Long-term nucleus basalis cholinergic depletion induces attentional deficits and impacts cortical neurons and BDNF levels without affecting the NGF synthesis

Dysregulation of Neurotrophin Expression in Prefrontal Cortex and Nucleus Basalis Magnocellularis During and After Adolescent Intermittent Ethanol Exposure

A preclinical model of human adolescent binge drinking, adolescent intermittent ethanol exposure (AIE) recreates the heavy binge withdrawal consummatory patterns of adolescents and has identified the loss of basal forebrain cholinergic neurons as a pathological hallmark of this model. Cholinergic neurons of the nucleus basalis magnocellularis (NbM) that innervate the prefrontal cortex (PFC) are particularly vulnerable to alcohol related neurodegeneration. Target derived neurotrophins (nerve growth factor [NGF] and brain-derived neurotrophic factor [BDNF]) regulate cholinergic phenotype expression and survival. Evidence from other disease models implicates the role of immature neurotrophin, or proneurotrophins, activity at neurotrophic receptors in promoting cholinergic degeneration; however, it has yet to be explored in adolescent binge drinking. We sought to characterize the pro- and mature neurotrophin expression, alongside their cognate receptors and cholinergic markers in an AIE model. Male and female Sprague Dawley rats underwent 5g/kg 20% EtOH or water gavage on two-day-on, two-day-off cycles from post-natal day 25-57. Rats were sacrificed 2 hours, 24 hours, or 3 weeks following the last gavage, and tissue were collected for protein measurement. Western blot analyses revealed that ethanol intoxication reduced the expression of BDNF and vesicular acetylcholine transporter (vAChT) in the PFC, while NGF was lower in the NbM of AIE treated animals. During acute alcohol withdrawal, proNGF in the PFC was increased while proBDNF decreased, and in the NbM proBDNF increased while NGF decreased. During AIE abstinence, the expression of neurotrophins, their receptors, and vAChT did not differ from controls in the PFC. In contrast, in the NbM the expression of both NGF and choline acetyltransferase (ChAT) were reduced long-term following AIE. Taken together these findings suggest that AIE alters the expression of proneurotrophins and neurotrophins during intoxication and withdrawal that favor prodegenerative mechanisms by increasing the expression of proNGF and proBDNF, while also reducing NGF and BDNF.

BDNF Signaling in Vascular Dementia and Its Effects on Cerebrovascular Dysfunction, Synaptic Plasticity, and Cholinergic System Abnormality

Vascular dementia (VaD) is the second most common type of dementia and is characterized by memory impairment, blood-brain barrier disruption, neuronal cell loss, glia activation, impaired synaptic plasticity, and cholinergic system abnormalities. To effectively prevent and treat VaD a good understanding of the mechanisms underlying its neuropathology is needed. Brain-derived neurotrophic factor (BDNF) is an important neurotrophic factor with multiple functions in the systemic circulation and the central nervous system and is known to regulate neuronal cell survival, synaptic formation, glia activation, and cognitive decline. Recent studies indicate that when compared with normal subjects, patients with VaD have low serum BDNF levels and that BDNF deficiency in the serum and cerebrospinal fluid is an important indicator of VaD. Here, we review current knowledge on the role of BDNF signaling in the pathology of VaD, such as cerebrovascular dysfunction, synaptic dysfunction, and cholinergic system impairment.

Recent advances in cholinergic mechanisms: A preface for the ISCM2022 special issue

This preface introduces the Journal of Neurochemistry special issue on Cholinergic Mechanisms that highlights the progress in the molecular, structural, neurochemical, pharmacological, toxicological, and clinical studies of the cholinergic system which underline its complexity and impact on health and disease. This issue comprises of (systematic) reviews and original articles, the majority of which have been presented at the 17th International Symposium on Cholinergic Mechanisms (ISCM2022) held in Dubrovnik, Croatia in May 2022. The symposium brought together leading "Cholinergikers" to shed new light on cholinergic transmission, ranging from the molecular to the clinical and cognitive mechanisms.

Cholinergic basal forebrain system degeneration underlies postural instability/gait difficulty and attention impairment in Parkinson's disease

BACKGROUND AND PURPOSE

The specific pathophysiological mechanisms underlying postural instability/gait difficulty (PIGD) and cognitive function in Parkinson's disease (PD) remain unclear. Both postural and gait control, as well as cognitive function, are associated with the cholinergic basal forebrain (cBF) system.

METHODS

A total of 84 PD patients and 82 normal controls were enrolled. Each participant underwent motor and cognitive assessments. Diffusion tensor imaging was used to detect structural abnormalities in the cBF system. The cBF was segmented using FreeSurfer, and its fiber tract was traced using probabilistic tractography. To provide information on extracellular water accumulation, free-water fraction (FWf) was quantified. FWf in the cBF and its fiber tract, as well as cortical projection density, were extracted for statistical analyses.

RESULTS

Patients had significantly higher FWf in the cBF (p < 0.001) and fiber tract (p = 0.021) than normal controls, as well as significantly lower cBF projection in the occipital (p < 0.001), parietal (p < 0.001) and prefrontal cortex (p = 0.005). In patients, a higher FWf in the cBF correlated with worse PIGD score (r = 0.306, p = 0.006) and longer Trail Making Test A time (r = 0.303, p = 0.007). Attentional function (Trail Making Test A) partially mediated the association between FWf in the cBF and PIGD score (indirect effect, a*b = 0.071; total effect, c = 0.256; p = 0.006).

CONCLUSIONS

Our findings suggest that degeneration of the cBF system in PD, from the cBF to its fiber tract and cortical projection, plays an important role in cognitive-motor interaction.

Early treatment with an M1 and sigma-1 receptor agonist prevents cognitive decline in a transgenic rat model displaying Alzheimer-like amyloid pathology

The application of the selective allosteric M1 muscarinic and sigma-1 receptor agonist, AF710B (aka ANAVEX3-71), has shown to attenuate Alzheimer's disease-like hallmarks in McGill-R-Thy1-APP transgenic rats when administered at advanced pathological stages. It remains unknown whether preventive treatment strategies applying this compound may be equally effective. We tested whether daily oral administration of AF710B (10 µg/kg) in 7-month-old, preplaque, McGill-R-Thy1-APP rats for 7 months, followed by a 4-week washout period, could prevent Alzheimer's disease-like pathological hallmarks. Long-term AF710B treatment prevented the cognitive impairment of McGill-R-Thy1-APP rats. The effect was accompanied by a reduction in the number of amyloid plaques in the hippocampus and the levels of Aβ42 and Aβ40 peptides in the cerebral cortex. AF710B treatment also reduced microglia and astrocyte recruitment toward CA1 hippocampal Aβ-burdened neurons compared to vehicle-treated McGill-R-Thy1-APP rats, also altering the inflammatory cytokines profile. Lastly, AF710B treatment rescued the conversion of brain-derived neurotrophic factor precursor to its mature and biologically active form. Overall, these results suggest preventive and disease-modifying properties of the compound.

Enhanced neuronal activity by suffruticosol A extracted from Paeonia lactiflora via partly BDNF signaling in scopolamine-induced memory-impaired mice

Neurodegenerative diseases are explained by progressive defects of cognitive function and memory. These defects of cognition and memory dysfunction can be induced by the loss of brain-derived neurotrophic factors (BDNF) signaling. Paeonia lactiflora is a traditionally used medicinal herb in Asian countries and some beneficial effects have been reported, including anti-oxidative, anti-inflammatory, anti-cancer activity, and potential neuroprotective effects recently. In this study, we found that suffruticosol A is a major compound in seeds of Paeonia lactiflora. When treated in a SH-SY5 cell line for measuring cell viability and cell survival, suffruticosol A increased cell viability (at 20 µM) and recovered scopolamine-induced neurodegenerative characteristics in the cells. To further confirm its neural amelioration effects in the animals, suffruticosol A (4 or 15 ng, twice a week) was administered into the third ventricle beside the brain of C57BL/6 mice for one month then the scopolamine was intraperitoneally injected into these mice to induce impairments of cognition and memory before conducting behavioral experiments. Central administration of suffruticosol A into the brain restored the memory and cognition behaviors in mice that received the scopolamine. Consistently, the central treatments of suffruticosol A showed rescued cholinergic deficits and BDNF signaling in the hippocampus of mice. Finally, we measured the long-term potentiation (LTP) in the hippocampal CA3-CA1 synapse to figure out the restoration of the synaptic mechanism of learning and memory. Bath application of suffruticosol A (40 µM) improved LTP impairment induced by scopolamine in hippocampal slices. In conclusion, the central administration of suffruticosol A ameliorated neuronal effects partly through elevated BDNF signaling.