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Host-derived metabolite trains the microbiota to develop colonization resistance.

To investigate whether taurine ameliorates mammary damage in a rat model of S. uberis mastitis by suppressing inflammation related to the toll-like receptors/nuclear factor kappa B (TLRs/NF-κB) signaling pathway. Starting on gestation day 14 and continuing until parturition, 100 mg/kg of taurine (group TS) or an equal volume of physiological saline (group CS) was administered daily to rats. Seventy-two hours after parturition, rats were infused with 100 cfu of S. uberis into each of 2 mammary glands. The resultant inflammation, evidenced by swelling, degeneration of secretory epithelium, increased tissue loss and neutrophil (PMN) infiltration was observed. Pretreatment with taurine attenuated inflammatory changes and significantly decreased mRNA expression of TLR-2 (8 h post S. uberis-injection, PI), NF-κB p65 (16 h and 24 h PI), and NF-κB DNA binding activity (16 h PI). Tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) levels were also decreased. Significant differences (P<0.05) were present at 24 h and 48 h PI for TNF-α and at 16 h PI for iNOS. TLR-4 mRNA expression was increased by taurine administration and significant differences were observed at 8h, 16 h and 24 h PI. These results suggest that the in vivo relationship of immunomodulatory reagents with TLRs is complex. Taurine may modulate inflammatory injury induced by S. uberis in mammary glands though TLR-2 and TLR-4. Suppression of inflammation may be related to TLRs/NF-κB and may be one mechanism of taurine action in controlling S. uberis mastitis., (Copyright © 2011 Elsevier B.V. All rights reserved.)

This review is an attempt to summarize our knowledge about taurine bromamine (TauBr) properties, its role in innate immunity and its therapeutic potential.TauBr and taurine chloramine (TauCl) are major haloamines generated by eosinophils and neutrophils at a site of inflammation. Both haloamines share anti-inflammatory and anti-oxidant properties. TauBr, similarly to TauCl, decreases the production of proinflammatory mediators. Their anti-inflammatory and anti-oxidant activities are enhanced by their ability to induce the expression of heme oxygenase-1 (HO-1). TauCl is more stable than TauBr. On the other hand, only TauBr was found to be highly membrane-permeable showing stronger microbicidal activity than TauCl.In the light of the anti-inflammatory and antimicrobial properties of TauBr we discuss its therapeutic potential in local treatment of inflammation, especially acne vulgaris, the most common inflammatory skin disorder. TauBr, at non-cytotoxic concentrations, is able to kill Propionibacterium acnes, the skin bacteria involved in pathogenesis of acne vulgaris.As topical antibiotics used in the therapy of acne are associated with the emergence of resistant bacteria, topical TauBr seems to be a good candidate for an alternative therapy.Recently, in a double blind trial, the efficacy of TauBr was compared with the efficacy of clindamycin, one of the most common topical antibiotics used in acne therapy. Comparable reduction of acne lesions was observed in the TauBr and clindamycin groups of patients with mild and moderate inflammatory facial acne vulgaris. We conclude that this pilot study supports our concept that TauBr can be used as a topical agent in the treatment of acne vulgaris, especially in patients who have already developed antibiotic resistance. Further studies are necessary to substantiate the more extended use of TauBr as an anti-inflammatory and anti-oxidant agent in human medicine.

Eradication of a urinary tract infection (UTI) appears to be related to a number of innate host defence mechanisms and their interactions with invading bacteria. Recurrent UTIs (rUTIs) pose a difficult problem in that these bacteria use both host and bacterial factors to evade elimination. Neutrophil bactericidal function is depressed, both systemically and in urine, in patients with a history of recurrent UTI. Taurine is a semi-essential amino acid and is successful in preserving neutrophil bactericidal function in urine. Taurine may preserve neutrophil function at the urothelium and thus aid UTI resolution. Adult female (6 weeks old) C57Bl/6 mice were randomised into three groups: a saline gavage only control group, a saline gavage + E. coli group, and a taurine gavage + E. coli group [21 g/70 kg taurine in 0.9% normal saline (N/S) for 5 days]. Whilst taurine gavage pre-treatment resulted in increased serum neutrophils respiratory burst activity, at the urothelial-endothelial interface it caused higher colony forming units in the urine and a higher incidence of E. coli invasion in the bladder wall with no evidence of increased bladder wall neutrophils infiltration on MPO assay of histological assessment. Histologically there was also evidence of reduced bladder inflammation and urothelial cell apoptosis. In conclusion, taurine effectively increases neutrophils activity but given its anti-inflammatory properties, at the expense of decreased urothelial-endothelial activation thus preventing clearance of active E. coli infection in the bladder. Despite the negative results, this study demonstrates the importance of modulating interactions at the urothelial interface.

Malignant tumor is one of the leading causes of death in the world. The efficacy of antitumor drugs is compromised due to their adverse effects such as damage to the bone marrow and immune system. Therefore, it is of significance to find ancillary drugs which cannot only enhance the therapeutic effects but also attenuate the adverse effects of antitumor drugs. This study aimed to investigate the enhancing effect of taurine on the function of leucocyte after chemotherapy of cyclophosphamide. Lewis lung carcinoma-bearing mice were given taurine combined with cyclophosphamide. Indexes including the tumor inhibition rate, the count of bone marrow nucleate cells, the count and classification of white blood cells, the spleen index, the thymus index, the lymphocyte proliferation and the phagocytic activity of peritoneal macrophage, peripheral blood neutrophilic granulocyte and monocyte were tested to analyze the effect of taurine on enhancing leucocyte function after cyclophosphamide chemotherapy. The tumor inhibition rates on Lewis lung carcinoma in taurine (40 mg/kg, 80 mg/kg, 160 mg/kg) combined with cyclophosphamide group were higher than that in the cyclophosphamide alone group. Compared with the cyclophosphamide group, the following indexes were found increased in the taurine (of all doses) plus cyclophosphamide groups: the count of bone marrow nucleate cells, the count and classification of white blood cells, the spleen index, the thymus index, the lymphocyte proliferation and the phagocytic activity of peritoneal macrophage, peripheral blood neutrophilic granulocyte and monocyte. In conclusion, taurine can enhance the function of the leucocyte after chemotherapy of cyclophosphamide.

Oxidative compounds that are physiologically generated in vivo can induce natural defense mechanisms to enhance the elimination of pathogens and to limit inflammatory tissue damage in the course of inflammation. Here, we have investigated WF10, a chlorite-based non-toxic compound for its functional activities on human PBMC in vitro. WF10 exerts potent immune-modulatory effects through generating endogenous oxidative compounds such as taurine chloramine. Proliferation and IL-2 production of anti-CD3 stimulated PBMC were inhibited by WF10, as was the nuclear translocation of the transcription factor NFATc. In PBMC and monocytes, however, WF10 induced pro-inflammatory cytokines like IL-1beta, IL-8, and TNF-alpha. In the monocytic cell line THP-1, the activation of the transcription factors AP-1 and NFkappaB by WF10 was demonstrated. Inhibition of NFAT regulated genes in activated lymphocytes in concert with the induction of several myeloid cell associated pro-inflammatory genes in monocytes represents a novel mechanism of immune modulation.

Nutrition and immunology are interrelated. Several nutrients like arginine, glutamine, omega-3-fatty acids and nucleotides enhance cellular immunity, modulate tumor cell metabolism and improve clinical outcome in stress situations. Glutamine supplementation has been shown to decrease incidence of sepsis and to reduce length of hospital stay in bone marrow transplant patients, low birth weight infants, surgical and multiple trauma patients. Studies with arginine have shown a reduction in infectious complications and lower mortality, however a better understanding of the biology of arginine is needed. Omega-3-fatty acid supplimentation as in fish oil stimulates the immune system. The beneficial effects of immunonutrition in surgical patients has been demonstrated in several studies. It significantly reduces infectious complications and length of hospital stay. In critically ill patients immunonutrition may decrease infectious complications but it is not associated with a mortality advantage. Pediatric experience is limited, but the future is promising.

Taurine chloramine (TauCl), a product of neutrophil myeloperoxidase - halide system, formed by a reaction of taurine with HOCl, is known as an anti-microbial and anti-inflammatory long-lived oxidant. We previously reported that TauCl inhibits in vitro the production of proinflammatory cytokines (IL-6, IL-8) by RA synoviocytes. Therefore we performed this study to investigate the effect of TauCl treatment on the development of collagen-induced arthritis (CIA) in DBA1/J mice. Early administration of TauCl (after primary immunization) resulted in the delay of the onset of CIA, but had no effect on severity of arthritis. TauCl, given daily for 21 days after booster immunization, did not reduce the symptoms of arthritis in those mice, which already developed CIA, but significantly diminished incidence of the disease (55% vs. 90% of placebo mice). The mechanism of this effect is unknown. This is the first in vivo study suggesting that TauCl may be used for immune intervention in chronic inflammatory diseases.

The distribution of taurine in the frog olfactory bulb was studied using light and electron microscopic immunohistochemical techniques. At the light microscopic level, taurine-like immunoreactivity (taurine-LI) was found in (i) fibers coursing from the olfactory nerve layer to the glomerular layer, (ii) cell bodies and processes primarily located in the caudal part of the granule cell layer (GCL), and (iii) puncta outlining unstained somata of mitral cells and cells in the GCL. In consecutive sections processed for taurine or GABA, numerous cells of the caudal GCL displayed taurine-LI and GABA-like immunoreactivity (GABA-LI). A bimodal distribution of the cross-sectional cell area for GABA-LI cells implied their morphological diversity, and the peak for larger GABA-LI cells coincided with the maximum for taurine-LI cells. At the electron microscopic level, single immunogold labeling showed that GABA-LI, but not taurine-LI, is present in granule cells, whereas both taurine-LI and GABA-LI were localized in a 'non-granule' type of cell. The double labeling procedure demonstrated coexistence of taurine-LI and GABA-LI in neurons of a 'non-granule' type. These cells had some ultrastructural features typical of short axon cells in the GCL of the mammalian olfactory bulb and were tentatively considered as short axon-like cells. Results suggest that, in the frog olfactory bulb, taurine is contained in primary olfactory afferents and short axon-like cells of the GCL co-localizing GABA and taurine.

HPLC analysis of the amino acid contents of the second- and third-order giant fibres at the giant synapse in the stellate ganglion of the squid Loligo vulgaris shows that there are significantly higher amounts of L-glutamate and L-aspartate in the second-order (presynaptic) fibre than in the third-order (postsynaptic) fibre. Immunocytochemical staining of sections of the ganglion with an antibody raised against L-glutamate produces specific positive staining in the synaptic region of the second-order fibre. In contrast, staining with antibodies raised against glutamate-receptors (mammalian GluR1 with GluR2/3) produces positive staining in the third-order fibre at the postsynaptic region. These data provide further evidence for the hypothesis that L-glutamate is an excitatory transmitter at the giant synapse.

We have previously shown that oral immunization with non-replicating antigens hardly induced serum IgG antibody response in chickens and addition of sodium fluoride (NaF) to the immunogen markedly improved their immunological states. In the present study, taurine, lithium and Quillaja saponin (Q-SAP) were compared with NaF with respect to their enhancement of serum IgG antibody response in chickens after oral immunization. The antibody titer of chickens which received Q-SAP as the mucosal adjuvant tended to be higher than that of chickens which received antigen plus NaF. Simultaneous administration of antigen with lithium or taurine elicited a higher antibody titer in chickens compared to those of chickens orally immunized with antigen alone, but the effect of these two adjuvants was less efficient compared with that of NaF. These results suggested that Q-SAP as well as NaF is useful as an oral adjuvant for chickens.

The localization of taurine was investigated in several tissues of the mouse. Immunohistochemical methods using a polyclonal antibody for taurine derived from rabbits was used in these studies. This method was used since it is a simple procedure and the results are clear and reliable. Tissues were fixed with paraformaldehyde, embedded in paraffin and treated in a microwave oven before using an avidin-biotin-complex method (ABC method). Control staining was accomplished by employing absorption staining using various amino acids: taurine, arginine, cysteine, hypotaurine and others. For purposes of comparison, radioautography (RAG) with 3H-taurine was performed to confirm the reliability of the immunohistochemical staining compared with the localization of the 3H-taurine incorporation in endothelial cells of the blood vessels of several tissues. In this investigation, immunoreactivity was broadly observed in many tissues: Purkinje cells of the cerebellum, glia cells of brain tissue, cardiac muscle cells, matrices of the bone, mucus granules of goblet cells of the intestines, and brown adipose cells of the fetus. Although the meaning of this widespread localization of taurine can not be explained completely, we surmise that taurine may have a different function in each of the tissues. In addition, taurine reactivity was observed in cell nuclei which was evidence of the presence of taurine in the nuclei.

Taurine is the second most abundant free amino acid in the brain where its osmoregulatory function is well established. Taurine-deprived kittens show retinal pathology leading to blindness. In the inner ear, taurine has been reported to be the most abundant free amino acid although its role in inner ear function is not known. Immunohistochemistry was employed here to investigate the localisation of taurine in normal cochleae of the guinea pig compared with two different conditions: experimentally induced endolymphatic hydrops and after oral administration of glycerol. In normal cochleae, by light microscopy, taurine-like immunoreaction was never observed in the sensory outer hair cells and appeared absent from the inner hair cells. In contrast taurine-like immunolabeling was found to be present in all supporting tissue with the striking exception of the tectorial membrane and the outer pillar cell which had no or little taurine immunoreactivity respectively. In early experimental endolymphatic hydrops, the distribution of taurine-like immunoreactivity appeared similar to that observed for normal cochleae. In long-term hydrops, degenerated outer hair cells were replaced by the swelling of the phalangeal process of the Deiters' cells which became highly immunoreactive to taurine. After glycerol administration, the tectorial membrane became more tightly bound to the apical surface of the sensory hair cells and distinctly immunoreactive to taurine. The localisation of taurine in the organ of Corti shown here is consistent with taurine being involved in the maintenance of osmotic equilibrium in the normal and perhaps also in the restructuration of the pathological organ of Corti.

We used post-embedding immunocytochemistry to determine the cellular localization of glutamate, gamma-amino butyric acid (GABA), glycine, aspartate, glutamine, arginine, and taurine in the normal and degenerating rat retina. Müller's cell function was also evaluated by determining the uptake and degradation characteristics for glutamate. Immunocytochemical localization of amino acids in adult Royal College of Surgeons (RCS) and control rat retinas were similar with respect to cell classes. Differences in the intensity of labelling for glutamate, aspartate, glutamine, and glycine were observed in several classes of neurons, but the most prominent differences were shown by bipolar cells of the adult RCS rat retina. In addition, glutamine labelling within Müller's cells was higher in the RCS rat than the control. These changes may have occurred because of alterations in the glutamate production or degradation pathways. We tested this hypothesis by determining Müller's cells glutamate uptake and degradation characteristics in adult and postnatal day 16 RCS retinas. High affinity uptake of 3[H]-glutamate revealed an accumulation of grains over Müller's cell bodies in the adult RCS retina implying glutamate degradation anomalies. We confirmed anomalies in glutamate metabolism in RCS Müller's cells by showing that exogenously applied glutamate was degraded over a longer time course in postnatal day 16 RCS retinas, compared to control retinas. Differences in arginine immunoreactivity in adult and immature RCS retinas conform to the presumed dysfunction of Müller's cells in these degenerating retinas. The anomalies of amino acid localization, uptake and degradation lead us to conclude that Müller's cells in the RCS retina show abnormal function by postnatal day 16; an earlier time to previously reported anatomical and functional changes in this animal model of retinal degeneration.

Taurine, 2-aminoethanesulfonic acid, is one of the most abundant amino acid present in the Central Nervous System. Nevertheless, its functions are remain uncertain. Taking as a basis the immunocytochemical pre-embedding PAP-techniques for demonstrating Taurine-Like substances on cerebellar cortex of rats we have observed positive immunoreaction within Purkinje cell bodies and their dendrites. Likewise, taurine has been demonstrated within mossy fibers and Golgi axons, as well as in glial processes. Our results demonstrate the wide distribution of Taurine in the cerebellar cortex, justifying its possible involvement as an inhibitory neurotransmitter, neuromodulator or as a gliotransmitter.

Taurine (2-aminoethanesulphonic acid) is reported to interact with the octopaminergic system. The distribution of taurine-like immunoreactivity (-LIR) in relation to octopamine-like immunoreactive dorsal unpaired median (DUM) neurones was investigated with the aim of revealing possible colocalization of these two neuromediators. The specificity of the anti-taurine serum used was demonstrated by dot blot immunoassay and by use of preabsorption controls. There was no crossreactivity with octopamine. The specificity of the octopamine antiserum employed has been described elsewhere. Taurine-LIR could be demonstrated in large dorso-median cells in the suboesophageal and the mesothoracic ganglion as well as in the abdominal ganglia. In addition taurine-LIR is distributed in numerous other regions of the ganglia. A comparison of the immunostaining for taurine and octopamine indicates that several of the taurine-like immunoreactive (-LI) neurones are probably members of the octopamine-immunoreactive DUM cell population. These taurine-LI neurones resemble octopamine-LI DUM cells in soma position and size as well as in the projections of their primary neurites. Colocalization of octopamine-LIR and taurine-LIR within the same neuronal element could be shown by alternate immunostaining of consecutive sections. It is probable that all octopamine-LI DUM neurones also exhibit taurine-LIR, and the possible physiological significance of this coexistence is discussed.

The localization of taurine, GABA and glutamate in developing feline cerebellum was performed using antibodies raised against the amino acids conjugated to bovine serum albumin with glutaraldehyde. Distinct patterns of immunostaining were observed for each of the amino acids. Taurine-like immunoreactivity reached a peak at 4 weeks after birth, as did GABA-like immunoreactivity, whereas glutamate-like immunoreactivity was greatest in the mature cerebellum. Purkinje cells are all taurine-positive in cerebellum from neonatal animals, whereas in the mature cerebellum they appear to contain only GABA and glutamate, with virtually no taurine, in contrast to observations reported with rodent cerebellum. Ultrastructural studies and immunogold labelling visualized by electron microscopy show that the band of taurine-like immunoreactivity observed in newborn feline cerebellum is localized within dendrites, axons and glial processes. Granule cells migrating through this region also show prominent taurine-like immunoreactivity.

The ontogenic pattern of development of taurine-like immunoreactivity (TLI) was studied in the mouse liver. The effect on adult mice of carbon tetrachloride or phenobarbital treatment was also examined. Light-microscopically, granules of TLI were first found in the liver from 17-day-old embryos, diffusely distributed throughout the lobules. These positive granules increased with age, were most numerous in the two-week-old mouse, and were notably decreased in the central region of some lobules in the three-week-old mouse. In mature mice, hepatocytes containing TLI-positive granules were distributed unevenly in each liver lobule, and were located predominantly in the peripheral region. Electron-microscopically, TLI was observed in small vesicles in the cytoplasm of hepatocytes and was found mainly in the cisternal lumen of smooth-surfaced endoplasmic reticulum. Some taurine-positive vesicles surrounding the reticulum seemed to associate with the protoplasm. Similar positive vesicles were often located near the bile canaliculi. In carbon tetrachloride-intoxicated mature mice, TLI was no longer limited to the peripheral region of lobules; hepatocytes situated in the central region of lobules also contained intense TLI. In mice injected with a small and repeated dose of phenobarbital, the distribution pattern of TLI was similar to that in the untreated group. However, in mice injected with a large dose of phenobarbital, TLI was markedly increased, especially in the central region of lobules. The results demonstrate that the distribution pattern of TLI in mouse liver changes during development, and that the pattern in mature mice is affected by intoxication with carbon tetrachloride or a toxic dose of phenobarbital.

The production, specificity and application of an antiserum against taurine conjugated to succinylated ovalbumin by means of 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide is reported. The antiserum was produced in rabbits. The carbodiimide was used also as a tissue fixative. The development of the antibody titre was followed by dot-blot tests on nitrocellulose filters using different amino acid conjugates and with immunohistochemical reaction in the rat and insect brain. Blocking controls were also used. Taurine antiserum, sufficiently specific and sensitive, developed after the fourth booster injection, after which the antiserum was characterized. In the insect brain, intense taurine-like immunoreactivity was observed in the photoreceptors, in the Kenyon cells and the neuropile of the mushroom bodies, in the lower part of the central body and in the antennal lobes. In the rat carebellum, intense taurine-like immunoreactivity was seen in the Purkinje cells. Immunoreaction was seen also in small cells most probably corresponding to the basket cells. The use of the carbodiimide in the production of antisera against taurine provides a parallel method for comparison of the distribution of taurine-like immunoreactivity obtained with antisera made against conjugates prepared with aldehydes.

Using an antibody prepared against taurine conjugated to bovine serum albumin with glutaraldehyde, the distribution of taurine in cerebellum of newborn and 8-week-old kittens from mothers fed 0, 0.02, 0.05, or 1% dietary taurine has been determined. In general, taurine-like immunoreactivity was greater in kittens from mothers fed the greatest amounts of taurine, as was the total cerebellar taurine concentration. The most notable feature in newborn kitten cerebellum was a dense band of staining in the inner molecular layer adjacent to the Purkinje cell layer, which corresponds to the short Purkinje cell dendrites. In cerebellum of 8-week-old kittens, taurine-like immunoreactivity was present in Purkinje cells and their dendrites, most granule cells, and a few interneurons in the molecular layer of the 0.02, 0.05, and 1% groups. The cerebellum of the 0% group was distinctive in that virtually no neurons were reactive, appearing as 'ghosts' against the background, and both white matter and the granule cell layer contained large numbers of reactive astrocytes. The presence of such large numbers of reactive astrocytes and the immunoglobulin within the brain suggests an impairment of the blood-brain barrier in such taurine-deficient kittens.

A plasma-derived HBV vaccine was administered to 86 healthy men ranging in age from 40-56 years. A relatively high rate of nonresponders was found among the men who received the HBV vaccine alone. There was a significantly higher HBs antibody response rate among the vaccinees who received an oral adjuvant (taurine) compared to those not receiving the adjuvant. In the vaccinees who received the oral adjuvant, an in vitro polyclonal antibody response to taurine was detected in 17 (58.6%) of the 29 HBs responders, but in none of the HBs nonresponders. The development of oral adjuvants other than aluminum may be a valuable approach to the study of HBV vaccination.

The ultrastructural localization of putative excitatory (glutamate, aspartate) and inhibitory (taurine, glycine) amino acid neurotransmitters is described in several selected rat brain regions. In general, axon terminal profiles immunoreactive for excitatory amino acids formed asymmetric synapses with non-immunoreactive small diameter dendritic profiles or dendritic spines. In the cerebellum, both mossy fiber terminals and parallel fiber terminals were immunoreactive for glutamate and aspartate. In the hippocampus, mossy fiber terminals within the stratum lucidum of the CA3 region were immunoreactive for glutamate. Localization of glutamate and aspartate to cerebellar parallel and mossy fibers, as well as the identification of glutamate in hippocampal mossy fibers, is consistent with the excitatory nature of these fibers as described in previous physiological studies. Glutamate-like immunoreactive terminals were also identified in subnucleus caudalis of the spinal trigeminal nucleus and in the dorsal horn of the spinal cord. Immunoreactive axon terminals for two putative inhibitory neurotransmitters, glycine and taurine, displayed a greater number of morphological variations in synaptic structure. In the cerebellum, taurine-like immunoreactivity was present in both basket cell axon terminals which formed symmetric synapses with Purkinje cell neurons, and in a few mossy fiber terminals which formed asymmetric synapses with dendritic spines. In the area dentata of the hippocampus, taurine-like immunoreactive profiles formed asymmetric synapses with dendritic elements. Glycine-like immunoreactive terminals formed symmetric synapses with cell perikarya in both the ventral horn of the spinal cord and in the cochlear nuclei, and on axon terminals in the spinal trigeminal and cochlear nuclei. In contrast, some glycine-like immunoreactive terminals formed asymmetric synapses with distal dendritic profiles in the spinal cord and spinal trigeminal nucleus. The localization of taurine to cerebellar basket cell axons and glycine to axon terminals that synapse on ventral horn motor neuron perikarya is consistent with the hypothesis that these amino acids are functioning as inhibitory neurotransmitters at these synapses. Taurine localization to cerebellar mossy fibers and to fibers in the molecular layer of the dentate gyrus may be more consistent with a proposed neuromodulator role of taurine.

This paper describes the first demonstration of taurine-like immunoreactivity in the mammalian retina using an antiserum raised in rabbits. In rat, cat and guinea pig retina a peroxidase-antiperoxidase immunocytochemical technique showed high levels of taurine immunostaining in photoreceptor inner segments and synaptic terminals, in subpopulations of amacrine and bipolar somata and their synaptic processes in the inner plexiform layer, including numerous large terminals near and on ganglion cell somata. Using the Protein A-gold technique for ultrastructural studies in the rat, the presence of synaptic ribbons confirmed that some of these taurine-containing terminals were from bipolar cells. Lower levels of immunostaining were seen in the pigment epithelium and distal parts of glial cells.

Hepatitis B (HB) vaccine is very promising for the prevention of HB infection. There exist, however, some non-responders to current vaccination trials. In this study, taurine, parotin and lithium were selected as adjuvants which can be administered orally. The mechanisms of these three materials as adjuvants and their effects on HB vaccine were investigated in mice. For instance, taurine induced polyclonal antibody production and exhibited adjuvant activity. Although taurine did not have any activity on the proliferation of thymocytes nor stimulate IL-2 production, taurine did induce IL-1 production by macrophages. It was considered that taurine-induced IL-1 would play an essential role in the proliferation and differentiation of B cells. Parotin also induced polyclonal antibody production and exhibited adjuvant activity. These effects of parotin were not affected even if macrophages or T cells were depleted, and parotin itself had an IL-1-like activity. Therefore, it was considered that parotin acted directly on B cells by its IL-1-like activity and mitogenic activity, resulting in the proliferation and differentiation of B cells. Lithium induced neither polyclonal antibody production, nor IL-1 or IL-2 production. However, when given with an antigen, lithium activated the humoral immune system, resulting in the augmentation of antibody production. Oral administration of taurine, parotin and lithium were capable of restoring antibody responses to HB surface antigen (HBsAg) in HBsAg-nonresponder mice. Furthermore, taurine, parotin and lithium enhanced the adjuvant effects of aluminium contained in the present HB vaccine. These observations indicate that use of these oral adjuvants may open new perspectives in the field of human HB vaccination.

An antiserum against taurine was generated in rabbits by immunization with taurine that was conjugated to carrier protein via glutaraldehyde. When the antiserum was applied to immunohistochemistry, structures with taurine-like immunoreactivity were observed in both neuronal and glial components of rat brain. The specificity of the serum was quantitatively examined using an enzyme-linked immunoassay method, which has been newly developed for detecting such small molecules as amino acids. The best serum obtained had a high titer against taurine. It showed low cross-reactivity with taurine metabolites and with other amino acids (less than 0.5%), while considerably higher reactivities were noted in the case of taurine-containing peptides such as gamma-glutamyl-taurine and glycyl-taurine. The results indicate that much care should be taken with taurine peptides in the evaluation of immunohistochemical results using taurine antiserum.

An antiserum raised against taurine conjugated to bovine serum albumin by glutaraldehyde produced intense staining of hippocampal pyramidal neurons at the CA1/CA3 transition (including CA2) and of a small proportion of the granule cells. Strongly immunoreactive neurons were also found in a zone overlapping the second reflected blade in the hilus. Most glial cells were unlabeled.

Taurine (2-aminoethanesulfonic acid) is one of the most abundant free amino acids in the insect central nervous system. We have investigated the distribution of taurine-like immunoreactivity in the brain of the honeybee with an antiserum recognizing fixed taurine. Taurine-like immunoreactivity appeared within neuronal perikarya, neurites, and terminals, whereas glial cells were unlabelled. All photoreceptor cells of the compound eyes and the ocelli were stained. So were the fibers of the anterior superior optic tract, which connects the optic lobes to the mushroom bodies in the median protocerebrum. In the mushroom bodies the majority of intrinsic Kenyon cells showed high levels of taurine-like immunoreactivity. The lateral antennoglomerular tract, which interconnects the mushroom bodies with the antennal lobes, was also intensely stained. In the antennal lobes, strong labelling was observed within a few fibers that invade a set of posterior glomeruli from the posterior margin. Sensory projections from the antennal nerve into the antennal lobes showed only intermediate levels of staining. Sensory projections into the dorsal lobe were devoid of taurine-like immunoreactivity. Labral, mandibular, maxillary, and labial nerves, which innervate the various parts of the feeding apparatus, contain a set of five to eight heavily stained fibers. A comparison of taurine-like immunoreactivity with glutamate- and GABA-like immunoreactivities in the brain of the honeybee indicates that the three amino acids are enriched in distinct neuronal populations.

Two monoclonal antibodies against fixative-modified taurine, Tau1 and Tau2, were produced, characterized, and used in the present study to analyze the distribution of taurine in the cerebellum of the rat. In addition, immunohistochemical colocalization experiments were performed to determine whether cerebellar neurons contain both taurine and its synthesizing enzyme, cysteine sulfinic acid decarboxylase (CSADC). In ELISAs, both Tau1 and Tau2 displayed high affinities for taurine conjugated to various carrier proteins and possessed some cross-reactivity for other amino acids which are present in lower concentrations in the brain than taurine. Tau2 was found to recognize only taurine and hypotaurine when paraformaldehyde was used to fix the amino acids to carrier proteins. With the use of glutaraldehyde fixation, Tau1 cross-reacted with conjugates of beta-alanine and hypotaurine and Tau2 cross-reacted strongly with conjugates of cysteic acid and hypotaurine and weakly with cysteine sulfinic acid. Despite different cross-reactivities, Tau1 and Tau2 exhibited almost identical patterns of neuronal staining in bands of Purkinje cells in the cerebellum. Staining of Purkinje cell dendrites was more prominent than staining of the soma. Light immunoreactivity was present in Golgi, stellate, and basket cells. A scattered population of granule cells displayed taurine-like immunoreactivity at the electron microscopic level. Immunostaining was identified in some terminals in the Purkinje cell layer and in a limited number of mossy fibers. Tau2-like immunoreactivity was colocalized with CSADC-like immunoreactivity in the cerebellar neurons described above. These immunoreactive cells may represent a subpopulation of neurons that contain a higher concentration of taurine than neighboring cells due to their ability to synthesize taurine. The intense immunoreactive staining of Purkinje cell dendrites provides support for the hypothesis that calcium-dependent release of taurine in the cerebellum may originate primarily from dendritic rather than synaptic processes and suggests a neuromodulator role for taurine in the cerebellum.

An immunological approach to the detection of taurine resulted in antibodies specific enough to be used for immunocytochemical studies. The experimental conditions were similar to those previously described for raising antibodies against some small-sized neurotransmitter molecules: antisera were obtained from rabbits immunized with taurine conjugated to carrier proteins via glutaraldehyde and purified by adsorption on the glutaraldehyde-treated protein carriers. Antibody affinity and specificity were determined in competition experiments between conjugated taurine and other conjugated amino acids or derivatives by enzyme-linked immunosorbent assay. The resulting cross-reactivity ratios, calculated at half-displacement, showed conjugated taurine to be the best recognized compound. Given the molecular structure of taurine and the method used to prepare the conjugate, it seemed necessary to perform an oxidation step. However, adsorption of antisera on reoxidized or nonreoxidized taurine conjugates suggested that reoxidation did not make a significant difference. Immunocytochemical application of the sera revealed populations of strongly immunopositive nerve cells in the cerebellum, striatum, and septum. The results confirmed that antitaurine antibodies can be used as specific tools for a better understanding of the role of taurine in the central nervous system.

Amino acid immunocytochemistry represents a new and powerful tool in neuroscience. Antisera are now available to a large number of amino acids, including those that are thought to serve a transmitter role. The antiserum described here against conjugated taurine seems to be of good specificity and can be used to demonstrate taurine in the CNS as well as in other organs; in normal tissue and in experimental and pathological conditions.