Protective Effect of a Fermented Substance from Saccharomyces cerevisiae on Liver Injury in Mice Caused by Acetaminophen

The protective effect of a fermented substance from Saccharomyces cerevisiae (FSSC) on liver injury caused by acetaminophen (AAP) was studied in mice. Mice were pretreated with FSSC (0.5–2.0 g/kg, p.o.) for 4 d, and on the fourth day, the mice received an overdose of AAP (500 mg/kg, i.p.). Subsequently, they were sacrificed at 7 h, and blood was drawn from the abdominal vein and liver samples were collected. Histological and biochemical examinations revealed that the administration of AAP caused liver injury in the mice, including increases in plasma alanine aminotransferase and asparate aminotransferase activities and decreases in the hepatic reduced form of glutathione (GSH) content and antioxidant enzyme activities. Prior to AAP treatment, the mice pretreated with FSSC showed significantly reduced levels of alanine aminotransferase (ALT) and aspirate aminotransferase (AST) activity. Liver histology in the FSSC-pretreated mice was significant. In these mice, pretreatment with FSSC also served to reduce hepatic GSH depletion and the inhibition of antioxidant enzyme activity caused by AAP overdose. In conclusion, oral administration of FSSC significantly reduced AAP-induced hepatic injury in the mice.     

Protective Effects of Pterostilbene against Acetaminophen‐Induced Hepatotoxicity in Rats

The present study was undertaken to evaluate the protective effect of pterostilbene against acetaminophen‐induced hepatotoxicity. Silymarin was used as a standard hepatoprotective agent. A single dose of acetaminophen (800 mg/kg i.p.), injected to male rats, caused significant increases in serum levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, bilirubin, total cholesterol, triglycerides, tumor necrosis factor alpha, and hepatic contents of malondialdehyde, nitric oxide, caspase‐3, hydroxyproline, with significant decreases in serum HDL‐cholesterol, total proteins, albumin, and hepatic activities of reduced glutathione, superoxide dismutase and catalase as compared with the control group. On the other hand, administration of each of pterostilbene (50 mg/kg, p.o.) and silymarin (100 mg/kg, p.o.) for 15 days before acetaminophen ameliorated liver function and oxidative stress parameters. Histopathological evidence confirmed the protection offered by pterostilbene from the tissue damage caused by acetaminophen. In conclusion, pterostilbene possesses multimechanistic hepatoprotective activity that can be attributed to its antioxidant, anti‐inflammatory, and antiapoptotic actions.     

Anticonvulsant Activity of Enantiomeric N‐trans‐Cinnamoyl Derivatives of 2‐Aminopropan‐1‐ols and 2‐Aminobutan‐1‐ols

Epilepsy, one of the most frequent neurological disorders, is still insufficiently treated in about 30% of patients. As a consequence, identification of novel anticonvulsant agents is an important issue in medicinal chemistry. In the present article we report synthesis, physicochemical, and pharmacological evaluation of N‐trans‐cinnamoyl derivatives of R and S‐2‐aminopropan‐1‐ol, as well as R and S‐2‐aminobutan‐1‐ol. The structures were confirmed by spectroscopy and for derivatives of 2‐aminopropan‐1‐ols the configuration was evaluated by means of crystallography. The investigated compounds were tested in rodent models of seizures: maximal electroshock (MES) and subcutaneous pentetrazol test (scPTZ), and also in a rodent model of epileptogenesis: pilocarpine‐induced status prevention. Additionally, derivatives of 2‐aminopropan‐1‐ols were tested in benzodiazepine‐resistant electrographic status epilepticus rat model as well as in vitro for inhibition of isoenzymes of cytochrome P450. All of the tested compounds showed promising anticonvulsant activity in MES. For R(–)‐(2E)‐N‐(1‐hydroxypropan‐2‐yl)‐3‐phenylprop‐2‐enamide pharmacological parameters were found as follows: ED₅₀ = 76.7 (68.2–81.3) mg/kg (MES, mice i.p., time = 0.5 h), ED₅₀ = 127.2 (102.1–157.9) mg/kg (scPTZ, mice i.p., time = 0.25 h), TD₅₀ = 208.3 (151.4–230.6) mg/kg (rotarod, mice i.p., time = 0.25 h). Evaluation in pilocarpine status prevention proved that all of the reported compounds reduced spontaneous seizure activity and act as antiepileptogenic agents. Both enantiomers of 2‐aminopropan‐1‐ols did not influence cytochrome P450 isoenzymes activity in vitro and are likely not to interact with CYP substrates in vivo. Chirality 28:482–488, 2016. © 2016 Wiley Periodicals, Inc.     

Protective effect of a fermented substance from Saccharomyces cerevisiae on liver injury in mice caused by acetaminophen

The protective effect of a fermented substance from Saccharomyces cerevisiae (FSSC) on liver injury caused by acetaminophen (AAP) was studied in mice. Mice were pretreated with FSSC (0.5-2.0 g/kg, p.o.) for 4 d, and on the fourth day, the mice received an overdose of AAP (500 mg/kg, i.p.). Subsequently, they were sacrificed at 7 h, and blood was drawn from the abdominal vein and liver samples were collected. Histological and biochemical examinations revealed that the administration of AAP caused liver injury in the mice, including increases in plasma alanine aminotransferase and asparate aminotransferase activities and decreases in the hepatic reduced form of glutathione (GSH) content and antioxidant enzyme activities. Prior to AAP treatment, the mice pretreated with FSSC showed significantly reduced levels of alanine aminotransferase (ALT) and aspirate aminotransferase (AST) activity. Liver histology in the FSSC-pretreated mice was significant. In these mice, pretreatment with FSSC also served to reduce hepatic GSH depletion and the inhibition of antioxidant enzyme activity caused by AAP overdose. In conclusion, oral administration of FSSC significantly reduced AAP-induced hepatic injury in the mice.     

MMP‐13 deletion decreases profibrogenic molecules and attenuates N‐nitrosodimethylamine‐induced liver injury and fibrosis in mice

Connective tissue growth factor (CTGF) is involved in inflammation, pathogenesis and progression of liver fibrosis. Matrix metalloproteinase‐13 (MMP‐13) cleaves CTGF and releases several fragments, which are more potent than the parent molecule to induce fibrosis. The current study was aimed to elucidate the significance of MMP‐13 and CTGF and their downstream effects in liver injury and fibrosis. Hepatic fibrosis was induced using intraperitoneal injections of N‐nitrosodimethylamine (NDMA) in doses of 10 μg/g body weight on three consecutive days of each week over a period of 4 weeks in both wild‐type (WT) and MMP‐13 knockout mice. Administration of NDMA resulted in marked elevation of AST, ALT, TGF‐β1 and hyaluronic acid in the serum and activation of stellate cells, massive necrosis, deposition of collagen fibres and increase in total collagen in the liver of WT mice with a significant decrease in MMP‐13 knockout mice. Protein and mRNA levels of CTGF, TGF‐β1, α‐SMA and type I collagen and the levels of MMP‐2, MMP‐9 and cleaved products of CTGF were markedly increased in NDMA‐treated WT mice compared to the MMP‐13 knockout mice. Blocking of MMP‐13 with CL‐82198 in hepatic stellate cell cultures resulted in marked decrease of the staining intensity of CTGF as well as protein levels of full‐length CTGF and its C‐terminal fragments and active TGF‐β1. The data demonstrate that MMP‐13 and CTGF play a crucial role in modulation of fibrogenic mediators and promote hepatic fibrogenesis. Furthermore, the study suggests that blocking of MMP‐13 and CTGF has potential therapeutic implications to arrest liver fibrosis.     

Hepatoprotective effect of bis(4‐methylbenzoyl) diselenide against CCl4‐induced oxidative damage in mice

From a pharmacological point of view, organoseleniums are compounds with important and interesting antioxidant and biological activities. The aim of this study was to evaluate the hepatoprotective effect of bis(4‐methylbenzoyl) diselenide (BMD) against carbon tetrachloride (CCl₄)–induced oxidative damage in mice. The animals received BMD (25 mg/kg p.o., for 3 days), and after 1 day, CCl₄ (1 mg/kg body weight) was administered by intraperitoneal route. One day after the CCl₄ exposure, the animals were euthanized for biochemical and histological analysis. Treatment with BMD (25 mg/kg p.o.) protected against aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, gamma‐glutamyl transferase and lactate dehydrogenase activity increases induced by CCl₄ plasma exposure. Treatment with BMD (25 mg/kg) protected against increases in thiobarbituric reactive species and decreasing non‐protein thiols and ascorbic acid levels in liver of mice. Catalase and superoxide dismutase activity inhibition in the liver caused by CCl₄ were protected by treatment with BMD (25 mg/kg). Glutathione S‐transferase activity was inhibited by CCl₄ and remained unaltered even after treatment with BMD. Sections of liver from CCl₄‐exposed mice presented an intense infiltration of inflammatory cells and loss of the cellular architecture. BMD (25 mg/kg) attenuated CCl₄‐induced hepatic histological alterations. The results demonstrated the hepatoprotective effects of BMD in the mouse liver, possibly by modulating the antioxidant status. Copyright © 2012 John Wiley & Sons, Ltd.     

Inhibition of NAALADase by 2‐PMPA attenuates cocaine‐induced relapse in rats: a NAAG‐mGluR2/3‐mediated mechanism

Pharmacological activation of group II metabotropic glutamate receptors (mGluR2/3) inhibits cocaine self‐administration and reinstatement of drug‐seeking behavior, suggesting a possible use of mGluR2/3 agonists in the treatment of cocaine dependence. In this study, we investigated whether elevation of the endogenous mGluR2/3 ligand N‐acetyl‐aspartatylglutamate (NAAG) levels by the N‐acetylated‐alpha‐linked‐acidic dipeptidase inhibitor 2‐(phosphonomethyl)pentanedioic acid (2‐PMPA) attenuates cocaine self‐administration and cocaine‐induced reinstatement of drug seeking. N‐acetylated‐alpha‐linked‐acidic dipeptidase is a NAAG degradation enzyme that hydrolyzes NAAG to N‐acetylaspartate and glutamate. Systemic administration of 2‐PMPA (10‐100 mg/kg, i.p.) inhibited intravenous self‐administration maintained by low unit doses of cocaine and cocaine (but not sucrose)‐induced reinstatement of drug‐seeking behavior. Microinjections of 2‐PMPA (3–5 μg/side) or NAAG (3–5 μg/side) into the nucleus accumbens (NAc), but not into the dorsal striatum, also inhibited cocaine‐induced reinstatement, an effect that was blocked by intra‐NAc injection of LY341495, a selective mGluR2/3 antagonist. In vivo microdialysis demonstrated that 2‐PMPA (10‐100 mg/kg, i.p.) produced a dose‐dependent reduction in both extracellular dopamine (DA) and glutamate, an effect that was also blocked by LY341495. Finally, pre‐treatment with 2‐PMPA partially attenuated cocaine‐enhanced extracellular NAc DA, while completely blocking cocaine‐enhanced extracellular NAc glutamate in rats during reinstatement testing. Intra‐NAc perfusion of LY341495 blocked 2‐PMPA‐induced reductions in cocaine‐enhanced extracellular NAc glutamate, but not DA. These findings suggest that 2‐PMPA is effective in attenuating cocaine‐induced reinstatement of drug‐seeking behavior, likely by attenuating cocaine‐induced increases in NAc DA and glutamate via pre‐synaptic mGluR2/3s.     

Effect of acetaminophen on hepatic content and biliary efflux of glutathione disulfide in mice

The increased expiration of ethane and pentane by mice treated with hepatotoxic doses of acetaminophen suggests the possibility of oxidant mechanisms associated with the necrosis. However, studies in rats are not consistent with oxidant stress mechanisms causing the damage, because acetaminophen given to rats does not increase GSSG efflux, a sensitive index of intrahepatic oxidant stress. To compare the extent of oxidant stress generated by acetaminophen in mice versus rats, hepatic content and biliary efflux of GSSG and GSH in mice have been examined. Bile was collected from anesthetized male ICR mice before and after intraperitoneal administration of acetaminophen (325 mg/kg, 2.15 mmol/kg), t-butyl hydroperoxide (TBHP) (1.5 mmol/kg), diethyl maleate (400 mg/kg, 2.33 mmol/kg, in corn oil) or saline (control) and GSH and GSSG were measured by the enzymatic recycling method of Tietze. An increase in biliary GSSG efflux was produced by t-butyl hydroperoxide, but not by the other agents. Biliary GSH/GSSG ratios decreased in acetaminophen-treated animals, presumably reflecting the marked depletion of hepatic GSH, since a similar decrease was observed with non-hepatotoxic doses of diethyl maleate. The failure of acetaminophen to increase the hepatic content or biliary efflux of GSSG in ICR mice is not consistent with the view that oxidant stress mechanisms cause the damage, despite the increases in alkanes expired after acetaminophen administration in this specific animal model.     

The interplay of LncRNA ANRIL and miR‐181b on the inflammation‐relevant coronary artery disease through mediating NF‐κB signalling pathway

This study was designed to investigate whether ANRIL affected the aetiology of coronary artery disease (CAD) by acting on downstream miR‐181b and NF‐κB signalling. Altogether 327 CAD patients diagnosed by angiography were included, and mice models of CAD were established. Human coronary endothelial cells (HCAECs) and human umbilical vein endothelial cells (HUVECs) were also purchased. In addition, shRNA‐ANRIL, shRNA‐NC, pcDNA3.1‐ANRIL, miR‐181b mimic, miR‐181b inhibitor and miR‐NC were transfected into the cells. The lipopolysaccharides (LPS) and pyrrolidine dithiocarbamate (PDTC) were also added to activate or deactivate NF‐κB signalling. Both highly expressed ANRIL and lowly expressed miR‐181b were associated with CAD population aged over 60 years old, with smoking history, with hypertension and hyperlipidemia, with CHOL H 4.34 mmol/L, TG ≥ 1.93 mmol/L and Hcy ≥ 16.8 μmol/L (all P < 0.05). Besides, IL‐6, IL‐8, NF‐κB, TNF‐α, iNOS, ICAM‐1, VCAM‐1 and COX‐2 expressions observed within AD mice models were all beyond those within NC and sham‐operated groups (P < 0.05). Also VEGF and HSP 70 were highly expressed within AD mice models than within NC and sham‐operated mice (P < 0.05). Transfection of either pcDNA‐ANRIL or miR‐181b inhibitor could significantly fortify HCAECs’ viability and put on their survival rate. At the meantime, the inflammatory factors and vascular‐protective parameters were released to a greater level (P < 0.05). Finally, highly expressed ANRIL also notably bring down miR‐181b expression and raise p50/p65 expressions within HCAECs (P < 0.05). The joint role of ANRIL, miR‐181b and NF‐κB signalling could aid in further treating and diagnosing CAD.     

NR2B‐deficient mice are more sensitive to the locomotor stimulant and depressant effects of ethanol

The NR2B subunit of N‐methyl d ‐aspartate glutamate receptors influences pharmacological properties and confers greater sensitivity to the modulatory effects of ethanol. This study examined behavioral responses to acute ethanol in a conditional knockout mouse model that allowed for a delayed genetic deletion of the NR2B subunit to avoid mouse lethality. Mice lacking the NR2B gene (knockout) were produced by mating NR2B[f/f] mice with CAMKIIa‐driven tTA transgenic mice and the tetO‐CRE transgenic mice. Adult male and female offspring representing each of the resultant genotypes (knockout, CAM, CRE and wildtype mice) were tested for open‐field locomotor activity following acute low‐ and high‐dose ethanol challenge as well as loss of righting reflex. Findings indicate that male and female mice lacking the NR2B subunit exhibited greater overall activity in comparison to other genotypes during the baseline locomotor activity test. NR2B knockout mice exhibited an exaggerated stimulant response to 1.5 g/kg (i.p.) and an exaggerated depressant response to 3.0 g/kg (i.p.) ethanol challenge. In addition, NR2B knockout mice slept longer following a high dose of ethanol (4.0 g/kg, i.p.). To evaluate pharmacokinetics, clearance rates of ethanol (1.5, 4.0 g/kg, i.p.) were measured and showed that female NR2B knockouts had a faster rate of metabolism only at the higher ethanol dose. Western blot analyses confirmed significant reduction in NR2B expression in the forebrain of knockout mice. Collectively, these data indicate that the NR2B subunit of the N‐methyl d ‐aspartate glutamate receptor is involved in regulating low‐dose stimulant effects of ethanol and the depressant/hypnotic effects of ethanol.     

Circ‐AKT3 inhibits the accumulation of extracellular matrix of mesangial cells in diabetic nephropathy via modulating miR‐296‐3p/E‐cadherin signals

Diabetic nephropathy is a leading cause of end‐stage renal disease globally. The vital role of circular RNAs (circRNAs) has been reported in diabetic nephropathy progression, but the molecular mechanism linking diabetic nephropathy to circRNAs remains elusive. In this study, we investigated the significant function of circ‐AKT3/miR‐296‐3p/E‐cadherin regulatory network on the extracellular matrix accumulation in mesangial cells in diabetic nephropathy. The expression of circ‐AKT3 and fibrosis‐associated proteins, including fibronectin, collagen type I and collagen type IV, was assessed via RT‐PCR and Western blot analysis in diabetic nephropathy animal model and mouse mesangial SV40‐MES13 cells. Luciferase reporter assays were used to investigate interactions among E‐cadherin, circ‐AKT3 and miR‐296‐3p in mouse mesangial SV40‐MES13 cells. Cell apoptosis was evaluated via flow cytometry. The level of circ‐AKT3 was significantly lower in diabetic nephropathy mice model group and mouse mesangial SV40‐MES13 cells treated with high‐concentration (25 mmol/L) glucose. In addition, circ‐AKT3 overexpression inhibited the level of fibrosis‐associated protein, such as fibronectin, collagen type I and collagen type IV. Circ‐AKT3 overexpression also inhibited the apoptosis of mouse mesangial SV40‐MES13 cells treated with high glucose. Luciferase reporter assay and bioinformatics tools identified that circ‐AKT3 could act as a sponge of miR‐296‐3p and E‐cadherin was the miR‐296‐3p direct target. Moreover, circ‐AKT3/miR‐296‐3p/E‐cadherin modulated the extracellular matrix of mouse mesangial cells in high‐concentration (25 mmol/L) glucose, inhibiting the synthesis of related extracellular matrix protein. In conclusion, circ‐AKT3 inhibited the extracellular matrix accumulation in diabetic nephropathy mesangial cells through modulating miR‐296‐3p/E‐cadherin signals, which might offer novel potential opportunities for clinical diagnosis targets and therapeutic biomarkers for diabetic nephropathy.     

Lophirones B and C halt acetaminophen hepatotoxicity by upregulating redox transcription factor Nrf‐2 through Akt,PI3K,and PKC pathways

We investigated the mechanism of lophirones B‐ and C‐mediated protection against acetaminophen hepatotoxicity. Mice were pretreated with 20 mg/kg body weight lophirones B and C for 7 days and challenged with acetaminophen on day 7. Acetaminophen raised nuclear factor‐κB (NF‐κB) in the liver of mice but lowered protein kinase B (Akt). Although, acetaminophen produced no significant alteration on nuclear erythroid related factor‐2 (Nrf‐2), phosphoinositide 3‐kinase (PI3K) and protein kinase C (PKC), lophirones B and C raised the level of these proteins and Akt. The acetaminophen‐mediated increase in NF‐κB was significantly reversed by lophirones B and C. Lophirones B and C prevented acetaminophen‐mediated alterations in serum biomarkers of hepatic injury. Similarly, lophirones B and C lowered the biomarkers of oxidative stress in the liver of acetaminophen‐treated mice. It can be inferred from this study that lophirones B and C prevent acetaminophen‐induced liver injury by enhancing Nrf‐2 through Akt, PI3K, and PKC pathways.     

A convenient microwave‐enhanced solid‐phase synthesis of short chain N‐methyl‐rich peptides

Structural modification of the peptide backbone via N‐methylation is a powerful tool to modulate the pharmacokinetic profile and biological activity of peptides. Here we describe a rapid and highly efficient microwave(MW)‐assisted Fmoc/tBu solid‐phase method to prepare short chain N‐methyl‐rich peptides, using Rink amide p‐methylbenzhydrylamine (MBHA) resin as solid‐phase support. This method produces peptides in high yield and purity, and reduces the time required for Fmoc‐N‐methyl amino acid coupling. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

MicroRNA‐27a‐3p suppression of peroxisome proliferator‐activated receptor‐γ contributes to cognitive impairments resulting from sevoflurane treatment

Sevoflurane is the most widely used anaesthetic administered by inhalation. Exposure to sevoflurane in neonatal mice can induce learning deficits and abnormal social behaviours. MicroRNA (miR)‐27a‐3p, a short, non‐coding RNA that functions as a tumour suppressor, is up‐regulated after inhalation of anaesthetic, and peroxisome proliferator‐activated receptor γ (PPAR‐γ) is one of its target genes. The objective of this study was to investigate how the miR‐27a‐3p–PPAR‐γ interaction affects sevoflurane‐induced neurotoxicity. A luciferase reporter assay was employed to identify the interaction between miR‐27a‐3p and PPAR‐γ. Primary hippocampal neuron cultures prepared from embryonic day 0 C57BL/6 mice were treated with miR‐27a‐3p inhibitor or a PPAR‐γ agonist to determine the effect of miR‐27a‐3p and PPAR‐γ on sevoflurane‐induced cellular damage. Cellular damage was assessed by a flow cytometry assay to detect apoptotic cells, immunofluorescence to detect reactive oxygen species, western blotting to detect NADPH oxidase 1/4 and ELISA to measure inflammatory cytokine levels. In vivo experiments were performed using a sevoflurane‐induced anaesthetic mouse model to analyse the effects of miR‐27a‐3p on neurotoxicity by measuring the number of apoptotic neurons using the Terminal‐deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) method and learning and memory function by employing the Morris water maze test. Our results revealed that PPAR‐γ expression was down‐regulated by miR‐27a‐3p following sevoflurane treatment in hippocampal neurons. Down‐regulation of miR‐27a‐3p expression decreased sevoflurane‐induced hippocampal neuron apoptosis by decreasing inflammation and oxidative stress‐related protein expression through the up‐regulation of PPAR‐γ. In vivo tests further confirmed that inhibition of miR‐27a‐3p expression attenuated sevoflurane‐induced neuronal apoptosis and learning and memory impairment. Our findings suggest that down‐regulation of miR‐27a‐3p expression ameliorated sevoflurane‐induced neurotoxicity and learning and memory impairment through the PPAR‐γ signalling pathway. MicroRNA‐27a‐3p may, therefore, be a potential therapeutic target for preventing or treating sevoflurane‐induced neurotoxicity.

     

Double-prodrugs of L-cysteine: differential protection against acetaminophen-induced hepatotoxicity in mice

A series of double-prodrugs of L-cysteine, designed to release L-cysteine in vivo and stimulate the biosynthesis of glutathione (GSH), were synthesized. To evaluate the hepatoprotective effectiveness of these double-prodrugs, male Swiss-Webster mice were administered acetaminophen (ACP) (2.45 mmol/kg (360 mg/kg), intraperitoneally (i.p.)). Prodrug (2.50 mmol/kg, i.p. or 1.25 mmol/kg, i.p., depending on the protocol) was administered 1 h before ACP as a priming dose. A supplementary dose of prodrug (2.5 mmol/kg, i.p. or 1.25 mmol/kg, i.p. depending on the protocol) was administered 0.5 h after ACP. The plasma alanine amino transferase (ALT) values, 24 h after ACP administration were transformed to logs and the 95% and 99% confidence intervals of the log values were plotted and compared for each group. Hepatoprotection was assessed by the degree of attenuation of plasma ALT levels. With these multiple dose schedules, the use of 2% carboxymethylcellulose as vehicle for the prodrugs was found to be detrimental; therefore, the prodrugs were dissolved in dilute aqueous base and the pH adjusted for administration. When a priming dose was given 1 h before ACP followed by a supplementary dose 0.5 h after ACP, only N,S-bis-acetyl-L-cysteine, where both the sulfhydryl and amino groups of L-cysteine were functionalized with the acetyl group, was found to be effective in protecting mice against the hepatotoxic effects of ACP. This suggests that these acetyl groups were rapidly hydrolyzed in vivo to liberate L-cysteine. In contrast, N-acetylation of 2(R,S)-methylthiazolidine-4(R)-carboxylic acid (MTCA) and its 2-n-propyl analog (PTCA), or N-acetylation of 2-oxothiazolidine-4-carboxylic acid (OTCA), reduced the hepatoprotective effects relative to the parent MTCA, PTCA, and OTCA, indicating that the release of L-cysteine in vivo from these N-acetylated thiazolidine prodrugs was metabolically unfavorable. The carbethoxy group, whether functionalized on the sulfhydryl or on the amino group of L-cysteine, or on the secondary amino group of MTCA, appears to be a poor "pro-moiety," since these carbethoxylated double-prodrugs of L-cysteine did not protect mice from ACP-induced hepatotoxicity.     

Changes in muscle free carnitine and acetylcarnitine with increasing work intensity in the Thoroughbred horse

Treadmill exercise in Thoroughbred horses of 2 min duration and increasing intensity resulted in increased formation and accumulation of acetylcarnitine in the working middle gluteal muscle. At high work intensities a plateau in acetylcarnitine formation was reached corresponding to approximately 70% of the total carnitine pool (approx. 30 mmol.kg-1 dry muscle). Formation of acetylcarnitine was mirrored by an equal fall in the free carnitine content, which stabilised, at the highest work intensities, at around 8 mmol.kg-1 dry muscle. Acetylcarnitine and carnitine reached their point of maximum change at a work intensity just below that resulting in the rapid production and accumulation of lactate and glycerol 3-phosphate. It is possible that the formation of acetylcarnitine is important in the regulation of the intramitochondrial acetyl CoA/CoA ratio; equally these changes may represent a blocking mechanism aimed at preventing the transfer of unwanted free fatty acids (as acylcarnitines) into the mitochondria at work intensities where they could contribute little to energy production.