Rho GTPase-dependent signaling is required for macrophage migration inhibitory factor-mediated expression of cyclin D1

RhoA-ROCK2 signaling possesses complex pathophysiological functions in cancer progression and shows promising therapeutic potential

The Rho GTPase signaling pathway is responsible for cell-specific processes, including actin cytoskeleton organization, cell motility, cell division, and the transcription of specific genes. The implications of RhoA and the downstream effector ROCK2 in cancer epithelial-mesenchymal transition, migration, invasion, and therapy resistance associated with stem cells highlight the potential of targeting RhoA/ROCK2 signaling in therapy. Tumor relapse can occur due to cancer cells that do not fully respond to adjuvant chemoradiotherapy, targeted therapy, or immunotherapy. Rho signaling-mediated mitotic defects and cytokinesis failure lead to asymmetric cell division, allowing cells to form polyploids to escape cytotoxicity and promote tumor recurrence and metastasis. In this review, we elucidate the significance of RhoA/ROCK2 in the mechanisms of cancer progression and summarize their inhibitors that may improve treatment strategies.

Mechanism of Hypoxia-Mediated Smooth Muscle Cell Proliferation Leading to Vascular Remodeling

Vascular remodeling refers to changes in the size, contraction, distribution, and flow rate of blood vessels and even changes in vascular function. Vascular remodeling can cause cardiovascular and cerebrovascular diseases. It can also lead to other systemic diseases, such as pulmonary hypertension, pulmonary atherosclerosis, chronic obstructive pulmonary disease, stroke, and ascites of broilers. Hypoxia is one of the main causes of vascular remodeling. Prolonged hypoxia or intermittent hypoxia can lead to loss of lung ventilation, causing respiratory depression, irregular respiratory rhythms, and central respiratory failure. Animals that are unable to adapt to the highland environment are also prone to sustained constriction of the small pulmonary arteries, increased resistance to pulmonary circulation, and impaired blood circulation, leading to pulmonary hypertension and right heart failure if they live in a highland environment for long periods of time. However, limited studies have been found on the relationship between hypoxia and vascular remodeling. Therefore, this review will explore the relationship between hypoxia and vascular remodeling from the aspects of endoplasmic reticulum stress, mitochondrial dysfunction, abnormal calcium channel, disordered cellular metabolism, abnormal expression of miRNA, and other factors. This will help to understand the detailed mechanism of hypoxia-mediated smooth muscle cell proliferation and vascular remodeling for the better treatment and management of diseases due to vascular remodeling.

Macrophage migration inhibitory factor promotes the migration of dendritic cells through CD74 and the activation of the Src/PI3K/myosin II pathway

Constitutively expressed by innate immune cells, the cytokine macrophage migration inhibitory factor (MIF) initiates host immune responses and drives pathogenic responses in infectious, inflammatory, and autoimmune diseases. Dendritic cells (DCs) express high levels of MIF, but the role of MIF in DC function remains poorly characterized. As migration is critical for DC immune surveillance, we investigated whether MIF promoted the migration of DCs. In classical transwell experiments, MIF^-/- bone marrow-derived DCs (BMDCs) or MIF^+/+ BMDCs treated with ISO-1, an inhibitor of MIF, showed markedly reduced spontaneous migration and chemotaxis. CD74^-/- BMDCs that are deficient in the ligand-binding component of the cognate MIF receptor exhibited a migration defect similar to that of MIF^-/- BMDCs. Adoptive transfer experiments of LPS-matured MIF^+/+ and MIF^-/- and of CD74^+/+ and CD74^-/- BMDCs injected into the hind footpads of homologous or heterologous mice showed that the autocrine and paracrine MIF activity acting via CD74 contributed to the recruitment of DCs to the draining lymph nodes. Mechanistically, MIF activated the Src/PI3K signaling pathway and myosin II complexes, which were required for the migration of BMDCs. Altogether, these data show that the cytokine MIF exerts chemokine-like activity for DC motility and trafficking.

Macrophage migration inhibitory factor regulates integrin-β1 and cyclin D1 expression via ERK pathway in podocytes

AIMS

Macrophage migration inhibitory factor (MIF) is found to increase in proliferative glomerulonephritis. MIF binds to the MIF receptor (CD74) that activates MAP kinase (ERK and p38). Integrins and cyclinD1 regulate cell proliferation, differentiation and adhesion. This study evaluates whether MIF can regulate integrin-β1/cyclin D1 expression and cell adhesion of podocytes.

MAIN METHODS

Expression of integrin-β1 mRNA/protein and cyclin D1 mRNA under stimulation of MIF was evaluated by real-time PCR and Western blotting. MIF receptor (CD74) and MAP kinase under MIF treatment were examined to determine which pathway regulated integrin-β1 and cyclin D1 expression. Cell adhesion was evaluated under MIF treatment and/or anti-integrin-β1 antibody by cell adhesion assay.

KEY FINDINGS

Protein levels of integrin-β1 were up-regulated under MIF treatment in a dosage-dependent manner. CD74 protein levels were not changed after MIF treatment. Integrin-β1 and cyclin D1 mRNA levels were up-regulated after MIF 100 ng/ml treatment. ERK inhibitor U0126 reduced MIF-induced the increase in integrin-β1 mRNA and protein expression following MIF stimulation. However, p38 inhibitor SB 203580 did not inhibit MIF-induced increase in integrin-β1 mRNA and protein expression following MIF stimulation. MIF-induced increase in cyclin D1 mRNA level also was inhibited only by U0126 following MIF stimulation. Podocyte adhesion was increased after MIF treatment, but, anti-integrin-β1 antibody decreased MIF-enhanced podocyte adhesion.

SIGNIFICANCE

MIF increases integrin-β1 and cyclin D1 expression through the ERK pathway in podocytes, and the up-regulated expression of integrin-β1 increases podocyte adhesion. These results provide further understanding for the role of MIF in developing proliferative glomerulonephritis.

Effect of voluntary running on expression of myokines in brains of rats with depression

This study aimed to demonstrate the histopathology and immunoexpression of exercise-derived myokines in dentate gyrus (DG), medial prefrontal cortex (mPFC) and cerebellum of depressed Wistar rats during depression and after practising voluntary running. Depression was developed by forced swimming for 2 weeks. Voluntary running was performed by voluntary running for 3 weeks. Brain sections were processed and immunostained to detect brain-derived neurotrophic factor (BDNF), macrophage migration inhibitory factor (MIF), vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6). ImageJ software was used to measure the optical density (OD). BDNF was expressed in neurons in DG, mPFC and granular and Purkinje cells in cerebellum. MIF was expressed in neurons of sub-granular zone in DG, mPFC and Purkinje cells. VEGF was expressed in many neurons in DG, mPFC and Purkinje cells. IL-6 was expressed in some neurons in DG, in neuropil of mPFC and in Purkinje cells. In depression, the OD of studied myokines significantly decreased in all examined areas. After voluntary running, the OD of myokines significantly increased in all areas. This study defines the immunohistochemical expression of myokines in brain areas in depression and after voluntary running and reveals the involvement of the mPFC and cerebellum in the pathophysiology of depression.

Two macrophage migration inhibitory factors (MIFs) from the clam Ruditapes philippinarum: Molecular characterization, localization and enzymatic activities

Macrophage migration inhibitory factor (MIF) is an evolutionarily ancient cytokine-like factor and plays a critical role in both innate and adaptive immunity. In the present study, two MIFs (designed as RpMIF-1 and RpMIF-2, respectively) were identified and characterized from the clam Ruditapes philippinarum by rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of RpMIF-1 and RpMFI-2 consisted of 531 and 722 nucleotides, encoding a polypeptide of 113 and 114 amino acid residues, respectively. Multiple alignments and phylogenetic analysis revealed that both RpMIF-1 and RpMIF-2 belonged to the MIF family. The conserved catalytic-site Pro² for tautomerase activity was identified in the deduced amino acid sequences of RpMIFs. Both RpMIF-1 and RpMIF-2 transcripts were constitutively expressed in examined tissues of R. philippinarum with dominant expression in hepatopancreas, gills and hemocytes. Immunolocalization analysis showed that RpMIF-1 and RpMIF-2 proteins were expressed in examined tissues with the exception of adductor muscle and foot. After Vibrio anguillarum and Micrococcus luteus challenge, the mRNA expression of RpMIFs was significantly modulated in hemocytes, gills and hepatopancreas. Recombinant RpMIF-1 and RpMIF-2 proteins possessed significant tautomerase activity and oxidoreductase activity, indicating that these two proteins was perhaps involved in inflammatory responses. In summary, our results suggested that RpMIF-1 and RpMIF-2 played an important role in the innate immunity of R. philippinarum.

Macrophage migration inhibitory factor (MIF) in the development and progression of pulmonary arterial hypertension

Macrophage migration inhibitory factor (MIF) has been described as a pro-inflammatory cytokine and regulator of neuro-endocrine function. It plays an important upstream role in the inflammatory cascade by promoting the release of other inflammatory cytokines such as TNF-alpha and IL-6, ultimately triggering a chronic inflammatory immune response. As lungs can synthesize and release MIF, many studies have investigated the potential role of MIF as a biomarker in assessment of patients with pulmonary arterial hypertension (PAH) and using anti-MIFs as a new therapeutic modality for PAH.

Pathogenic role for macrophage migration inhibitory factor in glioblastoma and its targeting with specific inhibitors as novel tailored therapeutic approach

Macrophage Migration Inhibitory Factor (MIF) is a pro-inflammatory cytokine expressed by a variety of cell types. Although MIF has been primarily studied for its role in the pathogenesis of autoimmune diseases, it has also been shown to promote tumorigenesis and it is over expressed in various malignant tumors. MIF is able to induce angiogenesis, cell cycle progression, and to block apoptosis. As tailored therapeutic approaches for the inhibition of endogenous MIF are being developed, it is important to evaluate the role of MIF in individual neoplastic conditions that may benefit from specific MIF inhibitors. Along with this line, in this paper, we have reviewed the evidence of the involvement of MIF in the etiopathogenesis and progression of glioblastoma and the preclinical data suggesting the possible use of specific MIF inhibition as a potential novel therapeutic strategy for brain tumors.

Oxidized macrophage migration inhibitory factor is a potential new tissue marker and drug target in cancer

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine, which was shown to be upregulated in cancers and to exhibit tumor promoting properties. Unlike other cytokines, MIF is ubiquitously present in the circulation and tissue of healthy subjects. We recently described a previously unrecognized, disease-related isoform of MIF, designated oxMIF, which is present in the circulation of patients with different inflammatory diseases. In this article, we report that oxMIF is also linked to different solid tumors as it is specifically expressed in tumor tissue from patients with colorectal, pancreatic, ovarian and lung cancer. Furthermore, oxMIF can be specifically targeted by a subset of phage display-derived fully human, monoclonal anti-MIF antibodies (mAbs) that were shown to neutralize pro-tumorigenic activities of MIF in vivo. We further demonstrate that anti-oxMIF mAbs sensitize human cancer cell lines (LNCaP, PC3, A2780 and A2780ADR) to the action of cytotoxic drugs (mitoxantrone, cisplatin and doxorubicin) in vitro and in an A2780 xenograft mouse model of ovarian cancer. We conclude that oxMIF is the disease related isoform of MIF in solid tumors and a potential new diagnostic marker and drug target in cancer.

Invariant Chain Complexes and Clusters as Platforms for MIF Signaling

Invariant chain (Ii/CD74) has been identified as a surface receptor for migration inhibitory factor (MIF). Most cells that express Ii also synthesize major histocompatibility complex class II (MHC II) molecules, which depend on Ii as a chaperone and a targeting factor. The assembly of nonameric complexes consisting of one Ii trimer and three MHC II molecules (each of which is a heterodimer) has been regarded as a prerequisite for efficient delivery to the cell surface. Due to rapid endocytosis, however, only low levels of Ii-MHC II complexes are displayed on the cell surface of professional antigen presenting cells and very little free Ii trimers. The association of Ii and MHC II has been reported to block the interaction with MIF, thus questioning the role of surface Ii as a receptor for MIF on MHC II-expressing cells. Recent work offers a potential solution to this conundrum: Many Ii-complexes at the cell surface appear to be under-saturated with MHC II, leaving unoccupied Ii subunits as potential binding sites for MIF. Some of this work also sheds light on novel aspects of signal transduction by Ii-bound MIF in B-lymphocytes: membrane raft association of Ii-MHC II complexes enables MIF to target Ii-MHC II to antigen-clustered B-cell-receptors (BCR) and to foster BCR-driven signaling and intracellular trafficking.

MIF allele-dependent regulation of the MIF coreceptor CD44 and role in rheumatoid arthritis

Fibroblast-like synoviocytes mediate joint destruction in rheumatoid arthritis and exhibit sustained proinflammatory and invasive properties. CD44 is a polymorphic transmembrane protein with defined roles in matrix interaction and tumor invasion that is also a signaling coreceptor for macrophage migration inhibitory factor (MIF), which engages cell surface CD74. High-expression MIF alleles (rs5844572) are associated with rheumatoid joint erosion, but whether MIF signaling through the CD74/CD44 receptor complex promotes upstream autoimmune responses or contributes directly to synovial joint destruction is unknown. We report here the functional regulation of CD44 by an autocrine pathway in synovial fibroblasts that is driven by high-expression MIF alleles to up-regulate an inflammatory and invasive phenotype. MIF increases CD44 expression, promotes its recruitment into a functional signal transduction complex, and stimulates alternative exon splicing, leading to expression of the CD44v3-v6 isoforms associated with oncogenic invasion. CD44 recruitment into the MIF receptor complex, downstream MAPK and RhoA signaling, and invasive phenotype require MIF and CD74 and are reduced by MIF pathway antagonists. These data support a functional role for high-MIF expression alleles and the two-component CD74/CD44 MIF receptor in rheumatoid arthritis and suggest that pharmacologic inhibition of this pathway may offer a specific means to interfere with progressive joint destruction.

Matrine inhibits diethylnitrosamine-induced HCC proliferation in rats through inducing apoptosis via p53, Bax-dependent caspase-3 activation pathway and down-regulating MLCK overexpression

The proliferation of hepatocellular carcinoma (HCC) cells is one of the leading causes of liver cancer mortality in humans. The inhibiting effects of matrine on HCC cell proliferation have been studied, but the mechanism of that inhibition has not been fully elucidated. Since, apoptosis plays an important role in HCC cell proliferation. We examined the apoptosis-inducing effect of matrine on tumor cells. Western blot analysis of p53, Bax, cleaved caspase-3 and myosin light chain kinase (MLCK) revealed that matrine induced tumor cell apoptosis by controlling anoikis. It activated p53, Bax-dependent caspase-3 and blocked the ECM-integrin mediated cell survival pathway through down-regulating MLCK over-expression in the liver of rats with diethyl nitrosamine (DENA)-induced HCC. Our results suggest that matrine can inhibit the proliferation of HCC cells through inducing tumor cell apoptosis via activation of the p53 pathway and inhibition of MLCK overexpression. Matrine may thus be used as a potentially promising reagent to inhibit HCC cell proliferation and MLCK may be a novel target for the treatment of HCC.

Small interfering RNA (siRNA)-mediated knockdown of macrophage migration inhibitory factor (MIF) suppressed cyclin D1 expression and hepatocellular carcinoma cell proliferation

Macrophage migration inhibitory factor (MIF), a proinflammatory and immunoregulatory chemokine, plays important roles in cancer-related biological processes. However, few studies have focused on the clinical relevance of MIF and cyclin D1 expression in hepatocellular carcinoma cells (HCCs). In this study, MIF and cyclin D1 expression levels in HCC tissues and cell lines were significantly upregulated compared with adjacent normal tissues or a normal liver cell line. In HCC specimens, MIF expression positively correlated with cyclin D1 expression. Additionally, MIF and cyclin D1 expression positively correlated with tumor size. MIF knockdown inhibited the proliferation of PLC and HepG2 cells and promoted apoptosis. However, small interfering RNA (siRNA) against MIF did not influence the cell cycle in these cells. In an in vivo xenograft model, MIF knockdown reduced the tumor growth rate. The expression levels of Bcl-2, p-caspase-3, BIM and Bax were upregulated, while the expression levels of cyclin D1, p-Akt and p-ERK were downregulated in MIF-knockdown cells. These findings indicate that MIF siRNA reduces proliferation and increases apoptosis in HCC cells. MIF knockdown inhibits the expression of growth-related proteins and induces the expression of apoptosis-related proteins, supporting a role for MIF as a novel therapeutic target for HCC.

Phenotypes of trypsin- and collagenase-prepared bovine corneal endothelial cells in the presence of a selective Rho kinase inhibitor, Y-27632

PURPOSE

To optimize isolation of viable bovine corneal endothelial cells (BCECs), we evaluated the effectiveness of various preparation protocols. This entailed comparing the effects of collagenase A and trypsin in the presence and absence of a Rho kinase inhibitor, Y-27632, on proliferation and tight junctional and cytoskeletal integrity during their expansion.

METHODS

5-bromo-2'-deoxyuridine (BrdU) incorporation evaluated cell proliferation. Western blot analysis evaluated F-actin, zonule occludin, and ZO-1 associated nucleic acid binding protein (ZONAB) and RhoA expression. Rho A pulldown assay evaluated Rho A activity.

RESULTS

In the trypsin (TrypLE)-prepared BCECs, BrdU incorporation decreased whereas nuclear ZONAB expression increased and became stable from day 3 to 7. In contrast, in the collagenase-A-prepared BCECs, we observed preserved ZO-1 integrity, invariant nuclear ZONAB expression, and dense cortical F-actin expression, and BrdU incorporation was invariant from days 1 to 7. Y-27632 did not increase BrdU incorporation and nuclear ZONAB expression in the TrypLE-prepared and the collagenase-A-prepared BCECs. Moreover, Y-27632 increased irregular cellular morphology and downregulated the expression of ZO-1 in the collagenase-A-prepared BCECs from days 1 to 7. Y-27632 inhibited RhoA activation irrespective of whether the cells were isolated with trypsin or collagenase A.

CONCLUSIONS

It is preferable to isolate BCECs with collagenase A and expand them without Y-27632. With this protocol, proliferative activity and tight junctional and cytoskeletal integrity are better preserved than if trypsin is used in the presence or absence of Y-27632.

Stromal-dependent tumor promotion by MIF family members

Solid tumors are composed of a heterogeneous population of cells that interact with each other and with soluble and insoluble factors that, when combined, strongly influence the relative proliferation, differentiation, motility, matrix remodeling, metabolism and microvessel density of malignant lesions. One family of soluble factors that is becoming increasingly associated with pro-tumoral phenotypes within tumor microenvironments is that of the migration inhibitory factor family which includes its namesake, MIF, and its only known family member, D-dopachrome tautomerase (D-DT). This review seeks to highlight our current understanding of the relative contributions of a variety of immune and non-immune tumor stromal cell populations and, within those contexts, will summarize the literature associated with MIF and/or D-DT.

MIF inhibits monocytic movement through a non-canonical receptor and disruption of temporal Rho GTPase activities in U-937 cells

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine that was initially identified by its ability to inhibit the movement of macrophages. Cell migration is a highly complex process involving changes to the cytoskeleton and cell adhesion molecules, and is regulated by the Rho GTPases. A simple model using human monocytic U-937 cells to elicit the classic MIF response was implemented to examine the mechanism of MIF-induced migration inhibition. Our results demonstrate that MIF inhibits migration of these U-937 cells through a non-canonical receptor, CXCR4, in the absence of the putative primary MIF receptor CD74. Migration inhibition is dependent upon a series of temporal perturbations of the activities of the Rho GTPases: initial activation followed by subsequent inactivation of RhoA, inactivation of Rac1, and cyclic activation of Cdc42. MIF-mediated changes in the activities of the Rho GTPases jointly contributed to migration inhibition in these cells. Collectively, these data suggest that the MIF-mediated migration inhibition is mediated by the outcome of G-protein signaling, and in less adherent cells such as those of the monocyte/macrophage lineage, RhoA directly affects net translocation through its ability to induce cell body contraction. These findings demonstrate that CXCR4 can mediate MIF signaling in the absence of CD74 in addition to serving as a MIF co-receptor along with CD74. These results correlate MIF activity to specific and sequential Rho GTPase activity perturbations, and given that CXCR4 functions in numerous processes, suggests potential roles for the modulation of cell movement in those events including development, cell survival and viral infection.

MIF: mood improving/inhibiting factor?

Although major depressive disorder imposes a serious public health burden and affects nearly one in six individuals in developed countries over their lifetimes, there is still no consensus on its pathophysiology. Inflammation and cytokines have emerged as a promising new avenue in depression research, and, in particular, macrophage migration inhibitory factor (MIF) has been shown to be significant in depression physiology. In this review we summarize current research on MIF and depression. We highlight the arguments for MIF as a pro- and antidepressant species and discuss the potential implications for therapeutics.

Kidney protection against ischemia/reperfusion injury by myofibrillogenesis regulator-1

BACKGROUND/AIMS

Ischemia/reperfusion (I/R) injury is characterized by cytoskeletal reorganization and loss of polarity in proximal tubule epithelial cells. Previously, we showed that myofibrillogenesis regulator (MR)-1 promoted actin organization in cardiomyocytes. MR-1 is also expressed in the kidney.

METHODS

In this study, we investigated MR-1 expression in acute renal failure induced by I/R in Sprague-Dawley rats. We determined the MR-1 expression and the ratio of fibrous actin (F-actin) to globular actin (G-actin). HK-2 cells were treated with or without hypoxia/reoxygenation (H/R), and MR-1 levels were increased by adenoviral overexpression or silenced by RNA interference.

RESULTS

I/R and H/R resulted in cellular injury and decreases of MR-1, the F-/G-actin ratio, and myosin light chain (MLC)-2. MR-1 overexpression attenuated H/R-induced cell injury and loss of surface membrane polarity of actin. MR-1 overexpression also increased the expression and phosphorylation of MLC-2 and MLC kinase, which were decreased in MR-1-silenced and H/R-treated cells.

CONCLUSION

Together, these data show that MR-1 promoted actin polarity on the membrane surface and protected HK-2 cells from H/R injury. The mechanism might involve the rapid organization of F-actin through the upregulation and phosphorylation of MLC-2.

SUMOylation of RhoGDIα is required for its repression of cyclin D1 expression and anchorage-independent growth of cancer cells

Selective activation of Rho GTPase cascade requires the release of Rho from RhoGDI (GDP-dissociation inhibitors) complexes. Our previous studies identified RhoGDIα SUMOylation at Lys-138 and its function in the regulation of cancer cell invasion. In the current study, we demonstrate that RhoGDIα SUMOylation has a crucial role in the suppression of cancer cell anchorage-independent growth as well as the molecular mechanisms underlying this suppression. We found that ectopic expression of RhoGDIα resulted in marked inhibition of an anchorage-independent growth with induction of G0/G1 cell cycle arrest, while point mutation of RhoGDIα SUMOylation at residue Lys-138 (K138R) abrogated this growth suppression and G0/G1 cell cycle arrest in cancer cells. Further studies showed that SUMOylation at Lys-138 was critical for RhoGDIα down-regulation of cyclin D1 protein expression and that MEK1/2-Erk was a specific downstream target of SUMOylated RhoGDIα for its inhibition of C-Jun/AP-1 cascade, cyclin d1 transcription, and cell cycle progression. These results strongly demonstrate that SUMOylated RhoGDIα suppressed C-Jun/AP-1-dependent transactivation specifically via targeting MEK1/2-Erk, subsequently leading to the down-regulation of cyclin D1 expression and anti-cancer activity. Our results provide new mechanistic insights into the understanding of essential role of SUMOylation at Lys-138 in RhoGDIα's biological function.

Arrest Functions of the MIF Ligand/Receptor Axes in Atherogenesis

Macrophage migration inhibitory factor (MIF) has been defined as an important chemokine-like function (CLF) chemokine with an essential role in monocyte recruitment and arrest. Adhesion of monocytes to the vessel wall and their transendothelial migration are critical in atherogenesis and many other inflammatory diseases. Chemokines carefully control all steps of the monocyte recruitment process. Those chemokines specialized in controlling arrest are typically immobilized on the endothelial surface, mediating the arrest of rolling monocytes by chemokine receptor-triggered pathways. The chemokine receptor CXCR2 functions as an important arrest receptor on monocytes. An arrest function has been revealed for the bona fide CXCR2 ligands CXCL1 and CXCL8, but genetic studies also suggested that additional arrest chemokines are likely to be involved in atherogenic leukocyte recruitment. While CXCR2 is known to interact with numerous CXC chemokine ligands, the CLF chemokine MIF, which structurally does not belong to the CXC chemokine sub-family, was surprisingly identified as a non-cognate ligand of CXCR2, responsible for critical arrest functions during the atherogenic process. MIF was originally identified as macrophage migration inhibitory factor (this function being eponymous), but is now known as a potent inflammatory cytokine with CLFs including chemotaxis and leukocyte arrest. This review will cover the mechanisms underlying these functions, including MIF’s effects on LFA1 integrin activity and signal transduction, and will discuss the structural similarities between MIF and the bona fide CXCR2 ligand CXCL8 while emphasizing the structural differences. As MIF also interacts with CXCR4, a chemokine receptor implicated in CXCL12-elicited lymphocyte arrest, the arrest potential of the MIF/CXCR4 axis will also be scrutinized as well as the recently identified role of pericyte MIF in attracting leukocytes exiting through venules as part of the pericyte “motility instruction program.”

Homotrimeric macrophage migration inhibitory factor (MIF) drives inflammatory responses in the corneal epithelium by promoting caveolin-rich platform assembly in response to infection

Acute inflammation that arises during Pseudomonas aeruginosa-induced ocular infection can trigger tissue damage resulting in long term impairment of visual function, suggesting that the appropriate treatment strategy should include the use of anti-inflammatory agents in addition to antibiotics. We recently identified a potential target for modulation during ocular infection, macrophage migration inhibitory factor (MIF). MIF deficiency protected mice from inflammatory-mediated corneal damage resulting from acute bacterial keratitis. To gain a better understanding of the molecular mechanisms of MIF activity, we analyzed the oligomeric states and functional properties of MIF during infection. We found that in human primary corneal cells infected with P. aeruginosa, MIF is primarily in a homotrimeric state. Homotrimeric MIF levels correlated with the severity of infection in the corneas of infected mice, suggesting that the MIF homotrimers were the functionally active form of MIF. During infection, human primary corneal cells released more IL-8 when treated with recombinant, locked MIF trimers than when treated with lower MIF oligomers. MIF promoted P. aeruginosa-induced IL-8 responses via the formation of caveolin-1-rich "signaling hubs" in the corneal cells that led to elevated MAPK p42/p44 activation and sustained inflammatory signaling. These findings suggest that inhibiting homotrimerization of MIF or the functional activities of MIF homotrimers could have therapeutic benefits during ocular inflammation.

Small interfering RNA-mediated MIF knockdown reduces cell invasion in murine colorectal cancer cell line CT-26

AIM: To investigate the effect of small interfering RNA (siRNA)-mediated knockdown of the macrophage migration-inhibitory factor (MIF) gene on cell invasion in murine colorectal cancer cell line CT-26 and to explore possible mechanisms involved.

METHODS: CT-26 cells were divided into three groups: experimental group, control group, and blank group. The experimental group and control group were treated with a siRNA specific for the MIF gene (MIF siRNA) and a nonspecific siRNA, respectively, while the blank group was not treated with any agent. Transwell assay was used to determine cell invasion. ELISA was used to determine the level of MIF protein in cell supernatants, and the expression of MIF, CD74, tiam1 and E-cadherin mRNAs was detected by RT-PCR.

RESULTS: Twenty-four hours after treatment, cell invasion was significantly inhibited and the level of MIF protein in supernatants significantly declined in the experimental group compared to the control and blank groups (P = 0.012, 0.020). Compared to the control and blank groups, the expression of MIF, CD74 and tiam1 mRNAs decreased significantly and that of E-cadherin mRNA increased significantly (P_E-Cadherin = 0.001) in the experimental group. In addition, the levels of MIF and CD74 proteins significantly declined in the experimental group compared to the control and the blank groups (P_MIF = 0.006; P_CD74 = 0.016).

CONCLUSION: MIF siRNA inhibits the invasion of CT-26 cells possibly by down-regulating the expression of MIF, CD74 and tiam1 and up-regulating the expression of E-cadherin.

Macrophage migration inhibitory factor deficiency is associated with impaired killing of gram-negative bacteria by macrophages and increased susceptibility to Klebsiella pneumoniae sepsis

The cytokine macrophage migration inhibitory factor (MIF) is an important component of the early proinflammatory response of the innate immune system. However, the antimicrobial defense mechanisms mediated by MIF remain fairly mysterious. In the present study, we examined whether MIF controls bacterial uptake and clearance by professional phagocytes, using wild-type and MIF-deficient macrophages. MIF deficiency did not affect bacterial phagocytosis, but it strongly impaired the killing of gram-negative bacteria by macrophages and host defenses against gram-negative bacterial infection, as shown by increased mortality in a Klebsiella pneumonia model. Consistent with MIF's regulatory role of Toll-like 4 expression in macrophages, MIF-deficient cells stimulated with lipopolysaccharide or Escherichia coli exhibited reduced nuclear factor κB activity and tumor necrosis factor (TNF) production. Addition of recombinant MIF or TNF corrected the killing defect of MIF-deficient macrophages. Together, these data show that MIF is a key mediator of host responses against gram-negative bacteria, acting in part via a modulation of bacterial killing by macrophages.

Focal adhesion disassembly is regulated by a RIAM to MEK-1 pathway

Cell migration and invasion require regulated turnover of integrin-dependent adhesion complexes. Rap1-GTP-interacting adaptor molecule (RIAM) is an adaptor protein that mediates talin recruitment to the cell membrane, and whose depletion leads to defective melanoma cell migration and invasion. In this study, we investigated the potential involvement of RIAM in focal adhesion (FA) dynamics. RIAM-depleted melanoma and breast carcinoma cells displayed an increased number, size and stability of FAs, which accumulated centrally at the ventral cell surface, a phenotype caused by defective FA disassembly. Impairment in FA disassembly resulting from RIAM knockdown correlated with deficient integrin-dependent mitogen-activated protein kinase kinase (MEK)-Erk1/2 activation and, importantly, overexpression of constitutively active MEK resulted in rescue of FA disassembly and recovery of cell invasion. Furthermore, RIAM-promoted Ras homologue gene family, member A (RhoA) activation following integrin engagement was needed for subsequent Erk1/2 activation. In addition, RhoA overexpression partially rescued the FA phenotype in RIAM-depleted cells, also suggesting a functional role for RhoA downstream of RIAM, but upstream of Erk1/2. RIAM knockdown also led to enhanced phosphorylation of paxillin Tyr118 and Tyr31. However, expression of phosphomimetic and nonphosphorylatable mutants at these paxillin residues indicated that paxillin hyperphosphorylation is a subsequent consequence of the blockade of FA disassembly, but does not cause the FA phenotype. RIAM depletion also weakened the association between FA proteins, suggesting that it has important adaptor roles in the correct assembly of adhesion complexes. Our data suggest that integrin-triggered, RIAM-dependent MEK activation represents a key feedback event required for efficient FA disassembly, which could help explain the role of RIAM in cell migration and invasion.

Macrophage migration inhibitory factor mediates hypoxia-induced pulmonary hypertension

Pulmonary hypertension (PH) is a devastating disease leading to progressive hypoxemia, right ventricular failure, and death. Hypoxia can play a pivotal role in PH etiology, inducing pulmonary vessel constriction and remodeling. These events lead to increased pulmonary vessel wall thickness, elevated vascular resistance and right ventricular hypertrophy. The current study examined the association of the inflammatory cytokine macrophage migration inhibitory factor (MIF) with chronic lung disease and its role in the development of hypoxia-induced PH. We found that plasma MIF in patients with primary PH or PH secondary to interstitial lung disease (ILD) was significantly higher than in the control group (P = 0.004 and 0.007, respectively). MIF involvement with hypoxia-induced fibroblast proliferation was examined in both a human cell-line and primary mouse cells from wild-type (mif⁺/⁺) and MIF-knockout (mif⁻/⁻) mice. In vitro, hypoxia-increased MIF mRNA, extracellular MIF protein accumulation and cell proliferation. Inhibition of MIF inflammatory activity reduced hypoxia-induced cell proliferation. However, hypoxia only increased proliferation of mif⁻/⁻ cells when they were supplemented with media from mif⁺/⁺ cells. This growth increase was suppressed by MIF inhibition. In vivo, chronic exposure of mice to a normobaric atmosphere of 10% oxygen increased lung tissue expression of mRNA encoding MIF and accumulation of MIF in plasma. Inhibition of the MIF inflammatory active site, during hypoxic exposure, significantly reduced pulmonary vascular remodeling, cardiac hypertrophy and right ventricular systolic pressure. The data suggest that MIF plays a critical role in hypoxia-induced PH, and its inhibition may be beneficial in preventing the development and progression of the disease.

Transcriptional profile of GTP-mediated differentiation of C2C12 skeletal muscle cells

Several purine receptors have been localised on skeletal muscle membranes. Previous data support the hypothesis that extracellular guanosine 5'-triphosphate (GTP) is an important regulatory factor in the development and function of muscle tissue. We have previously described specific extracellular binding sites for GTP on the plasma membrane of mouse skeletal muscle (C2C12) cells. Extracellular GTP induces an increase in intracellular Ca(2+) concentrations that results in membrane hyperpolarisation through Ca(2+)-activated K(+) channels, as has been demonstrated by patch-clamp experiments. This GTP-evoked increase in intracellular Ca(2+) is due to release of Ca(2+) from intracellular inositol-1,4,5-trisphosphate-sensitive stores. This enhances the expression of the myosin heavy chain in these C2C12 myoblasts and commits them to fuse into multinucleated myotubes, probably via a phosphoinositide-3-kinase-dependent signal-transduction mechanism. To define the signalling of extracellular GTP as an enhancer or modulator of myogenesis, we investigated whether the gene-expression profile of differentiated C2C12 cells (4 and 24 h in culture) is affected by extracellular GTP. To investigate the nuclear activity and target genes modulated by GTP, transcriptional profile analysis and real-time PCR were used. We demonstrate that in the early stages of differentiation, GTP up-regulates genes involved in different pathways associated with myogenic processes, including cytoskeleton structure, the respiratory chain, myogenesis, chromatin reorganisation, cell adhesion, and the Jak/Stat pathway, and down-regulates the mitogen-activated protein kinase pathway. GTP also increases the expression of three genes involved in myogenesis, Pp3ca, Gsk3b, and Pax7. Our data suggests that in the myogenic C2C12 cell line, extracellular GTP acts as a differentiative factor in the induction and sustaining of myogenesis.

Loss of macrophage migration inhibitory factor impairs the growth properties of human HeLa cervical cancer cells

OBJECTIVES

  This study aims to determine the role of macrophage migration inhibitory factor (MIF), a proinflammatory cytokine associated with cell proliferation and tumour growth in vivo.

MATERIALS AND METHODS

  Our team used RNA interference technology to knock down MIF expression in human HeLa cervical cancer cells and to establish a stable cell line lacking MIF function.

RESULTS

  Our results showed that long-term loss of MIF had little effect on cell morphology, but significantly inhibited their population growth and proliferation. The HeLa MIF-knockdown cells retained normal apoptotic signalling pathways in response to TNF-alpha treatment; however, they exhibited unique DNA profiles following doxorubicin treatment, suggesting that MIF may regulate a cell cycle checkpoint upon DNA damage. Our data also showed that knockdown of MIF expression in HeLa cells led to increased cell adhesion and therefore impaired their migratory capacity. More importantly, cells lacking MIF failed to either proliferate in soft agar or form tumours in vivo, when administered to nude mice.

CONCLUSION

  MIF plays a pivotal role in proliferation and tumourigenesis of human HeLa cervical carcinoma cells, and may represent a promising therapeutic target for cancer intervention.

Ectopic expression of CD74 in Ikkβ-deleted mouse hepatocytes

CD74, a Type II membrane glycoprotein and MHC class II chaperone involved in antigen processing, is normally expressed by cells associated with the immune system. CD74 also forms heterodimers with CD44 to generate receptors to macrophage migration inhibitory factor (MIF), a proinflammatory cytokine. Following targeted Alb-Cre-mediated deletion of Ikkβ in Ikkβ(Δhep) mice (Ikkβ(F/F):Alb-Cre, a strain highly susceptible to chemically induced hepatotoxicity and hepatocarcinogenesis), CD74 is expressed abundantly by adult hepatocytes throughout liver acini, albeit more intensely in midzonal-to-centrilobular regions. By comparison, CD74 expression is not observed in Ikkβ(F/F) hepatocytes, nor is it augmented in the livers of Ikkβ(+/+):Alb-Cre mice; CD74 is barely detectable in cultured embryonic fibroblasts from Ikkβ(-/-) mice. Microarray profiling shows that constitutive CD74 expression in Ikkβ(Δhep) hepatocytes is accompanied by significantly augmented expression of CD44 and key genes associated with antigen processing and host defense, including MHC class II I-Aα, I-Aβ, and I-Eβ chains, CIITA and CD86. Taken together, these observations suggest that Ikkβ(Δhep) hepatocytes might express functional capacities for class II-restricted antigen presentation and heightened responsiveness to MIF-signaling, and also suggest further roles for intrahepatocellular IKKβ in the suppression or inactivation of molecules normally associated with the formation and differentiation of cells of the immune system.

Macrophage migration inhibitory factor regulates neutrophil chemotactic responses in inflammatory arthritis in mice

OBJECTIVE

Macrophage migration inhibitory factor (MIF) facilitates multiple aspects of inflammatory arthritis, the pathogenesis of which has been significantly linked to the activity of neutrophils. The effects of MIF on neutrophil recruitment are unknown. This study was undertaken to investigate the contribution of MIF to the regulation of neutrophil chemotactic responses.

METHODS

K/BxN serum-transfer arthritis was induced in wild-type (WT), MIF(-/-) , and monocyte chemotactic protein 1 (MCP-1; CCL2)-deficient mice as well as in WT mice treated with monoclonal antibodies to cytokine-induced neutrophil chemoattractant (anti-KC). Leukocyte trafficking in vivo was examined using intravital microscopy, and neutrophil function in vitro was examined using migration chambers and assessment of MAP kinase activation.

RESULTS

K/BxN serum-transfer arthritis was markedly attenuated in MIF(-/-) mice, with reductions in the clinical and histologic severity of arthritis and the synovial expression of KC and interleukin-1. Arthritis was also reduced by anti-KC antibody treatment, but not in MCP-1-deficient mice. In vivo, neutrophil recruitment responses to KC were reduced in MIF(-/-) mice. Similarly, MIF(-/-) mouse neutrophils exhibited reduced chemotactic responses to KC in vitro, despite displaying unaltered chemokine receptor expression. Reduced chemotactic responses of MIF(-/-) mouse neutrophils were associated with reduced phosphorylation of p38 and ERK MAP kinases.

CONCLUSION

These findings suggest that MIF promotes neutrophil trafficking in inflammatory arthritis via facilitation of chemokine-induced migratory responses and MAP kinase activation. Therapeutic MIF inhibition could limit synovial neutrophil recruitment.

Macrophage migration inhibitory factor is critically involved in basal and fluoxetine-stimulated adult hippocampal cell proliferation and in anxiety, depression, and memory-related behaviors

Intensive research is devoted to unravel the neurobiological mechanisms mediating adult hippocampal neurogenesis, its regulation by antidepressants, and its behavioral consequences. Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine that is expressed in the CNS, where its function is unknown. Here, we show, for the first time, the relevance of MIF expression for adult hippocampal neurogenesis. We identify MIF expression in neurogenic cells (in stem cells, cells undergoing proliferation, and in newly proliferated cells undergoing maturation) in the subgranular zone of the rodent dentate gyrus. A causal function for MIF in cell proliferation was shown using genetic (MIF gene deletion) and pharmacological (treatment with the MIF antagonist Iso-1) approaches. Behaviorally, genetic deletion of MIF resulted in increased anxiety- and depression-like behaviors, as well as of impaired hippocampus-dependent memory. Together, our studies provide evidence supporting a pivotal function for MIF in both basal and antidepressant-stimulated adult hippocampal cell proliferation. Moreover, loss of MIF results in a behavioral phenotype that, to a large extent, corresponds with alterations predicted to arise from reduced hippocampal neurogenesis. These findings underscore MIF as a potentially relevant molecular target for the development of treatments linked to deficits in neurogenesis, as well as to problems related to anxiety, depression, and cognition.

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.

β-Arrestin1 mediates the endocytosis and functions of macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine, regulating inflammatory and immune responses. MIF binds to cell surface receptor CD74, resulting in both rapid and sustained ERK activation. It was reported that MIF-induced rapid ERK activation requires its co-receptor CD44. But the exact mechanism underlying sustained ERK activation is not well understood. In the current study, we described a detailed mechanism of MIF mediated sustained ERK activation. We found that β-arrestin1, a scaffold protein involved in the activation of the MAPK cascade, interacts with CD74 upon MIF stimulation, resulting in CD74-mediated MIF endocytosis in a chlorpromazine (CPZ)-sensitive manner. β-arrestin1 is also involved in endocytotic MIF signaling, leading to sustained ERK activation. Therefore β-arrestin1 plays a central role in coupling MIF endocytosis to sustained ERK activation.

A small-molecule macrophage migration inhibitory factor antagonist protects against glomerulonephritis in lupus-prone NZB/NZW F1 and MRL/lpr mice

Autoimmunity leads to the activation of innate effector pathways, proinflammatory cytokine production, and end-organ injury. Macrophage migration inhibitory factor (MIF) is an upstream activator of the innate response that mediates the recruitment and retention of monocytes via CD74 and associated chemokine receptors, and it has a role in the maintenance of B lymphocytes. High-expression MIF alleles also are associated with end-organ damage in different autoimmune diseases. We assessed the therapeutic efficacy of (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1), an orally bioavailable MIF antagonist, in two distinct models of systemic lupus erythematosus: the NZB/NZW F1 and the MRL/lpr mouse strains. ISO-1, like anti-MIF, inhibited the interaction between MIF and its receptor, CD74, and in each model of disease, it reduced functional and histological indices of glomerulonephritis, CD74(+) and CXCR4(+) leukocyte recruitment, and proinflammatory cytokine and chemokine expression. Neither autoantibody production nor T and B cell activation were significantly affected, pointing to the specificity of MIF antagonism in reducing excessive proinflammatory responses. These data highlight the feasibility of targeting the MIF-MIF receptor interaction by small-molecule antagonism and support the therapeutic value of downregulating MIF-dependent pathways of tissue damage in systemic lupus erythematosus.

The deubiquitinating enzyme USP17 is highly expressed in tumor biopsies, is cell cycle regulated, and is required for G1-S progression

Ubiquitination is a reversible posttranslational modification that is essential for cell cycle control, and it is becoming increasingly clear that the removal of ubiquitin from proteins by deubiquitinating enzymes (DUB) is equally important. In this study, we have identified high levels of the DUB USP17 in several tumor-derived cell lines and primary lung, colon, esophagus, and cervix tumor biopsies. We also report that USP17 is tightly regulated during the cell cycle in all the cells examined, being abundantly evident in G(1) and absent in S phase. Moreover, regulated USP17 expression was necessary for cell cycle progression because its depletion significantly impaired G(1)-S transition and blocked cell proliferation. Previously, we have shown that USP17 regulates the intracellular translocation and activation of the GTPase Ras by controlling Ras-converting enzyme 1 (RCE1) activation. RCE1 also regulates the processing of other proteins with a CAAX motif, including Rho family GTPases. We now show that USP17 depletion blocks Ras and RhoA localization and activation. Moreover, our results confirm that USP17-depleted cells have constitutively elevated levels of the cyclin-dependent kinase inhibitors p21(cip1) and p27(kip1), known downstream targets of Ras and RhoA signaling. These observations clearly show that USP17 is tightly regulated during cell division and that its expression is necessary to coordinate cell cycle progression, and thus, it may be considered a promising novel cancer therapeutic target.

Hypothesis: Targeted Ikkβ deletion upregulates MIF signaling responsiveness and MHC class II expression in mouse hepatocytes

Macrophage migration inhibitory factor (MIF) is causally related to the pathogenesis of chronic liver disease but its hepatocellular mechanisms of action are largely unknown. Scattered reports in the literature hint at functional connections between the expression of MIF and major histocompatibility complex (MHC) Class II molecules. Not surprisingly, these relationships have not yet been explored in hepatocytes because MIF and MHC Class II cell surface receptors are commonly expressed by other cell types including various antigen presenting cells of the immune system. On the other hand, mounting evidence suggests that heteromeric MIF receptors share a common molecule with intracellular MHC Class II complexes, viz., CD74, which also serves as the MHC Class II chaperone; and, while it is unclear what cancer-related role(s) MHC Class II receptors might play, increasing evidence suggests that MIF and CD74 are also implicated in the biology of hepatocellular carcinoma. These reports are provocative for two reasons: firstly, Ikkβ^Δhep mice carrying hepatocyte-targeted deletions of Ikkβ, an IκB kinase complex subunit required for the activation of the transcription factor NF-κB (nuclear factor-κB), have been shown to display heightened susceptibilities to hepatotoxins and chemical hepatocarcinogens; secondly, microarray profiling observations indicate that Ikkβ^Δhep hepatocytes constitutively and “ectopically” overexpress genes, particularly CD74, CD44 (a MIF-receptor subunit) and MHC Class II I-A/E β and I-A α chains, and gene families that regulate host immune process and immune defense responses. These findings together suggest that Ikkβ^Δhep mice might express functional MIF and MHC Class II receptors, leading to increased hepatocellular sensitivity to MIF signaling as well as to the unusual property of antigen presentation; both functions might contribute to the heightened liver disease phenotypes of Ikkβ^Δhep mice. The findings raise questions about the potential existence of cohorts of human patients with genetic abnormalities of Ikkβ that might confer heightened susceptibility to liver disease including hepatocellular carcinoma.

ERK and cell death: ERK1/2 in neuronal death

Extracellular signal-regulated kinase (ERK) is a versatile protein kinase that regulates many cellular functions. Growing evidence suggests that ERK1/2 plays a crucial role in promoting cell death in a variety of neuronal systems, including neurodegenerative diseases. It is believed that the magnitude and the duration of ERK1/2 activity determine its cellular function. In this review, we summarize recent evidence for a role of ERK1/2 in neuronal death. Furthermore, we discuss the mechanisms involved in ERK1/2 mediating neuronal death.

Histone deacetylase inhibitors repress macrophage migration inhibitory factor (MIF) expression by targeting MIF gene transcription through a local chromatin deacetylation

The cytokine macrophage migration inhibitory factor plays a central role in inflammation, cell proliferation and tumorigenesis. Moreover, macrophage migration inhibitory factor levels correlate with tumor aggressiveness and metastatic potential. Histone deacetylase inhibitors are potent antitumor agents recently introduced in the clinic. Therefore, we hypothesized that macrophage migration inhibitory factor would represent a target of histone deacetylase inhibitors. Confirming our hypothesis, we report that histone deacetylase inhibitors of various chemical classes strongly inhibited macrophage migration inhibitory factor expression in a broad range of cell lines, in primary cells and in vivo. Nuclear run on, transient transfection with macrophage migration inhibitory factor promoter reporter constructs and transduction with macrophage migration inhibitory factor expressing adenovirus demonstrated that trichostatin A (a prototypical histone deacetylase inhibitor) inhibited endogenous, but not episomal, MIF gene transcription. Interestingly, trichostatin A induced a local and specific deacetylation of macrophage migration inhibitory factor promoter-associated H3 and H4 histones which did not affect chromatin accessibility but was associated with an impaired recruitment of RNA polymerase II and Sp1 and CREB transcription factors required for basal MIF gene transcription. Altogether, this study describes a new molecular mechanism by which histone deacetylase inhibitors inhibit MIF gene expression, and suggests that macrophage migration inhibitory factor inhibition by histone deacetylase inhibitors may contribute to the antitumorigenic effects of histone deacetylase inhibitors.

Modulation of expression and cellular distribution of p21 by macrophage migration inhibitory factor

Background

The pleiotropic protein MIF, (macrophage migration inhibitory factor), has been demonstrated to modulate several key proteins governing cell cycle control and is considered to contribute to cell growth and differentiation. In this study we investigated the effect of MIF on the expression and cellular distribution of the CDK inhibitor p21.

Methods

The effect of endogenous MIF on p21 expression and distribution was examined by comparing murine dermal fibroblasts derived from wt and MIF -/- mice. The effect of MIF on cell growth and apoptotic rates was compared using ³H-Thymidine incorporation assays and annexin V/PI assays respectively. Total p21 protein levels were compared using flow cytometry and western blotting. p21 mRNA was assessed by RT-PCR. Intracellular p21 staining was performed to assess cellular distribution of total protein. To further confirm observations siRNA was used to knockdown MIF protein in wt cells. Cell cycle analysis was performed using PI incorporation assays.

Results

MIF-/- murine dermal fibroblasts exhibited reduced proliferative responses and were more susceptible to apoptosis. This was associated with reduced p21 expression and nuclear distribution. Treatment with recombinant MIF protein was demonstrated to reduce both basal and induced apoptosis and increase nuclear p21 expression. Reduced nuclear p21 expression was also observed in MIF siRNA treated wt cells.

Conclusion

The results demonstrate that in the absence of MIF p21 expression and nuclear distribution is reduced which is associated with a reduction in cell growth and increased apoptosis. MIF may therefore play a role in maintaining homeostatic control of p21.

Delineating the signals by which repetitive deformation stimulates intestinal epithelial migration across fibronectin

Repetitive strain stimulates intestinal epithelial migration across fibronectin via focal adhesion kinase (FAK), Src, and extracellular signal-related kinase (ERK) although how these signals act and interact remains unclear. We hypothesized that PI3K is central to this pathway. We subjected Caco-2 and intestinal epithelial cell-6 cells to 10 cycles/min deformation on flexible fibronectin-coated membranes, assayed migration by wound closure, and signaling by immunoblots. Strain stimulated PI3K, AKT, glycogen synthase kinase (GSK), and p38 phosphorylation. Blocking each kinase prevented strain stimulation of migration. Blocking PI3K prevented strain-stimulated ERK and p38 phosphorylation. Blocking AKT did not. Downstream, blocking PI3K, AKT, or ERK inhibited strain-induced GSK-Ser9 phosphorylation. Upstream of AKT, reducing FAK or Rac1 by siRNA blocked strain-stimulated AKT phosphorylation, but inhibiting Src by PP2 or siRNA did not. Transfection with FAK point mutants at Tyr397, Tyr576/577, or Tyr925 demonstrated that only FAK925 phosphorylation is required for strain-stimulated AKT phosphorylation. Myosin light chain activation by strain required FAK, Rac1, PI3K, AKT, GSK, and ERK but not Src or p38. Finally, blebbistatin, a nonmuscle myosin II inhibitor, blocked the motogenic effect of strain downstream of myosin light chain. Thus strain stimulates intestinal epithelial migration across fibronectin by a complex pathway including Src, FAK, Rac1, PI3K, AKT, GSK, ERK, p38, myosin light chain, and myosin II.

Early brain response to low-dose radiation exposure involves molecular networks and pathways associated with cognitive functions, advanced aging and Alzheimer's disease

Understanding the cognitive and behavioral consequences of brain exposures to low-dose ionizing radiation has broad relevance for health risks from medical radiation diagnostic procedures, radiotherapy and environmental nuclear contamination as well as for Earth-orbit and space missions. Analyses of transcriptome profiles of mouse brain tissue after whole-body irradiation showed that low-dose exposures (10 cGy) induced genes not affected by high-dose radiation (2 Gy) and that low-dose genes were associated with unique pathways and functions. The low-dose response had two major components: pathways that are consistently seen across tissues and pathways that were specific for brain tissue. Low-dose genes clustered into a saturated network (P < 10(-53)) containing mostly down-regulated genes involving ion channels, long-term potentiation and depression, vascular damage, etc. We identified nine neural signaling pathways that showed a high degree of concordance in their transcriptional response in mouse brain tissue after low-dose irradiation, in the aging human brain (unirradiated), and in brain tissue from patients with Alzheimer's disease. Mice exposed to high-dose radiation did not show these effects and associations. Our findings indicate that the molecular response of the mouse brain within a few hours after low-dose irradiation involves the down-regulation of neural pathways associated with cognitive dysfunctions that are also down-regulated in normal human aging and Alzheimer's disease.

Human cytomegalovirus paralyzes macrophage motility through down-regulation of chemokine receptors, reorganization of the cytoskeleton, and release of macrophage migration inhibitory factor

Macrophages contribute to host defense and to the maintenance of immune homeostasis. Conversely, they are important targets of human cytomegalovirus (HCMV), a herpesvirus that has evolved many strategies to modulate the host immune response. Because an efficient macrophage trafficking is required for triggering an adequate immune response, we investigated the effects exerted by HCMV infection on macrophage migratory properties. By using endotheliotropic strains of HCMV, we obtained high rates of productively infected human monocyte-derived macrophages (MDM). Twenty-four hours after infection, MDM showed reduced polar morphology and became unable to migrate in response to inflammatory and lymphoid chemokines, bacterial products and growth factors, despite being viable and metabolically active. Although chemotactic receptors were only partially affected, HCMV induced a dramatic reorganization of the cytoskeleton characterized by rupture of the microtubular network, stiffness of the actin fibers, and collapse of the podosomes. Furthermore, supernatants harvested from infected MDM contained high amounts of macrophage migration inhibitory factor (MIF) and were capable to block the migration of neighboring uninfected MDM. Because immunodepletion of MIF from the conditioned medium completely restored MDM chemotaxis, we could show for the first time a functional role of MIF as an inhibitor of macrophage migration in the context of HCMV infection. Our findings reveal that HCMV uses different mechanisms to interfere with movement and positioning of macrophages, possibly leading to an impairment of antiviral responses and to an enhancement of the local inflammation.

Surface expression of CD74 by type II alveolar epithelial cells: a potential mechanism for macrophage migration inhibitory factor-induced epithelial repair

Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory cytokine involved in acute lung injury and other processes such as wound repair and tumor growth. MIF exerts pro-proliferative effects on a variety of cell types including monocytes/macrophages, B cells, and gastric epithelial cell lines through binding to the major histocompatibility complex type II-associated invariant chain, CD74. In acute lung injury, inflammatory damage of the alveolar epithelium leads to loss of type I alveolar epithelial cells (AEC-I), which are replaced by proliferation and differentiation of type II alveolar epithelial cells (AEC-II). In this study we have investigated the potential of MIF to contribute to alveolar repair by stimulating alveolar epithelial cell proliferation. We show that murine AEC-II, but not AEC-I, express high surface levels of CD74 in vivo. Culture of AEC-II in vitro resulted in decreased mRNA levels for CD74 and loss of surface CD74 expression, which correlated with a transition of AEC-II to an AEC-I-like phenotype. MIF stimulation of AEC-II induced rapid and prolonged phosphorylation of ERK1/2 and Akt, increased expression of cyclins D1 and E, as well as AEC-II proliferation. Corresponding MIF signaling and enhanced thymidine incorporation was observed after MIF stimulation of MLE-12 cells transfected to overexpress CD74. In contrast, MIF did not induce MAPK activation, gene transcription, or increased proliferation in differentiated AEC-I-like cells that lack CD74. These data suggest a previously unidentified role of MIF-CD74 interaction by inducing proliferation of AEC-II, which may contribute to alveolar repair.

A novel, macrophage migration inhibitory factor suicide substrate inhibits motility and growth of lung cancer cells

Although chemokine and growth factor receptors are attractive and popular targets for cancer therapeutic intervention, structure-based targeting of the ligands themselves is generally not considered practical. New evidence indicates that a notable exception to this is macrophage migration inhibitory factor (MIF). MIF, an autocrine- and paracrine-acting cytokine/growth factor, plays a pivotal role in both the initiation and maintenance of neoplastic diseases. MIF possesses a nonphysiologic enzymatic activity that is evolutionarily well-conserved. Although small molecule antagonists of MIFs enzymatic active site have been reported to inhibit biological activities of MIF, universally high IC(50)s have limited their clinical appeal. Using a computational virtual screening strategy, we have identified a unique small molecule inhibitor that serves as a suicide substrate for MIF, resulting in the covalent modification of the catalytically active NH(2)-terminal proline. Our studies further reveal that this compound, 4-iodo-6-phenylpyrimidine (4-IPP), is approximately 5x to 10x times more potent in blocking MIF-dependent catalysis and lung adenocarcinoma cell migration and anchorage-independent growth than the prototypical MIF inhibitor, ISO-1. Finally, using an in silico combinatorial optimization strategy, we have identified four unique congeners of 4-IPP that exhibit MIF inhibitory activity at concentrations 10x to 20x lower than that of parental 4-IPP.

Gene Expression Studies Demonstrate that the K-ras/Erk MAP Kinase Signal Transduction Pathway and Other Novel Pathways Contribute to the Pathogenesis of Cumene-induced Lung Tumors

National Toxicology Program (NTP) inhalation studies demonstrated that cumene significantly increased the incidence of alveolar/bronchiolar adenomas and carcinomas in B6C3F1 mice. Cumene or isopropylbenzene is a component of crude oil used primarily in the production of phenol and acetone. The authors performed global gene expression analysis to distinguish patterns of gene regulation between cumene-induced tumors and normal lung tissue and to look for patterns based on the presence or absence of K- ras and p53 mutations in the tumors. Principal component analysis segregated the carcinomas into groups with and without K- ras mutations, but failed to separate the tumors based on p53 mutation status. Expression of genes associated with the Erk MAP kinase signaling pathway was significantly altered in carcinomas with K- ras mutations compared to tumors without K- ras mutations or normal lung. Gene expression analysis also suggested that cumene-induced carcinomas with K- ras mutations have greater malignant potential than those without mutations. In addition, significance analysis of function and expression (SAFE) demonstrated expression changes of genes regulated by histone modification in carcinomas with K- ras mutations. The gene expression analysis suggested the formation of alveolar/bronchiolar carcinomas in cumene-exposed mice typically involves mutation of K- ras, which results in increased Erk MAP kinase signaling and modification of histones.

Growth control by intracellular tension and extracellular stiffness

Integrin-mediated cell attachment to the extracellular matrix is an established regulator of the cell cycle, and the best-characterized targets of this process are the cyclin D1 gene and members of the cip and kip (cip/kip) family of cdk inhibitors. Manipulation of intracellular tension affects the same targets, supporting the idea that integrin activation and intracellular tension are closely related. Several signaling cascades, including FAK, Rho GTPases and ERK, transmit the integrin and tensional signals to pathways controlling the cell cycle. However, the experimental approaches that have generated these results alter cell adhesion and tension in ways that do not reflect the subtlety of those occurring in vivo. Increasing emphasis is therefore being placed on approaches that use micropatterning to control cell spreading, and deformable substrata to model the compliance of biological tissue.

Transcriptional patterns, biomarkers and pathways characterizing nasopharyngeal carcinoma of Southern China

BACKGROUND

The pathogenesis of nasopharyngeal carcinoma (NPC) is a complicated process involving genetic predisposition, Epstein-Bar Virus infection, and genetic alterations. Although some oncogenes and tumor suppressor genes have been previously reported in NPC, a complete understanding of the pathogenesis of NPC in the context of global gene expression, transcriptional pathways and biomarker assessment remains to be elucidated.

METHODS

Total RNA from 32 pathologically-confirmed cases of poorly-differentiated NPC was divided into pools inclusive of four consecutive specimens and each pool (T1 to T8) was co-hybridized with pooled RNA from 24 normal non-cancerous nasopharyngeal tissues (NP) to a human 8K cDNA array platform. The reliability of microarray data was validated for selected genes by semi-quantitative RT-PCR and immunohistochemistry.

RESULTS

Stringent statistical filtering parameters identified 435 genes to be up-regulated and 257 genes to be down-regulated in NPC compared to NP. Seven up-regulated genes including CYC1, MIF, LAMB3, TUBB2, UBE2C and TRAP1 had been previously proposed as candidate common cancer biomarkers based on a previous extensive comparison among various cancers and normal tissues which did not, however, include NPC or NP. In addition, nine known oncogenes and tumor suppressor genes, MIF, BIRC5, PTTG1, ATM, FOXO1A, TGFBR2, PRKAR1A, KLF5 and PDCD4 were identified through the microarray literature-based annotation search engine MILANO, suggesting these genes may be specifically involved in the promotion of the malignant conversion of nasopharyngeal epithelium. Finally, we found that these differentially expressed genes were involved in apoptosis, MAPK, VEGF and B cell receptor signaling pathways and other functions associated with cell growth, signal transduction and immune system activation.

CONCLUSION

This study identified potential candidate biomarkers, oncogenes/tumor suppressor genes involved in several pathways relevant to the oncogenesis of NPC. This information may facilitate the determination of diagnostic and therapeutic targets for NPC as well as provide insights about the molecular pathogenesis of NPC.

Decorin transfection induces proteomic and phenotypic modulation in breast cancer cells 8701-BC

Decorin is a prototype member of the small leucine-rich proteoglycan family widely distributed in the extracellular matrices of many connective tissues, where it has been shown to play multiple important roles in the matrix assembly process, as well as in some cellular activities. A major interest for decorin function concerns its role in tumorigenesis, as growth-inhibitor of different neoplastic cells, and potential antimetastatic agent. The aim of our research was to investigate wide-ranged effects of transgenic decorin on breast cancer cells. To this purpose we utilized the well-characterized 8701-BC cell line, isolated from a ductal infiltrating carcinoma of the breast, and two derived decorin-transfected clones, respectively, synthesizing full decorin proteoglycan or its protein core. The responses to the ectopic decorin production were examined by studying morphological changes, cell proliferation rates, and proteome modulation. The results revealed new important antioncogenic potentialities, likely exerted by decorin through a variety of distinct biochemical pathways. Major effects included the downregulation of several potential breast cancer biomarkers, the reduction of membrane ruffling, and the increase of cell-cell adhesiveness. These results disclose original aspects related to the reversion of malignant traits of a prototype of breast cancer cells induced by decorin. They also raise additional interest for the postulated clinical application of decorin.