Ameliorative effects of a combination of baicalin, jasminoidin and cholic acid on ibotenic acid-induced dementia model in rats

Effects of hippocampal damage on pain perception in a rat model of Alzheimer's disease induced by amyloid-β and ibotenic acid injection into the hippocampus

Patients with Alzheimer's disease (AD) present with a variety of symptoms, including core symptoms as well as behavioral and psychological symptoms. Somatosensory neural systems are generally believed to be relatively unaffected by AD until late in the course of the disease; however, somatosensory perception in patients with AD is not yet well understood. One factor that may complicate the assessment of somatosensory perception in humans centers on individual variations in pathological and psychological backgrounds. It is therefore necessary to evaluate somatosensory perception using animal models with uniform status. In the current study, we focused on the hippocampus, the primary site of AD. We first constructed a rat model of AD model using bilateral hippocampal injections of amyloid-β peptide 1-40 and ibotenic acid; sham rats received saline injections. The Morris water maze test was used to evaluate memory impairment, and the formalin test (1 % or 4 % formalin) and upper lip von Frey test were performed to compare pain perception between AD model and sham rats. Finally, histological and immunohistochemical methods were used to evaluate tissue damage and neuronal activity, respectively, in the hippocampus. AD model rats showed bilateral hippocampal damage and had memory impairment in the Morris water maze test. Furthermore, AD model rats exhibited significantly less pain-related behavior in phase 2 (the last 50 min of the 60-minute observation) of the 4 % formalin test compared with the sham rats. However, no significant changes were observed in the von Frey test. Immunohistochemical observations of the trigeminal spinal subnucleus caudalis after 4 % formalin injection revealed significantly fewer c-Fos-immunoreactive cells in AD model rats than in sham rats, reflecting reduced neuronal activity. These results indicate that AD model rats with hippocampal damage have reduced responsiveness to persistent inflammatory chemical stimuli to the orofacial region.

Scutellaria baicalensis and its constituents baicalin and baicalein as antidotes or protective agents against chemical toxicities: a comprehensive review

Scutellaria baicalensis (SB), also known as the Chinese skullcap, has a long history of being used in Chinese medicine to treat a variety of conditions ranging from microbial infections to metabolic syndrome and malignancies. Numerous studies have reported that treatment with total SB extract or two main flavonoids found in its root and leaves, baicalin (BA) and baicalein (BE), can prevent or alleviate the detrimental toxic effects of exposure to various chemical compounds. It has been shown that BA and BE are generally behind the protective effects of SB against toxicants. This paper aimed to review the protective and therapeutic effects of SB and its main components BA and BE against chemical compounds that can cause intoxication after acute or chronic exposure and seriously affect different vital organs including the brain, heart, liver, and kidneys. In this review paper, we had a look into a total of 221 in vitro and in vivo studies from 1995 to 2021 from the scientific databases PubMed, Scopus, and Web of Science which reported protective or therapeutic effects of BA, BE, or SB against drugs and chemicals that one might be exposed to on a professional or accidental basis and compounds that are primarily used to simulate disease models. In conclusion, the protective effects of SB and its flavonoids can be mainly attributed to increase in antioxidants enzymes, inhibition of lipid peroxidation, reduction of inflammatory cytokines, and suppression of apoptosis pathway.

Helicobacter pylori and Alzheimer's Disease-Related Metabolic Dysfunction: Activation of TLR4/Myd88 Inflammation Pathway from p53 Perspective and a Case Study of Low-Dose Radiation Intervention

Gut dysbiosis is observed in Alzheimer's disease (AD) and is frequently associated with AD-induced metabolic dysfunction. However, the extent and specific underlying molecular mechanisms triggered by alterations of gut microbiota composition and function mediating AD-induced metabolic dysfunction in AD remain incompletely uncovered. Here, we indicate that Helicobacter pylori (H. pylori) is abundant in AD patients with relative metabolic dysfunction. Fecal microbiota transplantation from the AD patients promoted metabolic dysfunction in mice and increased gut permeability. H. pylori increased gut permeability through activation of the TLR4/Myd88 inflammation pathway in a p53-dependent manner, leading to metabolic dysfunction. Moreover, p53 deficiency reduced bile acid concentration, leading to an increased abundance of H. pylori colonization. Overall, these data identify H. pylori as a key promoter of AD-induced metabolic dysfunction.

Distinct Bile Acid Signature in Parkinson's Disease With Mild Cognitive Impairment

BACKGROUNDS

Bile acid (BA) plays a crucial role in various neurodegenerative diseases, including Parkinson's disease (PD). However, no clinical evidence supports BA's potential role in patients with PD with mild cognitive impairment (PD-MCI).

OBJECTIVES

This study aimed at investigating the differential BA profile between patients with PD-MCI and those with normal cognitive function (PD-NC).

METHODS

Ultra-high performance liquid chromatography-MS/MS was applied for BA quantitation. After between-group differences of the BA profile were addressed, orthogonal projections to latent structures-discriminant analysis (OPLS-DA) and the area under the receiver-operating-characteristic curve (AUC-ROC) were implemented for further verification.

RESULTS

Lower levels of chenodeoxycholic acid (CDCA), cholic acid (CA), and ursodeoxycholic acid (UDCA) were significantly associated with PD-MCI (p < 0.01 for both; VIP ≈ 2.67, 1.66, and 1.26, respectively). AUC-ROC were 78.1, 74.2, and 74.5% for CDCA, CA, and UDCA, respectively.

CONCLUSION

CA, CDCA, and UDCA might be distinct BA signatures for patients with PD-MCI.

Cordycepin protects against β-amyloid and ibotenic acid-induced hippocampal CA1 pyramidal neuronal hyperactivity

Cordycepin exerts neuroprotective effects against excitotoxic neuronal death. However, its direct electrophysiological evidence in Alzheimer's disease (AD) remains unclear. This study aimed to explore the electrophysiological mechanisms underlying the protective effect of cordycepin against the excitotoxic neuronal insult in AD using whole-cell patch clamp techniques. β-Amyloid (Aβ) and ibotenic acid (IBO)-induced injury model in cultured hippocampal neurons was used for the purpose. The results revealed that cordycepin significantly delayed Aβ + IBO-induced excessive neuronal membrane depolarization. It increased the onset time/latency, extended the duration, and reduced the slope in both slow and rapid depolarization. Additionally, cordycepin reversed the neuronal hyperactivity in Aβ + IBO-induced evoked action potential (AP) firing, including increase in repetitive firing frequency, shortening of evoked AP latency, decrease in the amplitude of fast afterhyperpolarization, and increase in membrane depolarization. Further, the suppressive effect of cordycepin against Aβ + IBO-induced excessive neuronal membrane depolarization and neuronal hyperactivity was blocked by DPCPX (8-cyclopentyl-1,3-dipropylxanthine, an adenosine A₁ receptor-specific blocker). Collectively, these results revealed the suppressive effect of cordycepin against the Aβ + IBO-induced excitotoxic neuronal insult by attenuating excessive neuronal activity and membrane depolarization, and the mechanism through the activation of A₁R is strongly recommended, thus highlighting the therapeutic potential of cordycepin in AD.

Neuroprotective and Cognitive Enhancement Potentials of Baicalin: A Review

Neurodegenerative diseases are a heterogeneous group of disorders that are characterized by the gradual loss of neurons. The development of effective neuroprotective agents to prevent and control neurodegenerative diseases is specifically important. Recently, there has been an increasing interest in selecting flavonoid compounds as potential neuroprotective agents, owing to their high effectiveness with low side effects. Baicalin is one of the important flavonoid compounds, which is mainly isolated from the root of Scutellaria baicalensis Georgi (an important Chinese medicinal herb). In recent years, a number of studies have shown that baicalin has a potent neuroprotective effect in various in vitro and in vivo models of neuronal injury. In particular, baicalin effectively prevents neurodegenerative diseases through various pharmacological mechanisms, including antioxidative stress, anti-excitotoxicity, anti-apoptotic, anti-inflammatory, stimulating neurogenesis, promoting the expression of neuronal protective factors, etc. This review mainly focuses on the neuroprotective and cognitive enhancement effects of baicalin. The aim of the present review is to compile all information in relation to the neuroprotective and cognitive enhancement effects of baicalin and its molecular mechanisms of action in various in vitro and in vivo experimental models.

Pure mechanistic analysis of additive neuroprotective effects between baicalin and jasminoidin in ischemic stroke mice

Both baicalin (BA) and jasminoidin (JA) are active ingredients in Chinese herb medicine Scutellaria baicalensis and Fructus gardeniae, respectively. They have been shown to exert additive neuroprotective action in ischemic stroke models. In this study we used transcriptome analysis to explore the pure therapeutic mechanisms of BA, JA and their combination (BJ) contributing to phenotype variation and reversal of pathological processes. Mice with middle cerebral artery obstruction were treated with BA, JA, their combination (BJ), or concha margaritifera (CM). Cerebral infarct volume was examined to determine the effect of these compounds on phenotype. Using the hippocampus microarray and ingenuity pathway analysis (IPA) software, we exacted the differentially expressed genes, networks, pathways, and functions in positive-phenotype groups (BA, JA and BJ) by comparing with the negative-phenotype group (CM). In the BA, JA, and BJ groups, a total of 7, 4, and 11 specific target molecules, 1, 1, and 4 networks, 51, 59, and 18 canonical pathways and 70, 53, and 64 biological functions, respectively, were identified. Pure therapeutic mechanisms of BA and JA were mainly overlapped in specific target molecules, functions and pathways, which were related to the nervous system, inflammation and immune response. The specific mechanisms of BA and JA were associated with apoptosis and cancer-related signaling and endocrine and hormone regulation, respectively. In the BJ group, novel target profiles distinct from mono-therapies were revealed, including 11 specific target molecules, 10 functions, and 10 pathways, the majority of which were related to a virus-mediated immune response. The pure additive effects between BA and JA were based on enhanced action in virus-mediated immune response. This pure mechanistic analysis may provide a clearer outline of the target profiles of multi-target compounds and combination therapies.

Toxin-Induced Experimental Models of Learning and Memory Impairment

Animal models for learning and memory have significantly contributed to novel strategies for drug development and hence are an imperative part in the assessment of therapeutics. Learning and memory involve different stages including acquisition, consolidation, and retrieval and each stage can be characterized using specific toxin. Recent studies have postulated the molecular basis of these processes and have also demonstrated many signaling molecules that are involved in several stages of memory. Most insights into learning and memory impairment and to develop a novel compound stems from the investigations performed in experimental models, especially those produced by neurotoxins models. Several toxins have been utilized based on their mechanism of action for learning and memory impairment such as scopolamine, streptozotocin, quinolinic acid, and domoic acid. Further, some toxins like 6-hydroxy dopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and amyloid-β are known to cause specific learning and memory impairment which imitate the disease pathology of Parkinson's disease dementia and Alzheimer's disease dementia. Apart from these toxins, several other toxins come under a miscellaneous category like an environmental pollutant, snake venoms, botulinum, and lipopolysaccharide. This review will focus on the various classes of neurotoxin models for learning and memory impairment with their specific mechanism of action that could assist the process of drug discovery and development for dementia and cognitive disorders.

Effects of bile acids on neurological function and disease

Bile acids are synthesized from cholesterol and are known to be involved with the emulsification and digestion of dietary lipids and fat-soluble vitamins. Outside of this role, bile acids can act as cell signaling effectors through binding and activating receptors on both the cell membrane and nucleus. Numerous reports have investigated these signaling pathways in conditions where the liver is damaged. More recently, effort has been made to investigate the role of bile acids in diseases outside of those associated with liver damage. This review summarizes recent findings on the influences that bile acids can exert in normal neurological function and their contribution to diseases of the nervous system, with the intent of highlighting the role of these metabolites as potential players in neurological disorders.-McMillin, M., DeMorrow, S. Effects of bile acids on neurological function and disease.

Intrahippocampal Administration of Ibotenic Acid Induced Cholinergic Dysfunction via NR2A/NR2B Expression: Implications of Resveratrol against Alzheimer Disease Pathophysiology

Although several drugs revealed moderate amelioration of symptoms, none of them have sufficient potency to prevent or reverse the progression toward Alzheimer's disease (AD) pathology. Resveratrol (RSV), a polyphenolic compound has shown an outstanding therapeutic effect on a broad spectrum of diseases like age-associated neurodegeneration, inflammation etc. The present study was thus conducted to assess the therapeutic efficacy of RSV in ameliorating the deleterious effects of Ibotenic acid (IBO) in male Wistar rats. Stereotactic intrahippocampal administration of IBO (5 μg/μl) lesioned rats impairs cholinergic transmission, learning and memory performance that is rather related to AD and thus chosen as a suitable model to understand the drug efficacy in preventing AD pathophysiology. Since IBO is an agonist of glutamate, it is expected to exhibit an excitotoxic effect by altering glutamatergic receptors like NMDA receptor. The current study displayed significant alterations in the mRNA expression of NR2A and NR2B subunits of NMDA receptors, and further it is surprising to note that cholinergic receptors decreased in expression particularly α7-nAChR with increased m1AChR. RSV administration (20 mg/kg body weight, i.p.) significantly reduced these changes in IBO induced rats. Glutamatergic and cholinergic receptor alterations were associated with significant changes in the behavioral parameters of rats induced by IBO. While RSV improved spatial learning performance, attenuated immobility, and improvised open field activity in IBO induced rats. NR2B activation in the present study might mediate cell death through oxidative stress that form the basis of abnormal behavioral pattern in IBO induced rats. Interestingly, RSV that could efficiently encounter oxidative stress have significantly decreased stress markers viz., nitrite, PCO, and MDA levels by enhancing antioxidant status. Histopathological analysis displayed significant reduction in the hippocampal pyramidal layer thickness and live neurons in IBO induced rats, with slight pathological changes in the entorhinal cortex (EC) of rat brain, which was prevented on RSV administration. Our study thus concludes that RSV administration significantly ameliorated the deleterious effects in the IBO lesioned rat model for AD by alleviating cholinergic pathways, reducing oxidative stress and thereby improving spatial memory.

Experimental models of Alzheimer's disease for deciphering the pathogenesis and therapeutic screening (Review)

Despite decades of laboratory and clinical research, Alzheimer's disease (AD) is still the leading cause of dementia in adults and there are no curative therapies currently available for this disease. This may be due to the pathological features of AD, which include extensive extracellular amyloid plaques and intracellular neurofibrillary tangles, as well as subsequent neuronal and synaptic loss, which begin to appear several years prior to memory loss and the damge is already irreversible and extensive at the time of clinical diagnosis. The poor therapeutic effects of current treatments necessitate the introduction of experimental models able to replicate AD pathology, particularly in the pre-symptomatic stage, and then to explore preventive and therapeutic strategies. In response to this necessity, various experimental models reproducing human AD pathology have been developed, which are also useful tools for therapeutic screening. Although none of these models fully reproduce the key features of human AD, the experimental models do provide important insight into the pathological changes which occur in AD. This review summarizes the commonly used experimental models of AD and also discusses how the models may be used to decipher the pathogenesis underlying AD and to screen novel therapies for this disease.

Neuronal differentiation of human iPS cells induced by baicalin via regulation of bHLH gene expression

Efficient differentiation is important for regenerative medicine based on pluripotent stem cells, including treatment of neurodegenerative disorders and trauma. Baicalin promotes neuronal differentiation of neural stem/progenitor cells of rats and mice. To evaluate the suitability of baicalin for neuronal differentiation of human iPS cells, we investigated whether it promotes neuronal differentiation in human iPS cells and monitored basic helix-loop-helix (bHLH) gene expression during neuronal differentiation. Baicalin promoted neuronal differentiation and inhibited glial differentiation, suggesting that baicalin can influence the neuronal fate decision in human iPS cells. Notch signaling, which is upstream of bHLH proteins, was not involved in baicalin-induced neuronal differentiation. Baicalin treatment did not down-regulate Hes1 gene expression, but it reduced Hes1 protein levels and up-regulated Ascl1 gene expression. Thus, baicalin promoted neuronal differentiation via modulation of bHLH transcriptional factors. Therefore, baicalin has potential to be used as a small-molecule drug for regenerative treatment of neurodegenerative disorders.

Synergistic neuroprotective effect of microglial‑conditioned media treated with geniposide and ginsenoside Rg1 on hypoxia injured neurons

The synergistic mechanism underlying the effects of multi‑component combined drug use for complex diseases remains to be fully elucidated. Microglial activation following ischemia can either affect neural survival or cause neuronal injury. The aim of the present study was to determine the synergistic effect of geniposide and ginsenoside Rg1, based on microglial‑neuronal communication. N2a neuronal cells were divided into the following seven groups: Control group; normal cultured microglial cells in conditioned medium (N‑MG‑CM) group; oxygen‑glucose deprivation (OGD) model group; OGD‑injured MG‑CM (I‑MG‑CM) group; geniposide‑treated MG‑CM (G‑MG‑CM) group; ginsenoside Rg1‑treated MG‑CM (R‑MG‑CM) group; and combination‑treated MG‑CM (C‑MG‑CM) group. A series of assays were used to detect the effects of the different MG‑CM on neurons in terms of: (i) cell viability, determined using a Cell Counting Kit‑8; (ii) lactate dehydrogenase (LDH) leakage rate; (iii) expression of NMDAR1 and activated caspase‑3, detected using western blotting; (iv) mitochondrial transmembrane potential, determined by JC‑1; and (v) mitochondrial ultrastructural features, determined using electron microscopy. The experimental results demonstrated that MG‑CM including the integrated use of geniposide and ginsenoside Rg1 significantly protected neuronal cell viability and inhibited LDH leakage, suppressed the expression of N‑methyl‑D‑aspartate receptor subunit 1 and activated caspase‑3, increased the mitochondrial transmembrane potential and improved the mitochondrial ultrastructure. MG‑CM from separately used geniposide or ginsenoside Rg1 demonstrated differential neuroprotection at different levels. These findings revealed that the synergistic drug combination of geniposide and ginsenoside Rg1 in the treatment of stroke is a feasible approach for use.

Pharmacogenomics of Alzheimer's disease: novel therapeutic strategies for drug development

Alzheimer's disease (AD) is a major problem of health and disability, with a relevant economic impact on our society. Despite important advances in pathogenesis, diagnosis, and treatment, its primary causes still remain elusive, accurate biomarkers are not well characterized, and the available pharmacological treatments are not cost-effective. As a complex disorder, AD is a polygenic and multifactorial clinical entity in which hundreds of defective genes distributed across the human genome may contribute to its pathogenesis. Diverse environmental factors, cerebrovascular dysfunction, and epigenetic phenomena, together with structural and functional genomic dysfunctions, lead to amyloid deposition, neurofibrillary tangle formation, and premature neuronal death, the major neuropathological hallmarks of AD. Future perspectives for the global management of AD predict that genomics and proteomics may help in the search for reliable biomarkers. In practical terms, the therapeutic response to conventional drugs (cholinesterase inhibitors, multifactorial strategies) is genotype-specific. Genomic factors potentially involved in AD pharmacogenomics include at least five categories of gene clusters: (1) genes associated with disease pathogenesis; (2) genes associated with the mechanism of action of drugs; (3) genes associated with drug metabolism (phase I and II reactions); (4) genes associated with drug transporters; and (5) pleiotropic genes involved in multifaceted cascades and metabolic reactions. The implementation of pharmacogenomic strategies will contribute to optimize drug development and therapeutics in AD and related disorders.