Objective
The proposed studies will determine whether blocking signaling through the EP3 prostaglandin E2 receptor OR activating signaling through the EP4 prostaglandin E2 receptor can protect insulin-producing β cells from autoimmune attack by promoting β-cell survival, proliferation, and function while SIMULTANEOUSLY re-training the immune cells to be less inflammatory and less destructive towards the β cells. The EP3 and EP4 receptors are present on β cells and immune cells and are know to have opposite effects on cellular signaling. We will test whether drugs that specifically target these receptors can be used in the NOD mouse model of Type 1 diabetes to prevent or delay disease onset. By decreasing signaling through EP3 and/or increasing signaling through EP4, we hope to promote the beneficial effects of prostaglandin E2, while blocking its negative effects on inflammation. The goal is to positively affect both β cells and immune cells using a single treatment strategy.
Background Rationale
We have been working with a signaling molecule called prostaglandin E2 (PGE2), which is increased in the setting of inflammation and diabetes, and signals through two proteins present on β cells and immune cells called EP3 and EP4. In most cell types, these two proteins are present together and have opposite cell signaling effects. In a mouse model of Type 2 diabetes, we found that blocking EP3 or activating EP4 protects β cells. We also found that human β cells treated with drugs that block EP3 or activate EP4 are protected from death in the presence of toxic proteins produced by immune cells that normally kill β cells. We have some exciting preliminary data showing that treatment of the NOD mouse model of Type 1 diabetes with a drug that blocks EP3 activity results in decreased number of immune cells in the pancreatic islets and an increase in the number of β cells. Prostaglandin E2 (PGE2) is known to be increased in autoimmune diseases such as Type 1 diabetes, and it plays a role in the beginning stages of inflammation and autoimmunity. However, in normal cell and wound healing, prostaglandin E2 (PGE2) is also really important to allow for healing and decreased inflammation at the appropriate time. This phase of healing does not happen in autoimmune diseases and leads to cell death and destruction. Importantly, EP3 and EP4 proteins are found in β cells and immune cells, so a single drug therapy has the potential to affect both of he key cell types involved in the development of Type 1 diabetes. If we can learn how to harness the positive effects of prostaglandin E2 (PGE2) signaling while preventing the negative effects of prostaglandin E2 (PGE2) signaling we could promote healing and save the β cells from destruction.
Description of Project
Type 1 diabetes is characterized by immune cell destruction of the insulin-producing β cells in the pancreas. Much research and treatment strategies concentrate on suppressing the inappropriate immune cell attack on the β cells. However, it is becoming more and more clear, that in addition to the immune cell dysfunction the β cells themselves are active players in the process of their own destruction in the setting of Type 1 diabetes. Very few studies in Type 1 diabetes prevention are aimed at targeting both the immune system and the β cells at the same time using the same therapy. We have been working with a signaling molecule called prostaglandin E2 (PGE2), which is increased in the setting of inflammation and diabetes, and signals through two proteins present on β cells and immune cells called EP3 and EP4. In a mouse model of Type 2 diabetes, we found that blocking EP3 or activating EP4 protects β cells. We also found that human β cells treated with drugs that block EP3 or activate EP4 are protected from death in the presence of toxic proteins produced by immune cells. In the proposed study, we will examine whether treating NOD mice (the most commonly used model of Type 1 diabetes) with EP3 blockers or EP4 activators protects β cells from death and prevents the development of Type 1 diabetes, while simultaneously changing the immune cells in the pancreas to be more anti-inflammatory so that they are less likely to attack the β cells. There is evidence that PGE2 treatment can make immune cells behave in a more anti-inflammatory way. We will use multiple complementary techniques to examine the effects directly on β cells and also on the various types of immune cells known to be involved in Type 1 diabetes. We anticipate that blockade of EP3 or activation of EP4 will enhance β-cell number and survival, and reduce β-cell stress. We also predict that EP3 blockade or EP4 activation will decrease islet inflammation and decrease the number of immune cells present within the pancreas. Taken together, EP3 and EP4 appear to have direct but opposite effects on β cells and immune cells. We propose that shifting the islet microenvironment to an overall less inflammatory profile, while simultaneously enhancing β cell function and survival, could delay, prevent, or reverse T1D.
Anticipated Outcome
We anticipate that drugs that block EP3 receptor signaling and/or drugs that activate EP4 receptor signaling will have direct beneficial effects on both the β cells and the immune cells, thus preventing or delaying Type 1 diabetes in a mouse model of this disease, the NOD mouse. We predict that blocking EP3 and/or activating EP4 will result in a decrease in the number of immune cells in the pancreatic islets and that the remaining immune cells will behave in a less-inflammatory way, secreting proteins that promote a healing environment rather than a destructive environment within the islets. In addition, we predict that these same drugs will protect the β cells from any toxic proteins produced by immune cells, making them "blind" to these destructive proteins and allowing them to survive, multiply, and retain their normal function to control blood sugar levels. Thus, we predict that diabetes will not develop at all in NOD mice treated with these drugs or at the very least, these drugs will dramatically delay disease onset.
Relevance to T1D
Prostaglandin E2 (PGE2) is a circulating signaling molecule known to be increased in many autoimmune diseases including Type 1 diabetes. It acts mainly through two protein receptors called EP3 and EP4. In many different kinds of cells EP3 and EP4 have opposite effects on cell function. EP3 and EP4 proteins are both found on the pancreatic β cells and the immune cells that cause their destruction in Type 1 diabetes. Thus, it is not really the PGE2 that is the issue, it is which receptor is there in more abundance in the cell that will determine the cell response to PGE2. PGE2 plays a role in many stages in the process of normal inflammation. It is important for the start of an inflammatory response, but also very critical for the healing phase when the inflammation is over. In most autoimmune diseases, including Type 1 diabetes, the inflammation does not wind down normally, and continues unabated, leading to cell damage and destruction...in diabetes this leads to loss of insulin-producing β cells. There are drugs that can specifically turn on (activate) or turn off (block) the EP3 and EP4 receptors. By using these drugs we can harness the beneficial effects of activating EP4 while blocking the negative effects of EP3, and this can happen simultaneously on immune cells and β cells. We propose that this strategy will result in a dampening of the inflammation process, leading to more healing and little to no β-cell death and destruction.