There is growing evidence of a role of the immune system in the pathophysiology of ischemia-reperfusion (I/R) injury, but the influence of I/R injury on innate immunity is still undetermined. Sprague-Dawley rats were used. I/R injury was induced by clamping both renal arteries for 45 min, and the rats were killed 1, 3, 5, and 7 days later. Activation of innate immunity was evaluated in terms of the expression of toll-like receptor (TLR) 2 or TLR4 mRNAs and protein, by the level of the TLR ligand (heat shock protein [HSP] 70), and maturation of dendritic cells by double-label immunohistochemistry of dendritic cells for major histocompatibility complex (MHC) class II antigen. I/R injury increased TLR2 and TLR4 mRNA and protein expression, and they were mainly observed on renal tubular cells. I/R injury also produced endogenous TLR ligand (HSP70) on renal tubular cells. I/R injury increased not only the numbers of dendritic cells but also the production of MHC class II antigen in dendritic cells, suggesting maturation of these cells. Activation of innate immunity was observed at day 1, peaked at days 3 to 5 after I/R injury, and thereafter gradually decreased. I/R injury rapidly activates the innate immune response.

Ischemia/reperfusion (I/R) injury in the early posttransplant period is closely associated with delayed recovery of graft function, increased acute rejection, and late allograft dysfunction. Pharmacological preconditioning with low-dose cyclosporine (CsA) or FK506 was performed to induce ischemic tolerance in rat kidney with I/R injury. Low-dose CsA (3 mg/kg, administered i.v.) or FK506 (0.3 mg/kg i.v.) were used to induce ischemic tolerance in Sprague-Dawley rats, and the induction of heat shock protein (hsp) 70 by CsA or FK506 was evaluated overtime. Rats were pretreated with CsA or FK506 6 hr before I/R injury when hsp70 was maximally expressed, and were killed 24 hr later. The effect of pharmacological preconditioning on subsequent I/R injury was evaluated in terms of renal function, histopathology score, assays for apoptosis (DNA fragmentation analysis, TUNEL staining, expressions of pro-apoptotic genes, and caspase activity), and the expression of inflammatory cytokine genes (interleukin-1 and tumor necrosis factor-α). Preconditioning with low-dose CsA or FK506 significantly improved renal function and renal histology, compared to rats with I/R injury. Apoptotic cell death (typical DNA laddering and increased TUNEL-positive cells) in rat kidneys with I/R injury, was decreased by pretreatment with low-dose CsA or FK506. Increased expression of pro-apoptotic genes (Fas, Fas-ligand, caspase 1 and 3) and activated caspases in ischemic rat kidneys were decreased after CsA or FK506 pretreatment. Pretreatment with low-dose CsA or FK506 prevents subsequent I/R injury, and this effect may be related to the induction of hsp70. Pretreatment of renal donors with low-dose CsA or FK506 may result in an improvement in immediate posttransplant function.

Background/Aims: Apoptosis contributes to cyclosporine (CsA)-induced renal cell death. This study tested the effects of CsA-induced endoplasmic reticulum (ER) stress on apoptotic cell death in an experimental model of chronic CsA nephropathy. Methods: CsA (15 mg/kg per day) was given to rats for 7 or 28 days. The ER stress response was evaluated with BiP expression, and the proapoptotic response was assessed with CHOP and caspase 12 expression. ER structure was evaluated by transmission electron microscopy, and apoptotic cell death was detected with TUNEL staining. Results: Short-term treatment of CsA for 7 days activated both the ER stress response (induction of BiP mRNA and protein) and the proapoptotic response (upregulation of caspase 12 and CHOP mRNAs and proteins). However, long-term treatment with CsA for 28 days decreased BiP and further increased CHOP. The imbalance between the two responses coincided with the timing of the appearance of apoptotic cell death and the disruption of the ER structure. Conclusion: Prolonged CsA-induced ER stress causes apoptotic cell death by depleting molecular chaperones and activating the proapoptotic pathway.

Rosiglitazone (RGTZ) has protective effect against various types of injury. This study was performed to evaluate the effect of RGTZ on pancreatic and renal injury caused by cyclosporine (CsA). CsA (15 mg/kg) and RGTZ (3 mg/kg) were administered alone and together to the rats for 28 days. The effect of RGTZ on CsA-induced pancreatic injury was evaluated by intraperitoneal glucose tolerance test (IPGTT), plasma insulin concentrations and pancreatic beta-cell morphology. The effect of RGTZ on CsA-induced renal injury was evaluated by assessing renal function and pathology; mediators of inflammation and fibrosis such as angiotensin II (AngII), osteopontin (OPN) and transforming growth factor-beta1 (TGF-beta1) and apoptotic cell death. Four weeks of CsA treatment caused diabetes, renal dysfunction, typical pathologic lesions (arteriolopathy, interstitial fibrosis and inflammatory cells infiltration) and apoptotic cell death. RGTZ treatment decreased blood glucose concentration, increased plasma insulin concentration and preserved pancreatic beta islet mass. RGTZ treatment improved renal function and histopathology. Pro-inflammatory and pro-fibrotic molecules such as AngII, OPN and TGF-beta1, and apoptotic cell death also decreased with RGTZ treatment. These data suggest that RGTZ has a protective effect against CsA-induced pancreatic and renal injury.

The toll-like receptor (TLR) is stimulated by not only pathogen-associated molecular patterns but also endogenous TLR ligands provided by injured cells. The influence of cyclosporine A (CsA)-induced renal injury on TLR expression and subsequent signaling pathway was evaluated. Induction of chronic CsA nephropathy was made by administering CsA (15 mg/kg/day) for 28 days in rats. The TLR2 and TLR4 mRNA and protein expression, TLR-signaling pathway (MYD88, NF-κB and AP-1), putative TLR ligand (heat shock protein 70 [HSP70]), and maturation of dendritic cells were evaluated in CsA-treated rat kidneys. Long-term CsA treatment upregulated TLR2 and TLR4 mRNA and protein expression on renal tubular cells, and these were accompanied by increased MYD88, NF-κB and AP-1 expression. Putative TLR ligand (HSP70) was also significantly increased in CsA-treated rat kidney compared with vehicle-treated rat kidney. CsA-treatment increased expression of TNF-α mRNA, the number of dendritic cells, and expression of MHC class II antigen. Double-labeling of markers of dendritic cells and MHC class II antigen revealed that matured dendritic cells increased in CsA-treated rat kidney. CsA-induced renal injury stimulates components of innate immunity, and this finding suggests close association between CsA-induced renal injury and activation of innate immunity.