Low-dose taurine upregulates taurine transporter expression in acute myocardial ischemia

Taurine and enzymatically modified isoquercitrin protected against methotrexate-induced deteriorations in the conductivity and rhythmicity of the heart in rats: Antioxidant, anti-inflammatory, and histological architecture approach

Cardiotoxicity is one of the most devastating complications of cancer treatment by methotrexate (MTX). The present study aimed to investigate the potential anti-cardiotoxic efficacy of taurine (Tau) and enzymatically modified isoquercitrin (EMIQ) alone or combined against MTX-induced cardiotoxicity in adult male rats. A total of 36 rats were randomly divided into six groups (six animals each): control, MTX (a single i.p. dose of 20 mg/kg), EMIQ + MTX (26 mg/kg of EMIQ, p.o. for 16 days), Tau + MTX (500 mg/kg of Tau, p.o. for 16 days), EMIQ + Tau + MTX at the same previous doses, and (EMIQ + Tau)½ + MTX. MTX reduced the percentage of body weight change, the expression of dihydrofolate reductase (DHFR) and folypolyglutamyl synthetase (FPGS), the cleaved tumor necrosis factor alpha (TNF-α) level in the cardiac tissue, and the elevated serum TNF-α level. MTX extensively deteriorated the electrocardiography (ECG), inducing tachycardia with shortening of the time intervals between successive heartbeats (R-R interval), associated with elongation of ventricular depolarization (QRS interval), and the corrected total time for ventricular de- and repolarization (QTc) duration. Treatment with MTX resulted in a significant reduction in atrial depolarization (P amplitude) and rapid repolarization (T amplitude) and a significant elevation in plateau phase (ST height). MTX treatment resulted in swelling of cardiomyocytes with extensive vacuolization of sarcoplasm with numerous variably sized vacuoles in addition to apoptotic cells. Tau and EMIQ protected against MTX-induced deteriorations in the conductivity and rhythmicity of the heart through antioxidative, anti-inflammatory, and antiapoptotic activities. Treatment with tau and EMIQ combined at high or low doses offered superior protection to the heart than using each agent alone.

Taurine induces hormesis in multiple biological models: May have transformative implications for overall societal health

This paper represents the first integrative assessment and documentation of taurine-induced hormetic effects in the biological and biomedical areas, their dose response features, mechanistic frameworks, and possible public health, therapeutic and commercial applications. Taurine-induced hormetic effects are documented in a wide range of experimental models, cell types and for numerous biological endpoints, with most of these experimental findings being reported within the past five years. It is suggested that the concept of hormesis may have a transformative effect on taurine research and its public health and therapeutic applications.

Interaction of exercise training with taurine attenuates infarct size and cardiac dysfunction via Akt-Foxo3a-Caspase-8 signaling pathway

This research aimed to investigate the synergistic protective effect of exercise training and taurine on Akt-Foxo3a-Caspase-8 signaling related to infarct size and cardiac dysfunction. Therefore, 25 male Wistar rats with MI were divided into five groups: sham (Sh), control-MI(C-MI), exercise training-MI(Exe-MI), taurine supplementation-MI(Supp-MI), and exercise training + taurine-MI(Exe + Supp-MI). The taurine groups were given a 200 mg/kg/day dose of taurine by drinking water. Exercise training was conducted for 8 weeks (5 days/week), each session alternated 2 min with 25-30% VO2peak and 4 min with 55-60% VO2peak for 10 alternations. Then, the left ventricle tissue samples were taken from all groups. Exercise training and taurine activated Akt and decreased Foxo3a. Expression of the caspase-8 gene was increased in cardiac necrosis after MI, While, after 12 weeks of intervention decreased. Results exhibited that exercise training combined with taurine has a greater effect than either alone on activating the Akt-Foxo3a-caspase signaling pathway (P < 0.001). MI-induced myocardial injury leads to increase collagen deposition (P < 0.001) and infarct size and results in cardiac dysfunction via reduced stroke volume, ejection fraction, and fractional shortening (P < 0.001). Exercise training and taurine improved cardiac functional parameters (SV, EF, FS) and infarct size (P < 0.001) after 8 weeks of intervention in rats with MI. Also, the interaction of exercise training and taurine has a greater effect than alone on these variables. Interaction of exercise training with taurine supplementation induces a general amelioration of the cardiac histopathological profiles and improves cardiac remodeling via activating Akt-Foxo3a-Caspase-8 signaling with protective effects against MI.

Testosterone enhances taurine synthesis by upregulating androgen receptor and cysteine sulfinic acid decarboxylase expressions in male mouse liver

Taurine is an end-product of cysteine metabolism, whereas cysteine dioxygenase (CDO) and cysteine sulfinate decarboxylase (CSAD) are key enzymes regulating taurine synthesis. Sex steroids, including estrogens and androgens, are associated with liver physiopathological processes; however, we still do not know whether taurine and sex steroids interact in regulating liver physiology and hepatic diseases, and whether there are sex differences, although our recent study shows that the estrogen is involved in regulating taurine synthesis in mouse liver. The present study was thus proposed to identify whether 17-β-estradiol and testosterone (T) play their roles by regulating CDO and CSAD expression and taurine synthesis in male mouse liver. Our results demonstrated that testosterone did not have a significant influence on CDO expression but significantly enhanced CSAD, androgen receptor (AR) expressions, and taurine levels in mouse liver, cultured hepatocytes, and HepG2 cells, whereas these effects were abrogated by AR antagonist flutamide. Furthermore, our results showed that testosterone increased CSAD-promoter-luciferase activity through the direct interaction of the AR DNA binding domain with the CSAD promoter. These findings first demonstrate that testosterone acts as an important factor to regulate sulfur amino acid metabolism and taurine synthesis through AR/CSAD signaling pathway. In addition, the in vivo and in vitro experiments showed that 17-β-estradiol has no significant effects on liver CSAD expression and taurine synthesis in male mice and suggest that the effects of sex steroids on the taurine synthesis in mouse liver have sex differences. These results are crucial for understanding the physiological functions of taurine/androgen and their interacting mechanisms in the liver.NEW & NOTEWORTHY This study demonstrates that testosterone functions to enhance taurine synthesis by interacting with androgen receptor and binding to cysteine sulfinate decarboxylase (CSAD) promoter zone. Whereas estrogen has no significant effects either on liver CSAD expression or taurine synthesis in male mice and suggests that the effects of sex steroids on taurine synthesis in the liver have gender differences. These new findings are the potential for establishing effective protective and therapeutic strategies for liver diseases.

Taurine induces upregulation of p53 and Beclin1 and has antitumor effect in human nasopharyngeal carcinoma cells in vitro and in vivo

Taurine is an amino acid that has several physiological functions. Previously, we reported the apoptosis-inducing effect of taurine in human nasopharyngeal carcinoma (NPC) cells in vitro. However, the effect of taurine on NPC cell growth in vivo has not been elucidated. Autophagy plays an important role in cell metabolism and exhibits antitumor effects under certain conditions. In this study, we investigated the effects of taurine on apoptosis- and autophagy-related molecules in NPC cells in vitro and in vivo. In our in vitro study, NPC cells (HK1-EBV) were treated with taurine, and Western blot and immunocytochemical analyses revealed that taurine co-upregulated Beclin 1 and p53, with autophagy upregulation. In the in vivo study, we used a nude mouse model with subcutaneous xenografts of HK1-EBV cells. Once the tumors reached 2-3 mm in diameter, the mice were provided with distilled water (control group) or taurine dissolved in distilled water (taurine-treated group) ad libitum (day 1) and sacrificed on day 13. The volume and weight of the tumors were significantly lower in the taurine-treated group. Using immunohistochemistry (IHC), we confirmed that taurine treatment reduced the distinct cancer nest areas. IHC analyses also revealed that taurine promoted apoptosis, as evidenced by an increase in cleaved caspase-3, accompanied by upregulation of p53. Additionally, taurine increased LC3B and Beclin 1 expression, which are typical autophagy markers. The present study demonstrated taurine-mediated tumor growth suppression. Therefore, taurine may be a novel preventive strategy for NPC.

Investigation of the protective mechanism of leonurine against acute myocardial ischemia by an integrated metabolomics and network pharmacology strategy

Background

Leonurus japonicus Houtt has an obvious efficacy on cardiovascular diseases. As the most representative component in the herb, leonurine has attracted increasing attention for its potential in myocardial ischemia. However, its protective mechanism against myocardial ischemia remains incompletely elucidated.

Objectives

The present study aimed to reveal the potential mechanism of leonurine in acute myocardial ischemia using a strategy combining metabolomics and network pharmacology.

Methods

First, a metabolomics method was proposed to identify the differential metabolites of plasma in rats. Then, network pharmacology was performed to screen candidate targets of leonurine against acute myocardial ischemia. A compound-reaction-enzyme-gene network was thus constructed with the differential metabolites and targets. Finally, molecular docking was carried out to predict the binding capability of leonurine with key targets.

Results

A total of 32 differential metabolites were identified in rat plasma, and 16 hub genes were detected through network pharmacology. According to the results of compound-reaction-enzyme-gene network and molecular docking, what was screened included six key targets (GSR, CYP2C9, BCHE, GSTP1, TGM2, and PLA2G2A) and seven differential metabolites (glycerylphosphorylcholine, lysophosphatidylcholine, choline phosphate, linoleic acid, 13-HpODE, tryptophan and glutamate) with four important metabolic pathways involved: glycerophospholopid metabolism, linoleic acid metabolism, tryptophan metabolism and glutamate metabolism. Among them, glycerophospholipid and tryptophan metabolism were shown to be important, since the regulation of leonurine on these two pathways was also observed in our previous metabolomics study conducted on clinical hyperlipidemia patients.

Conclusion

This is the first study of its kind to reveal the underlying mechanism of leonurine against acute myocardial ischemia through a strategy combining metabolomics and network pharmacology, which provides a valuable reference for the research on its future application.

Taurine reduction associated with heart dysfunction after real-world PM2.5 exposure in aged mice

Ambient PM_2.5 has been proved to be an independent risk factor for cardiovascular diseases; however, little information is available on the age-dependent effects of PM_2.5 on the cardiovascular system and the underlying mechanisms following chronic exposure. In this study, multi-aged mice were exposed to PM_2.5 via the newly developed real-ambient PM_2.5 exposure system to investigate age-related effects on the heart after long-term exposure. First, the chemical and physical properties of PM_2.5 used in the exposure system were analyzed. The heart rate of conscious mice was recorded, and results showed that exposure of aged mice to PM_2.5 for 26 weeks significantly increased heart rate. Histological analysis and ELISA assays indicated that aged mice were more sensitive to PM_2.5 exposure in terms of inducing cardiac oxidative stress and inflammation. Furthermore, untargeted metabolomics revealed that taurine was involved with the PM_2.5-induced cardiac dysfunction. The reduced taurine concentration in the heart was examined by LC-MS and imaging mass spectrometry; it may be due to the increased p53 expression level, ROS and inflammatory cytokines. These results emphasize the age-dependent effects of PM_2.5 on the cardiovascular system and suggest that taurine may be the novel cardiac effect target for PM_2.5-induced heart dysfunction in the aged.

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.

In vitro and in vivo study on prevention of myocardial ischemic injury by taurine

Background

Myocardial ischemia (MI) often causes angina, arrhythmia, and cardiac insufficiency, sometimes resulting in death. Ischemia-induced myocardial tissue damage is attributed to the hypoxic damage of myocardial cells producing apoptosis and decreased proliferation. Taurine has been shown to improve MI, but its mechanism is largely unknown.

Methods

In this study, the relationship between taurine and severity of MI in vivo was evaluated by quantifying myocardial infarct areas and metabolic indicators of myocardial damage and measuring taurine levels in cardiac muscle and plasma by high performance liquid chromatography (HPLC). To elucidate how taurine might suppress ischemic injury, we established an in vitro ischemia model with isolated primary rat cardiomyocytes cultured without serum or glucose and under hypoxia. We evaluated the indicators of MI and damage, including lactic dehydrogenase (LDH), creatine kinase (CK), and cardiac troponin I (cTnI). We also examined the levels of taurine transporter (TauT), cysteine dioxygenase (CDO), and cysteine sulfinate decarboxylase (CSD) proteins involved in transport and synthesis of taurine in the myocardium and those of 2 apoptosis-associated proteins, namely, Bcl-2 associated X protein (BAX) and B-cell lymphoma-2 (Bcl-2).

Results

Exposure of myocardial cells to ischemia led to the decrease of taurine content, the suppression of cell proliferation, and led to calcium ion overload and apoptosis. Pretreatment with taurine alleviated the ischemic damage, with concomitant elevation of intracellular taurine concentrations. Molecular mechanism analysis showed that pretreatment with taurine upregulated the TauT, CDO, and CSD, 2 rate-limiting enzymes involved in taurine synthesis. These effects facilitated both taurine transport into cells and taurine synthesis, leading to taurine accumulation. In addition, apoptosis inhibition by taurine appeared to be mediated by upregulated Bcl-2 and downregulated BAX, as well as inhibition of calcium overload by suppression of calcium binding protein.

Conclusions

We demonstrated that TauT is critical for the attenuation of myocardial ischemic damage by taurine, facilitating taurine absorption and synthesis. These findings provided new insights and a theoretical foundation for future studies examining taurine as a potential treatment for MI.

Taurine Alleviates Sympathetic Innervation by Inhibiting NLRP3 Inflammasome in Postinfarcted Rats

ABSTRACT

The NLRP3 inflammasome is activated by myocardial infarction and then induces the activation of inflammatory caspase-1 activation and maturation of IL-1β, a regulator of synthesis of the nerve growth factor (NGF). Here, we studied whether taurine, 2-aminoethanesulphonic acid, can attenuate cardiac sympathetic reinnervation by modulating NLRP3 inflammasome-mediated NGF in a rat model of myocardial infarction. Male Wistar rats were subjected to coronary ligation and then randomized to either saline or taurine for 3 days or 4 weeks. Postinfarction was associated with activation of NF-κB (p65) and NLRP3 inflammasome component and increased the protein and expression of IL-1β. Macrophages at the border zone were shown to be positive for IL-1β 3 days postinfarction. Compared with vehicle, infarcted rats treated with taurine significantly attenuated myocardial messenger RNA and protein levels of NF-κB, NLRP3 inflammasome, mature caspase-1, and IL-1β. Immunofluorescent analysis, real-time quantitative reverse transcription polymerase chain reaction, and Western blotting of NGF showed that sympathetic hyperinnervation was blunted after administering taurine. Arrhythmia vulnerability in the taurine-treated infarcted rats was significantly improved than those in vehicle. Ex vivo studies showed that taurine infusion reduced myocardial IL-1β level at the extent similar to either pyrrolidine dithiocarbamate or CP-456,773, inhibitors of NF-κB and NLRP3 inflammasome, implying the key axis of NF-κB/NLRP3 inflammasome in mediating taurine-related anti-inflammation. Furthermore, administration of anti-IL-1β antibody reduced NGF levels. Taurine attenuated sympathetic innervation mainly by NLRP3 inflammasome/IL-1β-dependent pathway, which downregulated expression of NGF in infarcted rats. These findings may provide a new insight into the anti-inflammation effect of taurine.

Evidence of endometrial amino acid metabolism and transport modulation by peri-ovulatory endocrine profiles driving uterine receptivity

Background

In beef cattle, changes in the periovulatory endocrine milieu are associated with fertility and conceptus growth. A large preovulatory follicle (POF) and the resulting elevated concentrations of progesterone (P4) during diestrus positively affect pregnancy rates. Amino acids (AA) are important components of maternally derived secretions that are crucial for embryonic survival before implantation. The hypothesis is that the size of the POF and the concentration of P4 in early diestrus modulate the endometrial abundance of SLC transcripts related to AA transport and metabolism and subsequently impact luminal concentrations of AA. The follicle growth of Nelore cows was manipulated to produce two experimental groups: large POF and CL (LF-LCL group) and small POF and CL (SF-SCL group). On Day 4 (D4; Experiment 1) and Day 7 (D7; Experiment 2) after GnRH-induced ovulation (GnRH treatment = D0), the animals were slaughtered and uterine tissues and uterine washings were collected. qRT-PCR was used to evaluate the expression levels of AA transporters in D4 and D7 endometrial tissues. The concentrations of AA were quantified in D4 and D7 uterine washings by HPLC.

Results

Transcript results show that, on D4, SLC6A6, SLC7A4, SLC17A5, SLC38A1, SLC38A7 and SCLY and on D7 SLC1A4, SLC6A1, SLC6A14, SLC7A4, SLC7A7, SLC7A8, SLC17A5, SLC38A1, SLC38A7, SLC43A2 and DDO were more abundant in the endometria of cows from the LF-LCL group (P < 0.05). In addition, concentrations of AA in the uterine lumen were influenced by the endocrine profiles of the mother. In this context, D4 uterine washings revealed that greater concentrations of taurine, alanine and α-aminobutyric acid were present in SF-SCL (P < 0.05). In contrast, lower concentrations of valine and cystathionine were quantified on D7 uterine washings from SF-SCL cows (P < 0.05).

Conclusion

The present study revealed an association between the abundance of transcripts related to AA transport and metabolism in the endometrium and specific periovulatory endocrine profiles related to the receptive status of the mother. Such insights suggest that AAs are involved in uterine function to support embryo development.

Effect of taurine on intestinal recovery following intestinal ischemia-reperfusion injury in a rat

PURPOSE

Taurine (TAU) is a sulfur-containing amino acid that is involved in a diverse array of biological and physiological functions, including bile salt conjugation, osmoregulation, membrane stabilization, calcium modulation, anti-oxidation, and immunomodulation. Several studies have established that treatment with TAU significantly protects cerebral, cardiac and testicular injury from ischemia-reperfusion (IR). The purpose of the present study was to examine the effect of TAU on intestinal recovery and enterocyte turnover after intestinal IR injury in rats.

METHODS

Male Sprague-Dawley rats were divided into four experimental groups: (1) Sham rats that underwent laparotomy, (2) Sham-TAU rats that underwent laparotomy and were treated with intraperitoneal (IP) TAU (250 mg/kg); (3) IR-rats that underwent occlusion of both superior mesenteric artery and portal vein for 30 min followed by 48 h of reperfusion, and (4) IR-TAU rats that underwent IR and were treated with IP TAU (250 mg/kg) immediately before abdominal closure. Intestinal structural changes, Park's injury score, enterocyte proliferation and enterocyte apoptosis were determined 24 h following IR. The expression of Bax, Bcl-2, p-ERK and caspase-3 in the intestinal mucosa was determined using Western blot and immunohistochemistry.

RESULTS

Treatment with TAU resulted in a significant decrease in Park's injury score compared to IR animals. IR-TAU rats also demonstrated a significant increase in mucosal weight in jejunum and ileum, villus height in jejunum and ileum and crypt depth in ileum compared to IR animals. IR-TAU rats also experienced significantly lower apoptotic indices in jejunum and ileum which was accompanied by a higher Bcl-2/Bax ratio compared to IR animals.

CONCLUSIONS

Treatment with taurine prevents gut mucosal damage and inhibits intestinal epithelial cell apoptosis following intestinal IR in a rat.

TonEBP modulates the protective effect of taurine in ischemia-induced cytotoxicity in cardiomyocytes

Taurine, which is found at high concentration in the heart, exerts several protective actions on myocardium. Physically, the high level of taurine in heart is maintained by a taurine transporter (TauT), the expression of which is suppressed under ischemic insult. Although taurine supplementation upregulates TauT expression, elevates the intracellular taurine content and ameliorates the ischemic injury of cardiomyocytes (CMs), little is known about the regulatory mechanisms of taurine governing TauT expression under ischemia. In this study, we describe the TonE (tonicity-responsive element)/TonEBP (TonE-binding protein) pathway involved in the taurine-regulated TauT expression in ischemic CMs. Taurine inhibited the ubiquitin-dependent proteasomal degradation of TonEBP, promoted the translocation of TonEBP into the nucleus, enhanced TauT promoter activity and finally upregulated TauT expression in CMs. In addition, we observed that TonEBP had an anti-apoptotic and anti-oxidative role in CMs under ischemia. Moreover, the protective effects of taurine on myocardial ischemia were TonEBP dependent. Collectively, our findings suggest that TonEBP is a core molecule in the protective mechanism of taurine in CMs under ischemic insult.

Calreticulin translocation aggravates endoplasmic reticulum stress-associated apoptosis during cardiomyocyte hypoxia/reoxygenation

Background:

Calreticulin (CRT) is major Ca²⁺-binding chaperone mainly resident in the endoplasmic reticulum (ER) lumen. Recently, it has been shown that non-ER CRT regulates a wide array of cellular responses. We previously found that CRT was up-regulated during hypoxia/reoxygenation (H/R) and this study was aimed to investigate whether CRT nuclear translocation aggravates ER stress (ERS)-associated apoptosis during H/R injury in neonatal rat cardiomyocytes.

Methods:

Apoptosis rate and lactate dehydrogenase (LDH) leakage in culture medium were measured as indices of cell injury. Immunofluorescence staining showed the morphological changes of ER and intracellular translocation of CRT. Western blotting or reverse transcription polymerase chain reaction was used to detect the expression of target molecules.

Results:

Compared with control, H/R increased apoptosis rate and LDH activity. The ER became condensed and bubbled, and CRT translocated to the nucleus. Western blotting showed up-regulation of CRT, Nrf2, activating transcription factor 4 (ATF4), CHOP and caspase-12 expression after H/R. Exogenous CRT overexpression induced by plasmid transfection before H/R increased cell apoptosis, LDH leakage, ER disorder, CRT nuclear translocation and the expression of ERS-associated molecules. However, administration of the ERS inhibitor, taurine, or CRT siRNA alleviated cell injury, ER disorder, and inhibited ERS-associated apoptosis.

Conclusions:

Our results indicated that during H/R stress, CRT translocation increases cell apoptosis and LDH leakage, aggravates ER disorder, up-regulates expression of nuclear transcription factors, Nrf2 and ATF4, and activates ERS-associated apoptosis.