THE MICROBIOTA-GUT-BRAIN AXIS. A STUDY IN ZEBRAFISH (DANIO RERIO)

Bi-phasic change in BDNF gene expression following antidepressant drug treatment

Dysregulation of synaptic development and function has been implicated in the pathophysiology of neurodegenerative disorders and mental disease. A neurotrophin that has an important function in neuronal and synaptic development is brain-derived neurotrophic factor (BDNF). In this communication, we examined the effects of lead (Pb(2+)) exposure on BDNF-tropomyosin-related kinase B (TrkB) signaling during the period of synaptogenesis in cultured neurons derived from embryonic rat hippocampi. We show that Pb(2+) exposure decreases BDNF gene and protein expression, and it may also alter the transport of BDNF vesicles to sites of release by altering Huntingtin phosphorylation and protein levels. Combined, these effects of Pb(2+) resulted in decreased concentrations of extracellular mature BDNF. The effect of Pb(2+) on BDNF gene expression was associated with a specific decrease in calcium-sensitive exon IV transcript levels and reduced phosphorylation and protein expression of the transcriptional repressor methyl-CpG-binding protein (MeCP2). TrkB protein levels and autophosphorylation at tyrosine 816 were significantly decreased by Pb(2+) exposure with a concomitant increase in p75 neurotrophin receptor (p75(NTR)) levels and altered TrkB-p75(NTR) colocalization. Finally, phosphorylation of Synapsin I, a presynaptic target of BDNF-TrkB signaling, was significantly decreased by Pb(2+) exposure with no effect on total Synapsin I protein levels. This effect of Pb(2+) exposure on Synapsin I phosphorylation may help explain the impairment in vesicular release documented by us previously (Neal, A. P., Stansfield, K. H., Worley, P. F., Thompson, R. E., and Guilarte, T. R. (2010). Lead exposure during synaptogenesis alters vesicular proteins and impairs vesicular release: Potential role of N-Methyl-D-aspartate receptor (NMDAR) dependent BDNF signaling. Toxicol. Sci. 116, 249-263) because it controls vesicle movement from the reserve pool to the readily releasable pool. In summary, the present study demonstrates that Pb(2+) exposure during the period of synaptogenesis of hippocampal neurons in culture disrupts multiple synaptic processes regulated by BDNF-TrkB signaling with long-term consequences for synaptic function and neuronal development.

Objective To observe the effect of human β-nerve growth factor (β-NGF) and brain-derived neurotrophic factor (BDNF) gene co-transfection on the differentiation of rat bone marrow stromal stem cells (BMSCs). Methods BMSCs were isolated from the femoral and tibial bone marrow of SD rats by density-gradient centrifugation and identified using immunocytochemistry of Src homology 3 (SH3). The first-passage BMSCs were transfected with pSVCEP-NGF-CAT and pSVCEP-BDNF-CAT plasmids via liposome, and also with pEGFP-C1 as the marker of transfection. After a 4-week cell culture, the expression of EGFP in the transfected cells was detected using fluorescence microscope, and the transfection efficiency was calculated. Laser scanning confocal microscope was employed to observe the expressions of the neural precursor cell markers NGF, BDNF, nestin, neuron specific enolase (NSE), NF and glial fibrillary acidic protein (GFAP) and evaluate the differentiation of the transfected cells. Results The primary and passaged BMSCs with high purity were obtained successfully without any decrease in the proliferation and differentiation potentials. The long spindle-shaped cells in the early passages displayed high proliferative activity, and immunocytochemistry of SH3 identified the purified cells as the bona fide BMSCs. NGF and BDNF genes were stably expressed in the BMSCs after the transfection, and the transfected cells were also positive for nestin, NSE, NF-M and GFAP. Conclusions Effective ectopic expression of human β-NGF and BDNF genes is achieved in rat BMSCs after liposome-mediated gene tmnsfection. The BMSCs are capable of differentiating into neuronal precursor cells that express several neural proteins and resemble the immature neurons or glial cells after induction with neurotrophic factors. Key words: Bone marrow stromal stem cells; Nerve growth factor; Brain-derived neurotrophic factor; Liposome-mediated transfection; Cell differentiation

Tricyclic antidepressants and selective serotonin reuptake inhibitors are considered in theory to induce the outflow of neurotransmitters, norepinephrine, and serotonin from the synapses as a consequence of inhibiting their reuptake into the nerve terminals, resulting in the stimulation of glial cells surrounding the synapses in the brain. Then, we have investigated the direct actions of neurotransmitters on glial cell metabolism and function using rat C6 glioma cells as an in vitro model system and suggested that these neurotransmitters induce their differentiation probably through the production of 5alpha-reduced neurosteroids. On the other hand, the stimulation of the glioma cells with serotonin has been reported to enhance brain-derived neurotrophic factor (BDNF) gene expression, which may be closely related to the beneficial effects of antidepressant drugs. In the present study, to evaluate BDNF expression in differentiated glial cells, the glioma cells were pretreated with progesterone, and the effect of serotonin on BDNF messenger RNA levels in these cells was examined. Progesterone pretreatment enhanced the stimulatory action of serotonin on BDNF gene expression, and the enhancement of serotonin action observed in the cells pretreated with progesterone was almost completely abolished by finasteride, an inhibitor of the enzyme involved in the production of 5alpha-reduced neurosteroids. These findings propose the possibility that neurosteroid-mediated glial cell differentiation may result in the enhancement of serotonin-stimulated BDNF gene expression, which is considered to contribute to the survival, regeneration, and plasticity of neuronal cells in the brain, and hence, leading to the improvement of mood disorders and other symptoms in depressive patients.

Background: Alzheimer’s disease and dementia are commonly associated with aging, particularly in the context of Type II Diabetes Mellitus (Type II DM), which is known to exacerbate micro and macrovascular complications that affect cognitive functions. The Brain-Derived Neurotrophic Factor (BDNF) gene has been implicated in the neurodegenerative processes that underscore these conditions. Objective: This study aimed to investigate the expression of the BDNF gene in diabetic patients with dementia and analyze its correlation with cognitive impairment, to establish BDNF as a potential biomarker for early detection and therapeutic targeting. Methods: A cohort of 102 patients with diabetic dementia and 32 healthy controls was enrolled. EDTA blood samples were collected and processed to measure BDNF serum levels using a Chemiluminescent Immunoassay (CLIA). Genomic DNA was isolated, and its integrity was confirmed via UV spectrophotometry and gel electrophoresis. The bisulfite DNA modification and Methylation-Specific PCR were conducted to analyze BDNF gene expression, followed by quantitative real-time PCR. Cognitive function was assessed using Mini-Mental State Examination (MMSE). Results: The study revealed a significant decrease in BDNF serum levels in diabetic dementia patients (12.6 ng/mL) compared to healthy controls (34.8 ng/mL), with MMSE scores averaging at 13.2 and 24.6, respectively. BDNF gene expression showed a 4.1-fold decrease in the dementia group. Statistical analysis indicated that these differences were significant (p<0.05). Conclusion: The reduced expression of BDNF in patients with diabetic dementia confirms its potential as a biomarker for cognitive impairment. Early detection and intervention strategies that modulate BDNF could ameliorate the impact of dementia in the context of diabetes.

Clinical studies show that people suffering from chronic pain are often also burdened by depression. Antidepressants are used to treat some types of chronic pain; however, little is known about their mechanisms of action. This study addressed the effects of a nonsteroidal anti-inflammatory drug and a tricyclic antidepressant drug on pain- and stress-evoked gene expression in the rat spinal cord dorsal horn and hippocampus. Rats were pretreated with either indomethacin or imipramine and then challenged with either intraplantar complete Freund's adjuvant or a bout of immobilization stress. Results showed that indomethacin significantly reduced nociception-related peripheral edema, hyperalgesia, and reversed the pain-evoked up-regulation of neurokinin (NK)-1 receptor and brain-derived neurotrophic factor (BDNF) gene expression in the spinal cord to levels not statistically different from controls. However, indomethacin did not protect against significant pain-induced down-regulation of these genes in the hippocampus by approximately 50%, suggesting that although analgesic drug treatment reduces nociceptive sensory activation in the spinal cord, it is insufficient to prevent the impact of pain on the hippocampus. Conversely, although imipramine did not provide significant behavioral analgesia, it significantly blocked both pain- and stress-evoked alterations in hippocampal and spinal NK-1 and BDNF gene expression. Thus, these results show that application of either analgesic or antidepressant drugs alone does not fully protect against both the behavioral and molecular effects of persistent pain on both "sensory" and "affective" processing within the central nervous system.

Brain-derived neurotrophic factor (BDNF) is an essential neurotrophin and regulation of its expression is complex due to multiple 5' untranslated exons which are separately spliced to a common coding exon to form unique mRNA transcripts. Disruption of BDNF gene expression is a key to the development of symptoms in Huntington's disease (HD), a fatal neurodegenerative condition. Abnormal epigenetic modifications are associated with reduced gene expression in late-stage HD but such regulation of BDNF gene expression has yet to be investigated. We hypothesized that BDNF gene expression is altered in the HD hippocampus of pre-motor symptomatic R6/1 transgenic HD mice, correlating with a change in the DNA methylation profile. The effects of wheel-running and environmental enrichment on wild-type mice, in association with a proposed environment-mediated correction of BDNF gene expression deficits in HD mice, were also investigated. Using real-time PCR, levels of total BDNF mRNA were found to be reduced in the hippocampus of both male and female HD mice. Wheel-running significantly increased total BDNF gene expression in all groups of mice except male HD mice. In contrast, environmental enrichment significantly increased expression only in male wild-type animals. Further quantification of BDNF exon-specific transcripts revealed sex-specific changes in relation to the effect of the HD mutation and differential effects on gene expression by wheel-running and environmental enrichment. The HD-associated reduction of BDNF gene expression was not due to increased methylation of the gene sequence. Furthermore, environment-induced changes in BDNF gene expression in the wild-type hippocampus were independent of the extent of DNA methylation. Overall, the results of this study provide new insight into the role of BDNF in HD pathogenesis in addition to the mechanisms regulating normal BDNF gene expression.

Brain-derived neurotrophic factor (BDNF) may play a role in the pathophysiology of neuronal cell death after cerebral ischemia. We investigated alterations in BDNF gene expression and the effect of BDNF on neuronal death after transient forebrain ischemia in the rat brain. Transient forebrain ischemia was induced by occlusion of the bilateral common carotid arteries and by producing systemic hypotension for 8 minutes. The alterations in the BDNF messenger ribonucleic acid content in the hippocampus and the cerebral cortex were examined by Northern blot analysis, using a phosphorus-32-labeled mouse BDNF complementary deoxyribonucleic acid probe. Recombinant Chinese hamster ovary cells with BDNF-secreting capacity were established by expression vector transfection with BDNF complementary deoxyribonucleic acid. The effect of BDNF on neuronal death in the hippocampal CA1 region after ischemia was then examined by using a continuous intraventricular infusion of 200 microliters of normal (Group II, n = 6) or 30-times concentrated recombinant Chinese hamster ovary cell culture medium containing BDNF (Group IV, n = 6). Normal (Group I, n = 6) or 30-times concentrated (Group III, n = 6) Chinese hamster ovary cell culture medium, not including BDNF complementary deoxyribonucleic acid, was infused into the same ischemic brains, which served as controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations of BDNF and NT-3 genes expression in the nucleus paragigantocellularis during morphine dependency and withdrawal

Thyroid hormones play a vital function in the maturation in the course of mind development. Regarding the well-known effects of choline on brain-derived neurotrophic factor (BDNF), the study examined the effects of choline on hippocampal BDNF gene expression in maternal hypothyroidism rats. To induce the hypothyroidism, 6-propyl-2-thiouracil was introduced to the ingesting water from the sixth day of gestation to twenty-first postnatal day (PND). Choline-treatment started twice a day on the first day of gestation until PND 21. On PND28, pups were sacrificed. The expression of BDNF gene was evaluated after the hippocampus was harvested. Our results demonstrated that both male and female pre-pubertal offspring rats' BDNF gene expression was decreased by developmental hypothyroidism. Choline increases the ratio of relative gene expression of BDNF in the hippocampus of males and females in the control/hypothyroidism group, especially in males. It can be concluded that maternal choline supplementation on the first day of gestation until PND 21 improves brain development and cognitive function in pre-pubertal offspring rats regarding control/hypothyroidism groups.

Brain-derived neurotrophic factor (BDNF) is a growth factor that has a central role in sustaining brain function. Besides the brain, BDNF is also expressed in immune cells. In preclinical models, anthocyanins (AC) consumption has been associated with benefits in BDNF homeostasis. This study investigated in healthy adults if the simultaneous consumption of a high-fat meal (HFM) with a cyanidin/delphinidin-rich extract (CDRE) could affect circulating BDNF, and BDNF expression in peripheral blood mononuclear cells (PBMCs). Underlying mechanisms were investigated in Jurkat T cells. While the HFM did not affect serum BDNF in the placebo group, simultaneous CDRE consumption caused a significant cumulative (1-3 h) BDNF increase, peaking at 2 h post-meal. The area under the curve (AUC) for the most abundant phenolic acids measured in serum, i.e., 4-hydroxyhippuric acid (HA) and 4-hydroxy-3-methoxybenzoic acid (vanillic acid, VA)-3-O-glucuronide correlated with the AUC for serum BDNF. As evaluated in Jurkat T cells, this could be due to HA and VA's capacity to increase cytosolic calcium. The CDRE also increased BDNF expression in PBMCs 3 h post-consumption. In vitro and molecular modeling evidence point to two mechanisms of action: (i) indirect protection of BDNF expression through CDRE anti-inflammatory actions, and (ii) a direct capacity of HA and VA to activate the β2-adrenergic receptor and downstream cAMP/PKA/CREB-mediated increased BDNF gene expression. While the short-term effects of CDRE consumption can be due to HA and VA presence in the extract, AC and phenolic acid metabolism by the microbiota would later generate HA and VA and consequently benefit BDNF homeostasis.

Age-related decrease in brain-derived neurotrophic factor gene expression in the brain of the zitter rat with genetic spongiform encephalopathy

Facilitation of AVP(4–8) on Gene Expression of BDNF and NGF in Rat Brain

Maternal high-fat diet stimulates proinflammatory pathway and increases the expression of Tryptophan Hydroxylase 2 (TPH2) and brain-derived neurotrophic factor (BDNF) in adolescent mice hippocampus

Progesterone treatment has previously been reported to promote the differentiation of glial cells probably through the production of 5alpha-reduced neurosteroids, resulting in the enhancement of serotonin-stimulated brain-derived neurotrophic factor (BDNF) gene expression, which is considered to contribute to the survival, regeneration, and plasticity of neuronal cells in the brain and hence has been suggested to improve mood disorders and other symptoms in depressive patients. Based on these previous observations, the effects on glial cells of histone deacetylase (HDAC) inhibitors, which are known as agents promoting cell differentiation, were examined using rat C6 glioma cells as a model for in vitro studies. Consequently, trichostatin A (TSA), sodium butyrate (NaB), and valproic acid (VPA) stimulated glial fibrillary acidic protein (GFAP) gene expression, and their stimulatory effects on GFAP gene expression were inhibited by treatment of these cells with finasteride, an inhibitor of the enzyme producing 5alpha-reduced neurosteroids. In addition, HDAC inhibitors enhanced serotonin-stimulated BDNF gene expression, the enhancement of which could be abolished by the inhibition of 5alpha-reduced neurosteroid production in the glioma cells. These results suggest that HDAC inhibitors may be able to promote the differentiation of rat C6 glioma cells through the production of 5alpha-reduced neurosteroids, resulting in the enhancement of serotonin-stimulated BDNF gene expression as a consequence of promoting their differentiation, indicating the possibility that differentiated glial cells may be implicated in preserving the integrity of neural networks as well as improving the function of neuronal cells in the brain.