The question they looked at in this study is whether GRK2 plays any role after a heart attack. Most cardiology researchers theorized that it was protective, because expression of the protein is increased by three to four times immediately after a heart attack, Dr. Koch says. "People always thought that GRK2 was working to shut off beta receptors because injured hearts were pumping out too much adrenaline, and that this blocking of over activity in an injured heart is protective."
But what the researchers discovered is that over production of GRK2 following a heart attack actually stimulates pro-death pathways in myocyctes (heart cells) outside of the initial zone of damage. They specifically found an inverse link between GRK2 activity and the production of nitric oxide (NO), a molecular messenger that protects the heart against damage caused by a sudden loss of blood. "When there is more GRK2, there is less NO, and vice versa," Dr. Koch says. They believe that GRK2 may be affecting NO production by inhibiting the prosurvival protein kinase Akt, which itself regulates NO. (more)
The mice MI studies then proved that inhibiting GRK2 protected heart cells, Dr. Koch says.
"Our results clearly show that GRK2 is a pathological target in the heart, involved in both progressive heart failure and in death of heart cells after a heart attack," he says.
|Contact: Rick Cushman|
Thomas Jefferson University