PPAR agonists for the treatment of neuroinflammatory diseases

The expression of insulin signaling and N-methyl-D-aspartate receptor genes in areas of gray matter atrophy is associated with cognitive function in type 2 diabetes

Type 2 diabetes (T2DM) is associated with brain abnormalities and cognitive dysfunction, including increased risk for Alzheimer's disease. However, the mechanisms of T2DM-related dementia remain poorly understood. We obtained retrospective data from the Mayo Clinic Study of Aging for 271 individuals with T2DM and 542 demographically matched non-diabetic controls (age 51-89, 62% male). We identified regions of significant gray matter atrophy in the T2DM group and then determined which genes were significantly expressed in these brain regions using imaging transcriptomics. We selected 15 candidate genes involved in insulin signaling, lipid metabolism, amyloid processing, N-methyl-D-aspartate-mediated neurotransmission, and calcium signaling. The T2DM group demonstrated significant gray matter atrophy in regions of the default mode, frontal-parietal, and sensorimotor networks (p < 0.05 cluster threshold corrected for false discovery rate, FDR). IRS1, AKT1, PPARG, PRKAG2 , and GRIN2B genes were significantly expressed in these same regions (R 2 > 0.10, p < 0.03, FDR corrected). Bayesian network analysis indicated significant directional paths among all 5 genes as well as the Clinical Dementia Rating score. Directional paths among genes were significantly altered in the T2DM group (Structural Hamming Distance = 12, p = 0.004), with PPARG expression becoming more important in the context of T2DM-related pathophysiology. Alterations of brain transcriptome patterns occurred in the absence of significant cognitive deficit or amyloid accumulation, potentially representing an early biomarker of T2DM-related dementia.

Cannabidiol reduces neuropathic pain and cognitive impairments through activation of spinal PPARγ

The purpose of this study was to evaluate the participation of spinal peroxisome proliferator-activated receptor gamma (PPARγ) in the antiallodynic effect of cannabidiol, the expression of PPARγ in sites relevant to the spinal nociceptive processing, and the effect of this cannabinoid on cognitive deficits induced by neuropathic pain in female mice. Either acute or repeated treatment with cannabidiol reduced tactile allodynia and spontaneous pain (flinching) in female neuropathic mice. Cannabidiol induced a greater effect in female mice. Pioglitazone partially reduced tactile allodynia, and this effect was fully blocked by the PPARγ antagonist GW9662. Likewise, intrathecal injection of cannabidiol reduced tactile allodynia, while PPARγ antagonist GW9662 or 5-HT1A receptor antagonist WAY-100635, but not the PPARα antagonist GW6479, partially prevented this effect. GW9662 and WAY-100635 administrated per se did not modify tactile allodynia in neuropathic female mice. Co-administration of GW9662 and WAY-100635 fully prevented the antiallodynic effect of cannabidiol in mice. Nerve injury up-regulated PPARγ expression at the spinal cord and dorsal root ganglia, while cannabidiol further enhanced nerve injury-induced up-regulation of PPARγ expression in both tissues. Repeated intrathecal injection of cannabidiol reduced tactile allodynia and several pain makers (ERK, p-ERK, p38MAPK and p-p38MAPK). In addition, this treatment restored nerve injury-induced interleukin-10 down-regulation and increased PPARγ expression at the spinal cord. Repeated treatment with cannabidiol also improved nerve injury-induced cognitive impairment in mice. These results provide compelling evidence for the involvement of PPARγ in the antiallodynic effect of cannabidiol in mice and highlight its multifaceted therapeutic potential in neuropathic pain management and its comorbidities. PERSPECTIVE: The present study reveals cannabidiol's dual effects in female mice by reducing neuropathic pain through spinal PPARγ and 5-HT1A receptor activation and ameliorating nerve injury-induced cognitive impairment. These findings may assist clinicians seeking new therapeutic approaches for managing neuropathic pain and its associated cognitive deficits.

Design, synthesis, and biological evaluation of imidazolidinone derivatives as potent PPARα/δ agonists for the treatment of cholestatic liver diseases

Cholestatic liver disease (CLD) represents a significant and growing public health concern, and there is a lack of effective therapeutic drug in clinical practice. Peroxisome proliferator-activator receptors α/δ (PPARα/δ) are regarded as potential therapeutic targets for CLD. In this study, a series of novel imidazolidinone PPARα/δ agonists were developed, and the preferred compound 8 displayed potent and well-balanced agonistic activity. Compound 8 showed high selectivity over other related nuclear receptors and effectively regulated the PPARα/δ target genes expression in mice. Notably, compound 8 demonstrated good pharmacokinetic profiles and potent in vivo anti-CLD effects. Collectively, compound 8 holds promise for developing an anti-CLD agent.

Nicotinamide adenine dinucleotide alleviates neuroinflammation in rats with traumatic brain injury

OBJECTIVE

To characterize the pathology and pathophysiological processes within 6 h after Traumatic brain injury (TBI) in rats, elucidate the neuroprotective effects and the underlying mechanisms of Nicotinamide Adenine Dinucleotide (NAD) in the early stage of TBI to explore the feasibility and clinical benefits of applying NAD directly to the localized injury after TBI.

MATERIAL AND METHODS

54 male Sprague-Dawley (SD) rats aged 6-8 weeks were randomly assigned equally to three groups, sham-operated surgery (SO) with saline treatment (SO + Saline), TBI with saline treatment (TBI + Saline), and TBI with 10 μM NAD treatment (TBI + NAD). The whole brain tissues were collected at 1, 3, and 6 h following the procedure. Levels of biomarkers for TBI including S100β, TNF-α, occludin, PPARβ/δ were measured.

RESULTS

Significant neuroinflammation was observed in the rat brains after TBI, which peaked at 3 h following injury. Significant changes in S100β, TNF-α, PPARβ/δ, and occluding were also observed. Treatment with NAD significantly alleviated neuroinflammation at 1 h following TBI.

CONCLUSIONS

TBI caused severe neuroinflammation in rat brains, which peaked at 3 h following injury. Treatment with NAD alleviated neuroinflammation in TBI rats.

Drugs targeting peroxisome proliferator-activated receptors

The year 2024 witnessed the accelerated approvals of two peroxisome proliferator-activated receptor (PPAR) agonists for the treatment of primary biliary cholangitis (PBC). PPARs, including three isoforms (PPARα, PPARγ, and PPARδ), are therapeutic targets generating considerable debate yet also seeing significant advances in their successful targeting. Currently, selective PPAR agonists are used to manage hyperlipidemia, type 2 diabetes mellitus (T2DM), and PBC, and dual/pan-PPAR agonists have been developed to address various disorders. In this review, we summarize the PPAR agonists approved globally, and their pros and cons as therapeutic agents for various diseases, with a particular focus on those agonists marketed since 2010.

Peroxisome proliferator-activated receptors (PPARs) agonists as promising neurotherapeutics

Neurodegenerative disorders are characterized by a continuous neurons loss resulting in a wide range of pathogenesis affecting the motor impairment. Several strategies are outlined for therapeutics of synthetic and natural PPARs agonists in some neurological disorders; Parkinson's disease (PD), Alzheimer's disease (AD), Multiple sclerosis (MS), Amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). The aim of this review is to provide a recent update of the previously reported studies, and reviews dealing with the medicinal chemistry of PPARs and their agonists, and to highlight the outstanding advances in the development of both synthetic compounds including; PPARα agonists (fibrates), PPARγ agonists (thiazolidindiones), and PPARβ/δ agonists either as sole or dual acting PPAR full or pan agonists, in addition to the natural phytochemicals; acids, cannabinoids, and flavonoids for their different neuroprotection effects in the previously mentioned neurodegenerative disorders (PD, AD, MS, ALS, and HD). Moreover, this review reports the diverse pre-clinical and clinical studies of PPARs agonists in the neurodegenerative diseases via cellular, and animal models and human.

Anwulignan Alleviates Bone Cancer Pain by Modulating the PPARα/CXCR2 Signaling Pathway in the Rat Spinal Cord

AIMS

Advanced cancer patients frequently endure severe pain from bone metastases, and few effective treatments for bone cancer pain (BCP) exist. Although Anwulignan is known for its antioxidant, anti-inflammatory, and antitumor properties, its effects on BCP remain unclear. This study aims to explore the analgesic effects and mechanisms of Anwulignan on bone cancer pain.

METHODS

Western blotting and immunofluorescence assessed molecular expression and localization. X-ray, micro-CT, TRAP, and ALP staining examined bone destruction in rats. MTT, colony formation assays, and in vivo imaging analyzed tumor changes. RNA-Seq identified differentially expressed genes, validated by ChIP analysis.

RESULTS

Here, we showed that Anwulignan alleviated mechanical, thermal, and cold hypersensitivity and spontaneous pain, prevented bone destruction, and suppressed local tumor growth in rats with BCP. Furthermore, Anwulignan was firmly bound to proliferator-activated receptor alpha (PPARα), increasing its thermal stability. Intrathecal (i.t.) injection of PPARα siRNA increased pain sensitivity in naive rats, and PPARα siRNA abrogated the analgesic effect of Anwulignan in BCP model rats. Moreover, the PPARα agonist pirinixic acid reduced BCP hypersensitivity and abrogated the upregulation of CXC chemokine receptor 2 (CXCR2). Importantly, PPARα bound to the CXCR2 promoter region, and Anwulignan could reverse the reduced binding of PPARα to CXCR2 caused by BCP.

CONCLUSION

Taken together, these results indicate that Anwulignan is a potential antitumor and analgesic agent that exerts its effects via upregulation of PPARα expression to inhibit the expression of CXCR2 and could be used for treating BCP.

Effects of Sub-Chronic Exposure to Polystyrene Nanoplastics on Lipid and Antioxidant Metabolism in Sparus aurata

Nanoplastics (NPs) can cross cellular membranes and affect cellular performance. This study aims to determine the effects of polystyrene NPs (PS-NPs, 44 nm) on gilthead seabream (Sparus aurata) exposed for 14 days to 100 μg/L PS-NPs. The results show that biometric indicators (weight, length, Fulton's condition factor, and hepatosomatic index) were not affected after the experimental exposures. No significant effects were observed on white blood cell count, red blood cell count, mean corpuscular hemoglobin, or platelets compared to the control group. However, there was a significant decrease in hemoglobin concentration, hematocrit values, and mean corpuscular cell volume in fish exposed to PS-NPs. There were no significant effects on plasmatic cholesterol, triglyceride, alkaline phosphatase, or aspartate aminotransferase levels. The histological anatomy of both the gills and the intestine revealed no obvious signs of cellular damage, excessive mucous, or inflammation in the PS-NP group. The expression of transcripts related to lipid metabolism (pparα, pparβ), growth and development (igf1), detoxification (bche), and oxidative stress (sod, gpx1) were significantly downregulated in animals exposed to PS-NPs, indicating a slight impairment in lipid homeostasis and antioxidant response.

Revealing rutaecarpine's promise: A pathway to parkinson's disease relief through PPAR modulation

The pathological mechanisms of Parkinson's disease (PD) is complex, and no definitive cure currently exists. This study identified Rutaecarpine (Rut), an alkaloid extracted from natural plants, as a potential therapeutic agent for PD. To elucidate its mechanisms of action and specific effects in PD, network pharmacology, molecular docking, and experimental validation methods were employed. Our findings demonstrated the efficacy of Rut in ameliorating PD symptoms. Network pharmacology analysis indicated that Rut exerts its therapeutic effects through the PPAR signaling pathway and the lipid pathway. Molecular docking results revealed that Rut forms stable protein-ligand complexes with PPARα and PPARγ. Animal experiments showed that Rut improved motor function in PD mice, protected dopaminergic neurons, ameliorated lipid metabolism disorders, and reduced neuroinflammation. This study identified the critical molecular mechanisms and therapeutic targets of Rut in the treatment of PD, providing a theoretical foundation for future investigations into the pharmacodynamics of Rut as a potential anti-PD agent.

Network pharmacology study on the mechanism of berberine in Alzheimer's disease model

Research indicated that berberine (BBR) plays a protective role in modulating Alzheimer's disease (AD). This study aimed to explore the target genes of BBR associated with AD therapy using a network pharmacology study. Through network pharmacology analysis, two main potential target genes, β-amyloid precursor protein (APP) and peroxisome proliferator-activated receptor gamma (PPARG), of BBR for AD therapy were screened out. Further experiments demonstrated that BV2 and C8-D1A treated with BBR were decreased in the mRNA and protein expression of APP and presenilin 1 while PPARG was increased with a reduction in the NF-κB pathway. A similar result was shown in vivo. Through a network pharmacology study, this study supported that BBR played a protective role in the AD mice model via blocking APP processing and amyloid plaque formation. It also promotes PPARG expression to blockage of NF-κB pathway-mediated inflammatory response and neuroinflammation.

Metabolic reprogramming in the spinal cord drives the transition to pain chronicity

Acute injuries can progress into painful states that endure long after healing. The mechanism underlying this transition remains unclear, but metabolic adaptations to the bioenergy demands imposed by injury are plausible contributors. Here we show that peripheral injury activates AKT/mTORC1 in afferent segments of the mouse spinal cord, redirecting local core metabolism toward biomass production while simultaneously suppressing autophagy-mediated biomass reclamation. This metabolic shift supports neuroplasticity, but creates a resource bottleneck that depletes critical spinal cord nutrients. Preventing this depletion with a modified diet normalizes biomass generation and autophagy and halts the transition to chronic pain. This effect, observed across multiple pain models, requires activation of the nutrient sensors, sirtuin-1 and AMPK, as well as restoration of autophagy. The findings identify metabolic reprogramming as a key driver of the progression to pain chronicity and point to nutritional and pharmacological interventions that could prevent this progression after surgery or other physical traumas.

Recent Insights on the Role of Nuclear Receptors in Alzheimer's Disease: Mechanisms and Therapeutic Application

Nuclear receptors (NRs) are ligand-activated transcription factors that regulate a broad array of biological processes, including inflammation, lipid metabolism, cell proliferation, and apoptosis. Among the diverse family of NRs, peroxisome proliferator-activated receptors (PPARs), estrogen receptor (ER), liver X receptor (LXR), farnesoid X receptor (FXR), retinoid X receptor (RXR), and aryl hydrocarbon receptor (AhR) have garnered significant attention for their roles in neurodegenerative diseases, particularly Alzheimer's disease (AD). NRs influence the pathophysiology of AD through mechanisms such as modulation of amyloid-beta (Aβ) deposition, regulation of inflammatory pathways, and improvement of neuronal function. However, the dual role of NRs in AD progression, where some receptors may exacerbate the disease while others offer therapeutic potential, presents a critical challenge for their application in AD treatment. This review explores the functional diversity of NRs, highlighting their involvement in AD-related processes and discussing the therapeutic prospects of NR-targeting strategies. Furthermore, the key challenges, including the necessity for the precise identification of beneficial NRs, detailed structural analysis through molecular dynamics simulations, and further investigation of NR mechanisms in AD, such as tau pathology and autophagy, are also discussed. Collectively, continued research is essential to clarify the role of NRs in AD, ultimately facilitating their potential use in the diagnosis, prevention, and treatment of AD.

Targeting TCMR-associated cytokine genes for drug screening identifies PPARγ agonists as novel immunomodulatory agents in transplantation

Objective

T cell-mediated rejection (TCMR) remains a significant challenge in organ transplantation. This study aimed to define a TCMR-associated cytokine gene set and identify drugs to prevent TCMR through drug repurposing.

Methods

Gene expression profiles from kidney, heart, and lung transplant biopsies were obtained from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) between TCMR and non-TCMR groups were identified, and their intersection with cytokine-related genes yielded an 11-gene TCMR-associated cytokine gene set (TCMR-Cs). To evaluate the effectiveness of this gene set, a diagnostic predictive model was constructed using Lasso regression and multivariate logistic regression, with validation in independent datasets. Connectivity Map (CMap) analysis was employed to screen drugs targeting TCMR-Cs. Experimental validation of the identified drug was performed in vitro using T cell activation and Th1 differentiation assays, and in vivo in a mouse skin transplant model with survival analysis.

Results

The TCMR-Cs exhibited outstanding predictive performance for TCMR, achieving an AUC of 0.99 in the training cohorts and maintaining strong performance in the test cohorts. CMap analysis identified peroxisome proliferator-activated receptor gamma (PPARγ) agonists as potential therapeutic candidates. Experimental validation showed that the PPARγ agonist rosiglitazone significantly suppressed T cell activation and reduced Th1 differentiation in vitro without cytotoxic effects. The combination of rosiglitazone and rapamycin significantly prolonged graft survival.

Conclusions

This study defined a novel TCMR-associated cytokine gene set that effectively predicts TCMR and identified PPARγ agonists, which prevent TCMR and improve graft survival when combined with rapamycin.

Transcriptomic characterization of 2D and 3D human induced pluripotent stem cell-based in vitro models as New Approach Methodologies for developmental neurotoxicity testing

The safety and developmental neurotoxicity (DNT) potential of chemicals remain critically understudied due to limitations of current in vivo testing guidelines, which are low throughput, resource-intensive, and hindered by species differences that limit their relevance to human health. To address these issues, robust New Approach Methodologies (NAMs) using deeply characterized cell models are essential. This study presents the comprehensive transcriptomic characterization of two advanced human-induced pluripotent stem cell (hiPSC)-derived models: a 2D adherent and a 3D neurosphere model of human neural progenitor cells (hiNPCs) differentiated up to 21 days. Using high-throughput RNA sequencing, we compared gene expression profiles of 2D and 3D models at three developmental stages (3, 14, and 21 days of differentiation). Both models exhibit maturation towards post-mitotic neurons, with the 3D model maturing faster and showing a higher prevalence of GABAergic neurons, while the 2D model is enriched with glutamatergic neurons. Both models demonstrate broad applicability domains, including excitatory and inhibitory neurons, astrocytes, and key endocrine and especially the understudied cholinergic receptors. Comparison with human fetal brain samples confirms their physiological relevance. This study provides novel in-depth applicability insights into the temporal and dimensional aspects of hiPSC-derived neural models for DNT testing. The complementary use of these two models is highlighted: the 2D model excels in synaptogenesis assessment, while the 3D model is particularly suited for neural network formation as observed as well in previous functional studies with these models. This research marks a significant advancement in developing human-relevant, high-throughput DNT assays for regulatory purposes.

Counteracting Alzheimer's disease via normalizing neurovascular unit with a self-regulated multi-functional nano-modulator

The neurovascular unit (NVU) is highly responsible for cerebral homeostasis and its dysfunction emerges as a critical contributor to Alzheimer's disease (AD) pathology. Hence, rescuing NVU dysfunction might be a viable approach to AD treatments. Here, we fabricated a self-regulated muti-functional nano-modulator (siR/PIO@RP) that can intelligently navigate to damaged blood-brain barrier and release therapeutical cargoes for synergetic AD therapy. The resulting siR/PIO@RP enables self-regulation of its distribution in accordance with the physio/pathological state (low/high RAGE expression) of the target site via a feedback loop. siR/PIO@RP is capable of performing intricate tasks and goes beyond the capabilities of single-target therapeutic agents utilized in AD therapy, such as reducing cerebral Aβ load, relieving neuroinflammation, and alleviating the dysfunction of NVU. Overall, the current study provides proof of concept that normalizing NVU holds promise as a means of alleviating AD symptoms.

Key role of PPAR-γ-mediated suppression of the NFκB signaling pathway in rutin's antidepressant effect

BACKGROUND

Depression is a chronic and recurrent disorder with an unknown etiology. Efficacious antidepressant treatments with minimal side effects are urgently needed. Neuroinflammation may contribute to depression, as anti-inflammatory drugs have been shown to alleviate depressive symptoms in clinical practice. Rutin, a naturally occurring flavonoid derived from plants, is abundant in many antidepressant herbs, including Hemerocallis citrina Baroni. Historical Chinese medical texts, including the renowned Compendium of Materia Medica, document H. citrina Baroni as possessing antidepressant properties. Rutin, one of its primary active constituents, is recognized for its anti-inflammatory effects. Despite this, little is known about its specific target and mechanism.

METHODS

In the present study, molecular docking, and surface plasmon resonance imaging (SPRi) analysis were used to identify the special targets of rutin. Meanwhile, the potential antidepressant effects were evaluated in the chronic social defeat stress (CSDS) paradigm, an animal model of depression. Then, Western blotting, quantitative real-time polymerase chain reaction (qRT-PCR), Co-immunoprecipitation (Co-IP) as well as antagonists of PPAR-γ were utilized to investigate the mechanism underlying the antidepressant effect of rutin.

RESULTS

Both molecular docking and SPRi analysis showed high docking scores and interactions between rutin and PPAR-γ. In vivo, rutin promoted the nuclear translocation of PPAR-γ in the hippocampus of mice, inhibited NFκB-mediated inflammatory pathways, and subsequently reduced the expression of pro-inflammatory factors (e.g., iNOS, IL-6), aligning with an antidepressant effect. However, this therapeutic effect was attenuated by GW9662, a specific antagonist of PPAR-γ.

CONCLUSION

As a result of activating PPAR-γ and inhibiting NFκB pathway activation, rutin reduces neuroinflammation and exhibits an antidepressant effect. These findings shed light on the antidepressant mechanism of rutin and could be valuable for the development of new antidepressants.

Naturally Occurring Compounds Targeting Peroxisome Proliferator Receptors: Potential Molecular Mechanisms and Future Perspectives for Promoting Human Health

Background: Peroxisome-proliferator-activated receptors (PPARs) constitute nuclear transcription factors controlling gene expression associated with cell growth and proliferation, diverse proteins, lipids, and glucose metabolism, being related to several other pathophysiological states such as metabolic disorders, atherogenesis, carcinogenesis, etc. The present survey aims to analyze the natural compounds that can act as agonists for the PPAR-α, PPAR-β/δ, and PPAR-γ system targeting, highlighting how the amazing biochemical diversity of natural compounds can yield new insights into this “hotspot” of the scientific field. Methods: A narrative review was performed by searching the recent international literature for the last two decades in the most authoritative scientific databases, like PubMed, Scopus, Web of Science, and Embase, using appropriate keywords. Results: Several natural compounds and/or their synthetic derivatives can act as ligands of PPARs, stimulating their transcriptional activity and enabling their use as preventive and/or therapeutic agents for several disease states, such as inflammation, oxidative stress, metabolic disturbances, atherogenesis, and carcinogenesis. Although synthetic compounds are increasingly used as drugs to manage health problems, serious side effects have been observed, while their natural analogues exhibit only few minor side effects. Conclusions: Further clinical studies on natural compounds such as ligands of PPARs and the evaluation of the related molecular mechanisms are needed to implement an effective strategy concerning the pharmaco-technology, food chemistry, and nutrition to introduce them as part of clinical and dietary practice.

Puerarin: a hepatoprotective drug from bench to bedside

Pueraria is a time-honored food and medicinal plant, which is widely used in China. Puerarin, the main component extracted from pueraria, has a variety of pharmacological characteristics. In recent years, puerarin has received increasing attention for its significant hepatoprotective effects, such as metabolic dysfunction-associated steatotic liver disease, alcohol-related liver disease, and hepatic carcinoma. This paper explores the pharmacological effects of puerarin on various liver diseases through multiple mechanisms, including inflammation factors, oxidative stress, lipid metabolism, apoptosis, and autophagy. Due to its restricted solubility, pharmacokinetic studies revealed that puerarin has a low bioavailability. However, combining puerarin with novel drug delivery systems can improve its bioavailability. Meanwhile, puerarin has very low toxicity and high safety, providing a solid foundation for its further. In addition, this paper discusses puerarin's clinical trials, highlighting its unique advantages. Given its excellent pharmacological effects, puerarin is expected to be a potential drug for the treatment of various liver diseases.

TREM2-dependent activation of microglial cell protects photoreceptor cell during retinal degeneration via PPARγ and CD36

Retinal degeneration is a collection of devastating conditions with progressive loss of vision which often lead to blindness. Research on retinal microglial cells offers great therapeutic potential in deterring the progression of degeneration. This study explored the mechanisms underlying the TREM2-mediated protective function of activated microglial cells during retinal degeneration. N-methyl-N-nitrosourea (MNU)-induced retinal degeneration was established in C57BL/6 J (WT) and Trem2 knockout (Trem2-/-) mice. We discovered that MNU treatment led to the concurrent processes of photoreceptor apoptosis and microglia infiltration. A significant upregulation of disease-associated microglia signature genes was observed during photoreceptor degeneration. Following MNU treatment, Trem2-/- mice showed exacerbated photoreceptor cell death, decreased microglia migration and phagocytosis, reduced microglial PPARγ activation and CD36 expression. Pharmaceutical activation of PPARγ promoted microglial migration, ameliorated photoreceptor degeneration and restored CD36 expression in MNU-treated Trem2-/- mice. Inhibition of CD36 activity worsened photoreceptor degeneration in MNU-treated WT mice. Our findings suggested that the protective effect of microglia during retinal degeneration was dependent on Trem2 expression and carried out via the activation of PPARγ and the consequent upregulation of CD36 expression. Our study linked TREM2 signaling with PPARγ activation, and provided a potential therapeutic target for the management of retinal degeneration.

Roles of distinct nuclear receptors in diabetic cardiomyopathy

Diabetes mellitus induces a pathophysiological disorder known as diabetic cardiomyopathy and may eventually cause heart failure. Diabetic cardiomyopathy is manifested with systolic and diastolic contractile dysfunction along with alterations in unique cardiomyocyte proteins and diminished cardiomyocyte contraction. Multiple mechanisms contribute to the pathology of diabetic cardiomyopathy, mainly including abnormal insulin metabolism, hyperglycemia, glycotoxicity, cardiac lipotoxicity, endoplasmic reticulum stress, oxidative stress, mitochondrial dysfunction, calcium treatment damage, programmed myocardial cell death, improper Renin-Angiotensin-Aldosterone System activation, maladaptive immune modulation, coronary artery endothelial dysfunction, exocrine dysfunction, etc. There is an urgent need to investigate the exact pathogenesis of diabetic cardiomyopathy and improve the diagnosis and treatment of this disease. The nuclear receptor superfamily comprises a group of transcription factors, such as liver X receptor, retinoid X receptor, retinoic acid-related orphan receptor-α, retinoid receptor, vitamin D receptor, mineralocorticoid receptor, estrogen-related receptor, peroxisome proliferatoractivated receptor, nuclear receptor subfamily 4 group A 1(NR4A1), etc. Various studies have reported that nuclear receptors play a crucial role in cardiovascular diseases. A recently conducted work highlighted the function of the nuclear receptor superfamily in the realm of metabolic diseases and their associated complications. This review summarized the available information on several important nuclear receptors in the pathophysiology of diabetic cardiomyopathy and discussed future perspectives on the application of nuclear receptors as targets for diabetic cardiomyopathy treatment.

Current View on PPAR-α and Its Relation to Neurosteroids in Alzheimer's Disease and Other Neuropsychiatric Disorders: Promising Targets in a Therapeutic Strategy

Peroxisome proliferator-activated receptors (PPARs) may play an important role in the pathomechanism/pathogenesis of Alzheimer's disease (AD) and several other neurological/neuropsychiatric disorders. AD leads to progressive alterations in the redox state, ion homeostasis, lipids, and protein metabolism. Significant alterations in molecular processes and the functioning of several signaling pathways result in the degeneration and death of synapses and neuronal cells, leading to the most severe dementia. Peroxisome proliferator-activated receptor alpha (PPAR-α) is among the processes affected by AD; it regulates the transcription of genes related to the metabolism of cholesterol, fatty acids, other lipids and neurotransmission, mitochondria biogenesis, and function. PPAR-α is involved in the cholesterol transport to mitochondria, the substrate for neurosteroid biosynthesis. PPAR-α-coding enzymes, such as sulfotransferases, which are responsible for neurosteroid sulfation. The relation between PPAR-α and cholesterol/neurosteroids may have a significant impact on the course and progression of neurodegeneration/neuroprotection processes. Unfortunately, despite many years of intensive studies, the pathogenesis of AD is unknown and therapy for AD and other neurodegenerative diseases is symptomatic, presenting a significant goal and challenge today. This review presents recent achievements in therapeutic approaches for AD, which are targeting PPAR-α and its relation to cholesterol and neurosteroids in AD and neuropsychiatric disorders.

Microglial Pdcd4 deficiency mitigates neuroinflammation-associated depression via facilitating Daxx mediated PPARγ/IL-10 signaling

The dysregulation of pro- and anti-inflammatory processes in the brain has been linked to the pathogenesis of major depressive disorder (MDD), although the precise mechanisms remain unclear. In this study, we discovered that microglial conditional knockout of Pdcd4 conferred protection against LPS-induced hyperactivation of microglia and depressive-like behavior in mice. Mechanically, microglial Pdcd4 plays a role in promoting neuroinflammatory responses triggered by LPS by inhibiting Daxx-mediated PPARγ nucleus translocation, leading to the suppression of anti-inflammatory cytokine IL-10 expression. Finally, the antidepressant effect of microglial Pdcd4 knockout under LPS-challenged conditions was abolished by intracerebroventricular injection of the IL-10 neutralizing antibody IL-10Rα. Our study elucidates the distinct involvement of microglial Pdcd4 in neuroinflammation, suggesting its potential as a therapeutic target for neuroinflammation-related depression.

Roles of β-catenin in innate immune process and regulating intestinal flora in Qi river crucian carp (Carassius auratus)

In mammals, β-catenin participates in innate immune process through interaction with NF-κB signaling pathway. However, its role in teleost immune processes remains largely unknown. We aimed to clarify the function of β-catenin in the natural defense mechanism of Qi river crucian carp (Carassius auratus). β-catenin exhibited a ubiquitous expression pattern in adult fish, as indicated by real-time PCR analysis. Following lipopolysaccharide (LPS), Polyinosinic-polycytidylic acid (polyI: C) and Aeromonas hydrophila (A. hydrophila) challenges, β-catenin increased in gill, intestine, liver and kidney, indicating that β-catenin likely plays a pivotal role in the immune response against pathogen infiltration. Inhibition of the β-catenin pathway using FH535, an inhibitor of Wnt/β-catenin pathway, resulting in pathological damage of the gill, intestine, liver and kidney, significant decrease of innate immune factors (C3, defb3, LYZ-C, INF-γ), upregulation of inflammatory factors (NF-κB, TNF-α, IL-1, IL-8), and downregulation of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) activities, increase of Malondialdehyde (MDA) content. Following A. hydrophila invasion, the mortality rate in the FH535 treatment group exceeded that of the control group. In addition, the diversity of intestinal microflora decreased and the community structure was uneven after FH535 treatment. In summary, our findings strongly suggest that β-catenin plays a vital role in combating pathogen invasion and regulating intestinal flora in Qi river crucian carp.

MAPK/NF-κB signaling mediates atrazine-induced cardiorenal syndrome and antagonism of lycopene

Atrazine (ATZ) is the most prevalent herbicide that has been widely used in agriculture to control broadleaf weeds and improve crop yield and quality. The heavy use of ATZ has caused serious environmental pollution and toxicity to human health. Lycopene (LYC), is a carotenoid that exhibits numerous health benefits, such as prevention of cardiovascular diseases and nephropathy. However, it remains unclear that whether ATZ causes cardiorenal injury or even cardiorenal syndrome (CRS) and the beneficial role of LYC on it. To test this hypothesis, mice were treated with LYC and/or ATZ for 21 days by oral gavage. This study demonstrated that ATZ exposure caused cardiorenal morphological alterations, and several inflammatory cell infiltrations mediated by activating NF-κB signaling pathways. Interestingly, dysregulation of MAPK signaling pathways and MAPK phosphorylation caused by ATZ have been implicated in cardiorenal diseases. ATZ exposure up-regulated cardiac and renal injury associated biomarkers levels that suggested the occurrence of CRS. However, these all changes were reverted, and the phenomenon of CAR was disappeared by LYC co-treatment. Based on our findings, we postulated a novel mechanism to elucidate pesticide-induced CRS and indicated that LYC can be a preventive and therapeutic agent for treating CRS by targeting MAPK/NF-κB signaling pathways.