Monoclonal antibodies to rat brain acetylcholinesterase: comparative affinity for soluble and membrane-associated enzyme and for enzyme from different vertebrate species

Reconstruction of a 10-mm-long median nerve gap in an ischemic environment using autologous conduits with different patterns of blood supply: A comparative study in the rat

The aim of this study was to evaluate in the Wistar rat the efficacy of various autologous nerve conduits with various forms of blood supply in reconstructing a 10-mm-long gap in the median nerve (MN) under conditions of local ischemia. A 10-mm-long median nerve defect was created in the right arm. A loose silicone tube was placed around the nerve gap zone, in order to simulate a local ischemic environment. Rats were divided in the following experimental groups (each with 20 rats): the nerve Graft (NG) group, in which the excised MN segment was reattached; the conventional nerve flap (CNF) and the arterialized neurovenous flap (ANVF) groups in which the gap was bridged with homonymous median nerve flaps; the prefabricated nerve flap (PNF) group in which the gap was reconstructed with a fabricated flap created by leaving an arteriovenous fistula in contact with the sciatic nerve for 5 weeks; and the two control groups, Sham and Excision groups. In the latter group, the proximal stump of the MN nerve was ligated and no repair was performed. The rats were followed for 100 days. During this time, they did physiotherapy. Functional, electroneuromyographic and histological studies were performed. The CNF and ANVF groups presented better results than the NG group in the following assessments: grasping test, nociception, motor stimulation threshold, muscle weight, and histomorphometric evaluation. Radial deviation of the operated forepaw was more common in rats that presented worse results in the other outcome variables. Overall, CNFs and ANVFs produced a faster and more complete recovery than NGs in the reconstruction of a 10-mm-long median nerve gap in an ischemic environment in the Wistar rat. Although, results obtained with CNFs were in most cases were better than ANVFs, these differences were not statistically significant for most of the outcome variables.

Neurochemical characterization of the tree shrew dorsal striatum

The striatum is a major component of the basal ganglia and is associated with motor and cognitive functions. Striatal pathologies have been linked to several disorders, including Huntington’s, Tourette’s syndrome, obsessive–compulsive disorders, and schizophrenia. For the study of these striatal pathologies different animal models have been used, including rodents and non-human primates. Rodents lack on morphological complexity (for example, the lack of well defined caudate and putamen nuclei), which makes it difficult to translate data to the human paradigm. Primates, and especially higher primates, are the closest model to humans, but there are ever-increasing restrictions to the use of these animals for research. In our search for a non-primate animal model with a striatum that anatomically (and perhaps functionally) can resemble that of humans, we turned our attention to the tree shrew. Evolutionary genetic studies have provided strong data supporting that the tree shrews (Scadentia) are one of the closest groups to primates, although their brain anatomy has only been studied in detail for specific brain areas. Morphologically, the tree shrew striatum resembles the primate striatum with the presence of an internal capsule separating the caudate and putamen, but little is known about its neurochemical composition. Here we analyzed the expression of calcium-binding proteins, the presence and distribution of the striosome and matrix compartments (by the use of calbindin, tyrosine hydroxylase, and acetylcholinesterase immunohistochemistry), and the GABAergic system by immunohistochemistry against glutamic acid decarboxylase and Golgi impregnation. In summary, our results show that when compared to primates, the tree shrew dorsal striatum presents striking similarities in the distribution of most of the markers studied, while presenting some marked divergences when compared to the rodent striatum.

Co-localization of PRiMA with acetylcholinesterase in cholinergic neurons of rat brain: an immunocytochemical study

In the central nervous system, acetylcholinesterase (AChE) is present in a tetrameric form that is anchored to membranes via a proline-rich membrane anchor (PRiMA). Previously it has been found that principal cholinergic neurons in the brain express high concentrations of AChE enzymic activity at their neuronal membranes. The aim of this study was to use immunocytochemical methods to determine the distribution of PRiMA in these neurons in the rat brain. Confocal laser and electron microscopic investigations showed that PRiMA immunoreactivity is associated with the membranes of the somata, dendrites and axons of cholinergic neurons in the basal forebrain, striatum and pedunculopontine nuclei, i.e. the neurons that innervate forebrain and brainstem structures. In these neurones, PRiMA also co-localizes with AChE immunoreactivity at the plasma membrane. PRiMA label was absent from neighboring GABAergic neurons, and from other neurons of the brain known to express high levels of AChE enzymic activity including cranial nerve motor neurons and dopaminergic neurons of the substantia nigra zona compacta. A strong association of AChE with PRiMA at the plasma membrane is therefore a feature specific to principal cholinergic neurons that innervate the central nervous system.

Angiotensin II type 1 receptors may not influence response of spinal autonomic neurons to axonal damage

OBJECTIVES

Angiotensin II can promote cell stress, and the expression of its AT1 receptor is characteristic of neuronal populations that die off in multiple systems atrophy and Parkinson's disease. To explore the possible significance of these facts, we undertook to: (1) clarify the distribution of AT(1) in rat neurons; (2) use selective antagonists as a means of determining whether AT1 activation predisposes stressed neurons to die.

METHODS

AT1-expression was examined by immunohistochemistry and by autoradiography for [125I]-sarcosine1-angiotensin II binding in sensory, motor and autonomic neurons. To induce cell loss in a specific neuronal population, rats were given systemic i.v. injection of anti-acetylcholinesterase antibodies, which cause a delayed death of pre-ganglionic sympathetic neurons in the intermediolateral nucleus (IML). As pharmacologic intervention, some immunolesioned rats were treated with the selective AT1 antagonist, Candesartan.

RESULTS

Immunohistochemistry and autoradiography revealed AT1 expression in dorsal root ganglia, superior cervical ganglion. In the dorsal horn of the spinal cord, AT1 immunostainining and angiotensin binding were both prominent. In ventral horn and IML, immunoreactivity for AT1 and choline acetyltransferase co-localized in pre-ganglionic sympathetic and somatic motor neurons. Immunolesion caused over 50% loss of IML perikarya within 3 months. Concurrent treatment with the AT1 antagonist, Candesartan, did not affect the outcome.

DISCUSSION

AT1 expression is surprisingly widespread in sensory, autonomic and somatic motor neurons of the rat. This expression may be important to the normal physiology of these systems. Present data, however, do not support the concept that AT1 activation contributes to the loss of autonomic neurons after axonal damage.

Lateral hypothalamic acetylcholinesterase-immunoreactive neurons co-express either orexin or melanin concentrating hormone

The lateral hypothalamic area (LHA) contains a large population of neurons that express the enzyme acetylcholinesterase (AChE), but are not themselves cholinergic. Some of these neurons have been shown to contain melanin-concentrating hormone (MCH), a neuropeptide implicated in regulating feeding, but the identities of the remaining neurons are unknown. We now report that nearly all AChE-immunoreactive neurons in the LHA express immunoreactivity for either MCH or for orexin, a peptide implicated in regulating wakefulness. Furthermore, most orexin neurons and MCH neurons appear to contain AChE. AChE immunoreactivity appears to be a key feature of nearly all of the diffusely-projecting cortical systems.

Antiamylase-pullulanase enzyme monoclonals which specifically inhibit amylase or pullulanase activity

Monoclonal antibodies against amylase-pullulanase enzyme from Bacillus circulans F-2 have been produced to locate and characterize the catalytic sites of the enzyme. The antibodies have been examined for inhibition of both enzyme activities of amylase and pullulanase and then classified into four types: Type I which inhibited amylase activity, Type II which inhibited pullulanase activity, Type III which inhibited both enzyme activities, and Type IV which had no effect on either enzyme activity. Only two monoclonal antibodies (MAP-12 and MAP-17) as Type I and two antibodies (MAP-3 and MAP-5) as Type II were isolated. The inhibitory activities of the antibodies were characterized and compared. In Type II antibodies, the maximal demonstrated inhibition on the pullulanase activity was 88% for MAP-3 with 1 microg of antibody and 90% for MAP-5 with 2 microg of antibody, but did not inhibit the amylase activity. In Type I antibodies, in contrast, the maximal demonstrated inhibition on the amylase activity was 94% for MAP-12 and 97% for MAP-17 with 1 microg of antibody, respectively, but no inhibition of the pullulanase was noted. MAP-12 recognized sequential epitope, while MAP-17 recognized conformation-dependent epitope of amylase activity-related regions. However, both MAP-3 and MAP-5 recognized the conformation-dependent epitope of the pullulanase activity-related region. Furthermore, the antibodies of MAP-3, MAP-5, MAP-12, and MAP-17 did not compete with one another for binding to the enzyme, indicating that they have different target epitopes on the enzyme. Antibody binding of MAP-12 and MAP-17 to the enzyme was not specifically affected by any of the antiamylase compounds tested: (a) nojirimycin; and (b) 1-deoxynojirimycin. Kinetic analysis of their effects provides evidence that both antibodies of MAP-12 and MAP-17 decrease the catalytic rate of enzyme activity and have little or no effect on substrate binding.

Complement regulatory proteins and selective vulnerability of neurons to lysis on exposure to acetylcholinesterase antibody

Systemic injection of antibodies against acetylcholinesterase (AChE) induces complement-mediated destruction of preganglionic nerve terminals in paravertebral sympathetic ganglia, but spares other AChE-rich structures, such as nerve terminals in prevertebral sympathetic ganglia, parasympathetic ganglia, and the neuromuscular junction. This pattern of differing sensitivity to "AChE immunolesion" might be explained by a differing expression of proteins that serve to protect host cells from complement activation. Two major complement regulatory proteins in rats are Crry, which interferes with the assembly of C3 convertase, and CD59, which blocks formation of the terminal cytolytic membrane attack complex. The present study used immunohistochemistry to demonstrate an inverse relation between levels of CD59 and Crry expression and sensitivity to AChE immunolesion in several AChE-rich targets. Thus, the most sensitive structures, i.e., preganglionic nerve terminals in the adrenal gland and superior cervical ganglion (SCG), expressed undetectable levels of CD59 and Crry immunoreactivities. By contrast, AChE-rich, but antibody-resistant, cholinergic nerve terminals in the inferior mesenteric ganglia (IMG) and diaphragm muscle expressed significant amounts of CD59 and Crry. Such expression was functionally important because, after membrane-anchored CD59 was removed from explanted IMG with phosphatidylinositol phospholipase C, exposure to AChE antibody and complement caused greater immunolesion. It was concluded that differential expression of regulatory proteins in different parts of the nervous system influences regional vulnerability to complement mediated damage.

Distribution of choline acetyltransferase (ChAT) immunoreactivity in the brain of the adult trout and tract-tracing observations on the connections of the nuclei of the isthmus

The distribution of cholinergic neurons and fibers was studied in the brain and rostral spinal cord of the brown trout and rainbow trout by using an antiserum against the enzyme choline acetyltransferase (ChAT). Cholinergic neurons were observed in the ventral telencephalon, preoptic region, habenula, thalamus, hypothalamus, magnocellular superficial pretectal nucleus, optic tectum, isthmus, cranial nerve motor nuclei, and spinal cord. In addition, new cholinergic groups were detected in the vascular organ of the lamina terminalis, the parvocellular and magnocellular parts of the preoptic nucleus, the anterior tuberal nucleus, and a mesencephalic tegmental nucleus. The presence of ChAT in the magnocellular neurosecretory system of trout suggests that acetylcholine is involved in control of hormone release by neurosecretory terminals. In order to characterize the several cholinergic nuclei observed in the isthmus of trout, their projections were studied by application of 1,1;-dioctadecyl-3,3,3;, 3;-tetramethylindocarbocyanine perchlorate (DiI) to selected structures of the brain. The secondary gustatory nucleus projected mainly to the lateral hypothalamic lobes, whereas the nucleus isthmi projected to the optic tectum and parvocellular superficial pretectal nucleus, as previously described in other teleost groups. In addition, other isthmic cholinergic nuclei of trout may be homologs of the mesopontine system of mammals. We conclude that the cholinergic systems of teleosts show many primitive features that have been preserved during evolution, together with characteristics exclusive to the group.

Complement-mediated lesion of sympathetic ganglia in vitro with acetylcholinesterase antibodies

When administered to rats, antibodies against acetylcholinesterase (AChE) selectively destroy presynaptic inputs to sympathetic ganglia. To investigate the mechanism of this immunolesion, we created an in vitro system in which relevant components could be manipulated. Freshly dissected rat superior cervical ganglia (SCG) were incubated 15-20 h at 37 degrees C in fresh human serum (a potent source of complement) with continuous oxygenation. More than 96% of neurons in six control ganglia retained synaptic inputs, as defined by action potentials or excitatory postsynaptic potentials (EPSP) upon stimulation of the preganglionic trunk. However, when anti-AChE antibodies were present (0.16 mg/ml), none of 61 neurons from six incubated ganglia showed synaptic responses although membrane potential and input resistance remained normal. Staining for AChE and synaptophysin (a synaptic vesicle marker) was also disrupted in ganglia exposed to AChE antibodies in complement-sufficient serum. When complement was eliminated by substituting serum that was heat-inactivated or deficient in C3, synaptic input was retained in 60-90% of neurons incubated with AChE antibodies. Choline acetyltransferase activity (ChAT), an enzymatic marker of cholinergic cytoplasm in sympathetic ganglia, was largely lost after incubation with AChE antibodies and serum. However, incubation with AChE antibodies in heat-inactivated serum, or serum that was deficient in C3 or C8, caused no measurable loss of ganglionic ChAT activity. These findings strongly implicate the complement cascade in the destruction of preganglionic sympathetic terminals that follows binding of AChE antibodies.

A four-to-one association between peptide motifs: four C-terminal domains from cholinesterase assemble with one proline-rich attachment domain (PRAD) in the secretory pathway

The major type of acetylcholinesterase in vertebrates (AChET) is characterized by the presence of a short C-terminal domain of 40 residues, the 'tryptophan amphiphilic tetramerization' (WAT) domain. The presence of this domain is not necessary for catalytic activity but is responsible for hydrophobic interactions and for the capacity of AChET subunits to form quaternary associations with anchoring proteins, thereby conditioning their functional localization. In the collagen tail of asymmetric forms, we characterized a small conserved region that is sufficient for binding an AChET tetramer, the proline-rich attachment domain (PRAD). We show that the WAT domain alone is sufficient for association with the PRAD, and that it can attach foreign proteins (alkaline phosphatase, GFP) to a PRAD-containing construct with a glycophosphatidylinositol anchor (GPI), and thus anchor them to the cell surface. Furthermore, we show that isolated WAT domains, or proteins containing a WAT domain, can replace individual AChET subunits in PRAD-linked tetramers. This suggests that the four WAT domains interact with the PRAD in a similar manner. These quaternary interactions can form without intercatenary disulfide bonds. The common catalytic domains of AChE are not necessary for tetrameric assembly, although they may contribute to the stability of the tetramer.

Acetylcholinesterase immunolesioning: regional vulnerability of preganglionic sympathetic neurons in rat spinal cord

Rats given antibodies against acetylcholinesterase (AChE) develop sympathetic dysfunction stemming from losses of preganglionic neurons in spinal cord. Central effects of AChE antibodies are surprising since IgG does not readily cross the blood-brain barrier, and lesions of peripheral terminals should not cause cell death. This study was designed to explore the distribution of central neural damage and to investigate features that might account for vulnerability. Rat spinal cord and brainstem were stained for choline acetyltransferase (ChAT) and nitric oxide synthase (NOS) immunoreactivity. Four months after administration of AChE antibodies, ChAT-positive neurons in the intermediolateral nucleus (IML) were 61-66% fewer throughout the thoracolumbar cord (T1, T2, T8, T12, L1). NOS-positive neurons in these loci were affected to the same extent by antibody-treatment, although they were only two-thirds as numerous. By contrast, neurons in the central autonomic nucleus of the thoracolumbar cord were scarcely affected. These results point to immunochemical differences in the central autonomic outflow, which may partially explain the puzzling selectivity of neural damage in AChE immunolesioning. Different results were obtained after guanethidine sympathectomy, which ablated nearly all neurons in the superior cervical ganglion without any effect on preganglionic neurons in the IML. Therefore, if the central effects of antibodies are indirectly mediated by loss of trophic support from the periphery, this support cannot arise from adrenergic neurons but must come from other ganglionic cells.

Comparison of the in vitro sensitivity of rat acetylcholinesterase to chlorpyrifos-oxon: what do tissue IC50 values represent?

The toxicological literature is replete with studies which have attempted to correlate differences in in vivo sensitivity to anticholinesterases with a common in vitro measure: acetylcholinesterase (AChE) IC50 values. Generally, it is assumed that these IC50 values reflect the intrinsic sensitivity of the AChE molecule to the inhibitor. Our goal was to ascertain whether differences in AChe sensitivity to an organophosphate (i.e., IC50 values) are due to varying properties of the enzyme molecule (i.e., present assumption) or to extrinsic factors. Tissue samples were obtained from immature and adult Long-Evans rats. AChE IC50 values were determined by incubating tissue homogenates with chlorpyrifos-oxon (active metabolite of chlorpyrifos, a common organophosphate insecticide) for 30 min at 26 degrees C, and then measuring residual AChE activity. The following IC50 values were noted for postnatal day 4 and adult animals, respectively: brain, 10 nM for both ages; liver, 96 and 527 nM; plasma, 18 and 326 nm. Thus, the "apparent" sensitivity of AChe was prone to vary dramatically with age and tissue type. In contrast, when AChE was isolated from the same tissues by immunoprecipitation, there were no age- or tissue- related differences (IC50 approximately equal to 3 nM in every case). These data show clearly that IC50 values from a crude homogenate do not measure the true sensitivity of AChE to the inhibitor. Presumably, for chlorpyrifos-oxon, at least, the tissue IC50 values depend greatly on a tissue's propensity to sequester or hydrolyze chlorpyrifos-oxon.

Selective disruption of neurotransmission by acetylcholinesterase antibodies in sympathetic ganglia examined with intracellular microelectrodes

Antibodies to acetylcholinesterase (AChE) induce adrenergic dysfunction in rats by selective, complement-mediated destruction of preganglionic sympathetic nerve terminals. To analyze this phenomenon at the neuronal level, monoclonal antibodies to AChE (1.6 mg) were injected via the tail vein, and superior cervical ganglia (SCG) or inferior mesenteric ganglia (IMG) were studied in vitro. In control SCG, all impaled neurons generated action potentials during direct injection of depolarizing current or indirect stimulation through the preganglionic nerve. Current injection remained effective in ganglia from treated rats, but preganglionic stimulation was greatly impaired: at 12 h and 3 d, less than 10% of the neurons responded, even to a maximal stimulus (150 V); at 9 d, only 25% responded. By contrast, in IMG, synaptic transmission was much less affected by antibody exposure: 60% or more of examined neurons responded to preganglionic stimulation. Differences in antibody access did not explain differing sensitivities of SCG and IMG since immunohistochemistry showed rapid accumulation of IgG deposits in both ganglia. These results are believed to reflect widespread but subtotal preganglionic sympathectomy by AChE antibodies. Current information indicates that paravertebral ganglia are all antibody-sensitive, but some prevertebral ganglia are resistant, suggesting immunochemical differences between them.

Characterization of a monoclonal antibody that specifically inhibits pullulanase activity of Bacillus circulans amylase-pullulanase enzyme

A monoclonal antibody (MAb) against amylase pullulanase enzyme from Bacillus circulans, which hydrolyzes not only the alpha-1,6-glycosidic linkage but also the alpha-1,4-glycosidic linkage to the same extent, has been produced by the fusion of BALB/c mouse spleen cells immunized with the native enzyme and P3x63Ag8U1 myeloma cells, and examined for inhibition of pullulanase activity in order to characterize the catalytic site of the pullulanase. The MAb recognizes active enzyme, but not the SDS-denatured or heat-inactivated protein, indicating that the antibody is highly conformational-dependent, specific for active enzyme. The antibody inhibited the pullulanase activity, but not amylase activity. The monoclonal antibody immunoblotted the enzyme and immunoprecipitated the enzyme. The immunoprecipitation was inhibited in the presence of substrate, pullulan, and the MAb competitively inhibited the binding of pullulan to the enzyme. The MAb, therefore, recognizes the pullulan-binding site of the enzyme. Kinetic analysis showed that the MAb inhibited pullulanase activity with inhibition constant (Ki) of 0.77 microgram/mL, providing evidence that the antibody decreases the catalytic rate of enzyme activity and has an effect on substrate binding. These results strongly confirm the previous observations that APE may have two different active sites responsible for the expression of amylase and pullulanase activities (Kim, C.H. and Kim, Y.S. Eur. J. Biochem. 1995, 227, 687-693).

Effects of immunological sympathectomy on postnatal peptide expression in the rat adrenal medulla

Administration of monoclonal antibodies against acetylcholinesterase (AChE-mabs) to adult rats leads to a selective degeneration of the acetylcholine esterase-(AChE), choline acetyltransferase-(ChAT) and enkephalin-(ENK) positive preganglionic fibres of the splanchnic nerve innervating the adrenal gland. Here we used this approach of immunological sympathectomy, performed at postnatal day 2 (P2), in an attempt to study the development role of the preganglionic fibres in the adrenal medulla in more detail. Analysis was performed at P16 and revealed that the effect of this treatment varied considerably between animals, as judged by the number of remaining AChE-, ChAT- and ENK-positive fibres. The number and intensity especially of ENK fibres in the adrenal medulla correlated negatively with the number and staining intensity of ENK-immunoreactive chromaffin cells, suggesting a 'dose-response' relationship. Thus, the high early postnatal levels of ENK-like immunoreactivity generally persisted in chromaffin cells of adrenals with a successful immunosympathectomy, i.e. in those adrenals that lacked AChE-, ChAT- and ENK-positive nerves. In contrast, calcitonin gene-related peptide-like immunoreactivity in nerves and chromaffin cells was not affected. Large and strongly AChE-positive intra-adrenal ganglion neurones, recently termed type I ganglion neurones, were present also after AChE-mab treatment and had an apparently normal morphology. These results indicate a role for preganglionic fibres in the developmental regulation of ENK in the chromaffin cells. However, these fibres appear less important for the postnatal development of the type I ganglion neurones.

C-terminals on motoneurons: electron microscope localization of cholinergic markers in adult rats and antibody-induced depletion in neonates

C-terminals on motoneurons are defined as those accompanied by characteristic postsynaptic specializations termed subsurface cisterns. We have previously shown, by light microscope immunolabelling methods, that subsurface cisterns occur regularly beneath choline acetyltransferase- and acetylcholinesterase-containing boutons on motoneurons. In the present study, the cholinergic nature of C-terminals suggested by these results was further investigated by immunohistochemistry and electron microscopy in adult rats and in neonates treated with a murine monoclonal acetylcholinesterase antibody which was previously shown to cause immunological lesions of central cholinergic systems. In both the facial nucleus and lumbar segment of spinal cord of adult rats, C-terminals were seen intensely immunostained for the cholinergic markers choline acetyltransferase and acetylcholinesterase. Immunolabelled terminals made contact with either neuronal somata or large calibre dendrites, which were positive for the cholinergic markers, and exhibited club-shaped or thin elongated morphologies suggestive of terminal or en passant type synaptic interactions. The close relationship found between cholinergic markers and immunolabelled subsurface cisterns in adults was maintained on motoneurons of eight-day-old rats. While subcutaneous treatment of newborn rat with acetylcholinesterase antibody appeared to have no effect on the distribution of immunopositive subsurface cisterns in motoneurons when examined on postnatal day 8, the density of labelling for the two cholinergic markers around these neurons was reduced. Areas of neuropil immediately surrounding motoneurons in treated animals often showed signs of extensive swelling and deterioration indicative of a lesion event, and these motoneurons frequently displayed subsurface cisterns unapposed to C-terminals. These results support our earlier conclusion, based on light microscope investigation, that the majority if not all C-terminals are cholinergic in the areas investigated and demonstrate the potential utility of immunolesion methods in the study of C-terminal function.

Slow accumulation of acetylcholinesterase in rat brain during enzyme inhibition by repeated dosing with chlorpyrifos

When given to rats, O,O'-diethyl-O-[3,5,6-trichloro-2-pyridyl]- phosphorothionate (chlorpyrifos), a common insecticide, causes an unusually lengthy dose-dependent fall in the activity of brain acetylcholinesterase (AChE; EC 3.1.1.7). To determine whether the slow recovery involves impaired AChE synthesis, experiments were designed to measure AChE activity, immunoreactive AChE protein (AChE-IR) and AChE mRNA. Male, Long-Evans rats, maintained at 350 +/- 5 g, were dosed (s.c.) weekly for 4 weeks with 0, 15, 30, or 60 mg/kg chlorpyrifos in peanut oil. Brain tissue was harvested 1, 3, 5, 7 and 9 weeks after treatment began. AChE activity was measured by Ellman assay, and AChE-IR was estimated by two-site ELISA using monoclonal antibodies to rat brain AChE. While AChE activity fell significantly at all times and doses, AChE-IR increased at 3 and 5 weeks in the two higher dosage groups. Larger increases of AChE-IR were observed after chlorpyrifos was administered for 4 weeks by the oral route. Northern blots quantified with reference to cyclophilin were consistent with stable levels of AChE mRNA. Overall, it appears that chronically reduced brain AChE activity after chlorpyrifos reflects sustained enzyme inhibition, not loss of enzyme protein or suppression of AChE message.

Production and characterization of separate monoclonal antibodies to human brain and erythrocyte acetylcholinesterases

Four murine monoclonal antibodies (MAbs) of the IgM class were raised against human acetylcholinesterase (AChE; Ec 3.1.1.7). The MAbs BMS-3E4, BMS-7G10, and BMS-9F4 all recognized human erythrocyte AChE, while BMS-6D6 bound specifically to human soluble brain AChE, on the basis of immunobinding assays. Dose-response studies gave an ELISA ED50 titer of 4.5 x 10(-4) M for BMS-6D6, while BMS-3E4 gave the best titer at 8.8 x 10(-4) M. Sucrose density gradients demonstrated sedimentation of antigen-antibody complexes, consistent with earlier findings (i.e., BMS-6D6 bound with brain AChE while BMS-3E4 preferred erythrocyte (AChE). No cross-reactivity between the two MAbs against the two antigens was noted.

Comparison of standard chromatographic procedures for the optimal purification of soluble human brain acetylcholinesterase

With the view of purifying soluble human brain acetylcholinesterase (AChE) into its separate isoforms, various preparative chromatographic procedures were compared. Chromatofocusing of cerebrospinal fluid (CSF) AChE revealed two major activity peaks, whilst that of caudate nucleus AChE showed one major peak. Both CSF and caudate nucleus AChE eluted at isoelectric points (pI) of between 5.5 and 5.2. Chromatofocusing failed to separate AChE into its individual isoforms, based on qualitative isoelectric focusing. Preparative purification by affinity chromatography showed a better AChE yield with the use of procainamide as a ligand, vis-à-vis acridinium. Maximum recovery for CSF and caudate nucleus AChE was 10 and 43% using acridinium and procainamide, respectively. Qualitative analysis by SDS-PAGE of affinity-purified AChE revealed four major bands between 50 and 62 kDa, corresponding to the catalytic subunits of AChE as verified by an anti-AChE polyclonal antibody. A size-exclusion column also allowed brain AChE purification, with the latter eluting at a putative molecular mass of 310 kDa. Unfortunately, cation-exchange using the state-of-the-art SMART system failed to separate AChE into its isoforms. AChE aggregation is given as one major obstacle precluding good resolution of isoforms.

Immunologically induced sympathectomy of preganglionic nerves by antibodies against acetylcholinesterase: increased levels of peptides and their messenger RNAs in rat adrenal chromaffin cells

Systemic administration of murine monoclonal acetylcholinesterase antibodies to rats has been shown to cause selective degeneration of sympathetic preganglionic neurons. In the present study rats were subjected to a single i.v. injection of these acetylcholinesterase antibodies, or to normal IgG or saline for control. Exophthalmos, piloerection and eyelid-drooping (ptosis) were observed within 1 h after administration of the antibodies. Rats were killed at different time-points after antibody administration, and the adrenal glands were analysed by means of indirect immunohistochemistry and in situ hybridization histochemistry. As soon as 3 h after the antibody treatment, a marked increase in the number of chromaffin cells expressing mRNA encoding, respectively, enkephalin, calcitonin gene-related peptide, galanin, neurotensin and substance P was seen. At 12 h the peptide mRNA levels were still elevated and there was a concomitant increase in the number of peptide-immunoreactive cells. All peptide levels remained high for at least 48 h; however, 77 days after the antibody treatment only enkephalin-immunoreactive cells could be encountered. A disappearance of acetylcholinesterase- and enkephalin-immunoreactive cells could be encountered. A disappearance of acetylcholinesterase- and enkephalin-positive fibers was already seen 3 h after the antibody treatment, and after 24 h no fibers were encountered. In contrast, up until 48 h there was no apparent change in the number or intensity of immunofluorescent fibers expressing calcitonin gene-related peptide, galanin, neurotensin or substance P. However, 77 days after the antibody treatment the number of calcitonin gene-related peptide- and substance P-immunoreactive fibers was increased as compared to controls. In addition, reappearance of acetylcholinesterase- and enkephalin-immunoreactive fibers was seen 77 days after antibody administration, although their number was still low as compared to controls. Double-labeling immunohistochemistry revealed that the chromaffin cells expressing peptides after the antibody treatment preferentially were adrenaline storing cells (noradrenaline-negative). The majority of these cells expressed only one peptide. Both surgical transection of the splanchnic nerve as well as treatment with acetylcholine receptor antagonists mimicked the effects seen after the acetylcholinesterase-antibody treatment, although changes were less pronounced. The present results show that interruption of splanchnic transmission induces fast, marked, and selective increases in peptide expression in rat adrenal chromaffin cells.

Catecholamine release and excretion in rats with immunologically induced preganglionic sympathectomy

Plasma and urinary catecholamines were quantified to assess global sympathoadrenal function in rats with preganglionic lesions caused by antibodies to acetylcholinesterase (AChE). Rats were given intravenous injections of normal mouse IgG or murine monoclonal anti-acetylcholinesterase IgG (1.5 mg). Five or 16 days afterward, basal blood samples were taken through indwelling arterial cannulate. A few hours later, the rats were immobilized for 10 min in padded restrainers, and another blood sample was drawn. HPLC determinations showed low basal levels of norepinephrine and epinephrine (< 0.2 ng/ml in all rat plasma samples). In control rats, immobilization stress increased levels of plasma catecholamines up to 35-fold. In rats tested 5 days after injection of antibody, the norepinephrine response was much smaller (15% of control), and the epinephrine response was nearly abolished (5% of control). There was some recovery at 16 days after antibody treatment, but stress-induced catecholamine release was still markedly impaired. Reduced stress-induced release was not accompanied by major changes in tissue epinephrine or norepinephrine (heart, spleen, adrenal glands, and brain), although adrenal dopamine content dropped by 60%. Urinary excretion was studied in parallel experiments to gain insight into the effects of AChE antibodies on basal sympathoadrenal activity. Epinephrine, norepinephrine, dopamine, and selected metabolites were quantified in 24-h urine samples collected at frequent intervals for 30 days after antibody injection. No statistically significant changes were detected in the urinary output of dopamine, 3-methoxytyramine, normetanephrine, or 3-methoxy-4-hydroxyphenylglycol. On the other hand, epinephrine and norepinephrine output increased sharply at the time of antibody injection and then fell significantly below control levels. Norepinephrine output returned to normal after 2 weeks, but epinephrine output remained depressed. These results are consistent with previous evidence of widespread and persistent antibody-mediated damage to the preganglionic sympathetic system.

Evidence for the cholinergic nature of C-terminals associated with subsurface cisterns in alpha-motoneurons of rat

C-terminals can be distinguished at the ultrastructural level from other types of nerve endings on motoneurons by their prominent and regularly occurring postsynaptic specializations termed subsurface cisterns (SSC). We have previously shown (Yamamoto et al., 1991) that an antibody directed against a sequence within the gap junction protein connexin32 immunolabels these motoneuronal SSCs and can therefore serve as a immunohistochemical tool to visualize indirectly the location of C-terminals on motoneurons at the light microscope level. Here we have used this anti-SSC antibody in combination with antibodies against choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) to determine whether C-terminals on motoneurons contain these cholinergic enzyme markers. In sections at all major spinal cord levels and in several cranial motor nuclei examined, motoneuronal cell bodies and their proximal dendrites were studded with large ChAT-immunoreactive (ChAT-IR) boutons. Boutons having a similar distribution and appearance on motoneurons were also immunolabeled for AChE. In addition, motoneurons were surrounded by a dense plexus of AChE-immunoreactive (AChE-IR) varicose fibers and fine preterminal axons. In double-labeled sections, AChE-IR boutons corresponded to those immunolabeled for ChAT. In sections processed for simultaneous immunofluorescence detection of ChAT and SSCs, ChAT-IR boutons were very often found in apposition to immunolabeled SSCs. In sections processed for simultaneous labeling of AChE and SSCs. AChE-IR boutons were again frequently seen abutting labeled SSCs. These results provide the first strong evidence at the LM level that a large proportion, if not the entirety, of C-terminals are cholinergic and show that these terminals consist in part of relatively large varicosities along highly varicose axons that form en passant type contacts on motoneurons. At the same time, our results substantially narrow possibilities regarding the as yet undetermined source of C-terminals, which can now be considered to originate from cholinergic neurons, such as those located in the brainstem and/or the spinal cord.

Amphiphilic and hydrophilic forms of acetyl- and butyrylcholinesterase in human brain

Human brain acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) were sequentially extracted, first with a Tris-saline buffer (S1) and then with 1% (w/v) Triton X-100 (S2). About 20 and 30% of the AChE and BuChE activities were recovered in S1 and most of the remaining enzymes in S2. Main molecular forms of about 10.5 S and 12.0 S, G4 forms of AChE and BuChE, and smaller amounts of 4.5 S and 5.5 S forms, G1 species of AChE and BuChE, were measured in S1. Application of Triton X-114 phase partitioning and affinity chromatography on phenyl-agarose to S1 revealed that 25% of the AChE and none of the BuChE molecules displayed amphiphilic properties. Analysis of the enzyme activity retained by the phenyl-agarose showed that G1 AChE constituted the bulk of the amphiphilic molecules released without detergent. Main G4 forms of AChE and BuChE were found in the S2 extract. Eighty and 45% of the AChE and BuChE activities in S2 were measured in the detergent-rich phase by Triton X-114 phase partitioning. Thus, most of the AChE and about half of the BuChE molecules in S2 displayed amphiphilic properties. The main peak of BuChE, a 12.0 S form in gradients made with Triton X-100, splits into two peaks of 9.5 S and 12.5 S in Brij 96-containing gradients. This suggests that hydrophilic G4 BuChE forms are predominant in S1 and that hydrophilic and amphiphilic isoforms coexist in S2.

Effects of antibodies against acetylcholinesterase on the expression of peptides and catecholamine synthesizing enzymes in the rat adrenal gland

In the rat, systemic administration of murine monoclonal antibodies against acetylcholinesterase caused rapid piloerection and ptosis (within 30-60 min after the injection). Using indirect immunohistochemistry the effect of these antibodies on peptides and enzyme expression was studied in the rat adrenal gland. Four days after antibody administration a total disappearance of acetylcholinesterase-immunoreactive fibers was observed. However, groups of acetylcholinesterase-immunoreactive chromaffin cells and intramedullary ganglion cells, both cell types showing acetylcholinesterase immunoreactivity also in the control adrenal medulla, expressed increased immunoreactivity. Analysis revealed that the acetylcholinesterase-immunoreactive chromaffin cell groups lacked phenylethanolamine-N-methyltransferase staining both in controls and treated rats. Antibody administration also affected levels of several peptides present in nerve fibers and chromaffin cells. Thus, the number of cells expressing enkephalin, calcitonin gene-related peptide and galanin was dramatically increased compared to the very few cells observed containing these three peptides in the normal gland. The majority of cells expressing enkephalin after antibody treatment also showed phenylethanolamine-N-methyltransferase immunoreactivity. In contrast, the few chromaffin cells expressing strong enkephalin-like immunoreactivity in controls were phenylethanolamine-N-methyltransferase negative. The sparse networks of calcitonin gene-related peptide- and galanin-positive fibers found in control adrenals were unchanged after the antibody treatment. However, the dense network of enkephalin varicose fibers totally disappeared after the antibody injection. A few substance P- and somatostatin-immunoreactive cells, not present in the normal gland, appeared after administration of the antibodies, whereas no changes were encountered with regard to immunoreactive nerve fibers. No clear differences between normal and treated animals could be observed in chromaffin cells with regard to immunoreactivity for neuropeptide Y or any of the four catecholamine-synthesizing enzymes, tyrosine hydroxylase, aromatic 1-amino acid decarboxylase, dopamine beta-hydroxylase or phenylethanolamine-N-methyltransferase. The present findings demonstrating a disappearance of acetylcholinesterase- and enkephalin-immunoreactive nerve fibers in the adrenal gland after intravenous injection of acetylcholinesterase antibodies support earlier reports showing that these antibodies cause degeneration of preganglionic fibers, and that neuronal decentralization of the adrenal gland induces marked increases in the levels of several peptides in chromaffin cells.

Death of intermediolateral spinal cord neurons follows selective, complement-mediated destruction of peripheral preganglionic sympathetic terminals by acetylcholinesterase antibodies

Systemically injected anti-acetylcholinesterase antibodies in rats cause selective lesions of preganglionic sympathetic neurons. Adult rats were examined up to four months after a single i.v. injection of murine monoclonal acetylcholinesterase antibodies or normal immunoglobulin G (1.5 mg). Within 4 h, antibody-treated rats developed ptosis, a sign of sympathetic dysfunction that was never reversed. Persistent pupillary constriction reflected preserved and unopposed parasympathetic function. Weight gain was depressed, but locomotor activity, excitability, and sensorimotor responses were normal, and gross neuromuscular performance was near normal. These findings were supported by biochemical evidence for selective sympathetic damage. Acetylcholinesterase activity was reduced for the whole period of observation in sympathetic ganglia and adrenal glands but fell only transiently in muscle and serum. At all times, choline acetyltransferase activity (a marker of presynaptic terminals) was unaffected in muscle but grossly depleted in ganglia. Light and electron microscopy showed that preganglionic sympathetic terminals of superior cervical ganglia were severely damaged while parasympathetic ganglia were less affected and motor endplates of skeletal muscle were apparently spared. Immunocytochemistry revealed punctate deposits of murine immunoglobulin G and complement component C3 in ganglionic neuropil 12 h after antibody injection. This finding was consistent with complement-mediated lysis of preganglionic terminals. Morphometric analysis of preganglionic neurons in the intermediolateral nucleus of the spinal cord showed progressive loss of cholinergic perikarya over several months. We conclude that antibody-induced destruction of ganglionic terminals leads to death of preganglionic sympathetic neurons and, hence, permanent dysautonomia.

Lesion of central cholinergic systems by systemically administered acetylcholinesterase antibodies in newborn rats

To determine if systemically administered antibodies could reach antigenic targets and cause immunologic lesions in brains of newborn rats, murine monoclonal antibodies against rat acetylcholinesterase were injected i.p. on the first postnatal day. As early as 24 h after injection, antibodies were detected immunocytochemically in brain parenchyma, along with punctate debris that showed intense cholinesterase activity. Total acetylcholinesterase activity in the brain dropped by 30%, and 10S activity was almost undetectable at day 3, implying true enzyme loss since the antibodies did not directly impair catalytic function. At day 7, 10S acetylcholinesterase began to recover but the activity remained only half that of controls. At day 12, total acetylcholinesterase activity was still reduced (30% in whole brain, 40% in cerebral cortex), consistent with lasting damage to cholinesterase-expressing cortical neurons. This conclusion was confirmed by histochemical experiments showing a nearly complete disappearance of acetylcholinesterase fiber-staining in cerebral cortex and basal ganglia at days 4 and 8, with residual deficits at day 12. Choline acetyltransferase activity decreased in the cerebral cortex, implying a loss of cholinergic terminals, but specifically immunoreactive perikarya remained abundant in the basal forebrain. Immunocytochemistry showed no obvious changes in three non-cholinergic markers: tyrosine hydroxylase, tryptophan hydroxylase, and glutamic acid decarboxylase. Overall, it appeared that acetylcholinesterase antibodies induced widespread but reversible damage of cholinergic fibers and terminals, while sparing cholinergic cell bodies and many other neural systems.

Membrane-bound acetylcholinesterase: an early differentiation marker for skeletal myoblasts

Cell-bound acetylcholinesterase (AChE) was found to be an early differentiation marker on embryonic chick skeletal myoblasts in mixed primary cell cultures. AChE biosynthesis was detected and characterized by (a) a sensitive microtiter assay, (b) use of selective inhibitors, and (c) with mono- and polyclonal antibodies. Both secreted and cell-bound AChE appeared on the first day in culture, at a time when no muscle cell fusion was observed. Characterization of this enzyme revealed that true AChE was bound and secreted by myoblasts. BW284c51, which permeates cell membranes poorly, inhibited all the cell-associated AChE activity on myoblasts, suggesting that the activity measured was on the outer cell surface. On the other hand, fibroblasts appeared to have no or very little bound enzyme and the low level of secreted enzyme activity had the characteristics of pseudo-, or butyrylcholinesterase. Polyclonal anti-Torpedo californica electroplax AChE antibody and several monoclonal antibodies were found to bind specifically to chick myoblasts. Since the cells had not been made permeable before antibody binding, a membrane-bound form of the enzyme was most likely being detected. The cell-bound true AChE was present in identifiable quantities from the first day of culture. Membrane-bound AChE can thus serve as an early differentiation marker for embryonic chick myoblasts in mixed primary cultures.

Paraoxon toxicity is not potentiated by prior reduction in blood acetylcholinesterase

The role of blood acetylcholinesterase in moderating the effects of organophosphate challenge in rats was tested. Adult male rats (n = 42) were injected (iv) either with monoclonal antibodies (MAb) to rat acetylcholinesterase (EC 3.1.1.7; AChE) or normal mouse IgG (controls). Two days later, the rats were injected (sc) with either a mild (0.17 mg/kg) or moderate dosage (0.34 mg/kg) of paraoxon or with vehicle. Neurological integrity was assessed by a functional observational battery followed by motor activity, 3 to 4 hr after dosing. Blood, brain, and diaphragm tissues were then collected for determination of AChE activity. MAb treatment reduced whole blood and plasma AChE activity by 32 and 90%, respectively, but did not affect neurobehavioral parameters or the AChE activity of brain or diaphragm. The paraoxon challenge produced dose-related neurobehavioral changes and inhibition of brain and diaphragm AChE activity to the same extent in IgG- and MAb-treated rats. Thus, significant loss in blood AChE alone produced no detectable neurobehavioral deficits and did not alter the subsequent responses to paraoxon challenge.

Effect of intracerebral injection of monoclonal acetylcholinesterase antibodies on cholinergic nerve terminals in the rat central nervous system

In the rat, unilateral intrastriatal injection of monoclonal antibodies to acetylcholinesterase (AChE) produced ipsilateral disappearance of AChE-positive nerve terminals within striatum and adjacent cortex. No alterations in striatal staining patterns were observed for tyrosine hydroxylase, somatostatin, neuropeptide Y, substance P, or neurotensin. Ultrastructural studies demonstrated the presence of degenerating AChE-positive boutons ipsilaterally, while tyrosine hydroxylase positive terminals seemed unaffected. Apomorphine administration to rats which had received unilateral antibody injection resulted in ipsilateral rotational behavior. These data suggest that selective effects on cholinergic terminals with functional deficits can be produced within the central nervous system by intracerebral injection of AChE antibodies.

The monoclonal antibody 2G8 is carbohydrate-specific and distinguishes between different forms of vertebrate cholinesterases

The monoclonal antibody (mAb) 2G8 (subclass IgG2a) raised against acetylcholinesterase (AChE, EC 3.1.1.7) from electric organ of Torpedo nacline timilei crossreacted with AChE from Torpedo marmorata, electric eel (Electrophorus electricus), flounder (Platichthys flesus) body muscle, rat brain, bovine brain, and human brain, this suggests that the epitope to which mAb 2G8 bound had been highly conserved during evolution. No crossreaction was found with AChE from human and bovine erythrocytes, nor with butyrylcholinesterase (BtChE, EC 3.1.1.8) from human serum. Binding of mAb 2G8 to the globular G2 form of AChE from T. marmorata strongly decreased enzyme activity, while no significant inhibition was found with either collagen-tailed, asymmetric forms, or with the enzymes from flounder body muscle or mammalian sources. The possibility that mAb 2G8 bound to anionic sites of AChE could be excluded since neither edrophonium chloride nor decamethonium bromide influenced the binding of 2G8 to the enzymes. Enzyme-linked immunosorbent assay and Western blot showed that heat-denatured, diisopropylfluorophosphate-treated, CNBr- and trypsin-digested AChE from T. marmorata still reacted with mAb 2G8; this indicates that the epitope to which 2G8 bound, at least partially, belonged to a continuous determinant. Treatment of cholinesterases with N-glycosidase F abolished crossreaction with 2G8, showing that an essential part of the epitope consisted of N-linked carbohydrates.

Autoimmune preganglionic sympathectomy induced by acetylcholinesterase antibodies

Systemic injection of monoclonal antibodies to neural acetylcholinesterase in adult rats caused a syndrome with permanent, complement-mediated destruction of presynaptic fibers in sympathetic ganglia and adrenal medulla. Ptosis, hypotension, bradycardia, and postural syncope ensued. In sympathetic ganglia, acetylcholinesterase activity disappeared from neuropil but not from nerve cell bodies. Choline acetyltransferase activity and ultrastructurally defined synapses were also lost. Electrical stimulation of presynaptic fibers to the superior cervical ganglion ceased to evoke end-organ responses. On the other hand, direct ganglionic stimulation remained effective, and the postganglionic adrenergic system appeared intact. Motor performance and the choline acetyltransferase content of skeletal muscle were preserved, as was parasympathetic (vagal) function. This model of selective cholinergic autoimmunity represents another tool for autonomic physiology and may be relevant to the pathogenesis of human dysautonomias.

Selective complexing of acetylcholinesterase in brain by intravenously administered monoclonal antibody

Rats injected intravenously with monoclonal antibodies reactive with brain acetylcholinesterase (AChE) developed a prolonged depression of plasma AChE without changes in butyrylcholinesterase, lactic acid dehydrogenase, or hematocrit. One antibody, ZR1, accumulated in the brain and spinal cord. Within 3 days of injection, ZR1 bound to most of the AChE in cerebral cortex and certain other regions of the CNS. Examination of the molecular forms of cortical 10S AChE, whereas 4S AChE remained free. In vitro, however, ZR1 bound equally to solubilized 4S and 10S forms. These data provide direct evidence for the compartmentalization of different AChE forms in the CNS, 10S being mainly extracellular and 4S apparently intracellular. Development of a striking and persistent bilateral ptosis within hours of injection suggests that AChE in the autonomic nervous system is also accessible to antibodies and, furthermore, is the site of an immunopathological lesion. This novel model of cholinergic autoimmunity may have relevance for human neurological disorders of unknown etiology.

Cross-homologies and structural differences between human cholinesterases revealed by antibodies against cDNA-produced human butyrylcholinesterase peptides

To study the polymorphism of human cholinesterases (ChEs) at the levels of primary sequence and three-dimensional structure, a fragment of human butyrylcholinesterase (BuChE) cDNA was subcloned into the pEX bacterial expression vector and its polypeptide product analyzed. Immunoblot analysis revealed that the clone-produced BuChE peptides interact specifically with antibodies against human and Torpedo acetylcholinesterase (AChE). Rabbit polyclonal antibodies prepared against the purified clone-produced BuChE polypeptides interacted in immunoblots with denatured serum BuChE as well as with purified and denatured erythrocyte AChE. In contrast, native BuChE tetramers from human serum, but not AChE dimers from erythrocytes, interacted with these antibodies in solution to produce antibody-enzyme complexes that could be precipitated by second antibodies and that sedimented faster than the native enzyme in sucrose gradient centrifugation. Furthermore, both AChE and BuChE dimers from muscle extracts, but not BuChE tetramers from muscle, interacted with these antibodies. To reveal further whether the anti-cloned BuChE antibodies would interact in situ with ChEs in the neuromuscular junction, bundles of muscle fibers were microscopically dissected from the region in fetal human diaphragm that is innervated by the phrenic nerve. Muscle fibers incubated with the antibodies and with 125I-Protein A were subjected to emulsion autoradiography, followed by cytochemical ChE staining. The anti-cloned BuChE antibodies, as well as anti-Torpedo AChE antibodies, created patches of silver grains in the muscle endplate region stained for ChE, under conditions where control sera did not. These findings demonstrate that the various forms of human AChE and BuChE in blood and in neuromuscular junctions share sequence homologies, but also display structural differences between distinct molecular forms within particular tissues, as well as between similarly sedimenting molecular forms from different tissues.

Monoclonal antibodies specific for the different subunits of asymmetric acetylcholinesterase from chick muscle

The asymmetric (20S) acetylcholinesterase (AChE, EC 3.1.1.7) from 1-day-old chick muscle, purified on a column on which was immobilised a monoclonal antibody (mAb) to chick brain AChE, was used to immunise mice. Eight mAbs against the muscle enzyme were hence isolated and characterised. Five antibodies (4A8, 1C1, 10B7, 7G8, and 8H11) recognise a 110-kilodalton (kDa) subunit with AChE catalytic activity, one antibody (7D11) recognises a 72-kDa subunit with pseudocholinesterase or butyrylcholinesterase (BuChE, EC 3.1.1.8) catalytic activity, and two antibodies (6B6 and 7D7) react with the 58-kDa collagenous tail unit. Those three polypeptides can be recognised together in the 20S enzyme used, which is a hybrid AChE/BuChE oligomer. Antibodies 6B6 and 7D7 are specific for asymmetric AChE. Four of the mAbs recognising the 110-kDa subunit were reactive with it in immunoblots. Sucrose density gradient analysis of the antibody-enzyme complexes showed that the anti-110-kDa subunit mAbs cross-link multiple 20S AChE molecules to form large aggregates. In contrast, there is only a 2-3S increase in the sedimentation constant with the mAbs specific for the 72-kDa or for the 58-kDa subunit, suggesting that those subunits are more inaccessible in the structure to intermolecular cross-linking. The 4A8, 10B7, 7D11, and 7D7 mAbs showed cross-reactivity to the corresponding enzyme from quail muscle; however, none of the eight mAbs reacted with either enzyme type from mammalian muscle or from Torpedo electric organ. All eight antibodies showed immunocytochemical localisation of the AChE form at the neuromuscular junctions of chicken twitch muscles.

A comparison of the localization of acetylcholinesterase in the rat brain as demonstrated by enzyme histochemistry and immunohistochemistry

The localization of acetylcholinesterase (AChE) as revealed either by enzyme-histochemical or by immunohistochemical methods was compared in distinct regions of the rat brain. In general, the localization of AChE observed was nearly the same, whether revealed by histochemical demonstration of its catalytic activity or by immunohistochemical detection of the enzyme molecule itself, in all regions investigated. Penetration problems of the antibodies, however, arose on strong myelin sheaths of the facial nerve, for instance, where no immunohistochemical staining was found though there was a relatively strong histochemical reaction. These problems could be partly solved by increasing the normal concentration of Triton X-100 added to the immunohistochemical solutions (0.1%) to 2.5%. Furthermore, it seems that sites containing low amounts of AChE could be better detected by the enzyme-histochemical method, whereas the depiction of structures (particularly of nerve fibres) was somewhat sharper with the immunohistochemical method.

Monoclonal antibodies to human brain acetylcholinesterase: properties and applications

1. Acetylcholinesterase (AChE) was purified 20,000-fold in a 43% yield from 90 g of human cerebellum by combined immunoaffinity and ligand affinity chromatography. The purified enzyme migrated as a 68,000-dalton band during polyacrylamide gel electrophoresis under denaturing and reducing conditions. 2. Balb/c mice were immunized with multiple 10-micrograms injections of this material in order to raise monoclonal antibodies to human brain AChE. Three such antibodies were obtained and characterized. 3. Each antibody cross-reacted distinctively with AChEs from other mammals. No antibody recognized human plasma butyrylcholinesterase but all reacted with AChE from human red blood cells. 4. Antibodies HR5 and HR3 performed well in two-site immunoassays for AChE. With these assays we compared autopsy samples of cortical region A9 from six controls (nonneurological cases) and five patients with Alzheimer's disease. The latter showed a highly significant 60% deficit of AChE protein. 5. The present antibodies will permit additional immunochemical studies of cholinergic systems in dementia.

Two-site immunoassay for acetylcholinesterase in brain, nerve, and muscle

Two-site methods were developed for immunoassay of acetylcholinesterase (AChE; EC 3.1.1.7) in crude extracts of rat and human tissues. A radiometric assay for human AChE utilized a specific monoclonal AChE antibody adsorbed to polystyrene microtiter wells at alkaline pH. AChE bound strongly to this antibody after 24 h at 4 degrees C. Bound enzyme was detected with an 125I-labeled antibody against a different AChE epitope. The assay signal was quasi-linearly related to AChE concentration in purified and crude samples, with a detection threshold near 100 pg. Tetrameric and dimeric AChE behaved equivalently in the assay. Two-site methods with a different pair of species-selective antibodies worked equally well for immunoassay of rat AChE. Assays of the rat enzyme showed that immunoreactivity was lost as rapidly as enzyme activity during heating to 54 degrees C. On the other hand, immunoreactivity was preserved despite loss of enzyme activity after exposure to anticholinesterases or trypsin. A biotinylated second antibody detected by alkaline-phosphatase-conjugated avidin was used to develop an AChE enzyme-linked immunosorbent assay (ELISA) with a sensitivity similar to that of the radiometric assay. Either the ELISA or the radiometric immunoassay may be useful whenever proteolysis or other mechanisms are suspected of dissociating enzyme activity and immunoreactivity. In denervated muscle and ligated peripheral nerve, application of the two-site method showed closely parallel variations in immunoreactivity and enzyme activity.

Isolation and characterization of full-length cDNA clones coding for cholinesterase from fetal human tissues

To study the primary structure and regulation of human cholinesterases, oligodeoxynucleotide probes were prepared according to a consensus peptide sequence present in the active site of both human serum pseudocholinesterase (BtChoEase; EC 3.1.1.8) and Torpedo electric organ "true" acetylcholinesterase (AcChoEase; EC 3.1.1.7). Using these probes, we isolated several cDNA clones from lambda gt10 libraries of fetal brain and liver origins. These include 2.4-kilobase cDNA clones that code for a polypeptide containing a putative signal peptide and the N-terminal, active site, and C-terminal peptides of human BtChoEase, suggesting that they code either for BtChoEase itself or for a very similar but distinct fetal form of cholinesterase. In RNA blots of poly(A)+ RNA from the cholinesterase-producing fetal brain and liver, these cDNAs hybridized with a single 2.5-kilobase band. Blot hybridization to human genomic DNA revealed that these fetal BtChoEase cDNA clones hybridize with DNA fragments of the total length of 17.5 kilobases, and signal intensities indicated that these sequences are not present in many copies. Both the cDNA-encoded protein and its nucleotide sequence display striking homology to parallel sequences published for Torpedo AcChoEase. These findings demonstrate extensive homologies between the fetal BtChoEase encoded by these clones and other cholinesterases of various forms and species.

Monoclonal antibodies against chicken brain acetylcholinesterase. Their use in immunopurification and immunochemistry to demonstrate allelic variants of the enzyme

Acetylcholinesterase (AChE) from 1-day chicken brain was enriched over 2000-fold by affinity chromatography using N-methylacridinium-Sepharose. This preparation was used to prepare monoclonal antibodies (mAb) directed against AChE, of which two were extensively characterised for further application. Both mAbs bound to the enzyme from the chicken with high affinity (Kd approximately 8 X 10(-10) M) and one mAb, in addition, recognised AChE from quail brain and muscle. Neither mAb cross-reacted with mammalian or fish AChE. Both mAbs recognised AChE in the endplate region of adult chicken skeletal muscle and bound with equal affinity to the three major oligomeric forms found in early ambryonic muscle. One mAb was used to immunopurify chicken brain AChE to homogeneity (over 12000-fold enrichment), with nearly complete recovery of the enzyme and without detectable proteolytic breakdown. The other mAb recognised AChE after immunoblotting and was used to screen crude brain extracts from individual chickens for allelic variations. Evidence is presented to show that two allelic forms occur, represented in SDS-PAGE by a doublet polypeptide of Mr approximately 110,000, this pattern is maintained after deglycosylation of the N-linked oligosaccharides. This variation was found throughout development and in both the brain and the muscle of individuals. We conclude that the gene encoding the catalytic subunit of chicken AChE is polymorphic with either one or two equally active alleles being expressed.

An inhibitory monoclonal antibody to human acetylcholinesterases

The monoclonal antibody AE-2 raised against acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) from human erythrocytes is shown to inhibit the enzyme activity. The reaction of the antibody with a structural epitope is investigated further. The epitope resides on monomeric, dimeric and tetrameric species of the enzyme. The rate of phosphorylation of the enzyme by diisopropylfluorophosphate was not affected by the antibody. On the other hand, inhibitors directed towards the anionic site(s) competed with antibody binding, suggesting that one of these is the epitope. The titration with antibody is biphasic and yields about 80% inhibition even in the presence of a large excess of antibody. Inhibition is fully reversible upon dilution, in a time-dependent manner. AE-2 also inhibited human adult and fetal brain acetylcholinesterase (to the same extent). However bovine brain acetylcholinesterase was inhibited to a lesser extent and rat brain acetylcholinesterase did not interact with the antibody. Butyrylcholinesterase (EC 3.1.1.8) also showed no reactivity towards the antibody.

Soluble form of acetylcholinesterase from rabbit enterocytes: comparison of its molecular properties with those of the plasma membrane species

A soluble form of acetylcholinesterase was shown to be present in rabbit enterocytes. The enzyme was obtained from a high-speed supernatant (105,000 X g centrifugation) after homogenization of intestinal mucosa without detergent. It was shown to possess no obvious hydrophobic character and could be classified as a low-salt-soluble (LSS) acetylcholinesterase. Sucrose gradient centrifugation revealed a single enzyme species with a sedimentation coefficient of 3.9 +/- 0.2S. By gel filtration performed in HPLC the enzyme was eluted as a protein corresponding to an Mr of 72,000 +/- 3,000. It could be precipitated with concanavalin A by affinoelectrophoresis, but the catalytic activity was not affected by the lectin. Our results are consistent with a G1 globular form for this soluble acetylcholinesterase which differs very clearly from detergent-soluble forms also found recently in the plasma membranes of rabbit enterocytes.

The use of mRNA translation in vitro and in ovo followed by crossed immunoelectrophoretic autoradiography to study the biosynthesis of human cholinesterases

The synthesis of various cholinesterases in different fetal human tissues was studied using in vitro and in ovo translation of poly(A)+ RNA, followed by crossed immunoelectrophoretic autoradiography. When unfractionated poly(A)+ mRNA from fetal brain, muscle, or liver was translated in vitro, in the reticulocyte lysate cell-free system, polypeptides were synthesized which reacted with antibodies against either "true" acetylcholinesterase (acetylcholine hydrolase; EC 3.1.1.7) or "pseudo", butyrylcholinesterase (acylcholine acylhydrolase; EC 3.1.1.8). The two nascent cholinesterases could be separated by crossed immunoelectrophoresis followed by autoradiography, suggesting that acetylcholinesterase and butyrylcholinesterase are produced in all three tissues from nascent polypeptides containing different immunological domains. To examine whether the biosynthesis of cholinesterases includes posttranslational processing events, Xenopus oocytes were microinjected with mRNA from these tissues. Immunoelectrophoretic analysis of oocyte intracellular homogenates and incubation medium revealed various precipitation arcs, reflecting the synthesis and posttranslational processing of multiple forms of tissue-specific exported and intracellular acetylcholinesterase and butyrylcholinesterase. These findings demonstrate that polymorphic cholinesterases are produced from nascent polypeptide products which undergo further posttranslational processing events in a tissue-specific manner before they become mature compartmentalized cholinesterases.

Immunochemical differences among molecular forms of acetylcholinesterase in brain and blood

Molecular forms of acetylcholinesterase (acetylcholine acetylhydrolase, EC 3.1.1.7) differ in their solubility properties as well as in the number of their catalytic subunits. We used monoclonal antibodies to investigate the structure of acetylcholinesterase forms in brain, erythrocytes and serum of rats, rabbits and other mammals. Two antibodies were found to bind tetrameric acetylcholinesterase in preference to the monomeric enzyme. These antibodies also displayed lower affinity for certain forms of 'soluble' brain acetylcholinesterase than for the 'membrane-associated' counterparts. Furthermore, one of them was virtually lacking in affinity for the membrane-associated enzyme of erythrocytes. The basis for the antibody specificity was not fully determined. However, the immunochemical results were supported by measurements of enzyme thermolability, which showed that the catalytic activity of 'soluble' acetylcholinesterase was comparatively heat-resistant. These observations point toward structural differences among the solubility classes of acetylcholinesterase.