A functional CD40 receptor is expressed in pancreatic beta cells

Abstract

Aims/hypothesis: Despite differences in function and embryonic origin, pancreatic islet cells and neurons express proteins belonging to the tumour necrosis factor receptor superfamily. While neurons express the CD40 receptor, it is unknown whether islet cells also express it. We investigated CD40 expression in human and mouse pancreatic islets as well as in NIT-1 insulinoma cells. Methods: CD40 expression was studied by reverse transcriptase polymerase chain reaction, flow cytometry, immunohistochemistry and western blot. Responses mediated by CD40 were assessed by a luciferase gene reporter assay following stimulation with a CD40 agonist antibody. Results: We found that CD40 is expressed in mouse and human pancreatic islet cells. CD40 is expressed by beta cells, and its expression is upregulated by proinflammatory cytokines (IL-1β, IFN-γ and TNF-α). CD40 signalling in NIT-1 insulinoma cells activates nuclear factor kappa-B, demonstrating that CD40 is functional. Conclusions/ interpretation: We present evidence that, in addition to immune cell types, mouse and human pancreatic beta cells express CD40. Its expression is upregulated by proinflammatory stimuli, and signalling through this receptor activates NF-κB. We suggest that the effects of inflammatory stimuli that affect beta cell function and survival may be also mediated by signalling through the CD40 receptor. Thus, CD40 may have a role in processes associated with islet autoimmunity and transplantation.

Immunoglobulin-Like Transcript 3-Fc Suppresses T-Cell Responses to Allogeneic Human Islet Transplants in hu-NOD/SCID Mice

“…There is evidence that the constitutive and selective expression of CD40 on the surface of ␤-cells contributes to autoimmunity and islet allograft rejection by providing costimulatory signals to infiltrating lymphocytes (6,8,10,12,39,40). It is, therefore, possible that in addition to suppressing islet allograft rejection in diabetic patients, ILT3-Fc may also prevent recurrence of diabetes by inhibiting the CD40-CD40L interaction between pancreatic islet cells and autoaggressive T-cells, primed to diabetagenic islet cell peptides presented by self-APCs.…”

“…Such attempts include the blockade of the CD40-CD40L costimulatory pathway deemed to be crucial to the activation and differentiation of T effector cells. Because CD40 is expressed by pancreatic islet cells (8), blockade of this pathway may be particularly relevant (6 -12).…”

CD40–CD40 Ligand Interaction Activates Proinflammatory Pathways in Pancreatic Islets

“…Western blot: CD40 expression. NHP islets were lysed in SDS and Tris-HCl buffer (pH 6.8), and aliquots corresponding to 50 g of protein were subjected to Western blot analysis as previously described (22). Membranes were incubated with 1:200 rabbit anti-human CD40 antibody (C20; Santa Cruz Biotechnology) followed by secondary anti-rabbit horseradish peroxidaseconjugated antibody (1:25,000) and chemiluminescent detection (Amersham Biosciences, San Francisco, CA).…”

“…Initial studies indicate that CD40 signaling activates the proinflammatory transcription factor nuclear factor (NF)-B (22). This suggests that CD40-CD40L interaction in islets could activate MAPK pathways as well and induce a proinflammatory response.…”

CD40 activation in human pancreatic islets and ductal cells

“…We have previously reported that CD40 is expressed in murine and human pancreatic beta cells and that its expression is upregulated by a cocktail of diabetogenic cytokines (IL-1β, TNF-α and IFN-γ) [13]. The stimulation of CD40 receptor on islet cells increases extracellularly regulated kinases 1/2 (ERK1/2)-and nuclear factor-κB (NF-κB)-dependent inflammatory signals, resulting in secretion of cytokines such as IL-6, IL-8, macrophage inflammatory protein 1-beta (MIP-1") and monocyte chemoattractant protein-1 (MCP-1) [14].…”