A novel model to study mechanisms of cholestasis in human cholangiocytes reveals a role for the SIPR2 pathway.

BACKGROUND: Ductular reactivity is central to the pathophysiology of cholangiopathies. Mechanisms underlying the reactive phenotype activation by exogenous inflammatory mediators and bile acids are poorly understood. METHODS: Using human extrahepatic cholangiocyte organoids (ECOs) we developed an injury model emulating the cholestatic microenvironment with exposure to inflammatory mediators and various pathogenic bile acids. Moreover, we explored roles for the bile acid activated Sphingosine-1-phosphate receptor 2 (S1PR2) and potential beneficial effects of therapeutic bile acids UDCA and norUDCA. RESULTS: Synergistic exposure to bile acids (taurocholic acid, glycocholic acid, glycochenodeoxycholic acid) and TNF-α for 24 hours induced a reactive state as measured by ECO diameter, proliferation, lactate dehydrogenase activity and reactive phenotype markers. While NorUDCA and UDCA treatments given 8 hours after injury induction both suppressed reactive phenotype activation and most injury parameters, proliferation was improved by NorUDCA only. Extrahepatic cholangiocyte organoid stimulation with S1PR2 agonist sphingosine-1-phosphate reproduced the cholangiocyte reactive state and upregulated S1PR2 downstream mediators; these effects were suppressed by S1PR2 antagonist JET-013 (JET), downstream mediator extracellular signal-regulated kinase 1/2 inhibitor, and by norUDCA or UDCA treatments. JET also partially suppressed reactive phenotype after bile acid injury. CONCLUSIONS: We developed a novel model to study the reactive cholangiocyte state in response to pathological stimuli in cholestasis and demonstrated a contributory role of S1PR2 signaling in both injury and NorUDCA/UDCA treatments. This model is a valuable tool to further explore the pathophysiology of human cholangiopathies.

Modulation of Human Neutrophil Peptides on P. aeruginosa Killing, Epithelial Cell Inflammation and Mesenchymal Stromal Cell Secretome Profiles.

OBJECTIVE: Neutrophil infiltration and release of the abundant human neutrophil peptides (HNP) are a common clinical feature in critically ill patients. We tested a hypothesis that different cell types respond to HNP differently in lung microenvironment that may influence the host responses. METHODS: Plasma concentrations of HNP were measured in healthy volunteers and patients with sepsis. Cells including the bacteria P. aeruginosa, human lung epithelial cells and mesenchymal stromal cells (MSCs) were exposed to various concentrations of HNP. Bacterial killing, epithelial cell inflammation, MSC adhesion and behaviours were examined after HNP stimulation. RESULTS: Incubation of P. aeruginosa or stimulation of human lung epithelial cells with HNP resulted in bacterial killing or IL-8 production at a dose of 50 µg/mL, while MSC adhesion and alternations of secretome profiles took place after HNP stimulation at a dose of 10 µg/mL. The secretome profile changes were characterized by increased release of the IL-6 family members such as C-reactive protein (CRP), leukemia inhibitory factor (LIF) and interleukin (IL-11), and first apoptosis signal (FAS) and platelet-derived growth factor-AA as compared to a vehicle control group. CONCLUSION: Stimulation of MSCs with HNP resulted in changes of secretome profiles at 5-fold lower concentration than that required for bacterial killing and lung epithelial inflammation. This undisclosed risk factor of HNP in lung environment should be taken into consideration when MSCs are applied as cell therapy in inflammatory lung diseases.

Identification and Modulation of Microenvironment Is Crucial for Effective Mesenchymal Stromal Cell Therapy in Acute Lung Injury.

Rationale: There are controversial reports on applications of mesenchymal stromal cells (MSCs) in patients with acute respiratory distress syndrome (ARDS). Objectives: We hypothesized that lung microenvironment was the main determinant of beneficial versus detrimental effects of MSCs during ARDS. Methods: Lung proteome was profiled in three models of injury induced by acid instillation and/or mechanical ventilation in mice. Human gene of glutathione peroxidase-1 was delivered before MSC administration; or MSCs carrying human gene of IL-10 or hepatocyte growth factor were administered after lung injury. An inhibitory cocktail against IL-6, fibronectin, and oxidative stress was used in in vitro studies using human small airway epithelial cells and human MSCs after exposure to plasma of patients with ARDS. Measurements and Main Results: Distinct proteomic profiles were observed in three lung injury models. Administration of MSCs protected lung from ventilator-induced injury, whereas it worsened acid-primed lung injuries associated with fibrotic development in lung environment that had high levels of IL-6 and fibronectin along with low antioxidant capacity. Correction of microenvironment with glutathione peroxidase-1, or treatment with MSCs carrying human gene of IL-10 or hepatocyte growth factor after acid-primed injury, reversed the detrimental effects of native MSCs. Proteomic profiles obtained in the mouse models were also similarly observed in human ARDS. Treatment with the inhibitory cocktail in samples of patients with ARDS retained protective effects of MSCs in small airway epithelial cells. Conclusions: MSCs can be beneficial or detrimental depending on microenvironment at the time of administration. Identification of potential beneficiaries seems to be crucial to guide MSC therapy in ARDS.

Dual effects of human neutrophil peptides in a mouse model of pneumonia and ventilator-induced lung injury.

BACKGROUND: Pneumonia is a major cause of high morbidity and mortality in critically illness, and frequently requires support with mechanical ventilation. The latter can lead to ventilator-induced lung injury characterized by neutrophil infiltration. The cationic human neutrophil peptides (HNP) stored in neutrophils can kill microorganisms, but excessive amount of HNP released during phagocytosis may contribute to inflammatory responses and worsen lung injury. Based on our previous work, we hypothesized that blocking the cell surface purinergic receptor P2Y6 will attenuate the HNP-induced inflammatory responses while maintaining their antimicrobial activity in pneumonia followed by mechanical ventilation. METHODS: Plasma HNP levels were measured in patients with pneumonia who received mechanical ventilation and in healthy volunteers. FVB littermate control and HNP transgenic (HNP+) mice were randomized to receive P. aeruginosa intranasally. The P2Y6 antagonist (MRS2578) or vehicle control was given after P. aeruginosa instillation. Additional mice underwent mechanical ventilation at either low pressure (LP) or high pressure (HP) ventilation 48 h after pneumonia, and were observed for 24 h. RESULTS: Plasma HNP concentration increased in patients with pneumonia as compared to healthy subjects. The bacterial counts in the bronchoalveolar lavage fluid (BALF) were lower in HNP+ mice than in FVB mice 72 h after P. aeruginosa instillation. However, upon receiving HP ventilation, HNP+ mice had higher levels of cytokines and chemokines in BALF than FVB mice. These inflammatory responses were attenuated by the treatment with MRS2578 that did not affect the microbial effects of HNP. CONCLUSIONS: HNP exerted dual effects by exhibiting antimicrobial activity in pneumonia alone condition while enhancing inflammatory responses in pneumonia followed by HP mechanical ventilation. Blocking P2Y6 can attenuate the inflammation without affecting the antibacterial property of HNP. The P2Y6 receptor may be a novel therapeutic target in attenuation of the leukocyte-mediated excessive host responses in inflammatory lung diseases.

Chronic lung injury and impaired pulmonary function in a mouse model of acid ceramidase deficiency.

Farber disease (FD) is a debilitating lysosomal storage disorder (LSD) caused by a deficiency of acid ceramidase (ACDase) activity due to mutations in the gene ASAH1. Patients with ACDase deficiency may develop a spectrum of clinical phenotypes. Severe cases of FD are frequently associated with neurological involvement, failure to thrive, and respiratory complications. Mice homozygous ( Asah1P361R/P361R) for an orthologous patient mutation in Asah1 recapitulate human FD. In this study, we show significant impairment in lung function, including low compliance and increased airway resistance in a mouse model of ACDase deficiency. Impaired lung mechanics in Farber mice resulted in decreased blood oxygenation and increased red blood cell production. Inflammatory cells were recruited to both perivascular and peribronchial areas of the lung. We observed large vacuolated foamy histiocytes that were full of storage material. An increase in vascular permeability led to protein leakage, edema, and impacted surfactant homeostasis in the lungs of Asah1P361R/P361R mice. Bronchial alveolar lavage fluid (BALF) extraction and analysis revealed accumulation of a highly turbid lipoprotein-like substance that was composed in part of surfactants, phospholipids, and ceramides. The phospholipid composition of BALF from Asah1P361R/P361R mice was severely altered, with an increase in both phosphatidylethanolamine (PE) and sphingomyelin (SM). Ceramides were also found at significantly higher levels in both BALF and lung tissue from Asah1P361R/P361R mice when compared with levels from wild-type animals. We demonstrate that a deficiency in ACDase leads to sphingolipid and phospholipid imbalance, chronic lung injury caused by significant inflammation, and increased vascular permeability, leading to impaired lung function.

Tsr Chemoreceptor Interacts With IL-8 Provoking E. coli Transmigration Across Human Lung Epithelial Cells.

Bacterial colonization of epithelial surfaces and subsequent transmigration across the mucosal barrier are essential for the development of infection. We hypothesized that the methyl-accepting proteins (MCPs), known as chemoreceptors expressed on Escherichia coli (E. coli) bacterial surface, play an important role in mediating bacterial transmigration. We demonstrated a direct interaction between human interleukin-8 (IL-8) and Tsr receptor, a major MCP chemoreceptor. Stimulation of human lung epithelial cell monolayer with IL-8 resulted in increased E. coli adhesion and transmigration of the native strain (RP437) and a strain expressing only Tsr (UU2373), as compared to a strain (UU2599) with Tsr truncation. The augmented E. coli adhesion and migration was associated with a higher expression of carcinoembryonic antigen-related cell adhesion molecule 6 and production of inflammatory cytokines/chemokines, and a lower expression of the tight junction protein claudin-1 and the plasma membrane protein caveolin-1 in lung epithelial cells. An increased E. coli colonization and pulmonary cytokine production induced by the RP437 and UU2373 strains was attenuated in mice challenged with the UU2599 strain. Our results suggest a critical role of the E. coli Tsr chemoreceptor in mediating bacterial colonization and transmigration across human lung epithelium during development of pulmonary infections.

Mechanical Stress and the Induction of Lung Fibrosis via the Midkine Signaling Pathway.

RATIONALE: Lung-protective ventilatory strategies have been widely used in patients with acute respiratory distress syndrome (ARDS), but the ARDS mortality rate remains unacceptably high and there is no proven pharmacologic therapy. OBJECTIVES: Mechanical ventilation can induce oxidative stress and lung fibrosis, which may contribute to high dependency on ventilator support and increased ARDS mortality. We hypothesized that the novel cytokine, midkine (MK), which can be up-regulated in oxidative stress, plays a key role in the pathogenesis of ARDS-associated lung fibrosis. METHODS: Blood samples were collected from 17 patients with ARDS and 10 healthy donors. Human lung epithelial cells were challenged with hydrogen chloride followed by mechanical stretch for 72 hours. Wild-type and MK gene-deficient (MK(-/-)) mice received two-hit injury of acid aspiration and mechanical ventilation, and were monitored for 14 days. MEASUREMENTS AND MAIN RESULTS: Plasma concentrations of MK were higher in patients with ARDS than in healthy volunteers. Exposure to mechanical stretch of lung epithelial cells led to an epithelial-mesenchymal transition profile associated with increased expression of angiotensin-converting enzyme, which was attenuated by silencing MK, its receptor Notch2, or NADP reduced oxidase 1. An increase in collagen deposition and hydroxyproline level and a decrease in lung tissue compliance seen in wild-type mice were largely attenuated in MK(-/-) mice. CONCLUSIONS: Mechanical stretch can induce an epithelial-mesenchymal transition phenotype mediated by the MK-Notch2-angiotensin-converting enzyme signaling pathway, contributing to lung remodeling. The MK pathway is a potential therapeutic target in the context of ARDS-associated lung fibrosis.

Intervertebral disc-derived stem cells: implications for regenerative medicine and neural repair.

STUDY DESIGN: An in vitro and in vivo evaluation of intervertebral disc (IVD)-derived stem/progenitor cells. OBJECTIVE: To determine the chondrogenic, adipogenic, osteogenic, and neurogenic differentiation capacity of disc-derived stem/progenitor cells in vitro and neurogenic differentiation in vivo. SUMMARY OF BACKGROUND DATA: Tissue repair strategies require a source of appropriate cells that could be used to replace dead or damaged cells and tissues such as stem cells. Here we examined the potential use of IVD-derived stem cells in regenerative medicine approaches and neural repair. METHODS: Nonchondrodystrophic canine IVD nucleus pulposus (NP) cells were used to generate stem/progenitor cells (NP progenitor cells [NPPCs]) and the NPPCs were differentiated in vitro into chondrogenic, adipogenic, and neurogenic lineages and in vivo into the neurogenic lineage. NPPCs were compared with bone marrow-derived mesenchymal (stromal) stem cells in terms of the expression of stemness genes. The expression of the neural crest marker protein 0 and the Brachyury gene were evaluated in NP cells and NPPCs. RESULTS: NPPCs contain stem/progenitor cells and express "stemness" genes such as Sox2, Oct3/4, Nanog, CD133, Nestin, and neural cell adhesion molecule but differ from mesenchymal (stromal) stem cells in the higher expression of the Nanog gene by NPPCs. NPPCs do not express protein 0 or the Brachyury gene both of which are expressed by the totality of IVD NP cells. The percentage of NPPCs within the IVD is 1% of the total as derived by colony-forming assay. NPPCs are capable of differentiating along chondrogenic, adipogenic, and neurogenic lineages in vitro and into oligodendrocyte, neuron, and astroglial specific precursor cells in vivo within the compact myelin-deficient shiverer mouse. CONCLUSION: We propose that the IVD NP represents a regenerative niche suggesting that the IVD could represent a readily accessible source of precursor cells for neural repair and regeneration.

Notochordal cells protect nucleus pulposus cells from degradation and apoptosis: implications for the mechanisms of intervertebral disc degeneration.

INTRODUCTION: The relative resistance of non-chondrodystrophic (NCD) canines to degenerative disc disease (DDD) may be due to a combination of anabolic and anti-catabolic factors secreted by notochordal cells within the intervertebral disc (IVD) nucleus pulposus (NP). Factors known to induce DDD include interleukin-1 beta (IL-1ß) and/or Fas-Ligand (Fas-L). Therefore we evaluated the ability of notochordal cell conditioned medium (NCCM) to protect NP cells from IL-1ß and IL-1ß +FasL-mediated cell death and degeneration. METHODS: We cultured bovine NP cells with IL-1ß or IL-1ß+FasL under hypoxic serum-free conditions (3.5% O2) and treated the cells with either serum-free NCCM or basal medium (Advanced DMEM/F-12). We used flow cytometry to evaluate cell death and real-time (RT-)PCR to determine the gene expression of aggrecan, collagen 2, and link protein, mediators of matrix degradation ADAMTS-4 and MMP3, the matrix protection molecule TIMP1, the cluster of differentiation (CD)44 receptor, the inflammatory cytokine IL-6 and Ank. We then determined the expression of specific apoptotic pathways in bovine NP cells by characterizing the expression of activated caspases-3, -8 and -9 in the presence of IL-1ß+FasL when cultured with NCCM, conditioned medium obtained using bovine NP cells (BCCM), and basal medium all supplemented with 2% FBS. RESULTS: NCCM inhibits bovine NP cell death and apoptosis via suppression of activated caspase-9 and caspase-3/7. Furthermore, NCCM protects NP cells from the degradative effects of IL-1ß and IL-1ß+Fas-L by up-regulating the expression of anabolic/matrix protective genes (aggrecan, collagen type 2, CD44, link protein and TIMP-1) and down-regulating matrix degrading genes such as MMP-3. Expression of ADAMTS-4, which encodes a protein for aggrecan remodeling, is increased. NCCM also protects against IL-1+FasL-mediated down-regulation of Ank expression. Furthermore, NP cells treated with NCCM in the presence of IL-1ß+Fas-L down-regulate the expression of IL-6 by almost 50%. BCCM does not mediate cell death/apoptosis in target bovine NP cells. CONCLUSIONS: Notochordal cell-secreted factors suppress NP cell death by inhibition of activated caspase-9 and -3/7 activity and by up-regulating genes contributing anabolic activity and matrix protection of the IVD NP. Harnessing the restorative powers of the notochordal cell could lead to novel cellular and molecular strategies in the treatment of DDD.

The regenerative capacity of the notochordal cell: tissue constructs generated in vitro under hypoxic conditions.

OBJECT: The intervertebral disc (IVD) is a highly avascular structure that is occupied by highly specialized cells (nucleus pulposus [NP] cells) that have adapted to survive within an O(2) concentration of 2-5%. The object of this study was to investigate the effects of long-term hypoxic and normoxic tissue cultures of nonchondrodystrophic canine notochordal cells-cells that appear to protect the disc NP from degenerative change. METHODS: The authors obtained notochordal cells from nonchondrodystrophic canines according to their established methods and placed them into monolayer and 3D culture using sodium alginate globules under either hypoxic (3.5% O(2)) or normoxic (21% O(2)) conditions. Histological, immunohistochemical, scanning electron microscopy, and histomorphometric methods were used to evaluate the cells within the globules after 5 months in culture. RESULTS: Notochordal cells under in vitro hypoxic tissue culture conditions produced a highly complex, organized, 3D cellular construct that was strikingly similar to that observed in vivo. In contrast, traditional normoxic tissue culture conditions resulted in notochordal cells that failed to produce an organized matrix. Hypoxia resulted in a matrix rich in aggrecan and collagen II, whereas normoxic cultured cells did not produce any observable aggrecan or collagen II after 5 months of culture. CONCLUSIONS: Hypoxia induces notochordal cells to organize a complex 3D cellular/extracellular matrix without an external scaffold other than suspension within sodium alginate. These cells produce an extracellular matrix and large construct that shares exactly the same characteristics as the in vivo condition-robust aggrecan, and type II collagen production. Normoxic tissue culture conditions, however, lead to a failure of these cells to thrive and a lack of extracellular matrix production and significantly smaller cells. The authors suggest that future studies of NP cells and, in particular, notochordal cells should utilize hypoxic tissue culture conditions to derive meaningful, biologically relevant conclusions concerning possible biological/molecular interventions.

Epac is involved in cAMP-stimulated proglucagon expression and hormone production but not hormone secretion in pancreatic alpha- and intestinal L-cell lines.

Both Epac and PKA are effectors of the second messenger cAMP. Utilizing an exchange protein directly activated by cAMP (Epac) pathway-specific cAMP analog (ESCA), we previously reported that Epac signaling regulates proglucagon gene (gcg) expression in the glucagon-like peptide-1 (GLP-1)-producing intestinal endocrine L-cell lines GLUTag and STC-1. We now show that Epac-2 is also expressed in glucagon-producing pancreatic alpha-cell lines, including PKA-deficient InR1-G9 cells, and that ESCA stimulates gcg promoter and mRNA expression in the InR1-G9 cells. Using a dominant-negative Epac-2 expression plasmid (Epac-2DN), we found that Epac inhibition attenuated forskolin-stimulated gcg promoter expression in the PKA-active STC-1 cell line and blocked forskolin-stimulated gcg promoter expression in the InR1-G9 cells. Consistently, ESCA was shown to stimulate glucagon and GLP-1 production in the InR1-G9 and GLUTag cell lines, respectively. Surprisingly, ESCA treatment did not show a notable stimulation of glucagon or GLP-1 secretion from these two cell lines. This is in contrast to its ability to stimulate insulin secretion from the pancreatic INS-1 beta-cell line. Our findings suggest that Epac is selectively involved in peptide hormone secretion in pancreatic and intestinal endocrine cells and that distinct signaling cascades are involved in stimulating production vs. secretion of glucagon and GLP-1 in response to cAMP elevation.

Role of the exchange protein directly activated by cyclic adenosine 5'-monophosphate (Epac) pathway in regulating proglucagon gene expression in intestinal endocrine L cells.

Although proglucagon gene expression and the synthesis of proglucagon encoded peptide hormones could be activated by protein kinase A (PKA) activators such as forskolin/3-isobutyl-1-methylxanthine (IBMX) and cholera toxin, whether the activation is entirely attributed to PKA has not been previously examined. We found that forskolin/IBMX also activate ERK1/2 phosphorylation in intestinal and pancreatic proglucagon-producing cell lines. The MEK inhibitors PD98059 and U0126 were found to repress the expression of proglucagon promoter as well as endogenous proglucagon mRNA in two intestinal proglucagon-producing cell lines and to block the stimulatory effect of forskolin/IBMX on proglucagon mRNA expression. The repressive effect of the PKA-specific inhibitors H-89 and KT-5720, however, was either not observable or much less potent. Forskolin could activate ERK1/2 phosphorylation and proglucagon gene transcription on its own, whereas forskolin plus IBMX are required to effectively activate the PKA pathway in the proglucagon-producing cells. Exchange protein directly activated by cyclic AMP 2 (Epac2, or cAMP-binding guanine nucleotide exchange factor-2) was found to be expressed in gut and pancreatic proglucagon-producing cell lines, whereas the Epac-pathway-specific cAMP analog, 8-pMeOPT-2'O-Me-cAMP, effectively stimulated ERK1/2 phosphorylation as well as proglucagon mRNA expression. We therefore suggest that cAMP at least partially regulates proglucagon gene expression via the Epac-Ras/Rap-Raf-MEK-ERK signaling pathway.