Neurotrophic Factors in Experimental Cerebral Acanthamoebiasis.

To date, no studies have addressed the role of neurotrophins (NTs) in Acanthamoeba spp. infections in the brain. Thus, to clarify the role of NTs in the cerebral cortex and hippocampus during experimental acanthamoebiasis in relation to the host immune status, the purpose of this study was to determine whether Acanthamoeba spp. may affect the concentration of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4) in brain structures. Our results suggest that at the beginning of infection in immunocompetent hosts, BDNF and NT-3 may reflect an endogenous attempt at neuroprotection against Acanthamoeba spp. infection. We also observed a pro-inflammatory effect of NGF during acanthamoebiasis in immunosuppressed hosts. This may provide important information for understanding the development of cerebral acanthamoebiasis related to the immunological status of the host. However, the pathogenesis of brain acanthamoebiasis is still poorly understood and documented and, therefore, requires further research.

The significance of tyrosine kinase receptor B and brain-derived neurotrophic factor expression in salivary duct carcinoma.

Salivary duct carcinoma (SDC) is a high-grade salivary gland neoplasm. It may occur de novo or secondarily from pleomorphic adenoma (ex-PA), with secondary development accounting for more than 50% of the cases. In recent years, the expression of tyrosine kinase receptor B (TrkB), which is in the same family as HER2, has been confirmed in various types of carcinomas. However, there are a few studies on SDC. In order to examine the expression and role of TrkB in SDC, we investigated it. Immunohistochemistry was used to detect the expression of TrkB and its ligands, brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) in 20 patients with SDC. The mRNA levels of TrkB, BDNF, and NT-4 were analyzed using quantitative polymerase chain reaction. TrkB was negative in 10 cases and positive in 10 cases, BDNF was negative in 11 cases and positive in 9 cases, and NT-4 was positive in all cases. There was a high number of TrkB-positive cases in the pT4 group and The H-score of TrkB was also significantly higher in the stage III and IV groups. There was a high number of BDNF-positive cases in the ex-PA group and Histo-score of BDNF had a trend of high expression in ex-PA. There were no significant differences or correlations in mRNA expression. Our results suggest that TrkB may be involved in SDC tumor growth.

The Impact of Physical Exercise on the Circulating Levels of BDNF and NT 4/5: A Review.

(1) Background: One mechanism through which physical activity (PA) provides benefits is by triggering activity at a molecular level, where neurotrophins (NTs) are known to play an important role. However, the expression of the circulating levels of neurotrophic factors, brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4/5), in response to exercise, is not fully understood. Therefore, the aim was to provide an updated overview on the neurotrophin (NT) variation levels of BDNF and NT-4/5 as a consequence of a long-term aerobic exercise intervention, and to understand and describe whether the upregulation of circulating NT levels is a result of neurotrophic factors produced and released from the brain, and/or from neurotrophic secreting peripheral organs. (2) Methods: The articles were collected from PubMed, SPORTDiscus, Web of Science, MEDLINE, and Embase. Data were analyzed through a narrative synthesis. (3) Results: 30 articles studied humans who performed training protocols that ranged from 4 to 48 weeks; 22 articles studied rodents with an intervention period that ranged from 4 to 64 weeks. (4) Conclusions: There is no unanimity between the upregulation of BDNF in humans; conversely, concerning both BDNF and NT-4/5 in animal models, the results are heterogeneous. Whilst BDNF upregulation appears to be in relative agreement, NT-4/5 seems to display contradictory and inconsistent conclusions.

NT-4 attenuates neuroinflammation via TrkB/PI3K/FoxO1 pathway after germinal matrix hemorrhage in neonatal rats.

BACKGROUND: Neuroinflammation plays an important role in pathogenesis of germinal matrix hemorrhage (GMH). Neurotrophin-4 (NT-4) is a member of the neurotrophin family and interacts with the tropomyosin receptor kinase B (TrkB). NT-4 has been shown to confer neuroprotective effects following cerebral ischemia. We aimed to investigate the neuroprotective function of NT-4-TrkB signaling, as well as its downstream signaling cascade phosphatidylinositol-3-kinases (PI3K)/protein kinase B (Akt)/forkhead box protein O1 (FoxO1), following GMH in neonatal rats. METHODS: GMH was induced by intraparenchymal injection of bacterial collagenase (0.3 U) in P7 rat pups. A total of 163 pups were used in this study. Recombinant human NT-4 was administered intranasally at 1 h after the collagenase injection. The selective TrkB antagonist ANA-12, selective PI3K inhibitor LY294002, and FoxO1 activating CRISPR were administered intracerebroventricularly at 24 h prior to NT-4 treatment to investigate the underlying mechanism. Short-term and long-term neurobehavioral assessments, immunofluorescence staining, Nissl's staining, and Western blot were performed. RESULTS: Expression of phosphorylated TrkB increased after GMH, reaching the peak level at day 3 after hemorrhage. TrkB receptors were observed on neurons, microglia, and astrocytes. The administration of rh-NT-4 induced phosphorylation of TrkB, expression of PI3K, and phosphorylation of Akt. Meanwhile, it decreased FoxO1 and IL-6 levels. Selective inhibition of TrkB/PI3K/Akt signaling in microglia increased the expression levels of FoxO1 and pro-inflammatory cytokines. FoxO1 activating CRISPR increased the expression of IL-6, suggesting that FoxO1 might be a potential inducer of pro-inflammatory factors. These results suggested that PI3K/Akt/FoxO1 signaling may be the downstream pathway of activation of TrkB. The rat pups treated with rh-NT-4 performed better than vehicle-treated animals in both short-term and long-term behavioral tests. CONCLUSION: These data showed that rh-NT-4 reduced the expression levels of pro-inflammatory cytokines, improved neurological function, attenuated neuroinflammation, and thereby mitigated post-hemorrhagic hydrocephalus after GMH by TrkB/PI3K/Akt/FoxO1 pathway. These results indicated that rh-NT-4 could be a promising therapeutic strategy to ameliorate neuroinflammation and hydrocephalus after GMH or other similar brain injuries.

Correlation of metabolic parameters, neurotrophin-3, and neurotrophin-4 serum levels in women with schizophrenia and first-onset depression.

BACKGROUND: Neurotrophin-3 (NTF3) and neurotrophin-4 (NTF4) play a crucial role in the neurodevelopment, differentiation, survival, and protection of neurons in different brain regions. Schizophrenia and depression are highly associated with metabolic abnormalities. Longitudinal and cross-sectional comparisons of NTF3 and NTF4 levels, as well as clinical and metabolic parameters, were studied in schizophrenia, first-episode depression, and control groups. MATERIALS AND METHODS: Serum NTF3 and NTF4 levels, body mass index (BMI), fasting serum glucose and lipid profile: cholesterol, triglyceride, high-density lipoprotein (HDL-C) and low-density lipoprotein (LDL-C) were measured at baseline and week 8 in 133 women: 55 patients with schizophrenia (19 with first-episode and 36 chronic), 30 patients with a first-episode depression and 48 healthy controls. The severity of the symptoms was evaluated with the Positive and Negative Syndrome Scale, 17-item Hamilton Depression Rating Scale and the Beck Depression Inventory. RESULTS: Longitudinal and cross-sectional comparisons did not detect any differences in the serum levels of NTF3 and NTF4 between studied groups. NTF3 and NTF4 levels were strongly correlated. Correlation of NTF3 and HDL-C levels at baseline was observed. Significant changes in cholesterol and fasting serum glucose levels in first-episode depression patients during 8 weeks of treatment were detected. Significant differences in BMI and LDL-C levels between schizophrenia and first-episode depression patients were discovered. CONCLUSIONS: To our knowledge, this is the first research which correlates NTF3 and NTF4 with metabolic parameters. Our study does not support the theory that the peripheral levels of NTF3 and NTF4 are disturbed in schizophrenia or first-episode depression.

TrkB signalling pathway mediates the protective effects of exercise in the diabetic rat retina.

Diabetic retinopathy is a leading cause of vision loss. Treatment options for early retinopathy are sparse. Exercise protects dying photoreceptors in models of retinal degeneration, thereby preserving vision. We tested the protective effects of exercise on retinal and cognitive deficits in a type 1 diabetes model and determined whether the TrkB pathway mediates this effect. Hyperglycaemia was induced in Long Evans rats via streptozotocin injection (STZ; 100 mg/kg). Following confirmed hyperglycaemia, both control and diabetic rats underwent treadmill exercise for 30 min, 5 days/week at 0 m/min (inactive groups) or 15 m/min (active groups) for 8 weeks. A TrkB receptor antagonist (ANA-12), or vehicle, was injected 2.5 h before exercise training. We measured spatial frequency and contrast sensitivity using optokinetic tracking biweekly post-STZ; retinal function using electroretinography at 4 and 8 weeks; and cognitive function and exploratory behaviour using Y-maze at 8 weeks. Retinal neurotrophin-4 was measured using ELISA. Compared with non-diabetic controls, diabetic rats showed significantly reduced spatial frequency and contrast sensitivity, delayed electroretinogram oscillatory potential and flicker implicit times and reduced cognitive function and exploratory behaviour. Exercise interventions significantly delayed the appearance of all deficits, except for exploratory behaviour. Treatment with ANA-12 significantly reduced this protection, suggesting a TrkB-mediated mechanism. Despite this, no changes in retinal neurotrohin-4 were observed with diabetes or exercise. Exercise protected against early visual and cognitive dysfunction in diabetic rats, suggesting that exercise interventions started after hyperglycaemia diagnosis may be a beneficial treatment. The translational potential is high, given that exercise treatment is non-invasive, patient controlled and inexpensive.

Neurotrophins in Asthma.

PURPOSE OF REVIEW: Asthma is a chronic airway disease that affects more than 300 million people worldwide. Current treatment focuses on symptomatic relief by temporally dampening inflammation and relaxing the airway. Novel combative strategies against asthma and hopefully a cure are yet to be developed. The goal of this review is to summarize recent literature on neurotrophins (NTs) in experimental models and clinical settings of asthma research. RECENT FINDINGS: We highlight studies of early phases of asthma that collectively reveal a profound impact of elevated NT levels following initial detrimental insults on long-term airway dysfunction. We hope this review will foster insights into the complex interaction between NTs, nerves, immune cells, and airway structural cells during a critical time window of development and disease susceptibility. Future studies are required to better understand the role of NTs in asthma pathophysiology and to evaluate whether NTs and their receptors may serve as new drug targets.

Leukemia inhibitory factor impairs structural and neurochemical development of rat visual cortex in vivo.

Minipump infusions into visual cortex in vivo at the onset of the critical period have revealed that the proinflammatory cytokine leukemia inhibitory factor (LIF) delays the maturation of thalamocortical projection neurons of the lateral geniculate nucleus, and tecto-thalamic projection neurons of the superior colliculus, and cortical layer IV spiny stellates and layer VI pyramidal neurons. Here, we report that P12-20 LIF infusion inhibits somatic maturation of pyramidal neurons and of all interneuron types in vivo. Likewise, DIV 12-20 LIF treatment in organotypic cultures prevents somatic growth GABA-ergic neurons. Further, while NPY expression is increased in the LIF-infused hemispheres, the expression of parvalbumin mRNA and protein, Kv3.1 mRNA, calbindin D-28k protein, and GAD-65 mRNA, but not of GAD-67 mRNA or calretinin protein is substantially reduced. Also, LIF treatment decreases parvalbumin, Kv3.1, Kv3.2 and GAD-65, but not GAD-67 mRNA expression in OTC. Developing cortical neurons are known to depend on neurotrophins. Indeed, LIF alters neurotrophin mRNA expression, and prevents the growth promoting action of neurotophin-4 in GABA-ergic neurons. The results imply that LIF, by altering neurotrophin expression and/or signaling, could counteract neurotrophin-dependent growth and neurochemical differentiation of cortical neurons.

BDNF and NT4 play interchangeable roles in gustatory development.

A limited number of growth factors are capable of regulating numerous developmental processes, but how they accomplish this is unclear. The gustatory system is ideal for examining this issue because the neurotrophins brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT4) have different developmental roles although both of them activate the same receptors, TrkB and p75. Here we first investigated whether the different roles of BDNF and NT4 are due to their differences in temporal and spatial expression patterns. Then, we asked whether or not these two neurotrophins exert their unique roles on the gustatory system by regulating different sets of downstream genes. By using Bdnf(Nt4/Nt4) mice, in which the coding region for BDNF is replaced with NT4, we examined whether the different functions of BDNF and NT4 are interchangeable during taste development. Our results demonstrated that NT4 could mediate most of the unique roles of BDNF during taste development. Specifically, caspase-3-mediated cell death, which was increased in the geniculate ganglion in Bdnf(-/-) mice, was rescued in Bdnf(Nt4/Nt4) mice. In BDNF knockout mice, tongue innervation was disrupted, and gustatory axons failed to reach their targets. However, disrupted innervation was rescued and target innervation is normal when NT4 replaced BDNF. Genome wide expression analyses revealed that BDNF and NT4 mutant mice exhibited different gene expression profiles in the gustatory (geniculate) ganglion. Compared to wild type, the expression of differentiation-, apoptosis- and axon guidance-related genes was changed in BDNF mutant mice, which is consistent with their different roles during taste development. However, replacement of BDNF by NT4 rescued these gene expression changes. These findings indicate that the functions of BDNF and NT4 in taste development are interchangeable. Spatial and temporal differences in BDNF and NT4 expression can regulate differential gene expression in vivo and determine their specific roles during development.

Neurotrophin-4 promotes in vitro development and maturation of human secondary follicles yielding metaphase II oocytes and successful blastocyst formation.

STUDY QUESTION: Does a matrix-free culture system supplemented with neurotrophic factor 4 (NT4) improve human in vitro follicular development and meiotic maturation, ultimately resulting in fertilizable oocytes? SUMMARY ANSWER: NT4 supplementation of in vitro culture significantly enhances the growth, steroid hormone production, and maturity potential of human secondary follicles derived from fresh ovarian medulla (from post- and pre-pubertal patients), thereby yielding fertilizable oocytes. WHAT IS KNOWN ALREADY: Reconstituting folliculogenesis in vitro is of paramount importance in the realms of fertility preservation, reproductive biology research, and reproductive toxicity assessments. However, the efficiency of in vitro culture systems remains suboptimal, as the attainment of fertilizable oocytes from in vitro growth (IVG) of human follicles remains unachieved, with the data being particularly scant regarding follicles from prepubertal girls. We have previously found that mouse oocytes from secondary follicles derived from IVG are deficient in neuroendocrine regulation. NT4 and its corresponding receptor have been identified in human follicles. Significantly, the addition of NT4 during the IVG process markedly enhances both follicle growth and oocyte maturation rates in mice. STUDY DESIGN SIZE DURATION: Fresh medulla tissue obtained during tissue preparation for ovarian tissue cryopreservation (OTC) were collected from 10 patients aged from 6 to 21 years old, all of whom had undergone unilateral oophorectomy as a means of fertility preservation. Isolated secondary follicles were individually cultured in vitro with or without NT4 in a matrix-free system. PARTICIPANTS/MATERIALS SETTING METHODS: Secondary follicles, extracted via enzymatic digestion and mechanical disruption from each patient, were randomly allocated to either a control group or an NT4-supplemented group (100 ng/ml), followed by individual culture on an ultra-low attachment plate. Follicle growth and viability were assessed by microscopy. Levels of anti-Müllerian hormone (AMH), estradiol, and progesterone in the medium were quantified. An oocyte-specific marker was identified using confocal fluorescence microscopy following DEAD box polypeptide 4 (DDX4) staining. The competence of individual oocytes for maturation and fertilization were assessed after IVM and ICSI with donated sperm samples. MAIN RESULTS AND THE ROLE OF CHANCE: Overall, isolated follicles from both groups survived up to 6 weeks with increasing diameters over the duration (P < 0.05), reaching terminal diameters of almost 1 mm with confirmed steroidogenesis and expression of oocyte marker (DDX4), and producing morphologically normal MII oocytes. When compared with the control group, the NT4 group had a similar initial follicular diameter (206 ± 61.3 vs 184 ± 93.4 µm) but exhibited a significant increase in follicular diameter from the ninth day of culture onwards (P < 0.05). From Week 3, estradiol and progesterone production were significantly increased in the NT4 group, while no significant difference was observed in AMH production between groups. The proportion of 'fast-growth' follicles in the NT4 group was significantly higher than that in the control group (13/23 vs 6/24, P < 0.05). An increased efficiency of MII oocyte maturation per live follicle in the NT4 group was also observed (control group vs NT4 group, 4/24 vs 10/23, P < 0.05). It is noteworthy that an MII oocyte obtained from the control group exhibited abnormal fertilization after ICSI. In contrast, an MII oocyte acquired from the NT4 group progressed to the blastocyst stage and showed potential for transfer. LARGE SCALE DATA: N/A. LIMITATIONS REASONS FOR CAUTION: The cohort examined in this study was all patients diagnosed with beta-thalassemia major. Whether this culture system is effective for patients with other diseases remains unknown. Since the chosen dose of NT4 was established based on dose finding in mice, the optimal dose for use in a human IVG system needs further confirmation. The oocytes and embryos procured from this study have not been quantified for ploidy status or epigenetic signatures. WIDER IMPLICATIONS OF THE FINDINGS: Fresh medulla tissue obtained during tissue preparation for OTC may serve as a precious source of fertilizable oocytes for female fertility preservation, even for pre-pubertal girls, without the threat of tumour reintroduction. After further characterization and optimization of the system, this culture system holds the potential to provide a powerful future research tool, for the comprehensive exploration of human follicular development mechanisms and for conducting reproductive toxicity evaluations. STUDY FUNDING/COMPETING INTERESTS: This work was supported by the National Key R&D Program of China (grant number 2022YFC2703000) and National Natural Science Foundation of China (grant numbers 82271651 and 81871214). The medium used in human follicle in vitro culture in this study has been applied for a national invention patent in China (No. 202211330660.7). The inventors of the patent, in order, are: Y.G., C.F., and X.L.

Elevated specific peripheral cytokines found in major depressive disorder patients with childhood trauma exposure: a cytokine antibody array analysis.

Taking into consideration the previous evidence of revealing the relationship of early life adversity, major depressive disorder (MDD), and stress-linked immunological changes, we recruited 22 MDD patients with childhood trauma exposures (CTE), 21 MDD patients without CTE, and 22 healthy controls without CTE, and then utilized a novel cytokine antibody array methodology to detect potential biomarkers underlying MDD in 120 peripheral cytokines and to evaluate the effect of CTE on cytokine changes in MDD patients. Although 13 cytokines were identified with highly significant differences in expressions between MDD patients and normal controls, this relationship was significantly attenuated and no longer significant after consideration of the effect of CTE in MDD patients. Depressed individuals with CTE (TD patients) were more likely to have higher peripheral levels of those cytokines. Severity of depression was associated with plasma levels of certain increased cytokines; meanwhile, the increased cytokines led to a proper separation of TD patients from normal controls during clustering analyses. Our research outcomes add great strength to the relationship between depression and cytokine changes and suggest that childhood trauma may play a vital role in the co-appearance of cytokine changes and depression.

Neurotrophin-4 promotes the specification of trophectoderm lineage after parthenogenetic activation and enhances porcine early embryonic development.

Neurotrophin-4 (NT-4), a neurotrophic factor, appears to affect early embryonic development because it is secreted not only by neurons but also by oviductal and uterine epithelial cells. However, no studies have characterized the effects of NT-4 on early embryonic development in pigs. In this study, we applied the experimental model of parthenogenetic-activation (PA)-derived embryos. Herein, we investigated the effect of NT-4 supplementation during the in vitro culture (IVC) of embryos, analyzed the transcription levels of specific genes, and outlined the first cell lineage specification for porcine PA-derived blastocysts. We confirmed that NT-4 and its receptor proteins were localized in both the inner cell mass (ICM) and trophectoderm (TE) in porcine blastocysts. Across different concentrations (0, 1, 10, and 100 ng/mL) of NT-4 supplementation, the optimal concentration of NT-4 to improve the developmental competence of porcine parthenotes was 10 ng/mL. NT-4 supplementation during porcine IVC significantly (p < 0.05) increased the proportion of TE cells by inducing the transcription of TE lineage markers (CDX2, PPAG3, and GATA3 transcripts). NT-4 also reduced blastocyst apoptosis by regulating the transcription of apoptosis-related genes (BAX and BCL2L1 transcripts) and improved blastocyst quality via the interaction of neurotrophin-, Hippo-yes-associated protein (Hippo-YAP) and mitogen-activated protein kinase/extracellular regulated kinase (MAPK/ERK) pathway. Additionally, NT-4 supplementation during IVC significantly (p < 0.05) increased YAP1 transcript levels and significantly (p < 0.01) decreased LATS2 transcript levels, respectively, in the porcine PA-derived blastocysts. We also confirmed through fluorescence intensity that the YAP1 protein was significantly (p < 0.001) increased in the NT-4-treated blastocysts compared with that in the control. NT-4 also promoted differentiation into the TE lineage rather than into the ICM lineage during porcine early embryonic development. In conclusion, 10 ng/mL NT-4 supplementation enhanced blastocyst quality by regulating the apoptosis- and TE lineage specification-related genes and interacting with neurotrophin-, Hippo-YAP-, and MAPK/ERK signaling pathway during porcine in vitro embryo development.

Neurotrophin-4 and Brain-Derived Neurotrophic Factor Serum Levels in Renal Transplant Recipients with Chronic Pruritus.

INTRODUCTION: Chronic pruritus (CP) is a common symptom defined as a sensation that provokes the desire to scratch and which lasts for at least 6 weeks. CP remains a problem for up to 21.3% of renal transplant recipients (RTRs). Our research aimed to establish the possible association between serum levels of neurotrophin-4 (NT-4) and brain-derived neurotrophic factor (BDNF) and the presence and intensity of CP in RTR. METHODS: The study was performed on a group of 129 RTRs, who were divided according to the presence or absence of pruritus in the previous 3 days. The assessment of pruritus was performed with the use of a numeric rating scale (NRS), 4-Item Itch Questionnaire (4IIQ), and Itchy Quality of Life (Itchy QoL). A total of 129 blood samples with a volume of 9 ml were drawn from RTRs during the monthly routine control. Serum levels (pg/mL) of NT-4 and BDNF were measured by the ELISA. RESULTS: Pruritic RTRs have statistically significantly higher serum concentrations of NT-4 serum level compared to non-pruritic RTRs (229.17 ± 143.86 pg/mL and 153.08 ± 78.19 pg/mL [p = 0.024], respectively). Moreover, a statistically significant difference between pruritic and non-pruritic RTRs with healthy controls was shown (p < 0.001 and p < 0.001, respectively). Although there was a numerically higher serum concentration of BDNF in pruritic RTRs (32.18 ± 7.31 pg/mL vs. 31.58 ± 10.84 pg/mL), the difference did not reach statistical significance. No statistically significant difference was also seen in BDNF serum levels between RTRs and healthy controls. Furthermore, there was a statistically significant, positive correlation between serum concentration of NT-4 and NRS score (p = 0.008, r = 0.357). CONCLUSIONS: The results indicate higher NT-4 serum concentration in RTRs with pruritus compared to RTRs without pruritus. Furthermore, the study revealed a statistically significant, positive correlation between the serum concentration of NT-4 and NRS score.

Physiological and Functional Roles of Neurotrophin-4 During In Vitro Maturation of Porcine Cumulus-Oocyte Complexes.

Neurotrophin-4 (NT-4), a granulosa cell-derived factor and a member of the neurotrophin family, is known to promote follicular development and oocyte maturation in mammals. However, the physiological and functional roles of NT-4 in porcine ovarian development are not yet known. The aim of this study was to investigate the physiological role of NT-4-related signaling in the in vitro maturation (IVM) of porcine cumulus-oocyte complexes (COCs). The NT-4 protein and its receptors were detected in matured porcine COCs via immunofluorescence analysis. NT-4 was shown to promote the maturation of COCs by upregulating NFKB1 transcription via the neurotrophin/p75NTR signaling pathway. Notably, the mRNA expression levels of the oocyte-secreted factors GDF9 and BMP15, sperm-oocyte interaction regulator CD9, and DNA methylase DNMT3A were significantly upregulated in NT-4-treated than in untreated porcine oocytes. Concurrently, there were no significant differences in the levels of total and phosphorylated epidermal growth factor receptor and p38 mitogen-activated protein kinase between NT-4-treated and untreated cumulus cells (CCs); however, the level of phosphorylated ERK1/2 was significantly higher in NT-4-treated CCs. Both total and phosphorylated ERK1/2 levels were significantly higher in NT-4-treated than in untreated oocytes. In addition, NT-4 improved subsequent embryonic development after in vitro fertilization and somatic cell nuclear transfer. Therefore, the physiological and functional roles of NT-4 in porcine ovarian development include the promotion of oocyte maturation, CC expansion, and ERK1/2 phosphorylation in porcine COCs during IVM.

Elevated Level of Serum Neurotrophin-4, but Not of Brain-Derived Neurotrophic Factor, in Patients with Chronic Kidney Disease-Associated Pruritus.

Chronic kidney disease-associated pruritus (CKD-aP) is a bothersome condition that occurs in patients with advanced chronic kidney disease (CKD) and severely reduces their quality of life. Recently, much research has focused on the search for markers that are involved in the pathogenesis of CKD-aP and may become a therapeutic target. One of the suggested hypotheses is the increased activation of sensory neurons by molecules such as neurotrophins (NTs). An increased serum concentration of NTs has been demonstrated in pruritic patients, which may suggest their involvement in the pathogenesis of itch. The purpose of this study is to assess the serum concentration of neurotrophin-4 (NT-4) and brain-derived neurotrophic factor (BDNF) in hemodialysis patients. The study enrolled 126 patients undergoing dialysis. Participants were divided into 2 groups: with and without CKD-aP. NRS scale was used to evaluate itch severity. Serum levels of NT-4 and BDNF have been assessed using ELISA. The results showed a significantly higher level of NT-4 in the group with pruritus. No significant difference was reported in the serum level of BDNF between the two groups of patients. There was also no correlation between serum NT-4 nor BDNF levels and the severity of pruritus. In summary, NT-4 may play an important role in the pathophysiology of pruritus in dialysis patients. More research is needed to understand the exact mechanism by which NTs influence the pathogenesis of CKD-aP.

Neurotrophins in Zebrafish Taste Buds.

The neurotrophin family is composed of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), Neurotrophin 3 (NT3) and NT4. These neurotrophins regulate several crucial functions through the activation of two types of transmembrane receptors, namely p75, which binds all neurotrophins with a similar affinity, and tyrosine kinase (Trk) receptors. Neurotrophins, besides their well-known pivotal role in the development and maintenance of the nervous system, also display the ability to regulate the development of taste buds in mammals. Therefore, the aim of this study is to investigate if NGF, BDNF, NT3 and NT4 are also present in the taste buds of zebrafish (Danio rerio), a powerful vertebrate model organism. Morphological analyses carried out on adult zebrafish showed the presence of neurotrophins in taste bud cells of the oropharyngeal cavity, also suggesting that BDNF positive cells are the prevalent cell population in the posterior part of the oropharyngeal region. In conclusion, by suggesting that all tested neurotrophins are present in zebrafish sensory cells, our results lead to the assumption that taste bud cells in this fish species contain the same homologous neurotrophins reported in mammals, further confirming the high impact of the zebrafish model in translational research.

Beneficial Effects of Neurotrophin-4 Supplementation During in vitro Maturation of Porcine Cumulus-Oocyte Complexes and Subsequent Embryonic Development After Parthenogenetic Activation.

Neurotrophin-4 (NT-4) is a neurotrophic factor that plays an important role in follicular development and oocyte maturation. However, it is not yet known whether NT-4 is related to oocyte maturation and follicular development in pigs. This study aims to investigate the effects of NT-4 supplementation during in vitro maturation (IVM) of porcine oocytes and subsequent embryonic development after parthenogenetic activation (PA). First, NT-4 and its receptors (TrkB and p75NTR) were identified through fluorescent immunohistochemistry in porcine ovaries. NT-4 was mainly expressed in theca and granulosa cells; phospho-TrkB and total TrkB were expressed in theca cells, granulosa cells, and oocytes; p75NTR was expressed in all follicular cells. During IVM, the defined maturation medium was supplemented with various concentrations of NT-4 (0, 1, 10, and 100 ng/mL). After IVM, the nuclear maturation rate was significantly higher in the 10 and 100 ng/mL NT-4 treated groups than in the control. There was no significant difference in the intracellular reactive oxygen species levels in any group after IVM, but the 1 and 10 ng/mL NT-4 treatment groups showed a significant increase in the intracellular glutathione levels compared to the control. In matured cumulus cells, the 10 ng/mL NT-4 treatment group showed significantly increased cumulus expansion-related genes and epidermal growth factor (EGF) signaling pathway-related genes. In matured oocytes, the 10 ng/mL treatment group showed significantly increased expression of cell proliferation-related genes, antioxidant-related genes, and EGF signaling pathway-related genes. We also investigated the subsequent embryonic developmental competence of PA embryos. After PA, the cleavage rates significantly increased in the 10 and 100 ng/mL NT-4 treatment groups. Although there was no significant difference in the total cell number of blastocysts, only the 10 ng/mL NT-4 treatment group showed a higher blastocyst formation rate than the control group. Our findings suggest that supplementation with the 10 ng/mL NT-4 can enhance porcine oocyte maturation by interacting with the EGF receptor signaling pathway. In addition, we demonstrated for the first time that NT-4 is not only required for porcine follicular development, but also has beneficial effects on oocyte maturation and developmental competence of PA embryos.

Neurotrophin-4 is essential for survival of the majority of vagal afferents to the mucosa of the small intestine, but not the stomach.

Vagal afferents form the primary gut-to-brain neural axis, communicating signals that regulate gastrointestinal (GI) function and promote satiation, appetition and reward. Neurotrophin-4 (NT-4) is essential for the survival of vagal smooth muscle afferents of the small intestine, but not the stomach. Here we took advantage of near-complete labeling of GI vagal mucosal afferents in Nav1.8cre-Rosa26tdTomato transgenic mice to determine whether these afferents depend on NT-4 for survival. We quantified the density and distribution of vagal afferent terminals in the stomach and small intestine mucosa and their central terminals in the solitary tract nucleus (NTS) and area postrema in NT-4 knockout (KO) and control mice. NT-4KO mice exhibited a 75% reduction in vagal afferent terminals in proximal duodenal villi and a 55% decrease in the distal ileum, whereas, those in the stomach glands remained intact. Vagal crypt afferents were also reduced in some regions of the small intestine, but to a lesser degree. Surprisingly, NT-4KO mice exhibited an increase in labeled terminals in the medial NTS. These findings, combined with previous results, suggest NT-4 is essential for survival of a large proportion of all classes of vagal afferents that innervate the small intestine, but not those that supply the stomach. Thus, NT-4KO mice could be valuable for distinguishing gastric and intestinal vagal afferent regulation of GI function and feeding. The apparent plasticity of central vagal afferent terminals - an increase in their density - could have compensated for loss of peripheral terminals by maintaining near-normal levels of satiety signaling.

Protective effect of LIF-huMSCs on the retina of diabetic model rats.

AIM: To investigate the protective effect of human umbilical cord mesenchymal stem cells (hUCMSCs) modified by the LIF gene on the retinal function of diabetic model rats and preliminarily explore the possible mechanism. METHODS: A stably transfected cell line of hUCMSCs overexpressing leukemia inhibitory factor (LIF) was constructed. Overexpression was verified by fluorescent quantitative polymerase chain reaction (qPCR). Forty-eight adult Sprague-Dawley rats were randomly divided into a normal control group (group A), streptozotocin-induced diabetic control group (group B), diabetic rats at 3mo injected with empty vector-transfected hUCMSCs (group C) or injected with LIF-hUCMSCs (group D). Four weeks after the intravitreal injection, analyses in all groups included retinal function using flash electroretinogram (F-ERG), retinal blood vessel examination of retinal flat mounts perfused with fluorescein isothiocyanate-dextran (FITC-dextran), and retinal structure examination of sections using hematoxylin and eosin staining. Expression levels of adiponectin (APN), high-sensitivity C-reactive protein (hs-CRP), and neurotrophin-4 (NT-4) in each group was detected using immunohistochemistry, PCR, Western blotting, and ELISA, respectively. RESULTS: A stable transgenic cell line of LIF-hUCMSCs was constructed. F-ERG and FITC-dextran examinations revealed no abnormalities of retinal structure and function in group A, severe damage of the retinal blood vessels and function in group B, and improved retinal structure and function in group C and especially group D. qPCR, ELISA, and Western blot analyses revealed progressively higher APN and NT-4 expression levels in groups B, C, and D than in group A. hs-CRP expression was significantly higher in group B than in groups A, C, and D, and was significantly higher in group C than in group D (P<0.05). CONCLUSION: LIF-hUCMSCs protect the retina of diabetic rats by upregulating APN and NT-4 expression and downregulating hs-CRP expression in the retina.

Prevention of streptozotocin­induced Neuro­2a cell death by C8­B4 microglia transformed with repetitive low­dose lipopolysaccharide.

Diabetes­associated neuronal dysfunction (DAND) is one of the serious complications of diabetes, but there is currently no remedy for it. Streptozotocin [2­deoxy­2­(3­methy1­3­nitrosoureido) D­glucopyranose; STZ] is one of the most well­established diabetes inducers and has been used in vivo and in vitro DAND models. The aim of the present study was to demonstrate that C8­B4 microglia transformed by the stimulus of repetitive low­dose lipopolysaccharide (LPSx3­microglia) prevent STZ­induced Neuro­2a neuronal cell death in vitro. The ELISA results showed that neurotrophin­4/5 (NT­4/5) secretion was promoted in LPSx3­microglia and the cell viability assay with trypan blue staining revealed that the culture supernatant of LPSx3­microglia prevented STZ­induced neuronal cell death. In addition, reverse transcription­quantitative PCR showed that neurons treated with the culture supernatant of LPSx3­microglia promoted the gene expression of B­cell lymphoma­extra large and glucose­dependent insulinotropic polypeptide receptor. Furthermore, the inhibition of tyrosine kinase receptor B, a receptor of NT­4/5, suppressed the neuroprotective effect of LPSx3­microglia. Taken together, the present study demonstrated that LPSx3­microglia prevent STZ­induced neuronal death and that NT­4/5 may be involved in the neuroprotective mechanism of LPSx3­microglia.