Evidence that intracellular cyclophilin A and cyclophilin A/CD147 receptor-mediated ERK1/2 signalling can protect neurons against in vitro oxidative and ischemic injury

Extracellular cyclophilin A protects against blast-induced neuronal injury

Blast-induced traumatic brain injury (TBI) and subsequent neurobehavioral deficits are major disabilities suffered by the military and civilian population worldwide. Rigorous scientific research is underway to understand the mechanism of blast TBI and thereby develop effective therapies for protection and treatment. By using an in vitro shock tube model of blast TBI with SH-SY5Y human neuroblastoma cells, we have demonstrated that blast exposure leads to neurobiological changes in an overpressure and time dependent manner. Paradoxically, repeated blast exposures resulted in less neuronal injury compared to single blast exposure and suggested a potential neuroprotective mechanism involving released cyclophilin A (CPA). In the present study, we demonstrate accumulation of CPA in the culture medium after repeated blast exposures supporting the notion of extracellular CPA mediated neuroprotection. Post-exposure treatment of the cells with purified recombinant CPA caused significant protection against blast-induced neuronal injury. Furthermore, repeated blast exposure was associated with phosphorylation of the proteins ERK1/2 and Bad suggesting a potential mechanism of neuroprotection by extracellular CPA and may aid in the development of targeted therapies for protection against blast-induced TBI.

Microarray analyses of genes regulated by isoflurane anesthesia in vivo: a novel approach to identifying potential preconditioning mechanisms

BACKGROUND

Although general anesthetics are recognized for their potential to render patients unconscious during surgery, exposure can also lead to long-term outcomes of both cellular damage and protection. As regards the latter, delayed anesthetic preconditioning is an evolutionarily conserved physiological response that has the potential for protecting against ischemic injury in a number of tissues. Although it is known that delayed preconditioning requires de novo protein synthesis, knowledge of anesthetic-regulated genes is incomplete. In this study, we used the conserved nature of preconditioning to analyze differentially regulated genes in 3 different rat tissues. We hypothesized that by selecting those genes regulated in multiple tissues, we could develop a focused list of gene candidates potentially involved in delayed anesthetic preconditioning.

METHODS

Young adult male Sprague-Dawley rats were anesthetized with a 2% isoflurane/98% air mixture for 90 minutes. Immediately after anesthetic exposure, animals were euthanized and liver, kidney, and heart were removed and total RNA was isolated. Differential gene expression was determined using rat oligonucleotide gene arrays. Array data were analyzed to select for genes that were significantly regulated in multiple tissues.

RESULTS

All 3 tissues showed differentially regulated genes in response to a clinically relevant exposure to isoflurane. Analysis of coordinately regulated genes yielded a focused list of 34 potential gene candidates with a range of ontologies including regulation of inflammation, modulation of apoptosis, regulation of ion gradients, and maintenance of energy pathways.

CONCLUSIONS

Through using an analysis approach focusing on coordinately regulated genes, we were able to generate a focused list of interesting gene candidates with potential to enable future preconditioning studies.

Fine tuning the inhibition profile of cyclosporine A by derivatization of the MeBmt residue

Unique respect: The biological properties of four CsA derivatives were fine-tuned by tractable modifications of the MeBmt residue. The new CsA derivatives share strong inhibitory activity toward cyclophilins (Cyps), but each is unique with respect to immunosuppressive action and cellular localization. These CsA analogues can be used to study the physiological roles of extracellular Cyps.

1-(2,6-Dibenzyloxybenzoyl)-3-(9H-fluoren-9-yl)-urea: a novel cyclophilin A allosteric activator

Cyclophilin A (CypA) plays an important role in many physiology processes and its overexpression has been involved in many diseases including immune disease, viral infection, neuro-degenerative disease, and cancer. However, the actual role of CypA in the diseases is still far from clear, and a complete understanding of CypA is necessary in order to direct more specific and effective therapeutic strategies. Based on the screening of our in-house library through the isomer-specific proteolysis method, we find a CypA activator (1-(2,6-Dibenzyloxybenzoyl)-3-(9H-fluoren-9-yl)-urea), compound 1a, which can increase CypA's PPIase activity and give allosteric behavior. The binding affinity of compound 1a to CypA has been confirmed by Fortebio's Octet RED system and the increased phosphorylation of ERK in H446 cells is observed by treatment with both compound 1a and CsA. In order to further evaluate the binding mode between the activator and CypA, the allosteric binding site and allosteric mechanism of CypA are investigated by molecular dynamics (MD) simulations in combination with mutagenesis experiments. The results show that the allosteric binding site of CypA is 7Å away from its catalytic site and is composed of Cys52, His70, His54, Lys151, Thr152 and Lys155. Compound 1a binds to the allosteric site of CypA, stabilizing the active conformation of catalytic residues, and finally promotes the catalytic efficiency of CypA. We believe our finding of the CypA allosteric activator will be used as an effective chemical tool for further studies of CypA mechanisms in diseases.

Extracellular cyclophilin-A stimulates ERK1/2 phosphorylation in a cell-dependent manner but broadly stimulates nuclear factor kappa B

Background

Although the peptidyl-prolyl isomerase, cyclophilin-A (peptidyl-prolyl isomerase, PPIA), has been studied for decades in the context of its intracellular functions, its extracellular roles as a major contributor to both inflammation and multiple cancers have more recently emerged. A wide range of activities have been ascribed to extracellular PPIA that include induction of cytokine and matrix metalloproteinase (MMP) secretion, which potentially underlie its roles in inflammation and tumorigenesis. However, there have been conflicting reports as to which particular signaling events are under extracellular PPIA regulation, which may be due to either cell-dependent responses and/or the use of commercial preparations recently shown to be highly impure.

Methods

We have produced and validated the purity of recombinant PPIA in order to subject it to a comparative analysis between different cell types. Specifically, we have used a combination of multiple methods such as luciferase reporter screens, translocation assays, phosphorylation assays, and nuclear magnetic resonance to compare extracellular PPIA activities in several different cell lines that included epithelial and monocytic cells.

Results

Our findings have revealed that extracellular PPIA activity is cell type-dependent and that PPIA signals via multiple cellular receptors beyond the single transmembrane receptor previously identified, Extracellular Matrix MetalloPRoteinase Inducer (EMMPRIN). Finally, while our studies provide important insight into the cell-specific responses, they also indicate that there are consistent responses such as nuclear factor kappa B (NFκB) signaling induced in all cell lines tested.

Conclusions

We conclude that although extracellular PPIA activates several common pathways, it also targets different receptors in different cell types, resulting in a complex, integrated signaling network that is cell type-specific.

Hypoxia upregulates CD147 through a combined effect of HIF-1α and Sp1 to promote glycolysis and tumor progression in epithelial solid tumors

Hypoxia is one of the most pervasive physiological stresses within tumors. Hypoxia signaling contributes to the aggressive tumor behaviors through promoting tumor cells to undergo the fundamental metabolism adaptation. A series of evidence indicates that this process is mainly mediated by hypoxia-inducible factor (HIF). However, key molecules involved in tumor hypoxia adaptation remain to be characterized. In this study, we investigated the functional role of CD147, a transmembrane glycoprotein highly overexpressed on the surface of tumor cells, in hypoxic microenvironment using in vitro and in vivo assays. Immunohistochemical staining showed that CD147 expression was upregulated in hypoxic region of epithelial solid tumor tissues. In addition, our data indicated that hypoxia induced the upregulation of CD147 expression at both mRNA and protein levels in epithelial carcinoma cells in a time- and dose-dependent manner. Moreover, we demonstrated that hypoxia-induced CD147 upregulation was mainly mediated by a combined effect of transcription factors HIF-1 and specificity protein 1 (Sp1) on the activation of CD147 promoter. We also explored the metabolic functions of hypoxia-induced CD147 and found that upregulated CD147 promoted glycolysis in both tumor cell lines and nude mice tumor xenograft model, partially through the functional cooperation with MCT-1 and MCT-4. Finally, we observed that CD147 promoted tumor growth, inhibited tumor cell apoptosis and enhanced their invasion ability under hypoxia. In conclusion, our findings reveal a novel mechanism of hypoxia adaptation mediated by CD147 in epithelial solid tumors and suggest that CD147 may be a promising therapeutic target in cancer treatment.

Insights into pediatric diffuse intrinsic pontine glioma through proteomic analysis of cerebrospinal fluid

Diffuse intrinsic pontine glioma (DIPG) is a leading cause of brain tumor-related death in children. DIPG is not surgically resectable, resulting in a paucity of tissue available for molecular studies. As such, tumor biology is poorly understood, and, currently, there are no effective treatments. In the absence of frozen tumor specimens, body fluids--such as cerebrospinal fluid (CSF), serum, and urine--can serve as more readily accessible vehicles for detecting tumor-secreted proteins. We analyzed a total of 76 specimens, including CSF, serum, urine, and normal and tumor brainstem tissue. Protein profiling of CSF from patients with DIPG was generated by mass spectrometry using an LTQ-Orbitrap-XL and database search using the Sequest algorithm. Quantitative and statistical analyses were performed with ProteoIQ and Partek Genomics Suite. A total of 528 unique proteins were identified, 71% of which are known secreted proteins. CSF proteomic analysis revealed selective upregulation of Cyclophillin A (CypA) and dimethylarginase 1 (DDAH1) in DIPG (n = 10), compared with controls (n = 4). Protein expression was further validated with Western blot analysis and immunohistochemical assays using CSF, brain tissue, serum, and urine from DIPG and control specimens. Immunohistochemical staining showed selective upregulation of secreted but not cytosolic CypA and DDAH1 in patients with DIPG. In this study, we present the first comprehensive protein profile of CSF specimens from patients with DIPG to demonstrate selective expression of tumor proteins potentially involved in brainstem gliomagenesis. Detection of secreted CypA and DDAH1 in serum and urine has potential clinical application, with implications for assessing treatment response and detecting tumor recurrence in patients with DIPG.

High extracellular matrix metalloproteinase inducer/CD147 expression is strongly and independently associated with poor prognosis in colorectal cancer

As in most solid tumors, colorectal cancer prognosis strongly depends on the extent of local invasion and lymph node and distant metastases. Extracellular matrix metalloproteinase inducer (EMMPRIN) is a transmembrane glycoprotein that activates matrix metalloproteinases, a group of enzymes that play an important role in tumor invasion and metastasis formation. This study investigates the EMMPRIN expression in a large cohort of patients with colorectal cancer. Immunohistochemical analysis of tissue microarrays from 285 patients shows that increased EMMPRIN protein expression does not correlate with clinicopathologic parameters and is an independent prognostic factor of poor survival, with mean survival times of 103 months in EMMPRIN negative/low versus 57 months in EMMPRIN intermediate/high patients (P < .001). This pronounced association of increased EMMPRIN levels and--on average--a 45% reduction in overall survival could help improve the risk stratification in patients with colorectal cancer; moreover, the lack of correlations with classical measures of cancer invasion/spreading may suggest the relevance of alternative EMMPRIN pathways beyond matrix metalloproteinase activation.

Combined inhibition of cell death induced by apoptosis inducing factor and caspases provides additive neuroprotection in experimental traumatic brain injury

Neuronal programmed cell death (PCD) contributes to delayed tissue damage after traumatic brain injury (TBI). Both caspase-dependent and caspase-independent mechanisms have been implicated, with the latter including apoptosis inducing factor (AIF). The peptidyl-proplyl isomerase Cyclophilin A (CypA) transports AIF from the cytosol to the nucleus, a key step for AIF-dependent cell death. We compared the effects of single versus combined inhibition of caspase and AIF pathways in a mouse controlled cortical impact (CCI) model, by examining the effects of CypA gene knockout (CypA(-/-)), caspase inhibition with a pan-caspase inhibitor (boc-aspartyl(OMe)-fluoromethylketone, BAF), or combined modulation. TBI caused caspase activation as well as translocation of AIF to the nucleus. Markers of caspase activation including caspase-specific fodrin cleavage fragments and number of FLIVO-positive cells were reduced in BAF-treated CypA(+/+) mice, whereas markers of AIF activation including AIF/H2AX interaction and AIF translocation to the nucleus were attenuated in CypA(-/-) mice. Each single intervention, (CypA(-/-) or BAF-treated CypA(+/+)) reduced the number of apoptotic cells (TUNEL-positive) in the cortex and improved long-term sensorimotor function; CypA(-/-) also attenuated microglial activation after injury. Importantly, BAF-treated CypA(-/-) mice, showed greater effects than either intervention alone on multiple outcomes including: reduction in TUNEL-positive cells, decrease in neuroinflammation, improved motor and cognitive recovery, and attenuation of lesion volume and neuronal loss in the hippocampus. Using two in vitro neuronal cell death models known to induce AIF-mediated PCD, we also showed that neurons from CypA(-/-) animals were protected and that effects were unrelated to caspase activation. These data indicate that AIF-mediated and caspase-dependent pathways contribute independently and in parallel to secondary injury after TBI, and suggest that combined therapeutic strategies directed at multiple PCD pathways may provide superior neuroprotection than those directed at single mechanisms.

Role of cyclophilin A from brains of prion-infected mice in stimulation of cytokine release by microglia and astroglia in vitro

Prion diseases or transmissible spongiform encephalopathy diseases are typically characterized by deposition of abnormally folded partially protease-resistant host-derived prion protein (PrPres), which is associated with activated glia and increased release of cytokines. This neuroinflammatory response may play a role in transmissible spongiform encephalopathy pathogenesis. We previously reported that brain homogenates from prion-infected mice induced cytokine protein release in primary astroglial and microglial cell cultures. Here we measured cytokine release by cultured glial cells to determine what factors in infected brain contributed to activation of microglia and astroglia. In assays analyzing IL-12p40 and CCL2 (MCP-1), glial cells were not stimulated in vitro by either PrPres purified from infected mouse brains or prion protein amyloid fibrils produced in vitro. However, significant glial stimulation was induced by clarified scrapie brain homogenates lacking PrPres. This stimulation was greatly reduced both by antibody to cyclophilin A (CyPA), a known mediator of inflammation in peripheral tissues, and by cyclosporine A, a CyPA inhibitor. In biochemical studies, purified truncated CyPA fragments stimulated a pattern of cytokine release by microglia and astroglia similar to that induced by scrapie-infected brain homogenates, whereas purified full-length CyPA was a poor stimulator. This requirement for CyPA truncation was not reported in previous studies of stimulation of peripheral macrophages, endothelial cell cardiomyocytes, and vascular smooth muscle cells. Therefore, truncated CyPA detected in brain following prion infection may have an important role in the activation of brain-derived primary astroglia and microglia in prion disease and perhaps other neurodegenerative or neuroinflammatory diseases.

Comparative analysis of different peptidyl-prolyl isomerases reveals FK506-binding protein 12 as the most potent enhancer of alpha-synuclein aggregation

FK506-binding proteins (FKBPs) are members of the immunophilins, enzymes that assist protein folding with their peptidyl-prolyl isomerase (PPIase) activity. Some non-immunosuppressive inhibitors of these enzymes have neuroregenerative and neuroprotective properties with an unknown mechanism of action. We have previously shown that FKBPs accelerate the aggregation of α-synuclein (α-SYN) in vitro and in a neuronal cell culture model for synucleinopathy. In this study we investigated whether acceleration of α-SYN aggregation is specific for the FKBP or even the PPIase family. Therefore, we studied the effect of several physiologically relevant PPIases, namely FKBP12, FKBP38, FKBP52, FKBP65, Pin1, and cyclophilin A, on α-SYN aggregation in vitro and in neuronal cell culture. Among all PPIases tested in vitro, FKBP12 accelerated α-SYN aggregation the most. Furthermore, only FKBP12 accelerated α-SYN fibril formation at subnanomolar concentrations, pointing toward an enzymatic effect. Although stable overexpression of various FKBPs enhanced the aggregation of α-SYN and cell death in cell culture, they were less potent than FKBP12. When FKBP38, FKBP52, and FKBP65 were overexpressed in a stable FKBP12 knockdown cell line, they could not fully restore the number of α-SYN inclusion-positive cells. Both in vitro and cell culture data provide strong evidence that FKBP12 is the most important PPIase modulating α-SYN aggregation and validate the protein as an interesting drug target for Parkinson disease.

Selection of housekeeping genes for normalization of RT-PCR in hypoxic neural stem cells of rat in vitro

Gene expression analysis under various conditions using real-time reverse transcription polymerase chain reaction (RT-PCR) needs reliable control genes. Housekeeping genes are commonly used as the control. However, no validated housekeeping gene is available for study of hypoxic neural stem cell culture. To choose appropriate internal control genes, the expression of eight commonly used housekeeping genes was examined in rat neural stem cell model to find one or more stably expressed genes under hypoxic/ischemic conditions. Two genes, HPRT and RPL13A were identified as the most confidential housekeeping genes in this research by geNorm and NormFinder softwares. As a groundwork, the most stable housekeeping genes for neural stem cells under hypoxic/ischemic conditions are initially investigated and validated in this experiment, which might provide a better understanding for the gene expression study in ischemic and necrotic neural stem cell cultures or in ischemic diseases of the central nervous system (CNS).

Protein expression profile of human renal mesangial cells under high glucose

BACKGROUND

To understand the spectrum of proteins affected by diabetic nephropathy and to characterize the molecular functions and biological processes they control, the protein expression profile of human renal mesangial cells (HMCs) under high glucose was analyzed.

METHODS

HMCs were divided into a high glucose-cultured group (30 mmol/l) and a normal glucose-cultured group (5 mmol/l). The total proteins of the two groups were separated and analyzed by two-dimensional difference gel electrophoresis (DIGE). Spots that were differentially expressed were picked and digested with trypsin and subjected to MALDI-TOF MS for protein identification.

RESULTS

147 protein spots whose expression levels were significantly increased or decreased more than 1.5-fold in HMCs under high glucose culture were identified. 32 proteins were identified by peptide mass fingerprinting. The protein spots of phosphatidylethanolamine-binding protein 1, granulysin, ATP synthase, H(+) transporter, mitochondrial F0 complex and subunit F2 were observed only in the high glucose group. The expression of 24 proteins was upregulated by high glucose, including eosinophil cationic protein and others. The expression of 5 proteins was downregulated by high glucose, including proteasome β6 subunit precursor, among others.

CONCLUSION

32 protein expressions of human glomerular mesangial cells were regulated by high glucose. In-depth analysis of these differentially expressed proteins' function and crosstalk is expected to provide an experimental basis for clarifying the pathogenesis of diabetic nephropathy.

Human T cell microparticles circulate in blood of hepatitis patients and induce fibrolytic activation of hepatic stellate cells

Microparticles (MPs) are small cell membrane vesicles that are released from cells during apoptosis or activation. Although circulating platelet MPs have been studied in some detail, the existence and functional role of T cell MPs remain elusive. We show that blood from patients with active hepatitis C (alanine aminotransferase [ALT] level >100 IU/mL) contains elevated numbers of T cell MPs compared with patients with mild hepatitis C (ALT <40 IU/mL) and healthy controls. T cell MPs fuse with cell membranes of hepatic stellate cells (HSCs), the major effector cells for excess matrix deposition in liver fibrosis and cirrhosis. MP uptake is partly intercellular adhesion molecule 1-dependent and leads to activation of nuclear factor kappa B and extracellular signal-regulated kinases 1 and 2 and subsequent up-regulation of fibrolytic genes in HSCs, down-regulation of procollagen α1(I) messenger RNA, and blunting of profibrogenic activities of transforming growth factor β1. Ex vivo, the induced fibrolytic activity is evident in MPs derived from activated CD4+ T cells and is highest in MPs derived from activated and apoptotic CD8+ T cells. Mass spectrometry, fluorescence-activated cell sorting analysis, and function blocking antibodies revealed CD147/Emmprin as a candidate transmembrane molecule in HSC fibrolytic activation by CD8+ T cell MPs.

CONCLUSION

Circulating T cell MPs are a novel diagnostic marker for inflammatory liver diseases, and in vivo induction of T cell MPs may be a novel strategy to induce regression of liver fibrosis.

Nonmitogenic survival-enhancing autocrine factors including cyclophilin A contribute to density-dependent mouse embryonic stem cell growth

An improved understanding of the role of extracellular factors in controlling the embryonic stem cell (ESC) phenotype will aid the development of cell-based therapies. While the role of extracellular factors in controlling the pluripotency and differentiation of embryonic stem cells (ESCs) has been the subject of much investigation, the identity and role of extrinsic factors in modulating ESC growth under conditions supporting self-renewal remain largely unknown. We demonstrate that mouse ESC (mESC) growth is density dependent and that one of the mechanisms underlying this phenomenon is the action of survival-enhancing autocrine factors. Proteomic analysis of proteins secreted by mouse ESCs demonstrates significant levels of cyclophilin A which increases the growth rate of mouse ESCs in a dose-dependent manner. Additionally, inhibition of the cyclophilin A receptor CD147 decreases the growth rate of mESCs. These findings identify cyclophilin A as a novel survival-enhancing autocrine factor in mouse ESC cultures.

An Overview of Cyclophilins in Human Cancers

Cyclophilins (Cyps) belong to a group of proteins that have peptidyl-prolyl cis–trans isomerase (PPIase) and molecular chaperone activities. Originally, Cyps were identified as the intracellular receptors for the immunosuppressive drug cyclosporin A. Cyps are found in all prokaryotes and eukaryotes, and have been structurally conserved throughout evolution, implying their importance in cellular function. There are seven major Cyp isoforms in humans. CypA is up-regulated in many human cancers, and there is a strong correlation between over-expression of the CYPA gene and malignant transformation in some cancers. Moreover, CypA is directly under the transcriptional control of two critical transcription factors for cancer development: p53 and hypoxia inducible factor-1α. This review discusses the general biological functions of Cyps under a variety of stress conditions, and the importance and diverse roles of over-expression of CYP genes in human cancers, with a particular emphasis on CYPA. These oncogenic properties suggest that CypA is a promising target for cancer therapy.

The many faces of EMMPRIN - roles in neuroinflammation

The central nervous system (CNS) is a relatively immune-privileged organ, wherein a well-instated barrier system (the blood-brain barrier) prevents the entry of blood cells into the brain with the exception of regular immune surveillance cells. Despite this tight security immune cells are successful in entering the CNS tissue where they result in states of neuroinflammation, tissue damage and cell death. Various components of the blood-brain barrier and infiltrating cells have been examined to better understand how blood cells are able to breach this secure barrier. Proteases, specifically matrix metalloproteinases (MMP), have been found to be the common culprits in most diseases involving neuroinflammation. MMPs secreted by infiltrating cells act specifically upon targets on various components of the blood-brain barrier, compromising this barrier and allowing cell infiltration into the CNS. Extracellular matrix metalloproteinase inducer (EMMPRIN) is an upstream inducer of several MMPs and is suggested to be the master regulator of MMP production in disease states such as cancer metastasis. EMMPRIN in the context of the CNS is still relatively understudied. In this review we will introduce EMMPRIN, discuss its ligands and roles in non-CNS conditions that can help implicate its involvement in CNS disorders, showcase its expression within the CNS in healthy and disease conditions, elucidate its ligands and receptors, and briefly discuss the emerging roles it plays in various diseases of the CNS involving inflammation.

Cyclophilin-CD147 interactions: a new target for anti-inflammatory therapeutics

CD147 is a widely expressed plasma membrane protein that has been implicated in a variety of physiological and pathological activities. It is best known for its ability to function as extracellular matrix metalloproteinase inducer (hence the other name for this protein, EMMPRIN), but has also been shown to regulate lymphocyte responsiveness, monocarboxylate transporter expression and spermatogenesis. These functions reflect multiple interacting partners of CD147. Among these CD147-interacting proteins cyclophilins represent a particularly interesting class, both in terms of structural considerations and potential medical implications. CD147 has been shown to function as a signalling receptor for extracellular cyclophilins A and B and to mediate chemotactic activity of cyclophilins towards a variety of immune cells. Recent studies using in vitro and in vivo models have demonstrated a role for cyclophilin-CD147 interactions in the regulation of inflammatory responses in a number of diseases, including acute lung inflammation, rheumatoid arthritis and cardiovascular disease. Agents targeting either CD147 or cyclophilin activity showed significant anti-inflammatory effects in experimental models, suggesting CD147-cyclophilin interactions may be a good target for new anti-inflammatory therapeutics. Here, we review the recent literature on different aspects of cyclophilin-CD147 interactions and their role in inflammatory diseases.

Role of cyclophilin a during oncogenesis

Cyclophilins (Cyps) are ubiquitously expressed proteins that are evolutionarily conserved. CypA is the most abundant among the Cyps and is expressed in the cytosol. With its chaperone and PPIase activities, CypA contributes to the maintenance of correct conformation of nascent or denatured proteins and also provides protection against environmental insults. Also, its expression is induced in response to a wide variety of stressors including cancer. Upregulation of CypA in small cell lung cancer, pancreatic cancer, breast cancer, colorectal cancer, squamous cell carcinoma and melanoma has been reported. In some cancers a correlation between CypA overexpression and malignant transformation has been established. While molecular partners of CypA that promote cancer development are yet to be discovered, various mechanisms have been proposed to account for the cytoprotective functions of CypA during cancer development. CypA may promote the survival of cells under the stressful condition of cancer. CypA may well be essential for maintaining the conformation of oncogenic proteins, signalling proteins for cell proliferation, antiapoptotic components, transcription factors, or cell motility regulatory proteins. Antioxidant effects of CypA, which have been suggested by some researchers, may also become critical to reactive oxygen species (ROS) creating an oncogenetic environment. Developing new CypA inhibitors for therapeutics has been surmised from the cytoprotective functions of CypA and its overexpression in many cancer types. Therefore, CypA can be further investigated as a useful tool for early diagnosis, treatment and prevention of human cancers.

The Stimulation of CD147 Induces MMP-9 Expression through ERK and NF-kappaB in Macrophages: Implication for Atherosclerosis

BACKGROUND

CD147, as a cellular receptor for cyclophilin A (CypA), is a multifunctional protein involved in tumor invasion, inflammation, tissue remodeling, neural function, and reproduction. Recent observations showing the expression of CD147 in leukocytes indicate that this molecule may have roles in inflammation.

METHODS

In order to investigate the role of CD147 and its ligand in the pathogenesis of atherosclerosis, human atherosclerotic plaques were analyzed for the expression pattern of CD147 and CypA. The cellular responses and signaling molecules activated by the stimulation of CD147 were then investigated in the human macrophage cell line, THP-1, which expresses high basal level of CD147 on the cell surface.

RESULTS

Staining of both CD147 and CypA was detected in endothelial cell layers facing the lumen and macrophage-rich areas. Stimulation of CD147 with its specific monoclonal antibody induced the expression of matrix metalloproteinase (MMP)-9 in THP-1 cells and it was suppressed by inhibitors of both ERK and NF-kappaB. Accordingly, the stimulation of CD147 was observed to induce phosphorylation of ERK, phosphorylation-associated degradation of IkappaB, and nuclear translocation of NF-kappaB p65 and p50 subunits.

CONCLUSION

These results suggest that CD147 mediates the inflammatory activation of macrophages that leads to the induction of MMP-9 expression, which could play a role in the pathogenesis of inflammatory diseases such as atherosclerosis.

Basal and stimulated lactate fluxes in primary cultures of astrocytes are differentially controlled by distinct proteins

Lactate release by astrocytes is postulated to be of importance for neuroenergetics but its regulation is poorly understood. Basigin, a chaperone protein for specific monocarboxylate transporters (MCTs), represents a putatively important regulatory element for lactate fluxes. Indeed, basigin knockdown by RNA interference in primary cultures of astrocytes partially reduced both proton-driven lactate influx and efflux. But more strikingly, enhancement of lactate efflux induced by glutamate was prevented while the effect of sodium azide was significantly reduced by treatment of cultured astrocytes with anti-basigin small interfering RNA. Enhancement of glucose utilization was unaffected under the same conditions. Basal lactate uptake and release were significantly reduced by MCT1 knockdown, even more so than with basigin knockdown, whereas glutamate-driven or sodium azide-induced enhancement of lactate release was not inhibited by either MCT1, 2, or 4 small interfering RNAs. In conclusion, MCT1 plays a pivotal role in the control of basal proton-driven lactate flux in astrocytes while basigin is only partly involved, most likely via its interaction with MCT1. In contrast, basigin appears to critically regulate the enhancement of lactate release caused by glutamate (or sodium azide) but via an effect on another unidentified transporter at least present in astrocytes in vitro.

Microarray analyses of hypoxia-regulated genes in an aryl hydrocarbon receptor nuclear translocator (Arnt)-dependent manner

We investigated hypoxia-inducible factor (HIF)-dependent changes in the expression of 5592 genes in response to hypoxia (0.1% O(2), 16 h) by performing cDNA microarray analyses of mouse hepa1c1c7 and BpRc1 cells. BpRc1 cells are a hepa1c1c7 variant defective in HIF-beta/aryl hydrocarbon receptor nuclear translocator (Arnt), and are therefore unable to induce HIF target genes in response to hypoxia. By comparing hepa1c1c7 cells with BpRc1 cells, we were able to investigate hypoxia-regulated gene expression as well as the role played by HIF in regulating the hypoxic-dependent response of gene expression. This study identified 50 hypoxia-induced genes and 36 hypoxia-repressed genes. Quantitative PCR analysis of nine genes confirmed our ability to accurately analyze changes in hypoxia-induced gene expression by microarray analysis. By comparing quantitative PCR analyses of these nine genes in BpRc1 and hepa1c1c7 cells, we determined that eight of the nine hypoxia-induced genes are Arnt dependent. Additional quantitative PCR analyses of eight hypoxia-repressed genes confirmed, with a 50% probability, that microarray analysis was able to predict hypoxia-repressed gene expression. Only two of the four confirmed genes were found to be repressed in an Arnt-dependent manner. Collectively, six of these 13 genes (46.2% probability) showed a pattern of expression consistent with the microarray analysis with regard to Arnt dependence. Finally, we investigated the HIF-1alpha dependence of these 13 genes by quantitative PCR analysis in HIF-1alpha knockdown 3T3-L1 cells. These analyses identified novel hypoxia-regulated genes and confirmed the role of Arnt and HIF-1alpha in regulating their expression. These results identify additional HIF target genes and provide a more complete understanding of hypoxia signaling.

Cardiac-restricted overexpression of extracellular matrix metalloproteinase inducer causes myocardial remodeling and dysfunction in aging mice

The matrix metalloproteinases (MMPs) play a pivotal role in adverse left ventricular (LV) myocardial remodeling. The transmembrane protein extracellular MMP inducer (EMMPRIN) causes increased MMP expression in vitro, and elevated levels occur in patients with LV failure. However, the direct consequences of a prolonged increase in the myocardial expression of EMMPRIN in vivo remained unexplored. Cardiac-restricted EMMPRIN expression (EMMPRINexp) was constructed in mice using the full-length human EMMPRIN gene ligated to the myosin heavy chain promoter, which yielded approximately a twofold increase in EMMPRIN compared with that of the age/strain-matched wild-type (WT) mice; EMMPRINexp (n=27) and WT (n=33) mice were examined at 3.2+/-0.1 or at 13.3+/-0.5 mo of age (n=43 and 26, respectively). LV end-diastolic volume (EDV) was similar in young EMMPRINexp and WT mice (54+/-2 vs. 57+/-3 microl), but LV ejection fraction (EF) was reduced (51+/-1 vs. 57+/-1%; P<0.05). In old EMMPRINexp mice, LV EDV was increased compared with WT mice values (76+/-3 vs. 58+/-3 microl; P<0.05) and LV EF was significantly reduced (45+/-1 vs. 57+/-2%; P<0.05). In EMMPRINexp old mice, myocardial MMP-2 and membrane type-1 MMP levels were increased by >50% from WT values (P<0.05) and were accompanied by a twofold higher collagen content (P<0.05). Persistent myocardial EMMPRINexp in aging mice caused increased levels of both soluble and membrane type MMPs, fibrosis, and was associated with adverse LV remodeling. These findings suggest that EMMPRIN is an upstream signaling pathway that can play a mechanistic role in adverse remodeling within the myocardium.

Cyclophilin and the regulation of symbiosis in Aiptasia pallida

The sea anemone Aiptasia pallida, symbiotic with intracellular dinoflagellates, expresses a peptydyl-prolyl cis-trans isomerase (PPIase) belonging to the conserved family of cytosolic cyclophilins (ApCypA). Protein extracts from A. pallida exhibited PPIase activity. Given the high degree of conservation of ApCypA and its known function in the cellular stress response, we hypothesized that it plays a similar role in the cnidarian-dinoflagellate symbiosis. To explore its role, we inhibited the activity of cyclophilin with cyclosporin A (CsA). CsA effectively inhibited the PPIase activity of protein extracts from symbiotic A. pallida. CsA also induced the dose-dependent release of symbiotic algae from host tissues (bleaching). Laser scanning confocal microscopy using superoxide and nitric oxide-sensitive fluorescent dyes on live specimens of A. pallida revealed that CsA strongly induced the production of these known mediators of bleaching. We tested whether the CsA-sensitive isomerase activity is important for maintaining the activity of the antioxidant enzyme superoxide dismutase (SOD). SOD activity of protein extracts was not affected by pre-incubation with CsA in vitro.

Peroxiredoxin 2 overexpression protects cortical neuronal cultures from ischemic and oxidative injury but not glutamate excitotoxicity, whereas Cu/Zn superoxide dismutase 1 overexpression protects only against oxidative injury

We previously reported that peroxiredoxin 2 (PRDX2) and Cu/Zn superoxide dismutase 1 (SOD1) proteins are up-regulated in rat primary neuronal cultures following erythropoietin (EPO) preconditioning. In the present study, we have demonstrated that adenovirally mediated overexpression of PRDX2 in cortical neuronal cultures can protect neurons from in vitro ischemia (oxygen-glucose deprivation) and an oxidative insult (cumene hydroperoxide) but not glutamate excitotoxicity. We have also demonstrated that adenovirally mediated overexpression of SOD1 in cortical neuronal cultures protected neurons only against the oxidative insult. Interestingly, we did not detect up-regulation of PRDX2 or SOD1 protein in the rat hippocampus following exposure to either 3 min or 8 min of global cerebral ischemia. Further characterization of PRDX2's neuroprotective mechanisms may aid in the development of a neuroprotective therapy.

Generation of functional scFv intrabody to abate the expression of CD147 surface molecule of 293A cells

BACKGROUND

Expression of intracellular antibodies (intrabodies) has become a broadly applicable technology for generation of phenotypic knockouts in vivo. The method uses surface depletion of cellular membrane proteins to examine their biological function. In this study, we used this strategy to block the transport of cell surface molecule CD147 to the cell membrane. Phage display technology was introduced to generate the functional antibody fragment to CD147, and we subsequently constructed a CD147-specific scFv that was expressed intracellularly and retained in the endoplasmic reticulum by adenoviral gene transfer.

RESULTS

The recombinant antibody fragments, Fab and scFv, of the murine monoclonal antibody (clone M6-1B9) reacted specifically to CD147 by indirect enzyme-linked immunosorbent assays (ELISA) using a recombinant CD147-BCCP as a target. This indicated that the Fab- and scFv-M6-1B9 displaying on phage surfaces were correctly folded and functionally active. We subsequently constructed a CD147-specific scFv, scFv-M6-1B9-intrabody, in 293A cells. The expression of CD147 on 293A cell surface was monitored at 36 h after transduction by flow cytometry and demonstrated remarkable reduction. Colocalization of scFv-M6-1B9 intrabody with CD147 in the ER network was depicted using a 3D deconvolution microscopy system.

CONCLUSION

The results suggest that our approach can generate antibody fragments suitable for decreasing the expression of CD147 on 293A cells. This study represents a step toward understanding the role of the cell surface protein, CD147.

CD147 inhibits the nuclear factor of activated T-cells by impairing Vav1 and Rac1 downstream signaling

CD147 is a transmembrane protein that plays crucial roles in the development and function of the reproductive, visual, and nervous systems. CD147 also exerts positive and negative actions in T-cells by still obscure mechanisms. In this study, we have analyzed the expression, localization, and function of CD147 during T-cell receptor signaling responses. We show here that CD147 is an integral component of the T-cell immune synapse and that its overexpression leads to the inhibition of NF-AT (nuclear factor of activated T-cells) activity induced by Vav1, a Rac1 exchange factor. This inhibitory activity is mediated by the CD147 intracellular tail and is totally independent of its extracellular or transmembrane regions. The molecular dissection of the influence of CD147 on the Vav1 pathway indicates that its inhibitory action takes place downstream of Vav1 and Rac1 but upstream of the serine/threonine kinases JNK and Pak1. The interference of CD147 with these pathways is highly specific because the overexpression of CD147 does not affect the activity of other GDP/GTP exchange factors or the stimulation of the ERK cascade. Finally, we show that the CD147 knockdown in Jurkat cells promotes higher levels of NF-AT stimulation and Pak1 phosphorylation upon T-cell receptor cross-linking. Instead, the lack of CD147 does not affect other signaling cascades that participate in the same cellular response. Taken together, these results indicate that CD147, via the selective inhibition of specific downstream elements of the Vav1/Rac1 route, contributes to the negative regulation of T-cell responses.

Aging modifies brain region-specific vulnerability to experimental oxidative stress induced by low dose hydrogen peroxide

Our previous studies demonstrated a significant decline in brain function and behavior in Fischer 344 (F344) rats with age. The present study was designed to test the hypothesis that dysregulation in calcium homeostasis (as assessed through (45)Ca flux) may contribute to the increase in age-related vulnerability to oxidative stress in brain regions, and result in a deficit in behavior-mediated signaling. Crude membrane (P-2) and more purified synaptosomal fractions were isolated from the striatum, hippocampus, and frontal cortex of young (6 months) and old (22 months) F344 rats and were assessed for calcium flux and extracellular-regulated kinase activity 1 (ERK) under control and oxidative stress conditions induced by low dose hydrogen peroxide (final concentration 5 microM). The level of oxidative stress responses was monitored by measuring reactive oxygen species (ROS) and glutathione (GSH). The results showed a significant difference in oxidative stress responses between young and old rats in evaluated brain regions. Old rats showed higher sensitivity to oxidative stress than young rats. The present findings show the differential effects of oxidative stress on calcium flux in brain regions with age that are dependent upon the brain areas examined and the fraction assessed. The accumulation of ROS and the decrease in GSH in the frontal cortex were sufficient to decrease ERK activity in old rats. This is the first study, to our knowledge, that demonstrates age-related differential sensitivity to oxidative stress expressed as a function of behavior-mediated signaling and stress levels among different fractions isolated from brain regions controlling behavior.

CD147 immunoglobulin superfamily receptor function and role in pathology

The immunoglobulin superfamily member CD147 plays an important role in fetal, neuronal, lymphocyte and extracellular matrix development. Here we review the current understanding of CD147 expression and protein interactions with regard to CD147 function and its role in pathologic conditions including heart disease, Alzheimer's disease, stroke and cancer. A model linking hypoxic conditions found within the tumor microenvironment to upregulation of CD147 expression and tumor progression is introduced.

The PEA-15/PED protein protects glioblastoma cells from glucose deprivation-induced apoptosis via the ERK/MAP kinase pathway

PEA-15 (phosphoprotein enriched in astrocytes 15 kDa) is a death effector domain-containing protein, which is involved in the regulation of apoptotic cell death. Since PEA-15 is highly expressed in cells of glial origin, we studied the role of PEA-15 in human malignant brain tumors. Immunohistochemical analysis of PEA-15 expression shows strong immunoreactivity in astrocytomas and glioblastomas. Phosphorylation of PEA-15 at Ser(116) is found in vivo in perinecrotic areas in glioblastomas and in vitro after glucose deprivation of glioblastoma cells. Overexpression of PEA-15 induces a marked resistance against glucose deprivation-induced apoptosis, whereas small interfering RNA (siRNA)-mediated downregulation of endogenous PEA-15 results in the sensitization to glucose withdrawal-mediated cell death. This antiapoptotic activity of PEA-15 under low glucose conditions depends on its phosphorylation at Ser(116). Moreover, siRNA-mediated knockdown of PEA-15 abolishes the tumorigenicity of U87MG glioblastoma cells in vivo. PEA-15 regulates the level of phosphorylated extracellular-regulated kinase (ERK)1/2 in glioblastoma cells and the PEA-15-dependent protection from glucose deprivation-induced cell death requires ERK1/2 signaling. PEA-15 transcriptionally upregulates the Glucose Transporter 3, which is abrogated by the inhibition of ERK1/2 phosphorylation. Taken together, our findings suggest that Ser(116)-phosphorylated PEA-15 renders glioma cells resistant to glucose deprivation-mediated cell death as encountered in poor microenvironments, for example in perinecrotic areas of glioblastomas.