Integrins mediate adherence and migration of T lymphocytes on human peritoneal mesothelial cells

Molecular and Cellular Markers in Chlorhexidine-Induced Peritoneal Fibrosis in Mice

Understanding the tissue changes and molecular mechanisms of preclinical models is essential for creating an optimal experimental design for credible translation into clinics. In our study, a chlorhexidine (CHX)-induced mouse model of peritoneal fibrosis was used to analyze histological and molecular/cellular alterations induced by 1 and 3 weeks of intraperitoneal CHX application. CHX treatment for 1 week already caused injury, degradation, and loss of mesothelial cells, resulting in local inflammation, with the most severe structural changes occurring in the peritoneum around the ventral parts of the abdominal wall. The local inflammatory response in the abdominal wall showed no prominent differences between 1 and 3 weeks. We observed an increase in polymorphonuclear cells in the blood but no evidence of systemic inflammation as measured by serum levels of serum amyloid A and interleukin-6. CHX-induced fibrosis in the abdominal wall was more pronounced after 3 weeks, but the gene expression of fibrotic markers did not change over time. Complement system molecules were strongly expressed in the abdominal wall of CHX-treated mice. To conclude, both histological and molecular changes were already present in week 1, allowing examination at the onset of fibrosis. This is crucial information for refining further experiments and limiting the amount of unnecessary animal suffering.

A review of physiological and cellular mechanisms underlying fibrotic postoperative adhesion

Postoperative adhesions (PA) are fibrotic tissues that are the most common driver of long-term morbidity after abdominal and pelvic surgery. The optimal drug or material to prevent adhesion formation has not yet been discovered. Comprehensive understanding of cellular and molecular mechanisms of adhesion process stimulates the design of future anti-adhesive strategies. Recently, disruption of peritoneal mesothelial cells were suggested as the 'motor' of PA formation, followed by a cascade of events (coagulation, inflammation, fibrinolysis) and influx of various immune cells, ultimately leading to a fibrous exudate. We showed that a variety of immune cells were recruited into adhesive peritoneal tissues in patients with small bowel obstruction caused by PA. The interactions among various types of immune cells contribute to PA development following peritoneal trauma. Our review focuses on the specific role of different immune cells in cellular and humoral mechanisms underpinning adhesion development.

Transcriptome analysis of signaling pathways of human peritoneal mesothelial cells in response to different osmotic agents in a peritoneal dialysis solution

Background

Glucose is a primary osmotic agent in peritoneal dialysis (PD) solutions, but its long-term use causes structural alteration of the peritoneal membrane (PM). Hyperbranched polyglycerol (HPG) is a promising alternative to glucose. This study was designed to compare the cellular responses of human peritoneal mesothelial cells (HPMCs) to these two different osmotic agents in a hypertonic solution using transcriptome analysis.

Methods

Cultured HPMCs were repeatedly exposed to HPG-based or Physioneal 40 (PYS, glucose 2.27%) hypertonic solutions. Transcriptome datasets were produced using Agilent SurePrint G3 Human GE 8 × 60 microarray. Cellular signaling pathways were examined by Ingenuity Pathway Analysis (IPA). Protein expression was examined by flow cytometry analysis and Western blotting.

Results

The HPG-containing solution was better tolerated compared with PYS, with less cell death and disruption of cell transcriptome. The levels of cell death in HPG- or PYS- exposed cells were positively correlated with the number of affected transcripts (HPG: 128 at day 3, 0 at day 7; PYS: 1799 at day 3, 212 at day 7). In addition to more affected “biosynthesis” and “cellular stress and death” pathways by PYS, both HPG and PYS commonly affected “sulfate biosynthesis”, “unfolded protein response”, “apoptosis signaling” and “NRF2-mediated oxidative stress response” pathways at day 3. PYS significantly up-regulated HLA-DMB and MMP12 in a time-dependent manner, and stimulated T cell adhesion to HPMCs.

Conclusion

The lower cytotoxicity of hypertonic HPG solution is in agreement with its transient and minimal impact on the pathways for the “biosynthesis of cell constituents” and the “cellular stress and death”. The significant up-regulation of HLA-DMB and MMP12 by PYS may be part of its initiation of immune response in the PM.

Mesothelial cells and peritoneal homeostasis

The mesothelium was traditionally thought to be a simple tissue with the sole function of providing a slippery, nonadhesive, and protective surface to allow easy movement of organs within their body cavities. However, our knowledge of mesothelial cell physiology is rapidly expanding, and the mesothelium is now recognized as a dynamic cellular membrane with many other important functions. When injured, mesothelial cells initiate a cascade of processes leading either to complete regeneration of the mesothelium or the development of pathologies such as adhesions. Normal mesothelial healing is unique in that, unlike with other epithelial-like surfaces, healing appears diffusely across the denuded surface, whereas for epithelium healing occurs solely at the wound edges. This is because of a free-floating population of mesothelial cells which attach to the injured serosa. Taking advantage of this phenomenon, intraperitoneal injections of mesothelial cells have been assessed for their ability to prevent adhesion formation. This review discusses some of the functions of mesothelial cells regarding maintenance of serosal integrity and outlines the mechanisms involved in mesothelial healing. In addition, the pathogenesis of adhesion formation is discussed with particular attention to the potential role of mesothelial cells in both preventing and inducing their development.

Activation of salt-inducible kinase 2 promotes the viability of peritoneal mesothelial cells exposed to stress of peritoneal dialysis

Maintaining mesothelial cell viability is critical to long-term successful peritoneal dialysis (PD) treatment. To clarify the viability mechanism of peritoneal mesothelial cells under PD solutions exposure, we examined the mechanisms of cellular response to this stress conditions. Here we report that the proteasome activity is inhibited when treated with PD solutions. Proteasome inhibition-mediated activation of salt-inducible kinase 2 (SIK2), an endoplasmic reticulum-resident protein, is important for mesothelial cell viability. SIK2 is mobilized to promote autophagy and protect the cells from apoptosis under PD solution or MG132 treatment. Immunofluorescence staining showed that SIK2 is colocalized with LC3B in the autophagosomes of mesothelial cells treated with PD solution or derived from patients undergoing PD treatment. SIK2 activation is likely via a two-step mechanism, upstream kinases relieving the autoinhibitory conformation of SIK2 molecule followed by autophosphorylation of Thr175 and activation of kinase activity. These results suggest that activation of SIK2 is required for the cell viability when proteasome activity is inhibited by PD solutions. Maintaining or boosting the activity of SIK2 may promote peritoneal mesothelial cell viability and evolve as a potential therapeutic target for maintaining or restoring peritoneal membrane integrity in PD therapy.

Role of β1 integrins and bacterial adhesins for Yop injection into leukocytes in Yersinia enterocolitica systemic mouse infection

Injection of Yersinia outer proteins (Yops) into host cells by a type III secretion system is an important immune evasion mechanism of Yersinia enterocolitica (Ye). In this process Ye invasin (Inv) binds directly while Yersinia adhesin A (YadA) binds indirectly via extracellular matrix (ECM) proteins to β1 integrins on host cells. Although leukocytes turned out to be an important target of Yop injection by Ye, it was unclear which Ye adhesins and which leukocyte receptors are required for Yop injection. To explain this, we investigated the role of YadA, Inv and β1 integrins for Yop injection into leukocytes and their impact on the course of systemic Ye infection in mice. Ex vivo infection experiments revealed that adhesion of Ye via Inv or YadA is sufficient to promote Yop injection into leukocytes as revealed by a β-lactamase reporter assay. Serum factors inhibit YadA- but not Inv-mediated Yop injection into B and T cells, shifting YadA-mediated Yop injection in the direction of neutrophils and other myeloid cells. Systemic Ye mouse infection experiments demonstrated that YadA is essential for Ye virulence and Yop injection into leukocytes, while Inv is dispensable for virulence and plays only a transient and minor role for Yop injection in the early phase of infection. Ye infection of mice with β1 integrin-depleted leukocytes demonstrated that β1 integrins are dispensable for YadA-mediated Yop injection into leukocytes, but contribute to Inv-mediated Yop injection. Despite reduced Yop injection into leukocytes, β1 integrin-deficient mice exhibited an increased susceptibility for Ye infection, suggesting an important role of β1 integrins in immune defense against Ye. This study demonstrates that Yop injection into leukocytes by Ye is largely mediated by YadA exploiting, as yet unknown, leukocyte receptors.

Hyperglycemia: GDNF-EGR1 pathway target renal epithelial cell migration and apoptosis in diabetic renal embryopathy

Maternal hyperglycemia can inhibit morphogenesis of ureteric bud branching, Glial cell line-derived neurotrophilic factor (GDNF) is a key regulator of the initiation of ureteric branching. Early growth response gene-1 (EGR-1) is an immediate early gene. Preliminary study found EGR-1 persistently expressed with GDNF in hyperglycemic environment. To evaluate the potential relationship of hyperglycemia-GDNF-EGR-1 pathway, in vitro human renal proximal tubular epithelial (HRPTE) cells as target and in vivo streptozotocin-induced mice model were used. Our in vivo microarray, real time-PCR and confocal morphological observation confirmed apoptosis in hyperglycemia-induced fetal nephropathy via activation of the GDNF/MAPK/EGR-1 pathway at E12-E15. Detachment between ureteric branch and metanephrons, coupled with decreasing number and collapse of nephrons on Day 1 newborn mice indicate hyperglycemic environment suppress ureteric bud to invade metanephric rudiment. In vitro evidence proved that high glucose suppressed HRPTE cell migration and enhanced GDNF-EGR-1 pathway, inducing HRPTE cell apoptosis. Knockdown of EGR-1 by siRNA negated hyperglycemic suppressed GDNF-induced HRPTE cells. EGR-1 siRNA also reduced GDNF/EGR-1-induced cRaf/MEK/ERK phosphorylation by 80%. Our findings reveal a novel mechanism of GDNF/MAPK/EGR-1 activation playing a critical role in HRPTE cell migration, apoptosis and fetal hyperglycemic nephropathy.

Functional defects of CD46-induced regulatory T cells to suppress airway inflammation in mite allergic asthma

Defective recruitment of regulatory T cells (Treg) function to the airway is important in the pathogenesis of allergic asthma. Complement regulatory protein (CD46) is a newly defined costimulatory molecule for Treg activation, which together with IL-10/granzyme B production may aid in suppressing asthmatic inflammation. This study examines chemotaxis and adhesion molecule expression on CD3/CD46-activated CD4(+) T cells (Tregs) from patients with and without asthma to suppress mite allergen-induced respiratory epithelial cells inflammation and to elucidate the mechanism of CD46-mediated Treg activation. Diminished IL-10/granzyme B and CCR4 expression from CD3/CD46-activated Tregs appeared in asthmatic subjects. CD3/CD46-activated Tregs from asthma patients co-cultured with BEAS-2B cells suppressed Dermatophagoides pteronyssinus 2 induced nuclear factor-κB/p65 by cell contact inhibition. Decreased interaction of CD3/CD46-mediated Tregs and BEAS-2B cells from asthmatics was associated with downregulated phosphorylation of protein kinase B (AKT) expression. Results provide the first evidence that decreased interaction between CD46-mediated Tregs and lung epithelial cells with less IL-10/granzyme B production may cause airway inflammation in allergic asthma.

Leptin increases motility and integrin up-regulation in human prostate cancer cells

Prostate cancer is the most commonly diagnosed malignancy in men and shows a predilection for metastasis to distant organs. Leptin, an adipocyte-derived cytokine that is closely associated with obesity, has recently been shown to be involved in carcinogenesis and cancer progression. The aim of this study was to investigate whether leptin is associated with the motility of prostate cancer cells. We found that leptin increased the migration of human prostate cancer cells and expression of αvβ3 integrin on these cells. Leptin-mediated migration and increased integrin expression were attenuated by OBRl receptor antisense oligonucleotide (ODN). Activation of insulin receptor substrate (IRS-1), phosphatidylinositol 3-kinase (PI3K), Akt, and NF-κB pathways after leptin treatment was demonstrated. Furthermore, leptin-induced integrin expression and migration activity were inhibited by specific inhibitors; small interfering RNAs (siRNAs); and mutants of the IRS-1, PI3K, Akt, and NF-κB cascades. Therefore, this study shows that leptin stimulates the migration of human prostate cancer cells, one of the mechanisms underlying leptin-directed migration was transcriptional up-regulation of αvβ3 integrin expression through the OBR1/IRS-1/PI3K/Akt/NF-κB signal transduction pathway.

CCR7 regulates lymphocyte egress and recirculation through body cavities

T and B lymphocytes recirculate among blood, lymph, and extralymphoid tissues to ensure immune surveillance and the establishment of self-tolerance. The underlying mechanisms regulating homeostatic lymphocyte recirculation through body cavities are not fully understood. Here, we demonstrate that the homeostatic chemokine receptor CCR7 regulates homeostatic recirculation of lymphocytes through body cavities. CCR7 deficiency results in massive accumulation of CD4(+) and CD8(+) T cells and B-2 B cells in the peritoneal and pleural cavities. The increase in B-2 B and T lymphocytes is not associated with an altered maturation and/or activation status of these cells. Mechanistically, an increase in peritoneal lymphocyte numbers is caused by impaired egress of CCR7-deficient lymphocytes from body cavities. These results establish that CCR7 plays a crucial role in lymphocyte exit from the PerC.

Human papillomavirus DNA detected in peripheral blood samples from healthy Australian male blood donors

Recent studies have shown that human papillomavirus (HPV) DNA can be found in circulating blood, including peripheral blood mononuclear cells (PBMCs), sera, plasma, and arterial cord blood. In light of these findings, DNA extracted from PBMCs from healthy blood donors were examined in order to determine how common HPV DNA is in blood of healthy individuals. Blood samples were collected from 180 healthy male blood donors (18-76 years old) through the Australian Red Cross Blood Services. Genomic DNA was extracted and specimens were tested for HPV DNA by PCR using a broad range primer pair. Positive samples were HPV-type determined by cloning and sequencing. HPV DNA was found in 8.3% (15/180) of the blood donors. A wide variety of different HPV types were isolated from the PBMCs; belonging to the cutaneous beta and gamma papillomavirus genera and mucosal alpha papillomaviruses. High-risk HPV types that are linked to cancer development were detected in 1.7% (3/180) of the PBMCs. Blood was also collected from a healthy HPV-positive 44-year-old male on four different occasions in order to determine which blood cell fractions harbor HPV. PBMCs treated with trypsin were negative for HPV, while non-trypsinized PBMCs were HPV-positive. This suggests that the HPV in blood is attached to the outside of blood cells via a protein-containing moiety. HPV was also isolated in the B cells, dendritic cells, NK cells, and neutrophils. To conclude, HPV present in PBMCs could represent a reservoir of virus and a potential new route of transmission.