Acid α-glucosidase (GAA) activity and glycogen content in muscle biopsy specimens of patients with Pompe disease: A systematic review.

Pompe disease is a rare genetic disorder characterized by a deficiency of acid α-glucosidase (GAA), leading to the accumulation of glycogen in various tissues, especially in skeletal muscles. The disease manifests as a large spectrum of phenotypes from infantile-onset Pompe disease (IOPD) to late-onset Pompe disease (LOPD), depending on the age of symptoms onset. Quantifying GAA activity and glycogen content in skeletal muscle provides important information about the disease severity. However, the distribution of GAA and glycogen levels in skeletal muscles from healthy individuals and those impacted by Pompe disease remains poorly understood, and there is currently no universally accepted standard assay for GAA activity measurement. This systematic literature review aims to provide an overview of the available information on GAA activity and glycogen content levels in skeletal muscle biopsies from patients with Pompe disease. A structured review of PubMed and Google Scholar literature (with the latter used to check that no additional publications were identified) was conducted to identify peer-reviewed publications on glycogen storage disease type II [MeSH term] + GAA, protein human (supplementary concept), Pompe, muscle; and muscle, acid alpha-glucosidase. A limit of English language was applied. Results were grouped by methodologies used to quantify GAA activity and glycogen content in skeletal muscle. The search and selection strategy were devised and carried out in line with Preferred Reporting of Items in Systematic Reviews and Meta-Analysis guidelines and documented using a flowchart. Bibliographies of papers included in the analysis were reviewed and applicable publications not already identified in the search were included. Of the 158 articles retrieved, 24 (comprising >100 muscle biopsies from >100 patients) were included in the analysis, with four different assays. Analysis revealed that patients with IOPD exhibited markedly lower GAA activity in skeletal muscles than those with LOPD, regardless of the measurement method employed. Additionally, patients with IOPD had notably higher glycogen content levels in skeletal muscles than those with LOPD. In general, however, it was difficult to fully characterize GAA activity because of the different methods used. The findings underscore the challenges in the interpretation and comparison of the results across studies because of the substantial methodological variations. There is a need to establish standardized reference ranges of GAA activity and glycogen content in healthy individuals and in Pompe disease patients based on globally standardized methods to improve comparability and reliability in assessing this rare disease.

A phase 1 randomized, placebo-controlled study to investigate potential interactions between ASP8062, a positive allosteric modulator of the GABAB receptor, and morphine in recreational opioid users.

BACKGROUND: Recent increases in opioid use and subsequent opioid use disorder are a major public health crisis in the United States. AIMS: This phase 1 randomized, placebo-controlled study investigated the safety, tolerability, and pharmacokinetics (PKs) of ASP8062, a γ-aminobutyric acid B receptor-positive allosteric modulator, with and without administration of morphine in participants who used opioids recreationally. METHODS: Participants were randomly assigned (2:1) to daily dosing with ASP8062 25 mg or placebo on days 1-10. On day 10, all participants received morphine as a single oral dose of 45 mg; assessments were performed on days 11-16. The primary end point was safety, evaluated as the nature, frequency, and severity of adverse events, and end-tidal CO2 levels. PK end points were a secondary outcome measure. RESULTS: A total of 24 participants (aged 21-54 years) received ASP8062 (n = 16) or placebo (n = 8). There were no deaths or serious adverse events leading to treatment discontinuation during the study. Most adverse events were mild, with numerically lower absolute number of adverse events reported with ASP8062 plus morphine versus placebo plus morphine. ASP8062 plus morphine did not increase respiratory depression, potential drug abuse- or withdrawal-related adverse events. There were no significant PK interactions. CONCLUSIONS: In this phase 1 study, we did not observe any unexpected safety signals or notable PK interactions with concomitant morphine administration. These data suggest a potentially low risk for an increase in drug abuse- or withdrawal-related adverse events or respiratory distress in participants exposed to ASP8062 and morphine.

A phase 1b study to investigate the potential interactions between ASP8062 and buprenorphine/naloxone in patients with opioid use disorder.

BACKGROUND: There is an unmet need for therapeutics with greater efficacy and tolerability for the treatment of opioid use disorder (OUD). ASP8062 is a novel compound with positive allosteric modulator activity on the γ-aminobutyric acid type B receptor under development for use with standard-of-care treatment for patients with OUD. AIMS: To investigate the safety, tolerability, interaction potential, and pharmacokinetics (PK) of ASP8062 in combination with buprenorphine/naloxone (B/N; Suboxone®). METHODS: In this phase 1, randomized, double-masked, placebo-controlled study, patients with OUD began B/N (titrated to 16/4 mg/day) treatment upon enrollment (induction, Days 1-4; maintenance, Days 5-18; downward titration, Days 19-26; and discharge, Day 27). On Day 12, patients received a single dose of ASP8062 60 mg or placebo with B/N and underwent safety and PK assessments. Primary endpoints included frequency and severity of treatment-emergent adverse events (TEAEs), clinical laboratory tests, respiratory depression, and suicidal ideation. Secondary endpoints investigated the impact of ASP8062 on B/N PK. RESULTS: Eighteen patients were randomized and completed the study (ASP8062, n = 12; placebo, n = 6). With this sample size typical for phase 1 drug-drug interaction studies, ASP8062 was well tolerated; most TEAEs were mild in severity, and none led to treatment withdrawal. ASP8062 did not enhance substance use-related TEAEs, respiratory depression, or suicidal ideation and did not have a clinically significant impact on the PK of B/N. CONCLUSIONS: In this phase 1 study, ASP8062 was safe, well tolerated, and did not enhance respiratory suppression induced by buprenorphine. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT04447287.

A randomized phase 1 single-dose polysomnography study of ASP8062, a GABAB receptor positive allosteric modulator.

RATIONALE: Previous research suggests that sleep polysomnography and EEG endpoints can be used to assess GABAergic activity; however, the impact of GABAB receptor positive allosteric modulators on sleep endpoints remains unclear. OBJECTIVES: This phase 1 study compared a single dose of ASP8062 (35 mg or 70 mg), a GABAB receptor positive allosteric modulator, with placebo and paroxetine (40 mg). METHODS: Healthy adult volunteers were randomized to four treatments (35 mg ASP8062, 70 mg ASP8062, paroxetine 40 mg, or matching placebo), each separated by a 14-day washout. Primary endpoints obtained by polysomnography were time in stage N3 or SWS and time in rapid eye movement (REM) sleep. Secondary endpoints included impact on sleep stages and electroencephalography parameters, pharmacokinetics, nighttime growth hormone (GH), and safety/tolerability. RESULTS: In 20 randomized volunteers, ASP8062 led to a significant and seemingly dose-dependent increase in SWS over the entire night; this increase was mainly observed during the first third of the night. ASP8062 did not impact time in REM sleep. Paroxetine had no effect on SWS but produced a significant reduction in time spent in REM sleep. A dose-dependent trend in increased GH release was also observed with ASP8062. Headache and nausea were the most commonly reported treatment-emergent adverse events (TEAEs) for ASP8062; most TEAEs were mild in severity. CONCLUSIONS: Single-dose ASP8062 (35 and 70 mg) appeared to result in CNS penetration and enhanced GABAergic activity as measured by increases in slow-wave sleep and growth hormone release.

Efficacy and Safety of ASP0819 in Patients with Fibromyalgia: Results of a Proof-of-Concept, Randomized, Double-Blind, Placebo-Controlled Trial.

PURPOSE: ASP0819 is a novel, non-opioid KCa3.1 channel opener that reverses abnormal nerve firing of primary sensory afferent nerves. Currently available treatments for fibromyalgia provide only modest relief and are accompanied by a host of adverse side effects. PATIENTS AND METHODS: In this phase 2a, double-blind trial (NCT03056690), adults meeting fibromyalgia diagnostic criteria were randomized 1:1 to receive either 15 mg/day of oral ASP0819 (n=91) or placebo (n=95). The primary endpoint was the change from baseline to Week 8 in the mean daily average pain score. Changes in the Fibromyalgia Impact Questionnaire Revised (FIQR) symptoms, function, and overall impact subscales, as well as changes in the patients' global impression of change, were secondary endpoints; treatment effects on FIQR total score and impact on sleep were exploratory analyses. RESULTS: There was no statistically significant difference between ASP0819 and placebo for the primary endpoint (P=0.086); however, ASP0819 versus placebo significantly improved daily average pain at Weeks 2, 6, and 7 (all P<0.05). Numerical improvements were observed on the FIQR total score and several sleep items showed statistically significant improvements with ASP0819 versus placebo. There were no major safety concerns with ASP0819. Headache was the most common treatment-emergent adverse event (TEAE) occurring in both study arms; most TEAEs were mild or moderate in severity and no TEAEs suggestive of potential drug abuse were observed, as assessed by TEAE reporting and/or safety evaluations. Withdrawal effects also were not observed. CONCLUSION: ASP0819 demonstrated some signals suggestive of efficacy and had a good tolerability profile in patients with fibromyalgia. Further studies are required to determine if ASP0819 can be a novel non-opioid treatment option in this patient group. CLINICALTRIALSGOV REGISTRATION: NCT03056690.

Single- and Multiple-Dose Safety, Tolerability, and Pharmacokinetic Profiles of ASP8062: Results From 2 Phase 1 Studies.

ASP8062 is an orally active γ-amino-butyric acid type B (GABAB ) receptor positive allosteric modulator currently in phase 2 development. Safety and pharmacokinetic (PK) profiles of ASP8062 were evaluated in 2 studies in healthy subjects. The first study (a first-in-human study) evaluated single ascending doses (SAD) of ASP8062. The second study was composed of 2 parts: part 1 evaluated multiple ascending doses (MAD) of ASP8062 for 14 days, and part 2 was a single-dose arm to assess the PK of ASP8062 in cerebrospinal fluid (CSF). Fifty-six men (SAD) and 56 subjects (24 women and 32 men; MAD) were enrolled. Across the SAD dosing range, area under the concentration-time curve was dose proportional; increases in maximum plasma concentration appeared linear but were slightly less than dose proportional. Time to maximal concentration and half-life were 1-4 hours and ∼40-50 hours, respectively; no food effect was observed. ASP8062 PK properties at steady state were similar to those following a single dose. Steady state was achieved by ∼day 9 with ∼2-fold accumulation, and ASP8062 was detected in CSF. ASP8062 was well tolerated; no clear evidence of ASP8062's effects on safety, cognition, drug withdrawal, or suicidal ideation/behavior was observed. These data support the development of ASP8062 in indications where the GABAB receptor is a target.

Imaging the Enzyme 11ß-Hydroxysteroid Dehydrogenase Type 1 with PET: Evaluation of the Novel Radiotracer 11C-AS2471907 in Human Brain.

The 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) enzyme converts cortisone to cortisol and participates in the regulation of glucocorticoid levels in tissues. 11ß-HSD1 is expressed in the liver, kidney, adipose tissue, placenta, and brain. 11ß-HSD1 is a target for treatment of depression, anxiety, posttraumatic stress disorder, and also against age-related cognitive function and memory loss. In this study, we evaluated the radiotracer 11C-AS2471907 (3-(2-chlorophenyl)-4-(methyl-11C)-5-[2-[2,4,6-trifluorophenoxy]propan-2-yl]-4H-1,2,4-triazole) to image 11ß-HSD1 availability in the human brain with PET. Methods: Fifteen subjects were included in the study. All subjects underwent one 2-h scan after a bolus administration of 11C-AS2471907. Two subjects underwent an additional scan after blockade with the selective and high-affinity 11ß-HSD1 inhibitor ASP3662 to evaluate 11C-AS2471907 nondisplaceable distribution volume. Five subjects also underwent an additional scan to evaluate the within-day test-retest variability of 11C-AS2471907 volumes of distribution (VT). Results:11C-AS2471907 time-activity curves were best fitted by the 2-tissue-compartment (2TC) model. 11C-AS2471907 exhibited a regionally varying pattern of uptake throughout the brain. The VT of 11C-AS2471907 ranged from 3.7 ± 1.5 mL/cm3 in the caudate nucleus to 14.5 ± 5.3 mL/cm3 in the occipital cortex, with intermediate values in the amygdala, white matter, cingulum, insula, frontal cortex, putamen, temporal and parietal cortices, cerebellum, and thalamus (from lowest to highest VT). From the blocking scans, nondisplaceable distribution volume was determined to be 0.16 ± 0.04 mL/cm3 for 11C-AS2471907. Thus, nearly all uptake was specific and the binding potential ranged from 22 in the caudate to 90 in the occipital cortex. Test-retest variability of 2TC VT values was less than 10% in most large cortical regions (14% in parietal cortex) and ranged from 14% (cerebellum) to 51% (amygdala) in other regions. The intraclass correlation coefficient of 2TC VT values ranged from 0.55 in the white matter to 0.98 in the cerebellum. Conclusion:11C-AS2471907 has a high fraction of specific binding in vivo in humans and reasonable within-day reproducibility of binding parameters.

Safety, Pharmacokinetics, and Pharmacodynamics of ASP3662, a Novel 11ß-Hydroxysteroid Dehydrogenase Type 1 Inhibitor, in Healthy Young and Elderly Subjects.

Inhibition of the enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) represents a potential mechanism for improving pain conditions. ASP3662 is a potent and selective inhibitor of 11ß-HSD1. Two phase I clinical studies were conducted to assess the safety, tolerability, pharmacokinetics (PKs), and pharmacodynamics (PDs) of single and multiple ascending doses of ASP3662 in healthy young and elderly non-Japanese and young Japanese subjects. Nonlinear, more than dose-proportional PKs were observed for ASP3662 after single-dose administration, particularly at lower doses (≤ 6 mg); the PKs at steady state were dose proportional, although the time to ASP3662 steady state was dose dependent at lower doses (≤ 2 mg). Similar PKs were observed among young Japanese, young non-Japanese, and elderly non-Japanese subjects. Specific inhibition of 11ß-HSD1 occurred after both single and multiple doses of ASP3662. A marked dissociation between PKs and PDs was observed after single but not multiple doses of ASP3662. ASP3662 was generally safe and well tolerated.

A Thorough QT/QTc Study of Clobazam in Healthy Volunteers.

PURPOSE: A thorough QT study was conducted to assess the proarrhythmic potential of clobazam and its active metabolite, N-desmethylclobazam (N-CLB). METHODS: In this Phase I, single-site, randomized, double-blind, double-dummy, parallel-group study, healthy participants were randomized to 1 of 4 treatment groups: clobazam 40 mg/d (maximum therapeutic dosage), clobazam 160 mg/d (supratherapeutic dosage), placebo, or moxifloxacin 400 mg (active control). FINDINGS: Of 280 enrolled participants (n = 70 per treatment arm), 250 (92%) completed the study; 194 were included in the pharmacokinetics population (clobazam 40 mg/d, n = 66; clobazam 160 mg/d, n = 62; and moxifloxacin, n = 66). Mean changes from baseline in QT interval placebo-corrected for heart rate using the Fridericia formula (primary end point), Bazett formula, and individual correction method (QTcF, QTcB, and QTcI, respectively) with clobazam 40 and 160 mg/d revealed no effect on QTc. No clinically relevant or treatment-related arrhythmias were observed, and there were no instances of second- or third-degree atrioventricular block. Given that clobazam is primarily demethylated to N-CLB by cytochrome P450 (CYP) enzyme, CYP3A4, the mean plasma time-concentration profile of clobazam was unchanged with the exclusion of CYP2C19 poor metabolizers. As N-CLB is metabolized by CYP2C19, the exclusion of CYP2C19 poor metabolizers resulted in slightly decreased mean plasma time-concentration profiles of N-CLB. Using a linear mixed-effects model, the effects of the clobazam and N-CLB Cmax values on the placebo-corrected changes from baseline in QTcF, QTcI, and QTcB were near zero or slightly negative, and are not considered clinically important. The incidence of treatment-emergent adverse events was greatest in the clobazam groups (number of moderate AEs experienced by patients: PBO, 3/70; MOXI, 5/70; CLB 40 mg/d, 18/70; CLB 160 mg/d, 21/70; severe AEs: PBO, MOXI, & CLB 160 mg/d, 0; CLB 40 mg/d, 2/70); there were no serious AEs in any treatment group. A total of 10% of participants experienced benzodiazepine-withdrawal symptoms (16%, 23%, and 3% in the clobazam 40 and 160 mg/d groups and the moxifloxacin group, respectively). IMPLICATIONS: The findings from this thorough QT study are consistent with existing clinical data and support the lack of proarrhythmic potential with clobazam.

Bioequivalence of oral and intravenous carbamazepine formulations in adult patients with epilepsy.

OBJECTIVE: To evaluate the safety, tolerability, and comparative pharmacokinetics (PK) of intravenous and oral carbamazepine. METHODS: In this phase 1, open-label study, adult patients with epilepsy on a stable oral carbamazepine dosage (400-2,000 mg/day) were converted to intravenous carbamazepine (administered at 70% of the oral dosage). A 28-day outpatient period preceded an up to 10-day inpatient period and a 30-day follow-up period. Intravenous carbamazepine was administered over 15 or 30 min every 6 h on days 1-7; some patients in the 15-min group were eligible to receive four 2- to 5-min (rapid) infusions on day 8. Patients underwent blood sampling to determine the area under the concentration-time curve (AUC) for carbamazepine and metabolite carbamazepine-10,11-epoxide following oral (day 0) and intravenous carbamazepine administration (days 1, 7, and 8). Bioequivalence was evaluated in patients with normal renal function (creatinine clearance >80 ml/min). Safety assessments were conducted through day 38. RESULTS: Ninety-eight patients enrolled and 77 completed the PK component. The mean daily oral and intravenous carbamazepine dosage for 64 PK-evaluable patients with normal renal function was 962.5 and 675.1 mg (70% of oral dosage), respectively. Steady-state minimum concentration (C(min)) and overall exposure (AUC0-24) for intravenous carbamazepine infused over 30, 15, or 2-5 min were similar to oral carbamazepine. The 90% confidence intervals (CIs) for the ratios of the adjusted means for AUC0-24, maximum concentration (Cmax), and C(min) were within the 80%-125% bioequivalence range for 30-min intravenous infusions versus oral administration, but exceeded the upper limit for Cmax for the 15-min and rapid infusions. All intravenous carbamazepine infusions were well tolerated. SIGNIFICANCE: Intravenous carbamazepine infusions (70% of oral daily dose) of 30-, 15-, and 2- to 5-min duration, given every 6 h, maintained patients' plasma carbamazepine concentrations. Intravenous carbamazepine 30-min infusions were bioequivalent to oral carbamazepine in patients with normal renal function; rapid infusions were well-tolerated in this study.

Pharmacokinetic drug interactions between clobazam and drugs metabolized by cytochrome P450 isoenzymes.

STUDY OBJECTIVE: To investigate potential drug-drug interactions between clobazam and cytochrome P450 (CYP) isoenzyme substrates, inhibitors, and inducers. DESIGN: Two, prospective, open-label, single-center, drug-drug interaction (DDI) studies and a population pharmacokinetics analysis of seven multicenter phase II-III trials. SETTING: Clinical research unit. PARTICIPANTS: Fifty-four healthy adult volunteers were enrolled in the two drug-drug interaction studies; 53 completed the studies. The population pharmacokinetics analysis evaluated data from 171 participants from five studies with healthy volunteers and two studies with patients with Lennox-Gastaut syndrome. Participants in these studies received clobazam and stable dosages of the following antiepileptic drugs: phenobarbital, phenytoin, carbamazepine, valproic acid, lamotrigine, felbamate, or oxcarbazepine. INTERVENTION: In the first drug-drug interaction study, 36 participants received a single oral dose of clobazam 10 mg on day 1, followed by either ketoconazole 400 mg once/day or omeprazole 40 mg once/day on days 17-22, with a single dose of clobazam 10 mg coadministered on day 22, to study the effects of CYP3A4 or CYP2C19 inhibition, respectively, on clobazam and its active metabolite N-desmethylclobazam (N-CLB). In the second study, 18 participants received a drug cocktail consisting of caffeine 200 mg, tolbutamide 500 mg, dextromethorphan 30 mg, and midazolam 4 mg on days 1 and 19, and clobazam 40 mg/day on days 4-19, to study clobazam's effects on CYP1A2, CYP2C9, CYP2D6, and CYP3A4. MEASUREMENTS AND MAIN RESULTS: In the first DDI study, coadministration of ketoconazole (a CYP3A4 inhibitor) and clobazam increased clobazam's area under the concentration time curve from time zero extrapolated to infinity (AUC(0-∞) ) 54% and decreased clobazam's maximum plasma concentration (C(max) ) by 15% versus administration of clobazam alone, but the combination affected these pharmacokinetic parameters for N-CLB to a lesser degree. The CYP2C19 inhibitor omeprazole increased AUC(0-∞) and C(max) of N-CLB by 36% and 15%, respectively, but did not significantly affect the pharmacokinetics of clobazam. At steady state, N-CLB has 3-4 times greater exposure than clobazam. In the second DDI study, no clinically significant drug-drug interactions were observed between clobazam 40 mg and the CYP probe substrates caffeine or tolbutamide. Exposure to midazolam and its 1-hydroxymidazolam metabolite, however, decreased by 27% and increased 4-fold, respectively. Clobazam increased dextromethorphan (CYP2D6) AUC(0-∞) by 95% and C(max) by 59%. In the population pharmacokinetics analysis, stable dosages of common antiepileptic drugs that induce CYP3A4 or CYP2C19, or inhibit CYP2C19, had negligible effects on clobazam or N-CLB. Clobazam did not affect valproic acid or lamotrigine exposures. CONCLUSION: These findings suggest no clinically meaningful drug-drug interactions between clobazam and drugs metabolized by CYP3A4, CYP2C19, CYP1A2, or CYP2C9. Concomitant use of drugs metabolized by CYP2D6 may require dosage adjustment. Clobazam may be administered safely as adjunctive therapy in patients with Lennox-Gastaut syndrome, without meaningful changes in clobazam pharmacokinetics that would require dosage adjustment.

Oral toxicity of vigabatrin in immature rats: characterization of intramyelinic edema.

OBJECTIVES: Two toxicologic studies of vigabatrin were conducted with immature Sprague Dawley rats to characterize intramyelinic edema (IME) formation and assess potential impact on behavioral measures. Study 1 was a dosage-ranging characterization of overall toxicity of vigabatrin in young, developing rats. Study 2 evaluated vacuolar brain lesions found in Study 1. METHODS: During Study 1, immature Sprague Dawley rats were orally administered deionized water (vehicle control), or vigabatrin at 5, 15, or 50mg/kg/day for ≤ 9 weeks, beginning at postnatal day 4 (PND 4) and followed by a recovery period. Toxicologic observations were collected, including adverse clinical signs, body weight gains, food consumption, ophthalmoloscopy, electroretinograms, sexual maturation, motor activity, memory, and learning behaviors. At sacrifice, CNS tissues were examined by light microscopy for evidence of IME. In Study 2, immature Sprague Dawley rats were again orally administered vigabatrin (50mg/kg/day for ≤ 9 weeks, beginning at PND 4). At sacrifice, CNS tissues were examined by both light and transmission electron microscopy for evidence of IME. RESULTS: At 5-50mg/kg/day, dosage-related reduced food consumption, decreased body weight, and delayed sexual maturation were found. Persisting through recovery, effects were more pronounced in males. Increased degrees of vacuolation were observed on PND 67 only after a dosage of 50mg/kg/day, and were attenuated during recovery. Vacuolar-change morphology was characteristic of IME, with no evidence of cellular or neuritic degeneration. Ultrastructural analyses revealed brain vacuoles initiated as splits of myelin sheaths along intra-period lines. These splits expanded, evolving into large membrane-rich vacuoles, and were more prominent at later stages of myelin development. Hypomyelination and gliopathy were noted from PNDs 4-15, and were likely related to vigabatrin exposure during active myelination. A lesser degree of hypomyelination was observed from PNDs 4-46 and 4-65. Vacuolation was markedly attenuated in post-recovery-period rats. CONCLUSIONS: The present studies indicated toxicities in young rats at vigabatrin dosages lower than those reported for toxicities in older rats. Dosages <50mg/kg/day did not affect CNS, behavior, and reproductive development. However, at the greatest dosage, some retardation of physical growth, delay in sexual maturation, reduction in physical strength, and induction of CNS stimulation (handling-induced spasms) occurred. The key pathologic finding was vacuolar brain lesions in the white and gray matter, which generally reversed upon drug discontinuation. Vacuoles were confined to myelin sheaths, consistent with observations in adult rats. Vigabatrin delayed but did not eliminate myelination despite continued dosing, an effect greatest during active myelination.

Neurotrophins support regenerative axon assembly over CSPGs by an ECM-integrin-independent mechanism.

Chondroitin sulfate proteoglycans (CSPGs) and myelin-based inhibitors are the most studied inhibitory molecules in the adult central nervous system. Unlike myelin-based inhibitors, few studies have reported ways to overcome the inhibitory effect of CSPGs. Here, by using regenerating adult dorsal root ganglion (DRG) neurons, we show that chondroitin sulfate proteoglycans inhibit axon assembly by a different mechanism from myelin-based inhibitors. Furthermore, we show that neither Rho inhibition nor cAMP elevation rescues extracellular factor-induced axon assembly inhibited by CSPGs. Instead, our data suggest that CSPGs block axon assembly by interfering with integrin signaling. Surprisingly, we find that nerve growth factor (NGF) promotes robust axon growth of regenerating DRG neurons over CSPGs. We have found that, unlike naive neurons that require simultaneous activation of neurotrophin and integrin pathways for axon assembly, either neurotrophin or integrin signaling alone is sufficient to induce axon assembly of regenerating neurons. Thus, our results suggest that the ability of NGF to overcome CSPG inhibition in regenerating neurons is probably due to the ability of regenerating neurons to assemble axons using an integrin-independent pathway. Finally, our data show that the GSK-3beta-APC pathway, previously shown to mediate developing axon growth, is also necessary for axon regeneration.

Turning on the machine: genetic control of axon regeneration by c-Jun.

Upregulation of the transcription factor c-Jun has been correlated with axon regeneration after injury in multiple types of neurons. In this issue of Neuron, Raivich et al. use a nervous system-specific mutant to provide genetic evidence that c-Jun is necessary for efficient axon regeneration.

A heparin derived oligosaccharide normalizes the fear response of old Brown Norway rats.

Old animals exhibit impaired spatial learning and an exaggerated response to stress. It was predicted that the heparin derived oligosaccharide (HDO), C3, would reverse these age-related deficits. Young (4-5 months) and old (19-20 months) Brown Norway male rats ingested C3 (25 mg/kg per day, p.o.) or vehicle (drinking water) daily for 42-44 days. Two weeks after the initiation of drug treatment, the rats were examined using a series of behavioral tests. The old control rats evidenced: (1) increased neophobia and reduced exploratory behavior in a novel open field (OF); and (2) exaggerated freezing during the acquisition and retention of a conditioned response (CR) to a Pavlovian light-shock pairing ("foreground" conditioning). C3 treatment attenuated or reversed this age-related impairment of emotional behavior. Analysis of spatial learning using the Morris water maze (MWM), and of CR formation to the place in which the foreground conditioning was conducted ("background" conditioning) during context dependent fear conditioning (CDFC) did not reveal major age or drug effects on memory processes. It is hypothesized that C3 repairs damage to the extracellular matrix (ECM) that occurs during the aging process and thereby normalizes age-related exacerbated fear behaviors without affecting mnestic processes.

Low molecular weight glycosaminoglycan blockade of beta-amyloid induced neuropathology.

Previous studies have shown different roles for proteoglycans and glycosaminoglycans (GAGs) in Alzheimer's disease (AD) neuropathology. Using a rat model of beta-amyloid induced neuropathology, we tested whether low molecular weight glycosaminoglycans (Certoparin and C6) could be useful as preventative agents and/or as a potential therapeutic treatment for AD. Chronic subcutaneous low molecular weight glycosaminoglycan injections beginning either before or after an intra-amygdaloid beta-amyloid-(25-35) injection blocked abnormal intracellular tau changes and reactive astrocytosis but did not affect beta-amyloid's aggregation state. Also, low molecular weight glycosaminoglycan injections beginning 1 day prior to sacrifice did not block the effects of beta-amyloid nor did injections of a disaccharide, suggesting chronic low molecular weight glycosaminoglycan treatment is needed to block the effects of beta-amyloid. Furthermore, these data indicate that there is a molecular weight range of active low molecular weight glycosaminoglycans in this model; and supports the investigation of low molecular weight glycosaminoglycans as a preventative and/or therapeutic treatment of beta-amyloid induced neuropathology.