Effects on ALS
In rat vascular smooth muscle cells, homocysteine (5 mmol/L) and other ER stress inducers, including A23187, were found to decrease EC-SOD mRNA expression and protein secretion. Furthermore, they upregulated GRP78 mRNA expression and activated PERK. Taurine (0.5 to 10 mmol/L), conversely, prevented these actions induced by homocysteine.
- Takatani et al.: Taurine inhibits apoptosis by preventing formation of the Apaf-1/caspase-9 apoptosome. Am. J. Physiol., Cell Physiol. 2004;287:C949-53. PMID: 15253891. DOI. Cardiomyocyte apoptosis contributes to cell death during myocardial infarction. One of the factors that regulate the degree of apoptosis during ischemia is the amino acid taurine. To study the mechanism underlying the beneficial effect of taurine, we examined the interaction between taurine and mitochondria-mediated apoptosis using a simulated ischemia model with cultured rat neonatal cardiomyocytes sealed in closed flasks. Exposure to medium containing 20 mM taurine reduced the degree of apoptosis following periods of ischemia varying from 24 to 72 h. In the untreated group, simulated ischemia for 24 h led to mitochondrial depolarization accompanied by cytochrome c release. The apoptotic cascade was also activated, as evidenced by the activation of caspase-9 and -3. Taurine treatment had no effect on mitochondrial membrane potential and cytochrome c release; however, it inhibited ischemia-induced cleavage of caspase-9 and -3. Taurine loading also suppressed the formation of the Apaf-1/caspase-9 apoptosome and the interaction of caspase-9 with Apaf-1. These findings demonstrate that taurine effectively prevents myocardial ischemia-induced apoptosis by inhibiting the assembly of the Apaf-1/caspase-9 apoptosome.
- Sun et al.: Protective functions of taurine against experimental stroke through depressing mitochondria-mediated cell death in rats. Amino Acids 2011;40:1419-29. PMID: 20862501. DOI. Taurine, an abundant amino acid in the nervous system, is reported to reduce ischemic brain injury in a dose-dependent manner. This study was designed to investigate whether taurine protected brain against experimental stroke through affecting mitochondria-mediated cell death pathway. Rats were subjected to 2-h ischemia by intraluminal filament, and then reperfused for 22 h. It was confirmed again that taurine (50 mg/kg) administered intravenously 1 h after ischemia markedly improved neurological function and decreased infarct volume at 22 h after reperfusion. In vehicle-treated rats, the levels of intracellular ATP and the levels of cytosolic and mitochondrial Bcl-xL in the penumbra and core were markedly reduced, while the levels of cytosolic Bax in the core and mitochondrial Bax in the penumbra and core were enhanced significantly. There was a decrease in cytochrome C in mitochondria and an increase in cytochrome C in the cytosol of the penumbra and core. These changes were reversed by taurine. Furthermore, taurine inhibited the activation of calpain and caspase-3, reduced the degradation of αII-spectrin, and attenuated the necrotic and apoptotic cell death in the penumbra and core. These data demonstrated that preserving the mitochondrial function and blocking the mitochondria-mediated cell death pathway may be one mechanism of taurine's action against brain ischemia.
- Kumari et al.: Taurine and its neuroprotective role. Adv. Exp. Med. Biol. 2013;775:19-27. PMID: 23392921. DOI. Taurine plays multiple roles in the CNS including acting as a -neuro-modulator, an osmoregulator, a regulator of cytoplasmic calcium levels, a trophic factor in development, and a neuroprotectant. In neurons taurine has been shown to prevent mitochondrial dysfunction and to protect against endoplasmic reticulum (ER) stress associated with neurological disorders. In cortical neurons in culture taurine protects against excitotoxicity through reversing an increase in levels of key ER signaling components including eIF-2-alpha and cleaved ATF6. The role of communication between the ER and mitochondrion is also important and examples are presented of protection by taurine against ER stress together with prevention of subsequent mitochondrial initiated apoptosis.
- Nonaka et al.: Taurine prevents the decrease in expression and secretion of extracellular superoxide dismutase induced by homocysteine: amelioration of homocysteine-induced endoplasmic reticulum stress by taurine. Circulation 2001;104:1165-70. PMID: 11535574. BACKGROUND: Hyperhomocysteinemia is an independent risk factor for atherosclerosis. Homocysteine has been shown to induce endoplasmic reticulum (ER) stress in vascular endothelial cells. ER stress is a condition in which glycoprotein trafficking is disrupted and unfolded proteins accumulate in the ER. ER molecular chaperons, such as GRP78, are induced and an ER resident kinase, PERK, is activated when cells are subjected to ER stress. Conversely, taurine is reported to have antiatherogenic effects by unknown mechanisms. To elucidate the mechanisms by which homocysteine induces atherosclerosis and taurine prevents it, we examined whether homocysteine and taurine affect the expression and secretion of extracellular superoxide dismutase (EC-SOD), a glycoprotein secreted from vascular smooth muscle cells (VSMCs) that protects the vascular wall from oxidative stress. METHODS AND RESULTS: We assessed the expression of EC-SOD and GRP78 mRNA in cultured rat VSMCs by Northern blot analysis. The EC-SOD protein secreted into the culture medium was examined by Western blot analysis. Homocysteine (5 mmol/L) and other ER stress inducers, including A23187, were found to decrease EC-SOD mRNA expression and protein secretion. Furthermore, they upregulated GRP78 mRNA expression and activated PERK. Taurine (0.5 to 10 mmol/L), conversely, prevented these actions induced by homocysteine. CONCLUSIONS: Homocysteine induces ER stress and reduces the secretion and expression of EC-SOD in VSMCs, leading to increased oxidative stress in the vascular wall. Taurine restores the secretion and expression of EC-SOD by ameliorating ER stress induced by homocysteine.