Induction of MIF synthesis and secretion by tubular epithelial cells: a novel action of angiotensin II

MIF/CD74 axis in hepatic stellate cells mediates HBV-related liver fibrosis

Chronic hepatitis B virus (HBV) infection is a major risk factor for liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Despite advances in understanding HBV-related liver diseases, effective therapeutic strategies remain limited. Macrophage migration inhibitory factor (MIF) has been implicated in various inflammatory and fibrotic conditions, but its role in HBV-induced liver fibrosis has not been fully explored. This study investigates the involvement of MIF in liver fibrosis and evaluates its potential as a therapeutic target. We found that MIF expression was significantly elevated in hepatic stellate cells (HSCs) following stimulation with HBVcc (HBV cell culture) or HBV surface antigen (HBsAg). Through its receptor CD74, MIF enhanced the TGF-β/SMAD signaling pathway, promoting HSC activation and liver fibrosis progression. Histological analysis revealed higher MIF and CD74 expression in HBsAg-positive individuals compared to HBsAg-negative controls. Moreover, MIF expression correlated with the activation of fibrosis markers, including α-SMA and TGF-β-related proteins. Inhibition of MIF with the specific inhibitor ISO-1 attenuated fibrosis progression, suggesting that targeting MIF could offer a promising approach for treating HBV-related liver fibrosis. Our findings underscore the critical role of the MIF/CD74 axis in liver fibrosis and provide a basis for future therapeutic strategies targeting MIF in chronic liver diseases.

Dualistic roles and mechanistic insights of macrophage migration inhibitory factor in brain injury and neurodegenerative diseases

Macrophage migration inhibitory factor (MIF) is involved in various immune-mediated pathologies and regulates both innate and adaptive immune reactions, thus being related to several acute and chronic inflammatory diseases such as rheumatoid arthritis, septic shock, and atherosclerosis. Its role in acute and chronic brain pathologies, such as stroke and neurodegenerative diseases, has attracted increasing attention in recent years. In response to stimuli like hypoxia, inflammation or infection, different cell types can rapidly release MIF, including immune cells, endothelial cells, and neuron cells. Notably, clinical data from past decades also suggested a possible link between serum MIF levels and the severity of stroke and the evolving of neurodegenerative diseases. In this review, we summarize the major and recent findings focusing on the mechanisms of MIF modulating functions in brain injury and neurodegenerative diseases, which may provide important therapeutic targets meriting further investigation.

Macrophage migration inhibitory factor in acute kidneyinjury

Acute kidney injury (AKI) is a complex clinical syndrome with multiple etiologies and pathogenesis, which lacks early biomarkers and targeted therapy. Recently, macrophage migration inhibitory factor (MIF) family protein have received increasing attention owing to its pleiotropic protein molecule character in acute kidney injury, where it performed a dual role in the pathological process. macrophage migration inhibitory factor and macrophage migration inhibitory factor-2 are released into the peripheral circulation when Acute kidney injury occurs and interact with various cellular pathways. On the one hand, macrophage migration inhibitory factor exerts a protective effect in anti-oxidation and macrophage migration inhibitory factor-2 promotes cell proliferation and ameliorates renal fibrosis. On the other hand, macrophage migration inhibitory factor aggravates renal injury as an upstream inflammation factor. Herein, we provide an overview on the biological role and possible mechanisms of macrophage migration inhibitory factor and macrophage migration inhibitory factor-2 in the process of Acute kidney injury and the clinical application prospects of macrophage migration inhibitory factor family proteins as a potential therapeutic target.

Multifaceted interconnections between macrophage migration inhibitory factor and psychiatric disorders

Inflammation is involved in the pathogenesis of psychiatric disorders. Many previous studies have defined the important roles of inflammatory factors in the pathogenesis, diagnosis, and treatment outcomes of psychiatric disorders. Macrophage migration inhibitory factor (MIF), a pro-inflammatory factor, has been gradually recognized to be involved in the development of neurological diseases in recent years. Our current review focuses on discussing the potential beneficial and detrimental roles of MIF in psychiatric disorders. We will provide new mechanistic insights for the development of potential diagnostic and therapeutic biomarkers based on MIF for psychiatric diseases.

Macrophage migration inhibitory factor (MIF): A multifaceted cytokine regulated by genetic and physiological strategies

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine encoded within a functionally polymorphic genetic locus. MIF was initially recognized as a cytokine generated by activated T cells, but in recent days it has been identified as a multipotent key cytokine secreted by many other cell types involved in immune response and physiological processes. MIF is a highly conserved 12.5 kDa secretory protein that is involved in numerous biological processes. The expression and secretion profile of MIF suggests that MIF to be ubiquitously and constitutively expressed in almost all mammalian cells and is vital for numerous physiological processes. MIF is a critical upstream mediator of host innate and adaptive immunity and survival pathways resulting in the clearance of pathogens thus playing a protective role during infectious diseases. On the other hand, MIF being an immune modulator accelerates detrimental inflammation, promotes cancer metastasis and progression, thus worsening disease conditions. Several reports demonstrated that genetic and physiological factors, including MIF gene polymorphisms, posttranslational regulations, and receptor binding control the functional activities of MIF. Taking into consideration the multi-faceted role of MIF both in physiology and pathology, we thought it is timely to review and summarize the expressional and functional regulation of MIF, its functional mechanisms associated with its beneficial and pathological roles, and MIF-targeting therapies. Thus, our review will provide an overview on how MIF is regulated, its response, and the potency of the therapies that target MIF.

Assays for Inducing and Measuring Cell Death to Detect Macrophage Migration Inhibitory Factor (MIF) Release

Cell death is a vital process for maintaining tissue homeostasis and removing potentially harmful cells. Cell death can be both programmed and non-programmed and is commonly divided into two main forms, termed apoptotic and necrotic death modes. In this chapter cell death is classified into apoptosis, primary necrosis, pyroptosis, and necroptosis. This chapter outlines the measurement of these different types of cell death and the relationship of measuring MIF release in these assays.

Macrophage migration inhibitory factor promotes renal injury induced by ischemic reperfusion

Macrophage migration inhibitory factor (MIF) is pleiotropic cytokine that has multiple effects in many inflammatory and immune diseases. This study reveals a potential role of MIF in acute kidney injury (AKI) in patients and in kidney ischemic reperfusion injury (IRI) mouse model in MIF wild‐type (WT) and MIF knockout (KO) mice. Clinically, plasma and urinary MIF levels were largely elevated at the onset of AKI, declined to normal levels when AKI was resolved and correlated tightly with serum creatinine independent of disease causes. Experimentally, MIF levels in plasma and urine were rapidly elevated after IRI‐AKI and associated with the elevation of serum creatinine and the severity of tubular necrosis, which were suppressed in MIF KO mice. It was possible that MIF may mediate AKI via CD74/TLR4‐NF‐κB signalling as mice lacking MIF were protected from AKI by largely suppressing CD74/TLR‐4‐NF‐κB associated renal inflammation, including the expression of MCP‐1, TNF‐α, IL‐1β, IL‐6, iNOS, CXCL15(IL‐8 in human) and infiltration of macrophages, neutrophil, and T cells. In conclusion, our study suggests that MIF may be pathogenic in AKI and levels of plasma and urinary MIF may correlate with the progression and regression of AKI.

PPARγ maintains the metabolic heterogeneity and homeostasis of renal tubules

Background

The renal tubules, which have distant metabolic features and functions in different segments, reabsorb >99% of approximately 180 l of water and 25,000 mmol of Na ⁺ daily. Defective metabolism in renal tubules is involved in the pathobiology of kidney diseases. However, the mechanisms underlying the metabolic regulation in renal tubules remain to be defined.

Methods

We quantitatively compared the proteomes of the isolated proximal tubules (PT) and distal tubules (DT) from C57BL/6 mouse using tandem mass tag (TMT) labeling-based quantitative mass spectrometry. Bioinformatics analysis of the differentially expressed proteins revealed the significant differences between PT and DT in metabolism pathway. We also performed in vitro and in vivo assays to investigate the molecular mechanism underlying the distant metabolic features in PT and DT.

Findings

We demonstrate that the renal proximal tubule (PT) has high expression of lipid metabolism enzymes, which is transcriptionally upregulated by abundantly expressed PPARα/γ. In contrast, the renal distal tubule (DT) has elevated glycolytic enzyme expression, which is mediated by highly expressed c-Myc. Importantly, PPARγ transcriptionally enhances the protease iRhom2 expression in PT, which suppresses EGF expression and secretion and subsequent EGFR-dependent glycolytic gene expression and glycolysis. PPARγ inhibition reduces iRhom2 expression and increases EGF and GLUT1 expression in PT in mice, resulting in renal tubule hypertrophy, tubulointerstitial fibrosis and damaged kidney functions, which are rescued by 2-deoxy-d-glucose treatment.

Interpretation

These findings delineate instrumental mechanisms underlying the active lipid metabolism and suppressed glycolysis in PT and active glycolysis in DT and reveal critical roles for PPARs and c-Myc in maintaining renal metabolic homeostasis. FUND: This work was supported by the National Natural Science Foundation of China (grants 81572076 and 81873932; to Q.Z.), the Applied Development Program of the Science and Technology Committee of Chongqing (cstc2014yykfB10003; Q.Z.), the Program of Populace Creativities Workshops of the Science and Technology Committee of Chongqing (Q.Z.), the special demonstration programs for innovation and application of techniques (cstc2018jscx-mszdX0022) from the Science and Technology Committee of Chongqing (Q.Z.).

Blocking Macrophage Migration Inhibitory Factor Protects Against Cisplatin-Induced Acute Kidney Injury in Mice

Macrophage migration inhibitory factor (MIF) is elevated in patients with acute kidney injury (AKI) and is suggested as a potential predictor for renal replacement therapy in AKI. In this study, we found that MIF also plays a pathogenic role and is a therapeutic target for AKI. In a cisplatin-induced AKI mouse model, elevated plasma MIF correlated with increased serum creatinine and the severity of renal inflammation and tubular necrosis, whereas deletion of MIF protected the kidney from cisplatin-induced AKI by largely improving renal functional and histological injury, and suppressing renal inflammation including upregulation of cytokines such as interleukin (IL)-1β, tumor necrosis factor-alpha (TNF-α), IL-6, inducible nitric oxide synthase (iNOS), MCP-1, IL-8, and infiltration of macrophages, neutrophils, and T cells. We next developed a novel therapeutic strategy for AKI by blocking the endogenous MIF with an MIF inhibitor, ribosomal protein S19 (RPS19). Similar to the MIF-knockout mice, treatment with RPS19, but not the mutant RPS19, suppressed cisplatin-induced AKI. Mechanistically, we found that both genetic knockout and pharmacological inhibition of MIF protected against AKI by inactivating the CD74-nuclear factor κB (NF-κB) signaling. In conclusion, MIF is pathogenic in cisplatin-induced AKI. Targeting MIF with an MIF inhibitor RPS19 could be a promising therapeutic potential for AKI.

Calcitriol Ameliorates AngiotensinII-Induced Renal Injury Partly via Upregulating A20

Inflammation and reactive oxygen species (ROS) play crucial roles in the progression of chronic kidney diseases. Vitamin D has been shown anti-inflammatory effects, but the underlying mechanism is not fully understood. Here, we investigated whether calcitriol exerts protective effects via upregulating A20 in angiotensinII (AngII)-induced renal injury. Male C57BL/6 mice were infused with vehicle or AngII for 10 days. Calcitriol reduced infiltration of T lymphocytes and macrophages. This reduction of inflammatory cells was accompanied by elevated A20 and decreased pro-inflammatory cytokines (PICs) and reactive oxygen species (ROS). Calcitriol could inhibit NF-κB activation and necroptotic pathway. Induction of A20 was located primarily to the tubular epithelial cells. In rat proximal tubular epithelial cells (NRK-52E), calcitriol stably upregulated A20 and reduced the PICs and ROS. Inhibitory effect of A20 on PICs and ROS depended on suppressing NF-κB pathway and necroptotic pathway, respectively. A20 knockdown diminished the effect of calcitriol on suppressing NF-κB and necroptotic pathways. However, A20 deficiency could not abrogate the inhibitory effect of calcitriol on NF-κB and necroptotic pathways. Our results established that A20 is involved in the renoprotective effect by calcitriol via negatively modulating the NF-κB pathway and necroptotic pathway in AngII-induced renal injury.

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.

TWEAK increases CD74 expression and sensitizes to DDT proinflammatory actions in tubular cells

CD74 is a multifunctional protein and a receptor for Macrophage Migration Inhibitory Factor (MIF) and MIF-2 / D-dopachrome tautomerase (DDT) cytokines, upregulated in diabetic kidney disease. However, the drivers of CD74 expression and DDT function in kidney cells are poorly characterized. TWEAK is a proinflammatory cytokine that promotes kidney injury. We have now identified CD74 gene expression as upregulated in the kidneys in response to systemic TWEAK administration in mice, and have characterized the in vivo CD74 expression and the functional consequences in cultured cells. TWEAK administration to mice resulted in a progressive time-dependent (up to 24h) upregulation of kidney CD74 mRNA (RT-PCR) and protein (Western blot). Furthermore, the CD74 ligands MIF and DDT were also upregulated at the protein level 24h after TWEAK administration. Immunohistochemistry localized the increased CD74, MIF and DDT expression to tubular cells. In cultured tubular cells, TWEAK increased CD74 mRNA and protein expression dose-dependently, with a temporal pattern similar to in vivo. TWEAK-induced CD74 localized to the cell membrane, where it can function as a cytokine receptor. For the first time, we explored the actions of DDT in tubular cells and found that DDT amplified the increase in MCP-1 and RANTES expression in response to TWEAK. By contrast, DDT did not significantly modify TWEAK-induced Klotho downregulation. In conclusion, TWEAK upregulates CD74 and its ligands MIF and DDT in renal tubular cells. This may have functional consequences for kidney injury since DDT amplified the inflammatory response to TWEAK.

Macrophage migration inhibitory factor: A multifaceted cytokine implicated in multiple neurological diseases

Macrophage migration inhibitory factor (MIF) is a conserved cytokine found as a homotrimer protein. It is found in a wide spectrum of cell types in the body including neuronal and non-neuronal cells. MIF is implicated in several biological processes; chemo-attraction, cytokine activity, and receptor binding, among other functions. More recently, a chaperone-like activity has been added to its repertoire. In this review, we focus on the implication of MIF in the central nervous system and peripheries, its role in neurological disorders, and the mechanisms by which MIF is regulated. Numerous studies have associated MIF with various disease settings. MIF plays an important role in advocating tumorigenic processes, Alzheimer's disease, and is also upregulated in autism-spectrum disorders and spinal cord injury where it contributes to the severity of the injured area. The protective effect of MIF has been reported in amyotrophic lateral sclerosis by its reduction of aggregated misfolded SOD1, subsequently reducing the severity of this disease. Interestingly, a protective as well as pathological role for MIF has been implicated in stroke and cerebral ischemia, as well as depression. Thus, the role of MIF in neurological disorders appears to be diverse with both beneficial and adversary effects. Furthermore, its modulation is rather complex and it is regulated by different proteins, either on a molecular or protein level. This complexity might be dependent on the pathophysiological context and/or cellular microenvironment. Hence, further clarification of its diverse roles in neurological pathologies is warranted to provide new mechanistic insights which may lead in the future to the development of therapeutic strategies based on MIF, to fight some of these neurological disorders.

Graft-derived macrophage migration inhibitory factor correlates with hepatocellular injury in patients undergoing liver transplantation

Experimental studies suggest that macrophage migration inhibitory factor (MIF) mediates ischemia/reperfusion injury during liver transplantation. This study assessed whether human liver grafts release MIF during preservation, and whether the release of MIF is proportional to the extent of hepatocellular injury. Additionally, the association between MIF and early allograft dysfunction (EAD) after liver transplantation was evaluated. Concentrations of MIF, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and creatine kinase (CK) were measured in effluents of 38 liver grafts, and in serum of recipients. Concentrations of MIF in the effluent were greater than those in the recipients' serum before and after reperfusion (58 [interquartile range, IQR:23-79] μg/mL vs 0.06 [IQR:0.03-0.07] μg/mL and 1.3 [IQR:0.7-1.8] μg/mL, respectively; both P<.001). Effluent MIF concentrations correlated with effluent concentrations of the cell injury markers ALT (R=.51, P<.01), AST (R=.51, P<.01), CK (R=.45, P=.01), and LDH (R=.56, P<.01). Patients who developed EAD had greater MIF concentrations in effluent and serum 10 minutes after reperfusion than patients without EAD (Effluent: 80 [IQR:63-118] μg/mL vs 36 [IQR:20-70] μg/mL, P=.02; Serum: 1.7 [IQR:1.2-2.5] μg/mL vs 1.1 [IQR:0.6-1.7] μg/mL, P<.001).

CONCLUSION

Human liver grafts release MIF in proportion to hepatocellular injury. Greater MIF concentrations in effluent and recipient's serum are associated with EAD after liver transplantation.

Inhibition of Macrophage Migration Inhibitory Factor Protects against Inflammation and Matrix Deposition in Kidney Tissues after Injury

Background. Macrophage migration inhibitory factor (MIF) is an important immunoregulatory cytokine involved in inflammation, which may be one important reason resulting in matrix deposition in renal tissues after injury. However, the underlying mechanisms have not yet been elucidated. Methods and Results. We uncovered a crucial role of MIF in inflammation and collagen deposition in vivo and in vitro. In rats, ureteral obstruction induced tubular injury, matrix accumulation, and inflammatory cell infiltration. Additionally, enhanced MIF levels in the obstructed kidneys were closely related to the increasing numbers of CD68-positive macrophages. These obstruction-induced injuries can be relieved by recanalization, consequently resulting in downregulated expression of MIF and its receptor CD74. Similarly, ischemia reperfusion induced renal injury, and it was accompanied by elevated MIF levels and macrophages infiltration. In cultured tubular epithelial cells (TECs), aristolochic acid (AA) promoted matrix production and increased MIF expression, as well as the release of macrophage-related factors. Inhibition of MIF with an antagonist ISO-1 resulted in the abolishment of these genotypes in AA-treated TECs. Conclusion. MIF plays an important role in macrophage-related inflammation and matrix deposition in kidney tissues following injury. MIF as a specific inhibitor may have therapeutic potential for patients with inflammatory and fibrotic kidney diseases.

A genetic study of steroid-resistant nephrotic syndrome: relationship between polymorphism -173 G to C in the MIF gene and serum level MIF in children

There is no satisfactory explanation as to why some nephrotic syndrome (NS) patients respond to glucocorticoids and others do not. The aim of this study was to investigate an association between single nucleotide polymorphism of the MIF gene -rs755622 and serum MIF concentrations in NS patients. During a period between November 2011 and September 2012, 120 consecutive children divided into three groups [healthy children, steroid-resistant nephrotic syndrome (SRNS) and steroid-sensitive nephrotic syndrome (SSNS)] were examined. Children were defined as healthy when they had a normal estimated glomerular filtration rate and spot urinary albumin creatinine ratio <150 μg/mg creatinine. SRNS was diagnosed in children who did not respond to the usual doses of steroids within 4 weeks of initiating treatment. SSNS patients were defined as those who had remission after usual doses of steroids. The genotype of -173 G to C polymorphism of the MIF gene was determined using polymerase chain reaction restriction fragment length polymorphism methods. Serum MIF concentration was measured using sandwich enzyme-linked immunosorbent assay. The allele frequency of the C allele was higher in SRNS compared with that of SSNS patients (P=0.025). There was a trend toward an association between genotypes and serum MIF disturbances. In conclusion, this study noted elevated circulating serum MIF levels and higher frequency of the C allele of the MIF gene in SRNS patients. The presence of the C allele implies an increased risk for steroid resistance.

Macrophage Migration Inhibitory Factor Mediates Proliferative GN via CD74

Pathologic proliferation of mesangial and parietal epithelial cells (PECs) is a hallmark of various glomerulonephritides. Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that mediates inflammation by engagement of a receptor complex involving the components CD74, CD44, CXCR2, and CXCR4. The proliferative effects of MIF may involve CD74 together with the coreceptor and PEC activation marker CD44. Herein, we analyzed the effects of local glomerular MIF/CD74/CD44 signaling in proliferative glomerulonephritides. MIF, CD74, and CD44 were upregulated in the glomeruli of patients and mice with proliferative glomerulonephritides. During disease, CD74 and CD44 were expressed de novo in PECs and colocalized in both PECs and mesangial cells. Stress stimuli induced MIF secretion from glomerular cells in vitro and in vivo, in particular from podocytes, and MIF stimulation induced proliferation of PECs and mesangial cells via CD74. In murine crescentic GN, Mif-deficient mice were almost completely protected from glomerular injury, the development of cellular crescents, and the activation and proliferation of PECs and mesangial cells, whereas wild-type mice were not. Bone marrow reconstitution studies showed that deficiency of both nonmyeloid and bone marrow-derived Mif reduced glomerular cell proliferation and injury. In contrast to wild-type mice, Cd74-deficient mice also were protected from glomerular injury and ensuing activation and proliferation of PECs and mesangial cells. Our data suggest a novel molecular mechanism and glomerular cell crosstalk by which local upregulation of MIF and its receptor complex CD74/CD44 mediate glomerular injury and pathologic proliferation in GN.

Angiotensin II-induced hypertensive renal inflammation is mediated through HMGB1-TLR4 signaling in rat tubulo-epithelial cells

BACKGROUND AND PURPOSE

Angiotensin II is a vaso-constrictive peptide that regulates blood pressure homeostasis. Even though the inflammatory effects of AngII in renal pathophysiology have been studied, there still exists a paucity of data with regard to the mechanism of action of AngII-mediated kidney injury. The objective of this study was to elucidate the mechanistic role of HMGB1-TLR4 signaling in AngII-induced inflammation in the kidney.

EXPERIMENTAL APPROACH

Rat tubular epithelial cells (NRK52E) were treated with AngII over a preset time-course. In another set of experiments, HMGB1 was neutralized and TLR4 was knocked down using small interfering RNA targeting TLR4. Cell extracts were subjected to RT-PCR, immunoblotting, flow cytometry, and ELISA.

KEY RESULTS

AngII-induced inflammation in NRK52E cells increased gene and protein expression of TLR4, HMGB1 and key proinflammatory cytokines (TNFα and IL1β). Pretreatment with Losartan (an AT1 receptor blocker) attenuated the AngII-induced expression of TLR4 and inflammatory cytokines. TLR4 silencing was used to elucidate the specific role played by TLR4 in AngII-induced inflammation. TLR4siRNA treatment in these cells significantly decreased the AngII-induced inflammatory effect. Consistent observations were made when the Ang II treated cells were pretreated with anti-HMGB1. Downstream activation of NFκB and rate of generation of ROS was also decreased on gene silencing of TLR4 and exposure to anti-HMGB1.

CONCLUSIONS AND IMPLICATIONS

These results indicate a key role for HMGB1-TLR4 signaling in AngII-mediated inflammation in the renal epithelial cells. Our data also reveal that AngII-induced effects could be alleviated by HMGB1-TLR4 inhibition, suggesting this pathway as a potential therapeutic target for hypertensive renal dysfunctions.

Angiotensin AT2 receptor stimulation is anti-inflammatory in lipopolysaccharide-activated THP-1 macrophages via increased interleukin-10 production

Macrophages have an important role in the pathogenesis of hypertension and associated end-organ damage via the activation of the Toll-like receptors, such as Toll-like receptor-4 (TLR4). Accumulating evidence suggests that the angiotensin AT2 receptor (AT2R) has a protective role in pathological conditions involving inflammation and tissue injury. We have recently shown that AT(2)R stimulation is renoprotective, which occurs in part via increased levels of anti-inflammatory interleukin-10 (IL-10) production in renal epithelial cells; however, the role of AT(2)R in the inflammatory activity of macrophages is not known. The present study was designed to investigate whether AT(2)R activation stimulates an anti-inflammatory response in TLR4-induced inflammation. The effects of the anti-inflammatory mechanisms that occurred following pre-treatment with the AT(2)R agonist Compound 21 (C21) (1 μmol ml(-1)) on the cytokine profiles of THP-1 macrophages after activation by lipopolysaccharide (LPS) (1 μg ml(-1)) were studied. The AT(2)R agonist dose-dependently attenuated LPS-induced tumor necrosis factor-α (TNF-α) and IL-6 production but increased IL-10 production. IL-10 was critical for the anti-inflammatory effects of AT(2)R stimulation because the IL-10-neutralizing antibody dose-dependently abolished the AT(2)R-mediated decrease in TNF-α levels. Further, enhanced IL-10 levels were associated with a sustained, selective increase in the phosphorylation of extracellular signal-regulated kinase (ERK1/2) but not p38 mitogen-activated protein kinase (MAPK). Blocking the activation of ERK1/2 before C21 pre-treatment completely abrogated this increased IL-10 production in response to the AT(2)R agonist C21, while there was a partial reduction in IL-10 levels following the inhibition of p38. We conclude that AT(2)R stimulation exerts a novel anti-inflammatory response in THP-1 macrophages via enhanced IL-10 production as a result of sustained, selective ERK1/2 phosphorylation, which may have protective roles in hypertension and associated tissue injury.

Macrophage migration inhibitory factor regulates AKT signaling in hypoxic culture to modulate senescence of human mesenchymal stem cells

Hypoxic culture has been shown to delay premature senescence occurring during in vitro culture. Human mesenchymal stem cells (hMSCs) cultured under hypoxia have been reported to maintain their stemness properties and delay senescence compared to the cells cultured under normoxia. However, the molecular mechanism by which hypoxia regulates premature senescence has not been fully revealed. In this study, hMSCs were cultured under the conditions of 21% (normoxia) and 1% O2 (hypoxia) tension and analyzed for cell growth, expression of MSC surface markers, multilineage differentiation, and cellular senescence. Our results showed that more cells retained MSC surface markers in hypoxic culture than those in normoxic culture, and hypoxia was able to enhance multilineage differentiation of hMSCs. The hypoxic condition also delayed cellular senescence of hMSCs, increased activation of AKT signaling, and upregulated both intra- and extracellular levels of macrophage migration inhibitory factor (MIF) compared to the normoxic condition. Inhibition of AKT activity in hypoxic culture increased the number of cells with positive staining for senescence-associated β-galactosidase activity, upregulated expression levels of senescence-associated markers p16 and p21 mRNA transcripts, and decreased expression levels of potency-associated markers, including NANOG, OCT3/4, and SOX2. On the other hand, upregulated intra- and extracellular levels of MIF by stable MIF overexpression in normoxic culture increased the activation of AKT while decreasing mRNA expression of senescence-associated markers and increasing expression of potency-associated markers. Taken together, our findings suggest that hMSCs in hypoxic culture produce endogenous MIF to activate AKT signaling to delay the progression of cellular senescence.

Involvement of Src tyrosine kinase and protein kinase C in the expression of macrophage migration inhibitory factor induced by H2O2 in HL-1 mouse cardiac muscle cells

Macrophage migration inhibitory factor (MIF), a pleiotropic cytokine, plays an important role in the pathogenesis of atrial fibrillation; however, the upstream regulation of MIF in atrial myocytes remains unclear. In the present study, we investigated whether and how MIF is regulated in response to the renin-angiotensin system and oxidative stress in atrium myocytes (HL-1 cells). MIF protein and mRNA levels in HL-1 cells were assayed using immunofluorescence, real-time PCR, and Western blot. The result indicated that MIF was expressed in the cytoplasm of HL-1 cells. Hydrogen peroxide (H₂O₂), but not angiotensin II, stimulated MIF expression in HL-1 cells. H₂O₂-induced MIF protein and gene levels increased in a dose-dependent manner and were completely abolished in the presence of catalase. H₂O₂-induced MIF production was completely inhibited by tyrosine kinase inhibitors genistein and PP1, as well as by protein kinase C (PKC) inhibitor GF109203X, suggesting that redox-sensitive MIF production is mediated through tyrosine kinase and PKC-dependent mechanisms in HL-1 cells. These results suggest that MIF is upregulated by HL-1 cells in response to redox stress, probably by the activation of Src and PKC.

MIF, CD74 and other partners in kidney disease: tales of a promiscuous couple

Macrophage migration inhibitory factor (MIF) is increased in kidney and urine during kidney disease. MIF binds to and activates CD74 and chemokine receptors CXCR2 and CXCR4. CD74 is a protein trafficking regulator and a cell membrane receptor for MIF, D-dopachrome tautomerase (D-DT/MIF-2) and bacterial proteins. MIF signaling through CD74 requires CD44. CD74, CD44 and CXCR4 are upregulated in renal cells in diseased kidneys and MIF activation of CD74 in kidney cells promotes an inflammatory response. MIF or CXCR2 targeting protects from experimental kidney injury, CD44 deficiency modulates kidney injury and CXCR4 activation promotes glomerular injury. However, the contribution of MIF or MIF-2 to these actions of MIF receptors has not been explored. The safety and efficacy of strategies targeting MIF, CD74, CD44 and CXCR4 are under study in humans.

Role of the renin-angiotensin system in prostate cancer

Prostate cancer is highly prevalent in Western society, and its early stages can be controlled by androgen ablation therapy. However, the cancer eventually regresses to an androgen-independent state for which there is no effective treatment. The renin-angiotensin system (RAS), in particular the octapeptide angiotensin II, is now recognised to have important effects on growth factor signalling and cell growth in addition to its well known actions on blood pressure, fluid homeostasis and electrolyte balance. All components of the RAS have been recently identified in the prostate, consistent with the expression of a local RAS system in this tissue. This review focuses on the role of the RAS in the prostate, and the possibility that this pathway may be a potential therapeutic target for the treatment of prostate cancer and other prostatic diseases.

The MIF receptor CD74 in diabetic podocyte injury

Although metabolic derangement plays a central role in diabetic nephropathy, a better understanding of secondary mediators of injury may lead to new therapeutic strategies. Expression of macrophage migration inhibitory factor (MIF) is increased in experimental diabetic nephropathy, and increased tubulointerstitial mRNA expression of its receptor, CD74, has been observed in human diabetic nephropathy. Whether CD74 transduces MIF signals in podocytes, however, is unknown. Here, we found glomerular and tubulointerstitial CD74 mRNA expression to be increased in Pima Indians with type 2 diabetes and diabetic nephropathy. Immunohistochemistry confirmed the increased glomerular and tubular expression of CD74 in clinical and experimental diabetic nephropathy and localized glomerular CD74 to podocytes. In cultured human podocytes, CD74 was expressed at the cell surface, was upregulated by high concentrations of glucose and TNF-alpha, and was activated by MIF, leading to phosphorylation of extracellular signal-regulated kinase 1/2 and p38. High glucose also induced CD74 expression in a human proximal tubule cell line (HK2). In addition, MIF induced the expression of the inflammatory mediators TRAIL and monocyte chemoattractant protein 1 in podocytes and HK2 cells in a p38-dependent manner. These data suggest that CD74 acts as a receptor for MIF in podocytes and may play a role in the pathogenesis of diabetic nephropathy.

Anti-inflammatory renoprotective effect of clopidogrel and irbesartan in chronic renal injury

Recent evidence suggests that platelet activation and angiotensin II may each contribute to glomerular inflammation and fibrosis. Clopidogrel inhibits platelet activation and may also reduce inflammation. This study investigated the anti-inflammatory and renoprotective effects of clopidogrel and irbesartan in the five-sixths nephrectomy rat model of chronic kidney disease. After 8 wk of treatment, 24-h proteinuria, serum creatinine, and histologic scores of glomerular sclerosis and tubulointerstitial damage were significantly lower in treated compared with untreated rats. Clopidogrel/irbesartan combination therapy had greater effects than either drug alone. Rats that underwent five-sixths nephrectomy had higher markers of platelet activation (plasma GMP-140 and renal cortical fibrin deposition) than sham-operated rats, and clopidogrel attenuated these effects. Clopidogrel and irbesartan similarly reduced the accumulation of ED-1-expressing macrophages in the cortical glomeruli and the interstitium. Combination therapy almost completely abolished macrophage infiltration and attenuated the expression of monocyte chemoattractant protein-1, intercellular adhesion molecule-1, TGF-beta(1), and connective tissue growth factor. In conclusion, combination treatment with clopidogrel and irbesartan, more so than either alone, decreases early renal injury induced by five-sixths nephrectomy by inhibiting renal inflammation.

Overexpression of regucalcin suppresses cell response for tumor necrosis factor-alpha or transforming growth factor-beta1 in cloned normal rat kidney proximal tubular epithelial NRK52E cells

The regulatory role of regucalcin on cell responses for tumor necrosis factor-alpha (TNF-alpha) or transforming growth factor-beta1 (TGF-beta1) was investigated using the cloned normal rat kidney proximal tubular epithelial NRK52E cells overexpressing regucalcin. NRK52E cells (wild type) and stable regucalcin (RC)/pCXN2-transfected cells (transfectant) were cultured for 72 h in a medium containing 5% bovine serum (BS) to obtain subconfluent monolayers. After culture, cells were further cultured for 24-72 h in medium without BS containing either vehicle, TNF-alpha (0.1 or 1.0 ng/ml of medium), or TGF-beta1 (1.0 or 5.0 ng/ml). Culture with TNF-alpha or TGF-beta1 caused a significant decrease in the number of wild-type cells. This decrease was significantly prevented in transfectants overexpressing regucalcin. Agarose gel electrophoresis showed the presence of low-molecular-weight deoxyribonucleic acid (DNA) fragments of adherent wild-type cells cultured with TNF-alpha (1.0 ng/ml) or TGF-beta1 (5.0 ng/ml). This DNA fragmentation was significantly suppressed in transfectants. TNF-alpha- or TGF-beta1-induced cell death was significantly prevented in culture with caspase-3 inhibitor (10(-8) M). Nitric oxide (NO) synthase activity in wild-type cells was significantly increased by addition of calcium chloride (10 microM) and calmodulin (5 microg/ml) into the enzyme reaction mixture. This increase was significantly suppressed in transfectants. Culture with TNF-alpha caused a significant increase in NO synthase activity in wild-type cells. The effect of TNF-alpha was not seen in transfectants. Culture with TGF-beta1 did not cause a significant increase in NO synthase activity in wild-type cells and transfectants. Culture with TNF-alpha or TGF-beta1 caused a remarkable increase in alpha-smooth muscle actin in wild-type cells. This increase was significantly prevented in transfectants. The expression of Smad 2 or NF-kappaB mRNAs was significantly increased in transfectants as compared with that of wild-type cells. Smad 3 or glyceroaldehyde-3-phosphate dehydrogenase (G3PDH) mRNA expression was not significantly changed in transfectants. NF-kappaB mRNA expression in wild-type cells was significantly increased with culture of TNF-alpha. Smad 2 mRNA expression was significantly enhanced in wild-type cells cultured with TGF-beta1. These effects of TNF-alpha or TGF-beta1 were not significantly enhanced in transfectants. This study demonstrates that overexpression of regucalcin has suppressive effects on cell responses which are mediated through intracellular signaling pathways of TNF-alpha or TGF-beta1 in kidney NRK52E cells.

Macrophage migration inhibitory factor deficiency attenuates macrophage recruitment, glomerulonephritis, and lethality in MRL/lpr mice

Systemic lupus erythematosus (SLE) is a serious systemic autoimmune disease of unknown etiology. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that is operative in innate and adaptive immunity and important in immune-mediated diseases such as rheumatoid arthritis and atherosclerosis. The functional relevance of MIF in systemic autoimmune diseases such as SLE is unknown. Using the lupus-prone MRL/lpr mice, we aim to examine the expression and function of MIF in this murine model of systemic autoimmune disease. These experiments revealed that renal MIF expression was significantly higher in MRL/lpr mice compared with nondiseased control mice (MRL/MpJ), and MIF was also markedly up-regulated in skin lesions of MRL/lpr mice. To examine the effect of MIF on development of systemic autoimmune disease, we generated MRL/lpr mice with a targeted disruption of the MIF gene (MIF(-/-)MRL/lpr), and compared their disease manifestations to MIF(+/+)MRL/lpr littermates. MIF(-/-)MRL/lpr mice exhibited significantly prolonged survival, and reduced renal and skin manifestations of SLE. These effects occurred in the absence of major changes in T and B cell markers or alterations in autoantibody production. In contrast, renal macrophage recruitment and glomerular injury were significantly reduced in MIF(-/-)MRL/lpr mice, and this was associated with reduction in the monocyte chemokine MCP-1. Taken together, these data suggest MIF as a critical effector of organ injury in SLE.

Overexpression of regucalcin enhances its nuclear localization and suppresses L-type Ca2+ channel and calcium-sensing receptor mRNA expressions in cloned normal rat kidney proximal tubular epithelial NRK52E cells

The effect of regucalcin (RC), a regulatory protein in intracellular signaling pathway, on the gene expression of various mineral ion transport-related proteins was investigated using the cloned normal rat kidney proximal tubular epithelial NRK52E cells overexpressing RC. NRK52E cells (wild-type) and stable RC/pCXN2 transfectant were cultured for 72 h in medium containing 5% bovine serum (BS) to obtain subconfluent monolayers. After culture for 72 h, cells were further cultured 24-72 h in a medium containing either vehicle, aldosterone (10(-8) or 10(-7) M), or parathyroid hormone (PTH) (1-34) (10(-8) or 10(-7) M) without BS. RC was markedly localized in the nucleus of transfectants. Overexpression of RC caused a significant increase in rat outer medullary K(+) channel (ROMK) mRNA expression, while it caused a remarkable decrease in L-type Ca(2+) channel and calcium-sensing receptor (CaR) mRNA expressions. Overexpression of RC did not have an effect on epithelial sodium channel (ENaC), Na, K-ATPase (alpha-subunit), Type II Na-Pi cotransporter (NaPi-IIa), angiotensinogen, Na(+)-Ca(2+) exchanger, and glyceroaldehyde-3-phosphate dehydrogenase (G3PDH) mRNA expressions. Hormonal effect on gene expression, moreover, was examined. Culture with aldosterone (10(-8) or 10(-7) M) caused a significant increase in ENaC, Na, K-ATPase, and ROMK mRNA expressions in the wild-type cells. Those increases were weakened in the transfectants. Culture with PTH (10(-8) or 10(-7) M) significantly decreased NaPi-IIa mRNA expression in the wild-type cells. This effect was not altered in the transfectants. PTH significantly decreased angiotensinogen mRNA expression in the wild-type cells and the transfectants, while aldosterone had no effect. Culture with PTH (10(-8) or 10(-7) M) caused a significant decrease in L-type Ca(2+) channel and CaR mRNA expressions in the wild-type cells, while the hormone significantly increased Na(+)-Ca(2+) exchanger mRNA expression. The effects of PTH on L-type Ca(2+) channel, CaR, and Na(+)-Ca(2+) exchanger mRNA expressions were also seen in the transfectants. This study demonstrates that overexpression of RC caused a remarkable increase in its nuclear localization, and that it has suppressive effects on the gene expression of L-type Ca(2+) channel or CaR, which regulates intracellular Ca(2+) signaling, among various regulator proteins for mineral ions in NRK52E cells.

Overexpression of RGPR-p117 enhances regucalcin gene promoter activity in cloned normal rat kidney proximal tubular epithelial cells: involvement of TTGGC motif

A novel protein RGPR-p117 was discovered as regucalcin gene promoter region-related protein that binds to the TTGGC motif using a yeast one-hybrid system. RGPR-p117 is localized in the nucleus of kidney cells, and overexpression of RGPR-p117 can modulate regucalcin protein and its mRNA expression in the cloned normal rat kidney proximal tubular epithelial NRK52E cells. This study was undertaken to determine whether overexpression of RGPR-p117 enhances the regucalcin promoter activity using the -710/+18 LUC construct (wild-type) or -710/+18 LUC construct (mutant) with deletion of -523/-435 including TTGGC motif. NRK52E cells (wild-type) or stable HA-RGPR-p117/phCMV2-transfected cells (transfectant) were cultured in Dulbecco's minimum essential medium (DMEM) containing 5% bovine serum (BS). Wild-type cells or transfectants were transfected with the -710/+18 LUC construct vector or the -710/+18 LUC construct with deletion of -523/-435. Wild-type cells or transfectants with subconfluency were cultured for 48 h in a DMEM medium containing either vehicle, BS (5%), or parathyroid hormone (1-34) (PTH; 10(-7) M). Luciferase activity in wild-type cells was significantly increased with culture of BS or PTH. This increase was significantly blocked in the presence of various protein kinase inhibitors (staurosporine and PD 98059). Luciferase activity in transfectants was significantly increased as compared with that of wild-type cells in the absence of BS or PTH. The increase in luciferase activity in transfectants was completely decreased in mutant with deletion of -523/-435 sequence of regucalcin promoter. This was also seen using the -710/+18 LUC construct with deletion of -523/-503 sequence containing TTGGC motif. The increase in luciferase activity in transfectants was not significantly enhanced with culture of BS (5%), PTH (10(-7) M), Bay K 8644 (10(-6) M), phorbol 12-myristate 13-acetate (PMA; 10(-6) M), or N(6), 2'-dibutyryl cyclic adenosine 3', 5'-monophosphate (DcAMP; 10(-4) M). The increase in luciferase activity in transfectants was completely inhibited with culture of dibucaine (10(-6) M), staurosporine (10(-9) M), PD 98059 (10(-8) M), wortmannin (10(-8) M), genistein (10(-6) M), vanadate (10(-6) M), or okadaic acid (10(-6) M) which are inhibitors of various kinases and protein phosphatases. This study demonstrates that RGPR-p117 can enhance the regucalcin promoter activity which is related to the NF-1 consensus sequences including TTGGC motif, and that its enhancing effect is partly mediated through phosphorylation and dephosphorylation in NRK52E cells.

Pilot study of angiotensin II receptor blocker in advanced hormone-refractory prostate cancer

BACKGROUND

We previously demonstrated that an angiotensin II receptor blocker (ARB) had the potential to inhibit cell proliferation of prostate cancer. In this study, we examined whether an ARB could elicit an antiproliferative effect on hormone-refractory prostate cancer, clinically.

METHODS

Twenty-three patients with advanced hormone-refractory prostate cancer who had already received secondary hormonal therapy using dexamethasone, and who were no longer receiving conventional therapy, were enrolled. All of the patients received candesartan 8 mg once daily per os and, simultaneously, androgen ablation. Change in prostate-specific antigen (PSA) was determined as the primary endpoint. The secondary end-point was change in performance status (PS). To investigate angiotensin II type 1 (AT1) receptor expression in prostate cancer tissue, real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) was performed, using specimens, from untreated patients with prostate cancer.

RESULTS

Eight patients (34.8%) showed responsive PSA changes; six showed a decrease immediately after starting administration and two showed a stable level of PSA. Six men with a PSA decline of more than 50% showed an improvement in PS. The mean time to PSA progression (TTPP) in responders was 8.3 months (range, 1-24 months). Half of the patients showed stable or improved PS during treatment. With regard to toxic effects, only one patient showed hypotension during treatment. The RT-PCR showed that AT1 receptor expression in well-differentiated adenocarcinoma was higher than that in poorly differentiated adenocarcinoma.

CONCLUSION

These data showed that an ARB had potential biological effects on prostate cancer, suggesting the usefulness of the cytostatic activity of such agents on recurrent prostate cancer.

Spironolactone prevents diabetic nephropathy through an anti-inflammatory mechanism in type 2 diabetic rats

Aldosterone induces myocardial fibrosis and vascular inflammation via proinflammatory and profibrotic cytokines. The effect of spironolactone on renal inflammation and renal function was investigated in type 2 diabetic rats. For define the molecular mechanism of spironolactone, the effect of spironolactone on the synthesis of monocyte chemotactic peptide-1 (MCP-1) and its upstream transcription factor, NF-kappaB, was evaluated in cultured mesangial cells and proximal tubular cells. There were no changes in blood glucose concentration or BP after spironolactone treatment. Spironolactone treatment significantly reduced urinary albumin excretion and ameliorated glomerulosclerosis. Urinary levels of MCP-1 were significantly increased concurrently with renal expression of MCP-1, macrophage migration inhibitory factor, and macrophage infiltration. Spironolactone treatment significantly inhibited urinary excretion of MCP-1 as well as renal MCP-1 and migration inhibitory factor expression and macrophage infiltration. In addition, aldosterone induced upregulation of MCP-1 expression and NF-kappaB transcriptional activity in cultured cells, and spironolactone reduced both NF-kappaB activation and MCP-1 synthesis. Furthermore, NF-kappaB inhibition abolished aldosterone-induced MCP-1 production. Overall, these findings suggest that aldosterone-induced NF-kappaB activation leads to activation of proinflammatory cytokines, ultimately leading to renal injury in this model. These data suggest that mineralocorticoid blockade may be a potential therapeutic target in diabetic nephropathy.

Macrophage migration inhibitory factor: an intracellular inhibitor of angiotensin II-induced increases in neuronal activity

Angiotensin II (Ang II) elicits Ang II type 1 receptor (AT1-R)-mediated increases in neuronal firing within the hypothalamus and brainstem that are ultimately responsible for physiological actions such as increased blood pressure and fluid intake. Although there is a growing literature on the intracellular mechanisms that mediate the actions of Ang II via AT1-R in neurons, little is known about the mechanisms that diminish or "switch-off" the neuronal chronotropic action of Ang II. In the present study, we identified macrophage migration inhibitory factor (MIF) as an intracellular inhibitor of the actions of Ang II in neurons. The evidence is as follows. First, Ang II, acting via AT1-R, increases the intracellular levels of MIF in neurons cultured from rat hypothalamus and brainstem. Second, elevation of intracellular MIF by Ang II prevents further chronotropic actions of this peptide. Third, intracellular application of exogenous recombinant MIF abolishes the Ang II-induced chronotropic action in neurons. Finally, intracellular application of the MIF peptide fragment MIF-(50-65), which harbors the thiol oxidoreductase property of the MIF molecule, mimics the inhibitory actions of MIF on Ang II-stimulated neuronal firing. Thus, this study is the first to demonstrate the existence of an intracellular negative regulator of Ang II-induced actions in neurons and indicates that MIF may act as a physiological brake for the chronotropic effects of Ang II in rat neurons.

The expression of macrophage migration inhibitory factor 1alpha (MIF 1alpha) in human atherosclerotic plaques is induced by different proatherogenic stimuli and associated with plaque instability

OBJECTIVES

Macrophage migration inhibitory factor 1alpha (MIF), a cytokine with immunoregulatory functions has been suggested to be involved in atherosclerotic plaque development. However, little is known about MIF-inducing conditions in the atherosclerotic process and the association of MIF with plaque instability.

METHODS AND RESULTS

Forty-two carotid endatherectomy samples from 36 patients and 4 aortic samples from young accident victims (as healthy controls) were analyzed for MIF staining. MIF expressing tissues in the atherosclerotic plaques are mainly mononuclear cells (MNCs), but also endothelial cells of intimal microvessels (MVECs). The magnitude and the intensity of their MIF expression was associated with the progression of plaques from early lesions (Stary I-III) to complicated plaque stages (Stary IV-VIII). In highly inflammatory and neovascularized regions of the plaques the colocalization of MIF expressing MNCs with CD40-L+ and angiotensin II (Ang II)-producing MNCs could be established. This finding supports the notion that CD40-L fusion protein and Ang II are able to induce MIF production in the monocytic cell line THP-1. Furthermore hypoxia (< or =1% O2) as a further proinflammatory and especially proangiogenetic factor was able to stimulate MIF secretion by THP-1, human monocytes and HUVECs. Hyperglycemia and insulin remained without effect.

CONCLUSION

MIF is expressed in advanced atherosclerotic lesions in close correlation with signs of instability, such as mononuclear cell inflammation and neointimal microvessel formation. Furthermore, the colocalization of MIF with Ang II-producing MNCs and CD40-L+ cells in these plaques and the finding that proathero- and -angiogenic mediators such as CD40-L, Ang II and hypoxia are able to stimulate MIF expression in vitro suggest an important role of MIF in the modulation of atherosclerotic plaque stability.

Hormonal regulation on regucalcin mRNA expression in cloned normal rat kidney proximal tubular epithelial NRK52E cells

Regucalcin is a regulatory protein in cell signaling. This study was undertaken to determine whether regucalcin mRNA expresses in the cloned normal rat kidney proximal tubular epithelial NRK52E cells and its expression regulates due to hormones and cell signaling-related factors. Cells with subconfluency were cultured for 24, 48, or 72 h in a Dulbecco's modified Eagle medium supplemented with non-essential amino acid without bovine serum (BS). The result of Western blot analysis showed that regucalcin protein was present in the NRK52E cells. The expression of regucalcin mRNA in the cells was determined using reverse transcription-polymerase chain reaction (RT-PCR). Regucalcin mRNA expression in the NRK52E cells was significantly increased by culture with parathyroid hormone (PTH, 10(-8) or 10(-7) M), aldosterone (10(-8) or 10(-7) M), or dexamethasone (10(-8) M). The presence of 1,25-dihydroxyvitamin D(3) (1,25(OH)2D3, 10(-8) or 10(-7) M) or calcitonin (10(-9) or 10(-8) M) did not have a significant effect on regucalcin mRNA levels in the cells. Culture with dibutyryl cyclic AMP (DcAMP, 10(-5) or 10(-4) M) or phorbol 12-myristate 13-acetate (PMA, 10(-6) M), an activator of protein kinase C, caused a significant increase in regucalcin mRNA expression. The presence of staurosporine (10(-8) M) caused a significant decrease in regucalcin mRNA expression. Dibucaine (10(-7) M), PD98059 (10(-7) M), or vanadate (10(-6) or 10(-5) M) did not have an effect on regucalcin mRNA levels. The present study demonstrates that regucalcin mRNA and its protein are expressed in the cloned normal rat kidney proximal tubular epithelial NRK52E cells, and that the expression is enhanced by hormones which regulate ion transport in the proximal tubule.

Overexpression of regucalcin suppresses apoptotic cell death in cloned normal rat kidney proximal tubular epithelial NRK52E cells: Change in apoptosis-related gene expression

The effect of regucalcin, a regulatory protein in intracellular signaling pathway, on cell death and apoptosis was investigated using the cloned normal rat kidney proximal tubular epithelial NRK52E cells overexpressing regucalcin. NRK52E cells (wild type) and stable regucalcin (RC)/pCXN2 transfectants were cultured for 72 h in a medium containing 5% bovine serum (BS) to obtain subconfluent monolayers. After culture for 72 h, cells were further cultured for 24-72 h in a medium without BS containing either vehicle, tumor necrosis factor-alpha (TNF-alpha; 0.1 or 1.0 ng/ml of medium), lipopolysaccharide (LPS; 0.1 or 1.0 microg/ml), Bay K 8644 (10(-9)-10(-7) M), or thapsigargin (10(-9)-10(-7) M). The number of wild-type cells was significantly decreased by culture for 42-72 h in the presence of TNF-alpha (0.1 or 1.0 ng/ml), LPS (0.1 or 1.0 microg/ml), Bay K 8644 (10(-7)-10(-5) M), or thapsigargin (10(-8) or 10(-7) M). The effect of TNF-alpha (0.1 or 1.0 ng/ml), LPS (0.1 or 1.0 microg/ml), Bay K 8644 (10(-7)-10(-6) M), or thapsigargin (10(-7) M) in decreasing the number of wild-type cells cultured for 24-72 h was significantly prevented in transfectants overexpressing regucalcin. Agarose gel electrophoresis showed the presence of low-molecular-weight deoxyribonucleic acid (DNA) fragments of adherent wild-type cells cultured with LPS (1.0 microg/ml), Bay K 8644 (10(-7) M), or thapsigargin (10(-8) M) for 24 h, and this DNA fragmentation was significantly suppressed in transfectants. DNA fragmentation in adherent cells was not seen by culture with TNF-alpha (1.0 ng/ml). TNF-alpha-induced decrease in the number of wild-type cells was significantly prevented by culture with caspase-3 inhibitor (10(-8) M), while LPS- or Bay K 8644-induced decrease in cell number was significantly prevented by caspase-3 inhibitor or N omega-nitro-L-arginine methylester (NAME) (10(-5) M), an inhibitor of nitric oxide (NO) synthase. Thapsigargin-induced decrease in cell number was not prevented in the presence of two inhibitors. Bcl-2 and Akt-1 mRNA levels were significantly increased in transfectants cultured for 24 h as compared with those of wild-type cells, while Apaf-1, caspase-3, or glyceroaldehyde-3-phosphate dehydrogenase (G3PDH) mRNA expressions were not significantly changed in transfectants. Culture with TNF-alpha (1.0 ng/ml), LPS (1.0 microg/ml), Bay K 8644 (l0(-7) M), or thapsigargin (10(-8) M) caused a significant increase in caspase-3 mRNA levels in wild-type cells. LPS (1.0 microg/ml) significantly decreased Bcl-2 mRNA expression in the cells. Their effects on the gene expression of apoptosis-related proteins were not significantly changed in transfectants. This study demonstrates that overexpression of regucalcin has a suppressive effect on cell death and apoptosis induced by various factors which their action are mediated through many intracellular signaling pathways, and that it modulates the gene expression of apoptosis-related proteins.

Macrophages in mouse type 2 diabetic nephropathy: correlation with diabetic state and progressive renal injury

BACKGROUND

Macrophage-mediated renal injury has been implicated in progressive forms of glomerulonephritis; however, a role for macrophages in type 2 diabetic nephropathy, the major cause of end-stage renal failure, has not been established. Therefore, we examined whether macrophages may promote the progression of type 2 diabetic nephropathy in db/db mice.

METHODS

The incidence of renal injury was examined in db/db mice with varying blood sugar and lipid levels at 8 months of age. The association of renal injury with the accumulation of kidney macrophages was analyzed in normal db/+ and diabetic db/db mice at 2, 4, 6, and 8 months of age.

RESULTS

In db/db mice, albuminuria and increased plasma creatinine correlated with elevated blood glucose and hemoglobin A1c (HbA1c) levels but not with obesity or hyperlipidemia. Progressive diabetic nephropathy in db/db mice was associated with increased kidney macrophages. Macrophage accumulation and macrophage activation in db/db mice correlated with hyperglycemia, HbA1c levels, albuminuria, elevated plasma creatinine, glomerular and tubular damage, renal fibrosis, and kidney expression of macrophage chemokines [monocyte chemoattractant protein-1 (MCP-1), osteopontin, migration inhibitory factor (MIF), monocyte-colony-stimulating factor (M-CSF)]. The accrual and activation of glomerular macrophages also correlated with increased glomerular IgG and C3 deposition, which was itself dependent on hyperglycemia.

CONCLUSION

Kidney macrophage accumulation is associated with the progression of type 2 diabetic nephropathy in db/db mice. Macrophage accumulation and activation in diabetic db/db kidneys is associated with prolonged hyperglycemia, glomerular immune complex deposition, and increased kidney chemokine production, and raises the possibility of specific therapies for targeting macrophage-mediated injury in diabetic nephropathy.

Macrophage migration inhibitory factor mediates late cardiac dysfunction after burn injury

We have recently demonstrated that macrophage migration inhibitory factor (MIF) is a myocardial depressant protein and that MIF mediates late, prolonged cardiac dysfunction after endotoxin challenge in mice. Because many factors, including endotoxin, have been implicated in the pathogenesis of cardiac dysfunction after burn injury, we tested the hypothesis that MIF might also be the mediator of prolonged cardiac dysfunction in this model. At 4 h after 40% total body surface area burn in anesthetized mice, serum MIF levels increased significantly compared with baseline (2.2-fold). This increase was accompanied by a significant decrease in cardiac tissue MIF levels (2.1-fold decrease compared with controls). This pattern was consistent with MIF release from preformed cytoplasmic stores in the heart and other organs. To determine whether MIF mediates cardiac dysfunction after burn injury, mice were pretreated with anti-MIF neutralizing monoclonal antibodies or isotype control antibodies. Beginning 4 h after burn injury (and continuing through 48 h), burned mice demonstrated a significantly depressed left ventricular shortening fraction of 38.6 +/- 1.8%, compared with the normal controls (56.0 +/- 2.6%). Mice treated with anti-MIF displayed an initial depression of cardiac function similar to nontreated animals but then showed rapid restoration of cardiac function with complete recovery by 24 h, which persisted for the duration of the protocol. This study is the first to demonstrate that MIF mediates late, prolonged cardiac dysfunction after burn injury and suggests that MIF blockade should be considered a therapeutic target for the treatment of burn injury.

Regulatory role of C5a on macrophage migration inhibitory factor release from neutrophils

There is evidence that C5a and macrophage migration inhibitory factor (MIF) both play important roles in experimental sepsis. Humans with sepsis also show elevated levels of both mediators in the blood. Regulation of MIF during sepsis is poorly understood. We now demonstrate that neutrophil depletion greatly reduced serum MIF levels in rats and mice during the onset of sepsis after cecal ligation and puncture. In vitro, C5a induced MIF release from rat and mouse neutrophils. In vivo blockade of C5aR or absence of C5aR led to significantly reduced MIF generation during the onset of sepsis. C5a-induced release in vitro of MIF from neutrophils appeared to be due to up-regulation of MIF in cytoplasmic granules of neutrophils via activation of the protein kinase B signaling pathway together with involvement of PI3K. Our data suggest that C5a plays a role in enhancing MIF release from neutrophils in vitro and during sepsis. These findings represent a previously unrecognized function of C5a and neutrophils in the appearance of MIF in sepsis.

Regulated secretion of macrophage migration inhibitory factor is mediated by a non-classical pathway involving an ABC transporter

The cytokine macrophage migration inhibitory factor (MIF) is inducibly secreted by immune cells and certain other cell types to critically participate in the regulation of the host immune response. However, MIF does not contain a N-terminal signal sequence and the mechanism of MIF secretion is unknown. Here we show in a model of endotoxin-stimulated THP-1 monocytes that MIF does not enter the endoplasmatic reticulum and that MIF secretion is not inhibited by monensin or brefeldin A, demonstrating that MIF secretion occurs via a non-classical export route. Glyburide and probenicide but not other typical inhibitors of non-classical protein export strongly block MIF secretion, indicating that the export pathway of MIF involves an ABCA1 transporter.

The enigma of sepsis

Sepsis remains a serious cause of morbidity and mortality, and the pathophysiology of the disease is not clear. The definition of the clinical manifestations of sepsis is ever evolving. This review discusses the search for effective therapeutic interventions, hurdles in translational sepsis research, and new therapies in development in current clinical trials.