The multidirectional assessment of moderate caloric restriction and metformin treatment in obese patients

Obesity treatment is often burdensome for patients. We used the combination of moderate caloric restriction (CR) with hypoglycemic metformin to assess their multidirectional effect in obese patients. One group was treated only with moderate CR (n=21) the second was treated with moderate CR and 800 mg metformin twice daily (n=23). Serum was drawn before and after treatment. The following parameters were monitored: anthropometric, cardiovascular, inflammatory, metabolic, and markers characteristic for thyroid, liver, pancreas, and kidney functions. Both tested groups did not significantly differ in most tested parameters after the treatment. Two groups reduced anthropometric parameters (body mass, body mass index (BMI), waist circumference) and fat mass but also muscle and fat-free mass, improving systolic blood pressure, insulin and leptin concentration, insulin sensitivity, leptin to adiponectin ratio, and inflammatory markers. Unfortunately, there was little impact on improving dyslipidemia and the thyroid and liver parameters. Free triiodothyronine (fT3) and gamma glutamyl transferase (GGT) activity were decreased in both groups, but triglycerides were reduced only in patients treated with moderate CR. Metformin with CR treatment decreases uric acid and aspartate aminotransferase (AspAT) activity. Metformin treatment with moderate CR in obese patients mainly improved insulin sensitivity, resulting in a reduction of patients with glucose intolerance, improved anthropometric, cardiovascular, and inflammatory mediators, and only slightly enhanced liver and thyroid function. No changes in kidney and pancreas function were observed during the treatment. In conclusion, eight weeks of CR alone and CR with metformin in obese adults improved anthropometric and metabolic markers, reduced muscle mass, fT3, GGT, proinflammatory, and CV parameters, and displayed no changes in kidney and pancreas function. The group treated with metformin after the treatment was still more obese and had higher C-reactive protein (CRP) and homeostasis model assessment-an index of insulin resistance (HOMA-IR), but despite this, considerably reduced the number of patients with glucose intolerance.

Soluble receptor for advanced glycation end products (sRAGE) correlates with obesity-related parameters, and it is not easy to be modified by moderate caloric restriction in obese humans

Deficiency of a soluble form of the advanced glycation end products receptor (sRAGE) is implicated in obesity-induced complications. Serum sRAGE is inclined to be modified by changes in body weight. We analysed serum sRAGE concentrations in patients with obesity undergoing moderate calorie restriction, which mimics the real-life situation and is not harmful to obese humans. Serum sRAGE was measured by immunoassay in 50 patients with obesity who underwent calorie restriction by 300-500 kcal/day for 8 weeks. In effect calorie restriction resulted in an expected decrease in body weight (by 2.1 kg for an 8-week intervention, p<0.0001), as well as reduced systolic blood pressure, modified dyslipidemia (cholesterol, triglycerides), reduced obesity-related inflammation (tumor necrosis factor-alfa, interleukin-6, C-reactive protein), improved insulin sensitivity. However, it was not accompanied by any significant change in sRAGE concentration. There was a strong negative correlation between BMI and the sRAGE level. Accordingly, the levels of sRAGE were the highest in lean control. In conclusion: a modest weight reduction is unlikely to improve decreased sRAGE levels.

Mixed reality interactive visualization of cardiovascular anatomy in interventional lab – clinical implementation in transvascular patent ductus arteriosus closure

Aim

Three-dimensional (3D) noninvasively acquired datasets containing anatomical information about the heart are a modern option for procedural support during percutaneous cardiac interventions. We present initial experience of patent ductus arteriosus (PDA) closure with workflow integrated with innovative mixed reality display (MRD) to improve 3D perception and navigation in 3D computed tomography angiographic (CTA) datasets.

Methods

We report incorporation of intraprocedural mixed-reality display of segmented CTA (computed tomography angiography) data using a voice- and gesture controlled head-mounted display during routine percutaneous occlusions of PDA in adults. A dedicated software pathway was used for files conversion, real-time Wi-Fi streaming of 3D rendering from PC to device and manipulation of spatial data during the procedures.

Results

Pre-recorded CTA studies of aorta and ductus were manually segmented and uploaded into custom designed 3D DICOM for realtime export to MRD device. 3D holograms were successfully displayed during the procedure by commercially available head-mounted display allowing touchless control and image sharing within cath-lab. Wiring of PDA aortic orifice was assisted by 3D hologram controlled by the imaging specialist and shared by the operator. Thus, MRD using evolving versions of custom software was successfully executed with segmented data presented as a semitransparent cubic hologram positioned in a convenient part of visual field allowing real-world action and with touchless control by medical team. Operator appreciated the use of MRD hologram realistically visualizing spatial relationships as practical aid to establish anatomical relationships and facilitate entry into ductus orifice. Procedures were successfully completed using arteriovenous guidewire loop to implant vascular occluders.

Conclusions

We demonstrate the methodology and software evolution (segmentation, data fusion) allowing practical implementation of intraprocedural mixed reality display of 3D CTA data, with sterile, touchless control of holographic image shared by interventional and imaging team to support percutaneous PDA closure.

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): MEDAPP

The role of purinergic P2Y12 receptor blockers on the angiogenic properties of endothelial cells: an in vitro study

Pharmacotherapy with agents that inhibit platelet function has proven to be effective in the treatment of acute coronary syndrome. Proper re-endothelization after angioplasty prevents adverse cardiovascular events. Therefore, in this in vitro study we examined how antiplatelet P2Y₁₂ receptor blockers can affect endothelial cells' angiogenic properties. Endothelial cells were exposed to ticagrelor, prasugrel and clopidogrel in their highest concentrations obtained in serum after the treatment with loading and clinical doses. Further, the viability, apoptosis, and necrosis were tested and the following angiogenic properties such as proliferation, migration, invasiveness, tube formation, wound healing and the production of angiogenic mediators (bFGF, PDGF, MMP-2, Ang-2, TIMP-1). The results of this study showed that P2Y₁₂ receptor blockers in the tested concentrations are safe for endothelial cells. They neither induced necrosis or apoptosis nor changed the endothelial cell viability, migration, invasiveness, tube formation, wound healing, the production of VEGF or its receptors. However, they reduced cell proliferation. It was shown that out of these three drugs, ticagrelor in its loading concentration had the most potent angiogenic property. It reduced cell proliferation and changed the production of angiogenic (bFGF, MMP-2) and angiostatic mediators (Ang-2). In conclusion, P2Y₁₂ receptor blockers in the concentrations obtained in the serum during standard therapy reduced endothelial cell proliferation. Despite this slight antimitogenic effect, they did not change endothelial cell tube formation or wound healing. Out of the three tested drugs, ticagrelor had the most potent angiogenic effect in vitro, but not strong enough to disturb tube formation and wound healing.

Correlation between HSP-72 Expression and IL-8 Secretion in Human Mesothelial Cells

Background

Cytotoxicity of peritoneal dialysis fluid (PDF) and peritoneal inflammation are currently regarded as the two major culprits for chronic mesothelial injury and peritoneal membrane failure. In this study, we correlated induction of HSP-72, as a marker of the cellular stress response, to secretion of IL-8, as a marker for pro-inflammatory cytokines, in mesothelial cells upon sublethal PDF exposure.

Methods

Primary omental cell cultures of human mesothelial cells were subjected to sublethal PDF exposure times (CAPD2, Fresenius, Germany). At the end of a 24 hour recovery period, induction of HSP-72 in the cell homogenate and IL-8 secretion in the supernatant was assessed by immunodensitometry and ELISA, respectively.

Results

PDF exposure times from 15 min to 60 min resulted in progressively increased HSP-72 expression levels (267 vs 320 vs 419% of controls, p<0.05 vs controls) as well as increased IL-8 secretion (323 vs 528 vs 549% of controls, p<0.05 vs controls) with full cell viability (MTT unchanged to control). HSP-72 expression was statistically significantly correlated with IL-8 secretion. Conclusions: The significant correlation between HSP-72 expression and IL-8 secretion suggests that the regulation of pro-inflammatory pathways in mesothelial cells exposed to PDF may represent an integral part of their stress response. Future studies to investigate the cellular regulatory mechanism involved are warranted.

There is no difference in outcome between laparoscopic and open surgery for rectal cancer: a systematic review and meta-analysis on short- and long-term oncologic outcomes

Background

Until recently there has been little data available about long-term outcomes of laparoscopic rectal cancer surgery. But new randomized controlled trials regarding laparoscopic colorectal surgery have been published. The aim of this study was to compare the short- and long-term oncologic outcomes of laparoscopy and open surgery for rectal cancer through a systematic review of the literature and a meta-analysis of relevant RCTs.

Methods

A systematic review of Medline, Embase and the Cochrane library from January 1966 to October 2016 with a subsequent meta-analysis was performed. Only randomized controlled trials with data on circumferential resection margins were included. The primary outcome was the status of circumferential resection margins. Secondary outcomes included lymph node yield, distal resection margins, disease-free and overall survival rates for 3 and 5 years and local recurrence rates.

Results

Eleven studies were evaluated, involving a total of 2018 patients in the laparoscopic group and 1526 patients in the open group. The presence of involved circumferential margins was reported in all studies. There were no statistically significant differences in the number of positive circumferential margins between the laparoscopic group and open group, RR 1.16, 95% CI 0.89–1.50 and no significant differences in involvement of distal margins (RR 1.13 95% CI 0.35–3.66), completeness of mesorectal excision (RR 1.22, 95% CI 0.82–1.82) or number of harvested lymph nodes (mean difference = −0.01, 95% CI −0.89 to 0.87). Disease-free survival rates at 3 and 5 years were not different (p = 0.26 and p = 0.71 respectively), and neither were overall survival rates (p = 0.19 and p = 0.64 respectively), nor local recurrence rates (RR 0.88, 95% CI 0.63–1.23).

Conclusions

Laparoscopic surgery for rectal cancer is associated with similar short-term and long-term oncologic outcomes compared to open surgery. The oncologic quality of extracted specimens seems comparable regardless of the approach used.

Electronic supplementary material

The online version of this article (doi:10.1007/s10151-017-1662-4) contains supplementary material, which is available to authorized users.

Weight loss-dependent and -independent effects of moderate calorie restriction on endothelial cell markers in obesity

Endothelial cell dysfunction in obesity can be reduced by calorie restriction (CR), however it is unclear whether this benefit requires a concomitant weight loss or is it simply related to the reduced calorie intake per se. In our study serum was drawn from 41 obese women who were undergoing an 8-week dietary intervention with 15 - 30% energy deficit, and from 48 age- and sex-matched controls of normal weight. Serum was analysed for biomarkers of endothelial cell function, oxidative stress and inflammation. Compared with non-obese individuals, the obese patients had lower serum levels of nitric oxide (NO), adiponectin, and decreased serum antioxidant status. They also had significantly higher levels of adhesive molecules, thrombomodulin (TM), von Wilebrand factor (vWF), asymmetric dimethylarginine (ADMA), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and leptin. To further characterize the effect of moderate CR, the patients were ranked into two comparable groups according to the extent of weight loss - below and above the median (-5.8 kg). A moderate dietary intervention did not correct adiponectin, antioxidant status, vWF, TM, and plasminogen activator inhibitor-1 (PAI-1) but ameliorated changes in other parameters. Only changes in NO and - to a lesser degree - in sE-selectin showed a clear relationship with the magnitude of weight reduction. By contrast, a beneficial reduction in TNF-α occurred equally in patients who lost more or less weight after caloric restriction. We concluded that moderate calorie restriction could still improve several parameters of endothelial cell function irrespective of whether it was accompanied by changes in body mass. However, a significant improvement in nitric oxide, a key mediator of endothelial well-being, requires a substantial reduction in body weight.

The role of mTOR inhibitors and HMG-CoA reductase inhibitors on young and old endothelial cell functions, critical for re-endothelialisation after percutaneous coronary intervention: an in vitro study

Percutaneous coronary intervention (PCI) has become a standard treatment in patients with acute coronary syndrome. However, it is associated with endothelial cell denudation, which may predispose to in-stent thrombosis and restenosis. Pharmacological methods which prevent restenosis can delay post-PCI re-endothelialisation. We have therefore examined how atorvastatin (HMG-CoA reductase inhibitor), sirolimus and everolimus (mTOR inhibitors) affect young and old endothelial cell functions which are responsible for wound healing after PCI. Replicative senescence was induced by serial passages of human umbilical vein endothelial cells (HUVECs). The cells which were examined at their first passages and last passages were designated as 'young' and 'old' respectively. Young and old endothelium were grown to confluence and were wounded by scraping. Scratch healing in the presence or absence of atorvastatin (AT), rapamycin (SR) and everolimus (EV) was monitored by time-lapse microscopy. In addition cells were assessed for viability (MTT assay), migration (chemotaxis chamber), proliferation (³H-thymidine), and cytokine production (immunoassays). Senescent endothelial cells produce more proinflammatory cytokines, angiogenic VEGF and extracellular matrix proteins. They stop proliferating and have diminished migration. When compared to young endothelium, they have similar viability and can regenerate wounds in comparable time. The drugs that have been tested have anti-inflammatory properties but even after pretreatment old cells still produced significantly higher concentration of tested mediators in comparison with young ones. In the concentration obtained in serum after stent implantation, mTOR inhibitors in dose-dependent manner reduced cell proliferation, migration and wound healing. Reduced healing is more pronounced in young endothelium. Atorvastatin, at clinically relevant concentration, is safe for young and old cells. Atorvastatin, sirolimus and everolimus inhibited the secretion of pro-inflammatory mediators in young and old endothelium. In concentrations seen in serum during standard therapy, rapalogs impair endothelial cell regeneration after injuries mimicking those occurring during PCI, while atorvastatin does not affect the healing.

Simple obesity and renal function

Increasing evidence accumulate to suggest that obesity increases the risk of chronic kidney disease independently of dyslipidemia, diabetes, and hypertension. This so-called obesity-related glomerulopathy is characterized at early stages by glomerular hypertrophy with or without secondary focal segmental glomerulosclerosis. Since, however, kidney biopsies are usually not performed at this phase, an early diagnosis of the disease is often difficult. Here, we review new developments in the pathophysiology of obesity-associated kidney dysfunction and discuss the potential of appropriate monitoring of glomerular filtration rate and albuminuria for early detection of the disease. We also present the benefits conferred by even moderate dietary restriction on the course of the disease.

Atorvastatin does not impair endothelial cell wound healing in an in vitro model of vascular injury

Percutaneous coronary intervention (PCI) became standard treatment modality for coronary revascularization. However, it is associated with endothelial cell denudation, which may predispose to in-stent thrombosis and restenosis. Since statins may inhibit vascular cell proliferation, one may fear that their early administration will delay post-PCI re-endothelialization. We have therefore employed an in vitro scratch assay to examine how atorvastatin affects endothelial cell wound healing. Human umbilical vein endothelial cells (HUVEC) were grown to confluence and wounded by scraping. Scratch healing in the presence or absence of atorvastatin was monitored by time-lapse photo-microscopy. In addition cells were assessed for viability (MTT assay), migration (chemotaxis chamber), proliferation ((3)H-thymidine and bromodeoxyuridine incorporation), and cytokine production (immunoassays). The exposure of HUVEC to atorvastatin resulted in a dose-dependent decrease in cell viability and proliferation. However, this effect was observed only at doses ≥1 μM, which is well above the concentrations seen in vivo. At clinically relevant doses (≤0.1 μM) atorvastatin did not impair wound closure, nor did it inhibit cell viability, proliferation, and migration. It did however reduce the constitutive and the stimulated release of cytokines (IL-6, IL-8, MCP-1), adhesion molecules (sICAM-1) and matrix proteins (fibronectin). We conclude that atorvastatin at doses corresponding to concentrations seen in serum during standard therapy does not impair endothelial cell regeneration after injuries mimicking those occurring during PCI. It does, however, inhibits the secretion of pro-inflammatory mediators.

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.

PD and loss of peritoneal function

During long-term treatment with peritoneal dialysis both peritoneal membrane structure and function undergo significant changes that not only correlate with the time under treatment, but also with the frequency and severity of infections. In addition, peritoneal dialysis fluid bio-incompatibility may constitute a hazard for the longevity of the peritoneum as the dialysis membrane. In particular, the presence of glucose degradation products may lead to impaired peritoneal cell function as well as to increased protein glycation and peritoneal AGE deposition. Results from recent prospective randomised studies suggest that treatment with new GDP-depleted PD fluids may lead to a significant improvement of clinical outcomes in PD patients.

Role of mesothelial cell-derived granulocyte colony-stimulating factor in interleukin-17-induced neutrophil accumulation in the peritoneum

Recent studies suggest that peritoneal CD4(+) T lymphocytes may control recruitment of polymorphonuclear leukocytes (PMN) during peritonitis by an interleukin-17 (IL-17)-dependent mechanism. IL-17 and granulocyte colony-stimulating factor (G-CSF) have been proposed to form an axis that regulates PMN transmigration. Here we report on the role of G-CSF released by human peritoneal mesothelial cells (HPMCs) in IL-17A-mediated peritoneal PMN accumulation. In vitro exposure of HPMCs to IL-17A resulted in a time- and dose-dependent release of G-CSF. This effect was related to the induction of G-CSF mRNA and mediated through the nuclear factor-kappaB (NF-kappaB) pathway. The novel observation was that IL-17A-stimulated NF-kappaB activation in HPMCs followed a biphasic profile, with an early induction (45 min), followed by the return to basal levels (90 min), and a delayed induction (3 h). Tumor necrosis factor alpha synergistically amplified IL-17A-induced G-CSF production by enhanced NF-kappaB activation and through stabilization of G-CSF mRNA. Intraperitoneal (i.p.) administration of IL-17A in Balb/c mice resulted in increased local levels of G-CSF and selective PMN accumulation. Administration of anti-G-CSF blocking antibody before IL-17A injection significantly reduced the IL-17A-triggered PMN infiltration. This effect occurred despite increased i.p. levels of PMN-specific chemokines KC and macrophage inflammatory protein-2 seen in animals treated with anti-G-CSF antibody. These data demonstrate that the mesothelium-derived G-CSF plays an important role in IL-17A-induced PMN recruitment into the peritoneum.

Interleukin-17: a mediator of inflammatory responses

Interleukin-17 (IL-17) is a prototype member of a new cytokine family with six species identified to date. IL-17 is secreted mainly by activated CD4(+) and CD8(+) T lymphocytes, while its receptor is distributed ubiquitously. IL-17 has been classified as a proinflammatory cytokine because of its ability to induce the expression of many mediators of inflammation, most strikingly those that are involved in the proliferation, maturation and chemotaxis of neutrophils. Increased levels of IL-17 have been associated with several conditions, including airway inflammation, rheumatoid arthritis, intraperitoneal abscesses and adhesions, inflammatory bowel disease, allograft rejection, psoriasis, cancer and multiple sclerosis. This review provides an overview of IL-17 activities, concentrating on those that lead to neutrophil recruitment.

Influence of neutral-pH dialysis solutions on the peritoneal membrane: a long-term investigation in rats

OBJECTIVE

Glucose degradation products (GDPs) and low pH are potential causes of bioincompatibility of peritoneal dialysis fluids (PDFs). The aim of the present study was to compare the effect of 6 weeks' exposure of the peritoneum in rats to two different PDFs: a standard PDF with a low pH and high level of GDPs (CAPD 3: Fresenius Medical Care, Bad Homburg, Germany), and a modified PDF with a low level of GDPs and a physiologic pH (CAPD 3 Balance: Fresenius Medical Care).

METHODS

After catheter implantation, rats were exposed twice daily for 6 weeks to CAPD 3 fluid or to CAPD 3 Balance. At the beginning and at the end of the study, a 4-hour dwell was performed in every rat to evaluate intraperitoneal inflammation and its effect on total collagen synthesis in the in vitro cultured rat mesothelial cells (ex vivo study). Additionally, after 6 weeks' exposure, the peritoneal cavity was opened, and macroscopic changes were evaluated according to a semiquantitative scale. Peritoneal samples were also taken for morphology study.

RESULTS

In rats treated with CAPD 3 fluid, intraperitoneal inflammation was comparable at the beginning and at the end of the experiment. In animals exposed to CAPD 3 Balance, the intensity of the intraperitoneal inflammation decreased during the study (cell count, p = 0.0781; neutrophil:macrophage ratio, p < 0.01; nitrite concentration, p < 0.05; hyaluronan level, p < 0.05). The capacity of effluent dialysate from CAPD 3 rats to activate collagen synthesis in in vitro-cultured mesothelial cells was the same at the beginning and at the end of the study. In the CAPD 3 Balance group, this capacity was statistically significantly lower at the end of the study than at the beginning (p < 0.05). The mean thickness of the visceral peritoneum was comparable in both groups of animals, but, macroscopically, more severe fibrosis was found in the peritoneum of rats exposed to CAPD 3 as compared with animals treated with CAPD 3 Balance (p < 0.05).

CONCLUSION

We showed that, in the rat model of peritoneal dialysis, chronic exposure of the peritoneum to PDFs with low GDPs and a physiologic pH diminished the intraperitoneal inflammatory reaction induced by dialysis, and reduced peritoneal fibrosis.

Pathophysiology of ageing

Ageing is characterized by a gradual decline in organ functional reserves which reduces the ability to maintain homeostasis under conditions of stress. Introduction of cell culture and molecular biology techniques has provided new experimental tools for the analysis of ageing at the molecular level. During ageing progressive degeneration of cells and loss of regenerative capacity are enhanced and with time the alterations caused by them ultimately lead to death. In this paper the current knowledge of the mechanisms of ageing is summarized.

Differential regulation of chemokine production in human peritoneal mesothelial cells: IFN-gamma controls neutrophil migration across the mesothelium in vitro and in vivo

Leukocyte recruitment into the infected peritoneal cavity consists of an early, predominant polymorphonuclear leukocyte (PMN) influx and subsequent, prolonged mononuclear cell migration phase. Although chemokine secretion by resident peritoneal cells plays a primary role in mediating this migration, the mechanisms involved in controlling the switch in phenotype of cell infiltrate remain unclear. The present study investigates a potential role for the Th1-type cytokine IFN-gamma in the process of leukocyte recruitment into the peritoneal cavity. Stimulation of cultured human peritoneal mesothelial cells with IFN-gamma (1-100 U/ml) alone or in combination with IL-1beta (100 pg/ml) or TNF-alpha (1000 pg/ml) resulted in significant up-regulation of monocyte chemoattractant protein-1 and RANTES protein secretion. In contrast, IFN-gamma inhibited basal and IL-1beta-, and TNF-alpha-induced production of IL-8. The modulating effects of IFN-gamma on chemokine production occurred at the level of gene expression, and the degree of regulation observed was dependent on the doses of IL-1beta and TNF-alpha used. Analysis of the functional effects of IFN-gamma on IL-1beta-induced transmesothelial PMN migration with an in vitro human transmigration system and an in vivo murine model of peritoneal inflammation demonstrated that IFN-gamma was able to down-regulate PMN migration induced by optimal doses of IL-1beta. These effects were mediated in vivo via down-regulation of CXC chemokine synthesis. These findings suggest that IFN-gamma may play a role in controlling the phenotype of infiltrating leukocyte during the course of an inflammatory response, in part via regulation of resident cell chemokine synthesis.

Glucose degradation products and the peritoneal mesothelium

Conventional heat-sterilized, glucose-based peritoneal dialysis (PD) fluids contain significant amounts of glucose degradation products (GDPs) such as aldehydes and dicarbonyl compounds (glyoxal, methylglyoxal). These GDPs have been shown to impair cell functions in various in vitro experimental models. In peritoneal mesothelial cells, GDPs dose-dependently inhibit cell proliferation and mediator synthesis. In addition, some GDPs potently promote generation of advanced glycation end-products (AGEs). Immunohistochemistry finds AGEs in the peritoneal membrane of chronic continuous ambulatory peritoneal dialysis (CAPD) patients, suggesting that peritoneal AGE accumulation may be involved in chronic peritoneal fibrosis. The formation of GDPs might be prevented by filter-sterilization of PD fluids. Another option is to separate the glucose and the buffer system in dual-chambered or multi-chambered containers. In these systems, the glucose is kept in a separate compartment at high concentration and very low pH-both conditions being known to minimize the degree of glucose decomposition during autoclaving. Initial experimental evidence suggests that these novel, multi-chambered fluids significantly improve in vitro biocompatibility; however, the clinical relevance of these results remains to be established in clinical trials.

Synthesis of C-X-C and C-C chemokines by human peritoneal fibroblasts: induction by macrophage-derived cytokines

Leukocyte accumulation during peritonitis is believed to be controlled by chemotactic factors released by resident peritoneal macrophages or mesothelial cells. Recent data indicate, however, that in many tissues fibroblasts play a key role in mediating leukocyte recruitment. We have therefore examined human peritoneal fibroblasts (HPFBs) for the expression and regulation of C-X-C and C-C chemokines. Quiescent HPFBs secreted monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-8 constitutively. This release could be dose-dependently augmented with the pro-inflammatory cytokines IL-1beta and tumor necrosis factor-alpha. Stimulated IL-8 production reached a plateau within 48 hours while MCP-1 continued to accumulate throughout 96 hours. Induction of IL-8 and MCP-1 synthesis by HPFBs was also triggered by peritoneal macrophage-conditioned medium. This effect was partly related to the presence of IL-1beta as demonstrated by IL-1 receptor antagonist inhibition. Pretreatment of HPFBs with actinomycin D or puromycin dose-dependently reduced cytokine-stimulated IL-8 and MCP-1 secretion, which suggested de novo chemokine synthesis. Indeed, exposure of HPFBs to IL-1beta and tumor necrosis factor-alpha produced a significant up-regulation of IL-8 and MCP-1 mRNA. This effect was associated with the rapid induction of nuclear factor-kappaB binding activity mediated through p65 and p50 subunits, and with a transient increase in the mRNA expression for RelB and inhibitory protein kappaB-alpha proteins. These data indicate that peritoneal fibroblasts are capable of generating large quantities of chemokines under a tight control of nuclear factor-kappaB/Rel transcription factors. Thus, peritoneal fibroblast-derived chemokines may contribute to the intraperitoneal recruitment of leukocytes during peritonitis.

Glucose degradation products and peritoneal membrane function

BACKGROUND

The bioincompatibility of peritoneal dialysis fluids (PDF) in current use has been partially attributed to the presence of glucose degradation products (GDPs), which are generated during heat sterilization of PDF. Several of the GDPs have been identified and we have recently demonstrated that these GDPs per se may impair the viability and function of human peritoneal mesothelial cells (HPMC) in vitro. It is also possible that GDP-related toxicity is further exacerbated by the milieu of PDF. We review the current literature on GDP and present the results of experiments comparing the impact of heat- and filter-sterilized PDF on the viability and function of HPMC.

METHODS

Peritoneal dialysis fluids with low (1.5%) and high (4.25%) glucose concentrations were laboratory prepared according to the standard formula and sterilized either by heat (H-PDF; 121 degrees C, 0.2 MPa, 20 minutes) or filtration (F-PDF; 0.2 microns). The buildup of GDP was confirmed by UV absorbance at 284 nm. Confluent HPMC monolayers were exposed to these solutions mixed 1:1 with standard M199 culture medium. After 24 hours, cell viability was assessed with the MTT assay, and interleukin-1beta-stimulated monocyte chemotactic protein-1 (MCP-1) release with specific immunoassay.

RESULTS

Exposure of HPMC to H-PDF resulted in a significant decrease in cell viability, with solutions containing 4.25% glucose being more toxic than 1.5% glucose-based PDF (27.4% +/- 3.4% and 53.4% +/- 11.0% of control values, respectively). In contrast, viability of HPMC exposed to F-PDF was not different from that of control cells. Moreover, treatment with H-PDF impaired the release of MCP-1 from HPMC to a significantly greater degree compared to F-PDF (17.4% and 24.9% difference for low and high glucose PDF, respectively).

CONCLUSIONS

Exposure of HPMC to H-PDF significantly impairs cell viability and the capacity for generating MCP-1 compared to F-PDF. This effect is likely to be mediated by GDPs present in H-PDF but not in F-PDF.

IL-17 stimulates intraperitoneal neutrophil infiltration through the release of GRO alpha chemokine from mesothelial cells

IL-17 is a newly discovered cytokine implicated in the regulation of hemopoiesis and inflammation. Because IL-17 production is restricted to activated T lymphocytes, the effects exerted by IL-17 may help one to understand the contribution of T cells to the inflammatory response. We investigated the role of IL-17 in leukocyte recruitment into the peritoneal cavity. Leukocyte infiltration in vivo was assessed in BALB/Cj mice. Effects of IL-17 on chemokine generation in vitro were examined in human peritoneal mesothelial cells (HPMC). Administration of IL-17 i.p. resulted in a selective recruitment of neutrophils into the peritoneum and increased levels of KC chemokine (murine homologue of human growth-related oncogene alpha (GROalpha). Pretreatment with anti-KC Ab significantly reduced the IL-17-driven neutrophil accumulation. Primary cultures of HPMC expressed IL-17 receptor mRNA. Exposure of HPMC to IL-17 led to a dose- and time-dependent induction of GROalpha mRNA and protein. Combination of IL-17 together with TNF-alpha resulted in an increased stability of GROalpha mRNA and synergistic release of GROalpha protein. Anti-IL-17 Ab blocked the effects of IL-17 in vitro and in vivo. IL-17 is capable of selectively recruiting neutrophils into the peritoneal cavity via the release of neutrophil-specific chemokines from the peritoneal mesothelium.

[The role of cellular glucose transporters in pathogenesis of diabetic nephropathy]

The transport of glucose across plasma membranes is of paramount importance for the maintenance of cellular homeostasis and metabolism. Over the past few years it has been established that this process is mediated via a family of specialized and tissue-specific glucose transporters. It has been demonstrated that these facilitative glucose transporters may regulate the cellular uptake of glucose and consequently affect glucose metabolism. It has been suggested that increased utilization of glucose in glomerular cells results in the increased expression and activity of aldose reductase, protein kinase C and TGF-beta, which have been implicated in excessive extracellular matrix accumulation in diabetic nephropathy. In this report we review the identified forms of the glucose transporter family focusing on the systems expressed by the kidney. We also summarize the currently available experimental data suggesting that glomerular glucose transport systems may play a role in the development of diabetic nephropathy.

Biocompatibility and buffers: effect of bicarbonate-buffered peritoneal dialysis fluids on peritoneal cell function

BACKGROUND

Conventional peritoneal dialysis fluids (PDF) have been shown to compromise the function of both leukocytes and human peritoneal mesothelial cells (HPMC). Various in vitro studies have identified the low initial pH in combination with high lactate content, as well as the hyperosmolality and high glucose concentration present in currently used solutions as the primary determinants of their bioincompatibility. Bicarbonate buffered PDF (at neutral pH) display improved in vitro biocompatibility as compared to conventional, lactate buffered PDF. However, little information is currently available regarding the potential impact of PDF on the function of human peritoneal fibroblasts (HPFB), the major cell population present in peritoneal interstitium.

METHODS

The current study compares the effect of bicarbonate and lactate buffered PDF in a model system of resting peritoneal mesothelial cells and fibroblasts cultured from human omentum. Interleukin-1 beta-stimulated IL-6 release from HPMC and HPFB was used as the cell functional parameter.

RESULTS

While short (30 min) pre-exposure to lactate buffered PDF significantly reduced the IL-1 beta-stimulated IL-6 release from HPMC during a subsequent recovery period (24 hr), a significant decrease in HPMC IL-6 secretion with bicarbonate buffered PDF was only observed after prolonged (> or = 60 min) exposure. In contrast, no significant IL-6 inhibition was detected with HPFB pre-exposed to PDF for up to 90 minutes. A significant suppression of HPFB IL-6 secretion was only observed in coincubation experiments (24 hr) with dilutions of both types of PDF.

CONCLUSIONS

These results indicate that (i) bicarbonate buffered PDF are less inhibitory to peritoneal cell function as compared to conventional, lactate buffered PDF; and (ii) HPFB may be more resistant than HPMC to bioincompatible PDF.

Gas exchange of the lowest branches of young Scots pine: a cost-benefit analysis of seasonal branch carbon budget

A cost-benefit approach was developed to analyze the carbon budget of the lowest Scots pine (Pinus sylvestris L.) branches subject to abscission. In addition to within-branch growth and respiratory costs, the budget included an estimation of a branch's share of the maintenance respiration of the stem and root. A branch was considered productive if the budget was positive. Foliar gas exchange and woody-tissue respiration were non-destructively measured at monthly intervals during the growing season on the six lowest branches of 10-year-old Scots pine trees, to the moment when the branches died naturally. Photosynthetic light response and temperature response of respiration, together with measurements of canopy light conditions and meteorological data, were used to calculate seasonal carbon budgets for the branches. Maintenance respiration of stems and roots was estimated from published data. All but one of the branches studied were found to be nonproductive over the growing season. Following a decrease in photosynthetic capacity in July, the cumulative budget became negative and the branches died, indicating that a negative carbon budget corresponds with the onset of abscission of the lowest branches.

Insulin stimulates the activity of Na+/K(+)-ATPase in human peritoneal mesothelial cells

OBJECTIVE

To assess the effect of insulin on the Na+/K(+)-ATPase expression and activity in human peritoneal mesothelial cells (HPMC).

METHODS

HPMC were isolated from the omental tissue of non-uremic patients, grown to confluence and rendered quiescent by serum deprivation for 24 hours. The activity of Na+/K(+)-ATPase was determined by measuring the ouabain-sensitive 86Rb uptake. To assess whether the effect of insulin was related to changes in [Na+]i the sodium influx was measured with 22Na and the activity of Na+/K(+)-ATPase was assessed in the presence of amiloride. Expression of Na+/K(+)-ATPase alpha 1,alpha 2 and beta 1-subunit mRNAs was determined by RT/PCR.

RESULTS

Exposure of HPMC to insulin resulted in a time- and dose-dependent increase in the Na+/K(+)-ATPase activity. After 60 minutes the ouabain-sensitive 86Rb uptake (cpm/10(4) cells) was increased from 6650 +/- 796 in control cells to 9763 +/- 1212 in HPMC exposed to 100 mU/mL insulin (1.5-fold increase; n = 4, P < 0.05). In addition, incubation of HPMC with 100 mU/mL insulin resulted in a time-dependent increase in the 22Na influx. Pre-exposure of HPMC to 1mM amiloride reduced the activity of Na+/K(+)-ATPase but did not block the stimulatory effect of insulin. RT/PCR analysis revealed that HPMC constitutively expressed alpha 1- and beta 1-subunit mRNAs while the alpha 2-subunit mRNA was barely detectable. Exposure of HPMC to insulin for up to 24 hours was not associated with any changes in the expression of either alpha 1, alpha 2 or beta 1-subunit.

CONCLUSION

Insulin stimulates the Na+/K(+)-ATPase activity in HPMC in a time- and dose-dependent manner. This effect appears to mediated by an increase in [Na+]i and is not related to alterations in Na+/K(+)-ATPase subunit mRNAs expression.

Superinduction of IL-6 synthesis in human peritoneal mesothelial cells is related to the induction and stabilization of IL-6 mRNA

The initiation of peritonitis is accompanied by a massive increase in intraperitoneal levels of IL-6. The source of this cytokine and the mechanism by which its levels are increased so dramatically are unknown. We examined the mechanism of IL-6 secretion by HPMC exposed to the milicu present in the peritoneal cavity during the initiation of inflammation. Exposure of HPMC to spent peritoneal dialysis effluent (PDE) or IL-1 beta resulted in a time- and dose-dependent increase in IL-6 secretion. After 24 hours the IL-6 release (pg/microgram cell protein) was increased from 5.0 +/- 0.8 in control cells to 16.0 +/- 2.4 and to 83.8 +/- 17.4 in HPMC treated with PDE and IL-1 beta (1000 pg/ml), respectively (N = 5, P < 0.05). If, however, PDE and IL-1 beta were combined, then the secretion of IL-6 was synergistically increased to 747.7 +/- 349.9 (P < 0.05 vs. expected additive value). The same effect was evident when PDE was combined with TNF alpha or mixed with peritoneal macrophage conditioned medium. These changes were not a reflection of HPMC proliferation as estimated by 3H-thymidine incorporation. The "superinduction" of IL-6 release was associated both with the induction and stabilization of IL-6 mRNA. Competitive PCR demonstrated that the amount of IL-6 mRNA (fM/microgram total RNA) was increased from 0.35 +/- 0.13 in control cells to 11.66 +/- 3.89 and to 10.83 +/- 5.17 in HPMC treated with PDE and IL-1 beta (100 pg/ml), respectively (N = 5, P < 0.05). The combination of PDE + IL-1 beta synergistically increased IL-6 mRNA levels to 56.33 +/- 8.79 (P < 0.05 vs. additive value). RNA stability experiments using actinomycin D revealed that the half life of IL-6 mRNA (hours) was increased from 2.8 hours in control cells to 6.7 and 9.4 in HPMC exposed to PDE and IL-1 beta, respectively. The combination of PDE together with IL-1 beta resulted in a prolonged stabilization of IL-6 mRNA with levels remaining constant over the 12 hours of the experiment. These data demonstrate that HPMC IL-6 synthesis can be synergistically amplified in the presence of peritoneal dialysis effluent and PMO-derived cytokines. The results suggest that the peritoneal mesothelium may be responsible for the dramatic rise in IL-6 levels seen during the initial stages of CAPD peritonitis.

Effect of vitamin E on peroxidation and permeability of the peritoneum

Because of the evidence that peritoneal macrophages are activated during peritoneal dialysis, we hypothesised that the injury of the peritoneum is, at least in part, dependent on the intraperitoneal generation of free radicals. The aim of the study was to evaluate the effect of vitamin E on the peroxidation and permeability of the peritoneum during chronic peritoneal dialysis in rats. Supplementation of the intraperitoneally infused saline with vitamin E decreased the peroxidation of peritoneum estimated as the malondialdehyde (MDA) level in rats' omentum. However the permeability of the peritoneum to glucose and protein in vitamin E treated rats was increased. In in vitro study we have found that vitamin E is cytotoxic to human mesothelial cells (HMC) as measured by inhibition of their proliferation and this effect was irreversible. We conclude that vitamin E, despite its antioxidant effect, causes the changes of the peritoneum permeability which could decrease the effectiveness of peritoneal dialysis.

Effect of lactate-buffered peritoneal dialysis fluids on human peritoneal mesothelial cell interleukin-6 and prostaglandin synthesis

The present study focused on the evaluation of constitutive and cytokine-stimulated human peritoneal mesothelial cell (HPMC) IL-6 and 6-keto-PGF1 alpha release following pre-exposure to peritoneal dialysis fluid (PDF). Exposure of HPMC to PDF pH 5.2 resulted in a time-dependent increase in cell cytotoxicity [as assessed by lactate dehydrogenase (LDH) release] and concomitant inhibition of constitutive and IL-1 beta stimulated IL-6 and 6-keto-PGF1 alpha synthesis. After 15 minutes of exposure to PDF constitutive and IL-1 beta stimulated IL-6 release were reduced by 32.0 +/- 9.7% and 76.0 +/- 7.4% (N = 6, P < 0.046 and P < 0.027, respectively). PCR amplification of reverse transcribed mRNA from HPMC pre-exposed to PDF pH 5.2 demonstrated suppression of IL-1 beta stimulated IL-6 and cyclooxygenase (Cox-1 and Cox-2) transcripts. In order to mimic the dialysis cycle in vivo, an in vitro dialysis system was established. HPMC were exposed first to control medium, PDF pH 5.2 or PDF 7.3 for 15 minutes and then sequentially to pooled spent peritoneal dialysis effluent for up to four hours. The cells were subsequently allowed to recover in control medium for 12 hours in the presence or absence of IL-1 beta or TNF-alpha (both at 1000 pg/ml). There was no evidence of significant cell toxicity as assessed by LDH release during either the 'in vitro dialysis' or 'recovery' phases. Under these conditions short term exposure to PDF pH 5.2 followed by 'in vitro dialysis' resulted in significant inhibition of cytokine stimulated IL-6 (69.6 +/- 18.2 vs. 96.7 +/- 27.9 pg/microgram, N = 13; P < 0.020 for IL-1 beta) and 6-keto-PGF1 alpha (197.5 +/- 89.2 vs. 289.6 +/- 114.5 pg/microgram, N = 13; P < 0.020 for IL-1 beta) and 6-keto-PGF1 alpha (197.5 +/- 89.2 vs. 289.6 +/- 114.5 pg/microgram, N = 13; P < 0.003) release when compared to cells incubated in control medium. Adjustment of the pH of PDF to 7.3 reversed its inhibitory effects. We conclude that short-term exposure to PDF pH 5.2 significantly inhibits HPMC cytokine and prostaglandin release, an effect which appears to be related to its initial pH. Repeated exposure to nonphysiological PDF might impair mesothelial cell function and thus modulate intraperitoneal inflammatory processes.

Effect of methotrexate, doxorubicin and mitoxantrone on human peritoneal mesothelial cell function in vitro

Recent studies have demonstrated that intraperitoneal instillation of dialysis solutions and drug additives may adversely affect the function of peritoneal cell populations. Therefore the aim of the present investigation was to examine the short-term effects of antineoplastic agents on human peritoneal mesothelial cells (HPMC). We have assessed the integrity of HPMC membrane and mechanisms of intracellular potassium transport. There was no evidence of significant cytotoxicity (as measured by 86Rb release) during a 60-min exposure of HPMC to either methotrexate (10(-6)-10(-4) M), doxorubicin (10(-7)-10(-5) M) or mitoxantrone (10(-7)-10(-5) M). In HPMC exposed to doxorubicin (10(-6) M) the intracellular transport of potassium, as assessed with 86Rb as its analogue, was not affected. Methotrexate (10(-5) M) diminished Na,K-ATPase activity and simultaneously enhanced the 86Rb transport via furosemide-sensitive pathway. Mitoxantrone reduced the furosemide-sensitive 86Rb influx in a dose-dependent manner and at a concentration of 10(-4) M it also impaired the ouabain-dependent 86Rb influx. These data demonstrate that antineoplastic agents interfere with HPMC function which might contribute to the oncostatic-induced peritoneal toxicity.

In vitro culture of human peritoneal mesothelium for investigation of mesothelial dysfunction during peritoneal dialysis

There is a growing need for more biocompatible peritoneal dialysis fluid formulations. Using a method of in vitro cell culture we have examined the effect of osmotic agents, antiseptics and drug additives on various functions of human peritoneal mesothelial cells (HPMC). We have demonstrated that glucose and amino acids reduce the HPMC proliferation rate in a dose-dependent manner. 3H-methyl-thymidine incorporation into HPMC exposed to either 1.1% amino acid mixture or 2.0% glucose was decreased to (mean +/- SD) 32.5 +/- 6.1% and 16.8 +/- 1.2% of the control level respectively. Cultured HPMC have been shown to produce a fibrinolytic activity which may be estimated by the rate of plasma clot lysis. This activity may be diminished following the pre-incubation with 2.0% glucose and 1.1% amino acid mixture. We have found that povidone-iodine exerts a dose-dependent cytotoxic effect towards HPMC as measured by the increased 86Rb or 3H-inulin release from radiolabelled cells. We have also demonstrated that insulin enhances the 86Rb uptake and stimulates the Na, K-ATPase activity in HPMC but on the other hand is capable of reducing the phospholipids secretion from HPMC. Glucose, hydrocortisone or verapamil have also been shown to inhibit the release of mesothelial phospholipids. These data indicate that the mesothelial cell culture provides a convenient model for testing the biocompatibility of peritoneal dialysis solutions and assessing the dysfunction of mesothelial cells during peritoneal dialysis.

Glycerol toxicity for human peritoneal mesothelial cells in culture: comparison with glucose

Glycerol has been proposed as a substitute osmotic agent for glucose in peritoneal dialysis fluids. We have compared the effect of glycerol and glucose on the function of human peritoneal mesothelial cells (HPMC) in vitro. The viability of HPMC was not affected by glycerol (up to 250 mM), whereas it was reduced by glucose in a time- and dose-dependent manner, as assessed by the LDH release. Although the incubation of HPMC with glycerol induced a dose-dependent decrease in HPMC proliferation, the effect was significantly less inhibitory than that produced by glucose. In HPMC treated with 90 mM of glycerol or glucose the incorporation of [3H]-thymidine had reached 79.0 +/- 19.3% and 55.3 +/- 4.0% of the control (p < 0.05 and p < 0.01), respectively. As measured by the [methyl-14C]-choline incorporation, the intracellular amount of newly synthesized phospholipids was reduced from (cpm/microgram cellular protein) 147 +/- 58 in control HPMC to 59 +/- 15 in cells exposed to 90 mM of glucose (p < 0.01), but not affected by glycerol (163 +/- 65). On the other hand, both glycerol and glucose (90 mM) decreased the synthesis of proteins (as assessed by the [3H]-proline incorporation) and interfered with potassium (86Rb) transport mechanisms in HPMC. Our data suggest that there exist some possibly advantageous aspects of glycerol as far as mesothelial cell biocompatibility profile is concerned.

Effect of phosphatidylcholine on the function of human mesothelial cells in vitro

We tested the hypothesis that phosphatidylcholine (PC) molecules present in the dialysis solution may interact with the mesothelial cell membrane and modify its function. In vitro experiments were performed on human mesothelial cells (HMC) in culture. PC decreased proliferation of HMC when used at concentrations of 200 mg/l and higher. PC was also cytotoxic to HMC as measured by the release of lactate dehydrogenase from their cytosol. Cells exposed to PC had a diminished capacity for taking up 86Rb from medium. PC decreased the fibrinolytic properties of HMC and increased their procoagulant activity. Our results suggest that the positive short-term effect of the addition of PC to the dialysis solution (i.e., an increase in ultrafiltration) may be over-shadowed by its deleterious action on HMC membrane.

Toxicity of free radicals to mesothelial cells and peritoneal membrane

We studied the toxicity of free radicals to human mesothelial cells in vitro and to the peritoneal membrane of rats during peritoneal dialysis. Free radicals cause damage to mesothelial cells as measured by release of cytosolic markers such as 86Rb and lactate dehydrogenase. Vitamin E neutralized the toxic effect of free radicals in vitro. Human mesothelial cells exposed over 6 h to a mixture of essential and nonessential amino acids in medium are more vulnerable to the cytotoxic effect of free radicals than control cells exposed to medium alone. Cells exposed previously to glucose or glycerol are less vulnerable than controls. In rats free radicals generated intraperitoneally by a xanthine-xanthine oxidase system induce changes in peritoneal permeability similar to those observed during peritonitis: loss of ultrafiltration, increased glucose absorption from the dialysate and augmented transperitoneal loss of albumin. In addition lipids in the peritoneum became peroxidated. The addition of vitamin E to the peritoneal fluid with xanthine-xanthine oxidase prevents peroxidation of lipids and the subsequent loss of ultrafiltration. Our results show that free radicals may exert a potentially toxic effect on the peritoneal membrane during peritonitis. In such circumstances the addition of free radical scavenger to the dialysis fluid may preserve intact structure and function of peritoneum.