Blood-brain barrier targeting of BDNF improves motor function in rats with middle cerebral artery occlusion

Intravenous brain-derived neurotrophic factor (BDNF) causes a 65-70% reduction in stroke volume in rats with the middle cerebral artery occlusion (MCAO), provided the BDNF is conjugated to a blood-brain barrier (BBB) molecular Trojan horse. The latter may be a peptidomimetic monoclonal antibody (MAb) to the transferrin receptor. The present studies determine whether the effects on stroke volume correlate with an improvement in neuro-behavior using the rotarod test. The rotarod latency was >200 s at 16 RPM in all rats pre-MCAO. The latency was 30+/-7 s and 103+/-9 s at 24 h post-MCAO in the animals treated with BDNF alone and the BDNF-MAb conjugate, respectively. These studies show that when BDNF is formulated to enable transport across the BBB, the intravenous administration of the neurotrophin results in a reduction in stroke volume that is associated with a parallel improvement in functional outcome.     

Neurotrophins and neuronal migration in the developing rodent brain

Neurotrophins are known to be key regulators of neuronal survival, differentiation, function and plasticity in the developing and adult rodent brain. A novel role for neurotrophins has been emerging from recent research, that of motogenic and chemoattractant factors for several populations of migrating neuronal precursors in the developing mouse brain. The aim of the present article is to summarize and discuss the studies that have contributed to the existing body of evidence.     

Relation between plasma brain-derived neurotrophic factor and nerve growth factor in the male patients with alcohol dependence

Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are thought to be related to neuroprotection in cell culture and animal studies. Our aim was to verify the changes in human plasma BDNF and NGF concentrations induced by chronic alcohol use. Forty-one male patients with alcohol dependence were sampled the next morning of admission and compared with 41 healthy male subjects. Plasma BDNF and NGF were assayed using an enzyme-linked immunosorbent assay (ELISA). Mean plasma BDNF level was significantly higher in the patients with alcohol dependence (3502.21 ± 1726.9 pg/mL) compared with the healthy subjects (861.75 ± 478.9 pg/mL) (P = .000). Mean plasma NGF level was also significantly higher in patients with alcohol dependence (137.64 ± 32.7 pg/mL) than in healthy subjects (112.61 ± 90.2 pg/mL) (P = .012). Plasma BDNF and NGF levels showed significant negative correlation in alcohol dependence group (r = −0.388, P = .012). Increased plasma BDNF and NGF with negative correlation in alcohol-dependent patients may have some role in the regeneration of damage done by chronic alcohol use.     

Developmental co-expression and functional redundancy of tyrosine phosphatases with neurotrophin receptors in developing sensory neurons

Receptor-type protein tyrosine phosphatases (RPTPs) have been implicated as direct or indirect regulators of neurotrophin receptors (TRKs). It remains less clear if and how such RPTPs might regulate TRK proteins in vivo during development. Here we present a comparative expression profile of RPTP genes and Trk genes during early stages of murine, dorsal root ganglion maturation. We find little if any specific, temporal mRNA co-regulation between individual RPTP and Ntrk genes between E12.5 and E14.5. Moreover, a double fluorescent in-situ hybridization and immunofluorescence study of seven Rptp genes with Ntrks revealed widespread co-expression of RPTPs in individual neurons, but no tight correlation with Trk expression profiles. No Rptp is expressed in 100% of Ntrk1-expressing neurons, whereas at least 6 RPTPs are expressed in 100% of Ntrk2- and Ntrk3-expressing neurons. An exception is Ptpro, which showed very selective expression. Short hairpin RNA suppression of Ptprf, Ptprs or Ptpro in primary, E13.5 DRG neurons did not alter TRK signalling. We therefore propose that TRK signalling may not be simply dependent on rate-limiting regulation by individual RPTP subtypes during sensory neuron development. Instead, TRK signalling has the potential to be buffered by concurrent inputs from several RPTPs in individual neurons.     

Downregulation of BDNF mRNA and protein in the rat hippocampus by corticosterone

Previously, we showed that corticosterone regulates BDNF mRNA levels in the hippocampus. In the present study, we have investigated the time course and dose-dependency of this effect at both the mRNA and the protein level. Corticosterone was administered in doses of 30 and 1000 μg/kg b.w. subcutaneously to adrenalectomized animals. At 3, 6, 12 and 24 h after administration BDNF and trkB mRNA levels in hippocampal subfields were measured by in situ hybridization. Our results show a dose-dependent decrease in BDNF mRNA in dentate gyrus and CA1 at 3 h. After the high dose, this decrease was 70% and 40% respectively. In addition, ELISA was performed to study if this downregulation is also detectable at the protein level. Hippocampal tissue was used from adrenalectomized animals which had received 1000 μg/kg b.w. corticosterone 4 and 6 h before decapitation. At both time points, a decrease in BDNF protein was observed; 17% at 4 h and 14% at 6 h after corticosterone, as compared to the vehicle injected controls. TrkB mRNA levels were not affected by corticosterone. However, between 6 and 24 h after treatment, increases in trkB mRNA were observed. In conclusion, we have found a transient, dose-dependent decrease in BDNF mRNA and protein in the hippocampus, which may underly changes in neuronal plasticity in the hippocampus after short-term changes in corticosterone concentrations.     

Maternal obesity alters brain derived neurotrophic factor (BDNF) signaling in the placenta in a sexually dimorphic manner

IntroductionObesity is a major clinical problem in obstetrics being associated with adverse pregnancy outcomes and fetal programming. Brain derived neurotrophic factor (BDNF), a validated miR-210 target, is necessary for placental development, fetal growth, glucose metabolism, and energy homeostasis. Plasma BDNF levels are reduced in obese individuals; however, placental BDNF has yet to be studied in the context of maternal obesity. In this study, we investigated the effect of maternal obesity and sexual dimorphism on placental BDNF signaling.MethodsBDNF signaling was measured in placentas from lean (pre-pregnancy BMI < 25) and obese (pre-pregnancy BMI>30) women at term without medical complications that delivered via cesarean section without labor. MiRNA-210, BDNF mRNA, proBDNF, and mature BDNF were measured by RT – PCR, ELISA, and Western blot. Downstream signaling via TRKB (BDNF receptor) was measured using Western blot.ResultsMaternal obesity was associated with increased miRNA-210 and decreased BDNF mRNA in placentas from female fetuses, and decreased proBDNF in placentas from male fetuses. We also identified decreased mature BDNF in placentas from male fetuses when compared to female fetuses. Mir-210 expression was negatively correlated with mature BDNF protein. TRKB phosphorylated at tyrosine 817, not tyrosine 515, was increased in placentas from obese women. Maternal obesity was associated with increased phosphorylation of MAPK p38 in placentas from male fetuses, but not phosphorylation of ERK p42/44.DiscussionBDNF regulation is complex and highly regulated. Pre-pregnancy/early maternal obesity adversely affects BDNF/TRKB signaling in the placenta in a sexually dimorphic manner. These data collectively suggest that induction of placental TRKB signaling could ameliorate the placental OB phenotype, thus improving perinatal outcome.     

人神经营养素—4基因的扩增及序列分析

从人基因组DNA获取神经营养素－4（neurotrophin-4,NT-4)基因，并对该目的基因进行序列测定，本实验直接从人脑组织中提取基因组DNA，根据人神经营养素－4的cDNA序列，设计一对寡核苷酸引物，采用PCR，获得人NT－4基因，用DNA序列分析NT－4基因，结果，我们获取的人NT－4基因与献报道有五个碱基不同，我们认为：直接采用PCR来获取目的基因，出现碱基错配的可能性较大；测序仪器和实验条件对结果有一定影响关系。     

Increased neurogenesis and the ectopic granule cells after intrahippocampal BDNF infusion in adult rats

There is evidence that BDNF influences the birth of granule cells in the dentate gyrus, which is one of the few areas of the brain that demonstrates neurogenesis throughout life. However, studies to date have not examined this issue directly. To do so, we compared the effects of BDNF, phosphate-buffered saline (PBS), or bovine serum albumin (BSA) on neurogenesis after infusion into the hippocampus of the normal adult rat, using osmotic pumps that were implanted unilaterally in the dorsal hilus. BDNF, PBS, and BSA were infused for 2 weeks. The mitotic marker bromodeoxyuridine (BrdU) was administered twice daily during the 2-week infusion period. At least 1 month after infusion ended, brains were processed immunocytochemically using antibodies to BrdU, a neuronal nuclear protein (NeuN), or calbindin D28K (CaBP), which labels mature granule cells. Stereology was used to quantify BrdU-labeled cells in the dorsal hippocampus that were double-labeled with NeuN or CaBP. There was a statistically significant increase in BrdU(+)/NeuN(+) double-labeled cells in the granule cell layer after BDNF infusion relative to controls. The values for BrdU(+)/NeuN(+) cells were similar to BrdU(+)/CaBP(+) cells, indicating that most new neurons were likely to be granule cells. In addition, BrdU(+)/NeuN(+)-labeled cells developed in the hilar region after BDNF infusion, which have previously only been identified after severe continuous seizures (status epilepticus) and associated pathological changes. Remarkably, neurogenesis was also increased contralaterally, but BDNF did not appear to spread to the opposite hemisphere. Thus, infusion of BDNF to a local area can have widespread effects on hippocampal neurogenesis. The results demonstrate that BDNF administration to the dentate gyrus leads to increased neurogenesis of granule cells. They also show that ectopic granule cells develop after BDNF infusion, which suggests that ectopic migration is not necessarily confined to pathological conditions. These results are discussed in light of the evidence that BDNF increases neuronal activity in hippocampus. Thus, the mechanisms underlying neurogenesis following BDNF infusion could be due to altered activity as well as direct effects of BDNF itself, and this is relevant to studies of other growth factors because many of them have effects on neuronal excitability that are often not considered.