Maria-Luisa Alegre
Maria-Luisa Alegre, MD, PhD
Autoimmune Diabetes
Figure 2. Schematic representation of how
NF-κB activation is reduced in T cells from I?B??N transgenic mice. IκB∝ΔN-Tg mice express a superrepressor IκB∝ (IκB∝ΔN) transgene
selectively in T cells (Lck promoter/CD2 locus control). This transgene
cannot be phosphorylated and degraded upon TCR stimulation and
therefore retains NF-κB dimmers in the cytoplasm, preventing gene
transcription.
Type I diabetes (T1D) is an autoimmune disease in which T cells, activated by peptides derived from β cells, invade and destroy pancreatic islets resulting in low insulin secretion and hyperglycemia. Mice on the NOD (non obese diabetic) background develop spontaneous T1D, similarly to diabetic patients. My laboratory is interested in the biochemical pathways in T cells necessary for triggering T1D. T cell stimulation results in activation of several transcription factors, including AP-1, NFAT and NF-κB. In collaboration with Mark Boothby from Vanderbilt University, we have sought to determine whether activation of NF-κB in T cells is necessary for the development of T1D. To this end, NOD mice were crossed with mice that have reduced NF-κB activity selectively in T cells (IκB∝ΔN transgenic mice, see Figure 1). The resulting mice failed to develop T1D, demonstrating the essential role of NF-κB in T cells for T1D in vivo. In addition to investigating the mechanisms by which T1D is prevented in these mice, our laboratory is currently developing high throughput methods to identify small molecule inhibitors that can prevent NF-κB activation selectively in T cells. These drugs will be tested in different models of T1D to evaluate their efficacy at preventing or treating recent onset autoimmune diabetes.
Islets
Figure 1.
Reduction of NF-κB activity in T cells results in prolongation of
pancreatic islet allograft survival in mice. BALB/c islets (H-2d) were
transplanted under the left kidney capsule of C57BL/6 (H-2b) wildtype
(WT) or IκB∝ΔN transgenic mice previously made diabetic by an injection
of streptozotocin. Blood glucose levels were followed daily. Two
consecutive measurements of less than 250 mg/dl were considered
recurrence of diabetes because of allograft rejection. 50% of IκB∝ΔN
transgenic mice accepted pancreatic islets allografts long-term.
Prevention of T cell death by overexpression of the anti-apoptotic
factor Bcl-xL (IκB∝ΔN/Bcl-xL transgenic mice) restored allograft
rejection suggesting that transplant acceptance in IκB∝ΔN transgenic
mice is due to T cell death.The only available cure for type 1 diabetes (T1D) currently is the transplantation of a pancreas or of pancreatic islets. However, transplanted tissues must survive numerous insults to successfully produce insulin long term in the host. First, the process of ischemia/reoxygenation/inflammation inherent to all transplantation procedures results in substantial cell death. Second, the cells that survive this insult are also exposed to autoimmune and alloimmune T cells that would invariably destroy the transplant in the absence of immunosuppression. Therefore, transplant recipients must take numerous immunosuppressive drugs for the rest of their lives to prevent graft destruction. Our laboratory in interested in the biochemical pathways in T cells necessary for mounting autoimmune and alloreactive responses. T cell stimulation results in activation of several transcription factors, including AP-1, NFAT and NF-κB. In collaboration with Mark Boothby from Vanderbilt University, we have shown that mice with selective inhibition of NF-κB in T cells (IκB∝ΔN-Tg mice) display significantly prolonged survival of transplanted pancreatic islets (see Figure 1), indicating that NF-κB in T cells plays an important role in islet allograft rejection. Because rejection is not prevented in all animals, we are also investigating the mechanisms of death of pancreatic ? cells after transplantation. Our focus is on determining whether β-cell-NF-κB is necessary for resistance of these cells to ischemic or inflammatory signals as well as to damage by autoimmune and alloreactive T cells in vitro and in vivo. The long term goal is to modify β cells prior to transplantation by gene therapy to make them resistant to cell death after transplantation.
