Ageing-induced changes in the redox status of peripheral motor nerves imply an effect on redox signalling rather than oxidative damage

Ageing is associated with loss of skeletal muscle fibres, atrophy of the remaining fibres and weakness. These changes in muscle are accompanied by disruption of motor neurons and neuromuscular junctions although the direct relationship between the nerve and muscle degeneration is not understood. Oxidative changes have been implicated in the mechanisms leading to age-related loss of muscle mass and in degeneration of the central nervous system, but little is known about age-related changes in oxidation in specific peripheral nerves that supply muscles that are affected by ageing. We have therefore examined the sciatic nerve of old mice at an age when loss of tibialis anterior muscle mass and function is apparent. Sciatic nerve from old mice did not show a gross increase in oxidative damage, but electron paramagnetic resonance (EPR) studies indicated an increase in the activity of superoxide and/or peroxynitrite in the nerves of old mice at rest that was further exacerbated by electrical stimulation of the nerve to activate muscle contractions. Proteomic analyses indicated that specific redox-sensitive proteins are increased in content in the nerves of old mice that may reflect an adaptation to regulate the increased superoxide/peroxynitrite and maintain redox homoeostasis. Analysis of redox active cysteines showed some increase in reversible oxidation in specific proteins in nerves of old mice, but this was not universally seen across all redox-active cysteines. Detailed analysis of the redox-active cysteine in one protein in the nerve of old mice that is key to redox signalling (Peroxiredoxin 6, Cys 47) showed a minor increase in reversible oxidation that would be compatible with a change in its redox signalling function. In conclusion, the data presented indicate that sciatic nerve from old mice does not show a gross increase in oxidative damage similar to that seen in the TA and other muscles that it innervates. Our results indicate an adaptation to increased oxidation with minor changes in the oxidation of key cysteines that may contribute to defective redox signalling in the nerve

Host-parasite co-metabolic activation of antitrypanosomal aminomethyl-benzoxaboroles

<div><p>Recent development of benzoxaborole-based chemistry gave rise to a collection of compounds with great potential in targeting diverse infectious diseases, including human African Trypanosomiasis (HAT), a devastating neglected tropical disease. However, further medicinal development is largely restricted by a lack of insight into mechanism of action (MoA) in pathogenic kinetoplastids. We adopted a multidisciplinary approach, combining a high-throughput forward genetic screen with functional group focused chemical biological, structural biology and biochemical analyses, to tackle the complex MoAs of benzoxaboroles in <i>Trypanosoma brucei</i>. We describe an oxidative enzymatic pathway composed of host semicarbazide-sensitive amine oxidase and a trypanosomal aldehyde dehydrogenase TbALDH3. Two sequential reactions through this pathway serve as the key underlying mechanism for activating a series of 4-aminomethylphenoxy-benzoxaboroles as potent trypanocides; the methylamine parental compounds as pro-drugs are transformed first into intermediate aldehyde metabolites, and further into the carboxylate metabolites as effective forms. Moreover, comparative biochemical and crystallographic analyses elucidated the catalytic specificity of TbALDH3 towards the benzaldehyde benzoxaborole metabolites as xenogeneic substrates. Overall, this work proposes a novel drug activation mechanism dependent on both host and parasite metabolism of primary amine containing molecules, which contributes a new perspective to our understanding of the benzoxaborole MoA, and could be further exploited to improve the therapeutic index of antimicrobial compounds.</p></div

Critical science plan for the Daniel K. Inouye solar telescope (DKIST)

The National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute

Evaluation of a smoking cessation strategy for hospitals

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Cannabinoid1 receptor in the dorsal vagal complex modulates lower oesophageal sphincter relaxation in ferrets

Delta9-tetrahydrocannabinol (Δ9-THC) is an effective anti-emetic; however, other potential gastrointestinal therapeutic effects of Δ9-THC are less well-known. Here, we report a role of Δ9-THC in a vago-vagal reflex that can result in gastro-oesophageal reflux, that is, gastric distension-evoked lower oesophageal sphincter (LOS) relaxation. Oesophageal, LOS and gastric pressures were measured using a miniaturized, manometric assembly in decerebrate, unanaesthetized ferrets. Gastric distension (30 ml) evoked LOS relaxation (70 ± 8 % decrease from baseline). Δ9-THC administered systemically (0.2 mg kg−1, I.V.) or directly to the dorsal hindbrain surface (0.002 mg), significantly attenuated the nadir of the gastric distention-evoked LOS relaxation, and time to reach maximal response. Similar increases to maximal effect were observed after treatment with the cannabinoid receptor agonist WIN 55,212–2 (0.2 mg kg−1, I.V.). The effect of systemic Δ9-THC on gastric distention-evoked LOS relaxation was reversed by a selective cannabinoid1 (CB1) receptor antagonist, SR141617A (1 mg kg−1, I.V.). Since this reflex is vagally mediated, we used a CB1 receptor antiserum and immunocytochemistry to determine its distribution in ferret vagal circuitry. CB1 receptor staining was present in cell bodies within the area postrema, nucleus tractus solitarius (NTS) and nodose ganglion. Intense terminal-like staining was noted within the NTS and dorsal motor vagal nucleus (DMN). Neither nodose ganglionectomy nor vagotomy altered the CB1 receptor terminal-like staining in the dorsal vagal complex. Retrogradely labelled gastric- or LOS-projecting DMN neurones did not express CB1 receptors within their soma. Therefore, CB1 receptor staining in the NTS and DMN is not due to primary vagal afferents or preganglionic neurones. These novel findings suggest that Δ9-THC can modulate reflex LOS function and that the most likely site of action is via the CB1 receptor within the NTS. This effect of Δ9-THC may have implications in treatment of gastro-oesophageal reflux and other upper gut disorders