Abstract
Because taurine alleviates ethanol- (EtOH-) induced lipid peroxidation and liver damage in rats, we asked whether exogenous taurine could alleviate EtOH-induced oxidative stress in chick embryos. Exogenous EtOH (1.5 mmol/Kg egg or 3 mmol/Kg egg), taurine (4 μmol/Kg egg), or EtOH and taurine (1.5 mmol EtOH and 4 μmol taurine/Kg egg or 3 mmol EtOH and 4 μmol taurine/Kg egg) were injected into fertile chicken eggs during the first three days of embryonic development (E0–2). At 11 days of development (midembryogenesis), serum taurine levels and brain caspase-3 activities, homocysteine (HoCys) levels, reduced glutathione (GSH) levels, membrane fatty acid composition, and lipid hydroperoxide (LPO) levels were measured. Early embryonic EtOH exposure caused increased brain apoptosis rates (caspase-3 activities); increased brain HoCys levels; increased oxidative-stress, as measured by decreased brain GSH levels; decreased brain long-chain polyunsaturated levels; and increased brain LPO levels. Although taurine is reported to be an antioxidant, exogenous taurine was embryopathic and caused increased apoptosis rates (caspase-3 activities); increased brain HoCys levels; increased oxidative-stress (decreased brain GSH levels); decreased brain long-chain polyunsaturated levels; and increased brain LPO levels. Combined EtOH and taurine treatments also caused increased apoptosis rates and oxidative stress.
Highlights
Exogenous ethanol (EtOH) causes elevated brain and hepatic homocysteine (HoCys) levels, decreased brain and hepatic taurine levels, and increased apoptosis rates within embryonic chick brains and livers [1,2,3]
HoCys is converted to cystathionine through the use of cystathionine β-synthase (EC 4.2.1.22) and cystathionine is converted into αketobutyrate, reduced glutathione (GSH), or taurine [9, 10] (Figure 1)
Because EtOH reduced taurine levels within embryonic chick brains [2, 3], the overall objective of this study was to determine if taurine supplementation alleviated EtOH-induced oxidative stress within embryonic chick brains
Summary
Exogenous ethanol (EtOH) causes elevated brain and hepatic homocysteine (HoCys) levels, decreased brain and hepatic taurine levels, and increased apoptosis rates within embryonic chick brains and livers [1,2,3]. Exogenous EtOH and exogenous HoCys are both teratogenic in chick embryos. HoCys catabolism uses remethylation pathways and the transsulfuration pathway (Figure 1). HoCys is remethylated back to methionine by using either betaine homocysteine methyltransferase (EC 2.1.1.15; non-folate-dependent remethylation), or the cobalamindependent enzyme, methionine synthase (EC 2.1.1.13), which uses 5-methyltetrahydrofolate as the methyl donor [9]. HoCys is converted to cystathionine through the use of cystathionine β-synthase (EC 4.2.1.22) and cystathionine is converted into αketobutyrate, reduced glutathione (GSH), or taurine [9, 10] (Figure 1)
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