Distribution of taurine-like immunoreactivity in cerebellum of kittens from taurine-supplemented and taurine-deficient mothers

Taurine Partially Improves Abnormal Anxiety in Taurine-Deficient Mice

Taurine is abundant in various tissues including the brain, muscle, heart, spleen, liver and kidney with various physiological functions. Since taurine is produced by cysteine sulfinic acid decarboxylase (CSAD) in the liver and kidney, taurine-deficient mice without CSAD have been investigated for abnormal physiological functions such as retinal development, immune, pancreatic and liver function. In this study, the behavioral effects and abnormal brain development caused by low taurine in the developing brain were examined. In neonatal brains of homozygous CSAD knockout mice (HO), taurine was reduced by 85%, compared to wild-type mice (WT). Taurine was reduced by 35% in the brains of 2 month-old HO, compared to WT. Anxiety, motor coordination and autistic-like behaviors were evaluated at 2 months of age using five behavioral tests: elevated plus maze, open field, social approach, marble burying and accelerating rotarod. Mice were tested from 3 groups including WT, HO and HO with oral treatment of 0.2% taurine in the drinking water (HOT). HOT were born from HO dams treated with taurine from before pregnancy and were continuously treated with taurine in the drinking water after weaning. The taurine levels in the brain and plasma of HOT were restored to WT at 2 months of age. Taurine-deficiency did not lead to changes in autistic-like behaviors as the HO were not significantly different from WT in marble burying and social approach. However, taurine-deficiency increased anxiety-like behavior in HO in the elevated plus maze and open field, compared to WT. Taurine treatment significantly restored the HOT to WT levels of anxiety-like behavior in the elevated plus maze. However, changes in exploratory activity in the open field were not improved with taurine treatment. There was a slight difference in motor ability as the WT mice stayed on the accelerating rotarod longer that the HO and HOT, but the difference was significant in the HOT during the first trial only, compared to WT.These data support hypothesis that taurine is essential for the emotional development of the brain. First, taurine is remarkably low in the neonatal brain of HO, compared to the adult brain of HO. Second, taurine treatment in HO partially improves anxiety-like behavior to WT.

Development of a novel cysteine sulfinic Acid decarboxylase knockout mouse: dietary taurine reduces neonatal mortality

We engineered a CSAD KO mouse to investigate the physiological roles of taurine. The disruption of the CSAD gene was verified by Southern, Northern, and Western blotting. HPLC indicated an 83% decrease of taurine concentration in the plasma of CSAD^−/−. Although CSAD^−/− generation (G)1 and G2 survived, offspring from G2 CSAD^−/− had low brain and liver taurine concentrations and most died within 24 hrs of birth. Taurine concentrations in G3 CSAD^−/− born from G2 CSAD^−/− treated with taurine in the drinking water were restored and survival rates of G3 CSAD^−/− increased from 15% to 92%. The mRNA expression of CDO, ADO, and TauT was not different in CSAD^−/− compared to WT and CSAD mRNA was not expressed in CSAD^−/−. Expression of Gpx 1 and 3 was increased significantly in CSAD^−/− and restored to normal levels with taurine supplementation. Lactoferrin and the prolactin receptor were significantly decreased in CSAD^−/−. The prolactin receptor was restored with taurine supplementation. These data indicated that CSAD KO is a good model for studying the effects of taurine deficiency and its treatment with taurine supplementation.

Is Taurine A Biomarker?

Taurine, a sulfur-containing amino acid present in high concentrations in mammals, plays an important role in several essential biological processes. Taurine is not incorporated into protein and is the most abundant free amino acid in the heart, retina, skeletal muscle, brain, and leukocytes. The ideal biomarker or biological measure should be reliable, reproducible, noninvasive, simple to perform, and inexpensive. Samples for biological measures should be easily obtained from physiological fluids such as blood or urine. Taurine levels in physiologic fluids have been useful for both diagnosing pathology and establishing a disease modifying therapy. In the specific case of taurine, it is important that patient information include nutritional supplementation as well as information on disease status and medications. Taurine has been measured in biological fluids due to the importance of this simple amino acid and its relative ease of determination. Taurine has been measured in animal models of disease as well as a variety of human conditions. However, it remains unclear how taurine should be used as a biomarker and in which situations this measurement would be a good prognostic or diagnostic indicator.

Nonsynaptic glycine receptor activation during early neocortical development

Glycine receptors (GlyRs) contribute to fast inhibitory synaptic transmission in the brain stem and spinal cord. GlyR subunits are expressed in the developing neocortex, but a neurotransmitter system involving cortical GlyRs has yet to be demonstrated. Here, we show that GlyRs in immature neocortex are excitatory and activated by a nonsynaptically released endogenous ligand. Of the potential ligands for cortical GlyRs, taurine is by far the most abundant in the developing neocortex. We found that taurine is stored in immature cortical neurons and that manipulations known to elevate extracellular taurine cause GlyR activation. These data indicate that nonsynaptically released taurine activates GlyRs during neocortical development. As fetal taurine deprivation can cause cortical dysgenesis, it is possible that taurine influences neocortical development by activating GlyRs.

Dietary beta-alanine results in taurine depletion and cerebellar damage in adult cats

We have used the taurine analogue, beta-alanine, to perturb the taurine concentrations in taurine-supplemented and taurine-deprived adult cats. By using 5% beta-alanine in the drinking water for 20 weeks, both groups of cats had greatly reduced brain taurine concentrations. Taurine-supplemented cat brain accumulated relatively small amounts of beta-alanine whereas taurine-deprived cats accumulated large amounts of beta-alanine. The cerebellum of cats treated with beta-alanine had a number of pathological changes compared with similar cats drinking water alone. The changes were more severe in the taurine-deprived cats, and included reduced numbers of granule and Purkinje cells, with many of those remaining appearing pyknotic and dying. Long swollen fibers were seen in the white matter, resembling Rosenthal fibers described in some human cerebellar diseases. There was also prominent gliosis. Using antibodies to beta-alanine and taurine, beta-alanine was localized in Purkinje cell soma and dendrites, in Golgi II cells, and in some granule cells, especially in taurine-deprived cats treated with beta-alanine. Taurine appears to have been virtually eliminated from Purkinje and granule cells, and concentrated in Golgi II cells and glia. We conclude that beta-alanine is responsible for these neurotoxic pathological changes.

Distributions of taurine, glutamate, and glutamate receptors during post-natal development and plasticity in the rat brain

In summary, taurine and glutamate distributions seemed to be related spatio-temporally during development in the hippocampus and cerebellum and during plasticity of the adult dentate gyrus. In some cases, the amino acids appeared to be setting up adult localizations, while others involved a change in distribution from early development to adulthood that may indicate a related role for taurine and glutamate in dendritic outgrowth and synapse formation. Further elucidation of the subcellular localizations should provide some insight into the functions of taurine and glutamate during these critical periods in development. In addition, there appeared to be developmental patterns of decreased density of kainate and Met2 glutamate receptors that may be worth exploring in terms of interrelationships with taurine.

Altered GABA distribution in hamster brain is an early molecular consequence of infection by scrapie prions

Antibodies specific for GABA, glutamate and taurine were used to study the distribution of these amino acid neurotransmitters during the progression of scrapie in hamsters. Immunohistochemical distribution of glutamate and taurine were unaffected in scrapie hamsters compared with controls, but the distribution of GABA was altered by 21 days after inoculation. We found both a greater number of neurons showing GABA-like immunoreactivity and more intense staining in those neurons in scrapie-inoculated hamster brains, particularly in the hippocampus, inferior colliculus, frontal cortex and cerebellum. The overall concentrations of aspartate, GABA, glutamate and taurine, measured in seven different brain regions by PITC-amino acid analysis, were not significantly different between normal and scrapie-affected hamsters. The subtle alteration in GABA metabolism detected in this scrapie model suggests that PrPSc interacts directly with a component of the GABA system.

Changes in the localization of taurine-like immunoreactivity during development and regeneration in the rat brain

In summary, taurine appeared to be present in certain cell types, such as cerebellar Purkinje cells and hippocampal pyramidal cells, throughout development to adulthood and a differential function for taurine between these periods would be difficult to hypothesize simply based on localization. However, in both the cerebellum and hippocampus, there was a period including post-natal day 7 in the cerebellum and including both post-natal days 7 and 14 in the hippocampus in which taurine appeared not to be confined only to the dendrites of the aforementioned cells, but seemed ubiquitously present in the molecular layers of these two brain regions. This suggests that the taurine may be present in significantly higher concentrations in certain cell types or subcellular structures during development than in the adult rat brain. The elucidation of these taurine-containing structures with the use of electron microscopy may provide some insight into the functions of taurine during these critical periods in development. Finally, taurine appeared to reverse its developmental decline in concentration in the presence of regeneration, suggesting that it may play a role in axonal sprouting and/or synapse formation.

Visualization of taurine, GABA and glutamate in developing feline cerebellum by immunohistochemistry

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.

Taurine in toad brain and blood under different conditions of osmolality: an immunohistochemical study

The concentrations of taurine in blood and brain regions of the toad Bufo boreas have been measured. Most of these values are considerably lower than those found in mammals. Using an antibody prepared against conjugated taurine, the distribution of taurine in three brain regions of the toad has been visualized. The possible osmoregulatory functions of taurine have been investigated by making toads hyper- or hypo-osmotic in vivo. Induction of hypoosmolality is accompanied by a massive taurine tide in blood plasma, but has no immediate effects upon the taurine concentrations in the brain areas studied. However, histochemical visualization indicates a marked redistribution of taurine between cellular components and extracellular space of brain tissues. This may indicate that taurine has an osmoregulatory function in brain tissue under hypo-osmotic conditions. Hyperosmolality results in no elevation of the taurine concentration in blood plasma of toads, but rather in a very gradual decline of total plasma taurine content over a prolonged time period. Histochemical studies reveal little change in frontal cortex after 1 hour but deeper staining of many neurons in optic lobe accompanied by greater staining in the extracellular fluid. By 3 hours there is a depletion of taurine from all compartments of cerebral cortex tissues. No evidence of any prolonged direct osmoregulatory role for taurine is indicated under hyperosmotic conditions. A possible indirect osmoregulatory function of taurine is discussed.