Inhibition by Methylprednisolone Acetate Suggests an Indirect Mechanism for TGF-B Induced Angiogenesis

Abstract

Angiogenesis induced by transforming growth factor beta (TGFB) implanted in the rabbit cornea is accorripanied by an influx of inflammatory cells. To determine if the inflammatory cells are the mediators of the neovascularization, they were depleted by local administration of methylprednisolone acetate (MPA). Subconjunctival injections of 16 mg of MPA immediately following implantation of 50 ng of TGFB in the cornea prevented the inflammation and subsequent formation of capillaries. If the injections of MPA were delayed by 48 hr and the inflammatory cells were allowed to enter the cornea, angiogenesis occured, demonstrating that MPA had no adverse effects on the ability of endothelial cells to form capillaries. These results confirm the hypothesis that TGFB induces angiogenesis indirectly by recruiting inflammatory cells capable of stimulating direct angiogenesis.     

Impairment of the septal cholinergic neurons in MPTP-treated A30P α-synuclein mice

Dementia in Parkinson's disease (PDD) and dementia with Lewy bodies (DLB) are characterized by loss of acetylcholine (ACh) from cortical areas. Clinical studies report positive effects of acetylcholine esterase (AChE) inhibitors in PDD and dementia with Lewy bodies. We here report that the number of neurons expressing a cholinergic marker in the medial septum-diagonal band of Broca complex decreases in A30P α-synuclein-expressing mice during aging, paralleled by a lower AChE fiber density in the dentate gyrus and in the hippocampal CA1 field. After inducing dopamine depletion by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP), no acute but a delayed loss of cholinergic neurons and AChE-positive fibers was observed, which was attenuated by L-3,4-dihydroxyphenylalanine (DOPA) treatment. Expression of nerve growth factor (NGF) and tyrosine receptor kinase A (TrkA) genes was upregulated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride-treated wild type mice, but not in A30P α-synuclein expressing animals. In contrast, upregulation of sortilin and p75^NTR genes was found in the A30P α-synuclein-expressing mice. These results suggest that dopamine deficiency may contribute to the impairment of the septohippocampal system in patients with PDD and that L-3,4-dihydroxyphenylalanine may not only result in symptomatic treatment of the akinetic-rigid syndrome but may also alleviate the degeneration of basal forebrain cholinergic system and the cognitive decline.     

Analgesia via blockade of NGF/TrkA signaling does not influence fracture healing in mice

Abatement of fracture‐related pain is important in patient welfare. However, the frequently used non‐steroidal anti‐inflammatory drugs are considered to impair fracture healing through blockade of cyclooxygenase‐2. An alternative for fracture‐related pain treatment may be blockade of nerve growth factor (NGF)/neurotrophic tyrosine kinase receptor type 1 (TrkA) signaling. Because the effect of blocking this signal‐pathway on bone healing has not been extensively investigated, we addressed this issue by applying neutralizing antibodies that target NGF and TrkA, respectively, in a mouse fracture model. Mice with a knock‐in for human TrkA underwent femur osteotomy and were randomly allocated to phosphate‐buffered‐saline, anti‐NGF‐antibody, or anti‐TrkA‐antibody treatment. The analgesic effect of the antibodies was determined from the activity and the ground reaction force of the operated limb. The effect of antibody administration on fracture healing was assessed by histomorphometry, micro‐computed tomography, and biomechanics. NGF/TrkA‐signaling blockade had no negative effect on fracture healing as callus formation and maturation were not altered. Mice treated with anti‐TrkA antibody displayed significantly greater activity on post‐operative day 2 compared to PBS treatment indicating effective analgesia. Our data indicate, that blockade of NGF/TrkA signaling via specific neutralizing antibodies for pain reduction during fracture healing does not influence fracture healing. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1235–1241, 2015.     

Glia cell line‐derived neurotrophic factor mediates survival of murine sympathetic precursors

During embryonic development, neurons are first produced in excess, and final numbers are adjusted by apoptosis at later stages. Crucial to this end is the amount of target‐derived growth factor available for the neurons. By this means, the target size correctly matches the innervating neuron number. This target‐derived survival has been well studied for sympathetic neurons, and nerve growth factor (NGF) was identified to be the crucial factor for maintaining sympathetic neurons at late embryonic and early postnatal stages, with a virtual complete loss of sympathetic neurons in NGF knockout (KO) mice. This indicates that all sympathetic neurons are dependent on NGF. However, also different glia cell line‐derived neurotrophic factor (GDNF) KO mice consistently presented a loss of sympathetic neurons. This was the rationale for investigating the role of GDNF for sympathetic precursor/neuron survival. Here we show that GDNF is capable of promoting survival of 30% sympathetic precursors dissociated at E13. This is in line with data from GDNF KOs in which a comparable sympathetic neuron loss was observed at late embryonic stages, although the onset of the phenotype was unclear. We further present data showing that GDNF ligand and canonical receptors are expressed in sympathetic neurons especially at embryonic stages, raising the possibility of an autocrine/paracrine GDNF action. Finally, we show that GDNF also maintained neonatal sympathetic neurons (40%) cultured for 2 days. However, the GDNF responsiveness was lost at 5 days in vitro. © 2013 Wiley Periodicals, Inc.     

Oligodendrogenesis from neural stem cells: Perspectives for remyelinating strategies

Mobilization of remyelinating cells spontaneously occurs in the adult brain. These cellular resources are specially active after demyelinating episodes in early phases of multiple sclerosis (MS). Indeed, oligodendrocyte precursor cells (OPCs) actively proliferate, migrate to and repopulate the lesioned areas. Ultimately, efficient remyelination is accomplished when new oligodendrocytes reinvest nude neuronal axons, restoring the normal properties of impulse conduction. As the disease progresses this fundamental process fails. Multiple causes seem to contribute to such transient decline, including the failure of OPCs to differentiate and enwrap the vulnerable neuronal axons. Regenerative medicine for MS has been mainly centered on the recruitment of endogenous self-repair mechanisms, or on transplantation approaches. The latter commonly involves grafting of neural precursor cells (NPCs) or neural stem cells (NSCs), with myelinogenic potential, in the injured areas. Both strategies require further understanding of the biology of oligodendrocyte differentiation and remyelination. Indeed, the success of transplantation largely depends on the pre-commitment of transplanted NPCs or NSCs into oligodendroglial cell type, while the endogenous differentiation of OPCs needs to be boosted in chronic stages of the disease. Thus, much effort has been focused on finding molecular targets that drive oligodendrocytes commitment and development. The present review explores several aspects of remyelination that must be considered in the design of a cell-based therapy for MS, and explores more deeply the challenge of fostering oligodendrogenesis. In this regard, we discuss herein a tool developed in our research group useful to search novel oligodendrogenic factors and to study oligodendrocyte differentiation in a time- and cost-saving manner.     

Higher levels of brain derived neurotrophic factor but similar nerve growth factor in human milk in women with preeclampsia

Children born to mothers with preeclampsia have consistently been suggested to be at risk for cognitive and behavioral disorders in later life. Breastfeeding is said to be associated with better neurodevelopment outcomes. Our earlier studies indicated higher levels of docosahexaenoic acid (DHA) in human milk in women with preeclampsia. DHA is known to regulate the expression of neurotrophins and together they play a vital role in neurodevelopment and cognitive performance. The present study examines the levels of maternal plasma and milk neurotrophins [(nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF)] in women with preeclampsia and compares them with normotensive women who served as controls. Singleton pregnant women diagnosed with preeclampsia (n = 72) and controls (n = 102) were recruited for this study from Bharati Hospital, Pune. Plasma and milk samples were analyzed for NGF and BDNF levels using the Emax Immuno Assay System using promega kits. Maternal plasma NGF and BDNF levels were lower (p < 0.01 for both) in women with preeclampsia as compared to the control women. Milk NGF levels were similar while milk BDNF levels were higher (p < 0.05) in the preeclampsia group as compared to controls. Plasma NGF levels were positively correlated with milk NGF levels in the control group. Our results indicate the differential regulation of milk NGF and BDNF levels in women with preeclampsia. The present study suggests a role for both NGF and BDNF in human milk for postnatal brain development. Further studies need to examine the associations of DHA and BDNF in human milk with cognition at later ages.     

Short‐term environmental enrichment,in the absence of exercise,improves memory,and increases NGF concentration,early neuronal survival,and synaptogenesis in the dentate gyrus in a time‐dependent manner

Environmental manipulations can enhance neuroplasticity in the brain, with enrichment‐induced cognitive improvements being linked to increased expression of growth factors, such as neurotrophins, and enhanced hippocampal neurogenesis. There is, however, a great deal of variation in environmental enrichment protocols used in the literature, making it difficult to assess the role of particular aspects of enrichment upon memory and the underlying associated mechanisms. This study sought to evaluate the efficacy of environmental enrichment, in the absence of exercise, as a cognitive enhancer and assess the role of Nerve Growth Factor (NGF), neurogenesis and synaptogenesis in this process. We report that rats housed in an enriched environment for 3 and 6 weeks (wk) displayed improved recognition memory, while rats enriched for 6 wk also displayed improved spatial and working memory. Neurochemical analyses revealed significant increases in NGF concentration and subgranular progenitor cell survival (as measured by BrdU+ nuclei) in the dentate gyrus of rats enriched for 6 wk, suggesting that these cellular changes may mediate the enrichment‐induced memory improvements. Further analysis revealed a significant positive correlation between recognition task performance and BrdU+ nuclei. In addition, rats enriched for 6 wk showed a significant increase in expression of synaptophysin and synapsin I in the dentate gyrus, indicating that environmental enrichment can increase synaptogenesis. These data indicate a time‐dependent cognitive‐enhancing effect of environmental enrichment that is independent of physical activity. These data also support a role for increased concentration of NGF in dentate gyrus, synaptogenesis, and neurogenesis in mediating this effect. © 2013 Wiley Periodicals, Inc.     

Neurotrophin gene expression in rat brain under the action of Semax, an analogue of ACTH 4-10

The heptapeptide Semax, an analogue of the N-terminal adrenocorticotropic hormone fragment (4-10) (ACTH(4-10)), has been shown to exert a number of neuroprotective effects. There are some investigations that connected these effects with the increase of neurotrophin gene expression under the peptide drug application in neuron cell cultures [M.I. Shadrina, O.V. Dolotov, I.A. Grivennikov, P.A. Slominsky, L.A. Andreeva, L.S. Inozemtseva, S.A. Limborska, N.F. Myasoedov, Rapid induction of neurotrophin mRNAs in rat glial cell cultures by Semax, an adrenocorticotropic hormone analogue, Neurosci. Lett. 308 (2001) (2) 115-118]. In this work, we examined the action of Semax on rapid changes of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) gene expression in vivo. Male Wistar rats were treated for 1h with Semax (50 microg/kg, single intranasal application) and neurotrophin gene expression in rat brain was analyzed by real-time polymerase chain reaction (PCR). It was revealed that an intranasal application of Semax increased the expression of both neurotrophin genes in rat hippocampus. Bdnf gene expression also increased in the brainstem and cerebellum. Ngf gene expression decreased in rat frontal cortex. Thus, Semax induces rapid, gene- and region-specific changes in neurotrophin gene expression in normal rat brain.