Neurite Retraction In PC12 Cells Research Articles

Neuroprotection by Neurotropin through Crosstalk of Neurotrophic and Innate Immune Receptors in PC12 Cells.

Infected or damaged tissues release multiple “alert” molecules such as alarmins and damage-associated molecular patterns (DAMPs) that are recognized by innate immune receptors, and induce tissue inflammation, regeneration, and repair. Recently, an extract from inflamed rabbit skin inoculated with vaccinia virus (Neurotropin®, NTP) was found to induce infarct tolerance in mice receiving permanent ischemic attack to the middle cerebral artery. Likewise, we report herein that NTP prevented the neurite retraction in PC12 cells by nerve growth factor (NGF) deprivation. This effect was accompanied by interaction of Fyn with high-affinity NGF receptor TrkA. Sucrose density gradient subcellular fractionation of NTP-treated cells showed heretofore unidentified membrane fractions with a high-buoyant density containing Trk, B subunit of cholera toxin-bound ganglioside, flotillin-1 and Fyn. Additionally, these new membrane fractions also contained Toll-like receptor 4 (TLR4). Inhibition of TLR4 function by TAK-242 prevented the formation of these unidentified membrane fractions and suppressed neuroprotection by NTP. These observations indicate that NTP controls TrkA-mediated signaling through the formation of clusters of new membrane microdomains, thus providing a platform for crosstalk between neurotrophic and innate immune receptors. Neuroprotective mechanisms through the interaction with innate immune systems may provide novel mechanism for neuroprotection.

Kamishoyosan and Shakuyakukanzoto promote recovery from paclitaxel-induced neurite retraction in PC12 cells

BackgroundIn chemotherapy, the full round of treatment must be completed as scheduled to achieve the strongest therapeutic effect. However, peripheral neuropathy, a severe side effect of the chemotherapeutic agent paclitaxel, can force the premature discontinuation of treatment. As some kampo practitioners have suggested that it may be possible to counteract such side effects, we analyzed the effects of Kamishoyosan, Shakuyakukanzoto, and Goshajinkigan in an in vitro model of paclitaxel-induced peripheral neuropathy.MethodsPaclitaxel-treated PC12 cells were assessed for neurite length and performed Western blot analysis for growth-associated protein-43 (GAP-43) and light neurofilament protein (NF-L) levels in the presence of nerve growth factor (NGF); they were re-assessed, with additional testing for acetylcholinesterase levels, after application of one of the kampo. We also compared phosphorylation of extracellular signal-regulated kinase (Erk)1/2 and Akt via Western blot analysis. About effect of kampo to anticancer efficacy, we confirmed cell cytotoxicity in A549 cells using MTT assay.ResultsAddition of Kamishoyosan or Shakuyakukanzoto, but not Goshajinkigan, significantly improved neurite length and GAP-43 and NF-L levels from paclitaxel-treated PC12 cells, relative to those of only NGF-treated PC12 cells. The promoting effect of Kamishoyosan and Shakuyakukanzoto in neurite outgrowth is confirmed when NGF promoted neurite outgrowth, and it was inhibited partially when Erk1/2 and Akt were blocked by Erk1/2 inhibitor or Akt inhibitor alone. Furthermore, neurite outgrowth induced by TJ24 and TJ68 was inhibited more strongly when Erk1/2 inhibitor and Akt inhibitor were treated at the same time. NGF with Kamishoyosan or Shakuyakukanzoto promoted the proportion of phosphorylated Erk1/2 and phosphorylated Akt compare with NGF only. On the other hand, Kamishoyosan or Shakuyakukanzoto didn’t influence cytotoxicity of paclitaxel in A549 cells.ConclusionsKamishoyosan or Shakuyakukanzoto promotes neurite outgrowth with NGF via increasing the proportion of phosphorylated Erk1/2 and phosphorylated Akt in PC12 cells. The effect applies to recovery from paclitaxel-induced axonal involvement and might promote recovery from paclitaxel-induced neuropathy without influence of anticancer effect of paclitaxel.

Lysophospholipids in retinal axon guidance: roles and cell signaling.

Nerve regeneration in the central nervous system (CNS) has become a holy grail of biomedical research. To understand nerve growth that would be required for efficient regeneration, many scientists have turned to developing systems where nerve growth is abundant and normal neural connections are established. One aspect of this neural development, which would also be important in nerve regeneration, is axon guidance – the process by which a growing axon, through its growth cone, is guided to the correct target for synaptic connections.

1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one inhibits neurite outgrowth and causes neurite retraction in PC12 cells independently of soluble guanylyl cyclase

The effect of the potent soluble guanylyl cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) on neurite outgrowth and retraction was investigated in PC12 cells and SH-SY5Y human neuroblastoma cells. ODQ inhibited neurite outgrowth and triggered neurite retraction in the cells stimulated with nerve growth factor (NGF), staurosporine, or Y-27632. The nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (PTIO) had little effect on neurite outgrowth induced by Y-27632 or staurosporine. In the presence of ODQ, treatment of the cells with the cell-permeable cGMP analogue 8-bromo-cGMP failed to retrigger Y-27632- and staurosporine-induced neurite outgrowth. Furthermore, the depletion of sGC by RNA interference failed to prevent Y-27632- and staurosporine-induced neurite outgrowth. These results indicate that the NO/sGC/cGMP signaling cascade is not critically involved in ODQ-induced neurite remodeling. The MEK inhibitor PD98059 did not inhibit neurite outgrowth, and Y-27632 and staurosporine did not induce ERK phosphorylation, suggesting that the inhibitory effect of ODQ on neurite outgrowth is independent of the ERK signaling pathway. In contrast, pretreatment with dithionite or a hemin-glutathione mixture reversed the inhibitory effect of ODQ on Y-27632- and staurosporine-induced neurite outgrowth, indicating that ODQ might act on an intracellular redox-sensitive molecule. We conclude that ODQ inhibits Y-27632- and staurosporine-induced neurite outgrowth and triggers neurite retraction in an sGC-independent manner in neuronal cells and suggest that oxidation of unidentified redox-sensitive protein could be responsible for these effects.

Sphingosine 1-Phosphate-induced Cell Rounding and Neurite Retraction Are Mediated by the G Protein-coupled Receptor H218

Sphingosine 1-phosphate (SPP) is a lipid second messenger that also acts as a first messenger through the G protein-coupled receptor Edg-1. Here we show that SPP also binds to the related receptors H218 and Edg-3 with high affinity and specificity. SPP and sphinganine 1-phosphate bind to these receptors, whereas neither sphingosylphosphorylcholine nor lysophosphatidic acid compete with SPP for binding to either receptor. Transfection of HEK293 cells with H218 or edg-3, but not edg-1, induces rounded cell morphology in the presence of serum, which contains high levels of SPP. SPP treatment of cells overexpressing H218 cultured in delipidated serum causes cell rounding. A similar but less dramatic effect was observed in cells overexpressing Edg-3 but not with Edg-1. Cell rounding was correlated with apoptotic cell death, probably as a result of loss of attachment. Nerve growth factor-induced neuritogenesis in PC12 cells was inhibited by overexpression of H218 and to a lesser extent Edg-3. SPP treatment rapidly enhanced neurite retraction in PC12 cells overexpressing Edg-1, Edg-3, or H218. Thus, H218, and possibly Edg-3, may be the cell surface receptors responsible for cell rounding and neurite retraction induced by SPP. Moreover, the identification of these two additional SPP receptors indicates that a family of highly specific receptors exists that mediate different responses to SPP.

Lysophosphatidic Acid‐Induced Neurite Retraction in PC12 Cells: Control by Phosphoinositide‐Ca2+ Signaling and Rho

The endogenous phospholipid mediator lysophosphatidic acid (LPA) caused growth cone collapse, neurite retraction, and cell flattening in differentiated PC12 cells. Neurite retraction was blocked by cytochalasin B and ADP-ribosylation of the small-molecular-weight G protein Rho by the Clostridium botulinum C-3 toxin. LPA induced a transient rise in the level of inositol 1,4,5-trisphosphate, and retraction was blocked by inhibitors of phospholipase beta. Repeated application of LPA elicited homologous desensitization of the Ca2+ mobilization response. The activation of the phosphoinositide (PIP)-Ca2+ second messenger system played a permissive role in the morphoregulatory response. Blockers of protein kinase C--chelerythrine, a myristoylated pseudosubstrate peptide, staurosporine, and depletion of protein kinase C from the cells by long-term phorbol ester treatment--all diminished neurite retraction by interfering with LPA-induced Ca2+ mobilization, which was required for the withdrawal of neurites. A brief 15-min treatment with 4 beta-phorbol 12-myristate 13-acetate also blocked retraction and Ca2+ mobilization, by inactivating the LPA receptor. Inhibition of protein tyrosine phosphorylation by herbimycin diminished retraction. Although activation of the PIP-Ca2+ second messenger system appears necessary for the Rho-mediated rearrangements of the actin cytoskeleton, bradykinin, which activates similar signaling events, failed to cause retraction, indicating that a yet unidentified novel mechanism is also involved in the LPA-induced morphoregulatory response.

Lysophosphatidic Acid‐Induced Neurite Retraction in PC12 Cells: Neurite‐Protective Effects of Cyclic AMP Signaling

Effects of the cyclic AMP second messenger system were studied on the retraction of neurites elicited by the phospholipid mediator lysophosphatidic acid (LPA) in PC12 cells. LPA stimulation inhibited adenylyl cyclase, indicating that the LPA receptor couples to the heterotrimeric Gi proteins. However, pertussis toxin or expression of dominant negative Ras did not prevent neurite retraction. In contrast, cholera toxin, forskolin, and application of dibutyryl-cyclic AMP prevented neurite retraction. The neurite-protective effect of forskolin was blocked by Rp-adenosine 3',5'-phosphorothioate. Forskolin and dibutyryl-cyclic AMP both failed to protect neurites in A126-1B2 and 123.7 cells, which lack cyclic AMP-activated protein kinase. Data indicate that elevation of cyclic AMP levels triggers a cyclic AMP-activated protein kinase-dependent mechanism that opposes the functioning of the morphoregulatory signaling activated by LPA. ADP-ribosylation of Rho by the Clostridium botulinum C-3 toxin in 123.7 cells caused neuronal differentiation, indicated by neurite extension, and blocked LPA-induced neurite retraction. LPA activates Gq- and Gi-linked signaling in parallel; therefore, a morphoregulatory signaling network hypothesis is proposed versus the simplistic approach of a signaling pathway. The signaling network integrates the receptor-activated individual, sequential, and parallel signaling events into an interactive network whose individual components may fulfill required and permissive functions encoding the cellular response.

Inhibition of lysophosphatidate- and thrombin-induced neurite retraction and neuronal cell rounding by ADP ribosylation of the small GTP-binding protein Rho.

Addition of the bioactive phospholipid lysophosphatidic acid (LPA) or a thrombin receptor-activating peptide (TRP) to serum-starved N1E-115 or NG108-15 neuronal cells causes rapid growth cone collapse, neurite retraction, and transient rounding of the cell body. These shape changes appear to be driven by receptor-mediated contraction of the cortical actomyosin system independent of classic second messengers. Treatment of the cells with Clostridium botulinum C3 exoenzyme, which ADP-ribosylates and thereby inactivates the Rho small GTP-binding protein, inhibits LPA- and TRP-induced force generation and subsequent shape changes. C3 also inhibits LPA-induced neurite retraction in PC12 cells. Biochemical analysis reveals that the ADP-ribosylated substrate is RhoA. Prolonged C3 treatment of cells maintained in 10% serum induces the phenotype of serum-starved cells, with initial cell flattening being followed by neurite outgrowth; such C3-differentiated cells fail to retract their neurites in response to agonists. We conclude that RhoA is essential for receptor-mediated force generation and ensuing neurite retraction in N1E-115 and PC12 cells, and that inactivation of RhoA by ADP-ribosylation abolishes actomyosin contractility and promotes neurite outgrowth.

Lysophosphatidates bound to serum albumin activate membrane currents in Xenopus oocytes and neurite retraction in PC12 pheochromocytoma cells.

Serum contains a factor that co-purifies with albumin and causes neurite retraction in PC12 cells, inhibits the proliferation of tumor cells in vitro, and activates the phosphatidylinositol/Ca2+ second messenger system in Xenopus oocytes and other cells. The activity of serum albumin depends on several lysophospholipids bound to albumin. Thin layer chromatographic analysis of the lipids extracted by methanol from serum albumin revealed over a dozen components, several of which evoked oscillatory currents in oocytes. In contrast to serum albumin, most of these lipids were absent in plasma, which lacks the biological activity. The most abundant naturally occurring active component was identified as stearoyl-lysophosphatidic acid. Synthetically prepared lysophosphatidates reproduced the biological activities of the natural serum factor. Adding synthetic lysophosphatidates to inactive fatty acid-free albumin restored activity to the albumin, making the active factor nondialyzable against aqueous solvents and protecting against digestion by various lipases. Since the biologically active lysophosphatidates were produced during blood clotting, in the presence of platelets, and lysophosphatidates have been shown previously to activate platelets, we propose that lysophosphatidates may play an important role in linking platelet activation to receptor-mediated tissue regeneration.

The effect of active serum albumin on PC12 cells: I. Neurite retraction and activation of the phosphoinositide second messenger system

Vertebrate blood sera contain a factor that triggers oscillatory chloride currents in Xenopus oocytes through activation of the phosphoinositide/Ca 2+ second messenger system. The active serum component consists of lipids bound to an isoform of serum albumin that we have named active serum albumin (ASA). In undifferentiated PC12 cells, micromolar concentrations of ASA inhibit the early morphological changes induced by NGF, whereas in differentiated PC12 cells ASA caused a rapid withdrawal of neurites, which was reversible and dependent upon culture age. In contrast to normal serum, plasma and thrombin did not cause neurite retraction. Preincubation of ASA with monospecific antibodies to serum albumin suppressed its ability to induce neurite retraction in a dose dependent fashion. As in the oocyte, ASA activated the phosphatidylinositol second messenger system of PC12 cells, causing a several fold increase in Ins1,4,5P3 levels within minutes of application. The Ins1,4,5P3 increase was also blocked, in a titratable fashion, when ASA was preincubated with monospecific antibodies to serum albumin. This suggests that ASA-induced neurite retraction in PC12 cells may depend, at least in part, on activation of the phosphatidylinositol second messenger system. Results involving albumin-depleted sera show that ASA is the main factor responsible for serum vulnerability of neurites in PC12 cells. These findings point to some limitations in the use of serum in culture media, and raise the possibility that the serum factor may impair neuronal plasticity in disorders that are accompanied by the activation of blood coagulation together with a breakdown of the blood-brain barrier.

The effect of active serum albumin on PC12 cells: II. Intracellular Ca 2+ transients and their role in neurite retraction

In the preceding paper it was shown that an isoform of serum albumin (ASA: active serum albumin) causes a rapid retraction of neurites and increases intracellular content of Ins1,4,5P3 in PC12 cells. Here we examined whether ASA's effects in nerve growth factor-differentiated PC12 cells were mediated through the Ins1,4,5P3/Ca 2+ second messenger pathway by monitoring intracellular Ca 2+ (Ca 2+ i) with Fura2. It was found that ASA caused a dose-dependent increase in Ca 2+ i. In Ca 2+-free medium, the increase in Ca 2+ i elicited by ASA was smaller, but the rise in Ins1,4,5P3 content was not appreciably changed. The small Ca 2+ i increase seen in Ca 2+-free medium was probably due to the release of Ca 2+ from Ins1,4,5P3-sensitive intracellular stores. In Ca 2+-containing medium the Ca 2+ transient induced by ASA was not affected by organic Ca 2+ channel blockers, but decreased when Co 2+, Mn 2+ or Zn 2+ were present in the extracellular medium. The effect of other ligands, such as carbachol and bradykinin, whose receptors are coupled to the phosphoinositide system was also investigated. Carbachol at concentrations from 2 to 200 μM, and bradykinin at a concentration of 2 μM did not cause neurite retraction, whereas 200 μM bradykinin caused an approximately 40% decrease in neurite length. Thapsigargin, a Ca 2+-ATPase inhibitor, caused a sustained elevation of Ca 2+ i and retraction of neurites, whereas depolarization of the cells by high K + gave only a transient elevation of Ca 2+ i , and no neurite retraction. Therefore, a sustained elevation in Ca 2+ i might be a sufficient trigger to induce neurite retraction in differentiated PC12 cells. Since ASA induces only a transient rise in Ca 2+ i in most cells, the Ca 2+ i transient evoked by ASA alone may not be sufficient to cause neurite retraction in PC12 cells.