Sterile inflammation of peritoneal membrane caused by peritoneal dialysis: focus on the communication between immune cells and peritoneal stroma

Peritoneal dialysis is a widely used method for treating kidney failure. However, over time, the peritoneal structure and function can deteriorate, leading to the failure of this therapy. This deterioration is primarily caused by infectious and sterile inflammation. Sterile inflammation, which is inflammation without infection, is particularly concerning as it can be subtle and often goes unnoticed. The onset of sterile inflammation involves various pathological processes. Peritoneal cells detect signals that promote inflammation and release substances that attract immune cells from the bloodstream. These immune cells contribute to the initiation and escalation of the inflammatory response. The existing literature extensively covers the involvement of different cell types in the sterile inflammation, including mesothelial cells, fibroblasts, endothelial cells, and adipocytes, as well as immune cells such as macrophages, lymphocytes, and mast cells. These cells work together to promote the occurrence and progression of sterile inflammation, although the exact mechanisms are not fully understood. This review aims to provide a comprehensive overview of the signals from both stromal cells and components of immune system, as well as the reciprocal interactions between cellular components, during the initiation of sterile inflammation. By understanding the cellular and molecular mechanisms underlying sterile inflammation, we may potentially develop therapeutic interventions to counteract peritoneal membrane damage and restore normal function.

Calcium mediates cell shape change in human peritoneal mesothelial cells

Mast cells in the peritoneal membrane (PM) may degranulate to release preformed inflammatory mediators including histamine which is capable of diffusing into the surrounding interstitium, modulating cells in their vicinity including, human peritoneal mesothelial cells (hPMC). The present study aimed to investigate the quorum intracellular calcium ([Ca²⁺_i]) response to histamine compared to the membrane soluble ionophore, A23187, in adherent cultured hPMC. To examine [Ca²⁺_i] handling, Fura - 2 loaded cells were exposed to histamine and A23187. Agonist induced transient [Ca²⁺_i] event(s) (TCE) were defined and compared including, resting calcium, peak height, recovery and transient kinetics. Changes in cell shape were examined with immunocytochemistry of the cortical actin (CA) and microtubule (MT) cytoskeleton. To investigate whether histamine induced changes in cell shape were mediated by [Ca²⁺_i], mobilization of [Ca²⁺_i] was prevented with 20 μmol/l of the calcium chelator 1,2-bis-(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM). Histamine produced a dose dependent increase of [Ca²⁺_i], maximal at 1.0 mmol/l which recovered to the pre-challenge resting value. Transient multiplicity with repeated challenge was evident below a histamine threshold of 10^-2 mmol/l. Morphometric analysis of MTs and CA showed significant cell elongation plus histamine and A23187. The histamine induced cell elongation was eliminated with [Ca²⁺_i] clamping. This data indicated that increased [Ca²⁺_i] was essential for cell elongation and the formation of stress fibres and therefore has a pivotal role in the regulation of the PM barrier.

Case report of encapsulating peritoneal sclerosis: the interpretation of functional and structural peritoneal changes

A case report describing the evolution of encapsulating peritoneal sclerosis is presented to illustrate some of the functional and structural peritoneal membrane changes characteristic of this complication of peritoneal dialysis. The appropriate monitoring of peritoneal transport rates and ultrafiltration, together with attention to clinical signs and symptoms, are essential to the early diagnosis of peritoneal membrane deterioration. Recent reports suggest that timely interventions such as a peritoneal membrane rest period may effectively halt the progression of these functional and structural changes. While the optimal surgical and pharmacological treatment of encapsulating peritoneal sclerosis remains uncertain, the latest literature provides a certain degree of optimism.

Peritoneal mast cells in peritoneal dialysis patients, particularly in encapsulating peritoneal sclerosis patients

BACKGROUND

We assumed that increased mast cell numbers contribute substantially to the fibrosis often seen in the peritoneum of peritoneal dialysis (PD) patients, particularly those with encapsulating peritoneal fibrosis (EPS). Therefore, we investigated mast cells in different pathological conditions of the peritoneum.

METHODS

One hundred fifteen tissue probes with different peritoneal pathological states were selected (normal, n = 20; chronic appendicitis, n = 25; herniotomy, n = 24; fibrosis, n = 11; PD, n = 26; and EPS, n = 9). For staining of mast cells, we used alpha-naphtol-AS-d-chloracetate-esterase and mast cell tryptase. Next, we counted numbers of mast cells per square millimeter. Tryptase was measured by using image analysis.

RESULTS

Measurements by means of both methods correlated well (r = 0.812). Numbers of mast cells per square millimeter were as follows: normal, 26 +/- 16; chronic appendicitis, 241 +/- 217; herniotomy, 115 +/- 88; fibrosis, 99 +/- 66; PD, 81 +/- 64, and EPS, 24 +/- 23 (P = 0.00006). Amounts of tryptase present were 2.900 +/- 0.118, 2.871 +/- 0.150, 2.733 +/- 0.183, 3.041 +/- 0.176, 2.780 +/- 0.184, and 2.609 +/- 0.234, respectively (P = 0.00002).

CONCLUSION

We found upregulation of mast cells in specimens of chronic inflammatory diseases of the peritoneum. This also was true for PD patients, with the exclusion of patients with EPS. Therefore, loss-of-control functions of mast cells may contribute to the ill-understood disease entity of EPS.

Mesothelial primary cilia of peritoneal and other serosal surfaces

The conspicuous presence of primary cilia, a small immotile cilium present on most cell types, left researchers with little doubt of their functional relevance. Recently mechanosensitive functional significance was established and a link with the pathogenesis of polycystic kidney disease. Together these discoveries have raised the profile of this, previously considered "vestigial", organelle. Primary cilia are expressed on the apical surface of serosal mesothelium and display regional variation but are more abundant on biosynthetically active cells. Adult mesothelial cells are highly biosynthetic producing a phospholipid rich surfactant that lubricates and protects the visceral organs. The mesothelium is utilized as a semipermeable membrane during peritoneal dialysis for patients with end stage renal failure. However, little is known about the functional role of primary cilia on this highly specialized cell type. The present review, examines the significance of the primary cilium in serosal mesothelial cell biology with an emphasis on ciliary location, structure, form and function. Future research is identified and discussed in view of the emerging role cilia have in other cells and the established function of the serosal mesothelium in development, normal function, peritoneal dialysis and pathology of the serosal membranes.

Effects of bicarbonate buffered dialysate on human peritoneal mesothelial cell intracellular calcium homeostasis

This study compares the biocompatibility of two bicarbonate-based peritoneal dialysis (PD) solutions using the measurement of intracellular free calcium (Ca(i)2+)) as a sensitive parameter of cell function in human peritoneal mesothelial cells (hPMC). Fura-2-loaded hPMC suspensions were exposed to bicarbonate (38 mmol/L) and bicarbonate (25 mmol/L), lactate-buffered PD (15 mmol/L) solutions at pH 7.4 and compared with Krebs-Ringer physiological saline (KRS; pH = 7.4). Resting Ca(i)2+ values and 4br-A23187 (1.0 micro mol/L) induced transients were compared in treatment and control groups. In separate studies, the effect that low saline pH had on Ca(i)(2+) homeostasis was examined. Suspended cells or cells attached to coverslips were bathed in citric acid-phosphate (McIllvaine's) buffered saline (MBS, pH = 7.4). Cells were acidified (pH = 5.3) with citric acid and then challenged with ionophore. Ionophore challenge produced a significantly reduced Ca(i)2+ transient response in cells exposed to the bicarbonate/lactate fluid compared with bicarbonate or KRS. Acidified cell suspensions produced a small monophasic Ca(i)2+ transient rise that was short lived. Gradual recovery of MBS to pH 7.4 produced no changes to Ca(i)2+ homeostasis of cell monolayers. Ionophore treatment produced a biphasic response identical to cells bathed in KRS. This study has demonstrated that short-term exposure to bicarbonate did not alter Ca(i)2+ homeostasis directly, or subsequent modulation of intracellular pH. The MBS system provided a reliable method of modifying the external pH during continuous Ca(i)2+ measurement.

Mechanisms of histamine-induced intracellular Ca 2+ release and extracellular Ca 2+ entry in MG63 human osteosarcoma cells 1 1Abbreviations: [Ca2+]i; Cytosolic free Ca2+ concentration; and IP3, inositol 1,4,5-trisphosphate

The effect of histamine on intracellular free Ca2+ levels ([Ca2+](i)) in MG63 human osteosarcoma cells was explored using fura-2 as a Ca2+ dye. Histamine increased ([Ca2+](i)) in a concentration-dependent fashion with an EC(50) value of 0.5 microM. Extracellular Ca2+ removal inhibited the ([Ca2+](i)) signals. Histamine failed to increase ([Ca2+](i)) in Ca2+-free medium after cells were pretreated with thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor). Addition of Ca2+ induced concentration-dependent ([Ca2+](i)) increases after preincubation with histamine in Ca2+-free medium. Histamine-induced intracellular Ca2+ release was abolished by inhibiting phospholipase C with 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). The ([Ca2+](i)) increase induced by histamine in Ca2+ medium was abolished by cimetidine, but was not altered by pyrilamine, nifedipine, verapamil, and La(3+). Together, this study shows that histamine increased in ([Ca2+](i)) in osteosarcoma cells by stimulating H2 histamine receptors. The Ca2+ signal was caused by Ca2+ release from the endoplasmic reticulum in a phospholipase C-dependent manner. The Ca2+ release was accompanied by Ca(2+) influx.

Effect of middle-wave ultraviolet irradiation and red light on degranulation of peritoneal mast cell in rats

Middle-wave UV-irradiation inhibits liberator-induced histamine release from mast cells. Red light stimulated liberator-induced degranulation of mast cell. The existence of a membrane-dependent system activated by long-wave (red) light in mammalian cells is discussed.