Impact of Toll-like receptor 2 expression in renal allograft rejection.

BACKGROUND: An important role of TLR2 has been shown in various experimental models of renal ischaemia/reperfusion injury. To study the expression of TLR2 in renal allograft rejection systematically, we established an experimental rat transplantation model. METHODS: TLR2 expression was analysed in 99 human renal allograft biopsies, and in rat allografts at Day 6 and 28 after experimental renal transplantation. To discriminate whether regulation of TLR2 was following immunological processes after allogeneic transplantation or was a consequence from ischaemia/reperfusion injury, control animals subjected to syngeneic transplantation or to ischaemia/reperfusion damage were also investigated. RESULTS: TLR2 mRNA was significantly elevated in rat allografts with acute rejection on Day 6 and decreased spontaneously towards Day 28. TLR2 induction correlated with renal function and TLR2 excretion in the urine of transplanted rats. TLR2 staining was also significantly increased in human allografts with acute rejection. TLR2 protein could be localized in tubular epithelial cells and vascular endothelial cells, and in CD68- and CD4-positive infiltrating cells. CONCLUSIONS: TLR2 is markedly up-regulated in both experimental and human acute renal allograft rejection. Our data suggest a role for TLR2 during allogen-dependent graft damage after renal transplantation.

Head-to-head comparison of BNP and IL-6 as markers of clinical and experimental heart failure: Superiority of BNP.

Activation of BNP and IL-6 are hallmarks of left ventricular (LV) dysfunction and congestive heart failure (CHF). To assess the relative activation of BNP and IL-6 in clinical and experimental heart failure, we performed a human study in which plasma N-terminal proBNP (NT-proBNP) and IL-6 were measured in a large group of patients in the chronic phase after myocardial infarction (MI) and an animal study in which LV gene expression of BNP and IL-6 was assessed in rapid ventricular pacing-induced heart failure. In the human study, NT-proBNP and IL-6 were measured by non-extracted, enzyme-linked immunoassay in 845 subjects (n=468 outpatients after MI, MONICA MI register Augsburg; and 377 siblings without MI, control). NT-proBNP (295+/-23pg/mL vs. CTRL 84+/-8, P<0.05) and IL-6 (2.7+/-0.1pg/mL vs. CTRL 2.1+/-0.1, P<0.05) were both elevated in subjects with MI. These increases were particularly pronounced in the presence of concomitant CHF (both P<0.01 vs. CTRL) and LV dysfunction (EF<45%, both P<0.05 vs. CTRL). However, NT-proBNP was significantly correlated with several cardiac structural and functional parameters (EF, LVMI, history of MI, CHF symptoms; all P<0.05) upon regression analysis whereas IL-6 was only correlated with history of MI (P<0.001). Accordingly, MI subjects with symptomatic LV dysfunction were detected by NT-proBNP with a greater sensitivity, specificity, and ROC-area (85%, 88%, and 0.87, respectively) as compared to IL-6 (69%, 53%, and 0.67, respectively). In the animal study, IL-6 and BNP expression were both significantly elevated in CHF (both P<0.05) but with a much greater absolute activation of BNP. In addition, BNP mRNA expression displayed a stronger inverse correlation with LV function (r=-0.74; P<0.001) than IL-6 (r=-0.53; P=0.001) and was a markedly more sensitive and specific molecular marker of LV dysfunction (sensitivity 91%, specificity 100%, ROC-area 0.94) than IL-6 (sensitivity 74%, specificity 83%, ROC-area 0.87). Our animal study provides evidence that IL-6 expression is activated in heart failure but to a significantly lesser degree than that of BNP. Both the stronger expression of BNP and the better correlation with LV function provide the molecular basis for a diagnostic superiority of NT-proBNP in clinical LV dysfunction and heart failure.

Differential expression of potassium channels and abnormal conduction in experimental tachycardia-induced heart failure.

Heart failure causes electrophysiological changes in the heart. Downregulation of repolarizing K+-currents leads to a prolongation of the cardiac action potential. Nevertheless, little is known about the differential expression of atrial and ventricular K+-channels in the failing heart. Ten rabbits underwent progressive rapid right ventricular pacing for 30 days. Digitized ECGs and echocardiograms were obtained. Left ventricular and left atrial tissue was harvested and mRNA levels of BNP, Kv4.3, rERG, Kv1.5, and KvLQT1 were measured by real time PCR. Experimental heart failure was characterized by left ventricular dilatation (13 ± 1 mm vs. 9 ± 1, p < .001), depressed fractional shortening (25 ± 5% vs. 40 ± 4, p < .001), and left atrial remodeling with increased diameter (16 mm ± 2 vs. 12 ± 1, p = .002) and weight (1.3 g ± 0.2 vs. 0.5 ± 0.1, p = .01). A prolongation of P-wave (44 ± 5 ms vs. 40 ± 4, p = .001) and PQ-interval (73 ± 10 ms vs. 66 ± 9, p = .009) occurred. In heart failure, BNP mRNA levels showed a significant upregulation in the left ventricle and atrium (1.83 AU ±1.31 vs. 0.67 ± 0.65, p < .05 and 7.16 AU ±1.76 vs. 0.77 ± 0.48, p < .05). Left ventricular Kv1.5 mRNA was reduced by 50% (p < .001) and KvLQT1 was reduced by 70% (p < .001). rERG and Kv4.3 mRNA were unchanged (n = ns). In contrast, left atrial Kv4.3 and KvLQT1 were reduced by 70% (p < .001), whereas rERG and Kv1.5 were unchanged (p = ns). Significant correlations were present between BNP and K+-channel expressions. Heart failure is characterized by significant changes in the gene expression of repolarizing K+-currents with a differential atrial and ventricular pattern. These molecular changes occur together with changes in cardiac function, geometry, conduction, and BNP expression and provide a functional basis for electrical vulnerability in heart failure.