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The signaling mechanisms underlying cell differentiation have been extensively studied with the use of rat PC12 cells as a model system. Nerve growth factor (NGF) is atrophic factor inducing PC12 cell differentiation through the activation of the p35/cyclin-dependent kinase 5 (Cdk5) complex. It has been reported that adenylyl cyclase activation and cAMP production may be involved in NGF-dependent actions. Our previous results indicate that cAMP activates the p35/Cdk5 complex in reproductive cells. Therefore, the role of cAMP in NGF-triggered p35/Cdk5 activation and PC12 differentiation was interesting to explore. Our results indicate that roscovitine, a molecular inhibitor of Cdk5, blocks cAMP-triggered PC12 differentiation, which was evaluated by neurite initiation, a decrease in proliferation, and cell cycle [G.sub.1] arrest. The following data show that cAMP treatment increased Cdk5 activity through p35 upregulation, cAMP downstream components, protein kinase A (PKA) and phosphorylated cAMP response element binding protein (CREB), are involved in this regulation. The immunocytochemical results indicate that PKA inhibition disrupted cAMP-triggered p35/Cdk5 localization in PCI2 cells. In addition, adenylyl cyclase inhibition was found to diminish NGF-induced intracellular cAMP production, CREB phosphorylation, and p35 expression. The cAMP antagonist and the PKA inhibitors reduced NGF-induced p35 expression. Finally, NGF-triggered PC I2 differentiation was partially decreased by adenylyl cyclase or PKA inhibitors. In conclusion, these results demonstrate that cAMP may play a role in NGF-p35/Cdk5dependent PC 12 differentiation. adenosine 3',5'-cyclic monophosphate; nerve growth factor; cyclin-dependent kinase 5 doi: 10.1152/ajpcell.00534.2009.

Sympathetic nerves stimulate cardiac function through the release of norepinephrine and the activation of cardiac [[beta].sub.1]-adrenergic receptors. The sympathetic innervation of the heart is sculpted during development by chemoattractive factors including nerve growth factor (NGF) and the chemorepulsive factor semaphorin 3a. NGF acts through the TrkA receptor and the p75 neurotrophin receptor ([p75.sup.NTR]) in sympathetic neurons. NGF stimulates sympathetic axon extension into the heart through TrkA, but [p75.sup.NTR] modulates multiple coreceptors that can either stimulate or inhibit axon outgrowth. In mice lacking [p75.sup.NTR], the sympathetic innervation density in target tissues ranges from denervation to hyperinnervation. Recent studies have revealed significant changes in the sympathetic innervation density of [p75.sup.NTR]-deficient ([p75.sup.NTR-/-]) atria between early postnatal development and adulthood. We examined the innervation of adult [p75.sup.NTR-/-] ventricles and discovered that the sub-endocardium of the [p75.sup.NTR-/-] left ventricle was essentially devoid of sympathetic nerve fibers, whereas the innervation density of the sub-epicardium was normal. This phenotype is similar to that seen in mice overexpressing semaphorin 3a, and we found that sympathetic axons lacking [p75.sup.NTR] are more sensitive to semaphorin 3a in vitro than control neurons. The lack of subendocardial innervation was associated with decreased dP/dt, altered cardiac [[beta].sub.1]-adrenergic receptor expression and sensitivity, and a significant increase in spontaneous ventricular arrhythmias. The lack of [p75.sup.NTR] also resulted in increased tyrosine hydroxylase content in cardiac sympathetic neurons and elevated norepinephrine in the fight ventricle, where innervation density was normal. sympathetic innervation; nerve growth factor; semaphorin 3a; ventricular arrhythmias doi: 10.1152/ajpheart.01128.2009.

Guidance of axons by molecular gradients is crucial for wiring up the developing nervous system. It often is assumed that the unique signature of such guidance is immediate and biased turning of the axon tip toward or away from the gradient. However, here we show that such turning is not required for guidance. Rather, by a combination of experimental and computational analyses, we demonstrate that growth-rate modulation is an alternative mechanism for guidance. Furthermore we show that, although both mechanisms may operate simultaneously, biased turning dominates in steep gradients, whereas growth-rate modulation may dominate in shallow gradients. These results suggest that biased axon turning is not the only method by which guidance can occur. chemotaxis | growth cone | nerve growth factor | neural development | computational neuroscience doi: 10.1073/pnas.0909254107

NGF has been suggested to play a role in urinary bladder dysfunction by mediating inflammation, as well as morphological and functional changes, in sensory and sympathetic neurons innervating the urinary bladder. To further explore the role of NGF in bladder sensory function, we generated a transgenic mouse model of chronic NGF overexpression in the bladder using the urothelium-specific uroplakin II (UPII) promoter. NGF mRNA and protein were expressed at higher levels in the bladders of NGF-overexpressing (NGF-OE) transgenic mice compared with wild-type littermate controls from postnatal day 7 through 12-16 wk of age. Overexpression of NGF led to urinary bladder enlargement characterized by marked nerve fiber hyperplasia in the submucosa and detrusor smooth muscle and elevated numbers of tissue mast cells. There was a marked increase in the density of CGRP- and substance P-positive C-fiber sensory afferents, neurofilament 200-positive myelinated sensory afferents, and tyrosine hydroxylase-positive sympathetic nerve fibers in the suburothelial nerve plexus. CGRP-positive ganglia were also present in the urinary bladders of transgenic mice. Transgenic mice had reduced urinary bladder capacity and an increase in the number and amplitude of nonvoiding bladder contractions under baseline conditions in conscious open-voiding cystometry. These changes in urinary bladder function were further associated with an increased referred somatic pelvic hypersensitivity. Thus, chronic urothelial NGF overexpression in transgenic mice leads to neuronal proliferation, focal increases in urinary bladder mast cells, increased urinary bladder reflex activity, and pelvic hypersensitivity. NGF-overexpressing mice may, therefore, provide a useful transgenic model for exploring the role of NGF in urinary bladder dysfunction. nerve growth factor; urothelium; transgenic mouse; bladder hypersensitivity; inflammation; afferent innervation doi:10.1152/ajpregu.00367.2009

A subset of neurons in the normal vertebrate nervous system contains double the normal amount of DNA in their nuclei. These neurons are all thought to derive from aberrant mitoses in neuronal precursor cells. Here we show that endogenous NGF induces DNA replication in a subpopulation of differentiating chick retinal ganglion cells that express both the neurotrophin receptor p75 and the E2F1 transcription factor, but that lack the retinoblastoma protein. Many of these neurons avoid G2/M transition and remain alive in the retina as tetraploid cells with large cell somas and extensive dendritic trees, and most of them express [beta]2 nicotinic acetylcholine receptor subunits, a specific marker of retinal ganglion cells innervating lamina F in the stratum-griseum-et-fibrosum-superficiale of the tectal cortex. Tetraploid neurons were also observed in the adult mouse retina. Thus, a developmental program leading to somatic tetraploidy in specific retinal neurons exists in vertebrates. This program might occur in other vertebrate neurons during normal or pathological situations. AChR | cell cycle | dendritic tree | p75NTR | tectum www.pnas.org/cgi/doi/10.1073/pnas.0906121107

Elevated intraocular pressure (lOP) in glaucoma causes loss of retinal ganglion cells (RGCs) and damage to the optic nerve. Although lOP is controlled pharmacologically, no treatment is available to restore retinal and optic nerve function. We evaluated the effects of NGF eye drops in a rat model of glaucoma. We also treated 3 patients with progressive visual field defects despite lOP control. Glaucoma was induced in rats through injection of hypertonic saline into the episcleral vein. Initially, 2 doses of NGF (100 and 200 [micro]g/mL) were tested on 24 rats, and the higher dose was found to be more effective. Glaucoma was then induced in an additional 36 rats: half untreated and half treated with 200 [micro]g/mL NGF QID for 7 weeks. Apoptosis/ survival of RGCs was evaluated by histological, biochemical, and molecular analysis. Three patients with advanced glaucoma underwent psychofunctional and electrofunctional tests at baseline, after 3 months of NGF eye drops, and after 3 months of follow-up. Seven weeks of elevated lOP caused RGC degeneration resulting in 40% cell death. Significantly less RGC loss was observed with NGF treatment (2,530 [+ or -] 121 vs. 1,850 [+ or -] 156 RGCs/[mm.sup.2]) associated with inhibition of cell death by apoptosis. Patients treated with NGF demonstrated long lasting improvements in visual field, optic nerve function, contrast sensitivity, and visual acuity. NGF exerted neuroprotective effects, inhibiting apoptosis of RGCs in animals with glaucoma. In 3 patients with advanced glaucoma, treatment with topical NGF improved all parameters of visual function. These results may open therapeutic perspectives for glaucoma and other neurodegenerative diseases. NGF I optic nerve I retina

Although anticholinergic therapy inhibits bronchoconstriction in asthmatic patients and antigen-challenged animals, administration of atropine 1 h before antigen challenge significantly potentiates airway hyperreactivity and eosinophil activation measured 24 h later. This potentiation in airway hyperreactivity is related to increased eosinophil activation and is mediated at the level of the airway nerves. Since eosinophils produce nerve growth factor (NGF), which is known to play a role in antigeninduced airway hyperreactivity, we tested whether NGF mediates atropine-enhanced, antigen challenge-induced hyperreactivity. Antibody to NGF (Ab NGF) was administered to sensitized guinea pigs with and without atropine pretreatment (1 mg/kg iv) 1 h before challenge. At 24 h after challenge, animals were anesthetized, vagotomized, paralyzed, and ventilated. Electrical stimulation of both vagus nerves caused bronchoconstriction that was increased in challenged animals. Atropine pretreatment potentiated antigen challenge-induced hyperreactivity. Ab NGF did not affect eosinophils or inflammatory cells in any group, nor did it prevent hyperreactivity in challenged animals that were not pretreated with atropine. However, Ab NGF did prevent atropine-enhanced, antigen challenge-induced hyperreactivity and eosinophil activation (assessed by immunohistochemistry). This effect was specific to NGF, since animals given control IgG remained hyperreactive. These data suggest that anticholinergic therapy amplifies eosinophil interactions with airway nerves via NGF. Therefore, therapeutic strategies that target both eosinophil activation and NGF-mediated inflammatory processes in allergic asthma are likely to be beneficial. anticholinergic; asthma; muscarinic receptors; parasympathetic nerves; neurotrophins

Axon guidance by molecular gradients plays a crucial role in wiring up the nervous system. However, the mechanisms axons use to detect gradients are largely unknown. We first develop a Bayesian 'ideal observer' analysis of gradient detection by axons, based on the hypothesis that a principal constraint on gradient detection is intrinsic receptor binding noise. Second, from this model, we derive an equation predicting how the degree of response of an axon to a gradient should vary with gradient steepness and absolute concentration. Third, we confirm this prediction quantitatively by performing the first systematic experimental analysis of how axonal response varies with both these quantities. These experiments demonstrate a degree of sensitivity much higher than previously reported for any chemotacting system. Together, these results reveal both the quantitative constraints that must be satisfied for effective axonal guidance and the computational principles that may be used by the underlying signal transduction pathways, and allow predictions for the degree of response of axons to gradients in a wide variety of in vivo and in vitro settings. axon guidance | chemotaxis | growth cone | nerve growth factor | nerve regeneration

Midthoracic spinal cord injury is associated with ventricular arrhythmias that are mediated, in part, by enhanced cardiac sympathetic activity. Furthermore, it is well known that sympathetic neurons have a lifelong requirement for nerve growth factor (NGF). NGF is a neurotrophin that supports the survival and differentiation of sympathetic neurons and enhances target innervation. Therefore, we tested the hypothesis that paraplegia is associated with an increased cardiac NGF content, sympathetic tonus, and susceptibility to ischemia-induced ventricular tachyarrhythmias. Intact and paraplegic (6-9 wk posttransection, T5 spinal cord transection) rats were instrumented with a radiotelemetry device for recording arterial pressure, temperature, and ECG, and a snare was placed around the left main coronary artery. Following recovery, the susceptibility to ventricular arrhythmias (coronary artery occlusion) was determined in intact and paraplegic rats. In additional groups of matched intact and paraplegic rats, cardiac nerve growth factor content (ELISA) and cardiac sympathetic tonus were determined. Paraplegia, compared with intact, increased cardiac nerve growth factor content (2,146 [+ or -] 286 vs. 180 [+ or -] 36 pg/ml, P < 0.05) and cardiac sympathetic tonus (154 [+ or -] 4 vs. 68 [+ or -] 4 beats/min, P < 0.05) and decreased the ventricular arrhythmia threshold (3.6 [+ or -] 0.2 vs. 4.9 [+ or -] 0.2 min, P < 0.05). Thus altered autonomic behavior increases the susceptibility to ventricular arrhythmias in paraplegic rats. cardiovascular risks; arrhythmia

Ewing tumors (ET) are highly malignant, localized in bone or soft tissue, and are molecularly defined by ews/ets translocations. DNA microarray analysis revealed a relationship of ET to both endothelium and fetal neural crest. We identified expression of histone methyltransferase enhancer of Zeste, Drosophila, Homolog 2 (EZH2) to be increased in ET. Suppressive activity of EZH2 maintains stemness in normal and malignant cells. Here, we found EWS/FLI1 bound to the EZH2 promoter in vivo, and induced EZH2 expression in ET and mesenchymal stem cells. Down-regulation of EZH2 by RNA interference in ET suppressed oncogenic transformation by inhibiting clonogenicity in vitro. Similarly, tumor development and metastasis was suppressed in immunodeficient Rag[2.sup.-/-] [[gamma].sub.c.sup.- /-] mice. EZH2-mediated gene silencing was shown to be dependent on histone deacetylase (HDAC) activity. Subsequent microarray analysis of EZH2 knock down, HDAC-inhibitor treatment and confirmation in independent assays revealed an undifferentiated phenotype maintained by EZH2 in ET. EZH2 regulated sternness genes such as nerve growth factor receptor (NGFR), as well as genes involved in neuroectodermal and endothelial differentiation (EMP1, EPHB2, GFAP, and GAP43). These data suggest that EZH2 might have a central role in ET pathology by shaping the oncogenicity and stem cell phenotype of this tumor. epigenetic regulation | Ewing tumor | sternness

Visceral inflammation, including that arising from bladder inflammation, reduces the threshold to sensation of innocuous or noxious stimuli applied to peripheral structures (referred hyperalgesia). Cystitis may induce transient or persistent plastic changes mediated by neurotrophins, particularly nerve growth factor (NGF), which contribute to increased nociceptive input. In this study, acute or subacute cystitis was induced in female rats by one or three (at 72-h intervals) 400-[micro]1 intravesical instillations of 1 mM acrolein. Sensitivity of the hindpaws to mechanical and thermal stimuli was determined before and 4, 24, 48, 72, and 96 h after treatment. Other groups of rats were treated with intravesical or intrathecal k252a [a nonspecific antagonist of tyrosine kinase (trk) receptors, including trkA, the high-affinity receptor for NGF] before the first or third acrolein instillation. Some rats were intraperitoneally injected with specific NGF-neutralizing antiserum or normal serum before acrolein instillation. Acute and subacute cystitis induced mechanical, but not thermal, referred hyperalgesia that was attenuated by intravesical pretreatment with k252a. Systemic treatment with NGF-neutralizing antiserum before instillation of acrolein suppressed subsequent mechanical referred hyperalgesia. Expression of NGF was increased within the bladder by acute or subacute cystitis and in L6/S dorsal root ganglia by subacute cystitis. These results suggest that the bladder-derived NGF acting via trk receptors at least partially mediates peripheral sensitization to mechanical stimuli associated with acute and subacute acrolein-induced cystitis. k252a; peripheral nociception; visceral inflammation; hyperalgesia

During development of the nervous system, the tip of a growing axon, the growth cone (GC), must respond accurately to stimuli that direct its growth. This axonal navigation depends on extracellular concentration gradients of numerous guidance cues, including GABA. GCs can detect even weak directional signals, yet the mechanisms underlying this sensitivity remain unclear. Past studies in other eukaryotic chemotactic systems have pointed to the role of the spatial reorganization of the transduction pathway in their sensitive response. Here we have developed a single-molecule assay to observe individual [GABA.sub.A] receptors ([GABA.sub.A]Rs) in the plasma membrane of nerve GCs subjected to directional stimuli. We report that in the presence of an external GABA gradient [GABA.sub.A]Rs redistribute asymmetrically across the GC toward the gradient source. Single-particle tracking of [GABA.sub.A]RS shows that the redistribution results from transient interactions between the receptors and the microtubules. Moreover, the relocalization is accompanied by an enhancement in the asymmetry of intracellular calcium concentration. Altogether, our results reveal a microtubule-dependent polarized reorganization of chemoreceptors at the cell surface and suggest that this polarization serves as an amplification step in GABA gradient sensing by nerve GCs. axonal guidance | chemotaxis | single molecule | polarity

Elevated levels of nerve growth factor (NGF) and NGF-mediated neural plasticity may have a role in airway diseases such as asthma and chronic obstructive pulmonary disease (COPD). Although NGF is known to affect sensory and sympathetic nerves, especially during development, little is known regarding its effect on parasympathetic nerves, especially on adult neurons. The purpose of this study was to analyze the acute and chronic effects of NGF on the electrophysiological and anatomical properties of neurons in airway parasympathetic ganglia from adult guinea pigs. Using single cell recording, direct application of NGF caused a lasting decrease in the cumulative action potential afterhyperpolarization (AHP) and increased the amplitude of vagus nerve-stimulated nicotinic fast excitatory postsynaptic potentials. Neuronal responsiveness to nicotinic receptor stimulation was increased by NGF, which was blocked by the tyrosine kinase inhibitor, K-252a, implicating neurotrophin-specific (Trk) receptors. Neurotrophin-3 and brain-derived neurotrophic factor had no effect on the synaptic potentials, AHP, or nicotinic response; inhibition of cyclooxygenase with indomethacin inhibited the effect of NGF on the cumulative AHP. Forty-eight hours after in vivo application of NGF to the trachealis muscle caused an increase in dendritic length on innervating neurons. These results are the first to demonstrate that NGF increases the excitability of lower airway parasympathetic neurons, primarily through enhanced synaptic efficacy and changes to intrinsic neuron properties. NGF also had dramatic effects on the growth of dendrites in vivo. Such effects may indicate a new role for NGF in the regulation of parasympathetic tone in the diseased or inflamed lower airways. asthma; remodeling; bronchus; trachea; neurotrophins; synapse; autonomic

Eukaryotic translation initiation factor 5A (eIF5A), the only known protein containing the polyamine-derived amino acid hypusine, modulates protein synthesis. We show that neurotrophic and neuroprotective actions of nerve growth factor (NGF) are mediated by hypusinated eIF5A, which can account for the known roles of polyamines in cell growth and survival. NGF treatment of PC12 cells stimulates eIF5A formation. Moreover, prevention of hypusine formation by a selective inhibitor of deoxyhypusine synthase and by its depletion with RNA interference blocks the NGF-elicited augmentation of neurite outgrowth and cell survival of PC12 cells. In brain cultures, inhibition of hypusine formation also inhibits neuronal process extension. hypusine | spermidine | nerve growth factor | arginase deoxyhypusine synthase

Nerve growth factor (NGF) is involved in pain transduction mechanisms and plays a key role in many persistent pain states, notably those associated with inflammation. On this basis, both the NGF ligand and its receptor TrkA (tyrosine kinase A) represent an eligible target for pain therapy. Although the direct involvement of NGF in pain modulation is well established, the effect of a direct functional block of the TrkA receptor is still unknown. In this study, we have demonstrated that MNAC13, the only anti-TrkA monoclonal antibody for which function neutralizing properties have been clearly shown both in vitro and in vivo, induces analgesia in both inflammatory and neuropathic pain models, with a surprisingly long-lasting effect in the latter. The formalin-evoked pain licking responses are significantly reduced by the MNAC13 antibody in CD1 mice. Remarkably, treatment with the anti-TrkA antibody also produces a significant antiallodynic effect on neuropathic pain: repeated i.p. injections of MNAC13 induce significant functional recovery in mice subjected to sciatic nerve ligation, with effects persisting after administration. Furthermore, a clear synergistic effect is observed when MNAC13 is administered in combination with opioids, at doses that are not efficacious per se. This study represents a direct demonstration that neutralizing antibodies directed against the TrkA receptor may display potent analgesic effects in inflammatory and chronic pain. analgesia | behavior | mice | nerve growth factor

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.06.027 Byline: Po-Lin So (a), Ping K. Yip (b), Stephen Bunting (b), Liang-Fong Wong (c), Nicholas D. Mazarakis (c), Susan Hall (b), Stephen McMahon (b), Malcolm Maden (a), Jonathan P.T. Corcoran (a) Keywords: Retinoic; Regeneration; Neurite Abstract: Many studies have shown a role of retinoid signalling in neurite outgrowth in vitro, and that the retinoic acid receptor (RAR) [beta]2 is critical for this process. We show here that RAR[beta]2 is expressed predominantly in dorsal root ganglia (DRG) neuronal subtypes that express neurofilament (NF) 200 and calcitonin gene-related peptide (CGRP), and that these neurons extend neurites in response to RA. We demonstrate that retinoid signalling has a role in neurite outgrowth in vivo, by showing that in a peripheral nerve crush model there is less neurite outgrowth from RAR[beta] null DRG compared to wild-type. We identify sonic hedgehog (Shh) as a downstream target of the RAR[beta]2 signalling pathway as it is expressed in the injured DRG of wild-type but not RAR[beta] null mice. This regulation is direct as when RAR[beta]2 is overexpressed in adult motoneurons Shh is induced in them. Finally we show that Shh alone cannot induce neurite outgrowth but potentiates RAR[beta]2 signalling in this process. Author Affiliation: (a) The MRC Centre for Developmental Neurobiology, King's College London, Guy's Campus, London SE1 1UL, UK (b) Wolfson Centre For Age-Related Diseases, King's College London, Guy's Campus, London SE1 1UL, UK (c) Oxford BioMedica (UK) Limited, Medawar Centre Robert Robinson Avenue, The Oxford Science Park, Oxford OX4 4GA, UK Article History: Received 22 March 2006; Revised 5 June 2006; Accepted 15 June 2006

Sensory neurons innervating different tissues converge onto second-order neurons in the spinal cord. We examined whether inflammation or transient overexpression of nerve growth factor (NGF) in one tissue triggers hypersensitivity in referral sites. Thresholds to mechanical and thermal stimulation of the hindpaw, visceromotor responses to colorectal distension, and cystometrograms were performed in appropriate controls and mice with experimentally induced cystitis, inflammation of the hindpaw or front paw, or injection of viral vectors encoding NGF or green fluorescent protein (GFP). Cystitis and NGF but not GFP overexpression in the bladder triggered bladder hyperactivity associated with mechanical and thermal hypersensitivity in cutaneous referral sites and enhanced responses to colorectal distension. Hindpaw inflammation and injection of the NGF- but not GFP-encoding viral vector or front paw inflammation induced mechanical and thermal hyperalgesia in the affected hindpaw and increased responses to colorectal distension without altering the micturition reflex. In conclusion, sensitization of sensory pathways by inflammation or NGF contributes to the development of hypersensitivity in neighboring organs and cutaneous referral sites and provides a potential mechanism underlying the coexistence of pain syndromes in patients with functional diseases. visceral sensation; nerve growth factor; viscerosomatic convergence

Norepinephrine (NE) induces endoplasmic reticulum (ER) unfolded protein response and reduces maturation and translocation of NE transporter to cell membrane via enhanced formation of reactive oxygen species in PC-12 cells. In the present study, we investigated whether ER stress is also implicated in the proapoptotic effect of NE. We found that the apoptotic effect of NE was associated with increased processing of ER-resident pro-caspase-12, cleavage of caspase-9 and -3, and mitochondrial release of cytochrome c. ER stress was evidenced by upregulation of ER chaperone GRP78 and transcription factor CHOP and the translocation of XBP-1 from the ER to the nucleus by NE. NE also reduced phospho-Akt (Ser473), indicating suppression of the phosphatidylinositol 3-kinase (PI3-kinase)/Akt survival pathway. Similar results were produced by thapsigargin. NGF, which promotes the PI3-kinase/Akt activity, reduced the effects of NE and thapsigargin on apoptosis and activation of caspase-12 and -3. However, the effects of NE, but not of thapsigargin, were abolished by pretreatment with SOD and catalase. In contrast, the PI3-kinase inhibitors LY-294002 and wortmannin abolished the protective effects of both SOD/catalase and NGF on NE-induced apoptosis. The functional importance of caspase-12 activation was supported by the use of Z-ATAD-FMK, which reduced the NE-induced processing of caspase-12 and cell apoptosis, but the caspase-12, -9, and -3 inhibitors had no effects on the increase in cytosolic cytochrome c produced by NE. In contrast, the release of mitochondrial cytochrome c was abolished by SOD/catalase and NGF. These results indicate that NE induced cell apoptosis by both ER stress and a mitochondrial death pathway and that the effects of NE were mediated via oxidative stress and inhibition of the PI3-kinase/Akt survival pathway. caspase-12; superoxide dismutase; nerve growth factor: Z-Ala-ThrAla-Asp -fluoromethyl ketone: cytochrome c

Nerve growth factor (NGF), a member of the neurotrophin family, is an all-beta-sheet protein with a characteristic structure motif, the cystine knot. Unfolding of NGF in 6 M GdnHCl is described to involve an initial partial loss of structure and a subsequent very slow conversion to a second, completely unfolded state.

Estradiol valerate (EV)-induced polycystic ovaries (PCO) in rats are associated with higher ovarian release and content of norepinephrine, decreased [[beta].sub.2]-adrenoceptors (ARs), and dysregulated expression of [[alpha].sub.1]-AR subtypes, all preceded by an increase in the production of ovarian NGF. The aim of this study was to further elucidate the role of NGF in the ovaries by blocking the action of NGF during development of EV-induced PCO in rats. Control and EV-injected rats were treated with intraperitoneal injections of IgG (control and PCO groups) or with anti-NGF antibodies (anti-NGF and PCO anti-NGF groups) every third day for 5 wk starting from the day of PCO induction. Rat weight, estrous cyclicity, ovarian morphology, ovarian mRNA, and protein expression of [[alpha].sub.1]-AR subtypes, [[beta].sub.2]-AR, the NGF receptor tyrosine kinase A (TrkA), p75 neurotrophin receptor ([p75.sup.NTR]), and tyrosine hydroxylase (TH) were analyzed. Ovaries in both PCO and PCO anti-NGF groups decreased in size as well as in number and size of corpora lutea. mRNA expression of [[alpha].sub.1a]-AR and TrkA in the ovaries was lower, whereas expression of [[alpha].sub.1b]- and [[alpha].sub.1d]-AR and TH was higher, in the PCO group than in controls. Protein quantities of [[alpha].sub.1]-ARs, TrkA, [p75.sup.NTR], and TH were higher in the PCO group compared with controls, whereas the protein content of [[beta].sub.2]-AR was lower. Anti-NGF treatment in the PCO group restored all changes in mRNA and protein content, except that of [[alpha].sub.1b]-AR and TrkA mRNAs, to control levels. The results indicate that the NGF/NGF receptor system plays a role in the pathogenesis of EV-induced PCO in rats. nerve growth factors; sympathetic nervous system; ovarian innervation; tyrosine kinase A; p75 neutrophin receptor

Neurotrophins regulate sympathetic neuron cotransmission by modulating the activity-dependent release of norepinephrine and acetylcholine. Nerve growth factor promotes excitatory noradrenergic transmission, whereas brain-derived neurotrophic factor (BDNF), acting through the p75 receptor, increases inhibitory cholinergic transmission. This regulation of corelease by target-derived factors leads to the functional modulation of myocyte beat rate in neuron-myocyte cocultures. Calcium/calmodulin-dependent protein kinase II (CaMKII) has been implicated in the control of both pre- and postsynaptic mechanisms of synaptic plasticity. We demonstrate that CaMKII acts in conjunction with p75 signaling to regulate cholinergic transmission between sympathetic neurons and heart cells. Inhibition of presynaptic CaMKII prevents the BDNF-dependent shift to inhibitory neurotransmission, whereas presynaptic expression of a constitutively active CaMKII results in inhibitory neurotransmission in the absence of added BDNF, suggesting that activation of presynaptic CaMKII is both necessary and sufficient for a shift from excitatory to inhibitory transmission. Several isozymes of CaMKII are expressed in sympathetic neurons, with the [delta]-CaMKII being activated by BDNF and nerve growth factor. Activated CaMKII is less effective at promoting cholinergic transmission in the absence of p75 signaling, demonstrating that p75 and CaMKII act to coordinate neurotransmitter selection in sympathetic neurons. brain-derived neurotrophic factor | p75 | sympathetic neurons

The role of nerve growth factor in programmed cell death of retinal cells through low-affinity neurotrophin receptor p75 binding is presented.

Nerve growth factor (NGF) was identified originally as a survival factor for sensory and sympathetic neurons in the developing nervous system. In adults, NGF is not required for survival but it has a crucial role in the generation of pain and hyperalgesia in several acute and chronic pain states. The expression of NGF is high in injured and inflamed tissues, and activation of the NGF receptor tyrosine kinase trkA on nociceptive neurons triggers and potentiates pain signalling by multiple mechanisms. Inhibition of NGF function and signalling blocks pain sensation as effectively as cyclooxygenase inhibitors and opiates in rodent models of pain. Several pharmaceutical companies have active drug-discovery and development programs that are based on a variety of approaches to antagonise NGF, including NGF 'capture', blocking the binding of NGF to trkA and inhibiting trkA signalling. NGF antagonism is expected to be a highly effective therapeutic approach in many pain states, and to be free of the adverse effects of traditional analgesic drugs.