Rachel Brandeis

Age-related structural changes in the rat hippocampus: correlation with working memory deficiency.

Age-related histopathological changes in the hippocampal formation were correlated with cognitive performance, evaluated in rats at the 8-arm radial maze. Experiments were conducted using young (3 months), mature (12 months), middle-aged (17 months) and aged (24 months) Wistar rats. Significant memory impairments were already observed at the age of 12 months in all the measured parameters (correct choices, percent errors and total time). No further decline was observed between 12 and 17 months of age, while at 24 months additional decline was monitored mainly in the percent errors parameter. Morphometric analysis revealed a decrease in the area of cells within the hippocampus and the number of cells in the CA3 subfield. This pattern of morphological changes with age corresponded well with the cognitive impairments, with high correlation especially to lesions at the CA3 subfield. It had also been confirmed in this study that lipofuscin appeared to be a good histochemical marker for CNS cell degeneration. It is concluded that 12-month-old Wistar rats may serve as the animal model of choice for the study of specific age-related behavioral deficits and that the hippocampal CA3 region might play a major role in the age-dependent cognitive decline.

M1 muscarinic agonists can modulate some of the hallmarks in Alzheimer's disease: implications in future therapy.

M1 muscarinic receptors (M1 mAChRs) play a role in an apparent linkage of three major hallmarks of Alzheimer’s disease (AD): β-amyloid (Aβ) peptide; tau hyperphosphorylation and paired helical filaments (PHFs); and loss of cholinergic function conducive to cognitive impairments. We evaluated the M1 muscarinic agonists AF102B (Cevimeline, EVOXAC™: prescribed for Sjøgren’s syndrome), AF150(S), and AF267B on some of these hallmarks of AD. Activation of M1 mAChRs with these agonists leads, inter alia, to enhanced secretion of amyloid precursor protein (α-APP), (via α-secretase activation), to decreased Aβ (via γ-secretase inhibition), and to inhibition of Aβ- and/or oxidative stress-induced cell death. In several animal models mimicking different aspects of AD, these drugs restored cognitive impairments, and in select cases induced a decrease in brain Aβ elevation, with a high safety margin, following po administration. Notably, in mice with small hippocampi, unlike rivastigmine and nicotine, AF150(S) and AF267B restored cognitive impairments also on escape latency in a Morris water maze paradigm, in reversal learning. Studies from other labs showed that AF102B and talsaclidine (another M1 agonist) decreased cerbrospinal fluid (CSF) Aβ in AD patients following chronic treatment, being the first reported drugs with such a profile. The clinical significance of these studies remains to be elucidated, yet based on in vivo (rabbits) and in vitro studies (cell cultures), our M1 agonists can decrease brain Aβ, owing to a novel and dual complementary effect (e.g., inhibition of γ-secretase and activation of α-secretase). Remarkably, although M1 agonists can decrease CSF Aβ in AD patients, an increased AD-type pathology in Parkinson’s disease was recently been associated with chronic antimuscarinic treatment. In another aspect, these agonists decreased tau hyperphosphorylation in vitro and in vivo. Notably, nicotinic agonists or cholinesterase inhibitors increased tau hyperphosphorylation. In summary, the M1 agonists tested are effective on cognition and behavior and show unique disease-modifying properties owing to beneficial effects on major hallmarks of AD. This may place such drugs in the first line of modern AD therapies (e.g., β- or γ-secretase inhibitors, vaccines against Aβ, statins, and inhibitors of tau hyperphosphorylation).

NG-nitro-L-arginine enhances neuronal death following transient forebrain ischemia in gerbils.

Experiments were performed with Mongolian gerbils to study the effect of the specific nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine (L-NNA) on ischemic brain damage induced by 5 min bilateral carotid occlusion. A single i.p. injection of L-NNA did not result in any neuronal loss in the central nervous system. In animals undergoing ischemia, a selective destruction of hippocampal CA1 cells was observed whereas pretreatment with 50 mg/kg L-NNA 4 h before administration of ischemia produced significantly more extensive cell damage in the hippocampus and other brain regions. These findings demonstrate that in this model inhibition of nitric oxide generation augments ischemia-induced neuronal cell injury in the brain.

Prevention of soman-induced cognitive deficits by pretreatment with human butyrylcholinesterase in rats

This study examined the ability of pretreatment with human serum butyrylcholinesterase (HuBChE) to prevent soman-induced cognitive impairments. Behavioral testing was carried out using the Morris water maze task evaluating learning, memory, and reversal learning processes. Pretreatment with HuBChE significantly prevented the memory and reversal learning impairments induced by soman. A small deficiency in performance was observed only during part of the learning period in HuBChE-treated rats after administration of soman. Results support the contention that pretreatment alone with HuBChE is sufficient to increase survival and to prevent impairment in cognitive functioning following exposure to soman.

M1 Agonists for the Treatment of Alzheimer's Disease.

The AF series compounds, AF102B and congeners of AF150(S), are functionally selective agonists for m1 muscarinic receptors (m1AChRs). This is shown in stable transfected CHO and PC12 cells (PC12M1) with m1‐m5AChRs and m1AChRs, respectively. AF102B and AF150(S) are partial agonists, but AF150, AF151, and AF151(S) are full agonists in stimulating phosphoinositides hydrolysis or arachidonic acid release in these cells. Yet, all these compounds behave as antagonists when compared with carbachol in elevating cAMP levels. In PC12M1 cells, unlike carbachol, the AF series compounds induce only minimal to moderate neurite outgrowth. Yet, these agonists synergize strongly with NGF, which by itself mediates only a mild response. Stimulation of m1AChRs by AF102B, AF150(S) and AF151(S) in PC12M1 cells enhances secretion of β/A4 amyloid precursor protein derivatives (APPs). The enhanced APPs secretion induced by AF102B is potentiated by NGF. AF102B also stimulates APPs secretion from rat cortical slices. Stimulation of m1AChR in PC12M1 cells with carbachol or AF102B decreases tau phosphorylation as indicated by specific tau‐1 mAb and alkaline phosphatase treatment. Due to the above mentioned properties m1 agonists may be of unique value in delaying the progression of Alzheimers disease (AD). The AF series compounds show a wide safety margin and improve memory and learning deficits in animal models for AD. There is a dearth of clinical reports on m1 agonists. These include studies on AF102B and xanomeline, another m1 selective agonist. We tested AF102B in escalating doses of 20, 40, 60 mg, tid, po, (each dose for 2 weeks) for a total of 10 weeks. This was a single‐blind placebo‐controlled, parallel‐group study in patients with probable AD. AFl02B was signiticantly effective at 40 and 60 mg, tid in the ADAS, ADAS‐cognitive and ADAS‐word recognition scales.

M1 Muscarinic Agonist Treatment Reverses Cognitive and Cholinergic Impairments of Apolipoprotein E‐Deficient Mice

Abstract: Recent studies suggest that apolipoprotein E (apoE) plays a specific role in brain cholinergic function and that the E4 allele of apoE (apoE4), a major risk factor for Alzheimers disease (AD), may predict the extent of cholinergic dysfunction and the efficacy of cholinergic therapy in this disease. Animal model studies relevant to this hypothesis revealed that apoE‐deficient (knockout) mice have working memory impairments that are associated with distinct dysfunction of basal forebrain cholinergic neurons. Cholinergic replacement therapy utilizing M1‐selective muscarinic agonists has been proposed as effective treatment for AD patients. In the present study, we examined whether the memory deficits and brain cholinergic deficiency of apoE‐deficient mice can be ameliorated by the M1‐selective agonist 1‐methylpiperidine‐4‐spiro‐(2′‐methylthiazoline), [AF150(S)]. Treatment of apoE‐deficient mice with AF150(S) for 3 weeks completely abolished their working memory impairments. Furthermore, this reversal of cognitive deficit was associated with a parallel increase of histochemically determined brain choline acetyltransferase and acetylcholinesterase levels and with the recovery of these cholinergic markers back to control levels. These findings show that apoE deficiency‐related cognitive and cholinergic deficits can be ameliorated by M1‐selective muscarinic treatment. They also provide a novel model system for development and evaluation of therapeutic strategies directed specifically at the AD patients whose condition is attributed to the apoE genotype.

AF150(S) and AF267B: M1 muscarinic agonists as innovative therapies for Alzheimer's disease.

The M1 muscarinic agonists AF102B (Cevimeline, EVOXACTM: prescribed in USA and Japan for Sjogren’s Syndrome), AF150(S) and AF267B—1) are neurotrophic and synergistic with neurotrophins such as nerve growth factor and epidermal growth factor; 2) elevate the non-amyloidogenic amyloid precursor protein (α-APPs) in vitro and decrease β-amyloid (Aβ) levels in vitro and in vivo; and 3) inhibit Aβ- and oxidative-stress-induced cell death and apoptosis in PC12 cells transfected with the M1 muscarinic receptor. These effects can be combined with the beneficial effects of these compounds on some other major hallmarks of Alzheimer’s disease (AD) (e.g. τ hyperphosphorylation and paired helical filaments [PHF]; and loss of cholinergic function conducive to cognitive impairments.) These drugs restored cognitive impairments in several animal models for AD, mimicking different aspects of AD, with a high safety margin (e.g. AF150[S] >1500 and AF267B >4500). Notably, these compounds show a high bioavailability and a remarkable preference for the brain vs. plasma following po administration. In mice with small hippocampi, unlike rivastigmine and nicotine, AF150(S) and AF267B restored cognitive impairments also on escape latency in a Morris water maze paradigm in reversal learning. Furthermore, in aged and cognitively impaired microcebes (a natural animal model that mimics AD pathology and cognitive impairments), prolonged treatment with AF150(S) restored cognitive and behavioral impairments and decreased τ hyperphosphorylation, PHF and astrogliosis. Our M1 agonists, alone or in polypharmacy, may present a unique therapy in AD due to their beneficial effects on major hallmarks of AD.

Ocular injuries following sulfur mustard exposure: Pathological mechanism and potential therapy

Sulfur mustard (SM) is a potent vesicant, known for its ability to cause incapacitation and prolonged injuries to the eyes, skin and respiratory system. The toxic ocular events following sulfur mustard exposure are characterized by several stages: photophobia starting a few hours after exposure, an acute injury phase characterized by inflammation of the anterior segment and corneal erosions and a delayed phase appearing following a clinically silent period (years in human). The late injury appeared in part of the exposed eyes, expressed by epithelial defects and corneal neovascularization (NV), that lead to vision deficits and even blindness. During the last years we have characterized the temporal development of ocular lesions following SM vapor exposure in rabbits and have shown the existence of two sub-populations of corneas, those exhibiting delayed ocular lesions (clinically impaired) and those exhibiting only minor injuries if at all (clinically non-impaired). The aim of the present study was to investigate the pathological mechanism underlying the delayed injury by focusing on the unique characteristics of each sub-population and to test the efficacy of potential treatments. Clinically impaired corneas were characterized by chronic inflammation, increased matrix metalloproteinase (MMP) activity, poor innervation and limbal damage. Moreover, using impression cytology and histology, we identified the delayed lesions as typical for an ocular surface disorder under the category of limbal epithelial stem cell deficiency (LSCD). These results point to therapeutic directions, using anti-inflammatory drugs, MMPs inhibitors, neurotrophic factors and amniotic membrane transplantation. Topical anti-inflammatory drugs, either steroid (Dexamycin, DEX) or non-steroidal anti-infllammatory drug (NSAID, Voltaren Ophtha) were found to be beneficial in ameliorating the initial inflammatory response and in postponing the development of corneal NV, when given during the first week after exposure. When DEX was administered as a symptomatic treatment against NV, a significant regression in the angiogenic process was observed, however, the effect was temporal and blood vessels reappeared after therapy ceased. Chronic administration (8 weeks) of the MMP inhibitor Doxycycline was also effective in attenuation of the acute and delayed injury. Preliminary results, using amniotic membrane transplantation revealed some decrease of corneal edema with no effect on corneal NV. It is suggested that the chronic inflammation and prolonged impairment of corneal innervation are playing a role in the pathogenesis of the delayed LSCD following SM exposure by creating a pathological microenvironment to limbal epithelial stem cells, thus, leading to their slow death and to a second cascade of pathological events eventually resulting in severe long-term injuries. As of today, only topical anti-inflammatory drugs reached the criteria of an applicable efficient post-exposure ocular treatment for SM injuries. Further studies are required to investigate the effects of SM on epithelial stem cells and their involvement in the pathogenesis of the long-term injuries.

Caramiphen and Scopolamine Prevent Soman-Induced Brain Damage and Cognitive Dysfunction

Exposure to soman, a toxic organophosphate nerve agent, causes severe adverse effects and long term changes in the peripheral and central nervous systems. The goal of this study was to evaluate the ability of prophylactic treatments to block the deleterious effects associated with soman poisoning. scopolamine, a classical anticholinergic agent, or caramiphen, an anticonvulsant anticholinergic drug with anti-glutamatergic properties, in conjunction with pyridostigmine, a reversible cholinesterase inhibitor, were administered prior to sbman (1 LD50). Both caramiphen and scopolamine dramatically attenuated the process of cell death as assessed by the binding of [3H]RoS-4864 to peripheral benzodiazepine receptors (omega3 sites) on microglia and astrocytes. In addition, caramiphen but not scopolamine, blocked the soman-evoked down-regulation of [3H]AMPA binding to forebrain membrane preparations. Moreover, cognitive tests utilizing the Morris water maze, examining learning and memory processes as well as reversal learning, demonstrated that caramiphen abolished the effects of soman intoxication on learning as early as the first trial day, while scopolamine exerted its effect commencing at the second day of training. Whereas the former drug completely prevented memory deficits, the latter exhibited partial protection. Both agents equally blocked the impairment of reversal learning. In addition, there is a significant correlation between behavioral parameters and [3H]RoS-4864 binding to forebrain membrane preparations of rats, which participated in these tests (r(21) = 0.66, P < 0.001; r(21) = 0.66, P < 0.001, -0.62, P < 0.002). These results demonstrate the beneficial use of drugs exhibiting both anti-cholinergic and anti-glutamatergic properties for the protection against changes in cognitive parameters caused by nerve agent poisoning. Moreover, agents such as caramiphen may eliminate the need for multiple drug therapy in organophosphate intoxications.

Improvement of cognitive function by MAO-B inhibitor L-deprenyl in aged rats

This study evaluated the ability of the selective MAO-B inhibitor, L-deprenyl, to reverse cognitive impairments appearing in aged rats, using the reference memory, Morris Water Maze paradigm. L-Deprenyl significantly improved learning and memory deficits associated with old age in doses of 1.25 and 5 mg/kg PO (escape latency measure) and doses of 1.25, 2.5 and 5 mg/kg PO (path length measure). L-Deprenyl also improved reversal learning impairments in doses of 1.25, 2.5 and 5 mg/kg PO, as expressed by the escape latency measure. The data suggest that L-deprenyl possesses potential cognitive enhancement abilities probably due to an increase in dopaminergic activity.