ABSTRACT
Acute kidney injury remains an important cause of renal dysfunction. In this context, Toll-like receptors have been demonstrated to play a critical role in the induction of innate and inflammatory responses. Among these, Toll-like receptor 2 (TLR2) is constitutively expressed in tubular epithelial cells (TECs) of the kidney and is also known to mediate ischaemia reperfusion (IR) injury. Adult male C57BL/6JRj mice were randomized into seven groups (n = 8): a non-operative control group (CTRL) and six interventional groups in which mice were subjected to a 30 min. bilateral renal ischaemia. Immediately before reperfusion, mice were treated either with saline or with TLR2 antibody (clone T2.5) and harvested after ischaemia and reperfusion for 3, 24 and 48 hr. Analysed kidney homogenates of TLR2 antibody-treated mice displayed significantly decreased levels of TLR2 protein after 3 hr of IR compared to saline-treated mice. Accordingly, the degree of AKT phosphorylation was significantly decreased after 3 hr of IR compared to saline-treated animals. TUNEL staining revealed significantly higher apoptosis rates in TLR2 antibody-treated animals compared to saline-treated mice after 3 and 24 hr of IR. Further, a positive correlation between TLR2 protein expression and phosphorylation of AKT as well as a negative correlation with the number of TUNEL-positive cells could be observed. Inhibition of TLR2 and its signalling pathway by a single application of TLR2 antibody results in reduced phosphorylation of AKT and consecutively increased apoptosis.
Subject(s)
Acute Kidney Injury/drug therapy , Antibodies/pharmacology , Apoptosis/drug effects , Kidney/drug effects , Proto-Oncogene Proteins c-akt/metabolism , Reperfusion Injury/chemically induced , Toll-Like Receptor 2/antagonists & inhibitors , Acute Kidney Injury/enzymology , Acute Kidney Injury/immunology , Acute Kidney Injury/pathology , Animals , Antibodies/toxicity , Disease Models, Animal , Kidney/enzymology , Kidney/immunology , Kidney/pathology , Lipocalin-2/genetics , Lipocalin-2/metabolism , Male , Mice, Inbred C57BL , Neutrophil Infiltration/drug effects , Phosphorylation , Reperfusion Injury/enzymology , Reperfusion Injury/immunology , Reperfusion Injury/pathology , Signal Transduction/drug effects , Time Factors , Toll-Like Receptor 2/genetics , Toll-Like Receptor 2/immunology , Toll-Like Receptor 2/metabolismABSTRACT
Genetic or pharmacological ablation of toll-like receptor 2 (TLR2) protects against myocardial ischemia/reperfusion injury (MI/R). However, the endogenous ligand responsible for TLR2 activation has not yet been detected. The objective of this study was to identify HMGB1 as an activator of TLR2 signalling during MI/R. C57BL/6 wild-type (WT) or TLR2(-/-)-mice were injected with vehicle, HMGB1, or HMGB1 BoxA one hour before myocardial ischemia (30 min) and reperfusion (24 hrs). Infarct size, cardiac troponin T, leukocyte infiltration, HMGB1 release, TLR4-, TLR9-, and RAGE-expression were quantified. HMGB1 plasma levels were measured in patients undergoing coronary artery bypass graft (CABG) surgery. HMGB1 antagonist BoxA reduced cardiomyocyte necrosis during MI/R in WT mice, accompanied by reduced leukocyte infiltration. Injection of HMGB1 did, however, not increase infarct size in WT animals. In TLR2(-/-)-hearts, neither BoxA nor HMGB1 affected infarct size. No differences in RAGE and TLR9 expression could be detected, while TLR2(-/-)-mice display increased TLR4 and HMGB1 expression. Plasma levels of HMGB1 were increased MI/R in TLR2(-/-)-mice after CABG surgery in patients carrying a TLR2 polymorphism (Arg753Gln). We here provide evidence that absence of TLR2 signalling abrogates infarct-sparing effects of HMGB1 blockade.
