Purification and identification of secreted oxidative stress-induced factors from vascular smooth muscle cells

Strategy for Fluorescence/Photoacoustic Signal Maximization Using Dual-Wavelength-Independent Excitation

Dual-mode imaging of fluorescence-photoacoustics has emerged as a promising technique for biomedical applications. However, conventional dual-mode imaging is based on single-wavelength excitation, which often results in opposing fluorescence and photoacoustic signals due to competing photophysical processes in one agent, rendering the maximization of both signals infeasible. To meet this challenge, we herein propose a new strategy by using the dual-excitation approach, where one excitation wavelength generates a fluorescence signal and the other produces a photoacoustic signal, thus achieving simultaneous maximization of both signals in one fluorescence-photoacoustic molecule. Based on this strategy, three dye molecules were employed for comparison, and it was surprising to find that QHD dye with two types of excitation wavelengths could generate fluorescence and photoacoustic signals, respectively. Furthermore, this strategy was successfully implemented in dual-mode imaging of rheumatoid arthritis mice. Importantly, this study emphasizes a new design guideline for the maximization of fluorescence-photoacoustic signals by using dual-wavelength-independent excitation.

Natriuretic Peptide Signaling in Uterine Biology and Preeclampsia

Endometrial decidualization is a uterine process essential for spiral artery remodeling, embryo implantation, and trophoblast invasion. Defects in endometrial decidualization and spiral artery remodeling are important contributing factors in preeclampsia, a major disorder in pregnancy. Atrial natriuretic peptide (ANP) is a cardiac hormone that regulates blood volume and pressure. ANP is also generated in non-cardiac tissues, such as the uterus and placenta. In recent human genome-wide association studies, multiple loci with genes involved in natriuretic peptide signaling are associated with gestational hypertension and preeclampsia. In cellular experiments and mouse models, uterine ANP has been shown to stimulate endometrial decidualization, increase TNF-related apoptosis-inducing ligand expression and secretion, and enhance apoptosis in arterial smooth muscle cells and endothelial cells. In placental trophoblasts, ANP stimulates adenosine 5'-monophosphate-activated protein kinase and the mammalian target of rapamycin complex 1 signaling, leading to autophagy inhibition and protein kinase N3 upregulation, thereby increasing trophoblast invasiveness. ANP deficiency impairs endometrial decidualization and spiral artery remodeling, causing a preeclampsia-like phenotype in mice. These findings indicate the importance of natriuretic peptide signaling in pregnancy. This review discusses the role of ANP in uterine biology and potential implications of impaired ANP signaling in preeclampsia.

RNA Aptamer Targeting of Adam8 in Cancer Growth and Metastasis

Cancer progression depends on an accumulation of metastasis-supporting physiological changes, which are regulated by cell-signaling molecules. In this regard, a disintegrin and metalloproteinase 8 (Adam8) is a transmembrane glycoprotein that is selectively expressed and induced by a variety of inflammatory stimuli. In this study, we identified Adam8 as a sox2-dependent protein expressed in MDA-MB-231 breast cancer cells when cocultured with mesenchymal-stem-cell-derived myofibroblast-like cancer-associated fibroblasts (myCAF). We have previously found that myCAF-induced cancer stemness is required for the maintenance of the myCAF phenotype, suggesting that the initiation and maintenance of the myCAF phenotype require distinct cell-signaling crosstalk pathways between cancer cells and myCAF. Adam8 was identified as a candidate secreted protein induced by myCAF-mediated cancer stemness. Adam8 has a known sheddase function against which we developed an RNA aptamer, namely, Adam8-Apt1-26nt. The Adam8-Apt1-26nt-mediated blockade of the extracellular soluble Adam8 metalloproteinase domain abolishes the previously initiated myCAF phenotype, or, termed differently, blocks the maintenance of the myCAF phenotype. Consequently, cancer stemness is significantly decreased. Xenograft models show that Adam8-Apt-1-26nt administration is associated with decreased tumor growth and metastasis, while flow cytometric analyses demonstrate a significantly decreased fraction of myCAF after Adam8-Apt-1-26nt treatment. The role of soluble Adam8 in the maintenance of the myCAF phenotype has not been previously characterized. Our study suggests that the signal pathways for the induction or initiation of the myCAF phenotype may be distinct from those involved with the maintenance of the myCAF phenotype.

Organismal Roles of Hsp90

Heat shock protein 90 (Hsp90) is a highly conserved molecular chaperone that assists in the maturation of many client proteins involved in cellular signal transduction. As a regulator of cellular signaling processes, it is vital for the maintenance of cellular proteostasis and adaptation to environmental stresses. Emerging research shows that Hsp90 function in an organism goes well beyond intracellular proteostasis. In metazoans, Hsp90, as an environmentally responsive chaperone, is involved in inter-tissue stress signaling responses that coordinate and safeguard cell nonautonomous proteostasis and organismal health. In this way, Hsp90 has the capacity to influence evolution and aging, and effect behavioral responses to facilitate tissue-defense systems that ensure organismal survival. In this review, I summarize the literature on the organismal roles of Hsp90 uncovered in multicellular organisms, from plants to invertebrates and mammals.

Rab37 Promotes Endothelial Differentiation and Accelerates ADSC-Mediated Diabetic Wound Healing through Regulating Secretion of Hsp90α and TIMP1

Accumulating evidence indicates that adipose tissue-derived mesenchymal stem cells (ADSCs) are an effective treatment for diabetic refractory wounds. However, the application of ADSCs to diabetic wounds is still limited, indicating that we still lack sufficient knowledge regarding regulators/mediators of ADSCs during wound healing. Rab37, a member of RabGTPase, may function as regulator of vesicle trafficking, which is a crucial event for the secretion of cytokines by ADSCs. Our previous study indicated that Rab37 promotes the adiopogenic differentiation of ADSCs. In this study, we explored the role of Rab37 in ADSC-mediated diabetic wound healing. An in vivo study in db/db diabetic mice showed that Rab37-expressing ADSCs shortened the wound closure time, improved re-epithelialization and collagen deposition, and promoted angiogenesis during wound healing. An in vitro study showed that Rab37 promoted the proliferation, migration and endothelial differentiation of ADSCs. LC-MS/MS analysis identified Hsp90α and TIMP1 as up-regulated cytokines in conditioned media of Rab37-ADSCs. The up-regulation of Rab37 enhanced the secretion of Hsp90α and TIMP1 during endothelial differentiation and under high-glucose exposure. Interestingly, Rab37 promoted the expression of TIMP1, but not Hsp90α, during endothelial differentiation. PLA showed that Rab37 can directly bind to Hsp90α orTIMP1 in ADSCs. Moreover, Hsp90α and TIMP1 knockdown compromised the promoting effects of Rab37 on the proliferation, migration and endothelial differentiation of ADSCs. In conclusion, Rab37 promotes the proliferation, migration and endothelial differentiation of ADSCs and accelerates ADSC-mediated diabetic wound healing through regulating the secretion of Hsp90α and TIMP1.

Hsp90: From Cellular to Organismal Proteostasis

Assuring a healthy proteome is indispensable for survival and organismal health. Proteome disbalance and the loss of the proteostasis buffer are hallmarks of various diseases. The essential molecular chaperone Hsp90 is a regulator of the heat shock response via HSF1 and a stabilizer of a plethora of signaling proteins. In this review, we summarize the role of Hsp90 in the cellular and organismal regulation of proteome maintenance.

Immunological mechanisms of exercise therapy in dyslipidemia

Numerous studies demonstrated the strong link between dyslipidemia and the cardiovascular risk. Physical activity and exercise represent effective prevention and therapy strategies for dyslipidemia and at the same time counteract numerous comorbidities that often accompany the disease. The physiological mechanisms are manifold, and primary mechanisms might be an increased energy consumption and associated adaptations of the substrate metabolism. Recent studies showed that there are bidirectional interactions between dyslipidemia and the immune system. Thus, abnormal blood lipids may favor pro-inflammatory processes, and at the same time inflammatory processes may also promote dyslipidemia. Physical activity has been shown to affect numerous immunological processes and has primarily anti-inflammatory effects. These are manifested by altered leukocyte subtypes, cytokine patterns, stress protein expression, and by reducing hallmarks of immunosenescence. The aim of this review is to describe the effects of exercise on the treatment dyslipidemia and to discuss possible immunological mechanisms against the background of the current literature.

Regulation of Protein Transport Pathways by the Cytosolic Hsp90s

The highly conserved molecular chaperone heat shock protein 90 (Hsp90) is well-known for maintaining metastable proteins and mediating various aspects of intracellular protein dynamics. Intriguingly, high-throughput interactome studies suggest that Hsp90 is associated with a variety of other pathways. Here, we will highlight the potential impact of Hsp90 in protein transport. Currently, a limited number of studies have defined a few mechanistic contributions of Hsp90 to protein transport, yet the relevance of hundreds of additional connections between Hsp90 and factors known to aide this process remains unresolved. These interactors broadly support transport pathways including endocytic and exocytic vesicular transport, the transfer of polypeptides across membranes, or unconventional protein secretion. In resolving how Hsp90 contributes to the protein transport process, new therapeutic targets will likely be obtained for the treatment of numerous human health issues, including bacterial infection, cancer metastasis, and neurodegeneration.

Extracellular Heat Shock Protein-90 (eHsp90): Everything You Need to Know

“Extracellular” Heat Shock Protein-90 (Hsp90) was initially reported in the 1970s but was not formally recognized until 2008 at the 4th International Conference on The Hsp90 Chaperone Machine (Monastery Seeon, Germany). Studies presented under the topic of “extracellular Hsp90 (eHsp90)” at the conference provided direct evidence for eHsp90’s involvement in cancer invasion and skin wound healing. Over the past 15 years, studies have focused on the secretion, action, biological function, therapeutic targeting, preclinical evaluations, and clinical utility of eHsp90 using wound healing, tissue fibrosis, and tumour models both in vitro and in vivo. eHsp90 has emerged as a critical stress-responding molecule targeting each of the pathophysiological conditions. Despite the studies, our current understanding of several fundamental questions remains little beyond speculation. Does eHsp90 indeed originate from purposeful live cell secretion or rather from accidental dead cell leakage? Why did evolution create an intracellular chaperone that also functions as a secreted factor with reported extracellular duties that might be (easily) fulfilled by conventional secreted molecules? Is eHsp90 a safer and more optimal drug target than intracellular Hsp90 chaperone? In this review, we summarize how much we have learned about eHsp90, provide our conceptual views of the findings, and make recommendations on the future studies of eHsp90 for clinical relevance.

Extracellular HSP90 Machineries Build Tumor Microenvironment and Boost Cancer Progression

HSP90 is released by cancer cells in the tumor microenvironment where it associates with different co-chaperones generating complexes with specific functions, ranging from folding and activation of extracellular clients to the stimulation of cell surface receptors. Emerging data indicate that these functions are essential for tumor growth and progression. The understanding of the exact composition of extracellular HSP90 complexes and the molecular mechanisms at the basis of their functions in the tumor microenvironment may represent the first step to design innovative diagnostic tools and new effective therapies. Here we review the impact of extracellular HSP90 complexes on cancer cell signaling and behavior.

Atrial natriuretic peptide promotes uterine decidualization and a TRAIL-dependent mechanism in spiral artery remodeling

Atrial natriuretic peptide (ANP) is an important hormone in cardiovascular biology. It is activated by the protease corin. In pregnancy, ANP and corin promote uterine spiral artery remodeling, but the underlying mechanism remains unknown. Here we report an ANP function in uterine decidualization and TNF-related apoptosis-inducing ligand-dependent (TRAIL-dependent) death in spiral arterial smooth muscle cells (SMCs) and endothelial cells (ECs). In ANP- or corin-deficient mice, uterine decidualization markers and TRAIL expression were decreased, whereas in cultured human endometrial stromal cells (HESCs), ANP increased decidualization and TRAIL expression. In uterine spiral arteries from pregnant wild-type mice, SMC and EC loss occurred sequentially before trophoblast invasion. In culture, TRAIL from decidualized HESCs induced apoptosis in uterine SMCs, but not in ECs with low TRAIL receptor expression. Subsequently, cyclophilin B was identified from apoptotic SMCs that upregulated endothelial TRAIL receptor and caused apoptosis in ECs. These results indicate that ANP promotes decidualization and TRAIL expression in endometrial stromal cells, contributing to sequential events in remodeling of spiral arteries, including SMC death and cyclophilin B release, which in turn induces TRAIL receptor expression and apoptosis in ECs.

In vitro pulsatile flow study in compliant and rigid ascending aorta phantoms by stereo particle image velocimetry

The aorta is a high risk region for cardiovascular disease (CVD). Haemodynamic patterns leading to CVD are not well established despite numerous experimental and numerical studies. Most overlook effects of arterial compliance and pulsatile flow. However, rigid wall assumptions can lead to overestimation of wall shear stress; a key CVD determinant. This work investigates the effect of compliance on aortic arch haemodynamics experiencing pulsatility. Rigid and compliant phantoms of the arch and brachiocephalic branch (BCA) were manufactured. Stereoscopic particle image velocimetry was used to observe velocity fields. Higher velocity magnitude was observed in the rigid BCA during acceleration. However, during deceleration, the compliant phantom experienced higher velocity. During deceleration, a low velocity region initiated and increased in size in the BCA of both phantoms with irregular shape in the compliant. At mid-deceleration, considerably larger recirculation was observed under compliance compared to rigid. Another recirculation region formed and increased in size on the inner wall of the arch in the compliant during late deceleration, but not rigid. The recirculation regions witnessed identify as high risk areas for atherosclerosis formation by a previous ex-vivo study. The results demonstrate necessity of compliance and pulsatility in haemodynamic studies to obtain highly relevant clinical outcomes.

Mutant p53 Drives Cancer Metastasis via RCP-Mediated Hsp90α Secretion

Mutant p53 (mutp53) loses its tumor suppressor properties but gains oncogenic functions of driving malignancy. However, it remains largely unknown how mutp53 drives cancer metastasis. Here, we show that wild-type p53 (WTp53) suppresses the secretion of heat shock protein 90-alpha (Hsp90α), whereas mutp53 enhances Hsp90α vesicular trafficking and exosome-mediated secretion. Long-term delivery of an antibody that blocks extracellular Hsp90α (eHsp90α) function extends the survival of p53^-/- mice and attenuates the invasiveness of p53 mutant tumors. Furthermore, mass spectrometry and functional analysis identified a critical role for Rab coupling protein (RCP) in mutp53-induced Hsp90α secretion. RCP knockdown decreases eHsp90α levels and inhibits malignant progression. Notably, recombinant Hsp90α re-introduction markedly rescues the impaired migration and invasion abilities caused by RCP depletion. Taken together, these findings elucidate the molecular mechanisms by which mutp53 executes oncogenic activities via its downstream RCP-mediated Hsp90α secretion and a strategy to treat human cancers expressing mutp53 proteins.

HSP60 Regulates Monosodium Urate Crystal-Induced Inflammation by Activating the TLR4-NF-κB-MyD88 Signaling Pathway and Disrupting Mitochondrial Function

Acute gout is an inflammatory response induced by monosodium urate (MSU) crystals. HSP60 is a highly conserved stress protein that acts as a cellular "danger" signal for immune reactions. In this study, we aimed to investigate the role and molecular mechanism of HSP60 in gout. HSP60 expression was detected in peripheral blood mononuclear cells (PBMCs) and plasma of gout patients. The effect and molecular mechanism of HSP60 in gout were studied in MSU crystals treatment macrophages and C57BL/6 mice. JC-1 probe and MitoSOX Red were used to measure the mitochondrial membrane potential (MMP) and mitochondrial reactive oxygen species (mtROS). HSP60 expression was significantly upregulated in the PBMCs and sera of patients with acute gout (AG) compared to those with intercritical gout (IG) or healthy controls (HCs). MSU crystals induced the expression and secretion of HSP60 in the macrophages. HSP60 knockdown or overexpression affects TLR4 and MyD88 expression, IκBα degradation, and the nuclear localization of NF-κB in MSU crystal-stimulated inflammation. Further, HSP60 facilitates MMP collapse and mtROS production and activates the NLRP3 inflammasome in MSU crystal-stimulated macrophages. In MSU crystal-induced arthritis mouse models pretreated with HSP60 vivo-morpholino, paw swelling, myeloperoxidase (MPO) activity, and inflammatory cell infiltration significantly decreased. Our study reveals that MSU crystal stimulates the expression of HSP60, which accelerates the TLR4-MyD88-NF-κB signaling pathway and exacerbates mitochondrial dysfunction.

Secretomics to Discover Regulators in Diseases

Secretory proteins play important roles in the cross-talk of individual functional units, including cells. Since secretory proteins are essential for signal transduction, they are closely related with disease development, including metabolic and neural diseases. In metabolic diseases, adipokines, myokines, and hepatokines are secreted from respective organs under specific environmental conditions, and play roles in glucose homeostasis, angiogenesis, and inflammation. In neural diseases, astrocytes and microglia cells secrete cytokines and chemokines that play roles in neurotoxic and neuroprotective responses. Mass spectrometry-based secretome profiling is a powerful strategy to identify and characterize secretory proteins. This strategy involves stepwise processes such as the collection of conditioned medium (CM) containing secretome proteins and concentration of the CM, peptide preparation, mass analysis, database search, and filtering of secretory proteins; each step requires certain conditions to obtain reliable results. Proteomic analysis of extracellular vesicles has become a new research focus for understanding the additional extracellular functions of intracellular proteins. Here, we provide a review of the insights obtained from secretome analyses with regard to disease mechanisms, and highlight the future prospects of this technology. Continued research in this field is expected to provide valuable information on cell-to-cell communication and uncover new pathological mechanisms.

High Serum Cyclophilin C levels as a risk factor marker for Coronary Artery Disease

Cyclophilins (Cyps) are ubiquitous proteins that belong to the immunophilins family consistently associated with inflammatory and cardiovascular diseases. While levels of CypA have been extensively studied, less data are available for other Cyps. The purpose of this case-control study was to determine the relationship of Cyps (A, B, C and D) with coronary artery disease (CAD) and eight inflammation markers. Serum levels of Cyps, interleukins and metalloproteinases were measured in serum collected from 84 subjects. Participants were divided into two sub-groups based on CAD diagnosis: 40 CAD patients and 44 control volunteers. Serum levels of CypA, CypB and CypC, IL-1β and IL-6 were significantly higher in CAD patients. Bivariate correlation analysis revealed a significant positive correlation between Cyps and several blood and biochemical parameters. When the ability of Cyps levels for CAD diagnosis was evaluated, higher sensitivity and selectivity values were obtained with CypC (c-statistic 0.891, p < 0.001) indicating that it is a good marker of CAD disease, while less conclusive results were obtained with CypA (c-statistic 0.748, p < 0.001) and CypB (c-statistic 0.655, p < 0.014). In addition, significant correlations of traditional CAD risk factors and CypC were observed. In summary, high levels of CypC are a risk factor for CAD and therefore it can be proposed as a new biomarker for this disease.

Expression of REGγ in atherosclerotic plaques and promotes endothelial cells apoptosis via the cyclophilin A pathway indicates functional implications in atherogenesis

REGγ is a member of the 11S regulatory particles family of proteasome activators and has been shown to promote the degradation of intact cellular proteins in a ubiquitin- and ATP-independent manner in the progression of various diseases. Our previous studies showed that REGγ-proteasome promotes Protein kinase A catalytic subunit α (PKAcα) turnover to modulate Forkhead box protein O1 (FoxO1) cellular activity in vascular endothelial cell migration and angiogenesis. We, therefore, studied the expression and novel functional implications and pathways involving REGγ in atherogenesis. We studied the expression of REGγ in atherosclerotic plaques in the ApoE-/- mouse model. Using immunohistochemistry, we showed that REGγ was highly expressed in these plaques, and the result of RNA-seq in Human umbilical vein endothelial cells (HUVECs), led us to explore and indentify that REGγ significantly promoted cyclophilin A (CyPA) expression, which is a proinflammatory and proapoptotic molecule in atherosclerosis progression. Next, we studied the regulation of REGγ in CyPA expression, and the proapoptotic effect on Endothelial cells (ECs). REGγ promoted CyPA expression via the REGγ-PKA-FoxO1-CyPA axis, and stimulated CyPA-dependent ECs apoptosis in vitro. Our data indicated that REGγ had proapoptotic effects on ECs depends on CyPA pathway in vitro and functional implications in atherogenesis in vivo.

Comparative proteomic study reveals the enhanced immune response with the blockade of interleukin 10 with anti-IL-10 and anti-IL-10 receptor antibodies in human U937 cells

Blocking cytokine interleukin 10 (IL-10) at the time of immunisation enhances vaccine induced T cell responses and improves control of tumour cell growth in vivo. However, the effect of an IL-10 blockade on the biological function of macrophages has not been explored. In the current paper, a macrophage precursor cell line, U937 cells, was selected to investigate the differential expression of proteins and relevant cell signalling pathway changes, when stimulated with lipopolysaccharide (LPS) in the presence of antibodies to IL-10 or IL-10 receptor. We used a quantitative proteomic strategy to investigate variations in protein profiles of U937 cells following the treatments with LPS, LPS plus human anti-IL10 antibody and anti-IL10R antibody in 24hrs, respectively. The LPS treatment significantly activated actin-related cell matrix formation and immune response pathways. The addition of anti-IL10 and anti-IL10R antibody further promoted the immune response and potentially effect macrophage survival through PI3K/AKT signalling; however, the latter appeared to also upregulated oncogene XRCC5 and Cajal body associated processes.

Reactive Oxygen Species from NADPH Oxidase and Mitochondria Participate in the Proliferation of Aortic Smooth Muscle Cells from a Model of Metabolic Syndrome

In metabolic diseases, the increased reactive oxygen species (ROS) represents one of the pathogenic mechanisms for vascular disease probably by promoting vascular smooth muscle cell (SMC) proliferation that contributes to the development of arterial remodeling and stenosis, hypertension, and atherosclerosis. Therefore, this work was undertaken to evaluate the participation of ROS from NADPH oxidase and mitochondria in the proliferation of SMCs from the aorta in a model of metabolic syndrome induced by sucrose feeding in rats. After 24 weeks, sucrose-fed (SF) rats develop hypertension, intra-abdominal obesity, hyperinsulinemia, and hyperleptinemia. In addition SMCs from SF rats had a higher growth rate and produce more ROS than control cells. The treatment of SMCs with DPI and apocynin to inhibit NADPH oxidase and with tempol to scavenge superoxide anion significantly blocked the proliferation of both SF and control cells suggesting the participation of NADPH oxidase as a source of superoxide anion. MitoTEMPO, which targets mitochondria within the cell, also significantly inhibited the proliferation of SMCs having a greater effect on cells from SF than from the control aorta. The higher rate of cell growth from the SF aorta is supported by the increased content of cyclophilin A and CD147, proteins involved in the mechanism of cell proliferation. In addition, caldesmon, α-actin, and phosphorylated myosin light chain, contractile phenotype proteins, were found significantly lower in SF cells in no confluent state and increased in confluent state but without difference between both cell types. Our results suggest that ROS from NADPH oxidase and mitochondria significantly participate in the difference found in the rate of cell growth between SF and control cells.

Identification of Novel Therapeutic Targets for Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are fatal diseases; however, their pathogenesis still remains to be elucidated. We have recently screened novel pathogenic molecules and have performed drug discovery targeting those molecules. Pulmonary artery smooth muscle cells (PASMCs) in patients with PAH (PAH-PASMCs) have high proliferative properties like cancer cells, which leads to thickening and narrowing of distal pulmonary arteries. Thus, we conducted a comprehensive analysis of PAH-PASMCs and lung tissues to search for novel pathogenic proteins. We validated the pathogenic role of the selected proteins by using tissue-specific knockout mice. To confirm its clinical significance, we used patient-derived blood samples to evaluate the potential as a biomarker for diagnosis and prognosis. Finally, we conducted a high throughput screening and found inhibitors for the pathogenic proteins.

Heat shock protein 90: its inhibition and function

The molecular chaperone heat shock protein 90 (Hsp90) facilitates metastable protein maturation, stabilization of aggregation-prone proteins, quality control of misfolded proteins and assists in keeping proteins in activation-competent conformations. Proteins that rely on Hsp90 for function are delivered to Hsp90 utilizing a co-chaperone-assisted cycle. Co-chaperones play a role in client transfer to Hsp90, Hsp90 ATPase regulation and stabilization of various Hsp90 conformational states. Many of the proteins chaperoned by Hsp90 (Hsp90 clients) are essential for the progression of various diseases, including cancer, Alzheimer's disease and other neurodegenerative diseases, as well as viral and bacterial infections. Given the importance of these clients in different diseases and their dynamic interplay with the chaperone machinery, it has been suggested that targeting Hsp90 and its respective co-chaperones may be an effective method for combating a large range of illnesses.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

Oxidative Stress Induces HSP90 Upregulation on the Surface of Primary Human Endothelial Cells: Role of the Antioxidant 7,8-Dihydroxy-4-methylcoumarin in Preventing HSP90 Exposure to the Immune System

We have previously demonstrated that human heat shock protein 90 (HSP90), an intracellular self protein, is the target of cellular and humoral autoimmune responses in patients with carotid atherosclerosis. In this study, we evaluated in vitro whether oxidative stress, a feature of atherosclerotic plaque, alters HSP90 expression in endothelial cells, thus inducing surface localization of this molecule and whether the antioxidant compound 7,8-dihydroxy-4-methylcoumarin (7,8-DHMC) is able to prevent oxidative stress-induced alterations of HSP90 localization. By the use of flow cytometry, immunofluorescence, enzyme-linked immunosorbent assay, and semiquantitative reverse-transcription polymerase chain reaction, we demonstrated that exposure of human umbilical vein endothelial cells (HUVEC) to the prooxidant compound H₂O₂ upregulated HSP90 surface expression and reduced its secretion without altering HSP90 gene expression and intracytoplasmic protein levels. Pretreatment of HUVEC with 7,8-DHMC prevented H₂O₂-induced alterations of HSP90 cellular distribution and secretion. Our results suggest that the strong oxidative conditions of atherosclerotic plaques promote the upregulation of HSP90 surface expression on endothelial cells, thus rendering the protein a possible target of autoimmune reactions. The antioxidant 7,8-DHMC, by preventing oxidative-stress-triggered HSP90 surface upregulation, may be useful to counteract possible autoreactive reactions to HSP90.

Mitochondria-Accessing Ratiometric Fluorescent Probe for Imaging Endogenous Superoxide Anion in Live Cells and Daphnia magna

Superoxide anion (O₂^•-), as the precursor of other reactive oxygen species (ROS), is significantly important in the maintenance of redox homeostasis and various cellular signaling pathways. Here we present a ratiometric mitochondria-accessing fluorescent probe (NA-T) based on nucleophilic substitution mechanism for real-time measuring O₂^•-. By regulating the intramolecular charge of 1,8-naphthalimide, a ratiometric response model was obtained, which evinced 18-fold enhancement of fluorescence ratio ( I_540 nm/ I_475 nm) in the presence of O₂^•- over other ROS with rapid response (132 s), high sensitivity (DL = 0.370 μM) and selectivity. Confocal fluorescence images demonstrated that the probe could well permeate through plasma membrane for visualizing endogenous O₂^•- changes in mitochondria of living cells and in inflammatory Daphnia magna, indicating NA-T a potential tool for the diagnosis and research of corresponding diseases.

The role of secreted heat shock protein-90 (Hsp90) in wound healing - how could it shape future therapeutics?

INTRODUCTION

Defects in tissue repair or wound healing pose a clinical, economic and social problem worldwide. Despite decades of studies, there have been few effective therapeutic treatments. Areas covered: We discuss the possible reasons for why growth factor therapy did not succeed. We point out the lack of human disorder-relevant animal models as another blockade for therapeutic development. We summarize the recent discovery of secreted heat shock protein-90 (Hsp90) as a novel wound healing agent. Expert commentary: Wound healing is a highly complex and multistep process that requires participations of many cell types, extracellular matrices and soluble molecules to work together in a spatial and temporal fashion within the wound microenvironment. The time that wounds remain open directly correlates with the clinical mortality associated with wounds. This time urgency makes the healing process impossible to regenerate back to the unwounded stage, rather forces it to take many shortcuts in order to protect life. Therefore, for therapeutic purpose, it is crucial to identify so-called 'driver genes' for the life-saving phase of wound closure. Keratinocyte-secreted Hsp90α was discovered in 2007 and has shown the promise by overcoming several key hurdles that have blocked the effectiveness of growth factors during wound healing.

Prognostic Impacts of Plasma Levels of Cyclophilin A in Patients With Coronary Artery Disease

Objective—

Cyclophilin A (CyPA) is secreted from vascular smooth muscle cells, inflammatory cells, and activated platelets in response to oxidative stress. We have recently demonstrated that plasma CyPA level is a novel biomarker for diagnosing coronary artery disease. However, it remains to be elucidated whether plasma CyPA levels also have a prognostic impact in such patients.

Approach and Results—

In 511 consecutive patients undergoing diagnostic coronary angiography, we measured the plasma levels of CyPA, high-sensitivity C-reactive protein (hsCRP), and brain natriuretic peptide and evaluated their prognostic impacts during the follow-up (42 months, interquartile range: 25–55 months). Higher CyPA levels (≥12 ng/mL) were significantly associated with all-cause death, rehospitalization, and coronary revascularization. Higher hsCRP levels (≥1 mg/L) were also significantly correlated with the primary end point and all-cause death, but not with rehospitalization or coronary revascularization. Similarly, higher brain natriuretic peptide levels (≥100 pg/mL) were significantly associated with all-cause death and rehospitalization, but not with coronary revascularization. Importantly, the combination of CyPA (≥12 ng/mL) and hsCRP (≥1 mg/L) was more significantly associated with all-cause death (hazard ratio, 21.2; 95% confidence interval, 4.9–92.3,; P <0.001) than CyPA (≥12 ng/mL) or hsCRP (≥1 mg/L) alone.

Conclusions—

The results indicate that plasma CyPA levels can be used to predict all-cause death, rehospitalization, and coronary revascularization in patients with coronary artery disease and that when combined with other biomarkers (hsCRP and brain natriuretic peptide levels), the CyPA levels have further enhanced prognostic impacts in those patients.

Inflammatory stress of pancreatic beta cells drives release of extracellular heat-shock protein 90α

A major obstacle in predicting and preventing the development of autoimmune type 1 diabetes (T1D) in at-risk individuals is the lack of well-established early biomarkers indicative of ongoing beta cell stress during the pre-clinical phase of disease. Recently, serum levels of the α cytoplasmic isoform of heat-shock protein 90 (hsp90) were shown to be elevated in individuals with new-onset T1D. We therefore hypothesized that hsp90α could be released from beta cells in response to cellular stress and inflammation associated with the earliest stages of T1D. Here, human beta cell lines and cadaveric islets released hsp90α in response to stress induced by treatment with a combination of pro-inflammatory cytokines including interleukin-1β, tumour necrosis factor-α and interferon-γ. Mechanistically, hsp90α release was found to be driven by cytokine-induced endoplasmic reticulum stress mediated by c-Jun N-terminal kinase (JNK), a pathway that can eventually lead to beta cell apoptosis. Cytokine-induced beta cell hsp90α release and JNK activation were significantly reduced by pre-treating cells with the endoplasmic reticulum stress-mitigating chemical chaperone tauroursodeoxycholic acid. The hsp90α release by cells may therefore be a sensitive indicator of stress during inflammation and a useful tool in assessing therapeutic mitigation of cytokine-induced cell damage linked to autoimmunity.

The Potential Functions of Small Heat Shock Proteins in the Uterine Musculature during Pregnancy

The small heat shock protein B (HSPB) family is comprised of eleven members with many being induced by physiological stressors. In addition to being molecular chaperones, it is clear these proteins also play important roles in cell death regulation, cytoskeletal rearrangements, and immune system activation. These processes are important for the uterine smooth muscle or myometrium during pregnancy as it changes from a quiescent tissue, during the majority of pregnancy, to a powerful and contractile tissue at labor. The initiation and progression of labor within the myometrium also appears to require an inflammatory response as it is infiltrated by immune cells and it produces pro-inflammatory mediators. This chapter summarizes current knowledge on the expression of HSPB family members in the myometrium during pregnancy and speculates on the possible roles of these proteins during myometrial programming and transformation of the myometrium into a possible immune regulatory tissue.

In vitro and In vivo Antioxidant, Anti-hyperlipidemic Properties and Chemical Characterization of Centella asiatica (L.) Extract

The study aimed to identify the phenolic compounds present in Centella asiatica (L.) (C. asiatica) extract and evaluate the respective antioxidant potential as well as its cholesterol-lowering effects in the experimental animal model. Herein, the antioxidant potential of extracts was assessed by its free radical scavenging activity such as 2, 2-diphenyl -1- picrylhydrazyl as well as reducing capability. The anti-hyperlipidemic effects of C. asiatica extract (CAE) were evaluated in high cholesterol-fed (HCF) rats for 4 weeks, where different concentrations of extracts (0.25, 0.5, and 1 g/kg/day) were orally administrated daily. Lipid and antioxidant profiles, including total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C) and superoxide dismutase (SOD), together with the indices of hepatic functions were also examined. C. asiatica revealed excellent free radical scavenging activity as revealed by 2-2- diphenyl-1-picryl-hydrazyl (DPPH) assay, with the IC50 values (9.62 ± 0.88 μg/mL). Furthermore, C. asiatica extracts and fenofibrate remarkably lowered the level of TC, TG, LDL-C, and showed elevated levels of HDL-C, SOD. The histopathological observations further demonstrated clear differentiation and structural changes in liver of HCF and CAE treated group. Furthermore, gulonic acid, ferulic acid, kaempferol, chlorogenic acid, and asiatic acid were identified to be the major components which might be responsible for the antioxidant activity of the C. asiatica extract as evidenced from an ultra-high performance liquid chromatography-mass spectrometer. Taken together, these results signifies the excellent antioxidant and anti-hyperlipidemic properties of C. asiatica leaf extracts, which might be useful for the treatment of oxidative-stress related diseases such as hyperlipidemia.

Anti-Heat Shock Protein-27 Antibody Levels in Women with Breast Cancer: Association with Disease Complications and Two-Year Disease-Free Survival

Background and Aim:

Breast cancer is a major healthcare problem in women. There are many reports about up-regulation of Hsp27 in cancer tissues but less is known about the potential relationship between Hsp27 antibody levels and breast cancer complications. We here investigated concentrations of serum Hsp27 antigen and antibodies in subjects with and without breast cancer and assessed potential associations with two-year disease-free survival, histological grade and number of lymph nodes.

Materials and Methods:

Specifically, serum Hsp27 antigen and antibody levels from 97 patients with breast cancer, and 65 healthy controls were determined by enzyme-linkedimmunosorbent assays (ELISAs).

Results:

Serum Hsp27 and antibody levels were significantly (p<0.001) higher in patients with breast cancer compared to the control group, but no relationship were found with two-year disease free survival, histological grade or number of lymph nodes (p> 0.6, 0.2 and 0.9 respectively).

Conclusions:

Elevated levels of Hsp27 antibody occur with women with breast cancer but do not appear to be associated with the presence of disease clinical complications.

Induction of expression and phosphorylation of heat shock protein B5 (CRYAB) in rat myometrium during pregnancy and labour

During pregnancy the myometrium undergoes a programme of differentiation induced by endocrine, cellular, and biophysical inputs. Small heat shock proteins (HSPs) are a family of ten (B1–B10) small-molecular-weight proteins that not only act as chaperones, but also assist in processes such as cytoskeleton rearrangements and immune system activation. Thus, it was hypothesized that HSPB5 (CRYAB) would be highly expressed in the rat myometrium during the contractile and labour phases of myometrial differentiation when such processes are prominent. Immunoblot analysis revealed that myometrial CRYAB protein expression significantly increased from day (D) 15 to D23 (labour;P<0.05). In correlation with these findings, serine 59-phosphorylated (pSer59) CRYAB protein expression significantly increased from D15 to D23, and was also elevated 1-day post-partum (P<0.05). pSer59-CRYAB was detected in the cytoplasm of myocytes within both uterine muscle layers mid- to late-pregnancy. In unilaterally pregnant rats, pSer59-CRYAB protein expression was significantly elevated in the gravid uterine horns at both D19 and D23 of gestation compared with non-gravid horns. Co-immunolocalization experiments using the hTERT-human myometrial cell line and confocal microscopy demonstrated that pSer59-CRYAB co-localized with the focal adhesion protein FERMT2 at the ends of actin filaments as well as with the exosomal marker CD63. Overall, pSer59-CRYAB is highly expressed in myometrium during late pregnancy and labour and its expression appears to be regulated by uterine distension. CRYAB may be involved in the regulation of actin filament dynamics at focal adhesions and could be secreted by exosomes as a prelude to involvement in immune activation in the myometrium.

RhoA/Rho-Kinase in the Cardiovascular System

Twenty years ago, Rho-kinase was identified as an important downstream effector of the small GTP-binding protein, RhoA. Thereafter, a series of studies demonstrated the important roles of Rho-kinase in the cardiovascular system. The RhoA/Rho-kinase pathway is now widely known to play important roles in many cellular functions, including contraction, motility, proliferation, and apoptosis, and its excessive activity induces oxidative stress and promotes the development of cardiovascular diseases. Furthermore, the important role of Rho-kinase has been demonstrated in the pathogenesis of vasospasm, arteriosclerosis, ischemia/reperfusion injury, hypertension, pulmonary hypertension, and heart failure. Cyclophilin A is secreted by vascular smooth muscle cells and inflammatory cells and activated platelets in a Rho-kinase-dependent manner, playing important roles in a wide range of cardiovascular diseases. Thus, the RhoA/Rho-kinase pathway plays crucial roles under both physiological and pathological conditions and is an important therapeutic target in cardiovascular medicine. Recently, functional differences between ROCK1 and ROCK2 have been reported in vitro. ROCK1 is specifically cleaved by caspase-3, whereas granzyme B cleaves ROCK2. However, limited information is available on the functional differences and interactions between ROCK1 and ROCK2 in the cardiovascular system in vivo. Herein, we will review the recent advances about the importance of RhoA/Rho-kinase in the cardiovascular system.

Domains of STIP1 responsible for regulating PrPC-dependent amyloid-β oligomer toxicity

Soluble oligomers of amyloid-beta peptide (AβO) transmit neurotoxic signals through the cellular prion protein (PrP(C)) in Alzheimer's disease (AD). Secreted stress-inducible phosphoprotein 1 (STIP1), an Hsp70 and Hsp90 cochaperone, inhibits AβO binding to PrP(C) and protects neurons from AβO-induced cell death. Here, we investigated the molecular interactions between AβO and STIP1 binding to PrP(C) and their effect on neuronal cell death. We showed that residues located in a short region of PrP (90-110) mediate AβO binding and we narrowed the major interaction in this site to amino acids 91-100. In contrast, multiple binding sites on STIP1 (DP1, TPR1 and TPR2A) contribute to PrP binding. DP1 bound the N-terminal of PrP (residues 23-95), whereas TPR1 and TPR2A showed binding to the C-terminal of PrP (residues 90-231). Importantly, only TPR1 and TPR2A directly inhibit both AβO binding to PrP and cell death. Furthermore, our structural studies reveal that TPR1 and TPR2A bind to PrP through distinct regions. The TPR2A interface was shown to be much more extensive and to partially overlap with the Hsp90 binding site. Our data show the possibility of a PrP, STIP1 and Hsp90 ternary complex, which may influence AβO-mediated cell death.

Light and Dark of Reactive Oxygen Species for Vascular Function: 2014 ASVB (Asian Society of Vascular Biology)

Vascular-derived hydrogen peroxide (H2O2) serves as an important signaling molecule in the cardiovascular system and contributes to vascular homeostasis. H2O2 is a second messenger, transducing the oxidative signal into biological responses through posttranslational protein modification. The balance between oxidant and antioxidant systems regulates intracellular redox status, and their imbalance causes oxidative or reductive stress, leading to cellular damage in cardiovascular systems. Excessive H2O2 deteriorates vascular functions and promotes vascular disease through multiple pathways. The RhoA/Rho-kinase pathway plays an important role in various fundamental cellular functions, including production of excessive reactive oxygen species, leading to the development of cardiovascular diseases. Rho-kinase (ROCK1 and ROCK2) belongs to the family of serine/threonine kinases and is an important downstream effector of the small GTP-binding protein RhoA. Rho-kinase plays a crucial role in the pathogenesis of vasospasm, arteriosclerosis, ischemia/reperfusion injury, hypertension, pulmonary hypertension, stroke, and heart failure. Thus, Rho-kinase inhibitors may be useful for the treatment of cardiovascular diseases in humans. In this review, we will briefly discuss the roles of vascular-derived H2O2 and review the recent progress in the translational research on the therapeutic importance of the Rho-kinase pathway in cardiovascular medicine.

Emerging Roles of Extracellular Hsp90 in Cancer

Heat shock protein 90 (Hsp90) is a highly expressed chaperone that modulates the function and stability of hundreds of cellular client proteins. In this capacity, Hsp90 impacts human health in myriad ways and it is accordingly a high-interest molecular target in the oncology setting. This interest has led to a large number of clinical trials to evaluate the potential benefit of Hsp90 inhibitors in cancer treatment and, more recently, in combination with chemotherapeutic agents. Although these studies are still ongoing, some issues have arisen, such as toxicity effects associated with administration of these agents. We and others have identified a novel role for Hsp90 outside of cancer cells. This extracellular Hsp90 (eHsp90) was shown to be critical for the regulation of tumor invasiveness and metastasis, central processes associated with cancer lethality. Since these initial papers, a considerable cohort of studies has expanded upon this role, implicating eHsp90 in the activation of a number of proteins that support tumor cell invasion. As eHsp90 is preferentially detected on the surface of tumor cells, and within their surrounding microenvironment, it is possible that drugs capable of selectively targeting eHsp90 may exploit this differential expression. This selectivity may, in turn, enable treatment regimens with reduced target-related toxicity. This review will focus on our current understanding of eHsp90, particularly in cancer, and we will discuss the relevance of eHsp90 as a biomarker for invasive cancer and its potential as a drug target.

Transcriptomic and Proteomic Investigation of HSP90A as a Potential Biomarker for HCC

Background

Hepatocellular carcinoma (HCC) is the third most frequent cause of cancer-related death in adults. Despite recent advances in the clinical technologies, the screening and diagnostic efficacy for HCC remains poor. Discovering novel and reliable HCC biomarkers is urgently needed.

Material/Methods

We performed a transcriptome-proteome integrated assay to track the possible HCC biomarkers from the process of HCC-derived gene expression in malignant cells to its protein product released into serum.

Results

Our screening results demonstrated that heat shock protein 90A (HSP90A), which participates in the PI3K-Akt signaling pathway and many other cancer-related pathways, warrants further investigation. The expression of HSP90A was increased in the HCC cells, serum, and tissues. Immunohistochemistry analysis on 76 clinical tissue samples also suggested the relevance between HSP90A expression and HCC metastatic behavior.

Conclusions

These findings suggest a role for HSP90A in HCC pathogenesis and the potential use of HSP90A for the screening and diagnosis of this malignancy.

Cyclophilin A in cardiovascular homeostasis and diseases

Vascular homeostasis is regulated by complex interactions between many vascular cell components, including endothelial cells, vascular smooth muscle cells (VSMCs), adventitial inflammatory cells, and autonomic nervous system. The balance between oxidant and antioxidant systems determines intracellular redox status, and their imbalance can cause oxidative stress. Excessive oxidative stress is one of the important stimuli that induce cellular damage and dysregulation of vascular cell components, leading to vascular diseases through multiple pathways. Cyclophilin A (CyPA) is one of the causative proteins that mediate oxidative stress-induced cardiovascular dysfunction. CyPA was initially discovered as the intracellular receptor of the immunosuppressive drug cyclosporine 30 years ago. However, recent studies have established that CyPA is secreted from vascular cell components, such as endothelial cells and VSMCs. Extracellular CyPA augments the development of cardiovascular diseases. CyPA secretion is regulated by Rho-kinase, which contributes to the pathogenesis of vasospasm, arteriosclerosis, ischemia/reperfusion injury, hypertension, pulmonary hypertension, and heart failure. We recently reported that plasma CyPA levels are significantly higher in patients with coronary artery disease, which is associated with increased numbers of stenotic coronary arteries and the need for coronary intervention in such patients. Furthermore, we showed that the vascular erythropoietin (Epo)/Epo receptor system plays an important role in production of nitric oxide and maintenance of vascular redox state and homeostasis, with a potential mechanistic link to the Rho-kinase-CyPA pathway. In this article, I review the data on the protective role of the vascular Epo/Epo receptor system and discuss the roles of the CyPA/Rho-kinase system in cardiovascular diseases.

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.

2015 ATVB Plenary Lecture: translational research on rho-kinase in cardiovascular medicine

Rho-kinase (ROCKs) is an important downstream effector of the small GTP-binding protein Ras homolog gene family member A. There are 2 isoforms of ROCK, ROCK1 and ROCK2, and they have different functions in several vascular components. The Ras homolog gene family member A/ROCK pathway plays an important role in various fundamental cellular functions, including contraction, motility, proliferation, and apoptosis, whereas its excessive activity is involved in the pathogenesis of cardiovascular diseases. For the past 20 years, a series of translational research studies have demonstrated the important roles of ROCK in the pathogenesis of cardiovascular diseases. At the molecular and cellular levels, ROCK upregulates several molecules related to inflammation, thrombosis, and fibrosis. In animal experiments, ROCK plays an important role in the pathogenesis of vasospasm, arteriosclerosis, hypertension, pulmonary hypertension, and heart failure. Finally, at the human level, ROCK is substantially involved in the pathogenesis of coronary vasospasm, angina pectoris, hypertension, pulmonary hypertension, and heart failure. Furthermore, ROCK activity in circulating leukocytes is a useful biomarker for the assessment of disease severity and therapeutic responses in vasospastic angina, heart failure, and pulmonary hypertension. In addition to fasudil, many other ROCK inhibitors are currently under development for various indications. Thus, the ROCK pathway is an important novel therapeutic target in cardiovascular medicine.

Cyclophilin A is associated with peripheral artery disease and chronic kidney disease in geriatrics: The Tianliao Old People (TOP) study

Cyclophilin A (CyPA), secreted by vascular smooth muscle cells in response to oxidative stress, is important in the pathogenesis of progressive peripheral arterial occlusion disease (PAOD), which is common among chronic kidney disease. We explored the prevalence of PAOD in Taiwan’s elderly (≥ 65 years old) population and its association with CyPA and renal function. Residents of Tianliao District, a rural community in southern Taiwan, were surveyed. An ankle-brachial index (ABI) < 0.91 was defined as PAOD. Chronic kidney disease (CKD) was defined based on eGFR levels < 60 mL/min/1.73 m². Serum CyPA was measured. Of the 473 participants, 68 (14.4%) had PAOD. Multiple logistic regression analysis showed PAOD was significantly associated with lower eGFR, lower BMI, higher glycated hemoglobin and higher pulse pressure. Serum CyPA levels in participants with PAOD were significantly higher than those with normal ABI values (47.3 ± 0.4 vs. 25.5 ± 0.2 ng/mL, p < 0.001). Moreover, eGFR inversely correlated with serum CyPA level (p < 0.05) in participants with CKD, but not in participants with normal renal function. In conclusion, with a prevalence of PAOD as high as 14.4% in an elderly community, CyPA might be the link between PAOD and advanced impaired renal function.

Basigin mediates pulmonary hypertension by promoting inflammation and vascular smooth muscle cell proliferation

RATIONALE

Cyclophilin A (CyPA) is secreted from vascular smooth muscle cells (VSMCs) by oxidative stress and promotes VSMC proliferation. However, the role of extracellular CyPA and its receptor Basigin (Bsg, encoded by Bsg) in the pathogenesis of pulmonary hypertension (PH) remains to be elucidated.

OBJECTIVE

To determine the role of CyPA/Bsg signaling in the development of PH.

METHODS AND RESULTS

In the pulmonary arteries of patients with PH, immunostaining revealed strong expression of CyPA and Bsg. The pulmonary arteries of CyPA(±) and Bsg(±) mice exposed to normoxia did not differ in morphology compared with their littermate controls. In contrast, CyPA(±) and Bsg(±) mice exposed to hypoxia for 4 weeks revealed significantly reduced right ventricular systolic pressure, pulmonary artery remodeling, and right ventricular hypertrophy compared with their littermate controls. These features were unaltered by bone marrow reconstitution. To further evaluate the role of vascular Bsg, we harvested pulmonary VSMCs from Bsg(+/+) and Bsg(±) mice. Proliferation was significantly reduced in Bsg(±) compared with Bsg(+/+) VSMCs. Mechanistic studies demonstrated that Bsg(±) VSMCs revealed reduced extracellular signal-regulated kinase 1/2 activation and less secretion of cytokines/chemokines and growth factors (eg, platelet-derived growth factor-BB). Finally, in the clinical study, plasma CyPA levels in patients with PH were increased in accordance with the severity of pulmonary vascular resistance. Furthermore, event-free curve revealed that high plasma CyPA levels predicted poor outcome in patients with PH.

CONCLUSIONS

These results indicate the crucial role of extracellular CyPA and vascular Bsg in the pathogenesis of PH.

Antibodies in the pathogenesis of hypertension

It has long been known that circulating levels of IgG and IgM antibodies are elevated in patients with essential and pregnancy-related hypertension. Recent studies indicate these antibodies target, and in many cases activate, G-protein coupled receptors and ion channels. Prominent among these protein targets are AT₁ receptors, α₁-adrenoceptors, β₁-adrenoceptors, and L-type voltage operated Ca²⁺ channels, all of which are known to play key roles in the regulation of blood pressure through modulation of vascular tone, cardiac output, and/or Na⁺/water reabsorption in the kidneys. This suggests that elevated antibody production may be a causal mechanism in at least some cases of hypertension. In this brief review, we will further describe the protein targets of the antibodies that are elevated in individuals with essential and pregnancy-related hypertension and the likely pathophysiological consequences of antibody binding to these targets. We will speculate on the potential mechanisms that underlie elevated antibody levels in hypertensive individuals and, finally, we will outline the therapeutic opportunities that could arise with a better understanding of how and why antibodies are produced in hypertension.