Objective
Our overall objective is to (1) develop technology that targets drugs to β cells and (2) use that technology to prevent or treat diabetes in laboratory mice. First, we will design nanoparticles coated in small proteins (the key) that fit together with specific proteins found on β cells (the lock). We already know of one lock-and-key pair to use as a starting point. However, we aim to identify and test new lock-and-key pairs alongside these. We will then test the nanoparticles on β cells in a cell culture dish to see if they can deliver drugs to β cells. In this case, the “drug” is genetic material encoding a fluorescent protein called mScarlet, which we use as a tracer. We will know which β cells were targeted by the nanoparticles because they will glow red under a microscope.
Moving forward, we will inject mice with our nanoparticles to determine if they target β cells and bypass other cell types. After removing different organs from the mice, we will determine which cell types and tissues show mScarlet fluorescence. Of course, human β cells are different from mouse β cells, so it will be important to test if the nanoparticles also work on human β cells. To do this, we will transplant human islets (parts of the pancreas that contain β cells) into mice before injecting the mice with the nanoparticles.
Once we know that the nanoparticles specifically target β cells in a living organism, we will use them to deliver a drug that may prevent or treat diabetes. This time, the drug will be a protein called programmed death ligand 1, or PD-L1. When PD-L1 is displayed on the surface of β cells, it tells the immune cells not to attack. Thus, this treatment could block the immune cells from destroying β cells, which is what causes type 1 diabetes. We will inject these PD-L1-delivering nanoparticles into mice that are pre-diabetic (to measure prevention of diabetes) or already diabetic (to measure treatment). Ultimately, our goals are to test if PD-L1 was successfully delivered to β cells and if PD-L1 improved blood glucose in mice.
Background Rationale
In type 1 diabetes, immune cells destroy the β cells that make insulin, which means that they can no longer stabilize blood glucose levels. For years, researchers thought of the β cells as innocent victims. However, we now know that β cells invite the immune cells to attack them. When β cells are stressed, a whole alarm system is triggered, and cellular communication pathways are activated. Our lab and others have studied these emergency communication pathways. Some pathways order β cells to display neoantigens, the foreign-looking proteins that cause immune cells to attack. This means that we can now develop drugs to block these pathways in β cells. However, the problem is that the pathways we identified are present in all cells, not just in β cells. The rationale behind our proposal is to develop nanoparticle-based technology that we can use to target these pathways specifically in β cells.
Description of Project
In type 1 diabetes, a person’s own immune cells attack and destroy the β cells of the pancreas. Normally, β cells make insulin to keep blood glucose levels under control. Without insulin, uncontrolled blood glucose causes severe damage to cells and organs throughout the body. This is why patients with type 1 diabetes must rely on glucose monitoring and insulin injections for the rest of their lives.
New research suggests that β-cells are not so innocent victims. When β cells are stressed, they put on a disguise that tricks immune cells into thinking they are foreign invaders to attack. The disguise is an abnormal protein, called a neoantigen, that β cells display on their surface and that immune cells recognize as foreign. If we could stop β cells from making neoantigens, we could potentially stop the immune cells from targeting and destroying β cells.
The good news is that our lab and others have found drugs that stop β cells from making neoantigens. These drugs intercept the communication signals or pathways that tell stressed β cells to make neoantigens. The bad news is that these drugs can act on any cell in the body, not just β cells. Drugs targeting these pathways would then affect all cells, not just the β cells that we want to target. Ultimately, this would increase the chances of patients experiencing side effects due to the drug.
The goal of our research is to develop technology that targets drugs to β cells. To do this, we will package the drugs within a sphere of fat molecules to protect the drugs until they reach their destination (β cells). On the outside of this package (called a nanoparticle) will be small proteins. The small protein will act like a key that only fits into a specific lock — another larger protein found only on the surface of β cells. Once the key is within the lock, the drug can enter the cell. This will ensure that the drug acts on β cells and no other cells, avoiding unnecessary side effects. Our hypothesis is that we can use this technology to treat or prevent type 1 diabetes.
Anticipated Outcome
By combining the expertise of Drs. Fang and Mirmira, we anticipate that we will successfully make nanoparticles that target and deliver drugs to β cells. One lock-and-key pair has already been found, and we can use this to accelerate our nanoparticle design. Other lock-and-key pairs can be found using a special technique in which Dr. Fang is an expert. Therefore, we believe we will identify multiple ways to target β cells. Because our nanoparticles were designed to target β cells, we anticipate that a high number of β cells in the cell culture dish and in the mouse pancreas will show mScarlet fluorescence. On the other hand, we expect to see no mScarlet fluorescence in other cell and tissue types. This would indicate that our nanoparticles are on-target and effective at delivering drugs to β cells.
Because PD-L1 suppresses the immune response, delivering PD-L1 to β cells should save them from being attacked by immune cells. We anticipate that this will improve blood glucose levels in pre-diabetic and/or diabetic mice. These experiments will tell us if PD-L1 delivery to β cells using nanoparticles is a viable treatment for type 1 diabetes. The possibilities are endless with the specific drugs that are packaged into nanoparticles. Therefore, we believe our β cell-targeting technology will accelerate drug discovery for type 1 diabetes.
Relevance to T1D
The β cell is the epicenter of type 1 diabetes. These are the cells destroyed by the immune system. When they are destroyed, a patient can no longer make insulin or stabilize their blood glucose levels. We now know that β cells themselves invite the immune cells to attack. If we could give patients drugs that stop their β cells from communicating with their immune cells, we could stop the attack. Before we can do this, we need a way to specifically target drugs to β cells. In this proposal, we will develop nanoparticles that deliver drugs only to β cells. We will then use the nanoparticles to see if we can prevent or treat type 1 diabetes in mice. The goal is to eventually use this technology to treat patients with type 1 diabetes. Our β cell-targeting technology would greatly expand the treatment options for these patients, which could then include combination therapies directed at both β cells and immune cells. Fighting type 1 diabetes from multiple angles could be more effective than just suppressing the immune response. Most importantly, by treating the β cells early on, we could save them before they are permanently destroyed. Ultimately, patients with type 1 diabetes would not have to rely on daily insulin injections to save their lives.