Pro- and Anti-Inflammatory Prostaglandins and Cytokines in Humans: A Mini Review.

Inflammation has been described for two millennia, but cellular aspects and the paradigm involving different mediators have been identified in the recent century. Two main groups of molecules, the prostaglandins (PG) and the cytokines, have been discovered and play a major role in inflammatory processes. The activation of prostaglandins PGE2, PGD2 and PGI2 results in prominent symptoms during cardiovascular and rheumatoid diseases. The balance between pro- and anti-inflammatory compounds is nowadays a challenge for more targeted therapeutic approaches. The first cytokine was described more than a century ago and is now a part of different families of cytokines (38 interleukins), including the IL-1 and IL-6 families and TNF and TGFß families. Cytokines can perform a dual role, being growth promotors or inhibitors and having pro- and anti-inflammatory properties. The complex interactions between cytokines, vascular cells and immune cells are responsible for dramatic conditions and lead to the concept of cytokine storm observed during sepsis, multi-organ failure and, recently, in some cases of COVID-19 infection. Cytokines such as interferon and hematopoietic growth factor have been used as therapy. Alternatively, the inhibition of cytokine functions has been largely developed using anti-interleukin or anti-TNF monoclonal antibodies in the treatment of sepsis or chronic inflammation.

Old and New Blood Markers in Human Colorectal Cancer.

Cancer is a predominant cause of mortality all over the world. Lung, prostate, and colorectal cancer are the more frequent in men while breast and colorectal have a high incidence in women. Major progress aside, some cancers are still frequent and one major issue is improvements in detection methods. Imaging techniques have a major role, but inflammatory, tumoral markers and calculated scores may contribute to the assessment of prognosis. The erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and carcinoembryonic antigen cell adhesion molecule (CEACAM) have been used for decades and do not have a clear use for diagnosis or prognosis yet. The CEACAM family includes 12 human members, and some of them have a cluster differentiation (CD). CD66 may be an interesting indicator of disease severity. Beside interleukin-6 (IL-6), the high level of which is observed in patients with a high mortality rate, other cytokines IL-17A, IL-22, and transforming growth factor -ß (TGF-ß) are expressed at the tumor level. The detection of circulating tumor cells has been improved but is still of undetermined value. Circulating tumor DNA (ctDNA) was recently studied in CRC stage II patients and may be helpful for chemotherapy management.

Vascular Permeability in Diseases.

Vascular permeability is a selective mechanism that maintains the exchange between vessels, tissues, and organs. The regulation was mostly studied during the nineteenth century by physiologists who defined physical laws and equations, taking blood, tissue interstitial, and oncotic pressure into account. During the last decades, a better knowledge of vascular cell functions and blood-vessel interactions opens a new area of vascular biology. Endothelial cell receptors vascular cell adhesion molecule (VCAM), intercellular cell adhesion molecule (ICAM), vascular endothelial growth factor receptor (VEGFR-2), receptor for advanced glycation end products (RAGE), and mediators were identified and their role in homeostasis and pathological situations was described. The molecular differences of endothelial cell junctions (tight, gap, and adherens junctions) and their role in vascular permeability were characterized in different organs. The main mediators of vasomotricity and permeability, such as prostaglandins, nitric oxide (NO), prostacyclin, vascular growth factor (VEGF), and cytokines, have been demonstrated to possess major functions in steady state and pathological situations. Leukocytes were shown to adhere to endothelium and migrate during inflammatory situations and infectious diseases. Increased vascular permeability is linked to endothelium integrity. Glycocalyx, when intact, may limit cancer cell metastasis. Biological modifications of blood and tissue constituents occurring in diabetes mellitus were responsible for increased permeability and, consequently, ocular and renal complications. Vascular pressure and fluidity are major determinants of pulmonary and cerebral edema. Beside the treatment of the infectious disease, of the blood circulation dysfunction and inflammatory condition, drugs (cyclooxygenase inhibitors) and specific antibodies anti-cytokine (anti-VEGF) have been demonstrated to reduce the severity and the mortality in diseases that exhibited enhanced vascular permeability.

Endothelial Cell Participation in Inflammatory Reaction.

Inflammation is an old concept that has started to be considered as an important factor in infection and chronic diseases. The role of leukocytes, the plasmatic components, then of the mediators such as prostaglandins, cytokines, and, in recent decades, of the endothelium has completed the concept of the inflammation process. The function of the endothelium appeared to be crucial as a regulator or the initiator of the inflammatory process. Culture of human endothelial cells and experimental systems made it possible to define the molecular basis of inflammation in vascular diseases, in diabetes mellitus, atherosclerosis, vasculitis and thromboembolic complications. Advanced glycation end product receptor (RAGE), present on endothelial cells (ECs) and monocytes, participates in the activation of these cells in inflammatory conditions. Inflammasome is a cytosolic multiprotein that controls the response to diverse microorganisms. It is positively regulated by stimulator of interferon response CGAMP interactor-1 (STING1). Angiogenesis and thrombotic events are dysregulated during inflammation. ECs appear to be a protector, but also a possible initiator of thrombosis.

Cellular and Molecular Aspects of Blood Cell-Endothelium Interactions in Vascular Disorders.

In physiology and pathophysiology the molecules involved in blood cell-blood cell and blood cell-endothelium interactions have been identified. Platelet aggregation and adhesion to the walls belonging to vessels involve glycoproteins (GP), GP llb and GP llla and the GP Ib-IX-V complex. Red blood cells (RBCs) in normal situations have little interaction with the endothelium. Abnormal adhesion of RBCs was first observed in sickle cell anemia involving vascular cell adhesion molecule (VCAM)-1, α4ß1, Lu/BCAM, and intercellular adhesion molecule (ICAM)-4. More recently RBC adhesion was found to be increased in retinal-vein occlusion (RVO) and in polycythemia vera (PV). The molecules which participate in this process are phosphatidylserine and annexin V in RVO, and phosphorylated Lu/BCAM and α5 laminin chain in PV. The additional adhesion in diabetes mellitus occurs due to the glycated RBC band 3 and the advanced glycation end-product receptors. The multiligand receptor binds advanced glycation end products (AGEs) or S100 calgranulins, or ß-amyloid peptide. This receptor for advanced glycation end products is known as RAGE. The binding to RAGE-activated endothelial cells leads to an inflammatory reaction and a prothrombotic state via NADPH activation and altered gene expression. RAGE blockade is a potential target for drugs preventing the deleterious consequences of RAGE activation.

Activation of the receptor for advanced glycation end products and consequences on health.

Advanced glycation end products (AGE) resulted from a reaction between free amino group of proteins and carbohydrates. This reaction is followed by oxidation and molecular rearrangement. Alternatively AGEs can be produced by glycolysis and oxidation. AGEs bind to a cellular receptor RAGE. RAGE engagement by ligands AGE, ß-amyloid peptide, and S100 calgranulin induces a stimulation of NADPH oxidase, reactive oxygen intermediate formation, NFκB activation and gene transcription. This cascade of reaction leads to an inflammatory reaction responsible for alteration of microvessels in the retina and the kidney. Blockade of RAGE by antibodies anti-RAGE, TTP488 (azeliragon), or rRAGE prevents or limits the deleterious effect of AGEs.

JAK2V617F activates Lu/BCAM-mediated red cell adhesion in polycythemia vera through an EpoR-independent Rap1/Akt pathway.

Polycythemia vera (PV) is characterized by an increased RBC mass, spontaneous erythroid colony formation, and the JAK2V617F mutation. PV is associated with a high risk of mesenteric and cerebral thrombosis. PV RBC adhesion to endothelial laminin is increased and mediated by phosphorylated erythroid Lu/BCAM. In the present work, we investigated the mechanism responsible for Lu/BCAM phosphorylation in the presence of JAK2V617F using HEL and BaF3 cell lines as well as RBCs from patients with PV. High levels of Rap1-GTP were found in HEL and BaF3 cells expressing JAK2V617F compared with BaF3 cells with wild-type JAK2. This finding was associated with increased Akt activity, Lu/BCAM phosphorylation, and cell adhesion to laminin that were inhibited by the dominant-negative Rap1S17N or by the specific Rap1 inhibitor GGTI-298. Surprisingly, knocking-down EpoR in HEL cells did not alter Akt activity or cell adhesion to laminin. Our findings reveal a novel EpoR-independent Rap1/Akt signaling pathway that is activated by JAK2V617F in circulating PV RBCs and responsible for Lu/BCAM activation. This new characteristic of JAK2V617F could play a critical role in initiating abnormal interactions among circulating and endothelial cells in patients with PV.

Molecular basis of erythrocyte adhesion to endothelial cells in diseases.

Red blood cell (RBC) adhesion to endothelium can be studied in static and flow conditions. Increased RBC adhesion was first described in sickle cell disease. Several molecules were shown to be involved in this phenomenon: VCAM-1, α4ß1, Lu/BCAM, ICAM-4. In malaria, Plasmodium falciparum erythrocyte membrane protein1 binds to ICAM-1, PECAM-1 and facilitates the parasite dissemination. In diabetes mellitus augmented RBC adhesion is correlated to the severity of vascular complications. Glycated RBC band3 reacts with the endothelial Receptor for Advanced Glycation End products (RAGE). RAGE engagement induced endothelial cell dysfunction. In patients with Polycythemia Vera (PV), the most frequent myeloproliferative disorder, constitutive phosphorylation of RBC Lu/BCAM is responsible for an increased adhesion to endothelial cell laminin. Retinal vein occlusion (RVO) is a common cause of permanent visual loss. Spontaneous growth of erythroid precursors was observed in more than 25% of patients. RBC adhesion was enhanced and correlated to phosphatidyl serine (PS) expression on RBC. Anti-PS receptor blocked RVO RBC adhesion indicating that the counterpart of RBC PS is PS endothelial cell receptor. Erythrocyte adhesion is mediated by different molecule abnormalities in different diseases but is associated to a higher risk of thrombosis and vascular complications.

The different isoforms of the receptor for advanced glycation end products are modulated by pharmacological agents.

Elevated glucose concentration increases oxidation and Advanced Glycation End product (AGE) formation. The binding of circulatory AGEs or AGEs included in erythrocyte membrane to the receptor for AGEs (RAGE) generates in endothelial cells an oxidative stress and enhances the expression of inflammatory molecules. Engagement of RAGE by AGEs and subsequent signaling plays an important role in the development of diabetic complications. Soluble RAGE isoforms (sRAGE) neutralize the ligand-mediated damage by acting as a decoy. If the expression of RAGE is upregulated during the pathogenesis of inflammatory diseases, sRAGE mostly found decreased when complications ensue. By modulating RAGE isoform expression, it could be possible to reduce the incidence of complications. This review focused on the capability of Angiotensin Receptor Blockers (ARBs), which are used to treat patients with hypertension and/or diabetes, to modulate RAGE isoform expression because some data reported the interference with RAGE downstream. In this regard, three ARBs - irbesartan, telmisartan, candesartan cilexetil - were tested and provided evidence for their ability to inhibit in human endothelial cells the expression of membrane-bound and soluble RAGE isoforms induced by the inflammatory factor Tumor Necrosis Factor-alpha (TNF-alpha), demonstrating the potential benefits of these molecules in RAGE-oriented therapies. Modulating RAGE isoforms expression by correcting endothelial dysfunction is achievable by drugs already used for hypertension or diabetes treatment such as ARBs.

Intercellular adhesion molecule-4 and CD36 are implicated in the abnormal adhesiveness of sickle cell SAD mouse erythrocytes to endothelium.

BACKGROUND: Abnormal adhesiveness of red blood cells to endothelium has been implicated in vaso-occlusive crisis of sickle cell disease. The present study examined whether the SAD mouse model exhibits the same abnormalities of red blood cell adhesion as those found in human sickle cell disease. DESIGN AND METHODS: The repertoire of adhesive molecules on murine erythrocytes and bEnd.3 microvascular endothelial cells was determined by flow cytometry using monoclonal antibodies or by western blotting. Adhesion was investigated in dynamic conditions and measured at different shear stresses. RESULTS: CD36, CD47 and intercellular adhesion molecular-4, but not Lutheran blood group antigen/basal cell adhesion molecule, are present on mouse mature erythrocytes. alpha(4)beta(1) are not expressed on SAD and wild type reticulocytes. Endothelial bEnd.3 cells express alpha(V)beta(3), alpha(4)beta(1), CD47, vascular cell adhesion molecule-1, and Lutheran blood group antigen/basal cell adhesion molecule, but not CD36. Adhesion of SAD red cells is: (i) 2- to 3-fold higher than that of wild type red cells; (ii) further increased on platelet activating factor-activated endothelium; (iii) not stimulated by epinephrine; (iv) inhibited after treating the endothelium with a peptide reproducing one of the binding sequences of mouse intercellular adhesion molecular-4, or with mon-oclonal antibody against murine alpha(v) integrin; and (v) inhibited after pretreatment of red blood cells with anti-mouse CD36 monoclonal antibodies. The combination of treatments with intercellular adhesion molecular-4 peptide and anti-CD36 monoclonal antibodies eliminates excess adhesion of SAD red cells. The phosphorylation state of intercellular adhesion molecular-4 and CD36 is probably not involved in the over-adhesiveness of SAD erythrocytes. CONCLUSIONS: Intercellular adhesion molecular-4/alpha(v)beta(3) and CD36/thrombospondin interactions might contribute to the abnormally high adhesiveness of SAD red cells. The SAD mouse is a valuable animal model for investigating adhesion processes of sickle cell disease.

Red blood cell adhesion in diabetes mellitus is mediated by advanced glycation end product receptor and is modulated by nitric oxide.

Red blood cell (RBC) adhesion to endothelium is increased in diabetes mellitus and is correlated with the severity of vascular complications. Microangiopathy is the most frequent complications in patients suffering from diabetes mellitus. Elevated glucose concentration increases the oxidation phenomenon and advanced glycation end product (AGE) formation. Plasma proteins, structural proteins and also RBC proteins can be glycated such as glycated hemoglobin and RBC membrane proteins. Interaction of plasmatic AGE or RBC bearing AGE with the receptor for AGE (RAGE) alters vascular function leading to a vascular hyperpermeability inflammatory reaction including oxidant stress and cytokine production. Reactive oxygen species (ROS) react with nitric oxide (NO) limiting its vasodilatory effect and NO synthase function is altered. All these factors may be at the origin of high blood pressure which is deleterious for the eye and kidney vasculature. AGE can act directly on vascular function but also through RAGE. AGE binding to RAGE alters endothelial cell function stimulating NADPH oxidase and reactive oxygen species production. Limiting oxidation, reducing AGE formation or interaction with RAGE is achievable by drugs already used for hypertension or diabetes, but new treatment by NO modulators may limit the deleterious effect of RBC adhesion to endothelium.

Increased adhesion to endothelial cells of erythrocytes from patients with polycythemia vera is mediated by laminin alpha5 chain and Lu/BCAM.

Patients with polycythemia vera (PV) have a JAK2 (a cytosolic tyrosine kinase) mutation and an increased risk of vascular thrombosis related to red blood cell (RBC) mass and platelet activation. We investigated functional RBC abnormalities that could be involved in thrombosis. RBC adhesion to human umbilical vein endothelial cells (HUVECs) was measured by a radiometric technique and in a flow system by video microscopy, and adhesion molecule expression was determined using specific antibodies (against CD36, CD49d, ICAM-4, Lu/BCAM, CD147, and CD47) and flow cytometry in a group of 38 patients with PV and a group of 36 healthy volunteers. Adhesion of PV RBCs was 3.7-fold higher than that of normal RBCs (P < .001). Adhesion was inhibited when PV RBCs were incubated with anti-Lutheran blood group/basal cell adhesion molecule (Lu/BCAM) or when HUVECs were treated with anti-laminin alpha(5) and to a lesser extent with anti-alpha(3) integrin. Lu/BCAM was constitutively phosphorylated in PV RBCs. Transfection of K562 cells with JAK2 617V>F resulted in increased expression and phosphorylation of Lu/BCAM. Phosphorylation of Lu/BCAM increases RBC adhesion. Our results indicate that JAK2 mutation might be linked to Lu/BCAM modification and increased RBC adhesiveness, which may be a factor favoring thrombosis in PV.

Characterization of p43(ARF), a derivative of the p43 component of multiaminoacyl-tRNA synthetase complex released during apoptosis.

In human, nine aminoacyl tRNA synthetases are associated with the three auxiliary proteins, p18, p38, and p43, to form a stable multiprotein complex. The p43 component, which has a potent tRNA binding capacity, is associated to the complex via its N-terminal moiety. This protein is also the precursor of the endothelial monocyte-activating polypeptide II (p43(EMAPII), corresponding to the C-terminal moiety of p43), a cytokine generated during apoptosis. Here we examined the cellular pathway that, starting from the p43 subunit of the complex, leads to this extracellular cytokine. We identified a new intermediate in this pathway, named p43(ARF) for Apoptosis-released Factor. This intermediate is produced in cellulo by proteolytic cleavage of endogenous p43 and is rapidly recovered in the culture medium. This p43 derivative was purified from the medium of human U937 cells subjected to serum starvation. It contains 40 additional N-terminal amino acid residues as compared with the cytokine p43(EMAPII) and may be generated by a member of the matrix metalloproteinase family. Recombinant p43(ARF) is a monomer in solution and binds tRNA with a Kd of approximately 6 nM, 30-fold lower than that of p43. Highly purified p43(ARF) or p43(EMAPII) do not stimulate the expression of E-selectin by human umbilical vein endothelial cells. Our results suggest that the cleavage of p43 and its cellular delocalization, and thus the release of this tRNA binding subunit from the complex, is one of the molecular mechanisms leading to the shut down of protein synthesis in apoptosis.

Endothelial Lu/BCAM glycoproteins are novel ligands for red blood cell alpha4beta1 integrin: role in adhesion of sickle red blood cells to endothelial cells.

The Lutheran (Lu) blood group and basal cell adhesion molecule (BCAM) antigens are both carried by 2 glycoprotein isoforms of the immunoglobulin superfamily representing receptors for the laminin alpha(5) chain. In addition to red blood cells, Lu/BCAM proteins are highly expressed in endothelial cells. Abnormal adhesion of red blood cells to the endothelium could potentially contribute to the vaso-occlusive episodes in sickle cell disease. Considering the presence of integrin consensus-binding sites in Lu/BCAM proteins, we investigated their potential interaction with integrin alpha(4)beta(1), the unique integrin expressed on immature circulating sickle red cells. Using cell adhesion assays under static and flow conditions, we demonstrated that integrin alpha(4)beta(1) expressed on transfected cells bound to chimeric Lu-Fc protein. We showed that epinephrine-stimulated sickle cells, but not control red cells, adhered to Lu-Fc via integrin alpha(4)beta(1) under flow conditions. Antibody-mediated activation of integrin alpha(4)beta(1) induced adhesion of sickle red cells to primary human umbilical vein endothelial cells; this adhesion was inhibited by soluble Lu-Fc and vascular cell adhesion molecule-1 (VCAM-1)-Fc proteins. This novel interaction between integrin alpha(4)beta(1) in sickle red cells and endothelial Lu/BCAM proteins could participate in sickle cell adhesion to endothelium and potentially play a role in vaso-occlusive episodes.

Improved in vitro biocompatibility of bicarbonate-buffered peritoneal dialysis fluid.

BACKGROUND: Conventional peritoneal dialysis fluids (PDFs) have been shown to damage the mesothelial layer and are associated with the development of peritoneal fibrosis and neoangiogenesis. New-generation PDFs have therefore been developed with physiological pH and reduced levels of glucose degradation products (GDPs), precursors of advanced glycation end products (AGEs). In this work, we evaluated and compared the improved biocompatibility of two new-generation PDFs (Balance and bicaVera) using mesothelial cell biology; we also compared them to a standard PDF (stay.safe) (all PDFs by Fresenius Medical Care, Fresnes, France). METHODS: stay.safe, Balance, and bicaVera were tested for their effect on human peritoneal mesothelial cell (HPMC) viability by measuring cell proliferation and apoptosis, and oncosis induction. The formation of AGEs was evaluated by immunoassay. Transforming growth factor beta-1 and vascular endothelial growth factor (VEGF) were immunoassayed in HPMC supernatants exposed to the above PDFs. RESULTS: At 15 g/L glucose concentration, HPMC exposure to bicaVera resulted in higher cell proliferation compared to Balance (p < 0.001) and stay.safe (p < 0.001). Compared to the lactate-buffered PDFs (Balance and stay.safe), oncosis was significantly lower in cells exposed to bicaVera (p < 0.05). bicaVera, containing lower amounts of GDPs, generated less AGE formation (p < 0.05) and VEGF production (p < 0.05) than either Balance or stay.safe. CONCLUSIONS: New-generation PDFs with physiological pH and lower GDP levels, especially if bicarbonate-buffered (bicaVera), have fewer in vitro toxic effects on mesothelial cells and may contribute to peritoneal preservation, thus improving long-term treatment of PD patients.

Modulation of RAGE expression influences the adhesion of red blood cells from diabetic patients.

Atherothrombotic complications are frequent in patients with type 2 diabetes. Red blood cells (RBC) from diabetic patients exhibited an increased adhesion which correlated to the extent of vascular complications. In the present study we have investigated the adhesive interactions of RBCs with endothelium, using flow-based assessments. RBCs and endothelial cells were unstimulated or stimulated using respectively adrenaline and TNFalpha. Adhesion assays were carried-out by drawing the RBC suspension through a glass microcapillary tube precoated by human umbilical vein endothelial cells. These microslides were then incorporated into a controlled flow system equipped with a computerized video-microscopic image analysis. RBCs from diabetic patients bind to endothelial cells and could withstand wall shear stresses above 0.1 Pa. After stimulation by TNFalpha the adhesion was 1.5-fold higher. Blocking experiments demonstrated that the adhesion was mediated by the receptor for AGE (RAGE). Adrenaline-treated RBCs showed a transient increase in adhesion at low shear stresses. Inflammatory mediators or catecholamine amplifying diabetic RBC adhesion may aggravate endothelial cell damages.

Changes in glycation and oxidation markers in patients starting peritoneal dialysis: a pilot study.

BACKGROUND: The high incidence of cardiovascular disease in uremic patients makes it a major cause of morbidity and mortality in those patients. Uremia is associated with carbonyl and oxidative stress, which result in the enhanced formation of glycation and oxidation products respectively. In the present study, the blood levels of advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs) were investigated in uremic patients prior to and after initiation of peritoneal dialysis (PD). METHODS: 22 patients [11 nondiabetic (G1) and 11 diabetic (G2) subjects] were enrolled in a single-center prospective study. Prior to starting PD (TO) and 6 and 12 months later, changes in AGE and AOPP levels were analyzed in the total study population and in each group (Friedman test, intragroup). At each time point, a comparison was made between the levels of the above-mentioned products in G1 and G2 (Mann-Whitney test, intergroup). Correlations between AGE or AOPP levels and residual renal function, peritoneal creatinine clearance, glucose peritoneal equilibration test, or daily dextrose exposure were analyzed using the Pearson test. RESULTS: At TO, no significant difference was found between the two groups for AGE or AOPP levels. Initiation of PD was followed by an increase in AGE levels in all patients (p < 0.01 at 6 and 12 months). AGE Levels were higher in G2 than in G1 at 12 months after the start of PD (p < 0.05). In contrast to G2 results, initiation of PD in G1 led to reduced AOPP Levels (at 6 and 12 months, p = 0.01 and p < 0.05 respectively). However, no correlation between AGE or AOPP levels and residual renal function, peritoneal creatinine clearance, glucose peritoneal equilibration test, or daily dextrose exposure could be established. CONCLUSION: This study demonstrates that PD is associated with an increase in levels of blood glycation end products, particularly in diabetic patients, but also with a decrease in oxidative products such as AOPPs, especially in nondiabetic subjects.

Protein kinase A-dependent phosphorylation of Lutheran/basal cell adhesion molecule glycoprotein regulates cell adhesion to laminin alpha5.

Lutheran (Lu) blood group and basal cell adhesion molecule (B-CAM) antigens reside on two glycoprotein (gp) isoforms Lu and Lu(v13) that belong to the Ig superfamily and differ only by the size of their cytoplasmic tail. Lu/B-CAM gps have been recognized as laminin alpha5 receptors on red blood cells and epithelial cells in multiple tissues. It has been shown that sickle red cells exhibit enhanced adhesion to laminin alpha5 when intracellular cAMP is up-regulated by physiological stimuli such as epinephrine and that this signaling pathway is protein kinase A- and Lu/B-CAM-dependent. In this study, we analyzed the relationship between the phosphorylation status of Lu/B-CAM gps and their adhesion function to laminin alpha5. We showed that Lu isoform was phosphorylated in sickle red cells as well as in erythroleukemic K562 and epithelial Madin-Darby canine kidney cells and that this phosphorylation is enhanced by different stimuli of the PKA pathway. Lu gp is phosphorylated by glycogen synthase kinase 3 beta, casein kinase II, and PKA at serines 596, 598, and 621, respectively. Alanine substitutions of serines 596 and 598 abolished phosphorylation by glycogen synthase kinase 3 beta and casein kinase II, respectively, but had no effect on adhesion of K562 cells to laminin under flow conditions. Conversely, mutation of serine 621 prevented phosphorylation by PKA and dramatically reduced cell adhesion. Furthermore, stimulation of K562 cells by epinephrine increased Lu gp phosphorylation by PKA and enhanced adhesion to laminin. It is postulated that modulation of the phosphorylation state of Lu gp might be a critical factor for the sickle red cells adhesiveness to laminin alpha5 in sickle cell disease.

[Biocompatibility of peritoneal dialysis fluids]. / La biocompatibilité des solutions de dialyse péritonéale.

Repeated and long-term exposure to conventional glucose-based peritoneal dialysis fluids (PDFs) with poor biocompatibility plays a central role in the pathogenesis of the functional and structural changes of the peritoneal membrane. We have used immortalized human peritoneal mesothelial cells in culture to assess in vitro the biocompatibility of PDFs. Low pH, high glucose concentration and heat sterilization represent major factors of low biocompatibility. Two recent groups of glucose derivatives have been described. Glucose degradation products (GDPs) are formed during heat sterilization (glycoxidation) and storage. GDPs can bind protein and form AGEs (Advanced Glycation End-products), which can also result from the binding of glucose to free NH2 residues of proteins (glycation). The physiological pH, and the separation of glucose during heat sterilization (low GDP content) in the most recent PDFs dramatically increase the biocompatibility. The choice of PD programs with high biocompatibility PDFs allows preserving the function of the peritoneal membrane. Improvement of PDF biocompatibility may limit the occurrence of chronic chemical peritonitis and may allow long-term PD treatment.