Mechanical stress-induced heat shock protein 70 expression in vascular smooth muscle cells is regulated by Rac and Ras small G proteins but not mitogen-activated protein kinases

Phenotypic targeting using magnetic nanoparticles for rapid characterization of cellular proliferation regulators

Genome-wide CRISPR screens have provided a systematic way to identify essential genetic regulators of a phenotype of interest with single-cell resolution. However, most screens use live/dead readout of viability to identify factors of interest. Here, we describe an approach that converts cell proliferation into the degree of magnetization, enabling downstream microfluidic magnetic sorting to be performed. We performed a head-to-head comparison and verified that the magnetic workflow can identify the same hits from a traditional screen while reducing the screening period from 4 weeks to 1 week. Taking advantage of parallelization and performance, we screened multiple mesenchymal cancer cell lines for their dependency on cell proliferation. We found and validated pan- and cell-specific potential therapeutic targets. The method presented provides a nanoparticle-enabled approach means to increase the breadth of data collected in CRISPR screens, enabling the rapid discovery of drug targets for treatment.

Mechanical manipulation of cancer cell tumorigenicity via heat shock protein signaling

Biophysical cues of rigid tumor matrix play a critical role in cancer cell malignancy. We report that stiffly confined cancer cells exhibit robust growth of spheroids in the stiff hydrogel that exerts substantial confining stress on the cells. The stressed condition activated Hsp (heat shock protein)-signal transducer and activator of transcription 3 signaling via the transient receptor potential vanilloid 4-phosphatidylinositol 3-kinase/Akt axis, thereby up-regulating the expression of the stemness-related markers in cancer cells, whereas these signaling activities were suppressed in cancer cells cultured in softer hydrogels or stiff hydrogels with stress relief or Hsp70 knockdown/inhibition. This mechanopriming based on three-dimensional culture enhanced cancer cell tumorigenicity and metastasis in animal models upon transplantation, and pharmaceutically inhibiting Hsp70 improved the anticancer efficacy of chemotherapy. Mechanistically, our study reveals the crucial role of Hsp70 in regulating cancer cell malignancy under mechanically stressed conditions and its impacts on cancer prognosis-related molecular pathways for cancer treatments.

A single-cell atlas of non-haematopoietic cells in human lymph nodes and lymphoma reveals a landscape of stromal remodelling

The activities of non-haematopoietic cells (NHCs), including mesenchymal stromal cells and endothelial cells, in lymphomas are reported to underlie lymphomagenesis. However, our understanding of lymphoma NHCs has been hampered by unexplained NHC heterogeneity, even in normal human lymph nodes (LNs). Here we constructed a single-cell transcriptome atlas of more than 100,000 NHCs collected from 27 human samples, including LNs and various nodal lymphomas, and it revealed 30 distinct subclusters, including some that were previously unrecognized. Notably, this atlas was useful for comparative analyses with lymphoma NHCs, which revealed an unanticipated landscape of subcluster-specific changes in gene expression and interaction with malignant cells in follicular lymphoma NHCs. This facilitates our understanding of stromal remodelling in lymphoma and highlights potential clinical biomarkers. Our study largely updates NHC taxonomy in human LNs and analysis of disease status, and provides a rich resource and deeper insights into LN and lymphoma biology to advance lymphoma management and therapy.

Abe et al. profile, characterize and compare non-haematopoietic cells in normal human lymph nodes versus nodal lymphomas from patients, providing insights into stromal modelling in health and disease.

Identification and Functional Analysis of the Regulatory Elements in the pHSPA6 Promoter

Functional and expressional research of heat shock protein A6 (HSPA6) suggests that the gene is of great value for neurodegenerative diseases, biosensors, cancer, etc. Based on the important value of pigs in agriculture and biomedicine and to advance knowledge of this little-studied HSPA member, the stress-sensitive sites in porcine HSPA6 (pHSPA6) were investigated following different stresses. Here, two heat shock elements (HSEs) and a conserved region (CR) were identified in the pHSPA6 promoter by a CRISPR/Cas9-mediated precise gene editing strategy. Gene expression data showed that sequence disruption of these regions could significantly reduce the expression of pHSPA6 under heat stress. Stimulation studies indicated that these regions responded not only to heat stress but also to copper sulfate, MG132, and curcumin. Further mechanism studies showed that downregulated pHSPA6 could significantly affect some important members of the HSP family that are involved in HSP40, HSP70, and HSP90. Overall, our results provide a new approach for investigating gene expression and regulation that may contribute to gene regulatory mechanisms, drug target selection, and breeding stock selection.

Enhanced intratumoural activity of CAR T cells engineered to produce immunomodulators under photothermal control

Treating solid malignancies with chimeric antigen receptor (CAR) T cells typically results in poor responses. Immunomodulatory biologics delivered systemically can augment the cells' activity, but off-target toxicity narrows the therapeutic window. Here we show that the activity of intratumoural CAR T cells can be controlled photothermally via synthetic gene switches that trigger the expression of transgenes in response to mild temperature elevations (to 40-42 °C). In vitro, heating engineered primary human T cells for 15-30 min led to over 60-fold-higher expression of a reporter transgene without affecting the cells' proliferation, migration and cytotoxicity. In mice, CAR T cells photothermally heated via gold nanorods produced a transgene only within the tumours. In mouse models of adoptive transfer, the systemic delivery of CAR T cells followed by intratumoural production, under photothermal control, of an interleukin-15 superagonist or a bispecific T cell engager bearing an NKG2D receptor redirecting T cells against NKG2D ligands enhanced antitumour activity and mitigated antigen escape. Localized photothermal control of the activity of engineered T cells may enhance their safety and efficacy.

Modulation of Heat-Shock Proteins Mediates Chicken Cell Survival against Thermal Stress

Heat stress is one of the most challenging environmental stresses affecting domestic animal production, particularly commercial poultry, subsequently causing severe yearly economic losses. Heat stress, a major source of oxidative stress, stimulates mitochondrial oxidative stress and cell dysfunction, leading to cell damage and apoptosis. Cell survival under stress conditions needs urgent response mechanisms and the consequent effective reinitiation of cell functions following stress mitigation. Exposure of cells to heat-stress conditions induces molecules that are ready for mediating cell death and survival signals, and for supporting the cell's tolerance and/or recovery from damage. Heat-shock proteins (HSPs) confer cell protection against heat stress via different mechanisms, including developing thermotolerance, modulating apoptotic and antiapoptotic signaling pathways, and regulating cellular redox conditions. These functions mainly depend on the capacity of HSPs to work as molecular chaperones and to inhibit the aggregation of non-native and misfolded proteins. This review sheds light on the key factors in heat-shock responses for protection against cell damage induced by heat stress in chicken.

Cyclic Mechanical Stretch Up-regulates Hepatoma-Derived Growth Factor Expression in Cultured Rat Aortic Smooth Muscle Cells

Hepatoma-derived growth factor (HDGF) is a potent mitogen for vascular smooth muscle cells (SMCs) during embryogenesis and injury repair of vessel walls. Whether mechanical stimuli modulate HDGF expression remains unknown. The present study aimed at investigating whether cyclic mechanical stretch plays a regulatory role in HDGF expression and regenerative cytokine production in aortic SMCs. A SMC cell line was grown on a silicone-based elastomer chamber with extracellular matrix coatings (either type I collagen or fibronectin) and received cyclic and uniaxial mechanical stretches with 10% deformation at frequency 1 Hz. Morphological observation showed that fibronectin coating provided better cell adhesion and spreading and that consecutive 6 h of cyclic mechanical stretch remarkably induced reorientation and realignment of SMCs. Western blotting detection demonstrated that continuous mechanical stimuli elicited up-regulation of HDGF and proliferative cell nuclear antigen, a cell proliferative marker. Signal kinetic profiling study indicated that cyclic mechanical stretch induced signaling activity in RhoA/ROCK and PI3K/Akt cascades. Kinase inhibition study further showed that blockade of PI3K activity suppressed the stretch-induced tumor necrosis factor-α (TNF-α), whereas RhoA/ROCK inhibition significantly blunted the interleukin-6 (IL-6) production and HDGF overexpression. Moreover, siRNA-mediated HDGF gene silencing significantly suppressed constitutive expression of IL-6, but not TNF-α, in SMCs. These findings support the role of HDGF in maintaining vascular expression of IL-6, which has been regarded a crucial regenerative factor for acute vascular injury. In conclusion, cyclic mechanical stretch may maintain constitutive expression of HDGF in vascular walls and be regarded an important biophysical regulator in vascular regeneration.

Molecular cloning, bioinformatics analysis, and expression of small heat shock protein beta-1 from Camelus dromedarius, Arabian camel

Small heat shock protein beta-1 (HSPB-1) plays an essential role in the protection of cells against environmental stress.Elucidation of its molecular, structural, and biological characteristics in a naturally wild-type model is essential. Although the sequence information of the HSPB-1 gene is available for many mammalian species, the HSPB-1 gene of Arabian camel (Arabian camel HSPB-1) has not yet been structurally characterized. We cloned and functionally characterized a full-length of Arabian camel HSPB-1 cDNA. It is 791 bp long, with a 5′-untranslated region (UTR) of 34 bp, a 3′-UTR of 151 bp with a poly(A) tail, and an open reading frame (ORF) of 606 bp encoding a protein of 201 amino acids (accession number: MF278354). The tissue-specific expression analysis of Arabian camel HSPB-1 mRNA was examined using quantitative real-time PCR (qRT-PCR); which suggested that Arabian camel HSPB-1 mRNA was constitutionally expressed in all examined tissues of Arabian camel, with the predominately level in the esophagus tissue. Peptide mass fingerprint-mass spectrometry (PMF-MS) analysis of the purified Arabian camel HSPB-1 protein confirmed the identity of this protein. Phylogenetic analysis showed that the HSPB-1 protein of Arabian camel is grouped together with those of Bactrian camel and Alpaca. Comparing the modelled 3D structure of Arabian camel HSPB-1 protein with the available protein 3D structure of HSPB-1 from human confirmed the presence of α-crystallin domain, and high similarities were noted between the two structures by using super secondary structure prediction.

Linear-No-Threshold Default Assumptions are Unwarranted for Cytotoxic Endpoints Independently Triggered by Ultrasensitive Molecular Switches

Crump's response in this issue to my critique of linear-no-threshold (LNT) default assumptions for noncancer and nongenotoxic cancer risks (Risk Analysis 2016; 36(3):589-604) is rebutted herein. Crump maintains that distinguishing between a low-dose linear dose response and a threshold dose response on the basis of dose-response data is impossible even for endpoints involving increased cytotoxicity. My rebuttal relies on descriptions and specific illustrations of two well-characterized ultrasensitive molecular switches that govern two key cytoprotective responses to cellular stress-heat shock response and antioxidant response element activation, respectively-each of which serve to suppress stress-induced apoptotic cell death unless overwhelmed. Because detailed dose-response data for each endpoint is shown to be J- or inverted-J-shaped with high confidence, and because independent pathways can explain background rates of apoptosis, LNT assumptions for this cytotoxic endpoint are unwarranted, at least in some cases and perhaps generally.

Expression and functional proteomic analyses of osteocytes from Xenopus laevis tested under mechanical stress conditions: preliminary observations on an appropriate new animal model

Hitherto, the role of the osteocyte as transducer of mechanical stimuli into biological signals is far from settled. In this study, we used an appropriate model represented by the cortex of Xenopus laevis long bone diaphysis lacking (unlike the mammalian one) of vascular structures and containing only osteocytes inside the bone matrix. These structural features allow any change of protein profile that might be observed upon different experimental conditions, such as bone adaptation to stress/mechanical loading, to be ascribed specifically to osteocytes. The study was conducted by combining ultrastructural observations and two-dimensional electrophoresis for proteomic analysis. The osteocyte population was extracted from long bones of lower limbs of amphibian skeletons after different protocols (free and forced swimming). The experiments were performed on 210 frogs subdivided into five trials, each including free swimming frogs (controls) and frogs submitted to forced swimming (stressed). The stressed groups were obliged to swim (on movable spheres covering the bottom of a pool on a vibrating plate) continuously for 8 h, and killed 24 h later along with the control groups. Long bones free of soft tissues (periosteum, endosteum and bone marrow), as well as muscles of posterior limbs, were processed and analyzed for proteins differentially expressed or phosphorylated between the two sample groups. The comparative analysis showed that protein phosphorylation profiles differ between control and stressed groups. In particular, we found in long bones of stressed samples that both Erk1/2 and Akt are hyperphosphorylated; moreover, the different phosphorylation of putative Akt substrates (recognized by specific Akt phosphosubstrates-antibody) in stressed vs. control samples clearly demonstrated that Akt signaling is boosted by forced swimming (leading to an increase of mechanical stress) of amphibian long bones. In parallel, we found in posterior limb muscles that the expression of heat shock protein HSP27 and HSP70 stress markers increased upon the forced swimming condition. Because the cortexes of frog long bones are characterized by the presence of only osteocytes, all our results establish the suitability of the X. laevis animal model to study the bone response to stress conditions mediated by this cell type and pave the way for further analysis of the signaling pathways involved in these signal transduction mechanisms.

Predicting cell viability within tissue scaffolds under equiaxial strain: multi-scale finite element model of collagen-cardiomyocytes constructs

Successful tissue engineering and regenerative therapy necessitate having extensive knowledge about mechanical milieu in engineered tissues and the resident cells. In this study, we have merged two powerful analysis tools, namely finite element analysis and stochastic analysis, to understand the mechanical strain within the tissue scaffold and residing cells and to predict the cell viability upon applying mechanical strains. A continuum-based multi-length scale finite element model (FEM) was created to simulate the physiologically relevant equiaxial strain exposure on cell-embedded tissue scaffold and to calculate strain transferred to the tissue scaffold (macro-scale) and residing cells (micro-scale) upon various equiaxial strains. The data from FEM were used to predict cell viability under various equiaxial strain magnitudes using stochastic damage criterion analysis. The model validation was conducted through mechanically straining the cardiomyocyte-encapsulated collagen constructs using a custom-built mechanical loading platform (EQUicycler). FEM quantified the strain gradients over the radial and longitudinal direction of the scaffolds and the cells residing in different areas of interest. With the use of the experimental viability data, stochastic damage criterion, and the average cellular strains obtained from multi-length scale models, cellular viability was predicted and successfully validated. This methodology can provide a great tool to characterize the mechanical stimulation of bioreactors used in tissue engineering applications in providing quantification of mechanical strain and predicting cellular viability variations due to applied mechanical strain.

Loading-Induced Heat-Shock Response in Bovine Intervertebral Disc Organ Culture

Mechanical loading has been shown to affect cell viability and matrix maintenance in the intervertebral disc (IVD) but there is no investigation on how cells survive mechanical stress and whether the IVD cells perceive mechanical loading as stress and respond by expression of heat shock proteins. This study investigates the stress response in the IVD in response to compressive loading. Bovine caudal disc organ culture was used to study the effect of physiological range static loading and dynamic loading. Cell activity, gene expression and immunofluorescence staining were used to analyze the cell response. Cell activity and cytoskeleton of the cells did not change significantly after loading. In gene expression analysis, significant up-regulation of heat shock protein-70 (HSP70) was observed in nucleus pulposus after two hours of loading. However, the expression of the matrix remodeling genes did not change significantly after loading. Similarly, expressions of stress response and matrix remodeling genes changed with application and removal of the dynamic loading. The results suggest that stress response was induced by physiological range loading without significantly changing cell activity and upregulating matrix remodeling. This study provides direct evidence on loading induced stress response in IVD cells and contributes to our understanding in the mechanoregulation of intervertebral disc cells.

Sustained activation of ADP/P2ry12 signaling induces SMC senescence contributing to thoracic aortic aneurysm/dissection

Thoracic aortic aneurysm/dissection (TAAD) is characterized by excessive smooth muscle cell (SMC) loss, extracellular matrix (ECM) degradation and inflammation. However, the mechanism whereby signaling leads to SMC loss is unclear. We used senescence-associated (SA)-β-gal staining and analysis of expression of senescence-related proteins (p53, p21, p19) to show that excessive mechanical stretch (20% elongation, 3600cycles/h, 48h) induced SMC senescence. SMC senescence was also detected in TAAD specimens from both mice and humans. High-performance liquid chromatography and luciferin-luciferase-based assay revealed that excessive mechanical stretch increased adenosine diphosphate (ADP) release from SMCs both in vivo and in vitro. Elevated ADP induced SMC senescence while genetic knockout of the ADP receptor, P2Y G protein-coupled receptor 12 (P2ry12), in mice protected against SMC senescence and inflammation. Both TAAD formation and rupture were significantly reduced in P2ry12^-/- mice. SMCs from P2ry12^-/- mice were resistant to senescence induced by excessive mechanical stretch or ADP treatment. Mechanistically, ADP treatment sustained Ras activation, whereas pharmacological inhibition of Ras protected against SMC senescence and reduced TAAD formation. Taken together, excessive mechanical stress may induce a sustained release of ADP and promote SMC senescence via P2ry12-dependent sustained Ras activation, thereby contributing to excessive inflammation and degeneration, which provides insights into TAAD formation and progression.

Identification of transcription factors and gene clusters in rabbit smooth muscle cells during high flow-induced vascular remodeling via microarray

Sustained blood flow, especially high blood flow causes the remodeling of arteries. The molecular mechanism of vascular remodeling has been mainly investigated in cultured cells. However, the in vivo molecular mechanism is poorly understood. In this study, we performed microarray analysis to explore the gene expression profile of smooth muscle cells (SMCs) during vascular remodeling. Transcriptional profiles indicated that 947 genes were differentially expressed in SMCs responding to high flow compared with the sham control, of which 617 genes were up-regulated and 330 genes were down-regulated. Gene ontology analysis revealed the special participation of extracellular matrix related genes during high flow-induced vascular remodeling. KEGG pathway analysis showed the enrichment of metabolism and immune function associated genes in SMCs exposed to high flow. Besides, we also identified 25 differentially expressed transcription factors potentially impacted by hemodynamic insult. Finally, we revealed FOXN4 as a novel transcription factor that could modulate MMP2 and MMP9 transcriptional activity. Collectively, our results revealed major gene clusters and transcription factors in SMCs during vascular remodeling which may provide an insight into the molecular mechanism of vascular remodeling and facilitate the screening of candidate genes for vascular diseases.

Optimization of expression and purification of HSPA6 protein from Camelus dromedarius in E. coli

The HSPA6, one of the members of large family of HSP70, is significantly up-regulated and has been targeted as a biomarker of cellular stress in several studies. Herein, conditions were optimized to increase the yield of recombinant camel HSPA6 protein in its native state, primarily focusing on the optimization of upstream processing parameters that lead to an increase in the specific as well as volumetric yield of the protein. The results showed that the production of cHSPA6 was increased proportionally with increased incubation temperature up to 37 °C. Induction with 10 μM IPTG was sufficient to induce the expression of cHSPA6 which was 100 times less than normally used IPTG concentration. Furthermore, the results indicate that induction during early to late exponential phase produced relatively high levels of cHSPA6 in soluble form. In addition, 5 h of post-induction incubation was found to be optimal to produce folded cHSPA6 with higher specific and volumetric yield. Subsequently, highly pure and homogenous cHSPA6 preparation was obtained using metal affinity and size exclusion chromatography. Taken together, the results showed successful production of electrophoretically pure recombinant HSPA6 protein from Camelus dromedarius in Escherichia coli in milligram quantities from shake flask liquid culture.

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.

Changes in phosphorylated heat-shock protein 27 in response to acute ureteral obstruction in rats

AIM

In vivo, renal medullary interstitial cells (RMICs) and collecting duct principal cells (mpkCCD cells) are subjected to inflammatory, oxidative and mechanical stress as a result of unilateral ureteral obstruction (UUO). Because heat-shock protein (HSP) 27 and HSP70 are induced by cellular stresses and play a role in cytoprotection, we hypothesized that HSP27 and HSP70 are increased in rats subjected to acute UUO and in RMICs and mpkCCD cells exposed to inflammatory, oxidative or mechanical stress.

METHODS

Rats were subjected to acute UUO for 6 h and 12 h. To examine the expression of HSP27, phosphorylated HSP27 (pHSP27) and HSP70 in response to inflammatory, oxidative and mechanical stress in vitro, we exposed RMICs and mpkCCD cells to interleukin 1β (IL-1β), hydrogen peroxide (H2 O2 ), and stretch stimulation over time.

RESULTS

The phosphorylated form of HSP27 (pHSP27) was increased in the renal inner medulla (IM) after 6-h and 12-h UUO, while HSP27 and HSP70 were unchanged. Furthermore, after 6 h and 12 h of UUO, the expression of inflammatory (IL-1β) and oxidative [haem oxygenase 1 (HO-1)] markers was induced. Exposure to inflammatory, oxidative and mechanical stress changed HSP27 and pHSP27 expression in RMICs but not in mpkCCD cells, while HSP70 was not affected by any of the stress conditions. Exposure of RMICs to oxidative and mechanical stress induced HSP27 phosphorylation via a p38-dependent mechanism.

CONCLUSION

These data demonstrate that, in response to acute UUO, different forms of cellular stresses modulate HSP27 expression and phosphorylation in RMICs. This may affect the ability of renal cells to mount an effective cytoprotective response.

Stress-induced transcription of regulator of G protein signaling 2 (RGS2) by heat shock transcription factor HSF1

Expression of the RGS2 gene modulates RGS2 activity toward G protein-coupled signaling in diverse cellular processes. In this study, RGS2 transcription was induced in HeLa and rat aorta smooth muscle cells by exposure to febrile temperatures or proteotoxic stress. The promoter region of RGS2 contained a binding sequence of HSF1, which is an activator of the heat shock protein gene, and was inducibly bound by stress-activated HSF1. A single nucleotide change identified in the RGS2 promoter of hypertensive patients abolished HSF1-regulated expression of RGS2, suggesting that activated HSF1 is involved in blood pressure regulation via modulation of RGS2 expression.

Low-pressure pulsed focused ultrasound with microbubbles promotes an anticancer immunological response

Background

High-intensity focused-ultrasound (HIFU) has been successfully employed for thermal ablation of tumors in clinical settings. Continuous- or pulsed-mode HIFU may also induce a host antitumor immune response, mainly through expansion of antigen-presenting cells in response to increased cellular debris and through increased macrophage activation/infiltration. Here we demonstrated that another form of focused ultrasound delivery, using low-pressure, pulsed-mode exposure in the presence of microbubbles (MBs), may also trigger an antitumor immunological response and inhibit tumor growth.

Methods

A total of 280 tumor-bearing animals were subjected to sonographically-guided FUS. Implanted tumors were exposed to low-pressure FUS (0.6 to 1.4 MPa) with MBs to increase the permeability of tumor microvasculature.

Results

Tumor progression was suppressed by both 0.6 and 1.4-MPa MB-enhanced FUS exposures. We observed a transient increase in infiltration of non-T regulatory (non-Treg) tumor infiltrating lymphocytes (TILs) and continual infiltration of CD8+ cytotoxic T-lymphocytes (CTL). The ratio of CD8+/Treg increased significantly and tumor growth was inhibited.

Conclusions

Our findings suggest that low-pressure FUS exposure with MBs may constitute a useful tool for triggering an anticancer immune response, for potential cancer immunotherapy.

Protective effect of transplantation of neonatal liver cell nuclei on the model of acute toxic hepatitis

We present the results of comparative analysis of functional and morphological changes in the liver of animals with experimental CCl(4)-induced hepatitis under conditions of transplantation of neonatal liver cells and nuclei. It was found that transplantation of neonatal liver cell nuclei in acute toxic hepatitis provides better functional and structural state of the target organ.

Mechanotransduction in vivo by repeated talin stretch-relaxation events depends upon vinculin

The focal adhesion protein talin undergoes cycles of stretching and relaxation in living cells, suggesting a role in the transduction of mechanical into biochemical signals.

Mechanotransduction is a critical function for cells, in terms of cell viability, shaping of tissues, and cellular behavior. In vitro, cellular level forces can stretch adhesion proteins that link extracellular matrix to the actin cytoskeleton exposing hidden binding sites. However, there is no evidence that in vivo forces produce significant in vivo stretching to cause domain unfolding. We now report that the adhesion protein, talin, is repeatedly stretched by 100–350 nm in vivo by myosin contraction of actin filaments. Using a functional EGFP-N-Talin1-C-mCherry to measure the length of single talin molecules, we observed that the C-terminal mCherry was normally displaced in the direction of actin flow by 90 to >250 nm from N-EGFP but only by 50–60 nm (talin's length in vitro) after myosin inhibition. Individual talin molecules transiently stretched and relaxed. Peripheral, multimolecular adhesions had green outside and red proximal edges. They also exhibited transient, myosin-dependent stretching of 50–350 nm for 6–16 s; however, expression of the talin-binding head of vinculin increased stretching to about 400 nm and suppressed dynamics. We suggest that rearward moving actin filaments bind, stretch, and release talin in multiple, stochastic stick-slip cycles and that multiple vinculin binding and release cycles integrate pulling on matrices into biochemical signals.

How are mechanical forces that act on the surface of a cell transformed into biochemical signals within the cell? Studies of isolated proteins suggest that some of them can stretch, but whether this also happens in living cells remains unclear. In this study, we have been able to measure the stretching of single molecules of a cellular adhesion protein called talin in vivo by tagging each end of the protein with a different fluorescent marker and observing changes in the distance between the two markers with a new microscopic method. Talin is a large cellular protein that concentrates at sites where the cell attaches to the substratum and links integrins in the cell membrane to the actin filament network in the cell. In our study, a green tag at the integrin-binding site was close to the cell surface, whereas a red tag at the actin-binding site was displaced inward by actin flow. We observed repeated protein stretching to 5–8 times the native protein length and relaxation linked to the transduction process in living cells in culture. Individual molecules stretched for 6–16 seconds over ranges of 50–350 nm. Cell adhesion sites, where hundreds of talin molecules were displaced in concert, had similar dynamics. These cycles of stretching and relaxation required the contractile protein myosin. The head domain of vinculin—an adhesion site protein that binds strongly to the stretched talin—kept the adhesions stretched and blocked large oscillations in length. These observations indicate that there is repeated stretching of talin, and that adhesion proteins play a role in the transduction of mechanical signals into biochemical signals through binding and release of vinculin and possibly other focal adhesion proteins.

Distension of the uterus induces HspB1 expression in rat uterine smooth muscle

The uterine musculature, or myometrium, demonstrates tremendous plasticity during pregnancy under the influences of the endocrine environment and mechanical stresses. Expression of the small stress protein heat shock protein B1 (HspB1) has been reported to increase dramatically during late pregnancy, a period marked by myometrial hypertrophy caused by fetal growth-induced uterine distension. Thus, using unilaterally pregnant rat models and ovariectomized nonpregnant rats with uteri containing laminaria tents to induce uterine distension, we examined the effect of uterine distension on myometrial HspB1 expression. In unilaterally pregnant rats, HspB1 mRNA and Ser15-phosphorylated HspB1 (pSer15 HspB1) protein expression were significantly elevated in distended gravid uterine horns at days 19 and 23 (labor) of gestation compared with nongravid horns. Similarly, pSer15 HspB1 protein in situ was only readily detectable in the distended horns compared with the nongravid horns at days 19 and 23; however, pSer15 HspB1 was primarily detectable in situ at day 19 in membrane-associated regions, while it had primarily a cytoplasmic localization in myometrial cells at day 23. HspB1 mRNA and pSer15 HspB1 protein expression were also markedly increased in ovariectomized nonpregnant rat myometrium distended for 24 h with laminaria tents compared with empty horns. Therefore, uterine distension plays a major role in the stimulation of myometrial HspB1 expression, and increased expression of this small stress protein could be a mechanoadaptive response to the increasing uterine distension that occurs during pregnancy.

Cyclic strain upregulates VEGF and attenuates proliferation of vascular smooth muscle cells

Objective

Vascular smooth muscle cell (VSMC) hypertrophy and proliferation occur in response to strain-induced local and systemic inflammatory cytokines and growth factors which may contribute to hypertension, atherosclerosis, and restenosis. We hypothesize VSMC strain, modeling normotensive arterial pressure waveforms in vitro, results in attenuated proliferative and increased hypertrophic responses 48 hrs post-strain.

Methods

Using Flexcell Bioflex Systems we determined the morphological, hyperplastic and hypertrophic responses of non-strained and biomechanically strained cultured rat A7R5 VSMC. We measured secretion of nitric oxide, key cytokine/growth factors and intracellular mediators involved in VSMC proliferation via fluorescence spectroscopy and protein microarrays. We also investigated the potential roles of VEGF on VSMC strain-induced proliferation.

Results

Protein microarrays revealed significant increases in VEGF secretion in response to 18 hours mechanical strain, a result that ELISA data corroborated. Apoptosis-inducing nitric oxide (NO) levels also increased 43% 48 hrs post-strain. Non-strained cells incubated with exogenous VEGF did not reproduce the antimitogenic effect. However, anti-VEGF reversed the antimitogenic effect of mechanical strain. Antibody microarrays of strained VSMC lysates revealed MEK1, MEK2, phospo-MEK1^{T385, T291, T298}, phospho-Erk1/2^{T202+Y204/T185+T187}, and PKC isoforms expression were universally increased, suggesting a proliferative/inflammatory signaling state. Conversely, VSMC strain decreased expression levels of Cdk1, Cdk2, Cdk4, and Cdk6 by 25-50% suggesting a partially inhibited proliferative signaling cascade.

Conclusions

Subjecting VSMC to cyclic biomechanical strain in vitro promotes cell hypertrophy while attenuating cellular proliferation. We also report an upregulation of MEK and ERK activation suggestive of a proliferative phenotype. Hhowever, the proliferative response appears to be aborogated by enhanced antimitogenic cytokine VEGF, NO secretion and downregulation of Cdk expression. Although exogenous VEGF alone is not sufficient to promote the quiescent VSMC phenotype, we provide evidence suggesting that strain is a necessary component to induce VSMC response to the antimitogenic effects of VEGF. Taken together these data indicate that VEGF plays a critical role in mechanical strain-induced VSMC proliferation and vessel wall remodeling. Whether VEGF and/or NO inhibit signaling distal to Erk 1/2 is currently under investigation.

Molecular cloning and characterization of cDNA encoding a putative stress-induced heat-shock protein from Camelus dromedarius

Heat shock proteins are ubiquitous, induced under a number of environmental and metabolic stresses, with highly conserved DNA sequences among mammalian species. Camelus dromedaries (the Arabian camel) domesticated under semi-desert environments, is well adapted to tolerate and survive against severe drought and high temperatures for extended periods. This is the first report of molecular cloning and characterization of full length cDNA of encoding a putative stress-induced heat shock HSPA6 protein (also called HSP70B′) from Arabian camel. A full-length cDNA (2417 bp) was obtained by rapid amplification of cDNA ends (RACE) and cloned in pET-b expression vector. The sequence analysis of HSPA6 gene showed 1932 bp-long open reading frame encoding 643 amino acids. The complete cDNA sequence of the Arabian camel HSPA6 gene was submitted to NCBI GeneBank (accession number HQ214118.1). The BLAST analysis indicated that C. dromedaries HSPA6 gene nucleotides shared high similarity (77–91%) with heat shock gene nucleotide of other mammals. The deduced 643 amino acid sequences (accession number ADO12067.1) showed that the predicted protein has an estimated molecular weight of 70.5 kDa with a predicted isoelectric point (pI) of 6.0. The comparative analyses of camel HSPA6 protein sequences with other mammalian heat shock proteins (HSPs) showed high identity (80–94%). Predicted camel HSPA6 protein structure using Protein 3D structural analysis high similarities with human and mouse HSPs. Taken together, this study indicates that the cDNA sequences of HSPA6 gene and its amino acid and protein structure from the Arabian camel are highly conserved and have similarities with other mammalian species.

Heat-shock proteins in cardiovascular disease

Heat-shock proteins (HSPs) belong to a group of highly conserved families of proteins expressed by all cells and organisms and their expression may be constitutive or inducible. They are generally considered as protective molecules against different types of stress and have numerous intracellular functions. Secretion or release of HSPs has also been described, and potential roles for extracellular HSPs reported. HSP expression is modulated by different stimuli involved in all steps of atherogenesis including oxidative stress, proteolytic aggression, or inflammation. Also, antibodies to HSPs may be used to monitor the response to different types of stress able to induce changes in HSP levels. In the present review, we will focus on the potential implication of HSPs in atherogenesis and discuss the limitations to the use of HSPs and anti-HSPs as biomarkers of atherothrombosis. HSPs could also be considered as potential therapeutic targets to reinforce vascular defenses and delay or avoid clinical complications associated with atherothrombosis.

Involvement of RAGE, NADPH oxidase, and Ras/Raf-1 pathway in glycated LDL-induced expression of heat shock factor-1 and plasminogen activator inhibitor-1 in vascular endothelial cells

Atherothrombotic cardiovascular diseases are the predominant causes of mortality of diabetic patients. Plasminogen activator inhibitor-1 (PAI-1) is the major physiological inhibitor for fibrinolysis, and it is also implicated in inflammation and tissue remodeling. Increased levels of PAI-1 and glycated low-density lipoprotein (glyLDL) were detected in patients with diabetes. Previous studies in our laboratory demonstrated that heat shock factor-1 (HSF1) is involved in glyLDL-induced PAI-1 overproduction in vascular endothelial cells (EC). The present study investigated transmembrane signaling mechanisms involved in glyLDL-induced HSF1 and PAI-1 up-regulation in cultured human vascular EC and streptozotocin-induced diabetic mice. Receptor for advanced glycation end products (RAGE) antibody prevented glyLDL-induced increase in the abundance of PAI-1 in EC. GlyLDL significantly increased the translocation of V-Ha-Ras Harvey rat sarcoma viral oncogene homologue (H-Ras) from cytoplasm to membrane compared with LDL. Farnesyltransferase inhibitor-277 or small interference RNA against H-Ras inhibited glyLDL-induced increases in HSF1 and PAI-1 in EC. Treatment with diphenyleneiodonium, a nicotinamide adenine dinucleotide phosphate oxidase (NOX) inhibitor, blocked glyLDL-induced translocation of H-Ras, elevated abundances of HSF1 and PAI-1 in EC, and increased release of hydrogen peroxide from EC. Small interference RNA for p22(phox) prevented glyLDL-induced expression of NOX2, HSF1, and PAI-1 in EC. GlyLDL significantly increased V-raf-1 murine leukemia viral oncogene homolog 1 (Raf-1) phosphorylation. Treatment with Raf-1 inhibitor blocked glyLDL-induced increase of PAI-1 mRNA in EC. The levels of RAGE, H-Ras, NOX4, HSF1, and PAI-1 were increased in hearts of streptozotocin-diabetic mice and positively correlated with plasma glucose. The results suggest that RAGE, NOX, and H-Ras/Raf-1 are implicated in the up-regulation of HSF1 or PAI-1 in vascular EC under diabetes-associated metabolic stress.

SMAD4 is required for development of maximal endotoxin tolerance

Initial exposure of monocytes/macrophages to LPS induces hyporesponsiveness to a second challenge with LPS, a phenomenon termed LPS tolerance. Molecular mechanisms responsible for endotoxin tolerance are not well defined. We and others have shown that IL-1R-associated kinase (IRAK)-M and SHIP-1 proteins, negative regulators of TLR4 signaling, increase in tolerized cells. TGF-beta1, an anti-inflammatory cytokine, is upregulated following LPS stimulation, mediating its effect through SMAD family proteins. Using a monocytic cell line, THP1, we show that LPS activates endogenous SMAD4, inducing its migration into the nucleus and increasing its expression. Secondary challenge with high dose LPS following initial low-dose LPS exposure does not increase IRAK-M or SHIP1 protein expression in small hairpin (sh)SMAD4 THP-1 cells compared with control shLUC THP1 cells. TNF-alpha concentrations in culture supernatants after second LPS challenge are higher in shSMAD4 THP-1 cells than shLUC THP1 cells, indicating failure to induce maximal tolerance in absence of SMAD4 signaling. Identical results are seen in primary murine macrophages and mouse embryonic fibroblasts, demonstrating the biological significance of our findings. TGF-beta1 treatment does not increase IRAK-M or SHIP1 protein expression in shSMAD4 THP-1 cells, whereas it does so in shLUC THP1 cells, indicating that TGF-beta1 regulates IRAK-M and SHIP1 expression through a SMAD4-dependent pathway. Knockdown of endogenous SHIP1 by shSHIP1 RNA decreases native and inducible IRAK-M protein expression and prevents development of endotoxin tolerance in THP1 cells. We conclude that in THP-1 cells and primary murine cells, SMAD4 signaling is required for maximal induction of endotoxin tolerance via modulation of SHIP1 and IRAK-M.

Effect of cell transplantation on induction of heat shock proteins in damaged heart

Variations in the amount of heat shock proteins of various classes in the damaged myocardium of rats were studied after xenogeneic transplantation of heart cells.

Effects of cyclic strain and growth factors on vascular smooth muscle cell responses

Under physiological and pathological conditions, vascular smooth muscle cells (SMC) are exposed to different biochemical factors and biomechanical forces. Previous studies pertaining to SMC responses have not investigated the effects of both factors on SMCs. Thus, in our research we investigated the combined effects of growth factors like Bfgf (basic fibroblast growth factor), TGF-β (transforming growth factor β) and PDGF (platelet-derived growth factor) along with physiological cyclic strain on SMC responses. Physiological cyclic strain (10% strain) significantly reduced SMC proliferation compared to static controls while addition of growth factors bFGF, TGF-β or PDGF-AB had a positive influence on SMC growth compared to strain alone. Microarray analysis of SMCs exposed to these growth factors and cyclic strain showed that several bioactive genes (vascular endothelial growth factor, epidermal growth factor receptor, etc.) were altered upon exposure. Further work involving biochemical and pathological cyclic strain stimulation will help us better understand the role of cyclic strain and growth factors in vascular functions and development of vascular disorders.

Image-guided, noninvasive, spatiotemporal control of gene expression

Spatiotemporal control of transgene expression is of paramount importance in gene therapy. Here, we demonstrate the use of magnetic resonance temperature imaging (MRI)-guided, high-intensity focused ultrasound (HIFU) in combination with a heat-inducible promoter [heat shock protein 70 (HSP70)] for the in vivo spatiotemporal control of transgene activation. Local gene activation induced by moderate hyperthermia in a transgenic mouse expressing luciferase under the control of the HSP70 promoter showed a high similarity between the local temperature distribution in vivo and the region emitting light. Modulation of gene expression is possible by changing temperature, duration, and location of regional heating. Mild heating protocols (2 min at 43 degrees C) causing no tissue damage were sufficient for significant gene activation. The HSP70 promoter was shown to be induced by the local temperature increase and not by the mechanical effects of ultrasound. Therefore, the combination of MRI-guided HIFU heating and transgenes under control of heat-inducible HSP promoter provides a direct, noninvasive, spatial control of gene expression via local hyperthermia.

Heat shock protein expression in diabetic nephropathy

Heat shock protein (HSP) HSP27, HSP60, HSP70, and HSP90 are induced by cellular stresses and play a key role in cytoprotection. Both hyperglycemia and glomerular hypertension are crucial determinants in the pathogenesis of diabetic nephropathy and impose cellular stresses on renal target cells. We studied both the expression and the phosphorylation state of HSP27, HSP60, HSP70, and HSP90 in vivo in rats made diabetic with streptozotocin and in vitro in mesangial cells and podocytes exposed to either high glucose or mechanical stretch. Diabetic and control animals were studied 4, 12, and 24 wk after the onset of diabetes. Immunohistochemical analysis revealed an overexpression of HSP25, HSP60, and HSP72 in the diabetic outer medulla, whereas no differences were seen in the glomeruli. Similarly, exposure neither to high glucose nor to stretch altered HSP expression in mesangial cells and podocytes. By contrast, the phosphorylated form of HSP27 was enhanced in the glomerular podocytes of diabetic animals, and in vitro exposure of podocytes to stretch induced HSP27 phosphorylation via a P38-dependent mechanism. In conclusion, diabetes and diabetes-related insults differentially modulate HSP27, HSP60, and HSP70 expression/phosphorylation in the glomeruli and in the medulla, and this may affect the ability of renal cells to mount an effective cytoprotective response.

Highly sensitive detection of cytotoxicity using a modified HSP70B' promoter

We have previously found that the DNA fragment from nucleotides (nts) -287 to +110 in the HSP70B' gene is a functional promoter responding to Cadmium Chloride-induced cytotoxicity (Wada et al., Biotechnol Bioeng, 92, 410-415, 2005). In order to increase the cytotoxic response of this promoter, we first determined the location of the cytotoxic responding element (CRE) and then constructed tandem repeats of the CRE in front of the HSP70B' promoter. 5'- and 3'-deletion analysis revealed that the DNA fragment from nts -192 to -56 in the HSP70B' gene induces a significant response to cytotoxicity. When the AP-1 binding site in this region was mutated, the basal activity of HSP70B' gene promoter decreased but the cytotoxic response was unchanged. Thus, the CRE is located in nts -192 to -56 in the HSP70B' promoter, and the AP-1 binding site is not essential for the cytotoxic response. In addition, cells transfected with a luciferase construct carrying three tandem repeats of the CRE upstream of the HSP70B' promoter and containing AP-1 binding site mutation, showed a 2.28-fold higher response than that of no repeats. Moreover, the detection limit of Cadmium Chloride in the cells was 382 pmol/mL. Thus, highly sensitive sensor cells for Cadmium Chloride can be constructed using a HSP70B' promoter construct containing upstream tandem repeats of the CRE and mutation of the AP-1 binding site.

Can the stress protein response be controlled by 'membrane-lipid therapy'?

In addition to high temperature, other stresses and clinical conditions such as cancer and diabetes can lead to the alteration of heat-shock protein (HSP) levels in cells. Moreover, HSPs can associate with either specific lipids or with areas of special membrane topology (such as lipid rafts), and changes in the physical state of cellular membranes can alter hsp gene expression. We propose that membrane microheterogeneity is important for regulating the HSP response. In support of this hypothesis, when particular membrane intercalating compounds are used to alter membrane properties, the simultaneous normalization of dysregulated expression of HSPs causes beneficial responses to disease states. Therefore, these compounds (such as hydroxylamine derivatives) have the potential to become a new class of pharmaceuticals for use in 'membrane-lipid therapy'.

Stress, Heat Shock Proteins, and Autoimmunity: How Immune Responses to Heat Shock Proteins Are to Be Used for the Control of Chronic Inflammatory Diseases

Especially since the (re-)discovery of T cell subpopulations with specialized regulatory activities, mechanisms of anti-inflammatory T cell regulation are studied very actively and are expected to lead to the development of novel immunotherapeutic approaches, especially in chronic inflammatory diseases. Heat shock proteins (Hsp) are possible targets for regulatory T cells due to their enhanced expression in inflamed (stressed) tissues and the evidence that Hsp induce anti-inflammatory immunoregulatory T cell responses. Initial evidence for an immunoregulatory role of Hsp in chronic inflammation was obtained through analysis of T cell responses in the rat model of adjuvant arthritis and the findings that Hsp immunizations protected against the induction of various forms of autoimmune arthritis in rat and mouse models. Since then, immune reactivity to Hsp was found to result from inflammation in various disease models and human inflammatory conditions, such as rheumatoid arthritis (RA), type 1 diabetes, and atherosclerosis. Now, also in the light of a growing interest in T cell regulation, it is of interest to further explore the mechanisms through which Hsp can be utilized to trigger immunoregulatory pathways, capable of suppressing such a wide and diversified spectrum of inflammatory diseases.

Hyperfluidization-coupled membrane microdomain reorganization is linked to activation of the heat shock response in a murine melanoma cell line

Targeting of the Hsp function in tumor cells is currently being assessed as potential anticancer therapy. An improved understanding of the molecular signals that trigger or attenuate the stress protein response is essential for advances to be made in this field. The present study provides evidence that the membrane fluidizer benzyl alcohol (BA), a documented nondenaturant, acts as a chaperone inducer in B16(F10) melanoma cells. It is demonstrated that this effect relies basically on heat shock transcription factor 1 (HSF1) activation. Under the conditions tested, the BA-induced Hsp response involves the up-regulation of a subset of hsp genes. It is shown that the same level of membrane fluidization (estimated in the core membrane region) attained with the closely analogous phenethyl alcohol (PhA) does not generate a stress protein signal. BA, at a concentration that activates heat shock genes, exerts a profound effect on the melting of raft-like cholesterol-sphingomyelin domains in vitro, whereas PhA, at a concentration equipotent with BA in membrane fluidization, has no such effect. Furthermore, through the in vivo labeling of melanoma cells with a fluorescein labeled probe that inserts into the cholesterol-rich membrane domains [fluorescein ester of polyethylene glycol-derivatized cholesterol (fPEG-Chol)], we found that, similarly to heat stress per se, BA, but not PhA, initiates profound alterations in the plasma membrane microdomain structure. We suggest that, apart from membrane hyperfluidization in the deep hydrophobic region, a distinct reorganization of cholesterol-rich microdomains may also be required for the generation and transmission of stress signals to activate hsp genes.

Increased temperature, not cardiac load, activates heat shock transcription factor 1 and heat shock protein 72 expression in the heart

The expression of myocardial heat shock protein 72 (HSP72) postexercise is initiated by the activation of heat shock transcription factor 1 (HSF1). However, it remains unknown which physiological stimuli govern myocardial HSF1 activation during exercise. These experiments tested the hypothesis that thermal stress and mechanical load, concomitant with simulated exercise, provide independent stimuli for HSF1 activation and ensuing cardiac HSP72 gene expression. To elucidate the independent roles of increased temperature and cardiac workload in the exercise-mediated upregulation of left-ventricular HSP72, hearts from adult male Sprague-Dawley rats were randomly assigned to one of five simulated exercise conditions. Upon reaching a surgical plane of anesthesia, each experimental heart was isolated and perfused using an in vitro working heart model, while independently varying temperatures (i.e., 37°C vs. 40°C) and cardiac workloads (i.e., low preload and afterload vs. high preload and afterload) to mimic exercise responses. Results indicate that hyperthermia, independent of cardiac workload, promoted an increase in nuclear translocation and phosphorylation of HSF1 compared with normothermic left ventricles. Similarly, hyperthermia, independent of workload, resulted in significant increases in cardiac levels of HSP72 mRNA. Collectively, these data suggest that HSF1 activation and HSP72 gene transcriptional competence during simulated exercise are linked to elevated heart temperature and are not a direct function of increased cardiac workload.

Molecular basis of the effects of mechanical stretch on vascular smooth muscle cells

The pulsatile nature of blood pressure and flow creates hemodynamic stimuli in the forms of cyclic stretch and shear stress, which exert continuous influences on the constituents of the blood vessel wall. Vascular smooth muscle cells (VSMCs) use multiple sensing mechanisms to detect the mechanical stimulus resulting from pulsatile stretch and transduce it into intracellular signals that lead to modulations of gene expression and cellular functions, e.g., proliferation, apoptosis, migration, and remodeling. The cytoskeleton provides a structural framework for the VSMC to transmit mechanical forces between its luminal, abluminal, and junctional surfaces, as well as its interior, including the focal adhesion sites, the cytoplasm, and the nucleus. VSMCs also respond differently to the surrounding structural environment, e.g., two-dimensional versus three-dimensional matrix. In vitro studies have been conducted on cultured VSMCs on deformable substrates to elucidate the molecular mechanisms by which the cells convert mechanical inputs into biochemical events, eventually leading to functional responses. The knowledge gained from research on mechanotransduction in vitro, in conjunction with verifications under in vivo conditions, will advance our understanding of the physiological and pathological processes involved in vascular remodeling and adaptation in health and disease.

Monitoring Mesenchymal Stromal Cell Developmental Stage to Apply On-Time Mechanical Stimulation for Ligament Tissue Engineering

To evaluate the appropriate time frame for applying mechanical stimuli to induce mesenchymal stromal cell (MSC) differentiation for ligament tissue engineering, developmental cell phenotypes were monitored during a period of in vitro culture. MSCs were seeded onto surface-modified silk fibroin fiber matrices and cultured in Petri dishes for 15 days. Cell metabolic activity, morphology, and gene expression of extracellular matrix (ECM) proteins (collagen type I and III and fibronectin), ECM receptors (integrins alpha-2, alpha-5, and beta-1), and heat-shock protein 70 (HSP-70) were monitored during the culture of MSC. MSCs showed fluctuations in cell metabolic activity, ECM, integrin, and HSP-70 transcription potentially correlating to innate developmental processes. Cellular response to mechanical stimulation was dependent on the stage of cell development. At day 9, when levels of cell metabolic activity, ECM, integrin, and HSP-70 transcription peaked, mechanical stimulation increased MSC metabolic activity, alignment, and collagen production. Mechanical stimulation applied at day 1 and 3 showed detrimental effects on MSCs seeded on silk matrices. The results presented in this study identify a unique correlation between innate MSC development processes on a surface-modified silk matrix and dynamic environmental signaling.

Correlation of HSP70 expression and cell viability following thermal stimulation of bovine aortic endothelial cells

Thermal preconditioning protocols for cardiac cells were identified which produce elevated HSP70 levels while maintaining high cell viability. Bovine aortic endothelial cells were heated with a water bath at temperatures ranging from 44 to 50 degrees C for periods of 1-30 min. Thermal stimulation protocols were determined which induce HSP70 expression levels ranging from 2.3 to 3.6 times the control while maintaining cell viabilities greater than 90%. An Arrhenius injury model fit to the cell damage data yielded values of A = 1.4 X 10(66) s(-1) and Ea = 4.1 X 10(5) J/mol. Knowledge of the injury parameters and HSP70 kinetics will enhance dosimetry guideline development for thermal stimulation of heat shock proteins expression in cardiac tissue.

High intensity focused ultrasound-induced gene activation in sublethally injured tumor cells in vitro

Cultured human cervical cancer (HeLa) and rat mammary carcinoma (R3230Ac) cells were transfected with vectors encoding green fluorescent protein (GFP) under the control of hsp70B promoter. Aliquots of 10-microl transfected cells (5 x 10(7) cells/ml) were placed in 0.2-ml thin-wall polymerase chain reaction tubes and exposed to 1.1-MHz high intensity focused ultrasound (HIFU) at a peak negative pressure P- = 2.68 MPa. By adjusting the duty cycle of the HIFU transducer, the cell suspensions were heated to a peak temperature from 50 to 70 degrees C in 1-10 s. Exposure dependent cell viability and gene activation were evaluated. For a 5-s HIFU exposure, cell viability dropped from 95% at 50 degrees C to 13% at 70 degrees C. Concomitantly, gene activation in sublethally injured tumor cells increased from 4% at 50 degrees C to 41% at 70 degrees C. A similar trend was observed at 60 degrees C peak temperature as the exposure time increased from 1 to 5 s. Further increase of exposure duration to 10 s led to significantly reduced cell viability and lower overall gene activation in exposed cells. Altogether, maximum HIFU-induced gene activation was achieved at 60 degrees C in 5 s. Under these experimental conditions, HIFU-induced gene activation was found to be produced primarily by thermal rather than mechanical stresses.

Heat shock proteins as emerging therapeutic targets

Chaperones (stress proteins) are essential proteins to help the formation and maintenance of the proper conformation of other proteins and to promote cell survival after a large variety of environmental stresses. Therefore, normal chaperone function is a key factor for endogenous stress adaptation of several tissues. However, altered chaperone function has been associated with the development of several diseases; therefore, modulators of chaperone activities became a new and emerging field of drug development. Inhibition of the 90 kDa heat shock protein (Hsp)90 recently emerged as a very promising tool to combat various forms of cancer. On the other hand, the induction of the 70 kDa Hsp70 has been proved to be an efficient help in the recovery from a large number of diseases, such as, for example, ischemic heart disease, diabetes and neurodegeneration. Development of membrane-interacting drugs to modify specific membrane domains, thereby modulating heat shock response, may be of considerable therapeutic benefit as well. In this review, we give an overview of the therapeutic approaches and list some of the key questions of drug development in this novel and promising therapeutic approach.

The significance of lipid composition for membrane activity: New concepts and ways of assessing function

In the last decade or so, it has been realised that membranes do not just have a lipid-bilayer structure in which proteins are embedded or with which they associate. Structures are dynamic and contain areas of heterogeneity which are vital for their formation. In this review, we discuss some of the ways in which these dynamic and heterogeneous structures have implications during stress and in relation to certain human diseases. A particular stress is that of temperature which may instigate adaptation in poikilotherms or appropriate defensive responses during fever in mammals. Recent data emphasise the role of membranes in sensing temperature changes and in controlling a regulatory loop with chaperone proteins. This loop seems to need the existence of specific membrane microdomains and also includes association of chaperone (heat stress) proteins with the membrane. The role of microdomains is then discussed further in relation to various human pathologies such as cardiovascular disease, cancer and neurodegenerative diseases. The concept of modifying membrane lipids (lipid therapy) as a means for treating such pathologies is then introduced. Examples are given when such methods have been shown to have benefit. In order to study membrane microheterogeneity in detail and to elucidate possible molecular mechanisms that account for alteration in membrane function, new methods are needed. In the second part of the review, we discuss ultra-sensitive and ultra-resolution imaging techniques. These include atomic force microscopy, single particle tracking, single particle tracing and various modern fluorescence methods. Finally, we deal with computing simulation of membrane systems. Such methods include coarse-grain techniques and Monte Carlo which offer further advances into molecular dynamics. As computational methods advance they will have more application by revealing the very subtle interactions that take place between the lipid and protein components of membranes - and which are so essential to their function.

Extracellular pressure stimulates colon cancer cell proliferation via a mechanism requiring PKC and tyrosine kinase signals

Pressure in colonic tumours may increase during constipation, obstruction or peri-operatively. Pressure enhances colonocyte adhesion by a c-Src- and actin-cytoskeleton-dependent PKC-independent pathway. We hypothesized that pressure activates mitogenic signals.

METHODS

Malignant colonocytes on a collagen I matrix were subjected to 15 mmHg pressure. ERK, p38, c-Src and Akt phosphorylation and PKCalpha redistribution were assessed by western blot after 30 min and PKC activation by ELISA. Cells were counted after 24 h and after inhibition of each signal, tyrosine phosphorylation or actin depolymerization.

RESULTS

Pressure time-dependently increased SW620 and HCT-116 cell counts on collagen or fibronectin (P < 0.01). Pressure increased the SW620 S-phase fraction from 28 +/- 1 to 47 +/- 1% (P = 0.0002). Pressure activated p38, ERK, and c-Src (P < 0.05 each) but not Akt/PKB. Pressure decreased cytosolic PKC activity, and translocated PKCalpha to a membrane fraction. Blockade of p38, ERK, c-Src or PI-3-K or actin depolymerization did not inhibit pressure-stimulated proliferation. However, global tyrosine kinase blockade (genistein) and PKC blockade (calphostin C) negated pressure-induced proliferation.

CONCLUSIONS

Extracellular pressure stimulates cell proliferation and activates several signals. However, the mitogenic effect of pressure requires only tyrosine kinase and PKCalpha activation. Pressure may modulate colon cancer growth and implantation by two distinct pathways, one stimulating proliferation and the other promoting adhesion.

Inhibition of cross-bridge formation has no effect on contraction-associated phosphorylation of p38 MAPK in mouse skeletal muscle

Mitogen-activated protein kinases (MAPKs), in particular p38 MAPK, are phosphorylated in response to contractile activity, yet the mechanism for this is not understood. We tested the hypothesis that the force of contraction is responsible for p38 MAPK phosphorylation in skeletal muscle. Extensor digitorum longus (EDL) muscles isolated from adult male Swiss Webster mice were stimulated at fixed length at 10 Hz for 15 min and then subjected to Western blot analysis for the phosphorylation of p38 MAPK and ERK1/2. Contralateral muscles were fixed at resting length and were not stimulated. Stimulated muscles showed a 2.5-fold increase in phosphorylated p38 MAPK relative to nonstimulated contralateral controls, and there was no change in the phosphorylation of ERK1/2. When contractile activity was inhibited with N-benzyl-p-toluene sulfonamide (BTS), a specific inhibitor of actomyosin ATPase, force production decreased in both a time- and concentration-dependent manner. Preincubation with 25, 75, and 150 microM BTS caused 78+/-4%, 97+/-0.2%, and 99+/-0.2% inhibition in contractile force, respectively, and was stable after 30 min of treatment. Fluorescence measurements demonstrated that Ca2+ cycling was minimally affected by BTS treatment. Surprisingly, BTS did not suppress the level of p38 MAPK phosphorylation in stimulated muscles. These data do not support the view that force generation per se activates p38 MAPK and suggest that other events associated with contraction must be responsible.

Circulating heat-shock protein 70 is associated with postoperative infection and organ dysfunction after liver resection

BACKGROUND

Although extracellular heat-shock protein 70 (Hsp70) potentially mediates an inflammatory response, the association of circulating Hsp70 with complications after surgery is poorly understood.

METHODS

Perioperative plasma concentrations of Hsp70 and interleukin-6 were measured by immunoassays in 64 consecutive patients undergoing liver resection.

RESULTS

Plasma concentrations of Hsp70 and interleukin-6 showed a striking increase immediately after surgery, and on postoperative day 1. The Hsp70 levels correlated significantly with operation time, hepatic ischemia time, postoperative alanine aminotransferase levels, and maximum interleukin-6 levels (P <0.01). The Hsp70 and interleukin-6 concentrations were associated significantly with postoperative infection (P <0.05); Hsp70 concentrations and blood loss but not interleukin-6 were associated significantly with postoperative organ dysfunction (P <0.05) in multivariate analyses.

CONCLUSIONS

These results suggest that circulating Hsp70 and IL-6 potentially play a pivotal role in pathophysiology of postoperative infection, and that circulating Hsp70 and blood loss may represent a prognostic marker for postoperative organ dysfunction.

Rac regulates cardiovascular superoxide through diverse molecular interactions: more than a binary GTP switch

The small G protein Rac has been implicated in multiple cardiovascular processes. Rac has two major functions: 1) it regulates the organization of the actin cytoskeleton, and 2) it controls the activity of the key enzyme complex NADPH oxidase to control superoxide production in both phagocytes and nonphagocytic cells. In phagocytes, superoxide derived from NADPH has a bactericidal function, whereas Rac-derived superoxide in the cardiovascular system has a diverse array of functions that have recently been a subject of intense interest. Rac is differentially activated by cellular receptors coupled to distinct Rac-activating adapter molecules, with each leading to pathway-specific arrays of downstream effects. Thus it may be important to investigate not just whether Rac is activated but also where, how, and for what effector. An understanding of the biochemical functions of Rac and its effectors lays the groundwork for a dissection of the exact array of effects produced by Rac in common cardiovascular processes, including cardiac and vascular hypertrophy, hypertension, leukocyte migration, platelet biology, and atherosclerosis. In addition, investigation of the spatiotemporal regulation of both Rac activation and consequent superoxide generation may produce new insights into the development of targeted antioxidant therapies for cardiovascular disease and enhance our understanding of important cardiovascular drugs, including angiotensin II antagonists and statins, that may depend on Rac modulation for their effect.

Activation of heat shock transcription factor 1 in atherosclerosis

Previous work established that increased expression of heat shock proteins (HSPs) in the vessel wall might evoke proinflammatory and autoimmune reactions in the pathogenesis of atherosclerosis. The present study was designed to further scrutinize the molecular mechanisms of HSP expression involving activation of heat shock transcription factors (HSFs) in atherosclerotic lesions in animal models. Severe atherosclerotic lesions developed in the aortas of rabbits 16 weeks after feeding a 0.2% cholesterol diet. When protein extracts from the aortas were subjected to Western blot analysis, the level of HSF1 in proteins from atherosclerotic lesions of hypercholesterolemic rabbits were significantly higher than those of normal vessels. Gel mobility shift assays revealed the formation of protein-heat shock element complexes containing HSF1 in protein extracts from atherosclerotic lesion. Furthermore, triglyceride-rich lipoprotein, oxidized-triglyceride-rich lipoprotein, low-density lipoprotein, and oxidized low-density lipoprotein did not activate HSF1 in cultured smooth muscle cells, whereas HSF1 was highly activated in cells treated with tumor necrosis factor-alpha. Interestingly, mechanical stretching of smooth muscle cells resulted in HSF1 translocation from the cytoplasm to the nucleus and hyperphosphorylation followed by increased HSP70 expression. Thus, our findings provide the first evidence that HSF1 is activated and highly expressed in atherosclerotic lesions and that cytokine stimulation and disturbed mechanical stress to the vessel wall may be responsible for such activation.