Dealing with the family: CD147 interactions with cyclophilins

The origin and evolution of Basigin(BSG) gene: A comparative genomic and phylogenetic analysis

Basigin (BSG), also known as extracellular matrix metalloproteinase inducer (EMMPRIN) or cluster of differentiation 147 (CD147), plays various fundamental roles in the intercellular recognition involved in immunologic phenomena, differentiation, and development. In this study, we aimed to compare the similarities and differences of BSG among organisms and explore possible evolutionary relationships based on the comparison result. We used the extensive BLAST tool to search the metazoan genomes, N-glycosylation sites, the transmembrane region and other functional sites. We then identified BSG homologs from genomic sequences and analyzed their phylogenetic relationships. We identified that BSG genes exist not only in the vertebrate metazoans but also in the invertebrate metazoans such as Amphioxus B. floridae, D. melanogaster, A. mellifera, S. japonicum, C. gigas, and T. patagoniensis. After sequence analysis, we confirmed that only vertebrate metazoans and Cephalochordate (amphioxus B. floridae) have the classic structure (a signal peptide, two Ig-like domains (IgC2 and IgI), a transmembrane region, and an intracellular domain). The invertebrate metazoans (excluding amphioxus B. floridae) lack the N-terminal signal peptides and IgC2 domain. We then generated a phylogenetic tree, genome organization comparison, and chromosomal disposition analysis based on the biological information obtained from the NCBI and Ensembl databases. Finally, we established the possible evolutionary scenario of the BSG gene, which showed the restricted exon rearrangement that has occurred during evolution, forming the present-day BSG gene.

Spongionella Secondary Metabolites, Promising Modulators of Immune Response through CD147 Receptor Modulation

The modulation of the immune system can have multiple applications such as cancer treatment, and a wide type of processes involving inflammation where the potent chemotactic agent cyclophilin A (Cyp A) is implicated. The Porifera phylum, in which Spongionella is encompassed, is the main producer of marine bioactive compounds. Four secondary metabolites obtained from Spongionella (Gracilin H, A, L, and Tetrahydroaplysulphurin-1) were described to hit Cyp A and to block the release of inflammation mediators. Based on these results, some role of Spongionella compounds on other steps of the signaling pathway mediated by this chemotactic agent can be hypothesized. In the present paper, we studied the effect of these four compounds on the surface membrane CD147 receptor expression, on the extracellular levels of Cyp A and on the ability to migrate of concanavalin (Con A)-activated T lymphocytes. Similar to a well-known immunosuppressive agent cyclosporine A (CsA), Gracilin H, A, L, and tetrahydroaplysulphurin-1 were able to reduce the CD147 membrane expression and to block the release of Cyp A to the medium. Besides, by using Cyp A as chemotactic agent, T cell migration was inhibited when cells were previously incubated with Gracilin A and Gracilin L. These positive results lead us to test the in vivo effect of Gracilin H and L in a mouse ear delayed hypersensitive reaction. Thus, both compounds efficiently reduce the ear swelling as well as the inflammatory cell infiltration. These results provide more evidences for their potential therapeutic application in immune-related diseases of Spongionella compounds.

Identification of low abundance cyclophilins in human plasma

Cylophilins (Cyps) belong to the ubiquitously distributed enzyme class of peptidyl prolyl cis/trans isomerases (EC5.2.1.8), which are foldases capable of accelerating slow steps in the refolding of denatured proteins. At least 20 different Cyp isoenzymes are broadly distributed among all organs and cellular compartments in humans. Extracellularly localized Cyps came into the scientific focus recently because of their involvement in the control of inflammatory diseases, as well as viral and bacterial infections. However, detailed insights into Cyp functions are often hampered by the lack of sensitive detection methods. We present an improved method for affinity purification and detection of Cyp in biotic samples in this manuscript. The procedure takes advantage of two novel cyclosporine A derivatives. Derivative 1 was used to capture Cyps from the sample while derivative 2 was applied for selective release from the affinity matrix. Using this approach, eight different Cyp (CypA, CypB, CypC, Cyp40 (PPID), CypE, CypD (PPIF), CypH, and CypL1) were unambiguously detected in healthy human blood plasma. Moreover, extracellular CypA was found to be partially modified by N^ε acetylation on residues Lys44, Lys133, Lys155, as well as N^α  acetylation at the N-terminal Val residue. N^α  acetylation of Ser2 residue was also found for Cyp40.

Monocarboxylate transporters in the brain and in cancer

Monocarboxylate transporters (MCTs) constitute a family of 14 members among which MCT1-4 facilitate the passive transport of monocarboxylates such as lactate, pyruvate and ketone bodies together with protons across cell membranes. Their anchorage and activity at the plasma membrane requires interaction with chaperon protein such as basigin/CD147 and embigin/gp70. MCT1-4 are expressed in different tissues where they play important roles in physiological and pathological processes. This review focuses on the brain and on cancer. In the brain, MCTs control the delivery of lactate, produced by astrocytes, to neurons, where it is used as an oxidative fuel. Consequently, MCT dysfunctions are associated with pathologies of the central nervous system encompassing neurodegeneration and cognitive defects, epilepsy and metabolic disorders. In tumors, MCTs control the exchange of lactate and other monocarboxylates between glycolytic and oxidative cancer cells, between stromal and cancer cells and between glycolytic cells and endothelial cells. Lactate is not only a metabolic waste for glycolytic cells and a metabolic fuel for oxidative cells, but it also behaves as a signaling agent that promotes angiogenesis and as an immunosuppressive metabolite. Because MCTs gate the activities of lactate, drugs targeting these transporters have been developed that could constitute new anticancer treatments. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.

Accuracy of novel diagnostic biomarkers for hepatocellular carcinoma: An update for clinicians (Review)

Hepatocellular carcinoma (HCC) is the most common liver malignancy and a leading cause of cancer-related mortality worldwide. Accurate detection and differential diagnosis of early HCC can significantly improve patient survival. Currently, detection of HCC in clinical practice is performed by diagnostic imaging techniques and determination of serum biomarkers, most notably α-fetoprotein (AFP), fucosylated AFP and des-γ-carboxyprothrombin. However, these methods display limitations in sensitivity and specificity, especially with respect to early stages of HCC. Recently, high-throughput technologies have elucidated many new pathways involved in hepatocarcinogenesis and have led to the discovery of a plethora of novel, non-invasive serum biomarkers. In particular, the combination of AFP with these new candidate molecules has yielded promising results. In this review, we aimed at recapitulating the most recent (2013–2015) developments in HCC biomarker research. We compared promising novel diagnostic serum protein biomarkers, such as annexin A2, the soluble form of the receptor tyrosine kinase Axl and thioredoxin, as well as their combinations with AFP. High diagnostic performance (area under the curve >0.75) as shown by threshold-independent receiver operating characteristic curve analysis was a prerequisite for inclusion in this review. In addition, we discuss the role and potential of microRNAs in HCC diagnosis and associated methodological challenges.

CD147 stimulates hepatoma cells escaping from immune surveillance of T cells by interaction with Cyclophilin A

T cells play an important role in tumor immune surveillance. CD147 is a member of immunoglobulin superfamily present on the surface of many tumor cells and mediates malignant cell behaviors. Cyclophilin A (CypA) is an intracellular protein promoting inflammation when released from cells. CypA is a natural ligand for CD147. In this study, CD147 specific short hairpin RNAs (shRNA) were transfected into murine hepatocellular carcinoma Hepa1-6 cells to assess the effects of CD147 on hepatoma cells escaping from immune surveillance of T cells. We found extracellular CypA stimulated cell proliferation through CD147 by activating ERK1/2 signaling pathway. Downregulation of CD147 expression on Hepa1-6 cells significantly suppressed tumor progression in vivo, and decreased cell viability when co-cultured with T cells in vitro. Importantly, knockdown of CD147 on Hepa1-6 cells resulted in significantly increased T cells chemotaxis induced by CypA both in vivo and in vitro. These findings provide novel mechanisms how tumor cells escaping from immune surveillance of T cells. We provide a potential therapy for hepatocellular carcinoma by targeting CD147 or CD147-CypA interactions.

NS-398 promotes pancreatic cancer cell invasion by CD147 and MMP-2 via the activation of P38

The overexpression or abnormal activation of cyclo‑oxygenase‑2 (COX‑2) has been reported in pancreatic cancer cells. NS‑398, a selective inhibitor of COX‑2, is unable to inhibit pancreatic cancer cell proliferation, as determined by a Cell Counting Kit 8 assay. However, it does increase cancer cell invasiveness, and therefore the invasiveness of the PANC‑1 cells was determined, along with the activation of P38, which was assessed by western blotting. In the present study, to evaluate the mechanisms underlying the action of NS‑398 in pancreatic cancer cells, PANC‑1 cells were treated with NS‑398, and the invasion signaling pathways of cluster of differentiation (CD)147‑matrix metalloproteinase (MMP)‑2 and mitogen‑activated protein kinases were evaluated. The results showed that NS‑398‑induced the expression of CD147 and MMP‑2 via the activation of P38, which was involved in antiproliferative activity and induced pancreatic cancer cell invasiveness. The PANC‑1 cells were also co‑treated with CD147 small interfering (si)RNA and NS‑398, and it was found that the NS‑398‑induced activation of P38 was not inhibited by CD147 siRNA, however, the expression of MMP‑2 was inhibited. CD147 siRNA inhibited the invasiveness of the pancreatic cancer cells induced by NS‑398, but also restored NS‑398‑induced antiproliferative activity. These data indicated that P38 in the pancreatic cancer cells was non‑specifically activated by NS‑398. This activation induced the expression of CD147‑MMP‑2, opposed the antiproliferative activity of NS‑398 and increased the invasiveness of the PANC‑1 cells.

CD147/basigin limits lupus nephritis and Th17 cell differentiation in mice by inhibiting the interleukin-6/STAT-3 pathway

OBJECTIVE

Interleukin-17 (IL-17)-producing T cells (Th17 cells) play critical roles in the pathogenesis of immune-related diseases, including systemic lupus erythematosus. However, the fundamental mechanism regulating Th17 cell differentiation is not fully understood. Recently, we demonstrated that plasma levels of CD147/basigin (Bsg) in patients with lupus nephritis (LN) were closely associated with disease activity. but the molecular mechanism involving Bsg has been elusive. Here, we addressed the role of Bsg in the pathogenesis of LN.

METHODS

Injections of pristane (2,6,10,14-tetramethylpentadecane [TMPD]) were administered to Bsg(-/-) or Bsg(+/+) mice to induce LN. The mice were killed 6 months after being injected, for histologic and biochemical analyses of the kidneys and spleens.

RESULTS

Pristane induced LN more strikingly in Bsg(-/-) mice than in Bsg(+/+) mice, even though humoral autoimmunity was similarly increased in both genotypes. The increased number of Th17, but not Th1, Treg cells, was augmented in Bsg(-/-) mice. The expression of IL-17 was also increased in the kidneys of Bsg(-/-) mice, in proportion to LN disease activity. Furthermore, treatment with anti-IL-17 antibody reduced LN disease activity in Bsg(-/-) mice. Complementary to these phenotypes of Bsg(-/-) mice, Bsg expression was enhanced in activated CD4+ T cells in vivo and in vitro. Bsg deficiency selectively augmented in vitro differentiation of naive CD4+ T cells to Th17 cells and STAT-3 phosphorylation during this differentiation. Moreover, STAT-3 phosphorylation was suppressed by crosslinking of Bsg with its antibody.

CONCLUSION

Bsg plays an indispensable role in Th17 cell differentiation as a negative regulator by suppressing the IL-6/STAT-3 pathway.

Upregulation of extracellular matrix metalloproteinase inducer promotes hypoxia-induced epithelial-mesenchymal transition in esophageal cancer

Extracellular matrix metalloproteinase inducer (EMMPRIN) exerts important roles in tumor progression, including angiogenesis, metastasis and therapy resistance. The epithelial‑mesenchymal transition (EMT), which is induced by hypoxia, is an important process in cancer metastasis. However, the association between hypoxia and EMMPRIN remains to be elucidated in esophageal cancer. The expression of EMMPRIN was determined by western blotting and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR), and EMT markers were analyzed by western blotting, RT‑qPCR and immunofluoresence. The migration and invasion of cells was investigated by Transwell assay. The results indicated that the expression levels of EMMPRIN in esophageal cancer cells were markedly higher compared with those in normal esophageal cells. EMMPRIN was able to promote esophageal cancer cell migration and invasion under both hypoxic or normoxic conditions, as demonstrated by the migration and invasion assay. The expression levels of E‑cadherin were reduced, and those of snail family zinc finger 1, fibronectin, α‑smooth muscle actin and fibroblast secretory protein 1 increased in esophageal cancer cells following treatment with human recombinant EMMPRIN under hypoxic conditions. The mRNA expression levels of the EMT markers were similar to those of the protein expression levels. Furthermore, the results demonstrated that EMMPRIN was regulated by hypoxia‑inducible factor (HIF)‑1α. These data suggested that EMMPRIN promoted metastasis and the EMT in esophageal cancer cells by regulating HIF-1α.

Targeting Extracellular Cyclophilins Ameliorates Disease Progression in Experimental Biliary Atresia

Biliary atresia (BA) is a devastating liver disease of unknown etiology affecting children generally within the first 3 months of life. The disease is manifested by inflammation and subsequent obstruction of the extrahepatic bile ducts, fibrosis and liver failure. The mechanisms responsible for disease pathogenesis are not fully understood, but a number of factors controlled by the SMAD signaling pathway have been implicated. In this study, we investigated the role of a known proinflammatory factor, extracellular cyclophilin A (CypA), in the pathogenesis of biliary atresia using the rhesus rotavirus (RRV) murine model. We used a unique cyclosporine A derivative, MM284, which does not enter cells and therefore inactivates exclusively extracellular cyclophilins, as a potential treatment. We demonstrated that levels of CypA in plasma of RRV-infected mice were increased significantly, and that treatment of mice with MM284 prior to or one day after disease initiation by RRV infection significantly improved the status of mice with experimental BA: weight gain was restored, bilirubinuria was abrogated, liver infiltration by inflammatory cells was reduced and activation of the SMAD pathway and SMAD-controlled fibrosis mediators and tissue inhibitor of metalloproteinases (TIMP)-4 and matrix metalloproteinase (MMP)-7 was alleviated. Furthermore, treatment of human hepatic stellate cells with recombinant cyclophilin recapitulated SMAD2/3 activation, which was also suppressed by MM284 treatment. Our data provide the first evidence that extracellular cyclophilins activate the SMAD pathway and promote inflammation in experimental BA, and suggest that MM284 may be a promising therapeutic agent for treating BA and possibly other intrahepatic chronic disorders.

Platelet-bound cyclophilin A in patients with stable coronary artery disease and acute myocardial infarction

OBJECTIVE

Recently, we reported that extracellular cyclophilin A (CyPA) is an important agonist for platelets. Whereas soluble CyPA-levels have been associated with cardiovascular risk factors, cell-bound CyPA has not been investigated yet. In this study, we analyzed for the first time platelet-bound CyPA in patients with symptomatic coronary artery disease (CAD).

METHODS AND RESULTS

blood was obtained from 388 consecutive patients: 204 with stable CAD and 184 with acute coronary syndrome (76 with unstable angina, 78 with non ST-elevation myocardial infarction (NSTEMI), and 30 with STEMI). In vitro stimulation of platelets with classical agonists revealed an enhanced expression of CyPA on the platelet surface. In patients with stable CAD, platelet-bound CyPA correlated excellently with platelet activity measured by P-selectin exposure in flow cytometry. The analysis of classical risk factors for atherosclerosis revealed that patients with hypertension and hypercholesterolemia had significantly enhanced platelet-bound CyPA, whereas diabetes and smoking were not associated with enhanced CyPA-binding to the platelet surface. In multivariate analysis, hypercholesterolemia was the only significant predictor of enhanced platelet-bound CyPA. Interestingly, in patients with acute myocardial infarction (AMI) platelet-bound CyPA was significantly decreased compared with patients with stable CAD.

CONCLUSIONS

Enhanced platelet-bound CyPA is associated with hypertension and hypercholesterolemia in stable CAD patients. In patients with AMI platelet-bound CyPA is significantly decreased.

EMMPRIN in gynecologic cancers: pathologic and therapeutic aspects

The highly glycosylated transmembrane protein extracellular matrix metalloproteinase inducer (EMMPRIN) is associated with several pathological conditions, including various types of cancers. In different gynecological malignancies, such as ovarian, cervical, and endometrial cancers, EMMPRIN plays significant roles in cell adhesion modulation, tumor growth, invasion, angiogenesis, and metastasis by inducing the production of various molecules, including matrix metalloproteinases and vascular endothelial growth factor. Because of its high level of expression, EMMPRIN can possibly be used as a diagnostic marker of gynecological cancers. Recent studies have showed that targeting EMMPRIN, especially by RNA interference (RNAi) technology, has promising therapeutic potential in basic research on gynecological cancer treatments, which make a platform for the future clinical success. This review study focused on the association of EMMPRIN in gynecological cancers in the perspectives of pathogenesis, diagnosis, and therapeutics.

Apolipoprotein D Internalization Is a Basigin-dependent Mechanism

Apolipoprotein D (apoD), a member of the lipocalin family, is a 29-kDa secreted glycoprotein that binds and transports small lipophilic molecules. Expressed in several tissues, apoD is up-regulated under different stress stimuli and in a variety of pathologies. Numerous studies have revealed that overexpression of apoD led to neuroprotection in various mouse models of acute stress and neurodegeneration. This multifunctional protein is internalized in several cells types, but the specific internalization mechanism remains unknown. In this study, we demonstrate that the internalization of apoD involves a specific cell surface receptor in 293T cells, identified as the transmembrane glycoprotein basigin (BSG, CD147); more particularly, its low glycosylated form. Our results show that internalized apoD colocalizes with BSG into vesicular compartments. Down-regulation of BSG disrupted the internalization of apoD in cells. In contrast, overexpression of basigin in SH-5YSY cells, which poorly express BSG, restored the uptake of apoD. Cyclophilin A, a known ligand of BSG, competitively reduced apoD internalization, confirming that BSG is a key player in the apoD internalization process. In summary, our results demonstrate that basigin is very likely the apoD receptor and provide additional clues on the mechanisms involved in apoD-mediated functions, including neuroprotection.

An interactive network of elastase, secretases, and PAR-2 protein regulates CXCR1 receptor surface expression on neutrophils

CXCL8 (IL-8) recruits and activates neutrophils through the G protein-coupled chemokine receptor CXCR1. We showed previously that elastase cleaves CXCR1 and thereby impairs antibacterial host defense. However, the molecular intracellular machinery involved in this process remained undefined. Here we demonstrate by using flow cytometry, confocal microscopy, subcellular fractionation, co-immunoprecipitation, and bioluminescence resonance energy transfer that combined α- and γ-secretase activities are functionally involved in elastase-mediated regulation of CXCR1 surface expression on human neutrophils, whereas matrix metalloproteases are dispensable. We further demonstrate that PAR-2 is stored in mobilizable compartments in neutrophils. Bioluminescence resonance energy transfer and co-immunoprecipitation studies showed that secretases, PAR-2, and CXCR1 colocalize and physically interact in a novel protease/secretase-chemokine receptor network. PAR-2 blocking experiments provided evidence that elastase increased intracellular presenilin-1 expression through PAR-2 signaling. When viewed in combination, these studies establish a novel functional network of elastase, secretases, and PAR-2 that regulate CXCR1 expression on neutrophils. Interfering with this network could lead to novel therapeutic approaches in neutrophilic diseases, such as cystic fibrosis or rheumatoid arthritis.

Decrease in plasma cyclophilin A concentration at 1 month after myocardial infarction predicts better left ventricular performance and synchronicity at 6 months: a pilot study in patients with ST elevation myocardial infarction

BACKGROUND

Cyclophilin A (CyPA) concentration increases in acute coronary syndrome. In an animal model of acute myocardial infarction, administration of angiotensin-converting-enzyme inhibitor was associated with lower left ventricular (LV) CyPA concentration and improved LV performance. This study investigated the relationships between changes in plasma CyPA concentrations and LV remodeling in patients with ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

We enrolled 55 patients who underwent percutaneous coronary intervention for acute STEMI. Plasma CyPA, matrix metalloproteinase (MMP), interleukin-6 and high-sensitivity C-reactive protein concentrations were measured at baseline and at one-month follow-up. Echocardiography was performed at baseline and at one-, three-, and six-month follow-up. Patients with a decrease in baseline CyPA concentration at one-month follow-up (n = 28) had a significant increase in LV ejection fraction (LVEF) (from 60.2 ± 11.5% to 64.6 ± 9.9%, p < 0. 001) and preserved LV synchrony at six months. Patients without a decrease in CyPA concentration at one month (n = 27) did not show improvement in LVEF and had a significantly increased systolic dyssynchrony index (SDI) (from 1.170 ± 0.510% to 1.637 ± 1.299%, p = 0.042) at six months. Multiple linear regression analysis showed a significant association between one-month CyPA concentration and six-month LVEF. The one-month MMP-2 concentration was positively correlated with one-month CyPA concentration and LV SDI. Conclusions : Decreased CyPA concentration at one-month follow-up after STEMI was associated with better LVEF and SDI at six months. Changes in CyPA, therefore, may be a prognosticator of patient outcome.

Expression and clinical implications of HAb18G/CD147 in hepatocellular carcinoma

AIM

HAb18G/CD147 is an important factor in invasion and metastasis of hepatocellular carcinoma (HCC). However, the clinical implications of HAb18G/CD147 expression in HCC are still unclear. In this study, we clarify the clinical significance of HAb18G/CD147. We characterize the association between HAb18G/CD147 expression and presentation of fibrosis or chronic hepatitis B, as well as its effect on HCC development.

METHODS

The expression of HAb18G/CD147 in human hepatocarcinoma cell lines was analyzed by reverse transcription polymerase chain reaction and western blotting. Tumor tissues were obtained from HCC patients who underwent surgical resection between 2002 and 2006. All patients who had received previous therapy were excluded. HCC tissues were analyzed by immunohistochemistry using anti-HAb18G/CD147.

RESULTS

HAb18G/CD147 was widely expressed in Hep-G2, SMCC-7721 and BEL7402 cell lines, but not expressed in L-02, a human normal hepatic cell line. HAb18G/CD147 was mainly localized to the membrane of tumor cells in 74.0% (37/50) HCC patients. We found that higher HAb18G/CD147 expression and poor tumor differentiation were correlated with patient survival (P = 0.026 and P = 0.014, respectively). Furthermore, the distribution of HAb18G/CD147 was similar to that of hepatitis B virus (HBV) infection, but negatively related to hepatic cirrhosis.

CONCLUSION

HAb18G/CD147 has shown its potentials in HCC development and patient survival. Moreover, it may also cooperate with chronic HBV infection and cirrhosis during HCC development. Its functions in the two factors may be different. Therefore, HAb18G/CD147 may be a marker for poor prognosis in HCC patients and could be a useful therapeutic target for interfering with or reversing HCC progression.

Extracellular cyclophilin A activates platelets via EMMPRIN (CD147) and PI3K/Akt signaling, which promotes platelet adhesion and thrombus formation in vitro and in vivo

OBJECTIVE

Cyclophilin A (CyPA) is secreted under inflammatory conditions by various cell types. Whereas the important role of intracellular CyPA for platelet function has been reported, the effect of extracellular CyPA on platelet function has not been investigated yet.

APPROACH AND RESULTS

Inhibition of extracellular CyPA through a novel specific inhibitor MM284 reduced thrombus after ferric chloride-induced injury in vivo. In vitro extracellular CyPA enhanced thrombus formation even in CyPA(-/-) platelets. Treatment of isolated platelets with recombinant CyPA resulted in platelet degranulation in a time- and dose-dependent manner. Inhibition of the platelet surface receptor extracellular matrix metalloproteinase inducer (cluster of differentiation 147) by an anticluster of differentiation 147 monoclonal antibody significantly reduced CyPA-dependent platelet degranulation. Pretreatment of platelets with CyPA enhanced their recruitment to mouse carotid arteries after arterial injury, which could be inhibited by an anticluster of differentiation 147 monoclonal antibody (intravital microscopy). The role of extracellular CyPA in adhesion could be confirmed by infusing CyPA(-/-) platelets in CyPA(+/+) mice and by infusing CyPA(+/+) platelets in CyPA(-/-) mice. Stimulation of platelets with CyPA induced phosphorylation of Akt, which could in turn be inhibited in the presence of phosphoinositid-3-kinase inhibitors. Akt-1(-/-) platelets revealed a markedly decreased degranulation on CyPA stimulation. Finally, ADP-induced platelet aggregation was attenuated by MM284, as well as by inhibiting paracrine-secreted CyPA without directly affecting Ca(2+)-signaling.

CONCLUSIONS

Extracellular CyPA activates platelets via cluster of differentiation 147-mediated phosphoinositid-3-kinase/Akt-signaling, leading to enhanced adhesion and thrombus formation independently of intracellular CyPA. Targeting extracellular CyPA via a specific inhibitor may be a promising strategy for platelet inhibition without affecting critical functions of intracellular CyPA.

The roles of CD147 and/or cyclophilin A in kidney diseases

CD147 is a widely expressed integral plasma membrane glycoprotein and has been involved in a variety of physiological and pathological activities in combination with different partners, including cyclophilins, caveolin-1, monocarboxylate transporters, and integrins. Recent data demonstrate that both CyPA and CD147 significantly contribute to renal inflammation, acute kidney injury, renal fibrosis, and renal cell carcinoma. Here we review the current understanding of cyclophilin A and CD147 expression and functions in kidney diseases and potential implications for treatment of kidney diseases.

CD147 renal expression as a biomarker for progressive IgAN

BACKGROUND/AIMS

Recent studies have demonstrated that tubulointerstitial injury can predict renal outcomes better than the other histological parameters in patients with IgA nephropathy (IgAN). CD147 is a key regulator of renal tubulointerstitial fibrosis in cellular and animal models. However, it is not clear whether the expression of CD147 correlates with tubulointerstitial injury in IgAN patients.

METHODS

We analyzed the degree of CD147 expression and localization in renal biopsy tissues from IgAN patients and correlated their immunostaining scores with clinical and histological parameters.

RESULTS

Elevated CD147 expression was found in the basolateral membrane of renal tubules in IgAN patients; however, in normal kidney samples, positive staining for CD147 was not found in the tubular epithelial cells (P = 0.000). CD147 protein expression in the renal tubules showed a negative correlation with estimated glomerular filtration rate (eGFR; r = -0.600, P = 0.000) and a positive correlation with serum creatinine (Scr; r = 0.322, P = 0.002) and tubulointerstitial lesions (r = 0.525, P = 0.000). Moreover, a high level of CD147 correlated with the activation of Slug expression and E-cadherin repression in patients with IgAN. Kaplan-Meier survival curves showed that elevated CD147 expression was associated with decreased renal survival. Multivariate analyses further demonstrated that a high CD147 immunostaining score was an independent predictor of renal outcome in patients with IgAN (HR = 8.731, P = 0.041).

CONCLUSION

CD147 expression is associated with tubulointerstitial injury and predicts renal prognosis in IgA nephropathy. CD147 may be an early marker for tubulointerstitial injury IgA nephropathy.

CD147 and CD98 complex-mediated homotypic aggregation attenuates the CypA-induced chemotactic effect on Jurkat T cells

Homotypic cell aggregation plays important roles in physiological and pathological processes, including embryogenesis, immune responses, angiogenesis, tumor cell invasion and metastasis. CD147 has been implicated in most of these phenomena, and it was identified as a T cell activation-associated antigen due to its obvious up-regulation in activated T cells. However, the explicit function and mechanism of CD147 in T cells have not been fully elucidated. In this study, large and compact aggregates were observed in Jurkat T cells after treatment with the specific CD147 monoclonal antibody HAb18 or after the expression of CD147 was silenced by RNA interference, which indicated an inhibitory effect of CD147 in T cell homotypic aggregation. Knocking down CD147 expression resulted in a significant decrease in CD98, along with prominent cell aggregation, similar to that treated by CD98 and CD147 monoclonal antibodies. Furthermore, decreased cell chemotactic activity was observed following CD147- and CD98-mediated cell aggregation, and increased aggregation was correlated with a decrease in the chemotactic ability of the Jurkat T cells, suggesting that CD147- and CD98-mediated homotypic cell aggregation plays a negative role in T cell chemotaxis. Our data also showed that p-ERK, p-ZAP70, p-CD3ζ and p-LCK were significantly decreased in the CD147- and CD98-knocked down Jurkat T cells, which suggested that decreased CD147- and/or CD98-induced homotypic T cell aggregation and aggregation-inhibited chemotaxis might be associated with these signaling pathways. A role for CD147 in cell aggregation and chemotaxis was further indicated in primary CD4(+) T cells. Similarly, low expression of CD147 in primary T cells induced prominent cell aggregation and this aggregation attenuated primary T cell chemotactic ability in response to CypA. Our results have demonstrated the correlation between homotypic cell aggregation and the chemotactic response of T cells to CypA, and these data indicate that CD147 and CD98 might play important roles in cyclophilin-induced cell migration.

Enhancement of CD147 on M1 macrophages induces differentiation of Th17 cells in the lung interstitial fibrosis

Lung interstitial fibrosis is a chronic lung disease, and few effective therapies are available to halt or reverse the progression of the disease. In murine and human lung fibrosis, the expression of CD147 is increased. However, the role of CD147 in lung fibrosis has not been identified, and it remains to be determined whether lung fibrosis would be improved by decreasing the expression of CD147. A murine bleomycin-induced lung interstitial fibrosis model was used in the experiments, and HAb18 mAbs and CsA were administered during the induction of lung fibrosis. In our study, we found that the HAb18 mAbs markedly reduced the collagen score and down-regulated M1 macrophages and Th17 cells. In vitro, flow cytometry analysis showed that M1 macrophages induced higher Th17 differentiation than M2 macrophages. After treatment with HAb18 mAbs or after reducing the expression of CD147 by lentivirus interference in M1 macrophages, the level of Th17 cells were significantly inhibited. In conclusion, HAb18 mAbs or CsA treatment ameliorates lung interstitial fibrosis. CD147 promoted M1 macrophage and induced the differentiation of Th17 cells in lung interstitial fibrosis, perhaps by regulating some cytokines such as IL-6, IL-1β, IL-12 and IL-23. These results indicated that CD147 may play an important role in the development of lung interstitial fibrosis.

From chemical tools to clinical medicines: nonimmunosuppressive cyclophilin inhibitors derived from the cyclosporin and sanglifehrin scaffolds

The cyclophilins are widely expressed enzymes that catalyze the interconversion of the cis and trans peptide bonds of prolines. The immunosuppressive natural products cyclosporine A and sanglifehrin A inhibit the enzymatic activity of the cyclophilins. Chemical modification of both the cyclosporine and sanglifehrin scaffolds has produced many analogues that inhibit cyclophilins in vitro but have reduced immunosuppressive properties. Three nonimmunosuppressive cyclophilin inhibitors (alisporivir, SCY-635, and NIM811) have demonstrated clinical efficacy for the treatment of hepatitis C infection. Additional candidates are in various stages of preclinical development for the treatment of hepatitis C or myocardial reperfusion injury. Recent publications suggest that cyclophilin inhibitors may have utility for the treatment of diverse viral infections, inflammatory indications, and cancer. In this review, we document the structure-activity relationships of the nonimmunosuppressive cyclosporins and sanglifehrins in clinical and preclinical development. Aspects of the pharmacokinetic behavior and chemical biology of these drug candidates are also described.

Matrix as an interstitial transport system

The extracellular matrix (ECM) is best known for its function as a structural scaffold for the tissue and more recently as a microenvironment to sequester growth factors and cytokines allowing for rapid and localized changes in their activity in the absence of new protein synthesis. In this review, we explore this and additional new aspects of ECM function in mediating cell-to-cell communications. Fibrillar and nonfibrillar components of ECM can limit and facilitate the transport of molecules through the extracellular space while also regulating interstitial hydrostatic pressure. In turn, transmembrane communications via molecules, such as ECM metalloproteinase inducer, thrombospondins, and integrins, can further mediate cell response to extracellular cues and affect ECM composition and tissue remodeling. Other means of cell-to-cell communication include extracellular microRNA transport and its contribution to gene expression in target cells and the nanotube formation between distant cells, which has recently emerged as a novel conduit for intercellular organelle sharing thereby influencing cell survival and function. The information summarized and discussed here are not limited to the cardiovascular ECM but encompass ECM in general with specific references to the cardiovascular system.

Importance of N-glycosylation on CD147 for its biological functions

Glycosylation of glycoproteins is one of many molecular changes that accompany malignant transformation. Post-translational modifications of proteins are closely associated with the adhesion, invasion, and metastasis of tumor cells. CD147, a tumor-associated antigen that is highly expressed on the cell surface of various tumors, is a potential target for cancer diagnosis and therapy. A significant biochemical property of CD147 is its high level of glycosylation. Studies on the structure and function of CD147 glycosylation provide valuable clues to the development of targeted therapies for cancer. Here, we review current understanding of the glycosylation characteristics of CD147 and the glycosyltransferases involved in the biosynthesis of CD147 N-glycans. Finally, we discuss proteins regulating CD147 glycosylation and the biological functions of CD147 glycosylation.

Overexpression of EMMPRIN isoform 2 is associated with head and neck cancer metastasis

Extracellular matrix metalloproteinase inducer (EMMPRIN), a plasma membrane protein of the immunoglobulin (Ig) superfamily, has been reported to promote cancer cell invasion and metastasis in several human malignancies. However, the roles of the different EMMPRIN isoforms and their associated mechanisms in head and neck cancer progression remain unknown. Using quantitative real-time PCR, we found that EMMPRIN isoform 2 (EMMPRIN-2) was the only isoform that was overexpressed in both head and neck cancer tissues and cell lines and that it was associated with head and neck cancer metastasis. To determine the effects of EMMPRIN-2 on head and neck cancer progression, we transfected head and neck cancer cells with an EMMPRIN-2 expression vector and EMMPRIN-2 siRNA to exogenously modulate EMMPRIN-2 expression and examined the functional importance of EMMPRIN-2 in head and neck cancer invasion and metastasis. We found that EMMPRIN-2 promoted head and neck cancer cell invasion, migration, and adhesion in vitro and increased lung metastasis in vivo. Mechanistic studies revealed that EMMPRIN-2 overexpression promoted the secretion of extracellular signaling molecules, including matrix metalloproteinases-2(MMP-2), urokinase-type plasminogen activator(uPA) and Cathepsin B, in head and neck cancer cells. While MMP-2 and uPA have been demonstrated to be important mediators of EMMPRIN signaling, the role of Cathepsin B in EMMPRIN-mediated molecular cascades and tumorigenesis has not been established. We found that EMMPRIN-2 overexpression and Cathepsin B down-regulation significantly inhibited the invasion, migration and adhesion of Tca8133 cells, suggesting that Cathepsin B is required for EMMPRIN-2 enhanced cell migration and invasion in head and neck cancer. The results of our study demonstrate the important role of EMMPRIN-2 in head and neck cancer progression for the first time and reveal that increased extracellular secretion of Cathepsin B may be a novel mechanism underlying EMMPRIN-2 enhanced tumor progression in head and neck cancer.

Cyclophilin A and EMMPRIN (CD147) in cardiovascular diseases

Cyclophilin A (CyPA) is an abundantly expressed intracellular protein. It exerts a variety of functions due to its peptidyl-prolyl cis-trans isomerase (PPIase) activity. When released into the extracellular space, CyPA binds to its extracellular receptor CD147 (EMMPRIN) and thereby initiates a cascade of inflammatory processes. Recent data indicate that both extra- and intracellular CyPA significantly contribute to cardiovascular inflammation, myocardial ischaemia and reperfusion injury, and myocardial remodelling processes. Thus, CyPA appears to represent a novel target to treat vascular and myocardial inflammation.

Plasma level of cyclophilin A is increased in patients with type 2 diabetes mellitus and suggests presence of vascular disease

Aims/hypothesis

Cyclophilin A, an immunophilin is secreted from human monocytes activated by high glucose. Given its role as an inflammatory mediator of vascular tissue damage associated with inflammation and oxidative stress, we examined plasma levels of cyclophilin A in normal healthy volunteers and patients with type 2 diabetes (DM), with or without coronary artery disease (CAD).

Methods

Study subjects comprised of 212 patients with DM and CAD,101 patients with diabetes, 122 patients with CAD and 121 normal healthy volunteers. Diabetes was assessed by HbA1c levels while coronary artery disease was established by a positive treadmill test and/or coronary angiography. Plasma cyclophilin A was measured using a cyclophilin A ELISA Kit. Relationship of plasma cyclophilin A levels with blood markers of type 2 diabetes, blood lipid levels and medication for diabetes and coronary artery disease were also explored.

Results

Plasma Cyclophilin levels were higher in diabetes patients with or without CAD compared to normal subjects (P < 0.001). Age, fasting blood sugar levels and HbA1C levels were positively associated with increased plasma cyclophilin. Patients using metformin had reduced levels of plasma cyclophilin (p < 0.001).Serum levels of total cholesterol, LDL cholesterol and triglycerides had no significant association with plasma cyclophilin levels. In patients with increased serum CRP levels, plasma cyclophilin A was also elevated (p = 0.016). Prevalence odds for DM, DM + CAD and CAD are higher in those with high cyclophilin values, compared to those with lower values, after adjusting for age and sex, indicating strong association of high cyclophilin values with diabetes and vascular disease.

Conclusions/interpretations

Our study demonstrates that patients with type 2 diabetes have higher circulating levels of cyclophilin A than the normal population. Plasma cyclophilin levels were increased in patients with diabetes and coronary artery disease suggesting a role of this protein in accelerating vascular disease in type 2 diabetes. Considering the evidence that Cyclophilin A is an inflammatory mediator in atherogenesis, the mechanistic role of cyclophilin A in diabetic vascular disease progression deserves detailed investigation.

Plasma CD147 reflects histological features in patients with lupus nephritis

OBJECTIVE

A glycosylated transmembrane protein, CD147, has been implicated in regulating lymphocyte responsiveness and leukocyte recruitment. As lupus nephritis (LN) often follows a relapsing-remitting disease course, accurate understanding of the disease activity would be extremely helpful in improving prognosis. Unfortunately, neither clinical nor serological data can accurately reflect the histological features of LN. The present study investigated whether CD147 can accurately predict pathological features of LN.

METHODS

Plasma and spot urine samples were collected from 64 patients who underwent renal biopsy between 2008 and 2011. Disease activity for LN tissues was evaluated using the biopsy activity index, and compared to levels of biomarkers including CD147.

RESULTS

In LN tissues, CD147 induction was striking in injured glomeruli and infiltrating inflammatory cells, but not in damaged tubules representing atrophy. Plasma CD147 levels accurately reflected the histological disease activity. However, prediction using a single molecule would be quite difficult because of the complex pathogenesis of LN. The diagnostic accuracy of multiplex parameters indicated that the combination including plasma CD147 might yield excellent diagnostic abilities for guiding ideal LN therapy.

CONCLUSION

Plasma CD147 levels might offer useful insights into disease activity as a crucial biomarker in patients with LN.

Tertiary structure prediction and identification of druggable pocket in the cancer biomarker - Osteopontin-c

Background

Osteopontin (Eta, secreted sialoprotein 1, opn) is secreted from different cell types including cancer cells. Three splice variant forms namely osteopontin-a, osteopontin-b and osteopontin-c have been identified. The main astonishing feature is that osteopontin-c is found to be elevated in almost all types of cancer cells. This was the vital point to consider it for sequence analysis and structure predictions which provide ample chances for prognostic, therapeutic and preventive cancer research.

Methods

Osteopontin-c gene sequence was determined from Breast Cancer sample and was translated to protein sequence. It was then analyzed using various software and web tools for binding pockets, docking and druggability analysis. Due to the lack of homological templates, tertiary structure was predicted using ab-initio method server – I-TASSER and was evaluated after refinement using web tools. Refined structure was compared with known bone sialoprotein electron microscopic structure and docked with CD44 for binding analysis and binding pockets were identified for drug designing.

Results

Signal sequence of about sixteen amino acid residues was identified using signal sequence prediction servers. Due to the absence of known structures of similar proteins, three dimensional structure of osteopontin-c was predicted using I-TASSER server. The predicted structure was refined with the help of SUMMA server and was validated using SAVES server. Molecular dynamic analysis was carried out using GROMACS software. The final model was built and was used for docking with CD44. Druggable pockets were identified using pocket energies.

Conclusions

The tertiary structure of osteopontin-c was predicted successfully using the ab-initio method and the predictions showed that osteopontin-c is of fibrous nature comparable to firbronectin. Docking studies showed the significant similarities of QSAET motif in the interaction of CD44 and osteopontins between the normal and splice variant forms of osteopontins and binding pockets analyses revealed several pockets which paved the way to the identification of a druggable pocket.

Identification of CD147 (basigin) as a mediator of trophoblast functions

STUDY QUESTION

Does CD147 regulate trophoblast functions in vitro?

SUMMARY ANSWER

CD147 exists as a receptor complex on human trophoblast and regulates the implantation, invasion and differentiation of trophoblast.

WHAT IS KNOWN ALREADY

CD147 is a membrane protein implicated in a variety of physiological and pathological conditions due to its regulation of cell-cell recognition, cell differentiation and tissue remodeling. Reduced placental CD147 expression is associated with pre-eclampsia, but the mechanism of actions remains unclear.

STUDY DESIGN, SIZE, DURATION

A loss of function approach or functional blocking antibody was used to study the function of CD147 in primary human cytotrophoblasts isolated from first trimester termination of pregnancy and/or in the BeWo cell line, which possesses characteristics of human cytotrophoblasts.

PARTICIPANTS/MATERIALS, SETTING METHODS

CD147 expression was analyzed by immunofluorescence staining and western blotting. CD147-associated protein complex on plasma membrane were separated by blue native gel electrophoresis and identified by reversed-phase liquid chromatography coupled with quadrupole time-of-flight hybrid mass spectrometer. Cell proliferation and invasion were determined by fluorometric cell proliferation assays and transwell invasion assays, respectively. Matrix metalloproteinases (MMPs) and urokinase plasminogen activator (uPA) activities were measured by gelatin gel zymography and uPA assay kits, respectively. Cell migration was determined by wound-healing assays. Cell fusion was analyzed by immunocytochemistry staining of E-cadherin and 4',6-diamidino-2-phenylindole. The transcripts of matrix proteinases and trophoblast lineage markers were measured by quantitative PCR. Extracellular signal-regulated kinase (ERK) activation was analyzed by western blot using antibodies against ERKs.

MAIN RESULTS AND THE ROLE OF CHANCE

CD147 exists as protein complexes on the plasma membrane of primary human cytotrophoblasts and BeWo cells. Several known CD147-interacting partners, including integrin β1 and monocarboxylate transporter-1, were identified. Suppression of CD147 by siRNA significantly (P < 0.05) reduced trophoblast-endometrial cell interaction, cell invasion, syncytialization, differentiation and ERK activation of BeWo cells. Consistently, anti-CD147 functional blocking antibody suppressed the invasiveness of primary human cytotrophoblasts. The reduced invasiveness was probably due to the restrained (P < 0.05) enzyme activities of MMP-2, MMP-9 and uPA.

LIMITATIONS, REASONS FOR CAUTION

Most of the above findings are based on BeWo cell lines. These results need to be confirmed with human first trimester primary cytotrophoblast.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study on the role of CD147 in trophoblast function. Further investigation on the function of CD147 and its associated protein complexes will enhance our understanding on human placentation.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by the University of Hong Kong Grant 201011159200. The authors have no competing interests to declare.

Galectin-3 induces clustering of CD147 and integrin-β1 transmembrane glycoprotein receptors on the RPE cell surface

Proliferative vitreoretinopathy (PVR) is a blinding disease frequently occurring after retinal detachment surgery. Adhesion, migration and matrix remodeling of dedifferentiated retinal pigment epithelial (RPE) cells characterize the onset of the disease. Treatment options are still restrained and identification of factors responsible for the abnormal behavior of the RPE cells will facilitate the development of novel therapeutics. Galectin-3, a carbohydrate-binding protein, was previously found to inhibit attachment and spreading of retinal pigment epithelial cells, and thus bares the potential to counteract PVR-associated cellular events. However, the identities of the corresponding cell surface glycoprotein receptor proteins on RPE cells are not known. Here we characterize RPE-specific Gal-3 containing glycoprotein complexes using a proteomic approach. Integrin-β1, integrin-α3 and CD147/EMMPRIN, a transmembrane glycoprotein implicated in regulating matrix metalloproteinase induction, were identified as potential Gal-3 interactors on RPE cell surfaces. In reciprocal immunoprecipitation experiments we confirmed that Gal-3 associated with CD147 and integrin-β1, but not with integrin-α3. Additionally, association of Gal-3 with CD147 and integrin-β1 was observed in co-localization analyses, while integrin-α3 only partially co-localized with Gal-3. Blocking of CD147 and integrin-β1 on RPE cell surfaces inhibited binding of Gal-3, whereas blocking of integrin-α3 failed to do so, suggesting that integrin-α3 is rather an indirect interactor. Importantly, Gal-3 binding promoted pronounced clustering and co-localization of CD147 and integrin-β1, with only partial association of integrin-α3. Finally, we show that RPE derived CD147 and integrin-β1, but not integrin-α3, carry predominantly β-1,6-N-actyl-D-glucosamine-branched glycans, which are high-affinity ligands for Gal-3. We conclude from these data that extracellular Gal-3 triggers clustering of CD147 and integrin-β1 via interaction with β1,6-branched N-glycans on RPE cells and hypothesize that Gal-3 acts as a positive regulator for CD147/integrin-β1 clustering and therefore modifies RPE cell behavior contributing to the pathogenesis of PVR. Further investigations at this pathway may aid in the development of specific therapies for PVR.

CD147 promotes MTX resistance by immune cells through up-regulating ABCG2 expression and function

BACKGROUND

Methotrexate (MTX) is a drug used to treat psoriasis due to inducing immune cell apoptosis. However, certain patients show MTX resistant. CD147, highly expressed by psoriatic PBMCs, is assumed to regulate MTX sensitivity. The underlining mechanism is still relatively understudied.

OBJECTIVE

To understand the mechanisms of that CD147 promotes MTX resistance in immune cells.

METHODS

The expression of CD147 and ABCG2 in PBMCs from psoriatic patients, cellular apoptosis and intracellular MTX amount were measured. We also checked the cellular drug sensitivity of CHO (Chinese Hamster Ovary) cell lines with introduced CD147 and Jurkat T cells depeleted CD147. By immunoprecipitation, we detected the interaction between CD147 and ABCG2.

RESULTS

Both ABCG2 and CD147 are highly expressed in psoriatic PBMCs. Cultured in vitro, the PBMCs from psoriatic patients were more resistant to MTX-induced apoptosis comparing to PBMCs from healthy people. Further studies demonstrated that exogenous overexpression of CD147 in CHO cells increased ABCG2 protein level. After MTX treatment, CD147 overexpressing CHO cells showed lower apoptosis rate and lower intracellular MTX concentration. On the contrary, knockdown of CD147 by shRNA in Jurkat T cells decreased ABCG2 expression, as well as increased MTX-induced apoptosis and decreased MTX efflux. Immunoprecipitation experiment revealed that the trans-membrane domain of CD147 conferred its' interaction with ABCG2.

CONCLUSION

Our study suggests a role of CD147 in regulating ABCG2 transportation of MTX in immune cells. Strategies involving targeting CD147 could be considered in clinical treatment of psoriatic patients resistant to MTX.

Insights into the roles of cyclophilin A during influenza virus infection

Cyclophilin A (CypA) is the main member of the immunophilin superfamily that has peptidyl-prolyl cis-trans isomerase activity. CypA participates in protein folding, cell signaling, inflammation and tumorigenesis. Further, CypA plays critical roles in the replication of several viruses. Upon influenza virus infection, CypA inhibits viral replication by interacting with the M1 protein. In addition, CypA is incorporated into the influenza virus virions. Finally, Cyclosporin A (CsA), the main inhibitor of CypA, inhibits influenza virus replication through CypA-dependent and -independent pathways. This review briefly summarizes recent advances in understanding the roles of CypA during influenza virus infection.

CD147 in ovarian and other cancers

Ovarian cancer, a gynecological malignancy, is the most common cause of death in older women worldwide. The overall 5-year survival of ovarian cancer patients is only 20% because of late diagnosis, as well as distant metastasis and multidrug resistance. Therefore, predictive and prognostic markers are urgently required for the early diagnosis of ovarian cancer. CD147, an extracellular matrix metalloproteinase inducer, is overexpressed in ovarian cancers. Current knowledge suggests that CD147 is associated with the survival and progression of ovarian cancer, and is considered as a biomarker of poor outcome. Here, we specifically review the roles of CD147 in ovarian cancer progression and discuss the diagnostic and prognostic value of CD147 in patients with ovarian cancer. CD147 promotes ovarian cancer progression by its involvement in every facet of malignancy, including invasion, metastasis, survival, angiogenesis, and drug resistance. Although it is not fully confirmed, the combination of CD147 with other biomarkers might be of diagnostic value.

Functions of cyclophilin A in atherosclerosis

Cyclophilin A (CypA) is a ubiquitously distributed protein present both in intracellular and extracellular spaces. In atherosclerosis, various cells, including endothelial cells, monocytes, vascular smooth muscle cells and platelets, secrete CypA in response to excessive levels of reactive oxygen species. Atherosclerosis, a complicated disease, is the result of the interplay of different risk factors. Researchers have found that CypA links many risk factors, including hyperlipidemia, hypertension and diabetes, to atherosclerosis that develop into a vicious cycle. Furthermore, most studies have shown that secreted CypA participates in the developmental process of atherosclerosis via many important intracellular mechanisms. CypA can cause injury to and apoptosis of endothelial cells, leading to dysfunction of the endothelium. CypA may also induce the activation and migration of leukocytes, producing proinflammatory cytokines that promote inflammation in blood vessels. In addition, CypA can promote the proliferation of monocytes/macrophages and vascular smooth muscle cells, leading to the formation of foam cells and the remodelling of the vascular wall. Studies investigating the roles of CypA in atherosclerosis may provide new direction for preventive and interventional treatment strategies in atherosclerosis.

Cyclophilin A predicts clinical outcome in patients with congestive heart failure undergoing endomyocardial biopsy

AIMS

Cyclophilin A (CyPA) represents a ubiquitous intracellular protein, which is secreted by inflammatory and by dying/necrotic cells. The aim of this study was to evaluate the prognostic relevance of CyPA expression in endomyocardial biopsies of consecutive patients with congestive heart failure.

METHODS AND RESULTS

A total of 227 unselected patients (age 53.9 ± 15 years) with congestive heart failure undergoing endomyocardial biopsy for diagnostic reasons were enrolled. Biopsies were analysed using established histopathological and immunohistological criteria together with CyPA staining. Virus genome was studied by polymerase chain reaction. CyPA was significantly enhanced in patients with inflammatory cardiomyopathy (n = 127) as compared with patients with non-inflammatory cardiomyopathy (n = 100, P < 0.0001). During a mean follow-up of 16.3 months, 60 patients (26.4%) reached the primary endpoint, a composite of all-cause death, heart transplantation, malignant arrhythmia, and heart failure-related rehospitalization. Of all clinical (ejection fraction, New York Heart Association functional class), laboratory (brain natriuretic peptide), and immunohistological parameters (CyPA, extracellular matrix metalloproteinase inducer, CD68, CD3, major hisocompatibility complex II, and virus genome) tested, only CyPA was identified as an independent predictor for the composite endpoint [hazard ratio (HR) 2.4; 95% confidence interval (CI) 1.2-5.2; P = 0.019] as well as for all-cause death and heart transplantation alone (HR 4.7; 95% CI 1.1-19.8; P = 0.036). Subgroup analysis revealed CyPA as a predictor in patients with non-inflammatory cardiomyopathy for the composite endpoint (HR 3.0; 95% CI 1.3-6.6; P = 0.007) as well as all-cause death or heart transplantation alone (HR 6.4; 95% CI 1.4-28.1; P = 0.014).

CONCLUSIONS

CyPA is an independent predictor of clinical outcome in patients with congestive heart failure undergoing endomyocardial biopsy.

Low-salt diet and cyclosporine nephrotoxicity: changes in kidney cell metabolism

Cyclosporine (CsA) is a highly effective immunosuppressant used in patients after transplantation; however, its use is limited by nephrotoxicity. Salt depletion is known to enhance CsA-induced nephrotoxicity in the rat, but the underlying molecular mechanisms are not completely understood. The goal of our study was to identify the molecular effects of salt depletion alone and in combination with CsA on the kidney using a proteo-metabolomic strategy. Rats (n = 6) were assigned to four study groups: (1) normal controls, (2) low-salt fed controls, (3) 10 mg/kg/d CsA for 28 days on a normal diet, (4) 10 mg/kg/d CsA for 28 days on low-salt diet. Low-salt diet redirected kidney energy metabolism toward mitochondria as indicated by a higher energy charge than in normal-fed controls. Low-salt diet alone reduced phospho-AKT and phospho-STAT3 levels and changed the expression of ion transporters PDZK1 and CLIC1. CsA induced macro- and microvesicular tubular epithelial vacuolization and reduced energy charge, changes that were more significant in low-salt fed animals, probably because of their more pronounced dependence on mitochondria. Here, CsA increased phospho-JAK2 and phospho-STAT3 levels and reduced the phospho-IKKγ and p65 proteins, thus activating NF-κB signaling. Decreased expression of lactate transport regulator CD147 and phospho-AKT was also observed after CsA exposure in low-salt rats, indicating a decrease in glycolysis. In summary, our study suggests a key role for PDZK1, CD147, JAK/STAT, and AKT signaling in CsA-induced nephrotoxicity and proposes mechanistic explanations on why rats fed a low-salt diet have higher sensitivity to CsA.

Cyclophilin A and viral infections

Cyclophilin A (CyPA) is a peptidyl-prolyl cis/trans isomerase originally identified as the target of the immunosuppressive drug cyclosporine A. A number of reports have demonstrated that CyPA plays a critical role in the successful replication of viruses such as human immunodeficiency virus (HIV), hepatitis C virus (HCV), hepatitis B virus (HBV), etc. However, recent studies demonstrated that CyPA also possesses a repressive effect on the replication of some viruses like Influenza A virus and rotavirus. Moreover, CyPA could also regulate host IFN-I response to viral infections. Together, these evidences showed diverse roles of CyPA in viral infection.

Increased expression of extracellular matrix metalloproteinase inducer (CD147) in multiple myeloma: role in regulation of myeloma cell proliferation

Multiple myeloma (MM) is preceded by the asymptomatic pre-malignant state, monoclonal gammopathy of undetermined significance (MGUS). Although MGUS patients may remain stable for years, they are at increased risk of progressing to MM. A better understanding of the relevant molecular changes underlying the transition from an asymptomatic to symptomatic disease state is urgently needed. Our studies show for the first time that the CD147 molecule (extracellular matrix metalloproteinase inducer) may be having an important biological role in MM. We first demonstrate that CD147 is overexpressed in MM plasma cells (PCs) vs normal and pre-malignant PCs. Next, functional studies revealed that the natural CD147 ligand, cyclophilin B, stimulates MM cell growth. Moreover, when MM patient PCs displaying bimodal CD147 expression were separated into CD147(bright) and CD147(dim) populations and analyzed for proliferation potential, we discovered that CD147(bright) PCs displayed significantly higher levels of cell proliferation than did CD147(dim) PCs. Lastly, CD147-silencing significantly attenuated MM cell proliferation. Taken together, these data suggest that the CD147 molecule has a key role in MM cell proliferation and may serve as an attractive target for reducing the proliferative compartment of this disease.

Cyclophilin A affects inflammation, virus elimination and myocardial fibrosis in coxsackievirus B3-induced myocarditis

Extracellular cyclophilin A (CyPA) and its receptor Extracellular Matrix Metalloproteinase Inducer (EMMPRIN, CD147) modulate inflammatory processes beyond metalloproteinase (MMP) activity. Recently, we have shown that CyPA and CD147 are upregulated in patients with inflammatory cardiomyopathy. Here we investigate the role of CyPA and CD147 in murine coxsackievirus B3 (CVB3)-induced myocarditis. CVB3-infected CyPA(-/-) mice (129S6/SvEv) revealed a significantly reduced T-cell and macrophage recruitment at 8 days p.i. compared to wild-type mice. In A.BY/SnJ mice, treatment with the cyclophilin-inhibitor NIM811 was associated with a reduction of inflammatory lesions and MMP-9 expression but with enhanced virus replication 8 days p.i. At 28 days p.i. the extent of lesion areas was not affected bei NIM811, whereas the collagen content was reduced. Initiation of NIM811-treatment on day 12 (after an effective virus defense) resulted in an even more pronounced reduction of myocardial fibrosis. In conclusion, in CVB3-induced myocarditis CyPA is important for macrophage and T cell recruitment and effective virus defense and may represent a pharmacological target to modulate myocardial remodeling in myocarditis.