Krzysztof Ksiazek

Accelerated senescence of human peritoneal mesothelial cells exposed to high glucose : the role of TGF-β1

Cellular senescence can be activated in response to noxious environmental stimuli. A senescent-like phenotype has been detected in the peritoneal mesothelium of mice exposed to high intraperitoneal glucose. We have sought to examine whether high glucose (HG) can induce the senescence program in human peritoneal mesothelial cells (HPMC) in vitro. Senescence of omentum-derived HPMC was induced by serial passages. Cells were cultured in media containing either 5 mM glucose, 30 mM glucose, or 5 mM glucose and 25 mM mannitol (M) for osmotic control. Compared with HPMC cultured in low glucose, the growth rate of cells exposed to HG was significantly decreased so that the cells reached fewer population doublings before entering senescence. Exposure to HG led to increased expression of senescence-associated β-galactosidase (SA-β-Gal) and of the cell cycle inhibitors p21Waf1 and p27Kip1. Late-passage HPMC exposed to HG displayed marked hypertrophy and released increased amounts of fibronectin and TGF-β1. These effects were absent from HPMC treated with equimolar M. Exposure of early-passage HPMC to exogenous recombinant TGF-β1 induced a senescence marker SA-β-Gal in a dose-dependent manner and mimicked other senescence-associated alterations induced by HG. The addition of anti-TGF-β1 neutralizing antibody partially reduced the activation of HG-induced SA-β-Gal. These results indicate that chronic exposure to elevated glucose may result in TGF-β1-mediated accelerated senescence of HPMC in vitro, which may hypothetically contribute to the peritoneal membrane dysfunction during peritoneal dialysis in vivo.

Senescent Peritoneal Mesothelial Cells Promote Ovarian Cancer Cell Adhesion : The Role of Oxidative Stress-Induced Fibronectin

Adhesion of ovarian cancer cells to the peritoneal mesothelium is a key step in the malignant progression of the disease. In an in vitro study, we showed that the adherence of ovarian cancer cells (of the OVCAR-3, SKOV-3, and A2780 cell lines) to senescent human omentum-derived peritoneal mesothelial cells (HOMCs) was greater than to early passage cells. The process was mediated primarily by the increased interaction of the alpha5beta1 integrin on cancer cells with HOMC-associated fibronectin (FN). In comparison with early passage HOMCs, senescent cells exhibited increased FN mRNA expression levels and produced significantly more FN. To assess the effect of senescence-associated oxidative stress on FN release, HOMCs were rendered senescent by exposure to an oxidant, tert-butyl hydroperoxide. Treatment with tert-butyl hydroperoxide resulted in a significant increase in HOMC FN mRNA and protein expression levels. The effect of oxidative stress on FN synthesis was found to be mediated by transforming growth factor-beta1, whose signaling pathway was controlled at upstream and downstream levels by p38 MAPK. The activity of p38 MAPK increased markedly in senescent HOMCs. Treatment of HOMCs with antioxidants significantly attenuated senescence-associated increases in p38 MAPK activity, production of both transforming growth factor-beta1 and FN, and ovarian cancer cell adhesion. These data indicate that oxidative stress that accompanies senescence may increase FN production by HOMCs and thus facilitate binding and dissemination of ovarian cancer cells.

Senescence Induces a Proangiogenic Switch in Human Peritoneal Mesothelial Cells

The incidence of cancers that metastasize to the peritoneum increases with age. Intraperitoneal cancer dissemination depends largely on angiogenesis and interactions with the peritoneal mesothelium. We assessed the proangiogenic potential of human peritoneal mesothelial cells. Conditioned media collected from these cells at senescence stimulated proliferation of endothelial cells to a significantly greater extent compared to media from early-passage cells. The effect was accompanied by a significantly increased release of proangiogenic mediators -- VEGF, CXCL1/GROalpha, CXCL8/IL-8, and CCL2/MCP-1. These results indicate that the senescent mesothelium exhibits increased angiogenic activity, which may contribute to accelerated intraperitoneal cancer progression in the aged.

Vulnerability to oxidative stress and different patterns of senescence in human peritoneal mesothelial cell strains

Both the ascites fluid-derived mesothelial cell line LP-9 and primary cultures of human omentum-derived mesothelial cells (HOMCs) are commonly used in experimental studies. However, they seem to have a different replicative potential in vitro. In the present study, we have attempted to determine the causes of this discrepancy. HOMCs were found to divide fewer times and enter senescence earlier than LP-9 cells. This effect was coupled with earlier increases in the expression of senescence-associated-beta-galactosidase and cell cycle inhibitors p16INK4a and p21WAF1. Moreover, almost 3 times as many early-passage HOMCs as LP-9 cells bore senescence-associated DNA damage foci. In sharp contrast to LP-9 cells, the foci present in HOMCs localized predominantly outside the telomeres, and the HOMC telomere length did not significantly shorten during senescence. Compared with LP-9 cells, HOMCs were found to enter senescence with significantly lower levels of lipofuscin and damaged DNA, and markedly decreased glutathione contents. In addition, early-passage HOMCs generated significantly more reactive oxygen species either spontaneously or in response to exogenous oxidants. These results indicate that compared with LP-9 cells, HOMCs undergo stress-induced telomere-independent premature senescence, which may result from increased vulnerability to oxidative DNA injury.

Comparison of icodextrin- and glucose-based peritoneal dialysis fluids in their acute and chronic effects on human peritoneal mesothelial cells.

Background Icodextrin-based peritoneal dialysis fluids (PDFs) display several features that may potentially improve their biocompatibility compared to conventional glucose-containing solutions. So far, however, the studies assessing the biocompatibility profile of icodextrin toward human peritoneal mesothelial cells (HPMC) has produced mixed results. The present study was performed to examine the acute and chronic impact of icodextrin on HPMC in vitro in comparison with standard glucose-based PDF. Methods Omentum-derived HPMC were either acutely pre-exposed to or incubated chronically (for up to 10 days) in the presence of icodextrin-PDF. Parallel cultures were treated with conventional PDFs containing either 1.5% or 4.25% glucose. All fluids were tested at neutral pH. HPMC were assessed for viability, proliferation, IL-6 secretion and generation of reactive oxygen species (ROS). Results Incubation in the presence of icodextrin-PDF significantly reduced HPMC proliferation in a manner similar to that of 1.5% glucose-PDF In addition, exposure to icodextrin-PDF impaired viability and IL-6 release from HPMC. This effect occurred both after the short pre-treatment with neat icodextrin-PDF for 1–4 hours and after prolonged incubation (up to 10 days) in media supplemented with icodextrin-PDF (1:1). The dysfunction of icodextrin-treated HPMC was of the magnitude that was between the effects exerted by 1.5%- and 4.25%-glucose PDF. Furthermore, exposure of HPMC to icodextrin-PDF induced a dose-dependent increase in ROS generation which was comparable to that produced by 1.5%-glucose PDF. Conclusion Exposure to icodextrin-PDF may impair viability and function of HPMC. The detrimental effects of icodextrin-PDF are at least as serious as those produced by conventional heat-sterilized low glucose-based PDF.

Does increasing human life span really mean that societies age

only one of these in the FMR group. Moreover, patients in the PMR group were more likely to have a 1-year decline in motor abilities, defined as a loss of 27 or more points at the Barthel Index motor scores, than those in the FMR group. These results support Boyd’s findings, showing that poor motor recovery from pre-admission to RACU discharge is associated with further functional decline and a higher rate of death or institutionalization at the 1-year follow-up. It could be hypothesized that PMR membership could reflect a condition of frailty that can lead to a loss of homeostatic capacity and therefore to long-term adverse outcomes; the lower albumin serum levels and the poorer cognitive and functional performances at baseline in the PMR group than in their counterparts indirectly suggest this, although the data also suggest that postacute rehabilitation should maximize its efforts, where possible, to fully reinstate patient’s motor abilities, because evidence indicates that intensive exercise programs have positive effects on reducing disability in elderly persons in the middle to long term ( 1 year).