Antihypertensive treatment guided by genetics: PEARL-HT, the randomized proof-of-concept trial comparing rostafuroxin with losartan.

We compared a standard antihypertensive losartan treatment with a pharmacogenomics-guided rostafuroxin treatment in never-treated Caucasian and Chinese patients with primary hypertension. Rostafuroxin is a digitoxigenin derivative that selectively disrupts the binding to the cSrc-SH2 domain of mutant α-adducin and of the ouabain-activated Na-K pump at 10-11 M. Of 902 patients screened, 172 were enrolled in Italy and 107 in Taiwan. After stratification for country and genetic background, patients were randomized to rostafuroxin or losartan, being the difference in the fall in office systolic blood pressure (OSBP) after 2-month treatment the primary endpoint. Three pharmacogenomic profiles (P) were examined, considering: P1, adding to the gene variants included in the subsequent P2, the variants detected by post-hoc analysis of a previous trial; P2, variants of genes encoding enzymes for endogenous ouabain (EO) synthesis (LSS and HSD3B1), EO transport (MDR1/ABCB1), adducin (ADD1 and ADD3); P3, variants of the LSS gene only. In Caucasians, the group differences (rostafuroxin 50 µg minus losartan 50 mg in OSBP mmHg) were significant both in P2 adjusted for genetic heterogeneity (P2a) and P3 LSS rs2254524 AA [9.8 (0.6-19.0), P = 0.038 and 13.4 (25.4-2.5), P = 0.031, respectively]. In human H295R cells transfected with LSS A and LSS C variants, the EO production was greater in the former (P = 0.038); this difference was abolished by rostafuroxin at 10-11 M. Chinese patients had a similar drop in OSBP to Caucasians with losartan but no change in OSBP with rostafuroxin. These results show that genetics may guide drug treatment for primary hypertension in Caucasians.

Treatment with 24 hour istaroxime infusion in patients hospitalised for acute heart failure: a randomised, placebo-controlled trial.

AIM: Istaroxime is a first-in-class agent which acts through inhibition of the sarcolemmal Na+ /K+ pump and activation of the SERCA2a pump. This study assessed the effects of a 24 h infusion of istaroxime in patients hospitalised for acute heart failure (AHF). METHODS AND RESULTS: We included patients hospitalised for AHF with left ventricular ejection fraction ≤40% and E/e' > 10. Patients were randomised to a 24 h intravenous infusion of placebo or istaroxime at doses of 0.5 µg/kg/min (cohort 1: placebo n = 19; istaroxime n = 41) or 1.0 µg/kg/min (cohort 2: placebo n = 20, istaroxime n = 40). The primary endpoint of change in E/e' ratio from baseline to 24 h decreased with istaroxime vs. placebo (cohort 1: -4.55 ± 4.75 istaroxime 0.5 µg/kg/min vs. -1.55 ± 4.11 placebo, P = 0.029; cohort 2: -3.16 ± 2.59 istaroxime 1.0 µg/kg/min vs. -1.08 ± 2.72 placebo, P = 0.009). Both istaroxime doses significantly increased stroke volume index and decreased heart rate. Systolic blood pressure increased with istaroxime, achieving significance with the high dose. Self-reported dyspnoea and N-terminal pro-brain natriuretic peptide improved in all groups without significant differences between istaroxime and placebo. No significant differences in cardiac troponin absolute values or clinically relevant arrhythmias were observed during or after istaroxime infusion. Serious cardiac adverse events (including arrhythmias and hypotension) did not differ between placebo and istaroxime groups. The most common adverse events were injection site reactions and gastrointestinal events, the latter primarily with istaroxime 1.0 µg/kg/min. CONCLUSIONS: In patients hospitalised for AHF with reduced ejection fraction, a 24 h infusion of istaroxime improved parameters of diastolic and systolic cardiac function without major cardiac adverse effects.

In Vitro and In Vivo Anticancer Activity of Gimatecan against Hepatocellular Carcinoma

Objective: Gimatecan is a new camptothecin (CPT) analogue that inhibits tumor growth by targeting DNA topoisomerase I (TOP I) and introducing strong and persistent DNA cleavage. Anti-tumor activity has been demonstrated with a wide range of solid tumors in previous preclinical and clinical studies. Here, we investigated for the first time the effects of gimatecan on the proliferation of hepatocellular carcinoma (HCC) cells both in vitro and in vivo. Methods: Anticancer efficacy of gimatecan were evaluated in a panel of HCC cell lines and corresponding mouse xenograft models. Inhibition of cell proliferation was measured by CellTiter-Glo cell viability assay. In vivo, gimatecan and control preparations were orally administered every four days, for a total of four times. Tumor volume and body weights of the mice were measured twice weekly. Results: In vitro cytotoxicity evaluation showed that gimatecan inhibited the proliferation of a large panel of HCC cell lines in a dose dependent manner, with IC50 values ranging between 12.1~1085.0 nM. In vivo evaluation in mouse xenograft models showed significant antitumor effects of gimatecan at 0.8mg/kg and 0.4mg/kg as compared to the control group. Conclusion: This study suggested that gimatecan may have the potential to be used as a chemotherapeutic agent for the treatment of HCC.

A novel snake venom-derived GPIb antagonist, anfibatide, protects mice from acute experimental ischaemic stroke and reperfusion injury.

BACKGROUND AND PURPOSE: Ischaemic stroke is a serious disease with limited therapy options. Glycoprotein (GP)Ib binding to von Willebrand factor (vWF) exposed at vascular injury initiates platelet adhesion and contributes to platelet aggregation. GPIb has been suggested as an effective target for antithrombotic therapy in stroke. Anfibatide is a GPIb antagonist derived from snake venom and we investigated its protective effect on experimental brain ischaemia in mice. EXPERIMENTAL APPROACH: Focal cerebral ischaemia was induced by 90 min of transient middle cerebral artery occlusion (MCAO). These mice were then treated with anfibatide (4, 2, 1 µg·kg(-1) ), injected i.v., after 90 min of MCAO, followed by 1 h of reperfusion. Tirofiban, a GPIIb/IIIα antagonist, was used as a positive control. KEY RESULTS: Twenty-four hours after MCAO, anfibatide-treated mice showed significantly improved ischaemic lesions in a dose-dependent manner. The mice had smaller infarct volumes, less severe neurological deficits and histopathology of cerebrum tissues compared with the untreated MCAO mice. Moreover, anfibatide decreased the amount of GPIbα, vWF and accumulation of fibrin(ogen) in the vasculature of the ischaemic hemisphere. Tirofiban had similar effects on infarct size and fibrin(ogen) deposition compared with the MCAO group. Importantly, the anfibatide-treated mice showed a lower incidence of intracerebral haemorrhage and shorter tail bleeding time compared with the tirofiban-treated mice. CONCLUSIONS AND IMPLICATIONS: Our data indicate anfibatide is a safe GPIb antagonist that exerts a protective effect on cerebral ischaemia and reperfusion injury. Anfibatide is a promising candidate that could be beneficial for the treatment of ischaemic stroke.

Orally bioavailable and brain-penetrant pyridazine and pyridine-derived γ-secretase modulators reduced amyloidogenic Aß peptides in vivo.

Accumulation of amyloid ß (Aß) in brain is a pathological hallmark of Alzheimer's disease (AD). Aß is generated after sequential cleavage of its parental molecule, amyloid precursor protein (APP), by ß- and γ-secretases. Inhibition of γ-secretase activity is an effective approach for the reduction of Aß levels. Since γ-secretase targets many different substrates, selective inhibition of its cleavage of APP is believed to be critical in order to avoid undesirable side effects. γ-Secretase modulator (GSM) shifts the cleavage site on APP and production of amyloidogenic to non-amyloidogenic Aß fragments. Since GSMs only modulate and do not block cleavage of γ-secretase substrates, they are believed less likely to produce untoward adverse reactions. Here, we report in vivo Aß-lowering profiles of a pyridazine and a pyridine-derived GSM: GSM-C (Wan et al., 2011a) and GSM-D (Wan et al., 2011b). Both compounds reduced Aß40 and Aß42 productions, increased shorter Aß fragments, and had little effect on Notch signaling (∼100-fold selective). They had excellent oral bioavailability (97.8% for GSM-C, ∼100% for GSM-D) and good brain permeability (free brain to free blood AUC ratio of 0.41 and 1.10 for GSM-C and GSM-D, respectively). Oral administration of these compounds in both acute and sub-chronic conditions reduced Aß levels in plasma and brain in rats in a dose- and time-dependent manner. Therefore, GSM-C and GSM-D represent two GSMs that are orally bioavailable and brain-permeable. They could serve as excellent tools in the investigation of the role of Aß peptides in AD pathogenesis.

Γ-secretase modulators do not induce Aß-rebound and accumulation of ß-C-terminal fragment.

γ-secretase inhibitors (GSIs) have been developed to reduce amyloid-ß (Aß) production for the treatment of Alzheimer's disease by inhibiting the cleavage of amyloid precursor protein (APP). However, cross-inhibitory activity on the processing of Notch can cause adverse reactions. To avoid these undesirable effects, γ-secretase modulators (GSMs) are being developed to selectively reduce toxic Aß production without perturbing Notch signaling. As it is also known that GSIs can cause a paradoxical increase of plasma Aß over the baseline after a transient reduction (known as Aß-rebound), we asked if GSMs would cause a similar rebound and what the potential mechanism might be. Our studies were performed with one GSI (LY-450139) and two chemically distinct GSMs. Although LY-450139 caused Aß-rebound as expected in rat plasma, the two GSMs did not. Inhibition of APP processing by LY-450139 induced an accumulation of γ-secretase substrates, α- and ß-C-terminal fragments of APP, but neither GSM caused such an accumulation. In conclusion, we discover that GSMs, unlike GSIs, do not cause Aß-rebound, possibly because of the lack of accumulation of ß-C-terminal fragments. GSMs may be superior to GSIs in the treatment of Alzheimer's disease not only by sparing Notch signaling but also by avoiding Aß-rebound.

Pyridine-derived γ-secretase modulators.

SAR of a novel series of pyridine-derived γ-secretase modulators is described. Compound 5 was found to be a potent modulator in vitro, which on further profiling, was found to decrease Aß42 and Aß40, and maintain (or increase) the levels of total Aß. Furthermore, representative compounds 1 and 5 demonstrated in vivo efficacy to lower Aß42 in the brain without altering Notch processing in the peripheral.

Pyridazine-derived γ-secretase modulators.

SAR of a novel series of pyridazine-derived γ-secretase modulators is described. Compound 25 was found to be a potent modulator in vitro, which on further profiling, was found to decrease Aß42 and Aß40, and maintain the levels of total Aß. Furthermore, 25 demonstrated excellent pharmacokinetic parameters as well as good CNS penetration in the rat.

Transcriptional regulation of beta-secretase by p25/cdk5 leads to enhanced amyloidogenic processing.

Cyclin-dependent kinase 5 (cdk5) has been implicated in Alzheimer's disease (AD) pathogenesis. Here, we demonstrate that overexpression of p25, an activator of cdk5, led to increased levels of BACE1 mRNA and protein in vitro and in vivo. A p25/cdk5 responsive region containing multiple sites for signal transducer and activator of transcription (STAT1/3) was identified in the BACE1 promoter. STAT3 interacts with the BACE1 promoter, and p25-overexpressing mice had elevated levels of pSTAT3 and BACE1, whereas cdk5-deficient mice had reduced levels. Furthermore, mice with a targeted mutation in the STAT3 cdk5 responsive site had lower levels of BACE1. Increased BACE levels in p25 overexpressing mice correlated with enhanced amyloidogenic processing that could be reversed by a cdk5 inhibitor. These data demonstrate a pathway by which p25/cdk5 increases the amyloidogenic processing of APP through STAT3-mediated transcriptional control of BACE1 that could have implications for AD pathogenesis.

Interplay between cyclin-dependent kinase 5 and glycogen synthase kinase 3 beta mediated by neuregulin signaling leads to differential effects on tau phosphorylation and amyloid precursor protein processing.

Cyclin-dependent kinase 5 (cdk5) and glycogen synthase kinase 3beta (GSK3beta) have been implicated in pathogenic processes associated with Alzheimer's disease because both kinases regulate tau hyperphosphorylation and enhance amyloid precursor protein (APP) processing leading to an increase in amyloid beta (Abeta) production. Here we show that young p25 overexpressing mice have enhanced cdk5 activity but reduced GSK3beta activity attributable to phosphorylation at the inhibitory GSK3beta-serine 9 (GSK3beta-S9) site. Phosphorylation at this site was mediated by enhanced activity of the neuregulin receptor complex, ErbB, and activation of the downstream phosphatidylinositol 3 kinase/Akt pathway. Young p25 mice had elevated Abeta peptide levels, but phospho-tau levels were decreased overall. Thus, cdk5 appears to play a dominant role in the regulation of amyloidogenic APP processing, whereas GSK3beta plays a dominant role in overall tau phosphorylation. In older mice, GSK3beta inhibitory phosphorylation at S9 was reduced relative to young mice. Abeta peptide levels were still elevated but phospho-tau levels were either unchanged or showed a trend to increase, suggesting that GSK3beta activity increases with aging. Inhibition of cdk5 by a specific inhibitor reduced cdk5 activity in p25 mice, leading to reduced Abeta production in both young and old mice. However, in young mice, cdk5 inhibition reversed GSK3beta inhibition, leading to an increase in overall tau phosphorylation. When cdk5 inhibitor was administered to very old, nontransgenic mice, inhibition of cdk5 reduced Abeta levels, and phospho-tau levels showed a trend to increase. Thus, cdk5 inhibitors may not be effective in targeting tau phosphorylation in the elderly.

Anesthesia leads to tau hyperphosphorylation through inhibition of phosphatase activity by hypothermia.

Postoperative cognitive dysfunction, confusion, and delirium are common after general anesthesia in the elderly, with symptoms persisting for months or years in some patients. Even middle-aged patients are likely to have postoperative cognitive dysfunction for months after surgery, and Alzheimer's disease (AD) patients appear to be particularly at risk of deterioration after anesthesia. Several investigators have thus examined whether general anesthesia is associated with AD, with some studies suggesting that exposure to anesthetics may increase the risk of AD. However, little is known on the biochemical consequences of anesthesia on pathogenic pathways in vivo. Here, we investigated the effect of anesthesia on tau phosphorylation and amyloid precursor protein (APP) metabolism in mouse brain. We found that, regardless of the anesthetic used, anesthesia induced rapid and massive hyperphosphorylation of tau, rapid and prolonged hypothermia, inhibition of Ser/Thr PP2A (protein phosphatase 2A), but no changes in APP metabolism or Abeta (beta-amyloid peptide) accumulation. Reestablishing normothermia during anesthesia completely rescued tau phosphorylation to normal levels. Our results indicate that changes in tau phosphorylation were not a result of anesthesia per se, but a consequence of anesthesia-induced hypothermia, which led to inhibition of phosphatase activity and subsequent hyperphosphorylation of tau. These findings call for careful monitoring of core temperature during anesthesia in laboratory animals to avoid artifactual elevation of protein phosphorylation. Furthermore, a thorough examination of the effect of anesthesia-induced hypothermia on the risk and progression of AD is warranted.

Concentration-dependent modulation of amyloid-beta in vivo and in vitro using the gamma-secretase inhibitor, LY-450139.

LY-450139 is a gamma-secretase inhibitor shown to have efficacy in multiple cellular and animal models. Paradoxically, robust elevations of plasma amyloid-beta (Abeta) have been reported in dogs and humans after administration of subefficacious doses. The present study sought to further evaluate Abeta responses to LY-450139 in the guinea pig, a nontransgenic model that has an Abeta sequence identical to that of human. Male guinea pigs were treated with LY-450139 (0.2-60 mg/kg), and brain, cerebrospinal fluid, and plasma Abeta levels were characterized at 1, 3, 6, 9, and 14 h postdose. Low doses significantly elevated plasma Abeta levels at early time points, with return to baseline within hours. Higher doses inhibited Abeta levels in all compartments at early time points, but elevated plasma Abeta levels at later time points. To determine whether this phenomenon occurs under steady-state drug exposure, guinea pigs were implanted with subcutaneous minipumps delivering LY-450139 (0.3-30 mg/kg/day) for 5 days. Plasma Abeta was significantly inhibited at 10-30 mg/kg/day, but significantly elevated at 1 mg/kg/day. To further understand the mechanism of Abeta elevation by LY-450139, H4 cells overexpressing the Swedish mutant of amyloid-precursor protein and a mouse embryonic stem cell-derived neuronal cell line were studied. In both cellular models, elevated levels of secreted Abeta were observed at subefficacious concentrations, whereas dose-responsive inhibition was observed at higher concentrations. These results suggest that LY-450139 modulates the gamma-secretase complex, eliciting Abeta lowering at high concentrations but Abeta elevation at low concentrations.

Regulation of the NMDA receptor complex and trafficking by activity-dependent phosphorylation of the NR2B subunit PDZ ligand.

Interactions between NMDA receptors (NMDARs) and the PDZ [postsynaptic density-95 (PSD-95)/Discs large/zona occludens-1] domains of PSD-95/SAP90 (synapse-associated protein with a molecular weight of 90 kDa) family proteins play important roles in the synaptic targeting and signaling of NMDARs. However, little is known about the mechanisms that regulate these PDZ domain-mediated interactions. Here we show that casein kinase II (CK2) phosphorylates the serine residue (Ser1480) within the C-terminal PDZ ligand (IESDV) of the NR2B subunit of NMDAR in vitro and in vivo. Phosphorylation of Ser1480 disrupts the interaction of NR2B with the PDZ domains of PSD-95 and SAP102 and decreases surface NR2B expression in neurons. Interestingly, activity of the NMDAR and Ca2+/calmodulin-dependent protein kinase II regulates CK2 phosphorylation of Ser1480. Furthermore, CK2 colocalizes with NR1 and PSD-95 at synaptic sites. These results indicate that activity-dependent CK2 phosphorylation of the NR2B PDZ ligand regulates the interaction of NMDAR with PSD-95/SAP90 family proteins as well as surface NMDAR expression and may be a critical mechanism for modulating excitatory synaptic function and plasticity.

Role of cdk5 in the pathogenesis of Alzheimer's disease.

Alzheimer's disease (AD) is characterized by two pathological hallmarks, namely, senile plaques and neurofibrillary tangles (NFTs). The former are mainly composed of amyloid-beta peptides (Abeta) while the latter consists mainly of filaments of hyperphosphorylated tau. Cyclin-dependent kinase 5 (cdk5) has been implicated not only in the tangle pathology, but recent data also implicate cdk5 in the generation of Abeta peptides. Since both Abeta peptides and NFTs are believed to play a role in neurodegeneration in AD, this proline-directed serine/threonine protein kinase is likely to contribute to the pathogenesis of AD. In vitro and in vivo animal data demonstrate the ability of cdk5 to induce phosphorylation and aggregation of tau, and NFT deposition and neurodegeneration. Findings from AD brain samples also show an elevated cdk5 activity and conditions that support the activation of cdk5. Evidence for the role of cdk5 in regulating Abeta production is just emerging. The mechanisms for this potentially damaging activity of cdk5 are largely unknown although amyloid precursor protein and presenilin-1 are both cdk5 substrates.

Cdk5 is a key factor in tau aggregation and tangle formation in vivo.

Tau aggregation is a common feature of neurodegenerative diseases such as Alzheimer's disease, and hyperphosphorylation of tau has been implicated as a fundamental pathogenic mechanism in this process. To examine the impact of cdk5 in tau aggregation and tangle formation, we crossed transgenic mice overexpressing the cdk5 activator p25, with transgenic mice overexpressing mutant (P301L) human tau. Tau was hyperphosphorylated at several sites in the double transgenics, and there was a highly significant accumulation of aggregated tau in brainstem and cortex. This was accompanied by increased numbers of silver-stained neurofibrillary tangles (NFTs). Insoluble tau was also associated with active GSK. Thus, cdk5 can initiate a major impact on tau pathology progression that probably involves several kinases. Kinase inhibitors may thus be beneficial therapeutically.

Tau protein phosphorylation as a therapeutic target in Alzheimer's disease.

Neurofibrillary tangles (NFTs) are a distinguishing neuropathological feature found in postmortem brains of Alzheimer s disease (AD) and tauopathy patients. The density of these lesions correlates with severity of AD and their distribution follows a characteristic pattern of expansion as the disease progresses. The principle components of NFTs are highly phosphorylated forms of the microtubule-associated protein, tau. Tau phosphorylation is believed to initiate or facilitate dissociation from microtubules leading to microtubule destabilization, decay of cellular transport properties, and cell death. This review summarizes recent data and prevailing views on the roles of protein kinases and phosphatases in the regulation of tau phosphorylation in vitro and in vivo, taking into account data from human neurodegenerative diseases and from transgenic rodent models. Small molecule inhibitors of tau phosphorylation that serve as important research tools and possibly the basis of potential new therapeutics, are also described. Key challenges in developing effective therapeutic agents include identification of the relevant kinase(s) responsible for aberrant tau phosphorylation in AD, synthesis of inhibitors selectively targeting those kinases and establishment of appropriate animal models.

Cdk5 as a drug target for the treatment of Alzheimer's disease.

Cyclin-dependent kinase-5 (cdk5) is suggested to play a role in tau phosphorylation and contribute to the pathogenesis of Alzheimer's disease (AD). One of its activators, p25, is dramatically increased in AD brains where p25 and cdk5 are colocalized with neurofibrillary tangles. Several animal models have shown a correlation of p25/cdk5 activities with tau phosphorylation. Overexpression of p25/cdk5 in nueronal cultures not only leads to tau phosphorylation but also cytoskeletal abnormalities and neurodegeneration. Therefore, cdk5 kinase inhibitors are potential therapeutic agents for the treatment of AD. Availability of potent, selective, brain permeable cdk5 inhibitors and relevant animal models in which their efficacy can be treated will be critical in the development of these inhibitors.