The monocyte chemoattractant protein-1 (MCP-1)/CCR2 system is involved in peritoneal dialysis-related epithelial-mesenchymal transition of peritoneal mesothelial cells

High Salt Promotes Inflammatory and Fibrotic Response in Peritoneal Cells

Recent studies draw attention to how excessive salt (NaCl) intake induces fibrotic alterations in the peritoneum through sodium accumulation and osmotic events. The aim of our study was to better understand the underlying mechanisms. The effects of additional NaCl were investigated on human primary mesothelial cells (HPMC), human primary peritoneal fibroblasts (HPF), endothelial cells (HUVEC), immune cells (PBMC), as well as ex vivo on peritoneal tissue samples. Our results showed that a high-salt environment and the consequently increased osmolarity increase the production of inflammatory cytokines, profibrotic growth factors, and components of the renin-angiotensin-aldosterone system, including IL1B, IL6, MCP1, TGFB1, PDGFB, CTGF, Renin and Ace both in vitro and ex vivo. We also demonstrated that high salt induces mesenchymal transition by decreasing the expression of epithelial marker CDH1 and increasing the expression of mesenchymal marker ACTA2 and SNAIL1 in HPMCs, HUVECs and peritoneal samples. Furthermore, high salt increased extracellular matrix production in HPFs. We demonstrated that excess Na+ and the consequently increased osmolarity induce a comprehensive profibrotic response in the peritoneal cells, thereby facilitating the development of peritoneal fibrosis.

The antioxidative effects of empagliflozin on high glucose‑induced epithelial-mesenchymal transition in peritoneal mesothelial cells via the Nrf2/HO-1 signaling

High glucose (HG)-induced epithelial-mesenchymal transition (EMT) and oxidative stress play an important role in peritoneal fibrosis, which could be regulated by the nuclear factor erythroid-2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway. This study aimed to investigate whether empagliflozin could inhibit HG-induced EMT and oxidative stress via activating the Nrf2/HO-1 signaling pathway. We used HG-based peritoneal dialysis (PD) solution in rats and HG in human peritoneal mesothelial cells (HPMCs) to induce EMT in vivo and in vitro respectively. The peritoneal structure and function were evaluated by hematoxylin and eosin, Masson's trichrome staining, and the peritoneal equilibrium test. Oxidative stress was measured by assay kits. EMT was analyzed using immunohistochemistry and western blot. The PD rats showed decreased ultrafiltration capacity and increased levels of oxidative stress. Histopathological analysis revealed markedly peritoneal thickening, excessive collagen deposition, increased expression of α-SMA, Collagen-I, and Fibronectin, and decreased expression of E‑cadherin. Empagliflozin significantly ameliorated the aforementioned changes. The protein expression levels of nuclear Nrf2 (N-Nrf2) and HO-1 increased in PD rats, which were further promoted by treatment with empagliflozin. In in vitro experiments, the EMT of HPMCs was induced with 60 mM glucose for 24 h and inhibited by empagliflozin. Empagliflozin suppressed oxidative stress and promoted the protein expression of N-Nrf2 and HO-1 in HG‑stimulated HPMCs, which was reversed by the Nrf2 inhibitor. In conclusion, empagliflozin exerted a protective effect against HG-induced EMT and suppressed oxidative stress in PMCs by activating the Nrf2/HO-1 signaling pathway.

Mitochonic acid-5 ameliorates chlorhexidine gluconate-induced peritoneal fibrosis in mice

Peritoneal fibrosis is a serious complication of long-term peritoneal dialysis, attributable to inflammation and mitochondrial dysfunction. Mitochonic acid-5 (MA-5), an indole-3-acetic acid derivative, improves mitochondrial dysfunction and has therapeutic potential against various diseases including kidney diseases. However, whether MA-5 is effective against peritoneal fibrosis remains unclear. Therefore, we investigated the effect of MA-5 using a peritoneal fibrosis mouse model. Peritoneal fibrosis was induced in C57BL/6 mice via intraperitoneal injection of chlorhexidine gluconate (CG) every other day for 3 weeks. MA-5 was administered daily by oral gavage. The mice were divided into control, MA-5, CG, and CG + MA-5 groups. Following treatment, immunohistochemical analyses were performed. Fibrotic thickening of the parietal peritoneum induced by CG was substantially attenuated by MA-5. The number of α-smooth muscle actin-positive myofibroblasts, transforming growth factor β-positive cells, F4/80-positive macrophages, monocyte chemotactic protein 1-positive cells, and 4-hydroxy-2-nonenal-positive cells was considerably decreased. In addition, reduced ATP5a1-positive and uncoupling protein 2-positive cells in the CG group were notably increased by MA-5. MA-5 may ameliorate peritoneal fibrosis by suppressing macrophage infiltration and oxidative stress, thus restoring mitochondrial function. Overall, MA-5 has therapeutic potential against peritoneal fibrosis.

Ongoing Exposure to Peritoneal Dialysis Fluid Alters Resident Peritoneal Macrophage Phenotype and Activation Propensity

Peritoneal dialysis (PD) is a more continuous alternative to haemodialysis, for patients with chronic kidney disease, with considerable initial benefits for survival, patient independence and healthcare costs. However, long-term PD is associated with significant pathology, negating the positive effects over haemodialysis. Importantly, peritonitis and activation of macrophages is closely associated with disease progression and treatment failure. However, recent advances in macrophage biology suggest opposite functions for macrophages of different cellular origins. While monocyte-derived macrophages promote disease progression in some models of fibrosis, tissue resident macrophages have rather been associated with protective roles. Thus, we aimed to identify the relative contribution of tissue resident macrophages to PD induced inflammation in mice. Unexpectedly, we found an incremental loss of homeostatic characteristics, anti-inflammatory and efferocytic functionality in peritoneal resident macrophages, accompanied by enhanced inflammatory responses to external stimuli. Moreover, presence of glucose degradation products within the dialysis fluid led to markedly enhanced inflammation and almost complete disappearance of tissue resident cells. Thus, alterations in tissue resident macrophages may render long-term PD patients sensitive to developing peritonitis and consequently fibrosis/sclerosis.

Role of MCP-1 and IL-8 in viral anterior uveitis, and contractility and fibrogenic activity of trabecular meshwork cells

The inflammatory chemokines, monocyte chemoattractant protein (MCP)-1 and IL-8, are produced by normal trabecular meshwork cells (TM) and elevated in the aqueous humor of primary open angle glaucoma (POAG) and hypertensive anterior uveitis associated with viral infection. However, their role in TM cells and aqueous humor outflow remains unclear. Here, we explored the possible involvement of MCP-1 and IL-8 in the physiology of TM cells in the context of aqueous outflow, and the viral anterior uveitis. We found that the stimulation of human TM cells with MCP-1 and IL-8 induced significant increase in the formation of actin stress fibers and focal adhesions, myosin light chain phosphorylation, and the contraction of TM cells. MCP-1 and IL-8 also demonstrated elevation of extracellular matrix proteins, and the migration of TM cells. When TM cells were infected with HSV-1 and CMV virus, there was a significant increase in cytoskeletal contraction and Rho-GTPase activation. Viral infection of TM cells revealed significantly increased expression of MCP-1 and IL-8. Taken together, these results indicate that MCP-1 and IL-8 induce TM cell contractibility, fibrogenic activity, and plasticity, which are presumed to increase resistance to aqueous outflow in viral anterior uveitis and POAG.

CA-125 and CCL2 may indicate inflammation in peritoneal dialysis patients

Introduction:

Progressive structural changes in the peritoneal membrane occur over the course of treatment in peritoneal dialysis (PD), resulting in an increase in cytokines such as CCL2 and structural changes in peritoneal membrane triggering an increase in CA-125 in dialysate, which reflects a probable local inflammatory process, with possible loss of mesothelial cells. Thus, the current study aimed to evaluate the association between plasma and CCL2 and CA-125 dialysate levels in patients undergoing PD.

Methods:

Cross-sectional study was conducted with 41 patients undergoing PD. The assessments of CA-125 and CCL2 levels were performed using a capture ELISA. Correlations were estimated using Spearman's correlation and the investigation of the association between the explanatory variables (CCL2) and response variable (CA-125) was done for crude ratio of arithmetic means and adjusted utilizing generalized linear models.

Results:

A moderate positive correlation was observed between the levels of CA-125 and CCL2 in the dialysate (rho = 0.696). A statistically significant association was found between the levels in the CCL2 and CA-125 dialysate (RoM=1.31; CI = 1.20-1.43), which remained after adjustment for age (RoM = 1.31; CI=1.19-1.44) and for time in months of PD (RoM=1.34, CI=1.22-1.48).

Conclusion:

The association of CA-125 levels with CCL2 in the dialysate may indicate that the local inflammatory process leads to temporary or definitive changes in peritoneal membrane. A better understanding of this pathogenesis could contribute to the discovery of new inflammatory biomarkers.

Effect of aquaporin 1 on mouse peritoneal mesothelial cells after a long-term peritoneal dialysis

Aquaporin 1 (AQP1) is one member of the aquaporin family, also the deeply studied one. It is widely located on the endothelial cells, but the effect of AQP1 on the peritoneal mesothelial cells (PMCs) after long-term peritoneal dialysis (PD) has not been reported before. We divided normal mice into two groups, control group and dialysis group, to confirm the fibrotic changes and expression of APQ1 on peritoneal mesothelial cells. Then we assigned normal mice and AQP1 knockout mice into four groups: Control group, normal dialysis group, AQP1 knockout control group and AQP1 knockout dialysis group. The two dialysis groups received 4.25% glucose dialysis for 28 days. We found that mice in both dialysis groups showed peritoneal fibrotic changes, which were most severe in the AQP1 knockout dialysis group; the peritoneal thickness in the AQP1 knockout dialysis group was also thicker than that in the dialysis group (P < .05). We used electron microscopy to detect ultrastructural changes and observed changes in microvilli and vacuolar degeneration in mesothelial cells from all groups except the control group. The basement membranes were damaged in the AQP1 knockout dialysis group, and peritoneal mesothelial cells were disrupted and detached in this group. Together our findings indicate that AQP1 plays an important role in maintaining the physiological functions of peritoneal mesothelial cells, and AQP1 can protect mesothelial cells during dialysis.

Is the C-C Motif Ligand 2-C-C Chemokine Receptor 2 Axis a Promising Target for Cancer Therapy and Diagnosis?

C-C motif ligand 2 (CCL2) was originally reported as a chemical mediator attracting mononuclear cells to inflammatory tissue. Many studies have reported that CCL2 can directly activate cancer cells through a variety of mechanisms. CCL2 can also promote cancer progression indirectly through increasing the recruitment of tumor-associated macrophages into the tumor microenvironment. The role of CCL2 in cancer progression has gradually been understood, and various preclinical cancer models elucidate that CCL2 and its receptor C-C chemokine receptor 2 (CCR2) are attractive targets for intervention in cancer development. However, clinically available drugs that regulate the CCL2-CCR2 axis as anticancer agents are not available at this time. The complete elucidation of not only the oncological but also the physiological functions of the CCL2-CCR2 axis is required for achieving a satisfactory effect of the CCL2-CCR2 axis-targeted therapy.

Loosening of the mesothelial barrier as an early therapeutic target to preserve peritoneal function in peritoneal dialysis

Phenotype transition of peritoneal mesothelial cells (MCs) including the epithelial-to-mesenchymal transition (EMT) is regarded as an early mechanism of peritoneal dysfunction and fibrosis in peritoneal dialysis (PD), producing proinflammatory and pro-fibrotic milieu in the intra-peritoneal cavity. Loosening of intercellular tight adhesion between adjacent MCs as an initial process of EMT creates the environment where mesothelium and submesothelial tissue are more vulnerable to the composition of bio-incompatible dialysates, reactive oxygen species, and inflammatory cytokines. In addition, down-regulation of epithelial cell markers such as E-cadherin facilitates de novo acquisition of mesenchymal phenotypes in MCs and production of extracellular matrices. Major mechanisms underlying the EMT of MCs include induction of oxidative stress, pro-inflammatory cytokines, endoplasmic reticulum stress and activation of the local renin-angiotensin system. Another mechanism of peritoneal EMT is mitigation of intrinsic defense mechanisms such as the peritoneal antioxidant system and anti-fibrotic peptide production in the peritoneal cavity. In addition to use of less bio-incompatible dialysates and optimum treatment of peritonitis in PD, therapies to prevent or alleviate peritoneal EMT have demonstrated a favorable effect on peritoneal function and structure, suggesting that EMT can be an early interventional target to preserve peritoneal integrity.

Protein kinase C beta deficiency increases glucose-mediated peritoneal damage via M1 macrophage polarization and up-regulation of mesothelial protein kinase C alpha

BACKGROUND

Peritoneal membrane (PM) damage during peritoneal dialysis (PD) is mediated largely by high glucose (HG)-induced pro-inflammatory and neo-angiogenic processes, resulting in PM fibrosis and ultrafiltration failure. We recently demonstrated a crucial role for protein kinase C (PKC) isoform α in mesothelial cells.

METHODS

In this study we investigate the role of PKCβ in PM damage in vitro using primary mouse peritoneal macrophages (MPMΦ), human macrophages (HMΦ) and immortalized mouse peritoneal mesothelial cells (MPMCs), as well as in vivo using a chronic PD mouse model.

RESULTS

We demonstrate that PKCβ is the predominant classical PKC isoform expressed in primary MPMΦ and its expression is up-regulated in vitro under HG conditions. After in vitro lipopolysaccharides stimulation PKCβ-/- MPMΦ demonstrates increased levels of interleukin 6 (IL-6), tumour necrosis factor α, and monocyte chemoattractant protein-1 and drastically decrease IL-10 release compared with wild-type (WT) cells. In vivo, catheter-delivered treatment with HG PD fluid for 5 weeks induces PKCβ up-regulation in omentum of WT mice and results in inflammatory response and PM damage characterized by fibrosis and neo-angiogenesis. In comparison to WT mice, all pathological changes are strongly aggravated in PKCβ-/- animals. Underlying molecular mechanisms involve a pro-inflammatory M1 polarization shift of MPMΦ and up-regulation of PKCα in MPMCs of PKCβ-/- mice. Finally, we demonstrate PKCβ involvement in HG-induced polarization processes in HMΦ.

CONCLUSIONS

PKCβ as the dominant PKC isoform in MPMΦ is up-regulated by HG PD fluid and exerts anti-inflammatory effects during PD through regulation of MPMΦ M1/M2 polarization and control of the dominant mesothelial PKC isoform α.

Dyslipidemia and Intraperitoneal Inflammation Axis in Peritoneal Dialysis Patients: A Cross-Sectional Pilot Study

Background

We have hypothesized that the problem of dyslipidemia in peritoneal dialysis (PD) patients lies beyond certain levels of plasma lipoprotein and involves cardiovascular risk, but can also influence the development of chronic intraperitoneal inflammation.

Objectives

The aim of our work was to define whether the association of dyslipidemia with intraperitoneal inflammation really exists and if it could it be used in a prospective cohort of PD patients.

Patients and Methods

We performed a cross-sectional, single-center, pilot study involving 40 nondiabetic PD patients (27 men and 13 women with an average age of 49.3 ± 12.2 years). The median time on PD was 29 (18.5-37) months. The parameters dialysis adequacy, blood lipid profile, and the concentrations of tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, and interleukin (IL)-10 in peritoneal dialysate effluent (PDE) were determined. Cohen's d effect size was computed post hoc to determine the differences between groups in the concentrations of pro- and anti-inflammatory mediators.

Results

PD patients with atherogenic dyslipidemia had significantly high levels of MCP-1 compared with dyslipidemia-free patients (Cohen's d = 1.32). A reduced high-density lipoprotein cholesterol level was associated with a high intraperitoneal production of the proinflammatory mediator TNF-α (p < 0.0001) and anti-inflammatory IL-10 (p < 0.0001). Atherogenic index of plasma was directly correlated with MCP-1 (p < 0.0001) and TNF-α (p < 0.0001). In multiple regression analysis, MCP-1 appeared to predict PD inadequacy (R ² = 0.58; F ratio = 9.4; p = 0.006) independently of age and blood C-reactive protein level. Effect size was 1.38 with α = 0.05, n = 40, and 3 predictors.

Conclusions

Our cross-sectional pilot study first demonstrated a close interaction between the atherogenic lipid profile and a high concentration of MCP-1 in PDE; this might be a prognostic marker for PD inadequacy. The potential significance of our finding is that it provides useful preliminary information necessary for further research into this area.

Ligustrazine nanoparticles nano spray's activation on Nrf2/ARE pathway in oxidative stress injury in rats with postoperative abdominal adhesion

Background

Postoperative abdominal adhesions formation is considered a significant clinical entity implicating the healing process following major pelvic and abdominal surgery, with serious clinical complications and need for substantial health care expenditures. However, setting a physical barrier between the damage site and the neighboring tissues is a convenient and highly valid way to minimize or prevent peritoneal adhesions. The present experimental study evaluated the preventive effect of ligustrazine nanoparticles nano spray (LNNS) on postoperative abdominal adhesion in rats and explored its mechanism.

Methods

Sixty male Sprague Dawley (SD) rats were randomly divided into sham operation group, control group, sodium hyaluronate group and low, medium, and high dose LNNS groups. All groups were prepared with abdominal adhesion models except for the sham operation group. The models were made by opening the abdominal cavity to and filing the serosa in ileocecal junction. The abdominal cavity of rats in the sham operation group were only opened and sutured. The wound surface of rats in the sodium hyaluronate group, low, medium, and high dose LNNS groups were sprayed with sodium hyaluronate gel (0.5 mL/kg) and LNNS (2.5, 5, and 10 mL/kg). Rats in each group were sacrificed 7 days later. Degree of adhesion was evaluated by naked eyes and the pathological sections were scored afterwards. The collagen synthesis in adhesion tissues was detected by Masson's trichrome stain, and the activities of reactive oxygen species (ROS), nitric oxide (NO), superoxide dismutase (SOD) and malondialdehyde (MDA) in peritoneal fluid were detected with the method of chromogenic substrate. Levels of TNF-α and IL-1β in serum, and the protein levels of MCP-1 and MMP-9 in adhesion tissues were detected by ELISA and. immunohistochemistry respectively. RT-PCR and Western blot were utilized to identify the expression levels of Nrf2, heme-oxygenase-1, NQO1 mRNA and protein in adherent intestinal tissues.

Results

Compared with the control group, the incidence of postoperative abdominal adhesions decreased in the low, medium and high dose LNNS groups, while the expression of SOD in the peritoneal fluid significantly increased. The expression levels of ROS, MDA and NO were reduced remarkably (P<0.05), so were the expression levels of serum TNF-α and IL-1β (P<0.01) and the expression of MCP-1 protein in adhesion tissues. The MMP-9 protein expression, and Nrf2, heme-oxygenase-1, NQO1 mRNA and protein expressions increased.

Conclusions

LNNS with medium or high dose can significantly reduce the incidence of postoperative abdominal adhesions, the mechanism of which may be the activation of Nrf2/ARE pathway, resulting in the up-regulation of Nrf2, heme-oxygenase-1, NQO1 and mRNA expression, as well as the levels of TNF-α and IL-1β in peripheral blood and the expression of MCP-1 protein in adhesion tissues. Meanwhile, the content of MMP-9 protein in adhesion tissues were raised, and oxidative stress and inflammatory response are released.

Matrine suppresses lipopolysaccharide-induced fibrosis in human peritoneal mesothelial cells by inhibiting the epithelial-mesenchymal transition

Background:

Peritoneal fibrosis is the primary reason that patients with end-stage renal disease (ESRD) have to cease peritoneal dialysis. Peritonitis caused by Gram-negative bacteria such as Escherichia coli (E. coli) were on the rise. We had previously shown that matrine inhibited the formation of biofilm by E. coli. However, the role of matrine on the epithelial-mesenchymal transition (EMT) in peritoneal mesothelial cells under chronic inflammatory conditions is still unknown.

Methods:

We cultured human peritoneal mesothelial cells (HPMCs) with lipopolysaccharide (LPS) to induce an environment that mimicked peritonitis and investigated whether matrine could inhibit LPS-induced EMT in these cells. In addition, we investigated the change in expression levels of the miR-29b and miR-129-5p.

Results:

We found that 10 μg/ml of LPS induced EMT in HPMCs. Matrine inhibited LPS-induced EMT in HPMCs in a dose-dependent manner. We observed that treatment with matrine increased the expression of E-cadherin (F = 50.993, P < 0.01), and decreased the expression of alpha-smooth muscle actin (F = 32.913, P < 0.01). Furthermore, we found that LPS reduced the expression levels of miR-29b and miR-129-5P in HPMCs, while matrine promoted the expression levels of miR-29b and miR-129-5P.

Conclusions:

Matrine could inhibit LPS-induced EMT in HPMCs and reverse LPS inhibited expressions of miR-29 b and miR-129-5P in HPMCs, ultimately reduce peritoneal fibrosis. These findings provide a potential theoretical basis for using matrine in the prevention and treatment of peritoneal fibrosis.

MCP2 activates NF-κB signaling pathway promoting the migration and invasion of ESCC cells

MCP2, aliased CCL8, has been suggested to be implicated in the metastasis of cancer cells; however, no direct evidence has been established in esophageal squamous cell carcinoma (ESCC). In our present study, to investigate the role MCP2 played in the metastasis of ESCC cells; in vitro cell co-culture system was established. Wound-healing and Transwell assays were used to evaluate the migratory and invasive variation of ESCC cells before and after treatment with recombinant human MCP2. It was shown that MCP2 was able to activate the NF-κB signaling pathway inducing the epithelial-mesenchymal transition (EMT) and promoting the migration and invasion of ESCC cells in vitro. Our study provides an alternative working mechanism for M2 macrophage mediated the metastasis in tumor microenvironment in ESCC.

Chemokine (C‑C motif) ligand 21/C‑C chemokine receptor type 7 triggers migration and invasion of human lung cancer cells by epithelial‑mesenchymal transition via the extracellular signal‑regulated kinase signaling pathway

C-C chemokine receptor type 7 (CCR7) has been implicated in lymph node metastasis of various cancers. Previous studies have revealed that epithelial-mesenchymal transition (EMT) is involved in the chemotactic process mediated by CCR7 and its ligands in various types of carcinoma. However, the underlying mechanism of this process remains to be fully elucidated. The present study investigated whether chemokine (C-C motif) ligand 21 (CCL21)/CCR7 may activate EMT of lung cancer cells and their associated signaling pathways. A549 and H520 lung cancer cell lines were examined in vitro in the present study. The results indicated that A549 and H520 expressed CCR7, but reduced levels of CCL21. Following stimulation of lung cancer cell lines with CCL21, the expression of the epithelial marker E-cadherin was downregulated, and the mesenchymal markers Vimentin/Slug and extracellular signal-regulated kinase (ERK) were upregulated. In addition, the ERK inhibitor PD98059 may inhibit EMT caused by CCL21, and decreased cell migration and invasion initiated by CCL21. Furthermore, lung adenocarcinoma tissues from 50 patients who underwent lung cancer operations were investigated by immunohistochemistry. The findings revealed that CCR7, Slug and Vimentin were highly expressed in lung carcinoma tissues, and were significantly associated with lymph node metastasis and clinical pathological stages, respectively. CCR7 expression was correlated positively with expression levels of Slug and Vimentin. CCL21 was expressed positively in the endothelium of lymphatic vessels adjacent to cancer cells, and weakly in lung cancer cells. Collectively, these results demonstrated that CCL21/CCR7 may activate EMT in lung cancer cells via the ERK1/2 signaling pathway. The current study provides evidence that a close interaction exists between CCL21/CCR7chemotaxis and EMT procedures in lung cancer metastasis, providing a basis for the development of therapeutic targets.

CCL2 expression correlates with Snail expression and affects the prognosis of patients with gastric cancer

We aim to explore the associations of CCL2 and Snail in gastric cancer to the clinicopathologic features and prognosis of gastric cancer (GC). In our study, the expression of CCL2 and Snail in clinical specimens of 178 GC patients was detected by immunohistochemistry. High expression of CCL2 and Snail were closely related to the clinicopathologic features. The results showed there is a link between CCL2 and Snail expression at protein levels (Pearson Χ2=40.751, P<0.001). The Kaplan-Meier survival analysis showed that CCL2 or Snail expression was correlated with 5-year survival rate (P<0.001, P<0.001, respectively). Univariate analysis showed that CCL2, Snail, pTNM stage, depth of invasion, nodal involvement, metastasis and tumor diameter were significantly associated with 5-year survival rate respectively. Multivariate Cox analysis showed that the CCL2, Snail and nodal involvement were independent prognostic factor for patients with GC. In conclusion, the expression of CCL2 is significantly correlated with Snail expression and may be used as a predictive co-biomarker for patient prognosis and tumor aggressiveness in GC. The exactly mechanism between CCL2 and Snail in the process of EMT in GC need further investigation.

Recruited mast cells in the tumor microenvironment enhance bladder cancer metastasis via modulation of ERβ/CCL2/CCR2 EMT/MMP9 signals

Early clinical studies suggested that infiltrating mast cells could be associated with a poor outcome in bladder cancer (BCa) patients. The mechanisms of how mast cells influence the BCa progression, however, are unclear. Using the human clinical BCa sample survey and in vitro co-culture systems, we found BCa cells could recruit more mast cells than the surrounding non-malignant urothelial cells. The consequences of this better recruitment of mast cells toward BCa cells could then enhance BCa cell invasion. Mechanism dissection revealed that the enhanced BCa cell invasion could function via up-regulation of the estrogen receptor beta (ER&beta;) in both mast cells and BCa cells, which resulted in the increased CCL2/CCR2/EMT/MMP9 signals. Using the pre-clinical mouse BCa model, we further validated the mast cell-promoted BCa invasion. Interruption of the newly identified ER&beta;/CCL2/CCR2/EMT/MMP9 pathway via either ER&beta;-siRNA, ER&beta; antagonist PHTPP, or CCR2 antagonist can effectively reverse the mast cell-enhanced BCa cells invasion. Together, our finding could lead to the development of an alternative new therapeutic approach to better treat BCa metastasis.

MCP-1-induced ERK/GSK-3β/Snail signaling facilitates the epithelial-mesenchymal transition and promotes the migration of MCF-7 human breast carcinoma cells

Monocyte chemoattractant protein-1 (MCP-1) is a chemotactic cytokine that can bind to its receptor cysteine-cysteine chemokine receptor 2 (CCR2) and plays an important role in breast cancer cell metastasis. However, the molecular mechanisms underlying MCP-1-induced alterations in cellular functions during tumor progression are poorly understood. Here, we showed that MCP-1 stimulated the epithelial-mesenchymal transition (EMT) and induced the tumorigenesis of breast cancer cells by downregulating E-cadherin, upregulating vimentin and fibronectin, activating matrix metallopeptidase-2 (MMP-2), and promoting migration and invasion. Moreover, MCP-1 treatment reduced glycogen synthase kinase-3β (GSK-3β) activity via the MEK/ERK-mediated phosphorylation of serine-9 in MCF-7 cells. The inhibition of MEK/ERK by U0126 attenuated the MCP-1-induced phosphorylation of GSK-3β and decreased the expression of Snail, an EMT-related transcription factor, leading to the inhibition of MCF-7 cell migration and invasion. Inactivation of GSK-3β by LiCl (lithium chloride) treatment notably increased MMP-2 activity, vascular endothelial growth factor expression and EMT of MCF-7 cells. These findings revealed that MCP-1-induced EMT and migration are mediated by the ERK/GSK-3β/Snail pathway, and identified a potential novel target for therapeutic intervention in breast cancer.

Molecular Mechanisms Underlying Peritoneal EMT and Fibrosis

Peritoneal dialysis is a form of renal replacement alternative to the hemodialysis. During this treatment, the peritoneal membrane acts as a permeable barrier for exchange of solutes and water. Continual exposure to dialysis solutions, as well as episodes of peritonitis and hemoperitoneum, can cause acute/chronic inflammation and injury to the peritoneal membrane, which undergoes progressive fibrosis, angiogenesis, and vasculopathy, eventually leading to discontinuation of the peritoneal dialysis. Among the different events controlling this pathological process, epithelial to mesenchymal transition of mesothelial cells plays a main role in the induction of fibrosis and in subsequent functional deterioration of the peritoneal membrane. Here, the main extracellular inducers and cellular players are described. Moreover, signaling pathways acting during this process are elucidated, with emphasis on signals delivered by TGF-β family members and by Toll-like/IL-1β receptors. The understanding of molecular mechanisms underlying fibrosis of the peritoneal membrane has both a basic and a translational relevance, since it may be useful for setup of therapies aimed at counteracting the deterioration as well as restoring the homeostasis of the peritoneal membrane.

Transition of mesothelial cell to fibroblast in peritoneal dialysis: EMT, stem cell or bystander?

Long-term peritoneal dialysis (PD) can lead to fibrotic changes in the peritoneum, characterized by loss of mesothelial cells (MCs) and thickening of the submesothelial area with an accumulation of collagen and myofibroblasts. The origin of myofibroblasts is a central question in peritoneal fibrosis that remains unanswered at present. Numerous clinical and experimental studies have suggested that MCs, through epithelial-mesenchymal transition (EMT), contribute to the pool of peritoneal myofibroblasts. However, recent work has placed significant doubts on the paradigm of EMT in organ fibrogenesis (in the kidney particularly), highlighting the need to reconsider the role of EMT in the generation of myofibroblasts in peritoneal fibrosis. In particular, selective cell isolation and lineage-tracing experiments have suggested the existence of progenitor cells in the peritoneum, which are able to switch to fibroblast-like cells when stimulated by the local environment. These findings highlight the plastic nature of MCs and its contribution to peritoneal fibrogenesis. In this review, we summarize the key findings and caveats of EMT in organ fibrogenesis, with a focus on PD-related peritoneal fibrosis, and discuss the potential of peritoneal MCs as a source of myofibroblasts.

Mesothelial cells in tissue repair and fibrosis

Mesothelial cells are fundamental to the maintenance of serosal integrity and homeostasis and play a critical role in normal serosal repair following injury. However, when normal repair mechanisms breakdown, mesothelial cells take on a profibrotic role, secreting inflammatory, and profibrotic mediators, differentiating and migrating into the injured tissues where they contribute to fibrogenesis. The development of new molecular and cell tracking techniques has made it possible to examine the origin of fibrotic cells within damaged tissues and to elucidate the roles they play in inflammation and fibrosis. In addition to secreting proinflammatory mediators and contributing to both coagulation and fibrinolysis, mesothelial cells undergo mesothelial-to-mesenchymal transition, a process analogous to epithelial-to-mesenchymal transition, and become fibrogenic cells. Fibrogenic mesothelial cells have now been identified in tissues where they have not previously been thought to occur, such as within the parenchyma of the fibrotic lung. These findings show a direct role for mesothelial cells in fibrogenesis and open therapeutic strategies to prevent or reverse the fibrotic process.

Twist contributes to proliferation and epithelial-to-mesenchymal transition-induced fibrosis by regulating YB-1 in human peritoneal mesothelial cells

Twist is overexpressed in high glucose (HG) damage of human peritoneal mesothelial cells (HPMCs) in vitro. Herein, we further identified its precise function related to fibrosis of peritoneal membranes (PMs). The overexpression and activation of Twist and YB-1 (official name, YBX1) and a transformed fibroblastic phenotype of HPMCs were found to be positively related to epithelial-mesenchymal transition progress and PM fibrosis ex vivo in 93 patients who underwent continuous ambulatory peritoneal dialysis (PD), and also in HG-induced immortal HPMCs and an animal model of PD. Evidence from chromatin immunoprecipitation and luciferase reporter assays supported that YBX1 is transcriptionally regulated by the direct binding of Twist to E-box. Overexpression of Twist and YB-1 led to an increase in epithelial-mesenchymal transition, proliferation, and cell cycle progress of HPMCs, which might contribute to PM fibrosis. In contrast, the silencing of Twist or YB-1 inhibited HG-induced growth and cell cycle progression of HPMCs; this led to a down-regulation in the expression of cyclin Ds and cyclin-dependent kinases, finally inhibiting PM fibrosis. Twist contributes to PM fibrosis during PD treatment, mainly through regulation of YB-1.

Activation of nuclear factor of activated T cells 5 in the peritoneal membrane of uremic patients

Peritoneal inflammation and fibrosis are responses to the uremic milieu and exposure to hyperosmolar dialysis fluids in patients on peritoneal dialysis. Cells respond to high osmolarity via the transcription factor nuclear factor of activated T cells (NFAT5). In the present study, the response of human peritoneal fibroblasts to glucose was analyzed in vitro. Expression levels of NFAT5 and chemokine (C-C motif) ligand (CCL2) mRNA were quantified in peritoneal biopsies of five nonuremic control patients, five uremic patients before PD (pPD), and eight patients on PD (oPD) using real-time PCR. Biopsies from 5 control patients, 25 pPD patients, and 25 oPD patients were investigated using immunohistochemistry to detect the expression of NFAT5, CCL2, NF-κB p50, NF-κB p65, and CD68. High glucose concentrations led to an early, dose-dependent induction of NFAT5 mRNA in human peritoneal fibroblasts. CCL2 mRNA expression was upregulated by high concentrations of glucose after 6 h, but, most notably, a concentration-dependent induction of CCL2 was present after 96 h. In human peritoneal biopsies, NFAT5 mRNA levels were increased in uremic patients compared with nonuremic control patients. No significant difference was found between the pPD group and oPD group. CCL2 mRNA expression was higher in the oPD group. Immunohistochemistry analysis was consistent with the results of mRNA analysis. CD68-positive cells were significantly increased in the oPD group. In conclusion, uremia results in NFAT5 induction, which might promote early changes of the peritoneum. Upregulation of NFAT5 in PD patients is associated with NFκB induction, potentially resulting in the recruitment of macrophages.

Associations between the duration of dialysis, endotoxemia, monocyte chemoattractant protein-1, and the effects of a short-dwell exchange in patients requiring continuous ambulatory peritoneal dialysis

Background

Endotoxemia is exaggerated and contributes to systemic inflammation and atherosclerosis in patients requiring continuous ambulatory peritoneal dialysis (CAPD). The risk of mortality is substantially increased in patients requiring CAPD for >2 years. However, little is known about the effects of long-term CAPD on circulating endotoxin and cytokine levels. Therefore, the present study evaluated the associations between plasma endotoxin levels, cytokine levels, and clinical parameters with the effects of a short-dwell exchange on endotoxemia and cytokine levels in patients on long-term CAPD.

Methods

A total of 26 patients were enrolled and divided into two groups (short-term or long-term CAPD) according to the 2-year duration of CAPD. Plasma endotoxin and cytokine levels were measured before and after a short-dwell exchange (4-h dwell) during a peritoneal equilibration test (a standardized method to evaluate the solute transport function of peritoneal membrane). These data were analyzed to determine the relationship of circulating endotoxemia, cytokines and clinical characteristics between the two groups.

Results

Plasma endotoxin and monocyte chemotactic protein-1 (MCP-1) levels were significantly elevated in the long-term group. PD duration was significantly correlated with plasma endotoxin (r = 0.479, P = 0.016) and MCP-1 (r = 0.486, P = 0.012). PD duration was also independently associated with plasma MCP-1 levels in multivariate regression. Plasma MCP-1 levels tended to decrease (13.3% reduction, P = 0.077) though endotoxin levels did not decrease in the long-term PD group after the 4-h short-dwell exchange.

Conclusion

Long-term PD may result in exaggerated endotoxemia and elevated plasma MCP-1 levels. The duration of PD was significantly correlated with circulating endotoxin and MCP-1 levels, and was an independent predictor of plasma MCP-1 levels. Short-dwell exchange seemed to have favorable effects on circulating MCP-1 levels in patients on long-term PD.

The effect of statin on epithelial-mesenchymal transition in peritoneal mesothelial cells

Background

Statins have recently been highlighted for their pleiotropic actions distinct from cholesterol-lowering effects. Despite this interest, it is currently unknown whether statin therapy inhibits peritoneal dialysis (PD)-related epithelial-mesenchymal transition (EMT).

Methods

In vitro, human peritoneal mesothelial cells (HPMCs) were exposed to 5.6 mM glucose (NG) or 100 mM glucose (HG) with or without simvastatin (1 µM). In vivo, PD catheters were inserted into 32 Sprague-Dawley rats, and saline (C, n = 16) or 4.25% peritoneal dialysis fluid (PDF) (PD, n = 16) was infused for 4 weeks. Eight rats from each group were treated with 5 mg/kg/day of simvastatin intraperitoneally. Changes in the protein expression of EMT markers such as E-cadherin, α-SMA, Snail, and fibronectin in HPMCs and the peritoneum were evaluated by Western blot analysis and immunofluorescence or immunohistochemical staining. We also explored whether activation of the mevalonate pathway and its downstream small GTPases were involved in dialysis-related peritoneal EMT and could be inhibited by statin treatment.

Results

Compared to NG cells, E-cadherin expression was significantly decreased, while α-SMA, Snail, and fibronectin expression were significantly increased in HPMCs exposed to HG, and these changes were abrogated by simvastatin (p<0.05). In addition, the cobblestone-like appearance of normal HPMCs was converted into a fibroblast-like morphology after HG treatment, which was reversed by simvastatin. These EMT-like changes were also observed in HPMCs treated with geranyl-geranyl pyrophosphate (5 µM). HG significantly increased the protein expression of RhoA and Rac1 in the membrane fractions, and these increases were ameliorated by simvastatin (p<0.05). In PD rats, E-cadherin in the peritoneum was significantly decreased, whereas α-SMA, Snail, and fibronectin expression were significantly increased (p<0.05) compared to C rats. The thickness of the mesothelial layer in the peritoneum were also significantly greater in PD rats than in C rats (p<0.05). These changes of the peritoneum in PD rats were significantly attenuated by simvastatin.

Conclusion

This study demonstrated that PD-related EMT was mediated via the mevalonate pathway, and statin treatment inhibited the EMT changes in HG-treated HPMCs and PDF-stimulated PD rats. These findings suggest that statins may be a promising therapeutic strategy for preservation of peritoneal membrane integrity in long-term PD patients.

Astragalus membranaceus inhibits peritoneal fibrosis via monocyte chemoattractant protein (MCP)-1 and the transforming growth factor-β1 (TGF-β1) pathway in rats submitted to peritoneal dialysis

Inflammation and transforming growth factor-β1 (TGF-β1) contribute to the development of peritoneal fibrosis (PF), which is associated with peritoneal dialysis (PD). Astragalus membranaceus (Astragalus) has anti-inflammatory and anti-fibrotic effects in many diseases. The goal of this study was to determine the anti-fibrotic effects of Astragalus on the PF response to PD. A rat model of PD was induced using standard PD fluid, and PF was verified by HE and Masson’s staining, as well as through the expression of fibroblast surface protein (FSP) and collagen III. The expression levels of monocyte chemoattractant protein (MCP)-1, F4/80 (macrophage/monocyte marker in rat), TGF-β1 and the downstream proteins phospho-SMAD 2/3 in dialyzed peritoneal tissue treated with or without Astragalus was evaluated using immunohistochemistry analysis. Overall correlations between MCP-1 and TGF-β1 staining were analyzed using both the Spearman and Pearson methods. The results showed that Astragalus could inhibit the recruitment and activation of monocytes/macrophages, thereby reducing the production of TGF-β1 in the dialyzed peritoneal membrane. PF was also significantly decreased following treatment with Astragalus. MCP-1 expression had a strong positive correlation with TGF-β1 sensitivity, suggesting that the anti-fibrotic function of Astragalus was mediated by MCP-1 and the TGF-β1 pathway. Our results indicate that Astragalus could be a useful agent against PD-induced PF.

Histone deacetylase-3 mediates positive feedback relationship between anaphylaxis and tumor metastasis

Allergic inflammation has been known to enhance the metastatic potential of tumor cells. The role of histone deacetylase-3 (HDAC3) in allergic skin inflammation was reported. We investigated HDAC3 involvement in the allergic inflammation-promotion of metastatic potential of tumor cells. Passive systemic anaphylaxis (PSA) induced HDAC3 expression and FcεRI signaling in BALB/c mice. PSA enhanced the tumorigenic and metastatic potential of mouse melanoma cells in HDAC3- and monocyte chemoattractant protein 1-(MCP1)-dependent manner. The PSA-mediated enhancement of metastatic potential involved the induction of HDAC3, MCP1, and CD11b (a macrophage marker) expression in the lung tumor tissues. We examined an interaction between anaphylaxis and tumor growth and metastasis at the molecular level. Conditioned medium from antigen-stimulated bone marrow-derived mouse mast cell cultures induced the expression of HDAC3, MCP1, and CCR2, a receptor for MCP1, in B16F1 mouse melanoma cells and enhanced migration and invasion potential of B16F1 cells. The conditioned medium from B16F10 cultures induced the activation of FcεRI signaling in lung mast cells in an HDAC3-dependent manner. FcεRI signaling was observed in lung tumors derived from B16F10 cells. Target scan analysis predicted HDAC3 to be as a target of miR-384, and miR-384 and HDAC3 were found to form a feedback regulatory loop. miR-384, which is decreased by PSA, negatively regulated HDAC3 expression, allergic inflammation, and the positive feedback regulatory loop between anaphylaxis and tumor metastasis. We show the miR-384/HDAC3 feedback loop to be a novel regulator of the positive feedback relationship between anaphylaxis and tumor metastasis.

Monocyte chemoattractant protein-1 and the blood-brain barrier

The blood-brain barrier (BBB) is a dynamic structure that maintains the homeostasis of the brain and thus proper neurological functions. BBB compromise has been found in many pathological conditions, including neuroinflammation. Monocyte chemoattractant protein-1 (MCP1), a chemokine that is transiently and significantly up-regulated during inflammation, is able to disrupt the integrity of BBB and modulate the progression of various diseases, including excitotoxic injury and hemorrhage. In this review, we first introduce the biochemistry and biology of MCP1, and then summarize the effects of MCP1 on BBB integrity as well as individual BBB components.