High-mobility group box 1 is involved in the initial events of early loss of transplanted islets in mice

Abstract

Islet transplantation for the treatment of type 1 diabetes mellitus is limited in its clinical application mainly due to early loss of the transplanted islets, resulting in low transplantation efficiency. NKT cell-dependent IFN-γ production by Gr-1 + CD11b + cells is essential for this loss, but the upstream events in the process remain undetermined. Here, we have demonstrated that high-mobility group box 1 (HMGB1) plays a crucial role in the initial events of early loss of transplanted islets in a mouse model of diabetes. Pancreatic islets contained abundant HMGB1, which was released into the circulation soon after islet transplantation into the liver. Treatment with an HMGB1-specific antibody prevented the early islet graft loss and inhibited IFN-γ production by NKT cells and Gr-1 + CD11b + cells. Moreover, mice lacking either of the known HMGB1 receptors TLR2 or receptor for advanced glycation end products (RAGE), but not the known HMGB1 receptor TLR4, failed to exhibit early islet graft loss. Mechanistically, HMGB1 stimulated hepatic mononuclear cells (MNCs) in vivo and in vitro; in particular, it upregulated CD40 expression and enhanced IL-12 production by DCs, leading to NKT cell activation and subsequent NKT cell-dependent augmented IFN-γ production by Gr-1 + CD11b + cells. Thus, treatment with either IL-12-or CD40L-specific antibody prevented the early islet graft loss. These findings indicate that the HMGB1-mediated pathway eliciting early islet loss is a potential target for intervention to improve the efficiency of islet transplantation. IntroductionPancreatic islet transplantation, although an attractive procedure for the treatment of type 1 diabetes mellitus, usually fails to achieve insulin independence of a diabetic recipient from a single donor due to early loss of transplanted islets and therefore requires sequential transplantations of islets with the use of 2-3 donors (1). Thus, the low efficiency of islet transplantation has been a major obstacle facing islet transplantation and hampers its clinical application.We have previously shown in mice that loss of transplanted islets soon after transplantation is caused by NKT cell-dependent IFN-γ production by Gr-1 + CD11b + cells and is successfully prevented by treatment of NKT cells with repeated stimulation with their synthetic ligand, α-galactosylceramide (α-GalCer), to downregulate IFN-γ production of NKT cells, or by depletion of Gr-1 + CD11b + cells with anti-Gr-1 antibody (2). However, precisely how it is involved in the upstream events in the activation of NKT cells and Gr-1 + CD11b + cells in the early loss of transplanted islets remains to be solved.High-mobility group box 1 (HMGB1) protein was initially found to be a DNA-binding protein present in almost all eukaryotic cells, where it stabilizes nucleosome formation and acts as a nuclear factor that enhances transcription (3, 4). Recently,

Withaferin A inhibits pro-inflammatory cytokine-induced damage to islets in culture and following transplantation

“…Mouse islet isolation Islets were isolated from male inbred C57BL/6N mice (Harlan Labs, Houston, TX, USA) using a previously described procedure [22,23]. Islets were cultured at a purity greater than 95% in DMEM supplemented with kanamycin and 0.1% BSA (37°C, 5% CO 2 up to 96 h).…”

“…Mice were considered diabetic when their blood glucose was greater than 19.5 mmol/l for two consecutive days. Two-hundred islets were injected into the portal vein by puncturing the hepatic portal vein [22]. WA (1.25 mg/kg body weight) or vehicle (Dulbecco's phosphate-buffered saline [DPBS]) was injected into the peritoneal cavity.…”

“…Intraperitoneal glucose tolerance test Naive, transplanted and STZ-induced diabetic mice were used to perform an intraperitoneal glucose tolerance test (IPGTT) [22]. The mouse's food was removed for 12-14 h, then an injection of glucose (1 g/kg) was administered intraperitoneally.…”

“…TUNEL assay The TUNEL assay was performed with a ApopTag fluorescein in situ apoptosis detection kit (Millipore, Billerica, MA, USA) [22]. See ESM Methods for detailed procedure.…”

Thioredoxin-1 Attenuates Early Graft Loss after Intraportal Islet Transplantation in Mice

“…We examined whether the systemic administration of TRX had any effect on the accumulation of Gr1 + CD11b + (mainly neutrophils), CD1d + CD3e + (natural killer T (NKT) cells), and TF-positive Gr1 + CD11b + cells in the livers of mice receiving islets, which are thought to be essential components of early graft loss after islet transplantation [27][28][29]. No differences were detected between the TRX and control groups regarding the accumulation of Gr1 + CD11b + cells (Fig.…”