Taurine protects against carbon tetrachloride toxicity in the cultured neurons and in vivo

The Impact of Taurine on Obesity-Induced Diabetes Mellitus: Mechanisms Underlying Its Effect

This review explores the potential benefits of taurine in ameliorating the metabolic disorders of obesity and type 2 diabetes (T2D), highlighting the factors that bridge these associations. Relevant articles and studies were reviewed to conduct a comprehensive analysis of the relationship between obesity and the development of T2D and the effect of taurine on those conditions. The loss of normal β-cell function and development of T2D are associated with obesity-derived insulin resistance. The occurrence of diabetes has been linked to the low bioavailability of taurine, which plays critical roles in normal β-cell function, anti-oxidation, and anti-inflammation. The relationships among obesity, insulin resistance, β-cell dysfunction, and T2D are complex and intertwined. Taurine may play a role in ameliorating these metabolic disorders through different pathways, but further research is needed to fully understand its effects and potential as a therapeutic intervention.

Versatile Triad Alliance: Bile Acid, Taurine and Microbiota

Taurine is the most abundant free amino acid in the body, and is mainly derived from the diet, but can also be produced endogenously from cysteine. It plays multiple essential roles in the body, including development, energy production, osmoregulation, prevention of oxidative stress, and inflammation. Taurine is also crucial as a molecule used to conjugate bile acids (BAs). In the gastrointestinal tract, BAs deconjugation by enteric bacteria results in high levels of unconjugated BAs and free taurine. Depending on conjugation status and other bacterial modifications, BAs constitute a pool of related but highly diverse molecules, each with different properties concerning solubility and toxicity, capacity to activate or inhibit receptors of BAs, and direct and indirect impact on microbiota and the host, whereas free taurine has a largely protective impact on the host, serves as a source of energy for microbiota, regulates bacterial colonization and defends from pathogens. Several remarkable examples of the interaction between taurine and gut microbiota have recently been described. This review will introduce the necessary background information and lay out the latest discoveries in the interaction of the co-reliant triad of BAs, taurine, and microbiota.

Er-Chen Decoction Alleviates High-Fat Diet-Induced Nonalcoholic Fatty Liver Disease in Rats through Remodeling Gut Microbiota and Regulating the Serum Metabolism

Many studies have found that the dysfunction in gut microbiota and the metabolic dysfunction can promote nonalcoholic fatty liver disease (NAFLD) development. Er-Chen decoction (EC) can be used in the treatment of NAFLD. However, the mechanism of this hepatoprotection is still unknown. In this study, we constructed a rat model with NAFLD fed with high-fat chow and administered EC treatment. The therapeutic effects of EC on NAFLD were evaluated by measuring transaminases, blood lipid levels, and pathological changes in the liver. In addition, we measured the effects of EC on liver inflammatory response and oxidative stress. The changes in gut microbiota after EC treatment were studied using 16S rRNA sequencing. Serum untargeted metabolomics analysis was also used to study the metabolic regulatory mechanisms of EC on NAFLD. The results showed that EC decreased the serum transaminases and lipid levels and improved the pathological changes in NAFLD rats. Furthermore, EC enhanced the activities of SOD and GSH-Px and decreased MDA level in the liver. EC treatment also decreased the gene and protein levels of IL-6, IL-1β, and TNF-α in the liver and serum. The 16S rRNA sequencing and untargeted metabolomics indicated that EC treatment affected the gut microbiota and regulated serum metabolism. Correlation analysis showed that the effects of EC on taurine and hypotaurine metabolism, cysteine and methionine metabolism, and vitamin B6 metabolism pathways were associated with affecting in the abundance of Lactobacillus, Dubosiella, Lachnospiraceae, Desulfovibri, Romboutsia, Akkermansia, Intestinimonas, and Candidatus_saccharimonas in the gut. In conclusion, our study confirmed the protective effect of EC on NAFLD. EC could treat NAFLD by inhibiting oxidative stress, reducing inflammatory responses, and improving the dysbiosis of gut microbiota and the modulation of the taurine and hypotaurine metabolism, cysteine and methionine metabolism, and vitamin B6 metabolism pathways in serum.

CCl4 inhibits the expressions of hepatic taurine biosynthetic enzymes and taurine synthesis in the progression of mouse liver fibrosis

Carbon tetrachloride (CCl4) is a widely used hepatotoxin for the studies of liver fibrosis and cirrhosis, and taurine has function to abate liver fibrosis induced by CCl4. But the interacting mechanisms between taurine and CCl4 in liver are still largely unknown. These made us to hypothesize that CCl4 may induce liver fibrosis by affecting the expressions of taurine biosynthetic enzymes and taurine synthesis. We thus assayed the expressions of hepatic cysteine dioxygenase (CDO), cysteine sulfonate acid decarboxylase (CSAD) and taurine transporter (TauT) in the progression of mouse liver fibrosis induced by CCl4. The results demonstrated that CCl4 treatment markedly decreased hepatic CSAD, CDO expressions, and taurine levels in hepatic tissue, although TauT expression did not exhibit significant decline. It was contrasting that hepatic α-SMA, serum AST, ALT, ALP kept increasing, which were accompanied by the pathological characters of liver, whereas taurine supplement attenuated the progression of liver fibrosis induced by CCl4. These results demonstrate that CCl4 may induce liver fibrosis by inhibiting hepatic CSAD and CDO expressions and taurine synthesis, which are crucial for our understanding the mechanisms of liver fibrosis induced by CCl4, and also potential for establishing therapeutic strategies of liver fibrosis and related diseases.

Taurine as a Natural Antioxidant: From Direct Antioxidant Effects to Protective Action in Various Toxicological Models

Natural antioxidants have received tremendous attention over the last 3 decades. At the same time, the attitude to free radicals is slowly changing, and their signalling role in adaptation to stress has recently received a lot of attention. Among many different antioxidants in the body, taurine (Tau), a sulphur-containing non-proteinogenic β-amino acid, is shown to have a special place as an important natural modulator of the antioxidant defence networks. Indeed, Tau is synthesised in most mammals and birds, and the Tau requirement is met by both synthesis and food/feed supply. From the analysis of recent data, it could be concluded that the direct antioxidant effect of Tau due to scavenging free radicals is limited and could be expected only in a few mammalian/avian tissues (e.g., heart and eye) with comparatively high (>15-20 mM) Tau concentrations. The stabilising effects of Tau on mitochondria, a prime site of free radical formation, are characterised and deserve more attention. Tau deficiency has been shown to compromise the electron transport chain in mitochondria and significantly increase free radical production. It seems likely that by maintaining the optimal Tau status of mitochondria, it is possible to control free radical production. Tau's antioxidant protective action is of great importance in various stress conditions in human life, and is related to commercial animal and poultry production. In various in vitro and in vivo toxicological models, Tau showed AO protective effects. The membrane-stabilizing effects, inhibiting effects on ROS-producing enzymes, as well as the indirect AO effects of Tau via redox balance maintenance associated with the modulation of various transcription factors (e.g., Nrf2 and NF-κB) and vitagenes could also contribute to its protective action in stress conditions, and thus deserve more attention.

Protective role of taurine against oxidative stress (Review)

Taurine is a fundamental mediator of homeostasis that exerts multiple roles to confer protection against oxidant stress. The development of hypertension, muscle/neuro‑​associated disorders, hepatic cirrhosis, cardiac dysfunction and ischemia/reperfusion are examples of some injuries that are linked with oxidative stress. The present review gives a comprehensive description of all the underlying mechanisms of taurine, with the aim to explain its anti‑oxidant actions. Taurine is regarded as a cytoprotective molecule due to its ability to sustain normal electron transport chain, maintain glutathione stores, upregulate anti‑oxidant responses, increase membrane stability, eliminate inflammation and prevent calcium accumulation. In parallel, the synergistic effect of taurine with other potential therapeutic modalities in multiple disorders are highlighted. Apart from the results derived from research findings, the current review bridges the gap between bench and bedside, providing mechanistic insights into the biological activity of taurine that supports its potential therapeutic efficacy in clinic. In the future, further clinical studies are required to support the ameliorative effect of taurine against oxidative stress.

Nuclear magnetic resonance-based tissue metabolomic analysis clarifies molecular mechanisms of gastric carcinogenesis

Gastric cancer (GC) is one of the deadliest cancers worldwide, and the progression of gastric carcinogenesis (GCG) covers multiple complicated pathological stages. Molecular mechanisms of GCG are still unclear. Here, we undertook NMR-based metabolomic analysis of aqueous metabolites extracted from gastric tissues in an established rat model of GCG. We showed that the metabolic profiles were clearly distinguished among 5 histologically classified groups: control, gastritis, low-grade gastric dysplasia, high-grade gastric dysplasia (HGD), and GC. Furthermore, we carried out metabolic pathway analysis based on identified significant metabolites and revealed significantly disturbed metabolic pathways closely associated with the 4 pathological stages, including oxidation stress, choline phosphorylation, amino acid metabolism, Krebs cycle, and glycolysis. Three metabolic pathways were continually disturbed during the progression of GCG, including taurine and hypotaurine metabolism, glutamine and glutamate metabolism, alanine, aspartate, and glutamate metabolism. Both the Krebs cycle and glycine, serine, and threonine metabolism were profoundly impaired in both the HGD and GC stages, potentially due to abnormal energy supply for tumor cell proliferation and growth. Furthermore, valine, leucine, and isoleucine biosynthesis and glycolysis were significantly disturbed in the GC stage for higher energy requirement of the rapid growth of tumor cells. Additionally, we identified potential gastric tissue biomarkers for metabolically discriminating the 4 pathological stages, which also showed good discriminant capabilities for their serum counterparts. This work sheds light on the molecular mechanisms of GCG and is of benefit to the exploration of potential biomarkers for clinically diagnosing and monitoring the progression of GCG.

Expedition into Taurine Biology: Structural Insights and Therapeutic Perspective of Taurine in Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are characterized by the accumulation of misfolded proteins. The hallmarks of protein aggregation in NDs proceed with impairment in the mitochondrial function, besides causing an enhancement in endoplasmic reticulum (ER) stress, neuroinflammation and synaptic loss. As accumulation of misfolded proteins hampers normal neuronal functions, it triggers ER stress, which leads to the activation of downstream effectors formulating events along the signaling cascade—referred to as unfolded protein response (UPRER) —thereby controlling cellular gene expression. The absence of disease-modifying therapeutic targets in different NDs, and the exponential increase in the number of cases, makes it critical to explore new approaches to treating these devastating diseases. In one such approach, osmolytes (low molecular weight substances), such as taurine have been found to promote protein folding under stress conditions, thereby averting aggregation of the misfolded proteins. Maintaining the structural integrity of the protein, taurine-mediated resumption of protein folding prompts a shift in folding homeostasis more towards functionality than towards aggregation and degradation. Together, taurine enacts protection in NDs by causing misfolded proteins to refold, so as to regain their stability and functionality. The present study provides recent and useful insights into understanding the progression of NDs, besides summarizing the genetics of NDs in correlation with mitochondrial dysfunction, ER stress, neuroinflammation and synaptic loss. It also highlights the structural and functional aspects of taurine in imparting protection against the aggregation/misfolding of proteins, thereby shifting the focus more towards the development of effective therapeutic modules that could avert the development of NDs.

Investigation of the Role of a Supplementation with Taurine on the Effects of Hypoglycemic-Hypotensive Therapy Against Diabetes-Induced Nephrotoxicity in Rats

This study has examined the role of supplementing a treatment of diabetic rats with captopril (CAP), metformin (MET) or CAP-MET with the antioxidant amino acid taurine (TAU) on biochemical indices of diabetes-induced metabolic changes, oxidative stress and nephropathy. To this end, groups of 6 male Sprague-Dawley rats (250-375 g) were made diabetic with a single, 60 mg/kg, intraperitoneal dose of streptozotocin (STZ) in 10 mM citrate buffer pH 4.5 and, after 14 days, treated daily for up to 42 days with either a single oral dose of CAP (0.15 mM/kg), MET (2.4 mM/kg) or TAU (2.4 mM/kg), or with a binary or tertiary combination of these agents. Rats receiving only 10 mM citrate buffer pH 4.5 or only STZ served as negative and positive controls, respectively. All rats were sacrificed by decapitation on day 57 and their blood and kidneys collected. In addition, a 24 h urine sample was collected starting on day 56. Compared to normal rats, untreated diabetic ones exhibited frank hyperglycemia (+313%), hypoinsulinemia (-76%) and elevation of the glycated hemoglobin value (HbA1c, +207%). Also they showed increased plasma levels of Na+ (+35%), K+ (+56%), creatinine (+232%), urea nitrogen (+158%), total protein (-53%) and transforming growth factor-β1 (TGF-β1, 12.4-fold) values. These changes were accompanied by increases in the renal levels of malondialdehyde (MDA, +42%), by decreases in the renal glutathione redox state (-71%), and activities of catalase (-70%), glutathione peroxidase (-71%) and superoxide dismutase (-85%), and by moderate decreases of the urine Na+ (-33%) and K+ (-39%) values. Following monotherapy, MET generally showed a greater attenuating effect than CAP or TAU on the changes in circulating glucose, insulin and HbA1c levels, urine total protein, and renal SOD activity; and CAP appeared more potent than TAU and MET, in that order, in antagonizing the changes in plasma creatinine and urea nitrogen levels. On the other hand, TAU generally provided a greater protection against changes in glutathione redox state and in CAT and GPx activities, with other actions falling in potency between those of CAP and MET. Adding TAU to a treatment with CAP, but not to one with MET, led to an increase in protective action relative to a treatment with drug alone. On the other hand, the actions of CAP-MET, which were about equipotent with those of MET, became enhanced in the presence of TAU, particularly against the changes of the glutathione redox state and activities of antioxidant enzymes. In short, the present results suggest that the addition of TAU to a treatment of diabetes with CAP or CAP-MET, and sometimes to one with MET, will lead to a gain in protective potency against changes in indices of glucose metabolism and of renal functional impairment and oxidative stress.

Comparison of taurine and pantoyltaurine as antioxidants in vitro and in the central nervous system of diabetic rats

This study has comparatively evaluated the antiradical and antilipid peroxidizing actions of taurine (TAU) and its N-pantoyl analog pantoyltaurine (PTAU) in vitro, and has determined the extent to which these findings agree with the in vivo ability of these compounds to prevent changes in plasma glucose and in indices of oxidative stress in the plasma, brain and spinal cord induced by the diabetogen streptozotocin (STZ) in Sprague-Dawley rats. Using free radical-generating and oxidizing systems, PTAU was found more effective than TAU in scavenging DPPH, hydroxyl, peroxyl, and superoxide anion radicals and peroxynitrite, and in preventing lipid peroxidation of a brain homogenate by iron (III)-dopamine and the oxidation of dopamine by iron (III). On the other hand, when administered intraperitoneally (i.p.) at a 1.2mM/kg dose, 75min and 45min before a single i.p., 60mg/kg, dose of (STZ), TAU was about equipotent with PTAU in attenuating STZ-induced increases in glucose, malondialdehyde (MDA) and nitric oxide (NO), and the loss of reduced glutathione (GSH) in plasma collected at 24h post STZ. Moreover, the analysis of concurrently collected brain and spinal cords samples revealed that both TAU and PTAU were able to equally reverse the increases in MDA and NO concentrations and to effectively counteract the decrease in the GSH/GSSG ratio caused by STZ. Likewise, both compounds were very effective in preventing the losses of tissue catalase, glutathione peroxidase and superoxide dismutase activities. A comparison of the results for spinal cord and for brain parts such as the cerebellum, cortex and brain stem suggested the existence of regional differences in antioxidant potency between TAU and PTAU, especially in terms of antioxidant enzymes. In general, differences in antiradical and antioxidant potencies between TAU and PTAU derived from in vitro test are not reliable indicators of the antioxidant potencies these compounds may subsequently manifest in a living organism.

Mechanisms of Neuronal Protection against Excitotoxicity, Endoplasmic Reticulum Stress, and Mitochondrial Dysfunction in Stroke and Neurodegenerative Diseases

In stroke and neurodegenerative disease, neuronal excitotoxicity, caused by increased extracellular glutamate levels, is known to result in calcium overload and mitochondrial dysfunction. Mitochondrial deficits may involve a deficiency in energy supply as well as generation of high levels of oxidants which are key contributors to neuronal cell death through necrotic and apoptotic mechanisms. Excessive glutamate receptor stimulation also results in increased nitric oxide generation which can be detrimental to cells as nitric oxide interacts with superoxide to form the toxic molecule peroxynitrite. High level oxidant production elicits neuronal apoptosis through the actions of proapoptotic Bcl-2 family members resulting in mitochondrial permeability transition pore opening. In addition to apoptotic responses to severe stress, accumulation of misfolded proteins and high levels of oxidants can elicit endoplasmic reticulum (ER) stress pathways which may also contribute to induction of apoptosis. Two categories of therapeutics are discussed that impact major pro-death events that include induction of oxidants, calcium overload, and ER stress. The first category of therapeutic agent includes the amino acid taurine which prevents calcium overload and is also capable of preventing ER stress by inhibiting specific ER stress pathways. The second category involves N-methyl-D-aspartate receptor (NMDA receptor) partial antagonists illustrated by S-Methyl-N, N-diethyldithiocarbamate sulfoxide (DETC-MeSO), and memantine. DETC-MeSO is protective through preventing excitotoxicity and calcium overload and by blocking specific ER stress pathways. Another NMDA receptor partial antagonist is memantine which prevents excessive glutamate excitation but also remarkably allows maintenance of physiological neurotransmission. Targeting of these major sites of neuronal damage using pharmacological agents is discussed in terms of potential therapeutic approaches for neurological disorders.

Physiological role of taurine--from organism to organelle

Taurine is often referred to as a semi-essential amino acid as newborn mammals have a limited ability to synthesize taurine and have to rely on dietary supply. Taurine is not thought to be incorporated into proteins as no aminoacyl tRNA synthetase has yet been identified and is not oxidized in mammalian cells. However, taurine contributes significantly to the cellular pool of organic osmolytes and has accordingly been acknowledged for its role in cell volume restoration following osmotic perturbation. This review describes taurine homeostasis in cells and organelles with emphasis on taurine biophysics/membrane dynamics, regulation of transport proteins involved in active taurine uptake and passive taurine release as well as physiological processes, for example, development, lung function, mitochondrial function, antioxidative defence and apoptosis which seem to be affected by a shift in the expression of the taurine transporters and/or the cellular taurine content.

Protection of differentiated neuronal NG108-15 cells from P2X7 receptor-mediated toxicity by taurine

BACKGROUND

Strong P2X7 receptor (P2X7R) activation causes Ca(2+) overload and consequent cell death. We previously showed that depletion of Ca(2+) stores and endoplasmic reticulum (ER) stress in differentiated NG108-15 neuronal cells contributed to P2X7R-mediated cytotoxicity. In this work, we assessed whether taurine (2-aminoethanesulfonic acid) could prevent this P2X7R-mediated cytotoxicity in this neuronal cell line.

METHODS

Cytotoxicity markers were assessed by MTT assay and Western blotting. Cytosolic Ca(2+) and mitochondrial Ca(2+) concentrations were measured microfluorimetrically using fura-2 and rhod-2, respectively. Intracellular reactive oxygen species (ROS) production was assayed by the indicator 2',7'-dichlorodihydrofluorescein diacetate.

RESULTS

Selective P2X7R agonist BzATP treatment causes neuronal cell death by causing cytosolic Ca(2+) overload, depletion of Ca(2+) stores, endoplasmic reticulum (ER) stress, and caspase-3 activation (cleaved caspase 3). Remarkably, taurine (10mM) pretreatment could prevent P2X7R-mediated neuronal cell death by blocking BzATP-mediated ER stress as determined by phosphorylated eukaryotic translation initiation factor 2α (peIF2α) and C/EBP-homologous protein (CHOP). However, taurine did not block BzATP-induced Ca(2+) overload and depletion of ER Ca(2+) stores. Interestingly, P2X7R activation did not result in mitochondrial Ca(2+) overload, nor did it affect mitochondrial membrane potential. BzATP-induced generation of intracellular reactive oxygen species (ROS) was prevented by taurine.

CONCLUSIONS

The neuroprotective effect by taurine is attributed to the suppression of P2X7R-mediated ER stress and ROS formation.

Taurine: the comeback of a neutraceutical in the prevention of retinal degenerations

Taurine is the most abundant amino acid in the retina. In the 1970s, it was thought to be involved in retinal diseases with photoreceptor degeneration, because cats on a taurine-free diet presented photoreceptor loss. However, with the exception of its introduction into baby milk and parenteral nutrition, taurine has not yet been incorporated into any commercial treatment with the aim of slowing photoreceptor degeneration. Our recent discovery that taurine depletion is involved in the retinal toxicity of the antiepileptic drug vigabatrin has returned taurine to the limelight in the field of neuroprotection. However, although the retinal toxicity of vigabatrin principally involves a deleterious effect on photoreceptors, retinal ganglion cells (RGCs) are also affected. These findings led us to investigate the possible role of taurine depletion in retinal diseases with RGC degeneration, such as glaucoma and diabetic retinopathy. The major antioxidant properties of taurine may influence disease processes. In addition, the efficacy of taurine is dependent on its uptake into retinal cells, microvascular endothelial cells and the retinal pigment epithelium. Disturbances of retinal vascular perfusion in these retinal diseases may therefore affect the retinal uptake of taurine, resulting in local depletion. The low plasma taurine concentrations observed in diabetic patients may further enhance such local decreases in taurine concentration. We here review the evidence for a role of taurine in retinal ganglion cell survival and studies suggesting that this compound may be involved in the pathophysiology of glaucoma or diabetic retinopathy. Along with other antioxidant molecules, taurine should therefore be seriously reconsidered as a potential treatment for such retinal diseases.

Neuroprotective Mechanisms of Taurine against Ischemic Stroke

Ischemic stroke exhibits a multiplicity of pathophysiological mechanisms. To address the diverse pathophysiological mechanisms observed in ischemic stroke investigators seek to find therapeutic strategies that are multifaceted in their action by either investigating multipotential compounds or by using a combination of compounds. Taurine, an endogenous amino acid, exhibits a plethora of physiological functions. It exhibits antioxidative properties, stabilizes membrane, functions as an osmoregulator, modulates ionic movements, reduces the level of pro-inflammators, regulates intracellular calcium concentration; all of which contributes to its neuroprotective effect. Data are accumulating that show the neuroprotective mechanisms of taurine against stroke pathophysiology. In this review, we describe the neuroprotective mechanisms employed by taurine against ischemic stroke and its use in clinical trial for ischemic stroke.

Mechanism of the protective action of taurine in toxin and drug induced organ pathophysiology and diabetic complications: a review

Taurine (2-aminoethanesulfonic acid), a conditionally essential amino acid, is found in large concentrations in all mammalian tissues and is particularly abundant in aquatic foods. Taurine exhibits membrane stabilizing, osmoregulatory and cytoprotective effects, antioxidative properties, regulates intracellular Ca(2+) concentration, modulates ion movement and neurotransmitters, reduce the levels of pro-inflammatory cytokines in various organs and controls blood pressure. Recently, emerging evidence from the literature shows the effectiveness of taurine as a protective agent against several environmental toxins and drug-induced multiple organ injuries as the outcome of hepatotoxicity, nephrotoxicity, neurotoxicity, testicular toxicity and cardiotoxicity in several animal models. Besides, taurine is also effective in combating diabetes and its associated complications, including cardiomyopathy, nephropathy, neuropathy, retinopathy and atherosclerosis. These beneficial effects appear to be due to the multiple actions of taurine on cellular functions. This review summarizes the mechanism of the prophylactic role of taurine against several environmental toxins and drug-induced organ pathophysiology and diabetes.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Hepatoprotective activity of the edible snail (Bellamia bengalensis) flesh extract in carbon tetrachloride induced hepatotoxicity in rats

ETHNOPHARMACOLOGICAL RELEVANCE

In the folk-traditional medicine, snails were used to purify blood, boost immune system, prevent conjunctivitis and to treat liver problems.

OBJECTIVES

To evaluate the hepatoprotective activity of the edible snail (Bellamia bengalensis) flesh extract in male Wistar rats treated with carbon tetrachloride as an hepatotoxicant.

MATERIALS AND METHODS

Live adult Bellamia bengalensis was collected commercially from the Kolkata market. Aqueous flesh extract (BBE) was prepared in 0.9% saline and expressed in terms of wet weight basis. The aqueous flesh extract was administered orally (1, 2 g kg(-1)day(-1)) to male rats for 12 days. Liv52 was used as positive control. 24h after administration of extract, the rats were given a single oral dose of CCl(4) (1.25 ml kg(-1)), except vehicle control rats. After 24h of CCl(4) administration, all the animals were sacrificed to collect the blood and liver tissue.

RESULTS

BBE (1 and 2 g kg(-1)day(-1), p.o.×12 days) significantly prevented CCl(4) induced elevation of SGOT, SGPT, γGT, ACP, ALP, bilirubin, LDH and CCl(4) induced decrease in total protein, triglyceride level in male Wistar rats. BBE treated rat liver anti-oxidant parameters (LPO, SOD, GSH, CAT, GPx) were significantly antagonized for the pro-oxidant effect of CCl(4). Histopathological studies also supported the protective effect of BBE.

CONCLUSION

This study validated the folk and traditional use of snail in liver disorder through CCl(4)-induced rat experimental model.

Experimental evidence for therapeutic potential of taurine in the treatment of nonalcoholic fatty liver disease

The incidence of obesity is now at epidemic proportions and has resulted in the emergence of nonalcoholic fatty liver disease (NAFLD) as a common metabolic disorder that can lead to liver injury and cirrhosis. Excess sucrose and long-chain saturated fatty acids in the diet may play a role in the development and progression of NAFLD. One factor linking sucrose and saturated fatty acids to liver damage is dysfunction of the endoplasmic reticulum (ER). Although there is currently no proven, effective therapy for NAFLD, the amino sulfonic acid taurine is protective against various metabolic disturbances, including alcohol-induced liver damage. The present study was undertaken to evaluate the therapeutic potential of taurine to serve as a preventative treatment for diet-induced NAFLD. We report that taurine significantly mitigated palmitate-mediated caspase-3 activity, cell death, ER stress, and oxidative stress in H4IIE liver cells and primary hepatocytes. In rats fed a high-sucrose diet, dietary taurine supplementation significantly reduced hepatic lipid accumulation, liver injury, inflammation, plasma triglycerides, and insulin levels. The high-sucrose diet resulted in an induction of multiple components of the unfolded protein response in the liver consistent with ER stress, which was ameliorated by taurine supplementation. Treatment of mice with the ER stress-inducing agent tunicamycin resulted in liver injury, unfolded protein response induction, and hepatic lipid accumulation that was significantly ameliorated by dietary supplementation with taurine. Our results indicate that dietary supplementation with taurine offers significant potential as a preventative treatment for NAFLD.

Neuroprotective effects of active ingredients isolated from Pegasus laternarius on cultured cerebral neurons

Seamoth (Pegasus laternarius Cuvier) is extensively used to treat various diseases on the coastland of Guangdong Province in China, such as scrofula, cough, and diarrhea. The total extract of Pegasus laternarius (EP) was subjected to column chromatography to acquire three different constituents (EPC1, EPC2, and EPC3). Cerebral neuron injury was induced by glutamate, H₂O₂, and serum deprivation. After treating with or without different extracts, cell viability was assessed with the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and cell apoptosis was analyzed with Hoechst 33258 staining and agarose gel electrophoresis. We also determined the levels of lactate dehydrogenase (LDH), maleic dialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px). The results showed that both EP and EPC2 promoted the outgrowth of cultural neurons, increased antioxidant enzyme activity, and protected neurons from neuronal injury or apoptosis induced by glutamate, H₂O₂, and serum deprivation. EPC1 and EPC3 had little or no effect on neurons. These results suggest that the active ingredients obtained from Pegasus laternarius have potential neuroprotective effects on injured neurons by promoting the outgrowth of cultured neurons, increasing the activity of intracellular antioxidants, and exerting antiapoptotic effects. This neuroprotection may be attributable to specific active ingredients, such as taurine, novel ceramide, and cholesterol.

Protection effect of taurine on nitrosative stress in the mice brain with chronic exposure to arsenic

BACKGROUND

Arsenic exposure induces overproduction of reactive nitrogen species (RNS) in brain tissue and results in nucleic acid damage to the nerve cells. The 8-nitroguanine is one of the major products formed by the reaction of guanine, and ONOO-, and has been used as a popular biomarker of nucleic acid damage due to RNS attacking. In the present study, we examined whether the administration of taurine can protect against nucleic acid damage of brain neurons by arsenic-induced RNS.

MATERIALS AND METHODS

Sixty mice (30 male and 30 female) weighing 19.5 +/- 1.5 g were divided into 3 groups: (1) control group, (2) experimental group that received arsenic (As2O3), and (3) antagonistic group that received taurine with arsenic. Arsenic was administered for 60 days. 8-Nitroguanine expressions in brain neurons of mice were examined by the immunohistochemical method. Histopathological changes in brain tissues of mice were observed under light microscope and the immunohistochemistry method was used to investigate 8-nitroguanine expressions in cerebrum and cerebellum of mice.

RESULTS

In the control group, no abnormal histopathological changes were observed in brain tissue of the mice. In brain tissue of the mice exposed to arsenic, histopathological results showed swells, evident vacuolar degeneration in cytoplasm, karyorrhexis and karyolysis. Relatively light pathological changes were observed in brain of the mice co-administered arsenic and taurine. Little or no expression of 8-nitroguanine in brain tissue was observed in controls. However, intensive expression of 8-nitroguanine was found in brain tissue of mice exposed to arsenic and it was mainly distributed in nucleus neighbouring the nuclear membrane, but a little in cytoplasm. A weak expression of 8-nitroguanine was observed in brain cells of mice co-administered arsenic and taurine.

CONCLUSIONS

The brain neurons may be the major target cells of arsenic neurotoxicity. Co-administration of arsenic and taurine can alleviate DNA damage of brain neurons caused by arsenic through the RNS signal pathway.

Effects of oral administration of antioxidant taurine on haematological parameters in Wistar rats

The present study evaluates the effects of oral administration of taurine on haematological parameters in normal wistar rats. Tissue oxidative stress is implicated in pathogenesis of various clinical disorders and antioxidant taurine is emerging as prophylactic and therapeutic agent. However, studies on effects of taurine on normal physiology are not reported in literature. Normal saline (Group I) or 5% taurine in normal saline was administered in dose of 50 mg (Group II), 250 mg (Group III) or 500 mg kg(-1) of b.wt. (Group IV) through intragastric intubation for 60 days. The blood cell counts, haemoglobin content, packed cell volume, blood indices, bleeding time and clotting time were estimated using routine laboratory haematological techniques. Neutrophil's phagocytic activity was determined by nitroblue tetrazolium reduction test; serum lysozyme activity was estimated colorimetrically by the degree to lyse bacterial cell suspension and serum taurine levels were estimated by HPLC fluorimetric technique. Platelet count showed a decrease in Group III and IV when compared with Group I and II (p<0.001). Mean corpuscular haemoglobin of Group III and IV are significantly lowered when compared to Group I (p<0.001). A statistically significant decrease was observed in the mean corpuscular haemoglobin concentration between Group 1 and Group IV (p<0.001). The neutrophil percentage of Group II, Group III and Group IV showed a significant increase over Group I (p<0.001). The percentage of lymphocytes showed a significant decrease in Group II, III and Group IV when compared to Group I (p<0.001). Neutrophil's phagocytic activity is significantly lowered in Group III and IV when compared to Group I (p<0.001). The serum lysozyme activity of Group III and IV showed a significant increase over Group I (at p<0.001). From the present study it may be concluded that long term oral administration of taurine affects normal haematological functions.

Role of antioxidant activity of taurine in diabetes

The unifying hypothesis of diabetes maintains that reactive oxygen species (ROS) generated in the mitochondria of glucose-treated cells promote reactions leading to the development of diabetic complications. Although the unifying hypothesis attributes the generation of oxidants solely to impaired glucose and fatty acid metabolism, diabetes is also associated with a decline in the levels of the endogenous antioxidant taurine in a number of tissues, raising the possibility that changes in taurine status might also contribute to the severity of oxidant-mediated damage. There is overwhelming evidence that taurine blocks toxicity caused by oxidative stress, but the mechanism underlying the antioxidant activity remains unclear. One established antioxidant action of taurine is the detoxification of hypochlorous acid. However, not all of the antioxidant actions of taurine are related to hypochlorous acid because they are detected in isolated cell systems lacking neutrophils. There are a few studies showing that taurine either modulates the antioxidant defenses or blocks the actions of the oxidants, but other studies oppose this interpretation. Although taurine is incapable of directly scavenging the classic ROS, such as superoxide anion, hydroxyl radical, and hydrogen peroxide, there are numerous studies suggesting that it is an effective inhibitor of ROS generation. The present review introduces a novel antioxidant hypothesis, which takes into consideration the presence of taurine-conjugated tRNAs in the mitochondria. Because tRNA conjugation is required for normal translation of mitochondrial-encoded proteins, taurine deficiency reduces the expression of these respiratory chain components. As a result, flux through the electron transport chain decreases. The dysfunctional respiratory chain accumulates electron donors, which divert electrons from the respiratory chain to oxygen, forming superoxide anion in the process. Restoration of taurine levels increases the levels of conjugated tRNA, restores respiratory chain activity, and increases the synthesis of ATP at the expense of superoxide anion production. The importance of this and other actions of taurine in diabetes is discussed.

The protective effect of taurine against hepatic damage in a model of liver disease and hepatic stellate cells

Taurine plays a protective role against free radicals and toxins in various cells and tissues. However, the effect of taurine on hepatic injury and fibrosis developed by activated hepatic stellate cells (HSC) and myofibroblast-like cells is not fully understood. We investigated the effects of taurine on the hepatic fibrogenesis and damage in rats and isolated HSC. Rats were divided into a normal and two CCl4-induced liver damage (LD) groups, one untreated and the other maintained for 5 weeks on a 2% taurine diet. The HSC isolated from a normal rat were cultured either for a day only or for an additional 3-6 days with approximately 50 mM taurine. LD rats maintained on the taurine diet were resistant to CCl4-induced loss of taurine from the liver. The liver of the LD rats were also protected against histological damage, fibrosis, significant reductions in oxidative stress markers (LPO and 8-OHdG) and hepatic fibrogenic factors (TGF-beta1 mRNA, hydroxyproline, alpha-SMA). Proliferation, oxidative stress, and fibrogenesis were significantly inhibited in HSC by treatment with taurine. Thus, supplementation with taurine should be considered as a therapeutic approach to lessen the severity of oxidative stress-induced liver injury and hepatic fibrosis.

Taurine and guanidinoethanesulfonic acid (GES) differentially affects the expression and phosphorylation of cellular proteins in C6 glial cells

Effects of taurine and guanidinoethanesulfonic acid (GES), a taurine transport inhibitor, on the expression and phosphorylation of cellular proteins in C6 glial cells were examined using two-dimensional (2-D) gel electrophoresis and 2-D immunoblots. 2-D gels stained with Coomassie Blue or SYPRO Ruby showed differential distribution patterns of cellular proteins in the control, taurine-supplemented and GES-supplemented cells. 2-D immunoblot analysis using the anti-phosphotyrosine antibody recognized only few immuno-reactive proteins in all three samples, and their distribution patterns were different. On the other hand, 2-D immunoblot analysis using the anti-phosphothreonine antibody recognized many immuno-reactive proteins with distinctly different distribution patterns in the control, taurine-supplemented and GES-supplemented cells. In GES-supplemented cells, the relative number of the anti-phosphotyrosine immuno-reactive protein spots increased modestly, whereas the relative number of the anti-phosphothreonine immuno-reactive protein spots decreased markedly than those in the control and taurine-supplemented cells.

Cadmium-induced neurological disorders: prophylactic role of taurine

The present study was conducted to investigate whether the conditionally essential amino acid taurine could play any protective role against the potent neurotoxin cadmium (Cd)-induced oxidative impairment in mice brain. Cd administration in the form of CdCl(2 )(at a dose of 4 mg kg(-1) body weight for 3 days, orally) increased the intracellular accumulation of metallic Cd, reactive oxygen species and super oxide radicals. The toxin also augmented the extent of lipid peroxidation, protein carbonylation and the levels of glutathione disulfide. Activities of the antioxidant enzymes and the levels of reduced glutathione as well as total thiols have been significantly decreased due to Cd exposure. In addition, the toxin also caused significant DNA degradation (as evidenced from DNA smearing and diphenylamine reaction). Oral administration of taurine (at a dose of 100 mg kg(-1) body weight for 5 days) was found to be very effective in the prevention of Cd-induced oxidative impairment in the brain tissue of experimental mice. In addition, taurine treatment could also prevent the reduction in the in vivo antioxidant power linearly up to a dose of 100 mg kg(-1) body weight. The preventive role of taurine against Cd-induced cerebral oxidative damage was supported by the observation under scanning electron microscope as well as histological examination of brain segments. To validate the experimental results, a well-known water soluble antioxidant, vitamin C, was used as the positive control in the study. In all, the results suggest that taurine plays a beneficial role against Cd-induced cerebral oxidative stress.

Effect of vitamin A and/or E on plasma enzymatic antioxidant systems and total antioxidant capacity of broiler chickens challenged with carbon tetrachloride

This study was conducted to investigate the effect of vitamin A and E supplementation on the antioxidant defences of broiler chickens against carbon tetrachloride (CCl(4))-induced oxidative stress at 4 weeks of age. Superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities as well as total antioxidant (TAO) level were analysed before and after CCl(4) challenge. Day-old Lohman broiler chickens (n = 144) were randomly assigned to six factorially arranged dietary treatments consisting of vitamin A [1.35 (control) or +20 mg/kg] and vitamin E [20 (control), +40 or +60 mg/kg]. The background of vitamins A and E in the basal diet was 4500 IU (1.35 mg) and 30 IU (20 mg) respectively. At 4 weeks of age, eight chickens from each treatment were bled before interperitoneal injection with 1 ml of CCl(4) (mixed with olive oil in a ratio of 1:1) and bled again 24 h post-injection. Vitamin E supplementation decreased (p < 0.05) the activity of both SOD and GPX and showed a tendency (p = 0.07) for TAO reduction. CCl(4) attenuated SOD and GPX activities as well as TAO level. The decrease was profound (p < 0.05) in chickens fed the basal diet as well as those fed basal diet supplemented with 20 mg vitamin A. TAO levels behaved similarly when chickens were challenged with CCl(4). After CCl(4) injection, SOD activities of all experimental groups were equivalent. The presence of vitamin A decreased (p < 0.05) plasma GPX activity in chickens fed the basal diet supplemented with 40 mg/kg of vitamin E. Results of this experiment suggested that vitamin E supplementation elevated antioxidant enzyme activities while vitamin A supplementation attenuated this effect. Vitamin E supplementation improved the total reducing power by maintaining comparable levels of TAO upon CCl(4) challenge. Further experiments need to be carried out to investigate the role of vitamin A in oxidative stress and to evaluate the lipid peroxidation products.

Pegylated interferon-alpha plus taurine in treatment of rat liver fibrosis

AIM

To investigate the antifibrotic effects of peginterferon-alpha 2b and taurine on oxidative stress markers and hepatocellular apoptosis.

METHODS

Sixty rats with CCl4-induced liver fibrosis were divided into 4 groups (n=15). Group 1 was left for spontaneous recovery (SR). Groups 2-4 received peginterferon-alpha 2b, taurine, and their combination, respectively, for four weeks. Histological fibrosis scores, histomorphometric analysis, tissue hydroxyproline, tissue MDA, GPx and SOD activities were determined. Activated stellate cells and hepatocellular apoptosis were also evaluated.

RESULTS

The degree of fibrosis decreased in all treatment groups compared to spontaneous recovery group. Taurine alone and in combination with peginterferon-alpha 2b reduced oxidative stress markers, but peginterferon-alpha 2b alone did not. Apoptotic hepatocytes and activated stellate cells were higher in groups 2-4 than in group 1. Combined taurine and peginterferon-alpha 2b further reduced fibrosis and increased activated stellate cell apoptosis, but could not improve oxidative stress more than taurine alone.

CONCLUSION

Peginterferon-alpha 2b exerts anti-fibrotic effects on rat liver fibrosis. It seems ineffective against oxidative stress in vivo. Peginterferon-alpha 2b in combination with taurine seems to be an antifibrotic strategy.

Effect of β-alanine administration on carbon tetrachloride-induced acute hepatotoxicity

Mice were supplemented with beta-alanine (3%) in drinking water for one week. beta-Alanine intake reduced hepatic taurine levels, but elevated cysteine levels significantly. Hepatotoxicity of CCl4 in mice fed with beta-alanine was decreased as determined by changes in serum enzyme activities. Hepatic glutathione and taurine concentrations after CCl4 challenge were increased markedly by beta-alanine intake. The enhanced availability of cysteine for synthesis of glutathione and/or taurine appears to account for the hepatoprotective effects of beta-alanine against CCl4-induced liver injury.

Taurine prevents myocardial ischemia/reperfusion-induced oxidative stress and apoptosis in prolonged hypothermic rat heart preservation

Taurine (2-aminoethanesulfonic acid) is a potent antioxidant and inhibits cell apoptosis in ischemic reperfusion injury. In this study we evaluated whether addition of taurine to St. Thomas' cardioplegic solution enhances its myocardial protective effects in prolonged hypothermic heart preservation in rats. Hearts isolated from male Sprague-Dawley rats were mounted on a Langendorff apparatus to estimate baseline cardiac function, then arrested and stored in St. Thomas' cardioplegic solution, with taurine (10 mM; taurine group, n = 8) or without taurine (control group, n = 8), for 6 h at 4 degrees C. After storage, the hearts were reperfused and heart rate (HR), coronary flow (CF), left ventricular developed pressure (LVP), and positive maximum left ventricular developing pressure (max LV dp/dt) were measured. The LV tissue was examined immunohistochemically for determining DNA oxidative stress and cell apoptosis. Compared with control groups, recovery of LVP (P < 0.001), max LV dp/dt (P < 0.001), and coronary flow (P < 0.001) were significantly enhanced, whereas glutamic oxaloacetic transaminase (P < 0.01), lactate dehydrogenase (P < 0.05), creatine phosphate kinase (P < 0.01), 8-hydroxy-2'-deoxyguanosine index (P < 0.01), caspase-3 mRNA expression (P < 0.05), and percentage of TUNEL-positive cardiomyocytes (P < 0.05) were reduced in the taurine group. Addition of taurine to St. Thomas' cardioplegic solution improved cardiac function recovery for prolonged hypothermic rat heart preservation by suppressing DNA oxidative stress and cell apoptosis.

Taurine inhibits oxidative damage and prevents fibrosis in carbon tetrachloride-induced hepatic fibrosis

BACKGROUND/AIMS

The aim of the study was to examine the effects of taurine on hepatic fibrogenesis and in isolated hepatic stellate cells (HSC).

METHODS

The rats of the hepatic damage (HD) group were administered carbon tetracholoride (CCl4) for 5 weeks and a subgroup received, in addition, a 2% taurine containing diet for 6 weeks (HDT). The HSC were isolated from normal rats and cultured for 4 days.

RESULTS

The hepatic taurine concentration was decreased in the HD group. This loss and the hepatic histological damage and fibrosis (particularly in the pericentral region), were reduced following taurine treatment. Furthermore, the hepatic alpha-SMA, lipid hydroperoxide and 8-OHdG levels in serum and liver, as well as hepatic TGF-beta1 mRNA and hydroxyproline levels were significantly increased in the HD group, and most of these parameters were significantly reduced following taurine treatment. In contrast to the MAP-kinase and Akt expressions, which remained unchanged, the lipid hydroperoxide and hydroxyproline concentrations, as well as TGF-beta1 mRNA levels were significantly reduced by taurine in activated HSC.

CONCLUSIONS

Oral taurine administration enhances hepatic taurine accumulation, reduces oxidative stress and prevents progression of hepatic fibrosis in CCl4-induced HD rats, as well as inhibits transformation of the HSC.

Withania somnifera (ASHWAGANDHA) ATTENUATES ANTIOXIDANT DEFENSE IN AGED SPINAL CORD AND INHIBITS COPPER INDUCED LIPID PEROXIDATION AND PROTEIN OXIDATIVE MODIFICATIONS

Withania somnifera is classified in Ayurveda, the ancient Indian system of medicine, as a rasayana, a group of plant-derived drugs which promote physical and mental health, augment resistance of the body against disease and diverse adverse environmental factors, revitalize the body in debilitated conditions and increase longevity. We investigated the effects of Withania somnifera on copper-induced lipid peroxidation and antioxidant enzymes in aging spinal cord of Wistar rats. The activity of glutathione peroxidase (GPx) decreased significantly in the spinal cord from adult to aged mice. Treatment with Withania somnifera successfully attenuated GPx activity and inhibited lipid peroxidation in a dose dependent manner. Withania somnifera inhibited both the lipid peroxidation and protein oxidative modification induced by copper. These effects were similar to those of superoxide dismutase and mannitol. The results indicate the therapeutic potential of Withania somnifera in aging and copper-induced pathophysiological conditions.