Central angiotensin II-enhanced splenic cytokine gene expression is mediated by the sympathetic nervous system

We tested the hypothesis that central angiotensin II (ANG II) administration would activate splenic sympathetic nerve discharge (SND), which in turn would alter splenic cytokine gene expression. Experiments were completed in sinoaortic nerve-lesioned, urethane-chloralose-anesthetized, splenic nerve-intact (splenic-intact) and splenic nerve-lesioned (splenic-denervated) Sprague-Dawley rats. Splenic cytokine gene expression was determined using gene-array and real-time RT-PCR analyses. Splenic SND was significantly increased after intracerebroventricular administration of ANG II (150 ng/kg, 10 microl), but not artificial cerebrospinal fluid (aCSF). Splenic mRNA expression of IL-1beta, IL-6, IL-2, and IL-16 genes was increased in ANG II-treated splenic-intact rats compared with aCSF-treated splenic-intact rats. Splenic IL-1beta, IL-2, and IL-6 gene expression responses to ANG II were significantly reduced in splenic-denervated compared with splenic-intact rats. Splenic gene expression responses did not differ significantly in ANG II-treated splenic-denervated and aCSF-treated splenic-intact rats. Splenic blood flow responses to intracerebroventricular ANG II administration did not differ between splenic-intact and splenic-denervated rats. These results provide experimental support for the hypothesis that ANG II modulates the immune system through activation of splenic SND, suggesting a novel relation between ANG II, efferent sympathetic nerve outflow, and splenic cytokine gene expression.     

Conditioned suppression of contact sensitivity is independent of sympathetic splenic innervation

The present study investigated the role of sympathetic innervation of the spleen in conditioned suppression of a contact hypersensitivity (CHS) reaction. Behavioral conditioning was achieved by pairing saccharin drinking solution (conditioned stimulus, CS) with injection of cyclosporin A (CsA, 20 mg/kg; unconditioned stimulus, UCS). Four days after sensitization of the animals by application of a 5% 2,4-dinitrochlorobenzene (DNCB) to abdominal skin, the animals were challenged by applying a 1% DNCB solution to the ear. The CHS response was monitored by measuring the degree of ear swelling. Saccharin re-presentation reduced ear swelling to a magnitude that approached that achieved by CsA treatment. Histological examination demonstrated that the conditioned reduction of ear swelling was produced by a reduced leukocyte infiltration of the ear. Prior sympathetic denervation of the spleen did not alter the conditioned suppression of the CHS response. These data indicate that behavioral conditioning using CsA produces alterations of CHS that, unlike conditioned prolongation of heart allograft survival, are independent of sympathetically regulated conditioned alterations in the spleen.     

The sympathetic nervous system is involved in variant Creutzfeldt-Jakob disease

Prion epizoonoses spread from animals consumed by humans raise the question of which pathways lead to prion neuroinvasion after oral exposure of humans. Here we show that neurons of sympathetic ganglia of patients with variant Creutzfeldt-Jakob disease (vCJD) accumulate the abnormal isoform of the protein prion. This observation shows the involvement of the sympathetic nervous system in the pathogenesis of vCJD and suggests a role for GUT-associated sympathetic neurons in prion propagation in humans after oral contamination.     

Single-cell analysis of gene expression in the nervous system

The characteristic functions of tissues and organs results from the integrated activity of individual cells. Nowhere is this more evident than in the nervous system, where the activities of single neurons communicating via electrical and chemical signals mediate complex functions, such as learning and memory. The past decade has seen an explosion in the identification of genes encoding proteins, such as voltage-gated channels and neurotransmitter receptors, responsible for neuronal excitability. These studies have highlighted the fact that even within a neuroanatomically defined region, the coexistence of multiple cell types makes it difficult, if not impossible, to correlate patterns of gene expression with function The recent development of techniques sensitive enough to, study gene expression at the single-cell level promises to break this bottleneck to our further understanding. Using examples taken from our own laboratories and the work of others, we review these techniques, their application, and discuss some of the difficulties associated with the interpretation of the data.     

Expression of glycerokinase in brown adipose tissue is stimulated by the sympathetic nervous system

The effect of cold exposure (4 degrees C) or prolonged norepinephrine infusion on the activity and mRNA levels of glycerokinase (GyK) was investigated in rat interscapular brown adipose tissue (BAT). Cold exposure for 12 and 24 h induced increases of 30% and 100%, respectively, in the activity of BAT GyK, which was paralleled by twofold and fourfold increase in enzyme mRNA levels. BAT hemidenervation resulted in reductions of 50% and 30% in GyK activity and in mRNA levels, respectively, in denervated pads from rats kept at 25 degrees C, and suppressed in these pads the cold-induced increases in both GyK activity and mRNA levels. The increase in GyK activity induced by cold exposure was not affected by phenoxybenzamine, but was markedly inhibited by previous administration of propranolol or actinomycin D. BAT GyK activity did not change significantly after 6 h of continuous subcutaneous infusion of norepinephrine (20 microg/h), but increased twofold and fourfold after 12 and 24 h, with no further increase after 72 h of infusion. Norepinephrine infusion also activated mRNA production, but the effect was comparatively smaller than that on enzyme activity. beta-Adrenergic agonists also stimulated GyK activity with the following relative magnitude of response: CL316243 (beta(3)) > isoproterenol (non-selective) > dobutamine (beta(1)). In vitro rates of incorporation of glycerol into glyceride-glycerol were increased in BAT from rats exposed to cold. The data suggest that in conditions of a sustained increase in BAT sympathetic flow there is a stimulation of GyK gene expression at the pretranslational level, with increased enzyme activity, mediated by beta-adrenoreceptors, mainly beta(3).     

Immunoregulation mediated by the sympathetic nervous system.

A postulated immunoregulatory role for the autonomous nervous system was explored utilizing several in vivo and in vitro approaches. Local surgical denervation of the spleen in rats and general chemical sympathectomy by 6-hydroxydopamine combined with adrenalectomy yielded a similar removal of restraint expressed as enhancement in the number of PFC in response to immunization. Noradrenaline and the synthetic α-agonist clonidine which are, respectively, natural and artificial effector molecules of the sympathetic nervous system each strongly suppressed the in vitro induced immune response of murine spleen cells to SRBC. Further, radiometric-enzymatic assay of noradrenaline in the splenic pulp revealed a decrease in the content of this neurotransmitter just preceding the exponential phase of the immune response to SRBC (Days 3 and 4) in this site. Taken together, these findings point to a dynamic immunoregulatory relationship between the immune and sympathetic nervous system.     

Developmental expression of the myelin gene MOBP in the rat nervous system

The myelin-associated/oligodendrocyte basic proteins (MOBPs) are recently discovered constituents of myelin and are small, cytoplasmic, and highly basic proteins exclusively expressed postnatally by oligodendrocytes. Due to a clustering of positively charged amino acids observed in the most abundant MOBP isoform similar to myelin basic protein (MBP) and P0, it was speculated that MOBP could function in myelin sheath compaction. The present report strongly supports this view. A direct comparison of MBP and proteolipid protein (PLP) gene expression with that of MOBP by in situ hybridization revealed a very similar regional distribution. It was found that MOBP expression was abundant in the rat CNS at postnatal day 15 (P 15) but is restricted to densely myelinated regions. In contrast to MBP and PLP, expression of MOBP was undetectable in the peripheral nervous system during the entire development. Interestingly, MOBP mRNA was localized in oligodendrocyte processes even at early postnatal stages and throughout development. MOBP showed a very specific timing of expression: in spinal cord and brain, MOBP gene expression occurred significantly later (2–3 days) than that of MBP and PLP, but slightly earlier than myelin oligodendrocyte glycoprotein gene expression. MOBP proteins appeared in spinal cord and brain stem also after MBP protein, suggesting that the MOBPs functionally act after the structural myelin proteins MBP and PLP. Our findings imply a function of MOBP during the late steps of myelin formation, presumably at the initiation of sheath compaction.     

ming is expressed in neuroblast sublineages and regulates gene expression in the Drosophila central nervous system.

Cell diversity in the Drosophila central nervous system (CNS) is primarily generated by the invariant lineage of neural precursors called neuroblasts. We used an enhancer trap screen to identify the ming gene, which is transiently expressed in a subset of neuroblasts at reproducible points in their cell lineage (i.e. in neuroblast 'sublineages'), suggesting that neuroblast identity can be altered during its cell lineage. ming encodes a predicted zinc finger protein and loss of ming function results in precise alterations in CNS gene expression, defects in axonogenesis and embryonic lethality. We propose that ming controls cell fate within neuroblast cell lineages.