Diabetic neuropathic pain (DNP) is a common and distressing complication in patients with diabetes, and the underlying mechanism remains unclear. Tricyclic antidepressants (TCAs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are recommended as first-line drugs for DNP. Ammoxetine is a novel and potent SNRI that exhibited a strong analgesic effect on models of neuropathic pain, fibromyalgia-related pain, and inflammatory pain in our primary study. The present study was undertaken to investigate the chronic treatment properties of ammoxetine on DNP and the underlying mechanisms for its effects. The rat model of DNP was established by a single streptozocin (STZ) injection (60 mg/kg). Two weeks after STZ injection, the DNP rats were treated with ammoxetine (2.5, 5, and 10 mg/kg/day) for 4 weeks. The mechanical allodynia and locomotor activity were assayed to evaluate the therapeutic effect of ammoxetine. In mechanism study, the activation of microglia, astrocytes, the protein levels of pro-inflammatory cytokines, the mitogen-activated protein kinases (MAPK), and NF-κB were evaluated. Also, microglia culture was used to assess the direct effects of ammoxetine on microglial activation and the signal transduction mechanism. Treatment with ammoxetine for 4 weeks significantly relieved the mechanical allodynia and ameliorated depressive-like behavior in DNP rats. In addition, DNP rats displayed increased activation of microglia in the spinal cord, but not astrocytes. Ammoxetine reduced the microglial activation, accumulation of pro-inflammatory cytokines, and activation of p38 and c-Jun N-terminal kinase (JNK) in the spinal cord of DNP rats. Furthermore, ammoxetine displayed anti-inflammatory effects upon challenge with LPS in BV-2 microglia cells. Our results suggest that ammoxetine may be an effective treatment for relieving DNP symptoms. Moreover, a reduction in microglial activation and pro-inflammatory release by inhibiting the p-p38 and p-JNK pathways is involved in the mechanism.

The impact of host–microbiome interactions on cognitive health and disease has received increasing attention. Microbial-derived metabolites produced in the gut are one of crucial mechanisms of the gut–brain axis interaction, showing attractive perspectives. Urolithins (Uros) are gut microbial-derived metabolites of ellagitannins and ellagic acid, whose biotransformation varies considerably between individuals and decreases greatly with age. Recently, accumulating evidence has suggested that Uros may have specific advantages in preventing brain aging including favorable blood–brain barrier permeability, selective brain distribution, and increasingly supporting data from preclinical and clinical studies. However, the usability of Uros in diagnosis, prevention, and treatment of neurodegenerative diseases remains elusive. In this review, we aim to present the comprehensive achievements of Uros in age-related brain dysfunctions and neurodegenerative diseases and discuss their prospects and knowledge gaps as functional food, drugs, or biomarkers against brain aging.

Background/Objectives: Urolithin A (UA), a gut-derived metabolite of ellagitannins or ellagic acid, has recently gained attention for its potential benefits to brain health. The present research aimed to assess the antidepressant-like properties of UA in both in vitro and in vivo models and explored the molecular mechanisms underlying these effects. Methods: We investigated the antidepressant effects and mechanisms of UA in a model of corticosterone-induced damage to PC12 cells and in a model of chronic socially frustrating stress. Results: Our results demonstrate that UA treatment (5 and 10 μM) significantly alleviated cellular damage and inflammation in corticosterone (CORT)-treated PC12 cells. Furthermore, UA administration (50 and 100 mg/kg) significantly reduced immobility time in the mouse tail suspension test (TST) and forced swim test (FST), indicating its antidepressant-like activity. Additionally, treatment with UA led to the activation of the cAMP response element-binding protein (CREB)/brain-derived neurotrophic factor (BDNF) signaling cascade and triggered the activation of adenosine monophosphate-activated protein kinase (AMPK) during these processes. Importantly, pretreatment with AMPK-specific inhibitor Compound C abolished UA’s cytoprotective effects in PC12 cells, as well as its behavioral efficacy in the FST and TST, and its neurotrophic effects, highlighting the critical role of AMPK activation in mediating these effects. Furthermore, in the chronic social defeat stress (CSDS) mouse model, UA treatment (50 and 100 mg/kg) significantly alleviated depression-like behaviors, including reduced sucrose preference in the sucrose preference test, increased social avoidance behavior in the social interaction test, and anxiety-like behaviors, including diminished exploration, in the elevated plus maze test, suggesting the antidepressant-like and anxiolytic-like activities of UA. Moreover, UA treatment reversed elevated serum stress hormone levels, hippocampal inflammation, and the decreased AMPK/CREB/BDNF signaling pathway in the hippocampus of CSDS mice. Conclusions: Together, these results provide compelling evidence for UA as a viable dietary supplement or therapeutic option for managing depression.

Background/Objectives: Hypericum perforatum L. (H. perforatum), commonly known as St. John’s wort, has been widely used in clinical practice to treat mental disorders. Previous studies and clinical applications have primarily focused on its alcohol-soluble ingredients. Our research was designed to investigate the physicochemical properties, antidepressant-like effects, and anti-post-traumatic stress disorder (PTSD)-like effects of the alcohol-insoluble polysaccharide-rich ingredients from H. perforatum. Meanwhile, the underlying mechanisms were elucidated. Methods: The physicochemical properties of two polysaccharide-rich ingredients, designated as HPP1 and HPP2, were characterized using colorimetric assay, capillary electrophoresis, high-performance gel permeation chromatography, and fourier transform infrared spectroscopy. Behavioral despair tests were conducted to rapidly assess and compare their antidepressant-like effects in mice. Subsequently, behavioral despair mice and foot-shock mice were established to thoroughly explore the impact of HPP2 on depression-like and PTSD-like symptoms. The effects of HPP2 on cerebral pathological changes, neurotrophic factors, and gut microbiota in foot-shock mice were detected through hematoxylin & eosin staining, immunofluorescence staining, and 16S rDNA (V3 + V4 regions) gene sequencing. Results: HPP1 and HPP2 are predominantly composed of arabinose, glucose, galactose, mannose, and galacturonic acid. The molecular weight distribution of HPP1 ranges from 1133 to 67,278 Da, whereas that of HPP2 extends from 1493 to 38,407 Da. Acute pre-treatment with HPP1 or HPP2 (200 mg/kg, i.g.) could reduce mice’s immobility in behavioral despair tests, with HPP2 exhibiting superior efficacy. Additionally, both acute and sub-chronic pre-treatment with HPP2 (50, 200, and 800 mg/kg, i.g.) effectively alleviated depression-like symptoms in behavioral despair mice. Prolonged pre-treatment with HPP2 (200 mg/kg, i.g.) also mitigated the slow increase in body weight and behavioral abnormalities in foot-shock mice. Furthermore, HPP2 (200 mg/kg) successfully restored hippocampal histomorphological abnormalities, neurotrophic disturbance, and dysregulation of the gut microbiota in foot-shock mice. Conclusions: HPP2 exerts noteworthy antidepressant-like and anti-PTSD-like impact in mouse models via multiple targets, indicating a potential therapeutic candidate in depression and PTSD therapy.