Phoenixin-20 Ameliorates Lipopolysaccharide-Induced Activation of Microglial NLRP3 Inflammasome

L- lactate inhibits lipopolysaccharide-induced inflammation of microglia in the hippocampus

Objective: Depression is a common psychological and physiological disease in the world, which seriously affects the quality of life of patients and families. Exercise is an economic and noninvasive antidepressant measure, which has been widely recognized and applied in daily life and clinical practice, and the related mechanism research has also been paid attention to. In recent years, a new research report pointed out that peripheral administration of L-lactate can reverse depression-like behavior in mice, which suggesting that the lactic acid produced during exercise may be one of the factors leading to antidepressant effect, but the detailed mechanism is not clear. Inflammation is the pathogenic factor of many diseases and a large number of experiments have proved that inflammation is also an important pathogenic factor leading to depression. The purpose of our experiment is to explore whether lactic acid has anti-inflammatory and antidepressant effects.Methods: Based on the LPS induced inflammatory model, animal behavior observation, protein extraction, Western blotting, immunofluorescence and other techniques were used in this experiment.Results: Lactic acid could inhibit the change of some important inflammatory factors, such as TNF-αIL-1βphospho-NF-κB (p-NF-κB) and NLRP3 inflammasome complex (NLRP3/ASC/caspase-1) induced by LPS.Conclusion: Our current research suggested that lactic acid maybe exert antiinflammatory effect by inhibiting inflammatory factors.

Phoenixin knockout mice show no impairment in fertility or differences in metabolic response to a high-fat diet, but exhibit behavioral differences in an open field test

Phoenixin (PNX) is a conserved secreted peptide that was identified 10 years ago with numerous studies published on its pleiotropic functions. PNX is associated with estrous cycle length, protection from a high-fat diet, and reduction of anxiety behavior. However, no study had yet evaluated the impact of deleting PNX in the whole animal. We sought to evaluate a mouse model lacking the PNX parent gene, small integral membrane protein 20 (Smim20), and the resulting effect on reproduction, energy homeostasis, and anxiety. We found that the Smim20 knockout mice had normal fertility and estrous cycle lengths. Consistent with normal fertility, the hypothalamii of the knockout mice showed no changes in the levels of reproduction-related genes, but the male mice had some changes in energy homeostasis-related genes, such as melanocortin receptor 4 (Mc4r). When placed on a high-fat diet, the wildtype and knockout mice responded similarly, but the male heterozygous mice gained slightly less weight. When placed in an open field test box, the female knockout mice traveled less distance in the outer zone, indicating alterations in anxiety or locomotor behavior. In summary, the homozygous knockout of PNX did not alter fertility and modestly alters a few neuroendocrine genes in response to a high-fat diet, especially in the female mice. However, it altered the behavior of mice in an open field test. PNX therefore may not be crucial for reproductive function or weight, however, we cannot rule out possible compensatory mechanisms in the knockout model. Understanding the role of PNX in physiology may ultimately lead to an enhanced understanding of neuroendocrine mechanisms involving this enigmatic peptide.

Phoenixin-20 ameliorates Sevoflurane inhalation-induced post-operative cognitive dysfunction in rats via activation of the PKA/CREB signaling

Post-operative cognitive dysfunction (POCD) is a common complication after surgery due to the usage of anesthetics, such as Sevoflurane, which severely impacts the life quality of patients. Currently, the pathogenesis of Sevoflurane-induced POCD has not been fully elucidated but is reportedly involved with oxidative stress (OS) injury and aggravated inflammation. Phoenixin-20 (PNX-20) is a PNX peptide consisting of 20 amino acids with promising inhibitory effects on OS and inflammation. Herein, we proposed to explore the potential protective function of PNX-20 on Sevoflurane inhalation-induced POCD in rats. Sprague-Dawley (SD) rats were treated with 100 ng/g PNX-20 for 7 days with or without pre-inhalation with 2.2% Sevoflurane. Markedly increased escape latency and decreased time in the target quadrant in the Morris water maze (MWM) test, and aggravated pathological changes and apoptosis in the hippocampus tissue were observed in Sevoflurane-treated rats, which were markedly attenuated by PNX-20. Furthermore, the aggravated inflammation and OS in the hippocampus observed in Sevoflurane-treated rats were notably abolished by PNX-20. Moreover, the brain-derived neurotrophic factor (BDNF), protein kinase A (PKA), and phospho-cAMP response element binding protein/cAMP response element binding protein (p-CREB/CREB) levels were markedly decreased in Sevoflurane-treated rats, which were memorably increased by PNX-20. Our results indicated that PNX-20 ameliorated Sevoflurane inhalation-induced POCD in rats via the activation of PKA/CREB signaling, which might supply a new treatment approach for POCD.

The protective effects of Phoenixin-20 in tumor necrosis factor α (TNF-α)-induced cell senescence of rheumatoid arthritis fibroblast-like synoviocytes (FLS)

Rheumatoid arthritis (RA) is an age-related joint destruction disease that markedly impacts the normal life of patients. Currently, the clinical treatment strategies are far from satisfactory with severe side effects. Cellular senescence of fibroblast-like synoviocytes (FLS) has been reported to be involved in the pathological process of arthritis, which may provide an important research direction for RA treatment. Phoenixin-20 (PNX-20) is a peptide targeting G-protein-coupled receptor 173 (GPR173) with promising anti-inflammatory properties. Our study will probe into the function of PNX-20 on tumor necrosis factor α (TNF-α)- induced rheumatoid arthritis (RA) FLS cell senescence to provide a theoretical basis for treating RA with PNX-20. RA-FLSs were handled with 10 ng/mL TNF-α, followed by introducing Phoenixin-20 (10, 20 nM) or not for 7 days. Enhanced release of inflammatory cytokines, increased proportion of senescence-associated β-galactosidase (SA-β-gal) positive cells, and declined telomerase activity were all observed in TNF-α-treated RA-FLSs, accompanied by a noticeable decline in the p21 and p53 level, which were notably reversed by 10 and 20 nM PNX-20. Furthermore, the increased signal transducer and activator of transcription 6 (STAT6) level observed in TNF-α-treated RA-FLSs were signally repressed by PNX-20. Moreover, the impact of PNX-20 on TNF-α-induced cellular senescence in RA-FLSs was abrogated by the overexpression of STAT6. Collectively, PNX-20 protected the TNF-α-induced cell senescence in RA-FLSs by downregulating STAT6. Based on these findings, we speculate that PNX-20 might be a promising agent for the treatment of RA.

Exploring the Potential Link between Acute Central Serous Chorioretinopathy and Trimethylamine N-Oxide, Phoenixin, Spexin, and Alarin Molecules

PURPOSE

Acute central serous chorioretinopathy (ACSCR) is a condition characterized by decreased visual acuity, macular thickening, and edema under the retinal layer. Although the underlying mechanisms of the disease are not fully understood, oxidative stress is considered to be a critical risk factor. The aim of this study was to shed light on the pathophysiology of ACSCR by investigating the levels of circulating trimethylamine N-oxide (TMAO), phoenixin (PNX), alarin (ALA), and spexin (SPX) molecules in ACSCR patients.

METHODS

The study included 30 ACSCR patients and 30 healthy individuals as controls. ACSCR was diagnosed using optical coherence tomography (OCT) imaging. Five mL blood samples were collected from all participants following overnight fasting. The levels of TMAO, PNX, ALA, and SPX in the blood samples were measured using the ELISA method.

RESULTS

Visual acuity was found to be significantly reduced in ACSCR patients compared to the control group (<0.05), while macular thickness was increased (<0.05). Furthermore, TMAO, PNX, and ALA levels were significantly higher in ACSCR patients (<0.05), while SPX levels were significantly lower compared to the control group (<0.05). In ACSCR patients, there was a positive correlation between macular thickness and TMAO, PNX, and ALA; there was, however, a negative correlation with SPX. Additionally, visual acuity was negatively correlated with TMAO, PNX, and ALA, while SPX levels decreased as visual acuity decreased.

CONCLUSIONS

These results demonstrate a correlation between the TMAO, PNX, ALA, and SPX levels of ACSCR patients and their visual acuity and macular thickness. Given the role of these molecules in ACSCR's pathophysiology, they hold promise as potential diagnostic, therapeutic, and follow-up markers in the future.

PNX14 but not PNX20 as a novel regulator of preadipocyte differentiation via activating Epac-ERK signaling pathway in Gallus gallus

Small integral membrane protein 20 (SMIM20) could generate two main peptides, PNX14 and PNX20, which participate in multiple biological roles such as reproduction, inflammation and energy metabolism in mammals. However, little is known about their physiological functions in non-mammalian vertebrates. Using chicken (c-) as an animal model, we found cSMIM20 was moderately expressed in adipose tissues, and its expression was gradually increased during the differentiation of chicken preadipocytes, suggesting that it may play an important role in chicken adipogenesis. Further research showed cPNX14 could facilitate the differentiation of chicken preadipocytes into mature adipocytes by enhancing expression of adipogenic genes including PPARγ, CEBPα and FABP4, and promoting the formation of lipid droplets. This pro-adipogenic effect of cPNX14 was completely attenuated by Epac-specific and ERK inhibitor. Interestingly, cPNX20 failed to regulate the adipogenic genes and lipid droplet content. Collectively, our findings reveal that cPNX14 but not cPNX20 can serve as a novel adipogenesis mediator by activating the Epac-ERK signaling pathway in chickens.

Current state of phoenixin-the implications of the pleiotropic peptide in stress and its potential as a therapeutic target

Phoenixin is a pleiotropic peptide, whose known functions have broadened significantly over the last decade. Initially first described as a reproductive peptide in 2013, phoenixin is now recognized as being implicated in hypertension, neuroinflammation, pruritus, food intake, anxiety as well as stress. Due to its wide field of involvement, an interaction with physiological as well as psychological control loops has been speculated. It has shown to be both able to actively reduce anxiety as well as being influenced by external stressors. Initial rodent models have shown that central administration of phoenixin alters the behavior of the subjects when confronted with stress-inducing situations, proposing an interaction with the perception and processing of stress and anxiety. Although the research on phoenixin is still in its infancy, there are several promising insights into its functionality, which might prove to be of value in the pharmacological treatment of several psychiatric and psychosomatic illnesses such as anorexia nervosa, post-traumatic stress disorder as well as the increasingly prevalent stress-related illnesses of burnout and depression. In this review, we aim to provide an overview of the current state of knowledge of phoenixin, its interactions with physiological processes as well as focus on the recent developments in stress response and the possible novel treatment options this might entail.

The NLRP3 inflammasome in depression: Potential mechanisms and therapies

Increasing evidence suggests that the failure of clinical antidepressants may be related with neuroinflammation. The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome is an intracellular multiprotein complex, and has been considered as a key contributor to the development of neuroinflammation. Inhibition of NLRP3 inflammasome is an effective method for depression treatment. In this review, we summarized current researches highlighting the role of NLRP3 inflammasome in the pathology of depression. Firstly, we discussed NLRP3 inflammasome activation in patients with depression and animal models. Secondly, we outlined the possible mechanisms driving the activation of NLRP3 inflammasome. Thirdly, we discussed the pathogenetic role of NLRP3 inflammasome in depression. Finally, we overviewed the current and potential antidepressants targeting the NLRP3 inflammasome. Overall, the inhibition of NLRP3 inflammasome activation may be a potential therapeutic strategy for inflammation-related depression.

Phoenixin 14 ameloriates pancreatic injury in streptozotocin-induced diabetic rats by alleviating oxidative burden

Phoenixin-14 (PNX) is a neuropeptide that has been shown to prevent oxidative damage and stimulates insulin secretion. We investigated the effects of PNX on pancreatic injury induced by streptozotocin (STZ), and nicotinamide (NAD). Male Sprague-Dawley rats, in control (C) and diabetic (STZ) groups, were treated with either saline, or PNX (0.45 nmol/kg, or 45 nmol/kg) daily for 3 days 1 week after STZ injection. Fasting blood glucose (FBG) and gastric emptying rate (GER) were measured. Tissue and blood samples were collected. PNX treatments prevented pancreatic damage and β cell loss. Increased luminol and lucigenin levels in the pancreas, ileum and liver tissues of STZ groups were alleviated by PNX treatment in pancreatic and ileal tissues. PNX0.45 decreased FBG without any change in insulin blood level and pancreatic mRNA. GER increased in all diabetic rats while PNX0.45 delayed GER only in the C group. PNX diminishes pancreatic damage and lowers FBG by reducing oxidative load.

Regulation and physiological functions of phoenixin

Phoenixin is a newly discovered neuropeptide generated from small integral membrane protein 20. Phoenixin is a ligand for the G protein-coupled receptor 173 (GPR173) and has been detected in central and peripheral tissues of human, rats, mice, bovine, and zebrafish. It was initially involved in regulating reproductive function by stimulating the luteinizing hormone release from pituitary cells by increasing the level of gonadotropin-releasing hormone. Recently, many functions of phoenixin have been generalized, including regulation of food intake, memory, Alzheimer’s disease, anxiety, inflammation, neuronal and microglial activity, energy metabolism and body fluid balance, cardiovascular function, and endocrine activity. In addition, the interaction between phoenixin and nesfatin-1 have been revealed. The present article summarized the latest research progress on physiological function of phoenixin, suggesting that it is a potential target for novel drug development and clinical application.

Investigation of serum phoenixin levels in patients with hypertension

OBJECTIVE:

Hypertension is a major modifiable risk factor for cardiovascular disease and premature death worldwide. Phoenixin is a newly identified neuropeptide with multiple bioactivity. However, there was no published data about phoenixin levels in hypertension. The aim of this study was to evaluate the relationship between phoenixin and hypertension.

METHODS:

This study was performed in 36 patients with hypertension and 36 healthy controls. Serum phoenixin-14 and phoenixin-20 levels were determined by Enzyme-Linked ImmunoSorbent Assay method.

RESULTS:

Serum phoenixin-14 and phoenixin-20 values were significantly lower in hypertension patients compared with the control group (p<0.001). The levels of phoenixin-14 were negatively correlated with weight (r=-0.376; p<0.005), body mass index (r=-0.407; p<0.001), systolic blood pressure (r=-0.586; p<0.001), and diastolic blood pressure (r=-0.319; p<0.01). There was a negative correlation between serum phoenixin-20 and weight (r=-0.378; p<0.005), body mass index (r=-0.383; p<0.005), systolic blood pressure (r=-0.551; p<0.001), and diastolic blood pressure (r=-0.306; p<0.01). We used receiver operating characteristic curve analyses to compare the diagnosis value of Phoenixin-14 and Phoenixin-20 levels in hypertensive patients. We found that Phoenixin-14 value is an area under the curve of 0.87 (cutoff value 404.7 ng/L, sensitivity 92%, specificity 72%) and Phoenixin-20 value is an area under the curve of 0.83 (cutoff value 209.9 ng/L, sensitivity 86%, specificity 75%). Phoenixin-14 did nearly show equally compared to phoenixin-20 in predicting hypertension.

CONCLUSION:

Serum phoenixin-14 and phoenixin-20 may be related to the pathogenesis of hypertension. Our findings indicated that serum phoenixin-14 and phoenixin-20 may serve as a novel biomarker for the diagnosis of hypertension.

Phoenixin-20 ameliorates brain infarction by promoting microglia M2 polarization in an ischemic stroke model

Ischemic stroke is one of the most common causes of death worldwide. The transformation of microglia from the classic M1 to the alternative M2 state has been shown to have both deleterious and immunosuppressive roles in neuroinflammation. Microglial polarization toward the M2 phase is currently proposed to be a beneficial phenotype in brain ischemic injury. Phoenixin-20 is a newly identified pleiotropic neuropeptide expressed abundantly in different brain regions. In this study, we found that administration of Phoenixin-20 in ischemic stroke middle cerebral artery occlusion (MCAO) mice significantly reduced the brain infarction area but improved the neurological deficit score. Gene expression analysis showed Phoenixin-20 treatment inhibited pro-inflammatory M1 phase microglial markers: a cluster of differentiation molecule 11b (CD11b), cluster of differentiation molecule 86 (CD86), inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), and increased anti-inflammatory M2 phase markers (found in Inflammatory Zone 1 (FIZZ1), Arginase 1 (Arg-1), Chitinase 3-like 3 (YM1), and interleukin-10 (IL-10)) in the infarcted brain. We further investigated the molecular mechanism of Phoenixin-20 in cultured microglia. We found that treatment with it induced signature genes expression in microglial M2 state, including Fizz1, Arg-1, YM1, and IL-10, indicating the promotion of microglial polarization toward the M2 state. Furthermore, we found that treatment with the M2 phase cytokine interleukin 4 (IL-4) induced the expression of microglial G Protein-Coupled Receptor (GPR173), which is the receptor of Phoenixin-20. Silencing of the microglial signal transducer and activator of transcription 6 (STAT6) partially blocked the effect of IL-4 on GPR173, suggesting that STAT6 is the upstream regulator of GPR173. Finally, we showed that the silencing of GPR173 completely abolished the effect of Phoenixin-20 in microglia, indicating the dependency of its regulatory role on GPR173. Collectively, our study demonstrates that Phoenixin-20 has a protective role in the acute stroke model. Our cell-based study demonstrates Phoenixin-20 promotes microglia toward M2 transformation, which could be the mechanism of its neuroprotection.

Tert-butylhydroquinone prevents neuroinflammation and relieves depression via regulation of NLRP3 signaling in mice

Depression is a common psychiatric disorder, which seriously affects people's health and quality of life. Current treatments, which mainly focus on neurotransmitter levels, are not effective in many patients. Recent studies have shown that neuroinflammation has certain correlation with the pathogenesis of depression. Tert-butylhydroquinone (TBHQ) is an antioxidant with an anti-inflammatory effect. The present study evaluated the effects of TBHQ on the improvement of depression-like behaviors induced by lipopolysaccharide (LPS) in mice and its possible mechanism. Behavioral test results showed that TBHQ treatment could significantly improve the depression-like behaviors of mice. Western blot results showed that TBHQ treatment inhibited the protein expression of NLRP3, Caspase-1, IL-1β, and IL-18, which induced by LPS. Immunofluorescence staining results showed that TBHQ treatment inhibited the activation of microglia induced by LPS. These results suggested that, by inhibiting LPS-induced neuroinflammation and microglia activation, TBHQ could effectively improve LPS-induced inflammation-related depression-like behavior through modulating the NLRP3 signaling pathway.

Inflammatory Stress Induced by Intraperitoneal Injection of LPS Increases Phoenixin Expression and Activity in Distinct Rat Brain Nuclei

Due to phoenixin’s role in restraint stress and glucocorticoid stress, as well as its recently shown effects on the inflammasome, we aimed to investigate the effects of lipopolysaccharide (LPS)-induced inflammatory stress on the activity of brain nuclei-expressing phoenixin. Male Sprague Dawley rats (n = 6/group) were intraperitoneally injected with either LPS or control (saline). Brains were processed for c-Fos and phoenixin immunohistochemistry and the resulting slides were evaluated using ImageJ software. c-Fos was counted and phoenixin was evaluated using densitometry. LPS stress significantly increased c-Fos expression in the central amygdaloid nucleus (CeM, 7.2-fold), supraoptic nucleus (SON, 34.8 ± 17.3 vs. 0.0 ± 0.0), arcuate nucleus (Arc, 4.9-fold), raphe pallidus (RPa, 5.1-fold), bed nucleus of the stria terminalis (BSt, 5.9-fold), dorsal motor nucleus of the vagus nerve (DMN, 89-fold), and medial part of the nucleus of the solitary tract (mNTS, 121-fold) compared to the control-injected group (p < 0.05). Phoenixin expression also significantly increased in the CeM (1.2-fold), SON (1.5-fold), RPa (1.3-fold), DMN (1.3-fold), and mNTS (1.9-fold, p < 0.05), leading to a positive correlation between c-Fos and phoenixin in the RPa, BSt, and mNTS (p < 0.05). In conclusion, LPS stress induces a significant increase in activity in phoenixin immunoreactive brain nuclei that is distinctively different from restraint stress.

Phoenixin-14 Promotes the Recovery of Neurological Dysfunction After Spinal Cord Injury by Regulating Microglial Polarization via PTEN/Akt Signaling Pathway

Spinal cord injury (SCI) is a destructive event in central nervous system (CNS) with the hallmark of deficits in neuronal function. Phoenixin-14 (PNX-14) is a reproductive peptide that also has neuroprotective effects. However, the role of PNX-14 in SCI has not yet been studied. In this study, we firstly investigated the effects of PNX-14 on the recovery of neurological dysfunction and microglial polarization in a SCI mice model. We demonstrated that PNX-14 improved the recovery of neurological dysfunction with increased Basso Mouse Scale (BMS) scores, reduced lesion area volume and Evans blue (EB) dye extravasation. PNX-14 alleviated neuronal apoptosis and neuroinflammation in mice underwent SCI. In vitro co-culture assay proved that PNX-14 protected neurons injury in response to LPS- activated BV-2 cells. PNX-14 suppressed the LPS- induced microglia M1 phenotype polarization with decreased expression of M1-associated markers (CD16 and iNOS) and increased expression of M2-associated markers (CD206 and Arg1). PNX-14 also suppressed LPS- caused decrease in anti-inflammatory cytokines TGF-β, IL-10, and IL-13, as well increase in pro-inflammatory cytokines TNF-α, IL-1β, and IL-6 in BV2 cells. PNX-14 treatment caused increased PTEN expression and decreased p-Akt expression in BV2 cells against LPS induction. While inhibition of PTEN by SF1670 reversed the effects of PNX-14 on LPS- induced phenotypic transition of BV2 cells. Taken together, we found that PNX-14 exerted protective effects on neurological dysfunction and inflammation in SCI mice through modulating microglial polarization via PTEN/Akt signaling pathway.

The Regulation of Phoenixin: A Fascinating Multidimensional Peptide

The phoenixin (PNX) peptide is linked to the control of reproduction, food intake, stress, and inflammation. However, little is known about what regulates its gene and protein expression, information that is critical to understand the physiological role of PNX. In this review, we summarize what is known about the transcriptional control of Pnx and its receptor Gpr173. A main function of PNX is as a positive regulator of the hypothalamic-pituitary-gonadal axis, but there is a lack of research on its control by reproductive hormones and peptides. PNX is also associated with food intake, and its expression is linked to feeding status, fatty acids, and glucose. It is influenced by environmental and hormonal-induced stress. The regulation of Pnx in most contexts remains an enigma, in part due to conflicting and negative results. An extensive analysis of the response of the Pnx gene to factors related to reproduction, metabolism, stress, and inflammation is required. Analysis of the Pnx promoter and epigenetic regulation must be considered to understand how this level of control contributes to its pleiotropic effects. PNX is now linked to a broad range of functions, but more research on its gene regulation is required to understand its place in overall physiology and therapeutic potential.

Phoenixin-20 ameliorates gestational diabetes mellitus (GDM) symptoms and placental insults in an experimental mouse model

BACKGROUND AND PURPOSE

Gestational diabetes mellitus (GDM) is a complication commonly observed in pregnancy, closely associated with increased oxidative stress, inflammatory response, and endoplasmic reticulum (ER) stress. Phoenixin-20 (PNX-20) is a newly reproductive hormone from the hypothalamus that has displayed pleiotropic effects. The promising inhibitory effects of PNX-20 on inflammation have recently been widely reported. The present study aims to investigate the protective effect of PNX-20 on GDM induced placental insults.

METHODS

A GDM model was established on C57BLKsJ ^db/+ mice. The expression level of GPR173 was evaluated using RT-PCR and western blotting analysis. The serum level of glucose, insulin, lipid profiles, and oxidative stress indicators were detected with commercial kits. Fetal analysis was performed to evaluate the reproductive ability. ELISA was used to detect the production of inflammatory factors. The expressions of p-eIF-2α, ATF4, and GRP78 were evaluated with western blotting assay.

RESULTS

Firstly, we found that GPR173 is expressed in the placenta tissue. Secondly, the elevated blood glucose level and lipid level, declined serum insulin level, fetus alive ratio, fetal and placenta weight, and shorten crown-rump length, were observed in the placenta tissue of GDM mice, which were reversed by treatment with PNX-20. Thirdly, the excessively released inflammatory factors and activated oxidative stress in GDM mice were alleviated by the administration of PNX-20. Lastly, the activated eIF-2α/ATF4 ER stress signaling pathway in GDM mice was dramatically suppressed by PNX-20.

CONCLUSION

Our data revealed a protective property of PNX-20 against placental insults resulted from GDM.

Diet-Induced Hypothalamic Inflammation, Phoenixin, and Subsequent Precocious Puberty

Recent studies have shown a rise in precocious puberty, especially in girls. At the same time, childhood obesity due to overnutrition and energy imbalance is rising too. Nutrition and fertility are currently facing major challenges in our societies, and are interconnected. Studies have shown that high-fat and/or high-glycaemic-index diet can cause hypothalamic inflammation and microglial activation. Molecular and animal studies reveal that microglial activation seems to produce and activate prostaglandins, neurotrophic factors activating GnRH (gonadotropin-releasing hormone expressing neurons), thus initiating precocious puberty. GnRH neurons’ mechanisms of excitability are not well understood. In this review, we study the phenomenon of the rise of precocious puberty, we examine the physiology of GnRH neurons, and we review the recent literature regarding the pathophysiological mechanisms that connect diet-induced hypothalamic inflammation and diet-induced phoenixin regulation with precocious puberty.

Role of the Novel Peptide Phoenixin in Stress Response and Possible Interactions with Nesfatin-1

The novel peptide phoenixin was shown to be involved in several physiological processes ranging from reproduction to food intake. Interest in this protein has steadily increased over the last few years and its known implications have become much broader, playing a role in glucose homeostasis, anxiety, nociception, and pruritus. Phoenixin is expressed in a multitude of organs such as the small intestine, pancreas, and in the hypothalamus, as well as several other brain nuclei influencing numerous physiological functions. Its highly conserved amino-acid sequence amongst species leads to the assumption, that phoenixin might be involved in essential physiological functions. Its co-expression and opposing functionality to the extensively studied peptide nesfatin-1 has given rise to the idea of a possible counterbalancing role. Several recent publications focused on phoenixin’s role in stress reactions, namely restraint stress and lipopolysaccharide-induced inflammation response, in which also nesfatin-1 is known to be altered. This review provides an overview on the phoenixins and nesfatin-1 properties and putative effects, and especially highlights the recent developments on their role and interaction in the response to response.

Tripartite-motif protein 21 knockdown extenuates LPS-triggered neurotoxicity by inhibiting microglial M1 polarization via suppressing NF-κB-mediated NLRP3 inflammasome activation

Tripartite motif-containing 21 (TRIM21) has been confirmed to mediate the production of inflammatory mediators via NF-κB signaling. However, the function of TRIM21 in microglia-mediated neuroinflammation remains unclear. This study aimed to explore the effect of TRIM21 on LPS-activated BV2 microglia and its underlying mechanism. BV2 cells exposed to lipopolysaccharide (LPS) were used to simulated neuroinflammation in vitro. Loss-of-function and gain-of-function of TRIM21 in BV2 cells were used to assess the effect of TRIM21 on LPS-induced neuroinflammation. BV2 microglia and HT22 cells co-culture system were used to investigate whether TRIM21 regulated neuronal inflammation-mediated neuronal death. TRIM21 knockdown triggered the polarization of BV2 cells from M1 to M2 phenotype. Knockdown of TRIM21 reduced the secretion of TNF-α, IL-6, and IL-1β, while increased the content of IL-4 in LPS-treated cells. Knockdown of TRIM21 inhibited the expression of p65 and the binding activity of NF-κB-DNA. Additionally, TRIM21 siRNA eliminated the increase in NLRP3 and cleaved caspase-1 proteins expression and caspase-1 activity induced by LPS. TRIM21 knockdown could resist cytotoxicity induced by activated microglia, including increasing the viability of co-cultured HT22 cells and reducing the emancipation of LDH. Moreover, the increased apoptosis and caspase-3 activity of HT22 neurons induced by activated BV2 cells were blocked by TRIM21 siRNA. Blocking of NF-κB abolished the effect of TRIM21 in promoting the expression of M1 phenotype marker genes. Similarly, the blockade of NF-κB pathway eliminated the promotion of TRIM21 on neurotoxicity induced by neuroinflammation. TRIM21 knockdown suppressed the M1 phenotype polarization of microglia and neuroinflammation-mediated neuronal damage via NF-κB/NLRP3 inflammasome pathway, which suggested that TRIM21 might be a potential therapeutic target for the therapy of central nervous system diseases.

Modulatory effect of olanzapine on SMIM20/phoenixin, NPQ/spexin and NUCB2/nesfatin-1 gene expressions in the rat brainstem

Background

Phoenixin, spexin and nesfatin-1 belong to a family of newly discovered multifunctional neuropeptides that play regulatory roles in several brain structures and modulate the activity of important neural networks. However, little is known about their expression and action at the level of brainstem. The present work was, therefore, focused on gene expression of the aforementioned peptides in the brainstem of rats chronically treated with olanzapine, a second generation antipsychotic drug.

Methods

Studies were carried out on adult, male Sprague–Dawley rats that were divided into 2 groups: control and experimental animals treated with olanzapine (28-day-long intraperitoneal injection, at dose 5 mg/kg daily). All individuals were killed under anesthesia and the brainstem excised. Total mRNA was isolated from homogenized samples of both structures and the RT-PCR method was used for estimation of related SMIM20/phoenixin, NPQ/spexin and NUCB2/nesfatin-1 gene expression.

Results

Long-term treatment with olanzapine is reflected in qualitatively different changes in expression of examined neuropeptides mRNA in the rat brainstem. Olanzapine significantly decreased NPQ/spexin mRNA expression, but increased SMIM20/phoenixin mRNA level in the rat brainstem; while NUCB2/nesfatin-1 mRNA expression remained unchanged.

Conclusions

Olanzapine can affect novel peptidergic signaling in the rat brainstem. This may cautiously suggest the presence of an alternative mode of its action.

By Regulating the NLRP3 Inflammasome Can Reduce the Release of Inflammatory Factors in the Co-Culture Model of Tuberculosis H37Ra Strain and Rat Microglia

Objective

Tuberculosis infection of the Central Nervous System can cause severe inflammation in microglia, and NLRP3 inflammasome is also an important source of inflammation in microglia. Therefore, in this study, we used a co-culture model of rat microglia and tuberculosis H37Ra strain to explore the influence of tuberculosis infection on the NLRP3 inflammasome in microglia and its regulation mechanism.

Methods

We cultured primary microglia from SD rats and co-cultured with tuberculosis H37Ra strain for 4 hours to establish a co-culture model. At the same time, MCC950, Z-YVAD-FMK, BAY-11-7082, Dexamethasone, RU486, BzATP, BBG and extracellular high potassium environment were used to intervene the co-cultivation process. Subsequently, western blot, real-time PCR, ELISA and other methods were used to detect the changes of NLRP3 inflammasome-related molecules in microglia.

Results

After co-cultivation, the NLRP3 inflammasomes in microglia were activated and released a large amount of IL-18 and IL-1β. By regulating NLRP3 inflammasome complex, caspase-1, NF-κB and P2X7R during the co-culture process, it could effectively reduce the release of IL-18 and IL-1β, and the mortality of microglia.

Conclusion

Our results indicate that the NLRP3 inflammasome pathway is an important part of the inflammatory response of microglia caused by tuberculosis infection. By intervening the NLRP3 inflammasome pathway, it can significantly reduce the inflammatory response and mortality of microglia during the tuberculosis H37Ra strain infection. This research can help us further understand the inflammatory response mechanism of the central nervous system during tuberculosis infection and improve its treatment.

Phoenixin: More than Reproductive Peptide

Phoenixin (PNX) neuropeptide is a cleaved product of the Smim20 protein. Its most common isoforms are the 14- and 20-amino acid peptides. The biological functions of PNX are mediated via the activation of the GPR173 receptor. PNX plays an important role in the central nervous system (CNS) and in the female reproductive system where it potentiates LH secretion and controls the estrus cycle. Moreover, it stimulates oocyte maturation and increases the number of ovulated oocytes. Nevertheless, PNX not only regulates the reproduction system but also exerts anxiolytic, anti-inflammatory, and cell-protective effects. Furthermore, it is involved in behavior, food intake, sensory perception, memory, and energy metabolism. Outside the CNS, PNX exerts its effects on the heart, ovaries, adipose tissue, and pancreatic islets. This review presents all the currently available studies demonstrating the pleiotropic effects of PNX.

Phoenixin 14 Inhibits High-Fat Diet-Induced Non-Alcoholic Fatty Liver Disease in Experimental Mice

Introduction

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases. The development of NAFLD is closely associated with hepatic lipotoxicity, inflammation, and oxidative stress. The new concept of NAFLD treatment is to seek molecular control of lipid metabolism and hepatic redox hemostasis. Phoenixin is a newly identified neuropeptide with pleiotropic effects. This study investigated the effects of phoenixin 14 against high-fat diet (HFD)-induced NAFLD in mice.

Materials and Methods

For this study, we used HFD-induced NAFLD mice models to analyze the effect of phonenixin14. The mice were fed on HFD and normal diet and also given phoenixin 14 (100 ng/g body weight) by gastrogavage for 10 weeks. The peripheral blood samples were collected for biochemical assays. The liver tissues were examined for HFD-induced tissue fibrosis, lipid deposition and oxidative activity including SOD, GSH, and MDA. The liver tissues were analyzed for the inflammatory cytokines and oxidative stress pathway genes.

Results

The results indicate that phoenixin 14 significantly ameliorated HFD-induced obesity and fatty liver. The biochemical analysis of blood samples revealed that phoenixin 14 ameliorated HFD-induced elevated circulating alanine aminotransferase (ALT), aspartate aminotransferase (AST), total cholesterol, and triglyceride levels, suggesting that phoenixin 14 has a protective role in liver function and lipid metabolism. Hematoxylin-eosin (HE) and Oil Red O staining of the liver showed that phoenixin 14 alleviated HFD-induced tissue damage and lipid deposition in the liver. Furthermore, the mice administered with phoenixin 14 had increased hepatic SOD activity, increased production of GSH and reduced MDA activity, as well as reduced production of TNF-α and IL-6 suggesting that phoenixin 14 exerts beneficial effects against inflammation and ROS. The findings suggest an explanation of how mechanistically phoenixin 14 ameliorated HFD-induced reduced activation of the SIRT1/AMPK and NRF2/HO-1 pathways.

Conclusion

Collectively, this study revealed that phoenixin 14 exerts a protective effect in experimental NAFLD mice. Phoenixin could be of the interest in preventive modulation of NAFLD.