TLR4 Mediates Early Graft Failure After Intraportal Islet Transplantation

Abstract

We have previously shown that islet emboli in the portal vein block blood flow and induce local inflammatory reaction, resulting in functional loss of islet grafts following intraportal transplantation. This study was designed to test whether Toll-like receptor (TLR) activation mediates early islet graft failure. Syngeneic islet grafts were transplanted into chemically induced diabetic mice, and TLR deficient mice were used as donors and/or recipients of islet grafts. Islet viability, proinflammatory cytokines, high-mobility group box-1 (HMGB1) and NF-j B activation were analyzed by bioluminesce imaging (BLI), quantitative RT-PCR (qRT-PCR) and histology. Early islet graft failure was observed in mice with intraportal islet engrafts with increased proinflammatory cytokines, HMGB1 expression, NF-j B activation, caspase-3 and TUNEL positive cells. Deficiency of TLR4 in donor, but not in recipient, inhibited NF-j B activation, reduced proinflammatory cytokines and improved viability of islet grafts. Blockade of HMGB1 with anti-HMGB1 monoclonal antibody (mAb, 2g7) inhibited inflammatory reactions, as evidenced by reduced TNFa and IL-1ß production, and improved islet viability. We conclude that TLR4 activation mediates early graft failure following intraportal islet transplantation. Inhibition of TLR4 activation represents a novel strategy to attenuate early graft failure following intraportal islet transplantation.

Treatment with Anti-HMGB1 Monoclonal Antibody Does Not Affect Lupus Nephritis in MRL/lpr Mice

“…portal vein of the liver together with the transplanted islets (28). Collectively, these studies demonstrate that the anti-HMGB1 mAb 2G7, in comparable dosages and using similar administration routes, confers protective effects in various inflammatory disease models.…”

Monoclonal Anti-HMGB1 (High Mobility Group Box Chromosomal Protein 1) Antibody Protection in Two Experimental Arthritis Models

“…One mAb recognizing an epitope in the C-terminus of the HMGB1 molecule improved outcome in an experimental stroke model (33). The 2G7 mAb was previously demonstrated to improve survival in a gram-negative sepsis model (29) and to prevent TLR4-mediated early graft failure after pancreatic islet graft transplantation (30).…”

“…The anti-HMGB1 mAb (2G7) used in our studies has previously demonstrated beneficial therapeutic effects in models for experimental sepsis and pancreatic islet graft transplantation (29,30). Furthermore, the 2G7 mAb performs excellently in vitro to detect natural HMGB1 in the HMGB1-specific Elispot assay developed by our group (31), in immunohistochemistry studies (32) and to neutralize rHMGB1-induced TNF production in cultured macrophages (11).…”

“…CIA is the prototypi- The anti-HMGB1 mAb used in the present study, in the published sepsis and islet graft transplantation studies (29,30) and the mAb studied in the stroke model (33) are rodent IgG antibodies that need to be humanized before evaluation in clinical trials. However, the beneficial therapeutic outcomes in these diverse conditions, including arthritis, sepsis, organ transplantation and stroke, indicate strong proof-of-concept in support of a further development of monoclonal anti-HMGB1 antibodies.…”

THERAPY OF ENDOCRINE DISEASE: Islet transplantation for type 1 diabetes: so close and yet so far away

“…Over-expression of IL1 receptor antagonist in islets (93), inhibition of TF NF-kB which mediates the detrimental effects of these cytokines on islets (94), inhibition of toll-like receptor 4 and blockade of high mobility group box 1 (HMGB1) with anti-HMGB1 mAb (95) are among the strategies used to inhibit inflammatory cytokines. There is decreased expression of anti-oxidants in pancreatic islets in comparison to most other tissues.…”