Roflumilast, a Phosphodiesterase-4 Inhibitor, Ameliorates Sleep Deprivation-Induced Cognitive Dysfunction in C57BL/6J Mice

Persistent neuroinflammation and functional deficits in a murine model of decompression sickness

We hypothesized that early intra-central nervous system (CNS) responses in a murine model of decompression sickness (DCS) would be reflected by changes in the microparticles (MPs) that exit the brain via the glymphatic system, and due to systemic responses the MPs would cause inflammatory changes lasting for many days leading to functional neurological deficits. Elevations on the order of threefold of blood-borne inflammatory MPs, neutrophil activation, glymphatic flow, and neuroinflammation in cerebral cortex and hippocampus were found in mice at 12 days after exposure to 760 kPa of air for 2 h. Mice also exhibited a significant decline in memory and locomotor activity, as assessed by novel object recognition and rotarod testing. Similar inflammatory changes in blood, neuroinflammation, and functional impairments were initiated in naïve mice by injection of filamentous (F-) actin-positive MPs, but not F-actin-negative MPs, obtained from decompressed mice. We conclude that high pressure/decompression stress establishes a systemic inflammatory process that results in prolonged neuroinflammation and functional impairments in the mouse decompression model.NEW & NOTEWORTHY Elevated glymphatic flow due to astrocyte and microglial activation from high-pressure exposure triggers release of microparticles (MPs) to the circulation where neutrophil activation and production of filamentous (F)-actin expressing MPs result in a persistent feed-forward neuroinflammatory cycle and functional deficits lasting for at least 12 days.

Development of White Cabbage, Coffee, and Red Onion Extracts as Natural Phosphodiesterase-4B (PDE4B) Inhibitors for Cognitive Dysfunction: In Vitro and In Silico Studies

Human cognition fundamentally depends on memory. Alzheimer's disease exhibits a strong correlation with a decline in this factor. Phosphodiesterase-4 B (PDE4B) plays a crucial role in neurodegenerative disorders, and its inhibition is one of the promising approaches for memory enhancement. This study aimed to identify secondary metabolites in white cabbage, coffee, and red onion extracts and identify their molecular interaction with PDE4B by in silico and in vitro experiments. Crushed white cabbage and red onion were macerated separately with ethanol to yield respective extracts, and ground coffee was boiled with water to produce aqueous extract. Thin layer chromatography (TLC)-densitometry was used to examine the phytochemicals present in white cabbage, coffee, and red onion extracts. Molecular docking studies were performed to know the interaction of test compounds with PDE4B. TLC-densitometry analysis showed that chlorogenic acid and quercetin were detected as major compounds in coffee and red onion extracts, respectively. In silico studies revealed that alpha-tocopherol (binding free energy (∆Gbind) = -38.00 kcal/mol) has the strongest interaction with PDE4B whereas chlorogenic acid (∆Gbind = -21.50 kcal/mol) and quercetin (∆Gbind = -17.25 kcal/mol) exhibited moderate interaction. In vitro assay showed that the combination extracts (cabbage, coffee, and red onion) had a stronger activity (half-maximal inhibitory concentration (IC50) = 0.12 ± 0.03 µM) than combination standards (sinigrin, chlorogenic acid, and quercetin) (IC50 = 0.17 ± 0.03 µM) and rolipram (IC50 = 0.15 ± 0.008 µM). Thus, the combination extracts are a promising cognitive enhancer by blocking PDE4B activity.

PI3K/AKT signaling activation by roflumilast ameliorates rotenone-induced Parkinson's disease in rats

Parkinson's disease (PD) is the second most common progressive age-related neurodegenerative disorder. Paramount evidence shed light on the role of PI3K/AKT signaling activation in the treatment of neurodegenerative disorders. PI3K/AKT signaling can be activated via cAMP-dependent pathways achieved by phosphodiesterase 4 (PDE4) inhibition. Roflumilast is a well-known PDE4 inhibitor that is currently used in the treatment of chronic obstructive pulmonary disease. Furthermore, roflumilast has been proposed as a favorable candidate for the treatment of neurological disorders. The current study aimed to unravel the neuroprotective role of roflumilast in the rotenone model of PD in rats. Ninety male rats were allocated into six groups as follows: control, rotenone (1.5 mg/kg/48 h, s.c.), L-dopa (22.5 mg/kg, p.o), and roflumilast (0.2, 0.4 or 0.8 mg/kg, p.o). All treatments were administrated for 21 days 1 h after rotenone injection. Rats treated with roflumilast showed an improvement in motor activity and coordination as well as preservation of dopaminergic neurons in the striatum. Moreover, roflumilast increased cAMP level and activated the PI3K/AKT axis via stimulation of CREB/BDNF/TrkB and SIRT1/PTP1B/IGF1 signaling cascades. Roflumilast also caused an upsurge in mTOR and Nrf2, halted GSK-3β and NF-ĸB, and suppressed FoxO1 and caspase-3. Our study revealed that roflumilast exerted neuroprotective effects in rotenone-induced neurotoxicity in rats. These neuroprotective effects were mediated via the crosstalk between CREB/BDNF/TrkB and SIRT1/PTP1B/IGF1 signaling pathways which activates PI3K/AKT trajectory. Therefore, PDE4 inhibition is likely to offer a reliable persuasive avenue in curing PD via PI3K/AKT signaling activation.

Resveratrol prevents cognitive deficits induced by sleep deprivation via modulating sirtuin 1 associated pathways in the hippocampus

Accumulating evidence confirms that sleep insufficiency is a high risk factor for cognitive impairment, which involves inflammation and synaptic dysfunction. Resveratrol, an agonist of the Sirt1, has demonstrated anti-inflammation and neuroprotective effects in models of Alzheimer's disease, Parkinson's disease, and schizophrenia. However, the beneficial effects of resveratrol on sleep deprivation-induced cognitive deficits and its underlying molecular mechanisms are unclear. In the present study, thirty-two male C57BL/6 J mice were randomly divided into a Control+DMSO group, Control+Resveratrol group, SD+DMSO group, and SD+Resveratrol group. The mice in the SD+Resveratrol group underwent 5 days of sleep deprivation after pretreatment with resveratrol (50 mg/kg) for 2 weeks, while the mice in the SD+DMSO group only underwent sleep deprivation. After sleep deprivation, we evaluated spatial learning and memory function using the Morris water maze test. We used general molecular biology techniques to detect changes in levels of pro-inflammatory cytokines and Sirt1/miR-134 pathway-related synaptic plasticity proteins. We found that resveratrol significantly reversed sleep deprivation-induced learning and memory impairment, elevated interleukin-1β, interleukin-6, and tumor necrosis factor-α levels, and decreased brain-derived neurotrophic factor, tyrosine kinase receptor B, postsynaptic density protein-95, and synaptophysin levels by activating the Sirt1/miR-134 pathway. In conclusion, resveratrol is a promising agent for preventing sleep deprivation-induced cognitive dysfunction by reducing pro-inflammatory cytokines and improving synaptic function via the Sirt1/miR-134 pathway.

Caffeine-induced protein kinase A activation restores cognitive deficits induced by sleep deprivation by regulating O-GlcNAc cycling in adult zebrafish

Sleep deprivation (SD) is widely acknowledged as a significant risk factor for cognitive impairment. In this study, intraperitoneal caffeine administration significantly ameliorated the learning and memory (L/M) deficits induced by SD and reduced aggressive behaviors in adult zebrafish. SD led to a reduction in protein kinase A (PKA) phosphorylation, phosphorylated-cAMP response element-binding protein (p-CREB), and c-Fos expression in zebrafish brain. Notably, these alterations were effectively reversed by caffeine. In addition, caffeine mitigated neuroinflammation induced by SD, as evident from suppression of the SD-mediated increase in glial fibrillary acidic protein (GFAP) and nuclear factor-κB (NF-κB) activation. Caffeine restored normal O-GlcNAcylation and O-GlcNAc transferase (OGT) levels while reversing the increased expression of O-GlcNAcase (OGA) in zebrafish brain after SD. Intriguingly, rolipram, a selective phosphodiesterase 4 (PDE4) inhibitor, effectively mitigated cognitive deficits, restored p-CREB and c-Fos levels, and attenuated the increase in GFAP in brain induced by SD. In addition, rolipram reversed the decrease in O-GlcNAcylation and OGT expression as well as elevation of OGA expression following SD. Treatment with H89, a PKA inhibitor, significantly impaired the L/M functions of zebrafish compared with the control group, inducing a decrease in O-GlcNAcylation and OGT expression and, conversely, an increase in OGA expression. The H89-induced changes in O-GlcNAc cycling and L/M dysfunction were effectively reversed by glucosamine treatment. H89 suppressed, whereas caffeine and rolipram promoted O-GlcNAc cycling in Neuro2a cells. Our collective findings underscore the interplay between PKA signaling and O-GlcNAc cycling in the regulation of cognitive function in the brain, offering potential therapeutic targets for cognitive deficits associated with SD.NEW & NOTEWORTHY Our observation highlights the intricate interplay between cAMP/PKA signaling and O-GlcNAc cycling, unveiling a novel mechanism that potentially governs the regulation of learning and memory functions. The dynamic interplay between these two pathways provides a novel and nuanced perspective on the molecular foundation of learning and memory regulation. These insights open avenues for the development of targeted interventions to treat conditions that impact cognitive function, including SD.

Treatment with the selective PDE4B inhibitor A-33 or PDE4D inhibitor zatolmilast prevents sleep deprivation-induced deficits in spatial pattern separation

Sleep deprivation (SD) disrupts hippocampus-dependent memory, particularly in the dentate gyrus (DG) region, an area crucial for pattern separation. Previous research showed that non-selective phosphodiesterase type 4 (PDE4) inhibitors like roflumilast can alleviate these deficits. However, it remains unclear whether these outcomes are specific to a particular subfamily of PDE4. Hence, this study examined the specific impact of PDE4B inhibitor (A-33) and PDE4D inhibitor (zatolmilast) on spatial pattern separation in sleep deprived mice. Results demonstrated that SD impairs pattern separation, but both zatolmilast and A-33 alleviate these effects. However, A-33 impaired pattern separation in non-sleep deprived animals. The cognitive benefits of these inhibitors after SD may arise from alterations in relevant signaling pathways in the DG. This study provides initial evidence that inhibiting PDE4B or PDE4D holds promise for mitigating memory deficits due to SD.