Protective Effect Of Nerve Growth Factor Research Articles

NGF protects bone marrow mesenchymal stem cells against 2,5-hexanedione-induced apoptosis in vitro via Akt/Bad signal pathway.

Mesenchymal stem cell transplantation has been proposed as a promising therapy for regeneration of damaged tissues-especially, bone marrow mesenchymal stem cell (BMSC) transplantation therapy is considered to be an effective strategy for treating various injures in recent years. However, poor viability of transplanted BMSCs in injured tissues has limited their therapeutic efficiency. Nerve growth factor (NGF) has been reported to be a pro-survival factor in series of cells. Moreover, NGF could improve BMSC viability and activate anti-apoptotic pathway. Therefore, we are interested to know whether NGF promoted BMSC survival in transplanted tissue. In this study, we investigated the protective effect and potential mechanisms of NGF against apoptosis of BMSCs in vitro. 2,5-hexanedione (HD) was the apoptosis inducer. BMSCs were treated with 40mM HD and different concentrations of NGF (0, 50, 100, 200μg/L) together for 24h. Results showed that NGF treatment increased the viability of BMSCs exposed to HD. Moreover, NGF effectively suppressed HD-induced apoptosis which was characterized by inhibiting caspase-3 activity, as well as mitochondrial transmembrane potential depolarization. Mechanistically, it was found that NGF promoted phosphorylation of Akt and Bad, which is TrkA dependent. However, K252a and MK-2206 (TrkA and Akt inhibitor, respectively) suppressed the anti-apoptosis of NGF, indicating the protective effect of NGF on BMSCs apoptosis via a novel Akt/Bad pathway. The findings suggested that NGF may be used as an effective protective agent against BMSC apoptosis so as to promote the survival rate of transplanted BMSCs and their tissue repair capability.

Nerve growth factor alleviates cerebral infarction and neurologic deficits by regulating VEGF, SDF-1 and S100A12 expression through PI3K pathway

Stroke remains the leading cause of death and disability worldwide, which destroys the quality of patients’ lives and thus is becoming a heavy burden to the society. However, the current therapeutic approaches are far from satisfaction. The objective of this study is to elucidate the impact of nerve growth factor (NGF) on the brain damage induced by cerebral ischemia and its potential molecular mechanism. Middle cerebral artery occlusion (MCAO) rats were used as animal models and neurological functions were evaluated by modified Neurological Severity Score (NSS). Brain cell apoptosis was analyzed by TUNEL-positive staining while brain infarct size was determined according to 2% 2,3,5-triphenyltetrazolium chloride (TCC) staining volume. Rats receiving NGF demonstrated significantly alleviated brain damage, reflected by a substantial improvement in the neurobehavioral outcome, a decrease in brain cell apoptosis and shrinkage of brain infarct volume. Further analysis revealed a markedly elevated circulating vascular endothelial growth factor (VEGF) and stromal cell-derived factor 1 (SDF-1) levels as well as a significant downregulation of SA10012 expression in NGF treated group compared with the untreated group. Strikingly, the protective effect of NGF on cerebral ischemic injury was abolished in rats treated with both NGF and PI3K inhibitors, indicating that phosphoinositide-3-kinase (PI3K) signaling is essential for NGF function. In conclusion, NGF treatment might be a potential therapeutic approach against cerebral infarction by downregulating SA10012 expression and upregulating VEGF, SDF-1 in a PI3K signaling dependent manner.

Nerve growth factor-induced Akt/mTOR activation protects the ischemic heart via restoring autophagic flux and attenuating ubiquitinated protein accumulation.

The dysregulation of autophagy is related to a variety of cardiovascular diseases, such as myocardial ischemia/reperfusion (I/R). Nerve growth factor (NGF) has been shown to have therapeutic potential in ischaemic heart injury. In this study, we demonstrate that NGF administration can accelerate autophagic flux and attenuate protein ubiquitination in myocardial I/R heart. Our results showed that NGF could restored heart function and decreased the apoptosis of cardiomyocytes which induced by myocardial I/R injury. The protective effect of NGF is associated with the inhibition of autophagy related proteins. On another hand, NGF enhances the clearance of ubiquitinated protein and increases the survival of myocardial cell in vivo and in vitro. Additionally, NGF could activate the PI3K/AKT and mTOR signaling pathways. These results suggested that the cardioprotective effect of NGF is related to the restoration of autophagic flux and attenuation of protein ubiquitination via the activation of PI3K/AKT and mTOR pathway.

Nerve growth factor protects against palmitic acid-induced injury in retinal ganglion cells.

Accumulating evidence supports an important role for nerve growth factor (NGF) in diabetic retinopathy. We hypothesized that NGF has a protective effect on rat retinal ganglion RGC-5 cells injured by palmitic acid (PA), a metabolic factor implicated in the development of diabetes and its complications. Our results show that PA exposure caused apoptosis of RGC-5 cells, while NGF protected against PA insult in a concentration-dependent manner. Additionally, NGF significantly attenuated the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) in RGC-5 cells. Pathway inhibitor tests showed that the protective effect of NGF was completely reversed by LY294002 (PI3K inhibitor), Akt VIII inhibitor, and PD98059 (ERK1/2 inhibitor). Western blot analysis revealed that NGF induced the phosphorylation of Akt/FoxO1 and ERK1/2 and reversed the PA-evoked reduction in the levels of these proteins. These results indicate that NGF protects RGC-5 cells against PA-induced injury through anti-oxidation and inhibition of apoptosis by modulation of the PI3K/Akt and ERK1/2 signaling pathways.

Nerve growth factor protects retinal ganglion cells against injury induced by retinal ischemia–reperfusion in rats

In this study, we investigated the protective effect of mouse nerve growth factor (NGF) on retinal ganglion cell (RGC) injury induced by retinal ischemia–reperfusion (RIR) in rats and explored its possible mechanisms of action. RIR caused a significant injury to RGCs and an obvious impairment of the inner retina functions, which could be seen from flash electroretinogram and flash visual evoked potential recordings. RIR also increased the expression of the apoptotic protein Bax while decreasing the expression of Bcl-2 and the phosphorylation of protein kinase B (Akt) in RGCs. Preinjection (i.m.) of NGF for 22 d reversed the injury induced by RIR and ameliorated the inner retina functions. NGF also reduced the expression of Bax and reversed the reduction of Bcl-2 and the phosphorylated Akt induced by RIR. These results indicate that NGF produces a neuroprotective effect on RGCs against RIR injury and the protective effect of NGF is mainly mediated by the PI-3K/Akt signaling pathway.

Cyclic-AMP response element binding protein and tau are involved in the neuroprotective mechanisms of nerve growth factor during focal cerebral ischemia/reperfusion in rats

Nerve growth factor (NGF) has protective and therapeutic effects after cerebral ischemic injury. However, its mechanism of action is not clear. We explored the protective mechanism of exogenous NGF on rat hippocampal neurons after focal cerebral ischemia/reperfusion. Changes were detected in the expression of cyclic-adenosine monophosphate (AMP) response element binding protein (CREB) messenger ribonucleic acid (mRNA), CREB protein, phosphorylated CREB, tau mRNA, total tau protein and the state of phosphorylation of tau protein at the serine 199/202 site. NGF treatment significantly increased the expression of CREB mRNA, CREB and phosphorylated CREB in the hippocampal CA1 region. NGF alleviated the level of phosphorylation of tau and the expression level of total tau. It is possible that the protective effect of NGF on the ischemic neuron was due to the activation of transcription and translation of CREB, the reduction in the level of phosphorylation of tau protein, and the activation of a series of signal pathways.

Neuroprotection by NGF and BDNF Against Neurotoxin-Exerted Apoptotic Death in Neural Stem Cells Are Mediated Through Trk Receptors, Activating PI3-Kinase and MAPK Pathways

Neural stem cells (NSC) undergo apoptotic cell death during development of nervous system and in adult. However, little is known about the biochemical regulation of neuroprotection by neurotrophin in these cells. In this report, we demonstrate that Staurosporine (STS) and Etoposide (ETS) induced apoptotic cell death of NSC by a mechanism requiring Caspase 3 activation, poly (ADP-ribose) polymerase and Lamin A/C cleavage. Although C17.2 cells revealed higher mRNA level of p75 neurotrophin receptor (p75(NTR)) compared with TrkA or TrkB receptor, neuroprotective effect of both nerve growth factor (NGF) and brain-derived growth factor (BDNF) mediated through the activation of tropomyosin receptor kinase (Trk) receptors. Moreover, both NGF and BDNF induced the activation of the phosphatidylinositide 3 kinase (PI3K)/Akt and the mitogen-activated protein kinase (MAPK) pathway. Inhibition of Trk receptor by K252a reduced PARP cleavage as well as cell viability, whereas inhibition of p75(NTR) did not affect the effect of neurotrophin on neurotoxic insults. Thus our studies indicate that the protective effect of NGF and BDNF in NSC against apoptotic stimuli is mediated by the PI3K/Akt and MAPK signaling pathway via Trk receptors.

Neurotrophic Factors Stabilize Microtubules and Protect against Rotenone Toxicity on Dopaminergic Neurons

Parkinson disease is characterized by the selective degeneration of dopaminergic (DA) neurons in substantia nigra. Long term epidemiological studies have implicated exposure to agricultural pesticides as a significant risk factor. Systemic administration of rotenone, a widely used pesticide, causes selective degeneration of nigral DA neurons and Parkinson disease-like symptoms in rats. Our previous study has shown that the microtubule depolymerizing activity of rotenone plays a critical role in its selective toxicity on DA neurons. Rotenone toxicity is mimicked by the microtubule-depolymerizing drug colchicine and attenuated by the microtubule-stabilizing agent taxol. Here we show that nerve growth factor (NGF) significantly reduced rotenone toxicity on TH(+) neurons in midbrain neuronal cultures. The protective effect of NGF was completely abolished by inhibiting the microtubule-associated protein kinase kinase (MEK) and partially reversed by blocking phosphatidylinositol 3-kinase. In addition, NGF decreased colchicine toxicity on TH(+) neurons in a manner dependent on MEK but not phosphatidylinositol 3-kinase. The protective effect of NGF against rotenone toxicity was occluded by the microtubule-stabilizing drug taxol. In a MEK-dependent manner, NGF significantly attenuated rotenone- or colchicine-induced microtubule depolymerization and ensuing accumulation of vesicles in the soma and elevation in protein carbonyls. Moreover, other neurotrophic factors such as brain-derived neurotrophic factor and glia cell line-derived neurotrophic factor also reduced rotenone- or colchicine-induced microtubule depolymerization and death of TH(+) through a MEK-dependent mechanism. Thus, our results suggest that neurotrophic factors activate the microtubule-associated protein kinase pathway to stabilize microtubules, and this action significantly attenuates rotenone toxicity on dopaminergic neurons.

Possible Antiapoptotic Role for Nuclear PI(3,4,5)P 3

Nerve growth factor (NGF) is required for survival of some neurons. Ahn et al. examined potential signaling mechanisms that might mediate the antiapoptotic effects of NGF. In particular, they focused on a role for phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P 3 ], well known as a cytoplasmic second messenger but also likely to function in the nucleus. Previous work from the authors had shown that in an in vitro model recapitulating the nuclear DNA fragmentation associated with apoptosis, PI(3,4,5)P 3 mimicked the effect of NGF to inhibit DNA fragmentation. Therefore, they searched for proteins from nuclear extracts of NGF-treated cells that would interact specifically with PI(3,4,5)P 3 conjugated to beads. One candidate interacting protein was B23 (also called NPM or nucleophosmin), a nuclear phosphoprotein that has been implicated in numerous regulatory functions, including inhibition of apoptosis. Immunodepletion of B23 decreased the protective effect of NGF in the in vitro assay system, and depletion of B23 after treatment of PC12 cells with short-hairpin RNA increased DNA fragmentation after an apoptotic stimulus, an effect not reversed by treatment of cells with NGF. In the in vitro assay, addition of PI(3,4,5)P 3 enhanced the inhibitory effect of B23 on DNA fragmentation. In stably transfected PC12 cells, expression of a mutant form of B23 that no longer bound PI(3,4,5)P 3 was less effective than the wild-type protein in protecting against DNA damage. At least in stably transfected cells, B23 appeared to associate with caspase-activated DNAse (CAD), the enzyme that mediates DNA fragmentation in apoptosis. The authors proposed that some of the protective effects of NGF against apoptosis may occur through a mechanism where NGF-stimulated formation of PI(3,4,5)P 3 may enhance inhibition of CAD by B23. J.-Y. Ahn, X. Liu, D. Cheng, J. Peng, P.-K. Chan, P. A. Wade, K. Ye, Nucleophosmin/B23, a nuclear PI(3,4,5)P 3 receptor, mediates the antiapoptotic actions of NGF by inhibiting CAD. Mol. Cell 18 , 435-445 (2005). [PubMed]

Nerve growth factor and basic fibroblast growth factor protect cholinergic neurons against quinolinic acid excitotoxicity in rat neostriatum.

In the present work we have characterized a possible mechanism leading to the early survival of neostriatal cholinergic neurons after quinolinic acid injection. Different doses of quinolinic acid were injected in rat neostriatum and two different parameters were analysed 7 days after the lesion: choline acetyltransferase (ChAT) activity and nerve growth factor (NGF) levels. We have observed that ChAT activity decreased (until 68 nmol quinolinic acid) and NGF levels increased (until 34 nmol quinolinic acid) in a dose-dependent manner. In order to characterize the time-course of the lesion on NGF levels and ChAT activity, and the possible protective effect of NGF and basic fibroblast growth factor (bFGF) on cholinergic neurons, we have used the quinolinic acid dose (68 nmol) at which the first decrease of ChAT activity was observed. ChAT activity and NGF levels showed different patterns of response to quinolinic acid injection, since the maximal effect was reached at 1 day for ChAT activity and at 2 days for NGF levels. NGF or bFGF simultaneously injected with quinolinic acid (68 nmol) completely prevented the decrease in ChAT activity in a dose-dependent manner but NGF was more effective than bFGF. Furthermore, differences observed in ChAT activity after NGF but not bFGF treatment were correlated with changes in the number of ChAT immunoreactive cells. Finally, we have also observed that, although bFGF alone was not able to modify NGF levels, bFGF simultaneously injected with quinolinic acid produced an increase of NGF levels higher than that observed after quinolinic acid injection alone.(ABSTRACT TRUNCATED AT 250 WORDS)