Effects of sodium butyrate on the expression of sodium channels by neuronal cell lines derived from the rat CNS

Aging as a loss of morphostatic information: A developmental bioelectricity perspective

Maintaining order at the tissue level is crucial throughout the lifespan, as failure can lead to cancer and an accumulation of molecular and cellular disorders. Perhaps, the most consistent and pervasive result of these failures is aging, which is characterized by the progressive loss of function and decline in the ability to maintain anatomical homeostasis and reproduce. This leads to organ malfunction, diseases, and ultimately death. The traditional understanding of aging is that it is caused by the accumulation of molecular and cellular damage. In this article, we propose a complementary view of aging from the perspective of endogenous bioelectricity which has not yet been integrated into aging research. We propose a view of aging as a morphostasis defect, a loss of biophysical prepattern information, encoding anatomical setpoints used for dynamic tissue and organ homeostasis. We hypothesize that this is specifically driven by abrogation of the endogenous bioelectric signaling that normally harnesses individual cell behaviors toward the creation and upkeep of complex multicellular structures in vivo. Herein, we first describe bioelectricity as the physiological software of life, and then identify and discuss the links between bioelectricity and life extension strategies and age-related diseases. We develop a bridge between aging and regeneration via bioelectric signaling that suggests a research program for healthful longevity via morphoceuticals. Finally, we discuss the broader implications of the homologies between development, aging, cancer and regeneration and how morphoceuticals can be developed for aging.

Effect of Tiantai No.1 on beta-amyloid-induced neurotoxicity and NF-kappa B and cAMP responsive element-binding protein

OBJECTIVE

To investigate the effect and molecular mechanism of Tiantai No.1, a compound Chinese herbal preparation, for the prevention and reduction of neurotoxicity induced by beta-amyloid peptides (Abeta) in vitro and its effects on nuclear factor-kappa B (NF-kappa B) and cAMP responsive element-binding protein (CREB) pathways using the gene transfection technique.

METHODS

B104 neuronal cells were used to examine the effects of Tiantai No.1 on lowering the neurotoxicity induced by Abeta. The cells were pre-treated with Tiantai No.1 at doses of 50, 100, 150, or 200 micro g/mL respectively for 3 days and co-treated with Tiantai No.1 and beta-amyloid peptide1-40 (A beta 1-40, 10 micro mol/L) for 48 h or post-treated with Tiantai No.1 for 48 h after the cells were exposed to beta-amyloid peptides25-35 (A beta 25-35) for 8 h. In gene transfection assays, cells were treated with Tiantai No.1 at 50 micro g/mL and 150 micro g/mL for 5 days or co-treated with Tiantai No.1 and A beta 1-40 (5 micro mo/L) for 3 days after electroporation for the evaluation of NF-kappa B and CREB expression.

RESULTS

Pre-treating and co-treating B104 neuronal cells with Tiantai No.1 lowered the neurotoxicity induced by Abeta, and post-treating with Tiantai No.1 reduced or blocked B104 neuronal apoptotic death induced by Abeta (P<0.05, P<0.01). With a dose-dependent relationship, the same treatments increased the expression of NF-kappa B or CREB in B104 neuronal cells (P<0.05, P<0.01). Meanwhile, Tiantai No.1 reduced A beta -40 induced inhibition on NF-kappa B expression (P<0.01).

CONCLUSIONS

Tiantai No.1 can protect neurons against the neurotoxicity induced by Abeta. The neuroprotective mechanisms may be associated with the activation of NF-kappa B and cAMP cellular signal pathways.

B35 neuroblastoma cells: an easily transfected, cultured cell model of central nervous system neurons

A panel of neuronal cell lines was derived from tumors of the neonatal rat central nervous system (CNS) in 1974, and two of these lines are in wide use today. Both the B35 and B50 lines offer a number of advantages to researchers who study CNS neurons in culture: they are simple to grow, to differentiate, and to transfect. B50 cells have been used extensively in the study of neuronal cell death, toxicology, and differentiation, whereas B35 cells have proven useful in the molecular analysis of endocytosis and of signaling pathways, in particular those that guide axonal outgrowth and cell motility. This chapter provides protocols for growing and transfecting B35 cells, selecting stable transfectants, exploring protein function using an antisense approach, and assaying cell motility in a Transwell chamber. All of these protocols have been written for researchers who have some skill in basic cell culture techniques, but previous experience with cultured neurons is not required.

Plasticity of TTX-sensitive sodium channels PN1 and brain III in injured human nerves

Sensory neurones co-express voltage-gated sodium channels that mediate TTX-sensitive (TTX-S) and TTX-resistant (TTX-R) currents, which may contribute to chronic pain after nerve injury. We previously demonstrated that TTX-R channels were decreased acutely in human sensory cell bodies after central axotomy, but accumulated in nerve terminals after peripheral axotomy. We have now studied the TTX-S channels PN1 and Brain III, using specific antibodies for immunohistochemistry, in dorsal root ganglia (DRG) from 10 patients with traumatic central axotomy, nerves from 16 patients with peripheral axotomy, and controls. PN1 showed temporal changes similar to the TTX-R channels in sensory cell bodies of injured DRG. In contrast, Brain III was found only in injured nerves (not control nerves, or control/central axotomy DRG). PNI and Brain III are distinct targets for novel analgesics.

CNS voltage-dependent Na(+) channel expression and distribution in an undifferentiated and differentiated CNS cell line

Upon serum removal, CAD-R1 cells undergo neurite outgrowth and an increase in voltage-dependent Na(+) current (VDNaC) density without changing their activation and inactivation properties. Insulin and endothelial cell growth supplement inhibited the increase in VDNaC density but not the neurite outgrowth. RI, RII, RIII Na(+) channel proteins were expressed in CAD-R1 cells. These proteins exhibited both similar and different distribution and clustering patterns which suggested the channel's structural differences play a role in channel distribution.

TTX-sensitive and -resistant Na+ currents, and mRNA for the TTX-resistant rH1 channel, are expressed in B104 neuroblastoma cells

To examine the molecular basis for membrane excitability in a neuroblastoma cell line, we used whole cell patch-clamp methods and reverse transcription-polymerase chain reaction (RT-PCR) to study Na+ currents and channels in B104 cells. We distinguished Tetrodotoxin (TTX)-sensitive and -resistant Na+ currents and detected the mRNA for the cardiac rH1 channel in B104 cells. Na+ currents could be recorded in 65% of cells. In the absence of TTX, mean peak Na+ current density was 126 +/- 19 pA/pF, corresponding to a channel density of 2.7 +/- 0.4/micron 2 (mean +/- SE). Time-to-peak (t-peak), activation (tau m), and inactivation time constants (tau h) for Na+ currents in B104 cells were 1.0 +/- 0.04, 0.4 +/- 0.06, and 0.9 +/- 0.04 ms at -10 mV. The peak conductance-voltage relationship had a V 1/2 of -39.8 +/- 1.5 mV. V 1/2 for steady-state inactivation was -81.6 +/- 1.5 mV. TTX-sensitive and -resistant components of the Na current had half-maximal inhibitions (IC50), respectively, of 1.2 nM and, minimally, 575.5 nM. The TTX-sensitive and -resistant Na+ currents were kinetically distinct; time-to-peak, tau m, and tau h for TTX-sensitive currents were shorter than for TTX-resistant currents. Steady-state voltage dependence of the two currents was indistinguishable. The presence of TTX-sensitive and -resistant Na+ currents, which are pharmacologically and kinetically distinct, led us to search for mRNAs known to be associated with TTX-resistant channels, in addition to the alpha subunit mRNAs, which have previously been shown to be expressed in these cells. Using RT-PCR and restriction enzyme mapping, we were unable to detect alpha SNS, but detected mRNA for rH1, which is known to encode a TTX-resistant channel, in B104 cells. B104 neuroblastoma cells thus express TTX-sensitive and -resistant Na+ currents. These appear to be encoded by neuronal-type and cardiac Na+ channel mRNAs including the RH1 transcript. This cell line may be useful for studies on the rH1 channel, which is known to be mutated in the long-QT syndrome.

Sodium channel mRNA in the B104 neuroblastoma cell line

B104 neuroblastoma cells are excitable, but the ion channels underlying electrogenesis in these cells have not been identified. RT-PCR, restriction enzyme analysis and in situ hybridization were used to study sodium channel mRNAs in B104 cells. High levels of sodium channel alpha-subunit mRNAs III, NaG and Na6 and beta 1-subunit mRNA were detected by RT-PCR in B104 cells. Low levels of types I and II alpha-subunit mRNAs were also present. In situ hybridization with subtype-specific riboprobes detected sodium channel alpha-subunit mRNAs III, NaG and Na6 and beta 1-subunit mRNA in B104 cells; analysis of the percentage of B104 cells expressing each alpha-subunit mRNA subtype suggests that some cells express the mRNAs for several alpha-subunits.

Down-regulation of Na channel expression by A23187 in N1E-115 neuroblastoma cells

Growth of cultured N1E-115 neuroblastoma cells in 1 microM A23187 for 2 days to elevate internal Ca reduced both membrane Na current and the transient, but not steady state, component of outward K current. Na channel mRNA abundance was reduced by an average value of 45% without effect on Kv3.1. Increases in internal Ca may therefore control excitability by independent regulation of Na and K channel mRNA abundance in neurons.

Rat brain Na+ channel mRNAs in non-excitable Schwann cells

The expression of rat brain voltage-sensitive Na+ channel mRNAs in Schwann cells was examined using in situ hybridization cytochemistry and RT-PCR. The mRNAs of rat brain Na+ channel subtype II and III, but not subtype I, were detected in cultured Schwann cells from sciatic nerve and in intact sciatic nerve, which contains Schwann cells but not neuronal cell bodies. These results indicate that rat brain Na+ channel mRNAs, which have been considered as mainly neuronal-type messages, are also expressed in glial cells in vitro and in vivo.

Type III sodium channel mRNA is expressed in embryonic but not adult spinal sensory neurons, and is reexpressed following axotomy

1. In situ hybridization with subtype-specific probes was used to ask whether there is a change in the types of sodium channels that are expressed in dorsal root ganglion (DRG) neurons after axotomy. 2. Types I and II sodium channel mRNA are expressed at moderate-to-high levels in control DRG neurons of adult rat, but type III sodium channel mRNA is not detectable. 3. When adult rat DRG neurons are examined by in situ hybridization 7-9 days following axotomy, type III sodium channel mRNA is expressed at moderate-to-high levels, in addition to types I and II mRNA that are present at relatively high levels. 4. To determine whether the expression of type III sodium channel mRNA following axotomy represents up-regulation of a gene that had been expressed at earlier developmental stages, we also studied DRG neurons from embryonic (E17) rats. In these embryonic DRG neurons, type I sodium channel mRNA is expressed at low levels, type II mRNA at high levels, and type III at high levels. 5. These results demonstrate altered expression of sodium channel mRNA in DRG neurons following axotomy, and suggest that in at least some DRG neurons, there is a de-differentiation after axotomy that includes a reversion to an embryonic mode of sodium channel expression. Different channel characteristics, as well as an altered spatial distribution of sodium channels, may contribute to the electrophysiological changes that are observed in axotomized neurons.

The expression of rat brain voltage-sensitive Na+ channel mRNAs in astrocytes

Astrocytes from various regions of CNS have been shown to express voltage-activated Na+ currents. To date, three distinct subtypes (I, II and III) of Na+ channels have been cloned from rat brain. We have applied a combined technique of reverse transcription and polymerase chain reaction (RT-PCR) to examine the expression of rat brain Na+ channels in rat astrocytes in vivo and in vitro. Five PCR primer sets were used to amplify coding or 3' non-coding regions of subtype I, II, and III Na+ channels. We were able to amplify all three of these rat brain Na+ channel subtypes from rat optic nerve, which does not have neuronal cell bodies but does contain astrocytes known to express voltage-sensitive Na+ channels. In studies on cultured spinal cord astrocytes, we were also able to amplify all three subtypes of rat brain Na+ channel mRNAs. In control experiments, RT-PCR was performed on RNAs prepared from several rat tissues, including brain, skeletal muscle, and liver. Rat brain was shown to express the three Na+ channel subtypes as expected. In rat skeletal muscle, subtype I and III Na+ channel mRNAs, but not subtype II, were amplified. In rat liver, Na+ channel messages were not detectable. The present study provides the first direct evidence that astrocytes in vivo and in vitro express rat brain voltage-sensitive Na+ channel mRNAs, which have been considered as mainly neuronal-type Na+ channel messages.