From opium to analgesic tests: An introduction to the functioning and studying of the opioid system

Practice-oriented, student-friendly modernization of the biomedical education for strengthening the international competitiveness of the rural Hungarian universities TÁMOP-4.1.1.C-13/1/KONV-2014-0001 From opium to analgesic tests: An introduction to the functioning and studying of the opioid system Ferenc Zádor Laboratory of Opioid Research Institute of Biochemistry 2018.10.31.

Introduction: Why study the opioid system?

Introduction: Why study the opioid system? Nutt et al., 2007, Lancet

Introduction: The OxyContin story

Part I. What are opioids? Opium Opiates or opioids? Part II. How do they work? GPCRs in general Opioid receptors Endogenous opioids Part III. What do they do? Pain pathways Opioids and analgesia Tolerance and addiction Opioids in medicine Part IV. What is the future? Improving safety the safety Future applications Biochemical assays Analgesic tests

Part I: Opium, opiates, opioids János Kabay Morphine Codeine Thebaine Fentanyl Met-enkephalin Heroin Naloxone

Part I. What are opioids? Opium Opiates or opioids? Part II. How do they work? GPCRs in general Opioid receptors Endogenous opioids Part III. What do they do? Pain pathways Opioids and analgesia Tolerance and addiction Opioids in medicine Part IV. What is the future? Improving safety Future applications Biochemical assays Analgesic tests

Part II: G-protein coupled receptors in general ECL2 G Extracellular space 2AR TM1 ~50 Å 90 H8 TM5 G G BI 167107 G G G N ECL1 ECL2 ECL3 2012 BI-167107 1 2 3 4 5 6 7 ICL3 ICL1 ICL2 C Brian Kobilka 8 β Lipid anchors Robert Lefkowitz

Part II: G-protein coupled receptors in general Venkatakrishnan et al., 2013, Nature

Part II: G-protein coupled receptors in general Venkatakrishnan et al., 2013, Nature

Part II: G-protein coupled receptors in general Agonist G G β G GTP GDP Secondary messenger/effector protein

Part II: Opioid receptor signaling Opioid agonist N Extracellular space - - K+ Ca 2+ Periaqeductal gray - - - - -(midbrain) - - + - - Substantia gelatinosa - - - - - (spinal - - - - cord) Brainstem (respiration) Enteric neurons Analgesia Constipation (ACh) Respiratory depression Biological response (%) 1 2 3 4 5 6 7 GTP GDP 200 150 100 50 + α β Basal activity C Adenylate cyclase α β ATP camp Agonist Log drug concentration

Part II: Opioid receptor signaling μ (MOPr) δ (DOPr) N Opioid antagonist Opioid agonist Extracellular space 1 2 3 4 5 6 7 Adenylate cyclase GTP α β C β ATP camp Manglik et al., 2012 κ (KOPr) Wu et al., 2012 Granier et al., 2012 NOPr Thompson et al., 2012 Biological response (%) GDP 200 Agonist 150 Basal activity 100 Antagonist 50 Log drug concentration

Part II: Structure of the MOPr-G i complex

Part II: Endogenous opioids Met-enkephalin Morphine

Part II: Short summary Opioid receptors belong to the large GPCR superfamily GPCRs share several structural and functional similarities GPCRs have second messenger systems which forwards the signal of the bound ligand Opioid receptors overall inhibit the release of several neurotransmitters (GABA, ACh) Three types of opioid receptors (classically), with overlaping functionalities Endogenous opioid peptides mainly act as hormones and share certain structural motifs with exogenous ligands

Part I. What are opioids? Opium Opiates or opioids? Part II. How do they work? GPCRs in general Opioid receptors Endogenous opioids Part III. What do they do? Pain pathways Opioids and analgesia Tolerance and addiction Opioids in medicine Part IV. What is the future? Improving safety Future applications Biochemical assays Analgesic tests

Part III: The pain pathways

Part III: The opioid system and analgesia

Part III: Currently available classic opioid analgesics

Part III: Opioid use disorder

Part III: Opioid-induced tolerance

Part III: The reward system and addiction Prefrontal cortex Corpus callosum Pons Medulla oblongata Dopamine (3,4-dihydroxyphenethylamine) Nucleus accumbens Hippocampus Ventral tegmentum (ventral tegmental area) Cerebellum Substantia nigra

Part III: The reward system and opioids VTA GABA NA Soma GABA receptor Opioid receptor (mu type) Morphine/heroin

Part III: The traces of tolerance and addiction in the brain NA

Part III: The consequences: opioid withdrawal and overdose

Part III: Opioids for diarrhea, constipation and cough Loperamide Methylnaltrexone

Part III: Short summary The opioid system reduces pain signals both in the spinalcord and in the brain Opioid receptor activation results GABA, substance P neurotransmitter release inhibition in the descending pain pathways Opioid medications can cause serious side effects (opioid use disorder) Opioids can induce tolerance and addicition, which can cause serious withdrawal symptoms or fatal overdose The opioid system strongly interacts with the reward system and increases dopamine levels Medications targeting the opioid system can help to overcome withdrawal symptoms and addiction Opioids for diarrhea, constipation and as cough suppressants, due to the presence of the opioid system in the GI tract and respiratory control system

Part I. What are opioids? Opium Opiates or opioids? Part II. How do they work? GPCRs in general Opioid receptors Endogenous opioids Part III. What do they do? Pain pathways Opioids and analgesia Tolerance and addiction Opioids in medicine Part IV. What is the future? Improving the safety Future applications Biochemical assays Analgesic tests

Part IV: Approaches to overcome the side-effects MOR binding and agonist activity Antinociceptive activity Limited BBB penetrance Limited side-effects Morphine-6-O-sulfate 14-O-methylmorphine-6-O-sulfate Lackó et al. Curr Med Chem, 2012 Morphine 14-O-methylmorphine Zádor et al. Eu J Pharmacol, 2017 MOR binding, selectivity and agonist activity Antinociceptive activity Promising results in neurophatic pain Dr. Mahmoud Al-Khrasani Department of Pharmacology and Pharmacotherapy, Semmelweis University Budapest, Hungary

Part IV: Approaches to overcome the side-effects Functional selectivity or biased agonism

Part IV: Approaches to overcome the side-effects Buprenorphine + naloxone Oxycodone + naloxone Analgesic, modified-release Significantly reduces constipation μ opioid receptor agonist AND norepinephrine reuptake inhibitor Tapentadol

Part IV: Approaches to overcome the side-effects Mollica et al. Chem Biol Drug, 2014 Opioid receptor agonist AND N-type voltage dependent Ca 2+ channel blocker Dr. Adriano Mollica University of Chieti-Pescara, Italy

Part IV: Approaches to overcome the side-effects Zádor & Wollemann, Pharmacol Res, 2015

Part IV: Future plans Targeting endogenous opioid degrading enzymes (enkephalinase inhibitors) Appetite supression by opioid antagonists Treating anxiety and depression Against alcoholism

Part IV: How to study the opioid system N 1 Binding affinity, selectivity and capacity with labeled ligands Extracellular space 1 2 3 4 5 6 7 Adenylate cyclase GTP GDP α 2 β C β α ATP camp Agonist activity with radiolabeled campgtp 3 Smooth muscle contraction inhibition Acethylcholine release inihibition Isolated mouse vasa deferentia, rodent intestines, guinea pig illeum Ligand characterization

Part IV: How to study the opioid system 4 Antinociception Tail-flick test Plantar test Hot-plate test Thermal pain Paw pressure test Mechanical pain

Part IV: Short summary Introducing new chemical groups to the opioid structures to improve the safety profile of opioids Combination therapy, functional selective and multitarget compounds are also promising Further therapeutic applications are in developement We can study opioid receptors at the ligand binding and signaling level We can study thermal, mechanical or other pain types with animal behavior tests

Final summary 1 2 3 4 5 6 7 There are plant derived, half-synthetic and fully synthetic opioids, which mimic the molecular signitures of the endogenous opioids Opioid receptors are GPCRs, transferring the extracellular first messenger signal molecules (opioid ligands) through a molecular switch (G-protein) to second messenger systems (e.g. adenylate cyclase) Opioid ligands can bind to and activate opioid receptors (agonists) or bind to the receptor without triggering the signalling pathway (antagonists), the latter also blocks receptor activity Opioids reduce pain both in the brain and in the spinal cord by inhibiting the singals in the pain pathways through reducing the release of certain neurotransmitters (e.g. GABA, substance P) Opioids are highly addictive, they strongly interact with the reward system and increase dopamine levels The opioid system can be targeted for many therapuetic applications apart from analgesia (e.g. addiction, bowel movements, cough etc.) The opioid system can be studied in multiple levels with biochemical assays and animal behavior tests

Contact information Ferenc Zádor Ph.D. Email: zador.ferenc@gmail.com Room: 233, 135 Phone: 580 Edina Szűcs Email: szucs.edina@brc.mta.hu Room: 235b, 135 Laboratory of Opioid Research Sándor Benyhe D.Sc. Head of research group Ferenc Ötvös Ph.D. Senior research associate Zsuzsa Benyhe Laboratory assistant

THANK YOU FOR YOUR ATTENTION! This work is supported by the European Union, co-financed by the European Social Fund, within the framework of " Practiceoriented, student-friendly modernization of the biomedical education for strengthening the international competitiveness of the rural Hungarian universities " TÁMOP-4.1.1.C-13/1/KONV-2014-0001 project.