Methods for identifying compounds that inhibit G protein-coupled receptor (GPR84) agonist-stimulated chemotaxis
The present invention relates to methods and assays for identifying agents capable of modulating GPR84 activity in cells, in particular agents that inhibit GPR84-agonist stimulated chemotaxis. Inhibition of GPR84-agonist stimulated chemotaxis is useful in the prevention and/or treatment of inflammatory conditions. In particular, the present invention provides methods and assays for identifying agents for use in the prevention and/or treatment of inflammatory conditions (for example inflammatory bowel diseases (IBD), rheumatoid arthritis, vasculitis, lung diseases (e.g. chronic obstructive pulmonary disease (COPD) and lung interstitial diseases (e.g. idiopathic pulmonary fibrosis (IPF)), neuroinflammatory conditions, infectious diseases, autoimmune diseases and/or diseases involving impairment of immune cell functions.
1. A method for identifying a compound that inhibits G protein coupled receptor 84 (GPR84) agonist-stimulated chemotaxis, said method comprising:
a. exposing a population of cells expressing a GPR84 polypeptide comprising the amino acid sequence of SEQ ID NO: 1 to a test compound in the presence of a GPR84 agonist;
b. measuring GPR84 agonist-stimulated chemotaxis of said cells, wherein chemotaxis is measured by determining the number of migrated cells; and
c. comparing GPR84 agonist-stimulated chemotaxis of said cells in the presence of said test compound with a control in which GPR84 agonist-stimulated chemotaxis is not inhibited and identifying the compound as an inhibitor of GPR84 agonist-stimulated chemotaxis when chemotaxis in the presence of the compound is decreased compared to control.
2. The method of claim 1 , further comprising:
d. exposing a population of cells expressing a GPR84 polypeptide comprising the amino acid sequence of SEQ ID NO: 1 to a test compound in the presence of a chemotactic agent that is not a GPR84 agonist;
e. measuring non-GPR84 agonist-stimulated chemotaxis of said cells, wherein chemotaxis is measured by determining the number of migrated cells; and
f. comparing non-GPR84 agonist-stimulated chemotaxis of said cells in the presence of said test compound with a control in which non-GPR84 agonist-stimulated chemotaxis is not inhibited and identifying the compound as a specific inhibitor of GPR84 agonist-stimulated chemotaxis when non-GPR84 agonist-stimulated chemotaxis in the presence of the compound is not decreased compared to control.
3. The method of claim 2 , wherein said chemotactic agent is selected from the group consisting of Interleukin-8 (IL8; human), chemokine (C—X—C motif) ligand 1 (KC/CXCL1; rat), N-formylmethionyl-leucyl-phenylalanine (fMLP), leukotriene B4 or complement 5a.
4. The method of claim 3 , wherein said test compound identified as inhibiting GPR84 agonist-stimulated chemotaxis is contacted with cells stimulated with IL8- or LTB4 and identified as a specific inhibitor GPR84 agonist-stimulated chemotaxis if said compound does not inhibit IL8- or LTB4-stimulated chemotaxis in said cells.
5. The method of claim 1 , further comprising comparing GPR84 agonist-stimulated chemotaxis of said cells in the presence of said test compound with a control wherein said control comprises a population of cells expressing a GPR84 polypeptide comprising the amino acid sequence of SEQ ID NO: 1 exposed to a known antagonist of the GPR84 polypeptide in the presence of a GPR84 agonist.
6. The method of claim 1 wherein said population of cells are immune cells selected from the group consisting of dendritic cells, macrophages, and neutrophils.
7. The method according to claim 6 , wherein said population of cells are neutrophils.
8. The method of claim 1 wherein said GPR84 agonist is selected from the group comprising capric acid, undecanoic acid, lauric acid, 2,5-Dihydroxy-3-undecyl-2,5-cyclohexadiene-1,4-dione (Embelin), icosa-5,8,11,14-tetraynoic acid, 5S,6R-Dihydroxy-icosa-7,9,11,14-tetraynoic acid, diindorylmethane and indol-3-carbinol.
9. The method of claim 8 , wherein said GPR84 agonist is 2,5-Dihydroxy-3-undecyl-2,5-cyclohexadiene-1,4-dione (Embelin) or capric acid.
10. The method of claim 1 wherein said method for measuring the number of cells migrated is measurement of ATP level change in a chemotaxis measurement system comprising two separate compartments.
11. The method of claim 1 , wherein the method for determining the number of migrated cells is by using Zigmond chambers to perform time-lapse video microscopy.
12. The method of claim 1 , wherein the method for determining the number of migrated cells is with a Dunn chemotaxis chamber to obtain a microscopic readout.
13. The method of claim 1 , wherein the number of migrated cells is determined by a cell count of migrated cells.
14. The method of claim 1 , further comprising:
d. selecting a compound with a desired level of binding affinity to said polypeptide by:
i. contacting said test compound identified as inhibiting GPR84 agonist-stimulated chemotaxis with a GPR84 polypeptide comprising the amino acid sequence of SEQ ID NO: 1 and/or fragments thereof comprising an amino acid sequence selected from the group consisting of SEQ ID NO 2, 6, 10, and 14; and
ii. measuring the binding affinity of said test compound to said GPR84 polypeptide or fragment thereof; and
iii. selecting a compound with a desired level of binding affinity to said polypeptide.
15. The method according to claim 14 , wherein compounds are selected with a binding affinity of at least 10 μM.