No abstract

Metabolic acidosis frequently complicates sepsis and septic shock and may be deleterious to cellular function. Different types of metabolic acidosis (e.g., hyperchloremic and lactic acidosis) have been associated with different effects on the immune response, but direct comparative studies are lacking. Murine macrophage-like RAW 264.7 cells were cultured in complete medium with lactic acid or HCl to adjust the pH between 6.5 and 7.4 and then stimulated with LPS ( Escherichia coli 0111:B4; 10 ng/ml). Nitric oxide (NO), IL-6, and IL-10 levels were measured in the supernatants. RNA was extracted from the cell pellets, and RT-PCR was performed to amplify corresponding mediators. Gel shift assay was also performed to assess NF-κB DNA binding. Increasing concentrations of acid caused increasing acidification of the media. Trypan blue exclusion and lactate dehydrogenase release demonstrated that acidification did not reduce cell viability. HCl significantly increased LPS-induced NO release and NF-κB DNA binding at pH 7.0 but not at pH 6.5. IL-6 and IL-10 expression (RNA and protein) were reduced with HCl-induced acidification, but IL-10 was reduced much more than IL-6 at low pH. By contrast, lactic acid significantly decreased LPS-induced NO, IL-6, and IL-10 expression in a dose-dependent manner. Lactic acid also inhibited LPS-induced NF-κB DNA binding. Two common forms of metabolic acidosis (hyperchloremic and lactic acidosis) are associated with dramatically different patterns of immune response in LPS-stimulated RAW 264.7 cells. HCl is essentially proinflammatory as assessed by NO release, IL-6-to-IL-10 ratios, and NF-κB DNA binding. By contrast, lactic acidosis is anti-inflammatory.

Metabolic acidosis is among the most common abnormalities seen in patients suffering from critical illness. Its etiologies are multiple and treatment of the underlying condition is the mainstay of therapy. However, growing evidence suggests that acidosis itself has profound effects on the host, particularly in the area of immune function. Given the central importance of immune function to the outcome of critical illness, there is renewed interest in elucidating the effects of this all too common condition on the immune response. In this review we concentrate on the effects of extracellular acids on production and release of inflammatory mediators, and we demonstrate that different acids produce different effects despite similar extracellular pH. Finally, we discuss potential clinical implications.

Functional defect in DNA damage binding (DDB) activity has a direct relationship to decreased nucleotide excision repair (NER) and increased susceptibility to cancer. DDB forms a complex with cullin 4A (Cul4A), which is now known to ubiquitylate DDB2, XPC, and histone H2A. However, the exact role of DDB1 in NER is unclear. In this study, we show that DDB1 knockdown in human cells impaired their ability to efficiently repair UV-induced cyclobutane pyrimidine dimers (CPD) but not 6-4 photoproducts (6-4PP). Extensive nuclear protein fractionation and chromatin association analysis revealed that upon irradiation, DDB1 protein is translocated from a loosely bound to a tightly bound in vivo chromatin fraction and the DDB1 translocation required the participation of functional DDB2 protein. DDB1 knockdown also affected the translocation of Cul4A component to the tightly bound form in UV-damaged chromatin in vivo as well as its recruitment to the locally damaged nuclear foci in situ. However, DDB1 knockdown had no effect on DNA damage binding capacity of DDB2. The data indicated that DDB2 can bind to damaged DNA in vivo as a monomer, whereas Cul4A recruitment to damage sites depends on the fully assembled complex. Our data also showed that DDB1 is required for the UV-induced DDB2 ubiquitylation and degradation. In summary, the results suggest that (a) DDB1 is critical for efficient NER of CPD; (b) DDB1 acts in bridging DDB2 and ubiquitin ligase Cul4A; and (c) DDB1 aids in recruiting the ubiquitin ligase activity to the damaged sites for successful commencement of lesion processing by NER. (Cancer Res 2006; 66(17): 8590-7)

In this study, we examined the effects of apple polyphenols (APs) on hyperlipidemia, atherosclerosis, hepatic steatosis and endothelial function and investigated the potential mechanisms. ApoE−/− mice were fed a western-type diet and orally treated with APs (100 mg/kg) or atorvastatin (10 mg/kg) for 12 weeks. Hyperlipidemia and atherosclerosis in the aortic sinuses and, and hepatic lipidosis were measured. The treatment with APs or atorvastatin induced a remarkable reduction in the atherosclerotic lesions and hepatic steatosis and decreased the levels of low-density lipoprotein, triglyceride, CCL-2 and VCAM-1 levels in the plasma. Conversely, the APs significantly increased the plasma levels of high-density lipoprotein (HDL) cholesterol and markedly up-regulated the glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) levels in liver tissues. Moreover, the APs treatment modulated lipid metabolism by up-regulating the transcription of associated hepatic genes including PPARα, while down-regulating the transcription of SCAP and its downstream genes associated with lipid synthesis in the liver. Histological assessment showed that the APs treatment also reduced the macrophage infiltration in the aortic root plaque and the inflammatory cells infiltrations to the liver tissues. Moreover, we confirmed that the APs treatment greatly reduced the ox-LDL-induced endothelial dysfunction and monocyte adhesion to rat aortic endothelial cells (RAECs). Mechanistically, the APs treatment suppressed the ROS/MAPK/NF-κB signaling pathway, and consequently, reduced CCL-2, ICAM-1 and VCAM-1 expression. Our results suggest that the APs are a beneficial nutritional supplement for the attenuation of atherosclerosis.