Dolichol: A Component of the Cellular Antioxidant Machinery

Dolichol, an end product of the mevalonate pathway, has been proposed a biomarker of aging, but its biological role, not to mention its catabolism, has not been fully understood. UV-B radiation was used to induce oxidative stress in isolated rat hepatocytes by the collagenase method. Effects on dolichol, phospholipids-bound polyunsaturated fatty acids (PL PUFA) and known lipid soluble antioxidants [coenzyme Q (CoQ) and α-tocopherol] were studied. The increase in oxidative stress was detected by a probe sensitive to reactive oxygen species (ROS). Peroxidation of lipids was assessed by measuring the release of thiobarbituric acid reactive substances (TBARS). Dolichol, CoQ and α-tocopherol were assessed by high-pressure liquid chromatography (HPLC), PL PUFA by gas-liquid chromatography (GC). UV-B radiation caused an immediate increase in ROS as well as lipid peroxidation and a simultaneous decrease in the levels of dolichol and lipid soluble antioxidants. Decrease in dolichol paralleled changes in CoQ levels and was smaller than that in α-tocopherol. The addition of mevinolin, a competitive inhibitor of the enzyme 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoAR), magnified the loss of dolichol and was associated with an increase in TBARS production. Changes in PL PUFA were minor. These findings highlight that oxidative stress has very early and similar effects on dolichol and lipid soluble antioxidants. Lower levels of dolichol are associated with enhanced peroxidation of lipids, which suggest that dolichol may have a protective role in the antioxidant machinery of cell membranes and perhaps be a key to understanding some adverse effects of statin therapy

Evaluation of the anti-inflammatory effects of synthesised tanshinone I and isotanshinone I analogues in zebrafish

During inflammation, dysregulated neutrophil behaviour can play a major role in a range of chronic inflammatory diseases, for many of which current treatments are generally ineffective. Recently, specific naturally occurring tanshinones have shown promising anti-inflammatory effects by targeting neutrophils in vivo, yet such tanshinones, and moreover, their isomeric isotanshinone counterparts, are still a largely underexplored class of compounds, both in terms of synthesis and biological effects. To explore the anti-inflammatory effects of isotanshinones, and the tanshinones more generally, a series of substituted tanshinone and isotanshinone analogues was synthesised, alongside other structurally similar molecules. Evaluation of these using a transgenic zebrafish model of neutrophilic inflammation revealed differential anti-inflammatory profiles in vivo, with a number of compounds exhibiting promising effects. Several compounds reduce initial neutrophil recruitment and/or promote resolution of neutrophilic inflammation, of which two also result in increased apoptosis of human neutrophils. In particular, the methoxy-substituted tanshinone 39 specifically accelerates resolution of inflammation without affecting the recruitment of neutrophils to inflammatory sites, making this a particularly attractive candidate for potential pro-resolution therapeutics, as well as a possible lead for future development of functionalised tanshinones as molecular tools and/or chemical probes. The structurally related β-lapachones promote neutrophil recruitment but do not affect resolution. We also observed notable differences in toxicity profiles between compound classes. Overall, we provide new insights into the in vivo anti-inflammatory activities of several novel tanshinones, isotanshinones, and structurally related compounds

Chronic kidney disease and coenzyme Q10 supplementation

Among the potential causes of chronic kidney disease (CKD), mitochondrial respiratory chain (MRC) dysfunction, oxidative stress and inflammation have been implicated as contributor factors to the pathogenesis of this disorder. It is thought that CoQ10 supplementation may offer some therapeutic potential in the treatment of patients with CKD, since CoQ10 has a key role in normal MRC function, as well as having antioxidant and anti-inflammatory action. This article will outline the current knowledge on the use of CoQ10 in the treatment of CK

Serotonin release from mesencephalic raphe neurons grafted to the 5,7-dihydroxytryptamine-lesioned rat hippocampus : Effects of behavioral activation and stress

Transplants of fetal midbrain raphe neurons into the adult brain have been shown to promote recovery of complex behavioral deficits in several experimental models, but the mechanisms underlying these effects are only partially understood. In the present study, we have used a well-characterized model system to ascertain whether midbrain raphe graft can display behaviorally relevant changes in transmitter release and/or metabolism. Fetal mesencephalic raphe neurons were grafted unilaterally into the hippocampus previously deprived of its innate serotonergic innervation by intraventricular injections of 5,7-dihydroxytryptamine. The contralateral hippocampus remained as a non-grafted, lesioned control. Microdialysis probes were implanted in the hippocampus 5-7 months postgrafting. Under baseline conditions, extracellular levels of serotonin were similar to normal in the grafted hippocampi, but undetectable on the contralateral, non-grafted side. Levels of the serotonin metabolite, 5-hydroxyindoleacetic acid (5-HIAA), were markedly higher than normal in the grafted hippocampi, but dramatically reduced on the contralateral nongrafted side. Handling stimulation (gentle stroking of a rat's fur and tail for 15 min) induced a 64% increase in serotonin output in the intact rats and a small but significant 12% increase in the grafted animals. Non-noxious tail-pinch (15 min) enhanced serotonin release by 86% in the intact rats and 28% in the grafted ones. Extracellular 5-HIAA levels remained unchanged during both handling and tail-pinch in both the intact and the grafted rats. Forced immobilization of the rats for 15 min induced a transient 124% increase in extracellular serotonin levels in the intact rats and a significant 19% increase in the grafted animals, whereas swimming in temperate water (25-30°C; 15 min) induced no detectable changes in serotonin output in any of the groups. 5-HIAA levels remained unchanged during forced immobilization, but were significantly reduced during the swimming session in both the intact (-38%) and grafted (-15%) animals. The present results indicate that median raphe grafts can become functionally integrated in the denervated host hippocampus and respond by altered indole output when the animal is exposed to different types of environmental challenges

Reafferentation of the subcortically denervated hippocampus as a model for transplant-induced functional recovery in the CNS

Subcortical deafferentation of the hippocampal formation is known to induce profound behavioural deficits. Transplants of fetal septal or brainstem tissue are capable of restoring some aspects of normal physiological and behavioural function in subcortically deafferented (i.e. fimbria-fornix or septal lesioned) rats. Such grafts have been shown to re-establish extensive new afferent inputs to the denervated hippocampal formation. As shown for grafted cholinergic and noradrenergic neurons, the ingrowing axons form laminar innervation patterns which closely mimic those of the normal cholinergic and noradrenergic innervations. The ingrowth appears to be very precisely regulated by the denervated target: each neuron type produces distinctly different innervation patterns; the growth is inhibited by the presence of an intact innervation of the same type; and it is stimulated by additional denervating lesions. Both ultrastructually and electrophysiologically the graft-derived fibres have been seen to form extensive functional synaptic contacts. Biochemically, cholinergic septal grafts and noradrenergic locus coeruleus grafts restore transmitter synthesis and turnover in the reinnervated hippocampus. Intracerebral microdialysis has revealed that acetylcholine and noradrenaline release is restored to normal or supranormal levels in the graft-reinnervated hippocampus, and that the grafted neurons can be activated in a normal way from the host through behavioural activation induced by sensory stimulation or electrical stimulation of the lateral habenula. These results indicate that the grafted monoaminergic neurons can restore tonic regulatory neurotransmission at previously denervated synaptic sites even when they are implanted into the ectopic brain sites. Such functional reafferentation may be sufficient for at least partial restoration of function in the subcortically deafferented hippocampus

Acetylcholine release from intrahippocampal septal grafts is under control of the host brain.

The activity of intrahippocampal transplants of cholinergic neurons was monitored by microdialysis in awake, freely moving rats. Fetal septal-diagonal band tissue was implanted into rats with a complete transection of the fimbria-fornix cholinergic pathway either as a cell suspension injected into the hippocampus or as a solid graft implanted in the lesion cavity. The grafts restored baseline acetylcholine release in the graft-reinnervated hippocampus to normal or supranormal levels. The graft-derived acetylcholine release was dependent on intact axonal impulse flow, and it was markedly increased during behavioral activation by sensory stimulation or by electrical stimulation of the lateral habenula. The results demonstrate that the septal grafts, despite their ectopic location, can become functionally integrated with the host brain and that the activity of the transplanted cholinergic neurons can be modulated from the host brain during ongoing behavior. Anatomical observations, using immunohistochemistry and retrograde tracing, indicate that direct or indirect brainstem afferents to the graft could mediate this functional integration. Host afferent control of the graft may thus play a role in the recovery of lesion-induced functional deficits seen with these types of transplants

Acetylcholine release in the rat hippocampus as studied by microdialysis is dependent on axonal impulse flow and increases during behavioural activation

Changes in extracellular levels of acetylcholine and choline in the hippocampal formation were measured using intracerebral microdialysis coupled to high performance liquid chromatography with post-column enzyme reaction and electrochemical detection. Various pharmacological and physiological manipulations were applied to awake unrestrained normal rats and rats subjected to a cholinergic denervation of the hippocampus by a complete fimbria-fornix lesion (1-2 weeks previously). Low baseline levels of acetylcholine (about 0.3 pmol/15 min sample) could be detected in the absence of acetylcholinesterase inhibition in all animals. However, in order to obtain stable and more readily detectable levels, the acetylcholinesterase inhibitor neostigmine was added to the perfusion medium at a concentration of 5 or 10 microM and was used during all subsequent manipulations. Addition of neostigmine increased acetylcholine levels approximately 10-fold (to 3.7 pmol 15 min) in the normal rats, which was about 4-fold higher than the levels recovered from the denervated hippocampi. Depolarization by adding KCl (100 mM) to the perfusion fluid produced a 3-fold increase in the extracellular acetylcholine levels, and the muscarinic antagonist atropine (3 microM) resulted in a 4-fold increase in the normal rats, whereas these drugs induced only small responses in the denervated rats. Neuronal impulse blockade by tetrodotoxin (1 microM) resulted, in normal rats, in a 70% reduction in extracellular acetylcholine levels. Sensory stimulation by handling increased acetylcholine levels by 94% in the normal rats, whereas this response was almost totally abolished in the denervated hippocampi. Behavioural activation by electrical stimulation of the lateral habenula resulted in a 4-fold increase in acetylcholine release in normal animals, and this response was totally blocked by a transection of the lateral habenular efferents running in the fasciculus retroflexus. The levels obtained by lateral habenula stimulation were reduced by about 95% in the rats with fimbria-fornix lesions. Following an acute knife transection of the fimbria-fornix performed during ongoing dialysis, acetylcholine levels dropped instantaneously by 70%, indicating that the extracellular acetylcholine levels in the hippocampus are maintained by a tonic impulse flow in the septohippocampal pathway. The extracellular levels of choline were reduced by about 30% after the addition of neostigmine in the normal rats, and increased by about 50% in both normal and denervated rats after addition of KCl to the perfusion fluid. No changes could be detected after atropine, handling, lateral habenula stimulation, or acute fimbria-fornix or fasciculus retroflexus transection.(ABSTRACT TRUNCATED AT 400 WORDS