Lazaro Gotloib

Hemofiltration in septic ards. the artificial kidney as, an artificial endocrine lung

Twenty-four patients with high microvascular permeability pulmonary edema were initially treated by means of conventional supportive therapy for 1-12 days. Continued deterioration was treated by predilutional hemofiltration and induced a dramatic improvement in 22/24 patients. Survival was 92%. Sieving coefficients for autacoids and middle molecular weight vasoactive peptides involved in the development of high microvascular permeability pulmonary edema were higher than 0.88 indicating that clearing from blood of these peptides during one pass through the hemofilter is similar to that obtained during one pass through the pulmonary normal microvasculature. Hemofiltration seems to be a significant breakthrough in the treatment of ARDS secondary to severe sepsis.

High Glucose Induces a Hypertrophic, Senescent Mesothelial Cell Phenotype after Long in vivo Exposure

Previous studies, done using our mouse model for population analysis of the mesothelium, showed evidence indicating that in vivo, long-term exposure (up to 30 days) of the peritoneum to high-glucose (4.25% D-glucose) concentration dialysis solutions resulted in a hypertrophic mesothelial phenotype characterized by increased cell surface area, multinucleation, low proliferative capabilities, reduced cell viability, and enhanced enzymatic activity. These elements that define a senescent population of cells were not related to the pH of the fluid and its osmolality, or to the presence of buffer lactate. The present study was designed to explore the adverse effects of a lactate-free, filter-sterilized, high-D-glucose concentration solution (4.25%) at normal pH and prepared in Hanks’ buffered salt solution after 2 h, 15 and 30 days of once a day intraperitoneal injection. Analysis of our observations indicate that in vivo exposure of the mesothelium to a high-glucose concentration induced a decreased density of the cell population, made up by larger and multinucleated cells, the viability of which was significantly lower than that observed in intact unexposed mice. The prevalence of mitosis showed an early and short-lived acceleration (up to 3 days), followed by values near zero during the rest of the follow-up period. So far, the main effect of the high-glucose concentration appears to result not from a mechanism of cytotoxicity, but from a substantial change in the life cycle of the exposed cell population, leading to their premature senescence and death in apoptosis. We hypothesize that this outcome may well be mediated by sustained oxidative stress derived from both a reduced production of scavengers, as well as the increased generation of oxygen-reactive species.

Mesothelial Dysplastic Changes and Lipid Peroxidation Induced by 7.5% Icodextrin

Background: The issue of icodextrin biocompatibility is somehow ambiguous. Whereas some experimental data point at better bicompatibility of icodextrin compared with high glucose concentration fluid, other reports showed substantial cytotoxic effects upon monocytes and cultured mesothelial cells. The present investigation exposes the first attempt to investigate the biocompatibility issue in an in vivo and in situ setup. Methods: Mice were intraperitoneally injected once a day with the 7.5% icodextrin solution, during 30 consecutive days. Imprints of the mesothelial monolayer covering the anterior liver surface were taken after 2 h, 15 and 30 injections, as well as after recovery periods of 7, 30 and 60 days. Changes on the cell population were evaluated as a function of: density, cell surface area, cell radius, nuclear surface area, number of nucleoli per nucleus, nuclear cytoplasmic index, as well as for prevalence of multinucleation, mitosis, non-viable cells and apoptotic bodies. Additionally, peritoneal dialysis was performed in 3 groups of rats exposed to 4.25% glucose dialysis fluid, 1.1% amino acids solution, or to 7.5% icodextrin. Samples were taken for thiobarbituric acid reactive substances (TBARS) from each group. Results: Mesothelial cell populations of mice exposed to 7.5% icodextrin displayed significantly reduced density, increased cell size, higher increased nuclear/cytoplasmic index, increased numbers of heterogeneous nucleoli, extremely low prevalence of mitosis, atypical mitosis, micronuclei, reduced cell viability as well as a significantly higher prevalence of apoptosis. Rats exposed to the same experimental solution showed significantly higher levels of TBARS (basically malondialdehyde), testifying for an undergoing process of lipid peroxidation. Conclusions: Overall, these results suggest that the 7.5% icodextrin dialysis solution induced, through a mechanism of lipid peroxidation, substantial DNA injury, leading the exposed monolayer to commit protective cellular suicide. Consequently, this information raises some doubts about the safety of 7.5% icodextrin solution in peritoneal dialysis patients.

Icodextrin-induced lipid peroxidation disrupts the mesothelial cell cycle engine.

Fluids commonly used for peritoneal dialysis hold poor biocompatibility vis a vis the peritoneal membrane, basically due to the presence of osmotic agents. When rat mesothelium was exposed to glucose-enriched dialysis solutions for 2 h in vivo, an early and short-lived acceleration of cell life cycle was observed, which, after 30 d of exposure, resulted in a depopulated monolayer of senescent cells. These changes appear to result from persistent oxidative stress due to continuous exposure to high concentration of glucose and to substances generated by the Maillard reaction. Long-term exposure (30 d) of the peritoneal mesothelium to 7.5% icodextrin resulted in a depopulated monolayer consisting mostly of senescent cells, which, additionally, showed atypical nuclear changes and atypical mitosis suggesting DNA damage. These changes coincided with substantial lipid peroxidation, starting immediately after the introduction of the icodextrin solution into the rats abdominal cavity. So far, the currently used osmotic agents in peritoneal dialysis fluids induce substantial oxidative injury to the exposed monolayer in vivo. Use of high concentrations of glucose results in premature senescence of the exposed cell population. The 7.5% icodextrin dialysis fluid induces through lipid peroxidation substantial genomic damage, which, in turn, sets the biological mechanisms leading to protective cellular suicide in motion.

Protective effect of pyruvate upon cultured mesothelial cells exposed to 2 mM hydrogen peroxide

Rat peritoneal mesothelial cells in culture have the capability of generating hydrogen peroxide. Exposure of these cells to glucose-enriched, lactated-buffered fluids for peritoneal dialysis significantly increases the production of H2O2. Increased liberation of oxygen radicals also involves the risk of damaging the peritoneal membrane. Pyruvate being a natural oxidant scavenger abundantly present in mammalian cells, we hypothesized that its protective effects facing H2O2 can eventually be of relevance for the mesothelial monolayer of patients on long-term peritoneal dialysis. So far, we designed an experimental study in which rat peritoneal mesothelial cells in culture were exposed to 2 mM H2O2. Cell damage was estimated in terms of decreased capability of the mitochondrial dehydrogenases to reduce MTT. Addition of 2 mM sodium pyruvate to the medium prevented the negative effect of hydrogen peroxide. The MTT/protein values for the control group were 0.00357 ± 0.00075. The ratio after exposure to 2 mM H2O2 was 0.00217 ± 0.00028, whereas that detected in cells incubated in H2O2 plus pyruvate was 0.00325 ± 0.0082 (p < 0.05). These results indicate that pyruvate protected rat peritoneal mesothelial cells in culture against oxidant injury. These data are one more piece of evidence pointing at pyruvate as a potentially useful buffer for peritoneal dialysis solutions.

Effect of hyperosmolality upon the mesothelial monolayer exposed in vivo and in situ to a mannitol-enriched dialysis solution

Studies done using the in vivo mouse model of population analysis of mesothelium showed that dialysis solutions containing high concentrations of glucose induced the development of a hypertrophic phenotype. Since these changes were neither related to the low pH nor to the presence of lactate buffer, we hypothesized that the presence of glucose was at the origin of the observed alterations. Theoretical analysis of the problem points to three possible mechanisms: hyperosmolality; metabolic changes derived from the high-glucose concentration itself, and/or the presence of products derived from the nonenzymatic degradation of glucose. The present study was designed to demonstrate or rule out the eventual effect of hyperosmolality upon the monolayer, applying the in vivo mouse model of population analysis of mesothelium. For this purpose, morphometric observations made in mice injected once a day during 30 consecutive days with a filter-sterilized 4.25% solution of mannitol (233.29 mM) were compared with those seen in intact mice and in a previously reported group of animals exposed to heat-sterilized fluid, having an equimolar concentration of glucose (235.9 mM), and the same osmolality (486 mosm/l) and electrolyte concentrations. The main findings observed in the mannitol-treated mice during the period of exposure included increased cell size and cytoplasmic surface area, as well as decreased cell viability. The regenerative capabilities of the exposed mesothelium remained intact. After a recovery period of 7 days, the aforementioned parameters reverted to normal values. This pattern is significantly different from the hypertrophic, senescent and low regenerative phenotype observed in mice treated with the high-glucose concentration solution. We conclude that, at least in the in vivo and in situ setup, the detrimental effects of hyperosmolality alone upon the exposed mesothelium are quite limited and fully reversible within a recovery period of 7 days.

Mechanisms of Cell Death during Peritoneal Dialysis

AIMS To offer a condensed description of the modes of cell death and the involved mechanisms behind them as detected in the different layers of the peritoneal tissue during experimental and clinical, long-term peritoneal dialysis (PD). MAIN REMARKS Several types of cell death have been observed in the mesothelial monolayer: apoptosis, anoikis, secondary necrosis, pure necrosis and mitotic catastrophe. Death of mesothelial cells exposed to glucose-enriched solutions derives mainly from a degree of oxidative insult leading to DNA damage, provoked by glucose itself and/or its degradation products. Use of icodextrin is associated with a higher degree of oxidative injury that also leads to genomic damage and consequently to cell death. Peritoneal leukocytes exposed to glucose-enriched PD solutions share the fate of mesothelial cells. Endothelial cells treated in vitro with high glucose concentrations have higher rates of apoptosis induced by a degree of oxidative stress. Endothelial apoptosis plays an important role in remodeling the vascular network, since this development has been observed at the beginning of neo-angiogenesis and at the branching and regression of microvessels of neoformation. Acute osmotic stress results in increased proportions of mesothelial cells dying in apoptosis, anoikis, secondary necrosis as well as in pure necrosis. After long-term exposure, cells apparently adapt to the new hypertonic environment even though the eventual presence of functional changes cannot be ruled out. CONCLUSIONS All cells lining the peritoneal cavity or living near its immediate environment, exposed most of the time to nonphysiological fluids, undergo changes that lead to their death. This problem is behind the poor regenerative capabilities showed by the mesothelial monolayer, the microvascular changes that lead to neoangiogenesis, and, probably, to a defective response to peritoneal infection. Therapeutic modulation of apoptotic cell death could inhibit its progress. Since liberation of oxygen radicals is thereby causally involved in apoptosis, reduced levels of GDPs and/or use of antioxidants appear to be indicated in order to prevent mesothelial, endothelial cells and leukocyte death.

Decreased density distribution of mesenteric and diaphragmatic microvascular anionic charges during murine abdominal sepsis

Pulmonary edema of sepsis is a consequence of increased transmural conductance for water and proteins at the level of lung microvessels induced by vasoactive endogenous mediators, liberated after activation of complement by bacterial endotoxins. Intermittent opening of interendothelial junctions at the level of post-capillary venules has been implicated as being the pathway for the leaking plasma proteins and water. Microvascular basement membranes and endothelial cell surfaces have fixed anionic charges (AS) which prevent the escape of plasma proteins from the circulation as well as the adhesion of blood cells to the luminal endothelium. The density distribution of these AS was substantially reduced in visceral and systemic microvessels during murine abdominal sepsis. This observation suggest that MOF secondary to sepsis is the consequence of a severe and generalized alteration of the microvascular electronegative charge, induced by liberation of inflammatory mediators.

Biocompatibility of a Glucose-Free, Acidic Lactated Solution for Peritoneal Dialysis Evaluated by Population Analysis of Mesothelium

Glucose-enriched, racemic lactate buffered solutions for peritoneal dialysis induce a significant reduction of cell viability as well as a hypertrophic, senescent phenotype of the exposed monolayer. The present study was designed to verify whether the aforementioned changes resulted form the buffer, from the osmotic agent, or from a combined effect of both. Mice were acutely (2 h) and long-term (15 and 30 days) exposed to daily intraperitoneal injections of a racemic lactate, heat-sterilized, low-pH (5.2), glucose-free solution. Imprints of the monolayer were taken at the end of each time interval. The glucose-free lactated buffer used in the present study did not induce significant changes in density distribution, mean cell size, mean cytoplasmic surface area, prevalence of large cells, multinucleation, proportion of observed cells in mitosis, and cell viability. So far, the previously mentioned hypertrophic phenotype appears to derive from substantial alterations in the cell cycle of mesothelium exposed to high concentrations of glucose and/or advanced glycosylation end products and unrelated to lactate.

A short review of experimental peritoneal sclerosis: from mice to men.

Peritoneal sclerosis has been induced in rodents in vivo by exposing the membrane to a variety of experimental interventions: asbestos, 0.1% chlorexidine, iron dextran, glucose degradation products, AGE deposits derived from uremia per se, sodium hypochlorite, lypopolysaccharide, low pH, pure water, silica or zymosan. With a few exceptions (pure water, chlorhexidine and low pH), the other substances mentioned operate setting out different degrees of oxidative stress. This short review describes several experimental interventions in rodents, aimed at acute exfoliation or long-term, sustained injury of the mesothelial monolayer performed by means of intraperitoneal injections of different oxidant agents. Acute exfoliation induced by deoxycholate resulted in a depopulated monolayer coincident with immediate alteration of the peritoneal permeability, evidenced by increased urea D/P ratio, higher glucose absorption rate, elevated albumin losses in the effluent and significant reduction of the ultrafiltration rate. In the long term (30 days), these manifestations of membrane failure persisted and coincided with substantial peritoneal sclerosis. Peritoneal sclerosis was also induced by IP injections of 0.125% trypsin and 6.6 mM/L solution of formaldehyde. Using the doughnut rat model of mesothelial regeneration, exposure to 4.25% glucose or 7.5% icodextrin solutions severely hampered repopulation of the monolayer, which was replaced by a thick sheet of fibrous tissue. It is concluded that peritoneal sclerosis derives mostly from sustained oxidative injury to the peritoneal membrane. Loss of the mesothelial monolayer is the first step in the chain of events leading to this complication.