Parvalbumin as a sex-specific target in Alzheimer's disease research - A mini-review

Early social deficits in TgF344-AD rats are accompanied by sex-specific parvalbumin-positive interneuron reduction and altered brain oscillations in the hippocampal CA2

Social withdrawal and deficits in social cognition are hallmarks of Alzheimer's disease (AD). While early deficits in social behavior and memory have been documented in mouse AD models, they remain understudied in rat models. Early-stage AD is accompanied by dysfunction of parvalbumin-positive (PV+) interneurons, implicating their potential connection to early symptoms. In this study, we employed a 5-trial social memory task to investigate early deficits in social cognition in 6-month-old TgF344-AD male and female rats. We counted the number of PV+ interneurons and recorded local field potentials during social interactions in the hippocampal CA2 - a region critical for social information processing. Our results show decreased social interest and novelty preference in TgF344-AD male and female rats. However, reduced PV+ interneuron numbers were observed only in female rats and specific to the CA2 area. The electrophysiological recordings revealed reduced theta-gamma phase-amplitude coupling in the CA2 during direct social interactions. We conclude that deficits in social cognition accompany early-stage AD in TgF344-AD rats and are potentially linked to PV+ interneuron and brain oscillatory dysfunction in the CA2 region of the hippocampus.

The effects of amyloidosis and aging on glutamatergic and GABAergic synapses, and interneurons in the barrel cortex and non-neocortical brain regions

Previous studies on changes in the distribution of GABAergic interneurons and excitation/inhibition (E/I) balance in Alzheimer's disease (AD) and aging were mainly conducted in the neocortex and hippocampus. However, the limbic system is the primary and crucial location for AD progression. Therefore, in this study, we utilized AD and aging mouse models to investigate the E/I balance and the distribution of parvalbumin (PV)- and somatostatin (SST)-expressing cells in S1BF (barrel field of primary somatosensory cortex, barrel cortex), CA1 hippocampal area and brain regions beyond the neocortex and hippocampus, including retrosplenial cortex (RSC, which is composed of RSG and RSA), piriform cortex (Pir), amygdala (BMA), and hypothalamus (DM). We discovered that amyloidosis may disrupt the alignment of excitatory pre- and postsynaptic quantities. Amyloidosis reduces the quantity of synapses and SST cells, but does not impact the counts of PV cells. By contrast, aging is linked to a decline in synapses, I/E ratios, SST and PV cells. Amyloidosis affects the S1BF and BMA, while aging may harm all studied regions, including the S1BF, RSC, hippocampus, Pir, BMA, and DM. Aging mostly affects synapses and I/E ratios in Pir, BMA, and DM, and PV and SST interneurons in the hippocampus.

Dissociation-related behaviors in mice emerge from the inhibition of retrosplenial cortex parvalbumin interneurons

Dissociation, characterized by altered consciousness and perception, underlies multiple mental disorders, but the specific neuronal subtypes involved remain elusive. In mice, we find that dissociation-inducing doses of ketamine significantly inhibit retrosplenial cortex (RSC) parvalbumin interneurons (PV-INs), enhancing delta oscillations (1-3 Hz) and delta-gamma phase-amplitude coupling (δ-γ PAC) and inducing dissociation-like behaviors. Optogenetic inhibition of RSC PV-INs triggers delta oscillations, δ-γ PAC, and some dissociation-like behaviors without ketamine. Furthermore, activation of RSC PV-INs or knockdown of the N-methyl-D-aspartate receptor subunit NR1 and the hyperpolarization-activated cyclic nucleotide-gated channel 1 (HCN1) in RSC PV-INs attenuates ketamine-induced delta oscillations, δ-γ PAC, and certain dissociation-like behaviors. These findings reveal that PV-INs regulate delta oscillations and δ-γ PAC and identify NR1 and HCN1 as ketamine targets in PV-INs that may cooperatively affect dissociation, possibly providing potential therapeutic targets for dissociative symptoms.

Native-state proteomics of Parvalbumin interneurons identifies unique molecular signatures and vulnerabilities to early Alzheimer's pathology

Dysfunction in fast-spiking parvalbumin interneurons (PV-INs) may represent an early pathophysiological perturbation in Alzheimer's Disease (AD). Defining early proteomic alterations in PV-INs can provide key biological and translationally-relevant insights. We used cell-type-specific in-vivo biotinylation of proteins (CIBOP) coupled with mass spectrometry to obtain native-state PV-IN proteomes. PV-IN proteomic signatures include high metabolic and translational activity, with over-representation of AD-risk and cognitive resilience-related proteins. In bulk proteomes, PV-IN proteins were associated with cognitive decline in humans, and with progressive neuropathology in humans and the 5xFAD mouse model of Aβ pathology. PV-IN CIBOP in early stages of Aβ pathology revealed signatures of increased mitochondria and metabolism, synaptic and cytoskeletal disruption and decreased mTOR signaling, not apparent in whole-brain proteomes. Furthermore, we demonstrated pre-synaptic defects in PV-to-excitatory neurotransmission, validating our proteomic findings. Overall, in this study we present native-state proteomes of PV-INs, revealing molecular insights into their unique roles in cognitive resiliency and AD pathogenesis.

The Radioprotective Effect of LBP on Neurogenesis and Cognition after Acute Radiation Exposure

BACKGROUND

Radiation exposure has been linked to the development of brain damage and cognitive impairment, but the protective effect and mechanism of Lycium barbarum pills (LBP) on radiation-induced neurological damage remains to be clarified.

METHODS

Behavioral tests and immunohistochemical studies were conducted to evaluate the protective effects of LBP extract (10 g/kg orally daily for 4 weeks) against radiation-induced damage on neurogenesis and cognitive function in Balb/c mice exposed to 5.5 Gy X-ray acute radiation.

RESULTS

The results showed that the LBP extract significantly improved body weight loss, locomotor activity and spatial learning and memory. Immunohistochemical tests revealed that the LBP extract prevented the loss of proliferating cells, newly generated neurons and interneurons, especially in the subgranular area of the dentate gyrus.

CONCLUSION

The findings suggest that LBP is a potential neuroprotective drug for mitigating radiation-induced neuropsychological disorders.