PPAR-γ Ameliorates Neuronal Apoptosis and Ischemic Brain Injury via Suppressing NF-κB-Driven p22phox Transcription

Upregulation of peroxisome proliferator-activated receptor γ with resorcinol alleviates reactive oxygen species generation and lipid accumulation in neuropathic lysosomal storage diseases

Neuropathic lysosomal storage diseases (NLSDs), including ceroid lipofuscinosis neuronal 3 (CLN3) disease and Gaucher disease type 2 (GD2), are typically present in adolescents; however, there are no approved therapies. CLN3 disease is the most common of the 13 types of neuronal ceroid lipofuscinosis, and Gaucher disease is the most common type of lysosomal storage disease. These NLSDs share oxidative stress and lysosomal dysfunction with Parkinson's disease. In this study, we used patient-derived cells (PDCs) and resorcinol to develop a therapeutic agent based on peroxisome proliferator-activated receptor γ (PPARγ) activation. PPARγ is a major regulator of autophagy and reactive oxygen species (ROS). Resorcinol, a polyphenolic compound, has been reported to exhibit PPARγ agonistic potential. Protein levels were analyzed by immunoblotting and immunofluorescence microscopy. Changes in cellular metabolism, including ROS levels, lipid droplet content, and lysosomal activity, were measured by flow cytometry. Resorcinol reduced ROS levels by suppressing hypoxia-inducible factor 1α levels in CLN3-PDCs. Resorcinol upregulated autophagy and reduced lipid accumulation in CLN3-PDCs; however, these effects were abolished by autophagy inhibitors. Resorcinol increased nuclear PPARγ levels in CLN3-PDCs, and PPARγ antagonists abolished the therapeutic effects of resorcinol. Moreover, Resorcinol upregulated nuclear PPARγ levels and lysosomal activity in GD2-PDCs, and reduced lipid accumulation and ROS levels. In summary, resorcinol alleviated the shared pathogenesis of CLN3 disease and GD2 through PPARγ upregulation. These findings suggest that resorcinol is a potential therapeutic candidate for alleviating NLSD progression.

Exploring the molecular mechanisms of PPARγ agonists in modulating memory impairment in neurodegenerative disorders

Neurodegenerative diseases are characterized by progressive memory impairment and cognitive decline. This review aims to unravel the molecular mechanisms involved in the enhancement of memory function and mitigation of memory impairment through the activation of PPARγ agonists in neurodegenerative diseases. The findings suggest that PPARγ agonists modulate various molecular pathways involved in memory formation and maintenance. Activation of PPARγ enhances synaptic plasticity, promotes neuroprotection, suppresses neuroinflammation, attenuates oxidative stress, and regulates amyloid-beta metabolism. The comprehensive understanding of these molecular mechanisms would facilitate the development of novel therapeutic approaches targeting PPARγ to improve memory function and ultimately to alleviate the burden of neurodegenerative diseases. Further research, including clinical trials, is warranted to explore the efficacy, safety, and optimal use of specific PPARγ agonists as potential therapeutic agents in the treatment of memory impairments associated with neurodegenerative diseases.

PPARγ activation ameliorates cognitive impairment and chronic microglial activation in the aftermath of r-mTBI

Chronic neuroinflammation and microglial activation are key mediators of the secondary injury cascades and cognitive impairment that follow exposure to repetitive mild traumatic brain injury (r-mTBI). Peroxisome proliferator-activated receptor-γ (PPARγ) is expressed on microglia and brain resident myeloid cell types and their signaling plays a major anti-inflammatory role in modulating microglial responses. At chronic timepoints following injury, constitutive PPARγ signaling is thought to be dysregulated, thus releasing the inhibitory brakes on chronically activated microglia. Increasing evidence suggests that thiazolidinediones (TZDs), a class of compounds approved from the treatment of diabetes mellitus, effectively reduce neuroinflammation and chronic microglial activation by activating the peroxisome proliferator-activated receptor-γ (PPARγ). The present study used a closed-head r-mTBI model to investigate the influence of the TZD Pioglitazone on cognitive function and neuroinflammation in the aftermath of r-mTBI exposure. We revealed that Pioglitazone treatment attenuated spatial learning and memory impairments at 6 months post-injury and reduced the expression of reactive microglia and astrocyte markers in the cortex, hippocampus, and corpus callosum. We then examined whether Pioglitazone treatment altered inflammatory signaling mechanisms in isolated microglia and confirmed downregulation of proinflammatory transcription factors and cytokine levels. To further investigate microglial-specific mechanisms underlying PPARγ-mediated neuroprotection, we generated a novel tamoxifen-inducible microglial-specific PPARγ overexpression mouse line and examined its influence on microglial phenotype following injury. Using RNA sequencing, we revealed that PPARγ overexpression ameliorates microglial activation, promotes the activation of pathways associated with wound healing and tissue repair (such as: IL10, IL4 and NGF pathways), and inhibits the adoption of a disease-associated microglia-like (DAM-like) phenotype. This study provides insight into the role of PPARγ as a critical regulator of the neuroinflammatory cascade that follows r-mTBI in mice and demonstrates that the use of PPARγ agonists such as Pioglitazone and newer generation TZDs hold strong therapeutic potential to prevent the chronic neurodegenerative sequelae of r-mTBI.

Spatially resolved multiomics on the neuronal effects induced by spaceflight in mice

Impairment of the central nervous system (CNS) poses a significant health risk for astronauts during long-duration space missions. In this study, we employed an innovative approach by integrating single-cell multiomics (transcriptomics and chromatin accessibility) with spatial transcriptomics to elucidate the impact of spaceflight on the mouse brain in female mice. Our comparative analysis between ground control and spaceflight-exposed animals revealed significant alterations in essential brain processes including neurogenesis, synaptogenesis and synaptic transmission, particularly affecting the cortex, hippocampus, striatum and neuroendocrine structures. Additionally, we observed astrocyte activation and signs of immune dysfunction. At the pathway level, some spaceflight-induced changes in the brain exhibit similarities with neurodegenerative disorders, marked by oxidative stress and protein misfolding. Our integrated spatial multiomics approach serves as a stepping stone towards understanding spaceflight-induced CNS impairments at the level of individual brain regions and cell types, and provides a basis for comparison in future spaceflight studies. For broader scientific impact, all datasets from this study are available through an interactive data portal, as well as the National Aeronautics and Space Administration (NASA) Open Science Data Repository (OSDR).

Trained immunity induced by high-salt diet impedes stroke recovery

A high-salt diet (HSD) elicits sustained sterile inflammation and worsens tissue injury. However, how this occurs after stroke, a leading cause of morbidity and mortality, remains unknown. Here, we report that HSD impairs long-term brain recovery after intracerebral hemorrhage, a severe form of stroke, despite salt withdrawal prior to the injury. Mechanistically, HSD induces innate immune priming and training in hematopoietic stem and progenitor cells (HSPCs) by downregulation of NR4a family and mitochondrial oxidative phosphorylation. This training compromises alternative activation of monocyte-derived macrophages (MDMs) without altering the initial inflammatory responses of the stroke brain. Healthy mice transplanted with bone marrow from HSD-fed mice retain signatures of reduced MDM reparative functions, further confirming a persistent form of innate immune memory that originates in the bone marrow. Loss of NR4a1 in macrophages recapitulates HSD-induced negative impacts on stroke outcomes while gain of NR4a1 enables stroke recovery in HSD animals. Together, we provide the first evidence that links HSD-induced innate immune memory to the acquisition of persistent dysregulated inflammatory responses and unveils NR4a1 as a potential therapeutic target.

Activating Transcription Factor 3 Diminishes Ischemic Cerebral Infarct and Behavioral Deficit by Downregulating Carboxyl-Terminal Modulator Protein

Activating transcription factor 3 (ATF3) is a stress-induced transcription factor and a familiar neuronal marker for nerve injury. This factor has been shown to protect neurons from hypoxic insult in vitro by suppressing carboxyl-terminal modulator protein (CTMP) transcription, and indirectly activating the anti-apoptotic Akt/PKB cascade. Despite prior studies in vitro, whether this neuroprotective pathway also exists in the brain in vivo after ischemic insult remains to be determined. In the present study, we showed a rapid and marked induction of ATF3 mRNA throughout ischemia-reperfusion in a middle cerebral artery (MCA) occlusion model. Although the level of CTMP mRNA was quickly induced upon ischemia, its level showed only a mild increase after reperfusion. With the gain-of-function approach, both pre- and post-ischemic administration of Ad-ATF3 ameliorated brain infarct and neurological deficits. Whereas, with the loss-of-function approach, ATF3 knockout (KO) mice showed bigger infarct and worse functional outcome after ischemia. In addition, these congenital defects were rescued upon reintroducing ATF3 to the brain of KO mice. ATF3 overexpression led to a lower level of CTMP and a higher level of p-Akt(473) in the ischemic brain. On the contrary, ATF3 KO resulted in upregulation of CTMP and downregulation of p-Akt(473) instead. Furthermore, post-ischemic CTMP siRNA knockdown led to smaller infarct and better behaviors. CTMP siRNA knockdown increased the level of p-Akt(473), but did not alter the ATF3 level in the ischemic brain, upholding the ATF3→CTMP signal cascade. In summary, our proof-of-principle experiments support the existence of neuroprotective ATF3→CTMP signal cascade regulating the ischemic brain. Furthermore, these results suggest the therapeutic potential for both ATF3 overexpression and CTMP knockdown for stroke treatment.

Pharmacological properties and mechanisms of Notoginsenoside R1 in ischemia-reperfusion injury

Panax notoginseng is an ancient Chinese medicinal plant that has great clinical value in regulating cardiovascular disease in China. As a single component of panax notoginosides, notoginsenoside R1 (NGR1) belongs to the panaxatriol group. Many reports have demonstrated that NGR1 exerts multiple pharmacological effects in ischemic stroke, myocardial infarction, acute renal injury, and intestinal injury. Here, we outline the available reports on the pharmacological effects of NGR1 in ischemia-reperfusion (I/R) injury. We also discuss the chemistry, composition and molecular mechanism underlying the anti-I/R injury effects of NGR1. NGR1 had significant effects on reducing cerebral infarct size and neurological deficits in cerebral I/R injury, ameliorating the impaired mitochondrial morphology in myocardial I/R injury, decreasing kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin in renal I/R injury and attenuating jejunal mucosal epithelium injury in intestinal I/R injury. The various organ anti-I/R injury effects of NGR1 are mainly through the suppression of oxidative stress, apoptosis, inflammation, endoplasmic reticulum stress and promotion of angiogenesis and neurogenesis. These findings provide a reference basis for future research of NGR1 on I/R injury.

Mechanism of Ferroptosis and Its Relationships with Other Types of Programmed Cell Death: Insights for Potential Therapeutic Benefits in Traumatic Brain Injury

Traumatic brain injury (TBI) is a serious health issue with a high incidence, high morbidity, and high mortality that poses a large burden on society. Further understanding of the pathophysiology and cell death models induced by TBI may support targeted therapies for TBI patients. Ferroptosis, a model of programmed cell death first defined in 2012, is characterized by iron dyshomeostasis, lipid peroxidation, and glutathione (GSH) depletion. Ferroptosis is distinct from apoptosis, autophagy, pyroptosis, and necroptosis and has been shown to play a role in secondary brain injury and worsen long-term outcomes after TBI. This review systematically describes (1) the regulatory pathways of ferroptosis after TBI, (2) the neurobiological links between ferroptosis and other cell death models, and (3) potential therapies targeting ferroptosis for TBI patients.

Norepinephrine Inhibits Lipopolysaccharide-Stimulated TNF-α but Not Oxylipin Induction in n-3/n-6 PUFA-Enriched Cultures of Circumventricular Organs

Sensory circumventricular organs (sCVOs) are pivotal brain structures involved in immune-to-brain communication with a leaky blood-brain barrier that detect circulating mediators such as lipopolysaccharide (LPS). Here, we aimed to investigate the potential of sCVOs to produce n-3 and n-6 oxylipins after LPS-stimulation. Moreover, we investigated if norepinephrine (NE) co-treatment can alter cytokine- and oxylipin-release. Thus, we stimulated rat primary neuroglial sCVO cultures under n-3- or n-6-enriched conditions with LPS or saline combined with NE or vehicle. Supernatants were assessed for cytokines by bioassays and oxylipins by HPLC-MS/MS. Expression of signaling pathways and enzymes were analyzed by RT-PCR. Tumor necrosis factor (TNF)α bioactivity and signaling, IL-10 expression, and cyclooxygenase (COX)2 were increased, epoxide hydroxylase (Ephx)2 was reduced, and lipoxygenase 15-(LOX) was not changed by LPS stimulation. Moreover, LPS induced increased levels of several n-6-derived oxylipins, including the COX-2 metabolite 15d-prostaglandin-J2 or the Ephx2 metabolite 14,15-DHET. For n-3-derived oxylipins, some were down- and some were upregulated, including 15-LOX-derived neuroprotectin D1 and 18-HEPE, known for their anti-inflammatory potential. While the LPS-induced increase in TNFα levels was significantly reduced by NE, oxylipins were not significantly altered by NE or changes in TNFα levels. In conclusion, LPS-induced oxylipins may play an important functional role in sCVOs for immune-to-brain communication.

Peroxisome proliferator-activated receptor-γ ameliorates neuronal ferroptosis after traumatic brain injury in mice by inhibiting cyclooxygenase-2

Among the multiple kinds of neuronal cell death triggered by traumatic brain injury (TBI), ferroptosis, an iron-dependent lipid peroxidative regulatory cell death, has a critical role. Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear transcription factor that regulates lipid metabolism and suppresses neuronal inflammation. However, the role of PPARγ in neuronal ferroptosis induced by TBI remains unclear. Here, we investigated the regulatory effect of PPARγ on neuronal ferroptosis in a weight-drop TBI model in vivo and an RAS-selective lethal 3 (RSL3)-activated ferroptotic neuronal model in vitro. PPARγ was mainly localized in the nucleus of neurons and was decreased in both the in vivo TBI model and the in vitro ferroptotic neuronal model. The addition of a specific agonist, pioglitazone, activated PPARγ, which protected neuronal function post-TBI in vivo and increased the viability of ferroptotic neurons in vitro. Further investigation suggested that PPARγ probably attenuates neuronal ferroptosis by downregulating cyclooxygenase-2 (COX2) protein expression levels in vivo and in vitro. This study revealed the relationship among PPARγ, ferroptosis and TBI and identified a potential target for comprehensive TBI treatment.

Protective Effects of Nuciferine in Middle Cerebral Artery Occlusion Rats Based on Transcriptomics

Middle cerebral artery occlusion (MCAO), with the characteristics of high morbidity, high recurrence rate, high mortality, and disability rate, is a typical manifestation of ischemic stroke and has become a hot research topic in the clinical field. The protective effects of nuciferine on brain injury MCAO rats were investigated and its mechanisms of actions were revealed. The MCAO rats were established by the suture method. The pathological staining of the rat brain was processed and observed, the pharmacodynamics assay of nuciferine were studied, and the gene expression regulation by nuciferine was detected by transcriptome technology. The results showed that nuciferine significantly alleviated brain damage in MCAO rats, and the transcriptomic results suggested that nuciferine could exert therapeutic effects through the regulation of lipid metabolism, including arachidonic acid metabolism, sphingolipid metabolism, the PPAR signaling pathway and other related pathways. This finding provided new perspectives on the treatment of MCAO with nuciferine and facilitates the development of novel drugs for this disease.

Mechanisms of Vitamin C Regulating Immune and Inflammation Associated with Neonatal Hypoxic-Ischemic Encephalopathy Based on Network Pharmacology and Molecular Simulation Technology

Background

There are still controversies about the curative effect of vitamin C in treating HIE, and its mechanism of action is not entirely clear. This study is designed to explore the potential molecular mechanism of vitamin C in treating neonatal hypoxic ischemic encephalopathy (HIE).

Methods

The effect targets of vitamin C and the pathogenic targets of neonatal HIE were obtained via retrieval of public databases to screen out the molecular targets of vitamin C acting on neonatal HIE. Gene Ontology (GO) functional annotations and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the main targets. Vitamin C and the optimum target structural components are subjected to molecular docking and molecular dynamics simulation analysis via computer software so as to verify their binding activity and stability.

Result

Based on 16 overlapping targets of vitamin C and HIE, seven main targets were identified in this study. According to GO and KEGG analysis, molecular functions (top 25 items) and signal pathways (21 items) related to inflammatory reaction, immune response, and cell transcriptional control may be potential pathways for vitamin C to treat neonatal HIE. Molecular docking and molecular dynamics simulation were adopted to definitively determine the 4 optimum core target spots.

Conclusion

The efficacy of vitamin C on HIE is involved in the immunoregulation and inflammation-related functional processes and signal pathways. These molecular mechanisms, including core targets, will contribute to the clinical practice of neonatal HIE in the future.

Role of HSP90α in osteoclast formation and osteoporosis development

Osteoporosis (OP) is a systemic metabolic bone disease that occurs most frequently in the elderly. The main pathogenesis of OP is excessive proliferation and differentiation of osteoclasts, in which the peroxisome proliferator-activated receptor γ (PPARγ) pathway has a pivotal role. Recently, heat shock protein (HSP)90α has been identified as an important molecular chaperone with PPARγ, which regulates the effect of the PPARγ pathway. The aim of the present study was to investigate the role of HSP90α involved in the regulation of osteoclast formation and the process of osteoporosis. Firstly, the expression of HSP90α in osteoclast differentiation was detected by western blotting in vitro, then the effect of HSP90α inhibition on the formation and differentiation of osteoclasts was examined. Furthermore, the nuclear import of PPARγ was also assessed to confirm the synergistic effect of HSP90α. Finally, the inhibitory effect of HSP90α in vivo was explored, using a mouse model of osteoporosis. As a result, in the process of osteoclast differentiation and proliferation, the expression of HSP90α was upregulated. Inhibition of HSP90α could block the formation and differentiation of osteoclasts, and remit osteoporosis in mice. Regarding the underlying mechanism, inhibition of HSP90α could block the nuclear import of PPARγ to inhibit osteoclast differentiation and proliferation. In conclusion, these data indicated that the inhibition of HSP90α could block osteoclast formation and remit osteoporosis by reducing the nuclear import of PPARγ.

Involvement of FoxO1, Sp1, and Nrf2 in Upregulation of Negative Regulator of ROS by 15d-PGJ2 Attenuates H2O2-Induced IL-6 Expression in Rat Brain Astrocytes

Excessive production of reactive oxygen species (ROS) by NADPH oxidase (Nox) resulted in inflammation. The negative regulator of ROS (NRROS) dampens ROS generation during inflammatory responses. 15-Deoxy-∆12,14-prostaglandin J₂ (15d-PGJ₂) exhibits neuroprotective effects on central nervous system (CNS). However, whether 15d-PGJ₂-induced NRROS expression was unknown in rat brain astrocytes (RBA-1). NRROS expression was determined by Western blot, RT/real-time PCR, and promoter activity assays. The signaling components were investigated using pharmacological inhibitors or specific siRNAs. The interaction between transcription factors and the NRROS promoter was investigated by chromatin immunoprecipitation assay. Upregulation of NRROS on the hydrogen peroxide (H₂O₂)-mediated ROS generation and interleukin 6 (IL-6) secretion was measured. 15d-PGJ₂-induced NRROS expression was mediated through PI3K/Akt-dependent activation of Sp1 and FoxO1 and established the essential promoter regions. We demonstrated that 15d-PGJ₂ activated PI3K/Akt and following by cooperation between phosphorylated nuclear FoxO1 and Sp1 to initiate the NRROS transcription. In addition, Nrf2 played a key role in NRROS expression induced by 15d-PGJ₂ which was mediated through its phosphorylation. Finally, the NRROS stable clones attenuated the H₂O₂-induced ROS generation and expression of IL-6 through suppressing the Nox-2 activity. These results suggested that 15d-PGJ₂-induced NRROS expression is mediated through a PI3K/Akt-dependent FoxO1 and Sp1 phosphorylation, and Nrf2 cascade, which suppresses ROS generation through attenuating the p47^phox phosphorylation and gp91^phox formation and IL-6 expression in RBA-1 cells. These results confirmed the mechanisms underlying 15d-PGJ₂-induced NRROS expression which might be a potential strategy for prevention and management of brain inflammatory and neurodegenerative diseases.

Berberine exerts neuroprotective activities against cerebral ischemia/reperfusion injury through up-regulating PPAR-γ to suppress NF-κB-mediated pyroptosis

OBJECTIVE

Berberine (BBR) is an anti-inflammatory alkaloid compound extracted from herbs. The purpose of this study is to probe the possible effect and the mechanism of BBR against cerebral ischemia/reperfusion (I/R) injury.

METHODS

In vitro oxygen and glucose deprivation (OGD) model was established on neurons from rat hippocampus, which was then subjected to BBR, IVA337 (PPAR-γ agonist), or GW9662 (PPAR-γ antagonist) treatment, to identify their effects on neuronal pyroptosis. MTT assay was utilized to determine cell survival rates, TUNEL staining for observation of β-tubulin and MAP2 expressions, qRT-PCR for detection of mRNA expression of PPAR-γ, Western blot for assessment of protein expressions of PPAR-γ and pyroptosis-related proteins (AIM2, NLPR3, ASC, cleaved-Caspase-1, GSDMD, and GSDMD-N), and ELISA for examination of IL-18 and IL-1β expressions.

RESULTS

OGD modeling induced neuron pyroptosis, as evidenced by increased expression levels of pyroptosis-related proteins as well as IL-1β and IL-18, and elevated cell apoptosis rate. In addition, OGD exposure led to PPAR-γ up-regulation and NF-κB activation. Overexpression of PPAR-γ ameliorated cell pyroptosis, while knockdown of PPAR-γ intensified neuron pyroptosis that could be reversed by BBR. Furthermore, either BBR could block the activation of NF-κB signaling pathway through PPAR-γ.

CONCLUSION

BBR protects rats from cerebral I/R injury by up-regulating PPAR-γ to restrain NF-κB-mediated pyroptosis.

Icariin, an Up-and-Coming Bioactive Compound Against Neurological Diseases: Network Pharmacology-Based Study and Literature Review

Icariin is a biologically active substance in Epimedii herba that is used for the treatment of neurologic disorders. However, a comprehensive analysis of the molecular mechanisms of icariin is lacking. In this review, we present a brief history of the use of icariin for medicinal purposes; describe the active chemical components of Epimedii herba; and examine the evidence from experimental studies that have uncovered molecular targets of icariin in different diseases. We also constructed a protein–protein interaction network and carried out Gene Ontology and Kyoto Encyclopedia of Genes and Genomes functional enrichment analyses to predict the therapeutic actions of icariin in nervous system diseases including Alzheimer disease, Parkinson disease, ischemic stroke, depressive disorder, multiple sclerosis, glioblastoma, and hereditary spastic paraplegias. The results of our analyses can guide future studies on the application of icariin to the treatment of neurologic disorders.

Post-Treatment with Amorfrutin B Evokes PPARγ-Mediated Neuroprotection against Hypoxia and Ischemia

In this study, we demonstrate for the first time that amorfrutin B, a selective modulator of peroxisome proliferator-activated receptor gamma—PPARγ, can protect brain neurons from hypoxia- and ischemia-induced degeneration when applied at 6 h post-treatment in primary cultures. The neuroprotective effect of amorfrutin B suggests that it promotes mitochondrial integrity and is capable of inhibiting reactive oxygen species—ROS activity and ROS-mediated DNA damage. PPARγ antagonist and Pparg mRNA silencing abolished the neuroprotective effect of amorfrutin B, which points to agonistic action of the compound on the respective receptor. Interestingly, amorfrutin B stimulated the methylation of the Pparg gene, both during hypoxia and ischemia. Amorfrutin B also increased the protein level of PPARγ during hypoxia but decreased the mRNA and protein levels of PPARγ during ischemia. Under ischemic conditions, amorfrutin B-evoked hypermethylation of the Pparg gene is in line with the decrease in the mRNA and protein expression of PPARγ. However, under hypoxic conditions, amorfrutin B-dependent hypermethylation of the Pparg gene does not explain the amorfrutin B-dependent increase in receptor protein expression, which suggests other regulatory mechanisms. Other epigenetic parameters, such as HAT and/or sirtuins activities, were affected by amorfrutin B under hypoxic and ischemic conditions. These properties position the compound among the most promising anti-stroke and wide-window therapeutics.

Peroxisome Proliferator-Activated Receptor-Gamma (PPAR-ɣ): Molecular Effects and Its Importance as a Novel Therapeutic Target for Cerebral Ischemic Injury

Cerebral ischemic injury is a leading cause of death and long-term disability throughout the world. Peroxisome proliferator-activated receptor gamma (PPAR-ɣ) is a ligand-activated nuclear transcription factor that is a member of the PPAR family. PPAR-ɣ has been shown in several in vitro and in vivo models to prevent post-ischemic inflammation and neuronal damage by negatively controlling the expression of genes modulated by cerebral ischemic injury, indicating a neuroprotective effect during cerebral ischemic injury. A extensive literature review of PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out to understand the nature of the extensive work done on the mechanistic role of Peroxisome proliferator activated receptor gamma and its modulation in Cerebral ischemic injury. PPAR-ɣ can interact with specific DNA response elements to control gene transcription and expression when triggered by its ligand. It regulates lipid metabolism, improves insulin sensitivity, modulates antitumor mechanisms, reduces oxidative stress, and inhibits inflammation. This review article provides insights on the current state of research into the neuroprotective effects of PPAR-ɣ in cerebral ischemic injury, as well as the cellular and molecular mechanisms by which these effects are modulated, such as inhibition of inflammation, reduction of oxidative stress, suppression of pro-apoptotic production, modulation of transcription factors, and restoration of injured tissue through neurogenesis and angiogenesis.

Injectable bio-responsive hydrogel for therapy of inflammation related eyelid diseases

Eyelid plays a vital role in protecting the eye from injury or infection. Inflammation related eyelid diseases, such as blepharitis, are the most common ocular disorders that affect human's vision and quality of life. Due to the physiological barriers and anatomical structures of the eye, the bioavailability of topical administrated therapeutics is typically less than 5%. Herein, we developed a bio-responsive hydrogel drug delivery system using a generally recognized as safe compound, triglycerol monostearate (TG-18), for in-situ eyelid injection with sustained therapeutics release. In vitro, drug release and disassembly time of Rosiglitazone loaded hydrogel (Rosi-hydrogel) were estimated in the presence or absence of MMP-9, respectively. Moreover, the disassembly of TG-18 hydrogel was evaluated with 9-month-old and 12-month-old mice in vivo. Owing to the bio-responsive nature of Rosi-hydrogel, the on-demand Rosiglitazone release is achieved in response to local enzymes. These findings are proved by further evaluation in the age-related meibomian gland dysfunction mice model, and the bio-responsive hydrogel is used as an in-situ injection to treat eyelid diseases. Taken together, the in-situ eyelid injection with sustained drug release opens a window for the therapy of inflammation related eyelid diseases.

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This study is the first application of injectable bio-responsive hydrogel for therapy of inflammation related eyelid diseases.

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The enzyme response characteristic is extremely suitable for enhancing drug bioavailability in ocular drug delivery.

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In-situ release of rosiglitazone can effectively treat age-related meibomian gland dysfunction in the mice model.

Hyperglycemic Condition Causes Pro-Inflammatory and Permeability Alterations Associated with Monocyte Recruitment and Deregulated NFκB/PPARγ Pathways on Cerebral Endothelial Cells: Evidence for Polyphenols Uptake and Protective Effect

Hyperglycemia alters the function of cerebral endothelial cells from the blood-brain barrier, increasing the risk of cerebrovascular complications during diabetes. This study evaluated the protective effect of polyphenols on inflammatory and permeability markers on bEnd3 cerebral endothelial cells exposed to high glucose concentration. Results show that hyperglycemic condition increased nuclear factor kappa B (NFκB) activity, deregulated the expression of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin-10 (IL-10) and endothelial-leukocyte adhesion molecule (E-selectin) genes, raised MCP-1 secretion and elevated monocyte adhesion and transendothelial migration. High glucose decreased occludin, claudin-5, zona occludens-1 (ZO-1) and zona occludens-2 (ZO-2) tight junctions production and altered the endothelial permeability. Characterized polyphenolic extracts from the French medicinal plants Antirhea borbonica, Ayapana triplinervis, Dodonaea viscosa and Terminalia bentzoe, and their major polyphenols quercetin, caffeic, chlorogenic and gallic acids limited the pro-inflammatory and permeability alterations caused by high glucose. Peroxisome proliferator-activated receptor gamma (PPARγ) agonist also attenuated these damages while PPARγ antagonist aggravated them, suggesting PPARγ protective action. Interestingly, polyphenols improved PPARγ gene expression lowered by high glucose. Moreover, polyphenols were detected at the intracellular level or membrane-bound to cells, with evidence for breast cancer resistance protein (BCRP) efflux transporter role. Altogether, these findings emphasize the ability of polyphenols to protect cerebral endothelial cells in hyperglycemic condition and their relevance for pharmacological strategies aiming to limit cerebrovascular disorders in diabetes.

Recent Insights on the Role of PPAR-β/δ in Neuroinflammation and Neurodegeneration, and Its Potential Target for Therapy

Peroxisome proliferator-activated receptor (PPAR) β/δ belongs to the family of hormone and lipid-activated nuclear receptors, which are involved in metabolism of long-chain fatty acids, cholesterol, and sphingolipids. Similar to PPAR-α and PPAR-γ, PPAR-β/δ also acts as a transcription factor activated by dietary lipids and endogenous ligands, such as long-chain saturated and polyunsaturated fatty acids, and selected lipid metabolic products, such as eicosanoids, leukotrienes, lipoxins, and hydroxyeicosatetraenoic acids. Together with other PPARs, PPAR-β/δ displays transcriptional activity through interaction with retinoid X receptor (RXR). In general, PPARs have been shown to regulate cell differentiation, proliferation, and development and significantly modulate glucose, lipid metabolism, mitochondrial function, and biogenesis. PPAR-β/δ appears to play a special role in inflammatory processes and due to its proangiogenic and anti-/pro-carcinogenic properties, this receptor has been considered as a therapeutic target for treating metabolic syndrome, dyslipidemia, carcinogenesis, and diabetes. Until now, most studies were carried out in the peripheral organs, and despite of its presence in brain cells and in different brain regions, its role in neurodegeneration and neuroinflammation remains poorly understood. This review is intended to describe recent insights on the impact of PPAR-β/δ and its novel agonists on neuroinflammation and neurodegenerative disorders, including Alzheimer’s and Parkinson’s, Huntington’s diseases, multiple sclerosis, stroke, and traumatic injury. An important goal is to obtain new insights to better understand the dietary and pharmacological regulations of PPAR-β/δ and to find promising therapeutic strategies that could mitigate these neurological disorders.

The Protective Effects of Peroxisome Proliferator-Activated Receptor Gamma in Cerebral Ischemia-Reperfusion Injury

Cerebral ischemia-reperfusion injury (CI/RI) is a complex pathological process that often occurs secondary to trauma, surgery, and shock. Peroxisome proliferator activated receptor gamma (PPARγ) is a subunit of the PPAR and is a ligand-activated nuclear transcription factor. After being activated by its ligand, PPARγ can combine with specific DNA response elements to regulate the transcription and expression of genes. It has a wide range of biological functions, such as regulating lipid metabolism, improving insulin sensitivity, modulating anti-tumor mechanisms, and inhibiting inflammation. In recent years, some studies have shown that PPARγ exerts a protective effect during CI/RI. This article aims to summarize the research progress of studies that have investigated the protective effects of PPARγ in CI/RI and the cellular and molecular mechanisms through which these effects are modulated, including inhibition of excitatory amino acid toxicity, reduced Ca2+ overload, anti-oxidative stress, anti-inflammation, inhibition of microglial activation, maintain the BBB, promotion of angiogenesis, and neurogenesis and anti-apoptotic processes.

Clinacanthus nutans Mitigates Neuronal Death and Reduces Ischemic Brain Injury: Role of NF-κB-driven IL-1β Transcription

Neuroinflammation has been shown to exacerbate ischemic brain injury, and is considered as a prime target for the development of stroke therapies. Clinacanthus nutans Lindau (C. nutans) is widely used in traditional medicine for treating insect bites, viral infection and cancer, due largely to its anti-oxidative and anti-inflammatory properties. Recently, we reported that an ethanol extract from the leaf of C. nutans could protect the brain against ischemia-triggered neuronal death and infarction. In order to further understand the molecular mechanism(s) for its beneficial effects, two experimental paradigms, namely, in vitro primary cortical neurons subjected to oxygen-glucose deprivation (OGD) and in vivo rat middle cerebral artery (MCA) occlusion, were used to dissect the anti-inflammatory effects of C. nutans extract. Using promoter assays, immunofluorescence staining, and loss-of-function (siRNA) approaches, we demonstrated that transient OGD led to marked induction of IL-1β, IL-6 and TNFα, while pretreatment with C. nutans suppressed production of inflammatory cytokines in primary neurons. C. nutans inhibited IL-1β transcription via preventing NF-κB/p65 nuclear translocation, and siRNA knockdown of either p65 or IL-1β mitigated OGD-mediated neuronal death. Correspondingly, post-ischemic treatment of C. nutans attenuated IκBα degradation and decreased IL-1β, IL-6 and TNFα production in the ischemic brain. Furthermore, IL-1β siRNA post-ischemic treatment reduced cerebral infarct, thus mimicking the beneficial effects of C. nutans. In summary, our findings demonstrated the ability for C. nutans to suppress NF-κB nuclear translocation and inhibit IL-1β transcription in ischemic models. Results further suggest the possibility for using C. nutans to prevent and treat stroke patients.

Identification of inflammation‑associated circulating long non‑coding RNAs and genes in intracranial aneurysm rupture‑induced subarachnoid hemorrhage

Ruptured intracranial aneurysm (IA)-induced subarachnoid hemorrhage (SAH) triggers a series of immune responses and inflammation in the brain and body. The present study was conducted to identify additional circulating biomarkers that may serve as potential therapeutic targets for SAH-induced inflammation. Differentially expressed (DE) long non-coding RNAs (lncRNAs; DElncRNAs) and genes (DEGs) in the peripheral blood mononuclear cells between patients with IA rupture-induced SAH and healthy controls were identified in the GSE36791 dataset. DEGs were used for weighted gene co-expression network analysis (WGCNA), and SAH-associated WGCNA modules were identified. Subsequently, an lncRNA-mRNA regulatory network was constructed using the DEGs in SAH-associated WGCNA modules. A total of 25 DElncRNAs and 1,979 DEGs were screened from patients with IA-induced SAH in the GSE36791 dataset compared with the controls. A total of 11 WGCNA modules, including four upregulated modules significantly associated with IA rupture-induced SAH were obtained. The DEGs in the SAH-associated modules were associated with Gene Ontology biological processes such as ‘regulation of programmed cell death’, ‘apoptosis’ and ‘immune response’. The subsequent lncRNA-mRNA regulatory network included seven upregulated lncRNAs [HCG27, ZNFX1 antisense RNA 1, long intergenic non-protein coding RNA (LINC)00265, murine retrovirus integration site 1 homolog-antisense RNA 1, cytochrome P450 1B1-AS1, LINC01347 and LINC02193] and 375 DEGs. Functional enrichment analysis and screening in the Comparative Toxicogenomics Database demonstrated that SAH-associated DEGs, including neutrophil cytosolic factor (NCF)2 and NCF4, were enriched in ‘chemokine signaling pathway’ (hsa04062), ‘leukocyte transendothelial migration’ (hsa04670) and ‘Fc gamma R-mediated phagocytosis’ (hsa04666). The upregulated lncRNAs and genes, including NCF2 and NCF4, in patients with IA rupture-induced SAH indicated their respective potentials as anti-inflammatory therapeutic targets.

Communications Between Peripheral and the Brain-Resident Immune System in Neuronal Regeneration After Stroke

Cerebral ischemia may cause irreversible neural network damage and result in functional deficits. Targeting neuronal repair after stroke potentiates the formation of new connections, which can be translated into a better functional outcome. Innate and adaptive immune responses in the brain and the periphery triggered by ischemic damage participate in regulating neural repair after a stroke. Immune cells in the blood circulation and gut lymphatic tissues that have been shaped by immune components including gut microbiota and metabolites can infiltrate the ischemic brain and, once there, influence neuronal regeneration either directly or by modulating the properties of brain-resident immune cells. Immune-related signalings and metabolites from the gut microbiota can also directly alter the phenotypes of resident immune cells to promote neuronal regeneration. In this review, we discuss several potential mechanisms through which peripheral and brain-resident immune components can cooperate to promote first the resolution of neuroinflammation and subsequently to improved neural regeneration and a better functional recovery. We propose that new insights into discovery of regulators targeting pro-regenerative process in this complex neuro-immune network may lead to novel strategies for neuronal regeneration.

Role of peroxisome proliferator-activated receptors in stroke prevention and therapy-The best is yet to come?

Role of peroxisome proliferator-activated receptors (PPARs) in the pathophysiology of stroke and protective effects of PPAR ligands have been widely investigated in the last 20 years. Activation of all three PPAR isoforms, but especially PPAR-γ, was documented to limit postischemic injury in the numerous in vivo, as well as in in vitro studies. PPARs have been demonstrated to act on multiple mechanisms and were shown to activate multiple protective pathways related to inflammation, apoptosis, BBB protection, neurogenesis, and oxidative stress. The aim of this review was to summarize two decades of PPAR research in stroke with emphasis on in vivo animal studies. We focus on each PPAR receptor separately and detail their implication in stroke. This review also discusses recent clinical efforts in the field and the epidemiological data with regard to role of PPAR polymorphisms in susceptibility to stroke, and tries to draw conclusions and describe future perspectives.

Ginsenoside Rb1 Alleviated High-Fat-Diet-Induced Hepatocytic Apoptosis via Peroxisome Proliferator-Activated Receptor γ

Objective

High-fat-diet- (HFD-) induced hepatic cell apoptosis is common in mice with nonalcoholic fatty liver disease (NAFLD). We aim to investigate the effect of Ginsenoside Rb1 (GRb1) on hepatocyte apoptosis.

Methods

C57BL/6J mice with HFD were used to induce a liver-injured model with cell apoptosis. In addition, GRb1 was used to treat HFD-induced apoptosis in a liver with or without inhibitor of peroxisome proliferator-activated receptor γ (PPAR-γ).

Results

Compared with C57BL/6J mice with common chow, there are downregulated PPAR-γ but upregulated cell apoptosis in the liver of mice with HFD. Furthermore, GRb1 elevated the hepatic PPAR-γ level and suppressed hepatocytic apoptosis. However, GW9662 abolished the effects of GRb1 on apoptosis in the liver.

Conclusions

GRb1 alleviated HFD-induced apoptosis of hepatocytes of mice via PPAR-γ.

Taurine attenuates liver autophagy and injury of offspring in gestational diabetic mellitus rats

PURPOSE

Gestational diabetes mellitus (GDM) has many adverse effects on offspring, such as abnormal glycolipid metabolism, obesity, insulin resistance, mental retardation, schizophrenia and so on.

METHODS

We established a GDM rat model by injecting 1% streptozotocin associated with a high-fat diet one week before pregnancy, and offspring rats were sacrificed at 8 weeks of age to obtain liver tissue for study. We used hematoxylin-eosin (HE) staining to observe liver morphological changes, Tunel staining for hepatocyte apoptosis, transmission electron microscope for liver ultrastructure, and western blot for protein expression in liver tissue.

RESULTS

Compared with normal offspring rats, hepatocytes of GDM offspring rats showed obvious edema, liver organ index increased, and hepatocyte apoptosis and autophagosome in the liver were significantly increased; Bax, cleaved-caspase3/caspase3, LCII, Beclin 1, P-IKBα/IKBα and P-p65/p6 protein expression in the liver were significantly increased; Bcl2, p62 and PPARγ protein expression in the liver were significantly decreased. Tau prevented the GDM-related effects in the offspring: Tau decreased hepatocyte edema (or even disappears), liver organ index, hepatocyte apoptosis and the number of autophagosomes in the liver. In addition, Tau also decreased Bax, cleaved-caspase3/caspase3, LCII, Beclin 1, P-IKBα/IKBα and P-p65/p6 protein expression, and increased Bcl2, p62 and PPARγ protein expression in the liver of GDM offspring rats.

CONCLUSION

Taurine should be considered as a potential gestational nutritional supplement to prevent liver damage in GDM offspring.

The role of microglia in neuroprogressive disorders: mechanisms and possible neurotherapeutic effects of induced ketosis

A comprehensive review of molecular mechanisms involved in the promotion and maintenance of distinct microglia phenotypes is provided. The acquisition and perpetuation of predominantly pro-inflammatory microglial phenotypes have been implicated in the pathophysiology of several neuroprogressive diseases and is associated with reduced ATP production via oxidative phosphorylation, increased ATP generation by glycolysis, elevated oxidative and nitrosative stress and other metabolic, inflammatory and hormonal insults. Microglia can also adopt a predominantly anti-inflammatory phenotypes with neuroprotective properties. Strategies that promote and maintain a predominantly anti-inflammatory phenotype may hold promise as novel therapeutic opportunities for neuroprogressive illness. Induced ketosis may promote a transition towards predominantly anti-inflammatory microglial states/phenotypes by several mechanisms, including inhibition of glycolysis and increased NAD⁺ production; engagement of microglial GPR109A receptors; histone deacetylase inhibition; and elevated n-3 polyunsaturated fatty acids levels. Since microglia activation can now be assessed in vivo, these data provide a clear rationale for the design of transdiagnostic randomized controlled trials of the ketogenic diet and other ketosis-inducing strategies for neuroprogressive diseases, which may also provide mechanistic insights through the assessment of "target engagement".

RvE1 treatment prevents memory loss and neuroinflammation in the Ts65Dn mouse model of Down syndrome

Inflammation can be resolved by pro-homeostatic lipids called specialized pro-resolving mediators (SPMs) upon activation of their receptors. Dysfunctional inflammatory resolution is now considered as a driver of chronic neuroinflammation and Alzheimer's disease (AD) pathogenesis. We have previously shown that SPM levels were reduced and also that SPM-binding receptors were increased in patients with AD compared to age-matched controls. Individuals with Down syndrome (DS) exhibit accelerated acquisition of AD neuropathology, dementia, and neuroinflammation at an earlier age than the general population. Beneficial effects of inducing resolution in DS have not been investigated previously. The effects of the SPM resolvin E1 (RvE1) in a DS mouse model (Ts65Dn) were investigated with regard to inflammation, neurodegeneration, and memory deficits. A moderate dose of RvE1 for 4 weeks in middle-aged Ts65Dn mice elicited a significant reduction in memory loss, along with reduced levels of serum pro-inflammatory cytokines, and reduced microglial activation in the hippocampus of Ts65Dn mice but had no effects in age-matched normosomic mice. There were no observable adverse side effects in Ts65Dn or in normosomic mice. These findings suggest that SPMs may represent a novel drug target for individuals with DS and others at risk of developing AD.

Rhein attenuates lipopolysaccharide-primed inflammation through NF-κB inhibition in RAW264.7 cells: targeting the PPAR-γ signal pathway

Inflammation is a common inducer of numerous severe diseases such as sepsis. The NF-κB signaling pathway plays a key role in the inflammatory process. Its activation promotes the release of pro-inflammatory mediators like inducible nitric oxide synthase and tumor necrosis factor alpha. Peroxisome proliferator-activated receptor gamma (PPAR-γ) inactivates nuclear factor kappa B (NF-κB) and subsequently attenuates inflammation. Rhein, an agent isolated from rhubarb, has been known to have anti-inflammatory effects. However, its influence on PPAR-γ remains largely unknown. In this study, an inflammation model was constructed by stimulating RAW264.7 cells with lipopolysaccharide. Rhein was used as a therapeutic agent, while rosiglitazone (PPAR-γ activator) and GW9662 (PPAR-γ inhibitor) were used as disrupters for in depth studies. The results demonstrated that rhein inhibits NF-κB activation and inflammatory factor release. However, GW9662 significantly reduced this effect, indicating that PPAR-γ is a critical mediator in the rhein-mediated anti-inflammatory process. Additionally, positive modulation of PPAR-γ expression and activity by rosiglitazone correspondingly influenced the effects of rhein on inflammatory factors and NF-κB expression. We also found that rhein could enhance PPAR-γ, NF-κB, and histone deacetylase 3 (HDAC3) binding. These results indicate that rhein exerts its anti-inflammation function by regulating the PPAR-γ-NF-κB-HDAC3 axis.

PPAR-γ promotes p38 MAP kinase-mediated endothelial cell permeability through activating Sirt3

Background

Ischemia-reperfusion (I/R)-induced vascular dysfunction is the main factor to acute ischemic stroke. Sirt3 is one of the sirtuin family members, which plays an important role in the development of neurological diseases.

Methods

In this study, we constructed I/R injury model on HBMEC cells and induced the overexpression of Sirt3 in model cells. Meanwhile, the p38 activator U-46619 was used to examine the connection between Sirt3 and p38. We also examined the level of endothelial associated proteins, including occluding, ZO-1 and claudin-4 by using qRT-PCR and western blot.

Results

Our findings indicated that overexpression of Sirt3 decreased the permeability of model cells and promoted in the growth of endothelial cells. However, the activation of p38 could antagonize the function of Sirt3 in HBMEC cells. Moreover, Our results indicated a positive correlation between Sirt3 and inter-endothelial junction proteins. Importantly, PPAR-γ agonist and inhibitor were utilized to investigate the role of PPAR-γ in Sirt3 mediated cell function. Sirt3 was targeted by PPAR-γ in model cells.

Conclusions

Taken together, this research not only demonstrated PPAR-γ might benefit to the growth of endothelial cell though activating Sirt3 but also indicated its potential value in the treatment for ischemic stroke.

Peroxisome proliferator-activated receptor gamma participates in the acquisition of brain ischemic tolerance induced by ischemic preconditioning via glial glutamate transporter 1 in vivo and in vitro

Glial glutamate transporter 1 (GLT-1) plays a vital role in the induction of brain ischemic tolerance (BIT) by ischemic preconditioning (IPC). However, the mechanism still needs to be further explained. The aim of this study was to investigate whether peroxisome proliferator-activated receptor gamma (PPARγ) participates in regulating GLT-1 during the acquisition of BIT induced by IPC. Initially, cerebral IPC induced BIT and enhanced PPARγ and GLT-1 expression in the CA1 hippocampus in rats. The ratio of nuclear/cytoplasmic PPARγ was also increased. At the same time, the up-regulation of PPARγ expression in astrocytes in the CA1 hippocampus was revealed by double immunofluorescence for PPARγ and glial fibrillary acidic protein. Then, the mechanism by which PPARγ regulates GLT-1 was studied in rat cortical astrocyte-neuron cocultures. We found that IPC [45 min of oxygen glucose deprivation (OGD)] protected neuronal survival after lethal OGD (4 h of OGD), which usually leads to neuronal death. The activation of PPARγ occurred earlier than the up-regulation of GLT-1 in astrocytes after IPC, as determined by western blot and immunofluorescence. Moreover, the preadministration of the PPARγ antagonist T0070907 or PPARγ siRNA significantly attenuated GLT-1 up-regulation and the neuroprotective effects induced by IPC in vitro. Finally, the effect of the PPARγ antagonist on GLT-1 expression and BIT was verified in vivo. We observed that the preadministration of T0070907 by intracerebroventricular injection dose-dependently attenuated the up-regulation of GLT-1 and BIT induced by cerebral IPC in rats. In conclusion, PPARγ participates in regulating GLT-1 during the acquisition of BIT induced by IPC. Cover Image for this issue: doi: 10.1111/jnc.14532. Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/.

15-Deoxy-∆-12,14-Prostaglandin J2 (15d-PGJ2), an Endogenous Ligand of PPAR-γ: Function and Mechanism

15-Deoxy-∆-^12,14-prostaglandin J2 (15d-PGJ2), a natural peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, has been explored in some detail over the last 20 years. By triggering the PPAR-γ signalling pathway, it plays many roles and exerts antitumour, anti-inflammatory, antioxidation, antifibrosis, and antiangiogenesis effects. Although many synthetic PPAR-γ receptor agonists have been developed, as an endogenous product of PPAR-γ receptors, 15d-PGJ2 has beneficial characteristics including rapid expression and the ability to contribute to a natural defence mechanism. In this review, we discuss the latest advances in our knowledge of the biological role of 15d-PGJ2 mediated through PPAR-γ. It is important to understand its structure, synthesis, and functional mechanisms to develop preventive agents and limit the progression of associated diseases.

Neuroprotection mediated by the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage

The Wnt/Frizzled signaling pathway participates in many inflammation-linked diseases. However, the inflammatory response mediated by the Wnt/Frizzled signaling pathway in experimental subarachnoid hemorrhage has not been thoroughly investigated. Consequently, in this study, we examined the potential role of the Wnt/Frizzled signaling pathway in early brain injury in rat models of subarachnoid hemorrhage. Simultaneously, possible neuroprotective mechanisms were also investigated. Experimental subarachnoid hemorrhage rat models were induced by injecting autologous blood into the prechiasmatic cistern. Experiment 1 was designed to examine expression of the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage. In total, 42 adult rats were divided into sham (injection of equivalent volume of saline), 6-, 12-, 24-, 48-, 72-hour, and 1-week subarachnoid hemorrhage groups. Experiment 2 was designed to examine neuroprotective mechanisms of the Wnt/Frizzled signaling pathway in early brain injury induced by subarachnoid hemorrhage. Rats were treated with recombinant human Wnt1 (rhwnt1), small interfering Wnt1 (siwnt1) RNA, and monoclonal antibody of Frizzled1 (anti-Frizzled1) at 48 hours after subarachnoid hemorrhage. Expression levels of Wnt1, Frizzled1, β-catenin, peroxisome proliferator-activated receptor-γ, CD36, and active nuclear factor-κB were examined by western blot assay and immunofluorescence staining. Microglia type conversion and inflammatory cytokine levels in brain tissue were examined by immunofluorescence staining and enzyme-linked immunosorbent assay. Our results show that compared with the sham group, expression levels of Wnt1, Frizzled1, and β-catenin were low and reduced to a minimum at 48 hours, gradually returning to baseline at 1 week after subarachnoid hemorrhage. rhwnt1 treatment markedly increased Wnt1 expression and alleviated subarachnoid hemorrhage-induced early brain injury (within 72 hours), including cortical cell apoptosis, brain edema, and neurobehavioral deficits, accompanied by increasing protein levels of β-catenin, CD36, and peroxisome proliferator-activated receptor-γ and decreasing protein levels of nuclear factor-κB. Of note, rhwnt1 promoted M2-type microglia conversion and inhibited release of inflammatory cytokines (interleukin-1β, interleukin-6, and tumor necrosis factor-α). In contrast, siwnt1 RNA and anti-Frizzled1 treatment both resulted in an opposite effect. In conclusion, the Wnt/Frizzled1 signaling pathway may participate in subarachnoid hemorrhage-induced early brain injury via inhibiting the inflammatory response, including regulating microglia type conversion and decreasing inflammatory cytokine release. The study was approved by the Animal Ethics Committee of Anhui Medical University and First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China (approval No. LLSC-20180202) in May 2017.

miR-130 aggravates acute myocardial infarction-induced myocardial injury by targeting PPAR-γ

Cardiac remodeling is a common pathophysiological change associated with acute myocardial infarction (AMI). Recent evidence indicates that microRNAs are strong posttranscriptional regulators which play an important role in regulating the microenvironment of myocardial tissue after AMI. In this study, we sought to explore the potential role and underlying mechanism of miR-130 in AMI. H9c2 cells were cultured under hypoxic conditions to simulate myocardial infarction. The influence of aberrantly expressed miR-130 on H9c2 cells under hypoxia was also estimated with RT-PCR, western blot and enzyme-linked immunosorbent assay. Using bioinformatics methods, of miR-130 target genes were verified with luciferase reporter assay. Then, the effects of miR-130 on AMI were identified in an induced myocardial injury model in rats. The results show that miR-130 downregulation remarkably decreased hypoxia-induced inflammation and fibrosis related protein expression in H9c2 cells and reversed hypoxia-induced peroxisome proliferator-activated receptor γ (PPAR-γ) inhibition. A bifluorescein reporter assay further confirmed that PPAR-γ was a target gene of miR-130. This study verified that PPAR-γ has a cardioprotective effect by inhibiting NFκB-mediated inflammation and TGF-β1-mediated fibrosis. In vivo experiments confirmed that downregulation of miR-130 expression promotes PPAR-γ-mediated cardioprotective effects by suppressing inflammation and myocardial fibrosis. Taken together, these findings suggest that miR-130 knockdown alleviates infarction-induced myocardial injury by promoting PPAR-γ expression.

FGF21 Protects the Blood-Brain Barrier by Upregulating PPARγ via FGFR1/β-klotho after Traumatic Brain Injury

Blood-brain barrier (BBB) disruption and dysfunction result in brain edema, which is responsible for more than half of all deaths after severe traumatic brain injury (TBI). Fibroblast growth factor 21 (FGF21) has a potential neuroprotective function in the brain. However, the effects and underlying possible mechanism of action on BBB integrity following TBI remain unknown. The purpose of the current study was to determine the effects of FGF21 on BBB protection and TBI treatment. The effects of recombinant human FGF21 (rhFGF21) on BBB integrity and on tight junction (TJ) and adhesion junction (AJ) proteins were investigated both in a TBI mouse model and an in vitro BBB disruption model established with tumor necrosis factor alpha (TNF-α)-induced human brain microvascular endothelial cells (HBMECs). The ability of rhFGF21 to form an FGF21/FGFR1/β-klotho complex was confirmed by in vitro β-klotho small interfering RNA (siRNA) transfection and FGFR1 co-immunoprecipitation. In addition, the specific FGFR1 and peroxisome proliferator-activated receptor gamma (PPARγ) inhibitors PD173074 and GW9662, respectively, were applied to further explore the possible mechanism of rhFGF21 in BBB maintenance after TBI. rhFGF21 markedly reduced neurofunctional behavior deficits and cerebral edema degree, preserved BBB integrity, and recued brain tissue loss and neuron apoptosis in the mouse model after TBI. Both in vivo and in vitro, rhFGF21 upregulated TJ and AJ proteins, thereby preserving the BBB. Moreover, rhFGF21 activated PPARγ in TNF-α-induced HBMECs through formation of an FGF21/FGFR1/β-klotho complex. rhFGF21 protected the BBB through FGF21/FGFR1/β-klotho complex formation and PPARγ activation, which upregulated TJ and AJ proteins.

Combined Rosiglitazone and Forskolin Have Neuroprotective Effects in SD Rats after Spinal Cord Injury

The peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist rosiglitazone inhibits NF-κB expression and endogenous neural stem cell differentiation into neurons and reduces the inflammatory cascade after spinal cord injury (SCI). The aim of this study was to explore the mechanisms underlying rosiglitazone-mediated neuroprotective effects and regulation of the balance between the inflammatory cascade and generation of endogenous spinal cord neurons by using a spinal cord-derived neural stem cell culture system as well as SD rat SCI model. Activation of PPAR-γ could promote neural stem cell proliferation and inhibit PKA expression and neuronal formation in vitro. In the SD rat SCI model, the rosiglitazone + forskolin group showed better locomotor recovery compared to the rosiglitazone and forskolin groups. MAP2 expression was higher in the rosiglitazone + forskolin group than in the rosiglitazone group, NF-κB expression was lower in the rosiglitazone + forskolin group than in the forskolin group, and NeuN expression was higher in the rosiglitazone + forskolin group than in the forskolin group. PPAR-γ activation likely inhibits NF-κB, thereby reducing the inflammatory cascade, and PKA activation likely promotes neuronal cell regeneration.

Bazedoxifene and raloxifene protect neocortical neurons undergoing hypoxia via targeting ERα and PPAR-γ

Selective estrogen receptor modulators (SERMs) such as bazedoxifene and raloxifene are recognized to mainly act via estrogen receptors (ERs), but there is no study examining the involvement of PPAR-γ in their actions, especially in neurons undergoing hypoxia. Little is also known about age-dependent actions of the SERMs on neuronal tissue challenged with hypoxia. In this study, bazedoxifene and raloxifene protected neocortical cells against hypoxia at early and later developmental stages. Both SERMs evoked caspase-3-independent neuroprotection and increased protein levels of ERα (66 and 46 kDa isoforms) and PPAR-γ. In addition, bazedoxifene enhanced expression of ERα-regulated Cyp19a1 mRNA. Using double siRNA silencing, for the first time we demonstrated a key role of ERα and PPAR-γ in the neuroprotective action of the SERMs in neocortical neurons undergoing hypoxia. This study provides prospects for the development of a new therapeutic strategies against hypoxic brain injury that selectively target ERα and/or PPAR-γ.

Emodin Inhibition of Influenza A Virus Replication and Influenza Viral Pneumonia via the Nrf2, TLR4, p38/JNK and NF-kappaB Pathways

Lasting activations of toll-like receptors (TLRs), MAPK and NF-κB pathways can support influenza A virus (IAV) infection and promote pneumonia. In this study, we have investigated the effect and mechanism of action of emodin on IAV infection using qRT-PCR, western blotting, ELISA, Nrf2 luciferase reporter, siRNA and plaque inhibition assays. The results showed that emodin could significantly inhibit IAV (ST169, H1N1) replication, reduce IAV-induced expressions of TLR2/3/4/7, MyD88 and TRAF6, decrease IAV-induced phosphorylations of p38/JNK MAPK and nuclear translocation of NF-κB p65. Emodin also activated the Nrf2 pathway, decreased ROS levels, increased GSH levelss and GSH/GSSG ratio, and upregulated the activities of SOD, GR, CAT and GSH-Px after IAV infection. Suppression of Nrf2 via siRNA markedly blocked the inhibitory effects of emodin on IAV-induced activations of TLR4, p38/JNK, and NF-κB pathways and on IAV-induced production of IL-1β, IL-6 and expression of IAV M2 protein. Emodin also dramatically increased the survival rate of mice, reduced lung edema, pulmonary viral titer and inflammatory cytokines, and improved lung histopathological changes. In conclusion, emodin can inhibit IAV replication and influenza viral pneumonia, at least in part, by activating Nrf2 signaling and inhibiting IAV-induced activations of the TLR4, p38/JNK MAPK and NF-κB pathways.

Peroxisome proliferator-activated receptor γ (PPARγ): A master gatekeeper in CNS injury and repair

Peroxisome proliferator-activated receptor γ (PPARγ) is a widely expressed ligand-modulated transcription factor that governs the expression of genes involved in inflammation, redox equilibrium, trophic factor production, insulin sensitivity, and the metabolism of lipids and glucose. Synthetic PPARγ agonists (e.g. thiazolidinediones) are used to treat Type II diabetes and have the potential to limit the risk of developing brain injuries such as stroke by mitigating the influence of comorbidities. If brain injury develops, PPARγ serves as a master gatekeeper of cytoprotective stress responses, improving the chances of cellular survival and recovery of homeostatic equilibrium. In the acute injury phase, PPARγ directly restricts tissue damage by inhibiting the NFκB pathway to mitigate inflammation and stimulating the Nrf2/ARE axis to neutralize oxidative stress. During the chronic phase of acute brain injuries, PPARγ activation in injured cells culminates in the repair of gray and white matter, preservation of the blood-brain barrier, reconstruction of the neurovascular unit, resolution of inflammation, and long-term functional recovery. Thus, PPARγ lies at the apex of cell fate decisions and exerts profound effects on the chronic progression of acute injury conditions. Here, we review the therapeutic potential of PPARγ in stroke and brain trauma and highlight the novel role of PPARγ in long-term tissue repair. We describe its structure and function and identify the genes that it targets. PPARγ regulation of inflammation, metabolism, cell fate (proliferation/differentiation/maturation/survival), and many other processes also has relevance to other neurological diseases. Therefore, PPARγ is an attractive target for therapies against a number of progressive neurological disorders.

BIRC5 is a novel target of peroxisome proliferator‑activated receptor γ in brain microvascular endothelium cells during cerebral ischemia

Cerebral ischemia is a leading cause of ischemic stroke, which may lead to severe disability and mortality worldwide. There are some key factors concerned in cardioprotection, such as peroxisome proliferator-activated receptor γ (PPARγ), a ligand binding transcription factor involved in various biological functions including atherosclerosis, vascular dysfunction and hypertension, and baculoviral IAP repeat-containing 5 (BIRC5), which may protect human brain endothelial cells from ischemia-induced apoptosis. To determine the potential roles of PPARγ in brain microvascular endothelial (bEnd.3) cells during cerebral ischemia and the relationship between PPARγ and BIRC5, a cerebral ischemia model was established with bEnd.3 cells cells by oxygen-glucose deprivation (OGD) treatment. OGD treatment reduced proliferation and enhanced apoptosis of bEnd.3 cells in a time-dependent manner. PPARγ expression levels were decreased in bEnd.3 cells following OGD treatment. Upregulation of PPARγ expression protected bEnd.3 cells from ischemia injury and also upregulated BIRC5 expression. PPARγ-specific binding sites in the BIRC5 promoter were predicted bioinformatically and verified by luciferase reporter experiments. Results from electrophoretic mobility shift/supershift and chromatin immunoprecipitation assays suggested that BIRC5 may be a novel target of PPARγ transcriptional regulation during ischemic injury. The present results indicated that PPARγ may serve a protective role on bEnd.3 cells and that BIRC5 may be a downstream target of PPARγ regulation during cerebral ischemia.

MicroRNA-27a-3p suppression of peroxisome proliferator-activated receptor-γ contributes to cognitive impairments resulting from sevoflurane treatment

Sevoflurane is the most widely used anaesthetic administered by inhalation. Exposure to sevoflurane in neonatal mice can induce learning deficits and abnormal social behaviours. MicroRNA (miR)-27a-3p, a short, non-coding RNA that functions as a tumour suppressor, is up-regulated after inhalation of anaesthetic, and peroxisome proliferator-activated receptor γ (PPAR-γ) is one of its target genes. The objective of this study was to investigate how the miR-27a-3p-PPAR-γ interaction affects sevoflurane-induced neurotoxicity. A luciferase reporter assay was employed to identify the interaction between miR-27a-3p and PPAR-γ. Primary hippocampal neuron cultures prepared from embryonic day 0 C57BL/6 mice were treated with miR-27a-3p inhibitor or a PPAR-γ agonist to determine the effect of miR-27a-3p and PPAR-γ on sevoflurane-induced cellular damage. Cellular damage was assessed by a flow cytometry assay to detect apoptotic cells, immunofluorescence to detect reactive oxygen species, western blotting to detect NADPH oxidase 1/4 and ELISA to measure inflammatory cytokine levels. In vivo experiments were performed using a sevoflurane-induced anaesthetic mouse model to analyse the effects of miR-27a-3p on neurotoxicity by measuring the number of apoptotic neurons using the Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) method and learning and memory function by employing the Morris water maze test. Our results revealed that PPAR-γ expression was down-regulated by miR-27a-3p following sevoflurane treatment in hippocampal neurons. Down-regulation of miR-27a-3p expression decreased sevoflurane-induced hippocampal neuron apoptosis by decreasing inflammation and oxidative stress-related protein expression through the up-regulation of PPAR-γ. In vivo tests further confirmed that inhibition of miR-27a-3p expression attenuated sevoflurane-induced neuronal apoptosis and learning and memory impairment. Our findings suggest that down-regulation of miR-27a-3p expression ameliorated sevoflurane-induced neurotoxicity and learning and memory impairment through the PPAR-γ signalling pathway. MicroRNA-27a-3p may, therefore, be a potential therapeutic target for preventing or treating sevoflurane-induced neurotoxicity.

Clinacanthus nutans Mitigates Neuronal Apoptosis and Ischemic Brain Damage Through Augmenting the C/EBPβ-Driven PPAR-γ Transcription

Clinacanthus nutans Lindau (C. nutans) is a traditional herbal medicine widely used in Asian countries for treating a number of remedies including snake and insect bites, skin rashes, viral infections, and cancer. However, the underlying molecular mechanisms for its action and whether C. nutans can offer protection on stroke damage in brain remain largely unknown. In the present study, we demonstrated protective effects of C. nutans extract to ameliorate neuronal apoptotic death in the oxygen-glucose deprivation model and to reduce infarction and mitigate functional deficits in the middle cerebral artery occlusion model, either administered before or after hypoxic/ischemic insult. Using pharmacological antagonist and siRNA knockdown approaches, we demonstrated ability for C. nutans extract to protect neurons and ameliorate ischemic injury through promoting the anti-apoptotic activity of peroxisome proliferator-activated receptor-gamma (PPAR-γ), a stress-induced transcription factor. Reporter and chromatin immunoprecipitation promoter analysis further revealed C. nutans extract to selectively increase CCAAT/enhancer binding protein (C/EBP)β binding to specific C/EBP binding site (-332~-325) on the PPAR-γ promoter to augment its transcription. In summary, we report a novel transcriptional activation involving C/EBPβ upregulation of PPAR-γ expression to suppress ischemic neuronal apoptosis and brain infarct. Recognition of C. nutans to enhance the C/EBPβ → PPAR-γ neuroprotective signaling pathway paves a new way for future drug development for prevention and treatment of ischemic stroke and other neurodegenerative diseases.

Exosomes: A Rising Star in Falling Hearts

Although exosomes were previously recognized as a mechanism for discharging useless cellular components, growing evidence has elucidated their roles in conveying information between cells. They contribute to cell-cell communication by carrying nucleic acids, proteins and lipids that can, in turn, regulate behavior of the target cells. Recent research suggested that exosomes extensively participate in progression of diverse cardiovascular diseases (CVDs), such as myocardial infarction, cardiomyopathy, pulmonary arterial hypertension and others. Here, we summarize effects of exosome-derived molecules (mainly microRNAs and proteins) on cardiac function, to examine their potential applications as biomarkers or therapeutics in CVDs.

Identification of Differentially Expressed Micrornas Associate with Glucose Metabolism in Different Organs of Blunt Snout Bream (Megalobrama amblycephala)

Blunt snout bream (Megalobrama amblycephala) is a widely favored herbivorous fish species and is a frequentlyused fish model for studying the metabolism physiology. This study aimed to provide a comprehensive illustration of the mechanisms of a high-starch diet (HSD) induced lipid metabolic disorder by identifying microRNAs (miRNAs) controlled pathways in glucose and lipid metabolism in fish using high-throughput sequencing technologies. Small RNA libraries derived from intestines, livers, and brains of HSD and normal-starch diet (NSD) treated M. amblycephala were sequenced and 79, 124 and 77 differentially expressed miRNAs (DEMs) in intestines, livers, and brains of HSD treated fish were identified, respectively. Bioinformatics analyses showed that these DEMs targeted hundreds of predicted genes were enriched into metabolic pathways and biosynthetic processes, including peroxisome proliferator-activated receptor (PPAR), glycolysis/gluconeogenesis, and insulin signaling pathway. These analyses confirmed that miRNAs play crucial roles in glucose and lipid metabolism related to high wheat starch treatment. These results provide information on further investigation of a DEM-related mechanism dysregulated by a high carbohydrate diet.

Mangiferin protects against ‭intestinal ischemia/reperfusion-induced ‭liver injury: ‬‬Involvement of PPAR-‭γ, GSK-3β and Wnt/β-catenin pathway‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬

AIM

Mangiferin (MF), a xanthonoid from Mangifera indica, possesses anti-inflammatory, immunomodulatory, and potent antioxidant effects; however, its protective effect against mesenteric ischemia/reperfusion (I/R)-induced liver injury has not been fully clarified. The study was designed to assess the possible mechanism of action of MF against mesenteric I/R model.

MAIN METHODS

Male Wister rats were treated with MF (20mg/kg, i.p) or the vehicle for 3 days before I/R, which was induced by clamping the superior mesenteric artery for 30min followed by declamping for 60min.

KEY FINDINGS

The mechanistic studies revealed that MF protected the 2 organs studied, viz., liver and intestine partly via increasing the content of β-catenin and PPAR-γ along with decreasing that of GSK-3β and the phosphorylated NF-қB-p65. MF antioxidant effect was evidenced by increasing contents of total antioxidant capacity and GST, besides normalizing that of MDA. Regarding the anti-inflammatory effect, MF reduced IL-1β and IL-6, effects that were mirrored on the tissue content of MPO. Moreover, MF possessed anti-apoptotic character evidenced by elevating Bcl-2 content and reducing that of caspase-3. In the serum, intestinal I/R increased the activity of ALT, AST, and creatine kinase.

SIGNIFICANCE

The intimated protective mechanisms of MF against mesenteric I/R are mediated, partially, by modulation of oxidative stress, inflammation, and apoptosis possibly via the involvement of Wnt/β-catenin/NF-қβ/ PPAR-γ signaling pathways.