Agonism of Peroxisome Proliferator Receptor-Gamma may have Therapeutic Potential for Neuroinflammation and Parkinson's Disease

Megraw T, Ghaedi K. PPARgamma dependent PEX11beta counteracts the suppressive role of SIRT1 on neural differentiation of HESCs

The membrane peroxisomal proteins PEX11, play a crucial role in peroxisome proliferation by regulating elongation, membrane constriction, and fission of pre-existing peroxisomes. In this study, we evaluated the function of PEX11B gene in neural differentiation of human embryonic stem cell (hESC) by inducing shRNAi-mediated knockdown of PEX11B expression. Our results demonstrate that loss of PEX11B expression led to a significant decrease in the expression of peroxisomal-related genes including ACOX1, PMP70, PEX1, and PEX7, as well as neural tube-like structures and neuronal markers. Inhibition of SIRT1 using pharmacological agents counteracted the effects of PEX11B knockdown, resulting in a relative increase in PEX11B expression and an increase in differentiated neural tube-like structures. However, the neuroprotective effects of SIRT1 were eliminated by PPAR inhibition, indicating that PPARɣ may mediate the interaction between PEX11B and SIRT1. Our findings suggest that both SIRT1 and PPARɣ have neuroprotective effects, and also this study provides the first indication for a potential interaction between PEX11B, SIRT1, and PPARɣ during hESC neural differentiation.

The effects of pioglitazone and rosiglitazone on liver function in hypothyroid rats

OBJECTIVES

This study aimed to investigate the antioxidant effect of rosiglitazone (ROG) and pioglitazone (POG) on oxidative damage and dysfunction of hepatic tissue in hypothyroid rats.

METHODS

The male rats were classified into six groups: (1) Control; (2) Hypothyroid, (3) Hypothyroid-POG 10, (4) Hypothyroid-POG 20, (5) Hypothyroid-ROG 2, and (6) Hypothyroid-ROG 4. To induction hypothyroidism in rats, propylthiouracil (PTU) (0.05 %w/v) was added to drinking water. In groups 2-6, besides PTU, the rats were also intraperitoneal administrated with 10 or 20 mg/kg POG or 2 or 4 mg/kg ROG for six weeks. Finally, after deep anesthesia, the blood was collected to measure the serum biochemical markers and hepatic tissue was separated for biochemical oxidative stress markers.

RESULTS

Administration of PTU significantly reduced serum thyroxin concentration, total thiol levels, activity of superoxide dismutase (SOD) and catalase (CAT) enzymes, and increased serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (Alk-P) and malondialdehyde (MDA) in the liver. Additionally, our results showed that prescription of POG or ROG for six weeks to hypothyroid rats resulted in an improvement in liver dysfunction (decrease in serum levels of AST, ALT, and ALK-P) through reducing oxidative damage in hepatic tissue (increase in CAT, SOD, or total thiols and decrease in MDA levels).

CONCLUSIONS

The findings of the present study presented that the IP administration of POG and ROG for six weeks improves liver dysfunction induced by hypothyroidism in juvenile rats by reducing oxidative damage.

The MT1 receptor as the target of ramelteon neuroprotection in ischemic stroke

Stroke is the leading cause of death and disability worldwide. Novel and effective therapies for ischemic stroke are urgently needed. Here, we report that melatonin receptor 1A (MT1) agonist ramelteon is a neuroprotective drug candidate as demonstrated by comprehensive experimental models of ischemic stroke, including a middle cerebral artery occlusion (MCAO) mouse model of cerebral ischemia in vivo, organotypic hippocampal slice cultures ex vivo, and cultured neurons in vitro; the neuroprotective effects of ramelteon are diminished in MT1-knockout (KO) mice and MT1-KO cultured neurons. For the first time, we report that the MT1 receptor is significantly depleted in the brain of MCAO mice, and ramelteon treatment significantly recovers the brain MT1 losses in MCAO mice, which is further explained by the Connectivity Map L1000 bioinformatic analysis that shows gene-expression signatures of MCAO mice are negatively connected to melatonin receptor agonist like Ramelteon. We demonstrate that ramelteon improves the cerebral blood flow signals in ischemic stroke that is potentially mediated, at least, partly by mechanisms of activating endothelial nitric oxide synthase. Our results also show that the neuroprotection of ramelteon counteracts reactive oxygen species-induced oxidative stress and activates the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 pathway. Ramelteon inhibits the mitochondrial and autophagic death pathways in MCAO mice and cultured neurons, consistent with gene set enrichment analysis from a bioinformatics perspective angle. Our data suggest that Ramelteon is a potential neuroprotective drug candidate, and MT1 is the neuroprotective target for ischemic stroke, which provides new insights into stroke therapy. MT1-KO mice and cultured neurons may provide animal and cellular models of accelerated ischemic damage and neuronal cell death.

Dopamine in the Regulation of Glucose Homeostasis, Pathogenesis of Type 2 Diabetes, and Chronic Conditions of Impaired Dopamine Activity/Metabolism: Implication for Pathophysiological and Therapeutic Purposes

Dopamine regulates several functions, such as voluntary movements, spatial memory, motivation, sleep, arousal, feeding, immune function, maternal behaviors, and lactation. Less clear is the role of dopamine in the pathophysiology of type 2 diabetes mellitus (T2D) and chronic complications and conditions frequently associated with it. This review summarizes recent evidence on the role of dopamine in regulating insular metabolism and activity, the pathophysiology of traditional chronic complications associated with T2D, the pathophysiological interconnection between T2D and chronic neurological and psychiatric disorders characterized by impaired dopamine activity/metabolism, and therapeutic implications. Reinforcing dopamine signaling is therapeutic in T2D, especially in patients with dopamine-related disorders, such as Parkinson's and Huntington's diseases, addictions, and attention-deficit/hyperactivity disorder. On the other hand, although specific trials are probably needed, certain medications approved for T2D (e.g., metformin, pioglitazone, incretin-based therapy, and gliflozins) may have a therapeutic role in such dopamine-related disorders due to anti-inflammatory and anti-oxidative effects, improvement in insulin signaling, neuroinflammation, mitochondrial dysfunction, autophagy, and apoptosis, restoration of striatal dopamine synthesis, and modulation of dopamine signaling associated with reward and hedonic eating. Last, targeting dopamine metabolism could have the potential for diagnostic and therapeutic purposes in chronic diabetes-related complications, such as diabetic retinopathy.

PPARγ activation improved learning and memory and attenuated oxidative stress in the hippocampus and cortex of aged rats

Oxidative stress has an important role in brain aging and its consequences include cognitive decline and physiological disorders. Peroxisome proliferator-activated receptor-γ (PPARγ) activation has been suggested to decrease oxidative stress. In the current research, the effect of PPARγ activation by pioglitazone(Pio) on learning, memory and oxidative stress was evaluated in aged rats. The rats were divided into five groups. In the Control group, vehicle (saline-diluted dimethyl sulfoxide (DMSO)) and saline were injected instead of Pio and scopolamine (Sco), respectively. In the Sco group, the vehicle was injected instead of Pio and the rats were injected by Sco 30 min before the behavioral tests. In the Sco-Pio 10, Sco-Pio 20, and Sco-Pio 30 groups, 10, 20, and 30 mg/kg Pio was injected and finally, the rats were injected with Sco 30 min before the behavioral tests. Morris water mater maze(MWM) and passive avoidance(PA) tests were carried out, and finally, the hippocampus and cortex were removed for biochemical assessments. The results showed that the highest dose of Pio decreased the traveling time and distance during 5 days of learning and increased the time and distance in the target area on the probe day of MWM. The highest dose of Pio also prolonged the delay time for entering the dark and total time spent in the light while decreasing the total time spent in and the number of entries into the dark in PA test. Pio especially, in the medium and highest doses, decreased MDA while increasing thiol, superoxide dismutase, and catalase in the hippocampus and cortex. It is concluded that PPARγ activation by Pio as an agonist improved learning and memory in aged rats probably by attenuating oxidative stress in the hippocampus and cortex.

Cardiovascular protective effects of PPARγ agonists in hypothyroid rats: protection against oxidative stress

Hypothyroidism disturbs redox homeostasis and takes part in cardiovascular system dysfunction. Considering antioxidant and cardio-protective effects of PPAR-γ agonists including pioglitazone (POG) and rosiglitazone (RSG), the present study was aimed to determine the effect of POG or RSG on oxidants and antioxidants indexes in the heart and aorta tissues of Propylthiouracil (PTU)-induced hypothyroid rats.

MATERIALS AND METHODS

The animals were divided into six groups: (1) Control; (2) propylthiouracil (PTU), (3) PTU-POG 10, (4) PTU-POG 20, (5) PTU-RSG 2, and (6) PTU-RSG 4. Hypothyroidism was induced in rats by giving 0.05% propylthiouracil (PTU) in drinking water for 42 days. The rats of PTU-POG 10 and PTU-POG 20 groups received 10 and 20 mg/kg POG, respectively, besides PTU, and the rats of PTU-RSG 2 and PTU-RSG 4 groups received 2 and 4 mg/kg RSG, respectively, besides PTU. The animals were sacrificed, and the serum of the rats was collected to measure thyroxine level. The heart and aorta tissues were also removed for the measurement of biochemical oxidative stress markers.

RESULTS

Hypothyroidism was induced by PTU administration, which was indicated by lower serum thyroxine levels. Hypothyroidism also was accompanied by a decrease of catalase (CAT), superoxide dismutase (SOD) activities, and thiol concentration in the heart and aorta tissues while increased level of malondialdehyde (MDA). Interestingly, administration of POG or RSG dramatically reduced oxidative damage in the heart and aorta, as reflected by a decrease in MDA and increased activities of SOD, CAT, and thiol content.

CONCLUSION

The results of this study showed that administration of POG or RSG decreased oxidative damage in the heart and aorta tissues induced by hypothyroidism in rats.

Pentoxifylline alleviates ischemic white matter injury through up-regulating Mertk-mediated myelin clearance

BACKGROUND

Vascular dementia (VAD) is the second most common type of dementia lacking effective treatments. Pentoxifylline (PTX), a nonselective phosphodiesterase inhibitor, displays protective effects in multiple cerebral diseases. In this study, we aimed to investigate the therapeutic effects and potential mechanisms of PTX in VAD.

METHODS

Bilateral common carotid artery stenosis (BCAS) mouse model was established to mimic VAD. Mouse behavior was tested by open field test, novel object recognition test, Y-maze and Morris water maze (MWM) tests. Histological staining, magnetic resonance imaging (MRI) and electron microscopy were used to define white matter integrity. The impact of PTX on microglia phagocytosis, peroxisome proliferator-activated receptors-γ (PPAR-γ) activation and Mer receptor tyrosine kinase (Mertk) expression was assessed by immunofluorescence, western blotting and flow cytometry with the application of microglia-specific Mertk knockout mice, Mertk inhibitor and PPAR-γ inhibitor.

RESULTS

Here, we found that PTX treatment alleviated cognitive impairment in novel object recognition test, Y-maze and Morris water maze tests. Furthermore, PTX alleviated white matter injury in corpus callosum (CC) and internal capsule (IC) areas as shown by histological staining and MRI analysis. PTX-treatment group presented thicker myelin sheath than vehicle group by electron microscopy. Mechanistically, PTX facilitated microglial phagocytosis of myelin debris by up-regulating the expression of Mertk in BCAS model and primary cultured microglia. Importantly, microglia-specific Mertk knockout blocked the therapeutic effects of PTX in BCAS model. Moreover, Mertk expression was regulated by the nuclear translocation of PPAR-γ. Through modulating PPAR-γ, PTX enhanced Mertk expression.

CONCLUSIONS

Collectively, our results demonstrated that PTX showed therapeutic potentials in VAD and alleviated ischemic white matter injury via modulating Mertk-mediated myelin clearance in microglia.

Role of JAK-STAT and PPAR-Gamma Signalling Modulators in the Prevention of Autism and Neurological Dysfunctions

The Janus-kinase (JAK) and signal transducer activator of transcription (STAT) signalling pathways regulate gene expression and control various factors involved in normal physiological functions such as cell proliferation, neuronal development, and cell survival. JAK activation phosphorylates STAT3 in astrocytes and microglia, and this phosphorylation has been linked to mitochondrial damage, apoptosis, neuroinflammation, reactive astrogliosis, and genetic mutations. As a regulator, peroxisome proliferator-activated receptor gamma (PPAR-gamma), in relation to JAK-STAT signalling, prevents this phosphorylation and aids in the treatment of the above-mentioned neurocomplications. Changes in cellular signalling may also contribute to the onset and progression of autism. Thus, PPAR-gamma agonist upregulation may be associated with JAK-STAT signal transduction downregulation. It may also be responsible for attenuating neuropathological changes by stimulating SOCS3 or involving RXR or SMRT, thereby reducing transcription of the various cytokine proteins and genes involved in neuronal damage. Along with JAK-STAT inhibitors, PPAR-gamma agonists could be used as target therapeutic interventions for autism. This research-based review explores the potential involvement and mutual regulation of JAK-STAT and PPAR-gamma signalling in controlling multiple pathological factors associated with autism.

Repurposing Peroxisome Proliferator-Activated Receptor Agonists in Neurological and Psychiatric Disorders

Common pathophysiological mechanisms have emerged for different neurological and neuropsychiatric conditions. In particular, mechanisms of oxidative stress, immuno-inflammation, and altered metabolic pathways converge and cause neuronal and non-neuronal maladaptative phenomena, which underlie multifaceted brain disorders. The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors modulating, among others, anti-inflammatory and neuroprotective genes in diverse tissues. Both endogenous and synthetic PPAR agonists are approved treatments for metabolic and systemic disorders, such as diabetes, fatty liver disease, and dyslipidemia(s), showing high tolerability and safety profiles. Considering that some PPAR-acting drugs permeate through the blood-brain barrier, the possibility to extend their scope from the periphery to central nervous system has gained interest in recent years. Here, we review preclinical and clinical evidence that PPARs possibly exert a neuroprotective role, thereby providing a rationale for repurposing PPAR-targeting drugs to counteract several diseases affecting the central nervous system.

Intrinsic Innate Immune Responses Control Viral Growth and Protect against Neuronal Death in an Ex Vivo Model of West Nile Virus-Induced Central Nervous System Disease

Recruitment of immune cells from the periphery is critical for controlling West Nile virus (WNV) growth in the central nervous system (CNS) and preventing subsequent WNV-induced CNS disease. Neuroinflammatory responses, including the release of proinflammatory cytokines and chemokines by CNS cells, influence the entry and function of peripheral immune cells that infiltrate the CNS. However, these same cytokines and chemokines contribute to tissue damage in other models of CNS injury. Rosiglitazone is a peroxisome proliferator-activated receptor gamma (PPARγ) agonist that inhibits neuroinflammation. We used rosiglitazone in WNV-infected ex vivo brain slice cultures (BSC) to investigate the role of neuroinflammation within the CNS in the absence of peripheral immune cells. Rosiglitazone treatment inhibited WNV-induced expression of proinflammatory chemokines and cytokines, interferon beta (IFN-β), and IFN-stimulated genes (ISG) and also decreased WNV-induced activation of microglia. These decreased neuroinflammatory responses were associated with activation of astrocytes, robust viral growth, increased activation of caspase 3, and increased neuronal loss. Rosiglitazone had a similar effect on in vivo WNV infection, causing increased viral growth, tissue damage, and disease severity in infected mice, even though the number of infiltrating peripheral immune cells was higher in rosiglitazone-treated, WNV-infected mice than in untreated, infected controls. These results indicate that local neuroinflammatory responses are capable of controlling viral growth within the CNS and limiting neuronal loss and may function to keep the virus in check prior to the infiltration of peripheral immune cells, limiting both virus- and immune-mediated neuronal damage. IMPORTANCE West Nile virus is the most common cause of epidemic encephalitis in the United States and can result in debilitating CNS disease. There are no effective vaccines or treatments for WNV-induced CNS disease in humans. The peripheral immune response is critical for protection against WNV CNS infections. We now demonstrate that intrinsic immune responses also control viral growth and limit neuronal loss. These findings have important implications for developing new therapies for WNV-induced CNS disease.

A Review of the Properties of Anthocyanins and Their Influence on Factors Affecting Cardiometabolic and Cognitive Health

The incidence of cardiovascular and metabolic diseases has increased over the last decades and is an important cause of death worldwide. An upcoming ingredient on the nutraceutical market are anthocyanins, a flavonoid subgroup, abundant mostly in berries and fruits. Epidemiological studies have suggested an association between anthocyanin intake and improved cardiovascular risk, type 2 diabetes and myocardial infarct. Clinical studies using anthocyanins have shown a significant decrease in inflammation markers and oxidative stress, a beneficial effect on vascular function and hyperlipidemia by decreasing low-density lipoprotein and increasing high-density lipoprotein. They have also shown a potential effect on glucose homeostasis and cognitive decline. This review summarizes the effects of anthocyanins in in-vitro, animal and human studies to give an overview of their application in medical prevention or as a dietary supplement.

The role of PPARγ in chemotherapy-evoked pain

Although millions of people are diagnosed with cancer each year, survival has never been greater thanks to early diagnosis and treatments. Powerful chemotherapeutic agents are highly toxic to cancer cells, but because they typically do not target cancer cells selectively, they are often toxic to other cells and produce a variety of side effects. In particular, many common chemotherapies damage the peripheral nervous system and produce neuropathy that includes a progressive degeneration of peripheral nerve fibers. Chemotherapy-induced peripheral neuropathy (CIPN) can affect all nerve fibers, but sensory neuropathies are the most common, initially affecting the distal extremities. Symptoms include impaired tactile sensitivity, tingling, numbness, paraesthesia, dysesthesia, and pain. Since neuropathic pain is difficult to manage, and because degenerated nerve fibers may not grow back and regain normal function, considerable research has focused on understanding how chemotherapy causes painful CIPN so it can be prevented. Due to the fact that both therapeutic and side effects of chemotherapy are primarily associated with the accumulation of reactive oxygen species (ROS) and oxidative stress, this review focuses on the activation of endogenous antioxidant pathways, especially PPARγ, in order to prevent the development of CIPN and associated pain. The use of synthetic and natural PPARγ agonists to prevent CIPN is discussed.

Cannabidiol as a Therapeutic Target: Evidence of its Neuroprotective and Neuromodulatory Function in Parkinson's Disease

The phytocannabinoids of Cannabis sativa L. have, since ancient times, been proposed as a pharmacological alternative for treating various central nervous system (CNS) disorders. Interestingly, cannabinoid receptors (CBRs) are highly expressed in the basal ganglia (BG) circuit of both animals and humans. The BG are subcortical structures that regulate the initiation, execution, and orientation of movement. CBRs regulate dopaminergic transmission in the nigro-striatal pathway and, thus, the BG circuit also. The functioning of the BG is affected in pathologies related to movement disorders, especially those occurring in Parkinson’s disease (PD), which produces motor and non-motor symptoms that involving GABAergic, glutamatergic, and dopaminergic neural networks. To date, the most effective medication for PD is levodopa (l-DOPA); however, long-term levodopa treatment causes a type of long-term dyskinesias, l-DOPA-induced dyskinesias (LIDs). With neuromodulation offering a novel treatment strategy for PD patients, research has focused on the endocannabinoid system (ECS), as it participates in the physiological neuromodulation of the BG in order to control movement. CBRs have been shown to inhibit neurotransmitter release, while endocannabinoids (eCBs) play a key role in the synaptic regulation of the BG. In the past decade, cannabidiol (CBD), a non-psychotropic phytocannabinoid, has been shown to have compensatory effects both on the ECS and as a neuromodulator and neuroprotector in models such as 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and reserpine, as well as other PD models. Although the CBD-induced neuroprotection observed in animal models of PD has been attributed to the activation of the CB1 receptor, recent research conducted at a molecular level has proposed that CBD is capable of activating other receptors, such as CB2 and the TRPV-1 receptor, both of which are expressed in the dopaminergic neurons of the nigro-striatal pathway. These findings open new lines of scientific inquiry into the effects of CBD at the level of neural communication. Cannabidiol activates the PPARγ, GPR55, GPR3, GPR6, GPR12, and GPR18 receptors, causing a variety of biochemical, molecular, and behavioral effects due to the broad range of receptors it activates in the CNS. Given the low number of pharmacological treatment alternatives for PD currently available, the search for molecules with the therapeutic potential to improve neuronal communication is crucial. Therefore, the investigation of CBD and the mechanisms involved in its function is required in order to ascertain whether receptor activation could be a treatment alternative for both PD and LID.

Genome Wide Analysis Points towards Subtype-Specific Diseases in Different Genetic Forms of Amyotrophic Lateral Sclerosis

Amyotropic lateral sclerosis (ALS) is a lethally progressive and irreversible neurodegenerative disease marked by apparent death of motor neurons present in the spinal cord, brain stem and motor cortex. While more and more gene mutants being established for genetic ALS, the vast majority suffer from sporadic ALS (>90%). It has been challenging, thus, to model sporadic ALS which is one reason why the underlying pathophysiology remains elusive and has stalled the development of therapeutic strategies of this progressive motor neuron disease. To further unravel these pathological signaling pathways, human induced pluripotent stem cell (hiPSCs)-derived motor neurons (MNs) from FUS- and SOD1 ALS patients and healthy controls were systematically compared to independent published datasets. Here through this study we created a gene profile of ALS by analyzing the DEGs, the Kyoto encyclopedia of Genes and Genomes (KEGG) pathways, the interactome and the transcription factor profiles (TF) that would identify altered molecular/functional signatures and their interactions at both transcriptional (mRNAs) and translational levels (hub proteins and TFs). Our findings suggest that FUS and SOD1 may develop from dysregulation in several unique pathways and herpes simplex virus (HSV) infection was among the topmost predominant cellular pathways connected to FUS and not to SOD1. In contrast, SOD1 is mainly characterized by alterations in the metabolic pathways and alterations in the neuroactive-ligand-receptor interactions. This suggests that different genetic ALS forms are singular diseases rather than part of a common spectrum. This is important for patient stratification clearly pointing towards the need for individualized medicine approaches in ALS.

Minutes of PPAR-γ agonism and neuroprotection

Peroxisome proliferator-activated receptor gamma (PPAR-γ) is one of the ligand-activated transcription factors which regulates a number of central events and considered as a promising target for various neurodegenerative disease conditions. Numerous reports implicate that PPAR-γ agonists have shown neuroprotective effects by regulating genes transcription associated with the pathogenesis of neurodegeneration. In regards, this review critically appraises the recent knowledge of PPAR-γ receptors in neuroprotection in order to hypothesize potential neuroprotective mechanism of PPAR-γ agonism in chronic neurological conditions. Of note, the PPAR-γ's interaction dynamics with PPAR-γ coactivator-1α (PGC-1α) has gained significant attention for neuroprotection. Likewise, a plethora of studies suggest that the PPAR-γ pathway can be actuated by the endogenous ligands present in the CNS and thus identification and development of novel agonist for the PPAR-γ receptor holds a vow to prevent neurodegeneration. Together, the critical insights of this review enlighten the translational possibilities of developing novel neuroprotective therapeutics targeting PPAR-γ for various neurodegenerative disease conditions.

Texture Characteristics of Horse Meat for the Elderly Based on the Enzyme Treatment

Horse meat is nutritionally adequate to the elderly, but it has a comparatively hard texture in contrast to most of the food. In practice, the meat intake in the elderly is generally bated because the relatively difficult texture of the meat can diminish mastication. Thus, strategies are being developed to produce meat products remanding detracted mastication exertion and possibly exalt ingestion and nutritional stand, in the elderly. Hence, the effects of enzymes on textural characteristics of horse meat were studied, because they have well-known favorable efficacy on the meat tenderness by causing important demotion of the myo-fibrillar protein and collagen. Four treatments namely, papain, bromelin, pepsin, and pancreatin, alongside one control were invoked to the horse meat. Their effects on the texture parameters were determined. All the above enzymatic treatments significantly reduced hardness and resilience (p<0.001). These results present opportunities to produce essential fatty acids fortified horse meat with soft texture and satisfied technological characteristics. The intake of the essential fatty acids intensified horse meat could aid the elderly to get their aimed essential fatty acid demands. Results also suggest that horse meat tenderized through enzymatic processing stand for auspicious options for the comprehension of texture-revised diets in the elderly population.

Texture Characteristics of Horse Meat for the Elderly Based on the Enzyme Treatment

Horse meat is nutritionally adequate to the elderly, but it has a comparatively hard texture in contrast to most of the food. In practice, the meat intake in the elderly is generally bated because the relatively difficult texture of the meat can diminish mastication. Thus, strategies are being developed to produce meat products remanding detracted mastication exertion and possibly exalt ingestion and nutritional stand, in the elderly. Hence, the effects of enzymes on textural characteristics of horse meat were studied, because they have well-known favorable efficacy on the meat tenderness by causing important demotion of the myo-fibrillar protein and collagen. Four treatments namely, papain, bromelin, pepsin, and pancreatin, alongside one control were invoked to the horse meat. Their effects on the texture parameters were determined. All the above enzymatic treatments significantly reduced hardness and resilience (p<0.001). These results present opportunities to produce essential fatty acids fortified horse meat with soft texture and satisfied technological characteristics. The intake of the essential fatty acids intensified horse meat could aid the elderly to get their aimed essential fatty acid demands. Results also suggest that horse meat tenderized through enzymatic processing stand for auspicious options for the comprehension of texture-revised diets in the elderly population.

PPARγ and Cognitive Performance

Recent findings have led to the discovery of many signaling pathways that link nuclear receptors with human conditions, including mental decline and neurodegenerative diseases. PPARγ agonists have been indicated as neuroprotective agents, supporting synaptic plasticity and neurite outgrowth. For these reasons, many PPARγ ligands have been proposed for the improvement of cognitive performance in different pathological conditions. In this review, the research on this issue is extensively discussed.

PPAR-γ agonist GL516 reduces oxidative stress and apoptosis occurrence in a rat astrocyte cell line

AIMS

The worldwide increase in aging population is prevalently associated with the increase of neurodegenerative diseases. Peroxisome Proliferator-Activated Receptors (PPARs) are ligand-modulated transcriptional factors which belong to the nuclear hormone receptor superfamily which regulates peroxisome proliferation. The PPAR-γ is the most extensively studied among the three isoforms and the neuroprotective effects of PPAR-γ agonists have been recently demonstrated in a variety of preclinical models of neurological disorders. The aim of the study is to biologically evaluate the neuroprotective effects of new PPAR-γ selective agonists in an in vitro model.

MAIN METHODS

CTX-TNA2 rat astrocytes were treated with G3335, a PPAR-γ antagonist, to simulate the conditions of a neurological disorder. Newly synthetized PPAR-γ selective agonists were added to the cell culture. Cytotoxicity was assessed by MTT assay, catalase activity was investigated by a colorimetric assay, Reactive Oxygen Species (ROS) production and apoptosis occurrence were measured by flow cytometry. Western blotting were performed to measure the levels of protein involved in the apoptotic pathway.

KEY FINDINGS

Four PPAR-γ agonists were selected. Among them, the GL516, a fibrate derivative, showed low cytotoxicity and proved effective in restoring the catalase activity, reducing ROS production and decreasing the apoptosis occurrence triggered by the G3335 administration. The effects of this molecule appear to be comparable to the reference compound rosiglitazone, a potent and selective PPAR-γ agonist, mainly at prolonged exposure times (96 h).

SIGNIFICANCE

Based on recent evidence, hypofunctionality of the PPAR-γ in glial cells could be present in neurodegenerative diseases and could participate in pathological mechanisms through peroxisomal damage. The fibrate derivative PPAR-γ agonist GL516 emerged as the most promising molecule of the series and could have a role in preventing the pathophysiology of neurodegenerative disorders.

Novel Trajectories of Bromocriptine Antidiabetic Action: Leptin-IL-6/ JAK2/p-STAT3/SOCS3, p-IR/p-AKT/GLUT4, PPAR-γ/Adiponectin, Nrf2/PARP-1, and GLP-1

Bromocriptine (BC), a sympatholytic dopaminergic D2 receptor agonist, has been comprehensively used in clinic to treat Parkinson’s disease (PD) and prolactinomas. Besides, BC represents a novel therapeutic option in type 2 diabetes (T2DM); however, the precise mechanisms are not completely unveiled. Hence, the objective of the current work is to clarify the potential molecular pathways of the insulin sensitizing effect of BC in the skeletal muscle of diabetic rats and to evaluate its possible interaction with sitagliptin (SG) as an add-on therapy. Here experimental model impersonates unhealthy dietary habit and T2DM was adopted, in which rats were fed high caloric diet of fat and fructose for 6 weeks followed by a single sub-diabetogenic dose of streptozotocin (STZ) (35 mg/kg; HF/Fr/STZ). Diabetic rats were treated with BC, SG at two dose levels (SG10 and SG20) and combination of BC + SG10 for 2 weeks. BC successfully corrected glucose/lipid profile, as well as leptin and GLP-1. On the muscular molecular level, BC curtailed the inflammatory signal IL-6/JAK2/p-STAT3/SOCS3, while enhanced the PPAR-γ/adiponectin signaling, resulting in activation of the insulin signaling pathway (p-IR/p-AKT/GLUT4). Moreover, BC confirmed its antioxidant capabilities by altering Nrf2 and PARP-1; the study also highlighted novel mechanisms for SG as well. On almost all tested parameters/pathways, the combination regimen surpassed each drug alone to reach a comparable level to the high dose of SG. In conclusion, our finding shed some light on novel anti-diabetic mechanisms of BC. The study also points to the potential use of BC as an adds-on to standard anti-diabetic therapies.

High fat diet feeding induced insulin resistance exacerbates 6-OHDA mediated neurotoxicity and behavioral abnormalities in rats

Some of the clinical reports suggest that insulin resistance could be a risk factor for Parkinson's disease (PD) development, however experimental data is scarce. Our previous work has suggested that insulin resistance could be an important factor that leads to diabetes associated neurodegeneration. In the present study, we evaluated whether insulin resistance is linked to PD pathology or not. For this purpose, we first standardized an animal model which could mimic the co-morbid insulin resistance and PD condition. For development of insulin resistance, we fed the male Wistar rats with high fat diet (HFD) for eight weeks, followed by 6-hydroxydopamine (6-OHDA) administration, a toxin widely used for PD induction, in medial forebrain bundle (MFB) of rats. The 6-OHDA treatment resulted in neuronal damage and loss of striatal dopamine level. This dopamine loss was correlated with impaired performance in behavioral tasks such as rotarod, narrow beam walk test and locomotor activity. Interestingly, we found that exposure to HFD exacerbated the effects of 6-OHDA on striatal dopamine loss and behavioral parameters in rats, indicating that HFD-induced insulin resistance is associated with a diminished capacity of dopaminergic neurons to cope with 6-OHDA mediated neurotoxicity. Based upon these findings, it can be suggested that HFD feeding induced insulin resistance exacerbates the PD pathology.

The Role of Nuclear Hormone Receptors in Cannabinoid Function

Since the early 2000s, evidence has been accumulating that most cannabinoid compounds interact with the nuclear hormone family peroxisome proliferator-activated receptors (PPARs). This can be through direct binding of these compounds to PPARs, metabolism of cannabinoid to other PPAR-activating chemicals, or indirect activation of PPAR through cell signaling pathways. Delivery of cannabinoids to the nucleus may be facilitated by fatty acid-binding proteins and carrier proteins. All PPAR isoforms appear to be activated by cannabinoids, but the majority of evidence is for PPARα and γ. To date, little is known about the potential interaction of cannabinoids with other nuclear hormones. At least some (but not all) of the well-known biological actions of cannabinoids including neuroprotection, antiinflammatory action, and analgesic effects are partly mediated by PPAR-activation, often in combination with activation of the more traditional target sites of action. This has been best investigated for the endocannabinoid-like compounds palmitoylethanolamide and oleoylethanolamine acting at PPARα, and for phytocannabinoids or their derivatives activation acting at PPARγ. However, there are still many aspects of cannabinoid activation of PPAR and the role it plays in the biological and therapeutic effects of cannabinoids that remain to be investigated.

Peroxisome proliferator-activated receptor-γ agonist pioglitazone reduces the development of necrotizing enterocolitis in a neonatal preterm rat model

BACKGROUND

Factors affecting innate immunity and acting as inflammatory regulators, such as the nuclear peroxisome proliferator-activated receptors (PPAR) could be crucial in the pathogenesis of necrotizing enterocolitis (NEC). We hypothesized that the PPARγ agonist pioglitazone (PIO) might be effective in preventing the development of NEC and/or reducing its severity.

METHODS

We studied preterm rats in which NEC was induced using the hypoxia-hypothermia model. The treatment group (TG; n = 30) received enteral PIO (10 mg/kg/d) for 72 h and the control group (CG; n = 30) did not. Animals were sacrificed 96 h after birth. NEC was diagnosed evaluating histological ileum changes, and mRNA levels of IL-4, IL-12, IL-6, IL-10, INF-γ, and TNF-α cytokines were measured.

RESULTS

NEC occurrence was higher in the CG (18/30; 60%) than in the TG (5/30; 16.7%) and was more severe. Proinflammatory IL-12 and INF-γ mRNA levels were significantly lower in the TG than in the CG; conversely, the anti-inflammatory IL-4 mRNA level was significantly higher in the TG than in the CG.

CONCLUSION

Our results demonstrate for the first time that PIO is effective in reducing the incidence and severity of NEC and in decreasing renal injuries in a preterm rat model.

Effects and mechanisms of docosahexaenoic acid on the generation of angiopoietin-2 by rat brain microvascular endothelial cells under an oxygen- and glucose-deprivation environment

Objective

The aim of this study was to investigate the effects of docosahexaenoic acid (DHA) on the generation of angiopoietin-2 (Ang-2) by rat brain microvascular endothelial cells under an oxygen- and glucose-deprivation environment (OGD), and its relationship, if any, with cyclooxygenase 2 (COX-2) expression.

Methods

Annexin V and propidium iodide apoptosis assay was used to detect apoptosis. Enzyme linked immunosorbent assay was used to detect Ang-2, vascular endothelial growth factor (VEGF), prostaglandin E2 (PGE2), and prostaglandin I2 (PGI2) content. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect Ang-2 and VEGF mRNA expression. Western blot was used to detect expression of COX-2 protein.

Results

DHA reduced the apoptosis rate (P = 0.026) and decreased the secretion of Ang-2, VEGF, PGE2, and PGI2 (P = 0.006, P = 0.000, P = 0.002, P = 0.004 respectively). The relative expression of Ang2 and Vegf mRNA, as well as COX-2 expression, also decreased (P = 0.000, P = 0.005, P = 0.007 respectively). These effects were antagonized by GW9662 (peroxisome proliferator-activated receptor-γ antagonist). COX-2 protein expression levels were positively correlated with Ang2 and Vegf mRNA expression levels (γ = 0.69, P = 0.038 and γ = 0.76, P = 0.032, respectively). Ang-2 and VEGF mRNA levels were positively correlated with Ang-2 (γ = 0.84, P = 0.012) and VEGF (γ = 0.71, P = 0.036) secretion levels respectively.

Conclusion

DHA reduced apoptosis induced by an OGD environment, thus decreasing Ang-2 and VEGF synthesis. This phenomenon was associated with a decrease in COX-2 protein expression, PGE2 and PGI2 secretion, and generation regulation via intracellular transcriptional pathways.

Pioglitazone rapidly reduces neuropathic pain through astrocyte and nongenomic PPARγ mechanisms

Repeated administration of peroxisome proliferator-activated receptor gamma (PPARγ) agonists reduces neuropathic pain-like behavior and associated changes in glial activation in the spinal cord dorsal horn. As PPARγ is a nuclear receptor, sustained changes in gene expression are widely believed to be the mechanism of pain reduction. However, we recently reported that a single intrathecal (i.t.) injection of pioglitazone, a PPARγ agonist, reduced hyperalgesia within 30 minutes, a time frame that is typically less than that required for genomic mechanisms. To determine the very rapid antihyperalgesic actions of PPARγ activation, we administered pioglitazone to rats with spared nerve injury and evaluated hyperalgesia. Pioglitazone inhibited hyperalgesia within 5 minutes of injection, consistent with a nongenomic mechanism. Systemic or i.t. administration of GW9662, a PPARγ antagonist, inhibited the antihyperalgesic actions of intraperitoneal or i.t. pioglitazone, suggesting a spinal PPARγ-dependent mechanism. To further address the contribution of nongenomic mechanisms, we blocked new protein synthesis in the spinal cord with anisomycin. When coadministered intrathecally, anisomycin did not change pioglitazone antihyperalgesia at an early 7.5-minute time point, further supporting a rapid nongenomic mechanism. At later time points, anisomycin reduced pioglitazone antihyperalgesia, suggesting delayed recruitment of genomic mechanisms. Pioglitazone reduction of spared nerve injury-induced increases in GFAP expression occurred more rapidly than expected, within 60 minutes. We are the first to show that activation of spinal PPARγ rapidly reduces neuropathic pain independent of canonical genomic activity. We conclude that acute pioglitazone inhibits neuropathic pain in part by reducing astrocyte activation and through both genomic and nongenomic PPARγ mechanisms.

Glitazone Treatment and Incidence of Parkinson's Disease among People with Diabetes: A Retrospective Cohort Study

BACKGROUND

Recent in vitro and animal experiments suggest that peroxisome proliferation-activated receptor gamma (PPARɣ) agonist medications, such as antidiabetic glitazone (GTZ) drugs, are neuroprotective in models of Parkinson's disease (PD). These findings have not been tested in humans. We hypothesized that individuals prescribed GTZ drugs would have a lower incidence of PD compared to individuals prescribed other treatments for diabetes.

METHODS AND FINDINGS

Using primary care data from the United Kingdom Clinical Practice Research Datalink (CPRD), we conducted a retrospective cohort study in which individuals with diabetes who were newly prescribed GTZ (GTZ-exposed group) were matched by age, sex, practice, and diabetes treatment stage with up to five individuals prescribed other diabetes treatments (other antidiabetic drug-exposed group). Patients were followed up from 1999 until the first recording of a PD diagnosis, end of observation in the database, or end of the study (1 August 2013). An incidence rate ratio (IRR) was calculated using conditional Poisson regression, adjusted for possible confounders. 44,597 GTZ exposed individuals were matched to 120,373 other antidiabetic users. 175 GTZ-exposed individuals were diagnosed with PD compared to 517 individuals in the other antidiabetic drug-exposed group. The incidence rate (IR) of PD in the GTZ-exposed group was 6.4 per 10,000 patient years compared with 8.8 per 10,000 patient years in those prescribed other antidiabetic treatments (IRR 0.72, 95% confidence interval [CI] 0.60-0.87). Adjustments for potential confounding variables, including smoking, other medications, head injury, and disease severity, had no material impact (fully adjusted IRR 0.75, 0.59-0.94). The risk was reduced in those with current GTZ prescriptions (current GTZ-exposed IRR 0.59, 0.46-0.77) but not reduced among those with past prescriptions (past GTZ-exposed IRR 0.85, 0.65-1.10). Our study only included patients with diabetes who did not have a PD diagnosis when they were first prescribed GTZ, and thus, it cannot establish whether GTZ use prevents or slows the progression of PD.

CONCLUSIONS

In patients with diabetes, a current prescription for GTZ is associated with a reduction in incidence of PD. This suggests PPAR gamma pathways may be a fruitful drug target in PD.

Pleiotropic role of PPARγ in intracerebral hemorrhage: an intricate system involving Nrf2, RXR, and NF-κB

Intracerebral hemorrhage (ICH) is a subtype of stroke involving formation of hematoma within brain parenchyma, which accounts for 8-15% of all strokes in Western societies and 20-30% among Asian populations, and has a 1-year mortality rate >50%. The high mortality and severe morbidity make ICH a major public health problem. Only a few evidence-based targeted treatments are used for ICH management, and interventions focus primarily on supportive care and comorbidity prevention. Even in patients who survive the ictus, extravasated blood (including plasma components) and subsequent intrahematoma hemolytic products trigger a series of adverse events within the brain parenchyma, leading to secondary brain injury, edema and severe neurological deficits or death. Although the hematoma in humans gradually resolves within months, full restoration of neurological function can be slow and often incomplete, leaving survivors with devastating neurological deficits. During past years, peroxisome proliferator-activated receptor gamma (PPARγ) transcription factor and its agonists received recognition as important players in regulating not only glucose and lipid metabolism (which underlies its therapeutic effect in type 2 diabetes mellitus), and more recently, as an instrumental pleiotropic regulator of antiinflammation, antioxidative regulation, and phagocyte-mediated cleanup processes. PPARγ agonists have emerged as potential therapeutic target for stroke. The use of PPARγ as a therapeutic target appears to have particularly strong compatibility toward pathogenic components of ICH. In addition to its direct genomic effect, PPARγ may interact with transcription factor, NF-κB, which may underlie many aspects of the antiinflammatory effect of PPARγ. Furthermore, PPARγ appears to regulate expression of Nrf2, another transcription factor and master regulator of detoxification and antioxidative regulation. Finally, the synergistic costimulation of PPARγ and retinoid X receptor, RXR, may play an additional role in the therapeutic modulation of PPARγ function. In this article, we outline the main components of the role of PPARγ in ICH pathogenesis.

PPAR-α agonist fenofibrate protects against the damaging effects of MPTP in a rat model of Parkinson's disease

Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). The etiology and pathogenesis of PD are still unknown, however, many evidences suggest a prominent role of oxidative stress, inflammation, apoptosis, mitochondrial dysfunction and proteosomal dysfunction. The peroxisome proliferator-activated receptor (PPAR) ligands, a member of the nuclear receptor family, have anti-inflammatory activity over a variety of rodent's models for acute and chronic inflammation. PPAR-α agonists, a subtype of the PPAR receptors, such as fenofibrate, have been shown a major role in the regulation of inflammatory processes. Animal models of PD have shown that neuroinflammation is one of the most important mechanisms involved in dopaminergic cell death. In addition, anti-inflammatory drugs are able to attenuate toxin-induced parkinsonism. In this study we evaluated the effects of oral administration of fenofibrate 100mg/kg 1h after infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the SNpc. First, we assessed the motor behavior in the open field for 24h, 7, 14 and 21 days after MPTP. Twenty-two days after surgery, the animals were tested for two-way active avoidance and forced swimming for evaluation regarding cognitive and depressive parameters, respectively. Twenty-three days after infusion of the toxin, we quantified DA and turnover and evaluated oxidative stress through the measurement of GSH (glutathione peroxidase), SOD (superoxide dismutase) and LOOH (hydroperoxide lipid). The data show that fenofibrate was able to decrease hypolocomotion caused by MPTP 24h after injury, depressive-like behavior 22 days after the toxin infusion, and also protected against decreased level of DA and excessive production of reactive oxygen species (ROS) 23 days after surgery. Thus, fenofibrate has shown a neuroprotective effect in the MPTP model of Parkinson's disease.

PPAR- γ impairment alters peroxisome functionality in primary astrocyte cell cultures

Peroxisomes provide glial cells with protective functions against the harmful effects of H2O2 on neurons and peroxisome impairment results in nervous lesions. Agonists of the γ -subtype of the Peroxisome-Proliferator-Activated-Receptors (PPAR) have been proposed as neuroprotective agents in neurodegenerative disorders. Nevertheless, the role of PPAR- γ alterations in pathophysiological mechanisms and the relevance of peroxisome functions in the PPAR- γ effects are not yet clear. In a primary cell culture of rat astrocytes, the irreversible PPAR- γ antagonist GW9662 concentration-dependently decreased the activity of catalase, the most important antioxidant defense enzyme in peroxisomes. Catalase functionality recovered in a few days and the PPAR- γ agonist rosiglitazone promoted reversal of enzymatic damage. The reversible antagonist G3335 reduced both the activity and expression of catalase in a rosiglitazone-prevented manner. G3335 reduced also the glutathione reductase expression, indicating that enzyme involved in glutathione regeneration was compromised. Neither the PPAR- α target gene Acyl-Coenzyme-A-oxidase-1 nor the mitochondrial detoxifying enzyme NADH:ubiquinone-oxidoreductase (NDFUS3) was altered by PPAR- γ inhibition. In conclusion, PPAR- γ inhibition induced impairment of catalase in astrocytes. A general decrease of the antioxidant defenses of the cell suggests that a PPAR- γ hypofunction could participate in neurodegenerative mechanisms through peroxisomal damage. This series of experiments could be a useful model for studying compounds able to restore peroxisome functionality.

Suppression of neuroinflammation in forebrain-specific Cdk5 conditional knockout mice by PPARγ agonist improves neuronal loss and early lethality

Background

Cyclin-dependent kinase 5 (Cdk5) is essential for brain development and function, and its deregulated expression is implicated in some of neurodegenerative diseases. We reported earlier that the forebrain-specific Cdk5 conditional knockout (cKO) mice displayed an early lethality associated with neuroinflammation, increased expression of the neuronal tissue-type plasminogen activator (tPA), and neuronal migration defects.

Methods

In order to suppress neuroinflammation in the cKO mice, we first treated these mice with pioglitazone, a PPARγ agonist, and analyzed its effects on neuronal loss and longevity. In a second approach, to delineate the precise role of tPA in neuroinflammation in these mice, we generated Cdk5 cKO; tPA double knockout (dKO) mice.

Results

We found that pioglitazone treatment significantly reduced astrogliosis, microgliosis, neuronal loss and behavioral deficit in Cdk5 cKO mice. Interestingly, the dKO mice displayed a partial reversal in astrogliosis, but they still died at early age, suggesting that the increased expression of tPA in the cKO mice does not contribute significantly to the pathological process leading to neuroinflammation, neuronal loss and early lethality.

Conclusion

The suppression of neuroinflammation in Cdk5 cKO mice ameliorates gliosis and neuronal loss, thus suggesting the potential beneficial effects of the PPARγ agonist pioglitazone for the treatment for neurodegenerative diseases.

Melatonin and the theories of aging: a critical appraisal of melatonin's role in antiaging mechanisms

The classic theories of aging such as the free radical theory, including its mitochondria-related versions, have largely focused on a few specific processes of senescence. Meanwhile, numerous interconnections have become apparent between age-dependent changes previously thought to proceed more or less independently. Increased damage by free radicals is not only linked to impairments of mitochondrial function, but also to inflammaging as it occurs during immune remodeling and by release of proinflammatory cytokines from mitotically arrested, DNA-damaged cells that exhibit the senescence-associated secretory phenotype (SASP). Among other effects, SASP can cause mutations in stem cells that reduce the capacity for tissue regeneration or, in worst case, lead to cancer stem cells. Oxidative stress has also been shown to promote telomere attrition. Moreover, damage by free radicals is connected to impaired circadian rhythmicity. Another nexus exists between cellular oscillators and metabolic sensing, in particular to the aging-suppressor SIRT1, which acts as an accessory clock protein. Melatonin, being a highly pleiotropic regulator molecule, interacts directly or indirectly with all the processes mentioned. These influences are critically reviewed, with emphasis on data from aged organisms and senescence-accelerated animals. The sometimes-controversial findings obtained either in a nongerontological context or in comparisons of tumor with nontumor cells are discussed in light of evidence obtained in senescent organisms. Although, in mammals, lifetime extension by melatonin has been rarely documented in a fully conclusive way, a support of healthy aging has been observed in rodents and is highly likely in humans.

Dual role of PPAR-γ in induction and expression of behavioral sensitization to cannabinoid receptor agonist WIN55,212-2

Behavioral sensitization (B.S.) is a pathophysiological animal model for stimulant-induced psychosis and addiction. Accumulated evidence indicates that inflammatory processes are involved in psychostimulants effects in the CNS. Cannabinoids like WIN55,212-2 act as potential activators of PPAR-γ and affects the inflammatory status of the CNS. The purpose of this study is to determine PPAR-γ role in induction and expression of B.S. and the coincident inflammatory responses developed by WIN55,212-2 (WIN). Using open-field test, locomotor activity was monitored in animals treated with intraperitoneal low-dose WIN single or repeated injections. Concurrent striatal COX-2 and TNF-α levels and PPAR-γ activity were determined by immunoblotting assay. Effects of concomitant chronic or acute PPAR-γ pharmacological inhibition (with GW9662) were then investigated on behavioral and biochemical variables. WIN enhanced locomotor activity and while administered chronically augmented cytosolic COX-2 and TNF-α and also PPAR-γ nuclear levels. GW9662 co-administration completely prevented the induction of sensitizing effects of chronic WIN and altered the inflammatory responses. However, the expression of B.S. was intensified with GW9662 as assessed by increased locomotion after WIN challenge following 48 h withdrawal. Neuroinflammation and locomotor excitability in animals received just a single-dose WIN were also escalated with GW9662. Our findings conclude that PPAR-γ could play different key roles during B.S. development by WIN. Although PPAR-γ is mostly known for neuroprotective and anti-inflammatory effects, our data indicate that it mediates the B.S. induction by chronic WIN. However, while the B.S. was induced, PPAR-γ could play a homeostatic role opposing the expressed B.S. escalation.

Neuroprotective effects of PPAR-γ agonist rosiglitazone in N171-82Q mouse model of Huntington's disease

Huntington's disease (HD) is a devastating genetic neurodegenerative disease caused by CAG trinucleotide expansion in the exon-1 region of the huntingtin gene. Currently, no cure is available. It is becoming increasingly apparent that mutant Huntingtin (HTT) impairs metabolic homeostasis and causes transcriptional dysregulation. The peroxisome proliferator-activated receptor gamma (PPAR-γ) is a transcriptional factor that plays a key role in regulating genes involved in energy metabolism; recent studies demonstrated that PPAR-γ activation prevented mitochondrial depolarization in cells expressing mutant HTT and attenuated neurodegeneration in various models of neurodegenerative diseases. PPAR-γ-coactivator 1α (PGC-1 α) transcription activity is also impaired by mutant HTT. We now report that the PPAR-γ agonist, rosiglitazone (RSG), significantly attenuated mutant HTT-induced toxicity in striatal cells and that the protective effect of RSG is mediated by activation of PPAR-γ. Moreover, chronic administration of RSG (10 mg/kg/day, i.p) significantly improved motor function and attenuated hyperglycemia in N171-82Q HD mice. RSG administration rescued brain derived neurotrophic factor(BDNF) deficiency in the cerebral cortex, and prevented loss of orexin-A-immunopositive neurons in the hypothalamus of N171-82Q HD mice. RSG also prevented PGC-1α reduction and increased Sirt6 protein levels in HD mouse brain. Our results suggest that modifying the PPAR-γ pathway plays a beneficial role in rescuing motor function as well as glucose metabolic abnormalities in HD.

The role of glia in α-synucleinopathies

α-Synuclein (AS)-positive inclusions are the pathological hallmark of Parkinson’s disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA), all belonging to the category of α-synucleinopathies. α-Synucleinopathies represent progressive neurodegenerative disorders characterised by increasing incidences in the population over the age of 65. The relevance of glial reactivity and dysfunction in α-synucleinopathies is highlighted by numerous experimental evidences. Glial AS inclusion pathology is prominent in oligodendroglia of MSA (glial cytoplasmic inclusions) and is a common finding in astroglial cells of PD and DLB, resulting in specific dysfunctional responses. Involvement of AS-dependent astroglial and microglial activation in neurodegenerative mechanisms, and therefore in disease initiation and progression, has been suggested. The aim of this review is to summarise and discuss the multifaceted responses of glial cells in α-synucleinopathies. The beneficial, as well as detrimental, effects of glial cells on neuronal viability are taken into consideration to draw an integrated picture of glial roles in α-synucleinopathies. Furthermore, an overview on therapeutic approaches outlines the difficulties of translating promising experimental studies into successful clinical trials targeting candidate glial pathomechanisms.

Peroxisome proliferator-activated receptor gamma (PPAR-γ) and neurodegenerative disorders

As the growth of the aging population continues to accelerate globally, increased prevalence of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and stroke, has generated substantial public concern. Unfortunately, despite of discoveries of common factors underlying these diseases, few drugs are available to effectively treat these diseases. Peroxisome proliferator-activated receptor gamma (PPAR-γ) is a ligand-activated transcriptional factor that belongs to the nuclear hormone receptor superfamily. PPAR-γ has been shown to influence the expression or activity of a large number of genes in a variety of signaling networks, including regulation of insulin sensitivity, glucose homeostasis, fatty acid oxidation, immune responses, redox balance, cardiovascular integrity, and cell fates. Recent epidemiological, preclinical animal, and clinical studies also show that PPAR-γ agonists can lower the incidence of a number of neurological disorders, despite of multiple etiological factors involved in the development of these disorders. In this manuscript, we review current knowledge on mechanisms underlying the beneficial effect of PPAR-γ in different neurodegenerative diseases, in particular, AD, PD, and stroke, and attempt to analyze common and overlapping features among these diseases. Our investigation unveiled information suggesting the ability for PPAR-γ to inhibit NF-κB-mediated inflammatory signaling at multiple sites, and conclude that PPAR-γ agonists represent a novel class of drugs for treating neuroinflammatory diseases.

PPARγ and Oxidative Stress: Con(β) Catenating NRF2 and FOXO

Peroxisome-proliferator activator receptor γ (PPARγ) is a nuclear receptor of central importance in energy homeostasis and inflammation. Recent experimental pieces of evidence demonstrate that PPARγ is implicated in the oxidative stress response, an imbalance between antithetic prooxidation and antioxidation forces that may lead the cell to apoptotic or necrotic death. In this delicate and intricate game of equilibrium, PPARγ stands out as a central player devoted to the quenching and containment of the damage and to foster cell survival. However, PPARγ does not act alone: indeed the nuclear receptor is at the point of interconnection of various pathways, such as the nuclear factor erythroid 2-related factor 2 (NRF2), Wnt/β-catenin, and forkhead box proteins O (FOXO) pathways. Here we reviewed the role of PPARγ in response to oxidative stress and its interaction with other signaling pathways implicated in this process, an interaction that emerged as a potential new therapeutic target for several oxidative-related diseases.

Glial dysfunction in the pathogenesis of α-synucleinopathies: emerging concepts

Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) are adult onset neurodegenerative disorders characterised by prominent intracellular α-synuclein aggregates (α-synucleinopathies). The glial contribution to neurodegeneration in α-synucleinopathies was largely underestimated until recently. However, brains of PD and DLB patients exhibit not only neuronal inclusions such as Lewy bodies or Lewy neurites but also glial α-synuclein aggregates. Accumulating experimental evidence in PD models suggests that astrogliosis and microgliosis act as important mediators of neurodegeneration playing a pivotal role in both disease initiation and progression. In MSA, oligodendrocytes are intriguingly affected by aberrant cytoplasmic accumulation of α-synuclein (glial cytoplasmic inclusions, Papp-Lantos bodies). Converging evidence from human postmortem studies and transgenic MSA models suggests that oligodendroglial dysfunction both triggers and exacerbates neuronal degeneration. This review summarises the wide range of responsibilities of astroglia, microglia and oligodendroglia in the healthy brain and the changes in glial function associated with ageing. We then provide a critical analysis of the role of glia in α-synucleinopathies including putative mechanisms promoting a chronically diseased glial microenvironment which can lead to detrimental neuronal changes, including cell loss. Finally, major therapeutic strategies targeting glial pathology in α-synucleinopathies as well as current pitfalls for disease-modification in clinical trials are discussed.

Pioglitazone attenuates mitochondrial dysfunction, cognitive impairment, cortical tissue loss, and inflammation following traumatic brain injury

Following traumatic brain injury (TBI) there is significant neuropathology which includes mitochondrial dysfunction, loss of cortical gray matter, microglial activation, and cognitive impairment. Previous evidence has shown that activation of the peroxisome proliferator-activated receptors (PPARs) provide neuroprotection following traumatic brain and spinal injuries. In the current study we hypothesized that treatment with the PPAR ligand Pioglitazone would promote neuroprotection following a rat controlled cortical impact model of TBI. Animals received a unilateral 1.5mm controlled cortical impact followed by administration of Pioglitazone at 10mg/kg beginning 15min after the injury and subsequently every 24h for 5days. Beginning 1day after the injury there was significant impairment in mitochondrial bioenergetic function which was attenuated by treatments with Pioglitazone at 15min and 24h (p<0.05). In an additional set of animals, cognitive function was assessed using the Morris Water Maze (MWM) and it was observed that over the course of 4days of testing the injury produced a significant increase in both latency (p<0.05) and distance (p<0.05) to the platform. Animals treated with Pioglitazone performed similarly to sham animals and did not exhibit any impairment in MWM performance. Sixteen days after the injury tissue sections through the lesion site were quantified to determine the size of the cortical lesion. Vehicle-treated animals had an average lesion size of 5.09±0.73mm(3) and treatment with Pioglitazone significantly reduced the lesion size by 55% to 2.27±0.27mm(3) (p<0.01). Co-administration of the antagonist T0070907 with Pioglitazone blocked the protective effect seen with administration of Pioglitazone by itself. Following the injury there was a significant increase in the number of activated microglia in the area of the cortex adjacent to the site of the lesion (p<0.05). Treatment with Pioglitazone prevented the increase in the number of activated microglia and no difference was observed between sham and Pioglitazone-treated animals. From these studies we conclude that following TBI Pioglitazone is capable ameliorating multiple aspects of neuropathology. These studies provide further support for the use of PPAR ligands, specifically Pioglitazone, for neuroprotection.

Insulin and Insulin-Sensitizing Drugs in Neurodegeneration: Mitochondria as Therapeutic Targets

Insulin, besides its glucose lowering effects, is involved in the modulation of lifespan, aging and memory and learning processes. As the population ages, neurodegenerative disorders become epidemic and a connection between insulin signaling dysregulation, cognitive decline and dementia has been established. Mitochondria are intracellular organelles that despite playing a critical role in cellular metabolism are also one of the major sources of reactive oxygen species. Mitochondrial dysfunction, oxidative stress and neuroinflammation, hallmarks of neurodegeneration, can result from impaired insulin signaling. Insulin-sensitizing drugs such as the thiazolidinediones are a new class of synthetic compounds that potentiate insulin action in the target tissues and act as specific agonists of the peroxisome proliferator-activated receptor gamma (PPAR-γ). Recently, several PPAR agonists have been proposed as novel and possible therapeutic agents for neurodegenerative disorders. Indeed, the literature shows that these agents are able to protect against mitochondrial dysfunction, oxidative damage, inflammation and apoptosis. This review discusses the role of mitochondria and insulin signaling in normal brain function and in neurodegeneration. Furthermore, the potential protective role of insulin and insulin sensitizers in Alzheimer´s, Parkinson´s and Huntington´s diseases and amyotrophic lateral sclerosis will be also discussed.

12/15-Lipoxygenase inhibitor baicalein suppresses PPAR gamma expression and nuclear translocation induced by cerebral ischemia/reperfusion

Accumulating evidences have demonstrated the beneficial actions of peroxisome proliferator-activated receptor gamma (PPAR gamma) in a variety of animal stroke models. Following middle cerebral artery occlusion (60 min) and 2-24 hr reperfusion in rats, we observed cerebral ischemia/reperfusion (I/R) induced up-regulation of PPAR gamma protein expression and translocation from the cytoplasm into the nucleus in a time-dependent manner. We also found that PPAR gamma agonist rosiglitazone enhanced whereas PPAR gamma antagonist GW9662 inhibited the alteration of PPAR gamma stimulated by I/R, suggesting that the changes of PPAR gamma may result from the activation by endogenous ligands. Moreover, the link between the 12/15-lipoxygenase and the production of activating ligands for PPAR gamma has been proved in various tissues. However, the relation of them in brain tissue has not been identified. We demonstrated that the I/R-induced PPAR gamma alteration was reversed by baicalein, the specific inhibitor of 12/15-lipoxygenase. Baicalein treatment significantly inhibited the up-regulation of PPAR gamma expression and, furthermore, suppressed PPAR gamma nuclear accumulation as well as maintained PPAR gamma cytoplasmic retention. Together, these results suggest that I/R induces both PPAR gamma expression and translocation, probably through the activation by endogenous ligands in a 12/15-lipoxygenase inhibitor-sensitive way.

Neuroinflammation in Parkinson's disease: a target for neuroprotection?

Parkinson's disease is characterised by a slow and progressive degeneration of dopaminergic neurons in the substantia nigra. Despite intensive research, the cause of the neuronal loss in Parkinson's disease is poorly understood. Neuroinflammatory mechanisms might contribute to the cascade of events leading to neuronal degeneration. In this Review, we describe the evidence for neuroinflammatory processes from post-mortem and in vivo studies in Parkinson's disease. We further identify the cellular and molecular events associated with neuroinflammation that are involved in the degeneration of dopaminergic neurons in animal models of the disease. Overall, available data support the importance of non-cell-autonomous pathological mechanisms in Parkinson's disease, which are mostly mediated by activated glial and peripheral immune cells. This cellular response to neurodegeneration triggers deleterious events (eg, oxidative stress and cytokine-receptor-mediated apoptosis), which might eventually lead to dopaminergic cell death and hence disease progression. Finally, we highlight possible therapeutic strategies (including immunomodulatory drugs and therapeutic immunisation) aimed at downregulating these inflammatory processes that might be important to slow the progression of Parkinson's disease.

Protective properties afforded by pioglitazone against intrastriatal LPS in Sprague-Dawley rats

We created an inflammation-induced Parkinson's disease model, where microglia activation leads to oxidative stress, mitochondrial dysfunction, and dopaminergic neurodegeneration in the substantia nigra. Pioglitazone, an agonist of peroxisome proliferator activated receptor-gamma (PPAR-gamma), can prevent these deficits and protect dopaminergic neurons. To continue exploring the effects of pioglitazone in this model we focused on the expression of PPAR-gamma, uncoupling protein 2 (UCP2), and mitoNEET. We report that intrastriatal lipopolysaccharide (LPS) increases striatal PPAR-gamma, UCP2, and mitoNEET expression, and pioglitazone attenuates these LPS-induced changes.