ACTH(6-9)-Pro-Gly-Pro ameliorates anxiety-like and depressive-like behaviour and gut mucosal microbiota composition in rats under conditions of chronic restraint stress

Gallic acid ameliorates behavioral dysfunction, oxidative damage, and neuronal loss in the prefrontal cortex and hippocampus in stressed rats

Gallic acid (GA) is known to be a natural phenolic compound with antioxidant and neuroprotective effects. This study aims to investigate the impact of GA against restraint stress-induced oxidative damage, anxiety-like behavior, neuronal loss, and spatial learning and memory impairment in male Wistar rats. The animals were divided into four groups (n = 8) and subjected to restraint stress for 4 h per day for 14 consecutive days or left undisturbed (control without inducing stress). In the treatment group, the animals were treated with 2 mL normal saline plus 100 mg/kg GA per day for 14 consecutive days (STR + GA group). The animals received the drug or normal saline by gavage 2 h before inducing restraint stress. ELISA assay measured oxidative stress factors. Elevated-plus maze and Morris water maze tests assessed anxiety-like behavior and spatial learning and memory, respectively. Also, neuronal density was determined using Nissl staining. Restraint stress significantly increased MDA and reduced the activities of GPX and SOD in the stressed rats, which were reserved by treatment with 100 mg/kg GA. Restraint stress markedly enhanced the anxiety-like behavior and spatial learning and memory impairment that were reserved by GA. In addition, treatment with GA reduced the neuronal loss in the stressed rats in the hippocampus and prefrontal cortex (PFC) regions. Taken together, our findings suggest that GA has the potential to be used as a good candidate to attenuate neurobehavioral disorders as well as neuronal loss in the hippocampus and PFC induced by restraint stress via reducing oxidative damage.

Life Experience Matters: Enrichment and Stress Can Influence the Likelihood of Developing Alzheimer's Disease via Gut Microbiome

Alzheimer's disease (AD) is a chronic neurodegenerative disease, characterized by the presence of β-amyloid (Aβ) plaques and neurofibrillary tangles (NFTs) formed from abnormally phosphorylated tau proteins (ptau). To date, there is no cure for AD. Earlier therapeutic efforts have focused on the clinical stages of AD. Despite paramount efforts and costs, pharmaceutical interventions including antibody therapies targeting Aβ have largely failed. This highlights the need to alternate treatment strategies and a shift of focus to early pre-clinical stages. Approximately 25-40% of AD cases can be attributed to environmental factors including chronic stress. Gut dysbiosis has been associated with stress and the pathogenesis of AD and can increase both Aβ and NFTs in animal models of the disease. Both stress and enrichment have been shown to alter AD progression and gut health. Targeting stress-induced gut dysbiosis through probiotic supplementation could provide a promising intervention to delay disease progression. In this review, we discuss the effects of stress, enrichment, and gut dysbiosis in AD models and the promising evidence from probiotic intervention studies.

Synthetic Adrenocorticotropic Peptides Modulate the Expression Pattern of Immune Genes in Rat Brain following the Early Post-Stroke Period

Ischemic stroke is an acute local decrease in cerebral blood flow due to a thrombus or embolus. Of particular importance is the study of the genetic systems that determine the mechanisms underlying the formation and maintenance of a therapeutic window (a time interval of up to 6 h after a stroke) when effective treatment can be provided. Here, we used a transient middle cerebral artery occlusion (tMCAO) model in rats to study two synthetic derivatives of adrenocorticotropic hormone (ACTH). The first was ACTH(4-7)PGP, which is known as Semax. It is actively used as a neuroprotective drug. The second was the ACTH(6-9)PGP peptide, which is elucidated as a prospective agent only. Using RNA-Seq analysis, we revealed hundreds of ischemia-related differentially expressed genes (DEGs), as well as 131 and 322 DEGs related to the first and second peptide at 4.5 h after tMCAO, respectively, in dorsolateral areas of the frontal cortex of rats. Furthermore, we showed that both Semax and ACTH(6-9)PGP can partially prevent changes in the immune- and neurosignaling-related gene expression profiles disturbed by the action of ischemia at 4.5 h after tMCAO. However, their different actions with regard to predominantly immune-related genes were also revealed. This study gives insight into how the transcriptome depends on the variation in the structure of the related peptides, and it is valuable from the standpoint of the development of measures for early post-stroke therapy.

Effects of ACTH6-9-Pro-Gly-Pro Peptide on the Levels of Pro- and Anti-Inflammatory Cytokines in Wistar Rats under Conditions of Chronic Restraint Stress

We evaluated the effect of ACTH_6-9-Pro-Gly-Pro (ACTH_6-9-PGP) peptide on the serum levels of pro- and anti-inflammatory cytokines in experimental animals under conditions of chronic restraint stress. Stress exposure over 2 weeks led to an increase in the levels of IL-1β, IL-6, and IFNγ in rats. Daily intraperitoneal injection of ACTH_6-9-PGP in a dose of 5 μg/kg before stress exposure significantly decreased the levels of IL-6 and IFNγ by 4.8 and 49.3% respectively. Administration of the peptide in a dose of 50 μg/kg decreased the levels of IL-1β and IFNγ by 51.2 and 39.7%, respectively. However, no changes in the cytokine levels were observed after injection of the peptide in a dose of 500 μg/kg. Thus, ACTH_6-9-PGP administered in doses of 5 and 50 μg/kg prevented the stress-induced changes in the levels of pro- and inflammatory cytokines.

The Melanocortin System: A Promising Target for the Development of New Antidepressant Drugs

Major depression is one of the most prevalent mental disorders, causing significant human suffering and socioeconomic loss. Since conventional antidepressants are not sufficiently effective, there is an urgent need to develop new antidepressant medications. Despite marked advances in the neurobiology of depression, the etiology and pathophysiology of this disease remain poorly understood. Classical and newer hypotheses of depression suggest that an imbalance of brain monoamines, dysregulation of the hypothalamic-pituitary-adrenal axis (HPAA) and immune system, or impaired hippocampal neurogenesis and neurotrophic factors pathways are cause of depression. It is assumed that conventional antidepressants improve these closely related disturbances. The purpose of this review was to discuss the possibility of affecting these disturbances by targeting the melanocortin system, which includes adrenocorticotropic hormone-activated receptors and their peptide ligands (melanocortins). The melanocortin system is involved in the regulation of various processes in the brain and periphery. Melanocortins, including peripherally administered non-corticotropic agonists, regulate HPAA activity, exhibit anti-inflammatory effects, stimulate the levels of neurotrophic factors, and enhance hippocampal neurogenesis and neurotransmission. Therefore, endogenous melanocortins and their analogs are able to complexly affect the functioning of those body’s systems that are closely related to depression and the effects of antidepressants, thereby demonstrating a promising antidepressant potential.

Synthetic corticotropins and the GABA-receptor system: Direct and delayed effects

The central effectors of the stress system are greatly interconnected and include, among others, a large group of peptides derived from proopiomelanocortin. In addition to natural corticotropins, a number of artificial molecules that contain some ACTH fragments in their structure are also referred to members of this family. Some of them possess a wide range of biological activity. The molecular mechanism underlying the biological activity of such peptides is partly based on allosteric modulation of various receptors. We analyzed the ability of some biologically active synthetic corticotropins (ACTH(4-7)PGP, ACTH(6-9)PGP, ACTH(7-10)PGP), and glyproline PGPL to affect the GABA-receptor system of rat brain. The effects of the peptides were studied in the isolated plasma membranes of brain cells, as well as after systemic peptide administration in the rat model of acute restraint stress. The delayed effect of stress or preadministration of each of the studied peptides on [³ H]GABA binding was different for its high- and low-affinity-specific sites. The studied peptides individually affected the binding of [³ H]GABA in their own way. Acute restraint stress caused a decrease in [³ H]GABA binding at its low-affine site and did not affected the high-affine site. Preliminary peptide administration did not influence this effect of stress.

Total saponins of panax ginseng via the CX3CL1/CX3CR1 axis attenuates neuroinflammation and exerted antidepressant-like effects in chronic unpredictable mild stress in rats

Total saponins of Panax ginseng (TSPG) have antidepressant effects. However, the underlying antidepressant mechanism of TSPG remains not clear. This study aimed to predict the mechanism of TSPG by bioinformatics analysis and to verify it experimentally. Bioinformatics analysis showed that the antidepressant effects of TSPG may be related to inflammation, and CX3CL1/CX3CR1 may play a key mediating role. Wistar rats were exposed to chronic unpredictable mild stress (CUMS) for 6 weeks, and TSPG (50 mg/kg/d, 100 mg/kg/d) was administered throughout the modeling period. It was found that TSPG improves depressive behavior and reduces neuropathic damage in the hippocampus in rats. Meanwhile, TSPG decreased mRNA and protein expression of pro-inflammatory cytokines and CX3CL1/CX3CR1 and inhibited P38 and JNK protein phosphorylation in the hippocampus. Rat astrocytes were employed to explore further the potential mechanism of TSPG in regulating CX3CL1/CX3CR1. The results showed that CX3CL1 small interfering RNA (siRNA-CX3CL1) and CX3CR1 inhibitor (JMS-17-2) had similar effects to TSPG, that is, reduced inflammatory response, reactive oxygen species (ROS), and phosphorylation of P38 and JNK proteins, while overexpression of CX3CL1 (pcDNA-CX3CL1) counteracted the above effects of TSPG. It is suggested that the antidepressant effect of TSPG may be achieved through inhibition of CX3CL1/CX3CR1.

Anxiolytic effect of YangshenDingzhi granules: Integrated network pharmacology and hippocampal metabolomics

Anxiety disorder is one of the most common mental diseases. It is mainly characterized by a sudden, recurring but indescribable panic, fear, tension and/or anxiety. Yangshendingzhi granules (YSDZ) are widely used in the treatment of anxiety disorders, but its active ingredients and underlying mechanisms are not yet clear. This study integrates network pharmacology and metabolomics to investigate the potential mechanism of action of YSDZ in a rat model of anxiety. First, potential active ingredients and targets were screened by network pharmacology. Then, predictions were verified by molecular docking, molecular dynamics and western blotting. Metabolomics was used to identify differential metabolites and metabolic pathways. All results were integrated for a comprehensive analysis. Network pharmacology analysis found that Carotene, β-sitosterol, quercetin, Stigmasterol, and kaempferol in YSDZ exert anxiolytic effects mainly by acting on IL1β, GABRA1, PTGS1, ESR1, and TNF targets. Molecular docking results showed that all the affinities were lower than -5 kcal/mol, and the average affinities were -7.7764 kcal/mol. Molecular dynamics simulation results showed that RMSD was lower than 2.5 A, and the overall conformational changes of proteins were small, indicating that the small molecules formed stable complexes with proteins. The results of animal experiments showed that YSDZ exerts anxiolytic effects by regulating GABRA1 and TNF-α, ameliorating pathological damage in hippocampal CA1, and regulating metabolic pathways such as thiamine, cysteine and methionine metabolism, lysine biosynthesis and degradation. Altogether, we reveal multiple mechanisms through which YSDZ exerts its anti-anxiety effects, which may provide a reference for its clinical application and drug development.