 3%. All neurological events were in the hemisphere contralateral to the carotid surgery and symptoms had completely resolved prior to discharge from hospital. One patient required evacuation of a cervical haematoma and there were two transient XII nerve palsies. CONCLUSION: Combined CEA/CABG can be performed safely with acceptable morbidity and mortality in patients selected in accordance with strict criteria in a centre with a large experience of both cardiac and carotid surgery.

Amyloid beta-protein dimers rapidly form stable synaptotoxic protofibrils.

Nonfibrillar, water-soluble low-molecular weight assemblies of the amyloid ß-protein (Aß) are believed to play an important role in Alzheimer's disease (AD). Aqueous extracts of human brain contain Aß assemblies that migrate on SDS-polyacrylamide gels and elute from size exclusion as dimers (∼8 kDa) and can block long-term potentiation and impair memory consolidation in the rat. Such species are detected specifically and sensitively in extracts of Alzheimer brain suggesting that SDS-stable dimers may be the basic building blocks of AD-associated synaptotoxic assemblies. Consequently, understanding the structure and properties of Aß dimers is of great interest. In the absence of sufficient brain-derived dimer to facilitate biophysical analysis, we generated synthetic dimers designed to mimic the natural species. For this, Aß(1-40) containing cysteine in place of serine 26 was used to produce disulphide cross-linked dimer, (AßS26C)2. Such dimers had no detectable secondary structure, produced an analytical ultracentrifugation profile consistent for an ∼8.6 kDa protein, and had no effect on hippocampal long-term potentiation (LTP). However, (AßS26C)2 aggregated more rapidly than either AßS26C or wild-type monomers and formed parastable ß-sheet rich, thioflavin T-positive, protofibril-like assemblies. Whereas wild-type Aß aggregated to form typical amyloid fibrils, the protofibril-like structures formed by (AßS26C)2 persisted for prolonged periods and potently inhibited LTP in mouse hippocampus. These data support the idea that Aß dimers may stabilize the formation of fibril intermediates by a process distinct from that available to Aß monomer and that higher molecular weight prefibrillar assemblies are the proximate mediators of Aß toxicity.

Tanzanian farmers' knowledge and attitudes to GM biotechnology and the potential use of GM crops to provide improved levels of food security. A Qualitative Study.

BACKGROUND: Genetically Modified (GM) crops have been championed as one possible method to improve food security and individual nutritional status in sub Saharan Africa. Understanding and acceptability of GM crop technology to farmers and consumers have not been assessed. We developed a qualitative research study involving farmers as both producers and consumers to gauge the understanding of GM crop technology, its acceptability, and identifying issues of concern. METHODS: Nineteen individual interviews (10 male and 9 female) and five mixed gender focus group discussions with local farmers were conducted in 3 regions in Tanzania. Analysis took place concurrently with data collection. Following initial interviews, subsequent questions were adjusted based on emerging themes. RESULTS: Understanding, awareness and knowledge of GM crop technology and terminology and its potential risks and benefits was very poor in all regions. Receptivity to the potential use of GM crops was, however, high. Respondents focused on the potential benefits of GM crops rather than any potential longer term health risks. A number of factors, most significantly field trial data, would influence farmers' decisions regarding the introduction of GM crop varieties into their farming practice. Understanding of the potential improved health provision possible by changes in agricultural practice and food-related decision making, and the health benefits of a diet containing essential vitamins, minerals and micronutrients is also poor in these communities. CONCLUSION: This study forms a basis from which further research work can be undertaken. It is important to continue to assess opinions and attitudes of farmers and consumers in sub Saharan Africa towards potential use of GM technologies whilst highlighting the importance of the relationship between agriculture, health and development. This will allow people in the region to make accurate, informed decisions about whether they believe use of GM biotechnology is an appropriate way in which to tackle issues of food security, provide improved health and drive development.

Antimicrobial photodynamic therapy may promote periodontal healing through multiple mechanisms.

BACKGROUND: Antimicrobial photodynamic therapy (aPDT) as an adjunctive treatment in addition to scaling and root planing for the treatment of periodontitis has been shown to be clinically useful. Its beneficial effect is reported to be due to its potent bactericidal activity. However, aPDT treatment has the potential to inactivate bacterial and host factors that contribute to disease. In this report, we demonstrate that aPDT treatment can simultaneously kill Porphyromonas gingivalis and inactivate its virulence-associated protease. It also inactivates host destructive cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1 beta. METHODS: We developed a 96-well-based bacterial killing and protease inactivation assay that determined aPDT bactericidal and protease inactivation from the same sample. A cytokine inactivation assay that measured E-selectin expression in response to TNF-alpha and IL-1 beta was developed to measure the ability of aPDT to inactivate cytokine function. RESULTS: A single aPDT treatment in vitro potently inactivated protease activity and resulted in a 4-log(10) reduction in the viability of P. gingivalis. Dose and time-of-exposure experiments revealed that protease inactivation occurred at lower concentrations of photosensitizer and less time of light exposure. Also, aPDT treatment potently and functionally inactivated IL-1 beta and TNF-alpha. CONCLUSIONS: aPDT treatment may augment periodontal treatment by increasing bacterial killing, inactivating bacterial virulence factors, and inactivating host cytokines that impair periodontal restoration. Therefore, aPDT treatment may provide a more favorable healing environment.

The effects of IL-1 receptor antagonist on beta amyloid mediated depression of LTP in the rat CA1 in vivo.

Beta-amyloid (Abeta) is a neuro-peptide implicated in the pathogenesis of Alzheimer's disease (AD). Abeta-peptide is known to disrupt cellular processes, including synaptic plasticity. To date, the precise mechanisms leading to the Abeta-mediated impairment of normal neurophysiological function still remains elusive. A rise in the pro-inflammatory cytokine interleukin-1-beta (IL-1beta) has been previously reported, following Abeta peptide insult. IL-1beta in turn, activates a cascade of pro-apoptotic markers, gradually leading to cell death. In this work, we have investigated the possible protective effects of interleukin-1 receptor antagonist (IL-1ra) on the effects of Abeta-peptide on long-term potentiation (LTP) in the CA1 region of the rat hippocampus in vivo. We observed a significant depression of LTP in the group of animals that received intracerebroventricular (icv) injection of Abeta-peptide (1-40) compared with control animals injected with vehicle. Administration of IL-1ra alone (icv) also resulted in a depression of LTP; however, there was no change in the baseline synaptic response. Combined injection of Abeta(1-40) + IL-1ra caused an attenuation of the effects observed with Abeta(1-40) alone for a period of up to 15 min following LTP induction; rescuing post-tetanicpotentiation (PTP). Gradually however, EPSP-values declined to produce a level of LTP similar to that observed following treatment with Abeta(1-40) alone. These results suggest that the acute Abeta-mediated impairment of PTP and LTP may be partial as a result of activation of an inflammatory response and the release of IL-1beta. The attenuation of plasticity by IL-1ra alone supports the theory that low levels of IL-1beta are required for normal synaptic plasticity. The limited rescue of the Abeta-mediated effects on LTP, in the presence of IL-1ra, may represent the short half life found with this receptor antagonist in vivo.

Metabotropic receptor-activated calcium increases and store-operated calcium influx in mouse Müller cells.

PURPOSE: Metabotropic receptor agonists that signal through G(q)-coupled pathways increase Ca(2+) in mammalian Müller cells by release from intracellular stores and Ca(2+) influx pathways that have not been well described. The authors examined the involvement of voltage-dependent and non-voltage-dependent Ca(2+) channels in metabotropic muscarinic receptor-activated Ca(2+) increases and store-operated Ca(2+) influx in cultured mouse Müller cells. METHODS: Intracellular Ca(2+) was measured using fluorescence imaging with the ratiometric dye fura-2. Currents were recorded using the whole-cell patch-clamp recording method: mRNA and protein were identified using reverse transcriptase polymerase chain reaction (RT-PCR) and immunocytochemical approaches. RESULTS: The muscarinic receptor agonist carbachol (3-20 microM) produced increases in Ca(2+) that were blocked by the muscarinic receptor antagonists atropine and pirenzepine. RT-PCR confirmed mRNA for metabotropic M1 muscarinic receptors. Depletion of Ca(2+) stores by the sarcoplasmic/endoplasmic Ca(2+) ATPase (SERCA) inhibitors thapsigargin and cyclopiazonic acid or the inhibition of phospholipase C occluded the carbachol-activated increase in Ca(2+). Carbachol-activated Ca(2+) increases in Müller cells were enhanced by the diacylglycerol derivative 1-oleyl-2-acetyl-sn-glycerol and were blocked by transient receptor potential (TRP) channel blockers Gd(3+), La(3+), 2-APB, and flufenamic acid. Both muscarinic receptor activation and thapsigargin treatment depleted Ca(2+) stores and produced Ca(2+) entry that was attenuated by La(3+), 2-APB, Gd(3+), and flufenamic acid. mRNA and protein for TRPC1 and TRPC6 were present in mouse Müller cells, and carbachol activated a Gd(3+)-sensitive, TRP-like cation channel. CONCLUSIONS: Metabotropic muscarinic receptor-activated Ca(2+) increases in mouse Müller cells require the release of Ca(2+) from intracellular stores and the activation of Ca(2+) entry that involves TRP-like cation channels but is independent of voltage-dependent Ca(2+) channels.

Inhibition of LTP in vivo by beta-amyloid peptide in different conformational states.

We have investigated changes in the morphological structure of Abeta1-40 during different incubation time periods at 37 degrees C ranging from 1 h to 7 days using Thioflavin T, Congo red binding and electron microscopy. We found distinctive changes in Abeta assembly demonstrating the formation of beta pleated sheets following 7-day incubation. Here we demonstrate that samples of the same Abeta1-40 peptide that are morphologically distinct can both attenuate hippocampal long-term potentiation (LTP) in the CA1 in vivo. The peptides were applied via intracerebroventricular injection and the effects on synaptic transmission, post-tetanic potentiation (PTP) and LTP were observed. The effects of Abeta1-40 that had either been freshly solubilized (FS-Abeta) or incubated at 37 degrees C for 7 days (7D-Abeta) were examined. FS-Abeta and 7D-Abeta peptide were both found to significantly attenuate LTP, although the assembly states of these peptides appeared to be completely different. Paired pulse facilitation (PPF) with an inter-stimulus interval of 50 ms was also monitored prior to, following peptide injection and 60 min following LTP induction. 7D-Abeta caused an increase in PPF prior to LTP induction and also depressed PTP. Our data demonstrate that, while both forms of the peptide can attenuate LTP, the fibrillar form of the peptide may also influence transmitter release.

Modulation of amyloid-beta-induced and age-associated changes in rat hippocampus by eicosapentaenoic acid.

The age-related deficit in long-term potentiation (LTP) in the dentate gyrus is positively correlated with hippocampal concentration of the pro-inflammatory cytokine, interleukin-1beta (IL-1beta). Previous evidence also indicates that the inhibition of LTP induced by intracerebroventricular injection of amyloid-beta(1-40) (Abeta) is accompanied by increased hippocampal IL-1beta concentration and IL-1beta-stimulated signalling, specifically activation of the stress-activated protein kinase, c-jun N-terminal kinase (JNK). We considered that the underlying age-related neuroinflammation may render older rats more susceptible to Abeta administration and, to investigate this, young, middle-aged and aged rats were injected intracerebroventricularly with Abeta or vehicle. Hippocampal IL-1beta concentration, JNK phosphorylation, expression of the putative Abeta receptor, Receptor for advanced glycation end products (RAGE) and the microglial cell surface marker, CD40 were assessed. We report that Abeta inhibited LTP in a concentration-dependent manner in young rats and that this was accompanied by concentration-dependent increases in hippocampal IL-1beta and expression of phosphorylated JNK, RAGE and CD40. While 20 micromol/L Abeta exerted no significant effect on LTP in young rats, it inhibited LTP in middle-aged and aged rats and the increased vulnerability of aged rats was associated with increased IL-1beta concentration. Treatment of rats with eicosapentaenoic acid attenuated the inhibitory effect of 60 micromol/L Abeta on LTP in young rats and the effect of 20 micromol/L Abeta in middle-aged and aged rats. We present evidence which indicates that the effect of eicosapentaenoic acid may be linked with its ability to stimulate activation of peroxisome proliferator-activated receptor gamma.

Agonists of peroxisome proliferator-activated receptor-gamma attenuate the Abeta-mediated impairment of LTP in the hippocampus in vitro.

The data we present here suggest that agonists of peroxisome proliferator-activated receptor-gamma (PPARgamma) can attenuate the effects of beta-amyloid peptide (Abeta). Alzheimer's disease is associated with elevated levels of Abeta, and enhanced expression of PPARgamma. In this study, we determined that application of Abeta([1-40]) could impair hippocampal post-tetanic potentiation (PTP) and long-term potentiation (LTP) in vitro. We investigated the effects of PPARgamma agonists; troglitazone, ciglitazone and 15-deoxy-delta(12,14) prostaglandin J2 (PGJ2) on synaptic transmission and plasticity in area CA1. Both ciglitazone and PGJ2 increased baseline synaptic transmission significantly, without altering paired-pulse facilitation. PGJ2 produced a significant reduction in LTP, whereas ciglitazone and troglitazone had no significant effect. In addition, prior application of each ligand attenuated the previously observed Abeta([1-40])-mediated impairment of LTP. The effect of troglitazone on the Abeta([1-40])-mediated impairment of LTP was not reversed by the PPARgamma antagonist, GW-9662. These findings demonstrate that PPARgamma agonists attenuate the effects of Abeta on LTP, and support the potential use of these agents to alleviate the symptoms of Alzheimer's disease. We also suggest that PPARgamma agonists may regulate expression of hippocampal LTP in vitro.

The role of c-Jun N-terminal kinase in the A beta-mediated impairment of LTP and regulation of synaptic transmission in the hippocampus.

The effects of the beta-amyloid peptide (Abeta) fragment 25-35 were investigated on hippocampal synaptic transmission and long-term potentiation (LTP) in vitro. Abeta([25-35]) was found to impair both post-tetanic potentiation (PTP) and LTP in the hippocampal CA1. The anthra[1,9-cd]pyrazol-6(2H)-one, SP600125, was used to inhibit c-Jun N-terminal kinase (JNK) activity, which is believed to mediate cell death. Prior application of SP600125 attenuated the Abeta([25-35])-mediated impairment of PTP and LTP, when measured from the pre-drug baseline. In the presence of SP600125 alone, we observed an increase in baseline synaptic transmission and reduction in paired-pulse facilitation, consistent with an increase in synaptic transmission. There was no alteration in the level of PTP and LTP obtained, when measured from the pre-drug baseline. In the presence of both SP600125 and Abeta, however, PTP was greatly enhanced compared with controls. We therefore suggest that the activation of the JNK signalling pathway mediates the effects of Abeta on synaptic plasticity. Our data also indicate that endogenous JNK activity may regulate neurotransmitter release in the hippocampal CA1 in vitro.

Activation of the c-Jun N-terminal kinase signaling cascade mediates the effect of amyloid-beta on long term potentiation and cell death in hippocampus: a role for interleukin-1beta?

Amyloid-beta (Abeta) is a major constituent of the neuritic plaque found in the brain of Alzheimer's disease patients, and a great deal of evidence suggests that the neuronal loss that is associated with the disease is a consequence of the actions of Abeta. In the past few years, it has become apparent that activation of c-Jun N-terminal kinase (JNK) mediates some of the effects of Abeta on cultured cells; in particular, the evidence suggests that Abeta-triggered JNK activation leads to cell death. In this study, we investigated the effect of intracerebroventricular injection of Abeta(1-40) on signaling events in the hippocampus and on long term potentiation in Schaffer collateral CA1 pyramidal cell synapses in vivo. We report that Abeta(1-40) induced activation of JNK in CA1 and that this was coupled with expression of the proapoptotic protein, Bax, cytosolic cytochrome c, poly-(ADP-ribose) polymerase cleavage, and Fas ligand expression in the hippocampus. These data indicate that Abeta(1-40) inhibited expression of long term potentiation, and this effect was abrogated by administration of the JNK inhibitor peptide, D-JNKI1. In parallel with these findings, we observed that Abeta-induced changes in caspase-3 activation and TdT-mediated dUTP nick-end labeling staining in neuronal cultured cells were inhibited by D-JNKI1. We present evidence suggesting that interleukin (IL)-1beta plays a significant role in mediating the effects of Abeta(1-40) because Abeta(1-40) increased hippocampal IL-1beta and because several effects of Abeta(1-40) were inhibited by the caspase-1 inhibitor Ac-YVAD-CMK. On the basis of our findings, we propose that Abeta-induced changes in hippocampal plasticity are likely to be dependent upon IL-1beta-triggered activation of JNK.

Inhibition of L-type voltage dependent calcium channels causes impairment of long-term potentiation in the hippocampal CA1 region in vivo.

Long-term potentiation (LTP), in the hippocampal CA1 region is dependent on postsynaptic calcium influx. It is generally accepted that calcium influx occurs via activation of the NMDA receptor channel complex. However, studies in vitro using a high-frequency stimulus protocol (> or =200 Hz) demonstrated previously an NMDA receptor-independent form of LTP that is dependent upon activation of L-type voltage-dependent calcium channels (VDCCs). Here we have investigated a role for L-type VDCCs in LTP in vivo. Two structurally different, L-type VDCC blockers, verapamil (1, 3 and 10 mg/kg) and diltiazem (1, 10 and 20 mg/kg), depressed the induction of LTP in a dose-dependent manner. Increased activation of L-type VDCCs by Bay K 8644, an L-type agonist, however, did not enhance LTP. The NMDA receptor antagonist D-AP5 (5 and 20 mM injected i.c.v) impaired, but failed to block fully LTP in vivo. A reduced level of LTP could still be recorded following co-administration of verapamil and D-AP5. The level of LTP recorded was similar to that observed in the presence of either verapamil (10 mg/kg) or D-AP5 alone. These results suggest that activation of the NMDA receptor/channel and L-type VDCCs are involved in the induction of LTP in area CA1 in vivo. However, it appears that activation of other receptor/channels may also play a role in this form of LTP.