Intraluminal blockade of cell-surface CD74 and glucose regulated protein 78 prevents substance P-induced bladder inflammatory changes in the rat

Acyloxyacyl Hydrolase Protects against Kidney Injury via Inhibition of Tubular CD74-Macrophage Crosstalk

Renal fibrosis is the common pathway in the progression of chronic kidney disease (CKD). Acyloxyacyl hydrolase (AOAH) is expressed in various phagocytes and is highly expressed in proximal tubular epithelial cells (PTECs). Research shows that AOAH plays a critical role in infections and chronic inflammatory diseases, although its role in kidney injury is unknown. Here, we found that AOAH deletion led to exacerbated kidney injury and fibrosis after folic acid (FA) administration, which was reversed by overexpression of Aoah in kidneys. ScRNA-seq revealed that Aoah-/- mice exhibited increased subpopulation of CD74+ PTECs, though the percentage of total PTECs were decreased compared to WT mice after FA treatment. Additionally, exacerbated kidney injury and fibrosis seen in Aoah-/- mice was attenuated via administration of methyl ester of (S, R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid (ISO-1), an inhibitor of macrophage inhibition factor (MIF) and CD74 binding. Finally, AOAH expression was found positively correlated with estimated glomerular filtration rate while negatively correlated with the degree of renal fibrosis in kidneys of CKD patients. Thus, our work indicates that AOAH protects against kidney injury and fibrosis by inhibiting renal tubular epithelial cells CD74 signaling pathways. Targeting kidney AOAH represents a promising strategy to prevent renal fibrosis progression.

Feline Uroepithelial Cell Culture as a Novel Model of Idiopathic Cystitis: Investigations on the Effects of Norepinephrine on Inflammatory Response, Oxidative Stress, and Barrier Function

Feline idiopathic cystitis (FIC) is one of the most common urinary tract disorders in domestic cats. As stress is suggested to play a key role in the pathogenesis of FIC, the effects of norepinephrine (NE) as a stress mediator were investigated on a novel feline primary uroepithelial cell culture, serving as an in vitro model of the disease. The uroepithelial cells gained from the mucosa of the bladder of a euthanized cat were cultured for 6 days and were acutely exposed to NE (10, 100, and 1000 µM) for 1 h. NE increased the metabolic activity of the cultured cells and elevated the extracellular concentrations of the pro-inflammatory mediators interleukin-6 (IL-6) and stromal cell derived factor 1 (SDF-1), confirming that NE can trigger an inflammatory response in the uroepithelium. Cellular protein carbonyl levels were increased by NE exposure, while malondialdehyde and glucose regulated protein 78 concentrations remained unchanged, indicating that NE may provoke the oxidative damage of proteins without inducing lipid peroxidation or endoplasmic reticulum stress. Further, it can be strongly suggested that an acute NE challenge might diminish the barrier function of uroepithelial cells, as reflected by the decreased glycosaminoglycan concentration, claudin-4 protein expression, and reduced TER values of the NE-treated cell cultures. Based on these results, short-term NE exposure mimicking acute stress can provoke an inflammatory response and decrease the barrier integrity of cultured feline uroepithelial cells. Hence, it is highly expected that stress-associated NE release may play an important mediatory role in the pathogenesis of FIC.

Intravesical CD74 and CXCR4, macrophage migration inhibitory factor (MIF) receptors, mediate bladder pain

Background

Activation of intravesical protease activated receptor 4 (PAR4) leads to release of urothelial macrophage migration inhibitory factor (MIF). MIF then binds to urothelial MIF receptors to release urothelial high mobility group box-1 (HMGB1) and elicit bladder hyperalgesia. Since MIF binds to multiple receptors, we investigated the contribution of individual urothelial MIF receptors to PAR4-induced HMGB1 release in vivo and in vitro and bladder pain in vivo.

Methodology/Principal findings

We tested the effect of intravesical pre-treatment with individual MIF or MIF receptor (CD74, CXCR4, CXCR2) antagonists on PAR4-induced HMGB1 release in vivo (female C57/BL6 mice) and in vitro (primary human urothelial cells) and on PAR4-induced bladder hyperalgesia in vivo (mice). In mice, PAR4 induced HMGB1 release and bladder hyperalgesia through activation of intravesical MIF receptors, CD74 and CXCR4. CXCR2 was not involved in these effects. In primary urothelial cells, PAR4-induced HMGB1 release through activation of CD74 receptors. Micturition parameters in mice were not changed by any of the treatments.

Conclusions/Significance

Urothelial MIF receptors CD74 and CXCR4 mediate bladder pain through release of urothelial HMGB1. This mechanism may set up persistent pain loops in the bladder and warrants further investigation. Urothelial CD74 and CXCR4 may provide novel targets for interrupting bladder pain.

Elevated Urine Levels of Macrophage Migration Inhibitory Factor in Inflammatory Bladder Conditions: A Potential Biomarker for a Subgroup of Interstitial Cystitis/Bladder Pain Syndrome Patients

OBJECTIVE

To investigate whether urinary levels of macrophage migration inhibitory factor (MIF) are elevated in interstitial cystitis/bladder pain syndrome (IC/BPS) patients with Hunner lesions and also whether urine MIF is elevated in other forms of inflammatory cystitis.

METHODS

Urine samples were assayed for MIF by enzyme-linked immunosorbent assay. Urine samples from 3 female groups were examined: IC/BPS patients without (N = 55) and with Hunner lesions (N = 43), and non-IC/BPS patients (N = 100; control group; no history of IC/BPS; cancer or recent bacterial cystitis). Urine samples from 3 male groups were examined: patients with bacterial cystitis (N = 50), radiation cystitis (N = 18) and noncystitis patients (N = 119; control group; negative for bacterial cystitis).

RESULTS

Urine MIF (mean MIF pg/mL ±  standard error of the mean) was increased in female IC/BPS patients with Hunner lesions (2159 ± 435.3) compared with IC/BPS patients without Hunner lesions (460 ± 114.5) or non-IC/BPS patients (414 ± 47.6). Receiver operating curve analyses showed that urine MIF levels discriminated between the 2 IC groups (area under the curve = 72%; confidence interval 61%-82%). Male patients with bacterial and radiation cystitis had elevated urine MIF levels (2839 ± 757.1 and 4404 ± 1548.1, respectively) compared with noncystitis patients (681 ± 75.2).

CONCLUSION

Urine MIF is elevated in IC/BPS patients with Hunner lesions and also in patients with other bladder inflammatory and painful conditions. MIF may also serve as a noninvasive biomarker to select IC/BPS patients more accurately for endoscopic evaluation and possible anti-inflammatory treatment.

Experimental study of inhibitory effects of diallyl trisulfide on the growth of human osteosarcoma Saos-2 cells by downregulating expression of glucose-regulated protein 78

BACKGROUND

Diallyl trisulfide (DATS) is a natural organic sulfur compound isolated from garlic that has good anticancer activity according to many previous reports. There are many studies pointing out that DATS can downregulate expression of the glucose-regulated protein 78 (GRP78), which is associated with poor prognosis and drug resistance in various types of human cancers. However, it remains unknown whether DATS has the same effect on human osteosarcoma cells. This study attempted to clarify the potential molecular mechanisms of the action of DATS in human osteosarcoma Saos-2 cells.

METHODS

We used an inverted phase microscope and immunofluorescent staining to observe the morphological changes of Saos-2 cells after being cultured in different concentrations of DATS (0, 25, 50, and 100 μM) for 24 h, or for four time periods (24, 48, 72, and 96 h) in the same DATS concentration (50 μM). Quantitative real-time polymerase chain reaction and Western blot were used to detect the expression level of GRP78 mRNA and proteins in Saos-2 cells. GRP78 expression was suppressed in Saos-2 cells by utilizing small-interfering RNA, and the cells were subsequently used to study the anti-proliferative effects of DATS treatment.

RESULTS

The expression level of GRP78 mRNA and proteins was significantly downregulated due to the increased concentration and effective times of DATS (P<0.05). In addition, there were significant associations between GRP78 silencing and cell proliferation (P<0.05) of DATS treatment.

CONCLUSION

These results indicate that DATS inhibits the growth of human osteosarcoma Saos-2 cells by downregulating the expression of GRP78.

Proinflammatory Signature of the Dysfunctional Endothelium in Pulmonary Hypertension. Role of the Macrophage Migration Inhibitory Factor/CD74 Complex

RATIONALE

Inflammation and endothelial dysfunction are considered two primary instigators of pulmonary arterial hypertension (PAH). CD74 is a receptor for the proinflammatory cytokine macrophage migration inhibitory factor (MIF). This ligand/receptor complex initiates survival pathways and cell proliferation, and it triggers the synthesis and secretion of major proinflammatory factors and cell adhesion molecules.

OBJECTIVES

We hypothesized that the MIF/CD74 signaling pathway is overexpressed in idiopathic PAH (iPAH) and contributes to a proinflammatory endothelial cell (EC) phenotype.

METHODS

Primary early passage cultures of human ECs isolated from lung tissues obtained from patients with iPAH and controls were examined for their ability to secrete proinflammatory mediators and bind inflammatory cells with or without modulation of the functional activities of the MIF/CD74 complex. In addition, we tested the efficacies of curative treatments with either the MIF antagonist ISO-1 or anti-CD74 neutralizing antibodies on the aberrant proinflammatory EC phenotype in vitro and in vivo and on the progression of monocrotaline-induced pulmonary hypertension.

MEASUREMENTS AND MAIN RESULTS

In human lung tissues, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin expressions are markedly up-regulated in the endothelium of distal iPAH pulmonary arteries. Circulating MIF levels are increased in the serum of patients with PAH compared with control subjects, and T-cell lymphocytes represent a source of this overabundance. In addition, CD74 is highly expressed in the endothelium of muscularized pulmonary arterioles and in cultured pulmonary ECs from iPAH, contributing to an exaggerated recruitment of peripheral blood mononuclear cells to pulmonary iPAH ECs. Finally, we found that curative treatments with the MIF antagonist ISO-1 or anti-CD74 neutralizing antibodies partially reversed development of pulmonary hypertension in rats and substantially reduced inflammatory cell infiltration.

CONCLUSIONS

We report here that CD74 and MIF are markedly increased and activated in patients with iPAH, contributing to the abnormal proinflammatory phenotype of pulmonary ECs in iPAH.

Macrophage Migration Inhibitory Factor Mediates PAR-Induced Bladder Pain

Introduction

Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine, is constitutively expressed in urothelial cells that also express protease-activated receptors (PAR). Urothelial PAR1 receptors were shown to mediate bladder inflammation. We showed that PAR1 and PAR4 activator, thrombin, also mediates urothelial MIF release. We hypothesized that stimulation of urothelial PAR1 or PAR4 receptors elicits release of urothelial MIF that acts on MIF receptors in the urothelium to mediate bladder inflammation and pain. Thus, we examined the effect of activation of specific bladder PAR receptors on MIF release, bladder pain, micturition and histological changes.

Methods

MIF release was measured in vitro after exposing immortalized human urothelial cells (UROtsa) to PAR1 or PAR4 activating peptides (AP). Female C57BL/6 mice received intravesical PAR1- or PAR4-AP for one hour to determine: 1) bladder MIF release in vivo within one hour; 2) abdominal hypersensitivity (allodynia) to von Frey filament stimulation 24 hours after treatment; 3) micturition parameters 24 hours after treatment; 4) histological changes in the bladder as a result of treatment; 5) changes in expression of bladder MIF and MIF receptors using real-time RT-PCR; 6) changes in urothelial MIF and MIF receptor, CXCR4, protein levels using quantitative immunofluorescence; 7) effect of MIF or CXCR4 antagonism.

Results

PAR1- or PAR4-AP triggered MIF release from both human urothelial cells in vitro and mouse urothelium in vivo. Twenty-four hours after intravesical PAR1- or PAR4-AP, we observed abdominal hypersensitivity in mice without changes in micturition or bladder histology. PAR4-AP was more effective and also increased expression of bladder MIF and urothelium MIF receptor, CXCR4. Bladder CXCR4 localized to the urothelium. Antagonizing MIF with ISO-1 eliminated PAR4- and reduced PAR1-induced hypersensitivity, while antagonizing CXCR4 with AMD3100 only partially prevented PAR4-induced hypersensitivity.

Conclusions

Bladder PAR activation elicits urothelial MIF release and urothelial MIF receptor signaling at least partly through CXCR4 to result in abdominal hypersensitivity without overt bladder inflammation. PAR-induced bladder pain may represent an interesting pre-clinical model of Interstitial Cystitis/Painful Bladder Syndrome (IC/PBS) where pain occurs without apparent bladder injury or pathology. MIF is potentially a novel therapeutic target for bladder pain in IC/PBS patients.

Tachykinins and their receptors: contributions to physiological control and the mechanisms of disease

The tachykinins, exemplified by substance P, are one of the most intensively studied neuropeptide families. They comprise a series of structurally related peptides that derive from alternate processing of three Tac genes and are expressed throughout the nervous and immune systems. Tachykinins interact with three neurokinin G protein-coupled receptors. The signaling, trafficking, and regulation of neurokinin receptors have also been topics of intense study. Tachykinins participate in important physiological processes in the nervous, immune, gastrointestinal, respiratory, urogenital, and dermal systems, including inflammation, nociception, smooth muscle contractility, epithelial secretion, and proliferation. They contribute to multiple diseases processes, including acute and chronic inflammation and pain, fibrosis, affective and addictive disorders, functional disorders of the intestine and urinary bladder, infection, and cancer. Neurokinin receptor antagonists are selective, potent, and show efficacy in models of disease. In clinical trials there is a singular success: neurokinin 1 receptor antagonists to treat nausea and vomiting. New information about the involvement of tachykinins in infection, fibrosis, and pruritus justifies further trials. A deeper understanding of disease mechanisms is required for the development of more predictive experimental models, and for the design and interpretation of clinical trials. Knowledge of neurokinin receptor structure, and the development of targeting strategies to disrupt disease-relevant subcellular signaling of neurokinin receptors, may refine the next generation of neurokinin receptor antagonists.

Glucose regulated protein 78: a critical link between tumor microenvironment and cancer hallmarks

Glucose regulated protein 78 (GRP78) has long been recognized as a molecular chaperone in the endoplasmic reticulum (ER) and can be induced by the ER stress response. Besides its location in the ER, GRP78 has been found to be present in cell plasma membrane, cytoplasm, mitochondria, nucleus as well as cellular secretions. GRP78 is implicated in tumor cell proliferation, apoptosis resistance, immune escape, metastasis and angiogenesis, and its elevated expression usually correlates with a variety of tumor microenvironmental stresses, including hypoxia, glucose deprivation, lactic acidosis and inflammatory response. GRP78 protein acts as a centrally located sensor of stress, which feels and adapts to the alteration in the tumor microenvironment. This article reviews the potential contributions of GRP78 to the acquisition of cancer hallmarks based on intervening in stress responses caused by tumor niche alterations. The paper also introduces several potential GRP78 relevant targeted therapies.

Macrophage migration inhibitory factor and CD74 regulate macrophage chemotactic responses via MAPK and Rho GTPase

Macrophage migration inhibitory factor (MIF) promotes leukocyte recruitment to sites of inflammation. However, whether this stems from a direct effect on leukocyte migration is unknown. Furthermore, the role of the MIF-binding protein CD74 in this response has not been investigated. Therefore, the aim of this study was to examine the contributions of MIF and CD74 to chemokine-induced macrophage recruitment. Intravital microscopy studies demonstrated that CCL2-induced leukocyte adhesion and transmigration were reduced in MIF(-/-) and CD74(-/-) mice. MIF(-/-) and CD74(-/-) macrophages also exhibited reduced chemotaxis in vitro, although CD74(-/-) macrophages showed increased chemokinesis. Reduced CCL2-induced migration was associated with attenuated MAPK phosphorylation, RhoA GTPase activity, and actin polymerization in MIF(-/-) and CD74(-/-) macrophages. Furthermore, in MIF(-/-) macrophages, MAPK phosphatase-1 was expressed at elevated levels, providing a potential mechanism for the reduction in MAPK phosphorylation in MIF-deficient cells. No increase in MAPK phosphatase-1 expression was observed in CD74(-/-) macrophages. In in vivo experiments assessing the link between MIF and CD74, combined administration of MIF and CCL2 increased leukocyte adhesion in both MIF(-/-) and CD74(-/-) mice, showing that CD74 was not required for this MIF-induced response. Additionally, although leukocyte recruitment induced by administration of MIF alone was reduced in CD74(-/-) mice, consistent with a role for CD74 in leukocyte recruitment induced by MIF, MIF-treated CD74(-/-) mice displayed residual leukocyte recruitment. These data demonstrate that MIF and CD74 play previously unappreciated roles in CCL2-induced macrophage adhesion and migration, and they indicate that MIF and CD74 mediate this effect via both common and independent mechanisms.

Thrombin induces macrophage migration inhibitory factor release and upregulation in urothelium: a possible contribution to bladder inflammation

Purpose

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine expressed by urothelial cells that mediates bladder inflammation. We investigated the effect of stimulation with thrombin, a Protease Activated Receptor-1 (PAR1) agonist, on MIF release and MIF mRNA upregulation in urothelial cells.

Materials and Methods

MIF and PAR1 expression was examined in normal human immortalized urothelial cells (UROtsa) using real-time RT-PCR, Western blotting and dual immunostaining. MIF and PAR1 immunostaining was also examined in rat urothelium. The effect of thrombin stimulation (100 nM) on urothelial MIF release was examined in UROtsa cells (in vitro) and in rats (in vivo). UROtsa cells were stimulated with thrombin, culture media were collected at different time points and MIF amounts were determined by ELISA. Pentobarbital anesthetized rats received intravesical saline (control), thrombin, or thrombin +2% lidocaine (to block nerve activity) for 1 hr, intraluminal fluid was collected and MIF amounts determined by ELISA. Bladder or UROtsa MIF mRNA was measured using real time RT-PCR.

Results

UROtsa cells constitutively express MIF and PAR1 and immunostaining for both was observed in these cells and in the basal and intermediate layers of rat urothelium. Thrombin stimulation of urothelial cells resulted in a concentration- and time-dependent increase in MIF release both in vitro (UROtsa; 2.8-fold increase at 1 hr) and in vivo (rat; 4.5-fold) while heat-inactivated thrombin had no effect. In rats, thrombin-induced MIF release was reduced but not abolished by intravesical lidocaine treatment. Thrombin also upregulated MIF mRNA in UROtsa cells (3.3-fold increase) and in the rat bladder (2-fold increase) where the effect was reduced (1.4-fold) by lidocaine treatment.

Conclusions

Urothelial cells express both MIF and PAR1. Activation of urothelial PAR1 receptors, either by locally generated thrombin or proteases present in the urine, may mediate bladder inflammation by inducing urothelial MIF release and upregulating urothelial MIF expression.

GRP78 signaling hub a receptor for targeted tumor therapy

Glucose-regulated protein 78 (GRP78) is a potential receptor for targeting therapy in cancer and chronic vascular disease due to its overexpression at the cell surface in tumor cells and in atherosclerotic lesions. Presence of the GRP78 autoantibody in cancer patient sera is generally associated with poor prognosis since it signals a prosurvival mechanism in response to cellular stress. Association of GRP78 with various binding partners involves coordination of multiple signaling pathways that result in either cell survival or cell death. Binding of activated alpha2-macroglobulin to cell-surface GRP78 activates Akt to suppress apoptotic pathways through multiple downstream effectors, and concomitantly upregulates NF-kappaBeta and induces the unfolded protein response (UPR) so that cell proliferation prevails. Interaction of GRP78 with cell-surface T-cadherin promotes endothelial cell survival. Association of oncogenic Cripto with GRP78 nullifies TGF-beta superfamily-dependent signaling through Smad2/3 to promote cell proliferation. In contrast, association of GRP78 with the plasminogen kringle 5 domain or extracellular Par-4 promotes apoptosis. Interaction of GRP78 with microplasminogen induces the UPR while association with tissue factor inhibits procoagulant activity. The diverse and multiple binding proteins of GRP78 and their equally diverse functional outcomes reflect the regulatory cellular functions that GRP78 orchestrates. Several GRP78 targeting peptides have been isolated from different tumors and they show remarkable tumor specificity. Conjugation of GRP78-targeting peptides to an apoptosis-inducing peptide suppresses tumor growth in tumor xenografts, thereby demonstrating that GRP78 is a viable target by which clinical cancer therapies can be successfully developed as well as its potential utility in treating vascular disease.