Modified epinephrine selective for beta 1 and beta 3 adrenergic receptors and its use as a tocolytic. Morgan Connolly COSMOS, Cluster 8

Transcription

1 Modified epinephrine 1 Running head: Epinephrine modified to be an improved tocolytic. Modified epinephrine selective for beta 1 and beta 3 adrenergic receptors and its use as a tocolytic. Morgan Connolly COSMOS, Cluster 8

2 Modified epinephrine 2 Modified epinephrine selective for beta 1 and beta 3 adrenergic receptors and its use as a tocolytic. Abstract Preterm labor is a tragedy. About 12% of pregnancies end in preterm labor. Nearly 75% of these premature babies die within their first week of life. Tocolytics are used to cease uterine contractions and therefore halt preterm labor. Epinephrine is a natural tocolytic. However, epinephrine's usefulness as a tocolytic has been mitigated because it binds nonselectively to all adrenergic receptors. I hypothesized that epinephrine with a methyl group added would bind selectively to beta 1 and beta 3 adrenergic receptors. Epinephrine binds to five different types of adrenergic receptors: alpha 1, alpha 2, beta 1, beta 2, and beta 3. The myometral, uterine, adrenergic receptors are beta 1 and beta 3. Using the computer program Chemdraw I visualized my new drug. Using VIDA I filtered my drug to find out if it followed Lipinski's rules, or if it was toxic to the human body. Then, using FRED I located the active sight on beta 1 and beta 2 adrenergic receptors and docked my drug into it. I found that modified epinephrine bound well to beta 1 adrenergic receptors and poorly to beta 2 adrenergic receptors. Unfortunately, my drug is too insoluble to be easily metabolized. Epinephrine has been used as a drug for over a hundred years; it was the first hormone to be observed. Experiments with epinephrine began in 1894 when the physiologist Edward Sharpey-Schafer observed that adrenal extract constricted blood vessels. In 1899 the chemist John J. Abel produced a crystalline epinephrine-hydrate which he incorrectly

3 Modified epinephrine 3 believed had the same structure and function as the adrenal extract. It was not until 1901 that natural epinephrine was isolated by the Japanese American chemist Jokichi Takemine. The chemists F. Stoltz and H. D. Dankin separately discovered the process for synthesis of adrenaline in 1904 (Bennett, 1999). Figure 1a, Epinephrine (Chem3D Pro. CambridgeSoft Corporation, 2007)

4 Modified epinephrine 4 Figure 1b, Structure of epinephrine (Chem3D Pro. CambridgeSoft Corporation, 2007) Epinephrine (figures 1a and 1b) is adrenaline. It activates the sympathetic, "fight or flight", branch of the autonomic nervous system. In the human body epinephrine is synthesized in the adrenal medulla from hormone producing chromaffin cells. The amino acids tyrosine and phenylalanine are converted (in the adrenal medulla) to dopamine, then norepinephrine and finally epinephrine. Epinephrine and norepinephrine are very similar, differing only by a single methyl group. However, dopamine is a significantly different drug. It lacks the hydroxyl group of epinephrine and norepinephrine and binds to different receptors. (Mayberg, 2008) Epinephrine is an agonist to five different types of adrenergic receptors: alpha 1, alpha 2, beta 1, beta 2, and beta 3. All adrenergic receptors are part of the G proteincoupled receptor (GPCR) superfamily. As the name suggests, GPCR is a very large group

5 Modified epinephrine 5 of receptors. However, all receptors in this group share several characteristics. GPCRs are integral membrane proteins. All GPCRs undergo a conformational change when bound to by an appropriate ligand. Intracellular calcium concentrations rise directly from GPCR receptor activation. (Filmore, 2004) The primary effect of alpha 1 receptors is vasoconstriction. The activated alpha 2 receptor constricts the gastrointestinal sphincters, inhibits lypolysis in adipose tissue, and aggregates platelets.(goodman, 2001) Beta 1 receptors increase heart rate and relax uterine muscles, beta 2 receptors relax smooth mussels in the bronchi, which facilitates respiration, and dilate arteries. Beta 3 receptors are found mainly in adipose tissue and are involved in thermogenesis. (Mhaouty-Kodja, S, 2004) Epinephrine is an extremely useful drug with several forms. Albuterol, or sambutamol, is a form of epinephrine selective to beta 2 adrenergic receptors. It is used as an asthma medication. Phenylephrine is a somewhat controversial decongestant that activates alpha 1 adrenergic receptors. Isoproternol binds to beta 1 and beta 2 receptors and before the introduction of albuterol was commonly used to treat asthma. Now, it is mainly used to treat bradycardia. Dipivefrine is a prodrug derivative of epinephrine. A prodrug is a drug that undergoes a vital chemical change inside the human body. Dipivefrine is used to treat glaucoma. It is applied directly to the eye and is converted to epinephrine inside the cornea. (Carter, 1994)

6 Modified epinephrine 6 It was been known for over a century that epinephrine is useful as a tocolytic. Physiologically this function makes sense. If a mother beginning the process of labor is threatened the labor must halt to allow her to flee. In modern times this ancient reaction has medical purposes. However, epinephrine's usefulness as a tocolytic has been mitigated by its non-selectivity, it binds to all adrenergic receptors. The myometral adrenergic receptors are beta 1 and beta 3. (Segal, 1998) the myometral is the smooth muscle of the uterus. Figure 2a, Modified epinephrine (Chem3D Pro. CambridgeSoft Corporation, 2007)

7 Modified epinephrine 7 Figure 2b, Structure of modified epinephrine (Chem3D Pro. CambridgeSoft Corporation, 2007) Method I hypothesized that adding a methyl group (figures 2a and 2b) to epinephrine would cause it to bind selectively to beta 1 and beta 3 receptors. I used computational chemistry to test my hypothesis. First I built my drug in the computer program Chemdraw 3D. Then I used VIDA, another computer program, to filter my drug - to see if it broke any of Lipinski's rules, or was toxic to the human body. Finally I used FRED to dock my drug. FRED is a computer program used for finding the active sights of proteins and then discovering what molecules fit into, dock into, these active sights. When creating new drugs Lipinski's rules are commonly used as guidelines. There are five rules. First, there must be no more than five hydrogen bond donors in the molecule. Second there must be no more than ten hydrogen bond acceptors. The drug must have a molecular weight under five Dalton's. Finally the drug must have an octanol-water partition coefficient log P of less than 5. (Lipinski, 1997)

8 Modified epinephrine 8 Results I found that my drug bound to beta 1 adrenergic receptors very well, better then unmodified epinephrine. Modified epinephrine had an overall binding favorability score of Unmodified epinephrine had an overall binding favorability score of Negative scores represent lower energy states and are therefore more favorable. Modified epinephrine docked very poorly into beta 2 adrenergic receptors with a binding favorability score of Sadly, the carbon carbon bond in modified epinephrine makes it too insoluble to be a working candidate for a drug. In other words, my drug passed the docking process of drug development but failed the filter. Discussion Epinephrine as an effective tocolytic is still a possibility. The crystal structure for alpha 1 adrenergic receptors is not fully understood. The crystal structures for alpha 2 adrenergic receptors and beta 3 adrenergic receptors are not known. Because of this I could not test the effectiveness of my drug on them. Due to the similarities between beta 1 and beta 3 adrenergic receptors I believe modified epinephrine would bind well to beta 3 adrenergic receptors. I also believe that due to the structural similarities of albuterol (salbutamol) and modified epinephrine, modified epinephrine would not bind well to alpha adrenergic receptors. If modified epinephrine could be combined with a carbon carbon bond breaking catalyst it would have potential as an important, exciting drug.

9 Modified epinephrine 9 Acknowledgements I feel very grateful to be able to thank all the intelligent, incredibly knowledgeable people who have helped me this month. My wonderful professors: Dean Tantillo, who taught me how to look at a molecule and wonder how its electrons interact, Toby Allen, whose endless enthusiasm for chemistry made it fascinating, and Annaliese Franz whose labs were some of the most educational and fun things I ve ever done. I would also like to thank Danny Delgado, for all of his help and information, Rebecca Davis, for her extraordinary patience and skill in the computer lab, Phil Painter, Ngon Tran, Kaleb Jentzsch, and Josh Hanson. Bennett, M.R. (1999).One hundred years of adrenaline: the discovery of autoreceptors. CLIN AUTON RES, 9, Filmore, D. (2004).It's a GPCR world. MDD, 7(11), Goodman, A (2001). Goodman and Gilman's the pharmacological basis of therapeutics. McGraw-Hill. Mayburgh, JA; et al. (2008). A comparison of epinephrine and norepinephrine in critically ill patients. INTENS CARE MED, 35, Lipinski, C.A., Lombardo, F., & Dominy, B.W. (1997). Experimental and computational approaches to estimate solubility and permeability in drug discovery and development settings. ADV DRUG DEL REV, 23, Segal, S., Csavoy, A.N., & Datta, S. (1998). The tocolytic effect of catecholamines in the gravid rat uterus. ANESTH ANALG, 87,

10 Modified epinephrine 10 Annane, D, Vigon P, (2007). Norepinephrine plus dobutamine versus epinephrine alone for management of septic shock: a randomised trial. LANCET, 370, Mhaouty-Kodja, S., Houdeau, E., & Legrand, C. (2004). Regulation of myometrial phospholipase C system and uterine contraction by beta adrenergic receptors in midpregnant rat. BIOL REPROD, 70, Carter, WJ (1994).Comparison of the effects of salbutamol and clenbuterol on skeletal muscle mass and carcass composition in senescent rats. METAB CLIN EXP, 43,