Trehalose administration attenuates atherosclerosis in rabbits fed a high-fat diet

Disruption of macrophage autophagy is a major contributor to macrophage dysfunction and subsequent inflammation leading to atherosclerosis. Trehalose is a natural disaccharide that is able to induce macrophage autophagy-lysosomal biogenesis and reduce inflammation. Here, we studied the efficacy of intravenous trehalose administration in reducing atherosclerotic plaque burden in high-cholesterol-fed rabbits. Adult male New Zealand white Rabbits were fed with a high-fat diet containing 1% cholesterol for 8 weeks followed by a cholesterol-free diet for the next 4 weeks. In the latter 4-week phase of the cholesterol-free diet, one group received intravenous trehalose solution at a dose of 350 mg/kg, three times per week. In the control group, an equivalent volume of PBS (3 mL) was administered with the same protocol. At the end of the 12th week of the study, all rabbits were anesthetized and aortic arch sections were collected followed by hematoxylin and eosin staining and assessment of plaque grading. Fasting serum lipids were also measured using routine enzymatic methods. At the end of the 12th week, there were no significant differences in the body weight and blood lipids between the control- and trehalose-treated groups. Intravenous trehalose administration significantly attenuated atherosclerotic plaque development as revealed by reduced plaque grading ( P = 0.048) and intima/media thickness ratio ( P = 0.017). Intimal thickening was also found to be reduced in the trehalose versus control group, though this reduction did not reach statistical significance. The present study provided evidence as to the efficacy of short-term intravenous trehalose administration in regressing atherosclerotic plaque in high-fat-fed rabbits.     

Plausible biochemical mechanisms of chemotherapy-induced cognitive impairment (“chemobrain”), a condition that significantly impairs the quality of life of many cancer survivors

Increasing numbers of cancer patients survive and live longer than five years after therapy, but very often side effects of cancer treatment arise at same time. One of the side effects, chemotherapy-induced cognitive impairment (CICI), also called “chemobrain” or “chemofog” by patients, brings enormous challenges to cancer survivors following successful chemotherapeutic treatment. Decreased abilities of learning, memory, attention, executive function and processing speed in cancer survivors with CICI, are some of the challenges that greatly impair survivors' quality of life. The molecular mechanisms of CICI involve very complicated processes, which have been the subject of investigation over the past decades. Many mechanistic candidates have been studied including disruption of the blood-brain barrier (BBB), DNA damage, telomere shortening, oxidative stress and associated inflammatory response, gene polymorphism of neural repair, altered neurotransmission, and hormone changes. Oxidative stress is considered as a vital mechanism, since over 50% of FDA-approved anti-cancer drugs can generate reactive oxygen species (ROS) or reactive nitrogen species (RNS), which lead to neuronal death. In this review paper, we discuss these important candidate mechanisms, in particular oxidative stress and the cytokine, TNF-alpha and their potential roles in CICI.     

Proteoglycan 4 deficiency protects against glucose intolerance and fatty liver disease in diet-induced obese mice

Objective

Proteoglycan 4 (Prg4) has emerged from human association studies as a possible factor contributing to weight gain, dyslipidemia and insulin resistance. In the current study, we investigated the causal role of Prg4 in controlling lipid and glucose metabolism in mice.

Early intermediates in the transport cycle of the neuronal excitatory amino acid carrier EAAC1

Electrogenic glutamate transport by the excitatory amino acid carrier 1 (EAAC1) is associated with multiple charge movements across the membrane that take place on time scales ranging from microseconds to milliseconds. The molecular nature of these charge movements is poorly understood at present and, therefore, was studied in this report in detail by using the technique of laser-pulse photolysis of caged glutamate providing a 100-micros time resolution. In the inward transport mode, the deactivation of the transient component of the glutamate-induced coupled transport current exhibits two exponential components. Similar results were obtained when restricting EAAC1 to Na(+) translocation steps by removing potassium, thus, demonstrating (1) that substrate translocation of EAAC1 is coupled to inward movement of positive charge and, therefore, electrogenic; and (2) the existence of at least two distinct intermediates in the Na(+)-binding and glutamate translocation limb of the EAAC1 transport cycle. Together with the determination of the sodium ion concentration and voltage dependence of the two-exponential charge movement and of the steady-state EAAC1 properties, we developed a kinetic model that is based on sequential binding of Na(+) and glutamate to their extracellular binding sites on EAAC1 explaining our results. In this model, at least one Na(+) ion and thereafter glutamate rapidly bind to the transporter initiating a slower, electroneutral structural change that makes EAAC1 competent for further, voltage-dependent binding of additional sodium ion(s). Once the fully loaded EAAC1 complex is formed, it can undergo a much slower, electrogenic translocation reaction to expose the substrate and ion binding sites to the cytoplasm.     

Protection of intracellular dopamine cytotoxicity by dopamine disposition and metabolism factors

Dopamine has been hypothesized as a contributing factor for the selective degeneration of dopaminergic neurons in Parkinson's disease. However, the cytotoxic mechanisms of dopamine and its metabolites remain poorly understood. Using a stable aromatic amino acid decarboxylase (AADC) expressing a fibroblast cell line, we previously demonstrated a novel, non-oxidative cytotoxicity of intracellular dopamine. In this study, we further investigate the roles of dopamine metabolism and disposition proteins against intracellular dopamine cytotoxicity by co-expressing these factors in AADC-expressing cells. Our results indicate that overexpression of the vesicular monoamine transporter and monoamine oxidase A-induced protection against intracellular dopamine toxicity, and conversely that pharmacological inhibition of these pathways potentiated L-DOPA toxicity in catecholaminergic PC12 cells. Macrophage migration inhibitory factor and glutathione S-transferase (GST), factors that have recently been shown to be involved in dopamine metabolism, also exhibited a strong protective role against intracellular dopamine cytotoxicity. Our results support a potential role for non-oxidative cytoplasmic dopamine toxicity, and imply that disruption in dopamine disposition and/or metabolism could underlie the progressive degeneration of dopaminergic neurons in Parkinson's disease.     

Characterization of the blood-brain barrier choline transporter using the in situ rat brain perfusion technique

Choline enters brain by saturable transport at the blood-brain barrier (BBB). In separate studies, both sodium-dependent and passive choline transport systems of differing affinity have been reported at brain capillary endothelial cells. In the present study, we re-examined brain choline uptake using the in situ rat brain perfusion technique. Saturable brain choline uptake from perfusion fluid was best described by a model with a single transporter (V:(max) = 2.4-3.1 nmol/min/g; K(m) = 39-42 microM) with an apparent affinity (1/Km)) for choline five to ten-fold greater than previously reported in vivo, but less than neuronal 'high-affinity' brain choline transport (K(m) = 1-5 microM). BBB choline uptake from a sodium-free perfusion fluid using sucrose for osmotic balance was 50% greater than in the presence of sodium suggesting that sodium is not required for transport. Hemicholinium-3 inhibited brain choline uptake with a K(i) (57 +/- 11 microM) greater than that at the neuronal choline system. In summary, BBB choline transport occurs with greater affinity than previously reported, but does not match the properties of the neuronal choline transporter. The V:(max) of this system is appreciable and may provide a mechanism for delivering cationic drugs to brain.     

Selective down-regulation of the astrocyte glutamate transporters GLT-1 and GLAST within the medial thalamus in experimental Wernicke's encephalopathy

Although earlier studies on thiamine deficiency have reported increases in extracellular glutamate concentration in the thalamus, a vulnerable region of the brain in this disorder, the mechanism by which this occurs has remained unresolved. Treatment with pyrithiamine, a central thiamine antagonist, resulted in a 71 and 55% decrease in protein levels of the astrocyte glutamate transporters GLT-1 and GLAST, respectively, by immunoblotting in the medial thalamus of day 14 symptomatic rats at loss of righting reflexes. These changes occurred prior to the onset of convulsions and pannecrosis. Loss of both GLT-1 and GLAST transporter sites was also confirmed in this region of the thalamus at the symptomatic stage using immunohistochemical methods. In contrast, no change in either transporter protein was detected in the non-vulnerable frontal parietal cortex. These effects are selective; protein levels of the astrocyte GABA transporter GAT-3 were unaffected in the medial thalamus. In addition, astrocyte-specific glial fibrillary acidic protein (GFAP) content was unchanged in this brain region, suggesting that astrocytes are spared in this disorder. Loss of GLT-1 or GLAST protein was not observed on day 12 of treatment, indicating that down-regulation of these transporters occurs within 48 h prior to loss of righting reflexes. Finally, GLT-1 content was positively correlated with levels of the neurofilament protein alpha-internexin, suggesting that early neuronal drop-out may contribute to the down-regulation of this glutamate transporter and subsequent pannecrosis. A selective, focal loss of GLT-1 and GLAST transporter proteins provides a rational explanation for the increase in interstitial glutamate levels, and may play a major role in the selective vulnerability of thalamic structures to thiamine deficiency-induced cell death.     

Ceramide inhibits the outward potassium current in rat pinealocytes

CD1 mice lacking the CB1 receptors (knockout, KO) were compared with wild-type littermates for their ability to degrade N-arachidonoylethanolamine (anandamide, AEA) through a membrane transporter (AMT) and a fatty acid amide hydrolase (FAAH). The regional distribution and age-dependence of AMT and FAAH activity were investigated. Anandamide membrane transporter and FAAH increased with age in knockout mice, whereas they showed minor changes in wild-type animals. Remarkably, they were higher in all brain areas of 6-month-old knockout versus wild-type mice, and even higher in 12-month-old animals. The molecular mass (approximately 67 kDa) and isoelectric point (approximately 7.6) of mouse brain FAAH were determined and the FAAH protein content was shown to parallel the enzyme activity. The kinetic constants of AMT and FAAH in the cortex of wild-type and knockout mice at different ages suggested that different amounts of the same proteins were expressed. The cortex and hippocampus of wild-type and knockout mice contained the following N-acylethanolamines: AEA (8% of total), 2-arachidonoylglycerol (5%), N-oleoylethanolamine (20%), N-palmitoylethanolamine (53%) and N-stearoylethanolamine (14%). These compounds were twice as abundant in the hippocampus as in the cortex. Minor differences were observed in AEA or 2-arachidonoylglycerol content in knockout versus wild-type mice, whereas the other compounds were lower in the hippocampus of knockout versus wild-type animals.