Stress-induced Resistance Research Articles

A multi-omics analysis reveals the unfolded protein response regulon and stress-induced resistance to folate-based antimetabolites

Stress response pathways are critical for cellular homeostasis, promoting survival through adaptive changes in gene expression and metabolism. They play key roles in numerous diseases and are implicated in cancer progression and chemoresistance. However, the underlying mechanisms are only poorly understood. We have employed a multi-omics approach to monitor changes to gene expression after induction of a stress response pathway, the unfolded protein response (UPR), probing in parallel the transcriptome, the proteome, and changes to translation. Stringent filtering reveals the induction of 267 genes, many of which have not previously been implicated in stress response pathways. We experimentally demonstrate that UPR‐mediated translational control induces the expression of enzymes involved in a pathway that diverts intermediate metabolites from glycolysis to fuel mitochondrial one‐carbon metabolism. Concomitantly, the cells become resistant to the folate-based antimetabolites Methotrexate and Pemetrexed, establishing a direct link between UPR‐driven changes to gene expression and resistance to pharmacological treatment.

Endoplasmic Reticulum Stress-Induced Resistance to Doxorubicin Is Reversed by Mulberry Leaf Polyphenol Extract in Hepatocellular Carcinoma through Inhibition of COX-2.

Mulberry (Morus alba L.) leaves are used in Chinese medicine to treat metabolic disorders. Mulberry leaf polyphenol extracts (MLPE) have recently been shown to exhibit anticancer properties. Endoplasmic reticulum (ER) stress represents a pivotal obstacle in solid tumors, resulting in the antiapoptosis of tumor cells and drug resistance. In this study, pretreatment with the ER stress inducer tunicamycin (TM) attenuated the percentage of apoptosis induced by doxorubicin (DOX). Cotreatment with tunicamycin and MLPE reversed apoptosis induced by DOX. Simultaneously, induction of ER stress with tunicamycin resulted in an increased expression of Cyclooxygenase 2 (COX-2) and Glucose-regulated protein (GRP78) concomitant with the activation of p38 MAPK/PI3K/Akt in HepG2 cells. Furthermore, the suppression of ER stress with celecoxib or p38 MAPK inhibitor successfully recovered DOX-induced apoptosis. Consistent with the inhibition of COX-2 or p38 MAPK, copretreatment with TM and MLPE drastically recovered cytotoxicity and caspase-3 activation in the presence of DOX. These results reveal that MLPE reduces ER stress-induced resistance to DOX in hepatocellular carcinoma (HCC) cells through downregulation of COX-2- or p38 MAPK-mediated PI3K/Akt pathway.

Transcriptomic Profiling of Acute Cold Stress-Induced Disease Resistance (SIDR) Genes and Pathways in the Grapevine Powdery Mildew Pathosystem.

Temperatures from 2 to 8°C transiently induce quantitative resistance to powdery mildew in several host species (cold stress-induced disease resistance [SIDR]). Although cold SIDR events occur in vineyards worldwide an average of 14 to 21 times after budbreak of grapevine and can significantly delay grapevine powdery mildew (Erysiphe necator) epidemics, its molecular basis was poorly understood. We characterized the biology underlying the Vitis vinifera cold SIDR phenotype-which peaks at 24 h post-cold (hpc) treatment and results in a 22 to 28% reduction in spore penetration success-through highly replicated (n = 8 to 10) RNA sequencing experiments. This phenotype was accompanied by a sweeping transcriptional downregulation of photosynthesis-associated pathways whereas starch and sugar metabolism pathways remained largely unaffected, suggesting a transient imbalance in host metabolism and a suboptimal target for pathogen establishment. Twenty-six cold-responsive genes peaked in their differential expression at the 24-hpc time point. Finally, a subset of genes associated with nutrient and amino acid transport accounted for four of the eight most downregulated transcripts, including two nodulin 1A gene precursors, a nodulin MtN21 precursor, and a Dynein light chain 1 motor protein precursor. Reduced transport could exacerbate localized nutrient sinks that would again be transiently suboptimal for pathogen growth. This study links the transient cold SIDR phenotype to underlying transcriptional changes and provides an experimental framework and library of candidate genes to further explore cold SIDR in several systems, with an ultimate goal of identifying novel breeding or management targets for reduced disease.

Arctigenin Inhibits Etoposide Resistance in HT-29 Colon Cancer Cells during Microenvironmental Stress.

Microenvironmental stress, which is naturally observed in solid tumors, has been implicated in anticancer drug resistance. This tumor-specific stress causes the degradation of topoisomerase IIα, rendering cells resistant to topoisomerase IIα-targeted anticancer agents. In addition, microenvironmental stress can induce the overexpression of 78kDa glucose regulated protein (GRP78), which can subsequently block the activation of apoptosis induced by treatment with anticancer agents. Therefore, inhibition of topoisomerase IIα degradation and reduction in GRP78 expression may be effective strategies for inhibiting anticancer drug resistance. In this study, we investigated the active compound arctigenin, which inhibited microenvironmental stress-induced etoposide resistance in HT-29 cells. Arctigenin was also highly toxic to etoposide-resistant HT-29 cells, with an IC50 value of 10 μM for colony formation. We further showed that arctigenin inhibited the degradation of topoisomerase IIα and reduced the expression of GRP78. Thus, these results suggest that arctigenin is a novel therapeutic agent that inhibits resistance to etoposide associated with microenvironmental stress conditions.

Quercetin-3-O-glucuronide inhibits doxorubicin resistance by reducing endoplasmic reticulum stress in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is typically aggressive and is closely correlated with recurrence and poor survival. Endoplasmic reticulum (ER) stress is a critical problem because it causes drug resistance. Quercetin-3-O-glucuronide (Q3GA) has been shown to exhibit antiproliferative and antioxidant activities. However, the effects of Q3GA on ER stress-induced doxorubicin (DOX) resistance in human HCC cells have not been studied. The results of MTT assay and flow cytometry data indicated that pretreatment with tunicamycin (TM), an ER stress inducer, significantly reduced apoptosis induced by DOX in HepG2 cells. Moreover, Western blot analysis indicated that the induction of ER stress resulted in an increase in COX-2 expression and the phosphorylation of PI3K/Akt in HepG2 cells. In addition, Q3GA enhanced DOX-induced cytotoxicity and caspase-3 activation under ER stress. These results demonstrated that Q3GA attenuated ER stress-induced resistance to DOX in human HCC cells through the downregulation of the COX-2-mediated PI3K/Akt pathway.

Corticosterone Production during Repeated Social Defeat Causes Monocyte Mobilization from the Bone Marrow, Glucocorticoid Resistance, and Neurovascular Adhesion Molecule Expression.

Repeated social defeat (RSD) stress promotes the release of bone marrow-derived monocytes into circulation that are recruited to the brain, where they augment neuroinflammation and cause prolonged anxiety-like behavior. Physiological stress activates the sympathetic nervous system and hypothalamic-pituitary-adrenal gland (HPA) axis, and both of these systems play a role in the physiological, immunological, and behavioral responses to stress. The purpose of this study was to delineate the role of HPA activation and corticosterone production in the immunological responses to stress in male C57BL/6 mice. Here, surgical (adrenalectomy) and pharmacological (metyrapone) interventions were used to abrogate corticosterone signaling during stress. We report that both adrenalectomy and metyrapone attenuated the stress-induced release of monocytes into circulation. Neither intervention altered the production of monocytes during stress, but both interventions enhanced retention of these cells in the bone marrow. Consistent with this observation, adrenalectomy and metyrapone also prevented the stress-induced reduction of a key retention factor, CXCL12, in the bone marrow. Corticosterone depletion with metyrapone also abrogated the stress-induced glucocorticoid resistance of myeloid cells. In the brain, these corticosterone-associated interventions attenuated stress-induced microglial remodeling, neurovascular expression of the adhesion molecule intercellular cell adhesion molecule-1, prevented monocyte accumulation and neuroinflammatory signaling. Overall, these results indicate that HPA activation and corticosterone production during repeated social defeat stress are critical for monocyte release into circulation, glucocorticoid resistance of myeloid cells, and enhanced neurovascular cell adhesion molecule expression.SIGNIFICANCE STATEMENT Recent studies of stress have identified the presence of monocytes that show an exaggerated inflammatory response to immune challenge and are resistant to the suppressive effects of glucocorticoids. Increased presence of these proinflammatory monocytes has been implicated in neuropsychiatric symptoms and the development of chronic cardiovascular, autoimmune, and metabolic disorders. In the current study, we show novel evidence that corticosterone produced during stress enhances the release of proinflammatory monocytes from the bone marrow into circulation, augments their recruitment to the brain and the induction of a neuroinflammatory profile. Overproduction of corticosterone during stress is also the direct cause of glucocorticoid resistance, a key phenotype in individuals exposed to chronic stress. Inhibiting excess corticosterone production attenuates these inflammatory responses to stress.

Prevention of chronic immobilization stress-induced enhanced expression of glucocorticoid receptors in the prefrontal cortex by inactivation of basolateral amygdala

Repeated exposure to stress precipitates anxiety, depression and cognitive deficits. Stress-induced activation of the hypothalamus–pituitary–adrenal (HPA) axis is modulated by the prefrontal cortex (PFC) and basolateral amygdala (BLA). It is well established that BLA positively regulates the HPA axis and undergoes hypertrophy following chronic immobilization stress (CIS). However, it is not known whether inactivation of the BLA can modulate the stress-induced changes in the expression of glucocorticoid receptors (GRs) in the PFC. To address this, we stereologically estimated GR+ cell densities in the prelimbic (PrL) and anterior cingulate cortex (ACC). Following ibotenate lesioning of the BLA, rats were subjected to CIS and GR+ cell densities were assessed. CIS increases the GR+ cell densities in PrL and ACC. BLA lesion prior to CIS abolished the CIS-induced increase in GR+ cell densities in both regions. In the second part of experiments, we evaluated whether selective inactivation of BLA during CIS would mimic the effects of BLA lesion. Interestingly, the BLA inactivation specifically during CIS prevented the increase in GR+ cell densities in the PrL and ACC. The findings of our study suggest that BLA regulates the stress-induced increase in prefrontal GR expression, which might be crucial in the emergence of affective and cognitive symptoms following stress. We speculate that modulation of BLA during stress might prevent HPA axis dysfunctions and GR resistance in stress-related disorders, and could assist in the development of novel therapeutic strategies to treat stress and associated disorders like depression. Further, molecular studies are warranted for the understanding of stress-induced GR resistance and its prevention via BLA inactivation.

Antibiotic-induced oxidative stress and antibiotic resistance

This is a review of published data on oxidative stress-induced antibiotic resistance of pathogens caused by antimicrobials. Known mechanisms of oxidative stress in a bacterial cell include occurrence of oxygen reactive species, protein oxidation products, fat acids, intracellular molecular oxygen and transition metal ions. Investigations of bacterial antioxidant defense under antibiotic-induced oxidative stress are at an early stage. Understanding the relationship between oxidative stress and bacterial resistance to antibiotics could facilitate development of novel antimicrobials due to both stimulation of oxidation properties of antimicrobials and searching new ways for inhibition of antioxidant defense of pathogens.

Reliability of magnetic tunnel junctions with a spinel MgAl 2 O 4 film

We investigated the stress-induced resistance drift and breakdown characteristics in MgAl2O4 (MAO)-based magnetic tunnel junctions (MTJs) with the MAO thickness of ∼0.9 nm. The occurrence of trap sites around the tunnel barrier–electrode interfaces was characterised via interval voltage stress (IVS) and constant voltage stress (CVS) experiments, in which the occurrence of trap sites affects the resistance drift in IVS and time-dependent dielectric breakdown in CVS. The observed resistance drift ratios were almost the same for positive and negative applied voltages, indicating that the difference in the interface structure was negligibly small between the top and bottom MAO/CoFe interfaces in the MAO-based MTJs. More interestingly, the resistance drift ratios were very low compared with the results of a previous study on MgO-based MTJs. MAO-based MTJs is likely to be an effective alternative that can be used to improve MTJ device reliability.

αMSH promotes preadipocyte proliferation by alleviating ER stress-induced leptin resistance and by activating Notch1 signal in mice

Alpha-melanocyte stimulating hormone (αMSH) has an important role in the regulation of body weight and energy expenditure. Nevertheless, the molecular mechanisms of circulating αMSH on preadipocyte proliferation remain elusive. We found αMSH was reduced by high fat diet (HFD) while leptin was elevated in adipose tissue. Leptin resistance and endoplasmic reticulum (ER) stress of adipose tissue were increased in obese mice. αMSH increased leptin sensitivity and alleviated ER stress along with increased p-STAT3 level and reduced SOCS3, GRP78, CHOP, ATF4, p27 and p53 levels. αMSH and leptin co-treatment alleviated ER stress through decreasing the levels of GRP78 and CHOP. Tunicamycin (TM) or thapsigargin (Tg) induced ER stress blunted leptin sensitivity and inhibited preadipocyte proliferation. αMSH and leptin co-treatment increased the cell number, augmented G1-S transition, elevated leptin sensitivity, and reduced ER stress; it also activated Notch1 signal and stimulated preadipocyte proliferation, whereas ER stress marker genes were decreased during this process. However, the effects of αMSH and leptin were blocked by the specific inhibitor of Notch1 signal. In summary, our data revealed αMSH enhanced leptin sensitivity and preadipocyte proliferation, meanwhile inhibited ER stress of preadipocytes by activating Notch1 signal.

Stress-induced resistance to the fear memory labilization/reconsolidation process. Involvement of the basolateral amygdala complex

Consolidated memories can enter into a labile state after reactivation followed by a restabilization process defined as reconsolidation. This process can be interfered with Midazolam (MDZ), a positive allosteric modulator of the GABA-A receptor. The present study has evaluated the influence of prior stress on MDZ’s interfering effect. We also assessed the influence of both systemic and intra-basolateral amygdala (BLA) infusion of d-cycloserine (DCS), a partial agonist of the NMDA receptors, on the MDZ effect in previously stressed rats. Furthermore, we analyzed the effect of stress on the expression of Zif-268 and the GluN2B sites, two molecular markers of the labilization/reconsolidation process, following reactivation. The results revealed that prior stress resulted into a memory trace that was insensitive to the MDZ impairing effect. Both systemic and intra-BLA DCS administration previous to reactivation restored MDZ’s disruptive effect on memory reconsolidation in stressed animals. Further, reactivation enhanced Zif-268 expression in the BLA in control unstressed rats, whereas no elevation was observed in stressed animals. In agreement with the behavioral findings, DCS restored the increased level of Zif-268 expression in the BLA in stressed animals. Moreover, memory reactivation in unstressed animals elevated GluN2B expression in the BLA, thus suggesting that this effect is involved in memory destabilization, whereas stressed animals did not reveal any changes. These findings are consistent with resistance to the MDZ effect in these rats, indicating that stress exposure prevents the onset of destabilization following reactivation.In summary, prior stress limited both the occurrence of the reactivation-induced destabilization and restabilization.

Pathogenesis-Related Protein 1b1 (PR1b1) Is a Major Tomato Fruit Protein Responsive to Chilling Temperature and Upregulated in High Polyamine Transgenic Genotypes.

Plants execute an array of mechanisms in response to stress which include upregulation of defense-related proteins and changes in specific metabolites. Polyamines – putrescine (Put), spermidine (Spd), and spermine (Spm) – are metabolites commonly found associated with abiotic stresses such as chilling stress. We have generated two transgenic tomato lines (556HO and 579HO) that express yeast S-adenosylmethionine decarboxylase and specifically accumulate Spd and Spm in fruits in comparison to fruits from control (556AZ) plants (Mehta et al., 2002). Tomato fruits undergo chilling injury at temperatures below 13°C. The high Spd and Spm tomato together with the control azygous line were utilized to address role(s) of polyamines in chilling-injury signaling. Exposure to chilling temperature (2°C) led to several-fold increase in the Put content in all the lines. Upon re-warming of the fruits at 20°C, the levels of Spd and Spm increased further in the fruit of the two transgenic lines, the higher levels remaining stable for 15 days after re-warming as compared to the fruit from the control line. Profiling their steady state proteins before and after re-warming highlighted a protein of ∼14 kD. Using proteomics approach, protein sequencing and immunoblotting, the ∼14-kD protein was identified as the pathogenesis related protein 1b1 (PR1b1). The PR1b1 protein accumulated transiently in the control fruit whose level was barely detectable at d 15 post-warming while in the fruit from both the 556HO and 579HO transgenic lines PR1b1 abundance increased and remained stable till d 15 post warming. PR1b1 gene transcripts were found low in the control fruit with a visible accumulation only on d 15 post warming; however, in both the transgenic lines it accumulated and increased soon after rewarming being several-fold higher on day 2 while in 556HO line this increase continued until d 6 than the control fruit. The chilling-induced increase in PR1b1 protein seems independent of ethylene and methyl jasmonate signaling but may be linked to salicylic acid. We propose that polyamine-mediated sustained accumulation of PR1b1 protein in post-warmed chilled tomato fruit is a pre-emptive cold stress response and possibly a defense response mechanism related to Cold Stress-Induced Disease Resistance (SIDR) phenomenon.

Transcriptome Profiling Revealed Stress-Induced and Disease Resistance Genes Up-Regulated in PRSV Resistant Transgenic Papaya.

Papaya is a productive and nutritious tropical fruit. Papaya Ringspot Virus (PRSV) is the most devastating pathogen threatening papaya production worldwide. Development of transgenic resistant varieties is the most effective strategy to control this disease. However, little is known about the genome-wide functional changes induced by particle bombardment transformation. We conducted transcriptome sequencing of PRSV resistant transgenic papaya SunUp and its PRSV susceptible progenitor Sunset to compare the transcriptional changes in young healthy leaves prior to infection with PRSV. In total, 20,700 transcripts were identified, and 842 differentially expressed genes (DEGs) randomly distributed among papaya chromosomes. Gene ontology (GO) category analysis revealed that microtubule-related categories were highly enriched among these DEGs. Numerous DEGs related to various transcription factors, transporters and hormone biosynthesis showed clear differences between the two cultivars, and most were up-regulated in transgenic papaya. Many known and novel stress-induced and disease-resistance genes were most highly expressed in SunUp, including MYB, WRKY, ERF, NAC, nitrate and zinc transporters, and genes involved in the abscisic acid, salicylic acid, and ethylene signaling pathways. We also identified 67,686 alternative splicing (AS) events in Sunset and 68,455 AS events in SunUp, mapping to 10,994 and 10,995 papaya annotated genes, respectively. GO enrichment for the genes displaying AS events exclusively in Sunset was significantly different from those in SunUp. Transcriptomes in Sunset and transgenic SunUp are very similar with noteworthy differences, which increased PRSV-resistance in transgenic papaya. No detrimental pathways and allergenic or toxic proteins were induced on a genome-wide scale in transgenic SunUp. Our results provide a foundation for unraveling the mechanism of PRSV resistance in transgenic papaya.

Effect of Mg insertion on stress‐induced resistance drift in MgO‐based magnetic tunnel junctions

The stress-induced resistance drift in MgO-based magnetic tunnel junctions (MTJs) with Mg insertion layer above and below a MgO tunnel barrier is investigated. Mg insertion suppresses the resistance drift. Resistance drift characteristics are improved when electrons tunnel into the Mg-inserted barrier–electrode interface, indicating that Mg insertion significantly suppresses trap site formation at the anode-side barrier–electrode interface. However, transmission electron microscopy images confirm that there is little difference in interface crystallinity between the Mg-inserted and non-inserted interfaces. Therefore, it is shown that a slight modification of the barrier–electrode interface states has a significant impact on resistance drift characteristics, and Mg insertion on both interface sides appears to be an effective way to improve MTJ device reliability in practical applications.

Cold Stress-Induced Disease Resistance (SIDR): indirect effects of low temperatures on host-pathogen interactions and disease progress in the grapevine powdery mildew pathosystem

Erysiphe necator is an obligate biotroph capable of infecting three genera within the Vitaceae (Vitis, Parthenocissus, and Ampelopsis). The pathogen inhabits a niche unique to most powdery mildews, i.e., wholly external mycelial growth supported by haustoria within the subtending host epidermal cells. This growth habit coupled with its biotrophic reliance on the host makes E. necator sensitive to both direct effects of abiotic stresses on the pathogen and indirect abiotic effects via the host responses. Development of the pathogen during acute cold events (e.g., 1 h at 4 °C) results in death of hyphal segments and a prolonged latency, an effect further increased by the development of ontogenic resistance as epidermal tissues of leaves and berries age. Acute cold events can also stress the host prior to the arrival of the pathogen, and thereby reduce susceptibility to infection via cold Stress-Induced Disease Resistance (SIDR), a recently described phenomenon. This effect requires approximately 24 h post-cold before maximal resistance effect occurs, and is also transient in that the effect diminishes to a basal level within 48 h after exposure. Although the phenotypic responses to cold SIDR may be similar to those observed on ontogenically-resistant leaves, the effects of cold SIDR and ontogenic resistance are additive. Sufficient tools are now available for investigating the mechanistic basis of cold SIDR. While pathosystems involving obligate biotrophs complicate research on direct and indirect environmental effects on the pathogen, this requisite interaction also creates interesting systems to understand how the condition of the host may influence subsequent disease development. At the population level, the effects of repeated cold events have profound effects on the nature of epidemic progress and implications for management of grape powdery mildew. The objective in this review is to summarize our current knowledge regarding the indirect and consequential effects of low temperature on the development of grapevine powdery mildew.

Abstract 4571: Chronic oxidative stress increases resistance in renal carcinoma cells to doxorubicin-induced cytotoxicity potentially through epigenetic mechanism

Abstract Human renal cell carcinoma (RCC) is the most common form of kidney cancer. Regardless of therapeutic advancement, patients with metastatic RCC are failed to clinical treatment due to rapidly developing resistance. Resistance to chemotherapy can be of innate or acquired overtime following exposure to drug and can arise through a number of different intrinsic and extrinsic factors and their interactions. While some reports suggest role of ROS in developing drug resistance, response of cancer cells with chronic exposure to oxidative stress to chemotherapeutic drugs is not known. Hence, the objective of this study was to evaluate the impact of chronic exposure to elevated levels of oxidative stress in human kidney cancer cells. Caki-1 human renal carcinoma cells were given chronic (6 months) exposure to direct ROS source hydrogen peroxide (25 μM and 200 μM). Using these cells the effect of oxidative stress on sensitivity to doxorubicin-induced cytotoxicity was measured by MTT assay. The result was further confirmed by anchorage independent growth on soft agar and cell cycle analysis using flow cytometer. To understand the molecular mechanism, the expression of genes involved in drug resistance, cell survival, and DNA repair dependent apoptosis were measured by qRT- PCR. Results of MTT, soft agar assay, and cell cycle analysis showed that doxorubicin-induced cytotoxicity was significantly less in Caki-1 cells chronically exposed to H2O2 when compare to H2O2 unexposed control cells. The alterations in the expression of genes involved in drug transport further confirmed the increased resistance to doxorubicin-induced cytotoxicity in cells exposed to oxidative stress. Decreased expression of MSH2 gene in cells exposed to H2O2-induced oxidative stress suggests that loss of DNA repair-dependent apoptosis could be a potential mechanism for increased resistance to doxorubicin-induced cytotoxicity. To further evaluate the role of epigenetic process of DNA methylation in oxidative stress-induced drug resistance, cells were pretreated with demethylating agent 5-aza-2′ deoxycytidine (5-aza 2dC), and then treated with doxorubicin. The pretreatment with 5-aza 2dC significantly resensitized the chronic ROS adapted Caki-1 cells to doxorubicin-induced cytotoxicity and restored the expression of MSH2 gene in these cells. This suggests that epigenetic silencing of MSH2 and therefore DNA repair-dependent apoptosis could be a potential mechanism for oxidative stress-induced resistance to chemotherapeutic drugs in renal cancer cells. In summary, this study for the first time provides direct evidence for the role of oxidative stress in chemoresistance in renal carcinoma cells. Additionally, the findings of this study also suggest that epigenetic therapy may be a useful strategy in re-sensitizing the chemotherapeutic resistant RCC cells. Citation Format: Logeswari Ponnusamy, PrathapKumar S. Mahalingaiah, Kamaleshwar P. Singh. Chronic oxidative stress increases resistance in renal carcinoma cells to doxorubicin-induced cytotoxicity potentially through epigenetic mechanism. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4571. doi:10.1158/1538-7445.AM2015-4571

A mathematical model of the growth of uterine myomas.

Uterine myomas or fibroids are common, benign smooth muscle tumours that can grow to 10cm or more in diameter and are routinely removed surgically. They are typically slow- growing, well-vascularised, spherical tumours that, on a macro-scale, are a structurally uniform, hard elastic material. We present a multi-phase mathematical model of a fully vascularised myoma growing within a surrounding elastic tissue. Adopting a continuum approach, the model assumes the conservation of mass and momentum of four phases, namely cells/collagen, extracellular fluid, arterial and venous phases. The cell/collagen phase is treated as a poro-elastic material, based on a linear stress-strain relationship, and Darcy's law is applied to describe flow in the extracellular fluid and the two vascular phases. The supply of extracellular fluid is dependent on the capillary flow rate and mean capillary pressure expressed in terms of the arterial and venous pressures. Cell growth and division is limited to the myoma domain and dependent on the local stress in the material. The resulting model consists of a system of nonlinear partial differential equations with two moving boundaries. Numerical solutions of the model successfully reproduce qualitatively the clinically observed three-phase "fast-slow-fast" growth profile that is typical for myomas. The results suggest that this growth profile requires stress-induced resistance to growth by the surrounding tissue and a switch-like cell growth response to stress. Analysis of large-time solutions reveal that while there is a functioning vasculature throughout the myoma, exponential growth results, otherwise power-law growth is predicted. An extensive survey of the effect of parameters on model solutions is also presented, and in particular, the enhanced growth caused by factors such as oestrogen is predicted by the model.

64. Roles of glucocorticoid receptor and microRNA in repeated social disruption stress-induced glucocorticoid resistance in splenic macrophages

Chronic social stress has attracted interest due to its deleterious impact on health psychologically and physiologically. It has been shown using rodent models of chronic social stress, e.g., repeated social disruption stress (RSD), innate immune cells develop insensitivity to glucocorticoid (GC) stimuli and contribute to enhance inflammatory responses. Previous studies have found that one of the immune cells that is GC insensitive in response to RSD is the splenic macrophage, however, the underlying molecular mechanisms that contribute to this process are not fully understood. Current data showed RSD modified GC receptor expression and increased the expression ratio of FK506-binding protein 51 (FKBP51) to FKBP52, favoring to blockade of nuclear translocation of GC–GC receptor complexes in splenic macrophages. Using a NanoString nCounter miRNA Expression assay and the internet-based DIANA-micro T-CDS database (ver 5.0), the expression of 6 microRNAs was increased by RSD. The two highest expressed miRNAs (miRNA-29b and 340) were overexpressed in L929 cells and were found to completely block LPS-induced overexpression of GC receptors. These data suggest that miRNAs play a critical role in RSD-induced GC resistance in splenic macrophages, especially via an epigenetic mechanism of GC receptor expression at least. This was supported by grants funded through NIH/NIMH: R01MH093473 and R01MH097243.

Psychological stress as a modulator of functional recovery following spinal cord injury.

There is strong evidence indicating that the social environment triggers changes to the psychological stress response and glucocorticoid receptor function. Considerable literature links the subsequent changes in stress resiliency to physical health. Here, converging evidence for the modulatory role of chronic psychological stress in the recovery process following spinal cord injury (SCI) is presented. Despite the considerable advances in SCI research, we are still unable to identify the causes of variability in patients’ recovery following injury. We propose that individuals’ past and present life experiences (in the form of stress exposure) may significantly modulate patients’ outcome post-SCI. We propose a theoretical model to explain the negative impact of chronic psychological stress on physical and psychological recovery. The stress experienced in life prior to SCI and also as a result of the traumatic injury, could compromise glucocorticoid receptor sensitivity and function, and contribute to high levels of inflammation and apoptosis post-SCI, decreasing the tissue remaining at the injury site and undermining recovery of function. Both stress-induced glucocorticoid resistance and stress-induced epigenetic changes to the glucocorticoid receptor can modulate the nuclear factor-kappa B regulated inflammatory pathways and the Bcl-2 regulated apoptosis pathways. This model not only contributes to the theoretical understanding of the recovery process following injury, but also provides concrete testable hypotheses for future studies.

Caffeine attenuated ER stress-induced leptin resistance in neurons

Exposing the endoplasmic reticulum (ER) to stress causes the accumulation of unfolded proteins, and subsequently results in ER stress. ER stress may be involved in various disorders such as obesity, diabetes, and neurodegenerative diseases. Leptin is an important circulating hormone, that inhibits food intake and accelerates energy consumption, which suppresses body weight gain. Recent studies demonstrated that leptin resistance is one of the main factors involved in the development of obesity. We and other groups recently reported the role of ER stress in the development of leptin resistance. Therefore, identifying drugs that target ER stress may be a promising fundamental strategy for the treatment of obesity. In the present study, we investigated whether caffeine could affect ER stress and the subsequent development of leptin resistance. We showed that caffeine exhibited chaperone activity, which attenuated protein aggregation. Caffeine also inhibited the ER stress-induced activation of IRE1 and PERK, which suggested the attenuation of ER stress. Moreover, caffeine markedly improved ER stress-induced impairments in the leptin-induced phosphorylation of STAT3. Therefore, these results suggest caffeine may have pharmacological properties that ameliorate leptin resistance by reducing ER stress.