Anti-inflammatory Effect of Acetylpuerarin on Eicosanoid Signaling Pathway in Primary Rat Astrocytes

From Gut Microbiomes to Infectious Pathogens: Neurological Disease Game Changers

Gut microbiota and infectious diseases affect neurological disorders, brain development, and function. Compounds generated in the gastrointestinal system by gut microbiota and infectious pathogens may mediate gut-brain interactions, which may circulate throughout the body and spread to numerous organs, including the brain. Studies shown that gut bacteria and disease-causing organisms may pass molecular signals to the brain, affecting neurological function, neurodevelopment, and neurodegenerative diseases. This article discusses microorganism-producing metabolites with neuromodulator activity, signaling routes from microbial flora to the brain, and the potential direct effects of gut bacteria and infectious pathogens on brain cells. The review also considered the neurological aspects of infectious diseases. The infectious diseases affecting neurological functions and the disease modifications have been discussed thoroughly. Recent discoveries and unique insights in this perspective need further validation. Research on the complex molecular interactions between gut bacteria, infectious pathogens, and the CNS provides valuable insights into the pathogenesis of neurodegenerative, behavioral, and psychiatric illnesses. This study may provide insights into advanced drug discovery processes for neurological disorders by considering the influence of microbial communities inside the human body.

Investigating the Potential Therapeutic Mechanisms of Puerarin in Neurological Diseases

Plants and their derived phytochemicals have a long history of treating a wide range of illnesses for several decades. They are believed to be the origin of a diverse array of medicinal compounds. One of the compounds found in kudzu root is puerarin, a isoflavone glycoside commonly used as an alternative medicine to treat various diseases. From a biological perspective, puerarin can be described as a white needle crystal with the chemical name of 7-hydroxy-3-(4-hydroxyphenyl)-1-benzopyran-4-one-8-D-glucopyranoside. Besides, puerarin is sparingly soluble in water and produces no color or light yellow solution. Multiple experimental and clinical studies have confirmed the significant therapeutic effects of puerarin. These effects span a wide range of pharmacological effects, including neuroprotection, hepatoprotection, cardioprotection, immunomodulation, anticancer properties, anti-diabetic properties, anti-osteoporosis properties, and more. Puerarin achieves these effects by interacting with various cellular and molecular pathways, such as MAPK, AMPK, NF-κB, mTOR, β-catenin, and PKB/Akt, as well as different receptors, enzymes, and growth factors. The current review highlights the molecular mechanism of puerarin as a neuroprotective agent in the treatment of various neurodegenerative and neurological diseases. Extensive cellular, animal, and clinical research has provided valuable insights into its effectiveness in conditions such as Alzheimer's disease, Parkinson's disease, epilepsy, cerebral stroke, depression, and more.

Neuroprotective Mechanisms of Puerarin in Central Nervous System Diseases: Update

Due to global population aging and modern lifestyle changes, the incidence of central nervous system (CNS) disorders, such as neurodegenerative diseases, neuropsychiatric disorders, and cerebrovascular diseases, is increasing and has become a major public health challenge. Current medications commonly used in the clinic are far from satisfactory and may cause serious side effects. Therefore, the identification of novel drugs for the effective management of CNS diseases is very urgent. Puerarin, a highly bioactive ingredient isolated from Pueraria lobata, is known to possess a broad spectrum of pharmacological properties including anti-diabetic, anti-inflammatory, anti-antioxidant, neuroprotective, and cardioprotective features. However, its clinical application is limited due to its poor water solubility. Since puerarin has demonstrated a wide range of neuroprotective functions in various CNS diseases, such as Alzheimer’s disease, Parkinson’s disease, cerebral ischemia, depression, and spinal cord injury, it has been attracting increasingly intense attention worldwide. In this review, we intend to extensively summarize the research progress on neuroprotective mechanisms of puerarin in recent years and discuss the future directions of its application in CNS disease treatment.

Comparison of PPAR Ligands as Modulators of Resolution of Inflammation, via Their Influence on Cytokines and Oxylipins Release in Astrocytes

Neuroinflammation is a key process of many neurodegenerative diseases and other brain disturbances, and astrocytes play an essential role in neuroinflammation. Therefore, the regulation of astrocyte responses for inflammatory stimuli, using small molecules, is a potential therapeutic strategy. We investigated the potency of peroxisome proliferator-activated receptor (PPAR) ligands to modulate the stimulating effect of lipopolysaccharide (LPS) in the primary rat astrocytes on (1) polyunsaturated fatty acid (PUFAs) derivative (oxylipins) synthesis; (2) cytokines TNFα and interleukin-10 (IL-10) release; (3) p38, JNK, ERK mitogen-activated protein kinase (MAPKs) phosphorylation. Astrocytes were exposed to LPS alone or in combination with the PPAR ligands: PPARα (fenofibrate, GW6471); PPARβ (GW501516, GSK0660); PPARγ (rosiglitazone, GW9662). We detected 28 oxylipins with mass spectrometry (UPLC-MS/MS), classified according to their metabolic pathways: cyclooxygenase (COX), cytochrome P450 monooxygenases (CYP), lipoxygenase (LOX) and PUFAs: arachidonic (AA), docosahexaenoic (DHA), eicosapentaenoic (EPA). All tested PPAR ligands decrease COX-derived oxylipins; both PPARβ ligands possessed the strongest effect. The PPARβ agonist, GW501516 is a strong inducer of pro-resolution substances, derivatives of DHA: 4-HDoHE, 11-HDoHE, 17-HDoHE. All tested PPAR ligands decreased the release of the proinflammatory cytokine, TNFα. The PPARβ agonist GW501516 and the PPARγ agonist, rosiglitazone induced the IL-10 release of the anti-inflammatory cytokine, IL-10; the cytokine index, (IL-10/TNFα) was more for GW501516. The PPARβ ligands, GW501516 and GSK0660, are also the strongest inhibitors of LPS-induced phosphorylation of p38, JNK, ERK MAPKs. Overall, our data revealed that the PPARβ ligands are a potential pro-resolution and anti-inflammatory drug for targeting glia-mediated neuroinflammation.

Puerarin Inhibits Endothelium-Dependent Contractions in Mouse Carotid Arteries

Background

Many bioactive ingredients of medicinal plants are known to produce vaso-protective benefits. Puerarin is one of the major isoflavone glucosides found in the root of kudzu vine and it exerts an anti-inflammatory effect and many other pharmacological actions. However, the mechanism underlying the vascular effect of puerarin is incompletely understood. Therefore, the present study aims to examine how puerarin reduces endothelium-dependent contractions (EDCs) in mouse arteries.

Material/Methods

EDCs were evoked by acetylcholine (ACh) in isolated mouse carotid arteries with intact endothelium pretreated with Nω-NO2-L-Arg-OMe (L-NAME). The arteries were pretreated with puerarin and other pharmacological inhibitors before the addition of cumulative concentrations of ACh. The concentration of several prostaglandins (PGs) was measured by high performance liquid chromatography-coupled spectrometry (HPLC-MS).

Results

EDCs induced by ACh only presented in endothelium-intact arteries pretreated by L-NAME and EDCs were prevented by the treatment with cyclooxygenase (COX) inhibitor indomethacin (3 μmol/L) or thromboxane prostanoid receptor (TP receptor) antagonist S18886 (30 nmol/L). Acute 40-minute treatment with puerarin reduced EDCs in a concentration-dependent manner without affecting U46619-induced contraction. However, treatment with puerarin did not inhibit ACh-induced production of prostaglandins (PGs) in endothelium-intact arteries.

Conclusions

The present results show that puerarin is able to suppress EDCs in mouse carotid arteries, independent of inhibition of TP receptor or COX2-derived PGs.

Fumaric Acids Do Not Directly Influence Gene Expression of Neuroprotective Factors in Highly Purified Rodent Astrocytes

(1) Background: Dimethylfumarate (DMF) has been approved for the treatment of relapsing remitting multiple sclerosis. However, the mode of action of DMF and its assumed active primary metabolite monomethylfumarate (MMF) is still not fully understood. Former reports suggest a neuroprotective effect of DMF mediated via astrocytes by reducing pro-inflammatory activation of these glial cells. We investigated potential direct effects of DMF and MMF on neuroprotective factors like neurotrophic factors and growth factors in astrocytes to elucidate further possible mechanisms of the mode of action of fumaric acids; (2) Methods: highly purified cultures of primary rat astrocytes were pre-treated in vitro with DMF or MMF and incubated with lipopolysaccharides (LPS) or a mixture of interferon gamma (IFN-γ) plus interleukin 1 beta (IL-1β) in order to simulate an inflammatory environment. The gene expression of neuroprotective factors such as neurotrophic factors (nuclear factor E2-related factor 2 (NGF), brain-derived neurotrophic factor (BDNF), glial cell-derived neurotrophic factor (GDNF)) and growth factors (fibroblast growth factor 2 (FGF2), platelet-derived growth factor subunit A (PDGFa), ciliary neurotrophic factor (CNTF)) as well as cytokines (tumor necrosis factor alpha (TNFα), interleukin 6 (IL-6), IL-1β, inducible nitric oxide synthase (iNOS)) was examined by determining the transcription level with real-time quantitative polymerase chain reaction (qPCR); (3) Results: The stimulation of highly purified astrocytes with either LPS or cytokines changed the expression profile of growth factors and pro- inflammatory factors. However, the expression was not altered by either DMF nor MMF in unstimulated or stimulated astrocytes; (4) Conclusions: There was no direct influence of fumaric acids on neuroprotective factors in highly purified primary rat astrocytes. This suggests that the proposed potential neuroprotective effect of fumaric acid is not mediated by direct stimulation of neurotrophic factors in astrocytes but is rather mediated by other pathways or indirect mechanisms via other glial cells like microglia as previously demonstrated.

Acetylpuerarin inhibits oxygen-glucose deprivation-induced neuroinflammation of rat primary astrocytes via the suppression of HIF-1 signaling

In the central nervous system (CNS), ischemic injury induced by inflammation associated with astrocytes serves an important role in physiological and pathological processes. Neuroinflammation leads to the release of pro-inflammatory cytokines, including tumor necrosis factor-α and interleukin-1β. The aim of the present study was to investigate whether acetylpuerarin attenuates oxygen-glucose deprivation (OGD)-induced astrocyte inflammation and secretion of pro-inflammatory cytokines via inhibiting hypoxia-inducible factor-1 (HIF-1) activation and suppressing downstream primary astrocyte signaling in rats. The results demonstrated that acetylpuerarin attenuates astrocyte viability and induces morphological changes following OGD stress. Furthermore, acetylpuerarin suppresses the stimulation of HIF-1α and nuclear factor (NF)-κB signaling pathways, while attenuating the expression and secretion of pro-inflammatory cytokines via HIF-1 suppression in OGD-induced astrocytes. These findings indicate that acetylpuerarin may attenuate OGD-induced astrocyte damage and inflammation in rat primary astrocytes via suppressing HIF-1 activation and NF-κB signaling. These results suggest that acetylpuerarin regulates inflammation associated with astrocytes and may represent a novel therapeutic agent for the treatment of neuroinflammation in the CNS.

Preventive effect of genetic knockdown and pharmacological blockade of CysLT1R on lipopolysaccharide (LPS)-induced memory deficit and neurotoxicity in vivo

Previously we reported that cysteinyl leukotrienes (Cys-LTs) and the type 1 receptor for Cys-LTs (CysLT₁R) are related to amyloid β (Aβ)-induced neurotoxicity. The aim of the current study was to find out the role of CysLT₁R on lipopolysaccharide (LPS)-induced cognitive deficit and neurotoxicity. shRNA-mediated knockdown or pharmacological blockade (by pranlukast) of CysLT₁R were performed in ICR mice for 21days prior to systemic infusion of LPS. From day 22, LPS was administered for 7days and then a set of behavioral, histopathological and biochemical tests were employed to test memory, neuroinflammation and apoptotic responses in the mouse hippocampus. LPS (only)-treated mice showed poor performance in both Morris water maze (MWM) and Y-maze tests. However, shRNA-mediated knockdown or pranlukast-treated blockade of CysLT₁R improved performance of the mice in these tests. To find out the possible underlying mechanisms, we assessed several parameters such as microglial activation (by immunohistochemistry), level of CysLT₁R (by WB and qRT-PCR) and the inflammatory/apoptotic pathways (by ELISA or TUNEL or WB) in the mouse hippocampus. LPS-induced memory impairment was accompanied by activation of microglia, higher level of CysLT₁R, IL-1β, TNF-α and nuclear NF-κB p65. LPS also caused apoptosis in the hippocampus as detected by TUNEL staining, further supplemented by detection of increased Caspase-3 and a reduced Bcl-2/Bax ratio. All of these adverse changes in the mouse hippocampus were inhibited by pretreatment with CysLT₁R-shRNA and pranlukast. Through this study we suggest that CysLT₁R shares a strong correlation with LPS-associated memory deficit, neuroinflammation and apoptosis and CysLT₁R could be a novel target for preventive measures to intervene the progression of Alzheimer's disease (AD)-like phenotypes.

Celastrol modulates inflammation through inhibition of the catalytic activity of mediators of arachidonic acid pathway: Secretory phospholipase A2 group IIA, 5-lipoxygenase and cyclooxygenase-2

Elevated production of arachidonic acid (AA)-derived pro-inflammatory eicosanoids due to the concerted action of secretory phospholipase A₂ group IIA (sPLA₂IIA), 5-lipoxygenase (5-LOX) and cyclooxygenase-2 (COX-2) is a common feature of many inflammatory disorders. Hence, modulation of the bioactivity of these 3 enzymes is an important strategy to control inflammation. However, the failure of drugs specific for an individual enzyme (sPLA₂IIA-, 5-LOX- or COX-2) and the success of 5-LOX/COX-2 dual inhibitors in effectively controlling inflammation in clinical trials prompted us to evaluate a common inhibitor for sPLA₂IIA, 5-LOX and COX-2 enzymes. Celastrol, a quinone methide triterpene, was selected in this regard through molecular docking studies. We provide the first evidence for celastrol's ability to inhibit the catalytic activity of sPLA₂IIA, 5-LOX and COX-2 enzymes. Celastrol significantly inhibited the catalytic activity of sPLA₂IIA (IC₅₀=6μM) in vitro, which is independent of substrate and calcium concentration. In addition, celastrol inhibited the catalytic activities of 5-LOX (IC₅₀=5μM) and COX-2 (IC₅₀=20μM) in vitro; sPLA₂IIA-induced edema and carrageenan-induced edema in mice; and lipopolysaccharide-stimulated production of PGE₂ in human neutrophils. Thus, celastrol modulates inflammatory responses by targeting multiple enzymes of AA pathway.

Enhanced oral bioavailability of acetylpuerarin by poly(lactide-co-glycolide) nanoparticles optimized using uniform design combined with response surface methodology

Acetylpuerarin (AP), an acetylated derivative of puerarin, shows brain-protective effects in animals. However, AP has low oral bioavailability because of its poor water solubility. The objective of this study was to design and develop poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) to enhance the oral bioavailability of AP. The NPs were prepared using a solvent diffusion method optimized via uniform design (UD) combined with response surface methodology (RSM) and characterized by their morphology, particle size, zeta (ζ)-potential, encapsulation efficiency (EE), drug loading (DL), and in vitro drug release. A pharmacokinetic study was conducted in Wistar rats administered a single oral dose of 30 mg/kg AP. The optimized NPs were spherical and uniform in shape, with an average particle size of 145.0 nm, a polydispersity index (PI) of 0.153, and a ζ-potential of −14.81 mV. The release of AP from the PLGA NPs showed an initial burst release followed by a sustained release, following Higuchi’s model. The EE and DL determined in the experiments were 90.51% and 17.07%, respectively. The area under the plasma concentration-time curve (AUC_0−∞) of AP-PLGA-NPs was 6,175.66±350.31 h ng/mL, which was 2.75 times greater than that obtained from an AP suspension. This study showed that PLGA NPs can significantly enhance the oral bioavailability of AP.

Polysorbate 80-coated PLGA nanoparticles improve the permeability of acetylpuerarin and enhance its brain-protective effects in rats

Objectives

Acetylpuerarin (AP) is an acetylated derivative of puerarin (PUE). The study aimed to prepare polysorbate 80-coated poly(lactic-co-glycolic acid) (PLGA) nanoparticles to improve the permeability of AP across the blood–brain barrier (BBB) and enhance its brain-protective effects.

Methods

AP-loaded PLGA nanoparticles (AP-PLGA-NPs) were prepared using a solvent diffusion methodology. The NPs were characterized. The pharmacokinetics, tissue distributions and brain-protective effects of AP-PLGA-NPs were evaluated in animals.

Key findings

AP-PLGA-NPs were successfully prepared with a mean particle size of 145.0 nm and a zeta potential of −14.81 mV. The in-vitro release of AP from the PLGA-NPs showed a biphasic release profile. AP was metabolized into PUE in rats. The AUC0−∞ values of AP and PUE for AP-PLGA-NPs were 2.90- and 2.29-fold as great as those for AP solution, respectively. The values of the relative targeting efficiency in the brain were 2.40 and 2.58 for AP and PUE, and the ratios of peak concentration were 1.91 and 1.89 for AP and PUE, respectively. Compared with the crude drug, AP-PLGA-NPs showed better brain-protective effects in rats.

Conclusion

Polysorbate 80-coated PLGA-NPs can improve the permeability of AP cross the BBB and enhance its brain-protective effects in rats.

Simultaneous determination of acetylpuerarin and puerarin in rat plasma by liquid chromatography-tandem mass spectrometry: Application to a pharmacokinetic study following intravenous and oral administration

A rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the simultaneous determination of acetylpuerarin (AP) and its major metabolite puerarin (PUE) in rat plasma using genistein as the internal standard (IS). Plasma samples were pretreated by protein precipitation with a mixture of methanol and acetonitrile. Chromatographic separation was performed on a CAPCELL PAK C18 MGШ column with a mixture of 0.1% formic acid in water and methanol (35:65, v/v) as the mobile phase. The analytes were detected using a tandem mass spectrometer in the positive ionization and multiple-reaction monitoring mode. The ion transition of m/z 669.4→627.3, 417.5→297.6 and 271.3→153.0 was utilized to quantify AP, PUE and the IS, respectively. The calibration curves showed good linearity over the plasma concentration range of 1-2000ng/mL for AP and 2.5-5000ng/mL for PUE. The intra- and inter-day precisions (RSD %) for each analyte were less than 6.91%, and the accuracies ranged from -2.17% to 2.93%. The validated LC-MS/MS method was further successfully applied to a pharmacokinetic study of AP and PUE in rats following intravenous and oral administration.

Differential regulation of astrocyte prostaglandin response by kinins: possible role for mitogen activated protein kinases

The role of kinins, well known as peripheral inflammatory mediators, in the modulation of brain inflammation is not completely understood. The present data show that bradykinin, a B2 receptor agonist, enhanced both basal and lipopolysaccharide (LPS)-induced cyclooxygenase-2 mRNA and protein levels and prostaglandin E2 synthesis in primary rat astrocytes. By contrast, Lys-des-Arg(9)-bradykinin, which is a bradykinin breakdown product and a selective kinin B1 receptor agonist, attenuated both basal and LPS-induced astrocyte cyclooxygenase-2 mRNA levels and prostaglandin E2 production. Pre-treating the cells with p42/p44 MAPK but not with JNK or p38 inhibitors completely abrogated PGE2 synthesis in cells stimulated with LPS in the presence of bradykinin or bradykinin B1 receptor agonist. Bradykinin, but not the bradykinin B1 receptor agonist, augmented p42/p44 MAPK phosphorylation. The phosphorylation of JNK and p38 was not altered upon exposure to Bradykinin or the bradykinin B1 receptor agonist. These results suggest that the dual delayed effect of kinins on PGE2 synthesis may be due to differential regulation of COX-2 and signaling molecules such as p42/p44 MAPKs. Thus, kinins may exert opposing actions on brain inflammation and neurodegenerative diseases.

Antinociceptive effect of tetrandrine on LPS-induced hyperalgesia via the inhibition of IKKβ phosphorylation and the COX-2/PGE₂ pathway in mice

Tetrandrine (TET) is a bisbenzylisoquinoline alkaloid that is isolated from the Stephania Tetrandra. It is known to possess anti-inflammatory and immunomodulatory effects. We have shown that TET can effectively suppress the production of bacterial lipopolysaccharide (LPS)-induced inflammatory mediators, including cyclooxygenases (COXs), in macrophages. However, whether TET has an antinociceptive effect on LPS-induced hyperalgesia is unknown. In the present study, we investigated the potential antinociceptive effects of TET and the mechanisms by which it elicits its effects on LPS-induced hyperalgesia. LPS effectively evoked hyperalgesia and induced the production of PGE2 in the sera, brain tissues, and cultured astroglia. TET pretreatment attenuated all of these effects. LPS also activated inhibitor of κB (IκB) kinase β (IKKβ) and its downstream components in the IκB/nuclear factor (NF)-κB signaling pathway, including COX-2; the increase in expression levels of these components was significantly abolished by TET. Furthermore, in primary astroglia, knockdown of IKKβ, but not IKKα, reversed the effects of TET on the LPS-induced increase in IκB phosphorylation, P65 phosphorylation, and COX-2. Our results suggest that TET can effectively exert antinociceptive effects on LPS-induced hyperalgesia in mice by inhibiting IKKβ phosphorylation, which leads to the reduction in the production of important pain mediators, such as PGE2 and COX-2, via the IKKβ/IκB/NF-κB pathway.