Small molecule selectin ligand inhibition improves outcome in ischemic acute renal failure.

BACKGROUND: The pathophysiologic and potential therapeutic role of selectins in renal ischemia-reperfusion injury (IRI) is not fully understood, due in part to redundancy in the roles of individual selectins. We hypothesized that blockade of ligands for all three selectins using a novel small molecule (TBC-1269) would improve the course of renal IRI by overcoming redundancy issues. This was investigated in a rat model of renal IRI. METHODS: Rats were treated with TBC-1269 either during or post-IRI. The effects of TBC-1269 were investigated in two models of renal IRI: moderate IRI (30 minutes bilateral renal artery clamping) and severe IRI (45 minutes clamping). The combination of anti-E- and anti-P-selectin antibodies also was investigated in rats subjected to moderate IRI. Renal function, histological injury and mortality were assessed. RESULTS: Rats treated with TBC-1269 during moderate IRI showed significantly reduced serum creatinine (SCr) and tubular necrosis post-ischemia compared to control animals. By contrast, delayed treatment (post-IRI) did not show a reduction in SCr. In rats with severe IRI, TBC-1269 treatment during IRI significantly reduced mortality at 48 hours post-ischemia. Rats with moderate IRI and treated with the combination of anti-E- and anti-P-selectin antibodies showed significantly reduced SCr compared to control rats at 24 hours post-ischemia. CONCLUSIONS: Small molecule selectin ligand inhibition provides a novel and effective approach to attenuate ischemic acute renal failure. Timing of treatment is crucial to success.

Identification of the CD4(+) T cell as a major pathogenic factor in ischemic acute renal failure.

Leukocytes have been implicated in the pathogenesis of ischemic acute renal failure (ARF), but the roles of the individual cell types involved are largely unknown. Recent indirect evidence suggests that T cells may play an important role in a murine model of ARF. In the current study, we found that mice deficient in T cells (nu/nu mice) are both functionally and structurally protected from postischemic renal injury. Reconstitution of nu/nu mice with wild-type T cells restored postischemic injury. We then analyzed the contribution of the individual T cell subsets to postischemic injury and found that mice deficient in CD4(+) T cells, but not mice deficient in CD8(+) T cells, were significantly protected from ARF. Direct evidence for a pathophysiologic role of the CD4(+) T cell was obtained when reconstitution of CD4-deficient mice with wild-type CD4(+) T cells restored postischemic injury. In addition, adoptive transfers of CD4(+) T cells lacking either the costimulatory molecule CD28 or the ability to produce IFN-gamma were inadequate to restore injury phenotype. These results demonstrate that the CD4(+) T cell is an important mediator of ischemic ARF, and targeting this cell may yield novel therapies.

The relationship between modifiable health risks and future medical care expenditures: the Korea Medical Insurance Corporation (KMIC) Study.

CONTEXT: The relationship between lifestyle risk factors, morbidity, and mortality is well established, but the relationship between lifestyle risk factors and medical care costs is not as well defined. OBJECTIVES: To determine the ability of modifiable biometric and lifestyle risk factors to predict future medical care costs. DESIGN: Prospective cohort study. SETTING AND PARTICIPANTS: Data on modifiable risk factors collected in 1992 and medical care costs collected in 1998 by the Korea Medical Insurance Corporation in South Korea. Data were examined for a final cohort of 78,728 men and 50,414 women enrolled in the health insurance plan from 1990 through 1998. MAIN OUTCOME MEASURES: Outcome measures included likelihood of any inpatient, outpatient, and total medical care costs and outlier costs; amount of inpatient, outpatient, and total medical care costs; and portion of total medical costs attributable to each risk factor through unadjusted and adjusted multivariate analyses. RESULTS: Baseline modifiable risk factors measured in 1992 (including lifestyle factors such as smoking, high body mass index, exercise, and biometric measures such as cholesterol, blood sugar, blood pressure, and urinary sugar) were important predictors of the amount of medical care costs incurred 6 years later in 1998, even after controlling for age, perceived health status, and each of the other modifiable variables. These risk factors were generally better predictors than nonmodifiable demographic risk factors, including income level and type of job. For men, lifestyle risk factors were associated with total costs that were 2.4% (for high blood pressure) to 16.1% (for former smokers) higher than among men without those risk factors. Biometric risk factors were associated with costs ranging from 9.2% (for cholesterol) to 38.2% (for positive urinary glucose) higher. For women, lifestyle risk factors were associated with total costs that were 2.5% (for exercise) to 6.4% (for current smokers) higher than among those without the risk factors. Biometric risk factors were associated with costs ranging from 10.2% (for cholesterol) to 60.4% (for positive urinary glucose) higher. For men, a cluster of six heart disease risk factors were associated with total costs 54.7% higher, and a cluster of three stroke risk factors were associated with total costs 22.2% higher than in men who had none of these risk factors. Modifiable risk factors accounted for 23.1% of medical costs for men and 8.7% for women. CONCLUSIONS: These results suggest that modifiable biometric and lifestyle risk factors can predict a moderate portion of future medical care costs. If these risk factors can be reduced, future medical care costs may be reduced.

Health and productivity management: the concept, impact, and opportunity: commentary to Goetzel and Ozminkowski.

The author describes a model linking health, productivity and profit, why productivity is so important to business, and the potential impact productivity enhancement can have on health promotion.

Renal tubulointerstitial fibrosis. New thoughts on its development and progression.

Current investigation of the pathogenesis of tubulointerstitial injury indicates that both interstitial fibroblasts and renal tubular epithelial cells promote extracellular matrix accumulation. Moreover, two peptides--TGF-beta and angiotensin II--produced locally or delivered in the circulation, appear to play a central role in renal fibrosis. Pharmacologic amelioration of renal fibrosis may require methods directed at multiple factors involved in the fibrotic process, including angiotensin II, TGF-beta, and the proliferation and activation of interstitial fibroblasts.

Low-density lipoprotein-induced expression of interleukin-6, a marker of human mesangial cell inflammation: effects of oxidation and modulation by lovastatin.

Low-density lipoprotein (LDL) may contribute to the pathogenesis of glomerulosclerosis by stimulating a mesangial cell inflammatory response. Interleukin-6 (IL-6) is a marker of active inflammation and ongoing glomerular injury. Therefore, we investigated the effects of native and oxidized LDL on human mesangial cell production of IL-6 and a possible modulation of this inflammatory response by lovastatin, which has been shown to ameliorate experimental glomerulosclerosis. Human mesangial cells were exposed for 6 or 24 h to culture medium containing either native LDL alone or a LDL mixture containing 5 or 20% oxidized LDL. We found that native LDL stimulated 6 h mRNA expression and secretion of IL-6. This effect was further enhanced, in a dose-related manner, when mesangial cells were exposed to increasing concentrations of oxidized LDL. Lovastatin markedly inhibited mesangial cell expression of IL-6 mRNA and reduced IL-6 secretion. The inhibitory effects of lovastatin were overridden at least partially by exogenous mevalonate. We conclude that LDL, and particularly oxidized LDL, might contribute to the pathogenesis of glomerular disease by modulating the inflammatory response of human mesangial cells, as assessed by the stimulation of IL-6 expression. Moreover, this inflammatory response can be prevented by lovastatin, providing a potential direct anti-inflammatory mechanism by which HMG-CoA reductase inhibitors may attenuate lipid-induced glomerular injury.

The central role of nuclear factor-kappa B in mesangial cell activation.

BACKGROUND: Nuclear factor-kappa B (NF-kappa B) is a family of transcription factors that is recognized by the kappa B enhancer element. Numerous proinflammatory genes have binding sites for NF-kappa B, and the products of these genes are an integral part of cellular activation and inflammatory response systems. Because there is a close relationship between NF-kappa B and mediators of cell activation, it is possible that a disruption of NF-kappa B-activating pathways may effectively influence mesangial cell activation. METHODS: We reviewed available studies related to both NF-kappa B and mesangial cells in order to provide evidence for the role of NF-kappa B in mesangial cell activation. RESULTS: Studies reported by this laboratory and others showed that various experimental maneuvers that modulate NF-kappa B activation result in a parallel modulation of proinflammatory molecule production in cultured mesangial cells. Likewise, the ability of the inhibitors of NF-kappa B activation to down-regulate the inflammatory response in animal models of renal disease has been recently demonstrated. CONCLUSIONS: These data suggest a pivotal role of NF-kappa B in mesangial cell activation and designate it as an obvious target for the modulation of this activation. Studies are necessary to characterize the role of NF-kappa B in human renal injury.

Importance of geranylgeranyl pyrophosphate for mesangial cell DNA synthesis.

BACKGROUND: Farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP) are isoprenoid products of the intracellular mevalonate pathway used for prenylation of several low molecular weight G proteins, including Ras. It is likely that platelet-derived growth factor (PDGF) stimulation of mesangial cell proliferation requires prenylated, low molecular weight G proteins. The purpose of this study was to investigate the dependence of platelet-derived growth factor-stimulated mesangial cell DNA synthesis and cell membrane Ras incorporation on FPP and GGPP. METHODS: Quiescent human mesangial cells were exposed to PDGF (25 ng/ml) to stimulate DNA synthesis. Some cells were also treated with the HMG-CoA reductase inhibitor lovastatin (2.5 to 10.0 microM), which inhibits isoprenoid synthesis, in the presence or absence of exogenous FPP or GGPP. DNA synthesis was assessed by thymidine incorporation, and Western blot analysis was used to measure total cell membrane Ras. RESULTS: Stimulation of mesangial cells with PDGF did not increase total cell membrane Ras. Lovastatin reduced cell membrane Ras, and this was prevented by simultaneous exposure of mesangial cells to exogenous FPP (2.5 to 10.0 microM) or GGPP (1 to 5 microM). Lovastatin also reduced PDGF-stimulated mesangial cell DNA synthesis by 90%, and this was completely prevented by simultaneous exposure of cells to exogenous GGPP (1 microM), but not to FPP. CONCLUSIONS: The results of this study suggest that both FPP and GGPP can provide for mesangial cell membrane Ras localization and that PDGF-stimulated mesangial cell DNA synthesis requires the isoprenoid GGPP.

Lipophilic statins induce apoptosis of human vascular smooth muscle cells.

BACKGROUND: The accumulation of vascular smooth muscle cells (VSMC) in the intima is an early feature of atherosclerosis that results from a balance of migration from the media, proliferation, and eventual death (including programmed cell death) of VSMC. Several reports have described that HMG-CoA reductase inhibitors (statins) attenuate both the migration and proliferation of VSMC. However, the potential effect of statins on VSMC programmed cell death has received little attention. METHODS: Human and rat VSMC were incubated with different concentration of statins in the presence of fetal bovine serum as a survival factor. The presence of apoptosis was evaluated by morphological criteria, flow cytometry and DNA electrophoresis. RESULTS: Lipophilic statins induced, in a dose-dependent manner the appearance of VSMC apoptosis. The effect of statins was fully reversed by mevalonate, farnesylpyrophosphate, and geranylgeranypyrophosphate, but not by cholesterol or other mevalonate metabolites, suggesting a role for isoprenoids in VSMC apoptosis. In addition, the induction of apoptosis by statins was associated with the inhibition of prenylation of Rho B. CONCLUSIONS: The present results suggest that protein prenylation inhibition by statins may be involved in statin-induced VSMC apoptosis. These data provide a new potential mechanism by which statins may modulate the evolution of atherosclerotic lesions.

Effects of lovastatin on expression of cell cycle regulatory proteins in vascular smooth muscle cells.

BACKGROUND: The sequential appearance of cyclins D and E is thought to initiate subsequent DNA synthesis in proliferating cells. Previous studies have reported that DNA synthesis in cultured rat vascular smooth muscle cells (VSMCs) was suppressed by the HMG-CoA reductase inhibitor lovastatin. The effects of lovastatin on cell cycle regulatory proteins in proliferating VSMCs, however, are largely unknown. Thus, we investigated the sequential expression of cyclin D1, cyclin E, cyclin-dependent kinase (CDK) 4, CDK2, and p27Kip1 in cultured rat VSMCs stimulated by platelet-derived growth factor (PDGF)-BB in the presence or absence of lovastatin. METHODS: Quiescent VSMCs, with and without lovastatin (20 microM) pretreatment for nine hours, were stimulated by PDGF-BB (25 ng/ml). The incorporation of tritiated thymidine was done to assess DNA synthesis. VSMC lysates were obtained every 6 hours for up to 36 hours after stimulation and were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis using relevant polyclonal antibodies. Autoradiograms were analyzed using a densitometer. RESULTS: The peak expression of cyclins D1 and E occurred at 18 and 30 hours of PDGF stimulation, respectively. Concomitant expression of CDK4 and CDK2 was also observed. The expression of p27Kip1, by contrast, was reduced in association with DNA synthesis. Lovastatin suppressed DNA synthesis and reduced the expression of cyclin D1 and cyclin E, whereas p27Kip1 expression was strongly induced by lovastatin pretreatment. CDK4 and CDK2 expression was unaffected by lovastatin treatment. CONCLUSIONS: PDGF-BB induces cyclins D1 and E prior to the onset of DNA synthesis in VSMCs. Lovastatin may suppress DNA synthesis in VSMCs by inducing p27Kip1 and reducing expression of cyclins D1 and E.