Professor Timothy Hales

Professor (Teaching and Research)

Systems Medicine, School of Medicine

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Contact

Email

T.G.Hales@dundee.ac.uk

Phone

+44 (0)1382 383443

Location

Ninewells - Mailbox 6

Biography

Tim Hales graduated with a BSc (Hons) in Physiology from King’s College London in 1986 and a PhD from the University of Dundee in 1990. He completed postdoctoral training in the Department of Anesthesiology, University of California in Los Angeles and in 1997 was appointed Assistant Professor at the George Washington University in Washington DC where he gained tenure in 2002.  He became Professor in the Departments of Pharmacology and Anesthesiology & Critical Care Medicine and Director of Research in Anesthesiology at GWU in 2006.

Tim returned to Dundee in 2009 as Professor of Anaesthesia and non-clinical head of the Division of Neuroscience.  He was elected Fellow of the Royal College of Anaesthetists in 2011 and was appointed Associate Dean for Research-Led Teaching in the School of Medicine in 2017. His research group studies the mechanisms of action of anaesthetics and opioid analgesics, drugs that modulate neuronal communication through ion channel modulation. The group’s work on metastatic colon cancer cells identified voltage-activated Na+ channels as potential targets for anticancer medications. Inhibition of these channels by local anaesthetics inhibits cell invasion.

Tim’s goal is to improve anaesthesia and analgesia by 1) educating future researchers and anaesthetists and 2) by identifying molecular targets responsible for the desirable and detrimental effects of anaesthetics and analgesics. His research has received support by grants from Tenovus Scotland, the National Science Foundation and the National Institutes of Health, USA and the National Institute of Academic Anaesthesia, UK.

 

Research

Pain was an unavoidable consequence of injury, disease and infection before the advent of clinical anaesthesia. Now, thanks to skilled anaesthetists, pain-ameliorating analgesics and general anaesthetics (GAs), millions of people undergo surgery every year and most recover with relatively minor discomfort. While only a small minority of patients experience major negative consequences all anaesthetics have side effects. Most cause respiratory depression and some may cause neurodegeneration, a particular concern in the elderly. Analgesic agents also have severe side effects. Opioids such as morphine and fentanyl are commonly used to treat both perioperative and chronic pain; however their prolonged use leads to physical dependence and a loss of potency due to tolerance. Morphine can also cause hyperalgesia, a paradoxical increase in pain. There is a pressing need to develop better GAs and analgesics.

We are studying the mechanisms of action of opioids and GAs, drugs that influence neuronal excitability by binding to membrane proteins and thereby directly or indirectly regulating the activity of ion channels. By identifying the proteins responsible for their therapeutic and detrimental effects we hope to offer a strategy for improved safety and efficacy.

Opioid receptors (mu, delta and kappa) couple through G proteins to effectors, including K+ and Ca2+ channels. Morphine activates mu receptors thereby inhibiting Ca2+ channels, reducing excitatory transmission within the pain pathway. Prolonged morphine exposure leads to analgesic tolerance. Tolerance is attenuated in mice that lack beta-arrestin2, a protein that interacts with the mu receptor affecting its internalization and coupling it to signalling proteins including the tyrosine kinase, c-Src. We are testing the hypothesis that tolerance requires c-Src activity using electrophysiological recording and measurements of analgesia in mice.

Morphine induced hyperalgesia occurs in opioid receptor knock-out mice and is therefore independent of opioid receptor activation. We are using electrophysiological recording and behavioural assays to test the hypothesis that opioids directly modulate the activity of ion channels (e.g. the 5-HT3 receptor) and that these “off-target” actions contribute to their side effect profiles.

Research that began in the 1980’s in Dundee revealed that GAs, such as the induction agent propofol, enhance neuronal inhibition by the neurotransmitter gamma-aminobutyric acid (GABA) through a direct interaction with the GABAA receptor. GABA activates the GABAA receptor opening the integral Cl- channel and this activity is enhanced by GAs. The GABAA receptor is the primary target for induction agents. Since the 1980’s genes that encode 19 different GABAA receptor subunits have been cloned revealing considerable receptor heterogeneity. We identified the GABAA receptor epsilon subunit which reduces the enhancement of GABAA receptor function by GAs. The epsilon subunit may protect specific brain regions from inhibition by GAs. We are exploring the subtype specificity of GAs. Using chimeric constructs of the epsilon subunit and mutagenesis we are characterizing the nature of the GA interaction with the GABAA receptor.

Mutations in GABAA genes can profoundly affect the GA sensitivity of GABAA receptors. The artificial introduction of mutant receptors that are resistant to GA modulation makes mice resistant to immobilization by propofol validating GABAA receptors as the primary target of induction. We use homology modelling, mutagenesis and electrophysiological techniques to examine the relationship between structure and function of GABAA receptors and other related Cys-loop receptors. We recently demonstrated that mutations in individuals with epilepsy, which reduce GABA efficacy, enhance potentiation by propofol.

View full research profile and publications

Teaching

Level 3 and 4 Pharmacology and Neuroscience BSc and BMSc lectures in anaesthesia, anti-epileptics, drug dependence and opioids, University of Dundee

Supervision of BSc (Hons) and BMSc research projects.