Honokiol Alleviates Experimental Mesangial Proliferative Glomerulonephritis and Roles of Interleukin-18 in Chronic Renal Failure Patients

• Main Authors: Chih-Kang Chiang, 姜至剛
• Other Authors: Shing-Hwa Liu
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/79139092392758450174

博士 === 國立臺灣大學 === 毒理學研究所 === 94 === Part 1: Honokiol, a small molecular weight natural profuct, alleviates experimental mesangial proliferative glomerulonephritis Glomerulonephritis is still the most common cause of end-stage renal disease. Accumulation of glomerular macrophages, proliferation of mesangial cells, and deposition of extracellular matrix proteins are pathobiological hallmarks of glomerulonephritis. Pharmacological interventions that can inhibit these insults may be beneficial in the retardation of the progression of glomerulonephritis. Honokiol, a small molecular weight lignan, originally isolated from Magnolia officinalis, shows anti-oxidative, anti-inflammatory, and anti-proliferative activities in a variety of inflammation models. However, the therapeutic effect of honokiol on renal disease has never been reported. In this study, we investigated the in vivo effects of honokiol on rat anti-Thy1 nephritis. Anti-Thy1 nephritis was induced in Wistar rats by injecting mouse anti-rat Thy1 antibodies intravenously. Nephritic rats were randomly assigned to receive honokiol (2.5mg/kg, twice a day) or vehicle (phosphate-buffered saline) and were sacrificed at various time points. Urine protein excretion was determined. Glomerular histology and immunohistopathology were studied. Western blotting was conducted for markers of proliferation. Adhesion molecules, chemokine and extracellular matrix gene expression were evaluated by Northern blotting. Honokiol-treated nephritic rats excreted less urinary protein and had lower glomerular cellularity and sclerosis. The increased intraglomerular proliferating cell nuclear antigen and Akt phosphorylation in nephritic rats could be abolished by the treatment of honokiol. Honokiol also alleviated glomerular monocyte chemoattractant protein-1 and intracellular adhesion molecule-1, so as type I (α1) collagen and fibronectin mRNA levels of nephritic rats. These results indicate that honokiol may have therapeutic potential in mesangial proliferative glomerulonephritis. Part 2: Biomarker Interleukin-18 predicts dialysis outcome and influences by uremic toxin and hemodialysis process As the declining of renal function, patients with end-stage renal disease (ESRD) have to receive renal replacement therapy (RRT) to maintain their life. Currently, hemodialysis and peritoneal dialysis are still the most common dialytic modalities among patients with ESRD. In hemodialysis patients, they receive maintenance dialysis via the vascular access to draw out blood to dialytic tube and to exchange uremic toxins and water two to three times a week. In peritoneal dialysis patients, peritoneal catheters were implanted into peritoneal cavity. Uremic toxin and excess fluid was exchanged under the principle of semi-permeable membrane of peritoneum. Because of continuously exposed to uremic toxins and high concentrated dialysate with 1.5% dextrose, which led to a state of chronic inflammation in the local peritoneum and systemic immune system. Interleukin (IL)-18 is a proinflammatory cytokine that is a potent co-stimulator of interferon-γ (IFN-γ) release from peripheral immune cells, such as T helper type 1 (Th1) and natural killer cells, in combination with factors such as IL-12. IL-18 and other pro-inflammatory cytokines, such as IL-6 and tumor necrotic factor-α (TNF-α) established a complete network to mediate the chronic inflammation status. Roles of IL-18 in the chronic inflammation and the immune system differentiation are similar to the pathophysiologic mechanisms of the uremic patients. In agreement, the activity of IL-18 has been markedly up-regulated in ESRD patients. However, it has not been established whether elevated plasma IL-18 predicts outcome in hemodialysis patients. Recently, cardiovascular-related morbidity and mortality are high among patients with ESRD, and recent evidence suggests that this may be linked to inflammation. Elevated IL-18 has been demonstrated as a poor outcome predictor in cardiovascular diseases in the general population. Based on the above observation, we first hope to discuss the role of IL-18 in the outcome of hemodialysis patients. Second, we investigated the influence of biocompatibility on the changes of IL-18 levels before and after dialysis, and the possible association with other pro-inflammatory cytokines. Finally, we studied the influences of uremic toxin and renal clearance in the plasma IL-18 levels of chronic renal failure (CRF) and continuous ambulatory peritoneal dialysis (CAPD) patients. Furthermore, the relationship between IL-18 and other proinflammatory cytokines, such as IL-6, and tumor necrosis factor-alpha (TNF-alpha) were also investigated. First, to determine whether plasma IL-18 predicts overall hospitalization, we studied 184 ESRD patients (62% males, 58.5+/-1.0 years of age) undergoing maintenance HD treatment. The patients were followed for 12 months and were stratified by the tertiles of plasma IL-18 levels. Classic factors, such as age, body mass index, HD duration, nutritional and inflammatory parameters, co-morbidity, dialysis adequacy, and lipid status were entered into a Cox regression model to predict hospitalization. The Kaplan-Meier method was used to analyse the cumulative proportion of hospitalization-free events. Significantly different hospitalization days and frequencies (P<0.05) were observed when patients were divided according to tertiles of plasma IL-18 levels. Patients were stratified according to IL-18 tertiles and analysed separately according to the hospitalization-free period. In the Kaplan-Meier model, the upper tertile of IL-18 had the highest probability of a hospitalization event during the entire follow-up period (P log rank = 0.027). In the Cox proportional hazard model, the relative risk for first hospital admission for each increase in Ln IL-18 (pg/ml) concentration was associated with a 1.709 (95% CI, 1.114 to 2.620; P = 0.014) increase in the risk for future hospitalization events. Second, we based on the findings that elevated plasma IL-18 predicted poor outcomes in hemodialysis patients. In this study investigated changes of IL-18 levels before and after dialysis, and the possible association with other pro-inflammatory cytokines, such as IL-6 and TNF-alpha. Plasma IL-18 of healthy controls, and pre- and post-dialysis of uremic patients undergoing hemodialysis (HD) were evaluated by ELISA methodology. Plasma IL-18 levels were significantly increased in patients with maintenance HD (p <0.001) compared to its level in normal subjects. When compared to pre-dialysis levels, a significant increase in plasma IL-18 was measured at the end of HD (p = 0.032). There was a significant correlation among plasma IL-18, IL-6 and TNF-alpha levels in HD patients. Plasma IL-18 concentration was significantly higher in HD patients and was significantly elevated by cellulose-based HD processes. Finally, because of pending reports discussing the role of IL-18 in CAPD patients, we investigated IL-18, IL-6, and TNF-alpha in patients with CAPD. We also studied the influence of uremic toxins and renal clearance in plasma IL-18 levels on CRF patients. Plasma was evaluated by ELISA methodology in 15 healthy controls, 27 CRF and 15 CAPD patients. Plasma IL-18 levels in CRF (572.5 +/- 41.9 pg/ml) or CAPD (479.2 +/- 47.4 pg/ml) were significantly higher than normal (263.6 +/- 20.0 pg/ml), but there was no difference in IL-18 between CRF and CAPD patients. The IL-18 concentrations negatively correlated with creatinine clearance (Ccr). However, the duration of dialysis, normalized protein nitrogen appearance, weekly Ccr, and Kt/V(urea) were not correlated with plasma IL-18 in CAPD. The plasma IL-18 concentration was positively correlated with TNF-alpha but not with IL-6 in renal failure patients with or without CAPD. The present study demonstrated a strong predictive value of elevated IL-18 levels for poor outcome in HD patients. Pre-activation of immunologically active cells may contribute to the association between pre-dialysis IL-18 and post-dialysis IL-6 and TNF-alpha levels. Uremia, per se, is the principal origin of increased plasma IL-18 in these patients. Increased IL-18 levels may be associated with Th1 differentiation and elevated TNF-alpha.